A method for preparing a salt of carboxymethylcellulose sodium salt

Abstract

The application discloses a preparation method of salt-resistant sodium carboxymethyl cellulose, and relates to the technical field of oil fracturing materials. Stearic acid is reacted with ethylenediamine to obtain a monosubstituted intermediate, the monosubstituted intermediate is reacted with coconut acyl chloride to obtain an intermediate 1, the intermediate 1 is reacted with propylene oxide to obtain an intermediate 2, and the intermediate 2 is reacted with p-toluenesulfonyl chloride to obtain a hydrophobic intermediate. The sodium carboxymethyl cellulose solution is reacted with the hydrophobic intermediate to obtain modified sodium carboxymethyl cellulose, the modified sodium carboxymethyl cellulose is sulfonated by aminosulfonic acid to obtain a crude salt-resistant sodium carboxymethyl cellulose, and the crude salt-resistant sodium carboxymethyl cellulose is reacted with borax to obtain the salt-resistant sodium carboxymethyl cellulose. The salt-resistant sodium carboxymethyl cellulose prepared by adopting the step-by-step synthesis strategy has excellent salt resistance, temperature resistance, shear resistance and dissolution rate, and is suitable for thickening and sand carrying of a fracturing fluid for a high-temperature and high-salt oil and gas field.

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:

[0005] A preparation method of salt-resistant sodium carboxymethyl cellulose, comprising the following steps:

[0006] 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 for 6-8 h under 25-30 DEG C, 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 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 for 3-4 h under 0 DEG C, add concentrated hydrochloric acid to the above-mentioned reaction liquid, 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 for 1 h under 0-10 DEG C, wash with cold ethyl acetate for 3 times, and dry under vacuum to obtain a hydrophobic intermediate;

[0007] 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;

[0008] The amount ratio of the monosubstituted intermediate, coconut oil chloride, dichloromethane and triethylamine is (330-350) g:(190-200) g:(1400-1600) mL:(108-115) mL;

[0009] The concentration of the concentrated hydrochloric acid is 6 mol / L;

[0010] The amount 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;

[0011] The amount ratio of the intermediate 2, p-toluenesulfonyl chloride, dichloromethane and pyridine is (740-760) g:(230-287) g:(2800-3200) mL:(120-160) mL;

[0012] 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.

[0013] 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 the molecular chains by neutralizing the charge, resulting in chain curling, showing 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 modified carboxymethyl cellulose sodium salt molecular chain, expands 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, and improves the uniformity of the product.

[0014] S2, dispersing the carboxymethyl cellulose sodium salt in N-methyl pyrrolidone, adding a sodium hydroxide solution, stirring at room temperature for 1-2 h to obtain a carboxymethyl cellulose sodium salt solution; dissolving the hydrophobic intermediate and tetrabutylammonium bromide in N-methyl pyrrolidone, adding dropwise into the carboxymethyl cellulose sodium salt solution, reacting at 50-55°C for 3-5 h, adding an ice water mixture, adjusting the pH to 10-12, silica gel column chromatography, 10-30 kDa membrane ultrafiltration for 24 h, and freeze-drying to obtain the modified carboxymethyl cellulose sodium salt;

[0015] The concentration of the sodium hydroxide solution is 0.1-1 mol / L;

[0016] The amount ratio of the carboxymethyl cellulose sodium salt, N-methyl pyrrolidone and sodium hydroxide solution is 10 g:(200-300) mL:(50-100) mL;

[0017] 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;

[0018] 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;

[0019] It should be noted that sodium hydroxide converts the hydroxyl group of carboxymethyl cellulose sodium salt into alkoxide, and undergoes nucleophilic substitution reaction with the sulfonate of the hydrophobic intermediate to generate ether bond.

