Composite anionic cellulose ether as well as preparation method and application thereof

Abstract

The invention provides composite anionic cellulose ether as well as a preparation method and application thereof. The composite anionic cellulose ether is prepared by etherifying alkalized cellulose through an etherifying agent A and an etherifying agent B in sequence, the etherifying agent A is selected from water-soluble halogenated alkyl sulfonic acid and / or water-soluble halogenated alkyl sulfonate; the etherifying agent B is selected from water-soluble halogenated alkyl carboxylic acid and / or water-soluble halogenated alkyl carboxylate. According to the composite anionic cellulose ether, a sulfonic acid group and a carboxylic acid group are sequentially introduced, so that the composite anionic cellulose ether has relatively high temperature resistance and salt and calcium resistance; the compound can be used as a filtrate reducer for the drilling fluid, can effectively control the filter loss of the drilling fluid, and can improve the salt pollution resistance of the drilling fluid, especially the calcium and magnesium ion pollution resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of drilling fluids, and particularly relates to a composite anionic cellulose ether, a preparation method thereof, and an application thereof. Background Art

[0002] Poly anionic cellulose is a water-dispersible cellulose modified product after introducing anionic groups into the cellulose structure. It has properties such as thickening, dispersing, film-forming, bonding, and protecting colloids, and can be applied to fields such as oil drilling, textile, printing and dyeing, ceramics, coatings, building materials, papermaking, food, sewage treatment, daily chemicals, and medicine. Among them, carboxymethyl cellulose (CMC) and poly anionic cellulose (PAC), as widely used drilling and completion aids, can play roles such as increasing viscosity, improving mud cake quality, and reducing filtration loss in drilling fluids. They are important chemical treatment agents for maintaining the stability of drilling fluid performance, improving the rheology of drilling fluids, reducing the filtration of harmful liquids into the formation, stabilizing the wellbore, ensuring regular well diameter, and protecting oil and gas reservoirs.

[0003] With the exploration and development of deep oil and gas resources in China, higher requirements are placed on the environmental protection, high-temperature resistance, and salt and calcium resistance of treatment agents. Traditional poly anionic cellulose is prepared by an "alkalization and sulfonation two-step process" (the mechanism is referred to in the appendix Figure 1 ), and carboxymethyl is connected to the cellulose structure in the form of an ether oxygen bond. Due to structural limitations, the high-temperature resistance and salt and calcium resistance of poly anionic cellulose are limited. The use temperature is not higher than 150 °C, and the ability to resist divalent and trivalent ions such as calcium and magnesium is relatively low, which greatly limits the application range.

[0004] The high-temperature and salt resistance of cellulose-based treatment agents can be improved through chemical modification. Among them, Chinese Patent CN113322052A (Novel poly anionic cellulose filtration reducer and preparation method thereof) introduces hydrated groups carboxylic acid, hydrophobic groups ester bonds, and vinyl groups through the esterification reaction of cellulose and maleic anhydride (the product structure is referred to in the appendix Figure 2 ). As a filtration reducer for drilling fluids, the hydrophobic groups improve the film-forming property on the wellbore, which is beneficial to improving the mud cake quality and controlling water loss; however, the salt and calcium resistance is poor.

[0005] Chinese Patent CN 107298720A (Preparation method of poly anionic cellulose with high viscosity, high temperature resistance, and low filtration loss) developed a micro-crosslinked modified poly anionic cellulose ether by using a "three-step method" of sodium hydroxide alkalization, sodium chloroacetate etherification, and N,N-dimethylacrylamide crosslinking (the product structure is referred to in the appendix Figure 2) After aging at 150 °C for 16 h, the viscosity retention rate of the sample (3 wt% solution) is 53% - 82%, and the fluid loss in the API standard evaluated brine mud is 8.4 - 16.2 mL. Chinese Patent CN 115873135A (Polyanionic Cellulose and Its Preparation Method and Application) developed a polyanionic cellulose using the "two-step method" of alkalization with sodium hydroxide (potassium) and etherification with a composite etherifying agent (for the product structure, refer to Appendix Figure 2 ) When the addition amount of 4% w / v sodium bentonite base mud is 1% w / v and it is aged at 150 °C for 16 h, the viscosity retention rate is higher than 50%, and the medium-pressure fluid loss is not higher than 16 mL.

[0006] Introducing hydrophobic groups, cross-linked structures, and temperature-resistant groups (sulfonic acid groups) into polyanionic cellulose can improve the temperature resistance of cellulose ether filtrate reducers for drilling fluids. In Patents CN 113322052A and CN 107298720A, the introduced anionic group is a carboxyl group, and the calcium salt resistance is poor. Chinese Patent CN 115873135A uses a composite etherifying agent added simultaneously. However, since the activity of the sulfonic acid group etherifying agent is lower than that of the carboxylic acid group etherifying agent, there is a competitive reaction between the composite etherifying agent and cellulose. Therefore, the introduction rate of the sulfonic acid group in this invention needs to be verified by sulfonation degree and substitution degree, and the temperature resistance and calcium salt resistance of cellulose ether need further study. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a composite anionic cellulose ether and its preparation method and application. This composite anionic cellulose ether has strong temperature resistance and calcium salt resistance and can be used as a filtrate reducer for drilling fluids.

