CN103980432B - Polycarboxylate water reducer containing modified water-soluble acrylate and preparation method thereof - Google Patents

Abstract

The invention provides a polycarboxylate water reducer containing modified water-soluble acrylate and its preparation method. The preparation method: first react polyhydric alcohol carbohydrates with acrylic acid to directly react and esterify to prepare modified water-soluble Acrylate small monomer; then add polyether macromonomer into deionized water, fully dissolve to make reaction base liquid; dissolve acrylate small monomer, acrylic acid, initiator vitamin C, and chain transfer agent thioglycolic acid in deionized Add the initiator hydrogen peroxide into the reaction base liquid, drop the dripping liquid into the reaction base liquid at a constant speed, stir and react, and then adjust the pH value of the solution to 7-8 to obtain a polycarboxylate superplasticizer . The present invention directly includes the regulating effect of polyhydric alcohol carbohydrates in the water reducing agent, thereby optimizing the performance of the water reducing agent. The polycarboxylate water-reducing agent prepared by the invention has high water-reducing rate, obviously enhanced fluidity retention, and small concrete slump loss, so it can meet relatively high construction requirements.

Description

Polycarboxylate water reducer containing modified water-soluble acrylate and preparation method thereof

technical field

The invention relates to building materials, in particular to a water-reducer, and specifically belongs to a polycarboxylate water-reducer made of water-soluble acrylate modified by polyhydric alcohol carbohydrate esterification and a preparation method thereof.

Background technique

Water reducing agent is an essential component in modern concrete besides cement, sand, stone, water and admixtures. Water reducing agent is an admixture that reduces water consumption under the condition of ensuring the same workability of concrete mixture. The use of water reducing agent can reduce the amount of cement and improve the workability and durability of concrete. It is the core of ready-mixed concrete . It is generally believed that the development of water reducers is divided into three stages: the first generation of ordinary water reducers represented by wood calcium, the second generation of high-efficiency water reducers represented by naphthalene-based water reducers, and the current stage of polymer water reducers. Carboxylic acid superplasticizer is the third generation of high-performance superplasticizer stage.

The current mainstream product in the market is the copolymerization of acrylic acid and unsaturated polyether macromonomer to form polycarboxylate water reducer, and the small monomer is acrylic acid, which is prepared by free radical polymerization. The polymerized polycarboxylate superplasticizer has good performance, high water reducing rate, good retention effect, and good adaptability to cement, but this type of product has high requirements for concrete materials, is sensitive to the dosage, and is resistant to mud The strength is poor.

Glucose, citric acid, sorbitol, dextrin and other small molecule polyhydric alcohol carbohydrates are widely used in concrete building construction as additional retarding regulators. By compounding with high-efficiency polycarboxylate superplasticizers, it can improve Improve the working performance of concrete, increase the fluidity of concrete paste, and delay the setting time of concrete.

In the present invention, firstly, such small molecule polyhydric alcohol carbohydrates are directly reacted and esterified with acrylic acid to prepare water-soluble modified acrylate small monomers, and then the modified small monomers are used to polymerize to prepare polycarboxylic acid water-reducing agent, so that the regulating effect of the polyhydric alcohol regulator is directly included in the water reducing agent, which optimizes the performance of the water reducing agent.

Contents of the invention

The invention aims to provide a polycarboxylate water reducer containing modified water-soluble acrylate and a preparation method thereof.

A polycarboxylate superplasticizer containing modified water-soluble acrylate provided by the present invention is characterized in that the general structural formula is:

In the formula, M is an unsaturated polyether macromonomer, and the general structural formula is:

Wherein: a, b, c, m, n represent degree of polymerization, a=60-140, b=40-140, c=20-35, m=0-2, n=60-130;

R ₁ represents a polyhydric alcohol group, specifically glucose, sorbitol, citric acid, dextrin, etc.;

R ₂ represents —H atom or —CH ₃ group.

