JPH09272134A - Composite injection molded matter and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength of this matter by a method wherein a reinforcing sheet thinner than the specified thickness and thermoplastic resin are made into an integral body under the condition that the reinforcing sheet is a thermoplastic sheet containing unidirectional continuous reinforcing fibers or their laminated sheet. SOLUTION: A space 6, in which resin is injected, is formed by one mold 4 and the other mold 5. A reinforcing sheet 3 is brought into close contact with and fixed to the female mold 5 by means of vacuum ports 7. In this case, the thickness of the reinforcing sheet 3 must be 1,000μm or less. After the reinforcing sheet 3 is fixed to the other mold 5, resin is injected through a gate 8 provided in the lower part of the molds in the enclosed mold space 6. The resultant injection molded matter has uniform and extremely high strength performance and thin, lightweight and highly rigid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection-molded article in which a thermoplastic resin sheet containing reinforcing fibers arranged in one direction and a thermoplastic resin are integrated and an injection-molding method.

[0002]

2. Description of the Related Art In recent years, thermoplastic resins manufactured by an injection molding method have been progressing toward thinning and weight reduction as well as high strength. In particular, a laptop type product in the personal computer industry requires a lightweight and high-strength housing. However, in the injection molding method, it is unavoidable that the strength performance is changed by the orientation of the resin at the time of molding and the strength is lowered due to the occurrence of weld lines, and the strength is remarkably lowered by thinning.

A thermoplastic resin containing a reinforcing fiber is generally used as a molding material for the purpose of increasing the strength of a product. However, in a thermoplastic resin containing reinforced fibers for injection molding, it is necessary that the fibers are short fibers in order to uniformly fill the resin containing the fibers in the mold, and generally the fiber length is from several microns to 10 mm. However, when the fiber length is short, the strength of the obtained molded product is insufficient. Even if a resin pellet having a fiber of about 10 mm is used, it is cut by 1 m when being kneaded with a screw.
It will be shortened to around m, and the initial strength of the pellet will be significantly reduced. Further, since the thermoplastic resin containing fibers is significantly inferior in fluidity to a material containing no fibers, there is a problem that thin-wall molding is difficult. Further, the resin flow disturbs the uniform dispersion of the reinforcing fibers, and the strength of the molded product tends to vary. Further, even if the resin containing such fibers is used, the variation in strength due to the formation of the weld line and the orientation due to the flow of the resin cannot be avoided, and this portion must be padded or the shape must be changed. There was a problem.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an injection-molded article having excellent strength and a method for producing the same. Another object of the present invention is to provide an injection-molded article which is thin and has excellent strength, and a method for producing the same. Another object of the present invention is to provide an injection-molded article which has little variation in strength depending on the orientation direction of the resin and has excellent weld strength, and a method for producing the same.

[0005]

Means for Solving the Problems As a result of earnest studies by the present inventors, a composite molded article obtained by injection-molding a thin-walled fiber-reinforced thermoplastic resin sheet containing unidirectionally continuous reinforcing fibers and a thermoplastic resin and integrating them. The inventors have found that the strength of is extremely high and completed the present invention.

[0006] That is, the present invention is a thermoplastic resin sheet containing unidirectionally continuous reinforcing fibers or a laminated sheet thereof, which is a composite injection molding in which a reinforcing sheet having a thickness of 1000 µm or less and a thermoplastic resin are integrated. Object, a thermoplastic resin sheet containing continuous reinforcing fibers in one direction, or a laminated sheet of the same and having a thickness of 1000 μm or less, is previously fixed to the inner surface of the closed mold, and the thermoplastic resin sheet is formed in the mold. A method for producing the composite injection-molded article, which comprises injecting a resin, and a thermoplastic resin sheet containing unidirectionally continuous reinforcing fibers, or a laminated sheet thereof, having a thickness of 1000
A reinforcing sheet of μm or less is fixed in advance on the inner surface of a closed mold, a thermoplastic resin is injected into the mold, the thermoplastic resin is laminated on one side of the reinforcing sheet, and then a part of the mold. Is moved to provide a closed space between the other side of the reinforcing sheet and the mold, and the thermoplastic resin is injected into the space.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The thermoplastic resin sheet containing reinforcing fibers continuous in one direction of the present invention is generally called a prepreg, and a fiber sheet obtained by aligning continuous fibers in one direction is used as an aggregate and impregnated with a thermoplastic resin. It is a unidirectional fiber reinforced thermoplastic resin sheet. The thickness of one fiber is about 3 to 25 μm in diameter, and its content is usually 30 to 80% by volume. The thickness of the prepreg is usually 30 to 500 μm.

