JPH04170435A - Short carbon fiber aggreate and thermoplastic resin composition reinforced therewith - Google Patents

Abstract

PURPOSE:To obtain the title compsn. having good physical properties with an excellent processability under a stable feeding by compounding a thermoplastic resin with a short carbon-fiber aggregate surface-coated with an epoxy sizing agent emulsion having a specified mean particle diameter. CONSTITUTION:100 pts.wt. thermoplastic resin is compounded with 5-40 pts.wt. short carbon fiber aggregate surface-coated with a sizing agent emulsion mainly comprising an epoxy compd. and having a mean particle diameter of 0.3-1mum, pref. 0.4-0.6mum, (the amt. of the agent attached to the aggregate being 0.1-10wt.% based on the total wt.). giving the title compsn. A mixture comprising 45-95wt.%, pref. 45-65wt.%, epoxy compd. which is liq. at room temp (e.g. an epoxy compd. of a bisphenel A type having a mol.wt. of 470 or lower) and 5-45wt.%, pref. 35-45wt.%, epoxy compd. which is solid at room temp. (e.g. an epoxy compd, of a bisphenol A type having a mol.wt. of 900-5000) is pref. as the epoxy compd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to short carbon fiber aggregates and fiber-reinforced thermoplastic resin compositions using the same as reinforcing materials. More specifically, the present invention relates to short carbon fiber aggregates that are easy to handle and have excellent dispersibility in a matrix as reinforcing materials for short fiber-reinforced molding materials, and to fiber-reinforced thermoplastic resin compositions using the same as reinforcing materials. It is.

[Prior Art] In recent years, fiber-reinforced resin compositions made by mixing and dispersing short carbon fibers in various matrices have been developed to have high strength, high rigidity, low specific gravity, high electrical conductivity, low coefficient of thermal expansion, and high abrasion resistance. It is attracting attention as an industrially important material because it uses carbon fiber, which has excellent characteristics such as durability.

Generally, when carbon fibers are mixed and dispersed in various matrices such as polyester, polyamide, polyolefin, acrylic resin, epoxy resin, phenolic resin, etc. to obtain fiber reinforced resin materials, short carbon fiber aggregates are used as pellets or powder of thermoplastic resin. At the same time, a method is used in which the pellets are fed to an extruder, melt-extruded, pelletized, and then molded using an injection molding machine. At that time, a large number of short carbon fibers are aggregated in advance using a sizing agent or the like in order to facilitate handling of the carbon short fibers and improve workability in the mixing and dispersion steps. As a method for coating the surface of this sizing agent, for example, a bundle of hundreds to hundreds of thousands of long carbon fibers is coated with the sizing agent.
After impregnating with sizing agent, dry. The sizing agent used for surface coating may be dissolved in a solvent or the like, or an emulsion may be used. Various such sizing agents are known, and for example, matrix resins such as those described above are commonly used. Normally, the method of supplying short carbon fiber aggregates and thermoplastic resin to an extruder is as follows:
The following two methods are adopted.

1) A method of tri-blending a short carbon fiber aggregate and a thermoplastic resin, and then feeding the mixture to an extruder. (Tri-blend method) 2) A method in which a thermoplastic resin is first supplied to an extruder, and then a short carbon fiber aggregate is supplied to the melted portion of the thermoplastic resin. (Side Feed Method) In the case of carbon fiber-reinforced thermoplastic resins, it is known that the thread length in the molded body has a great effect on the physical properties of the composite material. Therefore, recently, 2)
The side-feed method has come to be used.

[Problems to be Solved by the Invention] However, in the conventional short carbon fiber aggregates, the aggregation was not sufficient and there were various problems in the process of mixing and dispersing into the matrix resin.

