CN112457452B - Degradable water reducing agent and synthesis method thereof - Google Patents

Abstract

The invention discloses a degradable water reducing agent and a synthesis method thereof, and specifically comprises the following steps: mixing (2-phosphonic acid-propylene) malonic acid, epoxy succinic acid and water, and adjusting the pH value to 6-8 to obtain a mixed monomer solution; stirring and heating allyloxy polyoxyethylene ether macromonomer and an initiator to 80-90 ℃, dropwise adding the mixed monomer solution obtained in the step (1), continuously reacting at constant temperature for 2-3 hours after dropwise adding is completed after 3-4 hours, cooling to below 50 ℃, and adjusting the pH value to 6-7 to obtain the degradable water reducer. The water reducer synthesized by the invention has high dispersibility, high slump retentivity and high retardation, effectively improves the performance of various low-activity concrete, has biodegradability, is degraded within a certain period of time when being exposed to the environment, and is an environment-friendly water reducer.

Description

Degradable water reducing agent and synthesis method thereof

Technical Field

The invention belongs to the technical field of concrete additional materials, and particularly relates to a degradable water reducing agent and a synthesis method thereof.

Background

With the continuous progress of the construction technology level in China and the updating of building facilities, the requirement on the performance of the concrete of the infrastructure material is higher and higher, and the concrete with high strength, high fluidity and high durability is favored. The concrete is prepared by mixing cement as cementing material, sand and stone as aggregate and water in certain proportion, and through stirring, forming and curing. The common building material concrete is mixed with additives for improving the material performance, the common additives comprise water reducing agents, retarders, air entraining agents, early strength agents, antifreezing agents, expanding agents and the like, and the water reducing agents are the most main components.

Due to the gradual depletion of concrete raw material resources such as traditional natural river sand, high-quality fly ash and the like, artificial aggregate, coal gangue, desulfurized ash and other low-activity industrial waste residues are gradually used in modern concrete, so that the adaptability of the traditional water reducing agent in a new concrete component system is increasingly poor. In practical application, the performance of the water reducing agent is influenced by new factors such as cement components and artificial aggregates, so that the defects of poor adaptability, high sensitivity and the like of novel cement concrete are easily caused, and the development of concrete technology is limited. The novel polycarboxylic acid water reducing agent has become an important product in the concrete admixture market at present due to the advantages of low mixing amount, high water reducing rate, good slump retaining property, strong molecular structure adjustability, environmental protection and the like. However, the simple polycarboxylic acid water reducing agent has poor adaptability to the retarding effect of low-activity admixture concrete, and the natural degradability is required with the enhancement of environmental awareness, so that modification treatment is required. Patent CN106905362B utilizes the reaction of acrylic acid and phosphorus trichloride to generate hydroxyl propylenediphosphonic acid with retarding effect. The patent CN105713150A introduces phosphate groups into a main chain structure of the block polycarboxylic acid with definite sequence structure distribution, so that the adsorption capacity of the block polycarboxylic acid is enhanced, the prepared water reducing agent has obvious sulfate resistance, and the water reducing, slump retaining and cement adaptability are obviously improved. The patent CN106008853A discloses a preparation method of a mud-resistant slump-retaining phosphate-containing polycarboxylic acid water reducer, which comprises the steps of firstly carrying out prepolymerization on unsaturated halohydrocarbon, unsaturated polyether and unsaturated carboxylic acid free radicals, and then carrying out Arbuzov reaction on the prepolymerized unsaturated halohydrocarbon and alkyl phosphate to obtain a phosphate-based copolymerization product. The patent CN107337749A provides a ternary polymerization phosphonic acid based concrete retarder and a preparation method thereof, and the retarder is mainly prepared by synthesizing an intermediate from 2-acrylamide-2-methyl propanesulfonic Acid (AMPS), a carboxylic acid or ester group monomer and (methyl) allyl chloride under the action of an initiator and a chain transfer agent, and then performing phosphinite acidification.

The patent CN111087422A of the present company provides a method for synthesizing monomer (2-phosphonic acid-propylene) malonic acid, which realizes coexistence of phosphonic acid groups and carboxyl groups in units, and the polycarboxylic acid water reducing agent prepared by polymerization with alkenyl polyoxyethylene ether macromonomer has high dispersibility, high slump retentivity and obvious retardation effect, is suitable for various concretes prepared by using low-activity fillers, and simultaneously effectively reduces unit dosage of the water reducing agent.

In summary, the modification of polycarboxylic acid water reducing agents is mainly focused on improving the water reducing performance, and the biodegradability of the polycarboxylic acid water reducing agents is not considered. Therefore, the research on the biodegradable water reducing agent and the synthesis method thereof has important significance.

