Preparation method of water-retention and retarding type polycarboxylic water reducing agent

Abstract

This invention discloses a method for preparing a water-retaining and retarding polycarboxylate superplasticizer, belonging to the field of concrete admixture technology. The method includes: using pentenol polyoxyethylene ether and / or methyl allyl polyoxyethylene ether, hydroxyethyl acrylate, hydrogen peroxide, vitamin C, mercaptopropionic acid, acrylic acid, and phosphorus-containing compounds as raw materials, a polycarboxylate superplasticizer is prepared via free radical polymerization; then, hydroxyl and carboxyl compounds are added sequentially for slow modification; after adjusting the system to a strongly alkaline state, refined cotton powder, chloromethane, and propylene oxide are added, and an etherification and crosslinking reaction is carried out under pressure and heating conditions; finally, the product is obtained by pressure filtration, pulverization, and drying. The polycarboxylate superplasticizer prepared by this invention possesses excellent water retention and retarding effects, effectively reducing concrete bleeding and segregation, extending setting time, improving concrete workability and durability, and exhibiting good compatibility with cement, making it suitable for high-temperature construction, large-volume concrete, and manufactured sand concrete projects.

Description

Technical Field

[0001] This invention relates to the field of water-reducing agent technology, specifically to a method for preparing a water-retaining and retarding polycarboxylate water-reducing agent. Background Technology

[0002] Polycarboxylate superplasticizers have become an indispensable key component in modern high-performance concrete engineering due to their advantages such as high water reduction rate, good slump retention, low dosage, rapid concrete strength development, and environmental friendliness. With the rapid development of large-scale projects such as high-speed railways, cross-sea bridges, and super high-rise buildings, concrete construction has placed more stringent requirements on the comprehensive performance of superplasticizers. They not only need to reduce water efficiently, but also need to take into account water retention, retarding properties, workability, and durability to adapt to complex working conditions such as long-distance transportation, high-temperature construction, large-volume concrete pouring, and special structural forming.

[0003] Currently, conventional polycarboxylate superplasticizers still have significant shortcomings in practical applications: On the one hand, ordinary polycarboxylate superplasticizers have weak water retention properties, and concrete is prone to bleeding, segregation, and stratification during mixing, transportation, and pouring, leading to a decrease in concrete homogeneity, surface sanding, and an increase in internal defects. Especially in harsh environments such as high temperatures and strong winds, the slump of concrete is lost too quickly, making it difficult to meet the requirements of long-term construction. On the other hand, conventional superplasticizers do not have a significant retarding effect. In the construction of large-volume concrete, the concentrated release of hydration heat can easily generate temperature stress cracks, affecting structural safety and service life.

[0004] In existing technologies, water-reducing agents, water-retaining agents, and retarders are typically mixed using physical compounding methods. While this can improve the individual properties to some extent, it suffers from poor compatibility, insufficient stability, easy antagonism of active ingredients, and rapid attenuation of effects, making it difficult to achieve a synergistic improvement in water retention, retardation, and water-reducing properties. Furthermore, commonly used retarding components and water-retaining components have poor compatibility, and the compounding process can easily lead to negative effects such as low early strength of concrete, excessively prolonged setting time, and bleeding / slurry return.

[0005] In addition, the traditional methods of introducing water-retaining materials and retarding components are crude and do not effectively combine with polycarboxylate molecular chains. This makes it impossible to achieve functional integration design at the molecular structure level, resulting in poor adaptability of the product under different cement systems and mix proportions. It is difficult to stably meet the comprehensive requirements of high-performance concrete for high water retention, controllable retarding, high water reduction, and high stability. Summary of the Invention

[0006] The present invention proposes a method for preparing a water-retaining and retarding polycarboxylate superplasticizer, which solves the above-mentioned problems existing in the use of the prior art.

