Preparation method of polyacrylamide reverse emulsion of hydroxamic acid type

Abstract

The application discloses a preparation method of hydroxamic acid type polyacrylamide reverse emulsion and belongs to the technical field of polymer synthesis. The method comprises the following steps: dissolving acrylamide monomers, acrylic acid monomers, an anionic hydrophobic monomer, a complexing agent, a stabilizer, an inorganic salt and an oxidizing agent in deionized water, stirring uniformly to obtain an aqueous phase; mixing an emulsifier and solvent oil, stirring uniformly to obtain an oil phase; adding the aqueous phase into the oil phase, stirring and emulsifying to obtain an emulsion; dropwise adding a reducing agent solution into the emulsion, controlling polymerization to obtain a base emulsion; adding hydroxylamine hydrochloride and sodium hydroxide into the base emulsion to perform modification and post-hydrolysis; and finally adding a reverse agent to obtain the hydroxamic acid type polyacrylamide reverse emulsion. The application synthesizes a high-stability base emulsion by adopting a "water-in-oil-in-water" system, so that hydroxylamine hydrochloride and solid sodium hydroxide can be directly added into the base emulsion to perform hydrolysis and modification, and a stable reverse emulsion type hydroxamic acid modified product is obtained.

Description

Technical Field

[0001] This invention belongs to the field of reverse emulsion-type water-soluble polymer synthesis technology, and in particular, a method for preparing an oxime acid-type polyacrylamide reverse emulsion. Background Technology

[0002] In alumina production, the Bayer process, sintering process, or a combination of these methods are generally used. Regardless of the method used, a large amount of red mud is generated, and the sedimentation and separation of red mud is a crucial step in the aluminum industry. Currently, common flocculants used for red mud sedimentation include anionic polyacrylamide and anionic polyacrylamide with oxime acid groups. Because the oxime acid groups have a special affinity for and adsorption capacity for iron, its application performance is superior to that of conventional anionic polyacrylamide.

[0003] Currently, oxime acid-type anionic polyacrylamides are generally synthesized through solution polymerization followed by modification, or through the synthesis of nonionic polyacrylamide followed by hydrolysis and modification. Products synthesized using these methods have several drawbacks, such as low molecular weight, low content, and poor solubility. While some researchers have published methods for preparing oxime acid-type polymers in reverse emulsion systems, such as our prior application CN109180862A, which improves product content to some extent, most are limited by the stability of the emulsion system. During modification, hydroxylamine needs to be prepared into an emulsion before being mixed with the reverse emulsion anionic polyacrylamide for modification, which not only introduces large amounts of solvent oil and emulsifiers but also significantly dilutes the content. Furthermore, the use of a 50% hydroxylamine solution poses a significant safety hazard. Summary of the Invention

[0004] To overcome the above-mentioned technical defects, the present invention provides a method for preparing an oxime acid-type polyacrylamide reverse emulsion, thereby solving the problems involved in the background art.

[0005] This invention provides a method for preparing an oxime acid-type polyacrylamide reverse emulsion, comprising:

[0006] Acrylamide monomer, acrylic acid monomer, anionic hydrophobic monomer, complexing agent, stabilizer, inorganic salt, and oxidant are dissolved in deionized water, the pH is adjusted to 7.0-9.0, and the mixture is stirred evenly to obtain the aqueous phase.

[0007] The emulsifier and solvent oil are mixed and stirred evenly to obtain the oil phase;

[0008] The aqueous phase is added to the oil phase and stirred to emulsify, thus obtaining an emulsion.

[0009] The above emulsion was purged with nitrogen to remove oxygen, and a reducing agent solution was added dropwise to control the polymerization reaction, thus obtaining the basic emulsion of reverse emulsion anionic polyacrylamide.

[0010] Hydroxylamine hydrochloride and sodium hydroxide were alternately added to the base emulsion prepared above, and the modification and subsequent hydrolysis reaction were carried out at a controlled temperature of 40-80℃.

