Alternating copolymer concrete admixture and its preparation method and application

Abstract

The present invention discloses an alternating copolymer concrete admixture, its preparation method, and application. The preparation method of the alternating copolymer concrete admixture comprises first preparing an alternating isotactic precursor by chemical reaction of monomer A and monomer B, and then preparing the alternating copolymer concrete admixture by reaction of the alternating isotactic precursor and monomer C. The alternating copolymer concrete admixture prepared by the present invention has a regular alternating molecular chain structure, the anchoring groups can be effectively adsorbed on the surface of cement particles, and the long side chains are regularly distributed, which can provide greater steric hindrance, thereby significantly improving the fluidity of concrete and reducing concrete viscosity. The preparation method has mild synthesis conditions, low dosage, high water reduction rate, and good viscosity reduction. The admixture can be widely used in various concretes.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and in particular to an alternating copolymerization concrete admixture, a preparation method thereof and an application thereof. Background Art

[0002] Currently, conventional admixtures used to improve concrete performance include polycarboxylate superplasticizers. Based on the theory of adsorption and steric hindrance, the anchoring groups on the polycarboxylate superplasticizer backbone adsorb onto the surface of cement particles, while the long hydrophilic side chains exert steric hindrance, thereby dispersing the cement particles. However, polycarboxylic acids are random copolymers, and the positions of the anchoring groups and long side chains are not fixed. This weakens their adsorption on the cementitious material surface and reduces the steric hindrance effect, resulting in a low water reduction rate. This makes it difficult to meet the high performance requirements of polycarboxylate superplasticizers in actual construction projects.

[0003] Alternating copolymers are polymers in which two or more monomers have alternating (or identical) monomer units arranged in a main chain, resulting in a regularly alternating pattern of repeating units. The preparation of alternating copolymerized polycarboxylate superplasticizers can evenly position anchoring groups and long side chains, improving adsorption efficiency and increasing steric hindrance, potentially enabling effective control of concrete fluidity and viscosity. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide an alternating copolymer concrete admixture with an alternating copolymer structure, which can effectively improve the fluidity of concrete and reduce the viscosity of concrete. A preparation method and application of the alternating copolymer concrete admixture with a simple preparation process and low cost are also provided.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0006] A method for preparing an alternating copolymerization concrete admixture comprises the following steps:

[0007] (1) dispersing monomer A, monomer B, and an initiator in a first solvent, stirring and reacting at 40° C. to 70° C., and then removing the first solvent to obtain an alternating isotactic precursor; wherein the monomer A is styrene or butadiene, and the monomer B is maleic anhydride;

[0008] (2) dispersing the above-obtained alternating isotactic precursor, monomer C and catalyst in a second solvent, stirring for reaction, and removing the second solvent to obtain an alternating copolymer concrete admixture; wherein the monomer C is methacrylate polyethylene glycol, allyl polyethylene glycol, isopentenyl polyethylene glycol, α-alkoxylated isoprenol, α-allyl-ω-methoxy polyethylene glycol, polyethylene glycol acrylate, methacrylate polyethylene glycol, methoxy polyethylene glycol methacrylate, hydroxyl-terminated One or more of polyethylene oxide methacrylate, methoxy-terminated polyethylene oxide methacrylate, polyethylene glycol monomethyl ether monomethacrylate, methoxy polyethylene glycol acrylate, methoxy polyethylene glycol itaconate, polyethylene glycol maleic acid half ester, allyl polyoxyethylene ether sulfate, butenyl alkylene polyoxyethylene-polyoxypropylene ether, α-allyl-ω-methoxy polyethylene glycol ether, methallyl polyethylene ether, isopentyl polyoxyethylene ether and alkoxylated hydroxybutyl vinyl ether.

[0009] The preparation method of the above-mentioned alternating copolymer concrete admixture, preferably, in step (1), the initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisoheptanenitrile methylbenzenesulfonic acid, azobiscyanovaleric acid and 2-carbamoyl azoisobutyronitrile; the first solvent is one or more of acetone, butanone, dichloromethane, tetrahydrofuran, dimethylformamide and methanol.

