Viscosity reduction type polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention discloses a viscosity reduction type polycarboxylate superplasticizer as well as a preparation method and application thereof, belongs to the field of concrete admixtures, and solves the problems of high system viscosity, low slurry fluidity and difficulty in pouring caused by low water-binder ratio of ultra-high performance concrete. The preparation method comprises the following steps: dissolving methyl allyl polyoxyethylene ether in water to prepare a base solution; the method comprises the following steps: dissolving a chain transfer agent and a reducing agent in water to prepare a solution A; dissolving an unsaturated carboxylic acid monomer, a monomer containing a sulfonic acid group and triethoxy vinyl silane in water to prepare a solution B; and adding the initiator into the base solution, dropwise adding the solution A and the solution B into the base solution at normal temperature, continuously reacting for 1-2 hours after dropwise adding is finished, and adding the residual formula amount of water to obtain the viscosity reduction type polycarboxylate superplasticizer. The invention overcomes the defects of high viscosity and poor working performance of a low water-binder ratio concrete system, has the advantages of simple preparation method, low production cost and good working performance, and can be used for ultra-high performance concrete.

Description

Technical Field

[0001] The present invention belongs to the field of concrete admixtures, and particularly relates to a viscosity-reducing polycarboxylate water reducer, a preparation method thereof, and an application thereof. Background Art

[0002] Polycarboxylate water reducer (PCE) has the characteristics of low dosage, high water reduction rate, strong dispersion ability, good workability with concrete, and good slump retention performance, and is the most widely used admixture in cement-based materials. The molecular structure of polycarboxylate water reducer is a comb-like structure. The main chain is an unsaturated carboxylic acid component, which can adsorb on the surface of the cementitious material to play an anchoring role, and the side chain is a polyether long chain, which plays a steric hindrance role. The two work together to achieve a good dispersion effect on the cementitious material.

[0003] Ultra-high performance concrete (UHPC) has received more and more attention in recent years due to its high mechanical strength, good durability, and low permeability. However, due to the low water-binder ratio (<0.25) of UHPC materials, the water reduction rate of the current water reducers on the market is not high, the adaptability is poor, and the dispersion effect on the UHPC system is not good, resulting in a large viscosity of the UHPC system, low slurry fluidity, and difficult pouring. Summary of the Invention

[0004] The purpose of the present invention is to provide a viscosity-reducing polycarboxylate water reducer to solve the problems of large viscosity of the system, low slurry fluidity, and difficult pouring caused by the low water-binder ratio of ultra-high performance concrete. Using this water reducer can reduce the viscosity of the UHPC system, improve the slurry fluidity, and improve its pouring performance, meeting the requirements of UHPC in practical engineering applications.

[0005] Another purpose of the present invention is to provide a preparation method of a viscosity-reducing polycarboxylate water reducer.

[0006] Another purpose of the present invention is to provide an application of a viscosity-reducing polycarboxylate water reducer.

[0007] The technical solution of the present invention is as follows: (1) A viscosity-reducing polycarboxylate water reducer has a general molecular structure formula as follows: In the formula, R is H or CH3, and a, b, c, d, and e respectively represent the polymerization degrees of each monomer in the polymer, where a∶b∶c∶d∶e = 1-3∶1-10∶1-3∶1-2∶1-2. (2) A preparation method of a viscosity-reducing polycarboxylate water reducer, the raw materials used and their parts by weight are as follows: 250-350 parts of methallyl polyoxyethylene ether, 32-47 parts of unsaturated carboxylic acid monomers, 4-8 parts of monomers containing sulfonic acid groups, 3-5 parts of triethoxyvinylsilane, 2-3.5 parts of initiator, 1.5-3 parts of chain transfer agent, 0.5-1 part of reducing agent, and 400-450 parts of water.

