Preparation method of salt-resistant sodium carboxymethyl cellulose

Abstract

The invention discloses a preparation method of salt-resistant sodium carboxymethyl cellulose, and relates to the technical field of petroleum fracturing materials. The preparation method comprises the following steps: reacting stearic acid with ethylenediamine to obtain a monosubstituted intermediate, reacting the monosubstituted intermediate with cocoyl chloride to obtain an intermediate 1, reacting the intermediate 1 with epoxypropane to obtain an intermediate 2, and reacting the intermediate 2 with paratoluensulfonyl chloride to obtain a hydrophobic intermediate; reacting a sodium carboxymethyl cellulose solution with the hydrophobic intermediate to obtain modified sodium carboxymethyl cellulose, and sulfonating the modified sodium carboxymethyl cellulose with sulfamic acid to obtain crude salt-tolerant sodium carboxymethyl cellulose; and reacting the crude product salt-resistant sodium carboxymethyl cellulose with borax to obtain the salt-resistant sodium carboxymethyl cellulose. The salt-resistant sodium carboxymethyl cellulose prepared by adopting a step-by-step synthesis strategy has excellent salt resistance, temperature resistance, shearing resistance and dissolution rate, and is suitable for thickening and sand carrying of high-temperature and high-salt oil and gas field fracturing fluid.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of oil fracturing materials, in particular to a preparation method of a salt-resistant sodium carboxymethyl cellulose. BACKGROUND

