Leatherlike Material And Process Of Making Same

Abstract

This invention is directed to a tenacious and moisture permeable leatherlike sheet material having breatheability and water absorbability and which is comparable to natural leathers in durability and wearing comfort. It comprises: a base fabric having a large content of its void spaces; a microporous and aqueous insoluble polyvinyl acetal resin, adhering to and entirely covering the structural fibers of said fabric, in the form of a unitary three dimensional network; and a layer of a different resin covering said polyvinyl acetal resin. The sheet material may have a grain side layer on at least one surface side thereof. A process for manufacturing such a sheet material comprises steps of: impregnating a base fabric with an aqueous solution of polyvinyl acetal; heating the impregnated fabric at 50.degree.-130.degree. C.; further impregnating said fabric with liquid comprising different resin; and curing. The resultant article is particularly useful for inner parts of shoe, such as insole, sole pad, inner lining and the like.

Description

This invention relates to a leatherlike material and a process for making the same and, more particularly, to such a leatherlike sheet material which has a combination of properties including an excellent air and moisture permeability and a high strength.

Numerous and various proposals in relation to manmade leathers and their preparation have been made heretofore and some of them have been accepted as a substitute for natural leather. However, a majority of manmade leathers in the past has been considerably inferior to natural leathers in ability to breathe comprising, for instance, water and moisture absorbability, moisture exhalability, moisture permeability, etc., so that such prior manmade leathers have fallen in the public estimation when used as shoes, suitings and similar protective clothing articles calling for the ability of the material to breathe, due to their uncomfortable wearing properties such as moist and humid feels. Particularly, the moistening or humidification of the inside of a shoe is not only awfully uncomfortable but also undesirable from the sanitary point of view, for in most cases, shoes are worn continuously for a long time throughout all seasons. Furthermore, the previously known manmade leathers have had such a drawback that when they are used as chair coverings, wall linings, motor-car panellings, upholstery materials and the like, those articles are apt to get moist or to have dew-drops condensed on their surface especially under moist atmospheric conditions, for instance, in a rainy day or in the rainy season, or owing to some variations in temperature. The drawback as such of the prior manmade leathers is principally ascribed to the fact that their hydrophilicity and porosity are so poor as compared with those of natural leathers that they lack breatheability by means of which leathers absorb and exhale moisture in the atmosphere, permeating air therethrough.

It is, therefore, an important object of the present invention to provide a novel and improved leatherlike material having air and moisture permeability, moisture absorptivity and moisture exhalability equivalent or superior to those of natural leathers.

Another object is the provision of a process of making flexible and tenacious moisture permeable sheet materials having a microporous polymeric component in adherence with fibers in their substrate.

Still another object is the provision of an economical process of making such sheet materials which are comparable with natural leathers in durability and comfort characteristics.

Other important objects will be apparent from the description of the invention which follows.

The above objects are accomplished according to the present invention by forming a leatherlike material comprising a base fabric and a microporous and aqueous insoluble resin consisting essentially of acetalized product of polyvinyl alcohol (hereinafter referred to as "polyvinyl acetal") adhering to and entirely covering the structural fibers of the said base fabric, the said resin forming a unitary three dimensional network containing a number of pores therein, the surface of the said resin being covered continuously by a layer comprising at least one resin different from the aforementioned resin. In particular, such a leatherlike material comprises a base fabric having a large content of void spaces and a microporous and aqueous insoluble polyvinyl acetal resin, specifically polyvinyl formal resin, adhering to and entirely covering the structural fibers of the said base fabric, which resin extending from the surface of the fibers towards void spaces formed among the fibers, interconnecting adjacent fibers and forming a unitary three dimensional network containing a number of pores therein, the said network uniformly existing in and extending over the fabric, the surface of the said resin being covered continuously by a layer comprising at least one resin different from the aforementioned polyvinyl acetal resin.

Another embodiment of the present invention is a leatherlike material comprising a substrate consisting of the above obtained leatherlike material, and a grain side layer formed on the surface of the substrate, which grain side layer comprising at least one resin selected from the class consisting of synthetic resins and natural resins.

The invention further comprises a process of making a leatherlike material which comprises first step of impregnating a base fabric with an aqueous solution containing water soluble polyvinyl acetal, second step of heating the impregnated fabric at 50.degree.-130.degree. C. to promote acetalization of said polyvinyl acetal, whereby resulting microporous and aqueous insoluble polyvinyl acetal resin adhering to and entirely covering the structural fibers of the said fabric, third step of further impregnating the resultant fabric with liquid containing emulsion or solution of at least one resin different from polyvinyl acetal selected from the class consisting of synthetic resins and natural resins and fourth step of curing the thus resin impregnated fabric.

It is a still further preferable embodiment of the present invention to make a leatherlike material by a process which comprises a coating liquid containing at least one resin selected from the class consisting of synthetic resins and natural resins on the surface of the material obtained through the aforementioned four steps, whereby forming a grain side layer thereupon.

