100% synthetic nonwoven wipes

Abstract

The present invention relates to wipes comprising at least one layer of a 100% synthetic nonwoven web. The wipes may be provided as a single layer of nonwoven web, or may be provided in a laminate material, such as one comprising spunlaid-meltblown-spunlaid (SMS) webs. The 100% synthetic nonwoven webs of the present invention may be made via a process comprising a fiber laying step selected from the group consisting of spunlaying, meltblowing, carding, airlaying, wetlaying and combinations thereof. The 100% synthetic nonwoven webs of the present invention may be made via a process comprising a fiber bonding step selected from the group consisting of hydroentanglement, cold calendering, hot calendering, air thru bonding, chemical bonding, needle punching and combinations thereof. The nonwoven webs may also comprise one or more polyolefins. In one embodiment of the present invention, the nonwoven webs may be spunlaid and HET.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. patent application Ser. No. 10/737,129, filed Dec. 15, 2003, which is a continuation of U.S. patent application Ser. No. 09/671,718, filed Sep. 27, 2000, which claims the benefit of U.S. Provisional Patent Application No. 60/156,286, filed Sep. 27, 1999.

FIELD OF THE INVENTION

This invention relates to 100% synthetic nonwoven wipes comprising at least one layer of a 100% synthetic nonwoven web. The wipes, which may be premoistened, can be used in a variety of applications. Wipe applications may include use in surface cleansing and surface cleansing products, as well as use as or in, absorbent products.

BACKGROUND OF THE INVENTION

Nonwoven webs and processes for making them are known in the art. Processes for making nonwoven webs may comprise three steps: fiber laying, precursor web formation, and fiber bonding. The fiber laying step may be comprised of the spunlaying, meltblowing, carding, airlaying, wetlaying and combinations thereof, of the fibers comprising the web onto a forming surface. The step of precursor web formation may prevent the fibers comprising the web from coming apart during the bonding step. Precursor web formation may be performed via a pre-bonding step, such as one that is chemical or mechanical in nature. The bonding step may then impart strength to the finished web. The bonding step may be comprised of subjecting the fibers comprising the web to hydroentanglement (HET), cold calendering, hot calendering, air thru bonding, chemical bonding, needle punching, and combinations thereof.

In general, precursor web formation may add to the cost of making nonwoven webs by requiring the separate step of pre-bonding the fibers comprising the web. Likewise, the pre-bonding steps may affect the properties of the nonwoven web. For example, while pre-bonding may increase the durability of a nonwoven web, it may also increase its stiffness and, in turn, decrease its softness to the touch. Examples of processes requiring precursor web formation and the nonwoven materials made thereby may be found in: U.S. Pat. Nos. 5,023,130, 5,573,841, 6,321,425, 6,430,788, and 6,430,788; European Patent EP 0 333 211 B1; International Published Application WO 01/51693 A1; and U.S. Patent Application Publication Number 2004/0010894.

Processes known in the art for making nonwoven webs may produce nonwoven webs having sufficient strength in the machine direction; however, they may not produce nonwoven webs that also have sufficient strength in the cross-direction. When such nonwoven webs are pulled in the cross-direction, they may stretch and ultimately tear.

SUMMARY OF THE INVENTION

100% synthetic nonwoven webs known in the art typically do not have the absorptive capacity of webs that are at least partially non-synthetic. Thus, a 100% synthetic nonwoven web having good machine and cross-directional strengths, as well as softness and high absorptive capacity may be desired. Moreover, the provision of such improved material from a single 100% synthetic raw material via a continuous in-line process in the absence of precursor web formation may also be desirable. Additionally, a wipe comprising at least one layer of such a 100% synthetic nonwoven web may be desirable.

The present invention relates to wipes comprising at least one layer of a 100% synthetic nonwoven web. The wipes may be provided as a single layer of nonwoven web, or may be provided in a laminate material, such as one comprising spunlaid-meltblown-spunlaid (SMS) webs. The wipes may have a saturation loading of from about 1.5 to about 6.0 g of liquid composition per g of the wipe, or even from about 2.0 to about 4.0 g of liquid composition per g of the wipe. The wipes may be pre-moistened with a liquid composition having a surface tension of below about 35 dynes/cm, or even below about 30 dynes/cm. The wipes may have a basis weight that is greater than about 30 grams per square meter (gsm), or even a basis weight that is from about 40 and about 70 gsm. The cross-direction bending moment of the wipes may be less than about 0.09 (gf-cm²) per cm. The wipes may have an absorptive capacity that is greater than about 4 grams of liquid composition per gram of the wipe, or even greater than about 8 grams of liquid composition per gram of the wipe. The 100% synthetic nonwoven webs of the present invention may be made via a process comprising a fiber laying step selected from the group consisting of spunlaying, meltblowing, carding, airlaying, wetlaying and combinations thereof. The 100% synthetic nonwoven webs of the present invention may be made via a process comprising a fiber bonding step selected from the group consisting of hydroentanglement, cold calendering, hot calendering, air thru bonding, chemical bonding, needle punching and combinations thereof. The nonwoven webs may also comprise one or more polyolefins. In one embodiment of the present invention, the nonwoven webs may be spunlaid and HET.

DETAILED DESCRIPTION OF THE INVENTION

The present invention may relate to wipes comprising at least one layer of a 100% synthetic nonwoven web. The 100% synthetic nonwoven web may be made in a continuous in-line process, wherein at least one layer of fibers may be bonded together by HET, cold calendering, hot calendering, air thru bonding, chemical bonding, needle punching and combinations thereof, to form the web. The aforementioned bonding processes may be performed in the absence of precursor web formation via pre-bonding of the fibers comprising the web. The resulting 100% synthetic nonwoven webs may not only have strength in the machine and cross directions, but may also be soft and have a high absorptive capacity without the integration of non-synthetic fibers such as wood pulp for example.

