Title of Invention	"AN EQUIPMENT FOR THE MANUFACTURE OF THIN MULTIFILAMENT FUSED QUARTZ FIBRE STRANDS AND A PROCESS THEREOF"
Abstract	An equipment for the manufacture of thin multifilament fused quartz fibre strands characterized by a movable mount (1,2,3) such as herein described, for holding a plurality of fused quartz rods(4) within a heat zone (5) such as herein described, a coating app!icator(6) being coaxially fixed surrounding strands of fibre below the said quartz rods (4) and said heat zone(5), a perforated silica disc (4a) is provided at the top of the said heat zone(5) to act as a heat shield-cum-rod(s) guide, a known gathering mechanism(7) fixed below the said coating applicator(6), a strand winding machine(8) is fixed below the said gathering mechanism(7) for rotational and transiational movement

Title of Invention

"AN EQUIPMENT FOR THE MANUFACTURE OF THIN MULTIFILAMENT FUSED QUARTZ FIBRE STRANDS AND A PROCESS THEREOF"

Abstract

An equipment for the manufacture of thin multifilament fused quartz fibre strands characterized by a movable mount (1,2,3) such as herein described, for holding a plurality of fused quartz rods(4) within a heat zone (5) such as herein described, a coating app!icator(6) being coaxially fixed surrounding strands of fibre below the said quartz rods (4) and said heat zone(5), a perforated silica disc (4a) is provided at the top of the said heat zone(5) to act as a heat shield-cum-rod(s) guide, a known gathering mechanism(7) fixed below the said coating applicator(6), a strand winding machine(8) is fixed below the said gathering mechanism(7) for rotational and transiational movement