[0008] The present invention provides a composite anionic cellulose ether, which is prepared by successively etherifying alkalized cellulose with etherifying agent A and etherifying agent B.

[0009] The etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates.

[0010] The etherifying agent B is selected from water-soluble haloalkyl carboxylic acids and / or water-soluble haloalkyl carboxylates.

[0011] Preferably, the structural formula of the haloalkyl sulfonic acid group in the etherifying agent A is X1-(CH2) n1 -SO3-, X1 is selected from Cl, Br or I, and n1 is 1 or 2.

[0012] The structural formula of the haloalkyl carboxylic acid group in the etherifying agent B is X2-(CH2) n2 -COO - -, X2 is selected from Cl, Br or I, and n2 is 1 or 2.

[0013] Preferably, the etherifying agent A is selected from one or more of sodium 2-chloroethylsulfonate, sodium 2-bromoethylsulfonate, and sodium chloroethylsulfonate.

[0014] The etherifying agent B is selected from chloroacetic acid or sodium chloroacetate.

[0015] Preferably, the total degree of substitution of the composite anionic cellulose ether is 0.5 - 1.3, and the degree of sulfonation is 0.4 - 0.8.

[0016] The present invention provides a preparation method of a composite anionic cellulose ether, comprising the following steps:

[0017] Under the action of a catalyst, the alkalized cellulose and the etherifying agent A are subjected to a first etherification reaction to obtain an intermediate etherification product; the etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates.

[0018] Then, the etherifying agent B is added for a second etherification reaction to obtain a multi-anionic cellulose ether; the etherifying agent B is selected from water-soluble haloalkyl carboxylic acids and / or water-soluble haloalkyl carboxylates.

[0019] Preferably, the temperature of the first etherification reaction is 70 - 80 °C, and the time is 3 - 7 h;

[0020] The temperature of the second etherification reaction is 60 - 70 °C, and the time is 1 - 3 h.

[0021] Preferably, the alkalized cellulose is prepared according to the following method:

[0022] The cellulose is dispersed in an alcohol solvent, and an aqueous sodium hydroxide solution is added for alkalization reaction to obtain alkalized cellulose;

[0023] The mass concentration of the aqueous sodium hydroxide solution is 20% - 60%, and the molar ratio of cellulose to sodium hydroxide in the aqueous sodium hydroxide solution is (0.05:1) - (2:1);

[0024] The temperature of the alkalization reaction is 10 - 40 °C, and the time is 0.5 - 2 h.

[0025] Preferably, the catalyst is selected from single quaternary ammonium salt catalysts or quaternary ammonium salt composite catalysts;

[0026] The molar ratio of the catalyst to the etherifying agent A is (0.05:1) - (2:1).

[0027] Preferably, after the second etherification reaction, an acid solution is added to adjust the pH value to 7 - 9, and the solvent is removed by centrifugation to obtain the composite anionic cellulose ether.

[0028] The present invention provides an application of the composite anionic cellulose ether described in the above technical solution as a filtration reducer for drilling fluids.

[0029] The present invention provides a composite anionic cellulose ether, which is prepared by successively etherifying alkalized cellulose with etherifying agent A and etherifying agent B; the etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates; the etherifying agent B is selected from water-soluble haloalkyl carboxylic acids and / or water-soluble haloalkyl carboxylates. By successively introducing sulfonic acid groups and carboxylic acid groups, the composite anionic cellulose ether has strong temperature and salt / calcium resistance; and it can be used as a filtration reducer for drilling fluids, which can effectively control the filtration loss of drilling fluids and improve the salt pollution resistance of drilling fluids, especially the ability to resist calcium and magnesium ion pollution. Description of the Drawings

[0030] Figure 1 It is a mechanism diagram of the common "two-step etherification method" for cellulose;

[0031] Figure 2 It is a product structure diagram corresponding to the method for improving cellulose ether treatment agents;

[0032] Figure 3 It is an infrared spectrum diagram of the composite anionic cellulose ether prepared in Example 6 of the present invention. Detailed Embodiments

[0033] The present invention provides a composite anionic cellulose ether, which is prepared by successively etherifying alkalized cellulose with etherifying agent A and etherifying agent B;

[0034] The etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates;

[0035] The etherifying agent B is selected from water-soluble haloalkyl carboxylic acids and / or water-soluble haloalkyl carboxylates.

[0036] In the present invention, the composite anionic cellulose ether is also called polyanionic cellulose ether. The anionic groups in the composite anionic cellulose ether include sulfonic acid groups and carboxylic acid groups. The carboxylic acid groups enhance the hydration, salt resistance and compatibility ability with other treatment agents of the composite anionic cellulose ether, and the sulfonic acid groups are beneficial to improving its temperature resistance, improving the thermal stability of drilling fluids and expanding the scope of use.

