EP1836343B1

EP1836343B1 - A procedure to make leather-like sheet

Info

Publication number: EP1836343B1
Application number: EP05820992A
Authority: EP
Inventors: Yoshida Yutaka; Kon Shigeto; Gianni Romani; Francesco Luciani
Original assignee: Alcantara SpA
Current assignee: Alcantara SpA
Priority date: 2004-12-22
Filing date: 2005-12-19
Publication date: 2011-06-29
Anticipated expiration: 2025-12-19
Also published as: ATE514812T1; WO2006067583A1; ITTO20050892A1; EP1836343A1

Abstract

The present invention provides a method for producing a leathery sheet material excellent in hand characteristics and 5 abrasion-resistance, said method being excellent in productivity. The present invention provides a method for producing a leathery sheet material which comprises applying a heat-sensitive coagulable emulsion (A) to a fiber material substrate without a softening and water-repellent treatment and successively carrying out heat coagulation, wherein said heat-sensitive coagulable emulsion (A) contains, as essential components, a polyurethane resin (a), a softening repellent (b), a nonionic surfactant with a cloud point of 40 to 98<SUP>°</SUP>C (c) , and an inorganic salt (d) , and the weight ratio (b)/(a) is in a range of 0.005 to 0.2.

Description

TECHNICAL FIELD

The invention relates to a method for producing a leathery sheet material and a leathery sheet material, and more particularly to a method for producing a leathery sheet material to be obtainable using heat-sensitive coagulable polyurethane resin emulsion and a leathery sheet material.

BACKGROUND ART

Conventionally, a method of applying a polyurethane resin as a binder to a fiber material substrate has been employed as a method for producing a leathery sheet material. Recently, with respect to polyurethane resins, as the restriction for reduction of organic solvents are strengthened by law, it has been promoted to shift a conventional wet method using polyurethane resin solutions to a dry method using polyurethane resin emulsions. However, the dry method using polyurethane resin emulsion is disadvantageous because sheets to be obtained are hard to be considerably inferior in hand characteristics and to be degraded in abrasion-resistance.
To improve the hand characteristics even in the case of the dry method using polyurethane resin emulsions, the following methods have been proposed: a method of applying an inorganic salt-containing polyurethane resin emulsion to a fiber material substrate and then carrying out heat-sensitive coagulation (reference to Japanese Kokai Publication Hei-6-316877 ) and a method of applying an inorganic salt-containing polyurethane resin emulsion to a fiber material substrate to which a softening repellent has already been applied and then carrying out heat-sensitive.coagulation (reference to Japanese Kokai Publication 2000-17581 ).

SUMMARY OF THE INVENTION

However, there is a problem that in the methods proposed in above-mentioned Japanese Kokai Publication Hei-6-316877 and Japanese Kokai Publication 2000-17581 , the hand characteristics and abrasion-resistance are not improved, and the method of Japanese Kokai Publication 2000-17581 requires a softening water repellent-applying step which lowers the productivity,

