JP2003227074A - Method of producing leather-like sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a leather-like sheet of practical use by improving the unbalance between the fabric hand and physical properties that is observed in the artificial leather production including the step where an ultrafine fiber-generating fiber is treated with alkali to remove or peel off the one component. <P>SOLUTION: The method of producing leather-like sheets mainly composed of ultrafine fibers and a polyurethane resin matrix comprises the following four steps: the step (1) where sheets are produced by using ultrafine fiber- generating fibers that can generate ultrafine fibers by treating with an alkaline aqueous solution; the step (2) where the sheets constituted with the ultrafine fiber-generating fibers are treated with an alkaline aqueous solution to generate ultrafine fibers; the step (3) where an isocyanate blocked with a blocking agent which dissociates at 40-100°C is applied to the sheets and the step (4) where the sheet is applied with a polyurethane resin. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a leather-like sheet having excellent strength. More particularly, the present invention relates to a method for producing a leather-like sheet having a good balance between texture and strength. 2. Description of the Related Art Conventionally, artificial leathers which are not inferior to natural leathers, using ultrafine fibers, having good naps, excellent flexibility and quality, are known. As this production method, for example, first, a felt is formed from a fiber using a component for forming an ultrafine fiber as one component of the conjugate fiber of the ultrafine fiber generation type and a component using a component soluble in an organic solvent as another component. Then, after applying a polyurethane resin solution using dimethylformamide as an organic solvent to the felt, one component of the composite fiber is dissolved and removed with an organic solvent to form ultrafine fibers, or a solution of the polyurethane resin after ultrafine fibers is applied. By doing so, the target is obtained. [0003] However, such a method requires an organic solvent for removing one component of the conjugate fiber or an organic solvent of a polyurethane resin. Such a solvent has a possibility of environmental pollution, and in particular, in recent years, from the viewpoint of global environmental protection, a new production method which does not require such an organic solvent has been strongly demanded. For this reason, an alkali-soluble polymer is used as a component for dissolving and removing the ultrafine fiber-generating conjugate fiber.
Means for processing the components are being considered. Further, by going one step further, studies are being made on a process using a polyurethane resin from a solution type to an aqueous emulsion type and using no solvent at all. However, when a felt obtained by dissolving and removing one component with an alkali is used, the feel of a leather-like sheet obtained by adding a polyurethane resin to the felt is very soft, but the physical properties are very low, and the balance between the two is inferior. There was a problem that it could not be taken. [0004] The present invention is to improve the imbalance of texture and physical properties observed in a method of producing artificial leather including a step of removing or peeling one component with alkali using ultrafine fiber-generating fibers, and to provide a leather-like material which can sufficiently withstand practical use. An object of the present invention is to provide a method for producing a sheet-like material. [0005] A method for producing a leather-like sheet according to the present invention which achieves the above object has the following constitution. That is, in producing a leather-like sheet mainly composed of ultrafine fibers and polyurethane resin,
This is a method including the following four steps. (1) A step of producing a sheet using ultrafine fiber-expressing fibers that generate ultrafine fibers by treatment with an alkaline aqueous solution. (2) A step of providing a sheet with a blocked isocyanate having a blocking agent that dissociates at 40 ° C. to 100 ° C. or lower. (3) A step of treating the sheet with an alkaline aqueous solution to generate ultrafine fibers. (4) A step of applying a polyurethane resin to the sheet. Hereinafter, a method for producing a leather-like sheet according to the present invention will be described in detail. [0008] The ultrafine fiber-generating fiber referred to in the present invention is 2
A conjugate fiber composed of at least one component and capable of forming (generating) an ultrafine fiber by removing at least one component. Typically, one component of the ultrafine fiber is resistant. The composite fiber has alkali solubility, and is composed of a component in which other components differ in alkali solubility (decomposition) property by 20 times or more, preferably 40 times or more. The form of such ultrafine fibers is disclosed in
No. 8-22126, inter-polymer fibers as disclosed in JP-B-51-21041, mixed spun fibers as disclosed in JP-B-60-21904, and JP-A-9-310230. Etc., based on nebula type, multi-layer type, hollow island type, etc., in combination, or deformed and developed, etc., one component is removed or peeled By doing so, it is possible to appropriately select from those capable of obtaining an ultrafine fiber of 0.3 dtex or less. As the combination of polymer components for obtaining such fibers, the alkali-resistant components for forming ultrafine fibers include polyesters such as polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate, copolyesters, nylon-6, nylon- Polyamides such as 6, 6 and copolymerized polyamides can be preferably used. In addition, the alkali-soluble component may have high spinnability and high solubility in an aqueous alkali solution, and can be used without any particular limitation.
