PL117108B1 - Method of glass heat treatment - Google Patents

Description

The subject of the invention is a method for heat treatment of glass, and in particular thermal tempering of sheets of flat glass or curved glass, for example glass for use individually as windshields of motor vehicles or as part of laminated windshields of motor vehicles, side and rear windows, lights, or for use in the construction of windshield assemblies in airplanes and locomotives. Polish patent description No. 111,643 describes a method of heat treating glass products by heating any glass object to a temperature above the stress release temperature and, in turn, rapidly cooling the glass products in a bed of fine-grained material fluidized with gas and in a uniformly expanded state of fluid at rest, which expands in the fine-grained material (the rate of gas flow through this material is regulated between the rate corresponding to the initial fluidization and the rate corresponding to ¬ maximum expansion of the particulate material. The fluidized bed condition is such that mixing of the fluidized fine-grained material is induced on the hot immersed glass surfaces as the glass undergoes cooling in the fluidized bed, but no tensile stress is transiently developed on the surface of the hot glass as as its front edge comes into contact with the fluidized bed, it is not so sharp as to expose the glass to damage. Therefore, the process has high efficiency. The degree of hardening of the glass pane immersed in such a fluidized bed depends on the rate of heat exchange between the particles of the fluidized material and the hot pane immersed in them, and on the speed of transfer of hot particles from the vicinity of the glass pane. with co-current flow and by bringing cooler particles from the fluidized bed close to the glass surface. The movement of particles at the glass surface is faster than the movement of particles in the bulk of the bed due to the rapid mixing of the fluidized fine-granular material that is induced on the hot immersed surfaces glass due to heating of the fine-grained material by the glass continuing as the glass is cooled in the fluidized bed. 20 The mixing of the fine-grained material on the glass surface is greatly enhanced if a fine-grained material is added which has latent gas evolution properties, so that when the material is placed at a short distance from the glass surface, rapid gas evolution occurs. Surprisingly, the existence of three factors that dominate in regulating the thermal toughening of glass in the fine-grained gas-fluidized material and, in particular, that regulate the degree of toughening of the hot glass sheet when contacting it with the fine-grained gas-fluidized material. These factors are as follows: 1. Gas-generating property of the fine-grained material. 2. Thermal capacity per unit volume of fine-grained material with minimal fluidization. It is derived from the specific heat of the material, measured at a temperature of 50°C, and the density m of the bed material, measured with minimal fluidization of the material. 3. Flowability of a fine-grained material, as defined below, which is the sum of the four data points assigned to the material 15 based on an estimate of four flow properties of the fine-grained material. As used herein, the term flowability has the meaning given. These four properties of the fine-grained material on flowability and the method of taking 2o four starting points are described in the article by Ralph L. Carr, Jr. "Evaluating Flow Properties of Solids", Chemdcal Engineering, volume 72, or 2 of January 18, 1965 and are as follows: 1. Compressibility = 100 /P—A/ 30 In the given formula, P is the density of the packed mass and A is the density of the aerated mass. 2. Angle of repose: it is the angle in degrees between the horizontal line and the inclination of a cone of fine-grained material falling from a point above the horizontal, until the measured angle is constant. 3. Kait spatula: the spatula is inserted horizontally into the bottom of the mass of dry fine-grained material and lifted with the material straight from the top. The average value of the angle in degrees between the horizontal and the side line of the pile of material on the blade is the blade angle. 4. Particle size distribution, called the uniformity coefficient in the above article. In the above article it was described as a numerical value derived from dividing the width of the sieve opening (i.e. the size of the particles/ through which Q0% of the fine-grained material will pass through the width of the 45th opening of the sieve through which only 1'0% of the crushed material will pass. All values of the particle size distribution given in the description were measured in a known method using a Coulter counter, determining the particle diameters according to the retained cumulative weight amounts of 40% and 90% corresponding to the width of the sieve holes through which 60% will pass and through which only 10% of the fine-grained material will pass. The numerical values of compressibility, angle of repose and blade angle were measured on the Hosakawa Powder Tester by Hosakawa. Micrjometrics Daboratory, The Hosakawa Iron Works,, Osaka, Japan. The above Powdiar Hester is intended specifically for the determination of the flowability of powders as defined above. The flowability of a ground material is essentially based on factors such as the average particle size, the particle size distribution and the particle shape which is sometimes referred to as the prismatic nature of the molecule, that is, whether it is rounded or angular. The fluidity value increases with an increase in the average particle size, with a narrowing of the particle size distribution and with a decrease in the prismatic size of the particles. The heat capacity per unit volume at minimum fluidization depends on the specific heat of the material and on the density of the fluidized bed at minimum fluidization, at whereby the density increases as the particle size distribution narrows. A high tempering stress is created in the glass when it is rapidly cooled in a fluidized bed for optimal fluidity. Some materials that produce the required tempering stresses may be commercially available. Other materials commercially available products can be modified to create the required quench stresses by screening them to change the average particle size of the material and the particle size distribution. The problem is that there is a limit to the extent to which the degree of quench stress induced in the material can be adjusted. and glass, by changes in the fluidity of commercially available materials. Materials with the required fluidity may not be commercially available. Producing a large quantity of material with the required flowability may involve screening a large quantity of fine material. Moreover, when using a single material, the only way to modify the heat capacity of a fluidized bed is to narrow the particle size distribution, so that the heat capacity cannot be modified independently of changes in fluidity that are created by reducing the particle size distribution. It has now been found that a fine-grained material with optimal gas generation, heat capacity and fluidity properties to create the required tempering stresses in glassware can be produced by using a mixture of fine-grained materials, each of which contributes to imparting the desired properties to the mixture . By selecting fine-grained materials and the proportions in which they are to be mixed, it is possible to prepare such a fine-grained material fluidized with gas so as to provide within a wide range all required hardening stresses. According to the invention, a method of heat treatment of glass in which the glass is heated to a predetermined temperature and contacts with a fine-grained material fluidized with gas is that a fine-grained material is used consisting of a mixture of many selected fine-grained materials, at least one of which has the property of generating gas after heating from (hot glass and stirring these materials are mixed in selected proportions, giving the mixture of fine-grained gas fluidized material such heat capacity and fluidity as to achieve the desired degree of heat treatment. In the method according to the invention, the above materials are mixed in selected, predetermined proportions. 108 "portions" so that the required tempering stresses of the glass are developed as it is cooled in the fine gas fluidized material from a temperature above its stress release temperature. 