[0009] The unsaturated carboxylic acid monomers are acrylic acid and maleic anhydride, and the mass ratio of acrylic acid to maleic anhydride is 3-7:1; The monomers containing sulfonic acid groups are sodium allylsulfonate or sodium methallylsulfonate; The chain transfer agent is 3-mercaptopropionic acid; The preparation method specifically includes the following steps: A. Dissolve methallyl polyoxyethylene ether in water to prepare a base solution; B. Dissolve the chain transfer agent and the reducing agent in water to prepare solution A; C. Dissolve the unsaturated carboxylic acid monomers, the monomers containing sulfonic acid groups and triethoxyvinylsilane in water to prepare solution B; D. After adding the initiator to the base solution, dropwise add solution A and solution B to the base solution at room temperature. The dropping time of solution A is controlled within 2-3 h, and the dropping time of solution B is controlled within 1.5-2 h. After the dropping is completed, continue to react for 1-2 h, and add the remaining formulated amount of water to obtain the viscosity-reducing polycarboxylate water reducer.

[0010] Furthermore, the parts by weight of the raw materials used are as follows: 250 parts of methallyl polyoxyethylene ether, 32 parts of unsaturated carboxylic acid monomers, 5 parts of monomers containing sulfonic acid groups, 3 parts of triethoxyvinylsilane, 2 parts of initiator, 1.5 parts of chain transfer agent, 0.5 part of reducing agent, and 400 parts of water.

[0011] Furthermore, the parts by weight of the raw materials used are as follows: 290 parts of methallyl polyoxyethylene ether, 40 parts of unsaturated carboxylic acid monomers, 4 parts of monomers containing sulfonic acid groups, 4 parts of triethoxyvinylsilane, 2.5 parts of initiator, 2.3 parts of chain transfer agent, 0.6 part of reducing agent, and 420 parts of water.

[0012] Furthermore, the parts by weight of the raw materials used are as follows: 300 parts of methallyl polyoxyethylene ether, 40 parts of unsaturated carboxylic acid monomers, 5 parts of monomers containing sulfonic acid groups, 3 parts of triethoxyvinylsilane, 2.2 parts of initiator, 2.6 parts of chain transfer agent, 0.65 part of reducing agent, and 425 parts of water.

[0013] Further, the weight parts of the raw materials used are as follows: 310 parts of methyl allyl polyoxyethylene ether, 40 parts of unsaturated carboxylic acid monomer, 8 parts of monomer containing sulfonic acid group, 5 parts of triethoxyvinylsilane, 2.5 parts of initiator, 2.7 parts of chain transfer agent, 0.8 part of reducing agent, and 430 parts of water.

[0014] Further, the weight parts of the raw materials used are as follows: 350 parts of methyl allyl polyoxyethylene ether, 47 parts of unsaturated carboxylic acid monomer, 8 parts of monomer containing sulfonic acid group, 5 parts of triethoxyvinylsilane, 3.5 parts of initiator, 3 parts of chain transfer agent, 1 part of reducing agent, and 450 parts of water.

[0015] Further, the initiator is a mixture of hydrogen peroxide and sodium hypophosphite, and the mass ratio of hydrogen peroxide to sodium hypophosphite is 0.3 - 4:1.

[0016] Further, the reducing agent is ascorbic acid. (III) An application of a viscosity-reducing polycarboxylate water reducer in ultra-high performance concrete, and the dosage of the viscosity-reducing polycarboxylate water reducer is 1.0% - 2.0% of the total mass of the cementitious materials. If the dosage is too low, the dispersion effect on the cementitious materials is not good and it will affect the strength of the concrete; if the dosage is too high, after the adsorption of the water reducer molecules on the cementitious materials reaches saturation, the water reducer molecules will entangle and aggregate with each other, resulting in a reduction in free water in the system and an increase in the system viscosity, which is instead not conducive to the dispersion of the cementitious materials.

[0018] The viscosity-reducing polycarboxylate water reducer of the present invention can be mixed and used in combination with at least one known concrete admixture in the prior art, including defoaming agents, early strength agents, slump retaining agents, air-entraining agents, expansive agents, etc.

