HUP0400649A2 - Thermally bonded fabrics and method of making same - Google Patents

Abstract

In the framework of a process for the production of non-woven material, a fibrous web is passed through a pair of rollers in order to produce a thermally bonded material with a high bonding area ratio. The high bonding area ratio is created by a pattern formed on at least one of the rollers. The engraved pattern has a large % bond point area and bond point angles that fall within wide limits. The non-woven material has increased tensile strength, elongation, abrasion resistance, bending stiffness and/or softness. HE

Description

PUBLICATION COPY

P0 4 0 064 9

Process for producing a non-renewable material and polymer-containing

NON-WOVEN MATERIAL

The invention relates to polymer-containing nonwoven materials, preferably formed from polyolefin polymers, and to methods for producing such materials.

Materials made from fibers include woven and nonwoven materials. Nonwoven materials are used for healthcare and medical purposes, including hospital gowns, patterned upholstery, and sanitary wipes. There are several processes for producing nonwoven materials. For example, heat and pressure can be applied to bond limited areas of a nonwoven web by passing the web through a nip of heated nip rolls with a pattern of ridges and depressions. During this bonding process, the bonding areas can be formed autogenously, depending on the type of fibers that make up the nonwoven, i.e. by fusing the fibers of the web together at least in the patterned areas, or by adding an adhesive. Advantages of thermally bonded nonwovens include low energy costs and speed of production.

Nonwovens can also be produced by a number of other processes, such as spunlacing or hydrodynamic entanglement (see, for example, U.S. Patents 3,485,706 and 4,939,016); carding or thermal bonding of staple fibers; spunbonding of continuous fibers in a single continuous operation; or melt-blowing fibers into a web and subsequent smoothing or thermal bonding of the resulting web.

The suitability of a nonwoven for different applications is determined by the different properties of the material. Nonwovens can be designed to have different combinations of properties to meet different needs. The different properties of nonwovens include liquid properties such as wettability, spreadability and absorbency, strength properties,

98859-8657/SZT/SZT

-2such as tensile strength and tear strength, softness properties, durability properties such as abrasion resistance, and aesthetic properties.

Due to its low cost, high strength and processability, polypropylene has been the primary polymer for nonwovens. However, nonwovens made from polypropylene generally do not have a soft, cotton-like feel. This has led to an increase in interest in polyethylene. Polyethylene produces a softer material, but has relatively low tensile strength and abrasion resistance.

Although properties of nonwovens such as liquid resistance, strength, softness, and durability are normally of primary importance, the appearance and feel of nonwoven products are often crucial to their success. Appearance and feel are particularly important for prominent parts of the product. For example, it is often desirable for the outer covering of nonwoven products to provide a garment-like feel and have a pleasant, decorative appearance.

Despite the above-described advantages, there is still a need to improve nonwovens and their manufacturing processes. In particular, there is a need to improve the following properties of nonwovens: tensile strength, elongation, abrasion resistance and softness, which are determined by the bending stiffness of the material. The present invention aims to improve these properties.

Our goal was achieved by developing a process for producing a nonwoven fabric with increased tensile strength, elongation, abrasion resistance, bending stiffness and/or softness, in which a fibrous web is passed through a pair of rollers to produce a thermally bonded fabric with a bond area ratio of at least 20%, where the bond area ratio is created by an engraved pattern with raised bonding points on one of the rollers. The engraved pattern has a high bond area ratio and/or a wide range of bond point angles.

In some embodiments, the nonwoven fabric preferably has a bond area fraction of at least about 16%, more preferably at least about 20%, or at least about 24%. The bond angle is preferably at least about 20°, more preferably

-3at least about 35°, at least about 37°, at least about 42°, and more preferably at least about 46°. The engraved pattern preferably comprises at least 1.55 x 10 ⁵ bonding points per square meter, more preferably at least 2.31 x 10 ⁵ bonding points, at least 3.1 x 10 ⁵ bonding points, at least 3.44 x 10 ⁵ bonding points, at least 4.6 x 10 ⁵ bonding points, and more preferably at least 4.65 x 10 ⁵ bonding points. The fibrous web may preferably comprise polyethylene, which may be a homopolymer of ethylene or a copolymer of ethylene and a comonomer. The polyethylene may preferably be formed in the presence of a single-site catalyst, such as a metallocene catalyst or a catalyst with an artificial geometry.

On the other hand, we achieved our goal by producing a polymer-containing, highly abrasion-resistant nonwoven material with a bonded area ratio of at least 20%, which is created by an engraved pattern with raised bonding points on a cylinder.

In some embodiments, the polymer is preferably polyethylene, which may be a homopolymer of ethylene or a copolymer of ethylene and a comonomer. The polyethylene may be formed in the presence of a single-site catalyst, such as a metallocene catalyst or an artificial geometry catalyst. In other possible embodiments, the nonwoven preferably has a bonded area fraction of at least about 16%, more preferably at least about 20%, and even more preferably at least about 24%.

The various embodiments of the invention and the advantages provided by the embodiments are described in detail below with reference to the accompanying drawings, in which: - Figure 1 shows a simplified diagram of the manufacturing process of the nonwoven fabric according to the invention;

- Figure 2A shows a top view of one possible arrangement of attachment points on a DIY cylinder;

- Figure 2B is a simplified view of a nonwoven fabric produced by the do-it-yourself roller of Figure 2A in the process of Figure 1;

- Figures 3A-3I schematically illustrate the bonding patterns used in possible embodiments of the invention to arbitrary scale; Figures 4A-4I are photomicrographs of non-woven materials prepared with the bonding patterns according to Figures 3A-3I for the PE1 resin used in Example 1;

- Figure 5 graphically illustrates the normalized peak load/temperature relationship of the material produced from PE1 resin with the bonding patterns according to Figures 3A-3I;

- Figure 6 graphically illustrates the relative elongation/temperature relationship of the material produced from the PE2 resin of Example 1 with the bonding patterns according to Figures 3A-3I;

- Figure 7 shows the characteristic stress/strain curves of the three materials produced in Example 1;

- Figure 8 graphically illustrates the wear resistance/temperature relationship of the material produced from PE1 resin with the bonding patterns according to Figures 3A-3I;

- Figure 9 graphically illustrates the bending stiffness/temperature relationship of the material produced from PE1 resin with the bonding patterns according to Figures 3A-3I;

- Figures 10A-10I show scanning electron micrographs of the bonding points of the nonwoven fabric produced from PE1 resin with the bonding patterns according to Figures 3A-3I, taken at 80x magnification;

- Figures 11A-11C show scanning electron micrographs of the tensile test fracture locations of nonwovens produced from different synthetic resins with the bonding patterns of Figures 3A-3I; while

- Figures 12A-12B show electron micrographs of points of worn bonding sites of nonwovens produced from various synthetic resins with the bonding patterns of Figures 3A-3I.

Embodiments of the invention relate to methods for producing nonwoven materials by thermal bonding. The material comprises a high proportion of bonding points formed by passing a fibrous web through a pair of rollers, at least one of which has an engraved pattern comprising a high proportion of bonding area with a high bonding point angle.

The term “nonwoven” is used herein and hereinafter to refer to a web or material consisting of individual fibers or yarns laid randomly but not identifiable as woven fabrics. The term “bonding” is used herein and hereinafter to refer to the application of force or pressure (in addition to or in excess of that required for drawing fibers of 50 denier or finer) to fuse the melted or softened fibers together. In some embodiments, the bonding force is at least 1500 grams. The

-5Thermal bonding, as used herein and hereinafter, refers to the application of force or pressure (over or above that required for drawing 50 denier or finer filaments) to reheat the filaments to melt (or soften) and bond them together. In some embodiments, the bonding force is at least 2000 grams. Techniques that draw and fuse the filaments together in a single or simultaneous operation or prior to any winding (e.g., onto a yarn guide spool), such as spunbonding, are not considered thermal bonding operations.

The thermal bonding process for producing a nonwoven fabric is illustrated in Figure 1. Such a process, or variations thereof, is described in the following U.S. Patents: 5,888,438; 5,851,935; 5,733,646; 5,654,088; 5,629,080; 5,494,736; 4,770,925; 4,635,073; 4,631,933; 4,564,533; 4,315,965. All of these disclosed processes may be used, with or without modification, in exemplary embodiments of the invention.

The fabric forming system 10, such as a carding system, shown in FIG. 1 is first used to form a fibrous web 12. The fibers are oriented primarily in the machine direction of the fabric formation, as indicated by arrow 13. Alternatively, spunbonding may be used to provide a more random orientation of the fibers. The web 12 may be passed through a preheating station 14. The web 12 is then passed through a nip of opposing rollers 20 and 22 in a bonding station. Roller 20 is a metal engraved roller and is heated to a temperature close to the melting point of the fibers. Roller 22 (i.e., the smoothing roller) is heated in a controlled manner to a temperature close to the melting point of the fibers, preferably below the adhesion point of these fibers. In some embodiments, the engraved pattern consists of circles, however, other shapes may be used, such as ovals, squares, and rectangles.

The engraved roll shown in Figure 2A is provided with areas, called nips, that are close to and exert pressure on the smoothing roll. These areas cause melting and create nips. The size of these areas determines the number of fibers bonded at a given point and the total area of the non-fibrous unit of the material. The number of fibers bonded at a nip can affect its resulting strength, but it can also contribute to its resulting stiffness. Three factors in the engraved pattern can affect the overall properties of the nonwoven material: the nip area, the nip angle or sidewall angle, and the nip density, usually defined as the number of nips per square unit.

