JP2002138370A - Chopped carbon fiber strand and fiber-reinforced thermoplastic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a chopped carbon fiber strand that has good fluidity and excellent cost performance, to obtain a fiber-reinforced thermoplastic resin composition produced by using the chopped strand and a formed body having good mechanical properties and electroconductivity produced by using the fiber- reinforced thermoplastic resin composition. SOLUTION: The objective chopped carbon fiber strand is surface-coated with a sizing agent including a polyether as a major component, and in addition, over-coated with another sizing agent including a thermoplastic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inexpensive carbon fiber chopped yarn which is useful in the production of a carbon fiber reinforced composite material, has excellent moldability, and a fiber reinforced thermoplastic resin using the chopped yarn. It relates to a composition.

[0002]

2. Description of the Related Art Carbon fiber reinforced composite materials have strength, rigidity,
Because of their excellent dimensional stability and conductivity, they are widely deployed in general industrial fields such as office equipment applications, automotive applications, and computer applications (IC trays, housings, etc.), and their demands are increasing year by year.

[0003] At this time, the fiber-reinforced resin composition as a raw material is generally formed by melting and kneading a chopped yarn obtained by cutting carbon fibers into a length of about 3 to 10 mm and various resins with an extruder to form pellets. It is manufactured by injection molding.

[0004] In such a manufacturing process (also referred to as a compounding process), it is required to improve the supply performance of chopped yarn with a screw feeder or the like.

[0005] In order to improve the supply performance, the flowability of the chopped yarn is important.
In extreme cases, the yarn may even become blocked in the supply hopper.

In order to improve the fluidity and the physical properties of the finally obtained molded product, for example, a sizing agent comprising a liquid epoxy resin and a solid epoxy resin is disclosed in
Japanese Patent Application Laid-Open Nos. 66616 and 1-92234 propose a sizing agent comprising an epoxy resin and a polyurethane resin.
JP, JP-A-10-7840 and JP-A-5-7840
It is proposed in, for example, Japanese Patent No. 1322863.

On the other hand, in recent years, so-called large tow carbon fibers (usually having a filament number of 50K or more), which are excellent in cost performance, are being used as reinforcing fibers.

When such carbon fibers are used as reinforcing fibers, the production cost is particularly important, and it is strongly desired not only to improve the convergence of the chopped yarn but also to improve the fluidity.

However, especially when such a large tow carbon fiber is used, when the above-mentioned conventional technique is applied, the fluidity is particularly insufficient in many cases.

[0010] On the other hand, it is known that the dispersibility of fibers in a molded article greatly affects the mechanical properties, conductivity, and surface smoothness of the molded article. Is preferred for improving the physical properties of the obtained molded article.

However, according to the above-mentioned prior art,
Such dispersibility is often insufficient, and chopped yarns having improved dispersibility and the above-mentioned fluidity and excellent in cost performance have not yet been found to be sufficiently satisfactory. It is.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive carbon fiber chopped yarn having excellent fluidity.
It is an object of the present invention to provide a fiber-reinforced thermoplastic resin composition using the chopped yarn, and a molded article using the resin composition and exhibiting good conductivity and the like.

[0013]

In order to achieve the above object, the present invention employs one of the following constitutions. That is, (1) a carbon fiber chopped yarn which is surface-coated with a sizing agent containing a polyether compound as a main component and further coated with a sizing agent containing a thermoplastic resin, and (2) a liquid epoxy resin as a main component Carbon fiber chopped yarn, which is surface-coated with a sizing agent to be further coated with a sizing agent containing a thermoplastic resin, or (3) a fiber-reinforced thermoplastic resin obtained by blending a specific amount of the chopped yarn A composition.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A chopped carbon fiber yarn according to the present invention has a surface coated with a sizing agent containing a polyether compound as a main component, and further coated thereon with a sizing agent containing a thermoplastic resin. Yarn (hereinafter simply referred to as chopped yarn).

Here, the "main component" means that the target compound is 55 to 99.9% by weight, preferably 6 to 9% by weight in the sizing agent.
0 to 99.9% by weight, more preferably 70 to 99.9% by weight, which means that it is contained together with other components.
"Main component" is used in this sense).

The amount of the polyether compound attached is preferably 0.05 to 1% by weight, and more preferably 0.1 to 0.5% by weight, based on 100% by weight of the fiber base material. If the content is less than 0.05% by weight, the thermoplastic resin does not sufficiently penetrate into the inside of the fiber bundle, the bunching property may be insufficient, and the dispersibility of the chopped yarn in the molded body may be deteriorated. When the content exceeds 1% by weight, the convergence of the chopped yarn becomes too high, and uneven adhesion of the thermoplastic resin may occur. Further, in this case, the dispersibility of the chopped yarn in the molded body may be deteriorated, and the conductivity or the like in the molded body may be reduced.

