Low-temperature rapid-dispersion-type polycarboxylic acid superplasticizer and preparation method therefor

Abstract

The present invention belongs to concrete admixtures, and particularly relates to a low-temperature rapid-dispersion-type polycarboxylic acid superplasticizer and a preparation method therefor. The preparation method of the present invention comprises two main steps. Firstly, a low-molecular-weight polyether A terminated with multiple adsorption groups is prepared by means of a transesterification reaction, and secondly, the obtained polyether A is subjected to a copolymerization reaction together with an allyl polyether macromonomer, an oxidizing agent, a reducing agent, a chain transfer agent and a chain extender, so as to obtain a low-temperature rapid-dispersion-type polycarboxylic acid superplasticizer. In the preparation method, specific monomers and reaction conditions are used to achieve the low-temperature rapid dispersion performance of the superplasticizer, such that the finally obtained superplasticizer can be widely applied to the preparation of various types of concrete, thereby improving the working efficiency and the performance of the concrete.

Description

A low-temperature fast-dispersing polycarboxylate water-reducing agent and its preparation method Technical Field

[0001] The invention relates to a concrete admixture, in particular to a low-temperature fast-dispersing polycarboxylate water-reducing agent and a preparation method thereof. Background Art

[0002] Using polycarboxylate superplasticizers (PCAs) to improve the dispersion properties of cementitious materials in low-temperature environments is a challenging problem. Traditional PCAs disperse slowly at low temperatures, resulting in poor initial water reduction, which limits the efficiency and quality of concrete construction in cold regions.

[0003] The existing polycarboxylate superplasticizers have some challenges and shortcomings in their dispersion performance under low-temperature environments, which are mainly manifested in the following aspects: (1) Slow dispersion speed under low temperature conditions: Under low-temperature conditions, the dispersion speed of traditional polycarboxylate superplasticizers is relatively slow, and they cannot quickly show a good dispersion effect, resulting in poor initial fluidity of concrete. (2) Unstable dispersion effect: Due to the influence of low temperature, the dispersion effect of existing polycarboxylate superplasticizers under low-temperature environments may fluctuate and cannot maintain stable dispersion performance. (3) Reduced concrete fluidity: The poor dispersion performance of polycarboxylate superplasticizers under low temperatures will lead to a decrease in the fluidity of concrete, bringing difficulties to construction and pouring. (4) Limited construction efficiency: Due to poor dispersion performance, the construction efficiency of concrete under low-temperature conditions is limited, increasing construction costs and time.

[0004] To address this problem, some improvement measures have been proposed, such as improving the low-temperature dispersion performance of polycarboxylate superplasticizers by adjusting their molecular structure. Other improvement measures can also be explored, such as adding specific additives during the preparation process or adopting special preparation processes to optimize the performance of polycarboxylate superplasticizers.

[0005] Therefore, in order to address the problem of poor dispersion performance of existing polycarboxylate water-reducing agents in low-temperature environments, it is necessary to further develop new polycarboxylate water-reducing agents or improve existing products to improve their dispersion speed and stability under low-temperature conditions, thereby promoting the efficiency and quality of concrete construction in low-temperature environments.

[0006] Summary of the Invention

[0007] In order to solve the problems raised in the above background technology, the present invention provides a low-temperature fast-dispersing polycarboxylate water-reducing agent and a preparation method thereof.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A low-temperature, fast-dispersing polycarboxylate water-reducing agent comprises the following raw materials, calculated by weight: 10 to 30 parts of polyether A, 80 to 100 parts of allyl polyether macromonomer, 1 to 2 parts of oxidizing agent, 0.2 to 0.8 parts of reducing agent, 10 to 15 parts of acrylic acid aqueous solution, 0.3 to 0.9 parts of chain transfer agent, and 0.2 to 0.5 parts of chain extender. The structure of the polyether A is as follows:

[0010] Wherein the value of n is 15 to 20, R1 is H, OH or Br, and R2 to R4 are H, OH, F or Br.

[0011] Preferably, the polyether A comprises the following raw materials, in parts by weight: 80 to 100 parts of isopentenyl polyethylene glycol ether, 5 to 8 parts of multi-adsorption group functional monomer ester, and 0.4 to 0.8 parts of catalyst.

