GB887755A - An improved method of siliconising a vitreous surface - Google Patents

Abstract

<PICT:0887755/III/1> A vitreous surface of an article that has been heat treated to establish the distribution of internal and/or superficial stresses therein is siliconized by bringing a preheated organosiloxane siliconizing medium into contact with the surface while the latter is at a temperature which will cause the organosiloxane to become polymerized on to the surface, the temperature of the siliconizing medium being such that it will not produce a substantial thermal change in the surface so that changes in the distribution of said stresses is avoided. The process may be carried out while the article is still hot from or still undergoing the establishing treatment. Cyclic organosiloxanes and linear organohalogenosiloxanes or their esterification or etherification products, in the form of a gas, vapour or mist at a temperature in the range of 150 DEG to 300 DEG C. may be used. As shown (Fig. 1), the selected organosiloxane is introduced from container 2 into the vaporizer 1 where it is heated by the heating element 3 to a temperature corresponding to a given vapour pressure. A carrier gas from vessel 6 is passed via the feed line 7 where it is heated by heater 8 to the scrubbing coil 1a into the liquid, becoming saturated with organosiloxane vapour. The saturated carrier is passed to a mixing chamber 13 where it is mixed with vapour free carrier gas in order to bring the organosiloxane content to the desired value, and at the same time the temperature recorded by thermometer 18 may be adjusted if necessary. A catalyst-water vapour, sulphuric acid vapour or organosilyl ester vapour-may be introduced via line 17 into the mixing chamber. The siliconizing medium then passes along line 15 to the treatment area A which it enters at the header 20, the temperature being adjusted by heater 16. From the header the medium passes into funnel 23 via a series of ports and comes into contact with the surface of the article 39, remaining in contact with it as it flows along the narrow passage 26 to the funnel 24. From here the exhausted medium is drawn by pump 19 to the cooler 5, the carrier gas passing over into vessel 6 and being recirculated. Traps 27 are provided to prevent communication between the funnels and the surrounding atmosphere, and if a thermal radiator 28 is to be used beyond the funnel 24, traps should be employed to prevent communication between funnel 24 and the radiator, and between the radiator and the atmosphere. Additional catalyst may be fed to the radiator 28 via line 29. Modifications for treating rod-like articles and the interior surface of a bottle are described.