JPH0337577B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyolefin composition with excellent electromagnetic wave shielding properties. BACKGROUND ART In recent years, with the advancement of industry and higher standard of household life, the number of sources of radiation of radio waves and magnetic waves has increased. For this purpose, various methods of shielding radio waves and magnetic waves have been proposed. For example, synthetic resins mixed with relatively large amounts of additives such as carbon powder and/or aluminum powder have been proposed as shielding materials. However, among these materials, electromagnetic wave shielding materials filled with metal fillers such as aluminum powder exhibit an electromagnetic wave shielding effect in the initial stage of manufacture, but the electromagnetic wave shielding effect decreases over time, especially at high temperatures. There were significant drawbacks in the use of The present invention was made for the purpose of improving such drawbacks of conventionally known electromagnetic wave shielding resin compositions, and consists of (1) polyolefin and (2) powdered aluminum metal or aluminum alloy. (3)N,N'-bis-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionylhydrazine or 3-sali Shiloylamide-1,
0.01-2% by weight of 2,4-triazole, and (4)
Phenolic and/or sulfur-based antioxidants
An electromagnetic wave shielding polyolefin composition characterized by containing 0.01 to 2% by weight. Examples of the polyolefin in the present invention include homopolymers such as ethylene, propylene, 1-butene, 1-pentene, and 3-methyl-1-pentene, copolymers of ethylene and propylene, and ethylene and/or propylene with carbon numbers. Mention may be made of polyolefins such as copolymers with at most seven other alpha-olefins and copolymers of ethylene with vinyl compounds such as vinyl acetate, acrylic esters and methacrylic esters. Among these, low-density or high-density polyethylene, polypropylene, copolymers of ethylene and propylene, or copolymers of ethylene or propylene with other α-olefins are preferred. Among the powdered, fibrous or flaky materials of aluminum metal or aluminum alloy in the present invention, the powdered materials generally have an average size of 20 to 250 meshes.
In addition, the fibrous material generally has an average diameter of 2 to 200 microns and a length of 10 mm or less.
Furthermore, as a flake-like material, the cross section is generally
Round, square, with dimensions from 0.1×0.1mm to 5×5mm
It can be of any shape, such as rectangular or polygonal, but preferably has a thickness of 0.1 mm or less.
These powdered materials, fibrous materials, and flaky materials may be used alone, but two or more types can also be used in combination. Further, the aluminum content in the aluminum alloy is usually 80% by weight or more. This aluminum alloy typically contains magnesium, iron, manganese, copper, silicon, zinc, chromium, etc. The electromagnetic wave shielding property deterioration prevention agent in the present invention is
N,N'-bis-β-(3,5-di-t-butyl-
4-hydroxyphenyl)propionylhydrazine or 3-salicyloylamide-1,2,4-
It is a triazole. Examples of the phenolic antioxidant in the present invention include so-called hindered phenolic compounds in which a large group such as a tert-butyl group is introduced into the O-position of the phenolic OH to eliminate the properties of the phenolic OH. For example, 2,6-di-t-butyl-4-methylphenol, octadecyl-3-
(3,5-di-t-butyl-4-hydroxyphenyl)propionate, tetrakis[methylene-
3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,3,5
-Tris(3-hydroxy-2,6-dimethyl-
4-t-butylbenzyl) isocyanurate,
1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 4,4'-thiobis-(3-methyl-6-t-butyl phenol), 1,1,3-
Tris(2-methyl-4-hydroxy-5-t-
butylphenyl)butane, tris(3,5-di-
Examples include t-butyl-4-hydroxybenzyl) isocyanurate. Among these, 2,6-di-t-butyl-4-methylphenol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,
Tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane and the like are preferred. Examples of sulfur-based antioxidants include esters of thiodipropionic acid, such as dilaurylthiodipropionate, distearylthiodipropionate, laurylstearylthiodipropionate, dimyristylthiodipropionate, and tetrakis-( Examples include methylene-3-dodecylthiopropionate) methane. The content of aluminum metal or aluminum alloy powder, fibers, or flakes in the electromagnetic shielding polyolefin composition of the present invention is 1 to 60% by weight, and the electromagnetic shielding property deterioration prevention agent is 0.01% by weight. ~2% by weight, preferably 0.1
~0.5% by weight. In addition, the phenolic and/or sulfur-based antioxidant in the composition is 0.01~
2% by weight, preferably 0.03-0.5% by weight. Powdered material of aluminum metal or aluminum alloy in the resin composition obtained by the present invention,
If the content of the fibrous or flake-like material is less than 1% by weight, there will be no shielding effect against electromagnetic waves, while if it exceeds 60% by weight, the moldability and mechanical strength of the composition will deteriorate, which is not preferred. In addition, substituted hydrazines or substituted amidotriazoles and phenolic and/or sulfur-based antioxidants, respectively.
