A kind of machine-made sand-adaptable polycarboxylic acid water-reducing agent synthesized from fluorinated polyether and its preparation method

Abstract

The present invention discloses a polycarboxylate water-reducing agent for machine-made sand synthesized from fluorine-containing polyether and a preparation method thereof. In order to introduce a functional group containing the fluorine element into the molecular structure of the ether bond, the present invention adds an epoxy compound containing the fluorine element after the polymerization reaction of ethylene oxide or propylene oxide or a mixture of the two, thereby synthesizing an unsaturated modified polyoxyethylene ether containing the fluorine element at the end group. The introduction of the fluorine element can greatly change the dispersibility and stone powder and soil resistance of the synthesized polycarboxylate water-reducing agent, thereby making it suitable for concrete engineering using machine-made sand.

Description

Technical Field

[0001] The invention relates to the technical field of polycarboxylate water reducers, and in particular to a machine-made sand-adaptable polycarboxylate water reducer synthesized from fluorine-containing polyether and a preparation method thereof. Background Art

[0002] Commercial precast concrete and precast concrete components play an important role in the development of my country's new building industrialization and residential industry modernization due to their stable product quality, high industrial production efficiency, less environmental pollution, and the promotion of effective and rational use of resources. In recent years, as the largest proportion of sand and gravel aggregates in concrete components, its demand has continued to remain high. As a natural river sand resource that is non-renewable in the short term, it has been facing an increasingly depleted situation after decades of traditional extensive mining. The application of machine-made sand has important economic and environmental value.

[0003] According to relevant literature, machine-made sand refers to rock that has been treated to remove soil, and is crushed and screened using sand-making equipment to obtain rock particles with a particle size of less than 4.75 mm. Compared with natural river sand, machine-made sand has many advantages. The strength and durability of concrete or mortar prepared with machine-made sand are better than those of natural river sand. However, since machine-made sand needs to go through a rock crushing process, it is inevitable to produce stone powder with extremely small particle sizes. The stone powder particles are mostly between 0.016 and 0.075 mm, and the specific surface area of ​​stone powder is larger than that of sand and gravel aggregates, which leads to the rapid consumption of polycarboxylic acid building admixtures, resulting in a significant decrease in the fluidity and workability of precast concrete in a short period of time, which limits the application of machine-made sand and increases the cost and difficulty of engineering use.

[0004] Many researchers have found that the performance of polycarboxylic acid-based high-efficiency water reducers is closely related to their molecular structure. Therefore, the molecular structure design of polycarboxylic acid-based water reducers is of great significance for exploring the relationship between structure and performance. In previous studies on polycarboxylic acid-based high-efficiency water reducers, the high content of stone powder in machine-made sand leads to a rapid consumption of building admixtures, which in turn affects the performance of precast concrete. This was mainly achieved by adding other surface performance functional groups.

[0005] In the prior art, the polyether synthesis method generally uses unsaturated enol compounds (allyl alcohol, methacrylic alcohol, isopentenol, etc.) and ethylene oxide or propylene oxide or a mixture of the two to synthesize unsaturated polyoxyethylene ethers through anionic ring-opening polymerization. Polycarboxylic acid water reducers generally use unsaturated carboxylic acids (such as acrylic acid, methacrylic acid, maleic anhydride (maleic anhydride), fumaric acid (fumaric anhydride), etc.) and unsaturated polyethers (isopentenyl polyoxyethylene ether (TPEG or IPEG), isobutylene polyoxyethylene ether (HPEG), propylene polyoxyethylene ether (APEG), etc.), and the molecular weight is generally between 800 and 4000. Polyethers with a smaller molecular weight are beneficial to the improvement of water reduction rate, and polyethers with a larger molecular weight are beneficial to slow setting and plasticity retention. In addition to the above two main reaction raw materials, unsaturated sulfonic acid compounds (sodium propylene sulfonate, sodium methacrylic sulfonate, etc.) and unsaturated amino and amide compounds (such as acrylamide, etc.) are added in the prior art.

