MXPA00006564A - Nonwoven, porous fabric produced from polymer composite materials - Google Patents

Abstract

A nonwoven, porous fabric produced from a water modifiable polyolefin-containing film. In a preferred embodiment, the nonwoven fabric includes groups of elongated polyolefin fibers substantially oriented along a longitudinal axis. The fibers have branches extending from themselves and are bonded therebetween. Elongated channels extend generally parallel to the longitudinal axis on the surface of the fabric and within the fabric. A substantial portion of the channels are interconnected to other channels. To produce the fabric, a polymer blend is formed with the polyethylene as the minority constituent and the dispersed phase, and with polyethylene oxide as thecontinuous phase. In another embodiment, wherein the polyethylene is the majority constituent and the polyethylene oxide is the minority constituent, a reactive blend is prepared during processing so that the blend exhibits an inverse phase morphology, the polyethylene oxide becoming the continuous phase and the polyethylene becoming the dispersed phase. In either embodiment, the blend is extruded into a film, which is then treated with an aqueous solvent to remove the polyethylene oxide to produce the nonwoven, porous fabric. The resulting nonwoven, porous fabric has a silk-like hand and shine ideal for disposable personal hygiene articles, and is flushable through waste water disposal systems.

Description

POROUS FABRIC NON-WOVEN PRODUCED FROM POLYMER COMPOUND MATERIALS BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a nonwoven porous fabric made of polymer composite materials useful in disposable personal hygiene articles. This invention more particularly relates to a porous woven fabric having directionally oriented and elongated fibers and interconnected elongate channels.

Description of Previous Art Disposable personal care products such as diapers, tampons, pant lining etc. are of great convenience. Such products conveniently provide the benefit of a one-time sanitary use and are quick and easy to use. However, the disposal of such products is a concern due to the space of filling land that is exhausted and the undesirable nature of the incineration. In addition, the difficulty and costs associated with the separation of such products in the preparation of the provision is also a concern. Consequently, there is a need for a non-woven, wettable and porous fabric which can maintain its intended structure during personal use, but which is completely acceptable in conventional drainage systems. Personal care products which are disposable with water discharge in conventional drainage systems provide the benefit of cost effective and convenient and thorough disposal.

Currently, commercially available fabrics of the composite polymers produced with the use of extrusion devices are often woven after the polymer composition is forced through the fine orifices of a spinning organ to form continuous filaments of the fiber made by the man. The subsequent pulling and twisting together of the fibers to form the yarn is called spinning. In addition, various spinning methods are known such as melt spinning, solution spinning and scintillation spinning. To make a fabric, the fibers are twisted together to make a strand of yarn and typically, the strands of yarn are then woven together.

There are commercially available fabrics of composite polymers which are not woven. These known non-woven fabrics are produced from processes which are also known. For example one of these non-woven fabrics is known as a yarn bonded fabric. A cloth linked with yarn uses a spinner organ to form fibers which fall down into an air gun. The fibers are sprayed with air so that the continuous fibers are randomly placed one on top of the other. The continuous and entangled fibers are then wound onto a forming wire. Since such fibers are not woven, the bond is necessary to allow the entangled fibers to maintain their desired shape. Adhesive or heating is often used to bond the entangled fibers to form the fabric.

A second type of non-woven fabric is a melt blown phone. In this example, the fibers are extruded from a spinning organ as with spinning, but these are very thin. A rapid stream of air is blown over the melt as it exits the holes in the spinning organ. The air pulls the melt to produce microfibers typically 3 to 5 microns in diameter. The tissue is collected on a forming wire. The fibers are hot when you fall in the mass and sign some union, but usually a step of thermal bonding or adhesive is usually taken in advance.

Another example of a non-woven fabric is a fabric placed by air and which is also produced from a known process. A non-woven fabric placed by air is produced from small lint-like fibers thrown into the air. A vacuum pulls the fibers down to make a collection of random fibers which can also be adhesively or thermally bonded.

The non-woven fabrics produced from these known processes can be characterized by their fiber lengths, orientation and resulting capillary channels or vessels between the fibers produced by the bonds between the fibers. In the case of non-woven fabrics designed for fluid fluid distribution management, the channels provide a place for the water to go. Both the elongated fibers and the channels are desired in order to obtain optimum fluid absorption and transmission together with a strong fabric. Yarn-linked fabrics include continuous and long fibers which form short channels therebetween. In the case of fabrics blown with fusion, both fibers and channels are short. Fabrics placed by air have short fibers but moderately elongated channels. In either case, the optimal configuration of the continuous and long fibers with the long channels does not exist in any known nonwoven fabric and furthermore, can not be produced by any known process. Therefore, the desired reinforcement as a result of the structural integrity of the continuous and bonded fibers in conjunction with the increased water absorption and transmission obtained from the elongated channels does not exist in the known nonwoven fabrics. In short, a disadvantage associated with typical non-woven fabrics is that the fibers are not directionally oriented or the channels are clogged by the bonds between the fibers. Nonwovens in and by themselves are not moisturizable unless they are treated or coated with surfactants. However, these surfactants are not permanent on non-woven fabrics.

There are some known patents that describe the processing of polymer compositions with the preparation of a polymer mixture by specifically dissolving or polymer component in another. For example, U.S. Patent No. 3,539,666 to Schirmir discloses a method for producing a nonwoven fabric type member. A thermoplastic composition comprising a mixture of different polymers is extruded through an annular die to form a seamless cell tube which is biaxially stretched by pulling on a mandrel. A substantial portion of the individual cells in the tube break to form a porous tissue-like structure that resembles a non-woven fabric. Once cooled, the resulting structure can be pulled out of the mandrel and cut to form a sheet.

U.S. Patent No. 5,178,812 issued to Sanford et al. Describes a method for making compounds having improved surface properties.

At Sanford, a polymer matrix is extracted from the interior of a composite material in order to increase the matrix concentration on the material surface. Before selectively dissolving the polymer matrix with an acidic solvent, the fibers can be formed by spinning, extruding a drug in the films or fibrillating the drug in the fibers. The Sanford process then involves treating the material with a solvent which dissolves the polymer matrix while essentially not dissolving the reinforcing polymer phase. Then, the solvent is removed so that at least some of the polymer matrix is removed from the interior of the material and the matrix concentration is increased at the surface of the material. In a nutshell, Sanford simply teaches a process to improve surface properties such as adhesiveness in a composite construction. Sanford does not describe a non-woven fabric as does the present invention.

U.S. Patent No. 5,096,640 issued to Brody et al. Describes a method for producing a highly porous, melt bonded fibrous tube for use as a separation medium. In Brody, a mixture of polymer components are placed in a solvent. One of the two components is then leached to produce a tube having a wall consisting of interpenetrating networks of two polymeric components. One of the two components in the interpenetrating network is filtered out to produce the tube.

Brody requires mixing to be spinnable. In addition, Brody does not teach a simple mixture or a permanently wettable fabric as does the present invention.

