CN101293946B - Preparation method of air-entraining controllable polycarboxylate water reducer - Google Patents

Abstract

The invention relates to a method for preparing an air entrainment-controllable polycarboxylate water-reducing agent. The method comprises the following steps: an aqueous solution of polyethylene glycol methyl ether methacrylate and methylacrylic acid is added dropwise into 75-80 DEG C water and an aqueous initiator solution is added dropwise in water at the same time, the temperature is maintained at 75-80 DEG C and the addition of reactants is completed within 6-7 hours, the temperature is maintained at 78-80 DEG C for 2-3 hours, the reaction product is naturally cooled down to room temperature and neutralized with a diluted alkali solution until the pH value is in the range from 6.5 to 7.5, and the air entrainment-controllable polycarboxylate water-reducing agent is obtained. The method has the advantages of simple synthetic processing equipment, controllable reaction conditions, no pollution, low cost and suitability for industrialized production. Under the condition of low mixing amount, the synthesized air entrainment-controllable polycarboxylate water-reducing agent exhibits high water-reducing rate, good fluidity and fluidity retention, and controllability in air content; and can efficiently increase concrete workability, prevent the bleeding and segregation of concrete and improve the frost resistance and water impermeability of hydraulic concrete.

Description

Preparation method of air-entraining controllable polycarboxylate water reducer

technical field

The invention belongs to a preparation method of a concrete water reducer, in particular to a preparation method of an air-entraining controllable polycarboxylate water reducer.

technical background

In my country, high-efficiency water reducers are widely used in industrial and civil buildings. With the development of construction technology and construction technology, high-strength concrete, high-fluidity concrete, and commercial concrete have developed rapidly in recent years, and these concretes must be mixed with high-efficiency water-reducing agents or composite water-reducing agents with high-efficiency water-reducing agents. The development of coastal development zones, Shanghai, Tianjin, Beijing and other places is particularly prominent. In addition, steam-cured, high-durability, high-impermeability concrete, bridges, sleepers and other concrete must also be mixed with superplasticizers. In recent years, my country's commercial concrete has developed at an alarming rate. In 1999, the total national output was 54.14 million cubic meters, and in 2000 it was 78.33 million cubic meters. In 2002, there were 26 cities with commercial concrete output exceeding one million cubic meters. These 26 cities The total output of concrete reached 110 million cubic meters. As the fifth component of concrete, high-efficiency superplasticizers have been widely used in various concretes. By the end of 2005, there were more than 200 synthetic high-efficiency superplasticizers in the country, including nearly 80 large-scale enterprises, with an annual output of high-efficiency superplasticizers. 1.11 million tons, with an annual sales revenue of about 5.1 billion yuan, ranking first in the world. At present, the most important product of high-efficiency water reducer is naphthalene-based water-reducer, but because the water-reducing rate of naphthalene-based high-efficiency water-reducer is not too high, the concrete slump loss is too fast, and the alkali content is high, it is difficult to meet the construction requirements of high-performance concrete. Requirements, while the performance of compound products is very unstable, which often affects the construction and performance of concrete. In addition, the synthetic raw material formaldehyde pollutes the environment, the process is relatively complicated, and the requirements for equipment are relatively high. All these have prompted the development of high-performance water reducers to a new generation of products.

On the one hand, due to the high performance of concrete superplasticizers and the need to prepare ultra-high-strength, ultra-durable, and high-fluidity concrete, on the other hand, traditional high-efficiency water-reducing agents have been unable to meet the needs of modern high-performance concrete development. The new polycarboxylate system Concrete high-performance water-reducing agent has been widely concerned at home and abroad for its high water-reducing rate, low slump loss, low alkali content, and good compatibility with cement. It has become a research hotspot in various countries in the world in recent years.

Polycarboxylate concrete high-performance water reducer is the third generation of high-performance chemical water reducer after the common water reducer represented by wood calcium and the high-efficiency water reducer represented by naphthalene. The synthesis of polycarboxylate water reducer belongs to the category of fine chemicals, and the products are used in construction engineering materials. The single product has become an important problem restricting the development of polycarboxylate superplasticizers. Due to the lack of research on the function control of water reducers, the diversified development of products cannot be realized.

