JP6844756B2 - Synthetic leather - Google Patents

Description

The present invention relates to synthetic leather.

The moisture-curable polyurethane hot-melt resin composition is widely used in the production of synthetic leather because it has excellent mechanical strength, flexibility, and the like. Among them, split leather having a floor leather, an adhesive layer, and an epidermis layer is similar in appearance and texture to natural leather, and therefore, demand is increasing with the recent rise in the price of natural leather.

As the resin composition for forming the split leather, for example, a resin composition containing dimethylformamide, a urethane resin, a long-chain fatty acid salt of a non-alkali metal, or the like is disclosed (see, for example, Patent Document 1). .).

However, it is assumed that the dimethylformamide will be difficult to use in the future due to concerns about health hazards, SVHC regulations in Europe, self-regulation by major apparel manufacturers, and VOC emission regulations in China. Will be done.

Japanese Unexamined Patent Publication No. 7-292399

An object to be solved by the present invention is to provide synthetic leather having excellent solidification rate, weather resistance, and appearance uniformity.

The present invention is a reaction product of a polyol (A) and a polyisocyanate (B), and has a cured product layer of a moisture-curable polyurethane hot melt resin composition containing a urethane prepolymer (i) having an isocyanate group. The synthetic leather is characterized in that the polyol (A) contains a crystalline polyester polyol (a1) made from a hexanediol as a raw material and does not contain an aromatic polyester polyol (a'1). It provides synthetic leather.

The synthetic leather of the present invention is excellent in solidification rate, weather resistance, and appearance uniformity, and can be particularly preferably used as split leather.

The moisture-curable polyurethane hot-melt resin composition used in the present invention is a reaction product of a specific polyol (A) and a polyisocyanate (B), and contains a urethane prepolymer (i) having an isocyanate group. is there.

The polyol (A) contains a crystalline polyester polyol (a1) made from hexanediol as a raw material, and does not contain an aromatic polyester polyol (a'1).

When the aromatic polyester polyol (a'1) is used as a raw material, the weather resistance becomes poor. In the present invention, if at least one aromatic ring is contained in the structure, the aromatic polyester polyol (a'1) is formed.

It is essential that the crystalline polyester polyol (a1) is made from hexanediol as a raw material. Since the crystalline polyester polyol made from hexanediol has excellent crystallinity, it can exhibit a certain degree of hardness immediately after the application of the moisture-curable polyurethane hot-melt resin composition, and therefore has an excellent solidification rate. Appearance uniformity (suppression of bubbles and a film having a uniform surface appearance can be obtained even when applied to a base material having irregularities. The same shall apply hereinafter), and adhesiveness (having excellent peel strength). The same applies hereinafter.) Can be obtained.

In the present invention, "crystallinity" means that the peak of heat of crystallization or heat of fusion can be confirmed in DSC (differential scanning calorimetry) measurement based on JISK7121: 2012, and is referred to as "amorphous". Indicates that the peak cannot be confirmed.

Specifically, as the crystalline polyester polyol (a1), for example, a reaction product of hexanediol and a polybasic acid can be used.

Examples of the hexanediol include 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 2,3-hexanediol, 2,4-hexanediol, and 2,5-hexanediol. 3,4-Hexanediol, 1,6-hexanediol and the like can be used. These compounds may be used alone or in combination of two or more. Among these, 1,6-hexanediol is preferably used from the viewpoint of obtaining good crystallinity.

Examples of the polybasic acid include succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedicarboxylic acid, eikosanic acid, citraconic acid, itaconic acid, citraconic anhydride, and anhydrous. Itaconic acid and the like can be used. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use one or more compounds selected from the group consisting of adipic acid, sebacic acid, and dodecanedicarboxylic acid from the viewpoint of obtaining good crystallinity.

The number average molecular weight of the crystalline polyester polyol (a1) is preferably in the range of 500 to 100,000 from the viewpoint of obtaining even more excellent solidification rate, appearance uniformity, and adhesiveness. The range of ~ 50,000 is more preferable, and the range of 800 to 10,000 is even more preferable. The number average molecular weight of the crystalline polyester polyol (a1) indicates a value measured by a gel permeation chromatography (GPC) method.