DETAILED DISCRIPTION OF THE INVENTION

The present inventors have made intensive investigations to solve these problems and consequently have come to the invention.
That is, the invention provides
a method for producing a leathery sheet material according to claim 1,
a leathery sheet material obtainable by said method; and
a leathery sheet obtainable by further post-processing said leathery sheet material.
Hereinafter, the invention will be described more in details.
The method for producing a leathery sheet material of the invention is
a method for producing a leathery sheet material
which comprises applying a heat-sensitive coagulable emulsion (A) to a fiber material substrate without a softening and water-repellent treatment and successively carrying out heat coagulation,
wherein said heat-sensitive coagulable emulsion (A) contains, as essential components, a polyurethane resin (a), a softening water-repellent (b), a nonionic surfactant with a cloud point of 40 to 98°C (c) , and an inorganic salt (d), and the weight ratio (b)/(a) is in a range of 0.005 to 0.2.
Examples of the fiber material substrate to be used in the invention may include nonwoven fabrics and woven fabrics etc. conventionally used as the fiber material substrate.
Examples of the nonwoven fabrics may include those having laminated woven fabrics etc. inside or on the surfaces thereof for the purpose of reinforcement. The component fibers thereof may be natural fibers and chemical fibers. Examples of the natural fibers are cotton, wool, silk, asbestos . Examples of the chemical fibers are regenerated fibers such was rayon and Tencel^(R), semi-synthetic fibers such as acetates and triacetates, and synthetic fibers such as polyamides, polyesters, polyolefins, acryl fibers. Also, mixed fibers derived from the above-mentioned fibers may be used properly.
The fiber material substrate to be used in the invention is untreated with a softening repellent in advance in terms of reduction of processing steps and improvement of abrasion-resistance.
In the invention, a softening repellent may be added as one of the components of the heat-sensitive coagulable emulsion in order to impregnate the fiber material substrate with the heat-sensitive coagulable emulsion to obtain improved abrasion-resistance.
That is, it can be assumed as follows: owing to use of the fiber material substrate untreated with the softening repellent in advance and addition of the softening repellent as one component of the heat-sensitive coagulable emulsion, the processing steps are reduced. Furthermore, the softening repellent is made to be dispersed in the polyurethane resin to form an island-in-sea structure, and then it adheres on the fiber surface so that the binding force could be strengthened and the leathery sheet material is provided with sufficient tensile strength. In addition, the softening repellent bleeds out on the polyurethane resin surface, so that the urethane resin can have a micro-porous structure. Simultaneously, the softening repellent unevenly exists on the urethane resin surface, so that the abrasion-resistance of the leathery sheet material to be obtained can be improved.
The heat-sensitive coagulable emulsion (A) of the invention contains, as essential components, a polyurethane resin (a), a softening water-repellent (b), a nonionic surfactant with a cloud point of 40 to 98°C (c), and an inorganic salt (d).
The content of (a) in (A) is preferably 2 to 40% by weight and more preferably 3 to 30% (hereinafter, % represents % by weight unless otherwise described); the content of (b) is preferably 0.1 to 10% and more preferably 0.2 to 5%; the content of (c) is preferably 0.1 to 10% and more preferably 0.2 to 5%; and the content of (d) is preferably 0.05 to 5% and more preferably 0.1 to 2% and the other component is an aqueous medium.
The total amount of (a) to (d) in (A) is preferably 2.3 to 65% and more preferably 3.5 to 42%.
The weight ratio (b)/(a) in (A) is in a range of 0.005 to 0.2 and preferably in a range of 0.01 to 0.15. If (b)/(a) is smaller than 0.005, the abrasion-resistance becomes insufficient and if it exceeds 0.2, the surface hand characteristics is worsened.
Furthermore, the weight ratio (c)/(d) in (A) is preferably in a range of 0.1 to 2 and more preferably in a range of 0.2 to 1 in terms of the storage stability.
In the invention, the polyurethane resin (a), which is an essential components of (A), is, for example, composed of an organic diisocyanate (a1), a high molecular weight polyol (a2), carboxyl group (-COOH) - and/or sulphonic group (-SO₃H) -containing polyol or its salt (a3), and if necessary a chain extending agent (a4) and/or a terminator (a5) and thereafter, if necessary, the carboxyl group and/or sulphonic group may be neutralized with a neutralizer (a6).
Hereinafter, the respective components will be described.
As the organic diisocyanate (a1), those which are conventionally used for polyurethane production may be used. Examples of (a1) are aromatic diisocyanates having 6 to 20 carbon atoms (except the carbon atoms in NCO group, hereinafter the same), aliphatic diisocyanates having 2 to 18 carbon atoms, alicyclic diisocyanates having 4 to 15 carbon atoms, and aromatic aliphatic diisocyanates having 8 to 15 carbon atoms, and modified compounds of these diisocyanates (carbodiimido-modified compounds, urethane-modified compounds, and urethodione-modified compounds), and mixture of two or more of these compounds.
Examples of the aromatic diisocyanates are 1,3- and/or 1,4-phenylene diisocyanate, 2,4- and/or 2,6-tolylene diisocyanate (hereinafter, abbreviated as TDI), 2,4'- and/or 4,4'-diphenylmethanediisocyanate (hereinafter, abbreviated as MDI), 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane and 1,5-naphthylene diisocyanate.
Examples of the aliphatic diisocyanates are ethylene diisocyanates, tetramethylene diisocyanate, hexamethylene diisocyanates, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanates, lysine diisocyanate, 2,6-diisocyanatomethylcaproate, bis (2-isocyanatoethyl) carbonate and 2-isocyanatoethyl-2,6-diisocyanatohexanoate.
Examples of the alicyclic diisocyanates are isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, cyclohexylene diisocyanate, methyl cyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexylene-1,2-dicarboxylate, 2,5- and/or 2,6-norbornane diisocyanate.
Examples of the aromatic aliphathic diisocyanate are m-and and/orp-xylylene diisocyanate and α, α, α', α' -tetramethylxylylene diisocyanate.
Preferable examples of (a1) are aromatic diisocyanates and alicyclic diisocyanates and particularly preferable examples are isophorone diisocyanate and 4,4'-dicyclohexylmethane diisocyanate.
Examples of the high molecular weight polyol (a2) are, for example, polyetherdiols (a21) and polyester diols (a22), mixtures of two or more of them.
Examples of the polyether diols (a21) are compounds having a structure formed by adding alkylene oxides (hereinafter, abbreviated as A0) to active hydrogen atom-containing bifunctional compounds, mixtures of two or more of them.
Examples of the active hydrogen atom-containing bifunctional compounds are dihydric alcohols, dihydricphenols and dicarboxylic acids.
The dihydric alcohols may be ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, bis(hydroxymethyl)cyclohexane, bis(hydroxyethyl)benzene . Dihydric phenols may include catechol and hydroquinone, bisphenols such as bisphenol A, bisphenol F and bisphenol S. Dicarboxylic acid may include aliphatic dicarboxylic acids such as succinic acid and adipic acid, aromatic dicarboxylic acids such as phthalic acid and terephthalic acid.
Two or more of the above-mentioned active hydrogen atom-containing bifunctional compounds may be used in combination.
Examples of AO to be added to the active hydrogen atom-containing bifunctional compounds are ethylene oxide (hereinafter, abbreviatedas EO), propylene oxide (hereinafter, abbreviated as PO), 1,2-, 2, 3-, or 1,3-butylene oxide, tetrahydrofuran (hereinafter, abbreviated as THF), styrene oxide, α-olefin oxide and epichlorohydrin.
AO may be used alone or two or more of these may be used in combination, and in the case of the latter, block addition, random addition, and mixtures of them may be included.
Preferable examples of AO are EO alone, PO alone, THF alone, a combination of PO and EO, and a combination of THF with PO and/or EO.
Addition of AO to the active hydrogen atom-containing bifunctional compounds can be carried out by a conventional method in the absence or presence of a catalyst (an alkali catalyst, an amine catalyst, or an acid catalyst).
Specific examples of (a21) are polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and preferred is polytetramethylene glycol.
The polyester diols (a22) include condensed polyester diols (a221) obtainable by reaction of low molecular weight diols and/or polyether diols having a molecular weight of 1,000 or lower with dicarboxylic acids; polycarbonate diols (a222) obtainable by reaction of low molecular weight diols and their mixtures with carbonic acid diesters of lower alcohols (e.g. methanol); polylactonediols (a223) obtainable by ring-opening polymerization of lactone.
Examples of the above-mentioned low molecular weight diols may include the above-exemplified dihydricalcohols. Examples of the polyether polydiols having a molecular weight of 1,000 or lower may include polytetramethylene ether glycol, polypropylene glycol, polyethylene glycol, mixtures of two or more of them.
