JPH0820021A - Manufacture of fiber reinforced thermoplastic resin composition and preformed body using the composition - Google Patents

Abstract

PURPOSE:To protect reinforcing fibers from getting broken or marked in a mixing process in air flow of thermoplastic resin powder constituting a matrix with reinforced fibers and manufacture a fiber reinforced resin composition for manufacturing a molded body of good mechanical properties, particularly good toughness, flexural properties and impact properties and also a preformed body using the composition. CONSTITUTION:When thermoplastic matrix resin powder is mixed with reinforcing fibers in air flow to manufacture a fiber reinforced thermoplastic resin composition, the surfaces of the reinforcing fibers are coated preliminarily with resin of the same kind as thermoplastic matrix resin or having affinity with thermoplastic resin having affinity with matrix resin.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fiber-reinforced thermoplastic resin composition for obtaining a fiber-reinforced resin molded product having excellent mechanical properties, particularly tensile strength, bending strength, toughness, impact properties and the like. The present invention relates to a method for producing a preformed body using the composition, and the composition or the preformed body obtained by these methods are fiber reinforced used for interior / exterior parts of automobiles, household electrical appliances, and various other fields. It can be effectively used as a material for thermoplastic resin moldings.

[0002]

2. Description of the Related Art A fiber-reinforced thermoplastic resin molded body in which a thermoplastic resin such as a polyolefin resin such as polyethylene or polypropylene is used as a matrix, and glass fibers or carbon fibers are used as reinforcing fibers in the matrix is relatively lightweight. In addition, it has excellent mechanical properties, and because it has the characteristics that it can be easily processed into any shape by secondary molding, it is widely used in various fields including the above-mentioned applications. It is used.

On the other hand, this type of fiber reinforced thermoplastic resin is
In general, continuous long-fiber reinforcing fibers have been widely used as a composite with a matrix resin, but recently, for example, a reinforcing fiber made of chopped strands obtained by cutting continuous fibers into an appropriate length such as BMC is thermoplastic resin. A fiber-reinforced resin composition which has been mixed with the resin composition and can be molded into various shapes has been widely used. As a method for producing such a chopped strand composite type fiber reinforced resin composition, for example, Japanese Patent Laid-Open No. 63-13555.
Techniques such as those disclosed in No. 0 and No. 63-199611 are proposed.

In this method, chopped strands of a glass fiber bundle are opened by mixing in a turbulent air flow, and at the same time, thermoplastic resin powder serving as a matrix is added to the mixing system to uniformly mix the glass fiber with glass fiber. It is intended to obtain a bulk molding resin composition in which thermoplastic resin powders are uniformly mixed, and this bulk composition can be molded into any shape by heat and pressure molding. Is expected to increase.

Further, a preformed body prepared by appropriately compressing the bulk composition and heating the surface thereof to melt the thermoplastic resin in the surface layer to form an outer coat is a simple fiber. The bulk density is significantly higher than that of a bulk composition consisting of a mixture of resin powder and resin powder, and it is convenient not only for transportation and handling, but also for standardizing the shape of the preform so that it can be heated and pressed thereafter. There is also an advantage that it can be easily applied to a molding device, and it is considered that practical application in such a form will be further advanced in the future.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted further research for the purpose of practical application and improvement of the method of mixing the reinforcing fibers and the resin powder constituting the matrix in an air stream as described above. However, I found that the following problems occurred during the research process. That is, as described above, in the method of mixing the reinforcing fiber and the thermoplastic resin powder in the air stream, when a material that is easily broken or damaged by an external force such as glass fiber is used as the reinforcing fiber, the material is reinforced in the mixing step. The surface of the reinforcing fibers is damaged or collides with the inner wall of the mixing device, the resin powder, or the like, and the surface is damaged or ruptured to have a short length. The effect of improving impact properties and the like decreases, and it is not possible to obtain a fiber-reinforced resin molded product having the expected physical properties.

Particularly recently, there has been a tendency to use very fine reinforcing fibers in order to improve the surface smoothness and precision of the molded product, and the mixing is sufficiently carried out to make the final molded product homogeneous. It is considered that the deterioration of the physical properties due to the breakage of the reinforcing fibers during the mixing with the resin powder cannot be neglected in combination with the above.

