DE2933431A1 - METHOD AND DEVICE FOR HEAT TREATING GLASS - Google Patents

Description

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PTLKINGTON BROTHERS LIMITED St. Helens, Merseyside WAlO Great Britain

Method and device for heat treatment of glass

The invention relates to the heat treatment of glass and more particularly to the heat toughening of flat or curved panes of glass, e.g. B. Glass panes for single use as a motor vehicle windshield or as a part an automobile composite windshield, a side light or a tail light for a motor vehicle or for use in the construction of windshield units for Plug-in tools or railroad locomotives.

In DE-OS 2 6 ^ 8 0 ^ 8 is a method for heat treatment of glass objects by heating the glass object to a temperature above its pre-stress relaxation point and then quenching the glass articles in a gas fluidized bed of particulate! material described that in a calm, uniformly expanded particle fluidization state by controlling the distribution

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ORIGINAL INSPECTED

283343-1

-θάβε fluidizing gas in the particulate material at a Gas flow rate through the particulate material between the rate at which fluidization begins and is brought to the speed corresponding to the maximum expansion of the particulate material.

This fluidization state of the bed is such that the movement of the fluidized particulate material acts on the hot surfaces of the glass as the glass cools in the fluidized bed, but the temporary ones Tensile stresses introduced into the surface of the hot glass when its leading edge first touches the fluidized bed are not so significant as to damage the glass. Therefore, the method has a high Yield.

The degree of toughening of a sheet of glass that is immersed in such a fluidized bed depends on the rate of heat transfer between the fluidized particulate material and the hot disk immersed therein and from the rapid transfer of hot particles away from the vicinity of the glass pane with simultaneous rapid supply of cooler particles from the Mass of the fluidized bed in the vicinity of the glass plate.

The movement of particles in the vicinity of the glass surfaces is faster than the movement of particles in the mass of the Layer due to the rapid movement of the fluidized particulate material resting on the hot immersed surfaces of the glass occurs due to the heating of the particulate material by the glass, which continues as the glass moves cools in the fluidized bed.

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ORIGINAL INSPECTED

The movement of the particulate material on the glass surfaces is significantly improved when using a selected particulate material which Has latent gas development properties such that a rapid development of gas from the particulate Material occurs when heated near the glass surfaces.

It has now been found that there are three factors that in controlling the heat stressing of glass in one particulate material fluidized by gas predominate and in particular the degree of bias of a hot Control the pane of glass in contact with a particulate material fluidized by gas.

These factors are as follows:

1. The gas generating properties of the particulate material.

2. The heat capacity of the particulate material per unit volume at minimal fluidization. It is derived from the ^{specific heat of the material measured at 50 °} C. and the density of the material of the fluidized bed measured with minimal fluidization.

3. The "flowability" of the particulate material, as defined below, which is the sum of four ratings given to the material by evaluating four properties of the flowable particulate material. The term "fluidity" when used herein has this meaning.

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ORIGINAL INSPECTED

These four properties of a flowable particulate material and the type of identification of evaluation numbers are described in the article "Evaluating Flow Properties of Solids" by Ralph L. Carr Jr., "Chemical Engineering", Vol. 72, No. 2, Jan. 18, 1965 and are as follows:

1. compressibility = %,

where P = densely packed mass density and A = aerated mass density

2. Slope Angle: This is the angle in degrees between the horizontal and the slope of a pile of the particulate material when it is from a point across the horizontal has fallen until a constant angle is measured.

3. Spatula angle: A spatula is placed horizontally in the Bottom of a mass of the dry particulate material is introduced and straight up and out of the material raised »An average value of the angle in - raden to the horizontal of the side of the pile of material on the spatula is the spatula angle.

^{4. Particle size distribution (called "uniformity coefficient n} " in the above-mentioned article): This is described in the above-mentioned article as the numerical value obtained by dividing the width of the sieve opening (ie particle size) through which 60% of the particulate material passes by the width of the Sieve openings that only 10 % of the particulate material pass through.

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ORiGiNAL INSPECTED

All particle size distribution values given here were measured in a known manner by a method using a "Coulter" counter to determine the appropriate particle diameter by retaining cumulative weight percentages of 40 and 90 % corresponding to the widths of sieve openings which are 60 % and just 10 %, respectively. of the particulate material pass.

The numerical values of the compressibility, the slope angle and the trowel angle were under Use of a "Hosakawa Powder Tester" from Hosakawa Micrometrics Laboratory of Hosakawa Iron Works, Osaka, Japan measured which powder tester is particularly suitable for use in determining the "flowability" of the powders, as indicated above, is designed.

The flowability of a particulate material is fundamentally related to factors such as: B. the average particle size, the particle size distribution and the shape of the particles in relation, sometimes with angularity of the Particle, d. H. whether they have a rounded or angled shape is indicated. The flowability value increases with it the increase in the average particle size, with the narrowing the particle size distribution and with a decrease in the angularity of the particles.

The heat capacity per unit volume with minimal fluidization depends on the specific heat of the material and the density of the fluidized bed with minimal fluidization, which density increases as the particle size distribution narrows.

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ORIGINAL INSPECTED

A high value of the pre-stress stress is created in glass when it is quenched in a fluidized bed with optimal flowability. Some materials that create required preload stresses may be commercially available. Other commercially available materials can be altered to produce the required pre-stressing stresses by sieving the material to ^: Change its average particle size and its particle size distribution.

However, there is a problem in that there is a limit to the extent to which the degree of pretension stress introduced into the glass by varying the flowability of commercially available materials can be controlled. "Materials with the required

possibly

Flowability may not be commercially available. The creation of a large amount of a material with the required skill can sifting a large amount of particulate! Require material. In addition, using a single material, the only way to change the heat capacity of the fluidized bed is the means the narrowing of the particle size distribution so that there is no possibility of changing the heat capacity regardless of

Flow
the change in capability achieved by narrowing the particle size distribution.

It has now been found that a particulate material with the optimal gas generating properties, the optimal Heat capacity and the optimal flowability to generate the necessary prestressing stresses in one Glass article can be produced using a mixture of particulate materials, each of which contributes to the optimal properties of the mixture. You cn

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Selection of particulate materials and the proportions in which they are mixed can be gas fluidized particulate material can be tailored to any preload stresses in a wide range as required achieve.

The invention is therefore based on the object of a method and a device for the heat treatment of glass, in which the Glass heated to a predetermined temperature and contacted with a gas fluidized particulate material will develop, with which the optimal gas generation properties, Heat capacity and fluidity of the particulate material used to produce desired ones Tensions in the glass can be achieved in a wide range.

The invention, with which this object is achieved, is a method for heat treatment of glass in which the glass is heated to a predetermined temperature and contacted with a gas fluidized particulate material characterized in that the particulate material is a mixture of a number of selected particulate Materials are used wherein at least one of the particulate materials having gas generating properties is used when heated by the hot glass, and mixes the materials in selected predetermined proportions that the imparting such heat capacity and fluidity to the gas fluidized mixture of the particulate materials, that a required heat treatment of the glass is achieved.

One embodiment of the invention provides that the materials are used in such selected predetermined proportions mixed so that the required voltage stresses in the

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Glass can be introduced when it is fluidized by the gas particulate material cools from a temperature above its pre-stress relaxation point.

A material can be selected as the gas-generating particulate material which is suitable for developing 4 to 37% of its own weight in gas when heated to a constant weight at 800 ^° C., and the particulate materials can be mixed in predetermined proportions, the "Her Mixture" Give heat capacity per unit volume with minimal fluidization in the range from 1.02 to 1.73 MJ / btk and a flowability in the range from 60 to 86.

