CN114478939B - Slow-release polycarboxylate superplasticizer and preparation method thereof - Google Patents

Slow-release polycarboxylate superplasticizer and preparation method thereof Download PDF

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CN114478939B
CN114478939B CN202210050135.3A CN202210050135A CN114478939B CN 114478939 B CN114478939 B CN 114478939B CN 202210050135 A CN202210050135 A CN 202210050135A CN 114478939 B CN114478939 B CN 114478939B
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slow
water
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chain transfer
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CN114478939A (en
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黄雪
宋健勇
王晓芳
盛思仲
鹿立云
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Nanjing Youxi Technology Group Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
    • C08F283/06—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polyethers, polyoxymethylenes or polyacetals
    • C08F283/065—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polyethers, polyoxymethylenes or polyacetals on to unsaturated polyethers, polyoxymethylenes or polyacetals
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/16—Sulfur-containing compounds
    • C04B24/18—Lignin sulfonic acid or derivatives thereof, e.g. sulfite lye
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F289/00—Macromolecular compounds obtained by polymerising monomers on to macromolecular compounds not provided for in groups C08F251/00 - C08F287/00
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
    • C04B2103/30—Water reducers, plasticisers, air-entrainers, flow improvers

Abstract

The invention relates to the technical field of concrete admixtures, in particular to a slow-release polycarboxylic acid water reducing agent and a preparation method thereof, wherein the slow-release polycarboxylic acid water reducing agent comprises the following raw materials: the concrete slump loss inhibitor comprises isopentene polyoxyethylene ether, acrylic acid, an acrylate monomer, sodium lignosulfonate, polyethylene glycol monomethyl ether methacrylate, an initiator and a chain transfer agent, and has the advantages of good slow release performance, high dispersity, strong adaptability and effective inhibition of concrete slump loss.

Description

Slow-release polycarboxylate superplasticizer and preparation method thereof
Technical Field
The invention relates to the technical field of concrete admixtures, in particular to a slow-release polycarboxylic acid water reducing agent and a preparation method thereof.
Background
The polycarboxylate superplasticizer can effectively provide the fluidity of concrete and improve the workability of the concrete, is widely applied to large-scale infrastructure projects such as subways, bridges, nuclear power, hydropower and the like, and becomes a mainstream product in the concrete superplasticizer industry. Because of the great difference of concrete raw materials, the phenomenon of too fast loss of the concrete slump often occurs in high-temperature weather or long-time and long-distance transportation. In practical engineering application, retarders such as sodium gluconate, white sugar and sodium hexametaphosphate are compounded, but the addition of the retarders cannot completely solve the problem of concrete slump loss, and can also cause the problems of segregation, delayed bleeding, putrefaction and deterioration of concrete.
The polycarboxylic acid water reducing agent generally selects monomer materials with different groups, and synthesizes polymerizable structural units into the water reducing agent with a preset structure and performance through addition reaction according to the molecular design principle. It is synthesized by free radical copolymerization of more than 2 kinds of monomers and some polymerizable monomers containing sulfonic acid group, ester group or other groups, and its chemical molecular structure contains structural units of-COOH, -OH, -SOH and PEO and other groups. Because the polycarboxylate superplasticizer has designability of a molecular structure, the combination of different structural units can realize the clipping of product functions, and products with different functional types can be prepared.
The slow-release polycarboxylate superplasticizer controls the dispersion process of water reducer molecules on cement particles in a physical or chemical mode, and enables the dispersion of the water reducer molecules on the cement particles to be continuously and slowly carried out within a certain time. The concrete adopting the water reducing agent has smaller slump at the initial stirring stage, but the slump of the concrete can be increased along with the increase of time, and the characteristic of the slow-release water reducing agent not only can keep the slump of the ready-mixed concrete after long-time transportation, but also can avoid the evaporation of mixing water caused by long-time transportation at high temperature, thereby bringing convenience to construction units and improving the construction efficiency.
