Moisture Responsive Synthetic Microporous Sheet Material

Abstract

A coriaceous vapor permeable microporous sheet material that absorbs water and expands under moist conditions is the subject of this invention. The novel material is particularly useful for making shoes and boots and provides better comfort and appearance than natural leather. The novel coriaceous material has a coating of a microporous polymer which is in firm adherence to a substrate of a polymer impregnated non-woven synthetic fibrous web. The novel sheet material under high humidity conditions as occur when a shoe or boot is worn has a particular moisture absorption, area expansion, and a decrease in tensile stress and also has a high permeability to water vapors. These particular characteristics provide a high degree of comfort to the wearer of shoes or boots made from the novel sheet material of this invention. BACKGROUND OF THE INVENTION This invention is related to a synthetic coriaceous microporous sheet material, and in particular, to a synthetic coriaceous microporous sheet material that absorbs moisture and expands under moist conditions and is an extremely comfortable shoe upper material. Synthetic coriaceous microporous sheet materials are well known in the art and are currently being sold to the shoe industry and are widely used in the manufacture of shoes. These microporous sheet materials can be made according to the processes taught in the following patents: Johnston et al. U.S. Pat. No. 3,000,757, issued Sept. 19, 1961; Holden U.S. Pat. No. 3,100,721, issued Aug. 13, 1963; Yuan U.S. Pat. No. 3,190,766, issued June 22, 1965; Holder U.S. Pat. No. 3,208,875, issued Sept. 28, 1965; Hulslander et al. U.S. Pat. No. 3,284,274,issued Nov. 8, 1966; Patsis U.S. Pat. No. 3,364,098, issued Jan. 16, 1968; Manwaring U.S. Pat. No. 3,391,049, issued July 2, 1968 and Einstman U.S. Pat. No. 3,418,198, issued Dec. 24, 1968. While excellent synthetic microporous sheet materials can be made according to the teachings of the aforementioned patents, all of the products manufactured according to these prior art patents have the same deficiency, i.e., the materials are hydrophobic and, therefore, absorb very little water and do not expand under moist conditions. For shoe comfort, it is extremely desirable to have a shoe upper material that is hydrophilic and will absorb water and expand under moist conditions. The reason is that an average person's foot expands during the day as the shoe is being worn; therefore, it is desirable to have a shoe upper material that will absorb water and expand under warm, moist conditions as exist in the interior of a shoe. The novel coriaceous microporous sheet material of this invention is hydrophilic and absorbs water and expands under high humidity conditions as exist in the interior of a shoe; therefore, the material is useful for making shoes and boots that are surprisingly comfortable and also are attractive and have the desirable characteristics of the prior art coriaceous synthetic microporous materials, i.e., scuff and abrasion resistance, excellent flexibility, and durability and leather-like appearance. Another highly advantageous characteristic of the novel sheet material of this invention is that the tensile stress of the material decreases as water is absorbed. This characteristic reduces the pressure on the wearer's foot in places where the shoe upper is tightly fitted and thereby increases the comfort of the shoe or boot. SUMMARY OF THE INVENTION A synthetic coriaceous moisture responsive microporous sheet material of this invention comprises a. a microporous topcoat of a synthetic polymeric material in firm adherence to b. a porous fibrous substrate of 1. a non-woven synthetic flexible fibrous web that has a density of 0.10- 0.40 grams/cubic centimeter and consists essentially of at least 50 percent by weight of synthetic fibers that have a moisture absorption of at least 5 percent by weight and in increase in length of at least 2 percent when exposed to a change in relative humidity of 0 to 95 percent at 25.degree. C.; 2. the non-woven web is impregnated with a polymeric binder that has a wet tensile strength of at least 500 pounds per square inch and has a moisture absorption of 5- 25 percent by weight when exposed to a change in relative humidity of 50 to 90 percent at 25.degree. C.; wherein the substrate has a binder to fiber ratio of about 0.2 to about 2/1; and wherein the coriaceous sheet material has an area expansion of 2- 10 percent, a moisture absorption of 0.5- 20 percent by weight and a decrease in tensile stress at 5 percent elongation of 20- 60 percent when exposed to change in relative humidity of 50- 90 percent at 25.degree. C. and has a water vapor permeability of at least 1,000 grams of water per 100 square meters of material per hour.

Description

DESCRIPTION OF THE INVENTION

The term "microporous" refers to a porous material in which the individual pores are not discernible to the naked eye.

The increase in length of the fiber is determined by conditioning the fiber at 0 percent relative humidity at 25.degree. C. and determining the length, then the fiber is conditioned at 95 percent relative humidity at 25.degree. C. and the length is determined. The increase in length of the fiber should be at least 2 percent and preferably, 2- 5 percent to provide a microporous sheet material that has excellent properties.

Similarly, the moisture absorption of the synthetic fibers used to form the non-woven web of the microporous sheet material of this invention is determined by the difference in moisture in the fiber at 0 percent relative humidity, 25.degree. C. and 90 percent relative humidity, 25.degree. C. The fibers should have a moisture absorption under these conditions of at least 5 percent by weight, and preferably, 8 to 30 percent by weight.

Tensile stress at 5 percent elongation is the force in pounds which is required to elongate a sample 5 percent divided by the cross section area of the sample with the results being expressed in pound per square inch (psi). Two test samples of about 1 inch by 4 inches are cut at right angles and are conditioned at 50 percent relative humidity and tested at 25.degree. C. The samples are tested at the above temperature and humidity conditions on an Instron Tensile Tester using about 1 inch between grips on the sample, a cross-head speed of 2 inches per minute and a chart speed of 10 inches per minute and the average value is recorded.