[0019] The present invention overcomes the defects of high viscosity and poor workability in the low water-cement ratio concrete system, has a simple preparation method, low production cost, good workability, and can be used in ultra-high performance concrete. Compared with the prior art, the present application has the following advantages: 1. In the molecular structure design of the viscosity-reducing polycarboxylate water reducer of the present invention, maleic anhydride containing a dicarboxylic acid component and a monomer containing a sulfonic acid group are added. This specific monomer combination can not only enhance the adsorption of the water reducer on the cementitious materials, but also further provide electrostatic repulsion, reduce the aggregation effect between the water reducer molecules, and fully exert the role of each water reducer molecule.

[0020] 2. The monomer containing sulfonic acid group introduced in the present invention has strong polarity and can interact with the chain transfer agent 3-mercaptopropionic acid through electrostatic interaction or hydrogen bond, enhancing the chain transfer activity of 3-mercaptopropionic acid. The interaction between the sulfonic acid group monomer and 3-mercaptopropionic acid makes the chain transfer reaction more uniform, reduces the polydispersity (PDI) of the molecular weight distribution, and a narrower molecular weight distribution can be obtained. This synergistic effect optimizes the reaction kinetics and makes the chain transfer reaction more controllable.

[0021] 3. The present invention adopts a ternary initiation system of hydrogen peroxide-sodium hypophosphite-ascorbic acid, which can efficiently generate free radicals under mild conditions. By adjusting the proportion of each component, the rate and molecular weight distribution of the polymerization reaction can be effectively controlled; the combination of this ternary initiation system and the chain transfer agent 3-mercaptopropionic acid can achieve more efficient free radical generation and chain transfer control during the polymerization process, thereby optimizing the molecular weight distribution and structure of the polymer.

[0022] 4. The present invention introduces a functional monomer triethoxyvinylsilane containing siloxane, which can further enhance the adsorption of the water reducing agent on the cementitious material.

[0023] 5. The raw materials used in the present invention contain hydrophobic groups such as methyl and siloxane, which can reduce the surface tension of the polycarboxylate water reducing agent in aqueous solution, thereby playing a role in viscosity reduction.

[0024] 6. The present invention adopts a two-component continuous dropping method for solution polymerization reaction, and the obtained viscosity-reducing polycarboxylate water reducing agent has a narrow molecular weight distribution, with a polydispersity coefficient of about 1.2 and a number average molecular weight concentrated in the range of 30,000 - 40,000. Detailed implementation mode

[0025] The present invention will be further described in detail below in conjunction with the specific implementation mode.

[0026] In the following examples, the molecular weight of methallyl polyoxyethylene ether is 2400.

[0027] Example 1 A preparation method of a viscosity-reducing polycarboxylate water reducing agent, comprising the following steps: A. Add 250 g of methallyl polyoxyethylene ether and 180 g of water into a four-necked flask, stir and dissolve to prepare a bottom liquid; B. Dissolve 1.5 g of 3-mercaptopropionic acid and 0.5 g of ascorbic acid in 90 g of water to prepare solution A; C. Dissolve 28 g of acrylic acid, 4 g of maleic anhydride, 5 g of allylsulfonic acid sodium, and 3 g of triethoxyvinylsilane in 25 g of water to prepare solution B; D. Add 1.0 g of hydrogen peroxide and 1.0 g of sodium hypophosphite to the base solution. After stirring for 5 min, use a peristaltic pump to dropwise add Solution A and Solution B to the base solution at room temperature. The dropping rate of Solution A is 0.75 mL / min, and the dropping rate of Solution B is 0.78 mL / min. After the dropping is completed, continue the reaction for 1.5 h. Then, add the remaining amount of water in the formula, and the solid content of the solution is about 40%, and a viscosity-reducing polycarboxylate water reducer can be obtained.

