JP2871005B2 - Manufacturing method of fiber reinforced thermoplastic resin composite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a fiber-reinforced thermoplastic resin composite in which reinforcing fibers are mixed in a matrix made of a thermoplastic resin, with a simple equipment and process. It relates to an improved method.

[Prior art] A fiber-reinforced thermoplastic resin composite in which reinforcing fibers such as glass fiber and carbon fiber are mixed in a thermoplastic resin,
Although the heat resistance is slightly insufficient, it can be formed into any shape only by applying heat and pressure, and has the advantages of easy post-processing and straightening, so it is exposed to such high temperatures. It has been put to practical use over a fairly wide range as a material for a molded body that does not need to be used.

By the way, as a method of obtaining a fiber-reinforced thermoplastic resin molded article, a method of heating and melting a thermoplastic resin serving as a matrix, dispersing the reinforcing fiber therein and injection molding, or impregnating the reinforcing fiber with a molten thermoplastic resin. In this method, a cobodit is formed, and this is formed into a final shape by compression molding or contact molding. However, the above method has a problem that the reinforcing fiber is significantly worn by the injection nozzle and the like, and the reinforcing fiber is clogged in the nozzle and the spool to cause molding failure. At present, the above method is mainly used.

[Problem to be solved by the invention] When the above method is carried out, the most important thing is
How to impregnate the reinforcing fibers with the thermoplastic resin during the production process of the composite. If a poorly impregnated composite is used, the poorly impregnated portion becomes void and becomes a defective product. Therefore, a method of impregnating by heating under high pressure using an autoclave molding method or the like is adopted. However, this method not only requires a large-scale pressure-resistant facility, but also requires a long time to raise the temperature for impregnation and to cool after impregnation, resulting in low productivity.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object to provide a simple open-type, void-free fiber-reinforced thermoplastic resin composite without the need for large-scale equipment. An object of the present invention is to provide a method that can be manufactured efficiently.

[Means for Solving the Problems] The configuration of the method of the present invention that can solve the above problems includes:
A mixture containing a reinforcing fiber and a thermoplastic resin fiber and having a blending amount of the reinforcing fiber of 60% or less is inserted into an open mold having a heat medium chamber into which a heating / cooling medium can be introduced. By introducing a heating medium into the mixture, the mixture is compressed while being heated to a temperature at which the thermoplastic resin fibers in the mixture melt or more, and then a cooling medium is introduced into the heating medium chamber under compression. The point is that the mixture is cooled to produce a fiber-reinforced thermoplastic resin composite. At this time,
It is preferable to use a pressure-adjustable piston as the compression means, since molding can be performed quickly and easily with simpler equipment.

[Action] In the present invention, a mixture containing a reinforcing fiber and a thermoplastic resin fiber is used as a raw material. In this mixture, as described later, both fibers are uniformly mixed with each other by, for example, blending or the like. One of the fibers is not locally unevenly distributed, and one of the fibers is partially uneven during the handling process. There is no fear of bias. Therefore, the mixture is inserted into an open mold having a heating medium chamber into which a heating / cooling medium can be introduced, and the heating medium is introduced into the heating medium chamber. When the fibers are melted by heating the fibers to a temperature higher than the melting temperature, and at the same time, a moderate compressive force is applied, the air existing between the fibers is sequentially pushed outward and the mixture is successfully compressed. As a result, it is possible to obtain a compressed mixture in which the thermoplastic resin melt is used as a matrix and the reinforcing fibers are uniformly distributed in the matrix. Next, a cooling medium is introduced into the heating medium chamber under compression to obtain a fiber-reinforced thermoplastic resin composite free from void defects, which cools and solidifies the mixture. Therefore, a composite without void defects can be easily produced by a simple heating and compression treatment using an open mold without using a high pressure-resistant facility such as an autoclave as in the conventional example. By the way, it is difficult to obtain a uniform mixture of the reinforcing fibers and the thermoplastic resin in the case where the reinforcing fibers are mixed with the granular or block-shaped thermoplastic resin, and the thermoplastic resin is partially unevenly distributed. Void defects are likely to occur in portions where the thermoplastic resin is small.

The open type configuration used in the present invention is not particularly limited, but an example thereof is as shown in FIGS. That is, FIG. 1 is a perspective view of the open mold 1 and FIG.
FIG. 2 is a cross-sectional view taken along the line II-II, in which a groove 3 forming a forming portion is formed on an upper surface side of a heat insulating material 2 made of glass wool, molding sand, or the like.
And a skin layer 4 made of A1 or the like is provided so as to cover the entire surface. A heating medium chamber 5 is provided on the lower surface side of the skin layer 4 in the groove portion 3, and the forming section is heated by flowing a heating medium such as steam or hot air into the heating medium chamber 5, and the heating medium is also discharged. The configuration is such that the forming section can be cooled by switching to the refrigerant. In this case, a configuration in which the heat medium and the refrigerant are alternately supplied by switching is preferable because a higher density and less void defects can be obtained. In the drawing, reference numeral 6 denotes a supply / discharge tube for the heat medium, and reference numeral 7 denotes an air vent tube used during compression processing.

