Patent Application
20200268568
The present invention generally relates to a leg gasketing cuff for use in an absorbent article comprising an adhesive that is tackifier-free.
It has long been known that absorbent articles such as conventional taped diapers offer the benefit of receiving and containing urine and/or other bodily exudates. To effectively contain exudates, the article should provide a snug fit around the waist and legs of a wearer. Absorbent articles are known to have a chassis comprising a topsheet, a backsheet, and an absorbent core.
Current diaper designs frequently include the use of an inner barrier leg cuff to prevent leakage of bodily exudates and an outer leg cuff which provides a covering over the inner leg cuff to minimize the visibility of exudates through the inner cuff and provide a secondary means to capture bodily exudates should they breach the inner barrier leg cuff. In many current diapers, the outer leg cuff comprises the polymeric film layer of the backsheet to provide high opacity required to cover the inner leg cuff as well as to prevent molten adhesive from passing through the cuff to the garment-facing surface of the article during manufacturing. The outer leg cuff contains the outer leg elastic strands, which create the contraction forces and gathers, and can be sandwiched between the cuff material and backsheet material. The elastic strands in the leg cuffs are typically joined with molten adhesive during manufacture, and the hot adhesive generally has the potential to pass through nonwoven materials during manufacture, causing contamination of manufacturing lines as well as the potential for stickiness on the outside surface of the article. The polymeric film generally is used to prevent these issues, however, results in a plastic-like look as well as a noisy application process. It can also be problematic to provide the elastic strands sufficiently close to the outermost portion of the product close to the skin so as not to provide the perception that the article may leak.
One solution is to provide a folded outer leg cuff design having finished edges with elastics that are close to the edge to maintain a close proximity to the skin, without a polymeric film in the elasticized region. Such a design can create improved fit, be a more aesthetically pleasing clothing-like design, and improve leakage protection. Also helpful in this design would be an adhesive that is very stable. Molten adhesives used in assembling articles are typically made by combining polymer with additive components in a substantially uniform thermoplastic blend. However, the additive components, such as tackifiers, for example, can migrate during product use and create instability issues that negatively affect the performance and consumer impression of the article. In addition, for some hot melt adhesives, tackifiers may be a significant portion of the overall formulation and/or the most expensive component in the hot melt adhesive. Therefore, there is a continuing need to minimize the cost and minimize stability issues that adhesive with tackifiers may have.
Accordingly, there is a need for adhesives used with leg gasketing cuffs that have reduced amounts of tackifier or that are substantially free of tackifiers.
A disposable absorbent article for wearing about the lower torso of a wearer, the disposable absorbent article comprising: a first waist region, a second waist region, a crotch region disposed between the first and second waist regions; a first waist edge and a second waist edge; and a first longitudinal edge and a second longitudinal edge, the disposable absorbent article comprising, a topsheet, a backsheet comprising a polymeric film, an absorbent core disposed between the topsheet and the backsheet, and a leg gasketing system, wherein the leg gasketing system comprises an inner cuff and an outer cuff; wherein the inner cuff comprises an inner cuff folded edge and an inner cuff material edge; wherein the outer cuff comprises an outer cuff folded edge and an outer cuff material edge such that the web of material is folded laterally inward to form the outer cuff folded edge and folded laterally outward to form the inner cuff material edge, wherein the leg gasketing system extends from the first waist edge to the second waist edge and is joined to the topsheet and/or backsheet between the inner cuff folded edge and the outer cuff folded edge in the crotch region by an adhesive, wherein the adhesive is a substantially tackifier-free adhesive.
As used herein, the following terms shall have the meaning specified thereafter:
“Disposable,” in reference to absorbent articles, means that the absorbent articles are generally not intended to be laundered or otherwise restored or reused as absorbent articles (i.e., they are intended to be discarded after a single use and, preferably, to be recycled, composted or otherwise discarded in an environmentally compatible manner).
“Absorbent article” refers to devices which absorb and contain body exudates and, more specifically, refers to devices which are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. Exemplary absorbent articles include diapers, training pants, pull-on pant-type diapers (i.e., a diaper having a pre-formed waist opening and leg openings such as illustrated in U.S. Pat. No. 6,120,487), refastenable diapers or pant-type diapers, incontinence briefs and undergarments, diaper holders and liners, feminine hygiene garments such as panty liners, absorbent inserts, and the like.
“Proximal” and “Distal” refer respectively to the location of an element relatively near to or far from the longitudinal or lateral centerline of a structure (e.g., the proximal edge of a longitudinally extending element is located nearer to the longitudinal centerline than the distal edge of the same element is located relative to the same longitudinal centerline).
“Body-facing” and “garment-facing” refer respectively to the relative location of an element or a surface of an element or group of elements. “Body-facing” implies the element or surface is nearer to the wearer during wear than some other element or surface. “Garment-facing” implies the element or surface is more remote from the wearer during wear than some other element or surface (i.e., element or surface is proximate to the wearer's garments that may be worn over the disposable absorbent article).
“Longitudinal” refers to a direction running substantially perpendicular from a waist edge to an opposing waist edge of the article and generally parallel to the maximum linear dimension of the article. Directions within 45 degrees of the longitudinal direction are considered to be “longitudinal” “Lateral” refers to a direction running from a longitudinal edge to an opposing longitudinal edge of the article and generally at a right angle to the longitudinal direction. Directions within 45 degrees of the lateral direction are considered to be “lateral.”
“Disposed” refers to an element being located in a particular place or position.
“Joined” refers to configurations whereby an element is directly secured to another element by affixing the element directly to the other element and to configurations whereby an element is indirectly secured to another element by affixing the element to intermediate member(s) which in turn are affixed to the other element.
“Film” refers to a sheet-like material wherein the length and width of the material far exceed the thickness of the material. Typically, films have a thickness of about 0.5 mm or less.
“Water-permeable” and “water-impermeable” refer to the penetrability of materials in the context of the intended usage of disposable absorbent articles. Specifically, the term “water-permeable” refers to a layer or a layered structure having pores, openings, and/or interconnected void spaces that permit liquid water, urine, or synthetic urine to pass through its thickness in the absence of a forcing pressure. Conversely, the term “water-impermeable” refers to a layer or a layered structure through the thickness of which liquid water, urine, or synthetic urine cannot pass in the absence of a forcing pressure (aside from natural forces such as gravity). A layer or a layered structure that is water-impermeable according to this definition may be permeable to water vapor, i.e., may be “vapor-permeable.”
“Extendibility” and “extensible” mean that the width or length of the component in a relaxed state can be extended or increased.
“Elasticated” and “elasticized” mean that a component comprises at least a portion made of elastic material.
“Elongatable material,” “extensible material,” or “stretchable material” are used interchangeably and refer to a material that, upon application of a biasing force, can stretch to an elongated length of at least about 110% of its relaxed, original length (i.e. can stretch to 10 percent more than its original length), without rupture or breakage, and upon release of the applied force, shows little recovery, less than about 20% of its elongation without complete rupture or breakage as measured by EDANA method 20.2-89. In the event such an elongatable material recovers at least 40% of its elongation upon release of the applied force, the elongatable material will be considered to be “elastic” or “elastomeric.” For example, an elastic material that has an initial length of 100 mm can extend at least to 150 mm, and upon removal of the force retracts to a length of at least 130 mm (i.e., exhibiting a 40% recovery). In the event the material recovers less than 40% of its elongation upon release of the applied force, the elongatable material will be considered to be “substantially non-elastic” or “substantially non-elastomeric”. For example, an elongatable material that has an initial length of 100 mm can extend at least to 150 mm, and upon removal of the force retracts to a length of at least 145 mm (i.e., exhibiting a 10% recovery).
“Elastomeric material” is a material exhibiting elastic properties. Elastomeric materials may include elastomeric films, scrims, nonwovens, and other sheet-like structures.
“Pant” refers to disposable absorbent articles having a pre-formed waist and leg openings. A pant may be donned by inserting a wearer's legs into the leg openings and sliding the pant into position about the wearer's lower torso. Pants are also commonly referred to as “closed diapers”, “prefastened diapers”, “pull-on diapers”, “training pants” and “diaper-pants.”
As used herein “homopolymer” means a polymer resulting from the polymerization of a single monomer, i.e., a polymer consisting essentially of a single type of repeating unit.
As used herein, the term “copolymer(s)” refers to polymer(s) formed by the polymerization of at least two different monomers. For example, the term “copolymer” includes the copolymerization reaction product of a monomer such as propene or butene, preferably 1-butene and an alpha-olefin, such as for example, ethylene, 1-hexene or 1-octene.
As used herein, the term “propene copolymer” or “propylene copolymer” means a copolymer of greater than 40 or 50 wt. % or more propene and at least one monomer selected from the group including ethylene and a C4 to C20 α-olefin.
As used herein, the term “butene copolymer” means a polymer of n-butene (1-butene) or 2-butene and at least one monomer selected from the group of C2-3 and C5-20 alpha olefins. Butene copolymers typically comprise a minimum amount at least about 40 or about 50 wt. % or more of a butene monomer such as 1-butene.
The term “heterophase” polymer means a polymer having an amorphous character and at least some substantial crystalline content (at least 5 wt. %, 10 wt. %, 20 wt. %, 40 wt. % or 50 wt. % crystalline content) that can provide cohesive strength in the cooled adhesive mass. The crystalline content can be in the form of stereoregular blocks or sequences.
The term “amorphous” means the substantial absence of crystallinity, (i.e.) less than 5% and less than 1%.
The term “sequence or block” means a polymer portion of repeating monomer that is similar in composition, crystallinity or other aspect.
As used herein, the term “open time” means the amount of time elapsed between application of a molten hot melt adhesive composition to a first substrate, and the time when useful tackiness or wetting out of the adhesive on a substrate effectively ceases due to solidification of the adhesive composition. Open time is also referred to as “working time.”
As used herein, the term “substrate” means any item having at least a partially or fully solidified fiber or planar surface with which contact with a hot melt adhesive composition is intended. In some cases the same area, circle, bead, line, filament or dot of hot melt adhesive composition is contacted with two or more substrates for the purpose of creating an adhesive bond there between. In some such cases the substrates are part of the same item: for example, folded film or folded non-woven, two sides of a cardboard sheet folded over, wherein the two sides are adhesively bonded together. In other such cases the substrates are part of different items: for example, a plastic film that is adhesively bonded to a non-woven or cardboard sheet. The substrates can be impermeable, permeable, porous or nonporous.
As used herein, the term “substantially” means generally the same or uniform but allowing for or having minor fluctuations from a defined property, definition, etc. For example, small measurable or immeasurable fluctuations in a measured property described herein, such as viscosity, melting point, etc. may result from human error or methodology precision. Other fluctuations are caused by inherent variations in the manufacturing process, thermal history of a formulation, and the like. The adhesive compositions of the, nonetheless, would be said to be substantially having the property as reported.
As used herein, the term “major proportion” means that a material or monomer is used at greater than 50 wt. %. As used herein, the term “primary component” means that a material or monomer is the more common substance or has the higher concentration in the mixture or polymer compared to others but may not be as much as 50 wt. %.
The transitional phrase “consisting essentially of” limits the scope of a claim to the specified materials but includes those that do not materially affect the basic and novel characteristics of the claimed materials. These characteristics include open time, cohesive strength (tensile strength), peel strength and viscosity. Meaningful amounts of a third polymer or amounts of a tackifier materially affect the basic and novel characteristics of the claimed materials.
The present invention is directed to a leg gasketing system that is joined to a topsheet and/or backsheet with a tackifier-free adhesive. The folded outer leg cuff design is advantageous in preventing penetration and adhesive bleedthrough without the use of a polymeric film layer in the elasticized region, and the particular adhesives have greater stability and less migration of additive components.
The outer periphery of chassis 22 is defined by longitudinal edges 12 and lateral edges 14. The longitudinal edges 12 may be subdivided into a front longitudinal edge 12a, which is the portion of the longitudinal edge 12 in the first waist region 36, and a rear longitudinal edge 12b, which is the portion of the longitudinal edge 12 in the rear waist region 38. The chassis 22 may have opposing longitudinal edges 12 that are oriented generally parallel to the longitudinal centerline 100. However, for better fit, longitudinal edges 12 may be curved or angled to produce, for example, an “hourglass” shape diaper when viewed in a plan view. The chassis 22 may have opposing lateral edges 14 that are oriented generally parallel to the lateral centerline 110.