5 In the method according to the invention, a fine-grained gas-generating material is used which is capable of releasing gas in an amount from 4% to 37% of its weight when heated to constant weight at a temperature of 800°C. The fine-grained io materials are mixed in predetermined proportions to give the mixture a heat capacity per unit volume with minimum fluidization in the range of 1.02-1.73 MJ/m*K and fluidity in the range of 60-86. During thermal tempering of soda-15, silicate glass panes with a thickness of 2-2"5 mm (in which the glass panes are heated to a temperature in the range of £10-680°C and the mixture is maintained in a state of rest, uniformly expanded fluidization fine-grained material is used ^ fine-grained material causing a central tensile stress in the glass pane in the range of 35-57 MPa. When producing glass for windshields of vehicles using the method according to the invention, poultry and noose-grained materials are mixed in predetermined proportions, giving mixture fluidity in the range of 71-83 and heat capacity per volume unit at minimum fluidization in the range of 1.09 MJ/ 7m»K - 1.38MJ/m*K. ¦ 30 Aluminum oxide can be used as a gas-generating material. aluminum y may be mixed with a aluminum oxide. The mixture may contain 7% to 86% by weight of aluminum oxide 7. Another method of implementing the invention consists in cooling a hot glass sheet in a gas-fluidized mixture of fine-grained gas-generating material and at least one fine-grained metal oxide, which has a heat capacity per unit volume at minimum fluidization of 1.76 MJ/m»K - 2.01 MJ/m8K. Fine-granular materials are mixed in predetermined proportions, giving the mixture a heat capacity per unit volume at minimum fluidization in the range of 1.27 MJ/m*K - 1.76 MJ/m*K and fluidity of 45 and in the range of 71-82. Spheroidal iron oxide (a - Fe^Os) may be used as a fine-grained metal oxide. The mixture may contain 30-70% by weight of spheroidal iron oxide. Furthermore, the mixture may contain 70%/«^30|% by weight of glyrium oxide as a gas-generating material. Another way of implementing the invention is to use a mixture consisting of 28-35% by weight of spheroidal iron oxide, 45-56% by weight of aluminum oxide and the remainder consisting of 1 aluminum oxide as the gas-generating material. Fine-grained metal oxide can be used mix zirconium compound ZrC2 Si02. The mixture may contain 10%-70% by weight of alumina monohydrate Al2O3 1H2O as the gas-generating material and 90%-30% by weight of the above zirconium compound. Another example of a fine-grained gas-generating material is an aluminosilicate. - 65 titers can be used as zeolite, and then 8-10% by weight of zeolite is mixed with 90-92% by weight of aluminum oxide to form a mixture. Aluminum oxide monohydrate (Al2Oj 1H20) can be used as a fine-grained gas-generating material Further in the process of the invention, the mixture may comprise silicon carbide SiC mixed with a fine gas-generating material. In one embodiment, the fine gas-generating material is aluminum oxide monohydrate Al2O3 1H2O and the mixture contains 17% by weight of aluminum oxide monohydrate mixed it with 83% by weight of silicon carbide. Another fine-grained gas-generating material used in the process of the invention may be aluminum oxide trihydrate A1203 3HfcO). The mixture may contain two fine gas-generating materials: aluminum oxide trihydrate (Al2O3 3HgO) and aluminum oxide in equal amounts. Yet another fine gas-generating material used in the process of the invention may be sodium acid carbonate (NaHCO3). The mixture may consist of 10% by weight of sodium acid carbonate mixed with 90% by weight of alumina. The method is carried out in a glass heat treatment device comprising a container of fine-grained material fluidized with gas, means for supplying gas to the container. to maintain the state of fluidization of the crushed material and elements for positioning the hot glass in the container, wherein the device fills the container with a gas-fluidized mixture of selected fine-grained materials, at least one of which has the property of generating gas after heating from hot glass. These materials are mixed in selected, predetermined proportions so that they give the gas-fluidized mixture such heat capacity and fluidity that the required heat treatment takes place. In order to better illustrate the invention, examples of its implementation are presented below. , with reference to the attached drawings in which: Fig. 1 shows a vertical cross-section through a device for thermal tempering of glass panes according to the invention, Fig. 2 - a graph of the dependence of the central tensile stress on the proportional content of fine-grained materials in the mixture constituting the gas-fluidized bed , showing the variation of stress as a function of these proportions; FIG. 3 is a graph similar to that shown in FIG. 3 illustrating changes in the surface compressive stress for glass with a thickness of 2.3 mm depending on changes in the composition of the gas fluidized bed, Fig. 5 - a graph similar to that shown in Fig. 3 illustrating the central tensile stress induced in glass of thickness 6 mm thick, Fig. 6 is a graph similar to that shown in Fig. 4 illustrating changes in the surface compressive stress induced in a 6 mm thick glass. Fig. 7 is a similar graph to Fig. 3 for a 12 mm thick glass. , Fig. 8 is a graph similar to that shown in Fig. 4 for glass with a thickness of 12 mm, and Figs. 9, 10 and 11 illustrate changes in the central tensile stress depending on the composition of the mixture and fine-grained material for three different embodiments of the invention. Referring to Fig. 1 the attached drawings show a vertical hardening furnace 1, which has side walls 2 and a roof 3. The side walls 2 and the roof S are made of ordinary fireproof material, and the bottom of the furnace has an open outlet in the form of an elongated slot 4 in the base plate 5 on which the furnace 1 rests. A sliding shutter is provided, the knife shown, for closing the opening 4 in a known manner. The glass sheet intended for bending and subsequent thermal hardening is suspended in the furnace 1 by means of tongs 7 which grip the upper edge of the glass pane 6. The tongs 7 are suspended on a hanging rod 8, which is suspended from a traditional hoist, not shown, and which runs on vertical guides downwards from the furnace for guiding, lowering and lifting up a hanging < * rod. A pair of bending presses 18 and 11 are placed directly under the opening 4 of the furnace in a heating chamber 12, maintained at such a temperature that the presses are at the same temperature as the hot glass to be bent. The chamber 12 is heated by hot gases introduced through the through hole 12a. When the dies are open, they are located on both sides; path of the glass sheet 6. The die 18 is a fixed convex die mounted on the press ram 13 and has a curved outer surface which imparts a curve when applied to the hot glass sheet. The die 11 is a concave annular frame guided by compressed rods 14 mounted on the back plate 15, which is mounted on the press slide 16. The curvature of the die of the frame 11* is adapted to the convex curvature of the front surface of the die 18. Guide rail 8 it projects downwards from both sides of the bending dies towards the container 17 of a fluidized bed 17 of a fine-grained fire-resistant material in which a hot curved glass sheet is to be cooled by introducing the sheet down the bed. .55 The fluidized bed container includes an open-top rectangular tank 18 mounted on a scissor support platform 18. When the platform 18 is in the raised position, the upper edge of the tank 18 is just below the bending dies 18 and 11. Through the base of the tank 18 passes a microporous membrane 28 with a high pressure drop. The edges of the membrane 28 are attached between the flange 21 on the tank and the flange 22 on the pressurized air chamber 28, which forms the base of the tank. The flanges and edges of the membrane 20 are screwed together as indicated in the drawing with marking 24. The air inlet channel 25 is connected to the pressurized air chamber and the fluidizing air is supplied through a channel with adjustable high pressure. There is a high a pressure drop of at least 60% of the pressure of the pressurized air chamber through the diaphragm 28 resulting in a uniform distribution of the fluidizing air in the fine-grained material at a rate of gas flow through the fine-grained material between ¬ particles barely suspended in the upward flowing air and a speed corresponding to the maximum expansion of the fine-grained material in which the dense fluidization phase is maintained. The expanded bed is basically around the bubbles in a state of resting fluidization of the fine-grained material with a resting horizontal phase the top one through which the glass deck enters the bed. * The membrane 28 may include a steel plate, has holes for adjustable distribution and multiple layers of strong microporous paper lying on the plate. For example, you can use 15 sheets of paper. The membrane assembly is complemented by a woven wire mesh lying on top of the paper layers, for example a stainless steel mesh. A basket may be placed around the membrane 28. for collecting debris, which is designed so as not to disturb the steady upward flow of the melting gas from the membrane. The guide rail 8 extends down to a point