PGA resin edge grafting modified graphene, composition, preparation method and application of composition, biodegradable polyester material, application of biodegradable polyester material and temporary plugging ball

Abstract

The invention belongs to the technical field of high polymer materials, and discloses PGA resin edge grafting modified graphene, a composition, a preparation method and application of the composition, a biodegradable polyester material, application of the biodegradable polyester material and a temporary plugging sphere. The PGA resin edge grafting modified graphene comprises graphene and polyglycolic acid resin grafted on the edge of the graphene, based on the total mass of the PGA resin edge grafting modified graphene, the mass percentage of the grafted polyglycolic acid resin in the PGA resin edge grafting modified graphene is 1-20%, preferably 3-15%. The PGA resin edge grafting modified graphene provided by the invention has good thermal conductivity and a relatively large aspect ratio.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a PGA-type resin edge-grafted modified graphene and its preparation method, a PGA composition and its preparation method and application, a biodegradable polyester material and its application, and a PGA temporary plugging ball. Background Technology

[0002] As existing proven oil and gas fields are continuously exploited, the abundance of oil and gas in reservoirs gradually declines. Therefore, reservoir fracturing is often used to adjust the permeability of underground reservoirs, thereby achieving sustainable exploitation of oil and gas resources in increasingly depleted underground reservoirs. As the most widely used layered fracturing technology, the ball-drop layered fracturing method utilizes the high fluid absorption capacity of already fractured oil and gas layers. After fracturing a target layer, a certain amount of temporary plugging balls are carried by fracturing fluid into the pores of the fractured layer to seal the pores, forcing the fracturing fluid into other unfractured layers, increasing the fracturing pressure, and thus fracturing another target reservoir requiring a higher fracturing pressure. This process is repeated until all target layers within the fracturing interval are fractured, achieving the goal of fracturing multiple production layers in a single operation. In the above operations, temporary plugging balls are the most commonly used downhole production tool. However, existing temporary plugging balls are generally made of non-degradable plastics, rubber, metal alloys, etc. In actual downhole production applications, the temporary plugging balls need to be unplugged after a section of production. Traditional plugging balls are often difficult to dissolve with common reagents. They either dissolve slowly and are difficult to dissolve, or even if they do dissolve, they easily become stuck in the wellbore, making them difficult to remove from the wellbore after the plugging and fracturing operation is completed. To address these issues, additional measures are needed to drill or retrieve the plugging balls, which significantly increases operating costs, reduces production efficiency, and typically uses more fluid during drilling, potentially causing secondary pollution to the underground reservoir. Furthermore, plugging balls made of metal alloys, due to their high rigidity and strength, require the addition of large amounts of electrolyte salts to the production fluid. After dissolution, the alloy often forms residues, further polluting the underground reservoir. When the wellbore shape is irregular, the high rigidity and low plasticity of the alloy material prevent it from deforming to adapt to the irregular shape, resulting in poor sealing and difficulty in establishing stable pressure resistance, significantly impacting the effectiveness of the plugging and fracturing operation. Chinese invention patent application 202011020847.8 discloses a three-layer composite temporary plugging ball with good temporary plugging effect, but the formula is complex and contains non-degradable polyvinyl alcohol, which is not easily returned with fracturing fluid after unplugging and will cause secondary pollution if left in the formation. Chinese invention patent application 202110861989.5 discloses a biodegradable temporary plugging ball. However, this temporary plugging ball contains 15-30 parts by weight of functional filler (functional zeolite powder) and 4-8 parts of EVA-grafted MAH, and these components cannot be completely degraded in the formation.

[0003] Graphene has attracted much attention due to its high light transmittance, high electrical conductivity, high thermal conductivity, high specific surface area, and excellent mechanical properties. To expand its application areas and fully utilize these properties, developing high-quality, low-cost preparation technologies for functionalized graphene is crucial and a prerequisite for large-scale commercial applications. Common graphene preparation methods include redox methods, mechanical exfoliation, chemical vapor deposition (CVD), arc discharge (ADM), and electrochemical methods. Among these, CVD, ADM, and electrochemical methods are costly and have complex processes. Mechanical exfoliation and redox methods both use natural or artificial graphite as raw materials, utilizing mechanical or chemical exfoliation techniques. Graphite raw materials are abundant, costs are controllable, and they are suitable for large-scale graphene production. However, redox methods use large amounts of strong acids and strong oxidants during production, inevitably leading to severe wastewater pollution. The resulting graphene may contain topological defects such as five-membered and seven-membered rings or structural defects such as hydroxyl groups, which will result in the loss of some properties and significantly limit the application range of graphene. Mechanical exfoliation methods include ball milling, sand milling, and ultrasonic methods, which yield graphene with low oxygen content and better performance. Although these methods can produce graphene on a large scale, the destructive effect of traditional mechanical exfoliation results in relatively severe structural damage to the graphene, leading to a size smaller than 100 nanometers and a greater tendency to aggregate. Summary of the Invention

[0004] The purpose of this invention is to provide edge-grafted graphene of PGA resin and its preparation method, PGA composition and its preparation method and application, biodegradable polyester material and its application, and PGA temporary plugging ball. The edge-grafted graphene of PGA resin of this invention has good thermal conductivity and a large aspect ratio. When added to a PGA composition, the prepared PGA temporary plugging ball has good rigidity, self-lubrication and plasticity at high temperature, and can be rapidly degraded by adding water, thereby meeting the requirements of segmented oil and gas extraction.

[0005] A first aspect of the present invention provides a PGA-based resin edge-grafted modified graphene, the PGA-based resin edge-grafted modified graphene comprising: graphene and a polyglycolic acid resin grafted thereon at its edges, wherein the mass percentage of the polyglycolic acid resin grafted in the PGA-based resin edge-grafted modified graphene is 1-20%, preferably 3-15%, based on the total mass of the PGA-based resin edge-grafted modified graphene.

[0006] A second aspect of the present invention provides a method for preparing the above-mentioned PGA-type resin edge-grafted modified graphene, the method comprising:

[0007] In the presence of a non-flammable gas mixture, polyglycolic acid resin and graphite are ground and mixed to obtain PGA-type resin edge-grafted modified graphene.

[0008] A third aspect of the present invention provides a PGA composition containing edge-grafted graphene of a PGA-type resin, the PGA composition comprising: a polyglycolic acid resin, the aforementioned edge-grafted graphene of the PGA-type resin, a bio-based elastomer, an antioxidant, a nucleating agent, a chain extender, and a hydrolysis inhibitor.