[0011] Finally, a reverse phase agent is added to obtain a high-content oxime acid-type polyacrylamide reverse emulsion.

[0012] Preferably or optionally, the anionic hydrophobic monomer is one or more of hydroxypropyl acrylate, ethyl acrylate, methyl acrylate, and vinyl acetate.

[0013] Preferably or optionally, the stabilizer is a low molecular weight anionic polymer with a molecular weight of 10,000 to 50,000.

[0014] Preferably or optionally, the low molecular weight anionic polymer is a polymer of one or more of acrylic acid, itaconic acid, and maleic acid.

[0015] Preferably or optionally, the inorganic salt is one or more of ammonium sulfate, sodium sulfate, potassium sulfate, ammonium chloride, sodium chloride, and potassium chloride;

[0016] Preferably or optionally, the complexing agent is EDTA-2Na and / or DTPA-5Na;

[0017] Preferably or optionally, the oxidant is one or more of hydrogen peroxide, tert-butyl hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, sodium bromate, and potassium bromate.

[0018] Preferably or optionally, the reducing agent is one or more of sodium metabisulfite, sodium bisulfite, and ferrous ammonium sulfate hexahydrate.

[0019] Preferably or optionally, the antiphase agent is a nonionic surfactant with an HLB value > 10;

[0020] Preferably or optionally, the antiphase agent is nonylphenol polyoxyethylene ether.

[0021] Preferably or optionally, in the emulsion, the total mass percentage of the reactive monomers, consisting of acrylamide, acrylic acid monomer, and anionic hydrophobic monomer, is 30-34%; the mass percentage of the complexing agent is 0.05-0.1%; the mass percentage of the stabilizer is 0.5-1.5%; the mass percentage of the inorganic salt is 1-4%; the mass percentage of the oxidant is 0.0005-0.001%; ​​the mass percentage of deionized water is 30-35%; the mass percentage of the emulsifier is 3-5%; and the mass percentage of the solvent oil is 22-27%.

[0022] Preferably or optionally, in the reactive monomers, the proportion of anionic hydrophobic monomers is 0.1-0.5%, the proportion of acrylamide is 70-100%, and the proportion of acrylic monomers (in the emulsion, the acrylic monomers are acrylic acid and / or sodium acrylate) is 0-30%.

[0023] Preferably or optionally, the hydroxylamine hydrochloride comprises 5-15% of the mass of the base emulsion; and the sodium hydroxide comprises 5-25% of the mass of the base emulsion.

[0024] This invention relates to a method for preparing an oxime acid-type polyacrylamide reverse emulsion, which has the following advantages compared to the prior art:

[0025] 1. This invention improves the polymer stability of the base emulsion by adding a certain amount of stabilizer, salt, and hydrophobic monomer to the aqueous phase, making it difficult for the polymer product molecular chains to unfold during the polymerization process, causing them to shrink, thus reducing the risk of demulsification in the emulsion system.

[0026] 2. This invention adds a stabilizer to the base emulsion. During the modification process using this base emulsion, the polymer in the system is protected by two layers (i.e., the first layer of electrostatic repulsion protection by the stabilizer and the second layer of steric hindrance protection by the emulsifier). When hydroxylamine hydrochloride and sodium hydroxide are directly added to the system, the system has strong containment, which keeps it stable and does not break the emulsion during the three dynamic processes of solid substance dissolution, oxime acid modification, and amide group hydrolysis, thus obtaining a stable product.

[0027] 3. This invention adds hydrophobic monomers to the base emulsion during polymerization, increasing the hydrophobicity of the molecular chain and accelerating the settling of red mud during application. The addition of hydrophobic anionic monomers also contributes to the stability of the emulsion system, making it easier to form a stable "water-in-oil" double-layer system. Furthermore, the introduction of hydrophobic structures into the polymer chain improves the product's performance.