The wet tensile strength of the binder is determined by testing a coalesced film of the binder on an Instron Tensile Tester using the above test procedure except the sample is soaked in water and tested at 25.degree. C. while the sample is wet with water. The wet tensile strength of the binder should be at least 500 pounds per square inch (psi) and up to 20,000 psi. Preferably, the wet tensile strength of the binder should be about 800 to 5,000 psi.

The decrease in tensile stress at 5 percent elongation when the microporous sheet material is subject to a change in relative humidity of 50- 90 percent at 25.degree. C. is determined by measuring the tensile stress, as indicated above, after the sample is conditioned at 50 percent relative humidity and again when the sample is conditioned at 90 percent relative humidity. The decrease in tensile stress of the microporous sheet material should be about 20- 60 percent to provide a shoe upper material of excellent comfort.

Binder/Fiber Ratio is the ratio of the weight of the polymeric binder in the substrate of the novel sheet material of this invention to the weight of the fiber in the substrate.

The moisture absorption of the binder is determined by conditioning a film of the polymeric binder at 50 percent relative humidity, 25.degree. C. then at 90 percent relative humidity, 25.degree. C. The moisture absorption under these conditions should be 5- 25 percent by weight, and preferably, 8- 20 percent by weight. The moisture absorption of the resulting microporous sheet material is similarly determined and should be about 0.5- 20 percent by weight, and preferably 5- 15 percent by weight.

Area expansion of the microporous sheet material is determined by conditioning the microporous sheet at 50 percent relative humidity, 25.degree.C. and then subjecting the sheet to 90 relative humidity, 25.degree. C. and determining the area increase. To form a microporous sheet material which provides excellent comfort, the sheet should have an area expansion of 2- 10 percent, and preferably, 3- 5 percent.

Water vapor permeability value of the novel sheet material of this invention is determined by sealing the sheet on top of a cup containing CaC1.sub.2. This sealed cup is stored at 90 percent relative humidity at 23.degree.C. and the weight increase of the cup due to moisture permeating through the material is determined and the water vapor permeability value of the sheet is calculated in

The novel sheet material of this invention should have a water vapor permeability of at least 1,000, and preferably, 2,000 - 12,000.

The novel microporous synthetic sheet material of this invention comprises a polymer impregnated non-woven web which has in firm adherence thereto a microporous coating. The polymer impregnated non-woven fibrous web of the novel sheet material of this invention gives the sheet its desirable characteristics that make the novel sheet particularly useful for shoes. The substrate absorbs moisture as the shoe is worn, and as the moisture is absorbed, the substrate expands as the wearer's foot expands and thereby forms a comfortable shoe. Another advantage of the novel sheet material of this invention is that as the substrate expands from water absorption, the tensile stress decreases and reduces pressure on a portion of the shoe that is in contact with the wearer's foot.

Polyamide fibers preferably are used to form the non-woven web of the novel sheet material of this invention. Polyamides absorb moisture and expand under moist conditions and show a reduction in tensile stress under these conditions and do not deteriorate but still form a contiguous, tough web. Preferably, a polyamide fiber or polymers that have the recurring structural unit of ##SPC1##

where R and R.sup.1 are divalent aliphatic hydrocarbon radicals having 3- 8 carbon atoms and n is an integer sufficiently high to give the polymer inherent viscosity of at least 0.4 when measured at 25.degree. C. in m-cresol solvent. Preferably, polyamides are used that have an inherent viscosity of 0.5 to 1.5.

Typical nylon fibers that can be used are nylon 4, a polymer of pyrrolidone; nylon 6, condensation polymer of caprolactam; nylon 66, polyhexamethyleneadipamide, nylon 610, polyhexamethylenesebacamide, nylon 7, polymer of ethylamino-heptanoate. Bicomponent nylon fiber can also be used, i.e., a composite fiber of two fibers having different physical properties which are spun together.

A blend of fibers can also be used to form the web but at least 50 percent of the fibers of the blend must have the aforementioned properties of moisture absorption and length increase. Typical fibers which can be used in the blend are rayon, polyacrylonitrile, polyvinyl chloride, blend of polyvinyl chloride and polyvinyl acetate, polyesters, such as polyethylene terephthalate, polvinyl alcohol, acrylic fibers, modified acrylic fibers, such as polyacrylonitrile modified with polyvinyl chloride or methacrylic acid. One preferred blend of fibers which forms a useful web comprises about 10- 30 percent by weight of rayon fibers and 90- 70 percent by weight of one of the aforementioned polyamide fibers.

The fibers used to form the web preferably have a denier of 0.5 to 5.0, and preferably, a denier of 1.0- 2.0 and a staple length of about 0.5 to 4 inches, preferably, 1.0- 2.0 inches.

The fibers are formed into a non-woven web having a thickness of 20- 60 mils and a density of 0.10- 0.40 grams per cubic centimeter and, preferably, 0.18- 0.22 grams per cubic centimeter by conventional techniques. The non-woven webs are prepared by forming fibers into a loose batt by any known method, such as carding, blowing fibers, dropping the fibers and the like. The batt is compacted by pressing the batt under heat and pressure. Further compaction can be accomplished by conventional techniques, such as mechanical needling or hydraulic needling, or by any other technique which will give a fiber entangled web. The resulting web can be further compacted by shrinking, for example, by immersing the web in the hot water. A web having properties of stretchability or shrinkability balanced in each direction can be formed by crosslapping the fibers into layers of dissimilar orientation within the plane of the web. When uni-directional stretchability or shrinkability is preferred, crosslapping is omitted and most of the fibers are laid so that they have a similar orientation to the plane of the web.

