JPH0219776B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a reinforced plastic screw-shaped molded article mainly composed of a crosslinked polymer and a method for producing the same. (Prior art) Examples of thread-shaped molded bodies such as bolts include:
Metal bolts have been known for a long time. This is manufactured by the rolling method, which has the fastest production speed for thread processing. Although metal bolts are made with high productivity, they have the fatal disadvantage of being heavy and prone to rust. In contrast, bolts are being produced that are made from plastic, which is lightweight and has excellent corrosion resistance. However, bolts made by injection molding of thermoplastic resins such as vinyl chloride and polycarbonate generally have low strength and can only be used for specific purposes such as decoration. Among thermoplastic resins, hard vinyl chloride, polyamide, and the like are relatively hard. Especially nylon 6, nylon 6.6,
Polyamides such as nylon MXD6 are engineering plastics with excellent properties such as toughness, self-lubricating properties, oil resistance, and chemical resistance. When reinforcing fibers such as glass fibers are added, even better reinforcing effects can be achieved. Therefore, a high quality bolt with the above properties is obtained. However, polyamide has high water absorption and is
When it comes into contact with a base, the hydrogen bonds between amide bonds are broken and the strength is significantly reduced. Dimensions also change.
Therefore, thread-shaped molded bodies made using polyamide cannot be said to have sufficient dimensional accuracy and strength.
The following measures can be considered to improve these properties of polyamide. Mix hydrophobic resin. A hydrophobic film such as Teflon or polymethyl methacrylate is formed on the surface of polyamide. Increases crystallinity of polyamide. Even if these measures are taken, the polyamide and the hydrophobic polymer are not mixed completely and uniformly, so an interface is formed between the two, resulting in a decrease in mechanical strength. No improvement in water resistance was observed either. In the method described above, the adhesion between the hydrophobic resin coating and the polyamide base material is poor, and the film easily peels off. Although the above method has some effect on both the strength and water absorption of the material, it is still insufficient when producing thread-shaped molded bodies such as bolts. (Objective of the Invention) An object of the present invention is to provide a plastic screw-shaped molded article that is lightweight, has corrosion resistance, chemical resistance, electrical insulation properties, and high strength, and a method for manufacturing the same. Another object of the present invention is to provide a plastic screw-shaped molded article whose strength does not decrease and whose dimensions do not change even when it comes into contact with water, acids, bases, etc., and a method for producing the same. (Structure of the Invention) The plastic thread-shaped molded article of the present invention is mainly composed of a resin composition containing a crosslinked polymer obtained from a polyamide and a collapsible polymer, thereby achieving the above object. Furthermore, the method for producing a plastic screw-shaped molded body of the present invention includes a step of molding a plastic material mainly containing polyamide and a collapsible polymer to obtain a molded body, and a step of irradiating the molded body with radiation, This achieves the above objective. The term "thread-shaped molded body" as used in the present invention refers to a molded body having threads made of a resin composition obtained by irradiating a plastic molded body with radiation and crosslinking the molded body. Specifically, Boruto and Natsuto. Polyamides used in the present invention include resins having an amide bond in the main chain, such as nylon 6, nylon 6.6, nylon 12, and nylon MXD6, which are commonly used as thermoplastic resins. The collapsible polymer of the present invention is a polymer that has the property that the carbon-carbon bonds in the main chain are severed when irradiated with radioactivity. It is preferred that the G-value for collapse of the collapsible polymer exceeds the G-value for crosslinking. Such degradable polymers include poly-4-fluoroethylene, poly-4
- Examples include fluorinated resins such as fluorinated ethylene/ethylene copolymer, polyvinylidene fluoride, polypropylene, and polyisobutylene. Two or more types of disintegrating polymers and polyamides can also be used as a mixture. The disintegrable polymer is used in an amount of 1 to 50 parts by weight, preferably 1 to 50 parts by weight, based on 100 parts by weight of the polyamide.
It is contained in a proportion of 10 to 30 parts by weight. If it is too small, the resulting molded product will have poor water resistance, and if it is too large, its strength will be reduced. The above-mentioned polyamide and collapsible polymer are uniformly mixed in the form of pellets or powder, and if necessary, inorganic reinforcing fibers are added. Examples of the inorganic reinforcing fiber include glass fiber, carbon fiber, boron fiber, and silicon carbide fiber. It is also possible to use a mixture of two or more of these fibers. There are no particular restrictions on the length of the fibers, as long as they can be sufficiently kneaded and dispersed with the polyamide. Furthermore, various additives such as a filler, a treatment agent for improving adhesion to fibers, a flame retardant, and an antioxidant may be added as necessary. The plastic material thus prepared is formed into a threaded body such as a bolt or nut by suitable means. The plastic material is formed into bolts using conventional molding machines, such as injection molding or extrusion molding of bolt shapes. Alternatively, it is formed into a cylindrical material using an injection molding machine or an extrusion molding machine that molds a simple cylindrical material, and the obtained cylindrical material is rolled to form a thread. The rolling method does not need to be special, and rolling machines such as a round die rolling machine and a flat die rolling machine, which are commonly used for forming the threads of metal screws, can be applied. When this threaded molded article is irradiated with radiation, the main chain of the collapsible polymer is cut, and a crosslinking reaction similarly proceeds between the collapsible polymer and the polyamide. Since the amide groups of the polyamide are crosslinked by this reaction, the water absorption of the resulting thread-shaped molded resin is suppressed. Furthermore, since the resin has a network structure, the mechanical strength of the resulting thread-shaped molded product is not impaired. As the radiation, gamma rays and electron beams are preferable. (Example) The present invention will be explained below with reference to Examples. Example 1 100 parts by weight of nylon 6.6 (Aramin manufactured by Toray Industries, Inc.) as a polyamide, 1 part by weight of 4-fluorinated ethylene/ethylene copolymer as a degradable polymer, and 101 parts by weight of glass fiber were melted and mixed. A cylindrical material with a diameter of 8.7 mm was molded using an extrusion molding machine. This was rolled to form a thread and then irradiated with 2.5 Mrad of gamma rays. The tensile strength of the obtained bolt was measured. Put this bolt in 60℃ hot water 168
The water absorption rate was calculated from the change in weight after soaking for a period of time. Furthermore, the tensile strength after immersion was measured. The respective values are shown in Table 1. Example 2 The same as Example 1 except that 5 parts by weight of the 4-fluorinated ethylene/ethylene copolymer and 105 parts by weight of glass fiber were used. Example 3 The same as Example 1 except that 10 parts by weight of the 4-fluorinated ethylene/ethylene copolymer and 110 parts by weight of glass fiber were used. Example 4 The same as Example 1 except that 20 parts by weight of the 4-fluorinated ethylene/ethylene copolymer and 120 parts by weight of glass fiber were used. Example 5 The same as Example 1 except that 30 parts by weight of the 4-fluorinated ethylene/ethylene copolymer and 130 parts by weight of glass fiber were used. Example 6 The same as Example 1 except that 50 parts by weight of the 4-fluorinated ethylene/ethylene copolymer and 150 parts by weight of glass fiber were used. Example 7 Same as Example 4 except that vinylidene fluoride was used as the degradable polymer. Example 8 Same as Example 4 except that polyisobutylene was used as the degradable polymer. Example 9 Same as Example 4 except that polypropylene was used as the degradable polymer. Comparative Example 1 Same as Example 1 except that 4-fluorinated ethylene/ethylene copolymer was not used and 100 parts by weight of glass fiber was used. The results are shown in Table 2. The results of the comparative examples are all shown in Table 2 below. Comparative Example 2 Same as Example 1 except that 60 parts by weight of 4-fluorinated ethylene/ethylene copolymer and 160 parts by weight of glass fiber were used. Comparative Example 3 Same as Example 1 except that γ-rays were not irradiated. Comparative Example 4 Same as Example 2 except that γ-rays were not irradiated. Comparative Example 5 Same as Example 3 except that γ-rays were not irradiated. Comparative Example 6 Same as Example 4 except that γ-rays were not irradiated. Comparative Example 7 Same as Example 5 except that γ-rays were not irradiated. Comparative Example 8 Same as Example 6 except that γ-rays were not irradiated.

