DE1269300B - Process for the finishing of glass produced by the float glass process - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C03b

German KL: 32 a -49 / ΘΘ-

Number: 1269 300

File number: P 12 69 300.4-45

Filing date: December 23, 1963

Open date: May 30, 1968

The invention relates to the finishing of glass produced by the float glass process and its treatment for bending or grinding.

When glass made by the float glass process is bent, the transparency goes in the area the bend is often lost, or the transparency deteriorates, whereby the swimming area the glass plate or sheet that is melted during manufacture with the carrier used Has been in contact with metal becomes iridescent. The elimination of the damage as it is in the appearance of iridescence is shown by grinding the glass after it has been bent economically unsustainable. The surface finishing by polishing the swimming surface of Non-bent float glass under polishing blocks with the help of fine abrasives is difficult to achieve, without the glass being damaged by the polishing blocks at the same time. In addition, here must compared to polishing the other side of the same sheet of glass or sheet at a very high rate Polishing pressure to be worked. Since errors are beginning or are already in the bud in the Swimming surface develop when the glass is bent and there the removal of the swimming surface Grinding the glass is more difficult when polishing the flat glass the swimming surface or skin is obviously often in an invisible, but actually present faulty condition.

According to the invention, there is now a method for refining items produced by the float glass method Glass has been proposed in which the floating surface of the glass is chemically removed will.

The process according to the invention is usually carried out in such a way that the Surface of the glass that comes into contact with the molten metal during manufacture has found, with an aqueous solution of hydrofluoric acid, preferably mixed with fluosilicic acid, is brought into contact. In general, this touch is carried out for so long to a small amount from the surface to a depth of little more than about 0.001 mm has been removed. After that, the solution is removed from the glass surface, allowing another attack of the glass is prevented.

The method according to the invention will now be described in detail with reference to the drawing which is a perspective view of a portion of a glass manufacturing line.

Process for finishing from to
glass made using the float glass process

Applicant:

Pittsburgh Plate Glass Company,

Pittsburgh, Pa. (V. St. A.)

Representative:

Dr.-Ing. H. Ruschke and Dipl.-Ing. H. Agular,

Patent attorneys,

8000 Munich 27, Pienzenauer Str. 2

Named as inventor:

William Curtis Harrell, Arnold, Pa .;

Henry Martin Demarest Jr., Natrona Heights,

Pa. (V. St. A.)

Claimed priority:

V. St. v. America 23 January 1963

(253 412),

dated May 24, 1963 (282 970)

The production of float glass is z. In U.S. Patents 2,911,759 and 3,083,551. In the method described in these patents, a sheet of flat glass is used during part of their movement towards the end of the production line from a bath of molten material Worn metal. The molten metal is typically Tin or a tin alloy. One of the reasons for using tin for this purpose is in that tin reacts little with the glass. The float glass itself is manufactured based on the commonly used lime-soda-sand approach as has long been used in the economical production of flat glass is used.

The glass produced does not need any iridescent glass until it is subsequently heated or bent To have surface defects. The iridescent, defective surface condition appears always on the floating surface of the glass (which was in contact with the metal), indifferent, whether it is the inside or the

809 557/195

3 4

Outside of the bend. Since the glass in front of it, a distance of 1 to 1.2 μ of the bending, initially under a precisely regulated surface, proved to be sufficient to eliminate the iridescent conditions until a plastic condition was reached. The resultant is heated, the web of the removal of this layer thickness was achieved by the fact that the glass probably does not have the same softness 5 that the swimming surface of the glass for 20 seconds as the rest of the glass or only softens at a higher temperature in a 10% hydrofluoric acid solution. Was immersed by microscopic lower, wherein the glass room temperature investigation determined that the iridescent layer and the solution had 49 ⁰ C. In the case of a glass plate, when it was on the outside of the path, which was at a rate of bending, moving under the tension of apparently 508 cm / minute along the conveyor belt, it was cracked at intervals a bath placed under the glass conveyor belt, while in the case when it was 165 cm long enough to treat the inside of the bend in the bath under the pressure-immersed swimming-glass surface, it was fluted or folded Rolls arranged behind, in and above the bathroom appeared to have been. Since the removal of one of the flaws already carried the glass, and a wiper blade, followed by the floating surface of such a water surface, the hydrogen fluoride glass removed by grinding far more difficult acid, which prepares after leaving the acid container than the removal of a similar one of the underside of the glass adhered. It was not necessary to brush the glass thickness from the opposite, in the oven in the presence of the acid or to otherwise process the ao polished by the action of heat.

