KR20210062084A - Synthetic Leather - Google Patents

Abstract

The present invention is a synthetic leather having a cured product layer of a moisture-curable polyurethane hot-melt resin composition containing a polyol (A) and a reaction product of a polyisocyanate (B) and a urethane prepolymer (i) having an isocyanate group, the polyol (A) is to provide a synthetic leather characterized in that it contains a crystalline polyester polyol (a1) containing hexanediol as a raw material and does not contain an aromatic polyester polyol (a'1). It is preferable that the said polyol (A) further contains a polyether polyol (a2) and other polyester polyol (a3). It is preferable that the said polyether polyol (a2) is polypropylene glycol and/or polytetramethylene glycol.

Description

Synthetic Leather

The present invention relates to synthetic leather.

The moisture-curable polyurethane hot-melt resin composition has excellent mechanical strength, flexibility, and the like, and is therefore widely used in the manufacture of synthetic leather. Among them, the split leather having a fleece, an adhesive layer, and a skin layer has an appearance and a similarity to that of natural leather, so the price of the recent natural leather is higher. As a result, demand is increasing.

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

However, since dimethylformamide is concerned about health hazards, it is assumed that subsequent use becomes difficult due to SVHC regulation in Europe, voluntary regulation by large apparel makers, and VOC emission regulation in China.

Japanese Unexamined Patent Application Publication No. Hei 7-292399

The problem to be solved by the present invention is to provide a synthetic leather excellent in solidification rate, weather resistance, and appearance uniformity.

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

The synthetic leather of the present invention is excellent in solidification rate, weather resistance, and appearance uniformity, and can be particularly suitably 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 polyisocyanate (B), and contains a urethane prepolymer (i) having an isocyanate group.

The polyol (A) contains a crystalline polyester polyol (a1) containing 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. Moreover, in this invention, if even one aromatic ring is contained in the structure, an aromatic polyester polyol (a'1) is constituted.

It is essential that the said crystalline polyester polyol (a1) uses hexanediol as a raw material. Since crystalline polyester polyols using hexanediol as a raw material have excellent crystallinity, they can exhibit a certain degree of hardness or more immediately after applying the moisture-curable polyurethane hot melt resin composition, so they have excellent solidification speed and appearance uniformity. (It is possible to obtain a film having a uniform surface appearance even when it is applied to suppression of air bubbles and to a base substrate having irregularities. The same applies hereinafter), and adhesiveness (having excellent peel strength. The same applies hereinafter) can be obtained. have.

In addition, in the present invention, "crystallinity" indicates that the peak of heat of crystallization or heat of fusion can be confirmed in DSC (differential scanning calorimeter) measurement in conformity with JISK7121:2012, and "amorphous" refers to the peak. Indicates that it cannot be confirmed.

As the crystalline polyester polyol (a1), specifically, for example, a reaction product of hexanediol and a polybasic acid may be used.

Examples of the hexanediol include 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 2,3-hexanediol, 2,4-hexanediol, 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, it is preferable to use 1,6-hexanediol 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, eicosandioic acid, citraconic acid, itaconic acid, cytraconic anhydride, Itaconic anhydride 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 at least one compound 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, and in the range of 700 to 50,000, from the viewpoint of obtaining a further excellent solidification rate, uniformity in appearance, and adhesion. It is more preferable, and the range of 800-10,000 is still more preferable. Moreover, the number average molecular weight of the said crystalline polyester polyol (a1) shows the value measured by the gel permeation chromatography (GPC) method.

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

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

As the other polyols, for example, polyether polyol (a2), other polyester polyols other than the crystalline polyester polyol (a3), polybutadiene polyol, hydrogenated polybutadiene polyol, dimerdiol, etc. can be used. . These polyols may be used alone or in combination of two or more. Among these, it is preferable to use polyether polyol (a2) and/or other polyester polyol (a3) from the viewpoint of obtaining even more excellent flexibility and flexibility, and polyether polyol (a2) and its It is more preferable to use the outer polyester polyol (a3) together.

Examples of the polyether polyol (a2) include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxytetramethylene glycol, and polyoxypropylene polyoxytetramethylene glycol. Etc. can be used. These polyether polyols may be used alone or in combination of two or more. Among these, it is preferable to use polypropylene glycol and/or polytetramethylene glycol, 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, more preferably in the range of 700 to 10,000, and more preferably in the range of 800 to 5,000 from the viewpoint of obtaining even more excellent flexibility and flexibility. The range is more preferred. In addition, the number average molecular weight of the polyether polyol (a2) represents a value measured by a gel permeation chromatography (GPC) method.