[0002] Cellulose derivatives have been widely used in the field of oilfield water-based fracturing fluids, but their poor salt resistance and temperature resistance have long hindered their performance in complex environments. Traditional carboxymethyl cellulose sodium is prone to molecular chain curling due to charge shielding effect in high-salt environments, resulting in a sharp drop in viscosity; under high-temperature conditions, the hydrogen bond is broken and the chain segment is disentangled, causing the colloidal stability to decrease. In step S3 of patent CN117924718A, acrylamide, purified AMPS and modified quaternary ammonium salt are copolymerized into a ternary polymer through a water solution free radical polymerization process. On the one hand, the quaternary ammonium salt may cause local self-polymerization to form a homopolymer by-product, and on the other hand, the inherent defects of free radical polymerization may cause the product molecular weight distribution index (PDI) to be wide. Although low temperature and oxygen control can limit chain transfer, the problem of wide product molecular weight distribution cannot be completely avoided. Existing modification technologies mostly improve salt resistance through physical blending or free radical polymerization, but such methods are difficult to balance the controllability of material structure and the synergistic effect of functional groups, and are often accompanied by problems such as wide product molecular weight distribution and many by-products, which are difficult to meet the harsh demands of high-temperature deep well fracturing or high-salt food processing scenes. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of salt-resistant sodium carboxymethyl cellulose to solve the problems raised in the background art.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: A preparation method of salt-resistant sodium carboxymethyl cellulose, comprising the following steps: S1, dissolve stearic acid and ethylenediamine in N,N-dimethylformamide under 0 DEG C ice water bath, add dicyclohexyl carbodiimide and 4-dimethylamino pyridine, stir and react at 25-30 DEG C for 6-8 h, cool, filter, wash and dry to obtain a monosubstituted intermediate; dissolve the monosubstituted intermediate and cocoyl chloride in dichloromethane under 0 DEG C ice water bath, add triethylamine dropwise to adjust the pH to neutral, stir and react for 2-3 h, cool, filter, wash and dry to obtain intermediate 1; dissolve intermediate 1, propylene oxide and tin tetrachloride in toluene, react at 0 DEG C for 3-4 h, add concentrated hydrochloric acid to the above reaction solution, heat to 35-40 DEG C and react for 1-2 h, filter, wash and dry to obtain intermediate 2; dissolve intermediate 2 and p-toluenesulfonyl chloride in dichloromethane, add pyridine, react at 0-10 DEG C for 1 h, wash with cold ethyl acetate for 3 times, and dry under vacuum to obtain a hydrophobic intermediate; The amount ratio of stearic acid, ethylenediamine, N,N-dimethylformamide, dicyclohexyl carbodiimide and 4-dimethylaminopyridine is (280-290) g:(62-68) g:(2000-2270) mL:(247-270) g:(6.1-12.2) g; The amount ratio of monosubstituted intermediate, coconut acid chloride, dichloromethane and triethylamine is (330-350) g:(190-200) g:(1400-1600) mL:(108-115) mL; The concentration of the concentrated hydrochloric acid is 6 mol / L; The amount ratio of intermediate 1, propylene oxide, tin tetrachloride, toluene and concentrated hydrochloric acid is (655-685) g:(210-350) mL:(13-26) g:(2500-2820) mL:(250-330) mL; The amount ratio of intermediate 2, p-toluenesulfonyl chloride, dichloromethane and pyridine is (740-760) g:(230-287) g:(2800-3200) mL:(120-160) mL; It should be noted that the reaction of dicyclohexyl carbodiimide with the carboxyl group of stearic acid generates a highly active O-acyl isourea intermediate through dehydration, significantly improving the electrophilicity of the carboxyl group. The coordination of 4-dimethylaminopyridine with the carbonyl oxygen of the O-acyl isourea intermediate promotes the polarization of C=O, making the acyl group more easily transfer to the nitrogen atom of 4-dimethylaminopyridine to generate a more active acylpyridinium salt intermediate, greatly reducing the activation energy of the reaction and inhibiting the generation of byproduct dicyclohexyl urea. Under controlled reaction conditions, one of the aminos in ethylenediamine reacts with the carbonyl carbon of the acylpyridinium salt to form an amide bond, while releasing the catalyst 4-dimethylaminopyridine, and the other amino remains in a free state due to steric hindrance and electronic effects. The reaction of excess monosubstituted intermediate with cocoyl chloride produces the product intermediate 1, which contains a free amino group and an alkyl chain with a cocoyl group, both of which further enhance hydrophobicity. Tin tetrachloride acts as a Lewis acid and coordinates with the oxygen atom of propylene oxide, polarizing the C-O bond of the epoxy ring through strong electron-withdrawing effect. This polarization causes the electron cloud to shift from the beta-carbon to the oxygen atom, reducing the electron density of the beta-carbon (terminal CH2 position) and significantly enhancing the electrophilicity of the beta-carbon (terminal carbon). The tetrahedral coordination structure of tin tetrachloride and the methyl group of propylene oxide occupy the alpha-carbon position, resulting in spatial crowding around the alpha-carbon. In contrast, the beta-carbon has less steric hindrance, and the long chain of intermediate 1 is more easily accessible from the beta-carbon side, further amplifying the selective attack of the beta-carbon. The condition of 0°C inhibits the thermodynamically stable alpha-carbon attack path (which requires higher activation energy), allowing the reaction to remain in the kinetically favored beta-carbon selective stage. Under the synergistic effect of low temperature (0°C) and steric hindrance, the amino group selectively attacks the beta-carbon to form a C-N bond, and the ring-opening of propylene oxide introduces a hydroxyl group, providing an active site for subsequent sulfonate esterification. The reaction of the sulfonate group (-SO2Cl) of p-toluenesulfonyl chloride with the hydroxyl group generates a sulfonate ester group, and pyridine absorbs the generated HCl, promoting the forward reaction. Low temperature (0°C) inhibits the hydrolysis of p-toluenesulfonyl chloride or other side reactions, converting the hydroxyl group to a strongly leaving sulfonate ester group, providing a reactive site for the subsequent Williamson etherification reaction.

[0005] It should be noted that in a high salt solution, the salt ions (such as Na + 、Ca 2+) will form an "ionic atmosphere" around the negatively charged carboxylate, weaken the electrostatic repulsion between molecular chains by neutralizing the charge, cause the chain to curl, and show viscosity reduction; on the one hand, the hydrophobic long chain forms a physical crosslinking network through intermolecular hydrophobic association in a high salt environment, reduces the molecular chain curling caused by salt ions, inhibits viscosity reduction, maintains the sand carrying capacity of the fracturing fluid, makes the modified carboxymethyl cellulose sodium salt molecular chain stretch, increases the hydrodynamic volume, reduces the chain contraction caused by salt ions, and improves the salt tolerance. On the other hand, the sulfonate group as a leaving group makes the modified intermediate undergo SN2 substitution reaction with the hydroxyl group of the modified carboxymethyl cellulose sodium salt in the subsequent step S2, ensuring the grafting of the hydrophobic intermediate, and the step-by-step synthesis avoids the problem of molecular weight distribution of free radical polymerization, improves the uniformity of the product.

