JPS599575B2 - Manufacturing method of flexible porous sheet material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a sheet material having excellent air permeability and moisture permeability, and a high degree of flexibility.

Traditionally, porous sheet materials have been produced by coating the surface of a fiber base fabric with an organic solvent solution of a polymer such as polyurethane.
The coated fibrous base fabric is immersed in a bath of a liquid that is miscible with the organic solvent in the polymer solution but non-solventful with the polymer in the solution, or exposed to a vapor atmosphere of the liquid. The method of forming a polymer layer having a large number of micropores on a base fabric is generally well known, and the resulting products are widely used as leather substitutes and the like. However, in order to obtain a porous sheet material with excellent air permeability, moisture permeability, and flexibility, it is necessary to use a low concentration polymer solution to form a structure with a larger number of pores than in conventional sheet materials. .

However, since the polymer coating layer obtained by the conventional method as described above has a low deposition density of the polymer per unit volume, the resistance to external forces such as scratching friction is small, and the strength of the polymer coating layer is significantly reduced. There are drawbacks to being exposed to. Furthermore, when the polymer concentration of the polymer solution is lowered, the viscosity of the solution decreases, which limits the thickness of the film that can be formed on the surface of the base fabric, making it difficult to obtain a desired film thickness using normal coating methods. be. Furthermore, when this polymer coating layer is immersed in a coagulation bath, this coating layer is subjected to the effects of pressure, vibration, etc., and there are various problems in the processing process, such as unevenness in the thickness of the coating layer. Therefore, the present inventors have completed the present invention while conducting intensive research on polymers and polymer solutions in particular, while paying attention to methods for producing porous sheet materials having desired properties.

That is, the gist of the present invention is that a solvent solution of polyurethane or a polymer mainly composed of polyurethane, a water-soluble polymer solution of the polyurethane dissolved in a non-solvent, or a polyurethane solvent added to the water-soluble polymer solution. A water-soluble polymer dispersion is mixed to create a mixture containing 6% by weight or more of the polyurethane and 0.5 to 4% by weight of the water-soluble polymer, and the mixture is left to mature for a predetermined period of time to form a gel. The water-soluble high The method of producing a flexible porous sheet material is characterized in that it is treated with a coagulating liquid whose main component is a liquid that is a molecular solvent and also a non-solvent for the polyurethane, coagulated into a porous structure, and dried.

The present invention utilizes the fact that the polymer liquid increases in viscosity due to structural viscosity when left to ripen, so in the case of a polymer liquid with a low polymer content of 10 to 20% by weight,
Not only is the coating extremely easy, but it is also possible to coat even a polymer liquid with a polymer content of 6 to 10% by weight, which has conventionally been difficult to coat due to its low viscosity.

In addition, since the above-mentioned non-solvent for polyurethane, that is, the main liquid of the coagulation treatment liquid and a substance that has an affinity for it, is added, the coagulation treatment liquid permeates into the polymer liquid layer quickly and creates extremely uniform porous pores. Not only is it possible to obtain a polyurethane coating that forms a structure and has excellent surface smoothness and surface hardness, but the low polymer content increases the number of voids, making the resulting product highly flexible, breathable, and air permeable. It has the property of having excellent moisture permeability. Furthermore, since it has the above-mentioned properties, it is of course possible to obtain an extremely flexible sheet-like material by impregnating a thread fiber base material such as a knitted fabric or a non-woven fabric with the polymer liquid used in the present invention.

Next, the present invention will be specifically explained in detail.

