JPH05272064A - Surface-modifying agent for carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the subject modifying agent effective in improving the adhesivity of carbon fiber to a matrix resin by forming a polyimide resin composed of a mixed diamine consisting of two specific kinds of primary diamines and an aromatic tetracarboxylic acid on the surface of a reinforcing carbon fiber. CONSTITUTION:A mixed diamine obtained by mixing a symmetric meta- substituted primary diamine of formula [X is O, SO2, S, C=O, CH2, C(CH3)2, C(CF3)2 or direct bond] with a symmetric aromatic para-substituted primary diamine at an equivalent ratio of (10-90):(90-10) is made to react with an aromatic tetracarboxylic acid dianhydride in nitrogen atmosphere to obtain a polyamic acid solution. A carbon fiber bundle is immersed in a liquid produced by diluting the above solution, dried with heat and heated in nitrogen atmosphere to convert the polyamic acid into polyimide and obtain a reinforcing carbon fiber having polyimide resin formed on the surface of carbon fiber. The obtained fiber has improved adhesivity to a matrix resin, especially thermoplastic resin and gives a molded article having remarkably improved mechanical strength by mixing with the resin and molding the mixture.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel surface modifier for carbon fiber.

[0002]

2. Description of the Related Art Carbon fibers have higher elasticity and lighter weight than glass fibers, and are especially superior in heat resistance such as polyimide resin, polyether ether ketone, polyether sulfone, polyether imide, and polyphenylene sulfide. When it is used as a reinforcing material for resin, it improves properties such as mechanical strength and can be an excellent material for automobile parts, machine parts and the like. Conventionally, epoxy resins have been widely used as surface modifiers for carbon fibers. Therefore, when the matrix is a thermosetting resin such as an epoxy resin, it is effective as a surface modifier, but when the matrix is a thermoplastic resin, the adhesiveness with the matrix is often poor and the mechanical strength, etc. Has not yet been fully improved. Therefore, as seen in JP-A-53-106752, it has been attempted to use a polyamide resin as a surface modifier for a thermoplastic resin.
However, when the superheat-resistant thermoplastic resin is used as the matrix, the molding temperature is higher than 300 ° C., so that the polyamide resin, which is the surface modifier, is thermally decomposed during the molding, resulting in the formation of voids and welds. Problems such as a decrease in strength occur, and a satisfactory surface modifier has not yet been obtained. on the other hand,
In order to solve the above-mentioned problem of thermal decomposition, it has been proposed to use a polyetherimide resin (JP-A-62-299580) and a polyimide resin (JP-A-64-40569) having excellent heat resistance as surface modifiers. However, a problem remains in the adhesiveness with the matrix thermoplastic resin, and a sufficient reinforcing effect has not yet been achieved.

[0003]

[Means for Solving the Problems] The present inventors finally conducted the present invention as a result of various studies for solving the above problems. That is, according to the present invention, the surface of the carbon fiber is modified such that the symmetrical meta-substituted primary diamine and the symmetrical aromatic para-substituted primary diamine are in an equivalent ratio of 10 to 90:90 to 1.
A surface modifier for carbon fibers, which is a polyimide resin produced by reacting with an aromatic tetracarboxylic dianhydride after mixing with 0. Alternatively, what modifies the surface of the carbon fiber is a polyamic acid (A) produced by reacting a symmetric meta-substituted primary diamine with an aromatic tetracarboxylic dianhydride, and a symmetric aromatic para-substituted primary diamine. A polyamic acid (B) produced by reacting a primary diamine and an aromatic tetracarboxylic dianhydride in an equivalent ratio of 10 to 9
A surface modifier for carbon fibers, which is a polyimide resin produced by further advancing the reaction after mixing at 0: 90-10. In a special case, the symmetric aromatic meta-substituted primary diamine is represented by the formula (1)

[0004]

[Chemical 2] (However, in the above formula, X is O, SO ₂ , S, CO, C
The surface modifier for carbon fibers is a polyimide resin represented by H ₂ , C (CH ₃ ) ₂ , C (CF ₃ ) ₂ or a direct bond). The symmetric aromatic meta-substituted primary diamine used in the present invention (hereinafter, m
-Abbreviated as diamine. ) Can be represented by the following general formula.