[0009] A fourth aspect of the present invention provides a method for preparing the above-mentioned PGA composition, the method comprising: mixing the polyglycolic acid resin, the above-mentioned PGA resin edge-grafted modified graphene, a bio-based elastomer, an antioxidant, a nucleating agent, a chain extender and a hydrolysis inhibitor uniformly to obtain the PGA composition.

[0010] A fifth aspect of the present invention provides a biodegradable polyester material, which is prepared by a method comprising the following steps: melt-mixing the above-mentioned PGA composition to obtain the biodegradable polyester material.

[0011] The sixth aspect of the present invention provides the use of the above-described PGA composition and the above-described biodegradable polyester material in the preparation of PGA temporary plugging balls.

[0012] A seventh aspect of the present invention provides a PGA temporary plugging ball, which is obtained by a method comprising the following steps: injection molding and annealing the above-mentioned biodegradable polyester material to obtain the PGA temporary plugging ball.

[0013] The technical solution of the present invention has the following beneficial effects:

[0014] 1. The PGA-type resin edge-grafted modified graphene of the present invention has good thermal conductivity and a large aspect ratio.

[0015] 2. Compared to grinding processes such as ultrasonication, ball milling, and sand milling, grinding discs have a weaker destructive effect on the graphite crystal structure, making it easier to prepare PGA edge-grafted graphene with a larger aspect ratio. The high strength and high modulus characteristics of PGA can synergistically work with the grinding disc, thereby improving the graphite sheet exfoliation efficiency and effect. During the exfoliation process, PGA utilizes its terminal carboxyl and hydroxyl groups to graft onto the edges of graphene, achieving graphene-PGA composite under non-oxidative conditions.

[0016] 3. PGA temporary plugging balls containing PGA resin edge-grafted modified graphene and combined additives have good rigidity, self-lubrication and plasticity at high temperatures, which can meet the pressure resistance requirements of temporary plugging balls, effectively fit the oil and gas boreholes to improve the temporary plugging efficiency, and can be rapidly degraded by adding water, thereby meeting the requirements of segmented oil and gas extraction.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0018] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0019] A first aspect of the present invention provides a PGA-based resin edge-grafted modified graphene, the PGA-based resin edge-grafted modified graphene comprising: graphene and a polyglycolic acid resin grafted thereon at its edges, wherein the mass percentage of the polyglycolic acid resin grafted in the PGA-based resin edge-grafted modified graphene is 1-20%, preferably 3-15%, for example 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, based on the total mass of the PGA-based resin edge-grafted modified graphene.

[0020] According to the present invention, preferably, the average sheet diameter of the PGA-type resin edge-grafted modified graphene is 2-6 μm;

[0021] And / or, the aspect ratio of the PGA-type resin edge-grafted modified graphene is (180-1850):1, preferably (200-1750):1, and more preferably (560-1650):1.

[0022] In this invention, the shearing and peeling action of the grinding disc is achieved by the action of PGA on graphite, which has a smaller destructive effect on graphene compared to methods such as ball milling and sand milling. Therefore, the edge-grafted modified graphene sheets of the PGA-type resin are relatively large.

[0023] The average sheet diameter of the PGA-type resin-grafted modified graphene can be obtained by randomly measuring the size of more than 10 graphene sheets using a scanning electron microscope (SEM) or atomic force microscope. The method for measuring the size of a single graphene sheet is as follows: draw three lines through the center of the graphene sheet, with an angle of approximately 60° between the lines. Measure the length of the graphene along these three lines and calculate the average value as the size of this graphene sheet.

[0024] According to the present invention, preferably, the thermal conductivity of the PGA-type resin edge-grafted modified graphene is 200-400 W / m·K, more preferably 220-320 W / m·K.

[0025] The grafted graphene obtained by edge grafting PGA resin to PGA resin of the present invention has excellent thermal conductivity and can be added as a filler to polyglycolic acid composition to make the composition have better thermal conductivity.

[0026] The structure and properties of the PGA-type resin edge-grafted modified graphene of the present invention are significantly different from those of existing grafted graphene oxide or grafted reduced graphene oxide.

[0027] Structurally, the national standard GB / T30544.13-2018 separately defines graphene oxide and reduced graphene oxide. Graphene oxide is chemically modified graphene obtained by oxidizing and exfoliating graphite; its surface has been strongly oxidized and has a high oxygen content. Reduced graphene oxide is graphene oxide with reduced oxygen content, but it still retains some oxygen-containing functional groups, and SP... 3 Chemical bonds cannot be completely reduced to sp. 2 Chemical bonds leave many topological defects. Therefore, the structures of graphene oxide and reduced graphene oxide differ significantly from those of graphene. This invention uses graphene, not graphene oxide or reduced graphene oxide. From a properties perspective, most reported PGA-modified graphene is based on the grafting reaction of oxygen-containing groups of graphene oxide with PGA, followed by reduction to prepare PGA-grafted graphene.

[0028] In this invention, the term "edge" refers to the outer edge of the graphene sheet / graphene lattice. "Edge grafting" refers to the connection of modified molecules with atoms at the edge of the graphene lattice through chemical bonds.

[0029] In this invention, the term "surface" refers to the exposed portion of the graphene sheet / graphene lattice except for its edges.

[0030] In this invention, the term "edge-grafted modified graphene" in the PGA-type resin edge-grafted graphene refers to at least 90% by weight, preferably at least 95% by weight, at least 96% by weight, 97% by weight, 98% by weight, more preferably at least 99% by weight, and most preferably at least 100% by weight of the grafted polymer being atomically grafted to the edge of the graphene lattice via chemical bonds.

[0031] A second aspect of the present invention provides a method for preparing the above-mentioned PGA-type resin edge-grafted modified graphene, the method comprising:

[0032] In the presence of a non-flammable gas mixture, polyglycolic acid resin and graphite are ground and mixed to obtain PGA-type resin edge-grafted modified graphene.

[0033] In this invention, the PGA-type resin edge-grafted modified graphene obtained after grinding and mixing is in powder form.

[0034] This invention relates to a PGA-based resin edge-grafted modified graphene prepared by using a PGA-based resin-assisted grinding disc to exfoliate graphite and generate heat while simultaneously performing in-situ grafting.