A kind of preparation method of the polycarboxylate superplasticizer containing modified water-soluble acrylate provided by the invention, the steps comprise:

(1) Esterification modification of acrylic acid: Add polyhydric alcohol carbohydrates to acrylic acid, then add polymerization inhibitor and catalyst, heat to dissolve, and then carry out esterification reaction at 90-105°C for 4-7 hours to obtain Acrylate small monomer;

The mol ratio of described polyhydric alcohol carbohydrate and acrylic acid is 1:3.2-4;

The catalyst is p-toluenesulfonic acid, and the addition amount is 2%-3.5% of the mass of acrylic acid;

The polymerization inhibitor is hydroquinone, p-quinone or p-methoxyphenol, and the addition amount is 0.5%-4% of the mass of acrylic acid;

The reaction temperature is preferably between 100°C and 105°C. In this reaction process, the reaction temperature needs to be strictly controlled. If it is lower than 100°C, the esterification reaction cannot be completely carried out, and there will be more polyhydric alcohols, and the reaction time needs to be prolonged; if it is higher than 110°C, acrylic acid will occur. Self-polymerization produces a gel-like substance that is insoluble in water.

(2) Utilize acrylate small monomers to carry out copolymerization reaction: add polyoxyethylene ether macromonomers and deionized water in the reactor, heat to make it fully dissolved, and make the reaction bottom liquid; make step (1) The small acrylate monomer, acrylic acid, vitamin C (initiator), and chain transfer agent were dissolved in deionized water to prepare a drop solution; the temperature of the reaction bottom liquid was controlled at 25-30°C, and hydrogen peroxide (initiator) was added, and then The dropping liquid is dropped into the reaction bottom liquid at a constant speed, the dropping time is 2-3 hours, and the reaction is stirred and kept at 25-30°C for 1 hour; then the pH value of the reaction solution is adjusted to 7-8 with aqueous sodium hydroxide solution, and the product containing Polycarboxylate superplasticizer with a solid content of 35-40%.

The molar ratio of the unsaturated polyether macromonomer, water-soluble acrylate small monomer, and acrylic acid is 1:2.8-4:0-2.2;

The dosage of the initiator vitamin C is 0.15%-0.3% of the total mass of the macromonomer;

The amount of hydrogen peroxide used as the initiator is 0.8%-1.5% of the total mass of the macromonomer;

The chain transfer agent is mercaptoacetic acid, and the dosage is 0.5%-1% of the total mass of the macromonomer.

The unsaturated polyether macromonomer is a polyoxyethylene ether macromonomer with a molecular weight range of 2500-5000, specifically a 3-carbon macromonomer allyl polyoxyethylene ether, a 4-carbon macromonomer methyl Allyl polyoxyethylene ether or 5-carbon macromonomer isopentenyl polyoxyethylene ether, etc.

Compared with prior art, advantage and beneficial effect of the present invention:

The novel modified acrylate prepared by the present invention uses polyhydric alcohol carbohydrates such as glucose as the raw material. The raw material is simple, the source is convenient, and it is safe, non-toxic and pollution-free; after the acrylate is prepared, it does not need to be purified and can be used directly In the synthesis of polycarboxylate superplasticizer, the process operation is simple.

The polymerization reaction process adopted in the present invention is polymerization under normal temperature conditions. After the reaction system is added with an initiator, heat will be released due to the polymerization reaction, which will raise the temperature of the reaction system by 5-10°C, so that the entire subsequent reaction process does not need to be heated by a heat source.

In the present invention, the steric hindrance of the water reducer is increased by grafting polyhydric alcohol group-modified acrylate on the main chain of the polycarboxylate water reducer, thus destroying the flocculation structure between cement particles , so that the mixing water between the particles is released, so that the fluidity of the concrete is enhanced; at the same time, the steric resistance of the water reducer increases, which can block the approach of water molecules and cement particles, thereby slowing down the hydration reaction of cement and prolonging the cement life. coagulation time.

