JPH0155294B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition containing a high concentration of metal foil pieces and a method for producing the same. BACKGROUND ART Recently, devices such as microwave ovens, TVs, and microcomputers that have built-in sources of electromagnetic waves have become widespread, and the chances of causing electromagnetic interference to communication devices, measuring instruments, etc. are increasing. Moreover, on the contrary, the chances that these devices will be affected by electromagnetic interference from the outside are increasing. When assembling these devices, metal casings are often used to avoid interference from electromagnetic waves, but since they require many processes such as molding and painting, they are not easy to mold. thermoplastic resin,
In addition, there was a desire to develop a material with a large amount of attenuation of electromagnetic waves passing through it. Thermoplastic resins are easy to mold, but if a large amount of metal foil (Al, Cu, etc.), which is effective at attenuating electromagnetic waves, is mixed and kneaded in order to provide an electromagnetic shielding effect, it will be difficult to form screws in a single-screw extruder. It was difficult to dig into the resin composition, and the metal foil pieces were difficult to be sufficiently dispersed in the resin by mechanical kneading alone, and the strength of the resulting resin composition was also unsatisfactory. The present inventors have discovered that the above-mentioned problems of the prior art can be solved by suspension polymerizing acrylic esters, especially aminoalkyl acrylates, in the presence of metal foil pieces (Japanese Patent Application No.
30051), and as a result of intensive research aimed at obtaining a composition with a large electromagnetic wave attenuation effect, the present invention was achieved. The above object of the present invention is to apply 1 to 10 parts by weight of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate, aminoalkyl acrylate and aminoalkyl methacrylate to a metal foil. Suspension polymerization was carried out in the coexistence of 100 parts by weight of
A thermoplastic resin composition containing metal foil pieces by adding 5 to 33 parts by weight of a mixture consisting of an aromatic vinyl monomer and a monomer copolymerizable with the aromatic vinyl monomer, and further suspension polymerizing the mixture. This is achieved by a method for producing an article, characterized in that the metal foil piece is a mixture of at least two types of metal foil pieces. The metal foil pieces used in the method of the present invention include thermoplastic resins such as aluminum (Al), zinc (Zn), copper (Cu), iron (Fe), tin (Sn), gold (Au), and silver (Ag). It is preferable to use a metal that is stable, does not melt or evaporate, and exhibits good electrical conductivity at the molding temperature (usually 230 to 260°C). When the at least two types of metal foil pieces to be mixed are combined to mutually differ from the groups of the periodic table to which the metals belong, the resistivity of the resulting composition is preferably reduced more significantly. For example, Al
- Combinations of Zn, Al-Cu, etc. give good results. The mixing ratio is as follows for the combination of Al-Zn foil pieces:
It is preferable that 3 to 70% by weight of the Zn foil pieces are Al foil pieces, and more preferably 5 to 20 weight% of the Zn foil pieces, with the remainder being Al foil pieces. The proportion of Zn foil pieces is less than 3% by weight or 70% by weight
In the case of exceeding 20%, no improvement was observed in specific resistance and electromagnetic wave attenuation compared to cases where only Al foil pieces or only Zn foil pieces were used, respectively. Al and
The above mixing ratio is also appropriate when mixing Cu foil pieces. The size of the metal foil piece is preferably a rectangular piece with a thickness of 5 to 50 μm and a side of 0.5 to 5 mm, more preferably a rectangular piece with a side of 1 to 2 mm. There is no problem with other shapes as well. The surface of these metal foil pieces is coated with a polymer of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylate, aminoalkyl acrylate, alkyl methacrylate, and aminoalkyl methacrylate. . These polymers are suitable because they have high adhesion to metal foil pieces. In this case, a piece of metal foil
A suitable polymer is obtained by polymerizing 1 to 10 parts by weight of the above monomer per 100 parts by weight. If it is less than 1 part by weight, there is no coating effect, and if it exceeds 10 parts by weight, the amount of polymer that does not adhere to the surface of the metal foil increases, which may adversely affect the physical properties of the composition, which is not preferable. The polymer used to coat the metal foil piece may be one obtained by polymerizing the above-mentioned monomers alone, or may be one obtained by polymerizing a mixture of two or more arbitrary monomers. For example, methyl methacrylate is polymerized alone, acrylic acid is 10 to 30 wt.
