JPS59129237A - Composition for electrically conductive foam - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which is excellent in extrudability during sheet molding and makes it possible to produce a foam at a high expansion ratin, by incorporating electrically conductive carbon in a resin mixture consisting of a crystalline thermoplastic polyolefin resin and a lowly crystalline thermoplastic resin in a specified mixing ratio. CONSTITUTION:The titled compsn. is obtd. by incorporating 3-40pts.wt. electrically conductive carbon such as acetylene black or furnace black and a blowing agent such as azodicarbonamide in 100pts.wt. resin mixture mainly composed of a crystalline thermoplastic polyolefin resin (A) such as PP or PE having a density of 0.910g/cm<3> or above and a lowly crystalline thermoplastic resin (B) such as ethylene/vinyl acetate copolymer in a weight ratio of 9<A/B<=32.3. This compsn. is excellent in extrudability during sheet molding and makes it possible to produce foams at a high expansion ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composition for a conductive N generator. More specifically, the present invention relates to a polyolefin thermoplastic resin composition containing conductive carbon.

2. Description of the Related Art Conductive resin compositions prepared by melt-kneading a polyolefin thermoplastic resin with conductive carbon added thereto have been known. On the other hand, in order to obtain a conductive foam, it is necessary to add a foaming agent together with conductive carbon, melt and knead the resin, and uniformly disperse them in the resin. However, when conductive carbon is mixed, the shear heat generation increases and the blowing agent is more likely to decompose, resulting in generation of bubbles in the sheet before foaming and deterioration of extrudability.

An object of the present invention is to improve such drawbacks and provide a composition for conductive foam that has excellent extrudability during sheet molding and is capable of achieving a high expansion ratio.

The object of the present invention is to mainly contain a crystalline polyolefin thermoplastic resin (A) and a low crystalline thermoplastic resin (B), and to have a weight mixing ratio of C ( A
) / (B) ) is 9< (A) / (B)≦32
．． 6 to 100 parts by weight of the resin mixture containing 5 to 40 parts by weight of conductive carbon and emitting? This is achieved by using a composition for conductive foam which also contains a toner agent.

Crystalline polyolefin thermoplastic resin in the present invention (
A) is a crystalline olefin polymer containing oni/fin as essential monomers, and has a density of 0.910? /C
n? The above are preferred. Specifically, polyethylene,
Examples include polypropylene, polybutene, polynotylbutene, polymethylpentene, etc., and these can be used alone or as a copolymer of two or more glazes or a mixture. Among these, polyethylene and polypropylene are particularly preferred.

The low-crystalline thermoplastic resin (B) in the present invention has a lower crystallinity than the resin (A), and typical examples thereof include rubber-like thermoplastic resins and modified polyolefin thermoplastic resins. Specifically, ethylene-vinyl acetate copolymer (although not particularly limited, vinyl acetate content 6 to 3
5 wt% is preferred), ethylene-C-thyl acrylate copolymer (although not particularly limited, ethyl acrylate content of 5 to 20 wt'% is preferred), ethylene-α-olefin copolymer , preferably a copolymer with a density of less than 0.910ii'% (although not limited to, α-olefin content of 5 to 30 wt%)
(preferably), thermoplastic butadiene resin (preferably syndiotactic 1,2-polybutadiene containing 90% or more of 1,2-bonds, although the percentage is not limited), thermoplastic styrene-butadiene Resin (styrene content 10 to 50 wt, although not particularly limited)
%), chlorinated polyethylene (although not particularly limited, chlorine content of 25 to 45♀-t% is preferable), and the like. In the above, the α-olefin is preferably an α-olefin having 6 to 8 carbon atoms such as propylene or butene.

The resin mixture of the present invention is a mixture mainly composed of a crystalline polyolefin thermoplastic resin (A) and a low crystalline thermoplastic resin (B), and the mixing ratio of the resin (A) and the resin (B) is CR - weight of (A)/weight of (B)] is 9 (R≦32
6 must be satisfied. In particular, this mixing ratio (R) is 1
It is preferable that 0≦R≦20 be satisfied.

If the above mixing ratio (R) exceeds 623, the dispersibility of the carbon black contained in the resin mixture will deteriorate, making it impossible to obtain stable conductivity, and uneven crosslinking will occur due to uneven dispersion of carbon black, so the surface layer during foaming will However, there are drawbacks such as localized gas leakage and the inability to obtain stable foamability.

On the other hand, if (R) is 9 or less, the extrudability during sheet molding will deteriorate, and the crosslinking properties of the obtained sheet will decrease, resulting in a high expansion ratio during foaming, and the development of bubbles, especially in the thickness direction. The disadvantage is that it is difficult to

In the present invention, conductive carbon means that it can be filled into polymers such as rubber and plastics to impart high conductivity and greatly reduce the specific volume resistivity of the polymer, for example, to 107Ω・m or less. Any carbonaceous material that can be used may be used, such as natural graphite, artificial graphite, carbon black, and carbon fiber. Normally, among carbon blacks, it has excellent electrical conductivity [Denka Black-1 (
Acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) and furnace black have been used for many years. Specifically, the furnace black is “Ketchin Black EC”.
” (manufactured by Akzo in the Netherlands), [Palcan XC72J (
(manufactured by CABOT, USA) [Asahi MS-sooJ (manufactured by Asahi Carbon), r Conductex SC #950, #975
There are commercially available products such as J (manufactured by Columbian Carbon).