[0005]

[Chemical 3] (In the above general formula, X is a direct connection, or O, SO
_{2, S, CO, CH 2} , C (CH 3) 2, C (CF 3)
Selected from ₂ , and each X may be the same or different. ) Examples of m-diamine represented by the above general formula include 3,3′-diaminodiphenyl ether and 3,3 ′.
-Diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, bis [4- (3-aminophenoxy) phenyl] methane, 2,2-bis [4- (3-aminophenoxy) ) Phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) benzene , 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy)
Phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, 4,4 '. -Bis (3-aminophenylsulfonyl) diphenyl ether, 4,4'-bis (3-aminothiophenoxy) diphenyl sulfone, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, and the like. Etc. can be used alone or in admixture of two or more. In addition, a symmetric aromatic para-substituted primary diamine (hereinafter referred to as p-
Abbreviated as diamine. ) Can be represented by the following general formula.

[0006]

[Chemical 4] (In the above general formula, X is directly connected, or O, S
O ₂ , S, CO, CH ₂ , C (CH ₃ ) ₂ , C (C
Selected from F ₃ ) ₂ and each X may be the same or different. ) Examples of p-diamine represented by the above general formula are 4,4′-diaminodiphenyl ether,
4,4'-diaminodiphenyl sulfide, 4,4'-
Diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, bis [4- (4-aminophenoxy) phenyl] methane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-
Aminophenoxy) phenyl] -1,1,1,3,3,3
3-hexafluoropropane, 1,3-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4 -(4-Aminophenoxy) phenyl] sulfoxide, bis [4- (4-
Aminophenoxy) phenyl] sulfone, bis [4-
(4-Aminophenoxy) phenyl] ether, 4,
4'-bis (4-aminophenylsulfonyl) diphenyl ether, 4,4'-bis (4-aminothiophenoxy) diphenyl sulfone, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene and the like can be mentioned. ,
These may be used alone or in combination of two or more.

On the other hand, the aromatic tetracarboxylic dianhydrides used in the present invention include pyromellitic dianhydride,
3,3 ', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic acid Dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis (3,2
4-dicarboxyphenyl) propane dianhydride, 2,2
-Bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1, 1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,3 , 6,7-Naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3 , 4-
Benzenetetracarboxylic dianhydride, 3,4,9,10
-Berylene tetracarboxylic dianhydride, 2,3,6,7
-Anthracene tetracarboxylic dianhydride, 1,2,
7,8-phenanthrene tetracarboxylic acid dianhydride and the like can be mentioned. These aromatic tetracarboxylic dianhydrides may be used alone or in combination of two or more.

The reaction for producing the polymer is usually carried out in an organic solvent. Examples of the organic solvent used in this reaction include N 2
-Methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethyl sulfoxide , Pyridine, dimethyl sulfone, hexamethylphosphoramide, tetramethylurea, N-methylcaprolactam, tetrahydrofuran, m-dioxane, p-dioxane, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2. -Bis (2-
Examples include methoxyethoxy) ethane and bis [2- (2-methoxyethoxy) ethyl] ether.

The polyamic acid, which is the precursor of the polyimide resin used in the present invention, comprises m-diamine and p-diamine in an equivalent ratio of m-diamine to p-diamine in an organic solvent of 0. 1-0.9: 0.9-0.1, the temperature is -20 ° C to 100 ° C, preferably 0 ° C to 40 ° C, and then aromatic tetracarboxylic dianhydride is added, 20 ° C to a temperature range lower than the boiling point of the solvent used, preferably 0 ° C to 40 ° C for 10 minutes or more, preferably 1 to 4
The reaction is carried out for 8 hours (method 1), or a temperature range below the boiling point of the solvent in which m-diamine and the aromatic tetracarboxylic dianhydride are used at -20 to preferably 0 ° C to 40
The polyamic acid (A) produced by reacting at 0 ° C. for 10 minutes or more, preferably 1 to 48 hours, and p-diamine and aromatic tetracarboxylic dianhydride under the same conditions and methods as the polyamic acid (A). Polyamic acid (B) produced by reaction
And the equivalent ratio in terms of diamine is 0.1 to 0.9: 0.9 to
It is obtained by mixing so as to be 0.1 (method 2). The polyamic acid thus obtained is then
The surface modifier for carbon fiber of the present invention is obtained by heating and dehydrating at 80 to 350 ° C to imidize.