Disclosure of Invention

Aiming at the problem of poor biodegradability of the water reducing agent in the prior art, the invention provides a degradable water reducing agent and a synthesis method thereof, the synthesized polycarboxylic acid water reducing agent has high dispersibility, high slump retentivity and high retardation, effectively improves the performances of various low-activity concrete, has biodegradability, is degraded within a certain period of time when exposed to the environment, and is an environment-friendly water reducing agent.

The invention is realized by the following technical scheme:

a degradable water reducing agent is synthesized by the following method:

(1) mixing (2-phosphonic acid-propylene) malonic acid, epoxy succinic acid and water, and adjusting the pH value to 6-8 to obtain a mixed monomer solution;

(2) stirring and heating allyloxy polyoxyethylene ether macromonomer and an initiator to 80-90 ℃, dropwise adding the mixed monomer solution obtained in the step (1), continuously reacting at constant temperature for 2-3 hours after dropwise adding is completed after 3-4 hours, cooling to below 50 ℃, and adjusting the pH value to 6-7 to obtain the degradable water reducer.

Further, the mass ratio of the (2-phosphonic acid-propylene) malonic acid, the epoxy succinic acid and the water in the step (1) is 1: 0.5-1: 1.5-2.

Further, the molecular weight of the allyloxy polyoxyethylene ether macromonomer in the step (2) is 1000-1500, and the amount of the allyloxy polyoxyethylene ether macromonomer is 1-1.5 times of the mass of (2-phosphonic acid-propylene) malonic acid.

Further, the amount of the initiator used in the step (2) is 5-10% of the mass of the epoxy succinic acid.

Further, in the step (1), 50% by mass of sodium hydroxide is used for adjusting the pH.

Further, the initiator in the step (2) is calcium hydroxide or molecular sieve immobilized potassium hydroxide.

Further, diluting the degradable water reducing agent in the step (2) to obtain a water reducing agent solution.

Advantageous effects

According to the invention, (2-phosphonic acid-propylene) malonic acid, epoxy succinic acid and an alkenyl polyoxyethylene ether macromonomer are used for anionic polymerization to synthesize the polycarboxylic acid water reducer, which has high dispersibility, high slump retentivity and high retardation, effectively improves the performances of various low-activity concretes, has biodegradability, is degraded within a certain period of time when exposed to the environment, and is an environment-friendly water reducer.

Detailed Description

The present invention is described in detail below by way of examples, which are intended to be illustrative only and not to be construed as limiting the scope of the invention, and one skilled in the art will be able to make variations within the scope of the invention based on the disclosure herein, in reagents, catalysts and reaction process conditions. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Part of raw material specifications are as follows:

the molecular weight of the allyloxy polyoxyethylene ether macromonomer is 1000, and the purity is 98%;

the purity of the epoxy succinic acid is 98 percent;

the purity of (2-phosphonic acid-propylene) malonic acid is 98%.

Example 1

(1) Uniformly mixing 1000g of (2-phosphonic acid-propylene) malonic acid, 500g of epoxy succinic acid and 1500g of deionized water, and adjusting the pH value to 7.2 by using a sodium hydroxide solution with the mass fraction of 50% to obtain 3603g of a mixed monomer solution;

(2) adding 1000g of allyloxy polyoxyethylene ether macromonomer and 25g of calcium hydroxide into a reaction kettle, stirring and heating to 82 +/-2 ℃, dropwise adding the mixed monomer solution into the reaction kettle at the flow rate of 18g/min, after 3.3h, continuing to react at 82 +/-2 ℃ for 2h, stopping the reaction, reducing the temperature to 49 ℃, adjusting the pH value of the system to 6.8 by using 50 mass percent of sodium hydroxide aqueous solution, diluting with water, and filtering to obtain 6783g of a light yellow degradable water reducing agent solution with the mass percent of 40.32%, which is recorded as R1.

Detecting the residual quantity of the monomer: 0.02% of (2-phosphonic acid-propylene) malonic acid and 0.4% of allyloxy polyoxyethylene ether macromonomer.

Example 2

(1) Uniformly mixing 800g of (2-phosphonic acid-propylene) malonic acid, 800g of epoxy succinic acid and 1600g of deionized water, and adjusting the pH value to 7.5 by using a sodium hydroxide solution with the mass fraction of 50% to obtain 4169g of a mixed monomer solution;

(2) adding 1200g of allyloxy polyoxyethylene ether macromonomer and 80g of molecular sieve immobilized potassium hydroxide into a reaction kettle, stirring and heating to 88 +/-2 ℃, dropwise adding the mixed monomer solution into the reaction kettle at the flow rate of 22g/min, after 3.9h, continuing to react at 88 +/-2 ℃ for 3h, stopping the reaction, cooling to 50 ℃, adjusting the pH value of the system to 6.5 by using 50% by mass of sodium hydroxide aqueous solution, diluting with water, and filtering to obtain 7906g of a light yellow degradable water reducing agent solution with the mass fraction of 40.17%, which is recorded as R2.

