US3869310A

US3869310A - Flexible sheet materials

Info

Publication number: US3869310A
Application number: US311130A
Authority: US
Inventors: Osamu Fukushima; Kunio Kogame; Masami Sato
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 1969-04-02
Filing date: 1972-12-01
Publication date: 1975-03-04
Anticipated expiration: 1992-03-04
Also published as: GB1300846A; DE2016522B2; BE748417A; NL7004683A; DE2016522A1; FR2038188A1; CA927223A; FR2038188B1

Abstract

A leather-like sheet material is manufactured by forming a nonwoven fibrous mat of mixed-spun fibers consisting of at least two polymeric materials, impregnating the mat with a liquid which is a solvent for at least one of the polymeric materials but is a non-solvent for the other polymeric materials and dissolving out at least one of the polymeric materials, and coagulating the resulting polymer solution with another liquid which is a nonsolvent for all of the polymeric materials constituting initially the fibers but is at least partially miscible with the liquid used for the prior impregnation of the mat into a porous polymeric structure.

Description

llnite States Patent [191 Fulrushima et a1.

FLEXIBLE SHEET MATERIALS Inventors: Osamu Fukushima; Kunio Kogame; Masami Sato, all of Kurashiki, Japan Assignee: Kuraray Co., Ltd., Kurashiki, Japan Filed: Dec. 1, 1972 Appl. No.: 311,130

Related U.S. Application Data Continuation of Ser. No. 22,390, March 24, 1970, abandoned,

Foreign Application Priority Data Apr. 2, 1969 Japan 44-25781 Apr. 24, 1969 Japan 44-32082 Apr. 26, 1969 Japan 44-32463 References Cited UNITED STATES PATENTS 1/1956 Gibson 161/150 1 Mar. 4, 1975 3,344,013 9/1967 Fahrbach 161/150 3,400,042 9/1968 Riedesel 161/170 3,427,179 2/1969 Dairs l61/D1G. 2 3,483,015 12/1969 Fukushima 117/63 3,510,390 5/1970 Bjorksten..... 156/314 3,574,523 4/1971 Hudson 161/170 3,647,591 3/1972 Morris 16l/D1G. 2

Primary Examiner-George F. Lesmes Assistant E.raminer-Ellis P. Robinson Attorney, Agent, or FirmStevens, Davis, Miller & Mosher [57] ABSTRACT A leather-like sheet material is manufactured by form ing a non-woven fibrous mat of mixed-spun fibers consisting of at least two polymeric materials, impregnating the mat with a liquid which is a solvent for at least one of the polymeric materials but is a non-solvent for the other polymeric materials and dissolving out at least one of the polymeric materials, and coagulating the resulting polymer solution with another liquid which is a non-solvent for all of the polymeric materials constituting initially the fibers but is at least partially miscible with the liquid used for the prior impregnation of the mat into a porous polymeric structure.

12 Claims, No Drawings ll FLEXIBLE SHEET MATERIALS This is a continuation of application Ser. No. 22,390, filed Mar. 24, 1970, now abandoned.

The present invention relates to producing of flexible sheet materials.

It has been proposed to produce flexible sheet materials by impregnating a non-woven fibrous mat with a polymer solution and coagulating the polymer solution by a wet process to deposit the polymer.

It would be possible to produce a relatively flexible product by the proposed method. However, it is difficult to produce a product having a satisfactory flexibility, a high substantialness and improved physical properties by the proposed method. Because, in order to obtain the product having flexibility and substantialness, it is required that the fibers are fine and that a sufficient amount of polymer is deposited uniformly in porous structure, however, it is difficult to form a non-woven fibrous mat with fibers of fine denier and further to impregnate the non-woven fibrous mat with a sufficient amount of polymer solution in view point of restriction of the concentration and viscosity of the polymer solutlon.

It is an object ofthe present invention to provide flexible sheet materials, particularly leather-like sheet materials having a satisfactory flexibility, a high substantialness and improved physical properties, and to pro vide a method for producing the same.

The sheet material of the present invention comprises; non-woven fibrous mat and polymeric impregnant, the mat comprising fibers consisting of a bundle of ultrafine fibers which are preferably bonded each other by themselves and/or fibers having a large number of cells inside. said fibers having initially been mixed-spun fibers which consist of at least two polymeric materials, the impregnant consisting of polymeric materials, the impregnant having a porous structure and the impregnant being substantially not bonded to said fibers, and the polymeric materials having initially con stituted a part of said individual initial mixed-spun fibers.

The method of the present invention comprises forming a non-woven fibrous mat of mixed-spun fibers made of a mixture of at least two polymeric materials, impregnating the mat with a liquid (called hereafter solvent) which is a solvent for at least one of the polymeric materials constituting the mixed-spun fibers but which is a non-solvent for the other polymeric materials and dissolving out at least one of but not all of the polymeric materials constituting the fibers in the mat, thereby impregnating the mat with the polymer solution which consists of the solvent and the dissolved polymeric material(s), and coagulating the polymer solution into a porous polymeric structure which is substantially not bonded to the fiber by treating the mat with another liquid (called hereafter non-solvent) which is a non-solvent for all of the polymeric materials constituting initially the fibers but which non-solvent is at least partially miscible the solvent with which the mat is impregnated.

