| 摘要 |
FIELD: chemistry. ^ SUBSTANCE: present invention relates to a method of preparing aqueous solutions of copolymers of acrylic or methacrylic acid with their alkoxy polyoxyalkylene esters. The invention describes a method of preparing aqueous solutions of copolymers, which involves a main copolymerisation step when acrylic or methacrylic acid is heated with alkoxy polyoxyalkylene esters of these acids of general formula CH2=C(R1)-C(O)-O-(Alk-O)n-R2, where R1 = H, CH3, R2 = C1-3 alkyl, Alk = C2-3 alkylene, n is an integer, or with mixtures of these esters with other monomers, an after-polymerisation step and a neutralisation step, where the main copolymerisation step is carried out in an aqueous medium in the presence of a water-soluble polymerisation initiator in amount of 1.0-2.5% of total weight of monomers and a phosphorus-containing chain-terminating agent through gradual addition of the mixture of monomers into the water and simultaneous separate addition of aqueous solutions of the polymerisation initiator and the chain-terminating agent, distinguished by that the main copolymerisation step is carried out using an alkoxy polyoxyalkylene ester of acrylic acid or methacrylic acid with n=10-25 in molar ratio of the chain-terminating agent to the polymerisation initiator equal to (3.5 -1.5):1, and the after-polymerisation step is carried out by holding the reaction mixture at polymerisation temperature for 10-30 minutes, subsequent addition of the initiator in amount of 10-25% of the initially added amount and then holding at polymerisation temperature for 50-90 minutes. ^ EFFECT: obtaining a copolymer with narrow molecular-weight distribution, which boosts the plasticising effect and strength of set cement when such copolymers are used in the cement mix. ^ 1 cl, 1 tbl, 9 ex |
