CS257627B1 - Mixture for the production of particularly solid solids - Google Patents

Abstract

The mixture for the production of extra-hard pencils contains graphite, a polymer binder, additives to facilitate processing and additives to regulate hardness. The polymer binder is made of a copolymer of vinyl chloride with vinyl acetate and a plasticizer. The additives to facilitate processing are made of a salt of stearic acid, glycerin, cyclohexanone and microcrystalline wax. The additives to regulate hardness are made of coumarone, phenol formaldehyde or furan type resins.

Description

BACKGROUND OF THE INVENTION The present invention relates to a composition for the production of particularly solid graphite, especially small cross-sections.

Clay is used as a binder component for the production of graphite in a conventional manner and is mixed with graphite and carbon black in an aqueous medium. The mixture is pressed to the desired cross-sections. After drying, the graphite bodies are fired at 800 to 1200 ° C. Due to the high temperature and sintering of the materials, a porous solid core is formed, which must be saturated with wax or other substances. It is only after this finishing that it is possible to write a sufficiently intensive line with the solid produced. However, the graphite produced in this way does not have sufficient torsional and flexural strength and is not suitable for producing graphite of small diameters.

More recently, organic resins or other polymeric substances have also been used as binders instead of clay. After firing, porous graphite leads are also created, 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 the lack of flexural strength.

These drawbacks are overcome by a graphite composition, in particular a small cross-section, consisting of a homogenized composition comprising graphite, a polymeric binder, processing aids and a hardness control additive according to the invention. It is based on the fact that the polymeric binder consists of 50 to 90 wt. parts by weight of copolymers of vinyl chloride with vinyl acetate and 1 to 50 wt. parts of a plasticizer based on phthalic or adipic acid ester; parts by weight of stearic acid salts, not more than 50% by weight % cyclohexanone and not more than 30 wt. the microcrystalline wax parts and the hardness control additive consist of phenol-formaldehyde, furan or coumarone resin. Adhesion to the rolling mill increases the solvent, for example, cyclohexanone, methylethylketone, acetone.

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

The invention and its effects are described in more detail below on several examples of forming a composition for producing particularly solid graphite according to the invention.

Example 1

A mixture of 14 wt. parts of graphite, 10 wt. parts by weight of polyvinyl chloride-VC-VAC copolymer (Ivory KV-172), 1 wt. part of furan resin, 11 wt. parts of methyl ethyl ketone,

0,7 hirDt. 0.5 parts by weight of carbon black (Chezasorb); % of stearate, and 1.5 wt. parts of dioctyl phthalate. The mixture was processed by kneading, rolling at elevated temperature, the graphite was formed by drawing from a press and further heat treated by carbonization. The resulting graphite had an HB gradation with excellent blackness.

Example 2

A mixture of 15 wt. parts of graphite, 11 wt. parts by weight of copolymers VC-VAC (Ivory1 KV-172), 0.8 wt. parts by weight of dioctyl phthalate, 0.7 wt. parts of dioctyldipate, 3 wt. parts of coumarone resin, 0.6 wt. parts by weight of zinc stearate, 1 wt. part of carbon black (Chezasorb), 12 wt. parts of methyl ethyl ketone and 0.5 g of microcrystalline wax. The mixture was processed by kneading, rolling at elevated temperature, the graphite was formed by drawing from a press and further heat treated by carbonization. The resulting leads had a gradation of HB with excellent redness.

Example 3

A mixture of 20 wt. parts of graphite, 14 wt. parts to VC-VAC (Ivory KV-172), 1.4 wt. parts by weight of carbon black (Chezasorb), 5 wt. parts by weight of phenol-formaldehyde resin (Novolak B), 0.8 wt. parts by weight of zinc stearate, 1.6 wt. parts of dioctyl phthalate, 0.8 wt. parts of dioctyladipate, 8 wt. parts of methyl ethyl ketone and from 8 wt. parts of acetone.

The mixture was processed by kneading, rolling at elevated temperature, the graphite was formed by drawing from a press and further heat treated by carbonization. The resulting graphite grades had an H gradation and were high strength.

Example 4

A mixture of 14 wt. parts of graphite, 0.7 wt. parts of carbon black, 11 wt. parts by weight of copolymer based on vinyl chloride vinyl acetate (Ivory KV 172), 0.5 wt. parts by weight of Novolak (Novolak B), 0.4 wt. parts by weight of zinc stearate, 1.4 wt. parts by weight of dioctyl phthalate, 0.2 wt. 6 parts by weight of methyl ethyl ketone, and 6 parts by weight of cyclohexanone; parts of acetone. The mixture was processed by kneading, rolling at elevated temperature, the graphite was formed by drawing the press and further heat treated by carbonization. The resulting graphite grades had an H gradation and were high strength.

Claims (1)

SUBJECT OF THE INVENTION, A composition for producing particularly solid leads, in particular of small cross-sections, consisting of a homogenized composition comprising graphite, carbon black, a polymeric binder, processing aids and additives for controlling the hardness of the solids, characterized in that the polymeric binder consists of 50 to 90 wt. parts by weight of a copolymer of vinyl chloride with vinyl acetate and 1 to 50 wt. parts of the phthalic or adipic ester plasticizer and the processing aid are not more than 30 wt. parts by weight of a salt of stearic acid, not more than 50% by weight % cyclohexanone and not more than 30 wt. parts of microcrystalline wax; and additives for controlling the hardness of the graphite consist of phenol-formaldehyde resins, furan resins, coumarone resins in an amount of not more than 25 wt. parts.