below the bending dies and ends near the upper edge of the tank. A fixed frame 27 is mounted on the tank 18 and has an upwardly curved foot 28 at the bottom to receive the lower edge of the glass sheet immersed in the fluidized bed as the hanging rod lowers below the dies that bend with the aid of a lift. To load the glass sheet the scissor support table 18 and the hanging rod are lowered into the device to their smallest position at the bottom of the guide rail and the glass sheet to be bent and tempered is placed in the clamps 7. The lift lifts the suspended glass sheet into the furnace 1, which is held is at a temperature, for example 850°C, so that the glass sheet is quickly heated to a temperature close to the stress release temperature, for example in the range of 810°C to 680°C. When the entire glass pane reaches the required temperature, the shutter closing the opening 4 opens and the hot glass pane is lowered down, using a lift, to a position between the open bending presses 18 and 11. The press slides 13 and 16 work so that the presses are closed. they become closed in order to bend the pane to the desired curvature. Once the desired curvature has been given to the tail, for example to enable use as a component of a laminated motor vehicle windshield, the dies are opened and the hot curved glass sheet is quickly lowered down into the fluidized bed in tank 18, which raises to the cooling position by lifting the scissor support table 19 while heating the glass sheet in furnace 1. The fluidized bed is maintained at a temperature between 30 and 150°C by means of a water cooling jacket permanently mounted to the flat long wall of the tank 18. Fluidized bed 17 consists of a gas-fluidized fine-grained material that is a mixture in a predetermined proportion of a plurality of fine-grained materials, at least one of which has gas-generating properties and is capable of releasing gas when the fluidized bed comes into contact with the hot glass. A suitable fine-grained gas-producing material is capable of releasing gas at a rate of 4.0% to 37% of its own weight when heated to constant weight at 800°C. Suitable materials are the oxide aluminum y (y—r—MiOi) which is a porous material and contains water absorbed in its vapors, aluminosilicates which are porous and contains water absorbed in its pores, aluminum oxide hydrates such as aluminum oxide trihydrate (Al^)3 *3H)) containing bound water of crystallization and aluminum oxide monohydrate (Al^Os-lH^) containing water of crystallization, which is also a porous material and contains water absorbed in its pores, and materials which produce gases other than water, for example acidic sodium carbonate NaHC03. In order to create the required tempering stresses in the glass, the components of the mixture of fine-grained materials are mixed together in predetermined proportions, giving the mixture a fluidity in the range of 60-86 and a heat capacity per unit volume in the range of 1.0(2- 1.75 MJ/m*K. Other components of the mixture that are mixed with the fine gas-producing material are fine-grained materials that are inert in the sense that they essentially do not evolve gas when the material is heated. Examples are aluminum oxide and (lot—Al/)3), zirconium compound ZrO2 SiO2, silicon carbide and spheroidal iron oxide (a—Fe^). These fine-grained materials are in a dense non-porous form and are selected to have a fluidity and heat capacity different from the fine-grained gas-producing material so that, depending on the proportional amount of dense non-porous material, they are effective in modifying the fluidity and heat capacity of the mixture of fine-grained materials in such range so that they can cause the formation of the required degree of tempering stress in the glass. It is assumed that when hot glass sheets are cooled in a gas-fluidized bed of such a mixture of fine-grained materials, rapid evolution and spread of the gas released from the fine-grained material occur. producing gas. By heating the fine-grained material close to the glass surface, the local mixing of the mixture of fine-grained materials on the glass surfaces increases in a manner similar to the boiling of a liquid. As a result, mixed layers of gas are formed and the fine-grained material flows stream over the glass surfaces as the glass cools in the fluidized bed. By mixing the components of the mixture in predetermined proportions, optimal heat transfer from the glass surface to and about the mass of the bed can be achieved, which induces the desired stresses in the glass. In addition, there is a continuous dissipation, towards the distant parts of the bed, of the heat received from the glass by "mixing the fluidized fine-grained material immediately surrounding the glass sheets. The water-cooled jacket 29 keeps the distant parts of the bed cool so that they function." they act as a heat sink. The vigorous mixing of the fine-grained material on the glass surfaces 20 continues after the glass is cooled below its stress release temperature, ensuring that a temperature gradient is maintained from the center to the surface of the glass, initially induced in the glass in the fluidized bed and as it is cooled through the stress release temperatures the required toughening stresses develop as the glass continues to cool while it is still immersed in the bed. 30 The lower edge of the hot glass sheet is cooled evenly as it reaches the horizontal resting surface of the expanded fluidized bed. Essentially the same tensile stresses are produced in different areas of the edge surface of the glass pane, so that there is a very low crack rate. When lowering the lower edge of the glass into the bed, each part of the lower edge is always in contact with the fluidized material, which is in a state of rest, uniformly expanded fine-grained fluidization, and thus uniform processing of the lower edge, regardless of the jet the flow of fine-grained material formed on hot glass surfaces by the evolution of gas from the gas-generating component in the mixture significantly prevents cracking and the consequent problems of the presence of pieces of glass in the bed. The above, together with the avoidance of glass losses due to changes in the shape of the glass panes and/or losses due to the reduction of surface quality, ensures industrially acceptable performance of tempered glass panes. A few examples of the operation of the invention with selected mixtures of fine-grained material are: 55. given below. In each of these examples, the numerical values for the particle density of the product in g/cm* and the average particle size in µm of each component of the mixture are below 220. These criteria are useful in assessing whether a given fine-grained material is suitable for fluidization in a in a uniformly expanded state of fine-grained fluidization when working with air at normal temperature and pressure. The mixture of the individual fine-grained materials is then capable of fluidization in the quiescent uniformly expanded state of the fine-grained fluidization. Example I. A fluidized bed 17 was prepared consisting of a mixture of alumina as the fine-grained gas-producing material and alumina. a. The γ-alumina used is a microporous material having pore diameters in the range of 2.7--4.9 mm and 20-40% of free pore space. The pores contained absorbed water, which was released as a gas by heating the material. The alumina had the following properties: average particle size 119 \un particle size distribution 2.34 fluidity 90.25 water content (weight loss at 800°C ) 4.3% heat capacity per unit volume with minimum fluidization 1.09 MJ/m*K The aluminum oxide used was in a dense, non-porous form with the following properties average particle size 30 lim particle size distribution 1.22 fluidity 70 heat capacity per unit volume at minimum fluidization 1.3 MJ/m8K. Tests were carried out with a mixture of alumina and a-alumina, which were mixed together in predetermined proportions. Panes of soda-lime-silicate glass with a thickness of 2.3 mm were cut and the edges of the cut pane were finished by rounding using a wheel with a fine-grained diamond. Each sheet was heated to a temperature of 660°C in furnace 1, before bending and cooling in the fluidized mixture, the coating was in a state of quiescent uniformly expanded fluidization of the fine-grained material. Table 1 gives the properties of various mixtures of these materials in the range of 30% - 90% by weight aluminum oxide a and 70%-10% by weight of alumina y, as well as the central tensile stress induced in the glass sheet upon cooling. For comparison, the central tensile stress* generated with the use of α-alumina alone and y-alumina alone is also given. Figure 2 shows a graph of changes in the central tensile stress* depending on the composition: mixture. The y-alumina itself is fluid. which is too high to produce maximum tension. hardening in a glass pane, especially due to its large average particle size and the fact that the particles