JPH0645733B2 - Conductive polypropylene composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductive polypropylene composition, and in particular, a shielding component for electromagnetic interference, a synthetic resin sheet heating element, an electromagnetic plate for a dust collector, and a battery. The present invention relates to a conductive polypropylene composition suitable for applications such as an electrode plate for a battery, a partition plate for a battery, an electrode plate for an electrolysis reaction tank, a ground and a conductive container.

[Conventional technology]

BACKGROUND ART Conventionally, as a conductive resin composition used for the above-mentioned applications, one in which a conductive filler such as carbon black or graphite is kneaded in polyethylene is known.

However, in recent years, a conductive resin has been used in various fields, and a material having higher heat resistance has been demanded. However, the above-mentioned conductive resin composition containing polyethylene as a matrix has insufficient heat resistance, and improvement thereof is required.

By the way, if only to improve the heat resistance of the conductive resin composition, there is a method of using polypropylene,
When actually mixing a large amount of conductive carbon filler to obtain a highly conductive resin molded product having a volume resistivity of 100 Ω-cm or less, various problems occur during molding and a normal molded product can be obtained. Absent. For example, when a sheet-shaped material is molded by an extruder, uneven flow of molten resin and surging are likely to occur, resulting in poor thickness accuracy and poor appearance,
Not only a sheet that is satisfactory in appearance cannot be obtained, but only those with low essential heat resistance and strength are obtained. That is, polypropylene is preferable as a base resin for plastic carbon because it has a higher heat distortion temperature and better mechanical strength than polyethylene, but since it has a tertiary carbon in its molecule, it tends to cause molecular cleavage by heat. Especially, in the presence of the conductive carbon filler, the tendency is remarkable. First, carbon black, which is the main component of the conductive carbon filler, has little effect if added in a small amount, but promotes thermal deterioration when added in a relatively large amount. Further, as for the graphite, although natural scaly graphite or artificial scaly graphite is usually used, impurities contained in these graphite accelerate the thermal deterioration of polypropylene, and thus it is desired to blend graphite with the above-mentioned highly conductive polypropylene. The reality is that expensive high-purity products can only be added in small amounts.

As described above, the above-mentioned defective phenomenon when using polypropylene and the conductive carbon filler is because the conductive carbon filler added in a large amount promotes thermal deterioration of the polypropylene. Therefore, a thermal deterioration inhibitor for a mixture of polypropylene and a conductive carbon filler has been studied conventionally, and as a standard formulation, for example, 2,6-di-t-butyl-4-methylphenol and calcium stearate are used. There is a combined use with. In addition, for example, in Japanese Patent Publication No. 61-7682, 4,4'-bis (2,
2'-Dimethyl-benzyl) diphenylamine has been proposed as a heat stabilizer for polyolefin and carbon black composites.

However, the former stabilizer composition is effective when the amount of the conductive carbon filler added to the polypropylene is small (for example, 10 parts by weight or less), but is thermally deteriorated when a large amount of the conductive carbon filler is added. Cannot be prevented.

On the other hand, the latter has a longer product life in a high temperature atmosphere (such as an oven test), but its performance is insufficient to improve the processing stability of the conductive carbon filler highly filled polypropylene. As described above, the fact is that there is nothing that can be put to practical use as a conductive plastic carbon molded body having a volume specific resistance of 100 Ω- _cm or less, which is a composite of polypropylene and a conductive carbon filler.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a conductive polypropylene composition that is stable against a heat history received during molding and has excellent conductivity and heat resistance.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and the gist thereof is 100 parts by weight of polypropylene and 15 to 250 parts by weight of conductive carbon filler. 0.05 to 3 parts by weight of tris- (4-hydroxyphenylalkylenyl) isocyanurate, and tris (2,4-di-t-butylphenyl) phosphite and 4,
A conductive polypropylene composition comprising one or both of 4'-thiobis (3-methyl-6-t-butylphenol) and 0.05 parts by weight or more, respectively, and 3 parts by weight or less in total.

The present invention will be described in detail below.

