JPH031907A - Production of fiber reinforced composite material - Google Patents

Abstract

PURPOSE:To obtain a fiber reinforced composite material imparting excellent mechanical properties and appearance quality to a molding by introducing reinforcing fiber rovings into a molten resin to mechanically accelerate the impregnation of said rovings with the resin and pulling out the impregnated rovings to form the same into a strand and cutting the strand into an arbitrary length. CONSTITUTION:For example, two glass fiber rovings are introduced into the molten nylon 66 resin in a die box 2 provided with three rolls 6 made of stain less steel SUS 304 while the tension of said rovings is controlled to a definite level and passed so as to be brought into contact with the free surfaces of the rolls 6 and pulled out from a circular nozzle 7 to obtain a strand-like fiber reinforced composite material 8. Further, this composite material 8 are cut into an arbitrally length to obtain pellet-like fiber reinforced composite materials 10.

Description

Detailed Description of the Invention Field of Application in the CM Industry] The present invention achieves a strand-like structure with excellent mechanical properties by uniformly dispersing and compounding continuous reinforcing fiber rovings into a molten thermoplastic resin. Alternatively, the present invention relates to a method of manufacturing a pellet-shaped fiber reinforced composite material.

[Conventional Technique v#] Thermoplastic resins are used in many fields, taking advantage of their characteristics such as a high degree of freedom in moldability and low specific gravity. However, it is inferior in strength compared to metal.

For this reason, fiber-reinforced composite materials in which reinforcing fibers such as glass fibers are filled regularly or irregularly into a matrix resin have been developed and used in a wide variety of ways to improve strength.

In order to obtain excellent mechanical properties and appearance characteristics by filling reinforcing fibers into thermoplastic resin, it is necessary that the filled reinforcing fibers have a certain length and are uniformly dispersed in the molded product. is necessary.

A method of producing pellets by kneading reinforcing fiber roving cut into 3-10 m lengths and a thermoplastic resin using an extruder, and then using the pellets as a raw material to obtain molded articles of fiber-reinforced composite material by injection molding or extrusion molding. is easy to manufacture, and it is relatively easy to disperse the fibers uniformly.However, during pellet production, the reinforcing fibers are damaged due to the cross-wire effect of the extruder's screws, and the degree of freedom in moldability and the appearance characteristics of the molded product are excellent. However, one cannot expect much improvement in mechanical properties, especially resistance to shock.

Sheet-like fiber-reinforced composite materials (e.g. stampable sheets) developed with the aim of suppressing breakage of reinforcing fibers and improving mechanical properties are made by filling thermoplastic resin with mat-like reinforcing fibers such as chopped strand mats. It is. However, since the molded product of this material is obtained by stamping molding, there is a reduction in the degree of freedom in moldability peculiar to the thermoplastic resin used as the matrix, and the reinforcing fibers are not uniformly dispersed, resulting in fiber bundles being molded. This causes deterioration of the appearance characteristics, such as embossed appearance on the surface of the product.

In order to develop fiber-reinforced composite materials that do not impair the moldability of the matrix resin and also provide excellent mechanical properties to molded products, continuous fiber coating methods, such as those used in the production of covered electric wires, are required. It has been adopted. In this process, a continuous reinforcing fiber roving is introduced into the die of an extruder, coated with molten resin, and pulled out from a nozzle to produce a strand-shaped fiber-reinforced composite material.After cooling, the fiber-reinforced composite material is cut into a desired length. Raw material pellets for injection molding or extrusion molding are obtained.

In this method, the matrix resin does not penetrate into the reinforcing fiber roving, and the reinforcing fiber roving is filled in a bundled state in the resin as shown in Figure 2 (A), or the reinforcing fiber roving is immersed in the reinforcing fiber roving. By controlling the introduction and coating method, it is possible to obtain a strand-like composite material in which a plurality of rovings are filled in the resin without coming into contact with each other, as shown in FIG. 2(B). These strands have drawbacks such as the reinforcing fibers being pulled out during cutting due to insufficient adhesion between the individual reinforcing fibers and the resin, and the resin covering the pellets cracking. is also restricted. During the molding process, fine fibers from such pellets scatter into the air, causing a deterioration of the working environment, impeding the smooth movement of the pellets in the molding machine, and causing damage to the cylinders and screws in contact with the pellets. This may cause significant wear such as deterioration of handling properties. In the molded product, the reinforcing fibers are not uniformly dispersed, and the expected strength cannot be obtained sufficiently, and the appearance characteristics are also deteriorated due to the reinforcing fiber bundles rising to the surface.

