JP2000265052A - Polyurethane emulsion and leather-like sheet produced using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leather-like sheet which gives a leather-like sheet excellent in light fastness and flexibility such as light yellowing resistance and light dyeing fastness, and a leather-like sheet produced using the emulsion. I will provide a. SOLUTION: In a polyurethane emulsion obtained by emulsifying a polyurethane obtained by reacting a polymer polyol, an organic diisocyanate, and a chain extender in an aqueous medium, the polymer polyol contains a hindered amine compound unit in an amount of 0.1% to the polymer polyol. The problem is solved by a polyurethane emulsion characterized by having 2 to 10% by weight, and a leather-like sheet obtained by impregnating the emulsion with a fibrous base material and coagulating it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyurethane emulsion. Since the polyurethane emulsion of the present invention contains, as a main component, a polyurethane having excellent light fastness such as light yellowing resistance and light dyeing fastness, it is useful for producing a leather-like sheet having excellent light fastness.

[0002]

2. Description of the Related Art Leather-like sheets using a resin component such as polyurethane as a binder for a fibrous base material have been conventionally produced as a substitute for natural leather. Typical production methods include a wet coagulation method in which an organic solvent solution of a resin component such as polyurethane is impregnated into a fibrous base material and then coagulated in a non-solvent, and a resin component such as polyurethane is dispersed in water or the like. It can be roughly classified into a dry coagulation method in which an emulsion or a solution dissolved in an organic solvent is impregnated into a fibrous base material and then dried. The wet coagulation method is different from the dry coagulation method,
Although it is possible to produce a sheet having a texture closer to that of natural leather, it is inferior in productivity and disadvantageous in that the use of an organic solvent such as dimethylformamide (DMF) is indispensable. On the other hand, in the dry coagulation method, it is possible to obtain a sheet without using an organic solvent by using an aqueous emulsion, but the texture of the obtained sheet is inferior to the wet coagulation method. Becomes However, in recent years, there has been a strong demand for switching from a wet coagulation method using an organic solvent such as DMF which causes environmental pollution to a dry coagulation method using an aqueous polyurethane emulsion.

[0003] Polyurethane used for producing a leather-like sheet material used for artificial leather must have light resistance such as light yellowing resistance and light dyeing fastness. In the production of a leather-like sheet by a conventional wet coagulation method, a method using a polyurethane in which a group having a function of improving light resistance is introduced into a molecular chain (JP-A-56-4347).
8, JP-B-63-31490, JP-A-4-2586
No. 42 gazette) has been proposed. In this method,
Polyurethane is produced by a solution polymerization method or a bulk polymerization method by reacting a light fastness improver having a polymerizable group with a general polymer polyol, an isocyanate compound and a diol as a chain extender.

[0004]

However, in the production of an aqueous polyurethane emulsion used for producing a leather-like sheet by a dry coagulation method, an emulsion polymerization method using a diamine as a chain extender is preferably used. According to this method, when a polyurethane emulsion is produced by reacting the light resistance improver having the above polymerizable group, a normal polymer polyol, an isocyanate compound and a chain extender, the reactivity of the light resistance improver is increased. Since it is lower than diamine, the light resistance improver remains unreacted in the leather-like sheet produced using the obtained polyurethane emulsion, and flows out in the post-treatment process such as the dyeing process. The problem is that unreacted light resistance improver bleeds out from the leather-like sheet. There is a problem that significantly impair the touch and appearance of the surface. As described above, as an aqueous polyurethane emulsion used in the production of a leather-like sheet by a dry coagulation method, a polyurethane that imparts sufficient light resistance such as light yellowing resistance and light-fastness required for a leather-like sheet is required. Is not obtained as a main component.

An object of the present invention is to provide a polyurethane emulsion which gives a leather-like sheet having excellent light fastness such as light yellowing resistance and light dyeing fastness, washing fastness and flexibility by a dry coagulation method, It is an object of the present invention to provide a leather-like sheet obtained by impregnating a solid base material and coagulating it.

[0006]

As a result of intensive studies by the present inventors, the present inventors have found that the above objects can be achieved by using a polymer polyol having a hindered amine compound unit as a raw material for producing a polyurethane emulsion. Was completed. That is, the present invention provides a polyurethane emulsion obtained by emulsifying a polyurethane obtained by reacting a polymer polyol, an organic diisocyanate and a chain extender in an aqueous medium, wherein the polymer polyol has a hindered amine compound unit with respect to the polymer polyol. A polyurethane emulsion characterized by having 0.2 to 10% by weight. The present invention relates to a polyurethane emulsion obtained by mixing a thermosensitive gelling agent with the above polyurethane emulsion. In addition, the present invention relates to a method for producing a leather-like sheet which impregnates and solidifies a fibrous base material with the above polyurethane emulsion. Further, the present invention relates to a leather-like sheet obtained by the above-mentioned production method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the polymer polyol having a hindered amine compound unit used in the present invention include polyester polyol, polyether polyol, polycarbonate polyol, polyester polycarbonate polyol and the like. These polymer polyols may be used alone or in combination of two or more. Among these, it is preferable to use polyester polyol, polyether polyol, and polycarbonate polyol as the polymer polyol.

[0008] The above polyester polyol is subjected, for example, to a direct esterification reaction or transesterification reaction of a dicarboxylic acid or an ester-forming derivative thereof such as an ester or an anhydride thereof with a low-molecular-weight polyol, or a lactone is opened according to a conventional method. It can be produced by ring polymerization.

As the low molecular weight polyol used in the production of the polyester polyol, those generally used in the production of polyester can be used.
For example, ethylene glycol, diethylene glycol,
Triethylene glycol, propylene glycol, 1,
3-propanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-
Butanediol, 1,4-butanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-
Octanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol,
1,9-nonanediol, 2,8-dimethyl-1,9-
Aliphatic diols having 2 to 15 carbon atoms such as nonanediol and 1,10-decanediol; alicyclic diols such as cyclohexanediol, cyclohexanedimethanol and dimethylcyclooctanedimethanol; 1,4-bis (β-hydroxyethoxy And) aromatic diols such as benzene. These low molecular polyols may be used alone or in combination of two or more. Among them, low molecular polyols include 3-
It is preferable to use an aliphatic diol having 4 to 10 carbon atoms such as methyl-1,5-pentanediol and 1,6-hexanediol.

