Crosslinked graft copolymers, processes for their preparation and use

Abstract

The application relates to the technical field of drilling fluid treating agents, and discloses a crosslinking graft copolymer as well as a preparation method and application thereof. The crosslinking graft copolymer contains: molecular chain A from a lignin sulfonate, molecular chain B from a proanthocyanidin, a connecting group C from an aldehyde crosslinking agent, structural unit D shown in formula (1) and structural unit E shown in formula (2); wherein the molecular chain A and the molecular chain B are connected through the connecting group C, the connecting group C is connected with carbon atoms on benzene rings contained in the molecular chain A and the molecular chain B; and the structural unit D and the structural unit E are grafted on hydroxyl groups of the molecular chain A and the molecular chain B. The crosslinking graft copolymer can keep excellent viscosity reduction performance under a high-temperature environment of 180 DEG C, is non-toxic and easy to degrade, and cannot cause environmental hazards.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid treatment agents, specifically to cross-linked graft copolymers, their preparation methods, and applications. Background Technology

[0002] In recent years, international research has focused on anionic polymer viscosity reducers using maleic anhydride (MA), sodium allyl sulfonate (AS), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as raw materials, as well as zwitterionic polymer viscosity reducers with cationic groups and organophosphorus viscosity reducers. Domestic research on drilling fluid viscosity reducers similarly focuses primarily on the modification of natural polymer materials and the synthesis of polymers.

[0003] In the field of natural polymer modification, Wang Song et al. prepared the viscosity reducer PNK by graft copolymerization of lignin sulfonate and acrylamide, followed by metal ion complexation and sulfonation treatment, achieving a temperature resistance of over 200℃. Wei Xiaoming et al. synthesized the lignin-based viscosity reducer MGAC-1 through a series of modification reactions including condensation of lignin sulfonate with formaldehyde, graft copolymerization, and metal ion complexation, achieving a temperature resistance of up to 180℃. Wang Zhonghua et al. prepared a tannic acid graft copolymer by graft copolymerization of AMPS and AA using tannic acid as raw material, achieving a temperature resistance of over 160℃. Zhang Jianyun et al. used taratanin, an extract from tara pod powder, through sulfonation and Fe... 2+ SMT-T, a viscosity reducer, was prepared by complexation, achieving a viscosity reduction rate of over 84% at 180℃-220℃. Zhang Liming et al. crosslinked lignin sulfonic acid and tannin extracts with formaldehyde; the product then reacted with Fe... 2+ The complexation process forms FTLS, a drilling fluid viscosity reducer, which has better viscosity reduction performance and temperature and salt resistance compared to traditional FCLS.

[0004] In the field of synthetic polymers, Huang Jinjun et al. prepared an amphoteric viscosity reducer, THIN, using acrylic acid, sodium propylene sulfonate, AMPS, and cationic monomers as raw materials. THIN exhibits excellent temperature resistance up to 220℃, good salt and calcium resistance, and superior viscosity-reducing effects compared to traditional drilling fluid viscosity reducers XY-27 and FCLS. Wang Zhonghua et al. synthesized an AMPS / DMAM / AM copolymer drilling fluid viscosity reducer using AMPS, acrylamide, and NN-dimethylacrylamide as raw materials and an oxidation-reduction initiation system. This copolymer exhibits good viscosity reduction, temperature and salt resistance, and a temperature resistance up to 210℃. Hu Caizhi et al. prepared an AA-IPPA copolymer using acrylic acid and isopropylene phosphonic acid (IPPA), which demonstrates good viscosity-reducing properties and a temperature resistance up to 200℃. Long Zhu et al. developed a method for synthesizing drilling fluid viscosity reducers using AMPS, AA, and DMDAAC from alkaline pulping wastewater as raw materials, with the product exhibiting a temperature resistance up to 150℃. Luo Yue et al. synthesized sulfonated styrene-maleic anhydride polymer (SSMA) using toluene and acetone as solvents and styrene and maleic anhydride as main raw materials, achieving a viscosity reduction rate of over 40% and a temperature resistance of 150℃. Liao Jiuming et al. prepared a novel organophosphorus viscosity reducer using poly(1,3-diamino-2-hydroxypropane) and hydroxymethylphosphine as raw materials, whose temperature and salt resistance properties were superior to FCLS. Shao Hui et al. prepared a non-toxic, easily degradable, green viscosity reducer using L-aspartic acid as a raw material, also achieving a good viscosity reduction effect, but its temperature resistance was only 120℃.

[0005] Existing drilling fluid viscosity reducers, both domestically and internationally, are mainly divided into two categories: modified natural polymers and synthetic polymers. Synthetic polymer viscosity reducers offer excellent temperature resistance but are difficult to degrade, thus lacking environmental friendliness. Modified polymer viscosity reducers primarily involve grafting acrylamide polymers onto natural polymers such as lignin, sacrificing some environmental performance in pursuit of higher temperature resistance. Currently, drilling fluid viscosity reducers face a dilemma: achieving both environmental friendliness and temperature resistance is difficult. Traditional modified natural macromolecular viscosity reducers, such as modified lignin and modified humic acid, while offering good environmental performance, lack sufficient temperature resistance, making them unsuitable for high-temperature deep and ultra-deep well drilling. Synthetic polymer viscosity reducers, on the other hand, offer higher temperature resistance but have poor biodegradability and are costly. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of existing drilling fluid viscosity reducers that are difficult to balance environmental protection and temperature resistance, and to provide cross-linked graft copolymers, their preparation methods and applications. These cross-linked graft copolymers can play an excellent viscosity-reducing role in high-temperature environments at the bottom of the well, and are non-toxic, easily degradable, and will not cause harm to the environment. They can be used as viscosity reducers in the formulation of water-based drilling fluids.