The above and other features of the leatherlike material of the present invention will be more fully understood from the following description when read in connection with the accompanying drawings wherein:

FIG. 1 is a magnified schematic cross-sectional view, somewhat diagrammatic and fragmentary in character, illustrating conditions of fibers when the base fabric is impregnated with a treating solution.

FIG. 2 is also a magnified schematic cross-sectional view, illustrating the structure of leatherlike material of the present invention, wherein the base fabric has been bound and entirely covered with the microporous, water-insoluble polyvinyl formal resin and the other polymer consolidated after the course of fourth step of the invention.

FIG. 3 is a diagrammatic side elevational view of an apparatus suitable for carrying out the process of the present invention.

FIGS. 4 and 5 are diagrams showing the relation between time elapsed from impregnation of water and water content with respect to insoles manufactured from the leatherlike material of the present invention and those in the market.

FIG. 6 is a perspective view, with a part broken away, of an ordinary shoe for gentlemen.

FIG. 7 is a vertical cross-sectional view of the shoe shown in FIG. 6.

Important characteristics called for by a base fabric to be employed in preparing the leatherlike material according to the process of the present invention are:

1. its thickness and strength sufficient to impart to the resulting leatherlike material durability, including resistance to tearing, repeated flexing and abrasion, and further its appropriate void content; and

2. its excellent adhesivity or compatibility to polyvinyl acetal.

As structural fibers of the base fabric, effectively applicable are natural fibers such as cotton, silk, wool and the like, artificial fibers such as cellulose acetate fibers, viscose rayons, cupra and the like, and synthetic fibers consisting of such a polymer as polyacrylonitrile, polyamide, polyester, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyolefin and the like. In particular, polyamide fibers such as nylon-6, nylon-66 and the like, polyvinyl alcohol fiber what is called Vinylon or the like and viscose rayon are suitable among the others.

It is desirable that the structure of the base fabric has a large content of void spaces and from this point of view, nonwoven fabrics such as web and batt, pile fabrics with projecting filaments, napped fabrics, terry, plush and the like are advantageously applicable.

In the first step of the process of the present invention, the aforementioned base fabric which has been relevantly prepared and selected is impregnated with an aqueous solution containing water soluble polyvinyl acetal as its principal ingredient. The treating solution i.e., and above-mentioned aqueous solution can be prepared in the following manner. An aqueous solution of polyvinyl alcohol is admixed with aldehydes such as formaldehyde, acetaldehyde, butylaldehyde, glyoxal, benzaldehyde and the like, and acids such as hydrochloric acid, sulfuric acid, hydrobromic acid, phosphoric acid, trichloroacetic acid, organic sulfonic acids and the like, to acetalize the polyvinyl alcohol. When the degree of acetalization has reached a range of 10- 30 percent by mole, an alkali is added to the reaction mixture to stop the reaction and water-soluble polyvinyl acetal, in this instance, a partially acetalized product of polyvinyl alcohol results. An aqueous solution of the thus obtained water-soluble polyvinyl acetal can be used as the above-mentioned treating solution, to which a catalyst for acetalization comprising aldehydes and the above-mentioned acids or their salts, a pore forming agent such as starch, dextrine and the like, or a coloring agent is incorporated, if required.

The treating solution may be applied to the base fabric by any conventional method, such as pad-squeezing, doctor coating, roll coating, brush coating and spraying. The application or impregnation of the solution may be effected from one side or both sides of the fabric. Generally, the amount of the solution adhered to the fabric is preferably 10- 20 percent by weight of its solid ingredients based on the weight of fabric, and more preferably 20- 100 percent by weight, although it differs according to the kind of fabric or its outlets;

The first step wherein the base fabric is impregnated with the treating solution, is successively followed by the second step in which the fabric is heated to promote acetalization of the polyvinyl acetal which has been applied to the fabric in the preceding step, up to a degree of acetalization of 30- 85 percent by mole, preferably 50- 75 percent, whereby the polyvinyl acetal is consolidated to form a microporous and water-insoluble polyvinyl acetal resin of a unitary three dimensional network in the base fabric. The heating is conducted preferably at a temperature of 50.degree.-130.degree. C., more preferably of 70.degree.-100.degree. C. As a manner of heating, either dry heating or steam heating may be adoptable and in general, the latter is more preferable. A heating period can be determined appropriately according to the temperature as well as the heating manner.

The fabric thus heat treated in the second step as mentioned above may be neutralized, washed to extract excess aldehydes, catalysts for acetalization, other water soluble substances and nonreacted substances therefrom, squeezed and dried, if required.

The method of thus forming the aqueous insoluble polyvinyl acetal in and over the base fabric in the manner mentioned above will be illustrated hereafter with reference to the accompanying diagrammatic drawings.

