Study on the Synthesis of Maleic Anhydride Series Polycarboxylate Superplasticizer
|Course||Materials Physics and Chemistry|
|Keywords||Maleic anhydride Polycarboxylate superplasticizers Synthesis Cement paste|
Polycarboxylate superplasticizer is a new type of superplasticizer, it has a low ash, high water reducing rate, dispersed retention, slump loss cement adaptable, environmental protection and other prominent advantages to better meet the requirements of high-performance concrete. According to the principle of molecular design, selection of maleic anhydride (MA), (methoxy) polyethylene glycol (MPEG / PEG), sodium vinyl sulfonate (SVS), methacrylic acid (MAA) is synthesized from a molecular structure containing a carboxylic acid group (-COOH), sulfonate group (-SO3-), a polyoxyalkylene vinyl ether group [- (O-CH2-CH2) n-] of a functional group such as maleic anhydride type polycarboxylate superplasticizer. Superplasticizer primarily through two steps: (1) esterification of maleic anhydride with (methoxy) polyethylene glycol in the catalyst to the esterification reaction of alcohol solution to obtain a maleic anhydride esterified macromonomer (methoxy) polyethylene glycol the monoester (MPEG-MA/PEG-MA); ② The polymerization, so that the esterified macromonomer maleic anhydride (methoxy) polyethylene glycol monoester (MPEG-MA/PEG -MA), and sodium vinyl sulfonate (SVS), methacrylic acid (MAA) in the role of initiator to the polymerization reaction, and then after the neutralization reaction of maleic anhydride class of polycarboxylate superplasticizers. Derived synthetic esterified macromonomer through discussion of the influence factors on the esterification, the optimum conditions of the maleic anhydride (methoxy) polyethylene glycol mono the ester (MPEG-MA/PEG-MA): the catalyst an amount of MPEG / 6% PEG, acid and alcohol than 1.15:1, reaction temperature of 110 ° C, the reaction time of 4 h, and the to take vacuum distillation before esterification; through discussion of polymerization influencing factors, derived synthetic maleic anhydride class the polycarboxylate superplasticizers the optimum conditions: an aqueous solution polymerization system, MPEG-MA/PEG-MA with SVS disposable feeding the MAA and initiator were continuously added dropwise, the initiator used in an amount of 7% of the total mass of monomer, n (MPEG-MA/PEG-MA): n (SVS): n (MAA) = 1:0.5:5, the reaction temperature was 80 ° C, and the reaction time was 6h, the reaction solution concentration of 15%; by the synthesized Infrared Spectroscopy Characterization superplasticizer prove successful experiments synthesized containing carboxylic acid group (-COOH), sulfonate group (-SO3-), polyoxyalkylene vinyl ether group [- (O-CH2-CH2) n- ] functional groups such as maleic anhydride type polycarboxylate superplasticizer. Polycarboxylate superplasticizer homemade maleic anhydride, performance testing, results show: homemade maleic anhydride class polycarboxylate superplasticizer can play a high dispersion at low dosage, dispersion effects ( methyl) acrylic superplasticizer there is some discrepancy, but at higher dosage dispersion effect with (meth) acrylic equivalent and the saturation dosage of between 0.5% to 0.6%, the fluidity of cement paste The retentivity is enhanced with the increase in dosage, and has better adaptability for different cement.