JPH0369284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a styrene resin molded article containing metal fibers.

Conventional technology In recent years, various proposals have been made to prevent electromagnetic interference, including methods that make only the surface conductive, such as vacuum evaporation, application of conductive paint, and zinc spraying, and methods that include conductive materials in resin. There are two main types of molding methods:

In the former, there are concerns about peeling during use, and in the case of complex shapes, there is great difficulty in implementing it, while in the latter, although it is a desirable method without the above-mentioned drawbacks, it is difficult to use conductive materials. It is difficult to disperse uniformly and to produce molded products with good appearance.

When incorporating a conductive material into a resin, a continuous metal fiber is used, and a polymer is extrusion coated onto the continuous metal fiber. The extrudate containing the metal fiber is then shredded into pellets. Methods of application to shielding materials and other materials have been proposed in JP-A-51-59944, JP-A-58-215313, JP-A-59-41246, etc., but these are likely to have been revised later. Unable to produce a satisfactory product during the molding process.

That is, the dispersion in the molded product may be poor and a product with a good appearance may not be obtained. Therefore, there is a need for a metal fiber-containing thermoplastic resin composition that has a good shielding effect against electromagnetic waves, has good dispersibility when molded into a molded product, and can give a molded product with a good appearance. A method for manufacturing a molding material containing a conductive filler is proposed in JP-A-59-128704.

However, depending on the selection of the thermoplastic resin used in this method, the filler-containing pellets and the matrix resin may not mix well, resulting in poor appearance of the molded product. This was a problem when manufacturing.

Problems to be Solved by the Invention An object of the present invention is to provide a method for producing a metal fiber-containing styrenic resin molded product that has a good shielding effect against electromagnetic waves and has good dispersibility in the molded product.

Means for Solving the Problems The present invention provides a method for producing a molded article of styrenic resin containing metal fibers, which includes the steps of: melting rubber-unmodified styrenic resin; The process of introducing a continuous metal fiber bundle, while the integrated rubber-unmodified styrenic resin and metal fiber bundle is in a molten or plastic state, the roll surface temperature is adjusted to the glass transition of the rubber-unmodified styrenic resin. A step of pressing with a roll heated to a temperature (Tg) or below, a step of cutting the metal fiber-containing rubber-unmodified styrenic resin composition into pellets, and a rubber-unmodified styrenic resin containing metal fibers obtained from the rubber-modified styrenic resin composition and rubber-modified resin composition. 1. A method for producing a metal fiber-containing styrenic resin molded product, which comprises mixing a styrene resin and molding the product, and using a styrene-acrylonitrile copolymer resin as the rubber-unmodified styrenic resin.

More preferably, when pressing with a roll, in order to prevent the resin, fibers, etc. from fuzzing, the surface temperature of the roll is heated to a temperature lower than that at which the rubber-unmodified styrenic resin used reaches a molten state. At that time, it is desirable to keep the surface temperature of the roll below the glass transition temperature (Tg) of the resin.

When applying the method of the present invention to produce a molded article mainly made of rubber-modified styrenic resin, a metal fiber-containing resin composition is prepared in advance using rubber-unmodified styrenic resin, and then the metal fiber-containing resin composition is After cutting to size, high impact polystyrene (HIPS),
Used by mixing with rubber-modified styrene resin such as ABS resin.

If necessary, a small amount of rubber-unmodified styrenic resin may be added.

Although we do not know the details of the reason for this, it is easy to impregnate the resin by combining the styrene resin, which does not substantially contain rubber, with the metal fiber bundle. It is easy to obtain pellets with a clean cut surface when cut, and when the pellets are mixed with rubber-modified styrene resin pellets and molded, it is impregnated with a styrene resin that does not substantially contain rubber. This is thought to be due to a combination of effects such as the ease with which the metal fiber bundles are easily dispersed during the plasticization process.

AS resin (styrene-acrylonitrile copolymer resin) is used as the rubber-unmodified styrene resin.

As the rubber-modified styrene resin, the rubber-modified resins listed above are used.

For example, high impact polystyrene (HIPS) which is a rubber modified polystyrene, ABS resin which is a rubber modified styrene-acrylonitrile copolymer resin,
ASA resin, rubber-modified resin of styrene-methyl methacrylate copolymer resin, rubber-modified resin of styrene-maleic anhydride copolymer resin, and other monomers that can be copolymerized with styrene, methylstyrene, and other vinyl aromatic monomers. These include rubber-modified resins of the resulting styrenic copolymer resins.

Rubbers used for modification include diene rubbers such as polybutadiene, SBR, natural rubber, and polyisoprene, acrylic ester rubber, ethylene propylene rubber, and ethylene propylene diene rubber.

The rubber-unmodified styrenic resin and rubber-modified styrenic resin used may contain additives such as stabilizers, flame retardants, mold release agents, dyes and pigments, and plasticizers (oil lubricants), and these additives may not be used. The agent is
It may be added at the stage of compositing the rubber-unmodified styrenic resin and metal fibers or at the time of molding the styrenic resin containing metal fibers and the rubber-modified styrenic resin.

