JPH06340745A - Method for producing powdery thermoplastic resin - Google Patents

Abstract

(57) [Summary] [Purpose] How to produce powdery thermoplastic resin with good fluidity.
Law and cost reduction. [Composition] A powdery thermoplastic resin characterized in that, when a powdery thermoplastic resin is produced by freeze-grinding a hydrophilic thermoplastic resin, the hydrophilic thermoplastic resin is impregnated with 0.5% by weight or more of water. A method for producing a plastic resin.

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 powdery thermoplastic resin, more specifically, a method for producing a powdery thermoplastic resin having good fluidity by freeze-grinding a hydrophilic thermoplastic resin. It is about.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a powdery thermoplastic resin, pulverization at room temperature is carried out at room temperature, freezing pulverization is carried out in which crushed material is embrittled by liquefied nitrogen and crushed into a fragile state,
There is a chemical pulverization method in which a crystalline resin is dissolved in a solvent and then recrystallized by changing temperature conditions, solid-liquid separated and dried to obtain a fine powder. However, since plastics, especially elastomers, have a low melting point and are highly elastic, it is almost impossible to pulverize them at room temperature, and even if they can be pulverized, they are inefficient. In addition, since freeze pulverization usually requires high pulverization energy, it uses a large amount of liquefied nitrogen, is expensive, and cannot be properly pulverized into granules. The fluidity of the product deteriorates. Also, chemical grinding requires the selection of a solvent that can be recrystallized,
There were problems in terms of recovery efficiency and solvent cost.

[0003]

SUMMARY OF THE INVENTION The present invention has been made with the object of overcoming the above-mentioned drawbacks and providing a method for producing a powdery thermoplastic resin having good fluidity.

[0004]

As a result of earnest research, the inventors of the present invention have found a manufacturing method in which a hydrophilic thermoplastic resin is impregnated with water, and have completed the present invention.

That is, in the present invention, when a powdery thermoplastic resin is produced by freeze-grinding a hydrophilic thermoplastic resin, the hydrophilic thermoplastic resin is impregnated with water in an amount of 0.5% by weight or more. It is a method for producing a powdered thermoplastic resin characterized.

The present invention will be described in more detail below. The freezing and pulverization in the present invention is carried out by a method in which a resin is cooled using a low temperature compressed liquefied gas such as liquefied nitrogen and dry ice and a solidified gas, and preferably pulverized at a temperature not higher than Tg of the resin. As a crusher, hammer type, pin type, turbo type,
Linrex type is used.

When the powdery thermoplastic resin of the present invention is freeze-pulverized, the temperature of the hydrophilic thermoplastic resin is -10 ° C or lower. Further, the freeze pulverization of the hydrophilic thermoplastic resin is preferably carried out at a temperature not higher than the Tg of the resin. The hydrophilic thermoplastic resin of the present invention contains 0.5% by weight or more of water, preferably 1.0% by immersion in water at 10 ° C to 90 ° C or contact under high temperature and high humidity (humidity of 95% or more). By impregnating it in an amount of not less than wt%, the crushing energy can be suppressed low, efficient crushing can be performed at low cost, and a powder having a uniform particle size distribution and good fluidity can be obtained. Further, it is possible to use an aqueous solution containing a water-soluble chemical.

The hydrophilic thermoplastic resin used in the present invention is a resin which can contain water in an amount of 0.5% by weight or more. Examples include thermoplastic polyester resins, polyamide resins, polyurethane resins and the like having groups such as

The thermoplastic polyurethane resin used in the present invention is a commonly used aromatic, alicyclic or aliphatic organic diisocyanate and ester type, ether type,
It is synthesized by reacting a lactone-based or carbonate-based polyol and a chain extender. As a method for synthesizing the thermoplastic polyurethane resin used in the present invention, there are a continuous synthesis method using an extruder, a batch synthesis method using a kneader having a kneading tank, and the like.

[0010]

INDUSTRIAL APPLICABILITY The powdery thermoplastic resin obtained by the present invention can suppress the grinding energy during grinding, has a low temperature rise during grinding, and uses the liquefied nitrogen during freeze grinding. There are few, and cost can be reduced. Also,
The softening and melting of the crushed material due to the temperature rise during crushing is avoided, the solidified and brittle state is maintained, and a large amount of crushing is possible at one time. The Tg of the thermoplastic polyurethane resin thus obtained is -5 ° C to -50 ° C.

Further, the powder obtained has a smaller particle size than that obtained by conventional freeze pulverization, has a uniform particle size distribution, and at the same time has no "whiskers" or the like and has a stable shape, so that the powder has a fluidity. It is good. From these things, a powdery thermoplastic resin effective for powder molding such as powder coating and powder rotational molding can be obtained. In particular, it is effective for a thermoplastic elastomer such as the above-mentioned thermoplastic polyester resin, polyamide resin, polyurethane resin having a low Tg and good impact resistance at low temperature.

[0012]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, "%" in Examples and Comparative Examples
Indicates "% by weight" unless otherwise specified.