[0035] In this invention, the grinding and mixing are preferably carried out in a high-pressure grinding disc kettle with a supercritical fluid circulation function. This high-pressure grinding disc kettle with supercritical fluid circulation function is conventional equipment in the art, comprising a high-pressure grinding disc kettle and a circulation unit. A moving grinding disc and a stationary grinding disc are disposed within the high-pressure grinding disc kettle. The circulation unit includes a high-pressure resistant circulation pump, a high-pressure resistant gas storage tank, and a booster pump. This high-pressure grinding disc kettle with supercritical fluid circulation function enables the supercritical fluid to circulate within the high-pressure grinding disc kettle.

[0036] During the exfoliation process, the moving / stationary grinding disc transmits shear force to the graphite sheets between the discs via PGA-like microparticles. Under shear stress, the graphite sheets initially align along the rotation direction of the grinding discs, and are then gradually exfoliated into thinner sheets, ultimately forming graphene. During exfoliation, many new edges are generated. The carbon atoms at these new edges are highly reactive and react with shear-thermally activated PGA to form PGA-grafted graphene. The method of this invention significantly reduces damage to the graphite lattice. After the exfoliation process is complete, the PGA-like resin grafted onto the edges of the graphene remains stable.

[0037] The PGA resin in this invention system has two functions: (1) to improve the peeling effect of the grinding disc on the graphite sheet, and (2) to form a grafted composition with graphene.

[0038] This invention employs a grinding disc process, in which PGA-based resin and graphite are cyclically exfoliated between grinding discs. The shearing force between the stationary and moving grinding discs is transferred to the graphite sheets through the PGA-based resin powder, achieving the exfoliation and preparation of graphene. Compared with methods such as ball milling, sand milling, and ultrasonication, the grinding disc process effectively utilizes the exfoliation force between the grinding discs, reducing graphite sheet breakage. Especially after the PGA-based resin undergoes self-shearing, heat generation, and thickening, the shearing force between the grinding discs is more effectively transferred to the graphite sheet layers through supercritical fluid, improving exfoliation efficiency and reducing destructive effects. Therefore, the graphene sheets prepared by the grinding disc method are larger, flatter, and less prone to agglomeration. Thus, the PGA-based resin edge-grafted modified graphene of this invention has broad applications in composite polymers, oil and gas extraction, and other fields.

[0039] According to the present invention, preferably, the graphite is natural graphite and / or artificial graphite; the natural graphite is selected from crystalline graphite and / or cryptocrystalline graphite; the artificial graphite is selected from pyrolytic graphite and / or highly oriented pyrolytic graphite.

[0040] The graphite is preferably crystalline graphite, and the crystalline graphite is preferably flake graphite; more preferably, the fixed carbon content of the flake graphite is ≥99.9% or the fixed carbon content is 94%-99.9%, and more preferably, the fixed carbon content of the flake graphite is ≥99.9%.

[0041] The cryptocrystalline graphite is preferably earthy graphite;

[0042] The graphite has a particle size of 100-5000 mesh, preferably 200-4000 mesh, more preferably 200-2000 mesh, and even more preferably 200-400 mesh.

[0043] According to the present invention, preferably, the melt flow rate of the polyglycolic acid resin at 230°C and 2.16 kg load is 5-60 g / 10 min, more preferably 10-50 g / 10 min, and more preferably 15-45 g / 10 min;

[0044] And / or, the weight-average molecular weight of the polyglycolic acid resin is 10,000-800,000, preferably 20,000-300,000, and more preferably 50,000-200,000;

[0045] And / or, the molecular weight distribution width Mw / Mn of the polyglycolic acid resin is 1-5, preferably 1.5-3.5;

[0046] And / or, the polyglycolic acid resin is homopolymer polyglycolic acid and / or copolymer polyglycolic acid, preferably homopolymer polyglycolic acid.

[0047] According to the present invention, preferably, the non-flammable mixture comprises carbon dioxide, nitrogen and optionally argon; and based on the total weight of the non-flammable mixture, the content of carbon dioxide is 30-50 wt%, the content of nitrogen is 45-65 wt%, and the content of argon is 0-5 wt%.

[0048] The grinding and mixing conditions include: a grinding speed of 5-250 rpm, preferably 10-200 rpm; a circulating grinding time of 10-300 hours, preferably 15-200 hours, more preferably 24-120 hours; a pressure inside the grinding and mixing equipment of 15-25 MPa; and a grinding and mixing temperature of 40-50℃.

[0049] The grinding and mixing are preferably carried out in a closed system with a circulation function, and more preferably in a high-pressure grinding disc kettle with a supercritical fluid circulation function.

[0050] A third aspect of the present invention provides a PGA composition containing edge-grafted graphene of a PGA-type resin, the PGA composition comprising: a polyglycolic acid resin, edge-grafted graphene of a PGA-type resin as described in any one of claims 1-3, a bio-based elastomer, an antioxidant, a nucleating agent, a chain extender, and a hydrolysis inhibitor.

[0051] According to the present invention, preferably, relative to 100 parts by weight of the resin composition, the content of the antioxidant is 0.15 to 0.25 parts by weight, the content of the nucleating agent is 0.13 to 0.46 parts by weight, the content of the chain extender is 0.1 to 2 parts by weight, preferably 0.2 to 1 part by weight, and the content of the hydrolysis inhibitor is 0.1 to 2 parts by weight, preferably 0.5 to 1.2 parts by weight;

[0052] The resin composition comprises polyglycolic acid, edge-grafted graphene of the above-mentioned PGA resin, and bio-based elastomer, wherein the mass ratio of the polyglycolic acid resin, the edge-grafted graphene of the above-mentioned PGA resin, and the bio-based elastomer is (80-95):(4-18):(1-6).

[0053] Preferably, the antioxidant comprises a primary antioxidant and a secondary antioxidant, wherein the mass ratio of the primary antioxidant to the secondary antioxidant is (0.5 to 1):1.

[0054] According to the present invention, preferably, the bio-based elastomer is selected from at least one of poly(saccharide-glycerol) elastomer, acrylated poly(saccharide-glycerol) elastomer, poly(citrate-1,8-octanediol) elastomer, copolymer of lactide-caprolactone, glycolide-lactide copolymer, glycolide-lactide-caprolactone terpolymer, poly(ester-carbonate) elastomer, poly(citrate-octanediol-saccharide) elastomer, poly(saccharide-glycerol-citrate) elastomer, poly(saccharide-1,2-propanediol-citrate) elastomer, poly(itaconate-isoprene-glycidyl methacrylate) elastomer, soybean oil-based elastomer, itacate elastomer containing a ternary epoxy structure, and myrcene-based bio-based elastomer;

[0055] Preferably, the bio-based elastomer has a weight-average molecular weight of 50,000 to 100,000 and a molecular weight distribution width (Mw / Mn) of 1 to 3.