In FIG. 1, structural fibers 1 are impregnated with treating solution 2. If such a fabric is subjected to a heat treatment, then as is shown in FIG. 2, insolubilized and consolidated acetalized product 3 having a microporous structure is formed therein, adhering to and entirely covering the structural fibers 1 as a unitary three dimensional network. The acetalized resinous product 3 extends from the surface of the structural fibers 1 towards void spaces formed among structural fibers, interconnecting adjacent structural fibers and occupies a part of said void spaces forming pores or cavities 4. The acetalized resinous product 3 now formed is water insoluble, comparatively hydrophilic and extremely microporous and which composes a unitary three dimensional network extending on and along the structural fibers. Accordingly, the product resulting from the aforementioned second step exhibits excellent water and moisture absorbability as well as moisture exhalability and furthermore displays superior water retentiveness and air permeability due to its numerous pores or cavities 4.

Now, the third step of the present invention will be described in details hereafter.

The product manufactured by the foregoing two steps may have its top surface buffed or abraded, or may be sliced or pressed so as to be as thick as is desired, by an appropriate method prior to being subjected to the third step. As preferable resins to be applicable for the preparation of the treating liquid used in the third step, mention may be made of: addition polymers such as acrylic and vinylic polymers; condensation polymers such as polyamides, polyesters, polyurethanes and the like; synthetic rubbers such as styrene/butadiene rubber, nitrile/butadiene rubber and the like; and natural rubber. Furthermore, materials for producing condensation resins, for instance, prepolymers of such condensation resins as a urea-formaldehyde resin, melamine-formaldehyde resin, phenols-formaldehyde resin and the like are also preferably applicable for the preparation of the treating liquid. Latex, and solution in organic solvent, of polyurethanes, polyacrylonitrile, polyacrylic acid esters, polyamides or polyvinyl chloride, and aqueous solution of precondensate of melamine-formaldehyde are especially preferable among the others.

The above-mentioned resins and their materials can be used either solely or in combination of more than one, in the form of emulsion, aqueous solution or solution in organic solvent according to their characteristics. Moreover, to the treating liquid, if required, other additives may be added, for instance: plasticizers such as butyl lauryl phthalate, butyl phthalyl butyl glycolate, dibutyl phthalate, diethyl phthalate, di-2-ethyl hexyl phthalate, dimethyl phthalate, di-n-octyl phthalate, tricresyl phosphate, ethylene glycol, glycerine and the like; catalysts for condensation reaction such as hydrochloric acid salts of organic amine, magnesium chloride, zinc nitrate, ammonium chloride and primary ammonium phosphate; coloring agents; softening agents; and hardening agents.

To impregnate the sheet material which has been obtained in the aforementioned two steps with the treating liquid, all of the same manners as applicable to the first step are also applicable to the third step.

The sheet material which has been treated in the third step is then subjected to the fourth step, wherein said sheet material is heated preferably at 50.degree.- 180.degree. C., although the suitable heating temperature varies depending upon characteristics of the resin impregnated to the material in the foregoing step. According to the fourth step, the applied resin covers the surface of the aforementioned polyvinyl acetal resin which uniformly exists in and extends over the base fabric, whereby interconnection or conjunction of structural fibers is secured, resulting in a tenacious and tough leatherlike material, which retains appropriate air and moisture permeability.

An amount of the resin to be fixed onto the sheet material in the fourth step is preferably 5- 100 percent by weight based on the weight of the base fabric and more preferably 10- 50 percent by weight, although the above stated preferable range may somewhat vary according as the kinds of resin and intended outlets of the product. At the above-mentioned heat treatment in the fourth step, the sheet material may be pressed on a cylinder heating apparatus or compressed by and between two hot plates under a pressure of 3- 20 kg./cm..sup.2, simultaneously with heating.

The aforementioned first to fourth steps can be carried out continuously and its embodiment will be illustrated with reference to the drawing. Referring now to FIG. 3, base fabric 5 is passed through a first saturator 6, impregnated with treating solution 7 and squeezed by squeeze rolls 8 to control the pickup. During its travel in steamer 9, the fabric is subjected to a heat treatment, then squeezed again by squeeze rolls 10 to remove an excess treating solution, fed into washer 11 consisting of first washing bath 12 and second washing bath 13, wherein the fabric is successively washed, and squeezed by squeeze rolls 14. The fabric which has been thus through the first and second steps of the invention, is continuously subjected to the third step, wherein it is led into a second saturator 15 to impregnate with treating liquid 16, squeezed by squeeze rolls 17 to regulate the pickup and wound up on a roll by a batch-up device 18. Thus processed and batched-up sheet material is then subjected to the fourth step of heating with or without pressing according as its contemplated outlets. In conventional methods for manufacturing manmade leathers, their process and steps have been so complicated that they have been difficult to carry out continuously, while according to the process of the present invention, a continuous process can be readily realized utilizing conventional equipments and machineries.

