JP2001081227A - Polymeric compound porous body and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively obtain a porous body having a high porosity and fine and uniform interconnecting pores by kneading a water dispersion of fine particles of a polymeric compound with water-absorbing salts to give an almost homogeneous non-flowable kneaded product, cold extrusion molding this kneaded product, subjecting a resultant molded product to a heat treatment and eluting and removing the salts. SOLUTION: A water dispersion of fine particles of a polymeric compound is manufactured by emulsion polymerization or a method comprising emulsification of a polymeric compound obtained by a method other than the emulsion polymerization. As the polymeric compound, there can be cited, for example, polystyrenes, polyurethanes, polyvinyl acetates, polyethylenes, natural rubbers. As water-absorbing salts, there can be exemplified sulfates, carbonates, nitrates, organic acid salts, and the like, and desirably sodium sulfate in particular. Desirably, the average particle size of the salts is 2,000 μm or less. The amount of the salts added is adjusted so that the kneaded product is obtained as a non-flowable clay-like mixture. This method can give a porous body having an average pore size ranging from 100 μm or less to around 2,000 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous polymer compound, and more particularly, to a method for producing a porous polymer having fine continuous pores and excellent water absorption and liquid absorption properties. About the method.

[0002]

2. Description of the Related Art Generally, a porous body made of a high molecular compound such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, fluororesin, phenol resin, urea resin, and polyvinyl acetal is lightweight and has a desired mechanical strength. It is widely used for absorbent materials, buffer materials, heat insulating materials, filling materials, and materials for miscellaneous goods.
Properties, structures, and shapes suitable for the application are used. As a method for forming pores of the porous polymer compound, a method using a foaming agent and a method using a pore forming agent are known.

[0003] Methods using a foaming agent are classified into a foaming agent decomposition method, a solvent diffusion method, a gas mixing method, a chemical reaction method, and the like, depending on the difference in the means for producing bubbles.

[0004] The blowing agent decomposition method is a method in which a blowing agent of an organic compound or an inorganic compound is mixed with a resin and heated to the decomposition temperature of the blowing agent to release gas. Examples of this method include a method of foaming at room temperature, a method of filling a raw material in a mold, heating to decompose a foaming agent, and foaming by releasing pressure, and a method of forming a thermoplastic resin containing a foaming agent in a molten state under a high pressure. And a method of foaming using a foaming agent and pressure change.

[0005] The solvent diffusion method is a method in which a volatile solvent is added to a resin, heated after molding, and the solvent is diffused. As the solvent, pentane, hexane, freon, dichloromethane, trichloroethylene and the like are used. According to this method, a thermoplastic resin such as polystyrene or polyethylene is obtained, and a porous body of a thermosetting resin such as a phenol resin or an epoxy resin is obtained by adding a foaming agent at a monomer stage.

The gas mixing method is a method of mechanically mixing a gaseous foaming agent such as air, nitrogen, or carbon dioxide at normal temperature and normal pressure with a resin. According to this method, a porous body such as a urea resin or polyvinyl chloride is manufactured.

In the chemical reaction method, a plurality of chemically reacting components are mixed and a gas generated during the polymerization process of the resin is used. Most of the porous polyurethane material is produced by this method.

However, in the above-mentioned method using a foaming agent, only a porous body having relatively large pores can be obtained, and if the porosity is low, the porous body has discontinuous independent pores. Therefore, the method using a foaming agent is not suitable for producing a porous body having fine continuous pores.

On the other hand, the method using a pore-forming agent is a method in which a soluble substance is mixed in a resin in advance, filled in a mold and molded, and then the solvent is used to elute and remove the pore-forming agent ( For example, see JP-A-4-63845.

[0010] In this method, a semi-fluid obtained by adding a water-absorbing salt to a water-dispersed polyurethane elastomer, stirring the salt, absorbing water, adding a water-soluble salt, and kneading the salt. The method includes injecting a mixed cream or sherbet-like mixture into a mold, performing drying and heat treatment, and then removing both salts by washing with water.

In the method using a salt as a pore-forming agent,
Usually, an average pore diameter of about 500 μm is obtained. The average pore diameter can be increased or decreased to some extent by changing the particle diameter of the salt, conditions of stirring and kneading, and the like.
Also, by using starch as a pore-forming agent,
A porous body having a fine pore diameter of 100 μm or less can be obtained.