[0007] To achieve the above objectives, a first aspect of the present invention provides a crosslinked graft copolymer comprising: a molecular chain A derived from lignin sulfonate, a molecular chain B derived from proanthocyanidins, a linking group C derived from an aldehyde crosslinking agent, a structural unit D represented by formula (1), and a structural unit E represented by formula (2); wherein the molecular chains A and B are connected by the linking group C, and the linking group C is bonded to carbon atoms on benzene rings contained in each of the molecular chains A and B; and the structural units D and E are grafted onto the hydroxyl groups of the molecular chains A and B.

[0008]

[0009] Among them, R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C10 straight-chain or branched alkyl groups;

[0010] X is a C1-C10 straight-chain or branched alkylene group;

[0011] M is hydrogen or an alkali metal.

[0012] A second aspect of the present invention provides a method for preparing a crosslinked graft copolymer, the method comprising the following steps:

[0013] (1) The lignin sulfonate and proanthocyanidins were cross-linked with an aldehyde cross-linking agent to obtain an intermediate product;

[0014] (2) In the presence of an initiator, the intermediate product is grafted with vinyl monomer I and vinyl monomer II to obtain a crosslinked graft copolymer.

[0015] A third aspect of the present invention provides a crosslinked graft copolymer prepared by the aforementioned preparation method.

[0016] A fourth aspect of the present invention provides the application of the aforementioned crosslinked graft copolymer in water-based drilling fluids; preferably, the crosslinked graft copolymer is used as a drilling fluid viscosity reducer.

[0017] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0018] 1) The cross-linked graft copolymer of this invention uses lignin sulfonate and proanthocyanidins, two natural biodegradable materials, as raw materials, giving it non-toxic, easily degradable, and environmentally friendly properties. Lignosulfonate is rich in sulfonic acid groups, which allows the product to form a thick hydration layer on the bentonite surface of the drilling fluid, thereby breaking down the bentonite network structure and reducing the viscosity of the drilling fluid. Proanthocyanidins are rich in phenolic hydroxyl groups, giving the product strong adsorption properties on the bentonite surface and making it difficult to desorb at high temperatures. The organic combination of these two raw materials enables the product to simultaneously possess excellent viscosity-reducing and adsorption properties under high-temperature conditions.

[0019] 2) This invention uses an aldehyde crosslinking agent to moderately crosslink lignin sulfonate rich in sulfonic acid groups and proanthocyanidins rich in phenolic hydroxyl groups, which enables the crosslinked product to simultaneously possess temperature resistance, adsorption, dispersibility, and environmental friendliness, making it particularly suitable as a high-temperature resistant and environmentally friendly viscosity reducer for water-based drilling fluids; by grafting and copolymerizing the two crosslinked natural macromolecules with two vinyl monomers, the temperature and salt resistance can be further improved, and the adsorption performance on the bentonite surface can be enhanced.

[0020] 3) The cross-linked graft copolymer of the present invention can be used as a viscosity reducer for water-based drilling fluids. It exhibits excellent viscosity-reducing properties at high temperatures, with a temperature resistance exceeding 180°C, a viscosity reduction rate exceeding 90%, and biotoxicity >90000 mg / L. It also has a biodegradable BOD5 / COD ratio. Cr >0.28. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] Through extensive research, the inventors of this invention discovered that by moderately crosslinking lignin sulfonates rich in sulfonic acid groups with proanthocyanidins rich in phenolic hydroxyl groups, the crosslinked product can simultaneously possess temperature resistance, adsorption, dispersibility, and environmental friendliness, making it particularly suitable as a high-temperature resistant and environmentally friendly viscosity reducer for water-based drilling fluids. This led to the completion of this invention.

[0023] A first aspect of the present invention provides a crosslinked graft copolymer comprising: a molecular chain A derived from lignin sulfonate, a molecular chain B derived from proanthocyanidins, a linking group C derived from an aldehyde crosslinking agent, a structural unit D represented by formula (1), and a structural unit E represented by formula (2); wherein the molecular chains A and B are connected by the linking group C, and the linking group C is bonded to carbon atoms on benzene rings contained in each of the molecular chains A and B; and the structural units D and E are grafted onto the hydroxyl groups of the molecular chains A and B.

[0024]

[0025] Among them, R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C10 straight-chain or branched alkyl groups;

[0026] X is a C1-C10 straight-chain or branched alkylene group;

[0027] M is hydrogen or an alkali metal.

[0028] In this invention, examples of the C1-C10 straight-chain or branched alkyl groups can be, for example, any one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, n-hexyl, isohexyl, n-heptyl, isoheptyl, 2-methylhexyl, 2-ethylhexyl, 1-methylheptyl, 2-methylheptyl, n-octyl, isooctyl, n-nonyl, isononyl, and 3,5,5-trimethylhexyl.

[0029] In this invention, examples of the C1-C10 straight-chain or branched alkylene groups may be, for example, any one of methylene, 1,2-ethylene, n-propylene, isopropylene, n-butylene, isobutylene, n-pentylene, isopentylene, n-hexylene, isohexylene, n-heptylene, isoheptylene, 2-methylhexylene, 2-ethylhexylene, 1-methylheptylene, 2-methylheptylene, n-octylene, isooctylene, and n-nonylene.

[0030] In this invention, examples of the alkali metal can be, for example, any one of Li, Na, and K.

[0031] In some preferred embodiments of the present invention, M is hydrogen or sodium, more preferably hydrogen.

[0032] In some preferred embodiments of the present invention, R1, R2, R3, R4, R5 and R6 are each independently hydrogen or a straight-chain or branched alkyl group of C1-C6, more preferably hydrogen or a straight-chain or branched alkyl group of C1-C4; and even more preferably hydrogen, methyl or ethyl.

[0033] In a particularly preferred embodiment of the present invention, R1 and R2 in formula (1) are both hydrogen, and in this case, the structural unit shown in formula (1) can be a structural unit derived from acrylamide.

