JP3250065B2 - Resin molding method and resin molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molding method and a resin molded article reinforced by mixing fibers.

[0002]

2. Description of the Related Art Resin molded articles are advantageous in reducing weight and can be suitably used in places in contact with water because there is no fear of corrosion due to rust. On the other hand, resin alone has poor tensile breaking strength and bending breaking strength. There are drawbacks. Therefore, a technique for increasing the strength by mixing fibers into a resin is generally known, and many resin molded articles using such a resin composition have been put to practical use. It is not an exaggeration to say that such reinforcement by mixing fibers largely depends on the adhesion between the fibers and the matrix resin, the strength of the fibers, the elongation of the fibers, and the orientation of the fibers.

[0003]

Conventionally, however, no consideration has been given to the problem of the orientation of the fiber, and when the strength is insufficient, it is common practice to reinforce it with ribs or to increase the wall thickness. . Therefore, a high-strength product that sufficiently exhibited the performance of the material could not be obtained. In addition, the fact has not been clarified.

[0004]

DISCLOSURE OF THE INVENTION The present invention clarifies the action of the contained fiber, thereby effectively utilizing the effect of the contained fiber to further improve the tensile breaking strength and the bending breaking strength, and stabilize the quality. This is a molding method that has succeeded in forming a molding. The configuration of the first means is to inject the thermoplastic synthetic resin composition containing the fiber into the cavity to be manufactured from the gate provided at one or two or more places, and to reduce More than two branches
By flowing the molten resin along the resin association section while simultaneously forming the resin association section from above the points, the fibers are strongly oriented in the direction in which the product is to be reinforced, and the resin association section is substantially flat. This is a resin molding method that cures as it is. As a specific means for branching and flowing into two or more of the first means, it is desirable to provide an obstruction member such as a pin perpendicular to the resin flow direction in front of a portion to be reinforced at the flow position in the molded article. . The configuration of the second means is that the thermoplastic synthetic resin composition containing the fiber is injected into the cavity to be manufactured from one or more gates provided at one or more places, and two points are formed in the resin molded article. The difference in flow speed is given above, and the bending stress in the direction of strengthening the product by strongly orienting the fiber along the resin association part caused by simultaneously joining two or more preceding resin flowing parts is considered. This is a resin molding method that provides a great improvement in strength. In addition, as a specific means for providing a difference in the flow speed at two or more locations of the second means, there is a method of providing a portion having a different thickness at a flow portion before a position to be strengthened. The structure of the third means is to simultaneously inject the thermoplastic synthetic resin composition containing the fiber into the cavity to be manufactured from the gates provided at two or more places on one end side, and to perform the resin flow at two or more places at the preceding point. This is a resin molding method in which fibers are strongly oriented along a resin association portion generated by merging portions, and a large improvement in strength against bending stress in a direction in which a product is to be strengthened. In addition,
In this method, the flow is divided into a plurality of flows at the time of injection into the cavity, which is different from the branch flow generated in the cavity. The configuration of the fourth means is that a cylindrical or prismatic shape to be manufactured from two or more gates provided with a thermoplastic synthetic resin composition containing fibers at equal angles and equidistant with respect to the central axis or symmetrical with respect to the central axis. This is a resin molding method in which the characteristics of the resin association portion generated by simultaneous injection into the cavity are utilized to greatly change the fiber orientation in the direction in which the product is to be reinforced. The structure of the fifth means is such that the thermoplastic synthetic resin composition containing fibers obtained by performing the method according to the first to fourth means is injected, and the resin association portion is formed in a direction in which the structure is to be reinforced. A resin molded product formed and having a greatly changed fiber orientation, wherein the fiber has a weight average fiber length of 0.3 mm or more in the molded product.