[0028] 4. This invention directly adds hydroxylamine hydrochloride and alkali to the emulsion. First, the heat release is distributed by the emulsion, avoiding the risk of explosion caused by temperature control errors that may occur when hydroxylamine hydrochloride is directly neutralized with alkali. Second, it replaces the process of first neutralizing and then preparing the hydroxylamine solution into an emulsion and then mixing it with the emulsion, reducing the loss of active hydroxylamine in the process. Finally, it eliminates the need for additional oil and emulsifiers to emulsify the hydroxylamine solution before mixing it with the emulsion, effectively increasing the product content and reducing the solvent oil content in the product. Detailed Implementation

[0029] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0030] Inventive concept

[0031] Currently, methods for preparing oxime acid polymers in reverse emulsion systems have improved the product content to some extent. However, most of these methods are limited by the stability of the emulsion system. During the modification process, hydroxylamine needs to be prepared into an emulsion before being mixed with reverse emulsion anionic polyacrylamide for modification. This not only introduces a large amount of solvent oil and emulsifier, but also greatly dilutes the content.

[0032] To address the above deficiencies, this invention synthesizes a highly stable base emulsion using a "water-in-oil" system. This base emulsion allows for the direct addition of hydroxylamine hydrochloride and solid sodium hydroxide for hydrolysis and modification, yielding a stable reverse emulsion-type oxime acid-modified product. The "water-in-oil" system involves adding a certain amount of small-molecule anionic polymer, salt, and hydrophobic monomer to the aqueous phase. This prevents the polymer chains of the polymer products during polymerization from unwinding, causing shrinkage and reducing the risk of demulsification, thus improving the polymer stability of the base emulsion. During modification using this base emulsion, the polymer is protected by two layers (the first layer being the electrostatic repulsion protection of the anionic small-molecule polymer, and the second layer being the steric hindrance protection of the emulsifier). When hydroxylamine hydrochloride and sodium hydroxide are directly added to the system, the system exhibits strong containment, maintaining stability and preventing demulsification during the three dynamic processes of solid dissolution, oxime acid modification, and amide hydrolysis, resulting in a stable product.

[0033] The present invention will be further described below with reference to the embodiments. The examples described are intended to explain the present invention and should not be construed as limiting the present invention.

[0034] Example 1

[0035] Preparation of the base emulsion: Weigh 660g of 50% acrylamide, 14g of ammonium sulfate and 25.49g of deionized water, then add 0.5g of EDTA-2Na and 0.01g of ammonium persulfate to obtain an aqueous phase for later use; dissolve 31.6g of Span80 and 13.4g of Tween81 in 255g of solvent oil D100 to obtain an oil phase; then add the aqueous phase to the oil phase and emulsify by shearing with a high-speed shear machine to obtain an emulsion; purify the obtained emulsion with nitrogen, then add 0.2% sodium metabisulfite aqueous solution to initiate polymerization, controlling the reaction temperature to be below 50℃ to obtain the base emulsion.

[0036] Modification and post-hydrolysis: 77.6g of hydroxylamine hydrochloride solid and 164g of sodium hydroxide solid were added alternately in 5 portions to the above 800g base emulsion. After all the materials were added, the material was heated to 40℃ and kept at that temperature for 4 hours, then heated to 75℃ and kept at that temperature for 3 hours. Finally, the temperature was lowered to below 30℃ and 16g of reverse agent TX-10 (nonylphenol polyoxyethylene ether) was added. After stirring evenly, the material was filtered to obtain the oxime acid type polyacrylamide product.

[0037] Example 2

[0038] Preparation of the base emulsion: Weigh 528g of 50% acrylamide, 14g of ammonium sulfate, 50.6g of acrylic acid, and 48.29g of deionized water. Then add 0.5g of EDTA-2Na and 0.01g of ammonium persulfate. Finally, add 58.6g of 48% sodium hydroxide while stirring, and adjust the pH to 7.0-7.3 to obtain an aqueous phase for later use. Dissolve 31.6g of Span80 and 13.4g of Tween81 in 255g of solvent oil D100 to obtain an oil phase. Then add the aqueous phase to the oil phase and emulsify it using a high-speed shear machine to obtain an emulsion. Purify the obtained emulsion by purging it with nitrogen, and then add 0.2% sodium metabisulfite aqueous solution dropwise to initiate polymerization. Control the reaction temperature to be below 50℃ to obtain the base emulsion.