In the case of using the polyether polyol (a2), the content of the polyether polyol (a2) in the polyol (A) is 30 to 70% by mass from the viewpoint of obtaining even more excellent flexibility and flexibility. It is preferable that it is a range, and the range of 30-50 mass% is more preferable.

As the above other polyester polyol (a3), it is preferable that it is not crystallinity and does not have an alicyclic structure from the viewpoint of obtaining further flexibility and flexibility. For example, a compound having a hydroxyl group and Reactants with polybasic acids 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, 2-methyl-1, 8-octanediol, 2,2-diethyl-1,3-propanediol, 2,2-diethyl-1,3pentanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,4 -Diethyl-1,5 pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol; Bisphenol A, bisphenol F, these alkylene oxide adducts, 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 not having a branched structure in combination from the viewpoint of obtaining a polyester polyol having no crystallinity easily, and the mass ratio thereof is in the range of 90/10 to 10/90 It is preferable, and the range of 20/80-80/20 is more preferable.

As the polybasic acid, for example, succinic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, dimer acid, sebacic acid, undecanedicarboxylic 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, more preferably in the range of 700 to 10,000, and more preferably in the range of 800 to 5,000, from the viewpoint of obtaining further excellent flexibility and flexibility. The range is more preferred. Moreover, the number average molecular weight of the said polyester polyol (a3) shows the value measured by the gel permeation chromatography (GPC) method.

In the case of using the polyester polyol (a3), the content rate of the polyether polyol (a3) in the polyol (A) is from 10 to 50% by mass from the viewpoint of obtaining even more excellent flexibility and flexibility. It is preferable that it is a range, and the range of 10-30 mass% is more preferable.

Examples of the polyisocyanate (B) include polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate isocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, and the like. Aromatic polyisocyanate; Aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and tetramethylxylylene diisocyanate can be used. These polyisocyanates may be used alone or in combination of two or more. Among these, since excellent reactivity and adhesiveness are obtained, it is preferable to use an aromatic polyisocyanate, and diphenylmethane diisocyanate is more preferable.

The amount of the polyisocyanate (B) used is preferably in the range of 5 to 40% by mass, and more 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).

The hot-melt urethane prepolymer (i) is obtained by reacting the polyol (A) and the polyisocyanate (B), and reacts with moisture present in the air or in the substrate to which the moisture-curable polyurethane hot-melt resin composition is applied to form a crosslinked structure. It has an isocyanate group that can be formed.

As a manufacturing method of the hot-melt urethane prepolymer (i), for example, the polyol (A) is put in a reaction vessel containing the polyisocyanate (B), and the isocyanate group of the polyisocyanate (B) is selected from the polyol ( It can be produced by reacting under conditions that become excessive with respect to the hydroxyl groups of A).

When preparing the hot-melt urethane prepolymer (i), as the equivalent ratio (isocyanate group/hydroxyl group) of the isocyanate group of the polyisocyanate (B) and the hydroxyl group of the polyol (A), further excellent adhesion is obtained. In this, it is preferable that it is a range of 1.1-5, and it is more preferable that it is a range of 1.5-3.

The isocyanate group content (hereinafter abbreviated as ``NCO%'') of the hot-melt urethane prepolymer (i) obtained by the above method is preferably in the range of 1.7 to 5, and 1.8 to The range of 3 is more preferable. In addition, the NCO% of the hot-melt urethane prepolymer (i) represents a value measured by a potential difference 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 as necessary.

As the other additives, for example, light stability, curing catalysts, tackifiers, plasticizers, stabilizers, fillers, dyes, pigments, optical brighteners, silane coupling agents, waxes, thermoplastic resins, 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 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 a skin layer.

Examples of the substrate include polyester fiber, polyethylene fiber, nylon fiber, acrylic fiber, polyurethane fiber, acetate fiber, rayon fiber, polylactic acid fiber, cotton, hemp, silk, wool, glass fiber, carbon fiber, and Fiber base materials such as nonwoven fabrics, woven fabrics, and knitted fabrics made of blended fibers or the like; What made the nonwoven fabric impregnated with a resin such as a polyurethane resin; Further providing a porous layer on the nonwoven fabric; A resin substrate or the like can be used.