[0006] S2, disperse the carboxymethyl cellulose sodium salt in N-methyl pyrrolidone, add sodium hydroxide solution, stir at room temperature for 1-2h, to obtain a carboxymethyl cellulose sodium salt solution; dissolve the hydrophobic intermediate and tetrabutylammonium bromide in N-methyl pyrrolidone, add dropwise to the carboxymethyl cellulose sodium salt solution, react at 50-55℃ for 3-5h, add ice water mixture, adjust pH to 10-12, silica gel column chromatography, 10-30kDa membrane ultrafiltration for 24h, freeze-drying to obtain modified carboxymethyl cellulose sodium salt; The concentration of the sodium hydroxide solution is 0.1-1mol / L; The amount ratio of the carboxymethyl cellulose sodium salt, N-methyl pyrrolidone and sodium hydroxide solution is 10g:(200-300)mL:(50-100)mL; The amount ratio of the hydrophobic intermediate, tetrabutylammonium bromide, N-methyl pyrrolidone and carboxymethyl cellulose sodium salt solution is (8-12)g:(0.08-0.15)g:(50-80)mL:(220-280)mL; The eluent used in the silica gel column chromatography is a mixed solution of ethyl acetate and methanol with a volume ratio of 9:1; It should be noted that sodium hydroxide converts the hydroxyl group of carboxymethyl cellulose sodium salt into alkoxide, which undergoes nucleophilic substitution reaction with the sulfonate of the hydrophobic intermediate to form ether bond.

[0007] S3, disperse the modified carboxymethyl cellulose sodium salt in a 0.5% sulfuric acid solution, adjust the pH to 1-4, add sulfamic acid, and react under ultrasonic treatment at 80-100℃ for 2-3h to obtain crude salt-tolerant carboxymethyl cellulose sodium salt; dissolve the crude salt-tolerant carboxymethyl cellulose sodium salt and borax in deionized water, adjust the pH to 9, and stir at 55-65℃ for 1-2h to obtain salt-tolerant carboxymethyl cellulose sodium salt; The ratio of the modified carboxymethyl cellulose sodium salt, sulfuric acid solution and aminosulfonic acid is 10 g: (80-120) mL: (2.5-3.5) g; The usage ratio of the crude salt-resistant carboxymethyl cellulose sodium salt, borax and deionized water is 10g: (0.2-0.4)g: (80-120)mL; It should be noted that H2SO4 partially hydrolyzes the β-1,4-glycosidic bond of the modified sodium carboxymethyl cellulose skeleton to generate short-chain cellulose, which enhances solubility; aminosulfonic acid is used as a sulfonating agent to convert the hydroxyl group of the modified sodium carboxymethyl cellulose into a sulfonic acid group, and the introduced sulfonic acid anion group repels Cl through its strong negative charge. - Borax dissociates in water and forms borate ester bonds with the hydroxyl groups of modified sodium carboxymethyl cellulose under alkaline conditions, thus constructing a cross-linked network, restricting the free movement of molecular weight, reducing chain entanglement under high temperature or high shear, and improving viscosity stability.

[0008] Compared with the prior art, the present invention has the following beneficial effects: (1) The introduction of hydrophobic chains forms a dynamic physical cross-linking network through intermolecular hydrophobic association, which effectively resists the compression effect of salt ions on the molecular chains and maintains the extended state of the molecular chains in salt solution.

[0009] (2) The sulfonic acid group maintains strong ionization characteristics under high salt and wide pH range, and maintains colloidal stability through electrostatic repulsion, so that the modified sodium carboxymethyl cellulose can still maintain stable thickening ability and suspension properties in high concentration salt solutions (such as NaCl, CaCl2), and is suitable for industrial applications in high-mineralization oilfield fracturing fluids and complex salt environments; the large volume and strong polar bonds of the sulfonic acid group give it rigidity, inhibit the thermal motion of the molecular chain at high temperature, and reduce the viscosity loss caused by chain segment disentanglement.

[0010] (3) The introduction of the borate cross-linked network enables the material to maintain three-dimensional structural stability in a high-temperature environment, thereby still exhibiting excellent viscosity retention under high-temperature shear conditions.