The chassis 22 may comprise a liquid permeable topsheet 24, a backsheet 26, and an absorbent core 28 between the topsheet 24 and the backsheet 26. The absorbent core 28 may have a body-facing surface and a garment facing-surface. The topsheet 24 may be joined to the core 28 and/or the backsheet 26. The backsheet 26 may be joined to the core 28 and/or the topsheet 24. It should be recognized that other structures, elements, or substrates may be positioned between the core 28 and the topsheet 24 and/or backsheet 26. In certain embodiments, the chassis 22 comprises the main structure of the absorbent article 20 with other features may added to form the composite diaper structure. While the topsheet 24, the backsheet 26, and the absorbent core 28 may be assembled in a variety of well-known configurations, preferred diaper configurations are described generally in U.S. Pat. Nos. 3,860,003; 5,151,092; 5,221,274; 5,554,145; 5,569,234; 5,580,411; and 6,004,306.
The topsheet 24 is generally a portion of the absorbent article 20 that may be positioned at least in partial contact or close proximity to a wearer. Suitable topsheets 24 may be manufactured from a wide range of materials, such as porous foams; reticulated foams; apertured plastic films; or woven or nonwoven webs of natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polyester or polypropylene fibers), or a combination of natural and synthetic fibers. The topsheet 24 is generally supple, soft feeling, and non-irritating to a wearer's skin. Generally, at least a portion of the topsheet 24 is liquid pervious, permitting liquid to readily penetrate through the thickness of the topsheet 24. One topsheet 24 useful herein is available from BBA Fiberweb, Brentwood, Tenn. as supplier code 055SLPV09U.
Any portion of the topsheet 24 may be coated with a lotion or skin care composition as is known in the art. Examples of suitable lotions include those described in U.S. Pat. Nos. 5,607,760; 5,609,587; 5,635,191; and 5,643,588. The topsheet 24 may be fully or partially elasticized or may be foreshortened so as to provide a void space between the topsheet 24 and the core 28. Exemplary structures including elasticized or foreshortened topsheets are described in more detail in U.S. Pat. Nos. 4,892,536; 4,990,147; 5,037,416; and 5,269,775.
The absorbent core 28 may comprise a wide variety of liquid-absorbent materials commonly used in disposable diapers and other absorbent articles. Examples of suitable absorbent materials include comminuted wood pulp, which is generally referred to as air felt creped cellulose wadding; melt blown polymers, including co-form; chemically stiffened, modified or cross-linked cellulosic fibers; tissue, including tissue wraps and tissue laminates; absorbent foams; absorbent sponges; superabsorbent polymers; absorbent gelling materials; or any other known absorbent material or combinations of materials. In one embodiment, at least a portion of the absorbent core is substantially cellulose free and contains less than 10% by weight cellulosic fibers, less than 5% cellulosic fibers, less than 1% cellulosic fibers, no more than an immaterial amount of cellulosic fibers or no cellulosic fibers. It should be understood that an immaterial amount of cellulosic material does not materially affect at least one of the thinness, flexibility, and absorbency of the portion of the absorbent core that is substantially cellulose free. Among other benefits, it is believed that when at least a portion of the absorbent core is substantially cellulose free, this portion of the absorbent core is significantly thinner and more flexible than a similar absorbent core that includes more than 10% by weight of cellulosic fibers. The amount of absorbent material, such as absorbent particulate polymer material present in the absorbent core may vary, but in certain embodiments, is present in the absorbent core in an amount greater than about 80% by weight of the absorbent core, or greater than about 85% by weight of the absorbent core, or greater than about 90% by weight of the absorbent core, or greater than about 95% by weight of the core. Non-limiting examples of suitable absorbent cores are described in greater details below.
Exemplary absorbent structures for use as the absorbent core 28 are described in U.S. Pat. Nos. 4,610,678; 4,673,402; 4,834,735; 4,888,231; 5,137,537; 5,147,345; 5,342,338; 5,260,345; 5,387,207; 5,397,316; and 5,625,222.
The backsheet 26 is generally positioned such that it may be at least a portion of the garment-facing surface 120 of the absorbent article 20. Backsheet 26 may be designed to prevent the exudates absorbed by and contained within the absorbent article 20 from soiling articles that may contact the absorbent article 20, such as bed sheets and undergarments. In certain embodiments, the backsheet 26 is substantially water-impermeable. Suitable backsheet 26 materials include films such as those manufactured by Tredegar Industries Inc. of Terre Haute, Ind. and sold under the trade names X15306, X10962, and X10964. Other suitable backsheet 26 materials may include breathable materials that permit vapors to escape from the absorbent article 20 while still preventing exudates from passing through the backsheet 26. Exemplary breathable materials may include materials such as woven webs, nonwoven webs, composite materials such as film-coated nonwoven webs, and microporous films such as manufactured by Mitsui Toatsu Co., of Japan under the designation ESPOIR NO and by EXXON Chemical Co., of Bay City, Tex., under the designation EXXAIRE. Suitable breathable composite materials comprising polymer blends are available from Clopay Corporation, Cincinnati, Ohio under the name HYTREL blend P18-3097. Such breathable composite materials are described in greater detail in PCT Application No. WO 95/16746 and U.S. Pat. No. 5,865,823. Other breathable backsheets including nonwoven webs and apertured formed films are described in U.S. Pat. No. 5,571,096. An exemplary, suitable backsheet is disclosed in U.S. Pat. No. 6,107,537. Other suitable materials and/or manufacturing techniques may be used to provide a suitable backsheet 26 including, but not limited to, surface treatments, particular film selections and processing, particular filament selections and processing, etc.
Backsheet 26 may also consist of more than one layer. The backsheet 26 may comprise an outer cover and an inner layer. The outer cover may be made of a soft, non-woven material. The inner layer may be made of a substantially liquid-impermeable film. The outer cover and an inner layer may be joined together by adhesive or any other suitable material or method. A particularly suitable outer cover is available from Corovin GmbH, Peine, Germany as supplier code A18AH0, and a particularly suitable inner layer is available from RKW Gronau GmbH, Gronau, Germany as supplier code PGBR4WPR. While a variety of backsheet configurations are contemplated herein, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention.
The absorbent article 20 may include front ears 40 and/or back ears 42. The ears 40, 42 may be extensible, inextensible, elastic, or inelastic. The ears 40, 42 may be formed from nonwoven webs, woven webs, knitted fabrics, polymeric and elastomeric films, apertured films, sponges, foams, scrims, and combinations and laminates thereof. In certain embodiments the ears 40, 42 may be formed of a stretch laminate such as a nonwoven/elastomeric material laminate or a nonwoven/elastomeric material/nonwoven laminate. Stretch laminates may be formed by any method known in the art. For example, the ears 40, 42 may be formed as a zero strain stretch laminate, which includes at least a layer of non-woven material and an elastomeric element. The elastomeric element is attached to the layer of non-woven material while in a relaxed or substantially relaxed state, and the resulting laminate is made stretchable (or more stretchable over a further range) by subjecting the laminate to an activation process which elongates the nonwoven layer permanently, but the elastomeric element temporarily. The nonwoven layer may be integral with at least a portion of the chassis 22, in which case the elastomeric element may be attached to the nonwoven layer and the non-woven/elastomeric element laminate is subsequently activated. Alternatively, the nonwoven layer may be a separate component, in which case the elastomeric element is attached to the nonwoven layer to form the laminate, which is then coupled to the main portion. If one or more layers of the side panel are provided separately, the laminate may be activated either before or after attachment to the main portion. The zero strain activation processes is further disclosed in U.S. Pat. Nos. 5,167,897 and 5,156,793. A suitable elastic ear may be an activated laminate comprising an elastomeric film (such as is available from Tredegar Corp, Richmond, Va., as supplier code X25007) disposed between two nonwoven layers (such as is available from BBA Fiberweb, Brentwood, Tenn. as supplier code FPN332).
The ears 40, 42 may be discrete or integral. A discrete ear is formed as separate element which is joined to the chassis 22. An integral ear is a portion of the chassis 22 that projects laterally outward from the longitudinal edge 12. The integral ear may be formed by cutting the chassis form to include the shape of the ear projection.
The absorbent article 20 may also include a fastening system 50. When fastened, the fastening system 50 interconnects the first waist region 36 and the rear waist region 38 resulting in a waist circumference that may encircle the wearer during wear of the absorbent article 20. The fastening system 50 may comprises a fastener such as tape tabs, hook and loop fastening components, interlocking fasteners such as tabs & slots, buckles, buttons, snaps, and/or hermaphroditic fastening components, although any other known fastening means are generally acceptable. Some exemplary surface fastening systems are disclosed in U.S. Pat. Nos. 3,848,594; 4,662,875; 4,846,815; 4,894,060; 4,946,527; 5,151,092; and 5,221,274. An exemplary interlocking fastening system is disclosed in U.S. Pat. No. 6,432,098. The fastening system 50 may also provide a means for holding the article in a disposal configuration as disclosed in U.S. Pat. No. 4,963,140. The fastening system 50 may also include primary and secondary fastening systems, as disclosed in U.S. Pat. No. 4,699,622. The fastening system 50 may be constructed to reduce shifting of overlapped portions or to improve fit as disclosed in U.S. Pat. Nos. 5,242,436; 5,499,978; 5,507,736; and 5,591,152.
The absorbent article 20 may include waistbands as disclosed and described in U.S. Ser. Nos. 13/490,543, 13/490,548, and 13/490,554, Attorney Docket Nos. 12178M, 12179M, and 12180M, respectively. In some embodiments, the article may have “differential contraction” or waistband laminates having different installed elongation strands in the front versus the back, such that only one waistband laminate is cut. Cutting of the waistband laminate is subsequent to the waistband application to the article; the waistband is applied such that it spans the intended article separation (cut) zone. Thus, the same waistband laminate can deliver different levels of contraction in the back and front, resulting in higher contraction in the back to help close the gap and lower contraction in the front. In other embodiments, the article may have “consolidation” which provides a waistband having the nonwoven material and the elastic strand(s) combined under a higher first strain (installed elongation) and the resulting waistband attached to the article under a lower applied waistband strain, such that the folded up nonwoven in the waistband provides a cushion/caliper in both the relaxed and stretched/in use states. The nonwoven material and the elastic strand(s) may be combined with the tackifier-free adhesives described herein, and the waistband may similarly be attached to the article with a tackifier-free adhesive.
The absorbent article 20 may include a leg gasketing system 70.
In one embodiment, the leg gasketing system 70 comprises one web of material. An embodiment having one web of material may provide a cost advantage over embodiments having more than one web of material. Further, an embodiment having one web of material may have fewer leaks, as there are no holes created by bonding more than one web of material. Also, an embodiment having one web of material may be more aesthetically pleasing, as few mechanical bonds are visible.
In one embodiment, the leg gasketing system 70 has an inner barrier leg cuff 71 comprised of an inner cuff folded edge 72 and an inner cuff material edge 73. The leg gasketing system 70 may further comprise an outer cuff 74 comprising an outer cuff folded edge 75 and an outer cuff material edge 76. In one embodiment, the web of material is folded laterally inward to form the outer cuff folded edge 75 and folded laterally outward to form the inner cuff folded edge 72. In one embodiment, the web of material is folded laterally inward to form the outer cuff folded edge 75 and folded laterally outward to form the inner barrier leg cuff. The barrier leg cuff material is folded laterally inward to form the inner cuff folded edge 72. The inner cuff comprises two layers of material and is folded laterally outward to form the inner barrier leg cuff and the barrier leg cuff fold 90, and laterally inward to form the inner cuff folded edge. In one embodiment, the leg gasketing system 70 extends from the first waist edge 36 to the second waist edge 38 and is joined to the topsheet 24 and/or backsheet 26 between the inner cuff folded edge 72 and the outer cuff folded edge 75 in the crotch region 37. In one embodiment, the outer cuff material edge 76 is disposed laterally inboard the inner cuff material edge 73. In one embodiment, the leg gasketing system 70 extends from the first waist edge 36 to the second waist edge 38 and is not joined to the topsheet 24. In one embodiment, the leg gasketing system is joined to the backsheet 26 between the inner cuff folded edge 72 and the outer cuff folded edge 75 in the crotch region 37. In one embodiment, the leg gasketing system is joined to the backsheet between the outer cuff material edge 76 and the topsheet 24.