For example, in the case of the tri-blend method, if the short carbon fibers have insufficient bundling, this aggregate will be defibrated by frictional force with the resin or heat before compounding, becoming fluff-like and entering the hopper of the extruder. In this case, short carbon fibers become fluffy, clogging the feeding process, making it impossible to feed, and making it difficult to consistently obtain a uniform resin composition. Furthermore, in the case of the side-feed method, higher convergence is required than in tri-blend because the short carbon fiber aggregate itself is fed by a screw feeder or the like. If the short carbon fibers have low cohesiveness,
It may become impossible to supply a constant amount of short carbon fibers, or even if the short carbon fibers have good convergence at room temperature, they may be defibrated in the screw feeder due to heat, making it impossible to supply uniform resin compositions on a regular basis. difficult to obtain.

Therefore, in order to improve the cohesiveness of short carbon fibers, methods have been proposed in which the amount of sizing agent is increased or the sizing agent is crosslinked to improve the cohesiveness. However, simply increasing the convergence too much will improve the feedability, but
Carbon fibers are not uniformly dispersed in the molded article, resulting in poor mechanical properties. For these reasons, it is a challenge to obtain a method that satisfactorily satisfies both convergence and dispersion.

[Means for Solving the Problems] Therefore, the present inventors have conducted intensive studies to solve not only various problems in the process of mixing and dispersing the matrix resin especially in the side feed method, but also to improve the mechanical properties at the same time. By blending short carbon fiber aggregates whose surface is coated with an epoxy emulsion-based sizing agent whose average particle diameter is controlled within a specific range into a thermoplastic resin, various types of carbon fiber aggregates that are surface-coated with an epoxy emulsion-based sizing agent whose average particle diameter is controlled within a specific range are mixed into a thermoplastic resin, and which are mixed into the matrix resin and dispersed in the process. The inventors have discovered that the above problems can be solved and a resin composition with excellent physical properties can be obtained, and the present invention has been achieved. That is, the object of the present invention is to provide a fiber-reinforced resin composition that has excellent workability and stable supply properties when producing a fiber-reinforced resin composition, and has excellent dispersibility in a matrix, and the resulting resin composition exhibits good physical properties. The object of the present invention is to provide short carbon fiber aggregates for the purpose of the present invention, as well as resin compositions having extremely excellent mechanical properties by combining such aggregates with thermoplastic resins.

The purpose is (1) to provide an aggregate of carbon short fibers whose surface is coated with an emulsion-based sizing agent containing an epoxy compound as a main component, wherein the average particle diameter of the emulsion of the epoxy emulsion-based sizing agent is 0.3 μm to 1 μm, and the content of the sizing agent is 0.1 to 1 μm based on the total amount of short carbon fibers.
10% by weight; and (2) a carbon short fiber aggregate whose surface is coated with an emulsion-based sizing agent containing an epoxy compound as a main component, the epoxy emulsion-based sizing agent The average particle diameter of the emulsion is in the range of 0.3 μm to 1 μm, and the content of the sizing agent is in the range of 0.1 to 1 μm based on the total amount of short carbon fibers.
Thermoplastic resin 1 contains carbon short fiber aggregate containing 10% by weight.
This can be easily achieved by using a fiber-reinforced thermoplastic resin composition in an amount of 5 to 40 parts by weight per 0.00 parts by weight.

The present invention will be explained in detail below.

The sizing agent in the present invention is preferably a mixture whose main components are an epoxy compound that is liquid at room temperature and an epoxy compound that is solid at room temperature, and the mixing ratio is preferably 45 to 95% by weight of the epoxy compound that is liquid at room temperature. is 45
~65% by weight, and 5-4 epoxy compounds solid at room temperature
5% by weight, particularly preferably from 35 to 45% by weight. If the content of the epoxy compound, which is liquid at room temperature, exceeds 95%, the tri-blendability and extrudability of the short carbon fiber aggregate and matrix resin will decrease, and if it is less than 45%, the mechanical properties of the short carbon fiber reinforced thermoplastic resin will deteriorate. descend.

