HK1020076B - Mechanical and internal softened nonwoven web and its articles - Google Patents

Description

Mechanically and internally softened nonwoven fabrics and articles thereof

Background

The present invention relates to the field of nonwoven fabrics and their manufacture. More particularly, the invention relates to nonwoven fabrics comprising at least one layer of staple fibers or filaments or multifilament filaments. These fibers typically comprise thermoplastic polymers such as polyamides, polyesters, polyethers; and contain polyolefins such as polypropylene, polyethylene, polybutylene; copolymers, and blends thereof are also included.

The microfiber webs are useful in the manufacture of personal care products such as diapers, full-crotch pants for the training of children to urinate and defecate, feminine hygiene products, adult incontinence products, infection control products such as surgical drapes, doctor's gowns, sterilization wraps, and various garments. The softness of the cloth for this purpose is an important factor, since the cloth may be in contact with the wearer for a long time.

Various methods of increasing the softness of nonwoven fabrics are well known in the art. These methods include water wash softening, mechanical stretching, and topical treatment of the fabric with softeners.

The water-washing softening technique of nonwoven fabrics is a very time-consuming batch operation, which does not meet the requirements of industrial production. Additionally, the large amount of water from the water washing process must be disposed of, either recycled or discarded, and the washed fabric must be dried. Drying nonwoven fabrics is an energy intensive process that is somewhat difficult to control in large scale production and sometimes results in re-melting, embrittlement or other damage to the nonwoven fabric.

Mechanical softening by stretching does not provide sufficient softness, which has been found in some applications. Topical treatments also do not provide the softness required for certain applications, but also have additional manufacturing limitations.

Us patent 5,413,811 to Fitting et al describes a treatment for improving the softness of a nonwoven fabric by both mechanical and chemical means. This patent describes how to produce a softer nonwoven fabric by localized chemical treatment and mechanical stretching by wetting a nonwoven fabric having an unstretched initial width and an initial cup crush value (cup crush value) with an aqueous solution of a softening agent, then drawing the saturated nonwoven fabric down to a second width of about 50-95% of the initial unstretched width, and drying at a temperature and for a time sufficient to remove 95% of the moisture from the nonwoven fabric.

Although this method produces very soft nonwoven fabrics, there is a need for a simpler method that results in fewer production steps and thus fewer opportunities for errors in production. At the same time, a more messy procedure of avoiding local treatment of the nonwoven fabric should also be considered as a priority.

It is also known in the art to have an internal additive to the nonwoven fabric as opposed to a topical treatment, for example to increase the protective properties of the fabric. This often involves the use of fluorocarbon additives that migrate to flow or "bloom" to the fabric surface after the fibers are formed. Examples of such additives can be found in U.S. Pat. No. 5,178,931 to Perkins et al and U.S. Pat. No. 5,482,765 to Bradley et al.

There is therefore a need for a nonwoven fabric which is made by a softening process or treatment procedure which avoids the use of topical treatments, but which is sufficiently flexible to be suitable for making garments. The process must soften faster than water washing, be cleaner than topical treatments, and be suitable for large-scale industrial production.

Accordingly, it is an object of the present invention to provide a microfiber nonwoven fabric which does not use topically applied chemicals, which can be continuously produced industrially, and which is sufficiently flexible for use in making garments.

Summary of The Invention

The present invention achieves the above objects by a fabric spun from a mixture of thermoplastic polymer and internal softening additives in an amount up to 3% by weight, and mechanically treated to increase its softness. The fabric has a final cup crush value of less than 50% of the initial cup crush value and a drop in cup crush value greater than the sum of the cup crush values of the individual treatments.

Brief Description of Drawings

Figure 1 shows a schematic of an apparatus that can be used to stretch or contract the fabric of the present invention.

Figure 2 shows a schematic diagram of a device that can be used to widen the fabric of the invention.

Definition of terms

The term "nonwoven fabric" as used herein refers to a fabric having a structure of layers of fibers or filaments which are interlaid, but not in an identifiable manner as in a knitted fabric. Nonwoven fabrics have been produced by a number of processes, such as, for example, meltblowing processes, spunbonding processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm), while the diameter of the fibers used is usually expressed in microns (note: osy is converted to gsm by multiplying osy by 33.91).

The term "microfibers" as used herein means very small diameter fibers having an average diameter of no greater than about 75 micrometers, such as an average diameter of from about 0.5 micrometers to about 50 micrometers, or more specifically, microfibers have an average diameter of from about 2 micrometers to about 40 micrometers. Another common fiber diameter is expressed as denier, which is defined as grams per 9000 meters of fiber and can be calculated as the fiber diameter in microns squared times the density in g/cc, times 0.00707. A lower denier indicates a finer fiber and a higher denier indicates a coarser or heavier fiber. For example, given a polypropylene fiber diameter of 15 microns, the square can be calculated as the denier multiplied by 0.89g/cc multiplied by 0.00707. Thus, the 15 micron polypropylene fiber has a denier of about 1.42 (15)²X 0.89 × 0.00707 ═ 1.415). Outside the United statesThe unit of measurement more commonly uses "tex", which is defined as grams per kilometer of fiber, and tex can be calculated as denier/9.