[0020] S3, dispersing the modified carboxymethyl cellulose sodium salt in a sulfuric acid solution with a mass fraction of 0.5%, adjusting the pH to 1-4, adding sulfamic acid, and reacting for 2-3 h under ultrasonic treatment at 80-100 DEG C to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt; dissolving the crude salt-tolerant carboxymethyl cellulose sodium salt and borax in deionized water, adjusting the pH to 9, and stirring and reacting for 1-2 h at 55-65 DEG C to obtain the salt-tolerant carboxymethyl cellulose sodium salt;

[0021] The amount ratio of the modified carboxymethyl cellulose sodium salt, the sulfuric acid solution and the sulfamic acid is 10 g:(80-120) mL:(2.5-3.5) g;

[0022] The amount ratio of the crude salt-tolerant carboxymethyl cellulose sodium salt, the borax and the deionized water is 10 g:(0.2-0.4) g:(80-120) mL;

[0023] It should be noted that the H2SO4 partially hydrolyzes the beta-1,4-glucosidic bonds of the skeleton of the modified carboxymethyl cellulose sodium salt to generate short-chain cellulose, thereby enhancing the solubility; the sulfamic acid is used as a sulfonating agent to convert the hydroxyl groups of the modified carboxymethyl cellulose sodium salt into sulfonic acid groups; the introduced sulfonic acid anion groups are repelled by strong negative charges, thereby reducing the neutralization effect of salt ions on the negative charges of the modified carboxymethyl cellulose sodium salt, inhibiting the salting-out effect, and maintaining the colloidal stability in a high-salt environment; the borax is dissociated in water and forms a borate ester bond with the hydroxyl groups of the modified carboxymethyl cellulose sodium salt under alkaline conditions, thereby constructing a crosslinking network, limiting the free movement of the molecular weight, reducing the chain entanglement under high temperature or high-speed shearing, and improving the viscosity stability. -

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] (1) The introduction of the hydrophobic chain forms a dynamic physical crosslinking network through intermolecular hydrophobic association, effectively resists the compression effect of salt ions on the molecular chain, and maintains the stretched state of the molecular chain in a salt solution.

[0026] (2) The sulfonic acid groups maintain strong ionization characteristics in a high-salt and wide-pH range, maintain colloidal stability through electrostatic repulsion, so that the modified carboxymethyl cellulose sodium salt still maintains stable thickening ability and suspension performance in a high-concentration salt solution (such as NaCl and CaCl2), and is suitable for high-mineralization oil field fracturing fluid and industrial application in a complex salt environment; the large volume and strong polar bond of the sulfonic acid groups endow them with rigidity, inhibit the thermal motion of the molecular chain at high temperature, and reduce the viscosity loss caused by chain segment disentanglement.

[0027] (3) The introduction of the borate ester crosslinking network enables the material to maintain three-dimensional structure stability in a high-temperature environment, so that it still exhibits excellent viscosity retention rate under high-temperature shearing conditions.

[0028] ​(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 by means of 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, which conforms to 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

[0029] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. 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.

[0030] The preparation steps of the hydrophobic intermediate are as follows:

[0031] (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;

[0032] The amount 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;

[0033] (2) Dissolve the monosubstituted intermediate and cocoyl chloride in dichloromethane under an ice water bath at 0 DEG C, drop 3 drops of triethylamine to adjust the pH to neutral, stir for 2 hours, cool, filter, wash and dry to obtain the intermediate 1;

[0034] The amount ratio of the monosubstituted intermediate, cocoyl chloride, dichloromethane and triethylamine is 340 g:195 g:1500 mL:111.3 mL;

[0035] (3) Dissolve the 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 the intermediate 2;

[0036] 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;

[0037] (4) Dissolve the intermediate 2 and p-toluenesulfonyl chloride in dichloromethane, add pyridine, and react at 5°C for 1 h, wash with cold ethyl acetate for 3 times, and dry under vacuum to obtain the hydrophobic intermediate;

[0038] The usage ratio of the intermediate 2, p-toluenesulfonyl chloride, dichloromethane and pyridine is 750 g: 258 g: 3000 mL: 140 mL.

