JPH0330916A - Manufacture of fiber reinforced plastic molded product - Google Patents

Abstract

PURPOSE:To enhance the mechanical strength of the product concerned by a method wherein composite sheet, which is produced by impregnating mat made of fiber with thermoplastic resin or thermosetting resin, is cut into pellets and, after that, molding is performed by forcing the pellets in a mold. CONSTITUTION:Thermoplastic resin or thermosetting resin can be used. These resins are used singly or in combination of two and more resins. As the fiber, of which mat is made, fiber made of organic compound such as polyarylate fiber, vinylon fiber or the like, glass fiber, carbon fiber or the like is preferable. The composite sheet can be easily manufactured by laminating one or more layers of mat made of fiber to one or more layers of sheet-like resin and heating the layers up to the flow temperature of resin under pressure or vacuum so as to impregnate the mat made of resin with resin. Pellets are made by cutting the obtained composite mat off so as to be used as molding material. A molded produce, the mechanical strength of which is fully improved, can be obtained by forcing the pellets in a mold through molding such as injection molding, transfer molding or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a fiber-reinforced plastic molded article.

[Conventional technology]

Traditionally, injection molding and transfer molding have been widely used as methods for molding fiber-reinforced plastic materials because of their short molding cycles, high molding efficiency, and ability to mold complex shapes with high precision. There is.

The following methods (a) to e) are known as methods for producing fiber-reinforced plastic materials, that is, pellets made by mixing reinforcing fibers and resin.

(a) A method of mechanically mixing fibers cut into appropriate lengths with powder or granular resin.

(b) A method in which the resin is dissolved or suspended in a solvent, the cut fibers are added to the resulting suspension, and the solvent is removed while stirring.

(・→ Dissolve or suspend the resin in a solvent to obtain 9 liters
The long fibers are continuously immersed in the W solution or suspension.

A method of cutting after drying and removing the solvent.

2) A method in which fibers cut into appropriate lengths and powdered granular resin are melt-mixed, and the mixture is extruded and cut using an extruder (see Japanese Patent Publication No. 25911/1983).

(@ Method of permeating molten resin into long fibers and cutting them (Japanese Patent Publication No. 43-7448 and Japanese Patent Publication No. 44
-Refer to Publication No. 16793).

[Problem to be solved by the invention]

However, with methods (a) and (n) described above, the resulting fiber-reinforced plastic material itself is bulky, and in extreme cases, the fibers aggregate, making it difficult to mold, and furthermore, the expected performance may not be achieved. However, there is a problem in that it is not possible to obtain a molded product having the following characteristics. Method (c) has the problem that it is necessary to recover the solvent and the apparatus becomes large. method) is Ij! This requires a rather strong cross-wire to prevent fiber agglomeration, and there is a problem that the fibers may break. Method (e) has the problem that the adhesion between the fiber and resin is poor and the fiber and resin separate during cutting. Furthermore, when the fiber-reinforced plastic materials produced by these methods are molded by injection molding or transfer molding, they are kneaded. A cutting of mm occurs,
There is also the problem that it is difficult to obtain molded products with improved mechanical strength.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a fiber-reinforced plastic molded product with sufficiently improved mechanical strength.

[Means to solve the problem]

According to the present invention, the above object is achieved by impregnating a mat made of fibers with a thermoplastic resin or a thermosetting resin (hereinafter, these resins may be simply referred to as resin), and using the resulting composite sheet. This is achieved by providing a method for manufacturing a fiber-reinforced plastic molded article, which is characterized by cutting the pellets into pellets, and then press-fitting the pellets into a mold for molding.

In the present invention, polyethylene,
Polyolefin resins such as polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins such as nylon 12 and nylon 66, AS resins, ABS resins, polycarbonates, etc. can be used, and thermosetting resins can also be used. As the material, epoxy resin, phenol resin, area resin, polyester resin such as unsaturated polyester, etc. can be used. These resins may be used alone or in combination of two or more. - Also, commonly used plasticizers, heat stabilizers, light stabilizers, nucleating agents, fillers, etc. can be added to these resins.

The fibers forming the mat used in the present invention are preferably organic compound fibers such as polyarylate fibers and vinylon fibers, glass fibers, carbon fibers, and the like. The performance of the fiber-reinforced plastic molded product obtained differs depending on the type of these fibers. For example, carbon fiber reinforced plastic molded products not only have excellent mechanical properties, but also have high heat deformation temperatures, and are also excellent in dimensional stability, lubricity, electromagnetic shielding properties, and electromagnetic wave shielding properties.
It is used for items that require dimensional accuracy or items that require sliding characteristics such as bearings, seal gaskets, and packings. In addition, vinylon fiber reinforced plastic moldings have excellent impact resistance and are used, for example, in helmets, while polyarylate fiber reinforced plastic moldings have excellent vibration damping properties, so they are used in sporting goods such as golf club heads. The surface of the fiber may be treated with a silane coupling agent to impart adhesiveness to the resin. There are no particular restrictions on the diameter and length of the fibers that form the mat, but the fibers may have a diameter of 2 to 30μ and a length of 2m.
It is preferable to use the above. Fibers are used in the form of filaments and strands.

Continuous strand mat, short 7') Formed into a strand mat, etc., and held together by adhesion with a binder or entanglement by needling,
Alternatively, it can be directly formed into a mat shape using a melt-blown spinning method.

The composite sheet in the present invention is a mat made of fibers.
By laminating more than one resin sheet-like material in layers, heating to a temperature at which the resin flows, and pressurizing or reducing the pressure,
It can be easily manufactured by impregnating a fiber mat with resin. When a thermosetting resin such as an epoxy resin is used as the resin, there is no need to apply pressure during impregnation. For example, a composite sheet can be produced by impregnating a fiber mat with the resin, and when the resin is in a semi-cured state, multiple layers of this composite sheet can be stacked.