Examples of the dicarboxylic acids may include aliphatic dicarboxylic acids (e.g. succinic acid, adipic acid, azelaic acid, sebacic acid), aromatic dicarboxylic acids (e.g. terephthalic acid, isophthalic acid, phthalic acid ), ester-formable derivatives of these dicarboxylic acids [e.g. acid anhydrides, lower alkyl (1 to 4 carbon atoms) esthers, mixtures of two or more kinds of these . Examples of the lactone may include ε-caprolactone, γ-butyrolactone, γ-valerolactone, mixtures of two or more of them.
The polyesterification reaction may be carried out by a conventional method, for example, a method of (condensation) reacting low molecular weight diols and/or polyetherdiols having a molecular weight of 1,000 or lower with dicarboxylic acids or their ester-formable derivatives, a method of adding lactone to initiators (low molecular weight diols and/or polyether diols having a molecular weight of 1,000 or lower).
Examples of (a221) are adipate type condensed polyester diols such as polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentylene adipate diol, polyethylene propylene adipate diol, polyethylene butylene adipate diol, polybutylene hexamethylene adipate diol, and poly (polytetramethylene ether) adipate diol; azelate type condensed polyester diols such as polyethylene azelate diol and polybutylene azelate diol; sebacate type condensed polyester diols such as polyethylene sebacate diol and polybutylene sebacate diol.
Examples of (a222) are polyalkylene carbonate diols of straight chain alkylenes having 4 to 10 carbon atoms (hereinafter, abbreviated as C4-10) (e.g. polytetramethylene carbonate diol, polyhexamethylene carbonate diol, polycarbonate diol of nonane diol); polyalkylene carbonate diols of branched C4-10 alkylenes (e.g. polycarbonate diols of 2-methylbutanediol, polycarbonate diol of 2-ethylbutanediol, polycarbonate diol of neopentyl glycol, polycarbonate diol of 2-methylpentanediol, polycarbonate diol of 3-methylpentanediol ; their copolymers.
Examples of (a223) are polycaprolactonediols and the like.
In terms of the hydrolysis resistance and durability, among (a2), polycarbonate diols (a222) are preferable and polytetramethylene carbonatediol, polyhexamethylene carbonate diol, polycarbonate diol of 3-methylpentaaediol, their copolymer are more preferable.
The lower limit of the number average molecular weight (hereinafter, abbreviated as Mn) of (a2) is preferably 500 and more preferably 1,000, and the upper limit thereof is 20,000, more preferably 10,000, and particularly preferably 3,000.
Mn of (a2) can be calculated from the hydroxyl value, and the hydroxyl value can be measured by a method standardized in JIS-K0070-1992 (potentiometric titration method).
The carboxyl group- and/or sulphonic group-containing polyol or its salt (a3) is a component to be used for introducing a carboxylate group or sulphonate group for a purpose of self-emulsification of the polyurethane resin in water.
Examples of (a3) are carboxyl group-containing polyols (a31) [e.g. dialkylolalkanoic acid {those of C6-24 such as 2,2-dimethylolpropionic acid (hereinafter, abbreviated as DMPA), 2,2-dimethylolbutanoic acid, 2,2-dimethylolheptanoic acid, 2,2-dimethyloloctanoic acid}], sulphonic group-containing polyols (a32) [e.g. sulphonic acid diols {such as 3-(2,3-dihydroxypropoxy)-1-propanesulphonic acid }, sulphamic acid diols {such as N,N-bis(2-hydroxyalkyl) sulphamic acid and its AO adducts }], combinations of two or more of them.
Examples of salts of (a3) are ammonium salts, amine salts [salts of C1-12 primary amines (primary monoamines such as methylamine, ethylamine, propylamine, and octylamine), salts of secondary monoamines (such as dimethylamine, diethylamine, and dibutylamine), salts of tertiary monoamines (aliphatic tertiary monoamines such as trimethylamine, triethylamine, triethanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine; heterocyclic tertiary monoamines such as N-methylpiperidine and N-methylmorpholine; aromatic ring-containing tertiary monoamines such as benzyldimethylamine, α-methylbenzyldimethylamine, and N-dimethylaniline)], salts of alkali metals (such as sodium, potassium, and lithium), combinations of two or more kinds of these.
Among these salts, amine salts are preferable, aliphatic tertiary monoamine salts are more preferable, and triethylamine salts are particularly preferable.
Examples of the chain extending agent (a4) are C2-10 diamines (e.g. ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, tolaenediamine ); polyamines (e.g. diethylenetriamine, triethylenetetramine); hydrazine or its derivatives (dibasic aciddihydrazide such as adipic aciddihydrazide); C2-15 polyhydric alcohols [the above-exemplified dihydric alcohols, trihydric alcohols (e.g. glycerin, trimethylolpropane ), low mole adduct of EO and/or PO of these polyhydric alcohols (molecular weight: lower than 500)], combinations of two more kinds of these compounds. Among them, ethylene diamine and isophoronediamine are preferable.
Examples of the terminator (a5) are C1-8 monohydric alcohols (e.g. methanol, ethanol, isopropanol, butanol, cellosolves, carbitols), C1-10 monoamines (e.g. monomethylamine, monoethylamine, monobutylamine, dibutylamine, monooctylamine, monoethanolamine, diethanolamine), combinations of two or more kinds of these. Among them, monoethylamine, monobutylamine, and monoethanolamine are preferable.
In the case where (a3) is a carboxyl group- and/or sulphonic group-containing polyol, not a salt, the carboxyl group and/or sulphonic group may be neutralized by using (a6) to be carboxylate group and/or sulfonate group.
Examples of neutralizer (a6) may include alkaline compounds, for example, ammonia, amines [C1-12 primary amines (primarymonoamine such as methylamine, ethylamine, propylamine, and octylamine), secondary monoamines (dimethylamine, diethylamine, and dibutylamine), tertiary monoamines (aliphatic tertiary monoamines such as trimethylamine, triethylamine triethanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine; heterocyclic tertiary monoamines such as N-methylpiperidine, N-methylmorpholine ; aromatic ring-containing tertiary monoamines such as benzyldimethylamine, α-methylbenzyldimethylamine, N-dimethylaniline)], alkali metals (sodium, potassium, and lithium), alkali metal hydroxides, combinations of two or more kinds of these. Among them, amines are preferable, aliphatic tertiary monoamines are more preferable, and triethylamine is particularly preferable.
The total amounts of (a4) and (a5) to be used is generally 0 to 100% by equivalent on the basis of the equivalent of NCO groups at the prepolymer terminals, and from a viewpoint of resin strength, preferably 20 to 80% by equivalent and more preferably 30 to 70% by equivalent.
The amount of (a6) to be used for neutralization is generally 20 to 200% by mole and preferably 30 to 150% by mole on the basis of the total of the carboxyl groups and the sulphonic groups. If the amount of (a6) to be used is 30% by mole or more, it is preferable in terms of the storage stability of an aqueous dispersion and if it is 150% by mole or less, it is preferable in terms of the viscosity of an aqueous dispersion.
In the invention, (a) contains carboxylate groups and/or sulfonate groups in an amount preferably at least 0.01%, more preferably at least 0.05%, and particularly preferably at least 0.08% and at highest 1.5%, more preferably at highest 0.75%, and particularly preferably at highest 0.50% on the basis of the weight of said polyurethane resin (a). If the content of sulphonate carboxylate groups and/or sulphonate groups is lower than 0.01%, it tends to be difficult to obtain stable (A) and on the other hand, if it exceeds 1.5%, the water resistance of a resin coating formed tends to be decreased.
The content of carboxylate groups and/or sulphonate groups in (a) can be calculated by heat drying 3 to 10 g of (A) at 130°C for 45 minutes, washing the obtained residues with water, again heat drying the residues at 130°C for 45 minutes, dissolving the resulting residues in dimethylformamide, and measuring the acid value by a method standardized in JIS-K0070 (potentiometric titration methods).
The Mn of (a) can be measured by gel permeation chromatography (hereinafter, abbreviated as GPC).
In the case where (a) is a non-crosslinkable (thermoplastic) one, the Mn is preferably 2,000 to 2,000,000 or higher, more preferably 10,000 to 1,500,000, and particularly preferably 100,000 to 500,000. In the case where (a) is a crosslinkable one, those having Mn higher than the above-mentioned range or Mn in the range impossible of GPC measurement may be used.
In the reaction for obtaining (a) in the invention, to promote the reaction, a common catalyst to be used reaction may be used, if necessary. Examples of the catalyst are amine catalysts, e.g. triethylamine, N-ethylmorpholine, triethylenediamine, cycloamidines described in US Patent No. 4,524,104 [1,8-diazabicyclo(5,4,0)undecene-7 (DBU, manufactured by San-Apro Ltd.); tin catalysts, e.g. dibutyltin dilaurate, dioctyltin dilaurate, tin octylate; titanium catalysts such as tetrabutyl titanate.
To produce (a) in the invention, the following two methods can be exemplified.