[0034] In a particularly preferred embodiment of the present invention, R3 and R4 in formula (2) are both hydrogen, R5 and R6 are both methyl, X is methylene, and M is hydrogen. In this case, the structural unit shown in formula (3) can be a structural unit derived from acrylate-2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0035] In this invention, the linking group C is bonded to the carbon atoms on the benzene rings contained in molecular chains A and B, preferably to the active carbon atoms on the benzene rings, wherein the active carbon atoms are preferably located ortho to the phenolic hydroxyl group or the sulfonic acid group and have a position that can provide bonding.

[0036] In this invention, crosslinking includes, but is not limited to: crosslinking of two molecules from lignin sulfonate with an aldehyde crosslinking agent, crosslinking of two molecules from proanthocyanidins with an aldehyde crosslinking agent, and crosslinking of molecules from lignin sulfonate and molecules from proanthocyanidins with an aldehyde crosslinking agent.

[0037] In this invention, structural units D and E are graft copolymerized with molecular chains A and B, wherein a free radical graft polymerization reaction occurs between the hydroxyl groups (alcoholic hydroxyl groups and / or phenolic hydroxyl groups) of molecular chains A and B and the vinyl double bonds of structural units D and E. That is, structural units D and E are grafted onto the hydroxyl groups of molecular chains A and B.

[0038] In this invention, grafting includes, but is not limited to: structural unit D grafted onto the hydroxyl group of molecular chain A, structural unit D grafted onto the hydroxyl group of molecular chain B, and structural unit D grafted onto both molecular chains A and B; structural unit E grafted onto the hydroxyl group of molecular chain A, structural unit E grafted onto the hydroxyl group of molecular chain B, and structural unit E grafted onto both molecular chains A and B; structural units D and E are simultaneously grafted onto the hydroxyl groups of said molecular chains A and / or B, wherein the hydroxyl groups are alcoholic hydroxyl groups and / or phenolic hydroxyl groups.

[0039] In this invention, the composition and structure of the cross-linked graft copolymer can be determined by methods such as infrared spectroscopy and nuclear magnetic resonance, or by the amount of raw materials fed.

[0040] In this invention, lignin sulfonate is rich in sulfonic acid groups, which allows the product to form a thick hydration layer on the bentonite surface of the drilling fluid, thereby breaking down the bentonite network structure and reducing the viscosity of the drilling fluid. Proanthocyanidins are rich in phenolic hydroxyl groups, giving the product strong adsorption properties on the bentonite surface and making it difficult to desorb at high temperatures. The organic combination of these two raw materials enables the product to possess both excellent viscosity-reducing and adsorption properties under high-temperature conditions. This invention uses lignin sulfonate and proanthocyanidins, two natural biodegradable materials, as raw materials, giving it non-toxic, easily degradable, and environmentally friendly characteristics.

[0041] This invention uses an aldehyde crosslinking agent to moderately crosslink lignin sulfonate rich in sulfonic acid groups with proanthocyanidins rich in phenolic hydroxyl groups, enabling the crosslinked product to simultaneously possess temperature resistance, adsorption, dispersibility, and environmental friendliness, making it particularly suitable as a high-temperature resistant and environmentally friendly viscosity reducer for water-based drilling fluids. By grafting and copolymerizing the two crosslinked natural macromolecules with two vinyl monomers, the temperature and salt resistance can be further improved, and the adsorption performance on the bentonite surface can be enhanced.

[0042] In some embodiments of the present invention, the weight ratio of molecular chain A to molecular chain B is 1:0.25-4, preferably 1:0.5-2.

[0043] In some embodiments of the present invention, the ratio of the total weight of the molecular chain A and the molecular chain B to the weight of the linking group C is 10-30:1, preferably 15-25:1, and more preferably 18-22:1.

[0044] In some embodiments of the present invention, the ratio of the total weight of structural unit D and structural unit E to the total weight of molecular chain A and molecular chain B is 1:5-10, preferably 1:6-9, and more preferably 1:7-8.

[0045] In some embodiments of the present invention, the weight ratio of the structural unit D to the structural unit E is 1:0.4-2.5, preferably 1:1-2, and more preferably 1:1-1.5.

[0046] In some embodiments of the present invention, the lignin sulfonate is selected from one or more of sodium lignin sulfonate, potassium lignin sulfonate, and calcium lignin sulfonate; preferably sodium lignin sulfonate and / or potassium lignin sulfonate, more preferably sodium lignin sulfonate.

[0047] In some embodiments of the present invention, the degree of sulfonation of the lignin sulfonate is 0.3-1, preferably 0.6-1, and more preferably 0.8-1. The higher the degree of sulfonation of the lignin sulfonate, the higher the number of sulfonic acid groups it carries, which makes the product have better hydration ability and less prone to dehydration at high temperatures, thus giving the crosslinked polymer better high-temperature viscosity reduction properties.

[0048] In some embodiments of the present invention, the weight-average molecular weight of the lignin sulfonate is 2000-12000 g / mol, preferably 4000-10000 g / mol, and more preferably 6000-8000 g / mol.

[0049] In some embodiments of the present invention, the proanthocyanidins are selected from one or more anthocyanin extracts selected from grapes, hawthorns, peanuts, ginkgo, cypress, cliff cypress, blueberries and black beans, preferably anthocyanin extracts from grapes and / or hawthorns, and more preferably anthocyanin extracts from grapes.

[0050] Proanthocyanidins are a general term for a large class of polyphenolic compounds widely found in plants. Their common characteristic is that they can all produce anthocyanins upon heating in an acidic medium. In this invention, proanthocyanidins refer to anthocyanin extracts obtained from the aforementioned substances.

[0051] In some embodiments of the present invention, the weight-average molecular weight of the proanthocyanidins is 500-3000 g / mol, preferably 1000-2000 g / mol, and more preferably 1500-2000 g / mol.

