Thermal treatment of glass
AssigneePilkington Brothers Limited
InventorsRaymond P. Cross, Gordon T. Simpkin
Life of this patent
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Abstract
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.
Claims30
A method of thermally toughening glass comprising:
- heating the glass to a temperature above its strain point;
- chilling the hot glass by contact with a gas-fluidised particulate material which comprises a mixture in predetermined proportions of a number of selected particulate materials, at least one of which has gas-generating properties;
- selecting the gas-generating particulate material from the group consisting of .gamma.-alumina, aluminum trihydrate, aluminum monohydrate, aluminosilicate and sodium bicarbonate;
- and
- mixing said selected particulate materials in predetermined proportions which are tailored to impart to the mixture a thermal capacity per unit volume at minimum fluidisation in the range 1.02 to 1.73 MJ/m.sup.3 K and a flowability in the range 60 to 86.
A method of thermally toughening glass comprising:
- heating the glass to a temperature above its strain point;
- chilling the hot glass by contact with a gas-fluidised particulate material which comprises a mixture in predetermined proportions of at least one particulate metal oxide whose thermal capacity per unit volume at minimum fluidisation is in the range 1.76 to 2.01 MJ/m.sup.3 K and at least one particulate material having gas-generating properties;
- selecting as the gas-generating particulate material a material which is capable of evolving from 4% to 37% of its own weight of gas when heated to a constant weight at 800.degree. C., said gas-generating particulate material being selected from the group consisting of .gamma.-alumina, aluminum trihydrate, aluminum monohydrate, aluminosilicate, and sodium bicarbonate;
- and
- mixing said selected particulate materials in predetermined proportions which are tailored to impart to the mixture a thermal capacity per unit volume at minimum fluidisation in the range 1.27 to 1.76 MJ/m.sup.3 K and a flowability in the range 73 to 78.
A method of thermally toughening glass comprising:
- heating the glass to a predetermined temperature above its strain point;
- contacting the hot glass with a gas-fluidised particulate material which comprises a mixture of selected particulate materials, including a particulate .gamma.-alumina and a particulate .alpha.-alumina, which .gamma.-alumina has gas-generating properties when heated by said hot glass;
- and
- mixing said selected particulate .gamma.-alumina and particulate .alpha.-alumina in selected predetermined proportions which are tailored to impart to the mixture a thermal capacity and flowability such that required toughening stresses are induced by the gas-fluidised mixture in the glass.
A method of thermally toughening glass comprising:
- heating the glass to a temperature above its strain point;
- contacting the hot glass with a gas-fluidised mixture of selected particulate materials including a proportion of .gamma.-alumina having gas-generating properties when heated by said hot glass;
- and
- tailoring the proportions of the .gamma.-alumina and at least one other particulate material in said mixture to impart to the mixture a thermal capacity, determined as the thermal capacity per unit volume at minimum fluidisation and a flowability, such that predetermined toughening stresses are induced in the glass as it cools in said gas-fluidised mixture.
A method of thermally toughening glass comprising:
- heating the glass to a predetermined temperature above its strain point;
- contacting the hot glass with a gas-fluidised particulate material which comprises from 8 to 10% by weight of a particulate aluminosilicate which has gas-generating properties when heated by hot glass and from 92 to 90% by weight of .alpha.-alumina;
- and
- mixing said aluminosilicate and .alpha.-alumina in selected predetermined proportions which are tailored to impart to the mixture a thermal capacity, determined as the thermal capacity per unit volume at minimum fluidisation, and a flowability such that required toughening stresses are induced in the glass as it cools in the gas-fluidised mixture.
A method of thermally toughening glass comprising:
- heating the glass to a predetermined temperature above its strain point;
- contacting the hot glass with a gas-fluidised particulate material which comprises particulate aluminum monohydrate (Al.sub.2 O.sub.3.1H.sub.2 O) and at least one inert particulate material selected from the group consisting of .alpha.-alumina, silicon carbide and zircon;
- and
- mixing the aluminum monohydrate and the inert material in selected predetermined proportions which are tailored to impart to the mixture a thermal capacity and flowability such that required toughening stresses are induced by said gas-fluidised mixture in the glass.