Chinese patent application CN101205127A discloses a formula of a sustained-release polycarboxylic acid high-performance water reducing agent and a preparation method thereof. The formula comprises an esterification reaction formula and a polymerization reaction formula, wherein the esterification reaction formula adopts a part of maleic anhydride, polyethylene glycol monomethyl ether with molecular weight of 600, polymerization inhibitor hydroquinone, catalyst p-toluenesulfonic acid and concentrated sulfuric acid as raw materials. Maleic anhydride, polyethylene glycol monomethyl ether with molecular weight of 600, hydroquinone as polymerization inhibitor and p-toluenesulfonic acid as catalyst are added at 75 ℃ to react for 2 hours, and concentrated sulfuric acid is added to continue the constant temperature reaction for 3 hours. Adding the rest part of maleic anhydride and allyl polyoxyethylene ether (with the polymerization degree of 26) water into the esterification reaction kettle, adding water into acrylic acid and sodium methallyl sulfonate to prepare a solution, adding water into ammonium persulfate to prepare a solution, respectively dropwise adding the solutions into the reaction kettle for 2 hours, reacting for 1.5 hours at constant temperature, cooling to 50 ℃, adding liquid alkali for neutralization, and obtaining the slow-release polycarboxylic acid high-performance water reducing agent. The invention adopts maleic anhydride as a reaction monomer, and the hydrolysis speed is high, but the slow release speed and the slow release performance are still not ideal.
Chinese patent application CN102040741A discloses a method for preparing a slow-release polycarboxylate superplasticizer by using a molecular assembly technology. The process comprises two steps, wherein the first step is a polymerization reaction, the raw material formula comprises a large monomer, a small monomer, thioglycollic acid and ammonium persulfate, the raw materials are prepared into an aqueous solution, the aqueous solution is dripped into water at the temperature of 50-100 ℃, and the reaction is continued to obtain an assembly precursor; and secondly, adding an assembling agent into the assembly precursor at the temperature of between 50 and 70 ℃, stirring and adding sodium hydroxide to obtain the slow-release polycarboxylic acid water reducing agent. The water reducing agent has excellent adaptability to the fluctuation of the quality of concrete raw materials, but the mixing amount of the water reducing agent is higher when the water reducing agent is used in concrete.
In addition, the following problems still exist in the use process of the general polycarboxylic acid water reducing agent: the common polycarboxylic acid water reducing agent has the problem of compatibility with different cement systems. When the same polycarboxylic acid water reducing agent is used for different cement systems, the polycarboxylic acid water reducing agent can show different dispersivity and dispersivity retention capability, and not only the initial fluidity is different, but also the change rule of the fluidity along with time is different. When a polycarboxylic acid water-reducing agent which exhibits good fluidity and fluidity retention ability for a certain type of cement is used for another type of cement, the loss of fluidity is too rapid, or the fluidity increases with time, and therefore, the polycarboxylic acid water-reducing agent has a problem of compatibility with cement. In addition, other raw materials than cement, such as fly ash, mineral powder, stone powder, clay, etc., in concrete also have compatibility problems with polycarboxylic acid water reducers. In practical application, the influence of the concrete raw material on the application performance of the polycarboxylate superplasticizer is very obvious.
Therefore, it is necessary to develop a slow-release polycarboxylic acid water reducing agent and a preparation method thereof, which can solve the above technical problems.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the slow-release polycarboxylate superplasticizer which has good slow-release performance, high dispersity and strong adaptability and effectively inhibits the slump loss of concrete and the preparation method thereof.
The invention is realized by the following technical scheme:
a slow-release polycarboxylic acid water reducing agent is prepared from the following raw materials: isopentene polyoxyethylene ether TPEG, acrylic acid AA, an acrylate monomer, sodium lignosulfonate, polyethylene glycol monomethyl ether methacrylate, an initiator and a chain transfer agent.
