JPH02292018A - Method of manufacturing thick wall hollow molding and apparatus therefor - Google Patents

Abstract

PURPOSE:To manufacture efficiently a high accurate thick wall hollow article with the excellent transferring property of a mold inner surface by extruding thermoplastic resin hollow parison from a plasticizing unit, and holding it with a press mold, and then molding under a specific pressure in sending high pressurized gas. CONSTITUTION:Thermoplastic resin follow parison is extruded from a plasticizing unit, and then held by a press mold, and after, pressurized gas is sent therein, whereby a thick wall hollow molding is manufactured by molding under a pressure of 10kg/cm<2>-200kg/cm<2>. Furthermore, by using two or more extruders and molding in extruding multi-layered parison and employing a raw material being pleasant to the senses and feelings as a surface material and excellent in appearance in this instance, there can be obtained an article with sufficient strength and excellent surface finishment. As resin used in this occasion, almost all resin used in ordinary extruding molding or the like can be used. Since the molding pressure is set in extraordinary high at 10-200kg/cm<2>, the mold surface can be transferred thereto faithfully.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to a new hollow press molded product manufacturing method and its device. This article relates to a method and apparatus for manufacturing thick-walled hollow molded products that can be applied to fields that require molded products.

[Conventional technology]

The mainstream of conventional blow-molded products is mainly blow-molded containers, in which the parison is extruded from an extrusion mill or an injection molding machine.
Molding was performed by blowing low-pressure air, and the outer wall was thin, making it unsuitable for rigidity and precision molding. On the other hand, injection molding heat-plasticizes synthetic resin and injects it into a mold under high pressure to form the mold, so it is suitable for small-scale production and mass production, and is superior in that it has high productivity, but it is not suitable for use. Low-molecular-weight resins with good flowability are preferred, and due to the nature of the molding machine, it was extremely difficult to reduce weight by creating a hollow part inside the molding machine, or to create multiple layers of materials. In recent years, synthetic resins have been applied to a wide range of fields, and in particular, interior parts such as automobile door trims, front panels, pillars, and rear cell shelves use relatively rigid resin molded products as a base material with a soft skin on the surface. A glued version is used. These interior parts have functions such as protecting various functional parts, sound insulation, waterproofing, and distribution, and have a better feel and appearance compared to interior parts painted on conventionally used steel plates. It has many advantages such as being excellent and lightweight. These resin interior parts are usually made by pasting the skin on a molded resin base material with adhesive, or by applying a brimer treatment to the surface that will become the base material in advance, and then applying adhesive to the base material. It is manufactured by bonding it to the surface of the material using compressed air or vacuum. Multilayer molding methods using multicolor molding are also widely used. [The problem that the invention is trying to solve] These parts are:
In terms of strength, blow molded products are weak, but there is no need for the entire body to be completely filled with resin like injection molded products. In order to meet the different requirements of the base material and surface material, two or three stages of processing were required. The present inventors have studied the development of a precision molding method that has appropriate rigidity, is lightweight, and has a beautiful surface finish, and as a result, has completed the present invention.