The method of the present invention has following features:

The non-woven fibrous mat can be easily impregnated with the solvent by a simple process, e.g., by

pressing the mat in or on a bath containing the solvent or by pouring the solvent onto the mat, without using any particular device for impregnating the solvent and the solvent can be easily purged out to adjust the impregnating-ratio of the solvent, because the solvent containing no polymeric material has usually low viscosity in comparison with the one containing polymeric material.

Furthermore, the fibers are changed into fibers consisting of a bundle of untra-fine fiber or fibers having a large number of cells inside and become flexible without losing the structure as a non-woven fibrous mat, when the soluble component in the mixed-spun fibers was dissolved by the solvent impregnated, and as the result of the above, the resulting sheet material has a very flexible texture. Of course, even if the soluble component is partially dissolved out so as to make the fiber fine in some degree by adjusting the dissolving amount of the polymeric material, the object of the present invention is achieved. However, it is preferred to dissolve out substantially all of the soluble component.

Moreover, according to the present invention, the polymer solution filled uniformly is so coagulated by treatment with the non-solvent that the polymeric material may be uniformly deposited between fibers in a cellular structure. Therefore, it is possible to obtain sheet materials having a substantialness and a flexibility.

The polymeric material to be used in the present invention include;

polyamides, such as nylon'6, nylon-66, nylon-7 and nylon-6,10;

modified polyamides, such as N-alkoxymethylated polyamide;

polyesters, such as polyethylene terephthalate and modified polyesters;

polystyrene;

polyolefins, such as polyethylene, and polypropylene;

polyvinyl chloride;

polyvinylidene chloride;

polyvinyl acetate;

polymethacrylate;

polyvinyl alcohol;

polyacrylonitrile and polyurethane elastomer.

Preferred combinations of polymeric materials having different solubilities for the solvent and solvent are as follows:

polymeric material having different solubilities for the solvent solvent toluene or solution These and other combinations may be selected depending upon the desired final product.

The mixed-spun filament to be used in the present invention may be manufactured by spinning the mixture of at least two ofirneric materials, e. g., as follows:

Chips obtained by melting a blend of at least two polymeric materials and by cooling the melt are melted and he m lt ;ewaqsthreaeh q i s s A mixture of at least two polymeric materials is die te en e ttqs hte h ri i es At least two polymeric materials are dissolved in a suitable common solvent and then the solution are spun by a dry or wet process through orifices. In general, there are few common solvents and the solution of polymeric materials may easily separated into multiple 7 phase, therefore themelt spinning is preferred.

The filament may be drawn, crimped and cut into staple fibers, if necessary. The non-woven fibrous mat may be manufactured by dispersing staple fibers in a liquid, such as water and then dipping up into a lap, or carding staple fibers and blowing off the fibers by air and collecting the fibers onto a base to form a web. Alternatively, the fibrous mat may be formed by collecting irregularly the filament to form a web. The resulting lap or web may be needled through a needle loom to entangle the filaments or fibers in three dimensional network structure and may also be treated with a polymeric emulsion and dried. The use of these non-woven fibrous mat is convenient to obtain a leather-like sheet material, because the fibers are deposited in random. Further, it is desirable in order to obtain sheet materials having improved texture, touch and appearance to deposit the polymers acting as a filler uniformly between the fibers. In addition, by such a means the uniformity of the physical properties ofthe resulting sheets may be improved. V

As the non-solvent, there may be used water, solutions of salts, low molecular weight organic solvents, and mixtures of these non-solvents with a solvent capable of dissolving out the polymeric material. For example, when a non-woven fibrous mat composed of mixed-spun fibers consisting of nylon-6 and polystyrene is used and polystyrene is dissolved out by toluene, meth anol may be used as the non-solvent; when a nonwoven fibrous mat composed of mixed-spun fibers consisting of nylon-6 and polypropylene is used and nylon- 6 is dissolved out by a solution of calcium chloride in methanol, water or a mixture of water and methanol can be used as the non-solvent; and when a non-woven fibrous mat composed of mixed-spun fibers consisting of polyvinyl chloride and polypropylene is used and polyvinyl chloride is dissolved out by dimethylformamide, water, methanol or a mixture of water and dimethylformamide can be used as the non-solvent.

As a process for depositing the dissolved high polymer in the mat, there is such a process that after the polymer is dissolved out in the mat, the solvent for the polymeric material is evaporated and removed to deposit the polymeric material in the mat. However, such a process is not preferable, because the polymeric material migrates to be distributed unevenly and it adheres 4 to the fibers rather than it is deposited between the fibers when the solvent is evaporated so that a heterogeneous sheet having a rigid texture is formed.

After the polymeric material is deposited in the mat by means of the non-solvent, the solvent is washed with the non-solvent and the resulting sheet is dried. The non-solvent used in the washing is washed with water, if necess ary,and thg1 the resulting sheet is dried.