The engraved pattern of the roll is provided by the bonding points. These points project from the engraved roll and, when they come into contact with the smoothing roll, create the bonding area. The bonding points generally provide the pattern of the nonwoven fabric, as shown in Figure 2B. The bonding point density of the engraved pattern is expressed in terms of the number of bonding points per square unit. In the preferred embodiment, the engraved pattern has about 1.55x10 ⁵ bonding points per square meter, preferably about 2.31x10 ⁵ bonding points per square meter, more preferably about 3.10x10 ⁵ bonding points per square meter, or about 3.44x10 ⁵ bonding points per square meter, or about 4.60x10 ⁵ bonding points per square meter, or about 4.65x10 ⁵ bonding points per square meter. Higher bond densities, such as 5.42x10 ⁵ bonds per square meter, 6.20x10 ⁵ bonds, 7.75x10 ⁵ bonds, 9.30x10 ⁵ bonds or even more bonds per square meter, are also possible.

The bond has a bond angle and a bond area. Figures 3A-3I show bond patterns with different bond angles and bond areas. The bond angle refers to the angle at which the bond emerges from the engraved cylinder. The bond angle is at least about 20°, preferably at least about 35°, more preferably at least about 37°, even more preferably at least about 42°, and even more preferably at least about 46°. Bond pattern No. 1 shown in Figure 3A has a bond angle of 46°, a bond area fraction of 20%, a bond density of 3.44x10 ⁵ dots/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 7.62x10' ⁴ m. The bond pattern No. 2 shown in Figure 3B has a bond angle of 20°, a bond area ratio of 16%, a bond density of 3.44x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 6.86x10' ⁴ m. The bond pattern No. 3 shown in Figure 3C has a bond angle of 20°, a bond area ratio of 24%, a bond density of 3.44x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10 ^-4 m, and a dot width of 8.38x10' ⁴ m. The bond pattern No. 4 shown in Figure 3D bond pattern bond angle 20°, bond area ratio 20%, bond density 2.31x10 ⁵ points/m ² , base width 1.7x10' ³ m, base height

-74.32x10' ⁴ m, and its dot width is 9.30χ10' ⁴ m. The bond pattern No. 5 shown in Figure 3E has a bond angle of 20°, a bond area ratio of 20%, a bond density of 4.60x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 6.60x1 O' ⁴ m. The bond pattern No. 6 shown in Figure 3F The bond pattern has a bond angle of 46°, a bond area ratio of 16%, a bond density of 3.44x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 6.86x1ο· ⁴ m. The bond pattern No. 7 shown in Figure 3G has a bond angle of 37°, a bond area ratio of 24%, a bond density of 3.44x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 8.38x10' ⁴ m. The bond pattern No. 8 shown in Figure 3H The bond pattern No. 9 shown in Figure 3I has a bond angle of 46°, a bond area ratio of 20%, a bond density of 2.31 x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 9.3x10' ⁴ m. The bond pattern No. 9 shown in Figure 3I has a bond angle of 35°, a bond area ratio of 20%, a bond density of 4.60x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 6.60x10' ⁴ m.

The nonwoven fabric is composed of bonded areas and unbonded areas. Bonded areas can be defined as the surface area of the nonwoven fabric occupied by the bond formed by the bonding point. In embodiments of the invention, the bonded area is preferably at least 16%, more preferably at least 20%, and even more preferably at least 24%, 30%, 35%, 40%, 45%, 50%, or even more.

Fibers and nonwoven fabric production

The web making system generally includes fiber production processes, such as dry spinning, wet spinning, polymer spinning, and other processes, to produce fibers that may be thermally bonded for use in the manufacture of nonwovens. In some embodiments, the fibers are produced by spunbonding, meltblown, or carding processes. These processes are described in detail in U.S. Patent Nos. 3,338,992; 3,341,394; 3,276,944; 3,502,538; 3,978,185; and 4,644,045. The spunbonding method generally employs a high-performance vacuum chamber to increase the speed of the fibers, thereby reducing the diameter of the fibers during the production of the continuous fiber. In the melt-blown method, air is blown in from above,

-8 and surface forces are used to draw the fiber at higher speeds to create very low denier staple fibers.

Conventional spunbonding processes are described in U.S. Patents 3,825,379; 4,813,864; 4,405,297; 4,208,366; and 4,334,340. The spunbonding technique is well known to those skilled in the textile industry. It generally involves extruding continuous filaments, laying them on an endless belt, and then bonding them together, usually with a heated squeegee or by adding an adhesive, and often to a second layer, such as a meltblown layer. An overview of the spunbonding technique can be found, for example, in the paper Nonwoven Fabrics / “Spunbonded and Melt Blown Processes” by L. C. Wadsworth and B. C. Goswami, published at the 8th Annual Nonwovens Workshop, July 30-August 3, 1990, with the support of the Woven and Nonwovens Development Center [(hereinafter: TANDEC), University of Tennessee, Knoxville, USA].

The term “meltblown” is used herein and hereinafter to refer to fibers produced by extruding a thermoplastic, molten polymer composition in the form of yarns or filaments through fine, generally circular die channels into high-velocity, cohering gas streams (e.g., air streams), the gas streams acting to reduce the diameter of the yarns or filaments. The filaments or yarns are then transported by the high-velocity gas streams and deposited on a collecting surface to form a web of randomly dispersed meltblown fibers; the resulting fibers typically have an average diameter of up to 10 μm.

The term "spunbond" is used herein and hereinafter to refer to fibers produced by extruding a thermoplastic, molten polymer composition through a fine, generally circular, die channel, where the diameter of the yarns or filaments is rapidly reduced, and the filaments are then arranged on a collecting surface to form a web of randomly dispersed spunbond fibers; the average diameter of the spunbond fibers thus obtained is generally between 7 μιτι and 30 μm.

-9Nonwovens can be produced by a number of processes. Most processes involve essentially the same basic steps: 1) material selection; 2) fabric preparation; 3) fabric consolidation; and 4) fabric finishing. Material selection ensures that the properties are suitable for the application. The fabric is formed from the fibers of the selected materials. The fabric is then bonded to create the fabric, and the fabric is finished, resulting in the final product that can be cut and folded.

The diameter of the fiber affects the properties of the material, including strength and bending stiffness. The diameter of the fiber can be measured and displayed in a number of ways. Typically, the diameter of the fiber is measured in denier per fiber. Denier is a term used in the textile industry to express the weight in grams of a 9000 meter long fiber. The term monofilament refers to an extruded bundle of fibers having a diameter of at least 15 denier per fiber, generally at least 30 denier. A fine denier fiber generally refers to a fiber of up to about 15 denier. A microdenier (i.e., microfiber) generally refers to a fiber having a diameter of up to about 100 microns. In the case of the fibers of the present invention, the diameter can vary widely without significantly affecting the elasticity of the fiber. The denier of the yarn can, however, be adjusted to suit the properties of the finished product and is preferably between about 0.5 and about 30 denier/yarn for a meltblown web, between about 1 and about 30 denier/yarn for a spunbonded web, and between about 1 and about 20,000 denier/yarn for a continuous spunbonded yarn. The yarn diameter can be converted from denier to meter using the formula _R I yarn diameter (denier) yarn diameter (meter) = 11.89χ 10 ⁶ x ----------——— salsuruseg (g/m ).

Fiber properties that influence the final properties of a nonwoven include fiber orientation, crystallinity, diameter, and cooling rate. The strength of the bond is a limiting factor in the strength of a nonwoven. A lower fiber orientation allows for a greater degree of melting during bonding, resulting in stronger bonding regions. In addition, the polymer can be stretched

-10% higher orientation causes a large amount of shrinkage during thermal bonding, thus making the material more difficult to process.

From the perspective of the thermal bonding process, the crystalline parts of the fiber are of particular interest due to the melting that occurs. The degree of melting and flow significantly affects the bond strength. If sufficient heat is applied to the polymer, the less stable crystals melt first, followed by the more stable or oriented crystals. Since the heat applied to the bonding area is only for a short time, only a portion of the crystals melt.

Once the web is loosely formed, the individual fabrics must be bonded together. The bonding of the web makes the material strong and rigid. The bonding processes for the web include mechanical, chemical, and thermal bonding. Mechanical bonding is achieved by intertwining fibers at various points in the web, including needle punching, fire bonding, spunlacing, or other mechanical bonding processes. Chemical bonding involves spraying or saturating the web with an adhesive, such as latex. Thermal bonding of the web is accomplished by commonly used bonding techniques, such as spot calendering, ultrasonic bonding, and thermal radiation bonding. In some embodiments, a spot calendered bond is used, which involves passing the web between two closely spaced rollers. One roller is an engraved roller with a raised (father) pattern, while the other is a smoothing roller. The fibers melt and flow into each other. After cooling, the nonwoven material is ready.

As the fibrous web enters the smoothing roller, several thermomechanical processes of varying intensity take place. These processes include conductive heat transfer, deformation heating, molten polymer flow, diffusion, and the Clapeyron effect.

