GB1571248A

GB1571248A - Method of preparing boron-containing glass batch

Info

Publication number: GB1571248A
Application number: GB45905/77A
Authority: GB
Inventors: Stanley F Brzozowski; Joseph E Cooper
Original assignee: PPG Industries Inc
Current assignee: PPG Industries Inc
Priority date: 1976-11-08
Filing date: 1977-11-04
Publication date: 1980-07-09
Also published as: FR2370001A1; FR2370001B1; NL7710110A; DE2749328A1; NL181989C; JPS5358510A; JPS59453B2

Description

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ERRATA SPECIFICATION No., 1, 571, 248 Page 1, line 45, for furance read furnace Page 2, line 29, after ceniimeters insert) Page 2, line 72, after coal insert Page 2, line 97, delete whole line insert (1) B+3H, 02H, BO, a .

Page 2, lines 103 and 104, delete whole lines insert (7) 5H20 2 6 1l -f-SH 0 A (Colemanite) 770"F (410 C) Page 4, line 64, after hour insert) Page 4, line 75, for mesaured recd rneasured Page 5, line 23, after could delete by insert be THE PATENT OFFICE 9th March, 1981 are fed to hber glass mr" extremely fine condition, i. e., almost all batch particles are less than 20 mesh (U. S.

Sieve Series), with the majority being less than 200 mesh (U. S. Sieve Series). Because of the fineness of the batch ingredients, dusting is encountered in fiber glass batch melting furnaces. In addition, fiber glass batches contain considerable quantities of boron-containing materials and other rather expensive ingredients, some of which are lost in the stack gases should dusting occur during feeding. Further, some of these batch materials volatilize into the stack gases as they are melted. By cohesively binding batch ingredients of the fineness normally encountered in a fiber glass batch, reduced dusting and volatilazation of the batch ingredients and the concomitant reduction in the loss of expensive ingredients can be achieved. In addition, by providing fiber glass batch in pelletized form, avantage can be taken of the sensible various binding preparation of briquettes for feeding to glass melting furnaces. U. S. Patent No. 2,976,162 describes a process of this nature. In other patent literature involved in the preparation of fiber glass type batches, special treatments have been applied to the glass batch to provide for prereaction of glass batch ingredients prior to feeding them to the glass melting furnace. A process of this character is described in U. S. Patent No.

3, 001, 881. Still further, the glass batch ingredients themselves have been carefully selected to provide boron-containing glass batch materials of specific character to help eliminate some of the foaming problems occurring during melting utilizing high boron-containing glass batches such as are encountered in the fiber glass industry. A patent describing one such process is U. S.

Patent No. 3, 287, 095. By practice of the present invention, there may be provided (54) METHOD OF PREPARING BORON-CONTAINING GLASS BATCH (71) We, PPG INDUSTRIES, INC, a Corporation organized and existing under the laws of the'State of Pennsylvania, United States of America, of One Gateway Center, Pittsburgh, State of Pennsylvania, 15222, United States of America, (assignee of STANLEY FRANK BRZOZOWSKI and JOSEPH EVERETT COOPER), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a process for preparing boron-containing glass batch compositions utilizing boric acid, boric oxide and/or colemanite as the boron source.

Fiber glass batches, unlike soda-lime glass batches and other commercial batches utilized to make containers and flat glass, are fed to fiber glass melting furnaces in an extremely fine condition, i. e., almost all batch particles are less than 20 mesh (U. S.

Sieve Series), with the majority being less than 200 mesh (U. S. Sieve Series). Because of the fineness of the batch ingredients, dusting is encountered in fiber glass batch melting furnaces. In addition, fiber glass batches contain considerable quantities of boron-containing materials and other rather expensive ingredients, some of which are lost in the stack gases should dusting occur during feeding. Further, some of these batch materials volatilize into the stack gases as they are melted. By cohesively binding batch ingredients of the fineness normally encountered in a fiber glass batch, reduced dusting and volatilazation of the batch ingredients and the concomitant reduction in the loss of expensive ingredients can be achieved. In addition, by providing fiber glass batch in pelletized form, advantage can be taken of the sensible heat contained in the furance flue gases to preheat the fiber glass batch pellets prior to feeding them to the glass melting furnace.

Further, the close contact between the particles within the pellets improves their heat transfer characteristics and thus results in faster melting, improved energy efficiency and reduced furnace wear.

