Viscosity-reducing polycarboxylate water reducer and preparation method thereof

Abstract

The application discloses a viscosity-reducing polycarboxylic water reducer and a preparation method thereof. The method comprises the following steps: mixing an ester type polyether monomer, an ether type monomer and water, and stirring until completely dissolved; adding acrylic acid; stirring and uniformly mixing; adding an oxidizing agent; then adding a first mixed solution obtained by mixing acrylic acid, the ester type polyether monomer and water, a second mixed solution obtained by mixing a chain transfer agent and water, a third mixed solution obtained by mixing a reducing agent and water, and a fourth mixed solution obtained by mixing liquid alkali and water; continuing to react for 0.5-1.0 hours after the dropping is completed; and adjusting the pH value to 6-7 to obtain the viscosity-reducing polycarboxylic water reducer. The viscosity-reducing polycarboxylic water reducer prepared by the method has a number average molecular weight distribution of 10000-20000, good adaptability and viscosity-reducing effect, and especially good use effect in concrete prepared by using machine-made sand.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polycarboxylic acid water reducing agent, and particularly relates to a viscosity-reducing polycarboxylic acid water reducing agent and a preparation method thereof. BACKGROUND

[0002] Concrete is one of the four building structure materials and is also the largest structural material consumed in the world. At present, the challenges in the concrete technology not only come from the harsh construction environment, but also are affected by the disadvantages of the concrete itself, which influences the application of the concrete. In recent years, with the rapid development of the infrastructure construction in China, high-grade concrete is gradually developed into one of the mainstream materials due to its high strength, good integrity and small self-weight. In particular, the high-grade concrete is widely used in large bridge engineering, airport and other major engineering. However, due to the need to reduce the water-binder ratio under the premise of ensuring the strength of most high-grade concrete, the high-grade concrete has the problems of high viscosity and slow flow rate, which brings great challenges to the construction site.

[0003] In view of the above defects, the prior art discloses some viscosity-reducing polycarboxylic acid water reducing agents. For example, Chinese patent CN110358026A discloses that the viscosity of concrete is reduced by introducing alkyl acrylate phosphate. However, the viscosity reducer uses methyl alkenyl polyoxyethylene ether and iso-pentenyl polyoxyethylene ether. The raw material cost of this kind of viscosity reducer is high, the polymerization activity of the polyether is low, the reaction induction period is long, the polycarboxylic acid water reducing agent needs to be treated for a long time, and the conversion rate of the water reducing agent product cannot be reasonably set by different acid-ether ratios. In addition, the water reducing agent synthesized by the polyether is sensitive to the clay and stone powder content in the sand and gravel aggregate, which causes the polycarboxylic acid water reducing agent to be adsorbed and consumed by the clay in the sand and gravel material, so that the polycarboxylic acid water reducing agent loses its original performance and its wide application is limited.

[0004] Chinese patent CN113087433A discloses that the viscosity is reduced by introducing methyl, and by further adding 3-oxetanone and dimethyl sebacate. The product obtained by mixing 3-oxetanone and dimethyl sebacate has good viscosity reduction effect. However, the development and synthesis process of this kind of viscosity reducer is complicated, the use cost is high, and it is difficult to be widely applied.

[0005] Most of the polycarboxylic acid water reducing agents on the market have high carboxylic acid content and large molecular weight, which leads to poor tolerance of the polycarboxylic acid to clay. In general sand and gravel materials, the polycarboxylic acid water reducing agent cannot exert its original effect. SUMMARY

[0006] To solve the above technical problems, the application provides a viscosity-reducing polycarboxylic acid water reducing agent and a preparation method thereof.