The present invention may relate to wipes comprising at least one layer of a 100% synthetic nonwoven web, wherein the web is made through a process comprised of forming the nonwoven web from at least one layer of fibers. Such a process may be performed in the absence of a pre-bonding treatment of the fibers prior to subjecting them to HET by a plurality of high pressure water jets for example. The properties of the plurality of high pressure water jets may be varied to control some of the properties obtained in the resulting nonwoven web and the wipe ultimately comprised by the nonwoven web. Additionally, the present invention may provide that the fibers comprising the nonwoven web layer(s), be made from a 100% thermoplastic monocomponent fiber, such as a polyolefin or polyester. In addition or in the alternative, the present invention may provide that the fibers be biconstituent fibers. In addition or in the alternative, the present invention may provide that the fibers of the wipe layer(s) be made from a 100% thermoplastic bicomponent fiber, such as a sheath/core fiber or side by side fiber of polyethylene/polypropylene.

Different characteristics may be imparted to the wipes of the present invention depending upon the desired use. For example, the wipe may be made hydrophilic using surfactants. The wipe may also be premoistened.

The wipes of the present invention may be useful in absorbent products, such as feminine hygiene and adult incontinence products. The wipes of the present invention may also comprise dry or wet wipes that are useful for dry and/or wet surface cleaning, dry and/or wet body cleansing, as well as for various combinations of uses.

The term “fiber” as used herein, means a unit which forms the basic element of the nonwoven web disclosed herein. The term “fiber” may be used interchangeably with the term “filament”.

As used herein, the term “continuous fiber” refers to a fiber of an indefinite or extreme length. The term “continuous fiber” is may be used interchangeably with the term “continuous filament”.

“Monocomponent fibers” as used herein, refers to thermoplastic fibers that are made from one polymer.

“Bicomponent fibers” as used herein, refers to thermoplastic fibers that are comprised of at least two different polymers, wherein the polymers may be in a sheath/core or a side by side arrangement. Bicomponent fibers comprised of polymers in a sheath/core arrangement, are comprised of a core fiber made from one polymer that is encased or substantially encased within a thermoplastic sheath made from a different polymer. 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. Additionally, the bicomponent fibers of the present invention may be concentric, eccentric and combinations thereof.

The term “wipes” as used herein is a general term used to describe an article that is comprised by one or more layers of web. When wipes are comprised by more than one web layer, the web layers may or may not be bonded together via known consolidation processes including, but not limited to, HET, cold calendering, hot calendering air thru bonding, chemical bonding and the like.

The term “web” as used herein, refers to a layer or layers of 100% synthetic fibers that are formed by various processes in the absence of any bonding of the fibers within the layer or between the layers comprising the web. Processes of use may include spunlaying, meltblowing, carding, airlaying, wetlaying and combinations thereof.

“Synthetic” as used herein, refers to a material based on synthetic organic polymers such as polyolefins for example.

“Non-synthetic” as used herein, refers to man-made and natural fibers.

“Laminate” as used herein, refers to superimposed layers of web.

“Biconstituent fibers” as used herein, refers to thermoplastic fibers that are comprised by a blend of two or more thermoplastic polymers. Biconstituent fibers generally do not have the core/sheath arrangement of “bicomponent fibers” as used herein.

“Liquid composition” as used herein, refers to any liquid, including, but not limited to a pure liquid such as water, a colloid, an emulsion, a suspension, a solution and mixtures thereof.

“Softness” as used herein may be quantified by the measurable physical parameter of bending moment. Bending moment is typically expressed in (grams force·centimeter²) per centimeter, which is abbreviated as (gf-cm²) per cm.

“Premoistened wipes” as used herein, are wipes which are moistened, such as by wetting the wipe with a liquid composition prior to use by the consumer. “Premoistened wipes” as used herein, may also refer to wipes which are moistened prior to packaging in a generally moisture impervious container or wrapper. Such premoistened wipes, which can also be referred to as “wet wipes” and “towelettes”, may be suitable for use in cleaning babies, as well as older children and adults. Such premoistened wipes may also be of use, or comprise articles that are useful for, the application of substances to the body, like make-up, skin conditioners, ointments and medications. Such premoistened wipes may also be of use, or comprise articles that are useful for, cleaning or grooming pets or may even be of use, or comprise articles that are useful for, general cleansing of surfaces and objects, such as household kitchen and bathroom surfaces, eyeglasses, exercise and athletic equipment, automotive surfaces and the like. “Premoistened wipes” as used herein may even include dry wipes that are impregnated with liquid compositions, including but not limited to cleaning agents. Such “Premoistened wipes” might be wetted by the consumer prior to use. Furthermore, “premoistened wipes” as referred to herein may in addition, or in the alternative, include wet wipes that have been premoistened with liquid compositions, including but not limited to liquid compositions such as cleaning agents or lotions.

“Saturation loading” as used herein refers to the amount of liquid composition applied to the wipe. In general, the amount of liquid composition applied may be chosen in order to provide maximum benefits to the end product comprised by the wipe. Saturation loading is typically expressed as grams of liquid composition per gram of dry wipe.

As used herein, the term “basis weight” means the weight per unit area of the wipe, or the web(s) comprising the wipe. One method of determining basis weight, therefore, is to weigh a known area sample that is representative of the wipe or the web(s) comprising the wipe. The units of basis weight are typically expressed as grams per square meter (gsm).

“Surface tension” as used herein, refers to the force at the interface between a liquid composition and air. Surface tension is typically expressed in dynes per centimeter (dynes/cm).

The term “surfactant” as used herein, refers to materials which preferably orient toward an interface. Surfactants include the various surfactants known in the art, including nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, zwitterionic surfactants and mixtures thereof.

As used herein with respect to nonwoven webs, the term “machine-direction” or “MD” refers to the direction of web travel as the nonwoven web is produced, for example on commercial nonwoven making equipment. Likewise, the term “cross-direction” or “CD” refers to the direction perpendicular to the machine direction and parallel to the general plane of the layered fibrous product and/or layered fibrous structure. With respect to individual wipes, the terms refer to the corresponding directions of the wipe with respect to the web used to produce the wipe. These directions are carefully distinguished herein because the mechanical properties of a nonwoven web may differ, depending on how the nonwoven web is oriented during testing. For example, tensile properties of a nonwoven web may differ between the machine-direction and the cross-direction, due to the orientation of the constituent fibers, and other process-related factors.

