Dual texture absorbent nonwoven web

FIELD OF THE INVENTION

[0001] The present invention relates to a dual texture coform nonwoven web prepared from thermoplastic meltblown filaments and at least one secondary material. The dual texture coform nonwoven web is useful as cleaning pads, wipes, and mops, among other articles of manufacture. One surface of the dual texture coform nonwoven web contains coarse meltblown filaments, which impart an abrasive characteristic to this surface of the nonwoven web, and the secondary material and the other surface contains fine meltblown filaments, which impart a non-abrasive or soft surface to the nonwoven web, and the secondary material. The present invention also relates to a process of producing the dual texture coform nonwoven web, a method of using the dual texture coform nonwoven web as a wipe, a mop and the like, along with cleaning kits containing the coform nonwoven web.

BACKGROUND OF THE INVENTION

[0002] Coform nonwoven webs or coform materials are known in the art and have been used in a wide variety of applications, including wipes. The term “coform material” means a composite material containing a mixture or stabilized matrix of thermoplastic filaments and at least one additional material, often called the “second material” or “secondary material”. Examples of the second material include, for example, absorbent fibrous organic materials such as woody and non-wood pulp from, for example, cotton, rayon, recycled paper, pulp fluff; superabsorbent materials such as superabsorbent particles and fibers; inorganic absorbent materials and treated polymeric staple fibers, and other materials such as non-absorbent staple fibers and non-absorbent particles and the like. Exemplary coform materials are disclosed in commonly assigned U.S. Pat. No. 5,350,624 to Georger et al.; U.S. Pat. No. 4,100,324 to Anderson et al. and U.S. Pat. No. 4,818,464 to Lau et al.

[0003] Dual texture nonwoven webs are also known in the art, and are described in, for example, U.S. Pat. No. 4,659,609 to Lamers et al., U.S. Pat. No. 5,639,541 to Adam, both of which are hereby incorporated by reference in their entirety. In Lamers et al., a layered nonwoven web is formed, and this layered nonwoven has a layer of coarse fibers meltblown onto a support substrate. The support substrate can be a wide variety of substrates, including substrates containing a combination of polymers and other fibers, such as cellulosic fibers. The coarse fibers of Lamers et al. have an average fiber diameter above 40 microns. In addition, the coarse fibers are in a separate layer of the layered nonwoven web and this coarse fiber layer does not contain a secondary material. That is, the coarse fibers are used alone in the coarse layer of Lamers. In Adam, a layered meltblown nonwoven web is produced by laying down layers of meltblown fibers, wherein at least one layer contains fine microfibers and at least one layer contains coarse fibers, having an average diameter between about 8 and 23 microns. The nonwoven web of Adam is used as an abrasion resistant, oil absorbent mat. The coarse fibers of Adam improve the durability of the nonwoven web and, like Lamers et al., are in a separate layer from the other fibers of the nonwoven web.

[0004] Coform nonwoven webs have been used in applications such as disposable absorbent articles, absorbent dry wipes, wet wipes, wet mops and dry mops. However, the prior coform materials did not have an abrasive surface to provide a scrubbing or scouring ability to the nonwoven web, wherein abrasive fibers or coarse fiber were integrated into secondary material.

[0005] There is a need in the art for a nonwoven web which can be used in absorbent dry wipes, wet wipes and wet or dry mops which provide a scrubbing or scouring ability along with a soft surface for general wiping, having an effective pick-up of dirt and debris.

SUMMARY OF THE INVENTION

[0006] The present invention provides a dual texture nonwoven web having a matrix containing 1) thermoplastic meltblown filaments and 2) at least one secondary material. The dual texture coform nonwoven web has a first exterior surface and a second exterior surface, wherein the first exterior surface has fine thermoplastic meltblown filaments having an average fiber diameter of less than about 15 microns and the secondary material; and the second exterior surface has coarse thermoplastic meltblown filaments having an average fiber diameter greater than about 15 microns and the secondary material.

[0007] In further aspects of the present invention, the first and second surfaces may contain both the fine filaments and the coarse filaments. That is, the first surface and the second surface both contain a matrix containing coarse filaments, fine filaments and at least one secondary material. In addition, the coarse filaments may be present is a gradient fashion, decreasing in weight percentage from the second surface towards the first surface.

[0008] The present invention also provides methods for producing the dual texture coform nonwoven web. One method for preparing a dual texture coform nonwoven web has the steps of:

[0009] a. providing a first stream of thermoplastic meltblown filaments having an average diameter of less than about 15 microns;

[0010] b. providing a second stream of thermoplastic meltblown filaments having an average diameter greater than about 15 microns;

[0011] c. converging the first stream of thermoplastic meltblown filaments and the second stream of thermoplastic meltblown filaments in an intersecting relationship to form an impingement zone;

[0012] d. introducing a stream containing at least one secondary material between the first and second streams of the thermoplastic meltblown filaments at or near the impingement zone to form a composite stream; and

[0013] e. depositing the composite stream onto a forming surface as a matrix of thermoplastic meltblown filaments and at least one secondary material to form a nonwoven web containing a first and a second exterior surface; the first exterior surface contains fine thermoplastic meltblown fibers having average diameter of less than about 15 microns and the secondary material, and the second exterior surface contains coarse thermoplastic meltblown fibers having an average diameter greater than about 15 microns and the secondary material.

[0014] Another method for producing the coform nonwoven web of the present invention includes the steps of:

[0015] a. providing a first stream of thermoplastic meltblown filaments;

[0016] b. introducing a stream containing at least one secondary material to the first stream of thermoplastic meltblown filaments to form a first composite stream;

[0017] c. providing a second stream of thermoplastic meltblown filaments;

[0018] d. introducing a stream at least one secondary material to the second stream of meltblown filaments to form a second composite stream;

[0019] e. depositing the first composite stream onto a forming surface as a matrix of thermoplastic meltblown filaments and at least one secondary material to form a first deposited layer; and

[0020] f. depositing the second composite stream onto the first deposited layer as a matrix of thermoplastic meltblown filaments and at least one secondary material to form a dual texture coform nonwoven web;

[0021] wherein one of the first stream of thermoplastic meltblown filaments or the second stream of thermoplastic meltblown filaments contains thermoplastic meltblown filaments having average diameter of less than about 15 microns and the other of the first stream of thermoplastic meltblown fibers or the second stream of thermoplastic meltblown fibers contains thermoplastic meltblown filaments having an average diameter greater than about 15 microns.

[0022] The dual texture coform nonwoven webs and laminates of the present invention are useful as dry wipes, absorbent wipes, pre-moistened wipes, dry mops, absorbent mops, pre-moistened mops, among other absorbent articles of manufacture.

[0023] The present invention also relates to a cleaning implement comprising a handle; a head; and a removable cleaning sheet; wherein the head is connected to the handle and the removable cleaning sheet is removably attached to the head. The cleaning sheet is prepared from the dual texture coform nonwoven web described above.

[0024] A further aspect of the present invention relates to a method of cleaning a surface by contacting and wiping the surface with the dual texture coform nonwoven web of the present invention.

[0025] The present invention also relates to a kit containing the cleaning implement of the present invention and a plurality of wipes or mops of the present invention.

[0026] In another aspect of the present invention, a stack of individual coform nonwoven webs which are premoistened is also provided. The stack of webs can be used as wipes or mops and can be removed from a container holding the stack of the material one or more at a time.

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0027]
FIG. 1 illustrates a process which can be used to prepare the dual texture nonwoven web of the present invention.

[0028]
FIG. 2 illustrates a second process which may be used to prepare a dual texture coform nonwoven web laminate of the present invention.

[0029]
FIG. 3 illustrates a cleaning implement of the present invention.

[0030]
FIG. 4 is a micrograph of the structure of a dual texture coform nonwoven web of the present invention.

DEFINITIONS

[0031] As used herein, the term “comprising” is inclusive or open-ended and does not exclude additional unrecited elements, compositional components, or method steps.

[0032] As used herein, the term “fiber” includes both staple fibers, i.e., fibers which have a defined length between about 2 and about 20 mm, fibers longer than staple fiber but are not continuous, and continuous fibers, which are sometimes called “substantially continuous filaments” or simply “filaments”. The method in which the fiber is prepared will determine if the fiber is a staple fiber or a continuous filament.

[0033] As used herein, the term “nonwoven web” means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a knitted web. Nonwoven webs have been formed from many processes, such as, for example, meltblowing processes, spunbonding processes, air-laying processes, coforming processes and bonded carded web processes. The basis weight of nonwoven webs is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns, or in the case of staple fibers, denier. It is noted that to convert from osy to gsm, multiply osy by 33.91.

