Patent Application
20150335498
The present invention relates to absorbent structures useful in absorbent articles such as diapers, incontinent briefs, training pants, diaper holders and liners, sanitary hygiene garments, and the like. Specifically, the present invention relates to an absorbent structure utilizing discrete foam pieces have vacuoles.
Open celled foams are used for their absorbent properties. Open celled foams include latex polymer foams, polyurethane foams, and foams created by polymerizing an emulsion. One type of an open celled foam is created from an emulsion that is a dispersion of one liquid in another liquid and generally is in the form of a water-in-oil mixture having an aqueous or water phase dispersed within a substantially immiscible continuous oil phase. Water-in-oil (or oil in water) emulsions having a high ratio of dispersed phase to continuous phase are known in the art as High Internal Phase Emulsions, also referred to as “HIPS” or HIPEs. Different foams may be chosen due to specific properties.
Traditionally, open celled foams are polymerized in a continuous sheet or in a tubular reaction. Either process represents that one must use polymerized open celled foam in a continuous form or break up the polymerized open celled foam to make open celled foam pieces.
Ultimately, in regards to an absorbent core, the current process represents using a core made solely of foam or a core that uses pieces of foam placed into or onto another material. This means that the pieces must be held in place by a cover layer or some form of adhesive. The process does not allow one to make an absorbent core wherein discrete portions of the foam are integrated into a substrate and parts of the substrate are integrated into the foam. Further, the process creates a uniform foam that does not allow for different types of pores in terms of size magnitude differences.
Therefore there exists a need to create a heterogeneous mass containing foam that has variant pores in the form of open cells and also has large openings or vacuoles. The foam may be integrated into the heterogeneous mass by enrobing enrobeable elements within the heterogeneous mass.
A heterogeneous mass comprising a longitudinal axis, a lateral axis, a vertical axis, one or more enrobeable elements and one or more discrete open cell foam pieces is disclosed. The open cell foam pieces comprise pores and vacuoles.
An absorbent article comprising a topsheet, a backsheet, and an absorbent core wherein the absorbent core comprises a heterogeneous mass comprising one or more enrobeable elements and one or more discrete open cell foam pieces is also disclosed. At least one of the discrete open cell foam pieces comprises vacuoles.
While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the present invention, it is believed that the invention can be more readily understood from the following description taken in connection with the accompanying drawings, in which:
As used herein, the term “bicomponent fibers” refers to fibers which have been formed from at least two different polymers extruded from separate extruders but spun together to form one fiber. Bicomponent fibers are also sometimes referred to as conjugate fibers or multicomponent fibers. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the bicomponent fibers and extend continuously along the length of the bicomponent fibers. The configuration of such a bicomponent fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another, or may be a side-by-side arrangement, a pie arrangement, or an “islands-in-the-sea” arrangement.
As used herein, the term “biconstituent fibers” refers to fibers which have been formed from at least two polymers extruded from the same extruder as a blend. Biconstituent fibers do not have the various polymer components arranged in relatively constantly positioned distinct zones across the cross-sectional area of the fiber and the various polymers are usually not continuous along the entire length of the fiber, instead usually forming fibrils which start and end at random. Biconstituent fibers are sometimes also referred to as multiconstituent fibers.
The term “disposable” is used herein to describe articles, which are not intended to be laundered or otherwise restored or reused as an article (i.e. they are intended to be discarded after a single use and possibly to be recycled, composted or otherwise disposed of in an environmentally compatible manner). The absorbent article comprising an absorbent structure according to the present invention can be for example a sanitary napkin or a panty liner. The absorbent structure of the present invention will be herein described in the context of a typical absorbent article, such as, for example, a sanitary napkin. Typically, such articles can comprise a liquid pervious topsheet, a backsheet and an absorbent core intermediate the topsheet and the backsheet.
As used herein, an “enrobeable element” refers to an element that may be enrobed by the foam. The enrobeable element may be, for example, a fiber, a group of fibers, a tuft, or a section of a film between two apertures. It is understood that other elements are contemplated by the present invention.
A “fiber” as used herein, refers to any material that can be part of a fibrous structure. Fibers can be natural or synthetic. Fibers can be absorbent or non-absorbent.
A “fibrous structure” as used herein, refers to materials which can be broken into one or more fibers. A fibrous structure can be absorbent or adsorbent. A fibrous structure can exhibit capillary action as well as porosity and permeability.
As used herein, the term “meltblowing” refers to a process in which fibers are formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually heated, gas (for example air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface, often while still tacky, to form a web of randomly dispersed meltblown fibers.
As used herein, the term “monocomponent” fiber refers to a fiber formed from one or more extruders using only one polymer. This is not meant to exclude fibers formed from one polymer to which small amounts of additives have been added for coloration, antistatic properties, lubrication, hydrophilicity, etc. These additives, for example titanium dioxide for coloration, are generally present in an amount less than about 5 weight percent and more typically about 2 weight percent.
As used herein, the term “non-round fibers” describes fibers having a non-round cross-section, and includes “shaped fibers” and “capillary channel fibers.” Such fibers can be solid or hollow, and they can be tri-lobal, delta-shaped, and are preferably fibers having capillary channels on their outer surfaces. The capillary channels can be of various cross-sectional shapes such as “U-shaped”, “H-shaped”, “C-shaped” and “V-shaped”. One practical capillary channel fiber is T-401, designated as 4DG fiber available from Fiber Innovation Technologies, Johnson City, Tenn. T-401 fiber is a polyethylene terephthalate (PET polyester).
As used herein, the term “nonwoven web” refers to a web having a structure of individual fibers or threads which are interlaid, but not in a repeating pattern as in a woven or knitted fabric, which do not typically have randomly oriented fibers. Nonwoven webs or fabrics have been formed from many processes, such as, for example, meltblowing processes, spunbonding processes, spunlacing processes, hydroentangling, airlaying, and bonded carded web processes, including carded thermal bonding. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (gsm). The basis weight of the laminate web is the combined basis weight of the constituent layers and any other added components. Fiber diameters are usually expressed in microns; fiber size can also be expressed in denier, which is a unit of weight per length of fiber. The basis weight of laminate webs suitable for use in an article of the present invention can range from 10 gsm to 100 gsm, depending on the ultimate use of the web.
As used herein, the term “polymer” generally includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc., and blends and modifications thereof. In addition, unless otherwise specifically limited, the term “polymer” includes all possible geometric configurations of the material. The configurations include, but are not limited to, isotactic, atactic, syndiotactic, and random symmetries.
As used herein, “spunbond fibers” refers to small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced.
Spunbond fibers are generally not tacky when they are deposited on a collecting surface. Spunbond fibers are generally continuous and have average diameters (from a sample size of at least 10 fibers) larger than 7 microns, and more particularly, between about 10 and 40 microns.
As used herein, a “tuft” or chad relates to discrete integral extensions of the fibers of a nonwoven web. Each tuft can comprise a plurality of looped, aligned fibers extending outwardly from the surface of the web. In another embodiment each tuft can comprise a plurality of non-looped fibers that extend outwardly from the surface of the web. In another embodiment, each tuft can comprise a plurality of fibers which are integral extensions of the fibers of two or more integrated nonwoven webs.
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.
The present invention relates to an absorbent structure that is a heterogeneous mass comprising one or more enrobeable elements and one or more discrete open cell foam pieces that have both pores and one or more vacuoles. The area at any given cross section of a vacuole are a magnitude of the area at any given cross section of a pore. The vacuoles may contain enrobeable elements and serve as areas wherein the open cell foam enrobes the enrobeable elements. The heterogeneous mass has a depth, a width, and a height. The absorbent structure may be used as any part of an absorbent article including, for example, a part of an absorbent core, as an absorbent core, and/or as a topsheet for absorbent articles such as sanitary napkins, panty liners, tampons, interlabial devices, wound dressings, diapers, adult incontinence articles, and the like, which are intended for the absorption of body fluids, such as menses or blood or vaginal discharges or urine. The absorbent structure may be used in any product utilized to absorb and retain a fluid including surface wipes. The absorbent structure may be used as a paper towel. Exemplary absorbent articles in the context of the present invention are disposable absorbent articles.
In an embodiment, the absorbent structure is a heterogeneous mass comprising enrobeable elements and one or more discrete portions of foam pieces. The one or more discrete portions of foam pieces enrobe the elements. The discrete portions of foam pieces are open celled foam. In an embodiment, the foam is a High Internal Phase Emulsion (HIPE) foam.
In an embodiment, the absorbent structure is an absorbent core for an absorbent article wherein the absorbent core comprises a heterogeneous mass comprising fibers and one or more discrete portions of foam that enrobe one or more of the fibers.
In the following description of the invention, the surface of the article, or of each component thereof, which in use faces in the direction of the wearer is called wearer-facing surface. Conversely, the surface facing in use in the direction of the garment is called garment-facing surface. The absorbent article of the present invention, as well as any element thereof, such as, for example the absorbent core, has therefore a wearer-facing surface and a garment-facing surface.
The present invention relates to an absorbent structure that contains one or more discrete open cell foam pieces foams that are integrated into a heterogeneous mass comprising one or more enrobeable elements integrated into the one or more open cell foams such that the two may be intertwined.
The open cell foam pieces may comprise between 1% of the heterogeneous mass by volume to 99% of the heterogeneous mass by volume, such as, for example, 5% by volume, 10% by volume, 15% by volume, 20% by volume, 25% by volume, 30% by volume, 35% by volume, 40% by volume, 45% by volume, 50% by volume, 55% by volume, 60% by volume, 65% by volume, 70% by volume, 75% by volume, 80% by volume, 85% by volume, 90% by volume, or 95% by volume.
The heterogeneous mass may have void space found between the enrobeable elements, between the enrobeable elements and the enrobed elements, and between enrobed elements. The void space may contain gas. The void space may represent between 1% and 95% of the total volume for a fixed amount of volume of the heterogeneous mass, such as, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% of the total volume for a fixed amount of volume of the heterogeneous mass.
The combination of open cell foam pieces and void space within the heterogeneous mass may exhibit an absorbency of between 10 g/g to 200 g/g of the heterogeneous mass, such as for example, 40 g/g, 60 g/g, 80 g/g, 100 g/g, 120 g/g, 140 g/g 160 g/g 180 g/g or 190 g/g of the heterogeneous mass. Absorbency may be quantified according to the Edana Nonwoven Absorption method 10.4-02.
The open cell foam pieces are discrete foam pieces intertwined within and throughout a heterogeneous mass such that the open cell foam enrobes one or more of the enrobeable elements such as, for example, fibers within the mass. The open cell foam may be polymerized around the enrobeable elements.
In an embodiment, a discrete open cell foam piece may enrobe more than one enrobeable element. The enrobeable elements may be enrobed together as a bunch. Alternatively, more than one enrobeable element may be enrobed by the discrete open cell foam piece without contacting another enrobeable element.
In an embodiment, the open cell foam pieces may enrobe an enrobeable element such that the enrobeable element is enrobed along the enrobeable elements axis for between 5% and 95% of the length along the enrobeable element's axis. For example, a single fiber may be enrobed along the length of the fiber for a distance greater than 50% of the entire length of the fiber. In an embodiment, an enrobeable element may have between 5% and 100% of its surface area enrobed by one or more open cell foam pieces.
In an embodiment, two or more open cell foam pieces may enrobe the same enrobeable element such that the enrobeable element is enrobed along the enrobeable elements axis for between 5% and 100% of the length along the enrobeable element's axis.
The open cell foam pieces enrobe the enrobeable elements such that a layer surrounds the enrobeable element at a given cross section. The layer surrounding the enrobeable element at a given cross section may be between 0.01 mm to 100 mm such as, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.4 mm, 2.6 mm, 2.8 mm, or 3 mm. The layer may not be equivalent in dimension at all points along the cross section of the enrobeable element. For example, in an embodiment, an enrobeable element may be enrobed by 0.5 mm at one point along the cross section and by 1.0 mm at a different point along the same cross section.
The open cell foam pieces are considered discrete in that they are not continuous throughout the entire heterogeneous mass. Not continuous throughout the entire heterogeneous mass represents that at any given point in the heterogeneous mass, the open cell absorbent foam is not continuous in at least one of the cross sections of a longitudinal, a vertical, and a lateral plane of the heterogeneous mass. In a non-limiting embodiment, the absorbent foam is not continuous in the lateral and the vertical planes of the cross section for a given point in the heterogeneous mass. In a non-limiting embodiment, the absorbent foam is not continuous in the longitudinal and the vertical planes of the cross section for a given point in the heterogeneous mass. In a non-limiting embodiment, the absorbent foam is not continuous in the longitudinal and the lateral planes of the cross section for a given point in the heterogeneous mass.
