JPH04153228A - Screw made from resin - Google Patents

Abstract

PURPOSE:To improve workability and shear strength by impregnating strands obtd. by aligning PVA fibers with a specific liq. resin compsn., forming the impregnated strands into a rod, and curing and working the rod. CONSTITUTION:A liq. resin having an elastic modules of at least 150kg/mm<2> after being cured (e.g. an epoxy resin) is compounded with a necessary amt. of a fibrous material cut to 2mm length or lower, such as glass, wholly arom. polyester aramid or high-tensible PVA fibers, giving a liq. resin compsn. Strands obtd. by aligning reinforcing fibers comprising PVA fibers having a tensible strength 15g/dr or higher and a Young's modulus of 300g/dr or higher are impregnated with the resin compsn., caused to pass through a die to remove excess compsn. from the impregnated strands to a fiber content of 60 vol.% or higher, and thereby molded simultaneously into a rod. The rod is cured and worked to give a screw.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a resin screw reinforced with high-strength polyvinyl alcohol fibers.

[Conventional technology]

Conventionally, glass 1, carbon fiber, aramid fiber, or other fiber strands, yarns, tapes, or string-like materials knitted from yarn bundles have been used as reinforcement materials, and thermosetting resins such as epochino resin or ester resins have been used as the fiber reinforcement material. Regarding synthetic resin screws processed from fiber-reinforced synthetic resin moldings obtained by impregnating thermoplastic resins such as
There are many proposals such as JP-A No. 1022, JP-A-63-224930, and JP-A-1-310941. and “Material J March 1990, Vol. 39, No. 438, No. 26
Pages 6 to 270 introduce center row hinges and glass fiber FRP bolts with blades.

[Problem to be solved by the invention]

Conventional reinforcing fibers for synthetic resin screws include long fibers, glass fibers and carbon fibers having a tensile modulus of 6,000 to 120,000 kg/am' and a tensile strength of 100 to 500 kg/+un''. Synthetic resin molded products reinforced with high fiber strands or yarn tape are hard, brittle, and difficult to cut.In addition, synthetic resin molded products reinforced with aramid fibers have high toughness and are difficult to cut and are brittle. Therefore, it is difficult to obtain a good cutting surface, and the adhesion between fiber and resin is not good.
There are problems such as difficulty in obtaining products with high shear fracture strength. The present invention provides a fiber-reinforced resin screw that has excellent workability and high shear fracture strength.

[Means to solve the problem]