The reinforcing fibers include glass fibers, inorganic fibers such as carbon fibers, polyamide fibers, polyester fibers,
Examples thereof include synthetic resin fibers such as aramid fibers, metal fibers such as titanium fibers, boron fibers, and stainless fibers, but are not necessarily limited thereto. The reinforcing fiber is preferably glass fiber.

On the other hand, examples of the thermoplastic resin impregnated in the reinforcing fibers include polystyrene, polyvinyl chloride, high density polyethylene, low density polyethylene, polypropylene, polycarbonate, polybutylene terephthalate, polyether sulfone, polysulfone, and polyetherimide. (Registered trademark “Ultem”), polyether ether ketone, polyphenylene sulfide, etc. may be mentioned, but the invention is not necessarily limited thereto. Preferred thermoplastic resin is polystyrene resin, polyethylene resin, polypropylene resin or polyvinyl chloride resin. Such a prepreg can be manufactured, for example, by the method disclosed in Japanese Patent Publication No. 4-42168.

The prepreg may be used alone, or a plurality of prepregs may be laminated (hereinafter, the prepreg used in the present invention or a laminate thereof may be referred to as a reinforcing sheet). However, the thickness thereof needs to be 1000 μm or less. The reason is that the molded product of the present invention exhibits its characteristics when it is thin, particularly when the thickness is 1 mm or less. That is, as described above, in injection molding, anisotropy in strength occurs due to orientation, and a decrease in strength due to the occurrence of weld lines cannot be avoided. This is not a serious problem in the case of a thick-walled molded product because the overall strength is large, but it is a fatal defect particularly in the case of a thin-walled molded product. However, in the present invention, the present inventors have found that, even if the reinforcing sheet is thin, when it is made into a composite with a resin, the strength is surprisingly increased, and the present invention was applied to a thin injection molded product. It has been found that in this case, the problems of conventional injection molded products can be solved. The thickness of the reinforcing sheet is preferably 30 to 1000 μm.

In order to stack the prepregs, for example, an arbitrary number of prepregs are stacked and a prepreg having a heating plate heated to a temperature at which the thermoplastic resin is melted is used to press 0.2 to
It may be heated and pressure-bonded at a pressure of 5 kg / cm ² and cooled.
In the fiber direction of the laminated sheet, other prepregs can be laminated at an arbitrary angle of 0 to 90 degrees with respect to the first prepreg.

Next, a method for producing an injection molded product will be described. First, the reinforcing sheet is fixed at a desired position in the mold. It is effective that this position is a portion considered to be weakest in strength, for example, a weld line or a portion where orientation is likely to occur. As a method for fixing the reinforcing sheet, for example, a method of fixing by pulling a vacuum from a vacuum hole provided in a mold can be mentioned. In this case, when the reinforcing sheet is thick, the rigidity is high, so that the reinforcing sheet does not adhere to the mold, and it is difficult to fix the resin, and the resin is washed or deformed when injected. However, in the present invention, since the reinforcing sheet has a thickness of 1000 μm or less, it has flexibility, it adheres to the mold, and even if the resin is injected into the mold at high pressure, it hardly flows or deforms. The reinforcing sheet is preferably arranged such that the direction of the fibers of the outermost layer portion that comes into contact with the resin when the resin is injected is substantially parallel to the flow direction of the resin. By arranging in this way, the disorder of the fibers due to the flow of the resin is reduced, and an injection molded article having an excellent balance of strength can be obtained. Then, the resin is injected from the gate into the mold.

FIG. 1 is an example of an injection-molded article obtained in this manner. FIG. 1 (a) is the front surface side, (b) is the back surface side, 1 is a main body, 2 is a gate portion and a fin gate. Has become. The bottom surface of the bottom is combined with the reinforcing sheet 3.

FIG. 2 is a view showing a mold for molding the molded product of FIG. The mold comprises one mold 4 and the other mold 5. 2A is a cross-sectional view of the mold, and FIG. 2B is a front view of the other mold 5, which is a female mold. One mold and four and the other mold 5
To form a space 6 through which the resin is injected. The reinforcing sheet 3 is fixed in close contact with the female mold 5 by the vacuum hole 7. FIG.
The arrow in (b) is the direction of the fibers of the layer of the reinforcing sheet that is in contact with the resin. After fixing the reinforcing sheet to the other mold 5 in this way, the resin is injected into the mold inner space 6 closed from the gate 8 below the mold.

