DE2749328A1 - Process for the production of a boron-containing glass batch for glass fibers - Google Patents

Description

PPO Industries, Inc., Pittsburgh, Pa., USA

VEBIiBBEH ZUB HEBSTELLUSG XIRZS BOBHALTIGIN GLASANBATZXS Jt) B OLASVASXBI

This invention is directed to a method of making boron-containing batches for processing au glass fibers, where boric acid, anhydrous boric acid or Colemanlt are used as boron-containing starting materials will.

Approaches of starting materials for the production of glass fibers are, in contrast to approaches for soda-lime glasses and other common approaches, which are used for the manufacture of containers or flat glass, the melting furnace for the production of the glass fibers in supplied in an extremely fine state, i.e. that almost all the particles in the batch have such a small particle size have that they pass through a 20-mesh sieve and the Hehrheit even through a 200-mesh sieve Meshes (US standard) to pass through, Vegen the delicacy of the components of the approach is a dust in the Observe the melting furnace during the production of glass fibers. In addition, the approaches for the production of glass fibers contain considerable amounts of boron-containing Materials and other relatively expensive raw materials, some of which are lost in the exhaust gases due to the formation of dust. In addition, some of the starting materials volatilize into the exhaust gas during melting. If you deny the Starting materials for the production of glass fibers, which have the usual fineness, are combined with one another, there is less dust formation and volatilization of these raw materials and at the same time the loss of expensive raw materials is reduced. By overriding the approach for the production of glass fibers

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in a tableted form can also be used to advantage nor the noticeable heat of the exhaust gases can be used to preheat the pelletized approach for glass fibers before it is fed to the melting furnace. In addition, the close contact between the particles within the tablets facilitates heat transfer improves, resulting in faster melting, improved energy yield and less wear of the oven.

There has recently been notable activity particularly in the approaches to soda-lime glasses took place, with the batch ingredients being tabletted for introduction into the melting furnaces. So is described in US-PS 38 80 639 the use of an agglomerated soda-Kalkglasansatzea, the tablets by means of direct heat exchangers preheated prior to introduction into the furnace.

Approaches have also been made for the production of glass fibers against dust before they are introduced into the Melting furnace treated, e.g. by adding various binders that are suitable for the production of briquettes. In US-PS 29 76 162 such a method is described. In other patents that involve making an approach for Concerning glass fibers, special treatments are provided in order to achieve a pre-reaction of the constituents of the glass batch before it is fed to the melting furnace. One method of this type is in U.S. Patent 30 01 881. In addition, the components of the glass attachment containing boron have been carefully selected Glaaaneätae of specific character made to eliminate some problems caused by the foaming occur that when melting approaches old one

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high boron content in the manufacture of glass fibers is observed. Such a process is described in US Pat. No. 3,287,095.

This invention now relates to a process for the production of a non-dusting boron-containing glass batch for processing into glass fibers, in which the Boron is provided by boric acid, anhydrous boric acid or colemanite and is characterized by that the. boron-containing starting materials are introduced into a tabletting zone * the starting materials are agglomerated with sufficient free water su tablets and the tablets are dried by heating them at a sufficient temperature for a sufficient period of time to make them hard, non-dusting To give tablets

In a preferred embodiment of the invention If there is a tablet device with an inclined, rotating disk in the tablet zone, as described in US Pat. No. 39,364. The starting materials of the approach and water are added in suitable amounts, so that on such a Tabletting device a continuous production of tablets of the glass base of the desired Size is possible. The nominal diameter of the tablets can be between about 0.317 and 2.54 cm, preferably 0.952 to 1.587 cm. To connect the starting materials, water is added in sufficient quantity, so that it comes to the formation of tablets from the starting materials. When using boric acid they contain Tablets preferably have a free water content of about 5 to 22% by weight; when using anhydrous boric acid if this content is between 10 and 25% by weight and when using colemanite, the content is free water preferably 5 and 20% by weight. Aa best is so much water

