JP3240497B2 - Resin molded products with end grooves - 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 molded article which is reinforced by mixing fibers, and particularly has a flat plate-shaped end groove formed with a gate at the center.

[0002]

2. Description of the Related Art Resin molded articles are advantageous in reducing weight and can be suitably used in places where they come in contact with water because there is no fear of corrosion due to rust, but on the other hand, resin alone has poor tensile and bending properties. There is. Therefore, a technique for increasing the strength by mixing fibers in a resin is generally known, and many products using such a resin composition have been put to practical use.

[0003]

However, it has been difficult to avoid warpage deformation due to anisotropy in molding shrinkage due to mixing of the fibers. It is not an exaggeration to say that the influence of the warpage deformation due to the incorporation of the fiber largely depends on the orientation state of the fiber. To this end, measures have been taken to prevent warping of molding conditions, product shapes, mold structures, and material prescriptions.However, measures for fiber orientation have not been sufficiently considered, and as a result, products with high precision and low warpage can be obtained. I couldn't. The fiber orientation of each part of the molded product is mainly affected by the shape, thickness, gate position and molding conditions of mold temperature, injection speed, viscosity of molten resin, fiber concentration, fiber length, etc. The state has a great influence on the molding shrinkage and the warpage. The weight average fiber length in the molded product is 0.
Explaining the tendency of the fiber orientation state using a product made of a long fiber reinforced material of 3 mm or more as an example, when the wall thickness is 2 mm or less, the fibers are strongly oriented in the flow direction due to the effect of shearing during filling, and the flow end is It is strongly oriented in a direction parallel to its end face. Also, as the thickness increases, the proportion of the core layer increases, and the proportion of orientation in the direction perpendicular to the flow tends to increase. Due to such non-uniform fiber orientation distribution, non-uniformity in anisotropy of molding shrinkage occurs in a molded product, which has a large adverse effect on warpage.

[0004]

SUMMARY OF THE INVENTION The present invention clarifies the orientation of fibers contained in a molded article, thereby controlling the orientation of the fibers, reducing the non-uniformity of the orientation anisotropy, and reducing the warpage. It is a resin molded product having an end groove that has succeeded in significantly improving deformation. The first means has a flat plate portion formed of a thermoplastic synthetic resin composition containing fibers.
A molded product to be formed, wherein a lightening groove is provided on the whole or a part of the outer peripheral end of the flat plate surface of the flat plate portion, and an end groove for strongly orienting the fiber substantially in a direction substantially parallel to the lightening groove direction. Goods. Here, “substantially parallel” refers to a state in which the fibers are parallel or almost parallel to the flow direction. Also,
The second means is a resin molded product in which the lightening groove forms an angle of 45 to 90 degrees with respect to the outer peripheral end of the flat plate surface . Is preferable as the third means. Similarly, the fourth
As a means, it is desirable that the lightening groove is a resin molded product having an end groove substantially parallel to the resin flowing direction. Further, it is desirable that the fiber has a weight average fiber length of 0.3 mm or more in the molded article.

[0005]

