A water retention agent for wet-mixed mortar at high temperatures, its preparation method and application

Abstract

The present invention discloses a water retention agent for wet-mixed mortar at high temperatures, its preparation method and application, belonging to the technical field of cement-based material admixtures. The water retention agent for wet-mixed mortar is a copolymer obtained by free radical copolymerization of monomer A, monomer B and monomer C with a molar ratio of 1:(2~4):(5~7), and the number average molecular weight of the copolymer is 1 million to 3 million; wherein, the structural formulas of the monomer A, monomer B and monomer C are respectively shown in general formulas I, II and III. The water retention agent of the present invention is a hydrophilic linear polymer with a high molecular weight, and its molecular main chain contains a large number of water retention groups (hydroxyl groups, amide groups), and at the same time contains a quaternary ammonium salt unit of a cation, so that the polymer has good water solubility and temperature adaptability at the same time, and can maintain good water retention performance at higher temperatures. Compared with traditional mortar water retention agents, the water retention agent of the present invention has more excellent performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of admixtures for cement-based materials, and particularly relates to a water retention agent for wet-mixed mortar at high temperatures, a preparation method thereof, and applications thereof. Background Art

[0002] With the continuous growth of the housing construction area in the construction industry, the demand for cement mortar is also increasing day by day. Due to the increasingly strict environmental protection requirements, on-site mixing of mortar is gradually prohibited in many cities, and the promotion of ready-mixed mortar is carried out. Ready-mixed mortar refers to various mortar mixtures used in construction projects, which are produced by professional manufacturers. It is a new type of building material developed in recent years in China, and has advantages such as health and environmental protection, stable quality, energy conservation and comfort. According to the usage occasions, ready-mixed mortar can be divided into plastering mortar, masonry mortar, waterproof mortar, thermal insulation mortar, floor mortar, etc. At present, ready-mixed mortar has entered the fast lane of development, and the admixtures for ready-mixed mortar have attracted more and more attention.

[0003] According to different production methods, ready-mixed mortar can be divided into dry-mixed mortar and wet-mixed mortar. Dry-mixed mortar is a mixture of cementitious materials, dry fine aggregates, admixtures, and other components determined according to performance. It is produced in a professional production factory according to a certain ratio, transported to the use location, and then mixed with water at the construction site. Wet-mixed mortar is a mortar composed of cementitious materials, fine aggregates, admixtures, and water. It is measured and mixed in a professional mixing station according to a certain ratio, transported to the use location, and used within a specified time. Compared with dry-mixed mortar, wet-mixed mortar has advantages such as low investment in equipment, low unit price, no need to dry sand, stable quality, and convenient construction. Therefore, it is the main development direction of mortar in many cities.

[0004] The admixtures for wet-mixed mortar mainly include air-entraining agents, water retention agents, retarders, and other added small materials, which are prepared in liquid form. The main evaluation indexes of wet-mixed mortar include bulk density, consistency, plastic retention time, water retention rate, compressive strength, etc. Among them, the plastic retention time is an important evaluation index, that is, within the interval time between mortar production and construction, the mortar still maintains workability (small loss of consistency and bulk density). However, in an environment with high temperature in summer (>30°C), the mortar will lose water too quickly, resulting in too fast loss of consistency, and thus lose workability prematurely, unable to reach the required plastic retention time. Therefore, it is of great practical significance to develop a water retention agent for wet-mixed mortar in high-temperature environments in summer.

[0005] Most of the commercially available mortar water retention agents are modified natural polymers (such as patent applications CN103496868A, CN103449754A, CN107827387A, CN108609906A, CN107827399A), such as cellulose ethers and bioadhesives. They all have a large number of hydrophilic hydroxyl groups, which can improve the bleeding phenomenon of mortar. However, their water solubility and stability are generally poor. In the wet-mixed mortar admixtures stored in the form of solution, they are prone to precipitation, delamination and deterioration. In addition, in the environment of high temperature in summer (>30 °C), their water retention ability has limitations, and the mortar often loses its workability prematurely due to excessive water loss. Therefore, it has very important practical significance to use chemical methods to change the chemical structure of traditional water retention agents to improve their performance. However, due to the limitation of interdisciplinary, few people are involved in this aspect of research. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a water retention agent for wet-mixed mortar at high temperature, its preparation method and application. The water retention agent has good water solubility and temperature adaptability at the same time, and can maintain good water retention performance at higher temperatures.

