JPS61266426A - Urethane resin for skin layer of synthetic leather - Google Patents

Abstract

PURPOSE:The titled resin freed from tortoise shell-like swelling and pinhole formation, comprising at least two chain extenders selected from among high-MW compounds having active hydrogen atoms on both ends and alkylene glycols and an organic diisocyanate compound. CONSTITUTION:At least two chain extenders selected from high-MW compounds having active hydrogen atoms on both ends (e.g., polyester-diol of a Mn of 500-10,000) and alkylene glycols [e.g., a mixture, Mn of 50-350, of ethylene glycol and 1,4-butanediol or the like (15-85:85-15 molar ratio)] are reacted with an organic diisocyanate (e.g., 4,4'-diphenylmethane diisocyanate) in a solvent (e.g., methyl ethyl ketone + dimethylformamide or the like) at an NCO/OH of 1/1 (molar ratio). The reaction is allowed to progress to such a degree of that a solid matter content of 30% and a viscosity of 100-1,500 P are reached to obtain a resin solution. This resin solution is mixed with other additives to obtain the titled resin. This resin is applied to a release paper, foamed by heating and bonded to a base through an adhesive. The release paper is peeled off to give an excellent skin of synthetic leather.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a urethane resin for the skin layer of synthetic leather that uses two or more specific chain extenders.

[Conventional technology]

Conventionally, the general structure of dry-processed synthetic leather has a three-layer structure: a resin for the skin layer, a resin for the intermediate adhesive layer, and a base fabric. The synthetic resins used are urethane resins for both the skin layer and the intermediate adhesive layer; thermoplastic urethane resins are often used for the skin layer, and thermosetting urethane resins are often used for the intermediate adhesive layer. The general method for making synthetic leather is to completely coat and dry the thermoplastic urethane resin for the outer skin layer on the release paper, then completely coat the thermosetting urethane resin for the intermediate adhesive layer on top of this, and then bond it to the base fabric. Dry at the same time, and then
A method of obtaining synthetic leather by peeling off the release paper is often used.

In addition to toughness, the thermoplastic urethane resin for the skin layer of synthetic leather has excellent surface smoothness.
It also needs to have excellent heat blocking properties, and because it is often used after being colored with pigments, it needs to have excellent pigment dispersibility and color development.

[Problems to be solved by the present invention]

When producing this synthetic leather, special performance is required for the urethane resin for the skin layer in addition to the above-mentioned performance. This is a problem in the suitability of overcoating the urethane resin for the skin layer during the step of overcoating the urethane resin for the adhesive layer on the urethane resin film for the skin layer in the synthetic leather manufacturing process mentioned above, and it is a problem in the overcoating suitability of the urethane resin for the skin layer during the process of overcoating the urethane resin for the adhesive layer on the urethane resin film for the skin layer, and it is different from the problem of the suitability of overcoating the urethane resin for the skin layer. , troubles due to poor aptitude are occurring frequently, and it is essential to satisfy this aptitude. That is, when a thermoplastic urethane resin solution for the skin layer is applied and dried on a release paper, and then a thermosetting urethane resin solution for the intermediate adhesive layer is applied thereon, a hexagonal pattern appears on the skin layer film that was first applied and dried. The appearance of the synthetic leather obtained by peeling off the release paper is severely damaged, resulting in defective products with no commercial value.

In the process of overcoating the urethane resin solution for the intermediate adhesive layer on the urethane resin film for the skin layer, the surface layer is coated with a solvent such as toluene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, etc. This phenomenon occurs because the urethane resin for the layer swells and deforms. That is, the thermoplastic urethane resin for the skin layer usually consists of a high molecular weight active hydrogen-containing compound, a low molecular weight active hydrogen-containing compound (chain extender), and a diisocyanate compound, and is a substantially linear polymer.

Structurally, it consists of repeating soft segment parts based on high molecular weight active hydrogen-containing compounds and hard segment parts based on chain extender-diisocyanates. The intermolecular cohesive force acts strongly between the hard segments to form pseudocrystalline gold, which imparts strong performance.

However, this characteristic has a negative effect in the overcoating process, and the hard segment portion of the outer skin film swells and deforms due to the solvent of the urethane resin solution for the adhesive layer, resulting in a complete hexagonal pattern.

In order to completely improve this, one idea is to use dimethylformamide, which is a strong good solvent for urethane resin, as a solvent for the urethane resin solution for the adhesive layer to completely dissolve the pseudocrystalline composition and prevent the hexagonal swelling phenomenon. However, the urethane resin for the epidermal layer is dissolved and pinholes occur frequently,
This can be said to be an impractical improvement method that reduces the hiding power or causes the urethane resin for the adhesive layer to migrate to the surface, greatly reducing surface smoothness, heat blocking properties, etc., and significantly impairing commercial value. .