According to a first aspect, the present invention provides a molded article having a flat plate portion formed of a thermoplastic synthetic resin composition containing fibers.
Thus, a lightening groove is provided on the whole or a part of the outer peripheral end of the flat plate surface of the flat plate portion, and the light emitting device has an end groove for strongly orienting the fiber substantially in a direction substantially parallel to the lightening groove direction. Fibers having the property of being strongly oriented by the influence of shearing have a small molding shrinkage in the orientation direction and a large molding shrinkage in the direction perpendicular thereto. In particular, the fibers are oriented along the end face in the vicinity of the end face of the flow end, but by appropriately disposing the lightening groove in each part of the molded product, it is possible to reduce the anisotropy of the molding shrinkage. Further, as a second means, the lightening groove forms an angle of 45 to 90 degrees with respect to the outer peripheral end of the flat plate surface , and in particular, the third means forms an angle of 90 degrees with the outer peripheral end of the flat surface. If the lightening groove has an end groove that is substantially parallel to the resin flowing direction, the warpage can be greatly improved.
Further, as a fifth means, these effects can be further enhanced by lengthening the fiber such that the fiber has a weight average fiber length of 0.3 mm or more in a molded article.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A resin molded product and a molding method according to the present invention,
A mold structure used in the method will be described with reference to the drawings. 1 to 4 show a flat plate shape according to the present invention.
Therefore, it has front and back flat plate surfaces and side plate surfaces orthogonal to them.
That is the molded article those exemplified. Figure 1 is 200x200
A front view showing a molded product which is a flat plate having a thickness of 3 mm and having no end groove is shown on the left of the drawing, and a cross-sectional view at the center of the molded product is shown on the right of the drawing. 2 to 4 are 200 x 200m
m is a drawing showing a molded product obtained by grooving a flow end portion of a 3 mmt flat plate, a front view at the upper left of the drawing, a side view showing a side plate surface at the lower left of the drawing, and a right view of the drawing at the right of the drawing. And a cross-sectional view at the center of the molded article . 1 is a sprue connected to a nozzle of a molding machine, 2 is a product part main body of a molded product to be manufactured, and 2a is a gate located at the center thereof. Reference numeral 3 denotes an outer peripheral end which is the four sides of the flat plate, and a portion in which a lightening groove is provided as an end groove. The mold of this portion has a nested structure which can be exchanged and formed according to the depth or length of the groove. did. In addition, although not shown, an ejector for projecting a molded product and a runner and a cooling circuit for controlling a cooling temperature of the mold are installed in the mold.

As the thermoplastic synthetic resin composition, any of those generally known as a fiber-reinforced thermoplastic resin can be used. However, it is possible to use a thermoplastic resin melted by an extruder into a long fiber such as glass fiber, carbon fiber or synthetic fiber. A material impregnated with a plastic, cut into a suitable length and pelletized is preferably used. In order to minimize breakage of long fibers, it is preferable that the thermoplastic synthetic resin composition has a low compression ratio, is provided with a deep groove screw, and is injected using an injection device having a large nozzle, and particularly a check valve. Those provided with are preferred.

Using such a thermoplastic synthetic resin composition, a resin molded product is molded by well-known injection means. The flow end injected from the gate 2a to the central portion of the cavity of the embodiment 2 spreads in a substantially circular shape, reaches the periphery of the flat plate shape, forms an end groove, and is filled. When the grooves are installed as shown in FIG. 2 to FIG. 4, the fiber orientation of the groove installation portion can be controlled. When the grooves are not installed, the fibers which are strongly oriented in the direction perpendicular to the flow along the outer peripheral end shape are parallel to the grooves. Direction (flow direction)
To reduce the non-uniformity of fiber orientation and anisotropy of molding shrinkage, thereby making it possible to approach molding shrinkage behavior other than at the outer peripheral end , and to greatly improve warpage deformation. The dimensions (length, width, depth, pitch, direction) of the lightening groove can be set arbitrarily, and the resin material matrix type,
The length varies from approximately 10 mm to 10
0 mm, width from 0.5 mm to 2.0 mm, depth from (basic thickness / 2) mm to (basic thickness-2) mm, pitch 5 mm
To 30 mm is preferred. In FIG. 2, the lightening groove is radially arranged with respect to the center gate, and 20 mm to 28 mm, width 1 mm, and depth 1.5 m from the outer peripheral edge of the flat plate surface.
m and the pitch are 20 mm at the outer peripheral end . FIG. 3 shows FIG.
The groove pitch was changed to 10 mm. FIG.
Is one in which the direction of the groove is fixed at 90 degrees with respect to the outer peripheral end face. In the case of a flat molded product, the lightening groove can be provided not only on one side but also on both sides. In the present invention, the lightening groove as described above is intentionally provided in order to achieve the object of the present invention, and is distinguished from a groove which is provided as an essential part in functioning as a product.