(1) A method for obtaining (a) in form of an emulsion by producing a prepolymer terminated with isocyanate groups (hereinafter, for short, referred to as NCO group-terminated urethane prepolymer) in advance and emulsifying the prepolymer in the presence of a dispersant, and if necessary, an emulsifier (a7), a chain-expanding agent (a4), a terminator (a5).
(2) A method by producing a polyurethane resin terminated with hydroxyl groups and obtaining (a) in form of an emulsion in the presence of a dispersant, and if necessary, an emulsifier (a7).

Between them, the method (1) is preferable.
The NCO group-terminated urethane prepolymer in the method (1) is obtainable by reacting an active hydrogen component composed of (a1) with that composed of (a2) and (a3) at a ratio of (NCO/hydroxyl groups) by equivalent in a range of generally 1.05 to 2.0, preferably 1.1 to 1.6, at generally 20°C to 150°C, preferably 60°C to 110°C in an one-shot manner or multi-step manner in the presence or absence of an organic solvent having no activehydrogen-containing group in the molecule (e.g. acetone, methylethylketone, tetrahydrofuran, N,N-dimethylformamide ) to obtain an urethane polymer terminated with hydroxyl groups and neutralizing the urethane polymer with (a6).
Examples of the dispersants required for producing an emulsion to be generally used include water and hydrophilic organic solvent, As the hydrophilic organic solvents, those having a solubility in water of 30 or more/100 g of water and for example, monohydric alcohols (e.g. methanol, ethanol isopropanol), glycols (e.g. ethylene glycol, propylene glycol, diethylene glycol), trihydric or higher alcohols (e.g. glycerin), cellosolves (e.g. methyl cellosolve, ethyl cellosolve) can be exemplified.
Among the dispersant, water is preferable. In the case where hydrophilic organic solvents are used in combination, the content of hydrophilic organic solvent is generally preferably 10% or lower based on the total of the dispersant.
The emulsion in the method (2) is obtainable by reacting an active hydrogen component composed of (a1) with that composed of (a2) and (a3) at a ratio of (NCO/hydroxyl group) by equivalent in a range of 0.5 to 0.99 in one-shot manner or multi-step manner in the presence or the absence of an organic solvent having no active hydrogen-containing group in the molecule to obtain an urethane polymer terminated with hydroxyl groups and neutralizing the urethane polymer with (a6).
The emulsifies (a7) to be used in the above-mentioned methods (1) and (2) may include the nonionic surfactant (c) with a cloud point of 40 to 98°C, which will be described later, another nonionic surfactant (a71), an anionic surfactant (a72), a cationic surfactant (a73), an amphoteric surfactant (a74), and a polymer type emulsifying dispersant (a75), and those described in US Patent Nos. 3,929,678 and 4,331,447 can be exemplified. Two or more kinds of these may be used in combination.
Among (a7), (c) described later is preferable in terms of heat-sensitive coagulation property.
Examples of (a71) include nonionic surfactants which have no cloud point or have a could point lower than 40°C or higher than 98°C among alkylene oxide-addition type nonionic surfactants and polyhydric alcohol type nonionic surfactants.
Examples of alkylene oxide-addition type nonionic surfactants of (a71) include nonionic surfactants which have no cloud point or have a could point lower than 40°C or higher than 98°C (e.g. nonylphenol EO 50 mole adduct) among aliphatic alcohol EO adducts, phenol EO adducts, nonylphenol EO adducts, alkyl (C8-22)-amine EO adduct, polypropylene glycol EO adducts. Examples of polyhydric alcohol type nonionic surfactants are fatty acid (C8-24) esters of polyhydric (tri to octa or higher) alcohol (C2-30) (e.g. glycerin monostearate, glycerin monooleate, sorbitan monolaurate, sorbitan monooleate), alkyl (C4-24) poly (1 to 10 polymerization degree)-glycocides .
Examples of (a72) are ether carboxylic acids having a C8-24 hydrocarbon group and their salts [e.g. lauryl ether acetate sodium salt, (poly) oxyethylene (addition mole number 1 to 100) lauryl ether acetate sodium salt]; sulphuric acid esters or ether sulphuric acid esters having a C8-24 hydrocarbon group and their salts [e.g. lauryl sulfate sodium salt, (poly) oxyethylene (addition mole number 1 to 100) lauryl sulphate sodium salt, (poly)oxyethylene (addition mole number 1 to 100) lauryl sulphate triethanolamine, (poly)oxyethylene (addition mole number 1 to 100) coconut oil fatty acid monoethanolamide sulphate sodium salt]; sulphonic acid salts having a C8-24 hydrocarbon group [e.g. dodecylbenzenesulphonic acid sodium salt]; sulfosuccinic acid salts having one or two C8-24 hydrocarbon groups; phosphoric acid esters and ether phosphoric acid esters having a C8-24 hydrocarbon group and their salts [e.g. lauryl phosphate sodium salt, (poly)oxyethylene (addition mole number 1 to 100) lauryl ether phosphate sodium salt]; fatty acid salts having a C8-24 hydrocarbon group [e.g. sodium laurate, lauric acid triethanolamine ]; acylated aminoacid salts having a C8-24 hydrocarbon group [e.g. coconut oil fatty acid methyltaurine sodium salt, coconut oil fatty acid sarcosine sodium salt, coconut oil fatty acid sarcosine triethanolamine, coconut oil fatty acid acyl-L-glutamic acid triethanolamine, N-coconut oil fatty acid acyl-L-glutamic acid sodium salt, lauroylmethyl-β-alanine sodium salt.
Examples of (a73) include quaternary ammonium salts type [e.g. stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, distearyldimethylammonium chloride, ethylsulfuric acid lanoline fatty acid aminopropylethyethyldimethylammonium]; amine salt types [e.g. stearic acid diethylaminoethylamide lactate, dilaurylamine hydrochlride, oleylamine lactate].
Examples of (a74) include betaine type amphoteric surfactants [coconut oil fatty acid amidopropyldimethylamino acetic acid betaine, lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, laurylhydroxysulfobetaine, lauroylamidoethylhydroxyethylcarboxymethylbetaine hydroxypropyl phosphate sodium salt]; aminoacid type amphoteric surfactants [β-laurylaminopropionic acid sodium salt].