[0010] In the above-mentioned method for preparing the alternating copolymer concrete admixture, preferably, in step (1), the mass ratio of the monomer A, the initiator, and the monomer B is 10-40:0.1-3.0:10-40, and the stirring reaction time is 1h-10h.

[0011] The preparation method of the above-mentioned alternating copolymer concrete admixture, preferably, in step (2), the catalyst is one or more of concentrated sulfuric acid, concentrated hydrochloric acid, p-toluenesulfonic acid and thionyl chloride, the mass fraction of the concentrated sulfuric acid is 98%, and the mass fraction of the concentrated hydrochloric acid is 38%; the second solvent is one or more of dichloromethane, tetrahydrofuran, dimethylformamide, methanol, acetone and butanone.

[0012] In the above-mentioned method for preparing the alternating copolymer concrete admixture, preferably, in step (2), the mass ratio of the alternating isotactic precursor, the monomer C, and the catalyst is 1-20:1-20:0.1-10, and the stirring reaction time is 1h-24h.

[0013] In the above-mentioned method for preparing the alternating copolymer concrete admixture, preferably, in step (1), the first solvent is removed by rotary evaporation; and in step (2), the second solvent is removed by rotary evaporation.

[0014] As a general technical concept, the present invention also provides an alternating copolymer concrete admixture prepared by the above-mentioned preparation method.

[0015] The above-mentioned alternating copolymer concrete admixture preferably has a regular alternating molecular chain structure, and the number average molecular weight of the alternating copolymer concrete admixture ranges from 4500 g / mol to 350000 g / mol.

[0016] As a general technical concept, the present invention also provides an alternating copolymer concrete admixture prepared by the above-mentioned preparation method or the use of the above-mentioned alternating copolymer concrete admixture in cement-based composite materials.

[0017] In the above application, preferably, the cement-based composite material comprises a cementitious material and the alternating copolymerization concrete admixture, and the addition amount of the alternating copolymerization concrete admixture is 0.1% to 5.0% of the total mass of the cementitious material.

[0018] The technical principle of the present invention is:

[0019] The applicant has discovered that the effectiveness of alternating copolymer admixtures in concrete is closely related to the steric hindrance of the adsorption groups and molecules. Therefore, during the structural design of the admixture, the anchoring groups should be adsorbed on the surface of cement particles as much as possible, and the steric hindrance of the side chains should be maximized. Based on this, the present invention prepares an alternating isotactic precursor by reacting specific monomers A and B. The alternating isotactic precursor and monomer C undergo an addition polymerization reaction to prepare the alternating copolymer concrete admixture.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] (1) The present invention provides an alternating copolymer concrete admixture, wherein the anchoring groups and long side chains of the concrete admixture are evenly distributed on the main chain, and the concrete admixture has the advantages of a large number of anchoring groups and a large steric hindrance. The large number of adsorption groups exposed in the molecular structure can be efficiently adsorbed on the surface of cement particles, and the regularly distributed long side chains can provide a steric hindrance effect and enhance the mutual repulsion between cement particles. Based on the improvement of the adsorption capacity and steric hindrance effect of the admixture, the alternating copolymer concrete admixture of the present invention can greatly improve the fluidity of concrete and reduce the viscosity of concrete, and has a high application value and a good application prospect.

[0022] (2) The present invention also provides a method for preparing an alternating copolymer concrete admixture. Based on improving the admixture's adsorption and steric hindrance effect, the method first produces an alternating isotactic precursor through a chemical reaction between monomers A and B. The alternating isotactic precursor then reacts with monomer C to produce the alternating copolymer concrete admixture. The method has the advantages of a simple preparation process, mild synthesis conditions, low cost, strong operability, and low environmental pollution, making it suitable for industrial applications.