Conductive heat transfer occurs through the steel roller/material interface. The amount of heat transferred by conduction is proportional to the temperature of the steel rollers and the length of time the web is under the tie pins (i.e. the speed of the rollers). Deformational heating also introduces heat into the system. Due to the high pressure between the steel rollers, the web very quickly assumes different shapes and mechanical work is done on the system ···· ·· _β ,ζ « · ··

-11- -‘· occurs. This mechanical work is converted into heat. These two types of heat increase the temperature of the web between the rollers, which is highest below the tie pin. Assuming that all mechanical work is converted into heat, this is

It is expressed by the equation [F(s)ds]a = VpCpAT + fÁH^pV, where F(s) is the force exerted on the web at a distance ds, a is the fraction of mechanical work converted into heat, V is the volume of the web, χ is the crystallinity, and f is the fraction of crystals that melt. The first term on the right-hand side of the equation is the amount of heat used to increase the temperature, and the second term is the amount of heat used to melt the polymer crystals.

When the temperature reaches the melting point, the high pressure under the taps causes the melt to flow to the lower pressure area. The polymer, also in the molten state, self-diffusions. After leaving the calender, the melt solidifies and mechanically fixes the fibers at the bonding point. In the case of polymers, the diffusion penetration distance during the bonding process is almost negligible. The penetration distance is

It can be given by the equation R = [t(2xD)] ^y2 , where R is the penetration distance, t is the time, and D is the self-diffusion coefficient. In general, most polymers have diffusion coefficients of the order of 10' ¹⁵ and spend 10-40 ms under the bonding pins. Using these estimates, it can be calculated that the penetration distance is only between 45 A and 100 A. Considering that most fibers used in thermal bonding have a diameter of about 20 pm, only 0.00000225% of the total diameter of the fibers diffuse. Therefore, it is likely that the main force holding the fibers together at the bonding point is the mechanical interlocking of the polymer melt around the fibers in the bonding area.

The increased pressure under the tie pins leads to an increase in the melting temperature, also known as the Clapeyron effect. The pressure causes the melting point of polypropylene to rise by 0.38°C per MPa. The typical pressure under the tie pin causes the melting point of polypropylene to rise by about 10°C. The melting point of polyethylene to rise by only about 5°C under typical tie pressure.

Several factors in the hot point calendering process, including temperature, pressure, speed, roll diameter and engraved pattern, affect the final properties of the nonwoven. The choice of temperature depends mainly on the material, but it should be noted that the total energy input to the web depends on the temperature, pressure, roll diameter and line speed. If the temperature selected is too low, the web will set too little and the material will likely have low strength. If the roll temperature is too high, the web will set too much and the resulting nonwoven will be too stiff or will melt completely and stick to the roll.

The effect of pressure on the material is small, but not negligible. At low pressures, the web is weakly bonded, and therefore has low strength. As the pressure is increased, the strength of the material changes as a function of both the bonding temperature and the pressure. However, at very high pressures, the strength of the material reaches a maximum and then decreases with increasing pressure. At lower pressures, the strength gradually increases, up to the melting point of the polymer.

The speed and diameter of the binding rolls affect the heat transfer to the web. If the diameter of the binding rolls is larger, the heated rolls are in closer contact with each other than with smaller rolls. This allows more heat to be transferred to the web. Similarly, slowly rotating rolls provide longer contact time than fast rotating rolls.

The time spent by the web in the cylinder gap (i.e. at the location of close contact) is given by at = AC' ^a R ^% V ¹ f=time

R= radius of the binding roller \/= speed of the binding roller

It can be given by the relationship Λ_ ₊ /C _R -C _W ^A , where C _o is the initial web thickness, C _N is the web thickness between the binding rolls, and C _R is the web thickness after compression by the binding rolls.

- 13The shape of the fiber is not limited, it can be any suitable shape. The cross-section of a typical fiber is, for example, circular, but the fibers can sometimes have different shapes, such as a three-leaf clover or flat (i.e. ribbon-like).

After the thermally bonded material leaves the bonding pins, the bonding regions are cooled and solidified. The rapid cooling rate of the material, especially the bonding region, affects the final properties of the material.

The main properties of a material include strength, elongation, peak load, abrasion resistance and flexural stiffness. The strength or tensile strength and elongation of a nonwoven are important for both post-processing and consumer applications. The stronger and more elastic the material, the sooner it can be combined with other materials to form a consumer end product. Another property of a nonwoven is its resistance to abrasion. When a nonwoven comes into contact with an abrasive surface, it pulls the fibers from the surface and causes fraying or pilling on the surface. Thus, it is desirable for nonwovens to have high abrasion resistance. Another important property of a nonwoven intended for human wear and in contact with the skin is the stiffness of the material. This property can be measured by flexural stiffness or by tactile evaluation.

Fiber-forming polymers

In preferred embodiments of the invention, any polymer suitable for fiber formation can be used, especially those which can be thermally bonded. Suitable polymers include, but are not limited to, α-olefin homopolymers and interpolymers comprising polypropylene, propylene/C4-C20 olefin copolymers, polyethylene, and ethylene/C3-C20 α-olefin copolymers, which may be either heterogeneous ethylene/α-olefin interpolymers or homogeneous ethylene/α-olefin interpolymers, including substantially linear ethylene/α-olefin interpolymers. Also included are aliphatic α-olefins having from 2 to 20 carbon atoms and polar groups. Suitable aliphatic α-olefin monomers which introduce polar groups into the polymer include, for example, ethylenically unsaturated nitriles such as acrylonitrile, methacrylonitrile. ethacrylonitrile, etc.; ethylenically unsaturated anhydrides such as maleic anhydride; ethylenically unsaturated amides such as acrylamide, methacrylamide, etc.; ethylenically

-14-unsaturated carboxylic acids (both monofunctional and difunctional), such as acrylic acid and methacrylic acid, etc.; esters of ethylenically unsaturated carboxylic acids (especially lower ones, e.g. C 1-C ₆ -alkyl esters), such as methyl methacrylate, ethyl acrylate, hydroxyethyl acrylate, n-butyl acrylate or methacrylate, 2-ethylhexyl acrylate or ethylene-vinyl acetate copolymers, etc.; ethylenically unsaturated dicarboxylic acid imides, such as N-alkyl or N-aryl maleimides, such as N-phenyl maleimide, etc. These monomers containing polar groups are preferably acrylic acid, vinyl acetate, maleic anhydride, and acrylonitrile. Halogen groups that can be introduced into polymers formed from aliphatic α-olefin monomers may be fluorine, chlorine, and bromine; preferably these polymers are chlorinated polyethylenes (CPEs). Polymers such as polyester or nylon may also be used.

Heterogeneous interpolymers differ from homogeneous interpolymers in that the latter have equal proportions of ethylene and comonomers in the interpolymer molecules, whereas heterogeneous interpolymers have unequal proportions of ethylene and comonomers in the interpolymer molecules. The term "compositionally broad distribution" as used herein describes the distribution of comonomers in heterogeneous interpolymers and means that the heterogeneous interpolymers have a "straight-line" fraction and that the heterogeneous interpolymers have multiple melting peaks (i.e., exhibit at least two different melting peaks) on a differential scanning calorimeter. The degree of branching of the heterogeneous interpolymers is 2 methyls or less per 1000 carbon atoms at 10% or more by weight, preferably more than 15% by weight, and especially more than 20% by weight. The degree of branching of the heterogeneous interpolymers is 25 methyls per 1000 carbon atoms or less, at 25% or less by weight, preferably less than 15% by weight, and especially less than 10% by weight.

The heterogeneous polymer component may be an α-olefin homopolymer, preferably polyethylene or polypropylene, or, preferably, an ethylene interpolymer with at least one C ₃ -C ₂ oa-olefin and/or C 4 -C 15 dienes. Copolymers of ethylene and propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene are also preferred.

Linear low density polyethylene (LLDPE) is produced either in solution or in a fluidized bed process. The polymerization is catalytic. To produce LLDPE

-15Ziegler Natta and single-site metallocene catalyst systems have been used. The resulting polymers are characterized by a substantially linear backbone. The density is determined by the incorporation of comonomers into the otherwise linear backbone. Various alpha-olefins are typically copolymerized with ethylene during the formation of LLDPE. Alpha-olefins, which preferably have 4-8 carbon atoms, are present in the polymer up to a level of about 10% by weight. The most typical comonomers are butene, hexene, 4-methyl-1-pentene, and octene. The comonomers affect the density of the polymer. LLDPE has a relatively wide density range, typically between 0.87 and 0.95 g/cm ³ (US Standard D-792).

The melt index of linear low density polyethylene is also controlled by the introduction of a chain terminator, such as hydrogen or a hydrogen transfer agent. The melt index of linear low density polyethylene, as defined in U.S. Standard D-1238 (formerly known as the "E-state" and also known as "l2") at 190°C/2.16 kg, can vary over a wide range from about 0.1 to about 150 g/10 min. For the purposes of the present invention, the melt index of LLDPE should be greater than 10, preferably 15 or greater for spunbonded fibers. Polymers with a density of 0.90 to 0.945 g/cm ³ and a melt index of greater than 25 are particularly preferred.

Examples of suitable commercially available linear low density polyethylene polymers include linear low density polyethylene polymers available from Dow Chemical Company, such as the ASPUN™ series of filament resins, Dow LLDPE 2500 (55 p. m., 0.923 density), Dow LLDPE 6808A (36 p. m., 0.940 density), and the Exxon Chemical Company series of linear low density polyethylene polymers, such as EXACT™ 2003 (31 p. m., 0.921 density).

