JP2660863B2 - Method and apparatus for manufacturing thick hollow molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a new hollow press molded article and an apparatus therefor. More specifically, the present invention relates to a method and an apparatus for manufacturing a thick-walled hollow molded article which is a hollow molded article which has high dimensional precision and is lightweight but has high rigidity and can be applied to a field requiring a rigid article.

[Prior art] Conventional blow molding products are mainly blow-molded containers, in which a parison is extruded from an extruder or an injection molding machine and molded by blowing low-pressure air, and the outer wall is thin and rigid. And not suitable for precision molding.

On the other hand, injection molding heats and plasticizes synthetic resin, injects it into a mold at high pressure, and molds it.It is suitable for small varieties and mass production, and has high productivity. It is very difficult to reduce the weight of the resin by providing a hollow portion inside the resin, and further to form a multilayered resin, because of the properties of the molding machine.

In recent years, synthetic resins have been applied to various fields, especially for interior parts such as car door trims, front panels, pillars, rear parcel shelves, etc., with relatively rigid resin molded products as the base material, and a soft skin on the surface. Is used.

Such interior parts have the functions of protecting various functions, sound insulation, waterproofing, vibration damping, etc., and have a better touch and appearance compared to conventionally used interior parts painted on steel plates. Has many advantages such as excellent light weight.

These resin-made interior parts are usually prepared by applying a skin to a molded resin base material with an adhesive, or applying a primer treatment to the surface of the base material in advance, and then applying an adhesive to the base material. It is manufactured by bonding to the surface of the material with compressed air and vacuum. In addition, a multi-layer molding method using multi-color molding is often used.

[Problems to be Solved by the Invention] These parts are weak in blow molding from the viewpoint of strength, but there is no necessity that the whole is completely filled with resin like an injection molding. In order to satisfy the different requirements of the base material and the surface material, two or three steps were required.

The present inventors have studied the development of a precision molding method which has appropriate rigidity, is lightweight, and has a beautiful surface finish, and as a result, has completed the present invention.

[Means for Solving the Problems] The present invention focuses on the lightness of a blow-molded product, and focuses only on the direction to eliminate the lack of rigidity due to thinness and the rigidity of injection molding and press molding but the lightness of synthetic resin. Investigate how to compensate for the problems to rely on, as well as sinks in molded products and lack of productivity of presses, and develop manufacturing methods and equipment to solve those problems while having the features of these products. Succeeded.

That narrow Mi thermoplastic resin hollow parison extrusion at a press die from plasticizing apparatus, press pressure in the parison with the press pressure is compression molded at 200 kg / cm ² from the product per unit area of 10 kg / cm ² from the following of 10kg / cm ² 150kg / cm
⁽²⁾ A method for producing a thick hollow molded article characterized by simultaneously forming a thicker part and a hollow part than a molten parison by injecting a high-pressure gas.

Furthermore, in this case, by using two or more extruders and extruding and molding a multi-layer parison, the surface material has a good touch, and by using a material having an excellent appearance, sufficient strength and a clean surface finish are obtained. A product is obtained.

An apparatus used in this manufacturing method is also provided.

As the resin used at this time, most of the resins usually used for extrusion molding and the like can be used.

In the method of the present invention, the parison may be a solid body (which may be a concentric or semicircular laminate or a multilayer plate-like laminate) or a hollow body (a hollow concentric body, a deformed multilayer annular body, etc.). ). When manufacturing a hollow molded product, a hollow body is preferable, but is not necessarily limited to this.

The pressure of the mold is several times to several tens of times greater than the pressure of the conventional blow molding method in the present molding method.

The gas pressure is also high, requiring a completely different compressor.

The injection of the high-pressure gas is not limited to the hollow part of the parison, but it is also possible to provide a gas injection port (needle) at a specific location of the mold and to inject the gas from there. In particular, when the parison is a solid body, it can be formed into a hollow molded article by injecting high-pressure gas into a portion where hollow is desired from a plurality of injection ports.

Since the molding pressure of the present invention is set as extremely high as 10 to 200 kg / cm ² , it is possible to faithfully transfer the surface of the mold.

Furthermore, because it is a hollow molded article, it is lightweight, but on the other hand, it is possible to manufacture products that are considerably thicker than conventional hollow molded articles, so it has high rigidity and the ability to easily perform precision molding from high molding pressure. is there.

In particular, when two or more extruders are used to extrude a multi-layer parison consisting of an interior having excellent mechanical properties and an exterior having a good touch and appearance, and molded by the method of the present invention, it is lightweight, rigid, and precisely molded hollow. A molded product can be obtained.

Hereinafter, an outline of a multilayer molding method and its apparatus will be described with reference to the drawings.

In FIGS. 1 and 2, two or more extruders (1) for plasticizing a thermoplastic resin, a measuring device (2) for measuring the thermoplastic resin plasticized by the extruder (1), and It consists of a die (3) of a portion which is charged into a fixed shape on a mold. (1), (2), (3)
Are on a numerically controlled two-dimensional or three-dimensionally movable table (8) and have a mechanism for simultaneously moving.