In an embodiment wherein the open cell foam is not continuous in at least one of the cross sections of the longitudinal, the vertical, and the lateral plane of the heterogeneous mass, one or both of either the enrobeable elements or the open cell foam pieces may be bi-continuous throughout the heterogeneous mass.
The open cell foam pieces may be located at any point in the heterogeneous mass. In a non-limiting embodiment, a foam piece may be surrounded by the elements that make up the enrobeable elements. In a non-limiting embodiment a foam piece may be located on the outer perimeter of the heterogeneous mass such that only a portion of the foam piece is entangled with the elements of the heterogeneous mass.
In a non-limiting embodiment, the open cell foam pieces may expand upon being contacted by a fluid to form a channel of discrete open cell foam pieces. The open cell foam pieces may or may not be in contact prior to being expanded by a fluid.
An open celled foam may be integrated onto the enrobeable elements prior to being polymerized. In a non-limiting embodiment the open cell foam pieces may be partially polymerized prior to being impregnated into or onto the enrobeable elements such that they become intertwined. After being impregnated into or onto the enrobeable elements, the open celled foam in either a liquid or solid state are polymerized to form one or more open cell foam pieces. The open celled foam may be polymerized using any known method including, for example, heat, UV, and infrared. Following the polymerization of a water in oil open cell foam emulsion, the resulting open cell foam is saturated with aqueous phase that needs to be removed to obtain a substantially dry open cell foam. Removal of the saturated aqueous phase or dewatering may occur using nip rollers, and vacuum. Utilizing a nip roller may also reduce the thickness of the heterogeneous mass such that the heterogeneous mass will remain thin until the open cell foam pieces entwined in the heterogeneous mass are exposed to fluid.
The open cell foam pieces may enrobe the enrobeable elements in a manner that creates a spacing or vacuole between the enrobing foam and the enrobeable element. The vacuole contains the enrobeable element and may surround the entire element, a cross section of the element, or a portion of the element. In an embodiment, the open cell foam pieces may be in direct contact with the element at one location and spaced by a vacuole in another. The vacuole may allow the enrobeable element to move within the vacuole. The size of the vacuole may be driven by the type of enrobeable element. In an embodiment, the vacuole diameter is greater than the fiber diameter which is greater than the foam pore size. The vacuole diameter may be, for example, between 1.0001 and 30,000 times the diameter of the fiber diameter, such as, between 1.2 and 20,000 times the diameter of the fiber, 10 and 10,000 times the diameter of the fiber, 15 and 1,000, such as, for example, 20 times the diameter of the fiber, 150 times the diameter of the fiber, 1,500 times the diameter of the fiber, 3,000 times the diameter of the fiber, 4,500 times the diameter of the fiber, 6,000 times the diameter of the fiber, 7,500 times the diameter of the fiber, 9,000 times the diameter of the fiber, 12,000 times the diameter of the fiber, 15,000 times the diameter of the fiber, 18,000 times the diameter of the fiber, 21,000 times the diameter of the fiber, 24,000 times the diameter of the fiber, 27,000, or 29,000 times the diameter of the fiber.
In an embodiment, one or more vacuoles may be irregularly shaped. In such embodiments, the cross-sectional surface area of the vacuoles may be between 1.0002 and 900,000,000 times the surface area created by a cross section of the fiber. When more than one fiber is located in the same vacuole, the cross-sectional surface area of the vacuoles may be between 1.0002 and 900,000,000 times the surface area created by the sum of the cross section of the fibers, such as, for example, between 10 to 100,000,000 times the surface area created by the sum of the cross section of the fibers, between 1,000 to 1,000,000 times the surface area created by the sum of the cross section of the fibers, or between 10,000 to 100,000 times the surface area created by the sum of the cross section of the fibers.
In an embodiment, the cross-sectional surface area of the vacuoles may be between 1.26 and 9,000,000 times the cross-sectional surface area of the pores in the open cell foam such as, for example between 10 and 5,000,000 times the cross-sectional surface area of the pores in the open cell foam, between 1,000 and 1,000,000 times the cross-sectional surface area of the pores in the open cell foam, between 100,000 and 500,000 times the cross-sectional surface area of the pores in the open cell foam. The cross sectional area of the pores may be between 0.001% and 99.99% of the cross sectional area of the vacuoles. The cross-sectional surface area of the vacuoles, pores (also referred to as cells) of the open-cell foams, and fiber diameters are measured via quantitative image analysis of cross-sectional micrographs of the heterogeneous mass.
Dependent upon the desired foam density, polymer composition, specific surface area, or pore size (also referred to as cell size), the open celled foam may be made with different chemical composition, physical properties, or both. For instance, dependent upon the chemical composition, an open celled foam may have a density of 0.0010 g/cc to about 0.25 g/cc. Preferred 0.04 g/cc.
Open cell foam pore sizes may range in average diameter of from 1 to 800 μm, such as, for example, between 50 and 700 μm, between 100 and 600 μm, between 200 and 500 μm, between 300 and 400 μm.
In some embodiments, the foam pieces have a relatively uniform cell size. For example, the average cell size on one major surface may be about the same or vary by no greater than 10% as compared to the opposing major surface. In other embodiments, the average cell size of one major surface of the foam may differ from the opposing surface. For example, in the foaming of a thermosetting material it is not uncommon for a portion of the cells at the bottom of the cell structure to collapse resulting in a lower average cell size on one surface.
The foams produced from the present invention are relatively open-celled. This refers to the individual cells or pores of the foam being in substantially unobstructed communication with adjoining cells. The cells in such substantially open-celled foam structures have intercellular openings or windows that are large enough to permit ready fluid transfer from one cell to another within the foam structure. For purpose of the present invention, a foam is considered “open-celled”if at least about 80% of the cells in the foam that are at least 1 μm in average diameter size are in fluid communication with at least one adjoining cell.
In addition to being open-celled, in certain embodiments foams are sufficiently hydrophilic to permit the foam to absorb aqueous fluids, for example the internal surfaces of a foam may be rendered hydrophilic by residual hydrophilizing surfactants or salts left in the foam following polymerization, by selected post-polymerization foam treatment procedures (as described hereafter), or combinations of both.
In certain embodiments, for example when used in certain absorbent articles, an open cell foam may be flexible and exhibit an appropriate glass transition temperature (Tg). The Tg represents the midpoint of the transition between the glassy and rubbery states of the polymer.
In certain embodiments, the Tg of this region will be less than about 200° C. for foams used at about ambient temperature conditions, in certain other embodiments less than about 90° C. The Tg may be less than 50° C.
The open cell foam pieces may be distributed in any suitable manner throughout the heterogeneous mass. In an embodiment, the open cell foam pieces may be profiled along the vertical axis such that smaller pieces are located above larger pieces. Alternatively, the pieces may be profiled such that smaller pieces are below larger pieces. In another embodiment, the open cell pieces may be profiled along a vertical axis such that they alternate in size along the axis.
In an embodiment, the open cell foam pieces may be profiled along the longitudinal axis such that smaller pieces are located in front of larger pieces. Alternatively, the pieces may be profiled such that smaller pieces are behind larger pieces. In another embodiment, the open cell pieces may be profiled along a longitudinal axis such that they alternate in size along the axis.
In an embodiment, the open cell foam pieces may be profiled along the lateral axis such the size of the pieces goes from small to large or from large to small along the lateral axis. Alternatively, the open cell pieces may be profiled along a lateral axis such that they alternate in size along the axis.
In an embodiment the open cell foam pieces may be profiled along any one of the longitudinal, lateral, or vertical axis based on one or more characteristics of the open cell foam pieces. Characteristics by which the open cell foam pieces may be profiled within the heterogeneous mass may include, for example, absorbency, density, cell size, and combinations thereof.
In an embodiment, the open cell foam pieces may be profiled along any one of the longitudinal, lateral, or vertical axis based on the composition of the open cell foam. The open cell foam pieces may have one composition exhibiting desirable characteristics in the front of the heterogeneous mass and a different composition in the back of the heterogeneous mass designed to exhibit different characteristics. The profiling of the open cell foam pieces may be either symmetric or asymmetric about any of the prior mentioned axes or orientations.
The open cell foam pieces may be distributed along the longitudinal and lateral axis of the heterogeneous mass in any suitable form. In an embodiment, the open cell foam pieces may be distributed in a manner that forms a design or shape when viewed from a top planar view. The open cell foam pieces may be distributed in a manner that forms stripes, ellipticals, squares, or any other known shape or pattern.
The distribution may be optimized dependent on the intended use of the heterogeneous mass. For example, a different distribution may be chosen for the absorption of aqueous fluids such as urine when used in a diaper or water when used in a paper towel versus for the absorption of a proteinaceous fluid such as menses. Further, the distribution may be optimized for uses such as dosing an active or to use the foam as a reinforcing element.
In an embodiment, different types of foams may be used in one heterogeneous mass. For example, some of the foam pieces may be polymerized HIPE while other pieces may be made from polyurethane. The pieces may be located at specific locations within the mass based on their properties to optimize the performance of the heterogeneous mass.
In an embodiment, the foam pieces and enrobeable elements may be selected to complement each other. For example, a foam that exhibits high permeability with low capillarity may enrobe an element that exhibits high capillarity to wick the fluid through the heterogeneous mass. It is understood that other combinations may be possible wherein the foam pieces complement each other or wherein the foam pieces and enrobeable elements both exhibit similar properties.
In an embodiment, profiling may occur using more than one heterogeneous mass with each heterogeneous mass having one or more types of foam pieces. The plurality of heterogeneous masses may be layered so that the foam is profiled along any one of the longitudinal, lateral, or vertical axis based on one or more characteristics of the open cell foam pieces for an overall product that contains the plurality of heterogeneous masses. Further, each heterogeneous mass may have a different enrobeable element to which the foam is attached. For example, a first heterogeneous mass may have foam particles enrobing a nonwoven while a second heterogeneous mass adjacent the first heterogeneous mass may have foam particles enrobing a film or one surface of a film.
In an embodiment, the open cell foam may be made from a polymer formula that can include any suitable thermoplastic polymer, or blend of thermoplastic polymers, or blend of thermoplastic and non-thermoplastic polymers.
Examples of polymers, or base resins, suitable for use in the foam polymer formula include styrene polymers, such as polystyrene or polystyrene copolymers or other alkenyl aromatic polymers; polyolefins including homo or copolymers of olefins, such as polyethylene, polypropylene, polybutylene, etc.; polyesters, such as polyalkylene terephthalate; and combinations thereof. A commercially available example of polystyrene resin is Dow STYRON® 685D, available from Dow Chemical Company in Midland, Mich., U.S.A.
Coagents and compatibilizers can be utilized for blending such resins. Crosslinking agents can also be employed to enhance mechanical properties, foamability and expansion. Crosslinking may be done by several means including electron beams or by chemical crosslinking agents including organic peroxides. Use of polymer side groups, incorporation of chains within the polymer structure to prevent polymer crystallization, lowering of the glass transition temperature, lowering a given polymer's molecular weight distribution, adjusting melt flow strength and viscous elastic properties including elongational viscosity of the polymer melt, block copolymerization, blending polymers, and use of polyolefin homopolymers and copolymers have all been used to improve foam flexibility and foamability. Homopolymers can be engineered with elastic and crystalline areas. Syndiotactic, atactic and isotactic polypropylenes, blends of such and other polymers can also be utilized. Suitable polyolefin resins include low, including linear low, medium and high-density polyethylene and polypropylene, which are normally made using Ziegler-Natta or Phillips catalysts and are relatively linear; generally more foamable are resins having branched polymer chains. Isotactic propylene homopolymers and blends are made using metallocene-based catalysts. Olefin elastomers are included.
Ethylene and α-olefin copolymers, made using either Ziegler-Natta or a metallocene catalyst, can produce soft, flexible foam having extensibility. Polyethylene cross-linked with α-olefins and various ethylene ionomer resins can also be utilized. Use of ethyl-vinyl acetate copolymers with other polyolefin-type resins can produce soft foam. Common modifiers for various polymers can also be reacted with chain groups to obtain suitable functionality. Suitable alkenyl aromatic polymers include alkenyl aromatic homopolymers and copolymers of alkenyl aromatic compounds and copolymerizable ethylenically unsaturated comonomers including minor proportions of non-alkenyl aromatic polymers and blends of such. Ionomer resins can also be utilized.
