Super-retarding polycarboxylic acid water reducing agent as well as preparation method and application thereof

Abstract

The invention discloses a super-retarding type polycarboxylic acid water reducing agent and a preparation method and application thereof, and belongs to the field of concrete water reducing agents. The preparation method comprises the following steps: taking acrylic acid AA, isobutenol polyoxyethylene ether HPEG and hydroxyethyl acrylate HEA as monomers, taking mercaptopropionic acid MPA as a chain transfer agent, taking hydrogen peroxide H2O2 and L-ascorbic acid Vc, and mixing in proportion to serve as an initiator; preparing a first and second monomer mixed solution; adding bottom water into the reaction kettle, and carrying out stepwise polymerization reaction; and cooling the reaction liquid, adjusting the pH value, filtering, and discharging to obtain the product. According to the invention, an ester functional monomer hydroxyethyl acrylate HEA is introduced, and a step-by-step polymerization technology is adopted to control the dispersion process of water reducing agent molecules on cement particles, so that the water reducing agent molecules continuously disperse the cement particles within a certain period of time; the problem that the slump loss is too fast due to long-time and long-distance transportation of concrete or transportation in high-temperature weather is effectively relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete water reducers, and in particular to a super-retarding polycarboxylate water reducer, a preparation method thereof, and an application thereof. Background Art

[0002] Polycarboxylate superplasticizer is a high-performance water reducer whose chemical structure typically consists of polyoxyethylene side chains and a carboxylic acid backbone. Conventional polycarboxylate superplasticizers are produced through the polymerization reaction of macromonomers (such as isobutylene alcohol polyoxyethylene ether HPEG, isopentenyl polyoxyethylene ether TPEG, etc.), micromonomers (such as acrylic acid AA, methacrylic acid MAA, etc.), chain transfer agents (such as thioglycolic acid TGA, mercaptopropionic acid MPAMPA, etc.), and initiators (such as ammonium persulfate APS, potassium persulfate KPS, or redox systems, etc.). Polycarboxylate superplasticizers are used in concrete construction to reduce water, maintain slump resistance, and improve workability. They are an indispensable additive in today's concrete construction.

[0003] However, when encountering complex situations such as high temperature weather, long-distance transportation, ultra-high-rise pumping and large-scale construction, conventional polycarboxylate water reducers cannot maintain the working performance of concrete for a long time; in addition, the initial dispersion effect of conventional polycarboxylate water reducers is not outstanding, which also limits its application scope. Summary of the Invention

[0004] The present invention aims to provide a super-retarding polycarboxylate water-reducing agent and a preparation method and application thereof, which solves the problems that conventional polycarboxylate water-reducing agents cannot maintain the working performance of concrete for a long time and have a poor initial dispersion effect.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions: A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; S2. Prepare monomer mixture All of acrylic acid AA, 28-32 wt% of hydroxyethyl acrylate HEA, and 42-48 wt% of mercaptopropionic acid MPA are dissolved in deionized water to obtain a first monomer solution, and all of isobutylene alcohol polyoxyethylene ether HPEG, the remaining 68-72 wt% of hydroxyethyl acrylate HEA, and the remaining 52-58 wt% of mercaptopropionic acid MPA are dissolved in deionized water to obtain a second monomer solution; S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 30±1°C, add 25-35wt% of initiator, add the first monomer solution dropwise, raise the temperature to 40±1°C after the addition is complete, add the remaining 65-75wt% of initiator, add the second monomer solution dropwise, raise the temperature to 45±1°C after the addition is complete, and keep warm for 1-2 hours to obtain a reaction solution; S4. Post-processing The reaction solution is cooled to room temperature, and the pH is adjusted to 6-7 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0006] A further improvement is that in step S1, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88.

[0007] A further improvement is that in step S1, the mass of the mercaptopropionic acid MPA accounts for 0.65 wt % of the mass of the isobutylene alcohol polyoxyethylene ether HPEG.

[0008] A further improvement is that in step S1, the hydrogen peroxide H A further improvement is that in step S2, the mass proportion of deionized water in the first monomer solution is 50-60 wt%, and the mass proportion of deionized water in the second monomer solution is 20-30 wt%.

[0009] A further improvement is that in step S3, stirring is performed at a speed of 200-300 rpm during the dropwise addition process, and the total dropwise addition time is controlled to be 3 hours.