[0012] Preferably, the structural formula of the allyl polyether macromonomer is as follows:

[0013] Wherein: c is an integer of 2 to 4, d is an integer of 30 to 110, and the molecular weight of the allyl polyether macromonomer is 2400 to 3000.

[0014] Preferably, the oxidant is potassium persulfate or hydrogen peroxide; the chain extender is 2,2-dihydroxymethylpropionic acid (DMPA) or 2,2-dihydroxymethylbutyric acid (DMBA); the reducing agent is thiosulfate, pyrosulfite, oxalic acid, vitamin C, Bruggolite-FF6 or Bruggolite-FF6M; and the chain transfer agent is mercaptoethanol, thioglycolic acid, mercaptopropionic acid, n-dodecyl mercaptan, secondary dodecyl mercaptan or tert-dodecyl mercaptan.

[0015] Preferably, the molecular weight of the isopentenyl polyethylene glycol ether is 1000-1200; and the catalyst is potassium hydroxide or sodium hydroxide.

[0016] A method for preparing a low-temperature, fast-dispersing polycarboxylate water-reducing agent comprises the following steps:

[0017] Step (1), preparation of polyether A terminated with multiple adsorption groups: isopentenyl polyethylene glycol ether and multi-adsorption group functional monomer ester are exchanged under the action of a catalyst to generate polyether A;

[0018] Step (2), preparation of low-temperature fast-dispersing polycarboxylate water-reducing agent: copolymerizing the polyether A obtained in step (1), allyl polyether macromonomer, and acrylic acid free radical solution to obtain low-temperature fast-dispersing polycarboxylate water-reducing agent.

[0019] Preferably, the reaction temperature of step (1) is 50-100° C., and the reaction time is 8-10 h.

[0020] Preferably, the step (2) comprises the following steps: adding 10 to 30 parts by weight of the polyether A obtained in step (1), 80 to 100 parts of the allyl polyether macromonomer, 1 to 2 parts of an oxidant, and 50 to 90 parts of water into a reactor, controlling the temperature at 20 to 40° C., then uniformly adding a reducing agent aqueous solution, an acrylic acid aqueous solution, and a chain transfer agent aqueous solution, respectively, for a dropwise addition time of 3 to 4 hours; simultaneously with the dropwise addition of the reducing agent aqueous solution, the chain extender aqueous solution is added dropwise for a dropwise addition time of 1 to 1.5 hours; after the dropwise addition is completed, the mixture is kept warm for 1 to 2 hours, and an appropriate amount of water is added to adjust the concentration of the reaction product to 50%; and adjusting the pH of the reaction product to 6.0 to 7.0 with sodium hydroxide to obtain a low-temperature fast-dispersing polycarboxylate water-reducing agent.

[0021] Preferably, the reducing agent aqueous solution is 0.2-0.8 parts of reducing agent dissolved in 30 parts of water; the chain transfer agent aqueous solution is 0.4-0.9 parts of chain transfer agent dissolved in 30 parts of water; the acrylic acid aqueous solution is 10-15 parts of acrylic acid dissolved in 30 parts of water; and the chain extender aqueous solution is 0.2-0.5 parts of chain extender dissolved in 30 parts of water.

[0022] The beneficial effects of the present invention are:

[0023] (1) The present invention can improve the expansion speed of polycarboxylate water-reducing agents in cement solutions, enabling the adsorption groups to function more quickly, thereby enhancing the initial water-reducing effect and dispersion performance. This will help improve the construction efficiency and engineering quality of cement-based materials in low-temperature environments, providing better technical support for the application of concrete in cold regions.

[0024] (2) Compared with traditional polycarboxylic acid copolymers, polycarboxylic acid water reducers prepared by low molecular weight polyethers capped with multiple adsorption groups have more adsorption groups and higher charge density. They have stronger adsorption force on the surface of cement-based material particles, and therefore have rapid adsorption capacity, which improves the dispersion speed of cement-based material particles.

[0025] (3) By regulating the use of chain extenders, a polycarboxylic acid water reducer with a relatively high molecular weight in the early stage of the copolymerization process was prepared. This polycarboxylic acid water reducer with a molecular weight distribution can effectively increase the adsorption rate, thereby allowing the cement-based material particles to disperse rapidly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the change in molecular weight of polycarboxylate water reducer during the copolymerization process.