U.S. Patent No. 5,227,101 to Mahoney et al. Teaches the preparation of a porous membrane of a polymer mixture by dissolving a component of the mixture. In Mahoney, the invention relates to a process for making microporous membranes for liquid or gas separations by mixing a polymer-type poly (ether ether ketone) polymer and a crystallizable polymer of low melting point. A plasticizer dissolves at least 10 percent by weight of the poly (etheretherketone) type polymer that is present at the membrane manufacturing temperature. The plasticizer can be made from a solvent so that at least 10 percent by weight of the poly (ether ether ether) type polymer is dissolved. Mahoney describes extruding the polymer blends into membranes and then immersing the membrane in a leachate bath. In Mahoney, the polymer mixture and the plasticizer are extruded through a spinning organ. The invention in Mahoney focuses on the manufacture of filtration and / or separation membranes. However, a non-woven fabric as in the present invention is not described.

U.S. Patent No. 3,323,978 issued to Rasmussen also describes the processing of a polymeric composition to form textile fibers. Rasmussen teaches a two-phase fibrous microstructure comprising a distinctive hydrophobic component and a distinctive hydrophilic component. The fibers are produced from a film material which is treated with a swelling agent for the distinctly hydrophilic component. The swollen product is subsequently divided into individual fibers or into one. coherent fiber network. By swelling, the material of the hydrophilic fibrils is weakened. The resulting surfaces of the division will remain in the hydrophilic substance so that the fibers will have an accumulation of hydrophilic substance on the surfaces which is what Rasmussen describes as desirable. Rasmussen also does not teach a nonwoven porous fabric as the present invention does.

Even though non-woven fabrics are known in the art, these known fabrics are not suitable or are totally impractical. The above non-woven fabrics typically have mixed fiber components that result in a fabric having a heterogeneous surface structure. The fibers of these known fabrics are essentially non-oriented. Furthermore, as previously mentioned herein, the fibers and channels of these known fabrics are not as elongated as the fabric of the present invention and the channels are not interconnected to the extent that the fabric of the present invention is so. The channels are typically blocked by the points of attachment between the fibers in these known fabrics which prevents the flow of fluid therethrough. Therefore these known fabrics are not permanently wettable as is the product of the present invention. The fabric of the present invention has a wide variety of surface structure and directional fiber distribution.

However, fibers formed of higher molecular weights such as film class polyethylene can not be easily formed into fibers, even deliberately by conventional and known spinning processes. For example, the difficulties of melt spinning arise from the extremely high viscosity of the resin of higher molecular weight than the cutting rate typically found in the melt spinning processes such as in the processes of meltblowing and meltblowing. . In addition, the higher molecular weight polyethylene has an inherently high melt strength and a melt pull under which it makes the aerodynamic pulling very difficult.

Therefore, in spite of the attempts described above to produce the non-woven fabrics and to form materials from the polymer blends, a method for producing a polyolefin fabric that is moist and which can be accepted as disposable with discharge has not been developed. of water through conventional wastewater disposal systems.

Due to its unique interaction with water and body fluids, polyethylene oxide (hereinafter referred to as polyethylene oxide) can be used as a component material for disposable products with polyethylene oxide water discharge, is a commercially available water soluble polymer which can be produced from the ring opening polymerization of polyethylene oxide, Due to its water-soluble properties, polyethylene oxide is desirable for waste disposal applications. However, there is a dilemma in using e polyethylene oxide in waste applications with water discharge.

The low molecular weight polyethylene oxide resins have melt viscosity and melt pressure properties desirable for extrusion processing but have limitations when processing the melt into structural articles such as thin films. An example of a low molecular weight polyethylene oxide resin is POLYOX® SR N-80 which is commercially available from Union Carbide. The POLYOX® WSR N-80 has an approximate average molecular weight of 200,000 grams per mole as determined by melt rheology measurements. As used herein, low molecular weight polyethylene oxide compositions are defined as polyethylene oxide compositions with an average molecular weight of less than and including about 200,000 grams per mole.

In the personal care industry, thin gauge films are desired for their commercial viability and ease of disposal. The low melt strength and low melt elasticity of the low molecular weight polyethylene oxide limit the ability of the low molecular weight polyethylene oxide to be pulled into films having a thickness of less than about 2 mils. Even though low molecular weight polyethylene oxide can be thermally processed into films, thin gauge films less than about 1 mil thick can not be obtained due to lack of melt strength and melt elasticity. of low molecular weight polyethylene oxide. The processing of the polyethylene oxide can be improved by mixing the polyethylene oxide with a second polymer, a copolymer of ethylene and of acrylic acid, in order to increase the strength of the melt. The ethylene / polyethylene oxide acrylic acid copolymer mixture can be processed into films about 1.2 mils thick. However, the mixture and the resulting film are not soluble in water. More importantly, thin films made of low molecular weight polyethylene oxide are very weak and brittle to be useful for personal care applications. Low molecular weight polyethylene oxide films have low tensile strength, low ductility, and are very brittle for commercial use. In addition, the films, produced from low molecular weight polyethylene oxide and mixtures containing low molecular weight polyethylene oxide, become brittle during storage at ambient conditions. Such films are broken and are not suitable for commercial applications.

High molecular weight polyethylene oxide resins are expected to produce films with improved mechanical properties compared to films produced from low molecular weight polyethylene oxide. An example of a higher molecular weight polyethylene oxide is POLYOX® WSR 12K which is commercially available from Union Carbide. POLYOX® WSR 12K has an approximate average molecular weight of 1'000, 000 grams per mole as determined by melt rheology measurements. As used herein, higher molecular weight polyethylene oxide compositions are defined as polyethylene oxide compositions with an average molecular weight of more than and including about 300,000 grams per mole.

The higher molecular weight polyethylene oxide has poor processing due to its high melt viscosity and poor melt pull. The melt pressure and the melt temperature are significantly high during the melt extrusion of the high molecular weight polyethylene oxide. During the extrusion of the higher molecular weight polyethylene oxide, a fracture of. severe cast Only very thick sheets can be made of the higher molecular weight polyethylene oxide. The higher molecular weight polyethylene oxide can not be thermally processed into films of less than about 7 mils in thickness. The higher molecular weight polyethylene oxide suffers from severe melt degradation during the extrusion process. This results in a breakdown of the polyethylene oxide molecules and the formation of bubbles in the extrudate. The inherent deficiencies of the higher molecular weight polyethylene oxide make it impossible to use the higher molecular weight polyethylene oxide in film applications. Still, the addition of the higher levels of plasticizer to the higher molecular weight polyethylene oxide does not improve the melt processing of the higher molecular weight polyethylene oxide in sufficient form to allow the production of thin films without a melt fracture occurring. and a movie break.

Porous non-woven films currently available are not practical for personal care applications. Therefore, there has been a need in the art for a non-woven polyolefin fabric that is produced without spinning or pulling the polymer components of variable molecular weight, which is strong enough for an extended personal use and which has an absorption and improved fluid transmission, and which can be permanently wettable and completely disposable with water discharge in conventional drainage systems.

SYNTHESIS OF THE INVENTION The invention seeks to provide a non-woven fabric of the aforementioned kind which has a silk type touch and silk type gloss, which is permanently wettable, and which can be used in articles such as personal care products. that are capable of being completely discarded in conventional drainage systems.

According to the invention, this object is achieved by providing a non-woven fabric comprising at least one group of elongated polyolefin fibers essentially oriented along the longitudinal axis, a plurality of branches of the fibers extending through of the multiple fibers in the fabric, the thermal bonds formed between the adjacent fibers and between the branches and the fibers crossed by the branches and the elongated channels extend generally parallel to the longitudinal axis of the surface of the fabric and inside the fabric. A substantial proportion of the channels are interconnected to other channels and are therefore continuous so that the fabric of the present invention has a significantly greater fluid absorption and transmission than that of the other known fabrics.

