Etching a substrate: processes – Forming or treating an ornamented article – Treating glass
Reexamination Certificate
2000-06-09
2002-10-29
Gulakowski, Randy (Department: 1746)
Etching a substrate: processes
Forming or treating an ornamented article
Treating glass
C216S097000, C065S472000, C065S473000
Reexamination Certificate
active
06471880
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a novel process for the chemical etching of glass.
2. Description of the Related Art
The term “etching of a glass slide” refers to the action of rendering it translucent, without being transparent, by rendering one of its surfaces opaque. The result of this action is an extensive roughness with a depth of a few microns, which roughness, according to its height, results in different macroscopic appearances of the surface thus treated. The terms “sparkling etched glass”, “matt etched glass”, “opaque glass” or “translucent glass” are then used.
Etching is generally carried out by sanding the surface, when it is large in size, by depositing a thin layer or by chemical attack. The latter process is more particularly employed on small surfaces or on objects with more or less complicated shapes. Chemical attack is often carried out using fluoride ions, the latter reacting with the silicon ions of the glass. The glass object is immersed, for a few seconds to a few minutes, either in a bath of concentrated hydrofluoric acid or in an acid bath comprising an initiator for fluoride ions, such as ammonium bifluoride. The glass is subsequently rinsed with water.
Examples of known compositions for etching glass include that disclosed in the German patent published under the number 1,596,961, which comprises hydrofluoric acid, ammonium hydrogen fluoride, subsequently known as ammonium bifluoride, and water, that disclosed in the British patent published under the number 1,276,550, comprising hydrofluoric acid, a water-soluble fluoride, such as ammonium bifluoride, and one or more aliphatic carboxylic acids comprising from one to three carbon atoms which are substituted or unsubstituted by radicals comprising one or more halogen atoms and/or one or more hydroxyl or amino groups, such as, for example, formic acid, acetic acid, propionic acid, monochloroacetic acid, trichloroacetic acid or glycolic acid, or the composition disclosed in the Soviet patent published under the number SU 1,675,244, comprising hydrofluoric acid, ammonium bifluoride, sodium fluorosilicate, potassium fluorosilicate and water. The combination of ammonium bifluoride and hydrofluoric acid makes it possible to improve both the efficiency of the chemical attack and the appearance of the etched glass obtained. On the other hand, it also induces the formation of ammonia, which, in order to meet European discharge standards, necessitates an additional treatment of the industrial effluents, which is expensive and difficult to carry out. The limits set by these standards vary from one river to another. However, it is accepted that a level of ammonia of less than or equal to 1 mg/dm
3
constitutes an acceptable average value. In point of fact, it has already been shown that the discharge of acid etching baths results in local concentrations of ammonia in a river of up to 3 to 5 times the maximum standard allowed.
Attempts have naturally been made, in order to overcome this disadvantage, to replace the ammonium bifluoride with sodium bifluoride or potassium bifluoride. Examples of compositions without ammonium salt include that disclosed in the Japanese patent application published under the number 334,841/1995, which comprises hydrofluoric acid, potassium bifluoride and water, or that disclosed in the Brazilian patent application published under the number 85 01205, which comprises hydrofluoric acid, potassium bifluoride, sodium fluoride, oxalic acid, glycerol and baryta. However, these etching compositions are prepared with hydrofluoric acid.
In point of fact, hydrofluoric acid is dangerous to store and handle and it is relatively expensive. For these reasons, etching products are marketed which comprise hydrochloric acid instead of hydrofluoric acid. However, these formulations also comprise ammonium bifluoride.
In the French patent application filed on Dec. 16, 1999 and registered under the number 99 15,887, the Applicant Company has disclosed and claimed a composition, characterized in that it comprises:
(a)—from 20% to 99% by weight of potassium bifluoride,
(b)—from 1% to 80% by weight of at least one water-soluble polyvalent cation salt, and optionally one or more of the following compounds:
(c)—up to 15% by weight of ammonium bifluoride,
(d)—sodium bifluoride in a proportion by weight of less than or equal to that of potassium bifluoride, it being understood that, when it comprises both ammonium bifluoride and sodium bifluoride, the total amount of these two bifluorides never exceeds that of potassium bifluoride,
(e)—from 5% to 60% by weight and more particularly from 10% to 30% by weight of at least one water-insoluble filler chosen from inorganic or organic products which are stable in an acidic medium, for example baryta or barium sulphate, gypsum, insoluble fluorides, such as calcium fluoride, insoluble fluorosilicates, such as sodium fluorosilicate or calcium fluorosilicate, calcium phosphate, calcium sulphate, inorganic oxides, in particular iron, zinc or titanium oxides, sugars and their polymers, such as cellulose or its derivatives, lignin or starch, high molecular weight ethylene oxide polymers, propylene oxide polymers or butylene oxide polymers, fatty acids and their derivatives which are solid at room temperature or insoluble high molecular weight polymers and resins, and/or
(f)—from 0.2% to 6% by weight and more particularly from 1% to 2% by weight of one or more surface-active agents which are stable in an acidic medium, such as, for example, alkoxylated fatty alcohols, phosphate-comprising fatty alcohols, phosphate-comprising alkoxylated fatty alcohols, ethylene and propylene oxide copolymers, fatty amides or cationic surface-active agents or the fluorinated derivatives of the said surface-active agents, silicone-comprising or fluorosilicone-comprising surface-active agents.
This composition can more particularly comprise:
from 1% to 60% by weight, in particular from 5% to 30% by weight and more specifically from 10% to 25% by weight of at least one water-soluble polyvalent cation salt. The water-soluble polyvalent cation salt is generally a divalent cation salt or a trivalent cation salt and is more particularly a calcium salt, a magnesium salt, a zinc salt, an iron salt or an aluminium salt, such as, for example, manganese chloride, magnesium chloride, magnesium sulphate, calcium chloride, ferric chloride, alumina or a mixture of these compounds, and/or
from 40% to 80% by weight of potassium bifluoride.
This composition is generally provided in the form of a mixture of powders, in the form of granules, in the form of pellets or in the form of pebbles.
In this same French patent application, filed on Dec. 16, 1999 and recorded under the number 99 15,887, the Applicant Company has also disclosed and claimed:
a glass etching solution, characterized in that it is capable of being obtained by mixing between 0.1 kg and 5 kg and preferably between 0.5 kg and 5 kg of the composition as defined above per liter of water or per liter of an aqueous solution of one or more inorganic or organic acids, it being understood that the inorganic acid optionally present in the said aqueous solution before mixing with the said composition is not hydrofluoric acid, and
a glass etching solution, characterized in that it is capable of being obtained by mixing, simultaneously or successively, from 0.1 kg to 4.95 kg of potassium bifluoride and from 0.005 kg to 4 kg of at least one water-soluble polyvalent cation salt per liter of water or per liter of an aqueous solution of one or more inorganic or organic acids, it being understood that the inorganic acid optionally present in the said aqueous solution before mixing with the said bifluoride and the said cation salt is not hydrofluoric acid. The latter solution is obtained while optionally also adding sodium bifluoride in an amount per liter of water or of acidic solution of less than or equal to that of the potassium bifluoride or up to 0.75 kg and preferably at most 0.25 kg of ammonium bifluoride or of
Bessoles Yves
Trouve Gerard
Gulakowski Randy
Smetana Jiri
Societe D'Exploitation de produits Pour les Industries Chim
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