When the non-woven fibrous mat is impregnated with a liquid which is a solvent for at least one of high polymers in the fiber and is a non-solvent for the other high polymers, it is preferable that the non-woven fibrous mat is impregnated with the liquid at such a low temperature that the liquid does not act as a solvent and then the temperature of the liquid is raised up to a temperature at which the liquid acts as a solvent to dissolve out at least one of the polymeric materials of the mixed-spun fiber in the mat. As the temperature of the liquid impregnated is sufficiently low not to dissolve the polymeric material, the soluble components in the fibers are not dissolved in the impregnating step and the viscosity of the liquid does not increase and the liquid can be uniformly impregnated. Accordingly, when the temperatureof the liquid is raised and the soluble component in the fiber are dissolved out, the polymer solution can fill throughout the mat. Moreover, the soluble components in the fiber are not dissolved out in the impregnating step and therefore even if the liquid impregnated is squeezed in order to adjust the ratio of the liquid impregnated, the polymeric material is not lost. Accordingly, a flexible sheet having a substantialness may be obtained, and the liquid recovered by the squeeze does not contain any polymeric materials and may be used again as such.

It is preferable for the production of leather-like articles to use polyamide as the soluble component and a polymeric material having a solubility for the solvent, which is different from that of polyamide, as the other component. In this case, it is also preferred that the non-woven fibrous mat is impregnated with a solvent for polyamide at such a low temperature that the polyamide is not dissolved out, and the ratio of the liquid impregnated is adjusted, after which the mat is heated to dissolve out the polyamide in the mixed-spun fibers between the fibers constituting the non-woven fabric. The low temperature, which can not dissolve out polyamide and the heating temperature suitable for dissolving out the polyamide depend upon the kind of so]- vents (the kind of metal salts, the kind of lower alcohols and the mixing ratio of the metal salt and the lower alcohol); the kind, the composition of polymeric materials constituting the mixed-spun fibers, the dispersed state of each polymeric materials, and the fineness of the mixed-spun fiber; and the apparent density and the thickness ofthe mat. These temperatures may be determined by a preliminary test in every case. Some embodiments, when non-woven fibrous mat having an apparent density of 0.10 and composed of mixed-spun fibers having a fineness of 3 deniers and consisting of 50 parts of nylon-6 and 50 parts of polypropylene, are shown in the following Table 1.

6 Table 1Continued Heating Metal salt Alcohol Metal salt/alcohol lmpregnating temper- (parts by weight) temperature ature do. do. 40/60 lower than at least C 40C CaCl do. 10/90 do. do. do. do. /85 do. do. do. do. /80 lower than do.

15C CaCl .2H,O do. [0/90 lower than at least 50C 60C do. do. 15/85 lower than at least 15C 40C do. do. 20/80 do. do. do. do. 30/70 do. do.

The polyamide to be used in the present invention 1n- EXAMPLE 1 cludes various polyamides, for example, nylon-6 and nylon-66, polycocondensates thereof and modified polyamides.

The component having a different solubility for a sol vent from that of the polyamide includes polyolefms, such as polyethylene and polypropylene, polyesters, such as polyethylene terephthalate and polypivalolactone, and vinyl polymers, such as polyvinyl chloride and polyacrylonitrile.

The solvent for the polyamide includes solutions of metal salts in lower alcohol; fatty acids, such as formic acid and acetic acid, aqueous solutions thereof; inorganic acids, such as sulfuric acid and nitric acid, and aqueous solutions thereof; and phenol series solvents, such as phenol and metacresol. Among then, solutions of metal salts in lower alcohols can be used most advantageously. Lower alcohols, such as methanol, may be. used as a solvent for modified polyamides, such as N- alkoxymethylated polyamide.

The metal salts to be used as the solution in lower alcohol include metal chlorides, such as CaCl ZnCl CuCl LiCl, SnCl, and TiCl,, and their hydrates. The lower alcohol includes CH OH, C H OH, C H OH.

For the coagulation of polyamide, there may be used any non-solvents for both the polyamide and the other components constituting the fiber, e.g., water, aqueous solutions of metal salts, lower alcohols, aqueous solutions of lower alcohols.

As the coagulation bath, use may be made of 5 to 60%, preferably 10 to 45% aqueous solution of the above metal salt, or an aqueous solution containing 5 to 40% of the above metal salt and 5 to 30% of the above lower alcohol. Coagulation is preferably effected by using such baths at a temperature of 10 to 60C for at least 5 minutes, preferably at least 10 minutes. After the coagulation, it is preferred that the salt is removed at 10 to 90C, preferably at 10 to 65C by washing.

When the amounts of metal salt and lower alcohol in the coagulation bath are smaller, the texture of the resulting sheet is rigid and the polyamide cellular structure is not uniform, while when these amounts are larger, the coagulation velocity is too slow and such amounts are not preferable. When the coagulation temperature is lower than 10C, coarse and non-uniform cellular structure is formed. When temperature is higher than 60C, the resulting sheet material has an unfavorable texture. A longer coagulation time is preferable.

