A pH-responsive ionic-nonionic block copolymer dispersant, a preparation method and application thereof

Abstract

This invention relates to a pH-responsive ionic-nonionic block copolymer dispersant, its preparation method, and its application. The invention first prepares a nonionic polymer using a RAFT chain transfer agent and the monomer acryloylmorpholine (ACMO), then embeds two ionic monomers, methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), to form a block polymer with clearly defined ionic and nonionic components. The resulting pH-responsive ionic-nonionic polymer is affected by pH, exhibiting different turbidity and surface activity at different pH values. It can be used as a dispersant for weighting materials such as micro-manganese, significantly prolonging static sedimentation and reducing particle size.

Description

Technical Field

[0001] This invention relates to a pH-responsive ionic-nonionic block copolymer dispersant, its preparation method and application, belonging to the technical field of dispersant preparation for weighting materials in drilling fluids and completion fluids. Background Technology

[0002] With the continuous development of oil extraction, high-density and ultra-high-density drilling fluid systems are used in more complex geological conditions, thus increasing the requirements for drilling fluid stability. Commonly used weighting agents include barite, ultrafine calcium carbonate, iron ore powder, and micromanganese ore powder. These materials vary in form and have their own advantages and disadvantages. Barite powder is relatively inexpensive and widely used in various drilling fluids, but its weighting capacity is limited as the solid content increases. Ultrafine calcium carbonate is also inexpensive, but its low density makes it difficult to meet the requirements of high-density drilling fluids. Iron ore powder has high density, hardness, and magnetic properties, causing significant wear on the drill bit. Micromanganese ore powder, with its smaller particle size compared to the others, can greatly overcome gravity settling and has good rheological properties, reducing the occurrence of complex downhole conditions. However, its high cost means it is often used in combination with other weighting agents and has received widespread attention in recent years. The proportion of weighting materials in drilling fluid is very large, and the phenomenon of particle agglomeration of weighting materials often occurs. This can also lead to poor stability of the drilling fluid system, increased plastic viscosity, and increased frictional resistance. In severe cases, it can cause stuck pipe. Dispersants are usually added to modify the surface of the weighting material particles to achieve suspension stability and reduce apparent viscosity.

[0003] pH-responsive ionic-nonionic block copolymer dispersants exhibit decreased hydrophilicity, increased turbidity, and strong surface activity under acidic conditions. As pH increases, their hydrophilicity gradually strengthens, turbidity decreases, and surface activity weakens. Simultaneously, the separation of ionic and nonionic regions results in a more compact structure, leading to a high concentration of functional groups within the polymer and more stable adsorption on particle surfaces. These properties give these polymers broader application prospects.

[0004] Therefore, developing dispersants that are low in cost, require small amounts, and have a stable suspension effect on weighting materials is of great research value for the widespread application of weighting materials in drilling fluids and completion fluids. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a pH-responsive ionic-nonionic block copolymer dispersant, its preparation method, and its application. By using block copolymerization, the functional groups are effectively separated, thereby improving the dispersion effect on micro-manganese materials.

[0006] This invention employs reversible addition-fragmentation chain transfer radical polymerization (RAFT), first introducing the nonionic group acryloylmorpholine (ACMO), and then introducing two ionic monomers, methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), to obtain a pH-responsive ionic-nonionic block copolymer. This copolymer is then applied to the dispersion of various weighting materials, such as micro-manganese, and exhibits a significant effect in extending the particle suspension time at extremely low dosages.

[0007] This invention is achieved through the following technical solution:

[0008] A pH-responsive ionic-nonionic block copolymer dispersant having the structure shown in Formula I:

[0009]

[0010] Where m = 25 to 100, n = 25 to 100, x = 25 to 200, and y = m + n.

[0011] According to a preferred embodiment of the present invention, the ratio of x to y is 1:1 to 8, preferably 1:2.

[0012] According to a preferred embodiment of the present invention, m = 50–100, n = 50–100, and x = 100–200.

[0013] According to the present invention, the ionic groups methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) structural units are arranged randomly.

[0014] The preparation method of the above-mentioned pH-responsive ionic-nonionic block copolymer dispersant includes the following steps:

[0015] (1) Prepare a mixed solvent by adding the monomer acrylamide (ACMO) and RAFT chain transfer agent to the mixed solvent;

[0016] (2) Add an initiator to the system in step (1), stir until completely dissolved, then pass an inert gas for protection and preheat. After the reaction is kept at a certain temperature, quench the reaction with liquid nitrogen to obtain a polymer.

