JP3166131B2 - Method for producing powdery thermoplastic resin - Google Patents

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, and more particularly, to 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, methods for producing a powdery thermoplastic resin include room temperature pulverization at room temperature, freeze pulverization in which a crushed material is embrittled by liquefied nitrogen, and pulverized into a friable state.
There is a chemical pulverization method in which a crystalline resin is dissolved in a solvent, then recrystallized by changing temperature conditions, and solid-liquid separated and dried to obtain a fine powder. However, plastics, particularly elastomers, have a low melting point and are highly elastic, so that pulverization at ordinary temperature is almost impossible, and even if pulverization is possible, it is inefficient. In addition, freeze pulverization usually requires a large amount of liquefied nitrogen because of high pulverization energy, and is expensive. The fluidity of the object deteriorates. In addition, 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 object of the present invention is to overcome the above-mentioned drawbacks and to provide a method for producing a powdery thermoplastic resin having good flowability.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found a production 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 hydrophilic thermoplastic resin is freeze-pulverized to produce a powdery thermoplastic resin, the hydrophilic thermoplastic resin is impregnated with 0.5% by weight or more of water. This is a method for producing a powdery thermoplastic resin, which is a feature.

Hereinafter, the present invention will be described in more detail. The freezing and pulverization in the present invention is performed by cooling the resin using a low-temperature compressed liquefied gas such as liquefied nitrogen or dry ice, a solidified gas, or the like, and preferably pulverizing the resin at a temperature equal to or lower than Tg of the resin. Hammer type, pin type, turbo type,
A Linlex type or the like is used.

In the present invention, the temperature of the hydrophilic thermoplastic resin when the hydrophilic thermoplastic resin is freeze-pulverized is −10 ° C. or less. In addition, the freeze pulverization of the hydrophilic thermoplastic resin is preferably performed at a temperature equal to or lower 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.
By impregnating water with 0.5% by weight or more, preferably 1.0% by weight or more by contact under constant humidity (humidity of 95% or more), the grinding energy can be suppressed to a low level, and low cost and efficient grinding To obtain a powder having a uniform particle size distribution and good fluidity. Furthermore, it is also possible to use an aqueous solution containing a water-soluble chemical.

[0008] 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. And the like. Thermoplastic polyester resins, polyamide resins, polyurethane resins and the like having groups such as

The thermoplastic polyurethane resin used in the present invention may be any of commonly used aromatic, alicyclic and aliphatic organic diisocyanates and esters, ethers and the like.
It is synthesized by reacting a lactone-based or carbonate-based polyol and a chain extender. Examples of the method for synthesizing the thermoplastic polyurethane resin used in the present invention include a continuous synthesis method using an extruder and a batch synthesis method using a kneader having a kneading tank.

[0010] 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 low, the temperature rise during grinding is low, and the consumption of liquefied nitrogen can be suppressed, so that the cost can be reduced. Further, softening and melting of pulverization due to temperature rise during pulverization can be avoided, solidification and embrittlement can be maintained, and a large amount of pulverization can be performed at once.

Further, the obtained powder has a small particle size and a uniform particle size distribution as compared with those obtained by conventional freeze-pulverization, and at the same time, has no “whisker” or the like and has a stable shape. The properties are good. From these, a powdery thermoplastic resin effective for powder molding such as powder coating and powder rotational molding can be obtained. In particular, the thermoplastic polyester resin, polyamide resin, polyurethane resin and the like are effective for thermoplastic elastomers having a low Tg ( normally -5 to -50 ° C ) and good impact resistance at low temperatures.

[0012]

EXAMPLES Next, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. "%" 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's REHOVIBRON)] pellets
After drying at 0 ° C. for 4 hours, the water content was measured. The water content was 0.02%. Using these pellets, a sheet of 120 mm × 120 mm × 2 mm was prepared by injection molding. The sheet and the pellet are mixed with hot water (80
C.) for 24 hours to impregnate with water. The moisture content of the pellets was 1.77%. Thereafter, the crack generation energy was measured using the sheet. On the other hand, the pellets impregnated with water were freeze-pulverized at −100 ° C., and the product particle shape, particle shape, and yield of the pulverized product were measured, and the amount of liquid nitrogen used in the freeze-pulverization was measured. Table 1 shows the results.

Example 2 The 4 hour-dried paraprene 22S pellets of Example 1 were used and left in a thermo-hygrostat (80 ° C., 95% or more) for 24 hours to be impregnated with water. All others were evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 3 The paraprene 22S pellets dried in 4 hours of Example 1 were immersed in normal-temperature water (25 ° C.) for one day to be impregnated with water. All others were evaluated in the same manner as in Example 1. Table 1 shows the results.

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

Example 5 A polyester elastomer manufactured by Dainippon Ink and Chemicals,
GREAK E-320 [Hardness 88 (JIS A), T
g-31 ° C.] after drying for 4 hours.
(0 ° C.) for 1 hour to impregnate with water. All others were evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 Evaluation was made in the same manner as in Example 1 using the paraprene 22S pellets dried in 4 hours of Example 1. Table 1 shows the results.

Comparative Example 2 Evaluation was performed in the same manner as in Example 1 except that the grease A-100 pellets dried in 4 hours of Example 4 were used. Table 1 shows the results.

Comparative Example 3 Evaluation was performed in the same manner as in Example 1 except that the pellets of Gleek E-320 dried in 4 hours of Example 5 were used. Table 1 shows the results.

[0021]

[Table 1]

Notes on Table 1 1) P22S: Paraprene 22S 2) GA-100: Relax A-100 3) GE-320: Relax E-320

Evaluation method in Table 1 (1) Water content The water content was measured using a Karl Fischer moisture meter manufactured by Kyoto Electronics Industry Co., Ltd. Heating furnace at 200 ° C using moisture vaporizer
And perform a sufficient nitrogen purge in the system before measurement.
The water content is determined by the following equation. (2) Crack generation energy This was performed using a graphic impact tester manufactured by Toyo Seiki. The measurement was performed at a falling height of 18 cm and a weight of 6.5 kg. (3) Freezing and pulverization It was cooled to −100 ° C. and pulverized using a Linsolex mill manufactured by Hosokawa Micron Corporation. (4) Particle size of product Automatic particle size distribution analyzer (CAPA-30) manufactured by HORIBA, Ltd.
0). (5) Grain shape This was performed using a microscope manufactured by Keyence Corporation. The observation was performed at a magnification of 250 times. (6) Yield Automatic particle size distribution analyzer (CAPA-30) manufactured by Horiba, Ltd.
0) and evaluated by the value obtained by dividing the yield passing 150 μm by the total amount.

Claims (2)

(57) [Claims] 1. A powder obtained by freeze-grinding a hydrophilic thermoplastic resin to produce a powdery thermoplastic resin by impregnating the hydrophilic thermoplastic resin with water in an amount of 0.5% by weight or more. For producing a thermoplastic resin in a liquid state. 2. The method for producing a powdery thermoplastic resin according to claim 1, wherein said hydrophilic thermoplastic resin is a thermoplastic polyurethane resin.