[0039] Example 1: S1, disperse 10 g of carboxymethyl cellulose sodium salt in 250 mL of N-methyl pyrrolidone, add 75 mL of 0.8 mol / L sodium hydroxide solution, stir at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution;

[0040] S2, dissolve 10 g of the hydrophobic intermediate and 0.12 g of tetrabutylammonium bromide in 65 mL of N-methyl pyrrolidone, dropwise add 250 mL of the carboxymethyl cellulose sodium salt solution, react at 50°C for 5 h, add an ice water mixture, adjust the pH to 10, perform silica gel column chromatography, perform ultrafiltration on a 15 kDa membrane for 24 h, and freeze-dry 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;

[0041] S3, disperse 10 g of the modified carboxymethyl cellulose sodium salt in 100 mL of a 0.5% by mass sulfuric acid solution, adjust the pH to 3, add 3 g of sulfamic acid, and react under ultrasonic treatment at 80°C for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt;

[0042] S4, dissolve 10 g of the crude salt-tolerant carboxymethyl cellulose sodium salt and 0.3 g of borax in 100 mL of deionized water, adjust the pH to 9, and stir-react at 60°C for 2 h to obtain a salt-tolerant carboxymethyl cellulose sodium salt;

[0043] Example 2: S1, disperse 10 g of carboxymethyl cellulose sodium salt in 200 mL of N-methyl pyrrolidone, add 50 mL of 0.8 mol / L sodium hydroxide solution, stir at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution;

[0044] S2, 10 g of the hydrophobic intermediate and 0.08 g of tetrabutylammonium bromide were dissolved in 50 mL of N-methylpyrrolidone, and were added dropwise into 220 mL of the carboxymethyl cellulose sodium salt solution, and were reacted at 55 °C for 4 h, an ice water mixture was added, the pH was adjusted to 11, silica gel column chromatography was performed, 15 kDa membrane ultrafiltration was performed for 24 h, and freeze drying was performed to obtain the modified carboxymethyl cellulose sodium salt; the eluent used in the silica gel column chromatography was a mixed solution of ethyl acetate and methanol at a volume ratio of 9:1;

[0045] S3, 10 g of the modified carboxymethyl cellulose sodium salt was dispersed in 80 mL of a 0.5% by mass sulfuric acid solution, the pH was adjusted to 2, 2.5 g of sulfamic acid was added, and reaction was performed under ultrasonic treatment at 80 °C for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt;

[0046] 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 reaction was performed under stirring at 55 °C for 2 h to obtain the salt-tolerant carboxymethyl cellulose sodium salt;

[0047] Example 3: S1, 10 g of the carboxymethyl cellulose sodium salt was dispersed in 300 mL of N-methylpyrrolidone, 100 mL of a 0.8 mol / L sodium hydroxide solution was added, and stirring was performed at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution;

[0048] S2, 10 g of the hydrophobic intermediate and 0.08 g of tetrabutylammonium bromide were dissolved in 50 mL of N-methylpyrrolidone, and were added dropwise into 220 mL of the carboxymethyl cellulose sodium salt solution, and were reacted at 55 °C for 4 h, an ice water mixture was added, the pH was adjusted to 11, silica gel column chromatography was performed, 15 kDa membrane ultrafiltration was performed for 24 h, and freeze drying was performed to obtain the modified carboxymethyl cellulose sodium salt; the eluent used in the silica gel column chromatography was a mixed solution of ethyl acetate and methanol at a volume ratio of 9:1;

[0049] S3, 10 g of the modified carboxymethyl cellulose sodium salt was dispersed in 80 mL of a 0.5% by mass sulfuric acid solution, the pH was adjusted to 2, 2.5 g of sulfamic acid was added, and reaction was performed under ultrasonic treatment at 80 °C for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt;

[0050] 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 reaction was performed under stirring at 55 °C for 2 h to obtain the salt-tolerant carboxymethyl cellulose sodium salt;

[0051] Comparative Example 1

[0052] S1, 10 g of the carboxymethyl cellulose sodium salt was dispersed in 250 mL of N-methylpyrrolidone, 75 mL of a 0.8 mol / L sodium hydroxide solution was added, and stirring was performed at room temperature for 2 h to obtain a carboxymethyl cellulose sodium salt solution;

[0053] S2, 10 g of the hydrophobic intermediate and 0.12 g of tetrabutylammonium bromide were dissolved in 65 mL of N-methylpyrrolidone, and the solution was added dropwise into 250 mL of a carboxymethyl cellulose sodium salt solution, and reacted at 50°C for 5 h, an ice water mixture was added, the pH was adjusted to 10, and column chromatography on silica gel was performed using a mixed solution of ethyl acetate and methanol (volume ratio of 9:1) as an eluent, and the product was ultrafiltered through a 15 kDa membrane for 24 h, and freeze-dried to obtain a modified carboxymethyl cellulose sodium salt;

[0054] 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 at 80°C under ultrasonic treatment for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt.