[0028] The structural formula of the prepared water reducer is as follows: Example 2 A method for preparing a viscosity-reducing polycarboxylate water reducer includes the following steps: A. Add 290 g of methallyl polyoxyethylene ether and 180 g of water to a four-necked flask, stir and dissolve to prepare a base solution. B. Dissolve 2.3 g of 3-mercaptopropionic acid and 0.6 g of ascorbic acid in 90 g of water to prepare Solution A. C. Dissolve 30 g of acrylic acid, 10 g of maleic anhydride, 4 g of allylsulfonic acid sodium, and 4 g of triethoxyvinylsilane in 25 g of water to prepare Solution B. D. Add 1.5 g of hydrogen peroxide and 1.0 g of sodium hypophosphite to the base solution. After stirring for 5 min, use a peristaltic pump to dropwise add Solution A and Solution B to the base solution at room temperature. The dropping rate of Solution A is 0.75 mL / min, and the dropping rate of Solution B is 0.78 mL / min. After the dropping is completed, continue the reaction for 1 h. Then, add the remaining amount of water in the formula, and the solid content of the solution is about 40%, and a viscosity-reducing polycarboxylate water reducer can be obtained.

[0029] The structural formula of the prepared water reducer is as follows: Example 3 A method for preparing a viscosity-reducing polycarboxylate water reducer includes the following steps: A. Add 300 g of methallyl polyoxyethylene ether and 180 g of water to a four-necked flask, stir and dissolve to prepare a base solution. B. Dissolve 2.6 g of 3-mercaptopropionic acid and 0.65 g of ascorbic acid in 90 g of water to prepare Solution A. C. Dissolve 34 g of acrylic acid, 6 g of maleic anhydride, 5 g of sodium methallylsulfonate, and 3 g of triethoxyvinylsilane in 25 g of water to prepare Solution B. D. Add 0.5 g of hydrogen peroxide and 1.7 g of sodium hypophosphite to the base solution. After stirring for 5 min, use a peristaltic pump to dropwise add Solution A and Solution B to the base solution at room temperature. The dropping rate of Solution A is 0.75 mL / min, and the dropping rate of Solution B is 0.78 mL / min. After the dropping is completed, continue the reaction for 1.2 h. Then, add the remaining amount of water in the formula, and the solid content of the solution is about 40%, and a viscosity-reducing polycarboxylate water reducer can be obtained.

[0030] The structural formula of the prepared water reducer is as follows: Example 4 A method for preparing a viscosity-reducing polycarboxylate water reducer includes the following steps: A. Add 310 g of methallyl polyoxyethylene ether and 180 g of water to a four-necked flask, stir and dissolve to prepare a base solution; B. Dissolve 2.7 g of 3-mercaptopropionic acid and 0.8 g of ascorbic acid in 90 g of water to prepare Solution A; C. Dissolve 35 g of acrylic acid, 5 g of maleic anhydride, 8 g of sodium methallylsulfonate, and 5 g of triethoxyvinylsilane in 25 g of water to prepare Solution B; D. Add 2 g of hydrogen peroxide and 0.5 g of sodium hypophosphite to the base solution. After stirring for 5 min, use a peristaltic pump to dropwise add Solution A and Solution B to the base solution at room temperature. The dropping rate of Solution A is 0.75 mL / min, and the dropping rate of Solution B is 0.78 mL / min. After the dropping is completed, continue the reaction for 2 h. Then, add the remaining amount of water in the formula, and the solid content of the solution is about 40%, and a viscosity-reducing polycarboxylate water reducer can be obtained.