Since there are a large number of hydroxyl groups (-OH) on polyhydric alcohols, this polar group can be adsorbed on the surface of cement particles through the action of hydrogen bonds, and has a strong affinity with cement particles, thereby forming a hydration state on the surface of cement particles. Membrane can improve the water reducing rate and enhance the fluidity retention.

During the cement hydration process, the modified acrylate slowly hydrolyzes on the surface of the cement, and continuously releases small molecules of polyhydric alcohol carbohydrates with the function of retarding the setting, so that the retarding effect of the small molecules can be exerted for a longer time, and the water-reducing effect is longer. It avoids the problem that the initial effect is too fast in the one-time addition process, and the later effect is obviously reduced.

In the present invention, compared with the unmodified water reducer, the modified polycarboxylate water reducer has a high water reducing rate, significantly enhanced fluidity retention, and small loss of concrete slump, so it can meet higher requirements. Construction requirements.

detailed description

Below in conjunction with embodiment, comparative example, the present invention is described in further detail.

In the preparation method of water-soluble acrylate listed in the following examples, the polyhydric alcohol carbohydrates such as acrylic acid and glucose, sorbitol, dextrin, citric acid used are all industrial grade products.

In the preparation method of the polycarboxylate superplasticizer listed in the following examples and comparative examples, the industrial grade acrylic acid used, initiator vitamin C and hydrogen peroxide, chain transfer agent thioglycolic acid, and industrial grade sodium hydroxide are all the same batch of products.

Example 1:

In a 500ml reaction flask equipped with a stirrer and a condenser, add 205g of acrylic acid, 144g of glucose, 4.4g of hydroquinone, and 6.88g of p-toluenesulfonic acid, and stir at room temperature for 10 minutes, but the raw materials are not completely dissolved. Heat slowly, and when the temperature rises to 80-90°C, the solution becomes clear and all the raw materials are dissolved. Continue to heat up, starting at 90°C, the color of the reaction solution turns yellow, and gradually turns dark brown, within 1 hour the temperature is raised to 95-100°C and maintained, and the stirring is continued for 4-5 hours to obtain a small water-soluble glucose acrylate monomer.

Add 180g of methallyl polyoxyethylene ether (4-carbon macromonomer) with an average molecular weight of 2500 into 99g of deionized water, heat properly and fully dissolve to make a reaction bottom liquid; Add 54.4g of glucose ester, 10.8g of acrylic acid, and 1.48g of thioglycolic acid into 62.5g of deionized water in sequence, mix and stir evenly, and prepare a dropwise solution; control the reaction temperature at 25-30°C, and add 2.1g of H ₂ O to the reaction bottom solution ₂ , and then drop the dripping solution at a constant speed, and the dropwise addition is completed in 3 hours; after continuing the heat preservation reaction for 1 hour, add a solution made of 18g NaOH and 214g water, and stir evenly to obtain a polycarboxylate superplasticizer.

Example 2:

In a 500ml reaction flask equipped with a stirrer and a condenser, add 205g of acrylic acid, 144g of glucose, 4.4g of hydroquinone, and 6.88g of p-toluenesulfonic acid, and stir at room temperature for 10 minutes, but the raw materials are not completely dissolved. Heat slowly, and when the temperature rises to 80-90°C, the solution becomes clear and all the raw materials are dissolved. Continue to heat up, starting at 90°C, the color of the reaction solution turns yellow, and gradually turns dark brown, within 1 hour the temperature is raised to 95-100°C and maintained, and the stirring is continued for 4-5 hours to obtain a small water-soluble glucose acrylate monomer.