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

As a manufacturing method of the synthetic leather, for example, after applying a material for forming a skin layer on a release paper, forming a skin layer, applying a material for forming an adhesive layer on the skin layer, forming an adhesive layer, and then forming a base material The method of bonding with, etc. are mentioned.

As the synthetic leather, if necessary, an intermediate layer, a wet porous layer, and a surface treatment agent layer may be separately provided. 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 suitably used as split leather.

The split leather includes a fleece 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 of manufacturing a split leather when the moisture-curable polyurethane hot-melt resin composition is used for the adhesive layer will be described.

As the fleece, known materials may be used. For example, among natural leathers such as cattle, horses, sheep, goats, deer, and kangaroos, those composed of a layer from which the epidermis and the nipple layer are removed may be used. It is preferable to use these fleeces that have been subjected to a known tanning step, a tanning step, and a dyeing/finishing step. The thickness of the fleece is appropriately determined depending on the intended use, but is, for example, in the range of 0.1 to 2 mm.

As a method of forming the adhesive layer on the fleece, for example, a method of coating the moisture-curable polyurethane hot-melt resin composition melted at, for example, 50 to 130°C on the fleece; A method of applying the moisture-curable polyurethane hot-melt resin composition melted at, for example, 50 to 130°C on a release paper, and then bonding the cured product layer to the fleece; On the skin layer formed on the release paper, for example, a method of applying the moisture-curable polyurethane hot-melt resin composition melted at 50 to 130° C., and then bonding the cured material layer to the fleece. .

In any of the above methods, as a method of coating the moisture-curable polyurethane hot melt resin composition, for example, a method of using a roll coater, a knife coater, a spray coater, a gravure coater, a comma coater, a T-die coater, an applicator, etc. Can be lifted.

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.

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

As a heating method for removing the solvent in the resin for forming the skin layer, for example, a method performed at a temperature of 50 to 120°C for 2 to 20 minutes may be mentioned.

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

(Example)

Hereinafter, the present invention will be described in more detail using examples.

[Example 1]

In a 4-neck flask equipped with a thermometer, agitator, inert gas inlet and reflux condenser, crystalline polyester polyol (1,6-hexanediol and adipic acid were reacted, number average molecular weight; 2,000, or less `` 150 parts by mass of polytetramethylene glycol (number average molecular weight; 1,000, hereinafter abbreviated as ``PTMG'') 250 parts by mass of polyester polyol (1,6-hexanediol, neopentyl glycol) , And adipic acid reacted, number average molecular weight; 2,000, hereinafter abbreviated as "other PEs1") 100 parts by mass was added, mixed, and heated under reduced pressure at 100°C, whereby the moisture in the flask was 0.05 It was dehydrated until it became mass% or less.

Then, the inside of the flask was cooled to 60° C., 113 parts by mass of 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as “MDI”) was added, and 110° C. until the isocyanate group content became constant in a nitrogen atmosphere. By reacting at for about 3 hours, a urethane prepolymer was obtained.

Next, on the release paper, a solvent-based urethane resin ("Crisbon TF-50P-C" manufactured by DIC Corporation) was coated so that the film thickness after drying became 30 µm, dried at 120° C. for 10 minutes, and the skin layer was formed. Got it. Subsequently, the moisture-curable polyurethane hot-melt resin composition melted at 110° C. for 1 hour was applied onto the skin layer to a thickness of 200 μm using a roll coater, and then the skin and the nipple layer were removed from the natural leather of the cow. It was bonded to the resulting fleece, and then left to stand for 2 days under conditions of a temperature of 23°C and a relative humidity of 50% to obtain a split leather.

[Examples 2 to 6, Comparative Examples 1 to 2]

A urethane prepolymer and a split leather were obtained in the same manner as in Example 1, except that the type and amount of the polyol (A) to be used and the amount of the polyisocyanate (B) were changed as shown in Tables 1-2.