[0017] (3) Add monomers methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to the polymer, and add mixed solvent and initiator. Then, pass in inert gas again and heat. After the reaction, quench the reaction with liquid nitrogen to obtain pH-responsive ionic-nonionic copolymer dispersant.

[0018] According to a preferred embodiment of the present invention, in step (1), the mixed solvent is a mixture of two or more of deionized water, 1,4-dioxane, tetrahydrofuran, or toluene.

[0019] More preferably, the mixed solvent is a mixture of deionized water and 1,4-dioxane, with a volume ratio of deionized water to 1,4-dioxane of 5 to 10:1. More preferably, the volume ratio of deionized water to 1,4-dioxane is 9:1.

[0020] According to a preferred embodiment of the present invention, in step (1), the mass-to-volume ratio of monomer acryloylmorpholine (ACMO) to mixed solvent is 0.1 to 2.0:1, g / mL.

[0021] According to a preferred embodiment of the present invention, in step (1), the structure of the RAFT chain transfer agent is shown in Formula II as follows:

[0022]

[0023] According to a preferred embodiment of the present invention, in step (1), the mass ratio of RAFT chain transfer agent to acrylomorpholine is 15 to 120:1.

[0024] According to a preferred embodiment of the present invention, in step (2), the initiator is azobisisobutyronitrile or 2,2'-azo[2-(2-imidazolin-2-yl)propane] dihydrochloride or 2,2'-azobis(2-methylpropylamidine) dihydrochloride.

[0025] More preferably, the initiator is 2,2'-azo[2-(2-imidazolin-2-yl)propane] dihydrochloride.

[0026] According to a preferred embodiment of the present invention, in step (2), the amount of initiator is 0.1 to 1.5% of the RAFT chain transfer molar amount.

[0027] More preferably, the amount of initiator is 1.0% of the molar amount of RAFT chain transfer agent.

[0028] According to a preferred embodiment of the present invention, in step (2), the inert gas is nitrogen or argon, the preheating temperature is 50-110°C, and the reaction time is 5-360 min.

[0029] Further preferably, the preheating temperature is 100℃ and the reaction time is 10min.

[0030] According to a preferred embodiment of the present invention, the structure of the obtained polymer is shown in Formula III as follows:

[0031]

[0032] Where x = 25 to 200.

[0033] According to a preferred embodiment of the present invention, in step (3), the molar ratio of monomeric methacrylic acid (MAA) to 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is 1 to 4:1.

[0034] According to a preferred embodiment of the present invention, in step (3), the total mass ratio of monomeric methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to the volume ratio of the added mixed solvent is 0.5 to 2.0:1, g / mL.

[0035] According to a preferred embodiment of the present invention, in step (3), the molar amount of the initiator added is 0.1 to 1.5% of the molar amount of the polymer.

[0036] More preferably, the molar amount of the added initiator is 1.0% of the molar amount of the polymer.

[0037] According to a preferred embodiment of the present invention, in step (3), the inert gas is nitrogen or argon, the reaction temperature is 60-110℃, and the reaction time is 5-360 min.

[0038] Further preferred, the reaction temperature is 90℃ and the reaction time is 10min.

[0039] According to a preferred embodiment of the present invention, in step (3), the post-treatment method of the final obtained reaction solution can be carried out in accordance with the prior art.

[0040] According to a preferred embodiment of the present invention, in step (3), after quenching the reaction, post-treatment is performed. The post-treatment specifically involves: loading the obtained reaction mixture into a dialysis bag, then placing it in water for dialysis at room temperature for 2 to 4 days, and freeze-drying the liquid in the dialysis bag to obtain a pH-responsive ionic-nonionic block copolymer dispersant. The molecular weight interception of the dialysis bag is 5000 Da.

[0041] The synthetic route for the pH-responsive ionic-nonionic block copolymer dispersant of this invention is as follows: Formula IV:

[0042]

[0043] The aforementioned pH-responsive ionic-nonionic block copolymer dispersant, used as a dispersant for weighting materials in drilling and completion fluids, is added at a dosage of 0.01–0.40 wt%. This can significantly extend the suspension time of the weighting materials.

[0044] The technical features and beneficial effects of this invention are as follows:

[0045] 1. This invention uses the RAFT method to obtain block copolymers with separated ionic and nonionic regions. The free radical activity, structure, molecular weight, and molecular weight distribution range are controllable throughout the polymerization process.