Other polymers that may be employed include natural and synthetic organic polymers including cellulosic polymers, methyl cellulose, polylactic acids, polyvinyl acids, polyacrylates, polycarbonates, starch-based polymers, polyetherimides, polyamides, polyesters, polymethylmethacrylates, and copolymer/polymer blends. Rubber-modified polymers such as styrene elastomers, styrene/butadiene copolymers, ethylene elastomers, butadiene, and polybutylene resins, ethylene-propylene rubbers, EPDM, EPM, and other rubbery homopolymers and copolymers of such can be added to enhance softness and hand. Olefin elastomers can also be utilized for such purposes. Rubbers, including natural rubber, SBR, polybutadiene, ethylene propylene terpolymers, and vulcanized rubbers, including TPVs, can also be added to improve rubber-like elasticity.
Thermoplastic foam absorbency can be enhanced by foaming with spontaneous hydrogels, commonly known as superabsorbents. Superabsorbents can include alkali metal salts of polyacrylic acids; polyacrylamides; polyvinyl alcohol; ethylene maleic anhydride copolymers; polyvinyl ethers; hydroxypropylcellulose; polyvinyl morpholinone; polymers and copolymers of vinyl sulfonic acid, polyacrylates, polyacrylamides, polyvinyl pyridine; and the like. Other suitable polymers include hydrolyzed acrylonitrile grafted starch, acrylic acid grafted starch, carboxy-methyl-cellulose, isobutylene maleic anhydride copolymers, and mixtures thereof. Further suitable polymers include inorganic polymers, such as polyphosphazene, and the like. Furthermore, thermoplastic foam biodegradability and absorbency can be enhanced by foaming with cellulose-based and starch-based components such as wood and/or vegetable fibrous pulp/flour.
In addition to any of these polymers, the foam polymer formula may also, or alternatively, include diblock, triblock, tetrablock, or other multi-block thermoplastic elastomeric and/or flexible copolymers such as polyolefin-based thermoplastic elastomers including random block copolymers including ethylene α-olefin copolymers; block copolymers including hydrogenated butadiene-isoprene-butadiene block copolymers; stereoblock polypropylenes; graft copolymers, including ethylene-propylene-diene terpolymer or ethylene-propylene-diene monomer (EPDM), ethylene-propylene random copolymers (EPM), ethylene propylene rubbers (EPR), ethylene vinyl acetate (EVA), and ethylene-methyl acrylate (EMA); and styrenic block copolymers including diblock and triblock copolymers such as styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), styrene-isoprene-butadiene-styrene (SIBS), styrene-ethylene/butylene-styrene (SEBS), or styrene-ethylene/propylene-styrene (SEPS), which may be obtained from Kraton Polymers of Belpre, Ohio, U.S.A., under the trade designation KRATON® elastomeric resin or from Dexco, a division of ExxonMobil Chemical Company in Houston, Tex., U.S.A., under the trade designation VECTOR® (SIS and SBS polymers) or SEBS polymers as the SEPTON® series of thermoplastic rubbers from Kuraray America, Inc. in New York, N.Y., U.S.A.; blends of thermoplastic elastomers with dynamic vulcanized elastomer-thermoplastic blends; thermoplastic polyether ester elastomers; ionomeric thermoplastic elastomers; thermoplastic elastic polyurethanes, including those available from E.I. Du Pont de Nemours in Wilmington, Del., U.S.A., under the trade name LYCRA® polyurethane, and ESTANE® available from Noveon, Inc. in Cleveland, Ohio, U.S.A.; thermoplastic elastic polyamides, including polyether block amides available from ATOFINA Chemicals, Inc. in Philadelphia, Pa., U.S.A., under the trade name PEBAX® polyether block amide; thermoplastic elastic polyesters, including those available from E.I. Du Pont de Nemours Company, under the trade name HYTREL®, and ARNITEL® from DSM Engineering Plastics of Evansville, Ind., U.S.A., and single-site or metallocene-catalyzed polyolefins having a density of less than about 0.89 grams/cubic centimeter such as metallocene polyethylene resins, available from Dow Chemical Company in Midland, Mich., U.S.A. under the trade name AFFINITY™; and combinations thereof.
As used herein, a tri-block copolymer has an ABA structure where the A represents several repeat units of type A, and B represents several repeat units of type B. As mentioned above, several examples of styrenic block copolymers are SBS, SIS, SIBS, SEBS, and SEPS. In these copolymers the A blocks are polystyrene and the B blocks are the rubbery component. Generally these triblock copolymers have molecular weights that can vary from the low thousands to hundreds of thousands and the styrene content can range from 5% to 75% based on the weight of the triblock copolymer. A diblock copolymer is similar to the triblock but is of an AB structure. Suitable diblocks include styrene-isoprene diblocks, which have a molecular weight of approximately one-half of the triblock molecular weight and having the same ratio of A blocks to B blocks. Diblocks with a different ratio of A to B blocks or a molecular weight larger or greater than one-half of triblock copolymers may be suitable for improving the foam polymer formula for producing low-density, soft, flexible, absorbent foam via polymer extrusion.
Suitably, the foam polymer formula includes up to about 90%, by weight, of polystyrene, and at least 10%, by weight, of thermoplastic elastomer. More particularly, the foam polymer formula may include between about 45% and about 90%, by weight, of polystyrene, and between about 10% and about 55%, by weight, of thermoplastic elastomer. Alternatively, the foam polymer formula may include between about 50% and about 80%, by weight, of polystyrene, and between about 20% and about 50%, by weight, of thermoplastic elastomer. In one embodiment, for example, the foam polymer formula may include equal amounts of polystyrene and thermoplastic elastomer.
In another embodiment, the foam polymer formula may include about 40% to about 80% by weight polystyrene and about 20% to about 60% by weight thermoplastic elastomer. In another embodiment, the foam polymer formula may include about 50% to about 70% by weight polystyrene and about 30% to about 50% by weight thermoplastic elastomer.
In accordance with the embodiment, a plasticizing agent can be included in the foam polymer formula. A plasticizing agent is a chemical agent that imparts flexibility, stretchability and workability. The type of plasticizing agent has an influence on foam gel properties, blowing agent migration resistance, cellular structure, including the fine cell size, and number of open cells. Typically plasticizing agents are of low molecular weight. The increase in polymer chain mobility and free volume caused by incorporation of a plasticizing agent typically results in a Tg decrease, and plasticizing agent effectiveness is often characterized by this measurement. Petroleum-based oils, fatty acids, and esters are commonly used and act as external plasticizing agents or solvents because they do not chemically bond to the polymer yet remain intact in the polymer matrix upon crystallization.
The plasticizing agent increases cell connectivity by thinning membranes between cells to the point of creating porous connections between cells; thus, the plasticizing agent increases open-cell content. Suitably, the plasticizing agent is included in an amount between about 0.5% and about 10%, or between about 1% and about 10%, by weight, of the foam polymer formula. The plasticizing agent is gradually and carefully metered in increasing concentration into the foam polymer formula during the foaming process because too much plasticizing agent added at once creates cellular instability, resulting in cellular collapse.
Examples of suitable plasticizing agents include polyethylene, ethylene vinyl acetate, mineral oil, palm oil, waxes, esters based on alcohols and organic acids, naphthalene oil, paraffin oil, and combinations thereof. A commercially available example of a suitable plasticizing agent is a small-chain polyethylene that is produced as a catalytic polymerization of ethylene; because of its low molecular weight it is often referred to as a “wax.” This low-density, highly branched polyethylene “wax” is available from Eastman Chemical Company of Kingsport, Tenn., U.S.A., under the trade designation EPOLENE® C-10.
In order for the foam to be used in personal care and medical product applications and many absorbent wiping articles and non-personal care articles, the foam must meet stringent chemical and safety guidelines. A number of plasticizing agents are FDA-approved for use in packaging materials. These plasticizing agents include: acetyl tributyl citrate; acetyl triethyl citrate; p-tert-butylphenyl salicylate; butyl stearate; butylphthalyl butyl glycolate; dibutyl sebacate; di-(2-ethylhexyl) phthalate; diethyl phthalate; diisobutyl adipate; diisooctyl phthalate; diphenyl-2-ethylhexyl phosphate; epoxidized soybean oil; ethylphthalyl ethyl glycolate; glycerol monooleate; monoisopropyl citrate; mono-, di-, and tristearyl citrate; triacetin (glycerol triacetate); triethyl citrate; and 3-(2-xenoyl)-1,2-epoxypropane.
In certain embodiments, the same material used as the thermoplastic elastomer may also be used as the plasticizing agent. For example, the KRATON® polymers, described above, may be used as a thermoplastic elastomer and/or a plasticizing agent. In which case, the foam polymer formula may include between about 10% and about 50%, by weight, of a single composition that acts as both a thermoplastic elastomer and a plasticizing agent. Described in an alternative manner, the foam may be formed without a plasticizing agent per se; in which case, the foam polymer formula may include between about 10% and about 50%, by weight, of the thermoplastic elastomer.
Foaming of soft, flexible polymers, such as thermoplastic elastomers, to a low density is difficult to achieve. The addition of a plasticizing agent makes foaming to low densities even more difficult to achieve. The method of the invention overcomes this difficulty through the inclusion of a surfactant in the foam polymer formula. The surfactant stabilizes the cells, thereby counteracting cellular collapse while retaining an open-cell structure. This stabilization of the cells creates cell uniformity and control of cell structure. In addition to enabling foaming of plasticized thermoplastic elastomer polymer containing foam formulations to low densities, the surfactant also provides wettability to enable the resulting foam to absorb fluid.
The foam pieces may be made from a thermoplastic absorbent foam such as a polyurethane foam. The thermoplastic foam may comprise surfactant and plasticizing agent. Polyurethane polymers are generally formed by the reaction of at least one polyisocyanate component and at least one polyol component. The polyisocyanate component may comprise one or more polyisocyanates. The polyol component may comprise one or more polyols. The concentration of a polyol may be expressed with regard to the total polyol component. The concentration of polyol or polyisocyanate may alternatively be expressed with regard to the total polyurethane concentration. Various aliphatic and aromatic polyisocyanates have been described in the art. The polyisocyanate utilized for forming the polyurethane foam typically has a functionality between from 2 and 3. In some embodiments, the functionality is no greater than about 2.5.
In one embodiment, the foam is prepared from at least one aromatic polyisocyanate. Examples of aromatic polyisocyanates include those having a single aromatic ring such as are toluene 2,4 and 2,6-diisocyanate (TDI) and naphthylene 1,5-diisocyanate; as well as those having at least two aromatic rings such as diphenylmethane 4,4′-, 2,4′- and 2,2′-diisocyanate (MDI).
In favored embodiments, the foam is prepared from one or more (e.g. aromatic) polymeric polyisocyanates. Polymeric polyisocyanates typically have a (weight average) molecular weight greater than a monomeric polyisocyanate (lacking repeating units), yet lower than a polyurethane prepolymer. Thus, the polyurethane foam is derived from at least one polymeric polyisocyanate that lacks urethane linkages. In other words, the polyurethane foam is derived from a polymeric isocyanate that is not a polyurethane prepolymer. Polymeric polyisocyanates comprises other linking groups between repeat units, such as isocyanurate groups, biuret groups, carbodiimide groups, uretonimine groups, uretdione groups, etc. as known in the art.
Some polymeric polyisocyanates may be referred to as “modified monomeric isocyanate”. For example pure 4,4′-methylene diphenyl diisocyanate (MDI) is a solid having a melting point of 38° C. and an equivalent weight of 125 g/equivalent. However, modified MDIs, are liquid at 38° C. and have a higher equivalent weight (e.g. 143 g/equivalent). The difference in melting point and equivalent weight is believed to be a result of a small degree of polymerization, such as by the inclusion of linking groups, as described above.
Polymeric polyisocyanates, including modified monomeric isocyanate, may comprise a mixture of monomer in combination with polymeric species inclusive of oligomeric species. For example, polymeric MDI is reported to contain 25-80% monomeric 4,4′-methylene diphenyl diisocyanate as well as oligomers containing 3-6 rings and other minor isomers, such as 2,2′ isomer.