“Comprising” as used herein means that various components, ingredients or steps can be conjointly employed in practicing the present invention. Accordingly, the term “comprising” encompasses the more restrictive terms “consisting essentially of” and “consisting of”.

100% Synthetic Nonwoven Web

The 100% wipe of the present invention is comprised of at least one layer of a 100% synthetic nonwoven web, which in turn is bonded by HET, cold calendering, hot calendering, air thru bonding, chemical bonding, needle punching and combinations thereof. The bonding process may be performed in the absence of any pre-bonding of the fibers, such as through chemical and/or mechanical pre-bonding for example. The nonwoven web may be comprised of a single layer, multiple layers, multiple layers with an absorbent core, and combinations thereof. Furthermore, the nonwoven web may include other fiber layer(s) that have been formed by various methods, including, but not limited to spunlaying, meltblowing, carding, airlaying, wetlaying and combinations thereof, in the absence of any bonding of the fibers to one another either within or between the web layer(s). When the nonwoven-web is comprised of a single layer, the fibers may be spunlaid. At least one of the layers of the nonwoven web may be comprised of fibers that are polymeric and continuous; as such, the present invention may eliminate the need to use non-synthetic fibers.

To provide a nonwoven web with high strength in the machine direction and cross-direction, with improved processability, both during and after manufacture, the nonwoven web may have a basis weight of from about 17 to about 150 gsm. In another embodiment, the nonwoven web may have a basis weight of from about 30 to about 100 gsm. In yet a further embodiment, the nonwoven web may have a basis weight of about 40 to about 70 gsm.

The fibers used to form the nonwoven web may be made using conventional extrusion apparatuses and techniques. The fibers may themselves be made of thermoplastic polymer(s) and may be comprised of monocomponent fibers, bicomponent fibers, biconstituent fibers and combinations thereof. The monocomponent fibers may include: polyolefins such as polypropylene and polyethylene; polyesters such as polyethylene terephthalate; polyamides; copolyamides; copolyesters; polyacrylates; polystyrenes; polyvinyl chloride; polyvinylidine chloride; polyvinyl acetate; polyethylvinyl acetate; polyacrylics; polyurethanes; polyhydroxyalkanoates; thermoplastic elastomers; and mixtures of these and other known fiber forming thermoplastic materials. In a further embodiment, the monocomponent fibers may be polyolefins such as polypropylene and polyethylene. In yet a further embodiment, the monocomponent fibers may be polypropylene. Biconstituent fibers may be made of a blend or blends of thermoplastic polymers including but not limited to polyolefins such as polypropylene and polyethylene; polyesters such as polyethylene terephthalate; polyamides; copolyamides; copolyesters; polyacrylates; polystyrenes; polyvinyl chloride; polyvinylidine chloride; polyvinyl acetate; polyethylvinyl acetate; polyacrylics; polyurethanes; polyhydroxyalkanoates; thermoplastic elastomers; and mixtures of these and other known fiber forming thermoplastic materials. Bicomponent fibers of use in the present invention may be concentric, eccentric, side by side and combinations thereof; eccentric bicomponent fibers may be desirable in providing more compressive strength at a given fiber thickness. The bicomponent fibers may be comprised of a sheath/core of: polyethylene/polypropylene, polyethylvinyl acetate/polypropylene, polyethylene/polyester, polypropylene/polyester, copolyester/polyester and mixtures of these and other known fiber forming thermoplastic materials. In one embodiment of the invention, bicomponent fibers of use may be those having a polypropylene or polyester core and a lower melting copolyester, polyethylvinyl acetate or polyethylene sheath. In a further embodiment of the invention, suitable bicomponent fibers may be comprised of a sheath/core of polyethylene/polypropylene. If the nonwoven web is comprised of multiple layers, then each layer may be of the same polymeric material. By using continuous fibers to form the nonwoven web, the present invention may provide for a wipe that not only has improved physical properties, but which may be made using only one raw material in an in-line, continuous process.

Varying the diameter of the fibers that comprise the 100% synthetic nonwoven web may be an effective means of altering the physical properties of the resulting web. The fibers may have a diameter of from about 0.1 to about 50 microns, from about 1 to 40 microns, or from about 5 to 35 microns.

Various physical properties, including, but not limited to, fluid-phobic, fluid-philic, fire retardant, absorbent, soft and anti-static properties, may be imparted to at least one portion of or to the entire 100% synthetic nonwoven web depending upon the use to which the resulting wipe is to be applied. In addition or in the alternative, physical properties including, but not limited to, low force extensibility, textured stretch without elastics, soft high elongation, flexibility, elasticity and extensibility may be imparted to at least one portion of or to the entire 100% synthetic nonwoven web via Solid State Formation (SSF) technology depending upon the use to which the resulting wipe is to be applied. At least one portion of the nonwoven web may include one or more of the layers which are in their entirety modified as to a given property. In the alternative, any pre-selected portion of the nonwoven web may be modified as to the pre-selected property. The desired property may be imparted to given areas in a variety of ways. SSF technologies that may be applied to the HET nonwoven web(s) that comprise the wipe may include, but are not limited to: ring rolling, as described in U.S. Pat. No. 5,143,679; structural elongation, as described in U.S. Pat. No. 5,518,801; consolidation, as described in U.S. Pat. Nos. 5,914,084, 6,114,263, 6,129,801 and 6,383,431; stretch aperturing, as described in U.S. Pat. Nos. 5,628,097, 5,658,639 and 5,916,661; differential elongation, as described in WO Publication No. 2003/0028165A1; and other SSF technologies as described in U.S. Publication No. 2004/0131820A1 and U.S. application Ser. No. 10/737430.

