CS276129B6 - Electrically conductive filler - Google Patents

Abstract

Electrically conductive carbon black with a specific surface area of 300 to 1,300 µm/g is coated with 50 to 95% by weight of an inorganic additive with an average particle size of 0.5 to 15 µm, impregnated with 0.05 to 2 parts by weight of binders such as fatty acids, their salts and esters, organosilanes and organotitanates, based on 100 parts by weight of the inorganic additive. Up to 0.1 to 20 parts by weight of processing additives can be added to 100 parts by weight of the resulting filler. It is used as a component of electrically conductive plastics with high thermal conductivity, suitable for the production of boards and direct electric heating.

Description

The invention relates to combined fillers for the production of thermoplastic composites with reduced electrical resistance, including semiconductor and conductive plastics.

A separate group of fillers used in the production of thermoplastic composites with reduced electrical resistances are electrically conductive carbon blacks. These carbon blacks are usually produced! oxidation of petroleum fractions in the presence of an oxygen-vapor mixture, they tend to have high chemical purity, specific surfaces in the order of hundreds of m / g and a fine so-called chain structure, which guarantees the conductivity of the material even at high porosity values. However, the difficulties to be encountered in processing this type of aazi into plaque are considerable: difficulties with the poor bulk properties of carbon black, which complicate all handling and dosing, uneven incorporation of carbon black into the plastic melt, difficult dispersion, flight of soot dust, blackening of handling carbon black material flow paths, which forces the processor to use the compounding line only for processing carbon black of very dark types of composites, because cleaning the line is practically impossible, potential danger of explosion of air suspension of carbon black, etc.

All the above-mentioned disadvantages of the types of carbon black hitherto used are solved by the electrically conductive filler according to the invention.

The subject of the invention is an electrically conductive filler based on electrically conductive carbon black, which contains 5 to 50% by weight, electrically conductive carbon blacks with a specific surface area of 300 to 1,300 m 2 / g coated with 50 to 95% by weight, inorganic admixture and average particle size in the range 0. 5 to 15 μα impregnated with 0.05 to 2% by weight, parts of binders such as higher fatty acids, their eols and esters, organosilenes and organotitanates, based on parts by weight of inorganic admixture.

The invention furthermore relates to this electrically conductive filler containing per 100 parts by weight, from 0.1 to 20 parts by weight, of processing aids, such as stabilizers, optical brighteners, antistatic additives, lubricants and reinforcing fillers.

The principle of the invention consists mainly in the use of high surface activity of electrically conductive carbon black, which is able to form a very strong bond with asymmetric molecules of surfactants anchored at acid-base centers of inorganic admixture. In this way, the individual particles of soot clusters are very tightly coated with particles of inorganic admixture, in which micron and submicron fractions of inorganic admixture are applied, which eekundally act on the soot clusters with a bubble effect - additional forces prevent the coated soot clusters to break into smaller units balance of forces and inertial forces. The combination of the specific surface area of the active carbon black, the particle size distribution and the amount of inorganic admixture and the quality of its surface coating together with the weight ratios of the electrically conductive filler Jeou.

The condition of an excess of inorganic admixture relative to the carbon black in a weight ratio of 50 to 95% to 5 to 50% is due to the need to achieve a high degree of carbon black dispersion in the composite material which the electrically conductive material must have to meet homogeneous isotropic electrical conductivity. This high degree of dispersion cannot be achieved at all under the presence of the above-mentioned relatively high amount of inorganic additive to carbon black under normal processing conditions. Another condition for the applicability of carbon black for an electrically conductive filler is the maximum specific surface area of the electrically conductive carbon black, limiting the mechanical properties of the composite containing this filler.

Addition of an electrically conductive filler by processing additives does not directly affect the quality of electrical properties, but can very significantly simplify the preparation of a complete scale for the production of plastic composites with lower electrical resistance by omitting another mixer in technology.

The bond between the carbon black and the filler is so strong that the advantageous handling and processing properties of the electrically conductive filler do not change even by not diluting up to 20% by weight. Other substances such as stabilizers, lubricants and more. The filler still remains loose. This fact can be advantageously used to simplify the compounding technology.

