JPH047113A - Injection molding method - Google Patents

Abstract

PURPOSE:To easily obtain a molded item having widely expressible multi-layer construction by a method wherein a thin-walled preformed article is installed between a female mold and a male mold having a sprue so as to be expanded to the inner wall of the female mold by injecting molten synthetic resin through the sprue. CONSTITUTION:A preformed article 4 is capped in a male mold 1. Under the state just mentioned above, the male mold 1 and a female mold 2 are mated to each other. In this case, the flange part 4a of the preformed article 4 is pinched between the male mold 1 and the female mold 2 so as to be fixed. In succession, when molten synthetic resin 5 is injected through a sprue 3, the thin-walled preformed article 4 is pushed by the molten synthetic resin, resulting in swelling in the fashion of blow molding and expanding to the inner wall of the female mold. Thus, surface layer 4b is formed on the surface of synthetic resin core material 5b, resulting in forming a cap. Other working example is the application to a compact container. When a preformed article, which is formed by laminating transparent film 23, leaf-shaped printed layer 22 and adherent modified polyolefin layer 21 onto the transparent resin layer 20 in the order is molded similarly as described in the case of the cap, printed pattern is seen floating above the surface of the core material 5, regulating in bringing about a unique appearance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an injection molding method, and particularly to a method for forming a surface layer on the surface of a core material.

[Conventional technology]

Cosmetic containers are generally molded from synthetic resin. If they are simply molded from a single-colored synthetic resin, they will look poor in appearance, so they are generally given a luxurious finish using various methods.

Examples of such methods include a method in which +4 synthetic resin raw material is mixed with burl powder or reflective fine powder in advance and molded, a surface treatment using so-called glitter coating, a method using clear or acryl paint, and a method using printing.

[Problem to be solved by the invention]

However, the above-mentioned conventional methods have limited expressive power, and may not be applicable to cosmetic containers that require a particularly high level of design effect.

Furthermore, depending on the molded product, it is necessary to not only improve the aesthetic appearance of the surface layer but also to improve the feel of the surface layer, so it may be necessary to change the surface layer material and the core material.

The present invention has been made in view of the above-mentioned matters, and a technical object of the present invention is to provide an injection molding method that allows a wide range of expressiveness to be obtained.Furthermore, it is a technical object to provide an injection molding method that can easily produce a molded product with a multilayer structure.

[Means to solve the problem]

In order to solve the above-mentioned technical problems, the present invention adopts the following method, that is, a thin preform is installed between a male mold and a female mold having a sprue.

Thereafter, molten plastic is injected from the sprue to expand the thin preform to the inner wall of the female mold.

As a result, a molded product having a surface layer on the surface of the core material made of the injected synthetic resin is molded.

Here, the thin preformed product is a multilayer molded product in which a printing layer is superimposed on a light-transmitting synthetic resin layer, and in particular, after molding, the transparent resin layer should be located between the core material and the printing layer. is preferably laminated on the back side of the printing layer.

[Effect]

In the present invention, a thin preform is molded in advance.

The thin preformed product used in the present invention may be a vacuum-formed product made of a synthetic resin sheet, or may be an injection-molded product with a sheet-like thickness. In some cases, it may be sufficient to leave it in sheet form.

The material is thermoplastic resin, and any material may be used as long as it can be softened and expanded by heat during injection and filling of the synthetic resin that is to become the core material. Further, the thickness of the thin preform is not limited as long as it can be expanded during injection and filling with the synthetic resin that is to become the core material. In addition, since it forms the surface layer, depending on the usage conditions of the molded product, weather-resistant materials such as polyolefin or flexible materials may be used as appropriate depending on the purpose of molding. Select material.

In addition, by preparing thin preforms of any color mixed with fine powder of burl material, lame material, fluorescent material, etc., and replacing these as appropriate, it is possible to produce a wide variety of products on one production line. .

This thin preform may be formed into a multilayer molded product. For example, it may be formed into a multilayer molded product in which a light-transmitting synthetic resin layer is overlaid with a printing layer, another synthetic resin layer, etc.

