Stable-release slow-release polycarboxylate superplasticizer and preparation method thereof
By adopting two unsaturated carboxylic acid esters and introducing amine monomers and polyols, new ester groups and amide groups are formed, and the release rate of sustained-release polycarboxylic acid water reducer is controlled, which solves the problem of concentrated release time and fast rate of existing polycarboxylic acid water reducer, extends the holding time of concrete slump, and improves workability and slump retention efficiency.
Patent Information
- Application Number
- CN202510297077.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-13
- Publication Date
- 2025-05-27
AI Technical Summary
The release time of existing polycarboxylic acid water reducing agent is concentrated and the release rate is fast, which leads to segregation and secretion of water during the release peak, and the slump loss is accelerated, the slump retention time is insufficient, the long-term slump retention effect is poor, and the slump retention efficiency is insufficient, resulting in the loss of working nature of the concrete.
Two unsaturated carboxylic acid esters are used as raw materials for the sustained-release polycarboxylic acid water reducer. The ester group in the unsaturated carboxylic acid esters is hydrolyzed into carboxylic groups under basic conditions, increasing the holding time of concrete slump, and by introducing amine monomers and polyols, new ester groups and amide groups are formed, and the release rate of the sustained-release polycarboxylic acid water reducer is controlled.
The slump retention time of concrete is extended, the workingability of concrete is improved, and the problem of excessive slump loss is avoided. By controlling the release rate, the smooth release of the sustained-release polycarboxylic acid water reducing agent is ensured.
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Figure CN120040682A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of concrete admixtures, and particularly relates to a sustained-release polycarboxylate superplasticizer with stable release and a preparation method thereof. Background Art
[0002] With the continuous development of infrastructure projects, the requirements for concrete building materials are also constantly increasing. As a commonly used material in the construction engineering industry, concrete has the characteristics of fast molding, low price, wide raw material sources, and high strength. However, when the content of sand and gravel materials in concrete is relatively high, it is very easy to have a large slump loss. At the same time, there is generally a certain distance between the general construction site and the concrete mixing station. Therefore, concrete must maintain good fluidity for a long time to meet the requirements of long-distance and long-time pumping. This requires concrete to have both high slump and slump retention functions.
[0003] As an environmentally friendly concrete chemical admixture, polycarboxylate superplasticizer has been gradually widely used in the industry due to its good water-reducing performance. Traditional polycarboxylate superplasticizers usually have good dispersion effects or water-reducing properties, but do not have the effect of maintaining long-term fluidity. Existing polycarboxylate superplasticizers use the method of functional group modification. By introducing non-hydrophilic small molecule monomers with hydrolyzable groups during the polymerization process of polycarboxylate superplasticizers, it is possible to protect the carboxylate groups in the molecule at the initial stage of cement hydration. At the same time, during the cement hydration process, the non-hydrophilic groups hydrolyze in an alkaline environment to release hydrophilic groups such as carboxyl groups, thereby slowly adsorbing onto the surface of cement particles to achieve the effect of maintaining the fluidity of cement. However, the release time of this type of sustained-release polycarboxylate superplasticizer is concentrated, the release rate is fast, and the peak is prominent. Concrete added with this type of sustained-release polycarboxylate superplasticizer will show phenomena such as segregation and bleeding at the release peak. After the release peak, the slump loss accelerates, resulting in insufficient subsequent slump retention time for concrete, poor long-term slump retention effect, insufficient slump retention efficiency, and loss of workability of concrete. Summary of the Invention
[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems in the prior art that the release time of polycarboxylate superplasticizer is concentrated, the release rate is fast, and the peak is prominent. Concrete added with this type of sustained-release polycarboxylate superplasticizer will show phenomena such as segregation and bleeding at the release peak. After the release peak, the slump loss accelerates, resulting in insufficient subsequent slump retention time for concrete, poor long-term slump retention effect, insufficient slump retention efficiency, and loss of workability of concrete. Thus, a sustained-release polycarboxylate superplasticizer with stable release and a preparation method thereof are provided.
[0005] On the one hand, the present invention provides a sustained-release polycarboxylate water reducer, which comprises raw materials in the following weight parts: a base liquid, a first mixed liquid and a second mixed liquid, an amine monomer and a polyol. The base liquid comprises a polyether monomer, a first reducing agent and an oxidizing agent. The first mixed liquid comprises an unsaturated fatty acid and an unsaturated carboxylic acid ester. The unsaturated carboxylic acid ester comprises a first unsaturated carboxylic acid ester and a second unsaturated carboxylic acid ester. The first unsaturated carboxylic acid ester and the second unsaturated carboxylic acid ester are not the same substance. The molar ratio of the polyether monomer to the unsaturated carboxylic acid ester is 1:2-6. The second mixed liquid comprises a second reducing agent and a chain transfer agent.
