A kind of adhesive for coated sucker rod and its preparation method

Abstract

The application belongs to the technical field of adhesives, and particularly relates to a coated adhesive for sucker rods and a preparation method thereof. The adhesive comprises a component A and a component B. The component A is prepared from the following raw materials in parts by mass: bisphenol A type epoxy resin 40-50 parts, bisphenol F type epoxy resin 20-35 parts, modified lignin 5-10 parts, graphene nanosheet 1-3 parts, hyperbranched polysiloxane 2-4 parts, silane coupling agent 0.5-1 part, diluent 5-10 parts, and defoaming agent 0.2-0.5 part. The component B is prepared from the following raw materials in parts by mass: curing agent 25-30 parts, 2-ethyl-4-methyl imidazole 0.5-1.2 parts, and silane coupling agent 1-2 parts. The adhesive prepared by the application is fully cured, has high crosslinking density, and has excellent properties such as hardness and corrosion resistance of the adhesive layer.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to an adhesive for coated sucker rods and its preparation method. Background Technology

[0002] In oil extraction, the sucker rod is a crucial component of the production equipment, and its performance directly impacts oil production efficiency and costs. With the increasing complexity of oil wells, such as deviated wells and heavy oil wells, sucker rods face severe corrosion and uneven wear problems. Traditional metal sucker rods have poor corrosion resistance, are heavy, and place a heavy load on equipment during deep well operations, leading to high oil production costs. To address these issues, coatings have been used to improve sucker rod performance, such as coating the surface of the sucker rod with materials like polyethylene and polyurethane.

[0003] The adhesive strength between the coating and the sucker rod body is one of the key factors affecting the performance of the coated sucker rod. If the adhesive strength is insufficient, the coating can easily detach from the sucker rod, affecting its performance. Epoxy resin-based adhesives are commonly found to easily detach from the sucker rod during use, impacting its quality. Therefore, a high-performance adhesive is needed to improve the adhesive strength between the coating and the sucker rod.

[0004] Chinese patent application CN118185533A discloses a one-component epoxy adhesive and its preparation method, comprising: 1) taking lignin sulfonate monomer, carboxylic acid ester derivative, and organic solvent and mixing them evenly to obtain modified lignin; 2) taking modified lignin and cyclic hydrocarbons and mixing them evenly, adding alkaline solution to react and obtain a one-component epoxy adhesive; the core of this technical solution is sodium lignin sulfonate modified epoxy adhesive, but sodium lignin sulfonate contains a large number of hydrophilic sulfonic acid groups, resulting in extremely strong hydrophilicity of the adhesive layer. In media such as oilfield brine, water molecules and corrosive ions can be quickly adsorbed through the sulfonic acid groups and penetrate into the interior of the adhesive layer, which cannot adapt to the harsh working environment of oil wells; at the same time, this solution relies on the reaction of lignin's own active groups with epichlorohydrin for curing, but the crosslinking density of this reaction is low, which easily leads to insufficient mechanical properties. Summary of the Invention

[0005] Existing adhesives suffer from poor corrosion resistance; to address this issue, this invention provides an adhesive for coated sucker rods and its preparation method.

[0006] To achieve the objectives of this invention, the following technical solution is adopted:

[0007] This invention provides an adhesive for coated sucker rods, comprising component A and component B. Component A is prepared from the following raw materials in parts by weight: 40-50 parts of bisphenol A epoxy resin, 20-35 parts of bisphenol F epoxy resin, 5-10 parts of modified lignin, 1-3 parts of graphene nanosheets, 2-4 parts of hyperbranched polysiloxane, 0.5-1 part of silane coupling agent, 5-10 parts of diluent, and 0.2-0.5 parts of defoamer. Component B is prepared from the following raw materials in parts by weight: 25-30 parts of curing agent, 0.5-1.2 parts of 2-ethyl-4-methylimidazole, and 1-2 parts of silane coupling agent.

[0008] By employing the above technical solutions, bisphenol A epoxy resin can provide high mechanical strength and good adhesion; bisphenol F epoxy resin is well compatible with bisphenol A epoxy resin and can improve the brittleness of the pure bisphenol A system; the combination of the two can balance the strength and toughness of the system; graphene nanosheets can form a physical barrier layer in the adhesive layer, extending the penetration path of corrosive media; hyperbranched polysiloxane has a highly branched structure and a siloxane-containing skeleton, exhibiting excellent hydrophobicity and chemical stability, and can synergistically work with graphene sheets to fill their gaps, effectively blocking the intrusion of water, oxygen, and corrosive ions; modified lignin introduces groups with better compatibility with epoxy groups, and its own aromatic ring structure also endows the system with certain chemical resistance. The synergistic effect of these three components gives the adhesive excellent corrosion resistance.

