JPS59179636A - Production of microporous structure - Google Patents

Abstract

PURPOSE:To produce a microporous structure having properties similar to those of natural leather, by impregnating a fiber base with an aqueous slurry of a specified polyurethane composition, evaporating the organic solvent in the aqueous slurry and drying the impregnated base. CONSTITUTION:A polyurethane composition is formed by chain-extending an isocyanato group-terminated prepolymer obtained by reacting a long-chain glycol (average MW of 500-5,000) with an organic diisocyanate by using a chain extender (A) which forms an easily soluble polyurethane, and a chain extender (B) which forms a difficultly soluble polyurethane and has a rate of chain extending lower than that of chain extender (A), in an organic solvent having a b.p. <=120 deg.C and dissolving 1-50g of water in 100g thereof (e.g., methyl ethyl ketone). Water in an amount corresponding to 10-95wt% of the critical amount of addition of water is added. A fiber base is impregnated with the produced aqueous slurry, the organic solvent is removed by selective evaporation, and the impregnated base is dried to form a microporous structure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a microporous structure in the form of a leather-like sheet. More specifically, the present invention relates to a method for producing a leather-like sheet-like microporous product having good natural leather properties from a specific polyurethane composition and Iga base fabric.

BACKGROUND OF THE INVENTION Methods for producing leather-like sheets using dry microporous polyurethane technology are known as shown in US Pat. No. 3,666,542 and US Pat. No. 3,895,134. However, in this method, although the particle size and weight ratio of the polyurethane insoluble particle component in the water-containing slurry serving as the impregnating liquid have a large effect on the impregnating property, solidification rate, or porosity of the molded product, Because it was difficult to control the process, the resulting product had unsatisfactory properties as a leather substitute.

Purpose of the Invention The purpose of the present invention is to improve impregnating property by reducing the particle diameter of polyurethane insoluble particle components in a water-containing slurry serving as an impregnating liquid, increasing the number of particles accordingly, and appropriately controlling the weight ratio of the particle components. The object of the present invention is to provide a sheet-like microporous structure with improved coagulation properties and good natural leather properties at a faster molding speed than conventional leather.

In other words, the present invention is an isocyanate-terminated prepolymer obtained from a long chain glycol with an average molecular weight of 500 to 5,000 and an organic diisocyanate, which has a boiling point of 120°C or higher and which dissolves 1 to 5 JJ of water per 100 g. In a solvent (a), a chain extension agent (△) which produces a polyurethane easily soluble in the organic solvent (a) when a chain extension reaction occurs in the organic solvent (a) and a chain extension reaction in the organic solvent (a). Chain elongation is carried out using a mixed chain extender (B) which produces a polyurethane that is poorly soluble in the organic solvent (a) when the elongation reaction occurs, and a chain extender (B) which has a slower chain elongation rate than the chain extender (A). 10 to 95% by weight of water based on the added amount of critical water is added to and mixed with the resulting polyurethane composition to form a water-containing slurry, and a fibrous base fabric is impregnated and/or coated with the water-containing slurry. This is a method for producing a leather-like sheet-like microporous structure having good natural leather properties, which comprises selectively evaporating the organic solvent (a) from the water-containing slurry and then drying it.

As the long chain glycol of the present invention, known polyesters and polyethers can be used, such as polyethylene adipate 1-. Polybutylene Adipe 1~. Polyethylene propylene adipate, polyethylene butylene adipate
1 to polydiethylene adipate, polyethylene succine-1-, polybutylene succinate, volite-1-ramedylene glycol.

Examples include polypropylene glycol and polyoxyethylene glycol, and the appropriate molecular weight of these is 500 to 5,000 in view of the properties of polyurethane. It is also possible to mix the above-mentioned glycols as long-chain glycols, and in particular, by using a mixture of hydrophobic glycol and polyoxyethylene glycol, when forming a water-containing slurry as described later, it increases its stability and has an advantage in forming porosity. becomes. In this case, polyoxyethylene glycol is preferably used in an amount of 1 to 15% by weight based on the weight of the polyurethane composition in view of its eye and mouth rectangle.

On the right side of the present invention, the diisocyanes 1 to 4 include, for example, 4,
4'-diphenylmethane diisocyanate-1-11,3-
xylene diisocyanate, 1,4-xylene diisocyanate 1~, 2.41~ruene diisocyanate 1~,
2.6-1~ruene diisocyanate-1~, 1,5-naphthylene diisocyanate i~, 1,5-dogphthylene diisocyanate 1m-phenylene diisocyanate, p-
to phenylene diisocyanate 1, hexamethylene diisocyanate 1 to . Examples include 4.4'--dicyclohexylmethane diisocyanate-1-.

