JP3964125B2 - Gradation molding method and molded body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gradation molding method and a molded body.
[0002]
[Prior art]
There are single-color molded bodies made of transparent resins and molded bodies in which colored non-transparent resins are inserted into the transparent resin by an insert molding method.
[0003]
Further, there is known a molded body which is not transparent but has a pattern in which the color tone changes continuously from red to blue on the surface.
[0004]
[Problems to be solved by the invention]
A molded body made of a transparent resin is transparent, but has only a single transparent color, so there is no change in color tone.
[0005]
In addition, a molded product in which a colored resin is inserted by insert molding has a monotonous change in color tone, and insert molding has two molding steps, which increases molding time and costs. It was.
[0006]
In addition, in the case of a molded product that has a pattern with a continuous color change from red to blue on the surface, the appearance is beautiful, but the pattern needs to be applied by painting or printing, and it is necessary from the viewpoint of manufacturing cost. There was a problem.
[0007]
An object of the present invention is to provide a molded product having transparency and a change in color tone by a simple method.
[0008]
[Means for Solving the Problems]
The invention according to claim 1 is a gradation molding method in which two or more inner layers made of a colored resin are injected into an outer layer made of a transparent or translucent resin, and a molded product having a change in color tone is formed. Alternatively, a translucent resin is injected into a mold to form an outer layer, and then a colored resin that forms a first inner layer, a transparent or translucent resin that forms a transparent intermediate layer, and a colored resin that forms a second inner layer Injected in order, the first inner layer is thinly stretched to have a lower concentration than the second inner layer .
[0009]
Here, transparent or translucent means that the inner layer is visible, and may be colored and transparent.
[0010]
The gradation means that the color density and the color tone change according to a certain regularity, for example, the case where the color becomes darker as the inner layer, or the case where the color changes to yellow-yellow-green-green.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1 and 2 show a procedure for molding a thick toothbrush handle 10 using the injection molding die 1 by the gradation molding method as described in the following (1) to (4).
[0012]
(1) A transparent (or translucent) resin is injected into the mold 1 for 3.0 seconds to mold the outer layer 11 (FIG. 1A). As the transparent resin, for example, polyethylene terephthalate (PET), polystyrene (PS), acrylonitrile styrene (AS), polyacryl (PMMA), or the like can be used.
[0013]
(2) A small amount of colored resin is injected into the outer layer 11 for 0.3 sec to form the first inner layer 12 (FIG. 1B). As the colored resin, for example, a resin obtained by adding a colorant to the transparent resin described in (1) above can be used. Here, a colorless and transparent polyethylene terephthalate resin was used.
[0014]
(3) The same transparent resin as in the above (1) is injected into the first inner layer 12 for 1.2 seconds to form the transparent intermediate layer 13 (FIG. 1C).
[0015]
(4) A colored resin of the same color as in (2) above is injected into the transparent intermediate layer 13 for 2.0 seconds to form the second inner layer 14 (FIG. 1 (D)), and finally the transparent resin is applied. Injection is completed for 4.5 seconds to complete filling (FIG. 1 (E)). The last injection of the transparent resin is preferable from the viewpoint of productivity because the next molding starts from the transparent resin, and is also preferable from the viewpoint that the colored resin can be completely embedded. In the handle 10, as shown in FIG. 2, a part (base) of the first inner layer 12 on the outer side wraps the second inner layer 14 on the inner side, and the color density of the first inner layer 12 is set to the second inner layer 14. The color density is lower than the color density. The first inner layer 12 is stretched long and thinly with a small amount of the colored resin to have a lower concentration than the second inner layer 14.
[0016]
In the handle 10, the shape of the inner layers 12, 14 is changed by appropriately changing the injection start timing and the injection end timing of the colored resin in the above (2) and (4) within the range where the handle 10 is completely filled. Can be transformed.
[0017]