[0005]

In the resin molded product of the first means, the molten resin flows along the resin association section while branching and flowing into two or more parts and simultaneously joining from two or more places to form a resin association section. The fibers are strongly oriented in the direction in which the resin is to be strengthened, and the resin association portion is cured while remaining substantially flat.
The configuration of the second means is that a thermoplastic synthetic resin composition containing fibers is provided with a difference in flow speed at two or more places in a resin molded product, and two or more preceding resin flowing parts are simultaneously merged. By the method, even in the resin flowing part where the injection timing into the cavity is different, the fiber is strongly oriented along the resin association part at the confluence to greatly increase the bending strength in the direction to strengthen the product. Bring. Third
A resin molding method for simultaneously injecting into the cavity to be manufactured from gates provided at two or more places on one end side of the means and simultaneously joining two or more preceding resin flowing parts in the direction of flow in the cavity. The fiber is strongly oriented along the resin association portion, thereby providing a large strength improvement against bending stress in the direction in which the product is to be reinforced. A resin molding method for simultaneously injecting into a cylindrical or prismatic cavity to be manufactured from gates provided at two or more locations equiangular, equidistant or centrally symmetric with respect to the central axis of the fourth means, etc. A weld can be formed at a specific location in the longitudinal direction of the shaped cavity. In this way, by intentionally generating weld,
The fibers can be strongly orientated in parallel along the weld-association surface, and can be strongly orientated in the flow direction by shearing during the flow, and the tensile strength and bending strength in the orientation direction can be greatly improved. Further, by using the fifth means of increasing the fiber length to 0.3 mm or more in the molded product, the degree of orientation of the reinforcing fibers can be increased and the strength can be further increased.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A resin molding method according to the present invention, a resin molded product thereof, and a mold structure thereof will be described with reference to the drawings. FIGS. 1 to 4 collectively exemplify the front, side, and plane of an injection mold including a fixed mold and a movable mold for a resin cylindrical test piece. 1 is a sprue connected to the nozzle of the molding machine, 2, 2A and 2B are runners for flowing molten resin from the sprue 1 toward the product cavity.
3, 3A and 3B are gates for flowing resin from the runners 2, 2A and 2B, and 4 is the gates 3 and 3A.
This is a product part cavity to be manufactured into which resin flows from 3B. In addition to the mold, although not shown, a molded product,
An ejector for projecting the runner and a cooling circuit for controlling the cooling temperature of the mold are provided. The dimensions of each member are as follows: the sprue 1 is φ4 mm at the tip and φ8 m at the root.
m, the runners 2, 2A, 2B had a circular cross section of φ8 mm, and the gates 3, 3A, 3B had a circular cross section of φ4 mm. FIG. 1 is an explanatory view of the basic structure of a resin cylindrical test piece mold in which gates are provided at two places on the side surface of a flange portion. The two runners 2A, 2B in FIG. 1 have the same distance from the sprue 1 to the gates 3A, 3B on one end, and their shapes are also equiangular, equidistant, and symmetric with respect to the central axis.
FIG. 3 shows an example in which two gates are provided on the upper surface of the flange.
As in FIG. 1, the runners 2 and 2 in FIG. 3 have the same distance from the sprue 1 to each of the gates 3 and 3 provided adjacent to the upper surface on one end side. It is equiangular, equidistant, and symmetric with respect to the central axis. FIG. 2 shows the gate 3 on the side of the flange 4A, and FIG.
Are provided on the upper surface of the flange portion 4A, respectively, and the molten resin is filled from the one-point gates 3 and 3A of the flange portion 4A. These are shown for comparison with FIGS. 1 and 3 as examples of the prior art, and do not provide the effects of the present invention. FIG. 5 and FIG.
This is an example of a cavity for an injection mold composed of a fixed mold and a movable mold of a resin cylindrical test piece. 5 is a direct gate which is also a sprue connected to a nozzle of a molding machine, and 6 is to manufacture. It has the structure of the product part cavity of the molded product. The cavity shown in FIG. 6 forms a thick portion 8b by partially removing the projection for the lightening 8a of FIG. 5 from the mold and reducing the number of protrusions from eight to four. Although not shown, an ejector for ejecting a molded article and a cooling circuit for controlling the cooling temperature of the mold are installed in the mold. The sprue 5 had a circular cross section of φ4 mm at the tip and φ8 mm at the root.

