JPH03140237A - Metal-plastic composite molded product and its manufacture - Google Patents

Abstract

PURPOSE:To contrive improvements in electric conductivity and heat conductivity along with giving of electromagnetic wave shielding properties, by a method wherein molding is performed into structure constituted of thermoplastic resin for a surface layer and a metallic layer, whose melting point is specific, for the central layer with an injection molding method. CONSTITUTION:When a screw 7 in an injection cylinder 8, which is heated up to an appropriate temperature, is turned, a plastic molding material is compressed and melted as it is fed forward. The molten material is accumulated at the front part of a cylinder with a backward movement of the screw. On the one hand, a metal 12 whose melting point is 47 deg.C-400 deg.C is stored within an injection piston 5 under a molten state. An insufficient quantity of the plastic is injected into a mold 2 by moving the screw 7 forward by opening a valve 9 in the first place Then the valve 9 is closed, a valve 10 is opened and the molten metal 12 is injected into the mold 2 with lowering of a piston 5. The valve 10 is closed for the next molding after this. When the mold is broken upon cooling, a molded product 1 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Fields The molded product manufactured according to the present invention can have an electrically conductive metal layer formed in the interior with an arbitrary thickness.

The obtained molded products can be used for parts that require a high degree of electromagnetic shielding, or for structural parts that use electrical conductivity to improve current-carrying circuits, static electricity prevention, thermal conductivity improvement, mechanical performance, etc. Available.

In addition, since the molding is performed using an injection molding machine, the process can be fully automated, making it very easy to perform, and the production speed is high, making it possible to revolutionize the production process of molded products for the above-mentioned applications, etc., and as a result, There are application fields where it can reduce the cost and improve the quality of products.

(B) Prior art As an example of the application of the present invention that is easiest to understand among the wide variety of applications, a mechanical component for improving electromagnetic shielding property will be explained first.

In recent electronic devices, automobiles, computers, various types of machinery, etc., electric circuit control using ICs has become common knowledge. Although this kind of device neck exhibits excellent functions, it uses very small air signals, so if you use this type of device in a place where electromagnetic waves are generated outside, it may malfunction due to the intruding electromagnetic waves. It is well known to do. In order to prevent this kind of operation, it is common practice to mount a conductive case, such as a metal shield case. On the other hand, recently, plastic has been increasingly used for covers of equipment due to design, cost, production, and other reasons. However, it is well known that plastic has the property of having no shielding properties against electromagnetic waves.

Therefore, as a countermeasure to such defects, (a) an electrically conductive paint is applied to the plastic molded product.

(b) Plating on plastic (c) Gluing metal tape using adhesive, (d) Manufacturing instrument covers using plastic molding materials mixed with metal fibers, carbon black, etc. Countermeasures are being taken.

However, the method of applying the paint requires more steps, and the conductive paint is expensive. When used for a long period of time, it has drawbacks such as peeling and falling of the paint.

Furthermore, the method of plating plastic is first of all expensive and the process is complicated. Plating has a limitation in that it is susceptible to cold and heat cycles, which cannot be applied to all plastic materials.

The method of mixing a conductive material into a plastic material significantly impairs the appearance of the molded product. Due to its low electrical conductivity, it is said to have drawbacks such as low shielding effect and high material cost. Therefore, the current situation is that there is still no definitive method for shielding plastics from electromagnetic waves.

(c) Problems to be solved by the invention: High electromagnetic shielding properties: It is said that electromagnetic shielding properties depend on the electrical conductivity of the material.

From this point of view, forming a metal layer in a plastic molded product provides excellent electromagnetic shielding properties no matter what kind of metal is used.

Appearance characteristics: Since the outer skin is made of plastic, the aesthetic characteristics are not affected in any way.

Durability: No matter how durable metal is used, problems such as corrosion will not occur because it is covered by the plastic outer shell.

Productivity 2. Since the manufacturing method according to the present invention is entirely based on the injection molding method, which is a conventional technology, the productivity is extremely high.The degree of freedom in configuration: Depending on the required performance of the structural parts.

The type of plastic, metal, thickness composition, etc. to be used can be freely selected.

Cost: High-speed, automated production is possible, and the materials used can be freely selected, making it possible to reduce the cost of 9 parts.

Electrical conductivity: It can also be used as an electrical circuit by using the metal layer formed inside.

It is possible to greatly improve the charging property that the chargeable niblastic has in this trade, that is, the electrostatic charging property.

