Preparation method of powdery polyacrylic acid thickener microspheres
The reverse suspension polymerization method was used to prepare powdered polyacrylic acid thickener microspheres with controllable particle size, which solved the problem of the reduced thickening ability of polyacrylic acid thickeners in high-salinity oilfields, and achieved a significant improvement in salt resistance and simplified production process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HIGH & NEW TECH RES CENT OF HENAN ACAD OF SCI
- Filing Date
- 2026-02-12
- Publication Date
- 2026-05-19
AI Technical Summary
Existing polyacrylic acid thickeners exhibit reduced thickening ability in salt solutions, making them difficult to apply in fields with high salinity. Furthermore, existing processes cannot easily introduce hydrophobic monomers to improve salt resistance.
By employing reverse suspension polymerization combined with specific hydrophobic monomers and a composite emulsion system, powdered polyacrylic acid thickener microspheres with controllable particle size were prepared. Hydrophobic long-chain monomers were introduced into the polymer backbone through copolymerization to form a reversible physical cross-linking network.
This invention enables the simple and cost-effective preparation of powdered thickeners with controllable particle size, significantly improving salt resistance and flowability, making them suitable for various applications.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer material synthesis technology, specifically relating to a method for preparing powdered polyacrylic acid thickener microspheres with excellent salt resistance. Background Technology
[0002] Polyacrylic acid thickeners are widely used in oil extraction, coatings, cosmetics, textile printing and dyeing, and the food industry due to their significant thickening effect and relatively low raw material cost. These thickeners are typically prepared by methods such as reverse emulsion polymerization, solution polymerization, or precipitation polymerization, yielding emulsion or powder products.
[0003] However, traditional polyacrylic acid thickeners generally suffer from poor electrolyte resistance. When applied to solutions containing salts (such as NaCl and CaCl2), the thickening ability drops sharply due to electrostatic shielding causing polymer chain contraction, resulting in low viscosity retention. This severely limits their use in specific fields such as oil recovery in high-salinity oilfields. To improve salt resistance, existing technologies often introduce hydrophobic groups into the polymer chain, using hydrophobic association to maintain solution viscosity. However, how to effectively introduce hydrophobic monomers into water-soluble polymer chains through a simple process, achieve powder production, and maintain good thickening and dispersibility remains a technical problem to be solved. Summary of the Invention
[0004] The present invention aims to overcome the shortcomings of the prior art and provide a simple and cost-effective method for preparing powdered polyacrylic acid microspheres. This method uses reverse suspension polymerization technology, combined with the introduction of specific hydrophobic monomers and the design of a composite emulsion system, to successfully prepare powdered thickener products with controllable particle size and excellent salt resistance.
[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A method for preparing powdered polyacrylic acid thickener microspheres, characterized by the following steps: using an unsaturated acidic monomer as the main monomer, a water-soluble bifunctional monomer as the crosslinking monomer, acrylamide and hydrophobic long-chain alkane esters of acrylic acid as salt-resistant functional monomers, a redox system as the initiation system, and a combination of Span-80 and LAE-6 as the surfactant, a polymerization reaction is carried out by reverse suspension polymerization, and after the reaction, the microspheres are obtained by water separation, cooling, filtration and drying.
[0006] The specific steps of the preparation method are as follows: (1) Preparation of aqueous phase: In a cold water bath, dissolve the unsaturated acidic monomer in distilled water, adjust the pH to 6-7 with alkaline solution, and then add acrylamide, water-soluble bifunctional monomer, oxidant and hydrophilic surfactant LAE-6, mix well to form an aqueous phase solution; (2) Preparation of oil phase and emulsification: In a reactor equipped with a stirrer, thermometer and condenser, add oil phase solvent, lipophilic surfactant Span-80 and hydrophobic long-chain alkane ester of acrylic acid, and stir at 400-600 rpm to form an oil phase system; (3) Polymerization reaction: Add the aqueous solution prepared in step (1) to the oil phase system in step (2), continue stirring and emulsifying for 40-90 minutes to form a stable reverse suspension system; then heat the system to 40-50℃, add a reducing agent aqueous solution to initiate polymerization, and react for 2-4 hours; (4) Post-processing: After the reaction is completed, the water in the system is removed by heating, cooled to room temperature, and the solid product is separated by vacuum filtration, washed and dried to obtain the powdered product. In the aqueous solution, the total mass of the monomers accounts for 30-35% of the mass of distilled water; the total mass of the surfactants accounts for 5-10% of the total mass of the monomers; and the volume of the oil solvent is 1-3 times the volume of the aqueous solution.
