JPH06254976A - Production of fiber reinforced thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To obtain a compsn. improved in the dispersibility of a fiber and reduced in taking-up force and yarn cutting, in a pultrusion method, by impregnating a reinforcing fiber while controlling the filling state of the molten resin in a die box to a starvation state. CONSTITUTION:A reinforcing fiber is impregnated with a resin while the filling degree of the molten resin 2 in a die box 3 is controlled so as to set the interior of the die box 3 to a starvation state (filled molten resin 8). As a result, the resistance due to the resin, that is, the damage of the fiber is reduced. Further, the opening properties of a fiber bundle are excellent even in an opening device and the impregnation due to the resin bonded to the fiber bundle also becomes well over the whole of the die box. A resin filling state is different according to impregnation properties due to the kind, melt viscosity or compatibility of a resin and a taking-up speed but pref. set to 2/3 or less the total resin use amt. in the die box. The pressure in the die box is pref. set to 5kgf/cm<2> or less.

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 fiber-reinforced thermoplastic resin composition for coating (impregnating) a reinforcing fiber with a thermoplastic resin, and an apparatus therefor. This resin composition is used for automobile parts, building materials, and parts in the industrial material field, which are required to have high rigidity, high impact resistance, and creep resistance.

[0002]

2. Description of the Related Art Conventionally, a method for producing a molding material composed of a composite of a thermoplastic resin and a reinforcing fiber is as follows: (1) fibers cut to an appropriate length (usually 3 to 6 mm) and powder Alternatively, a method in which granular thermoplastic resin is mixed, extruded by an extrusion molding machine, and cut to obtain a molding material (2) The thermoplastic resin is dissolved or suspended in a solvent, and long fibers are continuously dipped in the solvent, (3) The fiber is continuously dipped in a monomer containing an initiator or a reactive oligomer, and the mixture is heated and polymerized to obtain a molding material. (4) Resin is plasticized and melted by an extrusion molding machine, continuous fibers are continuously introduced to the discharge side of the melt, and the molten resin is infiltrated into the fibers and extruded. Electric wire coatings that are cut into molding materials A similar pultrusion method or a pultrusion method is known.

In the method (1) using short fibers, the initial length of the fibers cannot be increased so much and the fibers are crushed when they are mixed in an extruder, so that the reinforcing effect by the fibers becomes insufficient. There is a problem.

The method (2) using a solvent has a drawback that the used solvent needs to be recovered, which requires a long process and a large-scale facility, which greatly affects the cost.

In the method (3) of dipping and polymerizing in a monomer or oligomer, there are drawbacks that thermoplastic resins that can be used are limited and that the polymerization process is complicated and control thereof is difficult. .

In contrast to each of the above methods, the pultrusion method or the pultrusion method of (4) is simple in equipment and process, and the length of the fiber in the molding material is not accompanied by crushing of the fiber during the manufacturing process. Since it can be arbitrarily selected, it is easy to enhance the reinforcing effect. However, agglomeration of fiber bundles easily occurs,
The matrix resin did not sufficiently penetrate (impregnate) between the individual fibers, and the product tended to be poorly dispersed. In particular, increasing the blending amount of fibers to increase the reinforcing effect further enhances this cohesive property, so that the strength of the product to be originally reinforced is reduced, the appearance of the product is deteriorated, and in extreme cases, the fiber Even the bundles could fall out of the pellets, which had problems in reinforcement performance, appearance, safety and hygiene.

To improve this, for example, Japanese Examined Patent Publication No. 43-74.
48, Japanese Patent Publication No. 43-7468, Japanese Patent Publication No. 52-1014
No. 0, Japanese Patent Publication No. 55-16825, a proposal is made to improve by devising a crosshead die. However, the impregnability of the matrix resin into the individual filaments in the fiber bundle and the dispersion of the individual fibers in the resin composition. The sex was still insufficient.

On the other hand, in order to improve the impregnation property of the resin, a method of using a resin having a low melt viscosity, that is, a low molecular weight resin, or mixing a large amount of a low molecular weight additive to lower the viscosity of the melt, Also known is a method of lowering the viscosity of the resin, such as setting the temperature of the die part higher to lower the viscosity of the melt. However, with these methods, there is a limit to the extent to which the viscosity can be reduced, or thermal decomposition is caused, and further problems with the physical properties of the resulting molding material, particularly impact resistance and long-term reliability, have occurred. .

Further, in order to improve the resin impregnation property into individual fiber filaments, for example, Japanese Patent Publication No. 63-3769.
In 4 etc., spread the fiber bundle by using a spreader etc. (this includes protrusions such as pins, bars, rotating bodies, etc.)
Proposals have been made for a method for facilitating contact between individual fibers and a resin.