[0012]

The liquid absorption by the porous polymer compound is achieved by the liquid being sucked into the porous material by capillary action. Therefore, a high-molecular-weight porous material having a high porosity and having fine continuous pores can exhibit excellent water absorption and liquid absorption properties.

However, in the method using the foaming agent or the method using the pore-forming agent, it is difficult to make continuous pores fine and increase the porosity, and a porous polymer compound excellent in water absorption and liquid absorption is obtained. It was difficult. In addition, in the method in which salts and starch are used in combination as a pore-forming agent, the pores formed by the salts and the pores formed by the starch have different diameters, so that the polymer porous material having fine and uniform pores is formed. Was difficult to get.

The present inventors have made intensive studies in view of the above problems, and as a result, completed the present invention. A first object of the present invention is to provide a high-porosity high-porosity having fine and uniform continuous pores. It is an object of the present invention to provide a method capable of efficiently producing a molecular compound porous body. A second object of the present invention is to provide a method for producing a porous polymer compound having a desired pore size.

[0015]

In order to achieve the above object,
The method for producing a polymer compound porous material according to the present invention comprises the steps of: kneading an aqueous dispersion of polymer compound fine particles and salts capable of absorbing water substantially uniformly to produce a non-flowable kneaded product; The product is subjected to cold extrusion molding, the obtained molded product is subjected to heat treatment, and the salts are removed from the molded product after the heat treatment by elution.

The polymer compound may be polyurethane.

The average pore diameter of the porous polymer compound produced by the above method may be 100 μm or less.

[0018]

DETAILED DESCRIPTION OF THE INVENTION In general, an aqueous dispersion of polymer compound fine particles is produced by a method of emulsifying a polymer compound obtained by emulsion polymerization or a method other than emulsion polymerization, and the polymer compound fine particles as a dispersoid are prepared. And an aqueous solution as a dispersion medium.

The dispersion medium comprises a polymerization initiator, a surfactant, a water-soluble oligomer, water and the like used in the emulsion polymerization.

Examples of the polymer compound as a dispersoid include polystyrene, polyurethane, polyvinyl acetate, and the like.
Polyvinyl chloride, polyvinylidene chloride, polyethylene,
Synthetic polymers such as polyisopropylene, polychloroprene, polybutadiene, styrene butadiene copolymer, vinyl acetate ethylene copolymer, and methyl methacrylate butadiene copolymer; and natural products such as natural rubber. In addition, dispersoids are sometimes classified based on the ionicity of the polymer fine particles, and are classified into nonionic, anionic, and cationic types.

The aqueous dispersion of fine particles of the polymer compound used in the present invention is not particularly limited, and any compound can be used alone or in combination of two or more, and can be appropriately selected according to the purpose. is there. The ionicity of the aqueous dispersion of the polymer compound fine particles is not particularly limited, but a nonionic aqueous dispersion of the polymer compound fine particles is preferably used.

The salts capable of absorbing water used in the present invention are not particularly limited as long as they can be made into a clay-like non-flowable kneaded product when added to the aqueous dispersion of the polymer compound fine particles and kneaded. It is not something to be done. As the above salts,
For example, sulfates such as sodium sulfate, aluminum sulfate, potassium sulfate, and magnesium sulfate; carbonates such as sodium carbonate, potassium carbonate, and sodium hydrogen carbonate;
Examples include nitrates such as potassium nitrate and barium nitrate, phosphates such as sodium phosphate, chlorides such as calcium chloride and sodium chloride, and salts of organic acids such as calcium acetate and sodium acetate. In addition, two of these salts
More than one type can be used in combination. In the present invention, fine powdery salts are used, and sodium sulfate is particularly preferably used.

The pores of the polymer porous body obtained by the method of the present invention are formed by substantially uniformly kneading the aqueous dispersion of the polymer compound fine particles and the salts to form a non-flowable kneaded product. The kneaded product is formed by cold extrusion molding, heat-treating the obtained molded product, and eluting and removing the salts from the heat-treated molded product. Therefore, the pore diameter of the porous body is
It can be adjusted depending on the particle size of the salts, and the salts are pulverized and / or classified according to the purpose. Furthermore, the porosity of the porous body can be adjusted by adjusting the amount of the salt added.