Full Text	The present invention relates to an equipment for the manufacture of thin multifilament fused quartz fibre strands and a process thereof: Fused quartz fibres or filaments are very good candidates for structural composites because of their unique mechanical, thermal and electrical properties. Being the lightest structural fibres they have high tensile strength in unidirectional composite, very low coefficient of thermal expansion and good electrical characteristics of high resistivity and low dielectric constant maintained over a broad temperature and frequency ranges. Some other key features of these fibres are very low moisture absorption, high temperature resistance, high hardness and high composite lifetime along with excellent resin compatibility. These fibres in textile fonns as multiple fibre yarns, chopped strands, rovings, tapes, and mats where the continuous filament diameter varies from 9 to 15 microns find wide application in advanced composites structures, electro-magnetic windows, high-speed printed circuit boards, thermal insulation blankets for furnaces and aerospace engines, high performance cables etc. Present day method of making fused quartz fibre encompasses several processes. Reference for which may be made to the product references of Fiber Materials Incorporated, USA and Quartz Silice, France wherein single filament of quartz fibre was drawn by heating the quartz rod using hydrogen/oxygen flame. Here the fuel source is costly and handling of hydrogen is not safe but the contamination from hydrocarbon fuel is eliminated. In this process the end of the rod is first softened and subsequently the rod end is pulled into thin filament of 9 to 15 micron diameter on continuous basis onto a high speed rotating drum after applying suitable sizing or coating resin. The drawbacks of the above process are: (1) Each quartz rod with one hydrogen/oxygen burner assembly produces only one filament. By placing multiple stages of parallel rods with array of hydrgen/oxygen burners the thin fused/quartz fibres are drawn coating with sizing resin and accumulated with the help of a gathering mechanism to form strand. (2) The control of diameter of the individual fibre is difficult which incurs strength degradation in the ultimate fibre strand. (3) The control of environment is cost intensive due to the explosive nature of the fuel gas. (4) Contamination by foreign matter is possible resulting degradation in the fibre tensile strength. (5) Heating by hydrogen/oxygen flame does not give uniform necking in each stage also resulting in strength degradation. (6) The requirement of space to accommodate number of rods in a oxy/hydrogen burner assembly in a row is more which effectively increases the cost of the technology. Reference may be made of the inventors J. Murach and R. Bruckner in 'Structure sensitive investigations on alkali metasilicate glass fibres', J. Non. Crystalline Solids, 204 (1996) 282-293, wherein they described a nozzle drawing method for making silicate glass fibres where the mass flow rate is a function of the furnace temperature and pressure on the glass at the nozzle head . The major disadvantages of this process are that the fibres get contaminated by the nozzle material and fibre diameter can not be controlled due to change of diameter of nozzle orifice by erosion. Further reference may be made of the inventors J. Murach and R. Bruckner, in "Preparation and structure-sensitive investigations on silica glass fibers", J. Non-Crystalline Solids, 211 (1997) 250-261, wherein they developed a process for fabricating fused silica fibers by heating the end of the rotating silica glass rod by a moving hydrogen /oxygen burner. The mass flow of the rod drawing method depends on the driving speed of the silica rod or of the heating source and suitable temperature profile. The diameters of the fibers drawn are in the range 5 to 25 micron using 5 -8 mm diameter silica rods.. In addition to all the drawbacks mentioned above this method does not help in very high speed drawing of thin silica fibres . Still further reference may be made to British Patent Nos. 1,196,331 & 1,196,332 (1970) of PPG Industries Inc., wherein thin filament of high silicate glass fibre was drawn by bushing technology. World wide technology available for production of thin fibre is based on noble metal bushing and this process technology is capital intensive specifically suitable for large scale production. Here the process involves molten glass exuding) through the bush-nozzles under gravity or certain pressure transforms into thuTfibres by dynamic balance between the forces of surface tension and mechanical attenuation. Precise control of viscosity of the molten glass is needed to reduce fibre breaking rate. The multi filaments are drawn simultaneously from the melt through bushing which is maintained at uniform temperature and subsequently the strand is wound on a high speed drum after application of sizing resin mostly for low melting glasses. For each set of fibres the temperature profile has to be adjusted as per the environmental condition. (1) This technology has the limitation for making fibre having high attenuation temperature where glass fibre containing more than 95% silica is not possible by this technology. (2) Suitable bushing for drawing high purity quartz fibre better than 95% has not been developed and reported. (3) In this conventional technology the orifice of the bushing which is made of platinum-rhodium alloys, gradually increases due to erosion during the continuous fibre drawing process and needs to be reworked. Further reference may be made of the inventor, S. Kumar, "Glass composition for spinning fibre", in J. Non Crystalline Solids, 80 (1986) 122- 134, wherein 'A' glass fibre from waste strips of glass sheets are drawn. The fibre cools and frozen-in as it is drawn. An array of glass strips are placed in rectangular muffle furnace and thin fibres are drawn by rod pulling method. The main drawback of the process is that the technique is not suitable for high melting fused silica glass rods. Using the same process "N" glass fibres are also drawn where the thin fibre drawing temperature in all the cases is less than 1500°C. To summarise the drawbacks of the above processes it may be mentioned that (1) the above referred inventions are mainly involved in the heating of the starting silica rods and melting of quartz glass, (2) in case of using hydrogen/oxygen burner, the control of the individual fibre diameter is difficult: and it degrades the ultimate strength of the fibre strand, (3) the fibre drawing environment control is cost intensive due to explosive nature of the fuel gases, (4) the possibility of contamination during fibre drawing by foreign matter involves increase of breaking rates for continuous drawing, (5) while moving the hydrogen/oxygen burner and keeping the feeding rod fixed, the process does not give high drawing speed because of improper temperature profile surrounding the end of the silica rod and (6) the crucible melt technique does not provide suitable bushing for drawing high purity quartz fibre and it is limited by the maximum melt temperature around 1500°C, in case of silica glass melting the nozzled bushing does not withstand temperature above 2000 °C. The main object of the present invention is to provide an equipment for the manufacture of thin multifilament fused quartz fibre strands to obviate the above drawbacks. Another object of the present invention is to provide a process for the manufacture of thin multifilament fused quartz fibre strands using the equipment of the present invention. The equipment of the present invention for the manufacture of thin filament fused quartz fibre strands drawing system is developed is shown schematically in Figure 1. Of the drawing accompanying this specification. In figure 1(3) represents a mechanical jig for holding silica rods (4) in particular radial geometry. Other end of the device is made suitable for fixing vertically into, a six-jaw chuck (2) mounted in a X-Y micropositioner (1). The rod holding system is designed; in such a fashion that it can be adjusted in a fraction of a millimeter concentric to the opening of the induction furnace (5). The rising applicator system (6) consists of a rotating drum absolutely vibration free during operation. It is driven by a small induction motor. The whole system is placed on a precision micropositioner to make fine mechanical contact with the multiple fibres. The bunch of bibres piocls up all the size with which it comes into contact while passing over the surface of the drum or roller which is made of compressed graphite. The film thickness of the size formed around the roller is proportional to rotational speed of the roller. The wrap-round angle of the fibres over the roller is kept as low as 2° to minimize the abrasion. Below the resin applicator the fibres are bunched together with the help of a gathering shoe (7) self lubricated by the sizing solution carried by the fibres.. This is also made of compressed graphite with suitable groove on the roller. The collet drum (8) is made of stainless steel of diameter 200 mm and length 600 mm. The r.p.m. of collet drum can be achieved upto 1500 without much vibration to cause fibre breakage. The whole ropatating device is placed on a precision translation table powered by steper motor and controlled by a computer upto an accuracy of 1 micrometer per step. Accordingly the present invention provides an equipment for the manufacture of thin multifilament fused quartz fibre strands characterized by a movable mount (1,2,3) such as herein described, for holding a plurality