[0056] According to the present invention, preferably, the primary antioxidant is selected from at least one of antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; CAS No.: 6683-19-8), antioxidant 3114 (1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid; CAS: 27676-62-6), antioxidant 245 (triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate]), and antioxidant 330 (1,3,5-trimethyl-2,4,6-tris(3,5-tert-butyl-4-hydroxybenzyl)benzene; CAS: 1709-70-2).

[0057] The secondary antioxidant is selected from at least one of antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite; CAS: 31570-04-4), antioxidant 618 (pentaerythritol distearate diphosphite; CAS: 3806-34-6), bis(2,4-dicumylphenyl)pentaerythritol-diphosphite, pentaerythritol dioctadecyl diphosphite, and antioxidant 2,2'-ethylidene di(4,6-di-tert-butylphenyl)fluorophosphite (CAS: 118337-09-0).

[0058] According to the present invention, preferably, the chain extender is selected from at least one of styrene-glycidyl methacrylate copolymer, styrene-butyl acrylate-glycidyl methacrylate terpolymer, methylstyrene-methacrylate-glycidyl acrylate terpolymer, styrene-methyl methacrylate-glycidyl methacrylate terpolymer, and ethylene-butyl acrylate-glycidyl methacrylate terpolymer.

[0059] According to the present invention, preferably, the hydrolysis inhibitor is selected from polycarbodiimide, monomeric carbodimethylamine, dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 2,2',6,6'-tetraisopropylcarbodimethylamine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide salt. The salt, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-ethyl-3-(3-dimethylaminopropyl)carboammonium, 1-(3-dimethylaminopropyl)-3-ethyl-carbodiimide hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide hydrochloride and (3-dimethylaminopropyl)-3-ethylcarbodiamine.

[0060] According to the present invention, preferably, the nucleating agent is selected from at least one of hyperbranched polyamide, ethylene-methacrylate ionomer, diphenyl dihydrazide sebacate, diphenyl dihydrazide adipate, and zinc phenyl phosphate.

[0061] According to the present invention, preferably, the melt flow rate of the polyglycolic acid resin at 230°C and 2.16 kg load is 5-60 g / 10 min, more preferably 10-50 g / 10 min, and more preferably 15-45 g / 10 min;

[0062] And / or, the weight-average molecular weight of the polyglycolic acid resin is 10,000-800,000, preferably 20,000-300,000, and more preferably 50,000-200,000;

[0063] And / or, the molecular weight distribution width Mw / Mn of the polyglycolic acid resin is 1-5, preferably 1.5-3.5;

[0064] And / or the polyglycolic acid resin is homopolymer polyglycolic acid and / or copolymer polyglycolic acid, preferably homopolymer polyglycolic acid.

[0065] A fourth aspect of the present invention provides a method for preparing the above-mentioned PGA composition, the method comprising: mixing the polyglycolic acid resin, the above-mentioned PGA resin edge-grafted modified graphene, a bio-based elastomer, an antioxidant, a nucleating agent, a chain extender and a hydrolysis inhibitor uniformly to obtain the PGA composition.

[0066] The method for preparing the PGA composition of the present invention preferably involves mixing in a mixer at a speed of 1000-3000 rpm.

[0067] A fifth aspect of the present invention provides a biodegradable polyester material, which is prepared by a method comprising the following steps: melt-mixing the above-mentioned PGA composition to obtain the biodegradable polyester material.

[0068] In this invention, the melt mixing equipment is selected from at least one of a single-screw extruder, a single-screw reciprocating extruder, a twin-screw extruder, a three-screw extruder, and a mixer, with a twin-screw extruder being preferred. The pelletizing method after extrusion of the composition is preferably anhydrous air-cooled pelletizing.

[0069] In this invention, water-cooled pelletizing can also be used, and the pellets are dried after water-cooled pelletizing. In this invention, there are no particular limitations on the drying conditions, for example, the drying temperature is 50-90℃.

[0070] In this invention, as a specific embodiment, the biodegradable polyester material is prepared by a method comprising the following steps: melting, extruding, and granulating the above-mentioned PGA composition in a single-screw extruder and / or a twin-screw extruder to obtain the biodegradable polyester material; preferably, the extrusion temperature is 150-230°C, more preferably 170-190°C; and the screw speed is 250-350 rpm.

[0071] The sixth aspect of the present invention provides the use of the above-described PGA composition and the above-described biodegradable polyester material as raw materials for preparing PGA temporary plugging balls.

[0072] A seventh aspect of the present invention provides a PGA temporary plugging ball, which is obtained by a method comprising the following steps: injection molding and annealing the above-mentioned biodegradable polyester material to obtain the PGA temporary plugging ball.

[0073] In this invention, preferably, the biodegradable polyester material is preheated before injection molding to achieve drying of the biodegradable polyester material.

[0074] According to the present invention, preferably, the process parameters for injection molding include: injection pressure of 70-100 bar, holding pressure of 70-120 bar, mold temperature of 60-110°C, and injection speed of 10-20 cm. 3 / s;

[0075] The annealing temperature is 80-110℃, and the time is 1-5 hours.

[0076] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0077] Unless otherwise stated, all experimental reagents used in the following examples and comparative examples were commercially available.