are relatively smooth and non-angular in shape. Increasing the proportion of a-alumina, which has a lower fluidity than y-alumina due to the smaller average size of the a-alumina particle and the prismatic nature of its individual particles, reduces the fluidity of the mixtures. The fluidity of the mixture decreases as the amount of aluminum oxide increases in the mixture and there is a concomitant increase in the central tensile stress generated. The maximum isocontaining stress of 49 MtPa is achieved when the fluidity has been brought to the optimal value of 74 and the mixture contains approximately ¬ 70% by weight of a-alumina and 30% by weight of y-alumina - A-alumina has a higher heat capacity than y-alumina as the proportion of alumina increases in the mixture and there is a progressive increase in the thermal heat capacity of copper alumina which contributes to the increase in the achieved stress. Further addition of alumina up to an amount above 70% by weight increases the heat capacity somewhat more and maintains a good fluidity level but reduces the induced central tensile stress because the content of the gas-generating component, alumina has been reduced to too low a level. Example II. A fluidized bed was prepared by mixing alumina as a fine gas generating material and the oxide. aluminum a The alumina used was a microporous material with a pore size in the range of 2.7 - 4.9 mm and a free pore space of 20 - 40%. The pores contained absorbed water, which - Table 1 alumina and alumina y 1 fluidity of the mixture heat capacity of the mixture per unit volume at minimum fluidization (MJ/m*K) central tensile stress (MPa) % by weight in mixture 1; 0% 100% 90.25 1.09 41 30% 70% 81.5 1.16 43 50% 50% 75 1.20 49 50% 30% 74 1.24 49 90% 10% 72.25 1.28 47 100% L 0% f 70 [ b 1.3 \ h i 32 [117 108 13 11 :ra was released in the form of gas after heating the material. The aluminum oxide used had the following characteristics: average particle size particle size distribution fluidity content water (weight loss at 800°C) heat capacity per unit volume at minimum fluidization 64 {im 1.88 84 4% 1.06 MJ/m»K The aluminum oxide used was the same as in Example I. Tests carried out with mixtures of γ-alumina and γ-alumina, which were mixed together in predetermined proportions of 100% γ-alumina and 0%! alumina a to 0% alumina y and 100% alumina a. Table 2 gives the heat capacity per unit volume with minimal fluidization and liquid- Amounts of mixtures used: T a b 1 J Mixture % by weight alumina y 100 86 j 61 40 1 22 7 0 1 and aluminum oxide 0 14 39 60 78 93 100 ica 2 Thermal capacity 1 MJ/m*K ' 1.05 1.09 1.15 1.20 1.25 1.29 1.30 Fluidity 84 82.75 79 76 73.25 71 70 Panes of soda-lime-silicate glass with a thickness of 2.3 mm were cut and the edges of the cut panes were rounded using a wheel with fine-grained diamonds. Each pane was pressed using tongs 7 and heated in oven 1 before bending and cooling. The results are illustrated in Figures 3 and 4. The abscissa of each curve shows the composition of the mixture in weight%. In each of Figures 3 and 4 there are four curves corresponding to the central tensile stress (FIG. 3) and the surface compressive stress (FIG. 4) induced in a 2-3 mm thick glass sheet that was heated at a temperature of €10°C, 630°C, 650°C or 670°C and then cooled in the fluidized bed 17, which was maintained in a quiescent, uniformly expanded state of fluidization of the fine-grained material in the temperature range of 60°-B0°C. The curves show that it was advantageous to use from about 7% to about 86% by weight of α-alumina mixed with γ-alumina. Due to the increase in the α-alumina content in the mixture, the central tensile stress and the surface compressive stress induced in the glass during the thermal toughening process increase to a maximum , which is achieved with the amount of alumina in the mixture being approximately 70% to 80% by weight. Generally, the highest stress is 55-85% by weight. A higher content of alumina in the mixture causes a decrease in the induced stresses. Due to the appropriate selection of the proportions of alumina and alumina, the mixture has gas-generating properties, heat capacity per unit volume at minimum fluidization at a temperature of 50°C and fluidity, which produce consistently high values of central tensile stress and surface compressive stress in a 2.3 mm thick glass pane. For example, when the glass is heated to a temperature of 670°C and then cooled, the required central tensile stress is in the range of 42 MPa - 49 MPa and the corresponding surface compressive stress in the range of 83 MPa - 103 MPa can be induced in the glass by selecting the proportions of γ-alumina and aluminum oxide and in the mixture in the range of 7-86% by weight of γ-alumina and 93-14% by weight of aluminum oxide. Example III. Sheets of soda-lime-silicon glass with a thickness of 6 mm were cut, the edges were rounded, then heated and cooled in a fluidized bed in a quiescent, uniformly expanded state of fluidization of a fine-grained material consisting of a mixture of the same fine-grained aluminum oxide and aluminum oxide as described in Example II. Figures 5 and 6 are graphs similar to Figures 3 and 4 which illustrate the results obtained for glass sheets heated to temperatures of 610°C, 630°C, 650°C and 670°C and then cooled. The results indicate that the required tempering stresses can be induced in the glass, which are a function of the proportions of alumina and alumina in the mixture. Maximum stresses were achieved when the mixture contained approximately 65% to 95% by weight of α-alumina. For example, when the glass was heated to 670°C and then cooled in a fluidized mixture of 22% by weight of γ-alumina and 78% by weight of α-alumina, the tensile stress induced in the glass was 91 MPa and the surface compressive stress was 216 MPa. This very strong glass, 6 mm thick, was used to produce window units for airplanes and locomotives. Similar results were obtained when tempering glass sheets with soda -calcium-silicon, 10 mm thick. Such panes were used to produce window units for aircraft, which could, for example, consist of two panes of tempered glass 10 mm thick and an outer pane 3 mm thick. The glass sheets were laminated together with intermediate layers of plastic of a known type. Example IV. Sheets of 12 mm thick soda-lime-silica glass were cut, the edges were finished, then heated and cooled in a fluidized bed consisting of a mixture of aluminum oxide and aluminum oxide in predetermined proportions in the same manner as described in ¬ clade II.117 108 15 16 The results obtained for glass panes heated to temperatures of 610°C, 630°C, 650*0 and 670°C for the given proportions of γ-alumina and a-alumina are illustrated by the curves in Figs. 7 and 8 The measurements showed maximum stress values when the fluidized mixture contained approximately 65-85% alumina by weight. When the sheets were heated to 670°C and cooled in a fluidized bed consisting of a mixture of 22% aluminum oxide y and 78% by weight of alumina, the central tensile stress in the gas was 124 MPa and the surface compressive stress was 261 MPa. Figures 7 and 8 illustrate how a wide range of tempering stress values can, if necessary, be induced in the glass by selecting the composition ratio. the mixture of fine-grained materials and the appropriate temperature to which the glass is heated before cooling. The results presented in Figs. 3-8 together show higher hardening stresses, which are achieved as the content of the component with the higher heat capacity (alumina a) to the point where a further increase in the ratio reduces the content of the gas-generating component (y-alumina) to an insufficient level. The content of the gas-generating material and the other component or components of the mixture ensures the fluidity of the mixture in range of 60-06, which is such that the nature of mixing favors cooling of the glass at a rate at which the desired stress values in the glass are achieved. Cooling of the glass occurs due to the rapid mixing of the fine-grained material in the vicinity of the glass surface, the mixing resulting from essentially from the evolution of water vapor from the alumina, which is the mixed component. - A higher alumina content increases the rate of heat removal from the glass and also modifies the fluidity of the mixture. Example V. The fluidized bed consisted of a mixture of alumina as gas-generating component with the addition of Lferoidal iron oxide (a—Fe^) and one or two types of alumina a. The alumina had the following characteristics: average particle size particle size distribution fluidity water content (loss weight at 800°) heat capacity per unit volume at minimum fluidization 24 |im 1.94 87.25 6% 1.063 MJ/m»K Spheroidal iron oxide had the following characteristics: average particle size particle size distribution fluidity capacity heat per unit volume at minimum fluidization 41 [im 1.69 76.5 2.01 MJ/m»K The first alumina a was as