Detecting the residual quantity of the monomer: 0.01% of (2-phosphonic acid-propylene) malonic acid and 0.3% of allyloxy polyoxyethylene ether macromonomer.

Comparative example 1

(1) Uniformly mixing 400g of acrylic acid and 400g of deionized water to obtain 800g of monomer solution with the mass fraction of 50%;

(2) adding 600g of allyloxy polyoxyethylene ether macromonomer into a reaction kettle, keeping the temperature of the reaction kettle at 30 +/-2 ℃ under stirring, simultaneously dropwise adding 700g of VC-hydrogen peroxide solution with the mass fraction of 27% according to the flow rate of 3.5g/min, dropwise adding mixed monomer solution according to the flow rate of 4g/min, continuing to react for 3 hours after dropwise adding is finished after 20 minutes, adjusting the pH value of the system to be 6.3 by using sodium hydroxide aqueous solution with the mass fraction of 50%, adding water for diluting, and filtering to obtain 2807g of polycarboxylic acid water reducing agent solution with the mass fraction of 40.05%, wherein the weight fraction is recorded as S1.

Detecting the residual quantity of the monomer: 0.6 percent of allyloxy polyoxyethylene ether macromonomer.

Comparative example 2

(1) Preparing 144g of acrylic acid, 896g of (2-phosphonic acid-propylene) malonic acid and 1040g of deionized water into a mixed monomer solution, and adjusting the pH value to 6.7 by using a sodium hydroxide solution with the mass fraction of 50% to obtain 2720g of the mixed monomer solution;

(2) adding 1000g of allyloxy polyoxyethylene ether macromonomer into a reaction kettle, dropwise adding an initiator aqueous solution and the mixed monomer solution obtained in the step (1) into an initiation system which adopts a Vc-H2O2 system under a normal-temperature polymerization condition, uniformly stirring and dropwise adding for 3-4 hours, continuing to react for 2-3 hours after dropwise adding is finished, and finally neutralizing with a sodium hydroxide solution until the pH value is 6.5 to obtain the polycarboxylic acid high-performance water reducing agent mother liquor which is marked as S2.

Detecting the residual quantity of the monomer: 0.1% of (2-phosphonic acid-propylene) malonic acid and 0.4% of allyloxy polyoxyethylene ether macromonomer.

Performance testing

The experimental data of the fluidity of the cement paste, the concrete slump and the degradation of the different water reducing agents are shown in the following tables 1, 2 and 3.

Table 1: test results of cement paste fluidity of different samples

Table 2: concrete (setting time, air content and slump) test results of different samples

The experiments show that the polymer with phosphorous acid groups provided by the invention can obtain excellent working performance of cement and concrete under the condition of low mixing amount.

Table 3: data of degradation experiment part of different samples

The experiments show that the water reducing agent provided by the invention has certain biodegradability and can be biodegraded in a short time.

Claims (6)

1. A degradable water reducing agent is characterized by being synthesized by the following method:

(1) mixing (2-phosphonic acid-propylene) malonic acid, epoxy succinic acid and water, and adjusting the pH value to 6-8 to obtain a mixed monomer solution;

(2) stirring and heating allyloxy polyoxyethylene ether macromonomer and an initiator to 80-90 ℃, dropwise adding the mixed monomer solution obtained in the step (1), continuously reacting at constant temperature for 2-3 hours after dropwise adding is completed after 3-4 hours, cooling to below 50 ℃, and adjusting the pH value to 6-7 to obtain the degradable water reducer;

the initiator in the step (2) is calcium hydroxide and molecular sieve immobilized potassium hydroxide.

2. The degradable water reducer according to claim 1, characterized in that the mass ratio of (2-phosphonic acid-propylene) malonic acid, epoxy succinic acid and water in step (1) is 1: 0.5-1: 1.5-2.

3. The degradable water reducer according to claim 1, wherein the molecular weight of the allyloxy polyoxyethylene ether macromonomer in the step (2) is 1000-1500, and the amount of the allyloxy polyoxyethylene ether macromonomer is 1-1.5 times of the mass of the (2-phosphonic acid-propylene) malonic acid.

4. The degradable water reducer according to claim 1, characterized in that the amount of the initiator used in the step (2) is 5-10% of the mass of the epoxy succinic acid.

5. The degradable water reducer according to claim 1, characterized in that sodium hydroxide with a mass fraction of 50% is used for pH adjustment in step (1).

6. The degradable water reducer of claim 1, characterized in that the degradable water reducer in step (2) is diluted to obtain a degradable water reducer solution.