[0034] As used herein, the term “meltblown fibers” means fibers 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 hot, gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin, which is hereby incorporated by reference in its entirety. Meltblown fibers are microfibers, which may be continuous or discontinuous, and are generally smaller than 10 microns in average diameter, and are generally tacky when deposited onto a collecting surface.

[0035] As used herein, the term “coform nonwoven web” or “coform material” means composite materials comprising a mixture or stabilized matrix of thermoplastic filaments and at least one additional material, usually called the “second material” or the “secondary material”. As an example, coform materials may be made by a process in which at least one meltblown die head is arranged near a chute through which the second material is added to the web while it is forming. The second material may be, for example, an absorbent material such as fibrous organic materials such as woody and non-wood pulp such as cotton, rayon, recycled paper, pulp fluff; superabsorbent materials such as superabsorbent particles and fibers; inorganic absorbent materials and treated polymeric staple fibers and the like; or a non-absorbent material, such as non-absorbent staple fibers or non-absorbent particles. Exemplary coform materials are disclosed in commonly assigned U.S. Pat. No. 5,350,624 to Georger et al.; U.S. Pat. No. 4,100,324 to Anderson et al.; and U.S. Pat. No. 4,818,464 to Lau et al, U.S. Pat. No. 5,720,832 to Minto et al.; the entire contents of each is hereby incorporated by reference. In addition, coform material containing superabsorbent particles is disclosed in U.S. Pat. No. 4,429,001 to Koplin, also hereby incorporated in its entirety.

[0036] As used herein the term “spunbond fibers” refers to small diameter fibers of molecularly oriented polymeric material. Spunbond fibers may be 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 as in, for example, U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, U.S. Pat. No. 3,542,615 to Dobo et al, and U.S. Pat. No. 5,382,400 to Pike et al. Spunbond fibers are generally not tacky when they are deposited onto a collecting surface and are generally continuous. Spunbond fibers are often about 10 microns or greater in diameter. However, fine fiber spunbond webs (having an average fiber diameter less than about 10 microns) may be achieved by various methods including, but not limited to, those described in commonly assigned U.S. Pat. No. 6,200,669 to Marmon et al. and U.S. Pat. No. 5,759,926 to Pike et al.

[0037] 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. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the molecule. These configurations include, but are not limited to isotactic, syndiotactic and random symmetries.

[0038] As used herein, the term “multicomponent fibers” refers to fibers or filaments which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. Multicomponent fibers are also sometimes referred to as “conjugate” or “bicomponent” fibers or filaments. The term “bicomponent” means that there are two polymeric components making up the fibers. The polymers are usually different from each other, although conjugate fibers may be prepared from the same polymer, if the polymer in each component is different from one another in some physical property, such as, for example, melting point or the softening point. In all cases, the polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the multicomponent fibers or filaments and extend continuously along the length of the multicomponent fibers or filaments. The configuration of such a multicomponent fiber may be, for example, a sheath/core arrangement, wherein one polymer is surrounded by another, a side-by-side arrangement, a pie arrangement or an “islands-in-the-sea” arrangement. Multicomponent fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al.; U.S. Pat. No. 5,336,552 to Strack et al.; and U.S. Pat. No. 5,382,400 to Pike et al.; the entire content of each is incorporated herein by reference. For two component fibers or filaments, the polymers may be present in ratios of 75/25, 50/50, 25/75 or any other desired ratios.

[0039] As used herein, the term “multiconstituent fibers” refers to fibers which have been formed from at least two polymers extruded from the same extruder as a blend or mixture. Multiconstituent 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 or protofibrils which start and end at random.

[0040] As used herein, the phrase “fine meltblown filaments” is intended to represent meltblown filaments having an average fiber diameter less than about 15 microns.

[0041] As used herein, the phrase “coarse meltblown filaments” is intended to represent meltblown filaments having an average fiber diameter greater than about 15 microns.

[0042] As used herein, the phrase “dual texture” is intended to mean that the nonwoven web has at least two distinct surface textures. The two distinct surface textures may be on one or both sides of the nonwoven web. Preferably, there is a distinct surface texture on each side of the nonwoven web.

[0043] As used herein, the term “abrasive” is intended to represent a surface texture which enables the nonwoven web to scour a surface being wiped or cleaned with the nonwoven web and remove dirt and the like. The abrasiveness can vary depending on the polymer used to prepare the abrasive fibers and the degree of texture of the nonwoven web.

[0044] As used herein, the term “non-abrasive” is intended to represent a surface texture which relatively soft and generally does not have the ability to scour a surface being wiped or cleaned with the nonwoven web.

DETAILED DESCRIPTION

[0045] The present invention provides a dual texture coform nonwoven web having a matrix containing 1) thermoplastic meltblown filaments and 2) at least one secondary material. The dual texture coform nonwoven web has a first exterior surface and a second exterior surface, wherein the first exterior surface contains fine thermoplastic meltblown filaments having an average fiber diameter of less than about 15 microns and the secondary material; and the second exterior surface contains coarse thermoplastic meltblown filaments having an average diameter in greater than about 15 microns and the secondary material.

[0046] The first and second surfaces of the dual texture nonwoven web can contain both the coarse thermoplastic filaments and the fine thermoplastic filaments. In the present invention, the coarse thermoplastic filaments can be incorporated into the dual texture nonwoven web matrix in a random manner, in a substantially homogenous manner or in a gradient manner. Likewise the fine thermoplastic filaments can be incorporated into the dual texture nonwoven web matrix in a random manner, in a substantially homogenous manner, or in a gradient manner. It is preferred, but not required, that the concentration of the coarse meltblown filaments in the matrix can be in a gradient type structure, decreasing in a direction from the second exterior surface towards the first exterior surface. In addition, the coform nonwoven web of the present invention can be a single layer structure or a multi-layer structure. It is not critical to the present invention if the nonwoven web is a single layer or a multi-layer structure.

[0047] The meltblown filaments, both the fine filaments and the coarse filaments, are preferably prepared from thermoplastic polymers. Suitable thermoplastic polymers useful in the present invention include polyolefins, polyesters, polyamides, polycarbonates, polyurethanes, polyvinylchloride, polytetrafluoroethylene, polystyrene, polyethylene terephathalate, biodegradable polymers such as polylactic acid and copolymers and blends thereof. Suitable polyolefins include polyethylene, e.g., high density polyethylene, medium density polyethylene, low density polyethylene and linear low density polyethylene; polypropylene, e.g., isotactic polypropylene, syndiotactic polypropylene, blends of isotactic polypropylene and atactic polypropylene, and blends thereof; polybutylene, e.g., poly(1-butene) and poly(2-butene); polypentene, e.g., poly(1-pentene) and poly(2-pentene); poly(3-methyl-1-pentene); poly(4-methyl 1-pentene); and copolymers and blends thereof. Suitable copolymers include random and block copolymers prepared from two or more different unsaturated olefin monomers, such as ethylene/propylene and ethylene/butylene copolymers. Suitable polyamides include nylon 6, nylon 6/6, nylon 4/6, nylon 11, nylon 12, nylon 6/10, nylon 6/12, nylon 12/12, copolymers of caprolactam and alkylene oxide diamine, and the like, as well as blends and copolymers thereof. Suitable polyesters include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polytetramethylene terephthalate, polycyclohexylene-1,4-dimethylene terephthalate, and isophthalate copolymers thereof, as well as blends thereof.

[0048] Many polyolefins are available for fiber production, for example polyethylenes such as Dow Chemical's ASPUN 6811A linear low-density polyethylene, 2553 LLDPE and 25355 and 12350 high density polyethylene are such suitable polymers. The polyethylenes have melt flow rates in g/10 min. at 190° F. and a load of 2.16 kg, of about 26, 40, 25 and 12, respectively. Fiber forming polypropylenes include, for example, Basell's PF-015 polypropylene. Many other polyolefins are commercially available and generally can be used in the present invention. The particularly preferred polyolefins are polypropylene and polyethylene.