For example, polyethylene terephthalate or polybutylene terephthalate and the like, 5-sodium sulfoisophthalic acid, polyethylene glycol, sodium dodenylbenzenesulfonate, bisphenol A compound, isophthalic acid, adipic acid, dodecadionic acid, cyclohexylcarboxylic acid, etc. Copolymerized polyester copolymerized by mol% is preferred. Of these, it is preferable to use a polyethylene terephthalate copolymer obtained by copolymerizing 5-sodium sulfoisophthalic acid at 5 to 20 mol%. These copolymers may be not only binary but also multi-component copolymers of three or more. An ultrafine fiber-generating conjugate fiber is obtained from such a combination of polymers according to a conventionally known method. In the present invention, a sheet is formed using the ultrafine generation type composite fiber. In forming the sheet, non-woven fabric, woven fabric, knitted fabric and the like can be used as the form,
Although not particularly limited, a nonwoven fabric is preferable in terms of texture. As a means for forming the nonwoven fabric, any appropriate means can be used, and not only a method of laminating fibers with a cross wrapper to form a sheet, but also a sheet directly by spinning such as a spun bond method, a melt blow method, a flash spinning method. It can be arbitrarily selected according to the purpose such as the method. After the sheeting, a fiber entanglement treatment such as a needle punch or a water jet punch is performed as necessary. According to the present invention, the sheet thus obtained is treated with an alkaline aqueous solution, so that the ultrafine generation type fiber is ultrafine. Here, the alkaline aqueous solution refers to an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous ammonium salt solution, or the like. To treat with an alkaline aqueous solution in the present invention, generally, after immersing the sheet in these aqueous solutions,
This refers to neutralizing, washing, and drying the aqueous alkali solution in the sheet with acetic acid or the like. At this time, by appropriately adjusting the concentration, temperature, and the like of the alkaline aqueous solution, a more favorable treatment with the alkaline aqueous solution can be performed. It is also a preferred embodiment of the present invention that the treatment with the aqueous alkali solution is performed only on the surface layer of the sheet. That is, by stopping the generation of ultrafine fibers only in the vicinity of the surface layer, the inside remains as a thick fiber, so that a unique sheet with good surface touch and stiffness can be obtained. In order to achieve this, a thickener such as polyvinyl alcohol is added to coat the surface layer so that only a part of the surface layer is dissolved in order to prevent the alkaline aqueous solution from reaching the entire inside of the sheet. The thickener is removed in a subsequent suitable step. According to the present invention, prior to treatment with an alkali,
For the purpose of controlling the bond between the polyurethane resin and the fiber, it is also recommended that the sheet is previously provided with a hot water-soluble polymer such as polyvinyl alcohol or carboxymethyl cellulose having a high degree of saponification. In the method of the present invention, a sheet obtained by treating with an alkaline aqueous solution is provided with a polyurethane resin. The polyurethane resin used in the present invention can be basically used without any particular limitation. However, as shown below, each of a polycarbonate diol containing a polycarbonate as a part of a polyol component, a diisocyanate, and a chain extender is used. It is preferable to use a polyurethane resin obtained by appropriately combining and reacting the components. Polycarbonate
As todiol, for example, 1,4-butanediol,
Compounds obtained by reacting glycols such as 1,5-pentanediol, 1,6-hexanediol and diethylene glycol with dimethyl carbonate, diphenyl carbonate and phosgene are exemplified. Further, a copolymer obtained by combining the polycarbonate diol with a polyester diol, a polyether diol, or the like as another polyol component may be used. As the polyester diol, for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-
Examples thereof include pentanediol and 1,6-hexanediol, and are not particularly limited. Examples of the polyether diol include, but are not particularly limited to, ethylene glycol, diethylene glycol, triethylene glycol, and propylene glycol. The diisocyanate component of the polyurethane resin used in the present invention includes, for example, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 3,3
