CN113698550B

CN113698550B - Gradient slow-release type polycarboxylate superplasticizer and preparation method and application thereof

Info

Publication number: CN113698550B
Application number: CN202111041682.7A
Authority: CN
Inventors: 张金龙; 黄福仁; 邵强; 钟开红
Original assignee: Guangzhou Academy Of Building Sciences Group Co ltd
Current assignee: Guangzhou Academy Of Building Sciences Group Co ltd
Priority date: 2021-09-07
Filing date: 2021-09-07
Publication date: 2022-07-08
Anticipated expiration: 2041-09-07
Also published as: CN113698550A

Abstract

The invention provides a gradient slow-release type polycarboxylate superplasticizer as well as a preparation method and application thereof, and relates to the technical field of the superplasticizer. The gradient slow-release polycarboxylate superplasticizer comprises the following raw materials in parts by weight: 320-360 parts of ether monomer, 14-18 parts of unsaturated acid, 15-20 parts of slump retaining monomer, 12-16 parts of long slump retaining monomer, 3-6 parts of chain transfer agent, 8-12 parts of metal catalyst, 0.4-0.8 part of reducing agent and 2-3 parts of oxidizing agent; the slump-retaining monomer is selected from: one or more of hydroxyethyl acrylate, end-capped amide phosphate, maleic anhydride and dimethylamino ethyl acrylate; the long slump-retaining monomer is selected from: one or more of hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate. The gradient slow-release polycarboxylate superplasticizer disclosed by the invention has a gradient slow-release effect, can obviously prolong the slump retaining time of the polycarboxylate superplasticizer, and meets the requirement of long-distance transportation.

Description

Gradient slow-release type polycarboxylate superplasticizer and preparation method and application thereof

Technical Field

The invention relates to the technical field of water reducing agents, in particular to a gradient slow-release type polycarboxylate water reducing agent and a preparation method and application thereof.

Background

Along with the development of society, the population density of cities is continuously increased, the number of high-rise buildings is increased, the problem of long-distance concrete conveying is solved during the construction of the high-rise buildings, and the requirement that the concrete keeps fluidity for a long time is improved. Meanwhile, in recent years, based on the aim of environmental protection, the dependence on natural aggregates is encouraged to be reduced, and the mechanical sand or artificial sand is adopted to replace part of the natural aggregates, but the existing mechanical sand or artificial sand still has the problems of high powder content, poor quality and the like, and the requirements on the slump retaining performance of the concrete admixture are increasingly strict. In order to improve slump retaining performance, ester slump retaining monomers such as hydroxyethyl acrylate and the like are usually added in the synthesis process of the water reducer, and hydrolysis of ester groups is realized under the alkaline condition of cement, so that carboxylate ions capable of being adsorbed on the surfaces of cement particles again are released. However, the single slump retaining monomer has limited slow release time, and the common hydroxyethyl acrylate has the problem of too high slow release rate, so that the long-time slump retaining of concrete is difficult to realize, and the construction progress and the construction quality are seriously influenced.

Disclosure of Invention

In view of the above, it is necessary to provide a gradient slow-release type polycarboxylate water reducer having a gradient slow-release effect and capable of improving slump-retaining performance of the water reducer.

The gradient slow-release polycarboxylate superplasticizer comprises the following raw materials in parts by weight:

the slump-retaining monomer is selected from: one or more of hydroxyethyl acrylate, end-capped amide phosphate, maleic anhydride and dimethylamino ethyl acrylate; the long slump-retaining monomer is selected from: one or more of hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.

The inventor finds that ester monomers used in the traditional polycarboxylic acid water reducing agent, such as hydroxyethyl acrylate, maleic anhydride and the like, are hydrolyzed very quickly in the alkaline environment of cement, the hydrolysis degree can reach more than 90% within 1 hour, the slump retaining requirement can be met only within a short time, and the long-time fluidity of concrete is difficult to maintain. While the slump-retaining monomers such as hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate and the like can maintain long-time hydrolysis in an alkaline environment, the hydrolysis degree is only about 60% in 1h, the hydrolysis can be still maintained after 1h, and the hydrolysis degree reaches 90% after 2-3 h. In the prior art, on one hand, a proper type of long slump retaining monomer and a proper proportion of the short slump retaining monomer and the long slump retaining monomer cannot be selected, and on the other hand, a proper polymerization process cannot be developed to improve the polymerization conversion rate of the long slump retaining monomer, so that the obtained slump retaining type polycarboxylate water reducer has short slump retaining time and cannot meet the actual production and application requirements of concrete.