The content of the crystalline polyester polyol (a1) in the polyol (A) is 20% by mass or more from the viewpoint of obtaining even more excellent flexibility, abrasion resistance, and flexibility. It is preferably in the range of 20 to 60% by mass, more preferably in the range of 20 to 40% by mass.

As the polyol (A), in addition to the crystalline polyester polyol (a1), other polyols may be used in combination in consideration of other physical characteristics.

As the other polyol, for example, a polyether polyol (a2), another polyester polyol (a3) other than the crystalline polyester polyol, a polybutadiene polyol, a hydrogenated polybutadiene polyol, a dimer diol and the like can be used. These polyols may be used alone or in combination of two or more. Among these, a polyether polyol (a2) and / or another polyester polyol (a3) is preferably used from the viewpoint of obtaining even more excellent flexibility and flexibility, and the polyether polyol (a2) is preferable. ) And another polyester polyol (a3) are more preferable.

Examples of the polyether polyol (a2) include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene polyoxypropyran glycol, polyoxyethylene polyoxytetramethylene glycol, polyoxypropylene polyoxytetramethylene glycol and the like. Can be used. These polyether polyols may be used alone or in combination of two or more. Among these, polypropylene glycol and / or polytetramethylene glycol is preferably used, and polytetramethylene glycol is more preferable, from the viewpoint of obtaining even more excellent flexibility and flexibility.

The number average molecular weight of the polyether polyol (a2) is preferably in the range of 500 to 100,000, preferably 700 to 10,000, from the viewpoint of obtaining even more excellent flexibility and flexibility. The range is more preferred, and the range from 8 to 5,000 is even more preferred. The number average molecular weight of the polyether polyol (a2) is a value measured by a gel permeation chromatography (GPC) method.

When the polyether polyol (a2) is used, the content of the polyether polyol (a2) in the polyol (A) is 30 to 30 to obtain more excellent flexibility and flexibility. It is preferably in the range of 70% by mass, more preferably in the range of 30 to 50% by mass.

The other polyester polyol (a3) is preferably not crystalline and does not have an alicyclic structure from the viewpoint of further flexibility and flexibility, and has, for example, a hydroxyl group. A reaction product of the compound and a polybasic acid can be used.

Examples of the compound having a hydroxyl group include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, and 2-methyl-1,8-. Octanediol, 2,2-diethyl-1,3-propanediol, 2,2-diethyl-1,3 pentanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,4-diol-1 , 5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol; bisphenol A, bisphenol F, alkylene oxide adducts thereof and the like can be used. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use a compound having a branched structure and a compound having no branched structure in combination from the viewpoint that a polyester polyol having no crystallinity can be easily obtained, and the mass ratio thereof is 90/10 to 10 to 10. The range is preferably in the range of / 90, and more preferably in the range of 20/80 to 80/20.

As the polybasic acid, for example, succinic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, dimer acid, sebacic acid, undecandicarboxylic acid and the like can be used. These polybasic acids may be used alone or in combination of two or more.

The number average molecular weight of the polyester polyol (a3) is preferably in the range of 500 to 100,000, preferably in the range of 700 to 10,000, from the viewpoint of obtaining even more excellent flexibility and flexibility. Is more preferable, and a range of 8 to 00 to 5,000 is even more preferable. The number average molecular weight of the polyester polyol (a3) indicates a value measured by a gel permeation chromatography (GPC) method.

When the polyester polyol (a3) is used, the content of the polyether polyol (a3) in the polyol (A) is 10 to 50 from the viewpoint of obtaining even more excellent flexibility and flexibility. It is preferably in the range of% by mass, more preferably in the range of 10 to 30% by mass.

Examples of the polyisocyanate (B) include aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate isocyanate, xylylene diisocyanate, phenylenedi isocyanate, tolylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate and cyclohexane. An aliphatic or alicyclic polyisocyanate such as diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, or tetramethylxylylene diisocyanate can be used. These polyisocyanates may be used alone or in combination of two or more. Among these, aromatic polyisocyanates are preferably used, and diphenylmethane diisocyanates are more preferable, from the viewpoint of obtaining excellent reactivity and adhesiveness.