The homogeneous polymer component may be an α-olefin homopolymer, preferably polyethylene or polypropylene, or preferably an interpolymer of ethylene with at least one C ₃ -C ₂ α-olefin and/or C ₄ Cis-dienes. Ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene are particularly preferred.

The relatively recent introduction of metallocene-based catalysts to ethylene/α-olefin polymerization has resulted in the production of ethylene interpolymers known as homogeneous interpolymers.

-16 The homogeneous interpolymers useful for forming the fibers described herein have a homogeneous branching distribution. This means that the comonomer in these polymers is randomly distributed within the given polymer molecule and essentially each interpolymer molecule has the same ethylene/comonomer ratio. The homogeneity of polymers is typically described by the SCBDI (short chain branching distribution index) or CDBI (composition distribution branching index) and is defined as the weight percent of polymer molecules that have a comonomer content within 50% of the mean of the total molar comonomer content. CDBI is obtained by techniques known in the art, such as temperature-elevated elution fractionation (abbreviated herein as "TREF"), as described, for example, by Wild et al., Journal of Polymer Science, Poly. Phys. Ed., 20th ed., p. 441. (1982), described in U.S. Patents 4,798,081 and 5,008,204. The method for calculating CDBI is described in U.S. Patents 5,322,728 and 5,246,783. The homogeneous interpolymers used in the present invention preferably have SCBDI or CDBI values greater than about 30%, more preferably greater than about 50%, 70% or 90%.

The homogeneous interpolymers used in the process of the invention are essentially free of measurable "high density" fractions as measured by the TREF technique (i.e., the homogeneous ethylene/α-olefin interpolymers do not contain a polymer fraction with 2 or fewer methyl branches per 1000 carbon atoms). The homogeneous interpolymers are also free of very short chain branched fractions (i.e., they do not contain a polymer fraction with 30 or more methyl branches per 1000 carbon atoms).

Essentially linear ethylene/α-olefin polymers and interpolymers are also homogeneous interpolymers, but are described in detail in U.S. Patents 5,272,236 and 5,272,872. Such polymers are, however, unique in their excellent processability, unique flow properties, high melt elasticity, and resistance to melt fracture. These polymers can be successfully processed in a continuous polymerization process using engineered geometry metallocene catalyst systems.

-17The term "substantially linear" ethylene/α-olefin interpolymer means that the polymer backbones are replaced by between about 0.01 long chain branches per 1000 carbon atoms and about 3 long chain branches per 1000 carbon atoms, more preferably between about 0.01 long chain branches per 1000 carbon atoms and about 1 long chain branch per 1000 carbon atoms, and especially between about 0.05 long chain branches per 1000 carbon atoms and about 1 long chain branch per 1000 carbon atoms.

Long-chain branching is defined herein as having a chain length of at least two fewer and at least one more carbon atoms than the total number of carbon atoms in the comonomer, for example, an ethylene/octene essentially linear ethylene interpolymer has a long-chain branch of at least seven (7) carbon atoms (i.e., 2 of the 8 carbon atoms are equal to 6 carbon atoms, and one is equal to 7 carbon atoms). The long-chain branching may be approximately the same length as the polymer backbone. Long-chain branching is determined using ¹³ C nuclear magnetic resonance (NMR) spectroscopy and quantified using the Randall method (Rev. Macromol. Chern. Phys., C29 (2&3), pp. 285-297). Long-chain branching must of course be distinguished from short-chain branching, which results solely from the incorporation of comonomer, so for example, the short-chain branching of an essentially linear ethylene/octene polymer is six carbon atoms long, while the long-chain branching of the same polymer is at least seven carbon atoms long.

Additional suitable polymers are disclosed in the following U.S. Patents: 6,316,549; 6,281,289; 6,248,851; 6,194,532; 6,190,768; 6,140,442; 6,037,048; 5,603,888; 5,185,199 and 5,133,917.

Examples of commercially available fiber-forming polyethylenes are: ASPUN™ 6806A (melt index: 105.0g/10 min; density: 0.930 g/cm ³ ), ASPUN™ 6842A (melt index: 30.0g/10 min; density: 0.955 g/cm ³ ), ASPUN™ 6811A (melt index: 27.0g/10 min; density: 0.941 g/cm ³ ), ASPUN™ 6830A (melt index: 18.0g/10 min; density: 0.930 g/cm ³ ), ASPUN™ 6831A (melt index: 150.0g/10 min; density: 0.930 g/cm ³ ), and ASPUN™ 8635A (melt index: 17.0 g/10 min; density: 0.950 g/ ^cm3 ), all available from The Dow Chemical Company, Midland, Michigan, USA. These linear, low density polyethylenes can be produced by blending with a homogeneous, substantially linear ethylene polymer.

mixed with, for example, AFFINITY™ resin produced by The Dow Chemical Company.

Examples of commercially available fiber-forming polypropylenes include:

homopolypropylene, symbol: 5A10 (melt flow rate: 1.4 g/10min;

flexural modulus 1585 MPa); 5A28 (melt flow rate: 30 g/10min; flexural modulus 1585 MPa); 5A66V (melt flow rate: 4.6 g/10min; flexural modulus 1654 MPa); 5E17V (melt flow rate: 20.0 g/10min; flexural modulus 1344 MPa); 5E40 (melt flow rate: 9.6 g/10min; flexural modulus 1378 MPa); NRD5-1258 (melt flow rate: 100.0 g/10min; flexural modulus 1318 MPa); NRD5-1465 (melt flow rate: 20.0 g/10min;

flexural modulus flexural modulus flexural modulus flexural modulus flexural modulus

1344 MPa); NRD5-1502 (melt flow rate: 1.6 g/10min;

1347 MPa); NRD5-1569 (melt flow rate: 4.2 g/10min;

1378 MPa); NRD5-1602 (melt flow rate: 40.0 g/10min;

1172 MPa); SRD5-1572 (melt flow rate: 38.0 g/10min;

1298 MPa); SRD5-1258 (melt flow rate: 25.0g/10min);

and INSPIRE™ resin (melt flow rates ranging from 1.8 to 25 g/10 min), all available from The Dow Chemical Company. Melt flow rate is measured in accordance with US Standard D 1238 (230°C/2.16 kg) and flexural modulus is measured in accordance with US Standard D 790A.

It should be noted that resins from other companies, such as Exxon, Bassel, Mitsui, etc., may also be used.

Additives such as antioxidants (e.g., hindered phenolic materials such as IRGANOX™ 1010 or IRGANOX™ 1076, manufactured by Ciba Geigy), phosphites (e.g., IRGAFOS™ 168-AT, also manufactured by Ciba Geigy), tackifiers (e.g., PIB), pigments, colorants, fillers, and the like may be added to the fibrous materials disclosed herein.

Furthermore, other polymers may be blended with the polymers disclosed herein to modify certain characteristics, such as elasticity, processability, strength, thermal bonding or adhesion, to the extent that such modification does not adversely affect the desired properties.

Some useful materials for modifying polymers include, for example, other essentially linear ethylene polymers, as well as other polyolefins,

-19- .>J.·-· Λ· ·* * such as high pressure low density ethylene homopolymers (LDRE), ethylene vinyl acetate copolymers (EVA), ethylene carboxylic acid copolymers, ethylene acrylate copolymers, polybutylene (PB), ethylene/alpha-olefin polymers, including high density polyethylene (HDPE), medium density polyethylene, polypropylene, ethylene-propylene interpolymers, ultra-low density polyethylene (ULDPE), and graft modified polymers containing, for example, anhydrides and/or dienes or mixtures thereof.

Other suitable polymers for polymer modification include synthetic and natural elastomers and rubbers known to provide various levels of elasticity. AB and ABA block graft copolymers (where A is a thermoplastic end block, such as a styrene moiety, and B is an elastomeric mid block derived from, for example, conjugated dienes or lower alkenes), chlorinated elastomers and rubbers, ethylene-propylene-diene monomer (EDPM) rubbers, ethylene-propylene rubbers, and the like, and mixtures thereof, are examples of elastomers known in the art to be suitable for modifying the elastomers disclosed herein.

Polypropylene can be blended with a lower melting point polymer, such as polyethylene, in the bonding section to increase strength. Similarly, LLDPE can be blended with low melting point/low density polyethylene to achieve the same results.

The initial chemical structure of the polymer used to make nonwovens affects the properties of the material. The chemical structure of the polymer affects the density/crystallinity, viscosity, and molecular weight distribution of the polymer. The addition of two or more polymers for blending can also have a significant effect on the properties of the nonwoven. The strength of the material increases with the molecular weight distribution. As the molecular weight distribution increases, the orientation of the fibers decreases during the spinning process, resulting in greater melting during the rolling process.

Nonwoven fabrics according to embodiments of the invention may be useful in a variety of applications. Suitable applications include, but are not limited to, disposable personal hygiene products (e.g., lounge pants, diapers, absorbent underpants, incontinence products, feminine hygiene products, and the like), disposable garments (e.g., workwear, coveralls, headgear, underpants, pants, skirts, gloves, socks, and the like), and sanitation/hygiene products (e.g., surgical gloves and drapes, face masks, headgear, surgical caps and headbands, shoe covers, slippers, wound dressings, gauze, sterile rolls, wipes, lab coats, coveralls, pants, aprons, jackets, bedding, and sheets). The non-generic materials may also be used in the manner disclosed in the following U.S. Patents: 6,316,687; 6,314,959; 6,309,736; 6,286,145; 6,281,289; 6,280,573; 6,248,851; 6,238,767; 6,197,322; 6,194,532; 6,194,517; 6,176,952; 6,146,568; 6,140,442; 6,093,665; 6,028,016; 5,919,177; 5,912,194; 5,900,306; 5,830,810 and 5,798,167.