[0046] 2. The monomer methacrylic acid used in this invention can provide anchoring groups and has better temperature resistance compared to acrylic acid monomers. 2-Acrylamido-2-methylpropanesulfonic acid has sulfonic acid groups, which are one of the anchoring groups for weighting materials, have good temperature resistance, and have long side chains, which help to provide steric hindrance. Acryloylmorpholine has good amphiphilicity, and its rigid cyclic structure allows the polymer to have better temperature resistance. The carboxylic acid groups contained in the ionic region of methacrylic acid are sensitive to pH response and exhibit strong hydrophobicity under acidic conditions. Acryloylmorpholine, which combines the amphiphilic properties of the nonionic region, allows for control of the polymer's turbidity and amphiphilicity by adjusting the pH value.

[0047] 3. This invention concentrates ionic groups on one side. The carboxylic acid and sulfonic acid groups in the ionic region serve as anchoring groups for the weighting material, allowing the polymer of this invention to be more stably adsorbed onto the particle surface. The special preparation method, resulting in a specific structure, combined with specific monomers and controlled molecular weight within a certain range, enables all groups to work together, achieving excellent results with low dosage and long particle suspension time. Attached Figure Description

[0048] Figure 1 This is the infrared spectrum of the pH-responsive ionic-nonionic block copolymer dispersant prepared in Example 1 of this invention;

[0049] Figure 2 This is the pH-responsive ionic-nonionic block copolymer dispersant prepared in Example 1 of this invention. 1 H NMR spectrum;

[0050] Figure 3 The PDI diagrams for stability analysis of Example 1 of the present invention and the blank control group of micro-manganese weighting material are shown. a is the blank group and b is Example 1.

[0051] Figure 4 In Figure a, an optical microscope image of the blank control group of micro-manganese weighting material is shown, and in Figure b, an optical microscope image of the micro-manganese weighting material after adding the micro-manganese weighting material of Example 1 of the present invention is shown. Detailed Implementation

[0052] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0053] Example 1

[0054] The preparation method of pH-responsive ionic-nonionic block copolymer dispersants includes the following steps:

[0055] (1) Add 0.45 mL of deionized water, 0.05 mL of 1,4-dioxane, 0.5 g of acryloylmorpholine monomer, and RAFT chain transfer agent B (0.0333 g, 0.140 mmol) to a 5 mL reaction flask in sequence. Stir until completely dissolved and the solution is transparent and light yellow. Then add initiator C (0.0023 g, 0.0070 mmol). Vacuum and purge with argon three times while stirring. Place the flask in a preheated module at 100 °C and stir for 10 min. Then quickly transfer the flask to liquid nitrogen to quench the reaction and allow it to cool.

[0056] (2) Add 0.0753 g of methacrylic acid, 0.1811 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.225 mL of deionized water, 0.025 mL of 1,4-dioxane, and initiator (0.0005 g, 0.0015 mmol) to the reaction flask again, stir until completely dissolved, evacuate and purge with nitrogen three times, transfer to a heating module at 90°C, react for 10 min with rapid stirring, then quickly transfer to liquid nitrogen to quench the reaction and allow to cool.

[0057] Example 2

[0058] The preparation method is the same as that described in Example 1, except that:

[0059] In step (2), 0.1505 g of methacrylic acid, 0.3623 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.45 mL of deionized water, and 0.05 mL of 1,4-dioxane were added; other steps and conditions were the same as in Example 1.

[0060] Example 3

[0061] The preparation method described in Example 1 is the same as that described above, except that:

[0062] In step (2), 0.2258 g of methacrylic acid, 0.5434 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.70 mL of deionized water, and 0.08 mL of 1,4-dioxane were added; other steps and conditions were the same as in Example 1.

[0063] Example 4

[0064] The preparation method is the same as that described in Example 1, except that:

[0065] In step (2), 0.3013 g of methacrylic acid, 0.1811 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.45 mL of deionized water, and 0.05 mL of 1,4-dioxane were added; other steps and conditions were the same as in Example 1.

[0066] Example 5

[0067] The preparation method is the same as that described in Example 1, except that:

[0068] In step (2), 0.3623 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.60 mL of deionized water, and 0.07 mL of 1,4-dioxane were added; other steps and conditions were the same as in Example 3.

[0069] Example 6

[0070] The preparation method is the same as that described in Example 1, except that:

[0071] In step (2), 0.5434 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.76 mL of deionized water, and 0.09 mL of 1,4-dioxane were added; other steps and conditions were the same as in Example 3.

[0072] Example 7

[0073] The preparation method is the same as that described in Example 1, except that:

[0074] In step (2), 0.7245 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.90 mL of deionized water, and 0.10 mL of 1,4-dioxane were added; other steps and conditions were the same as in Example 3.

[0075] Example 8

[0076] The preparation method is the same as that described in Example 1, except that:

[0077] In step (1), 0.0167 g (0.070 mmol) of RAFT chain transfer agent and 0.0011 g (0.0034 mmol) of initiator were added. In step (2), 0.0003 g (0.0010 mmol) of initiator was added. Other steps and conditions were the same as in Example 1.

