MXPA98001610A - Method for covering a hydrophobic fibrous material with an anfifil polyelectrolyte - Google Patents

Abstract

A method for coating a hydrophobic fibrous material with an amphiphilic polyelectrolyte which involves coating the hydrophobic fibrous material with a foam under conditions sufficient to substantially uniformly coat the hydrophilic fibrous material with the amphiphilic polyelectrolyte. The foam is generated from a amphiphilic polyelectrolyte solution in water. The hydrophobic fibrous material can be a polyolefin, such as polyethylene or polypropylene. The hydrophobic fibrous material may also be a non-woven fabric, such as a non-woven fabric bonded with spinning formed with melt blowing. When the hydrophobic fibrous material is a nonwoven fabric, the fabric is typically coated with the foam, vacuum extracted, pressurized, and

Description

METHOD FOR COATING A HYDROPHOBIC FIBROUS MATERIAL WITH AN ANIFYLIC POLYELECTROLYTE Background of the Invention The present invention relates to a coated fibrous material.

The polymers are used extensively to make a variety of products which include blown and set films, extruded sheets, injection molded articles, foams, blown and molded articles, extruded pipes, monofilaments, and fibrous materials such as non-woven fabrics. Some of the polymers, such as polyolefins, do not have a functionality (for example reactive groups) and are naturally hydrophobic, and for many uses these properties are either a positive attribute or at least not a disadvantage.

There are a number of uses for polymers, however, where their hydrophobic / non-functional nature either limits their utility or requires some effort to modify the surface characteristics of the shaped articles made thereof. By way of example, polyolefins, such as polyethylene and polypropylene, are used to make polymeric fabrics which are used in the construction of such disposable absorbent articles as diapers, women's care products, incontinence products, underpants of training, cleaners and similar. Such polymeric fabrics are often non-woven fabrics prepared by, for example, such processes as melt blowing, coformming, and spin bonding. Frequently, such polymeric fabrics need to be moistening with water. Wettability can be obtained by spraying or otherwise coating (eg surface treatment or topical treatment) the fabric with a surfactant solution during or after its formation, and then drying the fabric.

Some of the most common surfactants applied topically are nonionic surfactants, such as polyethoxylated octylphenols and the condensation products of propylene oxide with propylene glycol, by way of illustration only. These surfactants are effective in making wettable fabrics normally hydrophobic polymeric. However, the surfactant is easily removed from the fabric, often after only a single exposure to an aqueous liquid.

The polymers are also used in the preparation of filter media. For example, deep type filters are generally made of fibrous, porous, or pellet media. The fibrous media constitute a layer, or mat, of non-numerous fine fibers (for example fiber diameters ranging from 0.5 to 30 microns). These fibers are randomly oriented, thus creating numerous tortuous conduits or pores in which the particles are trapped. The retention efficiency in conventional deep bed filters is achieved by means of a series of low efficiency particle catches. Absorbent surface forces (molecular and electrostatic) can improve attachment to the medium, which then improves retention within the filter. Absorbent surface forces can be achieved by introducing functional or ionic groups onto the fiber surfaces of the filter media. The commonly used solid materials are cellulose, cotton, glass and synthetics (for example, rayon, polypropylene).

Despite the above improvements to making a wettable polymeric fibrous material or introducing functional or ionic groups onto the fiber surfaces of the filter media, there are still opportunities for improvement in these areas.

Synthesis of the Invention The present invention addresses some of the difficulties and problems discussed above by providing a method for coating a hydrophobic fibrous material with an amphiphilic polyelectrolyte. The method involves coating the hydrophobic fibrous material with a foam composed of an amphiphilic polyelectrolyte and water under conditions sufficient to substantially uniformly coat the hydrophobic fibrous material with the amphiphilic polyelectrolyte.

The hydrophobic fibrous material is generally made of a synthetic hydrophobic polymer. Such polymers generally give contact angles with water of at least about 60 degrees and typically have surface-free energies of less than about 45 dynes / centimeter. Examples of such polymers include, by way of illustration only, aromatic polyesters, such as poly (ethylene terephthalate) and polyolefins, such as polyethylene and polypropylene. The hydrophobic fibrous material can also be a non-woven fabric. By way of example, the non-woven fabric can be a meltblown non-woven fabric. As another example, the non-woven fabric can be a non-woven fabric bonded with yarn. As a further example, the non-woven fabric can be a shaped non-woven fabric.

The amphiphilic polyelectrolyte may be any material both having a plurality of polar water soluble groups and a plurality of non-polar water-insoluble groups. For example, the amphiphilic polyelectrolyte may be a surfactant / polyelectrolyte complex. As another example, the amphiphilic polyelectrolyte can be a polymeric surfactant. As yet another example, the amphiphilic polyelectrolyte can be a hydrophobic polyelectrolyte.

In order to substantially uniformly coat the hydrophilic fibrous material with the amphiphilic polyelectrolyte, a relatively unstable foam is desired. That is, it is desired that the foam be folded with the coating of the hydrophobic fibrous material with the foam. In this case, the method involves: preparing an aqueous solution of an amphiphilic polyelectrolyte; generate a foam of the aqueous solution; Y coating the hydrophobic fibrous material with the foam under conditions sufficient to substantially uniformly coat the hydrophilic fibrous material with the amphiphilic polyelectrolyte.

