JP2001172419A - Method for producing new fiber-reinforced fluororesin composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fiber-reinforced plastic by crosslinking a polytetrafluoroethylene of a polytetrafluoroethylene composite with an ionizing radiation wherein the composite is obtained by using carbon fiber, glass fiber, silicon carbide fiber, silicon nitride fiber, PBO fiber, aramid fiber, or the like as a reinforcing fiber. SOLUTION: The fiber-reinforced crosslinked polytetrafluoroethylene is obtained by crosslinking a preform of the fiber-reinforced polytetrafluoroethylene by irradiating the ionizing radiation thereto and then laminating the preform under a condition of heating and pressurizing at 100-400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a fiber-reinforced plastic, wherein polytetrafluoroethylene (PTFE) is used as the base material, which is cross-linked by ionizing radiation to inherit the properties of polytetrafluoroethylene. The present invention relates to a method for producing a fiber-reinforced plastic.

That is, the present invention relates to carbon fibers, glass fibers,
In a method of producing a fiber-reinforced plastic by cross-linking polytetrafluoroethylene of a polytetrafluoroethylene composite material using ionizing radiation with a polytetrafluoroethylene composite material using silicon carbide fiber, silicon nitride fiber, PBO fiber, aramid fiber, etc. It is characterized in that the preformed body prepared with a reduced thickness is irradiated with ionizing radiation to crosslink, and then the preformed body is heated and laminated to form a desired formed body. And a method for producing a fiber-reinforced crosslinked polytetrafluoroethylene.

[0003]

2. Description of the Related Art Polytetrafluoroethylene has heat resistance,
Excellent plastic with chemical resistance, water repellency, antifouling property, lubricity, and abrasion resistance.By using these features, it has been used in traditional industries such as packing, gaskets, tubes, insulating tapes, bearings, and air dome roof membranes. It is a resin material that is being increasingly used for consumer and consumer use.

[0004] However, polytetrafluoroethylene is a resin that cannot be used in a radiation environment such as a nuclear facility because polytetrafluoroethylene has high sensitivity to radiation and its mechanical properties deteriorate when it exceeds 1 kGy. In addition, polytetrafluoroethylene is a crystalline polymer, and therefore has poor light transmittance in the visible light region, and has a disadvantage in that it has poor lighting properties even when used as a roof film of an air dome.

Although efforts have been made to overcome these drawbacks by the radiation crosslinking method, the radiation crosslinking method of molded articles is difficult to be practically used because of significant deformation, and after the radiation crosslinking treatment with a powder, the powder is fired again. A method of tying and molding is required. Furthermore, polytetrafluoroethylene has no suitable solvent for dissolving it, has a lower tensile strength and elastic modulus than other resin materials, and has a melt viscosity as high as 10 ¹¹ P even at a high temperature of 380 ° C., carbon fiber or glass. At present, it is not generally used as a matrix of a fiber-reinforced composite material because of its low adhesiveness to base fibers such as fibers.

In view of such circumstances, the present inventors have devised a method for producing fiber-reinforced crosslinked polytetrafluoroethylene by ionizing radiation in order to solve these problems at once.
An application has already been filed as Japanese Patent Application No. 10-359340. In the production method, when irradiating with ionizing radiation, it is necessary to achieve uniform dose and temperature control in an oxygen-free atmosphere, and if this is technically achieved, the size of the compact is naturally restricted. There are drawbacks. In particular, when irradiation is performed using an electron accelerator, it is unavoidable that it is difficult to construct a manufacturing process for a thick large molded product due to a short range of the radiation.

[0007]

SUMMARY OF THE INVENTION The present invention provides a simple irradiation equipment and a facility for preparing an irradiation atmosphere necessary for cross-linking polytetrafluoroethylene. An object of the present invention is to provide a method capable of producing tetrafluoroethylene.

For this purpose, it is necessary to suppress the thickness of the molded body to be irradiated to preferably 2 mm or less, and as a result of diligent studies, it has been found that a prepreg or a preform corresponding to a prepreg or a preform conventionally used in molding of fiber-reinforced plastics is used. By preparing materials for use, they have found a method for producing a fiber-reinforced crosslinked polytetrafluoroethylene that can be formed into an arbitrary size after irradiation.

[0009]

According to the present inventors, polytetrafluoroethylene does not have a molten state at a temperature lower than the crystal melting point such that the resin flows out. In addition, it was found that the same molten state was maintained, and that the resins retained the ability to melt and adhere to each other, thereby achieving the present invention.