Furthermore, in order to improve resin impregnation into the reinforcing fiber roving, the strand-shaped fiber-reinforced composite material obtained by the above method was crushed into a flat shape with a roll while the resin still had plasticity. A method of pelletizing after cooling has been proposed (Japanese Unexamined Patent Publication No. 59-128704).However, even with this method, when impregnating with resin by roll compression, a large amount of resin is required and the fiber content is limited. Since the pellet shape is flat, when it is used for molding, the smooth movement of the pellet is hindered, resulting in a decrease in handling properties.

[Problems to be Solved by the Invention] The present invention aims to solve the problems of the prior art as described above. 1. A fiber-reinforced composite material in the form of a strand with excellent mechanical properties, and a material obtained by cutting the same. In order to improve the mechanical properties and appearance characteristics of molded products obtained by injection molding or extrusion molding using pellet-shaped fiber reinforced composite materials as a molding material, reinforcing fibers are added to the reinforcing fiber roving in a continuous fiber coating method. An object of the present invention is to provide a method for producing a fiber-reinforced composite material in which reinforcing fibers are uniformly dispersed in a matrix resin in a monofilament or similar state, and exhibit good adhesion between the reinforcing fibers and the resin. It is something.

[Means for Solving the Problems] The present inventors have solved the problem by mechanically accelerating resin impregnation when covering a continuous reinforcing fiber roving with a thermoplastic resin in a method for producing a fiber-reinforced composite material. The resulting strand-shaped fiber-reinforced composite material has improved strength because the reinforcing fibers are uniformly dispersed and the adhesion with the resin is improved, and the fiber-reinforced composite material can be cut into arbitrary lengths and made into pellets. In this case, the reinforcing fibers do not pull out and the pellet coating resin does not crack, improving handling.

Furthermore, it was discovered that molded products obtained by injection molding or extrusion molding using this material as a raw material exhibit excellent mechanical properties and appearance characteristics, and based on this finding, the present invention was completed.

That is, in the present invention, a molten thermoplastic resin is supplied into a die box in which a roll is installed, and a continuous reinforcing fiber roving is introduced into the molten resin, and the roving contacts the roll surface in the molten resin. A method for producing a fiber-reinforced composite material, which comprises mechanically accelerating resin impregnation into the roving, and then pulling out the roving while squeezing out excess resin to form a strand, and the strand. This is a method for producing a fiber-reinforced composite material in which the fiber-reinforced composite material is cut into arbitrary lengths and made into pellets.

Hereinafter, the contents of the present invention will be explained in detail.

The reinforcing Mllll-bing used in the present invention is as follows:
Carbon ta fibers such as polyacrylonitrile, rayon, and pitch fibers, synthetic fibers such as glass fibers, asbestos fibers, polyester fibers, and polyamide fibers, stainless steel fibers, copper fibers, and nickel fibers.

Examples include one type or a combination of two or more of various inorganic, organic, and metal fibers such as amorphous alloy fibers. In addition, for each fiber and resin combination, the fibers can be subjected to appropriate surface treatment such as sizing treatment or application of a coupling agent.

Thermoplastic resins used for coating include polyethylene, polypropylene, polystyrene, polyacrylonitrile,
Polyoxymethylene, polyethylene terephthalate, polybutylene terephthalate.

Examples include synthetic resins such as polyamide, polyurethane, polyphenylene sulfide, and mixtures or copolymers thereof. Furthermore, these thermoplastic resins contain various additives to improve their properties, such as heat resistant agents, weather resistant agents, antioxidants, ultraviolet deterioration inhibitors, antistatic agents, lubricants, mold release agents, dyes, etc. Coloring agents such as pigments, crystallization promoters, flame retardants, etc., and inorganic, organic, and metallic powders such as calcium carbonate as a third component can also be added.

Next, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 shows an example of a thermoplastic resin pultrusion device used for manufacturing the fiber reinforced composite material of the present invention.

Thermoplastic resin melted and plasticized in extruder 1.