The organic solvent (a) for polyurethane used in the present invention must (i') have a boiling point of 120°C or less and satisfy conditions (a) and (0), dissolving 1 to 509 points per 1,100 g. .

When an organic solvent with a boiling point exceeding 120° C. is used, it is difficult to selectively evaporate the organic solvent from the water-containing slurry, and as a result, the microporous polyurethane targeted by the present invention cannot be obtained. Furthermore, if the organic solvent is not capable of dissolving 1 to 50 g of water per 100 g, a stable water-containing slurry cannot be obtained and the object of the present invention cannot be achieved.

An organic solvent that satisfies the above requirements (a) and (○)
Examples of a) include methyl ethyl ketone, methyl-
n-propyl ketone, methyl isobutyl ketone, diethyl kene, methylform A-mate, n-propyl formate, methyl acetate-1, ethylacetyl-1, isopropyl acetate, isobutyl acetate, 5e
Examples include a-butyl acetate and 1,2-dichloroethane. A mixed solvent of two or more of these can also satisfy the above requirements (a) and (01) and can therefore be used.

In addition, organic solvents that have a high solubility in water, such as acetone, tetrahydrofuran, or dioxane, and organic solvents that hardly dissolve water, such as benzene, 1
It is also possible to use a mixed solvent prepared by mixing 1 to 1 luene or n-hexadiene and adjusting it to satisfy the above requirements (a) and (i).

The prepolymer reaction of the present invention is a solventless reaction.

Any solvent reaction is possible, but in the case of a solvent reaction, it is necessary to satisfy the above requirements (a) and (0).
:i solvent (a > should be used).

The prepolymer concentration at the time of starting the chain extension reaction must be controlled appropriately by the organic solvent (a). This is because, although it varies depending on the chain extender used, the concentration at which the chain extension reaction starts affects the particle size and the number of particles of polyurethane fine particles, which are related to the improvement of impregnating properties and coagulation properties that are the objectives of the present invention. . Generally, when the chain extension reaction initiation concentration is high, the particle diameter of the obtained polyurethane fine particles tends to be large and the particle component ratio tends to be large. In the present invention, the particle size of the polyurethane fine particles is preferably small, so a low concentration is preferable as the starting concentration for the chain elongation reaction, but if the concentration is too low, the reaction time will become long, making it difficult in practice. Therefore, the reaction starting concentration must be determined by considering the above balance.

The chain extender used in the present invention consists of a chain extender <A> which produces a polyurethane that is easily soluble in the organic solvent (a) when a chain elongation reaction occurs in the organic solvent (a), and an organic solvent (a).
This mixed chain extender is composed of a chain extender (B) which produces a polyurethane that is poorly soluble in the organic solvent (a) when subjected to a chain extension reaction therein, and which has a chain extender (B) that has a slower chain extension reaction rate than the chain extender (A). An object of the present invention is to simultaneously produce a polyurethane component soluble in an organic solvent (a) and a fine particle component insoluble in the organic solvent (a) during a chain extension reaction, and to generate particles of the fine particle component insoluble in the organic solvent (a). The goal is to miniaturize the diameter, control the weight ratio, improve impregnating properties and coagulation properties, and achieve microporous molding that is more advantageous than conventional methods.
B) needs to have a slower chain elongation reaction rate than the chain extender (A>).If the chain elongation reaction rate of the chain extender (B) is faster than or the same as that of the chain extender (A>), The formation of insoluble particle components in the chain elongation reaction occurs at a rapid stage, and since the insoluble particle components have relatively low molecular weight and high crystallinity due to the urethane groups, the activity on the surface of the insoluble particles is high, and as the reaction progresses further, the particles grows and the particle size eventually becomes large, making it impossible to achieve the purpose of the present invention.Therefore, the present invention aims at reducing the reaction rate of the chain extender (13) to the chain extender (A).
By slowing down the reaction rate of the chain extender (△)
After giving priority to the chain elongation reaction (B) to produce a relatively high-molecular soluble polyurethane, the chain elongation reaction (B) is caused to gradually produce fine particles with low surface activity and difficult to grow. to obtain microparticles.