FIG. 3 shows an example in which the gate 8 is provided at the center of the molded product. By doing so, it is possible to shorten the flow distance of the thermoplastic resin and reduce the disorder of the fiber orientation for molding.

By the way, when the reinforcing sheet is compounded on one side of the molded article as in the case of FIGS. 1 to 3, warpage occurs when the linear expansion coefficient of the reinforcing sheet is different from that of the thermoplastic resin. -Stress relief measures such as ging are required. In order to avoid this, a composite molded article having a reinforced sheet in the center is effective.

FIG. 4 is a diagram showing a mold cross section and a molding method for molding a molded article in which such a reinforcing sheet is inside a resin. The mold is one mold 4 and the other mold 5
And has two gates 8a and 8b at the top and bottom.
The other die 5 further comprises a fixed die 5a and a slidable movable die 5b. In the state of FIG. 4A, the upper gate 8a is closed by the movable mold 5b. The reinforcing sheet 3 is fixed to the mold, and the resin is injected from the lower gate 8b into the closed space 6a. Then, as shown in FIG. 4B, the movable die 5b is slid to form a space 6b between the reinforcing sheet and the movable die. Further, at the same time, the upper gate 8a is opened at the same time. Then, by injecting the resin from the opened upper gate, it is possible to mold a molded product having the reinforcing sheet shown in FIG.

FIG. 5 is a diagram showing another method for molding a molded product in which the reinforcing sheet is inside the resin. In FIG. 5, the reinforcing sheet 3 is sandwiched between one mold 4 and the other mold 5 to form closed spaces 6a and 6b on both sides of the reinforcing sheet. The gate 8 is provided so as to communicate with the spaces on both sides, and resin is simultaneously injected into both spaces.

FIG. 6 shows an example of a mold for molding a composite molded product having a weld line. In general, the injection resin causes a weld line at the place where the flow hits, but the strength of this portion is significantly lower than that of other portions. By joining the reinforcing sheet according to the present invention to a part or all of the weld line, the weld strength can be significantly improved.

In the present invention, a surface material may be laminated and integrated on the surface of the reinforcing sheet. By using a resin sheet compatible with the resin to be injected as the surface material and arranging the surface material so that it is on the resin side of the reinforcing sheet, the injected injected thermoplastic resin melts with the surface material on the surface of the reinforcing sheet. Unify. Further, as described above, the flow direction of the resin is determined by the position of the gate, and it is necessary to consider the fiber direction of the reinforcing sheet so that the flow does not disturb the fibers, but when the surface material is laminated on the reinforcing sheet, Since the surface material suppresses the fiber disorder, the relationship between the position of the gate and the position of the reinforcing sheet becomes arbitrary, and the position of the gate that affects the appearance of the molded product can be freely selected.

When the thermoplastic resin impregnated in the reinforcing sheet and the thermoplastic resin injected and injected do not heat-weld differently, a non-woven fabric or the like is used as the surface material, so that the injected thermoplastic resin is The non-woven fabric is fixed by the anchor effect, and the effect of joining and integrating with the reinforcing sheet occurs.
Further, when the surface material is exposed on the outer surface of the composite molded article, the surface decoration effect is enhanced.

[0022]

EXAMPLES The present invention will be described below with reference to examples. Example 1 As shown in FIG. 2, a reinforcing sheet was previously fixed inside a mold, and polypropylene resin was injected and filled into the mold using an injection molding machine to obtain a composite molded product. The constitution and molding conditions of the reinforcing sheet are as follows. Composition Laminated sheet: thermoplastic resin; polypropylene resin Reinforcing fiber; glass fiber Fiber content: 70 wt% Sheet thickness; 180μ Laminated composition; Laminating two sheets at right angles to each other Molding conditions Mold temperature; 50 ℃ Molding temperature; 220 ℃ Injection speed; 2.8mm / sec Injection pressure; 1400kg / mm2 Holding pressure; 500kg / mm2 As a result, the adhesion between the laminated sheet and the thermoplastic resin is good and it has uniform rigidity. A composite molded product was obtained. Create a test piece from almost the center of the molded product, Izod impact,
The falling ball test and the bending elastic modulus were measured. The results are shown in Table 1.