Leatherlike materials thus manufactured are extremely excellent, compared with conventional manmade leathers, in air and moisture permeability, strength and toughness, and moreover do not provide any wearing discomfort or dew formation, so that they are suitable broadly for insole, sole pad, vamp, quarter lining and toe lining for shoe, wall lining, motor-car panelling, substrate for synthetic leather, etc.

The fifth step of the process of the invention will be explained hereafter. In this step, resin is applied onto the surface of the sheet material which has been prepared by and through the foregoing four steps and which is used as a substrate in the instant step, to form a grain side layer on the top side thereof. Resins to be employable to form the grain side layer are: synthetic polymers such as polyurethanes, polyamides and vinyl polymers; synthetic rubbers such as styrene/butadiene rubber, nitrile/butadiene rubber and the like; artificial resins such as cellulose acetate, cellulose nitrate and the like; and natural resins such as natural rubber. A treating liquid in the form of emulsion, aqueous solution or solution in organic solvent, of the above-mentioned resin is prepared, using the resin either solely or in combination of more than one, and which treating liquid is applied and coagulated on the top side of the substrate which has been obtained by the aforementioned four steps, to form a grain side layer thereupon. The kinds and amount of the resin to be applied may be properly selected and determined according to the kinds of structural fibers, the texture of base fabric, the kinds of resin employed in the third step, outlets of product and the type of machinery. To apply the liquid of resin onto the substrate, doctor coating, roll coating or any other conventional coatings are employable.

Leatherlike materials thus obtained have its flesh side and grain side layers resembling natural leathers and moreover, exhibit excellent moisture absorptivity, moisture exhalability, air permeability and hands comparable to natural leathers, so that they are suitable broadly for coats, chair coverings, bags, shoe uppers, wall materials, etc.

One of the most important applications of the leatherlike material of the present invention is insole and linings of shoe, which will be described in more detail. A shoes having its insole and linings composed of the leatherlike material of the present invention can provide its inner surface with microporous polyvinyl acetal resin layers having exceedingly numerous micropores therein, so that it exhibits highly intensified capillary action with the aid of the hydrophilic properties inherent to the polyvinyl acetal resin. Furthermore, the sheet material of the present invention possesses appropriate strength even if it absorbs water and therefore, in case it absorbs a lot of sweat, it can keep its original configuration unchanged. Thus an improved shoe providing an excellent wearing comfort with dry feel and having a light weight, as well as a compact size can be manufactured by employing the sheet material of the present invention as the insole and inner linings. Moreover, it is further an important advantage of the present invention that the process of the invention permits the rapid and economical production of continuous lengths of the sheet material in any desired width, is relatively easy to control and consistently yields a high quality product.

Especially important properties of the sheet material with respect to its utility as a shoe material are as follows:

1. Since it has a strong capillary action, sweat is rapidly absorbed and spread out in a broad range, so that a wearing comfort such as dry feel is retainable even under perspiration.

2. Since the absorbed sweat is rapidly spread out broadly as mentioned above so that the contact surface of the sweat with air, namely the surface area of the sweat is rapidly increased and evaporation of the sweat is accelerated, taking a latent heat out of the environment of the foot, whereby cooling the foot and keeping it dry.

3. The material has a highly increased water retentiveneness and an extremely small so-called equilibrium moisture regain at 25.degree. C., 65 percent R.H. as compared with conventional shoe materials, so that it has considerably increased capacity for absorbing sweat. Accordingly, even one who has a plenty of perspiration can keep one's feet in dry condition and feel.

4. In case the shoe is used on a rainy day and is quite wet, it can be dried up within a comparatively short period, for instance, overnight.

The above mentioned advantages and outstanding features of the present invention are further evidenced by the following comparative experimentations.

Equilibrium moisture regains at 25.degree. C. and 65 percent R.H., and percent saturated waters based on the weight of the sheet material with respect to the sheet material manufactured by the process of the present invention and those available in the market are given in table 1. It can be clearly understood from the experimental data given in table 1 that the insole of the present invention has a remarkably large capacity of absorbing water among all others, as was described in the above feature 3. ##SPC1##

Further, experimental data in relation to the water absorbing rate of sheet material, that is, heights (mm.) of water absorbed at a certain time (second) after the bottom end of the sheet material set upright is dipped in water are given in table 2, from which it is now clear that the material prepared according to the process of the invention is far superior to any of the conventional materials or even to the natural leather, in absorbed amount as well as absorbing time. ##SPC2##

In FIG. 4 of the attached drawings, the diagram shows water exhaling abilities with respect to insole H of the present invention, that F of natural leather, those A, B and C of regenerated material which are available in the market and those D and E of synthetic leather also available in the market, which were determined by the following manner:

Each specimen having a size of 100 mm..sup.2 taken from the above mentioned insoles was entirely soaked in water at 20.degree. C. for 24 hours, taken out of water and squeezed to remove excess water therefrom. The specimen was then allowed to stand in an atmosphere at 15.degree. C. and 65 percent R.H. under atmospheric pressure and change of water content in the insole according to elapsed time was measured. As is apparent from the diagram, the excellency in water exhaling ability of the product of the invention is evidenced by the fact that the line H relating to the insole of the present invention has the largest inclination among the other lines.

