JP5913017B2 - Method for producing polyurethane continuous pore porous body, polyurethane continuous pore porous body, and swab - Google Patents

Description

  The present invention relates to a method for producing a continuous pore porous body mainly composed of polyurethane, and a polyurethane continuous pore porous body that can be produced by the production method. The present invention also relates to a swab (wiping material) using the polyurethane continuous pore porous body.

  The continuous pore porous body refers to a resin porous body including bubbles (pores) continuous in a three-dimensional direction. A continuous pore porous body made of polyurethane (hereinafter referred to as “polyurethane continuous pore porous body”) is lightweight and absorbs and stores liquid, passes through liquids and gases, absorbs sound, and selects solids. It has functions such as removing and absorbing impact. Therefore, they are used for ink rolls, penetrating marks, brush pens, filters, cosmetic sponges, and the like.

  An example of a method for producing a polyurethane continuous porous material is a chemical reaction method. The chemical reaction method is a method in which a gas is included in a resin and pores are generated simultaneously with a polyurethane formation reaction. As chemical reaction methods, a method using a low-boiling compound that vaporizes by reaction heat of polyurethane formation (physical method), a method using carbon dioxide generated by the reaction of isocyanate and water as a blowing agent (chemical method) And the like. However, in the chemical reaction method, it is difficult to obtain a porous body mainly composed of pores having a uniform pore diameter (hereinafter sometimes referred to as “cell diameter”) and an average diameter of 200 μm or less. It cannot be applied to the production of a continuous pore porous body (sponge) that efficiently sucks up the gas.

  An elution method can also be mentioned as a manufacturing method of a continuous pore porous body. The elution method is a method of forming pores by mixing powders and particles (porosity generating agent) that can be dissolved and removed with water or other solvents, and then elution to form pores. For example, Patent Document 1 discloses.

  As a special case of the elution method, a pore-forming agent is mixed into a kneaded product of a resin and water-compatible solvent, and then the resin is solidified with a poor solvent and the pore-generating agent is eluted to form pores. A method is also known (Patent Documents 2, 3, etc.). For example, in Patent Document 3, a mixture of polyurethane dissolved in a solvent such as dimethylformamide (DMF) and a water-soluble pore-generating agent is solidified in a coagulating liquid to obtain a desired shape, and then the pore-generating agent is eluted. A method for producing a continuous pore porous body (elastic body) is described. According to this method, it is possible to stably produce a large amount of a continuous pore porous body having excellent properties such as instantaneous water absorption at a low cost, and the produced continuous pore porous body Suitable for use as a roller or swab to absorb adhering water.

  However, in the elution method as described above, the eluted pore-forming agent remains in the waste water. Therefore, wastewater treatment is required, and the cost increases for this reason. Therefore, it has been desired to develop a method for producing a continuous porous body mainly composed of fine pores having an average diameter of about 1 to 20 μm without using a pore-generating agent.

  Moreover, in order to obtain a continuous pore porous body (cell structure) mainly composed of fine pores having an average of about 1 to 20 μm by an elution method, a fine pore-forming agent having an average particle size of about 1 to 20 μm is required. . However, there is a problem that the cost is high for obtaining such a fine pore-generating agent. For example, when sodium chloride having an average particle diameter of about 1 to 20 μm is obtained by precipitation from an aqueous solution, it is necessary to strictly control the temperature, concentration, seed juice, etc. before the precipitation, resulting in high costs. Further, when the fine pore-forming agent is obtained by pulverizing or classifying / sieving particles, a dedicated fine pulverizer / classifier is required, which increases the cost of equipment and processing (such as pulverization and classification).

Japanese Patent Laid-Open No. 52-32971 JP 58-189242 A JP 2006-152202 A

  The present invention is a continuous pore porous body mainly composed of a polyurethane soluble in a solvent, and is a porous body mainly composed of fine pores and excellent in liquid absorption without using a pore-generating agent. It is an object of the present invention to provide a method for producing a continuous polyurethane porous body that can be produced.

  Another object of the present invention is to provide a polyurethane continuous pore porous body which is mainly composed of a solvent-soluble polyurethane, has fine pores and is excellent in liquid absorption.

  Another object of the present invention is to provide a swab using the above-mentioned continuous pore porous body excellent in liquid absorption.

  As a result of investigation by the present inventor in order to solve the above problems, a resin mainly composed of polyurethane was dissolved in a mixed solvent containing water, an organic solvent in which polyurethane is soluble, and an organic solvent in which polyurethane is swollen. Then, by cooling and precipitating a resin molded body and removing the solvent from the molded body, the average diameter (average cell diameter) is mainly composed of fine pores of about 1 to 20 μm and excellent liquid absorbency. It was found that a continuous polyurethane porous body was obtained, and the present invention was completed. That is, the above-described problem is solved by the invention having the configuration described below.

The first aspect of the present invention is:
A step of dissolving a polyurethane-based resin in a mixed solvent containing water, an organic solvent A in which polyurethane is soluble, and an organic solvent B that swells the polyurethane to obtain a polyurethane solution, cooling the polyurethane solution A method for producing a porous polyurethane porous body characterized in that it comprises a step of depositing a polyurethane molded product in a mixed solvent and a step of removing the mixed solvent from the polyurethane molded product.

  A resin containing polyurethane as a main component (hereinafter sometimes simply referred to as “polyurethane”) consists essentially of polyurethane, but other components are copolymerized or mixed within a range not impairing the gist of the present invention. It means an optional resin. Preferably, the polyurethane component is 80% by mass or more. Moreover, since this resin needs to be dissolved in the mixed solvent, it is a polyurethane that is soluble in an organic solvent.

  Specifically, the organic solvent A in which polyurethane is soluble is obtained by immersing polyurethane particles having a diameter of 3 to 3.5 mm in the solvent at a temperature 10 ° C. lower than the boiling point of the solvent for 2 hours with stirring. It is defined as an organic solvent that does not leave a gel that does not pass through a 1 mm mesh. Examples of the organic solvent A include DMF.

  The organic solvent B that swells polyurethane refers to an organic solvent that does not dissolve polyurethane and has a degree of swelling defined below of 40 or more. The degree of swelling is {(mass after immersion−mass before immersion) / mass before immersion when measuring mass change after immersing polyurethane particles having a diameter of 3 to 3.5 mm in the solvent at 30 ° C. for 24 hours. } × 100, which means a value defined by

  In this production method, first, polyurethane is dissolved in a mixed solvent containing water, an organic solvent A in which the polyurethane is soluble, and an organic solvent B that swells the polyurethane. The polyurethane can be dissolved by mixing water, an organic solvent A, an organic solvent B and the like to prepare a mixed solvent, and then adding the polyurethane to the mixed solvent and heating. Stirring may be performed to promote dissolution.