Example 1 A thermoplastic polyurethane resin manufactured by Nippon Polyurethane Industry,
Paraprene 22S [Hardness 82 (JIS A), Tg-6
℃ (TOYO BALDWIN REHOVIBRON) pellets 8
After drying at 0 ° C. for 4 hours, the water content was measured. The water content was 0.02%. Using this pellet, a sheet of 120 mm × 120 mm × 2 mm was prepared by injection molding. Heat the sheet and pellets with hot water (80
C.) for 24 hours to impregnate water. The water content of the pellets was 1.77%. Then, the crack generation energy was measured with the sheet. On the other hand, the pellets impregnated with water were frozen and pulverized at -100 ° C, the product grain shape, grain shape and yield of the pulverized product were measured, and the amount of liquid nitrogen used for the freeze pulverization was measured. The results are shown in Table 1.

Example 2 Using the paraprene 22S pellets dried in Example 1 for 4 hours, they were left in a thermo-hygrostat (80 ° C., 95% or more) for 24 hours to impregnate them with water. All others were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 The paraprene 22S pellets dried in Example 1 for 4 hours were used and immersed in normal temperature water (25 ° C.) for 1 day to impregnate them with water. All others were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 Pellets of polyamide elastomer manufactured by Dainippon Ink and Chemicals, Grelax A100 [hardness 88 (JIS A), Tg-30 ° C.] were dried for 4 hours and then hot water (80
C.) for 1 hour to impregnate water. All others were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 5 Polyester elastomer manufactured by Dainippon Ink and Chemicals,
Grelax E-320 [Hardness 88 (JIS A), T
g-31 ° C] pellets were dried for 4 hours and then hot water (8
It was immersed in water at 0 ° C. for 1 hour for impregnation with water. All others were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 Using the paraprene 22S pellets of Example 1 which had been dried for 4 hours, the same evaluation as in Example 1 was carried out. The results are shown in Table 1.

Comparative Example 2 Evaluation was conducted in the same manner as in Example 1 using the Grelax A-100 pellets dried in Example 4 for 4 hours. The results are shown in Table 1.

Comparative Example 3 The same evaluation as in Example 1 was carried out using the pellets of Grelax E-320 dried in Example 5 for 4 hours. The results are shown in Table 1.

[0021]

[Table 1]

Note 1 in Table 1) P 22S: Paraprene 22S 2) G-A-100: Grelax A-100 3) G-E-320: Grelax E-320

Evaluation method in Table 1 (1) Water content A Karl Fischer moisture meter manufactured by Kyoto Electronics Manufacturing Co., Ltd. was used. Use a water vaporizer to heat the furnace to 200 ° C.
Measure the temperature after heating to 0 ° C and thoroughly purging the system with nitrogen.
The water content is calculated by the following formula. (2) Crack generation energy This was performed using a graphic impact tester manufactured by Toyo Seiki. It was measured at a drop height of 18 cm and a weight of 6.5 kg. (3) Frozen pulverization It was cooled to -100 ° C and pulverized using a Linrex mill manufactured by Hosokawa Micron Co., Ltd. (4) Particle size of product Automatic particle size distribution measuring device (CAPA-30 manufactured by Horiba, Ltd.)
0) was used. (5) Grain shape It was performed using a microscope manufactured by Keyence Corporation. It was observed at a magnification of 250 times. (6) Revenue Automatic particle size distribution analyzer (CAPA-30 manufactured by Horiba, Ltd.)
0), and the yield that passed 150 μm was divided by the total amount and evaluated.

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[Procedure amendment]

[Submission date] September 18, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

When the hydrophilic thermoplastic resin according to the present invention is freeze-pulverized, the temperature of the hydrophilic thermoplastic resin is -10 ° C or lower. Further, the freeze pulverization of the hydrophilic thermoplastic resin is preferably carried out at a temperature not higher than the Tg of the resin. The hydrophilic thermoplastic resin in the present invention is immersed in water at 10 to 90 ° C. or kept at a constant temperature.
Impregnation of 0.5% by weight or more, preferably 1.0% by weight or more of water by contact under constant humidity (humidity 95% or more) makes it possible to suppress the crushing energy to a low level, resulting in low cost and efficient crushing. The powder having a uniform particle size distribution and good fluidity is obtained. Further, it is possible to use an aqueous solution containing a water-soluble chemical.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

Hydrophilic thermoplastic resin by the method of the present invention
In the case of freeze-grinding , the energy at the time of grinding can be suppressed to a low level, the temperature rise during the grinding is low, and the consumption of liquefied nitrogen can be suppressed, so that the cost can be reduced. Further, softening and melting of crushing due to temperature rise during crushing can be avoided, solidification and brittleness can be maintained, and a large amount of crushing can be performed at one time.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Further, the obtained powder has a smaller particle size and a uniform particle size distribution as compared with the conventional powder obtained by freezing and pulverization, and at the same time has no beard and the like and has a stable shape, so that the powder flow Good property. From these things, a powdery thermoplastic resin effective for powder molding such as powder coating and powder rotational molding can be obtained. Particularly, it is effective for a thermoplastic elastomer having a low Tg ( usually -5 to -50 ° C ) and a good impact resistance at low temperature, such as the above-mentioned thermoplastic polyester resin, polyamide resin and polyurethane resin.

Claims (2)

[Claims] 1. A powder characterized in that, when a powdery thermoplastic resin is produced by freeze-grinding a hydrophilic thermoplastic resin, the hydrophilic thermoplastic resin is impregnated with 0.5% by weight or more of water. Of producing thermoplastic thermoplastic resin. 2. The method for producing a powdery thermoplastic resin according to claim 1, wherein the hydrophilic thermoplastic resin is a thermoplastic polyurethane resin.