Considerable activity has taken place in recent years and particularly in relation to the preparation of soda-lime glass batches in which the batch ingredients have been pelletized for feed to glass melting furnaces.

Thus, a recent U. S. Patent No. 3, 880, 639 describes the utilization of an agglomerated soda-lime glass batch in which the pellets are preheated via direct heat exchangers prior to feeding them to a glass melting furnace.

Activity has also occurred in the preparation of fiber glass batches in that glass batches have been prepared with various binding materials for the preparation of briquettes for feeding to glass melting furnaces. U. S. Patent No. 2, 976, 162 describes a process of this nature. In other patent literature involved in the preparation of fiber glass type batches, special treatments have been applied to the glass batch to provide for prereaction of glass batch ingredients prior to feeding them to the glass melting furnace. A process of this character is described in U. S. Patent No.

Patent No. 3, 287, 095. By practice of the present invention, there may be provided compositions suitable for the preparation of glass fibers in which the batch, prior to its introduction into the furnace, is peiletized by adding water in sufficient quantities to maintain an adequate balling action and thus provide pellets in a form such that preheating by direct contact with flue ases does not cause deterioration of the pellets.

According to the present invention there is provided a method of preparing a boroncontaining glass fiber-forming glass batch wherein said boron is supplie as boric acid, boric oxide and/or colemanite, the method comprising introducing the batch ingredients into a pelletizing zone, agglomerating the ingredients with sufficient free water to produce pellets and drying the pellets by heating the pellets at sufficient temperature and for a sufficient period of time thereby to produce hard, non-dusting pellets.

An example of a suitable pelletizing zone is an incline rotating disc pelletizer, as is shown in U. S. Patent No. 3, 914, 364.

The pellets may range in nominal diameter, for example, from 0. 125 to 1. 00 inch (0.3175 to 2.54 centimeters) and preferably from 0.375 to 0.625 inch (0.9525 to 1. 5875 centimeters. Sufficient water is added to bind the batch ingredients together and provide pellets of the batch materials.

Preferably, these pellets, before drying, contain 5 to 22 percent by weight free water, when boric acid is employed, 10 to 25 percent free water when boric oxide is employed and 5 to 20 percent free water when colemanite is employed. Most preferably, the water is added to provide 11 to 13 percent by weight free water for boric acid, 15 to 17 percent free water for boric oxide and 10 to 13 percent free water for colemanite.

The pellets after formation are dried at a temperature of at least 450 F. (232.2 C.) for boric oxide, preferably at a temperature from 220 F. (104. 4 C.) to 1000 F.

(537.8 C.) for boric acid, and preferably at a temperature of not more than 770 F.

(410 C.) more preferably from 220 F.

(104. 4 C) to 770 F. (410 C.), for colemanite for a sufficient period of time to provide a free water content preferably of below I percent by weight. Hard, substantially nondusting pellets are thus produced. The hard, non-dusting pellets thus formed can be fed to a glass melting furnace and exposed to conditions in excess of 2700 F. (1482. 2 C.) without any explosions of the pellets occurring.

When colemanite is employed as a boron source, the batch ingredients may contain only colemanite as the boron source.

Optionally, a portion, for example up to 75 percent of the colemanite, based on B 03, may be substituted by boric acid, while adjusting for lost silica, calcium and alumina contained in the colemanite.

Typical"E"glass type boron containing glass fiber forming batch compositions, such as those illustrated in U. S. Patent No.

2,334,961, comprise silica, clay, limestone, coal fluorspar, sodium sulfate, ammonium sulfate and boric acid. In lieu of boric acid, colemanite may be used. The use of colemanite is described in U. S. Patent No.

3,274,006. Colemanite has a chemical composition of Ca2BsOlg 5H2O.

Optionally, boric acid may be substituted for a portion, for example up to 75 percent, of the colemanite on an equivalent B, O, basis while adjusting for lost silica, calcia and alumina from the colemanite. There is no caustic soda present in the compositions.

