JPS649485B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to fiber reinforced plastic bolts. Prior Art Metal bolts have been known as bolts for a long time. This is manufactured by the rolling method, which has the fastest production speed for thread processing. Although metal bolts are manufactured with such high productivity, they have the fatal disadvantage of being heavy and prone to rust. On the other hand, plastic bolts that are lightweight and have excellent corrosion resistance are already in practical use. However, plastic materials to which rolling can be applied are limited to non-fiber reinforced plastic materials such as hard vinyl chloride resin. This is because fiber-reinforced plastic materials have high strength and therefore have poor plastic deformability, making it impossible to form threads by rolling, which requires plastic deformability. Even if this is forcibly rolled, the threads will not form a normal triangular shape, and the top of the triangle will become two threads, or cracks will occur in the threads. Therefore, it has low strength and cannot be used as a screw. Bolts obtained by rolling non-fiber reinforced plastic materials have poor strength. Since its tensile strength is at most 4 to 6 kg/mm ² , it cannot withstand use as a bolt that requires strong fastening force. OBJECTS OF THE INVENTION An object of the present invention is to provide a plastic bolt that is lightweight, has corrosion resistance, chemical resistance, and electrical insulation properties, and is highly reinforced with reinforcing fibers. Another object of the present invention is to provide a high-strength plastic bolt by rolling, which is the most economical method for threading. Summary of the Invention The fiber-reinforced plastic bolt of the present invention is a plastic bolt made by rolling a cylindrical material made of thermoplastic resin and having a surface layer and a core layer to form a thread. The thickness of the part is 1/ of the thread height of the rolling die for thread processing.
2 or less and 1/20 or more, and the surface layer is 20% by volume
The above object is achieved by containing reinforcing fibers, and the reinforcing fiber content in the surface layer portion is 5% by volume or more lower than the reinforcing fiber content in the core layer portion. Examples of reinforcing fibers include inorganic fibers such as glass fibers, carbon fibers, boron fibers, and silicon carbide fibers; and organic fibers such as aramid fibers. It is also possible to use a mixture of two or more of these fibers.
There are no particular restrictions on the thickness and length of the fibers, as long as they can be dispersed in the thermoplastic resin molded into a cylindrical material. Usually, its diameter is from several μm to several tens of μm. Regarding the length, when long fibers are used, continuous long fibers are used, and when short fibers are used, chopped fibers cut into pieces of several mm to about 50 mm are used.
These reinforcing fibers are mixed with a thermoplastic resin using a mixer such as a super mixer, and then kneaded and molded using an extruder or the like to form a cylindrical material. Examples of thermoplastic resins include polyamide,
Polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyacetal, polypropylene, noryl, polyvinyl chloride, etc. are used. Needless to say, there is no need to be limited to this. These resins contain fillers, processing agents to improve adhesion to fibers, and
Various additives such as flame retardants and antioxidants may be mixed. As shown in FIG. 1, the cylindrical material 1 has a surface layer 1
1 and a core layer portion 12. The thickness of the surface layer portion 11 is 1/2 or less and 1/20 or more of the thread height of a rolling die used for threading thereon. The content of the reinforcing fibers 13 in the surface layer portion 11 is 20% by volume or less, and is lower than the content of the reinforcing fibers 13 in the core layer portion 12 by 5% by volume or more. Since the fiber content of the surface layer portion 11 is lower than the fiber content of the core layer portion 12, the deformability of the surface layer portion 11 is greater than the deformability of the core layer portion 12. As a result, as shown in FIG. 2, when the rolling dies 21 and 22 of the continuous forming machine 2 are pressed against the cylindrical material 1 and the material 1 is deformed, the surface layer 11 has priority over the core layer 12. It can be transformed by Since the fiber content of the surface layer portion 11 is lower than that of the core layer portion 12, peeling phenomenon at the interface between the fibers and the resin during deformation is unlikely to occur or does not occur at all. Therefore, the thread surface layer after molding has almost no difference in physical properties such as durability from before molding. Since the stretching effect is exhibited, the strength properties and the like are rather improved. However, if the fiber content in the surface layer exceeds the above-mentioned 20% by volume, the deformability of the surface layer becomes too small, and a peeling phenomenon occurs at the fiber interface during rolling processing, causing cracks and cracks. As a result, the resulting screw thread has low strength and cannot be put to practical use. Having a different fiber content between the surface layer and the core layer is very effective in improving the rolling properties, but if the difference is less than 5% by volume, the rolling properties become extremely poor. The types and forms of the resins constituting the surface layer and the core layer and the reinforcing fibers contained therein may be the same or different. However, regarding the fibers, it is preferable that short fibers having a length of several mm or less are dispersed in the surface layer. If long fibers are used in the surface layer, one fiber will be placed over several threads during the thread forming process, and as a result, the fibers will follow the thread shape. This is because it becomes difficult to form a good thread. Note that another high-strength core material such as metal may be further provided in the core layer portion. The rolling method used in the present invention does not need to be special, and rolling machines such as a round die rolling machine and a flat die rolling machine that are commonly used for thread forming of metal screws can be applied. The plastic bolt of the present invention is manufactured, for example, as follows: First, a resin such as polyamide and a chop fiber such as glass fiber of a desired diameter and length are separated into a surface layer portion and a core layer portion. Each is blended. The fiber-dispersed resin for the core layer is supplied to the supply port 31 of the extrusion molding machine 3 shown in FIG. 3, and is melt-kneaded by the extruder screw 32. Then, it is supplied to a crosshead die 4 located at the tip of the extruder 3. On the other hand,
A resin for the surface layer containing or not containing fibers is supplied to the supply port 51 of the extruder 5, and similarly,
The mixture is melted and kneaded by the screw 52 and supplied to the crosshead die 4. Both layer resins form a double structure in which the surface layer resin wraps the core layer resin, and are guided from the crosshead die 4 to the sizing die 6. Here, it is cooled and solidified to form a cylindrical material 1. The obtained raw material 1 is cut into a predetermined length and passed through a rolling machine 2. The rolling dies 21 and 22 are pressed against the material and rotated to obtain a plastic bolt with a desired thread. Examples The present invention will be described below with reference to examples. Example 1 A polyamide containing no reinforcing fibers (Amiran Nylon 66 manufactured by Toray Industries, Inc.) was used as the resin for the surface layer.
Polyad resin containing 50% by volume of reinforcing fibers (glass fibers with a diameter of 13 mm and a tip of 3 mm) was used as the resin for the core layer. The diameter of the obtained cylindrical material was 9 mm, and the thickness of its surface layer was 0.6 mm. This material was cut into lengths of 8 cm and rolled to obtain bolts. The rolling die used was for M10 bolts with a thread height of 1.25 mm. The presence or absence of cracks on the surface of the threads of the obtained bolts and the state of bulging of the threads were visually observed. The results are shown in the table below. At the same time, nuts were attached to both ends of the bolt and a tensile test was conducted in accordance with JISB 1051 to measure its breaking strength. The average value of the five samples is shown in the table below. The breaking strength includes not only the maximum tensile load at which the bolt body is about to break, but also the maximum tensile load at which the thread is about to break and the bolt comes out from the nut. Example 2 Everything was the same as in Example 1 except that the polyamide resin for the surface layer contained 13% by volume of glass fibers as reinforcing fibers. Example 3 Everything was the same as in Example 1 except that the polyamide resin for the surface layer contained 20% by volume of glass fibers as reinforcing fibers. Example 4 Everything is the same as in Example 1 except that the polyamide resins for the surface layer portion and the core layer portion contain glass fibers as reinforcing fibers in an amount of 20% by volume and 25% by volume, respectively. Example 5 Everything was the same as in Example 1 except that the thickness of the surface layer of the obtained cylindrical material was 0.3 mm. Example 6 Everything is the same as in Example 1 except that the polyamide resin for the surface layer contains 20% by volume of glass fibers as reinforcing fibers, and the thickness of the surface layer of the obtained cylindrical material is 0.3 mm. . Example 7 Everything was the same as in Example 1 except that the thickness of the surface layer of the obtained cylindrical material was 0.07 mm. Example 8 The polyamide resins for the surface layer and the core layer contain 20% by volume and 50% by volume of glass fiber as reinforcing fibers, respectively, and the thickness of the surface layer of the resulting cylindrical material is 0.07 mm. Everything else is the same as in Example 1. Example 9 The same as Example 8 except that the content of glass fiber in the core layer was 25% by volume. Comparative Example 1 All the same as Example 1 except that the polyamide resin for the surface layer and the core layer each contained 20% by volume of glass fiber, and the thickness of the surface layer of the obtained cylindrical material was 0.6 mm. It's the same. Comparative Example 2 Everything is the same as Comparative Example 1 except that the polyamide of the core layer resin contains 15% by volume of glass fiber. Comparative Example 3 Everything is the same as Comparative Example 1 except that the surface layer and core layer resins contain glass fibers at 25% by volume and 50% by volume, respectively. Comparative Example 4 The same as Example 1 except that the thickness of the surface layer of the obtained cylindrical material was 0.05 mm. Comparative Example 5 Everything is the same as Comparative Example 4 except that the resin for the surface layer contains 20% by volume of glass fiber. Comparative Example 6 Everything was the same as in Example 1 except that the thickness of the surface layer of the obtained cylindrical material was 0.8 mm. Comparative Example 7 Everything is the same as Comparative Example 6 except that the resin for the surface layer contains 20% by volume of glass fiber.

