Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/04—Re-forming tubes or rods
  • C03B23/053—Re-forming tubes or rods by centrifuging
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/04—Re-forming tubes or rods
  • C03B23/043—Heating devices specially adapted for re-forming tubes or rods in general, e.g. burners
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/04—Re-forming tubes or rods
  • C03B23/045—Tools or apparatus specially adapted for re-forming tubes or rods in general, e.g. glass lathes, chucks
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/04—Re-forming tubes or rods
  • C03B23/07—Re-forming tubes or rods by blowing, e.g. for making electric bulbs
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/04—Re-forming tubes or rods
  • C03B23/08—Re-forming tubes or rods to exact dimensions, e.g. calibrating
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/02—Pure silica glass, e.g. pure fused quartz
  • C03B2201/03—Impurity concentration specified
  • C03B2201/04—Hydroxyl ion (OH)
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2203/00—Production processes
  • C03C2203/40—Gas-phase processes
  • C03C2203/42—Gas-phase processes using silicon halides as starting materials
  • C03C2203/44—Gas-phase processes using silicon halides as starting materials chlorine containing

Definitions

• the invention relates to a method for producing a quartz glass tube by multi-stage molding, wherein in a first molding step using a mold, an intermediate cylinder made of quartz glass with an intermediate cylinder wall thickness and an intermediate cylinder outer diameter is formed and then cooled, and in a At least one longitudinal section of the cooled intermediate cylinder of a heating zone is fed to the second forming step, heated zone by zone to a softening temperature, and converted around its longitudinal axis to form the quartz glass tube with an end wall thickness and an end outside diameter.
• a quartz glass hollow cylinder By forming a quartz glass hollow cylinder in two or more forming stages, an increase in the tube outer diameter or a change in its cross-sectional profile is effected.
• the forming in several stages facilitates compliance with the specified radial dimensions such as outer diameter, inner diameter or wall thickness of the withdrawn pipe string.
• a generic two-stage forming process is known from DE 10 2007 061 609 A1.
• a first forming step which is referred to as "upsetting”
• an output cylinder of quartz glass rotating around its longitudinal axis is partially softened in a front heating zone produced by electrical heating, while being compressed by a mandrel fixed in the cylinder longitudinal axis and at the same time with its cylinder outer casing pressed against a molded part, which is arranged at a predetermined distance from the mandrel, thereby forming a hollow, cylindrical intermediate product of softened quartz glass generates, the inner diameter of the mandrel and its outer diameter determines the molding.
• the gap between mandrel and molded part defines the desired wall thickness of the hollow intermediate product.
• the intermediate product As soon as the intermediate product has reached a certain degree of dimensional stability, it is subjected to the second forming step, referred to as "inflation", in which the hollow intermediate product is continuously fed to a rear heating zone, also produced by electric heating, softened therein, and by applying a From there, a thin-walled quartz glass tube with an outer diameter of 305 mm in the direction of the tube longitudinal axis is withdrawn, whereby the "peeling" in an axial stabilization of the quartz glass tube can be exhausted without that the Quartz glass tube further elongating tensile force is applied to the quartz glass tube.
• inflation in which the hollow intermediate product is continuously fed to a rear heating zone, also produced by electric heating, softened therein, and by applying a From there, a thin-walled quartz glass tube with an outer diameter of 305 mm in the direction of the tube longitudinal axis is withdrawn, whereby the "peeling" in an axial stabilization of the quartz glass tube can be exhausted without that the Quartz glass tube
• a discontinuous two-stage forming process in order to produce a quartz glass tube made of synthetic quartz glass, a quartz glass is produced in a first forming stage. Glass block converted into a thick-walled hollow cylinder. The hollow cylinder is inflated in a second forming stage to a thin-walled quartz glass tube. In this case, the thick-walled hollow cylinder is clamped in a horizontal orientation in a glass lathe and softened zone by zone by means of a narrow induction-heated graphite heating element which is moved continuously along the hollow cylinder longitudinal axis.
• the softened area is elongated and at the same time inflated by applying a gas internal pressure without contact to a mold to a thin-walled quartz glass tube having a large outer diameter.
• a gas internal pressure without contact to a mold to a thin-walled quartz glass tube having a large outer diameter.
