Baking oven interior coating and process therefor

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...

Reexamination Certificate

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C524S304000, C524S342000, C524S474000, C428S461000, C428S462000, C126S27300R

Reexamination Certificate

active

06191201

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved material for the interior surface of baking ovens used at moderately high temperatures and to a liquid composition and a process for using this liquid composition to produce the improved interior surface material.
2. Discussion of Related Art
Baking ovens are necessary for practical utilization of many currently commercial high quality protective coatings, which are applied in liquid form and ultimately baked for at least several minutes and often much longer in order to reach their finally desired degree of chemical reaction, so that the protective value of the coatings is maximized. Most such coatings produce gaseous emissions during the baking process, and such emitted materials can react with themselves and/or the walls of the baking oven to form a coating on these walls. In many cases the coatings thus formed eventually accumulate to a sufficient thickness to consume an undue amount of the expensively heated space within the oven, and/or the oven wall coatings themselves emit products on further heating that can damage the cleanliness and other quality features of the protective coatings on other objects that are being cured in the baking ovens.
Accordingly, it would be advantageous to provide oven interior surfaces with a protective covering that reduces the accumulation of unwanted additional solid coatings thereon and/or can readily and cheaply be removed when the accumulations on it become troublesome in any respect. However, fully suitable materials for such a protective covering for oven interior walls have previously been unavailable, particularly when the ovens to be protected are used for extended periods at temperatures as high as 160° C.
DESCRIPTION OF THE INVENTION
Objects of the Invention
A major object of the invention is to provide an improved oven interior surfacing material that will provide satisfactory service under usage conditions as described above. Another concurrent or alternative object is to provide a liquid composition that can conveniently be coated onto a metal backing and then converted by a practical process into an improved oven interior surfacing material. Still another concurrent or alternative objective is to provide an interior surfacing material with tack, so that particulate matter will have a greater tendency to adhere to it rather than remaining in suspension in the gaseous atmosphere within the oven, where it would be more likely to blemish the surface of some object being baked in the oven. Other objects will be apparent from the description below.
General Principles of Description
Except in the claims and the specific examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight; the term “polymer” includes “oligomer”, “co-polymer”, “terpolymer”, and the like; the first definition or description of the meaning of a word, phrase, acronym, abbreviation or the like applies to all subsequent uses of the same word, phrase, acronym, abbreviation or the like and applies,
mutatis mutandis
, to normal grammatical variations thereof, the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; specification of materials in ionic form implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole; and any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention.
SUMMARY OF THE INVENTION
It has been discovered that metal substrates having surfaces that contain at least 45% of aluminum can be coated with a combination of tacky solid and two types of anti-oxidants in solvent and then converted to a solid coating by expelling most of the solvent by heating, to produce an excellent surfacing material for the interior of baking ovens. The outer “coated” side of this surfacing material, which faces the interior space within the oven when in use, remains tacky for at least a few days, even when aged at temperatures in excess of 160° C. When excessive undesirable deposits accumulate on this coated side of the surfacing material, the coating layer can easily be removed by heating to a higher temperature such as 275° C. in the presence of oxygen, such as in the ambient natural atmosphere. The covering then decomposes cleanly, along with most organic residues accumulated on it, and any non-combustible constituent(s) of the accumulated residues can easily be removed from the oven. The interior walls of the oven can then be recoated with a liquid composition according to the invention and heated at an appropriate temperature to convert the liquid coating thus formed to a solid protective coating, so that the oven is ready for continued use.
One embodiment of the invention is accordingly a suitable liquid coating composition which comprises, preferably consists essentially of, or more preferably consists of:
(A) a component of polymeric material that (i) is solid and (ii) has tack sufficient to be sensed by a brief touch by a normal human finger, both throughout a temperature range from 25 to 160° C.;
(B) a first stabilizing component selected from the group consisting of molecules and moieties
1
thereof, exclusive of molecules and moieties thereof that constitute component
1
Ordinarily, each of components (B) and (C) preferably is selected from individual and distinct molecules containing the chemical features recited for each component. However, all of the chemical features required for both the first and second stabilizing components could be incorporated into a single molecule and/or could be grafted onto polymer molecules that are part of component (A). The phrase “moieties thereof” in the description of components (B) and (C) is intended to embrace these possibilities. However, if an entire molecule present in a composition according to the invention includes all the chemical features required for component (B) or (C) and does not include all the chemical features required to constitute part of any other of components (A) through (C), the entire molecule rather than any moiety thereof is to be considered as part of the component (B) or (C) of which it can constitute a part. On the other hand, if a molecule present in a composition according to the invention includes both all the chemical features required to constitute a part of component (B) or (C) and also all the chemical features required to constitute a part of at least one other of components (A) through (C), only any smallest continuously bonded moiety of such a molecule that contains all the necessary features recited for component (B) is to be considered part of component (B) and only any smallest continuously bonded moiety of such a molecule ponet (A), each of the first stabilizing component molecules or moieties thereof containing (i) at least one benzene ring that is substituted with at least one hydroxyl moiety and at least two alkyl moieties and (ii) at least one carbon atom bonded by single bonds to four other carbon atoms, alternatively called a “tertiary” carbon atom;
(C) a second stabilizing component selected from the group consisting of molecules or moieties thereof, exclusive of molecules or moieties thereof that constitute component (A) or (B), each of said molecules or moieties thereof containing (i) at least one divalent sulfur atom that is bonded to two distin

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