[0055] The present comparative example differs from Example 1 in that the original step S4 of Example 1 was omitted.

[0056] Comparative Example 2

[0057] S1, 10 g of carboxymethyl cellulose sodium 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 at 80°C under ultrasonic treatment for 3 h to obtain a crude salt-tolerant carboxymethyl cellulose sodium salt;

[0058] 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 mixture was stirred at 60°C for 2 h to obtain a salt-tolerant carboxymethyl cellulose sodium salt.

[0059] The present comparative example differs from Example 1 in that the original steps S1 and S2 of Example 1 were omitted.

[0060] Comparative Example 3

[0061] S1, 10 g of carboxymethyl cellulose sodium was dispersed in 250 mL of N-methylpyrrolidone, 75 mL of a 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;

[0062] S2, 10 g of dodecylbenzenesulfonate and 0.12 g of tetrabutylammonium bromide were dissolved in 65 mL of N-methylpyrrolidone, and the solution was added dropwise into 250 mL of a carboxymethyl cellulose sodium salt solution, and reacted at 50°C for 5 h, an ice water mixture was added, the pH was adjusted to 10, and column chromatography on silica gel was performed using a mixed solution of ethyl acetate and methanol (volume ratio of 9:1) as an eluent, and the product was ultrafiltered through a 15 kDa membrane for 24 h, and freeze-dried to obtain a modified carboxymethyl cellulose sodium salt;

[0063] S3, 10 g of modified carboxymethyl cellulose sodium salt was dispersed in 100 mL of 0.5% 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;

[0064] 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 the salt-tolerant carboxymethyl cellulose sodium salt.

[0065] The difference between the present comparative example and Example 1 is that the hydrophobic intermediate added in original step S2 is not added, but dodecyl benzene sulfonate is added.

[0066] Test:

[0067] I. Salt tolerance test

[0068] The salt-tolerant carboxymethyl cellulose sodium salt prepared in Examples 1-3 and Comparative Examples 1-3 was dissolved in pure water (A), a 10000 ppm NaCl solution (B), a 30000 ppm NaCl solution (C), and a 10000 ppm CaCl2 solution (D) to prepare a 0.5% salt-tolerant carboxymethyl cellulose sodium salt solution. 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:

[0069] Table 1

[0070]

[0071] II. Temperature resistance test

[0072] 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 0.5% salt-tolerant carboxymethyl cellulose sodium salt solution. After swelling and stabilization, the viscosity was measured using a rheometer at a shear rate of 170 s -1 and a temperature of 120°C for 120 min. The test results are shown in Table 2:

[0073] Table 2

[0074]

[0075] III. Conclusion

[0076] Compared with Comparative Examples 1-3, the salt-tolerant carboxymethyl cellulose sodium salt prepared in Examples 1-3 of the present application has excellent salt tolerance and temperature resistance due to the inhibition of salt ion compression effect by hydrophobic association and the synergistic maintenance of high temperature stability by sulfonic acid group and borate ester.

[0077] In the description, references to "one embodiment," "an example," "certain examples" etc. mean that the particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the application. The appearances of an item in various examples or embodiments is not necessarily indicative of a frequency of occurrence in the various examples or embodiments. Moreover, descriptions of well-known methods associated are omitted so as not to obscure the disclosure.

[0078] The foregoing merely illustrates the principles of the application. Various modifications and adaptations will occur to those skilled in the art after consideration of the preceding description. All such modifications and adaptations employing the principles of the application are intended to be within the scope of the claims.