[0010] A further improvement is that in step S3, while adding the first monomer solution, a shikonin solution is also added simultaneously, and the amount of the shikonin solution accounts for 0.5-2 wt% of the total mass of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG and hydroxyethyl acrylate HEA.

[0011] A further improvement is that the preparation steps of the shikonin solution are: The dried lithospermum root was crushed into 60-80 mesh to obtain lithospermum powder, and the powder was dissolved in acetone at a mass ratio of 1:10-15, and refluxed at 40-50°C for 2-3 hours. After filtering, the extraction was repeated 1-2 times, and the filtrates were combined, and the solvent was removed by vacuum distillation, and the mixture was recrystallized and purified to obtain shikonin; The shikonin is placed in a container, dichloromethane is added at a ratio of 1 g shikonin: 15-18 mL dichloromethane, and stirred until dissolved. The temperature is then controlled to 25-30° C., and fuming sulfuric acid is added dropwise at a ratio of 1 g shikonin: 5-6 mL fuming sulfuric acid. After the addition is complete, the temperature is raised to 40-50° C., and the reaction is stirred for 4-6 hours. The reaction solution is then poured into ice water, and the pH is adjusted to neutral with a NaOH solution. Finally, the mixture is extracted, dried, rotary evaporated, and recrystallized to obtain sulfonated shikonin. The sulfonated shikonin is dissolved in 3-5 times the mass of ethanol to obtain a shikonin solution.

[0012] The present invention also provides a super-retarding polycarboxylate water-reducing agent, which is prepared by the above-mentioned preparation method.

[0013] The present invention also provides an application of the super-retarding polycarboxylate water-reducing agent in concrete construction.

[0014] The beneficial effects of the present invention are: (1) The present invention introduces hydroxyethyl acrylate (HEA) as an ester functional monomer and adopts a step-by-step polymerization technology based on low temperature, heating and maturation to adjust the molecular weight and structure of the water reducer molecules to achieve a sustained release effect, thereby controlling the dispersion process of the water reducer molecules on the cement particles, so that the water reducer molecules can continuously disperse the cement particles within a certain period of time, effectively alleviating the problem of rapid slump loss over time caused by long-term, long-distance transportation of concrete or transportation in high temperature weather, and making the concrete mixture have good working performance for a long time.

[0015] Specifically: the low-temperature stage of 30°C mainly involves the synthesis of short-chain main chains, i.e., the synthesis of hydrophilic short-chain skeletons rich in carboxylic acid groups and hydroxyl groups. When used, the short-chain main chains can be quickly adsorbed on the surface of cement particles to provide initial dispersibility; the warming stage of 40°C mainly involves the grafting of hydrophobic side chains, i.e., grafting HPEG long chains on the short-chain main chains. When used, the HPEG side chains slowly hydrolyze in an alkaline environment, gradually releasing dispersed components to offset the dispersibility attenuation caused by cement hydration. The aging stage of 45°C is mainly for the formation of a cross-linked network, i.e., an esterification reaction occurs between the hydroxyl groups of HEA and the carboxyl groups of AA to form a lightly cross-linked network. When used, the cross-linked network delays the desorption of molecular chains, and cooperates with the continuous release of side chains to significantly improve the slump retention rate.

[0016] (2) The present invention uses hydroxyethyl acrylate (HEA) to replace acrylic acid (AA) in an appropriate amount. Utilizing the hydroxyl group in hydroxyethyl acrylate (HEA), more polar groups are introduced into the polymer chain, which is better adsorbed on the surface of concrete particles, thereby enhancing the dispersion effect and improving the water reduction rate. In addition, the hydroxyl group can form a stronger complex with the calcium ions in the concrete, further dispersing the cement particles, improving the fluidity and working performance of the concrete, solving the problem of poor dispersion retention of conventional water reducers during the hydration process, and effectively improving the net paste fluidity and slump retention of the concrete.