Supplying the molten resin into the die box 2 through the supply port 3,
On the other hand, a plurality of continuous reinforcing fiber rovings 4 are introduced into the molten resin in the die box Z through the roving introduction port 5. The reinforcing fiber roving 4 is passed over and in contact with the surface of the free roll 6 in the die box 2 filled with molten resin to effectively mechanically impregnate the roving with the resin. By continuously pulling out the excess resin in the roving while squeezing it with the nozzle 7 at the tip, the reinforcing fibers are continuous in the matrix resin and are uniformly dispersed in a monofilament or similar state to form strand-shaped fiber reinforcement. A composite material 8 is obtained.

In Fig. 1, this strand-shaped fiber reinforced composite material 8 is continuously pulled out with a peltizer 9, cooled, and then cut into a desired length, so that reinforcing fibers equal to the cutting length are uniformly distributed in the resin as monofilaments or in a state close to it. 1 shows an apparatus for producing pellet-shaped fiber-reinforced composite material 10 dispersed in .

The present invention makes it possible to mechanically accelerate the impregnation of a thermoplastic resin into a continuous reinforcing fiber roving by improving thermoplastic resin pultrusion technology. This pultrusion device is very simple and an example is shown in FIG. 1. When the reinforcing fiber roving 4 passes over the free roll 6 surface in the die box 2 filled with molten resin, Resin impregnation is carried out.

Furthermore, since there is a highly viscous molten thermoplastic resin around the roll, a large tension is required when the strand-shaped fiber-reinforced composite material 8 is pulled out from the nozzle 7. When the strand is pulled out in the direction of arrow 11, the roll rotates in the direction of arrow 12. Then, the molten resin passes through the reinforcing fiber roving in the direction of arrow 13, and resin impregnation is effectively carried out.

In the manufacturing method of the present invention, the reinforcing fibers are uniformly dispersed in the matrix resin in the form of monofilaments or similar, as shown in FIG. A fiber reinforced composite material is obtained. Therefore, this strand-shaped fiber-reinforced composite material has a markedly increased tensile strength, and exhibits excellent properties even when used as a cement reinforcing material as a substitute for reinforcing steel, for example.

Thermoplastic prepreg can be manufactured by aligning this strand-shaped fiber-reinforced composite material and pulling it out in a sheet form from a die box, or by winding it in a plastic state around a drum or mandrel of any shape, or by making a filament. It is also possible to manufacture molded products by the winding method.

The strand shown in FIG. 2(C) obtained by the present invention has good cutting properties, and raw material pellets with good handling properties can be obtained at a higher filling rate than those shown in FIGS. 2(A) and 2(B). Furthermore, since the reinforcing fibers having a long fiber length were uniformly dispersed in the molded product, the mechanical properties were also sufficiently improved, and deterioration in appearance characteristics could be suppressed.

The method for producing a fiber-reinforced composite material according to the present invention mechanically promotes resin impregnation into the reinforcing fiber roving when the reinforcing fiber roving passes over the roll surface in a die box filled with molten thermoplastic resin. A strand-shaped fiber-reinforced composite material is obtained from this process, followed by a process in which the cross-sectional shape and fiber content are arbitrarily controlled by pulling the resin while it has plasticity through a nozzle according to the purpose. A pellet-shaped fiber-reinforced composite material is obtained by cutting the strand-shaped fiber-reinforced composite material into an arbitrary length.

The manufacturing apparatus or manufacturing process shown in FIG. 1 described above is only an example for realizing the same, and various combinations can be considered to implement the present invention.

For example, the extruder 1 may be any device that can continuously supply melted and plasticized thermoplastic resin, so it may be an extruder that simply melts and plasticizes the prepared pellets, or an extruder that simply melts and plasticizes the prepared pellets, or an extruder that contains multiple types of resins, various additives, and fillers. A device having a function of kneading etc. may also be used. Furthermore, it may be installed directly on the outlet side of the polymer polymerization equipment.

Figure 1 shows an example of a method for manufacturing fiber-reinforced composite materials using a closed die box, but this does not necessarily have to be done in a closed system, and it is also possible to separate the rolls and nozzles. . However, from the point of view of preventing oxidation of the matrix resin and improving the yield of excess resin removed by the nozzle, the die box method shown in Figure 1 is preferable, and if necessary, inert gas may be added to the die box. It is also possible to introduce In FIG. 1, a method has been described in which a free roll is used to promote resin impregnation, but a drive roll can also be installed by controlling the rotational speed of the roll and the speed at which the strand is pulled out. The material of the roll is not particularly limited as long as it has durability at the melting temperature of the thermoplastic resin, but metal or a material with hard plating such as chrome plating on the surface is preferable. The nozzle is used to control the cross-sectional shape of the strand and the fiber content by squeezing out the excess resin impregnated in the roving in a plastic state. Its shape can be set to a circle, an ellipse, a polygon, or any other shape depending on the purpose.