[0078] In the following embodiments and comparative examples:

[0079] Antioxidant I: A mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010) and tris[2,4-di-tert-butylphenyl] phosphite (168) in a mass ratio of 1:1;

[0080] Antioxidant II: A mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010) and tris[2,4-di-tert-butylphenyl] phosphite (168) in a mass ratio of 1:2;

[0081] Antioxidant III: a mixture of triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate (245) and tris[2,4-di-tert-butylphenyl]phosphite (168) in a mass ratio of 1:1;

[0082] Nucleating agent I: ethylene-methacrylic acid ionomer; specifically DuPont 4170;

[0083] Nucleating agent II: diphenyl dihydrazide sebacate; purchased from Bailingwei Company;

[0084] Nucleating agent III: diphenylhydrazide adipic acid; purchased from Bailingwei Company;

[0085] Chain extender I: Ethylene-butyl acrylate-glycidyl methacrylate terpolymer; specifically, Jia Yi Rong 3510;

[0086] Chain extender II: styrene-methyl methacrylate-glycidyl methacrylate terpolymer; specifically BASF's 4468;

[0087] PGAI: Homopolymer polyglycolic acid (PGA), purchased from Pujing Chemical, with a melt index of 17.3 g / 10 min (230℃, 2.16 kg) and a weight-average molecular weight of 13.4 × 10⁻⁶. 4 The molecular weight distribution width Mw / Mn = 1.63;

[0088] PGAII: Poly(glycolic acid-lactide) PGA-LA, purchased from Pujing Chemical, with a melt index of 23.54 g / 10 min (230℃, 2.16 kg) and a weight-average molecular weight of 7.9 × 10⁻⁶. 4 The molecular weight distribution width Mw / Mn = 1.54;

[0089] PGAIII: Poly(glycolic acid-caprolactone) PGA-CL, purchased from Pujing Chemical, with a melt index of 21.93 g / 10 min (230℃, 2.16 kg) and a weight-average molecular weight of 7.2 × 10⁻⁶. 4 The molecular weight distribution width Mw / Mn = 1.77;

[0090] Bio-based elastomer A: Poly(1,2-propanediol sebacic acid) ester (PPSC) elastomer, purchased from Beijing Research Institute of Chemical Industry, with a weight-average molecular weight of 6.5 × 10⁻⁶. 4 , The molecular weight distribution width is Mw / Mn=1.93;

[0091] Bio-based elastomer B: Poly(citric acid-octyl glycol-sebacic acid) ester elastomer, purchased from Beijing Research Institute of Chemical Industry, with a weight-average molecular weight of 8.4 × 10⁻⁶. 4 , The molecular weight distribution width Mw / Mn = 1.54;

[0092] Bio-based elastomer C: Poly(1,8-octanediol citrate) ester (POC) elastomer, purchased from Beijing Research Institute of Chemical Industry, with a weight-average molecular weight of 7.9 × 10⁻⁶. 4, The molecular weight distribution width Mw / Mn = 1.54;

[0093] Hydrolysis inhibitor A: 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride;

[0094] Hydrolysis inhibitor B: 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride.

[0095] Flake graphite with mesh sizes of 200, 300, 350, and 500 was purchased from Qingdao Santong Graphite Co., Ltd., and the fixed carbon content was 94%-99.9% by mass.

[0096] In the following examples and comparative examples, the melt flow index of the raw materials used was determined according to the methods specified in the national standard GB / T3682.2 "Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of plastics and thermoplastics - Part 2: Test methods for materials sensitive to time-temperature history and / or humidity". The specific conditions for testing the melt mass flow rate (MFR) of PGA resins were: 230°C, 2.16 kg. The weight-average molecular weight and molecular weight distribution width were determined as follows: The PGA resin sample was dissolved in hexafluoroisopropanol solution to prepare a 0.3% (w / w) solution, and heated at 90°C for 5 hours until dissolved. After filtration through a polytetrafluoroethylene (PTFE) filter membrane, 10 μL was injected into an Agilent 1260GPC sampler. The column temperature was set at 35℃; hexafluoroisopropanol containing 20 mmol / L sodium trifluoroacetate was used as the eluent; the flow rate was set at 1 mL / min; and the relative molecular mass was corrected using nine different standard polymethyl methacrylates with relative molecular masses ranging from 1010 to 766000 to obtain Mw and PDI.

[0097] In the following embodiments and comparative examples:

[0098] The mass percentage of PGA resin grafted onto graphene in PGA-based resin edge-grafted graphene can be determined by thermogravimetric analysis. For example, under nitrogen flow rate of 20.0 ml / min, the mass loss of the PGA-based resin edge-grafted graphene sample from 50.00℃ to 800.00℃ at a heating rate of 10.00℃ / min represents the mass percentage of PGA grafted onto the graphene.

[0099] The average sheet diameter (average sheet size) of PGA-based resin edge-grafted graphene can be obtained by imaging with a scanning electron microscope (SEM) and randomly measuring the size of more than 10 graphene sheets to calculate the average value. The method for measuring the size of a single graphene sheet is as follows: draw three lines through the center of the graphene sheet, with an angle of approximately 60° between the lines. Measure the length of the graphene sheet along these three lines and calculate the average value as the size of this graphene sheet. The aspect ratio is calculated as the average sheet diameter / average thickness of the PGA-based resin edge-grafted graphene. The scanning electron microscope used is a Hitachi S4800 from Japan.

[0100] The thermal conductivity of graphene was tested using a Netzsch LFA467 instrument from Germany, and the testing method followed the GB / T22588-2008 standard. The thermal conductivity (K) of the test sample can be calculated using the following formula: K=α×Cp×ρ, where α is the thermal diffusivity, Cp is the specific heat capacity, and ρ is the bulk density. The mechanism involves a laser source instantaneously emitting a light pulse at a set temperature, uniformly irradiating the sample surface. The surface absorbs the light energy, causing an instantaneous temperature rise, which then acts as a heat transfer point, propagating the energy in both planar and vertical directions via thermal conduction. An infrared detector continuously measures the corresponding temperature rise at the center of the sample surface, obtaining a curve showing the relationship between the detector signal (temperature) and time. A corrected curve is obtained through appropriate mathematical modeling, from which the thermal diffusivity can be calculated.

[0101] The test items in Table 4 should be performed according to the following method:

[0102] Pressure bearing strength: The temporary plugging ball with the measured diameter is installed in the temporary plugging ball pressure bearing evaluation instrument. The diameter of the temporary plugging ball d should be ≥ 1.25 cm and the diameter of the ball seat hole. The temporary plugging ball is subjected to pressure tests starting from 40 MPa. It is qualified if it does not puncture or leak after 5 minutes of pressure stabilization. The pressure at which the temporary plugging ball does not break within 3 hours of small-scale testing is the pressure bearing strength.

[0103] The 75MPa stabilization time is the time it takes for the temporary plug to rupture under a pressure of 75MPa.

[0104] The elastic deformation rate and elastic recovery rate were tested under the conditions of 25℃ and 50MPa pressure.

[0105] Determination of the coefficient of friction: GB / T 10006-2021 Determination of the coefficient of friction of plastic films and sheets. The coefficient of friction describes the ratio between sliding friction and normal force (force perpendicular to the contact surface) when two surfaces are in contact. The coefficient of friction tester used was purchased from IDM Instruments, Australia, model C0055-M3.

