JPH1052835A - Method for sandwich molding of resin molded article, its mold and resin molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evable filling of secondary resin in a projected part by a method wherein an occupying block is retreated and both resins are introduced into a space generated thereby. SOLUTION: Before resins are filled, an occupying block 9 is forwarded into a recessed part 8 to occupy the recessed part by the occupying block 9 and when the primary resin 10 has fully spread in the whole cavity 3, the occupying block 9 is retreated from the recessed part. As a space is formed in the recessed part by retreating the occupying block 9, the primary resin 10 flows into the recessed part as it is drawn thereinto and being accompanied with it, the secondary resin 11 is also drawn into the recessed part and the primary resin 10 and the secondary resin 11 are filled in the recessed part. Boss part of the molded article has a structure with the same characteristics as those for the parent body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a two-color molding machine to inject secondary resin for forming a core layer into the same cavity at the same time as or later than the primary resin for forming a skin layer. The present invention relates to a sandwich molding technique for a resin molded product that forms a resin molded product having an inner / outer double structure.

[0002]

2. Description of the Related Art Resins are suitable for weight reduction but lack strength. On the other hand, resins have sufficient strength but are too heavy.
Since the characteristics vary depending on the type, such as being suitable for a product having a dense and smooth surface and being extremely expensive, the resin used is selected from those satisfying the characteristics required for the product. . However, for example, a resin composition that satisfies all of the multiple properties required by a product, such as toughness and light weight, surface smoothness is required, and those properties are one rank higher, is intended for special applications. In many cases, it is difficult to obtain a small-volume product, or it cannot be adopted because of a price problem. Therefore, conventionally, for example, a sandwich layer for forming a product that satisfies both characteristics by wrapping a core layer formed of a high-strength and inexpensive foamable resin with a skin layer having a low strength and a high surface accuracy. Many molding methods are used.

[0003]

Among the injected resins, the secondary resin is concentrated at the center of the cavity.
In a product-shaped cavity having a small protrusion such as a boss or a seat, as shown in FIG. 10, a primary resin for forming a skin layer is formed in a recess 8 corresponding to a boss as a protrusion. Although 10 enters, the secondary resin 11 does not penetrate into the recess 8 and the boss portion is formed only of the skin layer having no core layer, so that the advantage of the sandwich molding is not utilized in the protruding portion.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a sandwich molding technique which allows a secondary resin to be filled in a projecting portion, and has a structure corresponding to the projecting portion in a product-shaped cavity having the projecting portion. When the occupied block is advanced into the space, and the cavity is filled with the first and second resins injected from the two-color molding machine,
Evacuate the occupied block and introduce both resins into the space created by that, and fill the secondary resin into the space corresponding to the protruding portion, or in the protruding portion in the product-shaped cavity having the protruding portion The corresponding space portion is enlarged, the occupation block is advanced into a space including at least the enlarged portion, and when the first and second resins injected from the two-color molding machine are filled in the cavity, the occupancy is increased. A method of sandwich-molding a resin molded product in which both blocks are introduced into the space created by retracting the block and the secondary resin is filled into the space corresponding to the protrusion, and a product-shaped cavity having the protrusion Into the space corresponding to the projecting portion or in the space of the enlarged portion formed by enlarging the projecting portion. Avoid possible occupy blocks provided a resin molded article of the sandwich mold, as well as the resin molded article formed by the method. The occupied block can be forcibly advanced and retracted by a cylinder, or advanced into a space by a spring force, and can be retracted by a resin pressure in a cavity.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sandwich molding method for a resin molded product according to the present invention will be described with reference to the drawings. FIG. 1 shows a molding apparatus using the mold of the present invention, wherein 1 is a primary cylinder, 2 is a secondary cylinder, 3 is a cavity formed in a mold 4,
Is a thin rectangle having a width of 120 mm, a length of 200 mm, and a thickness of 6.5 mm, and a gate 5 is provided at the center of one side surface. The gate 5 is connected via a sprue 6 formed in the mold 4 to a nozzle 7 having an inner / outer dual structure having an outlet of the secondary cylinder 2 coaxially arranged in the outlet of the primary cylinder 1. The primary cylinder 1, the secondary cylinder 2, and the nozzle 7 constitute a two-color molding machine. The cavity 3 is formed with a concave portion 8 corresponding to a boss which is a protrusion of a molded product. The concave portion 8 has an outer diameter of 50 mm, an inner diameter of 42 mm, and a height of 25 m.
The occupation block 9 occupying the inside of the concave portion 8 by projecting into the concave portion 8 has a cylinder 9a.
It is provided so that it can appear and disappear freely. The occupation block 9
When the occupation block 9 is fully advanced, the inside of the concave portion 8 is completely occupied and the resin does not flow into the concave portion 8.

