Method for preparing powdered polycarboxylic acid water reducer by adopting ultrasonics in bulk polymerization

Abstract

The invention relates to a method for preparing a powdered polycarboxylic acid water reducer by adopting ultrasonics in bulk polymerization. The polycarboxylic acid water reducer is prepared from thefollowing raw materials: a methylallyl polyoxyethylene ether macromonomer, acrylic acid, an initiator and a chain transfer agent. The method for preparing the powdered polycarboxylic acid water reducer comprises the steps: putting 85-150 parts (by mass) of the methylallyl polyoxyethylene ether macromonomer into a reaction vessel, heating the temperature of the methylallyl polyoxyethylene ether macromonomer to 65 DEG C to 75 DEG C with ultrasonic waves, and starting to carry out stirring to melt the methylallyl polyoxyethylene ether macromonomer; mixing 20.1-32.2 parts of acrylic acid with thechain transfer agent, and carrying out uniform stirring thoroughly, so as to prepare a solution A; adding the initiator into the reaction vessel after the monomer at the bottom of the reaction vesselis melted completely, carrying out stirring dissolving, then, starting to dropwise add the prepared solution A by adopting a constant-flow pump, and carrying out a heat-preserving aging reaction afterdropwise adding is completed; and carrying out discharging after the reaction ends up, and carrying out cooling, thereby obtaining the solid polycarboxylic acid water reducer. According to the method, the cycle of synthetic reaction is short, the production cost is low, the conversion ratio of the macromonomer is relatively high, and the preparation process is safe, reliable and environmentally friendly.

Description

technical field [0001] The invention relates to a preparation method of a polycarboxylate water reducer, in particular to a method for preparing a powder polycarboxylate water reducer by ultrasonic waves in bulk polymerization, which belongs to the preparation method of a concrete admixture. Background technique [0002] Water reducer is the most commonly used admixture in the concrete industry. Its main function is to reduce the water-cement ratio, which can greatly improve the performance of concrete while saving water. The development of water reducers has mainly gone through three stages: lignin sulfonate, naphthalene-based high-efficiency water reducer and polycarboxylate high-performance water reducer. Among them, polycarboxylate water reducer is the third generation product. Its advantages such as high water reducing rate, good slump retention performance, diversity of molecular design and harmless production process quickly occupied a large number of markets. Howeve...

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Problems solved by technology

This method avoids post-treatment processes such as high-temperature spray drying or solvent separation, but there are some problems in the whole reaction itself due to the absence of solvent in bulk polymerization. As a result, the mass transfer efficiency is affected, so its synthesis time is generally longer. On the other hand, in bulk polymerization, as the reaction time is prolonged, the viscosity of the entire product system will rise sharply, thereby affecting the initiation efficiency of the initiator in the product system. Therefore, the conversion rate of the product in bulk polymerization is usually not too high, and due to the high viscosity of the product, it will also cause difficulty in heat dissipation during the reaction process, and the temperature of the reaction system will increase, which will reduce the controllability of the entire reaction process.

[0005] The above technologies have not given specific instructions on how to make the method of preparing powder polycarboxylate water reducer in bulk polymerization short, the production cost is low, the conversion rate of macromonomer is high, the preparation process is safe and reliable, and it is environmentally friendly. mentoring program

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