Due to the air-entraining effect, a large number of tiny and independent air bubbles can be introduced into the concrete. These spherical air bubbles, like balls, greatly improve the workability of the concrete. Because the air bubbles increase the volume of the slurry and the lubrication of the mixture, as well as increase the viscosity and yield stress of the slurry, the air-entraining property of the water reducer can significantly improve the workability, plasticity and cohesion of the concrete. Professor Huang Shiyuan's research shows that the introduction of 4% air content in concrete can increase the impermeability of concrete by more than 15%. In recent years, many scholars in China have suggested adding air-entraining agents when using antifreeze in winter. They believe that air-entraining agents can reduce the frost heaving force of concrete in the early stage of freezing. It can be seen that proper air-entrainment in concrete can improve the workability of concrete, strengthen the interface transition zone, and improve the frost resistance and impermeability of hydraulic concrete. However, if there is too much air-entrainment, the concrete strength will decrease. Generally speaking, if the air-entrainment amount is greater than 4%, the air-entrainment amount will increase by 1%, and the concrete strength will decrease by 3% to 5%.

In the traditional method, the air-entraining agent is usually compounded in the water reducing agent to control its air content. There are many types of air-entraining agents, and the air-entraining effects vary greatly. At the same time, there are also compatibility problems with water reducing agents. The air-entraining controllable polycarboxylate water-reducer prepared by the present invention does not need post-compounding. During the synthesis of the water-reducer, by adjusting the molecular weight of polyethylene glycol monomethyl ether methacrylate, adjusting the carboxyl side chain and polyoxygen Vinyl side chain ratio to adjust the air content of the water reducing agent. Compared with the traditional method, the invention does not need follow-up process treatment, has stable air-entraining property, good compatibility with cement, can effectively avoid problems such as bleeding, segregation, and hardening, and improves the workability of concrete.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of single polycarboxylate superplasticizer parent product and the instability of traditional post-combination technology, realize the control of gas content in the synthesis process, and promote the diversified development of polycarboxylate superplasticizer parent product .

The invention is formed by polymerizing polyethylene glycol monomethyl ether methacrylate and methacrylic acid. The water reducing agent synthesized by this method contains carboxyl group and polyoxyethylene hydrophilic side chain group, which has good dispersion and dispersion retention for cement particles. By adjusting polyethylene glycol monomethyl ether methacrylate Molecular weight, adjust the ratio of carboxyl side chain and polyoxyethylene side chain, so as to control the air-entraining amount of the copolymer water reducer, which can effectively improve the workability of concrete and prevent concrete bleeding and segregation. At the same time, according to the different requirements of the actual project on the air-entraining property, a water reducer that meets the needs of the project can be synthesized. Simultaneously, the synthesis process equipment is simple, the reaction conditions are simple and easy to control, no pollution, low cost and easy to industrialized production.

The technical solution provided by the present invention is: the preparation method of air-entraining controllable polycarboxylate water reducer, in water at 75-80 °C, while adding polyethylene glycol monomethyl ether methacrylate and methacrylic acid dropwise Aqueous solution, while adding the initiator aqueous solution dropwise, the temperature is maintained at 75-80°C, the reactant is dropped within 6-7h, kept at 78-80°C for 2-3h, naturally cooled to room temperature, neutralized with dilute alkali solution to pH=6.5 ～7.5, the air-entraining controllable polycarboxylate water reducer is obtained; the weight percentage of the reactant components in the synthesis process is:

Methacrylic acid: 4-6%

Polyethylene glycol monomethyl ether methacrylate: 15-18%

Initiator: 0.7-0.9%

Water: 77-79%

The amount of water in polyethylene glycol monomethyl ether methacrylate and methacrylic acid aqueous solution is 24-27wt% of the total water amount, and the water amount in the initiator aqueous solution is 36-40wt% of the total water amount.

The above-mentioned initiator is a mixture of sodium bisulfite and ammonium persulfate, and its mass ratio is 1: (15-31).

The molecular weight of the polyethylene glycol monomethyl ether methacrylate is 400-2000, the defoaming time of the water reducing agent is in the range of 70-110s, and the air content of the concrete is in the range of 2-8%.

Compared with the previous polycarboxylate water reducers, the present invention has simple synthesis process equipment, simple and easy control of reaction conditions, no pollution, low cost and easy industrial production, and the synthesized air-entraining controllable polycarboxylate water reducer At a lower dosage, it has high water reducing rate, good fluidity and flow retention, can control air content, can effectively improve concrete workability, prevent concrete bleeding and segregation, strengthen interface transition zone, and improve hydraulic engineering. Frost resistance and impermeability of concrete.

