Abstract Polythiols having more than two terminal and/or pendant thiol groups per polymer molecule are formed by the free radical catalyzed addition of a monomer system made up of either hydrogen sulfide or a dithiol alone or in combination with an acetylenic compound to a polyolefin having at least three olefin sites. The polyolefin is preferably a triterminal olefin. The polythiol products are liquid, essentially gel-free materials having number average molecular weights varying from 200 to 30,000. The polyfunctional prepolymers of the invention can be cured to stable three-dimensional networks with inexpensive bi-functional oxidants such as lead dioxide. Additionally, prepolymer compositions having 3 or more pendant or terminal thiol groups per molecule when combined with polyfunctional organic reagents, such as diepoxides, form stable, high-tenacity adhesive systems.
The process of claim 1 wherein said hydrocarbon dithiol is a compound having the general formula: HSR'''' SH wherein R'''' is selected from the group consisting of (a) a C1 to C30 divalent saturated alkylene radical; (b) a C2 to C30 divalent unsaturated alkylene radical; (c) a C8 to C30 bis-alkylene substituted aromatic radical; (d) a C6 to C30 divalent aromatic radical; and (e) a C2 to C30 divalent organic radical containing at least one element selected from the group consisting of sulfur, oxygen and silicon in addition to carbon and hydrogen atoms.
Claim 2
Dependent Claim
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The process of claim 2 wherein the said acetylenic compound has a general formula selected from the group consisting of CH '''''' and '''' '' C '''' '' wherein R'''''' is selected from the group consisting of (a) a hydrogen radical; (b) a C1 to C30 alkyl radical; (c) a C2 to C20 alkenyl radical; (d) a C2 to C30 alkynyl radical; (e) a C7 to C20 aralkyl radical; and (f) a C1 to C3 hydroxyalkyl radical.
Claim 3
Dependent Claim
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The process of claim 3 wherein at least about 1 mole of the dithiol and hydrogen sulfide components of the monomer system is employed per mole of olefin unsaturation present in the reaction zone.
Claim 4
Dependent Claim
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The process of claim 3 wherein said polyolefin is a tri-terminal olefin having the general formula: R R'')xCH CH2)3 wherein R is a trivalent hydrocarbon radical having from one to 30 carbon atoms, R'' is a divalent radical having from one to 10 carbon atoms, and x varies from 0 to 1.
Claim 5
Dependent Claim
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The process of claim 5 wherein R is a trivalent hydrocarbon radical having from 1 to 12 carbon atoms and x is 0.
Claim 6
Dependent Claim
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The process of claim 6 wherein R'''' is an alkylene radical having from two to four carbon atoms and R'''''' is a C1 to C4 alkyl radical.
Claim 7
Dependent Claim
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The process of claim 4 wherein said polyolefin is a trivinyl-cyclohexane, R'''' is an alkylene radical having from two to four carbon atoms and said acetylenic compound is methylacetylene.