JPS6028302B2 - Manufacturing method for porous sheet with excellent deterioration resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a flexible porous sheet with excellent deterioration resistance, particularly hydrolysis resistance, and high commercial value.

More specifically, the present invention improves the wet coagulation property of a polyurethane elastomer solution by using at least two or more specific additives (coagulation regulators) in a solvent solution of a polyurethane elastomer having excellent hydrolysis resistance. significantly improved,
The present invention relates to a manufacturing method for providing a flexible porous sheet having a large number of uniform giant pores within a polyurethane elastomer layer. Porous sheets obtained by green coagulation of polyurethane elastomer solutions are widely used as materials for artificial leather or synthetic leather (simply referred to as leather-like sheets).
When producing porous sheets by wet coagulation, the most important thing is wet coagulation, for example, the formation of a desired uniform sponge structure within the polyurethane elastomer.
In addition, the surface is required to have good flatness. If the wet coagulation property is poor, the quality of the leather-like sheet made from the porous sheet, especially the surface flatness, texture, creases, and green transparency, will be poor, and the commercial value will be significantly reduced.
It is known that the wet coagulation property varies greatly depending on the type of polyurethane elastomer used. For example, a polyurethane elastomer whose soft segment is a polyalkylene ester glycol obtained by a condensation reaction of a glycol with a small number of carbon atoms and a dicarboxylic acid. Mer is relatively hydrophilic and has good wet coagulation properties. However, during use, the polyurethane elastomer is hydrolyzed and degraded by water or bacteria such as mold, which not only greatly impairs its appearance but also impairs its functionality. Things are happening right now where we are no longer able to accomplish our goals. Therefore, many attempts are being made to improve the coagulation properties of hydrophobic polyurethane elastomers, which have high resistance to deterioration, and use them in leather-like sheets. Methods of adding higher alcohols, carboxylic acids, esters, ethers, ketones, polyalkylene glycols, etc. to the extent that the transparency of the solution is not lost, or adding a large amount of water-soluble substances, or polyurethane elastomers. Methods such as colloidizing the polyurethane elastomer liquid with a non-solvent or adding salt to the coagulation phase have no effect or are somewhat effective on these hydrophobic polyurethane elastomers. However, these methods have not been successful due to drawbacks such as the difficulty in preparing the polyurethane elastomer solution and the poor stability of the polyurethane elastomer solution. A method of adding an anionic surfactant to improve the coagulability of the hydrophobic polyurethane elastomer has also been proposed, for example, in JP-A-51-31747.

However, if this proposed method is followed, it is necessary to add an extremely large amount of surfactant, resulting in a very high cost. Because a large amount of the agent is eluted, a significant amount of foam is generated, making it difficult to circulate the liquid in the pot and recover the solvent.
Problems arise, such as the drainage becoming more contaminated. Further, if the surfactant remains in the product, problems such as inhibiting properties such as deterioration resistance and surface strength or causing changes in gloss, color, etc. over time and impairing the appearance arise. Therefore, there are major drawbacks in industrially adopting such proposed methods. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for improving the coagulation properties of hydrophobic polyurethane elastomers which exhibit poor coagulation properties.