same glass plate or sheet, it is likely that the removal in the above-mentioned layer

that the swimming surface in its cohesive thickness could also be achieved in such a way that the Setting of that of the rest of the glass in a significant floating surface of the glass 20 seconds differs. aqueous solution with a content of 10% by weight

According to one embodiment of the invention, 25 percent hydrofluoric acid and 5 percent by weight According to the method, the swimming surface is submerged in fluosilicic acid, both the or skin of the glass by treatment with glass and the solution were at room temperature, removed dilute hydrofluoric acid. In particular with a glass plate or sheet that is with a

If an aqueous solution containing 5 to 15% fluorine at a rate of 508 cm / minute along the hydrofluoric acid has been found to be extremely suitable, a 165 cm bath under the glass conveyor is instructed to attack the swimming surface and to be arranged Sufficient length, remove, with only minimal costs and regulation problems to deal with the float glass surface immersed in the bath and only minimal safety. Arrangements need to be made behind, in and above the bathroom. According to nete roles wear the glass, and a wiper blade, another embodiment of the invention, followed by a water wash, removed the fluorous method is an aqueous solution of hydrofluoric acid and fluosilicic acid, which after turning, the fluosilicic acid and hydrofluoric acid leaving the acid tank contains acid on the underside of the glass. In general, the solution should adhere. It was not necessary to contain the glass in at least about 1% fluosilicic acid. Brushing in the presence of the acid solution or other special processing of an aqueous solution has proven to be suitable, and still desirable, if the 5 to 15% hydrofluoric acid and then namely the tendency to form from scratch to 25% fluosilicic acid contains. Regardless of line defects in the glass surface,
The difficulties that arise in trying to thickness the average glass removal can be made from

and composition of the glass is better known to the weight loss of a sheet of glass To change dimensions, it was found that 45 areas are determined. More precise measurements left the undesirable after-effects of bending occur in such a way that a small or polishing in a satisfactory and economical- ly richly covered surface prior to treatment licher way in most cases it was avoided, so that after the treatment his when the glass is measured on the order of 1 μ increase above the surrounding area (0.001 mm) from the swimming surface of the Flat-50. The regulation of the glass distance glass is removed. If the distance is on a can be due to the fact that the glass distance limited to such a small extent, the method can be a linear function over a limited range Carried out economically and quickly on the glass production line from (1) time, (2) temperature and (3) acid concentration will. The acid treatment needs tration represents to perform easily. So in the Neither limited to the floating glass surfaces to 55 case of a bend around a radius of at least that are to be bent, the 12 "still make a glass distance in the range of 0.5 to Cost of acid a localized removal from 0.75 μ proved sufficient. These in comparison Economic reasons necessary, since overall only about half as much as the above examples only a small amount of glass removal from the glass surface is achieved in that is removed. However, the glass should be treated by adding a sufficient amount of water to it before the iridescent defect has developed, as that of the solution increases the concentration of hydrogen fluoride removal of the glass in the order of magnitude of 1 μ acid to 5% and - if present - the fluosilicas an already curved glass is adjusted to about 2.5% to remove the acid, or by doing so, iridescent, faulty condition completely inadmissible that the immersion time is limited to about 10 seconds is sufficient. 65 turns. If the acid concentration has already been set

In the case of lime-soda-sand swimming glass samples e.g. B., which can be seen on the assembly line changes in extent have a nominal thickness of 6.35 mm and are particularly convenient in that way for glass removal If you want to bend a radius of 15.3 cm, you have to vary the temperature.

It is important that the procedure be carried out in a manner that allows deep penetration the glass surface is avoided. Otherwise the surface will be damaged. It was however, found that there was no great unevenness in the action of the solution on various Parts of the glass surface and therefore no severe surface damage occurs when the treatment is stopped before the concentration of fluosilicic acid is greater than about 3 μ and hydrofluoric acid by no more than 15 weight percent, preferably by no more than 10 percent by weight and preferably by less than 5 5 percent by weight - based on the weight of the Solution - change. Neither the concentration of hydrofluoric acid nor the concentration of Fluosilicic acid should exceed a value of 50 percent by weight, and in general should the

have been removed. The surface treatment should in any case be interrupted in the sum of the concentrations of these two acids before the transparency - not more than 50 percent by weight - based on the visibility of the glass is impaired.
The speed at which the glass passes through the