of fused quartz rods(4) within a heat zone (5) such as herein described, a coating applicator(6) being coaxially fixed surrounding strands of fibre below the said quartz rods (4) and said heat zone(5), a perforated silica disc (4a) is provided at the top of the said heat zone(5) to act as a heat shield-cum-rod(s) guide, a known gathering mechanism(7) fixed below the said coating applicator(6), a strand winding machine(S) is fixed below the said gathering mechanism(7) for rotational and translational movement. In an embodiment of present invention the movable mount (1,2,3) consist of rod holding jig (3) removable fixed to a jaw chuck (2) mounted onto a micropositioner (I). In another embodiment of the present invention the heat zone (5) may be a furnace such as induction furnace, resistive heating furnace capable of heating quartz rods at a temperature in the range of 1900-2300°C. In still another embodiment a perforated silica disc (4a) may be provided at the top of the furnace to act as a heat shield-cup-rod (s) guide. In another embodiment of the present invention the rotational and translational movement of the fibre strand winding machine (8) may be provided by prime movers such as a stepper motor and a servo-motor for precision winding of the thin multifilament fibre strands. Accordingly the present invention provides a process for the manufacture of thin multifilament fused quartz fibre strands using the equipment fothe present invention which comprises introducing a plurality of fused quartz rods mounted on a holding jig into a furnace at: a peak temperature in the range of 1900-2300°C with a Gaussian type temperature profile along the vertical direction of the furnace, drawing fibres inside the furnace by pulling the bulk end of the rod that initially comes through the bottom of the furnace, passing the fibre over a sizing solution applicator and a gathering shoe onto a collet drum. In embodiment of the present invention the quartz rods used may be made of silica such as type-I to IV with low to high OH content and small alkali and metal impurities of various dimensions of rod diameter ranging from 3 to 10 mm and of lengths 30 mm to 1000 mm. In another embodiment of the present invention the sizing solution may be prepared by hydrolyzing organ metallic silicone compound at a pH in the range of 5 to 5.5 by known methods. Process description: In figure 1 (3) represents a mechanical device for holding silica rods in particular radial geometry. Other end of the device is made suitable for fixing vertically into a six-jaw chuck (2) mounted in a X-Y micropositioner (1). The rod holding system is designed in such a fashion that it can be adjusted in a fraction of a millimeter concentric to the opening of the induction furnace 1. Furnace temperature is critically adjusted for getting precise temperature profile along the vertical direction of the furnace. The furnace is of radio frequency induction type where a specially designed zirconia susceptor is centrally mounted of 40 mm diameter and 90 mm long. Power is inductively fed onto the susceptor to get desired temperature. 2. Once the temperature is adjusted silica rods are introduced into the furnace through a perforated silica disc just placed above the furnace mouth. 3. Silica rods are mounted in the fixture (3) concentrically with the furnace cross- section so that each rod gets uniform temperature. This part is important otherwise at high speed drawing the thin fibres may be snapped due to uneven necking of the rods inside the furnace. As the inside temperature distribution along the cross section of the furnace is not uniform, the alignment of the rods inside the furnace is very critical. The fixture was designed in such a fashion that the silica rods could be placed parallel with the furnace wall and able to move vertically downward in the same condition. The temperature difference from the inside surface of the furnace element to the centre of the furnace is in the range of 40 to 60°C. 4. After the necking at the rod end inside the furnace when the temperature ranging from 1910 to 2020°C is critically adjusted suitable for particular rod diameter, initially the bulk ends or gobs start coming out through the bottom of the furnace and allowed to move till it touches the rotating collet drum. 5. Fibres are then cut and bunch together for fixing onto the rotating drum which is placed vertically down to the floor (~2 m) via a conventional gathering shoe. The rotating drum is specially designed with remote computer for precise rotational control and drum translation with ~1 micron accuracy. 6. At this stage sizing solution is applied with the help of a sizing applicator system where a rotating graphite roller (r.p.m.~30 - 60) carries the sizing solution from the cup, transfers in the form of a thin jacket onto the fibre surface by fine mechanical contact. 7. The sizing solution was prepared by hydrolysing organometallic silicone compound at pH value in the range of 5 to 5.5 , mixing with 2-5 grams ammonium chloride, 5 - 8 ml n-propyl amine, 2- 3 gins polyvinyl acetate emulsion, 1-3 gm cationic surfactant, 5-10 ml polyethylene glycol in 60-70 ml of distilled water. The viscosity of the solution and rotational speed of the drum are critically adjusted to get uniform thickness onto the fibre surface in order to get tensile strength of the fibres better than 2 Gpa. The centering of the system has been perfected by adjusting the applicator system with the help of a X-Y micropositioner. 8. Once the sizing resin starts coating uniformly onto the fibres the rotational speed of the collet drum is adjusted simultaneously with the feeding speed of quartz rods. This process part has been experimented with rods having diameters in the range of 2 to 10 mm. Utilizing the present designed system multi fibre strand are smoothly wound on to the collet drum. The diameter of the individual fibre is in the range 8 to 50 micron has easily been maintained in continuous long length. The rod feeding downward speed is critical in the present system which is 1.2 mm to 20 mm per minute and collet drum winding speed 400 to 1000 r.p.m. depending upon the diameter of the initial starting fused quartz rods. 9. This process for making thin filament fused quartz fibres where the furnace environment should be maintained very clean by applying downward laminar flow (1) of particulate air ( time in a heating zone which is exposed to atmosphere. The rod holding system integrates the space subsequently reduces the cost of the technology. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example - 1: Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.95% of diameter 3 mm at radial furnace temperature 1925°C measured at the surface of a zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament: • Fused quartz/silica rod downfeed speed 4.5 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 600 r.p.m. • Translational shift of the collet drum 10 micrometre/rotation • Rotational speed of the sizing applicator's roller 40 r.p.m. • Rotational speed of the gathering shoe 40 r.p.m • Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 grams ammonium chloride, 5ml n-propyl amine, 2 gms poly vinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water. » Diameter of the thin filament/fibre achieved 10 micrometre Example - 2: Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99 % of diameter 4 mm at radial furnace temperature 1930}C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament: • Fused quartz/silica rod downfeed speed 3 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 700 r.p.m. • Translational shift of the collet drum 10 micrometre/rotation • Rotational speed of the sizing applicator's roller 40 r.p.m. • Rotational speed of the gathering shoe 40 r.p.m • Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 grams ammonium chloride, 5ml n propyl amine, 2 gms poly vinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water. • Diameter of the thin filament/fibre achieved 10 micrometre Example-3: Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99% of diameter 5 mm at radial furnace temperature 1935°C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament: • Fused quartz/silica rod downfeed speed 1.6 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 600 r.p.m. • Translational shift of the collet drum 10 micrometre/rotation • Rotational speed of the sizing applicator's roller 60 r.p.m. • Rotational speed of the gathering shoe 60 r.p.m • Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15ml of hydrolysed organometallic silicone compound at pH value of 5, 2 grains ammonium chloride, 5ml n-propyl amine, 2 gms poly vinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water. • Diameter of the thin filament/fibre achieved 10 micrometre Example 4: Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99% of diameter 5 mm at radial furnace temperature 1935 oC measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament: • Fused quartz/silica rod downfeed speed 1.5 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 600 r.p.m. • Translational shift of the collet drum 10 micrometre/rotation • Rotational speed of the sizing applicator's roller 60 r.p.m. • Rotational speed of the gathering shoe 60 r.p.m « Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 grams ammonium chloride, 5ml n-propyl amine, 2 gms poly vinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water. ® Diameter of the thin filament/fibre achieved 9.5 micrometre Example-5: Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99% of diameter 5 mm at radial furnace temperature 1935°C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament: • Fused quartz/silica rod downfeed speed 1.5 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 650 r.p.m. • Translational shift of the collet drum 10 micrometre/rotation • Rotational speed of the sizing applicator's roller 60 r.p.m. • Rotational speed of the gathering shoe 60 r.p.m • Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 grains ammonium chloride, 5ml n-propyl amine, 2 gms polyvinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water. • Diameter of the thin filament/fibre achieved 8.7 micrometre Example -6: Fused silica fibre strand was made by the rapid attenuation of two silica rods of purity 99.99% of diameter 5 mm each at radial furnace temperature 1940o C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament: ® Fused quarlz/silica rod downfeed speed 1.5 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 600 r.p.m. • Translational shift of the collet drum 20 micrometre/rotation • Rotational speed of the sizing applicator's roller 60 r.p.m. • Rotational speed of the gathering shoe 60 r.p.m • Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 grams ammonium chloride, 5ml n-propyl amine, 2 gms polyvinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water. • Diameter of the thin filament/fibre achieved 9.5 micrometre Example 7: Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99% of diameter 5 mm at radial furnace temperature 1940°C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament: • Fused quartz/silica rod downfeed speed 1.5 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 650 r.p.m. • Translational shift of the collet drum 10 micrometre/rotation • Rotational speed of the sizing applicator's roller 60 r.p.m. • Rotational speed of the gathering shoe 60 r.p.m • Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5.3, 3 gms ammonium chloride, 7ml n-propyl amine, 2.5 gms polyvinyl acetate emulsion, 2 gm cationic surfactant, 8 ml polyethylene glycol in 65 ml of distilled water. • Diameter of the thin filament/fibre achieved 8.5 micrometre Example 8: Fused silica fibre strand was made by the rapid attenuation of three silica rods of purity 99.99% of diameter 5 mm each at radial furnace temperature 1940o C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing thin filament strand: • Fused quartz/silica rod downfeed speed 1.5 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 600 r.p.m. • Translational shift of the collet drum 30 micrometre/rotation • Rotational speed of the sizing applicator's roller 60 r.p.m. • Rotational speed of the gathering shoe 60 r.p.m • Sizing solution which was used during drawing of silica fibre was prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 gms ammonium chloride, 5ml n-propyl amine, 2 gins poly vinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water. • Diameter of the each fibre in three filament strand achieved 9.5 micrometre Example 9: Fused silica fibre strand was made by the rapid attenuation of five silica rods of purity 99.99% of diameter 5 mm each at radial furnace temperature 1940 oC measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing multi filament strand: • Fused quartz/silica rod downfeed speed 1.6 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 700 r.p.m. • Translational shift of the collet drum 40 micrometre/rotation • Rotational speed of the sizing applicator's roller 60 r.p.m. • Rotational speed of the gathering shoe 60 r.p.m • Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 gms ammonium chloride, 5ml n-propyl amine, 2 gms polyvinyl acetate emulsion, 1 gni cationic surfactant , 5 nil polyethylene glycol in 70 ml of distilled water. • Diameter of the each fibre in three filament strand achieved 9 micrometre • Five fibre strand drawing capacity is 25 gms/hr Example 10: Fused silica fibre strand was made by the rapid attenuation of five silica rods of purity 99.99% of diameter 5 mm each at radial furnace temperature 1935°C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing multi filament strand: • Fused quartz/silica rod downfeed speed 3.5 mm/min • Fibre pulling speed or rotational speed of the collet drum (200 mm diameter) 600 r.p.m. • Translational shift of the collet drum 40 micrometre/rotation • Rotational speed of the sizing applicator's roller 40 r.p.m. • Rotational speed of the gathering shoe 40 r.p.m • Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 gms ammonium chloride, 5ml n-propyl amine, 2 gms polyvinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water. • Diameter of the each fibre in three filament strand achieved 15 micrometre • Five fibre strand drawing capacity is 45 gms/hr According to the present invention tensile strength and productivity of manufacturing fibre strand can be improved whereas the referred prior art equipment and processes are mainly involved in the heating of the starting silica rods and melting of glass. In case of hydrogen/oxygen burner, the control of the individual fibre diameter is difficult and it degrades the ultimate strength of the fibre strand and the fibre drawing environment control is cost intensive due to explosive nature of the fuel gases. The present invention avoids these problems and the possibility of contamination during fibre drawing by foreign matter is also less. This enhances the tensile strength of the fibre. The crucible melt technique does not provide suitable bushing for drawing high purity quartz fibre and it is limited by the maximum melt temperature around 1500°C, in case of silica glass melting the nozzled bushing does not withstand temperature > 1500°C. The present invention is applicable to drawing thin fibre strand from very high purity of fused silica glass in the melting range of 1900° to 2300°C. Jn the present invention, the equipment and the process make it possible to draw thin multifilament fused quartz fibre strand in a radial heating zone where a precise vertical temperature profile can be maintained. Furthermore the advantages are as follows: a) The present invention manifests a process for manufacturing continuous multifi lament fused quartz fibre having uniform filament diameter which has very high attenuation temperature and can not be produced by multiple bushing technology. b) The process avoids explosive fuel gases like hydrogen and integrates the working area where multiple glass rods can be mounted in circular heatzone which is exposed to ambient air. It minimizes contamination onto the fibre coming from the fuel gases. c) Attenuation of the silica rod to thin fibre of 5 to 14 micron can be accomplished precisely in very short time and continuous fibre drawing at high drawing speed could be achieved maintaining high tensile strength of the fibre. d) Unlike the other process this technology helps to make multiple fibre strand having uniform diameter in continuous length. e) The gaussian type vertical temperature profile with peak temperature 1900 to 2300°C specifically required for making fused quartz fibre can easily be achieved in zirconia muffle furnace. f) By suitably increasing the furnace size more number of rods can be accommodated to increase the yield. g) The radial heating zone integrates the optimum space required for drawing fibres from high melting glass rods. h) Thin coherent fibre bundles of various dimension from 0.5 to 2 mm diameter can be fabricated for light guiding purpose. This fibre optic bundle has very high market potential at present and future. Claim: 1. An equipment for the manufacture of thin multifilament fused quartz fibre strands characterized by a movable mount (1,2,3) such as herein described, for holding a plurality of fused quartz rods(4) within a heat zone (5) such as herein described, a coating applicator(6) being coaxially fixed surrounding strands of fibre below the said quartz rods (4) and said heat zone(5), a perforated silica disc (4a) is provided at the top of the said heat zone(5) to act as a heat shield-cum-rod(s) guide, a known gathering mechanism(7) fixed below the said coating applicator(6), a strand winding machine(S) is fixed below the said gathering mechanism(7) for rotational and translational movement. 2. An equipment as claimed in claim 1 wherein the movable mount (1,2,3) consists of rod holding jig (3) removable fixed to a jaw chuck (2) mounted out a miocropositioner (1). 3. An equipment as claimed in claim 1-2 wherein the heat zone (5) is a furnace selected from induction furnace, resistive heating furnace for heating quartz rods at a temperature in the range of 1900-2300°C. 4. A process for the manufacture of thin multifilament fused quartz fibre strands using the equipment as claimed in claim 1 which comprises introducing a plurality of fused quartz rods mounted on a holding jig into a furnace at a peak temperature in the range of 1900-2300°C with a Gaussian type temperature profile along the vertical direction of the furnace, drawing fibres inside the furnace by pulling the bulk end of the rod that initially comes through the bottom of the furnace, passing the fibre over a sizing solution applicator and a gathering shoe onto a collect drum. 5. A process as claimed in claim 4 wherein the quartz rods used are such as type- I to IV with low to high OH content and small alkali and metal impurities of various dimensions of rod diameters ranging from 3 to 10 mm and lengths 30 mm to 1000 mm. 6. A process as claimed in claims 4-5 wherein the sizing solution is prepared by hydrolyzing organ metallic silicone compound at a pH in the range of 5 to 5.5 by known methods. 7. An equipment for the manufacture of thin multifilament quartz fibre strands substantially as herein described with reference to the examples and drawing accompanying the specification.