The chain extender (A>) should be determined by the solubility of the organic solvent <a> in the polyurethane. Generally, an ether group (-0-) or a thioether group (-3-
) etc. and aliphatic diglycols having side chains react with organic diisocyanates to form urethane bonds, reducing their crystallinity and making them soluble in organic solvents (a). This is preferable because it becomes like this. As specific examples of the chain extender (A), all can be used as long as they satisfy the conditions of the present invention, such as diethylene glycol, triethylene glycol, thiodiethanol, neopentyl glycol, and N-methyl glycol. Examples include tanolamine.

The chain extender (B) should be determined in consideration of the ability of the organic solvent <a) to dissolve polyurethane and the reaction rate of the chain extender (A). When reacting with an organic diisocyanate to produce a urethane group, it is necessary to produce a polyurethane that is insoluble in the organic solvent (a), and as a specific example, any polyurethane that satisfies the conditions of the present invention can be used. However, spiro ring-containing glycols represented by the following general formula are preferred.

(In the formula, 1 to R4 represent a C1 to C3 alkyl group, and 5 to P8 represent -H2 or -C1 (3)) In the above general formula, when P and -P8 are -H, primary However, due to the steric hindrance effect of the alkyl groups of P1 to P4, the reaction rate with organic diisocyanates is slower than that of ordinary primary glycols such as diethylene glycol and triethylene glycol, and the present invention satisfies the conditions for the chain extender (B).Also, R5.R
When either of 6 and R7゜R8 is -CH3, it becomes a secondary spiro ring-containing glycol, so the reaction rate with the organic diisocyanate is slower than that of the primary glycol, resulting in the chain extender (B) of the present invention. satisfies the conditions of

Moreover, the feature of the IC1 present invention is that when polyurethane is produced by using a mixture of the chain extender (A) and the chain extender (B), the solubility in the organic solvent (a') is lower than that of the chain extender (A). The character is intermediate between chain extenders (B), and conventionally common chain extenders such as ethylene glycol and 1,4
-Compared to the case where butanediol is used, the particle size obtained can be made smaller, and at the same time, the particle component ratio of the obtained fine particles can be stably produced. When using conventional ethylene glycol or 1,4-butanediol,
The timing of particle generation varies from lot to lot due to subtle differences in chain elongation reaction rate between raw material lots or the reaction temperature during particle generation, and the weight ratio of the resulting particle components is not constant.
As a result, it has been difficult to stabilize the softness and other properties of the final product, the leather-like sheet.

The mixing ratio of the chain extender (A) and the chain extender (B) should be determined by taking into account the solubility of the organic solvent (a) used in the polyurethane, and the insoluble particle component of the resulting polyurethane composition. It is better to adjust the ratio so that it is 30 to 60 wt ω% with respect to the solid polyurethane.If the ratio of the above-mentioned insoluble particle component is 30% or less, the solidification rate and microporous polyurethane aimed at in the present invention will not be achieved. It is difficult to obtain and is not preferable.Also, if the ratio of the above-mentioned insoluble particle component is 60
% or more, the strength of the microporous polyurethane obtained becomes undesirable. To decrease the ratio of insoluble particle components, reduce the ratio of chain extender (B) used, and conversely, to increase the ratio of insoluble particle components, use chain extender (B).
All you have to do is increase the usage ratio of .

In this way, in order to obtain the miniaturization of the particle size and the weight ratio of the insoluble particle components which are the objectives of the present invention, the mixing ratio of the chain extender (A> and the chain extender (B)) should be 80:20 to 80:20 in molar ratio. The particle size of the insoluble particle component of the polyurethane obtained by the chain extension reaction as described above is microscopic, and most of the particles are 5 microns or less.Furthermore,
The molecular weight of the long chain glycol that is the raw material for the prepolymer is j
Corrected and chain lengthened.

By optimizing the long reaction starting concentration and temperature, fine particles of 1 micron or less can be obtained.

