JPH06114859A - Production of bolt - Google Patents

Abstract

PURPOSE:To easily produce a lightweight tough bolt made of FRP having high strength and enhanced in the shearing strength of its screw thread in stable quality. CONSTITUTION:A mixture consisting of long reinforcing fibers and thermoplastic polymer fibers arranged in one direction is used as a core material 3 and the outer layer part of the core material is surrounded by a cylindrical structure of a composite sheet wherein thermoplastic polymer fibers are infiltrated in the interstices of long reinforcing fibers constituting a planer aggregate to be integrally entangled with the long reinforcing fibers to form a preform. This preform is molded into a rod shape and a screw thread 2 is formed to the surface layer of the molded rod using a mold to produce a bolt 1 made of FRP.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bolt made of a thermoplastic resin reinforced with long fibers.

[0002]

2. Description of the Related Art Fiber-reinforced synthetic resin bolts (hereinafter referred to as F
RP bolts) are lighter in weight and have better corrosion resistance than conventional metal bolts, and have recently been put to practical use in various fields as various machine parts. Several proposals have already been made for the method of manufacturing FRP bolts, for example, JP-A-59-185.
Japanese Laid-Open Patent Publication No. 625 proposes a method in which a columnar material is molded from a mixture of reinforcing short fibers and a thermoplastic resin, and the surface layer portion thereof is screwed by a rolling method. However, when the FRP bolt is manufactured by this method, the fiber length of the reinforcing short fiber becomes extremely short in the step of forming the columnar material, so that there is a problem that the strength of the screw thread is low.

Further, JP-A-59-158223 discloses a method in which a reinforcing rod and a thermosetting resin are used to form a round bar by a pultrusion method and the round bar is threaded with a die or a lathe. It is disclosed. However, in this method, the reinforcing long fibers used are cut at the thread portion when machining the round bar, so there is no connection of the reinforcing fiber between the shaft part of the bolt and the thread, and the thread However, there was a drawback that only bolts with extremely low shear strength could be obtained.
Further, in this excavation, since threading is performed by machining, there is a problem that productivity of bolt manufacturing is low.

Further, in Japanese Patent Application Laid-Open No. 59-148635, a molding intermediate having a circular cross section is prepared by impregnating a reinforcing long fiber bundle aligned in one direction with a thermosetting resin. A method has been proposed in which a resin is cured after being placed in a mold and shaped. In the bolt manufactured by this method, the reinforcing long fibers are not cut, but since the reinforcing long fibers are arranged substantially only in the axial direction of the bolt or a direction close to it, the circumferential direction of the screw thread is Has a problem that the screw thread is likely to be chipped due to impact, and the reinforcing long fibers are not connected between the shaft portion and the screw thread, so that delamination between the shaft portion and the screw thread portion occurs.

As a method for solving various problems of these methods, Japanese Patent Laid-Open No. 1-259932 discloses forming an intermediate body composed of a three-dimensional braid of reinforcing long fibers and various matrices and having a thread groove. A method of manufacturing a bolt has been proposed, which is characterized by forming a thread on the intermediate body using a pressing die and then hardening the thread. The bolt manufactured by this method has a feature that the shear strength of the thread portion is high because the reinforcing long fibers are connected between the shaft portion and the screw thread, but on the other hand, it is used in this method. Since all of the reinforcing filaments are components of the three-dimensional braid,
The proportion of reinforcing long fibers oriented in the axial direction decreases,
There is a problem that the tensile strength of the shaft portion is reduced, and as a result, the bending strength of the bolt is reduced. Further, in this method, it is necessary to arrange the three-dimensional braiding of the reinforcing long fibers over the whole including the central portion of the intermediate body, and therefore, the entire amount of the reinforcing long fibers to be used must be knitted into the three-dimensional braid. Therefore, there is a problem in that the manufacturing cost of the preform becomes expensive. When a thermoplastic resin is used as the matrix, if the prepreg in which the reinforcing resin is coated with the thermoplastic resin by the wire coating method as disclosed in JP-A 1-259932 is used, the matrix resin is reinforced. Since it does not enter inside the long fiber bundle for use in advance, the fact that the molten resin has a high viscosity,
The resin impregnability into the reinforcing long fiber bundle during molding is poor, and in order to obtain a molded product with a uniform structure, it is necessary to make molding conditions such as temperature and pressure more severe than necessary, and as a result, There are problems that the thermal decomposition of the thermoplastic resin is promoted, that the content of the reinforcing long fibers of the obtained molded product fluctuates locally, and that voids occur in the molded product.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and is a tough FR which is lightweight, has high tensile strength and bending strength, and has high thread shear strength.
It is intended to provide a method for easily and reproducibly manufacturing a P bolt.

