JPS5930732B2 - Manufacturing method of polyurethane film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an elastic film having better moisture absorption and moisture permeability than polyurethane having polyether as a soft segment. It is useful as a film for forming.

Conventionally, a method for producing an elastic film by wet coagulating polyurethane having polyether as a soft segment is widely known.

However, polyurethanes containing polyether as soft segments generally have poor wet coagulation properties, and for this reason, various improvements have been attempted in the past. For example,
In No. 25269 and Japanese Patent Publication No. 53084/1984, significant improvement in coagulation properties was obtained by using a mixture of polyether and polyester as the soft segment.

However, this method is after all an improvement of the polyurethane used, and has the drawback that the use of polyester for the soft segment may impair the original properties of the polyether polyurethane. As another example, as described in Japanese Patent Publication No. 40-13518, a polymer solution can be made into a colloid or a colloid by adding a non-solvent having affinity with the coagulation bath to the polymer solution. There is also a method to improve this by preparing the solution just before reaching .

However, this method has the disadvantage that it is difficult to control the gel point and there are also problems in stable production. 2
5. Another method is to form a polymer solution using a hygroscopic solvent, partially gel it by leaving it in water vapor or air containing a large amount of moisture, and then immerse it in a coagulation bath. A method has also been proposed.

However, even with this method, it was difficult to manufacture an elastic film 30 with ease of operation. Many applications have been filed for techniques for producing porous elastic films by using various coagulation modifiers, and each technique is well known. For example, leather powder, pulp powder, wood flour, etc. are often added, or a water-soluble inorganic compound (eg, common salt) is often added to the polymer solution. However, the former significantly impairs the physical properties such as surface friction strength and elastic behavior of the resulting elastic film, making it unsuitable for use as a leather-like sheet material, and the latter is not effective unless a large amount of coagulation regulator is used. The resulting film was also unsuitable for use on the silver surface of a leather-like sheet. A method has also been proposed in which higher alcohols, carboxylic acid esters of higher alcohols, amines having up to 30 carbon atoms, urethanes, ureides, etc. are added during direct wet coagulation of polyurethane solutions.

However, the compounds described in these specifications have excellent coagulation control effects for polyester-based polyurethanes, but although they are effective for polyurethanes made by soft segmenting polyethers, they do not have the required quality. In some cases, it was not always satisfactory. SUMMARY OF THE INVENTION An object of the present invention is to provide the most effective coagulation regulator for producing a film by directly immersing a solution of polyurethane containing polyether as a soft segment in a coagulation bath.

Another object of the present application is to produce an elastic film that is not only uniform even when produced by coagulation control, but also has high surface friction strength and scratch strength, and can maintain extremely high air and moisture permeability. is to obtain. Further, significant effects of the present invention will be described in the following specification. This object of the present invention was achieved through research by the present inventors by using polyoxyethylene sorbitan tricarboxylic acid ester as a coagulation regulator.

The polyurethane used in the present invention must be a polyurethane containing polyether as a soft segment.

With polyurethane containing polyester as a soft segment, coagulation progresses relatively smoothly even without the use of a coagulation regulator, but coagulation regulators made of conventionally known higher alcohols, carboxylic acid esters of high alcohols, urethanes, etc. are better. The effect is large, and even if the coagulation modifier of the present invention is used, no significant effect can be obtained. Such polyether has a molecular weight of 500 to 4000, preferably 800 to 30.
00 polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, or a mixed glycol thereof. The effect of adding the coagulation modifier of the present invention to polytetramethylene glycol is particularly remarkable.

Also, is there 50% weight in these glycols? Polyester glycol can also be added within a range not exceeding .
As the organic diisocyanate constituting the polyurethane, commonly used organic diisocyanates can be used as is, but diphenylmethane diisocyanate is particularly suitable, and other aromatic diisocyanates such as naphthylene diisocyanate, diphenyl diisocyanate, tolylene diisocyanate, xylylene diisocyanate, etc. Group diisocyanates are preferred.