The polyurethane composition containing the above fine particles is mixed with water to form a water-containing slurry, which is impregnated into a fibrous base fabric. If the fibrous base fabric at this time is a thick and dense non-woven fabric or woven fabric,
Since the fiber gap is about 10 microns, the particle size of the polyurethane fine particle component contained in this water-containing slurry must be smaller than this, otherwise the nonwoven fabric or woven fabric will not be uniformly impregnated with the fine particle component, and the object of the present invention will not be achieved. I can't do that. Furthermore, the fibrous base fabric has a fine denier of less than 0.5 denier! In the case of a high-density nonwoven fabric made of IN, the fiber gaps become even finer, and in order to achieve uniform impregnation, the particle size of the polyurethane fine particle component may be reduced to 1.
Micrometers or less are required. When polyurethane particle components are produced using conventional methods, the particle size is approximately 20
micron m. Therefore, when impregnating the above-mentioned thick and high-density non-woven fabric or woven fabric, the particle components accumulate on the surface of the non-woven fabric or woven fabric due to the filter effect, and only the soluble polyurethane component is impregnated into the inside. The solidification rate is slow and it is difficult to make the material microporous, resulting in unsatisfactory properties of the resulting leather-like sheet material. However, by the method of the present invention, it is possible to reduce the particle size of the polyurethane fine particle component to 1 micron or less, and it is possible to uniformly impregnate even the above-mentioned finely divided and high-density nonwoven fabric or woven fabric. It became.

The water-containing slurry impregnated into a nonwoven fabric or woven fabric becomes microporous polyurethane by selectively evaporating the organic solvent (a)1, and the solidification rate in this case is largely related to the number of particles of the polyurethane particle component. ing. The larger the number of particles of the fine particle component, the more the water-containing slurry solidifies due to selective evaporation of a small amount of the organic solvent (a), and the system fixation occurs.
It becomes easy to become microporous. Therefore, assuming that the weight ratio of the particle components in the whole polyurethane is the same, the particle diameter of the particle component of the present invention is 1 μm compared to the conventional particle diameter of 20 μm.
In terms of micron m, the number of particles of the present invention is (20/1) three times that of the conventional particle number, that is, 8,000 times, which improves the solidification rate and improves production efficiency. Furthermore, conventionally, during selective evaporation of the organic solvent (a), the impregnated slurry moved toward the surface of the impregnated nonwoven or woven fabric, which caused migration, but in the present invention, the coagulation property has been improved. This eliminates migration and greatly improves the properties as a leather substitute.

Water is added to the polyurethane composition containing the above-mentioned particulate components to form a water-containing slurry, but before that, the concentration must be adjusted with an organic solvent (a). The concentration is adjusted depending on the target properties of the final product, but from the viewpoint of liquid stability of the water-containing slurry, etc.
It is preferable to adjust the concentration to a range of % to 30%. Water in an amount of 10 to 95% by weight of the added amount of critical water is added to the polyurethane composition whose concentration has been adjusted while stirring and mixing to form a water-containing slurry that is a creamy W10 type emulsion. The critical water addition amount referred to here means that when water is added to and mixed with the polyurethane composition whose concentration has been adjusted, the water is first solubilized in the organic solvent (a) that is the solvent for the polyurethane composition, and then the water is further dissolved. W1 when added and mixed
When a W10 type emulsion is formed and water is further added and mixed, the W10 type emulsion is broken and the water is separated.

The amount of water added at which this W10 type emulsion is broken is called critical water addition (2). Therefore, the amount of critical water added is 9
If more than 5% by weight of water is added, a stable water-containing slurry cannot be obtained, and if less than 10% by weight of critical water addition 1 is added, a W10 type emulsion water-containing slurry is required to obtain microporous polyurethane. is difficult to obtain. The water-containing slurry obtained as described above is impregnated into a fibrous base fabric such as a nonwoven fabric or a woven fabric, and if necessary, it is coated, and then a water-containing slurry is formed in an atmosphere with controlled temperature and humidity. After selectively evaporating the organic solvent (a) and coagulating the polyurethane constituting the water-containing slurry while retaining the dispersed water, the dispersed water is dried. The temperature during selective evaporation of the organic solvent (a) is
If the temperature is set below the boiling point of the solvent and the humidity is high, selective evaporation of the solvent <a) can be carried out more selectively and more quickly.

The microporous structure obtained as described above exhibits good natural leather properties as a leather-like sheet material,
Its productivity will also be greatly improved compared to conventional methods.

The present invention will be specifically described below with reference to Example 0.

All parts in the examples indicate parts by weight. Note that the characteristics in the present invention were measured as follows.

1) Bending resistance Re Grip 2 cm of one end of a test piece of width 2.5 cm x length 9 cm, and bend the radius of curvature 2 at a position 2 cm from the other end.
The repulsive force when bent into a 1/4 cm semicircle is measured and converted to a value for a width of 1 cm.

2) Bending compression pressure P5 A test piece of width 2.5 cm x length 9 cm was bent in half, and the thickness of the curved part was 5771. /yyt, measure the cutting saw at that time, and convert it to a value for a width of 1 cm.

