JPS6311308A - Manufacture of carbon fiber reinforced thermoplastic resin - Google Patents

Abstract

PURPOSE:To enable a carbon fiber reinforced thermoplastic resin to be produced without decreasing of recovery of carbon fiber aggregate and to contrive not to generate deterioration of working environment due to scattering of carbon fiber by a method in which a bulky carbon fiber aggregate and a solid material of thermoplastic resin are cut together by a high speed rotary cutter, and they are pulverized and mixed, and then the cut and pulverized mixture is molten and kneaded. CONSTITUTION:A bulky carbon fiber aggregate and a solid material of thermoplastic resin are cut together, pulverized and mixed by a high speed rotary cutter, and then the cut and pulverized mixture is molten and kneaded. The bulky carbon fiber aggregate is e.g. mat, paper, tow or felt, etc., and it measures (thickness) 1-5cm X (width) 1-200cm X (length) 1-infinity cm, as for the bulk of the aggregate, the density of 0.008-0.08g/cc is preferable. The thermoplastic resin is a solid material of high molecular weight polymer having a heat- softening temperature of at least room temperature, preferably at least 40 deg.C, and it is e.g. polyethylenetelephthalate, polybutylenetelephthalate, polyacetal, polystyrene, etc. and their mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a thermoplastic resin reinforced with carbon fibers.

[Prior art and its problems]

Carbon fiber-reinforced thermoplastic resin (hereinafter abbreviated as CFRTP) that is made by kneading carbon fiber with thermoplastic resin to improve the bending strength and tensile strength of the resin, as well as improving the sliding properties and electrical properties.
is an indispensable material for complex-shaped objects, and is available in a wide range of product forms, from sporting goods to general industrial uses.

Generally, CFRTP is produced by solidly mixing thermoplastic resin pellets and carbon fibers cut into several pieces in a tumbler, etc., and then kneading and discharging the mixture using a continuous melt kneader such as an extruder.
After cutting into several pellets with a pelletizer, they are transferred to an injection molding machine and injected into a mold using a melt molding machine to form an injection molded product.

In this case, the technique of cutting the carbon fiber used as the reinforcing material into lengths of several layers or less can be used to continuously cut long filament carbon fibers with a rotary blade cutter. On the other hand, pitch-based general-purpose carbon fibers, which have been actively developed recently, are mainly short carbon fibers in the order of 2o to 100, but short fibers cannot be cut with the same cutter as above, so Various efforts have been made to achieve A.

For example, short pitch-based carbon fibers are bundled with an air sunker and after carbonization, the bulky bundle is fed to a rotary blade canter. ! A method of continuously cutting short carbon fibers, a method of forcibly feeding short A carbon fibers to a mill, and continuously cutting them into powder, and a method of continuously cutting the short A carbon fibers into a powder form, which was invented by the present inventors. A method in which short carbon fibers are mixed with the water, cut into patchwise pieces using a high-speed rotary cutting machine, and dried (Patent application No. 61-433)
No. 51) etc.

However, both methods require one or two steps before or after carbonization to mix with the thermoplastic resin, resulting in a decrease in yield and impairing economic efficiency, and the dust generated during cutting significantly degrades the working environment. It has the disadvantage of being contaminated.

[Means for resolving misunderstandings]

As a result of various studies, the present inventors have completed the present invention based on the following points (1) to (4). That is, (1) regardless of the spinning method, the most economical method for producing short A carbon fibers is to deposit the spun pitch fibers on a belt conveyor, continue to infusible, and then carbonize them; (2) this carbon fiber. forms a bulky aggregate, but even if the carbon fiber aggregate is forcibly pressed against a high-speed rotating blade, only the part that hits the blade can be cut.

(3) In the case of (2), if the solids are mixed at the same time, the carbon fibers will flow as the solids are stirred and scattered, and the cut carbon fibers of limited length and the crushed solids will flow together. (4) Carbon fibers that are too large for melt-kneading and/or melt-injection may break and settle to an appropriate length.

[Means for solving problems]

That is, the present invention provides a carbon fiber characterized in that (g) a bulky carbon fiber aggregate and a thermoplastic resin solid are both cut and pulverized using a high-speed rotary cutter, and the cut and pulverized mixture is melt-kneaded. The present invention relates to a method for producing reinforced thermoplastic resin (CFRTP).

〔composition〕

The raw material for carbon fibers may be PAN-based or pitch-based, but since such carbon fiber aggregates are often formed by melt spinning, pitch-based materials are the main material. Pitch melt spinning methods include the so-called centrifugal spinning method, the eddy current method, and the so-called air sucker method, in which the molten pitch is drawn with an air sucker. However, it may be made by any method.

The bulky carbon fiber aggregate of the present invention is an aggregate of carbon fibers intertwined with each other, such as a mat,
Paper, tow, felt, etc. The size of this aggregate is 1 to 5cm thick x 1 to 200cm wide x 1 to 20cm tall.
Those from Noura are preferably used. The bulk of this aggregate preferably has a density of o, oos to 0.081/cc. The density is o, osI! It may be larger than /ec, but since there is a problem that the oxidizing gas and inert gas cannot be quickly replaced during carbonization, it is preferable that it is smaller than 0, o, oosIi/cc. It is not preferable to use A, which may be a carbonaceous material, since there is a problem that the yield in the carbonization furnace impairs economic efficiency.