[0006] However, the above polycarboxylic acid water reducers cannot effectively slow down the consumption rate of water reducers by stone powder in machine-made sand. Therefore, those skilled in the art are in urgent need of studying a machine-made sand-compatible polycarboxylic acid water reducer synthesized from fluorinated polyether and its preparation method. Summary of the invention

[0007] The purpose of the present invention is to provide a polycarboxylic acid water-reducing agent for machine-made sand adapted by synthesizing fluorine-containing polyether and a preparation method thereof in view of the deficiencies in the prior art.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] The first aspect of the present invention is to provide a method for preparing a machine-made sand-compatible polycarboxylate water-reducing agent synthesized from a fluorinated polyether, comprising the following steps:

[0010] Step 1, using an unsaturated enol compound as a reaction raw material, adding an alkali metal alcoholate as a catalyst, and carrying out an anionic ring-opening polymerization reaction with ethylene oxide or propylene oxide or a mixture of the two, the reaction temperature is 125°C to 155°C, and the reaction time is 3h to 8h; then adding a fluorine-containing epoxy compound, adjusting the pH to 7 to 12 after the reaction is completed, and reacting to obtain an unsaturated modified polyoxyethylene ether containing fluorine element at the end group;

[0011] Step 2: The unsaturated modified polyoxyethylene ether containing fluorine element at the end synthesized in step 1 is subjected to free radical copolymerization reaction with unsaturated carboxylic acid compounds, the reaction temperature is 10°C to 30°C, and the reaction time is 2h to 6h to synthesize a polycarboxylic acid-based high-efficiency water reducer containing fluorine element functional groups. After the reaction is completed, the pH is adjusted to 5.0 to 7.0 to obtain a fluorine-containing polycarboxylic acid water reducer suitable for machine-made sand.

[0012] Furthermore, in the step 1, the pressure of the reaction device for the anionic ring-opening polymerization reaction is 1.7 MPa to 3.0 MPa.

[0013] Furthermore, in the step 1, the amount of the alkali metal compound used as a catalyst is 0.6% to 2.1% of the total mass of the reactants.

[0014] Furthermore, in the step 1, the molar ratio of the unsaturated enol compound to the epoxy compound is 1:(20-30); the molar ratio of the unsaturated enol compound to the fluorine-containing epoxy compound is 1:(1-3).

[0015] Furthermore, in the step 1, the unsaturated ene alcohol compound is one or more of allyl alcohol and methacrylic alcohol, and the specific reaction formula of the anionic ring-opening polymerization reaction is as follows:

[0016]

[0017] Wherein, n=20-130; R is -H or -CH3.

[0018] Furthermore, in the step 1, the fluorine-containing epoxy compound is tetrafluoroethylene oxide or hexafluoropropylene oxide, and the reaction formula after adding the fluorine-containing epoxy compound is as follows:

[0019]

[0020] Wherein, n=20-130; m=1-3; R is -H or -CH3; X is -F or -CF3.

[0021] Furthermore, in the step 2, the unsaturated carboxylic acid compound is acrylic acid or methacrylic acid or a mixture of the two, and the molar ratio of the unsaturated polyoxyethylene ether to the unsaturated carboxylic acid compound is 1:(2.5-6).

[0022] Furthermore, in step 2, the initiators used are hydrogen peroxide and vitamin C, wherein the mass ratio of hydrogen peroxide to vitamin C is 1:(0.2-0.6), and the total amount of the initiator is 0.8%-2.4% of the total mass of the reactants.

[0023] The second aspect of the present invention is to provide a machine-made sand-compatible polycarboxylic acid water-reducing agent synthesized from fluorine-containing polyether, which is prepared by the above-mentioned preparation method.

[0024] The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:

[0025] In order to introduce a functional group containing fluorine into the molecular structure of the ether bond, the present invention adds an epoxy compound containing fluorine after the polymerization reaction of ethylene oxide or propylene oxide or a mixture of the two, thereby synthesizing an unsaturated modified polyoxyethylene ether containing fluorine at the end group. The introduction of fluorine can greatly change the dispersibility and stone powder and soil resistance of the synthesized polycarboxylate water reducer, thereby making it suitable for concrete engineering using machine-made sand. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific embodiments, but is not intended to be limiting of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention may be combined with each other without conflict.

[0027] Example 1

[0028] Step 1: Add 0.72 kg of methyl allyl alcohol as a reaction raw material into a pressure reaction vessel, add 0.3 kg of metallic sodium alcoholate as a catalyst, and mechanically stir at 140 ° C. The pressure of the reaction device is 2.5 MPa. Add 30 kg of ethylene oxide for anionic ring-opening polymerization, and the reaction time is 5.5 hours. Add 3.5 kg of hexafluoropropylene oxide, continue to react for 1.5 hours, and adjust the pH to 10 after the reaction. The reaction produces an unsaturated modified polyoxyethylene ether A1 with an average molecular weight of about 3500 and a terminal group containing fluorine element.

[0029] Step 2: Add 0.72kg of acrylic acid to the reaction device, add 10kg of the above-mentioned synthetic unsaturated polyoxyethylene ether A1 under mechanical stirring conditions, control the reaction temperature to 20°C, add 0.08kg of hydrogen peroxide and 0.04kg of vitamin C as initiators for free radical copolymerization, and the reaction time is 4h. After the reaction is completed, add sodium hydroxide aqueous solution to adjust the pH to 6.5 to obtain a fluorine-containing polycarboxylic acid water reducer suitable for machine-made sand.