These glass batch ingredients, when prepared in accordance with the present invention, are believed to undergo several chemical reactions during their introduction into the pelletizing zone, for example during their deposition on the pelletizing disc, and while water in the quantity sufficient to produce the pellets is being added to the ingredients and during the drying of the pellets. The primary reactions involved in the preparation of the pellets in accordance with the present invention are believed to be as follows : (1) B2O3S+3H2PL#2H3BO3s (2) H3BO3S+H2OL#H3BO3L+H2OL#H3BO3S+H2O# (3) 2H3BO3AB203+3H2Ot (4) 4H3BO3+CaCO3#CaB4O7+CO2#+6H2O# (5) B03+Na2SOI+5H, ONa, B, O,. IOH, O+H, SO, (6) CaCO3+H2SO4#CaSO4+CO2#+H2O# (7) Ca2BeO,,-SHOQCa2BeO,+5H20 (Colemanite) 770 F. (410 C.) In reaction (1) the boric oxide, if employed, is reacted with water to form boric acid. In reaction (2) the boric acid and water react to dissolve the boric acid and then the boric acid is recrystallized as shown in the equation. The recrystallized boric acid is dehydrated during the drying step to drive water off, as can be seen in equation (3). Some of the boric acid itself, during the drying of the pellets, reacts with the calcium carbonate present to form hydrated calcium pyroborate, carbon dioxide and water in accordance with equation (4). Boric acid also reacts with the sodium sulfate present in the batch in accordance with equation (5) to form hydrated sodium tetraborate and sulfuric acid. Limestone and sulfuric acid may also react to form calcium sulfate, carbon dioxide and water, in accordance with equation (6).

Regardless of the reactions that take place, it is extremely important in the preparation of the glass batch pellets in accordance with the present invention that, if boric oxide is used as the boron source, during the drying step, the drying temperature be at least 450 F. (232.2 C).

Attempts to dry pellets below this temperature result in their disintegration and return to the powdery state. Thus, extreme care is taken to provide a hard, non-dusting pellet by regulating the drying operations such that the pellets are dried at sufficient temperatures to produce hard, non-dusting pellets, i. e. at least 450 F (232.2 C.). The pellets may be dried at any higher temperature up to the melting point of a given pellet, which, of course, will vary according to the exact batch composition.

By adhering to the temperature parameters hereinabove described with respect to their drying, pellets which are extremely hard and non-dusting are readily produced.

If boric acid is used as the boron source, the pellets may be dried slowly at temperatures of 220 F. (104. 4 C.) or they may be dried somewhat more rapidly at temperatures up to 1000 F. (537.8 C.) until they reach a non-dusting, hard state.

Temperatures below 220 F. or above 1000 F. may also be used to dry pellets using boric acid as the boron source. The only constraint on the uppermost drying temperature for a given pellet is its melting temperature which, of course, will vary depending upon its exact composition.

It is extremely important in the preparation of glass batch pellets in accordance with the present invention that if colemanite is used as the single source of B203, temperatures above 770 F (410 C) be avoided during the drying step. Attempts to dry these pellets above this temperature result in the disintegration of the pellets and their return to the powdery state. Thus, extreme care is taken to provide pellets by regulating the drying operation, such that the pellets are dried at temperatures not exceeding 770 F. (410 C.).

When boric acid is substituted for a portion, for example up to 75 percent, of the colemanite, with proper adjustments being made for silica, calcium and alumina in composition, these temperature parameters must still be followed. Hard, non-dusting pellets can be produced at drying temperatures up to 770 F. (410 C.).

When drying the colemanite containing pellets of the present invention, should the temperature of the pellets exceed 770 F.

(410 C.), it has been found that the pellets crack and disintegrate. This problem, however, may be solved by pretreating the colemanite prior to its addition to the glass batch, and then forming the glass batch using the pretreated colemanite into pellets.

This pretreatment comprises heating the colemanite at a temperature above 770 F.

(410 C) for a sufficient period of time until substantially all of the chemically bound water in the colemanite is driven from this material. An equation for this reaction is shown above as equation (7). This water amounts to approximately 21 to 22 percent by weight. There is also an expansion of up to 33 percent by volume of the colemanite when the chemically bound water is driven off, which accounts for the cracking of pellets when heated above this temperature using untreated colemanite. By employing this pretreatment to the colemanite prior to its introduction into the glass batch, pellets as heretofore described may be dried at any temperature up to the melting point of a given pellet, for example from 220 F.

(104.4 C) to the melting point of a given pellet, and preferably from 220 F. to 1000 F. (104. 4 C. and 537.8 C.), without fear of cracking, to produce hard, nondusting pellets.