If a sheet of soda-lime-silica glass with a thickness in the range from 2 to 2.5 ram is thermally toughened by heating the sheet of glass to a temperature in the range from 610 to 68O ⁰ C and the mixture in a quiet, even Holds an extended state of particle flow, according to the invention, the particulate material of this type can be used to generate a central tensile stress in the range of 35 to 57 MPa in the glass pane.

To produce a windshield glass, the process can be characterized by the fact that the particulate Materials mixed in predetermined proportions that give the mixture a fluidity in the range of 71 to 83 and a heat capacity per unit volume with minimal fluidization in the range from 1.09 to 1.38 MJ / nrK.

The gas generating material can be ^ -alumina. The f -alumina can be mixed with oil-alumina. the

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ORIGINAL INSPECTED

Mixture can contain 7 to 86% by weight of γ * aluminum oxide.

Another embodiment of the invention is characterized in that a hot glass sheet in a through Gas fluidized mixture of a gas generating particulate material and at least one particulate metal oxide deterring, its heat capacity per unit volume at Minimal fluidization in the range from 1.76 to 2.01 Mj / πτκ and the particulate materials are mixed in predetermined proportions which each have a heat capacity of the mixture Volume unit with minimal fluidization in the range of 1.27 up to 1.76 MJ / nrK and eiiB flowability in the range of 71 to 82 award,

The particulate metal oxide can kujigeliges iron oxide ((TC-Fe ₂ O,) ,, be DIs mixture ^can;:. 'To 70% by weight of spherical = iron oxide contained Further, the mixture may: 70' to 30 percent by *.

X -aluminium oxide as gaserzeugvnd ^ sf Lerial - keep up. In a variant of this Ausii "α ^ ^γ " e. . π ahrens the mixture can be 28 to 35 wt j K ^1, ι, If 3 and 45 to 56 wt ";? * 't </ - containing alumina." the remainder being Γ-alumina as a gas generating material.

The particulate metal oxide can also be zirconium (ZrO ₀ .SiCu). The mixture can then be 10 to 70 wt.% Aluminlummonchydrat (Al-O ^ 1 H- "O) as a gas-generating material and S> 0 to 30 wt .. # contain zirconium.

According to another embodiment, the gas-generating particulate material is an Älutniniumsilikat, the aluminum may be ill zeolite, and 8 to 10% by weight of the zeolites can ^rt - ^a. "

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be mixed with 90 to 92 wt. % ck, aluminum oxide to produce the mixture.

The gas generating particulate material can also be aluminum monohydrate (Al ₃ O “IH ₂ O).

According to the invention, the mixture can also contain silicon carbide (SIC ) with the addition of a gas-generating particulate material. According to a variant Bearing From this, the gas-generating particulate material is aluminum monohydrate (Al ₂ O, .IH ₂ O), and the mixture preferably contains 17 wt.% Alumina monohydrate and 83 wt.% Of silicon carbide.

In another embodiment of the process, the gas generating particulate material is aluminum trihydrate

The mixture may also contain equal parts of two gas generating particulate iterials such as aluminum trihydrate (Al ₂ O,. ^ H ₂ O) and ^ -alumina.

According to yet another embodiment of the invention, the gas-generating particulate material is sodium bicarbonate (Na (HO) is. The mixture may then from 10 wt. # Of sodium bicarbonate and 90 wt.% CC-alumina.

The invention also relates to a device for the heat treatment of glass according to the method according to the invention, having a container for particulate material fluidized by gas, one connected to the container

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Gas supply device to maintain the fluidization state the particulate material and an organ for placing hot glass in the container, with the mark, that is, the container is a selected mixture fluidized by gas contains particulate materials, at least one of which, when heated by the hot glass, are gas generant Having properties, and the particulate materials mixed in selected predetermined proportions which give the gas fluidized mixture such a heat capacity and fluidity that a required heat treatment of the glass can be achieved.

Finally, the invention relates to heat-treated glass, e.g. B. a thermally toughened flat glass pane, that or which is produced by the method according to the invention.

The invention is explained in more detail with reference to the exemplary embodiments illustrated in the drawing; in this demonstrate:

Fig. 1 schematically shows a vertical section through a device for heat prestressing of glass panes according to the method according to the invention;

FIG. 2 shows a diagram of the central tensile stress as a function of the proportions of the mixture of particulate materials making up the gas fluidized bed;

3 shows a diagram similar to FIG. 2 for illustration purposes the central tensile stress with changes in the proportions in a different mixture of particulate materials;

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FIG. 4 is a diagram similar to FIG. 3 to illustrate the change in the surface compressive stress in FIG 2.3 mm glass with the change in the composition of the gas fluidized bed;

FIG. 5 shows a diagram similar to FIG. 3 for illustration purposes the central tension introduced in 6 mm thick glass;

6 is a diagram similar to FIG. 4 to illustrate the change in glass introduced into 6 mm thick glass Surface compressive stress;

FIG. 7 is a diagram similar to FIG. 3 for 12 mm thick glass; FIG.

FIG. 8 is a diagram similar to FIG. 4 for 12 mm thick glass; FIG. and

9, 10 and 11 show the change in the central tensile stress with the composition of the mixture of particulate materials in three other embodiments of the method according to the invention.

A vertical toughening furnace 1 can be seen in FIG. 1 with side walls 2 and a roof 3 The side walls 2 and the roof 3 are made of the usual refractory material, and the bottom of the furnace has an open mouth which is defined by an elongated opening 4 in a base plate 5 on which the furnace 1 is supported. A slidable diaphragm, not shown, is provided around the mouth 4 in a known manner To lock catfish. A glass pane 6 to be curved and then thermally toughened is in the furnace 1 Pliers legs 7 suspended from the top of the glass pane

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capture. The pliers legs J hang? .N a pliers rod 8, which in turn on a conventional., Not shown

s-rail hoist is suspended and runs on vertical guide 9, which reach down from the furnace to guide the lowering and raising of the tong bar.

A pair of bending forms 10 and II is immediately below the mouth 4 of the furnace placed in a heated chamber 12, which is kept at such a temperature that the molds are at the same temperature as the hot glass are they bend. The chamber 12 is heated by means of hot gases supplied through openings 12a. When the forms are open, they are on both sides of the path of the glass pane 6, The mold 10 is a fixed one mounted on a punch IJ Patrix and has a curved face that defines the curvature to be applied to the hot glass sheet. Form is a ring frame die, which is carried by spars 14 which are mounted on a support plate 15, which in turn is mounted on a punch l6. The curvature of the frame shape: i fits exactly to the curvature of the front of the male mold 10.

The guide rails 9 range nac- =. down on both sides the bending molds to a container for a fluidized bed of particulate refractory material in which the Quench hot curved glass sheet by lowering the sheet into the fluidized bed.

The container for the fluidized bed has a rectangular tank 18 open at the top, which is mounted on a scissor-type joint platform is mounted. When the platform 19 is in your raised position, the top of the tank 18 is directly below bending forms 10 and 11.

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A high pressure drop microporous membrane 20 extends across the base of the tank 18.