[0009] Preferably, the method for preparing the modified lignin includes the following steps:

[0010] Sodium lignin sulfonate, oleic anhydride, 4-dimethylaminopyridine and N,N-dimethylformamide were mixed evenly and reacted at high temperature to obtain modified lignin.

[0011] By adopting the above technical solution, hydrophobic long-chain groups are introduced onto lignin, which can improve the compatibility with hydrophobic epoxy resin molecular chains; the modified lignin dispersed in epoxy resin can absorb or consume energy when the material is impacted, thereby improving the overall impact resistance.

[0012] Preferably, the mass ratio of sodium lignosulfonate to oleic anhydride is 1:(1.3-2.5).

[0013] By adopting the above technical solution, at this mass ratio, the hydrophilic hydroxyl groups on the lignin molecules are replaced by hydrophobic long chains, and the hydrophobic modification of lignin is sufficient, achieving a balance between dispersibility and strength.

[0014] Preferably, the amount of 4-dimethylaminopyridine used is 0.5%-1.5% of the mass of lignin sulfonate.

[0015] By adopting the above technical solution, the reaction can be carried out quickly and completely at this dosage, while reducing the residue of 4-dimethylaminopyridine.

[0016] Preferably, the reaction temperature is 80-95℃ and the reaction time is 2-5h.

[0017] By adopting the above technical solution, within the reaction temperature and time range, the molecular motion of sodium lignosulfonate, oleic anhydride, and catalyst 4-dimethylaminopyridine is intense and the collision frequency is high, thereby accelerating the reaction rate. If the temperature is too low, the reaction is slow, the reaction time increases, and the efficiency decreases. If the temperature is too high, it is easy to cause the decomposition of raw materials and affect the product.

[0018] Preferably, the preparation method of the hyperbranched polysiloxane includes the following steps:

[0019] Under anaerobic conditions, vinyltriethoxysilane, triethylene glycol, and barium hydroxide are mixed evenly and reacted at elevated temperature to obtain hyperbranched polysiloxane.

[0020] By adopting the above technical solution, this method is simple and can stably produce hyperbranched polysiloxanes, providing a basis for their toughening, anti-corrosion and other functions in adhesives; when added to epoxy resin, it can improve the toughness of epoxy resin without affecting its thermal stability and other properties.

[0021] Preferably, the mass ratio of vinyltriethoxysilane to triethylene glycol is 1:(1.2-1.5); the amount of barium hydroxide used is 0.4%-0.8% of the total mass of vinyltriethoxysilane and triethylene glycol.

[0022] By adopting the above technical solution, the system viscosity is moderate at this ratio, which can avoid local overheating, ensure the uniformity of the hyperbranched polysiloxane molecular structure, and has excellent stability; the dosage range of 0.4%-0.8% barium hydroxide ensures efficient reaction and avoids interference from residues on the performance of subsequent adhesives.

[0023] Preferably, the reaction temperature is 75-90℃ and the reaction time is 5-8h.

[0024] By adopting the above technical solution, within this temperature and time range, mild hydrolysis is facilitated, ensuring the orderly nature of the condensation reaction.

[0025] Preferably, the curing agent is prepared by mixing 4,4'-diaminodiphenylmethane and 4,4'-diaminodicyclohexylmethane in a mass ratio of (1-2):1.

[0026] By adopting the above technical solution, 4,4'-diaminodiphenylmethane and 4,4'-diaminodicyclohexylmethane are mixed and used in this ratio. At this ratio, 4,4'-diaminodicyclohexylmethane is distributed in the network constructed by 4,4'-diaminodiphenylmethane. The flexible segments can effectively absorb and disperse stress, so that the adhesive can maintain high strength while having good fatigue resistance.

[0027] Secondly, the present invention provides a method for preparing the above-mentioned adhesive for coated sucker rods, comprising the following steps:

[0028] S1: Bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified lignin, graphene nanosheets, hyperbranched polysiloxane, silane coupling agent, diluent and defoamer are dispersed evenly to obtain component A;

[0029] S2: Disperse the curing agent, 2-ethyl-4-methylimidazolium and silane coupling agent evenly to obtain component B;

[0030] S3: Mix component A and component B at a mass ratio of (3-4.5):1 to obtain an adhesive for coated sucker rods.