Chain extenders such as ethylene glycol, propylene glycol, butylene glycol, hexamethylene glycol, and diethylene glycol have 2 or more carbon atoms.
6 low molecular weight glycols, 0,0'-dichloro-P,V
-diaminodiphenylmethane, m-phenylenediamine, 4-methyl-m-phenylenediamine, ethylene S>
Diamines such as amines and hexamethylene diamine can be used, but glycols are more effective. The coagulation regulator effectively used in the present invention is polyoxyethylene sorbitan tricarboxylic acid ester (herein,
The number of moles of ethylene oxide added is 5 to 30, preferably 10 to 25, and the number of carbon atoms of carboxylic acid is 10 to 30, preferably 16 to 20). Polyoxyethylene sorbitan carboxylic acid esters include mono-, di-, and tri-carboxylic acid esters, but tricarboxylic acid esters, especially triesters of carboxylic acids having 16 to 20 carbon atoms, have smoothness and transparency. This tricarboxylic acid ester is preferred in terms of wettability and film homogeneity, and the present invention uses this tricarboxylic acid ester. The specific names of these compounds are as follows. Polyoxyethylene (10 mole addition) Sorbitan trioleate polyoxyethylene (20 mole addition) Sorbitan trioleate polyoxyethylene (2
0 mol addition) Sorbitan tristearate The amount of coagulation regulator used in the present invention is 5 to 40% by weight based on the weight of polyurethane? , preferably 10-30% by weight.
is within the range of

If the amount added is less than this range, a sufficient effect will not be obtained, and if it exceeds this range, the surface will be smooth, but the strength and bending properties of the film will be lowered, which is undesirable. The present invention is particularly effective when applied to a method for producing a polyurethane film by dissolving the above-mentioned specific polyurethane elastomer in a suitable solvent, coating it on a suitable support, and directly immersing it in a coagulation bath. That is, the coagulation modifier added to the polyurethane solution exhibits the remarkable effect of the present application only when it comes into contact with a large amount of polyurethane non-solvent. For example, when the coagulation modifier of the present invention is added to a hygroscopic polyurethane solution, When a method is adopted in which the film is added and gradually solidified with water vapor, the resulting film has excellent surface smoothness, but is inferior in internal structure uniformity. As a solvent for dissolving the polyurethane elastomer, N,N-dimethylformamide, N,N
- dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, tetramethylurea, dioxane, gamma-butyl lactone, etc. A non-solvent for polyurethane elastomer is used as a coagulation bath to coagulate a solution of polyurethane elastomer, but coagulation is too fast with non-solvent alone, resulting in non-uniform reaction.
Skin tends to form on the surface and cause wrinkles. Therefore,
In the present invention, it is preferable to solidify slowly in a mixed solvent of a non-solvent and a solvent. A preferred coagulation bath composition has a weight ratio of solvent to non-solvent in the range of 20:80 to 70:30. The concentration of the polyurethane elastomer solution in which the present invention is particularly effectively utilized is 7 to 30% by weight, particularly preferably 10 to 25% by weight. and once the viscosity of the solution is 30
The solution viscosity in a 10% by weight dimethylformamide solution at °C is 0.1 to 100 poise, preferably 0.5 to 100 poise.
It is 10 poise.

When the viscosity is within this range, the coagulation adjustment effect of the present invention is best due to the viscosity relationship with water, which is often used industrially as a non-solvent, and the obtained film has good air permeability and moisture permeability. In addition, the surface properties (scratch resistance, etc.) are also excellent.The coagulation conditions are the same as those known in the past, such as keeping the polyurethane solution at a high temperature and lowering the temperature of the coagulation bath.
Alternatively, the reverse operation can also be performed.

The polyurethane elastomer solution contains colorants, activators,
Stabilizers and other coagulation modifiers can be added, as well as polyacrylonyl-1-lyl, polyvinyl polyacetate, polyvinyl chloride, polymethacrylate, polyacrylate, vinyl halide polymers, etc. Can be mixed.

The added coagulation modifier may be removed from the elastic film thus obtained by washing with water, after drying, or at an earlier stage.