[0007] The technical scheme adopted by the application is as follows:

[0008] A preparation method of a viscosity-reducing polycarboxylic acid water reducing agent, the preparation method comprising the following steps:

[0009] The ester type polyether monomer, the ether type monomer and the water are mixed and stirred until completely dissolved, 0-10 parts of acrylic acid is added, and after stirring and mixing uniformly, 3.0-5.0 parts of an oxidizing agent is added, and then within 0.5-1.0 hours, a first mixed solution obtained by mixing 20-40 parts of acrylic acid, 5-20 parts of the ester type polyether monomer and 30-50 parts of water, a second mixed solution obtained by mixing 2-5 parts of a chain transfer agent and 30-50 parts of water, a third mixed solution obtained by mixing 0.5-1 part of a reducing agent and 30-50 parts of water, and a fourth mixed solution obtained by mixing 0-10 parts of liquid alkali and 30-50 parts of water are simultaneously added dropwise, after the dropwise addition is completed, the reaction is continued for 0.5-1.0 hours, after the reaction is completed, the pH value is adjusted to 6-7, and the viscosity-reducing polycarboxylic acid water reducing agent is obtained.

[0010] The molecular structure of the ester type polyether monomer is as follows:

[0011] wherein R1 is H or CH3, m=5-20, and n=1-8.

[0012] The molecular structure of the ether type monomer is as follows: wherein y=20-32.

[0013] The molecular weight of the ester type polyether monomer is 500-1000.

[0014] The molecular weight of the ether type monomer is 1000-1500.

[0015] The oxidizing agent is any one of hydrogen peroxide or ammonium persulfate.

[0016] The chain transfer agent is any one of mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol or sodium hypophosphite.

[0017] The reducing agent is any one or both of formaldehyde sodium bisulfite and L-ascorbic acid.

[0018] In the preparation method, the pH value is adjusted to 6-7 by using a sodium hydroxide solution with a mass concentration of 30%.

[0019] In the preparation method, the temperature of the whole reaction process is controlled to be 15-30 DEG C

[0020] The viscosity-reducing polycarboxylic acid water reducing agent prepared by the preparation method has methyl, ester group and polyoxyethylene branched chain structure, and has good adaptability and viscosity-reducing performance.

[0021] The viscosity-reducing polycarboxylic acid water reducing agent prepared by the preparation method has methyl, ester group and polyoxyethylene branched chain structure, and has good adaptability and viscosity-reducing performance. Figure 1

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] 1. The ester type polyether monomer is used, part of the monomer is ethyleneoxy polyoxyethylene ether, the monomer conversion rate is ensured under the condition of low acid ether ratio, and the adverse effect of the air entraining effect of the unconverted monomer on the compressive strength is inhibited

[0024] 2. The initiation reaction system is optimized, the chain transfer agent dosage is increased, the molecular weight of the finally prepared water reducing agent is reduced, the viscosity-reducing polycarboxylic acid water reducing agent synthesized has low molecular weight, short main chain, fast adsorption in cement-based materials, and has viscosity-reducing effect.

[0025] 3. The polyether side chain molecular weight is controlled to be generally not more than 1500, the short polyether side chain is helpful to reduce the adsorption layer thickness of the water reducing agent, the hydration film between the cement particles is thinned, the free water release and mutual movement between the cement particles are facilitated, and then the shear application between the cement particles is reduced.

[0026] 4. When R1 in the ester type polyether monomer is preferably methyl, the methyl in the methyl methacrylate in the esterified macromonomer has hydrophobicity and steric hindrance, can induce the contraction of the polycarboxylic acid water reducing agent molecular conformation, is conducive to reducing the adsorption layer thickness of the water reducing agent on the cement particles, and then reduces the shear stress of the cement slurry, so as to reduce the viscosity of the concrete.

[0027] 5. The present application uses an excess amount of an oxidation-reduction agent to provide more free radicals in an aqueous solution, initiate polymerization, reduce the final viscosity of the polymer, and at the same time, does not affect the viscosity-reducing performance of the polymer itself.

[0028] ​6. The present application reduces the polymerization activity of acrylic acid, delays the polymerization rate of acrylic acid, and makes acrylic acid and ester-type polyether monomers and polyether monomers copolymerize simultaneously, changes the molecular structure of the polymer, and improves the viscosity reduction performance of the polymer by neutralization through alkali dropwise addition. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A structure diagram of the viscosity-reducing polycarboxylic acid water reducer prepared in the present application. DETAILED DESCRIPTION

[0030] The present application will be described in detail below with reference to examples.