Examples of the carbon fiber used in the present invention include acrylic, rayon, lignin, pitch and the like. The form of the carbon fiber is not particularly limited, and may be any of chopped strand, tow (roving), woven fabric, and the like. When the polymer thus obtained is used as a carbon fiber surface modifier, (1) the carbon fiber surface is wetted with a solution of a polyamic acid which is a precursor of a polyimide resin, then desolvated, and then The surface of the carbon fiber is modified by imidization, and (2) the surface of the carbon fiber is modified by coating the surface of the carbon fiber in a molten state with a polyimide resin. In the case of (1), the polyamic acid solution is a solution of polyamic acid dissolved in an organic solvent, and was obtained by reacting m-diamine and p-diamine with tetracarboxylic dianhydride in the organic solvent. A reaction product liquid containing a polyamic acid may be used. Further, the resin to which the surface modifier can be applied is not particularly limited as long as it is a thermoplastic resin, and it can be applied to all currently known thermoplastic resins. Specific examples include polycarbonate resin, polyamide resin, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyether imide, thermoplastic imide resin, polyether sulfone, polyether ether ketone, polyether ketone and the like. Usually, the coating amount of the surface modifier of the present invention on carbon fiber is 1
0.1 to 20 parts by weight is better than 00 parts by weight, and 0.1
If it is less than 20 parts by weight, the effect of the present invention cannot be obtained, and if it is more than 20 parts by weight, improvement in physical properties cannot be expected. In addition, it is preferable to pre-treat the surface of the carbon fiber before the treatment with the above-mentioned modifier for carbon fiber in order to enhance the adhesiveness between the modifier and the carbon fiber. The surface treatment method is not particularly limited, and all ordinary methods can be used. For example, chemical oxidation (nitric acid, permanganate / sulfuric acid, etc.), liquid-phase oxidation such as electrolytic oxidation, heating in a gas phase (air, oxygen, ozone, etc.), plasma treatment, gas-phase oxidation such as corona discharge Etc.

Further, after the treatment with the carbon fiber surface modifier, it is possible to further heat-treat. The heating temperature is 500 ° C., preferably 300 to 450 ° C., 300
If the temperature is lower than 0 ° C, the effect of heat treatment cannot be exhibited, and if it is higher than 500, the surface modifier is thermally decomposed, which is not preferable. still,
The heating time is usually 0.1 to 30 hours. The roving of the carbon fiber surface-modified with the polyimide resin as described above is cut into chopped strands with a length of 1 to 150 mm, and then a desired heat-resistant thermoplastic resin such as a polyimide resin or polyether ether ketone is used. It can be pelletized by dry-blending with polyethersulfone or the like, then extruding while melting and kneading in an extruder, and then cutting into a predetermined length. The pellets are generally known molding methods, namely compression molding, injection molding,
A desired molded product can be obtained by extrusion molding. Further, it is also possible to prepare a prepreg by aligning the carbon fibers surface-modified with the polyimide resin in one direction and impregnating the heat-resistant thermoplastic resin by a usual method.
As the above-mentioned impregnation method, for example, JP-A-1-121363
And the melt impregnation disclosed in US Pat. The prepreg thus obtained can then be cut into a certain length, laminated so that the fibers are oriented in a predetermined direction, and then a molded body can be obtained by a usual method such as hot pressing.

[0012]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 In a vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube,
1. 3-bis (3-aminophenoxy) benzene 23.
4 g (0.08 mol) and 4,4'-diaminodiphenyl ether 24.0 g (0.12 mol) were dissolved in 420 ml N, N-dimethylacetamide. 64.4 g (0.20 mol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride was added to this solution under a nitrogen atmosphere, and the mixture was stirred at 10 ° C. for 24 hours to obtain a polyamic acid solution. Got The polyamic acid solution was further diluted with N, N-dimethylacetamide to 10% by weight. Then, an acrylic carbon fiber bundle (manufactured by Toho Rayon Co., Ltd., trademark HTA, number of filaments: 12000) was immersed in the polyamic acid solution at a speed of 60 m / min, dried by heating at 130 ° C. for 60 minutes, and then in a nitrogen atmosphere. Under heating at 260 ° C. for 1 hour, polyimidation was performed to obtain carbon fibers having 3% by weight of polyimide resin on the surface. Then, the carbon fiber obtained is length 3
Cut into mm to form chopped strands, and the strand is 30 wt% and AURUM4 which is a thermoplastic polyimide resin.
50 (Mitsui Toatsu Chemical Co., Ltd .; trademark) 70 wt% was dry-blended, and then extruded while being melt-kneaded at an extrusion temperature of 400 ° C. with a 40 mm diameter extruder to obtain uniformly compounded pellets. Next, the above-mentioned homogeneously blended pellets were heated at a cylinder temperature of 400 ° C. and a mold temperature of 210 using an ordinary injection molding machine.
Create a dumbbell test piece under the temperature condition of ℃, pulling speed 5mm
When the tensile strength was measured at 1 / min, it was 2800 Kg / cm ² .