First, the polypropylene used in the present invention is not limited to polypropylene homopolymers, and propylene / ethylene random copolymers, propylene / ethylene block copolymers, and propylene / olefin copolymers may be used alone or as a blend. Can be done.

Next, in the present invention, it is preferable that the conductive carbon filler contains carbon black as a main component, and at least one of graphite and carbon fiber is mixed therein. In this case, examples of the carbon black include conventionally known Ketjen black, acetylene black, furnace black, lamp black, thermal black, channel black, roll black, disk black and the like. Among these carbon blacks, particularly preferable is Ketjen black that gives excellent conductive material with excellent conductivity and low addition, but depending on the level of conductivity and the application, it is not limited thereto. Absent. Next, graphite is used in combination with carbon black to improve the moldability and conductivity, and the volume resistivity is 1Ω.
Necessary when making highly conductive plastic carbon material of the order of -cm. The graphite may be natural graphite or artificial graphite, and both of them have a scaly shape, and their particle size is 1 to 500 μm.
m, preferably 4 to 80 μm. In addition, carbon fiber is used in combination with carbon black to improve mechanical strength, heat distortion temperature, chemical resistance, and conductivity. The carbon fiber may be acrylonitrile-based or pitch-based, and the shape thereof is a short fiber having a diameter of 5 to 20 μm and a length / diameter ratio of 1 to 100,
Preferably, the diameter is 5-10 μm and the length / diameter ratio is
1.5 to 50 is preferable.

The main essence of the present invention lies in the selection of a processing stabilizer which prevents thermal deterioration of polypropylene in the presence of a large amount of conductive carbon filler.

That is, according to the findings obtained by the inventors of the present invention as a main stabilizer, based on the knowledge obtained as a result of intensive studies of a processing stabilizer capable of suppressing the thermal deterioration encountered when polypropylene containing a large amount of the above-mentioned various carbon fillers is melted by heating. -(4-Hydroxyphenylalkylenyl) isocyanurate with tris (2,4-di-t-butylphenyl) phosphite as co-stabilizer and 4,4'-thiobis (3-methyl-6-t-)
By blending one or both of them with butylphenol), a remarkable effect as a processing stabilizer is exhibited in the above composite system. This stabilizer not only has a remarkable effect as a processing stabilizer, but also has no bleed-out of the stabilizer to the surface of the molded product, which is a problem when adding the stabilizer, and is used as a conductive carbon plastic molded product in a high temperature environment. Withstand enough.

In this case, tris- (4-hydroxyphenylalkylenyl) isocyanurate compounded in the present invention has the general formula [In the formula, R is a 4-hydroxyalkylenyl group having the following formula.

(However, in the formula, n is an integer of 1 to 4, R ₁ and R ₂ represent hydrogen or an alkyl group having 4 to 8 carbon atoms, and R ₁ or R 2
_At least one of ₂ is an alkyl group. )]
It is represented by.

Among these, the preferred embodiment in the present invention is the substituent R
Is a 3,5-di-t-alkyl-4-hydroxybenzyl group, particularly preferred is tris- (3,5-
This is the case for di-t-butyl-4-hydroxybenzyl) isocyanurate.

In addition, the structural formula of tris (2,4-di-t-butylphenyl) phosphite compounded in combination with tris- (4-hydroxyphenylalkylenyl) isocyanurate in the present invention is as follows. is there.

Furthermore, in the present invention, it is used in combination with tris- (4-hydroxyphenylalkylenyl) isocyanurate or in the mixed system of the former and tris (2,4-di-t-butylphenyl) phosphite. 4'-thiobis (3-methyl-
The structural formula of 6-t-butylphenol) is as follows.

The reason why the combination of the above stabilizers and auxiliaries has a remarkable effect of preventing thermal deterioration in the composite system of conductive carbonaceous material and polypropylene is not clear at present, but it is probably nitrogen-containing sterically hindered phenol. Antioxidant function of compound tris- (4-hydroxyphenylalkylenyl) isocyanurate and tris (2,4-di-t-butylphenyl) phosphite and / or sulfur antioxidant which is a phosphorus-based antioxidant 4,4'-thiobis (3-
It is believed that (methyl-6-t-butylphenol) complements each other and efficiently blocks autoxidation.

