Degradable aqueous wetting dispersant and method of making same

Abstract

This invention relates to a biodegradable aqueous wetting and dispersing agent and its preparation method. A four-armed RAFT reagent is prepared from pentaerythritol, 2-bromopropionyl bromide, and potassium xanthate as raw materials. A macromonomer containing polymerizable double bonds is prepared by ring-opening esterification of carboxylated polyethylene glycol and GMA. A sulfonate monomer containing unsaturated double bonds is prepared from 6-amino-2-mercaptobenzothiazole, sodium 3-bromopropane sulfonate, and GMA as raw materials. The four-armed RAFT reagent, initiator AIBN, monomer MDO, unsaturated polyether carboxylic acid monomer, and unsaturated sulfonate monomer undergo free radical polymerization. The final product is dissolved in pure water to obtain the dispersant. This invention features a four-armed star structure, which provides stronger steric hindrance on the particle surface. Containing multiple anchoring groups, it achieves dual stabilizing effects of electrostatic repulsion and steric hindrance, exhibiting synergistic adsorption on the particle surface, enhancing the adsorption effect of the dispersant, effectively preventing collisional aggregation between particles, and is biodegradable in the natural environment.

Description

Technical Field

[0001] This invention relates to the field of dispersant technology, specifically to a biodegradable aqueous wetting and dispersing agent and its preparation method. Background Technology

[0002] Dispersants are chemical additives that can uniformly disperse solid particles in a liquid medium and prevent them from re-aggregating and settling. Dispersants can be classified into three main categories according to their chemical structure: 1. Inorganic dispersants, such as polyphosphates; 2. Organic dispersants, including anionic dispersants such as alkylbenzene sulfonates, cationic dispersants such as trimethylstearamide chloride, nonionic dispersants such as polyethylene glycol and polyvinyl alcohol, and amphoteric dispersants; 3. Polymer dispersants.

[0003] Wetting and dispersing agents combine wetting and dispersing functions and are widely used in coatings, inks, ceramics, rubber, and other fields. With increasingly stringent environmental regulations, traditional petroleum-based dispersants face growing environmental pressure, making biodegradable dispersants, as green and environmentally friendly additives, a hot topic in industry research. However, current research on water-based wetting biodegradable dispersants is relatively limited. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a biodegradable aqueous wetting and dispersing agent.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a biodegradable aqueous wetting and dispersing agent includes the following steps: S1. Preparation of the four-armed RAFT reagent Pentaerythritol and 2-bromopropionyl bromide are esterified under the action of DMAP to generate pentaerythritol tetrakis(2-bromopropionic acid) ester, which is then reacted with potassium xanthate to prepare a four-arm xanthate chain transfer agent. S2. Preparation of unsaturated polyether carboxylic acid monomers The ring-opening esterification reaction of carboxylated polyethylene glycol with glycidyl methacrylate yields a macromonomer containing polymerizable double bonds. S3, Preparation of unsaturated sulfonate monomers Starting with 6-amino-2-mercaptobenzothiazole, an S-alkylation reaction was first carried out with sodium 3-bromopropanesulfonate at room temperature under alkaline catalysis; then an epoxide ring-opening reaction was carried out with glycidyl methacrylate to introduce unsaturated double bonds. S4. Preparation of dispersant In a clean Schlenk flask, a four-armed RAFT reagent, initiator AIBN, monomer MDO, unsaturated polyether carboxylic acid monomer, unsaturated sulfonate monomer, and solvent 1,4-dioxane were added to carry out free radical polymerization; the final product was dissolved in pure water to prepare a dispersant.