The amount of the polyisocyanate (B) used is preferably in the range of 5 to 40% by mass, preferably in the range of 10 to 30% by mass, based on the total mass of the raw materials constituting the hot melt urethane prepolymer (i). Is more preferable.

The hot-melt urethane prepolymer (i) is obtained by reacting the polyol (A) with the polyisocyanate (B), and is coated with an air- or moisture-curable polyurethane hot-melt resin composition. It has an isocyanate group that can react with the water present in the base material to form a crosslinked structure.

As a method for producing the hot melt urethane prepolymer (i), for example, the polyol (A) is placed in a reaction vessel containing the polyisocyanate (B), and the isocyanate group contained in the polyisocyanate (B) is described. It can be produced by reacting with the hydroxyl group of the polyol (A) under an excessive condition.

The equivalent ratio (isocyanate group / hydroxyl group) of the isocyanate group of the polyisocyanate (B) to the hydroxyl group of the polyol (A) in producing the hot melt urethane prepolymer (i) is even more excellent. From the viewpoint of obtaining adhesiveness, the range is preferably in the range of 1.1 to 5, and more preferably in the range of 1.5 to 3.

The isocyanate group content of the hot melt urethane prepolymer (i) obtained by the above method (hereinafter, abbreviated as "NCO%") is 1.7 from the viewpoint that even more excellent adhesiveness can be obtained. The range is preferably in the range of ~ 5, and more preferably in the range of 1.8 to 3. The NCO% of the hot-melt urethane prepolymer (i) is a value measured by a potentiometric titration method in accordance with JISK1603-1: 2007.

The moisture-curable polyurethane hot-melt resin composition used in the present invention contains the urethane prepolymer (i) as an essential component, but other additives may be used if necessary.

Examples of the other additives include light-resistant stability, curing catalyst, tackifier, plasticizer, stabilizer, filler, dye, pigment, fluorescent whitening agent, silane coupling agent, wax, thermoplastic resin and the like. Can be used. These additives may be used alone or in combination of two or more.

Next, the synthetic leather of the present invention will be described.

The synthetic leather of the present invention has a cured product layer of the moisture-curable polyurethane hot-melt resin composition.

The synthetic leather has, for example, at least a base material, an adhesive layer, and an epidermis layer.

Examples of the base material include polyester fiber, polyethylene fiber, nylon fiber, acrylic fiber, polyurethane fiber, acetate fiber, rayon fiber, polylactic acid fiber, cotton, linen, silk, wool, glass fiber, carbon fiber, and a blend thereof. Fiber base materials such as non-woven fabrics, woven fabrics, and knitted fabrics made of fibers; those in which the non-woven fabric is impregnated with a resin such as polyurethane resin; those in which the non-woven fabric is further provided with a porous layer; ..

The cured product layer of the moisture-curable polyurethane hot-melt resin composition can form an adhesive layer and / or an epidermis layer.

As a method for producing the synthetic leather, for example, a material for forming an epidermis layer is applied on a release paper, the epidermis layer is formed, and then a material for forming an adhesive layer is applied on the epidermis layer to form an adhesive layer. After forming the above, a method of sticking to the base material and the like can be mentioned.

If necessary, the synthetic leather may be provided with an intermediate layer, a wet porous layer, and a surface treatment agent layer separately. When a material other than the moisture-curable polyurethane hot-melt resin composition is used for each layer, a known material can be used.

The synthetic leather of the present invention is excellent in solidification rate, weather resistance, and appearance uniformity, and can be particularly preferably used as split leather.

The split leather includes a floor leather, an adhesive layer, and a skin layer, and the moisture-curable polyurethane hot-melt resin composition can be suitably used as an adhesive layer for split leather. Hereinafter, a method for producing split leather when the moisture-curable polyurethane hot-melt resin composition is used for the adhesive layer will be described.

As the floor leather, known leather can be used. For example, natural leather such as cow, horse, sheep, goat, deer, and kangaroo, which is composed of a layer from which the epidermis and the papillary layer have been removed, is used. Can be used. As these floor leathers, it is preferable to use those that have undergone a known leather making process, tanning process, and dyeing / finishing process. The thickness of the leather is appropriately determined depending on the intended use, and is, for example, in the range of 0.1 to 2 mm.