In carrying out the present invention, as shown in FIG. 3, a mixture C composed of reinforcing fibers and a thermoplastic battle zone is charged into the groove 3 and a heating fluid is caused to flow through the heating medium chamber 5 to heat the mixture C. While heating above the melting temperature of the plastic resin fiber, the piston 3 is fitted into the groove 3 from above the open mold 1 and compressed, and at the same time, the internal air is sucked and discharged from the air vent pipe 7. By this heating, the thermoplastic resin fibers in the mixture C are melted, and the mixture C is compression-molded by compression and air bleeding. At this time, it is preferable to fit the mixed body in the direction of the fiber axis of the reinforcing fiber, because a compression-molded body having more excellent flexibility can be obtained.

Then, when the fluid in the heat medium chamber 5 is switched to a refrigerant after the compression molding and cooled, a fiber-reinforced thermoplastic resin composite in which the thermoplastic resin is used as a matrix and the reinforcing fibers are uniformly distributed therein can be obtained.

1 to 3 show an example in which the heating medium chamber 5 is provided and heating is performed. However, instead of this, a tubular heating medium flow path, a resistance wire heating source, or the like is provided, and heating is performed. It is also possible to adopt a method of cooling by providing a passage, and it is also effective to provide an air vent hole on the compression surface of the piston P instead of the air vent tube 7. The skin layer 4 is provided as a barrier layer for preventing the molten thermoplastic resin from invading the heat insulating material 2 and may be any material that can withstand heat and pressure during heating and compression processing. Any material may be used, A1
In addition to thin steel plates and other metal materials,
Further, it is also possible to form the skin layer 4 by coating a composite material having improved heat resistance and pressure resistance by mixing a metal powder, a ceramic powder or the like into a synthetic resin.
The skin layer 4 is desirably formed of a material having high thermal conductivity so that heating or cooling is performed quickly.

Next, as the reinforcing fibers used in the present invention, carbon fibers, glass fibers, metal fibers, inorganic fibers such as whiskers are the most common, but it is of course possible to use organic fibers such as aramid fibers. These can be used alone or in combination of two or more if necessary.
The form of the fiber does not matter whether it is a long fiber or a short fiber, and may be appropriately selected according to the required characteristics of the final molded pair. However, a long fiber is more preferable for enhancing the reinforcing effect. The type of the thermoplastic resin fiber is not particularly limited. Typical examples thereof include polyolefin fibers such as polypropylene; polyamide fibers such as nylon 6 and nylon 66; polyesters such as polyethylene terephthalate, polybutylene terephthalate and wholly aromatic polyester. Fiber: polycarbonate resin; modified polyether-based fibers such as polyethersulfone, polyetherimide, polyetherketone, etc., and the like, which may be unstretched, semi-stretched, or stretched. However, particularly preferred in practicing the present invention are those having a maximum temperature-rise heat shrinkage of 15% or less as defined by the following description. However, if a thermoplastic resin fiber having a high temperature rising maximum heat shrinkage rate is used, the reinforced battle area may be bent by the shrinkage force at the time of heating and compression, and the reinforcing effect may be reduced.

(Maximum Heat Shrinkage Rate) This means the dispersion measured by the dry heat shrinkage rate B method specified in JIS L1013. That is, an initial load is applied to the sample, 500 mm is accurately measured, and two points are hit. Next, remove the initial load, hang it in a dryer kept at
After leaving it for minutes, cool it down to room temperature,
The initial load is applied again, the length between the two points is measured, and the dry shrinkage ratio is calculated by the following formula (the number of tests is 5 each).

(The length between two points after shrinkage) The dry heat shrinkage was measured by changing the dryer temperature in various ways, and the relationship between the temperature and the dry heat shrinkage was determined. The heat shrinkage is used.

The mixture of the reinforcing fibers and the thermoplastic resin fibers includes all of long fibers, short fibers or a mixture of long fibers and short fibers, and most preferably, the both fibers are at a single fiber level. It is a mixture. Concretely, preferred examples include those obtained by weaving continuous filamenio of both fibers and superimposing them and passing them through a disturbance fluid, or fibers obtained by blending both fibers by cord cutting spinning. These mixtures are further used in various forms such as woven / knitted fabrics, multiaxial laminated knitted fabrics, uniaxially arranged aggregates, and the like.

However, in the present invention, it is necessary to use a mixture in which the amount of reinforcing fibers in the mixture is 60% by volume or more,
In addition, it is preferable to use a mixed fiber having a mixing ratio defined by the following formula of 10% or more.

Here, N indicates the total number of reinforcing fibers, NcX is the number of the reinforcing fibers divided into several groups, and X is the number of filaments included in one specific group in the group. Is shown.

Means a mixed state, and the smaller X is, the better the mixed state is.

Is the weight of the mixed fiber.

When the amount of the reinforcing fibers in the mixture exceeds 60% by volume, the absolute amount of the thermoplastic resin fibers becomes insufficient, so that a sufficient melt shrinkage force cannot be obtained, which causes void defects to remain. In order to avoid such a problem, the amount of the reinforcing fiber in the whole mixture must be suppressed to 60% by volume or less.

