JPH07314497A - Two-layer molding method - Google Patents

Abstract

PURPOSE:To provide a method for uniformly forming a thick layer over the entire periphery of one surface of one layer by the molds of a core side and a cavity side in the method for molding two layers of resin by injection molding. CONSTITUTION:Primary resin is injected from a gate 17 in a cavity, and cooled to be solidified by a cooling circuit 21. Simultaneously upon cooling, the cavity side (stationary mold 16 side) of a movable mold (core side) 15 is heated by a heater 22 to form a melted layer 23 of the primary resin. Then, secondary resin is injected from a gate 18 at the surface of the layer 23 at the mold (core side) 15 side, and a secondary resin layer is cooled to be solidified. Thus, a two-layer molded form having a uniformly thick primary resin layer over the entire periphery of the one side of the secondary resin layer can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-layer molding method of resin by injection molding, and more particularly, one core side and one cavity side.
An object of the present invention is to provide a two-layer molding method capable of forming a layer having a uniform thickness over the entire circumference of one surface of one layer by one mold.

[0002]

2. Description of the Related Art First, a conventional two-layer molding method by retreating a mold will be described with reference to FIG. In FIG.
The resin of the first layer is injected from the spool 1 of a pair of molds including the fixed mold (fixed mold) 2 on the cavity side and the movable mold (movable mold) 3 on the core side to fill the cavity with the resin. Then, the first layer is cooled and solidified. Next, as shown in FIG. 3B, the movable die 3 is retracted by the thickness of the resin of the second layer, the resin of the second layer is injected from the spool 1, and after the second layer is cooled and solidified, the metal mold is removed. Remove the mold.

The problem with this method is that the resin 4 of the second layer is not molded in the end face direction of the mold as shown in FIG. Although it depends on the taper angle, there is a problem that the second layer resin cannot go around.) Therefore, the second layer cannot be molded over the entire cavity side of the first layer, resulting in incomplete two-layer molding.

Next, two fixed molds on the cavity side,
A conventional method for obtaining a complete two-layer molded product by using one movable mold on the core side will be described with reference to FIG. FIG. 3A shows the molding process of the first layer, in which the fixed mold 7 and the movable mold 8 are used to inject the resin of the first layer from the spool & runner 10 to cool and solidify the resin to form the first layer. A molded product 9 is obtained. Next, the movable mold 8 is combined with the second fixed mold 12 while holding the molded product 9 of the first layer. At this time, spool &
The runners 10 and the like are automatically cut or placed at positions that do not hinder the molding of the second layer. The second fixed die 12 and the movable die 8 are combined by mechanical rotation or the like. The same figure (b) is the molding process of the second layer,
The resin of the second layer is injected from the spool & runner 14, the resin is cooled and solidified to obtain a molded product 13 of the second layer, and finally the mold is removed.

In this method, there is no problem that the second layer is not formed in the direction of the end face of the mold, unlike the above-mentioned method.
The second layer can be molded over the entire cavity side of the layer. (See Figure (c))

However, the above method requires two fixed dies or a mechanism for rotating the movable dies for exchanging the two fixed dies, thus increasing the size of the molding machine and increasing the die equipment. However, there was a problem in terms of cost and installation space.

[0007]

As described above, in the conventional two-layer molding method by retreating the mold, the second layer cannot be molded over the entire cavity side of the first layer, resulting in incomplete two-layer molding. In addition, the conventional method of using two molds on the cavity side has problems in terms of cost and installation space, such as an increase in the size of a molding machine and an increase in mold equipment.

According to the present invention, a two-layer molding method is possible in which a thick layer is uniformly formed over the entire circumference of one surface of one layer by using one mold for each of the core side and the cavity side without increasing cost and installation space. Is intended to provide.

[0009]

In order to solve the above problems, the present invention provides a two-layer molding method in which a two-layer molded product is obtained by using one die for each of the core side and the cavity side. A first step of injecting and filling a first resin into a cavity, which is a space between two dies when the respective dies are opposed to each other, and then cooling and solidifying the first resin; A second step of heating the cavity surface side of the core side mold with a heater to make the core side mold surface side part of the first resin which is being cooled and solidified into a molten layer; A third step of injecting a second resin onto the core-side mold surface side and then cooling and solidifying the second resin and the molten layer, wherein the molten layer is included in the second step. Pressure in the cavity and the melting There is provided a two-layer molding method is characterized by using a sensor for detecting the temperature of the layer.

[0010]

EXAMPLE An example of the present invention will be described. FIG. 1 is a view showing a cross-sectional structure of a mold, which includes one fixed mold 16 on the cavity side and one movable mold 15 on the core side.
Perform layer forming. The resin of the first layer is injected from the fixed mold side (cavity side) using the gate 17, and the resin of the second layer is injected from the movable mold side (core side) using the gate 18. .