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admitted that when using boric acid tablets with a free water content of about 11 to 13% by weight are formed, this free water content is 15 to 17% by weight when using anhydrous boric acid and 10 to 13% by weight when using oolemanite .%. After the tablets have been produced, they are dried. The drying temperatures are in use of boric acid from about 104 ⁰ C and below, to 538 ⁰ C and above, with the use of anhydrous boric acid least 232.2 ⁰ C and using colemanite about 104,4 ⁰ C or less to 410 ⁰ C. Drying times are sufficient to ensure that the free water content is preferably less than 1% by weight. This process ensures the production of solid, essentially non-dusting tablets. The solid, non-dusting tablets produced in this way can be introduced into a glass melting furnace and ^{exposed there to reaction temperatures of more than 1,482 °} C. without the tablets exploding.

If colemanite is used as the boron starting material, the batch can only contain colemanite. If necessary can contain up to 75% or more of the colemanite on a B2O basis be replaced by boric acid, with calcium and calcium to compensate for the lack of silicon dioxide in the colemanite Aluminum oxide are included.

On the attached drawing there is a graphic representation of the energy consumption in a glass fiber melting furnace, in which the tablets according to the invention are used.

Typical boron-containing approaches to making "E" glass for glass fibers such as those described in U.S. Patent No. 2,334,961, to which reference is made here are composed of silicon dioxide, clay, limestone, fluorspar,

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Sodium sulfate, ammonium sulfate and boric acid. Instead of boric acid, colemanite can be used. The use of colemanite is described in US Pat. No. 3,274. Colemanite has the former formula Ca ₂ BgO ₁₁ . 5H ₂ O. If desired, up to 75 percent or more of the colemanite can be _{replaced with boric acid on an equivalent B 2} O basis, with calcium oxide and aluminum oxide from the colemanite making up for the missing silica. The compounds do not contain caustic soda. It is assumed that the starting materials of the glass batch according to the method of the invention undergo various chemical reactions while they are added to the tablet disk with the addition of a sufficient amount of water for the production of the tablets and during the drying of the tablets. It is assumed that the reactions proceed according to the following chemical equations

(1). B ₂ O ₈ + 3 H ₂ 0 _L ^ 2 H ₃ BO ₃

(2) H ₃ BO ₃ + H ₂ O ^. H ₃ BO ₃ +

(3) 2 HJJO- V BO, + 3 H ₉ O ^

(4) 4 H-BO, + CaCO, CaB-O ₇ + CO ₀ A + 6

(5) 4 H ₃ BO ₃ + Na ₂ SO ₄ + 5 HjO- ^ ^Νβ 2 ^Β 4 ° 7 ^{'10 Η} 2 ° ^{+ H} 2 ^SO 4

(6) CaCO ₃ + H ₂ SO ₄ - ^. CaSO ₄ + CO ₂ ^ +

(7) Ca ₂ B ₆ O _n '5 H ₂ O - ^> Ca ₂ B ₆ O ₁₁ + 5

(Colemanite)

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In reaction (1), the anhydrous boric acid, if used, is reacted with the water and boric acid is formed. In the reaction (2), boric acid and water react so that the boric acid is dissolved whereupon, as shown in the equation, the boric acid is recrystallized. As As can be seen from equation (3), the boric acid recrystallized during the drying step dehydrated. According to equation (4), part of the Boric acid during the drying of the tablets with the calcium carbonate present to form aqueous calcium pyroborate, Carbon dioxide and water implemented. According to equation (5) boric acid is also present in the batch Sodium sulfate converted to aqueous sodium tetraborate and sulfuric acid. According to equation (6), Limestone and sulfuric acid also to calcium sulfate, Carbon dioxide and water are converted.

When using colemanite as the sole starting material for B ₃ O ₅ in the production of the tablet-shaped glass batch according to the invention, it is of the utmost importance that temperatures above about 410 ° C. are avoided during the drying stage. Attempts to dry these tablets at higher temperatures show that the tablets disintegrate and disintegrate again into the powdery state. Therefore, the tablets extreme care to preserve is to use the fact that the drying step is controlled such that the tablets are dried at temperatures that do not exceed 410 ⁰ C.