[0106] The calculation method for degradation rate, degradation rate D,

[0107] D = (m1 + m2 - m3) / m2 × 100%, where:

[0108] D-degradation rate,

[0109] M1 - Mass of rapid quantitative filter paper, g;

[0110] Mass of M2-temporarily plugging ball sample, g;

[0111] M3 - Mass of residue and residual filter paper after sample degradation, g

[0112] Example 1

[0113] (1) Preparation of graphene modified by edge grafting of PGA-based resins:

[0114] As shown in Table 1, 100.0 g of PGA-based resin and 120 g of flake graphite (Qingdao Santong Graphite Co., Ltd., with a fixed carbon content of 94%-99.9%) were added to a high-pressure grinding vessel equipped with supercritical fluid circulation. A mixture of carbon dioxide, nitrogen, and argon (carbon dioxide:nitrogen:argon = 30:65:5, by weight) was introduced, and the mixture was then ground and mixed in the high-pressure grinding vessel with supercritical fluid circulation to obtain PGA-based resin edge-grafted modified graphene powder. The grinding and mixing temperature was 45℃, the mixed gas pressure (i.e., the pressure of the high-pressure grinding vessel) was 15 MPa, the grinding speed was set to 100 rpm, and the grinding was carried out for 96 hours. The prepared PGA-based resin edge-grafted modified graphene was observed by scanning electron microscopy, and its average sheet size was approximately 3.1 μm, the average thickness was 2.7 nm, and the aspect ratio was 1148:1. TGA testing showed that the PGA grafted onto the edge-grafted graphene of the PGA-based resin contained 16.2% by mass. The thermal conductivity of the edge-grafted graphene of the PGA-based resin was measured to be 269 W / m·K.

[0115] (2) Preparation of biodegradable polyester materials

[0116] First, polyglycolic acid resin, edge-grafted graphene of PGA resin prepared in step (1), bio-based elastomer, antioxidant, nucleating agent, chain extender and hydrolysis inhibitor are mixed evenly in a mixer to obtain a PGA composition, wherein the mixing speed is 2000 rpm; then the PGA composition is melt-mixed, extruded and granulated in a twin-screw extruder to obtain the biodegradable polyester material; wherein the temperature of each section of the extruder is 150℃, 180℃, 200℃, 220℃, 230℃, 230℃, 225℃, 220℃, 200℃; the screw speed is 300 rpm; the specific formulation of the PGA composition is shown in Table 2.

[0117] (3) Preparation of PGA temporary plugging balls

[0118] Injection molding: The biodegradable polyester material prepared in step (2) was preheated at 80°C under a vacuum of 0.1 MPa. The granules were placed in an injection molding machine and heated to a molten state. The granules were then injected into the inner cavity of a spherical mold with a set diameter. After demolding, the temporary plugging balls were placed in a vacuum oven at 100°C for annealing for 3 hours to remove internal stress, thus obtaining PGA temporary plugging balls. Annealing temperature, annealing time, and injection molding process parameters: injection pressure, holding pressure, mold temperature, and injection speed are shown in Table 3. The hydrolysis test, sealing pressure, and elastic deformation test results of the temporary plugging balls are shown in Table 4. The diameter of the prepared temporary plugging balls is 20 mm.

[0119] Examples 2-9

[0120] (1) The preparation method of PGA resin edge-grafted modified graphene is the same as in Example 1. The specific contents of PGA resin and flake graphite, the type of PGA resin, the mesh size of flake graphite, the grinding process, as well as the yield, average size of flakes, mass percentage of PGA resin, aspect ratio and thermal conductivity of PGA resin edge-grafted modified graphene are shown in Table 1.

[0121] (2) The preparation method of biodegradable polyester material is the same as in Example 1. The specific formulation of the PGA composition is shown in Table 2.

[0122] (3) The only difference between the preparation method of the PGA temporary plugging ball and that of Example 1 is the process conditions, which are shown in Table 3. The performance of the prepared PGA temporary plugging ball is shown in Table 4. The diameter of the prepared temporary plugging ball is 20 mm.

[0123] Examples 10-11

[0124] (1) The preparation method of PGA resin edge-grafted modified graphene is the same as in Example 1. The specific contents of PGA resin and flake graphite, the type of PGA resin, the mesh size of flake graphite, the grinding process, as well as the yield, average size of flakes, mass percentage of PGA resin, aspect ratio and thermal conductivity of PGA resin edge-grafted modified graphene are shown in Table 1.

[0125] (2) The preparation method of biodegradable polyester material is the same as in Example 1. The specific formulation of the PGA composition is shown in Table 2.

[0126] (3) The only difference between the preparation method of the PGA temporary plugging ball in this embodiment and that in Example 1 is the use of the biodegradable polyester material prepared in step (2) of this embodiment; the properties of the prepared PGA temporary plugging ball are shown in Table 4. The diameter of the prepared temporary plugging ball is 20 mm.

[0127] Example 12

[0128] (1) Preparation method of PGA-based resin edge-grafted modified graphene: Add PGA (100g), graphite powder (300 mesh, 120g), and grinding beads to a ball mill jar according to Comparative Example 1. Seal the jar with flange screws. Introduce a mixed gas (carbon dioxide: nitrogen: argon = 30:65:5, weight ratio) into the jar through a gas filling device until the pressure reaches 15MPa. Remove the gas device, slowly open the gas valve at the other end of the jar, and empty the nitrogen in the jar. Repeat this filling process 3 times until all the air in the jar is exhausted, and set the temperature inside the spherical graphite jar to 45℃. Introduce the mixed gas (carbon dioxide: nitrogen: argon = 30:65:5, weight ratio) into the jar again until the pressure reaches 15MPa, and close the valve. Weigh all the filled ball mill jars to ensure that the total weight of all ball mill jars is consistent, and fix the ball mill jars on a planetary ball mill. Turn on the planetary ball mill and slowly increase the rotation speed to 100 rpm (same as the grinding disc speed in Example 1). Grind continuously for 96 hours, the same as in Example 1. Remove the grinding jar. Connect one end of a plastic gas pipeline to the gas valve and the other end to the water tank. Slowly open the gas valve to purge the gas from the jar. Keep the gas valve open, remove the fastening screws, open the grinding jar, and use a sieve to completely separate the PGA-based resin edge-grafted graphene from the grinding beads, obtaining the PGA-based resin edge-grafted graphene. Specific test results are shown in Table 1.