[0017] (3) The present invention adds shikonin solution during the step-by-step polymerization. The shikonin solution contains a naphthoquinone structure and a conjugated double bond, and after sulfonation activation treatment, the double bond reaction activity is improved, so that it participates in the copolymerization reaction. The conjugated double bond of shikonin naphthoquinone and the carboxyl group of acrylic acid AA are used to synergistically adsorb cement particles, enhance initial dispersion, and play a dual-effect retarding role, and finally prepare a super-retarding polycarboxylic acid water reducer. In addition, the test shows that the shikonin solution also has a significant promoting effect on the strength of concrete, which may be related to its excellent retarding effect, which can make the hydration reaction more uniform and more complete. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the present invention when performing a concrete slump test. DETAILED DESCRIPTION

[0019] The present application is described in further detail below in conjunction with the accompanying drawings. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0020] 1. Main Materials Acrylic acid AA: analytical grade, purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd. Isobutylene alcohol polyoxyethylene ether HPEG: HPEG2400, industrial grade, purchased from Haian Petrochemical Plant, Jiangsu Province; Hydroxyethyl acrylate (HEA): chemically pure, purchased from Adamas reagent; Mercaptopropionic acid MPA: ≥99%, purchased from MacLean Company; Hydrogen peroxide H2O2: 30%, analytical grade, purchased from Tianjin Damao Chemical Reagent Factory; L-ascorbic acid (Vc): analytically pure, purchased from Tianjin Tianli Chemical Reagent Co., Ltd.

[0021] 2. Implementation of the Experiment Example 1 A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; Among them, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88, the mass of mercaptopropionic acid MPA accounts for 0.65wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG, the molar ratio of hydrogen peroxide H2O2 and L-ascorbic acid Vc is n(H2O2):n(Vc)=2.5:1, and the mass of the initiator accounts for 1.17wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG.

[0022] S2. Prepare monomer mixture All of acrylic acid AA, 28 wt % of hydroxyethyl acrylate HEA, and 42 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a first monomer solution, and then all of isobutylene alcohol polyoxyethylene ether HPEG, the remaining 72 wt % of hydroxyethyl acrylate HEA, and the remaining 58 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a second monomer solution; the mass proportion of deionized water in the first monomer solution was 50 wt %, and the mass proportion of deionized water in the second monomer solution was 20 wt %.

[0023] S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 30±1°C, add 25wt% initiator, add the first monomer solution dropwise, raise the temperature to 40±1°C after the addition is completed, add the remaining 75wt% initiator, add the second monomer solution dropwise, raise the temperature to 45±1°C after the addition is completed, keep warm for 1 hour, and obtain a reaction solution; stir at 200 rpm during the addition process, and control the total addition time to be 3 hours.

[0024] S4. Post-processing The reaction solution was cooled to room temperature, and the pH was adjusted to 6 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0025] Example 2 A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; Among them, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88, the mass of mercaptopropionic acid MPA accounts for 0.65wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG, the molar ratio of hydrogen peroxide H2O2 and L-ascorbic acid Vc is n(H2O2):n(Vc)=2.5:1, and the mass of the initiator accounts for 1.17wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG.

[0026] S2. Prepare monomer mixture All acrylic acid AA, 30 wt % hydroxyethyl acrylate HEA and 45 wt % mercaptopropionic acid MPA were dissolved in deionized water to obtain a first monomer solution, and then all isobutylene alcohol polyoxyethylene ether HPEG, the remaining 70 wt % hydroxyethyl acrylate HEA and the remaining 55 wt % mercaptopropionic acid MPA were dissolved in deionized water to obtain a second monomer solution; the mass proportion of deionized water in the first monomer solution was 55 wt %, and the mass proportion of deionized water in the second monomer solution was 25 wt %.

[0027] S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 30±1°C, add 30wt% initiator, add the first monomer solution dropwise, raise the temperature to 40±1°C after the addition is completed, add the remaining 70wt% initiator, add the second monomer solution dropwise, raise the temperature to 45±1°C after the addition is completed, keep warm for 1.5h to obtain a reaction solution; stir at 250rpm during the addition process, and control the total addition time to be 3h.

[0028] S4. Post-processing The reaction solution was cooled to room temperature, and the pH was adjusted to 6.5 with a NaOH solution. The solution was then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0029] Example 3 A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; Among them, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88, the mass of mercaptopropionic acid MPA accounts for 0.65wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG, the molar ratio of hydrogen peroxide H2O2 and L-ascorbic acid Vc is n(H2O2):n(Vc)=2.5:1, and the mass of the initiator accounts for 1.17wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG.