-Dimethoxy-4,4-phenylene isocyanate; and the like, but is not particularly limited thereto. As the chain extender for the polyurethane resin used in the present invention, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, ethylenediamine, hexamethylenediamine, 4,4'- And diaminodiphenylmethane. These may be used alone or in combination of two or more. In the present invention, the polyurethane resin is applied to an ultrafine sheet, wet coagulated, and then dried. The amount of the polyurethane resin applied to the sheet is preferably from 5 to 150% by weight, more preferably from 10 to 100% by weight, based on 100% of the fibers in the sheet. If the applied amount is less than 5% by weight, the obtained sheet-like material may lack a sense of fulfillment and the leather-like texture may deteriorate. On the other hand, the application amount is 15
If the content is more than 0% by weight, the obtained sheet-like material becomes hard, and the texture of the leather may deteriorate. The polyurethane resin used in the present invention may be of a solution type, but is more preferably an emulsion type from the viewpoint of minimizing the use of an organic solvent. In the emulsion system, either a forced emulsification type or a self-emulsification type may be used, but in the case of the forced emulsification type, a nonionic surfactant shown below is contained in a proportion of 1 to 10 parts by weight based on 100 parts by weight of the polyurethane resin resin. Is preferred. If the amount of the nonionic surfactant is less than 1 part, when the emulsion is stored for a long period of time, phase separation occurs, the dispersoid is separated, a creamy precipitate is generated, and a coagulate that cannot be redispersed is generated. This causes a problem in storage stability. When the amount of the nonionic surfactant is more than 10 parts, the sensitivity of gelation is insufficient, and the time required for gelation even when heated is increased. Nonionic surfactants used in the emulsion polyurethane resin include surfactants having a hydroxyl group or a polyether unit which is not ionically dissociated in water as a hydrophilic group, and are commonly used polyethylene glycol. Type nonionic surfactants. Examples of the polyethylene glycol type nonionic surfactant include higher alcohol ethylene oxide adducts such as polyoxyethylene lauryl ether and polyoxyethylene cetyl ether; fatty acid polyethylene oxide esters, polyhydric alcohol fatty acid ester ethylene oxide adducts, and the like. No. The emulsion polyurethane resin used in the present invention may contain an organic solvent or may be a completely aqueous system containing no organic solvent. Those not containing are preferably used. Further, other resins may be used in combination with the emulsion polyurethane resin used in the present invention, as long as the heat-sensitive gelling property and storage stability are not impaired.
Examples of resins that can be used in combination include natural rubber, acrylonitrile-butadiene copolymer, and polybutadiene. These resins may be used alone or in combination of two or more. Further, if necessary, an ultraviolet absorber, an antioxidant, a colorant, and the like may be added. In the present invention, when an emulsion polyurethane resin is applied to a micronized sheet, a method of impregnating or applying a diluted emulsion polyurethane resin liquid to the sheet and performing dry heat coagulation is performed. Thereafter, there are a method of drying by heating, a method of immersing in a bath in which the inorganic salt is dissolved or a hot water bath for coagulation, and a method of combining these coagulation methods, but are not particularly limited. Also, when applying and coagulating the emulsion polyurethane resin liquid, since a difference occurs in the distribution of the polyurethane resin inside the sheet, by adding an inorganic salt to the emulsion polyurethane resin liquid in advance, or by adding a thickener or the like, There is also a process for controlling the distribution of the polyurethane resin. However, these treatments alone have low water resistance and low dyeing resistance, so that the substrate is preferably 90 ° C to 200 ° C.
1 to 60 minutes, more preferably 120 ° C.