[Thousand Steps to Solve the Problems] The present invention focuses on the lightness of blow molded products, and aims to solve the lack of rigidity due to thin walls, and although injection molding and press molding have the rigidity, only the lightness of synthetic resin is achieved. We considered how to compensate for the bending due to molding, sink marks in molded products, and lack of productivity in presses, and developed manufacturing methods and equipment that would solve these problems while having the features of these products. We succeeded in developing it. That is, a thermoplastic resin hollow palson is extruded from a plasticizing device, sandwiched between press molds, and high-pressure gas is introduced.
l O Kg/cm2 ~200 Kg/c
Provides a method for manufacturing thick hollow molded products by molding under a pressure of m2. Furthermore, in this case, two or more extruders are used to create multilayer extruders. By extruding and molding the parison, a product with sufficient strength and a beautiful surface finish can be obtained by using a material with a good feel and appearance as a surface material. Additionally, we will also provide the equipment used for this manufacturing method. Most of the resins that are normally used in extrusion molding can be used as the material used at this time. In the method of the present invention, the parison is a solid body (a concentric or semicircular laminate,
Alternatively, it may be a multilayer plate-like laminate. ) or a hollow body (a hollow concentric body, a deformed multilayer annular body, etc.).A hollow body is preferable when manufacturing a blow molded product, but it is not necessarily limited to this. The pressure of this molding method is several times to several tens of times higher than the pressure of conventional blow molding, so it is impossible to use a conventional blow molding machine as is.Also, the gas pressure is also high, so , a completely separate compressor is required.Injection of high-pressure gas is not limited to the hollow part of the parison; it is also possible to provide a gas injection port (needle) at a specific location in the mold and inject it from there. In particular, when the parison is a solid body, it can be made into a hollow molded body by injecting high-pressure gas into the desired hollow part from a plurality of injection ports. 0 KtH/cs
Since it is set extremely high as ``e'', it is possible to faithfully transfer the surface of the mold.Furthermore, since it is a hollow molded product, it is lightweight, but the wall thickness is considerably thicker than that of conventional hollow molded products. Because the product can be manufactured, it has high rigidity and can be easily precision molded under high molding pressure.In particular, by using two or more extruders, the interior has excellent mechanical properties, texture and appearance. When a multilayer parison with a good exterior is extruded and molded by the method of the present invention, a lightweight, rigid, precision-molded blow molded product can be obtained.Hereinafter, the multilayer molding method and its apparatus will be explained with reference to the drawings. An overview will be explained. In Figures 1 and 2, there are two or more extruders (1) that plasticize thermoplastic resin, and a measuring device (2) that weighs the thermoplastic resin plasticized by the extruders (1). ) and a die (3) that charges the weighed material into a certain shape onto the mold.It should be noted that (l), (2), and (3) are numerically controlled two-dimensional or Table that moves in three dimensions (8)
It is a mechanism that is placed on top of and moves at the same time. The extruder (!) has a single or twin screw type vented or non-vented screw, and its groove shape is either a full-flight type or a dalmage type.
A mixture of both types is also acceptable. The drive system for the extruded part that plasticizes is a hydraulic motor or an electric motor, and the rotation speed is changed and stopped by a microprocessor-based control system. The resin from the hopper (la) is plasticized at a predetermined temperature and sent to a meter. The measuring device (2) uses a positioning sensor to generate a signal to stop the extruder motor when the resin melt that has flowed from the extruder (1) reaches a predetermined volume. When the thermoplastic resin is weighed here, it is extruded by the piston.At the entrance of the die (3), there is a shirt valve that opens when extruding the thermoplastic resin from the scale. This prevents the resin from smearing from the die. The resin that has passed through the shattered valve is extruded as a multilayer melt from a circular die or an irregularly shaped die, and is pattern-charged onto a mold (9b) by a table (8) that is operated two-dimensionally or three-dimensionally. At this time, a cutter is attached to the tip of the die to cut off the multilayer melt sheet, and the cut is finally cut off, and the upper die is lowered to perform press forming. In FIGS. 1 and 2, the extruder (1) and the meter (2) may be structurally integrated, and may be replaced by, for example, an injection cylinder type structure. Figure 3 shows details of the part where (1) and (2) are integrated. In this case, when the thermoplastic resin is plasticized, the screw (5)
rotates and retreats, forming a measuring section filled with plasticized molten resin at the tip. When the total capacity of the m part (6) reaches a certain level, the screw (5) stops rotating. The screw {5) acts as a piston and moves forward, extruding the molten resin from the multilayer circular die (3) in the form of a multilayer parison.The speed of the piston can be changed by numerical control, and the thickness composition and thickness of the product can be changed. Both are programmed to be closely linked to the movement of the table (8) so that they can be changed as desired, and the thickness composition of the material can be changed in any part of the multilayer molded product. The injection cylinder is mounted on a table (8) of a mechanism driven by numerical control in two or three dimensions, and the molten resin is supplied from each tip of the cylinder to the circuit error die to form a multilayer structure. There is. The multilayer molten resin from the circular die is charged onto the mold in a predetermined pattern as a result of being driven by a table (8) according to a program under numerical control. After that, when the table is retracted and the die part is retracted from the mold, the press is lowered and the product is compression-molded at a pressure of 10 to 200 kg/cm2, and the 10 to 200 kg/cm2 is compressed from one side of the Nagisu parison or from any place. Kg/cs+” to 1