[0049] Examples of polyamides and their methods of synthesis may be found in “Polymer Resins” by Don E. Floyd (Library of Congress Catalog number 66-20811, Reinhold Publishing, N.Y., 1966). Particularly commercially useful polyamides are nylon 6, nylon-6,6, nylon-11 and nylon-12. These polyamides are available from a number of sources such as Custom Resins, Nyltech, among others. In addition, a compatible tackifying resin may be added to the extrudable compositions described above to provide tackified materials that autogenously bond or which require heat for bonding. Any tackifier resin can be used which is compatible with the polymers and can withstand the high processing (e.g., extrusion) temperatures. If the polymer is blended with processing aids such as, for example, polyolefins or extending oils, the tackifier resin should also be compatible with those processing aids. Generally, hydrogenated hydrocarbon resins are preferred tackifying resins, because of their better temperature stability. REGALREZ® and ARKON® P series tackifiers are examples of hydrogenated hydrocarbon resins. ZONATAC® 501 Lite is an example of a terpene hydrocarbon. REGALREZ® hydrocarbon resins are available from Hercules Incorporated. ARKON®P series resins are available from Arakawa Chemical (USA) Incorporated. The tackifying resins such as disclosed in U.S. Pat. No. 4,787,699, hereby incorporated by reference, are suitable. Other tackifying resins which are compatible with the other components of the composition and can withstand the high processing temperatures, can also be used.

[0050] The meltblown filaments may be monocomponent fibers, meaning fibers prepared from one polymer component, multiconstituent fibers, or multicomponent fibers. The multicomponent filaments may have either of an A/B or A/B/A side-by-side configuration, or a sheath-core configuration, wherein one polymer component surrounds another polymer component.

[0051] The secondary material of a coform nonwoven web of the present invention may be an absorbent material, such as absorbent fibers or absorbent particles, or non-absorbent materials, such as non-absorbent fibers or non-absorbent particles. The selection of the second material will determine the properties of the resulting dual texture coform nonwoven web. For example, the absorbency of the coform nonwoven web can be improved by using an absorbent material as the second material. The coform nonwoven web generally contains from about 5% to about 95% by weight of the absorbent material and about 95% to about 5% by weight of the thermoplastic meltblown filaments. Generally, the amount of the second material can be selected by those skilled in the art depending on the final utility of the coform nonwoven web. The second material may make up from about 20% to about 85% by weight of the coform nonwoven web or desirably about 30% to about 70% by weight of coform web. Correspondingly, the thermoplastic meltblown filaments make up about 15% to about 80% by weight of the coform nonwoven web or desirably about 30% to about 70% by weight of the coform nonwoven web. It is noted that the above percentages for the meltblown filaments includes both the fine meltblown filaments and the coarse meltblown filaments.

[0052] The absorbent materials useful in the present invention include absorbent fibers, absorbent particles and mixtures of absorbent fibers and absorbent particles. Examples of the absorbent material include, but are not limited to, fibrous organic materials such as woody or non-woody pulp from cotton, rayon, recycled paper, pulp fluff and also superabsorbent particles, inorganic absorbent materials, treated polymeric staple fibers and so forth. Desirably, although not required, the absorbent material is pulp, and/or superabsorbent fibers and/or particles.

[0053] The pulp fibers may be any high-average fiber length pulp, low-average fiber length pulp, or mixtures of the same. Preferred pulp fibers include cellulose fibers. The term “high average fiber length pulp” refers to pulp that contains a relatively small amount of short fibers and non-fiber particles. High fiber length pulps typically have an average fiber length greater than about 1.5 mm, preferably about 1.5-6 mm. Sources generally include non-secondary (virgin) fibers as well as secondary fiber pulp which has been screened. The term “low average fiber length pulp” refers to pulp that contains a significant amount of short fibers and non-fiber particles. Low average fiber length pulps typically have an average fiber length less than about 1.5 mm.

[0054] Examples of high average fiber length wood pulps include those available from Georgia-Pacific under the trade designations Golden Isles 4821 and 4824. The low average fiber length pulps may include certain virgin hardwood pulp and secondary (i.e., recycled) fiber pulp from sources including newsprint, reclaimed paperboard, and office waste. Mixtures of high average fiber length and low average fiber length pulps may contain a predominance of low average fiber length pulps. For example, mixtures may contain more than about 50% by weight low-average fiber length pulp and less than about 50% by weight high-average fiber length pulp. One exemplary mixture contains about 75% by weight low-average fiber length pulp and about 25% by weight high-average fiber length pulp.

[0055] The pulp fibers may be unrefined or may be beaten to various degrees of refinement. Crosslinking agents and/or hydrating agents may also be added to the pulp mixture. Debonding agents may be added to reduce the degree of hydrogen bonding if a very open or loose nonwoven pulp fiber web is desired. Exemplary debonding agents are available from the Quaker Oats Chemical Company, Conshohocken, Pa., under the trade designation Quaker 2028 and Berocell 509ha made by Eka Nobel, Inc. Marietta, Ga. The addition of certain debonding agents in the amount of, for example, 1-4% by weight of the pulp fibers, may reduce the measured static and dynamic coefficients of friction and improve the abrasion resistance of the thermoplastic meltblown polymer filaments. The debonding agents act as lubricants or friction reducers. Debonded pulp fibers are commercially available from Weyerhaeuser Corp. under the designation NB 405.

[0056] In another highly advantageous embodiment, a quantity of a superabsorbent material is combined with the thermoplastic meltblown polymer filaments, to improve the absorbency of the absorbent nonwoven web, with or without pulp fibers. The term “superabsorbent” or “superabsorbent material” refers to a water-swellable, water-insoluble organic or inorganic material capable, under the most favorable conditions, of absorbing at least about 10 times its weight and, more desirably, at least about 30 times its weight in an aqueous solution containing 0.9 weight percent sodium chloride, at room temperature and pressure.

[0057] The superabsorbent materials can be natural, synthetic and modified natural polymers and materials. In addition, the superabsorbent materials can be inorganic materials, such as silica gels, or organic compounds such as cross-linked polymers. The term “cross-linked” refers to any means for effectively rendering normally water-soluble materials substantially water insoluble but swellable. Such means can include, for example, physical entanglement, crystalline domains, covalent bonds, ionic complexes and associations, hydrophilic associations, such as hydrogen bonding, and hydrophobic associations or Van der Waals forces.

[0058] Examples of synthetic superabsorbent material polymers include the alkali metal and ammonium salts of poly(acrylic acid) and poly(methacrylic acid), poly(acrylamides), poly(vinyl ethers), maleic anhydride copolymers with vinyl ethers and alpha-olefins, poly(vinyl pyrrolidone), poly(vinylmorpholinone), poly(vinyl alcohol), and mixtures and copolymers thereof. Further superabsorbent materials include natural and modified natural polymers, such as hydrolyzed acrylonitrile-grafted starch, acrylic acid grafted starch, methyl cellulose, chitosan, carboxymethyl cellulose, hydroxypropyl cellulose, and the natural gums, such as alginates, xanthan gum, locust bean gum and the like. Mixtures of natural and wholly or partially synthetic superabsorbent polymers can also be useful in the present invention. Other suitable absorbent gelling materials are disclosed by Assarsson et al. in U.S. Pat. No. 3,901,236 issued Aug. 26, 1975. Processes for preparing synthetic absorbent gelling polymers are disclosed in U.S. Pat. No. 4,076,633 issued Feb. 28, 1978 to Masuda et al. and U.S. Pat. No. 4,286,082 issued Aug. 25, 1981 to Tsubakimoto et al, each hereby incorporated by reference.

[0059] Superabsorbent materials may be xerogels which form hydrogels when wetted. The term “hydrogel,” however, has commonly been used to also refer to both the wetted and unwetted forms of the superabsorbent polymer material. The superabsorbent materials can be in many forms such as flakes, powders, particulates, fibers, continuous fibers, networks, solution spun filaments and webs. The particles can be of any desired shape, for example, spiral or semi-spiral, cubic, rod-like, polyhedral, etc. Needles, flakes, fibers, and combinations may also be used.

[0060] Superabsorbents are generally available in particle sizes ranging from about 20 to about 1000 microns. Examples of commercially available particulate superabsorbents include SANWET® IM 3900 and SANWET® IM-5000P, available from Hoescht Celanese located in Portsmouth, Va., SANWET® 2035LD available from Dow Chemical Co. located in Midland, Mich., and FAVOR® 880, available from Stockhausen, located in Greensborough, N.C. An example of a fibrous superabsorbent is OASIS® 101, available from Technical Absorbents, located in Grimsby, United Kingdom.

[0061] When used, the superabsorbent material may be present within the absorbent nonwoven web in an amount from about 5 to about 75% by weight based on total weight of the coform nonwoven web. Preferably, the superabsorbent constitutes about 10-60% by weight of the coform nonwoven web, more preferably about 20-50% by weight. When the superabsorbent material is present, other absorbent fibers or particles may or may not be present. It is preferred, however, that the total weight of the absorbent material, including both the superabsorbent material and the other absorbent material, such as pulp, in the absorbent nonwoven web is between about 5 and about 95% by weight of the nonwoven web.

