JP3210694B2 - Method for producing fiber-reinforced composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic resin composite material reinforced with long fibers.

[0002]

2. Description of the Related Art Pultrusion molding has recently attracted attention as a method for producing a thermoplastic resin composition reinforced with long fibers. Above all, a method of impregnating a melt of a thermoplastic resin in a crosshead die while pulling a continuous reinforcing fiber bundle has an advantage that the operation is easy and the fiber content is easily controlled. Specifically, as a method of this type, for example, Japanese Patent Publication No. 49-41105 discloses a method of obtaining a long fiber reinforced resin composition through continuous fibers through a crosshead die. Further, U.S. Pat. No. 4,439,387 discloses a method of effectively impregnating a fiber with a molten resin by corrugating a crosshead. However, the method of impregnating a continuous fiber with a melt of a thermoplastic resin using these crossheads has the following problems. First, some of the fibers break inside the crosshead die,
This becomes fluff and adheres to the pulled strand,
Impairs product appearance. Secondly, since the impregnation cannot be performed completely, fibers that are not impregnated in the resin are generated at the time of cutting or hunting of the product although the amount is very small. Conventionally, in order to improve the impregnation, the molecular weight of the matrix used has been reduced to lower the melt viscosity.However, a molded article made of such a resin composition has a problem that the mechanical properties are reduced. I was

[0003]

SUMMARY OF THE INVENTION In view of such circumstances, the present inventors have considered that a continuous fiber reinforced thermoplastic resin composition in which a molten thermoplastic resin is impregnated in a crosshead die while pulling a continuous reinforcing fiber bundle. As a result of intensive studies to solve the above-mentioned problems in the method for producing a product, and to obtain a long-fiber-reinforced thermoplastic resin composition having no fluff and having excellent adhesion between the fiber and the matrix, a strand obtained by a conventional method was identified. Finding that it is effective to apply processing,
The present invention has been completed. That is, the present invention introduces a continuous reinforcing fiber roving into a molten thermoplastic resin, impregnates the molten resin with the fiber, and then continuously draws down an excessive amount of the resin with a nozzle using a drawing device. A step of drawing and a step in which the strand obtained in this step is heated to a temperature lower than the melting point of the resin (provided that the resin is polypropylene).
100% from the melting point for polyethylene terephthalate
The present invention relates to a method for producing a strand-like fiber-reinforced composite material, which comprises a step of pressing the strand in a ribbon shape with a roll controlled to a temperature lower than 150 ° C.) and a step of adjusting the shape of the pressed strand through a shaping nozzle.

[0004] In general, the crosshead die has advantages such as good operability and easy adjustment of the resin content. However, impregnation of the fiber bundle with the resin is not complete.
There is a disadvantage that the adhesion between the fiber and the matrix is insufficient. It is a feature of the present invention to obtain advanced products while taking advantage of such crosshead dies.

In the first step of the present invention, a continuous reinforcing fiber roving is introduced into a molten thermoplastic resin, and the molten resin is impregnated with the fiber. This is a step of continuously drawing while narrowing down, and this step is not different from the case of ordinary pultrusion molding.

When the cross section of the strand obtained by the method using the crosshead die is observed, the fiber filaments are often not distributed uniformly but in an S-like shape (see FIG. 2). If the impregnation is not sufficient, there is a lump of fibers only partially free of resin.

The second step of the present invention is a step in which the strand obtained in the first step is pressed in a ribbon shape by a roll, and the roving impregnated with the molten resin is pressed by the roll to obtain the resin. Can be mechanically impregnated with the molten resin into the fiber bundles not in contact with the fiber bundle. In the second step, the pressure of the pressing by the roll is not particularly limited, but it is preferable that the pressing is performed in a range satisfying the following expression from the viewpoint of improving the dispersion of the glass. b / a = 2 to 10 (where a is the strand diameter (cm) of the crosshead die,
b is the width (cm) of the pressed ribbon-like strand. Particularly preferred is the case where b / a = 2.5 to 4.

In the third step of the present invention, after the second step, the pressed strand is passed through a shaping nozzle to adjust the shape. When the strand is passed through the shaping nozzle, the roving once flattened. Since it becomes circular later, the fibers are uniformly distributed in the strand as shown in FIG.

The strands exiting the crosshead die are cooled in the air, but before being solidified, they are pressed into a flat ribbon shape by a roll and are folded by passing them through a shaping nozzle to form a cylindrical shape. Become. By controlling the temperature of the roll to be equal to or lower than the melting point of the resin, it is possible to completely prevent the resin and the fibers from adhering and entraining to the roll. The temperature of the roll is 100 to 150 ° C. lower than the melting point for resins having low crystallinity, such as polypropylene and polyethylene terephthalate, and 0 to 150 ° C. for resins having high crystallinity, such as nylon and polyacetal.
Preferably, the temperature is lower by 50 ° C.

