Wet-mixed mortar water-retaining agent used at high temperature as well as preparation method and application of wet-mixed mortar water-retaining agent

Abstract

The invention discloses a wet-mixed mortar water-retaining agent used at high temperature and a preparation method and application thereof, and belongs to the technical field of cement-based material admixtures, the wet-mixed mortar water-retaining agent is a copolymer obtained by free radical copolymerization of a monomer A, a monomer B and a monomer C according to the 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, the monomer B and the monomer C are respectively shown as general formulas I, II and III. The water-retaining agent is a hydrophilic linear polymer with high molecular weight, and the molecular main chain of the polymer contains a large number of water-retaining groups (hydroxyl and acylamino) and also contains a cationic quaternary ammonium salt unit, so that the polymer has good water solubility and temperature adaptability, and can maintain good water-retaining performance at high temperature. Compared with a traditional mortar water-retaining agent, the water-retaining agent provided by the invention has more excellent performance.

Description

Technical Field

[0001] The invention belongs to the technical field of cement-based material admixtures, and particularly relates to a wet-mix mortar water retaining agent for high temperature, and a preparation method and application thereof. Background Art

[0002] As the construction area of ​​houses in the construction industry continues to grow, the demand for cement mortar is also growing. Due to increasingly stringent environmental protection requirements, many cities are gradually banning on-site mixing of mortar and promoting the use of premixed mortar. Premixed mortar refers to various mortar mixtures produced by specialized manufacturers and used in construction projects. It is a new type of building material developed in my country in recent years. It has the advantages of health and environmental protection, stable quality, energy saving and comfort. According to the occasion of use, premixed mortar can be divided into plastering mortar, masonry mortar, waterproof mortar, thermal insulation mortar, floor mortar, etc. At present, premixed mortar has ushered in the fast lane of development, and the admixtures used in premixed mortar are also increasingly valued.

[0003] According to the different production methods, premixed 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, which are produced in a professional production plant in a certain proportion, transported to the place of use, and mixed with water at the construction site. Wet-mixed mortar is a mixture of cementitious materials, fine aggregates, admixtures and water, which are measured and mixed in a professional mixing station in a certain proportion, transported to the place of use, and used within a specified time. Compared with dry-mixed mortar, wet-mixed mortar has the advantages of low equipment investment, 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 of wet-mix mortar mainly include air entraining agent, water retaining agent, retarder and other small additives, which are prepared in the form of liquid. The main evaluation indicators of wet-mix mortar include bulk density, consistency, plastic retention time, water retention rate, compressive strength, etc. Among them, plastic retention time is an important evaluation indicator, that is, during the interval between mortar production and construction, the mortar still maintains workability (little loss of consistency and bulk density). However, in the high temperature environment in summer (>30℃), the mortar will lose its consistency too quickly due to excessive water loss, thereby losing its workability prematurely and failing to achieve the required plastic retention time. Therefore, it is of great practical significance to develop a water retaining agent for wet-mix mortar in high temperature environments in summer.

[0005] At present, most of the mortar water retainers on the market are modified natural polymers (such as patent applications CN103496868A, CN103449754A, CN107827387A, CN108609906A, CN107827399A), such as cellulose ether and bio-glue, which all have a large number of hydrophilic hydroxyl groups and can improve the bleeding of mortar. However, their water solubility and stability are generally poor. In wet-mixed mortar admixtures stored in solution form, they are prone to precipitation, stratification and deterioration. In addition, in the high temperature environment (>30℃) in summer, their water retention capacity is limited, and mortar often loses its workability prematurely due to rapid water loss. Therefore, it is of great practical significance to use chemical methods to change the chemical structure of traditional water retainers to improve their performance. However, due to the limitation of interdisciplinary studies, few people are currently involved in this research. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a wet-mix mortar water-retaining agent for use at high temperatures, a preparation method thereof, and an application thereof. The water-retaining agent has both good water solubility and temperature adaptability, and can maintain good water-retaining performance at higher temperatures.

