JP3392902B2 - Injection molded product with hollow rib - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molded product having a hollow rib portion which requires extremely high flatness.

[0002]

During BACKGROUND ART Injection molding, molding of the hollow molded article was injected gas body molten resin in the molten resin injection or after injection by performing (hereinafter sometimes referred to as gas injection molding), A method for producing an injection-molded article free of shrinkage and warpage is known. In gas injection molding, a passage for pressing a gas body into a molded product ( hereinafter referred to as
Lower, as may be referred to a gas channel), from a gas injection position into the molded article, the substrate defining a molded article, the width than the wall thickness defining a base, to form a large rib height <br / > Ru.

In conventional gas channel designs, the thick wall (
B) is disposed on one side (particularly the back side) of the base of the molded product, and the structure is usually invisible from the appearance of the product. Also, the gas channel is usually arranged on one side from the viewpoint of mold processing.

[0004]

In the fiber reinforced material, the random orientation of the fibers from the resin gate during injection molding causes
Usually , it causes warpage even in molding.

A conventional thick portion is arranged on one side of the base body of the molded product.
In the design of, when designing a gas channel to the site in need of flatness perform forming shapes experiment, when designing a gas channel on the flat portion of the molded article or a box shape of a flat plate shape, the gas injection molding, warpage was found that the increases.

That is, when a gas channel is arranged on one side of the product in a molded article having a flat plate-shaped portion, a beam effect is generated by the gas channel, and warpage is observed in the opposite direction of the gas channel. In particular, the use of composite reinforcing material as a molding material, a glass fiber in the gas channel, the gas injection
When hollowing by gas-based, is oriented in the traveling direction of the gas, results in beam effect is emphasized, the warpage becomes larger.

The present invention solves the above problems and provides a thick-walled injection-molded article requiring a high degree of flatness.

[0008]

Means for Solving the Problems The present inventor has designed a result of extensive studies to solve the above problems, a thick portion which is raised from the substrate on either side of the base defining a molded article as a gas channel As a result, they have found that the above problems can be solved, and have reached the present invention.

Accordingly, the present invention, a molten thermoplastic resin is injected into the mold cavity, then an injection molded article having a hollow rib portion obtained by injecting a pressurized gas member, the
Pressurized gas carrier injection site present in the hollow ribs, the hollow Li
Bed unit, said extends from the pressurized gas carrier injection site,且<br/> one, have a raised shape from both sides of the base defining the formed molded article
The present invention relates to an injection molded product having a hollow rib portion .

[0010] In the present invention, at the time of injection molding, hollow rib for pressurized gas carrier injection into molten resin in the molten resin injection or after injection is raised on both sides from the substrate defining a molded article Ru Oh in the gas channel.

As described above, the beam effect by the gas channel on one side of the flat plate portion is remarkably reduced by designing the thick portion (hollow rib portion) protruding from the base body on both sides.

[0012] Also, even when using a fiber reinforcement, the fiber orientation in the gas channels after hollowing can Tei hollow rib portion is disposed on both sides of the plane because, while preventing the occurrence of warpage, The warp can be greatly improved.

[0013] The width of the hollow rib portion is more than twice the thickness of the substrate
Yes, the height of one side of the hollow rib protruding from the base
It is preferable that not less than 0.2 times the thickness of the substrate. Furthermore, the width of the hollow rib portion is not less than twice the thickness of the substrate, group
The height of one side of the hollow rib part raised from the body is
0.2 times the thickness, and, in provided on both sides of the substrate
The sum of the height of the portion of the air-rib portion at least 1.3 times the base thickness
There it is particularly preferred.

[0014] As the cross-sectional shape of the portion of the hollow rib portions provided on one side of the substrate, the shape used in the conventional gas injection, further trapezoid, can be used a semicircular or the like, of hollow ribs provided on both sides shape can be a combination of the shape and the same cross-sectional shape or irregular cross-sectional shape.

When the cross-sectional shape is trapezoidal, semicircular, etc., the width of the rib portion is measured from the portion protruding from the substrate.

[0016] Thus, hollow raised from the base body on both sides
Flatness 0.1-0.3mm by providing ribs
It becomes possible to do the following, and it can also be applied to molded products such as laser beam printers, fax chassis, and paper feed parts of printers.

[0017]

Example 1 As shown in FIG. 1, at the center of a shape having a width of 150 mm, a length of 300 mm, a height of 25 mm, and a thickness of 2.5 mm, a thick portion shown in FIG. Of 3 mm) was provided , and an attempt was made to form a molded product having a gas channel in the thick portion. In FIG. 1, reference numerals “A” to “E” indicate resin gate positions, and the gas injection port is located at a position facing the resin gate A.

Polycarbonate resin (trade name: Iupilon S2030, manufactured by Mitsubishi Gas Chemical Co., Inc., glass fiber content 30% by weight) was used, and injection molding was carried out by an ordinary injection molding machine.

After melting the polycarbonate resin at a resin temperature of 310 ° C., it was injected into the mold cavity, and at the same time as the injection was completed, a pressurized gas body was injected from the gas injection port . Holding the gas pressure in the cooling step of the molten resin, after completion of the cooling, after returning the gas pressure in the molded product to atmospheric pressure before demolding the mold is opened.

The flatness of the obtained molded product was measured to be 0.2 mm.

Comparative Example 1 Injection molding was carried out using the same resin material and mold as in Example 1.

[0022] In this comparative example, the thick portion, FIG 3 (width is 7 mm, height 3mm) was a shape shown in FIG. The resin gate and the gas inlet are the same as in the first embodiment.

In the obtained molded product , the central portion of the flat plate was deformed so as to be warped downward, and the flatness thereof was measured and found to be 1.7 mm.

[0024]

By hollow rib according to the present invention is to raised features der Ru y de moldings from the substrate on either side of the substrate defining the molded article, increasing the molded article of dimensional accuracy (warpage, flatness) Can be done.

By forming the thick-walled portion having the hollow rib portion of the present invention, the application range of gas injection is broadly expanded from the internal mechanical parts of OA and home electric appliances to the external cover.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a molded product molded in Example 1.

2 is an enlarged view of a thick portion of a molded product molded in Example 1. FIG.

FIG. 3 is an enlarged view of a thick portion of a molded product molded in Comparative Example 1.

[Explanation of symbols]

AE: Resin gate part

Claims (3)

(57) [Claims] 1. An injection molded article having a hollow rib portion obtained by injecting a molten thermoplastic resin into a mold cavity and then injecting a pressurized gas body, wherein the hollow rib portion is pressed. There is a gas body injection site, and the hollow rib portion extends from the pressurized gas body injection site .
Ri, and an injection molded article having a hollow rib portion characterized by having a raised shape from both sides of the base defining the formed molded article. In 2. A width of the hollow rib portion is more than twice the thickness of the substrate
Yes, the height of one side of the hollow rib protruding from the base
Is 0.2 times or more the thickness of the substrate, and the injection-molded article having a hollow rib portion according to claim 1. Wherein the injection molded article the thermoplastic resin has a hollow rib portion of claim 1 or claim 2, characterized in that a resin composition containing a fibrous reinforcement.