[0062] When the absorbent material contains a mixture of a superabsorbent material and a non-superabsorbent material, such as pulp, the superabsorbent desirably is present in an amount less than about 50% by weight of the absorbent material present in the absorbent nonwoven web. This is because superabsorbent materials are generally slow to absorb fluids and/or release fluids. More preferably, the superabsorbent material is present in an amount of about 5 to about 25% by weight of the absorbent material present in dual texture coform nonwoven web. In each case, the balance of the absorbent material is a non-superabsorbent material, such as pulp.

[0063] In addition, non-absorbent secondary materials can be incorporated into the dual texture coform nonwoven web, depending on the end use of the dual texture coform nonwoven web. For example, in end uses where absorbency is not an issue, non-absorbent secondary materials may be used. These non-absorbent materials include nonabsorbent fibers and nonabsorbent particles. Examples of the fibers include, for example, staple fibers of untreated thermoplastic polymers, such as polyolefins and the like. Examples of nonabsorbent particles include activated charcoal, sodium bicarbonate and the like. The nonabsorbent material can be used alone or in combination with the absorbent material. It should be noted, however, that the total amount of the second material, whether absorbent or nonabsorbent should be between 5 and 95% by weight of the total weight of the dual texture coform nonwoven web, more preferably between about 30% and 70% by weight.

[0064] The secondary material may be incorporated into the dual texture nonwoven web in a gradient manner such that the concentration of the secondary material is lower at the surfaces and higher in the center portion of the nonwoven web, in a random manner or substantially homogenous distributed though-out the nonwoven web. Preferably, the secondary material is substantially homogenously distributed throughout the nonwoven web, wherein the exterior surfaces of the nonwoven web contain some of the secondary material.

[0065] The dual texture coform nonwoven web of the present invention is prepared by a method including:

[0066] a. providing a first stream of meltblown filaments having an average diameter of less than about 15 microns;

[0067] b. providing a second stream of meltblown filaments having an average diameter greater than about 15 microns:

[0068] c. converging the first stream of meltblown filaments and the second stream of meltblown filaments in an intersecting relationship to form an impingement zone;

[0069] d. introducing a stream containing at least one secondary material between the first and second streams of the meltblown filaments at or near the impingement zone to form a composite stream; and

[0070] e. depositing the composite stream onto a forming surface as a matrix of meltblown filaments and at least one secondary material to form a nonwoven web containing a first and a second exterior surface; the first exterior surface contains fine meltblown fibers having average diameter of less than about 15 microns and the secondary material, and the second exterior surface contains coarse meltblown fibers having an average diameter greater than about 15 microns and the secondary material. In order to obtain a better understanding of how to produce the dual texture coform nonwoven web of the present invention, attention is directed to FIG. 1. FIG. 1 shows an exemplary apparatus for forming a dual texture coform nonwoven web which is generally represented by reference numeral 10. In forming the dual texture coform nonwoven web of the present invention, pellets or chips, etc. (not shown) of a thermoplastic polymer are introduced into a pellet hopper 12, or 12′ of an extruder 14 or 14′, respectively.

[0071] The extruders 14 and 14′ each have an extrusion screw (not shown), which is driven by a conventional drive motor (not shown). As the polymer advances through the extruders 14 and 14′, due to rotation of the extrusion screw by the drive motor, it is progressively heated to a molten state. Heating the thermoplastic polymer to the molten state may be accomplished in a plurality of discrete steps with its temperature being gradually elevated as it advances through discrete heating zones of the extruders 14 and 14′ toward two meltblowing dies 16 and 18, respectively. The meltblowing dies 16 and 18 may be yet another heating zone where the temperature of the thermoplastic resin is maintained at an elevated level for extrusion.

[0072] Each meltblowing die is configured so that two streams of attenuating gas per die converge to form a single stream of gas which entrains and attenuates molten threads 20 and 21, as the threads 20 and 21 exit small holes or orifices 24 and 24′, respectively in each meltblowing die. The molten threads 20 and 21 are formed into fibers or, depending upon the degree of attenuation, microfibers, of a small diameter which is usually less than the diameter of the orifices 24. Thus, each meltblowing die 16 and 18 has a corresponding single stream of gas 26 and 28 containing entrained thermoplastic polymer fibers. The gas streams 26 and 28 containing polymer fibers are aligned to converge at an impingement zone 30.

[0073] One or more types of secondary fibers 32 and/or particulates are added to the two streams 26 and 28 of thermoplastic polymer fibers 20 and 21, respectively, and at the impingement zone 30. Introduction of the secondary fibers 32 into the two streams 26 and 28 of thermoplastic polymer fibers 20 and 21, respectively, is designed to produce a graduated distribution of secondary fibers 32 within the combined streams 26 and 28 of thermoplastic polymer fibers. This may be accomplished by merging a secondary gas stream 34 containing the secondary fibers 32 between the two streams 26 and 28 of thermoplastic polymer fibers 20 and 21 so that all three gas streams converge in a controlled manner.

[0074] Apparatus for accomplishing this merger may include a conventional picker roll 36 arrangement which has a plurality of teeth 38 that are adapted to separate a mat or batt 40 of secondary fibers into the individual secondary fibers 32. The mat or batt of secondary fibers 40 which is fed to the picker roll 36 may be a sheet of pulp fibers (if a two-component mixture of thermoplastic polymer fibers and secondary pulp fibers is desired), a mat of staple fibers (if a two-component mixture of thermoplastic polymer fibers and a secondary staple fibers is desired) or both a sheet of pulp fibers and a mat of staple fibers (if a three-component mixture of thermoplastic polymer fibers, secondary staple fibers and secondary pulp fibers is desired). In embodiments where, for example, an absorbent material is desired, the secondary fibers 32 are absorbent fibers. The secondary fibers 32 may generally be selected from the group including one or more polyester fibers, polyamide fibers, cellulosic derived fibers such as, for example, rayon fibers and wood pulp fibers, multi-component fibers such as, for example, sheath-core multi-component fibers, natural fibers such as silk fibers, wool fibers or cotton fibers or electrically conductive fibers or blends of two or more of such secondary fibers. Other types of secondary fibers 32 such as, for example, polyethylene fibers and polypropylene fibers, as well as blends of two or more of other types of secondary fibers 32 may be utilized. The secondary fibers 32 may be microfibers or the secondary fibers 32 may be macrofibers having an average diameter of from about 300 microns to about 1,000 microns.

[0075] The sheets or mats 40 of secondary fibers 32 are fed to the picker roll 36 by a roller arrangement 42. After the teeth 38 of the picker roll 36 have separated the mat of secondary fibers 40 into separate secondary fibers 32 the individual secondary fibers 32 are conveyed toward the stream of thermoplastic polymer fibers or microfibers 24 through a nozzle 44. A housing 46 encloses the picker roll 36 and provides a passageway or gap 48 between the housing 46 and the surface of the teeth 38 of the picker roll 36. A gas, for example, air, is supplied to the passageway or gap 46 between the surface of the picker roll 36 and the housing 48 by way of a gas duct 50.

[0076] The gas duct 50 may enter the passageway or gap 46 generally at the junction 52 of the nozzle 44 and the gap 48. The gas is supplied in sufficient quantity to serve as a medium for conveying the secondary fibers 32 through the nozzle 44. The gas supplied from the duct 50 also serves as an aid in removing the secondary fibers 32 from the teeth 38 of the picker roll 36. The gas may be supplied by any conventional arrangement such as, for example, an air blower (not shown). It is contemplated that additives and/or other materials may be added to or entrained in the gas stream to treat the secondary fibers.

[0077] Generally speaking, the individual secondary fibers 32 are conveyed through the nozzle 44 at about the velocity at which the secondary fibers 32 leave the teeth 38 of the picker roll 36. In other words, the secondary fibers 32, upon leaving the teeth 38 of the picker roll 36 and entering the nozzle 44 generally maintain their velocity in both magnitude and direction from the point where they left the teeth 38 of the picker roll 36.

[0078] Such an arrangement, which is discussed in more detail in U.S. Pat. No. 4,100,324 to Anderson, et al., hereby incorporated by reference, aids in substantially reducing fiber floccing.

[0079] The width of the nozzle 44 should be aligned in a direction generally parallel to the width of the meltblowing dies 16 and 18. Desirably, the width of the nozzle 44 should be about the same as the width of the meltblowing dies 16 and 18. Usually, the width of the nozzle 44 should not exceed the width of the sheets or mats 40 that are being fed to the picker roll 36. Generally speaking, it is desirable for the length of the nozzle 44 to be as short as equipment design will allow.

