JPH09131760A - Manufacture of synthetic resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously obtain a synthetic resin molding equipped with a sandwiched structure consisting of a core and outer layers and a second synthetic resin molding equipped with a single layer structure. SOLUTION: Outer layer molding material M1 is injected in the cavity 17 of a mold. Then, core molding material M2 is injected so as to be flown in the outer layer molding material M1 in the cavity 17 and, at the same time, both the materials M1 and M2 are run in the cavity 17. In the cavity 17, in which a synthetic resin molding 1 equipped with a sandwich structure is molded, a second molding cavity 19 for molding a second synthetic resin molding 5 having a single layer structure only made of the outer layer molding material M1 is communicated through a communicating hole 18 with an area 17b, in which the outer layer molding material M1 is filled preferentially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a synthetic resin molded article, and more particularly to the production of a synthetic resin molded article having a sandwich structure composed of a core and an outer layer covering the core. The first step of injecting the material into the molding cavity of the mold, and injecting the molding material for the core into the molding material for the outer layer in the cavity and flowing the molding material for the outer layer and the core into the cavity And a second step for improving the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a bumper for an automobile is known as a synthetic resin molding of this kind. The bumper is composed of a bumper main body extending from the center of the vehicle body in the left-right direction and a pair of bumper side portions connected to both ends of the bumper main body, and has a substantially uniform thickness over the entire body.

Therefore, the cavity of the mold has a main region for molding the bumper main body portion and a pair of side region regions for molding a pair of bumper side portions, and also the entire region depending on the thickness of the bumper. Has uniform spacing. The gate is open, for example, in a region where the upper portion of the bumper main body is formed in the main region.

[0004]

In this kind of manufacturing method, while the molding material for the outer layer is flowing in the cavity, the molding material for the core flows into the molding material for the outer layer. After the molding material is filled in the cavity and the flow is stopped, it is difficult to flow the core molding material into the outer layer molding material.

Under such a circumstance, according to the conventional method, the outer layer molding material injected into the cavity in the first step molds the lower portion of the bumper main body portion in the main region where the gate is opened. Since the flow is stopped by preferentially and early filling the filled area, the molding material for the core cannot flow into the material of the lower portion.

For this reason, according to the conventional method, it is difficult to obtain a bumper having a sandwich structure over the entire structure.

[0007]

The present invention makes it possible to obtain a synthetic resin molded product having a sandwich structure throughout by using a mold having a specific structure, and at the same time comprises only a molding material for an outer layer. It is an object of the present invention to provide the above-mentioned manufacturing method capable of obtaining a second molded product having a single layer structure.

[0008] To achieve the above object, according to the present invention,
In manufacturing a synthetic resin molded body having a sandwich structure composed of a core and an outer layer covering the core, a first step of injecting a molding material for the outer layer into a molding cavity through a gate of a mold, and a core A second step of injecting a molding material for the outer layer into the molding material for the outer layer in the gate and the cavity and flowing the molding material for the outer layer and the core in the cavity, There is provided a method for producing a synthetic resin molded body using a mold having the following configuration.

That is, for molding a second synthetic resin molded body having a single-layer structure composed of only the outer layer molding material, in a region where the outer layer molding material is preferentially filled in the molding cavity. The second molding cavity is in communication.

When the second cavity as described above is present in the mold, the material reaching the area where the molding material for the outer layer is preferentially filled does not stop there but the second cavity. Flows in. With the flow of the molding material for the outer layer, the molding material for the core flows into the material in the area, so that a synthetic resin molded body having a sandwich structure over the whole can be obtained. At the same time, the second cavity makes it possible to obtain a second synthetic resin molded body having a single-layer structure made of only the outer layer molding material.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
A bumper 1 as a synthetic resin molded body having a sandwich structure is attached to the front portion. The sandwich structure comprises a core 2 and an outer layer 3 covering the core, as shown in FIGS.

The bumper 1 is composed of a bumper main body 4 ₁ extending in the left-right direction from the center portion a of the vehicle body, and a pair of bumper side portions 4 ₂ connected to both ends of the bumper main body 4 ₁ , and is substantially uniform throughout. Has a wall thickness.

As shown in FIG. 1, simultaneously with the molding of the bumper 1, a pair of left and right L-shaped bumper protector moldings 5, which are second molded bodies, are molded. Each protector molding 5 is made of only the same material as the outer layer 3 and has a single-layer structure.

The molding material for the core 2 is polypropylene (P) modified with ethylene propylene rubber (EPR).
The main material is obtained by pulverizing a recovered bumper molded using P) and having a thermosetting synthetic resin coating film on the surface. The molding material of the outer layer 3 is mainly composed of polypropylene modified with ethylene propylene rubber.