It is necessary that the conductive carbon be contained in the foam composition of the present invention in an amount of 5 to 40 parts by weight, preferably 15 to 30 parts by weight, based on 100 parts by weight of the polymer component, that is, the resin mixture.

If the amount is less than 5 parts by weight/M, the conductivity of the emitter is insufficient, and the volume resistivity value is, for example, 10 8 Ω/M, which is not preferable. On the other hand, if it is added in an amount exceeding 40M parts, crosstalk with the resin will be extremely poor, making it difficult to obtain a good molded sheet.

The blowing agent in the present invention is a compound that decomposes or vaporizes when heated above the melting point of the polyolefin resin, and any blowing agent can be used as long as it does not substantially interfere with sheet formation or crosslinking reactions, but the blowing agent has a decomposition temperature. A temperature of 180°C or higher is desirable. Specific examples thereof include azodicarbonamide, monometallic azodicarbonate, dinitrosopentamethylenetetramine, hydrazodicarbonamide, and the like.

The blending amount of these promoters can be arbitrarily changed depending on the type of blowing agent used and the target expansion ratio.

For example, when using azodicarbonamide and aiming for an apparent foaming ratio of 15 to 25 times, the resin mixture should be
It is sufficient if the weight part is V and the door part is 10 to 20 parts heavy. In this way, the composition of J produced by the present invention has 1.
It is possible to create a sleeping body with a high initiation rate of 5 times or more, but on the other hand, by reducing the amount of the starter,
It is also possible to create a starter that is about 15 times larger.

The uninvented 7 silver 55 product is made by adding conductive carbon and a foaming agent to the resin mixture described above, but when the amount of conductive carbon added is 15 parts by weight or more,
Since its dispersibility and extrudability during sheet molding deteriorate, the polyolefin thermoplastic resin (A) has a density of 0.920? /cni' or more and a melt flow rate of 20 S'/io fractional polyolefin 60~
It is preferable to use a mixture of 70 parts by weight and 70 to 60 parts by weight of a well-flowing polyolefin having a density of 0920 ji'/lri or less and a melt flow rate of 30 y/1o min or more.

Specific examples of the well-flowing polyolefin mentioned here are [
Sumikasen G3061 (ρ=0.919, MI=50)
"G307j (ρ=0.92C1, MI=75) [Gaoaj (ρ=l], 916, MI=20'O) [
The above products are manufactured by Sumitomo Chemical Co., Ltd.], "FL60" (ρ=0.
915, MI=70) [manufactured by Mitsui Petrochemicals] and the like.

If the amount of the well-flowing polyolefin in the composition exceeds 70 parts by weight, the dispersibility of the conductive carbon and the extrudability during sheet molding will be good, but excessive crosslinking will likely occur. On the other hand, 30
If it is less than 1 part by weight, the effect of improving extrusion properties during sheet molding will be small.

Furthermore, a crosslinking agent and a crosslinking aid may be added to the composition for consumer use of the present invention, if necessary.

In addition, the foam composition of the present invention may contain different polymers, inorganic fillers,
Flame release agents, antioxidants, weathering agents, dispersants, etc. can also be blended.

Next, a method for producing the composition of the present invention will be explained. As mentioned above, the foam composition of the present invention contains specific amounts of a crystalline polyolefin thermoplastic resin, a low crystalline thermoplastic resin, and conductive carbon, a blowing agent, and, if necessary, a crosslinking agent and a crosslinking aid. , and others by uniformly mixing them.

As a method for mixing these components, any conventionally used means such as mixing rolls, Pan Bali mixers, various kneaders, etc. can be used. Furthermore, these mixtures may be pelletized using an extruder to form chips.

The composition of the present invention can be made into a foam in a conventional manner. That is, the composition is melt-extruded to a temperature of 120 to
It is usually converted into a pest by extruding it at about 150°C to form a sheet with a thickness of about 1 to 5 wings, and then crosslinking this sheet with electron beam irradiation or a crosslinking agent.

Usually, for crosslinking, a method of irradiating with ionizing radiation or a method of using an organic peroxide is used.

′In the case of female radiation scarlet bridge, α as a high energy ray
rays, β rays, γ rays, X rays, electron beams, neutron beams, etc.
Generally, a high-energy electron beam irradiator is used. For example, the formed sheet is crosslinked by irradiating it with a dose of 1 to 50 Mrad.

On the other hand, examples of organic peroxides include dicumyl peroxide, dikusha butyl peroxide, and 1,3-bis(cusha lipyl peroxyisoglobil) benzene, which are It is used in a range of 15 parts by weight. Crosslinking conditions are temperature 140-20
A temperature range of 0°C and a time of 1 to 60 minutes is suitable.