[0007] The present invention is achieved through the following technical solutions: A wet-mixed mortar water retaining agent for use at high temperatures, the wet-mixed mortar water retaining agent being 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), the number average molecular weight of the copolymer being 1 million to 3 million; wherein the structural formula of the monomer A is as 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.

[0008] The preparation method of the wet-mixed mortar water retaining agent for high temperature comprises the following steps: 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.

[0009] Preferably, the synthetic route of the synthetic monomer A in step 1) is as 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.

[0010] Preferably, the halogenated n-alkyl alcohol is a chlorinated or brominated n-alkyl alcohol containing 8 to 14 carbon atoms; and the molar ratio of the N,N-dimethylpropyleneamine to the halogenated n-alkyl alcohol is 1:(1 to 1.2).

[0011] Preferably, in step 2), the inert gas is nitrogen or argon.

[0012] Preferably, the initiator in step 2) is 2,2-azobis(2-methylpropylimidamide) dihydrochloride or ammonium persulfate.

[0013] Preferably, in step 2), the molar ratio of monomer A, monomer B, monomer C and initiator is 1:(2-4):(5-7):(0.1-0.2).

[0014] The wet-mix mortar water retaining agent mentioned above, or the wet-mix mortar water retaining agent prepared by the above preparation method, is used in the preparation of premixed mortar.

[0015] Preferably, 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.

[0016] Preferably, the solid dosage of the water retaining agent is 0.1‰~0.3‰ of the mass of the gel material in the mortar.

[0017] The beneficial effects of the present invention are as follows: The wet-mixed mortar water retainer for high temperature of the present invention is a hydrophilic linear polymer with high molecular weight from the perspective of chemical structure, and contains a large number of water retaining groups (hydroxyl groups, amide groups) in the main chain of the molecule, and contains cationic quaternary ammonium salt units, so that the polymer has good water solubility and temperature adaptability, and can maintain good water retention performance at higher temperatures. Compared with traditional commercially available mortar water retainers (cellulose ether, polyacrylamide, etc.), the water retainer of the present invention has better water solubility and temperature adaptability, and can have better water retention performance at higher temperatures (>30°C). DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to specific embodiments.

[0019] The materials used in the following examples are all commercially available chemicals, among which all reagents (chemically pure) used in the synthesis of water retaining agent are purchased from Anaiji Chemical Reagent Company and Sinopharm Chemical Reagent Co., Ltd. Polycarboxylate water reducer is from Jiangsu Subote New Materials Co., Ltd. The air entraining agent and retarder used in the wet mix mortar admixture are both from Jiangsu Subote New Materials Co., Ltd.

[0020] A wet-mix mortar water retaining agent for use at high temperatures, comprising 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), wherein the number average molecular weight of the copolymer is 1 million to 3 million; wherein the structure of the monomer A conforms to the general formula I:

[0021] Formula I In the general formula I: n is a natural number from 3 to 6; The structure of the monomer B conforms to the general formula II:

[0022] Formula II In the general formula II: R1 is CH3, CH3CH2 or CH3CH2CH2; The structure of the monomer C conforms to the general formula III:

[0023] Formula III In the general formula III: R2 is H or CH3.

[0024] A method for preparing a wet-mix mortar water retaining agent for high temperature, the specific steps are as follows: (1) Synthesize monomer A. The synthesis route is shown in reaction formula IV:

[0025] Reaction IV In reaction formula IV: X is Cl or Br, and n is a natural number of 3 to 6.

[0026] The specific steps are as follows: N,N-dimethylpropyleneamine and halogenated n-alkyl alcohol in a molar ratio of 1:(1-1.2) are dissolved in tetrahydrofuran, reacted at 60-70° C. for 1-3 days, and the solvent is removed by distillation under reduced pressure to obtain monomer A.