[0030] S2. Prepare monomer mixture All of acrylic acid AA, 32 wt % of hydroxyethyl acrylate HEA, and 48 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a first monomer solution, and then all of isobutylene alcohol polyoxyethylene ether HPEG, the remaining 68 wt % of hydroxyethyl acrylate HEA, and the remaining 52 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a second monomer solution; the mass proportion of deionized water in the first monomer solution was 60 wt %, and the mass proportion of deionized water in the second monomer solution was 30 wt %.

[0031] S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 30±1°C, add 35wt% initiator, add the first monomer solution dropwise, raise the temperature to 40±1°C after the addition is completed, add the remaining 65wt% initiator, add the second monomer solution dropwise, raise the temperature to 45±1°C after the addition is completed, keep warm for 2h to obtain a reaction solution; stir at 300rpm during the addition process, and control the total addition time to be 3h.

[0032] S4. Post-processing The reaction solution was cooled to room temperature, and the pH was adjusted to 7 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0033] Example 4 A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; in addition, a shikonin solution was prepared as an auxiliary agent; The preparation steps of the shikonin solution are: The dried lithospermum root was crushed into 60 mesh to obtain lithospermum powder, which was dissolved in acetone at a mass ratio of 1:10, and refluxed at 40°C for 3 h. After filtration, the extraction was repeated once, and the filtrates were combined, and the solvent was removed by vacuum distillation, and the mixture was recrystallized and purified to obtain shikonin. The shikonin was placed in a container, and dichloromethane was added at a ratio of 1 g shikonin: 15 mL of dichloromethane, and stirred until dissolved. The temperature was then controlled to 25° C., and fuming sulfuric acid was added dropwise at a ratio of 1 g shikonin: 5 mL of fuming sulfuric acid. After the addition was complete, the temperature was raised to 40° C. and stirred for 6 hours. The reaction solution was then poured into ice water, and the pH was adjusted to neutral with a NaOH solution. Finally, the mixture was extracted, dried, rotary evaporated, and recrystallized to obtain sulfonated shikonin. The sulfonated shikonin is dissolved in ethanol with a mass 3 times that of the sulfonated shikonin to obtain a shikonin solution.

[0034] Among them, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88, the mass of mercaptopropionic acid MPA accounts for 0.65wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG, and hydrogen peroxide H S2. Prepare monomer mixture All of acrylic acid AA, 32 wt % of hydroxyethyl acrylate HEA, and 48 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a first monomer solution, and then all of isobutylene alcohol polyoxyethylene ether HPEG, the remaining 68 wt % of hydroxyethyl acrylate HEA, and the remaining 52 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a second monomer solution; the mass proportion of deionized water in the first monomer solution was 60 wt %, and the mass proportion of deionized water in the second monomer solution was 30 wt %.

[0035] S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 30±1°C, add 35wt% initiator, add the first monomer solution dropwise, and simultaneously add the shikonin solution dropwise (control the addition to be completed at the same time as the first monomer solution); after the addition is completed, raise the temperature to 40±1°C, add the remaining 65wt% initiator, and add the second monomer solution dropwise. After the addition is completed, raise the temperature to 45±1°C, keep warm for 2h, and obtain a reaction solution; stir at 300rpm during the addition process, and control the total addition time to be 3h.

[0036] S4. Post-processing The reaction solution was cooled to room temperature, and the pH was adjusted to 7 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0037] Example 5 A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; in addition, a shikonin solution was prepared as an auxiliary agent; The preparation steps of the shikonin solution are: The dried lithospermum root was crushed into 80 mesh to obtain lithospermum powder, which was dissolved in acetone at a mass ratio of 1:15, and refluxed at 50°C for 2 h. After filtration, the extraction was repeated twice, and the filtrates were combined, and the solvent was removed by vacuum distillation, and the mixture was recrystallized and purified to obtain shikonin. The shikonin was placed in a container, and dichloromethane was added at a ratio of 1 g shikonin: 18 mL of dichloromethane, and stirred until dissolved. The temperature was then controlled to 30° C., and fuming sulfuric acid was added dropwise at a ratio of 1 g shikonin: 6 mL of fuming sulfuric acid. After the addition was complete, the temperature was raised to 50° C., and the reaction was stirred for 4 h. The reaction solution was then poured into ice water, and the pH was adjusted to neutral with a NaOH solution. Finally, the mixture was extracted, dried, rotary evaporated, and recrystallized to obtain sulfonated shikonin. The sulfonated shikonin is dissolved in 5 times the mass of ethanol to obtain a shikonin solution.