• the non-contact inflation of the hollow cylinder in the last forming step avoids drawing strips and similar defects, as they occur when using molds.
• compliance with a given dimensional accuracy of the withdrawn quartz glass tube proves to be problematic in this procedure.
• a solution to this problem is provided by a method variant known from JP 2004 149325 A, in which the last forming stage is repeated several times, so that the final diameter of the quartz glass tube is obtained by gradual enlargement. The diameter increase takes place by rotating the zonewise softened starting tube under the effect of centrifugal force.
• each enlargement step offers the possibility of taking into account and correcting existing deviations in the respective output tube.
• this procedure requires a lot of time and energy, but this is justifiable in the case of large quartz glass tubes and very high dimensional stability requirements.
• Geometry fluctuations increase exponentially with the outer diameter of the tailpipe.
• the larger the tailpipe diameter the more difficult it is to produce a dimensionally stable large pipe. It is therefore an object of the invention to provide a method that allows the production of quartz glass tubes at economically justifiable expense, which have a high dimensional accuracy, even with a large outer diameter of more than 500 mm.
• a molding tool is used in the first molding step, so that an intermediate cylinder having a defined outside diameter is obtained.
• the mold is, for example, mold baking, as described above, or a drawing die, as used in drawing quartz glass tubes from a crucible. In the latter case, a viscous quartz glass mass is formed by means of the die in a quartz glass strand.
• the problem with the second forming step is to achieve an economically acceptable degree of deformation - that is, to increase the outer diameter of the intermediate cylinder - while maintaining a predetermined dimensional accuracy.
• the second forming step may also be divided into several sub-forming steps with a lower degree of deformation, as is known from the above-mentioned prior art.
• the hydroxyl group content of the silica glass and its axial distribution over the length of the intermediate cylinder are crucial parameters.
• the hydroxyl group content of quartz glass has an effect on its viscosity. Accordingly, gradients in hydroxyl group concentration upon softening of the silica glass cause local viscosity differences in the intercylinder wall which can lead to undesirable and unpredictable deformations. This effect is further enhanced by the fact that the hydroxyl group content of the quartz glass also has an effect on the absorption of infrared radiation. A higher hydroxyl group content leads to an increased absorption and a higher radiation in the infrared wavelength range. Such quartz glass gets hotter faster and it cools faster than quartz glass with a lower hydroxyl group content. Variations in the hydroxyl group content therefore affect viscosity in several respects and lead to undesirable and barely controllable deformations in the forming process.
• quartz glass of naturally occurring raw material which generally has a low hydroxyl group content, should prove less sensitive to undesirable deformations.
• this is not confirmed in this unambiguity in practice.
• the transformation of quartz glass from natural raw material to large-scale to scale true is problematic. This can be attributed to other impurities present in the natural quartz raw material.
• Synthetically produced quartz glass usually shows a high purity, but often contains large amounts of hydroxyl groups due to the production, which can lead to unpredictable and undefined deformations at high degrees of deformation, as explained above.
• the invention now provides a method which, in compliance with narrow framework conditions, an economical processing of synthetic produced quartz glass to dimensionally large pipes allowed, even if this high degrees of deformation are required.
• the synthetic quartz glass of the intermediate cylinder has a low average hydroxyl group content of 10 ppm by weight or less, preferably 2 ppm by weight or less, and that the hydroxyl group content is longer than the inter-cylinder length is distributed so homogeneously, which differ in subdivision of the intermediate cylinder into lengths with a length of 1 cm, adjacent lengths in their average hydroxyl group content by less than 2 ppm by weight, preferably less than 1 ppm by weight, from each other.
• the production of synthetic quartz glass with such a low hydroxyl group content generally proceeds via a porous semifinished product of SiO 2 particles, which requires a drying treatment to eliminate it contained hydroxyl groups allows.
• the drying treatment of the porous SiO 2 body can be carried out purely thermally - assisted by negative pressure - or by chemical reaction with a drying reagent - such as chlorine.
• the setting of an average hydroxyl group content of less than 10 ppm by weight is less problematic than the generation of a uniform over the volume of the porous SiO 2 body concentration profile.
• DE 10 152 328 A1 describes a procedure for solving this problem, which already begins in an early phase of the production of the quartz glass tube.