[0031] The molecular structure of the ester-type polyether monomer used in each example is as follows: wherein R1 is H or CH3, m = 5-20, and n = 1-8. The molecular structure of the ether-type monomer used is as follows: wherein y = 20-32.

[0032] The raw materials used in each example and comparative example are shown in Table 1.

[0033] Table 1

[0034]

[0035]

[0036] The preparation method of each example is as follows:

[0037] Example 1

[0038] A preparation method of a viscosity-reducing polycarboxylic acid water reducer includes the following steps:

[0039] According to mass parts, 330 parts of ether-type monomer are weighed, 300 parts of water are added, and after being fully stirred and dissolved, 8 parts of acrylic acid are added, and the mixture is continuously stirred, mixed, and dissolved. Then, 3 parts of an oxidizing agent are added; the reaction temperature in the reaction container is maintained at 20℃, and within 40 min, a first mixed solution obtained by mixing 30 parts of acrylic acid, 20 parts of ester-type polyether monomer, and 40 parts of water, a second mixed solution obtained by mixing 3 parts of a chain transfer agent and 40 parts of water, a third mixed solution obtained by mixing 0.5 parts of a reducing agent and 40 parts of water, and a fourth mixed solution obtained by mixing 6 parts of liquid alkali and 40 parts of water are simultaneously added dropwise. After the dropwise addition is completed, the reaction is continued for 1.0 hour. After the reaction is completed, a 30% sodium hydroxide solution is added to adjust the pH value to 6-7, and the viscosity-reducing and anti-mud polycarboxylic acid water reducer is obtained.

[0040] Example 2

[0041] A preparation method of a viscosity-reducing polycarboxylic acid water reducer includes the following steps:

[0042] According to the mass fraction: take ester type polyether monomer 10 parts, ether type monomer 300 parts, add 300 parts of water, fully stir and dissolve, then add 4 parts of acrylic acid, continue to stir and mix evenly, fully mix and dissolve, then add 4 parts of oxidizing agent; keep the reaction temperature in the reaction vessel at 20℃, within 40 min, simultaneously drop the first mixed solution obtained by mixing 40 parts of acrylic acid, 5 parts of ester type polyether monomer and 40 parts of water, the second mixed solution obtained by mixing 3.5 parts of chain transfer agent and 40 parts of water, the third mixed solution obtained by mixing 1 part of reducing agent and 40 parts of water, and the fourth mixed solution obtained by mixing 8 parts of liquid alkali and 40 parts of water, after the dropping is completed, continue to react for 1.0 hour; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 6-7, and the viscosity reducing and anti-mud type polycarboxylic acid water reducing agent is obtained.

[0043] Example 3

[0044] A method for preparing a viscosity reducing type polycarboxylic acid water reducing agent, comprising the following steps:

[0045] According to the mass fraction: take ester type polyether monomer 5 parts, ether type monomer 330 parts, add 300 parts of water, fully stir and dissolve, then add 3 parts of acrylic acid, continue to stir and mix evenly, fully mix and dissolve, then add 5.0 parts of oxidizing agent; keep the reaction temperature in the reaction vessel at 25℃, within 50 min, simultaneously drop the first mixed solution obtained by mixing 30 parts of acrylic acid, 8 parts of ester type polyether monomer and 40 parts of water, the second mixed solution obtained by mixing 4 parts of chain transfer agent and 40 parts of water, the third mixed solution obtained by mixing 1 part of reducing agent and 40 parts of water, and the fourth mixed solution obtained by mixing 5 parts of liquid alkali and 40 parts of water, after the dropping is completed, continue to react for 1.0 hour; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 6-7, and the viscosity reducing and anti-mud type polycarboxylic acid water reducing agent is obtained.