4 and 5, an injection molding apparatus 6 used for manufacturing the bumper 1 injects a first injection unit 8 having a screw 7 for injecting an outer layer molding material, and a core molding material. Therefore, the second injection unit 10 having the screw 9, the nozzle 11 connecting the injection units 8 and 10, the hot runner block 12 connected to the nozzle 11, and the split mold 13 detachable from the hot runner block 12 are provided. It has and.

The supply path 14 of the nozzle 11 is a hot runner.
15 through the runner 16 of the mold 13 ₁To communicate with that la
Nanna 16₁Gate (gate) 16 extending from
_TwoCommunicates with the bumper molding cavity 17. In the figure, H
₁Is a band heater, H_TwoIs a cartridge heater.

The mold 13 is composed of a fixed mold 13 ₁ on the hot runner block 12 side and a plurality of lower moving molds 13 _{2 to} 13 ₅ which can move forward and backward with respect to the fixed mold 13 ₁ . Bumper molding cavity 17 of the mold 13 has a main area 17 ₁ for molding the bumper main portion 4 _1, and a ₂ pair of side areas 17 for molding the pair of bumper side portions 4 _2.

The film gate 16 ₂ is open in the main region 17 ₁ at the end of the lower section 17a forming the upper part 4a of the bumper main body 4 ₁ . In this case, as shown in FIG. 1, the runner 16 ₁ extends over substantially the entire length of the bumper main body 4 _{1 in} the left-right direction and the film gate 16 ₂
Has approximately the same length as the runner 16 ₁ .

Due to the arrangement of the film gate 16 _{2 as} described above, the bumper main body 4 is formed in the main region 17 ₁ .
_The upper region 17b for molding the lower portion 4b of _{1 is} a region where the outer layer molding material is preferentially and prematurely filled.

Therefore, a pair of communication holes 1 are provided in the upper area 17b.
The pair of second cavities 19 are communicated with each other through the inner ring 8 (only one of which is shown in FIG. 4), and the pair of protector moldings 5 are molded by the second cavities 19.

A hollow outer needle 20 ₁ in the nozzle 11
And a solid inner needle 20 ₂ are concentrically arranged.
In the outer needle 20 _1, the distal end side of the valve portion 20a is opposed to the supply passage 14, the piston 21 of the proximal cylinder 2
It is slidably fitted in the inside of 2. The piston 21 and the cylinder 22 form an operating mechanism 23 for opening and closing the supply path. In the inner needle 20 _2, the valve portion 24 of the tip end is opposed to the valve hole 25 formed in the outer needle 20 ₁ of the valve portion 20a, the piston 26 on the proximal end side is formed on the base end side of the outer needle 20 ₁ It is slidably fitted in the formed cylinder portion 27. The piston 26 and the cylinder 27 constitute a valve hole opening / closing operation mechanism 28.

The outer needle 20 ₁ has a tapered outer peripheral surface continuous with the valve portion 20 a, and an outer passage 29 is formed between the tapered outer peripheral surface and the inner peripheral surface of the nozzle 11. One end of the outer passage 29 is connected to the supply passage 14, and the other end is connected to the nozzle 11.
The first injection unit 8 and the first injection unit 8 are communicated with each other. The outer needle 20 ₁ has a straight outer peripheral surface at its base end side, it can be closed through hole 30 by the outer peripheral surface thereof.

The inner needle 20 ₂ has a tapered outer peripheral surface continuous with the valve portion 24, and an inner passage 31 is formed between the tapered outer peripheral surface and the inner peripheral surface of the outer needle 20 ₁ . One end of the inner passage 31 in the valve hole 25, the other end is adapted to respectively communicate with the second injection unit 10 through the hole 32, 33 of the outer needle 20 ₁ and the nozzle 11. Further, the inner needle 20 ₂ has a straight outer peripheral surface on its proximal end side, and the outer peripheral surface can close the through hole 32.

Next, a specific manufacturing example of the bumper 1 using the injection molding device 6 will be described.

1-3, the dimensions of each part of the bumper 1 are as follows. Based on the vehicle body 2, the left-right direction length b = 1700 mm of the bumper main body 4 ₁ and each bumper side 4 ₂
The length in the front-rear direction c = 550 mm, the height d of the bumper main body 4 ₁ = 320 mm, the height e of each bumper side 4 ₂ e = 300 mm,
The wall thickness of the bumper 1 is t ₁ = 4 mm. In each protector molding 5, one piece 5a has a length f = 300 mm, and the other piece 5b has a length g =
The thickness is 200 mm and the thickness t ₂ = 4 mm.

