CS255674B1 - Mixture for black lead production - Google Patents

Abstract

The present invention relates to a composition for the production of small-diameter graphite stiffnesses with high strength and good writing properties. The composition comprises graphite, polymeric binders and additives to facilitate processing. The polymeric binder is comprised of an emulsion paste-forming polyvinyl chloride and a plasticizer. The processing aids are composed of a salt of stearic acid, glycerine, white graphite, cyclohexanone, ethylene vinyl acetate copolymer and microcrystalline wax

Description

BACKGROUND OF THE INVENTION The present invention relates to a composition for the production of graphite, in particular small cross-sections, consisting of a homogenized composition comprising: graphite, polymeric binder, and processing aids.

In the present manufacturing process, a mixture of graphite, carbon black, clay is formed as a binder, which is diluted with water to the desired density required for extrusion into the final profiles.

After drying, the graphite bodies are fired at a temperature of 800 to 1200 ° C. A high temperature and sintering of the materials results in a porous solid core which has to be saturated with wax or other substances. It is only after this finishing that it is possible to produce it; to write a sufficiently intense line. However, the graphite produced in this way does not have sufficient torsional and flexural strength and is not suitable for the production of graphite of small cross-sections.

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Recently, instead of clay began; binders also use organic resins or other polymeric substances. After firing, porous graphite leads are formed, which must be saturated with oil or wax so that we can achieve a sufficiently intense line when writing. A disadvantage of the clay bonded graphite production methods used is their insufficient flexural strength.

These drawbacks are overcome by a lead composition of particularly small cross-section consisting of a homogenized composition comprising graphite, a polymeric binder and processing aids according to the invention. It is based on the fact that the polymeric binder consists of 50 to 90% by weight. % of an emulsion paste-forming polyvinyl chloride and 10 to 50 wt. plasticizers based on phthalic acid ester and / or chlorinated paraffin and the processing aids are 20 to 60% by weight. % stearic acid salt, not more than 30% % glycerin, not more than 50% by weight white graphite, not more than 50 wt. % cyclohexanone; % of a copolymer of ethylene vinyl acetate and not more than 30 wt. microcrystalline wax. According to another aspect of the invention, the plasticizer comprises di (2-ethylhexyl) phthalate and a stearic acid salt of zinc stearate.

Lubricants, stabilizers and adhesives are added to the mixture for ease of processing. Solvent, for example cyclohexanone, increases adhesion to the rolling mill. The composition according to the invention may furthermore comprise fluorinated graphite in addition to graphite. Di (2-ethylhexyl) phthalate with the addition of glycerin and / or butyl phthalyl butyl glycolate is used as plasticizer.

The main advantage of the composition according to the invention is that the graphite has a high-quality surface, better writing while maintaining low abrasion and having increased strength while maintaining low production costs.

The composition according to the invention is described in more detail below on several exemplary embodiments.

Example 1

Composition: 20 g graphite g emulsion paste-forming polyvinyl chloride

3,5 g di (2-ethylhexyl) phthalate 0,5 g zinc stearate 0,5 g glycerin

The mixture was processed by kneading, elevated temperature rolling, and the graphite was formed by drawing from a press. Then they were further heat treated by carbonization.

Example2

Mixture composition:

g graphite g emulsion paste-forming polyvinyl chloride g di (2-ethylhexyl) phthalate g chlorinated paraffins

0.5 g zinc stearate g white graphite g cyclohexanone

0.5 g microcrystalline wax 0.5 g polyethylene vinyl acetate 1

The mixture was processed by kneading and rolling at elevated temperature. The leads were created by drawing from a press and further heat treated by carbonization. The resulting leads had gradations of HB with excellent blackness.

Example 3

Composition of the mixture g graphite g emulsion paste-forming polyvinyl chloride 4 g butylphthalyl butyl glycolate 0.5 g chlorinated paraffins 0.5 g zinc stearate 1 g white graphite

0.5 g microcrystalline wax 0.5 g polyethylene vinyl acetate

The mixture was processed by kneading and rolling at elevated temperature. The leads were created by drawing from a press and further heat treated by carbonization. The resulting graphite had high strength gradations H.

SUMMARY OF THE INVENTION

Claims (2)

SUMMARY OF THE INVENTION CLAIMS 1. A composition for the production of graphite, in particular small cross-sections, comprising a homogenized composition comprising graphite, a polymeric binder and processing aids, wherein the polymeric binder is comprised of 50 to 90% by weight. % of an emulsion paste-forming polyvinyl chloride and 10 to 50 wt. phthalic acid ester and / or chlorinated paraffin emollients and processing aids are 20 to 60 wt. salts of stearic acid, not more than 30% glycerine, not more than 50% by weight % white graphite, not more than 50% wt. % cyclohexanone, not more than 30% % of copolymers of ethylene vinyl acetate and not more than 30 wt. microcrystalline wax. 2. A composition according to claim 1 wherein the plasticizer is di (2-ethylhexyl) phthalate and a stearic acid salt of zinc stearate.