The following examples are given in illustration of this invention and are not intended as limitation h f--Psrasssih rs niits s. b w i t.

Mixed-spun fibers having 3 deniers and composed of 50 parts of nylon-6' and 50 parts of polypropylene were crimped and cut and the staple fibers obtained were formed into a web by using an air flow. The web was subjected to a needle punching to obtain a three dimensionally entangled non-woven fibrous mat of 600 g/m The mat was impregnated with a solution consisting of 40 parts of zinc chloride and 60 parts of methanol, which is anon-solvent for polypropylene but is a solvent for nylon-6, at room temperature and the mat thus impregnated was squeezed by a press roll so as to adjust the amount of solution impregnated to 200 g/m he mat thus treated was left to stand for 20 minutes to allow the major part of nylon-6 in the mixed-spun fibers to dissolve out and to make a fibrous mat consisting of fibers which were composed of bundle of ultra-fine fibers of polypropylene and being impregnated with a solution of the nylon-6. Thereafter, the mat was dipped in water at 50C for 20 minutes to coagulate and deposit the nylon-6 solution between the fibers uniformly in cellular polymeric structure and then treated with water at C to remove zinc chloride and methanol and dried.

The resulting sheet was similar to leather in touch and texture and was excellent in tensile strength and tear strength.

EXAMPLE 2 Mixed-spun fibers having 5 deniers and composed of 60 parts of nylon-6 and 40 parts of polyester (polyethylene terephthalate) were crimped and cut and the staple fibers obtained were formed into a Web by using an air flow. The web was impregnated with a polyurethane emulsion in an approximately equivalent amount and dried to form a web having a stable shape. On the web a solution having a temperature of 80C and consisting of 20 parts of anhydrous calcium chloride and 80 parts of methanol, which solution is a non-solvent for polyester but is a solvent for nylon-6, was sprayed by a shower and the web was slightly pressed to allow the web to be impregnated with 400 g/m of the solution, then the web was left to stand at 50C for 5 minutes to dissolve the major part of nylon-6 and to make a fibrous mat consisting of fibers which were composed of bundle of ultra-fine fibers of polyester and being impregnated with a solution of nylon-6. Then, the mat was dipped in water at 50C for 20 minutes to coagulate and deposit the solution of nylon-6 between the fibers uniformly in H cellular polymeric structure and then treated with water at 80C to remove calcium chloride and methanol and dried.

The resulting sheet was similar to leather in touch and texture and had improved physical properties.

EXAMPLE 3 Mixed-spun fibers having 3 deniers and composed of 30 parts of nylon-6 and 70 parts of polypropylene were crimped and cut and the resulting staple fibers were formed into a web by using an air flow. The web was subjected to a needle punching to obtain a three dimensionally entangled non-woven fibrous mat of 400 g/m The mat was impregnated with a solution having a temperature of 50C and consisting of 50 parts of zinc chloride and 50 parts of methanol, which solution is a nonsolvent for polypropylene but is a-solvent for nylon-6, and the mat impregnated was squeezed by a press roll so as to adjust the amount of solution impregnated to 1,000 g/m The mat thus treated was left to stand at 50C for 20 minutes to dissolve out the major part of nylon-6 and to make fibrous mat consisting of cellular polypropylene fibers and being impregnated with a solution of nylon-6. Thereafter, the mat was dipped in water at 50C for 20 minutes to coagulate and deposit the nylon solution in the fibers uniformly in cellular polymeric structure and then treated with water at 80C to remove zinc chloride and methanol and then dried.

The resulting sheet was similar to leather in texture and touch and had improved physicalproperties.

EXAMPLE 4 Mixed-spun fibers having 3 deniers and composed of 50 parts of nylon-6 and 50 parts of polypropylene were crimped and cut. The staple fibers were formed into a web by using an air flow. The web was subjected to needle punching to form a three dimensionally entangled non-woven fibrous mat of 600 g/m The mat was impregnated with a solution consisting of 40 parts of zinc chloride and 60 parts of methanol, which solution is a non-solvent for polypropylene but is a solvent for nylon-6, at 120C and the mat impregnated was squeezed by a press roll so as to adjust the amount of solution impregnated to 1,200 g/m and then was left to stand at 60C for 20 minutes to dissolve out the major part of nylon-6,in the mixed-spun fibers and to make fibrous mat consisting of fibers which were composed of bundle of untra-fine fibers of polypropylene and being impregnated with a solution ofthe nylon-6. Thereafter the mat thus treated was dipped in water at 50C to coagulate and deposit the solution of nylon-6 between the fibers uniformly in cellular polymeric structure and then treated with water at 80C to remove zinc chloride and methanol and then dried.

.-The resulting sheet was similar to leather in touch and texture and had excellent tensile strength and tear strength.

