JPS6297806A - Manufacture of metal fiber containing styrene-based resin molded product - Google Patents

Abstract

PURPOSE:To manufacture a styrene-based molded product containing metal fibers, which have favorable shielding effect against electromagnetic waves and well disperse in the molded part, by a method wherein molding is performed by blending rubber modified styrene-based resin with rubber unmodified styrene- based resin containing the metal fibers. CONSTITUTION:Rubber unmodified styrene-based resin is charged through the hopper 2 of an extruder 1 so as to be melted in the extruder and to be fed to the die part 4 at the tip of the extruder by means of a screw 7. Metal fiber bundles are introduced from the inlet 3 for metal fiber bundle so as to be extruded integrally with the resin melted at the die part in the form of a strand in order to be pressed with rolls 5 while the resin is in the molten or plastic state. The resultant metal fiber containing resin strand is cut in proper lengths and, after that, use by blending them with rubber modified styrene-based resin such as high-impact polystyrene (HIPS), ABS resin or the like. With the operation as mentioned above, a styrene-based molded product containing metal fibers which have favorable electromagnetic wave shielding effect and favorable external appearance are obtained.

Description

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

Conventional technology In recent years, various proposals have been made to prevent electromagnetic interference, including methods to 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, continuous metal fibers are used, and a polymer is extruded and coated on top of the metal fibers.The extrudate containing the metal fibers is then shredded into pellets. Methods of application to shielding materials and other materials have been proposed in Japanese Patent Application Laid-open Nos. 51-59944, 58-215313, and 59-412413. It is not possible to produce a satisfactory product when subjected to 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, it has a good shielding effect against electromagnetic waves, and has good dispersibility when molded.
Therefore, a metal fiber-containing thermoplastic resin composition that gives molded products with a good appearance is desired, and a method for producing a molding material containing a conductive filler suitable for such purposes is disclosed in Japanese Patent Application Laid-Open No. 5-3.
-128704.

However, depending on the selection of thermoplastic resin used in this method, the mixture of filler-containing pellets and matrix resin may be poor, resulting in poor appearance of the molded product. It was a problem if you did.

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 relates to a method for producing a molded article of styrenic resin containing metal fibers.

■Process of melting rubber-unmodified styrenic resin; ■Process of introducing continuous metal fiber bundles into the melted rubber-unmodified styrenic resin; ■Integration of rubber-unmodified styrenic resin and metal fiber bundles. A step of pressing the rubber unmodified styrenic resin composition with a roll while it is in a molten or plastic state; ■ A step of cutting the metal fiber-containing rubber unmodified styrenic resin composition into pellets; This is a method for producing a metal am-containing styrenic resin molded article, which comprises mixing a resin and a rubber-modified styrenic resin and molding the mixture.

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 maintain 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 tata-containing resin composition is prepared in advance using rubber-unmodified styrenic resin, and then After cutting it into a size, it is mixed with a rubber-modified styrene resin such as high impact polystyrene (HIPS) or ABS resin for use.

Note that, 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 styrene resin, which does not contain rubber, by combining it with the metal fiber bundle, and when it is pressed with a roll and then cut with a cutter, etc. It is easy to obtain pellets with a clean cut surface, and when the pellets and rubber-modified styrene resin pellets are mixed and molded, metal tungsten & fibers impregnated with styrene resin that does not substantially contain rubber can be obtained. This is thought to be due to a combination of effects such as ease of dispersion during the plasticization process.

Rubber-unmodified styrenic resins used in such cases include polystyrene resins, AS resins (styrene-7crylonitrile copolymer resins), MS resins (styrene-methyl methacrylate copolymer resins), and styrene/anhydrous resins. 50% maleic acid resin, other styrene, methylstyrene
Copolymer resins with one or more monomers copolymerizable with the above monomers are used. In addition, the rubber content must be within a range that does not lose its unmodified rubber properties, that is, the rubber content is 1%.
The following may also be used:

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

For example, high impact polystyrene (HIPS) which is rubber modified polystyrene, ABS resin which is rubber modified styrene-acrylonitrile copolymer resin, ASA resin, rubber modified resin which is styrene-methyl methacrylate copolymer resin,
Rubber modified resin of styrene-maleic anhydride copolymer resin,
Other examples include rubber-modified styrene copolymer resins obtained from styrene, methylstyrene, and other vinyl aromatic monomers and monomers that can be copolymerized.

Rubbers used for modification include polybutadiene, 5BR
1. Natural rubber, polyisoprene, etc., diene rubber, acrylic ester rubber, ethylene propylene rubber, ethylene propylene diene rubber, etc.

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 a rubber-unmodified styrene resin,
It may be added at the stage of compositing with 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 process of melting the thermoplastic resin, any conventionally used equipment that can plasticize and melt the resin may be used. Any device that can continuously supply the thermoplastic resin in a molten state to the place where it is to be integrated with the metal fiber bundle can be used.

To introduce metal fiber bundles into molten thermoplastic resin,
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 to be 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 may be difficult to cut in the next step, or it may be difficult to cut, perhaps 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. In other words, 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 set by the operating conditions of the plasticizing and melting device, such as the screw rotation speed of the extruder. ,
Not only is this convenient, but roll suppression can be performed smoothly.

The surface temperature of the roll during pressing is preferably at a temperature at which the resin does not stick, since 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 purpose of heating the roll can be achieved by providing an internal heater or by externally applying infrared heating, and the temperature is set according to manufacturing conditions.

In addition, the obtained metal M Masato wrist strand is usually 3~
Cut into 20 mm pieces and use as 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. 101 m is suitable.

