Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06N—WALL, FLOOR, OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
  • D06N3/00—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof
  • D06N3/12—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof with macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. gelatine proteins
  • D06N3/14—Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof with macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. gelatine proteins with polyurethanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2201/00—Foams characterised by the foaming process
  • C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
  • C08J2201/054—Precipitating the polymer by adding a non-solvent or a different solvent
  • C08J2201/0542—Precipitating the polymer by adding a non-solvent or a different solvent from an organic solvent-based polymer composition
  • C08J2201/0544—Precipitating the polymer by adding a non-solvent or a different solvent from an organic solvent-based polymer composition the non-solvent being aqueous
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
  • C08J2375/04—Polyurethanes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/904—Artificial leather

Definitions

• This invention is concerned with a process for producing leather-like layers or coatings of polyurethane, preferably on a fibrous substrate so as to achieve an extremely fine pore structure as the outer surface layer of the finished article.
• This fine pore structure as a cover layer must be microporous in size and open-channeled to provide good air and vapor permeability while preventing the passage of liquid water.
• leather-like fiat shaped structures can be produced from a textile substrate in which an elastomeric binding agent is uniformly distributed.
• an elastomeric binding agent In preparing the textile base layer or substrate, it is preferable to use non-woven fibrous sheets or mats as a felt-like material although it is also possible to use woven or knitted fibrous textiles or even several layers of woven and/or n0n-woven sheets may also be used.
• the elastomeric binding agent various polymers have been used, for example: polyurethane, polyvinyl chloride and butadiene/ acrylonitrile copolymers. These polymers are generally sprayed onto the textile substrate in the form of solutions or are applied by dipping, impregnating or doctoring onto the substrate.
• a number of processes have become known for obtaining such cover layers or coatings which are preferably applied to a leather-like, elastomer-bound textile substrate.
• these processes one generally proceeds by first converting polyurethane or mixtures of polyurethane with polyvinyl chloride into their gel form in a suitable solvent, and then precipitating the gel on the textile base layer by treatment with a non-solvent, preferably water.
• a non-solvent preferably water.
• the polymer is first dissolved in a solvent, e.g. dimethyl formamide being especially useful as the solvent for polyurethane, and a non-solvent such as water or alcohol is incorporated into this polymer solution.
• the quantity of the non-solvent is added or dosed in an amount which is just sufficient to gel the polymer.
• Such a gel can be considered as a two phase system in which at least one substance is uniformly dispersed in another substance, both the dispersed substance and the dispersing medium being continuous or coherent phases which penetrate one another.
• both the dispersed substance and the dispersing medium being continuous or coherent phases which penetrate one another.
• water or mixtures of water with dimethyl formamide are used as the coagulating or precipitating bath.
• the polymer as the dispersed phase thereby hardens or coagulates and the dispersing medium as the second phase can then be removed from the solidified structure by washing, thereby leaving an open-channeled or interconnected porous solid structure.
• the macropores are defined as pores in the hardened or solidified gel which are so large in size as to be visible with the naked eye down to smaller sizes which are still visible or recognizable as small vacuoles on a photographic cross-section of the porous layer enlarged on a scale of approximately 1:100.
• These macropores generally lie close to or directly at the surface of the cover layer and are covered by an extremely thin film of the solid polymer or are separated from one another by such a thin film or membrane. This not only has a very unfavorable effect on the air permeability and water conductivity of the leather-like surface coating but also has a detrimental effect on its elastic qualities.
• micropores are defined as those pores in the leather-like coating or surface structure which are sufiiciently small in size so that no vacuoles can be seen in a cross-sectional photographic enlargement of 1:100.
• a crosssectional enlargement of times actual size will not show any evidence of vacuoles or bubbles which are usually covered or separated by a thin film of polymer.
• a polyurethane gel initially applied to a substrate is coagulated or hardened by treatment at about to 80 C. with an aqueous electrolytic solution having a pH-value between 3 and 9, preferably about 4.5 to 8, and a concentration of the electrolyte of at least by weight, preferably more than by weight, up to the saturation point of the electrolyte in the aqueous solution, i.e. up to the point at which the electrolyte forms a saturated solution in water at the coagulation temperature. Thereafter, the coagulated gel is washed and dried in conventional manner to remove the liquid portion thereof and the electrolyte, i.e. the soluble salt content of the gel.
