Each manufacturer has its own unique process recipe for the synthesis and formula of early strength mother liquor, but in summary, there are probably the following process recipes, and the main details may be slightly different.
The first method: post-polymerization functionalization method. This method mainly uses existing polymers to modify materials. Generally, early strength with a known content is used, and under the action of a catalyst, it is mixed with polyether at a higher The grafting occurs through an esterification reaction at high temperature to form a grafting prepolymer. This method is limited by the variety and specifications of the controlled early strength products, and it is difficult to adjust the composition and content. In addition, the compatibility between early strength and polyether during the production process is not very good, and the esterification process is difficult. As the esterification continues, water continues to escape, and phase separation is easy to occur. question. Typical production process: alkoxyamine H2N(BO)-R is used as the product and is grafted with polyacrylate (BO represents an oxyalkylene group, n is a natural number, R is an L1~C4 alkyl group), and the application The solubility of early strength in alkoxyamines enables the imidization to proceed more completely. During the reaction, the amount of amine product added is usually 12% to 30% of the mole number of -COOH. First heat the reaction mixture to a temperature higher than 130Co, react for 1.6~3h, then reduce the temperature to 150%~140%, add a metal catalyst and react for 1.6~3h to obtain the desired product.
The second method : In-situ polymerization and grafting method This method gets rid of the shortcomings of post-polymerization engineering method. Polyether is used as the reaction medium for carboxylic acid unsaturated monomers. The reaction integrates polymerization and esterification, which avoids the problem of poor compatibility between early strength and polyether. Typical preparation process: The solution of acrylate monomer, chain transfer agent, and initiator is gradually added dropwise into the solution of methoxypolyethylene glycol with a relative molecular mass of 3000. After reacting for 46mln under 65Co, the temperature is increased. Continuously remove water (about 60mln) from 130Co under N2 protection, add a metal catalyst to raise the temperature to 162Co, react for 1 hour, and deepen grafting to obtain the finished product. Although this method can control the content of the polymer, the main chain usually only has to select monomers containing -COOH groups, otherwise it is impossible to graft. Moreover, this grafting reaction is a reversible equilibrium reaction, and the system must be managed before the reaction. There is a lot of water in it, and its grafting degree will not be very high and cannot be controlled. This method has a simple process and low product cost. The disadvantage is that the molecular structure design is more difficult.
The third method: immediate copolymerization of polymerizable monomers. This generation method usually requires the preparation of macromonomers with polymerization specificity, such as methoxypolyethylene glycol methacrylate. The monomers that need to be prepared are then mixed together and solution polymerized directly to obtain the finished product. The core of this production process is the production of specific macromonomers, which requires a relatively complicated separation and purification process, which is costly. Japan uses short-chain methoxy polyethylene glycol methacrylate, long-chain methoxy polyethylene glycol methacrylate, and methacrylic acid to directly copolymerize to achieve this slump retention. Good concrete admixture. A typical production example is given: put 600 parts of water (mass parts, the same below) into a laminated glass reaction vessel equipped with a thermometer, stirring device, dropping funnel, N2 inlet tube and return condenser tube. , pass N2 to remove oxygen while stirring, heat to 90 degrees Celsius under N2 gas protection, and then add and mix 350 parts of short-chain methoxy polyethylene glycol methacrylate (OE addition mole) dropwise within 4 hours. The number is 4), 60 parts of long-chain methoxy polyethylene glycol methacrylate (the number of OE addition moles is 21), 150 parts of methacrylic acid, 130 parts of water and 13.5 parts of chain transfer agent 3-sulfide Monomeric solution of lactic acid bacteria and 50 parts of 12% perhydrochloric acid solution. After the dropwise addition, 12 parts of 12% perhydrochloric acid hinge solution was added dropwise within 1 hour and insulated for 1 hour to obtain a polymer solution with a weight average relative molecular mass of 20,000 as the final product.
Processing technology of early-strength water-reducing agent mother liquor
(1) Esterification reaction (preparation of macromonomer): Measure and verify polyethylene glycol, melt it in a water bath, Add the reaction tank, add methacrylic acid, and 1 part of its ingredients (hydroquinone and phenothiazine account for 5:1), raise the temperature to 95°C, add concentrated sulfuric acid (as a catalyst), and continue Raise the temperature to 130°C and maintain for 6.3 hours, then fill with nitrogen for 2 hours (6㎡/hour, 1 bottle every 40 minutes, 4 bottles in total), the reaction proceeds, and the intermediate biomacromonomer polyethylene glycol as the admixture is obtained. Alcohol monomethacrylate and water. (After reduced pressure → distillation → dehydration, the acidification reaction will be more complete).
(2) Polymerization reaction: Use ammonium persulfate-induced solution polymerization method. The esterified substances for measurement and verification are polyethylene glycol monomethacrylate, acrylate, content regulator dodecyl mercaptan, mixed with double distilled water, and pumped into the burette tank A for emergency use, which is material A. Measure and verify ammonium persulfate, add double distilled water, and pump it into the buret tank B for emergency use, which is material B. Add double distilled water into the reaction tank, raise the temperature to 86°C, and burette materials A and B together. It takes 3 hours to complete the buret of material A, 3.6 hours to complete the buret of material B, and the heat preservation period is 1.6 hours. (Temperature control: 95±2℃).
(3) Neutralization reaction (it is to neutralize the concentrated sulfuric acid metal catalyst used in the esterification reaction above), reduce the temperature of the reacted polymer to below 60°C, and add carbonic acid while stirring Ammonium hydrogenate, wait until the pH is around 7, the reaction will proceed, and the early-strength superplasticizer mother liquor will be obtained. </p
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