By injecting high-pressure gas of 0.0 kg/am2, it is possible to obtain a product that has a thicker part than the thickness of the molten parison and a hollow body in some parts. There are no particular restrictions on the resin used, but if a polyolefin and/or a high rigidity base material is required, a polyolefin material reinforced with a feeler is preferable. There are no limitations on the epidermal side. In general, materials with rubber properties include ethylene brobylene rubber, styrene butadiene rubber, and chloroprene rubber. The above method and apparatus differ from injection molding methods in which molten resin is injected through a gate, and the method and apparatus are
All you have to do is charge the molten multilayer body extruded from an extruder and press-form it. The pressure of normal molding is about 1/3 that of injection molding. Therefore, there is no need to use an expensive pressure-resistant material for the mold, and it is possible to use one that takes less time to create and is much cheaper. In addition, in multi-color molding, in conventional injection molding it is possible to partially change the thickness of the component material with two colors by mold design, but three
This was almost impossible when it came to color, but with the method of the present invention, this gap could be easily resolved. In addition, in multilayer blow molding, when blowing the parison, two
Compared to this, the present invention uses compressed air and press molding at high pressures under the above conditions, so it has excellent transferability on the mold surface, which is required for automobile interior parts. The processability of the surface of the molded chip, etc., is excellent.In addition, since fluid molding is performed using a press, it is possible to form parts that are thicker than the parison melt in some parts, so it is easier to form the product than with multilayer blow molding. There are no restrictions on design, and it can be applied to a wide range of parts.As described above, the molding method of the present invention has the feature that multi-layer molding can be performed easily. [Example] (Example 1) Figures 1 and 2 An article having the shape shown in Fig. 4 was molded using the molding machine shown in Fig. 4.The molding temperature was 200°C, and the material forming the first layer skin was a thermoplastic elastomer.The elastomer contained 30% by weight of polypropylene. Ethylene propylene rubber is 50% by weight, and the rest is oil for imparting flexibility. Chemical crosslinking is also performed using bar oxide and a crosslinking agent. The fraction was 34%.The fluidity was 0.1 when expressed as the Durham number of the weight flowing out from the orifice per 10 minutes at 230°C using a melt indexer.The second layer was made of glass. Polypropylene containing 15% fiber had a melt flow of 0.2 and a bending elongation of 30000 kg/cm''. The first layer (1) is 2 mm, the second layer (2) is 8 mm, the ratio (2)/(1) = 4, and the parison has a concentric hollow circular shape.
Its diameter is 150 mm. A two-layer parison is taken out from the circular die and placed on a mold with the shape shown in Figure 4 under numerical control. At this time, air is blown into the mold from the circular die side to prevent the parison from being crushed. The tip of the parison is punched in advance, the mold is closed, and a sliding high-pressure air injection bottle is driven into the parison from the side of the mold. 5
Inject high pressure air of 0 kg/cm2. In the section A-A of the molded product in Figure 4, the parison is crushed by the pressure of the press and becomes fluid and solid. On the other hand, the cross section BB is a hollow body whose skin thickness is tt. If the thickness of the base material is t2, then t2/t + cape 3.8, which is almost the composition ratio of the extruded parison. (Comparative Example 1) Using a mold with almost the same shape as shown in Fig. 4, 1 30 (1
t. Molding was performed using a two-color injection molding machine with a clamping pressure of . The base material was injected using polypropylene with a melt flow rate of 80 g/10 min, and then the mold was inverted and the same skin material as in Example 1 was injected. A molded product with only one side of the above example was obtained. Cross section B of molded product
- When the composition ratio of the material of H was taken, t*/t
Not only is there a large variation in r = i ~ 2.3, but the skin layer, which has poor fluidity, must be thick to be molded. In addition, the thickness of the skin layer of the molded product is uneven, resulting in flow marks and a cushiony feel that varies depending on the area, resulting in a rejected product. (Comparative Example 2) In Example 1, the high pressure air injection pressure was 9.0 Kg/Clm.
Example 1 was carried out as in Example 1, except that Example 2 was changed. Despite the mold clamping pressure being sufficiently high, the corners were poorly formed and the molding did not meet the dimensions, and the transfer of the chip surface on the inner surface of the mold was also poor (resulting in only rejected products). [Effects of the invention] The molding pressure is much higher than that of blow molding, and thick-walled hollow products with high precision can be manufactured efficiently with good transferability of the inner surface of the mold. Furthermore, when molding is carried out using the multi-layer molding machine explained above, not only is the cost of the molding machine and labor costs, which are included in the product, significantly reduced because the molding is done in one piece. Simplifying the bonding process can significantly reduce product defect rates and strengthen component cost competitiveness. In addition, the thickness structure of the material can be adjusted arbitrarily.
Moreover, since it can be partially changed, there is a large degree of freedom in terms of combinations. Even if you produce a large variety of products in small quantities, there is no need to change the manufacturing process, and even products with a wide variety of small lofts can be profitable.