[0007] The present invention is achieved by the following technical solutions:

[0008] A water retention agent for wet-mixed mortar at high temperature, the wet-mixed mortar water retention agent is a copolymer obtained by free radical copolymerization of monomer A, monomer B and monomer C with a molar ratio of 1:(2-4):(5-7), and the number average molecular weight of the copolymer is 1 million to 3 million; wherein, the structural formula of the monomer A is shown in general formula I:

[0009] General formula I;

[0010] In general formula I: n is a natural number from 3 to 6;

[0011] The structural formula of the monomer B is shown in general formula II:

[0012] General formula II;

[0013] In general formula II: R 1 is CH 3 、CH 3 CH 2 or CH 3 CH 2 CH 2 ;

[0014] The structural formula of the monomer C is shown in general formula III:

[0015] General formula III;

[0016] In General Formula III: R 2 is H or CH 3 .

[0017] The preparation method of the above-mentioned water retention agent for wet-mixed mortar at high temperature includes the following steps:

[0018] Step 1) Synthesize monomer A;

[0019] Step 2) Mix monomer A, monomer B and monomer C in proportion and prepare an aqueous solution with a total mass fraction of 10-20%. While under the protection of an inert gas, dropwise add an aqueous solution of an initiator into the solution and react at 60-90°C for 3-6 h to obtain the product.

[0020] Preferably, the synthesis route of synthesizing monomer A in step 1) is as shown in Reaction Formula IV:

[0021] Reaction Formula IV;

[0022] In Reaction Formula IV: X is Cl or Br, and n is a natural number from 3 to 6;

[0023] The specific steps are as follows:

[0024] Dissolve N,N-dimethylallylamine and halo-n-alkyl alcohol in tetrahydrofuran, react at 60-70°C for 1-3 days, and remove the solvent by vacuum distillation to obtain the product.

[0025] Preferably, the halo-n-alkyl alcohol is a chloro- or bromo-containing n-alkyl alcohol with 8-14 carbons; the molar ratio of N,N-dimethylallylamine to halo-n-alkyl alcohol is 1:(1-1.2).

[0026] Preferably, the inert gas in step 2) is nitrogen or argon.

[0027] Preferably, the initiator in step 2) is 2,2-azobis(2-methylpropylimid) dihydrochloride or ammonium persulfate.

[0028] Preferably, the molar ratio of monomer A, monomer B, monomer C and the initiator in step 2) is 1:(2-4):(5-7):(0.1-0.2).

[0029] The application of the above-mentioned water retention agent for wet-mixed mortar, or the water retention agent for wet-mixed mortar prepared by the above-mentioned preparation method, in the preparation of ready-mixed mortar.

[0030] Preferably, dissolve the water retention agent and other additives for wet-mixed mortar in water, mix them evenly, and then add them to the mortar and stir.

[0031] Preferably, the solid admixture content of the water retention agent is 0.1‰ - 0.3‰ of the mass of the gel material in the mortar.

[0032] The beneficial effects of the present invention are as follows:

[0033] The water retention agent for wet-mixed mortar at high temperatures of the present invention, from a chemical structure perspective, is a hydrophilic linear polymer with a high molecular weight. A large number of water retention groups (hydroxyl groups, amide groups) are contained in its molecular main chain, and at the same time, a quaternary ammonium salt unit containing cations is included, enabling the polymer to have good water solubility and temperature adaptability, and being able to maintain good water retention performance at relatively high temperatures. Compared with commercially available traditional mortar water retention agents (such as cellulose ether, polyacrylamide, etc.), the water retention agent of the present invention has better water solubility and temperature adaptability, and can have better water retention performance at relatively high temperatures (>30°C). Specific embodiments

[0034] The present invention will be further described in detail below with reference to specific embodiments.

[0035] All the materials used in the following examples are commercially available chemicals. All the reagents (chemically pure) used for the synthesis of the water retention agent are purchased from Anyiji Chemical Reagent Company and Sinopharm Chemical Reagent Co., Ltd. The polycarboxylate superplasticizer comes from Jiangsu Sobute New Materials Co., Ltd. The air-entraining agent and retarder used in the wet-mixed mortar admixture both come from Jiangsu Sobute New Materials Co., Ltd.