In one embodiment, the outer leg cuff 74 and inner barrier leg cuff 71 are the same color. In one embodiment, the outer leg cuff 74 and inner barrier leg cuff 71 are different colors. In one embodiment, there is an additional printed cuff.
In one embodiment, the outer leg cuff 74 comprises elastic members 77 positioned in a lateral array between the outer cuff folded edge 75 and outer cuff material edge 76; the outer leg cuff 74 optionally comprises at least two elastic members 77, at least three elastic member 77, at least four elastic members 77, at least five elastic members 77, at least six elastic members 77. In one embodiment, the elastic members 77 may be disposed between the outer cuff folded edge 75 and the inner cuff material edge 73.
In one embodiment, the inner barrier leg cuff 71 comprises an array of elastic members 78 in the area of the inner cuff folded edge 72; the inner barrier leg cuff 71 optionally comprises at least one elastic member 78, at least two elastic members 78, at least three elastic members 78, at least four elastic members 78, at least five elastic members 78. In one embodiment, the elastic members 78 may be disposed between the inner cuff folded edge 72 and the outer cuff material edge 76. The elastic members may be secured with adhesive.
In one embodiment, the outer leg cuff 74 comprises at least one more elastic member 77 than the inner leg cuff 71 elastic member 78. In one embodiment, the inner cuff material edge 73 is laterally outboard the outer cuff material edge 76.
In one embodiment, the elastic members 77 and 78 are spaced at least 2 mm apart from one edge to the other edge, optionally at least 3 mm apart; optionally at least 3.5 mm apart; optionally at least 4 mm apart; optionally at least 4.5 mm apart; optionally at least 5 mm apart; optionally at least 5.5 mm apart; optionally at least 6 mm apart; optionally at least 6.5 mm apart; optionally at least 7 mm apart; optionally at least 7.5 mm apart; optionally at least 8 mm apart; optionally at least 8.5 mm apart; optionally at least 9 mm apart; optionally at least 9.5 mm apart; optionally at least 10 mm apart; optionally at least 10.5 mm apart; optionally at least 11 mm apart; optionally at least 11.5 mm apart; optionally at least 12 mm apart. In one embodiment, the outermost elastic members 77 and 78 are less than about 2 mm from the outer cuff material edge 76 and inner cuff material edge 73; optionally less than about 1.5 mm, less than about 1 mm.
In one embodiment, the outer leg cuff 74 has four elastic members 77 that are about 4 mm apart. The outer leg cuff 74 may have four elastic members that are about 2 mm/7 mm/2 mm apart. The outer leg cuff 74 may have three elastic members 77 that are about 6 mm apart. The outer leg cuff 74 may have two elastic members that are about 12 mm apart. The outer leg cuff 74 may have two elastic members that are about 3 mm/6 mm/3 mm apart, as spaced from the outer cuff folded edge 75. In any embodiment, the elastic members may be about 2 mm from the outer cuff folded edge 75, optionally about 0 mm from the outer cuff folded edge 75.
The extensible properties of the leg gasketing system 70 are formed by the elastic members 77 in the outer leg cuff 74 and the elastic members 78 in the inner leg cuff 71 contracting to a relaxed length (l2) that is shorter than the stretched length (l1) (l2<l1). This contraction creates a force (F1) that is exerted on the aforementioned web of material that comprises the leg gasketing system 70. The force F1 exerted by the contraction of elastic members 77 and 78 cause the web of material to have a reaction force (F2) that results in the creation of gathers that contain the physical characteristics of waves—oscillations that have a wavelength, amplitude, and frequency within a given phase.
y(t)=A sin(wt+Δ), Wave Function:
The gathers created in the web of material in the leg gasketing system 70 can have different wave properties by varying the spacing of the elastic members 77 and 78 in the outer leg cuff 74 and inner leg cuff 71 respectively. Within a given contracted length (l2) of web of material in the leg gasketing system 70, wider spacing of the elastic members 77 and 78 forms gathers that have a higher amplitude and lower frequency compared to gathers created by elastic members 77 and 78 with narrower spacing. This phenomenon occurs due to the force (F1) created by the contraction to a relaxed length (l2) of the elastic members 77 and 78 being exerted over a larger total area (A1) for wider spacing of elastic members (s1) and a smaller total area (A2) for narrower spacing of elastic members (s2) (s1>s2). Wider spacing of elastic members 77 and 78 causes the force (F1) to be exerted over a larger total area (A1) resulting in less force to be exerted at any given point across the area of web of material in the leg gasketing system 70 comprised of the contracted elastic members 77 and 78. The reaction force (F2) of the web of material in the leg gasketing system 70 for wider spacing is also less at any given point based on Newton's Third law of physics (forces acting in equal and opposite direction) resulting in gathers that have a wider wavelength (l), higher amplitude (A), and lower frequency (w) than gathers that are created by narrower spacing of elastic members 77 and 78 with a higher reaction force (F2) resulting in higher force at any given point.
In one embodiment, the elastic members 77 and 78 are spaced apart from each other such that the outer leg cuff 74 and the inner leg cuff 71 are composed of differing tactile and aesthetic characteristics that create varying garment-like preferences. In one embodiment, the elastic members 77 and 78 can be strategically positioned to create regions of contraction that vary in amplitude and frequency. In one embodiment, the strategic positioning of the elastic members 77 and 78 can be spaced evenly or irregular to create contracted regions of uniform or changing amplitude and frequency in the outer leg cuff 74 and the inner leg cuff 71 such that a variety of garment-like preferences are achieved. In one embodiment, the elastic members 78 in the outer leg cuff 74 are strategically positioned to create contracted regions of smaller amplitude and higher frequency on the edges near the outer cuff folded edge 75 and the outer cuff material edge 76 and contracted region of higher amplitude and lower frequency in the center between the edges.
In one embodiment, the elastic members 77 are located between the inner cuff material edge 73 and the outer cuff folded edge 75. In one embodiment, the elastic members 78 are located between the outer cuff material edge 76 and the inner cuff folded edge 72. In one embodiment, an additional material may be located between the inner cuff material edge 73 and the outer cuff material edge 76; such material may include a topsheet 24; opacity strengthening patch 80; backsheet 28; core 26; or any other material optimally positioned in the design of the gasketing leg cuff 70. One such embodiment is shown in
In one embodiment, the leg gasketing system 70 has an inner barrier leg cuff 71 comprised of an inner cuff folded edge 72 and an inner cuff material edge 73. The leg gasketing system 70 may further comprise an outer cuff 74 comprising an outer cuff folded edge 75 and an outer cuff material edge 76. The leg gasketing system may comprise a first material comprising the inner barrier leg cuff 71 and a second material comprising the outer cuff 74. The first and second material may overlap and be joined together along a longitudinal edge of each material by any suitable bonding means, including with a substantially tackifier-free adhesive. In one embodiment, the web of material is folded laterally inward to form the outer cuff folded edge 75 and folded laterally outward to form the inner cuff folded edge 72. In one embodiment, the proximal edges of the outer cuff 74 are coterminous. In one embodiment, the proximal edges of the outer cuff 74 are spaced greater than about 2 mm apart; greater than about 4 mm; greater than about 6 mm; greater than about 10 mm apart. In one embodiment, the proximal material edges of the cuff are both bonded to the inner cuff. In one embodiment, only one of the proximal material edges of the outer cuff 74 are bonded to the inner cuff. In one embodiment, the proximal material edges of the outer cuff are held together with any suitable bonding means, including with a substantially tackifier-free adhesive.
In one embodiment, the leg gasketing system is spaced laterally inward of the chassis edge by about 10 mm, optionally about 20 mm, optionally about 30 mm. In another embodiment, the laterally outboard edge of the chassis is defined by the lateral edge of the outer leg cuff. In another embodiment, the backsheet and polymeric film is spaced laterally inward of the outer cuff edge by about 10 mm; optionally about 20 mm; optionally about 30 mm; optionally about 40 mm.
In one embodiment, the laterally outboard edge of the leg gasketing system 70 is disposed laterally inboard at least a portion of the longitudinal edge of the article in at least one of the waist regions. Thus, in one embodiment, the front ears 40 and/or back ears 42 extend past the leg gasketing system 70.
In one embodiment, the height of the inner leg cuff 71 is at least about 30 mm, at least about 32 mm, at least about 35 mm, at least about 38 mm. In one embodiment, the height of the outer leg cuff 74 is at least about 23 mm, at least about 25 mm, at least about 27 mm, at least about 30 mm. The height of the inner cuff is measured from inner cuff folded edge to the first point of connection to a material beyond the inner cuff material edge. The outer cuff height is measured from the outer cuff folded edge to the first point of connection the inner cuff has to a material beyond the inner cuff material edge. Thus, the inner and outer cuffs are measured from their respective folded edges to the point where the inner cuff is connected to the first material beyond the inner cuff material edge.
One advantage of the leg gasketing system 70 of the present invention is that when a substantially liquid-impervious material is used in construction of the cuff, the polymeric film layer may be narrowed or not present at all, resulting in more cost effective designs. Utilizing adhesive technologies that are more reliably processed results in more reliable performance and creates substantially liquid impervious seals. This technology enables narrowing the film layer to be only slightly wider than the absorbent core by reducing the need for redundant seals.
In one embodiment of the present invention, the backsheet polymeric film is less than about 50 mm wider than the absorbent core; optionally less than about 40 mm wider, less than about 30 mm wider. In one embodiment, the backsheet polymeric film is at least about 20 mm more narrow than the chassis width; optionally at least about 40 mm more narrow than the chassis width; optionally at least about 60 mm more narrow than the chassis width; optionally at least about 80 mm more narrow than the chassis width; optionally at least about 100 mm more narrow than the chassis width; optionally at least about 120 mm more narrow than the chassis width.
In one embodiment of the present invention, the leg cuff is joined to the topsheet and/or backsheet by a slot coated adhesive as described herein. In one embodiment, at least about 12 gsm of adhesive is applied; optionally at least about 15 gsm of adhesive is applied; optionally at least about 20 gsm of adhesive is applied; optionally, at least about 25 gsm of adhesive is applied; optionally at least about 40 gsm of adhesive is applied; optionally at least about 60 gsm of adhesive is applied. In one embodiment, the adhesive is at least about 1 mm wide; optionally at least about 3 mm wide; optionally at least about 7 mm wide. In one embodiment, the adhesive is at least about 2 mm inboard of the outboard lateral edge of the film; optionally at least 4 mm inboard of the outboard lateral edge of the film; optionally at least about 6 mm inboard of the outboard lateral edge of the film. In one embodiment, the leg cuff is joined to the topsheet and/or backsheet by two overlapping and redundant spiral adhesive sprays; optionally three overlapping and redundant spiral adhesive sprays.
The article 20 may include any of the leg gasketing systems as described in U.S. Ser. No. 13/457,521, Attorney Docket No. 12109M, and any of the opacity strengthening patch embodiments described in U.S. Ser. No. 13/457,523, Attorney Docket No. 12110M.
In one embodiment of the present invention, such as shown in
In one embodiment, the opacity strengthening patch is discrete and is located in the front and back waist regions of the article. In one embodiment, the opacity strengthening patch is about 70 mm long in the front, optionally about 90 mm long in the front; optionally about 120 mm long in the front. In one embodiment, the opacity strengthening patch is about 70 mm long in the back, optionally about 100 mm long in the back, optionally about 140 mm long in the back. In one embodiment, the opacity strengthening patch is continuous and spans the entire length of the product.
In one embodiment, the opacity strengthening patch has a hunter color opacity of greater than about 15%, optionally greater than about 25%, optionally greater than about 40%, optionally greater than 60%.
In one embodiment the opacity strengthening patch is laterally outboard of the polymeric film layer. In one embodiment, the opacity strengthening patch overlaps the polymeric film layer in the lateral direction such that it can be affixed to the polymeric film in order to transmit laterally directed application and wearing forces from the opacity strengthening patch to the polymeric film layer. Adhesives as described herein may be used to affix the opacity strengthening patch to the polymeric film layer. In one embodiment, the opacity strengthening patch overlaps the polymeric film layer by about 5 mm, optionally about 10 mm, optionally about 15 mm, optionally about 20 mm, optionally less than about 30 mm.