The thermoplastic resin of the present invention is a solid substance of a high molecular weight polymer having a heat softening temperature (softening point) of room temperature or higher, preferably 40° C. or higher, and is used as an engineering plastic. For example, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polystyrene, 6-nylon, 6,6-nylon, polysulfone, polycarbonate, polyphenylene oxide, polyphenylene sulfide, polyvinyl chloride, polyvinylidene chloride, polypropylene, polyethylene, polyethylene, Methyl methacrylate, polyetheretherketone, polytetrafluoroethylene, polyphenol, AB
S, diarylphenol, etc. and mixtures thereof. Lubricants, pigments, glass, other fibrous materials, fillers (e.g. calcium carbonate, Teflon powder,
There is no problem in adding graphite powder) or inorganic fillers.

The high-speed rotary blade cutting machine referred to in the present invention may be any cutting machine that is attached with a blade that rotates at a high speed of 100 rpm or more. For example, hammer mill, impeller breaker, disinch grater, attritor, cutter mill, pulperizer, etc. There are grinders such as rotors and edge runners, and mixers such as Henschel type mixers and juicer mixers.

The weight blending ratio of the carbon fiber aggregate and the thermoplastic resin may vary by b, but since the carbon fibers exhibit their effect in the thermoplastic resin at 5 to 50% by weight, it is best to mix them in a predetermined amount in advance. is good. Of course, there will be no problem if 50% by weight or more of carbon fiber is added for the purpose of making a masterbatch or the like.

The size of the thermoplastic resin solids is important.

Since the solid material itself is pulverized, if it is too fine, the powder mixture tends to be clumped together in the melt-kneading machine. On the other hand, if the size is too large, there is less opportunity for the particles to entrain fibers, resulting in a decrease in the cutting efficiency of the aggregate. Generally, pellets (cylinders of several lengths, preferably 1 to 5 inches, and 2 to 3 truns in diameter), which are commercially available thermoplastic resins for molding, are suitable.

The high-speed rotation of the blade agitates the pellets and cuts the aggregates little by little, but the aggregated carbon fibers are not cut into the same length, but instead are cut into threads with a wide length distribution. There is a tendency for the composition to be cut. However, since excessively long yarns will be cut during later melt-mixing or injection molding, there is no need to be particular about the yarn length distribution. If the yarn length is too short, such as 0.1 tries or less, the reinforcing effect tends to be reduced, so the average yarn length should be 0.3 to 3.
Preferably it is 0 mml. The size of the solids and the average thread length can be adjusted by the type, time and rotation speed of the rotary blade.

The physical properties of aggregated carbon fibers change depending on the carbonization temperature, but even graphite fibers carbonized at 2000°C or higher have good b0, and aggregated carbon fibers mainly have compatibility with thermoplastic resins. There is no problem even if the surface is treated for the purpose of improving it.

To mold CFRTP from a cut and pulverized mixture, any method that involves melting and molding with heat may be used, but in general, an extrusion melt molding machine and, in some cases, a melt injection molding machine are used. The most common method is to knead the pellets, take them out in the form of pellets, and mold them using an injection molding machine, but the method is not limited to this method.

〔effect〕

The manufacturing method of the present invention can produce CFRTP from the most economical carbon fiber aggregate without any decrease in yield, so the use of the CFRTP of the present invention has the advantage of obtaining extremely economical molded products. . Furthermore, since the work can be carried out in a sealed container, there is an advantage that the work environment may deteriorate due to scattering of carbon fibers.

The present invention will be explained below with reference to Examples, where "parts" and "chi" are based on weight unless otherwise specified.

[Example-1] Pitch fibers spun by the eddy current method and deposited on a belt conveyor were carbonized at 1000°C to obtain a carbon fiber mat. The shape of the mat is 3 cm thick x 30 cm wide.
The density was 0.01697cc. The length of the carbon fibers forming the mat is 10 to 20 crn, the tensile strength of one strand is 78 kg/w'', and the tensile modulus is 3.2 To
n/WI2, the elongation was 2.2 inches. 9 book mats
oog (6,24m) was cut off. Henschel type mixer of 30% polyphenylene sulfide (abbreviated as pps, manufactured by Philips Vetroleum, Rydon P-4)
) Belen) 2100.9 was added, then Mat 900I was forcibly pushed in, the lid was closed, and the mixture was stirred at 1600 rpm. The mat was cut from below, and after 4 minutes it became possible to stir completely uniformly, so the stirring was stopped after 5 minutes. The taken out solid mixture has carbon fibers ranging from a maximum length of 8 tons to a minimum length of 0.1 tons.
trm, average length of 0.6 rran, pps pellets were pulverized to about half or less, and both were well mixed. Next, use a single-screw extrusion bath melt-kneader with a diameter of 40 mm and the maximum cylinder temperature is 32 mm.
Extruded as a strand at 0℃, pelletized to 4fr
The pellet had a length of rM and a thickness of 1.8 wn.