Examples include laminating a printed layer, a colored resin film layer, etc. on the surface of a transparent or translucent resin layer or the back side of clothing, or laminating a transparent resin layer on the back side of a printed layer.

In such a multilayer molded product, if a transparent resin layer is provided on the back side of the printed layer, the resulting molded product will have a transparent resin layer between the printed layer and the core material. The layer creates a texture that appears to be lifted from the surface of the core material, giving it a beautiful appearance that cannot be obtained with clear coating.
1. The product value as a cosmetic container etc. can be increased.

Then, the force τ for attaching the thin preform between the male die and the female die, which has been prepared in advance, may be applied to the male die or the female die depending on the shape of the mold. A thin-walled preform may be installed inside.

After the thin preform is installed between the male mold and the female mold, the mold is closed and molten plastic is injected from the spray.The thin preform is softened by the injection heat and is pushed by the injection pressure to form the female mold. Extends to inner wall. This shape looks like a thin molded product made by blow molding.

As the synthetic resin to be injection-filled, synthetic resins conventionally used for injection molding can be used. Select the material +L
The quality of the molded product to be molded depends on the purpose of use. For example, if a soft feel is required, a foamable synthetic resin may be used as the core material.

Finally, the inside of the mold cavity is filled with molten synthetic resin 5. After cooling, a molded product with a surface layer on the surface of the core material made of the injected synthetic resin is molded.

In this way, unlike painting, there is no time-consuming process such as multiple coatings or drying, so productivity is excellent.

In addition, by simply replacing various thin preforms as appropriate, molded products with different appearances can be obtained, making it suitable for high-mix, low-volume production.

〔Example〕

Embodiments of the present invention will be described based on FIGS. 1 to 7.

First Example> This example is for manufacturing a cap for a cosmetic container.

First, the thin preform 4 is installed between the male mold 1 having the sprue 3 and the female mold 2. This female mold 2 has a substantially spherical dovetail shape, and is divided into parts for release. male type l
is formed into a substantially cylindrical shape, and a sprue 3 through which molten synthetic resin 5 is pumped is formed at the center thereof. A thread 1a is formed around the male mold 1.

The thin preformed product 4 is made of multicolored polypropylene with a thickness of 0.
．． It is a bottomed cylindrical molded product having a so-called marble pattern, which is injection molded to a diameter of 5 mm, and has a flange portion 4a around the opening edge.

Then, as shown in FIG. 1, the preform 4 is attached to the male die 1, and in this state, the male die 1 and the female die 2 are fitted together. At this time, the flange portion 4a is pressed and fixed between the male die 1 and the female die 2.

Subsequently, the molten synthetic resin 5 is injected from the sprue 3.

Then, as shown in FIG. 2, the thin preform 4 is pushed by the molten synthetic resin 5 and expands to the inner wall of the female mold like blow molding.

As a result, a surface layer 4b is formed on the surface of the synthetic resin core material 5b, thereby forming a cap as shown in FIG. An engaging thread 5a attached to the thread 1a is formed on the inside of this cap so that it can be screwed onto the opening lO of the broth container.

The reason why the flange portion 4a is fixed is to prevent the thin preform 4 from being drawn into the mold by the pressure when the molten synthetic resin 5 is injected.

Second Embodiment In the first embodiment, the flange portion 4a of the thin preform 4 was held down by a male mold, but in this embodiment, as shown in FIG. Holder mold 11
The flange portion 4a is fixed between the mold 2 and the female mold 2. In this embodiment, the metal fastening and the flange part 4 are
It is possible to set the release of fixation with a separately, which improves productivity.

The other parts are the same as those in the previous embodiment and will therefore be omitted.

Third Embodiment> This embodiment is applied to a compact container as shown in FIGS. 5 to 7.