Another object of the present invention is to provide a hydrophobic polyurethane elastomer layer with a large number of uniformly shaped giant pores, which is resistant to deterioration.
It is an object of the present invention to provide a leather-like sheet that is particularly flexible and has excellent hydrolysis resistance, and also has excellent foldability and texture.
The object of the present invention is to add fine particles of titanium oxide (
Additive 1) and water and/or lower alcohol (additive 0)
This was achieved by using a composition solution containing. The polyurethane elastomer used in the present invention is a hydrophobic polyurethane elastomer having a cloudiness value of 13 or less.
Here, the cloudiness value refers to a polyurethane elastomer solution (solvent dimethylformamide) with a concentration of 5% by weight.
While keeping the polyurethane elastomer solution warm and stirring with a magnetic stirrer, dimethylformamide/water (1/1) was added dropwise little by little with a burette. When the polyurethane elastomer solution became cloudy, the dimethylformamide/water 1/1
is the amount (CC number). Polyurethane elastomers with a cloudiness value of 13 or less include polyhexamethylene adipate glycol, polycaprolactone glycol, polyalkylene ester glycol, polypropylene glycol, polytetramethylene glycol, and polyalkylene ether glycol as a soft segment. A polyurethane elastomer is preferably used, in which a diol having 2 to 4 carbon atoms is used as a chain extender, and diphenylmethane-4,4'-diinocyanate is used as a diisocyanate. Among these, polyurethane containing polytetramethylene glycol as a soft segment, which has greatly improved wet coagulation properties and has good quality such as deterioration resistance, appearance, texture, creases, green transparency, and flexibility according to the present invention. Elastomers are the best choice. Furthermore, polyurethane using diamine as a chain extender is also used. The composition of the polyurethane elastomer, that is, the ratio of hard segments to soft segments, influences wet coagulation properties and product quality, and the N content based on diisocyanate is usually preferably 3 to 6% by weight. Further, the concentration of the polyurethane elastomer can be used in a range of 5 to 35% by weight, but from the viewpoint of operability and product quality, a concentration of 10 to 3% by weight is preferable. The titanium oxide used together with the polyurethane elastomer must exist stably in the polyurethane elastomer solution and must be fine particles in order to maximize the coagulation control effect. The size of the titanium oxide in the polyurethane elastomer solution is preferably 3 mm or less, especially IA or less, and is usually made into fine particles using a machine such as a ball mill or a kneader before or during preparation of the polyurethane elastomer solution. Titanium oxide has rutile type and anatase type, both of which can be used in the present invention. The amount of titanium oxide used is preferably in the range of 0.1 to 2% by weight, particularly 0.5 to 1% by weight, based on the polyurethane elastomer. If the amount used is less than 0.1% by weight, there is no effect, and if the amount is more than 20% by weight, the stability of titanium oxide becomes poor in the solution, and precipitation is likely to occur, as well as affecting the quality of the product, such as flexibility, Scratch resistance etc. may deteriorate. Unfortunately, in the specific polyurethane used in the present invention, even if the titanium oxide is used alone, no improvement effect on wet coagulation is observed.
When this is combined with water and/or lower alcohol (sometimes referred to as zero additives), its coagulation properties are significantly improved.

Here, the lower alcohol is a water-soluble alcohol such as methanol or ethanol. The amount of additive 0 used should be kept within a range that does not cause the polyurethane elastomer solution to gel, that is, within a range that does not lose its transparency when a transparent polyurethane elastomer solution is used. 0.1-8% by weight based on lastomer
The optimum amount is 1 to 6% by weight.

If the amount used is less than 0.1% by weight, there is no effect, and if it is more than 8% by weight, the solution becomes cloudy or gelatinous, resulting in poor stability. The present invention is achieved by dissolving the above-mentioned specific polyurethane elastomer in an organic solvent, preparing a composition in which additives 1 to 0 are mixed, and performing wet coagulation using the composition liquid.

A porous film can be made by coating this liquid composition on a support and removing the support after solidification, and it can also be applied to conventionally known fibrous substrates such as woven fabrics, knitted fabrics, and non-woven fabrics. The base fabric of the leather-like sheet can also be produced by impregnating and/or coating and solidifying. In the present invention, when producing a leather-like sheet using the fibrous base material, conventionally known materials suitable for producing a leather-like sheet can be used as they are, but in order to fully utilize the features of the present invention, special materials are required. It is better to choose a flexible fibrous material.