As described above, the above-mentioned salts used in the present invention are mixed with an aqueous dispersion of a high molecular compound to absorb a moisture from the aqueous dispersion, and to form a clay-like kneaded material having properties capable of being extruded. It has both a function of generating and a function as a pore-forming agent.

In order to produce a polymer porous material by the method of the present invention, first, a water-absorbable salt is added to an aqueous dispersion of polymer compound fine particles, and the mixture is stirred and kneaded. Absorbs moisture to produce a substantially uniform, non-flowable kneaded product. The amount of the salt added to the aqueous dispersion is not less than the saturation amount of the salt dissolved in the aqueous dispersion, but is appropriately determined in consideration of the amount of water in the aqueous dispersion to be used and the amount of water that the salts can absorb, What is necessary is just to adjust so that the obtained kneaded material becomes a clay-like mixture without fluidity.

The average particle size of the salts is preferably 2000 μm or less. If the average particle diameter exceeds 2,000 μm, the resulting polymer porous body has poor elasticity and pores are likely to be closed.

The salts are used after being ground and / or classified according to the desired pore diameter and porosity. For example, when manufacturing a porous body having an average pore diameter of about 30 μm, salts classified into an average particle diameter of about 15 μm may be used, and when manufacturing a porous body having an average pore diameter of about 600 μm, In addition, salts classified to have an average particle diameter of about 500 μm may be used.

The present invention is not limited at all by adding other components in addition to the aqueous dispersion of the polymer compound fine particles and the salts capable of absorbing water. For example, lubricants at the time of extrusion molding, such as ethylene glycol, glycerin, and polyethylene glycol, viscosity modifiers such as methylcellulose, carboxymethylcellulose, and sodium polyacrylate, and pigments for coloring a polymer compound porous body are used. It can be added as appropriate.

Next, the obtained kneaded material is subjected to cold extrusion. The extruder used is not particularly limited. For example, a vent-type or non-vent-type single-screw extruder, a co-rotating / different-rotating twin-screw extruder, or the like can be used.

Hereinafter, cold extrusion molding of a kneaded material will be described using an example of a molding machine.

The molding machine 1 shown in FIG. 1 is a two-stage extrusion type in which two vent-type single screw extruders 3 and 5 are connected in series. The upstream extruder 3 includes a cylinder 9, a screw 11 rotatably supported in the cylinder 9, a drive motor 13 for rotating the screw 11, and a funnel-shaped supply attached to the upstream end of the main body 9. Tube 15 and cylinder 9
And a heater 17 disposed on the outer peripheral surface of the heater. The extruder 5 on the downstream side includes a cylinder 19, a screw 21 rotatably supported in the cylinder 19, and a screw 2.
1, a driving motor 23 for rotating the cylinder 1, a die 25 attached to the downstream end of the cylinder 19, a heater 27 for heating arranged on the outer peripheral surface of the cylinder 19, and a cooling medium on the outer peripheral surface of the cylinder 19. Cooling unit 29 to be passed through
And a deaeration port 31 formed in the cylinder 19. The downstream end of the upstream cylinder 9 and the upstream end of the downstream cylinder 19 are connected by the connection pipe 7.

A non-fluid kneaded material 37 produced by adding a water-absorbable salt to an aqueous dispersion of fine particles of the polymer compound and kneading the mixture is introduced into the supply pipe 15, Is continuously supplied to the screw 11
Is pressed and transferred to the downstream side by the rotation of, and is supplied into the downstream side cylinder 19 through the connection pipe 7.

The kneaded material 37 supplied from the connection pipe 7 into the cylinder 19 is continuously pressed and transferred to the downstream side by the rotation of the screw 21, and passes through the die 25. The inside of the cylinder 19 is adjusted to the optimum processing temperature by the heater 27 and the cooling unit 29. The kneaded material 37 that has passed through the die 25 is continuously extruded as a molded product 39 having a desired cross-sectional shape. The molded product 39 extruded from the die 25 is appropriately cut.