Next, polypropylene, a conductive carbon filler, tris- (4-hydroxyphenylalkylenyl) isocyanurate, tris (2,4-di-t-butylphenyl) phos which constitutes the conductive polypropylene composition of the present invention. Fight, and 4,4'-thiobis (3-methyl-6-t
-Butylphenol), as described above, with respect to 100 parts by weight of polypropylene, 15 to 250 parts by weight of the conductive carbon filler, 0.05 to 3 parts by weight of tris- (4-hydroxyphenylalkylenyl) isocyanurate,
And one or both of tris (2,4-di-t-butylphenyl) phosphite and 4,4'-thiobis (3-methyl-6-t-butylphenol) are respectively 0.05 parts by weight or more and a total of 3 parts by weight or less. And preferably 30 to 30 parts by weight of conductive carbon filler with respect to 100 parts by weight of polypropylene.
200 parts by weight, 0.08 to 2 parts by weight of tris- (4-hydroxyphenylalkylenyl) isocyanurate, and tris (2,4-di-t-butylphenyl) phosphite and 4,
One or both of 4'-thiobis (3-methyl-6-t-butylphenol) is 0.08 parts by weight or more and 2 parts by weight or less.

First, if the amount of the conductive carbon filler is less than 15 parts by weight, the conductivity of 100 Ω-cm or less in volume resistivity, which is the object of the present invention, cannot be obtained. On the other hand, if it exceeds 250 parts by weight, the workability is deteriorated and it cannot be molded by a usual molding machine such as an extruder or an injection molding machine.

The composition ratio of the conductive carbon filler in the present invention is 15 to 25 relative to 100 parts by weight of polypropylene.
As a breakdown of 0 parts by weight, carbon black 10 to 100
It is suitable to use parts by weight, graphite 200 parts by weight or less, and carbon fiber 50 parts by weight or less.

When carbon black is less than 10 parts by weight, volume resistivity 1
The electrical conductivity of less than 00 Ω-cm cannot be exhibited, and when it exceeds 100 parts by weight, the moldability is extremely lowered, and it cannot be molded by an ordinary molding machine such as an extruder or an injection molding machine.

Further, graphite is added mainly for the purpose of improving the moldability of the above-mentioned carbon black, and it is not necessary to mix it within the range in which carbon black can be molded alone, and when the molding is difficult or impossible, polypropylene 100 is used. 200 parts by weight or less are blended with respect to parts by weight. If the amount of graphite exceeds 200 parts by weight, the moldability will worsen.

Further, the carbon fiber is added mainly for the purpose of improving the strength. If the strength is not so required, it is not necessary to add it, and if it exceeds 50 parts by weight, the moldability is deteriorated.

Next, if tris- (4-hydroxyphenylalkylenyl) isocyanurate is less than 0.05 parts by weight, it is not possible to prevent thermal deterioration during processing of a conductive polypropylene having a volume resistivity of 100 Ω-cm or less. Further, even if added over 3 parts by weight, the effect of preventing thermal deterioration does not change, rather,
It may cause bout out.

When one or both of tris (2,4-di-t-butylphenyl) phosphite and 4,4'-thiobis (3-methyl-6-t-butylphenol) are less than 0.05 parts by weight, the above-mentioned main component The synergistic effect with the stabilizer does not occur, and the effect as a processing stabilizer for conductive polypropylene cannot be exhibited. Further, even if the total amount exceeds 3 parts by weight, the effect of preventing thermal deterioration does not change, which also causes a bout.

The polypropylene, the conductive carbon filler, the adjustment of the conductive polypropylene composition having various stabilizers, the Kneader, Banbury mixer, within the above mixing ratio range.
Mixing rolls, twin-screw extruder, it is preferable to uniformly knead and knead by a conventional method using an appropriate blender such as an extruder to form pellets, and these pellets are extrusion-molded, injection-molded, compression-molded, etc. Molded articles of various shapes are formed by a molding method usually applied to thermoplastic resins.