The present invention has been made by paying attention to such a new problem, and the purpose thereof is to describe the above when mixing the thermoplastic resin powder constituting the matrix and the reinforcing fiber in an air stream. A fiber-reinforced resin composition and a method for producing a preformed body using the composition, which prevent breakage of the reinforcing fiber as described above and thereby provide a molded body having good mechanical properties, particularly toughness and impact properties. It is something to be established.

[0009]

The method for producing a fiber-reinforced thermoplastic resin composition according to the present invention, which has been able to solve the above-mentioned problems, comprises mixing a thermoplastic matrix resin powder and a reinforcing fiber in an air stream to form a fiber. In producing a reinforced thermoplastic resin composition, the surface of the reinforcing fiber is previously coated with a thermoplastic resin of the same type as the thermoplastic matrix resin, or a thermoplastic resin having an affinity with the matrix resin. There is a gist.

Further, the method for producing the preform according to the present invention is such that the resin composition obtained by the above method is compressed and the surface layer portion of the compressed body is heated so that the thermoplastic matrix resin and the reinforcing fiber are present in the surface layer portion. Is characterized in that a melt-integrated preform is obtained.

[0011]

As described above, in the present invention, it is premised that the thermoplastic matrix resin and the reinforcing fiber are mixed in an air stream, and the reinforcing fiber is used as a means for preventing breakage of the reinforcing fiber during the mixing. The fibers for use are previously coated with a thermoplastic resin of the same type as the matrix resin or another thermoplastic resin having an affinity with the matrix resin, and the resin coating is then mixed with the thermoplastic matrix resin powder. At that time, breakage of the reinforcing fiber is prevented. As a result, the reinforcing fiber maintains almost the same length as it was in the raw material state before mixing, and as a result, a resin composition giving a molded product having the physical properties expected in the raw material state in terms of toughness and impact properties. It is also possible to obtain a product, and by compressing this, heating the surface layer part to melt-integrate the thermoplastic matrix resin and the reinforcing fiber in the surface layer part, thereby forming a molded product with similarly excellent mechanical properties. A preform to be given can be obtained.

The type of reinforcing fiber used in the present invention is not particularly limited, and examples thereof include glass fiber, carbon fiber, metal fiber, ceramic fiber, aramid fiber, polyamide fiber, polyester fiber, acrylic fiber, and further SiC.
Whiskers and S ₃ N ₄ whiskers can all be used, and they can be used alone or in combination of two or more if necessary. Among these fibers, the fibers most effectively exhibiting the characteristics of the present invention are fibers such as glass fibers and ceramic fibers, which have low impact strength and are easily broken or damaged when subjected to an impact force.

These reinforcing fibers are more effective in terms of reinforcing effect as the number of filaments increases to some extent. However, considering the uniform dispersibility in the matrix resin and the workability in the heat and pressure molding process, etc. Preferred is a diameter of 8 to
It is a bundle of about 200 to 4000 filaments, more preferably about 400 to 1200 filaments of about 20 μm. The fiber length cannot be uniformly decided because it varies depending on the use, but in consideration of the uniform mixing property with the thermoplastic resin powder, the general length is about 1 to 50 mm, more generally 10 to 30 mm. It is a range of degrees.

As the matrix resin, a powdery thermoplastic resin is used. Examples thereof include general-purpose resins such as polyethylene, polypropylene, ABS, polyethylene terephthalate, polycarbonate, polystyrene, polyacetal, polyacrylate, polysulfone, polyphenylene sulfide, and the like. It is also possible to use a thermoplastic resin having excellent heat resistance such as polyetheretherketone, polyimide or polyamideimide. Of course, a part of these polymers may be modified, for example, acid-modified polypropylene or the like. These powdered thermoplastic resins are
A spherical shape with a diameter of 0.01 to 5 mm or a diameter of 0.5
～8Mm, length 1~10m about pellets, or cross-sectional area 5 to 30 mm ^2, but those rectangular parallelepiped having a length of about 1~8mm can be used, fibers in the mixing step of the reinforcing fibers in an air stream In order to minimize the impact force exerted on, it is preferable to use a shape such as a spherical shape or an elliptical shape having no sharp edge portion. Next, the type and surface coating method of the thermoplastic resin coated on the surface of the reinforcing fiber prior to the mixing in the air stream will be described.

The selection criteria of the coating resin are that it can be uniformly mixed with the matrix resin powder by mixing in the above-mentioned air flow, and that it is finally fused with the matrix resin in the state of being heated and pressed. It is necessary to select a resin that has an affinity, and a thermoplastic resin of the same kind as the above matrix resin or a thermoplastic resin having an affinity for the matrix resin is selected and used. Therefore, the thermoplastic resin for coating depends on the type of matrix resin used.