Add 180g of isoprenyl polyoxyethylene ether (5-carbon macromonomer) with an average molecular weight of 5000 into 99g of deionized water, heat properly and fully dissolve to make a reaction bottom liquid; Add 35.2g of glucose ester and 1.48g of thioglycolic acid into 62.5g of deionized water in turn, mix and stir evenly, and prepare a dropwise solution; control the reaction temperature at 25-30°C, add 1.6gH ₂ O ₂ to the reaction bottom solution, and then Add the solution dropwise, and the dropwise addition is completed in 3 hours; after continuing the heat preservation reaction for 1 hour, add a solution made of 8.0g NaOH and 162.2g water, and stir evenly to obtain a polycarboxylate superplasticizer.

Example 3:

Add 233.6g of acrylic acid, 145.6g of sorbitol, 5g of p-methoxyphenol, and 7.12g of p-toluenesulfonic acid into a 500ml reaction flask equipped with a stirrer and a condenser, and stir at room temperature for 10 minutes, but the raw materials are not completely dissolved. Heat slowly, and when the temperature rises to 80-90°C, the solution becomes clear and all the raw materials are dissolved. Continue to heat up, starting at 90°C, the color of the reaction solution turns yellow, and gradually turns dark brown, within 1 hour the temperature is raised to 105-110°C and maintained, and the stirring is continued for 4-5 hours to obtain a small water-soluble sorbitol acrylate monomer .

180g of allyl polyoxyethylene ether (3-carbon macromonomer) with an average molecular weight of 2500 was added to 99g of deionized water, heated and fully dissolved to make a reaction bottom liquid; Add 61.2g of ester and 1.48g of thioglycolic acid into 62.5g of deionized water in sequence, mix and stir evenly, and prepare a dropwise solution; control the reaction temperature at 25-30°C, add 1.6gH ₂ O ₂ into the reaction bottom solution, and then drop at a constant speed Add the dropwise solution, and the dropwise addition is completed in 2 hours; after continuing the heat preservation reaction for 1 hour, add a solution made of 12.8g NaOH and 200g water, and stir evenly to obtain a polycarboxylate superplasticizer.

Example 4:

Add 233.6g of acrylic acid, 145.6g of sorbitol, 4g of p-methoxyphenol, and 7.12g of p-toluenesulfonic acid into a 500ml reaction flask equipped with a stirrer and a condenser, and stir at room temperature for 10 minutes, but the raw materials are not completely dissolved. Heat slowly, and when the temperature rises to 80-90°C, the solution becomes clear and all the raw materials are dissolved. Continue to heat up, starting at 90°C, the color of the reaction solution turns yellow, and gradually turns dark brown, within 1 hour the temperature is raised to 105-110°C and maintained, and the stirring is continued for 4-5 hours to obtain a small water-soluble sorbitol acrylate monomer .

Add 180g of methallyl polyoxyethylene ether (4-carbon macromonomer) with an average molecular weight of 5000 into 99g of deionized water, heat properly and fully dissolve to make a reaction bottom liquid; Add 27.3g of sorbitol ester, 5.4g of acrylic acid, and 1.6g of thioglycolic acid into 62.5g of deionized water in sequence, mix and stir evenly, and prepare a dropwise solution; control the reaction temperature at 25-30°C, and add 2.3g of H ₂ O ₂ , then drop in the dripping solution at a constant speed, and the dropwise addition is completed in 3 hours; after continuing the heat preservation reaction for 1 hour, add a solution made of 9.2g NaOH and 166g water, and stir evenly to obtain a polycarboxylate superplasticizer.

Example 5:

In a 250ml reaction flask equipped with a stirrer and a condenser, add 102.4g of acrylic acid, 78g of dextrin, 4.0g of p-methoxyphenol, and 3.58g of p-toluenesulfonic acid, and stir at room temperature for 10 minutes, but the raw materials are not completely dissolved. Heat slowly, and when the temperature rises to 80-90°C, the system gradually becomes viscous. Continue heating and stirring, starting at 90°C, the raw material gradually dissolves into a solution and turns dark brown. The temperature is controlled at 100-105° C., and the stirring is continued for 4-5 hours to obtain a small water-soluble dextrin acrylate monomer.

