Compositions for making ene-thiol elastomers

Details Compositions for making ene-thiol elastomers Compositions for making ene-thiol elastomers

2002-09-23

2003-08-12

Lipman, Bernard (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From sulfur-containing reactant

C525S204000, C525S212000

Reexamination Certificate

active

06605691

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to curable compositions used for making ene-thiol elastomers and cured ene-thiol elastomers made therefrom.
BACKGROUND OF THE INVENTION
Electronic circuits must be protected from exposure to harsh corrosive environments to maintain the performance of the electronic device. Many electronic circuits are used in environments where they are exposed to corrosive liquids. For example, adhesives and encapsulants used to assemble ink jet cartridges must protect the flexible circuit that controls the ink jet head from exposure to corrosive inks. These adhesives and encapsulants experience long term exposure to very corrosive inks. If the adhesive or encapsulant degrade or excessively swell, the ink contacts and corrodes the circuit.
Thermosetting resins, frequently epoxy resins, are used to protect circuits from corrosive environments. Epoxy resins have several characteristics that limit their ability to perform well. Traces of chloride ion, which are frequently present in epoxy resins, promote the corrosion of circuits. Epoxy networks are somewhat hydrophilic and swell in aqueous environments because of the secondary alcohols produced in the curing reaction. Epoxy networks are frequently difficult to fully cure in the time/temperature constraints of electronic manufacturing processes. Unreacted epoxy groups are prone to hydrolysis, forming glycols, which further decreases the water resistance of the network. These epoxy characteristics limit their use as adhesives and encapsulants in corrosive environments.
Many combinations of polyfunctional olefins and mercaptans have been used to prepare ene-thiol networks. While many monomers have very attractive process characteristics (low viscosity and rapid UV curing), they do not provide networks having the requisite environmental resistance to withstand highly corrosive aqueous environments. Polyether dimercaptans are frequently used in ene-thiol compositions. These monomers introduce hydrophilic units to the cured network, resulting in excessive swelling in aqueous environments. Multifunctional mercaptoacetates and propionates are other commonly used thiol monomers. In addition to their hydrophilic character, the ester linkage introduces a site for hydrolysis and network degradation.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a curable composition for making an ene-thiol elastomer comprising a mixture of a polythiol, or a mixture of polythiols, having at least two thiol groups and free of hydrophilic groups, and an aromatic, heterocyclic, aliphatic, or cycloaliphatic polyene having at least two reactive unsaturated carbon to carbon bonds, wherein the composition in cured form, when immersed in a solution of 96 parts by weight water and 4 parts by weight n-butanol, shows a weight increase of not more than 4 weight percent, preferably, not more than 3 weight percent, and more preferably, not more than 2.5 weight percent in 15 days at a temperature of 22° C.
In another aspect, the invention provides a ene-thiol elastomer comprising the reaction product of a composition comprising a mixture of a polythiol having at least two thiol groups and free of hydrophilic groups and an aromatic, heterocyclic, aliphatic, or cycloaliphatic polyene having at least two reactive unsaturated carbon to carbon bonds, wherein the ene-thiol elastomer, when immersed in a solution of 96 parts by weight water and 4 parts by weight butyl alcohol, shows a weight increase of not more than 4 weight percent, preferably, not more than 3 weight percent, and more preferably, not more than 2.5 weight percent in 15 days at a temperature of 22° C.
In another aspect, the invention provides a curable composition for making an ene-thiol elastomer comprising a mixture of (a) a thiol terminated oligomer comprising the reaction product of a polythiol having two thiol groups and a first polyene or mixture of polyenes having two reactive unsaturated carbon to carbon bonds, and (b) a second polyene or a mixture of polyenes having at least 5 percent functional equivalents of unsaturated carbon to carbon bonds from polyenes having at least three unsaturated carbon to carbon bonds, wherein the composition in cured form, when immersed in a solution of 96 parts by weight water and 4 parts by weight n-butanol, shows a weight increase of not more than 4 weight percent, preferably, not more than 3 weight percent, and more preferably, not more than 2.5 weight percent in 15 days at a temperature of 22° C.
Generally, not more than 50 weight percent, preferably, not more than 30 weight percent, more preferably, not more than 20 weight percent, and even more preferably, none of the polythiol used to make the oligomer has hydrophilic groups. The first and second polyenes or mixtures of polyenes may be the same or different. Preferred first polyenes include divinyl ethers, and cyclic polyenes. Preferred polythiols include dimercaptodiethyl sulfide, 1,6-hexanedithiol, and 1,8-dimercapto-3,6-dithiaoctane.
In another aspect, the invention provides a ene-thiol elastomer comprising the reaction product of a composition comprising the reaction product of (a) a thiol terminated oligomer comprising the reaction product of a polythiol having two thiol groups and a first polyene or mixture of polyenes having two reactive unsaturated carbon to carbon bonds and (b) a second polyene or a mixture of polyenes having at least 5 percent functional equivalents of unsaturated carbon to carbon bonds from polyenes having at least three unsaturated carbon to carbon bonds, wherein the composition in cured form, when immersed in a solution of 96 parts by weight water and 4 parts by weight n-butanol, shows a weight increase of not more than 4 weight percent, preferably, not more than 3 weight percent, and more preferably, not more than 2.5 weight percent in 15 days at a temperature of 22° C.
Generally, not more than 50 weight percent, preferably, not more than 30 weight percent, more preferably, not more than 20 weight percent, and even more preferably, none of the polythiol used to make the oligomer has hydrophilic groups. The first and second polyenes or mixtures of polyenes may be the same or different. Preferred first polyenes include divinyl ethers, and cyclic polyenes. Preferred polythiols include dimercaptodiethyl sulfide, 1,6-hexanedithiol, and 1,8-dimercapto-3,6-dithiaoctane.
In another aspect, the invention provides ene-thiol elastomers comprising the reaction product of a composition comprising a mixture of a polythiol having at least two thiol groups and free of hydrophilic groups and an aromatic, heterocyclic, aliphatic, or cycloaliphatic polyene having at least two reactive unsaturated carbon to carbon bonds, wherein the ene-thiol elastomers have a water vapor transmission rate of less than 50, preferably less than 30, more preferably, less than 20 g-mm/m
2
-day at 40° C. according to ASTM D814.
In another aspect, the invention provides ene-thiol elastomers comprising the reaction product of a composition comprising the reaction product of (a) a thiol terminated oligomer comprising the reaction product of a polythiol having two thiol groups and a first polyene or mixture of polyenes having two reactive unsaturated carbon to carbon bonds and (b) a second polyene or a mixture of polyenes having at least 5 percent functional equivalents of unsaturated carbon to carbon bonds from polyenes having at least three unsaturated carbon to carbon bonds, wherein the ene-thiol elastomers have a water vapor transmission rate of less than 50, preferably less than 30, more preferably, less than 20 g-mm/m
2
-day at 40° C. according to ASTM D814.
In another aspect, the invention provides an ene-thiol elastomer comprising the reaction product of (a) an unsaturated carbon to carbon bond terminated oligomer comprising the reaction product of a first polythiol having two thiol groups and a polyene or mixture of polyenes having two reactive unsaturated carbon to carbon bonds; and (b) a second polythiol or mixture of polythiols having at least 5 percent functional thiol eq

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