[0011] (4) The synergistic effect of the hydrophobic chain and the sulfonic acid group increases the molecular hydrodynamic volume, so that the modified sodium carboxymethyl cellulose exhibits good shear recovery under high-speed shearing; the strong hydrophilicity of the carboxymethyl and sulfonic acid groups destroys the cellulose crystalline region, promotes water molecule penetration, shortens the dissolution time, and improves the liquid preparation efficiency. The preparation method of the salt-tolerant sodium carboxymethyl cellulose provided by the application adopts a step-by-step synthesis strategy, avoids the problems of wide molecular weight distribution and many by-products in traditional free radical polymerization through hydrophobic chain grafting, sulfonic acid group modification and borate ester crosslinking network, and at the same time, recyclable solvents and low-toxicity reagents are used to reduce waste emissions, in line with the development trend of green chemical industry; on the other hand, the salt-tolerant sodium carboxymethyl cellulose prepared by the application has excellent salt tolerance, temperature resistance, shear resistance and dissolution rate, is suitable for thickening and sand carrying of high-temperature and high-salt oil and gas field fracturing fluid, and provides a reliable solution for the development of functional cellulose materials. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the application will be described below clearly and completely. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the application.

[0013] The preparation steps of the hydrophobic intermediate are as follows: (1) Dissolve stearic acid and ethylenediamine in N,N-dimethylformamide under an ice water bath at 0 DEG C, add dicyclohexyl carbodiimide and 4-dimethylaminopyridine, stir at 25 DEG C for 8 hours, cool, filter, wash and dry to obtain a monosubstituted intermediate; The usage ratio of the stearic acid, ethylenediamine, N,N-dimethylformamide, dicyclohexyl carbodiimide and 4-dimethylaminopyridine is 284 g:66 g:2150 mL:256 g:9.3 g; (2) Dissolve the monosubstituted intermediate and cocoyl chloride in dichloromethane under an ice water bath at 0 DEG C, add triethylamine dropwise to adjust the pH to neutral, stir for 2 hours, cool, filter, wash and dry to obtain intermediate 1; The usage ratio of the monosubstituted intermediate, cocoyl chloride, dichloromethane and triethylamine is 340 g:195 g:1500 mL:111.3 mL; (3) Dissolve intermediate 1, propylene oxide and tin tetrachloride in toluene, react at 0 DEG C for 4 hours, add 6 mol / L concentrated hydrochloric acid to the above reaction solution, heat to 40 DEG C and react for 2 hours, filter, wash and dry to obtain intermediate 2; The usage ratio of the intermediate 1, propylene oxide, tin tetrachloride, toluene and concentrated hydrochloric acid is 670 g:280 mL:19.5 g:2680 mL:290 mL; (4) the intermediate 2, p-toluenesulfonyl chloride, dichloromethane and pyridine are used in a ratio of 750 g: 258 g: 3000 mL: 140 mL. The intermediate 2, p-toluenesulfonyl chloride, dichloromethane and pyridine are used in a ratio of 750 g: 258 g: 3000 mL: 140 mL.

