Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-06-16
2002-05-28
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S107000
Reexamination Certificate
active
06395922
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to chemical technology, and more particularly, to chemical compounds and compositions based on dibenzoylresorcinol.
BACKGROUND OF THE INVENTION
Thermoplastic resins often possess an attractive set of mechanical and physical properties, such as high heat resistance, impact resistance, dimensional stability, high ductility, and optical clarity. Polycarbonates are a good illustration of materials exhibiting many of these attributes. While these properties serve to encourage the use of thermoplastics in many commercial applications, other, less favorable properties often need to be rectified or somehow addressed. As an example, thermoplastics often exhibit low resistance to abrasion and chemical solvents. Moreover, thermoplastic materials are usually susceptible to photodegradation by ultraviolet (UV) light. This type of degradation typically leads to erosion and yellowing of the polymer surface. The discoloration represents a large problem in using products like those based on polycarbonate, which are especially noted for their transparency.
Efforts to alleviate these problems have been undertaken in the past. As an example, coating compositions that include ultraviolet light absorbers have been applied onto thermoplastic substrates and then cured. For the case of polycarbonates, the coating material is often based on a silicone hardcoat matrix, which when cured, provides a good abrasion barrier. The UV absorbing agents incorporated into the hardcoat matrix are often based on benzophenone or benzotriazoles. As described in U.S. Pat. No. 5,391,795 (J. Pickett), various patents disclose this general type of strategy for protecting thermoplastics. For example, U.S. Pat. No. 4,373,061 describes the use of a silicone hardcoat composition comprising benzophenones as the UV absorbing agents, while U.S. Pat. No. 4,278,804 discloses a matrix composition based in part on silanol-reactive alkoxysilyl- or alkanoyloxysilylalkyl ether adducts of aromatic UV absorbing agents. U.S. Pat. No. 5,391,795 itself describes the use of silylated derivatives of 4,6-dibenzoylresorcinols as UV absorbers for hardcoat compositions.
The UV absorbing agents themselves sometimes decompose to some degree, upon exposure to UV light. The decomposition can in turn lead to microcracks in the hardcoat, exposing the underlying polymer surface to the degrading effects of UV light, abrasion, and the like. Thus, the purpose of the hardcoat in protecting the thermoplastic substrate is defeated to some extent.
It's quite apparent that there is a continuing need for new compounds which are effective in providing UV protection for thermoplastics. The compounds should themselves exhibit a high degree of UV stability, i.e., photostability, while still being effective in protecting the substrate. Moreover, the new compounds should be amenable to various forms of use, e.g., they should be capable of being incorporated into a hardcoat composition which is coated onto the surface being protected. The new UV absorbing compounds should also be physically and chemically compatible with the substrate material, and with any type of hardcoat composition being employed. They should not interfere with any of the other properties possessed by the thermoplastic substrate, such as transparency. Furthermore, the new compounds should be relatively easy to manufacture, and their use should not involve an excessive increase in the cost of the thermoplastic product.
SUMMARY OF THE INVENTION
The present invention satisfies substantially all of the needs discussed above. One embodiment is directed to a dibenzoylresorcinol-based compound having the general formula (I):
wherein Ar
1
and Ar
2
are independently substituted or unsubstituted monocyclic or polycyclic aryl groups; and R is hydrogen, an aryl group, or a linear or branched all chain having less than about 10 carbon atoms. The group designated as “A” can be a radical derived from a very wide variety of alcohols or carboxylic acids. In that instance, the compound can be made in a process which usually involves two steps, in which a methylene carboxylate intermediate of 4,6-dibenzoylresorcinol is first prepared, and then reacted with an alcohol or a carboxylic acid to form the desired product. The product can include functional sites which permit further reaction with other materials.
“A” can alternatively be a substituted or unsubstituted aryl group which does not include a pendent hydroxyl group. Various types of aryl groups may be present, such as phenyl, alkyl-substituted phenyl groups, halogen-substituted phenyl groups, and alkoxy-substituted phenyl groups. The desired compounds of this type are prepared in a reaction which usually includes one primary step, involving the reaction of 4,6-dibenzoylresorcinol with a benzyl halide compound, an aqueous base, and a compatible phase transfer catalyst. Again, the product can include functional sites suitable for further reaction.
Another embodiment of this invention is directed to improved coating compositions for protecting thermoplastic substrates. Much of the improvement is a result of the enhanced photostability of the dibenzoylresorcinol compounds briefly described above. The coating compositions include those compounds, incorporated into a matrix composition which may be formed from a variety of materials, such as acrylics.
The protection afforded to the substrates usually relates to ultraviolet light resistance, and can also include other enhancements, such as abrasion resistance. Thus, another embodiment of this invention is directed to improved articles which comprise a substrate (usually thermoplastic), coated with a protective composition which comprises the dibenzoylresorcinol-based compounds described above, incorporated into a matrix composition.
Numerous other details regarding these inventive embodiments are provided below.
DETAILED DESCRIPTION OF THE INVENTION
As briefly mentioned previously, the compounds of the present invention have the formula
wherein Ar
1
and Ar
2
are independently substituted or unsubstituted monocyclic or polycyclic aryl groups; and R is hydrogen, an aryl group, or a linear or branched alkyl chain having less than about 10 carbon atoms. In preferred embodiments, Ar
1
and Ar
2
are phenyl or substituted phenyl groups. R is preferably hydrogen or phenyl.
In one primary embodiment of this invention, A is a radical deriving from an alcohol or a carboxylic acid, i.e., the group which results when an alcohol or a carboxylic acid is reacted with the dibenzoylresorcinol compound. The examples which follow provide an illustration of some of the possible alcohols and carboxylic acids which could be used according to this invention. However, it appears that almost any alcohol or carboxylic acid would be suitable.
For example, the alcohol could be a linear or branched aliphatic group, usually containing from 1 to about 20 carbon atoms. As a non-limiting illustration, the aliphatic portion of the alcohol could be methyl ethyl, propyl, isopropyl butyl, isobutyl, sec-butyl, tert-butyl, amyl, isoamyl, hexyl, octyl, decyl, dodecyl, and the like. Included within the definition of “alcohol” herein are the many derivatives, e.g., alcohols containing substituents such as halogens, or those containing carbocyclic or heterocyclic rings attached to the main aliphatic chain, or to a branch which itself is attached to the main chain.
The alcohol itself could alternatively be carbocyclic or heterocyclic, and can contain at least one aliphatic branch or aromatic ring which comprises from 1 to about 20 carbon atoms. Examples of carbocyclic alcohols are cyclohexanol, cyclopentanol, cyclooctanol, cyclodecanol, cyclododecanol, exo-norborneol, and derivatives of any of the foregoing which contain at least one aliphatic branch or aromatic carbon ring. These types of compounds are available commercially, or can usually be made by those skilled in the art, without undue effort.
Heterocyclic alcohols (containing one or more ring-structures) are also readily available. Most often, t
Brown S. Bruce
General Electric Company
Johnson Noreen C.
Killos Paul J.
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