Therefore, when the most common polyolefin such as polyethylene or polypropylene is used as the matrix resin, it is common to select the same type of polyolefin resin as the coating resin. in this case,
It is preferable to use, as the coating resin, a modified polyolefin resin having a polar group introduced therein instead of an acid-modified polyolefin resin, since the surface of the reinforcing fiber can be coated more efficiently.

The method of coating the fibers with these resins is not particularly limited, but as a general method, a solution of the resin in a volatile organic solvent or an aqueous emulsion in which the resin is dispersed in water (for example, The resin and the surface active agent are dispersed in water and heated and stirred to form a dispersion liquid, or the organic solvent solution of the resin is added to water and strongly stirred to be dispersed. To the surface of the fiber by melting and adhering the fine powder of the resin together with the fiber in a heated air flow after the solvent is volatilized and removed by the impregnation method, coating method, spray method or the like. It is possible to employ a method in which the coating is performed. Among these, particularly preferred is the former method of surface coating using a resin solution or resin emulsion, and this method allows the fiber surface to be easily and uniformly coated with a relatively small amount of resin. preferable.

The surface coating resin has the function of preventing the fibers from being broken or damaged during the subsequent air flow mixing with the matrix-constituting resin powder. In order to effectively exhibit such a function, It is desired that the adhered amount is about 0.1% by weight or more, and more preferably about 0.5% by weight or more with respect to the fiber. The resin coating amount also changes depending on the fiber diameter (that is, the specific surface area), and the specific surface area increases as the fiber having a smaller fiber diameter is used. Therefore, the weight ratio of the resin to be used should be increased.

The surface coating resin is then mixed with a thermoplastic resin powder in an air stream to obtain a fiber reinforced thermoplastic resin composition, or this is further compressed to heat the surface to form a preform, and then the final molded product is obtained. The upper limit is not limited at all because it is fused and integrated with the matrix-constituting resin in the state after the heat-press molding, but considering the workability and efficiency of the surface coating, it is 10% by weight with respect to the fiber. It is preferably about 4% by weight or less, more preferably about 2% by weight or less.

Thus, the fiber whose surface is coated with the resin is
Then, they are uniformly mixed in an air stream by the following method. For example, in a fiber-reinforced resin composition in which a reinforcing fiber and a matrix resin are combined, such as the conventional BMC, a method in which the reinforcing fiber is added to a molten matrix constituent resin and the mixture is forcibly mixed with high shear force is generally adopted. However, if such a method is adopted, a brittle fiber such as glass fiber will be broken and the composite reinforcing effect will not be effectively exhibited. Such a tendency is almost the same even when the fiber surface is previously coated with a resin as described above, and eventually the effect of the resin coating is not exhibited at all.

Therefore, in the production method of the present invention, the resin-coated fibers and the thermoplastic resin powder forming the matrix are mixed in an air stream in place of such forced mixing to which high shearing force is applied, whereby mixing is performed. The fibers are uniformly mixed with the resin powder without breaking the fibers in the process, and the reinforcing effect of the fibers is maximized effectively. Particularly, in the present invention, since the fiber surface is coated with the resin in advance as described above, the fibers are ruptured or scratched by the collision between the fibers or the resin powder as described above which is observed when the conventional air flow mixing method is adopted. Since the reinforcing fibers in the resulting resin composition are substantially maintained in the same size and shape as before mixing, the reinforcing effect of the reinforcing fibers is maximized. You can withdraw.

