JPH0433286B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to polyurethane dispersions and emulsions, and relates to polyurethane dispersions and emulsions that can provide porous sheet materials with excellent mechanical properties, water vapor permeability, and other properties with high productivity. The purpose is to provide liquid. (Prior Art) Many porous sheet materials made of polyurethane as natural leather substitutes and methods for producing them have been known, and can be roughly divided into wet methods and dry methods. (Problem to be solved by the invention) Both methods have their advantages and disadvantages, and the dry method is superior in terms of productivity. Such a dry method is disclosed in Japanese Patent Publication No. 48-4380 and Japanese Patent Publication No. 48-4380.
Publication No. 8742, Japanese Patent Application Laid-Open No. 1983-41063, Japanese Patent Application Publication No. 1973
Methods described in JP-A-66961 and JP-A-54-68498 are known. These known methods each provide porous sheet materials with excellent performance, but in order to obtain products with excellent performance by these methods, it is necessary to control the organic solvent used in the polyurethane emulsion used. It is necessary to selectively evaporate water and moisture, very strict temperature control is required for gelation and drying methods, and it takes a relatively long time, for example, 30 minutes to 1 hour, so other processes Although continuous production is possible, there is a problem in that productivity is extremely low due to the gelation and drying steps. Another problem with known methods is that the polyurethane dispersion used for the polyurethane emulsion has poor stability and tends to gel, making it impossible or difficult to prepare the polyurethane emulsion. There is also. Therefore, in order to improve productivity, the above method increases the stability of the polyurethane dispersion and eliminates the need for strict temperature control during the gelling and drying steps of the polyurethane emulsion layer. Moreover, there is a strong need in the industry for a method that can complete the gelling and drying steps within 10 minutes or less, preferably within a few minutes. In response to the above-mentioned needs of the prior art, the present inventor has improved the stability of the polyurethane dispersion used in the conventional method, and selectively uses the organic solvent and water in the gelling and drying steps of the polyurethane emulsion layer. It eliminates the complication of evaporation and completes the entire gelation and drying process in less than 10 minutes.
Moreover, as a result of intensive research to find a method that can provide products of excellent quality, we have found that when using a polyurethane emulsion using a specific polyurethane dispersion as the polyurethane emulsion used in these methods, the above-mentioned The present invention was completed based on the finding that the drawbacks of the prior art can be solved and the above-mentioned demands of the industry can be fully met. That is, the present invention uses fine particles obtained from (A) a polyurethane resin with a molecular weight of 20,000 to 500,000 and (B) an active hydrogen-containing polyfunctional compound with a molecular weight of 50 or less per functional group and an organic polyisocyanate. This is a polyurethane emulsion characterized by emulsifying water in an organic solvent that has limited mutual solubility with water. Next, to explain the present invention in more detail, the present inventor has solved the problems of the prior art as mentioned above, namely, the stability problem of the polyurethane dispersion used and the low temperature and long-term gelling of the polyurethane emulsion layer. This method solves the problems of gelation and drying, performs gelation and drying at a relatively high temperature, that is, 100℃ or higher, preferably 110℃ to 200℃, in a short period of time, and produces a porous sheet material with a porous layer with good properties. As a result of intensive research, we have found that, as a polyurethane dispersion for forming a polyurethane emulsion, specific fine particles that do not dissolve in an organic solvent solution of a polyurethane resin having a molecular weight within a certain range,
In other words, when using a dispersion of fine particles obtained from an active hydrogen-containing polyfunctional compound with a molecular weight of 50 or less per functional group and an organic polyisocyanate, a polyurethane milk prepared from such a dispersion is used. Even after impregnating and/or applying the suspension to the substrate, it is gelled and dried at significantly higher temperatures than in the prior art. Despite these high temperatures,