When the non-woven web is prepared by mechanical needling, a batt of air blown fibers is needled to yield a total penetration of about 200 to 20,000 holes per square inch to entangle the fibers. A conventional needle loom used in the textile industry can be used for this purpose. Preferably, a needle described in Weickert U.S. Pat. No. 2,882,585, issued Apr. 21, 1959, is used since this needle forms a high quality web with a high degree of fiber entanglement. Preferably, webs that are formed by mechanically needling are heat shrunk to further compact the web, preferably, by immersing the web in a hot water bath. The web can be further compacted by the palming technique in which the web is passed over a hot drying drum.

The non-woven webs used in this invention can be formed by the hydraulic needling technique. In this technique, the non-woven web is prepared from fibers by air blowing the fibers into a loose batt. The batt is then hydraulically needled using the process and apparatus disclosed in Canadian Pat. No. 739,652, issued Aug. 2, 1966, which is hereby incorporated by reference. Another method which forms a screen pattern on the non-woven web is disclosed in British Pat. No. 1,088,376, published Oct. 25, 1967, which is also incorporated by reference.

In the hydraulic needling technique, liquid jet streams penetrate the non-woven batt and consolidate the fibers into a self-coherent non-woven web. The non-woven web has areas of "fiber interentanglement" which are different in area density then other portions of non-woven web. Preferably, about 30- 10,000 apertures or holes per square inch and more preferably, 400- 4,000 holes per square inch are used to form these fiber entanglement areas.

The non-woven batt is placed on the supporting member prior to treatment. Jetting liquid is supplied at the pressure of at least 200 psi gauge from orifices less than about 0.014 inches in diameter. Fine streams of liquid having over 23,000 energy flux in foot-poundals/square inch/second at the treatment distance are formed. The supported batt is traversed by the streams along the path of the layer centered less than about 0.1 inch apart to apply treatment energy of at least 0.1 horsepower/hour/pound of fabric product. Under one set of conditions, the liquid streams are formed by jetting water from about 0.002 to 0.030 inch diameter orifices placed in a manifold arrangement at a frequency between 5 to 1,000 orifices per inch, and preferably, 20 to 40 orifices per inch.

The above energy flux in foot-poundals/square inch/second is calculated by the following formula:

Ef.sub.i = 77PG/a

where

P = liquid pressure in pounds per square inch gauge,

G = volumetric flow of the stream in cubic feet per minute, and

a = the initial cross-sectional area of the stream in square inches.

The treatment energy of horsepower/hour/pound of fabric is calculated by the following formula:

E.sub.1 = 0.125 (ypg/sb)

Y = number of orifices per linear inch of manifold

P = pressure of liquid in the manifold in pounds per square inch gauge,

G = volumetric flow in cubic feet per minute per orifice,

S = speed of passage of the web under the stream in feet per minute, and

b = the weight of the fabric produced in ounces per square yard.

The total amount of energy expended in hydraulically needling the web is the sum of the individual energy values for each treatment.

In the hydraulic needling technique, the orifice size may be varied depending on the material to be treated and the effect desired. In general for treating loose fibrous batts, it is preferred to vary the orifice size to the basis weight of the sheet material and the denier of the fibers used therein. Preferably, a small diameter orifice is used for a low basis weight, low denier materials, larger diameter orifices are used as the weight or denier increases.

By passing a sectionally columnar stream of liquid, such as water, through the orifices and directly into contact with the non-woven batt in a parallel and continuous pass, which can be straight, curved or zigzagged, a non-woven web is produced that has lines of entanglement in straight, curved or zigzagged patterns which correspond to the number and frequency of the orifices. The entanglement and strength of the web can be increased by repeating treatment or by prolonged treatment, for example, by slow passage of these streams over the substrate.

A non-patterned web of substantially uniformly entangled fibers can be prepared by the hydraulic needling technique by oscillating the jet streams at a high frequency, for example, 300 cycles per minute for a 2 yard per minute web speed. Another method is to interrupt the columnar streams before the stream reaches the batt and form intermittent streams. This is normally accomplished by placing a screen in the path of the streams between the orifices and the plane of the batt. If desired, the screen may be oscillated through the streams to provide interruptions during treatment. The screen is not used to restrain the batt or to influence the rearrangement of the fibers of the batt into a pattern but only to disrupt the columnar streams of water. Also, suitable non-pattern webs can be prepared by oscillating the columnar streams at a frequency as low as 15 cycles per minute.

If desired, the batt may be treated first with a wetting agent or other surface agents to increase the penetrating power of the streams during processing. These agents may be included in the liquid stream used to hydraulically needle the web. An example of a particularly suitable agent is a high molecular weight polyethylene oxide.

These hydraulically needled non-woven webs normally have an entanglement completeness (c) of at least 0.5, and an entanglement frequency (c) of at least 25 when measured under bond free conditions. (For example, by bond free, it is meant that the fibers of the non-woven fabric are not adhered with the binder or interfiber fusion bonds. In other words, the non-woven web is tested to determine the strength and other properties resulting solely from fiber entanglement).

The non-woven web is impregnated with a polymeric binder to provide a substrate which has a binder to fiber ratio of about 0.2/1 to 2/1. A variety of binders can be used provided the binder has a wet tensile strength of about 500- 15,000 pounds per square inch, preferably 800- 5,000 pounds per square inch and a moisture absorption when exposed to a change in relative humidity of 50 to 90 percent, 25.degree. C. of 5- 25 percent by weight, and preferably, 8- 20 percent by weight. The web may be impregnated by any of the well-known techniques and the binder may be applied from a solution, dispersion, latex or from an organosol and coagulated by any of the well-known techniques. One preferred process is disclosed in Einstman U.S. Pat. No. 3,492,154, issued Jan. 27, 1970.