Solution attacked varies with temperature

it is within the range of 1 to 20 percent by weight. The adjustment of the acid concentration takes place in such a way that one continuously

area (i.e. the area that was in contact with the metal bath during the manufacture of the glass hat) a variety of 5 inch by 8 inch samples

brought into contact with the following specified compositions. Then the samples were taken immediately washed and the amount of glass removed is determined. The following results were obtained:

the weight of the solution - make up. For most purposes a solution is satisfactory if containing 1 to 30 percent by weight fluosilicic acid.

the solution; the attack takes place as much as 15 The hydrofluoric acid concentration should be 30 Gerascher, the higher the temperature. In addition, do not exceed weight percent; usually the rate of glass removal begins at
constant hydrofluoric acid concentration with
increasing proportion of fluosilicic acid contained in the solution. 20 a fresh hydrofluoric acid solution is added and in a series of experiments the soil continuously became the consumed hydrofluoric acid

and withdrawing slurry containing fluosilicic acid. This will ensure even glass removal guaranteed if the concentration of float glass is kept constant for 20 seconds in the following 25 of the acid solution, specified temperatures with solutions of the in The solution can also contain small amounts of tin in

in dissolved form, usually in a concentration of 0.05 to 5 percent by weight, based on the weight of the solution. 30 The amount of glass removed can be slightly can be determined by the following experiment. A piece of strip-shaped material, e.g. B. off Lead or a plastic resistant to the solution is applied to the glass before treatment 35 or - in the case of a continuously moving glass path - to this moving one Glued glass sheet. The strip piece protects the covered glass from the solution, so that the protected Area remains unchanged. After treatment 40, the piece of strip is removed and the difference in height between the treated glass surface and the surface protected by the piece of strip measured with the help of a tactile instrument that scans the surface contour and the respective gemes-45 shows its height. The height difference is the amount of glass removed. With commercially available instruments In this way, height difference measurements can be carried out with The above table typically explains how an error limit within ± 0.05 μ can be carried out, by varying the individual conditions Varia- As can be seen from the description above,

In terms of the extent of glass removal 50, immersion times and acid levels are achieved can be. As below, the options are small and can also be made more convenient is explained in more detail, the manner according to the invention will regulate or vary. Under the descriptions treatment preferably in a continuously nen circumstances, in a clean, through the moving glass track made. To ensure that the top of the in such a process from hour to hour and 55 float glasses cover the entire glass plate or sheet Dive consistent results day to day without producing adverse effects, it is beneficial to have substantial fluctuations. However, the composition of the top of the glass, which is oven-polished on the glass, is determined by the action of heat in the glass to avoid effective solution, so that significant errors can occur due to the acid-handling fluctuations can be enlarged or deepened in the depth of penetration of the hole. For this solution can be prevented. Reason as well as to save on acid solution

As a general rule, when constant, preferably only the lower or swimming side of the Hydrofluoric acid concentration will depend on an increase in glass in the dilute acid solution the fluosilicic acid concentration by 1 weight - left, immersed or otherwise in it percent an increase in the speed of the glass 65 bathed.

removal by 2%, and vice versa. To under the described process conditions

From day to day, or at least from hour to hour, the presence of carrier roles in the acid hour represents Containers are not a serious problem to ensure consistent results. Rubber rollers

composition Fluo temperature Glass the solution silica the solution distance (Weight percent) 0 Fluorous water 5 ( ⁰ C) (μ) chemical acid 10 21 0.965 10 20th 21 1.07 10 25th 21 1.09 10 0 21 1.24 10 5 21 1.37 10 10 49 2.62 10 20th 49 2.69 10 49 2.69 10 49 3.00 10

ζ. B. are neither subject to chemical attack under the respective conditions the solution will still lead you to achieve any degree of glass removal. Patterning of the glass in the places where it

touch the lower glass surface in the presence of the acid. refinement of the floating surface side of the float glass A device for carrying out the invention 5 by polishing can be achieved much easier after According to the method on a float glass production line, the webbing is carried out by the method described above band is illustrated in the drawing in which an acid treatment step has been removed. Of the Glass plate 1, which moves in the direction of arrow over usual polishing section along the glass production flow line conveyor rollers 2 moves, a part of an endless one, it can be kept much shorter since one is with cooled and washed float glass sheet, there are fewer polishing stages required than polishing that comes out of the floating tank. The float of the same, but untreated glass on the The glass side is of course the underside. One under the same degree of polish are required. It was Web-arranged container assembly 3 also represents that found without prior removal Floating surface finishing station. The floating skin for polishing with polishing rollers The container itself is a shell 4, which has a suitable 15 and a slurry of a finely divided abrasive base End opening5 through which the immediate, e.g. polishing red, is used to process the broke the acid solution is introduced. The loading glass required very high polishing roller pressures container has an inner rim 6, which are either wider and that within a useful Druckbeöder narrower than the glass sheet to be treated, there is an excessive abrasion that can be untreated. In the execution shown in the drawing, the floating surface of the glass occurs, The shape of the upper surface of the glass, although depending on the respective