That is, according to the present invention, continuous long fibers impregnated with polytetrafluoroethylene are first formed into a sheet having a thickness of 2 mm or less, and short fibers are formed into a sheet so as to have a thickness capable of uniformly irradiating ionizing radiation. It is mixed and melted with tetrafluoroethylene and formed into flakes, or lumps or granules having a diameter of 2 mm or less. In these molded articles, temperature control of the molded articles during irradiation is facilitated, which is a favorable means for smoothly promoting a crosslinking reaction. The molded article is crosslinked by irradiating it with ionizing radiation below the crystalline melting point of polytetrafluoroethylene to produce a prepreg or preform. Thereafter, this is achieved by laminating this into a desired shape at a temperature equal to or higher than the crystal melting point of the crosslinked polytetrafluoroethylene as a raw material for processing, and then heating and pressing.

Thus, a method for controlling the temperature of polytetrafluoroethylene below the crystal melting point in an irradiation atmosphere, which is the most important of the present invention, ie, an oxygen-free atmosphere, and
Irradiation with short-range ionizing radiation by the low-energy electron accelerator can be performed without difficulty.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Japanese Patent Application No. 10-359340 has already been disclosed.
Carbon fiber, glass fiber,
A fiber-reinforced plastic is produced by cross-linking polytetrafluoroethylene of a polytetrafluoroethylene composite material using a continuous fiber or short fiber such as silicon carbide fiber, silicon nitride fiber, PBO fiber, or aramid fiber as a reinforcing material by ionizing radiation. In the method, a preformed body prepared with a reduced thickness, such as a thin sheet or flake having a thickness of 2 mm or less, or a lump or granule having a diameter of 2 mm or less, is placed in a non-oxidizing atmosphere,
C. to 400.degree. C., preferably from 327.degree. C. to 350.degree. C., which is higher than the crystalline melting point of polytetrafluoroethylene, and is irradiated with ionizing radiation in a dose range of 1 kGy to 20 MGy to form a conventional fiber-reinforced plastic. It is manufactured as a processing material corresponding to the prepreg or preform used in the above.

The preparation of the preformed body having a reduced thickness, such as a thin sheet or flake having a thickness of 2 mm or less, or a lump or granule having a diameter of 2 mm or less, is carried out by preparing a polytetrafluoroethylene called dispersion. This is performed by immersing the fibers in a liquid in which the powder of the powder is uniformly dispersed, or by applying a liquid in which the powder is uniformly dispersed to the fibers, or by mixing the fine powder of the polytetrafluoroethylene with the fibers. .

The liquid for efficiently dispersing the powder, that is, the dispersion medium is water and an emulsifier, water and alcohol, water and acetone, or a mixed solvent of water, alcohol and acetone. It can be easily selected and prepared by a house, and the powder particle size of polytetrafluoroethylene at this time is preferably 0.1 μm to
It is desirable that the diameter be in the range of 50 μm and sufficiently impregnated between the monofilaments of the fiber.

The fiber impregnated with the polytetrafluoroethylene powder is air-dried or hot-air-dried to remove the dispersing medium, or the particle diameter is several hundred μm.
A mixture of the fine powder of polytetrafluoroethylene and the fiber is immediately mixed at 300 ° C. to 400 ° C., preferably at 327 ° C.
By firing in a temperature range of 80 ° C., the preformed body having a reduced thickness can be obtained. Of course, baking and radiation irradiation may be performed simultaneously.

The method for producing a fiber-reinforced composite material according to the present invention is characterized in that the prepreg or the processing material corresponding to the preform is formed at a temperature of 100 ° C. to 400 ° C., preferably a crystal of cross-linked polytetrafluoroethylene serving as the base material. This is easily achieved by forming a desired molded product by laminating under heat and pressure in a temperature range not lower than the melting point.

The ratio of the fiber to the matrix of the fiber reinforced composite material thus produced, that is, the fiber volume content, is required by controlling the powder concentration of the dispersion and the impregnation time, or by repeating the impregnation and drying operations. Can be arbitrarily prepared.

The ionizing radiation in the present invention is an electron beam,
X-rays, neutron rays, high-energy ions alone or a mixture thereof. In addition, temperature control when irradiating with ionizing radiation is performed by heating using an indirect or direct heat source in a normal gas circulation type thermostat, infrared heater or panel heater, and electron beam obtained from an electron accelerator. The heat generated by controlling the energy of the heat can be used as a heat source without any problem.

The irradiation in an oxygen-free atmosphere of the present invention refers to an atmosphere in which the atmosphere is replaced with an inert gas such as helium or nitrogen in addition to a vacuum, and the crosslinking reaction of polytetrafluoroethylene during the irradiation. This means taking measures that can be suppressed and, conversely, prevent oxidative degradation from occurring.