In this embodiment, as shown in FIG. 7, a preformed product 4 is printed in advance, and an adhesive modified polyolefin (trade name: Atomer) layer 21 is interposed on the surface of a transparent resin layer 20, as shown in FIG. A leaf-shaped printed layer 22 is formed, and a transparent film 23 is further laminated on the surface of this printed layer 22 to form a preformed product.

This preformed product 4 is set in the male mold 1 and the pressing mold 11
In this embodiment, the female mold 2 is fixed, the female mold 2 is closed, and resin is injected and filled from the sprue to form a lid for a compact container having a surface layer 4b made of the preform 4 on the surface of the core material 5b. The transparent resin layer 20 exists under the printing layer 22, and the printing layer 22 is lifted from the core material 5b by the thickness of the transparent resin layer 20, so the printed pattern appears to stand out from the surface of the core material 5b, It can create a unique texture.

Fourth Example> This example is an example in which the lid of the compact container shown in FIG. 6 was manufactured by a method different from that of the third example.

In this embodiment, the fourth generation of the preformed product, in which the printing layer was transferred to the preformed product 4 at the same time as the lid was molded, is molded with a transparent resin different from the colored resin for the core material 5b.

Transfer film for printing layer transfer 6 As shown in Figure 9, an adhesive modified polyolefin (trade name: Atmer) is coated on the surface of a 0.5 mm thick adhesive transparent resin sheet 30.
A leaf-shaped or shaped printed layer 32 is formed through the layer 31, and a peelable base film 3 is further provided on the front surface of this printed layer 32.
3 are laminated.

Then, the adhesive transparent resin sheet 30, the polyolefin layer 31, and the printing layer 32 are integrated to form a transfer layer 34.
The base film 3 has a continuous band-like transfer layer 34.
3 and are laminated at predetermined intervals in a removable manner.

Then, as shown in FIG. 8, the preform 4 is inserted into the male mold 1
Fix the peripheral edge with the pressing mold 11, insert the transfer film between the male mold 1 and the female mold 2, close the female mold 2, and inject and fill the resin 5 from the sprue to the surface of the core material 5b. The transfer layer 34 of the compact container lid having the surface layer 4b of the preformed product 4 is peeled off from the base film 33.

As a result, a transparent resin sheet 30 and a surface layer 4b made of the transparent preform 4 exist below the printing layer 32, and the printing layer 32 has a core material 5b corresponding to the thickness of the transparent resin sheet 30 and the surface layer 4b.
Since it is more floating, the printed pattern appears to stand out from the surface of the core material 5b, creating a unique texture.

〔Effect of the invention〕

According to the present invention, a molded product with a surface layer formed on the surface of a synthetic resin core material can be produced by injection molding, so there is no need for multiple coatings or labor-intensive processes during the dry season, which is required for painting, resulting in excellent productivity.

Furthermore, since it has multiple layers compared to a simple injection molded product, it can be molded with different textures. Furthermore, compared to multilayer molded products made by other conventional methods, the multilayer molded product can be formed into a multilayer molded product having an arbitrary shape.

In addition, a wide variety of products can be produced on one production line simply by replacing thin preforms.

Sara & Mi When transparent sheets are used, a wide range of expressiveness that cannot be obtained with clear coating can be obtained, and the product value can be improved.

[Brief Description of the Drawings] Figures 1 to 9 show embodiments of the present invention. Figures 1 and 2 are cross sections of the first embodiment. Figure 3 is a cross section of the second embodiment. Figure 4. Figure 5 is the cross section of the product manufactured by this method. Figure 6 is the cross section of the third embodiment. Figure 7 is the enlarged cross section. Figure 8 is the cross section of the fourth embodiment. The figure is a cross-sectional view of the transfer film. l...male mold, 2...female, 3...sprue, 4...thin preformed product 5...molten synthetic resin, 5b...core material, 4b...surface layer.

Claims (1)

[Claims] (1) After installing a thin preform between a male mold and a female mold having a sprue, molten synthetic resin was injected from the sprue to expand the thin preform to the inner wall of the female mold, and then injected. An injection molding method characterized by molding a molded product having a surface layer on the surface of a core material made of synthetic resin.