Claims

1. A process for the preparation of a salt resistant sodium carboxymethylcellulose salt, characterized by: The method comprises the following steps: S1, dissolve stearic acid and ethylenediamine in N,N-dimethylformamide at 0℃ ice water bath, add dicyclohexyl carbodiimide and 4-dimethylaminopyridine, stir at 25-30℃ for 6-8h, cool, filter, wash and dry to obtain a monosubstituted intermediate; dissolve the monosubstituted intermediate and coconut acyl chloride in dichloromethane at 0℃ ice water bath, drop in triethylamine to adjust pH to neutral, stir for 2-3h, cool, filter, wash and dry to obtain intermediate 1; dissolve intermediate 1, propylene oxide and tin tetrachloride in toluene, react at 0℃ for 3-4h, add concentrated hydrochloric acid to the above reaction liquid, heat to 35-40℃ for 1-2h, filter, wash and dry to obtain intermediate 2; dissolve intermediate 2 and p-toluenesulfonyl chloride in dichloromethane, add pyridine, react at 0-10℃ for 1h, wash with cold ethyl acetate for 3 times, and dry under vacuum to obtain a hydrophobic intermediate; The stearic acid, ethylenediamine, N,N-dimethylformamide, dicyclohexyl carbodiimide and 4-dimethylaminopyridine are used in a ratio of (280-290)g:(62-68)g:(2000-2270)mL:(247-270)g:(6.1-12.2)g; The monosubstituted intermediate, coconut acyl chloride, dichloromethane and triethylamine are used in a ratio of (330-350)g:(190-200)g:(1400-1600)mL:(108-115)mL; The intermediate 1, propylene oxide, tin tetrachloride, toluene and concentrated hydrochloric acid are used in a ratio of (655-685)g:(210-350)mL:(13-26)g:(2500-2820)mL:(250-330)mL; The intermediate 2, p-toluenesulfonyl chloride, dichloromethane and pyridine are used in a ratio of (740-760)g:(230-287)g:(2800-3200)mL:(120-160)mL; S2, disperse sodium carboxymethyl cellulose in N-methyl pyrrolidone, add sodium hydroxide solution, stir at room temperature for 1-2h to obtain a sodium carboxymethyl cellulose solution; dissolve the hydrophobic intermediate and tetrabutylammonium bromide in N-methyl pyrrolidone, drop in the sodium carboxymethyl cellulose solution, react at 50-55℃ for 3-5h, add ice water mixture, adjust pH to 10-12, perform silica gel column chromatography, perform ultrafiltration through a 10-30kDa membrane for 24h, and freeze-dry to obtain modified sodium carboxymethyl cellulose; S3, disperse the modified sodium carboxymethyl cellulose in a 0.5% sulfuric acid solution, adjust pH to 1-4, add sulfamic acid, and react at 80-100℃ under ultrasonic treatment for 2-3h to obtain crude salt-tolerant sodium carboxymethyl cellulose; dissolve the crude salt-tolerant sodium carboxymethyl cellulose and borax in deionized water, adjust pH to 9, and stir at 55-65℃ for 1-2h to obtain salt-tolerant sodium carboxymethyl cellulose.

2. A process for the preparation of a salt of carboxymethylcellulose sodium salt resistant to salt according to claim 1, characterized by: The amount ratio of sodium carboxymethyl cellulose, N-methyl pyrrolidone and sodium hydroxide solution in step S2 is 10g:(200-300)mL:(50-100)mL.

3. A process for the preparation of a salt of carboxymethylcellulose sodium salt resistant to salt according to claim 1, characterized by: The amount ratio of hydrophobic intermediate, tetrabutylammonium bromide, N-methyl pyrrolidone and sodium carboxymethyl cellulose solution in step S2 is (8-12)g:(0.08-0.15)g:(50-80)mL:(220-280)mL.

4. A process for the preparation of a salt of carboxymethylcellulose sodium salt resistant to salt according to claim 1, characterized by: The eluent used in the silica gel column chromatography in step S2 is a mixed solution of ethyl acetate and methanol with a volume ratio of 9:

1.

5. A process for the preparation of a salt of carboxymethylcellulose sodium salt resistant to salt according to claim 1, characterized by: The amount ratio of modified sodium carboxymethyl cellulose, sulfuric acid solution and sulfamic acid in step S3 is 10g:(80-120)mL:(2.5-3.5)g.

6. A process for the preparation of a salt of carboxymethylcellulose sodium salt resistant to salt according to claim 1, characterized by: The amount ratio of crude salt-tolerant sodium carboxymethyl cellulose, borax and deionized water in step S3 is 10g:(0.2-0.4)g:(80-120)mL.

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