Pellets produced in accordance with the practice of the present invention thus provided to a glass melting furnace for the production of glass fibers are considerably less dusty than the loose batch ingredients conventionally employed. Further, since the boric acid is an excellent fluxing agent, the wetting of the boric acid upon its intimate contact with all batch ingredients, in addition to causing the reactions as indicated hereinabove in equations (2) through (6), provides for intimate contact of the boron contained in the batch with all of the other batch grains present. This assists in rapidly melting the silica and alumina constituents of the glass batch which, as will be readily understood, are the most difficult ingredients to melt. The pellets of the present invention may be preheated prior to their addition to the glass melting furnace such as, for example, by passing them through the flue gases of the furnace, or passing the gases through a bed of the pellets. In addition to preheating the pellets and thus reducing the amount of furnace input energy needed to melt them, this passage of flue gases through a bed of pellets may cause a reduction of air pollution from the flue gases by removing via a filtering action at least part of the harmful materials, such as F2, and B203, from the flue gases. Utilizing hot flue gases at temperatures typically in the range of 800 F. to 2850 F. (426.7 C. to 1565. 6 C.), pellets can be preheated to temperatures of 200 F. to 1500 F. (93.3 C. to 815. 6 C.) to recover sensible heat and assist in reducing the amount of fuel needed to melt the pellets fed to the furnace.

The present invention will now be further illustrated by way of the following Examples, and with reference to the accompanying drawing which is a graph representing energy consumption for a glass fiber melting tank using the pellets of the present invention.

EXAMPLE t An"E"type fiber forming glass batch comprising : Percent by Component Weight Silica 29.665 Clay 26.930 Limestone 27.786 Fluorspar 2.336 Sodium Sulfate 0.794 Ammonium Sulfate 0.224 Boric Acid 12. 181 Coal 0.084 was combined on a disc pelletier with sufficient water to produce pellets containing about 12 percent by weight free water. A portion of the pellets was dried at 220 F. (104. 4 C.) for 196 minutes and another portion was dried at l 000 F.

(537.8 C.) for 20 minutes. The pellets produced in each instance were hard and non-dusting and could be physically handled without damage.

Pellets of the above composition were produced on a production scale in the following manner: The batch materials were weighed out to give the desired compositions. This material was then fed to a 39. 37 inch (I meter) diameter inclined rotating disc pelletier havin, an angle of inclination of approximately 45 at a controlled rate of from 400 to 1000 pounds per hour (l81. 4 to453. 6 kilograms per hour). Water was fed to the disc at a controlled rate of from 54.5 to 136. 4 pounds per hour (24.7 to 61. 9 kilograms per hour. The pellets thus produced were dried in a gas fired oven at temperatures of 490 F. to 525 F. (254.4 C. to 273. 9 C.) for approximately 5 minutes.

The dried pellets were fed to a continuous melt glass fiber forming tank at a rate of about 756 pounds per hour (342. 9 kilograms per hour).

The graph in the drawing represents the energy consumption of the glass melting tank during a 52 day period. Energy consumption is mesaured by the total gas flow to the melting tank in cubic feet per hour consumed.

Point A on the graph represents the first day of measurements for the test. Between Point A and Point B, regular, unpelletized loose batch material was fed to the furnace.

Over this 15 day span, the average energy consumption was 8,635 cubic feet per hour.

At point B, pellets were initially added to the batch. During day 16, Point C, the glass tank reached the point where all batch material in the tank was fed to the tank from pellets.

From Point C to Point D, the pellets which were fed to the tank entered the tank at temperatures from 140 F. to 150 F.

(60 C. to 65 C.). During this time span, the average energy consumption was 8, 397 cubic feet per hour, a reduction of 2.8 percent from the average fuel consumption for the tank using loose batch material.

During day 30, Point D, at 12 noon, and continuing until Point E, pellets having a temperature of from 180 F. to 190 F.

(82 C. to 87.8 C.) were fed to the tank. The average energy consumption during this time span was 8, 129 cubic feet per hour, a 5.9 percent reduction from the loose batch, During the day between Points E and F, pellets having an average temperature of approximately 110 F. (43.3 C.) were fed to the tank.

During the day marked as Point G, one hopper of the pellets which was heated for approximately 1-1/2 hours was fed to the tank. Similarly, one heated hopper was fed to the tank during the day marked Point H.

During the day marked Point I, and continuing to Point J, pellets heated to a temperature of from 300 F. to 400 F.

(148. 9 C. to 204.4 C.) were fed to the tank.