• the synthetically produced quartz glass has a high average hydroxyl group content above 10 ppm by weight, it proves to be increasingly difficult to ensure the required dimensional stability of the large pile as a whole. If the axial concentration profile shows fluctuations of more than 2 ppm by weight / mm over a length of 1 cm, the second forming process will easily lead to local deviations in the wall thickness of the large pipe.
• the content of hydroxyl groups of the quartz glass is determined by measuring the IR absorption by the method of D.M. Dodd and D.B. Fräser, Optical determination of OH in fused silica, Journal of Applied Physics, Vol. 37 (1966), p. 391 1.
• the average content of hydroxyl groups of the quartz glass is determined by measuring through the pipe wall in the direction of the longitudinal axis of the intermediate tube.
• the average value of the hydroxyl group content in length sections of 1 cm is considered to be the measured value which, when measured in the geometric center of the respective length section, is obtained through the wall of the intermediate tube and perpendicular to its longitudinal axis.
• quartz glass halide starting materials are frequently used - for example SiCl 4 or halogen-containing drying reagents - for example chlorine- or halogen-containing dopants - for example fluorine. Because of this, large quantities of halogens can be contained in the synthetic quartz glass. However, it has been shown that, in addition to the hydroxyl group content, the halogen content in the second forming step old - and especially the chlorine content - can make the dimensional accuracy of the final quartz glass tube and on the bubble content noticeable.
• quartz glass is preferably used, the average chlorine concentration of less than 3000 ppm by weight.
• the chlorine concentration is determined as the mean value of test samples taken at three points uniformly distributed over the inter-cylinder length (start, middle, end) by dissolving the test samples in aqueous HF solution and the resulting solutions after addition of AgNO 3 be subjected to nephelometric analysis.
• a method variant has proven to be advantageous in which the quartz glass tube is not elongated in the second forming step, wherein the diameter increase based on centrifugal force or blowing pressure.
• holders are welded to the quartz glass cylinder to be formed on the front side, and these are clamped in the chuck of a glass lathe and rotated synchronously.
• a heating source is moved in zones along the quartz glass cylinder.
• a defined internal pressure can be adjusted in the inner bore of the quartz glass cylinder.
• the quartz glass tube is compressed in the second forming step in the direction of its longitudinal axis, so that its wall thickness after upsetting is between 70% and at most 100% of its wall thickness before upsetting.
• the aim of the second forming step is a diameter increase of the quartz glass tube while largely maintaining its wall thickness. This is achieved by shortening the initial length of the quartz glass tube in the forming step, so the output tube is compressed.
• the upsetting lies the wall thickness preferably between 70% and at most 100% of the initial value.
• the homogeneity of the temperature field and the composition of the atmosphere in the region of the heating zone have as important parameters for a reproducible forming process little control needed.
• the heating zone is formed by a plurality of annularly distributed around the circumference of the intermediate cylinder heat sources, which are selected from the group: plasma torch, gas burner, laser.
• the heating energy compared to a furnace can be set locally defined and metered faster and more accurate and thus set or corrected even a predetermined temperature field, even if it is not rotationally symmetrical.
• the heat sources are able to provide a high level of energy at specific points. At least five such heat sources are evenly distributed in a circular ring around the intermediate cylinder to be softened. Compared to an oven, the diameter of the circular ring shape can be more easily adapted to the diameter of the quartz glass cylinder to be softened, for example, even if the second forming step is divided into sub-forming steps each having a smaller degree of deformation, wherein the outer diameter of the quartz glass cylinder to be formed is gradually increased. With a view to avoiding the entry of hydroxyl groups, hydrogen-free plasma torches or CO 2 lasers are preferred.
• metal oxide impurities In addition to hydroxyl groups and halogens, metal oxide impurities also have an effect on the viscosity of the synthetic quartz glass, aluminum oxide in particular being mentioned here. Possible concentration fluctuations This contamination is the more pronounced and effective, the higher their average concentration.
• quartz glass is preferably used which has a concentration of aluminum (Al) of less than 1 ppm by weight and a total content of other metallic impurities of less than 4 ppm by weight.
• the quartz glass has a concentration of alkali and alkaline earth metal impurities of less than 0.3 ppm by weight.