[0039] Modification and post-hydrolysis: 77.6g of hydroxylamine hydrochloride solid and 131.2g of sodium hydroxide solid were added alternately in 5 portions to the above 800g base emulsion. After all the materials were added, the material was heated to 40℃ and kept at that temperature for 4 hours, then heated to 75℃ and kept at that temperature for 3 hours. Finally, the temperature was lowered to below 30℃ and 16g of the phase reverser TX-10 was added. After stirring evenly, the material was filtered to obtain the oxime acid type polyacrylamide product.

[0040] Example 3

[0041] Preparation of the base emulsion: Weigh 660g of 50% acrylamide, 14g of ammonium sulfate, 10g of 40% sodium polyacrylate, 1g of vinyl acetate, and 14.49g of deionized water, then add 0.5g of EDTA-2Na and 0.01g of ammonium persulfate to obtain an aqueous phase for later use; dissolve 31.6g of Span80 and 13.4g of Tween81 in 255g of solvent oil D100 to obtain an oil phase; then add the aqueous phase to the oil phase and emulsify it using a high-speed shearing machine to obtain an emulsion; purify the obtained emulsion with nitrogen, then add 0.2% sodium metabisulfite aqueous solution to initiate polymerization, controlling the reaction temperature to be below 50℃ to obtain the base emulsion.

[0042] Modification and post-hydrolysis: 77.6g of hydroxylamine hydrochloride solid and 164g of sodium hydroxide solid were added alternately in 5 portions to the above 800g base emulsion. After all the materials were added, the material was heated to 40℃ and kept at that temperature for 4 hours, then heated to 75℃ and kept at that temperature for 3 hours. Finally, the temperature was lowered to below 30℃ and 16g of the phase reverser TX-10 was added. After stirring evenly, the material was filtered to obtain the oxime acid type polyacrylamide product.

[0043] Example 4

[0044] Preparation of the base emulsion: Weigh 528g of 50% acrylamide, 14g of ammonium sulfate, 50.6g of acrylic acid, 10g of 40% sodium polyacrylate, 1g of vinyl acetate, and 37.29g of deionized water. Then add 0.5g of EDTA-2Na and 0.01g of ammonium persulfate. Finally, add 58.6g of 48% sodium hydroxide while stirring, and adjust the pH to 7.0 to 7.3 to obtain an aqueous phase for later use. Dissolve 31.6g of Span80 and 13.4g of Tween81 in 255g of solvent oil D100 to obtain an oil phase. Then add the aqueous phase to the oil phase and emulsify it using a high-speed shear machine to obtain an emulsion. Purify the obtained emulsion by purging it with nitrogen, and then add 0.2% sodium metabisulfite aqueous solution dropwise to initiate polymerization. Control the reaction temperature to be below 50℃ to obtain the base emulsion.

[0045] Modification and post-hydrolysis: 77.6g of hydroxylamine hydrochloride solid and 131.2g of sodium hydroxide solid were added alternately in 5 portions to the above 800g base emulsion. After all the materials were added, the material was heated to 40℃ and kept at that temperature for 4 hours, then heated to 75℃ and kept at that temperature for 3 hours. Finally, the temperature was lowered to below 30℃ and 16g of the phase reverser TX-10 was added. After stirring evenly, the material was filtered to obtain the oxime acid type polyacrylamide product.