It has been discovered that a porous sheet material with sufficient performance can be obtained in a short time without the porous layer being damaged or deformed by high temperatures. This surprising effect is due to the fact that the above-mentioned specific fine particles have many urea bonds and urethane bonds and have a high softening point, and therefore do not soften even at high gelling and drying temperatures. This is thought to be because the presence of many polar groups makes it possible to easily gel the coexisting polyurethane resin. The polyurethane resin itself used in the present invention is a conceptually known material, and is obtained by reacting a polyol, an organic polyisocyanate, and a chain extender. Examples of polyols include polyethylene adipate, polyethylene propylene adipate, polyethylene butylene adipate, polydiethylene adipate, polybutylene adipate, polyethylene succinate, polybutylene succinate, and polyethylene sebacate, each having a hydroxyl group at the end and a molecular weight of 300 to 4000. , polybutylene sebacate, polytetramethylene ether glycol, poly-ε-caprolactone diol, polyhexamethylene adipate, carbonate polyol, polypropylene glycol, and those containing appropriate polyoxyethylene chains in the above polyols. Examples of organic polyisocyanates include 4,4'-diphenylmethane diisocyanate (MDI), water-added MDI, isophorone diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 2,4-tolylene diisocyanate, There are 2,6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, etc., or these organic polyisocyanates and low molecular weight polyols or polyamines are combined to form terminal isocyanates. Of course, urethane prepolymers obtained by reacting with can also be used. Examples of chain extenders include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, ethylenediamine, 1,2-propylenediamine, trimethylenediamine, detramethylenediamine, Examples include hexamethylene diamine, decamethylene diamine, isophorone diamine, m-xylylene diamine, hydrazine, and water. Any polyurethane resin obtained from the above-mentioned materials can be used in the present invention, but preferred ones have a molecular weight of 20,000 to 500,000, and most preferred have a molecular weight of 20,000 to 250,000. be. The polyurethane resin having a molecular weight of 20,000 to 500,000 as described above can be easily obtained by conventionally known production methods and molecular weight adjustment methods. These polyurethane resins may be prepared without a solvent or in an organic bath, but in terms of the process, the organic solvent used to prepare the polyurethane emulsion, that is, water and Preparation in an organic solvent with a certain degree of mutual solubility is advantageous because it can be used as is for preparing a polyurethane emulsion. Preferred organic solvents include methyl ethyl ketone, methyl-n-propyl ketone,
Methyl isobutyl ketone, diethyl ketone, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, butyl acetate, etc. Also, acetone, cyclohexane, tetrahydrofuran,
Dioxane, methanol, ethanol, isopropyl alcohol, butanol, toluene, xylene, dimethylformamide, dimethyl sulfoxide, perchlorethylene, trichlorethylene,
Methyl cellosolve, butyl cellosolve, cellosolve acetate, etc. can also be used. Those that have limited mutual solubility with water in organic solvents or those that do not dissolve at all are used as a mixture with other organic solvents with limited mutual solubility with water. Of course, the above organic solvents can also be used as mixed organic solvents. A polyurethane resin solution can be obtained by preparing a polyurethane resin in such an organic solvent, and it is convenient to adjust the solid content to a range of about 5 to 60% by weight by adding or removing the same or other solvents. It is. The main feature of the present invention is that specific fine particles are used in combination with a polyurethane resin having a specific molecular weight as described above to produce a polyurethane dispersion with excellent stability. These fine particles are made of active hydrogen-containing polyfunctional compounds with a molecular weight of 50 or less per functional group, such as
An active hydrogen-containing polyfunctional compound that satisfies the above conditions from among the active hydrogen-containing polyfunctional compounds such as the chain extenders described above and the organic polyisocyanate described above are mixed at a temperature of 0 to 150°C for 2 to 30 minutes. Obtained by reacting for about 15 hours. Examples of active hydrogen-containing polyfunctional compounds other than the chain extenders mentioned above include monoethanolamine, diethanolamine, triethanolamine, diethylenetriamine, triethylenetetramine, tetramethylenetetramine, glycerin, trimethylolpropane, and pentaerythritol. Hydrogen-containing polyfunctional compounds are useful. Active hydrogen-containing polyfunctional compounds with a molecular weight of more than 50 per functional group may not be suitable for the purpose of the present invention because the solubility of the resulting fine particles in organic solvents may increase or the heat resistance of the fine particles may decrease. It becomes undesirable. The above-mentioned fine particles can be easily obtained by reacting the active hydrogen-containing polyfunctional compound and the organic polyisocyanate in an organic solvent in any ratio, preferably in a ratio close to equivalence of both. These fine particles are inert to common organic solvents, so they precipitate from the reaction solution as soon as they are formed.
