Preparation method of polycarboxylate superplasticizer with carbon dioxide
The present invention discloses a preparation method of a polycarboxylate superplasticizer with carbon dioxide, comprising the following steps: (1) preparing a polycarboxylate superplasticizer prepolymer: performing an oxidation-reduction radical polymerization of an unsaturated macromonomer, an unsaturated phenol derivative, a reducing agent, an initiator and a chain transfer agent with different proportions under a nitrogen atmosphere to obtain a novel polycarboxylate superplasticizer prepolymer with different molecular weight; adjusting the pH by adding an alkali; (2) preparing a polycarboxylate superplasticizer: performing a Koble-Schmitt reaction between the polycarboxylate superplasticizer prepolymer and a carbon dioxide for a certain time to obtain the polycarboxylate superplasticizer. The polycarboxylate superplasticizer prepared by the method of the present invention retains the advantages of the existing water-reducing admixture of the polyether monomer compounds, and the production process is simple, safe, controllable, less side effect and has a better cost effective and competitive advantage.
1. A method for preparing a polycarboxylate superplasticizer with carbon dioxide, comprising the following steps:
step 1: preparing a polycarboxylate superplasticizer prepolymer: performing an oxidation-reduction radical polymerization of an unsaturated macromonomer, an unsaturated phenol derivative, a reducing agent, an initiator and a chain transfer agent with different proportions under a nitrogen atmosphere at a temperature of 0-50° C., obtaining a novel polycarboxylate superplasticizer prepolymer with a molecular weight of 20000-80000 g/mol after reacting for 1-3 hours; adjusting a pH of the polycarboxylate superplasticizer prepolymer to 7-8 by adding an alkali; wherein a molar ratio of the unsaturated macromonomer, unsaturated phenol derivative, reducing agent, initiator and chain transfer agent is 1:(2-6):(0.03-0.05):(0.01-0.05):(0.003-0.005);
step 2: preparing a polycarboxylate superplasticizer: performing a Koble-Schmitt reaction between the polycarboxylate superplasticizer prepolymer obtained in step 1 and a carbon dioxide for 1-3 hours at 125-150° C. under an atmospheric pressure of 0.5-1 MPa to obtain the polycarboxylate superplasticizer; wherein a molar ratio of the polycarboxylate superplasticizer prepolymer to the carbon dioxide is 1:(1.0-1.5).
2. The method according to claim 1 , wherein a structural formula of the unsaturated phenol derivative is:
wherein in the formula, R1, R2 and R3 are respectively selected from a group consisting of H, methoxyl and C2-C5 unsaturated alkenyl group; wherein one of the R1, R2 and R3 is a C2-C5 unsaturated alkenyl group.
3. The method according to claim 1 , wherein the unsaturated phenol derivative in step 1 is one or more selected from a group consisting of 4-vinylphenol, 2-vinylphenol, 3-vinylphenol and 4-vinyl-2-methoxyl-phenol.
4. The method according to claim 1 , wherein the unsaturated macromonomer in step 1 is selected from a group consisting of unsaturated polyether macromonomer and unsaturated ester macromonomer.
5. The method according to claim 1 , wherein the unsaturated macromonomer in step 1 is one or more selected from a group consisting of acrylic polyethers, methyl acrylic polyethers, 3-methyl-3-butene-1-polyethylene glycol, 2-methyl acrylic polyethers, methoxypolyethylene glycol acrylate, methoxypolyethylene glycol monomethyl ether acrylate, methoxypolyethylene glycol methacrylate, polyethylene glycol methacrylate and polyethylene glycol acrylate; wherein the molecular weight of the unsaturated macromonomer is 300-8000 g/mol.
6. The method according to claim 1 , wherein the alkali in step 1 is one or more selected from a group consisting of potassium hydroxide and sodium hydroxide.
7. The method according to claim 1 , wherein the initiator in step 1 is selected from a group consisting of persulfate and peroxide.
8. The method according to claim 1 , wherein the initiator in step 1 is one or more selected from a group consisting of hydrogen peroxide, ammonium persulfate, sodium persulfate and potassium persulfate.
9. The method according to claim 1 , wherein the chain transfer agent in step 1 is one or more selected from a group consisting of thioglycolic acid, 2-mercaptopropionic acid, mercaptoethanol, 3-mercaptopropionic acid, sodium methacrylate and dodecanethiol.
10. The method according to claim 1 , wherein the reducing agent in step 1 is one or more selected from a group consisting of sodium formaldehyde sulfoxylate, sodium metabisulfite, N, N-dimethylaniline, sodium bisulfite, sodium formaldehyde sulfoxylate, ferrous sulfate, N, N-diethylaniline, ferrous pyrophosphate, tetraethyleneamine and sodium ascorbate.