[0006] Furthermore, the preparation process of the four-armed RAFT reagent is as follows: 1) Add 10 mmol pentaerythritol and 100 mL THF to a clean reaction flask, add 50 mmol triethylamine, transfer the reaction flask to an ice-water bath, and then slowly add a THF solution containing 40-44 mmol of 2-bromopropionyl bromide to the reaction flask under nitrogen protection. After the addition is complete, stir the reaction overnight at room temperature, add a large amount of diethyl ether, and extract with deionized water. Collect the organic phase, dry it with anhydrous magnesium sulfate, remove the solvent by rotary evaporation, redissolve it in diethyl ether, and recrystallize it at 0 °C. The resulting powder is dried under vacuum to obtain the intermediate pentaerythritol tetrakis(2-bromopropionic acid) ester. 2) Add 10 mmol of the powder from step 1) to a clean reaction flask, add DMF and stir to dissolve it. Transfer the reaction flask to an ice-water bath. Slowly add 40-44 mmol of potassium ethyl xanthate dissolved in DMF to the reaction flask. After the addition is complete, stir the reaction overnight at room temperature. After the reaction is complete, add 100 mL of deionized water, extract with dichloromethane, collect the organic phase, dry with anhydrous sodium sulfate, concentrate the product, and purify it by column chromatography using petroleum ether and ethyl acetate as the developing solvent to obtain a yellow solid, which is the product.

[0007] Furthermore, the preparation process of the unsaturated polyether carboxylic acid monomer is as follows: Carboxylated polyethylene glycol and glycidyl methacrylate were added to a clean reaction flask, along with triethylamine as a catalyst and hydroquinone as a polymerization inhibitor. The reaction was carried out at 55-65°C for 6-12 hours under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, precipitated in cold anhydrous diethyl ether, filtered, and dried under vacuum to obtain unsaturated polyether carboxylic acid monomer.

[0008] Furthermore, the carboxyl polyethylene glycol has the structural formula HOOCCH2O(CH2CH2O). n CH2COOH, where n = 40~120; the molar ratio of carboxylated polyethylene glycol to glycidyl methacrylate is 1:1~1.2.

[0009] Furthermore, the preparation process of the unsaturated sulfonate monomer is as follows: At room temperature, 100 mmol of potassium carbonate was dissolved in 20 mL of pure water and 50 mL of LDM was added and mechanically stirred until homogeneous. 50 mmol of 6-amino-2-mercaptobenzothiazole was added and stirred at room temperature for 20 min. 50 mmol of sodium 3-bromopropanesulfonate was added and stirred at room temperature for 1 h. The entire reaction solution was poured into ice water, allowed to settle, and the solid was collected by filtration. The solid was recrystallized with anhydrous ethanol and dried under vacuum to obtain sodium 3-(6-aminobenzoisothiazole-2-thio)propanesulfonate intermediate. 50 mmol of the intermediate was dissolved in anhydrous isopropanol, and trace amounts of triethylamine and hydroquinone were added. The mixture was heated in a 50 °C water bath, and 50 mmol of glycidyl methacrylate was added dropwise while stirring. After the addition was complete, the mixture was kept at a constant temperature of 55–65 °C for 6 h. The mixture was cooled to room temperature, and the reaction solution was poured into ice water. The crude product was extracted with ethyl acetate, washed with saturated brine, and the organic phase was collected. The product was dried over anhydrous sodium sulfate, concentrated by rotary evaporation, recrystallized from anhydrous ethanol, and dried under vacuum to obtain the final product.

[0010] Furthermore, the molar ratio of the four-armed RAFT reagent, AIBN, MDO, unsaturated polyether carboxylic acid monomer, and unsaturated sulfonate monomer is 1:0.1~0.5:100:10~50:50~90.

[0011] Furthermore, the free radical polymerization conditions are a reaction at 65-75°C for 12-24 hours.

[0012] Furthermore, after the free radical polymerization is completed, the solvent is removed by rotary evaporation of the reaction solution, and then dialyzed with pure water using a dialysis bag with a molecular weight cutoff of 3000 for 48 hours. After that, it is mixed and stirred with deionized water, and the pH of the system is adjusted to 7.0~7.5 to prepare an aqueous wetting and dispersing agent with a solid content of 40wt%.

[0013] The present invention further provides a biodegradable aqueous wetting and dispersing agent prepared by the preparation method described above.