The edges of the membrane 20 are secured between a flange on the tank 18 and a flange 22 on an antechamber 235 which forms the base of the tank. The flanges and the edges of the membrane 20 are screwed together, as indicated at 24. A gas inlet line 25 is connected to the antechamber, and the line 25 is supplied with fluidizing air at a regulated high pressure. There is a high pressure drop of at least 60 % of the antechamber pressure through the membrane 20, which results in an even distribution of the fluidizing air in the particulate material with a gas flow rate through the particulate material between the velocity corresponding to the minimal fluidization at which the particles are currently in the upwardly flowing air are suspended and at the rate corresponding to the maximum expansion of the particulate material at which dense phase fluidization is maintained. The extended fluidized bed is in a substantially bubble-free, calm, partial fluidization state with a horizontal calm surface through which the glass sheet enters the fluidized bed.

The membrane 20 can be a steel plate containing a regular distribution of holes and a number of Have layers of strong microporous paper laid on top of the plate. For example, 15 layers of paper can be used will. The membrane comes with a top on the paper layers

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laid wire mesh, ζ. B. a stainless steel mesh completed.

A basket for collecting debris may be located near the membrane 20 and is designed so that it does not interfere with the uniform upward flow of the fluidizing gas from the membrane.

The guide rails 9 extend down to a point under the bending forms and end in the area of the upper one Edge of the tank. A fixed frame 27 is mounted in the tank 18 and has upwardly bent feet 28 on it Base for holding the lower edge of a pane of glass immersed in the fluidized bed when the tong bar is below the bending form is lowered by the elevator.

In order to insert a sheet of glass into the device, the scissors-hinged platform 19 is lowered, and at the lowest Position the pliers rod on the bottom of the guide rails, the glass pane to be bent and toughened on the Pliers legs 7 attached.

The elevator then lifts the suspended glass sheet into the furnace 1, which is kept at a temperature of e.g. B. 850 ° C is held so that the sheet of glass is rapidly increased to a temperature near its pre-stress relaxation point, e.g. B. in the area is heated from 610 to 680 ° C. When the glass has reached the required temperature evenly, the the aperture 4 closing the shutter is opened, and a hot pane of glass is brought into its position between the open bending dies 10 and 11 are lowered. The stamps Ij5 and 16 are actuated and the molds close to the

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Bend the disc to a desired curvature. When the required curvature of the disc is achieved, e.g. B. to enable the use of the pane as part of a composite windshield for a motor vehicle, the molds open and the hot curved glass pane is quickly lowered into the fluidized bed in tank 18, which was raised for the quenching position by lifting the scissor-joint platform 19 while the glass pane was heated in oven 1. The fluidized bed is kept at a temperature of J> 0 to 150 ° C by a water cooling jacket 29 which is attached to the flat long walls of the tank 18.

The fluidized bed 17 consists of fluidized by gas particulate! Material which is a mixture of a number of particulate materials in certain proportions, at least one of which has gas-generating properties and is suitable for the development of gas, if the fluidized material touches the hot glass.

A suitable gas-generating particulate material is capable of developing from 4.0 to 37% of its own weight of gas when heated to constant weight at 8OO ⁰ C; suitable materials are J- alumina (T-Al ₀ O,) which is porous and adsorbed in its pores

^d j ium
Contains water, aluminosilicates, which are porous and contain water adsorbed in their pores, aluminum hydrates, such as. B. Aluminum trihydrate (Al 0 .JH 0), which contains bound crystal water, and aluminum _{monohydrate (A1?} O, .1H 0), which contains crystal water and is porous, i.e. also contains water adsorbed in the pores, and materials that contain other gases produce as water, e.g. B. Sodium Bicarbonate (NaHCOC) ./ Jim to generate the necessary prestressing stresses in the glass, the components of the mixture of

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particulate materials mixed in predetermined proportions, which give the mixture a flowability in the range of 60 to 86 and a heat capacity per unit volume with minimal fluidization in the range from 1.02 to 1.75 MJ / ητκ to lend.

Other components of the mixture which are mixed with the gas generating particulate material are particulate materials which are inert in the sense that essentially no gas is given off from the material when heated. Examples are <, - aluminum oxide (-3C-Al ₂ O,), zircon (ZrO ₃ .SiO ₃ ), silicon carbide and spherical iron oxide (

These particulate materials are dense, non-porous in shape and are selected to have fluidity and have heat capacity different from that of the gas generating particulate material, so that fn depends on the proportion of the density used, non-porous material are effective to the fluidity and heat capacity of the mixture of particulate Alter materials to such an extent that a desired level of prestressing is created in the glass.

It can be assumed that if a sheet of hot glass is in a gas fluidized layer of such a mixture of particulate materials is quenched which rapid development and expansion of the gas generating particulate material due to the heating thereof the gas evolved near the glass surfaces

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local movement of the mixture of particulate materials on the glass surfaces in a boiling one Improve liquid-like manner with the result that there are moving layers of gas and particulate ^ There are material flowing over the glass surfaces when the glass is quenched in the fluidized bed.

Mixing the constituents of the mixture in predetermined proportions results in an optimal heat transfer away from the glass surfaces into the bulk of the fluidized bed that is desired to be introduced into the glass There is a constant dissipation of the heat drawn from the glass to the more distant ones Dividing the fluidized bed by the movement of the fluidized particulate immediately surrounding the pane of glass Materials on.

The water-cooled jacket 29 keeps the more distant parts of the fluidized bed cool, so that they actually act as heat sinks works. A strong movement of the particulate material on the glass surfaces continues well until after the cooling of the glass below its pre-stress relaxation point which ensures that the initially introduced into the glass when the glass is in the fluidized bed Maintain center-to-surface temperature gradients stay when the glass relaxes through its bias ung point cools down, and the required prestressing loads are then applied during the continued Cooling of the glass develops while it is still immersed in this ■ fluidized bed.

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The lower edge of the hot pane of glass is quenched evenly when it hits the calm surface of the extended fluidized bed. Essentially the same tensile stresses will be in different Areas of the surface of the edge of the glass pane produced, so that there is little risk of breakage. During the sinking the lower edge of the glass ΐη touches the fluidized bed every part of the lower edge is always fluidized material that is in a calm, uniformly expanded particle fluidization state is, and this uniform treatment of the lower edge independent of the flow of the particulate Material that adheres to the hot glass surfaces due to the evolution of gas from the gas-generating component of the mixture largely counteracts breakage and the related problems associated with the occurrence of Glass fragments are connected in the fluidized bed. This ensures, together with the avoidance of losses Glass panes due to a change in shape of the glass panes and / or damage to the surface qualityj, a industrially useful yield of toughened glass panes.

Some examples of the practice of the invention with selected mixtures of particulate! Material will be below given. In each of these examples is the numerical value of the product of the particle density in g / cnr and the average particle size in / around each of the ingredients of the mixture under 220. This is a criterion that is useful in determining whether. a particular particulate material is suitable for fluidization in a calm, uniformly expanded particle fluidization state, when working with air in ambient conditions of normal temperature and normal pressure. A mix of each

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particulate materials are then in a calm, uniformly expanded, particulate fluidization state for fluidization suitable.

example 1

The fluidized bed 17 was made of a mixture of "Ϊ * -alumina as the gas generating particulate material and oO-alumina.

The If ™ alumina used was a microporous material with pores of diameters in the range from 2.7 to 4.9 nm and a free pore space of 20 to 40 %. The pores contain adsorbed water that is released as a gas when the material is heated.