[0046] Example 5

[0047] Preparation of the base emulsion: Weigh 264g of 50% acrylamide, 14g of ammonium sulfate, 151.7g of acrylic acid, 10g of 40% sodium polyacrylate, 1g of vinyl acetate, and 83.19g of deionized water. Then add 0.5g of EDTA-2Na and 0.01g of ammonium persulfate. Finally, add 175.6g of 48% sodium hydroxide while stirring, and adjust the pH to 7.0 to 7.3 to obtain an aqueous phase for later use. Dissolve 31.6g of Span80 and 13.4g of Tween81 in 255g of solvent oil D100 to obtain an oil phase. Then add the aqueous phase to the oil phase and emulsify it using a high-speed shear machine to obtain an emulsion. Purify the obtained emulsion by purging it with nitrogen, and then add 0.2% sodium metabisulfite aqueous solution dropwise to initiate polymerization. Control the reaction temperature to be below 50℃ to obtain the base emulsion.

[0048] Modification and post-hydrolysis: 77.6g of hydroxylamine hydrochloride solid and 65.6g of sodium hydroxide solid were added alternately in 5 portions to the above 800g base emulsion. After all the materials were added, the material was heated to 40℃ and kept at that temperature for 4 hours, then heated to 75℃ and kept at that temperature for 3 hours. Finally, the temperature was lowered to below 30℃ and 16g of the phase reverser TX-10 was added. After stirring evenly, the material was filtered to obtain the oxime acid type polyacrylamide product.

[0049] Example 6

[0050] Preparation of the base emulsion: Weigh 660g of 50% acrylamide, 14g of ammonium sulfate, 10g of 40% sodium polyacrylate and 15.49g of deionized water, then add 0.5g of EDTA-2Na and 0.01g of ammonium persulfate to obtain an aqueous phase for later use; dissolve 31.6g of Span80 and 13.4g of Tween81 in 255g of solvent oil D100 to obtain an oil phase; then add the aqueous phase to the oil phase and emulsify by shearing with a high-speed shear machine to obtain an emulsion; purify the obtained emulsion with nitrogen, then add 0.2% sodium metabisulfite aqueous solution to initiate polymerization, controlling the reaction temperature to be below 50℃ to obtain the base emulsion.

[0051] Modification and post-hydrolysis: 77.6g of hydroxylamine hydrochloride solid and 164g of sodium hydroxide solid were added alternately in 5 portions to the above 800g base emulsion. After all the materials were added, the material was heated to 40℃ and kept at that temperature for 4 hours, then heated to 75℃ and kept at that temperature for 3 hours. Finally, the temperature was lowered to below 30℃ and 16g of the phase reverser TX-10 was added. After stirring evenly, the material was filtered to obtain the oxime acid type polyacrylamide product.

[0052] Detection example

[0053] The products prepared in Examples 3 to 6 were diluted with 10 g / L alkaline water to a mass concentration of 0.25% and then subjected to red mud settling tests with mineral slurry.

[0054] The slurry used in this experiment came from a branch of Aluminum Corporation of China Limited, with a solid content of 85 g / L and a temperature of 103℃. The experimental method included: adding 1000 mL of slurry to two 1000 mL graduated cylinders, then adding 4 mL of the prepared flocculant aqueous solution to each cylinder in two separate additions of 2 mL each; then slowly stirring up and down six times, recording the time required for the flocs to settle from 900 mL to 700 mL, the thickness of the compressed layer at 3 minutes, and the turbidity of the supernatant after 5 minutes. The base emulsion filter residue was calculated as the ratio of the total amount of base polymer to the total amount of particulate matter after filtering the base polymer through an 80-mesh filter; the modified product filter residue was calculated as the ratio of the total amount of modified product to the total amount of particulate matter after filtering the modified product through an 80-mesh filter.

[0055] The experimental results are shown in the table below:

[0056]

[0057]

[0058] discuss

[0059] Referring to the examples and the table above, a comparison of Examples 1 to 6 shows that maintaining the stability of the "water-in-oil" system during the direct addition of hydroxylamine hydrochloride and alkali to the base emulsion yields a stable product. Comparing Examples 1 and 3, and Examples 2 and 4, adding a certain amount of stabilizer, salt, and hydrophobic monomer to the aqueous phase improves the polymer stability of the base emulsion. Comparing Examples 3 and 6 (compared to Example 3 without the addition of anionic hydrophobic monomers), it can be seen that the addition of anionic hydrophobic monomers further enhances the polymerization stability of the base emulsion, the stability of the modification process, and improves the application performance of the product. Comparing Examples 5 and 4, it can be seen that the lower the ionicity of the reactant monomers, the better the performance of the modified base emulsion using the post-hydrolysis process.