Also, examples of surfactants used in emulsions include polyoxymethylene castor? Examples include at least one type of surfactant selected from polyoxyethylene alkyl ethers or polyoxyethylene alkyl allyl ethers such as polyether, nonylphenyl ether, and styrenated phenyl ether, and polyvinyl alcohol. The amount of this surfactant is 10 to 25% by weight, preferably 10 to 25% by weight based on the epoxy compound.
A range of 20% by weight is preferred. If it is less than 10% by weight, the stability of the emulsion will decrease. If it exceeds 25% by weight,
The mechanical properties of the molded product tend to deteriorate.

The particle size of the emulsion is controlled by the mechanical stirring force during emulsification. As for the particle size, the average particle size is 0.3 μm ~
1 .mu.m, preferably 0.4 .mu.m - 0.6 .mu.m. If the particle size is too small, the convergence will be lowered by heat, and the yarn will be disintegrated during feeding, making it impossible to feed the yarn. In addition, when the particle size becomes coarse, the stability of the emulsion decreases and it becomes difficult to uniformly condense the emulsion.

The epoxy compounds that are liquid at room temperature used in the present invention include, for example, low polymers of epoxy compounds such as bisphenol type, novolac type, alicyclic type, resol type, and amine type, and these epoxy compounds and curing agents. Among these, preferred are bisphenol A type epoxy compounds with a molecular weight of 470 or less, or novolac type epoxy compounds with a molecular weight of 600 or less. for example,
"Epikoat 815", "Epicoat 8" manufactured by Shell Chemical Co., Ltd.
Epoxy compounds that are solid at room temperature include, for example, bisphenol type, novolak, etc. Examples include monomers of epoxy compounds such as type, alicyclic type, resol type, and amino type, low polymers, and partial reaction products of these epoxy compounds and curing agents.Among them, bisphenol A type with a molecular weight of 900 ~
5000, or a novolac type with a molecular weight of 1000
~2000 epoxy compounds are preferred. For example, "Epicoat 1001" manufactured by Shell Chemical Co., Ltd., "'Epicoat 1"
002", "Epicoat 1004", "Epicoat 10
07” and “’Epicote 1009”, CIBA-G
These are "Araldite ECN-1273" and "Araldite-1299" manufactured by EIGY.

In the present invention, such a sizing agent is coated on the surface of carbon short fibers and aggregated, and the content of the sizing agent used at this time is 0.1 to 10% by weight based on the total amount of short fibers, preferably 0.5 to 10% by weight. It is selected in the range of 7% by weight. and,
As a surface coating method, for example, a bundle of several hundred to several hundred thousand long carbon fibers is impregnated with the mixture of the epoxy emulsion compound and then dried. If the content of the sizing agent is less than 0.1% by weight, the convergence of the short carbon fiber aggregate will be poor, and if it exceeds 10% by weight, the physical properties of the short carbon fiber reinforced thermoplastic resin will deteriorate.

Various conventionally known carbon fibers are used as the carbon fibers used in the present invention, and specific examples include polyacrylonitrile-based, rayon-based, pitch-based, and polyvinyl alcohol-based carbon fibers. Thereafter, cut into lengths of 1 to 20 mm, preferably 3 to 10 m using a known cutting method.
It is best to cut it into lengths of m.

Next, a fiber reinforced resin composition using such a short carbon fiber aggregate as a reinforcing agent will be explained.

Examples of the thermoplastic resin used include polycarbonate, polystyrene, polyester, polyamide, polyolefin, acrylic resin, polyoxymethylene, polyphenylene sulfide, polyphenylene ether, polyphenylene oxide, polybutylene terephthalate, and polyether.

Known thermoplastic resins such as polymers such as ether ketone, polyphenylene sulfone, liquid crystal polyester, and fluororesin, or copolymers thereof, or polymer alloys thereof, and preferably polycarbonate, polyoxymethylene 1, polybutylene terephthalate 1 , polyphenylene oxide, and polyphenylene sulfide are preferably used.

The blending ratio is preferably 1 to 50 parts, preferably 5 to 40 parts per 100 parts by weight of the thermoplastic resin. Outside this range, for example, if the amount is less than 1 part per 100 parts by weight of the thermoplastic resin, the reinforcing effect of the carbon fibers will not be exhibited, and if it exceeds 50 parts per 100 parts by weight of the thermoplastic resin, the carbon fibers will be damaged by the matrix resin. Various problems tend to occur during the mixing and dispersion process.