FIG. 5 shows the same lines indicating the water content with respect to the above mentioned insoles as shown in FIG. 4, being somewhat rearranged only with their parts below a water content of 67 percent. Thus, lines A, D and B show water exhaling abilities of the corresponding insoles A, D and B beginning at their respective water content of 40 percent, 36 percent and 53 percent, and each of the beginning points is made to accord with the point of the same value of water content on the line H for the purpose of comparison with each other. As is clearly understood from FIG. 5 above, the leatherlike material of the present invention is extremely superior in water exhaling ability to any other conventional materials. Accordingly, the materials of the invention can provide shoes having such a wearing comfort that even though they are wet with water on a rainy day, they can be dried thoroughly by standing overnight and worn comfortably again on the next morning.

Moreover, from those diagrams shown in FIGS. 4 and 5 features the outstanding feature and merit of the invention as already described hereinbefore are clear, i.e. that absorbed sweat is rapidly spread out broadly and evaporation of the absorbed sweat is commenced instantaneously and rapidly, so that a latent heat of evaporation is taken out of an environment adjacent to the foot, thereby cooling the foot, preventing its further perspiration and keeping it in a dry and sanitary condition.

FIGS. 6 and 7 show a structure of an ordinary shoe for gentlemen, wherein between outsole 110 and circumference of slipsole 111, toe cap 112, vamp 113, counter 114, toe lining 116 and quarter lining 117 are tightly fastened and secured at their circumferences. Toe box is indicated as 115. Insole or inner sole 118 is placed upon the slipsole 111, heel pad 119 is superimposed upon a heel portion, 120 is a lace and 121 indicates a surface of the insole which is to be in contact with a foot. A leatherlike material of the invention having a continuous microporous structure comprising polyvinyl acetal, specifically polyvinyl formal may be employed to constitute at least a part of the insole 118 of the shoe as illustrated above, and further is applicable to form the toe lining 116, quarter lining 117, heel pad 119 or a sole pad (not shown in FIGS. 6 and 7).

The microporous resin of which the leatherlike material of the present invention is composed has numerous fine projections, such as coralline branches, on the surface of its pore, so that it exhibits an increased void content as well as a tremendously large surface area per unit volume. Thus the particular microstructural feature of the resin as such, greatly enhances the effects and merits of the leatherlike material of the present invention.

The examples which follow are given for the purpose of illustrating the invention in more detail but are not to be construed as limitative or as indicating that the products obtained are fully equivalent.

Determinations of moisture absorptivity, moisture exhalability and water content were conducted as follows:

1. Moisture absorptivity

A specimen was conditioned in an atmosphere having 65 percent R.H. at 20.degree. C. for 24 hours and its weight W.sub.1 was determined. The thus conditioned specimen was allowed to absorb moisture in a moist atmosphere having 100 percent R.H. at 30.degree. C. for an arbitrary period of time and its weight W.sub.2 was weighed. Then the moisture absorptivity of the specimen is given by the following equation:

2. Moisture exhalability

A specimen was allowed to stand in an atmosphere having 100 percent R.H. at 30.degree. C. for 24 hours and its weight W.sub.3 was determined. The thus treated specimen was placed in an atmosphere having 65 percent R.H. at 20.degree. C. for an arbitrary period of time and its weight W.sub.4 was determined. The moisture exhalability of the specimen is calculated according to the following equation:

3. Water content

A specimen having an initial weight of W.sub.5 was soaked in water at 20.degree. C. for 24 hours, taken out of the water and after removing excess water from its surface, the weight W.sub.6 of the wet specimen was determined. Then the water content is calculated according to the following equation:

4. Moisture permeability or water vapor permeability

The moisture permeability was determined in accordance with JIS (Japanese Industrial Standard) K6549-1965.

5. stiffness in flexure

The stiffness in flexure of the product of the invention was measured by the tentative method designated in ASTM-D-747-58T.

The word "part" used in the examples means "part by weight," unless otherwise indicated.

EXAMPLE 1

A web having a thickness of 6 mm. and a weight of 700 g./m..sup.2 which had been prepared from nylon-6 staples of 1.5 denier having fiber length of 38 mm. was employed as a base fabric. Prior to the first step of the process of the invention, a water soluble formalized product of polyvinyl alcohol having a degree of formalization of 20 percent by mole was prepared with a polyvinyl alcohol having an average degree of polymerization of 1,500, formaldehyde and sulfuric acid, and then a treating solution consisting of 40 parts of 10 percent solution of the above obtained formalized product of polyvinyl alcohol, 6 parts of formaldehyde of an industrial grade having its concentration of 37 percent, 5 parts of sulfuric acid of an industrial grade having its specific gravity of 50.degree. Be and 15 parts of water was prepared in advance.