[0014] Example 1: S1, 10 g of carboxymethyl cellulose sodium salt is dispersed in 250 mL of N-methyl pyrrolidone, 75 mL of 0.8 mol / L sodium hydroxide solution is added, and stirring is carried out at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution; S2, 10 g of the hydrophobic intermediate and 0.12 g of tetrabutylammonium bromide are dissolved in 65 mL of N-methyl pyrrolidone, and then added dropwise into 250 mL of the carboxymethyl cellulose sodium salt solution, and reaction is carried out at 50°C for 5 h, an ice water mixture is added, the pH is adjusted to 10, silica gel column chromatography is carried out, 15 kDa membrane ultrafiltration is carried out for 24 h, and freeze drying is carried out to obtain modified carboxymethyl cellulose sodium salt; the eluent used in the silica gel column chromatography is a mixed solution of ethyl acetate and methanol in a volume ratio of 9:1; S3, 10 g of the modified carboxymethyl cellulose sodium salt is dispersed in 100 mL of a 0.5% by mass sulfuric acid solution, the pH is adjusted to 3, 3 g of sulfamic acid is added, and reaction is carried out under ultrasonic treatment at 80°C for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt; S4, 10 g of the crude salt-tolerant carboxymethyl cellulose sodium salt and 0.3 g of borax are dissolved in 100 mL of deionized water, the pH is adjusted to 9, and stirring reaction is carried out at 60°C for 2 h to obtain a salt-tolerant carboxymethyl cellulose sodium salt; Example 2: S1, 10 g of carboxymethyl cellulose sodium salt is dispersed in 200 mL of N-methyl pyrrolidone, 50 mL of 0.8 mol / L sodium hydroxide solution is added, and stirring is carried out at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution; S2, 10 g of the hydrophobic intermediate and 0.08 g of tetrabutylammonium bromide are dissolved in 50 mL of N-methyl pyrrolidone, and then added dropwise into 220 mL of the carboxymethyl cellulose sodium salt solution, and reaction is carried out at 55°C for 4 h, an ice water mixture is added, the pH is adjusted to 11, silica gel column chromatography is carried out, 15 kDa membrane ultrafiltration is carried out for 24 h, and freeze drying is carried out to obtain modified carboxymethyl cellulose sodium salt; the eluent used in the silica gel column chromatography is a mixed solution of ethyl acetate and methanol in a volume ratio of 9:1; S3, 10 g of the modified carboxymethyl cellulose sodium salt is dispersed in 80 mL of a 0.5% by mass sulfuric acid solution, the pH is adjusted to 2, 2.5 g of sulfamic acid is added, and reaction is carried out under ultrasonic treatment at 80°C for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt; S4, 10 g of the crude salt-tolerant carboxymethyl cellulose sodium salt and 0.2 g of borax were dissolved in 80 mL of deionized water, the pH was adjusted to 9, and the reaction was stirred at 55°C for 2 h to prepare the salt-tolerant carboxymethyl cellulose sodium salt; Example 3: S1, 10 g of carboxymethyl cellulose sodium salt was dispersed in 300 mL of N-methyl pyrrolidone, 100 mL of 0.8 mol / L sodium hydroxide solution was added, and the mixture was stirred at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution; S2, 10 g of the hydrophobic intermediate and 0.08 g of tetrabutylammonium bromide were dissolved in 50 mL of N-methyl pyrrolidone, and 220 mL of the carboxymethyl cellulose sodium salt solution was added dropwise, and the mixture was reacted at 50°C for 5 h, then an ice water mixture was added, the pH was adjusted to 12, and the mixture was subjected to silica gel column chromatography, 15 kDa membrane ultrafiltration for 24 h, and freeze-drying to obtain a modified carboxymethyl cellulose sodium salt; the silica gel column chromatography used an eluent of a mixture of ethyl acetate and methanol in a volume ratio of 9:1; S3, 10 g of the modified carboxymethyl cellulose sodium salt was dispersed in 120 mL of a 0.5% by mass sulfuric acid solution, the pH was adjusted to 4, 3.5 g of sulfamic acid was added, and the mixture was reacted under ultrasonic treatment at 100°C for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt; S4, 10 g of the crude salt-tolerant carboxymethyl cellulose sodium salt and 0.4 g of borax were dissolved in 120 mL of deionized water, the pH was adjusted to 9, and the reaction was stirred at 65°C for 2 h to prepare the salt-tolerant carboxymethyl cellulose sodium salt; Comparative Example 1 S1, 10 g of carboxymethyl cellulose sodium salt was dispersed in 250 mL of N-methyl pyrrolidone, 75 mL of 0.8 mol / L sodium hydroxide solution was added, and the mixture was stirred at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution; S2, 10 g of the hydrophobic intermediate and 0.12 g of tetrabutylammonium bromide were dissolved in 65 mL of N-methyl pyrrolidone, and 250 mL of the carboxymethyl cellulose sodium salt solution was added dropwise, and the mixture was reacted at 50°C for 5 h, then an ice water mixture was added, the pH was adjusted to 10, and the mixture was subjected to silica gel column chromatography, 15 kDa membrane ultrafiltration for 24 h, and freeze-drying to obtain a modified carboxymethyl cellulose sodium salt; the silica gel column chromatography used an eluent of a mixture of ethyl acetate and methanol in a volume ratio of 9:1; S3, 10 g of the modified carboxymethyl cellulose sodium salt was dispersed in 100 mL of a 0.5% by mass sulfuric acid solution, the pH was adjusted to 3, 3 g of sulfamic acid was added, and the mixture was reacted under ultrasonic treatment at 80°C for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt.

[0015] The difference between this comparative example and Example 1 is that the original step S4 of Example 1 is omitted.

[0016] Comparative Example 2 S1, 10 g of carboxymethyl cellulose sodium was dispersed in 100 mL of 0.5% by mass sulfuric acid solution, the pH was adjusted to 3, 3 g of sulfamic acid was added, and the reaction was carried out at 80°C for 3 h under ultrasonic treatment to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt; S2, 10 g of the crude salt-tolerant carboxymethyl cellulose sodium salt and 0.3 g of borax were dissolved in 100 mL of deionized water, the pH was adjusted to 9, and the reaction was carried out at 60°C for 2 h under stirring to obtain a salt-tolerant carboxymethyl cellulose sodium salt. The difference between the present comparative example and Example 1 is that the original steps S1 and S2 of Example 1 are omitted.