As the dicarboxylic acid used in the production of the polyester polyol, those generally used in the production of polyester can be used. For example, succinic acid, glutaric acid, adipic acid, pimelic acid,
Suberic acid, azelaic acid, sebacic acid, dodecandioic acid, methylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, trimethyladipic acid, 2-methyloctanedioic acid, 3,8-dimethyldecandioic acid, 3, An aliphatic dicarboxylic acid having 4 to 12 carbon atoms such as 7-dimethyldecane diacid; an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid; an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, orthophthalic acid, and naphthalenedicarboxylic acid; Ester-forming derivatives and the like can be mentioned. These dicarboxylic acids may be used alone,
Two or more kinds may be used in combination. Among these, as the dicarboxylic acid, it is preferable to use an aliphatic dicarboxylic acid having 4 to 10 carbon atoms, such as adipic acid and sebacic acid.

Examples of the lactone include ε-caprolactone, β-methyl-δ-valerolactone and the like. These lactones may be used alone or in combination of two or more.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (methyltetramethylene glycol) and the like. These polyether polyols may be used alone or in combination of two or more. Among them, it is preferable to use polytetramethylene glycol as the polyether polyol.

As the polycarbonate polyol, for example, those obtained by reacting a low molecular weight polyol with a carbonate compound such as dialkyl carbonate, alkylene carbonate, diaryl carbonate and the like can be used. As the low molecular polyol constituting the polycarbonate polyol, the low molecular polyol exemplified above as the constituent component of the polyester polyol can be used. As the polycarbonate polyol, it is preferable to use polyhexamethylene carbonate diol.

As the polyester polycarbonate polyol, for example, those obtained by simultaneously reacting a low molecular polyol, a dicarboxylic acid and a carbonate compound can be used. Alternatively, a polyester polyol and a polycarbonate polyol which are synthesized in advance by the above-described method and then reacted with a carbonate compound, or a low-molecular polyol and a dicarboxylic acid, may be used.

The number average molecular weight of the high molecular polyol is 500 points from the viewpoint that the leather-like sheet produced by impregnating and coagulating the obtained polyurethane emulsion has excellent properties such as flex resistance and flexibility. It is preferably in the range of 5,000 to 5,000, more preferably in the range of 850 to 4,000, and still more preferably in the range of 1500 to 3,500. In addition, the number average molecular weight of the high molecular polyol referred to in this specification is calculated based on a hydroxyl value measured in accordance with JIS K1577.

The polymer polyol used in the present invention comprises:
The main chain has a hindered amine compound unit. The content of the hindered amine compound unit in the polymer polyol is based on the weight of the polymer polyol,
0.2 to 10% by weight, 0.3 to 9% by weight
Is more preferably within a range of 0.4 to 8% by weight. When the content of the hindered amine compound unit is less than 0.2% by weight, the leather-like sheet produced using the obtained polyurethane emulsion has insufficient light resistance such as light yellowing resistance and light dyeing fastness. . Further, when the content of the hindered amine compound unit is more than 10% by weight, it takes an extremely long time to produce a polymer polyol having the above number average molecular weight, which is inefficient and increases the production cost. The effect of improving light resistance is small. As long as the polymer polyol has a hindered amine compound unit in a ratio within the above range, 2
It is possible to use more than one kind of high molecular polyol, and if the content of the hindered amine compound unit is within the above range with respect to the total high molecular polyol,
You may use together the high molecular polyol which does not introduce a hindered amine compound unit. The content of the above hindered amine compound unit with respect to the polyurethane is 0.1%.
It is preferably in the range of 15 to 10% by weight,
More preferably, it is in the range of from about 8% by weight to about 8% by weight.
More preferably, it is in the range of 7% by weight.

As the hindered amine compound used as a raw material for producing a polymer polyol having a hindered amine compound unit, all of the four hydrogen atoms at the 2-position and the 6-position have carbon atoms such as methyl group and t-butyl group in the molecule. Those having a piperidine ring substituted with 1 to 5 alkyl groups and further having a reactive functional group such as an ester group, a hydroxyl group, and a carboxyl group are preferable. As such a compound, for example, the following general formula (2):

[0018]

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Wherein R ¹ is an alkylene group, R ² is a hydrogen atom or an alkyl group, and x is an integer of 4 to 20.

Hindered amine compound represented by the formula: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-)
4-piperidyl) sebacate, 1- [2- [3- (3,
5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy]
-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine and the like.

Among these, the hindered amine compound is a compound represented by the above general formula (2) because it has a large number of ester groups and can efficiently introduce a hindered amine compound unit into a polymer polyol by a transesterification reaction. preferable. In the above general formula (2),
The alkylene group represented by R ¹ is preferably an alkylene group having 1 to 10 carbon atoms, and more preferably an alkylene group having 1 to 6 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a 1,2-propylene group, and a 1,3-
Propylene group, 1,3-butylene group, 2-methyl-1,
Examples thereof include a 3-propylene group, and among them, an ethylene group is preferable. R ² is a hydrogen atom or an alkyl group, and the alkyl group has 1 to 10 carbon atoms.
Is preferred, and an alkyl group having 1 to 4 carbon atoms is more preferred. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Among them, R ² is preferably a hydrogen atom or a methyl group.

In the above general formula (2), x is 4 to 2
It is an integer of 0 and preferably an integer of 6 to 15.
When x is less than 4, it is necessary to incorporate a large amount of the hindered amine compound represented by the general formula (2) in order to obtain sufficient light resistance, so that the molecular weight of the obtained polymer polyol becomes too small, When a plurality of high-molecular polyols are used in combination, the compatibility with other high-molecular polyols tends to be low, so that they tend to be unsuitable as raw materials for producing high-molecular polyols. On the other hand, when x is larger than 20, the molecular weight of the hindered amine compound represented by the general formula (2) becomes too large, which has an adverse effect on the production of the polymer polyol, and the obtained polyurethane film has poor physical properties such as tensile strength. This tends to be unsuitable for producing a leather-like sheet.