A method of thermally toughening glass comprising:
- heating the glass to a predetermined temperature above its strain point;
- contacting the hot glass with a gas-fluidised particulate material which comprises a mixture of particulate .gamma.-alumina having gas-generating properties with at least one particulate metal oxide whose thermal capacity per unit volume at minimum fluidisation is in the range 1.76 to 2.01 MJ/m.sup.3 K;
- and
- mixing the .gamma.-alumina and metal oxide in selected predetermined proportions which are tailored such that required toughening stresses are induced in the glass as it cools in said gas-fluidised mixture.
A method of thermally treating glass comprising heating the glass to a predetermined temperature, contacting the hot glass with a gas-fluidised particulate material which comprises a mixture of a number of selected particulate materials, at least one of said particulate materials being capable of evolving from 4% to 37% of its own weight of gas when heated to a constant weight at 800.degree. C., and mixing said selected materials in selected predetermined proportions which are tailored to impart to the mixture of particulate materials a thermal capacity, determined as the thermal capacity per unit volume at minimum fluidisation in the range 1.02 to 1.73 MJ/m.sup.3 K, and a flowability in the range 60 to 86 such that a required thermal treatment of the glass by the gas-fluidised mixture is achieved whereby the tailored mixture imparts higher stresses than the stresses which could be achieved by any of the constituents of the tailored mixture used alone.
A method of thermally toughening glass comprising:
- heating the glass to a temperature above its strain point;
- chilling the hot glass by contact with a gas-fluidised particulate material which comprises a mixture in predetermined proportions of a number of selected particulate materials, at least one of which has gas-generating properties;
- selecting as the gas-generating particulate material a material which is capable of evolving from 4% to 37% of its own weight of gas when heated to a constant weight at 800.degree. C.;
- and
- mixing said selected particulate materials in predetermined proportions which are tailored to impart to the mixture a thermal capacity per unit volume at minimum fluidisation in the range 1.02 to 1.73 MJ/m.sup.3 K and a flowability in the range 60 to 86, whereby the tailored mixture imparts higher toughening stresses than the stresses which could be achieved by any of the constituents of the tailored mixture used alone.
A method of thermally toughening glass comprising:
- heating the glass to a temperature above its strain point;
- chilling the hot glass by contact with a gas-fluidised particulate material which comprises a mixture in predetermined proportions of a number of selected particulate materials, at least one of which has gas-generating properties;
- placing the gas-fluidised particulate material in a quiescent uniformly expanded state of particulate fluidisation by control of the distribution of fluidising gas in the particulate material at a gas flow velocity through the particulate material between that velocity corresponding to minimum fluidisation and that velocity corresponding to maximum expansion of the particulate material;
- selecting the gas-generating particulate material from the group consisting of .gamma.-alumina, aluminium trihydrate, aluminium monohydrate, aluminosilicate and sodium bicarbonate;
- and mixing said selected particulate materials in predetermined proportions which are tailored to impart to the mixture a thermal capacity per unit volume at minimum fluidisation in the range 1.02 to 1.73 MJ/m.sup.3 K and a flowability in the range 60 to 80.
A method of thermally treating glass comprising:
- heating the glass to a predetermined temperature;
- contacting the hot glass with a gas-fluidised particulate material which comprises a mixture of a number of selected particulate materials, at least one of said particulate materials being capable of evolving from 4% to 37% of its own weight of gas when heated to a constant weight at 800.degree. C.;
- placing said gas-fluidised particulate material in a quiescent uniformly expanded state of particulate fluidisation by control of the distribution of fluidising gas in the particulate material at a gas flow velocity through the particulate material between that velocity corresponding to minimum fluidisation and that velocity corresponding to maximum expansion of the particulate material;
- and
- mixing said selected materials in selected predetermined proportions which are tailored to impart to the mixture of particulate materials a thermal capacity, determined as the thermal capacity per unit volume at minimum fluidisation, in the range 1.02 to 1.73 MJ/m.sup.3 K, and a flowability in the range 60 to 86 such that a required thermal treatment of the glass by the gas-fluidised mixture is achieved whereby the tailored mixture imparts higher stresses than the stresses which could be achieved by any of the constituents of the tailored mixture used alone.
Dependencies are inferred from the claim text.