[0007] The technical solution of this invention is implemented as follows: A method for preparing a water-retaining and retarding polycarboxylate superplasticizer, characterized by comprising the following steps: S1: Add pentenol polyoxyethylene ether and / or methyl allyl polyoxyethylene ether and hydroxyethyl acrylate to the reaction vessel, dissolve and disperse them at 40~70℃, add hydrogen peroxide, and stir magnetically for 10~30 min to obtain the first mixture. S2: Add vitamin C and mercaptopropionic acid dropwise to the first mixture over a period of 3-6 hours, and add acrylic acid and a phosphorus-containing compound dropwise over a period of 2.5-5.5 hours to obtain the second mixture; S3: Add hydroxyl compound and carboxyl compound to the second mixture, and keep it at 50~70℃ for 1.5~3 h to obtain polycarboxylate superplasticizer; S4: Add strong alkaline solution and glycerin to polycarboxylate superplasticizer to make the system strongly alkaline; S5: Add refined cotton powder to the system obtained in S4, stir and dissolve at high temperature, slowly add chloromethane and propylene oxide, control the temperature at 30~60℃, react at 0.5~0.8 MPa for 20~60 min, then increase the pressure to 1.0~2.3 MPa within 5~40 min, and maintain the pressure at 60~130℃ for 45~120 min.

[0008] Preferably, the stirring method in step S1 is magnetic stirring.

[0009] Preferably, the hydroxyl compound in step S3 is selected from one or more mixtures of phenol, m-methylphenol, o-methylphenol, p-methylphenol, and thiophenol.

[0010] Preferably, the carboxyl compound in step S3 is selected from one or more mixtures of carboxymethyl chitosan, O-carboxymethyl chitosan, and N-carboxymethyl chitosan.

[0011] Preferably, the strong alkaline solution in step S4 is an aqueous solution of sodium hydroxide.

[0012] Preferably, the refined cotton powder in step S5 is obtained by pulverizing refined cotton or wood pulp.

[0013] Preferably, after the pressure-holding reaction in step S5 is completed, a post-processing step S6 is further included: the product is sequentially subjected to pressure filtration, wet pulverization, dry pulverization, and packaging.

[0014] A water-retaining and retarding polycarboxylate superplasticizer, characterized in that it is prepared by a method for preparing a water-retaining and retarding polycarboxylate superplasticizer.

[0015] In summary, this invention integrates three major functions—high-efficiency water reduction, controllable retardation, and long-lasting water retention—through molecular structure design and functionalized composite modification. Compared with traditional polycarboxylate superplasticizers and physically compounded products, it has the following significant advantages: 1. Excellent water-reducing performance, significantly improving the workability of concrete. This invention employs precise copolymerization of polyether macromonomers and monomers such as acrylic acid, retaining the advantages of conventional polycarboxylate superplasticizers such as high water reduction rate and low dosage. It can significantly reduce the water-cement ratio of concrete, improve the fluidity, cohesiveness and encapsulation of concrete, effectively avoid segregation and bleeding, and meet the requirements of long-term transportation and continuous construction.

[0016] 2. The retarding effect is controllable, making it suitable for large-volume and high-temperature construction. By introducing specific hydroxyl and carboxyl compounds as retarding components, mild retarding is achieved through chemical bonding and synergistic effects. This allows for precise control of concrete setting time, avoids concentrated release of hydration heat, significantly reduces the risk of cracking in large-volume concrete, and does not affect the later strength development of concrete. It is suitable for high-temperature, long-distance, and large-area pouring conditions.

[0017] 3. Excellent water retention performance, improving the homogeneity and durability of concrete. The water-retaining components, prepared from refined cotton, glycerin, chloromethane, propylene oxide, etc., are highly compatible with the main body of the water-reducing agent. They can form a stable water-retaining structure in the concrete system, significantly reduce water evaporation and loss, improve plastic shrinkage of concrete, reduce surface sanding and honeycomb pitting, and improve concrete density and long-term durability.

[0018] 4. Integrated functionality, enhanced stability and adaptability This invention employs in-situ compounding and chemical modification, rather than simple physical compounding. The functional components work synergistically and stably without antagonistic effects, solving problems such as stratification, precipitation, and effect attenuation in traditional compound products. It is more adaptable to different cements, admixtures, and mix proportions, and has stable and reliable construction performance.