As a concrete method of mixing in an air stream,
For example, the airflow mixing device 1 as shown in FIG. 1 may be used. That is, from a plurality of hoppers 4a, 4b attached to the upper part of the cylindrical container 10, a predetermined amount of reinforcing resin and thermoplastic resin powder whose surface is coated with resin and thermoplastic resin powder are separately or simultaneously supplied to the container wall surface. Compressed gas (air, nitrogen, inert gas, water vapor, etc.) is blown from the nozzle 3 provided, and the raw materials are mixed by the stirring force mainly of the air flow while slowly stirring with the stirrer 6 if necessary. In this case, it is also effective to provide two or more nozzles to further enhance the airflow stirring effect. The compressed gas is discharged to the outside air side from the filter 8 provided at a proper position on the wall surface of the container 10 through the exhaust port 9. The mixing conditions are not particularly limited, but usually, the pressure is 1 to 5 kg / cm ² , and the flow rate of the blown air is 0.1 to 0.1.
About 0.5 kg / min is adopted. Further, stirring with a stirrer that may be used in combination as necessary is 30 to 100.
About rpm is preferable. The mixture may be taken out in batches from the outlet 5 provided in the lower part of the container 10. This mixture may be commercialized as it is as a bulk fiber-reinforced resin composition in which surface-coated fibers and thermoplastic resin powder are uniformly mixed, or it may be compressed to heat its surface to form a thermoplastic resin on the surface. It is also effective to prepare a bulk preform by commercializing it by melting and skinning it.

In the case of a bulk preform, the homogeneous mixture obtained as described above is charged into a compression molding apparatus equipped with a heating mechanism (heat transfer heater or the like) on the inner surface side, The mixture is compressed to consolidate and the surface is heated to melt the thermoplastic resin powder on the surface, which is integrated with the reinforcing fibers in the surface layer and then cooled to make only the surface skinned, and the inside is for reinforcement. A bulk preform may be used in which the fibers and the resin powder are still mixed.

When glass fibers or ceramic fibers are used in combination with metal fibers, organic fibers or the like in the mixing in the airflow, only the glass fibers or ceramic fibers which are easily broken or scratched in the airflow mixing step are mentioned above. It is also possible to perform surface coating by such a method, and to mix metal fibers, organic fibers, etc. which are flexible by themselves and are less likely to break during air flow mixing, without being surface coated, and then mixed as they are.

In this mixing step, if necessary, an inorganic or organic filler such as carbon black, calcium carbonate or titanium dioxide is added for the purpose of imparting functionality to the resin composition or reducing the weight and cost. , Calcium sulphate, barium sulphate, kaolin clay, inorganic powdery fillers such as clay minerals such as quartz powder, inorganic hollow fine particle fillers such as shirasu balloon, glass balloon and fly ash balloon, used paper, wood powder, It is also possible to mix one or more kinds of organic powdery fillers such as coconut shell powder and organic crosslinked beads such as polystyrene and polyester.

The resin composition or preform obtained by the method of the present invention has the reinforcing fibers uniformly mixed with the resin powder constituting the matrix without causing breakage or scratching as described above. Even when producing a final molded product by heat-pressurizing, it is not necessary to apply high shearing force in the heat-melting or compression-molding stage, and a conventionally known injection compression molding machine or the like can be used with a low torque or a screw. Reinforcement by pretreatment before mixing (that is, surface coating with resin) when obtaining the resin composition, by forming with a method such as a melt-extruding device that does not damage the reinforcing fiber as much as possible. It is possible to make more effective use of the effect of preventing breakage and damage of the working fiber.

[0027]

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the present invention.
All changes and modifications made without departing from the spirits of the preceding and the following are included in the technical scope of the present invention.

Example 1 As a reinforcing fiber, glass fiber (fiber diameter: 10 μm, fiber length: 13 mm) was surface-coated by the following method, and a matrix resin (polypropylene resin) was added to the glass fiber surface in an amount of 0.7% by weight. Let it adhere. Surface Adhesion Method 1: After dissolving polypropylene resin in tetralin, glass fibers are immersed in this, and then the solvent is volatilized and removed while slowly stirring at 120 ° C. for 5 minutes. Surface adhesion method 2: Polypropylene resin powder (average particle size:
0.1 mm) and glass fiber at a pressure of 1.5 kg / cm ² ,
A flow rate of 0.2 kg / min and a temperature of 120 ° C. are mixed for 1 minute to melt and adhere the polypropylene resin powder to the glass fiber surface. Surface attachment method 3: Water / surfactant / polypropylene resin were mixed at a weight ratio of 100/1/5 to prepare an emulsion, which was impregnated with glass fiber and then at 5 ° C at 80 ° C.
Dry with slow agitation at 50 rpm for minutes.

The resulting resin-coated glass fiber and polypropylene
Len resin powder (average particle size 0.5 mm, spherical), weight ratio
Used at a ratio of 30/70 and the air flow disturbance as shown in Fig. 1.
Charge the stirrer and rotate the stirrer at a speed of 50 rpm.
While the pressure is 1.5 kg / cm ² At a flow rate of 0.2 kg / min
Pressurized air was blown in and mixed for 5 minutes. As a result,
Bulky mixing of fiber and resin powder
A compound was obtained.