[Means for resolving the gap]

As a result of intensive research, the present inventors have found that the structure of the urethane resin for the skin layer, especially the limitation of the hard segment portion, can be improved without using a strong good solvent, such as dimethylformamide, as a solvent for the urethane resin solution for the adhesive layer. The present inventors have discovered that all of these problems can be solved by the proposed structure, and have completed the present invention.

That is, the present invention provides a complete urethane resin for synthetic leather skin layer consisting of (a1 high molecular weight compound containing active hydrogen at both terminals, (bl) two or more chain extenders selected from alkylene glycols, and (c) organic diisocyanate compound. This is what we provide.

The reason why the urethane resin of the present invention is able to prevent the occurrence of tortoiseshell patterns is not certain, but it is likely that a certain chain extender is
This is thought to be because the combined use of more than one species controlled the crystallization rate of the pseudocrystals between the hard segments and delayed crystallization.

The compound containing active hydrogen at both terminals of the present invention (at has a number average molecular weight of 500 to 10,000, preferably 500 to 5
000 polyester diol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polycarbonate glycol, etc.

Examples of polyester diols include aliphatic glycols such as ethylene glycol% 1.4 butanediol, 1,6 hexanediol, neopentyl glycol, and diethylene glycol, and dibasic acids such as adipic acid,
It is obtained from aliphatic or aromatic dicarboxylic acids such as cono-phosphoric acid, azelaic acid, sepatic acid, inphthalic acid, and terephthalic acid.

The chain extender of the present invention (bl is a number average molecular weight of 50 to 350
Examples of the di-alkylene glycol include ethylene glycol, 1.4-butanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, and spiroglycol. Select these 2R mixed hills, and the quantitative ratio is (A): (Bl = 15 ~ 85:
It is preferably 85 to 15 (mol %). Moreover, when three types are selected and mixed, it is preferable to add 0 to 15 mol % as C1 to the above-mentioned (At, (Bl).

In addition to these chain extenders, other commonly used chain extenders such as low molecular weight diamines such as ethylene diamine,
Hexamethylene diamine, piperazine, inphorone diamine, dicyclohexylmethane diamine, N-methyljetanolamine, monoethanolamine, etc. may be used in combination.

The proportion used thereof is preferably 0 to 15 mol % based on the chain extenders of the above two types (A) and (Bl) in terms of molar ratio.

Further, it is desirable that the number average molecular weight of this diamine is 50 to 350.

As the organic diisocyanate compound C), for example, 4,
4'-diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, etc. can be used.

Further, small amounts of trimethylolpropane, glycerin, pentaerythritol, etc. can be used as long as the thermoplastic urethane resin does not substantially destroy the linear shape. The solvent used for the thermoplastic urethane resin is not particularly limited as long as it is inert to incyanate groups and uniformly dissolves them. Generally methyl ethyl ketone, acetone, dimethyl formamide, diethyl formamide,
Methyl isobutyl ketone, tetrahydrofuran, dioxane, ethyl acetate, butyl acetate, toluene, xylene,
N-methylpyrrolidone and the like may be used alone or in combination of two or more.

The method for producing the urethane resin of the present invention is as described above (
IL), (b), (C) components and solvent? NC010H=1 by the usual solution polymerization method of urethane resin using:
1 (molar ratio), with a solid content of 60% and 100 to 1
The reaction is continued until the pressure reaches 500 psb, preferably 500 to 1001 pm, to obtain the entire resin solution.

The obtained resin solution was placed in a release boat at a rate of 100 to 2001/(
20% solid content) and dried at 100 to 120°C for 1 to 2 minutes to obtain a total of 200 to 300 g of urethane resin for the adhesive layer.
/ is coated with (solid content 40%) and the entire base material is bonded 120 ~
Dry synthetic leather can be obtained by drying at 140° C. for 1 to 2 minutes and completely peeling off the mold release boat.

Furthermore, pigments, fillers, light stabilizers, gloss modifiers, tactile agents, etc. can be added to the resin of the present invention. Further, in order to further increase the toughness of the gold, a crosslinking agent or the like may be used in combination.

In order to explain the present invention in more detail, Examples and Comparative Examples are shown below. In the text, "parts" and "%" are based on weight unless otherwise specified.

Example 1 Butylene adipate (hereinafter referred to as BA-2000) with a molecular weight of t2000 obtained by completely reacting 1,4 butanediol and adipic acid as a high molecular weight compound (t) component in a reactor equipped with a stirrer, a thermometer, and a cooling tube. ) and 1000 parts of ethylene glycol (hereinafter referred to as EC) as a chain extender (b).
'i4 (S, 5 parts, 1.4 butanediol (hereinafter referred to as
1.4BG) e6zs part, organic diisocyanate compound e) t-500 parts of 4,4'-diphenylmethane diisocyanate (hereinafter referred to as MDI) per minute,
and 1880 parts of methyl ethyl ketone (hereinafter referred to as MEK) and dimethylformamide (hereinafter referred to as D) as a solvent.
1,880 parts of MF) was added and reacted at 65° C. for 10 hours to obtain a viscous thermoplastic urethane resin solution with a nonvolatile content of 30% and a viscosity of 550 ps.