[0046] Example 4

[0047] A method for preparing a viscosity reducing type polycarboxylic acid water reducing agent, comprising the following steps:

[0048] According to mass parts: take ester type polyether monomer 6 parts, ether type monomer 350 parts, add 300 parts of water, fully stir and dissolve, then add 5 parts of acrylic acid, continue to stir and mix uniformly, fully mix and dissolve, then add 3 parts of oxidizing agent; keep the reaction temperature in the reaction container at 25℃, within 50 min, simultaneously drop the first mixed solution obtained by mixing 30 parts of acrylic acid, 8 parts of ester type polyether monomer and 40 parts of water, the second mixed solution obtained by mixing 2.5 parts of chain transfer agent and 40 parts of water, the third mixed solution obtained by mixing 0.8 parts of reducing agent and 40 parts of water, and the fourth mixed solution obtained by mixing 4 parts of liquid alkali and 40 parts of water, after the dropping is completed, continue to react for 1.0 hour; after the reaction is completed, add 30% mass concentration of sodium hydroxide solution to adjust the pH value to 6-7, and the said viscosity reducing and mud resistant polycarboxylic acid water reducing agent is obtained.

[0049] Example 5

[0050] A preparation method of a viscosity reducing polycarboxylic acid water reducing agent, comprising the following steps:

[0051] According to mass parts: take ester type polyether monomer 6 parts, ether type monomer 350 parts, add 300 parts of water, fully stir and dissolve, then add 5 parts of acrylic acid, continue to stir and mix uniformly, fully mix and dissolve, then add 3 parts of oxidizing agent; keep the reaction temperature in the reaction container at 25℃, within 50 min, simultaneously drop the first mixed solution obtained by mixing 30 parts of acrylic acid, 8 parts of ester type polyether monomer and 40 parts of water, the second mixed solution obtained by mixing 2.5 parts of chain transfer agent and 40 parts of water, the third mixed solution obtained by mixing 0.8 parts of reducing agent and 40 parts of water, and the fourth mixed solution obtained by mixing 4 parts of liquid alkali and 40 parts of water, after the dropping is completed, continue to react for 1.0 hour; after the reaction is completed, add 30% mass concentration of sodium hydroxide solution to adjust the pH value to 6-7, and the said viscosity reducing and mud resistant polycarboxylic acid water reducing agent is obtained.

[0052] Example 6

[0053] A preparation method of a viscosity reducing polycarboxylic acid water reducing agent, comprising the following steps:

[0054] According to mass parts: take ester type polyether monomer 8 parts, ether type monomer 340 parts, add 260 parts of water, fully stir and dissolve, then add 4 parts of acrylic acid, continue to stir and mix uniformly, fully mix and dissolve, then add 3 parts of oxidizing agent; keep the reaction temperature in the reaction container at 20℃, within 55 min, simultaneously drop the first mixed solution obtained by mixing 35 parts of acrylic acid, 6 parts of ester type polyether monomer and 40 parts of water, the second mixed solution obtained by mixing 3.5 parts of chain transfer agent and 40 parts of water, the third mixed solution obtained by mixing 0.8 parts of reducing agent and 40 parts of water, and the fourth mixed solution obtained by mixing 4 parts of liquid alkali and 40 parts of water, after the dropping is completed, continue to react for 1.0 hour; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 6-7, thus the viscosity reducing and anti-mud type polycarboxylic acid water reducing agent is obtained.

[0055] Example 7

[0056] A preparation method of a viscosity reducing type polycarboxylic acid water reducing agent, comprising the following steps:

[0057] According to mass parts: take ester type polyether monomer 8 parts, ether type monomer 340 parts, add 260 parts of water, fully stir and dissolve, then add 4 parts of acrylic acid, continue to stir and mix uniformly, fully mix and dissolve, then add 3 parts of oxidizing agent; keep the reaction temperature in the reaction container at 20℃, within 55 min, simultaneously drop the first mixed solution obtained by mixing 35 parts of acrylic acid, 6 parts of ester type polyether monomer and 40 parts of water, the second mixed solution obtained by mixing 3.5 parts of chain transfer agent and 40 parts of water, the third mixed solution obtained by mixing 0.8 parts of reducing agent and 40 parts of water, and the fourth mixed solution obtained by mixing 4 parts of liquid alkali and 40 parts of water, after the dropping is completed, continue to react for 1.0 hour; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 6-7, thus the viscosity reducing and anti-mud type polycarboxylic acid water reducing agent is obtained.