The cross-sectional shape of the molded article 39 is not particularly limited, and can be freely set by selecting the internal cross-sectional shape of the die 25 according to the purpose of use of the porous body. For example, when the internal cross section of the die 25 is circular, a cylindrical molded product is obtained, when it is annular, a hollow cylindrical molded product is obtained, and when it is rectangular, a block-shaped or sheet-shaped molded product is obtained.

Next, the molded product extruded into a desired shape is subjected to a heat treatment. The heat treatment conditions vary depending on the shape and size of the molded product, the characteristics of the polymer compound used, and the like. For example, heat treatment is performed at a predetermined temperature within a range of 60 ° C. to 130 ° C. for a predetermined time within a range of 5 hours to 48 hours. By this heat treatment, moisture is removed from the molded product, the formation of the polymer compound fine particles proceeds, and a structure having sufficient mechanical strength is obtained.

Next, salts contained in the heat-treated molded product are removed by elution. The portions from which the salts have been removed become continuous voids, and continuous pores are formed.

The solvent used for eluting and removing salts from the molded article after the heat treatment is not particularly limited as long as it has a property of dissolving the salts and not dissolving the polymer compound. Water is preferably used. The method for eluting and removing salts with water is not particularly limited, either.
For example, a method of immersing the molded article after heat treatment in a water bath,
A method of supplying shower-like water to the molded product for a predetermined time can be used. The temperature of the water used for the elution removal may be appropriately adjusted in consideration of the solubility of the salts to be eluted and the properties of the polymer compound, and the like.

Finally, the molded product from which the salts have been removed is dried. As a result, the desired porous polymer compound is obtained. Further, by performing a heat treatment as needed, a porous polymer compound having high strength and excellent elasticity can be obtained.

The ambient temperature for drying the molded product from which the salts have been removed may be appropriately adjusted depending on the characteristics of the polymer compound, and is usually set in the range of 40 ° C. to 90 ° C.

[0040]

Example 1 36 kg of a polyurethane elastomer (trade name: Superflex E4500, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
60 kg of sodium sulfate having an average particle size of 15 μm and 0.36 kg of glycerin were stirred and kneaded in a kneader,
A clay-like kneaded product was obtained. Next, the obtained kneaded material was extruded into a hollow cylindrical roller shape having an outer diameter of 60 mm, an inner diameter of 20 mm, and a length of 600 mm using a vacuum extruder,
The obtained molded product was heat-treated at 80 ° C. for 24 hours to obtain a molded product having sufficient strength. Further, the molded product is heated at 40 ° C.
In hot water to elute and remove sodium sulfate in the molded product. After the sodium sulfate was eluted and removed, the molded product was sufficiently washed with water, and then dried at 60 ° C. for 24 hours to obtain a roller-shaped porous polyurethane.

The obtained polyurethane porous body is a porous body having extremely fine and uniform continuous pores having an average pore diameter of 30 μm, a porosity of 72% by volume, and a water retention of 280%, and exhibits excellent water absorption properties. did.

The average pore diameter, porosity, and water retention rate are values obtained by the following methods.

The average pore diameter was determined as an average value by measuring the major axis of each pore in three visual fields of an electron micrograph including 10 pores in one visual field of the fracture surface of the porous body.

The porosity is determined by measuring the true volume of the porous body by using a dry automatic watch (trade name: Acupic 1330, manufactured by Shimadzu Corporation).
Was calculated by the following formula.

Porosity (%) = (V1−V2) / V1 × 100 Here, V1 is an apparent volume calculated based on the outer dimensions of the porous body, and V2 is a true volume.

The water retention was calculated by the following equation.

Water retention rate (%) = (W1−W2) / W2 × 100 Here, W1 is the weight of the porous body when saturated with water, and W2 is the weight of the porous body when dried.

Example 2 36 kg of a polyurethane elastomer (trade name: Superflex E4500, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
54 kg of sodium sulfate pulverized and classified to a predetermined average particle diameter and 0.36 kg of glycerin were stirred and kneaded with a kneader to obtain a clay-like kneaded product. Next, the obtained kneaded material was 450 mm ×
Extruded into a block shape of 250 mm x 30 mm,
The obtained molded product was heat-treated at 80 ° C. for 24 hours to obtain a molded product having sufficient strength. Further, the molded product is heated at 40 ° C.
In hot water to elute and remove sodium sulfate in the molded product. After elution and removal of sodium sulfate, the molded product was sufficiently washed with water, and then dried at 80 ° C. for 24 hours to obtain a block-shaped porous polyurethane.

