Poly(phenylene ether)-polysiloxane composition and method
View Patent ↗A composition is prepared by oxidative copolymerization of specific amounts of 2,6-dimethylphenol, 2,3,6-trimethylphenol, and a hydroxyaryl-terminated polysiloxane. The composition exhibits an increased heat resistance relative to a corresponding composition prepared by copolymerizing 2,6-dimethylphenol and hydroxyaryl-terminated polysiloxane, without 2,3,6-trimethylphenol. The composition is useful as a flame-retardant additive in polymer compositions that require high heat resistance.
1. A method of preparing a thermoplastic composition, comprising:
oxidatively copolymerizing a monomer composition in an aromatic hydrocarbon solvent to form a solution comprising
a poly(2,6-dimethyl-1,4-phenylene ether-co-2,3,6-trimethyl-1,4-phenylene ether); and
a block copolymer comprising
a poly(2,6-dimethyl-1,4-phenylene ether-co-2,3,6-trimethyl-1,4-phenylene ether) block, and
a polysiloxane block comprising, on average, about 10 to about 100 siloxane repeating units;
wherein the poly(2,6-dimethyl-1,4-phenylene ether)-co-2,3,6-trimethyl-1,4-phenylene ether) block and the polysiloxane block are linked via an ether oxygen;
wherein the monomer composition comprises
about 65 to about 93 weight percent of 2,6-dimethylphenol,
about 5 to about 25 weight percent of 2,3,6-trimethylphenol, and
about 2 to about 10 weight percent of a hydroxyaryl-terminated polysiloxane;
wherein said oxidatively copolymerizing a monomer composition comprises a monomer addition period characterized by a first temperature, a build period following the addition period and characterized by a second temperature greater than the first temperature, and a temperature ramp period between the addition period and the build period; and wherein the temperature ramp period comprises increasing the temperature at an average rate of 0.1 to 0.3° C. per minute.
2. The method of claim 1 , wherein the monomer composition comprises about 10 to about 22 weight percent of the 2,3,6-trimethylphenol.
3. The method of claim 1 , wherein the monomer composition comprises about 13 to about 19 weight percent of the 2,3,6-trimethylphenol.
4. The method of claim 1 , wherein the hydroxyaryl-terminated polysiloxane has the structure
wherein n is about 35 to about 60.
5. The method of claim 4 , wherein the monomer composition comprises about 70 to about 88 weight percent of the 2,6-dimethylphenol, about 10 to about 22 weight percent of the 2,3,6-trimethylphenol, and about 3 to about 7 weight percent of the hydroxyaryl-terminated polysiloxane.