The term "spunbond fibers" as used herein refers to very small diameter fibers which are made by extruding molten thermoplastic material through a plurality of fine, usually circular, spinneret capillaries as filaments, and then rapidly reducing the diameter of the extruded filaments by the methods of the following patents, examples of which are: U.S. Pat. Nos. 4,340,563 to Appel et al; U.S. Pat. Nos. 3,692,618 to Dorschner et al; U.S. Pat. Nos. 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 and U.S. Pat. No. 3,542,615 to Dobo et al. Spunbond fibers are generally not tacky when they are placed on a collecting surface. Spunbond fibers are generally elongated and have average diameters (at least 10 samples) larger than 7 microns, and more particularly, between 10 and 20 microns.

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 descending high velocity, usually hot, gas (e.g. air) streams which attenuate the molten thermoplastic material, such as filaments, 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 nonwoven web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin. Meltblown fibers are microfibers which may be elongated or non-elongated, are generally smaller than 10 microns in average diameter, and are generally tacky when deposited onto a collecting surface.

The term "coform" is used herein to mean a process in which at least two dies surround a central discharge opening through which other materials are added to the nonwoven fabric as it is being formed. This other material may be pulp, superabsorbent particles, cellulose fibres or short fibres. A synergistic process is shown in commonly assigned U.S. patent 4,818,464 to Lau and U.S. patent 4,100,324 to Anderson et al. Nonwoven fabrics produced by a co-production process are commonly referred to as coform materials.

The term "multilayer laminate" is intended herein to mean a laminate in which some of the layers are spunbond fibers and some of the layers are meltblown fibers, such as spunbond/meltblown/spunbond (SMS) laminates, as well as other laminates such as those disclosed in the following patents: U.S. Pat. Nos. 4,041,203 to Brock et al; U.S. Pat. Nos. 5,169,706 to Collier et al; U.S. Pat. Nos. 5,145,727 to Potts et al; U.S. Pat. Nos. 5,178,931 to Perkins et al; and U.S. Pat. No. 5,188,885 to Timmons et al. The laminate may be made by sequentially placing a layer of spunbonded fabric on a moving forming belt, then a layer of meltblown fabric, and finally another layer of spunbonded fabric, and then bonding the laminate in the following condition; alternatively, the fabric layers may be separately prepared and rolled up and then bonded in a separate bonding step. The fabric has a basis weight of about 0.1 to 12osy (6 to 400gsm), or more specifically about 0.75 to 3 osy. The multilayer laminate may also have a variety of numbers of meltblown layers or spunbond layers, may be formed in a variety of different configurations, and may include other materials such as film (F) or coform materials such as SMMS, SM, SFS, and the like.

The term "polymer" herein generally includes (but is not limited to): a homopolymer; copolymers such as block copolymers, graft copolymers, random and substituted copolymers; terpolymers, etc., and blends and modifications thereof. In addition, unless otherwise specifically limited, the term "polymer" shall include all possible geometric configurations of the molecule, including (but not limited to): isotactic symmetry, syndiotactic symmetry and random symmetry.

The term "machine direction" or MD is used herein to refer to the length in the direction of fabric production. The term "cross-machine direction" or CD refers to the width of the fabric, i.e., often the direction perpendicular to the MD.

The term "monocomponent" fiber as used herein refers to a fiber made from one or more extruders using only one polymer. This is not meant to exclude additives made from one polymer, but small amounts of additives for coloration, antistatic properties, lubrication, hydrophilicity, etc. These additives, such as titanium dioxide colorants, are generally present in amounts less than about 5 weight percent, more typically less than about 2 weight percent.

The term "conjugate fibers" as used herein refers to a fiber made from at least two polymers extruded from a single extruder but spun together. Composite fibers are also sometimes referred to as multicomponent fibers or bicomponent fibers. Although the composite fibers may be monocomponent fibers, the polymers are generally not the same. The polymers are arranged in distinct zones of fixed position substantially throughout the cross-section of the composite fiber and extend continuously along the length of the composite fiber. Such composite fibers may be, for example, sheath-core, with one polymer surrounding the other, side-by-side, pie-shaped, or "islands-in-the-sea" in shape. Composite fibers are discussed in the following patents: U.S. Pat. Nos. 5,108,820 to Kaneko et al; U.S. Pat. No. 4,795,668 to Krueger et al and U.S. Pat. No. 5,336,552 to Strack et al. U.S. patent 5,382,400 to Pike et al also discusses composite fibers and indicates that the different expansion and contraction rates of two (or more) polymers can be utilized in the composite fibers to produce crimp. Crimped fibers can also be produced by mechanical means and the method of German patent DT 2513251A 1. For bicomponent fibers, the polymer ratios may be 75/25, 50/50, 25/75 or any other desired ratio. The shape of such fibers may be as described in Hogle et al, U.S. Pat. No. 5,277,976, Hills, U.S. Pat. No. 5,466,410, and Largman et al, U.S. Pat. Nos. 5,069,970 and 5,057,368, which are non-generic shaped fibers.