To optionally make all or a portion of the nonwoven web hydrophilic, the surface of the hydrophobic thermoplastic fibers which comprise the web may be rendered hydrophilic by treatment with a surfactant, such as a nonionic surfactant, anionic surfactant or mixtures thereof. For example, surfactants, or mixtures of surfactants, may be sprayed onto fibers, the fibers may be dipped into the surfactant or mixture of surfactants, and/or the surfactant or mixture of surfactants may be included as part of the polymer melt in producing the thermoplastic fiber. In the latter process, upon melting and re-solidification, the surfactant may tend to remain at the surfaces of the thermoplastic fiber. Further examples of suitable topical treatments for imparting hydrophilicity to nonwoven webs are described in U.S. Pat. Nos. 5,709,747 and 5,885,656. Suitable surfactants of use in the polymer melt include, but are not limited to, surfactants such as: Brij® 76 manufactured by ICI Americas, Inc. of Wilmington, Del. U.S.A.; various surfactants sold under the Pegosperse® trademark by Glyco Chemical, Inc. of Greenwich, Conn. U.S.A.; Standapol™, 1353A or 1480, as sold by Cognis Deutschland GmbH, Dusseldorf Germany; and Stantex® S 6327, as sold by Cognis Deutschland GmbH, Dusseldorf Germany. Surfactants suitable to be sprayed onto the fibers or into which the fibers may be dipped to impart hydrophilicity to the nonwoven web include, but are not limited to, those described in U.S. Pat. Nos. 5,709,747 and 5,885,656. Surfactants may be applied to the thermoplastic fibers at levels of, for example, from about 0.1 to about 1.0 grams per square meter of thermoplastic fiber.

Hydroentanglement of the Thermoplastic Fibers

In one embodiment of the present invention, the nonwoven wipe comprises at least one layer of a 100% synthetic nonwoven web, which in turn includes at least one layer of fibers bonded by hydroentanglement (HET). HET may be performed via the process described in U.S. Patent Application Publication No. 2004/0010894 A1, which may be summarized as follows. Before entering into the HET process, a desired spunlaid or meltblown layer (or layers) may be produced by a conventional method for producing fibers. If the layer is spunlaid, it may be comprised of continuous fibers. If the layer is meltblown, it may be comprised of low denier fibers, non-continuous fibers, and combinations thereof. The fibers may then be laid onto a moving support (or moving supports). Examples of useful moving supports include a moving mesh screen or a series of moving supports, such as perforated godet rollers. When a multi-layer material is being produced, second and subsequent layer(s) may be laid sequentially upon the prior formed layer(s) on the moving support. The layer or layers are then subjected to HET. The moving support may be structured to extend or transfer the layer or layers to the HET equipment such that the layer(s) is (are) essentially continually supported. The support may serve to maintain the structure of the layer(s) and to allow direct impact of water on the layer(s) from the plurality of high pressure water jets providing the HET while simultaneously preventing the destruction of the layer(s) when the water impacts the layer(s).

In the HET process itself, a plurality of water jets may be positioned above the moving support(s). The moving support(s) may be structured to allow for drainage of the water. The screen mesh or perforations in the godet rollers may have openings with a diagonal in the range of from about 0.1 to about 2.0 mm. The number of water jets present and the pressure at which the water is ejected are critical in determining the properties obtained in the treated nonwoven material. The water jets may be positioned so as to be spaced apart and to provide about 40 to about 50 water jets per linear inch. The water jets may be arranged to cover the width of the layer(s) being treated. A single line or a plurality of lines of water jets may be used. The support(s) for the layer(s) may move at a speed generally in a range of about 20 to about 250 meters per minute. Thus adequate exposure to the water jets may be provided. Water may be fed under pressure through nozzles, at a pressure of from about 20 to about 250 bar. Nozzle orifice diameters may be from about 0.1 to about 0.2 mm in order to provide the size of water streams desired.

Liquid Composition:

The wipes of the present invention may be premoistened with any liquid composition having a surface tension of below about 35 dynes/cm, or below about 30 dynes/cm. The liquid composition may for example be a colloid, an emulsion, a suspension, a solution and mixtures thereof. Generally, the liquid composition is of sufficiently low viscosity to impregnate the entire structure of the wipe. In some other instances, the composition can be primarily present at the wipe surface and to a lesser extend in the inner structure of the wipe. In one embodiment, the liquid composition may be releasably carried by the wipe; that is, the liquid composition may be contained either in or on the web(s) comprising the wipe, and may be readily releasable through the application of force to the wipe, such as by wringing the wipe, or wiping a surface, such as a child's bottom or a kitchen surface, with the wipe.

The liquid composition of the present invention may be comprised of any number of ingredients as long as the surface tension of the liquid composition is below 35 dynes/cm, or even below 30 dynes/cm. The ingredients may include, but are not limited to: water, perfumes, soothing agents, fragrances, preservatives, rheology modifiers, moisturizers, texturizers, colorants, medically active ingredients, such as healing actives and skin protectants, skin conditioning agents, surfactants, bleach, enzymes, detergents, organic cleaning solvents, salts, builders, chelants, suds suppressors, polymers, organic acids, odor control agents, peroxides, buffers and mixtures thereof.

Generally, the ingredients of the liquid composition are chosen based upon the desired end use for the premoistened wipe. For example, if the wipe is a “baby wipe”, the liquid composition may be an emulsion, such as an oil-in-water type of emulsion having as components an oily phase (in the form of an emollient), an emulsifier or surfactant component, and an aqueous phase that comprises further additives such as antimicrobial agents, soothing agents, rheology modifiers, and mixtures thereof.

Properties of 100% Synthetic Nonwoven Wipes

The 100% synthetic nonwoven wipes of the present invention exhibit various properties including, but not limited to, absorptive capacity and CD bending moment. Additionally, the liquid composition used to premoisten the nonwoven webs of the present invention exhibit the property of surface tension.

I. Absorptive Capacity

The following method is suitable to measure the absorptive capacity of any nonwoven web (when dry or wet) or finished wipe (when dry or wet).