[0006] In some embodiments, the polyether monomer comprises at least one of a four-carbon monomer, a five-carbon monomer and a six-carbon monomer, and is preferably a six-carbon monomer.
[0007] In some embodiments, the six-carbon monomer comprises at least one of 4-hydroxybutyl vinyl polyoxyethylene ether and ethylene glycol mono vinyl polyethylene glycol ether.
[0008] In some embodiments, the five-carbon monomer comprises isopentenyl polyethylene glycol ether.
[0009] In some embodiments, the four-carbon monomer comprises isobutenyl polyethylene glycol ether.
[0010] In some embodiments, the first unsaturated carboxylic acid ester or the second unsaturated carboxylic acid ester is independently selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate.
[0011] In some embodiments, the amine monomer comprises at least one of p-phenylenediamine, ethylenediamine, diethylenetriamine, tetraethylenepentamine or pentaethylenehexamine. Preferably, the amine monomer comprises p-phenylenediamine and ethylenediamine.
[0012] In some embodiments, the molar ratio of the amine monomer to the unsaturated fatty acid is 1:2-5.
[0013] In some embodiments, the polyol comprises at least one of sorbitol, maltitol, butanediol or propanediol.
[0014] In some embodiments, the molar ratio of the polyol to the unsaturated fatty acid is 1:2-6.
[0015] In some embodiments, the molar ratio of the first unsaturated carboxylic acid ester to the second unsaturated carboxylic acid ester is 1.5:1.5-4.
[0016] In some embodiments, the molar ratio of the unsaturated fatty acid to the polyether monomer is 1-2.5:1.
[0017] In some of these embodiments, the first reducing agent includes at least one of ferrous sulfate and sodium hypophosphite. Preferably, ferrous sulfate exists in the bottom liquid in the form of an aqueous solution of ferrous sulfate, and the concentration of the aqueous solution of ferrous sulfate is 0.5-2 wt%.
[0018] In some of these embodiments, the oxidizing agent includes at least one of hydrogen peroxide and ammonium persulfate. Preferably, hydrogen peroxide exists in the bottom liquid in the form of an aqueous solution of hydrogen peroxide, and the concentration of the aqueous solution of hydrogen peroxide is 25-30 wt%.
[0019] In some of these embodiments, the unsaturated fatty acid includes acrylic acid.
[0020] In some of these embodiments, the second reducing agent includes L-ascorbic acid;
[0021] In some of these embodiments, the chain transfer agent includes mercaptoethanol.
[0022] In some of these embodiments, in the bottom liquid, the mass parts of the polyether monomer are 300-380 parts, the mass parts of the first reducing agent are 0.5-3.5 parts, the mass parts of the oxidizing agent are 3-9 parts, and the bottom liquid also includes water, and the mass parts of water are 275-350 parts. Among them, the mass parts of the oxidizing agent are preferably 3.5-8.7 parts.
[0023] In some of these embodiments, in the first mixed liquid, the mass parts of the unsaturated fatty acid are 8.5-16 parts, and the first mixed liquid also includes water, and the mass parts of water are 15-30 parts.
[0024] In some of these embodiments, in the second mixed liquid, the mass parts of the second reducing agent are 0.5-3 parts, the mass parts of the chain transfer agent are 1-4.5 parts, and the second mixed liquid also includes water, and the mass parts of water are 112.5-118.5 parts.
[0025] On the other hand, the present invention provides a preparation method of a sustained-release polycarboxylate water reducer, including the following steps: reacting the first mixed liquid and the second mixed liquid with the bottom liquid to form a mixed liquid, and under alkaline conditions, aging and heat-treating the mixed liquid, and then adding an amine monomer and a polyol thereto.
[0026] In some of these embodiments, by means of dropping, the first mixed liquid and the second mixed liquid are dropped into the bottom liquid for reaction. The first mixed liquid and the second mixed liquid are uniformly dropped into the bottom liquid. The dropping time of the first mixed liquid is 45-60 min, and the dropping time of the second mixed liquid is 60-90 min.
[0027] In some of these embodiments, the first mixed liquid and the second mixed liquid are reacted with the bottom liquid to form a mixed liquid, and the pH value of the mixed liquid is adjusted to 8-9.