• the polyurethane gel can be applied to many different substrates depending upon the particular use of the final leatherlike film, sheet or cover layer, and in most instances is applied onto a fibrous substrate, e.g. woven and non-woven fiber-containing fabrics, fleeces or similar textile materials which may or may not be impregnated with a suitable binding agent.
• a fibrous substrate e.g. woven and non-woven fiber-containing fabrics, fleeces or similar textile materials which may or may not be impregnated with a suitable binding agent.
• Paper sheets composed of natural, artificial and/or synthetic organic fibers may also be used as a substrate, or one can even produce a microporous sheet or film by using a substrate from which the coagulated gel can be easily removed by stripping or peeling after being treated in accordance with the process of this invention.
• the invention is especially applicable, however, in providing an improved microporous surface coating on a fibrous non-woven fleece which has been impregnated with an elastomeric polymer to provide a leather-like, fiber-reinforced base layer.
• the gel can be prepared and applied according to conventional processes, e.g. by spreading, brushing, extrusion, coating with a doctor blade or the like.
• Polyurethanes which are suitable as a film-forming or coating material on a flat substrate to provide a porous elastomeric polymer surface layer are generally quite well known in this art.
• the desired elastomeric layer should consist predominately of a suitable polyurethane but may also contain a minor proportion of one or more other film-forming thermoplastic organic polymers of the many polymers and copolymers which are known to be compatible with a polyurethane gel, preferably other elastomeric polymers.
• polyurethanes are produced by reacting a diisocyanate with one or more organic compounds or substances which contain terminal hydroxy groups or reactive hydrogen atoms, especially with such polymers as polyethers, polyesters or polyesteramides, often with the further interaction of diamines, water or glycols.
• the polyurethane must be soluble in organic solvents suitable for gel formation and also should be capable of being coagulated or solidified from the gel so as to provide a porous structure which is insoluble in water.
• Suitable polyurethanes of this type, including compositions containing minor amounts of other film-forming thermoplastic polymers are disclosed in such references as U.S. Pats. No. 2,871,218 and No. 3,190,766.
• diisocyanates as tolylene-2,4- or -2,6-diisocyanate, diphenylmethane-4,4-diisocyanate, hexamethylene diisocyanate, naphthalene diisocyanates or various other alkylene and/or arylene diisocyanates.
• linear polymers to be reacted with the diisocyanate in forming the polyurethane include the following: polyethers such as polyethylene ether glycols, polypropylene ether glycols, polyhexamethylene ether glycols and the like; polyesters such as tetramethylene glycol adipate, hexamethylene glycol adipate, hexamethylene glycol terephthalate and the like; and polyesteramides which are the amides of the previously noted polyesters.
• diisocyanate and the linear polymer there may also be reacted with the diisocyanate and the linear polymer any number of other compounds having reactive hydrogen atoms including: glycols such as ethylene glycol, tetramethylene glycol, hexamethylene glycol; diamines such as ethylene diamine, phenylene diamine and dimethyl piperazine; or even small amounts of diethylene diimine.
• glycols such as ethylene glycol, tetramethylene glycol, hexamethylene glycol
• diamines such as ethylene diamine, phenylene diamine and dimethyl piperazine; or even small amounts of diethylene diimine.
• substantially linear polyurethanes are especially desirable, and in general such preferred polyurethanes should have a relative viscosity of about 20 to 100 poise as measured in a 20% dimethyl formamide solution at 20 C. (i.e. 20% by weight of the polyurethane being dissolved in the solvent).
• a polyurethane gel which contains about 15-35% by weight of the linear polyurethane, 0 to 15 by weight of one or more of the other film-forming thermoplastic polymers, 5 to 30% by weight of a non-solvent for the polyurethane and 20 to by weight of a solvent for the polyurethane in which the non-solvent is at least partly soluble or miscible.