The polymers used to impregnate the web should be moisture responsive, i.e., absorb moisture and show a decrease in tensile stress when the moisture content of the polymer increases. This can be accomplished by using a moisture responsive polymer or a blend of a non-moisture responsive polymer with a moisture responsive polymer such as polyvinyl acetate or polyvinyl pyrrolidone.

Typical polymers, or blends of polymers, that can be used to impregnate the web are, for example, polyurethanes, such as polyether urethanes and polyester urethanes, chain-extended polyether and/or polyester urethanes wherein the chain-extender is either a diamine or a glycol, blends of one of the aforementioned polyurethanes, polyvinyl chloride, polyureas, vinyl addition polymers, such as acrylics, conjugated diene polymers, such as a polymer of styrene/butadiene, butadiene/alkyl methacrylate or acrylate, carboxy modified polymer of styrene/butadiene, natural rubber, polychloroprene, copolymers of ethylene/vinyl acetate, polyvinyl acetate, polyvinyl pyrrolidone and the like.

One useful binder composition comprises 10- 40 percent by weight of polyvinyl pyrrolidone and 10- 60 percent by weight of a polyurethane of a polyalkyleneether glycol and an organic diisocyanate which is chain extended with hydrazine or a diamine.

The microporous layer of the novel sheet material of this invention is about 2- 50 mils in thickness, preferably 5 to 15 mils thick, and can be formed in a number of methods, for example, the processes disclosed in Johnston et al. U.S. Pat. No. 3,000,757; Holden U.S. Pat. No. 3,100,721; Yuan U.S. Pat. No. 3,190,766; Holden U.S. Pat. No. 3,208,875; Einstman U.S. Pat. No. 3,418,198, can be used. A suede layer can be formed according to the teachings of Hulslander et al. U.S. Pat. No. 3,284,274, issued Nov. 8, 1966.

One method for applying the microporous layer to the substrate is to cast a microporous film on a separate support, coagulate and dry the film and then laminate the film to the polymer impregnated non-woven web using a water vapor permeable adhesive, for example, a latex of an acrylic polymer or a polyurethane, to adhere the microporous coat to the substrate.

The preferred method for preparing a microporous coating is to form a solution having as essential constituents a polymeric component and a solvent for the polymeric component. A liquid miscible with the solvent but a non-solvent for the polymeric component is admixed with the solution in an mount up to and including the quantity which starts to transform the polymer solution into a substantially colloidal polymeric dispersion. When a substantially colloidal dispersion is used, it should have a viscosity greater than about 1 poise and a polymer concentration of greater than about 7 percent by weight. Finally, the polymeric dispersion is coated onto an impregnated web and the coating is bathed with an inert liquid which contains a non-solvent for the polymeric component and is miscible with the solvent, then the resulting product is dried.

In producing the microporous materials suitable for shoe uppers, however, it is an additional requirement that the polymeric component of the microporous coating has a secant tensile modulus at 5 percent elongation of above about 600 psi during the entire processing cycle, i.e., from the time the polymeric component is coagulated into a microporous structure until it is dried. Generally, a microporous structure formed from a polymer which in consolidated form has a secant tensile modulus below about 600 psi collapses as the liquid is being removed or after the liquid is removed from the micropores of the structure so that a relatively impermeable product is formed. Preferably, the secant modulus at 5 percent elongation of the polymer during the cycle is about 600 to 25,000 psi and more preferably, about 800 to 3,000 psi. The secant tensile modulus is the ratio of the stress to the strain at 5 percent elongation of the sample determined from the tensile stress-strain curve and is expressed as force per unit area, e.g., pounds/square inch. The secant tensile modulus measurement is carried out according to ASTM-D-882- 64-T modified as described in the aforementioned Einstman patent.

A preferred major polymeric component useful in this invention for forming the microporous coating of the novel sheet material of this invention is a polyurethane made by reacting an organic diisocyanate with an active hydrogen-containing polymeric material, such as a polyalkyleneether glycol or a hydroxyl terminated polyester to form an isocyanate terminated prepolymer. This prepolymer is then chain extended with hydrazine, substituted hydrazines, diamines such as N-methyl bispropylamine, diamines such as 1,4-diamino-piperazine, ethylene diamine and the like. Glycols and diols can also be used as chain-extenders, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol and the like. Ethylene glycol, hydrazine and a mixture of hydrazine and N-methylaminobis-propylamine are preferred chain-extenders.

The chain-extension reaction is usually carried out at a temperature below 120.degree. C. and often at about room temperature, particularly for hydrazine-extended polymers. During the reaction, prepolymer molecules are joined together into a substantially linear polyurethane polymer, the molecular weight of which is usually at least 5,000 and sometimes as high as 300,000 . The reaction can be carried out without a solvent in heavy duty mixing equipment or it can be carried out in a homogeneous solution. In the latter case, it is convenient to use as a solvent one of the organic solvents to be employed in the polymer solution for preparing the microporous coating.

A vinyl chloride polymer is another suitable component of the polymer solution when making microporous coatings for leather-like sheet materials. Superior product abrasion resistance is obtainable when a vinyl chloride polymer is used in combination with an elastomer such as the polyurethane described above. When making a shoe upper material or the like from a blend of polyurethane elastomer and vinyl chloride polymer, it is generally preferred to employ over 30 weight percent, preferably 75 percent of a polyurethane with the balance being polyvinyl chloride.