[0014] The beneficial effects of this invention are as follows: This invention uses a four-armed RAFT reagent to polymerize MDO, unsaturated polyether carboxylic acid monomers, and unsaturated sulfonate monomers to obtain a four-armed star structure, which endows the dispersant with a compact molecular configuration. This provides stronger steric hindrance on the particle surface. Combined with the nonionic hydrophilic segments provided by the unsaturated polyether carboxylic acid monomers and the anionic charged groups provided by the unsaturated sulfonate monomers, a dual stabilizing effect of electrostatic repulsion and steric hindrance is achieved. Containing multiple anchoring groups, it can effectively achieve synergistic adsorption on the particle surface, enhancing the adsorption effect of the dispersant and effectively preventing collisional aggregation between particles. The macromolecular polymer backbone is composed of PCL-like chains formed by ring-opening of MDO, which is biodegradable in the natural environment, decomposing the high molecular weight polymer into multiple low molecular weight polymers, making it more environmentally friendly. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below with reference to the 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.

[0016] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] Example 1: A biodegradable aqueous wetting and dispersing agent S1. Preparation of the four-armed RAFT reagent 1) Add 10 mmol pentaerythritol and 100 mL THF to a clean reaction flask, add 50 mmol triethylamine, transfer the reaction flask to an ice-water bath, and then slowly add a THF solution containing 44 mmol 2-bromopropionyl bromide dropwise to the reaction flask under nitrogen protection. After the addition is complete, stir the reaction overnight at room temperature, add a large amount of diethyl ether, and extract with deionized water. Collect the organic phase, dry it with anhydrous magnesium sulfate, remove the solvent by rotary evaporation, redissolve it in diethyl ether, and recrystallize it at 0 °C. The resulting powder is dried under vacuum to obtain the intermediate pentaerythritol tetrakis(2-bromopropionic acid) ester. 2) Add 10 mmol of the powder from step 1) to a clean reaction flask, add DMF and stir to dissolve it. Transfer the reaction flask to an ice-water bath. Slowly add 44 mmol of potassium ethyl xanthate dissolved in DMF to the reaction flask. After the addition is complete, stir the reaction overnight at room temperature. After the reaction is complete, add 100 mL of deionized water, extract with dichloromethane, collect the organic phase, dry with anhydrous sodium sulfate, concentrate the product, and purify it by column chromatography using petroleum ether and ethyl acetate as the developing solvent to obtain a yellow solid, which is the product.

[0018]

[0019] 1 H NMR (400 MHz, CDCl3): 4.62(q,8H,OCH2CH3),4.33(q,4H,SCHCH3),4.18(s,8H,C(CH2)4),1.59(d,12H,SCHCH3),1.23(t,12H,OCH2CH3). S2. Preparation of unsaturated polyether carboxylic acid monomers 1 mol of carboxylated polyethylene glycol (molecular weight 2000, Xiamen Sainuobang Biotechnology Co., Ltd.) and 1.1 mol of glycidyl methacrylate were added to a clean reaction flask. Triethylamine was added as a catalyst and hydroquinone as a polymerization inhibitor. The reaction was carried out at 55-65℃ for 6-12 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, precipitated in cold anhydrous diethyl ether, filtered, and dried under vacuum to obtain unsaturated polyether carboxylic acid monomer.

[0020]

[0021] S3, Preparation of unsaturated sulfonate monomers At room temperature, 100 mmol of potassium carbonate was dissolved in 20 mL of pure water and 50 mL of LDM was added and mechanically stirred until homogeneous. Then, 50 mmol of 6-amino-2-mercaptobenzothiazole (Sigma-Aldrich, purity > 97%) was added and stirred at room temperature for 20 min. Then, 50 mmol of sodium 3-bromopropanesulfonate (Sigma-Aldrich, purity > 97%) was added and stirred at room temperature for 1 h. The entire reaction solution was poured into ice water, allowed to settle, and the solid was collected by filtration. The solid was recrystallized with anhydrous ethanol and dried under vacuum to obtain sodium 3-(6-aminobenzoisothiazole-2-thio)propanesulfonate intermediate. 50 mmol of the intermediate was dissolved in anhydrous isopropanol, and trace amounts of triethylamine and hydroquinone were added. The mixture was heated in a 50 °C water bath, and 50 mmol of glycidyl methacrylate was added dropwise while stirring. After the addition was complete, the mixture was kept at a constant temperature of 55–65 °C for 6 h. The mixture was cooled to room temperature, and the reaction solution was poured into ice water. The crude product was extracted with ethyl acetate, washed with saturated brine, and the organic phase was collected. The product was dried over anhydrous sodium sulfate, concentrated by rotary evaporation, recrystallized from anhydrous ethanol, and dried under vacuum to obtain the final product.

