JPS612536A - Glass fiber reinforced plastic screwy molded shape - Google Patents

Abstract

PURPOSE:To obtain a lightweight screwy molded shape having corrosion resistance, chemical resistance and electrical insulating properties and high bonding force by mounting a fluoroplastic layer around glass short fibers exposed to the surface of a thread formed through rolling processing. CONSTITUTION:When a thread is formed to a molding blank made of a thermoplastic resin containing glass short fibers orientated in the direction of a main axis through rolling processing, the projecting sections of the surface of a rolling die are pushed so as to cross glass fibers orientated in the direction of the main axis of a columnar blank. The columnar blank is deformed in response to a die, and glass fibers existing in the vicinity of the surface of the blank are orientated along a formed thread, but one part of glass fibers is broken, and the end section thereof is exposed to the surface of the thread. A fluoroplastic layer is mounted to at least the periphery of the exposed glass fibers, and the effect of reduction of friction is obtained by the fluoroplastic layer. The titled molded shape is reinforced by glass fibers to a high degree and has high strength and high bonding force while the thread is not damaged because the surface of the thread hardly rubs on bonding and the titled molded shape resists repeated bonding, and the lightweight molded shape and corrosion resistance, chemical resistance and electrical insulating properties are acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a plastic thread-shaped molded body, and in particular to a plastic thread-shaped molded body highly reinforced with glass fibers.

(Prior Art) Metal bolts and metal nuts have been known as thread-shaped molded bodies. These strips are manufactured using the rolling method, which has the fastest production speed.

Although metal screw-shaped molded bodies can be produced with high productivity, they have the fatal disadvantage of being heavy and prone to rust. In contrast, plastic screw-shaped molded bodies that are lightweight and have excellent corrosion resistance are produced.For example, plastic bolts are obtained by injection molding of plastic materials.Plastic bolts obtained by injection molding have low strength; However, it has been proposed to use reinforced plastic materials containing glass fibers to increase the strength of plastic bolts.

The strength of the resulting plastic bolt is still insufficient, and the glass fibers exposed on the threaded surface cause too much surface friction, making it impossible for the bolt to perform its original tightening function satisfactorily.

(Object of the invention) An object of the invention is to provide a thread-shaped molded body that is lightweight, has corrosion resistance, chemical resistance, and electrical insulation properties, is highly reinforced with reinforcing fibers, and has high fastening force. . Another object of the present invention is to provide a thread-shaped molded product that has low friction on the thread surface during fastening and can withstand repeated use without damaging the threads. Another object of the present invention is to provide a high-strength plastic thread-shaped molded product by rolling, which is the most economical method for thread processing. Still another object of the present invention is to provide a plastic thread-like molded body that is particularly useful for structural fastening.

(Structure of the Invention) The glass fiber-reinforced plastic screw-shaped molded article of the present invention is a screw-shaped molded article in which threads are formed by rolling on a thermoplastic resin molding material containing short glass fibers oriented in the longitudinal direction. A fluororesin layer is provided at least around the short glass fibers exposed on both surfaces of the screw, thereby achieving the above object. The above objectives are achieved. The term "thread-shaped molded body" as used in the present invention refers to a molded body having screw threads, such as a bolt or nut.

Thermoplastic resins used in the present invention include polyamide, polyethylene, polypropylene, polyethylene fucrate,
Polybutylene phthalate, polyvinyl chloride, polyacetal, polycarbonate.

A general thermoplastic resin such as polyphenylene sulfide, which melts when heated and solidifies when cooled, is used. It goes without saying that there is no need to be limited to the above compounds.

The glass fibers mixed into the thermoplastic resin should have a diameter of 1 to 60 mm in order to be uniformly dispersed in the thermoplastic resin.
1m, length 0.01~1. It's OOm. However, even if the length deviates from this range by a few lines, it will be cut during kneading with the thermoplastic resin, resulting in a length of 0.01 to 1.0 (hl), so it is not particularly limited to the above range. In order to improve the adhesion of the glass fiber to the thermoplastic resin, the surface of the glass fiber may be treated with a silane coupling agent or the like. If the content is less than 10 parts by weight, the strength of the resulting wedge-shaped molded product will be insufficient.

In addition to the above thermoplastic resin, if necessary, a filler, a treatment agent for improving the adhesion between glass fiber and the resin, a flame retardant,
Antioxidants and the like may be added. These and glass fibers are kneaded using an extruder or the like to form a molding material having an appropriate size and shape. For example, when manufacturing a bolt, a cylindrical mold is used to mold the bolt into a cylindrical material. Most of the glass fibers contained in the cylindrical material must be oriented in the longitudinal direction of the cylindrical material.

Specifically, 50% or more of the total glass fibers must be oriented within ±5° with respect to the long axis direction of the cylindrical material, and 60% or more must be oriented. preferable. The degree of orientation of glass fibers can be determined by cutting a cylindrical material into thin sections and observing them under a microscope.