However, in this proposed method, it is necessary to increase the number of spreaders in order to increase the production speed.
This naturally lengthens the contact length between the highly viscous molten resin and the fiber, and as a result, there is the drawback that the take-up resistance increases and the tension increases. This means that when the fiber bundle is spread, that is, when the fiber is opened and when the viscosity of the molten resin is high, the shear resistance due to the molten resin existing between the spreader and the die inner wall and the fiber bundle increases. However, as a result, not only is it difficult to collect the filaments, but also a large number of individual filaments in the reinforcing fiber bundle are cut, which accumulates in the die box, causing a problem such as production interruption.

[0011]

SUMMARY OF THE INVENTION The present invention is an improvement of these pultrusion method or pultrusion method, in which a high molecular weight thermoplastic resin having a high melt viscosity can also be used, and in particular, individual filaments during roving. The object of the present invention is to improve the dispersibility in the molten thermoplastic resin which is the matrix and to improve the productivity in the pultrusion molding method. Finally, when the fiber-reinforced thermoplastic resin composition is molded by injection molding, compression molding, etc., it is reinforced with excellent mechanical and thermal strengths, especially creep resistance, impact resistance and product appearance. The purpose is to enable the production of resin molded products.

[0012]

SUMMARY OF THE INVENTION The present invention is a pultrusion method or a pultrusion method in which reinforcing fibers are coated (impregnated) with a thermoplastic resin to control the filled state of the molten resin in the die box to a starved state. While covering (impregnating)
The above object was achieved by developing a method for producing a fiber-reinforced thermoplastic resin composition characterized by carrying out the following.

The thermoplastic resin usable in the present invention is not particularly limited as long as it can be plasticized by an extruder, and examples thereof include polyethylene, polypropylene, polystyrene, polyamide, polycarbonate, polybutylene terephthalate and the like. Further, a blended product of these resins and a resin composition filled with various fillers may be used. Further, as a well-known technique, it is particularly preferable to use a modified resin having affinity with fibers. The melt viscosity of the resin is not particularly limited, but a shear rate of 10 ² sec ^-1 is preferable.
The viscosity is about 10 ¹ to 10 ⁴ poise.

The types of reinforcing fibers used in the present invention include glass fibers such as E-glass and S-glass, carbon fibers such as pitch-based and polyacrylonitrile-based fibers, aromatic polyamide fibers, silicon carbide fibers, Ceramic fibers such as alumina fibers, metal fibers, and organic fibers such as nylon fibers and polyester fibers when the matrix resin is a resin that can be plasticized at a relatively low temperature such as polyethylene, polypropylene or polystyrene. These can be used alone or in combination. The fiber thickness, surface treatment agent, sizing agent type, amount and the like may be the same as those usually used. The content of the reinforcing fiber in the fiber reinforced resin composition is not particularly limited, but generally there are some differences depending on the purpose of use, the type of resin, the type of fiber, etc., but 10% by weight To about 80% by weight.

The shape of the fiber reinforced resin composition obtained by the present invention is limited by changing the shape of the die box outlet nozzle, such as a rod shape, a sheet shape, a gutter shape, or an L shape. Although not a thing, it is usually suitably used as a molding material pellet cut into a length of 10 to 50 mm.

The present invention will be described below with reference to the drawings. FIG. 1 shows the structure of a typical die box. The reinforcing fiber bundle 1 composed of thousands to tens of thousands of filaments whose tension is adjusted in advance and which is preferably preheated to the melting point of the molten resin or more is heated from the outside through the die introduction port 4 to the melting point of the resin or more. It is supplied in line with the die box body 3.

At this time, the reinforcing fiber bundle is opened on a fiber opening device, for example, a fiber opening bar 5 installed inside the die, and impregnated by contacting with the molten resin 2 a plurality of times in the opened state. To be achieved. The reinforcing fiber bundle impregnated with the resin passes through the nozzle 6 provided at the die outlet, squeezes the excess resin, controls the amount of resin, and shapes it into an arbitrary shape, and cuts it into an appropriate length. A fiber reinforced resin composition.

The resin flow in the die box is mainly carried to the nozzle side in a form in which the molten resin adhering to the reinforcing fiber bundle is dragged by the fibers, and in the process, between the opening bar 5 and the reinforcing fibers. The resin impregnation mainly proceeds on the contact surface. In addition, excess resin carried by the reinforcing fiber bundle is accumulated from the front part of the die, and when the resin supply amount is excessive, the front part of the die is filled with the resin.