[0007] The unsaturated acidic monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and maleic anhydride, and the unsaturated acidic monomer accounts for 50-80% of the total mass of the monomers in step (1).
[0008] In step (1), the acrylamide accounts for 20-50% of the total mass of the monomers in step (1); the water-soluble bifunctional monomer is N,N-dimethylbisacrylamide, and the water-soluble bifunctional monomer accounts for 0.025% of the total mass of the monomers in step (1).
[0009] In step (2), the hydrophobic long-chain alkane ester of acrylic acid is (meth)acrylic acid C8-C. 16 Even-numbered carbon alcohol esters, with the general structural formula: ; Where R is H or -CH3, and n is an even number from 7 to 15; the amount of the hydrophobic long-chain monomer is 1%-5% of the mass of the unsaturated acidic monomer.
[0010] In step (2), the oil phase solvent is cyclohexane and / or n-hexane.
[0011] In step (1), the oxidant is ammonium persulfate or potassium persulfate; in step (3), the reducing agent is sodium bisulfite or sodium sulfite; the mass ratio of the oxidant to the reducing agent is (4-8):1, the total mass of the oxidant accounts for 0.1%-1.0% of the total mass of the monomer in step (1), and the concentration of the reducing agent aqueous solution is 5-100 mg / mL.
[0012] The mass ratio of the lipophilic surfactant Span-80 to the hydrophilic surfactant LAE-6 is (1-3):1.
[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) Simple process and easy product handling: The reverse suspension polymerization method is used to directly obtain powdered microspheres with a particle size in the range of tens to hundreds of micrometers. There is no need for complicated crushing process. The product has good flowability, which makes it easy to package, store and transport over long distances, thus reducing application costs.
[0014] (2) Significantly improved salt resistance: By copolymerizing hydrophobic long-chain monomers into the polymer backbone, intermolecular hydrophobic association can occur in aqueous solution, forming a reversible physical cross-linked network. This network is not easily destroyed in a high electrolyte environment, thus effectively maintaining the viscosity of the system and improving the salt resistance of the thickener.
[0015] (3) Controllable performance: By adjusting the emulsifier ratio, stirring speed and monomer composition, the particle size and surface morphology of microspheres can be controlled within a certain range, thereby affecting their dissolution rate and thickening behavior, and meeting the needs of different application scenarios. Detailed Implementation
[0016] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0017] In the following examples, the lipophilic surfactant Span-80, a nonionic surfactant composed of sorbitan ester and ethoxylated sorbitan ester fatty acids, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The hydrophilic surfactant LAE-6, lauroyl arginine ethyl ester hydrochloride, was purchased from Shanghai KBT Chemical Co., Ltd. Example 1
[0018] This embodiment provides a method for preparing powdered polyacrylic acid thickener microspheres, comprising the following steps: (1) Preparation of aqueous phase: In a beaker with a cold water bath, add 6g of acrylic acid and 31.5g of distilled water, slowly add 35% NaOH solution to neutralize to pH 6.5, then add 4g of acrylamide, 2.5mg of N,N-dimethylbisacrylamide, 30mg of potassium persulfate and 0.5g of LAE-6, stir to dissolve, and obtain aqueous phase solution.