Preferably, the slow-release polycarboxylate superplasticizer is prepared from the following raw materials in parts by weight: 20-30 parts of isopentenyl polyoxyethylene ether TPEG, 5-10 parts of acrylic AA, 5-10 parts of acrylate monomers, 4-8 parts of sodium lignosulfonate, 15-25 parts of polyethylene glycol monomethyl ether methacrylate, 0.3-0.8 part of an initiator and 1-2 parts of a chain transfer agent.
Preferably, the isopentenyl polyoxyethylene ether TPEG, mn =2000-2400.
Preferably, the acrylate monomers include at least one of hydroxyethyl acrylate HEA and hydroxypropyl acrylate HPA.
Preferably, the chain transfer agent comprises mercaptoethanol or thioglycolic acid.
Preferably, the initiator consists of ammonium persulfate, sodium bisulfite and dimethyl azodiisobutyrate in a mass ratio of 1.
The invention also relates to a preparation method of the slow-release polycarboxylate superplasticizer, which comprises the following steps:
(1) Adding water into isopentene polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and acrylate monomers, adding water and part of chain transfer agent to obtain mixed solution B;
(3) Adding water and the residual chain transfer agent into sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate to obtain a mixed solution C;
(4) Heating the mixed solution A to 40-60 ℃, simultaneously slowly adding the mixed solution B, the mixed solution C and the initiator, reacting at 50-70 ℃, cooling after the reaction is finished, and adjusting the pH of the solution to be =6.0-7.0 to obtain the catalyst.
Preferably, in step (1), isopentenyl polyoxyethylene ether is added with 1-3 times of water to obtain a mixed solution A.
Preferably, in the step (2), acrylic acid and acrylate monomers are taken, and 1-3 times of water and 30-50% of chain transfer agent are added to obtain a mixed solution B.
Preferably, in the step (3), sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate are taken, and 1-3 times of water and the rest of chain transfer agent are added to obtain a mixed solution C.
Preferably, in the step (4), the temperature of the mixed solution A is raised to 40-60 ℃, the mixed solution B and ammonium persulfate are slowly added at the same time, sodium bisulfite is added after 15-25min, the mixture reacts at 40-60 ℃ for 30-40min, the mixed solution C and dimethyl azodiisobutyrate are slowly added at the same time, the mixture reacts at 50-70 ℃ for 1-2h, and the pH =6.0-7.0 is adjusted after cooling, so that the catalyst is obtained.
More preferably, the preparation method comprises the following steps:
(1) Adding 1-3 times of water into isopentenyl polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and acrylate monomers, adding 1-3 times of water and 30-50% of chain transfer agent to obtain a mixed solution B;
(3) Taking sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate, adding 1-3 times of water and the rest of chain transfer agent to obtain a mixed solution C;
(4) Heating the mixed solution A to 40-60 ℃, slowly adding the mixed solution B and ammonium persulfate at the same time, adding sodium bisulfite after 15-25min, reacting at 40-60 ℃ for 30-40min, slowly adding the mixed solution C and dimethyl azodiisobutyrate at the same time, reacting at 50-70 ℃ for 1-2h, cooling, and adjusting the pH =6.0-7.0 to obtain the azodiisobutyrate.
The invention has the beneficial effects that:
the invention optimizes the composition of reaction monomers, adopts isopentenyl polyoxyethylene ether, acrylic acid, acrylate monomers, sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate for polymerization, introduces a plurality of groups such as ester groups, sulfonic groups, hydroxyl groups and the like into side chains, obviously improves the water reducing performance, simultaneously obtains the polycarboxylic acid water reducing agent with excellent slow release performance, excellent slump retaining performance and low sensitivity, solves the problem of over-quick slump loss in engineering, simultaneously has excellent mechanical property, has 28d compressive strength of over 65MPa and strong adaptability, and can adapt to cement varieties produced by a plurality of manufacturers and simultaneously maintain excellent compatibility and dispersibility through tests.
The invention optimizes the composition of the initiator, ensures the stability and controllability of the polymerization reaction and is beneficial to the practical application of the product.
The invention optimizes the adding sequence of the raw materials in the reaction process, and obviously improves the properties of the prepared polycarboxylic acid water reducer in all aspects.