Materials/Equipment

• 1. Sorption apparatus with computer. A suitable sorption apparatus is manufactured by Machinetek Corporation of Fairfield, Ohio U.S.A.
• 2. Cylinder/Piston Apparatus. A suitable piston apparatus is manufactured by Machinetek Corporation of Fairfield, Ohio U.S.A.
• 3. Balance which reads to four decimal places
• 4. 6000 mL Erlenmeyer flask

Preparation of the Apparatus

The apparatus consists of a piston/cylinder apparatus and a sorption apparatus. The piston/cylinder apparatus used for this measurement has three parts. A cylinder is bored from a transparent Lexan rod (or equivalent) and has an inner diameter of 6.00 cm (area=28.27 cm²), with a wall thickness of approximately 5 mm and a height of approximately 5 cm. The bottom of the cylinder is faced with a No. 400 mesh stainless-steel screen cloth that is biaxially stretched to tautness prior to attachment. The piston consists of a Teflon® or Kel-F® “cup” and a stainless steel weight. The cup is machined to fit into the cylinder within tight tolerances. The cylindrical stainless steel weight is machined to fit snugly within the cup and is fitted with a handle on the top. The combined weight of the cup and stainless steel weight is 1390 g, which corresponds to 0.70 psi for an area of 28.27 cm². A second stainless steel weight with the combined weight of the cup and weight being 596 g (0.30 psi) is also provided. Additionally, the samples can be tested without use of the piston/cup/cylinder assembly and new disk weights may be machined to obtain desired confining pressures. For absorbent material mopping systems, an in use pressure range of 0.07 to 0.10 psi is acceptable. For any modeling purposes, representative confining pressures should be determined on a case by case basis.

The components of the apparatus are sized such that the flow rate of the solution through the apparatus under a 10 cm hydrostatic head is at least 0.01 (g/cm²) per sec, where the flow rate is normalized by the area of the fritted disc in the apparatus. Factors particularly impacting system permeability may include the permeability of the fritted disc and the inner diameters of glass tubing and stopcocks.

The apparatus' reservoir is positioned on an analytical balance that is at least accurate to ±0.01 g with a drift of less than 0.1 g/hr. The balance is preferably interfaced to a computer with software that can: (i) monitor balance weight change at pre-set time intervals from the initiation of the absorptive capacity test and (ii) be set to auto-initiate on a weight change of 0.01-0.05 g, depending on balance sensitivity. The tube entering the reservoir should not contact either the bottom of the reservoir or its cover. The volume of fluid in the reservoir should be sufficient (e.g. at least 40 mL) such that, during the procedure, air is not drawn into the tube. The fluid level in the reservoir, at the initiation of the procedure, should be about 2 mm below the top surface of the fritted disc. This can be confirmed by placing a small drop of fluid on the disc and gravimetrically monitoring its slow flow back into the reservoir. This level should not change significantly when the piston/cylinder apparatus is positioned on the frit. The reservoir should have a sufficiently large diameter (e.g., about 15 cm) so that withdrawal of fluid during the procedure (e.g., about 40 mL) results in only a small change in the fluid height (e.g., less than 3 mm).

Once preparation of the apparatus is complete, prepare for each measurement by performing the following steps:

• 1. Forward flush the fritted disc with the test fluid so that it is filled with fresh fluid. Pour off the excess.
• 2. Cover the funnel.
• 3. Equilibrate the reservoir and the frit by opening the connecting valves.
• 4. Close all valves.
• 5. Drain the frit for 5 minutes by opening the 3-way valve to the drain.
• 6. Close the drain valve.

The quantity of fluid that drains from the frit in this procedure (called the frit correction weight) is measured by conducting the procedure (see below) for a time period of 15 minutes without the piston/cylinder apparatus. Essentially all of the fluid drained from the frit via this procedure is very quickly reabsorbed by the frit when the procedure is initiated. Thus, it is necessary to subtract this frit-correction weight from weights of fluid removed from the reservoir during the procedure. The frit correction is stable so this procedure may only be performed every 10-15 measurements.

Procedure

Before weighing the substrate, wipe the inner surface of the cylinder and outer surface of the cup with isopropanol (if using the cylinder assembly). Allow to air dry. If using the cylinder assembly, now insert the substrate into the piston cup and add to the cylinder. Place the cylinder or neat substrate onto the frit. Slip the desired stainless steel weight (pre-calculated for desired psi, nominally 0.04 psi) into the cup or directly onto the sample. Place the funnel cover on the fritted funnel. Check the balance for stability (i.e. the weight is constant, no change in the third decimal place). Initiate the measurement by opening the 3-way valve between the sample and the reservoir. With auto-initiation, data collection starts immediately, as the fritted disc begins to reabsorb fluid. Data is recorded for at least 3 minutes but should be confirmed against the sample for a smooth leveling of the absorption curve. Three sample replicates is minimally sufficient as long as a smooth curve is obtained.

Reagents

• 1. Distilled (DI) water.
• 2. Triton™ X-100-PC, which is: commonly known as (t-(t-Octylphenoxypolyethoxyethanol) that is peroxide and carboxyl-free; and is obtainable from Sigma Aldrich, Saint Louis, Mo. U.S.A.
  Preparation of the Reagents

When using deionized (DI) water, no additional preparatory steps are necessary. When using Triton™ X-100-PC, use the following preparatory steps. First, measure out 1000 g of DI water in a 1500 mL beaker. Using a scale with weight resolution of 0.01 g, measure out 1.0 g of Triton™ X-100-PC. Add the 1.0 g of Triton™ X-100-PC to the 1000 g of DI water. Stir with a stir-bar on a cold stir plate for approximately 5 minutes, or until the Triton™ X-100-PC has visually dissolved in the water. Add to the sorption apparatus.