[0038] Among them, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88, the mass of mercaptopropionic acid MPA accounts for 0.65wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG, and hydrogen peroxide H S2. Prepare monomer mixture All of acrylic acid AA, 32 wt % of hydroxyethyl acrylate HEA, and 48 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a first monomer solution, and then all of isobutylene alcohol polyoxyethylene ether HPEG, the remaining 68 wt % of hydroxyethyl acrylate HEA, and the remaining 52 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a second monomer solution; the mass proportion of deionized water in the first monomer solution was 60 wt %, and the mass proportion of deionized water in the second monomer solution was 30 wt %.

[0039] S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 30±1°C, add 35wt% initiator, add the first monomer solution dropwise, and simultaneously add the shikonin solution dropwise (control the addition to be completed at the same time as the first monomer solution); after the addition is completed, raise the temperature to 40±1°C, add the remaining 65wt% initiator, and add the second monomer solution dropwise. After the addition is completed, raise the temperature to 45±1°C, keep warm for 2h, and obtain a reaction solution; stir at 300rpm during the addition process, and control the total addition time to be 3h.

[0040] S4. Post-processing The reaction solution was cooled to room temperature, and the pH was adjusted to 7 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0041] Comparative Example 1 A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; Among them, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88, the mass of mercaptopropionic acid MPA accounts for 0.65wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG, the molar ratio of hydrogen peroxide H2O2 and L-ascorbic acid Vc is n(H2O2):n(Vc)=2.5:1, and the mass of the initiator accounts for 1.17wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG.

[0042] S2. Prepare monomer mixture All acrylic acid AA, all hydroxyethyl acrylate HEA and all mercaptopropionic acid MPA were dissolved in deionized water to obtain a monomer solution, wherein the mass proportion of deionized water in the monomer solution was 45 wt %.

[0043] S3, temperature-separated polymerization reaction Add bottom water to the reactor, raise the temperature to 30±1°C, and simultaneously add the initiator and monomer solution dropwise. In the middle of the dropwise addition process (the same heating time point as in Example 3), raise the temperature to 40±1°C, continue to add the initiator and monomer solution dropwise, and after the dropwise addition is completed, raise the temperature to 45±1°C and keep warm for 2 hours to obtain a reaction solution. Stir at 300 rpm during the dropwise addition process, and control the total dropwise addition time to 3 hours.

[0044] S4. Post-processing The reaction solution was cooled to room temperature, and the pH was adjusted to 7 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0045] Comparative Example 2 A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; Among them, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88, the mass of mercaptopropionic acid MPA accounts for 0.65wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG, the molar ratio of hydrogen peroxide H2O2 and L-ascorbic acid Vc is n(H2O2):n(Vc)=2.5:1, and the mass of the initiator accounts for 1.17wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG.

[0046] S2. Prepare monomer mixture All of acrylic acid AA, 32 wt % of hydroxyethyl acrylate HEA, and 48 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a first monomer solution, and then all of isobutylene alcohol polyoxyethylene ether HPEG, the remaining 68 wt % of hydroxyethyl acrylate HEA, and the remaining 52 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a second monomer solution; the mass proportion of deionized water in the first monomer solution was 60 wt %, and the mass proportion of deionized water in the second monomer solution was 30 wt %.

[0047] S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 40±1°C, add 35wt% initiator, and drop the first monomer solution. After the addition is completed, add the remaining 65wt% initiator at 40±1°C, and drop the second monomer solution. After the addition is completed, keep warm at 40±1°C for 2h to obtain a reaction solution. Stir at 300rpm during the addition process, and control the total addition time to 3h.

[0048] S4. Post-processing The reaction solution was cooled to room temperature, and the pH was adjusted to 7 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0049] Comparative Example 3 A method for preparing a super-retarding polycarboxylate water-reducing agent, comprising the following steps: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; in addition, a shikonin solution was prepared as an auxiliary agent; The preparation steps of the shikonin solution are: The dried lithospermum root was crushed into 80 mesh to obtain lithospermum powder, which was dissolved in acetone at a mass ratio of 1:15, and refluxed at 50°C for 2 h. After filtration, the extraction was repeated twice, and the filtrates were combined, and the solvent was removed by vacuum distillation, and the mixture was recrystallized and purified to obtain shikonin. The shikonin is dissolved in 5 times the mass of ethanol to obtain a shikonin solution.