Detailed Description
The invention is further described below in conjunction with specific embodiments, and the advantages and features of the invention will become more apparent as the description proceeds. These examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.
Example 1
The slow-release polycarboxylate superplasticizer comprises the following raw materials in parts by weight: 20 parts of isopentene polyoxyethylene ether (Mn = 2000), 5 parts of acrylic acid AA, 5 parts of hydroxyethyl acrylate HEA, 4 parts of sodium lignosulfonate, 15 parts of polyethylene glycol monomethyl ether methacrylate, 0.3 part of an initiator and 1 part of mercaptoethanol.
The initiator consists of ammonium persulfate, sodium bisulfite and dimethyl azodiisobutyrate, and the mass ratio of the ammonium persulfate to the sodium bisulfite to the dimethyl azodiisobutyrate is 1.
The preparation method of the slow-release polycarboxylate superplasticizer comprises the following steps:
(1) Adding 1 time of water into isopentene polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and hydroxyethyl acrylate, adding 1 time of water and 30% mercaptoethanol to obtain a mixed solution B;
(3) Taking sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate, adding 1 time of water and the rest mercaptoethanol to obtain a mixed solution C;
(4) Heating the mixed solution A to 40 ℃, slowly adding the mixed solution B and ammonium persulfate at the same time, adding sodium bisulfite after 15min, reacting at 40 ℃ for 30min, slowly adding the mixed solution C and dimethyl azodiisobutyrate at the same time, reacting at 50 ℃ for 1h, cooling, and adjusting the pH of the solution to be = 6.0.
Example 2
The slow-release polycarboxylate superplasticizer comprises the following raw materials in parts by weight: 30 parts of isopentenyl polyoxyethylene ether (Mn = 2400), 10 parts of acrylic acid AA, 10 parts of hydroxypropyl acrylate HPA, 8 parts of sodium lignosulfonate, 25 parts of polyethylene glycol monomethyl ether methacrylate, 0.8 part of an initiator and 2 parts of thioglycolic acid.
The initiator consists of ammonium persulfate, sodium bisulfite and dimethyl azodiisobutyrate in a mass ratio of 1.
The preparation method of the slow-release polycarboxylate superplasticizer comprises the following steps:
(1) Adding 3 times of water into isopentene polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and hydroxypropyl acrylate, and adding 3 times of water and 50% thioglycollic acid to obtain a mixed solution B;
(3) Taking sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate, adding 3 times of water and the rest thioglycolic acid to obtain a mixed solution C;
(4) Heating the mixed solution A to 60 ℃, simultaneously and slowly adding the mixed solution B and ammonium persulfate, adding sodium bisulfite after 25min, reacting for 40min at 60 ℃, simultaneously and slowly adding the mixed solution C and dimethyl azodiisobutyrate, reacting for 2h at 70 ℃, cooling, and adjusting the pH of the solution to be =7.0, thus obtaining the ammonium persulfate/sodium hydrosulfite composite material.
Example 3
The slow-release polycarboxylate superplasticizer comprises the following raw materials in parts by weight: 25 parts of isopentenyl polyoxyethylene ether (Mn = 2400), 8 parts of acrylic acid AA, 8 parts of hydroxyethyl acrylate HEA, 5 parts of sodium lignosulfonate, 20 parts of polyethylene glycol monomethyl ether methacrylate, 0.5 part of an initiator and 2 parts of mercaptoethanol.
The initiator consists of ammonium persulfate, sodium bisulfite and dimethyl azodiisobutyrate, and the mass ratio of the ammonium persulfate to the sodium bisulfite to the dimethyl azodiisobutyrate is 1.