When the hydrophobic fibrous material is a non-woven fabric, conditions sufficient to substantially uniformly coat the hydrophilic fibrous material with the amphiphilic polyelectrolyte typically include: coating the nonwoven with the foam described above; vacuuming the coated nonwoven fabric; subjecting the coated non-woven fabric extracted with vacuum to a pressure point; Y Dry the nonwoven fabric subjected to pressure point.

The method of the present invention converts normally hydrophobic surfaces into hydrophilic or wettable surfaces. In addition, such a method allows for additional surface modifications if desired. For example, compounds which help or promote skin well-being and have the appropriate functional groups may be associated with the surfaces of the fibrous materials adapted for use in such disposable absorbent products as diapers, women's hygiene products , and products for incontinence.

Without wishing to be bound by one theory, it is believed that the following advantages are increased by the method of the present invention in contrast to the use of amphiphilic polyelectrolyte solutions: (a) using air as a diluent instead of water allows a distribution more couple of a low level of added amphiphilic polyelectrolyte and reduces the amount of water that will be removed by drying, with a concomitant decrease in drying costs; Y (b) a desired external orientation of the hydrophobic groups of the amphiphilic polyelectrolyte is obtained in a foam since the hydrophobic groups are oriented towards the air and, as a consequence, can directly interact with a hydrophobic polymer surface, while, in a aqueous solution, the hydrophilic groups are oriented towards the water phase while the hydrophobic groups are oriented out of the water phase, which means that a reorientation of the polyelectrolyte has to occur so that the hydrophobic groups are able to interact with a hydrophobic group. Hydrophobic polymer surface.

Detailed description of the invention As used herein, the term "hydrophobic fibrous material" means any fibrous material which is hydrophobic, for example, non-wettable with water. In general, the fibrous material may be a woven or non-woven fabric or a fabric. When a non-woven fabric is used, it can be made by any process known to those having ordinary skill in the art. Such processes include, for example, melt blowing, coformming, spinning, hydroentanglement, carding, air laying, wet spinning, dry spinning, spinning solution, and wet forming.

A non-woven fabric will desirably be formed by such known processes as meltblowing, co-forming, spin-bonding, and the like. By way of illustration only, such processes are exemplified by the following references: (a) Meltblown references include, by way of example, United States of America patents 3,016,599 issued to RW Perry, Jr., 3,704,198 granted to JS Prentice, 3,755,527 granted to JP Keller and others, 3,849,241 granted to RR Butin et al., 3,978,185 awarded to RR Butin et al. And 4,663,220 granted to T. J. Wisneski et al. See, also V. A. Wente, "Super Fine Thermoplastic Fibers", Industrial Chemistry and Engineering, volume 48, number 8, pages 1342-1346 (1956); VA Wente et al., "Manufacture of Super Fine Organic Fibers", naval research laboratory, Washington DC, naval research laboratory report 4364 (111437), dated May 25, 1954, United States Department of Commerce , technical services office; Robert R. Butin and Dwight T. Lohkamp, "Melting Blow-A One-Step Tissue Process for New Non-Woven Products", Journal of the Pulp and Paper Industry Technical Association, volume 56, number 4, pages 74-77 (1973); (b) coformulation references (for example references describing a meltblowing process in which the fibers or particles are combined with the meltblown fibers as they are formed) include U.S. Patent Nos. 4,100,324 granted to RA Anderson and others and 4,118,531 granted to ER Hauser; Y (c) yarn union references include, among others, United States of America patents number 3,341,394 issued to Kinney, 3,655,862 issued to Dorschner et al., 3,692,618 issued to Dorschner et al., 3,705,068 issued to Dobo et al., 3,807,817. granted to Matsuki and others, 3,853,651 granted to Porte, 4,064,605 granted to Akiyama and others, 4,091,140 granted to Harmon, 4,100,319 granted to Schwartz, 4,340,563 granted to Appel and Morman, 4,405,297 granted to Appel and Morman, 4,434,204 granted to Hartman and others, 4,627,811 granted to Greiser and Wagner, and 4,644,045 granted to Fowells.

The hydrophobic fibrous material will typically be made from a synthetic hydrophobic polymer. Such polymers generally give contact angles with water of at least about 60 degrees and typically have surface-free energies of less than about 45 dynes / centimeter. Examples of such polymers include, by way of illustration only, aromatic polyesters, polyolefins, polytetrafluoroethylene, poly (methyl methacrylate), poly (vinylidene fluoride), polyamides, and polystyrenes.

Aromatic polyesters include, by way of example only, poly (ethylene terephthalate), poly (tertramene-terephthalate), poly (cyclohexane-1,4-dimethylene terephthalate), and a thermotropic liquid crystalline such as acid copolymers. hydroxybenzoic and hydroxynaphthoic acid.

Examples of the polyolefins include, again by way of illustration only, polyethylene, polypropylene, poly (1-butene), poly (2-butene), poly (1-pentene), poly (2-pentene), poly (3) -methyl-1-pentene), poly (4-methyl-1-pentene) and the like. Furthermore, such a term is intended to include mixtures of two or more polyolefins and random and block copolymers prepared from two or more different unsaturated monomers. Due to their commercial importance, the most preferred polyolefins are polyethylene and polypropylene.