Examples of the polyether compound include polyoxyethylene, polyoxyethylene (POE) polyoxypropylene (POP) block polymer, polyoxyethylene alkyl ether, POE / POP alkyl ether, bisphenol A polyoxyethylene adduct,
Water-soluble ones such as E-glycerin aliphatic ester can be used.

Further, the chopped yarn according to the present invention is a chopped yarn whose surface is coated with a sizing agent containing a liquid epoxy resin as a main component, and further coated thereon with a sizing agent containing a thermoplastic resin.

Here, the amount of the liquid epoxy resin adhered is preferably 0.2 to 2% by weight, more preferably 0.5 to 1.5% by weight, based on 100% by weight of the fiber base material. When the amount is less than 0.2% by weight, the thermoplastic resin does not sufficiently penetrate into the fiber bundle, and the sizing ability may be insufficient. In addition, the dispersibility of the chopped yarn in the molded body may be deteriorated, and May decrease in conductivity and the like. On the other hand, if it exceeds 2% by weight, the convergence of the chopped yarn becomes too high, which may cause uneven adhesion of the thermoplastic resin. Further, in this case, the dispersibility of the chopped yarn in the molded body is deteriorated, and the conductivity of the molded body may be reduced.

As liquid epoxy resin, room temperature 25 ° C.
For example, bisphenol A diglycidyl ether, polyglycerin polyglycidyl ether, sorbitol polyglycidyl ether, polyoxyethylene polyglycidyl ether, or the like, which is liquid at 1 atm and has a molecular weight of 300 to 1,000, preferably 350 to 700, is preferably used. .

Commercial products of such liquid epoxy resins include, for example, "Epicoat (trademark)" 828, "Epicoat (trademark)" 834 (all manufactured by Yuka Shell Epoxy Co., Ltd.), and "Araldite (trademark)". AER260
(Manufactured by Asahi Ciba) or the like can be used.

In the present invention, the above-mentioned thermoplastic resin is preferably applied in the form of a so-called water-based resin. It is good to be 3% by weight.

Here, "aqueous" means that the emulsion has an average diameter of 1 μm or less when emulsified. Here, the average emulsion diameter can be measured by, for example, a laser diffraction type particle size distribution device. If the amount is less than 0.5% by weight, the flowability of the chopped yarn is insufficient, and the yarn may be clogged by the supply hopper. If the amount exceeds 10% by weight, the convergence of the chopped yarn becomes too high, and In some cases, the dispersibility of the chopped yarn is deteriorated, and the conductivity and the like of the molded body are reduced.

Examples of the thermoplastic resin include, for example, thermoplastic resins such as polycarbonate, polyoxymethylene, polybutylene terephthalate, polyphenylene oxide, and polyphenylene sulfide dispersed in water with a surfactant, and hydrophilic functional groups (for example, , Sodium sulfonate) and hydrophilic structures (eg, polyoxyethylene)
Can be preferably used. In particular, it is preferable to use a polyamide resin, a polyester resin, or a mixture thereof.

As such a thermoplastic resin (aqueous thermoplastic resin), those having a heat resistance of 300 ° C. or higher can be used, and commercially available products include, for example, water-soluble nylon P70.
(Manufactured by Toray Industries, Inc., product number), ES2200 (manufactured by Dainippon Ink and Chemicals, product number) and the like can be preferably used.

The thermoplastic resin that can be used in the fiber-reinforced thermoplastic resin composition (hereinafter, simply referred to as a resin composition) according to the present invention includes ABS, polyamide, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, and polyetherimide. , Polysulfone, polyethersulfone, polyphenylene oxide, modified polyphenylene oxide, polyphenylene sulfide, polyether ketone, and the like, or polymer alloys composed of these resins, etc., but those in which a small amount of a thermosetting resin is mixed are also used. it can.

The above resin composition is preferably prepared by blending chopped yarn in an amount of 5 to 50 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the total amount of the resin composition. If the amount is less than 5 parts by weight, the effect of reinforcing the molded article and the effect of imparting conductivity may not be exhibited. If the amount is more than 50 parts by weight, the flowability of the chopped yarn is insufficient at the time of molding, and the process passability is deteriorated. May be.

The mixing ratio (weight ratio) of the chopped yarn and the resin is 3:97 to 70:30, preferably 3:97 to 50:50, more preferably 3:97 to 3
0:70 is preferable.

The resin composition may further include, as reinforcing fibers, carbon fibers, glass fibers, aramid fibers, boron fibers, silicon carbide fibers, whiskers, or a metal coating such as nickel, aluminum, or copper on these fibers. Short fibers subjected to the above-mentioned method can also be blended.