Full Text

The present invention relates to an equipment for the manufacture of thin multifilament fused quartz fibre strands and a process thereof:
Fused quartz fibres or filaments are very good candidates for structural composites because of their unique mechanical, thermal and electrical properties. Being the lightest structural fibres they have high tensile strength in unidirectional composite, very low coefficient of thermal expansion and good electrical characteristics of high resistivity and low dielectric constant maintained over a broad temperature and frequency ranges. Some other key features of these fibres are very low moisture absorption, high temperature resistance, high hardness and high composite lifetime along with excellent resin compatibility. These fibres in textile fonns as multiple fibre yarns, chopped strands, rovings, tapes, and mats where the continuous filament diameter varies from 9 to 15 microns find wide application in advanced composites structures, electro-magnetic windows, high-speed printed circuit boards, thermal insulation blankets for furnaces and aerospace engines, high performance cables etc.
Present day method of making fused quartz fibre encompasses several processes. Reference for which may be made to the product references of Fiber Materials Incorporated, USA and Quartz Silice, France wherein single filament of quartz fibre was drawn by heating the quartz rod using hydrogen/oxygen flame. Here the fuel source is costly and handling of hydrogen is not safe but the contamination from hydrocarbon fuel is eliminated. In this process the end of the rod is first softened and subsequently the rod end is pulled into thin filament of 9 to 15 micron diameter on continuous basis onto a high speed rotating drum after applying suitable sizing or coating resin. The drawbacks of the above process are:
(1) Each quartz rod with one hydrogen/oxygen burner assembly produces only one
filament. By placing multiple stages of parallel rods with array of hydrgen/oxygen
burners the thin fused/quartz fibres are drawn coating with sizing resin and
accumulated with the help of a gathering mechanism to form strand.
(2) The control of diameter of the individual fibre is difficult which incurs strength
degradation in the ultimate fibre strand.
(3) The control of environment is cost intensive due to the explosive nature of the
fuel gas.
(4) Contamination by foreign matter is possible resulting degradation in the fibre
tensile strength.
(5) Heating by hydrogen/oxygen flame does not give uniform necking in each stage
also resulting in strength degradation.
(6) The requirement of space to accommodate number of rods in a oxy/hydrogen
burner assembly in a row is more which effectively increases the cost of the
technology.
Reference may be made of the inventors J. Murach and R. Bruckner in 'Structure sensitive investigations on alkali metasilicate glass fibres', J. Non. Crystalline Solids, 204 (1996) 282-293, wherein they described a nozzle drawing method for making silicate glass fibres where the mass flow rate is a function of the furnace temperature and pressure on the glass at the nozzle head . The major disadvantages of this process are that the fibres get contaminated by the nozzle material and fibre diameter can not be controlled due to change of diameter of nozzle orifice by erosion. Further reference may be made of the inventors J. Murach and R. Bruckner, in "Preparation and structure-sensitive investigations on silica glass fibers", J. Non-Crystalline Solids, 211 (1997) 250-261, wherein they developed a process for fabricating fused silica fibers by heating the end of the rotating silica glass rod by a moving hydrogen /oxygen burner. The mass flow of the rod drawing method depends on the driving speed of the silica rod or of the heating source and suitable temperature profile. The diameters of the fibers drawn are in the range 5 to 25 micron using 5 -8 mm diameter silica rods.. In addition to all the drawbacks mentioned above this method does not help in very high speed drawing of thin silica fibres . Still further reference may be made to British Patent Nos. 1,196,331 & 1,196,332 (1970) of PPG Industries Inc., wherein thin filament of high silicate glass fibre was drawn by bushing technology. World wide technology available for production of thin fibre is based on noble metal bushing and this process technology is capital intensive specifically suitable for large scale production.
Here the process involves molten glass exuding) through the bush-nozzles under gravity or certain pressure transforms into thuTfibres by dynamic balance between the forces of surface tension and mechanical attenuation. Precise control of viscosity of the molten glass is needed to reduce fibre breaking rate. The multi filaments are drawn simultaneously from the melt through bushing which is maintained at uniform temperature and subsequently the strand is wound on a high speed drum after application of sizing resin mostly for low melting glasses. For each set of fibres the temperature profile has to be adjusted as per the environmental condition.
(1) This technology has the limitation for making fibre having high attenuation
temperature where glass fibre containing more than 95% silica is not possible by this
technology.
(2) Suitable bushing for drawing high purity quartz fibre better than 95% has not been
developed and reported.
(3) In this conventional technology the orifice of the bushing which is made of
platinum-rhodium alloys, gradually increases due to erosion during the continuous
fibre drawing process and needs to be reworked.
Further reference may be made of the inventor, S. Kumar, "Glass composition for spinning fibre", in J. Non Crystalline Solids, 80 (1986) 122- 134, wherein 'A' glass fibre from waste strips of glass sheets are drawn. The fibre cools and frozen-in as it is drawn. An array of glass strips are placed in rectangular muffle furnace and thin fibres are drawn by rod pulling method. The main drawback of the process is that the technique is not suitable for high melting fused silica glass rods. Using the same process "N" glass fibres are also drawn where the thin fibre drawing temperature in all the cases is less than 1500°C.
To summarise the drawbacks of the above processes it may be mentioned that
(1) the above referred inventions are mainly involved in the heating of the starting
silica rods and melting of quartz glass,
(2) in case of using hydrogen/oxygen burner, the control of the individual fibre
diameter is difficult: and it degrades the ultimate strength of the fibre strand,
(3) the fibre drawing environment control is cost intensive due to explosive nature of
the fuel gases,
(4) the possibility of contamination during fibre drawing by foreign matter involves
increase of breaking rates for continuous drawing,
(5) while moving the hydrogen/oxygen burner and keeping the feeding rod fixed, the
process does not give high drawing speed because of improper temperature profile
surrounding the end of the silica rod and
(6) the crucible melt technique does not provide suitable bushing for drawing high
purity quartz fibre and it is limited by the maximum melt temperature around 1500°C,
in case of silica glass melting the nozzled bushing does not withstand temperature
above 2000 °C.
The main object of the present invention is to provide an equipment for the manufacture of thin multifilament fused quartz fibre strands to obviate the above drawbacks.
Another object of the present invention is to provide a process for the manufacture of thin multifilament fused quartz fibre strands using the equipment of the present invention.
The equipment of the present invention for the manufacture of thin filament fused quartz fibre strands drawing system is developed is shown schematically in Figure 1. Of the drawing accompanying this specification.
In figure 1(3) represents a mechanical jig for holding silica rods (4) in particular radial geometry. Other end of the device is made suitable for fixing vertically into, a six-jaw chuck (2) mounted in a X-Y micropositioner (1). The rod holding system is designed; in such a fashion that it can be adjusted in a fraction of a millimeter concentric to the opening of the induction furnace (5).
The rising applicator system (6) consists of a rotating drum absolutely vibration free during operation. It is driven by a small induction motor. The whole system is placed on a precision micropositioner to make fine mechanical contact with the multiple fibres. The bunch of bibres piocls up all the size with which it comes into contact while passing over the surface of the drum or roller which is made of compressed graphite. The film thickness of the size formed around the roller is proportional to rotational speed of the roller. The wrap-round angle of the fibres over the roller is kept as low as 2° to minimize the abrasion. Below the resin applicator the fibres are bunched together with the help of a gathering shoe (7) self lubricated by the sizing solution carried by the fibres.. This is also made of compressed graphite with suitable groove on the roller. The collet drum (8) is made of stainless steel of diameter 200 mm and length 600 mm. The r.p.m. of collet drum can be achieved upto 1500 without much vibration to cause fibre breakage. The whole ropatating device is placed on a precision translation table powered by steper motor and controlled by a computer upto an accuracy of 1 micrometer per step.