Polymeric polyisocyanates typically have a low viscosity as compared to prepolymers. The polymeric isocyanates utilized herein typically have a viscosity no greater than about 300 cps at 25° C. and in some embodiments no greater than 200 cps or 100 cps at 25° C. The viscosity is typically at least about 10, 15, 20 or 25 cps at 25° C.
The equivalent weight of polymeric polyisocyanates is also typically lower than that of prepolymers. The polymeric isocyanates utilized herein typically have an equivalent weight of no greater than about 250 g/equivalent and in some embodiments no greater than 200 g/equivalent or 175 g/equivalent. In some embodiments, the equivalent weight is at least 130 g/equivalent.
The average molecular weight (Mw) of polymeric polyisocyanates is also typically lower than that of polyurethane prepolymers. The polymeric isocyanates utilized herein typically have an average molecular weight (Mw) of no greater than about 500 Da and in some embodiments no greater than 450, 400, or 350 Da. In some embodiments, the polyurethane is derived from a single polymeric isocyanate or a blend of polymeric isocyanates. Thus, 100% of the isocyanate component is polymeric isocyanate(s). In other embodiments, a major portion of the isocyanate component is a single polymeric isocyanate or a blend of polymeric isocyanates. In these embodiments, at least 50, 60, 70, 75, 80, 85 or 90 wt-% of the isocyanate component is polymeric isocyanate(s).
Some illustrative polyisocyanates include for example, polymeric MDI diisocyanate from Huntsman Chemical Company, The Woodlands, Tex., under the trade designation “RUBINATE 1245”; and modified MDI isocyanate available from Huntsman Chemical Company under the trade designation “SUPRASEC 9561”.
The aforementioned isocyanates are reacted with a polyol to prepare the polyurethane foam material. The polyurethane foams are hydrophilic, such that the foam absorbs aqueous liquids, particularly body fluids. The hydrophilicity of the polyurethane foams is typically provided by use of an isocyanate-reactive component, such as a polyether polyol, having a high ethylene oxide content.
Examples of useful polyols include adducts [e.g., polyethylene oxide, polypropylene oxide, and poly(ethylene oxide-propylene oxide) copolymer] of dihydric or trihydric alcohols (e.g., ethylene glycol, propylene glycol, glycerol, hexanetriol, and triethanolamine) and alkylene oxides (e.g., ethylene oxide, propylene oxide, and butylene oxide). Polyols having a high ethylene oxide content can also be made by other techniques as known in the art. Suitable polyols typically have a molecular weight (Mw) of 100 to 5,000 Da and contain an average functionality of 2 to 3.
The polyurethane foam is typically derived from (or in other words is the reaction product of) at least one polyether polyol having ethylene oxide (e.g. repeat) units. The polyether polyol typically has an ethylene oxide content of at least 10, 15, 20 or 25 wt-% and typically no greater than 75 wt-%. Such polyether polyol has a higher functionality than the polyisocyanate. In some embodiments, the average functionality is about 3. The polyether polyol typically has a viscosity of no greater than 1000 cps at 25° C. and in some embodiments no greater than 900, 800, or 700 cps. The molecular weight of the polyether polyol is typically at least 500 or 1000 Da and in some embodiments no greater than 4000 or 3500, or 3000 Da. Such polyether polyol typically has a hydroxyl number of at least 125, 130, or 140. An illustrative polyol includes for example a polyether polyol product obtained from the Carpenter Company, Richmond, Va. under the designation “CDB-33142 POLYETHER POLYOL”, “CARPOL GP-5171”.
In some embodiments, one or more polyether polyols having a high ethylene oxide content and a molecular weight (Mw) of no greater than 5500, or 5000, or 4500, or 4000, or 3500, or 3000 Da, as just described, are the primary or sole polyether polyols of the polyurethane foam. For example, such polyether polyols constitute at least 50, 60, 70, 80, 90, 95 or 100 wt-% of the total polyol component. Thus, the polyurethane foam may comprise at least 25, 30, 35, 40, 45 or 50 wt-% of polymerized units derived from such polyether polyols.
In other embodiments, one or more polyether polyols having a high ethylene oxide content are utilized in combination with other polyols. In some embodiments, the other polyols constitute at least 1, 2, 3, 4, or 5 wt-% of the total polyol component. The concentration of such other polyols typically does not exceed 40, or 35, or 30, or 25, or 20, or 15, or 10 wt-% of the total polyol component, i.e. does not exceed 20 wt-%, or 17.5 wt-%, or 15 wt-%, or 12.5 wt-%, or 10 wt-%, or 7.5 wt-%, or 5 wt-% of the polyurethane. Illustrative other polyols include a polyether polyol product (Chemical Abstracts Number 25791-96-2) that can be obtained from the Carpenter Company, Richmond, Va. under the designation “CARPOL GP-700 POLYETHER POLYOL” and a polyether polyol product (Chemical Abstracts Number 9082-00-2) that can be obtained from Bayer Material Science, Pittsburgh, Va. under the trade designation “ARCOL E-434”. In some embodiments, such optional other polyols may comprise polypropylene (e.g. repeat) units.
The polyurethane foam generally has an ethylene oxide content of at least 10, 11, or 12 wt-% and no greater than 20, 19, or 18 wt-%. In some embodiments, the polyurethane foam has an ethylene oxide content of no greater than 17 or 16 wt-%.
The kinds and amounts of polyisocyanate and polyol components are selected such that the polyurethane foam is relatively soft, yet resilient. These properties can be characterized for example by indentation force deflection and constant deflection compression set, as measured according to the test methods described in the examples. In some embodiments, the polyurethane foam has an indentation force deflection of less than 75N at 50%. The indentation force deflection at 50% may be less than 70N, or 65N, or 60 N. In some embodiments, the polyurethane foam has an indentation force deflection of less than 100N at 65%. The indentation force deflection at 65% may be less than 90N, or 80N, or 70 N, or 65N, or 60N. In some embodiments, the indentation force deflection at 50% or 65% is typically at least 30N or 35N. The constant deflection compression set at 50% deflection can be zero and is typically at least 0.5, 1 or 2% and generally no greater than 35%. In some embodiments, the constant deflection compression set at 50% deflection is no greater than 30%, or 25%, or 20%, or 15%, or 10%.
The polyurethane foam may comprise known and customary polyurethane formation catalysts such as organic tin compounds and/or an amine-type catalyst. The catalysts are preferably used in an amount of from 0.01 to 5 wt-% of the polyurethane. The amine-type catalyst is typically a tertiary amine. Examples of suitable tertiary amine include monoamines such as triethylamine, and dimethyl cyclohexylamine; diamines such as tetramethylethylenediamine, and tetramethylhexanediamine; triamines such as tetramethylguanidine; cyclic amines such as triethylenediamine, dimethylpiperadine, and methylmorphorine; alcoholamines such as dimethylaminoethanol, trimethylaminoethylethanolamine, and hydroxyethylmorphorine; ether amines such as bisdimethylaminoethyl ethanol; diazabicycloalkenes such as 1,5-diazabicyclo(5,4,0)undecene-7 (DBU), and 1,5-diazabicyclo(4,3,0)nonene-5; and organic acid salts of the diazabicycloalkenes such as phenol salt, 2-ethylhexanoate and formate of DBU. These amines can be used either singly or in combination. The amine-type catalyst can be used in an amount no greater than 4, 3, 2, 1 or 0.5 wt-% of the polyurethane.
The polyurethane typically comprises a surfactant to stabilize the foam. Various surfactants have been described in the art. In one embodiment a silicone surfactant is employed that comprises ethylene oxide (e.g. repeat) units, optionally in combination with propylene oxide (e.g. repeat) units such as commercially available from Air Products under the trade designation “DABCO DC-198”. In some embodiments, the concentration of hydrophilic surfactant typically ranges from about 0.05 to 1 or 2 wt-% of the polyurethane.
The polyurethane foam may comprise various additives such as surface active substances, foam stabilizers, cell regulators, blocking agents to delay catalytic reactions, fire retardants, chain extenders, crosslinking agents, external and internal mold release agents, fillers, pigments (titanium dioxide), colorants, optical brighteners, antioxidants, stabilizers, hydrolysis inhibitors, as well as anti-fungal and anti-bacteria substances. Such other additives are typically collectively utilized at concentrations ranging from 0.05 to 10 wt-% of the polyurethane.
In some embodiments, the absorbent foam is white in color. Certain hindered amine stabilizers can contribute to discoloration, such as yellowing, of the absorbent foam. In some embodiments, the absorbent foam is free of diphenylamine stabilizer and/or phenothiazine stabilizer.
In other embodiments, the absorbent foam may be a colored (i.e. a color other than white). The white or colored absorbent foam can include a pigment in at least one of the components. In preferred embodiments, pigment is combined with a polyol carrier and is added to the polyol liquid stream during manufacture of the polyurethane foam. Commercially available pigments include for example DispersiTech™ 2226 White, DispersiTech™2401 Violet, DispersiTech™ 2425 Blue, DispersiTech™ 2660 Yellow, and DispersiTech™ 28000 Red from Milliken in Spartansburg, S.C. and Pdi® 34-68020 Orange from Ferro in Cleveland, Ohio.
In the production of polyurethane foams, the polyisocyanate component and polyol component are reacted such that an equivalence ratio of isocyanate groups to the sum of hydroxyl groups is no greater than 1 to 1. In some embodiments, the components are reacted such that there are excess hydroxyl groups (e.g. excess polyol). In such embodiments, the equivalence ratio of isocyanate groups to the sum of the hydroxy groups is at least 0.7 to 1. For example, the ratio may be at least 0.75:1, or at least 0.8:1.
The hydrophilic (e.g. polyol(s)) component(s) of the (e.g. polyurethane) polymeric foam provide the desired absorption capacity of the foam. Thus the foam may be free of superabsorbent polymer. Further, the polyurethane foam is free of amine or imine complexing agent such as ethylenimine, polyethylenimine, polyvinylamine, carboxy-methylated polyethylenimines, phosphono-methylated polyethylenimines, quaternized polyethylenimines and/or dithiocarbamitized polyethylenimines; as described for example in U.S. Pat. No. 6,852,905 and U.S. Pat. No. 6,855,739.
The polymeric (e.g. polyurethane) foam typically has an average basis weight of at least 100, 150, 200, or 250 gsm and typically no greater than 500 gsm. In some embodiments the average basis weight is no greater than 450, or 400 gsm. The average density of the (e.g. polyurethane) polymeric foam is typically at least 3, 3.5 or 4 lbs/ft3 and no greater than 7 lbs/ft3.
In an embodiment, the open celled foam is a thermoset polymeric foam made from the polymerization of a High Internal Phase Emulsion (HIPE), also referred to as a polyHIPE. To form a HIPE, an aqueous phase and an oil phase are combined in a ratio between about 8:1 and 140:1. In certain embodiments, the aqueous phase to oil phase ratio is between about 10:1 and about 75:1, and in certain other embodiments the aqueous phase to oil phase ratio is between about 13:1 and about 65:1. This is termed the “water-to-oil” or W:O ratio and can be used to determine the density of the resulting polyHIPE foam. As discussed, the oil phase may contain one or more of monomers, comonomers, photoinitiators, crosslinkers, and emulsifiers, as well as optional components. The water phase will contain water and in certain embodiments one or more components such as electrolyte, initiator, or optional components.
The open cell foam can be formed from the combined aqueous and oil phases by subjecting these combined phases to shear agitation in a mixing chamber or mixing zone. The combined aqueous and oil phases are subjected to shear agitation to produce a stable HIPE having aqueous droplets of the desired size. An initiator may be present in the aqueous phase, or an initiator may be introduced during the foam making process, and in certain embodiments, after the HIPE has been formed. The emulsion making process produces a HIPE where the aqueous phase droplets are dispersed to such an extent that the resulting HIPE foam will have the desired structural characteristics. Emulsification of the aqueous and oil phase combination in the mixing zone may involve the use of a mixing or agitation device such as an impeller, by passing the combined aqueous and oil phases through a series of static mixers at a rate necessary to impart the requisite shear, or combinations of both. Once formed, the HIPE can then be withdrawn or pumped from the mixing zone. One method for forming HIPEs using a continuous process is described in U.S. Pat. No. 5,149,720 (DesMarais et al), issued Sep. 22, 1992; U.S. Pat. No. 5,827,909 (DesMarais) issued Oct. 27, 1998; and U.S. Pat. No. 6,369,121 (Catalfamo et al.) issued Apr. 9, 2002.