The f -alumina used had the following properties:

Average particle size = 119 / µm

Particle size distribution = 2, j54

Flowability = 90.25

Water content (weight loss at 800 ^° C.) - 4.3 %

Heat capacity per unit volume at, ^ _{n M}

Minimal fluidization ^{= 1} ^ ^{9 K}

The cC-alumina used was of dense, non-porous form with the following properties:

Average particle size = J> 0 / µm

Particle size distribution = 1.22

Flowability = 70

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Heat capacity per unit volume with minimal fluidization

-1.3 mj / vk

Experiments were carried out with mixtures of f- alumina and cC-alumina ^ which were mixed in predetermined proportions. Soda-lime-silica composition glass disks 2.3 ram thick were cut, and the edges of the cut disks were rounded off using a fine diamond splinter wheel; finished. Before bending and quenching, each disk was ^{heated to 660 °} C. in the fluidized mixture in furnace 1, which was in a calm, uniformly expanded particle fluidization state.

Table I shows the properties of various blends of these materials ranging from 30 to 90 wt. %

■ - '^ - aluminum oxide and 70 to 10% by weight χ aluminum oxide and also the central tensile stress introduced into the glass panes during quenching. For comparison, the central tensile stress generated using ⁰ ^ ^ alumina and alumina alone, listed in Table I below.

Table I.

Weight percentage
in the mix 0 % 30 % 50 % 70 % 90 % 100 % 70 ⁰ ^ alumina 100 % 70 % 50 % 30 % 10 % 0 % 1.3 ¹ TC aluminum oxide 90.25 81.5 75 74 72.25 32 Flowability of the
mixture 1.09
) 1.16 1.20 1.24 1.28 Heat capacity of
Mix by volume
unit at minimum,
fluidization (MJ / m ^ K 41 43 49 49 4 ₇ Central tension
(MPa)

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Figure 2 illustrates the change in central tension with the composition of the mixture.

The T-alumina alone has a flowability that too high for generating the maximum prestressing stress in the glass panes, which is particularly due to its high average particle size and the fact that the particles are relatively smooth, non-angular Shape are. The addition of a proportion of ^ -alumina, which has a lower flowability than that

T-alumina has because ^ / - alumina has a lower

e has an average particle size and an angularity of the individual particles, lowers the flowability of the mixture. The flowability of the mixture decreases as the amount of ^ U-alumina in the mixture is increased and there is a corresponding increase in the central tension generated. A maximum central tensile stress of 4-9 MPa is achieved when the flowability is set to the optimum value of 74 and the mixture was about 70 wt.% Alumina and OEO JO wt.% Ip-alumina.

The «? 0 alumina has a higher heat capacity than the ^ -alumina, and if the proportion of the cL-alumina is increased in the mixture, there is a continuous increase in the heat capacity of the mixture, the contributes to increasing the stress that is achieved.

Another additive vonoC alumina in an amount about 70 wt.% Increases the thermal capacity of a little more and keeps an acceptable flowability, however, lowers the inserted central tensile stress, since the proportion of

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gas generating ingredient, Tf-alumina low level was lowered.

Example 2

The fluidized bed consisted of a mixture of -alumina as the gas generating particulate material and <k / -alumina.

The ^ -alumina used was a microporous material with pores measuring in the range from 2.7 to 4.9 mm and with a free pore volume of 20 to 40 %. The pores contain adsorbed water which is given off as a gas when the material is heated .

The T-alumina used had the following properties:

Average particle size = 64 µm

Particle size distribution = 1.88

Flowability = 84

Water content (weight loss at .. ^ 800 ⁰ C) ^{= 4} *

Heat capacity per unit volume _ - _{η (} - _{MT / m} 3 _v with minimal fluidization - i, ue> Mj / m κ

The cO-alumina used was the same as in Example 1.

Experiments were conducted with mixtures of the If-alumina and the oC -alumina mixed together in predetermined proportions of 100 % ^ -alumina and 0 % dj -alumina to 0 % ft -alumina and 100 % cC -alumina.

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Table II shows the heat capacity per unit volume with minimal fluidization and the flowability of the used Mixtures:

Table II

mixture
Weight % Heat capacity Fluidity 84
82.75
79
76
75.25
71
70 TAlumini- <C-Alumi-
nium oxide nium oxide 1.05
1.09
1.15
1.20
1.25
1.29
1.50 100 0
86 14
61 59
40 60
22 78
7 95
0 100

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ORIGINAL INSPECTED

Glass sheets of soda-lime-silica composition with a thickness of 2.3 mm were cut, and the Edges of the cut slices were rounded off

Finished using a fine diamond splinter wheel. Each disk was suspended from the tong legs 7 and heated in furnace 1 before bending and quenching. The results are illustrated in Figs. The abscissa for each curve shows the composition of the mixture in wt. #. In each of Figs. 4 and 4 there are four curves corresponding to the central tensile stress (Fig. 3) and the surface compressive stress (Fig. 4) introduced into the 2.3 mm thick glass panes which are heated to a temperature of 610 and 610 respectively. 630 or 650 or 670 ⁰ C and then heated absehreckte in the fluidized bed 17, which was kept in a quiet, uniformly expanded Teilchenfluidisierungszustand in the temperature range from 6O ⁰ C to 80.

The curves show that was to be preferred, i.e. from about 7 to about 86 wt.%, To use aluminum oxide in admixture with 2P-alumina. As the proportion of "/." -Aluminium oxodine in the mixture is increased, the central tensile stress or the surface compressive stress introduced into the glass during the heat-toughening process increases to a maximum, which is reached when the amount of oC -alumina is about 70 ° C to 80 wt.% of the mixture weight. Generally, the highest stresses introduced when the existing oC alumina quantity of the mixture of 55 to 85 wt.%. A higher proportion of oG aluminum oxide in the mixture creates a drop in the stresses introduced.

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By suitable selection of the proportions of f-aluminum oxide and C-aluminum oxide, the mixture has gas generation properties, a heat capacity per unit volume with minimal fluidization at 50 ^° C. and a flowability that consistently high values of the central tensile stress and the surface compressive stress in the 2.3 mm thick panes of glass.

For example, if the glass is heated to 670 ° C. and then quenched, a required central tensile stress in the range of 42 to 49 MEa and a corresponding surface compressive stress in the range of 83 to 103 MEa can be generated in the glass by using the predetermined proportions of ft "cC alumina and alumina selected in the mixture in the range of 7 to 86 weight.% ^ alumina and 93-14 wt.% oO-alumina.

Example 3

Soda-lime-silica glass panes 6 mm thick were cut and finished on the edges, whereupon it is heated and in a fluidized bed in a calm, evenly expanded state of particle flooding.

became

frightens that consist of a mixture of the same particulate IP-alumina and <k. -Aluminium oxide materials was composed as in Example 2. FIGS. 5 and 6 Fig. 3 and 4 are similar diagrams that illustrate the results for heated to temperatures of 6IO, 630, 650 and 670 ⁰ C and then quenched glass sheets were obtained.

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- 53 -

The results show that required pre-stressing stresses can be created in the glass which are a function of the proportions of the Jp -alumina and the oC -alumina in the mixture. Maximum voltages were obtained when the blend comprises about 65 to 95 wt.% Alumina Λ contained. For example, the central tensile stress produced in the glass was when the glass is heated to 670 ⁰ C and was then quenched in a fluidized mixture of 22 wt.% T-alumina and 78 wt.% OC-alumina, 91 MPa, and the surface compressive stress was 216 MPa.

This high-strength, 6 mm thick glass is used to manufacture fixed units for aircraft and railroad locomotives used.

