JPS61188428A - Production of thermoplastic resin molding - Google Patents

Abstract

PURPOSE:To produce the title molding of excellent heat resistance without detriment to mechanical properties, by heat-treating a thermoplastic resin molding in a vacuum or in the presence of an inert gas. CONSTITUTION:A thermoplastic resin molding made of, e.g., a polyamide, polyester or polyacetal is heat-treated at a temperature >=120 deg.C for at least 30min in a vacuum >=60mmHg or in an inert gas atmosphere such as CO2 gas, He or Ar.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a thermoplastic resin molded article, which is characterized by heat-treating a thermoplastic resin molded article under vacuum or in the presence of an inert gas. It is something.

(Prior art) Thermoplastic resin molded products have been widely used for automobile parts, household goods, and other miscellaneous goods parts due to the advantage of good productivity when injection molding and extrusion molding methods are used. has been done. However, many of these applications, such as automobile parts, require heat resistance, mechanical strength, etc. (currently, the range of their applications is limited).

As a method to improve this, a method of reinforcing thermoplastic hfjflf( It has drawbacks such as severe wear of the molding machine screw.

Special thermoplastic resins with heat resistance have been developed as a method for this purpose, but these resins have the disadvantage of being expensive and lack versatility.

In the case of thermosetting resins, heat treatment is carried out at 100°C or higher for the purpose of accelerating the curing reaction and alleviating "stress strain," but in the case of thermoplastic resins, it is generally carried out at 70°C to 100°C.
It is carried out in air or hot water at 00°C.

Furthermore, in JP-A-59-193930, in order to suppress fluctuations in the water absorption rate of molded parts and stabilize their dimensions, the process of "water absorption treatment, water immersion treatment, and immersion in aqueous emulsion type lubricating oil" is carried out at 70 to 120°C. I'm introducing a method to do it, but the process is complicated and I'm not sure I'll be able to get anything I'm satisfied with.

(Problems to be Solved by the Invention) The present invention provides a method for manufacturing a thermoplastic resin molded product, which was achieved as a result of intensive research to improve the drawbacks of the prior art.

(Means for Solving the Problems) That is, the method of the present invention is to heat a thermoplastic molded article to at least 120'C! under vacuum or in the presence of an inert gas. It is characterized by heat treatment.

The thermoplastic resin in the present invention is not particularly limited as long as it exhibits plasticity and can be molded by heating, and includes, for example, polyamide, polyester, polyacetal, polyethylene, polystyrene, 4-rivinyl alcohol, polycarbonate, etc. Polyamide, polyester, and polyacetal are particularly preferred.

In addition, the thermoplastic resin used in the present invention includes various general additives used for modification, thermal deterioration inhibitors, weathering agents, nucleating agents, mold release agents, pigments, flame retardants, impact improvers, and reinforcing agents. It may also contain glass fibers, adenous fillers, carbon black, carbon fibers, granular phenolic resins, and the like.

As the molding method in the present invention, known methods such as injection molding, extrusion molding, blow molding film (sheet) molding, and monomer casting can be used.

The heat treatment method in the present invention is characterized in that it is carried out at at least 120° C. in vacuum or in the presence of an inert gas.

Heat treatment in the presence of an active gas, such as in air, causes severe oxidative deterioration due to oxygen, which is an active gas in the air, especially 120
When the weight is 'C' or above, the impact strength decreases significantly.

The degree of vacuum in the vacuum heat treatment method used in the present invention depends on the shape of the molded product,
Although it depends on the thickness, it is generally desirable to have a thickness of 60 mElf or more.

Regarding the heat treatment method in the presence of an inert gas, the inert gas may be nitrogen, carbon dioxide, helium, argon, neon, etc., and any gas that is inert within the heat treatment temperature range may be used. Carbon dioxide gas is preferable.

The heat treatment temperature of the present invention is at least 120°C, preferably 130°C or higher, and more preferably 150°C or higher. When the heat treatment temperature is less than 120° C., the expected improvement in heat resistance cannot be obtained, which is insufficient. In the manufacturing method disclosed in JP-A-59-193930, the operating temperature is as low as 70 to 120°C, and its purpose is to suppress fluctuations in water absorption rate due to the surface coating of molded parts, so it is heat resistant without impairing mechanical properties. A product with improved properties cannot be obtained.