The term "blend" means a mixture of two or more polymers, while the term "blend" means a sub-grade blend in which the components are immiscible but blended together.

The term "ultrasonic bonding" means a process carried out, for example, by passing the fabric between a sonic generating head and an anvil roll as described in U.S. Pat. No. 4,374,888 to Bornslaeger.

The term "thermal point bonding" relates to the passing of a fibrous web or fibrous nonwoven web to be bonded between a heated calender roll and an anvil roll. Calender rolls are not always, but often are formed in such a way that the entire fabric is not bonded to the entire surface, while anvil rolls are generally smooth. As a result, various calender roll patterns have been developed for functional and aesthetic reasons. An example of a pattern is described in U.S. patent 3,855,046 to Hansen and Pennings having points thereon, namely the Hansen Pennings or H & P pattern, having a bond area of about 30% and about 200 bond points per square inch. The H & P pattern had square spot or spot bond areas with each spot having a side dimension of 0.038 inches (0.965mm), an inter-spot spacing of 0.070 inches (1.778mm), and a bond depth of 0.023 inches (0.584 mm). The pattern so made has a bond area of about 29.5%). Another typical point bond pattern is the expanded Hansen Pennings or "EHP" bond pattern which produces a 15% bond area with each square point having an edge dimension of 0.037 inches (0.94mm) and an inter-point spacing of 0.097 inches (2.464mm) and a bond depth of 0.039 inches (0.991 mm). Another typical point bond pattern is labeled "714" and has a square point bond area with each point having a side dimension of 0.023 inches, a point-to-point spacing of 0.062 inches (1.575mm), and a bond depth of 0.033 inches (0.838 mm). The pattern thus produced had a bonding area of about 15%. In addition, a common pattern, referred to as the C star pattern, has a bond area of about 16.9%. The C-star has a transverse sliver or corduroy design, the sliver being interrupted by meteors. Additional common patterns include diamond patterns and wire weave patterns. The diamond pattern was a repeating slightly offset diamond with a bond area of about 16%; the wire weave pattern looks like a screen as the name implies, with a bond area of about 19%. The bond area is typically from about 10% to about 30% of the area of the fabric laminate. It is well known in the art that point bonding allows the layers of a laminate to be brought together by bonding the filaments and/or fibers within each layer, while also giving each individual layer integrity.

The term "necking or rock-drawing" refers to the process of elongating a nonwoven fabric, usually in the machine direction, and reducing its width in a controlled manner by a desired amount. Controlled stretching can be carried out at cool temperatures, room temperature or higher temperatures, and the overall dimension in the direction being stretched can be increased by as much as the elongation required to break the fabric, which in most cases is 1.2 to 1.4 times. When released, the nonwoven fabric will retract back toward its original dimensions. Such processes are disclosed, for example, in the following patents: U.S. Pat. nos. 4,443,513 to Meitnen and Notheis; U.S. Pat. nos. 4,965,122, 4,981,747 and 5,114,781 to Norman; and U.S. Pat. No. 5,244,482 to Hassenboehler Jr et al.

The term "shrink softening" (tack softening) is used herein to refer to drawing without heat, i.e. drawing the material in the machine direction at an external temperature. In shrink softening, the amount of fabric that is pulled down is, for example, 20%. This means that the fabric is stretched in the machine direction until its width reaches 80% of its original unstretched width.

The term "stretchable material" means herein a material that can be stretched.

The term "necked material" is used herein to refer to any material which has been necked in at least one vector, by stretching or gathering, for example.

The term "stretching" (un-stretching) is used herein to mean a process that is used to stretch a material by applying a pulling force, typically in a direction perpendicular to the original pulling force, that stretches it to a dimension that retracts it to at least about 50% when the pulling force is released.

The term "water-wash softened" means that sensation to the water-wash softened material in a common household washing machine.

The terms "elastic" and "elastomeric", when referring to a fiber, film or fabric, means a material that, when added to a biasing force, is capable of elongating to at least 150% of its relaxed, unstretched length, i.e., one and a half times its stretched, deflected length, which springs back to at least 50% of its elongation when the stretching biasing force is released.

The term "recovery" is used herein to refer to a material that is stretched and its amount of recovery when a biasing force is terminated after the material is stretched with the biasing force. For example, a material that is 1 inch in length in a relaxed undeflected state is stretched by 50% to 1.5 inches, and the stretched length of the material is 150% of its relaxed length. If the stretched material retracts to 1.1 inches after the deflection and stretching forces are released, the material is 80% (0.4 inches) of its elongation.

The term "garment" herein means any non-medical garment that is wearable. It includes industrial and long work clothes, underwear, pants, shirts, jackets, gloves, socks, etc.