The hindered amine compound represented by the general formula (2) is 1- (2-hydroxyethyl) -4-
It can be produced by polycondensing hydroxy-2,2,6,6-tetramethylpiperidine with dicarboxylic acid or dicarboxylic acid ester. Examples of the dicarboxylic acid or dicarboxylic acid ester include malonic acid, succinic acid, glutaric acid, adipic acid, methyl succinic acid, 2-methylglutaric acid, 3-methylglutaric acid, and other aliphatic dicarboxylic acids or methyl esters thereof, ethyl Examples thereof include alkyl esters such as esters, propyl esters, and butyl esters. As a hindered amine compound, 1- (2
-Hydroxyethyl) -4-hydroxy-2,2,6
Polycondensates of 6-tetramethylpiperidine and dimethyl succinate are preferred.

The polymer polyol having a hindered amine compound unit is, for example, in the case of a polyester polyol, a method in which a hindered amine compound having an ester group in a molecule is added to a raw material component of a usual polyester polyol and a transesterification reaction is carried out during a polymerization reaction. It can be produced by a method in which a hindered amine compound having one or more hydroxyl groups or carboxyl groups in a molecule is added to a usual raw material component of a polyester polyol and subjected to a polycondensation reaction.

If the number of hydroxyl groups per polymer polyol molecule is larger than 2, there is no problem in use as long as it does not hinder the emulsion synthesis. As a method for obtaining a polymer polyol having more than two hydroxyl groups, a method for producing a polymer polyol is to reduce the number of hydroxyl groups in one molecule so that the number of hydroxyl groups per molecule of the polymer polyol becomes a desired number. A method in which at least one low-molecular polyol is used in combination. For example, when producing a polyester polyol having more than two hydroxyl groups, a low molecular polyol having three or more hydroxyl groups is used in combination. Examples of the low-molecular polyol having three or more hydroxyl groups include, for example,
Examples thereof include glycerin, trimethylolpropane, butanetriol, hexanetriol, trimethylolbutane, and pentaerythritol, and one or more of these can be used.

As the organic diisocyanate, a known aliphatic, alicyclic or aromatic organic diisocyanate containing two isocyanate groups in a molecule, which has been conventionally used in the production of a normal emulsion polyurethane, is used. For example, isophorone diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexyl methane diisocyanate , 3,3'-dichloro-4,4'-diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, and the like. These organic diisocyanates may be used alone or in combination of two or more. Among them, as the organic diisocyanate, it is preferable to use an aromatic diisocyanate such as tolylene diisocyanate or 4,4'-diphenylmethane diisocyanate.

As the chain extender, a chain extender conventionally used in the production of an ordinary emulsion polyurethane can be used, and contains two or more hydrogen atoms capable of reacting with an isocyanate group in a molecule. It is preferable to use a low molecular compound having a molecular weight of 400 or less. Examples of such a chain extender include hydrazine, ethylenediamine, propylenediamine, xylylenediamine, isophoronediamine, phenylenediamine, tolylenediamine, adipic dihydrazide, isophthalic dihydrazide, hexamethylenediamine, and 4,4′-diamino. Diamines such as diphenylmethane and 4,4′-diaminodicyclohexylmethane, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol, bis (β-hydroxyethyl) terephthalate, Diols such as 3-methyl-1,5-pentanediol, cyclohexanediol, xylylene glycol, 1,4-bis (β-hydroxyethoxy) benzene, neopentyl glycol, Amino ethyl alcohol, and amino alcohols such as amino propyl alcohol can be given. These chain extenders may be used alone,
More than one species may be used in combination. Among these, as the chain extender, it is preferable to use a diamine such as isophoronediamine because it has high reactivity with isocyanate groups and few side reactions.

The polyurethane emulsion of the present invention can be produced by a method generally used for producing an emulsion. For example, the polyurethane is dispersed in an aqueous medium by a high mechanical shear force in the presence of an emulsifier such as a nonionic surfactant. It can be produced by a forced emulsification method of emulsifying therein, a self-emulsification method of emulsifying a polyurethane having a unit derived from a monomer having a hydrophilic functional group such as dimethylolpropionic acid into an aqueous medium, or the like. Among these methods, for example, as a forced emulsification method, a phase inversion emulsification method in which a liquid polyurethane polymer after completion of a reaction is emulsified with an emulsifier, a chain extension of a diamine or the like simultaneously with or after emulsifying and dispersing a terminal isocyanate prepolymer. A prepolymer method in which a chain extension reaction is performed with an agent to increase the molecular weight, and the like. Among them, in order to obtain a polyurethane which gives a leather-like sheet having excellent abrasion resistance, it is preferable to carry out a prepolymer method.

Further, in order to improve the emulsifying dispersibility,
Trifunctional amines such as diethylenetriamine and trimethylol are used as chain extenders in order to introduce units derived from polyethylene oxide or the like into the main chain or side chain of the polyurethane, and to improve solvent resistance, heat resistance and hot water resistance. Modification means by modifying the polyurethane itself, such as forming a crosslinked structure by reacting a trifunctional alcohol such as propane, etc., can also be suitably used in the present invention.

The polyurethane emulsion of the present invention was added to 50
90 μm of a film having a thickness of 100 μm obtained by drying at 90 ° C.
The elastic modulus at ℃ is 2.0 × 10 ^{7 to} 5.0 × 10 ⁸ d.
It is preferably in the range of yn / cm ² . When the elastic modulus is in the above range, the leather-like sheet obtained by impregnating the polyurethane emulsion into the fibrous base material and coagulating the coagulated polyurethane does not restrain the fibers, and partially coagulates the fibers. Since it is solidified by the release structure, it is possible to achieve both excellent flexibility and a sense of fulfillment, and a texture comparable to that of a leather-like sheet obtained by a wet coagulation method is exhibited. As used in conventional binders for nonwoven fabrics,
In the case of polyurethane having a modulus of elasticity at 90 ° C. of less than 2.0 × 10 ⁷ dyn / cm ² , the resulting leather-like sheet-like material approximates a nonwoven fabric without a sense of fulfillment because the fibers are constrained by the polyurethane. It tends to be. The elastic modulus at 90 ° C. is 5.0 × 10 ⁸ dyn /
In the case of polyurethane larger than cm ² , the obtained leather-like sheet tends to have a hard texture.