[0031] By adopting the above technical solution, the base resin, filler and additives are fully dispersed in advance and stored stably; the curing agent, accelerator and additives are mixed and stored independently; before use, component A and component B are mixed in proportion, which improves the practicality and stability of the product; the mixing of component A and component B in a ratio of (3-4.5):1 can make the curing reaction more complete, the crosslinking density higher, and the hardness, heat resistance, toughness and other properties of the adhesive layer optimal.

[0032] In summary, the beneficial effects of this invention are:

[0033] (1) The graphene nanosheets in component A of this invention can extend the penetration path of corrosive media and effectively block the intrusion of corrosive ions; the hyperbranched polysiloxane has excellent hydrophobicity and chemical stability due to its highly branched structure and siloxane-containing skeleton, which can fill the gaps between graphene sheets and work synergistically with graphene sheets to improve corrosion resistance; the modified lignin introduces groups with better compatibility with epoxy groups, and its own aromatic ring structure also endows the system with certain chemical resistance, effectively resisting corrosion.

[0034] (2) The bisphenol A type epoxy resin and bisphenol F type epoxy resin of the present invention are used as base resins, which can form a cross-linked dense network, providing high mechanical strength for the adhesive; the modified lignin has good dispersibility in the epoxy resin, which enables it to withstand external forces uniformly, ensuring that the adhesive can still maintain good mechanical properties under complex working conditions.

[0035] (3) In the present invention, the curing agent in component B is a mixture of 4,4'-diaminodiphenylmethane and 4,4'-diaminodicyclohexylmethane, which not only retains rigidity but also improves the elongation at break and impact strength of the adhesive layer.

[0036] (4) By controlling the ratio of component A and component B, the present invention can make the curing reaction more complete and the crosslinking density higher, thereby achieving the optimal properties of the adhesive layer such as hardness and corrosion resistance. The preparation process of the present invention is simple to operate and easy to realize industrial production. Detailed Implementation

[0037] The technical solution of the present invention will be explained in detail below with reference to several representative embodiments.

[0038] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available.

[0039] The sodium lignosulfonate used in the following examples and comparative examples has been pretreated. The specific steps of the pretreatment are as follows: the sodium lignosulfonate is dried in a vacuum drying oven at 80°C for 6 hours to remove moisture.

[0040] Preparation Example 1

[0041] The specific steps of the preparation method of the modified lignin in this example are as follows:

[0042] 30g of sodium lignin sulfonate and 300mL of N,N-dimethylformamide were added to a three-necked flask and stirred for 1h. Then, 0.45g of 4-dimethylaminopyridine was added and stirred for 30min. Finally, 54g of oleic anhydride was slowly added, and the mixture was heated to 85℃ and reacted for 4h. After the reaction was completed, the product was poured into anhydrous ethanol for alcohol precipitation, filtered, washed with anhydrous ethanol, and dried under vacuum at 80℃ for 8h to obtain modified lignin.

[0043] Preparation Example 2

[0044] The specific steps of the preparation method of the modified lignin in this example are as follows:

[0045] 30g of sodium lignin sulfonate and 300mL of N,N-dimethylformamide were added to a three-necked flask and stirred for 1h. Then, 0.3g of 4-dimethylaminopyridine was added and stirred for 30min. Finally, 75g of oleic anhydride was slowly added and the mixture was heated to 80℃ and reacted for 3h. After the reaction was completed, the product was poured into anhydrous ethanol for alcohol precipitation, filtered, washed with anhydrous ethanol, and dried under vacuum at 80℃ for 8h to obtain modified lignin.

[0046] Preparation Example 3

[0047] The specific steps of the preparation method of the modified lignin in this example are as follows:

[0048] 30g of sodium lignin sulfonate and 300mL of N,N-dimethylformamide were added to a three-necked flask and stirred for 1h. Then, 0.15g of 4-dimethylaminopyridine was added and stirred for 30min. Finally, 39g of oleic anhydride was slowly added, and the mixture was heated to 95℃ and reacted for 2h. After the reaction was completed, the product was poured into anhydrous ethanol for alcohol precipitation, filtered, washed with anhydrous ethanol, and dried under vacuum at 80℃ for 8h to obtain modified lignin.