[0006] From a device provided with a two-color molding machine having the primary cylinder 1 and the secondary cylinder 2, a primary resin 10 for forming a core layer and a secondary resin for forming a skin layer are injected almost simultaneously. , The secondary resin 1 injected from the secondary cylinder 2
1 is filled in the central portion of the primary resin 10 injected from the primary cylinder 1. In the examples, the primary resin forming the skin layer is provided with a melt index value (ASTM D12).
190 ° C, load 2.16 measured in accordance with No.39
Polyacetal having a value of 9.2 (g / 10 minutes) is used, and impact-resistant polystyrene having a melt index value of 3.6 (g / 10 minutes) is used as a secondary resin forming the core layer. did. The molding conditions were as follows: the cylinder temperature was 190 ° C. and the injection speed was 67 m on both the primary resin side and the secondary resin side.
m / sec, time difference between injection of primary resin and injection of secondary resin 1.5 seconds, maximum resin pressure during injection filling and holding pressure 30Mpa after injection filling, mold temperature 60 ° C, cooling time 85 seconds. First, the occupied block 9 is recessed 8
In the state of being retracted from the inside, the primary resin 10 and the secondary resin 11 were injected into the cavity 3 under the above conditions, and the molded product was examined. As a result, as expected, an injection pattern as shown in FIG. 2 was obtained, and the presence of the core layer in the recess 8 was not recognized.

Next, in order to mold by the method of the present invention, the occupied block 9 is formed as shown in FIG.
The occupation block 9 is occupied by the occupation block 9 and the occupation block 9 is evacuated from the depression 8 as shown in FIG. By retracting the occupation block 9, the recess 8
Since a space is formed in the inside, the primary resin 10 flows so as to be drawn into the concave portion 8, and accordingly, the secondary resin 11 is also drawn into the concave portion 8, and the primary resin 10 enters the concave portion 8.
And the secondary resin 11 are filled. Inspection of the molded product revealed that at least 50% or more of the core layer was present at a position 10 mm from the tip in the boss portion, and it was possible to form the core layer in the projecting portion, which was impossible with conventional means. Was confirmed (FIG. 5).

Thus, the primary resin 10 and the secondary resin 1
1 is filled in the concave portion 8, the boss portion of the molded product also has a structure having the same characteristics as the base body, and the base body 3a and the boss portion 8
The core layer 11a is continuous with each other, and the integral element is also high. The mold 3 can be replaced with a mold mounted on an existing device, so that the present invention can be implemented using the existing device.

In the above-mentioned embodiment, the occupation block 9 is forcibly advanced and retracted by the cylinder 9a in the recess 8 having a shape corresponding to the boss portion. As shown in FIG. The structure is such that the occupation block 9 is advanced into the recess 8 by using
When the cavity 3 is filled with the resin and the pressure is maximized, the pressure of the filled resin (3.
If the occupation block 9 is adjusted to retreat from the recess 8 at 0 Mpa), the state in which the occupation block 9 has advanced into the recess 8 is maintained until the cavity is filled with resin, and the operation timing of the occupation block 9 is automatically adjusted. Is controlled.
Therefore, when the primary resin 10 and the secondary resin are injected into the cavity 3 from the two-color molding machine under the same conditions as in the above-described embodiment by the above-described apparatus, the occupied block 9 is set when the pressure is maintained (a in FIG. 6). Was pushed back against the repulsive force of the spring 12, and the primary resin 10 and the secondary resin 11 were extruded into the recess 8 (FIG. 6B), and a molded product similar to that of the above embodiment was obtained. Note that the spring force for causing the occupation block 9 to advance into the recess 8 may use a pulling force as shown in FIG.

The occupied block 9 not only advances and retracts with respect to the concave portion 8 alone, but also the occupied block 9 shown in FIGS.
As illustrated in FIG.
Alternatively, the occupied block 9 is provided in the recess 8 including the enlarged portion 13.
Can be advanced and retracted, so that more secondary resin 11 can be filled in the recess 8. In this case, it is necessary to remove the molded portion corresponding to the enlarged portion from the molded product.

