JPH07308940A - Injection molding method and injection molding machine of double layer body molded product or composite molded product - Google Patents

Abstract

PURPOSE:To mold a composite molded product of a skin layer having a uniform thickness or a composite molded product having a favorable external appearance by the same equipments and mold. CONSTITUTION:The title machine is related to an injection molding machine for molding a double layer body molded product or a composite molded product by injecting at least two kinds of molding materials into a stationary mold 17 and movable mold 18 in order. Therefore, an inlet of the stationary mold 17 is provided with a gas blowing-in port 26 besides a sprue, gas piping 27 is joined to the gas blowing-in port 26, a gas cylinder 28 is joined to the same gas piping 27 through a solenoid valve 30 and reducing valve 29, a cave is formed by blowing pressure gas from the gas cylinder or the pressure gas is blown through by blowing in the pressure gas after partial filling of a molding material and then an another molding material is filled, through which the double layer molded product or the composite molded product is molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and an injection molding machine for molding a multi-layer molded product or a composite molded product made of a plurality of types of molding materials.

[0002]

2. Description of the Related Art Injection-molded articles made of plastic materials are
It is desirable to have a layered structure that takes advantage of the characteristics of each material, such as using a material that improves the appearance and feel on the surface and a material with high strength for the core part. In some cases, a plurality of colors are required for the same molded product in order to distinguish the type of the content product, and thus a plurality of resins having different colors may be injected to perform molding. As for the manufacturing method in the former case, for example, a core is injection-molded by a dedicated mold, then the core is put in another mold having a large volume by the thickness of the surface skin, and the skin-molding material is prepared by another injection unit. Although a method of injecting into a product is adopted, this method requires two sets of molds, the equipment is expensive, and a process for replacing the molded product with the mold is required, which is troublesome. There was a flaw.

In order to solve such a problem, a skin molding material is first extruded into a mold by a required amount, and then a core molding material is extruded into a skin material which is still in a soft state and filled into the mold. A filling method is introduced in JP-A-60-58825. Further, Japanese Patent Laid-Open No. 5-131494 proposes a method of filling a skin molding material on one side of a molded product in the same mold and integrally molding the same.
As shown in FIG. 8, by injection from the first-class molding material injection nozzle 1, a resin material is filled in a mold to form a primary molded product 12.
And the compressed gas 6 is sent from the inside of the lower mold to compress the primary molded product 12 before the molded product 12 solidifies, and the slide pin 4 is pulled into the space 6a created by the compression. This is a method of making a two-layer molded product by injecting the second type molding material 13 by opening the second type molding material injection nozzle 2. In order to meet the latter requirement for multiple colors, there is a method in which a plurality of injection nozzle ports are provided at separate positions in the same mold and the molding materials of different colors are simultaneously injected from the plurality of injection nozzle ports. .

As shown in FIG. 7 showing still another conventional technique, the combination of the molds 33 and 34 and the combination of the molds 35 and 34 are mounted on the rotary plate 37 so that the positions can be exchanged on the central longitudinal axis. First, the primary molding 36 is molded by injection from the first-class molding material injection nozzle 31, and then the upper and lower molds are separated, and then the rotary plate 37 is rotated 180 degrees to close the upper and lower molds. There is a method of making a two-color molded product by covering the next molded product 36 and injecting the two-molding material from the two-molding material injection nozzle 32.

[0005]

SUMMARY OF THE INVENTION In order to reduce the number of molds and simplify the structure of a molding machine, the above-mentioned JP-A-60-5 is used.
The method proposed in Japanese Patent No. 8825, that is, a method of extruding the required amount of the skin molding material into the mold and then extruding the core molding material into the skin material which is still soft to fill and fill the mold is Since the core material is injected in a state where the molten material for use floats in the mold, the shape of the molded product during injection is unstable and the skin thickness is not fixed, and the skin material and the core material easily mix. . In addition, the above-mentioned JP-A-5-1314
The method proposed in Japanese Patent Publication No. 94, that is, the method of filling the skin molding material on one side of the molded product in the same mold, is performed by pressing the first filled A material (skin material) to the cavity side by compressed gas. Form a gap between the product and the core mold,
The shrinkage rate of the molded product is 5 to 6% or less at the maximum, and the cavity gap for filling the B material is small.
The material tends to be a short shot, and by ejecting air from a large number of pores, the material A (skin material) does not form a constant layer, and in some cases, the material B appears on the surface, resulting in a marked deterioration in quality. There was a flaw. Further, a method in which a plurality of injection nozzle openings are provided at different positions in the same mold and different molding materials are simultaneously injected from the plurality of injection nozzle openings has a drawback that the boundary strength between the two kinds of materials is weakened. . In the method shown in FIG. 7 in which only the upper mold is replaced and the skin material is covered with the skin material, two-color molding is possible, but the material B (core material) is completely wrapped with the material A (skin material). There was a problem that sandwich molding could not be performed.