In the present invention, by using a mat made of fibers, the resin can easily infiltrate between the fibers, and the resin can be poured between the fibers by applying pressure without applying strong shear to the resin. In particular, the fibers and resin can be mixed uniformly simply by removing the air between the fibers.

The amount of mat made of fibers contained in the composite 7-t is 3~
It is preferably in the range of qoNm, 5 to 60 f
It is more preferable to fall within the range of fi%.

Further, the bulkiness of the mat is preferably in the range of 50 to 5ooy7rA, and more preferably in the range of 50 to 30fl/yA.

In the present invention, there is no particular restriction on the thickness of the composite sheet, but it is preferable that the composite sheet has a thickness that allows it to be easily fed into a molding machine during the next step of molding. The thickness of the composite sheet is preferably in the range of 1 to 50 mm.

In the present invention, the composite sheet thus obtained is cut into pellets and used as a molding material. The pellets may have any shape such as cubic, rectangular, cylindrical, spherical, flat spherical, etc.
Preferably, the size is in the range of XIXI. If the dimensions of the pellets are too large, a large amount of air will be drawn into the gaps between the pellets, and if the gaps are too small, only the portions that come into contact with the heating surface will melt quickly, forming a molten resin film, which will trap air inside the pellets. It remains in the air, causing air bubbles to be mixed in, and in either case, it is preferable. ! If the pellet size is uneven, the heating condition of the pellet will be uneven, and the quality of the molded product will likely be uneven. Therefore, it is recommended to use pellets of uniform size. preferable.

By press-fitting the pellets thus obtained into a mold by injection molding, transfer molding, or the like, a molded product with sufficiently improved mechanical strength can be obtained.

Normally, when fiber-reinforced plastics are manufactured using injection molding or transfer molding, the fibers are severely broken due to the melting and mixing of the fibers and resin twice, once when producing the molding pellet and once when producing the molded product. Although the reinforcing effect of fibers may be reduced, according to the method of the present invention,
Since the step of melting and kneading the resin and @fibers when producing pellets for molding is omitted, there is little breakage of the fibers, and the resulting molded product has excellent mechanical strength.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, the physical property values in the examples were measured and calculated using the following method.

Fiber length during molding: A test piece was cut out from the molded product and incinerated, the remaining components were photographed, the length of the fibers was measured, and the average value was determined.

Tensile strength (147'j): Measured and determined in accordance with JIS K8911.

Tensile modulus (kf/++j): , rIs K691
It was measured and determined in accordance with 1.

Bending strength (kf, /j): Measured and determined in accordance with JIS K6911.

Flexural modulus (kf/J): Measured according to JIS K6911.

Example 1 It was produced by the melt-prone method using as a raw material.

The bulk of this mat is 70? /rrl. 10 sheets of this pine) and 11 sheets of polybutylene terephthalate film with a thickness of 12μ were laminated alternately, and the laminate was inserted between a press heated to 270℃, and after preheating for 8 minutes,
Press for 2 minutes at a pressure of /crA to obtain a sheet with a thickness of 1.81EII. The fiber content in this sheet is 30% by weight
Met.

The obtained 7-t was cut to produce pellets of 4×4×1, 5 fl size.

On the other hand, for comparison, polybutylene terephthalate was melted, extruded and pelletized, and polybutylene terephthalate was coated with short carbon fibers (chopped strands with a length of 3 cods).
was added in an amount of 301:2, melted and mixed at 260°C, and then pelletized.

Each pellet was dried and sifted until the moisture content became 0.031 Eft%, then subjected to a screw in-line injection molding machine set at 260°C, and JIS
A test piece having a size specified by K6911 was prepared. The physical properties of these test pieces were measured and the results are shown in Table 1.

Space below the table Example 2 Five mats with a basis weight of 70'i/r111 made of irregular length polyarylate fibers with an average fiber diameter of 20μ and a minimum fiber length of 20 and six sheets of nylon 6-film with a thickness of 250μ were laminated alternately, The laminate was heated to 270''C and inserted between nine presses, and after preheating for 8 minutes, it was pressed for 2 minutes at a pressure of 100kt/- to obtain a sheet with a thickness of 1.8cm.

The fiber content in this sheet was 12 layers.

The obtained sheet was cut to produce a pellet with a size of 4 x 4 x 1.8 m.

This pellet was dried until the moisture content became 0.03 weight tS, and then molded at 260°C in the same manner as in Example 1, with a tensile strength of 11.0 kg/aJ b and a flexural modulus of 420 kf.
A molded product of /- was obtained.

Meanwhile, for Himaki, melt nylon 6 and press 1. 12. Add 12tt% of polyester fibers (chopped strands of 6 lengths) to nylon 6.
Melt and mix at 260°C and pelletize. Using these pellets, injection molding was performed in the same manner as in Example 1 to obtain respective molded products. The tensile strength of the molded products is 7.5 k/j (nylon 6 only), and 9.8
Gin/- (nylon 6 and chopped strands).

In addition, the bending elastic modulus is 2 sok/- (nylon 6
) and 360 kp/aJ (nylon 6 and chopped strands).

〔Effect of the invention〕

According to the present invention, a method for producing a fiber-reinforced plastic molded product whose mechanical strength is sufficiently improved is provided.

Claims (1)

[Claims] 1. A fiber characterized by impregnating a mat made of fibers with a thermoplastic resin or thermosetting resin, cutting the resulting composite sheet into pellets, and then press-fitting the pellets into a mold for molding. A method for producing reinforced plastic molded products.