JPH0618748B2 - Manufacturing method for multicolored plastic moldings - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a plastic molded product, particularly a multicolored plastic molded product having a unique design that is not reproduced.

[Conventional technology]

Up to now, many methods have been proposed for obtaining a molded product having a color pattern using only a molding resin.

The simplest method is a method in which a plurality of resin pellets of the same quality but different colors are mixed, charged into a molding hopper, and melt-kneaded in a cylinder. Fig. 5 shows a dedicated molding machine for high-accuracy mixing ratio and mass production. Two resin charging hoppers are installed on one screw having two grooves, and the rear hopper charges resin pellets into one groove, and the front hopper charges resin pellets having another color into the next groove. . These resins are lightly kneaded at the tip of the nozzle, and a molded product having shades on the blended color is obtained by injection molding.

[Problems to be Solved by the Invention]

In the conventional multicolor molding, the mixed resin is melted and kneaded through the screw of the molding machine, so that it is already blended at the tip of the nozzle. Therefore, when injection molding is carried out by this method, it is difficult to produce a clear color pattern due to the blended dark and light colors. There is also a method of manufacturing a marble-patterned molded product by mixing two kinds of resins having different melting temperatures, but the strength is poor because the resins are not completely melt-bonded.

It is an object of the present invention to provide a method for producing a molded product having a clear black ink-like disordered color pattern using only the same type of molding resin.

[Means for Solving the Problems]

1 and 2 show an embodiment of an apparatus for carrying out the method of the present invention.

Internal heater 12 and external heater 13 on gate sprue 15
Using a hot runner mold having a structure in which both are used together, first, the template is opened and a resin insert 10 having a color different from the base color of the molded product is inserted into the tip 16 of the hot chip and left as a solidified layer on the inner wall surface of the gate sprue. Next, a resin 11 having a base color of the molded product is injection-molded, and the solidified layer is gradually poured into the base resin 11 to obtain a molded product having a clear redwash-like color pattern.

By adjusting the melting amount of the inserted insert by controlling the external heater, the ratio of the insert mixed in the base resin can be changed.

In addition, a multicolor molded product can be obtained by using an insert as shown in FIG. FIG. 4a shows an insert consisting of only one color, and by this insert, a color different from the base resin is mixed into the one type base resin.
Fig. 4b shows an insert for mixing three colors, and by combining three parts of each color shown in the bottom of this figure as shown in the figure to form an insert, the three colors are made into the base resin. It can be mixed. Further, by combining parts as shown in FIG. 4c, it is possible to similarly mix three colors.

The resin usable in the method of the present invention is a thermoplastic resin,
For example, ABS, polyethylene, polypropylene, styrene, and polyacetal, but additives that exclude fluidity, for example, a resin containing no glass fiber are preferable.

The injection molding of the present invention may be performed under normal injection conditions. However, the color ratio is changed by controlling the external heater between the melting point of the resin and the decomposition limit thereof.

[Work]

The method of the present invention uses a hot runner mold having internal and external heaters to gradually flow out a solidified resin having a color different from that of the base resin on the inner wall surface of the gate sprue into the base resin due to internal pressure and preheating during molding. Form a pattern.

〔Example〕

FIG. 2 is a block diagram of an embodiment of the present invention, showing shell molding of a floppy disk. The injection molding machine uses 150TON,
The mold is a hot runner mold that takes two sets and is molded using ABS resin. The injection conditions are an injection pressure of 80 to 100 kg / cm ² , an injection time of 0.5 to 1.5 seconds, and a mold temperature of 15 to 60 ° C. In order to keep the base resin 11 in a molten state, the internal heater 12 of the gate sprue is set to 210 to 250 ° C. On the other hand, the external heater 13 is initially set to 0 ° C.

First, the bolt 15 is removed, and the template is moved in the direction of the arrow. After inserting the molded product insert 10 of red ABS resin, which is the color to be the molded product pattern, into the tip of the hot chip, return the template to its original position and tighten the bolts. Next, the black base resin 11 is melt-flow injection molded. At this time, the temperature of the external heater 13 is adjusted between 210 and 250 ° C. to give a red pattern of light and shade.

In this way, the molding insert 10 gradually flows out into the base resin 11 to form a unique black-and-white color pattern as shown in FIG.

〔The invention's effect〕

By the method of the present invention, a molded product having a multicolored and unique pattern can be obtained from the same kind of resin.

[Brief description of drawings]

FIG. 1 is a general view of an apparatus for carrying out the method of the present invention. FIG. 2 is a partially enlarged view of the device. FIG. 3 is a schematic diagram showing a color pattern obtained by this method. FIG. 4 is a schematic diagram showing various inserts. FIG. 5 is a schematic view showing a conventional multicolor molding machine. 10 …… Molded part insert, 11 …… Base resin, 12 …… Internal heater, 13 …… External heater, 14 …… Manifold heater, 15 …… Fixed side mold plate bolt.

Claims (3)

[Claims] 1. A method for producing a plastic molded product having two or more colors by a single injection molding, using a hot runner mold having a structure in which an internal heater and an external heater are used together in a gate sprue part. Open the hot tip and insert a resin insert with a color different from the base color of the molded product to leave it as a solidified layer on the inner wall surface of the gate sprue, and then injection-mold the resin with the base color of the molded product. How to become. 2. Method according to claim 1, characterized in that the amount of melt of the insert is adjustable by using a hot runner mold with a controllable external heater. 3. The method according to claim 1, wherein the insert is a combination of parts of several colors to enable multicolor molding even at a single point gate.