Obtained as fine particles. Such a dispersion of fine particles in an organic solvent may be used as it is or after being separated from the solvent. The most preferred embodiment is a method in which an active hydrogen-containing polyfunctional compound and an organic polyisocyanate are reacted to form fine particles during dissolution of a polyurethane resin having a molecular weight of 20,000 to 250,000. The polyurethane dispersions thus obtained exhibit superior stability compared to those of the prior art. Of course, when fine particles are generated in a polyurethane resin solution in this way, the chains of the polyurethane resin are also extended to some extent, and the molecular weight increases to, for example, about 30,000 to 500,000, but there is no particular problem. Of course, in this case as well, the fine particles produced are insoluble in the organic solvent, so they are produced as a fine dispersion. What is important at this time is that the molecular weight of the polyurethane resin in the solution before the generation of fine particles is 20,000 to 500,000, preferably 20,000 to 500,000.
It must be in the range of 250,000 to 250,000. In other words, if the molecular weight is less than 20,000, the reaction rate between these polyurethane resins and the active hydrogen-containing polyfunctional compound and/or organic polyisocyanate becomes too high, and the selective production of fine particles becomes insufficient. This is not preferable because the reaction solution may gel, the resulting fine particles may become difficult to precipitate, and the heat resistance of the product may deteriorate. On the other hand, if the molecular weight of the polyurethane resin exceeds 500,000, the viscosity of the polyurethane resin solution becomes too high due to chain elongation that occurs to some extent, and uniform generation of fine particles may be inhibited. The above problems will not occur if the fine particles are prepared separately and mixed with the polyurethane resin solution.
Although such a method is also included in the present invention, it is preferable to generate fine particles in a polyurethane resin solution to form a polyurethane dispersion as described above, although this method is not necessarily advantageous in terms of process. The particle diameter of the fine particles is not particularly limited, but is generally preferably about 0.01 to 5 μm. The ratio of the above-mentioned polyurethane resin with a molecular weight of 20,000 to 500,000 and the above-mentioned fine particles is also important; if the ratio of fine particles used is too small, the main effect of the present invention will be reduced, i.e., It is difficult to impregnate the polyurethane emulsion and/or gel and dry the applied layer, and the formed porous layer collapses, making it impossible to form a sufficiently porous layer. On the other hand, if the amount of fine particles used is too large, gelation and drying at high temperatures will not be a problem, but a problem will arise in the physical strength of the formed porous layer, which is not preferable. Therefore, the preferred proportion of the fine particles used is 30 to 300 parts by weight per 100 parts by weight of the polyurethane resin, and within this range a porous layer with sufficient performance can be formed at high temperatures in a short period of time. The concentration of the above polyurethane dispersion is preferably about 5 to 60% by weight in terms of solid content. The polyurethane dispersion of the present invention as described above is easily gelled and has poor stability, and it is difficult or impossible to prepare a polyurethane emulsion using it. On the other hand, it has excellent stability and is easy to prepare the polyurethane emulsion described below. In order to prepare a polyurethane emulsion from the polyurethane dispersion of the present invention, an appropriate amount of a water-in-oil emulsifier is added to the polyurethane dispersion as necessary, and the mixture is stirred vigorously. This can be obtained by adding a saturated amount or less of water, for example, about 50 to 500 parts by weight of water per 100 parts by weight of solids in the solution. As the emulsifier, any conventionally known water-in-oil emulsifier can be used, but particularly preferred are:
It is a polyurethane surfactant that has an appropriate amount of polyoxyethylene chains in its molecule. The emulsifier is