Similar results were obtained when soda-lime-silica glass panes 10 mm thick were toughened. Such panes of glass are used in the manufacture of window units for aircraft, e.g. B. two discs made of toughened glass with a thickness of 10 mm and an outer pane of 3 mm thickness. The discs are with Plastic intermediate layers of known type laminated.

Example 4

Soda-lime-silica glass disks 12 mm thick were cut and edged, after which they were heated and quenched in a fluidized bed composed of a mixture of "f -alumina and

<£ / -alumina in predetermined proportions in the same Way as it was composed according to the description in Example 2.

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Results were obtained for panes of glass heated to 610, 630, 650 and 670 ^° C. with a proportion range of X-alumina and & -alumina, and the results are illustrated by the curves in FIGS. 7 and 8.

Stress maximum values were measured when the fluidized mixture contained about 65 to 85% by weight cC -alumina. When a disc on 67o ⁰ C. and was quenched in a fluidized bed of a mixture of 22 wt.% ^ Alumina and 78 wt.% -0-alumina, was the central tensile stress in the glass of 124 MPa, and the surface compressive stress was 261 MPa .

Figures 7 and 8 illustrate how a wide range of values of preload stresses can be used in the Glass as needed by selecting the proportions of the ingredients of the mixture of particulate materials at the temperature suitable to which the glass is heated prior to quenching, can be generated.

Have the results illustrated in Figures 3-8 in common that higher prestressing stresses are achieved if the proportion of the component with the higher Heat capacity (oC -aluminium oxide) in the mixture up to is increased to a point where a further increase in the proportion increases the proportion of the gas generating component (y-aluminum oxide) lowers to an insufficient level.

The range of proportions of the gas generating material and the other ingredient or ingredients of the mixture ensures

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a fluidity of the mixture in the range of 60 to 86, which is such that the type of movement to the Cooling the glass is beneficial at a rate that generates the required stress levels in the glass.

The cooling of the glass occurs due to the rapid movement of the particulate material in the vicinity of the Glass surface, this movement being essentially due to the development of water vapor from the ^ -aluminium ^ estandteil due to the mixture.

A higher proportion of dj -alumina improves the rate of heat removal from the glass and changes the flowability of the mixture.

Example 5

The fluidized bed was formed from a mixture of ^ f -alumina as the gas generating component with a proportion of spherical iron oxide (X-Fe ₂ O,) and one or two kinds of ck -alumina.

The Jf alumina had the following properties:

Average particle size = 84 to

Particle size distribution = 1.94

Flowability = 87.25

Water content (weight loss at = 6 #

Soo c)

Heat capacity per unit volume at - _n / -, _MT / _3

i ^{= 1} ^ ^{065 MJ / m}

Heat capacity per unit volume at - _n / -, _MT / _3 "· Minimal fluidization ^{= 1} ^ ⁰⁶ - ^{5 MJ / m K}

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- 41 ,around = ι, 69 - 76 , 5 - 2, Ol M,

- 36 -

The spherical iron oxide had the following properties:

Average particle size Particle size distribution Flowability

Heat capacity per unit volume with minimal fluidization

The first oG aluminum oxide was that used in Example 1, the second «0 aluminum oxide had the following properties:

Average particle size = 24 µm

Particle size distribution = 1.25

Flowability = 66

Heat capacity per unit volume _ ι loo MT / m ^ ubin with minimal fluidization " ^L ' ^l ^ ^{d 1} ^ /""*.

Glass panes of a soda-lime-silica composition 2.3 mm thick were ^{heated to 660 °} C. and quenched in fluidized mixtures of the above materials which were in a calm, uniformly expanded, particle fluidization state.

The properties of the mixtures and the resulting central tensile stresses generated in the glass panes are given in the table.

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Table III

Wt.% In the mixture
(D (2) (3) (4) (5) 50 % 30 % 20 % 74 16 % ^ -Alumina 70 % 50 % 70 % 35 % 1.502 28 % Spherical iron oxide 30 % - - 45 % 57 36 % <£ -aluminium oxide (1) - - - - 20 % ^, - aluminum oxide (2) - 79 73 73.5 Flowability of the
mixture 82 1.54 1.726 1.44 Heat capacity of
Mix by volume
unit at minimum
fluidization
MJ / m ^ K 1.347 49 50 53.0 Central tension
(MPa) 45

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Fig. 9 illustrates the change in central tensile stress with the composition of the mixtures (1), (2) and (3)} of p-alumina, and "O-Fe ο _ln d _he Table III. The central tensile stresses obtained using the "^ -alumina alone and the cC-Fe 0 alone were 41 MPa and 32 MPa, respectively.

As in Example 1, the X-alumina used in this example had a flowability which is too high to generate the maximum prestressing stress in the glass panes. The spherical iron oxide has a lower flowability than the aluminum oxide, particularly because of its lower average value. The addition of increasing amounts of the spherical iron oxide to the ^ -alumina in mixtures (1), (2) and (3) of TableΠΙ has an increasing effect of lowering the fluidity of the mixture by continuously decreasing the average particle size of the mixture as the amount of spherical Iron oxide grows in the mix. As the flowability of the mixture decreases, there is a continuous increase in the central tensile stress generated in the glass panes. A maximum central tensile stress of 50 MPa is achieved when the mixture contains approximately 70 % spherical iron oxide and 30 % J * -alumina.

The flowability of the spherical iron oxide is not as low as that of the <£ -alumina used in Example 1, since it has a higher average particle size and the particles are smoothly rounded when compared to the compares angular particles of eC-alumina. Therefore the spherical iron oxide is not as effective at lowering the

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Flowability of the mixture, as is the case with cC-aluminum oxide in example 1 is.

The mixture (3) of this example with 70 wt.% Spherical iron oxide and 30 wt.% ^ Alumina! which produces the maximum central tensile stress of 50 MPa, has a melt flow of 78, which is higher than the optimum FlieSrähigkeit of 74 of the mixture of 70 wt.% Jj alumina and 30 wt.% X-alumina, the high central tensile stress in the Example 1 generated.

However, the maximum central tensile stress generated by the mixture (3) in the present example is approximately that same as the maximum central tension produced with the Example 1 blend. This is the case because, although the flowability of the mixture (3) is slightly higher than the optimum flowability at which the maximum Stress is generated, the iron oxide used in the mixture (3) has a significantly higher heat capacity than that of the ^ -alumina used in Example 1 has.

Since the flowability of the mixture (3) was held to be a little too high, the mixture (4) was then made with a Proportion of cC -aluminium oxide as used in Example 1 was, ago. This reduced the flowability of the mixture to an optimum of 74 and the mixture produced a further increase in the central tensile stress to 57 MPa despite the lowering of the heat capacity.

Mixture (4) has the same optimum flowability value, namely 74, as that of 30 % ^ -alumina

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and 70 % «Ό-aluminum oxide existing mixture of Example 1, which produces a maximum central tensile stress of 49 MPa. The fact that the mixture (4) generates a higher central tensile stress of 57 MPa is due to the higher heat capacity of the mixture (4), namely 1.502 MJ / nr ^ K compared with 1.24 MJ / nrK of the mixture in Example 1 traced back.

The further, resulting from the introduction of a portion of a second cC-alumina into the mixture (5) Reduction in flowability produced a decrease in the heat capacity of the mixture compared to that Mixture (4) with a simultaneous slight reduction in the central tensile stress.

Example 6

The fluidized bed was formed from a mixture of the gas-generating particulate material aluminum monohydrate (AlgO .1H ₂ O) and zircon (ZrOg.SiO ₂ ).