[0078] Example 9

[0079] The preparation method is the same as that described in Example 1, except that:

[0080] In step (1), 0.0083 g (0.035 mmol) of RAFT chain transfer agent and 0.0006 g (0.0019 mmol) of initiator were added. In step (2), 0.0002 g (0.0006 mmol) of initiator was added. Other steps and conditions were the same as in Example 1.

[0081] Example 10

[0082] The preparation method is the same as that described in Example 1, except that:

[0083] In step (1), 0.0043 g (0.018 mmol) of RAFT chain transfer agent and 0.0003 g (0.0010 mmol) of initiator were added. In step (2), 0.0001 g (0.0003 mmol) of initiator was added. Other steps and conditions were the same as in Example 1.

[0084] Experimental Example 1

[0085] 1. The infrared spectrum of the pH-responsive ionic-nonionic block copolymer dispersant prepared in Example 1 is shown in Figure 1. Figure 1 , 1 H NMR spectrum (see) Figure 2 This demonstrates that the present invention successfully prepared a pH-responsive ionic-nonionic block copolymer dispersant.

[0086] 2. In deionized water containing 20 wt% micromanganese, 0.06 wt% of the pH-responsive ionic-nonionic block copolymer dispersant from Example 1 was added, with no dispersant added as a blank control. The PDI chart for stability analysis is shown below. Figure 3 This demonstrates that the dispersant of the present invention can effectively maintain the stability of the system.

[0087] 3. In deionized water containing 0.5 wt% micromanganese, 0.06 wt% of a pH-responsive ionic-nonionic block copolymer dispersant was added, with no dispersant added as a blank control. Optical microscope images are shown below. Figure 4 ,pass Figure 4 It can be seen that, compared with the blank group, the particle size was significantly reduced after the dispersant was added, which improved the suspension performance of the suspension.

[0088] Experiment Example 2 Performance Testing

[0089] 1. Static sedimentation observation: 0.2wt% of the pH-responsive ionic-nonionic block copolymer dispersant prepared in Examples 1-8 was added to deionized water containing 20wt% micromanganese. At the same time, no dispersant was added as a blank control. The static sedimentation was observed in a 10ml graduated cylinder. The suspension effect was obtained according to formula (1). The test results are shown in Table 1 below.

[0090]

[0091] Table 1. Suspension properties of pH-responsive ionic-nonionic block copolymer dispersants

[0092]

[0093]

[0094] As shown in Table 1, the pH-responsive ionic-nonionic block copolymer dispersants of Examples 1-8 exhibited a significant suspending effect on micro-manganese particles, with Example 3 showing the best effect, maintaining a suspension efficiency of 90% after 24 hours. In contrast, the blank group showed a suspension rate of only 36% after 10 minutes and 22% after 24 hours. This indicates that the dispersant of the present invention can stably adsorb onto the surface of micro-manganese particles for a long time, providing a stable double-electron-layer structure and sufficiently strong steric hindrance, thus minimizing the influence of gravity on the micro-manganese particles, prolonging their suspension time, and maintaining the stability of the suspension system.

[0095] 2. Turbidity test: To observe the pH response performance, a pH-responsive ionic-nonionic block copolymer dispersant solution of 1000 mg / L was prepared using the dispersant of Example 4. The dispersant solution was adjusted to different pH values ​​using 1.0 mol / L, 0.2 mol / L hydrochloric acid solution, 1.0 mol / L, and 0.2 mol / L sodium hydroxide solution. The turbidity changes were observed using a turbidimeter. The turbidity at different pH values ​​is shown in Table 2.

[0096] Table 2 pH responsiveness of pH-responsive ionic-nonionic block copolymer dispersants

[0097]

[0098]

[0099] As can be seen from Table 2, the pH-responsive ionic-nonionic block copolymer dispersant prepared in the embodiments of the present invention is extremely sensitive at pH 1-5, exhibiting large variations in turbidity. At around pH 6-8, the carboxylic acid is gradually neutralized to sodium carboxylate, exhibiting good hydrophilicity. With continued addition of sodium hydroxide, the carboxylic acid groups are completely neutralized, and the turbidity tends to stabilize, no longer showing significant changes.

[0100] 3. Changes in micro-manganese particle size: In deionized water containing 0.5 wt% micro-manganese, 0.06 wt% of pH-responsive ionic-nonionic block copolymer dispersant was added, with no dispersant added as a blank control. The micro-manganese particle size was tested using a nanoparticle size potentiometer. The effect of the dispersant on the micro-manganese particles can be judged by the change in micro-manganese particle size. The experimental results are shown in Table 3 below.