If the amount of coagulation modifier added is small, there is no particular problem, but if a large amount of additive is added to increase the coagulation adjustment effect, the modifier may cause a finish such as coloring on the bullet film of the present invention. When it is put into practical use, it causes discoloration and the like, which is not desirable. Although there are no particular limitations on the means for removing it, the simplest industrial method is to thoroughly wash the elastic film with an alcohol such as methanol. The present invention will be described below with reference to Examples, in which e refers to weight unless otherwise specified.

Example 1 Polytetramethylene glycol with a molecular weight of 1000, 4,
Isocyanate-based N? A polyurethane solution having a concentration of 4.5 was dissolved in dimethylformamide (hereinafter abbreviated as DMF) to prepare a polyurethane solution having a concentration of 25%.

Next, the following additives were added to the polyurethane at a concentration of 23%, and this was placed on a glass plate to a dry thickness of 0.5%.
ml, and then 45% water-DMF55
It was coagulated by immersing it in a coagulation bath at a temperature of 50°C. Then, it was dried to obtain an elastic film. The surface smoothness and structural uniformity of the obtained elastic film were evaluated and the results are shown in Table 1. Note that the smoothness and uniformity of the structure are expressed by five levels of numbers, and the larger the number, the smoother and more uniform it is. (1
) Polyoxyethylene sorbitan tristearate (20 moles of ethylene oxide added) (2) Polyoxyethylene sorbitan monostearate (20 moles of ethylene oxide added) (3) Polyoxyethylene sorbitan monostearate (20 moles of ethylene oxide added) 5 mole addition) (4
) Polyoxyethylene sorbitan monooleate (5 moles of ethylene oxide added) (5) Sorbitan tristearate (6) Cetinogelcol ethylene oxide adduct (10 moles of ethylene oxide added) (7) Toluene Example 3 Molecular weight 2000 polytetramethylene glycol, 4,
DM polyurethane obtained using 4'-diphenylmethane diisocyanate and ethylene glycol as a chain extender.
It was dissolved in F to make a 22% solution.

The coagulation modifier used in (1) to (3) of Example 1 was added to the polyurethane in an amount of 20%, and then the polyurethane elastomer was impregnated with this solution and coagulated.(8) No additivesNote. Here, (5) to (8) are comparative examples.

Reference Example Wet coagulation was carried out in exactly the same manner as in Example 1 except that polybutylene adipate glycol was used instead of polytetramethylene glycol. Even in the absence of additives, the surface was smooth and the pore structure was relatively uniform. I got something.

Example 2 Polyurethane obtained using a mixed glycol of 70 parts of polytetramethylene glycol and 30 parts of polypropylene glycol was used in place of the polytetramethylene glycol of Example 1, and polyoxyethylene sorbitant was used as a coagulation regulator. Table 2 shows the results of changing only the amount of listearate (additional moles of ethylene oxide: 20).

Example 3 Polytetramethylene glycol with a molecular weight of 2000, 4,
DM polyurethane obtained using 4'-diphenylmethane diisocyanate and ethylene glycol as a chain extender.
It was dissolved in F to make a 22% solution.

The coagulation modifier used in (1) to (3) of Example 1 was added to this in an amount of 20% based on the polyurethane, and this solution was then impregnated with a polyurethane elastomer and coagulated into a nonwoven fabric (
50% water at a temperature of 40°C.
- By immersing and coagulating in a mixed coagulation bath containing 50% DMF, removing the solvent, and drying, an artificial leather with excellent surface smoothness was obtained.

The products that were then subjected to finishing processes such as coloring and embossing were found to have good durability b3 and extremely high commercial value. Of these, the use of (1) was the best.

Claims (1)

[Claims] 1. A polyoxyethylene sorbitane tricarboxylic acid ester is used as a coagulation modifier when wet coagulating a solution of polyurethane containing polyether as a soft segment in a mixed solvent of a solvent and a non-solvent. A method for producing a polyurethane film. 2. The method for producing a film according to claim 1, wherein the coagulation modifier is removed after wet coagulation. 3. The method for producing a film according to claim 1, using an alkylene polyether having 2 to 6 carbon atoms as the polyether. 4. The method for producing a film according to claim 3, wherein polytetramethylene glycol is used as the polyether.