The average energy consumption during this time span was 7, 952 cubic feet per hour, a 7.9 percent reduction over the loose batch.

At approximately 9: 20 a. m. on day 50, Point K, loose batch was again fed to the tank. As can be seen from the graph, the average energy consumption rose back into the range between Points A and B, when loose batch was previously employed.

EXAMPLE 11 An"E"type fiber forming glass batch comprising: Percent by Component by Weight Silica 31. 532 Clay 28.615 Limestone 29.380 Fluorspar 2.469 Sodium Sulfate 0.843 Ammonium Sulfate 0.238 Boric Oxide 6.835 Coal 0.088 was combined on a disc pelletier with sufficient water to produce pellets containing approximately 16 percent by weight free water. Portions of the pellets were dried at 220 F. (104. 4 C.) for 28 minutes, 460 F. (237.8 C.) for 35 minutes and 1000 F. (537.8 C.) for 28 minutes.

The pellets dried at 460 F. (237.8 C.) and 1000 F. (537.8 C.) were hard and nondusting, and could by physically handled without damage. However, the pellets dried at 220 F. (104. 4 C.) completely disintegrated within the 28 minutes of drying.

EXAMPLE III An"E"type fiber forming glass batch comprising : Percent by Component Weight Silica 30.758 Clay 27.986 Limestone 20.922 Coal 0.108 Fluorospar 2.454 Ammonium Sulfate 0.237 Sodium Sulfate 1.041 Colemanite 16. 494 was combined on a disc pelletier with sufficient water to produce pellets containing about 12 percent by weight free water. The pellets were dried at temperatures of 490 F. to 525 F. (254.4 C. to 273.9 C.) for approximately 5 minutes.

The resulting pellets produced were rigid, however, most could be crushed by hand pressure.

EXAMPLE IV An"E"glass type fiber forming batch comprising : Percent by Component weight Silica 31. 040 Clay 28.227 Limestone 21. 698 Boric Acid 3.566 Colemanite 11. 853 Flurospar 2.411 Sodium Sulfate 0.854 Ammonium Sulfate 0.251 Coal 0. 100 was combined into pellets. The colemanite used was treated at 1000 F. (537.84C.) for approximately two hours to remove its chemically bound water prior to its additon to the batch. This composition represented a 30 percent boric acid substitution for colemanite based on Bu03. The batch was pelletized and dried in the same manner as in Example 1II. The resulting pellets were hard and non-dusting and had good mechanical strength.

EXAMPLE V An"E"glass type fiber forming glass batch comprising : Percent by Component Weight Silica 30.302 Clay 27.632 Limestone 24.320 Colemanite 8. 206 Boric Acid 5.882 Fluorspar 2.373 Sodium Sulfate 0.939 Ammonium Sulfate 0.247 Coal 0. 099 was combined into pellets. In this example, the colemanite was not pretreated prior to its addition to the batch. This batch represented a 50 percent boric acid substitution for colemanite based on B203.

The batch was pelletized and dried as in Example III. The resulting pellets were hard and non-dusting and possessed good mechanical strength.

EXAMPLE VI An"E"glass type fiber forming glass batch comprising: Percent by Component Weight Silica 30.137 Clay 27.397 Limestone 26.174 Colemanite 4.061 Boric Acid 8.659 Fluorspar 2.348 Sodium Sulfate 0.881 Ammonium Sulfate 0.245 Coal 0.098 was combined into pellets. The colemanite was not pretreated prior to its addition to the batch. This batch composition represented a 75 percent substitution of boric acid for the colemanite based on Bu03. The batch materials were pelletized and dried as in Example I1I. The resulting pellets were hard and non-dusting and possessed good mechanical strength.

From the foregoing, it is clear that, by employing pellets of the present invention as the batch material for a glass fiber forming glass melt tank, significant energy savings are realized. Further, it is clear that when the pellets are preheated prior to their entry into the tank, even greater energy savings are realized.