used in Example I. The second alumina a had the following characteristics: Average size particle size distribution fluidity heat capacity per unit volume at minimum fluidization 24 tim 1.25 66 1.192 MJ/m*K Sheets of soda-lime-silicon glass with a thickness of 2.3 mm were heated to a temperature of 660°C and cooled at fluidized bed mixture of the above materials which have been in a state of quiescent uniformly expanded fluidization of the particulate material. I alumina % spheroidal iron oxide alumina a (1) 1 alumina a (2) fluidity of the mixture heat capacity of the mixture per unit volume at minimum fluidization MJ/m*K central tensile stress (MPa) Table (1) 70% 30% — — 82 l.r347 45 ; 3 % by weight in the mixture (2) 50% 50% — 79 1.54 49. (a) 30% 70% — — 78 1.726 50 (4) 20% 35% 45% — 7)4% 1.502 57 (5) 16% 28% 1 36% f 20% 1 73.5 | r 1.44 [ 53/) 1117 108 17 18 Properties of the mixture and; the resulting central tensile stresses generated in the glass panes are given in Table 3. Figure 9 illustrates the variation of the central tensile stress as a function of the composition of the mixtures of (1), <2) and (3) alumina y and a-Fe2O3 in Table 3. Central stress the tensile strength resulting from the use of alumina alone and α-Fe2O3 alone was 41 MPa and 32 MPa, respectively. As in Example I, the alumina used in this example had a fluidity too high to produce the maximum tempering stress of the glass sheet. . Spheroidal iron oxide has a lower fluidity than aluminum oxide, especially due to its smaller average particle diameter. The addition of increasing amounts of spheroidal iron oxide to the aluminum oxygen in mixtures (1), {2) and (3) of Table 3 has the effect of progressively reducing the flowability of the mixture due to the progressively decreasing average size of the mixture as the amount of spheroidal iron oxide increases. in the mixture. As the mixture becomes less fluid, there is a progressive increase in the central stress created in the glass sheet. The maximum central tensile stress of 50 MPa is achieved when the mixture contains approximately 70% spheroidal iron oxide and 30% γ alumina. The fluidity of the spheroidal iron oxide is not as low as that of the alumina used in Example I due to the fact that has a larger average particle size and that the particles are smoothly rounded compared to the angular particles of aluminum oxide <*. Therefore, spheroidal iron oxide is not as effective in reducing the flowability of the mixture as the alumina of Example 1. The mixture (3) of this example containing 70% by weight of spheroidal iron oxide and 30% by weight of aluminum oxide which produces the maximum central tensile stress of 50 MPa, has a fluidity of 78, higher than the optimal fluidity of 74 of the mixture of 70% by weight a-alumina and 30% by weight y-alumina which produces the high central tensile stress in Example I. The maximum central tensile stress produced by using the mixture (3) according to the present example is, however, approximately the same as the maximum central tensile stress produced using the mixture according to example I. This is because, although the fluidity of the mixture (3) is slightly higher than the optimal fluidity, at which the maximum stress is produced, the spheroidal iron oxide used in mixture (3) has a significantly higher heat capacity than the alumina used in Example 1. Since the fluidity of mixture (3) was expected to be slightly too large, the mixture (4) was supplemented to contain a certain amount of the alumina used in Example 1. This reduced the flowability of the mixture to an optimal value of 74 °C and the resulting mixture further increased the central tensile stress to 57 MPa, despite the reduction heat capacity. The mixture (4) had the same optimal flowability value of 74 as the mixture according to Example I consisting of 30% aluminum oxide and 70% aluminum oxide and generating a maximum central tensile stress of 49 MPa. The fact that the mixture (4) produces higher central tensile stresses of 57 MPa is due to the higher heat capacity of the mixture (4) is 1.502 MJ/msK compared to 1.42 MJ/m3K of the mixture according to example I. Further reduction flows resulting from the inclusion of part of the second aluminum oxide in the mixture (5) causes a reduction in the heat capacity of the mixture in evaporation with the mixture (4) with an accompanying slight reduction in the central tensile stress of the material. Example VI. The fluidized bed consisted of a mixture of a fine-grained gas-generating material consisting of aluminum oxide monohydrate, AlOs, 1H20, and a zirconium compound, ZrO, SiO2. The alumina monohydrate was in the form of boehmite, which is a porous material containing 15% by weight of crystallization water and 13% by weight of pore water. Mainly effective was the water absorbed in the pores, which was released as the glass cooled, generating gas causing increased mixing of the fine-grained material in the vicinity of the glass surface. '' 4 The alumina monohydrate used had the following characteristics: average particle size 51 [im particle size distribution 1.70, fluidity 78 water content (weight losses -^ - at 800°C) 28.4% heat capacity per unit volume ¬ volume at minimum fluidization 1.18 MJ/m*K The zirconium compound ZrO2 SiO^, which is a neutral, non-porous orithosilicate-zirconium oxide with a heat capacity higher than aluminum oxide, had the following characteristics: 30 35 40 45 50 55 average particle size 34 firm particle size distribution 1.73 fluidity 67 heat capacity per unit volume at minimum fluidization 1.75 MJ/m*K Glass sheets with a thickness of 2*3 mm were heated to a temperature of 660°C and cooled in the mixture. alumina monohydrate and zirconium compound as listed in Table 4, which shows the characteristics of the mixtures and the central tensile stress developed in the glass sheets. Figure 10 illustrates the variation of the central tensile stress with varying mixture composition. Alumina monohydrate has good gas-generating properties and a lower fluidity value than the aluminas discussed in Examples I and V. Jed-19 117 108 Table 4 20 alumina monohydrate ZrOj* SiOa mixture fluidity heat capacity of the mixture per unit volume at minimum low fluidization MJ/m*K J Central tensile stress (MPa) i * i % by weight In the mixture [ 100% 0% 78 1.005 37 70% 30% 75.5 1.277 42 50% 50% 74 1.41 44 20% 80% 73 1.62 46.5 10% 90% 71 1.70 39 0% 100% | k h 67 1 1.76 | 23 f therefore, the fluidity of alumina monohydrate is higher than the optimal fluidity, which produces the maximum central tensile stress and the heat capacity is relatively low. ZirO2 SiO2 has a lower fluidity and higher heat capacity than aluminum oxide monohydrate, and as the proportion of zirconium compound in the mixture increases, there is a progressive increase in the central tensile stress developed in the glass due to both the progressive decrease in fluidity and the increase in the heat capacity of the mixture.ZrOa SiO2 has a high heat capacity, which contributes significantly to the increase in the central tensile stress in the glass sheet in the same way as the spheroidal iron oxide of Example V. Due to the fact that the zirconium compound has a lower fluidity than the spheroidal iron oxide of Example V, it is more effective in reducing the flowability of the mixture and therefore contributes more to the increase in the central tensile stress caused by lowering the flowability value of the mixture. The maximum central tensile stress of 46.5 MPa is achieved when the mixture contains about 20% aluminum oxide monohydrate and 80% zirconium compound. This mixture has an optimal fluidity of 73. Further addition of a zirconium compound of approximately 80% by weight increases the heat capacity of the mixture, but as a result it reduces the central tensile stress due to a significant reduction in fluidity below the optimal value and a reduction in the proportional amount of the component. gas-generating alumina monohydrate to a less effective level. Example VII. A fluidized bed was prepared which consisted of a mixture of aluminum oxide and equal amounts of each of the four aluminum oxides. Table Average particle size (|xm) Particle size distribution Fluidity Water content (% weight loss at 800° C) heat capacity per unit volume at minimum fluidization (MJ/m»K) 5 aluminum oxides 1 A 70 U7 88.5 7 1.16 B 1 61 1.67 88 7 1.16 C 57 1.66 85 7 1.12 D 72 \ 1.65 1 86 ! 