3) Leather-like properties It is expressed as the value obtained by dividing the bending compressive stress P5 by the bending resistance R[3, and the larger this value is, the more the structural characteristics are similar to natural leather.

Example 1 473.9 parts of ramethylene glycol from Volite 1 with an average molecular l of 2,000 and 40 parts of polyoxyethylene glycol with an average molecular fi of 1,550 J3 and Il, +1
300.2 parts of ``-dino J-dylmethane diisocyanate was dissolved in 203.5 parts of methyledilke]hen, and the mixture was heated at 50°C.
The mixture was reacted with stirring for 90 minutes to prepare an isocyanate-terminated prepolymer. To this, 1 to 796.5 parts of methane was further added, the temperature was raised to 70'C, and 50.1 parts of diethylene glycol and 3,9-bis(1,1
-bismethyl-2-hydroxyethyl)-2,4,8,
10-tetraoxaspiro[5,5]undecane 135
．． As the viscosity increases, 3,000 parts of methyl ethyl ketone is gradually added, and finally a 20% thick polyurethane-medyl ethyl ketone composition (I) is prepared. Obtained 1, this polyurethane composition (
I) had the following properties.

Viscosity (B-type viscometer) (70°C) 1400 cps Particle diameter (maximum) 1 Mig 02 m Insoluble particle component weight ratio 35% (relative to the previous polyurethane) Appearance Transparent cloudy white The above polyurethane composition (I) was mixed with methyl ethyl ketone. The concentration was adjusted to 19.5 parts by dilution, and 27 parts of water corresponding to 70% of the critical water additive was added to 100 parts of this adjusted composition with stirring to obtain a creamy water-containing slurry (I). Created.

A nonwoven fabric made of polyester fibers with a weight of 1390 g/'rIi and a thickness of 1.3 m/m was impregnated with the above water-containing slurry (I) for 1 minute, and after scraping off the water-containing slurry adhering to the surface, the temperature was 60°C and the relative humidity was 60°C. 1 in an atmosphere of %
It was left to stand for 5 minutes and then dried at 110°C.

As a result, as shown in Table 2, a leather-like sheet material (I>) having unprecedented natural leather properties was obtained.

Comparative Example 1 564.3 parts of polytetramethylene glycol with an average molecular weight of 2,000, 40 parts of polyoxyethylene glycol with an average molecular weight of 1,550, and IJ, ll--Schiff 1-312. 6 parts were dissolved in 229.2 parts of methyl ethyl ketone and reacted at 50° C. with stirring for 90 minutes to prepare an isocyanate-terminated prepolymer. In addition, methyl-ethyl ketone 770.
8 parts of methyl ethyl ketone was added, the temperature was raised to 70°C, 83.1 parts of 1,4-butanediol was added to cause a chain extension reaction, and as the viscosity increased, 3000 parts of methyl ethyl ketone was gradually added to give a final concentration of 20%. A polyurethane-methylethylkeyne silk composition (Comparative T) was obtained.

This polyurethane composition (Comparative T) had the following properties.

Viscosity (B-type viscosity) (70°C) 1100 cps Particle diameter (maximum) 25 microns m Insoluble particle component weight ratio 39% (based on all polyurethane) Appearance Milky white Same as Example 1 using the above polyurethane composition (comparison king) A water-containing slurry (comparison ■) was prepared using the method described above, and impregnated onto the same nonwoven fabric as in Example 1 using the same method.

Selective evaporation and drying of methyl ethiketone was carried out to obtain a leather-like sheet material (comparison ■) having the properties shown in Table 2.

Example 2゜The surface of the leather-like sheet material (I) obtained in Example 1 was further coated with a water-containing slurry (I> to a thickness of 1.0'rrL/TrL, and the temperature was 50°C and the relative temperature was 65°C. 20% in an atmosphere
The mixture was allowed to stand for a minute, and then dried at 110°C to obtain a smooth-surfaced leather-like sheet material <II) having the properties shown in Table 2. Note that the apparent density of this coating layer is 0.
．． It was 509/an.

Comparative Example 2゜On the surface of the leather-like sheet material obtained in Comparative Example 1 (Comparative ■),
A water-containing slurry (Comparison ■) was coated to a thickness of i, om/m, and a smooth surface type leather-like sheet material having the characteristics shown in Table 2 was coated in the same manner as in Example 2 (Comparison ■). ) was obtained. The apparent density of this coating layer is 0.58q
/ClT1'.

