JPS63221169A - Carbon fiber/high-molecular material composite composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. having excellent flexural strength, flexural modulus, etc., consisting of a compd. having epoxy group, a specific high- molecular compd. (mixture) and carbon fiber having acidic functional group in the form of an alkali metal salt on the surface thereof. CONSTITUTION:Carbon fiber obtd. from PAN or pitch is subjected to a vapor phase oxidation treatment, electrolytic oxidation, liquid phase oxidation, etc. to form an acidic functional group such as COOH, OH,=O or lactone type functional group. The carbon fiber is then brought into contact with an alkaline substance such as NaOH, etc. to convert the functional group into an alkali metal salt, thus obtaining carbon fiber (B). A high-molecular compd. (A) having COOH groups or anhydride groups on its straight-chain or branched chain or a mixture (A) thereof with other high-molecular compd. such as a polyolefin is blended with 1-60wt.% component B and a compd. (C) having epoxy group and acting as a coupling agent between the components A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a polymer composite material reinforced with carbon fiber as a filler.

(Prior Art) Composite materials such as carbon fiber-reinforced resins are being developed for use in a wide range of fields, including sporting goods, leisure goods, aerospace materials, and electromagnetic shielding materials.

It is expected that its applications will further expand in the future, such as in fields that take advantage of the excellent properties of carbon fiber, such as specific strength and specific modulus, as well as fields that take advantage of its excellent electrical conductivity.

However, when compounding, the adhesive strength with the matrix is weak, and the characteristics of the material cannot be fully utilized. This is currently the biggest problem to be overcome in this field, and various proposals have been made to improve this problem. ing.

Oxidation treatment is a typical method for modifying carbon fibers. Oxidation treatment methods include gas phase oxidation, liquid phase oxidation using chemicals, and electrolytic oxidation that utilizes the electrical conductivity of carbon fibers.In commercial plants, electrolysis is the most widely adopted method due to its efficiency and controllability. has been done.

(Problems to be Solved by the Invention) No matter which of the above treatment methods is adopted, excessive oxidation treatment causes deterioration of the carbon material itself, so there is a natural limit to the treatment. Alternatively, even if a commercially available carbon fiber treated with a coupling agent is used as a filler and composited with a polymeric material, it does not necessarily exhibit good adhesion to the polymeric material. For example, when polyolefin is used as a matrix, the adhesion is poor, and when cross-sectionally observed after tensile fracture, the phenomenon of slippage at the interface between the matrix and the filler is frequently observed, and the composite performance is expected from the characteristics of each. However, the characteristics obtained are far lower than those obtained. With respect to various other polymeric materials that can be used as a matrix, the degree of achievement of the expected conduit properties varies depending on the material, but in any case, it cannot be said that they are fully satisfactory.

As an indicator of the degree of achievement of the conduit properties mentioned here, for example, in the case of long fibers, evaluation of additivity based on the volume content ratio is generally used for tensile strength, and in the case of short fibers, a more complicated evaluation is used. For example, the KellyTyson equation is used.

As mentioned above, with conventional techniques, it is not possible to obtain sufficient adhesion only by surface modification of carbon fibers, so when the matrix is polyolefin, a modified polymer is added as part of the composition for compounding. This is also being attempted.

For example, a copolymer or graft polymer of an olefin and an unsaturated monomer having an epoxy group and capable of radical copolymerization,
Alternatively, it is a modified teriolefin such as a copolymer or graft polymer of an olefin and an unsaturated dicarboxylic acid or its anhydride.

When these treatments are not applied to composite materials obtained by combinations of these, i.e., commercially available carbon fibers that have been oxidized and then treated with Cysong or coupling agents, modified polyolefins, and matrix polyolefins alone or in combination with copolymers. Although there are cases where an improvement is seen in mechanical evaluation when compared to There is a lot of room for improvement.

In addition, various other methods for modifying the surface of carbon fibers, such as grafting or coating with various polymers, have been proposed, but these methods have not been widely adopted due to the complexity of the process, the cost, and the effectiveness of the treatment. Not yet reached.

The present inventor has arrived at the present invention as a result of intensive studies aimed at obtaining a composite material that exhibits excellent properties through easy processing and combination with existing materials without deteriorating the properties of carbon fiber. It is.