Further, if necessary, carbon black,
Fillers such as molybdenum disulfide, mica, talc, calcium carbonate, various stabilizers, various lubricants, and other additives can be blended.

In the present invention, as a method for producing a molded article from the above resin composition, for example, an injection molding method can be preferably employed.

The method for producing a chopped yarn according to the present invention will be described below.

3,000 to 500,000, preferably 10,000 to 10
While widening with a roller immediately before impregnating a carbon fiber bundle composed of 000 single fibers, applying a treatment liquid containing the sizing agent by a so-called impregnation method, and then expanding the fiber bundle on the roller. After infiltrating the sizing agent into the inside of the carbon fiber bundle, it is dried with a hot air drier.

Here, the content of the polyether compound or the liquid epoxy resin in the sizing agent is 55 to 100% by weight, preferably 60 to 10% by weight, based on the total amount of the sizing agent.
The content is preferably 0% by weight, more preferably 70 to 100% by weight.

If the content is less than 55% by weight, the generation of fluff in the process may increase, and the bunching properties of the chopped yarn and the dispersibility in the resin composition may decrease.

In the treatment liquid, in addition to the sizing agent, various additives for improving water solubility, for example, bisphenol A polyoxyethylene adduct, bisphenol A.PO
At least one selected from the group consisting of E / POP adduct, higher alcohol POE adduct, and higher alcohol POE / POP adduct can be blended.

In the present invention, a solid epoxy resin, a polyester, a polyurethane, a leveling agent, and the like can be added to the sizing agent, if necessary.

After drying, a treatment liquid containing a thermoplastic resin is applied to the conveyed fiber bundle. At this time, the thermoplastic resin is preferably applied so as to be 0.5 to 10% by weight, preferably 0.5 to 3% by weight, based on 100% by weight of the fiber base material.
If the amount is less than 0.5% by weight, the convergence and the dispersibility in the resin composition may decrease. If the amount exceeds 10% by weight, the physical properties of the obtained molded article may decrease. At this time, it is preferable to apply the treatment liquid to the thermoplastic resin in an aqueous system because the treatment is easy.

When a sizing agent is applied to the fiber bundle in an aqueous system, it is preferable to incorporate an emulsifier in the treatment liquid. In this case, the treatment liquid is preferably adjusted so that the emulsion has an average emulsion diameter of 10 μm or less, preferably 5 μm or less, more preferably 1 μm or less (excluding 0 μm) (here, the liquid epoxy used). When the resin or the thermoplastic resin is a so-called self-emulsifying type or water-soluble, it is preferable to adjust the emulsion so that the emulsion has an average emulsion diameter of 0.1 μm or less. If the average emulsion diameter of the emulsion exceeds 1 μm, the emulsion or the like may settle and agglomerate in the application step, making it difficult to uniformly adhere to the fiber surface.

After the treatment liquid is applied to the fiber bundle as described above, the fiber bundle can be dried and cut according to a conventional method. At this time, the order of drying and cutting can be changed. The cutting length here is 1 to 20 mm, preferably 3 to 10 mm.

In the present invention, various carbon fibers such as polyacrylonitrile, rayon, pitch, and polyvinyl alcohol can be used as the carbon fiber.

[0042]

The present invention will be described more specifically with reference to the following examples. Here, the following methods were used to evaluate the chopped yarn, the formed body, and the like. Table 1 summarizes the contents of each example and comparative example. (1) Spreading index About 70 g of chopped yarn [weighing value M (g)] was collected, and 5
Pour into a 00 ml graduated cylinder.

Next, regarding the capacity of the chopped yarn in the measuring cylinder, using a rubber sheet having a thickness of 3 to 4 mm,
The value read after repeating the tapping process from a height of 2.54 cm about 60 times is defined as V ₁ (ml).

Next, the chopped yarn in the measuring cylinder is transferred to a 300 ml polyethylene cup, the number of revolutions is set to 400 rpm, and a 4-blade Marine blade is used as a stirring blade, and the mixture is stirred for about 3 minutes by a stirrer.

Thereafter, the chopped thread is inserted into the measuring cylinder inclined at about 45 ° with respect to the horizontal plane, and returned in the vertical direction, and the capacity of the chopped thread in the measuring cylinder is read to be V ₂ (ml). .

After such processing, the opening index K is obtained by the following equation.

K = D ₁ / D ₂ Here, D ₁ : Vibration filling bulk density before stirring D ₁ = M / V
₁ D ₂ : Non-vibration filling bulk density after stirring D ₂ = M / V ₂ (2) Amount of attached compound About 5 g of chopped yarn is collected and put into a heat-resistant glass container.

Next, the container was dried at 120 ° C. for 3 hours, cooled to room temperature while taking care not to absorb moisture, and the weighed value was defined as W ₁ (g).

