JPH075767B2 - Method for producing carbon fiber reinforced thermoplastic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermoplastic resin reinforced with carbon fibers.

Not only is it lightweight and has good mechanical properties, it also has heat resistance,
Carbon fiber with good chemical resistance, electrical conductivity and sliding properties
Composite materials mixed with thermoplastic resins such as nylon, polyester, polypropylene, and noryl resins have already been widely used as various industrial material parts.

On the other hand, research into producing carbon fiber itself from inexpensive raw materials has also become popular, and in recent years, in particular, research into producing high-performance and high-strength carbon fiber with higher strength and elasticity than petroleum or coal-based tarpits, or even if the performance is not so high, is economical. Studies have also been conducted to produce general-purpose carbon fibers that are general and versatile.

Carbon fibers obtained from pitches have various physical properties depending on the physical properties (isotropic or anisotropic) of spinning pitches, the method of melt spinning, and the carbonization temperature of the pitch fibers. In particular, carbon fibers are obtained by the method of melt spinning. The form of the fiber is fixed.

Generally, there are three types of melt spinning methods for pitch. Part 1
One is the same method as the melt spinning method for polyester fiber or polypropylene fiber, but it is the "continuous spinning method" in which the molten pitch is fed from the nozzle with an extruder, simultaneously drafted and continuously wound as fine yarn. is there.
The carbon fibers produced in this way take the form of long filaments.

The first is the "centrifugal spinning method," in which the molten pitch is fed to a high-speed rotating body with holes and is spun into fine yarn by centrifugal force.
Is. The carbon fiber produced by this method has a limited length because it cannot be wound continuously, but takes a relatively long cotton-like form.

Further, one method is to make a viscous pit flow down from an orifice and fiberize it by three or more hot gas streams having components gradually approaching and leaving the down axis. "Vortex method" (Japanese Patent Publication No. 58-57374)
Is. The carbon fiber produced by this method also has a limit in length because it cannot be wound continuously, and also has a cotton-like shape.

The centrifugal spinning method and the vortex method can produce only short carbon fibers, but they are suitable for producing general-purpose carbon fibers because the spinning process is economical. Among the two methods, the eddy current method has an advantage that it can spin finer yarns and that the spinning device is inexpensive, but has a drawback that only shorter pitch fibers can be spun.

Further, the most technical method is that the vortex-spun yarn is deposited on a belt conveyor, continuously infusibilized, and then carbonized in the form of a bulky matt into carbon fiber due to the characteristics of the fiberizing method. It is also economically advantageous. However, compared to the centrifugal spinning method, only shorter fibers can be spun, so it is spun like carbon fibers made by the centrifugal spinning method to form a single tow, which is then cut into chips or braided into a post-carbonization process. Is technically difficult. Therefore, it is difficult to obtain a carbon fiber chip that is usually used for fiber-reinforced thermoplastics.

The present inventors have paid attention to the superiority of the eddy current method, and as a result of earnestly studying to use this bulky carbon fiber mat as a reinforcing material for a thermoplastic resin, they have reached the present invention. That is, the present invention relates to, for example, the method described in Japanese Patent Publication No. 58-57374 (at least three pipes that are in a viscous state are discharged from an outflow orifice and are circumferentially spaced around the orifice). A high-speed gas stream is linearly blown out from the gas jet nozzle, wherein each of the gas streams is first directed toward the outflow direction of the substance and the tangential component along the outer periphery of the cross section that crosses the central axis of the substance. A component that gradually approaches the central axis of the substance and then gradually separates from the central axis, whereby the outflow of the pitch in the viscous state rotates about the central axis. It is made into fibers by a so-called vortex fiberization method, in which fibers are gradually thinned, made into a fibrous shape, ejected in a spiral shape, stretched, and made into a fiber, which is infusibilized and carbonized. Density 0.008~0.08g / cm ³ bulky carbon fiber mat is impregnated with a thermoplastic resin without a sheet form, and then to provide a process for the preparation of carbon fiber reinforced thermoplastic resin, characterized by molding. In the swirl method, high pressure air, high pressure steam, gas combustion waste gas, etc. are used as the hot gas flow.