Based on the findings, the inventor adds two or more ester monomers with different slow release rates or hydrolysis speeds into a water reducer system, develops a novel polymerization process to obtain the gradient slow-release polycarboxylate water reducer, and releases carboxylate ions in a cement environment for a long time to achieve the effect of gradient slow release, thereby obviously prolonging the slump retaining time of the polycarboxylate water reducer and meeting the requirement of long-distance transportation.

Moreover, the gradient slow-release polycarboxylate superplasticizer has more obvious advantages in machine-made sand concrete with high mud content. Concrete with high mud content has high concrete viscosity and large adsorption capacity to the polycarboxylate superplasticizer, and the common slump-retaining polycarboxylate superplasticizer is quickly consumed, so that the slump loss of the concrete is high, while the gradient slow-release polycarboxylate superplasticizer can slowly release carboxylate ions for a long time, prolong the consumed loss time of the concrete, and play a role in long-acting slump retention.

In one embodiment, the raw material further comprises 540-630 parts of water.

In one embodiment, the ether monomer is selected from: one or two of methyl allyl polyoxyethylene ether and isoamylol polyoxyethylene ether.

In one embodiment, the ether monomer has a molecular weight of 3000-4000 Da. The later slump retaining capacity of the water reducer is insufficient due to the fact that the molecular weight of the ether monomer is smaller (the side chain is shorter), the polymerization activity is weak due to the fact that the molecular weight is larger, and the conversion rate is reduced.

In one embodiment, the unsaturated acid is selected from: one or more of acrylic acid, methacrylic acid, 4-vinyl benzene sulfonic acid and 2-acrylamide-2-methyl propane sulfonic acid.

In one embodiment, the chain transfer agent is selected from: one or two of sodium methallyl sulfonate and sodium hypophosphite.

In one embodiment, the metal catalyst is selected from: one or two of ferrous chloride solution and ferrous sulfate solution.

In one embodiment, the mass concentration of the ferrous chloride or ferrous sulfate aqueous solution is 0.1-0.5%.

In one embodiment, the reducing agent is selected from: one or more of ascorbic acid, sodium bisulfite, sodium formaldehyde sulfoxylate, and Mohr's salt.

In one embodiment, the oxidizing agent is selected from: hydrogen peroxide.

The invention also provides a concrete admixture which comprises a high water-reducing polycarboxylic acid water reducing agent and the gradient slow-release polycarboxylic acid water reducing agent. Because the content of unsaturated acid in the gradient slow-release polycarboxylate superplasticizer is low, the initial water reducing capacity of the gradient slow-release polycarboxylate superplasticizer is poor, and the initial water reducing capacity can be improved by compounding the gradient slow-release polycarboxylate superplasticizer with the high water reducing polycarboxylate superplasticizer.

The high water-reducing polycarboxylate water reducer can be a commercially available high water-reducing polycarboxylate water reducer, such as MH-JS-102 polycarboxylate water reducer.

In one embodiment, the mass ratio of the high water-reducing polycarboxylate water reducer to the gradient slow-release polycarboxylate water reducer is 1: (0.8 to 1.2).

The invention also provides a preparation method of the gradient slow-release type polycarboxylate superplasticizer, which comprises the following steps:

s1, mixing an ether monomer, a chain transfer agent, a metal catalyst and a part of long slump retaining monomer, and adding water to dissolve to obtain a solution A; mixing unsaturated acid, slump retaining monomer and residual long slump retaining monomer, and adding water to dissolve to obtain a solution B;

s2, uniformly mixing the solution A with an oxidant, simultaneously starting to dropwise add the solution B and a reducing agent, and after dropwise addition is finished, keeping the temperature for a period of time to obtain the gradient slow-release polycarboxylate superplasticizer.

In one embodiment, in the step S1, when preparing the solution a, the added part of the long slump retaining monomer is 20% to 30% of the total mass of the long slump retaining monomer.

In one embodiment, in the S2, the dropping time of the solution B is 1.5-2.0 h, and the dropping time of the reducing agent is 1.5-2.0 h.