Polyamides include, by way of example only, poly (6-aminocaproic acid), (nylon 6), poly (hexamethylene sebacamide), (nylon 6, 10) and poly (octamethylene suberamide), (nylon 8, 8).

The term "amphiphilic polyelectrolyte" is used herein to mean any material both having a plurality of polar water soluble groups and a plurality of non-polar water-insoluble groups. For example, the amphiphilic polyelectrolyte may be a surfactant / polyelectrolyte complex. The surfactant can be cationic or anionic. When the surfactant is cationic, the polyelectrolyte will be anionic. Similarly, when the surfactant is anionic, the polyelectrolyte will be cationic.

The polyelectrolyte part of a surfactant / polyelectrolyte complex can be natural or synthetic. Natural polyelectrolytes include, by way of illustration only, polysaccharides, such as chitosan, glycol chitosan, cellulose, sodium carboxymethyl cellulose, and sodium carboxymethylhydroxyethyl cellulose; sulfates dextran; hyaluronic acid; heparin, chondroitin sulfate, and poly (galacturonic acid).

Synthetic polyelectrolytes include, also by way of illustration only, poly (acrylic acid), poly (methacrylic acid), poly (ethylene sulfonic acid), poly (vinylsulfonic acid), poly (styrenesulfonic acid), poly (vinylphenylsulfuric acid), phenol ester, maleic acid / alkene copolymer, alkyl vinyl ether / maleic acid copolymer, poly (glutamic acid), polylysine, poly (vinyl amine), polyethylene imine, poly (vinyl-4-alkylpyridinium salt), poly (methylene) -NN-dimethylpiperidinium salt, poly (vinylbenzyltrimethylammonium salt), poly (dimethyldiallylammonium chloride), poly (N, N, N ', N'-tetramethyl-N-p-xylylene-propylene diammonium chloride), poly (N-ethyl) -4-vinylpyridinium bromide), poly (vinyl-butylpyridinium bromide), poly (vinyl-N-methylpyridinium bromide), and poly (methacryloxyethyltrimethylammonium bromide). In general, a synthetic polyelectrolyte can have a weight average molecular weight of from about 5,000 to about 1,000,000 Daltons. For example, the polyelectrolyte can have a weight average molecular weight of from about 20,000 to about 100,000 Daltons.

The surfactants which can be used in the surfactant / polyelectrolyte complex are well known to those having ordinary skill in the art. Such surfactants include the anionic and cationic surfactants, examples of which include, by way of illustration only, the quaternary amine salts, such as dodecyltrimethylammonium chloride, didodecyldimethylammonium bromide, hexadecyltrimethylammonium chloride, cetyl dimethyl ethylammonium bromide, cebotrimethylammonium chloride, methyl bis (2-hydroxyethyl), cocoammonium chloride, methyldodecylbenzyltrimethylammonium chloride, lauryldimethylbenzyl ammonium chloride, octyl phenoxyethoxyethyldimethylbenzyl ammonium chloride, hydroxyethyl-4-benzyl-stearylimidazolinium 2-chloride, diethylheptadecylimidazolinium ethyl sulfate, laurylpyridinium chloride, and isoquinoline bromide lauryl; fatty acid salts such as lithium stearate, sodium myristate, sodium stearate, sodium naphthenate, potassium caprate, potassium undecylenate, ammonium laurate, morpholine oleate, and triethanolamine linoleate; sulfates, such as sodium n-octyl sulfate, sodium 2-ethylhexyl sulfate, sodium cetyl sulfate, lauryl triethanolamine sulfate, octylphenol sodium poly (oxyethylene), tetraethylene glycol sodium salt sulphated lauryl ether, and sulphated butyl sodium salt; sulfonates, such as sodium toluene sulfonate, sodium tridecylbenzene sulfonate, zylene ammonium sulfonate, triethanolammonium dodecylbenzene sulfonate, ammonium petroleum sulfate, petroleum sulfonate ethylenediamine, disodium dibutylphenylphenol disodium, sulfooleate amyl sodium, sulfoacetate lauryl sodium, and sodium diaminosulfosuccinate. See, for example, W. Linfield, Editor, "Anionic Surfactants," Marcel Dekker, New York, 1973; and E. Jungermann, Editor, "Cationic Surfactants", Marcel Dekker, New York, 1969.

Other surfactants include, by way of illustration only, the amines and amine derivatives, such as n-tetradecylamine, cocoamine, hydrogenated bait amine, soy amine, dimethyl octadecylamine, poly (oxyethylene) stearyl amine, poly (oxyethylene) , coco amine, octadecylamine acetate, imidazolinium hydroxide carboxymethylnonhydroxyethyl sodium, disodium-N-lauryl- / 3-imino dipropionate, cetyl betaine, myristamidopropyl betaine, and N-lauryl sarcosine.

