JPS6252771B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyolefin compositions. More specifically, (A) a polyolefin modified with an unsaturated carboxylic acid or a derivative thereof, or the modified polyolefin and a polyolefin, (B) a powder, fibrous and/or flake of aluminum metal or aluminum alloy. The present invention also relates to a polyolefin composition made of C conductive carbon black, and the object of the present invention is to provide a polyolefin composition having particularly excellent radio wave and magnetic shielding properties. The sources of radiation of radio waves and magnetic waves are increasing due to the advancement of industry and the standardization of household life. Therefore, leakage of radio waves and magnetic waves has negative effects such as dangerous harm to the human body and malfunction of ICs related to electronic devices, and has become a serious social problem. For these reasons, various methods have been adopted in recent years to shield radio waves and magnetic waves. In general, metals have the property of absorbing or reflecting radio waves and magnetic waves, so they cannot be used in microwave ovens.
It is used effectively as a shielding material for radio waves and magnetic waves in various communication devices. In addition, metal vapor deposition, painting, plating, etc. are applied to plastics for the same purpose. moreover,
Materials obtained by incorporating relatively large amounts of additives such as carbon powder and metal powder into plastics have also been used. However, methods that use metal as a material or methods that process plastics such as metal vapor deposition have drawbacks such as high specific gravity, poor workability, and difficult processing methods. Further, regarding the method of mixing additives, if a small amount of the additive is mixed, the effect cannot be fully exhibited. On the other hand, if a large amount is mixed in,
Although this method is effective, it has the drawback that the mechanical strength of the resulting molded product is significantly reduced. Based on the above, the present inventors conducted various searches to obtain a resin composition that does not have these drawbacks and has excellent radio and magnetic wave shielding properties. (A) "Unsaturated carboxylic acid or a polyolefin modified with a derivative thereof (hereinafter referred to as a "modified polyolefin"), or the modified polyolefin and a polyolefin [provided that the content of the unsaturated carboxylic acid and/or its derivative in (A) is 0.01 to 1.0% by weight (B) 5-50% by volume of aluminum metal or aluminum alloy powder, fibers and/or flakes; and (C) 5-50% by volume of conductive carbon black. A polyolefin composition consisting of a polyolefin and conductive carbon black or a polyolefin and an aluminum metal powder, fiber, or flake has a synergistic effect that cannot be imagined from the shielding properties against radio waves and magnetic waves obtained from a polyolefin and a conductive carbon black or a polyolefin and an aluminum metal powder, fiber, or flake. The present invention has been achieved based on the discovery that by showing the following and using a modified polyolefin as the polyolefin, the decrease in mechanical strength is so small that there is virtually no problem, and the processability is also excellent. The modified polyolefin used in the present invention can be obtained by modifying the polyolefin described below with an unsaturated carboxylic acid or a derivative thereof. Representative examples of unsaturated carboxylic acids or derivatives thereof include monobasic carboxylic acids with at most 10 carbon atoms and at least one double bond (e.g., acrylic acid, methacrylic acid); Dibasic carboxylic acids having at least one double bond (for example, maleic acid) and anhydrides of the dibasic carboxylic acids (for example, maleic anhydride, hymic anhydride). Among saturated carboxylic acids or derivatives thereof, maleic acid and maleic anhydride are particularly preferred. Modified polyolefins are generally prepared by treating polyolefins with unsaturated carboxylic acids and/or derivatives thereof in the presence of organic peroxides. The polyolefins include homopolymers of ethylene or propylene, copolymers of ethylene and propylene, copolymers of ethylene and/or propylene with other α-olefins having at most 7 carbon atoms ( copolymers of ethylene and vinyl compounds such as vinyl acetate, acrylic esters and methacrylic esters (copolymerization ratio of vinyl compounds is at most 50 mol%) , preferably at most 40 mol%).The molecular weight of these olefinic resins is generally 2 to 40% by mole.
