METHOD FOR PRODUCING LAMINATED GLAZING WITHOUT ENAMEL STICKING TO THE BACK-GLASS

Abstract

A process for manufacturing a laminated glazing that includes at least a first glass sheet and a second glass sheet, includes printing a face of the first glass sheet intended to be oriented toward the second glass sheet with a liquid enamel which is dried at a temperature not exceeding 400° C., then bending the first and second glass sheets together in contact with one another in their relative position of destination in the laminated glazing, by heating at a softening temperature of the glass, wherein the liquid enamel is an aqueous silicate paint including a refractory powder of pigments and a silicate binder powder, in the absence of glass frit, and wherein a weight ratio of pigments to silicates is greater than 1.

Claims

1. A process for manufacturing a laminated glazing comprising at least a first glass sheet and a second glass sheet, the process comprising printing a face of the first glass sheet intended to be oriented toward the second glass sheet with a liquid enamel which is dried at a temperature not exceeding 400° C., then bending the first and second glass sheets together in contact with one another in their relative position of destination in the laminated glazing, by heating at a softening temperature of the glass, wherein the liquid enamel is an aqueous silicate paint comprising a refractory powder of pigments and a silicate binder powder, in the absence of glass frit, and wherein a weight ratio of pigments to silicates is greater than 1.

2. The process as claimed in claim 1, wherein an organic fraction of the paint comprises at least 80% by weight of water, optionally at least one organic solvent and one or more additives.

3. The process as claimed in claim 1, wherein the paint comprises from 15% to 50% by weight of organic fraction.

4. The process as claimed in claim 1, wherein the pigments comprise Fe.sub.2O.sub.3, CuO and/or MnO.

5. The process as claimed in claim 1, wherein the printing of the first glass sheet is carried out by screenprinting.

6. The process as claimed in claim 1, wherein the liquid enamel is dried at a temperature not exceeding 350° C.

7. The process as claimed in claim 1, wherein the glass sheets are bent by heating at a temperature at least equal to 600° C. for at least 5 min.

8. The process as claimed in claim 1, wherein the glass sheets are bent by gravity sagging.

9. The process as claimed in claim 2, wherein the one or more additives include a thickener, a surfactant or both.

Description

EXAMPLE

[0020] Four aqueous silicate paints are prepared from mixtures of exclusively mineral powders constituting the solids content of these paints. These four powders are analyzed by x-ray fluorescence spectroscopy using a spectrometer sold by the company Malvern Panalytical Ltd (UK) under the reference MagiX PRO, and with the aid of the semiquantitative program Omnian from the same company.

[0021] Only the boron of these powders is assayed by inductively coupled plasma (ICP) spectroscopy using a Vista-PRO® spectrometer from the company Varian Inc (USA).

[0022] The results are recorded in % by weight in table 1 below. ND stands for: not detected.

TABLE-US-00001 TABLE 1 Paint No. 1 2 3 4 SiO.sub.2 35.1 29.9 17.3 34.1 MnO.sub.2 21.9 26.4 18.3 11.3 CuO 15.8 17.9 0.2 0.2 Na.sub.2O 12.0 9.9 0.5 0.6 Fe.sub.2O.sub.3 7.1 8.7 50.1 31.7 K.sub.2O 5.1 4.4 10.4 20.9 Al.sub.2O.sub.3 2.0 1.6 1.2 0.8 SO.sub.3 0.2 0.2 0.1 <0.1 CaO 0.1 <0.1 <0.1 <0.1 TiO.sub.2 <0.1 <0.1 <0.1 <0.1 P.sub.2O.sub.5 ND <0.1 0.3 <0.1 ZnO ND <0.1 <0.1 <0.1 ZrO.sub.2 ND <0.1 ND ND BaO ND ND 0.3 ND Cr.sub.2O.sub.3 ND ND 0.1 <0.1 Co.sub.3O.sub.4 ND ND 0.1 ND NiO ND ND <0.1 <0.1 B.sub.2O.sub.3 <0.05 <0.05 <0.05 <0.05

[0023] In each of the four paints, the pigments are capable of consisting exclusively of CuO, Fe.sub.2O.sub.3 and/or MnO.sub.2.

[0024] The paints are manufactured by adding to each of the four powders a liquid fraction consisting of water at more than 80% by weight, and minor amounts of additives (customary thickeners, surfactants, etc.) and optionally other solvents.

[0025] In table 2 below, the amounts are, like those of table 1, in % by weight. The proportion of organics (liquid fraction) is evaluated by thermogravimetric analysis.

TABLE-US-00002 TABLE 2 Paint No. 1 2 3 4 Organics 40 37 27 39 Pigments in the 44.8 53 68.6 43.2 solids content Pigments in the 27 33 50 26 liquid paint Pigments/Silicates 0.82 1.12 2.22 0.75 Absence of NOK OK OK NOK bonding Elements forming Cu, Fe, Mn Cu, Fe, Mn Fe, Mn Fe, Mn the pigments

[0026] The Pigments/Silicates row expresses the weight ratio of these two groups of compounds. The pigments consist of the refractory powders of the solids content (see table 1), namely CuO, Fe.sub.2O.sub.3, and MnO.sub.2, and the silicates consist of all the other constituents of the solids content: the binders.

[0027] Two 500 mm×300 mm×2.1 mm sheets of float soda-lime glass are used. One of the two glass sheets is printed with each of the four paints by screenprinting, in particular at its periphery and at the corners of the sheet. The paint is left to dry for 24 h in ambient air, which operation is optionally followed by passing through a furnace at 300° C. for 180 s, or else, according to a third drying mode, only the glass sheet passes through a furnace at 300° C. for 180 s.

[0028] The painted glass sheet is then paired up with the other unpainted glass sheet so that its painted surface is in contact with this other glass sheet. The bending of the two glass sheets thus in contact with one another is carried out by heating at 640° C. for 10 min in a furnace; the bending takes place by gravity sagging, upon softening of the glass.

[0029] The two glass sheets are then destined to be firstly separated, then bonded to one another by means of an adhesive interlayer for instance made of polyvinyl butyral (PVB). When they are thus separated, the paint remaining bonded to the counter-glass may damage at least one corner of one of the two glass sheets or both glass sheets, and/or be transferred at least partly to the counter-glass; this phenomenon is denoted by the expression “bonding of the paint”.

[0030] In table 2, this bonding is reported in the “Absence of bonding” row by the evaluation NOK. The evaluation OK denotes on the contrary an absence of a damaged glass sheet corner, and of transfer of paint to the counter-glass. This evaluation, for each of the four paints, is independent of that of the three drying modes that have been selected. There is absence of bonding if, in the paint, the weight of pigments is greater than that of the silicate binders.