The term "infection control article" as used herein means medical articles such as surgical gowns and drapes, face masks, head coverings such as bulky caps, operating caps and head towels; such as shoe covers, boot covers and slippers, sick and wounded clothes, bandages, disinfectant cloths and wipes; clothing such as laboratory gowns, aprons and jackets; bed bedding, stretcher and bassinet, and the like.

The term "personal care product" as used herein means diapers, full-crotch pants for training children to urinate and defecate, absorbent underpants, adult incontinence products, and feminine hygiene products.Test method

And (3) cup pressing test: the softness of the nonwoven fabric can be measured according to the "cup press" test. The cup crush test measures the stiffness of a fabric by measuring the peak load (also referred to as the "crush cup") required to punch a 23cm by 23cm piece of inverted cup fabric having a diameter of about 6.5cm and a height of 6.5cm using a hemispherical presser foot having a diameter of 4.5cm, while the cup fabric is surrounded by a cylinder having a diameter of about 6.5cm to ensure that the cup fabric deforms uniformly. The average of 10 readings was used. The presser foot and the cup are required to be arranged on a straight line so as to prevent the presser foot from contacting the edge of the cup to influence the reading. The peak load is measured when the presser foot is lowered at a rate of 0.25 inches per second (380 mm per minute), the load being in grams. The cup crush test also derives the total energy required to cup crush the sample ("cup crush energy"), which is the energy from the start of the test to the point of peak load, i.e., the area under the curve formed by the grams of load on one axis and the millimeters of foot travel on the other axis. The cup pressure can therefore be measured in g-mm. A lower cup crush parameter value indicates a softer fabric. A suitable apparatus for measuring cup crush parameters is a FTD-G-500 type load cell (measuring range 500G), available from Schaevitz, Pennsauken, N.J..

The values reported in the following table are cup crush load values.Detailed Description

The object of the invention is achieved by a fabric made of thermoplastic polymer fibres, the polymer of which has additives that increase the softness, and the fabric that is made being mechanically softened.

A variety of softeners are well known in the art and typically include several forms of silicone. Examples of silicones containing compounds that increase fabric wettability are given in U.S. patent 4,923,914 to Nohr and MacDonald. Another suitable Silicone containing compound is an ultra high molecular weight polymer in solid particulate form, a family of polymers available under the trade designation Dow Corning  MB 50 Silicone Masterbatch Polymer. A special Dow Corning  MB 50 Silicone Masterbatch polymer containing about 50% Silicone and an organic resin made from a 12 melt index polypropylene is available under the Dow Corning  MB 50-001 Silicone Masterbatch polymer. The Dow Corning  MB 50 Silicone Masterbatch polymers family of polymers is available from Dow Corning Corporation of Midland, Mich.

Preferred additives in the practice of the present invention are special grades of siloxanes having the general formula:

wherein n is from 3 to about 1000.

A commercial source of silicone suitable for use in the practice of the present invention is Dow corning corporation, located in Midland, michigan, which distributes this silicone under the registered name 200  fluid. Additional sources include General Electric, PPGIndindustries, Inc., Goldschmidt, and OSi.

In order to practice the present invention, the additives must be thoroughly mixed with the thermoplastic polymer. The mixture can be produced, for example, by compounding the components in a 30 or 60mm twin-screw extruder. Any other effective method of compounding polymers known to those skilled in the art may be used. In the following examples with the addition of internal additives, the mixture is made by blending the polymer (usually polypropylene) with each additive to a predetermined level in a twin-screw extruder. The mixture thus obtained was subsequently blended with the pure polymer in the dry state to achieve the percentage of additive described in each example.

The inventors have found that the silicone additive content should be less than 3 weight percent, since above this level there is a negative effect on the adhesion. They also found that silicone additives tend to migrate to the surface of the fiber or "bloom" to the surface, providing some degree of lubricity. The texture softness and surface lubricity provided by the silicone additive, coupled with mechanical softening, results in an unexpectedly softer and more drapeable fabric that is acceptable for commercial continuous production. The fabrics produced in the practice of the present invention have cup crush parameters at least 50% lower than fabrics produced without the combination of internal additives and mechanical treatment as in the present invention.

Mechanical treatment of fabrics can be carried out in a number of different ways, such as microcreping, cold embossing, roll-to-roll beating, stretching, spreading, passing through a nip, and combinations thereof. Other methods well known in the art may also be employed. The purpose of this is to loosen or break a sufficient number of inter-fibre bonds to produce a softer fabric.

Referring to fig. 1, in one embodiment of the present invention, the stretchable material 12 may be a multi-layer material having, for example, at least one layer of spunbond fabric attached to at least one layer of meltblown fabric, bonded carded fabric or other suitable material. For example, the stretchable material 12 may be a multi-layer material having a first layer of spunbond polypropylene having a basis weight of about 0.2-8 ounces (osy) per square yard, a layer of meltblown polypropylene having a basis weight of about 0.2-4 osy, and a second layer of spunbond polypropylene having a basis weight of about 0.2-8 osy.

