CN108250343B

CN108250343B - Compound, air-entraining copolymer, preparation method thereof and application of air-entraining copolymer as concrete rheology modifier

Info

Publication number: CN108250343B
Application number: CN201611237978.5A
Authority: CN
Inventors: 陈健; 乔敏; 高南萧; 冉千平; 吴井志; 吕志锋
Original assignee: Jiangsu Bote New Materials Co Ltd; Bote Building Materials Tianjin Co Ltd; Bote New Materials Taizhou Co Ltd
Current assignee: Jiangsu Bote New Materials Co Ltd; Bote Building Materials Tianjin Co Ltd; Bote New Materials Taizhou Co Ltd
Priority date: 2016-12-28
Filing date: 2016-12-28
Publication date: 2020-06-26
Anticipated expiration: 2036-12-28
Also published as: CN108250343A

Abstract

The invention provides a compound, an air-entraining copolymer, a preparation method thereof and application of the compound as a concrete rheology modifier. The preparation method of the air-entraining copolymer comprises the step of carrying out free radical copolymerization on a monomer A, a monomer B and a monomer C with a specific structure according to a molar ratio of 1 (0.5-2) to (0.01-0.04) to obtain the air-entraining copolymer, wherein the number average molecular weight of the air-entraining copolymer is 200-400 ten thousand. The monomer C is a surface active molecule and contains a hydrophilic phosphate group and a hydrophobic alkyl chain segment with 8-18 carbon atoms. The monomer C is introduced into the copolymer as an air-entraining component, so that the obtained copolymer has mild air-entraining performance, stable, tiny and uniform bubbles can be introduced into fresh concrete, and the fluidity of the concrete is improved while the segregation and bleeding resistance of the concrete is improved, so that the concrete has high workability.

Description

Compound, air-entraining copolymer, preparation method thereof and application of air-entraining copolymer as concrete rheology modifier

Technical Field

The invention relates to a compound, an air-entraining copolymer, a preparation method thereof and an application of the air-entraining copolymer as a concrete rheology modifier, belonging to the field of concrete admixtures.

Background

With the development of science and technology, concrete technology is also continuously promoted. The development of high-performance concrete admixtures is important to improve the comprehensive performance of concrete, and concrete rheology modifiers are a class of admixtures which are receiving increasing attention. Currently, most of the commercially available rheology modifiers are water-soluble polymers, and are roughly classified into modified natural polymers disclosed in publication No. CN105271883A and synthetic polymers disclosed in publication No. CN 105542090A. They can increase the viscosity of concrete mixture, reduce the separation tendency of each component, improve the homogeneity and alleviate the phenomena of segregation and bleeding. However, they also often reduce the flowability of fresh concrete, thereby affecting its workability.

Concrete air entraining agents are another important class of admixtures, which are generally surface active chemical substances, as disclosed in chinese patent publication No. CN105727827A or CN 105732442A. The proper amount of air entraining agent is added during the concrete stirring process, and proper amount of tiny, uniform and closed air bubbles can be introduced into the newly-mixed hardened concrete, so that the fluidity of the concrete is improved, and the workability is improved.

In order to solve the contradiction between segregation resistance bleeding property and fluidity of fresh concrete, the rheology modifier and the air entraining agent can be compounded. However, this physical method also has significant disadvantages: for example, the combination of several different compounds may destroy the stability of the components and generate precipitates; and for example, the adjustment of the ratio of the two is time-consuming and labor-consuming, and the performance is easy to be unstable. Therefore, the chemical structure of the traditional rheology modifier is changed by a chemical method, and the air entraining component is introduced to improve the comprehensive performance of the rheology modifier, so that the method has very important practical significance. However, due to the limitations of interdisciplinary studies, few studies are currently involved.

Disclosure of Invention

Object of the Invention

An object of the present invention is to provide an air-entraining copolymer which not only has good segregation resistance when used as a concrete rheology modifier, but also can introduce stable, fine, uniform bubbles into concrete to give the concrete good fluidity.