[0058] Comparative Example 1

[0059] A preparation method of a polycarboxylic acid water reducing agent, comprising the following steps:

[0060] By mass fraction: take ether monomer 360 parts, add 260 parts of water, fully stirred and dissolved, then add 5 parts of acrylic acid, continue to stir and mix evenly, fully mix and dissolve, then add 1.5 parts of oxidant; keep the reaction temperature in the reaction vessel at 20℃, within 60 min, drop in the first mixed solution obtained by mixing 20 parts of acrylic acid and 40 parts of water, the second mixed solution obtained by mixing 2 parts of chain transfer agent and 40 parts of water, the third mixed solution obtained by mixing 0.3 parts of reducing agent and 40 parts of water, and the fourth mixed solution obtained by mixing 2.4 parts of liquid alkali and 40 parts of water, continue to react for 1.0 hour; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 6-7, and the polycarboxylic acid water reducer is obtained.

[0061] Comparative Example 2

[0062] A preparation method of a polycarboxylic acid water reducer comprises the following steps:

[0063] By mass fraction: take ether monomer 360 parts, add 260 parts of water, fully stirred and dissolved, then add 10 parts of acrylic acid, continue to stir and mix evenly, fully mix and dissolve, then add 4 parts of oxidant; keep the reaction temperature in the reaction vessel at 15℃, within 45 min, drop in the first mixed solution obtained by mixing 30 parts of acrylic acid and 40 parts of water, the second mixed solution obtained by mixing 2.5 parts of chain transfer agent and 40 parts of water, the third mixed solution obtained by mixing 1 part of reducing agent and 40 parts of water, and the fourth mixed solution obtained by mixing 3 parts of liquid alkali and 40 parts of water, continue to react for 1.0 hour; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 6-7, and the polycarboxylic acid water reducer is obtained.

[0064] Comparative Example 3

[0065] A preparation method of a polycarboxylic acid water reducer comprises the following steps:

[0066] By mass fraction: take ether monomer 360 parts, add 260 parts of water, fully stirred and dissolved, then add 3 parts of oxidant; keep the reaction temperature in the reaction vessel at 15℃, within 60 min, drop in the first mixed solution obtained by mixing 30 parts of acrylic acid and 10 parts of hydroxyethyl acrylate and 40 parts of water, the second mixed solution obtained by mixing 2 parts of chain transfer agent and 40 parts of water, and the third mixed solution obtained by mixing 0.6 parts of reducing agent and 40 parts of water, continue to react for 1.0 hour; after the reaction is completed, add 30% sodium hydroxide solution to adjust the pH value to 6-7, and the polycarboxylic acid water reducer is obtained.

[0067] Comparative Example 4

[0068] A preparation method of a polycarboxylic acid water reducer comprises the following steps:

[0069] The ether monomer 360 parts by mass, 260 parts of water, after fully stirring and dissolving, 5 parts of acrylic acid was added, and the mixture was stirred and mixed uniformly. After fully mixing and dissolving, 3 parts of oxidant was added; the reaction temperature in the reaction vessel was maintained at 20℃, and within 60 min, a first mixed solution obtained by mixing 20 parts of acrylic acid and 20 parts of hydroxypropyl acrylate and 40 parts of water, a second mixed solution obtained by mixing 3.5 parts of chain transfer agent and 40 parts of water, a third mixed solution obtained by mixing 1.0 parts of reducing agent and 40 parts of water, and a fourth mixed solution obtained by mixing 4 parts of liquid alkali and 40 parts of water were added dropwise. After the dropwise addition was completed, the reaction was continued for 1.0 hour. After the reaction was completed, a 30% sodium hydroxide solution was added to adjust the pH value to 6-7, and the polycarboxylic acid water reducer was obtained.

[0070] The dropwise addition time of each mixed solution in the above examples and comparative examples is shown in Table 2.