The colored resin that constitutes the inner layers 12 and 14 is not limited to the transparent resin that constitutes the outer layer 11 and the transparent intermediate layer 13, but is different from the transparent resin that constitutes the outer layer 11 and the transparent intermediate layer 13. The material may be used. Further, the colored resins constituting each of the inner layers 12 and 14 are not limited to the same material, but may be different materials, or the colors may be different from each other. Further, since the inner layers 12 and 14 and the transparent intermediate layer 13 are enclosed in the outer layer 11, no adhesiveness is required between the outer layer 11, the first inner layer 12, the transparent intermediate layer 13, and the second inner layer 14.
[0018]
According to this embodiment, there are the following operations.
(1) Since the outer layer 11 is formed of a transparent or translucent resin and the inner layers 12 and 14 are formed of a colored resin, voids can be made invisible. At this time, two or more inner layers 12 and 14 inside the outer layer 11 are formed of colored resin, and the inner layer 14 closer to the inner side is covered by a part of the inner layer 12 closer to the outer side, and the color density of the inner layer 12 closer to the outer side is set. By making the color density lower than the color density of the inner layer 14 on the inner side, the inner layer 12 on the outer side is colored and translucent, and the inner layer 12 on the outer side does not wrap from the portion that wraps the inner layer 14 on the inner side. Thus, it is possible to obtain a change in color tone that gradually reduces the color density toward. Therefore, it is possible to obtain a beautiful handle 10 having a transparent feeling and a change in color tone.
[0019]
(2) The material of the handle 10 can be adjusted by using different materials for the outer layer 11 and the inner layers 12 and 14. That is, various resins can be used as the inner layers 12 and 14, and the degree of freedom in designing the handle 10 can be improved. For example, the handle 10 having high bending strength can be obtained by using a flexible resin for the outer layer 11 and a hard resin for the inner layers 12 and 14. Here, not only a hard resin is used for the inner layers 12 and 14, but also the strength thereof may be improved by kneading a pigment or the like. In particular, in the present invention, even when a transparent resin that is easily damaged by fatigue is used due to a continuous bending load during use, the transparent resin is molded integrally with the colored resin, and the colored resin is completely formed into the transparent resin. Since it is embedded, the inner layers 12 and 14 and the outer layer 11 do not peel or fall off, and fatigue failure can be prevented. Further, the handle 10 having a certain chemical resistance performance can be obtained at low cost while using a resin having a high chemical resistance only for the outer layer 11 and using a resin having a low chemical resistance for the inner layers 12 and 14. Further, a resin and a colorant that should be avoided from being used in the oral cavity are also used as the inner layers 12 and 14 and completely wrapped with the outer layer 11, thereby avoiding sanitary inconvenience.
[0020]
In addition, the molding machine used for implementation of this invention should just be a thing which can project a subsequent injection material into the inside of a prior injection material, for example, a FN-D color mixing molding machine (made by Nissei Plastic Industrial Co., Ltd.) is mentioned.
[0021]
Further, the molded article of the present invention may be one in which three or more inner layers are sequentially wrapped inside the outer layer. Further, not only the color density of the same color but also a color tone change at the same time so that the color tone becomes darker toward the inside, for example, from yellow to green.
[0022]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a molded article having a transparent feeling and a change in color tone by a simple method.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a molding procedure of a gradation molding method.
FIG. 2 is a sectional view taken along line II-II in FIG.
[Explanation of symbols]
10 Handle (molded body)
11 outer layer 12 first inner layer 13 transparent intermediate layer 14 second inner layer

Claims (2)

A gradation molding method in which two or more inner layers made of a colored resin are injected into an outer layer made of a transparent or translucent resin, and a molded product having a change in color tone is formed. The transparent or translucent resin is made of gold The outer layer is formed by injection into the mold, and then the colored resin forming the first inner layer, the transparent or translucent resin forming the transparent intermediate layer, and the colored resin forming the second inner layer are sequentially injected, and the first inner layer is injected. A gradation molding method in which the layer is stretched thinly so as to have a lower concentration than the second inner layer . The molded object shape | molded by the gradation shaping | molding method of Claim 1 .

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