[0019] (2) Preparation of oil phase and emulsification: In a 250 mL four-necked flask equipped with a stirrer, thermometer and condenser, add 40 g cyclohexane, 0.5 g Span-80 and 0.2 g octadecyl acrylate (hydrophobic monomer), place in an oil bath and stir at 500 rpm to dissolve.
[0020] (3) Polymerization reaction: Under stirring, the aqueous phase solution was slowly added to the oil phase in a four-necked flask, and the mixture was stirred and emulsified at 500 rpm for 60 minutes. Then the system was heated to 45°C, and 0.6 mL of sodium sulfite aqueous solution (reducing agent) with a concentration of 8 mg / mL was quickly added. The reaction was carried out at 45°C for 3 hours.
[0021] (4) After the reaction is complete, the temperature is raised to above 80°C to remove the water in the system through azeotropic extraction. After cooling to room temperature, the white solid is separated by filtration, washed twice with cyclohexane, and dried to constant weight in a vacuum oven at 60°C to obtain a white powder product. Example 2
[0022] This embodiment provides a method for preparing powdered polyacrylic acid thickener microspheres, comprising the following steps: (1) Preparation of aqueous phase: In a beaker with cold water bath, add 5g of acrylic acid and 33.3g of distilled water, slowly add 35% NaOH solution to neutralize to pH 6, then add 5g of acrylamide, 2.5mg of N,N-dimethylbisacrylamide, 100mg of potassium persulfate and 0.25g of LAE-6, stir to dissolve, and obtain aqueous phase solution.
[0023] (2) Preparation of oil phase and emulsification: In a 250 mL four-necked flask equipped with a stirrer, thermometer and condenser, add 35 g of n-hexane, 0.25 g of Span-80 and 0.05 g of octadecyl acrylate (hydrophobic monomer), place in an oil bath and stir at 400 rpm to dissolve.
[0024] (3) Polymerization reaction: Under stirring, the aqueous phase solution was slowly added to the oil phase in a four-necked flask, and the mixture was stirred and emulsified at 500 rpm for 40 minutes. Then the system was heated to 50°C, and 3.1 mL of sodium sulfite aqueous solution (reducing agent) with a concentration of 8 mg / mL was quickly added. The mixture was then kept at 45°C for 2 hours.
[0025] (4) After the reaction is complete, the temperature is raised to above 80°C to remove the water in the system through azeotropic extraction. After cooling to room temperature, the white solid is separated by filtration, washed twice with cyclohexane, and dried to constant weight in a vacuum oven at 60°C to obtain a white powder product. Example 3
[0026] This embodiment provides a method for preparing powdered polyacrylic acid thickener microspheres, comprising the following steps: (1) Preparation of aqueous phase: In a beaker with cold water bath, add 8g of acrylic acid and 28.6g of distilled water, slowly add 35% NaOH solution to neutralize to pH 7, then add 2g of acrylamide, 2.5mg of N,N-dimethylbisacrylamide, 10mg of potassium persulfate and 0.77g of LAE-6, stir to dissolve, and obtain aqueous phase solution.
[0027] (2) Preparation of oil phase and emulsification: In a 250 mL four-necked flask equipped with a stirrer, thermometer and condenser, add 90 g of n-hexane, 0.26 g of Span-80 and 0.25 g of octadecyl acrylate (hydrophobic monomer), place in an oil bath and stir at 600 rpm to dissolve.
[0028] (3) Polymerization reaction: Under stirring, the aqueous phase solution was slowly added to the oil phase in a four-necked flask, and the mixture was stirred and emulsified at 500 rpm for 90 minutes. Then the system was heated to 40°C, and 0.25 mL of sodium sulfite aqueous solution (reducing agent) with a concentration of 8 mg / mL was quickly added. The mixture was then kept at 45°C for 4 hours.
