JPH04308278A - Artificial leather having grain - Google Patents

Abstract

PURPOSE:To obtain the subject artificial leather free from surface whitening and clouding by covering a fibrous substrate with a non-porous layer of a silicone-based polyurethane having segments of a silicone compound on the main chain and/or the side chain. CONSTITUTION:A grained artificial leather exhibiting a weight loss of >=1.0% by perchloroethylene treatment is produced by covering the surface of a fibrous substrate layer composed of e.g. an ultrafine polyester fiber nonwoven fabric and a polyurethane elastic polymer with a non-porous layer of a silicone-based polyurethane having segments of a silicone compound on the main chain and/or the side chain. Since the leather is resistant to the whitening and clouding of the surface, it has extremely high commercial value.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is an artificial leather consisting of a fibrous base layer and a coating layer of a polymer mainly composed of polyurethane, which has a silver coating that does not cause whitening or clouding of the surface over a long period of time. It concerns artificial leather.

0002

BACKGROUND OF THE INVENTION Conventionally, silver-covered artificial leather is known which consists of a fibrous base layer and a coating layer of a polymer mainly composed of polyurethane. It is known that the silver surface of some of these artificial leathers becomes cloudy white after being left alone for one to two years, and cannot be removed or corrected even by dry cleaning or wiping with benzene. As a method for preventing such whitening and clouding of the silver surface, Japanese Patent Application Laid-open No. 58-
The methods disclosed in Japanese Patent Publication No. 41975 and Japanese Patent Publication No. 63-20947 have been proposed.

[0003] The method disclosed in Japanese Unexamined Patent Publication No. 58-41975 is as follows:
The surface is coated with a specific high modulus polyurethane to prevent bleeding of additives such as silicon added to polyurethane to impart functionality such as water repellency. Since this method has a high modulus coating layer on the surface, it tends to have a hard texture and has poor crease texture.
This results in poor bending resistance. The method disclosed in Japanese Patent Publication No. 63-20947 attempts to extract and remove oligomers in polyester fibers with a solvent at any step of the manufacturing process in order to prevent bleeding of polyester oligomers in artificial leather containing polyester fibers in the base layer. It is something to do. This method is uneconomical because it requires an additional extraction process using a solvent unless ultrafine fiber generation type fibers are subjected to ultrafine fiber treatment using a solvent.
Whitening due to bleeding of polyurethane additives cannot be prevented.

It has become clear that even among artificial leathers that do not have the causes shown in the prior art, there are still some silver-bearing artificial leathers that still cause whitening or clouding on the silver surface. That is, in some artificial leathers, for example, silvered artificial leathers with a polyurethane fused film laminated as a surface layer, whitening or clouding of the silver surface may occur even if polyester fiber oligomers and polyurethane additives are not included. be.

[0005]

[Problems to be Solved by the Invention] The present invention has an object that is flexible, has excellent sensitivity such as texture and crease texture, and physical properties such as bending resistance, and maintains silver even after being left for a long period of time, which could not necessarily be solved by conventional techniques. To provide silver-covered artificial leather that does not cause whitening or clouding of the surface.

[0006]

[Means for Solving the Problems] The present inventors have conducted intensive studies to identify substances that cause whitening other than oligomers of polyester fibers and additives of polyurethane, and have found that silver-plated artificial leather with whitening or clouding on the surface. As a result of scraping off and analyzing the whitened areas, it was discovered that the new causative agent of whitening and cloudiness was polyurethane oligomers. As a result of further studies to develop a flexible coating layer that can prevent these oligomers, polyurethane additives, etc. from bleeding onto the silver surface and causing whitening, the present invention was achieved.

That is, the present invention provides a silver-plated artificial leather comprising a fibrous base layer and a coating layer of a polymer mainly composed of polyurethane, and which has a weight loss rate of 1.0% or more when treated with perchlorethylene. The silver-covered artificial leather is characterized in that the surface of the coating layer is covered with a non-porous layer of polyurethane having silicon compound segments in the main chain and/or side chains.

[0008] The present invention also provides a silver-plated artificial material comprising a fibrous base layer and a coating layer of a polymer mainly composed of polyurethane, and which has a weight loss rate of 1.0% or more when treated with perchloroethene. This is a method for preventing surface whitening of silvered artificial leather, which is characterized in that a non-porous layer of polyurethane having silicon compound segments in the main chain and/or side chain is applied to the surface of the leather coating layer.