As another example, the amphiphilic polyelectrolyte may be a polymeric surfactant, such as a hydrophobically modified poly (acrylic acid) (partial esterification with long chain aliphatic alcohols), poly (methyl vinyl ether / maleic anhydride), polystyrene-block-poly ( 2-vinylpyridino), hydroxyethyl cellulose reacted with a substituted epoxide of dimethylammonium lauryl (Polyquaternium-24® and Quatrisoft®, from Amerchol Corporation of Edison, New Jersey), poly (vinyl pyridine) partially alkylated, poly (oxyethylene) -alkyl glycol copolymers and poly (vinyl pylorridone) / polyalkene copolymers. See for example J. Piirma, "Polymeric Surfactants", Marcel Dekker, New York, 1992.

As a further example, the amphiphilic polylletrolite can be a protein. As yet another example, the amphiphilic polyelectrolyte may be an associated thickener. See, for example, J. E. Glass, Editor, "Polymers in Aqueous Media Working through the Association," Advances in the Chemistry Series 223, American Chemical Society, Washington, D.C., 1989.

In its broadest embodiment, the method of the present invention involves coating the hydrophobic fibrous material with a foam composed of an amphiphilic polyelectrolyte and water under conditions sufficient to substantially uniformly coat the hydrophilic substrate with the amphiphilic polyelectrolyte.

Without wishing to be bound by a theory, it is believed that the use of the foams maximizes the exposure of the hydrophobic regions of the amphiphilic polyelectrolyte to the hydrophobic fibrous material surfaces, thereby promoting the homogeneity and durability of the amphiphilic polyelectrolyte coatings on the material. fibrous. Foam generation is believed to maximize these hydrophobic interactions by increasing the surface area of the air / solution interface, in which the amphiphilic polyelectrolytes orient their hydrophobic groups out of the aqueous solution and either air and, consequently, , towards the surfaces of the hydrophobic fibrous material.

As stated above, the foam is generated from a solution of the amphiphilic polyelectrolyte in water. The solution may contain other materials, such as acids or bases which may be required to ionize weak polyelectrolytes or surfactants based on amines or carboxylic acids; small particles with absorbing properties, such as. zeolites and activated carbon; dyes; metal salts having bioactivity; and smaller amounts of organic solvents miscible in water.

Desirably, the foam used to coat the hydrophobic fibrous material will be relatively unstable. As used herein, the term "relatively unstable" means only that the foam is folded over the fibrous material, either spontaneously or as a result of a subsequent action. For example, the foam can be destabilized by the presence of the fibrous material. Alternatively or additionally, the foam can be destabilized by the cutting forces. The cutting forces can be generated, for example by subjecting the fibrous material to a pressure point after application of the foam. Cutting forces can also be generated by applying the foam to the fibrous material and then vacuuming the foam through the material, resulting in even distribution through the material. If desired, the fibrous material can be subjected to a pressure clamping point after the draw step with vacuum to remove excess fluid and also help to fold the foam.

The present invention is further described by the following examples. Such examples, however, should not be considered as limiting in any way either the spirit or the scope of the present invention. In the examples, the hydrophobic fibrous materials used were non-woven fabrics blown with polypropylene melt of 0.5 oz per square yard or osy (about 17 grams per square meter or gsm) and non-woven fabrics bonded with 0.8 oz polypropylene yarn per square yard (about 27 grams per square meter). Both materials were prepared according to the known procedures. In addition, all percentages are percent by weight, unless otherwise indicated.

Example 1 Quatrisoft® LM200 is a hydrophobically modified cationic cellulose polymer. Chemically, this is a hydroxyethyl cellulose Polyquaternium-24 reacted with a substituted epoxide of dimethylammonium lauryl (from Amerchol Corporation, of Edison New Jersey). This was used as a model material to investigate foam coating methods. Quatrisoft® LM200 combines the properties of a surfactant / polymer blend and exhibits some of its properties. When dissolved in water, it self-associates through hydrophobic interactions, producing structures exhibiting a high viscosity. This type of structure also has the ability to solubilize water insoluble materials, including dyes, and produces very stable foams.

For initial investigations, a 1.5 percent solution of Quatrisoft® LM200 was prepared for initial foam generation investigations. A mix of 1. 5 grams of Quatrisoft® and 100 ml of deionized water was stirred for one hour in a Glas-Col Laboratory Rotator (catalog number RD 4512, Glas-Col, of Terre Haute, Illinois) on a number 5 placement. Ten milliliters of the resulting solution were placed in 25-50 micron porous glass while the air was passed through it to generate a foam ( method through liquid blowing). A second method which gave a more stable foam used a manual mixer to stir 50 ml of the 1.5 percent solution for one minute.

The foams were prepared from 0.5 percent and 1.0 percent Quatrisoft® solutions using the two methods described above to determine the best concentration and method for the preparation of the most stable foam. The hand mixer produced the best foam and was used to prepare the foams for the remaining experiments.

The Quatrisoft® produced a very stable foam when stirred with a manual mixer in the beating placement. The method of blowing through liquid generated bubbles that were much more airy and polyehedral in shape than with the manual mixer. All three solutions produced stable foams using the manual mixer. No preferential concentration of solids in the Quatrisoft® foam was observed. That is, the 1.5 percent solution of Quatrisoft® resulted in a foam which also had a solids content of 1.5 percent.

