ALKALI GLASS FOR THE PRODUCTION OF CONTINUOUS GLASS FIBER Yu, i. kolesov and a Kolesova UDC666.189.212:666.11.016.2 A constant improvement in the technology for making continuous glass fiber and in its use in rein forcing materials requires an urgent solution to problems of reducing the cost of the initial glass. At change to a new progressive single-stage method for making reinforcing materials, the fraction or the 9 present the cost is 10-30% of the cost of making the glass fiber materials. In the next 5-7 years, with glass cost will be even higher The high cost of the initial glass for making glass fiber is determined by the use of aluminoboro silicate glass. Boric acid is used in its composition, and it is an expensive raw material. In certain countries(England, FRG)[I about 50% of all reinforcing materials for fiber glass reinforced plastics are manufactured from inexpensive alkali glass. In spite of the fact that its use causes a reduction in the productivity of fiber drawing by 20% in comparison with that obtained from aluminoborosilicate glass, the final cost of the glass fiber materials made from it is 20-25% less than that of similar material made from The VNIISPV has performed investigations with the aim of developing an alkali glass composition that would provide the same productivity as the fiber-forming process obtained with aluminoborosilicate glass The investigations resulted in the development of alkali glass No. 7, which has favorable production and use properties [2]. However, its commercial introduction exposed several TABLE 1 drawbacks: a high tendency to crystallize, producing devitrification of the glass in the feeder, and a high residual glass content, causing Glass foaming of the glass in the glass melting vessel on drawing the glass fib No. 7A The purpose of our present investigation was to develop the technology for making spheres of an alkali glass that Temperature corresponding to would not exhibit the stated drawbacks, and also to correct the chemi cal composition of the glass and the batch, and to choose a suitable 1150 1190 feeder construction. We studied the changes in the working properties gn=36 of the glass and the fiber made from it for the following compositional Strength of glass fibre in g/mm[ 210 210 Ca0, 2.5 MgO, 2 Bao, 7.5-10 R,0,"0-2 Mng04, 2 ZrO2,10-14.5 Density in g/em Chemical durability 'of glass Based on a study of the viscosity and crystallization ability of fibre: Napo leached, in mg 4.814 27 the melted glasses, and also of the strength and chemical durability surface on boiling for 3 hours of the fiber, we selected a glass composition(No 7A)that exhibited a reduction in the upper limit of crystallization by 30'C and a shift of the 19.08 16 52 working range of the fiber towards a higher temperature zone in com inIN sulfuric acid 23.719.2 in 2N sodium hydroxid 820 500 parison with glass No.7 A comparative evaluation of the technological properties of the examined glasses was made by melting them in a gas-electric tank V L Panasyuk, Chemical Control of Pro furnace of the Severodonetsk factory of fiber reinforced fiber glasses luction [ in Russian], Gizlegprom(1952). The results of the comparison are presented in Table 1, and the All-Union Scientific Research Institute of Fiber Glass Reinforced Plastics and Fiber Glass. Trans lated from Steklo i Keramika, No 1, pp 25-27, January, 1973 o 1973 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N.Y. 10011. All rights reserved. This article cannot be reproduced for any purpose whatsoever without permission of the publis her. A copy of this article is available from the publisher for $15.00
ALKALI GLASS FOR THE PRODUCTION OF CONTINUOUS GLASS FIBER Yu. I. Kolesov and A. I. Kolesova UDC 666.189.212:666.11.016.2 A constant improvement in the technology for making continuous glass fiber and in its use in reinforcing materials requires an urgent solution to problems of reducing the cost of the initial glass. At present the cost is 10-30% of the cost of making the glass fiber materials. In the next 5-7 years, with a change to a new progressive single-stage method for making reinforcing materials, the fraction of the glass cost will be even higher. The high cost of the initial glass for making glass fiber is determined by the use of aluminoborosilicate glass. Boric acid is used in its composition, and it is an expensive raw material. In certain countries (England, FRG) [1], about 50% of all reinforcing materials for fiber glass reinforced plastics are manufactured from inexpensive alkali glass. In spite of the fact that its use causes a reduction in the productivity of fiber drawing by 20% in comparison with that obtained from aluminoborosilicate glass, the final cost of the glass fiber materials made from it is 20-25% less than that of similar material made from the aluminoborosilieate glass. The VNIISPV has performed investigations with the aim of developing an alkali glass composition that would provide the same productivity as the fiber-forming process obtained with aluminoborosilicate glass. The investigations resulted in the development of alkali glass No. 7, which has favorable production and use TABLE 1 Index Glass Upper crystallization lirnit ~ Temperature corresponding to to log viscosity, in ~ log ~ = 3.2 log 77 = 3.6 Working range in ~ Density in g/era ~ Strength of glass fibre in g/mm ~ Chemical durability *of glass fibre: Na20 leached, in mg Weight loss from 5000 cm 2 of surface on boiling for 3 hours in mg: in water in 1N sulfuric acid in 2N sodium hydroxide rNo. ~A I J 1150 1190 i 1100 1188 50 52 2. 