[0028] In some of these embodiments, while stirring the bottom liquid, the first mixture and the second mixture are dropped into the bottom liquid. The stirring rate is 180 - 250 rpm, and the stirring time is 30 - 60 min.
[0029] In some of these embodiments, the temperature of the heat treatment is 40 - 50 °C.
[0030] The sustained-release polycarboxylate water reducer provided by the present invention or the sustained-release polycarboxylate water reducer prepared by the preparation method of the sustained-release polycarboxylate water reducer can be applied to concrete.
[0031] The technical solution of the present invention has the following advantages:
[0032] 1. A sustained-release polycarboxylate water reducer provided by the present invention comprises raw materials in the following parts by weight: a bottom liquid, a first mixture and a second mixture, an amine monomer and a polyol. The bottom liquid comprises a polyether monomer, a first reducing agent and an oxidizing agent. The first mixture comprises an unsaturated fatty acid and an unsaturated carboxylic acid ester. The unsaturated carboxylic acid ester comprises a first unsaturated carboxylic acid ester and a second unsaturated carboxylic acid ester, and the first unsaturated carboxylic acid ester and the second unsaturated carboxylic acid ester are not the same substance. The molar ratio of the monomer to the unsaturated carboxylic acid ester is 1:2 - 6. The second mixture comprises a second reducing agent and a chain transfer agent. By using two unsaturated carboxylic acid esters as raw materials for synthesizing the sustained-release polycarboxylate water reducer, when the sustained-release water reducer is added to concrete, under alkaline conditions, the ester group in the unsaturated carboxylic acid ester is hydrolyzed into a carboxyl group, which can increase the retention time of the concrete slump, extend the working time, and avoid the problem of excessive slump loss during transportation. Further, by utilizing the difference in the hydrolysis rates of the two unsaturated carboxylic acid esters, the release rate of the sustained-release polycarboxylate water reducer can be effectively controlled to ensure the stable release of the sustained-release polycarboxylate water reducer; at the same time, by introducing an amine monomer and a polyol, an esterification reaction occurs between the hydroxyl group in the polyol and the carboxyl group in the unsaturated fatty acid to form a new ester group, and the new ester group serves as a sustained-release group. The sustained-release group releases a carboxyl group under alkaline conditions to extend the concrete slump retention time; by reacting the amine monomer with the carboxyl group of the unsaturated fatty acid to form a small amount of amide groups, by introducing amide groups into the sustained-release polycarboxylate water reducer, the amide groups are decomposed into carboxyl groups under strong alkaline conditions and the decomposition rate is slow, further increasing the stepwise nature of the release groups, which can further increase the retention time of the concrete slump and further control the release rate of the sustained-release polycarboxylate water reducer.
[0033] 2. A slow-release polycarboxylate water reducer provided by the present invention, wherein the polyether monomer includes at least one of a four-carbon monomer, a five-carbon monomer, and a six-carbon monomer, preferably a six-carbon monomer. The present invention selects four-carbon to six-carbon monomers as the material for the polyether monomer in the water reducer, which can improve the slow-release effect of the slow-release polycarboxylate water reducer. Among them, the preferred material is the six-carbon monomer. Using the six-carbon monomer as the raw material and taking advantage of the high reaction activity and high heat release of the six-carbon monomer, it can not only ensure the slow release of the slow-release polycarboxylate water reducer in concrete, but also ensure the smooth release of the slow-release polycarboxylate water reducer, and ensure that there is no sudden increase or decrease in the slump of the concrete during the release process.
[0034] 3. A slow-release polycarboxylate water reducer provided by the present invention, wherein the molar ratio of the unsaturated fatty acid to the polyether monomer is 1 - 2.5:1. The present invention utilizes the characteristics of the high polymerization activity and relatively high heat release during the polymerization process of the polyether monomer. By limiting the molar ratio of the unsaturated fatty acid to the polyether monomer, the heat during the polymerization process of the polyether monomer is further used to promote the reaction of the unsaturated carboxylic acid ester, and the synthetic heat is fully utilized.
