Cationic modified guar gum and its synthesis process

Abstract

The application relates to the technical field of modified guar gum, and discloses a cationic modified guar gum, which is obtained through the following steps: graft copolymerization of guar gum and acrylic acid, acyl chloride reaction and esterification reaction to obtain poly(acrylic acid-bromoethyl acrylate) grafted guar gum, and quaternary ammonium cationization reaction of pyridine and a tertiary amine group of N,N'-dimethyl-1,6-hexanediamine methylpyridine with a bromoethyl to crosslink to obtain the polymer grafted cationic modified guar gum; the modified guar gum contains rich hydrophilic carboxyl groups and quaternary ammonium cations; the modified guar gum after crosslinking has excellent water absorption rate, and the quaternary ammonium cations have good electrostatic interaction and adsorption performance on metal ions such as Cr(Ⅵ).

Description

Technical Field

[0001] This invention relates to the field of modified guar gum technology, specifically to a cationic modified guar gum. Background Technology

[0002] Guar gum (CGG) is an extract from a natural plant. As a large-molecule natural hydrophilic colloid, it is green and pollution-free, and has broad application prospects in food thickeners, petrochemicals, superabsorbent resins, and wastewater treatment. The paper "Preparation, Swelling Behavior and Water Retention Properties of Guar Gum-Based Superabsorbent Resin" utilizes the graft polymerization of natural guar gum and acrylic acid to obtain an environmentally friendly superabsorbent resin with excellent water absorption ratio and salt water absorption rate.

[0003] Graft copolymers of guar gum with monomers such as acrylic acid and acrylamide have broad application prospects in wastewater treatment. For example, the study "Influence of hydrophobic monomers on the adsorption performance of heavy metal ions in guar gum-g-(polyacrylic acid-Co-styrene) / attapulgite clay composite hydrogel" shows that the hydrogel obtained by graft copolymerization of guar gum with acrylic acid and styrene monomers and composite with attapulgite clay has a good adsorption effect on heavy metal ions. The present invention aims to synthesize a novel polymer-grafted cationic modified guar gum for the treatment of wastewater containing metals such as Cr(VI). Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a cationic modified guar gum.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a cationic modified guar gum, wherein the synthesis process of the cationic modified guar gum comprises the following steps:

[0008] (1) Dissolve 2-chloromethylpyridine hydrochloride and N,N'-dimethyl-1,6-hexanediamine in methanol solution and stir the reaction at 20-40℃ for 48-72h. Add potassium hydroxide aqueous solution dropwise during the reaction. After the reaction, concentrate under reduced pressure to remove methanol. Then add deionized water and dichloromethane for extraction. Dry and concentrate the organic layer. Add the product to dichloromethane for recrystallization to obtain N,N'-dimethyl-1,6-hexanediamine methylpyridine.

[0009] (2) Add acrylic acid to sodium hydroxide solution and control the degree of neutralization to 65-80%. Then add guar gum (CGG) and ammonium persulfate, and control the mass ratio of acrylic acid, guar gum and ammonium persulfate to 3-7:1:0.03-0.08. In a nitrogen atmosphere, stir and polymerize at 65-80℃ for 2-5 hours. After the reaction, cool and add hydrochloric acid solution dropwise to neutralize, and obtain polyacrylic acid grafted guar gum.

[0010] (3) Add polyacrylic acid grafted guar gum to thionyl chloride and stir the reaction at 65-80℃ for 2-8 hours under a nitrogen atmosphere. After the reaction, remove thionyl chloride by vacuum distillation. Then add the obtained polyacrylamide chloride grafted guar gum to N,N-dimethylformamide and add 2-bromoethanol, triethylamine and dichloromethane as cosolvents. After the reaction, filter the solvent and wash with deionized water and ethanol in sequence to obtain poly(acrylic acid-bromoethyl acrylate) grafted guar gum.

[0011] (4) Poly(acrylic acid-bromoethyl acrylate) grafted guar gum and N,N'-dimethyl-1,6-hexanediamine methylpyridine were added to N,N-dimethylformamide and the cosolvent isopropanol. After the reaction was cooled, the solvent was filtered, and the mixture was washed with deionized water and ethanol in sequence to obtain the polymer-grafted cationic modified guar gum.

[0012] Preferably, the molar ratio of 2-chloromethylpyridine hydrochloride and N,N'-dimethyl-1,6-hexanediamine in (1) is 2.2-2.6:1.

[0013] Preferably, in step (1), the pH of the reaction solution is controlled to be 13-14 by adding potassium hydroxide aqueous solution dropwise.