X-ray shielding property: Good X-ray shielding property is shown when lead is used in the metal layer.

(d) Means for solving the problems The present invention basically utilizes the means of injection molding. In other words, the injection molding machine has two material injection cylinders. - One book is used to plasticize and inject plastic materials, and the other one is used to inject metals in a molten state.

Plastic materials and metal materials have the ability to freely change injection pressure, quantity, temperature, and speed by setting injection conditions.

On the other hand, the mold that is normally used can be used as is, and no special mechanism is required.

A mold that can form the desired molded product is attached to the injection molding machine, and the temperature is adjusted if necessary.

The plastic material is plasticized to an appropriate amount using the screw of the molding machine, and the metal material is also melted at the temperature required for fluidity.

Describing the process in more detail using FIG. 1, heating was performed to an appropriate temperature. When the screw in the 8 qJ output cylinder is rotated, the plastic molding material is compressed and melted as it is sent forward, and the molten material is accumulated at the front of the cylinder as the screw retreats. On the other hand, the metal is stored in the injection piston in a molten state. First, the valve 9 is opened and the screw 7 is advanced to inject an insufficient amount of plastic into the mold 2. Then, the valve 9 is closed, the valve 10 is closed, and the screw 7 is advanced to inject an insufficient amount of plastic into the mold 2.
The 2 ill gold metal 5 is injected into the 2 molds by the lowering of the piston. After this, the IO valve is closed for the next molding. After cooling, the mold is opened to obtain a molded product 2.

Furthermore, depending on the shape of the molded product, plastic and molten metal can be filled into a mold almost simultaneously while controlling the amounts and molded.

If a smaller amount of plastic material is injected relative to the volume of the cavity, the metal layer will be thicker, and if a larger amount is injected, the metal layer will be thinner. The molten metal injected from behind flows through the inner layer of plastic, and as it is pushed in, the plastic at the tip forms a skin layer throughout the mold.

Metals also have a larger heat capacity than plastics, which helps the fluidity of plastics, and furthermore, metals can be heated to fairly high temperatures, making them applicable to thin-walled molded products.

As the material used in the present invention, any thermoplastic resin can be used.

For example, polyethylene, polypropylene, ABs, p
VC, nylon, acrylic resin, polycarport, AS
Examples include resins, modified PPO, PEEK, PES, polyacetal, polystyrene, etc. The following materials are examples of the materials according to their melting points.

Tin-bismuth-lead-cadmium indium (melting point 47°C), tin-bismuth-lead-indium (melting point 58°C)
°C), tin-bismuth-lead-cadmium (melting point 70 °C)
, tin-bismuth-indium (melting point 78°C), bismuth-lead-cadmium (melting point 92°C), bismuth-lead-
II (melting point 96°C), bismuth-tin-power dome (melting point 103°C), tin-indium (melting point 117°C), bismuth-lead (melting point 124°C), bismuth-tin-zinc (melting point 130°C), bismuth- Tin (melting point 138°C), Bismuthucadium (melting point 144°C).

Tin-lead single strength dome (1 & point 145℃), ti-
Cadmium (melting point 176℃), fl-lead (melting point 183℃)
℃）、! ! -Zinc (La199℃), ! -v1
(11 points 221℃),! I-Copper (melting point 227℃), lead-
Cadmium (I!I! point 249°C), Cadmium zinc (melting point 266°C), Cadmium antimony (melting point 292°C).

Among single metals, tin, lead, zinc, bismuth, etc. are advantageous in terms of cost.

The present invention makes it possible to manufacture functional parts in a wide variety of combinations. For example, materials with low heat resistance such as polyethylene and ABS can be replaced by alloys with relatively low melting points, and materials with high melting points such as polycarbonate and super engineering plastics can be used. By using a high melting point metal, it is possible to improve the heat resistance characteristics of the tM molded product.

The thickness of the metal layer is determined by the initial injection amount of the plastic material and is determined by its required characteristics.

Furthermore, with the present invention, there is no problem no matter how complex the shape of the molded product is, because the plastic material can be filled in the details in any way, and the metal has a shape that is approximately similar to the center layer of the molded product. It is.

(f) ExamplesExamples, Electronic component cover (radius 100mm, depth 70m)
A mold capable of molding a molded product with a height of 50 mm, a wall thickness of 3 mm, and a total volume of 66 m1) was prepared, and the mold was attached to an injection molding machine and the temperature was adjusted to 60°C.