Into the above treating solution soaked was the aforementioned base fabric, which was then squeezed so as to retain the treating solution of 5 times the weight of fabric, passed through a steamer having its effective heating length of 10 meters in which the fabric was steamed at 100.degree. C. for 10 minutes and subjected successively to rinsing, washing and dehydrating. The amount of the formalized polyvinyl alcohol consolidated and adhered onto the fabric was 32 percent by weight based on the base fabric.

The fabric thus treated in the foregoing two steps, i.e., the first and second steps, was transferred to the third step, wherein it was led and soaked into a treating liquid composed of 20 parts of Beckamin PM (a trade name of a material of resin, containing 80 percent of nonvolatile ingredients and comprising trimethylol melamine as its principal component, manufactured by Dainihon Ink Kogyo K.K.), 4 parts of Catalyst C-376 (a trade name of a catalyst for condensation reaction of Beckamin PM, comprising an organic amine salt and containing 30 percent of nonvolatile ingredients, manufactured by Dainihon Ink Kogyo K.K.) and 80 parts of water, impregnated with 100 percent by weight of the treating liquid based on the fabric and subjected to 5 minute cure at 130.degree. C. in the fourth step. The amount of the resin further adhered onto the fabric in the third and fourth steps was 16 percent by weight based on the fabric.

Properties of the thus obtained leatherlike material are given in tables 3, 4 and 5, comparing with those of conventional articles wherein comparative instance 1 is for an insole made of tanned natural oxhide, comparative instance 2 for that made of a regenerated leather available in the market, comparative instance 3 for that made of paper board available in the market and comparative instance 4 is for an intermediate product manufactured by the first and second steps in the process of the present invention. ##SPC3## --------------------------------------------------------------------------- TABLE 4

Water content and moisture permeability

Item Water content Moisture (%) permeability Specimen (mg./cm..sup.2 /hr.) __________________________________________________________________________ Example 1 315.0 10.2 Comparative 1 152.6 6.5 Comparative 2 60.9 3.0 Comparative 3 47.8 3.2 __________________________________________________________________________ ##SPC4##

As is apparent from tables 3 and 4 above, the leatherlike material obtained in this example of this invention is extremely high in moisture absorbing and exhaling abilities, water absorbability and water vapor permeability as compared with conventional manmade leathers prevailing in the market and moreover, exhibits rather greater values of those properties than natural leathers. Furthermore, although the leatherlike material prepared by all four steps of the process of the invention shows a slight decrease with respect to the water absorbability and water vapor permeability, yet it exhibits a considerable improvement in all other mechanical properties, as compared with the intermediate product prepared by only the first and second steps of the process of the invention, so that the utility of the leatherlike material of the present invention is greatly improved.

The leatherlike material manufactured according to the process as described in example 1 is suitable for insole and sole pad of shoes, wall linings, motor car panellings and the like.

EXAMPLE 2

The intermediate prepared in example 1 was impregnated with 40 parts of an emulsion (comprising 40 percent of solid component) of an acrylonitrile/acrylic acid butyl ester copolymer and 60 parts of water and squeezed to retain 100 percent by weight of the treating solution based on the fabric, as the third step of the process of the invention. As the fourth step, the impregnated fabric was subjected to a 3-minute hot press on a hot pressing machine at a surface temperature of 150.degree. C. and with a pressure of 4 kg./cm..sup.2, followed by drying. The amount of the resin adhered and fixed onto the fabric in this step was 16 percent by weight based on the fabric.

The top surface of the resultant sheet material was thereafter abraded and a leatherlike material having its thickness of 2 mm. was obtained. Properties of the obtained leatherlike material were as follows:

Water absorbability (%) 296 Moisture permeability (mg./cm..sup.2 /hr.) 9.6 Tensile strength at break in dry state (kg./mm..sup.2) 1.16 Elongation at break in dry state (%) 58 Tensile strength at break in wet state (kg./mm..sup.2) 1.09 Elongation at break in wet state (%) 68.0 Tearing strength in dry state (kg./mm.) 3.3 Stiffness in flexure in dry state (cm.g.) 140

The resultant leatherlike material had desirable properties for insoles, sole pads, side linings, quarter linings and toe linings of shoes.

EXAMPLE 3

The leatherlike sheet material manufactured in example 2 was sliced into sheets of 1 mm. thick, and which sheets were employed as substrates to be subjected to the fifth step according to the process of the present invention.

A colored treating liquid which had been prepared by admixing a black toner (a pigment paste) with Crisvon (a trade name of a N,N-dimethylformamide 30 percent solution of polyurethane of 35 percent ester type, manufactured by Dainihon Ink Kogyo K.K.) was applied to the top surface of the above-mentioned substrate by 0.6 mm. thick by means of a roll coater. Then the coated sheet was introduced into water and the liquid applied thereupon was coagulated and solidified to form a grain side layer. The sheet was thereafter subjected to a drying process, followed by an embossing process whereby a leatherlike superficial appearance was imparted to the product. The amount of resin adhered onto the substrate in the fifth step was 14 percent by weight based on the substrate.