Useful vinyl chloride polymers include polyvinyl chloride and copolymers having a major proportion, preferably at least 80 percent, of vinyl chloride and can contain a minor proportion of another ethylenically unsaturated monomer, such as vinyl acetate, vinylidene chloride, or diethyl maleate.

Within the secant tensile modulus range specified above, the polymeric component of the solution from which coating is formed can contain one or more of numerous types of polymers, which are exemplified by the following: polyurethanes, vinyl halide polymers, polyamides, polyesteramides, polyesters, polyvinyl butyral, polyalphamethylstyrene, polyvinylidene chloride, alkyl esters of acrylic and methacrylic acids, chlorosulfonated polyethylene, copolymers of butadiene and acrylonitrile.

When a polymer is used which is known to be compatible with plasticizers, for example, a vinyl chloride polymer, it can be blended with known plasticizers therefor in an amount up to but not including the amount which causes the secant tensile modulus at 5 percent elongation to drop below 600 psi. Other known additives for polymeric compositions can also be added to the polymeric component, such as pigments, fillers, stabilizers and antioxidants.

The polymer component selected is dissolved in enough solvent to yield a solution having the desired solids content and viscosity. For applying the microporous coatings, it is usually preferred to use a solution which, after addition of non-solvent, if any is employed, the solution has a polymer content of about 10 to 30 weight percent and a viscosity of about 10 to 500 poises. The organic solvent used in the solution should be one that is miscible, preferably, completely miscible, with the non-solvent liquid to be used in practicing the invention. N,N-dimethyl formamide is a preferred solvent for the polymers soluble therein in view of its high solvent power for many of the preferred polymers as well as its high miscibility with the generally preferred non-solvent liquids including water. Other useful solvents include dimethyl sulfoxide, tetrahydrofuran, tetramethyl urea, N,N-dimethyl acetamide, N-methyl-2 -pyrrolidone, ethyl acetate, dioxane, butyl carbitol, phenol, chloroform and gamma-buryrolactone.

After the coating solution is applied to the polymer impregnated web, the web is immersed into a bath of a non-solvent, preferably water, to coagulate the polymer into a microporous layer and after coagulation the material is washed in non-solvent, preferably water, and then dried to remove the non-solvent. The resulting sheet material then can be dyed according to the process described in Manwaring U.S. Pat. No. 3,337,289, issued Aug. 22, 1967. The finish is then applied to the dyed microporous sheet material to give the material a polished leather-like appearance. Typical finishes that can be used and the process for applying this finish are described in Dye U.S. Pat. No. 3,455,727, issued July 15, 1969, U.S. Pat. No. 3,481,766 and U.S. Pat. No. 3,481,767, both to Craven et al., and both issued Dec. 2, 1969, Hochberg et al. U.S. Pat. No. 3,501,326, issued Mar. 17, 1970.

It is possible to cast a film of the finish, dry the film and then laminate the film of the finish to the microporous topcoat. An adhesive of a latex of a moisture permeable polyurethane or an acrylic polymer can be used to adhere the finish to the microporous topcoat.

The following examples illustrate the invention and all parts and percentages are by weight unless otherwise specified.

EXAMPLE 1

A non-woven web is prepared by forming a batt of loosely entangled Nylon 6,6 fibers (polyhexamethylene adipamide) of 1.5 denier nylon, about 11/2 inch in length. These fibers have a moisture absorption of about 8 percent and an increase in length of about 2.4 percent when subjected to a change in relative humidity of 0- 95 percent at 25.degree. C. The batt is then mechanically needled using about 1,000 penetrations per square inch on a conventional needle loom. The resulting web is then heat shrunk in water at 125.degree. C., and is consolidated further by passing the web over a roll heated to 150.degree. C. The resulting web has a density of 0.19 and an average tensile strength in both directions of about 4.8 pounds per ounce per inch per square yard.

A chain-extended polyurethane for impregnating the above prepared web is then formed by using conventional polymerization techniques. About 0.5 moles of polyethyleneether glycol, molecular weight 1,000, is reacted with about 1.0 moles of methylene-bis-4 -phenol isocyanate to form an isocyanate terminated prepolymer. The prepolymer is diluted to 50 percent solids with dimethyl formamide and chain-extended with a hydrazine hydrate solution to form an amine terminated polymer. Dimethyl formamide is added to form a 12 percent solids polymer solution that has a viscosity of about 10 poises. The polymer has a wet tensile strength when measured according to ASTM D 882- 64T of 1,900 pounds per square inch.

The resulting polymer solution is cast on a glass plate and dried in an oven at 100.degree. C. The resulting polymer film has the following physical properties when subjected to a change in relative humidity from 50 percent relative humidity at 25.degree. C. to 90 percent relative humidity at 25.degree. C.: moisture absorption 20 percent by weight; area expansion 9.9 percent; change in tensile stress at 5 percent elongation -50 percent.

The above prepared web is impregnated with the aforementioned polymer solution by immersing the web in the polymer solution for about 5 minutes and removing the web from the solution and removing excess polymer solution. The polymer is then coagulated in the web by immersing the web in water at 25.degree. C. for about 30 minutes and then the impregnated web is dried at 100.degree. C. for about 15 minutes.

The resulting polymer impregnated web has the following physical properties:

Binder to fiber ratio 0.5/1 Density 0.3 grams/cubic centimeter

A microporous topcoating is then applied to the above prepared polymer impregnated substrate to form a leather-like material. The microporous topcoating is prepared according to the procedure described in Example 1 of Holden U.S. Pat. No. 3,100,721, issued Aug. 13, 1963. The final coating is about 15 mils thick. An acrylic finish is then applied and dried. The acrylic finish is described in Example 1 of Dye U.S. Pat. No. 3,455,727 except the finish is pigmented with titanium dioxide pigment. The material is then embossed to give a surface grain pattern.