[0052] In some embodiments of the present invention, the linking group C is selected from one or more of -CH2-, -CH2OCH2-, -CH(CH3)-, -CH(CH3)O(CH3)CH-, and -CH2-CH2-.

[0053] In this invention, the linking group C that crosslinks lignin sulfonate with proanthocyanidins can be a dimethylene bridge, for example, -CH2-, -CH(CH3)-, -CH2-CH2-; or a dimethylene ether bridge, for example, -CH2OCH2-, -CH(CH3)O(CH3)CH-.

[0054] In some embodiments of the present invention, the aldehyde crosslinking agent is a water-soluble lower aldehyde, preferably selected from one or more of formaldehyde, acetaldehyde, glyoxal and glutaraldehyde, more preferably formaldehyde and / or acetaldehyde, and even more preferably formaldehyde.

[0055] In some embodiments of the present invention, the weight-average molecular weight of the crosslinked graft copolymer is 10,000-100,000 g / mol, preferably 30,000-80,000 g / mol.

[0056] In some embodiments of the present invention, the cross-linked graft copolymer exhibits a temperature resistance ≥180℃, a viscosity reduction rate of ≥90% for 10wt% bentonite slurry, biotoxicity >90000 mg / L, and biodegradable BOD5 / COD ratio. Cr >0.28.

[0057] A second aspect of the present invention provides a method for preparing a crosslinked graft copolymer, the method comprising the following steps:

[0058] (1) The lignin sulfonate and proanthocyanidins were cross-linked with an aldehyde cross-linking agent to obtain an intermediate product;

[0059] (2) In the presence of an initiator, the intermediate product is grafted with vinyl monomer I and vinyl monomer II to obtain a crosslinked graft copolymer.

[0060] In this invention, in step (1), through a cross-linking reaction, the aldehyde cross-linking agent is bonded to the carbon atoms on the benzene ring contained in lignin sulfonate and proanthocyanidins, preferably to the active carbon atoms on the benzene ring, wherein the active carbon atom is preferably located at the ortho position of the phenolic hydroxyl group or sulfonic acid group and has a position that can provide bonding.

[0061] In this invention, in step (2), a free radical grafting polymerization reaction occurs between the hydroxyl groups (alcoholic hydroxyl and phenolic hydroxyl) in lignin sulfonate and proanthocyanidins and the vinyl double bonds in vinyl monomer I and vinyl monomer II.

[0062] In this invention, the structure and composition of the cross-linked graft copolymer can be determined by methods such as NMR, IR, GPC, and elemental analysis, or by the amount of raw materials fed during preparation.

[0063] In some embodiments of the present invention, the weight ratio of lignin sulfonate to proanthocyanidins is 1:0.25-4, preferably 1:0.5-2.

[0064] In some embodiments of the present invention, the total mass concentration of the lignin sulfonate and proanthocyanidins in water is 10%-40%, preferably 20%-30%.

[0065] In some embodiments of the present invention, the total weight ratio of the lignin sulfonate and proanthocyanidins to the weight of the aldehyde crosslinking agent is 10-30:1, preferably 15-25:1, and more preferably 18-22:1.

[0066] In some embodiments of the present invention, the total weight ratio of the vinyl monomer I and vinyl monomer II to the total weight ratio of the lignin sulfonate and proanthocyanidins is 1:5-10, preferably 1:6-9, and more preferably 1:7-8.

[0067] In some embodiments of the present invention, the weight ratio of vinyl monomer I to vinyl monomer II is 1:0.4-2.5, preferably 1:1-2, and more preferably 1:1-1.5.

[0068] In some embodiments of the present invention, the conditions for the crosslinking reaction include: pH 3-11, preferably 4-10, more preferably 7-9; temperature 60-100℃, preferably 70-90℃, more preferably 75-85℃; and time 1-4h, preferably 1.5-3h.

[0069] In this invention, the crosslinking reaction can be carried out under both acidic and alkaline conditions. The crosslinking reaction is a covalent crosslinking reaction, in which lignin sulfonate and proanthocyanidins are covalently crosslinked by an aldehyde crosslinking agent.

[0070] In some embodiments of the present invention, the conditions for the grafting reaction include: a temperature of 60-100°C, preferably 70-90°C, more preferably 75-85°C; and a time of 1-4 hours, preferably 1.5-3 hours.

[0071] In this invention, the grafting reaction is a graft copolymerization reaction, which is formed by two different polymer chains linked by chemical bonds. One of them is a polymer backbone (skeleton) composed of A1 and B1 units, i.e., the main chain; the other is a polymer branch composed of D1 and E1 units, i.e., the side chain.

[0072] In some embodiments of the present invention, the total weight ratio of the lignin sulfonate and proanthocyanidins to the weight of the initiator is 100-600:1, preferably 200-500:1, and more preferably 300-400:1.

[0073] In some embodiments of the present invention, the lignin sulfonate is selected from one or more of sodium lignin sulfonate, potassium lignin sulfonate, and calcium lignin sulfonate.

[0074] In some embodiments of the present invention, the proanthocyanidins are selected from one or more anthocyanin extracts from grapes, hawthorns, peanuts, ginkgo, cypress, cliff cypress, blueberries, and black beans.

[0075] In some embodiments of the present invention, the aldehyde crosslinking agent is a water-soluble lower aldehyde, preferably selected from one or more of formaldehyde, acetaldehyde, glyoxal, and glutaraldehyde.

[0076] In this invention, the selection of lignin sulfonate, proanthocyanidins and aldehyde crosslinking agents is the same as in the first aspect mentioned above, and will not be repeated here.

[0077] In some embodiments of the present invention, the initiator is selected from one or more of cerium ammonium nitrate, potassium persulfate, and ammonium persulfate.