It is preferably used in an amount of about 1 to 10 parts by weight per 100 parts by weight of the solid content of the polyurethane resin solution. The polyurethane emulsion thus obtained is a milky white cream-like fluid and remains stable even if left as is for several months. Such a polyurethane emulsion may optionally contain various additives such as coloring agents, crosslinking agents, stabilizers, fillers, etc., as required. Substrates used to produce porous sheets from the polyurethane emulsion as described above include, for example, various types of woven fabrics, knitted fabrics, nonwoven fabrics, release papers, plastic films, metal plates, glass plates, etc. It can also be made of wood. The polyurethane emulsion may be applied to the base material by any known method such as a coating method, a dipping method, or a combination of these methods, and the amount of impregnation and/or application is approximately 5 to 2000 g (compounded). liquid)/ ^m2 , which can be varied within a wide range depending on the purpose. When the above emulsion is used, the gelation and drying processes can be completed in a very short time and without the need for complicated treatments. Since drying is the rate-determining step in productivity, such short drying time is extremely advantageous compared to conventional methods. That is, the impregnated and/or coated substrate does not require any coagulation process as described in JP-A-51-41063, and is heated to temperatures above about 100°C, preferably
The desired porous sheet material can be obtained by simply drying at a temperature of 110°C to 200°C for about 1 to 10 minutes.
Such a short drying process is achieved because the fine particles used in the present invention have many urea bonds and urethane bonds, have strong cohesive force, and have a high softening point. As soon as the organic solvent begins to evaporate by heating after coating the emulsion, the polyurethane resin dissolved around the fine particles precipitates and gels. This is thought to be because the formed porous structure is stably maintained. (Action/Effect) The porous sheet material obtained using the polyurethane dispersion and emulsion of the present invention as described above has a very fine pore structure, has excellent various physical properties, and has excellent water vapor permeability. It is useful as a material for various synthetic leathers, clothing, shoes, waterproof cloth, tents, wallpaper, flooring materials, filtration materials, filters for air conditioners, etc. In addition, when the polyurethane dispersion and emulsion of the present invention are used in the production of porous sheets, the polyurethane dispersion has excellent stability and workability compared to the conventional technology, and at the same time, the polyurethane emulsion has excellent stability and workability. Because gelling and drying occur stably at very high temperatures and therefore a porous layer is formed in a very short time, the continuity of porous sheet materials is possible which is not possible with conventional gelling and drying temperatures. It became possible to manufacture Next, the present invention will be specifically explained with reference to Examples, Usage Examples, and Comparative Examples. Note that all numbers in the text and percentages are based on weight. Examples 1 to 5 (1) 1,4-butane ethylene adipate (average molecular weight approximately 1000, hydroxyl value 112) 1000 parts, 1,4-
31 parts of butanediol and 333 parts of diphenylmethane diisocyanate were added to 3,183 parts of methyl ethyl ketone and reacted at 70°C for 8 hours to obtain a polyurethane resin solution (A) with an average molecular weight of 65,000 and a solid content of 30%. . Next, 130 parts of ethylene glycol and 524 parts of diphenylmethane diisocyanate were added to the resin solution, and after reacting at 60°C for 10 hours,
Add 1,526 parts of methyl ethyl ketone, homogenize, and cool to room temperature while stirring. The polyurethane has an average molecular weight of 126,000, the precipitated particles have a particle size of 1 μm or less, and are milky white with a solid content of 30%. A polyurethane dispersion (1) was obtained. This dispersion was stable for more than 3 months at -10°C. (2) Add 1000 parts of polytetramethylene glycol (average molecular weight approximately 1000, hydroxyl value 112), 24 parts ethylene glycol, and 340 parts diphenylmethane diisocyanate to 3183 parts methyl ethyl ketone, and react at 70°C for 9 hours to determine the average molecular weight. 5
A polyurethane resin solution (B) having a solid content of 30% was obtained. Next, 116 parts of ethylene glycol and 465 parts of diphenylmethane diisocyanate were added to the above resin solution, and after reacting at 60°C for 10 hours,
Add 1,356 parts of methyl ethyl ketone, homogenize, and cool to room temperature while stirring to obtain a milky-white polyurethane with an average molecular weight of 103,000, a precipitated particle size of 1 μm or less, and a solid content of 30%. A polyurethane dispersion (2) was obtained. This dispersion was stable for more than 3 months at -10°C. (3) 2000 parts of 1,6-hexamethylene adipate (average molecular weight approximately 2000, hydroxyl value 56), 20 parts of 1,4-butanediol and 301 parts of diphenylmethane diisocyanate were added to 5416 parts of methyl ethyl ketone.