Heat treatment at 150 ° C. for about 2 to 20 minutes. In the present invention, after the polyurethane resin is applied to the sheet, the blocked isocyanate is applied. The blocked isocyanate used in the present invention refers to a compound having an isocyanate group whose terminal is masked with a blocking agent. The blocking agent referred to here is a compound that dissociates from 40 ° C to 100 ° C, and specifically, 2-pyridinol, 3-pyridinol, 4-pyridinol, 4-methyl-2-pyridinol, 4,6-dimethyl- 2-pyridinol, 2-chloro-3-pyridinol, 2-bromo-5
-Pyridinol, 3-nitro-4-pyridinol, 3-
Pyridinol derivatives such as nitro-5-bromo-4-pyridinol, 2-mercaptopyridine, 6-methyl-2-
Mercaptopyridine derivatives such as mercaptopyridine, 2,6-dimethyl-4-mercaptopyridine, 5-nitro-2-mercaptopyridine, 2-quinolinol, 3-quinolinol, 4-quinolinol, 8-quinolinol,
-Methyl-4-quinolinol, 1-benzo [f] quinolinol, 5-benzo [f] quinolinol, 3-methyl-
1-benzo [f] quinolinol, 4,6-dichloro-8
-Quinolinol, 4-nitro-8-quinolinol, 10
Quinolinol derivatives such as benzo [h] quinolinol,
Quinoline thiol derivatives such as quinoline-2-thiol and quinoline-8-thiol, 1-isoquinolinol,
Isoquinolinol, 5-isoquinolinol, 6-isoquinolinol, 8-isoquinolinol, 4-nitro-8-
Isoquinolinol derivatives such as isoquinolinol, hydroxypyridazine derivatives such as 3-hydroxypyridazine,
2-pyrimidinol, 5-pyrimidinol, 6-pyrimidinol, 2,4-dimethyl-6-pyrimidinol,
Pyrimidinol derivatives such as 4,6-dimethyl-2-pyrimidinol, 2-mercaptopyrimidinethiol,
Pyrimidine thiol derivatives such as mercapto-4-methyl-pyrimidine thiol, pyrazinol derivatives such as pyrazinol and 3,6-dimethylpyrazinol, cinnolinol derivatives such as 3-cinnolinol, 4-cinnolinol and 8-cinnolinol, 1 -Hydroxyphthalazine derivatives such as hydroxyphthalazine, 2-quinoxalinol,
Quinoxalinol derivatives such as 3-methyl-2-quinoxalinol, 2-hydroxy-1,7-naphthyridine, 8
-Hydroxy-1,7-naphthyridine, 4-hydroxy-1,5-naphthyridine, 2-hydroxy-1,5-naphthyridine, 8-hydroxy-1,6-naphthyridine,
Hydroxynaphthyridine derivatives such as 2-hydroxy-1,8-naphthyridine, 3-hydroxy-2,6-naphthyridine, 4-hydroxy-8-nitro-1,5-naphthyridine, 6-hydroxy-1,7- Phenanthroline,
4-chloro-10-hydroxy-1,7-phenanthroline, 5-chloro-6-hydroxy-1,7-phenanthroline, 2-hydroxy-4-methyl-1,10-phenanthroline, 5-hydroxy-4,7- Hydroxyphenanthroline derivatives such as phenanthroline, hydroxyanthrazoline derivatives such as 2-hydroxy-pyrido [2,3-g] quinoline and 2-hydroxy-pyrido [3,2-g] quinoline, 1-phenazinol, 2-phenazinol Phenazinols, 2-acridinol, etc.