[0078] Specifically, the above preparation method includes the following steps:

[0079] S1. Dissolve lignin sulfonate and proanthocyanidins in water and mix well to form a solution. Adjust the pH of the solution with alkali metal hydroxide. Then, heat to the specified temperature, add aldehyde crosslinking agent, and keep the reaction at a certain temperature for a certain time while stirring.

[0080] S2. After the reaction is complete, immediately add vinyl monomer I and vinyl monomer II to the reaction product obtained in step S1, and continue the reaction at the same temperature for a certain period of time with stirring.

[0081] S3. Dry the reaction product obtained in step S2 at 80-100℃ to constant weight, and then crush and sieve the obtained solid product.

[0082] The alkali metal hydroxide may be selected from sodium hydroxide or potassium hydroxide, preferably sodium hydroxide. The water may be selected from tap water, deionized water, or distilled water, preferably deionized water.

[0083] A third aspect of the present invention provides a crosslinked graft copolymer prepared by the aforementioned preparation method.

[0084] A fourth aspect of the present invention provides the application of the aforementioned crosslinked graft copolymer in water-based drilling fluids; preferably, the crosslinked graft copolymer is used as a drilling fluid viscosity reducer.

[0085] The cross-linked graft copolymer of the present invention can be used as a high-temperature resistant and environmentally friendly viscosity reducer for water-based drilling fluids. It exhibits excellent viscosity-reducing performance at high temperatures, with a temperature resistance ≥180℃, a viscosity reduction rate of ≥90% for 10wt% bentonite slurry, biotoxicity >90000mg / L, and biodegradable BOD5 / COD ratio. Cr >0.28.

[0086] The present invention will be described in detail below through embodiments.

[0087] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0088] In the following examples, the composition of the obtained crosslinked graft copolymer was determined by the amount of each raw material fed.

[0089] The method for determining biotoxicity is as follows: The determination shall be carried out in accordance with the "Evaluation Method for Environmental Protection of Water-Soluble Oilfield Chemical Agents" (SY / T6788-2020).

[0090] The biodegradation rate was determined according to the "Evaluation Method for Environmental Protection Technology of Water-Soluble Oilfield Chemical Agents" (SY / T6788-2020).

[0091] Example 1

[0092] 1) Add 12.5g sodium lignosulfonate (weight average molecular weight 8000, sulfonation degree 0.8), 12.5g proanthocyanidins (grape seed extract, weight average molecular weight 1500) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer, stir until completely dissolved, and then adjust the pH to 9 with NaOH.

[0093] 2) Heat the mixed monomer solution to 80°C using a constant temperature water bath, then add 2.78g of formaldehyde (36% concentration), and stir the reaction at 80°C for 2 hours;

[0094] 3) After step 2), add 2.5g acrylamide, 2.5g 2-acrylamide-2-methylpropanesulfonic acid and 0.016g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A1 is obtained.

[0095] The feeding data shows that in the cross-linked graft copolymer A1, molecular chain A comes from sodium lignosulfonate, molecular chain B comes from grape seed proanthocyanidins, linking group C comes from formaldehyde, structural unit D comes from acrylamide, and structural unit E comes from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 1:1; the weight ratio of the total weight of molecular chain A and molecular chain B to the weight of linking group C is 15:1; the weight ratio of the total weight of structural unit D and structural unit E to the total weight of molecular chain A and molecular chain B is 1:5; and the weight ratio of structural unit D to structural unit E is 1:1.

[0096] Example 2

[0097] 1) Add 20g sodium lignosulfonate (weight average molecular weight 8000, sulfonation degree 0.8), 5g grape seed proanthocyanidins (grape seed extract, weight average molecular weight 1500) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer. Stir until completely dissolved, and then adjust the pH to 9 with NaOH.

[0098] 2) Heat the mixed monomer solution to 80°C using a constant temperature water bath, then add 2.78g of formaldehyde (36% concentration), and stir the reaction at 80°C for 2 hours;

[0099] 3) After step 2), add 2.5g acrylamide, 2.5g 2-acrylamide-2-methylpropanesulfonic acid and 0.016g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A2 is obtained.

[0100] The feeding data reveals that in the cross-linked graft copolymer A2, molecular chain A originates from sodium lignosulfonate, molecular chain B originates from grape seed proanthocyanidins, linking group C originates from formaldehyde, structural unit D originates from acrylamide, and structural unit E originates from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 4:1; the ratio of the total weight of molecular chains A and B to the weight of linking group C is 15:1; the ratio of the total weight of structural units D and E to the total weight of molecular chains A and B is 1:5; and the weight ratio of structural units D to structural units E is 1:1.

[0101] Example 3

[0102] 1) Add 5g sodium lignosulfonate (weight average molecular weight 8000, sulfonation degree 0.8), 20g grape seed proanthocyanidins (grape seed extract, weight average molecular weight 1500) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer. Stir until completely dissolved, and then adjust the pH to 9 with NaOH.

[0103] 2) Heat the mixed monomer solution to 80°C using a constant temperature water bath, then add 2.78g of formaldehyde (36% concentration), and stir the reaction at 80°C for 2 hours;

[0104] 3) After step 2), add 2.5g acrylamide, 2.5g 2-acrylamide-2-methylpropanesulfonic acid and 0.016g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A3 is obtained.

[0105] The feeding data reveals that in the cross-linked graft copolymer A3, molecular chain A originates from sodium lignosulfonate, molecular chain B originates from grape seed proanthocyanidins, linking group C originates from formaldehyde, structural unit D originates from acrylamide, and structural unit E originates from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 1:4; the ratio of the total weight of molecular chains A and B to the weight of linking group C is 15:1; the ratio of the total weight of structural units D and E to the total weight of molecular chains A and B is 1:5; and the weight ratio of structural units D to structural units E is 1:1.