As the thermoplastic synthetic resin composition, any one generally known as a fiber-reinforced thermoplastic resin can be used, but it is melted into long fibers such as glass fiber, carbon fiber and synthetic fiber by an extruder. What is impregnated with a thermoplastic, cut into an appropriate length, and pelletized is preferably used. In order to minimize breakage of long fibers, the thermoplastic synthetic resin composition has a small compression ratio, is provided with a deep groove screw, and it is desirable to use an injection device having a large nozzle, and is provided with a check valve. Is preferred.

Using the above resin composition, an injection-molded product of a resin-made cylindrical test piece and a resin-made cylindrical test piece is molded by a well-known injection means using the above-mentioned injection mold. In the injection process of the cylindrical test piece, molten resin is injected into the product part cavity 4 from the gates 3A and 3B provided symmetrically with respect to the central axis of the part 4A corresponding to the flange as shown in FIG. When the filling is started at the same time, a weld W is generated in the flange portion 4A, and the resin flows along the resin association portion which is the weld W, and as shown by a dotted line, the weld is a planar resin association portion.
The fibers in the molten resin are strongly oriented in the direction parallel to the central axis, which is the flow direction, by hardening while forming the screen W, and as shown in the experiment described later, the strength is greatly improved with respect to the tensile load. Will bring. The same can be said for FIG. This tendency becomes more remarkable when the weight average fiber length in the molten resin is large. FIG. 7 schematically illustrates the flow of resin in the injection step of a cylindrical test piece. FIG. 7A is a perspective view of the cavity,
(B) is a vertical cross-sectional view taken along the chain line in (c) of the plan view, and a line segment L represents a flow pattern at each time on the cavity surface. Since the resin flow of the thick portion 8b precedes the resin flow of the other thin portion 8c faster, the weld W is formed in parallel with the flow direction on the thin portion 8c sandwiched between the thick portions 8b. As a result, the fibers in the molten resin are strongly oriented along the weld W, resulting in a great improvement in strength against bending stress as shown in an experiment described later. The present invention is characterized in that the weld is intentionally generated as described above, and the fibers are strongly oriented in the direction in which reinforcement is desired.

<Experimental Example 1> With respect to a cylindrical test piece made of resin, a comparison was made between tensile strength at break and weight average fiber length of a resin containing short fibers and a resin containing long fibers. In the experiment, an injection-molded product was obtained using the two-point gate mold of FIGS. 1 and 3 and the one-point gate mold of FIGS. The molding conditions, experimental conditions, and experimental results of Experimental Example 1 are shown in Tables 1 to 4 below. In addition, the fiber orientation of the cross section of the two-point gate molded product and the one-point gate molded product is observed. Each of the thermoplastic synthetic resin compositions used here was a short fiber reinforced resin material containing polyamide 66 as a matrix and containing 50% by weight of glass fiber and a long fiber reinforced resin material (pellet length 12.
7 mm).

[0010]

[Table 1] The molding machine used was OKM150 manufactured by Okuma Iron Works Co., Ltd.

[0011]

[Table 2] A universal tester DSS-500 manufactured by Shimadzu Corporation
0 was used.

[0012]

[Table 3]

[0013]

[Table 4]

Further, the fiber orientation of the cross section of the molded product by the two-point gate and the cross-section of the molded product by the one-point gate is shown by an end view of the cross section taken along line a--a in FIG. FIG. 9 is an end view of the cross section at b. 8 and 9, there is a skin layer S at the peripheral end and a core layer C on the inner periphery thereof. However, when a two-point gate is used, a weld W is seen in the center of the molded product, and fiber orientation is observed. Is observed. This is similarly observed for both short fiber resin and long fiber resin.

From the above results, it was confirmed that when a weld was intentionally generated and the weld was made parallel to the tensile direction, the tensile breaking load was improved. The effect is more preferable when the long fiber reinforced resin is used and the fiber has a weight average fiber length of 0.3 mm or more in the molded article.