[Brief explanation of drawings]

Figures 1 and 2 are. An example of an apparatus for carrying out the method of the present invention is shown, showing a plan view and a side view. Figure 3 is a longitudinal sectional view of the plasticizing section where the extruder and measuring device are integrated. Figure 4 shows an example of a molded product. l...Extruder. la... Hopper lb-... Drive unit. 2... Measuring instrument (piston), 3...
... Coextrusion die. 4...Heating heater 5...Screw 6...Measuring section. 7... Town plasticizing department 8... Operating table 9... Press molding machine. 9a...Earth metal mold, 9b...1 Lower mold Fig. 1

Claims (3)

[Claims] (1) Extrude a thermoplastic resin hollow parison from the plasticizing device, sandwich it between press molds, and feed high pressure gas to 10K.
A method for producing a thick-walled hollow molded product, which comprises molding under a pressure of g/cm^2 to 200 kg/cm^2. (2) Two or more extruders having a plasticizing section that plasticizes the thermoplastic resin, which is integrated and movable, a measuring section that measures the plasticized resin, and a mechanism that extrudes the measured resin. After charging the multilayer parison from a die into a predetermined pattern on a press mold using a press machine, the press pressure is 10Kg/cm^2 to 200Kg/cm^2 per unit area of the product.
Compression molding is performed in step 2, and 10kg is placed in a multilayer parison.
A method for producing a multilayer molded product, characterized by simultaneously forming a thicker part and a hollow part than a molten parison by injecting high-pressure gas of 150 kg/cm^2 to 150 kg/cm^2. (3) Two or more extruders each having a plasticizing section that plasticizes thermoplastic resin and a lightweight section that measures and extrudes the plasticized resin, and a molten multilayer that is commonly provided at the extrusion port of these extruders. a multilayer die that forms a parison; a moving means that integrates and moves the extruder and the multilayer die;
An apparatus for manufacturing thick-walled hollow molded products, characterized in that a press molding machine in which a mold is located within the movement range of the multilayer die and a high-pressure gas generator can operate in cooperation.