[0007]

According to the method of the present invention, a core material is a mixture of unidirectionally aligned reinforcing long fibers and thermoplastic polymer fibers, and the outside thereof is unidirectionally aligned. A composite sheet composed of a planar fiber assembly composed of reinforcing long fibers and a thermoplastic polymer fiber sheet, wherein the thermoplastic polymer fibers are intercalated between the reinforcing long fibers forming the planar fiber assembly. Surrounding with a tubular structure of a composite sheet for fiber-reinforced material that is entangled and integrated, form the obtained multilayer structure into a rod-shaped molded product, and then form a screw thread using a screw forming mold. It is characterized by.

The construction of the thermoplastic resin prepreg (composite sheet) used for knitting or weaving the tubular tissue body in the method of the present invention is described in detail in JP-A-3-47713. An example of the method for producing the composite sheet of the preferred embodiment is as follows. First, the thermoplastic polymer fibers are cut into a predetermined length, the obtained short fibers are dispersed in water, and the slurry is made into paper to form a short fiber web in which the short fibers are randomly oriented. Next, separately prepare a sheet in which reinforcing long fibers are aligned in one direction on a flat surface, and laminate a thermoplastic polymer short fiber web on the upper surface and the lower surface to obtain a reinforcing long fiber sheet aligned in one direction. Sandwich like a sandwich. Then, a high-pressure water jet is applied from the upper surface and the lower surface of the laminated sheet to cause the short fibers constituting the short fiber web to enter the reinforcing long fiber sheet, whereby the reinforcing long fibers and the thermoplastic polymer short fibers are entangled. Obtain an integrated composite sheet.

Glass fibers, carbon fibers, aramid fibers, silicon carbide fibers and the like can be used as the reinforcing long fibers constituting the composite sheet, and these fibers can be used alone or in combination. Further, the web of thermoplastic polymer fibers constituting the composite sheet is a nonwoven fabric in which long fibers are arranged in a swirl shape, even if the short fibers are arranged randomly or in one direction or in multiple directions. Although it may exist, it is preferable to use a short fiber non-woven fabric because it is easy to be entangled and integrated with the reinforcing long fiber sheet. When a short fiber non-woven fabric is used, the fiber length is 1 to 100 m in view of the ease of entanglement and integration with the reinforcing long fiber sheet.
The range of m is preferable, and the range of 1 to 50 mm is particularly preferable.

The diameter of the short fibers is preferably 100 μm or less, particularly preferably 50 μm or less. As the thermoplastic polymer forming the matrix fiber, use polyolefin, polyamide, polyester, polycarbonate, polyphenylene sulfide, polyethersulfone, polyetherketone, polyetheretherketone, polyetherketoneketone, polyetherimide or the like. You can

On the other hand, the volume content (V _f ) of the reinforcing long fibers in the composite sheet is usually 30 to 70, although it depends on the physical properties required for the bolt and the combination of the reinforcing long fibers and the thermoplastic polymer fibers. % Is preferable, and 45 to 60% is particularly preferable. If it is less than 30%, sufficient strength cannot be obtained. On the other hand, if it exceeds 70%, voids are formed between the fibers and sufficient strength cannot be obtained.

On the other hand, in the method of the present invention, as a mixture of unidirectionally aligned reinforcing long fibers and thermoplastic polymer fibers which can be used as a core material, a reinforcing sheet such as the above-mentioned composite sheet can be used. Fiber bundles and thermoplastic polymer long fiber bundles are simply aligned and assembled or partially mixed, mixed woven fabrics of reinforcing long fibers and thermoplastic polymer long fibers aligned in the longitudinal direction, and these Examples thereof include a mixed yarn in which two kinds of long fibers are mixed, a mixed woven fabric with a thermoplastic polymer long fiber in which the mixed yarn is arranged in the longitudinal direction, and the like.
Considering the manufacturing cost of the core material, it is practically preferable to use the reinforcing long-fiber bundle and the thermoplastic polymer long-fiber bundle that are simply aligned and assembled or partially mixed and the above-mentioned composite sheet. Further, in order to obtain a molded body that is homogeneous up to the center of the shaft, it is preferable to use the above-mentioned composite sheet.