In one embodiment, there is a lateral gap between the opacity strengthening patch and the polymeric film layer and the opacity strengthening patch is affixed by any suitable bonding means to the leg gasketing system (such as with a substantially tackifier-free adhesive), and the leg gasketing system is affixed to the polymeric film layer by any suitable bonding means (such as with a substantially tackifier-free adhesive), such that application and wearing loads can transmit from the opacity strengthening patch to the gasketing system and then from the gasketing system to the polymeric film layer. In this embodiment, the gap is preferably less than 30 mm, more preferably less than 20 mm, more preferably less than 10 mm.
In one embodiment, there is a lateral gap between the opacity strengthening patch and the polymeric film layer; the opacity strengthening patch may be affixed by any suitable bonding means to the leg gasketing system and the body facing and garment facing sides of the leg gasketing system may be affixed together by any suitable bonding means so that the loads from the opacity strengthening patch are shared by both layers of the leg gasketing system. The leg gasketing system may be affixed to the polymeric film layer by any suitable bonding means such that application and wearing loads can transmit from the opacity strengthening patch to the leg gasketing system and then from the leg gasketing system to the polymeric film layer.
In one embodiment, the opacity strengthening patch overlaps the leg gasketing system in the lateral direction such that it can be affixed securely to the opacity strengthening patch layer by any suitable bonding means as a way to transmit application and wearing forces from the opacity strengthening patch to the leg gasketing system. In this embodiment, the opacity strengthening patch may overlap the leg gasketing system by about 5 mm, optionally about 10 mm, optionally less than about 15 mm, optionally less than about 25 mm.
In one embodiment the leg gasketing system has about the same lateral tensile strength properties as the opacity strengthening patch. In one embodiment the combined properties of the leg gasketing system and the backsheet nonwoven outer cover has about the same lateral tensile strength as the opacity strengthening patch. In another embodiment the outercover nonwoven has very low lateral strength between about 0% and about 10% engineering strain. In one embodiment, the outercover nonwoven may exhibit the following tensile properties: at 10% engineering strain for a 1 inch wide sample, 0.4N.
It is recognized that there are many combinations of material lateral tensile properties that could form a substantially suitable force transmission pathway in the waist region or the article without excessive lateral stretch in the waist region, and that the material force pathways may go from the opacity strengthening patch directly into the polymeric film layer or into the polymeric film layer through a variety of other layers in the region immediately outboard the polymeric film layer. These layers may include the topsheet, backsheet nonwoven, cuff, absorbent assembly, leg gasketing system, or any other layer that is located in a region adjacent to the polymeric film layer.
In one embodiment, the material of the leg gasketing system 70 is made from a substantially liquid impervious material. The material may be selected from the group consisting of an SMS nonwoven, SMMS nonwoven material, or a nonwoven component layer comprising “N-fibers”.
Various nonwoven fabric webs may comprise spunbond, meltblown, spunbond (“SMS”) webs comprising outer layers of spunbond thermoplastics (e.g., polyolefins) and an interior layer of meltblown thermoplastics. In one embodiment of the present invention, the leg gasketing cuff 70 comprises a nonwoven component layer having fine fibers (“N-fibers”) with an average diameter of less than 1 micron (an “N-fiber layer”) may be added to, or otherwise incorporated with, other nonwoven component layers to form a nonwoven web of material. In some embodiments, the N-fiber layer may be used to produce a SNS nonwoven web or SMNS nonwoven web, for example.
The leg gasketing cuff 70 may comprise a first nonwoven component layer comprising fibers having an average diameter in the range of about 8 microns to about 30 microns, a second nonwoven component layer comprising fibers having a number-average diameter of less than about 1 micron, a mass-average diameter of less than about 1.5 microns, and a ratio of the mass-average diameter to the number-average diameter less than about 2, and a third nonwoven component layer comprising fibers having an average diameter in the range of about 8 microns to about 30 microns. The second nonwoven component layer is disposed intermediate the first nonwoven component layer and the third nonwoven component layer.
The N-fibers may be comprised of a polymer, e.g., selected from polyesters, including PET and PBT, polylactic acid (PLA), alkyds, polyolefins, including polypropylene (PP), polyethylene (PE), and polybutylene (PB), olefinic copolymers from ethylene and propylene, elastomeric polymers including thermoplastic polyurethanes (TPU) and styrenic block-copolymers (linear and radial di- and tri-block copolymers such as various types of Kraton), polystyrenes, polyamides, PHA (polyhydroxyalkanoates) and e.g. PHB (polyhydroxubutyrate), and starch-based compositions including thermoplastic starch, for example. The above polymers may be used as homopolymers, copolymers, e.g., copolymers of ethylene and propylene, blends, and alloys thereof. The N-fiber layer may be bonded to the other nonwoven component layers by any suitable bonding technique, such as the calender bond process, for example, also called thermal point bonding.
In some embodiments, the use of an N-fiber layer in a nonwoven web may provide a low surface tension barrier that is as high as other nonwoven webs that have been treated with a hydrophobic coating or a hydrophobic melt-additive, and still maintain a low basis weight (e.g., less than 15 gsm or, alternatively, less than 13 gsm). The use of the N-fiber layer may also provide a soft and breathable (i.e., air permeable) nonwoven material that, at least in some embodiments, may be used in single web layer configurations in applications which previously used double web layer configurations. Furthermore, in some embodiments, the use of the N-fiber layer may at least reduce the undesirable migration of hydrophilic surfactants toward the web and, therefore, may ultimately result in better leak protection for an associated absorbent article. Also, when compared to an SMS web having a similar basis weight, the use of a nonwoven web comprising the N-fiber layer may decrease the number of defects (i.e., holes or pinholes through the mechanical bond site) created during the mechanical bonding process. N-fibers are further discussed in WO 2005/095700 and U.S. patent application Ser. No. 13/024,844.
In one embodiment, the inner leg cuff 71 web of material has a hydrostatic head of greater than about 2 mbar, greater than about 3 mbar, greater than about 4 mbar. In one embodiment, the outer leg cuff 74 web of material has a hydrostatic head of less than about 200 mbar, less than about 100 mbar, less than about 75 mbar, less than about 50 mbar, less than about 25 mbar, less than about 15 mbar.
In one embodiment, the folded outer leg cuff web of material has a basis weight of 10 gsm; optionally 13 gsm; optionally 15 gsm; optionally 18 gsm.
In one embodiment, the inner leg cuff 71 web of material has an opacity of from about 15% to about 50% hunter opacity; optionally from about 20% to about 45% hunter opacity. In one embodiment, the outer leg cuff 74 web of material has an opacity of from about 45% to about 75% hunter opacity; optionally from about 50% to about 70% hunter opacity; optionally less than about 75% hunter opacity; optionally less than about 70% hunter opacity.
In one embodiment, the inner leg cuff 71 web of material has an air permeability of less than about 50 m3/m2/min; optionally less than about 45 m3/m2/min. In one embodiment, the outer leg cuff 74 web of material has an air permeability of greater than about 5 m3/m2/min; optionally greater than about 10 m3/m2/min; optionally greater than about 15 m3/m2/min; optionally greater than about 20 m3/m2/min.
In one embodiment, the inner leg cuff 71 web of material has a WVTR of less than about 5500 g/m2/24 hrs; optionally less than about 5400 g/m2/24 hrs. In one embodiment, the outer leg cuff 74 web of material has a WVTR of greater than about 4250 g/m2/24 hrs; optionally greater than about 4500 g/m2/24 hrs; optionally greater than about 5000 g/m2/24 hrs; optionally greater than about 5250 g/m2/24 hrs; optionally greater than about 5500 g/m2/24 hrs.
The gasketing cuffs 70 may be substantially inelastic or may be elastically extensible to dynamically fit at the wearer's leg. The gasketing cuff 70 may be formed by one or more elastic members 77 and 78 (such as elastic strands) operatively joined to the topsheet 24, backsheet 26, or any other suitable substrate used in the formation of the absorbent article 20. Suitable gasketing cuff construction is further described in U.S. Pat. No. 3,860,003
The inner barrier cuff 71 may span the entire longitudinal length of the absorbent article 20. The inner barrier cuff 71 may be formed by a flap and an elastic member 78 (such as elastic strands). The inner barrier cuff 71 may be a continuous extension of any of the existing materials or elements that form the absorbent article 20.
The inner barrier cuff 71 may comprise a variety of substrates such as plastic films and woven or nonwoven webs of natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polyester or polypropylene fibers), or a combination of natural and synthetic fibers. In certain embodiments, the flap may comprise a nonwoven web such as spunbond webs, meltblown webs, carded webs, and combinations thereof (e.g., spunbond-meltblown composites and variants). Laminates of the aforementioned substrates may also be used to form the flap. A particularly suitable flap may comprise a nonwoven available from BBA Fiberweb, Brentwood, Tenn. as supplier code 30926. A particularly suitable elastic member is available from Invista, Wichita, Kans. as supplier code T262P. Further description of diapers having inner barrier cuffs and suitable construction of such barrier cuffs may be found in U.S. Pat. Nos. 4,808,178 and 4,909,803. The elastic member 78 may span the longitudinal length of the inner barrier cuff 71. In other embodiments, the elastic member 78 may span at least the longitudinal length of the inner barrier cuff 71 within the crotch region 37. It is desirable that the elastic member 78 exhibits sufficient elasticity such that the inner barrier cuff 71 remains in contact with the wearer during normal wear, thereby enhancing the barrier properties of the inner barrier cuff 71. The elastic member 78 may be connected to the flap at opposing longitudinal ends. In certain embodiments, the flap may be folded over onto itself so as to encircle the elastic member 78.
The inner barrier cuff 71 and/or outer cuff 74 may be treated, in full or in part, with a lotion, as described above with regard to topsheets, or may be fully or partially coated with a hydrophobic surface coating as detailed in U.S. application Ser. No. 11/055,743, which was filed Feb. 10, 2005. Hydrophobic surface coatings usefully herein may include a nonaqueous, solventless, multicomponent silicone composition. The silicone composition includes at least one silicone polymer and is substantially free of aminosilicones. A particularly suitable hydrophobic surface coating is available from Dow Corning MI, Salzburg as supplier code 0010024820.
In one embodiment, an absorbent article includes an absorbent core 28 that is substantially cellulose free. Cross-sectional views of examples of suitable absorbent cores are schematically represented in
The first layer 281 comprises a first surface 2811 and a second surface 2812 and at least regions 2813 of the first surface are in direct facial relationship with a significant amount of absorbent material 283. In one embodiment an absorbent material is deposited on the first surface 2811 in a pattern to form regions 2813 on the first layer 281, which are in direct facial relationship with a significant amount of absorbent polymer material 283 and regions 2814 on the first web that are in facial relationship with only an insignificant amount of absorbent material. By “direct facial relationship with a significant amount of absorbent material” it is meant that some absorbent material is deposited on top of the regions 2813 at a basis weight of at least 100 g/m2, at least 250 g/m2 or even at least 500 g/m2. The pattern may include regions that all have the same shape and dimensions (i.e. projected surface area and/or height). In the alternative the pattern may include regions that have different shape or dimensions to form a gradient of regions. At least some of the regions 2813 can have a projected surface area of between 1 cm2 and 150 cm2 or even between 5 cm2 and 100 cm2. By “facial relationship with an insignificant amount of absorbent material” it is meant that some absorbent material may be deposited on top of the regions 2814 at a basis weight of less than 100 g/m2, less than 50 g/m2 or even substantially no absorbent material. At least some of the regions 2814 can have a projected surface area of between 1 cm2 and 150 cm2 or even between 5 cm2 and 100 cm2. The aggregate projected surface area of all the regions 2813 can represent between 10% and 90% or even between 25% and 75% of the total projected surface area of the first surface 2811 of the first layer 281. In one embodiment, the second layer 282 is a layer of a thermoplastic adhesive material. “Thermoplastic adhesive material” as used herein is understood to mean a polymer composition from which fibers are formed and applied to the absorbent material with the intent to immobilize the absorbent material in both the dry and wet state. Non-limiting examples of thermoplastic adhesive material may comprise a single thermoplastic polymer or a blend of thermoplastic polymers, and also the substantially tackifier-free adhesives described herein. The thermoplastic adhesive material may also be a hot melt adhesive comprising at least one thermoplastic polymer in combination with other thermoplastic diluents such as tackifying resins, plasticizers and additives such as antioxidants. In certain embodiments, the thermoplastic polymer has typically a molecular weight (Mw) of more than 10,000 and a glass transition temperature (Tg) usually below room temperature or −6° C.>Tg<16° C. In certain embodiments, typical concentrations of the polymer in a hot melt are in the range of about 20 to about 40% by weight. Exemplary polymers are (styrenic) block copolymers including A-B-A triblock structures, A-B diblock structures and (A-B)n radial block copolymer structures wherein the A blocks are non-elastomeric polymer blocks, typically comprising polystyrene, and the B blocks are unsaturated conjugated diene or (partly) hydrogenated versions of such. The B block is typically isoprene, butadiene, ethylene/butylene (hydrogenated butadiene), ethylene/propylene (hydrogenated isoprene), and mixtures thereof. Other suitable thermoplastic polymers that may be employed are metallocene polyolefins, which are polymers prepared using single-site or metallocene catalysts. In exemplary embodiments, the tackifying resin has typically a Mw below 5,000 and a Tg usually above room temperature, typical concentrations of the resin in a hot melt are in the range of about 30 to about 60% by weight, and the plasticizer has a low Mw of typically less than 1,000 and a Tg below room temperature, with a typical concentration of about 0 to about 15%.
