JPS5887142A - Polyolefin composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. with excellent barrier properties to electromagnetic waves, comprising polyolefin, powdered, fibrous or flaky material consisting mainly of metals, and conductive carbon black. CONSTITUTION:A polyolefin compsn. is composed of 94-40vol% polyoefin (A), 5-55vol% powdered, fibrous and/or flaky material consisting mainly of one or more metals selected from the group consisting of iron, copper, zinc, nickel, iron oxide and alloys consisting mainly of these metals (B), and 5-55vol% conductive carbon black (C), the total amt. of components (B) and (C) being 10- 60vol% in the compsn. The compsn. has good barrier properties to electromagnetic waves and excellent bending and impact strength, and is, in addn., processable and moldable in arbitrary shapes due to its light weight and thermoplasticity. No conversion cost required for barrier treatments for electromagnetic waves (e.g., electroplating, conductive coating) leads to drastic cost reduction.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention The present invention relates to a polyolefin composition. More specifically, it relates to a polyolefin composition comprising (6) a polyolefin, a powdered material, a fibrous material, and/or a straddle flake-like material containing a material containing a metal as a main component, and an electrically conductive carbon black. The object of the present invention is to provide a polyolefin composition with excellent electromagnetic wave shielding properties.

BACKGROUND OF THE INVENTION With the advancement of industry and the standard of home life, the radiation of electromagnetic waves is increasing. Therefore, leakage of electromagnetic waves can cause dangerous harm to the human body and damage to ICs in electronic equipment.
This has resulted in negative effects such as malfunction, and has become a serious social problem. In particular, electromagnetic waves emitted from computers and various office processing equipment are causing trouble to televisions and audio equipment.

For these reasons, various methods have been adopted in recent years to shield electromagnetic waves.

In general, metals have the property of absorbing or reflecting electromagnetic waves, so they are effectively used as electromagnetic wave shielding materials for microwave ovens and various communication devices. We also use metal vapor deposition, thermal spraying, painting, etc. on plastic for the same purpose.
Plating etc. are also applied. Additionally, materials obtained by mixing plastics with relatively large amounts of additives such as carbon powder and metal powder have also been used.

However, methods that use metals as materials or processes such as metal vapor deposition on plastics have drawbacks such as high specific gravity, poor workability, difficult processing methods, and high processing costs. be.

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, the effect can be exhibited, but there is a 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 electromagnetic wave shielding properties, and as a result, (5) unsaturated carboxylic acid or its derivative or the modified polyolefin and the polyolefin [however, the content of the unsaturated carboxylic acid and/or its derivative in the formula is 0.01 to 10% by weight] 90 to 40% by volume, (Bl Aluminum Metal or aluminum alloy powder, fibrous and/or flake 5-
A polyolefin composition consisting of a 50 volume fraction and ◎ conductive carbon black 5 to 50 volume fraction is an electromagnetic wave obtained from a polyolefin and a conductive carbon black, or a polyolefin and an aluminum metal powder, fiber, or flake. Furthermore, by using a modified polyolefin as the polyolefin, the decrease in mechanical strength is so small that there is practically no problem, and the processability is also excellent. We discovered this and proposed it previously (Japanese Patent Application No. 87772/1982).

The present inventors have also conducted various investigations into obtaining thermoplastic resin compositions with excellent electromagnetic wave shielding properties [iron, copper,
Powdered materials, fibrous materials, and/or materials containing at least one metal selected from the group consisting of oxides of zinc, nickel, and iron, and alloys containing these metals as a main component.
or "flake-like material" (hereinafter referred to as "metal powder, etc.") A composition consisting of a 5-55 volume factor and a conductive carbon black 5-55 volume factor, and the main component is the metal in the composition. It has been discovered that a polyolefin composition in which the total amount of powdered, fibrous and flaky substances and conductive carbon black is 10 to 60% by volume has good electromagnetic shielding properties, and the present invention has been achieved. did.

Effects of the P-Saving Invention The polyolefin composition obtained by the present invention not only has good electromagnetic wave shielding properties, but also has the following effects (
characteristics).

(1) It is lightweight.

(2) Since it is thermoplastic, it can be processed and molded into any shape.

(3) Mechanical properties such as bending strength and impact strength are good.

(4) There is no need for secondary processing costs required for electromagnetic wave shielding treatment (for example, metal spraying, conductive coating, metal plating), resulting in a significant cost reduction.