[0106] Example 4

[0107] 1) Add 12.5g sodium lignosulfonate (weight average molecular weight 8000, sulfonation degree 0.8), 12.5g grape seed proanthocyanidins (grape seed extract, weight average molecular weight 1500) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer, stir until completely dissolved, and then adjust the pH to 9 with NaOH.

[0108] 2) Heat the mixed monomer solution to 80°C using a constant temperature water bath, then add 6.94g of formaldehyde (36% concentration), and stir the reaction at 80°C for 2 hours;

[0109] 3) After step 2), add 2.5g acrylamide, 2.5g 2-acrylamide-2-methylpropanesulfonic acid and 0.016g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A4 is obtained.

[0110] The feeding data reveals that in the cross-linked graft copolymer A4, molecular chain A originates from sodium lignosulfonate, molecular chain B originates from grape seed proanthocyanidins, linking group C originates from formaldehyde, structural unit D originates from acrylamide, and structural unit E originates from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 1:1; the ratio of the total weight of molecular chains A and B to the weight of linking group C is 10:1; the ratio of the total weight of structural units D and E to the total weight of molecular chains A and B is 1:5; and the weight ratio of structural units D to structural units E is 1:1.

[0111] Example 5

[0112] 1) Add 12.5g sodium lignosulfonate (weight average molecular weight 8000, sulfonation degree 0.8), 12.5g grape seed proanthocyanidins (grape seed extract, weight average molecular weight 1500) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer, stir until completely dissolved, and then adjust the pH to 9 with NaOH.

[0113] 2) Heat the mixed monomer solution to 80°C using a constant temperature water bath, then add 2.78g of formaldehyde (36% concentration), and stir the reaction at 80°C for 2 hours;

[0114] 3) After step 2), add 1.25g acrylamide, 1.25g 2-acrylamide-2-methylpropanesulfonic acid and 0.008g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A5 is obtained.

[0115] The feeding data reveals that in the cross-linked graft copolymer A5, molecular chain A originates from sodium lignosulfonate, molecular chain B originates from grape seed proanthocyanidins, linking group C originates from formaldehyde, structural unit D originates from acrylamide, and structural unit E originates from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 1:1; the ratio of the total weight of molecular chains A and B to the weight of linking group C is 15:1; the ratio of the total weight of structural units D and E to the total weight of molecular chains A and B is 1:10; and the weight ratio of structural units D to structural units E is 1:1.

[0116] Example 6

[0117] 1) Add 12.5g sodium lignosulfonate (weight average molecular weight 8000, sulfonation degree 0.8), 12.5g grape seed proanthocyanidins (grape seed extract, weight average molecular weight 1500) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer, stir until completely dissolved, and then adjust the pH to 9 with NaOH.

[0118] 2) Heat the mixed monomer solution to 98°C using a constant temperature water bath, then add 2.78g of formaldehyde (36% concentration), and stir the reaction at 98°C for 2 hours;

[0119] 3) After step 2), add 3.5g acrylamide, 1.5g 2-acrylamide-2-methylpropanesulfonic acid and 0.016g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A6 is obtained.

[0120] The feeding data shows that in the cross-linked graft copolymer A6, molecular chain A comes from sodium lignosulfonate, molecular chain B comes from grape seed proanthocyanidins, linking group C comes from formaldehyde, structural unit D comes from acrylamide, and structural unit E comes from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 1:1; the weight ratio of the total weight of molecular chain A and molecular chain B to the weight of linking group C is 15:1; the weight ratio of the total weight of structural unit D and structural unit E to the total weight of molecular chain A and molecular chain B is 1:5; and the weight ratio of structural unit D to structural unit E is 1:0.43.

[0121] Example 7

[0122] 1) Add 12.5g sodium lignosulfonate (weight average molecular weight 8000, sulfonation degree 0.8), 12.5g grape seed proanthocyanidins (grape seed extract, weight average molecular weight 1500) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer, stir until completely dissolved, and then adjust the pH to 9 with NaOH.

[0123] 2) Heat the mixed monomer solution to 80°C using a constant temperature water bath, then add 2.78g of formaldehyde (36% concentration), and stir the reaction at 80°C for 4 hours;

[0124] 3) After step 2), add 1.5g acrylamide, 3.5g 2-acrylamide-2-methylpropanesulfonic acid and 0.016g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A7 is obtained.

[0125] The feeding data shows that in the cross-linked graft copolymer A7, molecular chain A comes from sodium lignosulfonate, molecular chain B comes from grape seed proanthocyanidins, linking group C comes from formaldehyde, structural unit D comes from acrylamide, and structural unit E comes from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 1:1; the weight ratio of the total weight of molecular chain A and molecular chain B to the weight of linking group C is 15:1; the weight ratio of the total weight of structural unit D and structural unit E to the total weight of molecular chain A and molecular chain B is 1:5; and the weight ratio of structural unit D to structural unit E is 1:2.3.

[0126] Example 8

[0127] 1) Add 12.5g sodium lignosulfonate (weight average molecular weight 8000, sulfonation degree 0.8), 12.5g grape seed proanthocyanidins (grape seed extract, weight average molecular weight 1500) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer, stir until completely dissolved, and then adjust the pH to 7 with NaOH.

[0128] 2) Heat the mixed monomer solution to 80°C using a constant temperature water bath, then add 2.78g of formaldehyde (36% concentration), and stir the reaction at 80°C for 4 hours;

[0129] 3) After step 2), add 2.5g acrylamide, 2.5g 2-acrylamide-2-methylpropanesulfonic acid and 0.016g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A8 is obtained.

[0130] The feeding data reveals that in the cross-linked graft copolymer A1, molecular chain A originates from sodium lignosulfonate, molecular chain B originates from grape seed proanthocyanidins, linking group C originates from formaldehyde, structural unit D originates from acrylamide, and structural unit E originates from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 1:1; the ratio of the total weight of molecular chains A and B to the weight of linking group C is 15:1; the ratio of the total weight of structural units D and E to the total weight of molecular chains A and B is 1:5; and the weight ratio of structural units D to structural units E is 1:1.