The emulsion can be withdrawn or pumped from the mixing zone and impregnated into or onto a mass prior to being fully polymerized. Once fully polymerized, the foam pieces and the elements are intertwined such that discrete foam pieces are bisected by the elements comprising the mass and such that parts of discrete foam pieces enrobe portions of one or more of the elements comprising the heterogeneous mass.
Following polymerization, the resulting foam pieces are saturated with aqueous phase that needs to be removed to obtain substantially dry foam pieces. In certain embodiments, foam pieces can be squeezed free of most of the aqueous phase by using compression, for example by running the heterogeneous mass comprising the foam pieces through one or more pairs of nip rollers. The nip rollers can be positioned such that they squeeze the aqueous phase out of the foam pieces. The nip rollers can be porous and have a vacuum applied from the inside such that they assist in drawing aqueous phase out of the foam pieces. In certain embodiments, nip rollers can be positioned in pairs, such that a first nip roller is located above a liquid permeable belt, such as a belt having pores or composed of a mesh-like material and a second opposing nip roller facing the first nip roller and located below the liquid permeable belt. One of the pair, for example the first nip roller can be pressurized while the other, for example the second nip roller, can be evacuated, so as to both blow and draw the aqueous phase out the of the foam. The nip rollers may also be heated to assist in removing the aqueous phase. In certain embodiments, nip rollers are only applied to non-rigid foams, that is, foams whose walls would not be destroyed by compressing the foam pieces.
In certain embodiments, in place of or in combination with nip rollers, the aqueous phase may be removed by sending the foam pieces through a drying zone where it is heated, exposed to a vacuum, or a combination of heat and vacuum exposure. Heat can be applied, for example, by running the foam though a forced air oven, IR oven, microwave oven or radiowave oven. The extent to which a foam is dried depends on the application. In certain embodiments, greater than 50% of the aqueous phase is removed. In certain other embodiments greater than 90%, and in still other embodiments greater than 95% of the aqueous phase is removed during the drying process.
In an embodiment, open cell foam is produced from the polymerization of the monomers having a continuous oil phase of a High Internal Phase Emulsion (HIPE). The HIPE may have two phases. One phase is a continuous oil phase having monomers that are polymerized to form a HIPE foam and an emulsifier to help stabilize the HIPE. The oil phase may also include one or more photoinitiators. The monomer component may be present in an amount of from about 80% to about 99%, and in certain embodiments from about 85% to about 95% by weight of the oil phase. The emulsifier component, which is soluble in the oil phase and suitable for forming a stable water-in-oil emulsion may be present in the oil phase in an amount of from about 1% to about 20% by weight of the oil phase. The emulsion may be formed at an emulsification temperature of from about 10° C. to about 130° C. and in certain embodiments from about 50° C. to about 100° C.
In general, the monomers will include from about 20% to about 97% by weight of the oil phase at least one substantially water-insoluble monofunctional alkyl acrylate or alkyl methacrylate. For example, monomers of this type may include C4-C18 alkyl acrylates and C2-C18 methacrylates, such as ethylhexyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, isodecyl acrylate, tetradecyl acrylate, benzyl acrylate, nonyl phenyl acrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, tetradecyl methacrylate, and octadecyl methacrylate.
The oil phase may also have from about 2% to about 40%, and in certain embodiments from about 10% to about 30%, by weight of the oil phase, a substantially water-insoluble, polyfunctional crosslinking alkyl acrylate or methacrylate. This crosslinking comonomer, or crosslinker, is added to confer strength and resilience to the resulting HIPE foam. Examples of crosslinking monomers of this type may have monomers containing two or more activated acrylate, methacrylate groups, or combinations thereof. Nonlimiting examples of this group include 1,6-hexanedioldiacrylate, 1,4-butanedioldimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,12-dodecyldimethacrylate, 1,14-tetradecanedioldimethacrylate, ethylene glycol dimethacrylate, neopentyl glycol diacrylate (2,2-dimethylpropanediol diacrylate), hexanediol acrylate methacrylate, glucose pentaacrylate, sorbitan pentaacrylate, and the like. Other examples of crosslinkers contain a mixture of acrylate and methacrylate moieties, such as ethylene glycol acrylate-methacrylate and neopentyl glycol acrylate-methacrylate. The ratio of methacrylate:acrylate group in the mixed crosslinker may be varied from 50:50 to any other ratio as needed.
Any third substantially water-insoluble comonomer may be added to the oil phase in weight percentages of from about 0% to about 15% by weight of the oil phase, in certain embodiments from about 2% to about 8%, to modify properties of the HIPE foams. In certain embodiments, “toughening” monomers may be desired which impart toughness to the resulting HIPE foam. These include monomers such as styrene, vinyl chloride, vinylidene chloride, isoprene, and chloroprene. Without being bound by theory, it is believed that such monomers aid in stabilizing the HIPE during polymerization (also known as “curing”) to provide a more homogeneous and better formed HIPE foam which results in better toughness, tensile strength, abrasion resistance, and the like. Monomers may also be added to confer flame retardancy as disclosed in U.S. Pat. No. 6,160,028 (Dyer) issued Dec. 12, 2000. Monomers may be added to confer color, for example vinyl ferrocene, fluorescent properties, radiation resistance, opacity to radiation, for example lead tetraacrylate, to disperse charge, to reflect incident infrared light, to absorb radio waves, to form a wettable surface on the HIPE foam struts, or for any other desired property in a HIPE foam. In some cases, these additional monomers may slow the overall process of conversion of HIPE to HIPE foam, the tradeoff being necessary if the desired property is to be conferred. Thus, such monomers can be used to slow down the polymerization rate of a HIPE. Examples of monomers of this type can have styrene and vinyl chloride.
The oil phase may further contain an emulsifier used for stabilizing the HIPE. Emulsifiers used in a HIPE can include: (a) sorbitan monoesters of branched C16-C24 fatty acids; linear unsaturated C16-C22 fatty acids; and linear saturated C12-C14 fatty acids, such as sorbitan monooleate, sorbitan monomyristate, and sorbitan monoesters, sorbitan monolaurate diglycerol monooleate (DGMO), polyglycerol monoisostearate (PGMIS), and polyglycerol monomyristate (PGMM); (b) polyglycerol monoesters of -branched C16-C24 fatty acids, linear unsaturated C16-C22 fatty acids, or linear saturated C12-C14 fatty acids, such as diglycerol monooleate (for example diglycerol monoesters of C18:1 fatty acids), diglycerol monomyristate, diglycerol monoisostearate, and diglycerol monoesters; (c) diglycerol monoaliphatic ethers of -branched C16-C24 alcohols, linear unsaturated C16-C22 alcohols, and linear saturated C12-C14 alcohols, and mixtures of these emulsifiers. See U.S. Pat. No. 5,287,207 (Dyer et al.), issued Feb. 7, 1995 and U.S. Pat. No. 5,500,451 (Goldman et al.) issued Mar. 19, 1996. Another emulsifier that may be used is polyglycerol succinate (PGS), which is formed from an alkyl succinate, glycerol, and triglycerol.
Such emulsifiers, and combinations thereof, may be added to the oil phase so that they can have between about 1% and about 20%, in certain embodiments from about 2% to about 15%, and in certain other embodiments from about 3% to about 12% by weight of the oil phase. In certain embodiments, coemulsifiers may also be used to provide additional control of cell size, cell size distribution, and emulsion stability, particularly at higher temperatures, for example greater than about 65° C. Examples of coemulsifiers include phosphatidyl cholines and phosphatidyl choline-containing compositions, aliphatic betaines, long chain C12-C22 dialiphatic quaternary ammonium salts, short chain C1-C4 dialiphatic quaternary ammonium salts, long chain C12-C22 dialkoyl(alkenoyl)-2-hydroxyethyl, short chain C1-C4 dialiphatic quaternary ammonium salts, long chain C12-C22 dialiphatic imidazolinium quaternary ammonium salts, short chain C1-C4 dialiphatic imidazolinium quaternary ammonium salts, long chain C12-C22 monoaliphatic benzyl quaternary ammonium salts, long chain C12-C22 dialkoyl(alkenoyl)-2-aminoethyl, short chain C1-C4 monoaliphatic benzyl quaternary ammonium salts, short chain C1-C4 monohydroxyaliphatic quaternary ammonium salts. In certain embodiments, ditallow dimethyl ammonium methyl sulfate (DTDMAMS) may be used as a coemulsifier.
The oil phase may comprise a photoinitiator at between about 0.05% and about 10%, and in certain embodiments between about 0.2% and about 10% by weight of the oil phase. Lower amounts of photoinitiator allow light to better penetrate the HIPE foam, which can provide for polymerization deeper into the HIPE foam. However, if polymerization is done in an oxygen-containing environment, there should be enough photoinitiator to initiate the polymerization and overcome oxygen inhibition. Photoinitiators can respond rapidly and efficiently to a light source with the production of radicals, cations, and other species that are capable of initiating a polymerization reaction. The photoinitiators used in the present invention may absorb UV light at wavelengths of about 200 nanometers (nm) to about 800 nm, in certain embodiments about 200 nm to about 350 nm. If the photoinitiator is in the oil phase, suitable types of oil-soluble photoinitiators include benzyl ketals, α-hydroxyalkyl phenones, α-amino alkyl phenones, and acylphospine oxides. Examples of photoinitiators include 2,4,6-[trimethylbenzoyldiphosphine]oxide in combination with 2-hydroxy-2-methyl-1-phenylpropan-1-one (50:50 blend of the two is sold by Ciba Speciality Chemicals, Ludwigshafen, Germany as DAROCUR® 4265); benzyl dimethyl ketal (sold by Ciba Geigy as IRGACURE 651); α-,α-dimethoxy-α-hydroxy acetophenone (sold by Ciba Speciality Chemicals as DAROCUR® 1173); 2-methyl-1-[4-(methyl thio)phenyl]-2-morpholino-propan-1-one (sold by Ciba Speciality Chemicals as IRGACURE® 907); 1-hydroxycyclohexyl-phenyl ketone (sold by Ciba Speciality Chemicals as IRGACURE® 184); bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (sold by Ciba Speciality Chemicals as IRGACURE 819); diethoxyacetophenone, and 4-(2-hydroxyethoxyl)phenyl-(2-hydroxy-2-methylpropyl) ketone (sold by Ciba Speciality Chemicals as IRGACURE® 2959); and Oligo [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] (sold by Lambeth spa, Gallarate, Italy as ESACURE® KIP EM.
The dispersed aqueous phase of a HIPE can have water, and may also have one or more components, such as initiator, photoinitiator, or electrolyte, wherein in certain embodiments, the one or more components are at least partially water soluble.
One component of the aqueous phase may be a water-soluble electrolyte. The water phase may contain from about 0.2% to about 40%, in certain embodiments from about 2% to about 20%, by weight of the aqueous phase of a water-soluble electrolyte. The electrolyte minimizes the tendency of monomers, comonomers, and crosslinkers that are primarily oil soluble to also dissolve in the aqueous phase. Examples of electrolytes include chlorides or sulfates of alkaline earth metals such as calcium or magnesium and chlorides or sulfates of alkali earth metals such as sodium. Such electrolyte can include a buffering agent for the control of pH during the polymerization, including such inorganic counterions as phosphate, borate, and carbonate, and mixtures thereof. Water soluble monomers may also be used in the aqueous phase, examples being acrylic acid and vinyl acetate.
Another component that may be present in the aqueous phase is a water-soluble free-radical initiator. The initiator can be present at up to about 20 mole percent based on the total moles of polymerizable monomers present in the oil phase. In certain embodiments, the initiator is present in an amount of from about 0.001 to about 10 mole percent based on the total moles of polymerizable monomers in the oil phase. Suitable initiators include ammonium persulfate, sodium persulfate, potassium persulfate, 2,2′-azobis(N,N′-dimethyleneisobutyramidine)dihydrochloride, and other suitable azo initiators. In certain embodiments, to reduce the potential for premature polymerization which may clog the emulsification system, addition of the initiator to the monomer phase may be just after or near the end of emulsification.