The molding machine has a mold clamping pressure of 100 tons and a plastic injection capacity of O.
An injection molding machine equipped with two cylinders with a metal injection capacity of ~280 g and a metal injection capacity of ~300 m was prepared. ABS is used as a plastic material, and bismuth is used as a metal material.
A tin eutectic alloy (melting point 138°C) was used. Each material was plasticized at an appropriate temperature. Of these materials, 80% of the required volume of plastic material was injected, and then metal was injected at a pressure of 500 kg/cm2 until the mold was completely filled. After cooling for 90 seconds, the mold was opened and the molded product was taken out. A metal layer with a uniform thickness was formed in the inner layer of the molded product.

Example 2. Using the mold and molding machine used in Example 1,
Polycarbonate was used as the plastic material, and a tin-lead eutectic alloy (melting point: 183°C) was used as the metal. The mold temperature was 90° C., the plastic material was plasticized at 280° C., and after 80% of its capacity was injected, the metal material was injected at 230° C. and 800 kg/cm 2 until the mold was filled. 9
After cooling the sand, the mold was opened and the molded product was taken out. A clean metal layer of about 0.6 mm was formed in the center layer Example 3 The mold and molding machine used in Example 1 were used, and glass fiber-filled nylon was used as the plastic material. The mold temperature is adjusted to 80℃, and the plastic material is regulated to 250℃.
It was plasticized. After injecting 50% of the required volume of plastic material.

Metal material (tin-zinc alloy, 1&point 199℃) at 250℃
until it melts and fills the mold, 500kg/cm
Filled with molten metal under a pressure of 2.

After cooling for 120 seconds, the mold was opened and the molded product was taken out. A metal layer with a thickness of 5 mm was formed in the center layer of the molded product.

(g) Effects of the invention Examples 1, 2, and 3. The electromagnetic wave shielding properties of the molded products obtained were measured.

TLlt(El Measurement frequency (mechanical help) 00 00 00 00 Attenuation (dB) Actual (1) Actual (2) Actual (3) 60 45 46 60 62 63 65 63 60 40 42 45 Engineering, l resistance example 11 ohm Example 2 below: Example 3 Below 1 ohm resistance] 1 ratio Example 1: 80"C No abnormality 10 hours at each temperature Example 2: No abnormality left at 20°C, appearance inspection Example 3: No abnormality at 120°C: Appearance characteristics carried out No difference in appearance was observed in any of the molded products obtained in Examples 2.3 and 2.3 compared to ordinary plastic molded products.

The molding cycle for both Examples 1 and 112*3 was within 120 seconds, which was no different from normal injection molding.

Although the present invention requires partial modification of the injection molding machine, the mold used for plastic molding can be used as is, and any complex-shaped product that can be molded by 11 injections can be molded. We were able to prove that it can be done. Furthermore, it has the great advantage of being able to freely select cost and performance by combining materials. Furthermore, it is a manufacturing method that has high productivity and can be carried out while maintaining the high-speed productivity of ordinary injection molding.

[Brief explanation of the drawing]

Figure 1 shows the principle diagram of the molding machine, l is the molded product forming part (called a cavity), 2 is the mold, 3 is the metal fIJU tank, 4
is a plunger type metal injection cylinder. 5 is a piston, 6 is a plastic raw material supply hopper, 7 is a screw, 8 is a heating cylinder, 9 is a plastic flow n
10 is a metal flow path opening/closing valve, 11 is molten plastic, and 12 is molten metal. Figure 2 shows the shape of the molded product and the cross-sectional structure of a part of it, 111 and 112.
113 indicates the plastic layer of the skin layer, and the metal layer injected into the center layer. Stem 1 Figure 12

Claims (1)

[Scope of Claims] 1. A plastic-metal composite molded article formed by injection molding into a structure consisting of a thermoplastic resin surface layer and a metal layer having a melting point of 47°C to 400°C as a center layer. 2. Using an injection molding machine that has the ability to inject both thermoplastic resin and metal, first, from the first cylinder through the same flow path (sprue), the total volume of the mold cavity is larger than the total volume of the mold cavity. A small amount of thermoplastic resin was injected and immediately thereafter melted to a suitable temperature from the second cylinder.
Injection molding to produce a molded product with a structure having a thermoplastic resin skin layer and a metal core layer by melting and injecting a metal with a melting point of 0°C to 400°C or by simultaneously injecting both. Law.