The preparation method of the slow-release polycarboxylic acid water reducing agent comprises the following steps:
(1) Adding 2 times of water into isopentene polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and hydroxyethyl acrylate, adding 2 times of water and 40% mercaptoethanol to obtain a mixed solution B;
(3) Adding 2 times of water and the residual mercaptoethanol into sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate to obtain a mixed solution C;
(4) Heating the mixed solution A to 50 ℃, slowly adding the mixed solution B and ammonium persulfate at the same time, adding sodium bisulfite after 20min, reacting at 50 ℃ for 35min, slowly adding the mixed solution C and dimethyl azodiisobutyrate at the same time, reacting at 60 ℃ for 1.5h, cooling, and adjusting the pH of the solution to be = 6.5.
Comparative example 1
The difference from the example 3 is only that the total amount of the components except the initiator and the mercaptoethanol and the ratio of the amount are not changed, the sodium lignosulfonate component is deleted, and the other conditions are the same.
Comparative example 2
The difference from the example 3 is only that the total amount of the components except the initiator and the mercaptoethanol is not changed, the amount and the proportion are different, and other conditions are the same, specifically as follows:
the slow-release polycarboxylate superplasticizer comprises the following raw materials in parts by weight: 35 parts of isopentene polyoxyethylene ether (Mn = 2400), 12 parts of acrylic acid AA, 4 parts of hydroxyethyl acrylate HEA, 5 parts of sodium lignosulfonate, 10 parts of polyethylene glycol monomethyl ether methacrylate, 0.5 part of an initiator and 2 parts of mercaptoethanol.
Comparative example 3
The method is different from the embodiment 3 only in that the total dosage of the initiator is unchanged, the specific composition is different, only ammonium persulfate and sodium bisulfite are contained, the mass ratio of the ammonium persulfate to the sodium bisulfite is 1, the other conditions are the same, and the specific preparation process comprises the following steps:
(1) Adding 2 times of water into isopentene polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and hydroxyethyl acrylate, adding 2 times of water and 40% mercaptoethanol to obtain a mixed solution B;
(3) Adding 2 times of water and the residual mercaptoethanol into sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate to obtain a mixed solution C;
(4) Heating the mixed solution A to 50 ℃, slowly adding the mixed solution B and ammonium persulfate at the same time, adding sodium bisulfite after 20min, reacting at 50 ℃ for 35min, slowly adding the mixed solution C, reacting at 60 ℃ for 1.5h, cooling, and adjusting the pH of the solution to be = 6.5.
Comparative example 4
The difference from the example 3 is that the total amount of the initiator is unchanged, the specific composition is different, only dimethyl azodiisobutyrate is contained, and the rest conditions are the same, and the specific preparation process is as follows:
(1) Adding 2 times of water into isopentene polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and hydroxyethyl acrylate, adding 2 times of water and 40% mercaptoethanol to obtain a mixed solution B;
(3) Adding 2 times of water and the residual mercaptoethanol into sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate to obtain a mixed solution C;
(4) Heating the mixed solution A to 50 ℃, simultaneously and slowly adding the mixed solution B and dimethyl azodiisobutyrate, slowly adding the mixed solution C after 55min, reacting for 1.5h at 60 ℃, cooling, and then adjusting the pH of the solution to be =6.5, thus obtaining the azodiisobutyrate.
Comparative example 5
The difference from the example 3 is only that the reaction sequence of the raw materials in the step (4) in the preparation process of the slow-release polycarboxylic acid water reducing agent is different, and the reaction sequence is as follows:
heating the mixed solution A to 50 ℃, slowly adding the mixed solution C and dimethyl azodiisobutyrate at the same time, reacting for 1.5h at 60 ℃, slowly adding the mixed solution B and ammonium persulfate at the same time, adding sodium bisulfite after 20min, reacting for 35min at 50 ℃, cooling, and adjusting the pH = 6.5.
Test example 1
The slow-release polycarboxylic acid water reducing agent prepared in the examples 1 to 3 and the comparative examples 1 to 5 is subjected to dispersibility test according to GB/T8077-2000 'test method for homogeneity of concrete admixture': southern cement M42.5, the water reducing agent folded solid content of 0.2%, the water usage was 87g, and the results are shown in Table 1.