In addition, as a method for blending such a matrix resin with the short carbon fiber aggregate of the present invention, it is usually preferable to use a side-feed method using a screw extruder or a twin-screw presser, but a tri-blend method is also effective. Express.

Furthermore, in addition to the above-mentioned components, other types of carbon fibers, glass fibers, aramid fibers,
Single fibers and long fibers such as poron fibers and silicon carbide fibers,
Whiskers, metal coatings such as nickel, aluminum, copper, fibrous reinforcing agents, or fillers such as carbon black, molybdenum disulfide, mica, talc, calcium carbonate, etc., stabilizers, lubricants, etc. Additives etc. can be added.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

In addition, each physical property was measured as follows.

(Emulsion particle size) The emulsion average particle size is “HORIBALA-50
0Particle 5ize analyzer".

(Bulk Density of Chopped Strand) After weighing approximately 30 g of chopped strand, place approximately 173 pieces of it into a 200 m graduated cylinder in sequence, and drop the graduated cylinder 10 times from a height of 5 cm each time the chopped strand is placed in the graduated cylinder. , Once the entire amount has been filled, read the volume.

Weight of chopped strand (W) and volume after filling (V
), calculate the bulk density (d) using the following formula.

d = v/w (loose retention rate at high temperature) Approximately 80g of chopped strands are inserted into IL (110mmφ
) in a beaker and maintained at a predetermined temperature (55°C). After that, the stirring method shown in Fig. 1 was carried out at 35 ORPM.
After stirring for 90 seconds, the rate of change in bulk density before and after stirring is measured.

(Physical properties of molded product) The physical properties of the molded article are measured in accordance with the ASTM method below.

Bending strength, D 790 Bending elasticity: D 790 Example 1 (A) Production of short carbon fiber aggregate Mesophase pitch-based long carbon fiber "' Dialead 2
23'' (manufactured by Mitsubishi Kasei Co., Ltd.), 6000 bottles were mixed with an emulsion solution (concentration 3% by weight, Emulsion average particle size 0
．． 6 □m) and then heated and dried at about 120° C. for 20 minutes, and then a 6 mm long carbon short fiber aggregate was produced using a cutting machine.

The epoxy compound content of the obtained short carbon fiber aggregate was 3
．． It was 1% by weight.

(B) Production of short carbon fiber reinforced molding material 20 parts by weight of the short carbon fiber aggregate and dried polycarbonate ("Tubalex 7022PJ" manufactured by Mitsubishi Kasei Corporation)
) After tri-blending 80 parts by weight, the mixture was poured into a screw extruder, melt-mixed, and extruded into a strand.
After cooling with water, it was cut into pellets. The charging into the press a was smooth, and the carbon short fiber aggregate and resin were uniformly dispersed.

The carbon short fiber reinforced molding material obtained in this way was
After drying at 0°C for 4 hours, it was molded by injection molding to obtain a test piece.

Example 2 (A) Production of short carbon fiber aggregate A short carbon fiber aggregate was produced in the same manner as in Example 1. The epoxy compound content of the obtained short carbon fiber aggregate was 3.
It was 0% by weight.

(B) Manufacture of short carbon fiber reinforced molding material Polycarbonate (Mitsubishi Kasei Corporation “Tubarex 702”)
2PJ") was poured into a screw extruder and melted. After that, 20 parts by weight of the short carbon fiber aggregate was charged from a hopper near the nozzle and melt-mixed. The mixture was extruded into a strand shape, cooled with water, and then cut into pellets. The carbon short fibers were smoothly charged into the extruder, and the carbon short fiber aggregate and the resin were uniformly dispersed.

The carbon short fiber reinforced molding material obtained in this way was
After drying at 0°C for 3 hours, it was molded by injection molding to obtain a test piece.