The polyurethane used in the present invention is a polymer manufactured from a polyvalent hydroxyl compound having a hydroxyl group at the end, an organic diisocyanate, and a polyfunctional extender, and is a polymer manufactured from a polyvinyl chloride, polyacrylonitrile, polyamino acid, etc. It may be blended in an amount of 1 to 50% by weight based on the polyurethane. The water-soluble polymer used in the present invention may be any polymer that is insoluble or swells in the polyurethane solvent and that imparts gelling and thickening properties to the polymer. Examples of materials having this property include polyvinyl alcohol and hydroxyethyl cellulose, but polyvinyl alcohol with a degree of saponification of 95% or less is particularly preferred. Examples of solvents for polyurethane include, but are not limited to, N-N dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, N-N dimethylacetamide, dioxane, and mixtures thereof. The water-soluble polymer may be one that does not dissolve and imparts a predetermined gelling and thickening property. A water-soluble polymer dispersion prepared by mixing a water-soluble polymer solution dissolved in a polyurethane non-solvent with a polyurethane solvent forms a soft pudding-like gel when left for a predetermined period of time. The gelation and thickening properties of the liquid mixture containing the water-soluble polymer and the water-soluble polymer are considered to be mainly due to the characteristics of the water-soluble polymer dispersion. Therefore, the water-soluble polymer used in the present invention is one in which the water-soluble polymer dispersion prepared by the above-mentioned method is stable for a certain period of time, and further gels into a soft pudding-like form that is easily broken after a certain period of time. is desirable. For example, a polyvinyl alcohol dispersion obtained by adding N-N dimethylformamide, which is a non-solvent, to polyvinyl alcohol, which is a polyurethane solvent, to an aqueous solution of polyvinyl alcohol with a degree of saponification of 95% or more is unstable at room temperature. Forms a relatively hard gel in a very short time. On the other hand, a polyvinyl alcohol dispersion obtained in the same manner using polyvinyl alcohol with a gelation degree of 95% or less is stable at room temperature for several hours or more, forms a soft pudding-like gel after a certain period of time, and has a saponification degree of 95% ( !) The following polyvinyl alcohols are particularly suitable as the water-soluble polymer of the present invention. In the present invention, a homogeneous polymer solution is prepared by mixing a polyurethane-based solvent solution and a water-soluble polymer solution, gelling the mixture, and then breaking the gel.As mentioned above, this polymer solution is water-soluble. It is a three-component system consisting of a polymer, its solvent, and a polyurethane solvent that is a non-solvent for the water-soluble polymer, and takes advantage of the fact that a soft gel is generated and this can be easily miniaturized.

That is, a mixture of a polyurethane solvent solution and a water-soluble polymer solution, or a water-soluble polymer dispersion prepared by adding a polyurethane solvent to the solution, is allowed to age and the resulting gel is broken to form a homogeneous polymer liquid. It is characterized by stabilizing the miniaturized gel in the solution by adjusting it. Therefore, the diameter of the pores in the porous structure can be controlled by the degree of miniaturization of the gel.
Furthermore, this gel tends to transition from a gel to a dissolved state at temperatures above 40°C, and the pore diameter can also be controlled by temperature. In addition, even if a porous polyurethane layer with a smooth surface is generally formed during the film-forming process during coagulation, it is not necessarily easy to maintain the porous structure during the subsequent drying process to remove the coagulant. It causes "shrinkage sticking phenomenon" and loses plane smoothness, and the porous structure disappears, resulting in loss of moisture permeability and air permeability, which may lead to unfavorable results when used as a leather substitute, etc. be.

In order to prevent this phenomenon, a method of adding a large amount of filler such as calcium carbonate, carbon black, or cellulose is known. Since the microgel is dispersed, it acts as a filler, and the polyurethane film obtained from the polymer liquid of the present invention has excellent planar smoothness and is effective in preventing shrinkage and sticking. The amount of water-soluble polymer added is limited by the concentration of the water-soluble polymer solution, but gelation occurs because it is added as a solution of polyurethane dissolved in a non-solvent. In order to sufficiently thicken the mixture, add 0.5~
It is necessary to add the polymer in an amount of 4% by weight, and when the polymer content is low, it is preferably added in an amount of 2 to 4% by weight.