1,000,000, preferably from 20,000 to 500,000, and particularly preferably from 50,000 to 300,000. Also low density and high density ethylene homopolymers,
Propylene homopolymers, copolymers of ethylene and propylene, and copolymers of ethylene or propylene with other α-olefins are preferred. To produce the modified polyolefin of the present invention,
Various known methods (e.g. solution method, suspension method,
Any manufacturing method based on the melting method) can be adopted. Among these production methods, when polyolefin is modified with an unsaturated carboxylic acid or its derivative by a solution method, the polyolefin and the unsaturated carboxylic acid and/or its derivative are added to a nonpolar organic solvent, and then radical initiation is performed. A modified polyolefin can be obtained by adding an agent and heating at a high temperature. Inorganic organic solvents used in this case include hexane, heptane, benzene, toluene, xylene, chlorobenzene and tetrachloroethane. In addition, as a radical initiator, 2,5-dimethyl-2,5-
Di(tert-butylperoxy)hexane, 2.5
-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and benzoyl peroxide. moreover,
The treatment temperature is the temperature at which the polyolefin used is dissolved, and is generally 110 to 160°C, particularly preferably 130 to 150°C. In addition, when polyolefin is modified with an unsaturated carboxylic acid or its derivative by a suspension method, the polyolefin and the unsaturated carboxylic acid and/or its derivative are added to a polar solvent (generally water), and then the above-mentioned It is obtained by adding a radical initiator and processing under high pressure at a temperature of 100°C or higher. Furthermore, when polyolefin is modified with an unsaturated carboxylic acid or its derivative by a melting method,
Using a melt-kneading machine (for example, an extruder) used in the field of general synthetic resins, the polyolefin, unsaturated carboxylic acid and/or its derivative, and the above-mentioned radical generator are melt-kneaded and processed. You can get it by twisting it. The kneading temperature at this time varies depending on the type of polyolefin and radical generator used, but is at least equal to or higher than the melting point of the polyolefin used.
The temperature range is below 300℃. In the case of polyethylene, it is generally 120-270°C, and in the case of polypropylene, it is generally 160-270°C. In carrying out the present invention, the modified polyolefin may be used as it is, or the modified polyolefin and the polyolefin may be mixed in advance,
The resulting composition and the powdered material, fibrous material and/or aluminum metal or aluminum alloy described below.
Alternatively, flakes and conductive carbon black may be mixed. Furthermore, without mixing the modified polyolefin and the polyolefin in advance, it is possible to combine them with the powdered material, fibrous material and/or the polyolefin.
Alternatively, flakes and conductive carbon black may be mixed at the same time. Even when using only modified polyolefin (without using polyolefin) or when using modified polyolefin and polyolefin together, the amount of unsaturated carboxylic acid and/or its derivative contained therein is generally 0.01 to 1.0% by weight. %
and particularly preferably 0.02 to 1.0% by weight. Among the aluminum metal or aluminum alloy powders, fibers and flakes used in the present invention, the average size of the powders is generally 250 meshes to 20 meshes. Further, the diameter of the fibrous material is generally 0.0020 to 0.20 mm, and a length of 10 mm or less is preferable because it is easy to process. Furthermore, as flakes, the cross-sectional area is from 0.1 x 0.1 mm to 5.
Any shape such as a circle, square, rectangle, or hexagon with a size of 5 mm can be used, but
Particularly desirable is one with a thickness of 0.1 mm or less. Among these, those having a hexagonal shape with a cross-sectional area of about 1×1 mm and a thickness of about 0.03 mm have good dispersibility. These powdery, fibrous, or flaky materials may be used alone, but by using two or more of them together, the effects of the present invention can be achieved with a small mixing ratio. This is suitable because it allows Further, the aluminum content in the aluminum alloy is usually 80% by weight or more. In addition, the conductive carbon black used in the present invention generally has a specific surface area of 20 to 1800 as measured by low temperature nitrogen adsorption method and BET method.
m ² /g and pore volume is 1.5 to 4.0 cc/g as measured by mercury intrusion method in the pore radius range of 30 to 7500 Å.