[0022]

[0023] 1 H NMR (400 MHz, dmso-d6): 7.55~6.62(m,3H,-ph-H), 6.48~6.4(dd,2H,-CH2), 5.37(s,1H,OH),4.48(m,2H,OCH2),4.12(m,1H,CH OH),3.51(t,2H,CH2SO3Na),3.45(t,2,SCH2),3.3~3.05(m,2H,CH2NH),2.01(s,3H,CCH3),1.77(q,2H,CH2CH2SO3Na). S4, Monomer MDO 2-Methylene-1,3-dioxane, purchased from aladdin, M194650, purity ≥95%.

[0024] S5. Preparation of dispersant In a clean Schlenk flask, add the four-armed RAFT reagent, initiator AIBN, monomer MDO, unsaturated polyether carboxylic acid monomer, unsaturated sulfonate monomer, and solvent 1,4-dioxane. After three cycles of freezing-vacuuming-melt-thawing, react at 65-75°C for 12-24 h under nitrogen protection. After polymerization, remove the solvent by rotary evaporation, then dialyze with pure water using a dialysis bag with a molecular weight cutoff of 3000 for 48 h. Afterward, mix and stir with deionized water, adjust the pH of the system to 7.0-7.5, and prepare an aqueous wetting and dispersing agent with a solid content of 40 wt%.

[0025] By changing the molar ratio of the four-armed RAFT reagent, AIBN, MDO, unsaturated polyether carboxylic acid monomer, and unsaturated sulfonate monomer in the dispersant preparation process, specific samples as shown in Table 1 can be obtained.

[0026] Table 1

[0027] Note: Sample 7 was obtained by reacting unsaturated polyether carboxylic acid monomers prepared from carboxylated polyethylene glycol with a molecular weight of 5000, while the others were obtained by reacting carboxylated polyethylene glycol with a molecular weight of 2000; Sample 8 was obtained by replacing the four-arm RAFT reagent with phenylacetyl xanthate.

[0028] 1. Surface tension: The surface tension of aqueous solutions of dispersants of different concentrations at 25°C was measured using a surface tension meter via the platinum plate method.

[0029] Dispersant aqueous solutions with mass concentrations of 0.05%, 0.1%, 0.20%, and 0.50% were prepared respectively, and their surface tension was measured under constant temperature conditions of 25℃, with the surface tension of pure water (72.8 mN / m) as a reference.

[0030] Table 2

[0031] Dispersant samples 2-4, at a concentration of 0.1%, reduced the surface tension of water from 72.8 mN / m to approximately 45-47 mN / m, with a reduction rate exceeding 35%, indicating that the dispersants of this invention possess good water-based wetting properties. With increasing concentration, the surface tension further decreased, exhibiting typical surfactant behavior. Sample 1, due to its low polyether carboxylic acid ratio, resulted in fewer hydrophilic segments and a shift in the hydrophilic-lipophilic balance, leading to slightly poorer wetting properties. Sample 5, due to its high polyether carboxylic acid ratio, experienced increased steric hindrance from the high molecular weight polyether segments, causing chain entanglement and decreased interfacial activity. Sample 8, using phenylacetyl xanthate, yielded a linear structure with reduced wetting properties, indicating that the four-armed star structure is beneficial for improving interfacial activity.

[0032] 2. Measurement of contact angle A 0.2% aqueous solution of the dispersant was prepared and dropped onto the surface of a hydrophobic polyethylene terephthalate (PET) film. The contact angle of the droplet on the film surface was measured using a contact angle meter. The smaller the contact angle, the better the wettability.

