Mud-resistant polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention relates to a mud-resistant polycarboxylate superplasticizer and a preparation method and application thereof, and the mud-resistant polycarboxylate superplasticizer is prepared from the following raw materials in parts by weight: 200-210 parts of unsaturated polyether macromonomer; 10 to 20 parts of a mud-resistant functional monomer; 8 to 16.5 parts of unsaturated carboxylic acid and / or unsaturated carboxylic ester; 0.5 to 2.5 parts of an initiator; 0.1 to 0.5 part of a reducing agent; 0.6 to 1.6 parts of a chain transfer agent; and a neutralizing agent; according to the synthesized anti-mud type polycarboxylic acid water reducer, unsaturated cyclic pyrophosphate is introduced into an unsaturated polyether side chain to serve as a main anti-mud functional monomer in a free radical solution copolymerization mode, and the slump retaining performance and the anti-mud performance of the polycarboxylic acid water reducer are improved.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures, in particular to an anti-mud type polycarboxylate water reducer and a preparation method and application thereof. Background Art

[0002] In the field of concrete, water reducers are beneficial to reducing the amount of water used in concrete, improving working performance, enhancing mechanical properties and improving durability. In the development of building materials, admixtures with water reducing effects mainly include: lignin sulfonates, naphthalene sulfonate formaldehyde condensates, melamine formaldehyde condensates, acetone sulfonate formaldehyde condensates, aminosulfonate formaldehyde condensates, and the third generation of polycarboxylate water reducers (PCE).

[0003] Among them, polycarboxylate water reducer is a general term for a series of polymers with specific molecular structures and properties. It is generally a comb-shaped copolymer with a linear main chain connected to multiple branches, which is polymerized by free radical reaction of monomers containing unsaturated double bonds and their derivatives. The main chain is connected with hydrophilic functional groups such as carboxyl, hydroxyl, sulfonic acid, and amino groups, and polyoxyethylene (polyoxypropylene) with different polymerization degrees is grafted as a side chain. Compared with other types of admixtures, polycarboxylate water reducer has outstanding advantages such as low dosage, good collapse retention performance, low concrete shrinkage, high durability, strong adjustability in molecular structure, great potential for high performance, and environmental protection during production. Therefore, its excellent performance has made it an indispensable element in pumping construction and widely used in various engineering projects.

[0004] However, polycarboxylate water reducers face a challenge: their polyoxyethylene (PEO) side chains tend to tightly bind to the aluminosilicate layer in the clay, resulting in PCE not relying on electrostatic effects to effectively adsorb on the cement surface to achieve dispersion in a muddy environment. Instead, their effectiveness is weakened due to the strong adsorption of clay, which manifests itself in problems such as high dosage requirements and poor aggregate adaptability.

[0005] To address the above challenges, researchers in the industry have been actively seeking solutions.

[0006] CN105367720B discloses a water-reducing and slump-retaining polycarboxylic acid water-reducing agent and a preparation method thereof, wherein hydroxyethyl methacrylate and 2-methacryloyloxyethyl phosphate are introduced to achieve the water-reducing and slump-retaining effect. This solution has good adaptability to cement, but is difficult to apply to floor materials with high mud content.

[0007] The CN109694213A patent proposes a mud-resistant polycarboxylic acid water-reducing agent with a unique hollow cylindrical side chain structure, which effectively resists clay adsorption by using the steric hindrance effect, significantly reducing the sensitivity of PCE to clay, but the improvement in collapse resistance is small, making it difficult to meet the needs of long-term transportation and pumping of concrete.

[0008] For example, the authorized patent CN112759725B discloses a method for producing a novel anti-mud and anti-slump nano polycarboxylic acid water reducer. This method uses a sulfonate polymerizable emulsifier, a polyether polyol anti-mud crosslinking agent and a monomer for emulsion polymerization to obtain a novel anti-mud and anti-slump nano polycarboxylic acid water reducer with a crosslinked structure, which can achieve an anti-mud effect to a certain extent. However, the use of emulsion polymerization has high requirements for water reducer production equipment and process control, and is difficult to apply.