[0035] 4. A preparation method of a slow-release polycarboxylate water reducer provided by the present invention includes the following steps: reacting a first mixed solution and a second mixed solution with a bottom solution to form a mixed solution, and under alkaline conditions, aging and heat-treating the mixed solution, and then adding an amine monomer and a polyol thereto. The present invention uses an unsaturated fatty acid and an unsaturated carboxylic acid ester to form a first mixed solution, uses a reducing agent and a chain transfer agent to form a second mixed solution, and forms a mixed solution by reacting the first mixed solution and the second mixed solution with a bottom solution mainly composed of a polyether monomer. By adjusting the pH value of the mixed solution, heat-treating it, and then adding an amine monomer and a polyol to the mixed solution, amidation reaction and esterification reaction are achieved. The present invention introduces an amine monomer and a polyol, and the hydroxyl group in the polyol reacts with the carboxyl group in the unsaturated fatty acid to form a new ester group. The new ester group serves as a slow-release group, and the slow-release group releases a carboxyl group under alkaline conditions, prolonging the slump retention time of the concrete; using the amine monomer to react with the carboxyl group of the unsaturated fatty acid to form a small amount of amide groups. By introducing amide groups into the slow-release polycarboxylate water reducer, the amide groups decompose into carboxyl groups under strong alkaline conditions, which can further increase the slump retention time of the concrete and further control the release rate of the slow-release polycarboxylate water reducer. Description of the Drawings
[0036] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0037] Figure 1 It is the slump result diagram of the concrete formed by Application Example 1 and Application Examples 12 - 16 at different times in the experimental examples of the present invention. Specific Embodiments
[0038] The following embodiments are provided to better further understand the present invention. It is not limited to the described optimal embodiment, and does not constitute a limitation to the content and protection scope of the present invention. Any product that is the same as or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.
[0039] For those embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.
[0040] Example 1
[0041] This example provides a preparation method of a slow - release polycarboxylate water - reducing agent. The specific steps and methods are as follows:
[0042] (1) Take 340 g of ethylene glycol mono - vinyl polyethylene glycol ether (average molecular weight is 3000 Da), 300 g of water, 1 g of ferrous sulfate aqueous solution (the concentration of ferrous sulfate in the ferrous sulfate aqueous solution is 0.5 wt%), 4 g of hydrogen peroxide aqueous solution (the concentration of the hydrogen peroxide solution is 27.5 wt%), 1 g of sodium hypophosphite, and 2 g of ammonium persulfate, and stir them at a stirring rate of 200 rpm for 30 min to form a bottom liquid;
[0043] Take 12.24 g of acrylic acid (0.17 mol), 19.74 g of hydroxyethyl acrylate (0.17 mol), 29.5 g of hydroxypropyl acrylate (0.227 mol), and 18.52 g of water, and shake well to form a first mixed liquid;
[0044] Take 1 g of vitamin C, 1.5 g of mercaptoethanol, and 117.5 g of water, and shake well until the solids in the solution are completely dissolved and clear and transparent to form a second mixed liquid.
[0045] (2) While stirring the bottom liquid at a speed of 200 rpm, drop the first mixed liquid and the second mixed liquid into the bottom liquid to form a mixed liquid. Among them, the dropping time of the first mixed liquid is 50 min, and the dropping time of the second mixed liquid is 80 min. The first mixed liquid and the second mixed liquid are dropped into the bottom liquid in a uniform speed. After the dropping is completed, add 20.8 g of sodium hydroxide aqueous solution (the concentration of the sodium hydroxide aqueous solution is 32 wt%) to adjust the pH value of the mixed liquid to 8, and continue to stir at a speed of 200 rpm for 30 min.
[0046] (3) Raise the temperature of the mixed solution to 50 °C. While stirring, add 1.38 g of ethylenediamine (0.023 mol), 2.61 g of p-phenylenediamine (0.028 mol), and 6.2 g of sorbitol (0.034 mol) to the mixed solution to form a sustained-release polycarboxylate water reducer. The stirring rate is 200 rpm, and the stirring time is 30 min.
[0047] Example 2
[0048] This example provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that the amount of ethylenediamine is 0.017 mol and the amount of p-phenylenediamine is 0.017 mol, that is, the molar ratio of amine monomer to unsaturated fatty acid is 1:5.
[0049] Example 3
[0050] This example provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that the molar ratio of hydroxyethyl acrylate to hydroxypropyl acrylate is 1:1.
[0051] Example 4
[0052] This example provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that the molar ratio of hydroxyethyl acrylate to hydroxypropyl acrylate is 1.5:4.
[0053] Example 5
[0054] This example provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that an equimolar amount of hydroxybutyl acrylate is used to replace hydroxypropyl acrylate.
[0055] Example 6
[0056] This example provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that the molar amount of acrylic acid is 0.113 mol, that is, the molar ratio of acrylic acid to polyether monomer is 1:1.