When the fiber mixing ratio is 10% or more, the reinforcing fibers and the thermoplastic resin fibers are sufficiently mixed uniformly, and the thermoplastic resin fibers are melted in the entire area inside the mixture during the heating and compression steps. Thus, a composite having no void defects can be easily obtained. However, when the fiber mixing ratio is less than 10%, the absolute amount of the thermoplastic resin fiber is insufficient, so that a portion having a particularly small amount of the fiber becomes insufficient in the matrix, which may cause void defects.

Note that the mixture used in the present invention contains reinforcing fibers and thermoplastic resin fibers as essential components as described above,
If necessary, a proper amount of powder filler may be mixed. However, when a powder filler is used in combination, it is desired that the filler is attached to any of the fibers by electrostatic adhesion or the like in order to uniformly disperse the powder filler.

Example 1 Example 1 An experiment was performed using an open mold 1 having a lattice-shaped groove 3 as shown in FIG. However, the width of groove 3 is 5mm and the depth is 20m
m, and the length between the centers of adjacent grooves was 20 mm. FIG. 5 is a longitudinal sectional view equivalent to one of the grooves 3 in which an A1 plate is coated as a skin layer 4 on the surface of a heat insulating material 2 made of glass wool. 5 so as to be able to supply heated air or cooling air.
A pore 7 for venting air was provided on the inner side wall of the. Then, a piston 8 having a shape fitted into the groove 3 was inserted from above the open mold 1 and heated and pressurized.

Glass fiber roving as reinforcing fiber (diameter: 13μ)
m), unstretched polyethylene terephthalate long fibers as thermoplastic resin fibers (diameter: 15 μm, maximum heat shrinkage after heating: 2)
%, Softening point: 100 ° C).
0: The latter was blended so as to be 60, and a blended yarn having a blending ratio of 35% and 10200 denier was obtained. This is aligned in the longitudinal direction and
Inserted and deposited along the groove in the open groove 3 shown in FIGS. Next, heated air is blown into the heating medium chamber 5 while being sucked from the air vent holes 7, so that the wall temperature in the groove 3 is heated to 280 ° C., and at the same time, the piston 8 is lowered to 5 kg / cm ^2.
And compressed. After maintaining in this state for 15 minutes, the heated air was switched to cooling air at room temperature (22 ° C.) and cooled for 10 minutes to obtain a lattice fiber reinforced thermoplastic resin composite having a thickness of 4.5 mm. The void ratio of the composite showed a very small value of 0.9%.

Example 2 Instead of the open type used in FIGS. 4 and 5, an electric resistance wire heater was used as a heating source, and an open type in which a heating medium chamber 5 was left as it was for cooling was used. A grid-like fiber-reinforced thermoplastic resin composite was molded in the same manner. The void ratio of the obtained molded body was 0.7%, which was better than the molded body obtained in Example 1.

Example 3 A mixed fiber (10150 denier) having a fiber mixing ratio of 33% was obtained in the same manner as in Example 1 except that the used amount ratio of the glass fiber and the polyethylene terephthalate undrawn fiber was changed to 67:33 by volume. Obtained. When the heating and press-molding was performed using the mixed fiber under the same conditions as in Example 1 below, the obtained shaped body had a very large void ratio of 6.7% and had void defects.

[Effects of the Invention] The present invention is configured as described above, and its effects are summarized as follows.

Using a simple open mold, a composite can be manufactured with a small compressive force.

Since the molding material is an aggregate of fibers, it is not a fixed shape but can be freely changed in shape, so it can be charged into any shape of open mold, and a composite of any shape can be used. Obtainable.

Since the thermoplastic resin fibers are melted by heating and act as a bonding agent for reinforcing fibers mixed together adjacently and extrude the internal air, a composite having a uniform density without void defects can be easily obtained.

[Brief description of the drawings]

FIGS. 1 and 2 illustrate an open type used in the present invention. FIG. 1 is a perspective view, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, and FIG. FIG. 4 is an explanatory cross-sectional view showing an example of a heating and pressing process. 4 and 5 show the open type used in the embodiment. FIG. 4 is a plan view, and FIG. 5 is a partial longitudinal sectional explanatory view. DESCRIPTION OF SYMBOLS 1 ... Open type 2 ... Insulation material 3 ... Groove 4 ... Skin layer 5 ... Heat medium chamber 7 ... Air vent pipe P ... Piston

Claims (2)

(57) [Claims] 1. A mixture containing a reinforcing fiber and a thermoplastic resin fiber, wherein a blending amount of the reinforcing fiber is 60% or less, is inserted into an open mold having a heat medium chamber capable of introducing a heating / cooling medium. By introducing a heating medium into the heat medium chamber, the mixture is compressed while being heated to a temperature at which the thermoplastic resin fibers in the mixture are melted, and then into the heat medium chamber under compression. A method for producing a fiber-reinforced thermoplastic resin composite, comprising cooling a mixture by introducing a cooling medium. 2. The method according to claim 1, wherein the compression of the mixture is performed by a pressure-adjustable piston.