[0031] The structural formula of the prepared water reducer is as follows: Example 5 A method for preparing a viscosity-reducing polycarboxylate water reducer includes the following steps: A. Add 350 g of methallyl polyoxyethylene ether and 180 g of water to a four-necked flask, stir and dissolve to prepare a base solution; B. Dissolve 3.0 g of 3-mercaptopropionic acid and 1 g of ascorbic acid in 90 g of water to prepare Solution A; C. Dissolve 40 g of acrylic acid, 7 g of maleic anhydride, 8 g of sodium methallylsulfonate, and 5 g of triethoxyvinylsilane in 25 g of water to prepare Solution B; D. Add 1.9 g of hydrogen peroxide and 1.6 g of sodium hypophosphite to the base solution. After stirring for 5 min, use a peristaltic pump to dropwise add Solution A and Solution B to the base solution at room temperature. The dropping rate of Solution A is 0.75 mL / min, and the dropping rate of Solution B is 0.78 mL / min. After the dropping is completed, continue the reaction for 1.5 h; then, add the remaining amount of water in the formula, and the solid content of the solution is about 40%, and a viscosity-reducing polycarboxylate water reducer can be obtained.

[0032] The structural formula of the obtained water reducer is as follows: Comparative Example 1 Use the commercially available Sichuan Shuangli SL-1(PC) polycarboxylate water reducer as the comparative example.

[0033] According to the method for measuring the fluidity of concrete admixtures in the "Concrete Admixture Specification" GB 8076-2008, detect the water-reducing effect of the water reducers in Examples 1-5 and Comparative Example 1. The materials used are P.O 42.5 portland cement produced by Anhui Conch Cement Co., Ltd. and silica fume produced by Lanzhou Cast Stone Co., Ltd. The water-binder ratio is 0.185, and the mass ratio of cement to silica fume is 918:162.

[0034] Prepare the water reducers in Examples 1-5 and Comparative Example 1 into 5 mg / mL solutions respectively. Use a RID-20A differential detector produced by Shimadzu, Japan, to test the molecular weight of the polycarboxylate water reducer. The chromatographic column used is OHpak SB-804HQ 300 type. The mobile phase in the chromatograph is 0.1 mol / L NaNO3, the column temperature is 25 °C, the flow rate is 0.8 ml / min, and the running time is 30 min; use a Sigma 701 full-automatic surface tension meter produced by Sweden to test the surface tension of the 10% water reducer solution; use a TOC-VCPH total organic carbon analyzer produced by Shimadzu, Japan, to test the adsorption amount of the water reducer on the surface of the cementitious material. The results are shown in Table 1.

[0035] Table 1 The experimental results in Table 1 show that: (1) The number-average molecular weights of the water reducers in Examples 1-5 are between 32,000 and 35,000, all lower than the number-average molecular weight of Comparative Example 1; (2) The surface tensions of the water reducers in Examples 1-5 are all lower than that of Comparative Example 1; (3) The adsorption amounts of the water reducers in Examples 1-5 on the cementitious material are significantly higher than that of Comparative Example 1.

[0036] The comparison of the basic performance tests of the water reducers in Examples 1-5 and Comparative Example 1 is shown in Table 2.

[0037] Table 2 Table 2 Experimental results show that: the mortar fluidity and water reduction rate in Examples 1-5 are higher than those in Comparative Example 1, and the flow emptying time is significantly less than that in Comparative Example 1. The optimal dosage of Examples 1-5 is 1.5%. Among them, the mortar fluidity and water reduction rate of Example 5 are the highest, and the flow emptying time is the shortest. Compared with Comparative Example 1, the viscosity-reducing polycarboxylate water reducer of the present invention has a good viscosity-reducing effect.

Claims

1. A viscosity-reducing polycarboxylate water reducer, characterized in that: The general molecular structure formula is as follows: In the formula, R is H or CH3, and a, b, c, d, and e respectively represent the degree of polymerization of each monomer in the polymer, where a∶b∶c∶d∶e = 1 - 3∶1 - 10∶1 - 3∶1 - 2∶1 - 2.