Photoinitiators present in the aqueous phase may be at least partially water soluble and can have between about 0.05% and about 10%, and in certain embodiments between about 0.2% and about 10% by weight of the aqueous phase. Lower amounts of photoinitiator allow light to better penetrate the HIPE foam, which can provide for polymerization deeper into the HIPE foam. However, if polymerization is done in an oxygen-containing environment, there should be enough photoinitiator to initiate the polymerization and overcome oxygen inhibition. Photoinitiators can respond rapidly and efficiently to a light source with the production of radicals, cations, and other species that are capable of initiating a polymerization reaction. The photoinitiators used in the present invention may absorb UV light at wavelengths of from about 200 nanometers (nm) to about 800 nm, in certain embodiments from about 200 nm to about 350 nm, and in certain embodiments from about 350 nm to about 450 nm. If the photoinitiator is in the aqueous phase, suitable types of water-soluble photoinitiators include benzophenones, benzils, and thioxanthones. Examples of photoinitiators include 2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride; 2,2′-Azobis[2-(2-imidazolin-2-yl)propane]disulfate dehydrate; 2,2′-Azobis(1-imino-1-pyrrolidino-2-ethylpropane)dihydrochloride; 2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide]; 2,2′-Azobis(2-methylpropionamidine)dihydrochloride; 2,2′-dicarboxymethoxydibenzal acetone, 4,4′-dicarboxymethoxydibenzalacetone, 4,4′-dicarboxymethoxydibenzalcyclohexanone, 4-dimethylamino-4′-carboxymethoxydibenzalacetone; and 4,4′-disulphoxymethoxydibenzalacetone. Other suitable photoinitiators that can be used in the present invention are listed in U.S. Pat. No. 4,824,765 (Sperry et al.) issued Apr. 25, 1989.
In addition to the previously described components other components may be included in either the aqueous or oil phase of a HIPE. Examples include antioxidants, for example hindered phenolics, hindered amine light stabilizers; plasticizers, for example dioctyl phthalate, dinonyl sebacate; flame retardants, for example halogenated hydrocarbons, phosphates, borates, inorganic salts such as antimony trioxide or ammonium phosphate or magnesium hydroxide; dyes and pigments; fluorescers; filler pieces, for example starch, titanium dioxide, carbon black, or calcium carbonate; fibers; chain transfer agents; odor absorbers, for example activated carbon particulates; dissolved polymers; dissolved oligomers; and the like.
The heterogeneous mass comprises enrobeable elements and discrete pieces of foam. The enrobeable elements may be a web such as, for example, nonwoven, a fibrous structure, an airlaid web, a wet laid web, a high loft nonwoven, a needlepunched web, a hydroentangled web, a fiber tow, a woven web, a knitted web, a flocked web, a spunbond web, a layered spunbond/melt blown web, a carded fiber web, a coform web of cellulose fiber and melt blown fibers, a coform web of staple fibers and melt blown fibers, and layered webs that are layered combinations thereof.
The enrobeable elements may be, for example, conventional absorbent materials such as creped cellulose wadding, fluffed cellulose fibers, wood pulp fibers also known as airfelt, and textile fibers. The enrobeable elements may also be fibers such as, for example, synthetic fibers, thermoplastic particulates or fibers, tricomponent fibers, and bicomponent fibers such as, for example, sheath/core fibers having the following polymer combinations: polyethylene/polypropylene, polyethylvinyl acetate/polypropylene, polyethylene/polyester, polypropylene/polyester, copolyester/polyester, and the like. The enrobeable elements may be any combination of the materials listed above and/or a plurality of the materials listed above, alone or in combination.
The enrobeable elements may be hydrophobic or hydrophilic. In an embodiment, the enrobeable elements may be treated to be made hydrophobic. In an embodiment, the enrobeable elements may be treated to become hydrophilic.
The constituent fibers of the heterogeneous mass can be comprised of polymers such as polyethylene, polypropylene, polyester, and blends thereof. The fibers can be spunbound fibers. The fibers can be meltblown fibers. The fibers can comprise cellulose, rayon, cotton, or other natural materials or blends of polymer and natural materials. The fibers can also comprise a super absorbent material such as polyacrylate or any combination of suitable materials. The fibers can be monocomponent, bicomponent, and/or biconstituent, non-round (e.g., capillary channel fibers), and can have major cross-sectional dimensions (e.g., diameter for round fibers) ranging from 0.1-500 microns. The constituent fibers of the nonwoven precursor web may also be a mixture of different fiber types, differing in such features as chemistry (e.g. polyethylene and polypropylene), components (mono- and bi-), denier (micro denier and >20 denier), shape (i.e. capillary and round) and the like. The constituent fibers can range from about 0.1 denier to about 100 denier.
In one aspect, known absorbent web materials in an as-made can be considered as being homogeneous throughout. Being homogeneous, the fluid handling properties of the absorbent web material are not location dependent, but are substantially uniform at any area of the web. Homogeneity can be characterized by density, basis weight, for example, such that the density or basis weight of any particular part of the web is substantially the same as an average density or basis weight for the web. By the apparatus and method of the present invention, homogeneous fibrous absorbent web materials are modified such that they are no longer homogeneous, but are heterogeneous, such that the fluid handling properties of the web material are location dependent. Therefore, for the heterogeneous absorbent materials of the present invention, at discrete locations the density or basis weight of the web may be substantially different than the average density or basis weight for the web. The heterogeneous nature of the absorbent web of the present invention permits the negative aspects of either of permeability or capillarity to be minimized by rendering discrete portions highly permeable and other discrete portions to have high capillarity. Likewise, the tradeoff between permeability and capillarity is managed such that delivering relatively higher permeability can be accomplished without a decrease in capillarity.
In an embodiment, the heterogeneous mass may also include superabsorbent material that imbibe fluids and form hydrogels. These materials are typically capable of absorbing large quantities of body fluids and retaining them under moderate pressures. The heterogeneous mass can include such materials dispersed in a suitable carrier such as cellulose fibers in the form of fluff or stiffened fibers.
In an embodiment, the heterogeneous mass may include thermoplastic particulates or fibers. The materials, and in particular thermoplastic fibers, can be made from a variety of thermoplastic polymers including polyolefins such as polyethylene (e.g., PULPEX®) and polypropylene, polyesters, copolyesters, and copolymers of any of the foregoing.
Depending upon the desired characteristics, suitable thermoplastic materials include hydrophobic fibers that have been made hydrophilic, such as surfactant-treated or silica-treated thermoplastic fibers derived from, for example, polyolefins such as polyethylene or polypropylene, polyacrylics, polyamides, polystyrenes, and the like. The surface of the hydrophobic thermoplastic fiber can be rendered hydrophilic by treatment with a surfactant, such as a nonionic or anionic surfactant, e.g., by spraying the fiber with a surfactant, by dipping the fiber into a surfactant or by including the surfactant as part of the polymer melt in producing the thermoplastic fiber. Upon melting and resolidification, the surfactant will tend to remain at the surfaces of the thermoplastic fiber. Suitable surfactants include nonionic surfactants such as Brij 76 manufactured by ICI Americas, Inc. of Wilmington, Del., and various surfactants sold under the Pegosperse® trademark by Glyco Chemical, Inc. of Greenwich, Conn. Besides nonionic surfactants, anionic surfactants can also be used. These surfactants can be applied to the thermoplastic fibers at levels of, for example, from about 0.2 to about 1 g. per sq. of centimeter of thermoplastic fiber.
Suitable thermoplastic fibers can be made from a single polymer (monocomponent fibers), or can be made from more than one polymer (e.g., bicomponent fibers). The polymer comprising the sheath often melts at a different, typically lower, temperature than the polymer comprising the core. As a result, these bicomponent fibers provide thermal bonding due to melting of the sheath polymer, while retaining the desirable strength characteristics of the core polymer.
Suitable bicomponent fibers for use in the present invention can include sheath/core fibers having the following polymer combinations: polyethylene/polypropylene, polyethylvinyl acetate/polypropylene, polyethylene/polyester, polypropylene/polyester, copolyester/polyester, and the like. Particularly suitable bicomponent thermoplastic fibers for use herein are those having a polypropylene or polyester core, and a lower melting copolyester, polyethylvinyl acetate or polyethylene sheath (e.g., DANAKLON®, CELBOND® or CHISSO® bicomponent fibers). These bicomponent fibers can be concentric or eccentric. As used herein, the terms “concentric” and “eccentric” refer to whether the sheath has a thickness that is even, or uneven, through the cross-sectional area of the bicomponent fiber. Eccentric bicomponent fibers can be desirable in providing more compressive strength at lower fiber thicknesses. Suitable bicomponent fibers for use herein can be either uncrimped (i.e. unbent) or crimped (i.e. bent). Bicomponent fibers can be crimped by typical textile means such as, for example, a stuffer box method or the gear crimp method to achieve a predominantly two-dimensional or “flat” crimp.
The length of bicomponent fibers can vary depending upon the particular properties desired for the fibers and the web formation process. Typically, in an airlaid web, these thermoplastic fibers have a length from about 2 mm to about 12 mm long, preferably from about 2.5 mm to about 7.5 mm long, and most preferably from about 3.0 mm to about 6.0 mm long. The properties-of these thermoplastic fibers can also be adjusted by varying the diameter (caliper) of the fibers. The diameter of these thermoplastic fibers is typically defined in terms of either denier (grams per 9000 meters) or decitex (grams per 10,000 meters). Suitable bicomponent thermoplastic fibers as used in an airlaid making machine can have a decitex in the range from about 1.0 to about 20, preferably from about 1.4 to about 10, and most preferably from about 1.7 to about 7 decitex.
The compressive modulus of these thermoplastic materials, and especially that of the thermoplastic fibers, can also be important. The compressive modulus of thermoplastic fibers is affected not only by their length and diameter, but also by the composition and properties of the polymer or polymers from which they are made, the shape and configuration of the fibers (e.g., concentric or eccentric, crimped or uncrimped), and like factors. Differences in the compressive modulus of these thermoplastic fibers can be used to alter the properties, and especially the density characteristics, of the respective thermally bonded fibrous matrix.
The heterogeneous mass can also include synthetic fibers that typically do not function as binder fibers but alter the mechanical properties of the fibrous webs. Synthetic fibers include cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylics (such as Orlon), polyvinyl acetate, non-soluble polyvinyl alcohol, polyethylene, polypropylene, polyamides (such as nylon), polyesters, bicomponent fibers, tricomponent fibers, mixtures thereof and the like. These might include, for example, polyester fibers such as polyethylene terephthalate (e.g., DACRON® and KODEL®), high melting crimped polyester fibers (e.g., KODEL® 431 made by Eastman Chemical Co.) hydrophilic nylon (HYDROFIL®), and the like. Suitable fibers can also hydrophilized hydrophobic fibers, such as surfactant-treated or silica-treated thermoplastic fibers derived from, for example, polyolefins such as polyethylene or polypropylene, polyacrylics, polyamides, polystyrenes, polyurethanes and the like. In the case of nonbonding thermoplastic fibers, their length can vary depending upon the particular properties desired for these fibers. Typically they have a length from about 0.3 to 7.5 cm, preferably from about 0.9 to about 1.5 cm. Suitable nonbonding thermoplastic fibers can have a decitex in the range of about 1.5 to about 35 decitex, more preferably from about 14 to about 20 decitex.
However structured, the total absorbent capacity of the heterogeneous mass containing foam pieces should be compatible with the design loading and the intended use of the mass. For example, when used in an absorbent article, the size and absorbent capacity of the heterogeneous mass may be varied to accommodate different uses such as incontinence pads, pantiliners, regular sanitary napkins, or overnight sanitary napkins. The heterogeneous mass can also include other optional components sometimes used in absorbent webs. For example, a reinforcing scrim can be positioned within the respective layers, or between the respective layers, of the heterogeneous mass.
The heterogeneous mass comprising open cell foam pieces produced from the present invention may be used as an absorbent core or a portion of an absorbent core in absorbent articles, such as feminine hygiene articles, for example pads, pantiliners, and tampons; disposable diapers; incontinence articles, for example pads, adult diapers; homecare articles, for example wipes, pads, towels; and beauty care articles, for example pads, wipes, and skin care articles, such as used for pore cleaning.
In one embodiment the heterogeneous mass may be used as an absorbent core for an absorbent article. In such an embodiment, the absorbent core can be relatively thin, less than about 5 mm in thickness, or less than about 3 mm, or less than about 1 mm in thickness. Cores having a thickness of greater than 5 mm are also contemplated herein. Thickness can be determined by measuring the thickness at the midpoint along the longitudinal centerline of the pad by any means known in the art for doing while under a uniform pressure of 0.25 psi. The absorbent core can comprise absorbent gelling materials (AGM), including AGM fibers, as is known in the art.
The heterogeneous mass may be formed or cut to a shape, the outer edges of which define a periphery. Additionally, the heterogeneous mass may be continuous such that it may be rolled or wound upon itself, with or without the inclusion of preformed cut lines demarcating the heterogeneous mass into preformed sections.
