A phosphorus-based polycarboxylic acid water reducing agent and a preparation method thereof

Abstract

The application discloses a phosphoric acid group polycarboxylic acid water reducing agent and a preparation method thereof, and relates to the technical field of phosphoric acid group polycarboxylic acid water reducing agents. The phosphoric acid group polycarboxylic acid water reducing agent is a copolymer formed by free radical copolymerization of an unsaturated polyether macromonomer, an unsaturated carboxylic acid monomer and an unsaturated phosphate monomer, wherein the unsaturated phosphate monomer is a compound R 1 -O-P(O)(OH) 2， wherein R 1 is an alkenyl group or a (methyl)acryloyloxy alkyl group containing a carbon-carbon double bond. By introducing a phosphoric acid group (P(O)(OH)2) with strong polarity and high complexing capacity into the molecular chain of polycarboxylic acid, compared with the traditional PCE containing only carboxyl groups, the phosphoric acid group can form stronger chemical bonding and complexing with cement hydration products (such as Ca2+), thereby enhancing the adsorption strength and stability of the polymer on the surface of cement particles, and improving the dispersibility and dispersion retention of the water reducing agent.

Description

Technical Field

[0001] This invention relates to the field of phosphate-based polycarboxylate superplasticizers, specifically to a phosphate-based polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] Polycarboxylate superplasticizers (PCEs) have become an indispensable key component in the preparation of modern high-performance concrete due to their high water reduction rate, excellent slump retention performance, and low shrinkage rate. Traditional polycarboxylate superplasticizers are usually produced by free radical copolymerization of carboxyl-containing unsaturated monomers (such as acrylic acid and methacrylic acid) and polyether macromonomers (such as methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether) in aqueous solution.

[0003] However, with the continuous development of concrete technology, especially the increasing demand for high-strength, ultra-high-strength, self-compacting and high-durability concrete, higher requirements have been placed on the performance of water-reducing agents. Existing polycarboxylate water-reducing agents still have the following shortcomings when applied to certain specific systems: (1) They are sensitive to dosage and their adaptability needs to be improved, especially in systems with low-quality aggregates or highly adsorbent cementitious materials, where dispersibility is easily interfered with; (2) They have poor compatibility with some admixtures such as early-strength agents and retarders; (3) In ultra-high-strength, low water-cement ratio systems, their ability to disperse and retain cement particles is sometimes insufficient, which may lead to accelerated workability loss; (4) Their protective effect on reinforcing steel is limited.

[0004] Phosphate groups have attracted much attention in materials science due to their unique chemical properties (strong complexing, polarity, and potential corrosion inhibition). Introducing phosphate groups into polymer molecular chains can theoretically impart stronger anchoring effects between the polymer and cement particle surfaces, improve adsorption behavior, and potentially bring additional beneficial effects. However, currently, there are few reports on the efficient and stable introduction of phosphate groups into the main chain or side chain of polycarboxylate superplasticizers to achieve significant performance optimization, and the synthesis processes often suffer from cumbersome steps, demanding conditions, or high monomer costs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a phosphate-based polycarboxylate superplasticizer and its preparation method, solving the problems mentioned in the background section. To achieve the above objectives, this invention is implemented through the following technical solution: A phosphate-based polycarboxylate superplasticizer is a copolymer formed by free radical copolymerization of unsaturated polyether macromonomers, unsaturated carboxylic acid monomers, and unsaturated phosphate ester monomers, wherein the unsaturated phosphate ester monomers are compounds having the general formula R. 1 -OP(O)(OH) 2， Where R 1 It is an alkenyl or (meth)acryloyloxyalkyl group containing a carbon-carbon double bond.

[0006] Preferably, the unsaturated phosphate monomer is selected from one or more of (meth)acryloyloxyethyl phosphate, vinyl phosphate, allyl phosphate, and mono(2-(meth)acryloyloxyethyl) phosphate.

[0007] Preferably, the unsaturated polyether macromonomer is an unsaturated monomer having polyoxyethylene ether segments and terminal olefin bonds, and the unsaturated carboxylic acid monomer is selected from one or more of (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid and their salts.

[0008] Preferably, the unsaturated polyether macromonomer is one or more of isopentenyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, vinyl polyoxyethylene ether, or methoxy polyethylene glycol (meth) acrylate.

[0009] Preferably, the copolymer further comprises at least one other functional monomer selected from unsaturated sulfonic acid monomers and unsaturated amide monomers.

[0010] Preferably, with the total molar number of all structural units in the copolymer being 100%, the molar percentage of each structural unit is as follows: Unsaturated polyether macromonomers: 10% - 40%; Unsaturated carboxylic acid monomers: 10% - 40%; Unsaturated phosphate monomers: 1% - 20%; Other functional units: 0% -10%.

[0011] Preparation method of phosphate-based polycarboxylate superplasticizer S1 In the reaction vessel, add unsaturated polyether macromonomer and part of deionized water, and stir to obtain the base liquid; S2. The reaction system is heated to 50-85℃, and solutions A and B are simultaneously added dropwise to the base solution. After the addition is complete, the solution is kept at the temperature for aging. Solution A is a mixed aqueous solution containing unsaturated carboxylic acid monomers, unsaturated phosphate ester monomers, chain transfer agents and deionized water. Solution B is an aqueous solution of a redox initiator. After the S3 reaction is complete, cool the solution and neutralize it with an alkaline substance to a pH of 5.0-7.0 to obtain the final product.

