Epoxypolysiloxane release coatings for adhesive materials
AssigneeMinnesota Mining and Manufacturing Company
InventorsRobert J. Koshar, Stephen W. Bany
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Abstract
This invention relates to cured epoxypolysiloxanes and their blends with epoxy-terminated silanes which are useful as release coatings for adhesive roll and sheet materials.
Claims24
A composite structure comprising a pressure-sensitive adhesive tape in which a backing is provided on one surface with a layer of normally tacky and pressure-sensitive adhesive and on the other surface with a low adhesion backsize which is the crosslinked, polymeric network reaction product of starting materials comprising
- (1) a curable epoxypolysiloxane, in solution or in the form of 100% solids, which is represented by the formula, ##STR14## wherein R is a lower alkyl group or radical of one to three carbon atoms,
- R.sup.1 is a monovalent hydrocarbon radical of 4 to 20 carbon atoms,
- E is a monovalent epoxy-containing hydrocarbon radical,
- M is a silyl group R.sub.3 Si--, R.sub.2 R.sup.1 Si-- or R.sub.2 ESi--, where R, R.sup.1, and E are defined above,
- a is 5 to 200,
- b is 0 or up to 20% of a,
- a+b is 5 to 200,
- c may be 0 when M is R.sub.2 ESi-- or is greater than 0 but less than 20% of the value of (a+b) when M is R.sub.3 Si--, R.sub.2 R.sup.1 Si-- or R.sub.2 ESi--, and
- n is 1 to 75;
- provided that the monovalent epoxy-containing hydrocarbon radical, E, contains at least one polymerizable epoxy group, ##STR15## the remainder being composed of carbon and hydrogen free of acetylenic unsaturation and in addition to the oxirane oxygen can contain ether, --O--, or carbonyl oxygen, ##STR16## (2) 0 to about 98% by weight of the epoxypolysiloxane described in (1) of an epoxy-terminated silane, which silane is represented by the formula, ##STR17## wherein E is an epoxy-containing monovalent hydrocarbon radical defined above, p is 1 to 3 and R.sup.2 can be an aliphatic hydrocarbon radical of less than 10 carbon atoms;
- and said materials are cured in the presence of a catalytically effective amount of an epoxy curing catalyst.
The composite structure according to claim 24 wherein the siloxane groups, ##STR18## are randomly arranged in said epoxypolysiloxane.
A method of making a low adhesion backsize coating for a pressure sensitive adhesive tape, said coating affording accurately predictable and controllable release for a wide variety of normally tacky and sensitive adhesives, which method includes the steps of:
- a. blending together in a mutually compatible solvent system, to form a solution, components comprising
- (1) a curable epoxypolysiloxane which is represented by the formula, ##STR22## wherein R is a lower alkyl group or radical of one to three carbon atoms,
- R.sup.1 is a monovalent hydrocarbon radical of 4 to 20 carbon atoms,
- E is a monovalent epoxy-containing hydrocarbon radical,
- M is a silyl group R.sub.3 Si--, R.sub.2 R.sup.1 Si--, or R.sub.2 ESi--, where R, R.sup.1, and E are defined above,
- a is 5 to 200,
- b is 0 or up to 20% of a,
- a+b is 5 to 200,
- c may be 0 when M is R.sub.2 ESi-- or is greater than 0 but lesser than 20% of the value of (a+b) when M is R.sub.3 Si--, R.sub.2 R.sup.1 Si-- or R.sub.2 ESi--, and
- n is 1 to 75;
- provided that the monovalent epoxy-containing hydrocarbon radical, E, contains at least one polymerizable epoxy group, ##STR23## the remainder being composed of carbon and hydrogen free of acetylenic unsaturated and in addition to the oxirane oxygen can contain ether, --O--, or carbonyl oxygen, ##STR24## and (2) 0 to about 98% by weight of the epoxypolysiloxane described in (1) of an epoxy-terminated silane wherein said epoxy-terminated silane is represented by the formula, ##STR25## wherein E is an epoxy-containing monovalent hydrocarbon radical defined above, p is 1 to 3 and R.sup.2 can be an aliphatic hydrocarbon radical of less than 10 carbon atoms,
- b. admixing an effective amount of an epoxy curing catalyst,
- c. coating the pourable liquid to form a thin film upon a substrate, and
- d. heating or irradiating to effect reacting and curing of (1) and (2).
A release liner in which a backing is provided on at least one surface with a thin release layer which is the crosslinked, polymeric network reaction product of starting materials comprising
- (1) a curable epoxypolysiloxane, in solution or in the form of 100% solids, which is represented by the formula, ##STR27## wherein R is a lower alkyl group or radical of one to three carbon atoms,
- R.sup.1 is a monovalent hydrocarbon radical of 4 to 20 carbon atoms,
- E is a monovalent epoxy-containing hydrocarbon radical,
- M is a silyl group R.sub.3 Si--, R.sub.2 R.sup.1 Si--, or R.sub.2 ESi--, where R, R.sup.1, and E are defined above,
- a is 5 to 200,
- b is 0 or up to 20% of a
- a+b is 5 to 200,
- c may be 0 when M is R.sub.2 ESi-- or is greater than 0 but less than 20% of the value of (a+b) when M is R.sub.3 Si--, R.sub.2 R.sup.1 Si-- or R.sub.2 ESi--, and
- n is 1 to 75;
- provided that the monovalent epoxy-containing hydrocarbon radical, E, contains at least one polymerizable epoxy group, ##STR28## the remainder being composed of carbon and hydrogen free of acetylenic unsaturation and in addition to the oxirane oxygen can contain ether, --O--, or carbonyl oxygen, ##STR29## (2) 0 to about 98% by weight of the epoxypolysiloxane described in (1) of an epoxy-terminated silane wherein said epoxy-terminated silane is represented by the formula, ##STR30## wherein E is an epoxy-containing monovalent hydrocarbon radical defined above, p is 1 to 3 and R.sup.2 can be an aliphatic hydrocarbon radical of less than 10 carbon atoms;
- cured in the presence of a catalytically effective amount of an epoxy curing catalyst.
Dependencies are inferred from the claim text.