[0060] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for preparing an oxime acid-type polyacrylamide reverse emulsion, characterized in that, include: Acrylamide monomer, acrylic acid monomer, vinyl acetate, complexing agent, stabilizer, inorganic salt, and oxidant are dissolved in deionized water, the pH is adjusted to 7.0-9.0, and the mixture is stirred evenly to obtain the aqueous phase. The emulsifier and solvent oil are mixed and stirred evenly to obtain the oil phase; The aqueous phase is added to the oil phase and stirred to emulsify, thus obtaining an emulsion. The above emulsion was purged with nitrogen to remove oxygen, and a reducing agent solution was added dropwise to control the polymerization reaction, thus obtaining the basic emulsion of reverse emulsion anionic polyacrylamide. Hydroxylamine hydrochloride and sodium hydroxide were alternately added to the base emulsion prepared above, and the modification and subsequent hydrolysis reaction were carried out at a controlled temperature of 40-80℃. Finally, a reverse phase agent was added to obtain an oxime-type polyacrylamide reverse emulsion; The stabilizer is a low molecular weight anionic polymer with a molecular weight of 10,000 to 50,000. In the emulsion, the total mass percentage of the reactive monomers, consisting of acrylamide, acrylic acid monomer, and vinyl acetate, is 30-34%; the mass percentage of the complexing agent is 0.05-0.1%; the mass percentage of the stabilizer is 0.5-1.5%; the mass percentage of the inorganic salt is 1-4%; the mass percentage of the oxidant is 0.0005-0.001%; ​​the mass percentage of deionized water is 30-35%; the mass percentage of the emulsifier is 3-5%; and the mass percentage of the solvent oil is 22-27%. In the reactant monomers, vinyl acetate accounts for 0.1-0.5%, acrylamide accounts for 70-100%, and acrylic acid monomer accounts for 0-30%, and the sum of the mass percentages of each component in the reactant monomers is 100%.

2. The method for preparing the oxime acid-type polyacrylamide reverse emulsion according to claim 1, characterized in that, The low molecular weight anionic polymer is a polymer of one or more of acrylic acid, itaconic acid, and maleic acid.

3. The method for preparing the oxime acid-type polyacrylamide reverse emulsion according to claim 1, characterized in that, The inorganic salt is one or more of ammonium sulfate, sodium sulfate, potassium sulfate, ammonium chloride, sodium chloride, and potassium chloride.

4. The method for preparing the oxime acid-type polyacrylamide reverse emulsion according to claim 1, characterized in that, The complexing agent is EDTA-2Na and / or DTPA-5Na.

5. The method for preparing the oxime acid-type polyacrylamide reverse emulsion according to claim 1, characterized in that, The oxidant is one or more of hydrogen peroxide, tert-butyl hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, sodium bromate, and potassium bromate.

6. The method for preparing the oxime acid-type polyacrylamide reverse emulsion according to claim 1, characterized in that, The reducing agent is one or more of sodium metabisulfite, sodium bisulfite, and ferrous ammonium sulfate hexahydrate.

7. The method for preparing the oxime acid-type polyacrylamide reverse emulsion according to claim 1, characterized in that, The antiphase agent is a nonionic surfactant with an HLB value > 10.

8. The method for preparing the oxime acid-type polyacrylamide reverse emulsion according to claim 7, characterized in that, The reverser is nonylphenol polyoxyethylene ether.

9. The method for preparing the oxime acid-type polyacrylamide reverse emulsion according to claim 1, characterized in that, The hydroxylamine hydrochloride comprises 5-15% of the mass of the base emulsion; the sodium hydroxide comprises 5-25% of the mass of the base emulsion.

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