<Experimental example> 200 × 2 shown in FIGS. 1 to 4
A flat plate having a thickness of 00 mm and a thickness of 3 mm was used to compare the anisotropy of fiber orientation between a product having a lightening groove as an end groove at a flow end portion and a molded product having no lightening groove. In the experiment, three types of injection molded articles having a lightening groove at the flow end and a flat plate without a lightening groove were used by using the molds obtained from the molded articles of FIGS. 1 to 4 of the above embodiment. The products were obtained, and the amount of warpage of each product was measured. The anisotropy due to fiber orientation was determined by measuring the linear expansion coefficient at the end of the flow at the position indicated by reference numeral 4 in each figure. The molding conditions, experimental conditions, and experimental results are shown in Tables 1 to 4 below. The thermoplastic synthetic resin composition used here,
A short fiber reinforced resin material and a long fiber reinforced resin material (pellet length: 12.7 mm) containing polypropylene as a matrix resin and containing 40% by weight of glass fibers.

[0010]

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

[0011]

[Table 2] The linear expansion coefficient was measured using a large sample linear thermal expansion meter manufactured by Rigaku Corporation.

[0012]

[Table 3]

[0013]

[Table 4]

From these results, when fibers are contained in the resin,
It can be seen that the adoption of the lightening groove at the flow end changes the orientation of the fibers and improves the anisotropy, and the warpage is greatly reduced. The higher the fiber orientation, the smaller the coefficient of linear expansion in the orientation direction.

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

[0016]

According to the present invention, in the thermoplastic synthetic resin containing fibers, an appropriate lightening groove is formed on the flat surface of the flat portion.
By providing the fibers at the outer peripheral end , the orientation of the fibers can be controlled, the anisotropy can be reduced, and the warpage can be greatly improved. Also, insert the lightening groove at the outer edge.
When it is provided on a flat resin molded article so as to form an angle of 45 to 90 degrees with respect to the portion , it is particularly preferable that the angle is 90 degrees, and it is possible to reduce non-uniformity of fiber orientation, and warp. Deformation is greatly improved. Further, when the weight average fiber length of the reinforcing fibers in the injection molded product is 0.3 mm or more using a long fiber reinforced resin material, the effect of improving the fiber orientation is large,
Warpage is greatly reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a molded product using a flat-plate molding experimental mold having no lightening groove.

FIG. 2 is an explanatory view of a molded product formed by a flat-plate molding experimental mold according to the present invention in which a lightening groove is provided substantially parallel to a resin flowing direction.

FIG. 3 is an explanatory diagram of a molded product by a flat plate molding experimental mold having a lightening groove provided substantially parallel to a resin flowing direction according to the present invention.

FIG. 4 is an explanatory view of a molded product made of a flat-plate molding experimental metal provided with a lightening groove at an angle of 90 ° with respect to an end face portion according to the present invention.

[Explanation of symbols]

1 ··· Sprue, 2 ··· Product part body, 3 ··· End face part, 4
..The linear expansion coefficient measurement position.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-100317 (JP, A) JP-A 8-142213 (JP, A) JP-A 7-290902 (JP, A) JP-A 7-290 1495 (JP, A) Japanese Utility Model Showa 61-129957 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/26-45/44 B29C 33/00-33/76 B29D 1/00-31/02

Claims (5)

(57) [Claims] 1. A molded article having a flat portion molded from a thermoplastic synthetic resin composition containing fibers, comprising:
A resin molded product having an end groove, wherein a lightening groove is provided on the whole or a part of the outer peripheral end of the flat surface of the plate portion, and the fibers are strongly oriented substantially in a direction substantially parallel to the lightening groove direction. . 2. The resin molded product having an end groove according to claim 1, wherein the lightening groove forms an angle of 45 to 90 degrees with respect to the outer peripheral end of the flat plate surface . 3. The resin molded product having an end groove according to claim 1, wherein the lightening groove forms an angle of 90 degrees with an outer peripheral end of the flat plate surface . 4. The method according to claim 1, wherein the lightening groove is formed in a direction in which the resin flows.
The resin molded product having an end groove according to claim 1, which is substantially parallel. 5. The method according to claim 5, wherein the fibers have a weight average fiber length of 0.5 in a molded article.
The resin molded product having an end groove according to claim 1, which is 3 mm or more.