  After the polyurethane is dissolved in the mixed solvent to obtain a polyurethane solution, the polyurethane solution is cooled. Upon cooling, polyurethane is precipitated and a polyurethane molded product is produced in the mixed solvent. Cooling is preferably done in the mold. A molded body having a desired shape can be easily obtained by cooling in the mold. The mixing ratio (solvent composition) of water, organic solvent A and organic solvent B, the temperature at which polyurethane is dissolved in the mixed solvent (heating temperature) and the cooling temperature are such that the polyurethane is dissolved in the mixed solvent, and the molded body is precipitated by cooling, And it selects from the range from which a polyurethane molding becomes a continuous pore porous body.

  By adjusting the mixing ratio, heating temperature, and cooling temperature to appropriate ranges, the polyurethane molded body produced in the mixed solvent is a porous body having a microporous structure having three-dimensional continuous pores and a uniform film thickness. It can be. Here, the porous body of fine pores having a uniform film thickness means an average cell thickness of 1 to 10 μm, preferably 1.5 to 7 μm, an average cell diameter of 20 μm or less, and an observed cell. A porous body having a film thickness of 70% or more in the range of 0.5 to 2.0 times the average film thickness. The cell is observed by SEM photographs as described later.

  However, this molded body contains the mixed solvent, and the molded body may be re-dissolved due to an increase in temperature. Therefore, a step of removing the mixed solvent from the polyurethane molded body is performed. By removing the mixed solvent from the polyurethane molded body, a polyurethane continuous pore porous body composed of uniform and fine three-dimensional continuous pores can be obtained.

  According to the method of the present invention, the mixing ratio of water, the organic solvent A and the organic solvent B, the temperature at which the polyurethane is dissolved in the mixed solvent (heating temperature), and the cooling temperature are adjusted from appropriate ranges without using the pore-generating agent. Just by selecting, a microporous polyurethane porous body having a uniform film thickness, that is, an average film thickness in the range of 1 to 10 μm, an average cell diameter of 20 μm or less, and 70% or more of the observed cell film A porous body having a film thickness of 0.5 to 2.0 times the average film thickness can be produced. In addition, according to this method, it is possible to produce a polyurethane continuous pore porous body excellent in liquid absorption speed (short in ethanol penetration time described later).

  Since the method of this invention does not use a pore-generating agent, the cost required for the treatment of waste water containing the pore-generating agent is unnecessary. In addition, according to the method of the present invention, the costly work for obtaining a fine pore-generating agent is unnecessary, and thus the manufacturing cost can be reduced also in this respect.

  The present invention also relates to the first aspect of the invention, wherein the step of removing the mixed solvent from the polyurethane molded body is a non-solvent of polyurethane, wherein the mixed body is precipitated in the mixed solvent. A process for producing a polyurethane continuous porous material, characterized by being a step of immersing in a liquid dissolving the solvent (hereinafter sometimes referred to as “non-solvent”), substituting the solvent and then drying. )I will provide a.

  In this method, after the polyurethane molded body is precipitated in a mixed solvent, solvent replacement between the mixed solvent and the non-solvent is performed. Specifically, the polyurethane molded body containing the mixed solvent is immersed in a non-solvent, and the mixed solvent contained in the polyurethane molded body is solvent-substituted with the non-solvent. After solvent replacement, the non-solvent and the polyurethane molded body are separated, and then dried to remove the non-solvent from the polyurethane molded body, thereby obtaining a polyurethane continuous porous body composed of uniform and fine three-dimensional continuous pores. be able to. Drying can be performed under reduced pressure. In order to increase the drying speed, it is preferable to carry out under reduced pressure.

  In order to perform the solvent replacement more completely, immersion in a non-solvent and separation of the non-solvent and the polyurethane molded product may be repeated before drying. Further, the type of non-solvent may be changed for each repetition. For example, a non-solvent with a low boiling point may be used for the last iteration to facilitate drying.

  The present invention also provides a process for producing a porous polyurethane porous body according to the first aspect of the invention, wherein the organic solvent A is DMF (Claim 3). Examples of the organic solvent A include DMF, tetrahydrofuran, 1,4 dioxane, dimethyl sulfoxide, N-methylpyrrolidone and the like. Preferably, a solvent selected from these may be used alone or in combination of two or more. it can. Among these, DMF is most commonly used as a solvent for polyurethane, and is preferable because it is relatively inexpensive.

  The present invention also provides a method for producing a continuous polyurethane porous body according to claim 3, that is, the case where the organic solvent A is DMF, and the total mass of water, the organic solvent A, and the organic solvent B. On the other hand, the organic solvent A is 22 to 54% by mass, the organic solvent B is 38 to 69% by mass, and the water is 3 to 12% by mass. I will provide a.

  When the organic solvent A is DMF, the mixing ratio of water, the organic solvent A, and the organic solvent B is usually the organic solvent A when the sum of the three solvents (water + organic solvent A + organic solvent B) is 100% by mass. Is preferably 22 to 54% by mass, more preferably 22 to 47% by mass, the organic solvent B is preferably 38 to 69% by mass, more preferably 44 to 69% by mass, and water is 3 to 12% by mass. % Is preferable, and more preferably 5 to 12% by mass.

  The present invention also provides the method for producing a porous polyurethane porous body according to the first aspect of the invention, wherein the swelling degree of the organic solvent B is 60 or more (Claim 5). To do. As the organic solvent B, those having a swelling degree of 60 or more are more preferable.

  The second aspect of the present invention is a continuous porous body made of a resin mainly composed of polyurethane, having an average film thickness in the range of 1 to 10 μm, an average cell diameter of 20 μm or less, and observed. Polyurethane continuous pore porous body characterized in that the film thickness of 70% or more in the cell is in the range of 0.5 to 2.0 times the average film thickness and the ethanol permeation time is within 10 seconds. (Claim 6). The resin mainly composed of polyurethane constituting the porous body is the same as the resin mainly composed of polyurethane used in the invention of the first aspect.

