Method for manufacturing pencil leads

Claim 1

A method for manufacturing pencil leads which comprises: mixing 100 parts by weight of graphite, 30 to 60 parts by weight of water-soluble nigrosine, an aqueous emulsion which contains 10 to 30 parts by weight of wax; said wax melting at a temperature between about 45° C. and about 90° C. and being selected from the group consisting of a. esters of higher fatty acids and higher aliphatic alcohols, b. petroleum wax, c. animal fats, d. vegetable fats, e. fatty acids of 2 to 12 carbon atoms, f. esters of fatty acids having 12 to 22 carbon atoms and a hydroxyl compound selected from the group consisting of phenols and aromatic alcohols, g. higher alkyl ketones selected from the group consisting of palmitone and stearone, h. amides selected from the group consisting of industrial grade palmitic acid amide and stearic acid amide, i. polyethylene having a molecular weight of about 1000 to 10000; and sufficient water to permit the mixture to be extruded; extruding the resultant base mixture from a die into rods; drying the extruded rods to remove the water contained therein; and baking the dried rods at elevated temperatures to form pencil leads.

Claim 2

A method for manufacturing pencil leads which comprises: mixing 100 parts by weight of graphite, 30 to 60 parts by weight of water-soluble nigrosine, an aqueous emulsion which contains 10 to 30 parts by weight of wax; said wax melting at a temperature between about 45° C. and about 90° C. and being selected from the group consisting of a. esters of higher fatty acids and higher aliphatic alcohols, b. petroleum wax, c. animal fats, d. vegetable fats, e. fatty acids of 2 to 12 carbon atoms, f. esters of fatty acids having 12 to 22 carbon atoms and a hydroxyl compound selected from the group consisting of phenols and aromatic alcohols, g. higher alkyl ketones selected from the group consisting of palmitone and stearone, h. amides selected from the group consisting of industrial grade palmitic acid amide and stearic acid amide, i. polyethylene having a molecular weight of about 1000 to 10000; and sufficient water to permit the mixture to be extruded; extruding the resultant base mixture from a die into rods; drying the extruded rods to remove the water contained therein; and baking the dried rods at elevated temperatures to form pencil leads.