[0009] The anti-mud type polycarboxylic acid water reducer prepared by the present invention has excellent anti-mud performance, good water-reducing and slump-preserving effect, has low requirements on water reducer production equipment and process control, and is conducive to meeting actual industrial application needs. Summary of the invention

[0010] Based on this, it is necessary to provide an anti-mud type polycarboxylate water reducer and its preparation method and application, which can introduce an unsaturated cyclic pyrophosphate anti-mud functional monomer, and can cooperate with some common unsaturated carboxylates, adopt room temperature free radical solution copolymerization synthesis technology, without heating, to prepare an anti-mud type polycarboxylate water reducer with excellent anti-mud performance, good dispersion and collapse retention effects and can meet the actual industrial application needs.

[0011] To achieve the above object, the present invention provides a technical solution:

[0012] An anti-mud type polycarboxylate water reducer, wherein the raw materials for preparing the anti-mud type polycarboxylate water reducer include, by weight:

[0013]

[0014] Wherein, the structural formula of the anti-mud functional monomer is as follows:

[0015]

[0016] In the formula, R1 is -CH2- or -CH2-CH2-.

[0017] In some embodiments of the present invention, the raw materials for preparing the anti-mud functional monomer include, by weight:

[0018]

[0019] In some embodiments of the present invention, the hydroxy monoacrylate includes at least one of hydroxyethyl acrylate and hydroxypropyl acrylate.

[0020] In some embodiments of the present invention, the catalyst includes at least one of triethylenediamine and triethylamine.

[0021] In some embodiments of the present invention, the preparation steps of the anti-mud functional monomer are as follows:

[0022] Stirring hydroxy monoacrylate, catalyst and organic solvent at 45°C-55°C until completely dissolved to obtain a first mixed solution;

[0023] Adding a 35-40% formaldehyde aqueous solution having a mass concentration of 1-1.5 times the amount of hydroxy monoacrylate to the first mixed solution, stirring for 1.5-2.5 hours, and adjusting the pH to 8-9 to obtain a second mixed solution, wherein the formaldehyde aqueous solution acts to undergo a substitution reaction with the hydroxy monoacrylate under the action of a catalyst;

[0024] Sodium chloride is added to the second mixed solution until the aqueous phase is saturated, hydrochloric acid is added to adjust the pH to neutral, and the liquids are separated to retain the organic phase; specifically, sodium chloride is the extract and hydrochloric acid is the pH adjuster.

[0025] Anhydrous sodium sulfate is added to the organic phase and stirred, filtered, and the filtrate is subjected to reduced pressure distillation after the solvent is removed to obtain an intermediate; specifically, the anhydrous sodium sulfate serves as a drying agent.

[0026] Add a polymerization inhibitor to the intermediate, add pyrophosphoric acid dropwise at 65° C. to 80° C. while stirring, and keep the temperature after the addition is completed to obtain an anti-mud functional monomer.

[0027] In some embodiments of the present invention, the time for adding pyrophosphoric acid dropwise is 1 h to 3 h, and the time for keeping warm is 1 h to 2 h.

[0028] In some embodiments of the present invention, the polymerization inhibitor includes two or three of hydroquinone, p-benzoquinone, p-hydroxyanisole and 2-tert-butylhydroquinone.

[0029] In some embodiments of the present invention, the organic solvent comprises at least one of acetonitrile and tetrahydrofuran.

[0030] In some embodiments of the present invention, the unsaturated macromonomer includes at least one of methoxy polyethylene glycol methacrylate, methoxy polyethylene glycol acrylate, allyl polyethylene glycol, 3-methyl-3-butene-1-polyethylene glycol, 2-methylallyl polyethylene glycol, ethylene glycol monovinyl polyethylene glycol ether and 4-hydroxybutyl vinyl polyoxyethylene ether, and the molecular weight is 1500-3000.

[0031] Another aspect of the present invention provides a method for preparing an anti-mud polycarboxylate water-reducing agent, comprising the steps of:

[0032] The polyether macromonomer, the chain transfer agent and water are stirred and mixed to obtain a base material aqueous solution;

[0033] The anti-mud functional monomer, unsaturated carboxylic acid and / or unsaturated carboxylic acid ester and water are uniformly mixed to prepare liquid A;

[0034] Mix the reducing agent and water evenly to prepare liquid B;

[0035] Add an oxidant to the aqueous solution of the base material, stir evenly, and dropwise add the A solution and the B solution respectively, with the dropping time being 1 to 3 hours;

[0036] After the dropwise addition is completed, the mixture is kept warm at 15-35° C. for 1 to 2 hours, and then a neutralizer is added to adjust the pH value of the mixed solution to 5.5-7.0 to obtain the anti-mud polycarboxylate water-reducing agent.

