JPH11322956A - Carbon-fiber-reinforced resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon-fiber-reinforced resin which is suitable to be laminated to a material having a positive coefficient of thermal expansion by selecting a resin of which the coefficient of thermal expansion has a specified minus value. SOLUTION: A carbon-fiber-reinforced resin having a coefficient of thermal expansion of -1.5×10<-6> / deg.C or lower is selected. By laminating this reinforced resin to a material having a positive coefficient of thermal expansion (e.g. a metal, a resin, glass, or a ceramic), the coefficient of thermal expansion of the resultant composite can be brought close to zero. Carbon fibers having a tensile modulus of 80 ton/mm<2> or higher are suitable for producing the reinforced resin. Pref., the carbon fibers are weaved into a fabric, and the use of a fabric which has a wt. per unit area of 400 g/m<2> and of which the thread count of carbon fiber tow per 25 mm in the fiber direction is 5-10 is pref. The use of a fabric of which the thread count of carbon fiber tow is 90-110 % of the theoretical thread count obtd. by the ratio of fabric width (mm)/width of carbon fiber tow (mm) is still pref.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon fiber reinforced resin which is lightweight, has high rigidity and high thermal conductivity, and particularly has a large negative coefficient of thermal expansion. It is preferably used in the field of equipment requiring high precision and high accuracy.

[0002]

2. Description of the Related Art In recent years, precision machines and electronic equipment have become more accurate.
As the densification and miniaturization have progressed, the importance of dimensional stability of parts and members has been increasing. Conventionally, as materials having good dimensional stability, metallic titanium, ceramics, and the like having a coefficient of thermal expansion close to 0 have been used. However, when used in places where more precision is required, the dimensional stability of the material must be reduced. To assist,
Ancillary equipment for temperature control has become necessary.

On the other hand, recently, a carbon fiber reinforced resin (hereinafter, referred to as “CFRP”) having a thermal expansion coefficient close to 0 as compared with a conventional material.
Is being used. CFRP
The coefficient of thermal expansion of can be controlled according to the application by a generally known CFRP manufacturing method, including the type of carbon fiber used, the sheet configuration, and the lamination configuration. C
The thermal expansion coefficient of FRP is -1.0 × 10 ⁻⁶ to −0.1 × 10 ⁻⁶ / ° C. when using PAN-based carbon fibers, and −1.2 × 10 ⁻⁶ to −0.1 × 10 when using pitch-based carbon fibers. ^-6
/ ° C. Recently, C is closer to 0 than conventional materials.
Alloy materials exhibiting the same coefficient of thermal expansion as FRP have also been developed, but since the alloy materials are heavy, the strength and rigidity of other parts must be improved, and as a whole, the equipment becomes larger and costs increase There is a problem.

[0004]

In particular, in the field of equipment requiring high precision and high precision, such as precision equipment, electronic equipment, space and aeronautics, there has been a demand for a material having a coefficient of thermal expansion closer to zero. CFRP having a negative coefficient of thermal expansion is a metal, resin,
When composites with ceramics or other materials having a positive coefficient of thermal expansion are used for various components and components as composites, the thermal expansion coefficient of the composite as a whole can be made closer to zero, and as a result, the dimensions due to heat can be reduced. Since the change and deformation can be suppressed, it contributes to the improvement of the precision of the apparatus, and the temperature control mechanism usually attached to precision equipment or the like can be simplified or eliminated.
For this reason, a material having an even more negative coefficient of thermal expansion is required.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, among the carbon fibers, pitch-based highly elastic carbon fibers having an excellent coefficient of thermal expansion have been formed into plain woven fabrics satisfying certain conditions. By using a graphitized woven fabric, the 90-degree weaves at the time of graphitization exhibit a change in the coefficient of thermal expansion of each carbon fiber as a synergistic effect, and a large negative coefficient of thermal expansion that could not be obtained conventionally. Have been found to obtain CFRP having That is, the gist of the present invention is to provide a CFR having a coefficient of thermal expansion of -1.5 × 10 ⁻⁶ / ° C. or less.
P and CFRP having a coefficient of thermal expansion of -1.5 × 10 ⁻⁶ / ° C. or less for lamination with a material having a positive coefficient of thermal expansion.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The CFRP of the present invention is obtained by melt-spinning a spinning pitch obtained by treating a carbonaceous raw material to form a pitch fiber, graphitizing the pitch fiber, obtaining a carbon fiber as a raw material, and then weaving the carbon fiber as a raw material. , And as a raw material carbon fiber fabric,
It is further graphitized into a carbon fiber fabric. It is obtained by impregnating the carbon fiber fabric with a resin.