• Alkali and alkaline earth ions already have a noticeable effect on the viscosity of quartz glass in a small amount and they promote its crystallization tendency.
• an initial hollow cylinder made of quartz glass is fed to an electrically heated furnace, softened in zones and continuously and rotating about its longitudinal axis with its cylinder outer shell against the mold and continuously formed by the mold to the intermediate cylinder.
• This procedure allows the production of thick-walled and yet accurate intermediate cylinders.
• An electrically heated oven generally causes higher energy costs than burner heating.
• the electric heating facilitates the maintenance of a predetermined temperature field and a low-hydrogen and hydrogen-poor atmosphere.
• an electrically heated furnace is used for the forming of the output cylinder to the intermediate cylinder.
• the dimensions of the furnace seen in the direction of the cylinder longitudinal axis are at least 500 mm and the distance between the outer wall of the intermediate cylinder and an inner wall of the furnace less than 100 mm.
• the intermediate cylinder obtained after the first forming process can be subsequently processed.
• FIG. 1 shows a device for carrying out a first forming process for the production of an intermediate tube made of synthetically produced quartz glass in a side view
• FIG. 2 shows a device for carrying out a second forming process for the purpose of producing a large pipe from the intermediate pipe in a side view.
• a hollow cylinder 1 made of synthetically produced quartz glass is provided, which satisfies high demands on its purity and on the homogeneity of the viscosity-influencing components.
• the preparation comprises the flame hydrolysis of SiCl 4 , in which SiO 2 particles are formed and deposited in layers on the cylinder jacket surface of a support rotating about its longitudinal axis to form a soot body.
• the method known from DE 10 152 328 A is used to produce a specific radial density profile within the soot body wall, that is, in the deposition of the first soot layers, a comparatively high surface temperature and thus a soot area with a comparatively high density generated by about 30%.
• the soot density then continues to gradually increase until it reaches about 32% in a "transitional area.”
• the surface temperature of the forming soot body is lowered continuously and thus the soot density reduced.
• a soot tube having a specific radial density profile is obtained.
• the soot tube is subjected to a dehydration treatment and treated in a vertical orientation in a dehydration oven initially at a temperature of about 900 ° C. in a chlorine-containing atmosphere.
• the treatment takes about eight hours. This sets a low hydroxyl group content.
• the process-related different effectiveness of the penetrating over the mantle surfaces in the soot body chlorine is compensated by the previously generated density profile, so that sets over the thickness of the wall, a substantially homogeneous, radial concentration profile for the hydroxyl groups.
• soot tube is placed in a vertically oriented vitrification furnace and treated therein with oxygen at a temperature around 1000 ° C to remove chlorine and to saturate any oxygen deficiency defects. Subsequently, the soot tube is sintered at a temperature around 1300 ° C by being fed to an annular heating zone and heated therein in zones.
• the hollow cylinder 1 thus produced (see FIG. 1) has a length of 300 cm, an outer diameter of 200 mm and an inner diameter of 40 mm. It consists of synthetic quartz glass with a low content of metal oxide impurities whose concentrations (in ppm by weight) are given in Table 1:
• the quartz glass has an average hydroxyl group content of 8.3 ppm by weight (measured over the tube longitudinal axis) and a mean chlorine concentration of 1710 ppm by weight. Viewed along the length of the thick-walled hollow cylinder, the hydroxyl group content determined at 29 measuring points at a distance of 10 cm varies by +/- 0.9 ppm by weight (standard deviation).
• the first forming step takes place by means of the method described in DE 10 2007 051 898 A1.
• FIG. 1 shows diagrammatically the device by means of which the thick-walled quartz glass hollow cylinder 1 is formed into a thin-walled intermediate cylinder 2 with an outer diameter of 320 mm, a wall thickness of 15 mm and a length of 6.20 m.
• the hollow cylinder 1 is pushed with a feed device continuously and under rotation about its longitudinal axis 3 at a feed rate of 4 cm / min in a resistance furnace 4, which surrounds the hollow cylinder 1 annular with an inner diameter of 400 mm and in zonewise to a temperature around 2100 ° C heated up.
• a (not shown in the figure) pulling device is used, which rotates the intermediate cylinder 2 about its longitudinal axis 3 rotating at a peel rate of about 12 cm / min in the direction of the longitudinal axis 3.