Calculation of Absorptive Capacity

Absorptive capacity is reported in units of grams of liquid composition per gram of the wipe substrate being tested. Absorptive capacity at any time is determined as follows: $\mathrm{Absorptive}\mathrm{Capacity}\left(t\right)=\frac{\left\{W_r\left(t=0\right)-W_r\left(t\right)-W_{\mathrm{fc}}\right\}}{W_{\mathrm{substrate};\mathrm{dry}\mathrm{basis}}}$
Where t is the elapsed time from initiation, W_r(t=0) is the weight in grams of the reservoir prior to initiation, W_r(t) is the weight in grams of the reservoir at elapsed time t, W_fc is the frit correction weight in grams (measured separately), and W_{substrate; dry basis} is the dry weight in grams of the substrate. Absorptive Capacity is typically reported for times of 3 minutes after initiation. Additionally, if an electronic data collection system is being used, a maximum absorptive capacity can be obtained by substituting the maximum weight in grams from the reservoir, W_r(max) for W_r(t). This resolves the maximum absorptive capacity of the material: $\mathrm{Absorptive}\mathrm{Capacity}\left(\max \right)=\frac{\left\{W_r\left(t=0\right)-W_r\left(\max \right)-W_{\mathrm{fc}}\right\}}{W_{\mathrm{substrate};\mathrm{dry}\mathrm{basis}}}$
Note that alternate sources of equivalent chemicals and equipment may be used, provided they meet or exceed the requirements necessary to preserve the accuracy and precision of the method.

The wipes of the present invention may have an absorptive capacity of greater than about 4 grams of liquid per wipe. The wipes of the present invention may also have an absorptive capacity of greater than about 6 grams of liquid per wipe. Additionally, the wipes of the present invention may also have an absorptive capacity of greater than about 8 grams of liquid per wipe.

II. Surface Tension of Liquid Composition

The following method is suitable to measure the surface tension of the liquid compositions used to premoisten the wipes of the present invention.

Materials/Equipment

• 1. Kruss Processor Tensiometer K-12, manufactured by Kruss, Charlotte, N.C. U.S.A.
• 2. Small Sample Volume Platinum Plate
• 3. Burner for Platinum Plate Cleaning
• 4. Glass sample vessel for K12 Kruss Processor Tensiometer
• 5. Liquid composition or pure liquid to be tested
• 6. High purity water
• 7. Dish Detergent
• 8. Isopropanol

Procedure

• 1. Refer to the Kruss Owners Manual for Kruss Processor Tensiometer.
• 2. Clean the glass sample vessel with detergent, then lots of high purity water, then rinse with isopropanol.
• 3. Rinse out the glass sample vessel with the appropriate liquid composition or pure liquid to be tested, then fill the glass sample vessel ⅔ to ¾ full. Place the glass sample vessel into the silver jacket in the tensiometer.
• 4. The first liquid composition to be tested is high purity water (water measuring 70-74 dynes/cm is acceptable). If the high purity water is out of the acceptable range refer to the Kruss Owners Manual.
• 5. After placing the liquid composition in the glass sample vessel and into the silver jacket of the tensiometer, take the platinum disc, rinse it with distilled water, then isopropanol. Allow the disc to dry. Flame the disc red hot, not white. Allow the disc to cool.
• 6. Make sure the tensiometer balance is locked, then place the platinum disc into the clip. Unlock the balance.
• 7. On the printer/control pad enter 2 for Plate Method.
• 8. Next Enter 1 for Surface Tension.
• 9. Then Enter 1 for Single Measure.
• 10. Then enter sample ID=date and whatever sample it is.
• 11. Push CR on control pad.
• 12. Move the liquid composition up close to the platinum disc without touching the liquid composition.
• 13. Push start.
• 14. Record the surface tension result shown, which is indicated in dynes/cm.
• 15. Press CR to exit the program.
• 16. Lock the balance. Lower the liquid composition away from the platinum disc. Pull out the platinum disc.
• 17. Clean the disc with distilled water, then isopropanal and allow it to dry. Then flame the disc red hot and allow it to cool.
• 18. Clean the glass sample vessels with detergent, lots of water, and then isopropanol.

The liquid composition used to premoisten the wipes of the present invention may have a surface tension below about 35 dynes/cm. The liquid composition used to premoisten the wipes of the present invention may have a surface tension below about 33 dynes/cm. Additionally, the liquid composition used to premoisten the wipes of the present invention may have a surface tension below about 30 dynes/cm.

III. Cross-Direction Bending Moment

The following method is suitable to measure the cross-direction bending moment of the wipes of the present invention.

Materials/Equipment

• 1. The tester is a Kawabata Evaluation System for Fabrics, KES-FB-2 AUTO-A, from Kato Tech Co., Ltd., Kyoto, Japan.
• 2. Triton™ X-100-PC, which is: commonly known as (t-(t-Octylphenoxypolyethoxyethanol) that is peroxide- and carboxyl-free; and is obtainable from Sigma Aldrich, Saint Louis, Mo. U.S.A.

Procedure

• 1. Cut the wipe into 15 cm wide specimens.
• 2. Saturate five specimens with 400% loading of a 0.1% Triton™ X-100-PC solution. For example, a specimen weighing 2 g will be saturated with 8 g of a 0.1% Triton™ X-100-PC solution.
• 3. Open the “Optional” measurement condition. Set SENS=“20×1” on the computer, set SENS=“20” on the tester. Set Kspan=“SET”
• 4. Set the check switch on “OSC” and confirm a deflection on the voltmeter of +10V.
• 5. Set the check switch on “BAL” and confirm a reading of 0V on the voltmeter for each SENS setting. If necessary, adjust to 0V with the apparatus screw “AC-Bal”
• 6. Select ZERO and set the value to 0V on the digital display with the “ZERO ADJ” screw (only for the sensitivity you will be using).
• 7. Select MES.
• 8. Insert the specimen in the tray from the clamping unit, making sure that it is centered properly and in the correct orientation. The sensor light will come on when the specimen reaches the proper position.
• 9. Press the MEASURE button on the tester (the tester automatically clamps the specimen). A light will blink when the tester is ready to start the measurement.
• 10. Start the measurement on the computer. The tester automatically unclamps the specimen when measurement is complete.
• 11. Repeat steps 8 through 10 until 5 specimens have been measured. Report the average bending moment per unit width, expressed in (gf-cm²) per cm.