[0037] In some embodiments of the present invention, the unsaturated carboxylic acid and / or unsaturated carboxylic acid ester is at least one of acrylic acid, methacrylic acid, maleic anhydride, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0038] The initiator is at least one of a 27.5% mass concentration hydrogen peroxide solution, ammonium persulfate or sodium persulfate.

[0039] In some embodiments of the present invention, the reducing agent is at least one of ascorbic acid, Bruggolite FF6 and Bruggolite E01.

[0040] In some embodiments of the present invention, the chain transfer agent is at least one of sodium hypophosphite, thioglycolic acid, and mercaptopropionic acid.

[0041] Beneficial effects of the present invention:

[0042] 1. The anti-mud polycarboxylate water reducer synthesized by the present invention introduces unsaturated cyclic pyrophosphate as the main anti-mud functional monomer in the unsaturated polyether side chain by free radical solution copolymerization. The pyrophosphate group can form a pyrophosphate layer with clay minerals, inhibiting the hydration expansion of clay and reducing the excessive adsorption of the water reducer on the clay. At the same time, the pyrophosphate group has a higher negative charge than the carboxylic acid group, and exhibits a stronger adsorption force on the surface of cement particles, making it easier for the polycarboxylate water reducer to play a dispersing role and improving the overall performance.

[0043] 2. The side chain of the polycarboxylate water-reducing agent synthesized by the present invention contains a cyclic pyrophosphate structure, which increases the physical size of the side chain of the polycarboxylate water-reducing agent, resists its insertion into the clay layer, and enhances the anti-mud property. In addition, in the alkaline environment of cement hydration, the ester group, pyrophosphate group and other groups in the water-reducing agent molecules are hydrolyzed to release carboxylate and phosphate ions, which improves the collapse resistance and anti-mud performance of the polycarboxylate water-reducing agent.

[0044] 3. The anti-mud polycarboxylate water-reducing agent synthesized by the present invention has excellent compatibility with polycarboxylic acid molecules, supports independent use or mixed application with conventional water-reducing agents, and has significant market potential.

[0045] 4. The anti-mud polycarboxylate water-reducing agent synthesized by the present invention is prepared by free radical copolymerization at room temperature, the process is simple and mild, no complicated temperature control steps are required, the energy consumption is low, and it has efficient production and practical value. DETAILED DESCRIPTION

[0046] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0047] In the examples, the test methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0048] Example 1

[0049] This embodiment prepares an anti-mud water reducing agent, and the specific process is as follows:

[0050] S1. Preparation of anti-mud functional monomer:

[0051] In parts by weight, 102 parts of hydroxy monoacrylate, 2.2 parts of triethylamine, and 100 mL of tetrahydrofuran were stirred at 55° C. until completely dissolved to obtain a first mixed solution;

[0052] Add 146 parts of a 36% formaldehyde aqueous solution to the first mixed solution, stir for 2 hours, and adjust the pH to 8-9 to obtain a second mixed solution;

[0053] Adding sodium chloride to the second mixed solution until the aqueous phase is saturated, adding hydrochloric acid to adjust the pH to neutral, separating the liquids, and retaining the organic phase;

[0054] Add anhydrous sodium sulfate to the organic phase and stir, filter, remove the solvent from the filtrate and perform vacuum distillation to obtain an intermediate;

[0055] 0.08 parts of hydroquinone were added to the intermediate, and 56 parts of pyrophosphoric acid were added dropwise at 70° C. with stirring for 2 hours. After the addition was completed, the temperature was kept at 1.5 hours to obtain an anti-mud functional monomer.