Then, the whole container was placed in a nitrogen atmosphere at 450
After heating at 15 ° C. for 15 minutes, the mixture is cooled to room temperature while taking care not to absorb moisture, and the weighed value is defined as W ₂ (g).

After the above treatment, the amount of the compound attached is determined by the following equation.

Amount of compound attached = (W ₁ −W ₂ ) / W ₂ (unit:% by weight) (3) Mechanical properties of molded article (Izod impact value) Chopped yarn was collected and reinforced in accordance with ASTM 256-93a. A test piece of a fiber-reinforced composite material was prepared with a fiber content Vf = 20%, and an atmosphere temperature of 23 ° C. and a relative humidity of 50 were prepared.
%, The Izod impact value is determined. (4) Surface Resistance (Conductivity) of Molded Body A chopped yarn is sampled, a test piece of a fiber-reinforced composite material is prepared according to ASTM D257-99 with a reinforcing fiber content Vf = 20%, and the surface resistance is determined. (Example 1) Total filament number 70,000, total fineness 49,500D
A treatment liquid is applied to the tow carbon fiber (D: denier) by a so-called impregnation method so that the amount of the polyether compound (bisphenol A polyoxyethylene adduct) attached to the fiber substrate is 0.2% by weight. After that, the fiber was opened on a roller and further dried by hot air drying.

Next, a water-soluble nylon (manufactured by Toray Industries, Inc., A
Q nylon P70 [product number]) with a tension of 2.5 kgf /
After applying the treatment liquid with a tow width of 5 to 6 mm, cut it with a roving cutter to a length of 6 mm, and then dry it with a dryer.
After drying at 90 ° C. for 5 minutes, a chopped yarn was obtained.

Further, the fluctuation rate of the supply speed of the chopped yarn in the extruder hopper at the time of producing a molded product using the polycarbonate resin was as low as 1.2%, and the fluidity in the process was good.

The Izod impact value of the molded article thus obtained was as good as 88 J / m ² . The surface resistance also showed a good value of about 1 × 10 ^0.8 . (Examples 2 to 6) When a processing liquid was prepared and a molded product was produced in the same manner as in Example 1, the fluidity of the chopped yarn in the extruder hopper was good, and the mechanical properties and electrical conductivity were excellent. A compact was obtained. (Comparative Examples 1 to 3) A treatment liquid was prepared and a molded article was produced in the same manner as in Example 1, but only a molded article having poor mechanical properties and electrical conductivity was obtained.

[0055]

[Table 1]

[0056]

The carbon fiber chopped yarn according to the present invention is
Since the polyether compound or the liquid polyepoxy resin is uniformly adhered to the fiber bundle surface, even when using so-called large tow carbon fibers, it becomes excellent in process passability and has excellent cost performance. Become.

Further, such a chopped yarn is uniformly dispersed in the resin composition when processed into a resin composition, and is excellent in adhesiveness to various thermoplastic resins used as a matrix material. A molded article excellent in both mechanical properties and conductivity can be manufactured.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) D06M 15/55 D06M 15/55 15/59 15/59 // D06M 101: 40 101: 40 F term (reference) 4F072 AA02 AA08 AB10 AC05 AC08 AC12 AD41 AK03 AK15 4J002 BN151 CF061 CF071 CG001 CH071 CH091 CL001 CM051 CN011 CN031 DA016 FA046 FB266 GN00 GQ00 4L033 AA09 AC12 AC15 BA14 CA48 CA49 CA55

Claims (7)

[Claims] 1. A carbon fiber chopped yarn which is surface-coated with a sizing agent containing a polyether compound as a main component and further coated thereon with a sizing agent containing a thermoplastic resin. 2. The chopped carbon fiber yarn according to claim 1, wherein the adhesion amount of the polyether compound is 0.05 to 1% by weight based on 100% by weight of the fiber base material. 3. A carbon fiber chopped yarn which is surface-coated with a sizing agent containing a liquid epoxy resin as a main component and further coated thereon with a sizing agent containing a thermoplastic resin. 4. The carbon fiber chopped yarn according to claim 3, wherein the amount of the liquid epoxy resin adhered is 0.2 to 2% by weight based on 100% by weight of the fiber base material. 5. The fiber base material 1 according to claim 1, wherein
2. The method according to claim 1, wherein the amount is 0.5 to 10% by weight based on 00% by weight.
5. The chopped carbon fiber yarn according to any one of items 1 to 4. 6. The chopped carbon fiber yarn according to claim 1, wherein the thermoplastic resin is a polyamide resin and / or a polyester resin. 7. The carbon fiber chopped yarn according to any one of claims 1 to 6 is added to the resin composition in an amount of 5 parts by weight based on 100 parts by weight.
A fiber-reinforced thermoplastic resin composition containing up to 50 parts by weight.