Examples of (a75) include polyvinyl alcohol, starch and its derivatives; cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose ; carboxyl group-containing (co)polymers having Mn = 1,000 to 50,000 such as poly (acrylic acid) sodium salt; polymer type dispersants having urethane bonds or ester bonds described in US Patent No. 5,906,704 [e.g. those obtainable by bonding polycaprolactone polyol and polyether diols by polyisocyanate], .
The softening water-repellent (b), one of the essential components of (A) in the invention is not particularly limited if it is a compound conventionally used as a softening water-repellent and for example, silicone compounds (b1), fluorine compounds (b2) can be exemplified. These compounds may be used alone and two or more kinds of these may be used in combination.
Examples of the silicone compounds (b1) include polysiloxanes and modified silicone oils. The polysiloxanes may be dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenepolysiloxane, diorganopolysiloxane diol. The modified silicone oils may be epoxy-modified silicone oil, alkyl-modified silicone oil, alkylaralkyl-modified silicone oil, amino-modified silicone oil, carboxyl-modified silicone oil, alcohol-modified silicone oil, fluorine-modified silicone oil, polyether-modified silicone oil.
Examples of fluorine compound (b2) include, for example, acrylic acid fluoroalkyl ester type copolymers (e.g. 1,1-dihydroperfluorooctyl acrylate polymers, perfluoroalkylethyl acrylate-alkyl acrylate-copolymers .
Among them, (b1) are preferable, polysiloxanes are more preferable, and dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenepolysiloxane, and combinations of them are particularly preferable.
The component (b) may be a silicone compound or a fluorine compound itself or may be in form of an emulsion emulsified and dispersed in an aqueous medium. In terms of the easiness of addition, an emulsion is more preferable.
An emulsifying agent to be used for (b) inform of an emulsion may be the emulsifying agent (a7) exemplified in the production of the emulsion of (a).
Commercially available (b) in form of an emulsion may include, as silicone compounds, SM8706^® (manufactured by Dow Corning Toray Co., Ltd., effective component 35%) and KM797^® (manufactured by Shin-Etsu Chemical Co., Ltd., effective component 38%), and, as fluorine compounds, Dicguard^® F-90N (manufactured by Dainippon Ink and Chemicals, Inc., effective component 20%).
The nonionic surfactant with a cloud point of 40 to 98°C (c), one of the essential components of (A) in the invention is not particularly limited if it is among nonionic surfactants with a cloud point of 40 to 98°C and preferably polyethylene glycol type nonionic surfactants. The cloudpoint is preferably 42 to 95°C and more preferably 42 to 80°C. If the cloud point of (c) is lower than 40°C, in the case where (A) is stored for a long duration, a problem of the storage stability, for example formation of coagulated matters, is caused. On the other hand, if the cloud point exceeds 98°C, the affinity of polyurethane with water becomes so high as to make heat-sensitive coagulation of (A) difficult.
The cloud point can be measured by heating a 2% aqueous solution of a nonionic surfactant under stirring and reading the temperature in a thermometer at which the surfactant becomes clouded.
The component (c) may be used as an emulsifier at the time of producing emulsion of (a) or (b) mentioned above and may also be added/incorporated newly after the production of emulsion.
Specific examples of (c) include aliphatic alcohol EO adducts [oleyl alcohol EO 11 to 16 mole adducts (cloud point 78 to 93°C), lauryl alcohol EO 8 to 11 mole adducts (cloud point 70 to 98°C); alkyl (C8-22) phenol EO adducts [octyl phenol EO 9.5 to 14 mole adducts (cloud point 65 to 94°C), nonyl phenol EO 10 to 15 mole adducts (cloud point 64 to 96°C) ]; alkyl (C8-22) amine EO adducts; polypropylene glycol EO adducts [polypropylene glycol (Mn = 700) EO 20 to 30 mole adducts] and these EO adducts may contain a small amount (30% by mole or lower) of random or block adducts with PO.
The lower limit of HLB of (c) is preferably 10, more preferably 11, and particularly preferably 12 and the upper limit is preferably 17, more preferably 16, and particularly preferably 15. If HLB of (c) is 10 or higher, even if the emulsion is stored for a long duration, no coagulated matter is formed and the storage stability is thus made excellent and therefore, it is preferable. On the other hand, if HLB is 17 or lower, the heat-sensitive coagulation is easily caused when the emulsion is heated and therefore, it is preferable.
HLB in the invention is a value calculated by Griffin' method described in "New Introduction to Surfactants", p. 128 (1992), written by Takehiko FUJIMOTO and issued by Sanyo Chemical Industries, Ltd. as follows. $H L B = (% b y w e i g h t o f h y d r o p h i l i c g r o u p s) \times (1 / 5)$
Examples of commercially available (c) include the following aliphatic alcohol EO adducts. EMULMIN^® NL-70; C12 higher alcohol EO adduct, cloud point = 44°C, HLB = 12.4, manufactured by Sanyo Chemical Industries, Ltd.; EMUZMIN^® 110; C16-18 higher alcohol EO adduct, cloud point = 56°C, HLB = 13.2, manufactured by Sanyo Chemical Industries, Ltd.; NAROACTY^® N-120; C14-15 higher alcohol EO adduct, cloud point = 77°C, HLB = 14.2, manufactured by Sanyo Chemical Industries, Ltd.; and
EMULMIN^® 140; C16-18 higher alcohol EO adduct, cloud point = 80°C, HLB = 14.2, manufactured by Sanyo Chemical Industries, Ltd.
Examples of the inorganic salt (d), one of the essential components of (A) in the invention, may include the following inorganic salts having a solubility in water at 25°C of 1 or higher and more preferably 10 or higher. The salt (d) has a function of coagulating an emulsion and examples of it are follows.