[0049] Preparation Example 4

[0050] The preparation method of this example for a hyperbranched polysiloxane includes the following specific steps:

[0051] 0.15 g of barium hydroxide was added to 15 g of triethylene glycol and stirred for 1 h to obtain a suspension. Under a nitrogen atmosphere, 10 g of vinyltriethoxysilane was added to a three-necked flask, and the suspension was added dropwise to the flask. The temperature was raised to 90 °C and the reaction was carried out for 6 h. After the reaction was completed, the reaction solution was poured into acetone to precipitate the precipitate. The precipitate was filtered, washed, and dried in a vacuum drying oven at 60 °C for 10 h to obtain hyperbranched polysiloxane.

[0052] Preparation Example 5

[0053] The preparation method of this example for a hyperbranched polysiloxane includes the following specific steps:

[0054] 0.19 g of barium hydroxide was added to 14 g of triethylene glycol and stirred for 1 h to obtain a suspension. Under a nitrogen atmosphere, 10 g of vinyltriethoxysilane was added to a three-necked flask, and the suspension was added dropwise to the flask. The temperature was raised to 75 °C and the reaction was carried out for 7 h. After the reaction was completed, the reaction solution was poured into acetone to precipitate the precipitate. The precipitate was filtered, washed, and dried in a vacuum drying oven at 60 °C for 10 h to obtain hyperbranched polysiloxane.

[0055] Preparation Example 6

[0056] The preparation method of this example for a hyperbranched polysiloxane includes the following specific steps:

[0057] 0.16 g of barium hydroxide was added to 12 g of triethylene glycol and stirred for 1 h to obtain a suspension. Under a nitrogen atmosphere, 10 g of vinyltriethoxysilane was added to a three-necked flask, and the suspension was added dropwise to the flask. The temperature was raised to 80 °C and the reaction was carried out for 8 h. After the reaction was completed, the reaction solution was poured into acetone to precipitate the precipitate. The precipitate was filtered, washed, and dried in a vacuum drying oven at 60 °C for 10 h to obtain hyperbranched polysiloxane.

[0058] Preparation Example 7

[0059] The preparation method of this example for a hyperbranched polysiloxane includes the following specific steps:

[0060] 0.11 g of barium hydroxide was added to 13 g of triethylene glycol and stirred for 1 h to obtain a suspension. Under a nitrogen atmosphere, 10 g of vinyltriethoxysilane was added to a three-necked flask, and the suspension was added dropwise to the flask. The temperature was raised to 85 °C and the reaction was carried out for 5 h. After the reaction was completed, the reaction solution was poured into acetone to precipitate the precipitate. The precipitate was filtered, washed, and dried in a vacuum drying oven at 60 °C for 10 h to obtain hyperbranched polysiloxane.

[0061] Example 1

[0062] An adhesive for a coated sucker rod according to this embodiment includes component A and component B;

[0063] Component A was prepared from the following raw materials by weight: 4.5 kg of bisphenol A epoxy resin, 2.5 kg of bisphenol F epoxy resin, 0.8 kg of modified lignin prepared in Preparation Example 1, 0.2 kg of graphene nanosheets, 0.4 kg of hyperbranched polysiloxane prepared in Preparation Example 4, 0.08 kg of silane coupling agent KH550, 0.6 kg of butyl glycidyl ether, and 0.03 kg of organosilicon defoamer;

[0064] Component B is prepared from the following raw materials by weight: 1.8 kg of 4,4'-diaminodiphenylmethane, 0.9 kg of 4,4'-diaminodicyclohexylmethane, 0.08 kg of 2-ethyl-4-methylimidazolium, and 0.2 kg of silane coupling agent KH550.

[0065] The preparation method of the adhesive for coated sucker rods in this embodiment includes the following specific steps:

[0066] S1: Bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified lignin, graphene nanosheets, hyperbranched polysiloxane, silane coupling agent KH550, butyl glycidyl ether and organosilicon defoamer are dispersed evenly to obtain component A.

[0067] S2: Disperse 4,4'-diaminodiphenylmethane, 4,4'-diaminodicyclohexylmethane, 2-ethyl-4-methylimidazolium and silane coupling agent KH550 evenly to obtain component B;

[0068] S3: Mix component A and component B at a mass ratio of 4:1 to obtain an adhesive for coated sucker rods.