[0057] Example 7
[0058] This example provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that the molar amount of acrylic acid is 0.2825 mol, that is, the molar ratio of acrylic acid to polyether monomer is 2.5:1.
[0059] Example 8
[0060] This embodiment provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Embodiment 1, except that the molar amount of sorbitol is 0.085 mol, that is, the molar ratio of sorbitol to unsaturated fatty acid is 1:2.
[0061] Example 9
[0062] This embodiment provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Embodiment 1, except that the molar amount of sorbitol is 0.028 mol, that is, the molar ratio of sorbitol to unsaturated fatty acid is 1:6.
[0063] Example 10
[0064] This embodiment provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Embodiment 1, except that isopentenyloxy polyethylene glycol ether (average molecular weight 3000 Da) of equal mass is used to replace ethylene glycol mono vinyl polyethylene glycol ether in step (1).
[0065] Example 11
[0066] This embodiment provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Embodiment 1, except that isobutenyloxy polyethylene glycol ether (average molecular weight 3000 Da) of equal mass is used to replace ethylene glycol mono vinyl polyethylene glycol ether in step (1).
[0067] Example 12
[0068] This embodiment provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are as follows:
[0069] (1) Take 600 g of ethylene glycol mono vinyl polyethylene glycol ether (average molecular weight 3000 Da), 350 g of water, 4 g of hydrogen peroxide aqueous solution (concentration of hydrogen peroxide aqueous solution is 27.5 wt%), 0.5 g of sodium hypophosphite and 4.7 g of sodium persulfate, and stir for 60 min at a stirring rate of 180 rpm to form a bottom liquid;
[0070] Take 0.3 mol of acrylic acid, 0.2 mol of hydroxyethyl acrylate, 0.2 mol of hydroxybutyl acrylate and 15 g of water, and shake well to form a first mixed solution;
[0071] Take 3 g of vitamin C, 4.5 g of mercaptoethanol and 118.5 g of water, and shake well until the solids in the solution are completely dissolved and the solution is clear and transparent to form a second mixed solution.
[0072] (2) While stirring, add the first mixed solution and the second mixed solution dropwise to the bottom solution to form a mixed solution. Among them, the stirring rate is 250 rpm, the dropping time of the first mixed solution is 60 min, the dropping time of the second mixed solution is 90 min, and the first mixed solution and the second mixed solution are dropped into the bottom solution in a uniform speed manner. After the dropping is completed, add 20.8 g of sodium hydroxide aqueous solution (the concentration of the sodium hydroxide aqueous solution is 32 wt%) to it, adjust the pH value of the mixed solution to 9, and continue to stir at a speed of 250 rpm for 30 min.
[0073] (3) Raise the temperature of the mixed solution to 40 °C. While stirring, add 0.023 mol of diethylenetriamine, 0.028 mol of p-phenylenediamine, and 0.034 mol of maltitol to the mixed solution to form a sustained-release polycarboxylate water reducer. The stirring rate is 250 rpm, and the stirring time is 30 min.
[0074] Example 13
[0075] This example provides a preparation method of a polycarboxylate water reducer. The specific steps and methods are as follows:
[0076] (1) Take 200 g of ethylene glycol monovinyl polyethylene glycol ether (average molecular weight is 3000 Da), 275 g of water, 2 g of ferrous sulfate (0.5 wt%), 2 g of hydrogen peroxide aqueous solution (the concentration of the hydrogen peroxide aqueous solution is 27.5 wt%), 1.5 g of sodium hypophosphite, and 1.5 g of sodium persulfate, and stir for 60 min at a stirring rate of 180 rpm to form a bottom solution;
[0077] Take 0.3 mol of acrylic acid, 0.2 mol of hydroxyethyl acrylate, 0.2 mol of hydroxybutyl acrylate, and 30 g of water, and shake well to form a first mixed solution;
[0078] Take 0.5 g of vitamin C, 1 g of mercaptoethanol, and 112.5 g of water, stir for 35 min at a stirring rate of 230 rpm, and shake well until the solids in the solution are completely dissolved and the solution is clear and transparent to form a second mixed solution.
[0079] (2) While stirring, add the first mixed solution and the second mixed solution dropwise to the bottom solution to form a mixed solution. Among them, the stirring rate is 180 rpm, the dropping time of the first mixed solution is 45 min, the dropping time of the second mixed solution is 60 min, and the first mixed solution and the second mixed solution are dropped into the bottom solution in a uniform speed manner. After the dropping is completed, add 20.8 g of sodium hydroxide solution (the concentration of the sodium hydroxide aqueous solution is 32 wt%) to it, adjust the pH of the mixed solution to 8, and stir at a speed of 200 rpm for 30 min.