[0029] (4) After the reaction is complete, the temperature is raised to above 80°C to remove the water in the system through azeotropic extraction. After cooling to room temperature, the white solid is separated by filtration, washed twice with cyclohexane, and dried to constant weight in a vacuum oven at 60°C to obtain a white powder product. Comparative Example 1
[0030] This example is used to investigate the effect of not adding hydrophobic monomers. Except for the absence of 0.4g of octadecyl acrylate, the amounts of other raw materials and the operating procedures are exactly the same as in Example 1. Comparative Example 2
[0031] This example is used to investigate the effect of emulsifier ratio. Except for changing the amount of Span-80 to 0.6g and the amount of LAE-6 to 0.4g, the amounts of other raw materials and the operating steps are exactly the same as in Example 1. Comparative Example 3
[0032] This example was used to investigate the effect of the absence of a hydrophilic emulsifier. Except for the absence of LAE-6 and the increase of Span-80 to 1.0g, the amounts of other raw materials and the operating procedures were exactly the same as in Example 1. Comparative Example 4
[0033] This example is used to investigate the effect of another emulsifier ratio. Except for changing the amount of Span-80 to 0.4g and the amount of LAE-6 to 0.6g, the other raw material amounts and operating procedures are exactly the same as in Example 1. Comparative Example 5
[0034] This example was used to investigate the effect of the absence of a lipophilic emulsifier. Except for the omission of Span-80 and the increase of LAE-6 dosage to 1.0 g, the other raw material dosages and operating procedures were exactly the same as in Example 1. Performance testing and characterization
[0035] 1. Sample morphology: The physical morphology of the dried product was observed visually and by optical microscopy.
[0036] 2. Thickening performance test: Accurately weigh 0.5g of the dried thickener sample, add 99.5g of distilled water, and stir magnetically for 2 hours to prepare a homogeneous viscous solution with a mass fraction of 0.5%. At room temperature (25℃), use an NDJ-1 rotational viscometer to measure the apparent viscosity (η6 and η) of the solution at rotational speeds of 6 r / min and 60 r / min, respectively. 60 Using η6 as the evaluation index for initial thickening ability, and comparing the viscosity ratio (PVI = η) at different rotational speeds... 60 / η6) characterizes its thixotropy (shear-thinning behavior), and the smaller the PVI value, the stronger the thixotropy.
[0037] 3. Electrolyte resistance test: To the prepared 0.5% thickener aqueous solution, add NaCl to achieve a concentration of 0.05% (mass fraction). After thorough mixing, measure the viscosity (η) again at a rotation speed of 6 r / min. 盐 The formula for calculating viscosity retention rate is: (η) 盐 / η6) × 100%. The higher the viscosity retention rate, the better the salt resistance of the sample. Test results: The morphology and performance test results of the products obtained in each embodiment are summarized in Table 1.
[0038]
[0039] Results Analysis As shown in the table above, the thickener microspheres prepared in Example 1 (preferred embodiment of the present invention) are uniform small particles with high initial viscosity (23.6 Pa·s) and excellent salt resistance (viscosity retention rate of 84.9%), and have a low PVI value, showing good thixotropy.
[0040] Comparative Example 1, without the addition of hydrophobic monomers, showed a significant decrease in salt resistance (viscosity retention rate of only 61.4%), demonstrating the crucial role of hydrophobic monomers in improving electrolyte resistance.
[0041] Comparative Examples 2 and 4 used different Span-80 / LAE-6 ratios and still obtained particulate products and high salt resistance, indicating that the emulsification system is effective within this ratio range.
[0042] Comparative Example 3, which used only Span-80, showed product adhesion and decreased salt resistance, indicating that the hydrophilic emulsifier LAE-6 is crucial for stabilizing aqueous droplets and promoting the distribution of hydrophobic monomers at the interface.
[0043] Comparative Example 5, using only LAE-6, could not form a stable reverse-phase suspension system, resulting in severe agglomeration during polymerization and the inability to obtain a powder product, thus proving the necessity of combining Span-80 with LAE-6.