[0129] (2) The only difference between the preparation method of the biodegradable polyester material in this embodiment and that in Example 1 is that the edge-grafted graphene of PGA resin is replaced with the edge-grafted graphene of PGA resin prepared in step (1) of this embodiment. All other aspects are the same as in Example 1. The specific formulation of the PGA composition is shown in Table 2.

[0130] (3) The only difference between the preparation method of the PGA temporary plugging ball in this embodiment and that in Example 1 is the use of the biodegradable polyester material prepared in step (2) of this embodiment; the performance of the prepared PGA temporary plugging ball is shown in Table 4. The diameter of the prepared temporary plugging ball is 20 mm.

[0131] Comparative Example 1

[0132] (1) The preparation method of the biodegradable polyester material in this comparative example differs from that in Example 1 only in that no bio-based elastomer is added; all other aspects are the same as in Example 1. The specific formulation of the PGA composition is shown in Table 2.

[0133] (2) The only difference between the preparation method of the PGA temporary plugging ball in this comparative example and that in Example 1 is the use of the biodegradable polyester material prepared in step (1) of this comparative example; the properties of the prepared PGA temporary plugging ball are shown in Table 4. The diameter of the prepared temporary plugging ball is 20 mm.

[0134] Comparative Example 2

[0135] (1) The preparation method of the biodegradable polyester material in this comparative example differs from that in Example 1 only in that no chain extender is added; all other aspects are the same as in Example 1. The specific formulation of the PGA composition is shown in Table 2.

[0136] (2) The only difference between the preparation method of the PGA temporary plugging ball in this comparative example and that in Example 1 is the use of the biodegradable polyester material prepared in step (1) of this comparative example; the properties of the prepared PGA temporary plugging ball are shown in Table 4. The diameter of the prepared temporary plugging ball is 20 mm.

[0137] Comparative Example 3

[0138] (1) The preparation method of the biodegradable polyester material in this comparative example differs from that in Example 1 only in that no nucleating agent is added; all other aspects are the same as in Example 1. The specific formulation of the PGA composition is shown in Table 2.

[0139] (2) The only difference between the preparation method of the PGA temporary plugging ball in this comparative example and that in Example 1 is the use of the biodegradable polyester material prepared in step (1) of this comparative example; the properties of the prepared PGA temporary plugging ball are shown in Table 4. The diameter of the prepared temporary plugging ball is 20 mm.

[0140] Comparative Example 4

[0141] (1) The preparation method of the biodegradable polyester material in this comparative example differs from that in Example 1 only in that no hydrolysis inhibitor is added; all other aspects are the same as in Example 1. The specific formulation of the PGA composition is shown in Table 2.

[0142] (2) The only difference between the preparation method of the PGA temporary plugging ball in this comparative example and that in Example 1 is the use of the biodegradable polyester material prepared in step (1) of this comparative example; the properties of the prepared PGA temporary plugging ball are shown in Table 4. The diameter of the prepared temporary plugging ball is 20 mm.

[0143] Table 1. Preparation and properties of PGA-based resin edge-grafted modified graphene

[0144]

[0145]

[0146]

[0147] A comparison of Examples 4-6 with Examples 1-3 reveals that when the grinding disc speed decreases to 80 rpm, the average sheet size increases, the PGA resin content in the grafted material decreases, and the thermal conductivity increases. In Example 7, compared to Example 1, under the same formulation conditions, reducing the grinding disc time increases the average sheet size, slightly increases the PGA resin content in the grafted material, and decreases the thermal conductivity. In Example 8, compared to Example 1, under the same formulation conditions, increasing the grinding disc time increases the average sheet size, slightly decreases the PGA resin content in the grafted material, and increases the thermal conductivity. In Example 9, compared to Example 1 (300 mesh, 48 μm), the grinding disc reaction conditions are the same, but the flake graphite diameter is reduced to 25 μm (500 mesh), resulting in a smaller average sheet size, a lower aspect ratio, a slightly increased PGA resin content in the grafted material, and a decreased thermal conductivity.

[0148] Table 2

[0149]

[0150]

[0151] Note: In Table 2, (1) the preparation of the PGA composition is based on the principle of similarity and compatibility. The type of PGA resin in the PGA composition is the same as the type of PGA resin used to prepare the edge-grafted modified graphene of PGA resin. The total weight of the PGA resin, the edge-grafted modified graphene of PGA resin, and the bio-based elastomer is 100 parts by weight. (2) The amount of each raw material is in parts by weight.

[0152] Table 3 Process parameters of PGA temporary plugging balls

[0153]

[0154] Table 4 Performance of PGA Temporary Stamping Ball

[0155]

[0156]

[0157] As shown in Tables 1-4, compared to Example 1, Comparative Example 1, without the addition of bio-based elastomers, exhibits higher stiffness but a shorter stabilization time. Compared to Example 1, Comparative Example 2, without the addition of chain extenders, shows lower compressive strength and a shorter stabilization time due to the lack of physical cross-linking points between molecules. Compared to Example 1, Comparative Example 3, without nucleating agents, shows lower stiffness, excessively high elastic deformation rate, and lower plugging efficiency. Compared to Example 1, Comparative Example 4, without hydrolysis inhibitors, exhibits faster hydrolysis, resulting in poor performance in terms of compressive strength and stabilization time in an aqueous environment. Table 4 also shows that, compared to Example 1, Example 10 shows a decrease in friction coefficient with increasing PGA edge-modified graphene content. Compared to Example 1, Example 11, using antioxidant III, shows a certain improvement in compressive strength of the PGA plugging ball and an 11% extension of the 75 MPa stabilization time.

[0158] Compared to Example 1, the temporary plugging ball in Examples 2-3 and Examples 5-6 compared to Example 4 has a lower compressive strength. This is because the polyglycolic acid is selected from copolymers, PGA-LA and PGA-CL, which have lower original flexural modulus and stiffness.

[0159] Compared to Example 12, Example 1 features edge-grafted modified graphene sheets with larger diameters, greater aspect ratios, and higher thermal conductivity, resulting in better reinforcement. When the amount of PGA edge-modified graphene added in Examples 1 and 12 is the same (4wt%), the resulting temporary plugging ball exhibits higher compressive strength, longer pressure stabilization time under a certain pressure, higher elastic recovery rate, and lower friction coefficient, thus better meeting the application requirements of temporary plugging balls in oil and gas development.