EXAMPLE 5 Mixed-spun fibers having 5 deniers and composed of 60 parts of nylon-6 and 40 parts of polyethylene terephthalate were crimped and out. The resulting staple fibers were formed into a web having 200 g/m by using an air flow and the web was treated with an acrylonitrile emulsion and dried. On the web a solution having a temperature of C and consisting of parts of anhydrous calcium chloride and 80 parts of methanol, which solution is a non-solvent for polyester but is a solvent for nylon-6, was sprayed by a shower and the mat thus treated was slightly pressed so as to adjust the amount of solution impregnated to 400 g/m The mat impregnated was so heated that the temperature of the solution was raised to 60C, whereby the major part of nylon-6 was dissolved out to make a fibrous mat constituted with cellular polyester fibers which mat was impregnated with a solution of the nylon-6. The mat was dipped in water at 50C for 20 minutes to coagulate and deposit the solution of the nylon-6 between the fibers uniformly in cellular polymeric structure and then treated with water at C to remove calcium chloride and methanol and then dried.

The resulting sheet was similar to leather in texture and touch and had excellent properties. I

EXAMPLE 6 A non-woven fibrous mat of 400 g/m having an apparent density of 0. l0 g/cm was prepared from mixedspun fibers composed of 50 parts of nylon-6 and 50 parts of polypropylene and having a fineness of 3 deniers and a length of 51 mm by means of a random webber and a needle loom. The mat was dipped in a bath composed of 20 parts of anhydrous zinc chloride and 80 parts of methanol at 15C to impregnate the mat with the zinc chloride solution in methanol without dissolution of the nylon-6. Thereafter, the mat was squeezed by means of a press roll so that the weight ratio of the mat to the zinc chloride-methanol solution was 1:3. The mat was heated on a hot plate at 60C for 5 minutes to dissolve out the nylon-6 in the mixed-spun fibers between fibers in the mat, and the mat was treated with water at 50C to coagulate the nylon-6 solution, demineralized at 80C, and then dried.

The resulting sheet material was flexible and had an improved substantialness and a leather-like texture and resilience. The sheet had an apparent density of 0.30 g/cm and a strength of 1.5 Kg/mm The sheet did not change the weight from the non-woven fibrous mat prior to the treatment above described, and the polyamide in the mixed-spun fibers was not lost.

EXAMPLE 7 The non-woven fibrous mat used in Example 6 was dipped in a bath kept at 10C and composed of40 parts of anhydrous zinc chloride and 60 parts of methanol to impregante the mat with the solution of zinc chloride in methanol. Thereafter, the mat was squeezed by means of a press roll so that the weight ratio of the mat to the. zinc chloride solution was 1:4. The mat was heated on a hot plate at 50C for 5 minutes to dissolve out the nylon-6 which consists of the mixed-spun fibers into the spaces of the mat, and was then treated with water at 50C to coagulate the nylon-6 solution, demineralized at 80C, and dried. The resulting sheet material did not change the weight from the non-woven fabric prior to the treatment above described, and had substantially the same properties as those in Example When the surface ofthe sheet was ground, the end of fibers were branched into fine fibers having a diameter of about 0.1 to 1p. to form a velour-like surface.

( EXAMPLE 8 A non-woven fibrous mat of 400 g/m having an apparent density of 0.08 g/cm was prepared from mixedspun fibers composed of 60 parts of nylon-6 and 40 parts of polyethylene terephthalate and having a fineness of 5 deniers and a length of 51 mm by means of a random webber and a needle loom. The mat was solution, and then squeezed by means of a press roll so that the weight ratio of the mat to the solution was 1:2. The mat was treated in the same manner as described in Example 6. The sheet material thus obtained had a leather-like appearance, structure and texture, and was excellent in the tensile strength, tear strength and heat resistance. The sheet is applisalaletsria ustaatasgs sash as 99 11..

EXAMPLE 9 and 60 parts of methanol at 10C, and then squeezed by means of a press roll so that the weight ratio of the mat to the solution was about 1:4. The mat was kept at 50C for 10 minutes to dissolve out the nylon-6 from the mixed-spun fibers and to make a fibrous mat composed of ultra-fine polypropylene fibers and impregnated with the solution of the nylon-6.

The mat containing the solution of the nylon-6 was treated in a coagulation bath composed of 30 parts of zinc chloride dihydrate and 70 parts of water at 50C for 30 minutes to coagulate the solution of the nylon-6, demineralized in water at 50C for 30 minutes, further demineralized in water at 80C for 30 minutes while repeatedly pressing, and then dried.

The obtained sheet had a leather-like texture and toughness.

EXAMPLE 10 A random web prepared from mixed-spun fibers composed of 50 parts of nylon-6,6 and 50 parts of polyethylene and having a fineness of4 deniers was formed into a non-woven fibrous mat having a three dimensional network structure by means of a needle loom. The mat was impregnated with a solution composed of 35 parts of calcium chloride, 62 parts of methanol and 3 parts of p-nonylphenol at C, and then squeezed so that the weight ratio of the mat to the solution was 1:5. The mat was kept at 50C for 10 minutes to dissolve out the nylon-6,6 from the mixed-spun fibers, treated in a coagulation bath composed of 50 parts of calcium chloride dihydrate and 50 parts of water at 50C for 30 minutes to coagualate the nylon-6,6 solution and then treated in the same manner as described in Example 9 to obtain a leather-like sheet.