[0033] Table 3

[0034] The dispersant of this invention can significantly reduce the contact angle of water on hydrophobic surfaces, from 82.5° to about 35~42°, indicating that it has good wetting and spreading ability.

[0035] 3. Pigment dispersibility Carbon black (average primary particle size 25 nm) was used as the dispersion target. 30 g of carbon black and 4 g of dispersant were added to 100 g of deionized water, and the mixture was dispersed at 2000 rpm for 30 min using a high-speed disperser. The volume average particle size (D) of the carbon black in the dispersion was determined using DLS. 50 ) and the Multiple Dispersion Index (PDI).

[0036] The carbon black dispersion was measured at 25°C for 100 seconds using a rotational viscometer. -1 Apparent viscosity at shear rate.

[0037] Let the dispersion stand for 30 days and observe whether there is any stratification.

[0038] Table 4

[0039] The carbon black dispersions of samples 2-4 have significantly smaller particle sizes than sample 8 in the blank sample box, and their particle size distribution is narrow, indicating that the dispersant prepared in this invention has excellent dispersion effect on carbon black. No stratification occurred after 30 days of standing, indicating that the dispersant of this invention can provide long-term stable dispersion effect, with sample 3 exhibiting the best overall dispersion performance.

[0040] 4. Biodegradability According to GB / T19277.1-2011, the degradation rate was tested after 30 days under composting conditions at 58℃.

[0041] Table 5

[0042] The dispersants in samples 1-5 exhibited a degradation rate exceeding 50% after 30 days. This was due to the presence of the monomer MDO, which introduced degradable polyester segments into the polymer backbone, causing ester bond breakage and decomposing the macromolecular chain into multiple low-molecular-weight segments. Sample 6, with its low MDO content and lower polymerization activity compared to the other two monomers, resulted in a decrease in the polyester segment content within the polymer backbone, leading to fewer breakable sites and a poorer degradation rate over the same time period.

[0043] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for preparing a biodegradable aqueous wetting and dispersing agent, characterized in that, Includes the following steps: S1. Preparation of the four-armed RAFT reagent Pentaerythritol and 2-bromopropionyl bromide are esterified under the action of DMAP to generate pentaerythritol tetrakis(2-bromopropionic acid) ester, which is then reacted with potassium xanthate to prepare a four-arm xanthate chain transfer agent. S2. Preparation of unsaturated polyether carboxylic acid monomers The ring-opening esterification reaction of carboxylated polyethylene glycol with glycidyl methacrylate yields a macromonomer containing polymerizable double bonds. S3, Preparation of unsaturated sulfonate monomers Starting with 6-amino-2-mercaptobenzothiazole, an S-alkylation reaction was first carried out with sodium 3-bromopropanesulfonate at room temperature under alkaline catalysis; then an epoxide ring-opening reaction was carried out with glycidyl methacrylate to introduce unsaturated double bonds. S4. Preparation of dispersant In a clean Schlenk flask, a four-armed RAFT reagent, initiator AIBN, monomer MDO, unsaturated polyether carboxylic acid monomer, unsaturated sulfonate monomer, and solvent 1,4-dioxane were added to carry out free radical polymerization; the final product was dissolved in pure water to prepare a dispersant. The molar ratio of the four-armed RAFT reagent, AIBN, MDO, unsaturated polyether carboxylic acid monomer and unsaturated sulfonate monomer is 1:0.1~0.5:100:10~50:50~90.

