Durability-enhanced polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention relates to the technical field of polycarboxylate superplasticizers, and discloses a durability-enhanced polycarboxylate superplasticizer and a preparation method thereof.The preparation method comprises the following steps that raw materials such as a polyether macromonomer are prepared, the polyether macromonomer and the like have the requirements for purity and dosage, deionized water and the polyether macromonomer are added into a reaction kettle to form a solution A, and the solution A is prepared; and preparing an initiator solution B with the mass concentration of 10-20% from ammonium persulfate, heating to 60-80 DEG C, stirring, firstly adding 1 / 3 of the initiator solution B to react, then preparing a mixed monomer solution from acrylic acid and the like, dropwise adding the mixed monomer solution and the residual initiator solution B within 2-3 hours, carrying out heat preservation reaction, cooling, and regulating the pH value to 6-8 by using sodium hydroxide to obtain a finished product. The sulfonic acid group of the introduced sodium methallyl sulfonate functional monomer can enhance the electrostatic repulsion between water reducer molecules and cement particles, so that the dispersing performance of the water reducer is improved, the agglomeration of the cement particles can be inhibited to a certain extent, and the fluidity of concrete can be maintained.

Description

Technical Field

[0001] The present invention relates to the technical field of polycarboxylate water reducers, and specifically relates to a durability-enhanced polycarboxylate water reducer and a preparation method thereof. Background Art

[0002] As a key admixture in the production of concrete, polycarboxylate water reducers play a crucial role in the modern construction field. In various large-scale construction projects, such as the construction of high-rise office buildings, cross-sea bridges, and water conservancy dams, the performance of concrete directly affects the safety and stability of the building structure. Polycarboxylate water reducers can significantly reduce the water-cement ratio of concrete, enhance its fluidity, make the concrete easier to pour and vibrate during construction, and effectively avoid quality defects caused by construction difficulties. At the same time, it can also improve the strength of concrete, ensure that the building structure has sufficient load-bearing capacity, and extend the service life of the building.

[0003] However, the polycarboxylate water reducers currently on the market have certain defects in terms of durability. During the long-term use of concrete, facing complex environmental factors, such as drastic temperature changes under harsh climate conditions, frequent wet-dry alternation, and the influence of erosive media (such as chloride ions, sulfate ions, etc.), the molecular structure of the polycarboxylate water reducer will be gradually damaged. This will not only reduce its dispersing ability for cement particles, resulting in poor fluidity of concrete and affecting the construction quality, but also accelerate the generation and development of microcracks inside the concrete, reduce the density of the concrete, and thus seriously weaken the durability of the concrete, causing the performance of the building structure to deteriorate prematurely, increasing the building maintenance cost, and even threatening the safe use of the building.

[0004] With the booming development of the construction industry, the requirements for the durability of concrete are becoming increasingly stringent. In the long run, it is urgent to solve the problem of insufficient durability of polycarboxylate water reducers. This is of great significance for improving the overall quality of construction projects, ensuring the long-term safe and stable operation of building structures, and realizing the sustainable development of the construction industry. Summary of the Invention

[0005] The purpose of the present invention is to propose a durability-enhanced polycarboxylate water reducer and a preparation method thereof in order to solve the above problems.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A durability-enhanced polycarboxylate water reducer and a preparation method thereof, including the following steps:

[0008] S1. Raw material preparation: Prepare polyether macromonomer, unsaturated carboxylic acid, functional monomer, initiator, chain transfer agent and pH regulator; the polyether macromonomer is allyl polyoxyethylene ether with a molecular weight of 2400, and the dosage is 40-60% of the total mass of the reaction system; the unsaturated carboxylic acid is acrylic acid with a purity ≥ 99%, and the dosage is 15-25% of the total mass of the reaction system; the functional monomer is sodium methallyl sulfonate with a purity ≥ 98%, and the dosage is 5-15% of the total mass of the reaction system; the initiator is ammonium persulfate, and the dosage is 0.5-2% of the total mass of the reaction system; the chain transfer agent is mercaptopropionic acid with a purity ≥ 98%, and the dosage is 0.3-1% of the total mass of the reaction system; the pH regulator is sodium hydroxide;