EXAMPLES

The following are examples of some embodiments of the invention. They are not intended to limit the invention otherwise described and claimed herein. All numbers in the examples are approximate. The following examples illustrate a number of processes for various nonwoven materials. Performance data for these materials has also been obtained. Most of the processes or tests, where applicable, were conducted in accordance with U.S. standards or known procedures.

Production of polymer blends

A HAAKE twin-screw extruder was used to prepare the polymer blends. The extruder has the following characteristics:

- 6 hammer sections with temperatures of 110°C, 120°C, 130°C, 135°C, 135°C and 135°C.

- two 18 mm diameter pulleys

- length/diameter ratio: 30

- melting point: 146°C

- extruder pressure: 2.64x10 ⁶ Pa

- torque: 3.44x10 ⁷ Pa

- speed: 200 rpm

PRODUCTION OF POLYMER FIBERS

The fibers were prepared by extruding polymer using a 2.5 cm diameter extruder driven by a gear pump. The gear pump forces the material through a rotating assembly that has a 40 micron sintered flat metal screen and a 108-hole spinneret. The spinneret holes are 400 micron in diameter and the cutting edge length (i.e., length/diameter ratio) is 4/1. The gear pump is operated to extrude approximately 0.3 grams of polymer through each spinneret hole per minute. The temperature of the polymer varies depending on the molecular weight of the polymer being spun. In general, the higher the molecular weight, the higher the melting temperature. Tempering air (slightly above room temperature - about 24°C) is used to help cool the molten, spun fibers. The conditioning air is located just below the spinneret, where it blows air onto the yarn immediately after extrusion. The flow rate of the conditioning air is low enough to be felt with the bare hand on the yarn under the spinneret. The yarns are wound onto a yarn drawing disc with a diameter of about 0.152 m. The speed of the yarn drawing disc is adjustable, but in the experiments presented here the yarn drawing disc speed was about 1500 rpm. The yarn drawing discs are located about 3 m below the spinneret press. The yarns are cut into yarns of 0.0381 m in length immediately after the spinning operation.

Production of non-genotyped material

The nonwoven fabric samples were prepared on a laboratory smoothing roller equipped with hardened and chromed engraved steel rollers according to the process described herein. The engraved pattern has a total bond area of 20% and 3.44x10 ⁵ bond points per square meter. Figures 3A-3I schematically illustrate the various bond patterns used in embodiments of the invention and their dimensions.

The following process was followed for each sample design. Each fiber was 3 denier. The fibers were fed into a carding machine. The fibers were vacuum-drawn into the RotorRing and pressed through a series of needles. They were then neatly arranged in a high-speed centrifuge for future carding. This process was repeated for each sample. The fibers were then evenly distributed on a 10 cm x 40 cm steel tray, where the leading end of the fiber web was received by a paper feed roller. This resulted in a web with a basis weight of 33 g/cm ³ . The

-22- 3.·-’ ·»« fiber web was placed between heated moving smoothing rollers, which bonded the web into a nonwoven material. The initial condition of the bonding roller was as follows:

- The temperature of the upper (engraved) cylinder was between about 110°C and about 121°C, which is the temperature given in the figures and tables.

- The temperature of the lower (plain) roller was between about 110°C and about 121.1°C, which is about 4°C higher than that of the upper roller, in order to prevent sticking to the upper roller.

- The hydraulic pressure is between about 4.82x10 ⁶ Pa and about 1.03x10 ⁷ Pa.

- Roller speed/disc setting: between about 3 and about 5 m/min.

Test procedures

The produced material is predominantly oriented in the machine direction. This is a very slight transverse orientation of the fibers. The characterization of the material and fiber orientation was performed using the following technique:

1. Optical micrographs were taken on randomly selected specimens of the experimental material. Both the color and the reverse side of the material were photographed at 40x magnification. Optical micrographs were also taken on the commercially available spunbond PP material manufactured by TANDEC.

2. The photomicrographs were transferred to Scion Imaging software and divided into four quadrants.

3. The angles of the fibers in each quadrant of the photomicrographs were measured with the machine direction being the vertical (0°) and the cross direction being the horizontal (90°).

After each fiber was measured, the following equation was used to quantify the orientation:

f _p = 2 * avg. (cos©) ² -1, where Θ is the angle of the thread and f _p is the orientation parameter, and where the value 0 corresponds to a random distribution and the value 1 corresponds to perfect alignment in a specific direction.

The tensile strength of each fiber sample was measured using an Instron 4501 tensile tester. Straight jaws were used to accelerate the fiber into the Instron. The “Standard Test Method for Breaking Strength and Elongation of Materials” (US Standard D 5035-90) was used with one exception. The strips were cut to lengths of 0.101 m rather than 0.152 m.

We have developed a standard abrasion resistance procedure using a Taber Abrasor Model 503 (rotating disc, dual-head process) with an 8-compartment sample holder, including the following steps:

1. The material was cut into 0.0762x0.0762 m pieces and labeled.

2. We attached a self-adhesive backing to the edges of the worn surface to prevent the edges from tearing.

3. The samples were individually weighed to 4 decimal places.

4. Place the samples in the sample holder, making sure there are no creases or loose parts. Place the samples in the machine direction, facing the center of the sample holder, with the engraved pattern side facing up.

5. The material samples were abraded using C02 rubber abrading wheels for a specified number of cycles. A glued release paper manufactured by American Tape was applied to the abraded surface and then removed with a smooth but rapid motion.

6. The material was measured again and a record was made.

Any samples that were torn or completely damaged during testing were discarded and removed from further testing.

The bending stiffness was measured according to US Standard D 1388-64. A spirit level was placed on the horizontal surface before the measurements to ensure consistency. The bending stiffness was calculated by taking into account the length of the protruding part and the basis weight of the material. Although the cantilever test is a tool for easily measuring the stiffness of any material, it is important to reconcile the results with consumer opinions. The material has different properties according to the touch of the human hand than according to the mechanical test. In addition, the surface of the material should also be soft to the touch.

All tactile tests were conducted with a 12-member panel selected to evaluate the graininess and stiffness of the material. Each panel member followed the following procedure:

1. Each committee member received 4 samples, which he assigned a corresponding number, where 1 was the least granular and least rigid, and 15 was the most granular and rigid. The samples and their corresponding numbers are given in Table 10.

2. The panelist placed the sample, pressed side up, on the table. Their wrist was on the table top while their index and middle fingers moved across the entire surface of the sample. This process was repeated in all four directions of the sample. The assessment of graininess was recorded.

3. The panelist placed the sample flat on the table, with their dominant hand on top of the sample. They positioned their fingers so that they pointed toward the top of the sample. They folded the sample by moving their fingers toward their palm while their other hand moved the sample toward the folded hand. They then squeezed and released the sample several times.

4. The stiffness value was recorded.

All samples were evaluated before being assigned a number. Due to the availability of committee members, only a select set of samples were tested.

EXAMPLE 1

Polyethylene (PE) polymer was obtained from The Dow Chemical Company. Polyethylene polymers have different densities and melt indices. Polypropylene (PP) polymer was also obtained from The Dow Chemical Company. The properties of the polymers are summarized in Table 1.

Table 1. Polymers used in the experiments.

polymer type density (g/cm ³ ) melt flow index (g/10 min) melting point (°C) PE1 0.955 29 131 PE2 0.941 27 125 PE3 0.950 17 129 PE4 0.870 1 55 PP1 0.910 35 165

The polyethylene representing PE1 contains ASPUN™ 6842A available from The Dow Chemical Company (Midland, Michigan, USA). The polyethylene representing PE2 contains ASPUN™ 6811 available from The Dow Chemical Company (Midland, Michigan, USA). The polyethylene representing PE3 contains ASPUN™ 6835A available from The Dow Chemical Company (Midland, Michigan, USA). The polyethylene representing PE4 contains AFFINITY™ EG8100 available from The Dow Chemical Company (Midland, Michigan, USA). The polypropylene representing PP1 contains H500-35 available from The Dow Chemical Company (Midland, Michigan, USA). Four samples were formed from the polyethylene samples. Three homopolymers and a 95%-5% PE1-PE4 blend were tested. The composition of the mixture was as described above. 4.75 kg of PE1 pellets and 0.25 kg of PE4 pellets were mixed and placed in the hopper of a twin screw extruder. After leaving the extruder, the polymer was placed in a cooling bath maintained at 5°C. The solidified polymer was then fed to a Berlyn Clay Group shredder which cut it into pellets. The polymer was cleaned for 15 minutes and the pellets were collected for 100 minutes.

The fibers were produced using the spinning conditions in Table 2 and the procedure described above.

Table 2. Spinning conditions for various fibers.

thread polymer extruder temperature (°C) thread pulling speed (1/min) thread drawing speed (m/min) estimated fiber diameter (μπι) total sample weight (g) 1 PE1 190 1800 900 21 540 2 PE2 190 1800 900 21 180 3 PE3 190 1800 900 21 180 4 PE1+PE4 190 1800 900 21 180 5 PP1 230 1800 900 21 180

Using the fibers prepared in Table 1, fibers were prepared from the procedures described above and coded as follows. A three-digit number was assigned to each sample. The first digit indicated the polymer used. The second digit indicated the bonding sample number, and the third digit indicated the bonding temperature. Table 2 lists the polymer numbers, and Figures 3A-3I

and is the knitting pattern number. This labeling system was used for convenience in identifying the patterns.