The aluminum monohydrate was in the form of boehmite, which is a porous material with 15 wt.% Bound water of crystallization, and 13 wt.% Of water in its pores *. The adsorbed water released when the glass is quenched is primarily effective in providing the gas generation which results in improved movement of the particulate material in the vicinity of the olas surfaces.

The aluminum monohydrate used had the following properties:

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Average particle size Particle size distribution Flowability

Water content (weight loss at 800 ^° C.)

= 51 / µm = 1.70 = 78

= 28.4 = 1.18

Heat capacity per unit volume with minimal fluidization

The zircon, which is an inert, non-porous zirconium oxide orthosilicate higher heat capacity than oG aluminum oxide, had the following characteristics:

Average Particle Size Particle Size Distribution Flowability

Heat capacity per ■ unit of volume with minimal fluidization

= 34, µm = 1.73 = 67

3 _T

= 1.76 MJ / nTK

2.3 mm thick glass panes were heated to 660 ° C and in mixtures of the aluminum monohydrate and zirconium as they are given in Table IV, the quenched characteristics of the blends and that produced in the panes of glass lists central tension.

Table IV

Wt.% In the mixture 100 % 70 % 50 % 20 % 10 fo 0% Aluminum monohydrate 0 % 30 % 50 % 8o fo 90 % $ 100 Zirconium orthosilicate 78 75.5 7 ^ 73 71 67 Flowability of the
mixture 1.005 1.277 IN THE 1.62 1.70 1.76 Heat capacity of
Mix "per volume
unit at minimum
fluidization
MJ / nAc 37 42 44 46.5 39 23 Central tension
(MPa)

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Fig. 10 shows the change in central tension with the composition of the mixture.

Aluminum monohydrate has good gas generating properties and a lower value of the fluidity than that of the ff-aluminas given in Examples 1 and 5. However, the flowability of the aluminum monohydrate is higher than the optimal flowability, which is the maximum central one Tensile stress is generated, and the heat capacity is relatively low. Zircon has a lower flowability and a higher heat capacity than aluminum monohydrate, and as the amount of zircon in the mixture is increased, there is a continuous increase in those produced in the glass central tensile stress due to both the continuous decrease in flowability and the increase in heat capacity the mix.

Zircon has a high heat capacity that is noticeable for Increase in the central tensile stress generated in the glass panes in the same way as the spherical iron oxide in the Example 5 contributes. Since zirconium has a lower flowability than the spherical iron oxide of Example 5, it is more effective in reducing the flowability of the mixture and therefore contributing more to increasing the central tensile stress with the decrease in the value of the fluidity of the mixture.

The maximum central tensile stress of 46.5 MPa is achieved when the mixture contains about 20 % aluminum monohydrate and 80 % zircon, which mixture has a flowability of an optimum value of 73.

Further addition of zircon in the amount of about 80 wt.% Increases the thermal capacity of the mixture, however, leads to a decrease of the central tensile stress due to

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noticeable reduction in the flowability below the optimum value and the reduction in the proportion of gas-generating Constituent, aluminum monohydrate, to a less effective level.

Example 7

The fluidized bed was formed from a mixture of ^C-0 AIuminiumoxid with equal proportions of each of four designated with A, B, C and D in Table V ^ aluminas showing the characteristics of the aluminas fr.

Table V

A. B. T-aluminas D. Average particle
size (/ um) 70 61 C. 72 Particle size distrib
lung 1.47 1.67 57 1.65 Fluidity 88.5 88 1.66 86 Water content (wt. ^)
Loss at 800 ^° C 7th 7th 85 7th Heat capacity each
Volume unit at
Minimal fluidization
(JM / m ^ K) 1.16 1.16 7th 1.12 1.12

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The properties of the - ^ - aluminum oxide were as follows: Average particle size = 22 / µm

Particle size distribution = 1.69

Flowability = 63

per volume unit _, _{ä MT /} J

Heat capacity per unit volume with minimal fluidization

Glass panes of a soda-lime-silica composition of 2.3 rora thickness were heated to 660 C and in by gas fluidized mixtures of the above materials, which are quenched in a calm, uniformly expanded particle fluidization state was.

The properties of the mixtures and the resulting central tensile stresses generated in the glass panes are given in Table VI.

Table VI

% By weight in the mixture 100 % 40 % 20 % 10 % o % Mixture of 4 Γ aluminum
mineral oxides 0 % 60 % 80 % 90 % 100 % cC -alumina 87 70 67 65 63 Flowability of the
mixture 1.14 1.20 1.22 1.23 1.24 Heat capacity of
Mixture per volume
unit at Mini
malfluidization
(MJ / nrTC) 39 40 ³⁵ ! 31 25th Central tension
(MPa)

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Fig. 11 shows the change in central tension with the composition of the mixture.

The previous examples passed like higher voltages Mixtures of a gas generating particulate material with an inert material can be created as per can be achieved using the gas generating particulate material alone. However, it may be desirable to produce lower voltage values than would be achieved using the gas generating particulate material are available alone.

In this example this is done using an oC alumina with a small average particle size and a relatively wide particle size distribution is achieved, resulting in a markedly lower Lead flowability than that of the ^ -aluminum oxides used in the previous examples.

The maximum central tensile stress generated was 40 MPa using a mixture of 40 % ^ -alumina and 60 % oC -alumina with a flowability of 70. This is only slightly higher than the central tensile stress of 39 MPa which is obtained using the <* - -Alumina alone was produced.

A progressive addition of further α-aluminum oxide in the mixtures rapidly reduces their flowability to such low values that the central tensile stress generated in the glass panes is lower than that generated using the X- aluminum oxides alone.

030010/0774

2933U1

Example 8

The fluidized bed was formed from a mixture of 9% by weight of zeolite, which is a porous, crystalline aluminosilicate with water adsorbed in its pores, and 91% by weight of th -alumina.

The Zeollth had the following characteristics:

Average particle size = 24 µm

Particle size distribution = 4

Flowability = 51

Water content (weight loss at _on y

800 ⁰ C) = 20 <&

Heat capacity per unit volume _ η fl μ

with minimal fluidization " ^υ * ° ¹

The «^ -alumina had the following properties:

Average particle size = 57 / µm

Particle size distribution = »1.682

Flowability »70

Heat capacity per volume unit _, ^ μ

with minimal fluidization ~ '

The heat capacity per unit volume with minimal fluidization of the mixture was 1.34 MJ / πΛζ, and the flowability of the mixture was 60.

A 2.3 mm thick glass pane was ^{heated to 660 °} C. and quenched in the fluidized mixture, as a result of which a central tensile stress of 41 MPa was generated in the pane. By varying the selected proportions of the components of the

030010/0774

ORlQlNAL INSPECTED

- 4γ -

Mixing, a central tensile stress within the range of 25 to 41 MPa could be generated in the disk.

Example 9

The mixture of particulate material to fluidize had 20 wt.% "^ Alumina and the 40 wt.% Of two« ^ -Aluminiumoxidsorten, which were readily available and instead of a single rare d / -Aluminiumoxidsorte were used.

The properties of the ff - alumina were as follows:

Average particle size = 57 µm

Particle size distribution = 1.66

Flowability = 85

Water content (weight loss at "^ 800 ⁵ C) = 7 %

Heat capacity per unit volume. _{ia MT /} 3 "with minimal fluidization - i.iö MJ / m κ ..

The properties of the two aluminum oxides, A and B, are given in Table VII.