In carrying out the present invention, in the step of melting the thermoplastic resin, any conventional equipment that can plasticize and melt the resin may be used for extrusion molding of resins. A suitable extruder is suitable, and any device can be used as long as the thermoplastic resin in a molten state is continuously supplied to the place where it is to be integrated with the metal fiber bundle.

To introduce a metal fiber bundle into a molten thermoplastic resin, the fibers are introduced into a die section (straight type, crosshead type, etc.) installed near the tip of an extruder or the like after the melting section. The diameter of the hole introduced is slightly larger than the size of the fiber bundle used to prevent backflow of the resin.

When the thermoplastic resin and metal fiber bundle obtained in this way are integrated, it is difficult to cut in the next step, or it is difficult to cut, probably because the fiber bundle contains gas components such as air. However, since the fibers may not be sufficiently dispersed in the molded product, it is necessary to press the molded product with a roll. The degree of pressure of the rolls may be such that air etc. are removed and the metal fiber bundle is sufficiently impregnated with the resin. If one stage is insufficient, the treatment may be performed using multiple stages of rolls.

Further, after the thermoplastic resin and the metal fiber bundle are integrated in a plasticizing and melting device such as an extruder, it is desirable to apply tension to prevent sag while pressing with rolls. That is, the amount of metal fibers in the pellets obtained by applying tension and pressing can be adjusted by adjusting the roll speed, etc., and the amount of resin can be adjusted by adjusting the screw rotation speed of the extruder, etc.
Since it can be set depending on the operating conditions of the plasticizing and melting device, it is not only convenient, but also enables smooth roll pressing.

The surface temperature of the roll during pressing is preferably at a temperature at which the resin does not stick, since the pressing is performed while the resin is in a molten state, and is preferably below the glass transition temperature (Tg) of the rubber-unmodified styrene resin used. It is desirable to do so.

The roll can be heated by installing a heater inside or
The purpose can be achieved by externally applying infrared heating, etc., and the temperature is set according to the manufacturing conditions.

The resulting metal fiber-containing strand is usually cut into pieces of 3 to 20 mm and used in the form of pellets.

In order to improve the shielding performance when manufacturing molded products using this metal fiber, it is desirable that the metal fiber be long, but if it is too long, it will tend to be difficult to disperse in the next molding process. 10mm is preferred.

As the metal fiber used in the present invention, continuous metal fibers of ordinary steel, stainless steel, shell, lead, etc. can be used, but stainless steel is preferable from the viewpoint of shielding effect and environmental resistance of the metal fiber itself.

The diameter of the metal fiber or the equivalent diameter expressed by the cross-sectional area pi of the 2√ fiber (hereinafter both are simply referred to as diameter) is 2 to 50 μm, preferably 8 to 25 μm. If the diameter is smaller than this, it becomes extremely difficult to impregnate the molten thermoplastic resin, and the shielding effect also decreases. Moreover, if the diameter is larger than 50 μm, the shielding effect will be lowered with the same addition amount, so it will be necessary to contain a large amount of fibers, which is not preferable.

In the present invention, metal fibers are introduced into a molten thermoplastic resin in a bundled state, but the number of metal fibers varies depending on the characteristics and shape of the final molded product, and may range from several hundred to tens of thousands. Supplied as collected metal fiber bundles.

The content of metal fiber in the molded product varies depending on the desired shielding effect, especially the type of radio wave or magnetic wave, frequency, and required dB value, but it is 0.5 vol%.
~3vol% is common.

FIG. 1 shows an outline of an apparatus for a basic manufacturing method for carrying out the present invention.

A non-rubber-modified styrene resin is charged into the hopper 2 of the extruder 1, melted in the extruder, and supplied by the screw 7 to the die section 4 at the tip of the extruder.

The metal fiber bundle is introduced from the inlet 3 of the metal fiber bundle, integrates with the molten resin in the die section, and then comes out in the form of a strand. While the resin is in a molten or plastic state, it is rolled by the roll 5. Press.

Thereafter, it is cut by a cutting machine 6 as needed and stored in a receiver 10.

FIG. 2 is an example of an apparatus using a crosshead die in the die section.

After pressing with a roll, it is customary to cool it and cut it with a strand cutter to form pellets, but in order to obtain the desired cross-sectional shape such as round or square, shape the pellets as shown in Figure 3. Passing through the die 11 is also an application of the present invention and is one of the embodiments.

Moreover, FIG. 4 shows an example of application of the present invention in the case of obtaining a plurality of strands using a plurality of metal fiber bundles, and 12 in the figure is an inlet of the plurality of metal fiber bundles.

Furthermore, it is also possible to charge a plurality of metal fiber bundles from one inlet.

Examples of the present invention are shown below.

Example 1 An apparatus having the configuration shown in FIG. 1 was used. Hopper 2
AS resin (manufactured by Nippon Steel Chemical Co., Ltd., ethylene AS-
41, Tg 104°C), and continuous stainless steel fiber bundles (filament diameter 15 μm, 1500 pieces, manufactured by Nippon Seisen Co., Ltd.) were supplied from the inlet 3 for supplying metal fiber bundles.