The thermoplastic adhesive material 282 can be disposed substantially uniformly within the absorbent material 283. In the alternative, the thermoplastic adhesive material 282 can be provided as a fibrous layer disposed on top of the absorbent material 283 and the regions 2814 of the first surface 2811 that are in facial relationship with only an insignificant amount of absorbent material. In one embodiment, a thermoplastic adhesive material is applied at an amount of between 1 and 20 g/m2, between 1 and 15 g/m2 or even between 2 and 8 g/m2. The discontinuous deposition of absorbent material on the first layer 281 imparts an essentially three-dimensional structure to the fibrous layer of thermoplastic material 282. In other words, the layer of thermoplastic adhesive material follows the topography resulting from the absorbent material 283 deposited on the first nonwoven fibrous web 281 and the regions 2814 that only include insignificant amounts of absorbent material. Without intending to be bound by any theory, it is believed that the thermoplastic adhesive materials disclosed herein enhance immobilization of the absorbent material in a dry and wet state.
In one embodiment, the absorbent core 28 may further comprise a second layer of a nonwoven fibrous material 284. This second layer may be provided of the same material as the nonwoven fibrous layer 281, or in the alternative may be provided from a different material. It may be advantageous for the first and second nonwoven fibrous layers 281, 284 to be different in order to provide these layers with different functionalities. In one embodiment, the surface energy of the first nonwoven layer can be different than the surface energy of the second nonwoven layer. In one embodiment, the surface energy of the second nonwoven layer is greater than the surface energy of the first nonwoven layer. Among over benefits, it is believed that when the surface energy of the second nonwoven layer is greater than the surface energy of the first nonwoven layer, liquids such as urine will be able to penetrate the second nonwoven layer more easily in order to reach and be retained by the absorbent material while at the same time reducing the chances that the liquid may penetrate and go through the first layer. This may be particularly advantageous when the first nonwoven layer is disposed against the backsheet of an absorbent article. The different surface energies of each layer may be obtained, for example, by applying a different amount of an agent such as a surfactant to the second nonwoven layer than the amount of surfactant (if any) applied to the first nonwoven layer. This may also be achieved by applying a different type of surfactant to the second nonwoven layer than the surfactant applied to the first nonwoven layer. This may still be achieved by applying a material to the first nonwoven layer that lowers its surface energy. In addition to having different surface energies, or in the alternative, the first and second nonwoven fibrous layers 281, 284 may also be different structurally. In one embodiment, the first nonwoven layer 281 may include different layers of fibers than the second nonwoven layer. For example, the second nonwoven layer 284 may only include one or more layers of spunbond fibers whereas the first nonwoven layer 281 includes one or more layers of spundbond fibers and one or more layers of meltblown fibers. In another embodiment, both nonwoven fibrous layers 281, 284 may include one or more layers of spunbond fibers and one or more layers of meltblow fibers but the first and second layers 281, 284 differ in terms of at least one of the chemical composition of the fibers used to form the nonwoven material, the denier of the fibers and/or the basis weight of the nonwoven material. In addition to or in the alternative than the above the first and second nonwoven layers 281, 284 may also differ in terms of at least one of their respective hydrohead values, their respective porosity, their respective Frazier permeability and their respective tensile properties. The second nonwoven layer 284 may applied directly on top of the first nonwoven layer 281, the absorbent material 283 and the thermoplastic adhesive material 282. As a result, the first and second nonwoven layers 281 and 284 further encapsulate and immobilize the absorbent material 283.
The regions 2813 may have any suitable shape in the x-y dimension of the absorbent core. In one embodiment, the regions 2813 form a pattern of disc that are spread on the first surface of the first web 281. In one embodiment, the regions 2813 form a pattern of longitudinal “strips” that extend continuously along the longitudinal axis of the absorbent core (i.e. along the y dimension). In an alternative embodiment, these strips may be are arranged to form an angle of at between 10 and 90 degrees, between 20 and 80 degrees, between 30 and 60 degrees, or even 45 degrees relative to the longitudinal axis of the absorbent article.
In one embodiment, the second nonwoven layer 284 has a first surface 2841 and a second surface 2842 and an absorbent material 283 applied to its first surface 2841 in order to form a pattern of regions 2843 that are in direct facial relationship with a significant amount of absorbent material 283 and regions 2844 on the first surface 2841 that are in facial relationship with only an insignificant amount of absorbent material as previously discussed. In one embodiment, a thermoplastic adhesive material 285 may further be applied on top of the second nonwoven layer 284 as previously discussed in the context of the first web/absorbent material/thermoplastic adhesive material composite. The second nonwoven layer 284 may then be applied on top of the first nonwoven layer 281. In one embodiment, the pattern of absorbent material present on the second nonwoven layer 284 may be the same as the pattern of absorbent material present on the first nonwoven layer 281. In another embodiment, the patterns of absorbent material that are present on the first and second nonwoven layers are different in terms of at least one of the shape of the regions, the projected surface areas of the regions, the amount of absorbent material present on the regions and the type of absorbent material present on the regions. It is believed that when the patterns of absorbent material that are present on the first and second nonwoven layers are different, each layer/absorbent composite may have different functionalities such as for example, different absorbent capacities and/or different acquisition rates of liquids. It can be beneficial for example to provide an absorbent core with a structure where the second pattern formed by the regions 2843 of absorbent material (i.e. on the second nonwoven layer 284) exhibits a slower acquisition rate than the first pattern of regions 2813 of absorbent material in order to allow liquids, such as urine, to reach and be absorbed by the absorbent material deposited on the first nonwoven layer 281 before expansion of the absorbent material in the regions 2843. Such a structure avoids any significant gel blocking by the absorbent material present in the regions 2843. It can also be advantageous to apply the second layer/absorbent material/thermoplastic adhesive material composite in such a way that at least some of or even all of the regions 2813 of the first nonwoven layer 281 that are in direct facial relationship with a significant amount of absorbent material are also in substantial facial relationship with corresponding regions 2844 of the second web 284, which are in facial relationship with an insignificant amount of absorbent material.
The absorbent core 28 may also comprise an auxiliary adhesive which is not illustrated in the figures. The auxiliary adhesive may be deposited on at least one of or even both the first and second nonwoven layers 281, 284 before application of the absorbent material 283 in order to enhance adhesion of the absorbent material as well as adhesion of the thermoplastic adhesive material 282, 285 to the respective nonwoven layers 281, 284. The auxiliary adhesive may also aid in immobilizing the absorbent material and may comprise the same thermoplastic adhesive material as described hereinabove or may also comprise other adhesives including but not limited to sprayable hot melt adhesives, such as H.B. Fuller Co. (St. Paul, Minn.) Product No. HL-1620-B. The auxiliary adhesive may be applied to the nonwoven layers 281, 284 by any suitable means, but according to certain embodiments, may be applied in about 0.5 to about 1 mm wide slots spaced about 0.5 to about 2 mm apart. Non-limiting examples of suitable absorbent material 283 include absorbent polymer material such as cross linked polymeric materials that can absorb at least 5 times their weight of an aqueous 0.9% saline solution as measured using the Centrifuge Retention Capacity test (Edana 441.2-01). In one embodiment, the absorbent material 283 is absorbent polymer material which is in particulate form so as to be flowable in the dry state.
In some embodiments, the thermoplastic adhesive material 282 may instead be a substantially tackifier-free adhesive as described herein, and in some embodiments, it may form a fiberized net structure over the absorbent material. In addition, in some embodiments, the substantially tackifier-free adhesives described herein may also be used as the auxiliary adhesive in the absorbent core.
As previously discussed, the absorbent material 283 present in the absorbent cores 28 of an absorbent article, does not need to be present along the entire length of the absorbent core. In one embodiment, the back section 328 of an absorbent article includes an insignificant amount of absorbent material 283 whereas at least the middle 228 and/or the front section 128 include a greater amount of absorbent material than the back section 328. For example, the back section 328 may include less than 5 grams, or less than 3 grams, less than 2 grams or even less than 1 g of a particulate absorbent polymer material. The middle section 228 may include at least 5 grams, or at least 8 grams, or even at least 10 grams of a particulate absorbent polymer material. The front section 128 may include between 1 and 10 grams, or between 2 and 8 grams of a particulate absorbent polymer material.
The leg gasketing systems of the present invention, which may include an opacity strengthening patch, may comprise hot melt adhesive material, used to bond various substrates. The hot melt adhesives may be made with substantially less than 40 wt. %, less than 20 wt. % or be substantially free of an effective amount of a conventional tackifier material that can add any aspect of open time, substrate wetting or tack to the adhesive material, ie., be substantially tackifier-free. Common hot melt adhesives are made by combining polymer and additive components in a substantially uniform thermoplastic blend.
In some embodiments, the adhesive composition may comprise a first amorphous polymer and a second heterophase polymer. The amorphous polymer comprises an amorphous or random polymer comprising an alpha olefin co-polymer comprising major proportion of propene. The second polymer comprises a heterophase alpha olefin-co-polymer having amorphous character and at least some substantial crystalline content. The crystalline content can be in the form of one or more polymer blocks or sequences that are stereoregular. In one embodiment, these sequences or blocks are substantially crystallizable sequences or blocks. The adhesive material may comprise a first polymer comprising a polyolefin comprising a substantially amorphous or randomly polymerized polymer material and a second polymer comprising a heterophase polymer.
In some embodiments, the adhesive material may comprise a first polymer comprising a polyolefin copolymer comprising a substantially amorphous or randomly polymerized polymer material comprising 1-butene and a second amorphous polymer comprising a compatible amorphous liquid butene polymer such as a polyisobutylene polymer or similar material. The polyisobutylene polymer may comprise a substantial proportion (greater than 50 mole % and often greater than 90 mole %) of an isobutylene monomer.
The first amorphous polymer may comprise typically butene (e.g.) 1-butene, and can be a copolymer or terpolymer that can contain ethylene, propene or a second C4-40 olefin polymer. These substantially amorphous low crystallinity polymers have less than 10% and preferably less than 5% crystalline character.
The second heterophase olefin polymer comprises a first poly alpha olefin polymer comprising a substantial proportion (greater than 40 or 50 mole %) of a propene monomer and comprises an amorphous polymer with some crystalline content.
The amorphous polymer is a butene-based copolymer (the minimum amount is at least about 30 or 40 or 50 or 60 wt. % of 1-butene), which may also be referred to as a random butene-α-olefin copolymer. The butene copolymer includes one or more units, i.e., monomer units, derived from propene, one or more comonomer units derived from ethylene or α-olefins including from 4 to about 20 carbon atoms.
The first copolymer comprises about 30 mole %-about 75 mole %, preferably about 40 mole % to about 70 mole %, about 50 mole %-about 65 mole %, of units derived from butene. In addition to butene-derived units, the present copolymer contains from about 70 mole %-about 30 mole % to about 60 mole %-about 40 mole %, of units derived from preferably ethylene, propene or at least one C5 to 10 alpha-olefin monomer.