The polyurethane emulsion of the present invention may contain an organic solvent or may be a completely aqueous system containing no organic solvent. However, from the viewpoint of the environment and the avoidance of a decrease in productivity due to the organic solvent recovery step. It is preferably a complete aqueous emulsion containing no organic solvent. further,
Other resins may be used in combination with the polyurethane constituting the emulsion, as long as the thermosensitive gelling property and the dispersion stability are not impaired. Examples of resins that can be used in combination with polyurethane include acrylonitrile-butadiene copolymer, polychloroprene, styrene-butadiene copolymer, polybutadiene, polyisoprene, ethylene-propylene copolymer, polyacrylate, silicone, polyurethane, and polyvinyl acetate. ,PVC,
Examples include synthetic elastic polymers such as polyester-polyether block copolymers and ethylene-vinyl acetate copolymers and natural rubbers. These resins may be used alone or in combination of two or more.

The polyurethane emulsion of the present invention includes:
If necessary, known additives such as an antioxidant, an ultraviolet absorber, a penetrant, a thickener, a fungicide, a dye, a pigment, a filler, a coagulation regulator and the like can be added.

The polyurethane emulsion of the present invention preferably has a thermosensitive gelling property. When a polyurethane emulsion having heat-sensitive gelling properties is used, when the polyurethane emulsion is impregnated into the fibrous base material and coagulated in the process of producing a leather-like sheet, the emulsion particles are unevenly coagulated in the fibrous base material. Since the solidification can be performed more uniformly without generating migration, the leather-like sheet obtained has an excellent texture. When coagulation is performed in warm water, which will be described later, the emulsion can be coagulated immediately without flowing out into the warm water bath.

A polyurethane emulsion having heat-sensitive gelling properties can be obtained by adding a heat-sensitive gelling agent to the emulsion. Examples of the heat-sensitive gelling agent used in this case include, for example, inorganic salts, polyethylene glycol-type nonionic surfactant, polyvinyl methyl ether, polypropylene glycol, silicone polyether copolymer, polysiloxane, and the like. May be used alone or in combination of two or more. Among them, a combination of an inorganic salt and a polyethylene glycol-type nonionic surfactant is preferable as the heat-sensitive gelling agent because migration hardly occurs. Examples of the polyethylene glycol type nonionic surfactant include ethylene oxide adducts of higher alcohols, ethylene oxide adducts of alkyl phenols, ethylene oxide adducts of fatty acids, ethylene oxide adducts of polyhydric alcohol fatty acid esters, higher alkyl Examples thereof include an ethylene oxide adduct of an amine and an ethylene oxide adduct of polypropylene glycol. As the inorganic salts, monovalent or divalent metal salts that lower the cloud point of the nonionic surfactant are used, for example, sodium carbonate, sodium sulfate, calcium chloride, sodium hydroxide, calcium sulfate, oxidized Zinc, zinc chloride, magnesium chloride, potassium chloride, potassium carbonate, sodium nitrate, lead nitrate and the like can be mentioned, among which calcium chloride is preferable.

The total weight of the ethylene glycol type surfactant and the inorganic salt is preferably in the range of 0.2 to 20 parts by weight based on 100 parts by weight of the polyurethane. The compounding ratio is preferably in the range of 90/10 to 50/50 by weight, and more preferably in the range of 80/20 to 60/40.

The leather-like sheet material using the polyurethane emulsion of the present invention is obtained by impregnating a polyurethane substrate obtained as described above into a fibrous base material, coagulating it,
It can be manufactured by drying. As the fibrous base material, various fibrous base materials that are conventionally used in the production of leather-like sheet materials can be used, and have a moderate thickness, a sense of fulfillment, and a soft texture. Is preferred. Examples of such a fibrous base material include, for example, ordinary forms of synthetic fibers, shrinkable fibers, spontaneous extensible fibers, multilayer-bonded latent splittable fibers, ultrafine fibers or bundled fibers thereof, and special porous fibers. Can be used alone or in combination. Examples of the material of the fibrous base material include polyester fibers, nylon fibers, acrylic fibers, semi-synthetic fibers, and natural fibers.

A synthetic fiber in a usual form as a fibrous base material,
When using a nonwoven fabric made of shrinkable fibers and spontaneously extensible fibers, if the nonwoven fabric is treated in advance with a water repellent containing a silicone compound that imparts flexibility, such as dimethylpolysiloxane, it will exhibit an excellent texture. A leather-like sheet can be obtained.

When a nonwoven fabric made of ultrafine fibers is used as the fibrous base material, a leather-like sheet having a soft and excellent feeling of fullness can be obtained. As such a nonwoven fabric, a nonwoven fabric made of various kinds of ultrafine fibers conventionally used for producing a leather-like sheet material can be used. The nonwoven fabric made of microfibers as used herein refers to a sea-island composite spun fiber or a mixed spun fiber composed of two or more polymer substances, in which a polymer substance as a sea component is extracted and removed with an organic solvent. It is a nonwoven fabric made of ultrafine fibers composed only of components. A sea-island type sea component and an island component are referred to as an island component and B as a sea component when the component A surrounds the component A in the cross section of the fiber. Examples of such high-molecular substances include polyamides such as 6-nylon, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene, polystyrene, polyvinylidene chloride, polyvinyl acetate, polymethacrylate, polyvinyl alcohol, and polyurethane. Among them, two or three or more polymer substances having different solubilities in organic solvents such as toluene and perchrene can be selected and used. The ratio of the components in the conjugate spun fiber or the mixed spun fiber can be appropriately selected depending on the use of the obtained leather-like sheet-like material, but is generally 15/85 to 85/15 in weight ratio of island component / sea component. It is preferably within the range, more preferably within the range of 25/75 to 75/25.