The wipes of the present invention may have a cross-direction bending moment of less than about 0.10 (gf-cm² ) per cm. The wipes of the present invention may have a cross-direction bending moment of less than about 0.09 (gf-cm²) per cm. Additionally, the wipes of the present invention may have a cross-direction bending moment of less than about 0.08 (gf-cm²) per cm.

Applications for 100% Synthetic Webs

The 100% synthetic webs of the present invention may be useful in a wide variety of applications. For example, the webs may be of use as a component of absorbent products such as disposable diapers; feminine hygiene products; adult incontinence products; medical products, particularly those that contact the human skin such as surgical gowns and masks; industrial garments; filtration media; and disposable dry or wet wipes, which may be premoistened.

The 100% synthetic webs of the present invention may comprise one or more layers of the wipes of the present invention. The wipes may be premoistened with a liquid composition or semi-liquid composition. In one embodiment of the present invention the premoistened wipe may be a “baby wipe”. A “baby wipe” is a wipe that may be designed for use on a child by a care giver during the changing of a soiled diaper. The wipe may be used to remove fecal matter, dried urine or the like, from an infant. Alternatively the “baby wipe” may be used to refresh a child in place of hand and/or face washing or even to remove dirt, food, vomit, mucus and the like, from the child and/or their clothing.

In another embodiment of the present invention, the wipe may be an “adult wipe”. That is the wipe is specially formulated for use by an adult for refreshing, removing make-up, applying make-up or lotions, food removal, cleaning, intimate use, etc.

In yet another embodiment, the wipe may be a “surface cleaning wipe”. Such a wipe may be designed for use on hard surfaces such as floors, counter tops, sinks, walls, tiles, etc. Hard surface cleaning wipes may be formulated for use on a variety of surfaces, such as tile, ceramic, wood, porcelain, metal and glass, including eyeglasses. Alternatively, they can be formulated for use in a specific area, such as in the kitchen, bathroom or motor vehicle. Wipes may also be used for cleaning or stain-treating fabrics. “Surface cleaning wipes” may be moistened prior to packaging, or may be dry wipes that are impregnated with liquid compositions. The latter type of wipe may or may not be moistened by the consumer prior to use.

EXAMPLES

The following examples are non-limiting examples of the present invention. Each starting nonwoven is made into a wet wipe by uniformly applying liquid compositions to the dry wipe. The wet wipe is saturation loaded to approximately 4.0 grams of liquid composition per gram of dry wipe. Different liquid compositions may be used. One liquid composition is deionized water, which has a surface tension of about 72 dynes/cm. A second liquid composition is 0.1% Triton™ X-100-PC in deionized water, which has a surface tension of about 31.5 dynes/cm. A third liquid composition is 0.0063% Triton™ X-100-PC in deionized water, which has a surface tension of about 37.6 dynes/cm. A fourth liquid composition is 0.00313% Triton™ X-100-PC in deionized water, which has a surface tension of about 42 dynes/cm. Non-limiting applications of wipes described in Examples 1-7 may include, but are not limited to, baby wipes, facial cleansing wipes, surface cleaning wipes, polishing wipes, and personal hygiene wipes.

Example 1

S-Tex 194050HO, manufactured by BBA Fiberweb, Nashville, Tenn. U.S.A., is used as the starting nonwoven. S-Tex 194050HO is a 50 gsm spunlaid nonwoven made from 100% polypropylene with a fiber titre of 2.0 dtex (dtex is the unit denoting grams per 10,000 linear meters of fiber) and thermally bonded. No surface treatment is added to the nonwoven.

The absorptive capacity, expressed in grams of liquid composition per gram of wipe of S-Tex 194050HO for the two different liquid compositions is summarized in the table below:

                                 Absorptive Capacity
Liquid                           [g liquid composition/g wipe]
Deionized Water                  0.15
0.1% Triton ™ X-100-PC in Deionized 8.9
Water

This example demonstrates the influence of the liquid on absorptive capacity.

Example 2

Fibrella 7458, manufactured by Suominen Nonwovens, Nakkila, Finland, is used as the starting nonwoven. Fibrella 7458 is a 58 gsm carded nonwoven made from 60% polypropylene staple fiber and 40% viscose fiber, each with a fiber titre of 1.5 dpf (dpf is the unit denoting grams per 9,000 linear meters of fiber) and hydroentangled. No surface treatment is added to the nonwoven.

The absorptive capacity of Fibrella 7458 for the two different liquid compositions is summarized in the table below:

                                 Absorptive Capacity
Liquid                           [g liquid composition/g wipe]
Deionized Water                  8.2
0.1% Triton ™ X-100-PC in Deionized 8.5
Water

When compared with Example 1, this example demonstrates that adding absorbent material to the nonwoven desensitizes the influence of the liquid composition on absorptive capacity.

Example 3

Avspun™ Phobic, manufactured by Avgol Nonwoven Industries, Holon, Israel, is used as the starting nonwoven. Avspun™ Phobic is a 50 gsm spunlaid nonwoven made from 100% polypropylene with a fibre titre of 1.4 dpf and hydroentangled. No surface treatment is added to the nonwoven.

The absorptive capacity of Avspun™ Phobic for the two different liquid compositions is summarized in the table below:

                                 Absorptive Capacity
Liquid                           [g liquid composition/g wipe]
Deionized Water                  0.14
0.1% Triton ™ X-100-PC in Deionized 12.8
Water

In conjunction with Example 1, this example demonstrates the influence of the liquid on absorptive capacity regardless of the method of nonwoven construction. This also illustrates that a significant increase in total absorptive capacity can be achieved by combining hydroentangled, continuous thermoplastic nonwovens and a low surface tension fluid.