The stretchable material 12 may also be a single layer of material such as a spunbond fabric having a basis weight of about 0.2 to 10 osy or a meltblown fabric having a basis weight of about 0.2 to 8 osy.

The stretchable material 12 may also be a composite or coform material made from a mixture of two or more different fibers or a mixture of fibers and particles. Such a mixture may be formed by adding fibers and/or particulates to a gas stream carrying meltblown fibers such that intimate entangled intermingling of the meltblown fibers with other materials, e.g., wood pulp, staple fibers or particulates such as superabsorbent materials, occurs before the fibers are collected on a collection device to produce a randomly distributed consolidated web of meltblown fibers with other materials, e.g., as disclosed in U.S. patent No. 4,100,324 to Anderson et al.

If the shrinkable material 12 is a nonwoven fabric made of fibers, the fibers should be bonded together to form a consolidated fabric structure that is resistant to shrinkage. Fiber-to-fiber bonding can also be created by entanglement between individual meltblown fibers. Entanglement of the fibers is inherent in the melt blowing process, but may also occur or be enhanced by methods such as hydroentanglement or needle punching. Alternatively or additionally, an adhesive may be used to strengthen the desired bond, or the bond may be effected by ultrasonic point bonding, printed point bonding or heat point bonding.

The stretchable material 12 passes over the faces of a series of steam cans 28-38 in a series of inverted S-belts after passing over the nip face of the drive roller assembly 18. The steam cans 28-38 typically have an outer diameter of 24 inches, but other size cans may be used. The contact time or residence time of the shrinkable material on the steam drum is such that the heat treatment is achieved, the length of time depending on such factors as the temperature of the steam drum, the type of material and/or the unit weight. For example, polypropylene shrinkable fabrics can be contacted for 1 to 300 seconds as they are passed over a series of steam cans heated to a measured temperature of from room temperature to about 150 c (302F) to effect heat treatment. More specifically, the temperature may be in the range of about 100 to 135 ℃ and the residence time may be in the range of about 2 to 50 seconds.

Because the circumferential speed of the drive rollers 20 and 22 is controlled to be lower than the circumferential speed of the vapor canisters 28-38, the stretchable material 12 is stretched between the vapor canisters 28-38 and the drive rollers 20 and 22. By adjusting the speed differential between the rollers, the stretchable material 12 is caused to contract from the initial unstretched width to the second width, by the desired amount, and to remain in this stretched condition as it passes over the heated steam cans 28-38. This action gives the stretchable material 12 a memory of the stretched state. The peripheral linear velocity of the rollers in the support roller assembly 42 can be maintained above the velocity of the steam cans 28-38 so that the necked material 12 is further stretched and cooled in the necked condition in the widening step leading to fig. 2. This completes the preparation of the expandable (refonked) material 44.

The extensible material 44 may be expanded to a third width, similar to its original pre-stretched dimension, after being subjected to a stretching force in a direction generally transverse to the machine direction. The stretching of the fabric can be accomplished by using commercially available equipment such as a tester rack that can grasp both edges of the fabric and pull it to the desired width, as shown in figure 2. In the practice of this type of stretcher, the stretchable material 44 is passed through a stretcher assembly 56, including a tent frame, as is well known to those skilled in the art. In the Tenter stand shown in FIG. 2, a plurality of clips 60 on the chain 58 are attached to the links and spaced along the chain 58, with similarly spaced clips 60 on the chain 62. The chains 58 and 62 are driven by gears 64 which are driven by a motor 65 (not shown). The chains 58 and 62 are not parallel, but diverge in a downstream direction (indicated by arrow 65A) (from a top view). As material 44 approaches assembly 56, the previously opened jaws 60 automatically close in sequence, gripping the edges of the laminate. As the chains 58 and 62 advance forward, the material 44 is stretched to diverge as the chain's path. When the jaws 60 reach the top end of the chain run, they automatically open, releasing the pulled fabric 44. After the tension is released, the material will retract to at least 50% of the stretched dimension. The finished fabric 44 may be wound onto rolls (not shown) for lifting and storage.

For the purposes of the present invention, it is contemplated that the softness required will be about 70g or less absolute cup crush load. The final cup crush load value of a fabric treated according to the method of the present invention should be at least 50% less than the initial cup crush parameter value for that fabric, i.e., the final cup crush load value is no greater than 50% of the initial cup crush load value. Furthermore, the various treatments described above, including the method of the present invention, are not so effective on lighter basis weight fabrics, since such fabrics, by virtue of their slimness and inherent adaptability, have very low cup crush parameter values. Fabrics having basis weights above about 1 osy (34 gsm) are most affected by the treatment method described below and are the primary field to which the invention is applicable.