Example 3 A polyurethane chassis was prepared in the same manner as in Example 1 using the following combination as a mixed chain extender, and a water-containing slurry and a leather-like sheet material were prepared in the same manner as in Example 1. The properties of each polyurethane composition are shown in Table 1, and leather-like sheets 1 to 1 were made from each of them! lz1 bamboo is shown in Table-2.

Comparative Example 3゜The same nonwoven fabric as in Comparative Example 1 was impregnated with the water-containing slurry prepared in Comparative Example 1 (Comparative ■) for 3 minutes, and then a leather-like sheet having the characteristics shown in Table 2 was prepared in the same manner as in Comparative Example 1. A leather-like sheet-like material (comparison ■) was obtained.The leather-like sheet-like material obtained here (comparison ■) was compared with the leather-like sheet-like material (1) obtained in comparative example ■.
Although the weight of the impregnated polyurethane is increased due to the longer impregnation time, the leather-like sheet materials i, I [[, IV, Va Yohi IV
It can be verified that the present invention has excellent impregnating properties.

Comparative Example 4 452.6 parts of Polyte 1-ramethylene glycol with an average molecular m of 2.000, 40 parts of polyoxyethylene glycol with an average molecular m of 1,550, and 288.1 parts of pp-diphenylmethane diisocyanate were mixed with 195 parts of methyl ethyl ketone. .2 parts and reacted at 50° C. with stirring for 90 minutes to prepare an isocyanate group-terminated prepolymer. In addition to this, methyl ethyl ketone 804.8
Add 2 parts of diethylene glycol and raise the temperature to 70°C.
6.2 parts and 135.8 parts of 3.9-bis(1,1-bismethyl-2-hydroxyethyl)-2,4,8,10-tetraoxasbiro[J5]undecane were added to initiate a chain elongation reaction. 3,000 parts of methyl ethyl ketone was gradually added to the final viscosity of 20% QI.
Polyurethane-methyl ethyl ketone composition of U (comparison)
■) is 1!1. This polyurethane composition (comparison -■)
As shown in Table 1, the particle size of the insoluble particle component is also large.
The weight ratio of Kuzukitsutsu was also over 60%.

A water-containing slurry and a leather sheet (Comparative IV) were prepared in the same manner as in Example 1.

This leather-like sheet material has a low strength of the polyurethane microporous material that it constitutes, making it unsuitable for practical use, and as shown in Table 2, it does not have the impregnability that is the objective of the present invention.

Effects of the Invention As detailed above, the method of the present invention improves impregnation and speeds up molding speed compared to conventional methods, and improves coagulation properties, resulting in good natural leather properties. Microporous 1111'? I give creations.

Claims (1)

[Claims] 1) Isocyanate 1 obtained from a long-chain glycol with an average molecular weight of 500 to 5,000 and an organic diisocyanate
~ The group-terminated prepolymer has a boiling point of 120°C or less and 10
Organic solvent that dissolves 1 to 50 cj of water per 0 g (a)
In the case of a chain extension reaction in the organic solvent (a) with a chain extender (A) that produces polyurethane that is easily soluble in the organic solvent (a), when a chain extension reaction occurs in the organic solvent (a). A chain extension reaction is carried out using a mixed chain extension agent which produces polyurethane that is poorly soluble in the precipitate-containing solvent (a) and which consists of a chain extension agent (B) which has a slower chain extension reaction rate than the chain extension agent (A). , 1 of the amount of critical water added to the resulting polyurethane composition
0 to 95% by weight of water is added and mixed to form a water-containing slurry, a fibrous base fabric is impregnated and/or coated with the water-containing slurry, and then an organic solvent is mixed from the water-containing slurry.
A method for producing a microporous structure, which comprises selectively evaporating a > and then drying. 2> Part of the long-chain glycol with an average molecular weight of m500 to 5,000 is polyoxyethylene glycol, and the proportion thereof used is 1 to 15% of the total polyurethane weight ii). A method for manufacturing a porous structure. 3) The chain extender (A) is neopenpur glycol. N-methyldiethanolamine, diethylene glycol, triethylene glycol, and neogetanol (all of which are a kind of compound, and a chain extender (B
) is the general formula (in the formula, P1 to islands represent C1 to C3 alkyl groups, and R
5 to P8 do not represent 1 or -CH3. ) The method for producing a microporous structure according to claim 1 or 2, wherein the spiro ring-containing glycol is a spiro ring-containing glycol.