[0037] In the present invention, both the etherifying agent A and the etherifying agent B are water-soluble haloanion salts, and the structural general formula is X-(CH2) n-Y; where Y is a carboxylic acid group (-COOH) or a sulfonic acid group (-SO3H); since the electron-withdrawing ability of the sulfonic acid group (-SO3H) is greater than that of the carboxylic acid group (-COOH), compared with the etherifying agent containing a carboxylic acid group, the etherifying agent containing a sulfonic acid group is more likely to undergo side reactions under alkaline conditions (refer to reaction formulas (1), (2), and (3)), consuming alkali and etherifying agent, resulting in a lower utilization rate of raw materials. Since the etherifying agent containing a sulfonic acid group is relatively more expensive, improving the etherification efficiency of related reagents is beneficial to product cost control.

[0038] NaOH + X(CH2) n Y → HO(CH2) n Y + NaX Formula (1

[0039] NaOH + HO(CH2) n Y → NaO(CH2) n Y + H2O Formula (2

[0040] NaO(CH2) n Y + X(CH2) n Y → Y(CH2) n O(CH2) n Y + NaX Formula (3)

[0041] The present invention adopts an etherification process of introducing a sulfonic acid group first and then a carboxylic acid group, so that the ionized cellulose is more likely to be dispersed and the configuration is stretched under the action of solvent molecules and its own electrostatic repulsion, increasing the contact probability with other etherifying agents, which can improve the introduction efficiency of the sulfonic acid group and is beneficial to production cost control.

[0042] The general structural formula of the etherifying agent A is X1-(CH2) n1 -Y1, where X1 is Cl, Br, or I, and Y1 is a carboxyl group; n1 is 1 or 2.

[0043] The general structural formula of the etherifying agent B is X2-(CH2) n2 -Y2,, where X2 is Cl, Br, or I, and Y2 is a sulfonic acid group; n2 is 1 or 2.

[0044] The schematic process of the etherification reaction using the above etherifying agent A and etherifying agent B respectively in the present invention is as follows:

[0045]

[0046] Specifically, the etherifying agent A is selected from one or more of sodium 2-chloroethylsulfonate, sodium 2-bromoethylsulfonate, and sodium chloroethylsulfonate; the etherifying agent B is selected from chloroacetic acid or sodium chloroacetate.

[0047] The total substitution degree of the composite anionic cellulose ether provided by the present invention is 0.8 to 1.3, and the sulfonation degree is 0.4 to 0.8. In specific embodiments, the substitution degree is 1.02 to 1.22, and the sulfonation degree is 0.41 to 0.78.

[0048] The present invention provides a preparation method of a composite anionic cellulose ether, comprising the following steps:

[0049] Under the action of a catalyst, subjecting alkalized cellulose and etherifying agent A to a first etherification reaction to obtain an intermediate etherification product; the etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates;

[0050] Then adding etherifying agent B to conduct a second etherification reaction to obtain a multi-anionic cellulose ether; the etherifying agent B is selected from water-soluble haloalkyl carboxylic acids and / or water-soluble haloalkyl carboxylates.

[0051] In the present invention, under the action of a catalyst, alkalized cellulose and etherifying agent A are subjected to a first etherification reaction to obtain an intermediate etherification product; the etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates. The catalyst in the present invention is a single quaternary ammonium salt catalyst or a quaternary ammonium salt composite catalyst; preferably one or more of tetrabutylammonium bromide, benzyltriethylammonium chloride, tetrabutylammonium chloride, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride. The molar ratio of the catalyst to the etherifying agent A is (0.05:1) to (2:1), preferably 0.05:1 to 0.5:1. In specific embodiments of the present invention, the molar ratio of the catalyst to the etherifying agent A is 0.05:1, 0.1:1, or 0.15:1.

[0052] The alkalized cellulose in the present invention is preferably prepared according to the following method:

[0053] Disperse cellulose in an alcohol solvent, add an aqueous sodium hydroxide solution for alkalization reaction to obtain alkalized cellulose.

[0054] The alcohol solvent in the present invention is selected from one or more of ethanol, isopropanol, and ethylene glycol; the mass ratio of the cellulose to the volume of the alcohol solvent is 10 g:(100 - 300) mL, preferably 10 g:(100 - 200) mL. The present invention preferably conducts the above alkalization reaction under a protective atmosphere; the protective atmosphere can be a protective atmosphere well-known to those skilled in the art without special limitation, such as nitrogen. The cellulose in the present invention is refined cotton powder with a polymerization degree of 1001.

[0055] In the present invention, the mass concentration of the sodium hydroxide aqueous solution is 20% to 60%, preferably 30% to 50%; in specific embodiments, the mass concentration of the sodium hydroxide aqueous solution is 30%, 40% or 50%. The molar ratio of cellulose to sodium hydroxide in the sodium hydroxide aqueous solution is (0.05:1) to (2:1); in specific embodiments, the mass ratio of cellulose to sodium hydroxide is 1:1, or 1:2 or 1:3. The temperature of the alkalization reaction is 10 to 40 °C, and the time is 0.5 to 2 h. In specific embodiments, the temperature of the alkalization reaction is 20 °C, 25 °C or 30 °C; the time of the alkalization reaction is 0.5 h, 1 h or 2 h.