[0069] Example 2

[0070] An adhesive for a coated sucker rod according to this embodiment includes component A and component B;

[0071] Component A was prepared from the following raw materials by weight: 5 kg of bisphenol A epoxy resin, 3 kg of bisphenol F epoxy resin, 1 kg of modified lignin prepared in Preparation Example 3, 0.1 kg of graphene nanosheets, 0.2 kg of hyperbranched polysiloxane prepared in Preparation Example 4, 0.1 kg of silane coupling agent KH550, 0.5 kg of butyl glycidyl ether, and 0.05 kg of organosilicon defoamer;

[0072] Component B is prepared from the following raw materials by weight: 1.5 kg of 4,4'-diaminodiphenylmethane, 1.5 kg of 4,4'-diaminodicyclohexylmethane, 0.1 kg of 2-ethyl-4-methylimidazolium, and 0.15 kg of silane coupling agent KH550.

[0073] The preparation method of the adhesive for coated sucker rods in this embodiment includes the following specific steps:

[0074] S1: Bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified lignin, graphene nanosheets, hyperbranched polysiloxane, silane coupling agent KH550, butyl glycidyl ether and organosilicon defoamer are dispersed evenly to obtain component A.

[0075] S2: Disperse 4,4'-diaminodiphenylmethane, 4,4'-diaminodicyclohexylmethane, 2-ethyl-4-methylimidazolium and silane coupling agent KH550 evenly to obtain component B;

[0076] S3: Mix component A and component B at a mass ratio of 4.5:1 to obtain an adhesive for coated sucker rods.

[0077] Example 3

[0078] An adhesive for a coated sucker rod according to this embodiment includes component A and component B;

[0079] Component A was prepared from the following raw materials by weight: 4 kg of bisphenol A epoxy resin, 2 kg of bisphenol F epoxy resin, 0.5 kg of modified lignin prepared in Preparation Example 1, 0.2 kg of graphene nanosheets, 0.25 kg of hyperbranched polysiloxane prepared in Preparation Example 4, 0.05 kg of silane coupling agent KH550, 0.8 kg of butyl glycidyl ether, and 0.02 kg of organosilicon defoamer;

[0080] Component B is prepared from the following raw materials by weight: 1.8 kg of 4,4'-diaminodiphenylmethane, 1 kg of 4,4'-diaminodicyclohexylmethane, 0.05 kg of 2-ethyl-4-methylimidazolium, and 0.1 kg of silane coupling agent KH550.

[0081] The preparation method of the adhesive for coated sucker rods in this embodiment includes the following specific steps:

[0082] S1: Bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified lignin, graphene nanosheets, hyperbranched polysiloxane, silane coupling agent KH550, butyl glycidyl ether and organosilicon defoamer are dispersed evenly to obtain component A.

[0083] S2: Disperse 4,4'-diaminodiphenylmethane, 4,4'-diaminodicyclohexylmethane, 2-ethyl-4-methylimidazolium and silane coupling agent KH550 evenly to obtain component B;

[0084] S3: Mix component A and component B at a mass ratio of 3:1 to obtain an adhesive for coated sucker rods.

[0085] Example 4

[0086] An adhesive for a coated sucker rod according to this embodiment includes component A and component B;

[0087] Component A was prepared from the following raw materials by weight: 4.8 kg of bisphenol A epoxy resin, 3.5 kg of bisphenol F epoxy resin, 0.6 kg of modified lignin prepared in Preparation Example 1, 0.3 kg of graphene nanosheets, 0.3 kg of hyperbranched polysiloxane prepared in Preparation Example 6, 0.07 kg of silane coupling agent KH550, 1 kg of butyl glycidyl ether, and 0.04 kg of organosilicon defoamer;

[0088] Component B is prepared from the following raw materials by weight: 1.4 kg of 4,4'-diaminodiphenylmethane, 1.4 kg of 4,4'-diaminodicyclohexylmethane, 0.12 kg of 2-ethyl-4-methylimidazolium, and 0.1 kg of silane coupling agent KH550.

[0089] The preparation method of the adhesive for coated sucker rods in this embodiment includes the following specific steps:

[0090] S1: Bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified lignin, graphene nanosheets, hyperbranched polysiloxane, silane coupling agent KH550, butyl glycidyl ether and organosilicon defoamer are dispersed evenly to obtain component A.

[0091] S2: Disperse 4,4'-diaminodiphenylmethane, 4,4'-diaminodicyclohexylmethane, 2-ethyl-4-methylimidazolium and silane coupling agent KH550 evenly to obtain component B;

[0092] S3: Mix component A and component B at a mass ratio of 3.5:1 to obtain an adhesive for coated sucker rods.