Acridinol derivatives such as 4-acridinol, hydroxytriazine derivatives such as 2-hydroxy-s-triazine, 3-hydroxy-as-triazine, 4-hydroxy-v-triazine, 3-hydroxy-1,2,4-benzotriazine; 5-hydroxy-v-tetrazine, 3
Hydroxytetrazine derivatives such as -hydroxys-tetrazine; sodium bisulfite; The use of sodium bisulfite among these blocking agents is preferred in that the feeling and strength of the sheet can be balanced. The compound having an isocyanate group which is a component of the blocked isocyanate used in the present invention includes, for example, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, , 2-butylene diisocyanate,
Aliphatic diisocyanates such as 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl caproate, 3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate,
1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methyl 2,4-cyclohexane diisocyanate, 1,3-bis (isocyanate Alicyclic diisocyanates such as methyl) cyclohexane,
For example, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate,
2,2′-diphenylmethane diisocyanate, 4,
Aromatic diisocyanates such as 4'-diphenyl diisocyanate, 2,4- or 2,6-tolylene diisocyanate or a mixture thereof, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate; 1,
Araliphatic diisocyanates such as 3- or 1,4-bis (1-isocyanate-1-methylethyl) benzene or mixtures thereof, triphenylmethane-4,
4 ', 4''-triisocyanate, 1,3,5-triisocyanatobenzene, polyisocyanate monomer such as organic tetraisocyanate such as 2,4,6-triisocyanate toluene, etc. Examples include a polyisocyanate having a 2,4,6-oxadiazinetrione ring obtained from the above-mentioned polyisocyanate monomer and carbon dioxide gas such as a derived dimer, trimer, buret, and allophanate. These can be used alone or in combination of two or more. From the viewpoint of obtaining the desired effects of the present invention, particularly preferred are 4,4′-diphenylmethane diisocyanate,
4- or 2,6-tolylene diisocyanate and mixtures thereof. Further, in order to activate the isocyanate group of the polyisocyanate and promote the reaction with the fiber surface, hydroxyl group or urethane group, an appropriate catalyst may be added to the blocked isocyanate or polyurethane resin. Examples of the catalyst include 1,4-diaza (2,2,2) bicyclooctane, dibutylin dilaurate, stannose octoate, N-methylmorpholine, N, N, N ′, N′-tetra These may be used alone or in a mixture of two or more such as methylbutanediamine. Such a blocked isocyanate is applied in the form of a solution, an emulsion or a suspension. As a surfactant used when dispersing in water, for example, sodium dodecylbenzenesulfonate,
Anionic surfactants such as sodium lauryl sulfate, sodium dodecyl diphenyl ether disulfonate and sodium dialkyl succinate sulfonate; nonionic surfactants such as polyoxyethylene alkyl ester and polyoxyethylene alkyl aryl ether; or lauryl betaine and stearin Examples include alkyl betaine type salts such as betaine salts, and amino acid type surfactants such as lauryl-β-alanine, lauryl di (aminoethyl) glycine, and octyl di (aminoethyl) glycine. These can be used alone or in combination of two or more. Among these, nonionic surfactants are preferred. As the blocked isocyanate compound used in the present invention, two or more different blocked isocyanates can be used in combination. In the present invention, when a blocked isocyanate is applied to a sheet, the amount of the applied isocyanate is generally difficult to determine and may be appropriately adjusted according to the situation. On the other hand, it becomes 0.1 to 50 weight. After applying such a blocked isocyanate to the sheet, heat treatment is performed. The heating temperature of the heat treatment depends on the dissociation temperature of the blocked isocyanate.
To 120 ° C., and the treatment time is preferably in the range of 1 minute to 30 minutes. When the treatment temperature is lower than 40 ° C., the blocking agent of the blocked isocyanate is difficult to dissociate, and when it is higher than 120 ° C., the color developability of the product after dyeing may be reduced. In applying the blocked isocyanate used in the present invention to a sheet, a conventionally known catalyst may be added in advance to the blocked isocyanate in order to increase the reactivity of the isocyanate group. The catalyst to be added is, for example, tetrabutyldiamine, triethylenediamine, dibutyltin dilaurate, tin octylic acid, or the like. In producing a leather-like sheet based on the method for producing a leather-like sheet according to the present invention, a step of adding a blocked isocyanate to a polyurethane resin in advance to provide a blocked isocyanate compound and a step of providing a polyurethane resin are provided. You can go at once. In consideration of the balance between the physical properties and texture of the leather-like sheet finally obtained, the order of the treatment with an aqueous alkali solution, the step of applying a polyurethane resin, and the step of applying a blocked isocyanate may be appropriately changed. I do not care. In the present invention, the sheet thus obtained is cut in half by an appropriate slicing machine (slice cutting in a direction perpendicular to the thickness direction so as to make two sheets each having a thickness of 1/2) according to the case. That is, buffing, dyeing, etc., to obtain a desired leather-like sheet. EXAMPLES The present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The physical properties shown in the following examples were measured according to the following methods. (1) Breaking strength Using a tensilon elongation measuring machine, sample length 15 cm,
The width was measured at 2 cm and a pulling speed of 15 cm / min, and the breaking strength (N / cm) was determined. Example 1 30 parts of polyethylene terephthalate obtained by copolymerizing 8 mol% of 5-sodium sulfoisophthalic acid as a sea component,
Polyethylene terephthalate as an island component in a ratio of 70 parts (1) A filament is made of 36 islands in a filament, and a staple of a sea-island type fiber having an average fineness of 3.8 dtex is used to create a web through a card and a cross wrapper. Needle punching was performed to produce a nonwoven fabric. The fiber substrate was impregnated with 30 parts by weight of an aqueous solution of polyvinyl alcohol having a saponification degree of 95 with respect to the island component, dried, and then heat-treated at 180 ° C. The fiber substrate after the heat treatment was immersed in a 10% by weight aqueous solution of sodium hydroxide at 40 ° C. for 30 minutes to remove sea components, washed with water, and dried. Next, Evaphanol AL is applied to the substrate made into a fine fiber.