[0080] (3) Raise the temperature of the mixed solution to 40 °C. While stirring, add 0.051 mol of diethylenetriamine and 0.034 mol of butanediol to the mixed solution to form a slow-release polycarboxylate water reducer. The stirring rate is 250 rpm and the stirring time is 30 min.
[0081] Comparative Example 1
[0082] This comparative example provides a preparation method of a slow-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that hydroxyethyl acrylate in molar amount is used to replace hydroxypropyl acrylate. That is, take 12.24 g of acrylic acid (0.17 mol), 45.31 g of hydroxyethyl acrylate (0.397 mol) and 18.52 g of water, and stir for 30 min at a stirring rate of 200 rpm to form a first mixed solution.
[0083] Comparative Example 2
[0084] This comparative example provides a preparation method of a slow-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that hydroxypropyl acrylate in molar amount is used to replace hydroxyethyl acrylate. That is, take 12.24 g of acrylic acid (0.17 mol), 39.75 g of hydroxypropyl acrylate (0.397 mol) and 18.52 g of water, and stir for 30 min at a stirring rate of 200 rpm to form a first mixed solution.
[0085] Comparative Example 3
[0086] This comparative example provides a preparation method of a slow-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that step (3) is not included. The specific steps are as follows:
[0087] (1) Take 340 g of ethylene glycol monovinyl polyethylene glycol ether (average molecular weight is 3000), 300 g of water, 1 g of ferrous sulfate (0.5 wt%), 4 g of hydrogen peroxide aqueous solution (concentration of hydrogen peroxide aqueous solution is 27.5 wt%), 1 g of sodium hypophosphite and 2 g of ammonium persulfate, and stir for 30 min at a stirring rate of 200 rpm to form a bottom liquid;
[0088] Take 12.24 g of acrylic acid (0.17 mol), 19.74 g of hydroxyethyl acrylate (0.17 mol), 29.5 g of hydroxypropyl acrylate (0.227 mol) and 18.52 g of water, and stir for 30 min at a stirring rate of 200 rpm to form a first mixed solution;
[0089] Take 1 g of vitamin C, 1.5 g of mercaptoethanol and 117.5 g of water, and stir for 30 min at a stirring rate of 200 rpm to form a second mixed solution.
[0090] (2) Add the first mixed solution dropwise to the base solution, and then add the second mixed solution dropwise thereto to form a mixed solution. Among them, the dropping time of the first mixed solution is 50 min, and the dropping time of the second mixed solution is 80 min. The first mixed solution and the second mixed solution are added dropwise to the base solution at a uniform speed. After the dropping is completed, add 10.6 g of sodium hydroxide solution (the concentration of the sodium hydroxide aqueous solution is 32 wt%) thereto and stir for 30 min.
[0091] Comparative Example 4
[0092] This comparative example provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that the mass of ethylene glycol monovinyl polyethylene glycol ether is 1191 g, that is, the molar amount of ethylene glycol monovinyl polyethylene glycol ether is 0.4 mol, and the molar ratio of ethylene glycol monovinyl polyethylene glycol ether to unsaturated carboxylic acid ester is 1:1.
[0093] Comparative Example 5
[0094] This comparative example provides a preparation method of a sustained-release polycarboxylate water reducer. The specific steps and methods are the same as those in Example 1, except that the molar amount of hydroxyethyl acrylate is 0.34 mol and the molar amount of hydroxypropyl acrylate is 0.454 mol, that is, the molar ratio of ethylene glycol monovinyl polyethylene glycol ether to unsaturated carboxylic acid ester is 1:7.
[0095] Application Examples 1 - 16
[0096] Mix 360 kg of cement, 794 kg of sand, 710 kg of medium-sized stones, 304 kg of small-sized stones, 215 kg of water, and 1 kg of water reducer to form concrete. Among them, the water reducers are the sustained-release polycarboxylate water reducers prepared in Examples 1 - 11 and Comparative Examples 1 - 5.
[0097] Experimental Example
[0098] Measure the slump of the concrete formed in Application Examples 1 - 16 at different times after mixing according to the national standard GB8076 - 2008, and the results are shown in Table 1.
