Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Patent
1994-05-06
1995-12-19
Lusignan, Michael
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
427386, 427387, 4273897, B05D 306
Patent
active
054766923
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of strengthening glass by applying a coating to a surface of the glass. The method of the present invention has particular application in the strengthening of glass containers.
A method of increasing the pressure-resistant strength and impact strength of a glass container has been proposed in published Australian Patent Application No. 15269/88. In the method of the Australian Patent Application a silane coupling agent is used in conjunction with a reactive compound having at least two (meth)-acryloyl groups in the molecule and capable of being polymerised by irradiation. The silane coupling agent is an organosilicon monomer having at least two different reactive groups in the molecule, one reactive group being capable of reacting with glass, and another reactive group being capable of reacting with the (meth)acryloyl groups.
In the said Australian Patent Application the reactive compound may be applied in a separate step after the surface of the glass container has been treated with the silane coupling agent or a mixture of the silane coupling agent and the reactive compound may be applied to the surface of the glass container in a single operation. In either case the reactive compound is applied in solution in an organic solvent, preferably methylethylketone.
Organic solvents such as methylethylketone require substantial precautions to be taken when used in an industrial process, for example there is a great need for fire precautions and a need to prevent the solvent escaping into the atmosphere. It is accordingly an object of the present invention to provide a method of strengthening glass, particularly glass containers, which does not involve the use of organic solvents.
According to the present invention there is provided a method of strengthening glass by applying a coating of a mixture of a silane and a resin containing at least two polymerisable unsaturated groups in the molecule to a surface of the glass and then curing the coating, wherein the silane is a reaction product of a silane coupling agent, which contains an epoxy group, with an unsaturated carboxylic acid, and the mixture of the silane and the resin is applied to the surface of the glass as an aqueous emulsion.
It has not previously been considered practicable to strengthen a glass container by application of a coating including a silane compound in an aqueous suspension because the silane gels on contact with water. In accordance with the present invention, however, the mixture comprising the resin and the reaction product of the silane coupling agent, which included an epoxy group, with the unsaturated carboxylic acid yields an aqueous coating mixture having a pH in a range at which the silane is stable in the presence of water and does not gel. The reaction product of the silane coupling agent with the unsaturated carboxylic acid may be stored and made up into a mixture for use in accordance with the present invention at a later date.
The reaction of the silane coupling agent with the unsaturated carboxylic acid also has the feature of introducing a double bond into the silane, thereby facilitating co-polymerisation between the silane and the resin to produce a strong coating on the surface of the glass.
Conveniently the silane coupling agent contains the epoxy group as a substituent in an organofunctional group, that is to say a reactive group which includes linked carbon atoms but may also include other atoms, for example oxygen or nitrogen atoms, linked with the carbon atoms. The organofunctional group may include a cyclic group.
Preferably the epoxy group is a substituent in an organofunctional group which comprises an alkyl chain having an ether linkage within the chain.
The silane coupling agent is advantageously a trialkoxyl silane having an alkyl chain including an ether linkage within the chain and the alkyl chain containing a substituent epoxy group. Preferably the substituent epoxy group is a terminal epoxy group. Such preferred silane coupling agents are of the general formula ##S
REFERENCES:
patent: 4056208 (1977-11-01), Prejean
patent: 4250068 (1981-02-01), Ali-Zaidi
patent: 4374879 (1983-02-01), Roberts et al.
World patents Index Latest, Accession No. 90-372481, Week 50, Derwent Publications Ltd. London, GB; & JP, A, 2269780 (Kansai Paint KK) 05, Nov. 1990, see abstract.
Chen Xiao M.
Ellis Bryan
Seddon Angela B.
British Technology Group Ltd
Lusignan Michael
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