The fabric of the present invention can be made using a method for extruding a polymer mixture, formed from a soluble component and a non-soluble component to form a film, and processing the film to produce the non-woven fabric. The non-soluble component must be the phase dispersed in the mixture, regardless of whether it is the majority or minority constituent of the mixture. After extruding the polymer mixture into a film, the film is washed to remove the suitable polymer component and to reveal the non-woven fabric. The non-soluble polymer does not dissolve significantly. The non-soluble polymer preferably is a polyolefin, such as polyethylene (PE). The soluble polymer preferably is polyethylene oxide (PEO). In preferred process, the components are mixed in a way that results in the fabric being porous. It is also possible to make the fabric moistened by using a reactive mixture of the components. This novel process eliminates the spinning and pulling process typically associated with the extrusion of polymer compositions. The non-soluble polymer component of the mixture (such as polyethylene) should be the dispersed phase. This allows an extruder to process the mixture to break the dispersed phase into small droplets of small diameter as a result of the shear forces within the extruder. These dispersed phase droplets are then elongated in the extruder due to the extensional flow field. The elongation of the droplets creates a continuous fiber formation in the film with the points attached through the fabric. The branches tend to form from the fibers, and the branches cross over the nearby fibers and join them. Washing the extruded film with the solvent removes the soluble polymer (such as polyethylene oxide) and reveals these fibers and bonding points and creates a non-woven fabric. In addition, the washing of the soluble polymer phase leaves capillary channels of random length to absorb the water. These air spaces left by the dissolved soluble polymer create the volume in the fabric.

The channels in the fabric are random in size and shape leading to increased absorption and fluid transmission. The water tends to be taken by the surface that spreads through the surface channels. Then the water is absorbed because the channels tend to be interconnected with each other across the depth of the fabric and along its length so that the water that enters a channel on the surface of the fabric tends to be transmitted by capillary action into the fabric. The fabric retains the water that it absorbs, of course under the forces of evaporation and physical applied to expel the water. Disposable personal care products produced from the resulting fabric will first be able to maintain structural integrity during extended storage and personal use while being capable of being discharged with water discharge in conventional drainage systems. Another advantage of the fabric is its silk-like surface texture, which makes the fabric ideal for placement against the skin.

A method for making the component non-soluble (such as polyethylene), the dispersed phase is to make this the minority constituent of the polymer mixture. In such a process, the polyethylene oxide, the continuous phase can be any molecular weight, but preferably has a low molecular weight, more preferably equal to or less than 200,000 grams per mole. Therefore, the non-woven fabric of the present invention can be formed from a non-reactive mixture of polyethylene and polyethylene oxide if the polyethylene as the dispersed component is also the minor constituent. However, a fabric produced from a non-reactive mixture is not wettable.

In another process, the non-woven fabric can be formed from a non-reactive mixture of soluble and insoluble components resulting in a single-phase morphology. In this alternative process, polyethylene oxide having a molecular weight of 100,000 grams per mole or less and polyethylene and polyethylene oxide are the majority and minority constituents respectively. With this last procedure, a phase inversion with the polyethylene will occur as the dispersed phase due to the lower molecular weight polyethylene oxide.

According to a third method, a reactive mixture of the soluble and insoluble components can be processed in an extruder as resulting in a single phase morphology in which the insoluble phase is the bulk volume while the phase remains dispersed in the mixture and in the resulting movie. To provide a reactive mixture, the inventive process comprises the step of mixing the mixture with a polar vinyl monomer and a free radical initiator under conditions sufficient to graft a polar vinyl monomer onto both phases of insoluble and soluble polymer. When the polyethylene oxide is the soluble phase, the grafting of the polar vinyl monomer improves the melt processing of the polyethylene oxide so that the melt viscosity, the melt pressure and the melt temperature are reduced. As a result of this, mixing in an extruder can maintain a majority constituent (such as polyethylene) as the phase dispersed in the polyethylene oxide. The level of graft reaction influences the morphology of the non-woven fabric formed by this process. Such a graft maintains a non-soluble grafted polyolefin as the dispersed phase through the range of possible mixing ratios of soluble to insoluble components regardless of whether the dispersed phase is the minority or majority constituent. The polyolefin is also grafted to around 0.1% to 5% by weight. Preferably, the polyolefin is grafted to about 0.2% to 5% by weight.

In a preferred embodiment, the polymer blend may comprise about 15 to 85% by weight of a polyolefin and 85 to 15% by weight of a polyethylene oxide. When the proportion of polyolefin is around 50-85% by weight, a graft monomer is added to the mixture in an amount dictated by the total weight of the polyolefin and the polyethylene oxide, but preferably from about 1% by weight to about 30% by weight. More preferably, the content of the monomer in the mixture comprises about 5% by weight to about 20% by weight. Polar vinyl monomers are unsaturated monomers that contain at least one polar functional group such as an acid, ester, thiol, carboxyl, amino, carbonyl and hydroxyl groups. The acrylates and methacrylates groups are the preferred polar groups and the 2-hydroethyl methacrylate and the polyethylene glycol methacrylate are preferred polar vinyl monomer structures. The process for making the reactive mixtures of polyolefins and polyethylene oxide is discussed in greater detail in U.S. Patent No. 5,700,872 entitled "MIXES OF POLYOLEPHINS AND POLY (ETHYLENE OXIDE) AND PROCESS FOR MIXING" . The full description of which is incorporated herein by reference. From the reactive mixtures, the cured films were extruded which were subsequently washed with water to remove the soluble part of water from the mixture which is grafted with polyethylene oxide.

This resulted in a non-woven fabric composed of grafted polyolefin (such as grafted polyethylene).

The thickness of the fabric can be varied to obtain different characteristics for different purposes. A thicker cloth is derived from a thicker film and after washing the film with water. However, a thicker film takes longer to wash and is much stronger than thinner films. A thicker fabric will have a paper-like consistency and very little if any pores that extend completely through the fabric. Such thicker fabric is humid and highly absorbent. On the other hand, a thinner fabric transmits water more quickly, and thus water can pass through pores into an absorbent layer adjacent to the fabric. Therefore, the thin versions of the fabric can be used as skin-friendly liners on an absorbent material in a garment. The thickness of the polyethylene fibers in the fabric can be controlled by varying the proportion of polyethylene in the polymer mixture. Generally, a higher proportion of polyethylene gives thicker polyethylene fibers. The additional advantages will be evident from here on out.

The foregoing has delineated some of the objects and pertinent features of the invention. These should be considered as being merely illustrative of some of the most prominent features and applications of the attempted invention. Many other resulting benefits can be obtained by applying the described invention in a different manner or by modifying the embodiments described. Therefore, other objects and a more comprehensive understanding of the invention can be obtained by referring to the detailed description of the preferred embodiment taken in conjunction with the accompanying drawings, in addition to the scope of the invention defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a more concise understanding of the nature and objects of the present invention, direct reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which: Figure 1 illustrates an embodiment of the mixing extruder, the air cooling unit and the pelletizer in relation to one another for the practice of a part of the present invention where grafting is necessary.

Figure 2 illustrates an embodiment of the mixing extruder, the air cooling unit and the pelletizer in relation to one another to practice a part of the present invention where grafting is unnecessary.