It is another object of the present invention to provide a process for preparing the above air-entraining copolymer.

It is another object of the present invention to provide the use of the above air-entraining copolymer as a concrete rheology modifier.

It is another object of the present invention to provide compounds that are comonomers to the air-entraining copolymer.

Summary of The Invention

According to the first aspect of the invention, the invention provides a preparation method of an air-entraining copolymer, which is obtained by carrying out free radical copolymerization on a monomer A, a monomer B and a monomer C with a molar ratio of 1 (0.5-2) to (0.01-0.04), wherein the monomer A has a structure shown in formula (I):

the structure of the monomer B is shown as the formula (II):

the structure of the monomer C is shown as the formula (III):

wherein R is₁And R₂Each independently represents H or CH₃，R₃Represents a linear alkyl group having 8 to 18 carbon atoms,

the number average molecular weight of the air-entraining copolymer is 200-400 ten thousand.

As a known technology in the field, the free radical copolymerization needs to be carried out in an aqueous solution with the pH value of 7-8, otherwise, the formation of gel due to agglomeration is easily caused. Under the above pH conditions, the acidic monomers A and C are partially neutralized to form salts, that is, the resulting air-entraining copolymer contains salt structures (carboxylate and phosphate) in its structure, as will be understood and determined by those skilled in the art. For convenience of presentation, the present invention adopts the shorthand writing method described above.

Specifically, the preparation method of the air-entraining copolymer comprises the following steps:

s1, mixing a monomer A, a monomer B and a monomer C to prepare an aqueous solution with the total mass fraction of 5-20%, and adjusting the pH value to 7-8 (usually adding NaOH or KOH to adjust the pH value);

s2, dropwise adding an initiator into the mixed solution in the step S1, and reacting for 3-6 h at 70-90 ℃ to obtain the air entraining type copolymer.

The initiator is selected conventionally in the art, and in step S2, the initiator is 2, 2-azobis (2-methylpropylammonium) dihydrochloride or persulfate. The initiator is generally added dropwise at 40-60 ℃.

As a common method, after the pH value is adjusted, non-reactive gas is firstly introduced for bubbling for 20-60 min, and then an initiator is dropwise added. As is well known to those skilled in the art, the reaction raw materials can be more uniformly mixed by bubbling before the radical copolymerization reaction, and the non-reactive gas is a gas which does not react with the reaction raw materials and water, such as nitrogen, an inert gas, or the like.

According to a second aspect of the present invention, there is also provided an air-entraining copolymer obtained by the above-mentioned production process.

According to a third aspect of the invention, the use of the air-entraining copolymer as a concrete rheology modifier.

The folding and fixing mixing amount of the air-entraining copolymer is 0.1-1 ten thousandth of the mass of the cementing material in the concrete.

According to a fourth aspect of the present invention, there is also provided a compound useful as monomer C, having the structure according to formula (III):

the compound can be prepared by the following steps:

s1-1, reacting maleic anhydride, 2-aminoethanol and p-toluenesulfonic acid in a toluene solvent at 110-130 ℃ for 8-16 h, and purifying to obtain a compound with a structure shown in a formula (VII), wherein the molar ratio of the maleic anhydride to the 2-aminoethanol to the p-toluenesulfonic acid is 1: (1-1.2): (0.05-0.2);

s1-2, mixing a compound with a structure shown in a formula (IV), phosphorus oxychloride, triethylamine and a low boiling point organic solvent (such as tetrahydrofuran and acetone, preferably tetrahydrofuran) which can be mutually dissolved with water, reacting for 4-8 h in an ice water bath at 0 ℃, and removing insoluble substances to obtain a solution of the compound with the structure shown in the formula (V), wherein the mol of the compound with the structure shown in the formula (IV), the phosphorus oxychloride and the triethylamine is 1: (1-1.2): (2-2.4);

s1-3, adding alkyl alcohol R into the solution of the compound with the structure shown in the formula (V)₃And (4) OH, reacting for 4-8 h in an ice water bath at 0 ℃, filtering to remove insoluble substances, adding water into filtrate, reacting for 1-3 h at room temperature, and purifying to obtain the compound serving as the monomer C, wherein the molar ratio of the compound with the structure shown as the formula (V) to alcohol is 1: (1-1.2); the amount of water added into the filtrate is about 20-40% of the volume of the low-boiling-point organic solvent added in the step S1-2, and the reaction at room temperature is 10-30 ℃.