[0050] Among them, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.88, the mass of mercaptopropionic acid MPA accounts for 0.65wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG, and hydrogen peroxide H S2. Prepare monomer mixture All of acrylic acid AA, 32 wt % of hydroxyethyl acrylate HEA, and 48 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a first monomer solution, and then all of isobutylene alcohol polyoxyethylene ether HPEG, the remaining 68 wt % of hydroxyethyl acrylate HEA, and the remaining 52 wt % of mercaptopropionic acid MPA were dissolved in deionized water to obtain a second monomer solution; the mass proportion of deionized water in the first monomer solution was 60 wt %, and the mass proportion of deionized water in the second monomer solution was 30 wt %.

[0051] S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 30±1°C, add 35wt% initiator, add the first monomer solution dropwise, and simultaneously add the shikonin solution dropwise (control the addition to be completed at the same time as the first monomer solution); after the addition is completed, raise the temperature to 40±1°C, add the remaining 65wt% initiator, and add the second monomer solution dropwise. After the addition is completed, raise the temperature to 45±1°C, keep warm for 2h, and obtain a reaction solution; stir at 300rpm during the addition process, and control the total addition time to be 3h.

[0052] S4. Post-processing The reaction solution was cooled to room temperature, and the pH was adjusted to 7 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

[0053] 3. Performance Testing The cement used in the test is ordinary Portland cement P·O 42.5, whose chemical composition is shown in Table 1 below. The fineness modulus of the sand used in the test is 2.88, and it is medium sand in Zone II.

[0054] Table 1: Main chemical composition of the cement used in the test

[0055] (1) Cement paste fluidity test The fluidity of cement paste is measured according to GB / T8077-2012, "Test Method for Homogeneity of Concrete Admixtures." The test uses a conical mold with an upper diameter of 36 mm, a lower diameter of 60 mm, and a height of 60 mm. The specific procedure is as follows: Place the glass plate in a horizontal position. Wipe the glass plate, truncated cone mold, agitator, and mixing pot with a damp cloth until the surfaces are damp but not water-stained. Place the truncated cone mold in the center of the glass plate and cover with a damp cloth until ready to use. Weigh 300 g of cement and pour it into the mixing pot. Add a water reducer (0.15% by weight of the cement) and 87 g of water. Mix immediately (slow speed for 120 seconds, pause for 15 seconds, and high speed for 120 seconds). Quickly pour the mixed slurry into the truncated cone mold, scrape it flat with a scraper, lift the truncated cone mold in the vertical direction, start the stopwatch at the same time, and let the cement slurry flow on the glass plate. After 30 seconds, use a ruler to measure the maximum diameters of the flowing part in two directions perpendicular to each other, and take the average value as the fluidity of the cement slurry. The initial and 1h fluidity of the cement slurry are tested respectively.

[0056] (2) Concrete slump test Concrete slump is measured according to GB / T8076-2008 "Concrete Admixtures." The test method is as follows: Pre-wet the slump cylinder and base plate, ensuring there is no visible water on the slump cylinder and base plate. Add the weighed cement, mineral powder, sand, and gravel to the concrete mixer all at once. The specific concrete mix ratio is as shown in Table 2 below: Table 2: Concrete mix table (unit: kg / m 3 )

[0057] Put cement, sand and stone into the mixer at once, dry mix them evenly, then add mixing water mixed with water reducer and stir for 2 minutes. After discharging, stir them manually on an iron plate until they are evenly mixed, and then test them (temperature 20±3℃). During the test, load them evenly into the slump cone in three layers, so that the height of each layer after tamping is about one-third of the height of the cone, and use a tamping rod to tamp each layer 15 times. When pouring the top layer, pour the concrete to the top of the cone. After the top layer is tamped, scrape off the excess concrete and smooth it with a trowel, then remove the concrete on the bottom plate of the cone, and lift the slump cone vertically and steadily. The lifting process of the slump cone should be completed within 5-10s. Figure 1 As shown, after lifting the slump cone, use a ruler to measure the difference between the slump cone height and the highest point of the concrete specimen after slumping. This is the blank concrete slump value of the concrete mix. After adding a water reducer, the slump measured is the slump of the water reducer. Immediately place the concrete after slump testing into a moistened basin, cover, and let it sit for 1 hour. Then pour it out, mix it immediately, and then test the corresponding slump.