Properties of the resultant leatherlike sheet material were as follows:

Water absorbability (%) 210 Moisture permeability (mg./cm..sup.2 /hr.) 4.0 Tensile strength at break in dry state (kg./mm..sup.2) 1.8 Elongation at break in dry state (%) 63

It had often happened in conventional manmade leathers that their grain side layer was readily split off the substrate, while since the grain side layer of the above manufactured sheet material of the invention had been bonded fastly to the substrate, as a matter of fact, it was impossible to split them off. The leatherlike sheet material thus obtained exhibited hands and feels resembling those of natural leathers, and suitable for shoe uppers, bags, chair coverings and the like.

EXAMPLE 4

A terry composed of polyamide staples having a cut length of 5 mm. was employed as a base fabric. Prior to the first step of the process of the invention, a water soluble formalized product of polyvinyl alcohol having a degree of formalization of 22 percent by mole was prepared with a polyvinyl alcohol having an average degree of polymerization of 1700 , and then a treating solution consisting of 40 parts of 10 percent solution of the above obtained formalized product of polyvinyl alcohol, 6 parts of formaldehyde of an industrial grade having its concentration of 37 percent, 5 parts of sulfuric acid of an industrial grade having its specific gravity of 50.degree. Be and 15 parts of 5 percent aqueous solution of potato starch was prepared in advance. Into the thus prepared treating solution soaked was the aforementioned base fabric which was then squeezed so as to retain 500 percent by weight of the treating solution based on the fabric, passed through a steamer having its effective heating length of 10 meters in which the fabric was steamed at 100.degree. C. for 7 minutes and subjected successively to rinsing, washing and dehydrating.

The fabric thus treated in the foregoing two steps, i.e., the first and second steps, was subjected to the third step wherein it was soaked in a treating liquid composed of 100 parts of Hydran F-24 (a trade name of a water soluble polyurethane resin, containing 30 percent of nonvolatile ingredients, manufactured by Dainihon Ink Kogyo K.K.), 10 parts of Beckamin PM, 2 parts of Catalyst C-376 and 300 parts of water, squeezed so as to retain 100 percent by weight of the treating liquid based on the fabric, followed by the fourth step wherein the fabric was cured at 130.degree. C. for 5 minutes.

In the fifth step, on the top surface of the resultant sheet material applied was a treating liquid consisting of 100 parts of 30 percent N,N-dimethylformamide of S-lec BH-2 (a trade name of a polyvinyl butylal resin having an average degree of polymerization of 1600 and an average degree of butylalization of 65 percent, manufactured by Sekisui Kagaku Kogyo K.K.) and 10 parts of butyl phthalyl butyl glycolate, in the same manner as in the fifth step of example 3, to form a grain side layer on the sheet material. The thus obtained leatherlike material had its properties as follows:

Water absorbability (%) 235 Moisture permeability (mg./cm..sup.2 /hr.) 4.2 Tensile strength at break in dry state (kg./mm..sup.2) 1.6 Elongation at break in dry state (%) 58

The resultant leatherlike material exhibited appropriate softness and preferable hands and was suitable for clothings such as a coat, chair coverings and bags.

Claims

What is claimed is:

1. A leatherlike sheet material comprising a base fabric, a resin adhering to and entirely covering the structural fibers of said fabric, said resin consisting essentially of microporous water-insoluble poly(vinyl formal) in the form of a porous unitary three-dimensional network in the fabric in a ratio by weight of poly(vinyl formal) to fabric of 1:10 to 2:1 and a continuous layer of at least one polymer selected from the group consisting of polyurethane, polyacrylonitrile, poly(acrylic ester), polyamide, and melamine-formaldehyde polymer in an amount of the polymer of 5- 100 percent by weight based on the weight of the fabric covering the surface of said resin, said material being produced by impregnating said base fabric with an aqueous solution containing a water-soluble poly(vinyl formal) having an average degree of formalization of 10- 30 mole percent, heating the impregnated fabric to 50.degree. to 130.degree. C. to increase the formalization of said poly(vinyl formal) to yield a microporous, water-insoluble poly(vinyl formal) having an average degree of formalization of 50- 75 mole percent and then impregnating the resultant fabric with at least one of said polymers.

2. A leatherlike material as claimed in claim 1, wherein the base fabric has a large content of void spaces formed among its structural fibers and said poly(vinyl formal) resin extends from the surface of the structural fibers towards said void spaces, interconnecting adjacent structural fibers.