[0131] Example 9

[0132] 1) Add 12.5g sodium lignosulfonate (weight average molecular weight 4000, sulfonation degree 0.6), 12.5g proanthocyanidins (hawthorn extract, weight average molecular weight 3000) and 100g deionized water to a three-necked flask equipped with a thermometer and stirrer. Stir until completely dissolved, and then adjust the pH to 9 with NaOH.

[0133] 2) Heat the mixed monomer solution to 80°C using a constant temperature water bath, then add 2.78g of glyoxal (36% concentration), and stir the reaction at 80°C for 2 hours;

[0134] 3) After step 2), add 2.5g acrylamide, 2.5g 2-acrylamide-2-methylpropanesulfonic acid and 0.016g ammonium persulfate to the mixed monomer solution, and continue to react at 80℃ for 4h. After drying and pulverizing, cross-linked graft copolymer A9 is obtained.

[0135] The feeding data reveals that in the cross-linked graft copolymer A9, molecular chain A originates from sodium lignosulfonate, molecular chain B originates from grape seed proanthocyanidins, linking group C originates from glyoxal, structural unit D originates from acrylamide, and structural unit E originates from 2-acrylamide-2-methylpropanesulfonic acid. The weight ratio of molecular chain A to molecular chain B is 1:1; the ratio of the total weight of molecular chains A and B to the weight of linking group C is 15:1; the ratio of the total weight of structural units D and E to the total weight of molecular chains A and B is 1:5; and the weight ratio of structural units D to structural units E is 1:1.

[0136] Comparative Example 1

[0137] The method described in Example 1 was followed, except that in step 1), proanthocyanidins were not added to obtain polymer D1.

[0138] Comparative Example 2

[0139] The method described in Example 1 was followed, except that sodium lignosulfonate was not added in step 1) to obtain polymer D2.

[0140] Comparative Example 3

[0141] The method described in Example 1 was followed, except that in step 1), acrylamide and 2-acrylamide-2-methylpropanesulfonic acid were not added to obtain polymer D3.

[0142] Comparative Example 4

[0143] Sodium iron-chromium lignin sulfonate produced by Hubei Xinrunde Chemical Co., Ltd. was used as polymer D4.

[0144] Test case

[0145] 1) Prepare two portions of bentonite-based slurry. For each portion, add 40.0g of bentonite for drilling fluid test slurry preparation (compliant with SY / T 5490) and 1.4g of anhydrous sodium carbonate to 400mL of distilled water. Stir at high speed for 20min, stopping at least twice during the process to scrape off the adhering material on the container wall. Let it stand in a sealed container at room temperature for 24h.

[0146] 2) Take one portion of the bentonite-based slurry and add 4.0g of sample A1 as a high-temperature resistant and environmentally friendly viscosity reducer. Both the sample slurry and the base slurry are placed in a high-temperature roller furnace and rolled at 180℃ for 16 hours. After cooling, they are stirred at high speed at 10000r / min for 5 minutes. The viscosity of the base slurry at 100r / min is measured using a six-speed rotational viscometer. The viscosity reduction rate of sample A1 is calculated according to formula (A).

[0147]

[0148] In the formula:

[0149] Y—Relative inhibition rate, %;

[0150] —Reading value of base slurry at 100r / min;

[0151] —Reading value at 100r / min for sample slurry.

[0152] 3) The viscosity reduction rate of viscosity-reducing agent samples A2-A9 and D1-D4 was determined according to steps 1) and 2), and the results are shown in Table 1.

[0153] Table 1 Measurement Results

[0154]

[0155] As can be seen from the results in Table 1, when the polymer of the present invention is added as a viscosity reducer to a 10% bentonite-based slurry and aged at 180°C for 16 hours, the viscosity reduction rate can reach 90%-96%, which is far superior to the iron-chromium lignin sulfonate commonly used in China. This indicates that the polymer of the present invention has good viscosity reduction and temperature resistance, and can effectively improve the rheological properties of water-based drilling fluids under high-temperature conditions.

[0156] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A crosslinked graft copolymer, characterized in that, The crosslinked graft copolymer contains: a molecular chain A from lignin sulfonate, a molecular chain B from proanthocyanidins, a linking group C from an aldehyde crosslinking agent, a structural unit D as shown in formula (1), and a structural unit E as shown in formula (2); wherein the molecular chain A and the molecular chain B are connected by the linking group C, and the linking group C is bonded to the carbon atoms on the benzene rings contained in the molecular chains A and B respectively; the structural units D and E are grafted onto the hydroxyl groups of the molecular chains A and B; Equation (1), Equation (2), Among them, R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C10 straight-chain or branched alkyl groups; X is a C1-C10 straight-chain or branched alkylene group; M is hydrogen or an alkali metal; The weight-average molecular weight of the proanthocyanidins is 500-3000 g / mol.

2. The crosslinked graft copolymer according to claim 1, wherein, The weight ratio of molecular chain A to molecular chain B is 1:0.25-4; And / or, the ratio of the total weight of the molecular chain A and the molecular chain B to the weight of the linking group C is 10-30:1; And / or, the ratio of the total weight of the structural unit D and the structural unit E to the total weight of the molecular chain A and the molecular chain B is 1:5-10; And / or, the weight ratio of the structural unit D to the structural unit E is 1:0.4-2.

5.

3. The crosslinked graft copolymer according to claim 2, wherein, The weight ratio of molecular chain A to molecular chain B is 1:0.5-2; And / or, the ratio of the total weight of the molecular chain A and the molecular chain B to the weight of the linking group C is 15-25:1; And / or, the ratio of the total weight of the structural unit D and the structural unit E to the total weight of the molecular chain A and the molecular chain B is 1:6-9; And / or, the weight ratio of the structural unit D to the structural unit E is 1:1-2.

