Implementation method of reversible addition fragmentation chain emulsion polymerization

Abstract

The invention discloses an implementation method of reversible addition fragmentation chain emulsion polymerization. 20-40 parts by weight of water, 0.1-2 parts by weight of bipolar macromolecule reversible addition fragmentation chain reagent, 1-20 parts by weight of monomer and 0.005-0.2 part by weight of micromolecule reversible addition fragmentation chain reagent are added into a reactor, stirring to be uniform is carried out, stirring is carried out, nitrogen is led in, heating is carried out until the temperature is increased to be 50-80 DEG C, 0.004-0.08 part by weight of water soluble initiator is added, initiated polymerization is carried out for 10-60min, 0-2 parts by weight of alkaline aqueous solution is added, and polymerization is continued for 0.5-5h. The invention utilizes bipolar macromolecule reversible addition fragmentation chain reagent with special structure as emulsifier and chain transfer agent, micromolecule reversible addition fragmentation chain is combined with emulsion polymerization, alkali is replenished, so as to improve the stability of emulsion; besides, process is simple, energy consumption is low, reaction time is short, conversion rate is high, no traditional emulsifier is adopted, molecular weight is consistent with design value, and molecular weight distribution is less than 2.0, thus having good industrialization prospect.

Description

technical field [0001] The invention relates to emulsion polymerization, in particular to a method for implementing reversible addition-fragmentation chain transfer emulsion polymerization. Background technique [0002] Compared with other traditional polymerization methods, emulsion polymerization has many advantages: the polymerization reaction occurs in the latex particles dispersed in the water phase. Although the viscosity inside the latex particles is high, since water is the continuous phase, the viscosity of the whole system is not high. The viscosity of the system does not change much during the entire reaction process, which makes the heat transfer of the entire system easy; due to the free radical isolation effect, high reaction rates and high molecular weight polymers can be achieved simultaneously in emulsion polymerization; most Emulsion polymerization uses water as the dispersion medium, which avoids the trouble of expensive solvents and recycling solvents, an...

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Problems solved by technology

However, in practice, no effective emulsion polymerization of small molecule reversible addition-fragmentation chain transfer reagents has been achieved: Luo et al. 1 People use benzoic acid 2-cyanoisopropyl dithioester as a small molecule reversible addition-fragmentation chain transfer reagent for emulsion polymerization, through a large amount of emulsifier, a large amount of initiator and reducing the amount of reversible addition-fragmentation chain transfer reagent Molecular weight can be controlled, molecular weight distribution is narrow, polymethyl methacrylate emulsion product with high colloidal stability, but when increasing target molecular weight, molecular weight distribution can be caused to broaden; People such as Monteiro 2,3 and Charmot et al. 4 Using a special reversible addition-fragmentation chain transfer reagent with a very low chain transfer constant for emulsion polymerization, the emulsion stability is good, but due to the very low chain transfer constant, the final molecular weight distribution is broad; Claverie et al. 5 Emulsion polymerization of styrene using the amidated reversible addition-fragmentation chain transfer reagent S-thiobenzoylthioglycolic acid, emulsion stability is good, but the final molecular weight distribution is greater than 1.70; Morbidelli et al. 6 Using cyclodextrin to help the reversible addition-fragmentation chain transfer reagent migrate to carry out emulsion polymerization, using cumyl dithiobenzoate as the reversible addition-fragmentation chain transfer reagent, the obtained emulsion has good stability, but the molecular weight distribution is relatively high. For formazan For methyl acrylate, the molecular weight matches and the molecular weight distribution is about 1.40, but for styrene, the molecular weight is out of control and the molecular weight distribution is greater than 2.20

The main problem of the current failure is that the structure of the emulsifier used by others for reversible addition-fragmentation chain transfer emulsion polymerization is not suitable. The conversion is low, the emulsion is unstable and there is a large amount of lumps

Progress has been made in emulsion polymerization using amphiphilic macromolecular reversible addition-fragmentation chain transfer reagents 7-11 , but only use the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent for emulsion polymerization. There are certain limitations in the control: Hawkett et al. found that using the neutralized polyacrylic acid-polybutylacrylate amphiphilic macromolecular reversible addition fragmentation chain transfer reagent for emulsion polymerization, the obtained particles often have a core-shell structure 12 , and the amphiphilic macromolecule reversible addition-fragmentation chain transfer reagent causes the final molecular weight of the reaction to deviate from the theoretical value, and the molecular weight distribution broadens 13

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