Figure 3 illustrates an incorporation of the extruder to convert the pellets into a precursor film of the system steps illustrated in any of Figures 1 or 2.

Figure 4 illustrates an alternate embodiment of the present invention wherein the formation of the mixture and the extrusion of the film can be carried out by the same extruder.

Figure 5 illustrates an embodiment for implementing an automated washing and drying step.

Figure 6 illustrates a particular detail of the washing device of Figures 4 and 5.

Figure 7 is a 30X optical micrograph of the typical fiber fabric separated by hand to expose the individual fibers made of a reactive mixture.

Figure 8 is a 150X electronic scanning micrograph of the typical unopened fiber tissue made in a film and treated with a solvent.

Figure 9 is a 2,000X electronic scanning micrograph illustrating the shape and size of particular variable fiber and branched fibers in a non-open fabric of the present invention; Y Figure 10 is a 1,500X electronic scanning micrograph illustrating a typical cross section of the fabric of the present invention after being pulled and separated by hand to expose the individual fibers.

Similar reference characters refer to similar parts through the various views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED INCORPORATIONS With reference to the drawings, the described embodiments of the present invention relate to a porous nonwoven fabric formed of extruded polyolefin and polyethylene oxide film. Polymer blends of polyolefins and polyethylene oxide have been shown to be modifiable in water with or without grafting of one or more monomers. The film composition of the present invention made from these blends and having about 15 to 85% by weight of a polyolefin and about 85 to 15% by weight of a modified polyethylene oxide responds to water. The resulting fabric, pro tanto, can be used in the manufacture of disposable personal hygiene articles. The inventors have produced a nonwoven fabric, formed of polymer composite materials, which also lends itself to increased fluid absorption and transmission. The novel fabric is weakened in water so that personal hygiene items can be discarded with water discharge in conventional drainage systems after use.

In one embodiment of the present invention the mixture comprises about 15% by weight to about 50% by weight of a polyolefin and from about 50% by weight to about 85% by weight of polyethylene oxide. In this embodiment, where the polyolefin is the minority constituent in the formation of the mixture, the film for producing the fabric can be obtained without grafting a monomer.

In another embodiment, the non-woven fabric can be formed from a non-reactive mixture of the soluble and insoluble components resulting in a single-phase morphology wherein the polyethylene and the polyethylene oxide are the majority and minority constituents respectively. In this embodiment, the polyethylene oxide should have a molecular weight of 100,000 grams per mole or less. Therefore, with this last procedure, a phase inversion with the polyethylene will occur, remaining as the dispersed phase due to the lower molecular weight polyethylene oxide.

In a third embodiment of the present invention, the mixture comprises about 50% by weight to about 85% by weight of a modified polyolefin and from about 50% by weight to about 15% by weight of the modified polyethylene oxide. . The amount of polar vinyl monomer added to the mixture is dictated by the total weight of the polyolefin and polyethylene oxide but is preferably from about 1% by weight to about 20% by weight. As a result of grafting the monomer, the processing of the reactive mixture results in a single reverse phase morphology wherein the polyolefin phase is the dispersed phase. In addition, the monomer graft imparts permanent wetting to the resulting fabric. However, the fabric produced from other reactive mixtures still has an increased fluid intake and non-grafted transmissions.

Wetting is an effect of chemical composition rather than physical structure. Whether or not a surface is "wettable" depends on how much water accumulates on the surface. A material is non-wettable if water droplets form on a surface and the resulting contact angle between the surface of the water is greater than 90 degrees. On the other hand, a surface is wettable where the water beads are scattered on the surface and the contact angle is less than 90 degrees. Preferably, the contact angle is closer to zero to be more wettable. The surfaces which are merely wettable as compared to being permanently wettable are surfaces where the wetting may eventually be washed out. A permanently wettable fabric does not have to change the surface wetting characteristics. On the other hand, a non-permanently wettable surface, such as a non-wettable surface coated or treated with a surfactant, loses surface wettability with washing with water. It is important to note that the increased fluid absorption and transmission may be characteristic of a fabric according to the present invention, even when the fabric is not wettable because a graft monomer has not been added to the components.

Preferably, the content of the polyethylene in the mixture comprises about 30% to 80% by weight. More preferably, the polyethylene content in the mixture comprises about 50% to 75% by weight.

The saturated ethylene polymers useful in the practice of this invention are ethylene homopolymers or copolymers and are essentially linear in structure. As used herein, the term "saturated" refers to polymers which are fully saturated, but include polymers containing up to about 5% unsaturation. Ethylene homopolymers include those prepared under either a low pressure, for example, linear low density polyethylene, or a high pressure, for example branched or low density polyethylene. High density polyethylenes are generally characterized by a density that is about equal to or greater than 0.94 grams per cubic centimeter (g / cc). Generally, the high density polyethylenes useful in the base resin of the present invention have a density ranging from about 0.94 grams per cubic centimeter to about 0.97 grams per cubic centimeter. Polyethylenes can have a melt index, as measured at 2.16 kilograms and 190 degrees centigrade, ranging from about 0.005 decigrams per minute (dg / minute) to 100 decigrams per minute. Desirably, polyethylene has a melt index of 0.1 to 20 decigrams per minute. Alternatively, the polyethylene blends can be used as the base resin for producing the graft copolymer compositions, and such a blend can have a melt index greater than 0.005 decigrams per minute to less than about 100 decigrams per minute.

Low density polyethylene has a density of less than 0.94 grams per cubic centimeter and is usually in the range of 0.91 grams per cubic centimeter to about 0.93 grams per cubic centimeter. The low density polyethylene has a melt index ranging from about 0.005 decigrams per minute to about 100 decigrams per minute and desirably from 0.05 decigrams per minute to about 20 decigrams per minute. The ultra low density polyethylene can be used according to the present invention. Generally, ultra-low density polyethylene has a density of less than 0.90 grams per cubic centimeter.

The polyolefins mentioned above can also be manufactured by using the well known multiple site Ziegler-Natta catalysts or the most recent single site metallocene catalysts. Metallocene-catalyzed polyolefins have better controlled polymer microstructures than polyolefins manufactured using Ziegler-Natta catalysts, including the narrowest molecular weight distribution, the highly controlled chemical composition distribution, the comonomer sequence length distribution, and the stereoregularity. Metallocene catalysts are known to polymerize propylene in atactic, isotactic, syndiotactic, isotactic-atactic stereoblock copolymer.

The ethylene copolymers which may be useful in the present invention may include copolymers of ethylene with one or more additional polymerizable unsaturated monomers. Examples of such copolymers include but are not limited to copolymers of ethylene and alpha olefins (such as propylene, butene, hexene or octene) including linear low density polyethylene, ethylene copolymers and vinyl esters of linear or branched carboxylic acids which they have 1-24 carbon atoms such as ethylene vinyl acetate copolymers and ethylene copolymers and linear, branched or cyclic albanic acrylic or methacrylic esters having 1-28 carbon atoms. Examples of the latter copolymers include ethylene-alkyl (meth) acrylate copolymers, such as ethylene-methyl acrylate copolymers.

The polyethylene oxide polymers suitable for the present invention can have a molecular weight ranging from 100,000 to 8,000,000 and preferably ranging from about 100,000 to about 400,000. Polyethylene oxide is available from Union Carbide Corporation under the trade name POLYOX®. Typically, the polyethylene oxide is a dry free-flowing white powder having a crystalline melting point in the order of about 65 degrees centigrade, above which the polyethylene oxide resin becomes thermoplastic and can be formed by molding, extrusion and other methods known in the art.