In the mold provided with the enlarged portion, as shown in FIGS. 9A, 9B and 9C, the occupation block 14 having the hollow portion 14a corresponding to the enlarged portion 13 is moved in the projecting direction of the boss. By moving it in the direction orthogonal to the
3, the hollow portion 14a and the solid portion 14b can be switched so that they are alternately located, and the solid portion 14b occupies the enlarged portion 13 until the recess 8 is filled with resin. When the resin is filled in the concave portion 8, the hollow portion 14 a becomes the enlarged portion 13.
The resin is introduced into the hollow portion 14a by retracting the occupied block (solid portion) so as to be positioned inside the hollow portion 14a.
When the resin is filled in the space a, the occupation block 14 is advanced again to separate the resin filled in the hollow portion 14a from the resin filled in the concave portion 8, so that there is no need to remove unnecessary portions after molding.

The protruding portion is not limited to the boss portion, but includes all protrusions integrally formed with the base such as ribs, rising walls, and tongue pieces. In addition, the present invention aims to advance the core layer to the protruding portion, and the occupied block does not deny the advancement into the cavity, even if the enlarged portion is provided, The occupied block that has been advanced can be retracted to a position where the occupied block is completely withdrawn from the enlarged portion. Conversely, the occupied block can be advanced halfway into the concave portion, and then withdrawn completely from the concave portion or the enlarged portion. It can be evacuated halfway through. Furthermore, the structure of the occupied block and the enlarged portion can be changed as appropriate without departing from the spirit of the present invention, such as forming the enlarged portion not only in the projecting direction of the protruding portion but also in the lateral direction with respect to the projecting direction.

[0013]

According to the sandwich molding method of the present invention, the protrusion can be filled with the secondary resin by the operation of retracting the occupied resin from the concave portion. And if you use the enlarged part that is formed continuously to the protruding part, the ratio of the core layer can be increased, and if the occupied block is made to advance by the spring force, the retracting timing can be adjusted by changing the spring force. No driving means such as a cylinder and the like is required. The mold provided with an occupied block that advances and retracts with respect to the recess can be used to carry out the resin sandwich molding method of the present invention by replacing the mold with a mold provided in an existing device, and can be formed by the method. Since the molded product has a core layer formed in the protrusion, the characteristics of the protrusion are at the same level as the base.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an apparatus for performing a resin sandwich molding method according to the present invention.

FIG. 2 is an explanatory diagram when injection molding is performed with an occupied block retracted.

FIG. 3 is an explanatory view of a molding step.

FIG. 4 is an explanatory view of a molding step.

FIG. 5 is an explanatory view of a molded product.

FIG. 6 is an explanatory diagram of a modified example.

FIG. 7 is an explanatory diagram of a modified example.

FIG. 8 is an explanatory diagram of a modified example.

FIG. 9 is an explanatory diagram of a modified example.

FIG. 10 is an explanatory diagram of a conventional example.

[Explanation of symbols]

1. Primary cylinder, 2. Secondary cylinder, 3. Cavity, 3a. Base, 4. Mold, 5. Gate, 6.
.. sprue, 7 nozzle, 8 recess, 8a boss, 9 occupied block, 9a cylinder, 10
· Primary resin, 11 · · · secondary resin, 11a · · · core layer, 1
2. Spring, 13 enlarged section, 14 occupied block, 14a hollow section, 14b solid section.

Claims (6)

[Claims] 1. A first and a second resin injected from a two-color molding machine into a cavity of a product-shaped cavity having a protruding portion in a space corresponding to the protruding portion in a product-shaped cavity. When the space is full, the occupied block is retracted, the two resins are introduced into the space created by the occupied block, and the secondary resin is filled into the space corresponding to the protruding portion. 2. A space portion corresponding to the protrusion in a product-shaped cavity having a protrusion is enlarged, and an occupied block is advanced into a space including at least the enlarged portion. When the first and second resins injected from the molding machine are full, the occupied block is retracted, the two resins are introduced into the space created thereby, and the secondary resin is filled into the space corresponding to the protrusion. Sandwich molding method for resin molded products. 3. The sandwich molding method for a resin molded product according to claim 1, wherein the occupied block is forcibly advanced and retracted by a cylinder. 4. The sandwich molding method for a resin molded product according to claim 1, wherein the occupied block is advanced into a space by a spring force and retracted by a resin pressure in a cavity. 5. An occupation block capable of moving in and out of a space corresponding to the projecting portion or a space of an enlarged portion formed by enlarging the projecting portion in a product-shaped cavity having a projecting portion. For sandwich molding of molded resin products. 6. A resin molded product formed by the molding method according to claim 1.