Alkali metal salts (d1) :

Alkali metal hydroxides [sodium hydroxide, potassium hydroxide, and lithium hydroxide], alkali metal carbonates [sodium carbonate, sodium hydrogens carbonate, potassium carbonate, potassium hydrogen carbonate, and lithium carbonate], alkali metal sulfates [sodium sulfate and potassium sulfate], alkali metal nitrates [sodium nitrate and potassium nitrate], alkali metal phosphates [sodium phosphate, sodium hydrogen phosphate, and potassium phosphate], alkali metal sulfites [sodium sulfite, sodium hydrogen sulfite, and potassium sulfite], and alkali metal halogen (chlorine, bromine, iodine and fluorine) compounds [sodium chloride, potassium chloride, sodium bromide, potassium iodine, and potassium fluoride] .

Alkaline earth metal salts (d2) :

Alkaline earth metal (calcium, magnesium, barium, strontium) hydroxides [calcium hydroxide, magnesium hydroxide, and strontium hydroxide], alkaline earth metal carbonates [calcium carbonate and magnesium carbonates], alkaline earth metal sulfates [calcium sulfate and magnesium sulfate], alkaline earth metal nitrates [calcium nitrate and magnesium nitrate], alkaline earth metal phosphates [calcium hydrogen phosphate, magnesium hydrogen phosphate], alkali earth metal sulfites [calcium sulfite and magnesium sulfite], alkaline earth metal halogen (chlorine, bromine, iodine, and fluorine) compounds [calcium chloride, magnesium chloride, calcium bromide, calcium iodide, magnesium fluoride]. Ammonium salts (d3) :
Ammonium halide (ammonium chloride ammonium bromide, ).
Among them, (d1) is preferable in terms of the storage stability of the emulsion for a relatively long duration.
The method for producing the heat-sensitive coagulable emulsion (A) in the invention is not particularly limited and the method involving adding (d) to the emulsion composed of (a), (b), and (c) are preferable in terms of the storage stability.
A method for producing the emulsion composed of (a), (b), and (c) may be the following methods.

(1) ; A method of adding emulsions (b) and (c) to an emulsion of (a).
(2) ; A method of mixing (c) and if necessary (a7) with any one or more of a hydroxyl-terminated polyurethane resin, an NCO-terminated urethane prepolymer and a dispersant for emulsifying them in a dispersant and then further adding an emulsion of (b).
(3); A method of mixing (c) and if necessary (a7) with either a hydroxyl-terminated polyurethane resin or an NCO-terminated prepolymer and then dispersing and emulsifying the obtained mixture in an emulsion of (b).
(4); A method of mixing (b) with either a hydroxyl-terminated polyurethane resin or an NCO-terminated prepolymer, adding (c) and mixing the resultant, and further emulsifying the mixture by adding water alone or a mixture of water and (c).
(5); A method of mixing (b) with either a hydroxyl-terminated polyurethane resin or an NCO-terminated prepolymer and then emulsifying the mixture by adding a mixture of water and (c).