In Figure 3A, the bond point angle of bond pattern No. 1 is 46°, the bond area ratio is 20%, the bond point density is 3.44x10 ⁵ points/m ² , the base width is 1.7x10' ³ m, the base height is 4.32x10' ⁴ m, and the dot width is 7.62x10' ⁴ m. In Figure 3B, the bond point angle of bond pattern No. 2 is 20°, the bond area ratio is 16%, the bond point density is 3.44x10 ⁵ points/m 2 , the base width is 1.7x10' ³ m, the base height is 4.32x10' 4 m, and the dot width is 6.86x10' 4 m. In Figure 3C, the bond point angle of bond pattern No. 3 is 20°, the bond area ratio is 16%, the bond point density is 3.44x10 5 points/m ² , the base width is 1.7x10' 3 m, the base height is 4.32x10' ⁴ m, and the dot width is 6.86x10' ⁴ m. The bond pattern No. 4 has a bond angle of 20°, a bond area ratio of 24%, a bond density of 3.44x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 8.38x10' ⁴ m. In Figure 3D, the bond pattern No. 4 has a bond angle of 20°, a bond area ratio of 20%, a bond density of 2.31x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 9.30x10' ⁴ m. In Figure 3E, the bond pattern No. 5 The bond pattern has a bond angle of 20°, a bond area ratio of 20%, a bond density of 4.60x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 6.60x10' ⁴ m. In Figure 3F, the bond pattern No. 6 has a bond angle of 46°, a bond area ratio of 16%, a bond density of 3.44x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 6.86x10' ⁴ m. In Figure 3G, the bond pattern No. 7 The bond pattern has a bond angle of 37°, a bond area ratio of 24%, a bond density of 3.44x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 8.38x1 O' ⁴ m. In Figure 3H, the bond pattern No. 8 has a bond angle of 46°, a bond area ratio of 20%, a bond density of 2.31x10 ⁵ points/m ² , a base width of 1.7x10' ³ m, a base height of 4.32x10' ⁴ m, and a dot width of 9.3x1 O' ⁴ m. In Figure 3I, the bond pattern No. 9 The bond pattern has a bond point angle of 35°, bond area ratio of 20%, bond point density of 4.60x10 ⁵ points/m ² , base width of 1.7x10 ^-3 m, base height of 4.32x10 ^-4 m, and point width of 6.60x10' ⁴ m.

Then, pieces of the material were cut from the center for tensile testing, abrasion resistance testing, and support testing. Due to the inconsistency of the fiber web and the edges due to the processing temperature, each sample was cut from the center.

The material was evaluated by visual inspection. Temperature, pressure and resin selection had no effect on the appearance of the material. The material is visible

The properties of the bonding roller pattern were noticeably affected. Figures 4A-4I are 20x photomicrographs of a nonwoven fabric made from 6824A resin at 119.4°C, which clearly show the differences in the fabric. The dark, diamond-shaped areas are the bonding areas of the fabric, while the lighter areas are the unbonded fibers.

A comparison of Figures 4A, 4F, 4G, 4H, and 4I with Figures 4B, 4C, 4D, and 4E shows that the 20° sidewall angle results in a smaller bond area than the samples with a larger sidewall angle. The bond area measurements for the material are given in Table 3. The data show that the bond area is larger than the cylindrical sample that produced the material for bond samples 1, 6, 7, and 8. This is due to the increased heat transfer due to the melt flow of the polymer under the tie pin and the compaction of the fibers in the voids between the tie pins. The fibers have less free space and the conductive heat transfer is greater. All samples with a 20° sidewall exhibit a smaller bond area than the cylindrical sample. This is likely due to the shrinkage of the polymer fibers. During the spinning process, the fibers are strengthened under tension in the oriented direction. When the material is exposed to higher temperatures under the tie pin, the polymer molecules shrink or contract to a more stable state.

Table 3. Measured bond area ratios of nonwoven materials.

resin sample temperature (°C) average bond area ratio (%) PE1 1 119.4 33.7 PE1 2 119.4 16.5 PE1 3 119.4 30.8 PE1 4 119.4 19.0 PE1 5 119.4 20.7 PE1 6 119.4 17.7 PE1 7 119.4 31.8 PE1 8 119.4 24.7 PE1 9 119.4 24.1 PE2 1 116.1 31.1 PE2 2 116.1 14.0 PE2 3 116.1 20.7 PE2 4 116.1 17.6 PE2 5 116.1 17.5 PE2 6 116.1 17.1 PE2 7 116.1 28.6 PE2 8 116.1 22.2 PE2 9 116.1 23.1 PE3 1 119.4 33.0 PE3 2 119.4 13.8 PE3 3 119.4 23.5 PE3 4 119.4 15.5 PE3 5 119.4 17.3 PE3 6 119.4 16.3 PE3 7 119.4 28.4 PE3 8 119.4 23.2 PE3 9 119.4 19.8 95% PE1 + 5% PE4 1 119.4 30.8 95% PE1 + 5% PE4 2 119.4 13.4 95% PE1 + 5% PE4 3 119.4 19.0 95% PEI + 5% PE4 4 119.4 17.0 95% PEI + 5% PE4 5 119.4 16.5 95% PEI + 5% PE4 6 119.4 15.3 95% PEI + 5% PE4 7 119.4 26.8 95% PEI + 5% PE4 8 119.4 21.8 95% PEI + 5% PE4 9 119.4 20.0

It appears that the 20° sidewall samples have less tightly packed fibers or are more porous. Bond samples 4,5,7 and 8 have the same proportion of bond area but different densities of dots per square meter. The distance between individual bond points is greater for samples with lower densities of dots per square meter.

The weight analysis of the material is given in Table 4. Due to the differences in the carding process and the treatment of the fiber webs, thin spots appear in the material. The differences in thickness can strongly influence the mechanical properties. The weight of a cm ² sample within the material shows very low variation.

Table 4. Within-sample and between-sample weight analysis.

resin sample average weight (g) PE1 1 0.021 PE1 2 0.023 PE1 3 0.023 PE1 4 0.020 PE1 5 0.019

Figures 4A-4I show photomicrographs of PE1 resin with a variable bond pattern taken at 119.4°C, which were also used to determine fiber orientation. By examining the figures, it can be seen that the majority of the fibers are aligned in one direction (up or down). This is the machine direction of the fibers. In most spunbond and meltblown materials, the fiber distribution is more random, so the material has both cross-directional and machine-directional strength. When evaluating the randomly selected materials, it can be seen that the orientation values (f _p ) of the commercially available spunbonded material are much lower than the samples produced and tested in these examples. The commercially available spunbonded material was made from polypropylene at TANDEC. The results are shown in Table 5. The f _p values are higher at the bottom of the material. This means that the fibers are more aligned in the machine direction at the bottom. The upper part of the knitting pins arrange the fibers in a more random state, while the lower fibers in contact with the smoothing roller maintain the orientation of the web.

5. Table. Data Collected from Orientation of Fibers Measurement

fabric _fP (1) _fP (2) _fP (3) average f _p PE (above) 0.56 0.54 0.53 0.54 PE (below) 0.70 0.82 0.69 0.74 spunbond PP 0.22 0.19 0.25 0.22 spunbond PP 0.16 0.18 0.22 0.19

Tables 6-9 show the various properties of nonwovens where different bonding patterns were used for each polymer fiber at different temperatures. Each sample was assigned a three-digit number. The first number indicates the polymer used. The second number indicates the bonding pattern number, and the third number indicates the bonding temperature in °C. The numbering of the polymers is given in Table 2, and the bonding patterns are given in Figures 3A-3I. For example, 11-116.1 means that the material was made from PE1 resin using bonding pattern No. 1 (Figure 3A) at a bonding temperature of 116.1 °C. The tensile properties of each sample were measured at peak load and elongation at break using an Instron 4501 and the previously described US Standard D 5035-90 procedure. Due to the variability of the materials under the same conditions, 6 tensile specimens were tested. The average wear tested for each processing condition is listed. In order to determine the flexural rigidity (FR) according to the US standard D 1388-64, the extension length was measured for each material in relation to the ream weight. The average flexural rigidity measured for each resin under each processing condition is listed.