In one or more embodiments, the alpha-olefin comonomer units can also be derived from other monomers such as ethylene, 1-butene, 1-hexane, 4-methyl-1-pentene and/or 1-octene. Exemplary alpha-olefins are selected from the group consisting of ethylene, butene-1, pentene-1,2-methylpentene-1,3methylbutene-1, hexene-1,3-methylpentene-1,4-methylpentene-1,3,3-dimethylbutene-1, heptene-1, hexene-1, methylhexene-1, dimethylpentene-1, trimethylbutene-1, ethylpentene-1, octene-1, methylpentene-1, dimethylhexene-1, trimethylpentene-1, ethylhexene-1, methylethylpentene-1, diethylbutene-1, propylpentane-1, decene-1, methylnonene-1, nonene-1, dimethyloctene-1, trimethylheptene-1, ethyloctene-1, methylethylbutene-1, diethylhexene-1, dodecene-1, and hexadodecene-1.
In one or more embodiments, amorphous copolymer comprises about 30 mole %-about 75 mole %, preferably about 40 mole % to about 60 mole % of units derived from butene and from about 70 mole %-about 30 mole % to about 60 mole %-about 40 mole %, about 50 mole %-about 65 mole %, of units derived from at least one alpha-olefin monomer selected from ethylene, propene, 1-hexene or 1-octene. Small amounts of α-olefin monomer(s) can be used in the range of about 0.1 to 20 mole %. The amorphous polymer has a weight average molecular weight (Mw) of about 1,000 to about 25,000 or less, or about 2,000 to 20,000, or from about 5000 to about 45,000.
In one or more embodiments, first copolymer comprises about 30 mole %-about 70 mole %, or about 40 mole % to about 60 mole % of units derived from butene and from about 70 mole %-about 30 mole % to about 60 mole %-about 40 mole %, of units derived from propene, while small amounts of α-olefin monomer(s) can be used in the range of about 0.1 to 20 mole %.
The amorphous polymer may have a weight average molecular weight (Mw) of about 1,000 to about 50,000 or less, or about 5,000 to 45,000.
The amorphous copolymer may have a viscosity of less than 10,000 mPa·s (1 centipoise [cps]=1 mPa·s), for example about 2000 to 8000 mPa·s, when measured by ASTM D3236 at 190° C.
Melt Viscosity was determined according to ASTM D-3236, which is also referred to herein as “viscosity” and/or “Brookfield viscosity”.
Some examples of amorphous polyolefin include the Rextac polymers made by Huntsman including Rextac E62, E-63, E-65, 2815, 2830, etc. See, for example Sustic, U.S. Pat. No. 5,723,546 for a description of the polymers and which is expressly incorporated herein. Other useful amorphous polymers are sold as Vestoplast® and Eastoflex® materials.
The adhesive material comprises a second polyolefin comprising a substantially heterophase copolymer. The heterophase polyolefin may comprise a propene copolymer (i.e.) propene-based polymer with other comonomer(s). The propene-based polymer backbone preferably comprises propene and one or more C2 or C4-20 α-olefins. The propene-based heterophase polymer, for example, may comprise propene and ethylene, hexene or optionally other C2 or C4-20 α-olefins. The polymer comprises about 99.5 to about 70 wt. %, preferably about 95 to about 75 wt. % of units derived from propene. In addition to propene derived units, the present copolymer contains from about 0.1 to 30 wt. % preferably from about 5 to 25 wt. %, of units derived from preferably at least C2-4 or a C5-10 alpha-olefin.
In one or more embodiments, the second copolymer comprises a major proportion of propene and about 0.1 to 30 wt. %, or 2 to 25 wt. % ethylene. In one or more embodiments, the second copolymer comprises a major proportion of propene and about 0.1 to 30 wt. %, or 2 to 25 wt. % 1-butene.
In one or more embodiments, the second copolymer comprises a major proportion of propene and about 0.1 to 30 wt. %, or 2 to 25 wt. % 1-hexene. In one or more embodiments, the second copolymer comprises a major proportion of propene and about 0.1 to 30 wt. %, or 2 to 25 wt. % 1-octene.
Other comonomer for use in either the first or second polyolefin comprise ethylene or α-olefins containing 4 to 12 carbon atoms. Exemplary α-olefins may be selected from the group consisting of ethylene; 1-butene; 1-pentene; 2-methyl-1-pentene; 3-methyl-1-butene; 1-hexene-3-methyl-1-pentene-4-methyl-1-pentene-3,3-dimethyl-1-butene; 1-heptene; 1-hexene; 1-methyl-1-hexene; dimethyl-1-pentene; trimethyl-1-butene; ethyl-1-pentene; 1-octene; methyl-1-pentene; dimethyl-1-hexene; trimethyl-1-pentene; ethyl-1-hexene; 1-methylethyl-1-pentene; 1-diethyl-1-butene; propyl-1-pentene; 1-decene; methyl-1-nonene; 1-nonene; dimethyl-1-octene; trimethyl-1-heptene; ethyl-1-octene; methylethyl-1-butene; diethyl-1-hexene; 1-dodecene and 1-hexadodecene. Preferred C4-10 alpha-olefins are those having 6 to 8 carbon atoms, with the most preferred alpha-olefin being 1-hexene and 1-octene.
Preferred propene copolymers are copolymers wherein the comonomer is ethylene, 1-butene, 1-hexene or 1-octene. The stereo-regular (isotactic or syndiotactic) sequence or block content of the polymers imparts a heterophase (partial amorphous and partial crystalline) character of crystallizable content to the polymers. As used herein and as applied to semi-crystalline heterophase copolymers, the term “crystallizable” describes those polymer sequences or blocks that can crystallize upon cooling. Crystalline content of the solidified semicrystalline copolymers increases the cohesive strength of the hot melt adhesives. Hot melt adhesive formulations based on metallocene polymerized semicrystalline copolymers can eventually build sufficient crystalline content over time to achieve good cohesive strength in the formulation.
The second heterophase polymer comprises crystallizable polymer blocks or sequences, preferably of stereoregular sequences of polymerized monomer such as ethylene or propene, which sequences are long enough to crystallize, typically at least repeating or block monomer units per sequence.
In preferred embodiments, the crystallizable segments can be stereoregular or isotactic. Isotacticity of the olefin sequences can be achieved by polymerization with the choice of a desirable catalyst composition. The Isotacticity is conventionally measured using DSC or C-13 NMR instrumental techniques.
The heterophase polymer has a crystallinity of at least 5 wt. %, 10 wt. %, 20 wt. %, 40 wt. % or 50 wt. %, preferably between 20% and 80%, more preferably between 25% and 70%.
The heat of fusion of the heterophase copolymers (by ASTM E793) is about 10 J/g to about 70 J/g and about 15 J/g to about 70 J/g, with a melting point less than 150° C. and about 105° C. to about 135° C.
The heterophase polymer has a weight average molecular weight (Mw) of about 20,000 or less, preferably about 10,000 or less, preferably about 500 to 8,000.
The heterophase copolymer has a viscosity of less than 20,000 mPa·s (1 centipoise [cps]=1 mPa·s), for example less than 15000 mPa·s, in certain application less than 10,000 mPa·s and less than 5,000 mPa·s when measured at 190° C. using a Brookfield viscometer (as measured by ASTM D 3236) which is also referred to herein as “viscosity” and/or “Brookfield viscosity.”
Some examples of heterophase polymers useful in the hot melt adhesive compositions of include polyolefin such as polyethylene, polypropylene, and copolymers thereof such as polypropylene based elastomers sold by ExxonMobil Chemical of Houston, Tex. under the trade name VISTAMAXX™ and polyethylene based elastomers such as those sold by Dow Chemical Company of Midland, Mich. under the trade names AFFINITY™ and ENGAGE™.
Other heterophase polymers that are useful in the hot melt adhesive compositions include the polyolefin elastomers VISTAMAXX™ 8816, VISTAMAXX™ 2230, and ENGAGE™ 8200. AFFINITY™ GA 1900 has a density of 0.870 g/cm3 according to ASTM D792, heat of fusion of 46.1 J/g, and a Brookfield viscosity of 8200 cP at 177° C. according to ASTM D 1084. AFFINITY™ GA 1950 has a density of 0.874 g/cm3 according to ASTM D792, heat of fusion of 53.4 J/g, and a Brookfield viscosity of 17,000 cP at 177° C. according to ASTM D 1084. ENGAGE™ 8200 has a density of 0.87 g/cm3 according to ASTM D792 and a melt index of 5 g/10 min at 190° C. These olefin elastomers are compatible with the propylene copolymers useful in the hot melt adhesive compositions and improve physical properties such as low temperature adhesive performance without sacrificing effective set time.
Any conventional polymerization synthesis processes may prepare the polyolefin copolymers. Preferably, one or more catalysts, which are typically metallocene catalysts or Zeigler-Natta, catalysts, are used for polymerization of an olefin monomer or monomer mixture. Polymerization methods include high pressure, slurry, gas, bulk, suspension, supercritical, or solution phase, or a combination thereof, preferably using a single-site metallocene catalyst system. The catalysts can be in the form of a homogeneous solution, supported, or a combination thereof. Polymerization may be carried out by a continuous, a semi-continuous or batch process and may include use of chain transfer agents, scavengers, or other such additives as deemed applicable. By continuous is meant a system that operates (or is intended to operate) without interruption or cessation. For example a continuous process to produce a polymer would be one where the reactants are continually introduced into one or more reactors and polymer product is continually withdrawn. In one embodiment, the propene copolymer described herein is produced in a single or multiple polymerization zones using a single polymerization catalyst. The heterophase polymers are typically made using multiple metallocene catalyst blends that obtain desired heterophase structure.
In some embodiments, the adhesive may comprise an amorphous polyolefin copolymer composition comprising more than 40 mole % 1-butene and a second amorphous polymer comprising at least one butene monomer, wherein the polymer is compatible with the polyolefin. In some embodiments, the adhesive may consist essentially of an amorphous polyolefin copolymer composition comprising more than 40 mole % 1-butene and a compatible second amorphous polymer comprising at least one butene monomer. The second polymer compatible with the polyolefin may have a molecular weight (MWn) of at least 1000. Such compatibility arises from a liquid amorphous material comprising at least one butene monomer (1-butene, cis and trans-2-butene, and isobutylene) isomer. Unlike conventional plasticizing oils such as white oils having a conventional hydrocarbon character, useful materials are sufficiently compatible and as a result improve add-on processability characteristics, reduce viscosity, and maintain adhesive bond while improving cohesive properties. The term “compatible or compatibility” of a blend of polymers, as the term is used in this disclosure, means that (1) the materials blend into a uniform hot melt and (2) the cohesive strength of a mixture (70/30 to 50/50) by weight of the amorphous 1-butene polymer and the second amorphous polymer is maintained for construction purposes. Preferred materials comprise a compatible extender, diluents, and viscosity modifier such as a polyisobutylene polymer. The polymer can comprise major proportion of isobutylene units or can be represented as:
[—C(CH3)2—CH2-]n;
wherein n=15 to 75. Preferred materials such as a polyisobutylene are viscous liquids with molecular weight of about 200-20,000, about 200-5,000 or about 500-3,000. The preferred liquid materials have a Saybolt Universal seconds (SUS) viscosity at 100° C. of about 100 to 20,000. The characteristic features of polyisobutylene are low gas permeability and high resistance to the action of acids, alkalis, and solutions of salts, as well as high dielectric indexes. They degrade gradually under the action of sunlight and ultraviolet rays (the addition of carbon black slows this process). In industry, polyisobutylene is produced by ionic (AlCl3 catalyzed) polymerization of the monomer at temperatures from −80° to −100° C.; they are processed using the ordinary equipment of the rubber industry. Polyisobutylene combines easily with natural or synthetic rubbers, polyethylene, polyvinyl chloride, and phenol-formaldehyde resins.
Any of the compositions disclosed herein can also comprise a plasticizer or plasticizing oil or extender oil that may reduce viscosity or improve tack properties in the adhesive. Any plasticizer known to a person of ordinary skill in the art may be used in the adhesion compositions disclosed herein. Nonlimiting examples of plasticizers include olefin oligomers, low molecular weight polyolefin such as liquid polybutene, low molecular weight non-aromatic polymers (e.g. REGALREZ 101 from Eastman Chemical Company), phthalates, mineral oils such as naphthenic, paraffinic, or hydrogenated (white) oils (e.g. Kaydol oil or ParaLux oils (Chevron U.S.A. Inc.)), vegetable and animal oil and their derivatives, petroleum derived oils, and combinations thereof. Low molecular weight polyolefin may include those with Mw as low as 100, in particular, those in the range of from about 100 to 3000, in the range of from about 250 to about 2000 and in the range of from about 300 to about 1000.