• the quartz glass hollow cylinder 1 is closed at its free end face with a gas-tight rotary feedthrough.
• a mold that has two water-cooled mold jaws 5, which are occupied with graphite fits (in Figure 1 only schematically indicated).
• a gas flow is introduced into the rotating quartz glass hollow cylinder 1, so that a controllable internal overpressure of about 10 mbar is established.
• the hollow cylinder 1 is thereby inflated against the mold jaws 5 to the target diameter of 340 mm, with a peripheral bead 6 forms in front of the mold jaws 5.
• the intermediate cylinder 2 can then be released from the mold jaws 5, so that the actually adjusting outer diameter may differ slightly from the distance of the mold jaws.
• a measuring and control device 13 For measuring and controlling the outer diameter, a measuring and control device 13 is shown schematically provided, the two high-resolution CCD cameras 7; 8 for detecting the longitudinal edges 10; 1 1 of the hollow cylinder 1 and 12 monitors that indicate the relative axial position of the optically detected longitudinal edges 10, 1 1.
• the control device 13 For further details of the operation of the control device 13, reference is made to DE 10 2007 051 898 A1.
• the thus obtained intermediate cylinder 2 is characterized by a defined outer diameter and overall high dimensional accuracy.
• the quality of the quartz glass corresponds unchanged to that of the hollow cylinder 1, as explained above. It is suitable as a defined starting material for the production of a large pipe.
• Second forming step for producing the large pipe Figure 2 shows schematically the apparatus for forming the intermediate cylinder 2 to the desired large pipe 22 with an outer diameter of 960 mm.
• a burner carriage 21 drives the intermediate cylinder 2 from right to left, as indicated by the directional arrow 23.
• a burner ring is mounted, which serves to heat and soften the intermediate cylinder 2.
• the burner ring 25 is formed from five gas burners which are circular and evenly distributed around the cylinder longitudinal axis 3.
• the intermediate cylinder 2 is continuously rotated under its longitudinal axis 3 at a speed of 60 rpm (corresponding to the axis of rotation) under the action of the torch ring and thus becomes high temperature 2,100 ° C heated.
• the inner bore 20 can be flushed with a gas and a defined and regulated internal pressure can be adjusted to about 100 mbar in the inner bore 20.
• the quartz glass tube (22) thus obtained serves as an intermediate cylinder 2 for further forming on the basis of the method shown in FIG.
• the intermediate cylinder 2 is gradually expanded to the quartz glass tube 22, wherein each deformation step makes a diameter widening of 65 mm or less.
• the outer diameter of the burner ring 25 can be easily adapted to the respective outer diameter of the deformation stage.
• the inflated large tube 22 has approximately the same wall thickness (100%) as the initially inserted intermediate tube 2 and is compressed to a final length of 2.976 m.
• a large tube 22 made of synthetic quartz glass with overall high dimensional accuracy is economically obtained with only two forming steps but in compliance with the above-mentioned boundary conditions with respect to the chemical composition of the quartz glass and its homogeneity.
• the wall thickness variation of the quartz glass bulk product 22 produced in this way is less than 0.42 mm per pipe length meter.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Manufacturing & Machinery (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
• Glass Melting And Manufacturing (AREA)

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Citations (10)

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• 2013
  • 2013-07-12 DE DE102013107435.9A patent/DE102013107435B4/de active Active
• 2014
  • 2014-06-25 TW TW103121820A patent/TWI565666B/zh active
  • 2014-07-08 KR KR1020167002808A patent/KR102117985B1/ko active Active
  • 2014-07-08 SG SG11201600207TA patent/SG11201600207TA/en unknown
  • 2014-07-08 US US14/904,308 patent/US20160168005A1/en not_active Abandoned
  • 2014-07-08 WO PCT/EP2014/064541 patent/WO2015004103A1/de not_active Ceased
  • 2014-07-08 EP EP14736800.5A patent/EP3019453A1/de not_active Withdrawn
  • 2014-07-08 CN CN201480039724.5A patent/CN105358494B/zh active Active
  • 2014-07-08 JP JP2016524788A patent/JP6478990B2/ja active Active

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