<Experimental Example 2> A comparative evaluation of the bending torque of a molded product due to a difference in the thickness of a hollow portion made of a resin-made cylindrical test piece was performed. The experiment was performed using the molds of FIGS. 5 and 6 of the apparatus of the above embodiment, with the lightening provided (FIG. 5) and with the lightening of FIG. 5 partially removed from the mold (FIG. 6). An injection molded product was obtained. The molding conditions, experimental conditions and experimental results are shown in Tables 5 to 7 below. The thermoplastic synthetic resin composition used here,
Long fiber reinforced resin material containing 40% by weight of glass fiber with polypropylene as matrix (pellet length 12.
7 mm).

[0017]

[Table 5] The molding machine used was OKM150 manufactured by Okuma Iron Works Co., Ltd.

[0018]

[Table 6] In addition, a universal testing machine IS-5000 manufactured by Shimadzu Corporation
It was used.

[0019]

[Table 7]

From the above results, it has been confirmed that when a weld is intentionally generated at a portion where rigidity is desired to be increased and the weld is made perpendicular to the direction of bending, the bending torque is improved. As a means for generating a weld inside the cavity, a means for providing a plurality of gates as shown in FIGS. 1 and 3 or a resin flow direction before the portion to be reinforced inside the cavity as shown in FIG. Is provided with a space portion 11 due to a pin failure or the like orthogonal to FIG.
A weld W, which is a planar resin association portion, is formed as described above.
There is a means to cure as it is. The upper side of FIG. 11 shows a plan view of the cavity, and the lower side shows a longitudinal sectional view including a gate. As a means for causing a velocity difference in the branch flow, there is a method of forming a thin portion 12 of the cavity by using a projection of a mold inside the cavity as shown in FIG. Note that the alternate long and short dash line L shown in FIGS. 11 and 12 indicates a flow pattern every time .

FIG. 13 is an explanatory view of the positions of gates provided at two or more locations on the bottom surface of a cylinder, which is one end side of a cylindrical cavity. (A), gates are provided at five locations that are equiangular, equidistant, and symmetric with respect to the central axis of the bottom surface. (B) is not appropriate because it is equiangular but not equidistant and not symmetric about the central axis. (C) is not equiangular (θ1 ≠ θ2) but is equidistant and symmetric about the central axis.
(D) is not equidistant but equiangular and central axis symmetric. The gates located on the central axis are not equiangular, equidistant, and symmetric with respect to the central axis, but it is appropriate because welds are created as many as the number of gates other than the positions. FIG.
It is explanatory drawing which shows the position of the gate provided in one end side other than the cylindrical bottom face of a cylindrical cavity from a side surface. (A)
When the resin flows in the longitudinal direction in order to strengthen the bending in the longitudinal direction, the upper side of the resin flow, which is one end of the side surface of the cylinder, is symmetrical, equiangular, and equidistant with respect to the central axis indicated by the dashed line. , Which is the same as FIG.
(B) is not appropriate because the resin flow direction which is the premise of the part to be reinforced is different. (C) and (d) are not suitable because they lack symmetry with the central axis.

Although the examples and experimental examples have been described for polyamide and polypropylene, other thermoplastic synthetic resin compositions such as PBT. PET. Similar results were confirmed for polyacetal, polyurethane, and the like, albeit with different numerical values, and the type of thermoplastic synthetic resin and fiber used in the present invention can be freely selected.

[0023]

According to the present invention, since the fibers are strongly oriented parallel to the direction in which the weld is formed, the tensile strength and bending strength in that direction can be greatly improved. Furthermore, by using technology to lengthen the fiber,
The degree of orientation of the reinforcing fibers can be increased to further increase the strength, and the fibers are more preferably 0.3 mm or more in weight average fiber length in the molded product.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic structure of a resin cylindrical test piece mold having two gates provided on a side surface of a flange portion according to the present invention, which is adopted in Experimental Example 1.