Accordingly the present invention provides an equipment for the manufacture of thin multifilament fused quartz fibre strands characterized by a movable mount (1,2,3) such as herein described, for holding a plurality of fused quartz rods(4) within a heat zone (5) such as herein described, a coating applicator(6) being coaxially fixed surrounding strands of fibre below the said quartz rods (4) and said heat zone(5), a perforated silica disc (4a) is provided at the top of the said heat zone(5) to act as a heat shield-cum-rod(s) guide, a known gathering mechanism(7)
fixed below the said coating applicator(6), a strand winding machine(S) is fixed below the said gathering mechanism(7) for rotational and translational movement.
In an embodiment of present invention the movable mount (1,2,3) consist of rod holding jig (3) removable fixed to a jaw chuck (2) mounted onto a micropositioner (I).
In another embodiment of the present invention the heat zone (5) may be a furnace such as induction furnace, resistive heating furnace capable of heating quartz rods at a temperature in the range of 1900-2300°C.
In still another embodiment a perforated silica disc (4a) may be provided at the top of the furnace to act as a heat shield-cup-rod (s) guide.
In another embodiment of the present invention the rotational and translational movement of the fibre strand winding machine (8) may be provided by prime movers such as a stepper motor and a servo-motor for precision winding of the thin multifilament fibre strands.
Accordingly the present invention provides a process for the manufacture of thin multifilament fused quartz fibre strands using the equipment fothe present invention which comprises introducing a plurality of fused quartz rods mounted on a holding jig into a furnace at: a peak temperature in the range of 1900-2300°C with a Gaussian type temperature profile along the vertical direction of the furnace, drawing fibres inside the furnace by pulling the bulk end of the rod that initially comes through the bottom of the furnace, passing the fibre over a sizing solution applicator and a gathering shoe onto a collet drum.
In embodiment of the present invention the quartz rods used may be made of silica such as type-I to IV with low to high OH content and small alkali and metal impurities of various dimensions of rod diameter ranging from 3 to 10 mm and of lengths 30 mm to 1000 mm.
In another embodiment of the present invention the sizing solution may be prepared by hydrolyzing organ metallic silicone compound at a pH in the range of 5 to 5.5 by known methods.
Process description:
In figure 1 (3) represents a mechanical device for holding silica rods in particular radial geometry. Other end of the device is made suitable for fixing vertically into a six-jaw chuck (2) mounted in a X-Y micropositioner (1). The rod holding system is
designed in such a fashion that it can be adjusted in a fraction of a millimeter concentric to the opening of the induction furnace
1. Furnace temperature is critically adjusted for getting precise temperature profile
along the vertical direction of the furnace. The furnace is of radio frequency
induction type where a specially designed zirconia susceptor is centrally mounted
of 40 mm diameter and 90 mm long. Power is inductively fed onto the susceptor to
get desired temperature.
2. Once the temperature is adjusted silica rods are introduced into the furnace through
a perforated silica disc just placed above the furnace mouth.
3. Silica rods are mounted in the fixture (3) concentrically with the furnace cross-
section so that each rod gets uniform temperature. This part is important otherwise
at high speed drawing the thin fibres may be snapped due to uneven necking of the
rods inside the furnace. As the inside temperature distribution along the cross
section of the furnace is not uniform, the alignment of the rods inside the furnace is
very critical. The fixture was designed in such a fashion that the silica rods could
be placed parallel with the furnace wall and able to move vertically downward in
the same condition. The temperature difference from the inside surface of the
furnace element to the centre of the furnace is in the range of 40 to 60°C.
4. After the necking at the rod end inside the furnace when the temperature ranging
from 1910 to 2020°C is critically adjusted suitable for particular rod diameter,
initially the bulk ends or gobs start coming out through the bottom of the furnace
and allowed to move till it touches the rotating collet drum.
5. Fibres are then cut and bunch together for fixing onto the rotating drum which is
placed vertically down to the floor (~2 m) via a conventional gathering shoe. The
rotating drum is specially designed with remote computer for precise rotational
control and drum translation with ~1 micron accuracy.
6. At this stage sizing solution is applied with the help of a sizing applicator system
where a rotating graphite roller (r.p.m.~30 - 60) carries the sizing solution from
the cup, transfers in the form of a thin jacket onto the fibre surface by fine
mechanical contact.
7. The sizing solution was prepared by hydrolysing organometallic silicone
compound at pH value in the range of 5 to 5.5 , mixing with 2-5 grams
ammonium chloride, 5 - 8 ml n-propyl amine, 2- 3 gins polyvinyl acetate
emulsion, 1-3 gm cationic surfactant, 5-10 ml polyethylene glycol in 60-70 ml of
distilled water. The viscosity of the solution and rotational speed of the drum are
critically adjusted to get uniform thickness onto the fibre surface in order to get
tensile strength of the fibres better than 2 Gpa. The centering of the system has been perfected by adjusting the applicator system with the help of a X-Y micropositioner.
8. Once the sizing resin starts coating uniformly onto the fibres the rotational speed of
the collet drum is adjusted simultaneously with the feeding speed of quartz rods.
This process part has been experimented with rods having diameters in the range
of 2 to 10 mm. Utilizing the present designed system multi fibre strand are
smoothly wound on to the collet drum. The diameter of the individual fibre is in the
range 8 to 50 micron has easily been maintained in continuous long length. The
rod feeding downward speed is critical in the present system which is 1.2 mm to
20 mm per minute and collet drum winding speed 400 to 1000 r.p.m. depending
upon the diameter of the initial starting fused quartz rods.
9. This process for making thin filament fused quartz fibres where the furnace
environment should be maintained very clean by applying downward laminar flow
(1) of particulate air ( time in a heating zone which is exposed to atmosphere. The rod holding system
integrates the space subsequently reduces the cost of the technology.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Example - 1:
Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.95% of diameter 3 mm at radial furnace temperature 1925°C measured at the surface of a zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament:
• Fused quartz/silica rod downfeed speed 4.5 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 600 r.p.m.
• Translational shift of the collet drum 10 micrometre/rotation
• Rotational speed of the sizing applicator's roller 40 r.p.m.
• Rotational speed of the gathering shoe 40 r.p.m
• Sizing solution which was used during drawing of silica fibre has been prepared
by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of
5, 2 grams ammonium chloride, 5ml n-propyl amine, 2 gms poly vinyl acetate
emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled
water.
» Diameter of the thin filament/fibre achieved 10 micrometre
Example - 2:
Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99 % of diameter 4 mm at radial furnace temperature 1930}C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament:
• Fused quartz/silica rod downfeed speed 3 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 700 r.p.m.
• Translational shift of the collet drum 10 micrometre/rotation
• Rotational speed of the sizing applicator's roller 40 r.p.m.
• Rotational speed of the gathering shoe 40 r.p.m
• Sizing solution which was used during drawing of silica fibre has been prepared
by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of
5, 2 grams ammonium chloride, 5ml n propyl amine, 2 gms poly vinyl acetate
emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled
water.
• Diameter of the thin filament/fibre achieved 10 micrometre
Example-3:
Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99% of diameter 5 mm at radial furnace temperature 1935°C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament:
• Fused quartz/silica rod downfeed speed 1.6 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 600 r.p.m.
• Translational shift of the collet drum 10 micrometre/rotation
• Rotational speed of the sizing applicator's roller 60 r.p.m.
• Rotational speed of the gathering shoe 60 r.p.m
• Sizing solution which was used during drawing of silica fibre has been prepared
by mixing 15ml of hydrolysed organometallic silicone compound at pH value of
5, 2 grains ammonium chloride, 5ml n-propyl amine, 2 gms poly vinyl acetate
emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water.
• Diameter of the thin filament/fibre achieved 10 micrometre
Example 4:
Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99% of diameter 5 mm at radial furnace temperature 1935 oC measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament:
• Fused quartz/silica rod downfeed speed 1.5 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 600 r.p.m.
• Translational shift of the collet drum 10 micrometre/rotation
• Rotational speed of the sizing applicator's roller 60 r.p.m.
• Rotational speed of the gathering shoe 60 r.p.m
« Sizing solution which was used during drawing of silica fibre has been prepared by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2 grams ammonium chloride, 5ml n-propyl amine, 2 gms poly vinyl acetate emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water.
® Diameter of the thin filament/fibre achieved 9.5 micrometre
Example-5:
Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99% of diameter 5 mm at radial furnace temperature 1935°C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament:
• Fused quartz/silica rod downfeed speed 1.5 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 650 r.p.m.
• Translational shift of the collet drum 10 micrometre/rotation
• Rotational speed of the sizing applicator's roller 60 r.p.m.
• Rotational speed of the gathering shoe 60 r.p.m
• Sizing solution which was used during drawing of silica fibre has been prepared
by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of
5, 2 grains ammonium chloride, 5ml n-propyl amine, 2 gms polyvinyl acetate
emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water.
• Diameter of the thin filament/fibre achieved 8.7 micrometre
Example -6:
Fused silica fibre strand was made by the rapid attenuation of two silica rods of purity
99.99% of diameter 5 mm each at radial furnace temperature 1940o C measured at the
surface of the zirconia heating element. Following were the settings in the fibre pulling
setup for drawing single thin filament:
® Fused quarlz/silica rod downfeed speed 1.5 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 600 r.p.m.
• Translational shift of the collet drum 20 micrometre/rotation
• Rotational speed of the sizing applicator's roller 60 r.p.m.
• Rotational speed of the gathering shoe 60 r.p.m
• Sizing solution which was used during drawing of silica fibre has been prepared
by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of
5, 2 grams ammonium chloride, 5ml n-propyl amine, 2 gms polyvinyl acetate
emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled
water.
• Diameter of the thin filament/fibre achieved 9.5 micrometre
Example 7:
Fused silica fibre was made by the rapid attenuation of silica rod of purity 99.99% of diameter 5 mm at radial furnace temperature 1940°C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing single thin filament:
• Fused quartz/silica rod downfeed speed 1.5 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 650 r.p.m.
• Translational shift of the collet drum 10 micrometre/rotation
• Rotational speed of the sizing applicator's roller 60 r.p.m.
• Rotational speed of the gathering shoe 60 r.p.m
• Sizing solution which was used during drawing of silica fibre has been prepared
by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of
5.3, 3 gms ammonium chloride, 7ml n-propyl amine, 2.5 gms polyvinyl acetate
emulsion, 2 gm cationic surfactant, 8 ml polyethylene glycol in 65 ml of distilled water.
• Diameter of the thin filament/fibre achieved 8.5 micrometre
Example 8:
Fused silica fibre strand was made by the rapid attenuation of three silica rods of purity 99.99% of diameter 5 mm each at radial furnace temperature 1940o C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing thin filament strand:
• Fused quartz/silica rod downfeed speed 1.5 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 600 r.p.m.
• Translational shift of the collet drum 30 micrometre/rotation
• Rotational speed of the sizing applicator's roller 60 r.p.m.
• Rotational speed of the gathering shoe 60 r.p.m
• Sizing solution which was used during drawing of silica fibre was prepared by
mixing 15 ml of hydrolysed organometallic silicone compound at pH value of 5, 2
gms ammonium chloride, 5ml n-propyl amine, 2 gins poly vinyl acetate emulsion,
1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled water.
• Diameter of the each fibre in three filament strand achieved 9.5 micrometre
Example 9:
Fused silica fibre strand was made by the rapid attenuation of five silica rods of purity 99.99% of diameter 5 mm each at radial furnace temperature 1940 oC measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing multi filament strand:
• Fused quartz/silica rod downfeed speed 1.6 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 700 r.p.m.
• Translational shift of the collet drum 40 micrometre/rotation
• Rotational speed of the sizing applicator's roller 60 r.p.m.
• Rotational speed of the gathering shoe 60 r.p.m
• Sizing solution which was used during drawing of silica fibre has been prepared
by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of
5, 2 gms ammonium chloride, 5ml n-propyl amine, 2 gms polyvinyl acetate
emulsion, 1 gni cationic surfactant , 5 nil polyethylene glycol in 70 ml of distilled water.
• Diameter of the each fibre in three filament strand achieved 9 micrometre
• Five fibre strand drawing capacity is 25 gms/hr
Example 10:
Fused silica fibre strand was made by the rapid attenuation of five silica rods of purity 99.99% of diameter 5 mm each at radial furnace temperature 1935°C measured at the surface of the zirconia heating element. Following were the settings in the fibre pulling setup for drawing multi filament strand:
• Fused quartz/silica rod downfeed speed 3.5 mm/min
• Fibre pulling speed or rotational speed of
the collet drum (200 mm diameter) 600 r.p.m.
• Translational shift of the collet drum 40 micrometre/rotation
• Rotational speed of the sizing applicator's roller 40 r.p.m.
• Rotational speed of the gathering shoe 40 r.p.m
• Sizing solution which was used during drawing of silica fibre has been prepared
by mixing 15 ml of hydrolysed organometallic silicone compound at pH value of
5, 2 gms ammonium chloride, 5ml n-propyl amine, 2 gms polyvinyl acetate
emulsion, 1 gm cationic surfactant, 5 ml polyethylene glycol in 70 ml of distilled
water.
• Diameter of the each fibre in three filament strand achieved 15 micrometre
• Five fibre strand drawing capacity is 45 gms/hr
According to the present invention tensile strength and productivity of manufacturing fibre strand can be improved whereas the referred prior art equipment and processes are mainly involved in the heating of the starting silica rods and melting of glass. In case of hydrogen/oxygen burner, the control of the individual fibre diameter is difficult and it degrades the ultimate strength of the fibre strand and the fibre drawing environment control is cost intensive due to explosive nature of the fuel gases. The present invention avoids these problems and the possibility of contamination during fibre drawing by foreign matter is also less. This enhances the tensile strength of the fibre. The crucible melt technique does not provide suitable bushing for drawing high purity quartz fibre and it is limited by the maximum melt temperature around 1500°C, in case of silica glass melting the nozzled bushing does not withstand temperature >
1500°C. The present invention is applicable to drawing thin fibre strand from very
high purity of fused silica glass in the melting range of 1900° to 2300°C.
Jn the present invention, the equipment and the process make it possible to draw thin
multifilament fused quartz fibre strand in a radial heating zone where a precise vertical
temperature profile can be maintained.
Furthermore the advantages are as follows:
a) The present invention manifests a process for manufacturing continuous multifi
lament fused quartz fibre having uniform filament diameter which has very high
attenuation temperature and can not be produced by multiple bushing technology.
b) The process avoids explosive fuel gases like hydrogen and integrates the working
area where multiple glass rods can be mounted in circular heatzone which is
exposed to ambient air. It minimizes contamination onto the fibre coming from the
fuel gases.
c) Attenuation of the silica rod to thin fibre of 5 to 14 micron can be accomplished
precisely in very short time and continuous fibre drawing at high drawing speed
could be achieved maintaining high tensile strength of the fibre.
d) Unlike the other process this technology helps to make multiple fibre strand having
uniform diameter in continuous length.
e) The gaussian type vertical temperature profile with peak temperature 1900 to
2300°C specifically required for making fused quartz fibre can easily be achieved
in zirconia muffle furnace.
f) By suitably increasing the furnace size more number of rods can be accommodated
to increase the yield.
g) The radial heating zone integrates the optimum space required for drawing fibres
from high melting glass rods.
h) Thin coherent fibre bundles of various dimension from 0.5 to 2 mm diameter can be fabricated for light guiding purpose. This fibre optic bundle has very high market potential at present and future.