The fibers used as the reinforcing substrate in the present invention include carbon fibers, glass fibers, silicon carbide, silicon nitride fibers, and PBO.
All fibers used in conventional fiber-reinforced plastics having heat resistance of 350 ° C. or higher, such as fibers and aramid fibers, are applied.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A polytetrafluoroethylene powder 60 having an average particle diameter of 0.3 μm was added to 100 parts of water and an emulsifier-based dispersion medium.
The operation of immersing one piece of carbon fiber woven cloth in the liquid in which the parts were dispersed and then drying was repeated six times, so that 100 parts of carbon fiber woven cloth was impregnated with 100 parts of polytetrafluoroethylene powder and fired at 340 ° C. Twelve preforms having a thickness of 0.2 mm were prepared.

Thereafter, these were transferred to an irradiation container at 340 ° C. in an argon gas atmosphere, and irradiated with 500 kGy of an electron beam from a 300 kV class low energy electron accelerator to obtain a prepreg for processing. Twelve prepregs were heated to 300 ° C. and laminated under pressure to obtain a molded product having a thickness of 2 mm. When a three-point bending test was performed on the molded product, the strength was remarkably improved as shown in Table 1 as compared with the uncrosslinked carbon fiber reinforced polytetrafluoroethylene laminated molded product.

These are impregnated by the same method, laminated and adjusted to a thickness of 2 mm, and irradiated with an electron beam of 500 kGy from an electron accelerator having an acceleration voltage of 2 MV and crosslinked to obtain a sample. No difference was made.

[0025]

[Table 1]

Example 2 Polytetrafluoroethylene powder 6 having an average particle size of 0.25 μm was added to 100 parts of water and an emulsifier-based dispersion medium.
The operation of immersing one glass fiber woven fabric in the liquid in which 0 part was dispersed and drying was repeated five times, and 100 parts of the glass fiber woven fabric was impregnated with 100 parts of polytetrafluoroethylene powder, and fired at 340 ° C. Eighteen preformed bodies having a thickness of 0.14 mm were prepared.

Thereafter, these were transferred to an irradiation container in a nitrogen gas atmosphere at 340 ° C., and irradiated with 450 kGy of electron beams from a 250 kV class low energy electron accelerator to obtain a working prepreg. The 18 prepregs were heated to 310 ° C. and laminated under pressure to obtain a molded body having a thickness of 2.2 mm.

The molded article was subjected to a three-point bending test. The strength was remarkably improved as shown in Table 2 as compared with the uncrosslinked glass fiber reinforced polytetrafluoroethylene laminated molded article.

Further, these were impregnated in the same manner and laminated to prepare a molded body having a thickness of 2.2 mm, and an acceleration voltage of 2 MV was applied.
No difference was found in comparison with the intensity of the sample obtained by irradiating 450 kGy of an electron beam from the electron accelerator and crosslinking.

[0030]

[Table 2]

Example 3 Water and an emulsifier-based dispersion medium (100 parts) were mixed with polytetrafluoroethylene powder 6 having an average particle size of 0.25 μm.
The operation of immersing one PBO fiber woven fabric in the liquid in which 0 part was dispersed and then drying was repeated six times, so that 100 parts of the PBO fiber woven fabric was impregnated with 120 parts of polytetrafluoroethylene powder, and baked at 340 ° C. Seven preforms having a thickness of 0.4 mm were prepared.

Thereafter, these were transferred to an irradiation container at 340 ° C. in a nitrogen gas atmosphere, and an acceleration voltage of 1 MV was applied from an electron accelerator.
Then, an electron beam was irradiated with 1 MGy to obtain a working prepreg.
Seven prepregs were heated to 285 ° C. and laminated under pressure to obtain a molded body having a thickness of 2.4 mm.

When the molded product was subjected to a three-point bending test, the strength was remarkably improved as shown in Table 3 as compared with the uncrosslinked PBO fiber reinforced polytetrafluoroethylene laminated molded product.

Further, these were impregnated in the same manner and laminated to form a molded body having a thickness of 2.4 mm.
No difference occurred in comparison with the intensity of a sample obtained by irradiating an electron beam with 1 MGy from the electron accelerator and crosslinking the sample.