In order to orient the glass fibers in the long axis direction of the cylindrical material, the extrusion molding method is preferably used as the molding method. According to injection molding, it is generally difficult to obtain the desired orientation of the glass fibers because the flow rate of the resin in the mold is high. Also,
Generally, the cross-sectional area of the resin injection gate is smaller than the cross-sectional area of a single cylindrical material mold, so turbulence occurs in the flow of the resin containing glass fibers near the gate q, and as a result, the glass fibers are not properly oriented. In order to obtain the cylindrical material of the present invention by injection molding, it is necessary to make the gate area of the injection molding machine equal to or larger than the cross-sectional area of the cylindrical material. Needless to say, the injection direction at this time is the long axis direction of the cylindrical material.

When molding, if necessary, a hexagonal head, such as a hexagonal head commonly used for bolts, may be integrally formed at one end of the molded product. In extrusion molding, a mold capable of forming this head is connected to the tip of an extruder.

In injection molding, a cylindrical blank mold integrally provided with two heads is used. Alternatively, it is also possible to use a compression molding method in which a molded cylindrical material is cut to an appropriate length, one end of which is reheated, and a separately prepared bolt head is compressed and added. The outer diameter of the cylindrical material is determined by the size of the final bolt. For example, JIS
When obtaining MIO size bolts, a cylindrical material with a diameter of about 9N is prepared in advance.

The rolling method employed in the thread forming of the thread-shaped molded body of the present invention does not need to be special, and a rolling machine commonly used for thread forming of metal threads can be applied as is.

An example of this is a two-roll rolling machine that rotates a pair of rolling rolls whose surfaces are threaded in the same direction and processes a cylindrical material by rolling or extruding the material between them. Round die rolling machine.

A flat die rolling machine or the like may also be used.

When a cylindrical material is run through a rolling machine, threads are formed on the cylindrical material by the threads of the rolling die. At this time, the convex portion on the surface of the rolling die is pressed so as to cross the glass fibers oriented in the longitudinal direction of the cylindrical material. Therefore, the cylindrical material is deformed in accordance with the die shape, and among the glass fibers contained therein, the glass fibers present near the surface of the material are oriented along the formed threads. Some of the glass fibers broke.

Its ends are exposed on both surfaces. As a result, fine cracks (microcranks) centering on the glass fibers occur around the exposed end of the glass fibers, and both surfaces of the screw become rough. For this reason, for example, when a bolt is tightened around a NAND, the friction between the threads and the NAND is large, and repeated tightening causes a so-called "thread seizure" phenomenon, which destroys the threads. Because of the large friction, sufficient axial fastening force (axial force) cannot be obtained.

In the thread-shaped molded article of the present invention, a fluororesin layer is provided at least around the exposed glass or fibers, and this fluororesin layer provides a friction reducing effect. Fluororesin has a perfluoroalkyl group in its main chain, and -COOH, -503, -OH at the molecular terminal.

It is a polymer having a molecular weight of 200 to 50,000 and having polar groups such as -CH=CL and -0COCH=CHz. This fluororesin can be dispersed in water or an organic solvent. A stable high polymer film is formed by spraying or baking a fluorine resin solution onto the surface of the bolt obtained by rolling. Even if the fluororesin film is formed over the entire threaded surface of the bolt.

Alternatively, it may be formed so as to cover the exposed glass fibers on the bolt surface and fill the micro cracks. When a bolt is tightened into a NAND, the threaded surface of the bolt is deformed under pressure, and the exposed glass fibers are compressed with relatively high strength. At this time, if a fluororesin film is formed at least around the exposed glass fibers, the microcracks around the glass fibers are filled with the fluororesin, and this fluororesin acts as a friction reducing material.

Therefore, the friction between the pile and the throat is reduced.

This effect is particularly noticeable when the bolt is repeatedly tightened with high axial forces. When the bolt is tightened with high axial force, the deformation of the threaded thread surface becomes large, but this pressure is preferentially received by the resin filled in the microcracker along with the exposed glass fibers, so the threaded thread surface Friction between the and Nando's is reduced. Therefore, even if the bolt is used repeatedly, the bolt does not seize, and therefore can be used repeatedly over a long period of time without damaging the threads.

Since the friction on the threaded surface is small, the axial force of the bolt also increases.

When the glass fibers of the cylindrical material are rolled in an insufficiently oriented state with an orientation degree of 50% or less in the major axis direction.

The glass fibers are not exposed at all or are completely exposed on the threaded surface. As a result of the entire surface being exposed, the glass fibers fall off the threaded surface. If the glass fibers fall off the threaded surface, large recesses will appear on the threaded surface, making it impossible to obtain sufficient strength. Even if such glass fibers are not properly oriented and/or a fluororesin film is formed on the bolt where the glass fibers have fallen off the threads, the desired thread surface strength and friction reduction effect will not be achieved. Not available at the same time. Therefore.