When the crosslinked sheet thus obtained is heated to 190 to 250°C in a hot air atmosphere or on a salt bath, the foaming agent is rapidly decomposed and a fermented product is obtained.

The composition for electrostatic thermoplastic resin foam of the present invention exhibits the following excellent effects.

■ Extrusion performance during sheet molding is lagging behind.

■ A foam with a high expansion ratio can be easily obtained.

Applications of the propellant obtained from the composition of the present invention include packaging materials for parts that avoid dust caused by static electricity (for example, 1.C, magnetic tape parts, precision equipment such as watches and cameras, etc.), and non-matching materials. Examples include radio wave absorbing materials. In addition, it can be widely applied to anti-static and anti-static applications that utilize the electrical conductivity and excellent processability of polyolefin foams such as heat fusion properties and vacuum formability.

Next, the present invention will be explained based on examples. The characteristic values in the examples are based on the following measurement method.

(1) Extrusion properties during sheet forming 30 m at a constant screw rotation speed (e.g. 2 ORPM)
So-called/Using the motor drive current when extruding with an extruder as a guide,
Low density polyethylene, Mirason #16 (ρ=0.921
, MI=6.7) is expressed as a ratio of 1 drive current.

The closer this value is to 1, the better the extrudability is. If this value is 1.25 or more, extrudability is extremely poor and shear heat generation increases, causing initial decomposition of the blowing agent and making extrusion molding difficult.

(2) Volume resistivity Measured according to the Japan Rubber Association standard (SRIS2301).

(6) Foaming ratio: 1 The apparent foaming ratio: 10crnX 1 rJcm square is cut out, the thickness is measured, and the volume is calculated. On the other hand, measure the heavy electricity of this thing,
The apparent density is defined as the weight per unit volume. This apparent value is the reciprocal of the density, which is the evil magnification.

11 Expansion ratio between thicknesses It is expressed as foam thickness U)/formed sheet thickness before foaming U).

The abbreviations used in this example are as follows.

ρ: Seedling density P/N) M: Melt flow rate (f/10m1n) Example 1
゜As a crystalline polyolefin thermoplastic resin, low density polyethylene (ρ=0.919?/lyr?, MI
=5or/1゜m1n) 95 parts by weight, and as a low crystalline thermoplastic resin, polyethylene/1-butene copolymer (ρ2 0.880, M I = 4.Off710min-
) 28 parts by weight of 4-tonne carbon (furnace black) per 100 parts by weight of a polymer component consisting of 5 parts by weight,
Using 14 parts by weight of azodicarbonamide as a blowing agent, the mixture was pelletized to obtain a uniformly dispersed compound.

This compound was melt-extruded using a 30-7 extruder to obtain a molded sheet with a thickness of 1.6M. This molded sheet was crosslinked by electron beam irradiation (10 Mrad), and
By heating and foaming on a salt bath at 5° C., a foam having a closed-cell turtle structure was obtained. The results are shown in Table 1.

The apparent density of this foam was 0049, the apparent magnification of one package was 206 times, and the foaming magnification in the thickness ζ direction was 30 times.

The extrudability is not much different from the blank (LDPE, Milan #16), and the conductivity of the foam is 4.6XiO''Ω, which is a clearly excellent value.As a result of the above, the present invention has excellent extrudability. It can be seen that a highly foamable conductive foam can be obtained.

Examples 2 to 7, Comparative Examples 1 to 5 All the procedures were the same as in Example 1 except that the composition and blending amount of the crystalline polyolefin thermoplastic resin and low crystalline thermoplastic resin and the amount of carbon black added were changed. . The results at this time are shown in Table 1.

In fact, all of Examples 2 to 7 met the requirements of the present invention, and extrudability and high light 2B magnification could be adjusted.

In Comparative Example 1, the amount of the low-crystalline thermoplastic resin was too small to meet the requirements of the present application, so there were disadvantages such as poor dispersion of carbon black, gas release due to uneven crosslinking, and large unevenness in conductivity and expansion ratio. In Comparative Example 2, the amount of carbon added was small and the tetraelectricity was insufficient. In Comparative Examples 3 to 5, the amount of the low-crystalline thermoplastic resin was too large, resulting in poor extrudability, and the extrusion 71β ratio was insufficient.

As is clear from the above, it is clear that the present invention can provide a composition for a tetraelectric thermoplastic resin body that has excellent extrudability during sheet molding and is capable of achieving a high expansion ratio.

4-430-6 Nishinomiyashita, Ageo City ■Submitted by: Tokyo Ink Co., Ltd. 2-7 Tabata Shinmachi, Kita-ku, Tokyo No. 15

Claims (1)

[Claims] Mainly composed of a crystalline polyolefin thermoplastic resin (A) and a low crystalline thermoplastic resin CB), and the weight mixing ratio of the resin (A) and the resin (B) is C (A) / (B) :)
A composition for a conductive foam, which contains 5 to 40 parts by weight of conductive carbon and also contains a blowing agent, based on 100M parts of a resin mixture where 9<(A)/(B)≦62.3. thing.