The bumper 1 and the protector molding 5
The dimensions of the respective parts of the cavities 17 and 19 are determined according to the shape of. In this case, the length h of the film gate 16 in the left-right direction is 1200 mm, and the length in the front-rear direction is k = 2 mm. A. Preparation of Molding Material for Core As the recovery bumper, a material molded using polypropylene modified with ethylene propylene rubber and having a two-component urethane coating film on its surface was selected. The composition of the recovered bumper was as follows.

Polypropylene 64% by weight Ethylene propylene rubber 28% by weight Talc 7% by weight Coating film 1% by weight A recovery bumper is put into a crusher for crushing and then crushing.
The material is put into a granulator and melt-kneaded.
Through an 80-100 mesh filter to remove coarse particles
After that, the melt-kneaded material is passed through a small tube with an inner diameter of about 1 mm.
To form a linear object.
Then, a pellet-shaped molding material for a core was obtained. B. Preparation of molding material for outer layer
Aiming at, a mixture of 63% by weight of polypropylene, 30% by weight of ethylene propylene rubber, and 7% by weight of talc is charged into a granulator, and the method described in the above section A is used.
A pellet-shaped molding material for an outer layer was obtained in the same manner. C. Manufacturing of bumper (i) In FIG. 4, the first injection unit 8 was molded for the outer layer.
The material is charged and held in a molten state at 210 ° C., and
The molding material for the core is charged into the second injection unit 10 and 2
It is kept in a molten state at 00 ° C. Fixed type 13₁And each
Movable type 13_Two~ 13_FivePreheating temperature is 40 ℃, 5
0 ° C. (ii) In the first step, as shown in FIG.
9 is “communication”, and the inside passage 31 is in the “blocked” state
Then, under the operation of the first injection unit 8, the outer layer molding material M₁
Supply path 14, hot runner 15, runner 16₁and
Film gate 16 _TwoFor bumper molding of die 13 through
It was injected into the cavity 17. (iii) As a second step, as shown in FIG.
Under operation of the unit 8, the supply passage 14 side of the outer passage 29 is valved.
It is squeezed by the portion 20a, and the inner passage 31 is in the "communication" state.
In the state, the core forming process is performed under the operation of the second injection unit 10.
Forming material M_TwoAnd molding material M for the core_TwoSupply
Road 14, hot runner 15, runner 16₁, Film film
16_TwoAnd molding material M for outer layer in cavity 17
₁Molded for outer layers and cores while flowing in
Material M₁, M_TwoFlow into the cavity 17 and
Layer molding material M₁Flow into the second cavity 19
Then, the operation of the second injection unit 10 was stopped. (iv) As a third step, as shown in FIG.
9 is “communication”, and the inside passage 31 is in the “blocked” state
Then, under the operation of the first injection unit 8, the outer layer molding material M₁
Supply path 14, hot runner 15, runner 16₁You
And film gate 16_TwoFor outer layer of double structure existing inside
And core molding material M₁, M_TwoInto cavity 17
Molding the core 2 and outer layer 3 by extrusion, then
The operation of the first injection unit 8 was stopped. (v) Separate the mold 13 from the hot runner block 12
Then, the mold is opened and the bumper 1 and the pair of left and right
Obtained Protectamol 5.

After the manufacturing process, since the outer layer molding material M ₁ is held in the hot runner 15 in a molten state, the bumper 1 and each protector molding 5 can be continuously molded.

Table 1 shows the first to the first methods for manufacturing the bumper 1.
Outer layer molding material M for the third step ₁And core molding
Material M_TwoInjection time and injection speed are shown.

[0030]

[Table 1]

FIG. 9 is a graph showing the relationship between the injection time and the injection speed based on Table 1. In this case, the injection speed is two steps for the outer layer molding material M ₁ in the first step, three steps for the core molding material M _{2 in} the second step, and two steps for the outer layer molding material M ₁ . In the three steps, the outer layer molding material M ₁ was controlled in one step.

[0032] In the mold 13, The presence of the second cavity 19 as described above, the material M ₁ to the outer layer forming material M ₁ has reached the upper section 17b of the main area 17 ₁ which is filled preferentially Is the communication hole 18 without stopping there.
And then flows into the second cavity 19. With the flow of the outer layer molding material M ₁ , the core molding material M ₂ flows into the material M ₁ in the upper region 17b.