62 2. 61 210 210 4.81 4.27 19. 08 16. 52 ~.3.7 19.2 820 500 * V. L Panasyuk, Chemical Control of Pro duction [in Russian], Gizlegprom (1952). properties [2]. However, its commercial introduction exposed several drawbacks: a high tendency to crystallize, producing devitrification of the glass in the feeder, and a high residual glass content, causing foaming of the glass in the glass melting vessel on drawing the glass fiber. The purpose of our present investigation was to develop the -- commercial technology for making spheres of an alkali glass that would not exhibit the stated drawbacks, and also to correct the chemical composition of the glass and the batch, and to choose a suitable feeder construction. We studied the changes in the working properties of the glass and the fiber made from it for the following compositional range (in %): 63-64.5 SiO 2, 6-12 R~O.~, 0-2 Mn.~Ot, 2 ZrO 2, 10-14.5 CaO, 2.5 MgO, 2 BaO, 7.5-10 R20. Based on a study of the viscosity and crystallization ability of the melted glasses, and also of the strength and chemical durability Df the fiber, we selected a glass composition (No. 7A) that exhibited a reduction in the upper limit of crystallization by 30~ and a shift of the working range of the fiber towards a higher temperature zone in comparison with glass No. 7. A comparative evaluation of the technological properties of the examined glasses was made by melting them in a gas-electric tank furnace of the Severodonetsk factory of fiber reinforced fiber glasses. The results of the comparison are presented in Table 1, and the All-Union Scientific Research Institute of Fiber Glass Reinforced Plastics and Fiber Glass. lated from Steklo i Keramika, No. 1, pp. 25-27, January, 1973. Trans- 9 1975 Consultants Bureau, a division of Plenum Publishing Corporation, 227 g/est 17th Street, New York, N. Y. 10011. All rights reserved. This article cannot be reproduced for any purpose whatsoever without permission of the publisher. A copy of this article is available from the publisher for $15.00. 41
Temperature,°C Fig. 1, Temperature dependence of viscosity: 1) glass No. 7 2)glass No. 7A; 3)nonalkali aluminoborosilicate glass Fig. 2. Feeder bowl after improvements: 1)dispersing spout; 2)bushing: 3)front wall of bowl temperature dependence of viscosity is shown in Fig. 1. It is apparent that glass No 7A is of more tech nological value than glass No. 7. The fiber properties(strength, chemical durability)of glass No 7A are also somewhat better We also made selective additions to the batch to minimize the gas content in the glass and to elimi nate foaming of the glass balls in the glass melting furnace. For this purpose, we laboratory tested ammonium, alkali, and alkaline earth sulfates and nitrates both separately and in combination with arsenic trioxide. The most effective of these(sodium sulfate and calcium nitrate in combination with As2O3)was tested by melting glass in a tank gas-electric furnace. The change in the residual gas content and foaming temperature of the glasses were studied using VNITSPV methods [3, 4]. The results of analyzing the glasses for gas content for different additions to the bath in comparison with the technology of the glass for fiber forming is presented in Table 2 The addition of potassium nitrate to the batch enabled the total gas content in the glass to be reduced in comparison with the glass melted using sodium sulfate by a factor of more than two, the foaming tem- perature to be increased by 40-60%, and the quality of the glass spheres to be increased. The decrease in gas content produced an improvement in the fiber-forming process, and an increase in the productivity of fiber making by more than 35%. The increase in glass quality was associated not only with a reduction in the total gas content, but also with the fact that the amount of water and So dissolved in the glass was re- duced and the content of dissolved oxygen was increased, which verified the previously published data for aluminoborosilicate glass [4] the technological properties of the glass for drawing fiber to be considerably improved. However, the as Selection of the optimum chemical composition of the alkali glass and of the batch composition enabled tained results did not permit us to completely eliminate devitrification of the glass at the feeder bushing where the glass balls are formed For improving the mass exchange and the isothermal characteristics of TABLE 2 。Aw、mm uctivity of