Add 180g of isoprenyl polyoxyethylene ether (5-carbon macromonomer) with an average molecular weight of 5000 into 99g of deionized water, heat properly and fully dissolve to make a reaction bottom liquid; Add 35.2g of dextrin ester and 1.48g of thioglycolic acid into 62.5g of deionized water in turn, mix and stir evenly, and prepare a dropwise solution; control the reaction temperature at 25-30°C, add 1.6gH ₂ O ₂ to the reaction bottom solution, and then Add the solution dropwise at a constant speed, and the addition is completed in 2.5 hours; after continuing the heat preservation reaction for 1 hour, add a solution made of 8.0g NaOH and 164.3g water, and stir evenly to obtain a polycarboxylate superplasticizer.

Embodiment 6:

In a 500ml reaction flask equipped with a stirrer and a condenser, add 154g of acrylic acid, 126.6g of citric acid, 3.6g of p-methoxyphenol, and 5.72g of p-toluenesulfonic acid, and stir at room temperature for 10 minutes, but the raw materials are not completely dissolved. Heat slowly, and when the temperature rises to 75-80°C, the solution becomes clear and all the raw materials are dissolved. Continue to heat up, starting at 90°C, the color of the reaction solution turns yellow, and gradually turns dark brown, within 1 hour the temperature is raised to 95-100°C and maintained, and the stirring is continued for 4-5 hours to obtain a water-soluble acrylic acid citrate small monomer .

Add 180g of methallyl polyoxyethylene ether (4-carbon macromonomer) with an average molecular weight of 2500 into 99g of deionized water, properly heat and fully dissolve to make a reaction bottom liquid; Add 54.4g of citrate, 14.4g of acrylic acid, and 1.8g of thioglycolic acid into 62.5g of deionized water in sequence, mix and stir evenly, and prepare a dropwise solution; control the reaction temperature at 25-30°C, and add 2.7gH ₂ O ₂ , then drop in the dripping solution at a constant speed, and the dropwise addition is completed in 3 hours; after continuing the heat preservation reaction for 1 hour, add a solution made of 19.2g NaOH and 218.5g water, and stir evenly to obtain a polycarboxylate superplasticizer.

Comparative example:

Add 180g of methallyl polyoxyethylene ether (4-carbon macromonomer) with an average molecular weight of 2500 into 99g of deionized water, heat properly and fully dissolve to make a reaction bottom liquid; add 0.37g of vitamin C, 19.8g of acrylic acid, Add 1.48g of acetic acid into 62.5g of deionized water in turn, mix and stir evenly, and prepare a dropwise solution; control the reaction temperature at 25-30°C, add 1.6gH ₂ O ₂ into the reaction bottom solution, and then drop into the dropwise solution at a constant speed, The dropwise addition was completed in 3 hours; after the heat preservation reaction was continued for 1 hour, a solution made of 10.4g NaOH and 136.2g water was added and stirred evenly to obtain a comparative polycarboxylate superplasticizer.

Comparative example, embodiment water reducing agent performance comparison:

The polycarboxylate water-reducer prepared in the above examples and the unmodified water-reducer (comparative example) were used to compare the cement slurry test and the concrete slump test, and the properties are shown in Table 1 and Table 2.

a. Clean slurry test: P.O42.5 cement of Hebei Jidong Group was used in accordance with GB/T8077-2000 "Concrete Admixture Homogeneity Test Method", the results are as follows:

Table 1 Experimental results of fluidity of cement slurry

It can be seen from the data in Table 1 that the water reducing agent prepared by the present invention can achieve a higher water reducing rate at the same dosage, and the ability to maintain fluidity is significantly improved. Compared with the comparative example, the water-reducing agent of the present invention has better water-reducing performance and retention capacity, and is more economical in use, which has great popularization significance.

b. Concrete performance test was carried out according to "Standard for Test Method of Ordinary Concrete Mixture Performance" GB/T50080-2002, the results are as follows:

Table 2 Concrete slump test results

It can be seen from Table 2 that in the concrete application examples, the concrete slump using the water reducing agent prepared by the present invention is significantly higher than that of the concrete using the comparative example, and the product of the present invention shows a higher performance than the unmodified water reducing agent. The water-reducing agent has better adsorption and water-reducing performance; the water-reducing agent prepared by the invention can significantly improve the slump retention of concrete, can adapt to a longer construction process, and greatly improves the working performance of concrete.