7 1 1.12 l I Mixture of 4 aluminum oxides and aluminum oxide and fluidity of the mixture heat capacity of the mixture per unit volume assuming minimum fluidization (MJ/m*K) central tensile stress (MPa) Table 6% by weight in the mixture 100% 0% 87 1.14 39 40% 60% 70 1.20 40 20% 80% 67 1.22 35 l€% 90% 65 1.23 31 0% 100% | 63 | 1.24 1 25 |117 108 and 21 22 nuy marked A, B„C and D in Table V, which gives the characteristics of aluminum oxides. The aluminum oxide had the following characteristics: average particle size 22 |tm particle size distribution 1.69 fluidity 63 heat capacity per unit volume at minimum fluidization 1.24 MJ/msK Sheets of soda-lime-silicon glass with a thickness of 2.3 mm were heated to a temperature of 660°C and cooled in a gas-fluidized mixture of the above materials , in the state of resting uniformly expanded fluidization of the fine-grained material. The properties of the mixtures and the resulting central tensile stresses in the glass sheets were as given in Table 6. Figure 11 illustrates the changes in the central tensile stress as a function of the change in the composition of the material. ¬ mixtures. The previous examples have shown how much higher stresses can be created by mixtures of fine-grained gas-producing material with an inert material, compared to those created using the fine-grained material alone. However, lower stress values may be desired than can be obtained using the fine gas produced material alone. In this example this was achieved by using alumina with a smaller average particle size and a relatively wide particle size distribution which resulted in a significantly lower fluidity than that of aluminum oxide used in the previous examples. i The maximum central tensile stress produced was 40 MPa using a mixture of 40% y-alumina and 60% a-alumina with a fluidity of 70. This is only slightly higher than the central tensile stress of 39 MPa produced using only y-alumina Progressive addition of further amounts of α-alumina to the mixture quickly reduced the flowability of the mixture to such a low range that the central tensile stress produced in the glass sheet was lower than that produced using α-alumina alone. Example VIII. A fluidized bed was prepared consisting of a mixture of 9% by weight of zeolite, which is a porous, crystalline aluminosilicate with water absorbed in its pores, and 91% by weight of aluminum oxide. The zeolite had the following characteristics: average particle size 24 | im particle size distribution 4 fluidity 51 water content (weight loss at 800°C) 20% heat capacity per unit volume at minimum fluidization / 0.8 MJ/msK Aluminum oxide a had the following characteristics: 10 20 25 30 35 40 45 50 55 average particle size 37 µm particle size distribution 1.682 fluidity 70 heat capacity per unit volume at minimum fluidization 1.4 MJ/m'K The heat capacity per unit volume at minimum fluidization of the mixture was 1.34 MJ/m'K a the fluidity of the mixture was 60. A 2.3 mm thick glass sheet was heated to a temperature of 660° C. and cooled in the fluidized mixture. A central tensile stress of 41 MPa was created in the sheet. By changing the selection of the proportions of the mixture components, it was possible to induce a central tensile stress in the glass pane in the range of 23 MPa - 41 MPa. Example IX. The mixture of fine fluidizing material consisted of 201% by weight of y-alumina and 4W' of each of two a-aluminas that were readily available and which were used in place of the single missing a-alumina. The y-alumina had the following characteristics: average particle size particle size distribution fluidity water content (weight loss at 800°C) heat capacity per unit volume at minimum fluidization 57 m 1.66 85 7% 1.18 MJ/m«K Characteristics of two aluminum oxides with A and B are given in Table 7. Table 7 average particle size |m particle size distribution fluidity 1 heat capacity per f unit volume at minimum fluidization (MJ/m8K) Aluminum oxide a 1 A 38 1.19 75 1, 14 B 24 | 1.25 1 66 1 Ii 65 The fluidity of the mixture was 73.5 and its heat capacity per unit volume at minimum fluidization was 1.25 MJ/m*K. Glass sheets with a thickness of 2.3 mm were heated to this temperature of 660°C and cooled in the fluidized mixture. The induced central tensile stress in the sheet was 48 MPa. By changing the relative proportions of the mixture components, it was possible to induce a selected central tensile stress in the sheet in the range of 34 MPa - 48 MPa. Example gas-generating components, each of which was a commercially readily available and relatively cheap material, creating mixtures with gas-generating properties and optimal fluidity and thermal capacity that induced the desired stresses in the glass cooled in these mixtures in the state of resting uniformly expanded fluidization of fine-grained material. In this example, the mixture contained 5% by weight of each of the four oxides of aluminum y A, B, C and D, the characteristics of which are given in Table 8. 1 And the average particle size - 1 |m distribution particle size fluidity water content (% weight loss at temperature aO^C) | I heat capacity- 1 per n,a unit of volume at i | minimum fluidization MJ/m*K) Table 8 1 aluminum oxide D 72 1.65 86 7 1.12 117 108 24 temperatures e60°C and cooled in the fluidized mixture. A central tensile stress of 49 MPa was induced in the sheet. By varying the selected proportions of alumina oxides constituting 20% by weight of the mixture, or by varying the proportion of alumina oxides constituting 80% by weight of the mixture, or by varying the relative proportions of the total amount of alumina oxide to the total amount of alumina and a selected central tensile stress in the range of 32-49 MPa can be induced in the mixture. EXAMPLE XI. The fluidized fine material consisted of 17% by weight of the aluminum oxide monohydrate from Example 6 mixed with 83% by weight of silicon carbide having the following characteristics: average particle size. 40 particle size distribution 1.32 fluidity 72.75 heat capacity per unit volume at minimum fluidization 1.21 MJ/m8K , F and \jr, the characteristics of which are given in Table 9 Table 9 1 average size of 1 particle |im particle size distribution l fluidity 1 heat capacity per 1 unit of volume 1 at minimum fluidization (MJ/m»K) oxide aluminum a 1 E 38 1.19 75 1.38 F 30 1.22 70 1.3 G 24 1 1.25 | 66 | 1.19 1 10 15 20 25 3fr 35 45 50 55 60 The fluidity of the mixture was 74 and its thermal fluidity per unit volume at minimum fluidization was 1.26 MJ/m»K. (2.3 mm thick glass sheets were heated to Fluidity mixture was 75 and its heat capacity per unit volume with minimal fluidization was 1.02 MJ/m*K* A 23 mm thick glass pane was heated to a temperature of 660°C and cooled in the fluidized mixture. central tensile stress of 51 MPa. These materials provided the ease of inducing a selected central tensile stress in a wide range of 32 MPa - 51 MPa by selecting predetermined proportions of ingredients in the mixture to prepare a fluidized mixture producing the required stress in glass.Example XII In a binary mixture, both fine-grained materials could have gas-generating properties.The mixture was made from equal weight amounts of γ-alumina and aluminum oxide trihydrate (AhO3H2O). During heating, water of crystallization was released from the aluminum oxide trihydrate, which increased the effect of water released from the pores of the aluminum oxide. The aluminum oxide had the following characteristics: average particle size, particle distribution size, fluidity, water content (weight loss at 800 °C) heat capacity per unit volume at minimum fluidization 60 lim 1.9 84 8% 1.05 MJ/m»K Aluminum oxide trihydrate had the following characteristics: average particle size particle size distribution fluidity water content (weight loss at a temperature of 80O°C) heat capacity per unit volume at minimum fluidization of 86 nm 1.42 86 34% 1.56 MJ/m»K The fluidity of the mixture was 85.25 and its capacity was -*117 108 25 26 thermal load the volume unit at minimum fluidization was 1.31 MJ/m*K. Glass sheets with a thickness of 2.3 mm were heated to a temperature of 660°C and cooled in the fluidized mixture. The induced central tensile stress was 47 MPa. It was possible to induce a central tensile stress in the range of 42 MPa - 47 MPa in the glass pane by appropriate selection of the relative proportions of the two gas-generating materials. it Example XIII. Fine-grained materials were used that produce a gas other than water when heated, for example acidic sodium carbonate, which releases carbon dioxide and also water. A mixture of 10% by weight of acidic carbonate was used. 15 sodium containing 0.6 wt.% colloidal silica to improve its fluidity with 90 wt.