This is because the porous sheet with relatively uniform large pores obtained in the present invention is sufficiently flexible and durable compared to conventional porous sheets, so it is important to select it as a fibrous material. . Such flexible and durable fibrous materials are also known, such as porous array fibers made by removing at least one component of mixed-grade yarn fibers, ultrafine fibers made from Higashi fibers, and composite paper yarns made from two or more types of polymers. There are fibers that can be treated with a solvent to extract one component, or subjected to a split treatment to become five or more ultrafine fibers of 0.5 denier or less. this. For example, the specific application of
It is disclosed in Japanese Patent Publication No. 46-41235, Japanese Patent Publication No. 28918-1982, and Japanese Patent Publication No. 3062-1987. The polyurethane elastomer solution may contain surfactants, softeners/stabilizers, fillers, pigments, dyes, etc. as necessary, as well as polymers with good compatibility in the solution state, such as polyvinyl chloride, polyvinyl acetate, and polyvinyl. Formal, methacrylic acid resin, vinylidene chloride-acrylonitrile copolymer, and vinyl chloride-pinyl acetate copolymer can be mixed.

Usually, a surfactant is often used in combination to improve the dispersion stability of titanium oxide, pigments, etc. in a polyurethane elastomer solution. Although the polyurethane elastomer solution can be used for either the binder or the coating layer of the fibrous material as described above, it is more effective when used for the latter.

Therefore, in the case of leather-like sheets with a porous covering layer, the covering layer must necessarily be prepared from the polyurethane elastomer solution. In the present invention, uniform large pores are created within a single layer of the polyurethane elastomer, and wet coagulation is preferably carried out in a coagulation bath with a relatively high concentration of non-solvent and a low temperature. The leather-like sheet obtained as described above is finally subjected to finishing treatments such as softening agent treatment, buffing, coloring, embossing or fir processing. The present invention will be specifically described below with reference to Examples.

All percentages in this example are by weight. Example 1
First, titanium oxide and dimethylformamide were charged into the attractor at a ratio of 1:9, and the mixture was heated at a rotational speed of 5 pm to 2 ml.
After a long period of time, a fine particle dispersion of titanium oxide was prepared.

Next, 3 parts of this dispersion, 3 parts of finely ground carbon black
A mixture of 2 parts of zinc stearate, 3 parts of water, and 335 parts of dimethylformamide was mixed with polytetramethylene glycol, ethylene glycol, and diphenylmethane-4.
60 parts of a 25% dimethylformamide solution of a polyurethane elastomer (N content 5.0%, cloudiness value 4) synthesized from 4'-diisocyanate was added, thoroughly mixed and defoamed. After dipping this solution into a non-woven fabric made of nylon fibers, the solution was coated with a solid content of 100 mm/strength and 4000 mm containing 40% dimethylformamide.
A leather-like sheet [A] was produced by coagulating with an aqueous solution of for 30 minutes, applying a remover for 2 hours with 60 to 70 q○ of warm water, and drying.

This product had many uniform giant pores in both the fibrous base and the coating layer, and the surface flatness was also very good. on the other hand,
Three types of polyurethane elastomer solutions were prepared by removing only titanium oxide, water, or both titanium oxide and water from the polyurethane elastomer solution described above, and from this solution and a nonwoven fabric of nylon fibers, they were prepared in the same manner as above. Leather-like sheets [B], [C] and [D] were produced, respectively.

Compared to the leather-like sheet [A], both the fibrous base and the coating layer had fewer large pores, were non-uniform, and had poor surface flatness. The above leather-like sheets [A], [
B], [C] and [D] contain 6% of the same polyurethane elastomer as above, 3% of carbon black, 21% of dimethylformamide, 35% of acetone and 3% of cyclohexanone.
A solution consisting of 5% and the same polyurethane elastomer as above, 7%, dimethylformamide 23%, acetone 35%
A solution consisting of 35% solid content and 35% cyclohexanone was sequentially applied using the gravure method at 1.5 ta' for 3 days a day, dried, and then embossed with a rough pattern.
Fir processing was performed. As shown in Table 1, the results of these evaluations show that the leather-like sheet [A] had extremely good not only flatness but also folding, texture, moisture permeability, etc.