  Generally, a porous body is divided into a porous body having closed cells in which each bubble (cell) is isolated from other bubbles independently, and a porous body having open cells in which each cell is continuous. Although classified, the porous body of the present invention is a porous body having open cells. More specifically, the cells are evenly continuous in the three-dimensional direction, and the surface of the cell, that is, the boundary with the adjacent cell has a structure composed of a resin film and an opening to the adjacent cell. .

  Further, the porous body of the present invention has an average film thickness in the range of 1 to 10 μm, an average cell diameter of 20 μm or less, and a film thickness of 70% or more in the observed cell is 0. It is in the range of 5 times to 2.0 times.

Here, the film thickness, the average film thickness, and the average cell diameter are values obtained from the SEM photograph of the porous body. Specifically, it is measured as follows.
• Cut the sample.
-Take a SEM picture of the cut surface. The brightest part in the SEM photograph of the cut surface is the cut surface of the resin constituting the porous body, and shows the outline of each cell (periphery of the pores). In the continuous pore porous body of the present invention, the outline of each cell is clear.
In the SEM photograph, the part where the cut surface (lightest part) of the resin is continuous is the part of the pore film, and the part where the cut surface is intermittent is the opening part between the pores. The thickness of the cut surface of this resin can be measured on a photograph, and the film thickness can be calculated from this measured value and the SEM magnification. Further, the size of the figure formed by the cut surface of the resin is measured on a photograph, and the cell diameter can be calculated from the measured value and the SEM magnification.

The film thickness is a value calculated from the measured value and the SEM magnification by drawing a diagonal line on the SEM photograph of the cut surface and measuring the length of each cut surface of the resin on the diagonal line on the photograph. “Average cell diameter” and “average film thickness” are the length L of the diagonal line, and the total length T of the cut surface of the resin on the diagonal line (T and L are calculated from the measured values on the photograph and the magnification of the SEM. The value calculated from the following equation from the number n of the cut surfaces of the resin on the diagonal and the number c of the cells on the diagonal.
Average film thickness = T / n
Average cell diameter = (LT) / c
In some cases, only a part of the cut surface or cell may exist at both ends of the diagonal line. To reduce the influence, it is possible to take SEM photographs so that the length of the diagonal line is 150 μm or more. preferable.

  The polyurethane continuous pore porous body of the present invention is further characterized in that the ethanol permeation time is within 10 seconds. The ethanol permeation time is the time required for ethanol to permeate the continuous porous porous body to a thickness of 3 mm. Specifically, the polyurethane continuous pore porous body is cut into a strip shape, and this is vertically placed and immersed from the lower end to a position of 2 mm in ethanol, and the time until the ethanol rises by 3 mm is defined as the ethanol penetration time. say.

  The ethanol permeation time is a standard indicating the liquid absorbency of the continuous porous porous body. That is, the shorter the ethanol permeation time, the better the properties of absorbing droplets instantaneously and the liquid absorption. The ethanol permeation time within 10 seconds means that a droplet of ethanol or the like can be instantly absorbed and the thickness of 3 mm can be moved within 10 seconds.

  In addition, the short ethanol permeation time indicates that the pores are open cells (communication) and the ratio of the openings is large. When the pores are not open cells, ethanol does not penetrate into the porous body, so that the ethanol penetration time becomes very long. Even in the case of open cells, if the ratio of the openings is small, ethanol does not easily penetrate into the porous body, so that the ethanol penetration time becomes long.

  The polyurethane continuous pore porous body of the present invention is a porous body having open pores (communication) and a large ratio of openings. As a result, it becomes a porous body excellent in the property of instantly sucking droplets made of alcohol or the like and the liquid absorbing property, and the ethanol permeation time is within 10 seconds.

  By incorporating a surfactant having a high HLB value into the polyurethane continuous pore porous body of the present invention, it is possible to impart high water absorption that instantaneously absorbs water, for example, water adhering to the substrate. In particular, when a surfactant having an HLB value of 8.0 or more is contained, the water absorption is excellent.

  This polyurethane continuous pore porous body can be produced by the invention of the first aspect, that is, the polyurethane continuous pore porous body production method of the present invention. According to the first aspect of the invention, a polyurethane continuous pore porous body composed of uniform and fine three-dimensional continuous pores can be obtained. As a result of the inventor's investigation, the average cell diameter and the average film thickness within the above ranges are obtained. It has been found that a novel polyurethane continuous pore porous body having an ethanol infiltration time can be obtained by the invention of the first aspect.

The present invention also provides a polyurethane continuous pore porous body (invention 7) according to the invention of the second aspect, wherein the apparent density is 0.20 to 0.50 g / cm ^3. provide.

The apparent density is a value measured according to JIS K 7222. The apparent density of the polyurethane continuous pore porous body of the present invention is preferably 0.20 to 0.50 g / cm ³ . Those having an apparent density of less than 0.2 g / cm ³ are difficult to produce. For example, in Example 4 in Table 3 to be described later, when Rezamin P880, which is a polyurethane manufactured by Dainichi Seika Co., Ltd., is reduced to 0.45 g, the apparent density can be reduced to 0.22 g / cm ^3. When reduced to .3 g, the apparent density increases to 0.57 g / cm ³ due to shrinkage during precipitation. Furthermore, it becomes difficult to obtain a stable shape due to shrinkage. In addition, a porous body having an apparent density of less than 0.2 g / cm ³ is inferior in shape retention and has a low utility value.

On the other hand, if the apparent density exceeds 0.50 g / cm ³ , the cells tend to be dispersed independently as seen in Comparative Examples 1 and 2, and the ethanol permeation time greatly exceeds 10 seconds.

  The present invention also provides a polyurethane continuous pore porous body (invention 8) according to the invention of the second aspect, wherein the thickness is 3 mm or more.

  Generally, a porous porous body is lightweight and has excellent functions such as absorbing liquid, storing liquid, passing liquid / gas, absorbing sound, sorting and removing solids, and absorbing impact. Therefore, it is used for ink rolls, penetrating marks, brush pens, filters, cosmetic sponges and the like. These products have a three-dimensional structure, and the thickness of the porous body is required to be 3 mm or more. According to the method for producing a polyurethane continuous pore porous body of the first aspect, the polyurethane continuous pore porous body can be obtained as a molded body having a thickness of 3 mm or more instead of a membrane. For example, a molded body having a thickness of 3 mm or more can be easily obtained by performing the cooling step in a mold.

  A third aspect of the present invention is a swab (Claim 9) characterized by using the polyurethane continuous pore porous body according to the second aspect.