Next, it was applied to an injection melt molding machine with a mold clamping pressure of 50 tons and a capacity of 3 ounces.
0kl? 7cm2, secondary pressure 600197cm",
A test piece was molded at a medium injection speed and a mold temperature of 120°C.

The physical properties of the molded product were as shown in Table-1.

Table 1 The length of the carbon fibers in the molded product was 6 to 0.1 mm, with an average length of 0.5 mm.

[Example-2] A carbon fiber mat was obtained in the same manner as in Example-1.

Cut this mat 9001 (6,24m).
6,6-nylon (
Put Asahi Kasei (Leona) pellets 2100.9, then forcefully push in 900g of mat, cover with a lid, and turn to 1600rpm.
The mixture was stirred at m. The mats were sequentially cut from below, and after 4 minutes it became possible to stir completely uniformly, so the stirring was stopped after 5 minutes. The solid material taken out had carbon fibers ranging from the longest 10 fibers to the shortest 0.1 cm, with an average length of 0.7 W, and the nylon pellets were pulverized into about half, and the two were well mixed.

Next, it was extruded as a strand using a single-screw extrusion melt-kneader with a diameter of 40 mm at a maximum cylinder temperature of 280°C, and pelletized with a pelletizer having a length of 4 mm and a thickness of 1.8 mm.

Next, it was put into the same injection molding machine as in Example 2 and the cylinder temperature was 12.
80℃, injection pressure car secondary pressure 1200 kg/cm2, secondary pressure 600 to 9/cm2. Medium injection speed, mold temperature 8
Test pieces were molded at 0°C.

The mechanical properties of the molded product were as shown in Table 2.

Clothes-2 [Example 3] Pitch fibers spun using a centrifugal spinning method were converged using an air sucker and deposited on Percon to form a mat. It was made infusible as it was and carbonized at 1000°C to obtain a carbon fiber mantle. The shape of the mat is 4.5 cm thick x 30 cm wide.
m, and the density was 0.0219/CC. The length of the carbon fibers forming the mat is 20 to 48 (1), the tensile strength of one strand is 86 ky/1 ras'', the tensile modulus is 3.OTon/Hp, and the elongation is 2.3 yen. Ta.

This mat costs 900. ! i' (3,17m) was cut out.

Pellets 2100Ii of flame retardant modified polybutylene terephthalate (Silanac BT-2200 manufactured by Dainippon Ink and Chemicals Co., Ltd.) were put into a 30 mm Henschel type mixer.
Next, forcefully push in the mat 900.9 and close the lid.
Stirred at 0 rpm. After 5 minutes, the mixture was almost completely homogeneous.

Next, it was extruded as a strand using a single-screw extrusion melt-kneading machine with a diameter of 40 W+m at a maximum cylinder temperature of 260°C, and pelletized with a pelletizer having a diameter of 4 mm and a thickness of 1.6 cm.

Next, it was applied to the injection molding machine used in Example-1, the cylinder temperature was 260℃, the injection pressure was 1200kg/cm2,
A test piece was molded at a secondary pressure of 600 kg/cm'', a medium injection speed, and a mold temperature of 80°C.

The physical properties of the molded article were as shown in Table 3.

Table 3 [Example 4] Carbon fiber made by centrifugally spinning pitch into a bulky tow (Guigen Kagaku Kurekato T-101F, diameter 12.5 μm,
Tensile strength: 79 kg/lrtm2. Tensile modulus 3.3
Ton/rran" elongation of 2.4%) was used. The standard N child, which is a measure of bulkiness, was 10.9/m.

301 Henschel Mixer Hepolyacecool (Celanese, Kematal M-450) Pellets 2400
Add 11, push in 600g of Kurekato, cover with 1
Stirred at 650 rpm. The mat started to break from below and was completely mixed after 5 minutes.

Next, it was extruded as a strand using a 401EIn single-screw melt-kneader at a maximum cylinder temperature of 300°C, and pelletized using a pelletizer with a length of 4 and a thickness of 1.8.

Next, using the same molding machine as in Example-1, the temperature of the cylinder was 300°C.
, injection pressure car secondary pressure 1200 kll/cm", secondary pressure 6
The test piece was molded at a medium injection speed of 00 kl/cm and a mold temperature of 120°C.

The physical properties of the molded article were as shown in Table 4.

Table 4 Comparative Example 1 900 g of the carbon fiber mat used in Example 1 was put into the 301 Henschel type mixer used in Examples 1 to 4, the lid was closed, and the mixture was stirred at 1,600 rpm, but the mat still remained after 2 hours. It didn't move at all, and only the part that touched the blade was cut off.

Claims (1)

[Claims] 1. (A) bulky carbon fiber aggregate and (B) thermoplastic resin solid are both cut, pulverized, and mixed using a high-speed rotary cutting machine, and the cut and pulverized mixture is melt-kneaded. A method for producing a carbon fiber-reinforced thermoplastic resin.