[0009] S2. Preparation of mixed solution: Add deionized water to the reaction kettle equipped with a stirring device, thermometer and dropping funnel. The dosage of deionized water is 30-50% of the total mass of the reaction system, and then add the polyether macromonomer and stir evenly to form solution A;

[0010] S3. Preparation of initiator solution: Dissolve ammonium persulfate in an appropriate amount of deionized water to prepare an initiator solution B with a mass concentration of 10-20%;

[0011] S4. Polymerization reaction: Heat the reaction kettle to 60-80 °C, start stirring, and control the rotation speed at 200-400 r / min. First, add 1 / 3 of the initiator solution B to solution A and react for 15-30 min. Then, mix acrylic acid, sodium methallyl sulfonate and mercaptopropionic acid evenly to prepare a mixed monomer solution, and slowly add it to the reaction kettle within 2-3 h, while evenly adding the remaining initiator solution B. During the dropping process, keep the reaction temperature at 60-80 °C. After the dropping is completed, continue to keep warm and react for 1-2 h;

[0012] S5. pH adjustment and finished product preparation: After the reaction is completed, cool the reaction kettle to room temperature, and adjust the pH value of the reaction product to 6-8 with sodium hydroxide solution to obtain the finished product of the durability-enhanced polycarboxylate water reducer.

[0013] Preferably, the mass ratio of the polyether macromonomer, unsaturated carboxylic acid, functional monomer, initiator, and chain transfer agent in the reaction system is 40-60:15-25:5-15:0.5-2:0.3-1.

[0014] Preferably, in the polymerization reaction step, the stirring speed is 300 r / min, the reaction temperature is 70 °C, the dropping time of the mixed monomer solution is 2.5 h, and the holding reaction time is 1.5 h.

[0015] Preferably, the mass concentration of the initiator solution B is 15%.

[0016] A durability-enhanced polycarboxylate water reducer prepared by a preparation method thereof.

[0017] Preferably, in the cement paste fluidity test, the initial fluidity is not less than 250 mm, the fluidity at 30 min is not less than 230 mm, and the fluidity at 60 min is not less than 210 mm.

[0018] Preferably, in the concrete durability test, the rapid freeze-thaw cycle test is adopted, and the number of freeze-thaw cycles is not less than 300 times.

[0019] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0020] 1. The sodium methallylsulfonate functional monomer introduced in the present invention, its sulfonic acid group can enhance the electrostatic repulsion between the water reducer molecule and the cement particles, not only improving the dispersion performance of the water reducer, but also inhibiting the agglomeration of cement particles to a certain extent, which helps to maintain the fluidity of concrete. At the same time, the presence of the sulfonic acid group enhances the stability of the water reducer molecular structure, making the molecular structure more difficult to be damaged when the water reducer faces a complex environment, thus significantly improving the durability. In addition, the optimized polymerization process and raw material ratio make the comb-shaped structure of the water reducer molecule more regular, further improving the slump retention performance of concrete and solving the problem of too fast slump loss during the construction of concrete. Detailed implementation manners

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0022] Example 1

[0023] Dosage of raw materials: 50 g of polyether macromonomer (APEG-2400), 20 g of acrylic acid, 10 g of sodium methallylsulfonate, 1 g of ammonium persulfate, 0.5 g of mercaptopropionic acid, 40 g of deionized water, and an appropriate amount of sodium hydroxide.

[0024] Preparation process: Operate according to the preparation steps in the invention content. First, add the polyether macromonomer into a reaction kettle containing 40 g of deionized water and stir to dissolve it to prepare solution A. Dissolve 1 g of ammonium persulfate in an appropriate amount of deionized water to prepare an initiator solution B with a mass concentration of 15%. Heat the reaction kettle to 70 °C, start stirring at a speed of 300 r / min, first add 1 / 3 of the initiator solution B to solution A and react for 20 min. Then mix acrylic acid, sodium methallylsulfonate, and mercaptopropionic acid evenly to prepare a mixed monomer solution, and slowly add it dropwise to the reaction kettle within 2.5 h, while evenly adding the remaining initiator solution B dropwise. After the dropping is completed, continue the heat preservation reaction for 1.5 h. After the reaction is completed, cool to room temperature and adjust the pH value to 7 with sodium hydroxide solution to obtain the finished product of polycarboxylate water reducer.