[0023] (3) The alternating copolymer concrete admixture of the present invention can be applied to cement-based composite materials, because the alternating copolymer concrete admixture can be efficiently adsorbed on the surface of cement particles, and the steric hindrance effect generated by its regularly distributed long side chains can make the cement particles more effectively dispersed. When the addition amount of the alternating copolymer concrete admixture is 0.1% to 5.0% of the total mass of the cementitious material, the fluidity of the concrete can be increased by 20% to 40%, the viscosity of the concrete can be reduced by 20% to 40%, the workability of the concrete can be significantly improved, and the mechanical properties and durability of ultra-high concrete can be enhanced. The alternating copolymer concrete admixture of the present invention has the advantages of high water reduction rate, good viscosity reduction, low dosage, good cement adaptability, etc., and can be widely used in a variety of concretes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the molecular structure of the alternating copolymer concrete admixture in Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available.

[0026] Example 1

[0027] A method for preparing an alternating copolymer concrete admixture of the present invention comprises the following steps:

[0028] (1) Disperse 10 g of styrene and 6 g of maleic anhydride in butanone, add 1.5 g of azobis(isoheptylnitrile)methylbenzenesulfonic acid, react at 50°C with magnetic stirring for 1 h, and then remove butanone by rotary evaporation for 50 min to obtain an alternating isotactic precursor;

[0029] (2) 10 g of the above-obtained alternating isotactic precursor and 100 g of α-allyl-ω-methoxy polyethylene glycol ether were dispersed in tetrahydrofuran, 3 g of p-toluenesulfonic acid was added, and the mixture was reacted under magnetic stirring at room temperature for 24 h. After the reaction was completed, the clear liquid was collected and the tetrahydrofuran was removed by rotary evaporation to obtain an alternating copolymer concrete admixture.

[0030] The alternating copolymer concrete admixture prepared in this embodiment has a structure as follows Figure 1 As shown, compared with the random copolymer admixture obtained by the existing preparation method, the anchoring groups and the long side chains in the molecular structure of the admixture of the present invention are alternately arranged on the main chain of the admixture, having a regular alternating molecular chain structure. The number average molecular weight of the alternating copolymer concrete admixture is 15,000 g / mol.

[0031] Example 2

[0032] A method for preparing an alternating copolymer concrete admixture of the present invention comprises the following steps:

[0033] (1) Disperse 20 g of styrene and 20 g of maleic anhydride in butanone, add 3.0 g of azobisisobutyronitrile, react at 50°C with magnetic stirring for 1 h, and then remove butanone by rotary evaporation for 50 min to obtain an alternating isotactic precursor;

[0034] (2) Disperse 10g of alternating isotactic precursor and 100g of methoxy-terminated polyethylene oxide methacrylate in tetrahydrofuran, add 4g of thionyl chloride, and react under magnetic stirring at room temperature for 14h. After the reaction is completed, collect the clear liquid and remove the tetrahydrofuran by rotary evaporation to obtain an alternating copolymer concrete admixture. Figure 1 As shown, the alternating copolymer concrete admixture has a regular alternating molecular chain structure, and the number average molecular weight of the alternating copolymer concrete admixture is 350,000 g / mol.

[0035] Example 3

[0036] A method for preparing an alternating copolymer concrete admixture of the present invention comprises the following steps:

[0037] (1) Disperse 10 g of butadiene and 15 g of maleic anhydride in acetone, add 2.7 g of dimethyl azobisisobutyrate, react at 60 °C with magnetic stirring for 1.5 h, and then remove the acetone by rotary evaporation for 60 min to obtain an alternating isotactic precursor;

[0038] (2) Disperse 20g of alternating isotactic precursor and 130g of isopentenyl polyethylene glycol in tetrahydrofuran, add 20g of 98wt% concentrated sulfuric acid, and react under magnetic stirring at room temperature for 20h. After the reaction, collect the clear liquid and remove the tetrahydrofuran by rotary evaporation to obtain an alternating copolymer concrete admixture. Figure 1 As shown, the alternating copolymer concrete admixture has a regular alternating molecular chain structure and a number average molecular weight of 20,000 g / mol.