[0080] The picker roll 36 may be replaced by a conventional particulate injection system to form a coform nonwoven structure 54 containing various secondary particulates. A combination of both secondary particulates and secondary fibers could be added to the thermoplastic polymer fibers prior to formation of the coform nonwoven structure 54 if a conventional particulate injection system was added to the system illustrated in FIG. 1. The particulates may be, for example, charcoal, clay, starches, and/or superabsorbent particles.

[0081]
FIG. 1 further illustrates that the secondary gas stream 34 carrying the secondary fibers 32 is directed between the streams 26 and 28 of thermoplastic polymer fibers so that the streams contact at the impingement zone 30. The velocity of the secondary gas stream 34 may be adjusted. If the velocity of the secondary gas stream is adjusted so that it is greater than the velocity of each stream 26 and 28 of thermoplastic polymer fibers 20 and 21 when the streams contact at the impingement zone 30, the secondary material is incorporated in the coform nonwoven web in a gradient structure. That is, the secondary material has a higher concentration between the outer surfaces of the coform nonwoven web than at the outer surfaces. If the velocity of the secondary gas stream 34 is less than the velocity of each stream 26 and 28 of thermoplastic polymer fibers 20 and 21 when the streams contact at the impingement zone 30, the secondary material is incorporated in the coform nonwoven web in a substantially homogenous fashion. That is, the concentration of the secondary material is substantially the same throughout the coform nonwoven web. This is because the low-speed stream of secondary material is drawn into a high-speed stream of thermoplastic polymer fibers to enhance turbulent mixing which results in a consistent distribution of the secondary material.

[0082] Although the inventors should not be held to a particular theory of operation, it is believed that adjusting the velocity of the secondary gas stream 34 so that it is greater than the velocity of each stream 26 and 28 of thermoplastic polymer fibers 24 when the streams intersect at the impingement zone 30 can have the effect that, during merger and integration thereof, between the impingement zone 30 and a collection surface, a graduated distribution of the fibrous components can be accomplished.

[0083] The velocity difference between the gas streams may be such that the secondary fibers 32 are integrated into the streams of thermoplastic polymer fibers 26 and 28 in such manner that the secondary material 32 become gradually and only partially distributed within the thermoplastic polymer fibers 20 and 21. Generally, for increased production rates the gas streams which entrain the thermoplastic polymer fibers 20 and 21 may have a comparatively high initial velocity, for example, from about 200 feet to over 1,000 feet per second. However, the velocity of those gas streams decreases rapidly as they expand and become separated from the meltblowing die. Thus, the velocity of those gas streams at the impingement zone may be controlled by adjusting the distance between the meltblowing die and the impingement zone. The stream of gas 34 which carries the secondary fibers 32 will have a low initial velocity when compared to the gas streams 26 and 28 which carry the meltblown fibers. However, by adjusting the distance from the nozzle 44 to the impingement zone 30 (and the distances that the meltblown fiber gas streams 26 and 28 must travel), the velocity of the gas stream 34 can be controlled to be greater or lower than the meltblown fiber gas streams 26 and 28. In the practice of the present invention, it is preferred that the pulp is homogenously integrated with both the coarse and fine meltblown filaments. In addition, the velocity of the thermoplastic fiber streams may also be adjusted to obtain the desired degree of mixing.

[0084] Due to the fact that the thermoplastic polymer fibers 20 and 21 are usually still semi-molten and tacky at the time of incorporation of the secondary fibers 32 into the thermoplastic polymer fiber streams 26 and 28, the secondary fibers 32 are usually not only mechanically entangled within the matrix formed by the thermoplastic polymer fibers 20 and 21 but are also thermally bonded or joined to the thermoplastic polymer fibers 20 and 21.

[0085] In order to convert the composite stream 56 of thermoplastic polymer fibers 20, 21 and secondary material 32 into a coform nonwoven structure 54, a collecting device is located in the path of the composite stream 56. The collecting device may be an endless belt 58 conventionally driven by rollers 60 and which is rotating as indicated by the arrow 62 in FIG. 1. Other collecting devices are well known to those of skill in the art and may be utilized in place of the endless belt 58. For example, a porous rotating drum arrangement could be utilized. The merged streams of thermoplastic polymer fibers and secondary fibers are collected as a coherent matrix of fibers on the surface of the endless belt 58 to form the coform nonwoven web 54. Vacuum boxes 64 assist in retention of the matrix on the surface of the belt 58.

[0086] The coform structure 54 is coherent and may be removed from the belt 58 as a self-supporting nonwoven material. Generally speaking, the coform structure has adequate strength and integrity to be used without any post-treatments such as pattern bonding and the like. If desired, a pair of pinch rollers or pattern bonding rollers may be used to bond portions of the material. Although such treatment may improve the integrity of the nonwoven web structure 54, it also tends to compress and densify the structure.

[0087] In the present invention, one meltblown stream 26 or 28 carries thermoplastic filaments having coarse meltblown fibers, having an average fiber diameter greater than about 15 microns. The other meltblown fiber stream carries thermoplastic filaments having an average fiber diameter of less than about 15 microns. Depending on various factors, including but not limited to, the velocity of the meltblown streams 26 and 26, the velocity of the secondary material stream 34, the characteristics of the resulting dual texture coform nonwoven web can be changed. For example, all of the thermoplastic filaments and secondary material can be substantially uniformly mixed, the absorbent material can be present in a gradient type structure, or absorbent material is present in a uniform type manner in the coform nonwoven web while the coarse fiber meltblown is present in a gradient type manner. In using this process, it is desirable, although not required, that the two surfaces of the coform nonwoven web have different characteristics. One surface will have an abrasive characteristic, which allows scrubbing on a surface to be cleaned and the other surface will have soft, nonabrasive feeling.

[0088] In addition, the concentration of the coarse meltblown fibers in the coform nonwoven web decreases from the surface having the abrasive characteristic towards the surface having the non-abrasive characteristic. Likewise, the concentration of the fine meltblown fibers in the coform nonwoven web decreases from the surface having the non-abrasive characteristic towards the surface having the abrasive characteristic. This can be seen in FIG. 4.

[0089] As an alternative method, the dual texture meltblown may be prepared by a method including the steps of:

[0090] a. providing a first stream of meltblown filaments;

[0091] b. introducing a stream containing at least one secondary material to the first stream of meltblown filaments to form a first composite stream;

[0092] c. providing a second stream of meltblown filaments;

[0093] d. introducing a stream at least one secondary material to the second stream of meltblown filaments to form a second composite stream;

[0094] e. depositing the first composite stream onto a forming surface as a matrix of meltblown filaments and a secondary material to form a first deposited layer; and

[0095] f. depositing the second composite stream onto the first deposited layer as a matrix of meltblown filaments and a secondary material to form a coform nonwoven web;

[0096] wherein one of the first stream of meltblown filaments or the second stream of meltblown filaments contains meltblown filaments having average diameter of less than about 15 microns and the other of the first stream of meltblown fibers or the second stream of meltblown fibers contains meltblown filaments having an average diameter greater than about 15 microns. This method sequentially lays down a coarse meltblown filament/secondary material layer and a fine meltblown filament/secondary material layer. It is noted that it is not critical to the present invention whether the first or second stream of meltblown filaments is the stream with the coarse meltblown filaments.

[0097] In this regard, attention is directed to FIG. 2, which shows an exemplary apparatus for forming a dual texture coform nonwoven web which is generally represented by reference numeral 100. In forming the dual texture coform nonwoven web of the present invention, pellets or chips, etc. (not shown) of a thermoplastic polymer are introduced into a pellet hopper 112, or 112′ of an extruder 114 or 114′, respectively.

[0098] The extruders 114 and 114′ each have an extrusion screw (not shown), which is driven by a conventional drive motor (not shown). As the polymer advances through the extruders 114 and 114′, due to rotation of the extrusion screw by the drive motor, it is progressively heated to a molten state. Heating the thermoplastic polymer to the molten state may be accomplished in a plurality of discrete steps with its temperature being gradually elevated as it advances through discrete heating zones of the extruders 114 and 114′ toward two meltblowing dies 116 and 118, respectively. The meltblowing dies 116 and 118 may be yet another heating zone where the temperature of the thermoplastic resin is maintained at an elevated level for extrusion.