• Especially preferred proportions of the gel components are as follows:
• Particularly suitable polymers other than polyurethanes contained in the gel composition include, for example: polyvinyl chloride; various copolymers of vinyl chloride, especially vinyl chloride/maleic acid anhydride or vinyl chloride/vinyl acetate copolymers; and butadiene-acrylonitrile and/or -styrene interpolymers.
• Chlorinated rubber or nitrocellulose are likewise especially useful.
• the nitrocellulose preferably has a nitrogen content of about 10.8 to 14% by weight.
• suitable copolymers which can be at least partially mixed into the gel-forming composition containing polyurethane the following table has been compiled as a further illustration of the additional film-forming thermoplastic polymers. All percentages are by weight with reference to the total weight of the copolymer so as to indicate the approximate proportions of the monomers.
• the procedure for producing the gel is generally well known.
• the polymer or polymer mixture is dissolved in a suitable solvent, preferably dimethyl formamide although dimethyl acetamide is also quite useful.
• suitable solvents for polyurethanes include dimethyl sulfoxide, tetrahydrofuran, gamma-butyrolactam, gamma-butyrolactone and epsiloncaprolactam.
• the polyurethane gel utilized in the present invention is most conveniently prepared with dimethyl formamide as the solvent.
• Suitable non-solvents for the preparation of polyurethane gels include water or lower alkanols such as methanol and ethanol. While the non-solvent is usually a liquid in which the polymethane elastomer is insoluble, it is also feasible to use ammonium nitrate as a precipitating agent in the form of a solid non-solvent or else ammonium nitrate dissolved in dimethyl formamide or other suitable sol vent for the polyurethane can be used as a liquid nonsolvent medium.
• the non-solvent should be at least partially soluble or miscible in the dimethyl formamide or other suitable solvent.
• the gels prepared for use in this invention contain as the preferred nonsolvent about 5-10% water or 5-30% by weight of ammonium nitrate.
• the gel In applying the gel to the substrate, e.g. a fibrous fleece or non-woven textile base layer, regardless of the particular technique used such as spraying, dipping or doctoring, it is usually most desirable to provide a layer thickness of about 0.4 to 1.5 mm. where the end-product is to have the surface appearance and characteristics which simulate natural leather.
• the applied gel may also contain pigments or dyes, and one can also add inert thickening agents, fillers or extenders in a conventional manner.
• the novel and critical step essential for achieving the improved results of the present invention is the coagulation or hardening of the applied polyurethane gel by treatment with the prescribed electrolytic solution.
• the following details of this step are therefore quite important and should be carefully observed in order to obtain the desired product.
• the treatment with the aqueous electrolytic solution takes place in the usual form of a liquid bath although it is also feasible to spray or flow the treating solution onto the gel-coating provided that the temperature is maintained within the range of approximately 5 to 80 C., preferably 15-60 C.
• the electrolytic solution is essentially an aqueous solution of a water-soluble metal salt in a concentration of at least 15 by weight and generally more than 20% by weight.
• the upper limit of concentration is not critical since saturated solutions of the metal salt at the coagulation temperature, i.e. between 5 and 80 C. are quite suitable.
• Both inorganic and organic metal salts, i.e. the metal salts of inorganic and organic acids are useful provided that the resulting solution in the prescribed concentration yields a pH-value of 3-9 and preferably from about 4.5 to 8.
• Mixtures of salts can also be used as the electrolyte provided that the mixture is soluble in water in the required concentration.
• the aqueous electrolytic solution can be prepared by dissolving in water any metal salt which will yield the desired pH and concentration required for the treatment bath.
• any metal salt which will yield the desired pH and concentration required for the treatment bath.
• suitable salts of the metals of Groups I and II of the Periodic Table preferably the alkali metal and alkaline earth metal salts.
• Ammonium and zinc salts are also quite useful for purposes of the present invention.
• salts of. mineral acids such as the phosphates, sulfates, chlorides and nitrates, or the salts of organic acids such as the acetates and formates. From readily available data or by a simple preliminary test, it can be determined whether any particular salt will meet the pH and concentration limitations of the method of the invention.
