In the patent, Hata, R. (Shin-Etsu Chemical) US Patent 12,030,902, 14-Jul-2024, tetrabutylammonium m-chlorobenzoate was used as an anionic catalyst for a “group transfer polymerization” to form a polymer crosslinking agent that is a (meth)acrylic-based graft silicone. The monomers were a long chain methacrylate (such as stearyl or dodecyl), 2-allyloxyethyl methacrylate, a silicone methacrylate ester and the initiator was dimethylketene methyl trimethylsilyl acetal.
The inventor did not explain why TBA m-chlorobenzoate was chosen as the anionic initiator though it is obvious that its solubility in the reaction mixture with THF as solvent and several liquid monomers ensures a homogeneous reaction mixture, which is critical for efficient polymerization and uniform polymer properties.
The choice of m-chlorobenzoate is not clear and it was used in all 7 examples of polymerization, even though 17 salts were cited in the teachings, including several fluoride salts that are known to be effective anionic catalysts for group transfer polymerizations of this type.
Background: Group transfer polymerization (GTP) is a type of living polymerization technique used primarily for the synthesis of acrylic polymers and copolymers and that is exactly what the inventor was describing. The key feature of GTP is its ability to produce polymers with well-defined molecular weights and narrow molecular weight distributions.
GTP involves the transfer of a silyl ketene acetal to a growing polymer chain. This process is initiated by a catalyst, often a fluoride ion, which facilitates the transfer of the silyl group. GTP is particularly effective for polymerizing methacrylates, acrylates, and other related monomers.
The technology described in this patent is consistent with all of the typical characteristics of GTP, except that m-chlorobenzoate was used instead of the more common fluoride anionic catalyst.
The application was for the cosmetics industry.