When used as an absorbent core, the shape of the heterogeneous mass can be generally rectangular, circular, oval, elliptical, or the like. Absorbent core can be generally centered with respect to the longitudinal centerline and transverse centerline of an absorbent article. The profile of absorbent core can be such that more absorbent is disposed near the center of the absorbent article. For example, the absorbent core can be thicker in the middle, and tapered at the edges in a variety of ways known in the art.
In an embodiment, the heterogeneous mass may be used to deliver actives to the user. Actives may be integrated into the open cell foam pieces, the enrobeable elements or the interphase between the enrobeable elements and the open cell foam pieces. The active agents may be disinfectants, antimicrobials, anti-proliferative agents, anti-inflammatory agents that could be directed to combat bacteria, viruses, and/or fungi, or treat another medical condition. The active agents may also include probiotics and prebiotics that could be directed to aide in the growth of a more preferred microbial environment. Suitable volatile active agents include, but are not limited to, essential oils, alcohols, and retinoids.
Desirably, the active agent may be an essential oil derived from 100% natural fats and oils that are derived from natural plant sources. Suitable natural fats or oils can include citrus oil, olive oil, avocado oil, apricot oil, babassu oil, borage oil, camellia oil, canola oil, castor oil, coconut oil, corn oil, cottonseed oil, evening primrose oil, green tea oil, hydrogenated cottonseed oil, hydrogenated palm kernel oil, jojoba oil, maleated soybean oil, meadowfoam seed oil, palm kernel oil, peanut oil, rapeseed oil, grapeseed oil, safflower oil, sweet almond oil, tall oil, lauric acid, palmitic acid, stearic acid, linoleic acid, stearyl alcohol, lauryl alcohol, myristyl alcohol, behenyl alcohol, rose hip oil, calendula oil, chamomile oil, eucalyptus oil, juniper oil, sandalwood oil, tea tree oil, sunflower oil, soybean oil, thyme oil, peppermint oil, spearmint oil, basil oil, anise oil, menthol, camphor, turpentine oil, ylang ylang oil, rosemary oil, lavender oil, sandalwood oil, cinnamon oil, marojoram oil, cajuput oil, lemongrass oil, orange oil, grapefruit oil, lemon oil, fennel oil, ginger oil, marjoram oil, pine oil, clove oil, oregano oil, rosewood oil, sage oil, parsley oil, myrrh oil, mugwort oil, elderberry oil, cedarwood oil, and combinations thereof. The active agent may be the volatile disinfectant, thymol. Thymol is an effective antimicrobial agent with proven efficacy against yeast, mold and mycobacteria.
Other active agents that may also be useful with the delivery agent include, but are not to be limited to, a-pinene, b-pinene, sabinene, myrcene, a-phellandrene, a-terpinene, limonene, 1,8-cineole, y-terpinene, p-cymene, terpinolene, linalool, terpinen-4-ol, a-terpineol, carvone, myrcene, caryophyllene, menthol, citronellal, geranyl acetate, nerol, geraniol, neral, citral, and combinations thereof.
An effective amount of an active agent would be at an amount necessary within the composition to produce the desired end benefit upon delivery to the surface. Typically, the delivery compositions comprise the active agent in an amount of from about 0.01% by weight of the delivery composition to about 5.0% by weight of the delivery composition, more typically from about 0.01% by weight of the delivery composition to about 4.0% by weight of the delivery composition, and more typically from about 0.01% by weight of the delivery composition to about 3.0% by weight of the delivery composition.
The delivery composition may be formulated with one or more conventional pharmaceutically-acceptable and compatible carrier materials to form a personal care delivery composition. The personal care delivery composition may take a variety of forms including, without limitation, aqueous solutions, gels, balms, lotions, suspensions, creams, milks, salves, ointments, sprays, foams, solid sticks, aerosols, and the like. The carrier is preferably anhydrous such that the carrier has typically less than 15% water present, more typically less than 10% water present, and even more typically less that 5% water present. Use of an anhydrous carrier avoids activating the water-triggerable matrix and releasing the active agents or expelling agents entrapped therein. The anhydrous carrier could include, but not be limited to, one or blends of the following ingredient types: fatty acids, fatty alcohols, surfactants, emollients, moisturizers, humectants, natural oils (vegetable derived), synthetic oils (petroleum derived), silicone oils, cosmetic emollient oils (including esters, ethers, hydrocarbons, etc.) as described below.
Examples of such suitable agents include emollients, sterols or sterol derivatives, natural and synthetic fats or oils, viscosity enhancers, rheology modifiers, polyols, surfactants, alcohols, esters, silicones, clays, starch, cellulose, particulates, moisturizers, film formers, slip modifiers, surface modifiers, skin protectants, humectants, sunscreens, and the like.
Thus, the delivery compositions may further optionally include one or more emollient, which typically acts to soften, soothe, and otherwise lubricate and/or moisturize the skin. Suitable emollients that can be incorporated into the compositions include oils such as petrolatum based oils, natural oils, petrolatum, mineral oils, alkyl dimethicones, alkyl methicones, alkyldimethicone copolyols, phenyl silicones, alkyl trimethylsilanes, dimethicone, dimethicone crosspolymers, cyclomethicone, lanolin and its derivatives, glycerol esters and derivatives, propylene glycol esters and derivatives, alkoxylated carboxylic acids, alkoxylated alcohols, and combinations thereof.
Ethers such as eucalyptol, ceteraryl glucoside, dimethyl isosorbic polyglyceryl-3 cetyl ether, polyglyceryl-3 decyltetradecanol, propylene glycol myristyl ether, and combinations thereof, can also suitably be used as emollients.
The delivery composition may include one or more emollient in an amount of from about 0.01% by weight of the delivery composition to about 70% by weight of the delivery composition, more desirably from about 0.05% by weight of the delivery composition to about 50% by weight of the delivery composition, and even more desirably from about 0.10% by weight of the delivery composition to about 40% by weight of the delivery composition. In instances wherein the composition is used in combination with a wet wipe, the composition may include an emollient in an amount of from about 0.01% by weight of the delivery composition to about 20% by weight of the delivery composition, more desirably from about 0.05% by weight of the delivery composition to about 10% by weight of the delivery composition, and more typically from about 0.1% by weight of the delivery composition to about 5.0% by weight of the delivery composition. Optionally, one or more viscosity enhancers may be added to the personal care composition to increase the viscosity, to help stabilize the composition, such as when the composition is incorporated into a personal care product, thereby reducing migration of the composition and improve transfer to the skin. Suitable viscosity enhancers include polyolefin resins, lipophilic/oil thickeners, polyethylene, silica, silica silylate, silica methyl silylate, colloidal silicone dioxide, cetyl hydroxy ethyl cellulose, other organically modified celluloses, PVP/decane copolymer, PVM/MA decadiene crosspolymer, PVP/eicosene copolymer, PVP/hexadecane copolymer, clays, carbomers, acrylate based thickeners, surfactant thickeners, and combinations thereof.
The delivery composition may desirably include one or more viscosity enhancers in an amount of from about 0.01% by weight of the delivery composition to about 25% by weight of the delivery composition, more desirably from about 0.05% by weight of the delivery composition to about 10% by weight of the delivery composition, and even more desirably from about 0.1% by weight of the delivery composition to about 5% by weight of the delivery composition.
The delivery composition may optionally further contain rheology modifiers. Rheology modifiers may help increase the melt point viscosity of the composition so that the composition readily remains on the surface of a personal care product.
Suitable rheology modifiers include combinations of alpha-olefins and styrene alone or in combination with mineral oil or petrolatum, combinations of di-functional alpha-olefins and styrene alone or in combination with mineral oil or petrolatum, combinations of alpha-olefins and isobutene alone or in combination with mineral oil or petrolatum, ethylene/propylene/styrene copolymers alone or in combination with mineral oil or petrolatum, butylene/ethylene/styrene copolymers alone or in combination with mineral oil or petrolatum, ethylene/vinyl acetate copolymers, polyethylene polyisobutylenes, polyisobutenes, polyisobutylene, dextrin palmitate, dextrin palmitate ethylhexanoate, stearoyl inulin, stearalkonium bentonite, distearadimonium hectorite, and stearalkonium hectorite, styrene/butadiene/styrene copolymers, styrene/isoprene/styrene copolymers, styrene-ethylene/butylene-styrene copolymers, styrene-ethylene/propylene-styrene copolymers, (styrene-butadiene) n-polymers, (styrene-isoprene) n-polymers, styrene-butadiene copolymers, and styrene-ethylene/propylene copolymers and combinations thereof. Specifically, rheology enhancers such as mineral oil and ethylene/propylene/styrene copolymers, and mineral oil and butylene/ethylene/styrene copolymers are particularly desirable.
The delivery composition can suitably include one or more rheology modifier in an amount of from about 0.1% by weight of the delivery composition to about 5% by weight of the delivery composition.
The delivery composition may optionally further contain humectants. Examples of suitable humectants include glycerin, glycerin derivatives, sodium hyaluronate, betaine, amino acids, glycosaminoglycans, honey, sorbitol, glycols, polyols, sugars, hydrogenated starch hydrolysates, salts of PCA, lactic acid, lactates, and urea. A particularly preferred humectant is glycerin. The delivery composition may suitably include one or more humectants in an amount of from about 0.05 by weight of the delivery composition to about 25% by weight of the delivery composition.
The delivery composition of the disclosure may optionally further contain film formers. Examples of suitable film formers include lanolin derivatives (e.g., acetylated lanolins), superfatted oils, cyclomethicone, cyclopentasiloxane, dimethicone, synthetic and biological polymers, proteins, quaternary ammonium materials, starches, gums, cellulosics, polysaccharides, albumen, acrylates derivatives, IPDI derivatives, and the like. The composition of the present disclosure may suitably include one or more film former in an amount of from about 0.01% by weight of the delivery composition to about 20% by weight of the delivery composition.
The delivery composition may optionally further contain slip modifiers. Examples of suitable slip modifiers include bismuth oxychloride, iron oxide, mica, surface treated mica, ZnO, ZrO2, silica, silica silyate, colloidal silica, attapulgite, sepiolite, starches (i.e. corn, tapioca, rice), cellulosics, nylon-12, nylon-6, polyethylene, talc, styrene, polystyrene, polypropylene, ethylene/acrylic acid copolymer, acrylates, acrylate copolymers (methylmethacrylate crosspolymer), sericite, titanium dioxide, aluminum oxide, silicone resin, barium sulfate, calcium carbonate, cellulose acetate, polymethyl methacrylate, polymethylsilsequioxane, talc, tetrafluoroethylene, silk powder, boron nitride, lauroyl lysine, synthetic oils, natural oils, esters, silicones, glycols, and the like. The composition of the present disclosure may suitably include one or more slip modifier in an amount of from about 0.01% by weight of the delivery composition to about 20% by weight of the delivery composition.
The delivery composition may also further contain surface modifiers. Examples of suitable surface modifiers include silicones, quaternium materials, powders, salts, peptides, polymers, clays, and glyceryl esters. The composition of the present disclosure may suitably include one or more surface modifier in an amount of from about 0.01% by weight of the delivery composition to about 20% by weight of the delivery composition.
The delivery composition may also further contain skin protectants. Examples of suitable skin protectants include ingredients referenced in SP monograph (21 CFR part 347). Suitable skin protectants and amounts include those set forth in SP monograph, Subpart B—Active Ingredients Sec 347.10: (a) Allantoin, 0.5 to 2%, (b) Aluminum hydroxide gel, 0.15 to 5%, (c) Calamine, 1 to 25%, (d) Cocoa butter, 50 to 100%, (e) Cod liver oil, 5 to 13.56%, in accordance with 347.20(a)(1) or (a)(2), provided the product is labeled so that the quantity used in a 24-hour period does not exceed 10,000 U.S. P. Units vitamin A and 400 U.S. P. Units cholecalciferol, (f) Colloidal oatmeal, 0.007% minimum; 0.003% minimum in combination with mineral oil in accordance with §347.20(a)(4), (g) Dimethicone, 1 to 30%, (h) Glycerin, 20 to 45%, (i) Hard fat, 50 to 100%, (j) Kaolin, 4 to 20%, (k) Lanolin, 12.5 to 50%, (l) Mineral oil, 50 to 100%; 30 to 35% in combination with colloidal oatmeal in accordance with §347.20(a)(4), (m) Petrolatum, 30 to 100%, (o) Sodium bicarbonate, (q) Topical starch, 10 to 98%, (r) White petrolatum, 30 to 100%, (s) Zinc acetate, 0.1 to 2%, (t) Zinc carbonate, 0.2 to 2%, (u) Zinc oxide, 1 to 25%.