In molding the conductive polypropylene composition, flame retardants, pigments, plasticizers, cross-linking agents, wetting agents, etc., which are commonly used for polypropylene, are used to improve the adhesion between the conductive carbon filler and polypropylene. One or more modifiers and the like can be appropriately selected and used as necessary.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.

Examples 1 to 5 Polypropylene (Mitsui Petrochemical Hipol F60
1), carbon black, graphite, carbon fibers, and tris- (3,5-di-t-butyl-4-) as a processing heat stabilizer.
Hydroxybenzyl) isocyanurate (Goodlight 3114, manufactured by Goodrich), tris (2,4-di-t-)
Butylphenyl) phosphite (Made by ADEKA ARGUS)
ARK3114), 4,4'-thiobis (3-methyl-6)
-T-butylphenol) (Yoshitomu Pharmaceutical Yoshinox S)
R) was blended in the proportions shown in Table 1, mixed for 5 minutes at 180 to 220 ° C. using a Banbury mixer, kneaded at 170 to 200 ° C. using a two-roll mill, and preliminarily used with a sheet cutter. It was made into pellets. Using a 40 mmφ vented extruder, the cylinder temperature of these preliminary pellets was set to 200.
Pellets were formed while degassing low volatile components at ˜230 ° C. and a vacuum degree of 20 to 50 Torr.

This pellet is 40mmφ with a 300mm wide T-die attached
Using an extruder, the cylinder temperature is 220 to 250 ° C and the thickness is 1
A sheet having a size of 270 mm and a width of 270 mm was formed, the formability and other physical properties were examined, and the results are shown in Table 1. As for moldability, the uniformity of discharge, the degree of uneven flow (meandering), and the unevenness of thickness are comprehensively evaluated as the degree of surging. , Of the other physical properties, the visual appearance of the sheet was evaluated by visually categorizing it into ⊚ mirror surface condition, ∘: good smoothness, Δ: slight unevenness, and x: unevenness or cracks. The bleed-out property is 60 ℃ for the sheet.
The wet state of the surface of the sheet after observing for 7 days in the air oven kept at was observed and classified into ◯: no wet, Δ: slightly wet, and ×: wet. The tensile strength was measured by a conventional method at a tensile speed of 5 mm / min. The volume resistivity was measured by the four-point probe method.

As is clear from the results shown in Table 1, the conductive carbon filler-containing polypropylene containing the processing heat stabilizer of the present invention does not undergo thermal deterioration even after undergoing heat history such as kneading and molding, and has good processability, appearance and conductivity. The physical properties are very good.

Comparative Examples 1 to 8 Using the same polypropylene, carbon black, graphite, and carbon fiber as in the examples, only the processing stabilizers, outside the range of the examples, and other commonly used commercial stabilizers are shown in Table 2. The components were blended in the proportions shown, and kneading, deaeration and extrusion sheet molding were carried out in the same manner as in the examples, and evaluation was carried out by the same evaluation method as in the examples. The results are shown in Table 2.

As is clear from the results shown in Table 2, when the processing stabilizer was not added and when the general processing stabilizer was used, surging occurred, the sheet surface was poor, and the strength was low. There wasn't.

[Effects of the Invention] According to the present invention, the thermoplastic resin is stable against thermal history in commercial molding methods such as injection molding and extrusion molding,
In addition, it is possible to obtain an electrically conductive polypropylene assembly which is also excellent in electrical conductivity and heat resistance, and the industrial effect is extremely remarkable.

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Claims (1)

[Claims] 1. A mixture of 100 parts by weight of polypropylene and 15 to 250 parts by weight of a conductive carbon filler is added to tris-.
0.05 to 3 parts by weight of (4-hydroxyphenylalkylenyl) isocyanurate, and tris (2,4-di-t-butylphenyl) phosphite and 4,4'-thiobis (3-methyl-6-t-butylphenol) ) And one or both of them and 0.05% by weight or more, respectively, and 3% by weight or less in total, are contained in the electrically conductive polypropylene composition.