The extruder has a cylinder temperature of 200 to 220°C and a die part.
The temperature was 220°C, and the screw rotation speed was 50 r.pm.

A strand-shaped resin composition containing stainless steel fiber bundles was obtained from the die outlet of the extruder. This was heated with an infrared heater from the rear of the roll and pressed with a roll 5 whose surface temperature was maintained at 45 to 50°C. The advancing speed of the strand was adjusted by the rotation speed of the roll, and the rotation speed of the roll 5 was adjusted so that tension was applied to the strand 8.

The obtained strand was cut into a length of 10 mm using a cutting machine 6 to form pellets. The cutting conditions in cutting machine 6 were good.

The pellets contained 34 wt% stainless steel fibers.

The obtained pellets and ABS resin were dry blended so that the stainless steel fiber content was 10wt%, and a test piece of 150mm x 150mm x 3mm thick was prepared using an injection molding machine, and the shielding effect was measured and the appearance was observed. I did it.

Electric field Magnetic field Shielding effect 44 dB 25 dB (100 MHz) Reference, 3 mm steel plate 58 dB 49 dB (same as above) In addition to showing a good shielding effect as described above, there were almost no fiber clumps and a good appearance.

For comparison, when the roll temperature was set to 150°C, not only did the yellowish-brown coloration occur due to the adhering resin, but the resulting strands became fluffy and cutting with a cutting machine did not proceed well.

Example 2 As a stainless steel fiber bundle, filament diameter
Example 1 using 8 μm and 4500 filaments.
Similarly, prepare metal fiber-containing pellets,
A molded product was obtained by mixing with ABS resin.

The shielding effect was 45 dB in electric field and 24 dB in magnetic field, and the appearance was good.

Comparative Example 1 GP polystyrene (manufactured by Nippon Steel Chemical Co., Ltd., Estyrene G-15, Tg 102°C) was used instead of AS resin,
HI polystyrene (Nippon Steel Chemical) instead of ABS resin
The same procedure as in Example 1 was conducted except that Esterene H-65 (manufactured by Co., Ltd.) was used. The results showed the same shielding effect as in Example 1, but there were more silver stripes than in Example 1, and the overall appearance was rather poor.

Comparative Example 2 Instead of GP polystyrene in Example 3,
HIPS (manufactured by Nippon Steel Chemical Co., Ltd., ester H-65,
Pellets containing stainless steel fibers were obtained (stainless steel fiber content: 35
%). At that time, by making the rolls more uneven than in Example 3, it was possible to cut them with a strand cutter.

The obtained pellets and HIPS were mixed so that the stainless steel fiber content was 10 wt%, and injection molding was performed in the same manner as in Example 3.

In the hopper of an injection molding machine, it was observed that normal pellets went to the screw section first and contained metal fibers, and the fragmented pellets tended to remain on top. ,
By putting it into a hopper, we were finally able to obtain a molded product.

Uneven distribution of fibers was observed in the molded product, and the appearance was not uniform and was in a rather poor condition.

Also, variations were observed in the shielding effectiveness.

Effects of the Invention According to the present invention, a styrenic resin molded product containing metal fibers that has a good electromagnetic shielding effect and a good appearance can be obtained with a relatively simple operation.

Furthermore, since a masterbatch containing a large amount of metal fibers can be obtained, by changing the mixing ratio with a resin that does not contain metal fibers, it is possible to provide a composition having a shielding effect that meets the requirements.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an outline of an apparatus for the basic manufacturing method of the present invention. FIG. 2 is an explanatory diagram of the present invention using a crosshead die in the die section. FIG. 3 is an explanatory view of the present invention in which a shaping die is inserted after being pressed by a roll. FIG. 4 is an explanatory diagram of the present invention in which a plurality of metal fiber bundles are used to obtain a plurality of strands. 1... Extruder, 2... Hopper (resin inlet), 3
...Inlet of metal fiber bundle, 4...Dice section, 5...press roll, 6...cutting machine, 7...screw of extruder, 8
...integrated metal fiber bundle and resin coming out of the die part, 9...strand after being pressed by rolls, 10...receiver, 11...forming die, 12...multiple metal fiber bundles entrance.

Claims (1)

[Scope of Claims] 1. A method for producing a molded article of styrenic resin containing metal fibers, comprising: a step of melting a rubber-unmodified styrenic resin; a continuous metal fiber bundle in the melted rubber-unmodified styrenic resin; The roll surface temperature is lowered to below the glass transition temperature (Tg) of the rubber-unmodified styrenic resin while the integrated rubber-unmodified styrenic resin and metal fiber bundle is in a molten or plastic state. a step of pressing with a roll heated to A method for producing a metal fiber-containing styrenic resin molded product, which comprises mixing and molding and using a styrene-acrylonitrile copolymer resin as the rubber-unmodified styrenic resin.