JPH0138911B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a carbon fiber reinforced material having polyimide resin as a matrix material (base material), which has excellent adhesiveness to the matrix resin at high temperatures and excellent processing stability. (Background Art) In recent years, carbon fibers have high strength, high elastic modulus, and specific gravity of 1.6 to 1.9, so they have been used in various matrix materials such as thermosetting or thermoplastic plastics in the form of fiber bundles (strands) or chops. It is mainly used in the fields of aircraft, automobiles, and sporting goods. In particular, carbon fiber reinforced materials using polyimide resin as a matrix material are expected to be used in areas that require high temperatures because the resin has very good heat resistance. For example, members around the engine are a typical example. However, when commonly used carbon fiber bundles are used as reinforcing agents for polyimide resins, the sizing agent attached to them to maintain workability gasifies at high temperatures, making them difficult to obtain. The disadvantage was that the reinforced materials had poor physical properties at high temperatures, especially poor adhesiveness. For this purpose, carbon fibers using heat-resistant resin as a sizing agent have been considered, but such carbon fibers tend to generate fuzz during processing, and the sizing agent itself changes over time, resulting in poor processability. It had the disadvantage of being unstable. (Problem to be solved by the invention) The present inventors have investigated a sizing agent-attached carbon fiber that can be used in a polyimide matrix resin and has excellent heat resistance, processability, and stability, and has solved the above-mentioned drawbacks. , which led to the present invention. (Structure and operation of the invention) The present invention is based on the general formula (1) (Here, R:

Carbon fibers for reinforcing polyimide resin to which 0.1 to 5% by weight of a sizing agent composition containing polymaleimide and epoxy resin represented by [Formula]) and having a viscosity of 10 to 5 x ¹⁰⁴ poise at 50°C are attached. be. Particularly desirably, the sizing composition has a polymaleimide content of 15% by weight or more,
In addition, the amount of weight loss after treatment at 230°C in air for 1 hour is 5% or less. The polymaleimide used in the present invention is obtained by reacting an aromatic amine at a ratio of 2 to 60 moles with respect to 1 mole of aromatic dialdehyde, and then undergoes an addition reaction with maleic anhydride to form polyamic acid, which is then dehydrated. Obtained by cyclization. Here, the aromatic aldehyde has the general formula These are 1.2-benzenedialdehyde, 1.3-benzenedialdehyde, and 1.4-benzenedialdehyde, and 1.4-benzenedialdehyde is preferable from the viewpoint of heat resistance. Further, aromatic amines include aniline, O-toluidine, m-toluidine, and P-toluidine, and aniline is usually preferred. The polymaleimide in the present invention may be a reaction product containing 60% by weight or more of the compound represented by general formula (1), or may be an extracted and purified product of this reaction product. The epoxy resins used in the present invention are usually diglycidyl ethers of bisphenol A, bisphenol F, and bisphenol S, and their commercial products include Epicote 827, Epicote 828, Epicote 834 (manufactured by Yuka Ciel Epoxy Co., Ltd.). Phenol novolac epoxy with an epoxy equivalent of 100 to 230, such as Epicote 152 and 154 (manufactured by Yuka Ciel Epoxy Co., Ltd.) and Araldite EPN1138 (manufactured by Ciba Geigy) with an epoxy equivalent of 170 to 182. ,
The urethane-modified epoxy resin is a commercially available product having an epoxy equivalent of 210 to 250, such as Adeka Resin EPU-6 and EPU-6A (manufactured by Asahi Denka Co., Ltd.), and is one or more of these. Epoxy resins made from other amino compounds are not preferred because the hardness of the fibers changes economically and processability deteriorates. In the present invention, a known nonionic surfactant consisting of a polymaleimide, an epoxy resin and, if necessary, a surfactant exhibiting lubricity of up to 10% by weight, such as a polyether adduct of an aliphatic or aromatic alkyl, and a focusing property are used. It is applied to carbon fibers in the form of a mixture with polyvinyl alcohol, etc., to give a viscosity of 10 to 5 x ¹⁰⁴ poise at 50°C.
It is preferable that the content is at least % by weight. If it is less than 15% by weight, the heat resistance of the molded product tends to be poor, which is not preferable. If the viscosity of the mixture at 50° C. is less than 10 poise, the carbon fibers to which the mixture is attached will not have sufficient cohesiveness, resulting in poor processability, which is not preferred. In addition, if it exceeds 5 x 10 ⁴ poise, the carbon fibers to which the mixture is attached will be impregnated with polyimide matrix resin, and the physical properties at high temperatures of the obtained molded product, especially the interlaminar shear strength (ILSS), will decrease. So I don't like it. Further, it is preferable that the weight loss of the mixture after being treated in air at 230° C. for 1 hour is 5% or less. If it exceeds 5%, the high-temperature physical properties of the molded product will deteriorate as described above. The higher the proportion of polymaleimide in the sizing composition, the less weight loss will occur, but the amount of weight loss will also be affected by the type of epoxy resin and the amount and type of added lubricant, surfactant, and focusing compound. Therefore, it is desirable to appropriately select the content of polymaleimide. The method of attachment is to melt and mix the polymaleimide, epoxy resin, and additives if necessary in a kneader or the like, or to mix each alone in a good solvent such as acetone, methyl ethyl ketone, or tetrahydrofuran at a concentration of 1.0 to 100 g/ml. The carbon fibers are immersed in the solution obtained by completely dissolving the carbon fibers, or the carbon fibers are sprayed with the solution so that the carbon fibers adhere to the carbon fibers in an amount of 0.1 to 5% by weight (relative to the total weight). If the amount of adhesion is less than 0.1% by weight, the processability of the carbon fiber will be poor, which is not preferable. If the amount exceeds 5% by weight, the impregnation of the matrix resin between the carbon fibers during molding will decrease, and in addition, the physical properties of the molded product at high temperatures will decrease.
In particular, this is not preferable because the interlaminar shear strength becomes low. The carbon fiber used in the present invention has a carbon content of 85
% by weight, and the diameter of a single fiber made from acrylonitrile fiber or pitch fiber as a starting material
It is a fiber bundle consisting of 0.1 to 20 microns, 100 to 100,000 fibers, and has a fiber strength of 1 to 7 gigapascals (GPa) and an elastic modulus of 100 to 500 gigapascals (GPa). The sizing agent-attached carbon fibers of the present invention can be made of polyimide matrix resins such as polyimide resins (product names such as PMR-11 and LARK), triazine-based bismaleide resins (product names such as BT Resin), etc.
Thermosetting resins such as polymaleimide resins such as NN'-4.4'-diphenylmethane bismaleimide and polyetherimide resins (trade name, Ultem, etc.)
The carbon fibers are preferably composited with thermoplastic resins such as carbon fibers, and the carbon fibers are used in the form of long fibers or single fibers. (Effects of the Invention) The sizing agent-attached carbon fibers of the present invention have excellent heat resistance, are easy to handle when processed into textiles, knitted fabrics, and sheet materials, and can be processed smoothly without generating fuzz. Because the fiber has excellent properties and stable processability even after long-term storage, it can be combined with heat-resistant resin, especially polyimide resin, which has a heat distortion temperature of 200℃ or higher, to create a fiber with excellent physical properties at high temperatures. It can be a heat-resistant composite material. Therefore, it can be used in place of metals conventionally used as materials for parts exposed to high temperatures, such as engines, and can be made into a material suitable for achieving energy savings by reducing weight. (Examples and Comparative Examples) The present invention will be described in more detail by giving examples. Unless otherwise specified, "%" and "part" are expressed by weight. Example 1 Polyamine obtained from 1.4-benzenedialdehyde (0.44 mol) and aniline (2.6 mol) (softening point 115-121°C, neutralization equivalent 118, perchloric acid titration method)
A reaction product (softening point: 160-180°C) was prepared by reacting 94.4 g with 78.6 g of maleic anhydride. This reactant has the formula (3) ( _R1 :

