An additive for inhibiting efflorescence in cement mortar and its preparation method

Abstract

This invention discloses an additive for inhibiting efflorescence in cement mortar and its preparation method, belonging to the field of cement additives. The additive has highly efficient water-reducing properties, reducing the amount of carriers for soluble alkalis and salts, thus improving the degree of efflorescence in cement mortar. It can also reduce the porosity of hardened cement mortar, reducing the migration channels for efflorescence, and further... ‑ With Ca 2+ The interaction forms a complex, which lowers the Ca content in the solution. 2+ The concentration of Ca(OH)2 is reduced, which delays the formation of Ca(OH)2 crystals and reduces the formation of C-H-S gel, thereby inhibiting the production of alkali. By introducing various functional groups, the water-reducing properties of the additive are greatly improved, and the additive is endowed with certain retarding, slump retention, crack resistance and compatibility, which has important application significance.

Description

Technical Field

[0001] This invention belongs to the field of cement additive technology, specifically, it relates to an additive for inhibiting efflorescence in cement mortar and its preparation method. Background Technology

[0002] Cement mortar is made of cement, fine aggregate, and water, i.e., cement + sand + water, mixed according to requirements. Mortar is a binding material used in bricklaying in construction. It is made by mixing sand and cementing materials (cement, lime paste, clay, etc.) with water in a certain proportion. It is also called mortar. Cement mortar is often used in masonry and plastering projects due to its excellent durability and moisture resistance. However, cement mortar contains minerals such as CS, C2S, and C3S. When these substances come into contact with humid air, they will form substances such as Na2CO3 and Ca(OH)2, which will cause efflorescence. These substances not only affect the appearance, but also directly corrode the wall material. Adding additives can effectively prevent efflorescence.

[0003] Common additives include naphthalene-based additives, aminosulfonate additives, and melamine additives. Naphthalene-based additives are readily available and have simple processing, but they suffer from rapid slump loss and poor compatibility with cement. Aminosulfonate additives are highly efficient additives with high water-reducing properties, but the raw materials are expensive, and the raw materials, including phenol and formaldehyde, are volatile and toxic substances. Melamine additives can significantly improve the durability of hardened concrete and have strong compatibility with cement, but they have high storage and transportation costs, require strict reaction conditions, and are difficult to control in terms of quality. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an additive for inhibiting efflorescence in cement mortar and a method for its preparation.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing an additive to inhibit efflorescence in cement mortar includes the following steps:

[0007] S1. Dichloromethylphosphine, 4-penten-1-ol and chlorobenzene were added to a three-necked flask equipped with a reflux reflux device. Aluminum trichloride was added as a catalyst, and the mixture was stirred and slowly heated to 65°C. The mixture was refluxed for 4 hours until no obvious HCl was released. The reaction was then stopped, and unreacted dichloromethylphosphine and solvent were removed by vacuum distillation to obtain intermediate 1. The ratio of dichloromethylphosphine, 4-penten-1-ol, chlorobenzene and aluminum trichloride was 13.1 g: 8.6 g: 50 mL: 0.3 g.

[0008] In the presence of aluminum trichloride as a catalyst, dichloromethylphosphine undergoes an esterification reaction with 4-penten-1-ol. By controlling the molar ratio of the two to be close to 1:1 and with a slight excess of dichloromethylphosphine, only one -Cl group on the dichloromethylphosphine participates in the reaction, yielding intermediate 1. The specific reaction process is shown below:

[0009]

[0010] S2. Add 8-aniline-1-naphthalenesulfonic acid and pyridine to a three-necked flask equipped with a stirrer, slowly add NaOH solution (12% by mass) to adjust the pH to 7, and generate sodium 8-aniline-1-naphthalenesulfonate. Remove water by rotary evaporation, introduce nitrogen gas into the apparatus, add intermediate 1, heat to 80℃, and stop heating after reacting for 5 hours. After the temperature in the reaction flask drops to 30℃, first rotary evaporate, then purify by column chromatography (using a mixed solvent of benzene / diethyl ether with a volume ratio of 2:1 as the eluent), remove the eluent by rotary evaporation, and vacuum dry to obtain intermediate 2; the ratio of 8-aniline-1-naphthalenesulfonic acid, pyridine, and intermediate 1 is 29.9 g: 100 mL: 18.3 g;