In some embodiments, the plasticizers include polypropylene, polybutene, hydrogenated polyisoprene, hydrogenated polybutadiene, polypiperylene, copolymers of piperylene and isoprene, and the like, having average molecular weights between about 350 and about 10,000. In other embodiments, the plasticizers include glyceryl esters of the usual fatty acids and polymerization products thereof a polymer of isobutylene.
As noted above, embodiments of preferred compositions are made with substantially less than 40 wt. %, less than 20 wt. % or are substantially free of an effective amount of a conventional tackifier material that can add any aspect of open time, substrate wetting or tack to the adhesive material. Avoiding the use of a tackifier reduces adhesive density, adhesive and product costs, and frees formulators from the use of materials in short supply. Further, tackifier can impart undesirable odor in disposable articles and can also act as carriers of low molecular weight plasticizers (like process oils that are used in SBC based adhesives) that can weaken the polyethylene film materials used in baby diapers. For example, back sheet integrity is becoming more important due to the downsizing of the polyethylene film thickness used in these articles. By the term “conventional tackifier resins”, those resins commonly available in the adhesive art and industry that are used in typical hot melt adhesives. Examples of conventional tackifing resins included in this range include an aliphatic hydrocarbon resins, aromatic modified aliphatic hydrocarbon resins, hydrogenated poly-cyclopentadiene resins, poly-cyclopentadiene resins, gum rosins, gum rosin esters, wood rosins, wood rosin esters, tall oil rosins, tall oil rosin esters, poly-terpene, aromatic modified poly-terpene, terpene-phenolic, aromatic modified hydrogenated poly-cyclopentadiene resins, hydrogenated aliphatic resins, hydrogenated aliphatic aromatic resins, hydrogenated terpene and modified terpene and hydrogenated rosin esters. Often in conventional formulations such resins are used in amounts that range from about 5 to about 65 wt. %, often about 20 to 30 wt. %.
In further embodiments, the compositions disclosed herein optionally can comprise an antioxidant or a stabilizer. Any antioxidant known to a person of ordinary skill in the art may be used in the adhesion composition disclosed herein. Non-limiting examples of suitable antioxidants include amine-based antioxidants such as alkyl diphenyl amines, phenyl-naphthylamine, alkyl or aralkyl substituted phenyl-naphthylamine, alkylated p-phenylene diamines, tetramethyl-diaminodiphenylamine and the like; and hindered phenol compounds such as 2,6-di-t-butyl-4-methylphenol; 1,3,5-trimethyl-2,4,6-tris(3′,5′-di-t-butyl-4′-hydroxybenzyl)benzene; tetra kis[(methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane (e.g., IRGANOX™1010, from Ciba Geigy, New York); octadecyl-3,5-di-t-butyl-4-hydroxycinnamate (e.g., IRGANOX™ 1076, commercially available from Ciba Geigy) and combinations thereof. Where used, the amount of the antioxidant in the composition can be from about greater than 0 to about 1 wt. %, from about 0.05 to about 0.75 wt. %, or from about 0.1 to about 0.5 wt. % of the total weight of the composition.
In further embodiments, the compositions disclosed herein optionally can comprise an UV stabilizer that may prevent or reduce the degradation of the composition by radiation. Any UV stabilizer known to a person of ordinary skill in the art may be used in the adhesion composition disclosed herein. Non-limiting examples of suitable UV stabilizers include benzophenones, benzotriazoles, aryl esters, oxanilides, acrylic esters, formamidine carbon black, hindered amines, nickel quenchers, hindered amines, phenolic antioxidants, metallic salts, zinc compounds and combinations thereof. Where used, the amount of the UV stabilizer in the composition can be from about greater than 0 to about 1 wt. %, from about 0.05 to about 0.75 wt. %, or from about 0.1 to about 0.5 wt. % of the total weight of the composition.
In further embodiments, the compositions disclosed herein optionally can comprise a brightener, colorant or pigment. Any colorant or pigment known to a person of ordinary skill in the art may be used in the adhesion composition disclosed herein. Non-limiting examples of suitable brighteners, colorants or pigments include fluorescent materials and pigments such as triazine-stilbene, coumarin, imidazole, diazole, titanium dioxide and carbon black, phthalocyanine pigments, and other organic pigments such as IRGAZINB, CROMOPHTALB, MONASTRALB, CINQUASIAB, IRGALITEB, ORASOLB, all of which are available from Ciba Specialty Chemicals, Tarrytown, N.Y. Where used, the amount of the brightener, colorant or pigment in the composition can be from about greater than 0 to about 10 wt %, from about 0.01 to about 5 wt %, or from about 0.1 to about 2 wt % of the total weight of the composition.
The compositions disclosed herein may also optionally comprise a fragrance such as a perfume or other odorant. Such fragrances may be retained by a liner or contained in release agents such as microcapsules that may, for example, release fragrance upon removal of a release liner from or compression on the composition.
In further embodiments, the compositions disclosed herein optionally can comprise filler. Any filler known to a person of ordinary skill in the art may be used in the adhesion composition disclosed herein. Non-limiting examples of suitable fillers include sand, talc, dolomite, calcium carbonate, clay, silica, mica, wollastonite, feldspar, aluminum silicate, alumina, hydrated alumina, glass bead, glass microsphere, ceramic microsphere, thermoplastic microsphere, barite, wood flour, and combinations thereof. Where used, the amount of the filler in the composition can be from about greater than 0 to about 60 wt. %, from about 1 to about 50 wt. %, or from about 5 to about 40 wt. %
One substantial advantage in the claimed adhesives relates to a density of the adhesive formulations. Conventional tackifier is at a density that often ranges from about 1.07-1.09 g-cm−3. Conventional formulated adhesives containing a conventional tackifier in amounts of about 40 to 60 wt. %, have a density greater than 0.9 g-cm′ or more. The formulated adhesives of the invention, substantially free of tackifier, have densities less than 0.9 g-cm−3, often in the range about 0.85-0.89 g-cm′ often 0.86-0.87 g-cm−3. Not only are these adhesives free of the problems arising from tackifier materials, but the use of the claimed adhesives, and a lower density, permits the use of a reduced amount when measured by weight, resulting in cost savings.
Another aspect is methods of manufacture employing the hot melt adhesive compositions. The method involves application of the molten compositions to a substrate, followed by contact of the adhesive composition with a second substrate within 0.1 second to 5 seconds after application of the adhesive composition to the first substrate, wherein the contacting results in an adhesive bond between the substrates.
The hot melt adhesive compositions have melt rheology and thermal stability suitable for use with conventional hot melt adhesive application equipment. The blended components of the hot melt adhesive compositions have low melt viscosity at the application temperature, thereby facilitating flow of the compositions through a coating apparatus, e.g., coating die or nozzle, without resorting to the inclusion of solvents or extender oil into the composition. Melt viscosities of the hot melt adhesive compositions are between 1500 cP and 3500 cP or about 2000 cP to 3000 cP in mille Pascal-seconds or centipoise (cP) using a Brookfield thermosel RVT viscometer using a rotor number 27 at 176.66° C. (50 rpm, 350° F.). The hot melt adhesive compositions have a softening point (ASTM D 3461-97 Standard Test Method for Mettler Softening Point Method) of about 80° C. to 140° C., in some embodiments about 115° C. to 130° C. For certain applications, the hot melt adhesive compositions have effective set times of about 5 seconds or less, for example about 0.1 second to 5 seconds, in embodiments about 0.1 second to 3 seconds, and in some embodiments about 0.2 second to 1 second. The effective set time of the hot melt adhesives are unexpectedly short, particularly given that the open time remains in the acceptable range.
The adhesives described herein may be used to bond any of the substrates of the leg gasketing system. Specific examples include, but are not limited to, adhering the substrates of the cuff, adhering elastic strands to an adjacent substrate, and adhering the opacity patch to an adjacent substrate.
The adhesive is typically applied in an amount of about 1 to about 100 or about 4 to about 90 or about 7 to about 70 grams per square meter (g/m2) of resulting bonded material. The material may be applied in an amount of about 0.1 to about 20 or about 0.2 to about 10 or about 0.3 to about 15 grams per square meter (g/m2) of resulting bonded material. The adhesive material can be used at an add-on rate of 0.5 to 2 g/m2, 0.6 to 1.7 g/m2 or 0.7 to 1.5 g/m2, for absorbent articles.
A number of hot melt adhesive compositions were prepared by blending first amorphous copolymer, second heterophase copolymer, polymer plasticizer/diluent and antioxidant under mixing conditions at elevated temperatures to form a fully homogenized fluid melt. Mixing temperatures varied from about 135 to about 200° C. preferably about 150 to about 175° C. A WiseStir® mixer was used to ensure full homogenization of components into a final adhesive composition.
Hot melt adhesive compositions were formulated by melt blending as described below, wherein specific components and amounts of the components are shown in the following table 3.
These data indicates that the materials will provide excellent bonding in disposable absorbent articles. Note viscosity relates to the resistance to flow of the material under certain conditions. This distinctive property determines the flowability, degree of wetting, and penetration of the substrate by the molten polymer. It provides an indication of its processability and utility as a hot melt adhesive material. Melt viscosity is generally directly related to a polymer molecular weight and is reported in Millipascal-second's or centipoise (cP) using a Brookfield thermosel RVT viscometer using a rotor number 27 at the stated temperature.
Mettler softening point in degrees Centigrade or degrees Fahrenheit is typically measured using ASTM D3104. The amorphous nature of the poly olefin materials results in a melting point, which is not sharp or definite. Rather as the temperature increases, amorphous polymers gradually change from a solid to a soft and then to a liquid material. No clearly defined glass transition or melting temperature is often noted. This temperature testament that generally measures the precise temperature at which a disc of polymer sample, heated at a rate of 2° C. per minute or 10° per minute becomes soft enough to allow the test object, a steel ball (grams) drops through the sample. The softening point of a polymer reported in degrees Centigrade or degrees Fahrenheit is important because it typically indicates the polymer's heat resistance, useful application temperatures and solidification points.
A number of hot melt adhesive compositions were prepared by blending first amorphous copolymer, second compatible copolymer and antioxidant under mixing conditions at elevated temperatures to form a fully homogenized melt. Mixing temperatures varied from about 135 to about 200° C. preferably about 150 to about 175° C. as needed to obtain uniformity. A traditional heated stirred blade (WiseStir®) mixer was used to ensure full homogenization in a heated container into a final adhesive composition.
Hot melt adhesive compositions were formulated by melt blending, as described below, wherein specific components and amounts of the components are shown in the following table 5.
Hot melt adhesive compositions are formulated by melt blending, as described below, wherein specific components and amounts of the components are shown in the following table 6. Comparative examples 1 and 2 each form a non-uniform composition that has insufficient cohesive/adhesive strength to be usefully measured.
All tests show adhesion and good bonding. The data from runs 2, 3, 4, 5, 9, 12, 15, 16, 17, 19, and 20 show values that all exceeded requirements for a successful construction adhesive for absorbent articles.
These data indicates that the materials will provide excellent bonding in disposable absorbent articles. Note viscosity relates to the resistance to flow of the material under certain conditions. This distinctive property determines the flowability, degree of wetting, and penetration of the substrate by the molten polymer. It provides an indication of its processability and utility as a hot melt adhesive material.
Melt viscosity is generally directly related to a polymer molecular weight and is reported in millipascal-second (mP·s) or centipoise (cP) using a Brookfield DV-II+Pro (Rotation 10 rpm—Spindle # SC4-27) at the stated temperature.
Mettler softening point in degrees Centigrade or degrees Fahrenheit is typically measured using ASTM D3104. The amorphous nature of the polyolefin materials results in a melting point, which is not sharp or definite. Rather as the temperature increases, amorphous polymers gradually change from a solid to a soft and then to a liquid material. No clearly defined glass transition or melting temperature is often noted. This temperature testament that generally measures the precise temperature at which a disc of polymer sample, heated at a rate of 2° C. per minute or 10° F. per minute becomes soft enough to allow the test object, a steel ball (grams) drops through the sample. The softening point of a polymer reported in degrees Centigrade or degrees Fahrenheit is important because it typically indicates the polymer's heat resistance, useful application temperatures and solidification points.
