Patent GB-792954-A (GB)
Title: Improvements relating to polyamide articles and method of production thereof
Inventor: STOTT LOUIS LATHROP
IPC: B29B13/00
Filed: 1954-07-01
Abstract: Articles are prepared by compressing a mixture (as claimed in Specification 792,955) of a polyamide with an average particle size not greater than 40 microns and up to 70 per cent of a lower melting polyamide powder at a pressure sufficient to allow the article to be removed from the mould, and then heating the article to a temperature between the meltingpoints of the two polyamides. Preferably compression is effected at a temperature substantially below the melting-point of either of the polyamides.  Inert fillers may be added for special effects, e.g. diamond dust, ground silica, carborundum, chalk, alundum, or tungsten carbide for abrasive articles, or metal powders, e.g. copper, lead or iron, or carbon, graphite, molybdenum sulphide, ceramic materials, titanium dioxide, titanates, magnetic material or polytetrafluorethylene for other kinds of article.  Oxidation inhibitors may also be added, preferably to the lower melting polyamide.  Finely-divided polyamide powder may be obtained by the processes described in Specifications 690,936, 691,114 and 740,356.  Both polyamides may be precipitated together from mixed solutions.  Before use, the powders may be tableted and the tablets then ground.  An example describes the production of a bearing from a mixture of 70 parts of granulated powder prepared from waste polyhexamethylene adipamide (M.P. 271 DEG  C.), and 20 parts of powder from virgin polyhexamethylene sebacamide (M.P. 224 DEG  C.). The compressed bearing was heated for 10 minutes at 225 DEG  C. in an oil bath.  Heating may be effected in vacuo, or in an inert atmosphere.  Polycaprolactam and interpolymers having a lower melting-point than polyhexamethylene sebacamide are also mentioned as suitable materials.  Specifications 763,939 and 763,940 also are referred to.ALSO:Articles are prepared by compressing a mixture (as claimed in Specification 792,955 [Group IV(a)] of a polyamide with an average particle size not greater than 40 microns and up to 70 per cent of a lower melting polyamide powder at a pressure sufficient to allow the article to be removed from the mould, and then heating the article to a temperature between the melting points of the two polyamides.  Preferably compression is effected at a temperature substantially below the melting point of either of the polyamides. Inert fillers may be added for special effect, e.g., diamond dust, ground silica, carborundum, chalk, alundum, or tungsten carbide for abrasive articles, or metal powders, e.g., copper, lead or iron, or carbon, graphite, molybdenum sulphide, ceramic materials, titanium dioxide, titanates, magnetic material or polytetrafluorethylene for other kinds of articles.  Oxidation inhibitors may also be added, preferably to the lower melting polyamide.  Finely divided polyamide powder may be obtained by the processes described in British Specifications 690,936, 691,114 and 740,356 [all in Group IV(a)]. Both polyamides may be precipitated together from mixed solutions. Before use the powders may be tabletted, and the tablets then ground. An example describes the production of a bearing from a mixture of 70 parts of granulated powder prepared from waste polyhexamethylene adipamide (M.Pt. 271 DEG C.) and 20 parts of powder from virgin polyhexamethylene sebacamide (M.Pt. 224 DEG C.).  The compressed bearing was heated for ten minutes at 225 DEG C. in an oil bath. Heating may be effected in vacuo, or in an inert atmosphere. Polycaprolactam and interpolymers having a lower melting point than polyhexamethylene sebacamide are also mentioned as suitable materials.  Specifications 763,939 and 763,940 [Group IV(a)] also are referred to.