[0011] Sodium 8-aniline-1-naphthalenesulfonate and intermediate 1 undergo an acylation reaction to generate intermediate 2; the specific reaction process is shown below:

[0012]

[0013] S3. Add ethylene oxide polyoxyethylene ether (EPEG, relative molecular mass 3000) and water to a four-necked flask, stir and heat to 40°C. After dissolving, add H2O2 solution (30% by mass), heat to the polymerization temperature of 80°C, and begin dropwise addition of component A and component B. Component A is a mixed solution of acrylic acid (AA), intermediate 2, and pyridine; component B is a mixed solution of 3-mercaptopropionic acid (MPA), ascorbic acid (Vc), and water. After the addition is complete... The mixture was kept at a constant temperature for 1 hour, then cooled down. When the temperature dropped to 45℃, NaOH solution (12% by mass) was added to neutralize the mixture and the pH was adjusted to 7. This yielded an additive to inhibit efflorescence in cement mortar. The ratio of the following components was: ethylene oxide polyoxyethylene ether, water, H2O2 solution, acrylic acid, intermediate 2, pyridine, 3-mercaptopropionic acid, and ascorbic acid.

[0014] The additive was synthesized via free radical aqueous solution polymerization using H₂O₂ and Vc redox as the initiating system and 3-mercaptopropionic acid as the chain transfer agent. The specific reaction process is shown below:

[0015]

[0016] Introducing -COO into the molecule -It acts as a retarder and slump protectant, delaying and inhibiting the setting time of cement and the hydration of C3A and C3S mineral components to suppress efflorescence. Additionally, -COO - With Ca 2+ The interaction forms a complex, which lowers the Ca content in the solution. 2+ Concentration delays Ca(OH)2 crystal formation and reduces CHS gel formation, thereby inhibiting alkali blooming; the introduction of -SO - The dominant role of 3 is to achieve high water reduction through efficient dispersion. This water reduction effect is achieved by forming intermolecular hydrogen bonds, and it can also improve the fluidity of cement. Furthermore, it can interact with -COO... - The combination produces highly efficient water-reducing properties; the introduction of polyoxyethylene chains can play a certain role in retarding setting, and also helps to improve the fluidity retention of concrete, greatly reducing the slump loss of fresh concrete and improving the compatibility of additives; the introduction of naphthalene further enhances the water-reducing properties, and the presence of benzene rings provides rigidity and improves mechanical properties; the high water-reducing properties cause the negative charge on the cement particles to generate electrostatic repulsion between the cement particles, which disperses the cement particles, increases the contact between cement particles and water, and allows the cement to fully hydrate, improving workability and reducing the amount of water required for mixing.

[0017] The beneficial effects of this invention are:

[0018] This invention provides an additive for inhibiting efflorescence in cement mortar. It not only acts as a water-reducing agent, reducing the amount of soluble alkali and salt carriers and improving the degree of efflorescence in cement mortar, but also reduces the porosity of hardened cement mortar, decreasing the migration channels for efflorescence and inhibiting its formation. By introducing multiple functional groups, it significantly improves water-reducing properties and endows the additive with certain retarding, slump retention, compatibility, and crack resistance properties, making it of significant application value. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1

[0021] Preparation of additives

[0022] S1. Add 13.1g of dichloromethylphosphine, 8.6g of 4-penten-1-ol and 50mL of chlorobenzene to a three-necked flask equipped with a reflux device, add 0.3g of aluminum trichloride, stir, slowly heat to 65℃, reflux for 4h until no obvious HCl escapes, stop the reaction, and remove unreacted dichloromethylphosphine and solvent by vacuum distillation to obtain intermediate 1;

[0023] S2. Add 29.9 g of 8-aniline-1-naphthalenesulfonic acid and 100 mL of pyridine to a three-necked flask equipped with a stirrer. Slowly add NaOH solution (12% by mass) to adjust the pH to 7, generating sodium 8-aniline-1-naphthalenesulfonate. Remove water by rotary evaporation. Purge nitrogen gas into the apparatus and add 18.3 g of intermediate 1. Heat to 80°C and react for 5 h. Stop heating and wait for the temperature inside the reaction flask to drop to 30°C. First, rotary evaporate the intermediate, then purify it by column chromatography (using a mixed solvent of benzene and diethyl ether in a volume ratio of 2:1 as the eluent). Remove the eluent by rotary evaporation and dry under vacuum to obtain intermediate 2.