  The swab means a structure in which a tip portion made of a liquid-absorbing porous body is provided at the tip of a rod-shaped shaft, and can be used as, for example, an industrial cleaning material (wiping material). Examples of the material forming the rod-shaped shaft include metal, wood, paper, and resin. As the tip portion, for example, a liquid-absorbing porous material having a spherical shape and covering the tip of the shaft can be mentioned.

  Generally, cloth, cotton, paper, liquid absorbent resin porous body, etc. are used as the liquid absorbent porous body, but the polyurethane continuous pore porous body of the second aspect of the present invention is Since it is excellent in liquid absorbency, it is suitably used as the tip of a swab, particularly a swab as an industrial cleaning material (wiping material). The porous polyurethane porous body of the second aspect is also suitable for the tip of the swab because it has wear resistance, which is an excellent feature of polyurethane.

  According to the method for producing a polyurethane continuous pore porous body according to the first aspect of the present invention, a continuous material having a fine pore having a uniform film thickness and having excellent liquid absorption properties, which is mainly composed of a polyurethane soluble in a solvent. A porous porous body can be produced only by a combination of solvents without using a pore-generating agent. As a result, the manufacturing cost can be reduced, and the treatment of the drainage containing the pore generating agent is unnecessary.

  The polyurethane continuous pore porous body according to the second aspect of the present invention is a porous body mainly composed of polyurethane, and has a fine pore having a uniform film thickness and excellent liquid absorption. It is. Therefore, it can be suitably used for applications such as swabs that efficiently suck fine droplets such as alcohol droplets. Furthermore, if hydrophilicity is imparted to the porous body by a method such as containing a surfactant having a high HLB value, a polyurethane continuous pore porous body having excellent water absorption can be obtained, and water droplets can be efficiently formed. It can be suitably used for applications such as blotting.

  The swab of the third aspect of the present invention is excellent in the property of efficiently sucking fine droplets such as alcohol droplets. Further, if hydrophilicity is imparted to the porous body at the tip, it is possible to obtain a swab excellent in water absorption that efficiently absorbs fine water droplets, and is suitably used in the field of electronic industry and the like.

2 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 1. 2 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 2. 4 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 3. 3 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 4. 6 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 5. 4 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 6. 4 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 7. FIG. 4 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 8. 4 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 9. 2 is a SEM photograph of the polyurethane continuous porous material obtained in Example 10. 3 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 11. 3 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 12. 4 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 13. 4 is a SEM photograph of the polyurethane continuous pore porous material obtained in Example 14. 4 is a SEM photograph of the polyurethane porous body obtained in Comparative Example 1. 4 is a SEM photograph of the polyurethane porous body obtained in Comparative Example 2. 4 is a SEM photograph of the polyurethane porous body obtained in Comparative Example 6. 4 is a SEM photograph of the polyurethane porous body obtained in Comparative Example 8. 4 is a SEM photograph of the polyurethane porous body obtained in Comparative Example 11. 3 is a SEM photograph of the polyurethane porous body obtained in Comparative Example 12. 4 is a SEM photograph of the polyurethane porous body obtained in Comparative Example 13. 4 is a SEM photograph of the polyurethane porous body obtained in Comparative Example 14.

  Hereinafter, the present invention will be described based on the embodiments. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

  The polyurethane used in the invention of the first aspect comprises a polyol component comprising a high molecular weight polyol (sometimes called a long-chain polyol) and a chain extender (sometimes called a short-chain glycol or a curing agent) and a polyisocyanate. Obtained by polymerizing the compound.

  Examples of the high molecular weight polyol include polyether polyols such as polypropylene glycol, polytetramethylene glycol, and polymer polyol, polyester polyols such as adipate polyol and polycaprolactone polyol, polycarbonate polyol, and polyolefin polyol. The preferred molecular weight of the polymer polyol is about 500 to 10,000, more preferably about 500 to 3,000.

  Examples of the chain extender include ethylene glycol, 1,4 butanediol, 1,6 hexanediol, 1,5 pentanediol, 3-methyl-1,5 pentanediol, 1,3 propanediol and the like. .

  Examples of the polyisocyanate compound include methylene diphenyl diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylene xylylene diisocyanate and other aromatic isocyanates, isophorone diisocyanate, dicyclohexylmethane diisocyanate and other alicyclic isocyanates, and the like. Examples thereof include aliphatic isocyanates such as hexamethylene diisocyanate, dimer acid diisocyanate, and norbornene diisocyanate.

  Polymerization methods for producing polyurethane can be divided into a one-shot method and a prepolymer method. Furthermore, as a special case, there is a method of obtaining polyurethane from solution polymerization. The one-shot method is superior in mass production, but the prepolymer method is also used in the case where the structure is clarified and features are to be obtained. In either case, a continuous polymerization method and a batch method are possible.

  Examples of the organic solvent B for swelling the polyurethane include furfural, propylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, and furfuryl alcohol.

  As described above, the mixing ratio of water, organic solvent A and organic solvent B, the temperature at which polyurethane is dissolved in the mixed solvent (heating temperature), and the cooling temperature are those in which polyurethane dissolves in the mixed solvent and the molded body is precipitated by cooling. Selected from a range. This range also varies depending on the amount of polyurethane added to the mixed solvent.

  Moreover, the addition amount of the resin mainly composed of polyurethane is larger than 0.063 times (mass ratio) and less than 0.63 times (mass ratio) of the total mass of the mixed solvent (water + organic solvent A + organic solvent B). And more preferably 0.093 times (mass ratio) or more and less than 0.32 times (mass ratio). In the case of 0.063 times or less, the polyurethane molded body precipitated in the mixed solvent tends to be difficult to maintain its shape. On the other hand, when it is 0.63 times or more, the polyurethane molded product tends to be closed cells instead of open cells. Further, in order to prevent the liquid from being separated during cooling and producing a supernatant, the amount of polyurethane is preferably 0.093 times or more the sum of the three solvents.

  When a polyurethane solution is obtained by dissolving polyurethane in a mixed solvent, it is preferable to heat. The heating temperature is usually from 40 ° C. to 100 ° C., but preferably in the range from minus 10 ° C. to less than plus 20 ° C. from the boiling point of the lowest boiling solvent in the mixed solvent. When the heating temperature is lower than minus 10 ° C. from the boiling point of the solvent having the lowest boiling point in the mixed solvent, the time required for dissolving the polyurethane becomes longer. On the other hand, when the temperature is higher than 20 ° C., the low boiling point solvent is not preferable because it may boil during heating and keep the composition of the mixed solvent.