Furthermore, when men's shoes were made and worn using this product, no abnormalities such as cracking were observed even after one year had passed, and the product value was high. On the other hand, the leather-like sheets [B], [C], and [D] were all very inferior in appearance and quality to the leather-like sheet [A], and their commercial value was low. Table-1 [Note] Convergence emptiness JISK-
6549: Evening/Day Example 2 Polyurethane elastomer with an N content of 4.0% synthesized from polyethylene propylene adibate glycol 1,4-butanediol and diphenylmethane-4,4'-disocyanate (
Cloudiness value 18) 15%, carbon black 0.5%, stearyl alcohol 1.2% and dimethylformamide 8
A non-woven fabric made of mixed drawn fibers of nylon and polystyrene (mixing ratio 1:1) was impregnated with a solution consisting of 3.3%, coagulated with a 40q0 aqueous solution containing 50% dimethylformamide for 3 minutes, and then soaked in polystyrene with hot toluene. After extraction and removal, the solvent was removed with hot water and dried to produce a fibrous substrate.

Separately, in the same manner as in Example 1, 10% titanium oxide, 6% Chromophthalene o-GR (manufactured by CiBA OY), 2% Mapulet R51W (manufactured by Titan Kogyo KK), and 82% dimethylformamide were mixed, and this pigment was mixed. Polypropylene glycol, 1.4-
Same as above with polyurethane elastomer solution prepared by adding to 48 parts of polyurethane elastomer (white turbidity value: 12) with N content of 4.5% synthesized from butanediol and diphenylmethane-4,4-disocyanate and mixing well. A polyurethane elastomer solution was separately applied to a polyethylene sheet at a solid content of 80 ta', coagulated for 30 minutes with a 30 ml aqueous solution containing 40% dimethylformamide, peeled off from the support, and dried. Porous films [E] and [F] were produced respectively.

All of these had many uniform giant pores and had good surface flatness. These porous sheets and the above-mentioned fibrous substrate whose surface had been made smooth by puffing were adhered to obtain leather-like sheets [E] and [F], respectively.

Finally, 5% polyurethane elastomer synthesized from these polyethylene glycol, ethanolamine and diphenylmethane-4,4-diisocyanate, 2% methacrylic acid resin, 2% lr scale lan BlackGBL (manufactured by Ci Gensha), and dimethylforma. A solution consisting of 21% Mido, 36% acetone, and 34% cyclohexanone was applied as solids for 3.5 days, and after drying, a comb pattern was embossed. All of these products had good flatness, texture, creases, moisture permeability, etc. When men's shoes were made and worn using these materials, no abnormalities were observed in the shoes using the leather-like sheet [E] even after one year, but only a few abnormalities were observed in the shoes using the leather-like sheet [F]. Severe cracking occurred after two weeks. Example 3 Polyurethane elastomer with an N content of 4.3% synthesized from polycaprolactone glycol, ethylene glycol and diphenylmethane-4,4'-diisocyanate
(White cloudiness value 9) 11%, polypinyl chloride 2%, titanium oxide 0.5%, phthalocyanine flu (pigment) 0.3%, methyl stearate 0.2%, water 1.5%, ethanol 1
．． 5% and dimethylacetamide 83% were mixed together in the same manner as in Example 1 using the same attritor used in Example 1, and this solution was applied to a nonwoven fabric of mixed spun fibers of polyethylene and nylon (mixing ratio 1:1). It was impregnated and coagulated for 30 minutes with a 35 oz aqueous solution containing 20% dimethylacetamide, the polyethylene was extracted and removed with hot toluene, and the solvent was removed with hot water, followed by drying.

Claims (1)

[Claims] 1. When producing a porous sheet by coagulating a hydrophobic polyurethane elastomer solution with a cloudiness value of 13 or less, the polyurethane elastomer solution contains finely divided titanium oxide (additive I), water and/or or lower alcohol (
A method for producing a porous sheet with excellent deterioration resistance, characterized by using a composition liquid containing additive II). 2. The method for producing a leather-like sheet according to claim 1, wherein the polyurethane elastomer is synthesized from polytetramethylene glycol, diphenylmethane 4,4-diisocyanate, and a glycol having 2 to 4 carbon atoms. 3. The manufacturing method according to claim 1, wherein additive II is water.
4. The manufacturing method according to claim 1, wherein additive II is alcohol. 5. The manufacturing method according to claim 1, in which water and alcohol are used in combination as additive II.