The resulting microporous sheet material has the following physical properties when subjected to a change in relative humidity of 50 percent relative humidity, 25.degree. C. to 90 percent relative humidity, 25.degree. C.:

moisture absorption 9.6% by weight Area expansion 4.5% Change in Tensile stress at 5% elongation -33%

The water vapor permeability of the microporous sheet is about 3,600 grams/100 m..sup.2 /hour.

The microporous sheet material is formed into shoes. Wearers of these shoes indicate that the shoes are very comfortable and have an excellent appearance and are scuff and abrasion resistant.

EXAMPLE 2

A non-woven web of 6.0 oz./square yard is prepared from nylon fibers described in Example 1 by forming a batt of closely entangled fibers by a conventional air laying technique. This web is then treated with columnar streams of water using the apparatus disclosed in Canadian Pat. No. 739,652, issued Aug. 2, 1966. In this apparatus, the liquid stream is passed through a 0.005 inch diameter orifices drilled into a manifold and are spaced at about 40 holes per inch. Special care is taken in cleaning and boring of the orifices to insure a sharp entry into the orifice. The cylindrical filter is mounted coaxially within the manifold assembly and is used to insure a uniform distribution of water to the orifices. The filter is a fine mesh wire screen that has 100 .times. 100 wires per square inch and a 30 percent open area.

The above prepared web is placed on a 40 .times. 40 mesh woven wire screen with a 36 percent open area and is passed under two streams of essentially columnar water at 30.degree. C. The liquid pressure in the manifold is approximately 200 pounds per square inch (psi.) in the first stream and 1,000 psi. in the second stream. The distance from the manifold to the web is approximately 1 inch. The web is then reversed and the treatment is repeated on the opposite side of the web. The web is dried under a blanket which applies a pressure of about 4 psi. The resulting web is smooth and dense and has the following properties:

thickness about 40 mils, density 0.23 gram per cubic centimeter, entanglement completeness 0.88, entanglement frequency 59, basis weight 6.0 oz. square yard.

This web is then impregnated with the polymer solution of Example 1 using the impregnation procedure of Example 1. The resulting impregnated web has a binder to fiber ratio of 0.6/1.

The web is then topcoated, finished and embossed using the identical constituents and procedure as used in Example 1. The resulting microporous sheet material has the following physical properties when subjected to a change in humidity of 50 percent relative humidity, 25.degree. C. to 90 percent relative humidity, 25.degree. C:

moisture absorption 12.3% area expansion 3.6% change in tensile stress at 5% elongation -48%

The water vapor permeability of the microporous sheet is about 3,000.

The microporous sheet material is formed into shoes. Wearers of these shoes indicate that the shoes are very comfortable and have an excellent appearance and are scuff and abrasion resistant.

EXAMPLE 3

A nonwoven web is prepared by forming a batt of loosely entangled Nylon 6,6 fibers and rayon fibers by a conventional air laying technique. The weight ratio of nylon to rayon fibers is 3:1. The nylon fibers are described in Example 1. The rayon fibers are three-quarter inch in length, 1.5 denier and have a moisture absorption of 27 percent and an increase in length of 3.4 percent when subjected to the humidity change described in Example 1. The batt is then hydraulically needled using the procedure described in Example 2.

The resulting web is smooth and dense and has the following properties: Thickness of about 40 mils, density of about 0.19 gram per cubic centimeter, entanglement completeness about 0.88, entanglement frequency 59, basis weight of about 6.0 oz. per square yard.

A chain-extended polyurethane solution is then prepared to impregnate the web. The chain-extended polyurethane polymer is prepared by forming a hydroxyl terminated dimer by reacting 2 mols of polytetramethylene glycol molecular weight 1,000 and 1 mol of toluene-2,4 -diisocyanate. One mol of this hydroxyl terminated dimer is then reacted with 2 mols of methylene bis(4-phenyl isocyanate) to form an isocyanate terminated prepolymer. This prepolymer is then chain-extended with hydrazine hydrate to form a solution of a chain-extended polyurethane having a viscosity of about 115 poises and a polymer solid content of about 25 percent. This chain-extended polyurethane solution is blended with polyvinyl pyrrolidone and dimethyl formamide. The resulting solution contains about 15 percent polymer solids and the polymer solids content consists of chain extended polyurethane and polyvinyl pyrrolidone in a 80:20 weight ratio.

A film is cast from the above prepared polymer solution then dried. The polymer film has a wet tensile strength of about 3,000 psi and a moisture absorption of 5.2 percent when exposed to a humidity increase of 50- 90 percent at 25.degree. C.

The above prepared web is immersed in the polymer solution and impregnated. The web is removed from the polymer solution then excess polymer is scraped from the surface of the web. The impregnated web is then immersed in water to coagulate the polymer and the web is dried. The resulting web has a binder to fiber ratio of about 0.6/1.

A microporous sheet is then formed by coating a 60 mil wet film on a glass plate of the polymer dispersion of Example 1 of Holden U.S. Pat. No. 3,100,721 and coagulating the film in water, washing the film and air drying the film. The resulting microporous film is then laminated to the above prepared substrate applying a thin layer of an acrylic latex that has a high water vapor permeability between the microporous film and the substrate. The resulting sheet is then dried. A finish layer is then applied by this lamination technique. A sheet of the finish is prepared from the finish composition used in Example 1 by casting a film of the finish on a glass plate and drying the film. This film is then laminated to the microporous sheet by applying the same acrylic latex between the finish layer and the microporous layer. The resulting sheet is then dried and embossed with a grain pattern.