[0058] (3) Concrete water reduction rate test According to GB / T8076-2008 "Concrete Admixtures" standard. First, test the initial slump of the blank control sample and record the mixing water amount at this time. Then add water reducer to the concrete to reduce the mixing water amount so that its initial slump is not less than that of the blank control. The ratio of the reduced mixing water amount to the blank control mixing water amount is recorded as the water reduction rate of the concrete. The specific formula is as follows:

[0059] Where WR is the water reduction rate, W0 is the mixing water consumption of the concrete in the blank control group, and W1 is the mixing water consumption of the concrete after adding the water reducer. The units are kg / m (4) Concrete compressive strength test Testing is conducted in accordance with GB / T50081-2019, "Standard for Test Methods of Mechanical Properties of Ordinary Concrete." Fresh concrete is placed in a 150mm x 150mm x 150mm cubic test mold, compacted using a vibrating table, and secured with a rubber hammer to create a uniform, dense standard concrete cube specimen. Immediately after forming, the specimen is covered with an impermeable film and placed in a curing chamber maintained at a constant temperature of 20±3°C. After a period of conventional curing, the specimen is demolded and cured in the curing chamber until the specified age. The ultimate compressive strength of the concrete is then determined using a universal testing machine.

[0060] 4. Results Analysis (1) Cement paste fluidity test Table 3: Cement paste fluidity results

[0061] (2) Concrete slump test Table 4: Concrete slump results

[0062] (3) Concrete water reduction rate test Table 5: Concrete water reduction rate results

[0063] (4) Concrete compressive strength test Table 6: Concrete compressive strength results

[0064] Analysis: As can be seen from Tables 2-6 above, the polycarboxylate water-reducing agent prepared in Example 3 of the present invention has outstanding application effects. Its initial fluidity reaches 310 mm, the fluidity increases to 330 mm after 1 hour, and the slump also increases from 210 mm to 215. It has good flow properties, small flow loss over time, and small slump loss over time. In addition, it has outstanding water-reducing effect and compressive strength performance.

[0065] Example 4 and Example 5 were adjusted on the basis of Example 3, and shikonin solution was added during the low-temperature polymerization stage, while other process conditions remained unchanged. The results showed that the flow properties of Example 4 and Example 5 were further significantly improved, especially the initial flow properties. In addition, the water reduction rate was basically equivalent to that of Example 3, and the compressive strength was also significantly improved. For example, the 28d compressive strength of Example 4 was increased by 13.6% relative to that of Example 3.

[0066] Comparative Example 1 was adjusted on the basis of Example 3. Step-by-step polymerization was not adopted. All monomers were mixed into one monomer solution, and only one initiator was added dropwise continuously. During the addition process, a simple temperature separation (30°C-40°C-45°C) treatment was performed. Other process conditions remained unchanged. The results showed that the flow properties and collapse retention properties of Comparative Example 1 were significantly reduced, and a certain amount of time loss occurred. The 28d compressive strength also decreased by 6.2% compared with Example 3.

[0067] Comparative Example 1 was adjusted on the basis of Example 3. Although the first monomer solution and the second monomer solution were also prepared for step-by-step polymerization, the temperature of the three stages was the same, all 40°C, and other process conditions remained unchanged. The results showed that the flow properties and collapse retention properties of Comparative Example 1 decreased, and the compressive strength also decreased to a certain extent.

[0068] Comparative Example 3 was adjusted on the basis of Example 5. During the preparation of the shikonin solution, no sulfonation activation treatment was performed, and other process conditions remained unchanged. The results showed that the flow properties and collapse retention properties of Comparative Example 3 were significantly reduced, and the 28d compressive strength was also reduced by 9.9% compared with Example 5.