2. The method for preparing the biodegradable aqueous wetting and dispersing agent according to claim 1, characterized in that, The preparation process of the four-armed RAFT reagent is as follows: 1) Add 10 mmol pentaerythritol and 100 mL THF to a clean reaction flask, add 50 mmol triethylamine, transfer the reaction flask to an ice-water bath, and then slowly add a THF solution containing 40-44 mmol of 2-bromopropionyl bromide to the reaction flask under nitrogen protection. After the addition is complete, stir the reaction overnight at room temperature, add a large amount of diethyl ether, and extract with deionized water. Collect the organic phase, dry it with anhydrous magnesium sulfate, remove the solvent by rotary evaporation, redissolve it in diethyl ether, and recrystallize it at 0 °C. The resulting powder is dried under vacuum to obtain the intermediate pentaerythritol tetrakis(2-bromopropionic acid) ester. 2) Add 10 mmol of the powder from step 1) to a clean reaction flask, add DMF and stir to dissolve it. Transfer the reaction flask to an ice-water bath. Slowly add 40-44 mmol of potassium ethyl xanthate dissolved in DMF to the reaction flask. After the addition is complete, stir the reaction overnight at room temperature. After the reaction is complete, add 100 mL of deionized water, extract with dichloromethane, collect the organic phase, dry with anhydrous sodium sulfate, concentrate the product, and purify it by column chromatography using petroleum ether and ethyl acetate as the developing solvent to obtain a yellow solid, which is the product.

3. The method for preparing the biodegradable aqueous wetting and dispersing agent according to claim 1, characterized in that, The preparation process of the unsaturated polyether carboxylic acid monomer is as follows: Carboxylated polyethylene glycol and glycidyl methacrylate were added to a clean reaction flask, along with triethylamine as a catalyst and hydroquinone as a polymerization inhibitor. The reaction was carried out at 55-65°C for 6-12 hours under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, precipitated in cold anhydrous diethyl ether, filtered, and dried under vacuum to obtain unsaturated polyether carboxylic acid monomer.

4. The method for preparing the biodegradable aqueous wetting and dispersing agent according to claim 1, characterized in that, The carboxyl-based polyethylene glycol has the structural formula HOOCCH2O(CH2CH2O). n CH2COOH, where n = 40~120; the molar ratio of carboxylated polyethylene glycol to glycidyl methacrylate is 1:1~1.

2.

5. The method for preparing the biodegradable aqueous wetting and dispersing agent according to claim 1, characterized in that, The preparation process of the unsaturated sulfonate monomer is as follows: At room temperature, 100 mmol of potassium carbonate was dissolved in 20 mL of pure water and 50 mL of LDM was added and mechanically stirred until homogeneous. 50 mmol of 6-amino-2-mercaptobenzothiazole was added and stirred at room temperature for 20 min. 50 mmol of sodium 3-bromopropanesulfonate was added and stirred at room temperature for 1 h. The entire reaction solution was poured into ice water, allowed to settle, and the solid was collected by filtration. The solid was recrystallized with anhydrous ethanol and dried under vacuum to obtain sodium 3-(6-aminobenzoisothiazole-2-thio)propanesulfonate intermediate. 50 mmol of the intermediate was dissolved in anhydrous isopropanol, and trace amounts of triethylamine and hydroquinone were added. The mixture was heated in a 50 °C water bath, and 50 mmol of glycidyl methacrylate was added dropwise while stirring. After the addition was complete, the mixture was kept at a constant temperature of 55–65 °C for 6 h. The mixture was cooled to room temperature, and the reaction solution was poured into ice water. The crude product was extracted with ethyl acetate, washed with saturated brine, and the organic phase was collected. The product was dried over anhydrous sodium sulfate, concentrated by rotary evaporation, recrystallized from anhydrous ethanol, and dried under vacuum to obtain the final product.

6. The method for preparing the biodegradable aqueous wetting and dispersing agent according to claim 1, characterized in that, The free radical polymerization conditions are a reaction at 65-75°C for 12-24 hours.

7. The method for preparing the biodegradable aqueous wetting and dispersing agent according to claim 1, characterized in that, After the free radical polymerization is completed, the solvent is removed by rotary evaporation of the reaction solution. Then, the solution is dialyzed with pure water for 48 hours using a dialysis bag with a molecular weight cutoff of 3000. After that, it is mixed with deionized water and stirred to adjust the pH of the system to 7.0~7.5, thus preparing an aqueous wetting and dispersing agent with a solid content of 40wt%.

8. A biodegradable aqueous wetting and dispersing agent prepared by any one of claims 1-7.

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