The reaction scheme for preparing the compound as monomer C according to the present invention is as follows:

in the step S1-1, the purification method after the reaction is finished includes: removing the solvent toluene, for example, evaporating toluene, recrystallizing with n-hexane, and drying to obtain the compound shown in formula (VII).

In step S1-3, the purification method after all reactions are completed is to filter, recrystallize the obtained solid with ethanol, and dry to obtain the compound as monomer C. The structure of the compound as monomer C may be represented by¹H NMR (nuclear magnetic resonance) determination.

The air-entraining copolymer is obtained by addition copolymerization of unsaturated carbon-carbon bonds in a monomer A, a monomer B and a monomer C, and the-C-C-is used as a main chain of the copolymer, so that the stability to temperature is good. The functional group of the monomer is on the side chain of the copolymer. Wherein, the monomer A and the monomer B are respectively unsaturated monomers with carboxyl and amide groups, and the monomers have good water solubility and high polymerization activity, so that the copolymer has high molecular weight. The monomer C is a surface active molecule and contains hydrophilic phosphate ester group and hydrophobic C8-C18 alkyl chain segment (R)₃). The monomer C is introduced into the copolymer as an air-entraining component, so that the obtained copolymer has mild air-entraining performance, stable, tiny and uniform bubbles can be introduced into fresh concrete, and the fluidity of the concrete is improved while the segregation and bleeding resistance of the concrete is improved, so that the concrete has high workability. In addition, the phosphate ester group in the copolymer is stable in the high-salt and high-alkali environment of concrete.

Drawings

FIG. 1 shows the preparation of the monomer C of example 1¹H NMR spectrum;

FIG. 2 shows the preparation of the monomer C of example 2¹H NMR spectrum;

FIG. 3 shows the preparation of the monomer C of example 3¹H NMR spectrum;

FIG. 4 shows the preparation of the monomer C of example 4¹H NMR spectrum.

Detailed Description

The technical solutions of the present invention will be further described in detail with reference to the following examples, but the present invention is by no means limited thereto, and any equivalent changes or modifications made according to the spirit of the present invention should be covered within the scope of the present invention.

All raw materials used in the invention are commercial products, wherein all reagents (analytically pure) used for synthesizing the rheology modifier are purchased from Saen chemical technology (Shanghai) Co., Ltd, all organic solvents (chemically pure) are purchased from national medicine group chemical reagent Co., Ltd, and the polycarboxylic acid water reducer is purchased from Jiangsu Subo new materials Co., Ltd. The molecular weights of the rheology modifiers in the examples of the invention were determined by aqueous Gel Permeation Chromatography (GPC) with the following test parameters:

gel column: shodex SB806+803 chromatographic columns were connected in series; eluent: 0.1M NaNO₃A solution; velocity of mobile phase: 0.8 ml/min; and (3) injection: 20 μ l of 0.5% aqueous solution; a detector: a refractive index detector of Shodex RI-71 type; standard substance: polyethylene glycol GPC standard (Sigma-Aldrich, molecular weight 1010000,478000,263000,118000,44700,18600,6690,1960,628,232).

Example 1

Mixing 10mmol of maleic anhydride, 10mmol of 2-aminoethanol, 0.5mmol of p-toluenesulfonic acid and 30mL of toluene in a reaction kettle with a water separator, reacting for 8h at 110 ℃, evaporating to remove the toluene, recrystallizing with n-hexane and drying to obtain the compound with the structure shown in the formula (VII).