Claim:
1. An equipment for the manufacture of thin multifilament fused quartz fibre
strands characterized by a movable mount (1,2,3) such as herein described, for
holding a plurality of fused quartz rods(4) within a heat zone (5) such as herein
described, a coating applicator(6) being coaxially fixed surrounding strands of
fibre below the said quartz rods (4) and said heat zone(5), a perforated silica
disc (4a) is provided at the top of the said heat zone(5) to act as a heat
shield-cum-rod(s) guide, a known gathering mechanism(7) fixed below the said
coating applicator(6), a strand winding machine(S) is fixed below the said
gathering mechanism(7) for rotational and translational movement.
2. An equipment as claimed in claim 1 wherein the movable mount (1,2,3) consists
of rod holding jig (3) removable fixed to a jaw chuck (2) mounted out a
miocropositioner (1).
3. An equipment as claimed in claim 1-2 wherein the heat zone (5) is a furnace
selected from induction furnace, resistive heating furnace for heating quartz rods
at a temperature in the range of 1900-2300°C.
4. A process for the manufacture of thin multifilament fused quartz fibre strands
using the equipment as claimed in claim 1 which comprises introducing a
plurality of fused quartz rods mounted on a holding jig into a furnace at a peak
temperature in the range of 1900-2300°C with a Gaussian type temperature
profile along the vertical direction of the furnace, drawing fibres inside the
furnace by pulling the bulk end of the rod that initially comes through the
bottom of the furnace, passing the fibre over a sizing solution applicator and a
gathering shoe onto a collect drum.
5. A process as claimed in claim 4 wherein the quartz rods used are such as type-
I to IV with low to high OH content and small alkali and metal impurities of
various dimensions of rod diameters ranging from 3 to 10 mm and lengths 30
mm to 1000 mm.
6. A process as claimed in claims 4-5 wherein the sizing solution is prepared by
hydrolyzing organ metallic silicone compound at a pH in the range of 5 to 5.5
by known methods.
7. An equipment for the manufacture of thin multifilament quartz fibre strands
substantially as herein described with reference to the examples and drawing
accompanying the specification.

Documents:

305-del-2001-abstract.pdf

305-del-2001-claims.pdf

305-del-2001-correspondence-others.pdf

305-del-2001-correspondence-po.pdf

305-del-2001-description (complete).pdf

305-del-2001-drawings.pdf

305-del-2001-form-1.pdf

305-del-2001-form-18.pdf

305-del-2001-form-2.pdf

305-del-2001-form-3.pdf

« Previous Patent

Next Patent »

Patent Number

231611

Indian Patent Application Number

305/DEL/2001

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

06-Mar-2009

Date of Filing

19-Mar-2001

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI- 110 001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	SHYAMAL KUMAR BHANDRA	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
2	SACHCHIDANANDA CHKRABARTI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
3	TARUN KUMAR BANDYOPADHYAY	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
4	KALYAN KUMAR PHANI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
5	NRIPATI RANJAN BOSE	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
6	KAMAL DASGUPTA	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
7	RANJAN SEN	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
8	MUKUL CHANDRA PAUL	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
9	MRINMAY CHANDRA PAL	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
10	TARUN KUMAR GANGOPADHYAY	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,
11	PREM PRAKASH GIRI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CALCUTTA 700 032,

PCT International Classification Number

C03B 37/01

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA