METHOD FOR DEPOSITING AN ORGANIC INTUMESCENT COATING ON A GLASS SHEET

Abstract

A method for the deposition of an organic intumescent coating on a glass sheet, includes the preparation of an organic intumescent coating composition by mixing a latex having a pH from 4 to 6 and an intumescent agent chosen from thermally degradable polycarboxylic acids, and the application of the organic intumescent coating composition to the glass sheet.

Claims

1. A process for the deposition of an organic intumescent coating on a glass sheet, comprising: preparing an organic intumescent coating composition by mixing a latex and an intumescent agent; and applying the organic intumescent coating composition to the glass sheet; wherein the latex has a pH from 4 to 6 and the intumescent agent is chosen from thermally degradable polycarboxylic acids.

2. The process as claimed in claim 1, wherein the latex is an aqueous dispersion of a polymeric organic binder derived from vinyl monomers chosen from α-alkenes, vinyl chloride, vinylidene chloride, styrene, vinyltoluene, acrylonitrile and vinyl esters.

3. The process as claimed in claim 2, wherein the organic binder is a copolymer based on α-alkene and on one or more esters of vinyl and/or vinyl chloride.

4. The process as claimed in claim 1, wherein the intumescent agent is chosen from oxalic acid, malonic acid, malic acid, tartaric acid, tartronic acid, maleic acid, citric acid, tricarballylic acid and 1,2,3,4-butanetetracarboxylic acid.

5. The process as claimed in claim 1, wherein the intumescent agent is citric acid.

6. The process as claimed in claim 1, wherein the coating composition comprises 5 to 50% by dry weight of intumescent agent.

7. The process as claimed in claim 1, wherein the coating composition comprises 0.5 to 15% by dry weight of a flame retardant.

8. The process as claimed in claim 7, wherein the flame retardant is an organophosphorus compound.

9. A glazing unit comprising a glass sheet coated with an organic intumescent coating, obtainable by the process as claimed in claim 1, wherein the organic coating comprises an organic binder and an intumescent agent, said intumescent agent being chosen from thermally degradable polycarboxylic acids.

10. The glazing unit as claimed in claim 9, wherein said coating has a total light transmission of greater than 85%.

11. The glazing unit as claimed in claim 9, wherein said coating has a haze of less than 15%.

12. The glazing unit as claimed in claim 9, wherein the organic binder is a homopolymer or copolymer derived from vinyl monomers chosen from α-alkenes, vinyl chloride, vinylidene chloride, styrene, vinyltoluene, acrylonitrile and vinyl esters.

13. The glazing unit as claimed in claim 9, wherein the intumescent agent is chosen from oxalic acid, malonic acid, malic acid, tartaric acid, tartronic acid, maleic acid, citric acid, tricarballylic acid and 1,2,3,4-butanetetracarboxylic acid.

14. The glazing unit as claimed in claim 9, wherein the intumescent agent is citric acid.

15. The process as claimed in claim 2, wherein the α-alkenes include ethylene, propylene or isoprene.

16. The glazing unit as claimed in claim 12, wherein the α-alkenes include ethylene, propylene or isoprene.

Description

EXAMPLES

[0024] The compositions of examples 1 (according to the invention) and 2 to 6 (comparative) were prepared by mixing various latices and 20% by weight of intumescent agents. These compositions were subsequently deposited by pouring onto the surface of a glass sheet 2.5 mm in thickness, then dried to obtain an organic intumescent coating of approximately 2 mm. The total light transmission (TL) and the haze of the coatings were measured with a hazemeter according to standard ASTM D1003-00 with illuminant C.

[0025] The coated glass sheets were subsequently subjected to temperatures of 300° C. for 10 minutes. The intumescence quality of the organic coating during this heat treatment was quantified by comparison of the thickness of the foam obtained relative to the initial thickness of the intumescent coating.

[0026] Unlike the previous examples, the compositions of examples 7 to 9 were not prepared from latex but from a crosslinkable resin based on acrylates (polyester acrylate and polyethylene glycol (PEG 400) acrylate—10:90 ratio by weight). The resin is mixed with a photoinitiator, then the intumescent agents (20% by dry weight) are introduced into the mixture. The formulation is subsequently deposited on a substrate and crosslinked under UV lamp.

[0027] Table 1 below summarizes the nature of the coating compositions and the properties of the intumescent coatings obtained. The processability, taking into account the ease of processing of the composition and the quality of the coating obtained, is graded as follows: .Math. application impossible; application possible but poor quality coating; ◯ application possible and good quality coating.

TABLE-US-00001 TABLE 1 Ex. Binder pH Intumescent agent Processability T.sub.L Haze Intumescence 1 Vinyl acetate/ 4.5-5.5 Citric acid ◯ >87% <10% >800% ethylene/vinyl ester terpolymer 2 Vinyl acetate/ 4.5-5.5 Sorbitol + urea + ◯ <87% >10% <800% ethylene/vinyl ester phosphoric acid terpolymer 3 Vinyl acetate/ 4.5-5.5 Ammonium ◯ <87% >10% >800% ethylene/vinyl ester polyphosphate + terpolymer melamine + pentaerythritol 4 Vinyl acetate/ 7-9 Citric acid .Math. n.m. n.m. n.m. ethylene/acrylate terpolymer 5 Acrylic ester/ 7.5-8.5 Citric acid .Math. n.m. n.m. n.m. ethylene/vinyl ester terpolymer 6 Acrylic ester/ .sup. 7-8.5 Citric acid .Math. n.m. n.m. n.m. methacrylic ester copolymer 7 Acrylate resin — Citric acid n.m. n.m. n.m. 8 Acrylate resin — Sorbitol + urea + n.m. n.m. n.m. phosphoric acid 9 Acrylate resin — Ammonium n.m. n.m. n.m. polyphosphate + melamine + pentaerythritol n.m.: not measurable

[0028] Only the composition of example 1 has good processability and makes it possible to obtain a coating having both satisfactory optical and intumescent properties. On the other hand, the coating compositions of examples 2 and 3 do not make it possible to obtain a coating having adequate haze and/or intumescence for an application on glass. The compositions of examples 4 to 9 do not have adequate processability: for examples 4 to 6, the composition gels quickly, preventing any application; for examples 7 to 9, the coating obtained cracks and/or delaminates following drying and crosslinking.