[Measurement method of number average molecular weight]

The number average molecular weight of the polyol used in Examples and Comparative Examples represents a value measured under the following conditions by a 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㎜I.D.×30cm)×1ea

「TSKgel G4000」(7.8㎜I.D.×30cm)×1ea

「TSKgel G3000」(7.8㎜I.D.×30cm)×1ea

「TSKgel G2000」(7.8㎜I.D.×30cm)×1ea

Detector: RI (differential refractometer)

Column temperature: 40°C

Eluent: Tetrahydrofuran (THF)

Flow rate: 1.0mL/min

Injection amount: 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 speed]

The urethane prepolymer obtained in Examples and Comparative Examples was melted at 110°C, and immediately after it was applied to a thickness of 200 μm on a release paper, the surface of the coating film was accelerated with a finger to reduce a tack feeling. The time until disappearance was measured and evaluated as follows.

「T」: within 10 minutes

「F」: Exceeds 10 minutes

[Method of evaluating weatherability]

The moisture-curable polyurethane hot-melt resin compositions obtained in Examples and Comparative Examples were melted at 110° C. for 1 hour, and then coated at 100 μm on a release paper placed on a hot plate heated at 110° C. in advance. This coated article was stored at 25°C and 50% humidity for 24 hours to cure to obtain a film. Using this film, a UV irradiation test was conducted using a QUV accelerated weather resistance tester "QUV/basic" equipped with a UVA-340 bulb (UV irradiation dose: 0.78 W/m2, temperature 45°C) to prevent discoloration before and after UV irradiation. According to the difference (ΔE), the evaluation of weather resistance was evaluated as follows.

"T"; ΔE is less than or equal to 10

"F"; ΔE exceeds 10

[Appearance uniformity evaluation method]

The split leather obtained in Examples and Comparative Examples was bent, and evaluated by visual and touch as follows.

「T」: No air bubbles were found, and no irregularities in the faux leather were felt.

「F」: Air bubbles are confirmed, or irregularities in the faux leather are felt.

[Method of evaluating flexibility]

The split leather obtained in Examples and Comparative Examples was subjected to a flexometer test (-10°C, 100 times/minute) in a flexometer ("Flexometer with low temperature bath" manufactured by Yasuda Seiki Co., Ltd.), The number of times until cracking occurred on the surface of the synthetic leather was measured, and evaluated as follows.

「T」: 100,000 times or more

「F」: Less than 100,000 times

[Table 1]

[Table 2]

Abbreviations in Tables 1 to 2 are as follows.

"Crystalline PEs2"; What made 1,6-hexanediol and sebacic acid react, and the number average molecular weight; 3500

"Crystalline PEs3"; What made 1,6-hexanediol and dodecanedicarboxylic acid react, and the number average molecular weight; 3700

"Other PEs2"; What made ethylene glycol, neopentyl glycol, 1,6-hexanediol, and adipic acid react, and the number average molecular weight; 5500

"Other PEs3"; What made 3-methyl-1,5-pentanediol and adipic acid react, number average molecular weight; 2000

"Aromatic PEs"; What made diethylene glycol, neopentyl glycol, and phthalic anhydride react, and the number average molecular weight; 975

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

On the other hand, in Comparative Example 1, although the crystalline polyester polyol (a1) using hexanediol as a raw material was not used, the solidification rate and appearance uniformity were poor.

In Comparative Example 2, although an aromatic polyester polyol (a1) was used, weather resistance and flexibility were poor.

Claims (7)

A synthetic leather having a cured product layer of a moisture-curable polyurethane hot-melt resin composition containing a polyol (A), and a urethane prepolymer (i) having an isocyanate group, which is a reactant of polyol (A) and polyisocyanate (B),
Synthetic leather, characterized in that the polyol (A) contains a crystalline polyester polyol (a1) containing hexanediol as a raw material and does not contain an aromatic polyester polyol (a'1). The method of claim 1,
Synthetic leather, wherein the polyol (A) further contains a polyether polyol (a2). The method of claim 2,
Synthetic leather wherein the polyether polyol (a2) is polypropylene glycol and/or polytetramethylene glycol. The method according to any one of claims 1 to 3,
Synthetic leather, wherein the polyol (A) further contains a polyester polyol (a3). The method according to any one of claims 1 to 4,
Synthetic leather in which the content rate of the crystalline polyester polyol (a1) in the polyol (A) is in the range of 20 to 60% by mass. The method according to any one of claims 1 to 5,
Synthetic leather wherein the cured product layer of the moisture-curable polyurethane hot-melt resin composition is an adhesive layer and/or a skin layer. The method according to any one of claims 1 to 5,
Synthetic leather which is a split leather having a cured layer of the moisture-curable polyurethane hot-melt resin composition on the fleece.