The electrically conductive filler according to the invention is produced by mixing the filler components in a slow-running mixer with a relative peripheral speed of the active part in the range of 0.15 to 2.5 m / s with a residence time of 2 to 120 minutes.

The method of manufacture specifies sensitive mixing of the conductive filler mixture, which limits the effect of inertial mixing forces only to the extent necessary to form a homogeneous mixture of components without significantly affecting the filler size of the coated carbon black clusters. The formation of solid coatings of filler particles around the carbon black agglomerates has a very favorable effect on handling the electrically conductive filler, in particular on increasing the bulk density of the concentrate by compacting the carbon black agglomerates by the presence of a higher specific gravity than carbon black. its origin in the high kinetic autonomy of the individual repulsive spherical clusters of carbon black-coated fillers and finally all handling of these conductive fillers is accompanied only by very small dust fractions of inorganic filler and not by dust fractions of soot, so pigment handling very little black transport path is safe. Mixing the carbon black concentrate into the plastic melt during compounding is easier than with the carbon black itself; the conditions for dispersing the carbon black in the melt are more favorable in the presence of inorganic particles because the local shear stress gradients in the melt increase *

This results in a very advantageous reduction of the threshold concentration of the content of electrically conductive carbon blacks in the polymer matrix of conductive composites when using the electrically conductive filler according to the invention compared to composites directly filled with electrically conductive carbon blacks.

The following examples illustrate the invention. The stated percentages and ratios of the components are by weight, the values of the specific internal resistance 9 * are determined by the procedure specified by ISO 3915 *

Example 1 (comparative)

In the twin-screw extruder WP 53, a composite of electrically conductive carbon black 2 Chezacarb EC with a specific surface area of 900 m / g was compounded in a polypropylene metric Mosten CHEZA 55212 with 10% of common stabilizers and lubricants. The production had to take place under a protective atmosphere with an O ₂ content of less than 10%, the melt strings were quite difficult to maintain, tore ss, dosing was accompanied by bridging in the hopper and the whole handling was accompanied by pollution of both equipment and workplace and air conditioning with soot dust. The achieved specific internal resistance of the electrically conductive composite was 18/2. cm.

Example 2

An electrically conductive filler according to the invention was prepared on a Henschel 10 HL fluid mixer. so that the electrically conductive carbon blacks of Chezacarb EC with a specific surface area of 900 m 2 / g were coated with an inorganic admixture of calcium carbonate with an average particle size d _{50 of} 6.5 μm with atearic acid treatment at 0.3% in a ratio of carbon black to inorganic admixture of 1: 1. The carbon black thus coated with an inorganic admixture was subsequently homogenized with a mixture of conventional stabilizers, lubricants and carbonate filler P20 U in a ratio of 80% to 20% to an electrically conductive filler which was used to produce electrically conductive composite based on polypropylene Mosten 55 212. Composite containing 30% The above-mentioned electric filler could be prepared without problems on a twin-screw extruder WP 53, it was not necessary to use a covering atmosphere, the strings did not tear, electrically conductive filler was dosed very well, did not form a vault in the tank tenths of a millimeter, which did not clog the equipment and did not tend to disintegrate into smaller particles or separate the individual components.

The electrically conductive composite showed a specific internal resistance of 10 ² A cm.

Example 3

Electrically conductive filler based on carbon black Chezacarb EC and with a specific surface area of 600 m ² / g and inorganic admixture of talc EK-I sorted to granulometry dgg 1.5 μm with silane treatment Y 9771 Union Carbide in the amount of 1.5% was prepared on a V mixer with a volume 20 l with a peripheral speed of the active part of 1.5 and / or by stirring a mixture containing 60% talc and 30% carbon black for 20 minutes. The resulting microclusters electrically conductive filler should in terms of handling and compounding PE Liten BB 29 matrix in a 7% concentration same excellent characteristics as that used in Example 2 * Achieved value of volume resistivity Qy »10/3 ^2/1 cm of the composite in comparison to · 10 ¹² jQ. cm, of a composite of the same type with the same content of the same type of carbon black, which is added to the composite directly and not by means of the electrically conductive filler according to the invention, is substantially lower. 3e it is therefore clear that for a given type of electrically conductive composite /

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CS 276129 B6.