Protected from splashing with the acid, different degrees of polish are required that the glass web may be required over the sides of the container or no polythene protrudes at all. The length of the inner edge is dimensioned so that what is needed is the successful completion of the sen, as it is carried out for a given glass treatment time 25 polishing work after a previous The acid treatment stage of the glass guided by the prevailing glass web speed is better is required. The solution flooded the container guaranteed. Another dry cleaning is and takes its way between the container and not required, and for bending e.g. B. it is also Glass in a gutter 7, which is between the pacifying when about 3 μ or less and inner Edge 6 and a protruding outer 30 comfortable about 1 μ after verren according to the invention Edge 8 is located. Under these conditions, driving from the swimming surface remains chemically entdie entire underside of the above the container can be removed - regardless of whether the polished glass lent glass in contact with the liquid. Which should be bent or not. The solution is used for processing and recycling in It goes without saying that the

the treatment tank in a (not shown) 35 treatment used acid solution in various Feed container returned, for which purpose can be put together in the Rin way. The main names7 Discharge openings 9 are provided. It is a condition that in the solution hydrogen and the treatment tank are transverse to the movement fluoride ions are present as they are in a watering direction the glass web support rollers 10 are arranged to present hydrofluoric acid. sulfuric acid The glass sagging or scratching or other acids can also be added to prevent the container edges. Preferred to reduce the build-up of compounds wise, the rollers 10 are in solubility within the container, which tend to be more submerged in a dull etch Direction adjustable to the weight causes, which is particularly dear case when one remove the jar from the edges of the container, allow the accumulation of reaction products, or to prevent a small gap between the glass and 45 on the glass, to create the inner edge. In any case, it should be obvious that the hydrogen ions

the feed rate of the feed of the treatment solution from the various column solutions be sufficient that the container can always come with ren and that the fluoride ions the solution is filled and that the entire above is added by dissolving the various fluorides The glass surface located in the container can lead into the solution 50. Bifiuoridverbindungen can immersed. can also be used.

The solution is removed from the glass after an economical maximum glass skin removal is achieved.

it has left the container. For this purpose, distances are viewed as a criterion, so high at the exit end from the container below the acid concentrations or high temperatures-glass sheet a wiper blade 11 and a perforated 55 can be turned, if special precautions ge water spray tube 12 arranged. Finally, one serves to be taken around the exposure time in Anbe-Paar Above and below the glass path, the high removal speed can be reduced Add wiper blades 13 and 14 to shorten the wash. Spraying the acid solution onto the wipe water off the glass. Bottom of a short length of the glass web can

With such an arrangement, the acid be- 60 z. B. followed by an alkaline wash, treatment of the swimming surface in an economical way in order to stop the chemical action immediately. Can be carried out continuously, regardless of - with very dilute solutions or low tempertures, whether at any particular time there is a temperature for removing the same amount of glass Webbing is formed on the glass or not. more time required. The necessary equipment The container can then usually take on larger dimensions for the periods in which there are no connections Web removal is desired, slightly reduced, or it increases labor costs without to be emptied; or the concentration of the solution may in itself make the process more convenient The manner outlined above can be varied to produce better results.

Claims (4)

Patent claims: 1. Process for the refinement (tempering) of glass produced by the float glass process, which has been carried on a liquid bath during a stage of its manufacture, thereby characterized in that at least part of the glass surface is then removed from the liquid bath, which has been in contact with the liquid is removed with an etching liquid. 2. The method according to claim 1, characterized in that an aqueous etching solution which essentially of dilute hydrofluoric acid, preferably in a mixture with fluosilicic acid, is used. 3. The method according to claim 2, characterized in that the solution is about 5 to 15 percent by weight Hydrogen fluoride and, if present, about 1 to 25 weight percent fluosilicic acid contains. 4. The method according to claims 1 to 3, characterized in that the method is carried out until the glass surface is detached to a depth of not more than about 3 μ. Considered publications:
German Patent No. 100141;
U.S. Patent No. 2936554;
"Consultation room", Coburg, 65th year, 1932, p. 5 until 1 sheet of drawings 809 557/195 5.68 © Bundesdruckerei Berlin