Examples of the carbonaceous raw material include, but are not particularly limited to, coal-based coal tar, coal-tar pitch, coal liquefaction, petroleum heavy oil, tar, pitch, and the like. Among them, coal-based coal tar and coal tar pitch are preferably used because they have a high aromaticity of the molecules constituting them and a spinning pitch in which graphite crystals are easily developed. These carbonaceous materials contain impurities such as free carbon, undissolved coal, ash, and catalysts. These impurities are well-known in the art, such as filtration, centrifugation, or stationary sedimentation using a solvent. It is desirable to remove in advance by a method. Further, the carbonaceous raw material may be preliminarily treated by, for example, a method of extracting a soluble component with a specific solvent after the heat treatment, a method of hydrogenating in the presence of a hydrogen-donating solvent, or hydrogen gas, or the like. .

The spinning pitch thus obtained is usually an optically anisotropic pitch, and its optical anisotropy ratio is usually 70% or more, preferably 90% or more, and more preferably 100% or more. is there. If the optical anisotropy ratio is lower than 70%, the graphitized carbon fibers have low graphite crystallinity, and it is difficult to obtain CFRP having a large negative coefficient of thermal expansion. The softening point of the spinning pitch determined by the Mettler method is usually from 260 to 340 ° C, preferably from 280 to 320 ° C, more preferably from 290 to 310 ° C. Softening point is 260
When the temperature is lower than ° C, fusion between fibers is liable to occur at the time of infusibility after spinning, and a carbon fiber bundle having poor spreadability tends to be formed. On the other hand, if the temperature is higher than 340 ° C., thermal decomposition of the pitch occurs during spinning, and there is a possibility that spinnability may be significantly reduced due to the generation of bubbles in the spinning nozzle due to the decomposition gas. In order to obtain such an optical anisotropy ratio and an optically anisotropic pitch of the METTLER softening point, the above-mentioned carbonaceous material, or a carbonaceous material which has been subjected to a pretreatment, is usually 350 to 500 ° C., preferably Is 3
80 to 450 ° C, usually for 2 minutes to 50 hours, preferably 5 minutes
It is preferable to perform the heat treatment in an atmosphere of an inert gas such as nitrogen, argon, or water vapor for a period of minutes to 5 hours.

Next, the spun pitch is melt spun to obtain pitch fibers. In the melt spinning, the fiber diameter and the number of fibers need to be determined so that the fineness of the finally obtained carbon fiber is 500 g / km or more, as described later. Usually, the fiber diameter is 6 to 20 μm, and the number of fibers is 1500. ~ 40000. First, an infusibilization treatment is applied to the obtained pitch fiber. The infusibilization treatment is usually performed by heating at 300 to 400 ° C. in an oxidizing atmosphere such as air, ozone, or nitrogen dioxide, or in an oxidizing liquid using nitric acid or the like, preferably in air. Thereby, an infusible fiber tow is obtained.

Further, the infusibilized fiber tow is carbonized and / or graphitized by heating at 800 to 2800 ° C. in an atmosphere of an inert gas such as nitrogen or argon. At this time, tension may or may not be applied. The obtained fiber is impregnated with a sizing agent to obtain a carbon fiber as a raw material of the carbon fiber fabric of the present invention. The sizing agent is impregnated in the fiber in an amount of 0.2 to 10% by weight, preferably 0.5 to 7% by weight. Before applying the sizing agent, the surface treatment of the carbon fiber itself may or may not be performed. If the sizing agent is less than 0.2%, "fluff" occurs during weaving. If the sizing agent is more than 10%, the fibers themselves are covered with carbides of the sizing agent after graphitization in the post-process. This is not preferred because the flexibility of the fabric is lost.

As the sizing agent, any commonly used sizing agent can be used. Specifically, epoxy compounds, water-soluble polyamide compounds, saturated or unsaturated polyesters,
Examples include vinyl acetate, water or alcohol, glycol alone or in mixtures. The carbon fiber used as a raw material thus obtained has a tensile modulus of 80 ton / mm ² or less, preferably 40 to 80 ton / mm ² , and more preferably 50 to 80 ton / mm ² .
It is important that ton / mm ² . Tensile modulus is 80to
If it exceeds n / mm ² , breakage of the carbon fiber occurs frequently during weaving for producing a woven fabric of carbon fibers, and the woven fabric cannot be formed. On the other hand, if the tensile modulus is too low, the carbon fiber itself undergoes dimensional change during graphitization at a temperature of 2800 ° C. or more after forming the carbon fiber fabric, and strain may be introduced into the carbon fiber fabric of the product. Yes, not preferred.