A polyurethane resin solution having an average molecular weight of 73,000 and a solid content of 30% was obtained by adding it to the solution and reacting at 70°C for 9 hours. Next, 390 parts of trimethylolpropane and 1091 parts of diphenylmethane diisocyanate were added to the above resin solution, and after reacting at 60°C for 10 hours,
Furthermore, 3456 parts of methyl ethyl ketone was added to homogenize the mixture, and the mixture was cooled to room temperature while stirring.
% of the milky white polyurethane dispersion (3) of the present invention was obtained. This dispersion was stable for more than 3 months at -10°C. (4) Add 160 parts of triethanolamine and 403 parts of diphenylmethane diisocyanate to 4547 parts of the polyurethane resin solution (A) of Example 1,
After reacting at ℃ for 8 hours, 1314 parts of methyl ethyl ketone was further added to homogenize the mixture, and the mixture was cooled to room temperature while stirring until the average molecular weight of the polyurethane was 14.
6,000, the diameter of the precipitated particles was 2 μm or less, and a milky white polyurethane dispersion (4) of the present invention with a solid content of 30% was obtained. This dispersion is -10℃
It remained stable for over 3 months. (5) Add 150 parts of glycerin and 611 parts of diphenylmethane diisocyanate to 4547 parts of the polyurethane resin solution (B) of Example 2, and after reacting at 50°C for 12 hours, further add 1776 parts of methyl ethyl ketone to homogenize, Cool to room temperature while stirring, and confirm that the average molecular weight of the polyurethane is 167,000, the particle size of the precipitated particles is 2 μm or less,
A milky white polyurethane dispersion (5) of the present invention with a solid content of 30% was obtained. This dispersion was stable for more than 3 months at -10°C. Examples 6 to 11 The products of Examples 1 to 5, an emulsifier, an organic solvent, and water were stirred in a homomixer to prepare the following polyurethane emulsions of the present invention. (6) Polyurethane emulsion (1) Polyurethane dispersion (1) 100 parts Urethane emulsifier 2 parts Methyl ethyl ketone 20 parts Xylene 20 parts Water 85 parts (7) Polyurethane emulsion (2) Polyurethane dispersion (2) 100 Parts Urethane emulsifier 2 parts Methyl ethyl ketone 20 parts Toluene 20 parts Water 80 parts (8) Polyurethane emulsion (3) Polyurethane dispersion (1) 100 parts Urethane emulsifier 2 parts Methyl ethyl ketone 150 parts Toluene 20 parts Water 80 parts (9) ) Polyurethane emulsion (4) Polyurethane dispersion (3) 100 parts PO/EO brick copolymer type emulsifier 4 parts Dioxane 10 parts Toluene 10 parts Water 70 parts Xylene 20 parts (10) Polyurethane emulsion (5) Polyurethane dispersion Body (4) 100 parts Urethane emulsifier 1 part Methyl isobutyl ketone 20 parts Toluene 20 parts Water 75 parts (11) Polyurethane emulsion (6) Polyurethane dispersion (5) 100 parts PO/EO block copolymer type emulsifier 1 part Tetrahydrofuran 20 parts Toluene 20 parts Water 60 parts Comparative Examples 1-2 Resin solutions (A) and (B) of Examples 1-2, emulsifier,
An organic solvent and water were stirred using a homomixer to prepare the following polyurethane emulsion. (1) Polyurethane emulsion (A) Polyurethane solution (A) 100 parts Urethane emulsifier 2 parts Methyl ethyl ketone 20 parts Toluene 20 parts Water 80 parts (2 ) Polyurethane emulsion (B) Polyurethane solution (B) 100 parts Urethane type Emulsifier 2 parts Methyl ethyl ketone 20 parts Toluene 20 parts Water 80 parts The properties of the above polyurethane emulsions (1) to (6), (A) and (B) are as shown in Table 1 below.

