Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1999-05-04
2001-05-15
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S148000, C522S904000, C528S033000
Reexamination Certificate
active
06232362
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to ultraviolet curable silicone coating compositions. More particularly, it relates to modified epoxy functional polydiorganosiloxane silicone fluids which are effectively cured by ultraviolet radiation in the presence of iodonium salt.
Silicone release coatings are used to render surfaces non-adherent to materials which would normally adhere thereto, and are widely used as coatings which release pressure-sensitive adhesives for labels, decorative laminates, transfer tapes, and the like. Such release coatings are advantageously formed by the cross-linking of epoxy functional polydiorganosiloxane silicone fluids in the presence of an ultraviolet (UV) cationic initiator. Suitable bis(aryl)iodonium salt cationic photocatalysts, for example bis(4-alkylphenyl)iodonium hexafluoroantimonate, have been disclosed in U.S. Pat. No. 4,279,717 to Eckberg et al., which is incorporated by reference herein. Another class of UV-sensitive catalyst is disclosed in U.S. Pat. No. 5,340,898 to Cavezzan et al., comprising tetrakis(perfluorophenyl) borate anions.
Despite extensive investigation into silicone release coating compositions and catalysts therefor, there remains a need for systems which provide faster, more efficient photocatalyzed curing of reactive epoxy functional silicones. U.S. Pat. No. 5,583,195 to Eckberg has reported synthesis and use of epoxy functional silicone polymers which have been partially or completely functionalized by a fluorescing, or a photosensitizing, or a simultaneously fluorescing and photosensitizing substituent bonded to the silicone polymer. These epoxy functionalized silicone derivatives are particularly useful for providing fluorescent dye marking compounds for determining the quality of the release coatings made therewith. In particular, Eckberg discloses reaction of an agent such as anthracene-9-carboxylate with an epoxy silicone to yield a functionalized epoxy silicone that possesses ultraviolet fluorescence activity and photosensitization activity. Such compounds are sensitizers for iodonium photocatalysts, promoting enhanced iodonium miscibility and enhanced photo cure response. Anthracenes however are expensive and therefore impractical for commercial use. Accordingly, there remains a continuing need in the art for commercially viable methods for the derivatization of epoxysilicones which will yield compounds of higher reactivity and excellent adhesion release coating properties.
SUMMARY OF THE INVENTION
Faster, more efficient photochemical curing of silicone release coatings is achieved by use of self-sensitized, modified epoxysilicones comprising napthalene derivatives incorporated into the silicone polymers. Such photosensitized silicones have the formula:
MD
n
D
E
m−p
D
p
*M
where
M is selected from the group consisting of R
3
SiO
1/2
and R
2
ESiO
1/2
; wherein each R is independently selected from the group consisting of monovalent hydrocarbon radicals having from 1 to 30 carbons, and E is an epoxide functionalized substituent selected from the group of epoxy ether substitutents having the formula C
6
H
11
O
2
or the group of alkyl cyclohexeneoxide substituents having the formula C
8
H
13
O;
D has the formula R
2
SiO
2/2
, wherein each R is independently selected from the group consisting of monovalent hydrocarbon radicals having from 1 to 30 carbons;
D
E
has the formula RESiO
2/2
wherein R is selected from the group consisting of monovalent hydrocarbon radicals having from 1 to 30 carbon atoms, and wherein E is an epoxide functionalized substituent selected from the group of epoxy ether substituents having the formula C
6
H
11
O
2
or the group of alkyl cylcohexeneoxide substituents having the formula C
8
H
13
O;
D* is defined as the reaction product of D
E
with a compound selected from the group consisting of R′COOH, (R′CO)
2
O, R′COX, R′SO
3
H, and R′SO
2
X wherein R′ is a photosensitizing naphthalene substituent and X is a halogen; and wherein the subscripts n, m, and p are integers where the sum of n+m+p is in the range from about 10 to about 2,000.