If colemanite is replaced by boric acid up to 75% and above, with an appropriate balance in the composition for silicon dioxide, calcium and aluminum oxide, this restriction on the drying temperature also applies. Solid, non-dusting tablets can be added

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Drying temperatures make up to 410 ⁰ C. When the tablets with colemanite content are dried in accordance with the process of the invention, it is found that if a temperature of 41O ° C. is exceeded, the tablets break and disintegrate. This problem can be solved by subjecting the colemanite to a pretreatment before it is added to the glass batch and then producing tablets from the glass batch containing the pretreated colemanite. This pretreatment consists in heating the colemanite at a temperature above 410 ^° C. for a period of time which is sufficient to drive off essentially all of the chemically bound water from the colemanite. This implementation is shown in equation (7). This water content in the colemanite is about 21-22% by weight. It is also shown that the volume of the colemanite increases by up to 33% when the chemically bound water is expelled, which explains why the tablets with non-pretreated colemanite burst above the specified temperature. If the colemanite is subjected to a similar pretreatment before it is added to the glass batch, the tablets can be dried as described above without the need to adhere to a specific maximum limit for the drying temperature. These temperatures can be arbitrarily selected from about 104 ⁰ C or less up to the melting point of each tablet, preferably without even the risk of Zerspring ens for the manufacture of solid, non-dusting pellets is between about 104 ° C and 538 ⁰ C,.

The tablets produced according to the process of the invention produce a significantly lower figure when used in a melting furnace for producing glass fibers

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Dust formation as usual glass batches, the starting materials of which are added in loose form. There Boric acid is also an excellent flux, the wetting of boric acid leads to it Contact with all starting materials of the glass base, not only with the conversions according to the equations (2-6), but also to a close contact with all other components of the glass attachment. This promotes rapid melting of the silica and alumina constituents of the glass batch, which are obviously the am are the most difficult raw materials to melt.

The tablets according to the invention can be preheated before they are introduced into the melting furnace, for example, by conveying them through the exhaust gas stream of the furnace, or by passing the exhaust gases through a bed of the tablets. In addition to saving energy by preheating the tablets, which can be melted with less energy consumption, this passage of exhaust gases through a tablet bed can reduce the air pollution caused by the exhaust gases, since the exhaust gases contain at least some of the pollutants such as F ~ and B ₂ O, is withdrawn. When using hot exhaust gases whose temperatures are usually between 4-27 and 15666 ⁰ C, preheating the tablets to temperatures of 93-816 ⁰ O can take place. This results in a significant gain in heat, which means a saving in the amount of energy that is still required to melt the tablets introduced into the furnace.

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example 1

Was used an ⁿ £ "type glass batch from the following starting materials *

Starting material content in% by weight Silica 29,663

Tone 26.930

Limestone 27.786

Fluorspar 2,336

Sodium sulfate 0.794 Ammonium sulfate 0.224

Boric acid 12,181

Coal 0.084

The mixture was added to a disk-shaped tablet means a sufficient amount of water for the production of tablets with a content of 12 wt.% Of free water · Sine subset of the tablets was 104.4 ⁰ O for a period of 196 min., Another subset was at 537.8 ⁰ C for a period of 20 min. dried. The tablets from both runs were firm, non-dusting, and of sufficient physical utility.

The tablets were manufactured using the following procedure:

There were the required quantities of the starting materials Weighed. This approach was an inclined, rotating tablet disk with a diameter of 1 m and fed to an angle of inclination of about 45 °. the Feed rate was between 24.7 and 61.9 kg / h «

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CIe tablets thus produced were dried in a gas oven at temperatures between about 254 · 4 and 273 »9 ⁰ C for about 5 min.. The dried tablets were fed into a continuous melting furnace for the production of glass fibers. The feed rate was 3 ^ 2.9 kg / h.

The graph shows the energy consumption of the glass melting furnace over a period of 52 Days. The energy consumption was based on the recording of the total gas flow of the melting furnace in 0.02832 nr / h measured.