Example 2 In a vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube,
4,4'-bis (3-aminophenoxy) biphenyl 2
2.1 g (0.06 mol) and 4,4'-diaminodiphenyl ether 28.0 g (0.14 mol) were added to N, N-
Dissolve in 350 ml of dimethylacetamide, cool to around 0 ° C, and pyromellitic dianhydride 43.6 under nitrogen atmosphere.
g (0.2 mol) was added, and the mixture was stirred at around 0 ° C. for 2 hours.
Next, the solution was returned to room temperature and stirred under a nitrogen atmosphere for about 20 hours. The polyamic acid solution thus obtained was further diluted to 10% by weight with N, N-dimethylacetamide. Then, 60 acrylic carbon fiber bundles (trade name HTA, manufactured by Toho Rayon Co., Ltd., 12000 filaments)
Immerse in the above polyamic acid solution at a speed of m / min.
After heating and drying at 10 ° C. for 10 minutes and further at 160 ° C. for 20 minutes, it was heated in a nitrogen atmosphere at 270 ° C. for 20 minutes for polyimidization to obtain carbon fibers having 3% by weight of polyimide resin on the surface. Then, the same treatment as in Example 1 was carried out to measure the tensile strength, which was 3010 kg / ccm ² .

Example 3 The procedure was carried out except that the carbon fiber surface was irradiated with plasma for 5 seconds before being immersed in the polyamic acid solution, the microwave oscillation output was 1.0 kW, and the treatment gas was oxygen. When treated in the same manner as in Example 1 and measured for tensile strength, it was 3000 kg / cm ² .

Example 4 The tensile strength was measured in the same manner as in Example 2 except that the carbon fiber treated with plasma under the same conditions as in Example 3 was used, and the tensile strength was 3200 Kg / cm ² .

Comparative Example 1 Acrylic carbon fiber (trade name HTA, manufactured by Toho Rayon Co., Ltd.) surface-modified with epoxy resin was used in place of the carbon fiber modified with the surface modifier of the present invention. Example 1
When the same treatment as above was performed and the tensile strength was measured, it was 2300 Kg.
It was / cm ² . Comparative Example 2 Instead of the carbon fiber modified with the surface modifier of the present invention,
Tensile strength was obtained by treating in the same manner as in Example 1 except that acrylic carbon fiber (manufactured by Toho Rayon Co., Ltd., trade name HTA) surface-modified with polyetherimide (manufactured by Engineering Plastics Co., Ltd. Ultem 1000) was used. When measured, it was 2250 Kg / cm ² .

Comparative Example 3 Instead of the carbon fiber modified with the surface modifier of the present invention,
By the same method as in Example 1 using a polyamic acid obtained from 4,4′-bis (3-aminophenoxy) biphenyl and pyromellitic dianhydride, an imidized and surface-modified acrylic carbon fiber (Toho Rayon Co., Ltd., trade name HTA) was obtained, and the tensile strength was measured in the same manner as in Example 1 and it was 2350 Kg / m ² .

Example 4 In Example 1, a polyether ether ketone resin (trade name Victorex PEEK450P, manufactured by ICI, UK) was used in place of the thermoplastic polyimide resin as the resin, and the extrusion temperature was 400 to 380 ° C. Mold temperature is 210 ℃
To 200 ° C., the same treatment as in Example 1 was carried out, and the tensile strength was measured and found to be 2450 Kg / cm ² .

Comparative Example 4 The tensile strength was measured as in Example 4 except that the carbon fiber used in Comparative Example 1 was used, and the tensile strength was measured to be 2100 Kg / cm ^2.
Met.

Example 5 Example 2 was repeated except that 51.6 g (0.14 mol) of 4,4′-bis (4-aminophenoxy) biphenyl was used instead of 28.0 g of 4,4′-diaminodiphenyl ether. When the same treatment was performed and the tensile strength was measured, it was 30
It was 50 Kg / cm ² .