2. The preparation method of the viscosity-reducing polycarboxylate water reducer according to claim 1, characterized in that: The raw materials used and their parts by weight are: 250 - 350 parts of methyl allyl polyoxyethylene ether, 32 - 47 parts of unsaturated carboxylic acid monomer, 4 - 8 parts of monomer containing sulfonic acid group, 3 - 5 parts of triethoxyvinylsilane, 2 - 3.5 parts of initiator, 1.5 - 3 parts of chain transfer agent, 0.5 - 1 part of reducing agent, and 400 - 450 parts of water; The unsaturated carboxylic acid monomer is acrylic acid and maleic anhydride; The monomer containing sulfonic acid group is sodium allylsulfonate or sodium methallylsulfonate; The chain transfer agent is 3 - mercaptopropionic acid; The preparation method specifically includes the following steps: A. Dissolve methyl allyl polyoxyethylene ether in water to prepare a bottom solution; B. Dissolve the chain transfer agent and the reducing agent in water to prepare solution A; C. Dissolve the unsaturated carboxylic acid monomer, the monomer containing sulfonic acid group, and triethoxyvinylsilane in water to prepare solution B; D. After adding the initiator to the bottom solution, dropwise add solution A and solution B to the bottom solution at room temperature. After the dropping is completed, continue to react for 1 - 2 h, and add the remaining formulated amount of water to obtain a viscosity - reducing polycarboxylate superplasticizer.

3. The preparation method of the viscosity-reducing polycarboxylate water reducer according to claim 2, characterized in that: The parts by weight of the raw materials used are: 250 parts of methyl allyl polyoxyethylene ether, 32 parts of unsaturated carboxylic acid monomer, 5 parts of monomer containing sulfonic acid group, 3 parts of triethoxyvinylsilane, 2 parts of initiator, 1.5 parts of chain transfer agent, 0.5 part of reducing agent, and 400 parts of water.

4. The preparation method of the viscosity-reducing polycarboxylate superplasticizer according to claim 2, characterized in that: The parts by weight of the raw materials used are: 290 parts of methyl allyl polyoxyethylene ether, 40 parts of unsaturated carboxylic acid monomer, 4 parts of monomer containing sulfonic acid group, 4 parts of triethoxyvinylsilane, 2.5 parts of initiator, 2.3 parts of chain transfer agent, 0.6 part of reducing agent, and 420 parts of water.

5. A preparation method of the viscosity-reducing polycarboxylate water reducer according to claim 2, characterized in that: The parts by weight of the raw materials used are: 300 parts of methyl allyl polyoxyethylene ether, 40 parts of unsaturated carboxylic acid monomer, 5 parts of monomer containing sulfonic acid group, 3 parts of triethoxyvinylsilane, 2.2 parts of initiator, 2.6 parts of chain transfer agent, 0.65 part of reducing agent, and 425 parts of water.

6. A preparation method of the viscosity-reducing polycarboxylate water reducer according to claim 2, characterized in that: The parts by weight of the raw materials used are: 310 parts of methyl allyl polyoxyethylene ether, 40 parts of unsaturated carboxylic acid monomer, 8 parts of monomer containing sulfonic acid group, 5 parts of triethoxyvinylsilane, 2.5 parts of initiator, 2.7 parts of chain transfer agent, 0.8 part of reducing agent, and 430 parts of water.

7. A preparation method of the viscosity-reducing polycarboxylate superplasticizer according to claim 2, characterized in that: The parts by weight of the raw materials used are: 350 parts of methyl allyl polyoxyethylene ether, 47 parts of unsaturated carboxylic acid monomer, 8 parts of monomer containing sulfonic acid group, 5 parts of triethoxyvinylsilane, 3.5 parts of initiator, 3 parts of chain transfer agent, 1 part of reducing agent, and 450 parts of water.

8. A preparation method of the viscosity-reducing polycarboxylate superplasticizer according to any one of claims 2-7, characterized in that: The initiator is a mixture of hydrogen peroxide and sodium hypophosphite.

9. A preparation method of the viscosity-reducing polycarboxylate water reducer according to any one of claims 2-7, characterized in that: The reducing agent is ascorbic acid.

10. Application of the viscosity-reducing polycarboxylate water reducer according to claim 1 in ultra-high performance concrete, characterized in that: The dosage of the viscosity - reducing polycarboxylate superplasticizer is 1.0% - 2.0% of the total mass of the cementitious material.

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