[0014] Preferably, the mass ratio of polyacrylamide chloride grafted with guar gum, 2-bromoethanol, and triethylamine in (3) is 1:1.2-4:1-3.

[0015] Preferably, in step (3), the reaction is first stirred at 20-35°C for 5-15 hours, and then deionized water is added and stirred for 3-8 hours for hydrolysis.

[0016] Preferably, in (4), the mass ratio of poly(acrylic acid-bromoethyl acrylate) grafted guar gum and N,N'-dimethyl-1,6-hexanediamine methylpyridine is 1:0.3-1.5.

[0017] Preferably, the reaction in (4) is carried out at 100-140°C for 24-72 hours.

[0018] (III) Beneficial Technical Effects

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] This cationic modified guar gum is produced by graft copolymerization of guar gum and acrylic acid, followed by acyl chloride and esterification reactions. The reaction is further modified by adjusting the amount of 2-bromoethanol, which reacts with a portion of the acryloyl chloride. The unreacted acyl chloride groups are then hydrolyzed to obtain poly(acrylic acid-bromoethyl acrylate) grafted guar gum. The bromoethyl group undergoes a quaternary ammonium cationization reaction with the pyridine and tertiary amine groups of N,N'-dimethyl-1,6-hexanediamine methylpyridine, resulting in crosslinking and obtaining the polymer-grafted cationic modified guar gum. This modified guar gum contains abundant hydrophilic carboxyl groups and quaternary ammonium cations, giving it excellent water absorption capacity. The quaternary ammonium cations also exhibit good electrostatic interaction and adsorption performance for metal ions such as Cr(VI), resulting in high adsorption efficiency, large adsorption capacity, and environmental friendliness. It has broad application prospects in the treatment of wastewater containing metals such as Cr(VI). Attached Figure Description

[0021] Figure 1 It is the reaction formula of 2-chloromethylpyridine hydrochloride and N,N'-dimethyl-1,6-hexanediamine.

[0022] Figure 2 This is a diagram illustrating the synthesis mechanism of polymer-grafted cationic modified guar gum.

[0023] Figure 3 This is a water absorption rate test table for modified guar gum.

[0024] Figure 4 This is a test table of the adsorption capacity of modified guar gum for Cr(VI). Detailed Implementation

[0025] To achieve the above objectives, the present invention provides the following embodiments.

[0026] Example 1

[0027] (1) 2.5 g of 2-chloromethylpyridine hydrochloride and 1 g of N,N'-dimethyl-1,6-hexanediamine were dissolved in methanol solution and stirred at 40 °C for 60 h. Potassium hydroxide aqueous solution was added dropwise during the reaction to control the pH of the reaction solution to 13. After the reaction, the methanol was removed by vacuum concentration. Then, deionized water and dichloromethane were added for extraction. The organic layer was dried and concentrated. The product was added to dichloromethane for recrystallization to obtain N,N'-dimethyl-1,6-hexanediamine methylpyridine.

[0028] (2) Add 6g of acrylic acid to sodium hydroxide solution and control the degree of neutralization to 70%. Then add 2g of guar gum (CGG) and 0.06g of ammonium persulfate. In a nitrogen atmosphere, stir the polymerization reaction at 80°C for 3h. After the reaction, cool and add hydrochloric acid solution dropwise to neutralize, and obtain polyacrylic acid grafted guar gum.

[0029] (3) Add 5g of polyacrylic acid grafted guar gum to thionyl chloride and stir at 65°C for 4h under a nitrogen atmosphere. After the reaction, remove thionyl chloride by vacuum distillation. Then add 5g of polyacrylamide chloride grafted guar gum to N,N-dimethylformamide, add 6g of 2-bromoethanol, 5g of triethylamine and dichloromethane as a co-solvent, stir at 35°C for 5h, then add deionized water and stir for 3h to hydrolyze. After the reaction, filter the solvent and wash with deionized water and ethanol in sequence to obtain poly(acrylic acid-bromoethyl acrylate) grafted guar gum.

[0030] (4) 3g of poly(acrylic acid-bromoethyl acrylate) grafted guar gum and 0.9g of N,N'-dimethyl-1,6-hexanediamine methylpyridine were added to N,N-dimethylformamide and the cosolvent isopropanol. The mixture was reacted at 100℃ for 48h. After the reaction, the mixture was cooled, the solvent was filtered, and the mixture was washed with deionized water and ethanol in sequence to obtain the polymer-grafted cationic modified guar gum.