The action of changing the cross-sectional shape of the strand from a flat ribbon shape to a folding circular shape allows the fibers to be uniformly dispersed. The dispersibility is improved by repeating the combination of the roll and the shaping die. In the present invention, the fiber bundle is impregnated with the crosshead die and the roll separately, so that the operating temperature can be lowered as compared with the case where only the crosshead die is used, thereby deteriorating the matrix. Can be prevented, and the mechanical properties can be improved. Further, by dividing the impregnation step, the speed of taking the roving can be remarkably improved, and the productivity can be drastically increased.

[0011] The method for producing a fiber-reinforced composite material of the present invention comprises:
The above-described production method itself is characteristic, and there are no particular restrictions on the fibers, thermoplastic resins, and the like to be used, and any high-melting point (high softening point) fibers such as glass fibers, carbon fibers, and aromatic polyamide fibers can be used. Any of continuous fibers such as rovings, yarns and monofilaments can be used. or,
As a thermoplastic resin impregnating fibers, polyethylene,
Polyester such as polypropylene, polyethylene terephthalate and polybutylene terephthalate, nylon 6,
Known thermoplastic resins such as polyamides of nylon 66, nylon 11, nylon 12, nylon 610, nylon 612 tower, polycarbonate, polyurethane, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyetherketone, polyetheramide, polyetherimide and the like. Any of those copolymers and modified products can be used. The strand obtained by the above-mentioned production method is used as it is or cut into an arbitrary length and used as a pellet.

[0012]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1, Comparative Example 1 A glass-reinforced polypropylene having a glass content of 40% by weight was produced using a crosshead die, a roll and a shaping nozzle shown in FIG. That is, a polypropylene homopolymer containing 10% by weight of modified polypropylene was used as a thermoplastic resin, glass fibers were used as fibers, and roving 1 was supplied to a crosshead die shown in FIG.
The strand 3 that has exited the crosshead die is pressed by a pressing roll 4
, And shaped by the shaping nozzle 5. In addition,
The diameter (a) of the strand that has exited the pad die is 0.236 cm and is pressed.
Width of ribbon-shaped strand pressed by roll (b)
Was 0.776 cm 2. The operating conditions are as follows. On the other hand, for comparison, the same glass-reinforced polypropylene having a glass content of 40% by weight as in Example 1 was produced using only a crosshead die. These products were evaluated as follows. Tensile strength; measured according to ASTM D-638. Impact strength: The notched Izod impact strength was measured (thickness of the test piece: 6.3 mm) in accordance with ASTM D-256. Unimpregnated glass content in the product: The product pellets were washed with a 1% alcohol aqueous solution, the washing solution was filtered, and the weight (ppm) of the glass collected by filter paper was measured.

Productivity: The discharge rate was measured when the roving take-off speed was maximized in a state where no fluff was generated and no strand was cut.

Table 1 shows the results.

Example 2 and Comparative Example 2 Glass-reinforced polypropylene was produced in the same manner as in Example 1 and Comparative Example 1 except that the glass content was 50% by weight and the pellet length was 1/2 inch. evaluated. Table 2 shows the results
Shown in

[0017]

[Table 1]

[0018]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a schematic view showing an apparatus used for a manufacturing method of the present invention.

FIG. 2 is a schematic diagram showing a state in which the shape of a strand changes according to the present invention.

[Description of Signs] 1. Roving 2. Crosshead Die 3. Strand 4. Press Roll 5. Molding Nozzle

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29B 15/12 B29B 11/16 C08J 5/00-5/24

Claims (2)

(57) [Claims] 1. A continuous reinforcing fiber roving is introduced into a molten thermoplastic resin, and the molten resin is impregnated with the fiber. Then, the excess resin is continuously narrowed down with a nozzle using a drawing device. A step of drawing, and a step in which the strand obtained in this step is heated to a temperature lower than the melting point of the resin (however,
And the resin is polypropylene, polyethylene terephthalate
Strand-like fiber reinforced composite material consisting of a process of pressing in a ribbon shape with a roll controlled to a temperature lower by 100 to 150 ° C from the melting point, and a process of adjusting the shape of the pressed strand through a shaping nozzle. Manufacturing method. 2. The method for producing a strand-like fiber reinforced composite material according to claim 1, wherein in the step of pressing the strand with a roll, the pressing with the roll is performed within a range satisfying the following expression. b / a = 2 to 10 (where a is the strand diameter (c
m) and b are the width (cm) of the pressed ribbon-like strand. )