[0012] Preferably, in S2, the chain transfer agent is selected from one or more of mercaptoacetic acid, mercaptopropionic acid, 2-mercaptoethanol, isooctyl 3-mercaptopropionate, dodecyl mercaptan, and isopropanol, and its amount is 0.5%-3.0% of the total mass of the unsaturated polyether macromonomer, unsaturated carboxylic acid monomer, and unsaturated phosphate ester monomer.

[0013] Preferably, in S2, the oxidant in the redox initiator is selected from one or more of hydrogen peroxide, ammonium persulfate, potassium persulfate, and sodium persulfate; the reducing agent is selected from one or more of ascorbic acid, sodium formaldehyde sulfoxylate, sodium bisulfite, and ferrous sulfate; and the amount of each of the oxidant and reducing agent is independently 0.5%-3.0% of the total mass of the unsaturated polyether macromonomer, unsaturated carboxylic acid monomer, and unsaturated phosphate ester monomer.

[0014] Preferably, in S2, the dripping time is 2-6 hours, the heat preservation and ripening time is 1-3 hours, and in S3, the alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia, triethanolamine, diethanolamine, and monoethanolamine.

[0015] The advantages of this application are: This invention introduces phosphate groups (P(O)(OH)2) with strong polarity and high complexing ability into the polycarboxylic acid molecular chain. Compared with traditional PCE containing only carboxyl groups, the phosphate groups can react with cement hydration products (such as Ca). 2+ This forms stronger chemical bonds and complexations, enhancing the adsorption strength and stability of the polymer on the surface of cement particles, thereby improving the dispersibility and dispersion retention of the water-reducing agent.

[0016] 2. The phosphate-based polycarboxylate superplasticizer provided by this invention not only has a high water reduction rate (up to 30% or more), but also exhibits outstanding slump retention performance, making it particularly suitable for concrete projects requiring long-distance transportation or extended construction periods. Furthermore, it has wider adaptability to different types of cement and better compatibility with other admixtures.

[0017] 3. Phosphate groups possess certain corrosion-inhibiting properties. Their introduction is expected to form a protective adsorption film in the pore fluid of concrete, thus inhibiting steel corrosion and providing a new possibility for improving the durability of reinforced concrete structures.

[0018] 4. The "one-step" aqueous solution free radical copolymerization method directly involves unsaturated monomers containing phosphate groups in the copolymerization reaction. The process is simple, the reaction conditions are mild (usually carried out in water at 60-75℃), no complicated post-modification steps are required, the production cost is controllable, and it is suitable for large-scale industrial production. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] A phosphate-based polycarboxylate superplasticizer is a copolymer formed by free radical copolymerization of unsaturated polyether macromonomers, unsaturated carboxylic acid monomers, and unsaturated phosphate ester monomers. The unsaturated phosphate ester monomers are compounds with the general formula R. 1 -OP(O)(OH) 2， Where R 1 It is an alkenyl or (meth)acryloyloxyalkyl group containing a carbon-carbon double bond.

[0021] The unsaturated phosphate monomer is selected from one or more of (meth)acryloyloxyethyl phosphate, vinyl phosphate, allyl phosphate, and mono(2-(meth)acryloyloxyethyl) phosphate.

[0022] The unsaturated polyether macromonomer is an unsaturated monomer with polyoxyethylene ether segments and terminal olefin bonds, and the unsaturated carboxylic acid monomer is selected from one or more of (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid and their salts.

[0023] The unsaturated polyether macromonomer is one or more of isopentenyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, vinyl polyoxyethylene ether, or methoxy polyethylene glycol (meth) acrylate.

[0024] The copolymer also contains at least one other functional monomer selected from unsaturated sulfonic acid monomers and unsaturated amide monomers.

[0025] Assuming the total molar number of all structural units in the copolymer is 100%, the molar percentage of each structural unit is as follows: Unsaturated polyether macromonomers: 10% - 40%; Unsaturated carboxylic acid monomers: 10% - 40%; Unsaturated phosphate monomers: 1% - 20%; Other functional units: 0% -10%.