-3 (Nichika Chemical) blocked isocyanate solution on substrate 1
4 parts by weight per 100 parts by weight was impregnated and dried. Next, the substrate was steam-treated immediately after impregnating with 12% by weight of an aqueous emulsion polyurethane resin so that the solid content of the aqueous polyurethane resin was 48 parts by weight with respect to the island component, and heat-treated at 130 ° C. for 5 minutes. Next, the polyvinyl alcohol inside the substrate was removed with hot water at 100 ° C., then cut in half with a slicing machine, buffed, and dyed with a disperse dye using a jet dyeing machine. The breaking strength of the green machine before dyeing was 55.7 N / c.
m, the breaking strength of the dyed product was 49 N / cm. The texture and resilience of the dyed product were equivalent to those obtained by a conventionally known manufacturing method. Comparative Example 1 30 parts of polyethylene terephthalate obtained by copolymerizing 8 mol% of 5-sodium sulfoisophthalic acid as a sea component,
The filament was a form in which 36 islands were contained in the filament at a ratio of 70 parts of polyethylene terephthalate as the island component, and a web was formed through a card and a cross wrapper using staples of sea-island type fibers having an average fineness of 3.8 dtex. Thereafter, needle punching was performed to prepare a nonwoven fabric. After impregnating the fiber substrate with 30 parts by weight of an aqueous solution of polyvinyl alcohol with respect to the island component and drying,
The heat treatment of ° C was performed. After the heat treatment, the fiber substrate is
After immersion in a 10% by weight aqueous sodium hydroxide solution for 30 minutes to remove sea components, the product was washed with water and dried. Next, a steamer treatment was carried out immediately after impregnating the 12% by weight aqueous polyurethane resin resin solution so that the ultrafine fiberized substrate contained 48% by weight of the aqueous polyurethane resin resin solid content with respect to the island component. A heat treatment of 5 ° C. was performed for 5 minutes. Next, the polyvinyl alcohol inside the substrate was removed with hot water at 100 ° C., then cut in half with a slicing machine, buffed, and dyed with a disperse dye using a jet dyeing machine. The breaking strength of the pre-dyeing green machine is 58.8 N / c.
m, the breaking strength of the dyed product was as low as 20.4 N / cm. The texture of the dyed product was higher than that of a product obtained by a conventionally known manufacturing method, but the resilience was low. According to the method of the present invention, it is possible to produce a leather-like sheet having excellent breaking strength and having the same durability and flexibility as products obtained by a conventional production method. Can be.

Claims (1)

Claims: 1. A method for producing a leather-like sheet, comprising the following four steps for producing a leather-like sheet mainly comprising ultrafine fibers and a polyurethane resin. (1) A step of producing a sheet using ultrafine fiber-expressing fibers that generate ultrafine fibers by treatment with an alkaline aqueous solution. (2) A step of treating the sheet composed of the ultrafine generation fibers with an alkaline aqueous solution to generate ultrafine fibers. (3) A step of applying a blocked isocyanate having a blocking agent that dissociates at 40 ° C. to 100 ° C. or lower on the sheet. (4) A step of applying a polyurethane resin to the sheet.