Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/1005—Forming solid beads
  • C03B19/104—Forming solid beads by rolling, e.g. using revolving cylinders, rotating discs, rolls
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/1005—Forming solid beads
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/1005—Forming solid beads
  • C03B19/102—Forming solid beads by blowing a gas onto a stream of molten glass or onto particulate materials, e.g. pulverising
  • C03B19/1025—Bead furnaces or burners
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/1005—Forming solid beads
  • C03B19/1055—Forming solid beads by extruding, e.g. dripping molten glass in a gaseous atmosphere
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/109—Glass-melting furnaces specially adapted for making beads
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/1095—Thermal after-treatment of beads, e.g. tempering, crystallisation, annealing

Definitions

• the invention relates to a method for producing glass spheres by solidification from a glass melt, the transformation range of which lies at a temperature T G. Furthermore, the invention relates to a device for producing glass spheres comprising a container for glass melt having an outlet nozzle and a cooling device.
• glass balls are used for. B. with special optical, electrical, mechanical or chemical properties are required, which on the one hand should have a high quality with respect to the spherical shape and on the other hand a grain size spectrum, the scattering of which is small.
• the present invention is based on the problem of a method and an apparatus for producing corresponding glass spheres by solidifying glass to provide melt, in particular given a high quality with respect to the spherical shape and the scattering of the grain size spectrum should be small. Furthermore, simple measures are to be used to open up the possibility that the glass spheres exhibit desired and reproducible chemical and / or physical properties.
• the problem is essentially solved in that the glass melt is thermally or chemically tempered, that the solidified glass melt is broken into pieces of glass, that the pieces of glass are melted and moved along a free path of a length such that the surface tension of the molten glass pieces this forms into glass balls, and that the balls thus formed are then cooled.
• the glass melt is formed as a glass ribbon and then thermally or chemically tempered.
• the glass ribbon which can also be called flat glass, is produced from a glass melt.
• the size of the glass pieces to be produced and thus the glass balls to be obtained are influenced by the thickness of the flat glass produced.
• a glass melt can be spread out under the influence of gravity, viscosity and surface energy.
• the shaping takes place according to a proposal without mechanical treatment or machining.
• Parameters that influence the resulting glass strip thickness include the composition of the melt and the temperature at which the glass melt leaves the melting furnace.
• glass melt preferably by two counter-rotating water-cooled rollers are given.
• a glass tape thickness between 3 and 15 mm can be achieved here.
• the glass thickness itself can be adjusted via the amount of glass flowing out per unit of time and the speed of rotation of the rollers.
• the glass ribbon is formed from the glass melt by pulling it vertically upwards.
• Achievable glass thicknesses with a corresponding drawing process are between 0.6 mm and 6 mm.
• the thickness of the glass ribbon depends in particular on the drawing speed.
• a melt with or without bubbles can be used to influence the density of the glass.
• a bubble-rich melt leads to a low density, from which light glass balls can be obtained.
• the glass melt is placed in the form of a ribbon on a cooling surface that is preferably moving and rotating.
• a cooling surface that is preferably moving and rotating.
• This can be a water-cooled cylinder, if necessary.
• the following options are available for pre-tensioning the glass ribbon, in order to subsequently extract the glass pieces that are transferred into the glass ball.
• the glass ribbon produced almost structure to a temperature above the transformation range of a Tempera ⁇ or a temperature range T G cooled and then blown through to ⁇ as-quenched metal plates with cold air or by pressing it onto cold plates.
• the transformation range T G of a glass is the temperature range at which the supercooled glass melt changes from plastic to the brittle state typical of glass.
• the glass solidifies faster on the surface than on the inside.
• the glass structure is therefore less dense in the area near the surface than in the interior of the glass body.