The resulting microporous sheet material has the following physical properties when subjected to a relative humidity change of 50- 90percent, 25.degree. C.:

moisture absorption 9% area expansion 2% change in tensile stress at 5% elongation -55%

The water vapor permeability of the microporous sheet material is about 3,500.

The microporous sheet material is made into shoes. Wearers of these shoes indicate that the shoes are very comfortable and have an excellent appearance and are scuff and abrasion resistant.

EXAMPLE 4

The polymer impregnated non-woven web of Example 1 is used to prepare a microporous sheet material. A nylon tricot fabric of 15 denier, Nylon 6,6 (polyhexamethylene adipamide) have a basis weight of 2 ounces per square yard is used as an interlayer fabric and is positioned between the substrate and the microporous topcoat of the sheet material. The microporous sheet material is prepared by using the process of Example 1 of Einstman U.S. Pat. No. 3,418,198. The coating composition for the microporous topcoat is the same as composition used in Example 1.

The resulting sheet is dried and a finish is applied as in Example 1 and has the following physical properties when exposed to a relative humidity change of 50- 90 percent, 25.degree. C.:

moisture absorption 9% area expansion 3% change in tensile stress at 5% elongation -21%

The water vapor permeability of the microporous sheet is about 3,000 grams/100m.sup.2 /hour.

The microporous sheet material is made into shoes. Wearers of these shoes indicate that the shoes are very comfortable and have an excellent appearance and are scuff and abrasion resistant.

EXAMPLE 5

A nonwoven web is prepared by laminating together four layers of a spun bonded Nylon 6,6 web having a basis weight of 1.2 oz/yd..sup.2. The individual webs are adhered together by using a thin acrylic latex layer between the webs. The web is then dried and then the web is impregnated with the polymer solution of Example 1 using the same procedure as in Example 1. The resulting web has a binder to fiber ratio of about 0.5/1.

A microporous topcoat is applied and the sheet is finished using the identical constituents and procedures used in Example 1. The resulting microporous sheet material has the following physical properties when subjected to a relative humidity change of 50- 90 percent, 25.degree. C.:

moisture absorption 8% area expansion 3% change in tensile stress at 5% elongation -40%

The water vapor permeability of the sheet material is about 3,300 grams/100m..sup.2 /hour.

The microporous sheet material is made into shoes. Wearers of these shoes indicate that the shoes are very comfortable and have an excellent appearance and are scuff and abrasion resistant.

EXAMPLE 6

A nonwoven web of Example 2 is impregnated with an acrylic latex of a copolymer of methylmethacrylate and butyl acrylate. The polymer is coagulated and the web is dried. The resulting web has a binder to fiber ratio of about 0.8/1.

A chain extended polyurethane for forming the microporous topcoat on the web is prepared by using the following procedure.

About 647 pounds of poly(tetramethyleneether) glycol molecular weight 2,088, 52 pounds of ethylene glycol, 1,825 pounds of dimethyl formamide are charged into the batch reactor. These materials are mixed in he batch reactor for about 45 minutes while being blended with the agitator running at about 100 rpm. The temperature during admixing is held at about 45.degree. C. and after the ingredients are mixed, the temperature is raised to 52.degree. C. 291 pounds of a mixture of methylene-bis- (4-phenyl isocyanate) and about 0.05 percent by weight, based on the weight of the mixture of benzoyl chloride are charged into the kettle over a 3 -minute period with the ingredients being constantly agitated. During the addition, the temperature rises to 70.degree. C. because of the heat of the reaction. The recycle pump is engaged and the ingredients were recycled at a rate of 125 gallons per minute and the temperature of the kettle is controlled at 70.degree. C. and the agitator is set at 60 rpm. The reaction mixture is held at 70.degree. C. under constant agitation for about 3 hours and the viscosity of the mixture increased to 124 poises.

2.3 pounds of N-butyl amine dissolved in 17 pounds of dimethyl formamide are then charged into the reactor while the ingredients are being agitated. Agitation is continued 3 minutes. A constant pressure across the viscometer indicates the reaction has stopped. The intrinsic viscosity of the polymer is about 0.63. The resulting polymer solution has a 35 percent polymer solids content and the polymer has a weight average molecular weight of about 100,000 and a -NH-content of about 3.53 percent by weight.

2,200 pounds of a 15 percent polyvinyl chloride solution in dimethyl formamide are blended with the above prepared chain-extended glycol extended polyurethane to form a coating composition. The temperature of the blend is heated to 45.degree. C. and about 4 percent by weight, based on the weight of the total composition, of water, is added and blended with the composition. The resulting composition has a 21 percent solids content. The temperature is then reduced to about 35.degree. C. and a colloidal dispersion which is useful for preparing microporous coatings is formed.

This dispersion is then coated at about 35.degree. C. onto the above prepared web with a doctor blade using a wet coating thickness of about 50 mils. The coating is then coagulated by immersing the coated sheet in water to form a microporous structure. The sheet material is then washed with water and a white finish is applied as in Example 1. The resulting sheet material has a microporous coating about 15- 20 mils in thickness, and has the following physical properties when subjected to a change in relative humidity of 50-90, 25.degree. C.:

moisture absorption 2.5% area expansion 2.0% change in tensile stress at 5% elongation -21%

The water vapor permeability of the sheet material is about 3,000 - 4,000 grams/100 m..sup.2 /hour.

The microporous sheet material is made into shoes. Wearers of these shoes indicate that the shoes are very comfortable and have an excellent appearance and are scuff and abrasion resistant.

