JPH03286815A - Injection molded body with thick wall structure - Google Patents

Abstract

PURPOSE:To manufacture a molded body without sink and warp, light in weight, of large rigidity and of superior surface state by providing hollow section in a thick wall structure. CONSTITUTION:At least one or more thick wall structures 2 of apparent wall thickness are formed on an injection molded body provided with thick wall structures, and hollow sections 3 are provided in the thick wall structures 2, and the injection molded body is integrated with a thin wall structure which forms a section other than the thick wall structures 2. One hollow sections 3 can be formed in the thick wall structure 2, or a plurality of same can be provided adjacently each other. The injection molded body with the thick wall structure 2 can be formed by injecting molten resin into a mold cavity by the injection molded body with the thick wall structure and injecting pressurized gas for forming the hollow sections while the molten resin is uncured simultaneously or after the injection of molten resin and cooling and solidifying the molten resin while the pressure of pressurized gas is retained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to, for example, automobile door mirrors, armrests,
The present invention relates to an injection molded product having thick-walled structural parts in at least 6 places of the molded product, such as a molded product used for bumpers, instrument panels, housings for office equipment, home appliances, audio equipment, etc., container pallets, caps, etc.

[Prior Art] Conventionally, injection molded products having a thick-walled structure at at least one location on the molded product include those shown in FIGS. 2 to 4.
The following structures are known.

(1) As shown in FIG. 2, the thick structure portion 2 is solid.

(2) As shown in FIG. 3, the thick wall structure portion 2 has a comb-shaped space with regular spacing.

(3) As shown in FIG. 4, the inside of the thick structure portion 2 has a foam structure.

[Problems to be Solved by the Invention] However, the following problems remain in the above-mentioned conventional injection molded body having the thick-walled structure portion 2.

In the injection molded article (1), the amount of thermal contraction of the thick-walled structure 2 during cooling and solidification increases, and depressions called "sink marks" occur, resulting in poor appearance.

In addition, in the case of long and large molded bodies, the difference in the amount of heat shrinkage occurs between the thick-walled structure part 2 and the thin-walled structure part 1, resulting in "warpage".
occurs.

(2) is a structure designed to improve sink marks, but if the comb pattern is made rough, sink marks cannot be completely prevented. Becomes expensive.

(3) is also a structure devised to improve "sink marks," but since the inside of the thick structure part 2 is foamed, poor appearance is likely to occur on the surface due to foam patterns and pinholes.

Furthermore, not only is the foaming agent added to the raw material expensive, but the molding cycle must be lengthened to prevent secondary foaming, resulting in poor productivity.

[Means for Solving the Problems] In order to solve the above problems, the means taken in the present invention will be explained with reference to drawings (a) and (b) corresponding to one embodiment of the present invention. The injection molded article having the thick structure part 2 according to the invention is characterized in that it has the thick structure part 2 in at least one place in appearance, and the inside of the thick structure part 2 is a hollow part 3. It is something to do.

[Function J] In the present invention, the provision of the hollow portion 3 inside the thick-walled structure portion 2 serves to reduce the substantial thickness thereof.

[Example] An injection molded article having a thick-walled structure according to the present invention will be described with reference to FIGS. 1(a) and 1(b).

The injection molded article having a thick structure of the present invention has a thick structure 2 that is thick in appearance in at least one place, and a hollow part 3 is provided inside the thick structure 2. Ori,
It is an injection molded body integrally constructed with a thin wall structure section 1 which is a portion other than the thick wall structure section 2.

Only one hollow part 3 may be provided inside the thick structure part 2 as shown in FIG. 1(a), or a plurality of hollow parts 3 may be provided adjacently as shown in FIG. 1(b). .

The volume ratio of the hollow part 3 refers to the proportion of the volume of the hollow part 3 in the total volume of the thick structure part 2 including the hollow part 3, and is 5
~50% is preferred. Alternatively, a structure in which a plurality of hollow portions 3 are provided adjacent to each other within the thick structure portion 2 may be used. Creating multiple cavities is accomplished by providing the mold with vials or protrusions that protrude from the mold.

The injection molded article having a thick-walled structure of the present invention is produced by injecting molten resin into a mold cavity and forming a hollow part at the same time as the injection of the molten resin or while the molten resin is still unsolidified after injection. It can be obtained by injecting pressurized gas and cooling and solidifying the molten resin while maintaining the pressure of the pressurized gas.

The molten resin used in the present invention may be injection moldable thermoplastic resins, thermoplastic elastomers, thermosetting resins, or blends of these with conventionally known additives and fillers; Thermoplastic elastomers, and conventionally known additives, stabilizers, fillers,
Blends with reinforcing agents such as glass fibers are preferred.

The pressurized gas is generally a gas such as nitrogen, carbon dioxide, air, etc., which is harmless and does not liquefy under the molding temperature and injection pressure, but liquids or oligomers that are incompatible with the molten resin may not be used. You can also do it.

[Effects of the Invention] The present invention is as described above, and has the following effects.

<1) Since it is possible to obtain a molded product with no sink marks and an excellent surface condition, it is possible to save the time and effort of finishing, and it is possible to easily obtain a molded product whose appearance is important.

(2) Since it is possible to obtain a molded product that is lightweight and has great rigidity without warping, it is possible to easily obtain a long and large injection molded product. The range of applications for injection molded products can be expanded.

(3) By shortening the cooling assimilation time, the molding cycle can be shortened, so productivity can be increased.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) show an example of an injection molded article having a thick-walled structure according to the present invention, and FIG. 2 shows an example of an injection-molded article having a conventional solid thick-walled structure. FIG. 3 is an example of an injection molded article having a conventional thick structure with a thinning structure, and FIG. 4 is an example of an injection molded article having a conventional thick structure with a foamed structure. 1: Thin structure part 2: Thick structure part 3: Hollow part

Claims (1)

[Claims] An injection molded article having a thick structure, characterized in that the thick structure has an externally thick structure at at least one location, and the inside of the thick structure is hollow.