The viscosities of the Quatrisoft® solutions were determined using a Brookfield viscometer model DVII + with a spindle number of cp-41 and a spindle speed of 100 revolutions per minute (Brookfield Engineering Laboratory, Inc., of Stoughton, Massachusetts). The viscosities for the solutions of 0.5 percent, 1.0 percent, and 1.5 percent were 3.8 x 10"3 Pa s, 13.0 x 10'3 Pa s, and 36.1 x 10" 3 Pa s, respectively. The surface tensions were 58.2 x 10"5 N, 57.3 x 10.5 N, and 56.4 x 10" 5 N, respectively. The surface tension was determined by means of the DuNouy Ring method with a Fisher Scientific model surface tensiometer 20 (Fisher Scientific Corporation, of Pittsburgh, Pennsylvania).

The seven-inch diameter pieces of the meltblown fabric were coated with foams prepared from the three Quatrisoft® solutions. Each piece of non-woven fabric was coated by means of a doctor blade placed at a height of 100 mil (about 2.5 mm). The samples were then dried in an oven at around 77 degrees Celsius. The uniformity of each coating was characterized using iodine spotting and an optical microscope.

The iodine spotting was carried out by placing the treated samples in a glass chamber enclosed with solid iodine for 30 minutes. Iodine vapor resulted in the staining of polyelectrolytes (primarily quaternized species) on the fiber surfaces of non-woven fabrics. The development of a rust color verified the modification of the surfaces of the fibers by the polyelectrolyte and allowed a visual assessment of the homogeneity of the coating.

The visual assessment was achieved by means of an Olympus BH-2 microscope equipped with an MTV-3 video adapter, Hitachi video camera, a Panasonic Ag-EP60 color video printer and a Sony CVM-1271 monitor. A Bausch & Stereo microscope was used. Lomb to observe the collapse of the foam.

After careful analysis, the 1.5 percent solution resulted in the most promising foam coating; for example, this provided the best coating. The lower concentrations did not coat the material as uniformly and consistently as is shown by iodine staining and optical microscopy. However, none of the coatings were present on all the fibers.

E j emp l o 2 Therefore, the procedure of Example 1 was repeated, followed by subjecting to clamping after application of the foam. Specifically, a foam of a 1.5 percent solution of Quatrisoft® was prepared by means of the manual mixer put in the "shake" placement. The 100 mil foam thickness was applied as described above to a piece of 7 inch diameter meltblown fabric using a Doctor Pacific® Scientific blade. The foam-coated sample was subjected to the attachment point in an Atlas laboratory squeezer having a 30 pound (13.6 kilogram) pressure point placement (Atlas Electric Devices Company, Chicago, Illinois) and then placed in an oven 77 degrees Celsius for 45 minutes. The foam coatings were characterized by iodine staining. Again the coatings were not uniform and were essentially absent from the underside of the fibers.

Since the use of a doctor blade and a pressure point did not provide a complete coating of the meltblown fibers, vacuum extraction of the foam through the fabric was investigated. The samples of the meltblown fabric were coated with foam produced from a 1.5 percent solution of Quatrisoft® as described above. Each foam-coated sample was then placed in either an eight-inch diameter Buchner funnel or a medium porosity porous glass mounted in a filter bottle having a side arm connected to a vacuum source. The vacuum was applied until the foam was sucked through the entire sample.

The fastening point was used in conjunction with the vacuum extraction to remove excess foam on the fibers and to give a more even coating distribution. The coated and pressurized samples were dried in an oven at 77 degrees centigrade for 45 minutes. Coverage was again assessed through iodine staining.

The porous glass removed much of the excess foam observed with the Buchner funnel above the holes of the funnel and provided a more uniform coverage. The samples were observed having uniform coverage on both sides of the fabric as well as the interior of the fabric.

E j e mp l o 3 The yarn-bound fabric was used in further experiments because the fibers were much longer than those of the melted cloth and could be seen through the optical microscope to more easily observe the foam coatings on the individual fibers.

The use of a heat gun was investigated to determine if the foam would fold more quickly on the fibers under direct heating. The differences in the coatings imparted by the variable drying techniques were monitored through iodine staining and microscopy. The following foam coating techniques were employed (in each case, the foam was prepared from a 1.5 percent solution of Quatrisoft® by means of the manual mixer over the "shake" placement): Sample A Doctor knife to 100 thousand (about 2.5 millimeters), extraction with vacuum, pressure point to 30 pounds (13.6 kilograms), oven drying at 77 degrees Celsius for 45 minutes.

Sample B Doctor blade to 100 thousand (about 2.5 millimeters), vacuum extraction, subjected to a clamping point at 30 pounds (13.6 kilograms), dried with a heat gun at 260 degrees centigrade for 3 minutes.

Sample C Doctor knife to 100 thousand (about 2.5 millimeters), extraction with vacuum, dried in the oven at 77 degrees Celsius for 45 minutes.

Sample D Doctor blade to 100 thousand (about 2.5 millimeters), vacuum extraction, dried with a heat gun at 260 degrees centigrade for 3 minutes.

The differences in the drying methods did not constitute a significant difference in the uniformity of the coatings. Immediate drying of the gun with heat had no benefit over the resulting coating on drying in the oven, but drying in the oven required 30 minutes while the heat gun took 3 minutes. The oven was selected as the drying technique of choice because it had less labor intensive.