To prepare the grafted polyethylene and the grafted polyethylene oxide constituents of the film of the invention, the polyolefin and the polyethylene oxide are reacted with the polar vinyl monomer in the presence of a free radical initiator. The initiator serves to initiate the free radical grafting of the monomer. The grafting method of the polymer blends includes melt mixing the desired weight ratios of a combination of the polyolefin, the polyethylene oxide, the monomer and the free radical initiator in an extruder and at a reaction temperature where the Polyolefin and polyethylene oxide are converted to a polymer melt. Therefore, a preferred method includes adding the polyolefin, the polyethylene oxide, the monomer and the free radical initiator simultaneously to the extruder before the constituents of the polymer, for example the polyolefin and the polyethylene oxide have been melted. Desirably, the molten extruder used to mix with melt can introduce various constituents into the mixture at different places along the length of the screw. For example, the free radical initiator, cross-linking agents, or other reactive additives may be injected into the mixture before or after one or more of the polymer constituents is completely melted or mixed. More preferably, the polyolefin and the polyethylene oxide are added at the beginning of the extruder. After melting, the monomer is added to the molten polymers and below the extruder barrel, the free radical initiator is supplied to the melt mixture.

The polyolefin (such as polyethylene) and the polyethylene oxide comprising the film having therein grafted with an effective amount of the monomer which unexpectedly produces in the film a reverse phase morphology. Polyolefin can be the main constituent. One skilled in the art would expect polyethylene, as the main constituent, to form the continuous phase wherein the polyethylene oxide is distributed there as the discontinuous phase. However, the present film has the grafted polyethylene oxide as the continuous phase with the grafted polyethylene distributed as the discontinuous phase although there is a greater amount of polyethylene. The reverse phase morphology of the present film is described in greater detail in the co-pending patent application having serial number 08 / 855,324 filed on May 13, 1997 and entitled "POLYETHYLENE AND POLYETHYLENE OXIDE MIXTURES WHICH HAVE MORPHOLOGY OF INVERSE PHASE AND METHOD TO MAKE MIXES "whose full description of which is incorporated herein by reference.

Free radical initiators which can be used to graft the monomer into the polyolefin include acyl peroxides such as benzoyl peroxide; the dialkyl; the diaryl; or the aralkyl peroxides such as di-t-butyl peroxide; dicumyl peroxide; butyl cumyl peroxide, 1, l-di-t-butylperoxy-3,5,5,5-trimethylcyclohexane; 2,5-dimethyl-2,5-di (t-butylperoxy) hexane; 2,5-dimethyl-2,5-bis (t-butylperoxy) hexino-3 and bi (s-t-butyl peroxyisopropylbenzene); peroxyesters such as t-butyl peroxypivalate; t-butyl peroctoate; t-butyl perbenzoate; 2,5-dimethylhexyl-2,5-di (perbenzoate); t-butyl di (perftalate); dialkyl peroxymonocarbonates and peroxydicarbonates; hydroperoxides such as t-butyl hydroperoxide, p-methane hydroperoxide, pinano hydroperoxide and eumeno hydroperoxide and ketone peroxides such as cyclohexanone peroxide and methyl ethyl ketone peroxide. Azo compounds such as azobisisobutyronitrile can also be used.

The amount of free radical initiator added to the extruder must be a sufficient amount to graft from about 1% to 100% of the monomer in the polyolefin and in the polyethylene oxide. This varies from about 0.1% by weight to about 10% by weight of initiator, and preferably, from about 0.1% by weight to about 5% by weight where all those ranges are based on the amount of monomer added to the melt mixture. The method of polar grafting groups on polyethylene and polyethylene oxide is also described in greater detail in U.S. Patent No. 5,700,872 entitled "MIXES OF POLYOLEPHINE AND POLYETHYLEN OXIDE AND PROCESS FOR MIXING". However, grafting of the polar groups in polyethylene and polyethylene oxide is described in greater detail in the patent applications of the United States of America series number 08 / 733,410 filed on October 18, 1996 and entitled "METHOD TO MAKE A POLIOLEFIN THAT HAS MORE THAN 5% OF 2-HYDROXYETHYL METHACRYLATE AND GRAFTED TO IT, and application of the United States of America series number 08 / 733,551 filed on October 18, 1996 and entitled "POLIOLEFINA THAT HAS MORE THAN 5% OF 2-HYDROXYETHYL METHACRYLATE AND GRAFTED TO THIS, "the full descriptions of which are incorporated herein by reference.

The present invention is illustrated in more detail by the specific examples presented below. It is understood that these examples are illustrative embodiments and are not intended to limit the invention but rather are widely considered within the scope and content of the appended claims.

MIXING A COMPARATIVE EXAMPLE Figures 1 and 2 each illustrate an incorporation of the mixing part of the system 10 (Figure 4) carried out during the inventive process. For a comparative example, a resin mixture of 60/40 percent by weight of low density polyethylene (PE) and polyethylene oxide (PEO) was melt mixed using an extruder lia as shown in Figure 2. polyethylene has a melt index of 1.9 decigrams per minute (dg / minute) and a density of 0.917 grams per cubic centimeter (g / cc) (Dow 5031, available from the Dow Chemical Company of Midland, Michigan). The polyethylene oxide had a reported molecular weight of 200,000 grams per mole (POLYOX® WSR N-80 available from Union Carbide Corporation). The extruder used to make the mix was a Werner & Pfleiderer Corporation, of Ramsey, New Jersey). The extruder lia can have multiple processing barrels allowing additional materials to be added while the mixture is made. The extruder used during the present process had 14 barrels of processing available as illustrated in Figures 1 and 2.

The resin mixture was supplied to the extruder at a rate of 34 pounds / hour. The extruder had a pair of co-rotating screws arranged in parallel. The central distance between the two axes was 26.2 millimeters. The nominal screw diameter was 30 millimeters. The current external screw diameter was 30 millimeters. The inner screw diameter was 21.3 millimeters. The thread depth was 4.7 millimeters. The extruder lia had 14 barrels of processing, with 13 heated barrels divided into 7 heating zones. The overall processing length was 1,338 millimeters. The 7 heating zones were all set at 180 degrees centigrade (degrees centigrade). The screw speed was set at 300 revolutions per minute. Figure 2 illustrates the initial mixing of the comparative example in the extruder to which it is subsequently pelleted into pellets 32 to be received in the extruder 11b as shown in Figure 3 and discussed below. However, the film of the mixture having polyethylene oxide of a molecular weight of 200,000 grams per mole without the reactive mixing, produced as described below, could not be washed with water to produce a non-woven fabric. The resulting film was not wettable with water and behaved like a typical polyethylene film.

MIXING EXAMPLES 1-11 (reactive, wettable) For Examples 1-11, a resin mixture of 60/40 percent by weight polyethylene and polyethylene oxide, as described in the comparative example was fed to a multi-chamber extruder ZSK-30 lia as shown in Figure 1. Examples 1-11 are reactive mixtures of polyethylene and polyethylene oxide with PEG-MA and the free radical initiator. The polyethylene oxide has a molecular weight of 200,000 grams / mol. The temperature and screw speed settings for the examples are specified in Table 1. The resin rates are specified in Table 2.

