Pilkington Brothers P.l.c.

Gordon T Simpkin

Raymond Peter Cross

Donald C Wright

Kenneth Ashcroft

Glass is heated to a temperature above its strain point and is thermally toughened by chilling with a quiescent gas-filuidized particulate material which has gas-generating properties and a mean particle size in the range 30 .mu.m to 120 .mu.m, a particle size distribution in the range 1.15 to 2.78, a flowability in the range 69.5 to 92, and a thermal capacity per unit volume at minimum fluidization in the range 0.7 to 1.59 MJ/m.sup.3 K. The invention is particularly suitable for thermally toughening glass sheets for vehicle windscreens.

Method of thermal toughening of glass in a fluidized bed

The thermal treatment of glass is effected by contacting the glass, when it is hot, with a gas-fluidized mixture of particulate materials, at least one of which is selected to have gas-generating properties when heated by the hot glass. The materials are mixed in selected pre-determined proportions which impart to the mixture a thermal capacity and flowability which are such that a required thermal treatment is achieved. The method is particularly suitable for the thermal toughening of glass sheets for vehicle windscreens.

Thermal treatment of glass

The invention provides a method and apparatus for treating articles with particulate material, for example for thermally toughening glass sheets. The particulate material consists of or contains permanently magnetized particles and is subjected to an electromagnetic field which travels linearly through the treatment space and is effective to sustain a dispersion of the particulate material in the treatment space. The article is contacted with that dispersion.

Thermally treating articles with particulate material and apparatus

An interleaving material for separating glass sheets and protecting them from scratching and staining during storage or transit comprises a porous finely divided support material, such as wood flour, impregnated with a weakly acidic material such as an organic acid (e.g. adipic acid) or an acid reacting salt, and fine particles of a chemically inert plastics material, e.g. a methyl methacrylate, preferably of slightly larger particle size than the acid-impregnated support material.

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Ormskirk, United Kingdom

Gordon T Simpkin