【table】

[Table] Usage Examples 1 to 7 The polyurethane emulsions (1) to (6) in Table 1 above were impregnated and/or applied to various substrates and dried to obtain various porous sheet materials. Comparative Use Examples 1-2 The polyurethane emulsions (A) and (B) shown in Table 1 above were impregnated and/or applied onto various substrates and dried to obtain various porous sheet materials.

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[Table] Use example 8 The drying temperature in use example 3 was 140℃ and 160℃, respectively.
Four types of porous sheet materials were obtained at temperatures of 180°C, 180°C, and 200°C, and micrographs of these materials were taken. As shown in Figures 1 to 8, the porous layers maintained sufficient porosity. Comparative use example 3 The drying temperature in comparative use example 2 was 140℃,
Four comparative examples of porous sheet materials were obtained at 160°C, 180°C, and 200°C, and micrographs of these were taken. As shown in Figures 9 to 16, the porous layer had almost lost its porosity. was. Comparative Example 3 Polytetramethylene glycol (average molecular weight approx.
1000, hydroxyl value 112) 1000 parts, ethylene glycol 24 parts and diphenylmethane diisocyanate
Add 289 parts to 3064 parts of methyl ethyl ketone and add 70
The reaction was carried out at ℃ for 9 hours to obtain a polyurethane resin solution having an average molecular weight of 6000 and a solid content of 30%. Next, add ethylene glycol to the resin solution.
116 parts and diphenylmethane diisocyanate
After adding 516 parts of polyurethane and reacting at 60°C for 10 hours, 1475 parts of methyl ethyl ketone was added to homogenize it, and the mixture was cooled to room temperature while stirring.The average molecular weight of the polyurethane was 123,000, and the particle size of the precipitated particles was
A milky white polyurethane dispersion (6) with a solid content of 30% and a diameter of 7 μm or less was obtained. This dispersion gelled after 8 days at -10%. Comparative Example 4 Polytetramethylene glycol (average molecular weight approx.
1000, hydroxyl value 112) 1000 parts, ethylene glycol 24 parts, diphenylmethane diisocyanate 346
1 part was added to 3197 parts of methyl ethyl ketone and reacted at 70°C for 9 hours to obtain a polyurethane resin solution with an average molecular weight of 312,000 and a solid content of 30%. Next, add ethylene glycol to the resin solution.