[0056] S2. Preparation of anti-mud polycarboxylate water reducer:

[0057] In parts by weight, 18.4 parts of anti-mud functional monomer, 14.6 parts of acrylic acid and 28.2 parts of water were mixed evenly to prepare aqueous solution A;

[0058] 0.34 parts of ascorbic acid and 32.8 parts of water were mixed evenly to prepare aqueous solution B;

[0059] Add 204 parts of polyether macromonomer, 1.2 parts of sodium hypophosphite and 152 parts of water into a three-necked flask, maintain 15-35° C., and stir to prepare a base material aqueous solution;

[0060] S3. Add 2.0 parts of 27.5% hydrogen peroxide to the three-necked flask and stir evenly;

[0061] S4. The aqueous solution A and the aqueous solution B are simultaneously added dropwise to a three-necked flask for 2 hours. After the addition is completed, the mixture is kept warm for 2 hours. Then, a 32% sodium hydroxide solution is added to the three-necked flask, and the pH value of the mixed solution is adjusted to 5.5-7.0 (within this nearly neutral acid-base range, the product performance is almost the same), thereby obtaining the anti-mud polycarboxylic acid water reducer.

[0062] Example 2

[0063] This embodiment prepares an anti-mud type water reducing agent, and the specific process is different from that of embodiment 1 as follows:

[0064] In step S2, aqueous solution A: 16.6 parts of anti-mud functional monomer, 10.6 parts of acrylic acid, 4.6 parts of hydroxyethyl acrylate and 29.4 parts of water;

[0065] Aqueous solution B: 0.29 parts ascorbic acid and 39.6 parts water;

[0066] Primer aqueous solution: 1.6 parts of sodium hypophosphite and 155 parts of water;

[0067] In step S3, 0.18 parts of 2.2 parts of 27.5% hydrogen peroxide are added to the three-necked flask;

[0068] The present invention also provides the following comparative examples:

[0069] Comparative Example 1

[0070] Commercially available anti-mud type polycarboxylate water reducer Point-T.

[0071] Comparative Example 2

[0072] This comparative example prepares a water reducing agent, which differs from Example 1 in that:

[0073] Step S1 is not included, and the anti-mud functional monomer in step S2 is replaced by acrylic acid.

[0074] Comparative Example 3

[0075] This comparative example prepares a water reducing agent, which differs from Example 1 in that:

[0076] Step S1 is not included, and no anti-mud functional monomer is added in step S2.

[0077] Comparative Example 4

[0078] This comparative example prepares a water reducing agent, which differs from Example 1 in that:

[0079] In step S2, the amount of anti-mud functional monomer used is 26 parts.

[0080] Comparative Example 5

[0081] This comparative example prepares a water reducing agent, which differs from Example 1 in that:

[0082] In step S1, pyrophosphate is replaced with phosphoric acid.

[0083] Comparative Example 6

[0084] This comparative example prepares a water reducing agent, which differs from Example 1 in that:

[0085] The anti-mud functional monomer is replaced in equal amounts with the blocked amide pyrophosphate monomer prepared in Example 1 of patent CN118388530A.

[0086] In order to further illustrate the performance effect of the anti-mud polycarboxylate water-reducing agent provided by the present invention, according to GB 8076-2008 "Concrete Admixtures" standard, the above embodiments and comparative examples were subjected to cement concrete working performance tests, wherein the water-binder ratio was 0.44; using the same compounding conditions, the concrete mix ratio was as shown in Table 1, and the concrete performance test results were as shown in Table 2.

[0087] Table 1 Concrete mix ratio

[0088]

[0089] The unit in the table is kg / m 3

[0090] Table 2 Concrete working performance test results

[0091]

[0092]

[0093] From the results in Table 2, we can see that:

[0094] Under the condition of equal dosage of the polycarboxylate water-reducing agent in the embodiment, the dispersion and retention performance in high mud content machine-made sand concrete are better than those in comparative examples 1 to 6, and the workability is better, and the mud resistance and collapse resistance are excellent.

[0095] In comparative example 2, after the anti-mud functional monomer was replaced with acrylic acid, the anti-mud performance was poor. The dispersion effect was significantly weakened in high-mud content machine-made sand concrete, and the concrete workability was poor.

[0096] In comparative example 3, no anti-mud functional monomer is added, and the anti-mud performance is poor. The dispersion effect is significantly weakened in high-mud content machine-made sand concrete, the slump loss is significantly accelerated, and the concrete workability is poor.