[0093] Comparative Example 1

[0094] The difference from Example 1 is that no modified lignin was added in this comparative example.

[0095] Comparative Example 2

[0096] The difference from Example 1 is that this comparative example uses an equal amount of sodium lignin sulfonate instead of modified lignin.

[0097] Comparative Example 3

[0098] The difference from Example 1 is that this comparative example does not contain hyperbranched polysiloxane.

[0099] Comparative Example 4

[0100] The difference from Example 1 is that no graphene nanosheets were added in this comparative example.

[0101] Comparative Example 5

[0102] The difference from Example 1 is that the curing agent in this comparative example is 4,4'-diaminodiphenylmethane.

[0103] Comparative Example 6

[0104] The difference from Example 1 is that the curing agent in this comparative example is 4,4'-diaminodicyclohexylmethane.

[0105] Related performance tests

[0106] The adhesives prepared in Examples 1-4 and Comparative Examples 1-6 were uniformly applied to the surface of an aluminum plate, dried, and then placed in acid and alkali solutions respectively after curing. After being placed at room temperature for 24 hours, the samples were taken out and their shear strength was tested. The test results are shown in Table 1.

[0107] Table 1 Test Results

[0108]

[0109] As can be seen from Table 1, the test results of Examples 1-4 are better than those of Comparative Examples 1-6, indicating that the adhesive for coated sucker rods prepared in this invention has good corrosion resistance.

[0110] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. An adhesive for encapsulated sucker rods, characterized in that, The product comprises component A and component B. Component A is prepared from the following raw materials in parts by weight: 40-50 parts of bisphenol A epoxy resin, 20-35 parts of bisphenol F epoxy resin, 5-10 parts of modified lignin, 1-3 parts of graphene nanosheets, 2-4 parts of hyperbranched polysiloxane, 0.5-1 part of silane coupling agent, 5-10 parts of diluent, and 0.2-0.5 parts of defoamer. Component B is prepared from the following raw materials in parts by weight: 25-30 parts of curing agent, 0.5-1.2 parts of 2-ethyl-4-methylimidazole, and 1-2 parts of silane coupling agent. The method for preparing the modified lignin includes the following steps: mixing sodium lignin sulfonate, oleic anhydride, 4-dimethylaminopyridine and N,N-dimethylformamide evenly, heating and reacting to obtain modified lignin; The preparation method of the hyperbranched polysiloxane includes the following steps: under anaerobic conditions, vinyltriethoxysilane, triethylene glycol and barium hydroxide are mixed evenly and heated to react, so as to obtain hyperbranched polysiloxane. The curing agent is prepared by mixing 4,4'-diaminodiphenylmethane and 4,4'-diaminodicyclohexylmethane.

2. The adhesive for a coated sucker rod according to claim 1, characterized in that, The mass ratio of sodium lignosulfonate to oleic anhydride is 1:(1.3-2.5).

3. The adhesive for a coated sucker rod according to claim 1, characterized in that, The amount of 4-dimethylaminopyridine used is 0.5%-1.5% of the mass of sodium lignosulfonate.

4. The adhesive for a coated sucker rod according to claim 1, characterized in that, In the preparation method of modified lignin, the reaction temperature is 80-95℃ and the reaction time is 2-5h.

5. The adhesive for a coated sucker rod according to claim 1, characterized in that, The mass ratio of vinyltriethoxysilane to triethylene glycol is 1:(1.2-1.5); the amount of barium hydroxide used is 0.4%-0.8% of the total mass of vinyltriethoxysilane and triethylene glycol.

6. The adhesive for a coated sucker rod according to claim 1, characterized in that, In the preparation method of hyperbranched polysiloxane, the reaction temperature is 75-90℃ and the reaction time is 5-8h.

7. The adhesive for a coated sucker rod according to claim 1, characterized in that, The curing agent is prepared by mixing 4,4'-diaminodiphenylmethane and 4,4'-diaminodicyclohexylmethane in a mass ratio of (1-2):

1.

8. A method for preparing an adhesive for coated sucker rods according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified lignin, graphene nanosheets, hyperbranched polysiloxane, silane coupling agent, diluent and defoamer are dispersed evenly to obtain component A; S2: Disperse the curing agent, 2-ethyl-4-methylimidazolium and silane coupling agent evenly to obtain component B; S3: Mix component A and component B at a mass ratio of (3-4.5):1 to obtain an adhesive for coated sucker rods.

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