Among these methods, the method (2) is preferable in terms of the storage stability of (A).
An apparatus to be employed for the mixing and emulsifying process in the invention is not particularly limited and emulsifying apparatuses in the following methods are available, for example: 1) an anchor type stirring method, 2) a rotator-stator method [e.g. Ebara Milder^®: manufactured by Ebara Corp.], 3) a line mill method [e.g. a line flow mixer], 4) a static pipe mixing method [e.g. a static mixer], 5) a vibration type [e.g. VITRO MIXER^®; manufactured by Reica Co., Ltd.], 6) an ultrasonic impact method [e.g. an ultrasonic homogenizer], 7) a high pressure impact method [e.g. Goulin^® homogenizer, manufactured by Goulin Inc.], 8) a membrane emulsification method [e.g. a membrane emulsifying module], and 9) a centrifugal thin film contact method [e.g. FILMICS^®]. Among them, 1), 2), and 9) are preferable.
The heat-sensitive coagulation temperature of (A) in the invention is preferably 35 to 90°C and more preferably 40 to 80°C in terms of storage stability and coagulation property. Thatis, the heat-sensitive coagulable emulsion (A) is preferable to be coagulated when the temperature itself reaches 35 to 90°C.
The heat-sensitive coagulation temperature can be measured with a thermometer by heating each emulsion and reading the temperature at which the emulsion is coagulated and does not fluidize.
The volume average particle diameter of (A) of the invention is preferably 0.01 µm to 1 µm and more preferably 0.02 µm to 0.5 µm. The volume average particle diameter means the volume average particle diameter of dispersed phase dispersed in the dispersant in form of an emulsion.
The volume average particle diameter can be measured by ELS-80^® model electrophoresis light scattering photometer manufactured by Otauka Electronics Co., Ltd.
The tensile strength of a film obtainable by leaving (A) of the invention at a room temperature (25°C) for 24 hours and successively drying at 105°C for 3 hours is preferably 10 to 100 MPa and more preferably 20 to 60 MPa. To produce the film, if necessary, a film formation assisting agent may be used.
The tensile strength can be measured by the following method. The obtained film is cut by No. 3 Dumbbell Cutter^® for obtaining a specimen for a test and using an autograph [AGS-500D^®, manufactured by Shimadzu Corp.], the specimen is pulled at a pulling speed of 300 mm/min, and the strength at the time of tensile is measured. In this connection, the test is carried out at a temperature of 25°C and a relative humidity of 65% RH and it is required to keep the test specimen in the same conditions for 2 hours or longer before the measurement.
If necessary, (A) of the invention may contain a coloring agent such as titanium oxide, an ultraviolet absorbent (e.g. benzophenone type or benzotriazole type one), various kinds of stabilizers such as an antioxidant [e.g. hydantophenols such as triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] ; organic phosphite such as triphenylphosphite and trichloroethylphosphite], a preservative, a crosslinking agent (e.g. polyepoxy compounds, polyisocyanates, ), and an inorganic filler (e.g. calcium carbonate).
The total amount of these additives is preferably 5 parts by weight or less and more preferably at least 0.1 parts by weight and at highest 3 parts by weight in 100 parts by weight of the solid matter of (A).
Supply of (A) of the invention to the fiber material substrate is carried out by impregnation or application and any kinds of conventionally employed methods may be employed.
For example, a method of impregnating the fiber material substrate in (A) and adjusting the pick-up of the material by squeezing it with a mangle and other methods using a knife coating, an air knife coating, a roll coating, a spray coating can be exemplified.
A coagulating and drying method of (A) applied to the substrate may be, for example, (1) a method of blowing heated steam for carrying out heat-sensitive coagulation and then heat drying or air drying by a drying apparatus, (2) a method of introducing it into a drying apparatus for heat coagulation and drying. The method (1) is preferable between them.
The ambient temperature for heat-sensitive coagulation of (A) applied to the substrate is preferably 40 to 180°C, more preferably 60 to 150°C, and particularly preferably 70 to 120°C in terms of stability of the coagulation bath and quick completion of the coagulation of the polyurethane resin. The time for the heat-sensitive coagulation is 0.1 minutes to 30 minutes and preferably 0.5 minutes to 20 minutes although depending on the temperature.
The drying temperature after coagulation is generally 100 to 200°C, preferably 120 to 180°C and the drying time is 1 to 60 minutes and preferably 2 to 30 minutes.
The leathery sheet material of the invention is obtained by the above-mentioned method.
The adhesion weight of the polyurethane (a) to the fiber material substrate is preferably at least 3 parts by weight, more preferably at least 10 parts by weight, and particularly preferably 20 parts by weight and preferably at highest 150 parts by weight, more preferably at highest 100 parts by weight, and particularly preferably at highest 50 parts by weight to the fiber material substrate 100 parts by weight.
The leathery sheet of the invention is obtainable by carrying out post-treatment such as dyeing, washing, grinding or drying for the leathery sheet material obtained in the above-mentioned manner.
The dyeing can be carried out by conventionally known methods using a circular dyeing apparatus. The dyes to be used for the dyeing are not particularly limited and dyes mainly containing dispersion dyes, metal complex dyes, acidic dyes can be exemplified.
The washing is carried out for removing the unreacted dyes, surfactants, inorganic salts. The method for washing is not particularly limited and methods of rubbing by a circular dyeing apparatus using hot or cold water, immersing in a water bath and squeezing by a mangle, can be exemplified.
The grinding is carried out for raising the surface of the artificial leather. The method for grinding is not particularly limited and a method of using an emery wheel can be exemplified.
The drying is carried out for removing water after impregnation, improving the strength of the resin. The method for drying is not particularly limited and may be a hot air drying using a pin tenter, an infrared heating, a microwave heating.
The leathery sheet of the invention has a proper leather strength and improved abrasion-resistance and good hand characteristics similar to that of natural leather and therefore is very useful. The leathery sheet of the invention may be used for various purposes such as mattresses, bag-lining materials, clothes, core materials for shoes, cushion fabrics, interior materials of automobiles, wall materials.
The method for producing the leathery sheet material of the invention requires no additional process for applying a softening repellent and is excellent in productivity, and the obtained leathery sheet material is excellent in hand characteristics and abrasion-resistance.
The method for producing a leathery sheet material of the invention requires no additional process for applying a softening repellent and is excellent in productivity, and the obtained leathery sheet material is excellent in hand characteristics and abrasion-resistance. Furthermore, the leathery sheet material and the leathery sheet obtainable by the method of the invention are useful for mattresses, bag-lining materials, clothes, core materials for shoes, cushion fabrics, interior materials of automobiles, wall materials.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, the invention will be described more in details with reference to examples, however it is not intended that the invention be limited to the illustrated examples. It is noted that the term "part" means "part by weight" below.
"Mn" in the following production examples was calculated from the hydroxy value measured by the method standardized in JIS-K0070-1992 (potentiometric titration method).

Production Example 1

330 parts of polyhexamethylene carbonate diol having Mn 2,000, 6.5 parts of 2,2-dimethylolpropionic acid (DMPA), 98 parts of 4, 4' -dicyclohexylmethane diisocyanate, and 235 parts of acetone were loaded into a tightly closed reaction bath equipped with a thermometer and a stirrer, the reaction system was replaced with nitrogen gas, and then the mixture was reacted at 90°C for 10 hours under stirring to obtain an acetone solution of NCO-terminated urethane prepolymer. The obtained acetone solution was cooled to 40°C and 5.0 parts of triethylamine was added. Next, as (c), a solution obtained by dissolving 21.7 parts of NAROACTY^® N-120 (manufactured by Sanyo Chemical Industries, Ltd.; HLB = 14.2, cloud point = 77°C) in 412 parts of water was added to the acetone solution, stirred for 1 minute by a homo-mixer for emulsification, and then to the solution obtained was added 1.0 part of ethylene diamine dissolved in 230 parts of water. Then, chain expansion reaction was carried out, acetone was removed by distillation in reduced pressure, and the concentration was adjusted by adding water to obtain a polyurethane resin emulsion 1 with a nonvolatile residue 40% and an average dispersed particle diameter 0.5 µm,
The carboxylate content was 0.51% on the basis of weight of (a) in the obtained polyurethane resin emulsion 1.