In the extruder (1), the screw is a single-screw type or a twin-screw type vent or non-vent, and its groove shape is either a full flight type or a dalmage shape. A mixture of both types may be used. The drive system of the extruding part to be plasticized is a hydraulic motor or an electric motor, and the rotation speed is changed or stopped by a control system by a microprocessor.

The resin from the hopper (1a) is plasticized at a predetermined temperature and sent to a measuring device. The meter (2) has a mechanism for generating a signal for stopping the motor of the extruder by a positioning sensor when the resin melt flowing from the extruder (1) reaches a predetermined volume to a predetermined volume capacity in advance. Where it is metered and pushed out by the piston.

At the entrance of the die (3), there is a shut valve, which is opened when the thermoplastic resin is extruded from the measuring device, so as to prevent resin dripping from the die. The resin that has passed through the shut valve is pattern-charged onto a mold (9b) by a table (8) that is operated two-dimensionally or three-dimensionally while being extruded as a multilayer melt from a circular die or a deformed die. At that time, a cutter for cutting off the multilayer melt sheet is attached to the tip of the die, and is finally cut off, the upper mold is lowered, and press molding is performed.

In FIGS. 1 and 2, the extruder (1) and the meter (2) are structurally integrated, and may be replaced with, for example, an injection cylinder type structure. FIG. 3 shows details of a portion where (1) and (2) are integrated. In this case, when the thermoplastic resin is plasticized, the screw (5) retreats while rotating, and a measuring portion filled with the plasticized molten resin at the tip is formed. Measuring unit (6)
When reaches a certain capacity, the screw (5) stops rotating. The screw (5) moves forward as a piston, and extrudes the molten resin from the multilayer circular die (3) as a multilayer parison. The speed of the piston can be changed by numerical control, and the thickness configuration and thickness of the product can be changed. Any of them is programmed so as to be closely linked to the movement of the table (8) so that the thickness of the material can be changed at any part of the multilayer molded article.

The injection cylinder is provided on a table (8) of a mechanism driven by two-dimensional or three-dimensional numerical control, and is configured to supply a molten resin from each of the ends of the cylinder to a circular die to form a multilayer. . The multilayer molten resin from the circular die is driven by a table (8) according to a program under numerical control on a mold, and as a result, is charged in a predetermined pattern.

Thereafter, dice table is retracted is when retracted from the mold, the press is 10 to 200 kg / cm ² together with the compression molded at a press pressure from one of the molten parison or any of the following locations pressing pressure drop 10kg / cm ² to 150kg /
A product having a portion thicker than the thickness of the molten parison and a partially hollow body can be obtained by injecting a high-pressure gas of cm ² .

The resin to be used is not particularly limited, but if a base material requires polyolefin and / or a material having high rigidity, a polyolefin material reinforced by feeler is preferable. There is no limitation on the skin side, but generally a material having rubber properties is preferable, and examples thereof include ethylene propylene rubber, styrene butadiene rubber, and chlorobrene rubber.

Since the above method and apparatus are different from those in which a molten resin is injected from a gate as in an injection molding method, a molten multilayer body extruded from an extruder is charged on a press die, and this may be press-molded. However, the pressure for normal molding is about 1/3 of that for injection molding. Therefore, it is not necessary to use a pressure-resistant expensive material as the material of the mold, and it is possible to use a material having a short construction period and a significantly low price.

In addition, in the conventional multi-color molding, it is possible to partially change the thickness of the component material by the mold design in two colors in the conventional injection molding, but it is almost impossible in the three colors. In the method of the present invention, this problem was easily solved.

In the multilayer blow molding, compressed air of 2 to 6 kg / cm ² is used when blowing the parison. In comparison with this, in the present invention, pressurized air and press molding are performed at a high pressure under the above conditions, so It is excellent in transferability, and has excellent workability on the surface of grain and the like required for automotive interior parts.

On top of that, flow molding by a press is involved, so that a part thicker than the parison melt can be formed. Therefore, there is no restriction on product design compared to multilayer blow molding, so that it can be widely applied to parts. As described above, the molding method of the present invention is characterized in that multilayer molding can be easily performed.

Example (Example 1) An article having the shape shown in FIG. 4 was molded using the molding machine shown in FIG. 1 and FIG. The molding temperature is 200 ° C., and the material for the skin of the first layer is a thermoplastic elastomer.

The elastomer is 30% by weight of polypropylene, 50% by weight of ethylene propylene rubber, and the rest is oil for imparting flexibility. Chemical crosslinking is performed using peroxide and a crosslinking assistant. The degree of crosslinking was 34% as a gel fraction as the unmelted xylene. Its fluidity was 0.1 expressed in grams of weight flowing out of the orifice per 10 minutes at 230 ° C. using a melt indexer.

