Temperature-resistant and anti-collapse multi-branched polymer fluid loss reducer and preparation method thereof

A preparation method of a temperature-resistant and anti-collapse polymer fluid loss reducer, including the following steps:

• adding polymerized monomer raw materials into a solvent, mixing and stirring, and pass in N2 to remove O2 for 30 min to obtain a raw material mixture;
• wherein the polymerized monomer raw materials include a first monomer, a second monomer and a third monomer, the first monomer is acrylamide and the second monomer is 2-acrylamido-2-methylpropanesulfonic acid, and the molar ratio of the first monomer, the second monomer and the third monomer is (20˜80):(20˜80):(2˜30);
• adding an initiator to the raw material mixture, and initiating the polymerization reaction after heating up to obtain a viscous mixture;
• wherein the initiator is azobisisobutyronitrile or a mixture consisting of ammonium persulfate and sodium bisulfite in a 1:1 mass ratio, and the amount of the initiator added is the total mass of the polymerized monomer raw materials 0.01˜0.1%;
• wherein the viscous mixture is subjected to a post-treatment process to obtain a temperature-resistant and anti-collapse multi-branched polymer fluid loss reducer;
• wherein the post-treatment process is:
• repeatedly immersing the viscous mixture in acetone, washing in ethanol, and then drying and pulverizing;
• wherein the main chain of the temperature-resistant and anti-collapse multi-branched polymer fluid loss reducer is composed of the following repeating unit (I):
• when the R1 and R2 groups are different, R1 is —H, R2 is any one of —(CH2)aNH2—(CH2)aN[(CH2)bNH2]2, —(CH2)aN[(CH2)bN[(CH2)cNH2]2]2;
• —(CH2)aN[(CH2)bN[(CH2) cN[(CH2)dNH2]2]2]2, —(CH2)aN[(CH2)bN[(CH2)cN[(CH2)dN[(CH2)eNH2]2]2]2]2;
• a, b, c, d, e are any integers from 1 to 5;
• when the R1 and R2 groups are the same, R1 and R2 is any one of —(CH2)aNH2, —(CH2)aN[(CH2)bNH2]2, —(CH2)aN[(CH2)bN[(CH2)cNH2]2]2, —(CH2)aN[(CH2)bN[(CH2) cN[(CH2)dNH2]2]2]2, —(CH2)aN[(CH2)bN[(CH2)cN[(CH2)dN[(CH2)eNH2]2]2]2]2;
• a, b, c, d, e are any integers from 1 to 5;
• wherein the third monomer is the polymerized monomer raw material which forms
• of the repeating unit (I).