Peel test values were obtained by forming a laminate from a SMS non-woven (11.6 g/m2) micro-porous polyethylene film (0.5 mil/0.127 micron) using lamination conditions as shown in Table 4. The laminate is cut into 1 inch/25.4 mm wide strips in the cross machine direction. Peel force was measured by separating the laminate at room temperature using a TMax pull tester at a rate of 20 in/sec (50.8 cm/sec) with the peek force averaged over a 15 period.
Opacity is measured using a 0° illumination/45° detection, circumferential optical geometry, spectrophotometer with a computer interface such as the HunterLab LabScan XE running Universal Software (available from Hunter Associates Laboratory Inc., Reston, Va.) or equivalent instrument. Instrument calibration and measurements are made using the standard white and black calibration plates provided by the vendor. All testing is performed in a room maintained at 23±2° C. and 50±2% relative humidity.
The spectrophotometer is configured for the XYZ color scale, D65 illuminant, 10° standard observer, with UV filter set to nominal. The instrument is standardized according to the manufacturer's procedures using the 0.7 inch port size and 0.5 inch area view. After calibration, the software is set to the Y opacity procedure which prompts the operator to cover the sample with either the white or black calibration tile during the measurement.
Articles are pre-conditioned at 23° C.±2 C.° and 50%±2% relative humidity for two hours prior to testing. To obtain a specimen, the article is stretched flat on a bench, body facing surface upward, and the total longitudinal length of the article is measured. A testing site on the inner and outer cuffs is selected at the longitudinal midpoint of the article. Using scissors, a test specimen is cut 60 mm long by the entire height of the inner cuff centered at the longitudinal midpoint of the left cuff. Next, a second test specimen is cut, this time from the outer cuff, 60 mm long by the entire height of the outer cuff, centered at the longitudinal midpoint of the left outer cuff. In like fashion, inner and outer cuff specimens are prepared from the cuffs on the right side of the article.
The specimen is placed over the measurement port. The specimen should completely cover the port with the surface corresponding to the inner-facing surface of the cuff directed toward the port. The specimen is gently extended until taut in its longitudinal direction so that the cuff lies flat against the port plate. Adhesive tape is applied to secure the cuff to the port plate in its extended state for testing. Tape should not cover any portion of the measurement port. The specimen is then covered with the white standard plate. A reading is taken, then the white tile is removed and replaced with the black standard tile without moving the specimen. A second reading is taken, and the opacity is calculated as follows:
Opacity=(Y value(black backing)/Y value(white backing))×100
Specimens from five identical articles (10 inner cuff (5 left and 5 right) and 10 outer cuff (5 left and 5 right)) are analyzed and their opacity results recorded. The average opacity for the inner cuffs and the outer cuffs are calculated and report separately, each to the nearest 0.01%.
Water Vapor Transmission Rate (WVTR) is measured using the wet cup approach. A cylindrical cup is filled with water, maintaining a constant headspace between the water surface and a specimen sealed over the cup's upper opening. The vapor loss is measured gravimetrically after heating the assembled cup for a specified time in an oven. All testing is performed in a room maintained at 23° C.±2 C.° and 50%±2% relative humidity.
Articles are preconditioned at 23° C.±2 C.° and 50%±2% relative humidity for two hours prior to testing. The article stretched flat on a bench, body facing surface upward, and the total longitudinal length of the article is measured. A testing site on the inner and outer cuffs is selected at the longitudinal midpoint of the article. Using scissors, a test specimen is cut 60 mm long by the entire height of the inner cuff centered at the longitudinal midpoint of the left cuff. Next, a second test specimen is cut, this time from the outer cuff, 60 mm long by the entire height of the outer cuff, centered at the longitudinal midpoint of the left outer cuff. In like fashion, inner and outer cuff specimens from the cuffs on the right side of the article are prepared.
Glass straight walled, cylindrical vials, 95 mm tall with a 17.8 mm internal diameter at the opening are used as WVTR test vials. Each test vial is filled with distilled water accurately to a level 25.0 mm±0.1 mm from the upper lip of the vial's opening. The specimen is placed, inner-facing surface of the cuff downward, over the vial's opening. The specimen is gently pulled taut and secured around the vial's circumference with an elastic band. The specimen is further sealed by wrapping Teflon tape around the vial's circumference. A preferred Teflon tape is a thread sealant tape 0.25″ wide available from McMaster Carr (cat. No. 4591K11) or equivalent. The Teflon tape is applied up to the top edge of the vial but should not cover any portion of the vial's opening. The mass of the vial assembly (vial+specimen+sealing tape) is weighed to the nearest 0.0001 gram. This is the starting mass.
The vial assemblies are placed upright in a mechanical convection oven (e.g. Lindberg/BlueM oven available from ThermoScientific or equivalent) maintained at 38±1° C. for 24 hours, taking care to avoid contact between the water in the vials and the specimens. After 24 hours has elapsed, the vial assemblies are removed from the oven and allowed to come to room temperature. The mass of each vial assembly is measured to the nearest 0.0001 gram. This is the final mass.
The WVTR is calculated using the following equation:
WVTR (g/m2/24 hrs)=([starting mass (g)−final mass (g)]/surface area (m2))/24 hrs
Specimens from five identical articles (10 inner cuff (5 left and 5 right) and 10 outer cuff (5 left and 5 right)) are analyzed and their WVTR results recorded. The average WVTR for the inner cuffs and the outer cuffs are each reported separately to the nearest 1 g/m2/24 hrs.
Air permeability is tested using a TexTest FX3300 Air Permeability Tester (available from Advanced Testing Instruments, Greer, S.C.) with a custom made 1 cm2 circular aperture (also available from Advanced Testing Instruments) or equivalent instrument. The instrument is calibrated according to the manufacturer's procedures. All testing is performed in a room maintained at 23° C.±2 C.° and 50%±2% relative humidity.
The articles are pre-conditioned at 23° C.±2 C.° and 50%±2% relative humidity for two hours prior to testing. To obtain a specimen, the article is stretched flat on a bench, body facing surface upward, and the total longitudinal length of the article is measured. A testing site on the inner and outer cuffs is selected at the longitudinal midpoint of the article. Using scissors, a test specimen is cut 60 mm long by the entire height of the inner cuff centered at the longitudinal midpoint of the left cuff. Next, a second test specimen is cut, this time from the outer cuff, 60 mm long by the entire height of the outer cuff, centered at the longitudinal midpoint of the left outer cuff. In like fashion, inner and outer cuff specimens are prepared from the cuffs on the right side of the article.
The specimen is centered over the measurement port. The specimen should completely cover the port with the surface corresponding to the inward-facing surface of the cuff directed toward the port. The specimen is gently extended in its longitudinal direction until taut so that the cuff lies flat across the port. Adhesive tape is applied to secure the cuff across the port in its extended state for testing. Tape should not cover any portion of the measurement port. The test pressure is set to allow air to pass through the specimen. For non-woven cuffs the pressure is typically set for 125 Pa and for cuffs containing films typically 2125 Pa is used. The sample ring is closed and the measuring range is adjusted until the range indicator shows green to indicate that the measurement is within the accepted limits of the instrument. The air permeability is recorded to the nearest 0.1 m3/m2/min.
Hydrostatic head is tested using a TexTest FX3000 Hydrostatic Head Tester (available from Advanced Testing Instruments, Greer, S.C.) with a custom made 1.5 cm2 circular measurement port (also available from Advanced Testing Instruments). Two annular sleeve rings, the same dimensions as the gaskets around the measurement ports, are cut from the standard protective sleeves for fine nonwovens (part FX3000-NWH, available from Advanced Testing Instruments). The sleeve rings are then adhered with two-sided adhesive tape to the sample facing surfaces of the upper and lower gaskets of the TexTest instrument to protect the specimen during clamping. Standardize the instrument according to the manufacturer's procedures. All testing is performed in a room maintained at about 23° C.±2 C.° and about 50%±2% relative humidity.
Precondition the articles at about 23° C.±2 C.° and about 50%±2% relative humidity for two hours prior to testing. To obtain a specimen, lay the article stretched flat on a bench, body facing surface upward, and measure the total longitudinal length of the article. Select a testing site on the inner and outer cuffs, at the longitudinal midpoint of the article. Using scissors cut a test specimen 70 mm long by the entire height of the inner cuff centered at the longitudinal midpoint of the left cuff. Next cut a second test specimen, this time from the outer cuff, 70 mm long by the entire height of the outer cuff, centered at the longitudinal midpoint of the left outer cuff. In like fashion, prepare inner and outer cuff specimens from the cuffs on the right side of the article.
Place the specimen centered over the port of the upper test head. The specimen should completely cover the port with the surface corresponding to the outward-facing surface of the cuff directed toward the port (inner-facing surface will then be facing the water). Gently extend the specimen taut in its longitudinal direction so that the cuff lies flat against the upper test plate. Adhesive tape is applied to secure the cuff to the test plate in its extended state for testing. Tape should not cover any portion of the measurement port.
Fill the TexTest syringe with distilled water, adding the water through the measurement port of the lower test plate. The water level should be filled to the top of the lower gasket. Mount the upper test head onto the instrument and lower the test head to make a seal around the specimen. The test speed is set to 3 mbar/min for samples that have a hydrostatic head of 50 mbar or less and a speed of 60 mbar/min for samples with a hydrostatic head above 50 mbar. Start the test and observe the specimen surface to detect water droplets penetrating the surface. The test is terminated when one drop is detected on the surface of the specimen or the pressure exceeds 200 mbar. Record the pressure to the nearest 0.5 mbar or record as >200 mbar if there was no penetration detected.
A total of five identical articles (10 inner cuff and 10 outer cuff specimens) are analyzed and their hydrostatic head results recorded. Calculate and report the average hydrostatic head for the inner cuffs and the outer cuffs and report each to the nearest 0.1 mbar.
The low surface tension fluid strikethrough time test is used to determine the amount of time it takes a specified quantity of a low surface tension fluid, discharged at a prescribed rate, to fully penetrate a sample of a web (and other comparable barrier materials) which is placed on a reference absorbent pad.
For this test, the reference absorbent pad is 5 plies of Ahlstrom grade 989 filter paper (10 cm×10 cm) and the test fluid is a 32 mN/m low surface tension fluid.
This test is designed to characterize the low surface tension fluid strikethrough performance (in seconds) of webs intended to provide a barrier to low surface tension fluids, such as runny BM, for example.
Lister Strikethrough Tester: The instrumentation is like described in EDANA ERT 153.0-02 section 6 with the following exception: the strike-through plate has a star-shaped orifice of 3 slots angled at 60 degrees with the narrow slots having a 10.0 mm length and a 1.2 mm slot width. This equipment is available from Lenzing Instruments (Austria) and from W. Fritz Metzger Corp (USA). The unit needs to be set up such that it does not time out after 100 seconds.
Reference Absorbent Pad: Ahlstrom Grade 989 filter paper, in 10 cm×10 cm areas, is used. The average strikethrough time is 3.3+0.5 seconds for 5 plies of filter paper using the
32 mN/m test fluid and without the web sample. The filter paper may be purchased from Empirical Manufacturing Company, Inc. (EMC) 7616 Reinhold Drive Cincinnati, Ohio 45237.
Test Fluid: The 32 mN/m surface tension fluid is prepared with distilled water and 0.42+/−0.001 g/liter Triton-X 100. All fluids are kept at ambient conditions.
Electrode-Rinsing Liquid: 0.9% sodium chloride (CAS 7647-14-5) aqueous solution (9 g NaCl per 1 L of distilled water) is used.
The claims may suitably comprise, consist of, or consist essentially of, or be substantially free of any of the disclosed or recited elements. The invention illustratively disclosed herein can also be suitably practiced in the absence of any element which is not specifically disclosed herein.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numeral values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”.
All documents cited in the Detailed Description of the Invention are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this written document conflicts with any meaning or definition of the term in a document incorporated by reference, the meaning or definition assigned to the term in this written document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
This application claims priority, under 35 U.S.C. § 120, to U.S. application Ser. No. 15/377,011, filed on Dec. 13, 2016, which claims the benefit, under 35 U. S.C. § 119(e), of U.S. Provisional Application Ser. No. 62/267,543, filed on Dec. 15, 2015, the entire disclosures of each are incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 62267543 | Dec 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15377011 | Dec 2016 | US |
| Child | 16829117 | US |