TABLE 1
Figure BDA0003473565610000061
Figure BDA0003473565610000071
Test example 2
The slow-release polycarboxylic acid water reducing agent prepared in the examples 1 to 3 and the comparative examples 1 to 5 is tested according to GB 8076-2008 concrete admixture, the folded solid content of the water reducing agent is 0.2%, and the results are shown in Table 2.
TABLE 2
Figure BDA0003473565610000072
The above detailed description is specific to one possible embodiment of the present invention, and the embodiment is not intended to limit the scope of the present invention, and all equivalent implementations or modifications without departing from the scope of the present invention should be included in the technical scope of the present invention.

Claims (7)

1. The slow-release polycarboxylate superplasticizer is characterized by comprising the following raw materials in parts by weight: 20-30 parts of isopentenyl polyoxyethylene ether, 5-10 parts of acrylic acid, 5-10 parts of acrylate monomer, 4-8 parts of sodium lignosulfonate, 15-25 parts of polyethylene glycol monomethyl ether methacrylate, 0.3-0.8 part of initiator and 1-2 parts of chain transfer agent;
the initiator consists of ammonium persulfate, sodium bisulfite and dimethyl azodiisobutyrate, and the mass ratio of the ammonium persulfate to the sodium bisulfite to the dimethyl azodiisobutyrate is 1-2;
the preparation method of the slow-release polycarboxylate superplasticizer comprises the following steps:
(1) Adding water into isopentene polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and acrylate monomers, adding water and part of chain transfer agent to obtain mixed solution B;
(3) Taking sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate, adding water and the rest of chain transfer agent to obtain a mixed solution C;
(4) Heating the mixed solution A to 40-60 ℃, slowly adding the mixed solution B and ammonium persulfate at the same time, adding sodium bisulfite after 15-25min, reacting at 40-60 ℃ for 30-40min, slowly adding the mixed solution C and dimethyl azodiisobutyrate at the same time, reacting at 50-70 ℃ for 1-2h, cooling, and adjusting the pH =6.0-7.0 to obtain the azodiisobutyrate.
2. The slow-release polycarboxylate water reducer of claim 1, wherein the isopentenyl polyoxyethylene ether has Mn =2000-2400.
3. The slow-release polycarboxylate water reducer according to claim 1, wherein the acrylate monomers comprise at least one of hydroxyethyl acrylate HEA and hydroxypropyl acrylate HPA.
4. The slow-release polycarboxylate water reducer according to claim 1, wherein the chain transfer agent comprises mercaptoethanol or mercaptoacetic acid.
5. A preparation method of the slow-release polycarboxylic acid water reducing agent disclosed by any one of claims 1 to 4, which is characterized by comprising the following steps of:
(1) Adding water into isopentene polyoxyethylene ether to obtain a mixed solution A;
(2) Taking acrylic acid and acrylate monomers, adding water and part of chain transfer agent to obtain mixed solution B;
(3) Adding water and the residual chain transfer agent into sodium lignosulfonate and polyethylene glycol monomethyl ether methacrylate to obtain a mixed solution C;
(4) Heating the mixed solution A to 40-60 ℃, simultaneously and slowly adding the mixed solution B and ammonium persulfate, adding sodium bisulfite after 15-25min, reacting at 40-60 ℃ for 30-40min, simultaneously and slowly adding the mixed solution C and dimethyl azodiisobutyrate, reacting at 50-70 ℃ for 1-2h, cooling, and adjusting the pH of the solution to be =6.0-7.0, thus obtaining the ammonium sulfate.
6. The preparation method according to claim 5, wherein in the step (1), isopentenyl polyoxyethylene ether is added with 1-3 times of water to obtain a mixed solution A; and (3) taking sodium lignosulphonate and polyethylene glycol monomethyl ether methacrylate, adding 1-3 times of water and the rest of chain transfer agent to obtain a mixed solution C.
7. The preparation method according to claim 5, wherein in the step (2), the acrylic acid and the acrylic ester monomer are taken, and 1-3 times of water and 30-50% of chain transfer agent are added to obtain a mixed solution B.
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