The fibrous base layer of the silvered artificial leather, which is the object of the present invention, is made of ordinary fibers, such as synthetic fibers such as polyester, polyamide, polyacrylonitrile, polyolefin, and polyvinyl alcohol, chemical fibers such as regenerated cellulose, Natural fibers or special fibers, such as ultrafine fibers such as polyester, polyamide, polyacrylonitrile, etc., or multi-component fibers that can be transformed into ultrafine fiber bundles, special porous fibers, etc. by dissolving and removing at least one component. Composed of fibers selected from fibers,
One type of fabric selected from fiber-entangled nonwoven fabrics treated by needle punching or high-speed fluid flow, fiber-raised knitted fabrics, laminated fabrics of nonwoven fabrics and knitted woven fabrics, or a polyurethane polymer added to the fabrics. The main fiber is impregnated with a resin-based impregnating composition, and then, if necessary, a polymer coating composition is applied and coagulated into a sponge structure in a non-solvent of the polymer. It is a sheet-like material obtained by converting into ultrafine fiber bundles or special porous fibers. If ordinary fibers, especially those made of polyester or polyamide fibers, are used as the base layer, the leather-like sheet will have appropriate stiffness and excellent shape retention, and if one made of ultra-fine bundled fibers is used, When processed into shoes with a flexible texture, the top line will be sharp, and if made from special porous fibers, it will have a moderate waist and lightness.

The coating layer of the silvered artificial leather of the present invention consists of a porous layer and/or a non-porous layer of a polymer mainly composed of polyurethane. The surface coating layer can be laminated onto the fibrous base layer by applying a polymer solution or dispersion directly onto the surface of the fibrous base layer and coagulating it wet or dry, or by applying a polymer solution or dispersion on a release paper. A method of applying a liquid and solidifying it wet or dry and then adhering it to a fibrous base layer with an adhesive, or laminating it with a fibrous base layer before solidifying and solidifying it, or a method of laminating a melt-molded film on a fibrous base layer. Either method can be used. The polyurethane-based polymer used for impregnation into the fibrous base layer and coating layer is
Conventionally known polyester-based, polyether-based, polyester ether-based, polycarbonate-based or polylactone-based polymer polyols and organic diisocyanates,
Furthermore, if necessary, any polyurethane for artificial leather obtained by polymerizing a chain extender can be used. No particular treatment is required to reduce the oligomer content of the polyurethane.

[0011] The silvered artificial leather that is the subject of the present invention has a weight loss rate of 1.0% when treated with perchlorethylene.
That's all. The components eluted by perchlorethylene treatment are mainly polyurethane oligomers, etc.
It is a component that tends to cause bleeding on the silver surface due to long-term storage. Artificial leather with a weight loss rate of less than 1.0% contains fewer components that cause whitening, such as oligomers, and usually does not cause whitening or clouding of the surface due to bleeding even if left for a long time. Perchlorethylene soluble components in artificial leather are 1.
If it is present in an amount of 0% or more, the soluble components will bleed onto the silver surface if left at room temperature for a long period of one year or more, causing whitening and clouding of the silver surface. According to experiments conducted by the present inventors, this bleed phenomenon can be confirmed by an accelerated test at high temperatures; for example, when left in an atmosphere at 40° C. for one week, it corresponds to the state when left in an atmosphere at room temperature for about one year. Here, the weight loss rate due to perchlorethylene treatment is calculated by immersing artificial leather in perchlorethylene at a bath ratio of approximately 1:100 and a temperature of 30°C for 1 hour, stirring, and then drying. The weight change is expressed as a percentage.

The perchlorethylene soluble components are oligomers of the fibers constituting the base layer, various additives to polyurethane such as coagulation regulators and modifiers, and oligomers of polyurethane. Fiber oligomers are usually not included in fibers other than polyester fibers, and
Even when ultrafine fiber generation type fibers are subjected to ultrafine fiber processing using a solvent, almost no fiber oligomers are contained. The oligomer content of polyurethane varies depending on the polymerization process of polyurethane, thermal history, etc., but in general, the longer it is exposed to high temperatures, the higher the oligomer content. In the manufacturing process of artificial leather, laminated molten films contain a large amount of polyurethane oligomers, and the oligomer content also increases by heating embossing. Furthermore, the amount of polyurethane oligomers increases due to heat treatment such as thermoforming when processing artificial leather into various products. The method of the present invention is also effective when the amount of polyurethane oligomer increases due to post-treatment.