  The heating is performed until the polyurethane dissolves to become a uniform solution, and the specific heating time is not limited, but is usually 1 to 2 hours. Stirring may be used to promote dissolution.

  The cooling conditions for depositing the polyurethane molded body in the mixed solvent depend on the composition of the mixed solvent and the mass ratio of the resin to the mixed solvent. Usually, when water increases, it tends to precipitate, and the cooling temperature may be relatively high. Further, if the mass ratio of the resin is large, the resin tends to precipitate, and the cooling temperature may be relatively high.

  The cooling temperature is usually selected from the range of −80 ° C. to + 30 ° C., but −20 ° C. to + 30 ° C. is preferable as a practical temperature range. The cooling time is preferably 5 minutes or more. Moreover, within 24 hours is preferable from the viewpoint of productivity. The confirmation of the precipitation is performed by visually determining whether or not the white solid is formed. At this time, when the supernatant is produced by liquid separation, it is not suitable for the purpose of obtaining a three-dimensional structure because the desired shape and dimensional accuracy are not obtained, and therefore it is preferable to carry out under conditions that do not produce a supernatant. As described above, the amount of polyurethane is preferably 0.093 mass times or more of the sum of the three solvents (water + organic solvent A + organic solvent B) in order to prevent liquid separation and generation of a supernatant.

  When removing the mixed solvent from the polyurethane molded body by immersing it in a non-solvent (polyurethane non-solvent and liquid that dissolves the mixed solvent) and then drying the solvent, the non-solvent used is Can include water, lower monohydric alcohols such as methyl alcohol and ethyl alcohol.

  In the production method of the present invention, since the pore-generating agent is not used, the separated used solvent (drainage) does not contain the pore-generating agent. Therefore, it is easy to reuse the used solvent by distillation or the like.

[Measurement of swelling degree of solvent]
The swelling degree of various solvents described in Table 1 was measured for the following various polyurethanes by the following procedures 1) to 3).
1) A polyurethane particle having a diameter of 3 to 3.5 mm constituting a polyurethane continuous pore porous body is prepared, and its weight is measured to the last two digits. The measured value is the mass before immersion.
2) The particles are immersed in a solvent at 30 ° C. for 24 hours. After immersion for 24 hours, the particles are taken out from the solvent, the solvent adhering to the particle surface is removed, and the weight is measured to the last two digits. The measured value is the mass after immersion.
3) {(mass after immersion−mass before immersion) / mass before immersion} × 100 is calculated, and the calculated value is defined as the degree of swelling of the solvent for the polyurethane. This method is a method that conforms to the JIS ^{K 7114 -1995.}

(Various polyurethanes)
Polyurethanes manufactured by Dainichi Seika Kogyo Co., Ltd. were used for each of the following.
Rezamin P880 (polyurethane whose polyol component is polycarbonate polyol: In Table 1, it is represented as “P880 (polycarbonate)”.)
Rezamin P2275 (polyurethane whose polyol component is a polyether-based polyol: in Table 1, represented as “P2275 (polyether)”)
Rezamin P1275 (polyurethane whose polyol component is an adipate-based polyol: in Table 1, it is represented as “P1275 (adipate)”)
Rezamin P4038 (polyurethane whose polyol component is polycaprolactone polyol: In Table 1, it is represented as “P4038 (caprolactone)”.)

  As is apparent from Table 1, acetone and furfuryl alcohol have a swelling degree of 40 or more with respect to any polyurethane and can be used as the organic solvent B. On the other hand, water and propylene glycol have a swelling degree of 0 for any polyurethane and do not become the organic solvent B. Propylene glycol-α-monomethyl ether (PME) is not suitable as organic solvent B because the type of polyurethane is polyurethane when the polyol component is polycarbonate polyol, and the degree of swelling is 38. In the case of other types of polyurethane, it can be used as the organic solvent B.

  Next, the evaluation method of the polyurethane continuous pore porous body obtained in each Example and Comparative Example is shown.

[Film thickness, average film thickness, average cell diameter]
The value obtained by the above method. That is, an SEM photograph of the cut surface of the sample is taken, a diagonal line is drawn on the SEM photograph, the length of each cut surface of the resin on the diagonal line is measured on the photograph, and the film thickness is calculated from the measured value and the SEM magnification. Was calculated. Also, the length L of the diagonal line, the total length T of the cut surface of the resin on the diagonal line (T and L are values calculated from the measured values on the photograph and the SEM magnification), and the cutting of the resin on the diagonal line From the number n of faces and the number c of cells on the diagonal, the average film thickness and the average cell diameter were calculated by the following equations. Note that the SEM photograph is an 800 × photograph taken using a scanning electron microscope JSM-5500LV manufactured by JEOL.
Average film thickness = T / n
Average cell diameter = (LT) / c

[Apparent density]
It measured based on JISK7222.

[Measurement of ethanol penetration time]
The ethanol penetration time was measured by the method shown below.
The obtained porous body is cut into strips (dimensions: 2 mm × 2 mm × length 10 mm). This is set up vertically and immersed in ethanol at 25 ° C. from the lower end to a position of 2 mm, and the time until ethanol rises by 3 mm is measured with a stopwatch. For easy recognition, colored ethanol prepared as follows is used as ethanol.

(Adjustment of colored ethanol)
To 5 g of ethyl alcohol (specific alcohol: traceable 99 first grade: manufactured by Nippon Alcohol Sales Co., Ltd.), 2 drops of quick-drying killer whale red oil (manufactured by killer whale hat) were dropped and stirred well.

  The “mixing state” and “precipitation state” in “Observation” in the table indicate the mixing state in the dissolution step and the precipitation state of the molded body in the cooling step, respectively. , ○, Δ or ×.

1 Mixing state in the dissolution process (“Mixed state” in the table)
○: All the polyurethane is dissolved and uniformly mixed.
X: All of the polyurethane is not dissolved, and undissolved residue is observed.
2 Precipitation state of the compact in the cooling process ("Precipitation state" in the table)
○: A white solid (molded body) precipitates upon cooling and does not dissolve even at room temperature.
(Triangle | delta): White solid (molded object) precipitates by cooling, but a visible amount of solvent isolate | separates (a supernatant liquid arises).
X: A white solid (molded body) precipitates upon cooling, but returns to a transparent liquid at room temperature.