The ultrafine treatment of the sea-island type fiber may be performed before or after the impregnation and coagulation of the polyurethane emulsion, but a method of performing the ultrafine treatment after the impregnation and coagulation of the emulsion is obtained. For leather-like sheet,
It is preferable because it is more flexible and can express a natural leather-like texture. Among them, the present invention relates to a nonwoven fabric comprising a mixed spun fiber in which the sea component is polyethylene or polystyrene and the island component is 6-nylon, or a nonwoven fabric comprising a composite spun fiber in which the sea component is polyethylene or polystyrene and the island component is polyethylene terephthalate. The method of impregnating and coagulating the polyurethane emulsion described above and dissolving and removing the sea component with toluene is preferable in that a leather-like sheet having a texture very similar to natural leather is obtained as a material for artificial leather.

The thickness of the fibrous base material can be arbitrarily selected depending on the intended use of the obtained leather-like sheet, and is not particularly limited, but is in the range of 0.3 to 3.0 mm. Is more preferable, and more preferably in the range of 0.6 to 2.5 mm. In addition, the apparent density of the fibrous base material is in the range of 0.1 to 0.5 g / cm ^{3 in} the case of a fiber in a normal form, in order to obtain a sheet having a soft texture, In the case, after removing the sea component, 0.1 to 0.1.
Is preferably in the range of 5 g / cm ^3, more preferably in the range of Both 0.15~0.45g / cm ^3. If the apparent density is larger than 0.5 g / cm ³ ,
The resulting leather-like sheet tends to have no stiffness or have a rubber-like texture. On the other hand, the apparent density is 0.1
If it is less than g / cm ³ , the resilience and the feeling of waist are inferior, and the texture like natural leather tends to be impaired.

The leather-like sheet produced using the polyurethane emulsion of the present invention is prepared by impregnating the above-mentioned polyurethane emulsion into a non-woven fabric and squeezing it with a press roll or the like to obtain an appropriate amount of impregnation with a doctor knife or the like. Or in a hot water bath at 70 ° C. or higher, or after coagulation in a steam atmosphere, followed by drying in a dryer.

The amount of the polyurethane adhered to the sheet obtained by impregnating and coagulating the emulsion is preferably in the range of 5 to 150% by weight, preferably 10 to 100% by weight, based on the weight of the fibrous base material. % Is more preferable. If the amount of the attached polyurethane is less than 5% by weight, the obtained sheet-like material tends to be insufficient in a feeling of fulfillment.
If the content exceeds% by weight, the resulting sheet tends to be hard.

The leather-like sheet produced using the polyurethane emulsion of the present invention has a texture and appearance similar to that of natural leather, and has little discoloration or deterioration even after long-term use. In addition, since the hindered amine compound is not eluted from the leather-like sheet by the dyeing process, the process of thinning the fibrous base material, dry cleaning, washing, etc., it is especially used for clothing, shoes, interiors, car seats, etc. Are suitable.

[0044]

EXAMPLES The present invention will be described below in more detail with reference to examples and the like, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, measurement or determination of the elastic modulus, light yellowing resistance, and light fastness to light staining were performed by the following methods.

[Modulus of elasticity]
Using a film having a thickness of 100 μm obtained by drying at 0 ° C., measurement was performed at a frequency of 11 Hz using a viscoelasticity measuring apparatus (FT Rheospectral DVE-V4 manufactured by Rheology Co., Ltd.), and the elastic modulus at 90 ° C. Was.

[Light Yellowing Resistance] The leather-like sheet was subjected to a fade tester (Suga Test Instruments Co., Ltd. UV long life fade meter FAL-5H B BR, UV carbon arc lamp, 63 ° C) for 80 hours and 160 hours. After the light irradiation, the number of discoloration degree of the leather-like sheet was determined by gray scale. The smaller the value is, the more discoloration is shown.

[Light-fast Dyeing Fastness] After the dyed leather-like sheet was irradiated with light for 20 hours using the above fade tester, the number of discoloration degree of the leather-like sheet was determined by gray scale. The smaller the value is, the more discoloration is shown.

The abbreviations of the compounds used in Reference Examples, Examples and Comparative Examples are shown below.

――――――――――――――――――――――――――――――――― Abbreviation: Compound name ―――――――――― ――――――――――――――――――――――― PMPA2000: Polyester diol having a number average molecular weight of 2000 (3-Methyl-1,5 pentanediol is reacted with adipic acid) Production) PHC2000: polyhexamethylene carbonate diol having a number average molecular weight of 2000 PTG2000: polytetramethylene glycol having a number average molecular weight of 2000 TDI: 2,4-tolylene diisocyanate DMPA: 2,2-dimethylolpropionic acid MEK: 2-butanone TEA : Triethylamine DETA: Diethylenetriamine IPDA: Isophoronediamine ――――――――――――――― ――――――――――――――――――

[Reference Example 1] <Production of fibrous base material (nonwoven fabric)> A mixture of 40 parts of highly fluid polyethylene and 60 parts of 6-nylon was spun and stretched to obtain a fineness of 4 denier and a length of 51 mm. Multi-component fiber (6
-Nylon island component), through each process of card, cross wrapper and needle punch, apparent density 0.16
A fiber entangled nonwoven fabric of 0 g / cm ³ was prepared. The nonwoven fabric was heated and the sea component polyethylene was melted and heat-fixed to obtain a fiber-entangled nonwoven fabric having an apparent density of 0.285 g / cm ³ , which had been smoothed on both sides. Hereinafter, this nonwoven fabric is referred to as a nonwoven fabric.

[Reference Example 2] <Production of fibrous base material (non-woven fabric)> It was composed of 70 parts of polyethylene terephthalate and 30 parts of low density polyethylene.
A three-dimensional entangled nonwoven fabric composed of sea-island fibers having 15 islands (polyethylene terephthalate is an island component) and a fineness of 4 denier is shrunk in warm water to have an area shrinkage of 30%, thereby melting the polyethylene of the sea component. The fiber entangled nonwoven fabric which was heat-fixed and had an apparent density of 0.35 g / cm ³ was smoothed on both sides. Hereinafter, this nonwoven fabric is referred to as a nonwoven fabric.