Claims

WHAT WE CLAIM IS :- 1. A method of preparing a boroncontaining glass fiber-forming glass batch wherein said boron is supplied as boric acid, boric oxide and/or colemanite, the method comprising introducing the batch ingredients into a pelletizing zone, agglomerating the ingredients with sufficient free water to produce pellets and drying the pellets by heating the pellets at sufficient temperature and for a sufficient period of time thereby to produce hard, non-dusting pellets.
2. A method as claimed in claim I wherein said pelletizing zone comprises an incline, rotating disc pelletizer.
3. A method as claimed in claim I or claim 2 wherein said pellets are produced having nominal diameters of from 0.375 to 0.625 inch (0.9525 to !. 5875 centimeters).
4. A method as claimed in any one of claims I to 3, wherein the pellets are driedto a free water content of 1 percent or less, by weight.
5. A method as claimed in any one of claims I to 4, wherein the pellets contain boric oxide and wherein the free water content, before drying, is 10 to 25 percent by weight.
6. A method as claimed in claim 5, wherein the free water content of the pellets, before drying, is 15 to 17 percent by weight.
7. A method as claimed in any one of claims I to 4, wherein the pellets contain boric oxide and are dried at a temperature of at least 450 F. (232.2 C.).
8. A method as claimed in claim 5 or claim 6, wherein the pellets contain boric oxide and are dried at a temperature of at least 450 F. (232 C.).
9. A method as claimed in any one of claims I to 4, wherein the pellets contain boric acid and wherein the free water content, before drying, is 5 to 22 percent by weight.
i0. A method as claimed in claim 9 wherein the free water content, before drying, is
11 to 13 percent by weight.

I1. A method as claimed in any one of claims I to 4 wherein the pellets contain boric acid and are dried at a temperature from 220 F. (104. 4 C.) to 1000 F.

(537.8 C.).
12. A method as claimed in claim 9 or claim 10 wherein the pellets contain boric acid and are dried at a temperature from 220 F. (104. 4 C.) to 1000 F. (537.8 C).
13. A method as claimed in any one of claims I to 4 wherein the pellets contain colemanite and wherein the free water content, before drying, is 5 to 20 percent by weight.
14. A method as claimed in claim 13 wherein the free water content, before drying, is 10 to 13 percent by weight.
15. A method as claimed in any one of claims I to 4 wherein the pellets contain colemanite and are dried at a temperature of up to 770 F. (410 C.).
16. A method as claimed in claim 13 or claim 14 wherein the pellets contain colemanite and are dried at a temperature of up to 770 F. (410 C.).
17. A modification of the method as claimed in any one of claims 1 to 4, wherein colemanite is employed as a batch material and wherein said colemanite is pretreated prior to its agglomeration by heating it at a temperature of at least 770 F. (410 C.) for a sufficient period of time to drive off substantially all of the chemically bound water within said. colemanite.
18. A method as claimed in claim 17 wherein said pellets are dried at a temperature of from 220 F. (104. 4 C.) to 1000 F. (537. 8 C.).
19. A modification of the method as claimed in any one of claims 13, 14 or 16 wherein colemanite is employed as a batch material and wherein said colemanite is pretreated prior to its agglomeration by heating it at a temperature of at least 770 F.

(410 C.) for a sufficient period of time to drive off substantially all of the chemically bound water within said colemanite.
20. A method as claimed in claim 19 wherein said pellets are dried at a temperature of from 220 F. (104. 4 C.) to 1000 F. (537.8 C.).
21. A method as claimed in any one of claims 13, 14, 16, 19 or 20, wherein up to 75 percent of said colemanite based on B203, is replace by boric acid.
22. A method as claimed in any one of claims 15, 17 or 18 wherein up to 75 percent of said colemanite based on B203, is replace by boric acid.
23. A method of preparing a boroncontaining glass fiber-forming glass batch substantially as hereinbefore described and with reference to Example 2.
24. A method of preparing a boroncontaining glass fiber-forming glass batch substantially as hereinbefore described and with reference to any one of Examples 3 to 6.
25. A method of preparing a boroncontaining glass fiber-forming glass batch substantially as hereinbefore described and with reference to Example I and as illustrated in the accompanying drawing.
26. A boron-containing glass fiber forming glass batch whenever prepared by a process as claimed in any one of claims I to 4, 7, 11, 15, 17, 18 or 22.
27. A boron-containing glass fiberforming glass batch whenever prepared by a process as claimed in any one of claims 5,6, 8 or 23.
28. A boron-containing glass fiberforming glass batch whenever prepared by a process as claimed in any one of claims 9, 10, 12 or 25.
29. A boron-containing glass fiberforming glass batch whenever prepared by a process as claimed in any one of claims 13, 14, 16, 19, 20, 21 or 24.