As the metal fiber used in the present invention, continuous metal fibers such as ordinary steel, stainless steel, shell, lead, etc. can be used.
In terms of shielding effect and the environmental resistance of the metal fiber itself,
Stainless steel is preferred.

The diameter of the metal fiber or the equivalent diameter expressed by (hereinafter both simply referred to as diameter) is 2 to 50 IL11, preferably 8 to 25 IL11. If the diameter is smaller than this, it will be extremely difficult to impregnate the molten thermoplastic resin, and the shielding effect will also be reduced.

Moreover, if it is larger than 50 mm, the shielding effect will be lowered with the same addition amount, and it will be necessary to contain a large amount of fiber, 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 several hundred to several hundred fibers are collected. Supplied as metal fiber bundles.

The content of metal fibers in the molded article is determined by the desired shielding effect, especially the type of radio or magnetic waves, the frequency and the required d
Although it varies depending on the B value etc., it is generally about 0.5 mmol 1% to 3 mmol 1%.

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

A non-rubber-modified styrene-based resin is charged into the hopper 2 of the extruder 1, melted within 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 a fiber bundle, integrates with the melted resin in the die section, and then comes out in the form of a strand, so it is passed through the roll 5 while the resin is in a molten or plastic state. Press with .

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 cross-to-rad die in the die section.

After roll compression, it is customary to cool and cut with a strand cutter to form pellets, but in order to obtain the desired cross-sectional shape such as round or square, it is necessary to Passing the die 11 is also an application of the present invention,
This 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. AS from hopper 2
Resin (manufactured by Nippon Steel Chemical Co., Ltd., estyrene AS-41,7
, 104°C), and a continuous stainless steel fiber bundle (filament diameter 15 pot) is supplied from the inlet 3 for supplying the metal fiber bundle.
, 1,500 pieces (manufactured by Nippon Kumisen Co., Ltd.) were supplied.

The extruder has a cylinder temperature of 200 to 220°C and a die part of 2
The temperature was 20° C., and the screw rotation speed was 50 r, p, m.

A strand-shaped resin composition containing stainless steel fiber bundles was obtained from the die outlet of the extruder. This is heated from the back of the roll using an infrared heater to bring the surface temperature to 45-50℃.
It was pressed with a roll 5 maintained at a constant temperature. The advancing speed of the strand was determined by the number of rotations of the roll, and the number of rotations of the roll 5 was adjusted so that tension was applied to the strand 8.

The obtained strand was cut into a low length using a cutting machine 6 to form pellets. The cutting conditions in Cuts II & 6 were good.

The pellets contained 34 wt% stainless steel fibers.

The obtained pellets and ABS resin were mixed into stainless steel 1
Tri-blending was carried out so that ata was 10 wt%, and a test piece of 150 mm x 15 axial layers x 3 mm thick was prepared using an injection molding machine, and the shielding effect was measured and the appearance was observed.

Electric field Magnetic field shielding effect 44dB 25dB (10
0 MHz) Reference, 3 quantities ■ 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, the resultant resin not only developed a brownish color, but also the resulting strands stood up and could not be easily cut by a cutting machine. It didn't progress.

Example 2 As a stainless steel fiber bundle, filament diameter 8 gm,
Using 4,500 filaments, metal H and fiber containing pellets were prepared in the same manner as in Example 1, and mixed with ABS resin to obtain a molded product.

The shielding effect is 45 dB for electric field and 24 dB for magnetic field.
The appearance was also good.

Example 3 Instead of AS resin, GP polystyrene (manufactured by Nippon Steel Chemical Co., Ltd., Estyrene G-15, Tg 102°C) was used,
The same procedure as in Example 1 was conducted except that HI polystyrene (Estyrene H-85, manufactured by Nippon Steel Chemical Co., Ltd.) was used instead of the ABS resin. 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 1 Instead of GP polystyrene in Example 3, HIPS
(Manufactured by Nippon Steel Chemical Co., Ltd., Esterene H-65, Tg 1
00° C.) to obtain pellets containing stainless steel fibers (stainless steel fiber content 35%). that time,
By cutting the roll into much smaller pieces than in Example 3, it was possible to cut it with a strand cutter.

The obtained pellets and HIPS were mixed so that the stainless steel fibers were 10 w and t%, 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 a part of the screw first and contained metal fibers, and the fragmented pellets tended to remain on top, so the mixed pellets were removed little by little. - By putting it into the hopper, we were finally able to obtain a molded product.

Uneven distribution of fibers was observed in the molded product, and the appearance was uneven.
It was in 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 Master 4-7 containing a large amount of metal fibers can be obtained, by changing the mixing ratio with 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 cross-to-rad die in the die portion. 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 input port), 3
...Entrance of metal fiber bundle, 4. Fighting, Dice part, 5φ fist.
Pressing roll, 6. Φ cutting machine, 7... Screw of extruder, 8... Integration of metal m and resin coming out of the die part, 9... Pressed with Φ roll. Rear strand, 10... Receiver, 11, φ, shaping die, 1
2...Inlet of multiple metal fiber bundles.

Claims (1)

[Scope of Claims] (1) A method for producing a molded article of styrenic resin containing metal fibers, comprising: (1) melting a rubber-unmodified styrenic resin;
) a step of introducing a continuous metal fiber bundle into the molten rubber-unmodified styrenic resin; (3) while the integrated rubber-unmodified styrenic resin and metal fiber bundle is in a molten or plastic state; (4) cutting the metal fiber-containing rubber-unmodified styrenic resin composition into pellets; A method for producing a metal fiber-containing styrenic resin molded product, which comprises mixing and molding. (2) The manufacturing method according to claim (1), wherein the roll surface temperature during pressing with the roll is heated to a temperature equal to or lower than the glass transition temperature (Tg) of the rubber-unmodified styrenic resin.