• the precipitation, coagulation or hardening of the elastomer gel by the electrolytic solution requires the bath to be in intimate contact with the gel under controlled temperature conditions, but the time required to complete the coagulation is not critical. In general, the duration of the bath treatment need not exceed 15 minutes and shorter periods of time are usually quite suitable. The reaction time required for coagulation naturally depends upon the temperature of the coagulating both. In the case of very hot baths of about C., the precipitation or coagulation of the gel can be substantially com pleted after only about one minute. In order to assure a uniform microporous structure of the coating or surface layer, it has been found advantageous to complete the precipitation of the gel with the electrolytic solution within a period of about 2 to 10 minutes.
• the polymer gel After the polymer gel has been coagulated, it is washed with water in a conventional manner so as to substantially completely remove the solvent and non-solvent components of the original gel and especially to remove the water-soluble salts. After washing, the coagulated gel is dried in the usual way, e.g. by using heated air.
• the use of salt solutions as an electrolytic bath does not prolong the time normally required for washing the coagulated gel since the water-soluble salts used as the electrolyte are more easily extracted than the solvents such as dimethyl formamide.
• the textile base layer or substrate coated with this gel was then conducted through an aqueous coagulating bath consisting of an aqueous solution of 20% by weight NaCl at a bath temperature of 20 C. After a reaction period or time of treatment of five minutes, the coagulated gel was washed with water and dried.
• the resulting product exhibits a surface layer having a highly uniform microporous structure. Pores with a diameter of 10 microns or more could not be observed, most of the micropores being much smaller.
• the finished article exhibited a permeability to water vapor of 650 g./m. /day. In a comparative test wherein the same procedures were followed except that pure water was used in coagulating the applied gel, the finished article had a surface coating in which there were dispersed a large number of macropores with a diameter above 20 microns.
• EXAMPLE 2 As described in Example 1, the fiber fleece sheet material was coated with a surface layer of the polymer gel. However, in order to coagulate the gel, an electrolytic bath was used which contained 10% by weight dimethyl formamide as Well as the 20% by weight NaCl. The treatment with this bath took place at a temperature of 50 C. The resulting leather-like product has an extremely fine pored surface structure. In testing for water vapor permeability according to DIN 53333 (German Industrial Standard), the finished article exhibited a value of 750 g./m. day.
• EXAMPLE 3 The same procedure was followed as in Example 1 except that the coagulating bath consisted of a 50% by weight solution of MgCl in place of the sodium chloride solution.
• the polyurethane surface coating was again found to be substantially free of macropores while exhibiting a uniform distribution of micropores.
• EXAMPLE 4 By following exactly the same procedure as in Example 1 but using a 50% by weight sodium acetate solution in water as the aqueous coagulating bath to precipitate the gel coating, it was again possible to obtain a uniform microporous surface structure substantially free of macropores.
• EXAMPLE 5 A non-woven fibrous fleece in the form of a sheet was produced in the usual manner on a papermaking machine from staple lengths of polyamide (nylon) and regenerated cellulose (rayon) fibers. The fibrous sheet was then impregnated with an elastomeric binder consisting of a linear polyurethane in admixture with polyvinyl chloride, and this binder was then hardened, washed with water and dried to form a textile base layer. Onto this base layer there was applied a surface coating or layer of 0.8 mm.
• thickness of a polymer gel having approximately the following composition: 25% by weight of polyurethane; 5% by weight of a copolymer of 80 parts by weight of vinyl chloride to 20 parts by weight of maleic 8 acid anhydride; 10% by weight of water and 60% by weight of dimethyl formamide.
• the coating substrate was then conducted through a coagulating bath of water containing 32% by weight of KNO as the electrolyte while maintaining the bath temperature at C.
• the coated substrate had a residence time of 3 minutes in this bath.
• the coagu lated coating was washed with water and dried to yield a very fine and uniform porous surface structure substantially free of macropores.