  According to Examples 1 to 3 and Comparative Examples 1 to 4 shown below, the amount of water added for causing the polyurethane to precipitate a molded body by dissolution and cooling (thermal phase separation) was examined.

Example 1
Polycarbonate-based polyurethane (polyurethane whose high-molecular-weight polyol component is a polycarbonate-based polyol. The following is also expressed in the same way. Dainippon Seika Kogyo Co., Ltd .: Resamine P-880) No.2: Inner diameter 16 mm, height 40 mm), add a mixed solvent consisting of 1.4 g of dimethylformamide, 2.0 g of acetone, and 0.2 g of water, and heat to 65 ° C. using a stir bar and a magnetic stirrer. While stirring, a polyurethane solution was obtained after 1 hour. When the stirrer was removed and the mixture was cooled at −20 ° C. for 24 hours, a compact was precipitated. The molded body was taken out, immersed in 10 g of ethanol, and ethanol was changed twice every 3 hours. Then, after being immersed in ethanol for 18 hours, the molded body was taken out from ethanol. The molded body was dried at 25 ° C. under reduced pressure for 24 hours to obtain a polyurethane porous body (dimensions: a substantially cylindrical shape having a diameter of 12 mm and a thickness of 12 mm). An SEM photograph of the obtained porous body is shown in FIG. In addition, the average cell diameter, average film thickness, and ratio of the film (resin cut surface) within the range of 0.5 to 2.0 times the average film thickness (%, In the table, it is simply referred to as “film thickness ratio.” The same applies to the following examples, comparative examples, and the tables after Table 3), the apparent density, and the ethanol penetration time. The results are shown in Table 2.

Example 2 and Example 3
A mixed solvent consisting of 1.4 g of dimethylformamide, 2.0 g of acetone and 0.3 g of water (Example 2), or a mixed solvent consisting of 1.4 g of dimethylformamide, 2.0 g of acetone and 0.4 g of water (implemented) A porous body was obtained in the same manner as in Example 1 except that Example 3) was used. SEM photographs of the obtained porous body are shown in FIGS. 2 and 3, respectively. Table 2 shows the measurement results of average cell diameter, average film thickness, film thickness ratio, apparent density, and ethanol penetration time.

Comparative Example 1 and Comparative Example 2
The mixed solvent is replaced with a mixed solvent consisting of 1.4 g of dimethylformamide and 2.0 g of acetone (Comparative Example 1), or a mixed solvent consisting of 1.4 g of dimethylformamide, 2.0 g of acetone and 0.1 g of water (Comparative Example 2). Except for the above, porous bodies were obtained in the same manner as in Example 1. The SEM photograph of the obtained porous body is shown in FIGS. Table 2 shows the measurement results of the apparent density and the ethanol penetration time. In Comparative Examples 1 and 2, in the SEM photograph, huge independent pores are scattered as compared with Example 1, and the ethanol permeation time is also increased by one digit.

Comparative Example 3 and Comparative Example 4
A mixed solvent consisting of 1.4 g of dimethylformamide, 2.0 g of acetone and 0.5 g of water (Comparative Example 3), or a mixed solvent consisting of 1.4 g of dimethylformamide, 2.0 g of acetone and 0.6 g of water (Comparison) Except for substituting Example 4), each was carried out in the same manner as in Example 1. However, in any case, the desired porous material could not be obtained because the polyurethane remained undissolved in the solvent.

  The addition amount range of acetone for thermal phase separation was examined by Example 3 (existing) and Example 4 and Comparative Examples 5 and 6 shown below.

Example 4
A porous material was obtained in the same manner as in Example 1 except that the mixed solvent was replaced with a mixed solvent composed of 1.4 g of dimethylformamide, 3.0 g of acetone and 0.4 g of water. An SEM photograph of the obtained porous body is shown in FIG. Table 3 shows the measurement results of average cell diameter, average film thickness, film thickness ratio, apparent density, and ethanol penetration time.

Comparative Example 5
The same procedure as in Example 1 was carried out except that the mixed solvent was changed to a mixed solvent consisting of 1.4 g of dimethylformamide and 0.4 g of water. However, the desired porous material was obtained because the polyurethane remained poorly dissolved in the solvent. I couldn't.

Comparative Example 6
The same procedure as in Example 1 was carried out except that the mixed solvent was changed to a mixed solvent consisting of 1.4 g of dimethylformamide, 4.0 g of acetone and 0.4 g of water. A homogeneous solution was obtained upon heating and solidified by cooling at -20 ° C., but changed to a transparent liquid when ethanol substitution was performed at room temperature. Although the porous body was obtained, it became huge independent pores as seen in the SEM photograph of FIG. 17, and as shown in Table 3, the ethanol permeation time was 18 seconds. Also, the apparent density was clearly larger than that of the example.

  The amount of DMF added for thermal phase separation was examined in Example 3 (explained above) and Examples 5, 6, 6, and 8 shown below.

Example 5
A porous material was obtained in the same manner as in Example 1 except that the mixed solvent was changed to a mixed solvent composed of 1.0 g of dimethylformamide, 2.0 g of acetone and 0.4 g of water. In this case, the solvent was slightly separated as a result of cooling and solidification. An SEM photograph of the obtained porous body is shown in FIG. Table 4 shows the measurement results of average cell diameter, average film thickness, film thickness ratio, apparent density, and ethanol penetration time.

Example 6
A porous material was obtained in the same manner as in Example 1 except that the mixed solvent was changed to a mixed solvent composed of 2.1 g of dimethylformamide, 2.0 g of acetone and 0.4 g of water. An SEM photograph of the obtained porous body is shown in FIG. Table 4 shows the measurement results of average cell diameter, average film thickness, film thickness ratio, apparent density, and ethanol penetration time.

Comparative Example 7
The same procedure as in Example 1 was performed except that the mixed solvent was changed to a mixed solvent consisting of 2.0 g of acetone and 0.4 g of water, but the desired porous body was obtained because the polyurethane remained poorly dissolved in the solvent. There wasn't.

Comparative Example 8
The same procedure as in Example 1 was conducted except that the mixed solvent was changed to a mixed solvent consisting of 2.8 g of dimethylformamide, 2.0 g of acetone and 0.4 g of water. A homogeneous solution was obtained upon heating and solidified by cooling at -20 ° C., but changed to a transparent liquid when ethanol substitution was performed at room temperature. Although a porous body was obtained, it became huge independent pores as seen in the SEM photograph of FIG. 18, and as shown in Table 4, the ethanol permeation time was 21 seconds. Also, the apparent density was clearly larger than that of the example.