[0099] Table 1 Experimental Results of Concrete
[0100]
[0101]
[0102] In practical applications, the slump of concrete fluctuates greatly, which will not only make it difficult to pour and vibrate the concrete evenly, affecting the compactness of the concrete, but also lead to uneven internal structure of the concrete, affecting the overall strength. A sudden increase in the slump of concrete will cause bleeding and segregation of the concrete, affecting the construction quality and the durability of the building. While a too rapid decrease in the slump will cause the concrete to be unable to be pumped, and even result in pipe blockage and loss of workability, etc. In the present invention, two unsaturated carboxylic esters are used as raw materials for synthesizing the slow-release polycarboxylate water reducer. When the slow-release water reducer is added to the concrete, under alkaline conditions, the ester groups in the unsaturated carboxylic esters are hydrolyzed into carboxyl groups, which can increase the retention time of the concrete slump, extend the working time, and avoid the problem of excessive slump loss during transportation. Further, by utilizing the difference in the hydrolysis rates of the two unsaturated carboxylic esters, the release rate of the slow-release polycarboxylate water reducer can be effectively controlled to ensure the steady release of the slow-release polycarboxylate water reducer. At the same time, in the present invention, an amine monomer and a polyol are introduced. The hydroxyl group in the polyol reacts with the carboxyl group in the unsaturated fatty acid to form a new ester group, and the new ester group serves as a slow-release group. The slow-release group releases carboxyl groups under alkaline conditions to extend the retention time of the concrete slump. By reacting the amine monomer with the carboxyl group of the unsaturated fatty acid to form a small amount of amide groups, by introducing amide groups into the slow-release polycarboxylate water reducer, the amide groups are decomposed into carboxyl groups under strong alkaline conditions, which can further increase the retention time of the concrete slump and further control the release rate of the slow-release polycarboxylate water reducer.
[0103] According to Table 1 and Figure 1It can be seen that, compared with Comparative Examples 1-5, the slow-release polycarboxylate superplasticizer provided by the embodiments of the present invention has a good slow-release effect. During the test time, the change in slump is relatively gentle. In Comparative Example 1 or 2, a slow-release polycarboxylate superplasticizer formed by only one unsaturated carboxylic acid ester is used. Among them, the slump of the slow-release polycarboxylate superplasticizer formed in Comparative Example 1 drops suddenly at 1 h, and the slump of the slow-release polycarboxylate superplasticizer formed in Comparative Example 2 increases suddenly at 1 h, then reaches the peak at 2 h, and then drops suddenly. However, the slow-release polycarboxylate superplasticizer prepared in the embodiments of the present invention can significantly reduce the slump loss over time. By using two unsaturated carboxylic acid esters, it is possible to maintain a stable release during the slow-release process of the superplasticizer without sudden increase or decrease. Further, the superplasticizer formed in Comparative Example 3 does not contain amine monomers and polyols, increases suddenly to the peak at 1 h, and then drops suddenly. In the embodiments of the present invention, an amide group is introduced through the reaction of amine monomers to further reduce the release rate, ensuring that the release of the superplasticizer proceeds step by step. At the same time, a protecting group is introduced through the addition of polyols to ensure that the concrete reaches a high slump retention time and the release of the superplasticizer proceeds smoothly. Compared with Comparative Example 4 or 5, the slump value is too low to meet the requirements of the concrete. Especially after 2 h for the concrete formed in Comparative Example 4 and after 1 h for the concrete formed in Comparative Example 5, the concrete no longer has fluidity. By limiting the molar ratio of the polyether monomer to the unsaturated carboxylic acid ester to 1:2-6 in the embodiments of the present invention, the release rate of the slow-release polycarboxylate superplasticizer can be controlled, the stable release of the slow-release polycarboxylate superplasticizer can be maintained, the slump retention time can be extended, and the service life of the concrete can be improved.
[0104] Obviously, the above embodiments are only examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.
Claims
1. A sustained-release polycarboxylate water-reducing agent, characterized in that: The invention comprises the following raw materials in parts by weight: Base liquid, first mixed liquid and second mixed liquid, amine monomer and polyol, The base liquid comprises a polyether monomer, a first reducing agent and an oxidizing agent, The first mixed liquid includes unsaturated fatty acid and unsaturated carboxylic acid ester, the unsaturated carboxylic acid ester includes a first unsaturated carboxylic acid ester and a second unsaturated carboxylic acid ester, the first unsaturated carboxylic acid ester and the second unsaturated carboxylic acid ester are not the same substance, The molar ratio of the polyether monomer to the unsaturated carboxylic acid ester is 1:2-6, The second mixed liquid includes a second reducing agent and a chain transfer agent.