[0017] Comparative Example 3 S1, 10 g of carboxymethyl cellulose sodium salt was dispersed in 250 mL of N-methyl pyrrolidone, 75 mL of 0.8 mol / L sodium hydroxide solution was added, and the mixture was stirred at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution; S2, 10 g of dodecylbenzenesulfonate and 0.12 g of tetrabutylammonium bromide were dissolved in 65 mL of N-methyl pyrrolidone, and the mixture was added dropwise into 250 mL of the carboxymethyl cellulose sodium salt solution, and the reaction was carried out at 50°C for 5 h, then ice water mixture was added, the pH was adjusted to 10, and the mixture was subjected to silica gel column chromatography, 15 kDa membrane ultrafiltration for 24 h, and freeze-drying to obtain a modified carboxymethyl cellulose sodium salt; the eluent used in the silica gel column chromatography was a mixed solution of ethyl acetate and methanol in a volume ratio of 9:1; S3, 10 g of the modified carboxymethyl cellulose sodium salt was dispersed in 100 mL of 0.5% by mass sulfuric acid solution, the pH was adjusted to 3, 3 g of sulfamic acid was added, and the reaction was carried out at 80°C for 3 h under ultrasonic treatment to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt; S4, 10 g of the crude salt-tolerant carboxymethyl cellulose sodium salt and 0.3 g of borax were dissolved in 100 mL of deionized water, the pH was adjusted to 9, and the reaction was carried out at 60°C for 2 h under stirring to obtain a salt-tolerant carboxymethyl cellulose sodium salt.

[0018] The difference between the present comparative example and Example 1 is that the original step S2 is not added, but dodecylbenzenesulfonate is added.

[0019] Test: I. Salt tolerance test The salt-tolerant carboxymethyl cellulose sodium salts prepared in Examples 1-3 and Comparative Examples 1-3 were dissolved in pure water (A), 10,000 ppm NaCl solution (B), 30,000 ppm NaCl solution (C), and 10,000 ppm CaCl2 solution (D) to prepare a 0.5% by mass salt-tolerant carboxymethyl cellulose sodium salt solution, and after swelling and stabilization, the viscosity was measured using a rheometer at a shear rate of 170 s -1 , and a temperature of 25°C. The test results are shown in Table 1: Table 1

[0020] II. Temperature resistance test The salt-tolerant carboxymethyl cellulose sodium salt prepared in Examples 1-3 and Comparative Examples 1-3 was dissolved in pure water to prepare a salt-tolerant carboxymethyl cellulose sodium salt solution with a mass fraction of 0.5%. After swelling and stabilization, the viscosity was measured using a rheometer at a shear rate of 170 s -1 , a temperature of 120℃, and a shearing time of 120 min. The test results are shown in Table 2: Table 2

[0021] III. Conclusion Compared with Comparative Examples 1-3, the salt-tolerant carboxymethyl cellulose sodium salt prepared in Examples 1-3 has excellent salt tolerance and temperature resistance due to the inhibition of the compression effect of salt ions by hydrophobic association and the maintenance of high-temperature stability by the synergistic effect of sulfonic acid groups and borate esters.

[0022] In the description of the specification, the description of the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0023] The above is only an example and description of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as they do not deviate from the invention or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