"~o 3,0 "" > ~ 2,5 ". o o ~0 llO0 "120g 1300 14"00 Temperature, * C I I / I : / 1 2 3 Fig. 1 Fig. 2 Fig. 1. Temperature dependence of viscosity: 1) glass No. 7; 2) glass No. 7A; 3) nonalkali aluminoborosilicate glass. Fig. 2. Feeder bowl after improvements: 1) dispersing spout; 2) bushing; 3) front wall of bowl. temperature dependence of viscosity iS shown in Fig. 1. It is apparent that glass No. 7A is of more technological value than glass No. 7. The fiber properties (strength, chemical durability) of glass No. 7A are also somewhat better. We also made selective additions to the batch to minimize the gas content in the glass and to eliminate foaming of the glass bails in the glass melting furnace. For this purpose, we laboratory tested ammonium, alkali, and alkaline earth sulfates and nitrates both separately and in combination with arsenic trioxide. The most effective of these (sodium sulfate and calcium nitrate in combination with AszO~ ) was tested by melting glass in a tank gas-electric furnace. The change in the residual gas content and foaming temperature of the glasses were studied using VNIISPV methods [3, 4]. The results of analyzing the glasses for gas content for different additions to the bath in comparison with the technology of the glass for fiber forming is presented in Table 2. The addition of potassium nitrate to the batch enabled the total gas content in the glass to be reduced in comparison with the glass melted using sodium sulfate by a factor of more than two, the foaming temperature to be increased by 40-60%, and the quality of the glass spheres to be increased. The decrease in gas content produced an improvement in the fiber-forming process, and an increase in the productivity of fiber making by more than 35%. The increase in glass quality was associated not only with a reduction in the total gas content, but also with the fact that the amount of water and SO.~ dissolved in the glass was reduced and the content of dissolved oxygen was increased, which verified the previously published data for aluminoborosiHcate glass [4]. Selection of the optimum chemical composition of the alkali glass and of the batch composition enabled the technological properties of the glass for drawing fiber to be considerably improved. However, the attained results did not permit us to completely eliminate devitrification of the glass at the feeder bushing where the glass balls are formed. For improving the mass exchange and the isothermal characteristics of TABLE 2 lTypl of fin- 3ulfate 7A Sulfate with AsuOa Potassium nitrate with AhOs i r,..) [Gas content in ~ with reference to the ~ Itotal volume of a ~lass ball ~ ~ tTotal [ ,~ ~ Ivolumd H0o so, co, o, N2 o g igases 1120 1140 1180 291 141 307 173 190 100 14n 65 J 85 16,5 [ 49,5 55,6 15,7 I 21 41,7 10,0 2,0 67,5 10,5 1,0 1,6 65,5 7,5 Average daily productivity of eiectrofurnace. kg /thickness os fiber 16.7 "rex" 37:1 39,2 57,4 60,2 42
the glass in the feeder bowl, we her with workers from the glass melting plant of the Severodonetsk pastic. factory of fiber glass reinforced plastics, developed and tested a new configuration of the bowl with a dis- persing spout. The presence of a spout enabled us to change the flow of glass, to almost completely elimi- nate "stagnant" glass and devitrifie of the glass in the front part of the bowl(Fig. 2). The tempera ture here was increased to 1160-1165C As a result of these studies and of the commercial trials, we improved the composition of the alkali glass and developed the technology for melting it and for making glass balls from it. The good results achieved in making fiber from glass No. 7A indicates a real possibility for considerably reducing the cost of reinforcing materials made from alkali glass LITERATURE CITED ociety of Plastics Industry, Proceedings of the 22nd Annual Technical Conference, Washington (1965) 2. E. P. Dain et al. in: Composition and Properties of Glasses for the Production of Glass Fiber [in Russian TsINTILegprom (1963) 4. K. v. Nagulevich, V. P. Polyakov, and Yu. I Kolesov, Steklo i Keram, No 5(1968) K. V. Nagulevich and Yu. I. Kolesov, ibid., No 6(1968)
the glass in the feeder bowl, we, together with workers from the glass melting plant of the Severodonetsk factory of fiber glass reinforced plastics, developed and tested a new configuration of the bowl with a dispersing spout. The presence of a spout enabled us to change the flow of glass, to almost completely eliminate "stagnant" glass and devitrification of the glass in the front part of the bowl (Fig. 2). The temperature here was increased to 1160-1165~ As a result of these studies and of the commercial trials, we improved the composition of the alkali glass and developed the technology for melting it and for making glass balls from it. The good results achieved in making fiber from glass No. 7A indicates a real possibility for considerably reducing the cost of reinforcing materials made from alkali glass. i, 2. 3. 4. LITERATURE CITED Society of Plastics Industry, Proceedings of the 22nd Annual Technical Conference, Washington (1965). E. P. Dain et al., in: Composition and Properties of Glasses for the Production of Glass Fiber [in Russian], TsINTILegprom (1963). K. V. Nagulevieh, V. P. Polyakov, and Yu. I. Kolesov, Steklo i Keram., No. 5 (1968). K. V. Nagulevieh and Yu. I. Kolesov, [bid., No. 6 (1968). 43