Patent GB-1106014-A (GB)
Title: Molding comminuted nonplastic inorganic material
IPC: B22F3/02
Filed: 1965-07-15
Abstract: Sintered articles are produced from comminuted non-plastic inorganic material by  (a) mixing the material as a major component by weight with a melted organic vehicle which is solid at normal room temperature and pressure, melts below 200 DEG C. and has a vapour pressure of at least 1 mm Hg at its M.P.T. under one atmosphere, and with an organic deflocculant which is free of water and soluble in the melted vehicle,  (b) Moulding the mixture while the vehicle is molten,  (c) Cooling and solidifying the mixture to a rigid green body,  (d) Subliming the vehicle therefrom and  (e) Sintering the resultant material.  The non-plastic inorganic material may be a metal, alloy, or cermet, e.g. copper, or nickel and the vehicle, chloracetic or benzoic acids, phthalic anhydride, camphor, or preferably naphthalene or p-dichlorobenzene.  The deflocculant is selected from diverse materials, viz. surfactants, aliphatic monocarboxylic acids of at least 3 carbon atoms, esters thereof with alcohols of at least 3 carbon atoms (including fats, oils, lecithins and waxes), amides thereof, salts thereof, and monohydroxy alcohols of at least 8 carbon atoms.  The batch may also include an organic binder to assist moulding.  Copper of particle size -325 Tyler mesh, and nickel (as carbonyl) of 3-5 microns are exemplified (Exs 12, 13). The moulding techniques used may be: pressing, injection, transfer, gravity or slip casting, extruding, rolling, spraying or spinning.ALSO:Sintered articles are produced from comminuted non-plastic inorganic material by, (a) mixing the material as a major component by weight with a melted organic vehicle which is solid at normal room temperature and pressure, melts below 200 DEG  C. and has a vapour pressure of at least 1 mm. Hg at its M.Pt. under one atmosphere, and with an organic deflocculant which is free of water and soluble in the melted vehicle, (b) moulding the mixture while the vehicle is molten, (c) cooling and solidifying the mixture to a rigid green body, (d) subliming the vehicle therefrom and (e) sintering the resultant material.  The non-plastic inorganic material may be a ceramic, glass, glass-ceramic, cermet, metal, alloy or mixture thereof, in particular alumina, fused silica, silica glass,\sW borosilicate glass,* zircon, calcined magnesite, high alumina porcelain, b -spodumene + petalite, or metallic copper or nickel (used as carbonyl) and is generally - 200 mesh (Tyler).  Specific organic vehicles are chloracetic acid, benzoic acid, phthalic anhydride, camphor, and especially naphthalene and p-dichlorobenzene. The deflocculant may be chosen from a wide range of materials, viz. surfactants, aliphatic monocarboxylic acids of at least 3 carbon atoms, esters thereof with C3 + alcohols (including fats, oils, lecithins and waxes), amides thereof; salts thereof, and monohydroxy alcohols of at least 8 carbon atoms. To assist moulding the batch mixture may include as organic binder carnauba, microcrystalline or oxidized microcrystalline wax, polymethyl methacrylate, polyvinyl acetate or alcohol, polystyrene, chlorinated naphthalene or a polyethylene glycol.  \sWSilica glass analysing 96.5% SiO2, 3% B2O3, 0.5% Al2O3, by weight.  *Borosilicate glass analysing (i) 79.2% SiO2, 18.4% B2O3, 2.4% K2O, by weight, or (ii) 80% SiO2, 12.2% B2O3, 4% Na2O, 2.6% Al2O3, 0.4% K2O and 0.8% CaO.  Before the subliming step, two green bodies may be heated in contact to seal the surfaces, as by a soldering gun.