Example 2 Butylene adipate with a molecular weight of 1000 (7) (hereinafter referred to as BA-
1000 parts of 1000 parts), 74.4 parts of EGft as the chain extender (b), 27 parts of 1.4HG in total, 625 parts of MDI as the diisocyanate (e) component, and 2010 parts of MEK and 2010 parts of DMF as the solvent. The reaction was carried out in the same manner as in Example 1, and the nonvolatile content was 30% and the viscosity was 650.
EXAMPLE 3 Using the same apparatus as in Example 1, 1000 parts of BA-2000 as a high molecular weight compound (IL) and a chain extender (K as BL) were obtained.
18.6 parts of Gt'', 108 parts of 1.48G, 500 parts of MDI as the diisocyanate (c) component, and 1900 parts of MEK and 1900 parts of DMF as solvents were added and reacted in the same manner as in Example 1, with a non-volatile content of 30%. Viscosity 6
Example 4 A viscous thermoplastic urethane resin solution of 0.00 pm was obtained using the same apparatus as in Example 1 to prepare 41 ml of polyoxytetramethylene glycol with a molecular weight of 2000 (
Below, 1000 parts of Hr was added to PTMG-2000, 46.5 parts of EG was added to chain elongation Xbl, and 1.4BGt-6
[L75 parts, 1,6-hexane diol (hereinafter referred to as 1,6H
C), 500 parts of MDIi as the diisocyanate (c) component, and MEK as the solvent.
1,890 parts of DMF and 1,890 parts of DMF were added and reacted in the same manner as in Example 1. The non-volatile content was 50% and the viscosity was 5,001)! 1 of a viscous thermoplastic urethane resin solution was obtained.

Example 5 In the same apparatus as in Example 1, 1000 parts of the high molecular weight compound 'ItXal was added to PTMG-2000, 3 parts of EGt-9, 54 parts of 1.43G, and 1.5H
G total 88.5 copies, Bisocyane 1930 copies, DMF 1
Add 950 parts and react in the same manner as in Example 1 to reduce the non-volatile content to 6.
A viscous thermoplastic urethane resin solution with a viscosity of 700p* was obtained at 0%.

Comparative Example 1 Using the same apparatus as in Example 1, 1000 parts of a high molecular weight compound (1% ml) of BA-1000 parts, 93 parts of EC as a chain extender, 2000 parts of MEK and 20 parts of DMF were added.
00 parts and reacted in the same manner as in Example 1 to reduce the nonvolatile content to 30 parts.
A viscous thermoplastic urethane resin solution with a viscosity of 600 pm was obtained.

Comparative Example 2 BA was used as the high molecular weight compound a) in the same apparatus as in Example 1.
-1000 parts of 2000, 135 parts of 1.4BG as a chain extender Oki Socyane-￥;a as MDIt-50CI
parts, and 1910 parts of MEK as solvent, DMF
1910 parts were added and reacted in the same manner as in Example 1 to obtain a viscous thermoplastic urethane resin solution with a nonvolatile content of 30% and a viscosity of 600 ps.

The thermoplastic urethane resin solutions for the skin layer obtained in Examples 1 to 5 and Comparative Examples 1 to 2 were applied to release paper DN-T manufactured by Inu Nippon Printing Co., Ltd.
It was coated on P-AP-Z (DE-3) to a thickness of 111 m and dried at 100° C. for 2 minutes with hot air to obtain a 30 μm film for the skin layer.

Next, an adhesive consisting of the following composition was applied to a total thickness of 0.1 mm, and a cotton napkin (4P3010) was immediately attached to the adhesive for 120 minutes.
℃ for 2 minutes. After aging at 40° C. for 40 hours, the release paper was peeled off and the results were counted to determine whether hexagonal swelling occurred and the occurrence of pinholes.

The results are shown in Table 1.

The urethane resin for the skin layer of synthetic leather according to the present invention does not generate hexagonal patterns or pinholes even when overcoating the urethane resin solution for the adhesive layer of synthetic leather, which is commonly used, and has a wide range of practical applications. It was confirmed that On the other hand, all of the urethane resins for synthetic leather skin layers of Comparative Examples were completely impractical due to the occurrence of tortoiseshell patterns.

Claims (1)

[Scope of Claims] (a) a high molecular weight compound containing active hydrogen at both terminals; (b) two or more chain extenders selected from alkylene glycols;
and (c) an organic diisocyanate-based compound, a urethane resin for a synthetic leather surface layer.