Reference Example 3 <Production of fibrous base material (nonwoven fabric)> A card and a cross wrapper were prepared from polyethylene terephthalate fiber (fineness: 2 denier, length: 51 mm) having a shrinkage rate of 25% in hot water at 70 ° C. Was used to make a web of 240 g / m ² . The web was passed through a needle locker room and needle-punched, and then immersed in 70 ° C. hot water for 2 minutes to shrink to 56% of the original area. This was treated at 155 ° C. using a cylinder belt press to obtain a nonwoven fabric having a thickness of 1.2 mm and an apparent density of 0.30 g / cm ³ . This nonwoven fabric was impregnated with a 5% aqueous solution of Geranex SH (a silicone soft water repellent manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), squeezed with a roll, and then squeezed with a roll.
Dry at 30 ° C. for 30 minutes. Hereinafter, this nonwoven fabric is referred to as a nonwoven fabric.

[Reference Example 4] <Production of polymer polyol with hindered amine compound unit> 730 g of adipic acid, 708 g of 3-methyl-1,5-pentanediol, dimethyl succinate and 1- (2
-Hydroxyethyl) -4-hydroxy-2,2,6
12.1 g of a polycondensate with 6-tetramethylpiperidine (number average molecular weight 3200) was placed in a three-necked flask, reacted at 200 ° C. for 3 hours under a nitrogen atmosphere, and distilled water was recovered. And polymerized at 200 ° C. under reduced pressure for 8 hours. 36.6 g of distilled water was added thereto, and the mixture was dehydrated with stirring at 100 ° C. for 2 hours to deactivate the catalyst. The number average molecular weight of the obtained hindered amine compound unit-introduced polymer polyol was 2144 (1.0% by weight of the hindered amine compound unit was introduced into the polymer polyol). Hereinafter, this polymer polyol is referred to as a polymer polyol.

[Reference Example 5] <Production of polymer polyol with hindered amine compound unit> The dimethyl succinate and 1- (2
-Hydroxyethyl) -4-hydroxy-2,2,6
A polymer polyol obtained by introducing a hindered amine compound unit in an amount of 3.0% by weight to a polymer polyol in the same manner except that the amount of the polycondensate with 6-tetramethylpiperidine (number average molecular weight: 3200) is changed to 36.3 g. Manufactured. The number average molecular weight of this polymer polyol was 1989. Hereinafter, this polymer polyol is referred to as a polymer polyol.

Example 1 <Production of Polyurethane Emulsion> In a three-necked flask, 600.0 g of a polymer polyol, TDI 10
9.7 g of DMPA and 6.76 g of DMPA were weighed and stirred at 90 ° C. for 2 hours under a dry nitrogen atmosphere to quantitatively react hydroxyl groups in the system to obtain an isocyanate group-terminated prepolymer. After 227.2 g of MEK was added thereto and uniformly stirred, the temperature in the flask was lowered to 40 ° C., 5.1 g of TEA was added, and the mixture was stirred for 10 minutes to neutralize DMPA. Then
Nonionic surfactant Emulgen 911 as an emulsifier
53.0 g (7 parts per 100 parts by weight of the polyurethane component) of distilled water (680 g) was manufactured by Kao (HLB = 13.7).
The aqueous solution dissolved in water was added to the prepolymer, and the mixture was stirred with a homomixer for 1 minute to emulsify.
14.7 g, IPDA 12.1 g and distilled water 230.0 g
Was added thereto, and the mixture was stirred with a homomixer for 1 minute to perform a chain extension reaction. Thereafter, MEK was removed by a rotary evaporator, and distilled water was added to obtain a polyurethane emulsion having a solid content of 40% by weight. 20 parts by weight of distilled water and 80 parts by weight of this polyurethane emulsion, a heat-sensitive gelling agent [water: nonionic surfactant Emulgen 910 (manufactured by Kao, HLB = 12.2): calcium chloride: weight ratio 5: 4: 4 parts by weight (equivalent to 5 parts by weight of a surfactant as a heat-sensitive gelling agent per 100 parts by weight of polyurethane constituents)
A polyurethane emulsion having a thermosensitive gelling property (hereinafter, referred to as a PU emulsion) was obtained. The film obtained by drying this emulsion had an elastic modulus at 90 ° C. of 3.2 × 10 ⁷ dyn / cm ² .

<Preparation of Leather-Like Sheet> The PU emulsion was immersed in a non-woven fabric, squeezed with a press roll, and then solidified in a 90 ° C. hot water bath for 1 minute.
Was dried in a hot air dryer for 30 minutes to obtain a sheet. This sheet is treated in hot toluene,
The resultant was squeezed five times with a press roll of kg / cm ² to remove polyethylene as a sea component, thereby obtaining a sheet material in which polyurethane was attached to a 6-nylon ultrafine fiber bundle fiber entangled nonwoven fabric.
The attached weight of the polyurethane resin was 54% by weight based on the weight of the nonwoven fabric fiber. The sheet was a natural leather-like sheet having flexibility and a sense of fulfillment. One side of this sheet was fluffed with emery paper, and the light yellowing resistance was evaluated by the above method. In addition, this raised material 10
0 parts by weight of a gold-containing dye (Irgaran Green G
L) Dyeing was carried out at a ratio of 1 part by weight at a bath ratio of 30: 1 and 90 ° C., and the light fastness to light staining was evaluated by the above method.

Comparative Example 1 A polyurethane emulsion (hereinafter referred to as PU emulsion) was prepared in the same manner as in Example 1 except that PMPA2000 containing no hindered amine compound unit was used as the polymer polyol. The film obtained by drying this emulsion had an elastic modulus at 90 ° C. of 3.2 × 10 ⁷ dyn / cm ² . Except for using this PU emulsion, a sheet was prepared in the same manner as in Example 1, and the light yellowing resistance and the light fastness to light staining were evaluated.

