Flame retardant pressure-sensitive adhesive and method of making
A method of making a (meth)acrylate copolymer having pendent phosphate-containing groups and a pressure-sensitive adhesive that contains the (meth)acrylate copolymer having pendent phosphate-containing groups are provided. The method includes reacting a precursor (meth)acrylate copolymer having pendent carboxylic acid groups with an epoxy-functionalized phosphate compound. The pendent phosphate-containing groups on the reaction product can function as a flame retardant for the pressure-sensitive adhesive.
1. A method of forming a (meth)acrylate copolymer having a pendent phosphate-containing group, the method comprising:
providing a precursor (meth)acrylate copolymer having a monomeric unit comprising a pendent carboxylic acid group;
forming a reaction mixture comprising the precursor (meth)acrylate copolymer and an epoxy-functionalized phosphate compound; and
reacting the epoxy-functionalized phosphate compound with the pendent carboxylic acid group of the precursor (meth)acrylate copolymer to form the (meth)acrylate copolymer having the pendent phosphate-containing group.
2. The method of claim 1 , wherein the (meth)acrylate copolymer having the pendent phosphate-containing compound is a component of a pressure-sensitive adhesive.
3. The method of claim 1 , wherein the epoxy-functionalized phosphate compound has a single epoxy group and one to three phosphate groups.
4. The method of claim 1 , wherein the epoxy-functionalized phosphate compound is of Formula (I)
wherein
R 1 is hydrogen or methyl;
R 2 is a C1-C8 alkylene or a C3-C8 ether group;
R 3 is a C1-C4 alkyl, a benzyl, or combines with R 4 to form a cyclic group with 5 or 6 ring members that is optionally substituted with a C1-C3 alkyl; and
R 4 is a C1-C4 alkyl, benzyl, or combines with R 3 to form a cyclic group with 5 or 6 ring members that is optionally substituted with a C1-C3 alkyl.
5. The method of claim 4 , wherein the epoxy-functionalized phosphate compound of Formula (I) is of Formula (I-C)
wherein
R 9 is hydrogen or a C1-C3 alkyl;
R 10 is a C1-C3 alkyl; and
R 11 in a C1-C3 alkyl.
6. The method of claim 1 , wherein the epoxy-functionalized phosphate compound is of Formula (II)
wherein
R 12 is an alkylene having 1 to 2 carbon atoms;
R 13 is an alkylene having 2 to 4 carbon atoms;
R 14 is a C1-C4 alkyl or combines with R 15 to form a cyclic group with 5 or 6 ring members that is optionally substituted with a C1-C3 alkyl; and
R 15 is a C1-C4 alkyl or combines with R 14 to form a cyclic group with 5 or 6 ring members that is optionally substituted with a C1-C3 alkyl.
7. The method of claim 1 , wherein the precursor (meth)acrylate comprises 1 to 20 weight percent of the monomeric unit comprising a pendant carboxylic acid group based on a total weight of the precursor (meth)acrylate.
8. The method of claim 7 , wherein the at least 50 percent of the monomeric unit comprising a pendant carboxylic acid group in the precursor (meth)acrylate are reacted with the epoxy-functionalized phosphate compound.
9. A pressure-sensitive adhesive comprising a (meth)acrylate copolymer having pendent phosphate-containing groups, wherein the (meth)acrylate copolymer having pendent phosphate-containing groups is a reaction product of a reaction mixture comprising:
a) a precursor (meth)acrylate copolymer having a monomeric unit comprising a pendent carboxylic acid group; and
b) an epoxy-functionalized phosphate compound, wherein an epoxy group of the epoxy-functionalized phosphate compound undergoes a ring opening reaction with the monomeric unit comprising a pendent carboxylic acid group.
10. An article comprising:
a permanent or temporary substrate; and
the pressure-sensitive adhesive composition of claim 9 positioned adjacent to the permanent or temporary substrate.
11. The article of claim 10 , wherein the substrate is a polyimide film and wherein the article has a flammability rating of UL94 VTM-0.