-31 Table 6. Data for PE1 resin.

sample code average elongation (%) normalized average peak load (g) average wear (mg/cm ² ) average FR (mg*cm) 1-1-116.1 43.17 1974 0.76 29.1 1-1-117.7 52.20 2026 0.71 33.8 1-1-119.4 70.00 2161 0.55 45.9 1-2-116.1 16.77 920 1.02 17.6 1-2-117.7 17.40 882 1.01 20.3 1-2-119.4 31.61 1186 0.83 22.0 1-2-116.1 17.00 927 0.77 30.4 1-3-117.7 20.06 1032 0.71 28.8 1-3-119.4 27.81 1330 0.53 33.6 1-4-116.1 20.73 956 1.08 17.8 1-4-117.7 19.66 915 0.92 19.6 1-4-119.4 27.64 1141 0.64 19.6 1-5-116.1 9369 806 0.99 17.9 1-5-117.7 0.89 25.3 1-5-119.4 19.37 1073 0.66 32.4 1-6-116.1 32.08 1253 0.93 28.4 1-6-117.7 49.86 1393 0.89 38.4 1-6-119.4 76.48 1619 0.75 50.8 1-7-116.1 41.15 1511 0.72 48.0 1-7-117.7 52.51 1821 0.66 51.4 1-7-119.4 93.13 2149 0.54 70.1 1-8-116.1 48.27 1517 0.97 41.4 1-8-117.7 75.35 1666 0.83 46.2 1-8-119.4 70.34 1865 0.61 56.0 1-9-116.1 24.08 1193 0.94 45.7 1-9-117.7 28.04 1335 0.85 55.6 1-9-119.4 53.75 1493 0.64 85.2

Table 7. Data for PE2 resin.

sample code average elongation (%) normalized average peak load (g) average wear (mg/cm ² ) average FR (mg*cm) 2-1-112.7 24.62 1646 0.94 31.8 2-1-114.4 31.54 1912 0.80 43.3 2-1-116.1 45.24 2075 0.68 66.2 2-2-112.7 49.30 1228 1.20 30.1 2-2-114.4 60.96 1336 0.92 36.7 2-2-116.1 36.26 1188 0.75 50.3 2-3-112.7 63.42 1370 1.00 35.9 2-3-114.4 62.79 1544 0.74 41.8 2-3-116.1 33.12 1336 0.59 55.1 2-4-112.7 81.15 1482 1.06 20.2 2-4-114.4 90.96 1525 0.78 24.2 2-4-116.1 39.15 1316 0.65 35.9 2-5-112.7 54.37 1409 0.97 35.0 2-5-114.4 64.09 1508 0.84 40.1 2-5-116.1 19.75 1344 0.61 51.5 2-6-112.7 74.57 1530 1.06 39.6 2-6-114.4 56.29 1438 0.93 52.8 2-6-116.1 38.05 1057 0.75 57.4 2-7-112.7 68.12 1583 0.96 43.0 2-7-114.4 64.24 1743 0.78 54.3 2-7-116.1 50.48 1858 0.58 72.5 2-8-112.7 95.53 1594 1.04 35.5 2-8-114.4 91.61 1617 0.75 40.3 2-8-116.1 33.78 1122 0.65 48.6 2-9-112.7 60.33 1685 0.95 54.6 2-9-114.4 78.11 1705 0.83 54.1 2-9-116.1 73.58 1950 0.61 60.8

Table 8. Data for PE3 resin.

sample code average elongation (%) normalized average peak load (g) average wear (mg/cm ² ) average FR (mg*cm) 3-1-116.1 17.74 1447 0.92 40.0 3-1-117.7 21.50 1702 0.61 41.0 3-1-119.4 27.82 1919 0.55 46.3 3-2-116.1 13.53 1242 1.09 41.4 3-2-117.7 23.23 1785 0.97 40.1 3-2-119.4 32.40 1992 0.79 46.0 3-2-116.1 21.65 1922 0.89 36.8 3-3-117.7 28.69 2021 0.62 44.8 _3-3-119.4 40.03 2274 0.56 44.9 3-4-116.1 22.66 1721 1.06 27.7 3-4-117.7 26.83 1845 0.89 38.7 3-4-119.4 38.57 2035 0.69 42.1 3-5-416.1 12.33 1248 1.05 28.8 3-5-117.7 16.31 1582 0.87 35.4 3-5-119.4 28.89 1975 0.70 40.3 3-6-116.1 18.79 1138 1.03 60.4 3-6-117.7 28.29 1677 0.88 88.4 3-6-119.4 41.52 1980 0.80 98.0 3-7-116.1 24.87 1597 0.94 82.9 3-7-117.7 41.28 1879 0.66 90.1 3-7-119.4 51.97 2376 0.55 125.5 3-8-116.1 26.63 1255 0.97 74.1 3-8-117.7 43.24 1806 0.81 79.9 3-8-119.4 36.78 2017 0.68 88.4 3-9-116.1 16.56 904 0.90 80.7 3-9-117.7 16.83 1279 0.84 103.7 3-9-119.4 20.26 1456 0.65 116.4

-34·.:· J. ·-· ·»·

Table 9. Data for a resin containing 95% PE1 and 5% PE4.

sample code average elongation (%) normalized average peak load (g) average wear (mg/cm ² ) average FR (mg*cm) 4-1-116.1 54.03 2065 0.96 22.9 4-1-117.7 81.32 2288 0.75 35.8 4-1-119.4 31.72 1988 0.50 39.0 4-2-116.1 20.23 1322 1.09 32.6 4-2-117.7 33.20 1659 1.00 42.0 4-2-119.4 33.48 1676 0.72 53.4 4-2-116.1 27.46 1485 0.95 35.3 4-3-117.7 36.27 1735 0.71 32.6 4-3-119.4 51.98 2192 0.53 49.0 4-4-116.1 27.59 1452 1.33 26.5 4-4-117.7 39.67 1756 1.05 30.3 4-4-119.4 42.27 1928 0.77 29.4 4-5-116.1 19.75 1344 1.28 31.0 4-5-117.7 34.79 1800 1.03 47.7 4-5-119.4 41.19 2017 0.70 48.7 4-6-116.1 34.41 1590 0.97 56.9 4-6-117.7 60.42 1812 0.84 71.0 4-6-119.4 28.85 1589 0.63 91.0 4-7-116.1 49.89 1920 0.93 67.9 4-7-117.7 75.67 2241 0.73 82.0 4-7-119.4 32.57 1861 0.48 102.7 4-8-116.1 54.02 1862 0.99 46.5 4-8-117.7 45.77 2076 0.85 62.4 4-8-119.4 46.92 1884 0.64 77.9 4-9-116.1 29.05 1362 1.03 67.7 4-9-117.7 53.70 1737 0.85 80.7 4-9-119.4 57.83 1862 0.58 109.6

The peak load values range from 800 g to 2400 g. These values are much lower than those for typical PP samples. When the bond sample No. 2 is applied at 136.6°C, the peak load of PP1 is 4875 g. In general, the normal peak load increases in parallel with the increase in temperature, bond area and bond angle. In the case of the PE2 resin and the 95% PE1 and 5% PE4 blend, the peak load decreased when the temperature was increased from 4.4°C to 116.1°C for PE2 and from 117.7°C to 119.4°C for the blend. This may be due to a change in the fracture mechanism. A pairwise comparison of the samples results in a peak load higher at a bond area ratio of 24% than at 16%. As previously shown, the bond angle has a dramatic effect on the actual bond strength of the samples. Figure 5 plots the normalized peak load versus temperature for PE2 resin at different temperatures and using different bond patterns. The peak load was linearly normalized to a ream weight of 33g/ ^m2 , as the peak load is highly dependent on the ream weight.

Figure 6 graphically shows the relationship between the elongation and temperature of PE2 resin at different temperatures and different bond patterns. The elongation of PE nonwovens ranged from 10% to 95%. When using bond pattern No. 2 at 136.6°C, the elongation of PP reached only 31%, and 37% was the highest value achieved under any conditions. Reducing the density of the bonding points significantly increases the elongation. The PE2 resin actually almost doubled its elongation at 114.4°Con by reducing the bond density from 4.60x10 ⁵ to 2.31x10 ⁵ . The exception to this is the 95% PE1 and 5% PE4 blend resin, which does not show a large difference in elongation with the decrease in bond density. This may be explained by the high elasticity of PE4, which may be more significant than the effect of the bonding patterns. Temperature control is important. A 1.6°C difference in temperature can reduce elongation by 100%.

Figure 7 shows three typical strain-stress curves of the PE1 resin. The samples were processed using PE1 resin with bond pattern No. 3 at 116.1 °C, 117.7’0 and 119.4’C. The peak load increases with temperature. At the highest temperature of 119.4°C, the elongation of the material decreases. The initial modulus of the material produced at 119.4°C is also higher than that produced at lower temperatures. This is typical for all material samples.

Figure 8 shows the typical temperature/wear curve for PE1 resin. The data generally show that the elongation at all

-36 depends on the processing factor. As the interrelated bond area and bond angle increase, the elongation of the material also increases. Abrasion resistance is generally mostly temperature dependent, although significant differences can be seen between bond patterns. This can be explained by the fracture mechanism. When the surface wears, the fibers pull out of the bond points. Due to the abrasion fracture mechanism, the amount of surface fluff depends more on the bond strength than on the bond size. The abrasion values ranged from 0.48 mg/cm ² to more than 1 mg/cm ² . The abrasion value of the PP sample produced at 136.6°C with bond pattern no. 2 is 0.15 mg/cm ² , which is more than three times lower than the abrasion value of PE.

Figure 9 shows the temperature/flexural stiffness curve for PE2 resin. This is a typical curve and shows trends observed for other resins. A long elongation indicates a stiff material. A high ream weight also contributes to stiffness, as the material carries more weight when hanging by its edge. The average of the upward and downward elongations of the side of the material facing the engraved cylinder gives the total elongation of the nonwoven fabric. The average value was taken for each piece. This was done with the idea that this would better represent the overall stiffness of the material, as the material flexes in both directions during use. Four measurements were taken for each sample in this manner.