As shown in FIG. 9, if the injection speed Vc of the core molding material M ₂ in the second step is set to be faster than the injection speeds Va, Vb of the outer layer molding material M ₁ in the first step, As shown in FIG. 7, the outer layer molding material M ₁
When the front side of the molding direction M of the core reaches the vicinity of the end of the second cavity 19, the front side of the molding material M ₂ of the core can exist in the molding material M ₁ for the outer layer in the upper section 17b. . In this case, the injection speeds Vb and Vf of the outer layer molding material M ₁ are set to the injection speeds Va and Vf in the first step.
Below Vb, in this embodiment, the main injection speed Vf is Vf <
By setting Va and Vb, the injection speed difference between the two materials M ₁ and M ₂ can be increased without increasing the injection speed Vc of the core molding material M ₂ so much.

Further, the molding material M ₁ for the outer layer in the third step
The injection speed Vg of the outer layer molding material M ₁ in the second step
Of the final injection speed Vf or less, and in this embodiment, the injection speed Vg
Is set to Vg <Vf, the outer layer molding material M ₁ does not flow into the core molding material M ₂ in the third step, so that the film gate communicating portion of the bumper 1 is formed only by the outer layer molding material M _1. Can be molded by.

In this way, the bumper 1 having a sandwich structure over the whole can be obtained, and at the same time, the second cavity 19 allows the pair of left and right pairs having a single-layer structure composed only of the outer layer molding material M ₁ . The protector molding 5 was obtained.

In this bumper 1, since the filling rate of the core molding material M ₂ prepared from the recovery bumper is high, it is effective in reducing the production cost of the bumper 1 and saving resources.

As the outer layer molding material M ₁ used for manufacturing the bumper 1, the following materials can be mentioned in addition to the above materials. [Formulation Example 1] Polypropylene 63% by weight Ethylene propylene rubber 30% by weight Talc 7% by weight Weather resistance stabilizer 1phr Ultraviolet absorber 1phr Carbon black (pigment) 3phr Paintability improving modifier 3phr [Formulation Example 2] Polypropylene 60% by weight ethylene-propylene rubber 30% by weight talc 10% by weight weathering stabilizer 1phr ultraviolet absorber 1phr carbon black as the core forming material M ₂ used in the manufacture of (pigment) 3 phr coatability improving modifier 3 phr bumper 1, the In addition to the following, the following can be mentioned. (1) Polypropylene 93% by weight obtained by simultaneously synthesizing 30% by weight of ethylene propylene rubber in a polymerization step,
7% by weight of talc in the final step of the polypropylene synthesis
Added molding material. This molding material is cheaper than a compound of polypropylene and ethylene propylene rubber. (2) Molding material containing the following synthetic components Polypropylene 60% by weight Ethylene propylene rubber 30% by weight Talc 10% by weight FIG. 10 shows molding material for outer layer M ₁ at the same time as molding of bumper 1.
A pair of left and right fog lamp covers 34 having a single-layer structure made of only the above is obtained. In this case, the entrance of the communication hole 18 is the grill mounting window 35 in the mold 13.
An opening is formed in the surface forming the lower inner surface.

[0038]

According to the present invention, by using the mold specified as described above, a synthetic resin molding having a sandwich structure having a good quality can be obtained, and at the same time, a single layer structure can be obtained. It is possible to obtain the synthetic resin molded body of No. 2.

[Brief description of the drawings]

FIG. 1 is a perspective view of a bumper and a protector molding.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a longitudinal sectional view of the injection molding apparatus.

FIG. 5 is a vertical sectional view showing a side region in a cavity of a mold.

FIG. 6 is a first process diagram.

FIG. 7 is a second process chart.

FIG. 8 is a third process diagram.

FIG. 9 is a graph showing a relationship between an injection time and an injection speed in the example.

FIG. 10 is a perspective view of a bumper and a fog lamp cover.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 bumper (synthetic resin molded body) 2 core 3 outer layer 5 protector molding (second molded body) 13 mold 16 ₂ film gate (gate) 17 cavity 17b upper area (area) 19 second cavity 34 fog lamp cover ( Second molded body) M ₁ outer layer molding material M ₂ core molding material

Claims (1)

[Claims] 1. When manufacturing a synthetic resin molding (1) having a sandwich structure consisting of a core (2) and an outer layer (3) covering the core (2), a molding material (M) for the outer layer. ₁ ) Injecting ₁ ) into the molding cavity (17) of the mold (13), and injecting core molding material (M ₂ ) into the outer layer molding material (M) in the cavity (17). ₁ ) and a second step of flowing the molding materials (M ₁ , M ₂ ) for the outer layer and the core into the cavities (17), and using the second step as the mold (13) below. A method for producing a synthetic resin molded body, characterized in that a synthetic resin molded body having a structure as described above is used. A region (17b) in the molding cavity (17) in which the outer layer molding material (M ₁ ) is preferentially filled.
A second molding cavity (19) for molding a second synthetic resin molded body (5) having a single-layer structure composed of only the outer layer molding material (M ₁ ) is communicated with.