In addition to the compositions of the present invention the present invention also provides a method of preparing silicones of the formula:
MD
n
D
E
m−p
D*
p
M
comprising reacting a silicone of the formula MD
n
D
E
m
M with a compound selected from the group consisting of R′COOH, (R′CO)
2
O,R′COX, R′SO
3
H, and R′SO
2
X where R′ is a photosensitizing naphthalene substituent and X is a halogen; and the subscripts m, n and p are integers where the sum of m+n is in the range from about 10 to about 2,000.
DETAILED DESCRIPTION OF THE INVENTION
Photosensitized UV (or EB) photocurable epoxysilicone release coatings may be prepared via the reaction of a photosensitizing molecule containing at least one acid functionality or functionality convertible to an acid functionality, e.g., an acid halide, with an epoxysilicone via an acid catalyzed oxirane ring opening reaction. Using 4-ethylcyclohexene oxide as an exemplary oxide, the general reaction is:
wherein “H-Naphthyl” indicates the acid form of a photosensitizing naphthyl species, and “X-Naphthyl” indicates the acid halide form of a photosensitizing naphthyl species, the halides including fluoride, chloride, bromide and iodide. More specifically:
wherein R″ is a photosensitizing naphthyl or naphthyl derivative. Suitable naphthyl derivatives include alkyl-substituted naphthalenes, wherein the carboxylate or other functionality comprises a substituted or unsubstituted hydrocarbon having from 1 to 10 carbons, i.e., 1-naphthylacetic acid, (1-naphthoxy)acetic acid, (2-naphthoxy)acetic acid, and the like. The naphthyl moiety may itself be substituted, e.g., with hydroxyl, halogen, or other substituents, e.g., 4-hydroxy-2-naphthylacetic acid and the like. Substituents within the scope of the present invention do not adversely affect derivatization or photosensitization.
The reaction with carboxylic acid halides (fluorides, chlorides, bromides, or iodides) or with sulfonic acid halides is similarly facile. Thus 100 parts of an epoxysilicone with an epoxy equivalent weight of 1,000, when reacted with one part of 1-naphthoic acid will yield silicone polymers having approximately 94% of the cycloaliphatic epoxy groups intact, i.e., unreacted, and also containing about 1.0 weight percent of a photosensitizing substituent as well. The reaction is generalizable to any photosensitizing naphthyl that can be chemically bonded via an acid substituent by the acid catalyzed oxirane ring opening reaction to an epoxysilicone.
The epoxy-functional photosensitizing polydimethylsiloxanes of the present invention have the formula:
MD
n
D
E
m−p
D*
p
M
wherein M is R
3
SiO
1/2
or R
2
ESiO
1/2
; D is R
2
SiO
2/2
; and D
E
is RESiO
2/2
. In the preceding formulae, R selected from the group consisting of monovalent saturated or unsaturated hydrocarbon radicals, generally having from one to about thirty carbon atoms for alkyl radicals, from two to about thirty carbon atoms for alkenyl and alkynyl radicals, from six to thirty carbon atoms for aryl radicals, and from six to thirty carbon atoms for alkylaryl radicals, from seven to thirty carbon atoms for monovalent alkylaryl hydrocarbon radicals, from one to thirty carbon atoms for monovalent halogen substituted alkyl hydrocarbon radicals, from two to thirty carbon atoms for halogen substituted alkenyl hydrocarbon radicals having, from two to thirty carbon atoms for monovalent halogen substituted alkynyl hydrocarbon, from six to thirty carbon atoms for monovalent halogen substituted aryl hydrocarbon radicals, and having from seven to thirty carbon atoms for monovalent halogen substituted alkylaryl hydrocarbon radicals. Preferably, R is phenyl, trifluoromethyl, or methyl.
Further in the preceding formulae, E is preferably an substituted or unsubstituted ether-containing hydrocarbon group, preferably epoxy ether substituents of the formula C
6
H
11
O
2
, e.g.,
or
Agars Robert F.
Eckberg Richard P.
Berman Susan W.
General Electric Company
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