In particular, those having a specific surface area of 600 to 1200 m ² /g are effective. Examples of the carbon black include channel black, acetylene black, and carbon black produced by the furnace black method. Regarding these carbon blacks, please refer to "Carbon Black Handbook" edited by Carbon Black Association (Tosho Publishing Co., Ltd., published in 1972) and "Handbook of Rubber and Plastic Compound Chemicals" (Rubber Digest Co., Ltd., published in 1972), edited by Rubber Digest Co., Ltd. The manufacturing method and physical properties thereof are well known, as described in the above-mentioned "Synthetic Rubber Handbook" (Publisher). The content of fibrous or flake-like materials is 5 to 50% by volume, and the content of conductive carbon black is 5 to 50% by volume.Furthermore, the total amount of both in the composition is 10 to 60% by volume. The important point of the present invention is that aluminum metal or aluminum alloy powder, fibers, or flakes and conductive carbon black are used together in the composition, and furthermore, the sum of the two is 10~60
% by volume. In particular, the sum of these is 25
~50% by volume is desirable. Further, it is preferable that the capacity ratio of the aluminum metal or aluminum alloy powder, fiber or flake to the conductive carbon black is in the range of 2.5:1 to 1:2.5. In particular, by mixing conductive carbon black, which has a shielding effect in the low frequency range (KHz), and aluminum metal flakes, which has an electromagnetic wave shielding effect in the high frequency range (MHz),
They have discovered that not only do they exhibit a shielding effect over a wider frequency range, but they also exhibit a significant shielding effect when used in combination, even in areas where they would have little effect when used alone. . The reason for this remarkable effect is not clear, but electromagnetic wave energy reflected or absorbed by aluminum metal or aluminum alloy powder, fibers, or flakes is grounded through conductive carbon black. It is estimated to be. An effect that supports this reason is that the conductivity of the composition of the present invention is significantly improved by the combined use of conductive carbon black. If the sum of aluminum metal or aluminum alloy powder, fibrous or flake-like materials and conductive carbon black in the composition obtained by the present invention is 10% by volume or less, the shielding effect is particularly high in the low frequency range. are unable to fully demonstrate their abilities. On the other hand, if it exceeds 60% by volume, the moldability of the composition decreases, which is not preferable. When producing the composition of the present invention, oxygen and heat stabilizers, metal deterioration inhibitors, fillers, lubricants and flame retardants commonly used in the field of olefinic resins may also be added. The compositions of the present invention may also be dry blended using mixers commonly used in the polyolefin industry, such as Henschel mixers, Banbury mixers, kneaders, roll mills, and screw extruders. It can be obtained by melt-kneading using. At this time, a uniform composition can be obtained by dry blending in advance and melt-kneading the resulting composition (mixture). In this case, the mixture is generally melt-kneaded and then formed into pellets, which are then subjected to the forming described later. Examples of the molding method include extrusion molding, injection molding, and press molding. Furthermore, stamping method, press molding method using extruded sheet,
Molding methods commonly used in the field of polyolefins, such as vacuum forming methods, may also be applied. In the case of melt kneading and molding as described above,
Both methods must be carried out at a temperature higher than the softening point of the modified polyolefin and polyolefin used, but if carried out at a temperature of 250°C or higher, the modified polyolefin and a portion of the polyolefin may undergo thermal deterioration. It goes without saying that the process must be carried out at a temperature below this temperature. As described above, the composition of the present invention has excellent processability, so it can be molded into various shapes by the molding method described above and used in a wide variety of fields. Hereinafter, the present invention will be explained in more detail with reference to Examples. In addition, in the examples and comparative examples, melt
The index (hereinafter referred to as "MI") is JIS K-
According to 6760, temperature is 190℃ and load is 2.16
Measured under Kg conditions. In addition, the melt flow index (hereinafter referred to as "MFI") is based on JIS K-
According to 6758, temperature is 230℃ and load is 2.16
Measured under Kg conditions. The tensile strength was measured according to JIS K-6760 for polyethylene, and according to JIS K-6758 for polypropylene. Moreover, the bending strength was measured according to JIS K-7203. Furthermore, Izod impact strength was measured according to JIS K-7110. Examples 1 to 5, Comparative Examples 1 to 4 High density polyethylene (density 0.960 g/cm ³ , M.
I.8.1g/10 minutes) 100 parts by weight, 2.5 of 0.01 parts by weight
-Dimethyl-2,5-di(butylperoxy)hexane (as an organic peroxide) and maleic anhydride were previously dry blended for 5 minutes using a Henschel mixer. The resulting mixture was melt-kneaded using an extruder (diameter: 40 mm, resin temperature: 200°C) to produce modified high-density polyethylene (hereinafter referred to as "modified PE"). The content of maleic anhydride in this modified PE was 0.6% by weight. The modified PE obtained as above, hexagonal aluminum flakes (hereinafter referred to as "Al flakes", cross-sectional area 1 x 1 mm, thickness 0.03 mm) and conductive carbon black with an average particle size of about 30 mm.