[0056] In the present invention, the molar ratio of the etherifying agent A to cellulose is 0.5:1 to 2:1. In specific embodiments, the molar ratio of the etherifying agent A to cellulose is 0.5:1, or 1:1, or 1.5:1.

[0057] In the present invention, the temperature of the first etherification reaction is 70 to 80 °C, and the time is 3 to 7 h; in specific embodiments, the temperature of the first etherification reaction is 70 °C, 75 °C or 80 °C; the time of the first etherification reaction is 3 h, 4 h or 6 h.

[0058] After the first etherification reaction is completed, it is preferred in the present invention to cool down to 40 to 50 °C, and then add the etherifying agent B to carry out the second etherification reaction; the molar ratio of the etherifying agent B to cellulose is 0.5:1 to 2:1; in specific embodiments, the molar ratio of the etherifying agent B to cellulose is specifically 1:1, or 1.5:1, or 2:1.

[0059] The temperature of the second etherification reaction is 60 to 70 °C, and the time is 1 to 3 h. In specific embodiments, the temperature of the second etherification reaction is 60 °C, 65 °C or 70 °C; the time is 1 h, 2 h or 3 h.

[0060] After the second etherification reaction is completed in the present invention, it is preferred to add an acid solution to adjust the pH value to 7 to 9, and centrifuge to remove the solvent to obtain a polyanionic cellulose ether. In the present invention, it is preferred to use one or more of hydrochloric acid solution, acetic acid solution and sulfuric acid solution. After centrifugation, it is preferred in the present invention to wash with an aqueous alcohol solution, and dry after centrifugation to obtain a composite anionic cellulose ether.

[0061] The preparation method provided by the present invention has simple process, low production cost, high production efficiency, stable product quality, and is beneficial to application.

[0062] The present invention also provides an application of the composite anionic cellulose ether described in the above technical solution as a filtration reducer for drilling fluids.

[0063] The compound anionic cellulose ether can effectively control the filtration loss of the drilling fluid while improving the salt pollution resistance of the drilling fluid, especially the ability to resist calcium and magnesium ion pollution. Compared with carboxymethyl cellulose and sulfonated cellulose used in drilling fluids, the multi-anionic cellulose provided by the present invention has obvious cost-performance advantages. It not only improves the temperature resistance and salt resistance, but also reduces the product cost.

[0064] The drilling fluid described in the present invention is fresh water drilling fluid, saturated salt water drilling fluid or calcium chloride drilling fluid.

[0065] The present invention preferably adds a compound anionic cellulose ether with a mass fraction of 0.5% - 2% to the above-mentioned drilling fluid.

[0066] In order to further illustrate the present invention, the following examples are used to describe in detail a compound anionic cellulose ether provided by the present invention, its preparation method and application, but they should not be construed as limiting the protection scope of the present invention.

[0067] Example 1

[0068] Under the conditions of stirring and nitrogen protection, 10 g of refined cotton powder (degree of polymerization is 1001) is added to 200 mL of ethanol solvent, and then 8.23 g of sodium hydroxide solution with a mass concentration of 30% is added. The alkalization reaction is carried out in a water bath at 20 °C for 0.5 h; 2-bromoethanesulfonic acid sodium (6.5 g, 31 mmol) and tetrabutylammonium bromide (0.99 g, 3.0 mmol) with a molar ratio of etherifying agent, catalyst to refined cotton of 0.5:0.05:1 are added. The temperature is raised to 70 °C, and after maintaining the etherification reaction for 3 h, the temperature is lowered to 50 °C; then chloroacetic acid (5.83 g, 62 mmol) with a molar ratio of 1:1 to refined cotton is added, and the temperature is raised to the etherification reaction temperature of 60 °C and the reaction is maintained for 1 h. After the reaction is completed, it is neutralized to a pH value of 7 - 9 with hydrochloric acid solution, then the reactant is centrifuged to separate the organic solvent, and then repeatedly washed and centrifuged with ethanol solution, and finally dried in a vacuum drying oven to obtain multi-anionic cellulose ether.

[0069] Example 2

[0070] Under stirring and nitrogen protection conditions, 10 g of refined cotton powder (degree of polymerization is 1001) was added to 150 mL of ethanol solvent, and then 12.3 g of sodium hydroxide solution with a mass concentration of 40% was added. The alkalization reaction was carried out in a water bath at 25 °C for 1.0 h; 2-chloroethylsulfonate (11.36 g, 68 mmol) and benzyltriethylammonium chloride (1.4 g, 6.0 mmol) with a molar ratio of etherifying agent, catalyst to refined cotton of 1:0.1:1 were added. The temperature was raised to 75 °C, and the etherification reaction was maintained for 4 h, then the temperature was lowered to 50 °C; then chloroacetic acid (3.9 g, 40 mmol) with a molar ratio of 3:2 to refined cotton was added, and the temperature was raised to the etherification reaction temperature of 65 °C, and the reaction was maintained for 2 h. After the reaction was completed, it was neutralized with hydrochloric acid solution to a pH value of 7-9, then the reactant was centrifuged to separate the organic solvent, and then repeatedly washed and centrifuged with ethanol solution. Finally, it was dried in a vacuum drying oven to obtain polyanionic cellulose ether.