• a state of tension is formed in which a compressive stress is present in the glass surface, while the interior of the glass body is under tension.
• the glass is destroyed into small regular fragments due to the tensile stress existing inside the glass body.
• the size of the glass pieces or crumbs can be determined or set beforehand with the thermal prestressing.
• the preload itself depends on
• the achievable temperature difference between the glass surface and the inside of the glass ribbon that is, inter alia, the glass thickness and the thermal conductivity of the glass
• So z. B. with soda lime silicate glass can be tempered at a thickness of over 4 mm.
• the glass pieces can preferably be classified in order in this way to be able to eliminate undesired grain size deviations.
• the volume of the glass pieces or splinter particles can be specified, as mentioned, by the degree of glass bracing, by the thickness of the glass band applied to the cooling surface, the pouring speed of the glass melt onto the cooling surface and / or the speed of the moving cooling surface.
• the spherical volume of the glass spheres produced can be determined by the casting temperature, cooling surface temperature, cooling surface speed, casting speed and the cross section of the glass melt stream flowing onto the cooling surface, which in turn is predetermined by a casting nozzle. At the same time, these parameters keep the scatter of the diameter of the glass spheres produced within narrow limits.
• the thermal expansion of a glass is described by the linear coefficient of thermal expansion. In general, an average value is given over a certain temperature range.
• the coefficient of thermal expansion is between 0.5 10 "6 1 / K (SiO 2 glass) and 15.0 10 " 6 1 / K (B 2 O 3 glass) in a temperature range of 0 up to 200 ° C. Glasses with a Thermal expansion coefficients ⁇ ⁇ 6 10 " ⁇ 1 / K are called hard glasses, glasses with ⁇ > 6 10 " 6 1 / K as soft glasses.
• Pure SiO 2 glass has the greatest thermal conductivity. If further oxides such as sodium oxide are inserted into the glass composition, the thermal conductivity of the glass is reduced by the formation of separation points in the glass structure.
• the use of a glass with the lowest possible thermal conductivity is advantageous.
• the temperature compensation between the glass surface and inside immediately after quenching the. Glass surface is thus delayed accordingly. As a result, there is a large temperature gradient in the glass.
• a glass ribbon z. B. can be cooled from a soda-lime silicate glass to a temperature below the transformation range T G.
• the compressive stresses in the surface of the glass are generated by replacing the alkali ions in the glass surface with alkali ions with a larger ion radius.
• the initial glass a sodium-containing silicate glass
• the potassium-containing glass melt Due to the diffusion of the sodium ions from the glass into the molten salt and the potassium ions from the molten salt into the glass, the larger potassium ion is incorporated into the glass. This causes compressive stress in the glass surface.
• the amount of the preload depends on the difference in radii of the alkali ions involved in the ion exchange.
• a chemical prestress can also be carried out with a silicate glass containing lithium, which is immersed in a salt melt containing sodium, sodium and potassium or in a potassium salt for ion exchange.
• the size of the radius difference of the ions involved in the exchange can thus be selected.
• thin glass strips which cannot be thermally tempered, can be tempered using this method.
• the method according to the invention also opens up the possibility of producing not only dense glass spheres but also porous ones.
• the glass spheres produced such as, for. B. borosilicate glass balls are first annealed for solution separation, then at the annealed balls a wet chemical treatment such. B. in the aforementioned glass to etch out the boron oxide portion.
• ⁇ through results in a sphere of desired porosity.
• a further idea of the solution according to the invention provides that a porosity treatment takes place before the balls are produced, that is to say after the glass pieces or the chips have been obtained.
• the glass pieces or the chippings can first be annealed and then subjected to a wet chemical treatment, in order to subsequently melt the glass pieces or the chippings treated in this way, so that the spherical shape is established due to the surface tension.
• the glass spheres produced in this way can have a solid or porous inner zone or core with a closed or partially closed outer shell.
• Sodium borosilicate glasses are particularly suitable for the production of porous glass balls.
• the glasses can have the following compositions:
• Glasses of these compositions can be annealed at temperatures of 500-650 ° C. It is separated in the smallest areas of the glass. A phase which is easily soluble in acid is formed.
• a glass with approximately 96% by weight SiO 2 is obtained which contains continuous pores.
• the specific surface of the porous glass can be influenced by the heat treatment for the separation process and is between 100 and 300 m 2 / g. This glass can be sintered together at temperatures of approximately 1100 ° C.
• a device for producing glass spheres comprising an
• the container for glass melt having a nozzle and a cooling device is characterized in that the cooling device is a moving cooling surface on which the glass melt solidifies, that a crushing element is provided for destroying the solidified flat glass melt to obtain pieces of glass, and that the crushing element is followed by a free-falling or flying-through section for the glass pieces which merges into or is a heating zone which is followed by a cooling zone.
• the cooling surface is the surface of a heat sink in the form of e.g. B. a cylinder or a band.
• the heat sink itself is subjected to a rotational or translational movement.
• Another proposal of the invention provides that the heating zone is preceded by a classifier.
• the heating and / or cooling zone is the area of a collecting container and column, which has a glass ball discharge on the bottom.
• a glass melt (14) is located in a melting or casting container (12), preferably surrounded by insulation (10), the temperature of which is determined by means of a Heating (32) is set.
• the container (12) has an outlet nozzle (16).
• the glass melt stream flowing out of the container (12) reaches a cooling surface (18) in order to solidify there in the form of a glass band (20).
• the thickness S of the glass ribbon depends on the size of the sphere to be produced. The range can be in the um or mm range
• the cooling surface (18) is the peripheral surface of a cooling body in the form of a cooling cylinder (22) which is set in rotation, so that a peripheral speed v k results.
• a cooling device (24) is provided so that the cooling surface (18) has a desired temperature difference ⁇ T k to the temperature T ⁇ of the glass melt.
• a crushing element (26) is provided so that the glass band (20) that moves along the outer circumference of the cylinder (22) is destroyed to pieces of glass with a grain size S '.
• the breaking element (26) is in the position in which the destroyed glass, that is to say the glass pieces with the grain size S ', can fall freely from the surface of the cylinder (22).
• a classifier (28) can be provided in order to produce glass spheres with little scatter in the grain size spectrum. However, this is not mandatory.
• the glass pieces After the glass pieces have passed through the classifier (28), they fall through a heating zone (30) in free fall, in which the glass pieces are melted to the extent that they are formed into spheres under the effect of their surface tension.
• the heating zone is preferably run through in free fall, a desired trajectory can also optionally be specified.
• the heating in the heating zone (30) is carried out by a heater (32), which can be an electric heater, a gas heater or a plasma burner.
• the glass pieces now having a spherical shape After passing through the heating zone (30), the glass pieces now having a spherical shape enter a cooling zone (34) in which the glass spheres solidify. Cooling (38) is provided for this purpose. The balls then arrive at a ball discharge (36), where they are removed.
• the heating zone (30) and the cooling zone (34) can be sections of a container such as a column which has the ball discharge (36) on the bottom.
• Calcium silicate glasses can preferably be used according to the invention. These glasses comprise the largest proportion of the industrially manufactured glasses. Typical compositions and properties of these glasses are:
• Viscosities ⁇ 10 7 - 6 : 710 -735 ° C (processing range)

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Glass Compositions (AREA)
• Surface Treatment Of Glass (AREA)
• Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=6449449

Family Applications (1)

Country Status (4)

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Family Cites Families (14)

• 1992
  • 1992-01-14 DE DE19924200674 patent/DE4200674A1/de not_active Withdrawn
• 1993
  • 1993-01-13 EP EP93902179A patent/EP0621856A1/de not_active Withdrawn
  • 1993-01-13 WO PCT/EP1993/000054 patent/WO1993014037A1/de not_active Application Discontinuation
  • 1993-01-13 JP JP5512136A patent/JPH07505113A/ja active Pending

Non-Patent Citations (1)

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