[0039] Comparative Example 1

[0040] A method for preparing a concrete admixture comprises the following steps:

[0041] (1) Dissolve 100 g of α-allyl-ω-methoxypolyethylene glycol ether in water, add 1.5 g of azobisisoheptylnitrile methylbenzenesulfonic acid, and stir for 1 to 2 minutes to obtain a first mixed solution, dissolve 10 g of styrene in 60 g of water to obtain a second mixed solution, and dissolve 6 g of maleic anhydride in 50 g of water to obtain a third mixed solution;

[0042] (2) 3 g of p-toluenesulfonic acid, the second mixed solution, and the third mixed solution were simultaneously added dropwise to the first mixed solution for 3.5 h. After the addition was completed, the reaction was continued for 1 h. The pH value was adjusted to 6 with solid sodium hydroxide to obtain a comb-type random polymerization admixture with a number average molecular weight of 25,000 g / mol.

[0043] Comparative Example 2

[0044] A method for preparing a concrete admixture comprises the following steps:

[0045] (1) dissolving 200 g of isopentenyl polyethylene glycol in water, adding 2.5 g of dimethyl azobisisobutyrate, and stirring for 1 to 2 min to obtain a first mixed solution, dissolving 15 g of butadiene in 60 g of water to obtain a second mixed solution, and dissolving 8 g of maleic anhydride in 70 g of water to obtain a third mixed solution;

[0046] (2) 6 g of concentrated sulfuric acid, the second mixed solution, and the third mixed solution were simultaneously added dropwise to the first mixed solution. The addition time was 2.5 h. After the addition was completed, the reaction was continued for 1.5 h. The pH value was adjusted to 6 with solid sodium hydroxide to obtain a comb-type random polymerization admixture with a number average molecular weight of 65,000 g / mol.

[0047] The effect of the alternating copolymer concrete admixture of the present invention on the basic properties of concrete was investigated, specifically using the alternating copolymer concrete admixtures prepared in Examples 1-3 and the concrete admixtures prepared in Comparative Examples 1-2, comprising the following steps:

[0048] The alternating copolymer concrete admixtures prepared in Examples 1-3 and the concrete admixtures prepared in Comparative Examples 1-2 were added to the cementitious material in an amount of 0.5% of the total mass of the cementitious material. The obtained cementitious materials containing the admixtures were added to concrete. The concrete used PI 42.5 benchmark cement and had a water-cement ratio of 0.29.

[0049] Evaluation indicators: fluidity, viscosity; test standards: The fluidity of the cement paste was measured according to the method for determining the fluidity of cement paste with admixtures in GB8076-2008 "Specifications for Concrete Admixtures", and the viscosity of the paste was measured by a rheometer according to the standard in GB / T10274-2008 "Viscosity Measurement Method". The results are shown in Table 1.

[0050] Table 1 Test results of basic properties of concrete containing admixtures of Examples 1-3 and Comparative Examples 1-2

[0051]

[0052] It can be seen from Table 1 that, compared with the comb-type water-reducing and viscosity-reducing admixtures prepared in Comparative Examples 1 and 2, the alternating copolymerization concrete admixtures prepared in Examples 1, 2 and 3 of the present invention can effectively improve the fluidity of concrete and reduce the viscosity of concrete.

[0053] The alternating copolymer concrete admixture of the present invention can also be mixed with at least one other admixture known in the prior art, including early strength agents, air entraining agents, defoaming agents, shrinkage reducing agents, expansion agents, etc.

[0054] In summary, the alternating copolymer concrete admixture of the present invention and its preparation method have the following beneficial effects: (1) mild synthesis conditions; (2) novel molecular structure, composed of multiple alternating comb-like structures PCE, which can expose a large number of anchoring groups; (3) low dosage, high water reduction rate, good viscosity reduction, and can be widely used in various concretes. When applied to concrete, the admixture of the present invention can effectively improve the fluidity of concrete and reduce the viscosity of concrete.