In the barrel 4 of the extruder lia, a monomer, a polyethylene glycol methacrylate (PEG-MA); Catalog No. 40,954-5 with a molecular weight of 246 grams per mole; available from Aldrich Chemical Company, Milwaukee, Wisconsin) was added at the rate specified in Table 2. In barrel 5 of the extruder lia, a free radical initiator (2,5-dimethyl-2,5-di (t-butylperoxy ) hexane, supplied by Atochem, of 2000 Market Street, Philadelphia, Pennsylvania under the trade name LUPERSOL® 101 or otherwise known as LlOl) was added at the rate specified in Table 2.

The films of Examples 1-11 had a phase inversion and could be washed with water to produce a non-woven fabric as described below. Examples 1-11 of the extruder lia are subsequently pelletized in the pelletizer 30 to form the pellets 32. The pellets 32 are then received in the extruder 11b to extrude the films as shown in Figure 3 and discussed below.

Table Table MIXING EXAMPLE 12 (non-reactive, non-wettable) A mixture of 60/40 percent by weight polyethylene and polyethylene oxide resin having a reported molecular weight of 100,000 grams per mole (POLYOX® WSRN-10), without reactive mixing, was fed to a ZSK-30 extruder lia, as shown in Figure 2, at a rate of 35 pounds / hour. A monomer or an initiator was not added. The 7 heating zones were all set at 180 degrees Celsius. The screw speed was set at 300 revolutions per minute. Example 12 is also pelleted in pelletizer 30 to form pellets 32 as shown in Figure 4. The film of Example 12 with the lowest molecular weight of 100,000 grams per mole, produced as described below, had no investment of phase when the extruder 11b was extruded and can be washed with water to produce a non-woven fabric as described below.

MIXING EXAMPLE 13 (reactive, wettable) A resin mixture of 30/70 percent by weight of low density polyethylene (polyethylene, Dow 5031) and polyethylene oxide (polyethylene oxide, POLYOX® WSRN-80) was mixed with melted using the extruder lia. The extruder used to make this mix was also a HAAKE twin counter-rotating screw extruder equipped with a two-hole wire array. The extruder had a length of 300 millimeters. Each conical screw had a diameter of 30 millimeters in the supply port and a diameter of 20 millimeters in the matrix.

The extruder lia had 4 heating zones set at 170, 180, 180 and 190 degrees centigrade. The screw speed was 150 revolutions per minute. The resin mixture was fed to the extruder at a rate of 5 pounds / hour. Concurrently with the supplied polymer, polyethylene glycol methacrylate was added at a rate of 0.5 lbs / hour and LUPERSOL 101 was added at 0.025 lbs per hour. The polymer was extruded, cooled in air and pelletized. The film of example 13 produced as described below, had no phase inversion when extruded from extruder 11b because polyethylene was the minority constituent. But the film could be washed with water to produce a non-woven fabric. When washed, the resulting nonwoven fabric had the appearance and characteristics similar to that of the 60/40 polyethylene / polyethylene oxide blends and the reactive blends of the preceding examples. However, the resulting fabric did not possess any noticeable differences in the sense that the fabric was thinner with fewer fibers while a less bound and weaker fabric was produced. Also the fabric is very soft. These differences are attributed primarily to a smaller amount of polyethylene.

MIXING EXAMPLE 14 (reactive, wettable) A resin mixture of 80/20 percent by weight of polyethylene and polyethylene oxide was mixed with melt using the HAAKE extruder. As was done before, the extruder had four heating zones set at 170, 180, 180 and 190 degrees centigrade. The screw speed was 150 revolutions per minute. The resin mixture was fed to the extruder at a rate of 5 pounds per hour. Concurrently with the supplied polymer, polyethylene glycol was added at a rate of 0.5 pounds / hour and LUPERSOL 101 was added at 0.025 pounds per hour. The polymer was extruded, cooled in air and pelletized. The film of this example also had phase inversion when extruded from the extruder 11b due and could be washed with water to produce a non-woven fabric. When washed, the resulting nonwoven fabric produced from Example 14 also had the appearance and characteristics similar to the 60/40 polyethylene / polyethylene oxide reactive mixtures and the reactive mixtures of the preceding examples. Also the fabric was much tighter.

FILM PROCESSING The films of the reactive mixtures of this invention can be prepared by both a set extrusion process or a blown film extrusion process but are not limited thereto. All films of the melt blends in the Comparative Example and in Examples 1-14 were made using a Haake counter-rotating twin screw, a multi-chamber extruder 11b (available from Haake, 53 West Century Road, of Paramus, New Jersey 07652) equipped with a four or eight inch cutting die. The extruder 11b had a length of 300 millimeters. The conical screws were 30 millimeters in diameter in the supply port and 20 millimeters in diameter in the film matrix 14. The extruder 11b had four heating zones set at 170, 180, 180 and 190 degrees centigrade.

As shown in Figure 3, the nd extruder 11b receives the pellets 32. Within the extruder 11b, the pellets are melted and mixed. The mixture will have a phase morphology in which the polyethylene is the dispersed phase while it is being extruded in the films of Examples 1-14 through the film matrix 14. Pellets 32 formed from the comparative example did not have a morphology of reverse phase but could nonetheless be extruded in a film. Alternatively, the initial mixing of the polymer mixture and the subsequent extrusion into the desired film, both functions previously described as being performed separately in the extruders lia and 11b respectively, can be carried out simultaneously in an extruder 11. Figure 4 illustrates the extruder 11 wherein the mixtures of examples 1-14 are formed with the polyethylene as the dispersed phase and are extruded into the film 18.

When two extruders are used and the extruder produces pellets in an optional embodiment of the method of production of the present invention, the extruded yarns of the extruder are air cooled as they extrude from the extruder as shown in either FIG. 2. The wires fall into an air cooling unit 20 which blows air directly onto the wires. The air cooling unit 20 uses multiple fans 21 to blow the air which can be cooled or at room temperature. The band 22 of the air chiller unit 20 moves in the direction of flow of the threads towards a pelletizer 30 the pelletizer 30 pellets the threads in the pellets 32.

In an embodiment as shown in any of Figures 3 or 4, the extruded film 18 of the extruder 11b (or of a single extruder) is pulled to reduce its thickness on a chill roll 16 where it is cooled and collected as a film. 18 to 4-5 thousandths of an inch. Preferably the cooling roller 16 is operated at a sufficient speed to wind a film having a thickness of about 4 mils (about 0.004 inches) and is maintained at a temperature of 15-20 degrees centigrade.

Even when the use of particular extruders is described in the preferred embodiment, other processing methods are encompassed by the present invention. The preferred form has been made only by way of example and it should be realized by those skilled in the art that the equivalent processing steps can be used without departing from the spirit and scope of the invention.

FILM WASHING According to the method of the invention, a non-woven fabric 80 can be produced, as shown in Figures 4-6. This novel process is superior to other existing processes for making a polyethylene fabric in the sense that the present invention does not require a spinning organ or need any aqueous solvents which can cause environmental concerns. This process also forgets the fiber pull operation typically associated with these other known processes.

In order to treat film 18 and remove the phase of soluble polyethylene oxide to produce the non-woven fabric 80, film 18 is soaked in water. A method for removing the polyethylene oxide involves immersing the film 18 in water for about 6 minutes so that the continuous phase of water-soluble polyethylene oxide is substantially removed. The remaining non-woven polyethylene film is rinsed with water and placed flat to be dried on a paper towel or other absorbent material.