4. The crosslinked graft copolymer according to claim 1 or 2, wherein, The lignin sulfonate is selected from one or more of sodium lignin sulfonate, potassium lignin sulfonate, and calcium lignin sulfonate. And / or, the degree of sulfonation of the lignin sulfonate is 0.3-1; And / or, the weight-average molecular weight of the lignin sulfonate is 2000-12000 g / mol.

5. The crosslinked graft copolymer according to claim 4, wherein, The lignin sulfonate is sodium lignin sulfonate and / or potassium lignin sulfonate; And / or, the degree of sulfonation of the lignin sulfonate is 0.6-1; And / or, the weight-average molecular weight of the lignin sulfonate is 4000-10000 g / mol.

6. The crosslinked graft copolymer according to claim 1 or 2, wherein, The proanthocyanidins are selected from one or more anthocyanin extracts from grapes, hawthorn, peanuts, ginkgo, cypress, cliff cypress, blueberries and black beans; And / or, the weight-average molecular weight of the proanthocyanidins is 1000-2000 g / mol.

7. The crosslinked graft copolymer according to claim 6, wherein, The proanthocyanidins are anthocyanin extracts from grapes and / or hawthorns.

8. The crosslinked graft copolymer according to claim 1 or 2, wherein the linking group C is selected from one or more of -CH2-, -CH2OCH2-, -CH(CH3)-, -CH(CH3)O(CH3)CH-, and -CH2-CH2-.

9. The crosslinked graft copolymer according to claim 1 or 2, wherein, The aldehyde crosslinking agent is selected from one or more of formaldehyde, acetaldehyde, glyoxal, and glutaraldehyde.

10. The crosslinked graft copolymer according to claim 1 or 2, wherein, The weight-average molecular weight of the crosslinked graft copolymer is 10,000-100,000 g / mol; And / or, the cross-linked graft copolymer has a temperature resistance ≥180℃, a viscosity reduction rate of ≥90% for 10wt% bentonite slurry, a biotoxicity >90000mg / L, and a biodegradable BOD5 / COD ratio. Cr >0.

28.

11. The crosslinked graft copolymer according to claim 10, wherein, The weight-average molecular weight of the cross-linked graft copolymer is 30,000-80,000 g / mol.

12. A method for preparing a crosslinked graft copolymer, characterized in that, The preparation method includes: (1) The lignin sulfonate and proanthocyanidins were cross-linked with an aldehyde cross-linking agent to obtain an intermediate product; (2) In the presence of an initiator, the intermediate product is grafted with vinyl monomer I and vinyl monomer II to obtain a crosslinked graft copolymer; The weight-average molecular weight of the proanthocyanidins is 500-3000 g / mol. The vinyl monomer I is acrylamide; the vinyl monomer II is 2-acrylamide-2-methylpropanesulfonic acid.

13. The preparation method according to claim 12, wherein, The weight ratio of lignin sulfonate to proanthocyanidins is 1:0.25-4; And / or, the total mass concentration of the lignin sulfonate and proanthocyanidins in water is 10%-40%; And / or, the total weight ratio of the lignin sulfonate and proanthocyanidins to the weight of the aldehyde crosslinking agent is 10-30:1; And / or, the total weight ratio of the vinyl monomer I and vinyl monomer II to the total weight ratio of the lignin sulfonate and proanthocyanidins is 1:5-10; And / or, the weight ratio of vinyl monomer I to vinyl monomer II is 1:0.4-2.

5.

14. The preparation method according to claim 13, wherein, The weight ratio of lignin sulfonate to proanthocyanidins is 1:0.5-2; And / or, the total mass concentration of the lignin sulfonate and proanthocyanidins in water is 20%-30%; And / or, the total weight ratio of the lignin sulfonate and proanthocyanidins to the weight ratio of the aldehyde crosslinking agent is 15-25:1; And / or, the total weight ratio of the vinyl monomer I and vinyl monomer II to the total weight ratio of the lignin sulfonate and proanthocyanidins is 1:6-9; And / or, the weight ratio of vinyl monomer I to vinyl monomer II is 1:1-2.

15. The preparation method according to claim 12 or 13, wherein, The conditions for the cross-linking reaction include: pH 3-11, temperature 60-100℃, and time 1-4h; And / or, the conditions for the grafting reaction include: a temperature of 60-100°C and a time of 1-4 hours.

16. The preparation method according to claim 15, wherein, The conditions for the cross-linking reaction include: pH 4-10, temperature 70-90℃, and time 1.5-3h; And / or, the conditions for the grafting reaction include: a temperature of 70-90°C and a time of 1.5-3 hours.

17. The preparation method according to claim 12 or 13, wherein, The total weight ratio of the lignin sulfonate and proanthocyanidins to the weight of the initiator is 100-600:

1.

18. The preparation method according to claim 17, wherein, The total weight ratio of the lignin sulfonate and proanthocyanidins to the weight of the initiator is 200-500:

1.

19. The preparation method according to claim 12 or 13, wherein, The lignin sulfonate is selected from one or more of sodium lignin sulfonate, potassium lignin sulfonate, and calcium lignin sulfonate. And / or, the proanthocyanidins are selected from one or more anthocyanin extracts from grapes, hawthorns, peanuts, ginkgo, cypress, cypress, blueberries, and black beans; And / or, the aldehyde crosslinking agent is selected from one or more of formaldehyde, acetaldehyde, glyoxal, and glutaraldehyde; And / or, the initiator is selected from one or more of cerium ammonium nitrate, potassium persulfate, and ammonium persulfate.

20. A crosslinked graft copolymer prepared by any one of claims 12-19.

21. The use of the crosslinked copolymer as described in any one of claims 1-11 and 20 in water-based drilling fluids.

22. The application according to claim 21, wherein, The crosslinked copolymer is used as a drilling fluid viscosity reducer.

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