Water is commonly used as a solvent for water-soluble polymers and a non-solvent for polyurethane, regardless of the type of water-soluble polymer used in the present invention. For example, in the case of polyvinyl alcohol, water Other examples include a mixture of water and methanol, diethylenetriamine, triethylenetetramine, etc., but it is industrially most advantageous to use water.

If the water-soluble polymer used in the present invention is added as an aqueous solution to a polyurethane solvent solution, local coagulation of the polyurethane may occur, so it is added as a dispersion mixture of the water-soluble polymer aqueous solution and a polyurethane solvent. It is preferable to do so.

When a water-soluble polymer is mixed as an aqueous solution with a solvent solution of polyurethane, water is also added together with the addition of the water-soluble polymer, but if the amount of water added to the polymer liquid obtained by the present invention exceeds a predetermined amount, Since phase separation occurs, it is necessary to add the water-soluble polymer aqueous solution so that the amount of water added does not exceed a predetermined amount.

The amount of water added at which the polymer liquid begins to undergo phase separation is approximately 10% by weight, but this value varies depending on the type of water-soluble polymer and polyurethane, the temperature of the polymer liquid, etc., and for example, the higher the temperature, the greater the amount of water added. Become. The polymer mixture of the present invention does not lose its desired gelling and thickening properties even when dyes or pigments are added as colorants. In addition, after coating or impregnating the polymer liquid obtained in the present invention on a fiber base material such as a textile fabric or non-woven fabric, or coating it on a substrate such as a film or plate of any shape, Treatment is carried out using a coagulation liquid whose main component is a liquid that dissolves the added water-soluble polymer, that is, wet coagulation treatment.

Particularly preferred liquids for coagulation include water and a mixture of water and methanol. Through this treatment, the polyurethane is coagulated and the water-soluble polymer is easily eluted during the coagulation process.

If the water-soluble polymer remains in the polyurethane coating, it will impair the physical properties of the coating, such as flexibility, so it is preferable to completely dissolve it. Since the polymer mixture according to the present invention has a low polymer content, the polyurethane coating formed after wet coagulation has many voids, which not only provides excellent moisture permeability and air permeability but also extremely flexibility. Because it has thickening properties, it is extremely easy to apply.

Therefore, the porous sheet material obtained by applying or impregnating the polymer liquid of the present invention onto a textile substrate such as a knitted fabric or nonwoven fabric, or by applying it onto a substrate of any shape has extremely excellent properties as a leather substitute. and is industrially advantageous.

The present invention will be explained below with reference to Examples.

In the examples, "parts" and "%" refer to "parts by weight" and "%".
% by weight. Example 1 29 parts of 4-4'-diphenylmethane diisocyanate was added to 100 parts of polyester (molecular weight 1500) synthesized from adipic acid and 1-4 butanediol, and the mixture was heated for 8 hours under a nitrogen stream.
The product obtained by reacting at 0°C for 3 hours was mixed with 185 parts of N.
-N dimethylformamide (hereinafter abbreviated as DMF), and then 1.7 parts of hydrazine hydrate and 25 parts of ethylene glycol were dissolved in DMF and reacted for 1 hour at 40°C under a nitrogen stream to form a solid. A 30% polyester urethane solution in DMF was obtained.

Next, 60t of this solution was dissolved in DMF6Ot and diluted to 1
A 5% polyurethane solution was made. On the other hand, polyvinyl alcohol (saponification degree 86.5-89.0) (hereinafter referred to as PVA)
) was dissolved in water to make a 30% aqueous solution, and DMFl4Of was added to 40 t of this aqueous solution to form PVA water-DMF.
180 t of mixed dispersion was prepared and mixed with the polyurethane solution to obtain polyurethane 6.0 (:F6, PVA4.O (F
A polymer solution containing 6 was prepared and left to mature overnight to form a gel.