% alumina aA according to Example 9. The sodium acid carbonate/colloidal silicon-90 mdonka mixture had the following characteristics: Average particle size particle size distribution fluidity content H20 + CC2 (weight loss at 800°C) heat capacity per unit volume at minimum fluidization 70 lim 1.98 75 37% 1.41 MJ/m3K 30 35 The fluidity of the fluidized mixture was 75 and its heat capacity at the volume unit at minimum fluidization was 1.38 MJ/m8K. A 2.3 mm thick glass sheet was heated to a temperature of 660°C and then cooled in the fluidized mixture. A central tensile stress of 53.5 MPa was induced in the glass pane. By appropriately selecting the relative proportions of the mixture components, it was possible to induce selected central tensile stresses in the glass pane in the range of 34 MPa to approximately 55 MPa. In many examples, the indication of the stresses induced in the glass during cooling in a fluidized mixture of fine-grained materials 45 are given as stresses induced in a 2.3 mm thick glass pane made of soda-lime-silicon glass heated to a temperature of 660°C and then cooled. In this way, as described in Examples II, III and IV, it was possible to achieve different stresses by changing the temperature to which the glass was heated. Proportionately higher stresses were induced in the thicker glass. All examples illustrate how to select the proportions of a fine-grained gas-producing material, which is capable of releasing gas at an amount of 4-47% of its weight when heated to constant weight at a temperature of 800 °C and then mix the gas-generating material in predetermined proportions with other fine-grained gas-generating materials or with inert materials, the mixture being prepared to produce the desired fluidity in the range of 60-86 and a heat capacity per unit of volume in the range of 1 .02-1.75 MJ/msK, which ensures that the glass sheet 65 cooled in the mixture is thermally toughened to the desired degree, indicated in the examples by the central tensile stresses. As is normal in thermally toughened glass, the ratio of the surface compressive stress to the central tensile stress is of the order of 2:1 and the induced surface compressive stress is usually twice the central tensile stress. By using the method of the invention, the tempering conditions can be easily changed regenerate and it is possible to use a wide range of fine-grained materials as they are purchased or it is possible to use cheaper and more easily available mixtures instead of rarer and more expensive individual components of the mixture, which reduces the costs of the process. Moreover, through the appropriate selection of fine-grained materials and the proportions in which they are mixed, it is possible is to create selected higher tempering stresses in the glass than could be achieved by any component in the mixture used alone. Some of the particulate materials described above were commercially available with an appropriate average particle size, particle size distribution, fluidity and heat capacity. When there are no commercially available materials with the desired characteristics, e.g. alumina, screening of materials is used to obtain purified crushed materials with the desired characteristics for mixing with other ingredients to obtain a mixture which in fluidized state can induce the desired toughening stresses in the glass. As was found, the fluidized mixtures from Examples I-IV and XIII were particularly suitable for thermal tempering of glass panes into laminates for the production of automotive windshields. The fluidity of such mixtures is in the range of 71-83, their gas content expressed as weight loss after heating to constant weight at 800°C is in the range of 4-37% and their heat capacity per unit volume with minimal fluidization is in the range of 1.09-1^38 MJ /m3K. The selection of the proportions of the components in the mixture allows for the creation of lower stresses in the glass than those generated by the gas-generating component itself. This is illustrated by Example VII. Patent claims 1. A method of thermal treatment of glass, in which the glass is heated to a predetermined temperature and contacted with a fine-grained material fluidized with a gas, characterized in that the fine-grained material consists of a mixture many selected fine-grained materials, at least one of which has the latent property of releasing gas after heating: from hot glass, and these materials are mixed in selected proportions to give the gas-fluidized mixture of fine-grained material such a heat capacity and fluidity to achieve the desired degree of heat treatment.117 108 27 ^8 2. The method according to claim. 1, characterized in that the materials are mixed in proportions selected to induce the required toughening stresses in the glass sheet as it is cooled in the fine-grained gas fluidized material from a temperature higher than the stress decay temperature. 3. The method according to claim 2, characterized in that the fine-grained gas-generating material is selected as a material which, when heated to a constant weight at a temperature of 80K)°C, is capable of generating gas in an amount of 4-37% of its weight, and the fine-grained material is mixed in predetermined proportions. portions, giving the mixture a heat capacity per unit volume at minimum fluidization in the range of 1.02-1/73 MJ/m3K and fluidity in the range of 60-86. 4. The method according to claim 3, characterized in that in the case of thermal tempering of soda-lime-silicon glass panes with a thickness of 2-2.5 mm, in which the glass panes are heated to a temperature in the range of 610-680°C and the mixture is maintained In the state of rest, uniformly expanded fluidization of a fine-grained material, a fine-grained material is used that induces a central tensile stress in the glass sheet in the range of 35-57 MPa. 5. The method according to claim 3 or 4, characterized in that the fine-grained material is mixed in predetermined proportions, giving the mixture 39 a fluidity in the range of 71-83 and a heat capacity per unit volume with minimal fluidization in the range of 1.09-1.38 MJ/m3K. 6. The method according to claim 1, characterized in that aluminum oxide is used as the fine-grained gas-generating material 35. 7. The method according to claim 1. 6, characterized in that the fine-grained gas-generating material is aluminum oxide mixed with aluminum oxide. AQ 8. The method of claim 1. 7, characterized in that a mixture is used which contains 7-86% by weight of γ-alumina and 93-14% by weight of aluminum oxide. a. 9. method according to claim 45, characterized in that the hot glass sheet is cooled in a gas-fluidized mixture of a fine-grained gas-generating material and at least one fine-grained metal oxide whose heat capacity per unit volume at minimum fluidization is ll76—2.01 MJ/m*K, where the mixed fine-grained materials in predetermined proportions give the mixture a heat capacity per unit volume with minimum fluidization in the range of 1.27—1.76 MJ/m3K and a fluidity of 55 in the range of 71— 82. 10. The method according to claim 9, characterized in that spheroidal iron oxide (a-FeaOj) is used as the fine-grained metal oxide. 11. The method according to claim 10, characterized in that a mixture containing 30-70% by weight of spheroidal iron oxide is used. 12. The method according to claim 10, characterized in that the gas-generating material is a mixture containing 70-30% by weight of alumina. 13. The method according to claim 10. The method of claim 10, characterized in that a mixture of 28-35% by weight of spheroidal iron oxide, 45-56% by weight of a-alumina and the remainder y-alumina is used as the gas-generating material. 14. The method according to claim 9, characterized in that a zirconium ZrC2 SiO2 compound is used as the fine-grained metal oxide. 15. The method according to claim 14, characterized in that a mixture is used which contains 10-70% by weight of aluminum oxide monohydrate (A1203 1H20) as gas generating material and 90-30% by weight of the above zirconium compound. 16. The method according to claim The process of claim 1, characterized in that an aluminosilicate is used as the fine-grained gas-generating material. 17. The method according to claim 16, characterized in that zeolite is used as the aluminosilicate, and the mixture is formed from 8-10% by weight of zeolite and 90-92% by weight of alumina. 18. The method according to claim 16. The process of claim 1, characterized in that aluminum oxide monohydrate (A1203-1H20) is used as the fine-grained gas-generating material. 19. The method according to claim The process of claim 1, characterized in that a mixture containing silicon carbide mixed with a fine-grained gas-generating material is used. 20. The method according to claim 19, characterized in that aluminum oxide monohydrate (A1203 1H20) is used as the fine-grained gas-generating material. the mixture containing 17% by weight of aluminum oxide monohydrate mixed with 83% by weight of silicon carbide. 21. The method according to claim 1, characterized in that aluminum oxide trihydrate (A1203 * 3H20) is used as the fine-grained gas-generating material. 22. The method according to claim The method of claim 1, characterized in that a mixture of two fine-grained materials generating the gas aluminum oxide trihydrate and γ-alumina in equal proportion is used. 23. The method according to claim The process of claim 1, characterized in that the fine-grained gas-generating material is a material containing sodium acid carbonate. 