In this example, five types of porous bodies were produced using five types of sodium sulfate having different average particle diameters, and the characteristics of each porous body were measured. Table 1 below shows the average particle size of sodium sulfate and the properties of the obtained polyurethane porous body. Incidentally, the average pore diameter in Table 1,
The porosity and the water retention are values obtained by the same method as in Example 1 above.

[0050]

[Table 1] Table 1 shows that the pore size can be adjusted according to the particle size of the salts used, and that a porous body having a pore size suitable for the purpose can be produced. In addition, it can be seen that the obtained porous body has a large amount of water retention (high water retention rate) and has excellent water absorption. Furthermore, when the average pore diameter is 10
From those having extremely fine pores of 0 μm or less (using sodium sulfate having an average particle diameter of 15 μm) to those having pores having an average pore diameter of about 2000 μm (using sodium sulfate having an average particle diameter of 2000 μm) ), It can be seen that they can be manufactured by the same method. When sodium sulfate having an average particle diameter of 2500 μm was used, the obtained polyurethane porous body had low elasticity and pores were closed, and was therefore excluded from the measurement.

Third Example 36 kg of a polyurethane elastomer (trade name: Superflex E4500, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Using sodium sulfate having an average particle size of 30 μm and 0.36 kg of glycerin, in the same manner as in Example 2 above. A porous polyurethane body was obtained.

In this example, five types of porous bodies having different added amounts of sodium sulfate (weight ratio of polyurethane elastomer and sodium sulfate) were produced, and the characteristics of each porous body were measured. Table 2 below shows the weight of sodium sulfate and the characteristics of the obtained polyurethane porous body.
The average pore diameter, porosity, and water retention in Table 2 are values obtained by the same method as in Example 1 above.

[0053]

[Table 2] Table 2 shows that the porosity of the obtained porous body can be adjusted by the amount of the salts to be mixed, and that a porous body having a porosity suitable for the purpose can be produced.

[0054]

According to the present invention, an aqueous dispersion of fine particles of a high molecular compound and a salt capable of absorbing water are kneaded to obtain a uniform and high-density pore having a continuous pore with little variation between pore diameters. The molecular porous body can be manufactured stably.
In addition, by adjusting the particle diameter of the salts, from the porous body having extremely fine pores having an average pore diameter of 100 μm or less to the porous body having pores having an average pore diameter of about 2000 μm, the same method is used. can do. Therefore, a polymer porous body having excellent water absorption and liquid absorption properties can be efficiently and simply manufactured by extrusion molding.

If the same cross section is continuous,
Extrusion molding into an arbitrary shape such as a columnar shape, a hollow cylindrical shape, a block shape, and a sheet shape is possible. Also, if necessary,
Post-processing such as precision processing can be performed before or after heat treatment after extrusion. Therefore, a polymer porous body having a shape according to the purpose of use can be easily manufactured.

Further, the pore diameter and porosity of the obtained porous body can be adjusted by appropriately adjusting the particle diameter and the mixing amount of the salts that absorb water from the aqueous dispersion of the polymer compound fine particles.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a molding machine used in an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 molding machine 9 cylinder 11 screw 19 cylinder 21 screw 25 die 37 kneaded product 39 molded product

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F074 AA78 AC13 AC14 AC25 AC28 AC30 AC31 AD10 CB03 CB14 CB16 CC04Y CC42 DA03 DA13 4J002 AA001 CK021 DD056 DD066 DE226 DF036 DG046 DH046 EG026 EG036 FD206

Claims (4)

[Claims] 1. An aqueous dispersion of polymer compound fine particles and a water-absorbable salt are kneaded substantially uniformly to form a non-flowable kneaded product, and the kneaded product is cold-extruded to obtain a kneaded product. A method for producing a porous polymer compound, comprising heat-treating a molded article obtained by heat treatment and removing the salts from the molded article after heat treatment by elution. 2. The method according to claim 1, wherein the high molecular compound is a polyurethane. 3. A porous polymer compound produced by the method according to claim 1 or 2. 4. The polymer compound porous body according to claim 3, wherein the average pore diameter is 100 μm or less.