Next, this gelled product was stirred with a homomixer for 10 minutes to break the gel and prepare a uniform polymer. Similarly, by changing the amount of the PVA aqueous solution added, the polyurethane concentration was 6.
．． Mixtures containing 0% PVA but varying amounts in the range of 2.0 to 4.5% were created. Table 1 shows the viscosity change of the mixed liquid at this time. For comparison, a sample containing no PVA is also shown. However, the viscosity was measured using a Tokyo Keiki B-type rotational viscometer with a 30-meter rotational speed at 6 rpm.
, at 25°C. As is clear from Table 1, with polyurethane concentration 6.0 (F6), coating was not possible at all without the addition of PVA, but coating was possible by adding 2.0 to 2.5% by weight or more of PVA. You can see that the viscosity has increased.

Furthermore, when PVA was added in an amount of 4.5% or more, the amount of water added was too large, resulting in phase separation, making uniform coating impossible. Add 2.5 to 4.0% of PVA and break the gel to form a homogeneous polymer liquid on cotton flannel to a thickness of 0.8 m.
1 in a 50℃ hot water bath containing 30q6 DMF.
After treatment for 0 minutes, the sample was further washed in a hot water bath at 50°C and dried.・Subsequently, a surface treatment agent was applied by spraying to perform surface treatment. The obtained product was extremely soft and had a feel similar to natural leather, making it suitable for use in clothing. Example 2 Molecular weight 2
4-4'- to 100 parts of polyethylene adipate
Add 25 parts of diphenylmethane diisocyanate and react at 80° C. for 3 hours under a nitrogen stream to obtain a prepolymer.

This was dissolved in 190 parts of N-N-dimethylformamide (hereinafter abbreviated as DMF), and 4.5 parts of trimethylenediamine was dissolved in DMF and reacted for 2 hours at 30°C under a nitrogen stream to form a solid. A 30% DMF solution of polyester urethane was obtained. Next, add this solution to D
A 20% solution was prepared by dissolving and diluting with MF. On the other hand, hydroxyethyl cellulose (hereinafter abbreviated as HEC) was dissolved in water to make a 10% aqueous solution, DMF was added to this, and HEC was dissolved in water.
An EC-water-DMF mixed dispersion was prepared and added to the polyurethane solution with careful stirring to give a polyurethane concentration of 15% and HECl. A mixed solution containing O(f) and 9.0% water was prepared and left to mature for one day and night.

After ripening, the mixture turned into a pudding-like gel, but this was stirred with a homomixer to break it into fine gels and prepare a homogeneous polymer liquid. The viscosity of the polymer liquid after this adjustment is 2600 at 25°C.
cp8 atsuta. This polymer liquid was applied to a silicone rubber sheet to a thickness of 0.7 Tm, and was heated at 50°C containing DMF3O weight%.
After treatment in a hot water bath for 10 minutes, the sample was further washed in a DMF-free hot water bath at 50° C. and dried. The flexibility of the film created at this time was 5.5% using the cantilever method (45 method).
The 5wm1 moisture permeability was 6500t/24hrz.
The viscosity of the polyurethane 1501) solution without HEC addition is 650 cps'T at 25°C! Although it was coated to a thickness of 0.7 m, due to the low viscosity, the shape retention of the coated solution layer was poor, and the film obtained by wet coagulation under the same conditions as above was inferior in planar smoothness. Example 3 Polyvinyl alcohol (Saponification degree 86.5-89.0)
(hereinafter abbreviated as PVA) was dissolved in water to prepare a 25(f) aqueous solution.