In order to investigate the effect of heat on foam collapse, foam samples were prepared with the manual mixer of 1.5 percent Quatrisoft® solution and placed in petri dishes and exposed to the direct heat of a heat gun at 260 degrees centigrade. With drying, the folding of the foam was observed by means of a Bausch & Stereo microscope. Lomb at a 30x magnification. A similar experiment was carried out to observe the sticking of foam on the spunbonded fabric after different drying times. Four different samples of spin-bonded and foam-treated cloth having several drying times were observed under the optical microscope at a magnification of 40x and 100x to determine whether the foam differed as a result of drying.

Sample E Doctor blade to 100 thousand (about 2.5 millimeters), extraction with vacuum, subjected to pressure point to 30 pounds (about 13.6 kilograms), iodine spotted for 5 minutes.

Sample F Doctor blade to 100 thousand (about 2.5 millimeters), extraction with vacuum, subjected to pressure point of pounds (13.6 kilograms), dried in a convection oven at 72 degrees Celsius for 5 minutes, stained with iodine for 5 minutes.

Sample G Doctor blade to 100 thousand (about 2.5 millimeters), extraction with vacuum, subjected to pressure point to 30 pounds (about 13.6 kilograms), drying in convection oven at 72 degrees Celsius for 10 minutes, stained with iodine for 5 minutes Sample H Doctor blade to 100 thousand (about 2.5 millimeters), vacuum extraction, subjected to pressure point pounds (about 13.6 kilograms), dried in a convection oven at 72 degrees Celsius for 15 minutes, stained with iodine for 5 minutes.

Quatrisoft® foams were very stable, apparently as a result of the high solution viscosity. The foams did not fold spontaneously on drying in the petri dishes or on the spunbonded fabric. In each case the dried foam retained its original bubble shape. In such cases, a physical folding of the foam through, for example, a fastening point is necessary.

E j emp l o 4 The procedure of Example 3 was repeated in order to evaluate the effect of foam thickness on the quality of the coating. Foam thicknesses of 100 mil (about 2.5 mm) and 50 mil (about 1.2 mm) were coated onto the non-woven fabric samples joined with spinning separated by means of a doctor blade, followed by vacuum extraction, subjection to the point of attachment of 30 pounds (about 13.6 kilograms) and drying in a convection oven at 72 degrees centigrade. The uniformity of each coating was established by iodine staining.

Similar experiments were carried out to evaluate the effect of using a constant added weight using two different concentrations of the Quatrisoft® solution from which the foam was prepared. A 100-mil (about 2.5 mm) thick foam prepared from a 1.5 percent solution and a 150-mil thick (about 3.8 mm) foam prepared from a 0.5 percent solution each gave an added of 2 percent by weight on a dry weight basis. As before, the foams were applied by doctor blade, followed by a vacuum extraction, the subjection to clamping point pounds (about 13.6 kilograms) and drying at 72 degrees centigrade in a convection oven. Spotting with iodine was used to evaluate the samples.

Changing the initial foam thickness using the doctor blade resulted in differences in the foam coatings when used with a constant concentration of solution-a higher foam thickness provided better coverage. For a solids solution of a given percent, a foam thickness of 100-mil (about 2.5-mm) proved sufficient. The higher concentration of Quatrisoft® provided a better coating, even at a lower thickness. A decrease in foam thickness with the same percent of Quatrisoft® gave a less evenly coated cloth.

E j e mp l o 5 The procedure of Example 3 was repeated to allow a comparison of the foam coating with a solution coating. A first sample of the spunbond non-woven fabric was coated with a solution containing 0.5 percent Quatrisoft® by vacuum extraction. The sample was then subjected to pressure as described above and dried at 72 degrees centigrade for 45 minutes in a convection oven. After submitting to the pressure point, the sample had a wet aggregate of 100 percent.

A second sample of yarn-bound fabric was coated with foam prepared from a 1.5 percent solution of Quatrisoft® as already described (doctor's blade at 100 mil or about 2.5 mm, vacuum extraction, 30 lb. attachment point). (13.6 kilograms), and dried in a convection oven at 72 degrees Celsius).

The durability of the solution and of the foam coatings was assessed by iodine staining and sessile drop wettability. The wettability of the treated samples was measured by placing the water droplets on a surface of each sample. If water droplets were absorbed into the material, the treated sample was considered wettable.

The durability of the treatments or surface coatings was assessed by soaking the treated sample in 100 milliliters of water for 30 minutes and then letting it dry in the convection oven at 72 degrees centigrade for 30 minutes. Iodine staining and wettability with water droplets were used to evaluate the durability of the coating to this water soaking.

Based on the results of spotting with iodine as observed through the optical microscope, the first sample coated with solution did not show as complete a coating of the fibers as did the second sample coated with foam. There were patches of areas on the sample treated with solution that had no coating present.

Durability studies also showed the effectiveness of using the foam coating on the solution coating. After rinsing the samples in water, the Quatrisoft® remained on the surfaces of the fibers. There was a decrease in the amount of Quatrisoft®, but the foam-coated samples retained higher coating levels after a water rinse than did the solution-coated samples. Wettability studies also showed the effectiveness of the use of foam coatings. After rinsing, the sample treated with foam remained wettable. . Wettability in water was significantly decreased for the sample treated with solution.