As the reinforcing long fibers constituting this mixture, glass fibers, carbon fibers, aramid fibers, silicon carbide fibers and the like can be used alone or in combination. As the thermoplastic polymer fiber, a short fiber containing polyolefin, polyamide, polyester, polycarbonate, polyphenylene sulfide, polyethersulfone, polyetherketone, polyetheretherketone, polyetherketoneketone, polyetherimide or the like as a constituent component, or Although long fibers can be used, fibers made of the same type of polymer as the thermoplastic polymer fibers that form the composite sheet used for knitting or weaving a tubular tissue body are usually used.

Further, the V of the reinforcing long fibers in this mixture is
_{Although f} depends on the physical properties required for the bolt and the combination of the reinforcing long fiber and the thermoplastic polymer fiber, _f is preferably in the range of 30 to 70%, particularly preferably in the range of 45 to 60%.
In the present invention, a mixture of reinforcing long fibers aligned in one direction and a thermoplastic polymer fiber as a core material in the present invention is used as a core material, and a multilayer structure formed by surrounding the outside thereof with a tubular structure of a thermoplastic resin prepreg, While continuously supplying the above mixture to the central portion of the knitting mechanism or the weaving mechanism using a cylinder knitting machine, a braiding machine, or a loom for weaving a cylindrical woven fabric, the core material is surrounded by a certain width. It can be manufactured by knitting or weaving the tape of the above composite sheet slit into a tubular shape. The slit width of the tape is preferably in the range of 2 to 10 mm, particularly preferably in the range of 3 to 7 mm, in view of workability in slitting the composite sheet and operability in knitting or weaving the tubular tissue.

Depending on the size of the bolt to be manufactured, the obtained tubular tissue body is used as a core material, and the tubular tissue body of the composite tape is layered or woven in the same manner so that the tubular tissue body of the composite tape is stacked. Can be made. The tubular structure referred to in the present invention can be produced by using a knitting machine, a knitting machine, or a weaving machine for weaving a cylindrical fabric. When the tubular knitting machine is used, warp tapes are used as weft tapes. A tubular braid having a structure entangled with each unit is obtained, and when a braiding machine is used, a braid (braid) in which a plurality of tapes are arranged in a spiral shape intersecting each other at a certain angle is obtained. When a loom is used, a cylindrical woven fabric in which warp tapes and weft tapes are uniformly arranged is obtained.
In the multilayer structure of the present invention, in order to manufacture a bolt having a high screw thread strength and a high tensile strength of the shaft portion, the weight content ratio of the tubular tissue body is set in the range of 20 to 50%. It is preferably in the range of 25 to 40% and particularly preferably.

From the thus obtained multilayer structure,
As a method of manufacturing a rod-shaped molded product, a method of mounting the multilayer structure in a mold, heating and pressing with a press machine, followed by cooling and solidification, continuously guiding the multilayer structure to a pultrusion molding machine. , A method of drawing and the like. At this time, prior to molding, the multilayer structure is heated at a temperature not lower than the glass transition point and not higher than the melting point of the thermoplastic polymer constituting the multilayer structure.
By applying pressure, the bulk density can be increased beforehand.

The molding method is selected according to the shape and quantity of the bolt to be manufactured. When manufacturing a U-shaped bolt,
Usually, a press molding method is used. In the method of the present invention, the rod-shaped molded product thus obtained is mounted on a die having a thread groove, heated and pressurized by using a press machine, cooled and solidified, and a screw thread is formed on the surface layer portion thereof. The FRP bolt can be manufactured by forming. Also, the FRP bolt can be manufactured in the same manner by continuously guiding the rod-shaped molded product to a molding die having a thread groove after the pultrusion molding and performing the pultrusion process while rotating the die. You can In any case, in order to obtain sufficient screw thread strength, the depth of the thread groove is preferably in the range of 30 to 80% of the thickness of the tubular tissue layer forming the rod-shaped body, and 40 to 65. The range of% is particularly preferable.