[0025] Example 2

[0026] Dosage of raw materials: 45 g of polyether macromonomer (APEG-2400), 22 g of acrylic acid, 12 g of sodium methallylsulfonate, 1.2 g of ammonium persulfate, 0.6 g of mercaptopropionic acid, 42 g of deionized water, and an appropriate amount of sodium hydroxide.

[0027] Preparation process: The same as the preparation process of Example 1, only the dosage of raw materials is adjusted.

[0028] Example 3

[0029] Dosage of raw materials: 55 g of polyether macromonomer (APEG-2400), 18 g of acrylic acid, 8 g of sodium methallylsulfonate, 0.8 g of ammonium persulfate, 0.4 g of mercaptopropionic acid, 38 g of deionized water, and an appropriate amount of sodium hydroxide.

[0030] Preparation process: The same as the preparation process of Example 1, only the dosage of raw materials is adjusted.

[0031] Comparative Example 1

[0032] Dosage of raw materials: 50 g of polyether macromonomer (APEG-2400), 20 g of acrylic acid, 1 g of ammonium persulfate, 0.5 g of mercaptopropionic acid, 40 g of deionized water, and an appropriate amount of sodium hydroxide (sodium methallylsulfonate is not added).

[0033] Preparation process: Carry out according to the preparation steps of Example 1, but do not add sodium methallylsulfonate.

[0034] Comparative Example 2

[0035] Dosage of raw materials: 50 g of polyether macromonomer (APEG-2400), 20 g of acrylic acid, 10 g of sodium methallylsulfonate, 1 g of ammonium persulfate, 40 g of deionized water, and an appropriate amount of sodium hydroxide (mercaptopropionic acid is not added).

[0036] Preparation process: Follow the preparation steps of Example 1, but without adding mercaptopropionic acid.

[0037] Performance test

[0038] Test of fluidity of cement paste: The test is carried out in accordance with GB / T8077-2012 "Test Methods for Homogeneity of Concrete Admixtures". Add 300 g of cement (P・O 42.5 ordinary Portland cement) into the cement paste mixer, then add the polycarboxylate superplasticizer sample calculated as 0.2% of the cement mass according to the solid content and 87 g of water. After stirring evenly, quickly pour the cement paste into the frustum cone mold. Lift the mold and measure the spread diameter of the cement paste on the glass plate. The initial fluidity is recorded as D0, and the fluidity is measured again after 30 min and 60 min, and recorded as D30 and D60 respectively.

[0039] Test of concrete durability: The rapid freeze-thaw cycle test method is adopted and carried out in accordance with GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". Put the prepared concrete specimens (size: 100 mm×100 mm×400 mm) into the freeze-thaw test box, and carry out freeze-thaw cycles between -20°C and +20°C. Observe the appearance of the specimens and measure the relative dynamic elastic modulus of the specimens after every 25 cycles. When the relative dynamic elastic modulus drops below 60%, record the number of freeze-thaw cycles at this time as the durability index of the concrete.

[0040] Test of slump retention performance: According to the relevant method in JGJ / T377-2016 "Technical Specification for Concrete Crack Control", add the polycarboxylate superplasticizer during the concrete mixing process, and control the initial slump at 200±20 mm. Measure the slump of the concrete after 0.5 h, 1 h, and 1.5 h respectively, and calculate the slump loss rate.

[0041] The fluidity of cement paste, the durability of concrete and the slump retention performance of Examples 1-3 are all better than those of Comparative Example 1 and Comparative Example 2. In Comparative Example 1, sodium methallylsulfonate was not added, and its fluidity of cement paste was small and the slump loss was fast, and the number of freeze-thaw cycles of the concrete was small, indicating that sodium methallylsulfonate plays a key role in improving the dispersion performance, slump retention performance and durability of the superplasticizer. In Comparative Example 2, mercaptopropionic acid was not added, and its various performances were also inferior to those of the examples, indicating that mercaptopropionic acid is of great significance in regulating the molecular structure during the polymerization reaction and thus improving the performance of the superplasticizer.