Millimicron Furnace Black (manufactured by Cabot Inc., product name: Vulcan)
72, density approximately 1.8 g/cc, surface area 220 m ² /g, hereinafter referred to as "CB", in the amounts shown in Table 1-1 in advance using a Henschel mixer (volume ratio 11
%) and was uniformly dry blended for 5 minutes. Each of the obtained mixtures was kneaded and pelletized using an extruder (diameter: 40 mm, resin temperature: 200°C). Each pellet was molded to a thickness of 3 mm using a 5 oz injection molding machine (set at 200°C).
A test piece was prepared. The surface resistivity, attenuation rate (frequency 200MHz), tensile strength, elongation rate, bending strength, and isot impact strength (notched) of the obtained test piece were measured. These results are shown in Table 1-2. Examples 6 and 7, Comparative Examples 5 and 6 Instead of the modified PE used in Example 1,
Polypropylene with MFI of 2.0g/10min (density 0.900
A modified product of maleic anhydride (hereinafter referred to as "modified PP", maleic anhydride content: 0.6% by weight) was prepared under the same conditions as in Example ¹ , except that PP (maleic anhydride content: 0.6% by weight) was used. In place of the modified PE used in Example 1, 10 parts by volume of the modified PP obtained as described above was used, and propylene-ethylene block copolymer (ethylene content 15% by weight, 17 g/10 min, hereinafter referred to as "non-prepared") was added. In Example 6, 60 parts by volume of
Dry blending was carried out in the same manner as in Example 1, except that in Example 7, 50 parts by volume were used, and in Comparative Examples 5 and 6, 70 parts by volume were each used. The obtained mixture was treated under the same conditions as in Example 1 (however, the resin temperature was 230°C).
After pelletizing, the resulting pellets were injection molded (temperature set at 230°C) to prepare test pieces. The surface resistivity, attenuation rate, tensile strength, elongation rate, bending strength, and isot impact strength (notched) of this test piece were measured.
These results are shown in Table 1-2. Examples 8 and 9 Instead of the Al flakes used in Example 6, the same amount (15 parts by volume) of aluminum fibers (length 6 mm, 65 microns, hereinafter "Al fiber") was used.
A mixture was prepared by dry blending in the same manner as in Example 6, except that a mixture of the following types was used (Example 8). The same amount (15 parts by volume) of 100 to 200 mesh (particle size 74 to 150 microns) of aluminum powder (hereinafter referred to as "Al powder") was used instead of the Al flakes used in Example 6. A mixture was prepared by dry blending in the same manner as in Example 6 (Example 9). Each of the mixtures obtained as described above was pelletized in the same manner as in Example 6. Each of the obtained pellets was injection molded in the same manner as in Example 6 to prepare test pieces. The surface resistivity, attenuation rate, tensile strength, elongation rate, bending strength, and isot impact strength (notched) of each of the obtained test pieces were measured. These results are shown in Table 1-2.

【table】

【table】

[Table] From the results of the above Examples and Comparative Examples, it was found that polyethylene or polypropylene modified with unsaturated carboxylic acid or its anhydride has a conductivity of aluminum metal or aluminum alloy powder, fiber, or flake. By using carbon black in combination, the radio wave shielding properties and magnetic wave shielding properties of the composition of the present invention can be improved compared to aluminum.
It is clear that the composition exhibits a remarkable effect compared to the composition of the comparative example in which either flake-like material or conductive carbon black is used alone.

Claims (1)

[Scope of Claims] 1 (A) A polyolefin modified with an unsaturated carboxylic acid or a derivative thereof, or the modified polyolefin and a polyolefin [However, (A)
The content of the unsaturated carboxylic acid and/or its derivative is 0.01 to 1.0% by weight]
(B) 5-50 volume % of aluminum metal or aluminum alloy powder, fibers and/or flakes; and (C) 5-50 volume % of conductive carbon black. thing.