The inventors also believe that fabrics treated with the internal softeners and mechanical methods described above may also benefit from topical treatment if desired. For example, the topical treatment described in Fitting et al, U.S. patent 5,413,811, may be effective in further reducing the cup crush parameter value of the fabric. In the fixing patent, the softener is added prior to mechanical softening in an amount of between 0.1 and 10% by weight of the nonwoven fabric. These softeners may be any chemical well known to those skilled in the art for softening textiles. The softening agent may be a silicone, anionic, nonionic or cationic softening agent, but cationic softening agents are preferred.

Anionic softeners are typically chemical compounds, for example sulfonated oils such as castor oil, olive oil and soybean oil; sulfonated synthetic aliphatic esters such as triolein; and high molecular weight sulfonated aliphatic alcohols.

Nonionic softeners are highly compatible with other finishes and are typically compounds such as glycols, glycerin, sorbitol, urea, and the like. Fatty acid compounds such as polyethylene glycols of high molecular weight saturated fatty acids such as palmitic acid and stearic acid, and others.

Cationic softeners are generally long chain amide, imidazoline and quaternary nitrogen compounds. One suitable cationic softening agent is a quaternary ammonium compound based on animal fat under the trade name Varisoft . Textile softeners are known from Riggs, C.L. and Sherill, J.C. patentsTextile Laundering Technology(1979) This is discussed in the book (p.71-74), and also in American Dyestuff Reporter, September 1973 (p.24-26) and Textile World, December 1973 (p.45-46).

The following examples illustrate the effect of various treatment methods in terms of cup crush parameter values for nonwoven fabrics. Note that each data point represents the measurement of at least five individual fabrics, due to the standard deviation of the cup crush test. Note also that there is only an embodiment of the present invention in embodiment 8.Example 1

A spunbond-meltblown-spunbond (SMS) nonwoven laminate was made according to the general method of U.S. patent 4,041,203, with the layers being sequentially laid down on a moving forming wire. The total basis weight of the laminate was 1.5 osy (51 gsm) and the basis weights of the layers were 0.5-0.5-0.5 osy (17-17-17 gsm), respectively. The polymer from which each layer was made was PF-304, respectively, available from Himont Corporation; 3795G, available from Exxon chemical Company; and PF-304. The laminated fabric is a bonded nonwoven fabric made by point bonding with heat.

In this embodiment, the laminated cloth is washed with water in a common household washing machine. The washing cycle was 30 minutes with warm water, added with 1/2 cups of Tide^A detergent. In samples washed more than once, more detergent was added after each wash and the next wash started without drying between cycles. After all wash cycles were completed, each sample was placed in a conventional household spin dryer and spun down at a set low speed for 30 minutes. The SMS laminate was then subjected to cup crush parameter value tests, the results of which are shown in table 1.

TABLE 1

Sample (I) Control Sample (I) Change%1.5 osy SMS 205 and left-1.5 osy SMS water washed 1 time 20570-661.5 osy SMS water washed 5 times 20550-76

The results clearly show a surprising increase in softness achieved by mechanical softening with a simple water wash. Not only did the water wash significantly reduce the percentage of the cup crush parameter value, but the absolute value of the cup crush parameter also showed this to be a very soft fabric.

Unfortunately, water washing is a very water, labor and energy intensive process for softening nonwoven fabrics. Washing is a batch process which is not suitable for continuous production of large quantities of fabric.Example 2

A spunbond-meltblown-spunbond (SMS) nonwoven laminate was made according to the general method of U.S. patent 4,041,203, with the layers being sequentially laid down on a moving forming wire. The total basis weight of the laminate is 1.6 osy (54 gsm) and the basis weights of the layers are 0.55-0.5-0.55 osy (19-17-19 gsm), respectively. The polymers for making each layer were the same as in example 1 above. The laminated fabric is a bonded nonwoven fabric made by point bonding with heat.

In this example, the laminated cloth was softened by stretching and shrinking to a width of 80% of the original unstretched width (i.e., 20% stretched). The laminated fabric was then subjected to cup crush parameter value tests, the results of which are shown in Table 2.

TABLE 2

Sample (I) Control Sample (I) Change%1.6 osy SMS, without stretch-softening 295 and with a left-1.6 osy SMS, with a stretch-softening 20% 295243-18

The results show that stretch softening can reduce the cup crush parameter of the nonwoven fabric considerably.Example 3

Spunbonded-meltblown-spunbonded (SMS) nonwoven laminate used in this example and

the same applies to example 2.

In this example, the laminated fabric was stretched between 230 and 250F (110 to 121℃) in the percentage of the original unstretched width shown in Table 3. The SMS laminate was then subjected to cup crush parameter value testing and the results are shown in table 3.

TABLE 3

Draw and shrink% Control Sample (I) Change%

0180 same left-

20 180 140 -22

30 180 120 -33

40 180 116 -36

50 180 105 -42

60 180 94 -48

The results show that the cup pressing parameters for the reduction of the drawing process are approximately proportional to the drawing amount. But the absolute value of the cup crush parameter is much higher than the result of mechanical water washing alone.Example 4

The spunbond-meltblown-spunbond (SMS) laminate used in this example was the same as that used in example 1.