In the present invention, the fineness (weight per unit length of the fiber bundle) of the carbon fiber as a raw material is usually 50%.
It is important that the weight is 0 g / km or more, preferably 700 to 5000 g / km, and more preferably 1000 to 3000 g / km. If the fineness is less than 500 g / km, the weight per unit sectional area of the woven fabric (hereinafter referred to as “FAW”) is 400 g / m ^2.
There is a possibility that the carbon fiber fabric described above cannot be produced. On the other hand, if the fineness is too large, the bundle of the carbon fiber tow becomes too thick, and it is not preferable because the weaving becomes difficult in the weaving machine and the like.

The fineness [g / km] is generally determined from the specific gravity [g / cm ³ ] of the carbon fiber, the cross-sectional area [μm ² ] of the fiber, and the number [carbon fibers] of the carbon fiber tow. . The cross-sectional area of the fiber is determined by the fiber diameter [μm]. Here, the specific gravity of the carbon fiber as a raw material is usually 1.9 to 2.3 g /
cm ³ , preferably 2.0 to 2.2 g / cm ³ . If the specific gravity is less than 1.9 g / cm ³ , 2
At the time of graphitization at a temperature of 800 ° C. or more, the carbon fiber itself undergoes dimensional change, and the carbon fiber fabric of the product may be distorted. On the other hand, if it exceeds 2.3 g / cm ³ , It is not preferable because the elastic modulus of the carbon fiber is increased and the carbon fiber is frequently broken at the time of weaving for producing the carbon fiber woven fabric so that the woven fabric cannot be formed.

The fiber diameter of the carbon fiber used as a raw material is usually 6 to 20 μm, preferably 7 to 15 μm, and more preferably 8 to 12 μm. If the fiber diameter is less than 6 μm,
Inevitably, the number of carbon fibers needs to be increased, and the spinning equipment needs to be enlarged. On the other hand, if it exceeds 20 μm, it is not preferable because yarn breakage occurs at a single yarn level at a bent portion or the like during the process. A plurality of carbon fibers as a raw material are bundled to form a carbon fiber tow as a raw material.

The number of carbon fibers as raw materials constituting the carbon fiber tow as raw materials is usually from 1500 to 40000,
Preferably 3000 to 30000, more preferably 5
2,000 to 20,000. If the number is less than 1500, the diameter of the carbon fiber must be increased, and the yarn breaks in the process as described above. Also, 4
If the number exceeds 0000, it is not preferable because the spinning equipment becomes too large or a twining equipment needs to be installed.

Next, the carbon fiber tow is woven using a carbon fiber tow as a raw material, for example, using a shuttle loom or a rapier loom, and is preferably made into a plain weave, a twill weave, a satin weave or the like, preferably a plain weave. Get the fabric. Next, the carbon fiber fabric as the raw material is graphitized to obtain a carbon fiber fabric. It is preferable that the material be placed in a graphitic crucible during the graphitization and then subjected to the graphitization treatment, because external physical and chemical actions can be blocked. The size and shape of the graphite crucible are not particularly limited as long as the desired amount of the carbon fiber fabric as the raw material can be put therein. In order to prevent damage to the carbon fiber fabric due to reaction with the oxidizing gas or carbon vapor in the inside, a highly airtight one with a lid is preferred.

The temperature of the graphitization treatment is usually 2800 ° C. or higher, preferably 2800 to 3500 ° C., more preferably 2800 to 3300 ° C. If the temperature is lower than 2800 ° C., the coefficient of thermal expansion of the carbon fiber does not reach the target value, and if the graphitization temperature is too high, the sublimation of “carbon” starts, causing a great deal of damage to the product and the furnace body. Absent. The graphitization time is usually 1 hour at 2800 ° C or more.
It is 0 minute to 100 days, preferably 30 minutes to 30 days. The equipment for graphitization is not particularly limited as long as it can be processed at a temperature of 2800 ° C. or higher, but it is preferable to use an Acheson resistance heating furnace from the viewpoint of production efficiency.