EXAMPLE ll A non-woven fibrous mat was prepared from mixedspun fibers composed of 10 parts of nylon-6, 25% of which were methoxymethylated, 40 parts of nylon-6 and 50 parts of polyethylene terephthalate in the same manner as described in Example 9. The mat was impregnated with a solution composed of 40 parts of calcium chloride dihydrate and 60 parts of methanol at 5C, and then squeezed so that the weight ratio of the mat to the solution was l:4. The mat was kept at 40C for minutes to dissolve out the nylons, treated in a coagulation bath composed of 10 parts of calcium chloride dihydrate and 90 parts of water at 30C for 50 minutes to coagulate the nylon solution, demineralized in water at C for 60 minutes while pressing, and dried to obtain a flexible and tough leather-like sheet.

EXAMPLE 12 A random web was prepared from mixed-spun fibers composed of 50 parts of nylon-6 and 50 parts of polypropylene and having a fineness of 3 deniers, and the random web was formed into a non-woven fibrous mat having a three dimensional network structure by means ofa needle loom. The mat was impregnated with a solution composed of 40 parts of zinc chloride dihydrate and 60 parts of methanol at 10C, and squeezed by means of a press roll so that the weight ratio of the mat to the solution was about 1:4. The mat was kept at 50C for 10 minutes to dissolve out the nylon-6 from the mixed-spun fibers and to form a fibrous mat composed of ultra-fine polypropylene fibers and impregnated with the nylon-6 solution. The mat containing the nylon-6 solution was treated in a coagulation bath composed of 30 parts of zinc chloride dihydrate, 20 parts of methanol and 50 parts of water at 50C for 30 minutes to coagulate the nylon-6 solution, demineralized in water at 50C for 30 minutes, further demineralized in water at 80C for 30 minutes while repeatedly pressing, and then dried.

The sheet material obtained had a leather-like texture and toughness.

EXAMPLE 13 A random web prepared from mixed-spun fibers composed of 50 parts of nylon-6,6 and 50 parts of polyethylene and having a fineness of 4 deniers was formed into a non-woven fibrous mmat having a three dimensional network structure by means of a needle loom. The mat was impregnated with a solution composed of 35 parts of calcium chloride, 62 parts of methanol and 3 parts of p-nonylphenol at 15C, and then squeezed so that the weight ratio of the mat to the solution was 1:5. The mat was treated in a coagulation bath composed of 50 parts of calcium chloride dihydrate, 5 parts of methanol and 45 parts of water at 50C for 30 minutes to co agulate the nylon-6,6 solution, and then treated in the same manner as described in Example 12 to obtain a leather-like sheet.

EXAMPLE 14 5C, and then squeezed so that the weight ratio of the mat to the solution was 1:4. The mat was kept at 40C for 20 minutes to dissolve out the nylons, treated in a coagulation bath composed of 10 parts of calcium chloride dihydrate, 15 parts of methanol and parts of water at 30C for 50 minutes to coagulate the nylon solution, demineralized in water at 70C for 60 minutes while pressing, and dried to obtain a flexible and tough leather-like sheet.

EXAMPLE l5 Mixed-spun fibers consisting of 60 parts of nylon-6 and 40 parts of polyester (polyethylene terephthalate) and having 5 deniers were crimped and cut. The resulting staple fibers were formed into a web of 200 g/m by means of an air flow. The web was impregnated with a polyurethane emulsion in substantially the same amount as the fiber and dried to form a web stable shaped. Then, a solution at 10C composed of 20 parts of anhydrous calcium chloride and 80 parts of methanol, which solution is a non-solvent for polyester but is a solvent for nylon-6, was sprayed on the web by means of a shower and then pressed slightly to contain this solution of 400 g/m Thereafter, the web thus treated was heated at 50C for 5 minutes to dissolve out the major part of nylon-6 and to make the non-woven fibrous mat composed of ultra-fine polyester fibers impregnated with the nylon solution.

Then, said mat was dipped in a coagulation bath consisting of 37 parts of calcium chloride and 63 parts of water at 60C for 10 minutes and further in water at 50C for minutes to coagulate thoroughly and then treated with water at 80C to remove calcium chloride and methanol and dried. The sheet material thus obtained had leather-like texture and touch and excellent physical properties.

EXAMPLE l6 Mixed-spun fibers consisting of 45 parts of nylon-6,6 and 55 parts of polystyrene and having 3.5 deniers were crimped and cut, and the resulting staple fibers were formed into a web by means of an air flow, and the web was needle-punched to form a three dimensionally entangled non-woven fibrous mat of 600 g/m The mat was impregnated with toluene, which is a non-solvent for nylon-6,6 but is a solvent for polystyrene, at room temperature and squeezed by means of a press roll so as to contain toluene of 1,200 g/m. The mat thus treated was heated to 60C and then left to stand for 20 minutes at this temperature to dissolve out the major part of polystyrene in the fibers and to make the nonwoven fibrous mat constituted with cellular nylon-6,6 fibers impregnated with the polystyrene solution. Then, the mat was dipped in a methanol solution at 50C for 20 minutes to coagulate and deposit uniformly the polystyrene solution between the fibers in cellular structure, and treated with water at 80C to remove methanol and toluene and dried.