FIG. 2 is a diagram illustrating a basic structure of a resin-made cylindrical test piece mold in which a gate according to the related art is provided at one position on a side surface of a flange portion, which is adopted in Experimental Example 1.

FIG. 3 is a diagram illustrating a basic structure of a resin column-shaped test piece mold in which two gates according to the present invention are provided on the upper surface of a flange portion, which are adopted in Experimental Example 1.

FIG. 4 is a view illustrating a basic structure of a resin column-shaped test piece mold in which a gate according to the related art is provided at one place on the upper surface of a flange portion, which is adopted in Experimental Example 1.

FIG. 5 shows an example around the gate as a specific example according to the prior art.
FIG. 9 is a diagram illustrating a basic structure of a resin-made cylindrical test piece mold provided with individual hollow portions and adopted in Experimental Example 2.

FIG. 6 shows a concrete example of the present invention, which is a resin cylindrical test piece mold provided with four lightenings instead of every other eight lightenings in FIG. FIG.

FIG. 7 is a schematic view showing a filling pattern of a resin in an injection step of a cylindrical test piece.

FIG. 8 is an end view of a cross section taken along line aa in FIG. 3;

FIG. 9 is an end view of a cross section taken along line bb in FIG. 4;

FIG. 10 is an explanatory view showing a state of a bending test of the molded product of FIGS. 5 and 6;

FIG. 11 is an explanatory diagram of another embodiment.

FIG. 12 is an explanatory diagram of another embodiment.

FIG. 13 is an explanatory diagram of a position of a gate.

FIG. 14 is an explanatory diagram of a position of a gate.

[Explanation of symbols]

1 ... sprue, 2, 2A, 2B ... runner, 3, 3
A, 3B: gate, 4: product cavity, 4A: flange, 5: sprue, 6: cylindrical molded product, 7: cylindrical portion subjected to bending load, 8a: basic shape of lightening, 8
b: a portion where the thickness is removed and the thickness is increased 8c: a cylindrical basic shape, 9: a fixing jig, 10: a handle 11: a thickness, 12: a thin portion, L: a flow pattern, W:
Weld, S: skin layer, C: core layer, F: load.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84 B29D 23/00

Claims (5)

(57) [Claims] 1. A thermoplastic synthetic resin composition containing fibers is injected into a cavity to be manufactured from a gate provided at one or two or more places, and is injected into two or more resin molded articles. Resin association while forming a resin association part by branching and flowing simultaneously from two or more places
The Rukoto in flowing molten resin along the section, the product fibers are oriented strongly in the direction to be reinforced with a resin meeting portion
Resin molding method in which the resin is cured while remaining substantially flat . 2. A thermoplastic synthetic resin composition containing fibers is injected into a cavity to be manufactured from one or more gates provided at one or more locations, and is injected into two or more locations in a resin molded product. Bending stress in the direction of strengthening the product by strongly orienting the fibers along the resin association caused by simultaneously joining two or more preceding resin flowing parts by making the flow speed different. Great strength against
Resin molding method which improves the degree . 3. A thermoplastic synthetic resin composition containing fibers is simultaneously injected into cavities to be manufactured from gates provided at two or more locations on one end side , and
The fibers are strongly oriented along the resin association caused by the simultaneous merging of two or more preceding resin flow sections.
The bending stress in the direction in which the product is to be strengthened.
A resin molding method that provides a great improvement in strength . 4. A cylindrical or prism-shaped cavity to be manufactured from two or more gates provided with a thermoplastic synthetic resin composition containing fibers at an equiangular, equidistant or central axis symmetry with respect to a central axis. A resin molding method that utilizes the characteristics of a resin association portion caused by simultaneous injection into the interior to greatly change the fiber orientation in the direction in which the product is to be reinforced. 5. A resin molded article molded by the resin molding method according to claim 1, wherein the fiber has a weight average fiber length of 0.3 mm or more in the molded article.