[0030] Example 2

[0031] Step 1: Add 0.58 kg of allyl alcohol as a reaction raw material into a pressure reaction vessel, add 0.32 kg of metallic sodium alcoholate as a catalyst, and mechanically stir at 145 ° C. The pressure of the reaction device is 2.8 MPa. Add 13.5 kg of ethylene oxide for anionic ring-opening polymerization, and the reaction time is 4.5 hours. Add 4.15 kg of hexafluoropropylene oxide, continue to react for 1.0 hours, and adjust the pH to 10 after the reaction. The reaction produces an unsaturated modified polyoxyethylene ether A2 with an average molecular weight of about 1800 and a terminal group containing fluorine element.

[0032] Step 2: Add 1.5kg of acrylic acid to the reaction device, add 10kg of the above-mentioned synthetic unsaturated polyoxyethylene ether A2 under mechanical stirring conditions, control the reaction temperature to 25°C, add 0.12kg of hydrogen peroxide and 0.05kg of vitamin C as initiators for free radical copolymerization, and the reaction time is 4.5h. After the reaction is completed, add sodium hydroxide aqueous solution to adjust the pH to 6.0 to obtain a fluorine-containing polycarboxylic acid water reducer suitable for machine-made sand.

[0033] Example 3

[0034] Step 1: Add 0.86 kg of isopentenol as a reaction raw material into a pressure reaction vessel, add 0.4 kg of metallic sodium alcoholate as a catalyst, and mechanically stir at 150 ° C. The pressure of the reaction device is 2.9 MPa. Add 46.4 kg of propylene oxide for anionic ring-opening polymerization, and the reaction time is 7.5 hours. Add 1.8 kg of hexafluoroethylene oxide and continue to react for 0.5 hours. After the reaction is completed, adjust the pH to 10.5. The reaction produces an unsaturated modified polyoxyethylene ether A3 with an average molecular weight of about 4800 and a terminal group containing fluorine element.

[0035] Step 2: Add 0.72kg of acrylic acid to the reaction device, add 10kg of the above-mentioned synthetic unsaturated polyoxyethylene ether A1 under mechanical stirring conditions, control the reaction temperature to 20°C, add 0.08kg of hydrogen peroxide and 0.04kg of vitamin C as initiators for free radical copolymerization, and the reaction time is 4h. After the reaction is completed, add sodium hydroxide aqueous solution to adjust the pH to 6.5 to obtain a fluorine-containing polycarboxylic acid water reducer suitable for machine-made sand.

[0036] Example 4

[0037] Step 1: Add 0.72kg of allyl alcohol as a reaction raw material into a pressure reaction vessel, add 0.35kg of metallic sodium alcoholate as a catalyst, and mechanically stir at 130°C. The pressure of the reaction device is 1.8Mpa. Add 22kg of ethylene oxide and 29kg for anionic ring-opening polymerization, and the reaction time is 5h. Add 3.0kg of hexafluoropropylene oxide and continue the reaction for 1h. After the reaction is completed, adjust the pH to 11.5. The reaction produces an unsaturated modified polyoxyethylene ether A4 with an average molecular weight of about 5500 and a terminal group containing fluorine element.

[0038] Step 2: Add 1.0 kg of methacrylic acid to the reaction device, add 10 kg of the above-mentioned synthetic unsaturated polyoxyethylene ether A4 under mechanical stirring conditions, control the reaction temperature to 25°C, add 0.15 kg of hydrogen peroxide and 0.1 kg of vitamin C as initiators for free radical copolymerization, and the reaction time is 4.5 hours. After the reaction is completed, add sodium hydroxide aqueous solution to adjust the pH to 6.8 to obtain a fluorine-containing polycarboxylic acid water reducer suitable for machine-made sand.

[0039] Example 5

[0040] Step 1: Add 0.72kg of allyl alcohol as a reaction raw material into a pressure reaction vessel, add 0.25kg of metallic sodium alcoholate as a catalyst, and mechanically stir at 140°C. The pressure of the reaction device is 2.3Mpa. Add 25kg of ethylene oxide for anionic ring-opening polymerization, and the reaction time is 4.5h. Add 1.5kg of hexafluoropropylene oxide and 1kg of hexafluoroethylene oxide, and continue the reaction for 1h. After the reaction is completed, adjust the pH to 8.5. The reaction produces an unsaturated modified polyoxyethylene ether A5 with an average molecular weight of about 2800 and a terminal group containing fluorine element.