[0097] In comparative example 4, the amount of anti-mud functional monomer is high, the anti-mud performance is good, but the slump retention performance is significantly weakened. In high-mud content machine-made sand concrete, the slump loss is fast and the concrete workability is poor.

[0098] In comparative example 5, pyrophosphoric acid was replaced by phosphoric acid, and the mud resistance was weakened. In high mud content machine-made sand concrete, the dispersion effect was weakened, the slump loss was fast, and the concrete workability was poor.

[0099] In comparative example 6, the anti-mud functional monomer is replaced with the blocked amide pyrophosphate monomer prepared in Example 1 of CN118388530A, and the 2h time loss increases and the collapse protection performance weakens. This is because the anti-mud functional monomer is a composite of ester group and pyrophosphate, the hydrolysis rate of high mud content machine-made sand concrete is appropriate, and the concrete fluidity state is maintained well, while the amide group in the blocked amide pyrophosphate monomer has a weak hydrolysis ability and a too slow hydrolysis rate, which is difficult to keep up with the concrete time loss speed, so the time loss is even greater.

[0100] It should be noted that the specific parameters or some reagents in the above embodiments are specific embodiments or preferred embodiments of the present invention, rather than limiting the present invention; those skilled in the art can make adaptive adjustments within the scope of the present invention.

Claims

1. An anti-mud type polycarboxylate water reducer, characterized in that: The raw materials for preparing the anti-mud type polycarboxylate water-reducing agent include, by weight: Wherein, the structural formula of the anti-mud functional monomer is as follows: In the formula, R1 is -CH2- or -CH2-CH2-.

2. The anti-mud type polycarboxylate water reducer according to claim 1, characterized in that: In parts by weight, the raw materials for preparing the anti-mud functional monomer include:

3. The anti-mud type polycarboxylate water reducer according to claim 2, characterized in that: The hydroxy monoacrylate includes at least one of hydroxyethyl acrylate and hydroxypropyl acrylate.

4. The anti-mud type polycarboxylate water reducer according to claim 2, characterized in that: The catalyst includes at least one of triethylenediamine and triethylamine.

5. The anti-mud type polycarboxylate water reducer according to claim 2, characterized in that: The preparation steps of the anti-mud functional monomer are as follows: Stirring an organic solvent formed by hydroxy monoacrylate and a catalyst at 45° C. to 55° C. until completely dissolved to obtain a first mixed solution; Adding formaldehyde aqueous solution to the first mixed solution, stirring for 1.5 to 2.5 hours, and adjusting the pH to 8-9 to obtain a second mixed solution; Adding sodium chloride and hydrochloric acid to the second mixed solution, separating the liquids, and retaining the organic phase; Add anhydrous sodium sulfate to the organic phase and stir, filter, remove the solvent from the filtrate and perform vacuum distillation to obtain an intermediate; Add a polymerization inhibitor to the intermediate, add pyrophosphoric acid dropwise at 65° C. to 80° C. while stirring, and keep the temperature after the addition is completed to obtain an anti-mud functional monomer.

6. The anti-mud type polycarboxylate water reducer according to claim 5, characterized in that: The time for adding pyrophosphoric acid dropwise is 1 h to 3 h, and the time for keeping warm is 1 h to 2 h.

7. The anti-mud type polycarboxylate water reducer according to claim 5, characterized in that: The polymerization inhibitor includes two or three of hydroquinone, p-benzoquinone, p-hydroxyanisole and 2-tert-butylhydroquinone.

8. The anti-mud type polycarboxylate water reducer according to claim 5, characterized in that: The organic solvent includes at least one of acetonitrile and tetrahydrofuran.

9. A method for preparing the anti-mud type polycarboxylate water-reducing agent according to any one of claims 1 to 8, characterized in that: Includes steps: The aqueous solution A formed by the anti-mud functional monomer, unsaturated carboxylic acid and / or unsaturated carboxylic acid ester, and the aqueous solution B prepared by the reducing agent are added dropwise to the base aqueous solution of the polyether macromonomer and the chain transfer agent, and polymerization reaction and pH adjustment are carried out.

10. Use of the anti-mud polycarboxylate water-reducing agent according to any one of claims 1 to 8 in the preparation of precast concrete components.

Images