[0027] Figure 2 is a schematic diagram of the change of cement paste fluidity over time. DETAILED DESCRIPTION

[0028] It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0029] Embodiment 1:

[0030] (1) Preparation of polyether A1: 80 g of isopentenyl polyethylene glycol ether, 8 g of (s)-2,3-dihydroxypropionic acid methyl ester, and 0.4 g of potassium hydroxide were added to a four-necked flask equipped with a thermometer, a stirrer, and a water separator. The reaction temperature was kept at 50°C under stirring for 8 hours, and then cooled to obtain a low molecular weight polyether A1 capped with multiple adsorption groups.

[0031] (2) Preparation of polycarboxylate water reducer: 10 g of A1, 80 g of hexanediol monoallyl polyethylene glycol ether, 1 g of hydrogen peroxide, and 50 g of water were added to a reactor, and the temperature was controlled at 40°C. Then, sodium formaldehyde sulfoxylate aqueous solution, acrylic acid aqueous solution, and thioglycolic acid aqueous solution were added dropwise at a uniform rate for 3 h. Simultaneously with the addition of the reducing agent aqueous solution, 2,2-dihydroxymethylpropionic acid aqueous solution was added dropwise for 1 h. After the addition was completed, the temperature was kept at 40°C for 1 h. An appropriate amount of water was added to adjust the concentration of the reaction product to 50%. The pH of the reaction product was adjusted to 6.0-7.0 with sodium hydroxide to obtain a low-temperature fast-dispersing polycarboxylate water reducer.

[0032] The sodium formaldehyde sulfoxylate aqueous solution was prepared by dissolving 0.2 g of sodium formaldehyde sulfoxylate in 30 g of water, the thioglycolic acid aqueous solution was prepared by dissolving 0.4 g of thioglycolic acid in 30 g of water, the acrylic acid aqueous solution was prepared by dissolving 10 g of acrylic acid in 15 g of water, and the 2,2-dimethylolpropionic acid aqueous solution was prepared by dissolving 0.2 g of 2,2-dimethylolpropionic acid in 15 g of water. The molecular weight of the isopentenyl polyethylene glycol ether was 1000, and the molecular weight of the hexanediol monoallyl polyethylene glycol ether was 3000.

[0033] Example 2

[0034] (1) Preparation of polyether A2: 100 g of isopentenyl polyethylene glycol ether, 8 g of methyl 3-hydroxypropionate, and 0.8 g of sodium hydroxide were added to a four-necked flask equipped with a thermometer, a stirrer, and a water separator. The reaction temperature was set at 100° C. under stirring. After the reaction was allowed to react for 10 hours, the reaction was cooled to obtain a low molecular weight polyether A2 terminated with multiple adsorption groups.

[0035] (2) Preparation of polycarboxylate water reducer: 30 g of A2, 100 g of butanediol monoallyl polyglycol ether, 2 g of potassium persulfate and 90 g of water were added to a reactor, and the temperature was controlled at 20°C. Then, vitamin C aqueous solution, acrylic acid aqueous solution and n-dodecyl mercaptan aqueous solution were added dropwise at a uniform rate for 3 h. At the same time as the reducing agent aqueous solution was added dropwise, 2,2-dihydroxymethylbutyric acid aqueous solution was added dropwise for 1 h. After the addition was completed, the mixture was kept warm for 1 h. An appropriate amount of water was added to adjust the concentration of the reaction product to 50%. The pH of the reaction product was adjusted to 6.0-7.0 with sodium hydroxide to obtain a low-temperature fast-dispersing polycarboxylate water reducer.

[0036] The vitamin C aqueous solution consists of 0.8g of vitamin C dissolved in 30g of water, the n-dodecyl mercaptan aqueous solution consists of 0.9g of n-dodecyl mercaptan dissolved in 30g of water, the acrylic acid aqueous solution consists of 15g of acrylic acid dissolved in 15g of water, and the 2,2-dihydroxymethylbutyric acid aqueous solution consists of 0.5g of 2,2-dihydroxymethylbutyric acid dissolved in 15g of water. The molecular weight of the isopentenyl polyethylene glycol ether is 1200, and the molecular weight of the butanediol monoallyl polyethylene glycol ether is 2400.