• Example 6 The procedure of Example 5 was repeated except that the coagulating bath consisted of an aqueous 19% by weight solution of KNO With this lower concentration of the electrolyte, a few macropores appeared in the otherwise microporous coating.
• EXAMPLE 7 As described in Example 5, the polymer gel was appiled to the non-woven fibrous substrate impregnated with the elastomeric binder.
• the polymer gel had the same composition as described in Example 5 except that the vinyl chloride/maleic acid anhydride copolymer was rereplaced by nitrocellulose in the same quantity, i.e. 5% by weight with reference to the total weight of the gel.
• the coated substrate was conducted through a 50% by weight NH NO solution in water, the bath temperature being maintained at 23 C., for a total residence time in the bath of 8 minutes. After washing with water and drying, a fiat surface coated microporous structure resembling leather was obtained. This finished product remained undamaged after 500,000 flexures during a test of its flexing or bending strength carried out in accordance with 1UP 20 by means of a Bally flexometer.
• EXAMPLE 8 The procedure of Example 7 was repeated except that the concentration of the NH 'NO in the coagulating bath was varied in a series of tests in which this concentration was reduced from 50% to 10%. At a concentration of 25% by weight of NH NO some macropores can be observed which increase in size and number as the concentration of the salt in the coagulating bath decreases. During these tests the bath had a pH-value of between about 5 and 6.
• EXAMPLE 9 Using a polyurethane impregnated fibrous fleece for the textile base layer as in the preceding examples, a polymer gel coating was applied on the surface thereof to a thickness of 0.5 mm.
• This polymer gel contained approximately the following amounts of individual components: 24% by weight of a linear polyurethane; 6% by weight of ammonium nitrate and by weight of dimethyl formamide.
• aqueous electrolytic solution consisting of 22% by weight of a mixture of 70 parts by weight NaCl to 30 parts by weight KCl. The temperature of the solution was maintained at 30 C. during the bath treatment.
• the linear polyurethane used to form the surface layer or coating on the textile substrate was prepared as described in US. 2,871,- 218 from polybutyladipate (molecular weight of 1000), diphenyl-methane-4,4-diisocyanate and a small amount of butanediol as a chain extender.
• This is the polyester type of polyurethane and has a solution viscosity of 50-70 poise when measured as a 20% solution in dimethyl formamide at 20 C.
• This same linear polyurethane can be used to impregnate the fibrous substrate as an elastomeric binding agent, preferably in admixture with polyvinyl chloride as pointed out in Examples 1 and 5.
• the particular substrate is not critical, the examples herein using an impregnated fibrous fleece as an illustration of a preferred artificial leather product.
• the aqueous electrolytic solution employed as the coagulating bath in each of the foregoing examples exhibited a pH-value ranging between about 5 and 9 depending upon the particular electrolyte used in each case.
• the minimum concentration of the electrolyte will tend to vary to some extent, but it has been found that more than 20% by weight is usually required, and the formation of macropores can be eliminated in any case by simply increasing the concentration up to the saturation value of the electrolyte in Water at the coagulation temperature.
• the coating or covering layer produced according to the invention has a distinctly better resistance to bending, i.e. a longer flexing life, than coatings which still contain macropores.
• the thin film of polymer above or between the visible bubbles or vacuoles break or tear during a repeated flexural strength test. Once this break takes place, the crack in the surface coating continues to tear very quickly and extends through the rest of the structure.
• IUP 20 Bally flexometer
• cover layers or coatings containing such macropores are destroyed, on an average, after about 10,000 fiexures, while the microporous coatings produced according to the present invention remain undamaged up to about 200,000 fiexures or more.
• the polyurethane polymer coatings or fiat surface film structures of the present invention are thus distinguished not only by their excellent microporous structure but also by their resistance to bending or flexing. Since artificial leather products are often subjected to such stress, for example when used in footwear or the like, an increased flexing life is a very substantial advantage. At the same time, a uniform microporous structure contributes to the desired air and water vapor permeability of the artificial leather product.