[0026] Preparation method of phosphate-based polycarboxylate superplasticizer S1 In the reaction vessel, add unsaturated polyether macromonomer and part of deionized water, and stir to obtain the base liquid; S2: The reaction system is heated to 50-85℃, and solutions A and B are simultaneously added dropwise to the base solution. After the addition is complete, the mixture is kept at this temperature for maturation. Solution A is a mixed aqueous solution containing unsaturated carboxylic acid monomers, unsaturated phosphate ester monomers, chain transfer agents, and deionized water. Solution B is an aqueous solution of a redox initiator. The chain transfer agent is selected from one or more of mercaptoacetic acid, mercaptopropionic acid, 2-mercaptoethanol, isooctyl 3-mercaptopropionate, dodecyl mercaptan, and isopropanol, and its dosage is determined by the ratio of unsaturated polyether macromonomers, unsaturated carboxylic acid monomers, and unsaturated polyether macromonomers. The amount of oxidant and reducing agent is 0.5%-3.0% of the total mass of unsaturated polyether macromonomer, unsaturated carboxylic acid monomer and unsaturated phosphate ester monomer. The oxidant is selected from one or more of hydrogen peroxide, ammonium persulfate, potassium persulfate and sodium persulfate. The reducing agent is selected from one or more of ascorbic acid, sodium formaldehyde sulfoxylate, sodium bisulfite and ferrous sulfate. The amount of oxidant and reducing agent is 0.5%-3.0% of the total mass of unsaturated polyether macromonomer, unsaturated carboxylic acid monomer and unsaturated phosphate ester monomer. The dropping time is 2-6 hours and the heat preservation and curing time is 1-3 hours.

[0027] After the S3 reaction is complete, cool the solution and neutralize it with an alkaline substance to a pH of 5.0-7.0. The alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia, triethanolamine, diethanolamine, and monoethanolamine.

[0028] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A phosphate-based polycarboxylate superplasticizer, characterized in that, It is a copolymer formed by free radical copolymerization of unsaturated polyether macromonomers, unsaturated carboxylic acid monomers, and unsaturated phosphate ester monomers, wherein the unsaturated phosphate ester monomers are compounds with the general formula R. 1 -OP(O)(OH) 2， Where R 1 It is an alkenyl or (meth)acryloyloxyalkyl group containing a carbon-carbon double bond.

2. The phosphate-based polycarboxylate superplasticizer according to claim 1, characterized in that: The unsaturated phosphate monomer is selected from one or more of (meth)acryloyloxyethyl phosphate, vinyl phosphate, allyl phosphate, and mono(2-(meth)acryloyloxyethyl) phosphate.

3. The phosphate-based polycarboxylate superplasticizer according to claim 1, characterized in that: The unsaturated polyether macromonomer is an unsaturated monomer having polyoxyethylene ether segments and terminal olefin bonds, and the unsaturated carboxylic acid monomer is selected from one or more of (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid and their salts.

4. The phosphate-based polycarboxylate superplasticizer according to claim 3, characterized in that: The unsaturated polyether macromonomer is one or more of isopentenyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, vinyl polyoxyethylene ether, or methoxy polyethylene glycol (meth) acrylate.

5. The phosphate-based polycarboxylate superplasticizer according to claim 1, characterized in that: The copolymer also contains at least one other functional monomer selected from unsaturated sulfonic acid monomers and unsaturated amide monomers.

6. The phosphate-based polycarboxylate superplasticizer according to claim 5, characterized in that: With the total molar number of all structural units in the copolymer being 100%, the molar percentage of each structural unit is as follows: Unsaturated polyether macromonomers: 10% - 40%; Unsaturated carboxylic acid monomers: 10% - 40%; Unsaturated phosphate monomers: 1% - 20%; Other functional units: 0% -10%.

7. A method for preparing the phosphate-based polycarboxylate superplasticizer according to any one of claims 1-6, characterized in that: S1 In the reaction vessel, add unsaturated polyether macromonomer and part of deionized water, and stir to obtain the base liquid; S2. The reaction system is heated to 50-85℃, and solutions A and B are simultaneously added dropwise to the base solution. After the addition is complete, the solution is kept at the temperature for aging. Solution A is a mixed aqueous solution containing unsaturated carboxylic acid monomers, unsaturated phosphate ester monomers, chain transfer agents and deionized water. Solution B is an aqueous solution of a redox initiator. After the S3 reaction is complete, cool the solution and neutralize it with an alkaline substance to a pH of 5.0-7.0 to obtain the final product.

8. The method for preparing the phosphate-based polycarboxylate superplasticizer according to claim 7, characterized in that: In S2, the chain transfer agent is selected from one or more of mercaptoacetic acid, mercaptopropionic acid, 2-mercaptoethanol, isooctyl 3-mercaptopropionate, dodecyl mercaptan, and isopropanol, and its amount is 0.5%-3.0% of the total mass of the unsaturated polyether macromonomer, unsaturated carboxylic acid monomer, and unsaturated phosphate ester monomer.

9. The method for preparing the phosphate-based polycarboxylate superplasticizer according to claim 7, characterized in that: In S2, the oxidant in the redox initiator is selected from one or more of hydrogen peroxide, ammonium persulfate, potassium persulfate, and sodium persulfate; the reducing agent is selected from one or more of ascorbic acid, sodium formaldehyde sulfoxylate, sodium bisulfite, and ferrous sulfate; the amount of the oxidant and the reducing agent is independently 0.5%-3.0% of the total mass of the unsaturated polyether macromonomer, the unsaturated carboxylic acid monomer, and the unsaturated phosphate ester monomer.

10. The method for preparing the phosphate-based polycarboxylate superplasticizer according to claim 7, characterized in that: In S2, the dripping time is 2-6 hours, and the heat preservation and maturation time is 1-3 hours. In S3, the alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia, triethanolamine, diethanolamine, and monoethanolamine.