(Means for Solving the Problems) The present invention is a composite composition of carbon fibers (including graphite fibers) and a polymer compound, comprising: (A) a compound having an epoxy group; (B) a linear or branched compound; A polymer compound having a carboxylic acid group or its anhydride group in its chain, or a mixture of this polymer compound and another polymer compound other than a compound having an epoxy group (C) Acidic functionality on the surface It is characterized by being made of carbon fiber whose base is an alkali metal salt.

According to the present invention, without reducing the properties of carbon fiber,
By improving the adhesion between carbon fibers and polymeric materials, it is possible to obtain carbon fiber-reinforced polymer composite compositions that exhibit excellent properties.

The present inventor has developed a composition consisting of a carbon fiber and a polymer in which the acidic groups on the surface have been treated with alkali metal salts, and in which the amount of polymers having epoxy groups in the linear or branched chains of the polymer is reduced. A patent application has been filed for a composite composition characterized by containing a portion of both.

As a result of further research into this, the present invention has found that after the acidic group on the surface of the carbon fiber reacts with the epoxy group, an even better product can be obtained by utilizing the reactivity with the carboxylic acid group or its anhydride group. It is a composite composition with high performance.

Regarding the properties of composite compositions, in the case of thermosetting adhesive strength can be evaluated using ILSS, etc., and in the case of thermoplastic compositions, although it cannot be directly evaluated by ILSS etc., the obtained composition If we look at the improvement in the mechanical properties of the product, it is clear that this is due to the improvement in adhesiveness, and this can be used for evaluation.

The acidic group generated on the surface of carbon fiber is -COOH.

-OH, =O5, and their combined lactone type.

To attach these acidic groups to the surface of carbon fibers, carbon fibers are oxidized in a gas phase (for example, in air) or electrolytically oxidized.

Treatment such as liquid phase oxidation may be performed.

It is reported in the literature that a small amount of acidic groups exist on the surface of carbon fibers even before oxidation treatment as a surface treatment.
It is also reported in ``Carbon Fiber'' edited by Inutani Sugibe, p. 222 (published by Kindai Editorial Company, 1981).

However, since there are only a few naturally occurring acidic groups, oxidation treatment is generally performed by the method described above. Preferably, 10 equivalents/f (CF) or more of acidic groups are added (CF is the English abbreviation for carbon fiber).

The upper limit varies depending on the type of carbon fiber, but the treatment should be stopped at a level that does not cause a decrease in mechanical strength due to fiber damage.
i O-' ”AM/? (CF) 8-ch 9
The carbon fibers used are all known carbon fibers such as PAN type, pitch type, vapor growth type, etc., and these can be used regardless of heat treatment conditions such as carbonized fibers and graphitized fibers.

To convert the acid groups on the surface of carbon fibers into alkali metal salts, combine the carbon fibers with an alkaline substance (NaOH).

KOH, etc.) can be used to neutralize the acidic groups on the surface, such as a gas phase method in which the carbon fiber is placed in an atmosphere containing an alkaline substance, or a method in which the carbon fiber is immersed or coated in a liquid. Any method can be used if it can be achieved. Those treated in liquid are then washed with water and dried before use.

The present invention is a composite material of surface-treated carbon fiber and a polymer compound.
It is used as a coupling agent between an alkali metal salt of an acidic group on the surface of carbon fiber and a polymer compound having a carboxylic acid group or its anhydride group.

A monomer is a compound having an epoxy group.

Any of the oligomers or oligomers may be used, such as glycidyl methacrylate.

Styrene oxide, epichlorohydrin, etc., and oligomers obtained by known methods, and polymers include bisphenol A-based and other epoxy resins.
Commercially available resins are used (see "Epoxy Resins" edited by Hiroshi Kakiuchi (published in June 1977 by Shokodo), pages 51 to 105).

The polymer compound having a carboxylic acid group or its anhydride group in a straight chain or a branched chain includes a copolymerization of an unsaturated monomer having a carboxylic acid group or its anhydride group and capable of radical copolymerization with a polyolefin, etc. Examples include coalescence or graft polymers.