[0036] A water retention agent for wet-mixed mortar at high temperatures, a copolymer obtained by free radical copolymerization of monomers A, B, and C with a molar ratio of 1:(2 - 4):(5 - 7), the number average molecular weight of the copolymer is 1 million - 3 million; wherein, the structure of the monomer A conforms to the general formula I:

[0037]

[0038] General formula I

[0039] In the general formula I: n is a natural number from 3 to 6;

[0040] The structure of the monomer B conforms to the general formula II:

[0041]

[0042] General formula II

[0043] In the general formula II: R 1 is CH 3 、CH 3 CH 2 or CH 3 CH 2 CH 2 ;

[0044] The structure of the monomer C conforms to the general formula III:

[0045]

[0046] General formula III

[0047] In general formula III: R 2 is H or CH 3 .

[0048] A preparation method of a water retention agent for wet-mixed mortar at high temperature, the specific steps are as follows:

[0049] (1) Synthesize monomer A, and the synthesis route is shown in reaction formula IV:

[0050]

[0051] Reaction formula IV

[0052] In reaction formula IV: X is Cl or Br, and n is a natural number from 3 to 6.

[0053] The specific steps are as follows:

[0054] Dissolve N,N-dimethylacrylamide and halo-n-alkyl alcohol with a molar ratio of 1:(1~1.2) in tetrahydrofuran, react at 60~70 °C for 1~3 days, and remove the solvent by vacuum distillation to obtain monomer A.

[0055] The halo-n-alkyl alcohol is a chloro- or bromo-containing n-alkyl alcohol with 8~14 carbons.

[0056] (2) Mix monomer A, monomer B and monomer C in proportion and prepare an aqueous solution with a total mass fraction of 10~20%, and dropwise add an aqueous solution of an initiator to the solution under the protection of nitrogen or argon, and react at 60~90 °C for 3~6 h to obtain the water retention agent for wet-mixed mortar at high temperature.

[0057] The initiator is 2,2-azobis(2-methylpropylimid) dihydrochloride or ammonium persulfate.

[0058] The molar ratio of monomer A, monomer B, monomer C and the initiator is 1:(2~4):(5~7):(0.1~0.2).

[0059] Example 1

[0060] A preparation method of a water retention agent for wet-mixed mortar at high temperature, the specific steps are as follows:

[0061] (1) Dissolve 10 mmol of N,N-dimethylallylamine and 10 mmol of n-octyl chloroalcohol (in Reaction Formula IV, X is Cl, n = 3) in 100 mL of tetrahydrofuran, react at 60 °C for 1 day, and remove the solvent by vacuum distillation to obtain monomer A.

[0062] (2) Mix 10 mmol of monomer A, 20 mmol of 2-butenol (in General Formula II, R 1 is CH 3 ), and 50 mmol of acrylamide (in General Formula III, R 2 is H) and make an aqueous solution with a total mass fraction of 10%. Under nitrogen protection, dropwise add an aqueous solution of 2 mmol of 2,2'-azobis(2-methylpropylimid) dihydrochloride to the solution, and react at 60 °C for 3 h to obtain a water-retaining agent for wet-mixed mortar with a number-average molecular weight of 1.98 million.

[0063] Example 2

[0064] A preparation method of a water-retaining agent for wet-mixed mortar at high temperature, the specific steps are as follows:

[0065] (1) Dissolve 10 mmol of N,N-dimethylallylamine and 11 mmol of n-decyl bromide (in Reaction Formula IV, X is Br, n = 4) in 100 mL of tetrahydrofuran, react at 60 °C for 2 days, and remove the solvent by vacuum distillation to obtain monomer A.

[0066] (2) Mix 10 mmol of monomer A, 40 mmol of 2-butenol (in General Formula II, R 1 is CH 3 ), and 70 mmol of acrylamide (in General Formula III, R 2 is H) and make an aqueous solution with a total mass fraction of 15%. Under nitrogen protection, dropwise add an aqueous solution of 2 mmol of 2,2'-azobis(2-methylpropylimid) dihydrochloride to the solution, and react at 70 °C for 4 h to obtain a water-retaining agent for wet-mixed mortar with a number-average molecular weight of 1.77 million.