[0041] Step 2: Add 0.72kg acrylic acid and 0.86kg methacrylic acid into the reaction device, add 10kg of the above-mentioned synthetic unsaturated polyoxyethylene ether A5 under mechanical stirring, control the reaction temperature to 25°C, add 0.09kg hydrogen peroxide and 0.04kg vitamin C as initiators for free radical copolymerization, and the reaction time is 2.5h. After the reaction is completed, add sodium hydroxide aqueous solution to adjust the pH to 5.5 to obtain a fluorine-containing polycarboxylic acid water reducer suitable for machine-made sand.

[0042] Concrete admixtures were synthesized using the technical solutions of Examples 1-5 and Comparative Example 1, and the effects of such concrete admixtures on the initial performance and time-dependent performance of cement mortar were determined. The cement used was standard cement, and the sand used was machine-made sand. The detection method was based on GB / T 8077-2012 Concrete admixture homogeneity test method, and the unit of fluidity expansion diameter was millimeter (mm). The experimental results are shown in Table 1 below:

[0043] Table 1

[0044] initial 30min 60min 90min 120min Comparative Example 1 290 283 262 231 210 Example 1 311 298 286 269 245 Example 2 307 292 285 261 240 Example 3 313 295 289 275 260 Example 4 298 287 275 262 230 Example 5 306 290 271 258 225

[0045] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a polycarboxylate water-reducing agent for machine-made sand adapted by synthesizing fluorinated polyether, characterized in that: The steps include: Step 1, using an unsaturated enol compound as a reaction raw material, adding an alkali metal alcoholate as a catalyst, and carrying out an anionic ring-opening polymerization reaction with ethylene oxide or propylene oxide or a mixture of the two, the reaction temperature is 125°C to 155°C, and the reaction time is 3h to 8h; then adding a fluorine-containing epoxy compound, adjusting the pH to 7 to 12 after the reaction is completed, and reacting to obtain an unsaturated modified polyoxyethylene ether containing fluorine element at the end group; Wherein, the fluorine-containing epoxy compound is tetrafluoroethylene oxide or hexafluoropropylene oxide; Step 2: The unsaturated modified polyoxyethylene ether containing fluorine element at the end synthesized in step 1 is subjected to free radical copolymerization reaction with unsaturated carboxylic acid compounds, the reaction temperature is 10°C to 30°C, and the reaction time is 2h to 6h to synthesize a polycarboxylic acid-based high-efficiency water reducer containing fluorine element functional groups. After the reaction is completed, the pH is adjusted to 5.0 to 7.0 to obtain a fluorine-containing polycarboxylic acid water reducer suitable for machine-made sand.

2. The preparation method according to claim 1, characterized in that: In the step 1, the pressure of the reaction device for the anionic ring-opening polymerization reaction is 1.7 MPa to 3.0 MPa.

3. The preparation method according to claim 1, characterized in that: In the step 1, the amount of the alkali metal compound used as a catalyst is 0.6% to 2.1% of the total mass of the reactants.

4. The preparation method according to claim 1, characterized in that: In the step 1, the molar ratio of the unsaturated enol compound to the epoxy compound is 1:(20-30); the molar ratio of the unsaturated enol compound to the fluorine-containing epoxy compound is 1:(1-3).

5. The preparation method according to claim 1, characterized in that: In the step 1, the unsaturated ene alcohol compound is one or more of allyl alcohol and methacrylic alcohol, and the specific reaction formula of the anionic ring-opening polymerization reaction is as follows: Wherein, n=20-130; R is -H or -CH3.

6. The preparation method according to claim 5, characterized in that: In the step 1, the reaction formula after adding the fluorine-containing epoxy compound is as follows: Wherein, n=20-130; m=1-3; R is -H or -CH3; X is -F or -CF3.

7. The preparation method according to claim 1, characterized in that: In the step 2, the unsaturated carboxylic acid compound is acrylic acid or methacrylic acid or a mixture of the two, and the molar ratio of the unsaturated polyoxyethylene ether to the unsaturated carboxylic acid compound is 1:(2.5-6).

8. The preparation method according to claim 1, characterized in that: In the step 2, the initiators used are hydrogen peroxide and vitamin C, wherein the mass ratio of hydrogen peroxide to vitamin C is 1:(0.2-0.6), and the total amount of the initiator is 0.8%-2.4% of the total mass of the reactants.

9. A machine-made sand-compatible polycarboxylic acid water-reducing agent synthesized from fluorinated polyether, prepared by the preparation method according to any one of claims 1 to 8.

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