As will be described later, the composition of the present invention is effective with a very small amount of a compound having epoxy, a polymer compound having a carboxylic acid group, etc. In addition to these compounds, polyolefin, ethylene-vinyl acetate copolymer, etc. Polymer compounds such as the following can be included.

In this case, for example, when polyzolopyrene is used in combination, a copolymer of polyzolopyrene and an unsaturated monomer capable of graft polymerization is suitable as a compound having a carboxylic acid group etc., considering its compatibility with polyzolopyrene. Atmer (trademark manufactured by Mitsui Petrochemical Co., Ltd.) is a product that is used for this purpose.

Next, the composition ratio in the composition of the present invention will be explained.

Ring opening of a compound having an epoxy group is promoted by the alkali metal salt on the surface of the carbon fiber, and the ring-opened product bonds to a compound having a carboxylic acid group or its anhydride group through these groups. The amount of these compounds is preferably such that the amount of epoxy groups, carboxylic acid groups, or their anhydride groups is equivalent to or more than the alkali metal salt, but according to experimental results, Even at the following amounts, the effect of Kanashi is observed. There is no particular restriction on the upper limit of the amount, but it can be determined as appropriate based on the characteristics and intended use of the composition, as well as the combination of polymer compounds other than those mentioned above.

The amount of carbon fiber in the composition of the present invention can vary widely depending on the application, ranging from as little as 1 to 2% (by weight, hereinafter the same) to as much as 60%.

When a thermoplastic resin is included in the polymer compound, the method for mixing or further molding these composite compositions is to first treat carbon fibers with a compound having an epoxy group;
Next, a polymer having a caldic acid group or its anhydride group and a thermoplastic resin are tri-blended and then made into R-lett or injection molded using a kneading extruder, or a method of tri-blending them from the beginning and then using a kneading extruder It is common to combine them.

Further, when using a thermosetting polymer, in addition to the method of triblending and then thermosetting, it is also possible to make a carbon fiber solegreg composition and then mold it into a shape and thermosetting.

(Function) The acidic functional groups obtained by the oxidation treatment of the surface of carbon fibers were converted into alkali metal salts.This promoted the ring opening of the jepoxy groups, and the subsequent ring opening and cal? It is believed that as a result of the chemical bonding of the acid groups or their anhydride groups, a composite material with properties superior to those of carbon fiber-reinforced polymer materials produced by conventional methods was obtained.

After carbon fiber is treated with an acid, it is necessary to convert it into an alkali salt, for example, by separately preparing an alkali metal salt of an organic acid.
Even if this is attached to the surface of carbon fibers, the effects of the present invention cannot be obtained.

(Effect) According to the present invention, without deteriorating the characteristics of carbon fiber,
By simple processing and combination of specific polymers, mechanical properties such as flexural strength and flexural modulus can be improved as shown in Examples later.

(Example) (1) Reaction of carbon fiber and glycicin methacrylate Commercially available PΔ carbon fiber (manufactured by Toho Bethlon: HTA-0
6) was extracted with acetone for 6 hours at 55° C. to remove the sizing agent (the surface condition at this point was a state where oxidation treatment was performed after carbonization).

After drying, add excess KOH aqueous solution (1150N)
When the total acidic groups on the carbon fiber surface were quantified by back titration with C1 aqueous solution (1150N), it was 4 × 10 equivalents/P (CF
)Met.

After removing the sizing agent, the dried carbon fiber was treated with 10 times the equivalent of K.
It was immersed in an OH aqueous solution, treated at 80°C for 4 hours, and then washed with water. After washing with water, the carbon fibers were vacuum dried at 100° C. to obtain carbon fibers in which the acidic groups on the surface were made into alkali metal salts.

Next, 30 f of the above-treated carbon fiber, 300 m of glycidyl methacrylate, 700 m of nitrobenzene as a solvent, and 2?N-phenyl-β-naphthylamine as a radical polymerization inhibitor. Put it in a separable flask, stir it, and add 12
It was treated at 0°C for 2 hours. After the reaction was completed, methanol was added to precipitate the polymer, which was separated by filtration. The polymer and carbon fibers remaining on the ν paper were extracted with chloroform and dried to obtain carbon fibers reacted with a monomer having an epoxy group.