In addition, the production process of the embodiment of the present invention is an aqueous solution reaction system, the utilization rate of raw materials is high, there are no reaction by-products, and no purification is required. The polymerization process is carried out at room temperature, and the raw materials used and the production process do not produce pungent odors, and there is no "three wastes" emission, and the production process is green and environmentally friendly.

Claims (4)

1. A polycarboxylate water-reducer containing modified water-soluble acrylate, characterized in that general structural formula and preparation method are as follows: Described structural general formula is: In the formula, M is an unsaturated polyether macromonomer, and the general structural formula is: Wherein: a, b, c, m, n represent degree of polymerization, a=60-140, b=40-140, c=20-35, m=0-2, n=60-130; R ₁ is sorbitol, citric acid or dextrin; R ₂ is H or -CH ₃ ; Described preparation method, the steps are: (1) Add polyhydric alcohol carbohydrates to acrylic acid, then add polymerization inhibitor and catalyst, heat to dissolve, and then carry out esterification reaction at 90-105°C for 4-7 hours to obtain small acrylate monomers; The mol ratio of described polyhydric alcohol carbohydrate and acrylic acid is 1:3.2-4; The catalyst is p-toluenesulfonic acid, and the addition amount is 2%-3.5% of the mass of acrylic acid; The polymerization inhibitor is hydroquinone, p-quinone or p-methoxyphenol, and the addition amount is 0.5%-4% of the mass of acrylic acid; (2) Add unsaturated polyether macromonomer and deionized water into the reactor, heat to make it fully dissolved, and make the reaction bottom liquid; the acrylate small monomer, acrylic acid, vitamin C. The chain transfer agent is dissolved in deionized water and prepared as a drop solution; control the temperature of the reaction bottom liquid at 25-30°C, add hydrogen peroxide, and then slowly drop the drop solution into the reaction bottom solution, and the dropping time is 2-3 hours , stirring and heat-retaining at 25-30°C for 1 hour; then using aqueous sodium hydroxide solution to adjust the pH to 7-8 to obtain a polycarboxylate water reducer with a solid content of 35-40%; Described polyhydric alcohol carbohydrate is sorbitol, citric acid or dextrin; The molar ratio of the unsaturated polyether macromonomer, acrylate small monomer and acrylic acid is 1:2.8-4:0-2.2; The amount of vitamin C is 0.15%-0.3% of the total mass of unsaturated polyether macromers; The amount of hydrogen peroxide is 0.8%-1.5% of the total mass of unsaturated polyether macromers; The chain transfer agent is mercaptoacetic acid, and the dosage is 0.5%-1% of the total mass of the unsaturated polyether macromonomer. 2. A polycarboxylate water reducer containing modified water-soluble acrylate according to claim 1, characterized in that the reaction temperature in the step (1) is between 100°C and 105°C. 3. a kind of polycarboxylate water-reducer containing modified water-soluble acrylate as claimed in claim 1, is characterized in that, the unsaturated polyether macromonomer of described step (2) is molecular weight 2500- 5000 polyoxyethylene ether macromonomer. 4. A kind of polycarboxylate water-reducer containing modified water-soluble acrylate as claimed in claim 3, is characterized in that, described polyoxyethylene ether macromonomer is allyl polyoxyethylene ether, Methallyl ethoxylate or isopentenyl ethoxylate.