The present invention has a flexural modulus of 150 kg/a after solidification or hardening.
m' or more, and 60% by volume or more of polyvinyl alcohol synthetic fibers having a tensile strength of 15 g/dr or more and a Young's modulus of 300 g/dr or more, and 60% or more of the polyvinyl alcohol synthetic fibers are aligned. This is a resin screw characterized by the fact that it is That is, the resin screw of the present invention has a tensile strength of 80 kg.
/am' or more, tensile modulus is 2000kg/am' or more, flexural modulus is 150-4000kg/■lI! in,
In addition, the resin material has no buckling point due to the compression shearing method and has a shear stress of 2 kg/gum' or more using the tensile shearing method. The fiber used as a reinforcing material in the present invention is a high-strength polyvinyl alcohol fiber having a cutting strength of 15 g/denier or more and a cutting elongation of 2.5 to 6%. If the physical properties of the fibers are outside the above range, the machinability and processability will be poor and a good finish will not be obtained, or the physical properties of the screw, especially the shear fracture strength, will be poor. The reinforcing fibers used are strands, twisted yarns, braided cords, etc. drawn in one direction to form a strand. The thickness of this reinforcing fiber strand is appropriately set depending on the size of the screw. Further, by making the polyvinyl alcohol fibers used in the present invention flat in cross section with a cross-sectional solidity of 70% or less, a screw having even better shear fracture strength can be obtained. (F: cross-sectional area, B: wide width in cross-sectional area) In addition, the synthetic resin forming the thread is selected from thermoplastic resins or thermosetting resins, and has a bending elastic modulus of 150 kg/mm' or more, preferably bending Synthetic resin with an elastic modulus of 180 to 1,800 kg/mm', such as epoxy resin (flexural modulus of 700 k
g/m+n'), unsaturated polyester resin (800
kg/mm' or more), #V curable resins such as hinyl ester resins, phenol resins, melamine resins, urea resins, polyethylene terephthalate resins (700 kg or more)
/+am"), methacrylic ester resins, thermoplastic polyesters, polyphenylene oxide, polycarbonate, nylon-66, nylon-MXD6, and other thermoplastic resins (200 kg/am" or more). If this bending modulus is small, machinability and thread shape stability are poor. On the other hand, if the bending modulus is too large, the resin itself becomes brittle, resulting in damage to the threads due to impact and loss of toughness as a screw without losing shear resistance. Further, the resin may be used as a resin composition in which short fibers of 2 cm or less, such as glass fibers, wholly aromatic polyester fibers, aramid fibers, and high-strength polyvinyl alcohol fibers, are added as necessary. Next, in the Hime-zukuri method for synthetic resin moldings, in the case of thermosetting resins, strands of reinforcing fibers are crushed in a liquid material of a curable resin composition or its initial condensate, and passed through a molding die. Excess resin liquid is removed to make the fiber content 60% by volume or more, and after molding, heat treatment is performed in a heating zone of at least 100°C to harden the resin to obtain a rod-shaped synthetic resin molded body. The arrangement of fibers in the molded body affects the tensile strength, tensile modulus, bending modulus, and shearing force of the FRP rod. Therefore, unless 60% or more of the fibers in the resin are uniformly arranged in the length direction, the resin will not exhibit its physical properties. Next, the rod-shaped synthetic resin molded body is cut to form a threaded groove, or the synthetic resin has deformability and is molded with a thread mold to form a threaded groove. The resulting synthetic resin dough is subjected to finishing treatments such as heat treatment, if necessary, and then manufactured into a product. The performance of resin screws is that they do not rust compared to metal ones.
It has the advantages of excellent chemical resistance to acids, alkalis, salts, etc., and is light and easy to handle. Mechanical performance must be high, with a tensile strength of 80 kg/l+a' or more, and a tensile modulus of 200
0kg/mm' or more preferably 3000kg/■"
The above is necessary. Furthermore, the bending elastic modulus is 150 to 6000.
Does it need to be kg/am'? 150kg/+++
If it is less than n', it will be too flexible and will creep and will not function as a screw, and if it exceeds 4,000 kg/t2, it will become brittle and unfavorable in terms of handling. The next important thing is that the tensile shear stress is 2 kg/am' or more. This means that stress is applied to the surface of the bolt and the stress must be transmitted evenly to the center.
If this shearing force is less than 2 kg/mm, interfacial separation between the fiber and resin will occur and the stress in the nut part will not be transmitted, which is not preferable. If the screws were used, interfacial peeling between the resin and the fibers would occur in the container, resulting in a buckling phenomenon.The present invention is a highly tough FRP screw that does not have these buckling points.

[For use]

According to the present invention, a molded body made of a single strand of polyvinyl alcohol fibers having specific fiber properties and a synthetic resin having a specific flexural modulus can approximate the cutting characteristics of the fibers and the synthetic resin. In addition to improving the cutting ability of the screw, it is possible to obtain a resin screw with high toughness and excellent shear fracture strength due to the good affinity between the fiber and the resin.