Table VII

ovV - aluminum oxide Mean particle size (/ um)
Particle size distribution
Fluidity
Heat capacity per unit volume
with minimal fluidization (MJ / iAc) AWAY 38 24
1.19 1.25
75 66
1.14 1.19

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The flowability of the mixture was 73.5 and its heat capacity per unit volume at minimal fluidization was 1.25 MJ / m ^ K.

A 2.3 mm thick glass pane was ^{heated to 660 °} C. and quenched in the fluidized mixture, the central tensile stress generated in the pane being 48 MPa. By varying the selected relative proportions of the components of the mixture, a selected central tensile stress in the range of 34 to 48 MPa could be generated in the disk.

Example 10

The versatility of the method according to the invention is further enhanced by adjusting a mixture with the aid of the Mixing multiple gas generating ingredients and multiple inert ingredients illustrated, all of which are available and relatively cheap materials are a mixture with gas generating properties and a to generate optimal flowability as well as heat capacity, with which the necessary stresses in the in this Mixture quenched glass can be achieved when it is in a calm, uniformly expanded particle fluidization state is located.

In this example, the mixture contained per 5 wt.% Of four oC -Aluminiumoxidsorten, A, B, C and D, whose properties are listed in Table VIII.

030010/0774

- 49 Table VIII

If -alumina A. B. C. D. Average particle size
(/ »Ο 70 61 57 72 Particle size distribution 1.47 1.67 1.66 L, 65 Fluidity 38.5 88 85 86 Water content (wt. ^ Ver
lust at 800 ⁰ C 7th 7th 7th 7th Heat capacity per volume
unit for minimal fluid
ization (mj./πκΚ) 1.16 1.16 1.12 1.12

This total amount of 20 percent. # ^ Of alumina was Ό aluminas E, F and G each mixed with 26.67 wt.% Of three ', whose properties are listed in Table IX.

Table IX

oC aluminum oxide F. G Mean particle size (/ um) E. 30th 24 Particle size distribution 38 1.22 1.25 Fluidity 1.19 70 66 Heat capacity per volume
in the case of minimal fluidization
(MJ / m ⁵ K) 75 1.3 1.19 1.38

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The flowability of the mixture was 74 and its heat capacity per unit volume at minimal fluidization was 1.26 MJ / m ^ K.

A 2.3 mm thick glass pane was ^{heated to 660 °} C. and quenched in the fluidized mixture, the central tensile stress generated in the pane being 49 MPa .

Performing, by varying the proportions of the selected along 20% of the mixture ft aluminas or by varying the proportions of 80 wt.% Of the mixture constituting cC-aluminas or by varying the relative proportions of the total ^ ¹ to the entire alumina c (/ alumina A selected central tensile stress in the range from 32 to 49 MPa could be generated in the mixture.

Example 11

The fluidized particulate material consisted of 17% by weight of the aluminummonohydrate of Example 6 mixed with 83% by weight of a silicon carbide having the following characteristics..:

Average particle size = 40 µm

Particle size distribution = * 1.32

Flowability = 72.75

Heat capacity per unit volume _{Λ ol} u

with mini-fluidization " ^l ' ^dl " «

The flowability of the mixture was 75 and its heat capacity per unit volume at minimal fluidization was 1.02 MJ / m ^ K.

030010/0774

293343

A 2.3 mm thick glass sheet was heated to 660 ⁰ C and cooled in the fluidiserten mixture whereby a central tensile stress of 51 MPa was produced in the disc. These materials provided the ability to produce a selected central tensile stress in a wide range of 32 to 51 MPa by selecting the predetermined proportions of the components of the mixture to tune the fluidized mixture to produce the required stress in the glass.

Example 12

In a two component mixture, both particulate materials can have gas generating properties. It became a mixture of equal parts by weight of

J ¹ aluminum oxide and aluminum trihydrate (AIpO .3HpO). A part of the water of crystallization of the aluminum trihydrate is given off when it is heated, which is added to the effect of the water released from the pores of the p-aluminum oxide.

The properties of the f -alumina were as follows:

Average part size = 60 µm

Particle size distribution = 1.9

Flowability = 84

Water content (weight loss at _Q ^

800 ⁰ C) ^{= ö%}

Heat capacity per volume unit _. _{nK MT} , 7) _v with minimal fluidization -J- »";? rcj / m-κ ..

030010 / 077A

The properties of the aluminum trihydrate were as follows:

Average particle size = 86 / µm

Particle size distribution = 1.42

Flowability = 86

Water content (weight loss at _, ι, ^

800 ⁰ C) - ^%

Heat capacity per unit of volume at _, ^ f- _MT / _3 _V

Minimal fluidization "^{1> 5} ° ^{nd / m Km}

The flowability of the mixture was 85.25, and theirs Heat capacity per unit volume with minimal fluidization was ^

mm
A 2.3Vclick glass pane was heated to 660 C and

quenched in the fluidized mixture and the central tensile stress created in the disk was 47 MPa. It could a selected central tensile stress in the range of 42 to 47 MPa in the glass sheet by suitable selection of the relative proportions of the two gas-generating materials are generated.

Example 13

Gas generating particulate materials that give off gases other than water vapor when heated, for example sodium bicarbonate (NaHCO,), which gives off carbon dioxide as well as water, can also be used. % A mixture of 10 wt.% Of a 0.6 wt. Colloidal silica to improve its flowability containing sodium bicarbonate with 90 wt.% Of alumina rC A from Example 9 was

030010 / 077A

used. The properties of the mixture of sodium bicarbonate and colloidal silica were as follows:

Average particle size = 70 / µm

Particle size distribution = 1.98

Flowability = 75

H ~ 0 + C0_ content (weight loss -, "^

^{2 2} at 800 ⁰ C) = 37%

Heat capacity per unit volume at _, I _{11 MT /} 3

Minimal fluidization - i, * u rw / m

The flowability of the fluidized mixture was 75 and its heat capacity per unit volume at minimal fluidization was 1.38 MJ / M ^ K.

A 2,3ydicke glass sheet was heated to 66Ο ⁰ C and then quenched in the fluidised mixture, and the central tensile stress generated in the disc was 53 * 5 MPa. By suitable selection of the relative proportions of the constituents of the mixture, it was possible to generate a selected central stress in the range from Jk to about 55 MPa in the glass pane.

In many of the examples, an indication of the in the glass when quenching is in the fluidized mixture of particulate Materials generated stresses specified as the stresses in a 2.3 mm thick, heated to 660 C and then Quenched disk made of soda-lime-silica glass. Ih the same way as in Examples 2, 3 and described, different voltages can be created by variation

030010/0774

the temperature to which the glass is heated, and proportionally higher stresses will be in thicker ones Glass produced.

The examples all illustrate how the selection of a portion of a gas-generating particulate material that is suitable for the development of 4-47% of its own weight of gas when heated to constant weight at 800 ⁰ C, and then mixing this gas generating material in predetermined proportions balance the mixture with other gas generating particulate materials or with inert materials

to generate a desired flowability in the range from 60 to 86 and a heat capacity per unit volume with minimal flow in the range from 1.02 to 1.75 MJ / nrK. allow, which ensures that the glass sheet quenched in the mixture is thermally toughened to the required degree, as indicated in the examples by the central tensile stress. As is customary with thermally toughened glass, the ratio of the surface ^{compressive stress U3 to the} central tensile stress is of the order of magnitude of 2: 1, and the surface compressive stress generated is usually about twice the stated central tensile stress.