The gradient slow-release polycarboxylate superplasticizer is synthesized by adopting a one-step method, no additional heat source is needed in the preparation process, the energy is saved, the environment is protected, the prepared gradient slow-release polycarboxylate superplasticizer has the gradient slow-release effect, the slump retaining time of the polycarboxylate superplasticizer can be obviously prolonged, and the long-distance pumping requirement is met.

In the preparation method, the long slump retaining monomer is divided into two parts, the two parts are respectively prepared into the solution A and the solution B, titration is carried out, the long slump retaining monomer has stronger hydrophobicity compared with a common slump retaining monomer, the solubility of the long slump retaining monomer can be improved by utilizing the polyether macromonomer by adding part of the long slump retaining monomer into the solution A, and the long slump retaining monomer can be uniformly distributed in a molecular chain of the polycarboxylic acid water reducing agent by adopting a partial dripping mode, so that the slump retaining effect is better. If the long slump retaining monomer is completely placed in the solution A or the solution B, the conversion rate is easily reduced, and the slump retaining capability in the later period is insufficient.

In one embodiment, in the step S2, water is added after heat preservation until the mass concentration of the water reducing agent is 38-42%.

In one embodiment, in the S2, the initial reaction temperature is 20-25 ℃. The oxidation-reduction reaction between the oxidant and the reducing agent provides required free radicals for polymerization reaction, does not need to additionally provide a heat source to induce the polymerization reaction, and realizes low-temperature/normal-temperature polymerization.

Compared with the prior art, the invention has the following beneficial effects:

the gradient slow-release polycarboxylate superplasticizer disclosed by the invention has a gradient slow-release effect, can obviously prolong the slump retaining time of the polycarboxylate superplasticizer, and meets the long-distance pumping requirement. Moreover, the water reducing agent has more obvious advantages in concrete with high mud content, is beneficial to reducing the dependence on natural aggregate and expanding the application range of machine-made sand. The preparation method is simple and easy to operate, does not need an additional heat source, and is energy-saving and environment-friendly.

Drawings

FIG. 1 is an infrared spectrum of a polycarboxylic acid water reducing agent HS-1 in example 1.

Detailed Description

To facilitate an understanding of the invention, a more complete description of the invention will be given below in terms of preferred embodiments. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

The parts in the following examples and comparative examples are parts by weight.

Example 1

A gradient slow-release polycarboxylate superplasticizer HS-1 is prepared by the following method:

(1) 330 parts of methyl allyl polyoxyethylene ether (with the molecular weight of 3000Da), 15 parts of acrylic acid, 15 parts of hydroxyethyl acrylate, 12.5 parts of hydroxypropyl acrylate, 4 parts of sodium hypophosphite, 10 parts of ferrous sulfate aqueous solution (with the concentration of 0.3 wt%), 0.45 part of ascorbic acid and 2.5 parts of hydrogen peroxide are weighed.

(2) Mixing methyl allyl polyoxyethylene ether, 2.5 parts of hydroxypropyl acrylate, sodium hypophosphite and a ferrous sulfate aqueous solution, and adding 330 parts of water to obtain a solution A.

(3) Mixing acrylic acid, hydroxyethyl acrylate and 10 parts of hydroxypropyl acrylate, and adding 60 parts of water to obtain a solution B.

(4) Ascorbic acid was mixed with 60 parts of water to obtain solution C.

(5) Adding hydrogen peroxide into the solution A at the temperature of 20 ℃, uniformly mixing, and simultaneously beginning to dropwise add the solution B and the solution C, wherein the dropwise adding time of the solution B is 2.5 hours, and the dropwise adding time of the solution C is 3.0 hours. After the dropwise addition is finished, the temperature is kept for 1h, and water is added to adjust the mass concentration to 40% so as to obtain the polycarboxylate superplasticizer HS-1.

Taking polycarboxylate superplasticizer HS-1 for infrared lightThe results of the spectrum test are shown in FIG. 1, from which it can be seen that 1725cm^-1The wave number absorption peak is attributed to the carboxyl-C ═ O stretching vibration peak in the polycarboxylic acid molecular chain, 1100cm^-1The wave number absorption peak is attributed to-C-O-C-ether bond stretching vibration in polyoxyethylene ether, 2900cm^-1Wave number absorption peak is ascribed to methylene-CH on main chain₂-CH₂The results show that the expected gradient slow-release type polycarboxylate superplasticizer is successfully obtained.

