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US 4,306,953 AGranted
Cationically polymerizable compositions containing sulfonium salt photoinitiators and stable free radicals as odor suppressants and _method of polymerization using same
AssigneeAmerican Can Company
InventorSheldon I. Schlesinger
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Abstract
Photopolymerizable compositions using sulfonium salt photoinitiators to effect polymerization of cationically polymerizable monomers additionally include a stable free radical to reduce or eliminate the sulfur odor generated upon photodecomposition of the sulfonium salt photoinitiator. The stable free radicals are soluble in the polymerizable material and are stable in the composition at ambient temperatures. Especially useful is 2,2-diphenyl-1-picrylhydrazyl.
Claims15
A photopolymerizable composition comprising:
- A. 50-99 percent by weight of a cationically polymerizable material;
- B. at least 0.1 percent by weight of a sulfonium salt photoinitiator which decomposes upon exposure to an electromagnetic radiation to provide a Lewis acid to initiate polymerization of said cationically polymerizable material, said sulfonium salt photoinitiator upon decomposition generating an odorous organic sulfur compound;
- and
- C. 0.1-15 percent by weight of a stable free radical operable to react with the organic sulfur compound released upon photodecomposition of said sulfonium salt photoinitiator to reduce the sulfur odor generated thereby, said stable free radical being soluble in the polymerizable material and stable in the composition at ambient temperatures.
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In a method of cationic polymerization, the steps comprising:
- A. admixing 50-99 parts by weight of a cationically polymerizable material, at least 0.1 part by weight of a sulfonium salt photoinitiator which decompoes upon exposure to electromagnetic radiation to provide a Lewis acid to initiate polymerization of said cationically polymerizable material, said sulfonium salt photoinitiator upon decomposition generating an odorous organic sulfur compound;
- and 0.1-15 percent by weight of a stable free radical operable to react with the organic sulfur compound released upon photodecomposition of said sulfonium salt photoinitiator to reduce the sulfur odor genrated thereby, said stable free radical being soluble in the polymerizable material and stable in the composition at ambient temperatures;
- and
- B. exposing said composition to electromagnetic radiation to decompose said sulfonium salt photoinitiator to generate a Lewis acid to initiate polymerization of said polymerizable material, said free radical reacting with organic sulfur compounds generated by decomposition of said sulfonium salt photoinitiator, said polymerization being characterized by substantial freedom from malodorous sulfur compounds.
1 more element
Dependencies are inferred from the claim text.