Example 2 <Production of Polyurethane Emulsion> In a three-necked flask, 300.0 g of a polymer polyol, PHC2000
300.0 g (1.5% by weight of hindered amine compound unit based on the total amount of the polymer polyol), TDI 113.1
7 g and 7.26 g of DMPA were weighed, and stirred at 90 ° C. for 2 hours in a dry nitrogen atmosphere to quantitatively react hydroxyl groups in the system to obtain an isocyanate group-terminated prepolymer.
After adding 228.4 g of toluene to this and stirring uniformly, the temperature in the flask was lowered to 40 ° C. and 5.48 g of TEA was added.
Was added and stirred for 10 minutes to neutralize DMPA. Next, a nonionic surfactant Emulgen 12 was used as an emulsifier.
0 (manufactured by Kao, HLB = 15.3) in distilled water 6
An aqueous solution dissolved in 83.5 g was added to the prepolymer, and the mixture was emulsified by stirring with a homomixer for 1 minute. Immediately, 15.2 g of DETA and 12.6 g of IPDA were added to distilled water 23.
An aqueous solution dissolved in 0 g was added, and the mixture was stirred with a homomixer for 1 minute to perform a chain extension reaction. Thereafter, toluene was removed by a rotary evaporator, and distilled water was added to obtain a polyurethane emulsion having a solid content of 40% by weight. A thermosensitive gelling agent [solution obtained by mixing water: nonionic surfactant Emulgen 106 (manufactured by Kao, HLB = 10.5): calcium chloride at a weight ratio of 5: 4: 1] to 80 parts by weight of this polyurethane emulsion. By mixing 6 parts by weight, a polyurethane emulsion having heat-sensitive gelling property (hereinafter referred to as PU emulsion) was obtained. The elastic modulus at 90 ° C. of the film obtained by drying the PU emulsion was 4.2 × 10 ⁷ dyn / cm ² .

<Preparation of Leather-Like Sheet> The PU emulsion was immersed in a non-woven fabric, squeezed by a press roll, and then squeezed under a steam atmosphere at a pressure of 0.5 kg / cm ^2.
After solidifying for 30 minutes, the sheet was dried in a hot air dryer at 130 ° C. for 30 minutes to obtain a sheet. This sheet was treated in hot toluene, squeezed five times with a 2 kg / cm ² press roll to remove polyethylene as a sea component, and a polyurethane terephthalate ultrafine fiber bundle entangled non-woven fabric with polyurethane attached. A product was obtained. The adhesion weight of the polyurethane resin is 40 with respect to the weight of the nonwoven fabric.
% By weight. The sheet was a natural leather-like sheet having flexibility and a sense of fulfillment. One side of this sheet was fluffed with emery paper, and the light yellowing resistance was evaluated by the above method. Further, a disperse dye (Dis. Red HLFS) 1 was added to 100 parts by weight of the napping material.
Dyeing at a bath ratio of 20: 1 at 130 ° C. in parts by weight,
Light fastness to light was evaluated by the above method.

Example 3 <Production of Polyurethane Emulsion> In a three-necked flask, 300.0 g of a polymer polyol, PTG2000
300.0 g (0.5% by weight of a hindered amine compound unit based on the total high molecular weight polyol), TDI 112.1
g, 7.00 g of DMPA and weighed under a dry nitrogen atmosphere.
The mixture was stirred at 90 ° C. for 2 hours to quantitatively react the hydroxyl groups in the system to obtain an isocyanate group-terminated prepolymer. After 228.2 g of MEK was added thereto and uniformly stirred, the temperature in the flask was lowered to 40 ° C., 5.28 g of TEA was added, and the mixture was stirred for 10 minutes to neutralize DMPA. Next, an aqueous solution obtained by dissolving 53.2 g of a nonionic surfactant Emulgen 930 (manufactured by Kao, HLB = 15.1) as an emulsifier in 683 g of distilled water was added to the above prepolymer, and the mixture was stirred with a homomixer for 1 minute to emulsify. Later, immediately DETA1
An aqueous solution in which 5.6 g and 12.8 g of IPDA were dissolved in 230 g of distilled water was added, and the mixture was stirred with a homomixer for 1 minute to perform a chain extension reaction. Thereafter, MEK was removed by a rotary evaporator, and distilled water was added to the solid content of 40%.
A% by weight polyurethane emulsion was obtained. To 80 parts by weight of this polyurethane emulsion, a heat-sensitive gelling agent [water: nonionic surfactant Emulgen 910 (manufactured by Kao, HLB = 12.2): calcium chloride: weight ratio 5:
4: 1), to obtain a polyurethane emulsion having heat-sensitive gelling property (hereinafter referred to as PU emulsion). The elastic modulus at 90 ° C. of the film obtained by drying the PU emulsion is 2.
It was 5 × 10 ⁷ dyn / cm ² .

<Preparation of Leather-Like Sheet> The PU emulsion was immersed in a non-woven fabric, squeezed with a press roll, and dried in a 130 ° C. hot air drier for 30 minutes to obtain a leather-like sheet. . The attached weight of the polyurethane resin was 43% by weight based on the weight of the nonwoven fabric. The light yellowing resistance of this sheet was evaluated by the above method. Further, a disperse dye (Blue) was added to 100 parts by weight of the raw material.
BG-CF) at a ratio of 3 parts by weight and a bath ratio of 20: 1, 13
Dyeing was carried out at 0 ° C., and light fastness to light was evaluated by the method described above.

Comparative Example 2 <Production of Polyurethane Emulsion> A three-necked flask was charged with 100.0 g of a polymer polyol and PTG2000.
500.0 g (0.17% by weight of a hindered amine compound unit based on the total high molecular weight polyol), TDI
6 g and 7.16 g of DMPA were weighed out and stirred at 90 ° C. for 2 hours in a dry nitrogen atmosphere to quantitatively react hydroxyl groups in the system to obtain an isocyanate group-terminated prepolymer.
After 228.2 g of MEK was added thereto and uniformly stirred,
The temperature in the flask was lowered to 40 ° C., 5.40 g of TEA was added, and the mixture was stirred for 10 minutes to neutralize DMPA. Next, 53.2 g of a nonionic surfactant Emulgen 930 (manufactured by Kao, HLB = 15.1) as an emulsifier was added to 683 g of distilled water.
Was added to the above prepolymer, and the mixture was emulsified by stirring with a homomixer for 1 minute.
An aqueous solution in which 5.3 g and 12.6 g of IPDA were dissolved in 230 g of distilled water was added, and the mixture was stirred with a homomixer for 1 minute to perform a chain extension reaction. Thereafter, MEK was removed by a rotary evaporator, and distilled water was added to the solid content of 40%.
A% by weight polyurethane emulsion was obtained. To 80 parts by weight of this polyurethane emulsion, a heat-sensitive gelling agent [water: nonionic surfactant Emulgen 910 (manufactured by Kao, HLB = 12.2): calcium chloride: weight ratio 5:
4: 1), to obtain a polyurethane emulsion having heat-sensitive gelling property (hereinafter referred to as PU emulsion). The elastic modulus at 90 ° C. of the film obtained by drying the PU emulsion is 2.
It was 5 × 10 ⁷ dyn / cm ² .