In the conventional pultrusion method or pultrusion method, as shown in FIG. 2, the die box is operated in a state where it is completely filled with the molten resin, so that the reinforcing fiber bundle is in the die box. It will be taken against the shearing force of the high viscosity molten resin. In particular, since the fiber bundle is opened on the opening device, the contact surface is significantly increased, and therefore the opened fiber bundle needs to be pulled by a pulling force equal to or higher than the shearing force of the molten resin.

This shearing force becomes more remarkable when the temperature of the resin in the die box decreases, when a resin having a high melt viscosity is used, or when the take-up speed is increased.
This means that a large amount of tension is applied to the reinforcing fiber,
Part of individual filaments in the fiber bundle may be cut and stayed in the die box, or a lump of stagnant fibers may be extruded intermittently to produce a product in which the fibers pop out. In an extreme case, the nozzle may be clogged to cause a problem that the operation cannot be performed.

Further, since the molten resin is filled in the die box, the reinforcing fiber bundle is surrounded by the molten resin before coming into contact with the first-stage opening device, so that the fiber is opened on the opening device. Is likely to be incomplete.

It has been found that these problems can be solved by controlling the filling degree of the molten resin in the die box and placing the inside of the die box in a starvation state (filled molten resin 8) as shown in FIG. As a result, it was found that the resistance due to the resin, that is, the damage to the fiber, was reduced, the fiber opening property of the fiber opening device 5 was excellent, and the impregnation with the resin attached to the fiber bundle was good throughout the die box. .

The resin filled state varies depending on the type of resin, the melt viscosity, the impregnating property due to the affinity, the take-up speed, etc.
It is preferable that the amount is 2/3 or less of the total amount of resin used in the die box. However, it is needless to say that at least the vicinity of the nozzle at the exit of the die box must be filled with resin in order to prevent uneven resin adhesion. Further, in the case of a resin that is easily deteriorated by heat, an inert gas may be injected into the void in the die box to suppress the decomposition of the resin.

Further, the control of the filled position of the molten resin can be performed by a highly sensitive pressure sensor attached to the tip of the die box as shown in FIGS.
That is, it was revealed that a pressure due to the flow resistance of the reinforcing fiber bundle and the resin was generated at the tip of the die box, and the pressure was increased as the resin filled in the die box was increased. However, since this pressure changes depending on the take-up speed of the fiber bundle, etc., it is necessary to obtain the pressure under optimum conditions in advance. Moreover, since the pressure value is as low as approximately 5 kgf / cm ² or less, its detection and control requires special instrumental measures.

FIG. 3 shows an example of the control method. For example, the pressure of the molten resin at the tip of the die box is detected by the highly sensitive pressure gauge 7, and this is electrically converted and amplified by the converter 10, and the process controller 11 performs control processing such as response. Based on that, change the rotation speed of the extruder motor 13 with the extruder controller 12,
By controlling the amount of resin supplied to the die 3, the fiber-reinforced thermoplastic resin composition can be produced while maintaining the molten resin in the die box in a starved state.

[0026]

In the present invention, when the molten resin is coated (impregnated) while the reinforcing fiber bundle is opened by the opening device provided in the die box by the pultrusion method or the pultrusion method, the resin near the outlet is always filled. However, it is necessary to fill the molten resin in the die box incompletely (starvation state) to improve the uniformity of the coating) and to cut the individual filaments of the fiber bundle. We have found that the amount can be reduced significantly.

That is, the filling degree of the molten resin in the die box is almost proportional to the pressure inside the die and the take-up force of the reinforcing fiber bundle, and surprisingly, the impregnating ability of the resin is inversely proportional to the filling degree of the molten resin. I have found something.

Therefore, by controlling the filling degree of the molten resin in the die box, it is possible to improve the impregnation property with respect to the fiber bundle, prevent yarn breakage and suppress the take-up force to a low level. This can be achieved by detecting the pressure inside the die box as a means and controlling the supply of resin from the extruder.

Although this exact mechanism could not be confirmed, since the reinforcing fiber bundle supplied to the die box is first opened and then comes into contact with the molten resin, the coating in a preferable state at the initial stage of contact with the molten resin. (Impregnation) is considered to be performed. After that, the fiber bundle covered with the molten resin (however, the molten resin is not filled) is opened by the opening device from the second stage onwards and impregnated with the resin, but the molten resin is It is estimated that the degree of impregnation will be improved compared to the case where the impregnation degree is full because the opening operation in the unfilled section is efficient.

Since the die box is not completely filled with the molten resin, when the fiber bundle is taken up, the shearing force of the molten resin becomes unnecessary in the unfilled section, which lowers the take-up resistance. It is presumed to reduce the cutting of individual filaments of.