Example 6 In a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube,
31.7 g (0.08 mol) of bis [4- (3-aminophenoxy) phenyl] ketone and 24.0 g (0.12 mol) of 4,4′-diaminodiphenyl ether were added to N, N.
-Dissolved in 400 ml of dimethylacetamide, and under a nitrogen atmosphere, 43.6 g (0.2 mol) of pyromellitic dianhydride.
Was added and stirred for 24 hours. The polyamic acid solution thus obtained was further diluted to 10% by weight with N, N-dimethylacetamide. Then, an acrylic carbon fiber bundle (trade name HTA, manufactured by Toho Rayon Co., Ltd., filament number 12000)
The present) is dipped in the above polyamic acid solution at a speed of 60 m / min, dried by heating at 130 ° C. for 10 minutes and further at 160 ° C. for 20 minutes, and then heated in a nitrogen atmosphere at 270 ° C. for 20 minutes to perform polyimidization, A carbon fiber having 3% by weight of a polyimide resin on the surface was obtained. Then, the same treatment as in Example 1 was carried out and the tensile strength was measured and found to be 3020 kg / cm ² .

Example 7 In a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube,
24.0 g (0.06 mol) of bis [4- (3-aminophenoxy) phenyl] sulfide and 51.6 g (0.04 mol) of 4,4′-bis (4-aminophenoxy) biphenyl.
14 mol) was dissolved in 420 ml of N, N-dimethylacetamide, and pyromellitic dianhydride 43.
6 g (0.2 mol) was added and stirred for 24 hours. The polyamic acid solution thus obtained was further diluted to 10% by weight with N, N-dimethylacetamide. Then, an acrylic carbon fiber bundle (manufactured by Toho Rayon Co., Ltd., trademark HTA, number of filaments: 12000) is dipped in the above polyamic acid solution at a speed of 60 m / min, and further 160 minutes at 130 ° C. for 160 minutes.
After heating and drying at ℃ for 20 minutes, under a nitrogen atmosphere at 270 ℃,
It was heated for 20 minutes to be polyimidized to obtain carbon fiber having 3% by weight of polyimide resin on the surface. Then, the same treatment as in Example 1 was carried out and the tensile strength was measured and found to be 3020 kg / cm ² .

Example 8 25.9 g (0.06 mol) of bis [4- (3-aminophenoxy) phenyl] sulfone was used in place of 24.0 g of bis [4- (3-aminophenoxy) phenyl] sulfide. Other than that, the same treatment as in Example 7 was carried out, and the tensile strength was measured and found to be 3050 Kg / cm ² .

Example 9 21.1 g (0.06 mol) of 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane was added to bis [ The tensile strength was measured in the same manner as in Example 7 except that 24.0 g of 4- (3-aminophenoxy) phenyl] sulfide was used instead, and the tensile strength was 3070 Kg / cm ² .

Example 10 In a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube,
1,3-bis (3-aminophenoxy) benzene 23.
4 g (0.08 mol) was dissolved in 200 ml of N, N-dimethylacetamide, and this solution was added under nitrogen atmosphere.
25.7 g (0.08 mol) of 3 ', 4,4'-benzophenone tetracarboxylic dianhydride was added, and the mixture was allowed to stand at room temperature for 24 hours.
After stirring for a time, a polyamic acid solution was obtained. This solution is designated as solution A. Further, 2,4 g (0.12 mol) of 4,4'-diaminodiphenyl ether was dissolved in 250 ml of N, N-dimethylacetamide, and 3,3 ', 4,4'-benzophenone was dissolved in this solution under a nitrogen atmosphere. 38.7 g (0.12 mol) of tetracarboxylic dianhydride was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution. This solution is referred to as solution B. Next, mix 59 g of solution A and 74 g of solution B,
The equivalence ratio of the amic acid of the liquid A and the amic acid of the liquid B is 40: 6.
Adjusted to 0. This polyamic acid solution is further added with N, N-
Dilute to 10% by weight with dimethylacetamide. Then, an acrylic carbon fiber bundle (trade name H, manufactured by Toho Rayon Co., Ltd.)
(TA, 12,000 filaments) is immersed in the above polyamic acid solution at a speed of 60 m / min, heated and dried at 150 ° C. for 60 minutes, and then heated in a nitrogen atmosphere at 260 ° C. for 30 minutes to perform polyimidization. Resin 3% by weight
The carbon fiber which has on the surface was obtained. Then, the carbon fiber obtained is cut into a length of 3 mm to form chopped strands,
30% by weight of the strand and 70% by weight of AURUM450 (trademark of Mitsui Toatsu Chemicals, Inc.) which is a thermoplastic polyimide resin
After dry-blending, and, the mixture was extruded with a 40 mm diameter extruder at an extrusion temperature of 400 ° C. while being melt-kneaded to obtain uniformly mixed pellets. Next, using the usual injection molding machine, a dumbbell test piece is prepared from the above-mentioned uniformly mixed pellets under the temperature conditions of a cylinder temperature of 400 ° C. and a mold temperature of 210 ° C.
When the tensile strength was measured at a tensile speed of 5 mm / min, it was 290.
It was 0 Kg / cm ² .