By using the method according to the invention the bias conditions can be easily reproduced and it is possible to make use of a wide range of particulate materials as they are available, and mixtures of cheaper and more readily available particulate materials instead of scarcer and more

030010/0774

to use expensive individual components of the mixture, so that the running cost is reduced.

Further it is through suitable selection, the particulate Materials and the proportions in which they are mixed are possible, higher bias voltages selected in the glass than creating the stresses achieved with any component of the mixture used alone could.

Some of the particulate materials described above were commercially available with, an appropriate average particle size, particle size distribution, flowability and thermal capacity.

If these properties of the required material, e.g. B. ^r £ -alumina, were not present in commercial materials, sieving is used to produce classified particulate materials having the properties required for mixing with other ingredients to produce a mixture which, when fluidized, produces the necessary bias values in the glass.

The fluidized mixtures of Examples 1 to 4 and 1 ~ *> have been found to be particularly suitable for the thermal toughening of glass panes for lamination in the manufacture of motor vehicle windshields. The flowability of such mixtures is in the range from 71 to 85, their gas content, expressed as weight loss when heated to constant weight at 800 ^° C., is in the range from % to 37 %, and their heat capacity per unit volume with minimal fluidization is in the range of 1, 09 to 1.58 MJ / m ^ K.

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A selection of the proportions of the components of the mixture is also possible for generating lower stresses in the glass than those generated by the gas-generating component alone. Example J illustrates this.

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Claims (1)

Claims (Iy method of heat treatment of glass in which the glass heated to a predetermined temperature and contacted with a particulate material fluidized by gas, characterized in that the particulate material is a mixture of a number of selected particulate materials are used, at least one of the particulate materials having gas generating properties When heated by the hot glass picks out and the materials in selected predetermined Proportions mixed that the gas fluidized mixture of the particulate materials has such a heat capacity and impart fluidity so that a required heat treatment of the glass is achieved. 2. The method according to claim 1, characterized in that the materials are mixed in such selected predetermined proportions as to provide the required stress loads are introduced into the pane of glass when they are in the particulate fluidized by gas! Material of one temperature cools above its pre-stress-relaxation point. 3, method according to claim 2, characterized in that a material is selected as the gas-generating particulate material which is suitable for the development of 4 to 37% of its own weight in gas when heated to a constant weight at 800 ⁰ C, and the particulate materials in mixed in predetermined proportions, which give the mixture a heat capacity per unit volume with minimal fluidization in the range of 1.02 078 (50662) TP 30010/0774 293343 to 1.75 Mj / m and a flowability in the range of 60 to 86. 4. The method according to claim 3 for heat pre-stressing a pane of soda-lime-silica glass with a thickness in the range from 2 to 2.5 mm, in which the glass pane is ^{heated to a temperature in the range from 610 to 680 0} C and the mixture holds in a steady, uniformly expanded particle fluidization state, characterized in that the particulate material / is used to generate a central tensile stress in the range of 35 to 57 MPa in the glass pane. 5. The method according to claim 3 or 4, characterized in that the particulate materials are mixed in predetermined proportions which give the mixture a flowability in the range from 71 to 83 and a heat capacity per unit volume with minimal fluidization in the range from 1.09 to 1.38 Give Mj / m ⁵ K. 6. The method according to any one of claims 1 to 5, characterized characterized in that it is used as a gas-generating particulate Material * T-aluminum oxide used. 7. The method according to claim 6, characterized in that one uses mixed with J / aluminum oxide t 'aluminum oxide. 8. The method according to claim 7, characterized in that a mixture of 7 to 86 wt. % If aluminum oxide and 93 to 14 wt. % EC aluminum oxide is used. 030010/0774 ORIGINAL INSPECTED 9. The method according to claim j3 or 4, characterized in that placing a hot sheet of glass in a gas fluidized mixture of a gas generating particulate material and quenching at least one particulate metal oxide whose heat capacity per unit volume at minimal fluidization is in the range of 1.76 to 2.01 MJ / nrK, and the particulate materials are mixed in predetermined proportions, that of the mixture has a heat capacity per unit volume bet minimal fluidization in the range from 1.27 to 1.76 Mj / nrK and impart a flowability in the range of 71 to 82. IC. Method according to claim 9 »characterized in that one as particulate metal oxide spherical iron oxide (<-Pe 0,) used. 11. The method according to claim 10, characterized in that a mixture with J> is used from 0 to 70 wt.% Nodular iron oxide. 12. The method according to claim 11, characterized in that a mixture with 70 to 30% by weight of f -aluminum oxide is used as the gas-generating material. 15. The method according to claim 11, characterized in that a mixture of 28 to 35 wt. % Spherical iron emide and 45 to 56 wt. % OC aluminum oxide, the remainder X aluminum oxide is used as the gas-generating material. 14. The method according to claim 9, characterized in that man as te: used. _{zirconium (ZrO?} .SiO _p ) is used as a particulate metal oxide 030010/0774 ORIGINAL INSPECTED 15. The method according to claim 14, characterized in that a mixture of 10 to 70 wt.% Aluminiununonohydrat (Al _2. O., IH ₂ O) used as the gas generating material and 90 to 50 wt.% Zirconium. 16. The method according to any one of claims 1 to 4, characterized in that as the gas-generating particulate Material used an aluminosilicate. 17. The method according to claim l6, characterized in that there is used as the aluminosilicate zeolite and 8 to 10 wt.% Of zeolites having 90 to 92 wt.% Alumina mixed ° L for illustrating the mixture. 18. The method according to any one of claims 1 to 4, characterized in that aluminum monohydrate (Al ₂ O, .IH ₂ O) is used as the gas-generating particulate material. 19. The method according to any one of claims 1 to 4, characterized in that one mixture of silicon carbide (SiC) and a gas generating particulate material is used. 20. The method according to claim 19 * characterized in that as the gas-generating particulate material is aluminum monohydrate (Al ₂ O - lH-0 ,.) used and the mixture 17% by weight of aluminum monohydrate and 83 wt% of silicon carbide contains... 21. The method according to any one of claims 1 to 4, characterized in that aluminum trihydrate (Al ₂ O, .3H ₂ O) is used as the gas-generating particulate material. 030010/0774 ORIGINAL INSPECTED 22. The method according to any one of claims 1 to 4, characterized in that a mixture with two gas-generating particulate materials, namely aluminum trihydrate (Al ₂ O, .3HpO) and X aluminum oxide is used in equal parts. 23. The method according to any one of claims 1 to 5, characterized characterized as being the gas generating particulate Material sodium bicarbonate (naHCO ^) used. 24. The method of claim 2J5, characterized in that mixing for illustrating the mixture of 10% alumina oG wt.% Sodium bicarbonate and 90 wt.. 25. Apparatus for heat treatment of glass according to a method according to claim 1, comprising a container for fluidized by gas particulate material, one associated with the container Gas supply device for maintaining the plumbing state of the particulate material and an organ for arranging hot glass in the container, characterized in that the container (18) is fluidized by gas Mixture (17) of selected particulate materials, at least one of which when heated by the hot glass (6) has gas generating properties, and the particulate materials in selected predetermined Proportions are mixed which give the mixture fluidized by gas such a heat capacity and fluidity, that a required heat treatment of the glass can be achieved. 26. Heat-treated glass, characterized in that it is produced according to a method according to any one of claims 1 to 24 is. 030010/0774 ORIGINAL INSPECTED -S- 27.Thermally pre-stressed flat glass pane, characterized in that that it is produced according to a method according to any one of claims 1 to 24. 030010/0774 ORIGINAL INSPECTED