[0035]

[Table 3]

Example 4 Ten prepregs for processing having a thickness of 0.4 mm prepared in the same manner as in Example 3 were heated at 290 ° C. and laminated under pressure to obtain a molded product having a thickness of 3.3 mm. . The coefficient of friction and the coefficient of wear were measured for the sample. The exam includes
Using a thrust type friction and wear tester, JISK721
8 and S45C cylindrical ring (outer diameter φ25.6
mm, inner diameter φ20.6 mm), a pressure of 20 kgf / cm ² is applied to the test object, and the speed is 10 m / min.
Performed under the following conditions.

The results obtained showed a low coefficient of friction supporting good lubrication as shown in Table 4, and had excellent wear resistance. In addition, there is no difference in comparison with the strength of a sample obtained by impregnating in a similar manner, laminating, and preparing a molded body having a thickness of 3 mm by irradiating an electron beam with 1 MGy from an electron accelerator having an acceleration voltage of 2 MV and cross-linking it. I didn't.

[0038]

[Table 4]

Example 5 50 g of a 2 mm diameter massive preform prepared by mixing 2 wt% of 1 mm long short PBO fibers with polytetrafluoroethylene powder having an average particle diameter of 500 μm and firing at 340 ° C. Was prepared. After that, these are 34
It is transferred to an irradiation container in a helium gas atmosphere at 0 ° C. and irradiated with 100 kGy of an electron beam from an electron accelerator having an acceleration voltage of 2 MV.
A prepreg for processing was obtained. 40 g of the prepreg is 330
The mixture was heated to ℃ and laminated under pressure to obtain a molded body having a thickness of 0.5 mm.

When the molded product was subjected to a tensile test, the strength was remarkably improved as shown in Table 5 as compared with the uncrosslinked PBO fiber reinforced polytetrafluoroethylene laminated molded product. These materials were mixed in the same manner, and were previously laminated to a thickness of 0.5 mm. The molded body was irradiated with 100 kGy of electron beam from an electron accelerator having an acceleration voltage of 2 MV and crosslinked to obtain a sample obtained by crosslinking. There was no difference.

[0041]

[Table 5]

Example 6 40 g of a 2 mm-diameter lump for processing prepared in the same manner as in Example 4 were heated at 330 ° C. and laminated under pressure to obtain a molded product having a thickness of 3.1 mm. The coefficient of friction and the coefficient of wear were measured for the sample. For the test, a thrust-type friction and wear tester was used.
218, an S45C cylindrical ring (outer diameter φ2
5.6 mm, inner diameter φ20.6 mm), a pressure of 20 kgf / cm ² was applied to the test object, and a speed of 10 m / cm ² was applied.
min.

As shown in Table 6, the results showed a low coefficient of friction supporting good lubricity and excellent abrasion resistance. These were mixed in the same manner, and were previously laminated to a thickness of 3 mm. The molded body was irradiated with 100 kGy of an electron beam from an electron accelerator having an acceleration voltage of 2 MV and crosslinked to obtain a sample. There was no difference.

[0044]

[Table 6]

[0045]

According to this method, the irradiation radiation source and the equipment for preparing the irradiation atmosphere necessary for cross-linking polytetrafluoroethylene are simple, and are equivalent to a prepreg or a preform by a small irradiation equipment such as a low energy accelerator. By preparing a processing material to be processed, a fiber-reinforced crosslinked polytetrafluoroethylene which can be laminated and formed into an arbitrary shape after irradiation can be produced.

Continued on the front page F term (reference) 4F072 AA02 AA04 AB05 AB06 AB08 AB09 AB10 AC01 AD07 AG03 AG04 AG05 AG16 AJ16 AK04 AK05 AL03 AL09 AL17 4F073 AA05 BA16 BA47 BB01 BB02 CA42

Claims (3)

[Claims] 1. Carbon fiber, glass fiber, silicon carbide fiber,
In a method for producing a fiber-reinforced plastic by cross-linking polytetrafluoroethylene of a polytetrafluoroethylene composite material using continuous fibers or short fibers such as silicon nitride fibers, PBO fibers, and aramid fibers as a reinforcing material by ionizing radiation, The molded body is irradiated with ionizing radiation to crosslink, and then the preformed body is heated to 100 ° C to 4 ° C.
A method comprising forming a desired molded product by laminating under heat and pressure in a temperature range of 00 ° C. 2. The method according to claim 1, wherein the preform is in the form of a sheet or flake having a thickness of 2 mm or less, or a lump or granule having a diameter of 2 mm or less. 3. Irradiation with ionizing radiation is performed under an oxygen-free atmosphere.
2. The method according to claim 1, wherein the irradiation is performed in a temperature range of 00 to 400 [deg.] C., and a dose range required for irradiation is 1 kGy to 20 MGy.