A polymerized mixture of methyl methacrylate and acrylic acid containing 30 to 70 wt% of aminoalkyl acrylate or aminoalkyl methacrylate is used, and in particular, a polymerized mixture of methyl methacrylate and aminoalkyl methacrylate containing 30 to 70 wt% of aminoalkyl methacrylate is used because of the electromagnetic waves. It is excellent in terms of damping properties, coverage of metal foil pieces, and compatibility with other resins. In this case, the aminoalkyl group is dimethylaminoethyl group ((CH ₃ ) ₂ NCH ₂ CH ₂ −)
is preferred, but other diethylaminoethyl groups,
Dimethylaminopropyl group and the like can also be used. Further, as the alkyl group, a linear, branched, or cyclic alkyl group having about 1 to 10 carbon atoms is used, but a methyl group or an ethyl group is preferable from the viewpoint of physical properties of the resulting polymer, such as tensile strength. . The blending ratio of each monomer mixture is not limited to the above range, but if it is within the above range, good results can be obtained in terms of coverage, dispersibility, physical properties, etc. of the surface of the metal foil piece. . In order to coat a metal foil piece with the above-mentioned polymer, it is appropriate to use a method in which two types of metal foil pieces are mixed in advance and then subjected to suspension polymerization in the presence of the metal foil mixture. Subsequently, 5 to 33 parts by weight of a polymer obtained by polymerizing a mixture consisting of an aromatic vinyl monomer and a monomer copolymerizable with the monomer to 100 parts by weight of the initially used metal foil piece. parts and the polymer used to coat the surface of the metal foil piece so that the total amount is 6 to 43 parts by weight based on 100 parts by weight of the metal foil piece initially used. If the amount of the aromatic vinyl monomer and the monomer copolymerizable with it is less than 5 parts, the bulk density of the resulting composition will be low, making it difficult to blend with ABS resin, etc. Become. Also, if it exceeds 33 parts by weight,
When blending with ABS resin and other thermoplastic resins,
This is not preferred because it becomes difficult to increase the concentration of the metal foil pieces. Examples of the aromatic vinyl monomer used in the present invention include styrene, α-methylstyrene, vinyltoluene, and nuclear halogenated styrene. Further, as the "copolymerizable monomer", acrylonitrile, methacrylonitrile, and alkyl esters of acrylic acid and methacrylic acid are suitable. The appropriate concentration of these "copolymerizable monomers" in the monomer mixture is 20 to 50 wt%. If it is outside the above range, the compatibility with other resins may deteriorate, which is not preferable. In order to produce the composition according to the present invention, it is preferable to carry out suspension polymerization of each of the above monomers in the presence of a piece of metal foil. That is, 100 parts by weight of metal foil pieces, as well as acrylic acid, methacrylic acid, alkyl acrylate,
1 to 10 parts by weight of a monomer or monomer mixture selected from the group consisting of aminoalkyl acrylate, alkyl acrylate, and aminoalkyl methacrylate are suspended in water and subjected to suspension polymerization by a conventional method. . The use of a water-soluble initiator (such as persulfate) provides better coverage of the foil surface. After the polymerization is completed, 5 to 33 parts by weight of a mixture of an aromatic vinyl monomer and a monomer copolymerizable therewith are added to further carry out suspension polymerization. The effects of the present invention cannot be obtained even if the metal foil pieces are coated individually with a polymer of the above monomers without being mixed in advance and then used in combination. The resulting composition was in the form of a pellet made of several dozen metal foils laminated, had a high bulk density, and had good compatibility with ABS resin and the like. The composition according to the present invention can be used as it is, but it can also be used in combination with ABS resin, AS resin, etc. In this case, compounding can also be carried out using a single screw extruder. Furthermore, both the resistivity and the attenuation characteristics of electromagnetic waves were much better than when a single type of metal foil piece was used. Next, the method of the present invention will be explained in more detail based on Examples, Comparative Examples, and Application Examples. Example 1 2.0 kg of deionized water and a piece of aluminum foil (1.4 mm
×1mm×0.025mm, Transmet K-102) 280g
Add 40g of zinc foil pieces (2.0mm x 1mmmm x 0.020mm, manufactured by Fukuda Metal Foil Co., Ltd.) and stir well. to this,
After adding 8 g of methyl methacrylate and 8 g of dimethylaminoethyl methacrylate and purging the inside of the flask with nitrogen gas, the temperature was raised to 70°C.