[Table] Effects of the Invention According to the present invention, it is extremely easy to form threads by rolling on a plastic material highly reinforced with reinforcing fibers. Since thread forming by rolling is highly productive, bolts can be produced economically. Moreover, the thread shape of the obtained plastic bolt is good, and the top of the thread does not form two threads or crack or break. Furthermore, the bolt has all the characteristics inherent to fiber-reinforced plastic materials, such as high strength, light weight, and excellent corrosion resistance.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of an embodiment of a cylindrical material according to the present invention, and FIG. 2 is a front view of essential parts showing an example of a rolling machine used when manufacturing the bolt of the present invention.
FIG. 3 is a front cross-sectional view of essential parts showing an example of an extruder for molding the cylindrical material of the present invention. 1... Cylindrical material, 2... Rolling machine, 3, 5...
Extruder, 4...Crosshead die, 6...Sizing die, 11...Surface layer part, 12...Core layer part, 1
3... Reinforcing fiber, 21, 22... Rolling die, 3
2,52... Screw.

Claims (1)

[Claims] 1 A plastic bolt made by rolling a cylindrical material made of thermoplastic resin and having a surface layer and a core layer to form a thread. The thread height of the rolling die is 1/2 or less and 1/20 or more, the surface layer contains 20% or less reinforcing fiber by volume, and the reinforcing fiber content in the surface layer is equal to that of the core layer. A fiber-reinforced plastic bolt characterized by having a reinforcing fiber content less than 5% by volume.