The delivery composition may also further contain sunscreens. Examples of suitable sunscreens include aminobenzoic acid, avobenzone, cinoxate, dioxybenzone, homosalate, menthyl anthranilate, octocrylene, octinoxate, octisalate, oxybenzone, padimate 0, phenylbenzimidazole sulfonic acid, sulisobenzone, titanium dioxide, trolamine salicylate, zinc oxide, and combinations thereof. Other suitable sunscreens and amounts include those approved by the FDA, as described in the Final Over-the-Counter Drug Products Monograph on Sunscreens (Federal Register, 1999:64:27666-27693), herein incorporated by reference, as well as European Union approved sunscreens and amounts.
The delivery composition may also further contain quaternary ammonium materials. Examples of suitable quaternary ammonium materials include polyquaternium-7, polyquatemium-10, benzalkonium chloride, behentrimonium methosulfate, cetrimonium chloride, cocamidopropyl pg-dimonium chloride, guar hydroxypropyltrimonium chloride, isostearamidopropyl morpholine lactate, polyquatemium-33, polyquaternium-60, polyquaternium-79, quaternium-18 hectorite, quaternium-79 hydrolyzed silk, quaternium-79 hydrolyzed soy protein, rapeseed amidopropyl ethyldimonium ethosulfate, silicone quaternium-7, stearalkonium chloride, palmitamidopropyltrimonium chloride, butylglucosides, hydroxypropyltrimonium chloride, laurdimoniumhydroxypropyl decylglucosides chloride, and the like. The composition of the present disclosure may suitably include one or more quaternary material in an amount of from about 0.01% by weight of the delivery composition to about 20% by weight of the delivery composition.
The delivery composition may optionally further contain surfactants. Examples of suitable additional surfactants include, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, zwitterionic surfactants, non-ionic surfactants, and combinations thereof. Specific examples of suitable surfactants are known in the art and include those suitable for incorporation into personal care compositions and wipes. The composition of the present disclosure may suitably include one or more surfactants in an amount of from about 0.01% by weight of the delivery composition to about 20% by weight of the delivery composition.
The delivery composition may also further contain additional emulsifiers. As mentioned above, the natural fatty acids, esters and alcohols and their derivatives, and combinations thereof, may act as emulsifiers in the composition. Optionally, the composition may contain an additional emulsifier other than the natural fatty acids, esters and alcohols and their derivatives, and combinations thereof. Examples of suitable emulsifiers include nonionics such as polysorbate 20, polysorbate 80, anionics such as DEA phosphate, cationics such as behentrimonium methosulfate, and the like. The composition of the present disclosure may suitably include one or more additional emulsifier in an amount of from about 0.01% by weight of the delivery composition to about 20% by weight of the delivery composition.
The delivery composition may additionally include adjunct components conventionally found in pharmaceutical compositions in their art-established fashion and at their art-established levels. For example, the compositions may contain additional compatible pharmaceutically active materials for combination therapy, such as antimicrobials, antioxidants, anti-parasitic agents, antipruritics, antifungals, antiseptic actives, biological actives, astringents, keratolytic actives, local anesthetics, anti-stinging agents, anti-reddening agents, skin soothing agents, and combinations thereof. Other suitable additives that may be included in the compositions of the present disclosure include colorants, deodorants, fragrances, perfumes, emulsifiers, anti-foaming agents, lubricants, natural moisturizing agents, skin conditioning agents, skin protectants and other skin benefit agents (e.g., extracts such as aloe vera and anti-aging agents such as peptides), solvents, solubilizing agents, suspending agents, wetting agents, humectants, preservatives, pH adjusters, buffering agents, dyes and/or pigments, and combinations thereof.
Components of the disposable absorbent article (i.e., diaper, disposable pant, adult incontinence article, sanitary napkin, pantiliner, etc.) described in this specification can at least partially be comprised of bio-sourced content as described in US 2007/0219521A1 Hird et al published on Sep. 20, 2007, US 2011/0139658A1 Hird et al published on Jun. 16, 2011, US 2011/0139657A1 Hird et al published on Jun. 16, 2011, US 2011/0152812A1 Hird et al published on Jun. 23, 2011, US 2011/0139662A1 Hird et al published on Jun. 16, 2011, and US 2011/0139659A1 Hird et al published on Jun. 16, 2011. These components include, but are not limited to, topsheet nonwovens, backsheet films, backsheet nonwovens, side panel nonwovens, barrier leg cuff nonwovens, super absorbent, nonwoven acquisition layers, core wrap nonwovens, adhesives, fastener hooks, and fastener landing zone nonwovens and film bases.
In at least one embodiment, a disposable absorbent article component comprises a bio-based content value from about 10% to about 100% using ASTM D6866-10, method B, in another embodiment, from about 25% to about 75%, and in yet another embodiment, from about 50% to about 60% using ASTM D6866-10, method B.
In order to apply the methodology of ASTM D6866-10 to determine the bio-based content of any disposable absorbent article component, a representative sample of the disposable absorbent article component must be obtained for testing. In at least one embodiment, the disposable absorbent article component can be ground into particulates less than about 20 mesh using known grinding methods (e.g., Wiley® mill), and a representative sample of suitable mass taken from the randomly mixed particles.
In at least one embodiment, a foam piece or an enrobeable element comprises a bio-based content value from about 10% to about 100% using ASTM D6866-10, method B, in another embodiment, from about 25% to about 75%, and in yet another embodiment, from about 50% to about 60%. Foam pieces may be made from bio-based content such as monomers as described in US2012/0108692 A1 Dyer published May 3, 2012.
In order to apply the methodology of ASTM D6866-10 to determine the bio-based content of any foam piece or enrobeable element, a representative sample of the foam piece or the enrobeable element must be obtained for testing. In at least one embodiment, the foam piece or the enrobeable element can be ground into particulates less than about 20 mesh using known grinding methods (e.g., Wiley® mill), and a representative sample of suitable mass taken from the randomly mixed particles.
Validation of Polymers Derived from Renewable Resources
A suitable validation technique is through 14C analysis. A small amount of the carbon dioxide in the atmosphere is radioactive. This 14C carbon dioxide is created when nitrogen is struck by an ultra-violet light produced neutron, causing the nitrogen to lose a proton and form carbon of molecular weight 14 which is immediately oxidized to carbon dioxide. This radioactive isotope represents a small but measurable fraction of atmospheric carbon. Atmospheric carbon dioxide is cycled by green plants to make organic molecules during photosynthesis. The cycle is completed when the green plants or other forms of life metabolize the organic molecules, thereby producing carbon dioxide which is released back to the atmosphere. Virtually all forms of life on Earth depend on this green plant production of organic molecules to grow and reproduce. Therefore, the 14C that exists in the atmosphere becomes part of all life forms, and their biological products. In contrast, fossil fuel based carbon does not have the signature radiocarbon ratio of atmospheric carbon dioxide.
Assessment of the renewably based carbon in a material can be performed through standard test methods. Using radiocarbon and isotope ratio mass spectrometry analysis, the bio-based content of materials can be determined. ASTM International, formally known as the American Society for Testing and Materials, has established a standard method for assessing the bio-based content of materials. The ASTM method is designated ASTM D6866-10.
The application of ASTM D6866-10 to derive a “bio-based content” is built on the same concepts as radiocarbon dating, but without use of the age equations. The analysis is performed by deriving a ratio of the amount of organic radiocarbon (14C) in an unknown sample to that of a modern reference standard. The ratio is reported as a percentage with the units “pMC” (percent modern carbon).
The modern reference standard used in radiocarbon dating is a NIST (National Institute of Standards and Technology) standard with a known radiocarbon content equivalent approximately to the year AD 1950. AD 1950 was chosen since it represented a time prior to thermo-nuclear weapons testing which introduced large amounts of excess radiocarbon into the atmosphere with each explosion (termed “bomb carbon”). The AD 1950 reference represents 100 pMC.
“Bomb carbon” in the atmosphere reached almost twice normal levels in 1963 at the peak of testing and prior to the treaty halting the testing. Its distribution within the atmosphere has been approximated since its appearance, showing values that are greater than 100 pMC for plants and animals living since AD 1950. It's gradually decreased over time with today's value being near 107.5 pMC. This means that a fresh biomass material such as corn could give a radiocarbon signature near 107.5 pMC.
Combining fossil carbon with present day carbon into a material will result in a dilution of the present day pMC content. By presuming 107.5 pMC represents present day biomass materials and 0 pMC represents petroleum derivatives, the measured pMC value for that material will reflect the proportions of the two component types. A material derived 100% from present day soybeans would give a radiocarbon signature near 107.5 pMC. If that material was diluted with 50% petroleum derivatives, for example, it would give a radiocarbon signature near 54 pMC (assuming the petroleum derivatives have the same percentage of carbon as the soybeans).
A biomass content result is derived by assigning 100% equal to 107.5 pMC and 0% equal to 0 pMC. In this regard, a sample measuring 99 pMC will give an equivalent bio-based content value of 92%.
Assessment of the materials described herein can be done in accordance with ASTM D6866. The mean values quoted in this report encompasses an absolute range of 6% (plus and minus 3% on either side of the bio-based content value) to account for variations in end-component radiocarbon signatures. It is presumed that all materials are present day or fossil in origin and that the desired result is the amount of biobased component “present” in the material, not the amount of biobased material “used” in the manufacturing process.
The heterogeneous mass may serve as any portion of an absorbent article. In an embodiment, the heterogeneous mass may serve as the absorbent core of an absorbent article. In an embodiment, the heterogeneous mass may serve as a portion of the absorbent core of an absorbent article. In an embodiment, more than one heterogeneous mass may be combined wherein each heterogeneous mass differs from at least one other heterogeneous mass in either the choice of enrobeable elements or by a characteristic of its open cell foam pieces. The different two or more heterogeneous masses may be combined to form an absorbent core. The absorbent article may further comprise a topsheet and a backsheet.
In an embodiment, the heterogeneous mass may be used as a topsheet for an absorbent article. The heterogeneous mass may be combined with an absorbent core or may only be combined with a backsheet.
In an embodiment, the heterogeneous mass may be combined with any other type of absorbent layer such as, for example, a layer of cellulose, a layer comprising superabsorbent gelling materials, a layer of absorbent airlaid fibers, or a layer of absorbent foam. Other absorbent layers not listed are contemplated herein.
In an embodiment, the heterogeneous mass may be utilized by itself for the absorption of fluids without placing it into an absorbent article.
According to an embodiment, an absorbent article can comprise a liquid pervious topsheet. The topsheet suitable for use herein can comprise wovens, non-wovens, and/or three-dimensional webs of a liquid impermeable polymeric film comprising liquid permeable apertures. The topsheet for use herein can be a single layer or may have a multiplicity of layers. For example, the wearer-facing and contacting surface can be provided by a film material having apertures which are provided to facilitate liquid transport from the wearer facing surface towards the absorbent structure. Such liquid permeable, apertured films are well known in the art. They provide a resilient three-dimensional fibre-like structure. Such films have been disclosed in detail for example in U.S. Pat. No. 3,929,135, U.S. Pat. No. 4,151,240, U.S. Pat. No. 4,319,868, U.S. Pat. No. 4,324,426, U.S. Pat. No. 4,343,314, U.S. Pat. No. 4,591,523, U.S. Pat. No. 4,609,518, U.S. Pat. No. 4,629,643, U.S. Pat. No. 4,695,422 or WO 96/00548.
The absorbent articles of
Especially when the absorbent article finds utility as a sanitary napkin or panty liner, the absorbent article can be also provided with a panty fastening means, which provides means to attach the article to an undergarment, for example a panty fastening adhesive on the garment facing surface of the backsheet. Wings or side flaps meant to fold around the crotch edge of an undergarment can be also provided on the side edges of the napkin.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical 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.”
Values disclosed herein as ends of ranges are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each numerical range is intended to mean both the recited values and any integers within the range. For example, a range disclosed as “1 to 10” is intended to mean “1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.”
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 document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this 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.
| Number | Date | Country | |
|---|---|---|---|
| 62001960 | May 2014 | US | |
| 62115921 | Feb 2015 | US |