Point A in the drawing represents the first day of the measurements for the experiment. Between point A and point B, a normal, non-tableted glass batch with raw materials in loose form was introduced into the oven. During this period of 15 days the average gas consumption was 244.5 m ³ / h.

At point B, the introduction of the glass batch in tableted form was started. At point G, in the course of the On the 16th day of the experiment, it was so far that the entire glass batch in the furnace was made of pellets Starting material existed.

From point C to point D, the tablets were introduced into the oven ^{at temperatures between approximately 60 and 65 ° C.} During this period the average gas consumption was 237.8 nr / h. Compared to the average energy consumption of the furnace during loading with the usual loose glass attachment, this was a saving of 2.8%.

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Starting, ^oon of the experiment until point £ tablets were introduced at point D on the 30th day I2 with temperatures of between about 82.2 and 87.8 ⁰ C in the oven. The average energy consumption within this period was 23JO.2 nr / h, which means a saving of 5.9% compared to consumption with a loose glass attachment. Between point E and point F tablets were introduced at a mean temperature of about 43.3 ⁰ C in the oven.

At point G was a funnel with tablets that previously heated for about 1.5 hours were introduced into the oven, at point H an equally heated filling funnel was introduced.

In the period from point I bii point J tablets were introduced at temperatures between about 148.9 ° and 204.4 O ⁰ C in the oven. The average gas consumption within this period was 225 ₁ 2 mvh, a saving of 7 * 9% compared to the consumption with loose glass attachment '

At point E, around 9 ²⁰ "on the 50th day of the experiment, the furnace was started again with loose glass attachment. As can be seen in the drawing, the average energy consumption rose again to the range in which it was between points A and B, the period in which a loose glass attachment was originally introduced.

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Example 2

A glass batch was made with the following starting materials used:

Base material proportion in% by weight Silica 31 »532

Tone 21.615

Limestone 29,380

Fluorspar 2,469

Sodium sulfate 0.843 Ammonium sulfate 0.238 Boric Acid Anhydrous 6,835

Coal 0.088

A sufficient amount of water for the production of tablets with a content of about 16% by weight of free water was added to the batch on a disk-shaped tablet device. Aliquots of the pellets were dried at 104.4 ⁰ C. for a period of 28 min., 237.8 ⁰ C for a period of 35 min. And 537.8 ⁰ C for a period of 28 min..

The tablets, which had been dried at the temperatures of ⁰ C and 237.8 537.8 ⁰ C, were firm, non-dusting and physical availability of sufficient. The dried at a temperature of 104.4 ⁰ C tablets were, however, during the drying period of 28 Hin. completely disintegrate.

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Example 3

It became a glass approach with the following Auegangestoffe used

Starting material proportion in weight bottle Silicon dioxide 30.758

Tone 27.986

Kalketein 20,922

Coal 0.108

Fluorspar 2,454

Ammonium sulfate 0.237 Sodium sulfate 1.041

Colemanite 16,494

A sufficient amount of water for the production of tablets with a content of about 12% by weight of free water was added to the glass batch on a disk-shaped tablet device. The tablets were kept at temperatures of about 234.4 to 273.9 ⁰ C for about 5 Hin. dried. The tablets produced were firm, but for the most part could be crumbled with simple hand pressure.

Example 4

A glass approach was made with the following starting materials used:

Starting material content in% by weight Silica 31,040

Tone 28.227

Kalketein 21,698

Boric acid 3 * 566

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Starting material content in% by weight

Colemanite 11.853

Fluorspar 2,411

Sodium sulfate 0.854

Ammonium sulfate 0.251

Coal 0.100

The glass batch was converted into tablet form. The colemanite used was preheated before addition to the batch to 537.8 ⁰ C for about 2 hours, to drive off the chemically bound water therein. In this compound, 30% of the ΒοΟ, -based colemanite was replaced with boric acid. The batch was tabletted (as in Example 3) and dried. The tablets produced in this way were firm, non-dusting and had good mechanical strength.