[0055] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing an alternating copolymer concrete admixture, characterized in that: The following steps are involved: (1) dispersing monomer A, monomer B, and an initiator in a first solvent, stirring and reacting at 40° C. to 70° C., and then removing the first solvent to obtain an alternating isotactic precursor; wherein the monomer A is styrene or butadiene, and the monomer B is maleic anhydride; (2) dispersing the above-obtained alternating isotactic precursor, monomer C and catalyst in a second solvent, stirring for reaction, and removing the second solvent to obtain an alternating copolymer concrete admixture; wherein the monomer C is methacrylate polyethylene glycol, allyl polyethylene glycol, isopentenyl polyethylene glycol, α-alkoxylated isoprenol, α-allyl-ω-methoxy polyethylene glycol, polyethylene glycol acrylate, methacrylate polyethylene glycol, methoxy polyethylene glycol methacrylate, hydroxyl-terminated One or more of polyethylene oxide methacrylate, methoxy-terminated polyethylene oxide methacrylate, polyethylene glycol monomethyl ether monomethacrylate, methoxy polyethylene glycol acrylate, methoxy polyethylene glycol itaconate, polyethylene glycol maleic acid half ester, allyl polyoxyethylene ether sulfate, butenyl alkylene polyoxyethylene-polyoxypropylene ether, α-allyl-ω-methoxy polyethylene glycol ether, methallyl polyethylene ether, isopentyl polyoxyethylene ether and alkoxylated hydroxybutyl vinyl ether.

2. The preparation method of the alternating copolymerization concrete admixture according to claim 1, characterized in that, In step (1), the initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisoheptanenitrile toluenesulfonic acid, azobiscyanovaleric acid and 2-carbamoyl azoisobutyronitrile; and the first solvent is one or more of acetone, butanone, dichloromethane, tetrahydrofuran, dimethylformamide and methanol.

3. The preparation method of the alternating copolymerization concrete admixture according to claim 1, characterized in that, In step (1), the mass ratio of the monomer A, the initiator, and the monomer B is 10-40:0.1-3.0:10-40, and the stirring reaction time is 1 h to 10 h.

4. The method for preparing the alternating copolymerization concrete admixture according to any one of claims 1 to 3, characterized in that: In step (2), the catalyst is one or more of concentrated sulfuric acid, concentrated hydrochloric acid, p-toluenesulfonic acid and thionyl chloride, the mass fraction of the concentrated sulfuric acid is 98%, and the mass fraction of the concentrated hydrochloric acid is 38%; the second solvent is one or more of dichloromethane, tetrahydrofuran, dimethylformamide, methanol, acetone and butanone.

5. The method for preparing the alternating copolymer concrete admixture according to any one of claims 1 to 3, characterized in that: In step (2), the mass ratio of the alternating isotactic precursor, the monomer C, and the catalyst is 1-20:1-20:0.1-10, and the stirring reaction time is 1 h to 24 h.

6. The method for preparing the alternating copolymerization concrete admixture according to any one of claims 1 to 3, characterized in that: In step (1), the first solvent is removed by rotary evaporation; in step (2), the second solvent is removed by rotary evaporation.

7. An alternating copolymerization concrete admixture prepared by the preparation method according to any one of claims 1 to 6.

8. The alternating copolymer concrete admixture according to claim 7, characterized in that: The alternating copolymer concrete admixture has a regular alternating molecular chain structure, and the number average molecular weight of the alternating copolymer concrete admixture ranges from 4500 g / mol to 350000 g / mol.

9. Use of the alternating copolymerization concrete admixture prepared by the preparation method according to any one of claims 1 to 6 or the alternating copolymerization concrete admixture according to claim 7 or 8 in cement-based composite materials.

10. The use according to claim 9, characterized in that The cement-based composite material comprises a cementitious material and the alternating copolymerization concrete admixture, and the addition amount of the alternating copolymerization concrete admixture is 0.1% to 5.0% of the total mass of the cementitious material.

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