The polyolefin composition obtained by the present invention has good electromagnetic wave shielding properties. Moreover, since it has the above-mentioned excellent effects, it can be used in a wide variety of fields. Typical applications: Housing materials for office equipment such as processors (2) Housing materials for electronic equipment such as televisions, videos, computers, etc., and their internal items.

The polyolefin used in the present invention includes a homopolymer of ethylene or a homopolymer of propylene, a copolymer of ethylene and propylene, ethylene and/or propylene, and other α-olefins having at most 7 carbon atoms. copolymers of ethylene with vinyl compounds such as vinyl acetate, acrylic esters and methacrylic esters (copolymerization ratio of vinyl compounds of is at most 50 mol%, preferably at most 40 mol%
) can be given. The molecular weight of these polyolefins is
In general, it is from 20,000 to 1 million, 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.

Furthermore, it is desirable to use the modified polyolefin obtained as described below or the modified polyolefin and the modified polyolefin because the mechanical strengths such as tensile strength and flexural strength of the composition of the present invention can be improved.

The modified polyolefin used in the present invention can be obtained by modifying the above polyolefin with an unsaturated carboxylic acid or a derivative thereof.

Representative examples of unsaturated carboxylic acids or their derivatives include:
dicarboxylic acids having at most 10 carbon atoms and at least one double bond (e.g., acrylic acid, methacrylic acid) and having at most 15 carbon atoms and at least one double bond; Examples include dibasic carboxylic acids (for example, maleic acid) having a dibase carboxylic acid, as well as anhydrides of the dibase carboxylic acids (for example, maleic anhydride, anhydride) and imitsuic acid. Among these unsaturated carboxylic acids or derivatives thereof, maleic acid and maleic anhydride are particularly preferred.

Modified polyolefins are generally obtained by treating polyolefins with unsaturated carboxylic acids and/or derivatives thereof in the presence of organic peroxides.

In order to produce the modified polyester 17 fin of the present invention, any of various known production methods (eg, solution method, suspension method, melting method) can be employed.

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 a radical initiator is added. A modified polyolefin can be obtained by adding and heating at a high temperature. Inorganic organic solvents used in this case include hexane, heptane, benzene, toluene, quinolene, chlorobenzene, and tetrachloroethane. In addition, as a radical initiator, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(
Examples include organic peroxides such as tertiary butylperoxy)hexyne-3 and benzoyl peroxide.

Furthermore, the treatment temperature is a temperature at which the polyolefin used is dissolved, and is generally 110 to 160°C, particularly preferably 130 to 150°C.

However, when modifying a polyolefin with a fully 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 aforementioned radicals are added. It is obtained by adding the entire initiator and treating under high pressure at a temperature of 100° C. or higher.

Furthermore, when modifying a polyolefin with an unsaturated carboxylic acid or its derivative by a melting method, a melt kneading machine used in the field of general synthetic resins (for example,
It can be obtained by melt-kneading a polyolefin, an unsaturated carboxylic acid and/or a derivative thereof, and the radical generator described above using an extruder. The kneading temperature at this time varies depending on the type of polyolefin and radical generator used, but is in the temperature range from above the melting point of the polyolefin used to below 300°C. In the case of polyethylene, generally 12
0 to 270°C, and in the case of polypropylene, generally 160 to 270°C.

Even when using modified polyolefin alone (when no polyolefin is used) or when using a combination of shredded modified polyolefin and polyolefin, the amount of unsaturated carboxylic acid and/or its derivative contained therein is generally 0.01 ~10% by weight, especially 002-1002
~10% by weight.

0 Metal powder etc. Also, the metal powder used in the present invention includes iron,
Powdered, fibrous and/or flaky substances whose product is at least one metal selected from the group consisting of oxides of copper, zinc, nickel, iron, and alloys containing these metals as main components It is a thing. In addition, iron oxides are found in nature such as hematite (α-Feρ3) and magnetite (Fe3).
0) is known. Artificially produced iron compounds include γ-Fe2O3 (margemite) and MPeO4, also known as ferrite (where M is Fe, Mn,
Zn N N I, Cn, and other divalent metals). Further, the alloy is an alloy containing at least 50% of the above metals by weight, and typical examples include silicon steel (Si1.Ti'e), tin bronze (S
n, Cu), Fernico (N1, CO,, Mn,,
Fe), phosphor bronze (Sn.