It is possible to add a smaller amount of electrically conductive carbon black when using the filler according to the invention than in conventional production.

Example 4

Dolomitic microfine inorganic additive according to Czechoslovakia. of author's certificate No. 259 935 from · 3.5 .mu.m with a treatment of 0.7% of a mixture of glycerol monostearate and stearic acid in a ratio of 6: 1 2 was coated on Chezacarb EC carbon black with a specific surface area of 1,000 m / g in a ratio of 75%: 25% on 1.5 m ^{3 of a} Nauta mixer with a peripheral speed of 0.3 m / s. The resulting electrically conductive filler had the same excellent properties as described in Example 2 when processed in a PVC matrix Neralit and 652 into a semiconducting composite containing 4% carbon black.

Achieved value of specific internal resistance PVC ^ 1/10 ⁸ . XI cm is 4 orders of magnitude lower compared to electrically conductive carbon blacks.

Example 5

Commercial Mg (OH) ₂ Kiauma filler from _{2.0 mm} containing 3.0% of a mixture of fatty acids was used as an inorganic additive to form an electrically conductive filler by coating Chezacarb EC carbon black with a specific surface area of 900 m 2 / g and subsequent homogenization with a mixture of conventional stabilizers. lubricants and reinforcing fillers in a ratio of 45:40:15 on a Papenmeier KM 300 mixer with a stirrer speed circuit of 1.2 m / a for 4 minutes. The resulting electrically conductive filler, which had the same good handling characteristics and workability properties as filler example 2, used in the manufacture of semiconductive polystyrene based matrix 562. Krosten compounding 15% of this filler polyetyrenem composite was made with the specific internal resistance of 10 ⁴ Q Λ . cm, which is 3 orders of magnitude lower internal resistance than the same type of composite, which, however, was added by carbon black directly, without the use of the electrically conductive filler according to the invention.

Example 6

The aluminum hydroxide-based filler from Sol, Micral 932 from _g Q 0.9, was treated with a% surfactant, based on stearic acid. This inorganic additive coated under the conditions of Example 5 on Chezacarb EC carbon black with a spec, surface area of 900 m 2 / g and subsequently homogenized with a mixture of stabilizers and lubricants in a ratio of 89%: 8%: 3%. The resulting electrically conductive filler, the handling properties of which corresponded to the quality of Example 2, was used to produce a semiconducting non-flammable composite by compounding 75% of this filler and 25% of LLDPE Union Carbide polyethylene on a Buse kneader. Achieved value of specific internal resistivity 3.10 ⁴ .cm. Compounding of the same type of carbon black-doped semiconducting composite directly without the use of the electrically conductive filler according to the invention on the machine used by us is not technically possible.

Example 7 ‘

Example 7 identical to Example 5 only the percentage of the additive mixture of lubricant stabilizers and reinforcing fillers was increased to 30%, i.e. the soot ratio of inorganic additive and additives was 35: 35: 30. significantly worse ee processed into a composite.

Claims (2)

PATENT CLAIMS 1. Electrically conductive filler based on electrically conductive carbon black, characterized in that it contains 5 to 50% by weight, electrically conductive carbon black with a specific surface area of 300 to 1,300 m ² / g coated with 50 to 95% by weight, inorganic impurities with average particle size in the range of 0.5 to 15 .mu.m, impregnated with 0.05 to 2 parts by weight, of parts of binders, such as higher fatty acids, their salts and esters, organoilanes and organotitanates, based on 100 parts by weight, of parts of inorganic admixture. . / · '' /. CS 276129 B6 4 2. An electrically conductive filler according to claim 1, characterized in that it contains 0.1 to 20 parts by weight of processing additives such as stabilizers, optical brighteners, antistatic additives, lubricants and reinforcing fillers per 100 parts by weight.