The polyurethane having a silicon compound segment in its main chain and/or side chain to be applied to the surface of the coating layer is selected from the group of polyester diol, polyether diol, polyester ether diol, polycaprolactone diol, polycarbonate diol, etc. at least one type of polyol having an average molecular weight of 500 to 2,500, a polysiloxane polyol or polysiloxane polyamine having an average molecular weight of 500 to 1,500 and having a siloxane bond in the molecule, and an aromatic diisocyanate, an aromatic triisocyanate, an alicyclic diisocyanate, At least one organic polyisocyanate selected from the group of aliphatic diisocyanates having a cyclic group, triphenylmethane 4,4,4-triisocyanate, etc. and a low molecular compound having at least two active hydrogen atoms as a chain extender. It is a silicone-based polyurethane resin obtained by reaction. Furthermore, from the viewpoint of the durability and texture of the film,
The melting point of the polyurethane resin is 120°C or higher, and the 100% elongation modulus value when dissolved in a solvent to form a dry film is at least 50 kg/cm2 or more and 300 kg/cm2.
It is preferable that it is below.

[0014] The method of coating with polyurethane having silicon compound segments can be carried out by conventionally known methods such as roll coating using a gravure roll, spray coating, coating using a doctor knife, etc., and transfer using release paper. . When coating, care must be taken to ensure that the film is substantially non-porous. If the coating is intermittent or has openings, oligomers will bleed through the openings, causing whitening or clouding of the silver surface. In the roll coating method, it is possible to coat with a relatively high viscosity solution, but if a high viscosity solution is used with a scored gravure roll, mesh-like openings are likely to occur, so a relatively low viscosity coating solution is used. Alternatively, before drying, press with release paper or the like to form a substantially non-porous coating layer. Spray coating is preferred for forming a thin, uniform, non-porous coating layer.

The coating amount is the amount necessary to form a substantially non-porous layer, and the solid content is 1 to 30 g/m2.
, preferably 3 to 20 g/m2. If the coating amount is too small, the strength of the coating will be weak and the durability will be poor, and bleeding of polyurethane oligomers and the like will not be prevented, resulting in whitening and clouding of the silver surface. On the other hand, if the coating amount is too large, the texture of the artificial leather will become hard and the sensitivity will be poor.

[0016]

[Effect] The reason why bleeding of polyurethane oligomers, etc. can be prevented by coating the surface with polyurethane having silicone-based compound segments is not necessarily clear, but the compatibility between silicone-based compounds and polyurethane oligomers, etc. is not very good. It is presumed that this effect is due to the fact that there is no such thing.

[0017]

[Example] Next, embodiments of the present invention will be explained with reference to Examples. In addition, parts and percentages in the examples refer to weight unless otherwise specified.

Example 1, Comparative Example 1 A surface coating layer made of a fused polyurethane film was applied to the surface of a fibrous base layer in which a polyurethane elastic polymer was contained in a porous structure in an ultrafine fiber nonwoven fabric of polyethylene terephthalate using a polyurethane adhesive. A leather-like sheet 1 was obtained by bonding the sheets together. A dimethylformamide solution of polyurethane containing a black pigment was coated on the surface of the leather-like sheet 1 using a gravure roll to give a polyurethane solid content of 5 g/m 2 , dried, and heat-embossed to obtain a leather-like sheet 2 . Furthermore, a 10% dimethylformamide solution of polyurethane having a silicon compound segment in its main chain was coated with a solid content of 5 g/m2 by a roll coating method and dried to obtain artificial leather 1.

The surface of the obtained artificial leather 1 was covered with a non-porous layer of silicone polyurethane, and was flexible, had good blackness and gloss, and was excellent in water repellency. The weight loss rate of the artificial leather 1 due to perchlorethylene treatment was 1.8%, but there was no whitening or clouding of the surface even after one week of dry heat treatment at 40°C, and there was no whitening or clouding of the surface after one week of dry heat treatment at 40°C. Similarly, no surface changes were observed. On the other hand, leather-like sheet 2 not coated with silicone polyurethane
Whitening of the surface due to bleeding of polyurethane oligomers, etc. was observed both after one week of dry heat treatment at 40°C and after one year of standing at room temperature.