Example 5

It was a Glasansatζ with the following starting materials used:

Starting material content in% by weight Silica 30,302

Tone 27.632

Limestone 24,320

Colemanite 8.206

Boric acid 5,882

Fluorspar 2,373

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O , 939 O , 247 O , 099

Starting material content in% by weight Sodium sulfate Ammonium sulfate

money

The batch was converted into tablet form. In this example, the colemanite was added to the Glass batch not pretreated · It was found that 50% dea Colemanite, based on BgOi, penetrated the glass batch Boric acid were replaced

Example 6

A glass batch was made with the following starting materials used:

Starting material content in% by weight Silica 30,137

Tone 27.397

Limestone 26,174

Colemanite 4.061

Boric acid 6.659

Fluorspar 2,348

Sodium sulfate 0.681 Ammonium sulfate 0.245

Coal 0.098

The batch was converted into tablet form. The colemanite was not pretreated before the addition to the glass batch. In this glass batch, 75% of the colemanite, based on B ₂ Ox-BaSiS, had been replaced by boric acid. The so-called

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determined tablets were non-dusting and of good mechanical strength.

From these statements it follows that by using tablets according to the invention Processes were made as GlaeansatB significant energy savings are to be achieved for the production of glass fibers in melting furnaces. aside from that is obvious that the energy savings are even larger if the tablets are heated prior to introduction into the oven.

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Claims (8)

Dr. Michael Hann patent attorney Ludwigstrasse 6? Giessen (1057) H / Ha / Fe FPG Industries, Inc., Pittsburgh, Pa., USA METHOD OF MANUFACTURING A BORON-BASED GLASS BOTTOM FOB GLASS FASEBN Priorities »November 8, 1976 / USA / Ser.No. 739,883 November 8, 1976 / USA / Ser. No.739,884 November 8, 1976 / USA / Ser.No. 739,885 claims 1. Process for the production of a boron-containing glass batch for processing into glass fibers, in which the boron as boric acid, anhydrous boric acid or Colemanite is provided, characterized in that the boron-containing starting materials in. A tabletting zone are introduced, the starting materials are agglomerated with sufficient free water to form tablets and the tablets by heating them at a sufficient temperature for a sufficient period of time dried to give hard, non-dusting tablets. 2. The method according to claim 1, dadur ο h characterized in that the tabletting zone includes a tabletting device with an inclined rotating disk . 809819/0884 3. The method according to claim 1, characterized in that the tablets have nominal diameters can be made between 0.952 and 1.587 cm. 4. The method according to any one of claims 1 to 3 »characterized in that the tablets contain anhydrous boric acid and are dried ^{at a temperature of at least 232 0 O.} 5. The method according to any one of claims 1 to 4, characterized in that the tablets are dried to a free water content of 1 percent or less. 6. The method according to claim 1, characterized in that the tablets contain anhydrous boric acid and before drying contain a content of 10 to 25% by weight of free water. 7. The method according to claim 6, characterized in that the free water content is 15 to 17 wt. # lies. 8. The method according to claim 1, characterized in that the tablets contain boric acid and before drying have a free water content of 5-22 Gew.96. 809819/0884 9 method according to inepruoh β, characterized in that the free water content is 11 to 13 % By weight. 10. The method according to claim 1, characterized in that the tablets contain boric acid and dried at a temperature of 104 to 558 ⁰ C. 11. The method according to claim 1, characterized in that the tablets contain colemanite and dried at a temperature below 41O ⁰ C. 12. The method according to claim 1, characterized in that the tablets contain oolemanite and before Drying have a content of free Vaeser of 5 to 20% by weight. 13 method according to claim 12, characterized , that the free water content is 11 to 13 percent lies. 14. The method according to claim 1, characterized in that colemanite is used as the boron-containing starting material and the colemanite is ^{pretreated before its agglomeration with the other constituents at a temperature of at least 410 °} C. for a period sufficient to drive off essentially all of its chemically bound water. 809819/0884 15 method according to claim 14, characterized in that the tablets obtained from the colemanite-containing starting materials are dried ^{at a temperature between 104 and 538 ° C.} 16. The method according to claim 11, characterized in that up to 75 percent or more of the colemanite is replaced by boric acid on a B ~ 0, basis. 809819 / 088Λ