Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1998-03-05
2000-04-25
Marquis, Melvyn I.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524430, 524437, 524783, 524786, 524837, C08K 318
Patent
active
060545224
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The field is a material system and a process for coating articles, particularly glass and glass-ceramic articles, to impart durable, non-stick and non-wetting properties
BACKGROUND OF THE INVENTION
Considerable effort has been directed at producing an effective, non-stick and non-wetting coating on the surface of an inorganic article, in particular a utensil for preparing and/or serving food. The term "non-stick" signifies a surface that resists adherence of foreign substances, such as food. This property permits easy cleaning of dishes in which foods are cooked or baked. The term "non-wetting" indicates a surface that repels liquids such as water. The property is evidenced by a large contact angle between a drop of water and the surface on which the drop rests. An advancing angle of at least 90.degree. is considered as representative of a non-wettable surface.
Non-stick, non-wetting articles are commonly produced by coating article surfaces with a polytetrafluoroethylene (PTFE) layer. For example, U.S. Pat. No. 4,683,168 (Hares et al.) describes a process for coating glass or glass-ceramic articles with such a layer to produce non-stick cooking utensils. However, PTFE coatings exhibit the disadvantage of being opaque. Also, they require a thermal sintering process at 350.degree.-400.degree. C. for their production, are relatively expensive to produce, and do not provide a desired degree of abrasion resistance.
French Patent No. 2674862 (Carre) discloses an alternative material system and process for producing durable, non-stick and water repellent coatings on glass and glass-ceramic surfaces. The process involves applying a mixture of a selected silane with a lower alkanol and water which may be acidified. The silane has the formula R.sub.n SiX.sub.4-n, where R is an alkyl radical and X is a hydrolyzable alkoxy or chloro group. The mixture is applied to a surface containing hydroxyl groups, the silane is hydrolyzed and the alkanol-water mixture eliminated to form a polysiloxane coating adhering to the surface.
Numerous other processes and material systems have been proposed for rendering inorganic surfaces, particularly vitreous surfaces, non-sticking and water repellent. The desired properties can be obtained initially. However, there has persisted a problem with respect to wear during use, in particular, scratching by cleaning agents. It is, then, a purpose of the present invention to improve on the Carre process bv imparting a greater abrasion resistance to the coating there disclosed
SUMMARY OF THE INVENTION
The present invention resides in part in a material system for imparting non-stick and non-wetting properties to an inorganic article having hydroxyl groups on its surface, the system comprising a silane having the formula R.sub.n SiX.sub.4-n wherein n is 1-2 and X is a hydrolyzable group, a metal alkoxide having at least three hydrolyzable branches and a formula R MX.sub.3 or MX.sub.4 wherein M is a metal and X is a hydrolyzable branch, and an acidified aqueous mixture with a lower alkanol.
The invention further resides in a method of imparting non-stick and non-wetting properties to an inorganic article having hydroxyl groups on its surface which comprises mixing a silane having a formula R.sub.n SiX.sub.4-n l, with a metal alkoxide having a formula R MX.sub.3, or MX.sub.4, adding an acidified aqueous mixture of a lower alkanol, applying a coating of the mixture to a surface on the inorganic article, thermally processing the coating at a temperature of at least 100.degree. C. to form a solid, transparent film on the article surface
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 A graphical illustration showing contact angle as a function of mol % of dethoxy dimethyl silane (DEDMS).
FIG. 2 A graphical illustration showing contact angle as a function of the ratio of acid to the sum of silane of FIG. 1 plus alkoxide.
DESCRIPTION OF THE INVENTION
The present invention arose from studies directed at improving the polysiloxane, non-stick coating disclosed in French Patent
REFERENCES:
patent: 4652467 (1987-03-01), Brinker et al.
patent: 5175027 (1992-12-01), Holmes-Farley et al.
Carre Alain
Prassas Michel
Waku-Nsimba Jean
Corning Incorporated
Gheorghiu Anca C.
Marquis Melvyn I.
Peterson Milton M.
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