Comparative Example 2 After extracting the leather-like sheet 1 of Example 1 with an organic solvent, colored polyurethane coating and heat embossing were performed in the same manner as in Example 1 to obtain a leather-like sheet 3. The leather-like sheet 3 has a weight loss rate of 0 due to perchlorethylene treatment.
．． 2%, 40℃ dry heat treatment for 1 week and room temperature storage 1
No whitening or clouding of the surface was observed during any of the years. However, the surface of the leather-like sheet 3 was severely roughened due to organic solvent treatment, had poor graininess, and had no commercial value as artificial leather.

Example 2 An entangled nonwoven fabric of short polyester fibers with a fineness of 1.5 denier was impregnated with a 20% dimethylformamide solution of polyethylene adipate polyurethane containing a blue colorant, and the polyurethane solution was further applied to the surface to make it a solid content. 150g/
A leather-like sheet 4 having a polyurethane microporous surface layer was obtained by applying m2, coagulating in a 40% dimethylformamide aqueous solution, dewashing, and drying. A 10% dimethylformamide solution of polyurethane containing a black pigment was applied to the surface of the leather-like sheet 4 using a gravure roll, with a polyurethane solid content of 1
After coating at 0 g/m2 and drying, it was heated and embossed. Furthermore, a 10% dimethylformamide solution of polyurethane having a segment of a silicone compound in the main chain was applied to the surface by a roll coating method at a solid content of 5 g/m 2 and dried to obtain artificial leather 2.

The surface of the obtained artificial leather 2 was covered with a non-porous layer of silicone polyurethane, and had good blackness and gloss, and excellent water repellency. The weight reduction rate of the artificial leather 2 due to perchlorethylene treatment was 2.2
%, but there was no whitening or clouding of the surface even after one week of dry heat treatment at 40°C, and no surface change was observed even after one year of standing at room temperature.

Comparative Example 3 In Example 2, after extracting the leather-like sheet 4 with an organic solvent, a colored polyurethane solution was added at a solid content of 20 g/m2.
After applying 2 and drying, heat embossing was performed to obtain artificial leather 3. The weight reduction rate of artificial leather 3 due to perchlorethylene treatment was 0.4%, and no whitening or clouding of the surface was observed either after one week of dry heat treatment at 40° C. or after one year of standing at room temperature. However, the surface of the artificial leather 3 was severely roughened due to the organic solvent treatment, had a poor texture, and had no commercial value as an artificial leather.

Examples 3 to 5, Comparative Example 4 On the surface of the leather-like sheet 4 of Example 2, a 10% dimethylformamide solution of polyurethane containing a black pigment was applied using a gravure roll at a polyurethane solid content of 20 g/m2, and dried. It was then heated and embossed. Furthermore, a 10% dimethylformamide solution of polyurethane having a segment of a silicone compound in the side chain was applied to the surface by a spray method and dried to obtain artificial leather. Table 1 shows the amount of polyurethane applied and the performance of each artificial leather.

[0025]

[Table 1]

(Note) 1. Whitening was visually evaluated after one week of dry heat treatment at 40℃ ◎: No whitening or clouding occurred, ×: White powder sprayed 2
．． Other items are evaluated by sensory evaluation ◎: Extremely good, ○: Excellent, △: Slightly poor, ×: Very poor

[0027]

Effects of the Invention The silver-finished artificial leather of the present invention does not reduce its commercial value due to whitening or clouding of the surface even if it is left for a long period of time. Furthermore, since there is no need to extract and remove polyurethane or fiber oligomers during the manufacturing process, even polyurethane with poor solvent resistance can be used, expanding the variety of silver-covered artificial leather.

Claims (2)

[Claims] 1. Silver-covered artificial leather comprising a fibrous base layer and a coating layer of a polymer mainly composed of polyurethane, and having a weight loss rate of 1.0% or more when treated with perchlorethylene, 1. A silver-covered artificial leather characterized in that the surface of the coating layer is covered with a non-porous layer of polyurethane having segments of a silicone compound in the main chain and/or side chains. Claim 2: A coating layer of silvered artificial leather consisting of a fibrous base layer and a coating layer of a polymer mainly composed of polyurethane, which has a weight loss rate of 1.0% or more when treated with perchloroethene. 1. A method for preventing surface whitening of silver-covered artificial leather, which comprises applying a non-porous layer of polyurethane having segments of a silicone compound in its main chain and/or side chain to the surface of the leather.