It cannot withstand repeated use. Even if a fluororesin is coated on a plastic bolt whose threads are formed by injection molding using a composite material of glass fiber and thermoplastic resin, good results cannot be obtained. This is because the glass fibers are not oriented along the threaded thread surface, the end faces of the glass fibers are not exposed on the threaded threaded surface, and there are no microcracks.

The effects of the fluororesin membrane in the present invention can be exhibited only when the fluororesin membrane is formed on a thread-shaped molded body obtained by rolling a material containing glass fibers oriented in the axial direction.

(Example) The present invention will be explained below using examples.

Example 1 A resin containing 100 parts by weight of nylon 6.6 and 43 parts by weight of glass fiber (manufactured by Toshi Co., Ltd.: Amine CM30)
01 G-30> was molded into a round bar with a diameter of 9fi using an extruder. In order to form a cylindrical material with a diameter of 9 nm, the extruder had a flow path with an inner diameter of 9 mm at the tip.

An adapter was connected to connect the tip of the extruder to a cylindrical mold with an inner diameter of 9 mm. The obtained round bar was cut into a length of 10 cm to obtain a cylindrical material. An electron micrograph of the cross section of the cylindrical material was taken, and the number of glass fibers present in directions within ±5° of the axial direction was investigated. The ratio of glass fibers having an orientation degree within ±5° in the axial direction to the total glass fibers (orientation degree of glass fibers) was 95%. A cylindrical material was rolled using a rolling machine to obtain a 1M10 size bolt. The surface of the bolt was coated with tetrafluoroethylene as a fluorine resin to a thickness of 50 μm to obtain a plastic bolt. Twelve plastic bolts were manufactured, four were subjected to a tensile test, and eight were subjected to a repeated tightening test. The results are shown in the table below. Each test was conducted in the following manner. The nuts used in the test were MIO-sized nuts obtained by injection molding using the same resin as the bolts.

Tensile test: Attach a NAND to both ends of the bolt.

The distance between two Nando's was 70 cranes. Bo Autograph the NANDs at both ends of the route. (manufactured by Shimadzu Corporation) at 5 joosu/min. Pull it at a tensile speed and the bolt will break. Measure the maximum load just before breaking It was defined as tensile strength.

Repeated tightening test: 6 when compressed with 250 kg
A spring with a length of 70 inches and an inner diameter of 1211 mm was prepared. I put a bolt through this spring and attached Nandos to both ends of the bolt. Tighten the Nando until the length of the spring is 60m.

After that, the length of the spring becomes 700. Loosen the nut as shown in step 1. Tighten the bolt twice. The pile is crushed and tightening becomes impossible. The number of tightening operations until It was measured.

Example 2 - The inner diameter of the adapter is 8N and the degree of orientation of the glass fiber is 81
% of the cylindrical material was obtained. The results are shown in the table below.

Example 3 The same as Example 1 except that the inner diameter of the adapter was 6.5n and a cylindrical material with a glass fiber orientation of 62% was obtained. The results are shown in the table below.

Comparative Example 1 A resin containing 100 parts by weight of nylon 6.6 and 43 parts by weight of glass fiber (manufactured by Toshi Co., Ltd.: Amilan CM30)
01 G-30) was injection molded to obtain an MIO size bolt with a length of 10 am. A bolt made of 12 wood was manufactured by coating the bolt with fluorine resin in the same manner as in Example 1. This bolt was tested in the same manner as in Example 1. The results are shown in the table below.

Comparative Example 2 The inner diameter of the adapter is 4 mm, and the degree of orientation of the glass fiber is 4.
The procedure was the same as in Example 1 except that a cylindrical material having a weight of 8% was obtained.

Northern comparison ■↓ Same as Example 1 except that the bolt surface was not coated with fluororesin.

(Effects of the Invention) The thread-shaped molded article of the present invention is thus highly reinforced with glass fibers and has high strength and high fastening force. Since there is little friction on the thread surface during fastening, the threads are not damaged and can withstand repeated fastening. It also has the inherent characteristics of plastic, such as being lightweight, corrosion resistant, chemical resistant, and electrically insulating. This thread-shaped molded body is manufactured by rolling, which is the most economical method of threading. The thread-shaped molded body thus obtained is particularly useful for structural fastening.

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Claims (1)

[Claims] 1. A screw-shaped molded article in which a thread is formed by rolling on a thermoplastic resin molded material containing short glass fibers oriented in the longitudinal direction, the short glass fibers being exposed on the surface of the thread. A glass fiber-reinforced plastic thread-shaped molded body provided with a fluororesin layer at least around the periphery.