GB1235303A - Thermoplastic binders for continuously produced leads for pencils, copying pencils and coloured pencils - Google Patents

Abstract

1,235,303. Pencil leads. FARBENFABRIKEN BAYER A.G. 24 Sept., 1968 [4 Oct., 1967], No. 45222/68. Heading B6P. [Also in Division C3] A pencil lead comprises graphite or a colouring agent and (A) 1 to 100 parts by weight of a graft polymer of (a) an ethylene-vinyl acetate copolymer, and (b) grafted-on vinyl chloride, which graft polymer may be at least partially replaced by copolymer (a); and (B) 99 to 0 parts of a polymer comprising (a) a butadiene polymer optionally containing up to 30% by weight of copolymerized styrene, acrylonitrile or isoprene or up to 70% of a C 1 to C 6 -alkyl acrylate or methacrylate or an alkyl vinyl ether and (b) a copolymer of styrene and acrylonitrile in a weight ratio of 95: 5 to 50: 50, wherein these two monomers may be at least partially replaced by their respective alkyl derivatives, or by methyl methacrylate, the styrene and acrylonitrile being polymerized either separately from the butadiene polymer, or wholly or in part in the presence thereof. Examples are given in which leads are extruded from compositions comprising (i) (A) ethylene-vinyl acetate copolymer grafted with vinyl chloride, optionally (B) polybutadiene grafted with styrene and acrylonitrile, alone or together with additional styrene - acrylonitrile copolymer, a C 15 - alkylphenol sulphonate, barium cadmium laurate, ethylene diamine bis-stearamide and graphite; (ii) (A) ethylene-vinyl acetate copolymer; (B) as in (i), benzyl octyl adipate, calcium stearate and graphite; (iii) (A) ethylene-vinyl acetate copolymer, ethylene diamine bis-stearamide dibutyl phthalate and graphite; (iv) (A), (B) and the sulphonate and laurate as in (i), cadmium sulphide selenide pigment and talc; and (v) (A) as in (i), (B) butadiene-styrene copolymer grafted with styrene and acrylonitrile, barium cadmium laurate, dibutyl phthalate, ethylene diamine bis-stearamide and graphite.