In the production method of the present invention, the composite sheet used for knitting or weaving the tubular tissue body is a thermoplastic sheet in which random reinforcing fibers are oriented in one direction while the reinforcing long fibers are opened. Since the polymer short fibers are entangled and integrated, the rigidity is low, and in the manufacturing process of the composite sheet,
Because a high-pressure fluid jet is applied to the sheet, the reinforcing long fiber bundle is well opened by the rubbing action, and the sizing agent attached to the reinforcing long fibers and the thermoplastic polymer fibers is inevitably removed. As a result, since it is extremely flexible and rich in drape, it is easy to knit a tubular knitted fabric or a braid. When a rod-shaped molded article for producing a bolt is formed using a multilayer structure including a knitted body made of this composite sheet, reinforcing long fibers and thermoplastic polymer fibers are mixed in the composite sheet at a single yarn level. The matrix resin is reinforced because it is entangled and integrated, and the long fiber bundles for reinforcement are well opened by the rubbing action in the manufacturing process of the composite sheet, and most of the sizing agent attached to the surface is removed. There is an advantage that the fibers for use are easily and uniformly impregnated. Good impregnation of resin into the reinforcing fibers leads to more mild molding conditions (temperature, pressure, time) when manufacturing rod-shaped molded products for bolt production, The heat history at that time is small, and as a result, the thermal decomposition of the thermoplastic polymer, which causes the deterioration of the physical properties of the molded product and the fluctuation thereof, is suppressed, and it is possible to manufacture a bolt with stable quality and high physical properties.

Since the bolt manufactured by the method of the present invention contains the reinforcing long fibers arranged in parallel to the axial direction in at least the inner layer portion of the shaft portion, the bolt has high bending strength and the shaft portion. Since the outer layer portion and the threads include the reinforcing long fibers knitted or woven in a tubular shape, there is a connection of the reinforcing long fibers between the shaft portion and the threads, and the shear strength of the thread portion is high. It has characteristics.

[0020]

The present invention will be described with reference to the following examples.

[0021]

[Reference Example 1] Nylon 6 polymer was melt-spun and 770
A long fiber of denier / 770 filament was obtained. A large number of these long fibers were collected and cut into short fibers with a length of 10 mm using a guillotine cutter. Next, this short fiber
A slurry was prepared by dispersing it in water containing polyacrylic amide, and the slurry was continuously made into paper by using a wire mesh of 200 mesh to obtain a paper sheet having a basis weight of 50 g / m ² .

Separately from this, 195 polyacrylonitrile-based carbon fibers (Hikerboron 12kf, manufactured by Shin-Asahi Kasei Carbon Fiber Co., Ltd.) were continuously drawn out from the creel while the carbon fibers were aligned in one direction 150.
into a sheet of g / m ^2, the upper and lower surfaces of the sheet, by arranging the papermaking sheet of the above basis weight 50 g / m ^2, sandwiching the carbon fiber sheet sandwich. This sandwich-like sheet was placed on a 200-mesh wire net moving at a speed of 4 m / min, and the sandwich-like sheet had a diameter of 0.
It has 500 2mm nozzles and 5 in the width direction of the net.
The width of the nylon 6 short fibers interlaced and integrated between the carbon fibers by vertically applying a water flow with a pressure of 30 kg / cm ² using a water jetting device that performs a reciprocating motion of mm at a speed of 150 times / min. A 500 mm water-containing composite sheet was obtained. This hydrous composite sheet was dried for 2 hours using a hot air dryer at 110 ° C. to give a total basis weight of 250 g.
A composite sheet having a / m ² and V _f of 50% was obtained.

[0023]

[Reference Example 2] The composite sheet of Reference Example 1 was replaced with 15 kg / cm.
^{2 By} heat treatment under pressure at 200 ° C. for 3 minutes, a composite sheet having an increased bulk density was obtained.

[0024]

Example 1 A multi-layer structure having a composite sheet bundle in which reinforcing long fibers are arranged so as to be aligned in one direction as a core material, and having a tubular braid of the composite sheet consisting of two layers on the outside thereof is a bolt. Was prepared as a preform for making. Core material: Using the slitter, the composite sheet of Reference Example 2
A collection of 45 tapes slit into a width of 10 mm Inner layer tubular knit: Using the slitter, the composite sheet of Reference Example 1 was used with 12 tapes slit into a width of 5 mm, a cylinder inner diameter of 17 mm, and the number of needles Cylinder knitted on the outside of the core material by using 12 cylinder knitting machines. Outer layer tubular knit: The composite sheet of Reference Example 1 was 5 m wide.
Twelve tapes slit in m are used, and a tubular knitting machine having a cylinder inner diameter of 26 mm and a needle number of 12 is used to further perform tubular knitting on the outer side of the above-mentioned inner layer tubular knitted fabric. Diameter of 3 layers including wood, about 4
A braid of 0 mm and weight of 328 g / m was prepared.

The preform (braided cord) thus obtained is mounted on a die and pressed by a pressing machine at 10 kg /
After heat treatment at 250 ° C. for 3 minutes under a pressure of cm ² , the diameter is reduced to 1 by cooling and releasing from the mold.
A 6.5 mm rod-shaped molded body was produced. The surface of this rod-shaped compact was polished with a centerless machine to give a diameter of 1
The rod was 5.7 mm.