It contained 68% of a polymaleimide compound represented by the following formula. 35% of this reaction product and 65% of Epicote 828 (manufactured by Yuka Ciel Epoxy Co., Ltd.), which is a diglycidyl ether of bisphenol A, were mixed, and the resulting mixture was dissolved in acetone to a concentration of 1.5%. Carbon fibers (strength 4.2 GPa, elastic modulus 250 GPa) consisting of 6,000 fibers with a diameter of 7 microns were immersed in this solution, and 80% of the solution was adhered to the fibers, and the mixture was dried at 130°C. Carbon fiber was obtained. When the adhering mixture was extracted from the obtained carbon fiber by acetone reflux extraction method, the amount of adhesion was 1.18%, and the viscosity of the extracted mixture was measured using a viscosity measuring device (Rheometrics RD-7700 type). When measured, it was 1300 poise at 50°C. Regarding the hardness of the fibers before and after storing the carbon fiber bundles coated with the above mixture in a room at 25℃ for 6 months,
The processability of the acetone refluxed extract was evaluated based on the fuzz condition of the fiber surface when rolled up at 60 m/min into a paper tube (outer diameter 3 inches, length 11 inches), and the heat resistance of the acetone reflux extract (inner diameter 45 mm, height 50 mm). In addition to examining the oxidation weight loss when 1 gram of the object to be measured was placed in the air and treated at 230°C for 1 hour, 0.25% of diazabicyclooctane was added as a catalyst to Compimide H-800 (manufactured by Technochemy), which is a bismaleimide resin. %
(for resin) to make a unidirectional prepreg,
Molded plate in autoclave at 190℃ for 3 hours under 4Kgf/ ^cm2 [thickness (t) 1mm, fiber volume content (vf) 60
Volume %] was further heated at 210°C for 15 hours, and the interlaminar shear strength (ILSS) of the obtained molded plate was measured at 25°C and 250°C (the measuring device was an Instron universal testing machine, and the measuring method was ASTMD). −
2344). As shown in Table 1, the fibers have good processability and good processability even after long-term storage.Furthermore, the sizing agent has good heat resistance and the molded product has good adhesion at high temperatures (ILSS). ) were also excellent.

【table】

[Table] Examples 2 to 3 and Comparative Examples 1 to 3 The polymaleimide obtained in Example 1 and Epicote 152 (manufactured by Yuka Ciel Epoxy Co., Ltd.), which is a phenol novolak type epoxy resin, were mixed as shown in Table 2. Carbon fibers were obtained in the same manner as in Example 1, except that carbon fibers were used as the sizing agent. The results of examining the properties of the fibers are also shown in Table 2. Within the scope of the present invention, the processability of the fiber is good;
In addition, it shows good processability even after long-term storage, and
The heat resistance of the sizing agent and the adhesion of molded products at high temperatures (ILSS) were also excellent.

【table】

[Table] Examples 4 to 5 A sizing agent (A ) and a diglycidyl ether compound of bisphenol A (manufactured by Yuka Ciel Epoxy Co., Ltd., Epicoat 815) in place of tetraglycidyldiaminophenylmethane as shown in Table 3. Carbon fibers were obtained in the same manner as in Example 1 except for the following. Table 3 shows the results of investigating its properties.

【table】

[Table] Example 6 In Example 2, 1, 5, and 10 parts of polyoxyethylene (n=10) lauryl ether having lubricity as an additive were added to 100 parts of the mixed system of polymaleimide and epoxy resin. , Example 1
Oxidation loss was measured in the same manner as above. The results were 2.3%, 2.5%, and 2.7%, respectively, showing good values. Further, the viscosities of the obtained sizing agent compositions were 1.2×10 ⁴ , 1.0×10 ⁴ and 7.0×10 ³ poise, respectively. The sizing agent composition was applied to carbon fibers in an amount of 1.5% in the same manner as in Example 1, and various properties were measured. There was no change in the hardness of the fiber bundle after 6 months, and there was no change in the processability of the fibers after 6 months, and the ILSS of each molded product was 12.3 ± 0.1 GPa at 25°C and 5.3 ± 0.1 GPa when measured at 250°C. It was hot inside.

Claims (1)

[Claims] 1 General formula (1) (Here, R: [Formula]) A polyimide system containing 0.1 to 5% by weight of a sizing agent composition containing a polymaleimide represented by the formula and an epoxy resin and having a viscosity of 10 to 5 x ¹⁰⁴ poise at 50°C Carbon fiber for resin reinforcement. 2. The carbon fiber for reinforcing polyimide resin according to claim 1, wherein the content of polymaleimide in the sizing composition is 15% by weight or more. 3. The carbon fiber for reinforcing polyimide resin according to claim 1, wherein the weight loss of the sizing composition after being treated in air at 230° C. for 1 hour is 5% or less.