[0019] 5. The process is highly controllable and suitable for industrial production. The preparation process is mild, with easily controllable temperature and pressure ranges. The reaction path is clear and reproducible, and the post-processing is simple, making it suitable for large-scale industrial production. It can be widely used in high-performance concrete, precast components, large-volume projects, tunnels, and water conservancy projects. Detailed Implementation

[0020] 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. Example

[0021] Raw material ratio (parts by mass): Pentenol polyoxyethylene ether: 80 parts Hydroxyethyl acrylate: 15 parts Hydrogen peroxide (30%): 2.5 parts Vitamin C: 0.8 parts Mercaptopropionic acid: 1.2 parts Acrylic acid: 18 parts Phosphorus-containing compound (sodium hypophosphite): 3 parts Hydroxy compound (phenol): 5 parts Carboxylated compound (carboxymethyl chitosan): 4 parts Strong alkaline solution (30% NaOH solution): 20 parts Glycerin: 10 parts Refined cotton powder: 25 parts Chloromethane: 30 parts Propylene oxide: 15 parts Preparation steps: S1: Add 80 parts of pentenol polyoxyethylene ether and 15 parts of hydroxyethyl acrylate to a four-necked flask, heat to 55°C, and after magnetic stirring to disperse evenly, add 2.5 parts of hydrogen peroxide and continue stirring for 20 min to obtain the first mixture. S2: Add 0.8 parts of vitamin C and 1.2 parts of mercaptopropionic acid dropwise through port A for 4 hours; simultaneously add 18 parts of acrylic acid and 3 parts of sodium hypophosphite dropwise through port B for 3.5 hours to obtain the second mixture.

[0022] S3: Add 5 parts phenol and 4 parts carboxymethyl chitosan to the second mixture, heat to 60°C, and keep warm for 2 hours to obtain polycarboxylate superplasticizer.

[0023] S4: Add 20 parts of 30% NaOH solution and 10 parts of glycerol to the above polycarboxylate superplasticizer to adjust the system to strong alkalinity (pH about 12~13).

[0024] S5: Add 25 parts of refined cotton powder, heat to 80℃, and stir at high temperature to dissolve. Slowly add 30 parts of chloromethane and 15 parts of propylene oxide, control the temperature at 45℃, and react at 0.6 MPa for 40 min; then increase the pressure to 1.8 MPa within 20 min, and heat to 100℃, and maintain the pressure for 90 min.

[0025] S6: After the reaction is complete, the mixture is sequentially subjected to pressure filtration, wet pulverization, and dry pulverization, and finally packaged to obtain a water-retaining and retarding polycarboxylate superplasticizer. Example

[0026] Raw material ratio (parts by mass): 100 parts of methyl allyl polyoxyethylene ether Hydroxyethyl acrylate: 20 parts Hydrogen peroxide (30%): 3 parts Vitamin C: 1.0 serving Mercaptopropionic acid: 1.5 parts Acrylic acid: 22 parts Phosphorus-containing compounds (phosphorous acid): 4 parts Hydroxy compound (m-methylphenol and thiophenol in a 1:1 mass ratio): 6 parts Carboxyl compound (O-carboxymethyl chitosan): 5 parts Strong alkaline solution (40% KOH solution): 25 parts Glycerin: 12 parts Refined cotton powder: 30 parts Chloromethane: 35 parts Propylene oxide: 18 parts Preparation steps: S1: Add 100 parts of methyl allyl polyoxyethylene ether and 20 parts of hydroxyethyl acrylate to a four-necked flask, heat to 65°C, and after magnetic stirring to disperse evenly, add 3 parts of hydrogen peroxide and stir for 15 min to obtain the first mixture.

[0027] S2: Add 1.0 part of vitamin C and 1.5 parts of mercaptopropionic acid dropwise through port A for 5 hours; simultaneously add 22 parts of acrylic acid and 4 parts of phosphorous acid dropwise through port B for 4.5 hours to obtain the second mixture.

[0028] S3: Add 6 parts of mixed hydroxyl compound (m-methylphenol:thiophenol = 1:1) and 5 parts of O-carboxymethyl chitosan to the second mixture, heat to 65°C, and keep warm for 2.5 h to obtain polycarboxylate superplasticizer.

[0029] S4: Add 25 parts of 40% KOH solution and 12 parts of glycerol to adjust to strong alkalinity.

[0030] S5: Add 30 parts of refined cotton powder and heat to 85℃ to dissolve. Slowly add 35 parts of chloromethane and 18 parts of propylene oxide, control the temperature at 55℃, and react at 0.7 MPa for 50 min; then increase the pressure to 2.0 MPa and heat to 110℃ within 30 min, and maintain the pressure for 100 min.