[0031] Example 2

[0032] (1) 2.7 g of 2-chloromethylpyridine hydrochloride and 1 g of N,N'-dimethyl-1,6-hexanediamine were dissolved in methanol solution and stirred at 20 °C for 72 h. During the reaction, potassium hydroxide aqueous solution was added dropwise to control the pH of the reaction solution to 14. After the reaction, the methanol was removed by vacuum concentration. Then, deionized water and dichloromethane were added for extraction. The organic layer was dried and concentrated. The product was added to dichloromethane for recrystallization to obtain N,N'-dimethyl-1,6-hexanediamine methylpyridine.

[0033] (2) Add 8g of acrylic acid to sodium hydroxide solution and control the degree of neutralization to 80%. Then add 2g of guar gum and 0.09g of ammonium persulfate. In a nitrogen atmosphere, stir the polymerization reaction at 70°C for 2 hours. After the reaction, cool and add hydrochloric acid solution dropwise to neutralize, and obtain polyacrylic acid grafted guar gum.

[0034] (3) Add 5g of polyacrylic acid grafted guar gum to thionyl chloride and stir at 70°C for 2h under nitrogen atmosphere. After the reaction, remove thionyl chloride by vacuum distillation. Then add 5g of polyacrylamide chloride grafted guar gum to N,N-dimethylformamide, add 12g of 2-bromoethanol, 8g of triethylamine and dichloromethane as cosolvent, stir at 20°C for 8h, then add deionized water and stir for 4h for hydrolysis. After the reaction, filter the solvent and wash with deionized water and ethanol in sequence to obtain poly(acrylic acid-bromoethyl acrylate) grafted guar gum.

[0035] (4) 3g of poly(acrylic acid-bromoethyl acrylate) grafted guar gum and 2.2g of N,N'-dimethyl-1,6-hexanediamine methylpyridine were added to N,N-dimethylformamide and the cosolvent isopropanol. The mixture was reacted at 100℃ for 72h. After the reaction, the mixture was cooled, the solvent was filtered, and the mixture was washed with deionized water and ethanol in sequence to obtain the polymer-grafted cationic modified guar gum.

[0036] Example 3

[0037] (1) 2.9 g of 2-chloromethylpyridine hydrochloride and 1 g of N,N'-dimethyl-1,6-hexanediamine were dissolved in methanol solution and stirred at 30 °C for 72 h. During the reaction, potassium hydroxide aqueous solution was added dropwise to control the pH of the reaction solution to 14. After the reaction, the methanol was removed by vacuum concentration. Then, deionized water and dichloromethane were added for extraction. The organic layer was dried and concentrated. The product was added to dichloromethane for recrystallization to obtain N,N'-dimethyl-1,6-hexanediamine methylpyridine.

[0038] (2) Add 14g of acrylic acid to sodium hydroxide solution and control the degree of neutralization to 60%. Then add 2g of guar gum and 0.16g of ammonium persulfate. In a nitrogen atmosphere, stir the polymerization reaction at 70°C for 4h. After the reaction, cool and add hydrochloric acid solution dropwise to neutralize, and obtain polyacrylic acid grafted guar gum.

[0039] (3) Add 5g of polyacrylic acid grafted guar gum to thionyl chloride and stir at 65°C for 5h under a nitrogen atmosphere. After the reaction, remove thionyl chloride by vacuum distillation. Then add 5g of polyacrylamide chloride grafted guar gum to N,N-dimethylformamide, add 20g of 2-bromoethanol, 15g of triethylamine and dichloromethane as a co-solvent, stir at 35°C for 12h, then add deionized water and stir for 8h for hydrolysis. After the reaction, filter the solvent and wash with deionized water and ethanol in sequence to obtain poly(acrylic acid-bromoethyl acrylate) grafted guar gum.

[0040] (4) 3g of poly(acrylic acid-bromoethyl acrylate) grafted guar gum and 4.5g of N,N'-dimethyl-1,6-hexanediamine methylpyridine were added to N,N-dimethylformamide and the cosolvent isopropanol. The mixture was reacted at 140℃ for 24h. After the reaction, the mixture was cooled, the solvent was filtered, and the mixture was washed with deionized water and ethanol in sequence to obtain the polymer-grafted cationic modified guar gum.

[0041] Comparative Example 1

[0042] (1) 2.6 g of 2-chloromethylpyridine hydrochloride and 1 g of N,N'-dimethyl-1,6-hexanediamine were dissolved in methanol solution and stirred at 20 °C for 48 h. During the reaction, potassium hydroxide aqueous solution was added dropwise to control the pH of the reaction solution to 14. After the reaction, the methanol was removed by vacuum concentration. Then, deionized water and dichloromethane were added for extraction. The organic layer was dried and concentrated. The product was added to dichloromethane for recrystallization to obtain N,N'-dimethyl-1,6-hexanediamine methylpyridine.