[0071] Example 3

[0072] Under stirring and nitrogen protection conditions, 10 g of refined cotton powder (degree of polymerization is 1001) was added to 100 mL of ethanol solvent, and then 14.8 g of sodium hydroxide solution with a mass concentration of 50% was added. The alkalization reaction was carried out in a water bath at 30 °C for 2.0 h; 2-chloroethylsulfonate (17.0 g, 100 mmol) and tetradecyltrimethylammonium chloride (2.69 g, 9.2 mmol) with a molar ratio of etherifying agent, catalyst to refined cotton of 1.5:0.15:1 were added. The temperature was raised to 80 °C, and the etherification reaction was maintained for 6 h, then the temperature was lowered to 50 °C; then chloroacetic acid (2.92 g, 30 mmol) with a molar ratio of 2:1 to refined cotton was added, and the temperature was raised to the etherification reaction temperature of 70 °C, and the reaction was maintained for 3 h. After the reaction was completed, it was neutralized with hydrochloric acid solution to a pH value of 7-9, then the reactant was centrifuged to separate the organic solvent, and then repeatedly washed and centrifuged with ethanol solution. Finally, it was dried in a vacuum drying oven to obtain polyanionic cellulose ether.

[0073] Example 4

[0074] Under stirring and nitrogen protection, 10 g of refined cotton powder (degree of polymerization is 1001) was added to 100 mL of ethanol solvent, and then 12.3 g of sodium hydroxide solution with a mass concentration of 40% was added. The alkalization reaction was carried out in a water bath at 25 °C for 1.0 h; 2-chloroethylsulfonate (17.0 g, 60 mmol) and tetradecyltrimethylammonium chloride (2.69 g, 9.2 mmol) with a molar ratio of etherifying agent, catalyst to refined cotton of 1.5:0.15:1 were added. The temperature was raised to 80 °C, and after maintaining the etherification reaction for 4 h, the temperature was lowered to 50 °C; then sodium chloroacetate (3.58 g, 38 mmol) with a molar ratio of 2:1 to refined cotton was added, and the temperature was raised to the etherification reaction temperature of 70 °C and the reaction was maintained for 3 h. After the reaction ended, it was neutralized to a pH value of 7-9 with hydrochloric acid solution, then the reactant was centrifuged to separate the organic solvent, and then repeatedly washed and centrifuged with ethanol solution. Finally, it was dried in a vacuum drying oven to obtain polyanionic cellulose ether.

[0075] Example 5

[0076] Under stirring and nitrogen protection, 10 g of refined cotton powder (degree of polymerization is 1001) was added to 100 mL of ethanol solvent, and then 12.3 g of sodium hydroxide solution with a mass concentration of 40% was added. The alkalization reaction was carried out in a water bath at 25 °C for 1.0 h; 2-chloroethylsulfonate (17.0 g, 60 mmol) and benzyltriethylammonium chloride (2.1 g, 9.2 mmol) with a molar ratio of etherifying agent, catalyst to refined cotton of 1.5:0.15:1 were added. The temperature was raised to 80 °C, and after maintaining the etherification reaction for 6 h, the temperature was lowered to 50 °C; then sodium chloroacetate (3.58 g, 38 mmol) with a molar ratio of 2:1 to refined cotton was added, and the temperature was raised to the etherification reaction temperature of 70 °C and the reaction was maintained for 3 h. After the reaction ended, it was neutralized to a pH value of 7-9 with hydrochloric acid solution, then the reactant was centrifuged to separate the organic solvent, and then repeatedly washed and centrifuged with ethanol solution. Finally, it was dried in a vacuum drying oven to obtain polyanionic cellulose ether.

[0077] Example 6

[0078] Under stirring and nitrogen protection, 10 g of refined cotton powder (degree of polymerization: 1001) was added to 100 mL of ethanol solvent, and then 12.3 g of sodium hydroxide solution with a mass concentration of 40% was added. The alkalization reaction was carried out in a water bath at 25 °C for 1.0 h. 2-chloroethylsulfonate sodium (11.36 g, 68 mmol) and benzyltriethylammonium chloride (1.4 g, 6.1 mmol) with a molar ratio of etherifying agent, catalyst to refined cotton of 1.0:0.1:1 were added. The temperature was raised to 80 °C, and the etherification reaction was maintained for 6 h, then the temperature was lowered to 50 °C. Then sodium chloroacetate (3.58 g, 38 mmol) with a molar ratio of 2:1 to refined cotton was added, and the temperature was raised to the etherification reaction temperature of 65 °C, and the reaction was maintained for 3 h. After the reaction was completed, it was neutralized with hydrochloric acid solution to a pH value of 7-9, then the reactant was centrifuged to separate out the organic solvent, and then repeatedly washed and centrifuged with ethanol solution, and finally dried in a vacuum drying oven to obtain polyanionic cellulose ether.