Example 2

A gradient slow-release polycarboxylate superplasticizer HS-2 is prepared by the following method:

(1) 350 parts of prenyl alcohol polyoxyethylene ether (with the molecular weight of 3300Da), 16 parts of methacrylic acid, 18 parts of hydroxyethyl acrylate, 14.5 parts of hydroxyethyl methacrylate, 5 parts of sodium methallyl sulfonate, 12 parts of ferrous sulfate aqueous solution (with the concentration of 0.3 wt%), 0.5 part of sodium formaldehyde sulfoxylate and 3.0 parts of hydrogen peroxide are weighed.

(2) Mixing prenyl alcohol polyoxyethylene ether, 3.5 parts of hydroxyethyl methacrylate, sodium methallyl sulfonate and a ferrous sulfate aqueous solution, and adding 350 parts of water to obtain a solution A.

(3) Methacrylic acid, hydroxyethyl acrylate and 11 parts of hydroxyethyl methacrylate were mixed, and 60 parts of water was added to obtain a solution B.

(4) Sodium formaldehyde sulfoxylate was mixed with 60 parts of water to obtain solution C.

(5) Adding hydrogen peroxide into the solution A at the temperature of 20 ℃, uniformly mixing, and simultaneously beginning to dropwise add the solution B and the solution C, wherein the dropwise adding time of the solution B is 3.0h, and the dropwise adding time of the solution C is 3.0 h. After the dropwise addition is finished, the temperature is kept for 1h, and water is added to adjust the mass concentration to 40% so as to obtain the polycarboxylate superplasticizer HS-2.

Example 3

A gradient slow-release polycarboxylate superplasticizer HS-3 is prepared by the following method:

(1) weighing 360 parts of methyl alkenyl polyoxyethylene ether (with the molecular weight of 3000Da), 16 parts of acrylic acid, 20 parts of hydroxyethyl acrylate, 4 parts of hydroxypropyl methacrylate, 10 parts of hydroxypropyl acrylate, 5 parts of sodium hypophosphite, 10 parts of ferrous sulfate aqueous solution (with the concentration of 0.3 wt%), 0.6 part of sodium bisulfite and 3.0 parts of hydrogen peroxide.

(2) Mixing methyl alkenyl polyoxyethylene ether, hydroxypropyl methacrylate, sodium hypophosphite and a ferrous sulfate aqueous solution, and adding 360 parts of water to obtain a solution A.

(3) Mixing acrylic acid, hydroxyethyl acrylate and hydroxypropyl acrylate, and adding 60 parts of water to obtain a solution B.

(4) Sodium bisulfite was mixed with 60 parts of water to give solution C.

(5) Adding hydrogen peroxide into the solution A at the temperature of 20 ℃, uniformly mixing, and simultaneously beginning to dropwise add the solution B and the solution C, wherein the dropwise adding time of the solution B is 3.0 hours, and the dropwise adding time of the solution C is 3.5 hours. After the dropwise addition is finished, the temperature is kept for 1h, and water is added to adjust the mass concentration to 40% so as to obtain the polycarboxylate superplasticizer HS-3.

Example 4

A preparation method of the gradient slow-release polycarboxylate superplasticizer HS-4 is basically the same as that in example 1, except that the addition amount of hydroxypropyl acrylate is 0 part when preparing a solution A, and the use amount of hydroxypropyl acrylate is 12.5 parts when preparing a solution B.

Example 5

A preparation method of the gradient slow-release polycarboxylate superplasticizer HS-5 is basically the same as that in example 1, and the difference is that the molecular weight of the methyl allyl polyoxyethylene ether is 2400 Da.

Comparative example 1

A polycarboxylic acid water-reducing agent was prepared in substantially the same manner as in example 1 except that the amount of the metal catalyst used was 0.

Comparative example 2

A polycarboxylic acid water-reducing agent was prepared in substantially the same manner as in example 1 except that hydroxypropyl acrylate was replaced with equal parts by weight of hydroxyethyl acrylate.

Experimental example 1

The polycarboxylate superplasticizers of examples and comparative examples are applied to C30 concrete, and the weight ratio of the concrete is as follows: coal ash: mineral powder: sand: stone: water 200: 80: 50: 795: 1050: 155.

because the polycarboxylic acid water reducing agents in the examples and the comparative examples have low unsaturated acid content and poor initial water reducing capacity, the polycarboxylic acid water reducing agents are compounded with a commercially available water reducing polycarboxylic acid water reducing agent JS-102 according to the mass ratio of 1:1 (namely JS: HS is 1:1) to improve the initial water reducing capacity.