Mixing 10mol of a compound with a structure shown as a formula (VII), 10mmol of phosphorus oxychloride, 20mmol of triethylamine and 30mL of tetrahydrofuran, reacting for 4 hours in an ice water bath at about 0 ℃, and filtering to remove insoluble substances after the reaction is finished to obtain a solution of the compound with the structure shown as a formula (VIII).

Adding 10mmol octanol directly into the solution of the compound with the structure shown in the formula (VIII), reacting for 4h in ice water bath at 0 ℃, filtering to remove insoluble substances, adding 10mL water into the filtrate, reacting for 1h at 20 ℃ and room temperature, filtering, recrystallizing the obtained filter residue with ethanol, and drying to obtain pure monomer C (the code is C-8, R is R-8)₃Is CH₃(CH₂)₇Nuclear magnetic spectrum namely¹H NMR as shown in FIG. 1).

10mmol of acrylic acid (A), 5mmol of acrylamide (B) and 0.1mmol of C-8 were dissolved in 15mL of water, the pH of the aqueous solution was adjusted to 7 with NaOH, and bubbling was carried out with nitrogen for 20 min. The temperature was raised to 40 ℃ and 0.1mol of V50(2, 2-azobis (2-methylpropylammonium) dihydrochloride) was dissolved in 5mL of water and added dropwise slowly over 0.5 h. The reaction was continued at 70 ℃ for 3h to give the rheology modifier 1 having a number average molecular weight of 234 ten thousand.

Example 2

Mixing 10mmol of maleic anhydride, 11mmol of 2-aminoethanol, 1mmol of p-toluenesulfonic acid and 30mL of toluene in a reaction kettle with a water separator, reacting at 120 ℃ for 12h, evaporating to remove the toluene, recrystallizing with n-hexane and drying to obtain the compound with the structure shown in the formula (VII).

Mixing 10mol of a compound with a structure shown as a formula (VII), 11mmol of phosphorus oxychloride, 22mmol of triethylamine and 30mL of tetrahydrofuran, reacting for 6 hours in an ice water bath at about 0 ℃, and filtering to remove insoluble substances after the reaction is finished to obtain a solution of the compound with the structure shown as a formula (VIII).

Adding 11mmol dodecanol directly into the solution of the compound with the structure shown in the formula (VIII), reacting for 6h in ice water bath at about 0 ℃, filtering to remove insoluble substances, adding 10mL water into filtrate, reacting for 2h at 25 ℃ and room temperature, filtering, recrystallizing the obtained filter residue with ethanol, and drying to obtain pure monomer C (the code is C-12, R is C-12)₃Is CH₃(CH₂)₁₁Nuclear magnetic spectrum namely¹HNMR is shown in fig. 2).

10mmol of methacrylic acid (A), 10mmol of acrylamide (B) and 0.2mmol of C-12 were dissolved in 20mL of water, the pH of the aqueous solution was adjusted to 8 with NaOH, and bubbling was carried out with nitrogen for 40 min. The temperature was raised to 50 ℃ and 0.15mol of sodium persulfate was dissolved in 5mL of water and added dropwise slowly over 1 h. The reaction was continued for 4h at 80 ℃ to give the rheology modifier 2 described, with a number average molecular weight of 278 ten thousand.

Example 3

Mixing 10mmol of maleic anhydride, 12mmol of 2-aminoethanol, 1.5mmol of p-toluenesulfonic acid and 30mL of toluene in a reaction kettle with a water separator, reacting for 16h at 130 ℃, evaporating to remove the toluene, recrystallizing with n-hexane and drying to obtain the compound with the structure shown in the formula (VII).

Mixing 10mol of a compound with a structure shown as a formula (VII), 12mmol of phosphorus oxychloride, 24mmol of triethylamine and 30mL of tetrahydrofuran, reacting for 8 hours in an ice water bath at about 0 ℃, and filtering to remove insoluble substances after the reaction is finished to obtain a solution of the compound with the structure shown as a formula (VIII).