[0037] Example 3

[0038] (1) Preparation of polyether A3: 90 g of isopentenyl polyethylene glycol ether, 7 g of methyl 3-bromopropionate, and 0.7 g of potassium hydroxide were added to a four-necked flask equipped with a thermometer, a stirrer, and a water separator. The reaction was stirred at 60° C. for 9 hours, and then cooled to obtain a low molecular weight polyether A3 capped with multiple adsorption groups.

[0039] (2) Preparation of polycarboxylate water reducer: 20 g of A3, 90 g of hexanediol monoallyl polyethylene glycol ether, 1.5 g of hydrogen peroxide and 70 g of water were added to a reactor, and the temperature was controlled at 30°C. Then, sodium thiosulfate aqueous solution, acrylic acid aqueous solution and tert-dodecyl mercaptan aqueous solution were added dropwise at a uniform rate for 3 h. At the same time as the reducing agent aqueous solution was added dropwise, 2,2-dihydroxymethylpropionic acid aqueous solution was added dropwise for 1 h. After the addition was completed, the mixture was kept warm for 1 h. An appropriate amount of water was added to adjust the concentration of the reaction product to 50%. The pH of the reaction product was adjusted to 6.0-7.0 with sodium hydroxide to obtain a low-temperature fast-dispersible polycarboxylate water reducer.

[0040] The sodium thiosulfate aqueous solution was prepared by dissolving 0.5 g of sodium thiosulfate in 30 g of water, the tert-dodecyl mercaptan aqueous solution was prepared by dissolving 0.6 g of tert-dodecyl mercaptan in 30 g of water, the acrylic acid aqueous solution was prepared by dissolving 13 g of acrylic acid in 15 g of water, and the 2,2-dimethylolpropionic acid aqueous solution was prepared by dissolving 0.4 g of 2,2-dimethylolpropionic acid in 15 g of water. The molecular weight of the isopentenyl polyethylene glycol ether was 1100, and the molecular weight of the hexanediol monoallyl polyethylene glycol ether was 2800.

[0041] Example 4

[0042] (1) Preparation of polyether A4: 80 g of isopentenyl polyethylene glycol ether, 8 g of methyl 2-bromopropionate, and 0.4 g of sodium hydroxide were added to a four-necked flask equipped with a thermometer, a stirrer, and a water separator. The reaction was stirred at 70° C. for 8 hours, and then cooled to obtain a low-molecular-weight polyether A4 capped with multiple adsorption groups.

[0043] (2) Preparation of polycarboxylic acid water reducer: 10 g of A4, 80 g of hexanediol monoallyl polyethylene glycol ether, 1 g of hydrogen peroxide and 50 g of water were added to a reactor, and the temperature was controlled at 40°C. Then, oxalic acid aqueous solution, acrylic acid aqueous solution and thioglycolic acid aqueous solution were added dropwise at a uniform rate for 3 hours. At the same time as the reducing agent aqueous solution was added dropwise, 2,2-dihydroxymethylpropionic acid aqueous solution was added dropwise for 1 hour. After the addition was completed, the mixture was kept warm for 1 hour. An appropriate amount of water was added to adjust the concentration of the reaction product to 50%. The pH of the reaction product was adjusted to 6.0-7.0 with sodium hydroxide to obtain a low-temperature fast-dispersing polycarboxylic acid water reducer.

[0044] The oxalic acid aqueous solution was prepared by dissolving 0.2 g of oxalic acid in 30 g of water, the thioglycolic acid aqueous solution was prepared by dissolving 0.5 g of thioglycolic acid in 30 g of water, the acrylic acid aqueous solution was prepared by dissolving 10 g of acrylic acid in 15 g of water, and the 2,2-dimethylolpropionic acid aqueous solution was prepared by dissolving 0.2 g of 2,2-dimethylolpropionic acid in 15 g of water. The molecular weight of the isopentenyl polyethylene glycol ether was 1000, and the molecular weight of the hexanediol monoallyl polyethylene glycol ether was 3000.