[0099] Each meltblowing die is configured so that two streams of attenuating gas 117 and 117′ per die converge to form a single stream of gas which entrains and attenuates molten threads 120 and 121, as the threads 120 and 121 exit small holes or orifices 124 and 124′, respectively. The molten threads 120 and 121 are formed into filaments or, depending upon the degree of attenuation, microfibers, of a small diameter which is usually less than the diameter of the orifices 124 and 124′. Thus, each meltblowing die 116 and 118 has a corresponding single stream of gas 126 and 128 containing entrained thermoplastic polymer fibers. The gas streams 126 and 128 containing polymer fibers directed toward the forming surface and are generally preferred to be substantially perpendicular to the forming surface.

[0100] One or more types of secondary fibers 132 and 132′ and/or particulates are added to the two streams 126 and 128 of thermoplastic polymer fibers 120 and 121, respectively. Introduction of the secondary fibers 132 and 132′ into the two streams 126 and 128 of thermoplastic polymer fibers 120 and 121, respectively, is designed to produce a generally homogenous distribution of secondary fibers 132 and 132′ within streams 126 and 128 of thermoplastic polymer fibers.

[0101] Apparatus for accomplishing this merger may include a conventional picker roll 136 and 136′. The operation of a conventional picker roll is described above for in the discussion of FIG. 1. The picker rolls 136 and 136′ may be replaced by a conventional particulate injection system to form a coform nonwoven structure 154 containing various secondary particulates. A combination of both secondary particulates and secondary fibers could be added to the thermoplastic polymer fibers prior to formation of the coform nonwoven structure 154 if a conventional particulate injection system was added to the system illustrated in FIG. 2. The particulates may be, for example, charcoal, clay, starches, and/or superabsorbent particles.

[0102] Due to the fact that the thermoplastic polymer fibers 120 and 121 are usually still semi-molten and tacky at the time of incorporation of the secondary fibers 132 and 132′ into the thermoplastic polymer fiber streams 126 and 128, the secondary fibers 132 and 132′ are usually not only mechanically entangled within the matrix formed by the thermoplastic polymer fibers 120 or 121′ but are also thermally bonded or joined to the thermoplastic polymer fibers 120 or 121′.

[0103] In order to convert the composite stream 156 and 156′ of thermoplastic polymer fibers 120, 121 and secondary material 132 and 132′, respectively, into a coform nonwoven structure 154, a collecting device is located in the path of the composite streams 156 and 156′. The collecting device may be an endless belt 158 conventionally driven by rollers 160 and which is rotating as indicated by the arrow 162 in FIG. 2. Other collecting devices are well known to those of skill in the art and may be utilized in place of the endless belt 158. For example, a porous rotating drum arrangement could be utilized. The merged streams of thermoplastic polymer fibers and secondary fibers are collected as a coherent matrix of fibers on the surface of the endless belt 158 to form the coform nonwoven web 154. Vacuum boxes 164 and 164′ assist in retention of the matrix on the surface of the belt 158.

[0104] The coform structure 154 is coherent and may be removed from the belt 158 as a self-supporting nonwoven material. Generally speaking, the coform structure has adequate strength and integrity to be used without any post-treatments such as pattern bonding, calendering and the like. However, the structure can be further stabilized by thermally bonding or compressing the coform structure. For example, a pair of pinch rollers or pattern bonding rollers, which may or may not be heated, may be used to bond portions of the material. Although such treatment may improve the integrity of the coform nonwoven web structure 154, it also tends to compress and densify the structure.

[0105] In the present invention, one meltblown stream 126 or 128 carries thermoplastic filaments having coarse meltblown fibers, having an average fiber diameter greater than about 15 microns. The other meltblown fiber stream carries thermoplastic filaments having an average fiber diameter of less than about 15 microns. As a result, the two surfaces of the coform nonwoven web have different characteristics. One surface will have an abrasive characteristic, which allows scrubbing on a surface to be cleaned and the other surface will have soft, nonabrasive feeling. Although it is not critical to the present invention which stream is used to produce the coarse meltblown filaments, generally stream 128 is the stream used to produce the coarse meltblown filaments.

[0106] The characteristics of the meltblown filaments can be adjusted by manipulation of the various process parameters used for each extruder and die head in carrying out the meltblowing process. The following parameters can be adjusted and varied for each extruder and die head in order to change the characteristics of the resulting meltblown filaments:

[0107] 1. Type of Polymer,

[0108] 2. Polymer throughput (pounds per inch of die width per hour—PIH),

[0109] 3. Polymer melt temperature,

[0110] 4. Air temperature,

[0111] 5. Air flow (standard cubic feet per minute, SCFM, calibrated the width of the die head),

[0112] 6. Distance from between die tip and forming belt and

[0113] 7. Vacuum under forming belt.

[0114] For example, the coarse filaments may be prepared by reducing the primary air temperature from the range of about 5000-540° F. (260°-282° C.) to about 420°-460° F. (2160-2380° C.) for the coarse filament bank. These changes result in the formation of larger fibers. Any other method which is effective may also be used and would be in keeping with the invention.

[0115] In practice of the present invention, the average fiber diameter of the coarse meltblown filaments are preferably in the range of about 15 to about 39 microns, more preferably in the range of about 20 to about 35 microns. The average fiber diameter of the fine meltblown filaments is preferably less than 12 microns, more preferably less than 8 microns and most preferably about 0.5-5 microns.

[0116] Preparing the coform nonwoven web by the second method disclosed above has some additional advantages over intermingling the fine meltblown filaments, coarse meltblown filaments and pulp. Specifically, the amount of second material can be varied at each surface of the coform nonwoven web, giving a coform nonwoven web with a layered structure. Each layer of the layered structure may have the same or different percentages of the secondary material and/or may contain the same or different secondary materials. One advantage of being able to modify the secondary material content is that the coarse filaments sometimes do not capture the secondary material as well as the fine fiber, especially at high secondary material content, which may cause linting of secondary material from the coform nonwoven web. Generally, it is preferred, but not required, that the secondary material content in the coarse meltblown containing surface is about 20% to about 80% by weight of the coarse meltblown and secondary material mixture. A more preferred range is about 30% to about 65% by weight of the secondary material in the coarse meltblown filament containing surface. In addition, varying the amount of the secondary material at each surface can help the fluid distribution within the coform nonwoven web by creating a gradient structure for the secondary material. Further, it is preferred, but not required, that the secondary material content in the fine meltblown containing surface is about 20% to about 85% by weight of the fine meltblown and secondary material mixture. A more preferred range is about 30% to about 70% by weight of the secondary material in the fine meltblown filament containing surface. However, if the secondary material content is greater than about 65-70% by weight in a layer, it is preferred that an additional layer be placed onto the coform material to help prevent the secondary material from “linting” out of the coform. Additional layers are discussed below.

[0117] The coform material preferably has a total basis weight in the range of about 34 gsm to about 600 gsm. More preferably, the basis weight is in the range of about 75 gsm to about 400 gsm. Most preferably, the basis weight should be in the range of about 100 gsm to about 325 gsm. It is pointed out, however, that the basis weight is highly dependent on the end use. For pre-saturated mop applications it is preferred that the basis weight is about 75 gsm to about 325 gsm, while the basis weight for a absorbent mop is preferably in the range of about 175 gsm to about 325 gsm. For hand wipes and the like, the basis weight is generally dependent of the particular utility of the wipe. In the production of the dual texture coform by the apparatus of FIG. 2, the percentage of the basis weight can be varied. Generally, the fine fiber coform layer can constitute between about 35 and about 65% by weight of the overall laminate. Likewise, the coarse fiber coform layer can constitute between about 35% and about 65% by weight of the overall laminate. More preferably, the fine fiber coform layer is about 40% to about 60% by weight of the overall coform material, and ideally about 50% by weight.

[0118] The coform material of the present invention can be prepared on or laminated to an additional material. It is pointed out that this lamination is not required in the present invention. For example, an additional material may be supplied to the process of FIG. 1 or FIG. 2 before or after the formation of the coform material. If the material is supplied before the formation of the coform, the coform is formed on the additional material. That is, the additional layer is laid down on the forming surface and the coform is placed on the additional layer. In the alternative, the additional layer may be laminated to the coform of the present invention after the coform is formed. If an additional layer is laminated to the coform material, or if the coform material is prepared on an additional material, it is preferred that the surface of the coform nonwoven web which has the fine filaments is in contact with the material which is laminated to the coform material. This will still provide a coform material with an abrasive surface which can be used for scrubbing. As is noted above, lamination of an additional material to the coform is not required, however, if the secondary material content is greater than about 65-70% by weight in the coform material, it is preferred that an additional layer be placed onto the coform material to help prevent the secondary material from “linting” out of the coform.