[0024] S3. Add 300g of ethylene oxide polyoxyethylene ether and 500mL of water to a four-necked flask, stir and heat to 40℃. After dissolving, add 50mL of H2O2 solution (30% by mass). Heat to the polymerization temperature of 80℃ and start adding component A and component B dropwise. Component A is a mixed solution of 7.2g acrylic acid (AA), 45.4g intermediate 2, and 100mL pyridine. Component B is a mixed solution of 10.6g 3-mercaptopropionic acid (MPA), 5g ascorbic acid (Vc), and 500mL water. After the addition is complete, keep the temperature constant for 1 hour, then cool down. When the temperature drops to 45℃, add NaOH solution (12% by mass) to neutralize and adjust the pH to 7 to obtain an additive that inhibits efflorescence in cement mortar.

[0025] Example 2

[0026] Preparation of additives

[0027] S1. Add 26.2g of dichloromethylphosphine, 17.2g of 4-penten-1-ol and 100mL of chlorobenzene to a three-necked flask equipped with a reflux device, add 0.6g of aluminum trichloride, stir, slowly heat to 65℃, reflux for 4h until no obvious HCl escapes, stop the reaction, remove unreacted dichloromethylphosphine and solvent under reduced pressure to obtain intermediate 1;

[0028] S2. Add 59.8 g of 8-aniline-1-naphthalenesulfonic acid and 200 mL of pyridine to a three-necked flask equipped with a stirrer. Slowly add NaOH solution (12% by mass) to adjust the pH to 7, generating sodium 8-aniline-1-naphthalenesulfonate. Remove water by rotary evaporation, introduce nitrogen gas into the apparatus, add 37.6 g of intermediate 1, heat to 80°C, and stop heating after reacting for 5 h. After the temperature in the reaction flask drops to 30°C, first rotary evaporate, then purify by column chromatography (using a mixed solvent of benzene and diethyl ether in a volume ratio of 2:1 as the eluent). Remove the eluent by rotary evaporation and vacuum dry to obtain intermediate 2.

[0029] S3. Add 600g of ethylene oxide polyoxyethylene ether and 1000mL of water to a four-necked flask, stir and heat to 40℃. After dissolving, add 100mL of H2O2 solution (30% by mass). Heat to the polymerization temperature of 80℃ and start adding component A and component B dropwise. Component A is a mixed solution of 14.4g acrylic acid (AA), 90.8g intermediate 2, and 200mL pyridine. Component B is a mixed solution of 21.2g 3-mercaptopropionic acid (MPA), 10g ascorbic acid (Vc), and 500mL water. After the addition is complete, keep the temperature constant for 1 hour, then cool down. When the temperature drops to 45℃, add NaOH solution (12% by mass) to neutralize and adjust the pH to 7 to obtain an additive that inhibits efflorescence in cement mortar.

[0030] Example 3

[0031] Using a planetary cement mortar mixer conforming to JC / T 681, the following procedure was followed: First, 300g of cement and 680g of fine aggregate were slowly added to the mixing pot and stirred slowly for 30s to disperse them evenly; then, 200mL of water and 20g of the additive prepared in Example 1 were slowly poured into the mixing pot and stirred slowly for 120s; the mixing blades and the material on the mixing pot were cleaned, and stirring was stopped after 75s to produce cement mortar.

[0032] Example 4

[0033] Using a planetary cement mortar mixer conforming to JC / T 681, the following procedure was followed: First, 300g of cement and 660g of fine aggregate were slowly added to the mixing pot and stirred slowly for 30s to disperse them evenly; then, 200mL of water and 40g of the additive prepared in Example 2 were slowly poured into the mixing pot and stirred slowly for 120s; the mixing blades and the material on the mixing pot were cleaned, and stirring was stopped after 75s to produce cement mortar.

[0034] Comparative Example 1

[0035] The additives in Example 3 were replaced with commercially available naphthalene-based water-reducing agents, and the remaining steps were the same as in Example 3.

[0036] Comparative Example 2

[0037] The additive in Example 3 was replaced with WH-011, a product of a waterproof material company in Jiangxi Province. The remaining steps were the same as in Example 3.

