JP2519192B2 - Method for producing polyurethane porous body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a polyurethane sponge, and more particularly to a method for producing a polyurethane sponge having fine continuous pores.

(Prior Art) A sponge made of polyurethane resin is hydrophobic and lightweight, and is used as a cushioning material, a heat insulating material, a filling material, a general-purpose item, or the like, having physical properties and a structure suitable for each. . For example, as a puff material for makeup, a material with a fine textured surface and good water absorption has a good feel and can be effectively used for cosmetics, but a material with too large porosity is not preferable because of lack of volume and bottoming phenomenon. . Further, a material having a good water absorbing property is suitable for use as a cleaning material.

Conventionally, polyurethane sponges are manufactured by a method using a foaming agent. As the foaming agent, carbon dioxide, freon, air, etc., as well as decomposable organic foaming agents are used. However, with the method using a foaming agent, only those with relatively large bubbles can be obtained, and when the porosity is lowered, the pores are not continuous pores but independent pores and poor in water absorption. It was necessary to make it extremely large (for example, 95% by volume or more). That is, in the conventional method, it has a fine pore diameter, has continuous pores, and has a porosity of 50, which is suitable for a puff material for makeup and a cleaning material.
It was extremely difficult to obtain a material of about 90% by volume.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for easily, stably and efficiently producing a polyurethane sponge having fine continuous pores and rich in volume.

(Means for Solving the Problems) The object of the present invention is to add a salt capable of absorbing water of crystallization to an aqueous dispersion of a polyurethane elastomer and stir the mixture to absorb water, and then to dissolve the water-soluble salt. Is added to the mixture to knead it into a semi-fluid state, which is subsequently cast in a mold, dried and heat-treated, and then washed with water to remove both salts, thereby producing a polyurethane porous body. Achieved by the method.

The aqueous dispersion of the polyurethane elastomer used in the present invention is a non-reactive polyurethane elastomer that is forcedly emulsified or self-emulsified. Among them, a forced emulsification type in which a hydrophobic urethane elastomer is emulsified and dispersed with a small amount of a special surfactant is preferable because it is excellent in water resistance and hot water resistance.

The salt capable of absorbing water of crystallization used in the present invention is a salt which can contain water of crystallization in a crystal, and a salt which does not contain water of crystallization or which can further contain water of crystallization. Such salts include sodium sulfate (Na ₂ S
O ₄ ), copper sulfate (Cu ₂ SO ₄ ), etc., for example, sodium sulfate is known to have a water temperature of 7 and a water temperature of 10 and 1 mol of anhydrous sodium sulfate absorbs 10 mol of water in its crystal. can do. In order to obtain a large water absorption, the salt is preferably an anhydride having no water of crystallization, and a powdery one is usually used.

The water-soluble salts used in the present invention are not salts which can absorb or have already absorbed the water of crystallization described above, salts which cannot contain water of crystallization in the crystals, and salts which are easily dissolved in water and have deliquescent properties. May be Examples of such water-soluble salts include sodium chloride and magnesium chloride, with sodium chloride being preferred.

To produce a polyurethane porous body by the method of the present invention,
First, to the water dispersion of the polyurethane elastomer, a salt capable of absorbing the water of crystallization is added and stirred, and evenly mixed and water is absorbed by the added salt to precipitate a polyurethane elastomer in a water dispersed state. , A mixture of polyurethane elastomer and salts with water of crystallization. This is a powdery mixture which has no fluidity as a whole, preferably in a slightly moist state. The amount of the salt added here may be appropriately selected in consideration of the amount of water contained in the aqueous dispersion of the polyurethane elastomer used and the amount of water that the salt can absorb.

Next, the above water-soluble salts are added to the obtained powdery mixture and sufficiently kneaded, and water is extracted from the above-mentioned salts having water of crystallization to obtain a creamy or sorbet having semi-liquidity as a whole. Convert it into a shape. The amount of the water-soluble salt added here may be appropriately selected so that it has a fluidity such that it can be easily poured into the mold, and, for example, when water is absorbed with anhydrous sodium sulfate, it is added to the weight of the anhydrous sodium sulfate added. It is sufficient to add about 10 to 15% by weight of sodium chloride.

Subsequently, the obtained semi-fluid mixture was poured into a mold, which was then dried to remove water and solidified, and the solid obtained was taken out of the mold and subsequently heat-treated to obtain polyurethane. The elastomer is formed into a film to form a molded body. The temperature and time of the heat treatment may be appropriately selected according to the type of polyurethane elastomer used.

Subsequently, the obtained molded product is sufficiently washed with water to dissolve and remove the remaining two kinds of salts to give a porous structure, whereby the polyurethane porous product produced by the method of the present invention can be obtained. Incidentally, in order to form a stronger film of the polyurethane elastomer, it is preferable to continue drying and heat treatment.

In the method of the present invention, by adding a water-soluble salt as described above, it is possible to impart fluidity to the powdery mixture, and as a result, it becomes easy to pour it into a mold, and further, the porosity is 60%. A porous body of up to 90% by volume can be efficiently produced. When the water-soluble salt is not added in the method of the present invention, it is not easy to uniformly put the powdery mixture in the mold, and it is necessary to press-mold with a press or the like after putting it in the mold. Therefore, it becomes difficult to obtain a porous body having a dense structure and a high porosity.