[0043] (2) Add 10g of acrylic acid to sodium hydroxide solution and control the degree of neutralization to 70%. Then add 2g of guar gum and 0.12g of ammonium persulfate. In a nitrogen atmosphere, stir the polymerization reaction at 80°C for 2 hours. After the reaction, cool and add hydrochloric acid solution dropwise to neutralize, and obtain polyacrylic acid grafted guar gum.

[0044] (3) Add 5g of polyacrylic acid-grafted guar gum to thionyl chloride and stir at 80°C for 3h under a nitrogen atmosphere. After the reaction, remove thionyl chloride by vacuum distillation. Then add 5g of polyacrylamide chloride-grafted guar gum to N,N-dimethylformamide, add 10g of 2-bromoethanol, 8g of triethylamine and dichloromethane as a co-solvent, stir at 20°C for 15h, then add deionized water and stir for 5h to hydrolyze. After the reaction, filter the solvent and wash with deionized water and ethanol in sequence to obtain poly(acrylic acid-bromoethyl acrylate)-grafted modified guar gum.

[0045] Add 0.1g of modified guar gum (M0) to 200mL of deionized water, allow it to swell and adsorb until equilibrium is reached, then remove the modified guar gum, drain excess water, and weigh M. 吸 Calculate the water absorption ratio Q, Q = (M 吸 -M0) / M0.

[0046] K₂Cr₂O₇ was dissolved in 200 mL of deionized water to prepare a 50 mg / L Cr(VI) solution. Then, 20 mg of modified guar gum was added, and the mixture was stirred at room temperature until adsorption reached equilibrium. The concentration of Cr(VI) ions after adsorption was then measured, and the adsorption capacity W was calculated. W = (C₀ - C₂) / (C₂O₇) = 1 / 2 * (C₀ - C₂O₇) / ( ... 吸 )×V / m, C0 is the initial mass concentration of Cr(VI), C 吸 V represents the equilibrium mass concentration of heavy metal ions after adsorption, V is the total volume of the solution, and m is the mass of the modified guar gum.

Claims

1. A cationic modified guar gum, characterized in that: The synthesis process of the cationic modified guar gum includes the following steps: (1) Dissolve 2-chloromethylpyridine hydrochloride and N,N'-dimethyl-1,6-hexanediamine in methanol solution, stir the reaction at 20-40℃ for 48-72h, add potassium hydroxide aqueous solution dropwise during the reaction, and obtain N,N'-dimethyl-1,6-hexanediamine methylpyridine after the reaction. (2) Add acrylic acid to sodium hydroxide solution and control the degree of neutralization to 65-80%. Then add guar gum and ammonium persulfate and control the mass ratio of acrylic acid, guar gum and ammonium persulfate to 3-7:1:0.03-0.

08. In a nitrogen atmosphere, stir the polymerization reaction at 65-80℃ for 2-5 hours to obtain polyacrylic acid grafted with guar gum. (3) Add polyacrylic acid grafted guar gum to thionyl chloride and stir the reaction at 65-80℃ for 2-8 hours under nitrogen atmosphere. After the reaction, remove thionyl chloride by vacuum distillation. Then add the obtained polyacrylamide chloride grafted guar gum to N,N-dimethylformamide, add 2-bromoethanol, triethylamine and dichloromethane as cosolvents, and react to obtain poly(acrylic acid-bromoethyl acrylate) grafted guar gum. (4) Poly(acrylic acid-bromoethyl acrylate) grafted guar gum and N,N'-dimethyl-1,6-hexanediamine methylpyridine were added to N,N-dimethylformamide and the cosolvent isopropanol to react and obtain polymer-grafted cationic modified guar gum. The molar ratio of 2-chloromethylpyridine hydrochloride and N,N'-dimethyl-1,6-hexanediamine in (1) is 2.2-2.6:1; In step (1), potassium hydroxide aqueous solution is added dropwise to control the pH of the reaction solution to 13-14; In (3), the mass ratio of polyacrylamide chloride grafted with guar gum, 2-bromoethanol, and triethylamine is 1:1.2-4:1-3; The reaction in (3) is first stirred at 20-35℃ for 5-15h, and then deionized water is added and stirred for 3-8h for hydrolysis. In (4), the mass ratio of poly(acrylic acid-bromoethyl acrylate) grafted guar gum and N,N'-dimethyl-1,6-hexanediamine methylpyridine is 1:0.3-1.5; The reaction in (4) is carried out at 100-140℃ for 24-72 hours.

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