  From the results of Tables 2 to 4, when the polyurethane is a polycarbonate-based polyurethane and the organic solvent A is DMF, the composition of each solvent in the mixed solvent is DMF: 24-54 mass%, acetone (organic solvent B) : 38 to 69% by mass, water: 3 to 12% by mass, a microporous polyurethane porous body having a uniform film thickness, that is, an average film thickness in the range of 1 to 10 μm, and an average cell diameter Is 20 μm or less, and the film thickness of 70% or more of the observed cell membrane is in the range of 0.5 to 2.0 times the average membrane thickness, and the ethanol permeation time is within 10 seconds (ie, It is shown that a continuous polyurethane porous body having excellent liquid absorbability can be produced. Actually, in Examples 1 to 6, the average cell diameter is 7 μm or less, and the ethanol permeation time is 3 seconds or less.

  The range of the solvent swelling degree for thermal phase separation was examined by Example 3 (existing) and Examples 7 to 10, Comparative Example 9, and Comparative Example 10 shown below.

Example 7, Example 8, Example 9, Example 10
A combination of 0.6 g of polycarbonate-based polyurethane (Rezamin P880 manufactured by Dainichi Seika Kogyo Co., Ltd.) and 2.0 g of acetone in Example 3,
0.6 g of adipate-based polyurethane (P1275 manufactured by Dainichi Kogyo Co., Ltd.), 2.0 g of propylene glycol-α-monomethyl ether (PME) (Example 7),
Caprolactone-based polyurethane (P4038 manufactured by Dainichi Seika Kogyo Co., Ltd.), PME 2.0 g (Example 8),
Ether type polyurethane (P2275 manufactured by Dainichi Seika Kogyo Co., Ltd.) 0.6 g, PME 2.0 g (Example 9) or polycarbonate polyurethane (P880 manufactured by Dainichi Seika Kogyo Co., Ltd.) 0.6 g, Furfuryl alcohol 2.0 (Example) 10)
A porous body was obtained in the same manner as in Example 3 except that each of the combinations was replaced. SEM photographs of the obtained porous body are shown in FIGS. 7, 8, 9 and 10, respectively. Table 5 shows the measurement results of average cell diameter, average film thickness, film thickness ratio, apparent density, and ethanol penetration time.

Comparative Example 9 and Comparative Example 10
Instead of 2.0 g of acetone in Example 3, 2.0 g of propylene glycol (PG) (Comparative Example 9) or 2.0 g of PME (Comparative Example 10) was used, respectively. An attempt was made to obtain a porous material, but the desired porous material could not be obtained because polyurethane was poorly dissolved in the solvent and remained undissolved.

  As shown in Table 5, from the experimental results of Example 3, Examples 7 to 10, Comparative Example 9, and Comparative Example 10, in order to perform thermal phase separation, the range of solvent swelling degree should be 40 or more. It was necessary, and it was confirmed that it is preferably 60 or more. If the range of the degree of solvent swelling is 40 or more, even if the polyurethane is an adipate polyurethane, caprolactone polyurethane, or ether polyurethane, the effect of the present invention is achieved as in the case of polycarbonate polyurethane. It has been shown.

  Experiments were conducted to confirm the range of the amount of polyurethane added for thermal phase separation in Example 3 (explained above) and Examples 11, 12 and Comparative Examples 11-14 shown below.

Example 11 and Example 12
Except that the amount of polycarbonate polyurethane (manufactured by Dainichi Seika Kogyo Co., Ltd., Rezamin P-880) was changed from 0.6 g to 0.45 g (Example 11) or 1.2 g (Example 12), each Example In the same manner as in Example 1, a porous material was obtained. In the case of Example 11, some solvent separation was observed during cooling and solidification. SEM photographs of the obtained porous body are shown in FIGS. 11 and 12, respectively. Table 6 shows the measurement results of the apparent density and the ethanol penetration time.

Comparative Example 11
A porous body was obtained in the same manner as in Example 1 except that the amount of the polycarbonate-based polyurethane (Rezamin P-880) was changed from 0.6 g to 0.3 g. In this case, the solvent was clearly separated as a result of cooling and solidification. An SEM photograph of the obtained porous body is shown in FIG. Table 6 shows the measurement results of the apparent density and the ethanol penetration time. The obtained porous body was a continuous pore porous body. As shown in Table 6, the diameter of the substantially cylindrical shape, in particular, the height was extremely low, and a large shrinkage was observed.

Comparative Example 12, Comparative Example 13, Comparative Example 14
Implementation was performed except that the amount of the polycarbonate-based polyurethane (Rezamine P-880) was changed from 0.6 g to 2.4 g (Comparative Example 12), 3.9 g (Comparative Example 13), or 4.5 g (Comparative Example 14). A porous material was obtained in the same manner as in Example 1. All of the obtained porous bodies were closed cells and did not penetrate ethanol. SEM photographs are shown in FIGS. 20, 21, and 22, respectively. Table 6 shows the measurement results of the apparent density and the ethanol penetration time.

  From Table 6, in Comparative Example 11 in which the amount of polyurethane (polycarbonate system: resamine P-880) is 0.063 times (mass ratio) or less of the amount of the mixed solvent (DMF + acetone + water), molding is performed during cooling and solidification. There is significant contraction of the body. On the other hand, in Comparative Examples 12 to 14 which is 0.63 times (mass ratio) or more, the porous body does not become a continuous pore porous body, but becomes a closed-cell porous body, and a solvent such as ethanol is used. It did not penetrate. From this result, it can be said that the amount of polyurethane is preferably larger than 0.063 times (mass ratio) and less than 0.63 times (mass ratio) of the amount of the mixed solvent (DMF + acetone + water).

  In the above, dimethylformamide was used as the organic solvent A, but in the following examples, the use of dioxane was examined.

Example 13 and Example 14
Polycarbonate-based polyurethane (Rezamine P-880) 0.12 g, dioxane 0.25 g, acetone 0.75 g and water 0.10 g were made into a homogeneous solution with heat in the same manner as in Example 1, cooled at -20 ° C. and phase separated. I was allowed to. The standing time at that time was changed to 1 hour, 3 hours, 5 hours, 7 hours, 10 hours, 18 hours, 3 days, and 7 days to obtain a porous body. A porous body could be produced from a cooling time of 1 hour.