This aqueous solution 24? 76r of N-N dimethylformamide (hereinafter abbreviated as DMF) was added to make a polyvinyl alcohol-water-DMF dispersion, and the DMF solution of the polyester urethane obtained in Example 2 was diluted and dissolved in DMF to adjust the polyurethane concentration. Carefully added to 200f of the 27% solution with vigorous stirring. Polyurethane 18%, which exhibits thixotropy when added, PVA 2. A mixed solution containing O% is obtained, which gels into a pudding-like state when left for a day and night. This gelled product was broken into a homogeneous polymer liquid using a homomixer, and defoamed at room temperature and under reduced pressure.The viscosity at this time was 27,000 cps at 25°C, and application was extremely easy. After applying the polymer liquid to a thickness of 0.8 m on a polyurethane-impregnated nonwoven fabric, the temperature was 50°C.
The sample was immersed for 10 minutes in a hot water bath containing 30% DMF, washed for 20 minutes in a 60°C hot water bath containing no DMF, and then dried. After drying, the surface-treated product had an appearance extremely similar to natural leather, and had excellent flexibility. Also, the moisture permeability of this product is 7201/24 according to JISZ-0208 method.
It had an hr/a rating and had excellent moisture permeability. Observation using an electron microscope revealed that the polyurethane layer had an extremely uniform porous structure with many voids. For comparison, a 18% polyurethane solution of the DMF solution of the polyester urethane was prepared without adding PVA, and this was applied to the nonwoven fabric at a concentration of 0.8%.
It was applied to Tfr1n. The viscosity at this time is 210 at 25℃
At 0 cps, the viscosity was low and the shape retention of the coating layer was low. This was treated in a 50°C hot water bath containing 30% DMF for 10 minutes and then in a 50°C hot water bath containing no DMF for 20 minutes in the same manner as above, but the coagulation rate was slow and a considerable amount of DMF remained. Therefore, it was necessary to treat for 30 minutes or more to remove the solvent. After washing and drying to remove solvent for 1 hour, the moisture permeability of the product, which was surface treated in the same way as above, was 210t/24.
hr/I, the flexibility was inferior to that obtained using a polymer liquid to which PVA was added.

Furthermore, due to the low viscosity, the polyurethane layer was seen to have penetrated into the inside of the nonwoven fabric, and observation using an electron microscope showed that the pores in the polyurethane layer were localized near the surface and there were few voids. Example 4 Dissolve the polyester urethane obtained in Example 1 in N1N dimethylformamide (hereinafter abbreviated as DMF) at 7fL120
A 18% polyurethane solution was prepared by dissolving and diluting V with DMF8O7.

On the other hand, polyvinyl alcohol (degree of saponification 88.0±1.0
) (hereinafter abbreviated as PVA) in water to make a 25% aqueous solution, and 76 liters of DMF was added to 24 t of this aqueous solution to prepare PVA.
100f of water-DMF mixed solution was prepared and mixed with the polyurethane solution to obtain 12% polyurethane and 2% PVA. O(
A mixed solution containing L was prepared and left to ripen overnight to form a gel. Next, this gelled product was stirred for 10 minutes using a homomixer to break the gel and adjust to a uniform polymer liquid, which had a viscosity of 6200 cps at 25°C. Similarly, Table 2 shows the change in viscosity of the mixture when PVA was added using the 25% PVA aqueous solution. However, the polyurethane concentration was constant at 12%. For comparison, the viscosity change when no PVA is added is also shown. From Table 2, it can be seen that as the amount of PVA added increased, the viscosity after gel breakdown increased rapidly, and the viscosity was increased to a viscosity that was extremely easy to apply.

Claims (1)

[Claims] 1. Mixing a solvent solution of polyurethane or a polymer mainly composed of polyurethane and a water-soluble polymer solution of the polyurethane dissolved in a non-solvent, or a water-soluble polymer dispersion in which a polyurethane solvent is added to the water-soluble polymer solution. 6% by weight or more of the polyurethane and 0.0% of the water-soluble polymer.
A mixed solution containing 5 to 4% by weight is prepared, the mixed solution is left to mature for a predetermined period of time to gel and thicken, and then the gel is broken to prepare a uniform polymer solution, which is coated on a fiber base material or After being impregnated or coated on a releasable substrate of any shape, it is treated with a coagulating liquid mainly composed of a liquid that is a solvent for the water-soluble polymer and a non-solvent for the polyurethane to form a porous structure. A method for producing a flexible porous sheet material characterized by solidifying and drying the material.