【table】

【table】

[Table] (Effects of the Invention) According to the present invention, since the polyamide and the collapsible polymer are crosslinked by radiation irradiation, the hygroscopicity of the resulting thread-shaped molded product is extremely low. The same applies to acids and alkalis. Therefore, even if this molded body comes into contact with water, acid, or alkali, the strength will not decrease and no dimensional change will occur. The thread-shaped molded body has all the characteristics that plastics generally have, such as being lightweight and highly corrosion resistant. This molded body can also be obtained by thread rolling, which is the most economical method for thread processing.

Claims (1)

[Scope of Claims] 1. A plastic screw-shaped molded article made of a resin composition containing a crosslinked polymer obtained mainly from polyamide and a collapsible polymer. 2. The molded article according to claim 1, wherein the collapsible polymer is contained in a proportion of 1 to 50 parts by weight based on 100 parts by weight of the polyamide. 3. The molded article according to claim 1, wherein the resin composition contains inorganic reinforcing fibers. 4. The molded body according to claim 1, wherein the threaded molded body is a bolt or a nut. 5. A method for producing a plastic screw-shaped molded body, which includes the steps of molding a plastic material mainly containing polyamide and a collapsible polymer to obtain a molded body, and irradiating the molded body with radiation. 6. The method according to claim 5, wherein the degradable polymer is contained in a proportion of 1 to 50 parts by weight based on 100 parts by weight of the polyamide. 7. The method according to claim 5, wherein the resin composition contains inorganic reinforcing fibers. 8. The method according to claim 5, wherein the thread-shaped molded body is a bolt or a nut.