[0079] Comparative Example 1

[0080] Under stirring and nitrogen protection, 10 g of refined cotton powder (degree of polymerization: 1001) was added to 200 mL of ethanol solvent, and then 8.23 g of sodium hydroxide solution with a mass concentration of 30% was added. The alkalization reaction was carried out in a water bath at 20 °C for 0.5 h. Chloroacetic acid (5.83 g, 62 mmol) with an addition amount with a molar ratio of 1:1 to refined cotton was added. The temperature was raised to the etherification reaction temperature of 60 °C, and the reaction was maintained for 1 h. After the reaction was completed, it was neutralized with hydrochloric acid solution to a pH value of 7-9, then the reactant was centrifuged to separate out the organic solvent, and then repeatedly washed and centrifuged with ethanol solution, and finally dried in a vacuum drying oven to obtain carboxymethyl cellulose ether.

[0081] Comparative Example 2

[0082] Under stirring and nitrogen protection, 10 g of refined cotton powder (degree of polymerization: 1001) was added to 200 mL of ethanol solvent, and then 8.23 g of sodium hydroxide solution with a mass concentration of 30% was added. The alkalization reaction was carried out in a water bath at 20 °C for 0.5 h. 2-bromoethylsulfonate sodium (5.68 g, 27 mmol) and tetrabutylammonium bromide (0.99 g, 99 mmol) with a molar ratio of etherifying agent, catalyst to refined cotton of 0.5:0.05:1 were added. The temperature was raised to 70 °C, and the etherification reaction was maintained for 3 h. After the reaction was completed, it was neutralized with hydrochloric acid solution to a pH value of 7-9, then the reactant was centrifuged to separate out the organic solvent, and then repeatedly washed and centrifuged with ethanol solution, and finally dried in a vacuum drying oven to obtain sulfonated cellulose ether.

[0083] Comparative Example 3

[0084] Under stirring and nitrogen protection, 10 g of refined cotton powder (degree of polymerization is 1001) was added to 200 mL of ethanol solvent, and then 8.23 g of sodium hydroxide solution with a mass concentration of 30% was added. The alkalization reaction was carried out in a water bath at 20 °C for 0.5 h; chloroacetic acid (5.83 g, 62 mmol) with a molar ratio of 1:1 to the refined cotton was added, and the temperature was raised to the etherification reaction temperature of 60 °C and the reaction was maintained for 1 h. Then, 2-bromoethanesulfonic acid sodium salt (6.5 g, 31 mmol) and tetrabutylammonium bromide (0.99 g, 3.0 mmol) with a molar ratio of 0.5:0.05:1 to the refined cotton were added as etherifying agent and catalyst, and the temperature was further raised to the reaction temperature of 70 °C and the reaction was maintained for 3 h. After the reaction was completed, it was neutralized with hydrochloric acid solution to a pH value of 7-9, and then the reactant was centrifuged to separate the organic solvent, and then washed and centrifuged repeatedly with ethanol solution, and finally dried in a vacuum drying oven to obtain polyanionic cellulose ether.

[0085] The present invention analyzed the material ratio and substitution degree of the examples and comparative examples, and the results are shown in Table 1:

[0086] Table 1 Material ratio and substitution degree of the products prepared in the comparative examples and examples

[0087]

[0088] The modified cellulose ether obtained in Example 6 was analyzed by infrared spectroscopy to obtain its infrared spectrogram, as Figure 3 shown. It can be seen from Figure 3 that cellulose has a relatively broad stretching vibration peak of associated hydroxyl group (-OH) at 3020 - 3600 cm -1 , and the peak becomes narrower after modification. At the same time, cellulose has a stretching vibration of secondary alcohol group (-CHR1OH) at 1055.2 cm -1 , and a bending vibration of hydroxyl group (-OH) at 1280.1 cm -1 . In the infrared spectrogram of the composite anionic cellulose ether, the corresponding peaks become weak or even disappear, which is consistent with the fact that a large number of hydroxyl groups are converted into ether oxygen bonds during the etherification reaction; for the C-H stretching vibration peak at 2898.9 cm -1 , after modification, two obvious peaks at 2923.2 cm -1 and 2849.6 cm -1 appear, while the two peaks at 2960.1 cm -1 and 2885.4 cm -1 are not obvious, and there is an absorption peak near 716.5 cm -1 , indicating that there are multiple methylene groups (CH2) in the structure of the modified cellulose, which is in line with the introduction of more methylene groups during the etherification reaction; cellulose has a peak at 1637.5 cm -1There is a medium-intensity carbonyl (C=O) stretching vibration peak, which may originate from the open-chain structure of cellulose. The carbon atom at the C(1) position becomes an aldehyde group. After modification, 1636.8 cm -1 、1620.5 cm -1 Two new carbonyl peaks appear, which can be attributed to the stretching vibration peaks of the carboxyl group (-COOH) introduced by the etherification reaction; at 1261.3 cm -1 、1017.4 cm -1 、792.2 cm -1 Absorption peaks of three sulfur-containing groups, namely C-O-SO3, S=O, and C-O-S, appear. At 1261.3 cm -1 、1017.4 cm -1 The peaks at are attributed to the symmetric and asymmetric stretching vibration peaks of S=O, and at 792.2 cm -1 The peak at is attributed to the C-O-SO3 group; at 1325.5 cm -1 is the C-H bending vibration of the glucose ring, and at 1113.7 cm -1 is the C-O-C stretching vibration peak of the cyclic ether structure, and at 1055.2 cm -1 The characteristic absorption of cellulose ether β-(1,4)-dianhydride bond. The infrared spectrogram shows that on the basis of retaining the characteristic structure of cellulose β-(1,4)-dianhydride bond, carboxylic acid groups and sulfonic acid groups are successfully introduced into the cellulose structure in the form of ether oxygen bonds through the etherification reaction.