(2) Reaction between charcoal 1 fibers and styrene oxide According to the method shown in JP-A-58-180615, a liquid in which ultrafine iron powder was dispersed in ethyl alcohol using hydrogen gas as a carrier was placed in a reaction tube. The vapor-grown carbon fiber obtained by the injection method was heated to 48% by heating with 60% HNO at 100°C.
Hr oxidation treatment was performed. After treatment, it was washed with water until it reached pi-17.

It was crushed, treated at 80°C for 2 hours, and then washed with water.

After washing with water, the carbon fibers were vacuum dried at 100° C. to obtain carbon fibers in which the acidic groups on the surface were made into alkali metal salts.

Next, the treated carbon fiber 301. Styrene oxide (250 m) and nitrobenzene (750 m) as a solvent were placed in a separable flask and treated at 110°C for 3 hours with stirring. After the reaction was completed, methanol was added to precipitate the polymer, which was separated by filtration. The polymer and carbon fibers remaining on the F paper were extracted with chloroform and dried to obtain carbon fibers reacted with a monomer having an epoxy group.

(3) Caldic acid-modified polypropylene (trade name Nijiyo Aroma-2 brand: MA510) 10
0P, maleic anhydride (manufactured by Toju Kasei) 75SL#benzoyl peroxide (manufactured by Tokyo Kasei) 0.75 P was placed in xylene 1.6 II as a solvent and reacted at 120° C. for 2.5 hours. After the reaction was completed, acetone was added, flJmer was precipitated, and unreacted monomers were washed out by redissolution and reprecipitation to obtain modified polypropylene containing carboxylic acid anhydride groups.

The amount of grafting was calibrated by infrared absorption spectrum. The amount of grafting was 0.4% by weight.

(A) Comparative Carbon Fiber A commercially available carbon fiber (HTA-C6 manufactured by Toho Peslon) was used as it was. Note that this fiber has been oxidized and added with a sizing agent by the manufacturer.

(5) Comparative carbon fiber The carbon fiber described above was subjected to the sizing agent removal treatment by acetone extraction as shown in Example 1.

In other words, it corresponds to the surface condition of carbon fibers subjected to only oxidation treatment.

(6) Comparative carbon fiber The carbon fiber of (5) above was treated in the same manner as in (1) up to and including converting the acidic groups on the surface into alkali metal salts.

(7) Comparative carbon fiber The vapor-grown carbon fiber shown in (2) has been subjected to oxidation treatment.

(8) The same treatment procedure as comparative carbon fiber (2), but the vapor-grown carbon fiber is treated to convert the acidic groups on the surface into alkali metal salts◇ (9) Method of comparative carbon fiber (2) Preparation of carbon fiber 0 00 composite material as produced in the gas phase and its properties The above-mentioned carbon fibers, modified I-ligropyrene and polyzorogylene having a carmono-anhydride group (trade name: Nijiyo Aroma - Brand: MA510) Radezolast Mill (manufactured by Toyo Seiki Seisakusho: Type 2B-1) was prepared using the compounding ratio shown in Table 1.
25, Roller mixer model 1'! -60) was used for kneading. The carbon fiber used was a PAN type carbon fiber with a length of about 6 fibers, and after kneading, the average length was 300 μm. Further, fine carbon fibers were used in the vapor phase method.

Mixed wire conditions Temperature: 170° C. Time: Resin wire: 5 minutes Addition of carbon fiber: Kneading After cooling, the obtained mixed wire material was cut into an average size of 2 to 4 fl cubes, and molded at 220 C using a hot plate press. Test pieces were punched out to a predetermined size from a flat plate and subjected to bending strength, flexural modulus, tensile strength, and Izot impact tests.

The results are summarized in Table 1.

It has become clear that the properties of a composite obtained by combining both PAN-based carbon fiber and phase-grown carbon fiber using the powder method are significantly improved compared to the case where one of the combinations is missing.

Claims (1)

[Scope of Claims] (A) A compound having an epoxy group (B) A polymer compound having a carboxylic acid group or its anhydride group in a straight or branched chain, or a compound other than the polymer compound and an epoxy group. (C) A carbon fiber composite polymer composition comprising carbon fibers in which the acidic functional group on the surface is an alkali metal salt.