[0067] Example 3

[0068] A preparation method of a water-retaining agent for wet-mixed mortar at high temperature, the specific steps are as follows:

[0069] (1) Dissolve 10 mmol of N,N-dimethylallylamine and 11 mmol of n-dodecyl bromide (in Reaction Formula IV, X is Br, n = 5) in 100 mL of tetrahydrofuran, react at 70 °C for 3 days, and remove the solvent by vacuum distillation to obtain monomer A.

[0070] (2) Mix 10 mmol of monomer A, 30 mmol of 2-pentenol (in general formula II, R 1 is CH 3 CH 2 ) and 60 mmol of N,N-dimethylacrylamide (in general formula III, R 2 is CH 3 ), and make an aqueous solution with a total mass fraction of 20%. Under argon protection, dropwise add an aqueous solution of 1 mmol of ammonium persulfate to the solution, and react at 80 °C for 5 h to obtain a water retention agent for wet-mixed mortar with a number-average molecular weight of 2.35 million.

[0071] Example 4

[0072] A preparation method of a water retention agent for wet-mixed mortar at high temperature, the specific steps are as follows:

[0073] (1) Dissolve 10 mmol of N,N-dimethylallylamine and 12 mmol of 1-bromotetradecanol (in reaction formula IV, X is Br, n = 6) in 100 mL of tetrahydrofuran, react at 70 °C for 3 days, and remove the solvent by vacuum distillation to obtain monomer A.

[0074] (2) Mix 10 mmol of monomer A, 30 mmol of 2-hexenol (in general formula II, R 1 is CH 3 CH 2 CH 2 ) and 60 mmol of N,N-dimethylacrylamide (in general formula III, R 2 is CH 3 ), and make an aqueous solution with a total mass fraction of 20%. Under argon protection, dropwise add an aqueous solution of 1 mmol of ammonium persulfate to the solution, and react at 90 °C for 6 h to obtain a water retention agent for wet-mixed mortar with a number-average molecular weight of 2.14 million.

[0075] Comparative Example 1

[0076] A preparation method of a water retention agent for wet-mixed mortar, the specific steps are as follows:

[0077] Mix 30 mmol of 2-hexenol (in general formula II, R 1 is CH 3 CH 2 CH 2 ) and 60 mmol of N,N-dimethylacrylamide (in general formula III, R 2 is CH 3)(Mix and prepare an aqueous solution with a total mass fraction of 20%. While under argon protection, add an aqueous solution of 1 mmol of ammonium persulfate dropwise to the solution, and react at 90 °C for 6 h to obtain a water-retaining agent for wet-mixed mortar with a number-average molecular weight of 2.56 million.)

[0078] Comparative Example 2

[0079] Commercially available traditional mortar water-retaining agent: hydroxypropyl methylcellulose ether (molecular weight 150,000), which is directly used as the water-retaining agent for wet-mixed mortar.)

[0080] Comparative Example 3

[0081] Commercially available traditional mortar water-retaining agent: anionic polyacrylamide (molecular weight 2-3 million), which is directly used as the water-retaining agent for wet-mixed mortar.)

[0082] Test Example 1 Preparation and performance evaluation of wet-mixed mortar using a water-retaining agent

[0083] The mortar mix ratio is as follows: 160 g of Conch 52.5 R.P. II cement, 70 g of fly ash, 1400 g of river sand (fineness modulus Mx = 2.5), and 205 g of water.)

[0084] The admixture formula is as follows: 10 g of water-retaining agent (converted to solid), 60 g of air-entraining agent, 130 g of retarder, and 800 g of water.)

[0085] Mix the above components evenly, and the dosage in the mortar is 6 g. First, mix and stir the dry mortar for 30 s, and then add water and admixtures and stir slowly for 90 s. Refer to the relevant regulations of the national standard GB / T 25181-2019 "Ready-mixed Mortar" to test the performance indicators of the wet-mixed mortar. After placing the mortar samples outdoors in summer (the highest temperature is about 35 °C) for 24 h, retest the performance of each sample.)

[0086] The water-retaining agents tested are the 7 water-retaining agents for wet-mixed mortar obtained in Examples 1-4 and Comparative Examples 1-3, and the experimental results are shown in Table 1.)