P, Cu) and permanent steel (Ni, Pe); and stainless steel whose main component is iron.

Powders of these materials generally have an average size of 250 to 20 mesh. As a fibrous material, its diameter is usually 0.0020 to 0.020
It is preferable to have a body with a length of 10 or less because it is easy to process. Furthermore, as a flake-like material, the cross-sectional area is 0.
IXo, any shape such as circular, rectangular, square, hexagonal with dimensions from 1 mm to 5×5 can be used, but preferably the thickness is 0.1 nrm or less.

ρ carbon black Furthermore, the conductive carbon black used in the present invention generally has a specific surface area of 20 to 1800 m"/t and a pore volume of 30 to 1,800 m"/t as measured by the low-temperature nitrogen adsorption method and BET method. It is 15 to 40 cc/f measured by mercury porosimetry in the range of 7500 A, and those with a specific surface area of 600 to 12007 n2/7 are particularly 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 the Carbon Black Handbook edited by the Carbon Black Association (Tosho Publishing Co., Ltd., published in 1972), Rubber Digest Company Line-＼Handbook, and Rubber and Plastic Compound Chemicals (Rubber Digest Company, published in 1972). ), their manufacturing methods and physical properties are well known from the above-mentioned Six Synthetic Rubber Handbooks.

0 Blending ratio (mixing ratio) In the present invention, the blending ratio of the metal fluoride powder etc. in the polio-in composition is 5 to 55% by volume,
The blending ratio of conductive carbon black is 5 to 55% by volume. Furthermore, the total amount of metal powder etc. and conductive carbon black in the composition is 10
-60 capacity, particularly preferably 25-50 capacity. It is preferable that the capacity ratio of the crushed metal powder and the like to the conductive carbon black is in the range of 25:1 to 1:25. In particular, by mixing a conductive carbon blank that has a shielding effect in the high frequency range (?vllll-fz) and a metal powder that has an electromagnetic wave shielding effect in the low frequency range (IGIz), a wider frequency range can be achieved. Not only does it show a shielding effect over a wide range of areas, but even in areas where it would hardly be effective if used alone, a combination of both exhibits a remarkable shielding effect. Although the reason for this remarkable effect is not clear, it is presumed that the electromagnetic wave energy reflected or absorbed by the metal powder is grounded through the conductive carbon blank. The result of all these reasons 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 the metal powder, etc. and the conductive carbon black in the composition obtained by the present invention is less than 10% by volume, the shielding effect, particularly in the low frequency range, cannot be sufficiently exhibited. On the other hand, when the volume is less than 60, the moldability of the composition decreases, which is not preferable.

■ Production of composition, molding method, etc. When producing the composition of the present invention, stabilizers against oxygen and heat, plasticizers, metal deterioration inhibitors, fillers, and lubricants commonly used in the field of polyolefins are further added. You may.

Further, the composition of the present invention may be triblended using a mixer such as a Henschel mixer, which is commonly used in the thermoplastic resin industry, and may be triblended using a mixer such as a Banbury mixer, a kneader, a roll mill, or an O. It can be obtained by melt-kneading using a mixer such as a one-piece extruder.

At this time, a homogeneous composition can be obtained by triblending in advance and melt-kneading the resulting composition (mixture). In this case, the mixture is generally melt-kneaded and then molded into a pellet-like material, which is then subjected to the molding described later.

Examples of the molding method include extrusion molding, injection molding, and press molding. Furthermore, molding methods commonly used in the field of polyolefins, such as stamping, press molding using an extruded sheet, and vacuum forming, may also be applied.

Both melt-kneading and molding described above must be carried out at a temperature above the softening point of the polyolefin used; however, as some of the polyolefin used may undergo thermal deterioration, It goes without saying that if you don't do the following, you won't get 1.

In producing the polyolefin composition of the present invention, all ingredients may be mixed simultaneously.

Furthermore, a so-called masterbatch may be prepared by previously mixing the polyolefin, a metal powder, etc., and a portion of the conductive carbon black, and the resulting masterbatch may be mixed with the remaining ingredients. in short,
In order to produce the composition of the present invention, the purpose can be achieved by adjusting all the ingredients to be within the range of the above-mentioned mixing ratios and to be uniform.