E j e m p l o 6 The polyelectrolyte / surfactant complexes were also investid. The complexes were prepared from a polyacrylic acid having a weight average molecular weight of 50,000 Daltons (obtained as 25 percent by weight of an aqueous pH 7 solution from Polysciences, Warrington, Pennsylvania) and didodecyldimethylammonium bromide (Aldrich Chemical Company , of Milwaukee, Wisconsin, and JT Baker, of Pillipsburg, New Jersey). Solutions having molar portions of polyacrylic acid (polyelectrolyte or P) to didodecyldimethylammonium bromide (surfactant or S) of 100: 1, 50: 1, 20: 1, 10: 1, and 5: 1 were prepared as summarized below.

Solution to P: S of 100: 1, consisting of a surfactant solution of 6.4 ml of 1 percent and 100 ml of 1 percent polyelectrolyte solution. The viscosity of the solution was 2.7 X 10"5 N and its surface tension was 38.4 X 10 ~ 3 Pa s.

Solution B P: S of 50: 1, consisting of 12.83 ml of a 1 percent surfactant solution and 100 ml of a 1 percent polyelectrolyte solution. The viscosity and surface tension of the solution were 3.2 X 10.5 N and 31.7 X 10"3 Pa s.

Solution C P: S of 20: 1, consisting of 0.33 grams of sonicated surfactant in 22 ml of water and 100 ml of a 1 percent polyelectrolyte solution. The solution viscosity and surface tension were not determined.

Solution D P: S of 10: 1, consisting of 0.66 grams of sonicated surfactant in 22 ml of water and 100 ml of 1 percent polyelectrolyte solution. The viscosity of the solution was 2. 5 X 10"5 N the surface tension of the solution was 30.4 X 10 ° Pa s.

Solution E P: S of 5: 1, consisting of 1.32 grams of sonicated surfactant in 33 ml of water and 100 ml of polyelectrolyte solution. The viscosity of the solution was 2.2 X 10"N and its surface tension was 31.8 X 10'3 Pa s.

Because the surfactant / polyelectrolyte complex solutions have had low viscosities, the hand mixer did not produce foams sufficiently stable to allow subsequent application of the foam to a substrate. Therefore, the method of blowing through the liquid described in Example 1 was used to generate the foams.

The foams were generated from solutions A and D and placed on a polypropylene film. The coated films were observed under the stereo microscope while they were dried with the heat gun at 260 degrees centigrade. The foams were folded over the film, apparently due to the low viscosity of the solutions from which the foams were generated.

The foams were prepared from all five solutions. The foams were applied as described in Example 1 to 2.25 inch (about 5.7-cm) diameter samples of the spunbond non-woven fabric, followed by vacuum extraction, pressurization to 30 pounds ( about 13.6 kilograms), and dried in the convection oven at 72 degrees Celsius for 30 minutes. The foam coatings were compared to the solution coatings with characterization by iodine staining and microscopy. Less viscous surfactant / polyelectrilite solutions were found to provide a less stable foam that easily folds over the substrate, including both the film and the fibers. The folding of the foams resulted in a better coverage of the PP fibers.

Durability was assessed by the foam coatings prepared from a 1 percent surfactant solution (Control), Solution A and Solution D by iodine staining and the wettability test by water droplets as previously described.

The Control solution had a low viscosity but produced a relatively stable foam using the liquid blowing method. However, the prepared foam from the control did not provide the necessary function for the durability of the coating that provided a polyelectrolyte / surfactant complex. Solution D generated the best foam. Solution A did not contain enough surfactant to produce a sufficiently stable foam; Solution E was not used because it formed a precipitate.

The polyelectrolyte / surfactant complex demonstrated an enriched concentration of solids in the foam; for example, with Solution D, 2.6 percent solids in the foam compared to 1.4 percent solids in the solution.

Surfactant / polyelectrolyte complex solutions generally produce a sufficiently stable foam to coat the spunbond non-woven fabric samples. The iodine staining indicated that the foam coatings using Solution D provided uniform coverage of the fabric fibers, while the foam of Solution A did not essentially coat the fibers. Iodine staining, however, did not confirm the presence of the polyelectrolyte on the surfaces of the fibers. The presence of the polyelectrolyte was confirmed by infrared-Fourier transformation spectroscopy with attenuated total reflectance. A strong absorbance at 1,545 centimeters'1 and a lower one at 1,400 centimeters "1 were indicative of a carboxylic acid salt anion (COO"). Note that the polyacrylic acid is converted to the salt form due to its interactions with the cationic surfactant. The infrared spectroscopy of Fourier transformation of attenuated total reflectance was carried out by placing the sample to be analyzed on the upper surface of a ZnSe crystal with a phase angle of 45 degrees. The estimated penetration depth was approximately 2 micrometers (Nicolet Model 740 Fourier Transform Infrared Spectrophotometer with SpectraTech Horizontal ATR Accessory).

The coatings made from Solution D produced the best individual fiber coverage with an increase in uniformity. The durability tests showed that such coatings remained on the fibers after rinsing with water. Solution D, applied as a solution and not as a foam, did not show much decrease in the coating after rinsing with water, but the solution gave an uneven coating.