If it is less than 0.01% by weight, it will not be effective in preventing the deterioration of electromagnetic wave shielding property, while if it exceeds 2 parts by weight, the effect of preventing deterioration in electromagnetic wave shielding property will not be further improved.
On the other hand, this is not preferable because it causes contamination of the mold during molding and significant plate-out on the surface of the molded product. The composition of the present invention can be obtained by blending and uniformly mixing the above-mentioned components. For example, a uniform composition can be obtained by dry blending the above-mentioned components using a Henschel mixer, tumbler blender, etc., and then melt-kneading them using a screw extruder, Banbury mixer, kneader, roll, etc. At this time, it is effective to mix each component by adding by a master batch method or by kneading each component in advance and using a pellet form as a raw material. Furthermore, the composition obtained by melt-kneading is generally formed into pellets and then subjected to various molding processes. Examples of the molding method include injection molding, compression molding, and extrusion molding. Furthermore, molding methods commonly used in the field of thermoplastic resins such as stamping, compression molding using an extruded sheet, and vacuum molding can also be applied. In addition, when manufacturing the above composition, various additives such as ultraviolet absorbers, fillers, lubricants, nucleating agents, metal soaps, flame retardants, antistatic agents, pigments, etc. commonly used in thermoplastic resins are added. Additional agents may be added. As described above, the composition of the present invention not only has excellent electromagnetic wave shielding properties, but also has a good effect of preventing deterioration of the shielding properties over time, is lightweight, and can be processed and molded into any shape. Therefore, it is suitable for housing materials of office equipment such as facsimile machines, printers, and word processors, and electronic equipment such as televisions, video cameras, and electronic computers, as well as internal articles thereof. Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that % in Examples and Comparative Examples indicates weight, and the effect of preventing a decrease in electromagnetic wave shielding property was evaluated by measuring the volume resistivity over time. In the volume resistivity test, the resistance of a 2 mm thick test piece was measured in an atmosphere with a temperature of 23° C. and a humidity of 60%, and the resistance was calculated using the following formula. Volume resistivity (Ω・cm)=R×T×W/L Here, R is the measured resistance value (Ω), T is the thickness of the test piece (cm), W is the width of the test piece (cm), and L represents the distance (cm) between the electrodes. Examples 1 to 6 Comparative Example 1 Melt flow index (measured under the conditions of temperature 230℃ and load 2.16Kg according to JIS K6758) 20g/10
of propylene-ethylene block copolymer (ethylene content: 7% by weight), aluminum alloy fibers (hereinafter referred to as Al alloy fibers) in the proportions shown in Table 1, N,N'-bis-β-(3,5- G-t-
butyl-4-hydroxyphenyl)propionylhydrazine [hereinafter referred to as electromagnetic shielding property deterioration inhibitor (A)], 3-salicyloylamide-1,2,4-triazole [hereinafter referred to as electromagnetic shielding property deterioration inhibitor (B)] ], 2,6-di-t-butyl-4-methylphenol [hereinafter referred to as antioxidant (A)], tetrakis[methylene-3-(3,5-di-t-butyl-4-
hydroxyphenyl) propionate] methane [hereinafter referred to as antioxidant (B)], distearyl thiodipropionate [hereinafter referred to as antioxidant (C)], and metal soap (calcium stearate) 0.03%
were blended and dry blended using a Henschel mixer, and then the mixture was melt-kneaded using an extruder at 200°C to form pellets. Using this pellet, a sheet with a thickness of 2 mm was molded by injection molding. This sheet was used as a test piece before heat treatment and at 150℃.
After heat treatment in an air oven, the changes in volume resistivity over time and the heat resistance life (number of days until discoloration) were observed, and the results are shown in Table 1.

【table】

[Table] Examples 7 to 9 Comparative Example 2 In Example 1, melt index (JIS
Using high-density polyethylene with a density of 0.960 g/cm ³ (measured using K6760 at a temperature of 190°C and a load of 2.16 kg) at 20 g/10 minutes, Al alloy fibers, an electromagnetic shielding property deterioration inhibitor, and an antioxidant were prepared. The volume resistivity was measured in the same manner except that the ratio shown in Table 2 was used, and the results are shown in Table 2.

【table】

Claims (1)

[Claims] 1 (1) Polyolefin, (2) 1 to 60% by weight of aluminum metal or aluminum alloy powder, fibers, or flakes, (3) N,N'-bis-β-(3,5- di-t-butyl-4-hydroxyphenyl)propionylhydrazine or 3
- electromagnetic wave shielding characterized by containing 0.01 to 2% by weight of salicilloylamide-1,2,4-triazole, and (4) 0.01 to 2% by weight of a phenolic and/or sulfur-based antioxidant. polyolefin composition.