[0069] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A method for preparing a super slow-setting polycarboxylate water-reducing agent, characterized in that the steps include: S1. Raw material preparation Acrylic acid AA, isobutylene glycol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA were weighed as monomers, mercaptopropionic acid MPA was weighed as a chain transfer agent, and hydrogen peroxide H2O2 and L-ascorbic acid Vc were weighed and mixed in proportion as an initiator; S2. Prepare monomer mixture All of acrylic acid AA, 28-32 wt% of hydroxyethyl acrylate HEA, and 42-48 wt% of mercaptopropionic acid MPA are dissolved in deionized water to obtain a first monomer solution, and all of isobutylene alcohol polyoxyethylene ether HPEG, the remaining 68-72 wt% of hydroxyethyl acrylate HEA, and the remaining 52-58 wt% of mercaptopropionic acid MPA are dissolved in deionized water to obtain a second monomer solution; S3, step-by-step polymerization Add bottom water to the reactor, raise the temperature to 30±1°C, add 25-35wt% of initiator, add the first monomer solution dropwise, raise the temperature to 40±1°C after the addition is complete, add the remaining 65-75wt% of initiator, add the second monomer solution dropwise, raise the temperature to 45±1°C after the addition is complete, and keep warm for 1-2 hours to obtain a reaction solution; S4. Post-processing The reaction solution is cooled to room temperature, and the pH is adjusted to 6-7 with a NaOH solution, and then filtered and discharged to obtain the super slow-setting polycarboxylate water-reducing agent.

2. The method for preparing a super slow-setting polycarboxylate water-reducing agent according to claim 1, wherein: In step S1, the molar ratio of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG, and hydroxyethyl acrylate HEA is n(AA):n(HPEG):n(HEA)=4.25:1:4.

88.

3. The method for preparing a super slow-setting polycarboxylate water-reducing agent according to claim 1, wherein: In step S1, the mass of the mercaptopropionic acid MPA accounts for 0.65 wt % of the mass of the isobutylene alcohol polyoxyethylene ether HPEG.

4. The method for preparing a super slow-setting polycarboxylate water-reducing agent according to claim 1, wherein: In step S1, the molar ratio of hydrogen peroxide H2O2 to L-ascorbic acid Vc is n(H2O2):n(Vc)=2.5:1, and the mass of the initiator accounts for 1.17wt% of the mass of isobutylene alcohol polyoxyethylene ether HPEG.

5. The method for preparing a super slow-setting polycarboxylate water-reducing agent according to claim 1, wherein: In step S2, the mass proportion of deionized water in the first monomer solution is 50-60 wt%, and the mass proportion of deionized water in the second monomer solution is 20-30 wt%.

6. The method for preparing a super slow-setting polycarboxylate water-reducing agent according to claim 1, wherein: In step S3, stirring is performed at a speed of 200-300 rpm during the dropwise addition process, and the total dropwise addition time is controlled to be 3 h.

7. The method for preparing a super slow-setting polycarboxylate water-reducing agent according to claim 1, wherein: In step S3, while the first monomer solution is being added dropwise, the shikonin solution is also added dropwise simultaneously, and the amount of the shikonin solution used accounts for 0.5-2 wt % of the total mass of acrylic acid AA, isobutylene alcohol polyoxyethylene ether HPEG and hydroxyethyl acrylate HEA.

8. The method for preparing a super slow-setting polycarboxylate water-reducing agent according to claim 7, wherein: The preparation steps of the shikonin solution are: The dried lithospermum root was crushed into 60-80 mesh to obtain lithospermum powder, and the powder was dissolved in acetone at a mass ratio of 1:10-15, and refluxed at 40-50°C for 2-3 hours. After filtering, the extraction was repeated 1-2 times, and the filtrates were combined, and the solvent was removed by vacuum distillation, and the mixture was recrystallized and purified to obtain shikonin; The shikonin is placed in a container, dichloromethane is added at a ratio of 1 g shikonin: 15-18 mL dichloromethane, and stirred until dissolved. The temperature is then controlled to 25-30° C., and fuming sulfuric acid is added dropwise at a ratio of 1 g shikonin: 5-6 mL fuming sulfuric acid. After the addition is complete, the temperature is raised to 40-50° C., and the reaction is stirred for 4-6 hours. The reaction solution is then poured into ice water, and the pH is adjusted to neutral with a NaOH solution. Finally, the mixture is extracted, dried, rotary evaporated, and recrystallized to obtain sulfonated shikonin. The sulfonated shikonin is dissolved in 3-5 times the mass of ethanol to obtain a shikonin solution.

9. A super slow-setting polycarboxylate water-reducing agent, characterized in that: The super slow-setting polycarboxylate water-reducing agent is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the super-retarding polycarboxylate water-reducing agent according to claim 9 in concrete construction.

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