116 parts and diphenylmethane diisocyanate
After adding 459 parts of polyurethane and reacting at 60℃ for 10 hours, 1342 parts of methyl ethyl ketone was added to homogenize it, and the mixture was cooled to room temperature while stirring.The average molecular weight of the polyurethane was 597,000, and the particle size of the precipitated particles was
A milky-white polyurethane dispersion (7) with a solid content of 30% and a diameter of 1 μm or less was obtained, but this dispersion is similar to a pudding-like gel-like substance, and it is difficult to carry out subsequent emulsification, coating, or impregnation steps. was impossible. Comparative Example 5 (Example of JP-A-54-68498) 585 parts of polybutylene adipate (molecular weight 1709)
311 parts of polytetramethylene ether glycol (molecular weight 1493), 126 parts of 2,2-bis[4-(β-
Hydroxyethoxy)phenyl]propane, 670
A mixture of 1 part of diphenylmethane-4,4'-diisocyanate, 0.05 part of triethylenediamine (catalyst) and 411 parts of methyl ethyl ketone (solvent) was reacted at 50°C for 80 minutes in a reaction vessel equipped with a stirrer to form a mixture with an average molecular weight of 2000 or less. A polyurethane prepolymer was obtained. Then, 156 parts of 1,
4-Butanediol and 3.2 parts of trietheranediamine (catalyst) were added, and while 6789 parts of methyl ethyl ketone was gradually added dropwise, the reaction was carried out at 80°C for 4 hours. The polyurethane dispersion (8) thus obtained is
The concentration was 20%, and it contained polyurethane fine particles with a diameter of 10 μm or less. This dispersion is -10℃
It gelated after one day. Comparative Examples 6 to 9 The products of Comparative Examples 3 and 5, an emulsifier, an organic solvent, and water were stirred in a homomixer to prepare the following polyurethane emulsions. (6) Polyurethane emulsion (C) Polyurethane dispersion (6) 100 parts Emulsifier (urethane type) 2 parts Methyl ethyl ketone 20 parts Toluene 20 parts Water 80 parts (7) Polyurethane emulsion (D) Polyurethane dispersion (6) 100 parts Emulsifier (urethane type) 2 parts Methyl ethyl ketone 50 parts Toluene 20 parts Water 38 parts (8) Polyurethane emulsion (E) Polyurethane dispersion (8) 100 parts Emulsifier (urethane type) 1.3 parts Toluene 13 parts Water 53 parts ( 9) Polyurethane emulsion (F) Polyurethane dispersion (8) 100 parts Emulsifier (urethane type) 1.3 parts Toluene 13 parts Water 25 parts Examples 12 and 13 (12) Polyurethane emulsion (7) Polyurethane dispersion (1) ) 100 parts Emulsifier (urethane type) 2 parts Methyl ethyl ketone 20 parts Toluene 20 parts Water 80 parts (13) Polyurethane emulsion (8) Polyurethane dispersion (1) 100 parts Emulsifier (urethane type) 2 parts Methyl ethyl ketone 50 parts Toluene 20 parts Water 38 parts The properties of the above polyurethane emulsions (C) to (F), 7 and 8 are as shown in Table 4 below.

[Table] Usage Examples 9 to 12 Polyurethane emulsions 7 and 8 shown in Table 4 above were impregnated and/or applied onto various substrates and dried to obtain various porous sheet materials. Comparative Use Examples 4 to 11 The fourth polyurethane emulsions C to F were impregnated and/or applied onto various substrates and dried to obtain various porous sheet materials.

【table】

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[Table] As mentioned above, there is no difference due to drying conditions in Usage Examples 9 to 12, good porous sheets can be obtained in a short time by high temperature drying, and workability is also very good. Similar to the used example, it had an excellent pore structure as shown in the attached drawings. The stability of the dispersion of the present invention was also significantly better than that of the comparative example. On the other hand, in Comparative Use Examples 4 to 11, there were large differences depending on the drying conditions, and a good porous sheet could not be obtained at relatively high temperatures and for a short time, resulting in very poor work efficiency. Furthermore, the stability of the dispersion used was poor and long-term storage was impossible. As described above, according to the present invention, a porous sheet material with excellent physical properties can be formed at high gelling and drying temperatures.
It can be obtained in a very short time.

[Brief explanation of drawings]

Figures 1 to 8 show micrographs of the fiber shapes and particle structures of porous sheets according to usage examples of the present invention, and Figures 9 to 16 show the fiber shapes and particle structures of porous sheets of comparative usage examples. A micrograph is shown.

Claims (1)

[Claims] 1. (A) A polyurethane resin with a molecular weight of 20,000 to 500,000 and (B) A polyfunctional compound containing active hydrogen with a molecular weight of 50 or less per functional group and fine particles obtained from an organic polyisocyanate. A polyurethane emulsion characterized by emulsifying water in an organic solvent that has limited mutual solubility.