[0119] The additional layer can provide additional strength to the coform or provides other properties, such as barrier properties. Laminating another material to the fine filament side of the coform is especially useful in mop applications, by providing extra strength to the nonwoven web and by providing a liquid barrier between the mop material and the mop attachment means. Examples of barrier materials include, for example such as polymeric films, laminate nonwoven materials, combinations thereof and the like. Generally, any material which is liquid impervious may be any suitable. Examples of strengthening layers include, nonwoven webs, such as spunbond, bonded carded webs and the liked, knitted webs, and woven materials. These materials are known to those skilled in the art and are readily available.

[0120] Due to cost considerations, spunbond materials are preferably laminated to the fine filament side of the nonwoven web in order to provide additional strength to the coform material, if a material is to be laminated to the coform nonwoven web of the present invention. Typically, a spunbond having a basis weight in the range of 0.1 gsm to about 2.0 gsm, more preferably about 0.2 gsm to about 0.8 gsm, is preferred.

[0121] In another alternative laminate structure of the present invention, the coform nonwoven web may also have a barrier layer. The liquid barrier layer desirably comprises a material that substantially prevents the transmission of liquids under the pressures and chemical environments associated with surface cleaning applications. Desirably, the liquid barrier layer comprises a thin, monolithic film. The film desirably comprises a thermoplastic polymer such as, for example, polyolefins (e.g., polypropylene and polyethylene), polycondensates (e.g., polyamides, polyesters, polycarbonates, and polyarylates), polyols, polydienes, polyurethanes, polyethers, polyacrylates, polyacetals, polyimides, cellulose esters, polystyrenes, fluoropolymers and so forth. Desirably, the film is hydrophobic. Additionally, the film desirably has a thickness less than about 2 mil and still more desirably between about 0.5 mil and about 1 mil. As a particular example, the liquid barrier layer can comprise an embossed, polyethylene film having a thickness of approximately 1 mil.

[0122] The liquid barrier layer can be bonded together with the other layer or layers of the cleaning sheet to form an integrated laminate through the use of adhesives. In a further aspect, the layers can be attached by mechanical means such as, for example, by stitching. Still further, the multiple layers can be thermally and/or ultrasonically laminated together to form an integrated laminate. The method of bonding is not critical to the present invention.

[0123] The dual texture coform nonwoven web of the present invention can be used to form a pre-saturated or absorbent cleaning sheet, used as a wiper, a sheet for a mop or other hand held implements. The term “cleaning sheet” encompasses dry wipes, pre-saturated wipes, absorbent mops, pre-saturated mops and the like. The size and shape of the cleaning sheet can vary with respect to the intended application and/or end use of the same. Desirably, the cleaning has a substantially rectangular shape of a size which allows it to readily engage standard cleaning equipment or tools such as, for example, mop heads, duster heads, brush heads and so forth. For example, the cleaning sheet may have an unfolded length of from about 2.0 to about 80.0 centimeters and desirably from about 10.0 to about 25.0 centimeters and an unfolded width of from about 2.0 to about 80.0 centimeters and desirably from about 10.0 to about 25.0 centimeters. As one particular example, in order to fit a standard mop head, the cleaning sheet may have a length of about 28 cm and a width of about 22 cm. However, the particular size and/or shape of cleaning sheet can vary as needed to fit upon or otherwise conform to a specific cleaning tool. In an alternative configuration, the cleaning sheet of the present invention could be formed into a mitten shaped article for wiping and cleaning, which would fit over the user's hand.

[0124] As indicated herein above, the cleaning sheets of the present invention are well suited for use with a variety of cleaning equipment and, more particularly, are readily capable of being releasably-attached to the head of a cleaning tool. As used herein, “releasably-attached” or “releasably-engaged” means that the sheet can be readily affixed to and thereafter readily removed from the cleaning tool. In reference to FIG. 3, cleaning tool 240 can comprise handle 248, head 244 and fasteners 246. Cleaning sheet 243 can be superposed with and placed against head 244 such that the liquid barrier layer, if present, faces head 244. If the cleaning sheet is a multilayer laminate, the side of the sheet with the abrasive surface should face away from the head. Flaps 247 can then be wrapped around head 244 and releasably-attached to head 244 by fasteners 246, e.g. clamps. With cleaning sheet 243 affixed to head 244, cleaning tool 240 can then be used in one or more wet and/or dry cleaning operations. Thereafter, when the cleaning sheet becomes heavily soiled or otherwise spent, the used sheet can be quickly and easily removed and a new one put in its place. The specific configuration of the cleaning tool can vary in many respects. As examples, the size and/or shape of the handle can vary, the head can be fixed or moveable (e.g. pivotable) with relation to the handle, the shape and/or size of the head can vary, etc. Further, the composition of the head can itself vary, as but one example the head can comprise a rigid structure with or without additional padding. Further, the mechanism(s) for attaching the cleaning sheet can vary and exemplary means of attachment include, but are not limited to, hook and loop type fasteners (e.g. VELCRO™ fasteners), clamps, snaps, buttons, flaps, cinches, low tack adhesives and so forth.

[0125] The cleaning sheets of the present invention are well suited for a variety of dry and wet cleaning operations such as: mopping floors; cleaning of dry surfaces: cleaning and drying wet surfaces such as counters, tabletops or floors (e.g. wet surfaces resulting from spills); sterilizing and/or disinfecting surfaces by applying liquid disinfectants; wiping down and/or cleaning appliances, machinery or equipment with liquid cleansers; rinsing surfaces or articles with water or other diluents (e.g. to remove cleaners, oils, etc.), removing dirt, dust and/or other debris and so forth. The cleaning sheets have numerous uses as a result of its combination of physical attributes, especially the uptake and retention dirt, dust and/or debris. Additionally, the cleaning sheet provides a durable cleaning surface with good abrasion resistance. This combination of physical attributes is highly advantageous for cleaning surfaces with or without liquids such as soap and water or other common household cleaners. Further, the cleaning fabrics of the present invention are of a sufficiently low cost to allow disposal after either a single use or a limited number of uses. By providing a disposable cleaning sheet it is possible to avoid problems associated with permanent or multi-use absorbent products such as, for example, cross-contamination and the formation of bad odors, mildew, mold, etc.

[0126] The cleaning sheets can be provided dry or pre-moistened. In one aspect, dry cleaning sheets can be provided with solid cleaning or disinfecting agents coated on or in the sheets. In addition, the cleaning sheets can be provided in a pre-moistened condition. The pre-moistened of the present invention contain the dual texture nonwoven web of the present invention and a liquid which partially or fully saturates the coform material. The wet cleaning sheets can be maintained over time in a sealable container such as, for example, within a bucket with an attachable lid, sealable plastic pouches or bags, canisters, jars, tubs and so forth. Desirably the wet, stacked cleaning sheets are maintained in a resealable container. The use of a resealable container is particularly desirable when using volatile liquid compositions since substantial amounts of liquid can evaporate while using the first sheets thereby leaving the remaining sheets with little or no liquid. Exemplary resealable containers and dispensers include, but are not limited to, those described in U.S. Pat. No. 4,171,047 to Doyle et al., U.S. Pat. No. 4,353,480 to McFadden, U.S. Pat. No. 4,778,048 to Kaspar et al., U.S. Pat. No. 4,741,944 to Jackson et al., U.S. Pat. No. 5,595,786 to McBride et al.; the entire contents of each of the aforesaid references are incorporated herein by reference. The cleaning sheets can be incorporated or oriented in the container as desired and/or folded as desired in order to improve ease of use or removal as is known in the art. Such folded configurations are well known to those skilled in the art and include c-folded, z-folded, quarter-folded configurations and the like. The stack of folded wet wipes may be placed in the interior of a container, such as a plastic tub, to provide a package of wet wipes for eventual sale to the consumer. Alternatively, the wet wipes may include a continuous strip of material which has perforations between each wipe and which may be arranged in a stack or wound into a roll for dispensing.

[0127] With regard to pre-moistened sheets, a selected amount of liquid is added to the container such that the cleaning sheets contain the desired amount of liquid. Typically, the cleaning sheets are stacked and placed in the container and the liquid subsequently added thereto. The sheet can subsequently be used to wipe a surface as well as act as a vehicle to deliver and apply cleaning liquids to a surface. The moistened and/or saturated cleaning sheets can be used to treat various surfaces. As used herein “treating” surfaces is used in the broad sense and includes, but is not limited to, wiping, polishing, swabbing, cleaning, washing, disinfecting, scrubbing, scouring, sanitizing, and/or applying active agents thereto. The amount and composition of the liquid added to the cleaning sheets will vary with the desired application and/or function of the wipes. As used herein the term “liquid” includes, but is not limited to, solutions, emulsions, suspensions and so forth. Thus, liquids may comprise and/or contain one or more of the following: disinfectants; antiseptics; diluents; surfactants, such as nonionic, anionic, cationic, waxes; antimicrobial agents; sterilants; sporicides; germicides; bactericides; fungicides; virucides; protozoacides; algicides; bacteriostats; fungistats; virustats; sanitizers; antibiotics; pesticides; and so forth. Numerous cleaning compositions and compounds are known in the art and can be used in connection with the present invention. The liquid may also contain lotions and/or medicaments. The present invention also relates to new cleaning sheets which have an abrasive scrubbing surface while maintaining adequate strength and resiliency. The premoistened cleaning sheets of the present invention can be used for, hand wipes, face wipes, cosmetic wipes, household wipes, industrial wipes and the like.