Adding 12mmol tetradecanol directly into the solution of the compound with the structure shown in the formula (VIII), reacting for 8h in ice water bath at 0 ℃ or so, filtering to remove insoluble substances, adding 10mL water into the filtrate, reacting for 3h at room temperature of 30 ℃, filtering, recrystallizing the obtained filter residue with ethanol, and drying to obtain pure monomer C (the code is C-14, R is R)₃Is CH₃(CH₂)₁₃Nuclear magnetic spectrum namely¹HNMR is shown in fig. 3).

10mmol of acrylic acid (A), 15mmol of N, N-dimethylacrylamide (B) and 0.3mmol of C-14 were dissolved in 20mL of water, the pH of the aqueous solution was adjusted to 7 with KOH, and bubbling was carried out for 60min with argon. The temperature is raised to 60 ℃, 0.2mol of potassium persulfate is dissolved in 5mL of water and the dropwise addition is slowly completed within 1.5 h. The reaction was continued at 80 ℃ for 5h to give the rheology modifier 3 described with a number average molecular weight of 344 ten thousand.

Example 4

Mixing 10mmol of maleic anhydride, 12mmol of 2-aminoethanol, 2mmol of p-toluenesulfonic acid and 30mL of toluene in a reaction kettle with a water separator, reacting for 16h at 130 ℃, evaporating to remove the toluene, recrystallizing with n-hexane and drying to obtain the compound with the structure shown in the formula (VII).

Adding 12mmol of octadecanol directly into the solution of the compound with the structure shown in the formula (VIII), reacting for 8 hours in ice water bath at 0 ℃, filtering to remove insoluble substances, adding 10mL of water into filtrate, reacting for 3 hours at room temperature of 20 ℃, filtering, recrystallizing the obtained filter residue with ethanol, and drying to obtain pure monomer C (the code is C-18,R₃is CH₃(CH₂)₁₇Nuclear magnetic spectrum namely¹HNMR is shown in fig. 4).

10mmol of methacrylic acid (A), 20mmol of N, N-dimethylacrylamide (B) and 0.4mmol of C-18 were dissolved in 25mL of water, the pH of the aqueous solution was adjusted to 8 with KOH, and bubbling was carried out for 60min with argon. The temperature is raised to 60 ℃, 0.2mol of ammonium persulfate is dissolved in 5mL of water and is slowly added in a dropwise manner within 2 h. And continuously reacting for 6 hours at 90 ℃ to obtain the rheology modifier 4 with the number average molecular weight of 389 ten thousand.

Comparative example 1

Comparative rheology modifier 1 was synthesized following essentially the same procedure as in example 1, except that: no monomer C-8 was added during the polymerization and the number average molecular weight of the resulting comparative rheology modifier 1 was 231 ten thousand.

Comparative example 2

Comparative rheology modifier 2 was synthesized following essentially the same procedure as in example 1, except that: the monomer C-8 is not added in the polymerization process, and 0.1mmol of the monomer C-8 is added after the polymerization is finished, and then the mixture is compounded and mixed evenly.

The rheology modifier preparation parameters for examples 1 to 4 and comparative examples 1 to 2 are shown in table 1:

TABLE 1 rheology modifier preparation parameters

Application example 1:

the rheology modifiers prepared in examples 1-4, the comparative rheology modifiers prepared in comparative examples 1-2, and the commercially available hydroxypropyl methyl cellulose ether (HPMC) were tested for the bleeding behavior of the cement paste. The test method comprises the following steps: after 1500g of cement, 900g of water and 5g of rheology modifier with the solid content of 2 percent are fully mixed, 100mL of the mixture is placed in a measuring cylinder and stands for 20min, 40min and 60min respectively, and the bleeding height of the mixture is tested. The test results are shown in table 2:

TABLE 2 results of testing the bleeding properties of the rheology modifiers neat cement paste

From the results in table 2, it can be seen that the bleeding conditions of 20,40 and 60min are improved obviously after the rheology modifier prepared by the invention is blended into cement paste, and the bleeding resistance of the rheology modifier is slightly better than that of the commercial rheology modifier HPMC, which indicates that the rheology modifier of the invention has better bleeding resistance.