Claims

What is claimed is:

1. A synthetic coriaceous moisture responsive sheet material comprising

a. a microporous topcoat of a synthetic polymeric material wherein the polymeric component has a secant tensile modulus at 5 percent elongation of above about 600 pounds per square inch and is in firm adherence to

b. a porous fibrous substrate consisting essentially of

1. a non-woven synthetic flexible fibrous web having a density of 0.10- 0.40 grams/cubic centimeter consisting essentially of at least 50 percent by weight of synthetic fibers that have a moisture absorption of at least 5 percent by weight and an increase in length of at least 2 percent when exposed to a change in relative humidity of 0 to 95 percent at 25.degree. C.: in which the non-woven web consists essentially of at least 50 percent by weight of polyamide fibers having the recurring structural unit of ##SPC2##

wherein R and R.sup.1 are divalent aliphatic hydrocarbon radicals having 3- 8 carbon atoms and n is an integer sufficiently high to give an inherent viscosity of at least 0.4 measured at 25.degree. C. in m-cresol solvent and 0 to 50 percent by weight of rayon fibers;

2.

2. said web being impregnated with a polymeric binder that has a wet tensile strength of at least 500 pounds per square inch and has a moisture absorption of 5- 25 percent by weight when exposed to a change in relative humidity of 50 to 90 percent at 25.degree. C.; in which the polymeric binder is a chain-extended polyurethane which is the reaction product of an isocyanate terminated prepolymer of a polyalkyleneether glycol and an organic diisocyanate chain-extended with a compound having at least one reactive hydrogen atom attached to each end of the compound;

wherein the substrate has a binder to fiber ratio of about 0.2/1 to 2/1, and

wherein the coriaceous sheet material has an area expansion of 2- 10 percent, a moisture absorption of 0.5 - 20 percent by weight and a decrease in tensile stress at 5 percent elongation of 20- 60 percent when exposed to a change in relative humidity of 50- 90 percent at 25.degree. C. and has a water vapor permeability of at least 1,000 and up to 12,000

grams of water per 100 square meters of material per hour. 2. The sheet material of claim 1 in which the fibrous web is of 10- 30 percent rayon fibers and 90- 70 percent of said polyamide fibers.

3. The sheet material of claim 1 in which the polyurethane is the reaction products of an isocyanate terminated prepolymer of a polyethyleneether glycol molecular weight about 500- 1,500, methylene-bis-4-phenyl isocyanate and is chain-extended with hydrazine.

4. The sheet material of claim 1 in which the polymeric binder is a blend of a chain-extended polyurethane and a moisture absorbing material.

5. The sheet material of claim 4 in which the chain-extended polyurethane is an isocyanate terminated prepolymer of an aromatic diisocyanate and a polymeric material having a molecular weight of 500-1,500 and having active hydrogen atoms selected from the group consisting of polyalkyleneether glycol and a hydroxyl terminated polyester and is chain extended with a compound having an active hydrogen attached to each end of the compound and in which the moisture absorbing material is polyvinyl pyrrolidone.

6. The sheet material of claim 5 in which the chain-extended polyurethane is an isocyanate terminated prepolymer of a toluene diisocyanate, methylene-bis-4-phenyl isocyanate polytetramethyleneether glycol molecular weight 500-2,000 which is chain-extended with a blend of hydrazine and N,N-bis-(amino-propyl)methylamine.

7. The sheet material of claim 1 which has a fabric of polyamide fibers between the microporous polymeric coating and the porous fibrous substrate, the polymeric coating being sufficiently thick to penetrate the fabric and firmly bond the fabric to the substrate while the exposed surface of said coating is smooth.

8. The sheet material of claim 1 in which the fibrous web is hydraulically needled and has a substantially uniform dense structure of interentangled fibers characterized by random fiber segments that are oriented transversely to the plane of the substrate and have a fiber entanglement completeness of at least 0.5, and an entanglement frequency of at least 25 per inch when measured in a bond-free condition.

9. The sheet material of claim 1 in which the polymeric component of the microporous topcoat is a blend of a chain-extended polyurethane and polyvinyl chloride and the non-woven web is of polyhexamethylene adipamide fibers and the web is impregnated with a chain-extended polyurethane of a polyalkyleneether glycol and aromatic diisocyanate which is chain-extended with a compound having at least one active hydrogen attached to each amino nitrogen atom.

10. The sheet material of claim 1 in which the polymeric component of the microporous topcoat is a blend of a chain-extended polyurethane and polyvinyl chloride and the non-woven web is hydraulically needled and has a substantially uniform dense structure of interentangled fibers characterized by random fiber segments that are oriented transversely to the plane of the substrate and have a fiber entanglement completeness of at least 0.5, and an entanglement frequency of at least 25 per inch when measured in a bond-free condition and the web is impregnated with a chain-extended polyurethane of a polyalkyleneether glycol and aromatic diisocyanate which is chain extended with a compound having at least one active hydrogen attached to each amino nitrogen atom.

11. The sheet material of claim 1 in which the polymeric component of the microporous topcoat is a blend of a chain-extended polyurethane and polyvinyl chloride and the non-woven web is a blend of polyamide and rayon fibers and the web is impregnated with a polymer blend of a chain-extended polyurethane of an aromatic diisocyanate and a polyalkyleneether glycol chain-extended with hydrazine and blended with polyvinyl pyrrolidone.

12. The sheet material of claim 1 in which the substrate is impregnated with an acrylic binder and the microporous topcoat is of a chain-extended polyurethane of an aromatic diisocyanate and a polyalkyleneether glycol chain-extended with a glycol having 1-5 carbon atoms.