The second layer is a polypropylene containing 15% glass fibers and has a melt flow of 0.2. The flexural modulus was 30,000 kg / cm ² .

The first layer (1) is 2 mm, the second layer (2) is 8 mm and the ratio is (2) / (1) = 4, the parison is a concentric hollow circle, and the diameter is 150 mm. The two-layer parison is taken out from the circular die and placed on a mold having the shape shown in FIG. 4 by numerical control. At this time, the parison is charged into the mold while blowing air from the circular die side so as not to be crushed. Pinch the tip of the parison in advance, close the mold and drive the sliding high-pressure air injection pin into the parison from the side of the mold.
Inject high pressure air of kg / cm ² .

The parison in the section AA of the molded article in FIG. 4 is crushed by the pressure of the press, and flows into a solid body. On the other hand, the cross section BB is a hollow body, and its skin thickness t ₁ and base material thickness t ₂
Then, t ₂ / t ₁ ≒ 3.8, which is almost the composition ratio of the extruded parison.

(Comparative Example 1) Molding was performed using a two-color injection molding machine having a mold clamping pressure of 1300 t using a mold having substantially the same shape as that shown in FIG. The base material was injected using polypropylene having a melt flow rate of 80 g / 10 minutes, and then the mold was inverted and the same skin material as in Example 1 was injected. A molded article on only one side of the above example was obtained.

When the composition ratio of the material of the cross section BB of the molded product is taken,
In addition to the large variation of t ₂ / t ₁ = _{1 to} 2.3, the skin layer having poor fluidity cannot be formed unless the thickness is increased.
Also, because the thickness of the skin layer of the molded product is uneven,
Due to the non-uniformity, the flow mark and the cushion feeling felt from the touch vary depending on the part, and the product is rejected.

(Comparative Example 2) The same operation as in Example 1 was performed except that the high-pressure air injection pressure was changed to 9.0 kg / cm ² . Despite the mold clamping pressure being sufficiently high, the molding was not good at the corners and did not conform to the dimensions, and the transfer of the crimp surface on the inner surface of the mold was poor, and only rejected products were obtained.

[Effect of the Invention] A thick hollow product having a much higher molding pressure and higher precision than blow molding can be efficiently produced with good transferability on the inner surface of the mold.

In addition, when molding is performed using the multilayer molding machine described above, not only the molding machine and labor costs occupying the product due to the integral molding are significantly reduced, but also the simplification of the laminating process is reduced. Significantly reduce product rejection rates and enhance component cost competitiveness. Further, since the thickness configuration of the material can be arbitrarily and partially changed, the degree of freedom in combination is large.

There is an advantage that even small lots of various kinds can be profitable without changing the manufacturing process of the product, even in small lots with many variations.

[Brief description of the drawings]

1 and 2 show an example of an apparatus for carrying out the method of the present invention, and are a plan view and a side view. FIG. 3 is a longitudinal sectional view of a plasticizing section in which an extruder and a measuring device are integrated. FIG. 4 shows an example of a molded product. DESCRIPTION OF SYMBOLS 1 ... Extruder, 1a ... Hopper 1b ... Drive part, 2 ... Measuring device (piston), 3 ... Co-extrusion die, 4 ... Heater, 5 ... Screw, 6 ... Measuring section, 7 …… Plasticizing section 8 …… Operation console, 9 …… Press molding machine, 9a …… Upper mold, 9b …… Lower mold

Claims (3)

(57) [Claims] 1. A extruded thermoplastic resin hollow parison from plasticizing apparatus, narrow Mi by a press die, pressing pressure from the product per unit area of 10 kg / cm ² of the parison while the compression molded at 200 kg / cm ² 150kg from the press pressure following of 10kg / cm ² in /
A method of producing a thick-walled hollow molded product, wherein a thicker portion and a hollow portion than a molten parison are simultaneously formed by injecting a high-pressure gas of cm ² . 2. At least two units each having a plasticizing unit for plasticizing a thermoplastic resin which is integrally and movably provided, a measuring unit for measuring the plasticized resin, and a mechanism for extruding the measured resin. using the extruder, after charged to a predetermined pattern a multilayer parison onto the press die than the die, in the multi-layer parison with the press pressure is compression molded at 200 kg / cm ² from the product per unit area of 10 kg / cm ² Press pressure below 10kg / c
By injecting high pressure gas 150 kg / cm ² from the m ^2, a method for manufacturing a multilayer molded article and forming a thick portion and a hollow portion from a molten parison simultaneously. 3. Two or more extruders each having a plasticizing part for plasticizing the thermoplastic resin, a light-weight part for measuring and extruding the plasticized resin, and a melter provided in common at the extrusion ports of these extruders. Die for forming a multilayered parison, moving means for integrally moving the extruder and the multilayer die, a press forming machine in which a mold is located within a moving range of the multilayer die, a high-pressure gas generator And an apparatus for producing a thick hollow molded article, which can operate in cooperation with each other.