Application example 2

The slump/expansion, air content and outflow time of the concrete were measured by using the rheology modifiers prepared in examples 1-4, the comparative rheology modifiers prepared in comparative examples 1-2 and the commercially available hydroxypropyl methyl cellulose ether (HPMC) according to the relevant regulations of the national standard GB/T14902-. The water reducing agent adopted in the invention is a polycarboxylic acid water reducing agent, and the folding solid content is 0.25%; the cement is 52.5R.P.II cement of the small open-field; the sand is medium sand with fineness modulus Mx of 2.6; the stone is crushed stone with 5-25mm grain size and continuous gradation. The concrete mixing proportion is as follows: 5.4kg of cement, 1.8kg of fly ash, 1.8kg of mineral powder, 16.0kg of sand, 13.0kg of large stone, 5.6kg of small stone and 3.3kg of water. All the rheology modifiers are used in the same amount, the anchoring amount is 0.25 ten-thousandth of the mass of the cementing material, and the measurement results are shown in Table 3:

TABLE 3 determination of the Properties of the rheology modifiers

As can be seen from Table 3, the rheology modifier prepared by the invention can make fresh concrete have better segregation and bleeding resistance. At the same time, they had significant air-entraining properties, greater slump/spread, and shorter run-out times, indicating that they had better flow properties, as compared to comparative rheology modifier 1 (without air-entraining component), comparative rheology modifier 2 (with physical compounding blend of air-entraining component), and the commercially available HPMC.

The combination of the above shows that the rheology modifier of the invention can effectively solve the contradiction between segregation resistance bleeding property and fluidity of fresh concrete, so that the rheology modifier has high workability, and simultaneously shows the feasibility and the necessity of introducing air-entraining components by using a chemical copolymerization method.

Claims

1. A method for preparing an air-entraining copolymer, which is characterized in that: the air-entraining copolymer is obtained by carrying out free radical copolymerization on a monomer A, a monomer B and a monomer C in a molar ratio of 1: 0.5-2: 0.01-0.04, wherein the structure of the monomer A is shown as the formula (I):

the structure of the monomer B is shown as the formula (II):

the structure of the monomer C is shown as the formula (III):

2. The process for preparing an air-entraining copolymer according to claim 1 wherein: the method comprises the following steps:

s1, mixing a monomer A, a monomer B and a monomer C to prepare an aqueous solution with the total mass fraction of 5-20%, and adjusting the pH value to 7-8;

3. The process for preparing an air-entraining copolymer according to claim 2 wherein: in step S2, the initiator is 2, 2-azobis (2-methylpropylammonium) dihydrochloride or persulfate.

4. The process for preparing an air-entraining copolymer according to claim 2 wherein: after the pH value is adjusted, firstly introducing non-reactive gas for bubbling for 20-60 min, and then dropwise adding an initiator.

5. The process for preparing an air-entraining copolymer according to claim 2 wherein: in the step S2, the initiator is dripped at the temperature of 40-60 ℃.

6. An air-entraining copolymer obtained by the production process according to any one of claims 1 to 5.

7. Use of the air-entraining copolymer according to claim 6 as a concrete rheology modifier.

8. The use according to claim 7, wherein the air-entraining copolymer has a folding-anchoring content of 0.1 to 1 ten thousandth of the mass of the cementitious material in the concrete.

9. The preparation method of any one of claims 1 to 5, wherein the monomer C has a structure represented by formula (III):

wherein R is₃Represents a linear alkyl group having 8 to 18 carbon atoms.