[0006]

Therefore, the present invention provides a single or plural molding materials in an injection molding method of a multi-layer molded article, in which two or more molding materials are sequentially injected into a mold for molding. After partially filling, the cavity obtained by blowing pressure gas is filled with another type of molding material, and then the pressure gas is blown to form a cavity to repeat the filling, which is a means for solving the problem. To do. Further, the present invention is an injection molding method for a multi-layer molded product, in which two or more molding materials are sequentially injected into a mold to mold, and after the first molding material is partially filled, a pressurized gas is blown in to blow it out. After attaching the molding material to a part of the inner surface of the mold,
The mold cavity is filled with another molding material, and a pressure gas is further blown in and blown out to repeat the filling. This is a means for solving the problem. Furthermore, the present invention provides an injection molding machine for injecting two or more kinds of molding materials into a cavity formed between a fixed mold and a movable mold to mold a multi-layer molded product or a composite molded product. In addition to the sprue, a gas inlet is provided at the mold inlet, a gas pipe is connected to the gas inlet, and a gas cylinder is connected to the gas pipe via a solenoid valve and a pressure reducing valve. Is a means for.

[0007]

First, the mold is first partially filled with the material A (skin), and immediately after that, gas is blown to spread the material A into the mold space to form a blow-molded molded product. At this time, in order to remove the gas in the cavity, the solenoid valve is switched and the gas inside the molded article is discharged to the atmosphere. There is also a method of opening the end of the blow-shaped molded article in order to remove the gas in the cavity (adjusted by the initial filling amount of material A). Therefore, the gas in the cavity can be used for foaming the B material. If the filling amount of material A is small,
The blow-molded molded product is blown out, and the skin layer is partially formed into a composite molding. Further, since the material A is blown by the gas pressure, the material A is cooled and solidified, and the surface of the material A is not disturbed when the material B is filled.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIG. 1 is a partial side sectional view of an ordinary injection molding machine having two sets of injection units and a mold clamping mechanism according to one embodiment of the present invention. FIG. 2 is a side sectional view of the mold clamping mechanism showing the compressed gas operating mechanism and the compressed gas path. In the figure, 15 is a die head, 16 is a platen, 17 is a fixed mold, and 18 is a movable mold. The two sets of injection units include an injection cylinder 19,
19 'and the injection screws 20, 20'. Figure 1
Has a structure in which the molten resin outlet passages 21 a and 21 b at the tips of the injection cylinders 19 and 19 ′ merge with one nozzle 21. Therefore, the mold sprue (gate) 23 is 1
Although it is a place, a nozzle is provided for each injection unit,
A plurality of molding mold sprues 23 may be provided. It is also possible to provide two or more sets of injection units. Reference numeral 24 denotes a mold gate, and 25 denotes a parting surface of the fixed mold 17 and the movable mold 18. In FIG. 2, 28 is a high pressure gas cylinder, 29 is a pressure reducing valve for adjusting the gas pressure, and 30 is an electromagnetic valve for opening and closing the gas pipe 27 leading to the mold. In addition to the sprue 23, a gas injection port 26 is provided at the mold inlet.
FIG. 3 shows a perspective view of the molded product 22. (23) (24)
(26) are sprue 23 and mold gate 2 respectively
4 shows the external shape of the molded product molded by the gas blowing port 26.

Next, the operation will be described with reference to FIGS. 4 to 6. FIG. 4 shows a mold clamping / injection block circuit. The two or more molding materials injected here have different materials, the same materials but different colors, strength, elasticity, coagulation rate, and other additive materials that affect foamability. Needless to say, the presence or absence is included.

First, the operation of forming a multi-layer molded product will be described with reference to FIG. In FIG. 5, the movable mold 18 is moved to close the mold, and the back pressure of the mold is increased. Next, the molds 17 and 18 are partially filled with the material A (skin) [see FIG.
(A)] Immediately after that, a gas is blown to spread the material A into the mold space [FIG. 5 (b)], and a blow-molded molded product is prepared [FIG. 5 (c)]. The gas pressure inside the blow-molded product is switched to the electromagnetic valve 30 and discharged to the atmosphere. At this time, there is also a method of opening the end of the blow-molded molded product in order to remove the gas in the cavity (adjusted by the initial filling amount of the material A). Subsequently, the material B is injection-filled [FIG. 5 (d)]. After the injection is completed [Fig. 5 (e)], the mold is opened and the molded product is taken out after the cooling time. The above is the molding in the case of two layers, but in the case of more layers, after injection filling of B material,
Further layers can be formed by repeating the process of blowing gas and injecting the next material amount. Further, the gas in the cavity in the above step [FIG. 5 (c)] can also be used for foaming the B material. In this case, since the material A is blown by the gas pressure, the material A is cooled and solidified.
The surface of the material is not disturbed. As a result, it is possible to reduce the weight by making the material B a foam material and to prevent moisture by making the material A a normal plastic.
It goes without saying that the material can be made a transparent material and the material B can be a desired color material to give a glossy and high-class feeling, and by stacking various materials in multiple layers, the strength can be increased. Nor.