【Example】

Next, embodiments of the present invention will be explained with specific examples. Note that parts and percentages in the examples refer to volumes unless otherwise specified. a) The bending elastic modulus of the resin and screw used is JTSK -
Measured according to 6911. b) The tensile modulus of the obtained screw is JIS-711
Measured according to 3. C) Method for Measuring Shear Fracture Strength An example of the measuring method is shown in FIG. 1, and will be explained below with reference to this figure.・Short beam method distance between fulcrums and specimen length are each 3 times the rod diameter,
This is a method in which the final strength is measured by three-point loading using a stress-deflection curve of 18 mm and 24 n+m. At the final point, the shear force can be determined from the stress and cross-sectional area at the moment when the buckling point occurs. - Compression shear method Make cuts with a width of 1 mm up to 1/2 of the rod diameter in opposite and symmetrical directions. The inner distance of the notch is 167 times the diameter of the specimen, and the total length of the specimen is 4 times the diameter of the rod.
two. That is, the shearing distance is 10+nm, the compression distance is 24mm,
Both end surfaces of the sample lot were mirror-finished, and the buckling strength was determined from the load-strain curve when a compressive load P was applied from both ends, and the compressive shearing force was determined from the stress cross-sectional area. - For the tensile shearing method, make cuts with a width of 1 mm up to 1/2 of the lot diameter in opposite directions. The inner distance of the notch was set to 2.0 times the diameter of the specimen, that is, 12 mm, and the load P was determined while pulling at a constant speed to attach it to the fixing jig at both ends, and the tensile shear force was obtained by dividing it by the shear cross-sectional area. . Examples 1 to 3 High strength polyvinyl alcohol fiber (cutting strength 17.3
g/dr, cutting elongation 4.9%, hereinafter referred to as "rPVA fiber") 176 filament yarns of 1800 dr - 1000 fil were combined to form a strand. On the other hand, the following three types of resin compositions or resins were prepared as synthetic resins to be applied to the fibers. (1) Epoxy resin composition (referred to as "EPX") Cured resin tensile strength 590 kg/a11', cutting elongation 3.2%
, bending strength 920 kg/cm', bending modulus 730 kg
/mm" (2) Unsaturated polyester resin composition ("tJ
The tensile strength of the cured resin is 455 kg/cm', and the cutting elongation is 3.
0%, bending strength 825 kg/cm", bending modulus 105
0 kg/mm' (3) Polyamide resin (referred to as "PAM") Resin tensile strength 810 kg/cm', cutting elongation 48%, bending strength 1100 kg/cm', flexural modulus 270 kg, /+
nm' Next, the epoxy resin composition and the unsaturated polyester resin composition are prepared by dipping the aligned fiber strands in a resin impregnation tank, and then drawing them into a round bar through a molding nozzle heated to 110°C. A round bar with a diameter of 6.2 mm was obtained by curing in a room at 120° C. for 7 hours. In addition, the polyamide resin is made by using a melt extruder at a melting zone temperature of 275°C and a molding die temperature of 280°C, and the molten polyamide resin is incorporated into aligned fiber strands, which are taken out and cooled to form round bars with a diameter of 6.2 mm. Obtained. These round bars were threaded with a die to make bolts with a diameter of 6 mm. Comparative Example 1 Instead of the polyvinyl alcohol fiber of Example 1, a glass fiber strand made of 11 glass fiber rovings was used and impregnated with an epoxy resin composition, and the diameter was 7.5 mm in the same manner as in Example 1. I made a 2mm bolt. The physical properties of the obtained 1 nvolt were measured and shown in Table 1. (Hereinafter referred to as margins) In other words, the products of Examples had excellent shear fracture strength and also had a good cutting finish. In contrast, the product of the comparative example suffered shear failure at a relatively low load. Observation of this fractured part revealed that the fibers and resin had separated and no integral molded body was formed.

【Effect of the invention】

The present invention uses strands of high-strength polyvinyl alcohol fibers as reinforcing fibers, and molds them with a synthetic resin having a specific bending elastic modulus, resulting in a synthetic resin molding that has a high affinity between the fibers and the resin. A synthetic resin screw with high toughness and excellent shear fracture strength can be obtained. Furthermore, it is possible to approximate the cutting characteristics of fibers and synthetic resins, resulting in good thread machinability and synthetic resin screws with a good finish from small screws to large screws.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of the method for measuring shear fracture strength used in the present invention. Diagram

Claims (1)

[Claims] It consists of a resin with a flexural modulus of 150 kg/mm^2 or more after solidification or hardening, and 60 volume % or more of polyvinyl alcohol-based synthetic fibers with a tensile strength of 15 g/dr or more and a Young's modulus of 300 g/dr or more. A resin screw characterized in that 60% or more of polyvinyl alcohol-based synthetic fibers are aligned.