[0045] Example 5

[0046] (1) Preparation of polyether A5: 80 g of isopentenyl polyethylene glycol ether, 8 g of methyl 2-bromopropionate, and 0.4 g of sodium hydroxide were added to a four-necked flask equipped with a thermometer, a stirrer, and a water separator. The reaction temperature was kept at 70° C. under stirring for 8 hours, and then the reaction was cooled to obtain a low molecular weight polyether A5 capped with multiple adsorption groups.

[0047] (2) Preparation of polycarboxylic acid water reducer: 10 g of A5, 80 g of hexanediol monoallyl polyethylene glycol ether, 1 g of hydrogen peroxide and 50 g of water were added to a reactor, and the temperature was controlled at 40°C. Then, Bruggolite-FF6M aqueous solution, acrylic acid aqueous solution and thioglycolic acid aqueous solution were added dropwise at a uniform rate for 3 h. At the same time as the reducing agent aqueous solution was added dropwise, 2,2-dihydroxymethylpropionic acid aqueous solution was added dropwise for 1 h. After the addition was completed, the temperature was kept at 40°C for 1 h. An appropriate amount of water was added to adjust the concentration of the reaction product to 50%. The pH of the reaction product was adjusted to 6.0-7.0 with sodium hydroxide to obtain a low-temperature fast-dispersing polycarboxylic acid water reducer.

[0048] The Bruggolite-FF6M aqueous solution consists of 0.2g of Bruggolite-FF6M dissolved in 30g of water, the thioglycolic acid aqueous solution consists of 0.6g of thioglycolic acid dissolved in 30g of water, the acrylic acid aqueous solution consists of 10g of acrylic acid dissolved in 15g of water, and the 2,2-dimethylolpropionic acid aqueous solution consists of 0.2g of 2,2-dimethylolpropionic acid dissolved in 15g of water. The molecular weight of the isopentenyl polyethylene glycol ether is 1000, and the molecular weight of the hexanediol monoallyl polyethylene glycol ether is 3000.

[0049] Example 6

[0050] (1) Preparation of polyether A6: 80 g of isopentenyl polyethylene glycol ether, 8 g of methyl 3-hydroxypropionate, and 0.4 g of potassium hydroxide were added to a four-necked flask equipped with a thermometer, a stirrer, and a water separator. The reaction temperature was kept at 70° C. under stirring for 8 hours, and the mixture was cooled to obtain a low molecular weight polyether A6 capped with multiple adsorption groups.

[0051] (2) Preparation of polycarboxylate water reducer: 10 g of A6, 80 g of hexanediol monoallyl polyglycol ether, 1 g of hydrogen peroxide, and 50 g of water were added to a reactor, and the temperature was controlled at 40°C. Then, sodium formaldehyde sulfoxylate aqueous solution, acrylic acid aqueous solution, and thioglycolic acid aqueous solution were added dropwise at a uniform rate for 3 h. Simultaneously with the addition of the reducing agent aqueous solution, 2,2-dihydroxymethylpropionic acid aqueous solution was added dropwise for 1 h. After the addition was completed, the temperature was kept at 40°C for 1 h. An appropriate amount of water was added to adjust the concentration of the reaction product to 50%. The pH of the reaction product was adjusted to 6.0-7.0 with sodium hydroxide to obtain a low-temperature fast-dispersible polycarboxylate water reducer.

[0052] The sodium formaldehyde sulfoxylate aqueous solution was prepared by dissolving 0.2 g of sodium formaldehyde sulfoxylate in 30 g of water, the thioglycolic acid aqueous solution was prepared by dissolving 0.7 g of thioglycolic acid in 30 g of water, the acrylic acid aqueous solution was prepared by dissolving 10 g of acrylic acid in 15 g of water, and the 2,2-dimethylolpropionic acid aqueous solution was prepared by dissolving 0.2 g of 2,2-dimethylolpropionic acid in 15 g of water. The molecular weight of the isopentenyl polyethylene glycol ether was 1000, and the molecular weight of the hexanediol monoallyl polyethylene glycol ether was 3000.

[0053] Comparative Example 1

[0054] The difference from Example 1 is that in the preparation process of the polycarboxylate water-reducing agent, 10 g of hexanediol monoallyl polyethylene glycol ether is used instead of 10 g of A1, and the temperature is controlled at 20°C.

[0055] Comparative Example 2

[0056] The difference from Example 1 is that the 2,2-dimethylolpropionic acid aqueous solution is not added dropwise during the preparation of the polycarboxylate water-reducing agent.