In the present invention, only one type of polyolefin, metal powder, etc., and conductive carbon black may be used, or two or more types may be used in combination.

EXAMPLES AND COMPARISON 1] The present invention will be described in more detail below with reference to examples.

In the implementation and comparative examples, the volume resistivity test was carried out using an abrasion meter (manufactured by Takeda Riken Co., Ltd., high quality digital multimeter TR-6856), using a test piece with a thickness of 2, at a temperature of 25°C and humidity. The resistance of the specimen was measured in an atmosphere of 60% and calculated according to the formula below.

Here, S is the electrode area of the specific resistivity measurement electrode, and R
is the resistance value of the specimen, and t represents the thickness of the specimen. To measure the shielding effect of electromagnetic waves, a sample box of 10 x 10 x 30 ctn was made using a 3-pot thick sheet, and a vertical oscillator was installed inside the box at a predetermined frequency (200 MHz).
).

This box was placed in an anechoic chamber, and the radio waves emitted from the oscillator inside the box were measured using a receiving antenna using a microwave power meter after passing through a detector. The radio waves from the oscillator were measured in the same way with the box manufactured from the sheet removed, and the ratio of the electric field strength (μ■) depending on the presence or absence of the sample box was expressed in decibels (dB) and used as the electromagnetic wave attenuation of the sample sheet.

Example 1] 1 to 9, Comparison rows 1 to 6 The polyolefin, metal-based substance, and conductive carbon black used in Actual Mf111911 and Comparison [+lJ] are as follows.

[Prisoner Modified polyethylene]

High density polyethylene (density 0.960 S'/a
d.

M, 1. 8.14710 minutes) 100 parts by weight, 0.01
Parts by weight of 2,5-dimethyl-2,5-di(butylperoxy)hexane (as an organic peroxide) and maleic anhydride were triblended in advance for 5 minutes using a Henschel mixer. The resulting mixture was melt-kneaded using an extruder (diameter: 40°C, resin temperature: 200°C) to produce modified high-density polyethylene (hereinafter referred to as modified PEJ).

The content of maleic anhydride in this modified PE was 0.6% by weight.

[0-Modified Polypropylene] The high-density polyethylene glue 9 used in producing the above-mentioned modified PE was given a melt flow index (according to JIS K-6758, at a temperature of 230°C and a load of 2.16 Ky). Measured under the following conditions): 12.0
Except for using polypropylene with f/l 0 minutes, modified P
Modified polypropylene (hereinafter referred to as "modified PPJ") was manufactured under the same conditions as for manufacturing E.

The content of maleic anhydride in the obtained modified PP was 0.6% by weight.

[Ω Conductive carbon blank]

Furnace black with an average particle size of approximately 30 mm as a conductive carbon black [manufactured by Cabot Corporation in the United States,
High quality name Vulcan XC-72, density approximately 1. g y /CC% surface area 220/7,
Hereinafter referred to as "C, B,"] was used.

[D Powder-like materials and flake-like materials whose main component is metal]

Furthermore, Table 1 shows the particle size, particle type, and manufacturing method of the metal-based powder and flakes used in Example 11 and Comparative Example.

These modified PE, modified PP, conductive carbon black, and metal-based powders and flakes were mixed in amounts shown in Table 2 using a Hennel mixer (volume ratio 11 inches). Tri-blending was carried out evenly for 5 minutes. Each mixture obtained was passed through an extruder (
Pelletization was performed while kneading using a diameter of 40++++++ and a resin temperature of 200°C. Each pellet was made into 3-inch thick specimens using a 5 oz. injection molding machine (set at 200° C.). The volume resistivity and electromagnetic wave attenuation of the obtained test piece were measured. The results are shown in Table 3.

Table 3 Patent applicant: Showa Denko Co., Ltd. Representative Patent Attorney Sei Kikuchi

Claims (1)

[Claims] (A) Polyolefin 90-40% iron, copper,
Powdered, fibrous and/or flake-like substances containing at least one metal as a main component selected from the group consisting of oxides of zinc, nickel, iron, and alloys containing these metals as main components 5 -55 capacity factor and (G conductive carbon black) A composition consisting of 5 to 55 capacity factor, and powdery, fibrous and flake-like materials containing metal as a main component and conductive carbon black. The total amount of carbon black is 10 to 60% by volume.