2. The sustained-release polycarboxylate water-reducing agent according to claim 1, characterized in that: The polyether monomer comprises at least one of a four-carbon monomer, a five-carbon monomer and a six-carbon monomer, preferably a six-carbon monomer; and / or, The first unsaturated carboxylic acid ester or the second unsaturated carboxylic acid ester is independently selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate; and / or, The amine monomer includes at least one of p-aniline, ethylenediamine, diethylenetriamine, tetraethylenepentamine or pentaethylenehexamine.
3. The sustained-release polycarboxylate water-reducing agent according to claim 2, characterized in that: The amine monomer includes at least one of p-aniline, ethylenediamine, diethylenetriamine, tetraethylenepentamine or pentaethylenehexamine; and / or, The molar ratio of the amine monomer to the unsaturated fatty acid is 1:2-5.
4. The sustained-release polycarboxylate water-reducing agent according to claim 2, characterized in that: The polyol comprises at least one of sorbitol, maltitol, butylene glycol or propylene glycol; and / or, The molar ratio of the polyol to the unsaturated fatty acid is 1:2-6.
5. The sustained-release polycarboxylate water-reducing agent according to claim 1, characterized in that: The molar ratio of the first unsaturated carboxylic acid ester to the second unsaturated carboxylic acid ester is 1.5:1.5-4; and / or, The molar ratio of the unsaturated fatty acid to the polyether monomer is 1-2.5:
1.
6. The sustained-release polycarboxylate water-reducing agent according to claim 2, characterized in that: The six-carbon monomer includes at least one of 4-hydroxybutyl vinyl polyoxyethylene ether and ethylene glycol monovinyl polyethylene glycol ether; and / or, The five-carbon monomer includes isopentenyl polyethylene glycol ether; and / or, The four-carbon monomer includes isobutylene polyethylene glycol ether; and / or, The first reducing agent includes at least one of ferrous sulfate and sodium hypophosphite; and / or, The oxidant comprises at least one of aqueous hydrogen peroxide solution and ammonium persulfate; and / or, The unsaturated fatty acid comprises acrylic acid; and / or, The second reducing agent comprises L-ascorbic acid; and / or, The chain transfer agent includes mercaptoethanol.
7. The sustained-release polycarboxylate water-reducing agent according to claim 6, characterized in that: In the base liquid, the mass fraction of the polyether monomer is 300-380 parts, the mass fraction of the first reducing agent is 0.5-3.5 parts, the mass fraction of the oxidant is 3-9 parts, and the base liquid further includes water, the mass fraction of the water is 275-350 parts; and / or, The first mixed solution contains 8.5-16 parts by weight of unsaturated fatty acids, and the first mixed solution further contains 15-30 parts by weight of water; and / or, In the second mixed liquid, the mass fraction of the second reducing agent is 0.5-3 parts, the mass fraction of the chain transfer agent is 1-4.5 parts, and the second mixed liquid also includes water, and the mass fraction of the water is 112.5-118.5 parts.
8. A method for preparing the sustained-release polycarboxylate water-reducing agent according to any one of claims 1 to 7, characterized in that: The following steps are included: The first mixed liquid and the second mixed liquid react with the base liquid to form a mixed liquid, and the mixed liquid is aged and heat-treated under alkaline conditions, and then an amine monomer and a polyol are added thereto.
9. The method for preparing the sustained-release polycarboxylate water-reducing agent according to claim 8, characterized in that: The first mixed solution and the second mixed solution are dripped into the base solution for reaction by dripping, the first mixed solution and the second mixed solution are dripped into the base solution at a uniform speed, the dripping time of the first mixed solution is 45-60 minutes, and the dripping time of the second mixed solution is 60-90 minutes; and / or, The first mixed solution and the second mixed solution react with the base solution to form a mixed solution, wherein the pH value of the mixed solution is adjusted to 8-9; and / or, While stirring the base liquid, the first mixed liquid and the second mixed liquid are added dropwise to the base liquid, the stirring rate is 180-250 rpm, and the stirring time is 30-60 min; and / or, The temperature of the heat treatment is 40-50°C.
10. Use of the slow-release polycarboxylate water-reducing agent according to any one of claims 1 to 7 or the slow-release polycarboxylate water-reducing agent prepared by the method for preparing the slow-release polycarboxylate water-reducing agent according to any one of claims 8 to 9 in concrete.