Alternatively, the fabric can be dried by means of a drain device with vacuum or by means of a heated drum process.

Alternatively, the film can run through a semiautomatic water bath with pressure point rollers and a wire carrier. The film is immersed in water for about 2 minutes, it is turned over and immersed for another 2 minutes. The bath is equipped with a final rinse and the cloth is again dried on an air cooling strip with a carrier wire or by means of any of the drying methods identified above.

Figure 6 illustrates a version of a washing device 40 which can be used to practice the present invention. The film 18 is received in the washing device 40 on a roller 41 and is deposited on a continuous band 50. The band 50 is driven by a driving pulley 42 which can be operated by hand or by means of a motor (not shown). ). The impeller 42 drives a roller 44 which contacts the web 50. Four free rollers 43a, 43b hold the film 18 downward and in contact with the web 50 as the film 18 is delivered through the washing device 40.

The web 50 is placed inside a tank 60. The water (not shown) is fed to the tank 60 through an inlet 61 and outward through an outlet 62. The flow of water through the tank 60 is continuous during the operation. Water must be kept within a temperature at which the soluble polymer is soluble, and therefore must be maintained at ambient temperatures in the case of polyethylene oxide which is soluble at ambient temperatures. The water level in tank 60 should be maintained just above two lower rollers 43b. The two lower rollers 43b keep the film 18 in contact with the web 50 and under the water to allow the water-soluble resins to dissolve. A plurality of the free rollers 45 maintain the band at its proper tension. An upper central roller 45a acts as a higher tension adjustment. A pair of lower rollers 45b act as external tension adjustments. Together, the rollers 45 adjust the stroke and control of the belt loosening.

A rinser 48 rinses the resulting fabric with a curtain of water as it emerges from the water bath. A high pressure water curtain is used to clean any soluble water dissolved resin from the film fabric. The water and dissolved water-soluble resin are carried in the tank 60 by the inclined end wall 64 of the tank 60. A separator 63 in the tank restricts the movement of the rinse water and the dissolved material and directs it towards the outlet 62 The water must be continuously cleaned of dissolved solids by means of the separation system (not shown) downstream of outlet 62.

The new cleaned water can be introduced through rinsing 48 to maintain the water level in tank 60.

An air knife 47 removes excess water from the fabric just before it leaves the washing device 40 on a roller 46. All the rinse water removed by the air curtain is returned to the tank 60 by the end wall. inclined 64.

The inventors have the vision of any number of different ways to wash the film with water to remove the polyethylene oxide. One sway would be to wash the film with an automated water bath that does not require a wire carrier so that the film could be uniformly exposed to water.

As shown in Figure 5, once the resulting fabric leaves the washing device 40, the fabric was unwound on a winding reel 70 to produce a roll of any diameter.

Figures 7-10 illustrate the fiber fabric of the present invention. It is characteristic of the polyethylene / thermoplastic polyethylene oxide reactive mixture film of the present invention, the views using an electron scanning microscope and using scattered electronic detector images show that the polyethylene oxide forms the continuous phase wherein the modified polyolefin it is in a discontinuous phase, that is, dispersed through the grafted polyethylene oxide phase. A constituent having a lower atomic number produces a lower intensity of imaging by electron microscopy spread posteriorly as described in more detail in the work of Linda C. Sawyer and David T. Grubb, Polymer Microscopy, Chapman & Hall, London 1987, page 25. Desirably, the polyolefin portions of the thermoplastic film have an average cross-sectional diameter ranging from about 0.1 microns to about 50 microns, preferably from about 0.5 microns to about 30 microns. microns and more preferably from about 0.5 microns to about 25 microns. S"polyolefin parts" can be solidified polyolefin bags, fibers or combinations thereof.

Briefly, the film produced as a result of the present invention is modifiable with water. As used herein, the water-modifiable media that when a film is immersed in water under the conditions described, the water removes the soluble phase. Water-modifiable polyolefin-containing films are described in greater detail in the co-pending United States of America patent application having serial number of the United States of America 08 / 813,571 filed on March 6, 1997 and entitled " FILM CONTAINING DISPOSABLE POLYOLEPHINE WITH WATER DISCHARGE AND MODIFIED WITH WATER ", whose full description of which is incorporated herein by reference.

The fiber weave illustrated in Figure 7 has been pulled and separated by hand to better illustrate the structure of the fabric, and in particular to illustrate the formation of continuous fiber with multiple attachment points through the fabric. Figures 8 and 9 better illustrate extension, random size and capillary channels shaped to absorb and transport water. Figure 10 is a cross-sectional view of the fabric fabric produced by the present invention which illustrates the microstructure of each of the fibers of the continuous fabric. As can be seen in Figure 10, the individual fibers may have holes or microcapillaries that extend into the fibers.

The polyethylene fibers in the fabric tend to be directionally oriented along a longitudinal axis, as shown in Figures 8 and 9. The fibers will vary widely in diameter and shape. Some are circular in cross section, some oval, some irregular and some ribbon type. As the film is extruded prior to washing to form the fabric, the fibers tend to branch out, and the branches can be seen lying across multiple neighboring fibers in the Figures. Thermal joints are created during extrusion and pulling at intermittent points between adjacent and transverse fibers and between branches and fibers through which they lie.

The spaces or channels formed between the fibers also vary widely in the cross-sectional shape. The channels are elongated and extend generally parallel to the longitudinal axis on the surface within the fabric. A substantial part of the channels are interconnected to one another. In the case of the reactive mixtures, wherein the polyolefin and the polyethylene oxide is grafted as described above, the resulting fabric is permanently wettable.

A nonwoven porous fabric according to the present invention has the following characteristics: • elongated polyolefin fibers essentially oriented along a longitudinal axis; • a plurality of branches of the fibers that extend through multiple fibers in the fabric; • thermal junctions formed between the adjacent fibers and between the branches and the fibers crossed by the branches; • elongated channels extending generally parallel to the longitudinal axis on the surface of the fabric and inside the fabric, a substantial proportion of the channels being interconnected to one another channels; an increased fluid absorption and transmission; • a silk type feeling and shine; Y • permanent wetting in relation to reactive mixtures (grafts).

These characteristics can be seen in the electron scanning micrographs of Figures 7-10. In addition, large pieces of the fabric (eg, diaper-sized or larger) can be discharged with water discharge through the waste water disposal systems without blocking or clogging such systems, because The fabric is humid, soft, flexible and smooth.

The characteristics of the resulting fabric are presented in Tables 3-5 given below. In summary, the ideal fabric includes internal voids averaging in a range of from about 3% to about 51% of the volume of the fabric. The preferred fabric should have surface pores that have an average open area in a range of from about 5% to about 24%. Also the preferred fabric should have surface pores having an average equivalent hydraulic diameter in a range of from about 1.5 micrometers to about 40 micrometers and an average equivalent circular diameter in a range of from about 1.5 micrometers to about 40 micrometers . There is a wide variety of surface structure and fiber distribution in the fabric of the present invention.

Table 3 Synthesis of Surface Porosity Data Table (Examples 1-11) Table 4 Summary Table of Average Fiber Diameter Statistics of Surface Images (Examples 1-11) The fiber diameter listed in Table 4 is based on the metallurgical grain size method, obtained by dividing the field area by the horizontal field projection length, or in this case, the field area by the vertical interception. Since some individual fibers can not be easily and automatically isolated, this method was necessary.