Next, this rod was set in a mold having a thread groove with a pitch of 2.00 mm, and it was pressed with a press machine to 25
After heating for 1 minute at 0 ° C., cooling was performed and the mold was released from the mold to form threads on the surface layer of the rod. A partial sectional view of the obtained bolt is shown in FIG. The tensile strength of the bolt thus obtained was measured by AG manufactured by Shimadzu Corporation.
It measured using the 10TA type | mold autograph. Tensile strength is measured by fixing a nut with a thickness of 18 mm and a width of 20 mm in the parallel portion to both ends of a screw portion of a bolt with a length of 200 mm.
The tensile speed was 1 mm / min.

Further, the bending strength of the bolt is measured by measuring the length 15
Using a full-threaded screw bolt cut to 0 mm as a test piece, the autograph was used to perform a 3-point bending method with a span distance of 100 mm. Further, the torque strength of the bolt was measured according to JIS B using a torque tester manufactured by Canon Inc. using a full-threaded screw bolt cut to a length of 50 mm as a test piece.
It measured based on 4650.

The rate of change in tensile strength was calculated based on the results of measurements on 20 bolts. The obtained results are summarized in Table 1. Next, the M16 bolt obtained in this way is cut in three places perpendicular to the length direction,
When the cut surface was polished and observed with an optical microscope,
No resin-impregnated portion or void was observed in any of the portions, and the carbon fibers were uniformly distributed.

[0029]

COMPARATIVE EXAMPLE 1 251 800 TEX carbon fiber yarns and 1,260 denier / yarn nylon 6 yarns 9
FRP bolts were manufactured in the same manner as in Example 1 except that only the fiber assembly obtained by simply aligning 13 fibers was used as a raw material, and the physical properties thereof were measured. The measurement results are summarized in Table 1. Further, when the cross section of the bolt was observed in the same manner as in Example 1, a part in which the nylon 6 resin was not completely impregnated between the carbon fibers was observed in a part, and a part having a high carbon fiber content ratio, A portion having a low content rate was observed throughout.

[0030]

Example 2 87 cores of carbon fiber yarn of 800 TEX and nylon 6 of 1,260 denier / yarn were used as core materials.
Same as Example 1 except that 315 yarns were aligned and used, and the diameter including three layers including the core material was about 4
A braid of 0 mm and weight of 328 g / m was prepared.

The preform thus obtained is
A rod-shaped molded body having a diameter of 16.5 mm was produced by introducing the molded product into a pultrusion molding machine having a three-stage mold and performing pultrusion molding at a speed of 3 cm / min. First stage mold: length 1.5m, temperature 180 ° C, hole diameter 40mm Second stage mold: length 1.5m, temperature 250 ° C, hole diameter 15.8mm Third stage mold: length 1.0m, temperature 160 ° C. Hole diameter 15.7 mm From this rod-shaped molded body, a FRP bolt was manufactured in the same manner as in Example 1 and its physical properties were measured. The physical property measurement results
It is summarized in Table 1.

[0032]

COMPARATIVE EXAMPLE 2 251 800 TEX carbon fiber yarns and 1,260 denier / yarn nylon 6 yarns 9
FRP bolts were manufactured in the same manner as in Example 2 except that only the fiber assembly obtained by simply aligning 13 fibers was used as a raw material, and the physical properties thereof were measured. The physical property measurement results are summarized in Table 1.

[0033]

[Table 1]

[0034]

According to the manufacturing method of the present invention, a tough FRP bolt which is lightweight, has high strength, and has high shear strength in the thread portion can be easily manufactured with stable quality.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a bolt according to a first embodiment manufactured by a method of the present invention. (Unit: mm)

[Explanation of symbols]

 1 bolt 2 screw thread 3 core layer 4 tubular knit layer

Claims (1)

[Claims] 1. A planar fiber assembly comprising a core material comprising a mixture of unidirectionally aligned reinforcing long fibers and a thermoplastic polymer fiber, the outside of which is composed of unidirectionally aligned reinforcing long fibers. A composite sheet composed of a body and a thermoplastic polymer fiber sheet, for a fiber reinforced material in which thermoplastic polymer fibers are interlaced and integrated between reinforcing long fibers constituting a planar fiber assembly A method for producing a bolt, which comprises surrounding a composite sheet with a tubular structure, molding the obtained multilayer structure into a rod-shaped molded product, and then forming a screw thread using a screw molding die.