[0038] Comparative Example 3

[0039] No additives were added, and the remaining steps were the same as in Example 3.

[0040] The cement mortars obtained in Examples 3-4 and Comparative Examples 1-3 were used to prepare specimens according to GB / T 17671, and the following functional tests were conducted:

[0041] The flowability of cement mortar was tested according to the national standard GB / T 2419-2016 "Determination of Flowability of Cement Mortar".

[0042] The degree of efflorescence was determined using the "spray-dry" cycle method specified in JC / T 1024-2007 "Wall Finishing Mortar".

[0043] The crack resistance was determined according to JC / T951-2005 "Test Method for Crack Resistance of Cement Mortar";

[0044] The slump and spread were measured using CECS203:2006 "Technical Specification for Application of Self-Compacting Concrete";

[0045] Weigh each specimen separately, immerse them in water, remove them after 30 minutes, wipe off the surface moisture, weigh them again, and calculate the water absorption. Water absorption (g) = mass of specimen after immersion (g) - mass of specimen before immersion (g);

[0046] The measured results are shown in Table 1:

[0047] Table 1

[0048]

[0049] The slump and spread results are shown in Table 2:

[0050] Table 2

[0051]

[0052] As can be seen from the two tables above, the additive obtained by this invention has extremely strong water-reducing properties, and also possesses certain retarding, slump retention, compatibility, and crack resistance properties, which are of great application significance.

[0053] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0054] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for the preparation of an additive for inhibiting efflorescence of cement mortar, characterized in that, The method comprises the following steps: S1, adding dichloromethyl phosphine, 4-penten-1-ol and chlorobenzene into a three-necked flask with reflux device, adding aluminum chloride, stirring, slowly heating to 65℃, refluxing for 4h until no HCl is generated, stopping the reaction, and distilling under reduced pressure to obtain intermediate 1; S2, adding 8-aniline-1-naphthalenesulfonic acid and pyridine into a three-necked flask with stirring device, slowly adding NaOH solution to adjust the pH to 7 to generate 8-aniline-1-naphthalenesulfonic acid sodium, removing water by rotary evaporation, introducing nitrogen into the device, adding intermediate 1, heating to 80℃, stopping heating after reacting for 5h, and then removing the eluent by rotary evaporation and column chromatography, and vacuum drying to obtain intermediate 2; S3, adding ethyleneoxy polyoxyethylene ether and water into a four-necked flask, stirring and heating to 40℃, dissolving, and then adding H2O2 solution, heating to 80℃, and then starting to drop A material and B material, the A material is a mixed solution of acrylic acid, intermediate 2 and pyridine, and the B material is a mixed solution of 3-mercaptopropionic acid, ascorbic acid and water, after dropping, constant temperature for 1h, cooling, and then adding NaOH solution to neutralize when the temperature is 45℃, and adjusting the pH to 7 to obtain the cement mortar efflorescence inhibiting additive.

2. A method for preparing an additive for inhibiting efflorescence of cement mortar according to claim 1, characterized in that, The amount ratio of dichloromethyl phosphine, 4-penten-1-ol, chlorobenzene and aluminum chloride in step S1 is 13.1g:8.6g:50mL:0.3g.

3. The method for preparing the additive for inhibiting efflorescence of cement mortar according to claim 1, characterized in that, The amount ratio of 8-aniline-1-naphthalenesulfonic acid, pyridine and intermediate 1 in step S2 is 29.9g:100mL:18.3g.

4. The method for preparing the additive for inhibiting efflorescence of cement mortar according to claim 1, characterized in that, The amount ratio of ethyleneoxy polyoxyethylene ether, water, H2O2 solution, acrylic acid, intermediate 2, pyridine, 3-mercaptopropionic acid and ascorbic acid in step S3 is 300g:500mL:50mL:7.2g:45.4g:100mL:10.6g:5g.

5. The method for preparing the additive for inhibiting efflorescence of cement mortar according to claim 1, characterized in that, The relative molecular mass of ethyleneoxy polyoxyethylene ether in step S3 is 3000.

6. An additive for inhibiting efflorescence of cement mortar, characterized by, Prepared according to the method in any one of claims 1-5. The cement mortar efflorescence inhibiting additive prepared according to the method in any one of claims 1-5.

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