# US 4,400,193 A · Method of thermal toughening of glass in a fluidized bed

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- Number: US 4,400,193 A
- Document ID: US4400193A
- Status: Granted
- Kind: A
- Application number: 06/086,322
- Filed: 1979-10-19
- Granted: 1983-08-23
- Earliest claimed: 1978-08-17
- Assignees: Pilkington Brothers Limited
- Inventors: Raymond P. Cross; Gordon T. Simpkin
- Web page: https://patentgrep.com/patent/US4400193A

## CPC

- C03C 23/007: {by thermal treatment}
- C03B 27/02: using liquid
- C03B 27/04: using gas
- C03B 27/0413: {Stresses, e.g. patterns, values or formulae for flat or bent glass sheets}
- C03B 27/052: for flat or bent glass sheets being in a vertical position
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES

## Abstract

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.

## Claims

### Claim 1

A method of thermally toughening glass comprising heating the glass to a temperature above its strain point and chilling the hot glass with a gas-fluidised particulate material in a quiescent uniformly expanded state of particulate fluidisation, wherein the particulate material is aluminium trihydrate (Al.sub.2 O.sub.3.3H.sub.2 O) having a mean particle size in the range 62 to 86 .mu.m, a particle size distribution in the range 1.64 to 2.73, a flowability point score in the range 69.5 to 82, and a thermal capacity per unit volume at minimum fluidisation in the range 1.52 to 1.59 MJ/m.sup.3 K.

### Claim 2

A method of thermally toughening glass comprising heating the glass to a temperature above its strain point and chilling the hot glass with a gas-fluidised particulate material in a quiescent uniformly expanded state of particulate fluidisation, wherein the particulate material is aluminium monohydrate (Al.sub.2 O.sub.3.1H.sub.2 O) having a mean particle size in the range 45 to 57 .mu.m, a particle size distribution in the range 1.15 to 2.78, a flowability point score in the range 74 to 80, and a thermal capacity per unit volume at minimum fluidisation in the range 1.16 to 1.18 MJ/m.sup.3 K.

### Claim 3

A method of thermally toughening glass comprising heating the glass to a temperature above its strain point and chilling the hot glass with a gas-fluidised particulate material in a quiescent uniformly expanded state of particulate fluidisation, wherein the particulate material is magnesium hydroxide containing combined water of crystallisation.

### Claim 4

A method of thermally toughening glass comprising heating the glass to a temperature above its strain point, and chilling the hot glass with a gas-fluidised particulate material in a quiescent uniformly expanded state of particulate fluidisation, wherein the particulate material is a hydrated iron oxide (FeO.OH) containing combined water of crystallisation having 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 point score in the range 69.5 to 92, and thermal capacity per unit volume at minimum fluidisation in the range 0.7 to 1.59 MJ/m.sup.3 K.

### Claim 5

A method of thermally toughening glass comprising heating the glass to a temperature above its strain point, and chilling the hot glass with a gas-fluidised particulate material in a quiescent uniformly expanded state of particulate fluidisation, wherein the particulate material is magnesium hydroxide containing combined water of crystallisation having 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 point score in the range 69.5 to 92, and thermal capacity per unit volume at minimum fluidisation in the range 0.7 to 1.59 MJ/m.sup.3 K.