3. A leatherlike material as claimed in claim 1, wherein the base fabric comprise its structural fibers which are compatible to the poly(vinyl formal) resin. 4. A leatherlike material as claimed in claim 1, wherein the base fabric comprise structural fibers consisting of a fiber forming material selected from the group consisting of nylon-6, nylon-66,

polyvinyl acetal and regenerated cellulose. 5. A leatherlike material as claimed in claim 1, wherein the base fabric consists of nonwoven fabric,

pile fabric with projecting filaments, napped fabric, terry or plush. 6. A leatherlike material as claimed in claim 1, wherein the ratio by weight of

said poly(vinyl formal) resin to said base fabric is 1:5 to 1:1. 7. A leatherlike material as claimed in claim 1, wherein the amount of the said resin is 10-50 percent by weight based on the weight of the base fabric.

A leatherlike sheet material as claimed in claim 1, wherein the fabric bound with the said poly(vinyl formal) resin and said polymer has a grain side layer superimposed on a surface thereof comprising a resin selected from synthetic polymers, synthetic rubbers, regenerated cellulose and natural resins, the grain side layer being formed by further applying and coagulating a liquid containing the resin on the fabric after the curing

step. 9. A leatherlike sheet material as claimed in claim 8, wherein resin

forming the grain layer is a polyurethane or poly(vinyl butyral). 10. A shoe made at least in part of the leatherlike sheet material of claim 1.

. A process of making a leatherlike sheet material as claimed in claim 1, which comprises: (1) first step of impregnating a base fabric with an aqueous solution containing water soluble polyvinyl acetal, (2) second step of heating the impregnated fabric at 50.degree.-130.degree. C. to promote acetalization of said polyvinyl acetal, whereby resulting a microporous and aqueous insoluble polyvinyl acetal resin adhering to and entirely covering the structural fibers of said fabric, (3) third step of further impregnating the resultant fabric with liquid containing emulsion or solution of at least one resin different from polyvinyl acetal selected from the class consisting of synthetic resins and natural resins and (4)

fourth step of curing the resin impregnated fabric. 12. A process of making a leatherlike sheet material as claimed in claim 1, which comprises: (1) first step of impregnating a base fabric with an aqueous solution containing water soluble polyvinyl acetal, (2) second step of heating the impregnated fabric to 50.degree.- 130.degree. C. to promote acetalization of said polyvinyl acetal, whereby resulting a microporous and aqueous insoluble polyvinyl acetal resin adhering to and entirely covering the structural fibers of said fabric, (3) third step of further impregnating the resultant fabric with liquid containing emulsion or solution of at least one resin different from polyvinyl acetal selected from the group consisting of synthetic resins and natural resins, (4) fourth step of curing the resin impregnated fabric and (5) applying liquid containing at least one resin selected from the class consisting of synthetic resins and natural resins on at least one surface of the sheet material obtained by the preceding steps, whereby forming a grain side

layer thereupon. 13. A process as claimed in claim 11, wherein the base fabric has a large content of void spaces formed among its structural

fibers. 14. A process as claimed in claim 11, wherein the water soluble polyvinyl acetal has an average degree of acetalization of 10- 30 percent

by mole. 15. A process as claimed in claim 11, wherein the aqueous solution further contains catalyst for acetalization comprising aldehydes

and acids or their salts. 16. A process as claimed in claim 11, wherein the aqueous solution further contains catalyst for acetalization and a

pore forming agent. 17. A process as claimed in claim 11, wherein the base fabric is impregnated with the aqueous solution in an amount of 10- 200 percent by weight of its solid ingredients based on the weight of the

fabric. 18. A process as claimed in claim 11, wherein the base fabric is impregnated with the aqueous solution in an amount of 20- 100 percent by

weight of its solid ingredients based on the weight of the fabric. 19. A process as claimed in claim 11, wherein the heating temperature in the

second step is in the range of 70.degree.- 100.degree. C. 20. A process as claimed in claim 11, wherein the heating in the second step is conducted for a period of time sufficient to promote the average degree of acetalization of the polyvinyl acetal which has been applied to the fabric

in the preceding step, up to 30- 85 percent by mole. 21. A process as claimed in claim 11, wherein the heating in the second step is conducted for a period of time sufficient to promote the average degree of acetalization of the polyvinyl acetal which has been applied to the fabric

in the preceding step, up to -50- 75 percent by mole. 22. A process as claimed in claim 11, wherein the heating in the second step is effected by

steaming. 23. A process as claimed in claim 11, wherein the sheet material which has been processed in the first and second steps is rinsed and

washed prior to the third step. 24. A process as claimed in claim 11, wherein the resin employed in the third step is selected from the group consisting of latex, polyurethanes, polyacrylonitrile, polyacrylic acid esters, polyamides, polyvinyl chloride and melamine-formaldehyde polymer.

5. A process as claimed in claim 11, wherein the curing in the fourth

step is effected at a temperature of 50.degree.-180.degree. C. 26. A process as claimed in claim 11, wherein the curing in the fourth step is effected by means of hot pressing under a pressure of 3- 20 kg./cm..sup.2.

7. A process as claimed in claim 11, wherein the said sequential four steps are carried out continuously.