Example 3.4 A sample was prepared in the same manner as in Example 2 by changing the mechanical stirring conditions during emulsification to prepare a sizing agent with an emulsion average particle size of 0.4 pm and 0.811 m. The short fibers were smoothly charged into the extruder, and the carbon short fiber aggregate and resin were uniformly dispersed.

The carbon short fiber reinforced molding material obtained in this way was
After drying at 0°C for 3 hours, it was molded by injection molding to obtain a test piece.

Comparative Example 1 (A) Production of short carbon fiber aggregate Mesophase pitch-based long carbon fiber “Dialead 22
3" (manufactured by Mitsubishi Kasei Co., Ltd.) were mixed with an emulsion solution (concentration 3% by weight, Emulsion average particle size 0
．． After impregnating the fibers into a 2 μm thick carbon fiber, the fibers were heated and dried at about 120'C for 20 minutes, and then a 6 mm long carbon short fiber aggregate was produced using a cutting machine.

The epoxy compound content of the obtained short carbon fiber aggregate was 3
．． It was 4% by weight.

(B) Manufacture of short carbon fiber reinforced molding material Polycarbonate (Mitsubishi Kasei Corporation “Tubarex 702”)
After pouring 80 parts by weight of 2PJ'') into a screw extruder and melting it, 20 parts by weight of the carbon short fiber aggregate was charged from a hopper near the nozzle and melted and mixed, but the carbon short fiber aggregate, which had been fed without any problems at first, After a few minutes, the feed stopped. When the inside of the hopper was examined, the yarn was loose. The temperature inside the hopper was 50°C.

Comparative Example 2 When an attempt was made to prepare a sample in the same manner as in Example 2 by changing the emulsion average particle diameter and changing the mechanical stirring conditions during emulsification to prepare a 1.2P sizing agent, the stability of the sizing agent was Unfortunately, the emulsion system broke down and the epoxy resin precipitated before use, making it unusable.

Comparative Example 3 Polycarbonate (manufactured by Mitsubishi Kasei 'Tubarex 702
2PJ") alone into a screw extruder, melted, extruded into strands, cooled with water, and cut into pellets. After drying this molding material at 120°C for 3 hours,
A test piece was obtained by injection molding.

Table 1 shows the feed properties and mechanical properties of the yarns of Examples 1 to 4 and Comparative Examples 1 to 3.

Table 1 [Effects of the Invention] The carbon short fiber aggregate of the present invention has extremely excellent bundling properties, and when producing a fiber-reinforced resin molding material using the carbon short fiber aggregate, the carbon The short fiber aggregate has good fluidity in the extruder hopper and is stably supplied to the extruder screw, greatly improving the productivity of fiber-reinforced resin molding materials.

Furthermore, because the short carbon fiber aggregate has excellent affinity for the matrix, the mechanical properties of molded products obtained using this fiber-reinforced resin molding material show extremely good values, making it extremely useful in industry. It is.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a stirrer used in an embodiment of the present invention. 1: Stirring board 2: Beaker

Claims (2)

[Claims] (1) A short carbon fiber aggregate whose surface is coated with an emulsion-based sizing agent containing an epoxy compound as a main component, wherein the average particle diameter of the emulsion of the epoxy emulsion-based sizing agent is in the range of 0.3 μm to 1 μm. , the content of the sizing agent is 0.1 to 0.1 to the total amount of carbon short fibers.
A short carbon fiber aggregate characterized by having a content of 10% by weight. (2) A short carbon fiber aggregate whose surface is coated with an emulsion-based sizing agent containing an epoxy compound as a main component, wherein the average particle diameter of the emulsion of the epoxy emulsion-based sizing agent is in the range of 0.3 μm to 1 μm. , the content of the sizing agent is 0.1 to 0.1 to the total amount of carbon short fibers.
The short carbon fiber aggregate containing 10% by weight was added to the thermoplastic resin 1.
A fiber-reinforced thermoplastic resin composition containing 5 to 40 parts by weight per 00 parts by weight.