As a method of forming the adhesive layer on the floor leather, for example, a method of applying the moisture-curable polyurethane hot-melt resin composition melted at 50 to 130 ° C. on the floor leather. A method of applying the moisture-curable polyurethane hot-melt resin composition melted at, for example, 50 to 130 ° C. on the release paper, and then adhering the cured product layer to the floor leather; on the release paper. Examples thereof include a method in which the moisture-curable polyurethane hot-melt resin composition melted at 50 to 130 ° C. is applied onto the formed skin layer, and then the cured product layer is attached to the floor leather. Be done.

In any of the above methods, as a method for applying the moisture-curable polyurethane hot-melt resin composition, for example, a roll coater, a knife coater, a spray coater, a gravure coater, a comma coater, a T-die coater, an applicator or the like is used. The method can be mentioned.

After coating the moisture-curable polyurethane hot-melt resin composition, it can be dried and cured by a known method.

The thickness of the cured product layer (adhesive layer) of the moisture-curable urethane hot-melt resin composition is, for example, in the range of 5 to 300 μm.

As the resin for forming the skin layer, known ones can be used, and for example, solvent-based urethane resin, water-based urethane resin, solvent-free urethane resin, solvent-based acrylic resin, water-based acrylic resin and the like can be used. Can be done. These resins may be used alone or in combination of two or more.

Examples of the heating method for removing the solvent in the resin for forming the epidermis layer include a method of performing at a temperature of 50 to 120 ° C. for 2 to 20 minutes.

The thickness of the epidermis layer is, for example, in the range of 5 to 100 μm.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[Example 1]
Crystalline polyester polyol (1,6-hexanediol and adipic acid reacted in a four-necked flask equipped with a thermometer, agitator, an inert gas inlet and a reflux condenser, number average molecular weight; 2 000, hereinafter abbreviated as "crystalline PEs1") by 150 parts by mass, polytetramethylene glycol (number average molecular weight; 1,000, hereinafter abbreviated as "PTMG") by 250 parts by mass, polyester polyol (1, Reaction of 6-hexanediol, neopentyl glycol, and adipic acid, number average molecular weight; 2,000, hereinafter abbreviated as "other PEs1") Add 100 parts by mass, mix, and reduce the pressure at 100 ° C. By heating, the flask was dehydrated until the water content in the flask was 0.05% by mass or less.
Next, the inside of the flask is cooled to 60 ° C., 113 parts by mass of 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as “MDI”) is added, and the temperature is 110 ° C. until the isocyanate group content becomes constant under a nitrogen atmosphere. A urethane prepolymer was obtained by reacting for about 3 hours.
Next, a solvent-based urethane resin (“Chrisbon TF-50P-C” manufactured by DIC Corporation) was applied onto the paper pattern so that the film thickness after drying was 30 μm, and dried at 120 ° C. for 10 minutes. An epidermis layer was obtained. Next, the moisture-curable polyurethane hot-melt resin composition melted at 110 ° C. for 1 hour is applied onto the epidermis layer using a roll coater to a thickness of 200 μm, and then from natural cow leather. The epidermis and the papillary layer were removed and bonded to a leather-made floor leather, and then left to stand for 2 days under the conditions of a temperature of 23 ° C. and a relative humidity of 50% to obtain split leather.

[Examples 2 to 6, Comparative Examples 1 to 2]
The urethane prepolymer and split leather were prepared in the same manner as in Example 1 except that the type and amount of the polyol (A) used and the amount of the polyisocyanate (B) were changed as shown in Tables 1 and 2. Obtained.

[Measurement method of number average molecular weight]
The number average molecular weight of the polyols used in Examples and Comparative Examples shows the values measured under the following conditions by the gel permeation chromatography (GPC) method.

Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series and used.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 This "TSKgel G2000" (7.8 mm ID x 30 cm) x 1 Detector: RI (Differential Refractometer)
Column temperature: 40 ° C
Eluent: tetrahydrofuran (THF)
Flow velocity: 1.0 mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

[Evaluation method of solidification rate]
Immediately after the urethane prepolymers obtained in Examples and Comparative Examples were melted at 110 ° C. and then applied to a release paper to a thickness of 200 μm, the surface of the coating film was palpated with a finger to eliminate the feeling of tackiness. The time until was measured and evaluated as follows.
"T": Within 10 minutes "F": Exceeds 10 minutes.