In this example, the laminated cloth was topically treated with two softeners. The softening agent is Y-12230 and Triton  X-405. The former is a polyoxyalkylene modified polydimethylsiloxane available from OSi (a division of Union Carbide corp., as) from Danberg, connecticut; the latter are alkylaryl polyether alcohols available from Rohn & Hass Company of Philadelphia, Pa. These softeners were mixed with water to form an aqueous solution containing the softeners in the weight percentages shown in table 4. The nonwoven fabric is treated by the aforementioned "pad" method, although alternatives such as spraying are also possible. The SMS laminated fabric was then tested for cup crush parameter values and the results are shown in table 4.

TABLE 4

Sample (I) Control Sample (I) Change%1.5 osy SMS, untreated 205 and left-1.5 osy SMS, 0.5% Y-12230205179-131.5 osy SMS, 0.3% Triton  X-405205161-21

The results show that treatment with certain topical chemicals alone can reduce the cup crush parameter of the nonwoven fabric by about 15-20%.Example 5

The spunbond-meltblown-spunbond (SMS) laminate used in this example was the same as that used in example 2.

In this example, the laminate was stretched 30% at a temperature of 230F (110℃) and then treated with three different softeners. In table 5, the first two rows show the test results for the base fabric without stretch (N.S.) or treatment and the fabric with simple stretch, respectively. The softeners used were Y-12230, Triton  X-405 and Ultralube , a proprietary hydrocarbon mixture of surfactants available from MFG Chemical and Supply, Inc. of Dalton, Georgia. These softeners were mixed with water to form an aqueous solution containing the chemicals in the weight percentages shown in table 5. The nonwoven fabric is treated by the aforementioned "pad" method, although alternatives such as spraying are also possible. The SMS laminated fabric was then tested for cup crush parameter values and the results are shown in table 5.

TABLE 5

Sample (I) Control Sample (I) Change%No N.S. untreated 226 and left-30% N.S. untreated226114 5030% N.S. then 1.0% Y-12230226119 4730% N.S. then 1.0% Triton  X-405226143 and 3730% N.S. then 1.0% Ultralube  226156-31

The test results show that a stretching followed by a topical treatment with a softening agent reduces the cup crush parameter of the nonwoven fabric by up to 50%. However, the absolute value of the cup pressing parameter is still much larger than the result of pure mechanical water washing.Example 6

The spunbond-meltblown-spunbond (SMS) laminate used in this example was the same as that used in example 1.

In this example, the laminate was treated with three different topical softeners and then stretched 30%, except for the last sample, which was stretched 40% at a temperature of about 245 ° F (118 ℃). In table 6, the first row shows the test results for the base fabric without stretch-shrink or treatment.

The topical softeners used were Y-12230, Triton  X-405, and Varisoft  137, available from Sherex Chemical Co., of Dublin, Ohio. Varisoft is the dihydrogenated dimethyl ammonium sulfate dimethyl ester with the CAS number G8002-58-4. The hexanol acts as a co-surfactant for Y-12230 and is dispersed during the drying of the nonwoven fabric so that it does not leave any significant amount in the final product. The softener was mixed with water to form an aqueous solution containing the chemicals in the weight percentages shown in Table 6. The nonwoven fabric is treated by the aforementioned "pad" method, although alternatives such as spraying are also possible. The SMS laminated fabric was then subjected to cup crush parameter value tests, the results of which are shown in table 6.

TABLE 6

Sample (I) Control Sample (I) Change%Untreated, no N.S. 226 with left-30% N.S. with 0.5% Y-12230226112-5030% N.S. with 0.3% Triton  X-405226110-5230% N.S. with 1.0% Varisoft 226102-5540% N.S. with 1.0% Varisoft 0.5% Y-12230, and 0.5% hexanol (1.6 osy SMS) 22672-68

The results show that topical treatment with certain softeners followed by shrinkage can reduce the cup crush parameter of the nonwoven fabric by up to 70%. And generating data about absolute values of cup pressing parameters of the washed fabric.Example 7

The spunbond-meltblown-spunbond (SMS) laminate used in this example was the same as that used in example 2.

In this example, the laminate is stretched to the listed amount at about 230-250F (110-121℃) and then stretched to about 20% greater than the original width following the procedure described above. In table 7, the first row shows the test results for the base fabric without stretch-shrinking, treatment or widening.

Topical treatment of the treated nonwoven fabric is by the above-described "pad" method, although alternatives such as spraying are also possible. The SMS laminated fabric was then tested for cup crush parameter values and the results are shown in table 7.