Cooling of the strand pulled out from the nozzle.

This is done as appropriate depending on the resin used and the desired cross-sectional shape.

In addition to compressed air, gases such as nitrogen can be used for cooling, and cooling can be performed by spraying or immersing liquids such as water, or indirectly cooling with cooling jackets, cooling rolls, etc. .

[Example] Example 1 Using the fiber-reinforced composite material manufacturing apparatus shown in Fig. 1, a glass fiber roving with a tax number (g/km) of 1280 (about 3000 fibers with a diameter of about 13μ and φ) was produced. .

) Two stainless steel SO3304 rolls were introduced into the molten nylon 66 resin in a die box with three rolls while adjusting the tension to a constant 150 kgf, and the rovings were passed over the free roll surface so that they were in contact with each other. Diameter 2.
A strand-shaped fiber-reinforced composite material was obtained by pulling it out from a 51φ circular nozzle, and this was further cut into 10 a+m pieces to produce a pellet-shaped fiber-reinforced composite material.

Comparative Example 3 A glass fiber roving cut into 11I+ lengths and a nylon 66 resin were blended to have a fiber content of 40vt%.
The mixture was kneaded using a 0 mmφ single-screw extruder, and the strands were pulled out through a circular nozzle with a diameter of 3 mmφ and cut into 6 ma+ pieces to produce a pellet-like fiber composite material.

The strand of Example 1 was embedded in an epoxy resin, its cross section was polished, and the state of resin impregnation into the glass fiber roving was observed using a microscope. the result.

It was observed that in Example 1, a product comparable to that shown in FIG. 2(C) was obtained.

Furthermore, a tab 17 was attached to the strand of Example 1 as shown in FIG. 3, and a tensile test was conducted.

The test speed was set at 5 m1n#+in, and the results are shown in Table 1. In the strand of Example 1, the reinforcing fibers are uniformly dispersed in the resin and the adhesion between the reinforcing fibers and the resin is good. The same strength was obtained.

Using the material pellets obtained in Example 1 and Comparative Example, the cylinder temperature of the injection molding machine was set high and melt-kneaded without applying screw back pressure, and test pieces of various specifications shown in Table 2 were prepared. , was prepared by directly molding the reinforcing fibers to minimize breakage.

Table 2 shows the results of measuring mechanical properties using the above test piece.
It was shown to.

The raw material pellets of Example 1 were sufficiently impregnated with resin, so they had good handling properties, and the molded products had excellent mechanical properties, especially impact strength, which was about twice as good as those of the comparative example. Both products exhibited good appearance characteristics because the reinforcing fibers in the molded products were uniformly dispersed in the form of monofilaments.

Example 2 Using the fiber-reinforced composite material manufacturing apparatus shown in FIG.
Three glass fiber rovings of the same size as the table *The values in parentheses indicate the standard deviation value, which was adjusted to a constant force of 150 kgf, and stainless steel m5u.
Three S304 rolls were introduced into molten nylon 6 resin in a die box, and the rovings were passed through the free roll surface in contact with each other, and the strands were pulled out from a circular nozzle with a diameter of 3.0 mm. A fiber-reinforced composite material in the form of pellets was produced by cutting into 10-m pieces.

Example 3 Using the fiber-reinforced composite material manufacturing apparatus shown in FIG.
Two glass fiber rovings with the same tension as 150 kgf.
With constant control, three rolls made of stainless steel 5US304 were introduced into the molten polyphenylene sulfide resin in a die box with three rolls, passed in such a way that the rovings were in contact with each other on the free roll surface, and the rolls were rolled with a diameter of 2.5+++ m.
The strand pulled out from the φ circular nozzle is 10011
A fiber-reinforced composite material in the form of pellets was produced by cutting into 1 pieces.