Next, the injection method will be described. FIG. 2 shows an outline of filling the primary resin (first layer resin). The primary resin is injected into the cavity from the primary resin gate 17 as a resin having large particles that does not enter the bosses and ribs of the 20 provided on the movable mold 15. Fixed type 1
After the surface of the cavity 6 is filled with the primary resin, it is cooled by the cooling circuit 21 and the primary resin is hardened.

Simultaneously with the cooling and solidification (or after the cooling and solidification),
The surface of the movable mold (core side) 15 on the cavity side is heated by the heater 2
The core side surface of the primary resin layer which is being heated and cooled and solidified by 2 is melted to form a molten layer 23. Melting layer 23
The thickness, temperature, etc. are controlled by the pressure / temperature sensor 25 so as to have predetermined values. The pressure / temperature sensor 25 is shown in FIG.
As shown in FIG. The molten layer 23 plays an important role for filling the secondary resin (second layer resin).

FIG. 3 shows an outline of the secondary resin filling. The secondary resin is injected from the secondary resin gate 18 onto the surface of the molten layer 23 on the movable mold (core) 15 side. After the injection of the predetermined amount of the secondary resin is completed, water or the like is caused to flow through the cooling circuit 27 to cool and solidify the secondary resin layer 26. At this time, the secondary resin boundary surface 28
As shown in FIG. 5, the molten layer 23 of the primary resin is pushed into the cavity-side primary resin layer by the injection pressure of the resin (in the direction of arrow 29). The molten layer 23 is solidified 1
Since it is cooled by the next resin layer, the primary resin layer side of the molten layer 23 is solidified to be a layer having a relatively high density and a high specific gravity. Therefore, the joint surface between the primary resin layer and the secondary resin layer after being cooled and solidified becomes a strong joint surface 24 due to the anchor effect having complicated irregularities as shown in FIG. 3B.

FIG. 6 shows an outline of a two-layer molded product after cooling and solidification. This molded product is removed from the mold and the gate cut part 3
At 0 and 31, the gate and runner are separated and completed as a molded product.

As shown in FIG. 6, in the method of the present embodiment, one die for each of the core side and the cavity side, which is almost the same as the conventional one, does not cause an increase in cost and installation space, and one side of the secondary resin layer It is possible to obtain a two-layer molded product provided with a primary resin layer having a uniform thickness over the entire circumference.

For example, a two-layer molded product in which the primary resin layer is a soft resin and the secondary resin layer is a hard resin is
The primary resin layer is used as an outer side for a housing of a television receiver (see FIGS. 10 and 11). Since the primary resin layer is thick, it is made of cushion material, and this two-layer molded product is hard to be scratched and has a soft touch appearance.
Further, it is also effective as a casing other than the television receiver, for example, a casing of a radio cassette player, a vacuum cleaner, or the like that is easily scratched and is often moved such as being carried around.

In the above embodiment, the cavity side is the fixed type and the core side is the movable type, but the opposite may be the case, and the primary resin layer may be filled from the core side.

[0018]

As described above, the two-layer molding method of the present invention is
A layer having a uniform thickness can be uniformly formed over the entire circumference of one surface of one layer by using one mold for each of the core side and the cavity side without increasing cost and installation space. Furthermore, the joint surface between the two layers is a strong joint surface due to the anchor effect.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a mold used in the present invention.

FIG. 2 is a diagram showing an outline of primary resin filling in one example.

FIG. 3 is a diagram showing an outline of secondary resin filling in one example.

FIG. 4 is a diagram showing a position of a pressure / temperature sensor.

FIG. 5 is a diagram showing a state of a molten layer of a primary resin.

FIG. 6 is a diagram showing an outline after completion of injection of a secondary resin according to an embodiment.

FIG. 7 is a diagram showing an example of use of a product molded according to the present invention.

FIG. 8 is a diagram showing an example of use of a product molded according to the present invention.

FIG. 9 is a diagram showing a conventional example.

FIG. 10 is a diagram showing a conventional example.

[Explanation of symbols]

 15 Movable type (core side) 16 Fixed type (cavity side) 17, 18 Gate 22 Heater 23 Melt layer of primary resin 25 Pressure / temperature sensor

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // B29L 9:00

Claims (1)

[Claims] 1. A two-layer molding method for obtaining a two-layer molded product by using one mold for each of a core side and a cavity side, in which two molds for one core side and one cavity side are opposed to each other.
A first step of injecting and filling a first resin into a cavity that is a space between two molds, and then cooling and solidifying the first resin; And a second step of forming the core-side mold surface side portion of the first resin that is being cooled and solidified into a molten layer, and a second resin on the core-side mold surface side of the molten layer. And then a third step of cooling and solidifying the second resin and the molten layer, wherein in the second step, the inside of the cavity is formed in order to make the molten layer have a predetermined thickness. A two-layer molding method, characterized in that a sensor for detecting the pressure and the temperature of the molten layer is used.