Table 5 Transverse Section Analysis Summary Table (Examples 1-11) The surface characteristic of samples 1-11 as presented in Tables 3-5 can be summarized as follows. The samples were examined with the high contrast / electronic posterior scattering method (BSE / HICON) with photomontage of planar surfaces in both directions XY and YZ. The conditions chosen to make the samples created large differences in surface porosity, fiber diameters thicknesses in the Z-direction and internal hollow contents. Briefly, sample 11 had the highest surface porosity but not the largest average pore size. Sample 1 had the largest average pore size. Sample 11 also had the largest number of protruding fibers and was therefore the fuzzier. Sample 3 and sample 11 had the smallest average fiber diameter. Sample 5 had a very closed surface and very little internal hollow content. Therefore, sample 5 had very large fibers and low surface hair. Sample 3 was the thickest and had the largest internal hollow content. Sample 8 was the thinnest.

When Examples 13 and 14 were washed, the resulting nonwoven fabric had the appearance and characteristics similar to that of the 60/40 polyethylene / polyethylene oxide blends and the reactive blends of the preceding examples.

After producing the non-woven fabric, several optional finishing steps can be carried out. For example, several strata of the fabric can be thermally bonded together between heated calendering rollers to form a multi-layer fabric which transmits water better than a single stratum fabric. Also, the resistance of the fabric transverse to the machine direction can be increased by the point joining of a single stratum in spaced and spaced locations over the area of the fabric. Another option is to laminate the fabric to another type of film, sheet, paper, woven or non-woven fabric or other substrate.

The present invention has been illustrated in more detail by the specific examples given above. It should be understood that these examples are illustrative embodiments and that the invention is not limited to any of the Examples or details in the description. Those skilled in the art will recognize that the present invention is capable of many modifications and variations without departing from the scope of the invention. Therefore, the detailed description and the examples are intended to be illustrative and are not intended to be limiting in any way to the scope of the invention as set forth in the following claims. Rather the appended claims herein should be broadly considered within the scope and spirit of the invention.

Claims (26)

R E I V I N D I C A C I O N S

1. A non-woven fabric comprising primarily a single insoluble polyolefin including: at least one group of elongated fibers of said polyolefin essentially oriented along a longitudinal axis; a plurality of branches of said fibers that extend through the multiple fibers in said fabric; thermal bonds formed between the adjacent fibers and between said branches and fibers crossed by said branches; Y elongate channels extending generally parallel to said longitudinal axis on the surface of said fabric and within said fabric a substantial portion of said channels are interconnected to other channels, said fabric has an increased absorption and transmission of fluid.

2. The nonwoven fabric as claimed in clause 1 characterized in that said fabric is permanently wettable.

3. The non-woven fabric as claimed in clause 1 characterized in that said fabric is produced from a film.

4. The nonwoven fabric as claimed in clause 1 characterized in that said elongated fibers are of variable cross sectional shape and of variable diameter.

5. The non-woven fabric as claimed in clause 1 characterized in that said fabric is porous.

6. The non-woven fabric as claimed in clause 5 characterized in that said fabric defines surface pores having an average open area in a range of from about 5% to about 24%.

7. The non-woven fabric as claimed in clause 6 characterized in that said fabric includes internal voids averaging in a range of from about 3% to about 51% of the volume of said fabric.

8. The non-woven fabric as claimed in Clause 1 characterized in that said fabric includes internal voids averaging in a range of from about 3% to about 51% of the volume of said fabric.

9. The non-woven fabric as claimed in clause 5 characterized in that said fabric defines surface pores having an average equivalent hydraulic diameter in a range of from about 1.5 microns to about 40 microns.

10. The non-woven fabric as claimed in clause 5 characterized in that said fabric defines surface pores having an average equivalent circular diameter in a range of from about 1.5 microns to about 160 microns.

11. The non-woven fabric as claimed in clause 1 characterized in that said fibers are formed of polyethylene.

12. The non-woven fabric as claimed in clause 1 characterized in that said fabric is weakened in water so that the fabric loses rigidity during prolonged contact with water.

13. The non-woven fabric as claimed in clause 1 characterized in that said fabric is produced from grafted polyolefins.

14. The non-woven fabric as claimed in clause 13 characterized in that said polyolefins are grafted with a polar vinyl monomer.

15. The non-woven fabric as claimed in clause 14 characterized in that said polar vinyl monomer is polyethylene glycol methacrylate.

16 A nonwoven fabric comprising: groups of elongated polyolefin fibers essentially oriented along a longitudinal axis, said fibers having branches extending therefrom and joined therebetween; Y elongated channels extending generally parallel to said longitudinal axis on the surface of said fabric and within said fabric, a substantial portion of said channels being interconnected to other channels, whereby said fabric has an increased fluid absorption and transmission.

17. The non-woven fabric as claimed in clause 16 characterized in that said fabric is permanently wettable.

18. The non-woven fabric as claimed in clause 16 characterized in that said bonds have been formed during extrusion to form said polyolefin fibers.

19. The non-woven fabric as claimed in clause 16 characterized in that said fibers are thermally bonded.

20. The nonwoven fabric as claimed in clause 16 characterized in that said elongated fibers are of variable cross sectional shape and of variable diameter.

21. The non-woven fabric as claimed in clause 16 characterized in that said fabric is porous.

22. The non-woven fabric as claimed in clause 16 characterized in that said polyolefin fibers are formed of polyethylene.

23. The non-woven fabric as claimed in clause 16 characterized in that said fabric is weakened with water so that the fabric loses rigidity during prolonged contact with water.

24. An article for personal hygiene that includes: a porous non-woven fabric including elongated polyolefin fibers essentially oriented along a longitudinal axis, said fibers having branches extending therebetween and joined therebetween; Y elongate channels extending generally parallel to said longitudinal axis on the surface of said fabric and within said fabric, a substantial portion of said channels being interconnected to other channels.

25. The article for personal hygiene as claimed in clause 24 characterized in that said towel is permanently wettable.

26. The article for personal hygiene as claimed in clause 24 characterized in that said elongated fibers are of a variable cross sectional shape and of a variable diameter. U M E N A porous non-woven fabric produced from a polyolefin-containing film modifiable with water. In a preferred embodiment, the non-woven fabric includes groups of elongated polyolefin fibers essentially oriented along the longitudinal axis. The fibers have branches that extend from themselves and are joined between them. The elongate channels extend generally parallel to the longitudinal axis on the surface of the fabric and inside the fabric. A substantial part of the channels are interconnected to other channels. To produce the fabric, a polymer mixture is formed with the polyethylene as the minor constituent and the dispersed phase, and with the polyethylene oxide as the continuous phase. In another embodiment, where polyethylene is the major constituent and polyethylene oxide is the minor constituent, a reactive mixture is prepared during processing so that the mixture exhibits a reverse phase morphology, the polyethylene oxide becomes the continuous phase and the polyethylene oxide becomes the dispersed phase. In any incorporation, the mixture is extruded into a film which is then treated with an aqueous solvent to remove the polyethylene oxide to produce the porous nonwoven fabric. The resulting non-woven porous fabric has a silk-like shine and feel ideal for disposable personal hygiene articles, and is disposable with water discharge through the water disposal systems.