The reduction in water surface tension after exposure to a treated sample was measured by first determining the surface tension of 75 milliliters of water in a 100 ml beaker. The surface tension of the water was then measured after the treated sample was soaked for 30 minutes. Surface tension reduction studies indicated that wettability with water occurred without reducing the surface tension of the water for materials treated with the foam coating Solution D. The materials treated with the foam and Control solution (surfactant only) they soaked both with the soaked in water. The levels of these coatings were not significantly reduced by the soaking, but water humidification occurred by means of the reduction of surface tension. This demonstrates the efficiency of using the polyelectrolyte / surfactant complex to provide a modified polymer surface with respect to wettability without the reduction of surface tension in contrast to traditional surfactant treatments.

Even though the description has been made in detail with respect to the specific modalities thereof, it will be appreciated that those skilled in the art, to achieve an understanding of the foregoing, can easily conceive alterations, variations and equivalents to these modalities. For example, more than one amphiphilic polyelectrolyte may be present in the solution from which a foam is produced. As another example, more than one surfactant and / or more than one polyelectrolyte can be employed when the amphiphilic polyelectrolyte is a surfactant / polyelectrolyte complex. Other variations and equivalents will be readily apparent by those having ordinary skill in the art. Therefore, the scope of the present invention should be established as that of the appended claims and of any equivalent thereof.

Claims (21)

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

1. A method for coating a hydrophobic fibrous material with an amphiphilic polyelectrolyte which comprises: coating the hydrophobic fibrous material with a foam comprising an amphiphilic polyelectrolyte and water under conditions sufficient to substantially uniformly coat the hydrophilic fibrous material with the amphiphilic polyelectrolyte.

2. The method as claimed in clause 1 characterized in that the hydrophobic fibrous material is a polyolefin.

3. The method as claimed in clause 2 characterized in that the polyolefin is polyethylene or polypropylene.

4. The method as claimed in clause 1 characterized in that the hydrophobic fibrous material is a non-woven fabric.

5. The method as claimed in clause 4 characterized in that the nonwoven fabric is a nonwoven fabric formed by meltblowing.

6. The method as claimed in clause 4, characterized in that the nonwoven fabric is a non-woven fabric joined with spinning.

7. A method for coating a hydrophobic fibrous material with an amphiphilic polyelectrolyte which comprises: preparing an aqueous solution of an amphiphilic polyelectrolyte; generate a foam of the aqueous solution; Y coating the hydrophobic fibrous material with the foam under conditions sufficient to substantially uniformly coat the hydrophilic fibrous material with the amphiphilic polyelectrolyte.

8. The method as claimed in clause 7 characterized in that the hydrophobic fibrous material is a polyolefin.

9. The method as claimed in clause 8 characterized in that the polyolefin is polyethylene or polypropylene.

10. The method as claimed in clause 7 characterized in that the hydrophobic fibrous material is a non-woven fabric.

11. The method as claimed in clause 10 characterized in that the non-woven fabric is a non-woven fabric formed by meltblowing.

12. The method as claimed in clause 10 characterized in that the non-woven fabric is a non-woven fabric joined with spinning.

13. The method as claimed in clause 7 characterized in that the amphiphilic polyelectrolyte is a polymer.

14. The method as claimed in clause 7 characterized in that the amphiphilic polyelectrolyte is a surfactant / polyelectrolyte complex.

15. The method as claimed in clause 7 characterized in that the amphiphilic polyelectrolyte is a polymeric surfactant.

16. A method for coating a hydrophobic nonwoven fabric with an amphiphilic polyelectrolyte which comprises: preparing an aqueous solution of an amphiphilic polyelectrolyte; generate a foam of the aqueous solution; coating the hydrophobic fibrous material with the foam; vacuuming the coated nonwoven fabric; subjecting the coated nonwoven fabric with a vacuum to a pressure point; Y Dry the nonwoven fabric subjected to pressure point.

17. The method as claimed in clause 16 characterized in that the non-woven fabric is a meltblown nonwoven fabric.

18. The method as claimed in clause 16 characterized in that the non-woven fabric is a non-woven fabric bonded with spinning.

19. The method as claimed in clause 16 characterized in that the amphiphilic polyelectrolyte is a polymer.

20. The method as claimed in clause 16 characterized in that the amphiphilic polyelectrolyte is a surfactant / polyelectrolyte complex.

21. The method as claimed in clause 16 characterized in that the amphiphilic polyelectrolyte is a polymeric surfactant. SUMMARY A method for coating a hydrophobic fibrous material with an amphiphilic polyelectrolyte which involves coating the hydrophobic fibrous material with a foam under conditions sufficient to substantially uniformly coat the hydrophilic fibrous material with the amphiphilic polyelectrolyte. The foam is generated from a amphiphilic polyelectrolyte solution in water. The hydrophobic fibrous material can be a polyolefin, such as polyethylene or polypropylene. The hydrophobic fibrous material may also be a non-woven fabric, such as a non-woven fabric bonded with spinning formed with melt blowing. When the hydrophobic fibrous material is a non-woven fabric, the fabric is typically coated with the foam, vacuum extracted, pressurized and dried.