Example 4

Avspun™ philic, manufactured by Avgol Nonwoven Industries, Holon, Israel, is used as the starting nonwoven. Avspun™ philic is a 50 gsm spunlaid nonwoven made from 100% polypropylene with a fiber titre of 1.4 dpf and hydroentangled. A hydrophilic surface treatment is added to the nonwoven.

The absorptive capacity of Avspun™ philic with a low surface tension liquid is presented in the table below:

                                 Absorptive Capacity
Liquid                           [g liquid composition/g wipe]
0.1% Triton ™ X-100-PC in Deionized 12.0
Water

This example illustrates that the high level of absorptive capacity is maintained with a hydrophilic surface treatment of the nonwoven.

Example 5

Avspun™ Lot# AVTI2489/2004 , manufactured by Avgol Nonwoven Industries, Holon, Israel, is used as the starting nonwoven. Avspun™ Lot# AVTI2489/2004 is a 45 gsm spunlaid-meltblown-spunlaid nonwoven made from 100% polypropylene with a spunlaid fiber titre of 1.6 dpf and hydroentangled. No surface treatment is added to the nonwoven.

The absorptive capacity of Avspun™ Lot# AVTI2489/2004 for three different liquid compositions is summarized in the table below:

                                 Absorptive Capacity
Liquid                           [g liquid composition/g wipe]
Deionized Water                  ˜0
0.00313% Triton ™ X-100-PC in    5.3
Deionized Water
0.0063% Triton ™ X-100-PC in     5.6
Deionized Water
0.1% Triton ™ X-100-PC in Deionized 14.4
Water

This example illustrates that the absorptive capacity is dependent upon the surface tension of a liquid. Deionized water has a surface tension of about 72 dynes/cm and the resulting absorptive capacity is low. 0.00313% Triton™ X-100-PC solution has a surface tension of about 42 dynes/cm and the resulting absorptive capacity is 5.6 grams of liquid per gram of wipe. 0.0063% Triton™ X-100-PC solution has a surface tension of about 37.6 dynes/cm and the resulting absorptive capacity is 5.3 grams of liquid per gram of wipe. 0.1% Triton™ X-100-PC solution has a surface tension of about 31.5 dynes/cm and the resulting absorptive capacity is 14.4 grams of liquid per gram of wipe.

Example 6

A 30 gsm variant of the Avspun™ Phobic nonwoven cited in example 3 is used as the starting nonwoven. The absorptive capacity of this nonwoven with Deionized Water and with 0.1% Triton™ X-100-PC in Deionized Water is the same as with the 50 gsm variant.

Example 7

A 70 gsm variant of the Avspun Phobic™ nonwoven cited in example 3 is used as the starting nonwoven. The absorptive capacity of this nonwoven with Deionized Water and with 0.1% Triton™ X-100-PC in Deionized Water is the same as with the 50 gsm variant.

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.

Claims

1. A wipe comprising at least one layer of a 100% synthetic nonwoven web, wherein said wipe is: characterized by saturation loading of from about 1.5 to about 6.0 grams of liquid composition per gram of said wipe; and premoistened with said liquid composition having a surface tension of below about 35 dynes per cm.

2. The wipe according to claim 1, wherein said liquid composition has a surface tension of below about 30 dynes per cm.

3. The wipe according to claim 1, wherein said wipe is characterized by saturation loading from about 2.0 to about 4.0 grams of liquid composition per gram of said wipe.

4. The wipe according to claim 1, wherein said wipe has a basis weight greater than about 30 grams per square meter.

5. The wipe according to claim 1, wherein said wipe has a basis weight from about 40 to about 70 grams per square meter.

6. The wipe according to claim 1, wherein said wipe has a cross-direction bending moment of less than about 0.09 (grams force·centimeter2) per centimeter.

7. The wipe according to claim 1, wherein said wipe has an absorptive capacity of greater than about 4 grams of liquid composition per gram of said wipe.

8. The wipe according to claim 1, wherein said wipe has an absorptive capacity of greater than about 8 grams of liquid composition per gram of said wipe.

9. The wipe according to claim 1, wherein said 100% synthetic nonwoven web is made via a process comprising a fiber laying step selected from the group consisting of spunlaying, meltblowing, carding, airlaying, wetlaying and combinations thereof.

10. The wipe according to claim 1, wherein said 100% synthetic nonwoven web is made via a process comprising a fiber bonding step selected from the group consisting of hydroentanglement, cold calendering, hot calendering, air thru bonding, chemical bonding, needle punching and combinations thereof.

11. The wipe according to claim 1, wherein said 100% synthetic nonwoven web is comprised by one or more polyolefins.

12. The wipe according to claim 1, wherein said wipe is comprised by a laminate of two or more layers of said 100% synthetic nonwoven web.

13. A wipe comprising at least one layer of a 100% synthetic nonwoven web, wherein said web is spunlaid and hydroentangled to form said wipe, and further wherein said wipe is: characterized by saturation loading from about 1.5 to about 6.0 g of liquid composition per gram of said wipe; and premoistened with a liquid composition having a surface tension of below about 35 dynes per cm.

14. The wipe according to claim 13, wherein said liquid composition has a surface tension of below about 30 dynes per cm.

15. The wipe according to claim 13, wherein said wipe is characterized by saturation loading from about 2.0 to about 4.0 grams of liquid composition per gram of said wipe.

16. The wipe according to claim 13, wherein said wipe has a basis weight greater than about 30 grams per square meter.

17. The wipe according to claim 13, wherein said wipe has a basis weight from about 40 and about 70 grams per square meter.

18. The wipe according to claim 13, wherein said wipe has a cross-direction bending moment of less than about 0.09 (grams force·centimeter2) per centimeter.

19. The wipe according to claim 13, wherein said wipe has an absorptive capacity of greater than about 4 grams of liquid composition per gram of said wipe.

20. The wipe according to claim 13, wherein said wipe has an absorptive capacity of greater than about 8 grams of liquid composition per gram of said wipe.

21. The wipe according to claim 13, wherein said liquid composition is comprised by bleach.