Example 2 Molding was carried out under the same conditions as in Example 1 except that the mold shown in FIG. 4 was used to obtain a composite molded article having a laminated sheet in the center thereof. Test pieces were prepared in the same manner as in Example 1, and the Izod impact, falling ball test, and bending elastic modulus were measured. Table 1 shows the results
Shown in

Example 3 A molding having a weld line W at the center as shown in FIG. 7 was molded using a mold having two gates. The molding conditions were the same as in Example 1. A test piece T was prepared from this molded product as shown in FIG. 7, and the weld strength was measured when a tensile force was applied to the weld portion. The results are shown in Table 2.

Comparative Example 1 A polypropylene molded product was obtained by molding under the same conditions as in Example 1 except that the laminated sheet 1 was not used. Example 1
Test pieces were prepared in the same manner as above, and the Izod impact, falling ball test, and bending elastic modulus were measured. The results are shown in Table 1.

Comparative Example 2 Molding was performed under the same conditions as in Example 3 except that the laminated sheet 1 was not used, and a polypropylene molded product having a weld in the center was obtained. A test piece T was prepared in the same manner as in Example 3, and the weld strength was measured when a tensile force was applied to the weld portion. The results are shown in Table 2.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

As is apparent from the above, according to the present invention, it is possible to provide an injection-molded article in which a thermoplastic resin sheet containing unidirectionally continuous reinforcing fibers and a thermoplastic resin are compositely integrated. Since such an injection-molded product has uniform strength performance and extremely high strength, it is thin, lightweight and highly rigid.

[Brief description of drawings]

FIG. 1 is a view showing an injection-molded article of the present invention, in which a reinforcing sheet is compounded on one side of the molded article.

FIG. 2 is a view showing a mold for molding the injection-molded article of FIG.

FIG. 3 is a diagram showing a mold for molding an injection-molded product of the present invention, in which a gate is located at a central portion of the molded product.

FIG. 4 is a view showing an aspect of a mold for molding an injection-molded article in which a reinforcing sheet is inside a thermoplastic resin.

FIG. 5 is a view showing another embodiment of a mold for molding an injection-molded product in which a reinforcing sheet is inside a thermoplastic resin.

FIG. 6 is a view showing an aspect of a mold for molding an injection-molded product having a weld line.

FIG. 7 is a view showing an injection-molded article of the present invention having a weld line.

[Explanation of symbols]

 1 Molded Product Main Body 2 Molded Fin Gate Part 3 Reinforcement Sheet 4 One Mold 5 Other Mold 6 Space 7 Vacuum Hole 8 Gate W Weld Line T Specimen

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B29K 309: 08 B29L 9:00 (72) Inventor Hiroshi Tanabe 1190 Kasamacho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (9)

[Claims] 1. A thermoplastic resin sheet containing unidirectionally continuous reinforcing fibers or a laminated sheet thereof, having a thickness of 1
A composite injection molded product in which a reinforced sheet of 000 μm or less and a thermoplastic resin are integrated. 2. The composite injection-molded article according to claim 1, wherein the reinforced sheet is inside and integrated with the thermoplastic resin. 3. The composite injection-molded article according to claim 1, wherein the thinnest portion has a wall thickness of 1 mm or less. 4. The composite injection-molded article according to claim 1, wherein a surface material is laminated and integrated on the surface of the thermoplastic resin sheet or a sheet obtained by laminating the same. 5. The composite injection-molded article according to claim 1, wherein the thermoplastic resin is a polystyrene resin, a polyethylene resin, a polypropylene resin or a polyvinyl chloride resin. 6. The composite injection-molded article according to claim 1, wherein the reinforcing fibers are glass fibers. 7. A thermoplastic resin sheet containing reinforcing fibers continuous in one direction or a laminated sheet thereof, having a thickness of 1
The method for producing a composite injection-molded article according to claim 1, wherein a reinforcing sheet having a thickness of 000 μm or less is fixed in advance on the inner surface of the closed mold, and the thermoplastic resin is injected into the mold. 8. A thermoplastic resin sheet containing unidirectionally continuous reinforcing fibers or a laminated sheet thereof, having a thickness of 1
A reinforcing sheet having a thickness of 000 μm or less is fixed in advance on the inner surface of a closed mold, a thermoplastic resin is injected into the mold, the thermoplastic resin is laminated on one side of the reinforcing sheet, and then a part of the mold is formed. 3. A method for producing a composite injection-molded article according to claim 2, wherein a closed space is provided between the mold and the other side of the reinforcing sheet by moving, and the thermoplastic resin is injected into the space. 9. The fiber direction of the outermost layer of the thermoplastic resin sheet or a sheet in which the thermoplastic resin sheet is laminated and which is in contact with the injected resin is substantially parallel to the flow direction of the resin in the mold.
Or the manufacturing method of 8.