The raw material pellets of Examples 2 and 3, which were manufactured by changing the matrix resin, were also directly injection molded into test pieces with as little damage to the reinforcing fibers as possible, and the mechanical properties were measured. Table 3 shows the results of measuring the mechanical properties.
It was shown to. In Examples 2 and 3, the raw material pellets had good handling properties as in Example 1, and the molded products had excellent impact strength that was about twice that of the conventional product, and the reinforcing fibers in the molded products were superior to those of monofilament. Because it was uniformly dispersed, it exhibited the same appearance characteristics as conventional products.

Example 4 The influence of the fiber breakage state in the specimen on the impact strength was investigated.

Using the raw material pellets of Example 2, the screw back pressure of the injection molding machine was changed to 1 kgf/cm2.5 kgf/ctrr.
” was set. Test specimens with different reinforcing fiber breakage states were molded and the Izot impact strength was measured.Furthermore, the breakage states of the reinforcing fibers were measured by sieving.The injection molding machine of Example 2 Izotsu impact test pieces molded without applying screw back pressure and these Izotsu impact test pieces were burned to collect glass fibers, and a water jet was used to make the pores with an opening diameter of 0.
The samples were separated using a 71.1.0.5.0 mm sieve, and each sample was measured. As a result, the sieve opening diameter is 0.7in+m
In the following part, approximately 85% of the fibers with a length of 2 mm or less are captured in the fiber long garment x (), so the value separated only by this sieve indicates the state of fiber damage. It was expected that the results would be reflected fairly well.

This fiber of approximately 2+++m or more (sieve pore diameter 0.71n)
Figure 4 shows the relationship between the content of (supplemented with v or more) and impact strength. As the screw back pressure increases,
It was observed that the fiber damage state of the reinforcing fibers progressed and the Izot impact strength decreased. It is clear that maintaining the fiber length in the molded article results in improved impact strength.

From the above results, 1. The manufacturing method of the present invention improves mechanical properties.
It has become possible to produce fiber-reinforced composite materials in the form of strands or pellets that are excellent in all aspects including the fiber dispersed layer in the molded product, fiber breakage, appearance quality, and handling properties.

[Effects of the Invention] The present invention improves thermoplastic resin pultrusion, promotes mechanical resin impregnation into reinforcing fiber rovings, and enables reinforcing fibers to be uniformly dispersed in the matrix resin as monofilaments or in a state close to it. , a method for producing a fiber-reinforced composite material in the form of strands or pellets that exhibits good adhesion between reinforcing fibers and resin, and according to the present invention, injection molding, It has become possible to produce fiber-reinforced composite materials that give excellent mechanical properties and appearance quality to molded products obtained by extrusion molding.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the entirety of an example of a thermoplastic resin pultrusion device used for manufacturing a fiber-reinforced composite material according to the present invention. Figures 2 (A), (B), and (C) are explanatory diagrams of the cross-sectional state of a fiber-reinforced composite material in which continuous reinforcing fiber rovings are coated with molten thermoplastic resin. Figure 3 is a strand-shaped fiber-reinforced composite material. Fig. 4 is an explanatory diagram of a tensile test piece, and Fig. 4 is a diagram showing the influence of fiber breakage state in the test piece on impact strength. 1: Extruder, 2: Die box, 3: Molten resin supply port, 4: Continuously reinforced fiber roving, 5: Roving introduction port, 6: Free roll, 7: Nozzle, 8: Strand-shaped fiber reinforced composite material, 9: Pelletizer, 10
; Pellet-like fiber reinforced composite material, 11: Strand drawing direction, 12: Roll rotation direction, 13: Resin impregnation direction, 14: Reinforcing fiber roving, 15: Matrix resin, 16: Reinforcing fiber monofilament, 17: Tab. Figure Patent applicant: Nippon Steel Corporation Nippon Steel Chemical Co., Ltd.

Claims (2)

[Claims] (1) A molten thermoplastic resin is supplied into a die box in which a roll is installed, and a continuous reinforcing fiber roving is introduced into the die box so that it comes into contact with the roll surface in the molten thermoplastic resin. A method for manufacturing a fiber-reinforced composite material, which comprises passing through the roving to promote resin impregnation into the roving, and then continuously pulling out the roving while squeezing the excess resin to form a strand. (2) A method for producing a fiber-reinforced composite material, which comprises cutting the strand-shaped fiber-reinforced composite material obtained by the method according to claim (1) into arbitrary lengths to form pellets.