Thus, the carbon fiber fabric used in the present invention can be obtained. Weight per unit sectional area of the fabric when this (hereinafter, referred to as "FAW") is 400 g / m ² or more, preferably 500 to 2000 g / m ^2, more preferably from 500
１０００1000 g / m ² . FAW is 150 g / m ²
If it is less than 2, the necessity of laminating a large number of sheets when producing CFRP arises, and the coefficient of thermal expansion in the thickness direction may be deteriorated, which is not preferable. Further, if the FAW is too large, the CFRP becomes unnecessarily thick depending on the application, which is not preferable. The tensile modulus of the carbon fiber fabric is usually 80 Ton / mm ² or more, preferably 90 Ton / mm ² . 80Ton /
If it is less than mm ² , the effect of reducing the coefficient of thermal expansion may not be sufficiently exhibited due to insufficient rigidity of CFRP in a composite material such as a metal, a resin, and a ceramic having a positive coefficient of thermal expansion.

As the carbon fiber woven fabric thus obtained, a woven fabric having 5 to 10 carbon fiber tows per 25 mm of carbon fiber woven fabric is preferably used. If the number of carbon fiber tows is less than 5 per 25 mm in the fiber direction of the carbon fiber woven fabric, the texture of the woven fabric does not sufficiently exhibit a synergistic effect of a change in the coefficient of thermal expansion of each other during graphitization, while the number is more than 10 And finally obtained CFRP
May be insufficient in practical use. In the carbon fiber woven fabric, the number of carbon fiber tows to be driven is determined by the fiber width (m).
m) / A woven fabric having a range of 90% to 110% of the number of theoretical driving lines determined by the width (mm) of the carbon fiber tow is preferably used. If the number of carbon fiber tow is less than 90% of the theoretical number of the carbon fiber tow, the texture of the woven fabric does not sufficiently exhibit the synergistic effect of the change in the coefficient of thermal expansion during the graphitization,
On the other hand, if it is more than 110%, the toughness of the finally obtained CFRP may be practically insufficient. Here, the width of the carbon fiber tow represents the longest diameter of the carbon fiber tow in a cross section perpendicular to the fiber direction of the carbon fiber.

After impregnating a carbon fiber woven fabric with a matrix resin according to a standard method, the resin is molded and cured to obtain
CFRP is obtained. Examples of the matrix resin to be impregnated include thermosetting resins such as epoxy resins, vinyl ester resins and unsaturated polyester resins, preferably epoxy resins and vinyl ester resins. For molding and curing, an open mold method by hand lay-up or spray-up, a press method, an autoclave method, a filament winding method, a pultrusion method, an extrusion method, an RTM method, and the like are used.

The CFRP thus obtained usually contains 30 to 75% by volume of carbon fiber and 25 to 70% by volume of resin. The coefficient of thermal expansion of CFRP is -1.5 × 1
0 ⁻⁶ / ° C. or less, preferably −2 × 10 ⁻⁶ to −3 × 10 ⁻⁶
/ ° C. When the coefficient of thermal expansion is larger than -1.5 × 10 ⁻⁶ / ° C., the control range of the coefficient of thermal expansion becomes narrower when used as a composite material, and when it is smaller than −3 × 10 ⁻⁶ / ° C., the toughness is reduced. It may be damaged. In the present invention, the coefficient of thermal expansion is a value obtained by increasing the temperature from 30 ° C. to 150 ° C. at a rate of 2 ° C./min and measuring the coefficient of thermal expansion in the temperature range of 50 ° C. to 100 ° C. by the TMA method. Say.

The CFRP of the present invention is usually in the form of a sheet, and is cut into an appropriate size depending on the intended use. Also CF
The thickness of the RP is usually 0.2 to 50 mm. CFRP
In the above, the woven fabric is usually disposed so as to be substantially parallel to the sheet plane. The woven fabric used for CFRP may be one sheet or two or more sheets may be laminated.

The CFRP of the present invention can make the coefficient of thermal expansion of the composite material as a whole close to zero by laminating it with a material having a positive coefficient of thermal expansion. Materials having a positive coefficient of thermal expansion generally include metals, resins, glasses, ceramics, and the like, preferably materials having a coefficient of thermal expansion of 0 to 1 × 10 ⁻⁴ / ° C., more preferably metals, and most preferably metals. Is made of aluminum, steel or the like. These materials having a positive coefficient of thermal expansion are preferably plate-like bodies. The lamination of the CFRP of the present invention and a material having a positive coefficient of thermal expansion is performed by bonding using an adhesive. As the adhesive, a thermoplastic resin,
Although any of thermosetting resins may be used, an epoxy resin and a vinyl ester resin, particularly preferably an epoxy resin using a polyamine as a curing agent, and a bisphenol A type vinyl ester resin are preferably used. CFR of the present invention
P and a material having a positive coefficient of thermal expansion are laminated via an adhesive, and pressed using a device such as a press at a temperature, a pressure, and a time according to the characteristics of the adhesive to form a composite material. Obtainable.