Pitch fibers fiberized by the vortex method usually have a length of 5 mm to 50 c.
m, diameter 4 to 20 μm, deposited on a mesh belt conveyor, for example. The deposition density and amount can be controlled by changing the conveyor speed and the fiberization speed. In order to infusibilize and carbonize subsequently, the deposition density needs to be a bulky deposit so that air or nitrogen gas can sufficiently flow therethrough. On the other hand, considering the efficiency of the furnace, it is preferable that the density is high. Therefore, the density of the carbon fiber mat is preferably 0.008 to 0.08 g / cm ³ . After being carbonized, this bulky carbon fiber mat is optionally surface-treated and then sized. Such mats are generally rolled and stored in rolls, or continuously fed from a carbonization furnace to an impregnator and optionally continuously dried and stored as sheets.

Since the carbon fiber mat according to the present invention is two-dimensionally accumulated in a plane, even if compressed from the direction perpendicular to the mat plane, the yarn is less likely to be broken and the compression is possible up to about 1/15. The compression may be carried out before or after the mat is impregnated with the resin, but the post-impregnation compression is preferred in which the resin-impregnated sheet-like body which does not cause loss of yarn and facilitates the compression operation is compressed. A pressure roll is preferable for the compression operation.

The step of impregnating the mat of the present invention with a thermoplastic resin is, if the mat has sufficient breaking strength, an impregnating device or a photomelt device equipped with a feed roll, a squeezing roll, a dryer, an impregnation bath or a melter winding roll, etc. Can be done continuously through. When the breaking strength is insufficient, it can be carried out by a similar device using Teflon or a metal sheet and a mesh film as a supporting belt. Further, as the method of impregnation, in addition to the method of immersing in a solution or melt, the method of sprinkling and impregnating a necessary amount as a powder includes the method of adhering and impregnating from a kiss ring roll.

The thermoplastic resin referred to in the present invention is a polymer compound having a thermal softening temperature of room temperature or higher. For example, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polystyrene, 6-nylon, 6-6 nylon, polysulfone, polycarbonate, polyphenylene oxide, polyphenylene sulfide, polyurethane, polypropylene, polyethylene, polybutylene, polymethyl methacrylate, poly There are ether ether ketone, polytetrafluoroethylene, polyphenol resin, ABS, diallyl phenol and mixtures thereof. There is no problem even if a lubricant, a pigment, glass, an inorganic filler or the like is added to this resin. The carbon fibers are preferably blended in these thermoplastic resins in an amount of 0.5 to 60% by weight.

The carbon fiber referred to in the present invention is obtained from pitch as a raw material regardless of whether it is petroleum-based or coal-based, isotropic or anisotropic. The carbonization temperature can be changed from 800 ° C to 2800 ° C, resulting in
Both carbon fibers and graphite fibers are useful in the present invention. Therefore, the carbon fiber of the present invention also includes graphite fiber.

The sheet of the present invention can be molded as a stamping sheet by a thermocompression molding machine such as a stamping press. Several mm
Unlike the stamping sheet that is mixed with
Since the longer carbon fibers are blended, the merits of the longer fibers, such as the reinforcing effect and the conductive effect, are recognized.

Further, the sheet of the present invention is broken into particles or powder,
An extrusion molding machine or an injection molding machine can be used to form various shapes.

Since the resin is impregnated into the bulky mat, the carbon fiber content is generally low. Therefore, in order to provide a sufficient reinforcing effect, a necessary amount of carbon fibers may be mixed with the powder or granules already containing carbon fibers. The compounding means includes an extruder and various kneaders.

Further, according to the present invention, not only the physical strength of the thermoplastic resin can be increased, but also the electric conductivity and sliding characteristics can be improved.

Next, the present invention will be specifically described with reference to Examples.

Example 1 An isotropic pitch obtained by adjusting a coal tar pitch was fibrillated by a vortex method, and then deposited on a belt conveyor to continuously make it infusible, then carbonized at 1000 ° C., height 42 mm, width Bulky matte carbon fibers of 300 mm were obtained. Density is 0.02g / cm ³ , fiber length is 10-100mm (center is about 60mm), thread diameter is 10-15μ
(Center is 13μ). In addition, the tensile strength of the yarn is 80 Kg / m
m ² , the tensile elastic modulus was 4 Ton / mm ² , and the elongation was 1.9%.

