GB877528A - Highly filled shaped polyamide articles and a method of making them - Google Patents

Abstract

A mixture of finely divided high melting synthetic linear polyamide particles and finely divided particles of a solid inorganic nonlubricant filler, the latter constituting from 40%-75% by volume of the mixture, is cold pressed to form a shaped green article capable of being handled without distortion which is then fused by heating to a temperature above the melting point of the polyamide. The polyamide, e.g. polyhexamethylene adipamide, polyhexamethylene sebacamide, or polycaprolactam, is first precipitated from a solution by a precipitating agent, or is dissolved in a solvent which can dissolve the polyamide at elevated temperature but not at room temperature and is then precipitated as a fine powder by cooling the solution. The powder should have an average ultimate particle size of less than 40 microns. Suitable fillers include plaster of Paris, calcium carbonate, carbon black, zircon, cement and talc. It is advantageous to add a small percentage of finely divided lubricant filler, e.g. polytetrafluoroethylene in an amount from 0,1%-2% by weight of the mixture of polyamide and non-lubricant filler. The polytetrafluoroethylene acts as a mould release additive and, in effecting a reduction in the coefficient of friction of the resulting piece, is of special advantage when forming bearings according to the invention. The green article should be fused at a temperature not more than 50 DEG F. above the melting point of the polyamide.ALSO:A mixture of finely divided high melting synthetic linear polyamide particles and finely divided particles of a solid inorganic non-lubricant filler, the latter constituting from 40 to 75% by volume of the mixture, is cold pressed to form a shaped green article capable of being handled without distortion which is then fused by heating to a temperature above the melting point of the polyamide. The polyamide, e.g. polyhexamethylene adipamide polyhexamethylene sebacamide, or polycaprolactum, is precipitated from a solution by the addition of a precipitating agent or is first dissolved in a solvent which can dissolve the polyamide at elevated temperature but not at room temperature and is then precipitated as a fine powder by cooling the solution. The powder should have an average ultimate particle size of less than 40 microns. Suitable fillers include plaster of Paris, calcium carbonate, carbon black, zircon, cement and talc. It is advantageous to add a small percentage of finely divided lubricant filler, e.g. polytetrafluoroethylene in an amount from 0,1 to 2% by weight of the mixture of polyamide and non-lubricant filler. The polytetrafluoroethylene acts as a mould release additive and, in effecting a reduction in the coefficient of friction of the resulting piece, is of special advantage when forming bearings according to the invention. The green article should be fused at a temperature not more than 50 DEG F. above the melting point of the polyamide.