[0024]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The coefficient of thermal expansion is ULVAC
Temperature rise rate 2 ° C by TA-1500 type manufactured by Vacuum Riko Co., Ltd.
/ Minute from 30 ° C to 150 ° C and 50 ° C to 10 ° C.
The coefficient of thermal expansion in the temperature range of 0 ° C. was measured by the TMA method.

<Example 1> From the coal tar pitch, the optical anisotropy ratio observed under a polarizing microscope was 100%.
A mesophase pitch having a softening point of 302 ° C. determined by the Mettler method was prepared. The mesophase pitch was introduced into a spinneret having a total of 10,000 nozzles, and continuous spinning was performed. The fiber diameter of the obtained pitch fiber is about 12
The number of fibers constituting the μm tow was about 10,000. The obtained pitch fibers are 380 stepwise in air.
After the temperature was raised to ℃ to perform the infusibilization treatment, the graphite was continuously graphitized to a final temperature of 2,500 ℃ in argon gas, and 2% of an epoxy sizing agent was added. The obtained carbon fiber as a raw material has a fiber diameter of about 10 μm and is 1420 g / km.
And a tensile modulus of 64 ton / mm ² and a tensile strength of 300 kg / mm ² . Next, using the carbon fiber tow as a raw material, plain weave by a rapier weaving machine, fold 7 carbon fiber tows per 25 mm for both warp and weft into a cloth, and obtain carbon fiber as a raw material of FAW = 790 g / m ^2. A woven fabric was obtained.

Next, the obtained carbon fiber fabric as a raw material was placed in a graphite crucible and graphitized at 3000 ° C. in an Acheson resistance heating furnace. The residence time at 3000 ° C. was 5 hours.
The FAW of the obtained carbon fiber fabric was 794 g / m ² . The tensile strength is 360 kg / mm ² and the tensile modulus is 92
ton / mm ² . The number of carbon fiber tows driven per 25 mm in the fiber direction of this woven fabric is 7, the width of the carbon fiber tow is 3.5 mm, the theoretical number of driven is 7 and the actual number of driven is the theoretical number of driven. 10
It was 0%. A bisphenol A type epoxy resin (Dainippon Color Material Co., Ltd .: L-26) is used for this carbon fiber fabric.
26 (LV)) at a ratio of 30% by weight to prepare a prepreg. Two prepregs are stacked at a temperature of 100
Autoclave molding was performed at a temperature of 6 ° C. and a pressure of 6 kg / cm ² for 1 hour to obtain a CFRP plate. The carbon fiber content was 55% by volume. As a result of measuring the coefficient of thermal expansion, it was -2.5 × 10 ⁻⁶ / ° C. The obtained CFRP plate can be made into a composite material by laminating a metal and an adhesive.

[0027]

According to the present invention, it is possible to provide a material and a composite material which provide parts and members having excellent dimensional stability.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 7/06 C08K 7/06 C08L 101/00 C08L 101/00

Claims (9)

[Claims] 1. A carbon fiber reinforced resin having a coefficient of thermal expansion of -1.5 × 10 ⁻⁶ / ° C. or less. 2. A carbon fiber reinforced resin for laminating with a material having a positive coefficient of thermal expansion, having a coefficient of thermal expansion of -1.5 × 10 ⁻⁶ / ° C. or less. 3. The carbon fiber reinforced resin according to claim 1, wherein a carbon fiber having a tensile modulus of 80 Ton / mm ² or more is used. 4. The carbon fiber reinforced resin according to claim 1, wherein the carbon fiber is a woven fabric. 5. A woven fabric in which the weight per unit sectional area of the woven fabric of carbon fibers is 400 g / m ² or more, and the number of carbon fiber tows applied per 25 mm in the fiber direction of the woven fabric is 5 to 10. The carbon fiber reinforced resin according to any one of claims 1 to 4, wherein: 6. A woven fabric in which the number of carbon fiber tows to be driven is in the range of 90 to 110% of the theoretical number of fibers to be driven obtained by the ratio of the width of the woven fabric (mm) / the width of the carbon fiber tow (mm). The carbon fiber reinforced resin according to claim 4. 7. The carbon fiber reinforced resin according to claim 1, wherein the resin is a thermosetting resin. 8. A resin comprising 25 to 70% by volume and carbon fibers containing 3% by volume.
The carbon fiber reinforced resin according to any one of claims 1 to 7, which is 0 to 75% by volume. 9. A laminate of the carbon fiber reinforced resin according to any one of claims 1 to 8 and a metal plate.