Next, the operation of molding the composite molded article will be described with reference to FIG. In FIG. 6, the working process in the case of the composite molding is almost the same as that of the multilayer body molding. First, the movable mold 18 is moved to close the mold, and the back pressure of the mold is increased. At first, the molds 17 and 18 are filled with a small amount of material A (skin) [Fig. 6 (a)], and immediately after that gas is blown to spread the material A into the mold space [Fig. 6 (b)]. Then, the inner side of the die space is covered halfway to form a tubular molded product [FIG. 6 (c)]. Subsequently, the material B is injection-filled [FIG. 6 (d)]. After the injection is completed [Fig. 6 (e)], the mold is opened after a cooling time and the molded product is taken out. Also in this case, since the A material is blown by the gas pressure as in the step of forming the multilayer body, the A material is cooled and solidified, and the surface of the A material is not disturbed when the B material is filled. The above is the case of combining two materials, but it goes without saying that when combining or repeating various kinds of materials, the blowing and the injection may be repeated. As a result, by making the materials A and B the same and making only the colors different, it is possible to inexpensively manufacture a product with rich colors.

[0012]

EFFECTS OF THE INVENTION In the conventional molding of a multilayer body, the unsolidified A
Since the skin layer of the material A is formed by filling the core material B inside the material, the skin layer is broken or disturbed when the material B is injected. The A material filled in the mold is blow-molded by gas pressure to form a skin layer, and the B material is filled in the cavity of the solidified A material, so that a complete multi-layered body is formed and a relatively thick wall is formed. A uniform skin layer is obtained, the strength of the core B material is maintained, and the appearance is good. On the other hand, in the case of a composite molded product, since the skin layer of the material A is cooled and solidified and then the material B is filled, the boundary between the materials A and B becomes clear, and the composite molded product has a good appearance in which the materials A and B are not mixed. Since the core is formed integrally with the B material, there is no problem of strength reduction. In addition, it is possible to perform two kinds of moldings of a multi-layered molded product and a composite molded product with the same equipment and the same mold.

[Brief description of drawings]

FIG. 1 is a partial side sectional view of an injection molding machine for carrying out the method of the present invention.

FIG. 2 is a side sectional view of a mold clamping mechanism showing a compressed gas working machine and a compressed gas path according to an embodiment of the present invention.

3 is a perspective view of a molded product molded by the injection molding machine of FIG. 1. FIG.

4 is a mold clamping / injection block circuit diagram of the injection molding machine of FIG. 1. FIG.

FIG. 5 is an explanatory drawing of a molding process of a multilayer body molded product by the method of the present invention.

FIG. 6 is an explanatory diagram of a molding process of a composite molded product by the method of the present invention.

FIG. 7 is a cross-sectional view of a die part for explaining an injection molding process of a conventional multi-layer molded product.

FIG. 8 is a cross-sectional view of a mold part for explaining another example of the conventional injection molding process for a multilayer product.

[Explanation of symbols]

 17 Fixed mold 18 Movable mold 19,19 'Injection cylinder 20,20' Injection screw 21 Nozzle 22 Molded product 26 Gas injection port 27 Gas pipe 28 Gas cylinder 29 Pressure reducing valve 30 Solenoid valve

Claims (3)

[Claims] 1. An injection molding method for a multi-layered molded article, which comprises sequentially injecting two or more molding materials into a mold to form a single or a plurality of molding materials, and then blowing a pressure gas. An injection molding method for a multi-layer molded article, characterized in that the obtained cavity is filled with a different kind of molding material, and further pressure gas is blown to form a cavity to repeat the filling. 2. An injection molding method for a multi-layered molded article, which comprises sequentially injecting two or more molding materials into a mold to mold the first molding material, after partially filling the molding material with a pressure gas. Injection molding of a composite molded product characterized in that the molding material is adhered to a part of the inner surface of the mold by the method, then the molding cavity is filled with another molding material, and further pressure gas is blown in and blown out to repeat the filling. Method. 3. An injection molding machine for injecting two or more kinds of molding materials into a cavity formed between a fixed mold and a movable mold to mold a multi-layer molded product or a composite molded product. In addition to the sprue, a gas inlet was provided at the mold inlet, a gas pipe was connected to the gas inlet, and a gas cylinder was connected to the gas pipe via a solenoid valve and a pressure reducing valve. Injection molding machine for molded products or composite molded products.