Claims

1. A method for preparing salt-tolerant carboxymethyl cellulose sodium salt, characterized in that: The following steps are involved: S1. Dissolve stearic acid and ethylenediamine in N,N-dimethylformamide in an ice-water bath at 0°C, add dicyclohexylcarbodiimide and 4-dimethylaminopyridine, stir and react at 25-30°C for 6-8 hours, cool and filter, wash and dry to obtain a monosubstituted intermediate; dissolve the monosubstituted intermediate and coconut oil chloride in dichloromethane in an ice-water bath at 0°C, add triethylamine dropwise to adjust the pH to neutral, stir and react for 2-3 hours, cool and filter, wash and dry to obtain intermediate 1; dissolve intermediate 1, propylene oxide and tin tetrachloride in toluene, react at 0°C for 3-4 hours, add concentrated hydrochloric acid to the reaction solution, heat to 35-40°C, react for 1-2 hours, filter, wash and dry to obtain intermediate 2; dissolve intermediate 2 and p-toluenesulfonyl chloride in dichloromethane, add pyridine, react at 0-10°C for 1 hour, wash 3 times with cold ethyl acetate, and vacuum dry to obtain a hydrophobic intermediate; S2. Dispersing carboxymethyl cellulose sodium salt in N-methyl pyrrolidone, adding sodium hydroxide solution, and stirring at room temperature for 1-2 hours to obtain a carboxymethyl cellulose sodium salt solution; dissolving the hydrophobic intermediate and tetrabutylammonium bromide in N-methyl pyrrolidone, adding dropwise to the carboxymethyl cellulose sodium salt solution, reacting at 50-55° C. for 3-5 hours, adding an ice-water mixture, adjusting the pH to 10-12, performing silica gel column chromatography, ultrafiltration with a 10-30 kDa membrane for 24 hours, and freeze-drying to obtain modified carboxymethyl cellulose sodium salt; S3. Disperse modified carboxymethyl cellulose sodium salt in a 0.5% by mass sulfuric acid solution, adjust the pH to 1-4, add sulfamic acid, and react under ultrasonic treatment at 80-100°C for 2-3 hours to obtain crude salt-resistant carboxymethyl cellulose sodium salt; dissolve the crude salt-resistant carboxymethyl cellulose sodium salt and borax in deionized water, adjust the pH to 9, and react with stirring at 55-65°C for 1-2 hours to obtain salt-resistant carboxymethyl cellulose sodium salt.

2. The method for preparing salt-tolerant carboxymethyl cellulose sodium salt according to claim 1, wherein: In step S1, the usage ratio of stearic acid, ethylenediamine, N,N-dimethylformamide, dicyclohexylcarbodiimide and 4-dimethylaminopyridine is (280-290) g: (62-68) g: (2000-2270) mL: (247-270) g: (6.1-12.2) g.

3. The method for preparing a salt-tolerant carboxymethyl cellulose sodium salt according to claim 1, wherein: In step S1, the usage ratio of the monosubstituted intermediate, coconut oil chloride, dichloromethane and triethylamine is (330-350) g: (190-200) g: (1400-1600) mL: (108-115) mL.

4. The method for preparing a salt-tolerant sodium carboxymethyl cellulose according to claim 1, wherein: In step S1, the usage ratio of the intermediate 1, propylene oxide, tin tetrachloride, toluene and concentrated hydrochloric acid is (655-685) g:(210-350) mL:(13-26) g:(2500-2820) mL:(250-330) mL.

5. The method for preparing salt-tolerant carboxymethyl cellulose sodium salt according to claim 1, wherein: In step S1, the usage ratio of the intermediate 2, p-toluenesulfonyl chloride, dichloromethane and pyridine is (740-760) g: (230-287) g: (2800-3200) mL: (120-160) mL.

6. The method for preparing a salt-tolerant sodium carboxymethyl cellulose according to claim 1, wherein: In step S2, the usage ratio of the sodium salt of carboxymethyl cellulose, N-methyl pyrrolidone and sodium hydroxide solution is 10 g: (200-300) mL: (50-100) mL.

7. The method for preparing salt-tolerant carboxymethyl cellulose sodium salt according to claim 1, wherein: In step S2, the usage ratio of the hydrophobic intermediate, tetrabutylammonium bromide, N-methylpyrrolidone and carboxymethyl cellulose sodium salt solution is (8-12) g: (0.08-0.15) g: (50-80) mL: (220-280) mL.

8. The method for preparing salt-tolerant carboxymethyl cellulose sodium salt according to claim 1, wherein: In step S2, the eluent used for the silica gel column chromatography is a mixed solution of ethyl acetate and methanol in a volume ratio of 9:

1.

9. The method for preparing salt-tolerant carboxymethyl cellulose sodium salt according to claim 1, wherein: In step S3, the usage ratio of the modified carboxymethyl cellulose sodium salt, the sulfuric acid solution, and the aminosulfonic acid is 10 g: (80-120) mL: (2.5-3.5) g.

10. The method for preparing salt-tolerant carboxymethyl cellulose sodium salt according to claim 1, wherein: In step S3, the usage ratio of the crude salt-resistant sodium carboxymethyl cellulose, borax and deionized water is 10 g: (0.2-0.4) g: (80-120) mL.

Images