[0027] The halogenated n-alkyl alcohol is a chlorinated or brominated n-alkyl alcohol containing 8 to 14 carbon atoms.

[0028] (2) Monomer A, monomer B and monomer C are mixed in proportion to prepare an aqueous solution with a total mass fraction of 10-20%, and an aqueous solution of an initiator is added dropwise to the solution under the protection of nitrogen or argon. The mixture is reacted at 60-90° C. for 3-6 h to obtain the wet-mixed mortar water retaining agent for high temperature.

[0029] The initiator is 2,2-azobis(2-methylpropylimidazole) dihydrochloride or ammonium persulfate.

[0030] The molar ratio of the monomer A, the monomer B, the monomer C and the initiator is 1:(2-4):(5-7):(0.1-0.2).

[0031] Example 1 A method for preparing a wet-mix mortar water retaining agent for high temperature, the specific steps are as follows: (1) 10 mmol of N,N-dimethylpropyleneamine and 10 mmol of chlorooctyl alcohol (in reaction formula IV, X is Cl, n=3) were dissolved in 100 mL of tetrahydrofuran, reacted at 60°C for 1 day, and the solvent was removed by distillation under reduced pressure to obtain monomer A.

[0032] (2) 10 mmol of monomer A, 20 mmol of 2-butenol (in general formula II, R1 is CH3) and 50 mmol of acrylamide (in general formula III, R2 is H) were mixed to prepare an aqueous solution with a total mass fraction of 10%. Under nitrogen protection, 2 mmol of an aqueous solution of 2,2-azobis(2-methylpropylimidamide) dihydrochloride was added dropwise to the solution. The mixture was reacted at 60 °C for 3 h to obtain a wet-mix mortar water-retaining agent with a number average molecular weight of 1.98 million.

[0033] Example 2 A method for preparing a wet-mix mortar water retaining agent for high temperature, the specific steps are as follows: (1) 10 mmol of N,N-dimethylpropyleneamine and 11 mmol of bromodecyl alcohol (in reaction formula IV, X is Br, n=4) were dissolved in 100 mL of tetrahydrofuran, reacted at 60°C for 2 days, and the solvent was removed by distillation under reduced pressure to obtain monomer A.

[0034] (2) 10 mmol of monomer A, 40 mmol of 2-butenol (in general formula II, R1 is CH3) and 70 mmol of acrylamide (in general formula III, R2 is H) were mixed to prepare an aqueous solution with a total mass fraction of 15%. 2 mmol of an aqueous solution of 2,2-azobis(2-methylpropylimidamide) dihydrochloride was added dropwise to the solution under nitrogen protection. The mixture was reacted at 70 °C for 4 h to obtain a wet-mix mortar water-retaining agent with a number average molecular weight of 1.77 million.

[0035] Example 3 A method for preparing a wet-mix mortar water retaining agent for high temperature, the specific steps are as follows: (1) 10 mmol of N,N-dimethylpropyleneamine and 11 mmol of n-dodecanol bromide (in reaction formula IV, X is Br, n=5) were dissolved in 100 mL of tetrahydrofuran, reacted at 70°C for 3 days, and the solvent was removed by distillation under reduced pressure to obtain monomer A.

[0036] (2) 10 mmol of monomer A, 30 mmol of 2-pentenol (in general formula II, R1 is CH3CH2) and 60 mmol of N,N-dimethylacrylamide (in general formula III, R2 is CH3) were mixed to prepare an aqueous solution with a total mass fraction of 20%. 1 mmol of an aqueous solution of ammonium persulfate was added dropwise to the solution under argon protection. The mixture was reacted at 80 °C for 5 h to obtain a wet-mix mortar water-retaining agent with a number average molecular weight of 2.35 million.

[0037] Example 4 A method for preparing a wet-mix mortar water retaining agent for high temperature, the specific steps are as follows: (1) 10 mmol of N,N-dimethylpropyleneamine and 12 mmol of tetradecanol bromide (in reaction formula IV, X is Br, n=6) were dissolved in 100 mL of tetrahydrofuran, reacted at 70°C for 3 days, and the solvent was removed by distillation under reduced pressure to obtain monomer A.