<Preparation of Leather-Like Sheet> The PU emulsion was immersed in a non-woven fabric, squeezed by a press roll, and dried in a 130 ° C. hot air drier for 30 minutes to obtain a leather-like sheet. . The attached weight of the polyurethane resin was 42% by weight based on the weight of the nonwoven fabric. The light yellowing resistance of this sheet was evaluated by the above method. Further, a disperse dye (Blue) was added to 100 parts by weight of the raw material.
BG-CF) at a ratio of 3 parts by weight and a bath ratio of 20: 1, 13
Dyeing was carried out at 0 ° C., and light fastness to light was evaluated by the method described above.

Comparative Example 3 <Production of Polyurethane Emulsion> PMPA200
0 600.0 g, TDI 113.4 g, DMPA
7.65 g was weighed and stirred at 90 ° C. for 2 hours in a dry nitrogen atmosphere to quantitatively react hydroxyl groups in the system to obtain an isocyanate group-terminated prepolymer. To this, toluene 2
After adding 28.6 g and stirring uniformly, the temperature in the flask was lowered to 40 ° C., and 5.8 g of TEA was added and stirred for 10 minutes to neutralize DMPA. Then, a nonionic surfactant Emulgen 911 (manufactured by Kao, HLB =
13.7) An aqueous solution obtained by dissolving 53.3 g (7 parts by weight per 100 parts by weight of the polyurethane component) in 684 g of distilled water was added to the above prepolymer, and the mixture was stirred for 1 minute with a homomixer to emulsify. 7g, IP
An aqueous solution obtained by adding 12.1 g of DA to 230.0 g of distilled water, and dimethyl succinate and (2-hydroxyethyl) -4
Solution obtained by dissolving 6.0 g of polycondensate (number-average molecular weight 3200) with hydroxy-2,2,6,6-tetramethylpiperidine (corresponding to 1.0% by weight based on the polymer polyol) in 60 g of toluene Was added and stirred with a homomixer for 1 minute to carry out a chain extension reaction and introduction of a hindered amine compound. Thereafter, toluene was removed by a rotary evaporator, and distilled water was added to the solid to obtain a solid content of 40% by weight.
Thus, a polyurethane emulsion was obtained. 20 parts by weight of distilled water with respect to 80 parts by weight of this polyurethane emulsion,
Thermosensitive gelling agent [Water: Nonionic surfactant Emulgen 9]
10 (manufactured by Kao, HLB = 12.2): A solution obtained by mixing calcium chloride at a weight ratio of 5: 4: 1] 4 parts by weight (5 parts by weight of a surfactant as a heat-sensitive gelling agent per 100 parts by weight of a polyurethane component) ) To obtain a polyurethane emulsion having heat-sensitive gelling properties (hereinafter referred to as PU emulsion). The elastic modulus at 90 ° C. of the film obtained by drying this emulsion was 3.1 × 1.
It was 0 ⁷ dyn / cm ^2.

<Preparation of Leather-Like Sheet-like Material> A PU emulsion was immersed in a nonwoven fabric, and thereafter, a sheet-like material containing polyurethane in a 6-nylon ultrafine fiber bundle entangled nonwoven fabric was obtained in the same manner as in Example 1. Was. The attached weight of the polyurethane resin was 55% by weight based on the weight of the nonwoven fabric fiber. The sheet was a natural leather-like sheet having flexibility and a sense of fulfillment. One side of this sheet was fluffed with emery paper, and the light resistance was evaluated by the above method. Further, a ratio of 1 part by weight of a gold-containing dye (Irgaran GreenGL) to 100 parts by weight of the napping raw material is as follows:
Dyeing was carried out at a bath ratio of 30: 1 at 90 ° C., and light fastness to light staining was evaluated by the above method. Table 2 shows the results. The light-fast yellowing resistance and the light-fastness to dyeing were inferior to those of the examples because the reaction of the hindered amine compound was insufficient and the compound was eluted in the polyethylene extraction step with toluene.

[0066]

[Table 1]

[0067]

According to the present invention, a polyurethane emulsion which gives a leather-like sheet having excellent light fastness and flexibility such as light yellowing resistance and light dyeing fastness, and impregnating a fibrous base material with the emulsion, A leather-like sheet obtained by coagulation is provided.

Continued on the front page F-term (reference) 4F071 AA30 AA51 AA53 AB15 AB18 AB21 AB22 AB24 AF57 AH19 BA04 BC02 4J002 CG022 CK031 CK041 EU086 FD042 FD046 HA07 4J034 CA04 CA13 CA15 CA24 CC12 CC26 CC45 CC52 CC01 CC66 DB03 DA03 DA03 DC14 DC15 DC19 DC20 DC35 DC43 DE02 DF01 DF02 DF03 DF11 DF12 DF14 DF15 DF16 DF17 DF19 DF20 DF21 DF32 DG01 DG02 DG03 DG04 DG06 DR04 HA01 HA06 HA07 HA13 HC01 HC02 HC03 HC11 HC12 HC17 HC22 HC46 HC53 HC MA17 MA22 QC05 RA03

Claims (5)

[Claims] 1. A polyurethane emulsion obtained by emulsifying a polyurethane obtained by reacting a polymer polyol, an organic diisocyanate and a chain extender in an aqueous medium, wherein the polymer polyol has a hindered amine compound unit of 0 to the polymer polyol. Polyurethane emulsion having a content of 2 to 10% by weight. 2. The hindered amine compound unit is represented by the following general formula (1): 2. The polyurethane emulsion according to claim 1, wherein R ¹ is an alkylene group, and x is an integer of 4 to 20. 3. 3. A polyurethane emulsion comprising the polyurethane emulsion according to claim 1 and a thermosensitive gelling agent. 4. A method for producing a leather-like sheet which impregnates and solidifies a fibrous base material with the polyurethane emulsion according to claim 1. 5. A leather-like sheet obtained by the production method according to claim 4.