[0044] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the preferred embodiments have been described in detail, those skilled in the art can still make appropriate modifications or equivalent substitutions to the solutions of the present invention, and such modifications or substitutions should be considered to still fall within the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for preparing powdered polyacrylic acid thickener microspheres, characterized in that... Includes the following steps: Using unsaturated acidic monomers as the main monomers, water-soluble bifunctional monomers as crosslinking monomers, acrylamide and hydrophobic long-chain alkane esters of acrylic acid as salt-resistant functional monomers, a redox system as the initiation system, and a combination of Span-80 and LAE-6 as surfactants, the polymerization reaction was carried out by reverse suspension polymerization. After the reaction, the product was dehydrated, cooled, filtered and dried to obtain powdered polyacrylic acid thickener microspheres.
2. The preparation method according to claim 1, characterized in that, The specific steps are as follows: (1) Preparation of aqueous phase: In a cold water bath, dissolve the unsaturated acidic monomer in distilled water, adjust the pH to 6-7 with alkaline solution, and then add acrylamide, water-soluble bifunctional monomer, oxidant and hydrophilic surfactant LAE-6, mix well to form an aqueous phase solution; (2) Preparation of oil phase and emulsification: In a reactor equipped with a stirrer, thermometer and condenser, add oil phase solvent, lipophilic surfactant Span-80 and hydrophobic long-chain alkane ester of acrylic acid, and stir at 400-600 rpm to form an oil phase system; (3) Polymerization reaction: Add the aqueous solution prepared in step (1) to the oil phase system in step (2), continue stirring and emulsifying for 40-90 minutes to form a stable reverse suspension system; then heat the system to 40-50℃, add a reducing agent aqueous solution to initiate polymerization, and react for 2-4 hours; (4) Post-processing: After the reaction is completed, the water in the system is removed by heating, cooled to room temperature, and the solid product is separated by vacuum filtration, washed and dried to obtain the powdered product. In the aqueous solution, the total mass of the monomers accounts for 30-35% of the mass of distilled water; the total mass of the surfactants accounts for 5-10% of the total mass of the monomers; and the volume of the oil solvent is 1-3 times the volume of the aqueous solution.
3. The preparation method according to claim 2, characterized in that, In step (1), the unsaturated acidic monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and maleic anhydride, and the unsaturated acidic monomer accounts for 50-80% of the total mass of the monomers in step (1).
4. The preparation method according to claim 2, characterized in that, In step (1), the acrylamide accounts for 20-50% of the total mass of the monomers in step (1); the water-soluble bifunctional monomer is N,N-dimethylbisacrylamide, and the water-soluble bifunctional monomer accounts for 0.025% of the total mass of the monomers in step (1).
5. The preparation method according to claim 2, characterized in that, In step (2), the hydrophobic long-chain alkane ester of acrylic acid is (meth)acrylic acid C8-C. 16 Even-numbered carbon alcohol esters, with the general structural formula: ； Where R is H or -CH3, and n is an even number from 7 to 15; the amount of the hydrophobic long-chain monomer is 1%-5% of the mass of the unsaturated acidic monomer.
6. The preparation method according to claim 2, characterized in that, In step (2), the oil phase solvent is cyclohexane and / or n-hexane.
7. The preparation method according to claim 2, characterized in that, In step (1), the oxidant is ammonium persulfate or potassium persulfate; in step (3), the reducing agent is sodium bisulfite or sodium sulfite; the mass ratio of the oxidant to the reducing agent is (4-8):1, the total mass of the oxidant accounts for 0.1%-1.0% of the total mass of the monomer in step (1), and the concentration of the reducing agent aqueous solution is 5-100 mg / mL.
8. The preparation method according to claim 2, characterized in that, The total mass of the lipophilic surfactant Span-80 and the hydrophilic surfactant LAE-6 accounts for 5-10% of the total mass of the monomers, and the mass ratio of the lipophilic surfactant Span-80 to the hydrophilic surfactant LAE-6 is (1-3):1.