The method of the present invention uses two kinds of salts as a pore-forming material, that is, a salt capable of absorbing water of crystallization and a water-soluble salt in combination, and the size of the obtained pore diameter depends on the particle diameter of the salt to be added or It can be adjusted by stirring, kneading conditions, etc., but it is not easy to obtain one having a small pore size of, for example, 100 μm or less. Therefore, in order to obtain a finer pore size, starch can be used together as a pore-forming material in the method of the present invention. Here, the starch may be added to the water dispersion of the polyurethane elastomer before or simultaneously with the addition of the salt capable of absorbing water of crystallization. In the method of the present invention, in addition to starch, pulp powder, fiber flakes, sponge powder, polyvinyl acetal sponge flakes, or the like can be used as the pore-forming material to improve water retention or hydrophilicity. It is also possible.

The polyurethane porous body produced according to the method of the present invention has relatively fine continuous pores having an average pore size of 500 μm or less and a porosity of 60 to 90% by volume, is excellent in flexibility and water absorption, and is rich in volume. Is. In addition, the method of the present invention in which starch is used as a pore-forming material is about 500 μm.
It is suitable for cosmetic puffs, which has a mixture of pores of large and small sizes of 00 μm or less and has a very good feel.

(Effect of the Invention) According to the method of the present invention, it is extremely difficult to obtain by the conventional foaming method, and the fine pore diameter is 90% by volume.
A polyurethane sponge having continuous pores can also be produced below. Further, according to the method of the present invention, casting into a mold is easy, and pressure molding by a press machine or the like is not required. If starch or the like is used in combination with the method of the present invention, the pore size will be
It is also possible to obtain an extremely fine pore size of 100 μm or less.

The polyurethane sponge produced by the method of the present invention has fine continuous pores having an average pore diameter of 500 μm or less and a porosity of 60 to 90% by volume, is excellent in water absorption, flexibility, and has a feeling of volume without sagging. It has a very good feel and is suitable as a puff for makeup and a cleaning material.

(Example 1) 800 g of a polyurethane elastomer aqueous dispersion <trade name: Superflex E-4000, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., 45% emulsion> was collected, and 2000 g of anhydrous sodium sulfate powder was added thereto, and Shinagawa was added. Stir and knead with a type mixer,
The powder was in a powdery state with a slight loss of fluidity. To this, 200 g of sodium chloride was added and further mixed with stirring to obtain a creamy semi-liquidity. This was poured into a mold and dried at 90 ° C for a whole day and night, then taken out from the mold and further dried at 90 ° C for 2 days, followed by heat treatment at 120 ° C for 24 hours to obtain a molded body. This molded body was thoroughly washed with warm water to elute and remove sodium sulfate and sodium chloride, dried at 90 ° C for 2 hours, and further treated at 120 ° C for 1 hour.

The obtained polyurethane porous body has an average pore diameter of 500μ,
An elastic body having a porosity of 60% by volume and having good impact resilience. Further, the pore structure was based on continuous pores having a three-dimensional network structure having a shape different from the conventional foaming method. The conventional polyurethane sponge having continuous pores by the foaming method had a peculiar bottoming feeling, but the obtained polyurethane porous body had no such bottoming feeling,
It was rich in volume. The other physical properties are shown in Table 1.

(Example 2) 500 g of the polyurethane elastomer aqueous dispersion used in Example 1 was collected, to which 2400 g of anhydrous sodium sulfate powder and 12 g of potato starch were dispersed in 500 g of water, and the mixture was stirred and mixed, and 1100 g of sodium chloride was added. Was added, and the mixture was further stirred and mixed to obtain a semi-liquid state. This was poured into a mold, and a polyurethane porous body was obtained in the same manner as in Example 1 below. The fluidity at the time of casting is rapidly lost by the heating in the drying step, and the settling of the cast mixed liquid is not observed. Therefore, the porous body structure as a whole is more uniform than that of the product of Example 1. Became.

The obtained polyurethane porous body has continuous pores having a mixture of pore diameters of about 500μ and about 120μ, has a slightly softer texture than the product of Example 1, and is very suitable for a cosmetic puff. It was a nice touch. Other physical properties are shown in Table 1.

(Example 3) A polyurethane porous body was produced in the same manner as in Example 2 except that the potato starch used in Example 2 was replaced with a processed starch which was obtained by once gelatinizing and then pulverizing potato starch. The fluidity during casting was lost more quickly than in Example 2 by heating in the drying step, and a more uniform porous body structure was obtained.

The obtained polyurethane porous body had continuous pores in which some having a pore size of about 500 μ and some having a pore size of about 200 to 300 μ coexisted. The other physical properties were as shown in Table 1.

Example 4 A polyurethane porous body was produced in the same manner as in Example 3 except that 6 g of pulp powder was added together with the processed starch in Example 3.

The physical properties of the obtained product are as shown in Table 1, and the water absorption and water retention were improved by the addition of pulp powder.

(Example 5) A polyurethane porous body was produced in the same manner as in Example 4 except that the pulp powder added in Example 4 was changed to 12 g instead of 6 g. The physical properties of the obtained product are shown in Table 1.

Claims (1)

(57) [Claims] 1. A semi-fluid state in which a salt capable of absorbing water of crystallization is added to an aqueous dispersion of a polyurethane elastomer, and the mixture is stirred to absorb water and then a water-soluble salt is added and kneaded. The method for producing a polyurethane porous body is characterized in that it is subsequently cast in a mold, dried and heat-treated, and then washed with water to remove both salts.