Production Example 2

A polyurethane resin emulsion 2 was obtained in the same manner as Production Example 1, except that 3-methyl-1,5-pentanediol/1,6-hexanediol copolymer polycarbonate diol having Mn 2,000 was used in place of the polyhexamethylene carbonate diol having Mn 2, 000 and as (c), EMULMIN NL^®-70 (manufactured by Sanyo Chemical Industries, Ltd.; HLB = 12.4, cloud point = 44°C) was used.
The carboxylate content was 0.50% on the basis of weight of (a) in the obtained polyurethane resin emulsion 2.

Production Example 3

A polyurethane resin emulsion 3 was obtained in the same manner as Production Example 1, except that Nonipol^® 500 (nonylphenol EO adduct, manufactured by Sanyo Chemical Industries, Ltd.; HLB = 18.2, cloud point = 100°C or higher) was used in place of NAROACTY^® N 120 of (c).
The carboxylate content was 0.48% on the basis of weight of (a) in the obtained polyurethane resin emulsion 3.

Production Example 4

A laminate sheet was produced from polyethylene terephthalate short fibers, the sheet was needle-punched at a hitting number of 280 punch/cm² and dried to obtain a nonwoven fabric A with a weight of 380 g/m² and an apparent density of 0.18 g/cm².

Comparative Production Example 1

The nonwoven fabric A was impregnated in an emulsion type (R) silicone SM 8706 (manufactured by Dow Corning Toray Co., Ltd.) diluted to 5% pure component and dried at 120°C for 20 minutes to obtain a nonwoven fabric B to which silicone adhered at 2% adhesion ratio.

Example 1

A heat-sensitive coagulable emulsion of the invention was obtained by adding 3 parts of the emulsion type silicone SM 8706^® (manufactured by Dow Corning Toray Co., Ltd.) as (b) and 8 parts of a 10% aqueous solution of calcium chloride as (d) to 100 parts of the polyurethane resin emulsion 1 and adding water so as to adjust a nonvolatile residue to be 20%. The nonwoven fabric A was impregnated in the emulsion, squeezed by a mangle in a manner that the adhesion ratio of the resin to the nonwoven fabric weight was 30%. Then, the obtained fabric was heated in saturated steam at 100°C for 2 minutes, further dried at 120°C for 20 minutes by a hot air drier, washed with water, and again dried at 120°C for 20 minutes by a hot air drier to obtain a leathery sheet material.

Example 2

A leathery sheet material was obtained in the same manner as Example 1, except that as (b), 6 parts of an emulsion type silicone KM 797^® (manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

Example 3

A leathery sheet material was obtained in the same manner as Example 1, except that as (b), 6 parts of an emulsion type fluoro compound Dicguard^® F-90N (manufactured by Dainippon Ink and Chemicals, Inc.) was used.

Example 4

A leathery sheet material was obtained in the same manner as Example 1, except that the polyurethane resin emulsion 2 was used in place of the polyurethane resin emulsion 1.

Comparative Example 1

A leathery sheet material was obtained in the same manner as Example 1, except that the polyurethane resin emulsion 3 was used in place of the polyurethane resin emulsion 1.

Comparative Example 2

A leathery sheet material was obtained in the same manner as Example 1, except that (d) was not added.

Comparative Example 3

A leathery sheet material was obtained in the same manner as Example 1, except that (b) was not added.

Comparative Example 4

A leathery sheet material was obtained in the same manner as Example 4, except that (b) was not added.

Comparative Example 5

A leathery sheet material was obtained in the same manner as Comparative Example 3, except that the nonwoven fabric B was used in place of the nonwoven fabric A.
The components and the heat-sensitive coagulation temperature of the heat-sensitive coagulable emulsions used in Examples and Comparative Examples and the types of the nonwoven fabrics used are shown in Table 1 and Table 2.
In this connection, the heat-sensitive coagulation temperature was measured by heating each emulsion and reading the temperature by a thermometer when the emulsion was coagulated and did not fluidize.

With respect to the leathery sheet material produced in Examples and Comparative Examples, the adhesion ratio (% by weight) of resin, abrasion-reaistance (the average nap length), and hand characteristics were evaluated by the following evaluation method. The results are shown in Table 1 and Table 2.

[Adhesion ratio of resin (% by weight)]

It was calculated according to the following equation: $100 \times [(w e i g h t o f l e a t h e r y s h e e t m a t e r i a l) - (w e i g h t o f f i b e r m a t e r i a l s u b s t r a t e)] / (w e i g h t o f f i b e r m a t e r i a l s u b s t r a t e)$

[Abrasion-resistance]

The abrasion-resistance was evaluated based on the average nap length (µm) by observing the ground face of each leathery sheet material by a scanning electron microscope when the sheet was subjected to a test 500 times at 1 kg load with an abrasive wheel H-18 by a taber type abration tester, and it was determined that those having long nap without being cut by the abration tester were good.

[Hand characteristics]

Those of the leathery sheet materials having hand characteristics just like natural leather were marked "excellent" : those which are slightly inferior in the softness as compared with natural leather were marked "Fair": and those which are insufficient in softness and showed no natural leathery hand characteristics were marked "Poor". The determination was done by hand characteristics by a sensory test.

Claims

A method for producing a leathery sheet material which comprises applying a heat-sensitive coagulable emulsion (A) to a fiber material substrate without a softening and water-repellent treatment and successively carrying out heat coagulation, said heat-sensitive coagulable emulsion (A) containing a polyurethane resin (a), a nonionic surfactant with a cloud point of 40 to 98°C (c), and an inorganic salt (d),
characterized in that said heat-sensitive coagulable emulsion (A) further comprises a softening water-repellent (b), the weight ratio (b)/(a) being in a range of 0.005 to 0.2.
The method for producing a leathery sheet material according to Claim 1
wherein (a) is a polyurethane resin containing carboxylate groups and/or sulphonate groups in an amount 0.01 to 1.5% by weight on the basis of the weight of (a).
The method for producing a leathery sheet material according to Claim 1 or 2
wherein (b) is a silicone compound and/or a fluorine compound.
The method for producing a leathery sheet material according to any one of Claims 1 to 3
wherein the heat-sensitive coagulation is carried out at a temperature of 40 to 180°C.
A leathery sheet material obtainable by the method according to any one of Claims 1 to 4.
A leathery sheet obtainable by further post-processing the leathery sheet material according to Claim 5.