24. The method according to claim 23" characterized in that a mixture of 10% by weight of sodium acid carbonate and 90% by weight of aluminum oxide is used a.117 108 V.7-Al203 100 90 80 70 60 50 40 30 20 » O V.7-Al^3 m/.a-Al203 O W 20 30 40 50 60 70 80 90 100 'Aa-At^ Composition of the mixture (Z reprimanded) rlG.c.117 108 Y*7-Al203 Y. ot-Al203 Glass 2.3 mm Composition of the mixture (% by weight) 10 O % 7-ai^03 90 100 Y.oc-Al203 F/G.J.Szkto 2y3mm 670 °C %7-M203 ioO Y.a-Al203 90 10 80 20 70 30 60 40 50 50 40 60 30 70 20 80 Composition of the mixture (% by weight) 10 o -0/- r-Ai203 90 100 Y.cx-Al203 F/gA117 108 7^ i .8 55*1 O) . « P £ Sb Vj c F & c: ? « V c^ v. *v £ ,*J 95- l 90- 85- 60i 75- /O- "A7-M203 KO 3) 3 % S5 50 35 30 lo 10 O %1-M& '/M-AI2O3 O 10 20 30 40 50 60 10 80 90 100 Ka-At&s w* r* .FlGS octaa mixed f% w/wJ V.7-Al203 100 90 60 70 60 50 40 V.a-At203 O 10 20 30 40 50 60 30 20 7 0 80 Composition of the mixture (% by weight) 10 0 CA7~AI203- 90 100 %a-Al203 F/ad117108 fy.7-Al203 100 .90 60 70 60 50 40 30 20 10 O %7-Al203 %a-Al203 O 10 20 30 40 50 60 70 60 90 100 V.tt-M&3 Composition of the mixture (% by weight) F/aZ V.7-Al203 100 90 60 70 60 %ol-A1203 O 10 20 30 40 50 40 30 20 50 60 70 60 Composition mixtures (% by weight) 10 o V. 7-AI2O3 90 100 y.cc-A(203 F/G.8.117 108 I I £3 50] 40] ! 30] '/ 7-AI203 204 100 0 90 10 80 20 70 30 60 40 50 50 40 60 30 70 20 Sktod of the mixture Cfawagone) 10 O V. r-Ai203 90 100 '/.a-Fe^Oj Fig. 9. 7. Al203. IHp 100 9080706050403020 10 O '/. Al203. IH20 V.Zr02.Si02 O 10 20 30 40 50 60 70 80 90 100 °/.Zr02.SiO^ SKLaol mixture (% rtogone) Fig. /O.117 108 C3 and I !40] 30] 20\ io] %7 -AI203 % u-AI203 0-1 . ¦ , 1 ¦ r- 100 90 80 70 60 50 40 O 10 20 30 40 50 60 30 20 10 0 V.7-AI203 70 80 90 100 '/.a-AI203 Composition mAmount (% by weight) F/G. //.ZGK 5, Btm. order 9293 - 95 copies C« out of 109 quantity PL PL PL PL

Claims (1)

1. Patent claims 1. A method of thermal treatment of glass, in which the glass is heated to a predetermined temperature and contacted with a fine-grained material fluidized with a gas, characterized in that a fine-grained material is used, consisting of a mixture of many selected fine materials. ¬ fine-grained, at least one of which has the latent property of releasing gas when heated: from hot glass, and these materials are mixed in selected proportions, giving the mixture of fine-grained material fluidized with gas such heat capacity and fluidity as to achieve given degree of heat treatment.117 108 27 ^82. The method according to claim 1, characterized in that the materials are mixed in proportions selected to induce the required toughening stresses in the glass sheet as it is cooled in the gas-fluidized fine-grained material from a temperature higher than the stress decay temperature.3. The method according to claim 2, characterized in that the fine-grained gas-generating material is selected as a material which, when heated to a constant weight at a temperature of 80K)°C, is capable of generating gas in an amount of 4-37% of its weight, and the fine-grained material is mixed in predetermined proportions. portions, giving the mixture a heat capacity per unit volume at minimum fluidization in the range of 1.02^-1/73 MJ/m3K and fluidity in the range of 60-86.4. The method according to claim 3, characterized in that in the case of thermal tempering of soda-lime-silicon glass panes with a thickness of 2-2.5 mm, in which the glass panes are heated to a temperature in the range of 610-680°C and the mixture is maintained In the state of rest, uniformly expanded fluidization of a fine-grained material, a fine-grained material is used that induces a central tensile stress in the glass sheet in the range of 35-57 MPa.5. The method according to claim 3 or 4, characterized in that the fine-grained material is mixed in predetermined proportions, giving the mixture 39 a fluidity in the range of 71-83 and a heat capacity per unit volume with minimal fluidization in the range of 1.09-1.38 MJ/m3K. 6. The method according to claim 1, characterized in that aluminum oxide a.7 is used as the fine-grained gas-generating material 35. The method according to claim 6, characterized in that the fine-grained gas-generating material is aluminum oxide mixed with aluminum oxide. AQ8. The method according to claim 7, characterized in that a mixture is used which contains 7-86% by weight of γ-alumina and 93-14% by weight of aluminum oxide. a. 9. method according to claim 45, characterized in that the hot glass sheet is cooled in a gas-fluidized mixture of a fine-grained gas-generating material and at least one fine-grained metal oxide whose heat capacity per unit volume at minimum fluidization is ll76—2.01 MJ/m*K, where the mixed fine-grained materials in predetermined proportions give the mixture a heat capacity per unit volume with minimum fluidization in the range of 1.27—1.76 MJ/m3K and a fluidity of 55 in the range of 71— 82. 10. The method according to claim 9, characterized in that spheroidal iron oxide (a-FeaOj) is used as the fine-grained metal oxide. 11. The method according to claim 10, characterized in that a mixture containing 30-70% by weight of spheroidal iron oxide is used. 12. The method according to claim 10, characterized in that the gas-generating material is a mixture containing 70-30% by weight of alumina. 13. The method according to claim 10. The method of claim 10, characterized in that a mixture of 28-35% by weight of spheroidal iron oxide, 45-56% by weight of a-alumina and the remainder y-alumina is used as the gas-generating material. 14. The method according to claim 9, characterized in that a zirconium compound ZrC2 • SiO2 is used as the fine-grained metal oxide. 15. The method according to claim 14, characterized in that a mixture is used which contains 10-70% by weight of aluminum oxide monohydrate (A1203.1H20) as gas generating material and 90-30% by weight of the above zirconium compound. 16. The method according to claim The process of claim 1, characterized in that an aluminosilicate is used as the fine-grained gas-generating material. 17. •17. The method according to claim 16, characterized in that zeolite is used as the aluminosilicate, and the mixture is formed from 8-10% by weight of zeolite and 90-92% by weight of alumina. 18. The method according to claim 16. The process of claim 1, characterized in that aluminum oxide monohydrate (A1203-•1H20) is used as the fine-grained gas-generating material. 19. The method according to claim The process of claim 1, characterized in that a mixture containing silicon carbide mixed with a fine-grained gas-generating material is used. 20. The method according to claim 19, characterized in that aluminum oxide monohydrate (A1203 • •1H20) is used as the fine-grained gas-generating material. the mixture containing 17% by weight of aluminum oxide monohydrate mixed with 83% by weight of silicon carbide. 21. The method according to claim 1, characterized in that aluminum oxide trihydrate (A1203 * 3H20) is used as the fine-grained gas-generating material. 22. The method according to claim The method of claim 1, characterized in that a mixture of two fine-grained materials generating the gas aluminum oxide trihydrate and γ-alumina in equal proportion is used. 23. The method according to claim The process of claim 1, characterized in that the fine-grained gas-generating material is a material containing sodium acid carbonate. 24. The method according to claim 23" characterized in that a mixture of 10% by weight of sodium acid carbonate and 90% by weight of aluminum oxide is used a.117 108 V.7-Al203 100 90 80 70 60 50 40 30 20 » O V.7-Al^3 m/.a-Al203 O W 20 30 40 50 60 70 80 90 100 'Aa-At^ Composition of the mixture (Z reprimanded) rlG.c.117 108 Y*7-Al203 Y. ot-Al203 Glass 2.3 mm Composition of the mixture (% by weight) 10 O % 7-ai^03 90 100 Y.oc-Al203 F/G.J. Glass 2y3mm 670 °C %7-M203 ioO Y.a-Al203 90 10 80 20 70 30 60 40 50 50 40 60 30 70 20 80 Composition of the mixture (% by weight) 10 o -0/- r-Ai203 90 100 Y.cx- Al203 F/gA117 108 7^ i .8 •55*1 O) .«• P £ Sb Vj c F & c: ?« V c^ v. *v £ ,*J 95- l 90- 85- 60i 75 - /O- "A7-M203 KO 3) 3 % S5 50 35 30 lo 10 O %1-M& '/M-AI2O3 O 10 20 30 40 50 60 10 80 90 100 Ka-At&s w* • • r* . FlGS octaa mixed f% w/wJ V.7-Al203 100 90 60 70 60 50 40 V.a-At203 O 10 20 30 40 50 60 30 20 70 80 Composition of the mixture (% w/w) 10 0 CA7~AI203- 90 100 %a-Al2 03 F/ad117108 fy.7-Al203 100 .90 60 70 60 50 40 30 20 10 O %7-Al203 %a-Al203 O 10 20 30 40 50 60 70 60 90 100 V.tt-M&3 Mixture composition (% by weight) F/aZ V.7-Al203 100 90 60 70 60 %ol-A1203 O 10 20 30 40 50 40 30 20 50 60 70 60 Composition of the mixture (% by weight) 10 o V. 7-Al2O3 90 100 y.cc-A (203 F/G.8.117 108 I I £3 50] 40] ! 30] '/•7-AI203 204 100 0 90 10 80 20 70 30 60 40 50 50 40 60 30 70 20 From Cfawagone mixture) 10 O V. r-Ai203 90 100 '/.a-Fe^Oj Fig.9. 7.Al203.IHp 100 9080706050403020 10 O '/. Al203.IH20 V.Zr02.Si02 O 10 20 30 40 50 60 70 80 90 100 °/.Zr02.SiO^ SKLaol mixture (% rtogone) Fig./O.117 108 C3 and I ! 40] 30] 20\ io] %7-AI203 % u-AI203 0-1 . ¦ , 1 ¦ r- 100 90 80 70 60 50 40 O 10 20 30 40 50 60 30 20 10 0 V.7-AI203 70 80 90 100 '/.a-AI203 Composition mCeszantny (% by weight) F/G./ /. ZGK 5, Btm. order 9293 - 95 copies C« out of 109 quantity PL PL PL PL