[Evaluation method of weather resistance]
The moisture-curable polyurethane hot-melt resin composition obtained in Examples and Comparative Examples was melted at 110 ° C. for 1 hour, and then coated at 100 μm on a release paper placed on a hot plate preheated to 110 ° C. Worked. This coated product was stored at 25 ° C. and 50% humidity for 24 hours and cured to obtain a film. Using this film, a UV irradiation test was conducted using a QUV accelerated weathering tester "QUV / basic" equipped with a UVA-340 light bulb (UV irradiation amount: 0.78 W / m ^{2, temperature 45 ° C).} The weather resistance was evaluated as follows based on the difference in discoloration (ΔE) before and after UV irradiation.
"T"; ΔE is 10 or less.
"F"; ΔE exceeds 10.

[Evaluation method of appearance uniformity]
The split leathers obtained in Examples and Comparative Examples were bent and evaluated visually and by touch as follows.
"T": No bubbles are confirmed and the unevenness of the leather is not felt.
"F": Bubbles are confirmed, or the unevenness of the leather is felt.

[Evaluation method of flexibility]
The split leather obtained in Examples and Comparative Examples was subjected to a flexibility test (-10 ° C, 100 times / minute) with a flexometer (“Flexometer with low temperature tank” manufactured by Yasuda Seiki Seisakusho Co., Ltd.) and synthesized. The number of times until the surface of the leather cracked was measured and evaluated as follows.
"T": 100,000 times or more "F": less than 100,000 times

The abbreviations in Tables 1 and 2 are as follows.
"Crystallinity PEs2": reaction of 1,6-hexanediol and sebacic acid, number average molecular weight; 3500
"Crystallinity PEs3"; reaction of 1,6-hexanediol and dodecanedicarboxylic acid, number average molecular weight; 3700
"Other PEs2"; ethylene glycol, neopentyl glycol, 1,6-hexanediol, and adipic acid reacted, number average molecular weight; 5500
"Other PEs3"; reaction of 3-methyl-1,5-pentanediol and adipic acid, number average molecular weight; 2000
"Aromatic PEs"; reaction of diethylene glycol, neopentyl glycol, and phthalic anhydride, number average molecular weight; 975

It was found that Examples 1 to 6, which are the synthetic leathers of the present invention, are excellent in solidification rate, weather resistance, appearance uniformity, and toughness.

On the other hand, Comparative Example 1 was an embodiment in which the crystalline polyester polyol (a1) made from hexanediol was not used, but the solidification rate and appearance uniformity were poor.

Comparative Example 2 is an embodiment using an aromatic polyester polyol (a1), but has poor weather resistance and flexibility.

Claims (5)

A synthetic leather that is a reaction product of polyol (A) and polyisocyanate (B) and has a cured product layer of a moisture-curable polyurethane hot-melt resin composition containing a urethane prepolymer (i) having an isocyanate group. hand,
The polyol (A) contains a crystalline polyester polyol (a1) and a polyether polyol (a2) using only hexanediol as a glycol raw material, and other non- crystalline polyester polyol (a3), and is aromatic. The polyester polyol (a'1) that does not contain the polyester polyol (a'1) and the other non- crystalline polyester polyol (a3) is made from a compound having a hydroxyl group, and the compound having a hydroxyl group has a branched structure. A synthetic leather characterized by a combination of a compound having a compound having a compound and a compound having a branched structure. The polyether polyol (a2) is, polypropylene glycol and / or claim 1 synthetic leather according polytetramethylene glycol. The synthetic leather according to claim 1 or 2, wherein the content of the crystalline polyester polyol (a1) in the polyol (A) is in the range of 20 to 60% by mass. The synthetic leather according to any one of claims 1 to 3 , wherein the cured product layer of the moisture-curable polyurethane hot-melt resin composition is an adhesive layer and / or a skin layer. The synthetic leather according to any one of claims 1 to 4 , which is a split leather having a cured product layer of the moisture-curable polyurethane hot-melt resin composition on the floor leather.