As described above, the present invention is characterized by improving the drawbacks of the prior art and improving heat radiation properties while maintaining mechanical properties. The physical properties were measured using the following methods.

(1) Heat Resistant Temperature The heat deformation temperature of A8TM D-648 under a load of 18.6 & 9/d was defined as the heat resistance temperature.

(2) Tensile strength Measured according to A8TM L)-638.

(3) Bending strength, bending modulus A8TM L)-790'.

(4) Impact strength An Izot impact test according to A8TM 1)-256 was conducted. A notched test piece having a thickness of 1/4 inch was used.

(Example) Example 1 After drying nylon 6 resin (Kanebo Gosei fiMO112L) pellets under reduced pressure at 90°C for 18 hours, the cylinder temperature was 230°C, the mold temperature was 50'C, and the injection pressure was 60#.
Molding was carried out at /d. Each molded body was placed in a pressure-tight sealed container, and after being sufficiently purged with nitrogen at 0.5 g/dG (repeating the nitrogen purging operation 5 times), the respective temperatures were maintained while maintaining the pressure at 0.5 g/dG. The temperature was raised to 24 hours, and heat treatment was performed for 24 hours, and the heat distortion temperature, tensile strength, flexural modulus, and impact strength were measured. In A2 of Table 1, the heat treatment temperature was low and almost no effect of improving heat resistance was observed. In black 3~&5,
Compared to Black 1 before heat treatment, the heat resistance temperature is improved without deteriorating other physical properties.

Table 1 Example 2 Nylon 66.1 resin (BASF A3) pellets
After drying under reduced pressure at 'C for 18 hours, the cylinder temperature was 2.
75℃ 1 mold temperature 50℃ 1 injection pressure 6s Okti/cyl
The molding was done with. The molded bodies were each placed in air at a vacuum level of 550ygHf and 600 fins HP17501ffllH.
Heat treatment was carried out at 150"C for 24 hours under f, and each physical property was measured. An aspirator or a vacuum pump was used to reduce the pressure. As a result, for the heat-treated products in the air of No. 7 in Table 2, the heat resistance was Improves tensile strength, bending strength,
Impact strength is significantly reduced. For black 8~l and 10, the heat resistance is improved and the mechanical properties decrease less.
2 Note) Heat treatment time: 24 hours Example 3 After drying polybutylene lenticule 1-Q resin (Barox, manufactured by GE, USA) pellets under reduced pressure at 110°C for 18 hours, the cylinder temperature was 250°C and the mold temperature was Molding was carried out at 50° C. and an injection pressure of 650 kg/cd. The molded body is heated to a vacuum degree of 75
Place it in a vacuum dryer at 5 Torr for 20 minutes.
Heat treatment was performed at 0° C. for each time, and then each physical property was measured. Table 3 shows the results.

Table 3 (Effects of the invention) According to the method of the present invention, it is possible to provide a thermoplastic resin molded product with improved heat resistance without impairing mechanical properties in a simple manner, and it is possible to provide a thermoplastic resin molded product with improved heat resistance without impairing mechanical properties. It can be used in fields that require heat resistance, such as parts and miscellaneous goods parts.

Claims (7)

[Claims] (1) A method for producing a thermoplastic resin molded article, which comprises heat-treating the thermoplastic resin molded article at at least 120° C. under vacuum or in the presence of an inert gas. (2) The method according to claim 1, wherein the thermoplastic resin is polyamide, polyester, or polyacetal. (3) The method according to claim 1, wherein the degree of vacuum is at least 600 mmHg. (4) The method according to claim 1, wherein the inert gas is nitrogen or carbon dioxide. (5) The method according to claim 1, wherein the heat treatment temperature is at least 130°C. (6) The method according to claim 1 or 5, wherein the heat treatment temperature is at least 150°C. (7) The method according to claim 1, wherein the heat treatment time is at least 30 minutes.