GB615209A - Improved moulding compositions - Google Patents

Abstract

Mottled articles, of which the individual colours harmonise with each other without showing hard dividing lines or smudging, result when employing moulding compositions obtained by blending together a plurality of different coloured powders each containing a thermosetting resin, a wood flour filler and finely divided metal pigment. Metal powders known in the trade as "bronzes" are preferred, and best results are obtained by using powders made up of irregularly shaped large particles, e.g. up to 1/2 inch diameter. A base for the composition is obtained by condensing urea with formaldehyde in molar proportions of 1-1.5 for 2 1/2 to 3 1/2 hours at a pH of 7.5-8 to give a syrup which is mixed with wood flour in the proportions of 306 parts to 208 parts. The impregnated syrup is dried to a moisture content of 10 per cent and mixed with 0.2 per cent zinc stearate and 0.5 per cent trimethyl phosphate and the mixture malaxated on rolls and broken into 1/4 -\ba1/2 inch flakes; 300 parts of the base are mixed with 15 parts pale gold lac bronze or 15 parts copper bronze. A similar base is obtained by condensing melamine and formaldehyde in molar ratio of 1 : 3 for 90 mins. at a pH of 6.8 and mixing the syrup with alpha cellulose flock or by mixing 48 parts wood flour, 30 parts phenol novolak, 1,6 part cresylic novolak, 5.42 parts hexa, 2.4 parts lime and 2 parts stearin. The following pigments are specified: gold and copper bronzes, aluminium powder, Fast Violet R, Fast Blue GS, Rose Ultramarine, Blue Lake 21035. Specifications 489,467 and 519,298 are referred to.