A kind of molecular weight regulator for emulsion polymerization and preparation method thereof

Abstract

The invention belongs to the technical field of molecular weight regulators, and discloses a molecular weight regulator for emulsion polymerization and a preparation method thereof. In the formamide solvent, the etherification reaction is carried out to obtain the 2-polyethylene glycol monomethyl ether-3-amyl alcohol crude product, and the polyethylene glycol monomethyl ether and the dodecyl trithiopropionic acid are mixed with N, N- Dimethylformamide is used as a solvent, and esterification is carried out in a catalytic system composed of dicyclohexylcarbodiimide and 4-dimethylaminopyridine to obtain polyethylene glycol monomethyl ether monododecyl trithiopropionate The crude product, the two crude products were separated and purified by column chromatography. The synthesis process of the invention is easy, the yield is high, there is no bad smell of mercaptan, and at the same time, it has different degrees of water solubility, exists in the water phase of the emulsion polymerization, is more easily diffused into the latex particles, increases the diffusion rate, and has protection The ability of colloid has a certain emulsifying ability.

Description

technical field [0001] The invention belongs to the technical field of molecular weight regulators, in particular to a molecular weight regulator for emulsion polymerization and a preparation method thereof. Background technique [0002] At present, in chain polymerization reactions, such as free radical polymerization, ring-opening polymerization, coordination polymerization and cationic addition polymerization reactions, in addition to chain initiation, chain growth, chain termination and other elementary reactions, it is often accompanied by chain transfer reactions. occur. [0003] In actual production, it is very common to apply the principle of chain transfer to control molecular weight. For example, the molecular weight of polyvinyl chloride is mainly determined by the transfer to the monomer, which is controlled by temperature; the molecular weight of styrene-butadiene rubber is regulated by tert-dodecyl mercaptan as a chain transfer agent; solution polymerization i...

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Problems solved by technology

As the thiol carbon chain grows, its solubility in water decreases sharply, which will lead to limited transfer of chain transfer agents to latex particles

Due to the decrease of the rate of diffusion from the water phase, the reaction rate of the monomer in the latex particles is very fast, so that the concentration of the chain transfer agent in the latex particles is lower than the concentration at the thermodynamic equilibrium, which eventually leads to a decrease in the regulation efficiency of the chain transfer agent.

[0008] In summary, the problems in the prior art are: (1) the molecular weight regulator tert-dodecyl mercaptan used in the existing emulsion polymerization has an unpleasant stench, which is not conducive to environmental protection

[0009] (2) The solubility of tert-dodecyl mercaptan in water is small, and when emulsion polymerization is carried out, the chain transfer agent is not easy to diffuse into the latex particles

[0010] (3) As a chain transfer agent, tert-dodecyl mercaptan has no emulsifying function and no ability to protect colloid

[0011] Difficulty in solving the above-mentioned technical problems: Compared with tert-dodecyl mercaptan, the prepared molecular weight regulator has slightly poor molecular weight regulation ability during emulsion polymerization

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