[0071] Table 2

[0072]

[0073] The GPC test results of the polycarboxylic acid water reducer prepared in the above examples and comparative examples are shown in Table 3:

[0074] Table 3 GPC results of examples

[0075]

[0076] Application Example

[0077] In the application example, unless otherwise specified, the cement used is ordinary Portland cement (P.O 42.5). In order to compare the dispersion performance and dispersion retention performance of the water reducer prepared in the application, the cement paste fluidity test was carried out according to the GB8077-2012 standard, the cement was 300g, the water amount was 87g, and the solid content of the water reducer was as shown in Table 4. After stirring for 4 minutes, the cement paste fluidity was measured on a flat glass, and the paste fluidity at different times was tested, and the test data are shown in Table 4. The concrete slump and spread were tested according to the relevant provisions in GB / T50080-2002 "Standard Test Methods for Performance of Ordinary Concrete Mixture", and the concrete V-shaped box flow loss time was tested according to the relevant provisions in GB / T50080-2016 "Standard Test Methods for Performance of Ordinary Concrete Mixture". The test results are shown in Table 5, all in seconds.

[0078] Table 4 Cement paste fluidity test

[0079]

[0080] Table 5 Concrete performance test

[0081]

[0082]

[0083] As can be seen from the above Tables 4-5, the cement and concrete to which the viscosity-reducing polycarboxylate superplasticizer prepared in each embodiment of the present application is added has greater cement paste fluidity, good concrete slump retention, and shorter V-shaped groove emptying time.

[0084] The above detailed description of the viscosity-reducing polycarboxylate superplasticizer and the preparation method thereof according to the reference embodiments is illustrative rather than restrictive, and several embodiments can be listed within the limited range, and thus variations and modifications without departing from the overall concept of the present application shall fall within the scope of the present application.

Claims

1. A method for preparing a viscosity-reducing polycarboxylate water reducer, characterized by, The preparation method comprises the following steps: 0-10 parts of ester type polyether monomer, 300-360 parts of ether type monomer, 240-300 parts of water are mixed and stirred until completely dissolved, 0-10 parts of acrylic acid is added, after stirring and mixing uniformly, 3.0-5.0 parts of oxidizing agent is added, then a first mixed solution obtained by mixing 20-40 parts of acrylic acid and 5-20 parts of ester type polyether monomer and 30-50 parts of water, a second mixed solution obtained by mixing 2-5 parts of chain transfer agent and 30-50 parts of water, a third mixed solution obtained by mixing 0.5-1 part of reducing agent and 30-50 parts of water, and a fourth mixed solution obtained by mixing 0-10 parts of liquid alkali and 30-50 parts of water are simultaneously dropped within 0.5-1.0 hours, after dropping, the reaction is continued for 0.5-1.0 hours; after the reaction is completed, the pH value is adjusted to 6-7, and the viscosity-reducing polycarboxylic acid water reducer is obtained. The molecular structure of the ester type polyether monomer is as follows: wherein R1is H, CH3, m = 5-20, n = 1-8; the molecular structure of the ether type monomer is: wherein, y = 20-32.

2. The production method according to claim 1, characterized by, The molecular weight of the ester type polyether monomer is 500-1000.

3. The preparation method according to claim 1, characterized in that, The molecular weight of the ether type monomer is 1000-1500.

4. The method of claim 1, wherein, The oxidizing agent is any one of hydrogen peroxide and ammonium persulfate.

5. The preparation method according to claim 1, characterized in that, The chain transfer agent is any one of mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol and sodium hypophosphite.

6. The method of claim 1, wherein, The reducing agent is any one or both of formaldehyde sodium bisulfite and L-ascorbic acid.

7. The preparation method according to claim 1, characterized in that, The pH value is adjusted to 6-7 by using a 30% sodium hydroxide solution.

8. The method of claim 1, wherein, The temperature of the whole reaction process is controlled to be 15-30°C.

9. The viscosity-reducing polycarboxylic acid water reducer prepared by the preparation method according to any one of claims 1-8.

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