In addition, SEM photographs of the porous bodies obtained by carrying out the non-solvent (solvent for solvent replacement) in two ways of ethanol (Example 13) or water (Example 14) with a cooling time of 7 hours are respectively shown in the figure. 13 and FIG. When the average film thickness, average cell diameter, apparent density, and ethanol penetration time were measured, Example 13 (ethanol extraction) was 3.65 μm, 15.9 μm, 0.30 g / cm ³ , and 4 seconds, respectively. 14 (water extraction) were 4.99 μm, 16.5 μm, 0.26 g / cm ³ , and 4 seconds, respectively.

  From this result, it is shown that even when dioxane is used as the organic solvent A, the effect of the present invention is achieved.

Example 15
A hot melt having the same composition as the polyurethane solution (hot melt) obtained in Example 3 was poured into a 9 mm inner diameter plastic rod kept at 60 ° C., and when the bubbles disappeared at −20 ° C. Cooled to. Thereafter, a rod-like molded product (rod-like sponge) having a diameter of 7 mm and a length of 30 mm was obtained in the same manner as in Example 1. This rod-like sponge was cut into a length of 15 mm, and the IPA (isopropyl alcohol) uptake time and spindle oil uptake time were measured by the following methods, and the surface scratching property was evaluated. The results are shown in Table 7.

[IPA wicking time]
Swab a 15 mm long stick-like sponge, and quickly dip the tip (surface cut to 15 mm length) into the liquid surface of isopropyl alcohol at a liquid temperature of 25 ± 5 ° C. until the isopropyl alcohol suction surface rises by 3 mm. Measure.
[Spindle oil suction time]
The tip of a 15 mm long rod-like sponge is quickly immersed in the surface of spindle oil (ISO VG10) with a liquid temperature of 25 ± 5 ° C., and the time until the spindle oil suction surface rises by 3 mm is measured.
[Surface damage]
The surface of the compact disk is wiped twice with a tip of a 15 mm long rod-like sponge at a load of 10 g / cm ² , and the wiping surface is observed with the naked eye and a scanning electron microscope.

Comparative Example 15
A rod-shaped molded product having a diameter of 8.3 mm and a length of 15 mm was obtained in the same manner as in Example 15 except that the hot melt was changed to a hot melt having the same composition as that of the hot melt obtained in Comparative Example 1. This was cut into a length of 7.5 mm, the IPA wicking time and the spindle oil wicking time (3 mm height) were measured by the above method (the same method as in Example 15), and the surface scratching property was evaluated. The results are shown in Table 7.

  As is clear from the “formulation” shown in Table 7, the continuous pore porous body constituting the tip of the swab obtained in Example 15 is a porous body obtained by the production method of the present invention, while comparing The continuous pore porous body constituting the tip of the swab obtained in Example 15 is not a porous body obtained by the production method of the present invention. As is apparent from the IPA wicking height and spindle oil wicking height shown in the column of “Physical Properties” in Table 7, the swab obtained in Example 15 has excellent liquid absorbency, but obtained in Comparative Example 15. The swab obtained was poor in liquid absorbency.

Test example 1
The swabs obtained in Example 15 and Comparative Example 15 were used to wipe the IPA droplets on the glass plate. In the swab obtained in Example 15, the IPA droplet was sucked into the continuous pore elastic body within 1 to 2 seconds, and the IPA droplet on the glass plate could be completely wiped off. In the swab, the IPA droplets on the glass plate could not be completely wiped off without being sucked into the continuous pore elastic body even after 5 seconds. This result also shows that the swab obtained in Example 15 has excellent liquid absorbency, but the swab obtained in Comparative Example 15 is inferior in liquid absorbency.

  Polyurethane continuous pore porous body of the present invention includes a water absorbing material such as a water absorbing roll and a water absorbing sheet, a cleaning material for cleaning a hard disk, a silicon wafer, a glass substrate, a filter membrane such as a liquid filter and an air filter, a metal, and a stone material. It is suitably used for applications such as polishing materials for glass, resin, etc. and high precision finishing work, car care products, ink rolls, penetrating marks as applicators, brush pens, cosmetic materials such as cosmetic sponges. Furthermore, it can also be suitably used as an alternative to cotton swabs and flocking brushes, chemical solution impregnation materials, wiping materials, microbial carriers for water treatment, and conductive sponges provided with conductive materials.

Claims (9)

  A step of dissolving a polyurethane-based resin in a mixed solvent containing water, an organic solvent A in which polyurethane is soluble, and an organic solvent B that swells the polyurethane to obtain a polyurethane solution, cooling the polyurethane solution A process for producing a polyurethane continuous pore porous body, comprising: a step of depositing a polyurethane molded body in a mixed solvent; and a step of removing the mixed solvent from the polyurethane molded body.   The step of removing the mixed solvent from the polyurethane molded product is a step of drying the molded product deposited in the mixed solvent by immersing the molded product in a liquid that dissolves the mixed solvent, which is a non-solvent of polyurethane, and then drying. The method for producing a porous polyurethane porous body according to claim 1, wherein:   The method for producing a porous polyurethane porous body according to claim 1 or 2, wherein the organic solvent A is dimethylformamide.   The organic solvent A is 22 to 54% by mass, the organic solvent B is 38 to 69% by mass, and the water is 3 to 12% by mass with respect to the total mass of water, the organic solvent A, and the organic solvent B. Item 4. A method for producing a porous polyurethane porous body according to Item 3.   The method for producing a porous polyurethane porous body according to any one of claims 1 to 4, wherein the degree of swelling of the organic solvent B is 60 or more. It is a continuous pore porous body made of a resin whose main component is polyurethane, and its cells are evenly continuous in the three-dimensional direction, and the boundary between adjacent cells extends to the resin film and the adjacent cells. has a structure composed of the opening of, and the average cell diameter is 20μm or less, an average film thickness of 1 to 10 [mu] m, 0 70% or more of the film thickness in the observed cell is the mean film thickness Polyurethane continuous pore porous material characterized in that it is in the range of 5 times to 2.0 times and ethanol permeation time is within 10 seconds.
The polyurethane continuous pore porous body according to claim 6, wherein the apparent density is 0.20 to 0.50 g / cm ³ .   The polyurethane continuous pore porous body according to claim 6 or 7, wherein the thickness is 3 mm or more.   A swab comprising the polyurethane continuous porous material according to any one of claims 6 to 8.