The sheet material obtained had leather-like touch and texture and excellent tensile strength and tear strength.

EXAMPLE 17 A mixture of aqueous polyvinyl alcohol (PVA) solution and polyvinyl chloride (PVC) emulsion was extruded into a Glaubers salt bath and then was hot drawn to form mixed-spun fibers consisting of 60 parts *of PVA and 40 parts of PVC which were cut into 7 mm.

90 parts of the resulting staple fibers and 10 parts of polyvinyl alcohol (PVA) fiber for a papermaking binder were formed into a fibrous mat having a weight of 150 g/m by a wet process. This mat was impregnated with dimethylformamide (DMF), which is a nonsolvent for PVA but is a solvent for PVC, at room temperature and squeezed by means ofa press roll so as to contain DMF of 300 g/m The mat thus treated was heated at 50C for 5 minutes to dissolve out the major part of PVC and to make the mat constituted with cellular PVA fibers impregnated with PVC solution. Then, the mat was dipped in a bath composed of 50 parts of DMF and 50 parts of water at 50C for 10 minutes to coagulate and deposite uniformly PVC solution between the fibers of the mat in cellular structure, and

treated with water at 80C to remove DMF and dried. The sheet material obtained had leather-like texture and touch. This sheet was treated with a plasticizer such as dioctyl phthalate and dibutyl phthalate to obtain a highly flexible sheet material, which was similar to a leather for clothes.

EXAMPLE l8 Mixed-spun fibers consisting of 50 parts of polypropylene (PPr) and 50 parts of ester-series polyurethane elastomer (PU) and having 3 deniers were cut and the resulting staple fibers were formed into a web of 200 g/m by means of an air flow. This web was treated with polyacrylate emulsion and dried to obtain a web applied with polyacrylate resin of 15% based on the fiber. This web was sprayed with dimethylformamide (DMF), which is a non-solvent for PPr but is a solvent for PU, at room temperature by means of a shower and then pressed slightly to contain DMF of 300 g/m Thereafter, the web thus treated was heated at C for 5 minutes to dissolve out the major part of PU and to make the web constituted with ultra-fine PPr fibers impregnated with PU solution. Then, the web thus obtained was dipped in a bath composed of 50 parts of DMF and 50 parts of water at 50C for 20 minutes to coagulate and deposite uniformly PU solution between the fibers in cellular structure, and treated with water at 80C to remove DMF and dried.

The sheet material thus obtained had leather-like texture, touch and physical properties.

EXAMPLE 19 A mixed solution consisting of a solution of polyacrylonitrile (PAN) in DMF and a solution of esterseries polyurethane elastomer (PU) in DMF was extruded into a bath composed of 50 parts of DMF and 50 parts of water at C and was drawn to obtain mixed-spun fibers consisting of 50 parts of PAN and 50 parts of PU and having 5 deniers, which were cut, and the resulting staple fibers were formed into a web of 250 g/m by means of an air flow. This web was sprayed with a solution consisting of 60 parts of DMF and 40 parts of water and pressed and dried at 50C to obtain a web having an apparent density of 0.25 g/m. Then, this web was sprayed with tetrahydrofuran (THF), which is a solvent for PU but is a non-solvent for PAN, at 15C by means of a shower and then pressed slightly to contain THF of 400 g/m Thereafter, the web thus treated was heated at 40C for 5 minutes to dissolve out the major part of PU and to make the web constituted with ultra-fine PAN fibers impregnated with PU solution. Then, the web thus obtained was dipped in a bath composed of 30 parts of THF and parts of water at 30C for 20 minutes to coagulate and deposit uniformly PU solution between the fibers in cellular structure, and treated with water at 60C to remove THF and dried.

The sheet material thus obtained had leather-like texture and physical properties. Furthermore, the sheet was subjected to a buffing to obtain a sheet material having chamois-like texture and touch. Moreover, when this Chamois-like sheet was sprayed with DMF and pressed at 50C, a sheet material had texture, touch and physical properties to be used as shoe-upper.

What is claimed is:

l. A process for preparing a fibrous sheet, comprising forming a non-woven fibrous mat of mixed-spun fibers comprising at least two kinds of polymeric materials selected from the group consisting of polyamides, N- methoxymethylated polyamides, polyesters, polystyrene, polyolefins, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polymethacrylates, polyvinyl alcohol, polyacrylonitrile and polyurethane elastomers, said at least two kinds of polymeric materials having different solvent solubilities,

impregnating said mat with a first liquid which is a solvent for at least one ofsaid polymeric materials but a non-solvent for the other polymeric materials at a temperature sufficiently low that said liquid substantially does not dissolve the polymeric materials for which it is a solvent;

heating the impregnated mat to a temperature at which said polymeric material is partially or wholly dissolved, and the solution of said polymeric material is distributed through the fibrous mat, while substantially none of the other polymeric materials are dissolved into the first liquid, and

coagulating said polymer solution by treating said mat with a second liquid which is a non-solvent for all of the polymeric materials which constitute said mixed-spun fibers and which is at least partially miscible with said first liquid to form a porous polymeric structure which is substantially nonbonded to the fibers of said fibrous mat.

