Firstly, let's introduce the raw materials for synthesizing polycarboxylate superplasticizer monomers. The raw materials for synthesizing polycarboxylate superplasticizers generally include: methyl acrylic acid, acrylic acid, ethyl acrylate, hydroxyethyl acrylate, sodium allyl sulfonate, methyl methacrylate, 2-acrylamido-2-methyl acrylic acid, methoxy polyoxyethylene methacrylate, ethoxy polyethylene glycol acrylate, allyl ether, etc.
The initiators that can be used in the polymerization process are: persulfate salt based initiators, benzoyl peroxide, and azodiisobutyl cyanide; Chain transfer agents include 3-hydrophobic propionic acid, hydrophobic acetic acid, hydrophobic ethanol, and isopropanol.
Polycarboxylate high-performance water reducer is a high molecular weight surfactant with a comb like structure synthesized by free radical copolymerization principle in aqueous solution, which contains sulfonic acid groups, carboxyl groups, amino groups, and polyoxyethylene side chains.
The synthesis method is as follows: in a round bottom flask equipped with an electric stirrer, thermometer, droplet device, and reflux condenser, slowly add the polymerization monomer solution and initiator solution by heating in a water bath. When selecting the polymerization monomer, its competitive rate should be fully considered. The reaction temperature can be determined according to the specific type of reaction monomer, and generally the temperature range of 70-95 ℃ can be chosen as the reaction temperature. Add the monomer solution dropwise within one hour, then add the residual initiator solution dropwise within 20 minutes. Finally, raise the temperature by 5 ℃ and continue the reaction for 1 hour. After cooling to 40 ℃, neutralize and discharge the material.
Polyurethane water reducing agent refers to the ability to reduce the water consumption of the mixture and improve the strength of concrete under the same conditions of concrete workability and cement dosage; Or additives that can save cement usage while maintaining the same workability and strength. Water reducing agent is the core material in concrete admixtures and a widely used type of admixture in concrete engineering. Its dosage accounts for more than 80% of the total dosage of admixtures and has become the fifth component of concrete after cement, sand, stone, and water. The workability of concrete is represented by construction operations such as transportability, pouring, compaction, and forming, and the ability to achieve uniform and dense concrete quality. Due to the vast territory, obvious seasonal changes, and significant differences in concrete raw materials in China, excessive slump loss of fresh concrete has always been an urgent problem that needs to be solved for normal construction. When concrete mixtures must be transported for a long time, especially in hot weather, they should be kept at the initial slump level as much as possible to ensure smooth transportation, pumping, and pouring of concrete.
The development of slow-release polycarboxylate superplasticizer has been relatively mature. As the main raw material for synthesizing superplasticizers, polycarboxylate superplasticizer monomers have a significant impact on the performance of the superplasticizer. As a third-generation water reducer, polycarboxylate superplasticizer is widely used in concrete due to its excellent water reducing performance, which can greatly reduce the water consumption in concrete and significantly improve its strength.
Polycarboxylate water reducing agent monomers are used to prepare water reducing agents.
CN201910444069 discloses a rosin modified polycarboxylate water reducer and its preparation method. By ester exchanging the carboxyl groups of rosin derivatives with vinyl acetate, rosin modified vinyl esters containing double bonds are obtained as monomers, which are then polymerized with other polycarboxylate superplasticizer monomers in aqueous solution to obtain the rosin modified polycarboxylate superplasticizer. The proportion of rosin modified vinyl ester in the mixed monomer is preferred to produce polycarboxylate superplasticizer with excellent performance. When used as an additive in cement and concrete mixing, it has a high water reduction rate at a low dosage of 0.12%. Meanwhile, the rosin modified polycarboxylate water reducer provided by the present invention also significantly improves the flowability and compressive strength of cement and concrete. In the above technical solution provided by the present invention, rosin derivatives have a wide range of sources, low cost, are green, environmentally friendly, and renewable, and have good market promotion value.