[0087] Table 1 Performance comparison of different water-retaining agents in wet-mixed mortar (35 °C)

[0088]

[0089] As can be seen from Table 1, compared with Comparative Example 1 lacking comonomer A (cationic monomer), and commercially available traditional mortar water retention agents hydroxypropyl methyl cellulose ether (Comparative Example 2) and polyacrylamide (Comparative Example 3), the water retention agents prepared in Examples 1-4 can keep the wet-mixed mortar samples at a relatively low bulk density and high consistency data after being placed at a high temperature (35°C) for 24 h. The consistency loss rate and mass loss rate (reflecting water loss) after 24 h are significantly improved, and good workability is still maintained.

[0090] In summary, the water retention agent for wet-mixed mortar at high temperatures of the present invention can more effectively solve the water retention problem of wet-mixed mortar under high temperature conditions, enabling the wet-mixed mortar to maintain workability within the required plasticizing time.

[0091] The embodiments described above are only a part of the embodiments of the present invention, rather than all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the present invention claimed, but merely represents the selected embodiments of the present invention. The protection scope of the present invention shall be subject to the scope claimed in the claims. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A wet-mix mortar water retaining agent for use at high temperatures, characterized in that: The wet-mixed mortar water retaining agent is a copolymer obtained by free radical copolymerization of monomer A, monomer B and monomer C in a molar ratio of 1:(2-4):(5-7), and the number average molecular weight of the copolymer is 1 million to 3 million; wherein the structural formula of the monomer A is shown in general formula I: Formula I; In the general formula I: n is a natural number from 3 to 6; The structural formula of the monomer B is shown in general formula II: Formula II; In the general formula II: R1 is CH3, CH3CH2 or CH3CH2CH2; The structural formula of the monomer C is shown in general formula III: Formula III; In the general formula III: R2 is H or CH3.

2. The method for preparing a wet-mix mortar water retaining agent for high temperature according to claim 1, characterized in that: The following steps are involved: Step 1) synthesizing monomer A; Step 2) Monomer A, monomer B and monomer C are mixed in proportion and prepared into an aqueous solution with a total mass fraction of 10-20%. An aqueous solution of an initiator is added dropwise to the solution under the protection of an inert gas, and the mixture is reacted at 60-90° C. for 3-6 h to obtain the product.

3. The method for preparing a wet-mix mortar water retaining agent for high temperature according to claim 2, characterized in that: Step 1) The synthetic route of the synthetic monomer A is shown in reaction formula IV: Reaction formula IV; In reaction formula IV: X is Cl or Br, and n is a natural number of 3 to 6; The specific steps are as follows: Dissolve N,N-dimethylpropyleneamine and halogenated n-alkyl alcohol in tetrahydrofuran, react at 60-70°C for 1-3 days, and remove the solvent by distillation under reduced pressure to obtain the product.

4. The method for preparing a wet-mix mortar water retaining agent for high temperature according to claim 3, characterized in that: The halogenated n-alkyl alcohol is a chlorinated or brominated n-alkyl alcohol containing 8 to 14 carbon atoms; the molar ratio of the N,N-dimethylpropyleneamine to the halogenated n-alkyl alcohol is 1:(1 to 1.2).

5. The method for preparing a wet-mix mortar water retaining agent for high temperature according to claim 2, characterized in that: Step 2) The inert gas is nitrogen or argon.

6. The method for preparing a wet-mix mortar water retaining agent for high temperature according to claim 2, characterized in that: Step 2) The initiator is 2,2-azobis(2-methylpropylimidazole) dihydrochloride or ammonium persulfate.

7. The method for preparing a wet-mix mortar water retaining agent for high temperature according to claim 2, characterized in that: Step 2) The molar ratio of monomer A, monomer B, monomer C and initiator is 1:(2-4):(5-7):(0.1-0.2).

8. Use of the wet-mix mortar water-retaining agent according to claim 1, or the wet-mix mortar water-retaining agent prepared by the preparation method according to any one of claims 2 to 7 in the preparation of premixed mortar.

9. The use according to claim 8, characterized in that: The water retaining agent is dissolved in water together with other wet-mix mortar admixtures, mixed evenly, and then added into the mortar and stirred.

10. The use according to claim 9, characterized in that: The solid dosage of the water retaining agent is 0.1‰~0.3‰ of the mass of the gel material in the mortar.

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