[0089] To verify that the invention product has strong abilities of resisting temperature, salt, and high-valent metal ions, the following various drilling fluid base slurries are prepared for comparison of drilling fluid properties.

[0090] (1) Performance evaluation in fresh water drilling fluid:

[0091] Add 0.56 g of anhydrous sodium carbonate and 16 g of bentonite for preparing drilling fluid (in accordance with the industry standard SY / T 5490-2016, the bentonite for preparing drilling fluid test is uniformly the bentonite for preparing drilling fluid of Bohai Drilling) into 400 mL of tap water, stir at high speed for 20 min, and cure at room temperature for 24 h to obtain a fresh water base slurry. Add 0.5% dosage of the polyanionic cellulose ether products obtained in Examples 1-6 above and the cellulose ether products obtained in Comparative Examples 1-3 to the fresh water base slurry, stir at high speed for 20 min, and respectively obtain fresh water drilling fluids. Age at 150 °C for 16 h under high temperature rolling, then take out, cool to room temperature, stir at high speed for 5 min, and respectively measure the drilling fluid properties. The results are shown in Table 2.

[0092] (2) Performance evaluation in saturated salt water drilling fluid:

[0093] Add 144 g of sodium chloride to 400 mL of 4% fresh water base slurry, stir at high speed for 20 min, cure at room temperature for 24 h to obtain saturated brine base slurry. Add the polyanionic cellulose ether products obtained in Examples 1-6 and the cellulose ether products obtained in Comparative Examples 1-3 with an addition amount of 2.0% to the saturated brine base slurry, stir at high speed for 20 min to obtain saturated brine drilling fluids respectively. Age at 150 °C under high temperature rolling for 16 h, then take out, cool to room temperature, stir at high speed for 5 min, and measure the drilling fluid properties respectively. The results are shown in Table 2.

[0094] (3) Performance evaluation in calcium chloride drilling fluid:

[0095] Add 8 g of calcium chloride to 400 mL of 4% fresh water base slurry, stir at high speed for 20 min, cure at room temperature for 24 h to obtain 3% calcium chloride base slurry. Add the polyanionic cellulose ether products obtained in Examples 1-6 and the cellulose ether products obtained in Comparative Examples 1-3 with an addition amount of 2.0% to the 3% calcium chloride base slurry, stir at high speed for 20 min to obtain calcium chloride drilling fluids respectively. Age at 150 °C under high temperature rolling for 16 h, then take out, cool to room temperature, stir at high speed for 5 min, and measure the drilling fluid properties respectively. The results are shown in Table 2.

[0096] Table 2 Comparison of product performances of examples and comparative examples

[0097]

[0098]

[0099] As can be seen from Table 2, the medium pressure filtration loss and apparent viscosity of the polyanionic cellulose obtained in Examples 1 to 6 after high-temperature aging at 150°C in fresh water pulp, saturated salt pulp, and calcium chloride pulp are significantly superior to those of carboxymethyl cellulose in Comparative Example 1 and Comparative Example 3. Compared with the sulfonated cellulose in Comparative Example 2, the filtration loss reduction performance also has advantages. Moreover, from the analysis of the material ratios and substitution degrees of each example in Table 1, it can be known that the feeding cost of the etherifying agent in Example 1 is lower than that of the etherifying agent in Comparative Example 2 (the cost of etherifying agent B is much lower than that of etherifying agent A). This shows that the synergistic effect of the sulfonic acid group and carboxylic acid group in the product of this invention not only exhibits good temperature resistance, salt resistance, and calcium resistance, but also reduces the raw material cost and improves the cost performance of the product compared with the single introduction of the temperature-resistant sulfonic acid group. Compared with Comparative Example 3, the total substitution degree and sulfonation degree in Example 1 are larger because the etherification reaction activity order of hydroxyl groups in cellulose AGU is C6>C2>C3, and the etherification reaction is a heterogeneous reaction. Since the volume of the sulfonic acid group in the etherifying agent is larger than that of the carboxyl group, the carboxylic acid etherifying agent has higher activity. The etherifying agent preferentially reacts with the C6-position hydroxyl group with higher activity, and sulfonation first improves the introduction rate of the sulfonic acid group with lower etherification activity, with less impact on the introduction rate of the carboxylic acid group with higher activity. However, if carboxylation is carried out first, the hydroxyl groups with higher activity are etherified, which is not conducive to the subsequent etherification reaction of the sulfonic acid group with lower activity, resulting in lower total substitution degree and sulfonation degree.