The air-entraining controllable polycarboxylate water reducer of the present invention has strong product adaptability and is suitable for various types of cement. When the water reducing agent with a concentration of 20wt% is used and the dosage is 1.0% of the cement weight, the water reducing rate can reach 30%, and the air content of the concrete can be controlled within the range of 2-8%. The prepared concrete is 3d, 28d, 90d The compressive strength can be increased by 60%, 50%, and 30% respectively. In addition, it has low alkali content, does not contain chloride ions, and is non-corrosive to steel bars; it can be widely used in various dams, bridges, railways and other large-scale high-strength and high-performance concrete buildings that have high requirements for durability. The product does not contain formaldehyde, does not pollute the environment, and has stable performance.

Description of drawings

Fig. 1 is the molecular weight of polyethylene glycol monomethyl ether methacrylate used in the present invention and the defoaming time relation diagram of the water reducer of the present invention;

Figure 2 is a graph showing the relationship between the molecular weight of polyethylene glycol monomethyl ether methacrylate used in the present invention and the gas content of the water reducer of the present invention.

Detailed ways

Example 1:

Add 138.65g of water into the reactor, and when it is preheated to 75-80°C, add dropwise On the other side, add dropwise a mixed solution consisting of 0.125g sodium bisulfite, 3.875g ammonium persulfate and 138.65g water, drop it in 6~7h, keep it warm for 2~3h after the reaction, cool to room temperature, and use hydrogen Sodium oxide adjusts pH=6.5-7.5 to obtain the air-entraining controllable polycarboxylate water reducer of the present invention. Experiments have proved that the defoaming time of the water reducer is 80s, and the air content of the prepared concrete is 4.5%.

Example 2:

Add 138.65g of water into the reactor, and when it is preheated to 75-80°C, add dropwise On the other side, add dropwise a mixed solution consisting of 0.125g sodium bisulfite, 3.875g ammonium persulfate and 138.65g water, drop it in 6~7h, keep it warm for 2~3h after the reaction, cool to room temperature, and use hydrogen Sodium oxide adjusts pH=6.5-7.5 to obtain the air-entraining controllable polycarboxylate water reducer of the present invention. Experiments have proved that the defoaming time of the water reducer is 30s, and the air content of the prepared concrete is 3.0%.

Example 3:

Add 138.65g of water into the reactor, and when it is preheated to 75-80°C, add dropwise On the other side, add dropwise a mixed solution consisting of 0.25g sodium bisulfite, 3.75g ammonium persulfate and 138.65g water, drop it in 6~7h, keep it warm for 2~3h after the reaction, cool to room temperature, and use hydrogen Sodium oxide adjusts pH=6.5-7.5 to obtain the air-entraining controllable polycarboxylate water reducer of the present invention. Experiments have proved that the defoaming time of the water reducer is 22s, and the air content of the prepared concrete is 2.0%.

Fig. 1 and Fig. 2 are diagrams of experimental results of the relationship between the molecular weight of different polyethylene glycol monomethyl ether methacrylates and the defoaming time and gas content of the water reducer of the present invention. The experiment proves (referring to Fig. 1, Fig. 2), the present invention can control the polycarboxylate superplasticizer long side chain polyoxyethylene base molecular weight (that is methacrylic acid polyethylene glycol monomethyl ether) by adjusting product air-entraining Molecular weight 400~2000) ratio, so as to realize the controllability of air-entrained polycarboxylate superplasticizer.

Claims (2)

1. the preparation method of a bleed air bleed air controllable polycarboxylic acids water reducing agents, it is characterized in that: in 75～80 ℃ water, drip Methylacrylic acid polyethylene glycol single armor ether ester and methacrylic aqueous acid on one side, drip initiator solution on one side, temperature keeps 75～80 ℃, drips off reactant in 6～7h, 78～80 ℃ of insulation 2～3h, naturally cool to room temperature, be neutralized to pH=6.5～7.5, obtain bleed air bleed air controllable polycarboxylic acids water reducing agents with dilute alkaline soln; The weight percent of reactant composition is in the building-up process:

Methacrylic acid: 4-6%

Methylacrylic acid polyethylene glycol single armor ether ester: 15-18%

Initiator: 0.7-0.9%

Water: 77-79%

Wherein the amount of water is that the amount of water is the 36-40wt% of Total Water among the 24-27wt%, initiator solution of Total Water in Methylacrylic acid polyethylene glycol single armor ether ester and the methacrylic aqueous acid.

2. preparation method according to claim 1 is characterized in that: initiator is the mixture of sodium bisulfite and ammonium persulphate, and its mass ratio is 1: (15～31).

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