Remove this mixture from the stirring vessel and
At 0 kg / cm ² , thickness 1 mm x width 200 mm x length 30
It is compression-molded into a rectangular shape of 0 mm and then heated at 220 ° C. for 4 minutes to melt the resin powder only in the surface layer to be integrated with the glass fiber, and the surface of the preform has a skin-like preformed body (density: 0.45 g / Cc) was obtained. This preform 3
All the resin powders were melted and integrated with the glass fibers by compression molding at a pressure of 200 kg / cm ² and a temperature of 110 ° C. for 1 minute to obtain a glass fiber reinforced resin molded product having a thickness of 3 mm. . The bending strength of the molded body is 1
The mechanical strength was 22 MPa and the impact strength was 28 kgf · cm / cm ^2, showing excellent strength characteristics.

Example 2 In the above Example 1, spherical calcium carbonate having an average particle diameter of 0.5 mm was used as still another raw material, and glass fiber / calcium carbonate / polypropylene resin in a weight ratio of 2 was used.
A bulk mixture was obtained by air-flow mixing in exactly the same manner as in Example 1 except that the mixture was mixed at a ratio of 0/10/70, and only the surface layer portion was heated in the same manner as above to prepare a preform having a skin-covered surface ( Density: 0.5 g / cc) was obtained. Further, heat and pressure molding was performed in exactly the same manner as in the above example to obtain a thickness of 3
mm glass fiber reinforced resin molded product was obtained, and its physical properties were investigated. As a result, the molded product had a bending strength of 118 MPa and an impact strength of 26 kgf · cm / cm ² , indicating that it had excellent strength characteristics. confirmed.

Comparative Example 1 Preparation of a preform and heat and pressure molding of a glass fiber reinforced resin molding were carried out in the same manner as in Example 1 except that glass fiber which had not been surface treated was used. It was The bending strength of the obtained molded body is 89MP.
The impact strength was 18 kgf · cm / cm ² , which was considerably inferior to the molded products obtained in the examples.

[0033]

The resin composition of the present invention is constituted as described above, and when the reinforcing fiber and the thermoplastic matrix resin powder are uniformly mixed in the air stream, the reinforcing fiber is previously mixed with the matrix resin. By coating the same type of resin or a resin having an affinity with the matrix resin, it is possible to prevent breakage or damage of the reinforcing fiber during air flow mixing as much as possible, and thereby the reinforcing fiber. A fiber-reinforced thermoplastic resin composition and a preform thereof, which can maximize the reinforcing effect expected of the composition and give a molded article having extremely excellent mechanical properties such as toughness, bending characteristics and impact resistance. I was able to provide it.

[Brief description of drawings]

FIG. 1 is an example of an air flow mixing device used in the method of the present invention.

[Explanation of symbols]

 3 Compressed air blowing nozzles 4a, 4b Raw material charging hopper 5 Mixture discharge port 6 Stirrer 8 Filter 9 Air discharge port 10 Stirring container

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Mika Nishida 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Co., Ltd. Kobe Research Institute (72) Inventor Takako Takeda Takatsuka, Nishi-ku, Kobe-shi, Hyogo Prefecture 1-5-5 stand, Kobe Steel, Ltd. Kobe Research Institute

Claims (3)

[Claims] 1. When a thermoplastic matrix resin powder and reinforcing fibers are mixed in an air stream to produce a fiber-reinforced thermoplastic resin composition, the surface of the reinforcing fibers is treated with the same kind of heat as the thermoplastic matrix resin. A method for producing a fiber-reinforced thermoplastic resin composition, which is characterized by being previously coated with a plastic resin. 2. When a thermoplastic matrix resin powder and reinforcing fibers are mixed in an air stream to produce a fiber-reinforced thermoplastic resin composition, the surface of the reinforcing fibers is treated with a heat having an affinity with the matrix resin. A method for producing a fiber-reinforced thermoplastic resin composition, which is characterized by being previously coated with a plastic resin. 3. A preliminary composition in which the thermoplastic matrix resin and reinforcing fibers are melt-integrated in the surface layer by compressing the resin composition obtained in claim 1 or 2 and heating the surface layer of the compressed body. A process for producing a fiber-reinforced thermoplastic resin preform characterized by obtaining a formed product.