After the polymerization system reaches 70℃, add 0.8g of potassium persulfate.
was added and reacted for 1.5 hours. Subsequently, the temperature was raised to 90°C and the mixture was reacted for 1 hour. Next, the temperature of the polymerization system was set at 80°C, 50 g of styrene, 34 g of acrylonitrile, 1 g of terpinolene as a chain transfer agent, 2 g of benzoyl peroxide and 0.5 g of azobisisobutyronitrile were added as an initiator, and polymerization was carried out for 2 hours. I did this. After the reaction is complete,
The temperature was raised to 90°C, and unreacted monomers were removed for 1 hour under nitrogen gas flow. The polymer containing the focused metal foil pieces was then separated using a 200 mesh wire mesh. The bulk density of the obtained polymer was 0.45 g/cm ² and the content of metal foil pieces was 82.6%. Example 2 A composition containing metal foil pieces was produced in the same manner as in Example 1, except that the metal foils used were changed to 300 g of aluminum foil pieces and 20 g of zinc foil pieces. The content of metal foil pieces was 83.5%. Example 3 A composition containing metal foil pieces was produced in the same manner as in Example 1 except that the metal foils used were changed to 160 g of aluminum foil pieces and 160 g of zinc foil pieces. The content of metal foil pieces was 82.0%. Example 4 A composition containing metal foil pieces was produced in the same manner as in Example 1 except that the metal foils used were changed to 280 g of aluminum foil pieces and 40 g of copper foil pieces. The content of metal foil pieces was 81.6%. Comparative Example 1 In Example 1, 320g of aluminum foil pieces
Example 1 except that no zinc foil pieces were added.
A composition containing metal foil pieces was produced in the same manner as above. The content of metal foil pieces was 83.3%. Comparative Example 2 Example 1 except that the aluminum foil piece was not added and the zinc foil piece was 720g.
A metal foil piece-containing composition was produced in the same manner as above.
The content of metal foil pieces was 91.0%. Comparative Example 3 In Example 1, only a piece of copper foil was used as the metal foil.
A composition containing metal foil pieces was produced in the same manner as in Example 1 except that 320 g was used. The content of metal foil pieces was 83.0%. Application Examples 1 to 7 The compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were
After dry blending with ABS resin (Mitsubishi Monsanto Chemical Co., Ltd. TFX-455AB) to a concentration of 45wt%,
It was pelletized and injection molded. The physical properties of the resulting composition molded article were as shown in Tables 1 and 2. Application Example 6 The compositions obtained in Comparative Examples 1 and 2 were applied to an Al foil piece of 87.5
After mixing the Zn foil pieces in a proportion of 12.5% by weight, dry blending with ABS resin was performed in the same manner as in Application Example 1, and the physical properties were measured. The results are shown in Table 1. Application Example 7 After mixing 87.5% by weight of the Al foil pieces used in Example 1 and 12.5% by weight of the Zn foil pieces, ABS resin (used in Application Example 1) was mixed using a twin-screw extruder so that the metal content was 45% by weight. The result of blending with
It is shown in Table and Table 2.

[Table] The specific resistance of the 1.27 cm x 1.27 cm x 10 cm test piece is 10
It was calculated by measuring the resistance between cm.

[Table] To measure the electromagnetic wave attenuation, a 3.2 mm thick disk-shaped sample piece with an outer diameter of 90 mm and a hole with a diameter of 25 mm formed in the center is installed inside a coaxial transmission pipe, and input and The power ratio of the output was measured.

Claims (1)

[Scope of Claims] 1. 1 to 10 parts by weight of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate, aminoalkyl acrylate, and aminoalkyl methacrylate to 100 parts by weight of a metal foil piece. Subsequently, 5 to 33 parts by weight of a mixture consisting of an aromatic vinyl monomer and a monomer copolymerizable with the aromatic vinyl monomer are added for further suspension polymerization. A method for producing a thermoplastic resin composition containing a piece of metal foil, characterized in that the piece of metal foil is a mixture of at least two types of metal foil pieces. 2. The method according to claim 1, wherein the metal foil pieces are a mixture of 3 to 70% by weight zinc foil pieces and the balance aluminum foil pieces. 3. The method according to claim 2, wherein the metal foil pieces are a mixture of 5 to 20% by weight of zinc foil pieces and the balance aluminum foil pieces. 4. The method according to claim 1, wherein the metal foil pieces are a mixture of 3 to 70% by weight copper foil pieces and the balance aluminum foil pieces. 5. The method according to claim 1, wherein the metal foil pieces are a mixture of 5 to 20% by weight copper foil pieces and the balance aluminum foil pieces.