TABLE 7

Sample (I) Control Sample (I) Change%Untreated, no N.S. 180 and left-30% N.S. 18095 and 4740% N.S. 180865240% N.S. with 1.0% Varisoft 0.5% Y-12230, and 0.5% hexanol 18051-72

The results show that topical treatment with certain softeners, followed by stretching and stretching, can reduce the cup crush parameter of the nonwoven fabric by about 70%, yielding data on the absolute value of the cup crush parameter for laundered fabrics. Such a fabric and process is further described in Fitting et al, U.S. patent 5,413,811.Example 8

A spunbond fabric having a basis weight of 1.2 osy (41 gsm) was made from a polypropylene polymer available from Exxon Chemical under the ESCORENE  PD-3445 polypropylene. The silicone additive 200  fluid was mixed with the polymer prior to extrusion in the amounts shown in Table 8. The fabric was spun at 430 ° F (221 ℃) at a rate of 0.6 g/hole/min. The fabric was bonded by heat calendering at a forming roll temperature of 280F (138 c) using an expanded Hansen Pennings pattern with a 15% bond area as described in U.S. patent No. 3,855,046 to Hansen and Pennings. Several samples were stretch-softened at an external temperature by shrinkage, the amount of which is shown in table 8, and then stretched to approximately the pre-stretch width. The samples were then tested for cup crush parameter values and the results are shown in Table 8.

TABLE 8

Sample (I) Control Sample (I) Change%No additive, no N.S. 149149-3% additive, no N.S. 149115-230% additive, 50% N.S. 149105-303% additive, 20% N.S. 14994-373% additive, 45% N.S. 14968543% of additive, 53% of N.S. 14961-59

The results show that internal treatment with certain chemicals, followed by stretching and stretching, can reduce the cup crush parameter of the nonwoven by about 60%, yielding data on the absolute value of the cup crush parameter for the water-washed fabric. The inventors believe that SMS lamination would also give this result.

This example shows that by internal chemical and mechanical treatment, but also in a continuous, large-scale industrial process, a nonwoven fabric having a softness comparable to that of a water-washed fabric can be produced. The fabric thus produced, while soft, retains a sufficient amount of its original properties, such as strength, to be useful in a variety of products. The internal treatment method used in the present invention is simpler to implement in production adjustment, since it involves only the incorporation of an additional compounding agent into the polymer composition. The partial processing method of example 7 is admittedly quite effective, but it is a comparatively messy method involving additional equipment and process steps.

Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function claims are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. For example, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface to secure wooden parts, in the context of fastening wooden parts, a nail and a screw may be equivalent structures.

It should further be noted that any patent, patent application, or publication mentioned in this specification is incorporated by reference in its entirety.

Claims (17)

1. A nonwoven fabric comprising a polymer and between a positive value greater than zero and about 3% by weight of an internal softening agent which is a silicone of the formula:wherein n is 3 to about 1000; and the nonwoven fabric is also mechanically softened, wherein the nonwoven fabric has a cup crush parameter value that is less than 50% of the value of the same nonwoven fabric cup crush parameter without the internal additive and without the mechanical softening.

2. The nonwoven fabric of claim 1 wherein said mechanical softening is selected from the group consisting of microcreping, cold embossing, roll-to-roll beating, draw-down, stretch-out and combinations thereof.

3. The nonwoven fabric of claim 1 wherein said mechanical softening is draw down to a second width of about 50 to 95% of its original, non-drawn down first width.

4. The nonwoven fabric of claim 3 wherein said mechanical softening comprises stretching to a third width after stretching, said third width corresponding to about 80 to about 150% of its original, unstretched width.

5. The nonwoven fabric of claim 1 which has been further treated for localized softening prior to said mechanical treatment.

6. The nonwoven fabric of claim 1 wherein said polymer is selected from the group consisting of polyolefins, polyamides, polyetheresters, and polyurethanes.

7. The nonwoven fabric of claim 6 wherein said polymer is a polyolefin.

8. The nonwoven fabric of claim 7 wherein said polyolefin is polypropylene.

9. The nonwoven fabric of claim 7 wherein said polyolefin is polyethylene.

10. The nonwoven fabric of claim 1 comprising at least one meltblown layer and at least one spunbond layer.

11. The nonwoven fabric of claim 10 wherein said nonwoven fabric is a laminate comprising a first spunbond layer, a meltblown layer and a second spunbond layer, the layers being bonded together.

12. The nonwoven fabric of claim 11 wherein said nonwoven fabric is bonded by heat points.

13. A garment comprising the nonwoven fabric of claim 1.

14. A personal care product comprising the nonwoven fabric of claim 1.

15. An infection control article comprising the nonwoven fabric of claim 1.

16. A nonwoven fabric comprising between positive values greater than zero and about 3% by weight of a silicone softener of the formula:

wherein n is from 3 to about 1000,

and the nonwoven is drawn down to a second width of about 50 to 95% of its original, non-drawn width and then stretched to a third width corresponding to about 80 to 150% of its original, non-drawn width, the nonwoven having a cup crush parameter value of less than 50% of the same nonwoven without the internal additive and without the mechanical softening.

17. A surgical gown for a surgeon comprising the nonwoven fabric of claim 16.