[0128] The amount of liquid contained within each premoistened cleaning sheet may vary depending upon the type of material being used to provide the pre-moistened cleaning sheet, the type of liquid being used, the type of container being used to store the wet wipes, and the desired end use of the wet wipe. Generally, each pre-moistened cleaning sheet can contain from about 150 to about 900 weight percent, depending on the end use.

[0129] For example, for a low lint countertop or glass wipe a saturation level of about 150 to about 650 weight percent is desirable. For a pre-saturated mop application, the saturation level is desirably from about 500 to about 900 weight percent liquid based on the dry weight of the cleaning sheet, preferably about 650 to about 800 weight percent. If the amount of liquid is less than the above-identified ranges, the cleaning sheet may be too dry and may not adequately perform. If the amount of liquid is greater than the above-identified ranges, the cleaning sheet may be oversaturated and soggy and the liquid may pool in the bottom of the container.

[0130] The cleaning sheets of the present invention can be provided in a kit form, wherein a plurality of cleaning sheets and a cleaning tool are provided in a single package.

[0131] It has been discovered that the coform materials of the present invention have overall better wiping properties than prior dual texture wipes. Prior dual texture wipes would tend to “skate” across a surface to be cleaned, often leaving streaks in the cleaned surface when a cleaning solution was used. It has been discovered that the dual texture coform material of the present invention does not tend to streak while providing an abrasive cleaning surface.

EXAMPLES

Example 1

[0132] Using the process described in FIG. 2, on a polypropylene spunbond nonwoven fabric having a basis weight of 14 gsm a first coform layer is formed. The first layer of coform is a fine coform layer comprises 70% by weight pulp (Golden Isles 4824, available from Georgia-Pacific) and 30% by weight polypropylene (PF-015 available from Basell) and has a fine fiber diameter of about 4 microns. The polypropylene was meltblown at a rate of about six (6) pounds per hour, through a die having 30 orifices per inch and having an average orifice diameter of about 0.0145 inches, at a primary air temperature of 515° F., using a primary air flow rates of about 330 cfm (cubic feet per minute) A coarse coform layer comprising 40% by weight pulp (Golden Isles 4824, available from Georgia-Pacific) and 60% by weight polypropylene (PF-015 available from Basell) is then formed on the fine coform layer wherein the coarse fiber layer has an average fiber diameter of about 28 microns. The polypropylene for the coarse fiber layer was meltblown at a rate of about 12 pounds per hour, through a die having 30 orifices per inch an having an average orifice diameter of about 0.0145 inches, at a primary air temperature of about 460° F., using a primary air flow rates of about 250 cfm. The resulting dual texture coform nonwoven fabric has a basis weight of about 116 gsm, including the spunbond layer and any moisture. FIG. 4 is a micrograph showing the structure of the coform material prepared in this example.

Comparative Example 1

[0133] Using the process describe in FIG. 2 above, on a polypropylene spunbond nonwoven fabric having a basis weight of 14 gsm a first coform layer is formed. The first coform layer is a fine coform layer comprises 50% by weight pulp (Golden Isles 4824, available from Georgia-Pacific) and 50% by weight polypropylene (PF-015 available from Basell) and has a fine fiber diameter of about 4 microns. The polypropylene was meltblown at a rate of about ten (10) pounds per hour, through a die having 30 orifices per inch and having an average orifice diameter of about 0.0145 inches, at a temperature of 480° F., using a primary air flow rates of about 330 cfm. A second fine meltblown fiber layer of coform comprising 50% by weight pulp (Golden Isles 4824, available from Georgia-Pacific) and 50% by weight polypropylene (PF-015 available from Basell) is then formed on the fine coform layer under the same conditions as the first layer. The resulting single texture coform nonwoven fabric has a basis weight of about 116 gsm, including the spunbond layer and any moisture.

Procedure for Testing Cleaning Efficiency of Wipers

[0134] Equipment needed: Vinyl flooring tiles affixed to ½″ plywood backing

[0135] Plastic template with 0.25″-diameter hole

[0136] 1-lb block with clamps which is 3 inches by 4 inches,

[0137] Two 2″-diameter string loops

[0138] Spatula

[0139] 1) The food was place on the template next to the hole. The template was firmly pressed against the vinyl flooring, and the food was scraped over the hole using a spatula. Good contact between the spatula and template was maintained to get a uniform surface of food that was flush with the template upper surface. This process was repeated several times to ensure that no voids or irregularities were present. The food was allowed to dry overnight for approximately 15 hours. The resulting food stain had a diameter of about 0.25 inches in diameter and a thickness of about 0.016 inches.

[0140] 2) The wipers were prepared by cutting to 3″×7″, and saturating to 75% of the fabric's liquid capacity with a cleaning liquid (Pledge™ Grab-it™ Wet Cleaning fluid). The wipers were placed in an air-tight plastic container to allow equilibration of the wipers.

[0141] 3) The wet wiper was applied to the 1-lb block. The block next was placed next to the dried food stain, oriented to be pulled over the stain in the block's long direction. Next, the string loops were attached to the clamp hooks. The block assembly with the wiper attached was pulled over the food stain, back and forth, counting each pass over the stain, until the stain is no longer visible. The number of passes required to remove the stain was recorded.

[0142] The results were recorded for each wipe prepared above and for a commercially available wipe. This test was repeated for 10 samples each and the results are shown in Table 1.

1TABLE 1Average Number of Wipes to Remove StainFood StainExample 1Comp. Example 1Swiffer Wet ™1Ketchup6.58.89.21Available from Procter and Gamble Company, Cincinnati, Ohio

[0143] Using a Gardner Wet Abrasion Scrub Tester (Cat. No. 5000), the ability of the dual texture coform material of the present invention to clean a surface is compared to the material of Comparative Example 1 and another commercially available material. The Tester was modified by removing the brushes and filling the cavities with LUCITE® blocks. Clamps held 2.25 in. (5.7 cm) by 8 in. (20.3 cm) samples of each material to the sleds of the Tester. A pressure of about 0.10 psi (3.9 g/cm2) was applied to each wipe as it is passed across the food stain.

[0144] Chocolate or vanilla pudding samples were placed on white Delrin® polyacetal resin sheets or black Cobex/Leneta plastic panels, respectively. The pudding was placed on the template, which is described above, next to the hole. The template was firmly pressed against the glass panel, and the pudding was scraped over the hole using a spatula. Good contact between the spatula and template was maintained to get a uniform surface of pudding that was flush with the template upper surface. This process was repeated several times to ensure that no voids or irregularities were present. The pudding was allowed to dry overnight for approximately 15 hours. The resulting pudding stain had a diameter of about 0.25 inches in diameter and a thickness of about 0.016 inches.

[0145] The panels having the dried pudding stain were placed into the Tester. The sled was allowed to pass back and forth over the stain until the stain was no longer visible. The number of cycles (back and forth motion) required to remove the stain was recorded. This test was repeated for 10 samples and the results are shown in Table 2.

2TABLE 2Average Number of Wipes to Remove StainFood StainExample 1Comp. Example 1Swiffer Wet ™1Vanilla pudding6.0 (σ = .47)7.1 (σ = 1.3)6.3 (σ = .67)Chocolate pudding6.2 (σ = .67)6.8 (σ = .44)7.0 (σ = 1.0)1Available from Procter and Gamble Company, Cincinnati, Ohio

[0146] As can be seen in Tables 1 and 2, the coform nonwoven web of the present invention has superior wiping properties as compared to a coform material not having the coarse meltblown thermoplastic filaments and other commercially available wipes/mops.

[0147] While the invention has been described in detail with respect to specific embodiments thereof, and particularly by the example described herein, it will be apparent to those skilled in the art that various alterations, modifications and other changes may be made without departing from the spirit and scope of the present invention. It is therefore intended that all such modifications, alterations and other changes be encompassed by the claims.

Dual texture absorbent nonwoven web

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