Method for preparing polycarboxylic acid retarding water reducer

Abstract

The invention belongs to the technical field of methods for preparing polycarboxylic acid water reducers. A method for preparing a polycarboxylic acid water reducer comprises the following: a step 1 of esterification, in which a poly(ethylene glycol methyl ether)acrylate macromonomer is synthesized by using methoxy polyethylene glycol and acrylic acid in a molar ratio of 1:1.1 to 1:1.5 at 100 to 120 DEG C, water is separated out in a reaction process, and the molecular weight of the macromonomer is 1,250 to 3,000; and a step 2 of polymerization, in which aqueous solution of the macromonomer is prepared, an unsaturated monomer and a catalyst A are added in turn at 40 to 50 DEG C, the temperature is kept constant at 28 to 40 DEG C, aqueous solution of anhydrous sodium hydrogensulfite or vitamin c is dripped, the concentration of a solid content is kept between 35 to 45 percent by adjusting water content, stirring is stopped, and the solution is allowed to stand for 1 to 1.5 hours, the pH value is kept between 6 and 8 by alkaline reagent after the reaction is finished, and the catalyst A is peroxyacetic acid or potassium peroxydisulfate. The invention has the advantages of low cost, simple process and high product performance.

Description

technical field [0001] The invention relates to a method for preparing a water reducer, in particular to a method for preparing a polycarboxylate cement water reducer. Background technique [0002] Since 2000, polycarboxylate water reducer has gradually been recognized by the concrete engineering industry in my country, and now it has been widely used in railway system concrete projects, key tunnel projects and municipal key projects. It is a new type of high-efficiency water reducer based on melamine, aliphatic and sulfamate-based water reducers, which has obvious advantages over previous generations of water reducers, and has low dosage (solid dosage: 0.15%-0.25%) It can produce ideal water-reducing and strengthening effects, and has little effect on concrete setting time, good slump retention, relatively good adaptability to cement and admixtures, little effect on concrete dry shrinkage, production The process does not use formaldehyde and does not exclude waste liquid, SO ...

AI Technical Summary

Problems solved by technology

[0003] However, due to cost and technical performance problems, domestic research on polycarboxylate superplasticizer products is only in the laboratory development stage, and there are still very few manufacturers that actually form products, which is far from meeting the needs of high-performance concrete development.

Most of the polycarboxylate water reducers produced by manufacturers are expensive, the reaction conditions are harsh and difficult to control, and the process is complicated, so they cannot achieve good results in practical applications.

[0004] At present, the synthesis process of polycarboxylate water-reducing agent on the market is mainly to add appropriate amount of monomers such as methacrylic acid and initiator to esterified products such as polyethylene glycol monomethyl ether acrylate, and then pass nitrogen gas into it, and heat it at 70 ° C ~ React at 90°C for 5 to 8 hours, and adjust the pH value with sodium hydroxide after the reaction. This type of process requires nitrogen as a protective agent, high reaction temperature, long reaction time, high energy consumption, and the price of raw material methacrylic acid High, resulting in high cost of polycarboxylate superplasticizers, compared with naphthalene-based superplasticizers, the price gap is large, lack of market competitiveness; the reaction process is complex, difficult to control, resulting in the product performance of polycarboxylate superplasticizers can not reach market requirements