[0057] Comparative Example 3

[0058] The difference from Example 1 is that during the preparation of the polycarboxylate water-reducing agent, 10 g of hexanediol monoallyl polyethylene glycol ether was used instead of 10 g of A1; and no 2,2-dimethylolpropionic acid aqueous solution was added dropwise.

[0059] High-performance gel permeation chromatography (GPC) was used to determine the molecular weight changes of polycarboxylate superplasticizers during copolymerization. The instrument models were a Waters 1515 Isocratic HPLP pump / Waters 2414, and the acquisition and analysis system was Breeze software. The columns were Ultrahydragel™ 250 and Ultrahydragel™ 500 connected in series, and the mobile phase was 0.1 mol / L sodium nitrate solution in water at a flow rate of 0.8 mL / min. The results are shown in Figure 1.

[0060] As can be seen from Figure 1, compared with Comparative Example 2 and Comparative Example 3, Examples 1 to 6 and Comparative Example 1 have higher molecular weights in the early stage of the copolymerization process (first 60 min). Examples 1 to 6 and Comparative Example 1 mainly increase the molecular weight of the water reducer in the early stage of the copolymerization process by adding a chain extender in the early stage of the copolymerization process.

[0061] Referring to the basic method of GB / T 8077-2012 "Test method for homogeneity of concrete admixtures", the fluidity of cement paste is tested to characterize the dispersion performance of the product.

[0062] Weigh 300g of cement and add 87g of water. Adjust the polycarboxylate superplasticizer dosage to achieve the desired fluidity. Using a slurry mixer in a slow, continuous mixing mode, the fluidity of the cement paste was monitored at stirring times of 20s, 40s, 60s, 120s, 180s, and 240s, using the same polycarboxylate superplasticizer dosage, to characterize the dispersion speed of the superplasticizer product. The results are shown in Figure 2.

[0063] As can be seen from Figure 2:

[0064] (1) Compared with Comparative Example 2, Examples 1 to 6 significantly increase the dispersion speed of cement particles. The cement slurries of Examples 1 to 6 reach their maximum fluidity at 20 seconds, while the cement slurry of Comparative Example 2 reaches its maximum fluidity at 60 seconds. The main reason is that the chain extender is added dropwise in the early stage of copolymerization in Examples 1 to 6, resulting in a polycarboxylate water-reducing agent with a relatively high molecular weight in the early stage of copolymerization. This polycarboxylate water-reducing agent with such a molecular weight distribution can effectively increase the adsorption speed, thereby allowing the cement-based material particles to disperse rapidly.

[0065] (2) Compared with Comparative Example 1, Examples 1 to 6 significantly improve the dispersion speed of cement particles. The fluidity of the cement slurries of Examples 1 to 6 reaches its maximum at 20 seconds, while the fluidity of the cement slurry of Comparative Example 1 reaches its maximum at 60 seconds. The main reason is that the polycarboxylate water reducers prepared by Examples 1 to 6 using low-molecular-weight polyethers capped with multiple adsorption groups have more adsorption groups and higher charge density than traditional polycarboxylate copolymers, and thus have stronger adsorption force on the surface of cement-based material particles, thus having rapid adsorption ability and improving the dispersion speed of cement-based material particles.

[0066] (3) Compared with Comparative Example 3, Examples 1 to 6 significantly increased the dispersion speed of cement particles. The cement slurries of Examples 1 to 6 reached their maximum fluidity at 20 s, while the cement slurry of Comparative Example 3 reached its maximum fluidity at 120 s. This is mainly due to the synergistic effect of the higher molecular weight in the early stage of the copolymerization process of Examples 1 to 6, the multiple adsorption groups, and the high charge density, which effectively increased the adsorption speed of the polycarboxylate water reducer and promoted the rapid dispersion of the mud-based material particles.

[0067] The above-described embodiments merely illustrate several implementations of the present invention, and while their 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, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A low-temperature fast-dispersing polycarboxylate water-reducing agent, characterized in that: The following raw materials are included by weight: 10 to 30 parts of polyether A, 80 to 100 parts of allyl polyether macromonomer, 1 to 2 parts of oxidant, 0.2 to 0.8 parts of reducing agent, 10 to 15 parts of acrylic acid aqueous solution, 0.3 to 0.9 parts of chain transfer agent, and 0.2 to 0.5 parts of chain extender. The structure of the polyether A is as follows: Wherein the value of n is 15 to 20, R1 is H, OH or Br, and R2 to R4 are H, OH, F or Br.