• a process for the production of a microporous artificial leather coating which comprises: applying to a porous substrate a polyurethane gel containing a solvent for said polyurethane, coagulating the applied gel at a temperature of about 5 to 80 C. with an aqueous electrolytic solution having a pH-value between 3 and 9 and a concentration of a water soluble metal or ammonium salt electrolyte of at least by Weight up to the saturation point of the electrolyte in said aqueous solution, and subsequently washing and drying the coagulated gel to form a microporous coating.
• polymer of said gel consists essentially of a linear polyurethane having a relative viscosity of to 100 poise measured in a 20% dimethyl formarnide solution at 20 C.
• a process as claimed in claim 1 wherein said gel contains 15 to 35 by weight of a linear polyurethane, up to 15% by weight of at least one other film-forming thermoplastic polymer, 5 to 30% by weight of a nonsolvent for polyurethanes and 20 to 80% by weight of a solvent for polyurethanes in which said non-solvent is as least partially soluble.
• said gel contains 20 to 30% by weight of a linear polyurethane, up to 10% by weight of at least one other film-forming thermoplastic polymer, 5 to 15% by weight of a nonsolvent for polyurethanes and 45 to 75% by weight of a solvent for polyurethanes in which said non-solvent is at least partially soluble.
• polymer content of said gel consists essentially of a linear polyurethane having a relative viscosity of 20 to 100 poise measured in a 20% dimethyl formamide solution at 20 C. and at least one other polymer selected from the class consisting of polyvinyl chloride, vinyl chloride/ maleic acid anhydride copolymers, vinyl chloride/vinyl acetate copolymers, and copolymers of butadiene with at least one of the monomers acrylonitrile and styrene.
• polymer content of said gel consists essentially of a linear polyurethane having a relative viscosity of 20 to 100 poise measured in a 20% dimethyl formamide solution at 20 C. and nitrocellulose.
• ammonium nitrate is used as the non-solvent in an amount of 5 to 30% by weight with reference to the total weight of the gel.
• a process for the production of a microporous artificial leather film layer which comprises: applying to a porous substrate a polyurethane gel containing about 15 to 35% by weight of a linear polyurethane having a relative viscosity of about 20 to 100 poise measured in a 20% dimethyl formamide solution at 20 C., from 0 up to 15% by weight of another film forming thermoplastic polymer, about 5 to 30% by Weight of a nonsolvent for polyurethanes and about 20 to by weight of a solvent for polyurethanes in which said non-solvent is at least partly soluble; coagulating the applied gel at a temperature of about 5 to 80 C.
• aqueous solution of at least about 25% by weight of a Water soluble electrolyte selected from the class consisting of the salts of alkali metals, alkaline earth metals, zinc and ammonium, said electrolyte being sufiicient to provide an electrolytic solution with a pH-value of about 3 to 9; and subsequently washing the coagulated gel to form a microporous layer substantially free of macropores.
• a Water soluble electrolyte selected from the class consisting of the salts of alkali metals, alkaline earth metals, zinc and ammonium, said electrolyte being sufiicient to provide an electrolytic solution with a pH-value of about 3 to 9; and subsequently washing the coagulated gel to form a microporous layer substantially free of macropores.
• a process as claimed in claim 12 wherein said solvent for polyurethanes is dimethyl formamide.
• thermoplastic polymer is selected from the class consisting of polyvinyl chloride, vinyl chloride copolymers, and copolymers of butadiene with at least one of the monomers acrylonitrile and styrene.
• thermoplastic polymer is nitrocellulose

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Textile Engineering (AREA)
• Materials Engineering (AREA)
• Dispersion Chemistry (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
• Synthetic Leather, Interior Materials Or Flexible Sheet Materials (AREA)
• Transforming Light Signals Into Electric Signals (AREA)

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Citations (11)

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  • 1967-06-06 NO NO00168487A patent/NO128666B/no unknown
  • 1967-06-15 LU LU53887D patent/LU53887A1/xx unknown
  • 1967-06-16 NL NL6708454A patent/NL6708454A/xx unknown
  • 1967-06-16 US US648186A patent/US3527653A/en not_active Expired - Lifetime

Patent Citations (11)

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