[0100] As can be seen from the above examples, the present invention provides a composite anionic cellulose ether, which is prepared by successively etherifying alkalized cellulose with etherifying agent A and etherifying agent B; the etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates; the etherifying agent B is selected from water-soluble haloalkyl carboxylic acids and / or water-soluble haloalkyl carboxylates. By successively introducing sulfonic acid groups and carboxylic acid groups, this composite anionic cellulose ether has strong temperature resistance and salt and calcium resistance; and it can be used as a filtration loss reducer for drilling fluids, which can effectively control the filtration loss of drilling fluids and improve the salt contamination resistance of drilling fluids, especially the resistance to calcium and magnesium ion contamination. The experimental results show that when 0.5% of the composite anionic cellulose ether is added to the fresh water base slurry, the medium pressure filtration loss is 15.0 - 17.4 mL, and the apparent viscosity is 16 - 35 mPa·s; when 2.0% of the composite anionic cellulose ether is added to the saturated salt water slurry, the medium pressure filtration loss is 10.0 - 12.4 mL, and the apparent viscosity is 4.0 - 5.5 mPa·s; when 2% of the composite anionic cellulose ether is added to the 3% calcium chloride slurry, the medium pressure filtration loss is 44.0 - 54.0 mL, and the apparent viscosity is 3.5 - 6.0 mPa·s.

[0101] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A composite anionic cellulose ether is prepared by successively etherifying alkalized cellulose with etherifying agent A and etherifying agent B; The etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates; The etherifying agent B is selected from water-soluble haloalkyl carboxylic acids and / or water-soluble haloalkyl carboxylates.

2. The composite anionic cellulose ether according to claim 1, wherein The structural formula of the haloalkylsulfonic group in the etherifying agent A is X1-(CH2) n1 -SO3 - , X1 is selected from Cl, Br or I, and n1 is 1 or 2; The structural formula of the haloalkyl carboxyl group in the etherifying agent B is X2-(CH2) n2 -COO - , X2 is selected from Cl, Br or I, and n2 is 1 or 2.

3. The composite anionic cellulose ether according to claim 1, characterized in that, The etherifying agent A is selected from one or more of sodium 2-chloroethanesulfonate, sodium 2-bromoethanesulfonate, and sodium chloroethanesulfonate; The etherifying agent B is selected from chloroacetic acid or sodium chloroacetate.

4. The composite anionic cellulose ether according to claim 1, characterized in that, The total substitution degree of the composite anionic cellulose ether is 0.5 to 1.3, and the sulfonation degree is 0.4 to 0.

8.

5. A preparation method of a composite anionic cellulose ether, comprising the following steps: Under the action of a catalyst, the alkalized cellulose and the etherifying agent A are subjected to a first etherification reaction to obtain an intermediate etherification product; The etherifying agent A is selected from water-soluble haloalkyl sulfonic acids and / or water-soluble haloalkyl sulfonates; Then, the etherifying agent B is added for a second etherification reaction to obtain a multi-anionic cellulose ether; the etherifying agent B is selected from water-soluble haloalkyl carboxylic acids and / or water-soluble haloalkyl carboxylates.

6. The preparation method according to claim 5, characterized in that, The temperature of the first etherification reaction is 70 to 80 °C, and the time is 3 to 7 h; The temperature of the second etherification reaction is 60 to 70 °C, and the time is 1 to 3 h.

7. The preparation method according to claim 5, wherein The alkalized cellulose is prepared by the following method: The cellulose is dispersed in an alcohol solvent, and an aqueous sodium hydroxide solution is added for alkalization reaction to obtain alkalized cellulose; The mass concentration of the aqueous sodium hydroxide solution is 20% to 60%, and the molar ratio of cellulose to sodium hydroxide in the aqueous sodium hydroxide solution is (0.05:1) to (2:1); The temperature of the alkalization reaction is 10 to 40 °C, and the time is 0.5 to 2 h.

8. The preparation method according to claim 5, characterized in that, The catalyst is selected from single quaternary ammonium salt catalysts or quaternary ammonium salt composite catalysts; The molar ratio of the catalyst to the etherifying agent A is (0.05:1) to (2:1).

9. The preparation method according to claim 5, characterized in that, After the second etherification reaction is completed, an acid solution is added to adjust the pH value to 7 to 9, and the solvent is removed by centrifugation to obtain the composite anionic cellulose ether.

10. Use of the composite anionic cellulose ether according to any one of claims 1 to 4 as a fluid loss reducer for drilling fluids.

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