2. A low-temperature fast-dispersing polycarboxylate water-reducing agent according to claim 1, characterized in that: The polyether A comprises the following raw materials in parts by weight: 80 to 100 parts of isopentenyl polyethylene glycol ether, 5 to 8 parts of multi-adsorption group functional monomer ester, and 0.4 to 0.8 parts of a catalyst.

3. A low-temperature fast-dispersing polycarboxylate water-reducing agent according to claim 1, characterized in that: The structural formula of the allyl polyether macromonomer is as follows: Wherein: c is an integer of 2-4, d is an integer of 30-110, and the molecular weight of the allyl polyether macromonomer is 2400-3000.

4. A low-temperature fast-dispersing polycarboxylate water-reducing agent according to claim 1, characterized in that: The oxidant is potassium persulfate or hydrogen peroxide; the chain extender is 2,2-dihydroxymethylpropionic acid (DMPA) or 2,2-dihydroxymethylbutyric acid (DMBA); the reducing agent is thiosulfate, pyrosulfite, oxalic acid, vitamin C, Bruggolite-FF6 or Bruggolite-FF6M; the chain transfer agent is mercaptoethanol, thioglycolic acid, mercaptopropionic acid, n-dodecyl mercaptan, secondary dodecyl mercaptan or tert-dodecyl mercaptan.

5. A low-temperature fast-dispersing polycarboxylate water-reducing agent according to claim 2, characterized in that: The molecular weight of the isopentenyl polyethylene glycol ether is 1000-1200; and the catalyst is potassium hydroxide or sodium hydroxide.

6. A method for preparing the low-temperature fast-dispersing polycarboxylate water-reducing agent according to claim 1, characterized in that: The following steps are involved: Step (1), preparation of polyether A terminated with multiple adsorption groups: isopentenyl polyethylene glycol ether and multi-adsorption group functional monomer ester are exchanged under the action of a catalyst to generate polyether A; Step (2), preparation of low-temperature fast-dispersing polycarboxylate water-reducing agent: copolymerization of the polyether A obtained in step (1), allyl polyether macromonomer and acrylic acid free radical solution to obtain low-temperature fast-dispersing polycarboxylate water-reducing agent.

7. The method for preparing a low-temperature fast-dispersing polycarboxylate water-reducing agent according to claim 6, characterized in that: The reaction temperature of step (1) is 50-100° C., and the reaction time is 8-10 hours.

8. The method for preparing a low-temperature fast-dispersing polycarboxylate water-reducing agent according to claim 6, characterized in that: In parts by weight, the step (2) comprises the following steps: adding 10 to 30 parts of the polyether A obtained in the step (1), 80 to 100 parts of the allyl polyether macromonomer, 1 to 2 parts of an oxidant and 50 to 90 parts of water into a reaction kettle, controlling the temperature at 20 to 40° C., then uniformly adding a reducing agent aqueous solution, an acrylic acid aqueous solution and a chain transfer agent aqueous solution respectively, the dropping time being 3 to 4 hours, and simultaneously dropping a chain extender aqueous solution for 1 to 1.5 hours, keeping the temperature for 1 to 2 hours after the dropping is completed, and adding a suitable amount of water to obtain a reaction product with a concentration of 50%; adjusting the pH of the reaction product to 6.0 to 7.0 with sodium hydroxide to obtain a low-temperature fast-dispersing polycarboxylic acid water-reducing agent.

9. The method for preparing a low-temperature fast-dispersing polycarboxylate water-reducing agent according to claim 8, characterized in that: The reducing agent aqueous solution is 0.2-0.8 parts of reducing agent dissolved in 30 parts of water; the chain transfer agent aqueous solution is 0.4-0.9 parts of chain transfer agent dissolved in 30 parts of water; the acrylic acid aqueous solution is 10-15 parts of acrylic acid dissolved in 30 parts of water; the chain extender aqueous solution is 0.2-0.5 parts of chain extender dissolved in 30 parts of water.

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