Concrete experiments are carried out under the same formula and mixing amount, and the mixing amount of the water reducing agent is 2.0 percent of the mass of the cementing material. The concrete slump/slump loss with time was measured according to GB/T50080-2016 and the results are shown in Table 1.

TABLE 1 loss of slump/extension of C30 concrete over time

The slow-release type polycarboxylate water reducer has poor initial dispersing performance, but the water-reducing dispersing performance can be provided by a commercial water-reducing polycarboxylate water reducer. From the above results, it can be seen that the concrete of examples and comparative examples exhibited different laws in the change of slump/slump with time.

The concrete of examples 1 to 3 has a small change in expansion and slump with time, a good slump retaining property, and a slump retaining time of 3 hours or more. In example 4, no hydroxypropyl acrylate (long slump-retaining monomer) was added at the time of preparing solution A, and all of the hydroxypropyl acrylate was added at the time of preparing solution B, resulting in a decrease in the conversion rate and insufficient slump-retaining ability at the later stage. The use of 2400Da methallyl polyoxyethylene ether with a shorter side chain in example 5 resulted in insufficient slump retention at the later stage, a significant drop in slump/fluidity, and a slump retention that was inferior to that of example 1 (using 3000Da methallyl polyoxyethylene ether). In the comparative example 1, no metal catalyst is added, so that the monomer conversion rate in the system is low, the expected polycarboxylic acid water reducing agent cannot be obtained, the later slump retaining capability is obviously insufficient, and the fluidity is completely lost at 3 h. In comparative example 2, no long slump retaining monomer was added, the slump retaining ability was strong in a short time, and the slump/fluidity decreased due to the fact that the slump retaining ability was weakened at 3 hours and the large-scale reversion occurred at 1 hour, due to the fact that the sustained-release time was too short.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The gradient slow-release polycarboxylate superplasticizer is characterized by comprising the following raw materials in parts by weight:

the slump-retaining monomer is selected from: one or more of hydroxyethyl acrylate, end-capped amide phosphate, maleic anhydride and dimethylamino ethyl acrylate; the long slump-retaining monomer is selected from: one or more of hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate;

the ether monomer is selected from: one or two of methyl allyl polyoxyethylene ether and isoamylol polyoxyethylene ether, wherein the molecular weight of the ether monomer is 3000-4000 Da;

the preparation method of the gradient slow-release polycarboxylate superplasticizer comprises the following steps:

s1, mixing an ether monomer, a chain transfer agent, a metal catalyst and a part of long slump retaining monomer, and adding water to dissolve to obtain a solution A; mixing unsaturated acid, slump retaining monomer and residual long slump retaining monomer, and adding water to dissolve to obtain a solution B; when the solution A is prepared, the added part of the long slump-retaining monomer accounts for 20-30% of the total mass of the long slump-retaining monomer;

2. The gradient slow-release type polycarboxylate water reducer according to claim 1, characterized in that the unsaturated acid is selected from the group consisting of: one or more of acrylic acid, methacrylic acid, 4-vinyl benzene sulfonic acid and 2-acrylamide-2-methyl propane sulfonic acid.

3. The gradient slow-release type polycarboxylate water reducer according to claim 1, wherein the chain transfer agent is selected from the group consisting of: one or two of sodium methallyl sulfonate and sodium hypophosphite.

4. The gradient slow-release type polycarboxylate water reducer according to claim 1, wherein the metal catalyst is selected from the group consisting of: one or two of ferrous chloride solution and ferrous sulfate solution.

5. The gradient slow-release type polycarboxylate water reducer according to any one of claims 1-4, wherein the reducing agent is selected from the group consisting of: one or more of ascorbic acid, sodium bisulfite, sodium formaldehyde sulfoxylate and Mohr's salt; the oxidant is selected from: hydrogen peroxide.

6. The gradient slow-release type polycarboxylate water reducer according to claim 1, wherein in S2, the dropping time of the solution B is 1.5-2.0 h, and the dropping time of the reducing agent is 1.5-2.0 h.

7. The application of the gradient slow-release type polycarboxylate superplasticizer according to any one of claims 1 to 6 as a concrete admixture.