It was observed that the bond samples 6-9 with a higher bond angle had higher values than the bond samples 2-5 with a bond angle of 20°. The bending stiffness for all PE samples ranged from a value of just over twenty to a value of 125 mg*cm measured for sample 3-7-119.4. These are relatively low values, considering that the typical bending stiffness of PP is over 200 mg*cm. Under the same conditions, compared to other resins, the PE2 resin showed the lowest stiffness. This is probably due to the low density of the polymer. The highest bending stiffness was obtained for PE3, which is due to the high density of the polymer. The addition of PE4 and PE1 resulted in higher bending stiffness. This is probably due to the increase in the melt in the bond area and/or the shrinkage of the fibers and the material. Regarding the bond pattern, it can be shown that small bond areas, small sidewall angles and low bond density result in the lowest bending stiffnesses. It should be noted that small bond area ratios, sidewall angles and bond densities

-37 can also affect other properties, e.g. wear. Thus, due to the low modulus of PE, flexural stiffness values may not be as important as other properties.

The effect of the bonding roller patterns on the stiffness of the material and the graininess of the surface was evaluated by manual tactile testing. A total of 12 panel members rated the two properties on a scale of 1 to 15. The anchors listed in Table 10 were considered (used as a baseline). PE1 resin processed with each bonding pattern at 119.4°C was used as the samples. Table 11 summarizes the average of the two manual evaluations for each bonding pattern.

Table 10. Anchor materials and corresponding anchor values.

type of test anchor material anchor number granularity bleached mercerized cotton poplin 2.1 granularity military carded cotton satin bleached 4.9 granularity cotton momie fabric 9.5 granularity cotton canvas greige 13.6 rigidity single knit 50%-50% polyester/cotton 1.3 stiffness! bleached mercerized printed cotton fabric 4.7 stiffness. bleached mercerized cotton poplin 8.5 stiffness! cotton organza 14.0

Table 11. Manual examination obtained data. sample code stiffness granularity 1-1-119.4 2.5 5.6 1-2-119.4 0.9 2.9 1-3-119.4 1.8 3.9 1-4-119.4 1.6 4.0 1-5-119.4 1.1 2.8 1-6-119.4 1.7 3.5 1-7-119.4 3.0 5.4 1-8-119.4 1.5 4.0 1-9-119.4 2.5 4.9 5-2-140 5.3 6.4

Scanning electron microscopy (SEM) was used to evaluate the effects of processing conditions on the surface, bond perimeter, cross-section and fracture mechanism of nonwovens. It was shown that processing conditions affect the feel of nonwovens and the strength of the material. In the following, we analyze the relationship between the surface and properties of the material, and identify the fracture mechanisms depending on the processing conditions.

Surface views and cross-sectional views were obtained using the following procedure:

1. The cross-section of the material was obtained by placing the nonwoven fabric between two sheets of paper, then immersing the sample in liquid nitrogen for 1 minute, and then cutting it perpendicular to the machine direction with a razor blade.

2. The sample was placed on a platform with conductive tape and the edges were covered with conductive graphite paint.

3. A Denton Vacuum Hi-Res 100 high-resolution chrome sputtering setup was used to coat the nonwoven fabric with a thin layer of 100-120 A thickness.

4. The sample was placed in a sample compartment and a vacuum of 1.3x10' ⁵ Pa was created in the sample compartment.

5. Out of the available 20 keV, 5 keV was used due to charge accumulation problems on the surface of the nonwoven material.

6. We took photomicrographs at different magnifications.

7. Scion imaging software was used to display and measure the photomicrographs.

Each specimen examined was photographed at 60x and 100x magnification, focusing on the junction. Since no surface variation was apparent at each temperature, each photograph was taken 1.6°C below the pour point. This was 119.4°C for all specimens except for PE2 resin, which was 119.4°C. The nine PE1 resin bond specimens are shown in Figures 10A-10J. Each junction has a large flat surface in the center that becomes more prominent toward the edge. Bond specimens 1, 6, 7, and 8 have large lateral angles. This effect is not as noticeable for PE1 resin as for the others, and

-39.*«- *· *·· ·1· probably due to the high melt index. Small side angle patterns produce a bond with a smaller flat area, where the bond point has a more rounded geometry. Since the bond point produced with a 20° side angle has a rounded shape and covers a smaller area, as we saw earlier, the space between each bond point is larger. The larger area results in a softer feel of the material due to the increased exposed area of the fibers. This correlates well with the tactile evaluation data. Conversely, small bond point coverage results in less entangled fibers and reduces the strength of the material. We saw this earlier in the elongation data.

One of the effects of processing conditions on a nonwoven is the failure mechanism during destructive tests, such as tensile or abrasion tests. Three types of failure can occur. The fibers can pull out of the bond, break at the perimeter of the bond, or break off the bond. SEM micrographs were also used to determine the failure mechanism of selected nonwoven samples. Examples of the tensile failure mechanism are shown in Figures 11A-11C. Under most processing conditions, polyethylene material fails by pulling its fibers out of weak bond points. In some cases, at high temperatures, it was evident that the bonds were strong enough to cause fiber breakage at the perimeter of the bond. Adding 5% PE4 resin to PE1 resin at 119.4°C increased the bond strength sufficiently to cause some fibers to break at the bond perimeter. At this point, there was evidence of two failure mechanisms, including fibers pulling out of the bond and fibers breaking at the perimeter.

When analyzing the mechanisms of wear-induced failure, there was no indication of fracture at the bond perimeter. Figures 12A and 12B show two examples of wear-induced bond failure. The two ribbon-like parts are the remains of a previously thermally bonded point. Even for these samples that did not pass the tensile test due to stiffness! fiber breakage, different failure mechanisms were observed. After wear, the material failed at the bond point. These phenomena may explain why the wear resistance does not reach a peak value and then decreases with increasing processing temperature, as is the case for tensile strength and elongation. The wear resistance depends only on the bond strength.

-40- *<· íi

As described above, embodiments of the invention provide a nonwoven fabric having relatively higher tensile strength, elongation, abrasion resistance, flexural rigidity, and/or softness. Other features and advantages of embodiments of the invention will be apparent to those skilled in the art.

While the invention has been described in relation to a limited number of embodiments, variations and modifications are possible. For example, the nonwoven composition need not be prepared as a blend composition as set forth above; it may contain other components in any amount so long as the desired properties of the composition are maintained. It should be noted that the application of the composition is not limited to sanitary articles; it may be used in any environment where a thermally bonded nonwoven is required.

Claims (22)

“ 4. ^Γ ** ·»· PATENT CLAIMS 1. A method for producing a nonwoven fabric, characterized in that a thermally bonded fabric having a bonded area ratio of at least 20% is produced by passing a fibrous web through a pair of rollers, wherein the bonded area ratio is created by an engraved pattern having raised bonding points on one of the rollers. 2. A polymer-containing nonwoven fabric, characterized in that it has a bonded area fraction of at least 20%, which is created by an engraved pattern having raised, bonded points on a cylinder. 3. The thermally bonded nonwoven fabric of claim 2, wherein the polymer is polyethylene. 4. The method of claim 1 or the nonwoven material of claim 2, characterized in that the bond area ratio is at least 24%. 5. The method of claim 1 or the nonwoven fabric of claim 2, characterized in that the bonding points have a bonding point angle of at least 20°. 6. The method of claim 1 or the nonwoven fabric of claim 2, characterized in that the bonding points have a bonding point angle of at least 35°. 7. The method of claim 1 or the nonwoven fabric of claim 2, wherein the bonding points have a bonding point angle of at least 37°. 8. The method of claim 1 or the nonwoven fabric of claim 2, wherein the bonding points have a bonding point angle of at least 42°. 9. The method of claim 1 or the nonwoven fabric of claim 2, wherein the bonding points have a bonding angle of at least 46°. 10. The method of claim 1 or the nonwoven fabric of claim 2, wherein the raised engraved pattern has at least 1.55x10 ⁵ bonding points per square meter. 11. The method of claim 1 or the nonwoven fabric of claim 2, wherein the raised engraved pattern has at least 2.31x10 ⁵ bonding points per square meter. 12. The method of claim 1 or the nonwoven fabric of claim 2, wherein the raised engraved pattern has at least 3.1x10 ⁵ bonding points per square meter. 13. The method of claim 1 or the nonwoven fabric of claim 2, wherein the raised engraved pattern has at least 3.44x10 ⁵ bonding points per square meter. 14. The method of claim 1 or the nonwoven fabric of claim 2, wherein the raised engraved pattern has at least 4.6x10 ⁵ bonding points per square meter. 15. The method of claim 1 or the nonwoven fabric of claim 2, wherein the raised engraved pattern has at least 4.65x10 ⁵ bonding points per square meter. 16. The method of claim 1, wherein the fibrous web comprises polyethylene. 17. The nonwoven fabric of claim 3 or the method of claim 16, wherein the polyethylene is a homopolymer of ethylene. 18. The non-woven material of claim 3 or the method of claim 16, wherein the polyethylene is a copolymer of ethylene and a comonomer. 19. The nonwoven fabric of claim 3 or the process of claim 16, wherein the polyethylene is formed in the presence of a metallocene catalyst. 20. The nonwoven fabric of claim 3 or the process of claim 16, wherein the polyethylene is formed in the presence of a catalyst with an artificial geometry. 21. The nonwoven fabric of claim 3 or the process of claim 16, wherein the polyethylene is formed in the presence of a single-site catalyst. 22. A material obtained by the process according to any one of claims 1 and 4-21. Patent and Trademark Office Ltd. Our file number: 98859-8657/SZT/SZT Our administrator: Zsolt Szabó