Example 11 In a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube,
4,4'-bis (3-aminophenoxy) biphenyl 2
2.1 g (0.06 mol) was dissolved in 150 ml of N, N-dimethylacetamide, and 13.1 g (0.06 mol) of pyromellitic dianhydride was added to this solution under a nitrogen atmosphere at room temperature. After stirring for 24 hours, a polyamic acid solution was obtained. This solution is referred to as solution C. In addition, 28.0 g (0.14 mol) of 4,4'-diaminodiphenyl ether was added.
Dissolved in 240 ml of N, N-dimethylacetamide, and added pyromellitic dianhydride 3 to this solution under a nitrogen atmosphere.
0.5 g (0.14 mol) was added, and the mixture was stirred at room temperature for 24 hours to obtain a polyamic acid solution. This solution is designated as solution D.

Next, 44 g of C liquid and 71 g of D liquid are mixed, and C
The equivalence ratio of the amic acid of the liquid and the amic acid of the liquid D is 30:70.
Adjusted to. The polyamic acid solution was further diluted with N, N-dimethylacetamide to 10% by weight. Then,
Acrylic carbon fiber bundle (trade name HT, manufactured by Toho Rayon Co., Ltd.
A, 12,000 filaments) was immersed in the above polyamic acid solution at a speed of 60 m / min, heated and dried at 150 ° C. for 60 minutes, and then heated in a nitrogen atmosphere at 260 ° C. for 30 minutes to perform polyimidization. A carbon fiber having 3% by weight of resin on the surface was obtained. Then, the obtained carbon fiber is cut into a length of 3 mm to form a chopped strand, which is 30 wt% of the strand and a thermoplastic polyimide resin A.
URUM450 (trade name, manufactured by Mitsui Toatsu Kagaku Co., Ltd.) 70 wt% was dry-blended, and then extruded while being melt-kneaded at an extrusion temperature of 400 ° C. in a 40 mm diameter extruder to obtain a uniform blended pellet. Next, a dumbbell test piece was prepared from the above homogeneously mixed pellets using an ordinary injection molding machine under the conditions of a cylinder temperature of 400 ° C. and a mold temperature of 210 ° C., and the tensile strength was measured at a tensile speed of 5 mm / min.
It was Kg / cm ² .

[0028]

Effects of the Invention The surface-modified carbon fiber according to the present invention can be greatly improved in mechanical strength and the like by being filled with a highly heat-resistant engineering resin, and has great industrial significance.

Claims (3)

[Claims] 1. A method for modifying the surface of a carbon fiber, wherein a symmetrical meta-substituted primary diamine and a symmetrical aromatic para-substituted primary diamine are mixed at an equivalent ratio of 10-90: 90-10. A surface modifier for carbon fibers, which is a polyimide resin produced by reacting with an aromatic tetracarboxylic dianhydride. 2. A polyamic acid (A) produced by reacting a symmetric meta-substituted primary diamine with an aromatic tetracarboxylic dianhydride and a symmetric aromatic paraffin for modifying the surface of carbon fiber. Polyamic acid (B) produced by reacting a substituted primary diamine with an aromatic tetracarboxylic dianhydride
A surface modifying agent for carbon fibers, which is a polyimide resin produced by further mixing and mixing 10 to 90:90 to 10 in an equivalent ratio, and further advancing the reaction. 3. The symmetric aromatic meta-substituted primary diamine has the formula (1) (However, in the above formula, X is O, SO ₂ , S, CO, C
_{H 2, C (CH 3)} 2, C (CF 3) claims a ₂ or represents a direct connection) the first term, or carbon fiber for surface modifier according second term.