It has also been found that the filling degree of the molten resin in the die box can be easily controlled by providing a pressure detector at the tip of the die box.

[0032]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. Example 1 About 4,000 E-glass fibers having a fiber diameter of 16 μm were lined up as reinforcing fibers, and a roving subjected to a predetermined surface treatment and a focusing treatment was used. Further, as the matrix resin, homopolypropylene having MFR = 30 g / 10 min modified with 0.5 phr of maleic anhydride was used. As the molding apparatus, the control method shown in FIG. 4 was used. As the pressure sensor 3, a low pressure device of 15 kgf / cm ² range was used, and a dedicated converter (amplifier) 10 was used. Further, the proportional band and the integration time were adjusted by the process controller 11 so that the set pressure value could be maintained. An inverter was used as the extruder controller 12 to control the rotation speed of the extruder motor. When the pressure at the tip of the die box is 20 m / min and 2.3 kgf / cm ² , the take-up force is about 18 kgf, the molten resin filling degree in the die box is about 50%, and the impregnation property is good. Almost no yarn breakage occurred. The pultruded product extruded from a nozzle having a diameter of about 3 mm was cut into 13 mm to produce pellets of the fiber-reinforced thermoplastic resin composition. The composition ratio is 40% by weight of fiber and 60% by weight of homopolypropylene. Then, the pellets are injection molded under the conditions of a resin temperature of 210 ° C. and a mold temperature of 40 ° C. to prepare a test piece, a bending test,
A tensile test, an impact test (Izod; with notch), and a tensile creep test were carried out to evaluate the physical properties.

Tensile test: JIS K-7054 (23 ° C.) Bending test: JIS K-7055 (23 ° C.) Impact test (IZOD): JIS K-7110 (23
C) Tensile creep: JIS K-7115 (60 ° C, stress 200 kgf / cm ² ).

(Example 2) Using a glass fiber roving and equipment similar to those of Example 1 using maleic anhydride modified (modification amount 0.5 phr) homopropylene having an MFR of 15 g / 10 min and melting in a die box. The resin filling degree was also set to about 50%. Collection speed 20m /
At min, the take-up force at this time was 21 kgf, which was slightly higher than that in Example 1, but the yarn breakage and the resin impregnation property were good. The physical property evaluation results are shown in Table 1.

Comparative Example Using the same glass fiber roving, modified polypropylene and equipment as in Example 1, molding was carried out under the same conditions. However, the pressure at the tip of the die box should be 7
When the pressure was set to kgf / cm ² , the inside of the die box was filled with molten resin, the take-up force was 30 kgf at a take-up speed of 20 m / min, yarn breakage occurred, and molding was somewhat difficult. The evaluation results are shown in Table 1.

[0036]

[Table 1]

[0037]

INDUSTRIAL APPLICABILITY According to the present invention, in the pultrusion molding method or the pultrusion method in which the reinforcing fibers are dispersed in the thermoplastic resin, even if the melt viscosity of the resin is high or the resin is taken at a high speed, the matrix resin It is possible to provide a method for producing a fiber-reinforced thermoplastic resin material which has good impregnation properties into fibers, mechanical properties such as impact resistance and creep resistance, and excellent product appearance.

[Brief description of drawings]

FIG. 1 shows a molten resin filled state in a pultrusion molding method die box according to the present invention.

FIG. 2 shows a molten resin filling state in a die box of a conventional pultrusion method.

FIG. 3 shows an example of a pultrusion molding method control method of the present invention.

[Explanation of symbols]

 1 Reinforced Fiber 2 Molten Resin 3 Die 4 Inlet 5 Opening Bar 6 Nozzle 7 Pressure Gauge 8 Filled Molten Resin 9 Extruder 10 Converter 11 Process Controller 12 Extruder Controller 13 Motor

Claims (3)

[Claims] 1. In a pultrusion method or a pultrusion method in which reinforcing fibers are coated (impregnated) with a thermoplastic resin, coating (impregnation) is performed while controlling the filled state of the molten resin in the die box to a starvation state. A method for producing a fiber-reinforced thermoplastic resin composition, comprising: 2. The method for producing a fiber-reinforced thermoplastic resin composition according to claim 1, wherein the amount of molten resin supplied is adjusted so that the filled state of the resin in the die box is controlled to 2/3 or less of the space of the die box. 3. The fiber-reinforced heat according to claim 1 or 2, wherein the pressure in the die box is maintained at 5 kgf / cm ² or less by controlling the amount of resin supplied to control the filled state of the molten resin in the die box. A method for producing a plastic resin composition.