After compressing this mat to 1/2 thickness with a roll, it is passed through a melter in which 6,6-nylon is melted, and further squeezed roll
It was compressed to 1/2 thickness to obtain a sheet having a thickness of about 10 mm. This nylon sheet contained about 10% by weight of carbon fiber.

The sheet was crushed and passed through a mesh sieve having a diameter of 7 mm to obtain granules having a carbon fiber content of about 10% by weight. Next, 2.0 kg of these granules and 570 g of the above mat that was cut to an average length of 8 mm were mixed well with a tumbler, kneaded and extruded with an extrusion molding machine, and with a chipper.
A pellet having a length of 4 mm and a diameter of 1.3 mm was obtained. This pellet was injection-molded to obtain various test pieces. The results are shown in Table-1.

Example 2 A bulky carbon fiber mat was obtained in the same manner as in Example 1. Density 0.04 g / cm ³ , thickness 3.0 mm, width 300 mm,
Fiber length is 20-60mm (center is about 40mm), thread diameter is 8-11μ
(Center is 9μ). The physical properties of the yarn were almost the same as in Example 1.

This mat was adjusted by needle punching to a thickness of 1/3 and cut into a mat having a length and width of 300 mm. On the other hand, 72 g of polyphenylene sulfide (manufactured by Philippe Petroleum) was made into a fine powder, and the mat was placed on a smooth pallet, which was pressed with a stainless steel plate and heated at 420 ° C. for 2 hours. The sheet was taken out, put on a press molding machine, and hot pressed to a thickness of 5 mm. Table 2 shows the results of measuring the physical properties by cutting out a test piece of the ASTM test method from this sheet.

Example 3 Anisotropic pitch obtained by adjusting coal tar pitch was vortexed to form fibers, and then deposited on a belt conveyor to continuously make it infusible, then carbonized at 1100 ° C., height 30 mm, width 300 mm
A bulky matte carbon fiber was obtained. Density is 0.03g / cm ³ ,
Fiber length is 20-60mm (center is 40mm), thread diameter is 7-10μ
(Center is 8μ). The tensile strength of the yarn is 220 kg /
mm ² , the tensile elastic modulus was 11 Ton / mm ² , and the elongation was 1.3%.

This mat is compressed to 1/2 thickness with a roll, then passed through a melter in which polybutylene terephthalate (manufactured by Toyobo) is melted, and further compressed to 1/2 thickness with a squeezing roll to obtain a sheet with a thickness of about 8 mm. It was The electrical resistance of this sheet was a volume resistivity of 10 ³ to 10 ⁵ Ohm · cm. From this sheet ASTM
The results of measuring the physical properties by cutting out the test pieces of the test method are shown in Table 3.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location D01F 9/14 7199-3B D04H 1/42 E 7199-3B 1/58 Z 7199-3B // B29C 70/10 (72) Inventor Yuji Matsumura 2-17-611 Rokugencho, Nishinomiya-shi, Hyogo Prefecture (72) Keiichiro Tanaka 4-32-11 Kasugaoka, Itami-shi, Hyogo Prefecture

Claims (1)

[Claims] 1. A viscous pitch is discharged from an outflow orifice, and a high-speed hot gas stream is linearly blown out from at least three gas ejection nozzles arranged at intervals in the circumferential direction around the orifice. , Where each of the gas streams gradually approaches the central axis of the pitch and then gradually approaches the central axis of the pitch in the direction of the tangential component along the outer periphery of the cross-section crossing the central axis of the pitch and the outflow direction of the pitch. It has a component that gradually separates from the axis, whereby the outflow of the pitch in the viscous state gradually turns around the central axis while gradually thinning, becoming fibrous, and jumping out in a spiral shape. Is melted, stretched and fiberized, infusibilized Pitch fibers deposited by the so-called vortex method,
Carbonized densities of 0.008 to 0.08 g / cm ^{3 that} are bulky carbon fiber mats impregnated with a thermoplastic resin to form a sheet,
Then, a method for producing a carbon fiber reinforced thermoplastic resin, characterized by molding.