2. A process according to claim 1, in which said first liquid dissolves a major portion of said first polymeric material.

3. A process according to claim 2, in which said first liquid dissolves substantially all of said first polymeric material,

4. A process according to claim 1, in which said first polymeric material is a polyamide, said first liquid is a solution of a metal chloride in a lower alcohol, acetic acid or formic acid or an aqueous solution thereof, an inorganic acid or an aqueous solution thereof or a phenol series solvent and said second liquid is water, an aqueous solution of a metal chloride, a lower alcohol or an aqueous solution of a lower alcohol.

5. A process according to claim 1, in which said first polymeric material is an N-methoxymethylated polyamide and said first liquid is a lower alcohol.

6. A process according to claim 5, in which said lower alcohol is methanol.

7. A process according to claim 1, in which said polyamide is selected from the group consisting of nylon-6, nylon-6,6 nylon-7 and nylon-6,10.

8. A process according to claim], in which said polyolefin is polyethylene or polyproplene.

9. A process according to claim 1, in which said second liquid is an aqueous solution comprising from 5 to per cent of a metal chloride.

10. A process according to claim 1, in which said aqueous solution comprises from 10 to'45 per cent of said metal chloride.

11. A process according to claim 1, in which said second liquid is an aqueous solution comprising from 5 to 40 per cent of a metal chloride and from 5 to 30 per cent of a lower alcohol.

12. A process according to claim 4, in which said metal chloride is calcium chloride, zinc chloride, cupric chloride, lithium chloride, stannic chloride or titanium tetrachloride.

Claims

1. A PROCESS FOR PREPARING A FIBEROUS SHEET, COMPRISING FORMING A NON-WOVEN FIBROUS MAT OF MIXED-SPUN FIBERS COMPRISING AT LEAST TWO KINDS OF POLYMERIC MATERIALS SELECTED FROM THE GROUP CONSISTING OF POLYAMIDES, N-METHOXYMETHYLATED POLYAMIDES, POLYESTERS, POLYSTYRENE, POLYOLEFINS, POLYVINYL CHLORIDE, POLYVINYLIDENE CHLORIDE, POLYVINYL ACETATE, POLYMETHACRYLATES, POLYVINYL ALCOHOL, POLYVINYL ACETATE, POLYMETHTHANE ELASTOMER, SAID AT LEAST TWO KINDS OF POLYMERIC MATERIALS HAVING DIFFERENT SOLVENT SOLUBILITIES, IMPREGNATING SAID MAT WITH A FIRST LIQUID WHICH IS A SOVELENT FOR AT LEAST ONE OF SAID POLYMERIC MATERIALS BUT A NONSOLVNT FOR THE OTHER POLYMERIC MATERIALS AT A TEMPERATURE SUFFICIENTLY LOW THAT SAID LIQUID SUBSTANTIALLY DOES NOT DISSOLVE THE POLYMERIC MATERIALS FOR WHICH IT IS A SOLVENT; HEATING THE IMPREGNATED MAT TO A TEMPERATURE AT WHICH SAID POLYMERIC MATERIAL IS PARTIALLY OR WHOLLY DISSOLVED, AND THE SOLUTION OF SAID POLYMERIC MATERIAL IS DISTRIBUTED THROUGH THE FIBROUS MAT, WHILE SUBSTANTIALLY NONE OF THE OTHER POLYMERIC MATERIALS ARE DISSOLVED INTO THE FIRST LIQUID, AND COAGULATING SAID POLYMER SOLUTION BY TREATING SAID MAT WITH A SECOND LIQUID WHICH IS A NON-SOVENT FOR ALL OF THE POLYMERIC MATERIALS WHICH CONSTITUTE SAID MIXED-SPUN FIBERS AND WHICH IS AT LEAST PARTIALLY MISCIBLE WITH SAID FIRST LIQUID TO FORM A POROUS POLYMERIC STRUCTURE WHICH IS SUBSTANTIALLY NONBONDED TO THE FIBERS OF SAID FIBROUS MAT.

3. A process according to claim 2, in which said first liquid dissolves substantially all of said first polymeric material.

6. A process according to claim 5, in which said lower alcohol is methanol.

8. A process according to claim 1, in which said polyolefin is polyethylene or polyproplene.

9. A process according to claim 1, in which said second liquid is an aqueous solution comprising from 5 to 60 per cent of a metal chloride.

10. A process according to claim 1, in which said aqueous solution comprises from 10 to 45 per cent of said metal chloride.