[0042] The foregoing description of the embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polycarboxylate superplasticizer with enhanced durability and its preparation method, characterized in that, It includes the following steps: S1. Raw material preparation: Prepare polyether macromonomer, unsaturated carboxylic acid, functional monomer, initiator, chain transfer agent and pH regulator; the polyether macromonomer is allyl polyoxyethylene ether with a molecular weight of 2400, and the dosage is 40 - 60% of the total mass of the reaction system; the unsaturated carboxylic acid is acrylic acid with a purity of ≥99%, and the dosage is 15 - 25% of the total mass of the reaction system; the functional monomer is sodium methallylsulfonate with a purity of ≥98%, and the dosage is 5 - 15% of the total mass of the reaction system; the initiator is ammonium persulfate, and the dosage is 0.5 - 2% of the total mass of the reaction system; the chain transfer agent is mercaptopropionic acid with a purity of ≥98%, and the dosage is 0.3 - 1% of the total mass of the reaction system; the pH regulator is sodium hydroxide; S2. Preparation of mixed solution: Add deionized water to a reaction kettle equipped with a stirring device, a thermometer and a dropping funnel. The amount of deionized water used is 30 - 50% of the total mass of the reaction system, and then add the polyether macromonomer and stir evenly to form solution A; S3. Preparation of initiator solution: Dissolve ammonium persulfate in an appropriate amount of deionized water to prepare an initiator solution B with a mass concentration of 10 - 20%; S4. Polymerization reaction: Heat the reaction kettle to 60 - 80 °C, start stirring, and control the rotation speed at 200 - 400 r / min. First, add 1 / 3 of the initiator solution B to solution A and react for 15 - 30 min. Then, mix acrylic acid, sodium methallylsulfonate and mercaptopropionic acid evenly to prepare a mixed monomer solution, and slowly add it to the reaction kettle within 2 - 3 h. At the same time, evenly add the remaining initiator solution B. During the dropping process, keep the reaction temperature at 60 - 80 °C. After the dropping is completed, continue to keep the temperature for reaction for 1 - 2 h; S5. pH adjustment and finished product preparation: After the reaction is completed, cool the reaction kettle to room temperature, and adjust the pH value of the reaction product to 6 - 8 with sodium hydroxide solution to obtain a finished product of a durability-enhanced polycarboxylate water reducer.

2. The preparation method of a durability-enhanced polycarboxylate water reducer according to claim 1, characterized in that, The mass ratio of the polyether macromonomer, unsaturated carboxylic acid, functional monomer, initiator and chain transfer agent in the reaction system is 40 - 60:15 - 25:5 - 15:0.5 - 2:0.3 - 1.

3. The preparation method of a durability-enhanced polycarboxylate water reducer according to claim 1, characterized in that, In the polymerization reaction step, the stirring speed is 300 r / min, the reaction temperature is 70 °C, the dropping time of the mixed monomer solution is 2.5 h, and the holding time for reaction is 1.5 h.

4. The preparation method of a durability-enhanced polycarboxylate water reducing agent according to claim 1, characterized in that, The mass concentration of the initiator solution B is 15%.

5. A durability-enhanced polycarboxylate water reducer prepared by the preparation method of a durability-enhanced polycarboxylate water reducer according to claim 1.

6. The durability-enhanced polycarboxylate water reducer according to claim 5, characterized in that In the cement paste fluidity test, the initial fluidity is not less than 250 mm, the fluidity at 30 min is not less than 230 mm, and the fluidity at 60 min is not less than 210 mm.

7. The durability-enhanced polycarboxylate water reducer according to claim 5, characterized in that, In the concrete durability test, the rapid freeze-thaw cycle test is adopted, and the number of freeze-thaw cycles is not less than 300 times.