[0031] S6: Filter press, wet pulverization, dry pulverization, and packaging to obtain the product.

[0032] Example 3 (Preferred Formula) Raw material ratio (parts by mass): Pentenol polyoxyethylene ether: 60 parts 40 parts of methyl allyl polyoxyethylene ether Hydroxyethyl acrylate: 18 parts Hydrogen peroxide (30%): 2.8 parts Vitamin C: 0.9 parts Mercaptopropionic acid: 1.3 parts Acrylic acid: 20 parts Phosphorus-containing compound (sodium hypophosphite): 3.5 parts Hydroxyl compound (p-methylphenol): 5.5 parts Carboxyl compound (N-carboxymethyl chitosan): 4.5 parts Strong alkaline solution (30% NaOH solution): 22 parts Glycerin: 11 parts Refined cotton powder: 28 parts Chloromethane: 32 parts Propylene oxide: 16 parts The preparation steps are the same as in Example 1, wherein: S1 temperature: 60℃, stirring time: 25 min; S2 addition time: Vitamin C / mercaptopropionic acid 4.5 h, acrylic acid / phosphorus-containing compound 4 h; S3 insulation: 65℃, 2 h; S5: Control the temperature at 50℃ and the pressure at 0.65 MPa for 45 min, increase the pressure to 2.0 MPa within 20 min, and maintain the pressure at 105℃ for 80 min.

[0033] The products obtained in the above embodiments all have excellent water retention and retarding effects, which can significantly reduce concrete bleeding and segregation, prolong setting time, and have good compatibility with cement.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a water-retention and retarding type polycarboxylic water reducing agent, characterized by, Includes the following steps: S1: Add pentenol polyoxyethylene ether and / or methyl allyl polyoxyethylene ether and hydroxyethyl acrylate to the reaction vessel, dissolve and disperse them at 40~70℃, add hydrogen peroxide, and stir magnetically for 10~30 min to obtain the first mixture. S2: Add vitamin C and mercaptopropionic acid dropwise to the first mixture over a period of 3-6 hours, and add acrylic acid and a phosphorus-containing compound dropwise over a period of 2.5-5.5 hours to obtain the second mixture; S3: Add hydroxyl compound and carboxyl compound to the second mixture, and keep it at 50~70℃ for 1.5~3 h to obtain polycarboxylate superplasticizer; S4: Add strong alkaline solution and glycerin to polycarboxylate superplasticizer to make the system strongly alkaline; S5: Add refined cotton powder to the system obtained in S4, stir and dissolve at high temperature, slowly add chloromethane and propylene oxide, control the temperature at 30~60℃, react at 0.5~0.8 MPa for 20~60 min, then increase the pressure to 1.0~2.3 MPa within 5~40 min, and maintain the pressure at 60~130℃ for 45~120 min.

2. The preparation method of a water-retaining and retarding polycarboxylate superplasticizer according to claim 1, characterized in that, The stirring method in step S1 is magnetic stirring.

3. The preparation method of a water-retaining and retarding polycarboxylate superplasticizer according to claim 1, characterized in that, The hydroxyl compound in step S3 is selected from one or more mixtures of phenol, m-methylphenol, o-methylphenol, p-methylphenol, and thiophenol.

4. The preparation method of a water-retaining and retarding polycarboxylate superplasticizer according to claim 1, characterized in that, The carboxyl compound mentioned in step S3 is selected from one or more mixtures of carboxymethyl chitosan, O-carboxymethyl chitosan, and N-carboxymethyl chitosan.

5. The preparation method of a water-retaining and retarding polycarboxylate superplasticizer according to claim 1, characterized in that, The strong alkaline solution mentioned in step S4 is an aqueous solution of sodium hydroxide.

6. The preparation method of a water-retaining and retarding polycarboxylate superplasticizer according to claim 1, characterized in that, The refined cotton powder mentioned in step S5 is obtained by pulverizing refined cotton or wood pulp.

7. The preparation method of a water-retaining and retarding polycarboxylate superplasticizer according to claim 1, characterized in that, After the pressure-holding reaction in step S5 is completed, the post-processing step S6 is also included: the product is sequentially subjected to pressure filtration, wet pulverization, dry pulverization and packaging.

8. A water-retaining and retarding polycarboxylate superplasticizer, characterized in that, It is prepared by any one of claims 1 to 7.