[0038] (2) 10 mmol of monomer A, 30 mmol of 2-hexenol (in general formula II, R1 is CH3CH2CH2) and 60 mmol of N,N-dimethylacrylamide (in general formula III, R2 is CH3) were mixed to form an aqueous solution with a total mass fraction of 20%. 1 mmol of an aqueous solution of ammonium persulfate was added dropwise to the solution under argon protection. The mixture was reacted at 90 °C for 6 h to obtain a wet-mix mortar water-retaining agent with a number average molecular weight of 2.14 million.

[0039] Comparative Example 1 A method for preparing a wet-mix mortar water-retaining agent, the specific steps are as follows: 30 mmol of 2-hexenol (in general formula II, R1 is CH3CH2CH2) and 60 mmol of N,N-dimethylacrylamide (in general formula III, R2 is CH3) were mixed to form an aqueous solution with a total mass fraction of 20%. 1 mmol of an aqueous solution of ammonium persulfate was added dropwise to the solution under argon protection, and the mixture was reacted at 90°C for 6 h to obtain a wet-mixed mortar water-retaining agent with a number average molecular weight of 2.56 million.

[0040] Comparative Example 2 The traditional mortar water retaining agent on the market: Hydroxypropyl methylcellulose ether (molecular weight 150,000) is directly used as a wet-mix mortar water retaining agent.

[0041] Comparative Example 3 The traditional mortar water-retaining agent on the market: anionic polyacrylamide (molecular weight 2 to 3 million), is directly used as a wet-mix mortar water-retaining agent.

[0042] Test Example 1 Preparation and performance evaluation of wet-mixed mortar using water-retaining agent The mortar mix ratio is: 160 g Conch 52.5 RP II cement, 70 g fly ash, 1400 g river sand (fineness modulus Mx=2.5), and 205 g water.

[0043] The admixture formula is: 10 g water-retaining agent (converted into solid), 60 g air-entraining agent, 130 g retarder, and 800 g water.

[0044] Mix the above components evenly and add 6 g to the mortar. First, mix the dry mortar for 30 seconds, then add water and admixtures and stir slowly for 90 seconds. According to the relevant provisions of the national standard GB / T 25181-2019 "Premixed Mortar", the various performance indicators of wet mortar were tested. After the mortar samples were placed outdoors in summer (maximum temperature of about 35°C) for 24 hours, the performance of each sample was retested.

[0045] The water retaining agents tested were 7 kinds of wet-mixed mortar water retaining agents obtained in Examples 1-4 and Comparative Examples 1-3. The experimental results are shown in Table 1.

[0046] Table 1 Comparison of performance of different water retaining agents in wet mixed mortar (35℃)

[0047] As can be seen from Table 1, compared with Comparative Example 1 lacking comonomer A (cationic monomer), and the commercially available traditional mortar water retaining agents hydroxypropyl methylcellulose ether (Comparative Example 2) and polyacrylamide (Comparative Example 3), the water retaining agents prepared in Examples 1-4 can enable the wet-mixed mortar samples to maintain a lower bulk density and higher consistency data after being placed at high temperature (35°C) for 24 hours. The 24-hour consistency loss rate and mass loss rate (reflecting water loss) are significantly improved, and good workability is still maintained.

[0048] In summary, the wet-mixed mortar water retaining agent for use at high temperatures of the present invention can more effectively solve the water retention problem of the wet-mixed mortar under high temperature conditions, so that the wet-mixed mortar can maintain workability within the required plastic preservation time.

[0049] The embodiments described above are only some 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 invention claimed for protection, but merely represents selected embodiments of the present invention. The scope of protection of the present invention shall be subject to the scope required by the claims. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work shall fall within the scope of protection 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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