[0101] Table 3. Particle size variation of micro-manganese particles

[0102]

[0103] The macroscopic manifestation of well-dispersed micro-manganese weighting materials is a stable and long suspension time, while the microscopic manifestation is that sufficient spacing is maintained between micro-manganese particles. The pH-responsive ionic-nonionic block copolymer dispersant provides sufficiently strong electrostatic and steric hindrance interactions between the micro-manganese particles, allowing the micro-manganese weighting material to be dispersed in the solution as individual particles, reducing agglomeration and decreasing the average particle size of the micro-manganese, thus verifying the excellent effect of the dispersant. Table 3 shows that the pH-responsive ionic-nonionic block copolymer dispersant significantly improves the particle size of micro-manganese. The particle size of the blank group without dispersant was 1029 nm, while after adding dispersant, the particle size decreased to below 830 nm, and in Example 3, the particle size decreased to 701 nm, indicating the maximum dispersion of micro-manganese particles and resulting in the best suspension performance.

[0104] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples. Any substitutions, modifications, combinations, changes, simplifications, etc., made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A pH-responsive ionic-nonionic block copolymer dispersant having the structure shown in Formula I: in, m = 25–100, n = 25–100, x = 25–200, y = m + n, and the ratio of x to y is 1:1–8.

2. The pH-responsive ionic-nonionic block copolymer dispersant according to claim 1, characterized in that, m = 50–100, n = 50–100, x = 100–200, the ratio of x to y is 1:2, and the ionic groups methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) structural units are arranged randomly.

3. The preparation method of the pH-responsive ionic-nonionic block copolymer dispersant according to claim 1, comprising the following steps: (1) Prepare a mixed solvent by adding the monomer acrylamide (ACMO) and RAFT chain transfer agent to the mixed solvent; (2) Add an initiator to the system in step (1), stir until completely dissolved, then pass an inert gas for protection and preheat. After the reaction is kept at a certain temperature, quench the reaction with liquid nitrogen to obtain a polymer. (3) Add monomers methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to the polymer, and add mixed solvent and initiator. Then, pass in inert gas again and heat. After the reaction, quench the reaction with liquid nitrogen to obtain pH-responsive ionic-nonionic copolymer dispersant.

4. The preparation method according to claim 3, characterized in that, In step (1), the mixed solvent is a mixture of two or more of the following: deionized water, 1,4-dioxane, tetrahydrofuran, or toluene.

5. The preparation method according to claim 3, characterized in that, The mixed solvent is a mixture of deionized water and 1,4-dioxane, with a volume ratio of deionized water to 1,4-dioxane of 5 to 10:

1.

6. The preparation method according to claim 3, characterized in that, In step (1), the mass-to-volume ratio of monomer acrylomorpholine (ACMO) to the mixed solvent is 0.1–2.0:1, g / mL, and the structure of the RAFT chain transfer agent is shown in Formula II below: The mass ratio of RAFT chain transfer agent to acrylomorpholine is 15–120:

1.

7. The preparation method according to claim 3, characterized in that, In step (2), the initiator is azobisisobutyronitrile or 2,2'-azo[2-(2-imidazolin-2-yl)propane] dihydrochloride or 2,2'-azobis(2-methylpropylamidine) dihydrochloride, the amount of initiator is 0.1-1.5% of the RAFT chain transfer molar amount, the inert gas is nitrogen or argon, the preheating temperature is 50-110℃, and the reaction time is 5-360 min.

8. The preparation method according to claim 3, characterized in that, In step (3), the molar ratio of monomeric methacrylic acid (MAA) to 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is 1 to 4:1, the total mass ratio of monomeric methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to the volume ratio of the added mixed solvent is 0.5 to 2.0:1, g / mL, the molar amount of added initiator is 0.1 to 1.5% of the molar amount of polymer, the inert gas is nitrogen or argon, the reaction temperature is 60-110℃, and the reaction time is 5 to 360 min.

9. The preparation method according to claim 3, characterized in that, After the quenching reaction, post-processing is performed. Specifically, the resulting reaction mixture is placed in a dialysis bag and then dialyzed in water at room temperature for 2-4 days. The liquid in the dialysis bag is freeze-dried to obtain a pH-responsive ionic-nonionic block copolymer dispersant. The molecular weight interception of the dialysis bag is 5000 Da.

10. The application of the pH-responsive ionic-nonionic block copolymer dispersant according to claim 1, as a dispersant for weighting materials in drilling fluids and completion fluids, wherein the addition amount is 0.01 to 0.40 wt%.

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