[0160] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A PGA-based resin edge-grafted modified graphene, characterized in that, The PGA-type resin edge-grafted modified graphene comprises: graphene and polyglycolic acid resin grafted onto its edges. Based on the total mass of the PGA-type resin edge-grafted modified graphene, the mass percentage of the grafted polyglycolic acid resin in the PGA-type resin edge-grafted modified graphene is 1-20%, preferably 3-15%.

2. The PGA-type resin edge-grafted modified graphene according to claim 1, wherein, The average sheet diameter of the PGA-type resin edge-grafted modified graphene is 2-6 μm; And / or, the aspect ratio of the PGA-type resin edge-grafted modified graphene is (180-1850):1, preferably (200-1750):1, and more preferably (560-1650):

1.

3. The PGA-type resin edge-grafted modified graphene according to claim 1, wherein, The thermal conductivity of the PGA-type resin edge-grafted modified graphene is 200-400 W / m·K, preferably 220-320 W / m·K.

4. The method for preparing PGA-type resin edge-grafted modified graphene according to any one of claims 1-3, characterized in that, The preparation method includes: In the presence of a non-flammable gas mixture, polyglycolic acid resin and graphite are ground and mixed to obtain PGA-type resin edge-grafted modified graphene.

5. The preparation method according to claim 4, wherein, The graphite is natural graphite and / or artificial graphite; the natural graphite is selected from crystalline graphite and / or cryptocrystalline graphite; the artificial graphite is selected from pyrolytic graphite and / or highly oriented pyrolytic graphite. The graphite is preferably crystalline graphite, and the crystalline graphite is preferably flake graphite; more preferably, the fixed carbon content of the flake graphite is ≥99.9% or the fixed carbon content is 94%-99.9%, and more preferably, the fixed carbon content of the flake graphite is ≥99.9%. The cryptocrystalline graphite is preferably earthy graphite; The graphite has a particle size of 100-5000 mesh, preferably 200-4000 mesh, more preferably 200-2000 mesh, and even more preferably 200-400 mesh.

6. The preparation method according to claim 4, wherein, The melt flow rate of the polyglycolic acid resin at 230°C and 2.16 kg load is 5-60 g / 10 min, preferably 10-50 g / 10 min, and more preferably 15-45 g / 10 min; And / or, the weight-average molecular weight of the polyglycolic acid resin is 10,000-800,000, preferably 20,000-300,000, and more preferably 50,000-200,000; And / or, the molecular weight distribution width Mw / Mn of the polyglycolic acid resin is 1-5, preferably 1.5-3.5; And / or, the polyglycolic acid resin is homopolymer polyglycolic acid and / or copolymer polyglycolic acid, preferably homopolymer polyglycolic acid.

7. The preparation method according to claim 4, wherein, The non-flammable gas mixture includes carbon dioxide, nitrogen, and optionally argon; the carbon dioxide content is 30-50 wt%, the nitrogen content is 45-65 wt%, and the argon content is 0-5 wt% based on the total weight of the non-flammable gas mixture. The grinding and mixing conditions include: a grinding speed of 5-250 rpm, preferably 10-200 rpm; The cyclic grinding time is 10-300 hours, preferably 15-200 hours, and more preferably 24-120 hours; the pressure inside the grinding and mixing equipment is 15-25 MPa; and the grinding and mixing temperature is 40-50℃. The grinding and mixing are preferably carried out in a closed system with a circulation function, and more preferably in a high-pressure grinding disc kettle with a supercritical fluid circulation function.

8. A PGA composition containing edge-grafted modified graphene from PGA-type resin, characterized in that, The PGA composition comprises: polyglycolic acid resin, edge-grafted graphene of the PGA resin as described in any one of claims 1-3, bio-based elastomer, antioxidant, nucleating agent, chain extender and hydrolysis inhibitor.

9. The PGA composition according to claim 8, wherein, Relative to 100 parts by weight of the resin composition, the content of antioxidant is 0.15 to 0.25 parts by weight, the content of nucleating agent is 0.13 to 0.46 parts by weight, the content of chain extender is 0.1 to 2 parts by weight, preferably 0.2 to 1 part by weight, and the content of hydrolysis inhibitor is 0.1 to 2 parts by weight, preferably 0.5 to 1.2 parts by weight; The resin composition comprises polyglycolic acid, edge-grafted graphene of PGA resin according to any one of claims 1-3, and bio-based elastomer, wherein the mass ratio of the polyglycolic acid resin, edge-grafted graphene of PGA resin according to any one of claims 1-3, and bio-based elastomer is (80-95):(4-18):(1-6). Preferably, the antioxidant comprises a primary antioxidant and a secondary antioxidant, wherein the mass ratio of the primary antioxidant to the secondary antioxidant is (0.5 to 1):

1.

10. The PGA composition according to claim 8 or 9, wherein, The bio-based elastomer is selected from at least one of the following: poly(sebacate-glycerol) elastomer, acrylated poly(sebacate-glycerol) elastomer, poly(citrate-1,8-octanediol) elastomer, copolymer of lactide-caprolactone, glycolide-lactide copolymer, glycolide-lactide-caprolactone terpolymer, poly(ester-carbonate) elastomer, poly(citrate-octanediol-sebacate) elastomer, poly(sebacate-glycerol-citrate) elastomer, poly(sebacate-1,2-propanediol-citrate) elastomer, poly(itaconate-isoprene-glycidyl methacrylate) elastomer, soybean oil-based elastomer, itacate elastomer containing a ternary epoxy structure, and myrcene-based elastomer. Preferably, the bio-based elastomer has a weight-average molecular weight of 50,000 to 100,000 and a molecular weight distribution width (Mw / Mn) of 1 to 3.

11. The PGA composition according to claim 9, wherein, The primary antioxidant is selected from at least one of antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; CAS No.: 6683-19-8), antioxidant 3114 (1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid; CAS: 27676-62-6), antioxidant 245 (triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate]), and antioxidant 330 (1,3,5-trimethyl-2,4,6-tris(3,5-tert-butyl-4-hydroxybenzyl)benzene; CAS: 1709-70-2). The secondary antioxidant is selected from at least one of antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite; CAS: 31570-04-4), antioxidant 618 (pentaerythritol distearate diphosphite; CAS: 3806-34-6), bis(2,4-dicumylphenyl)pentaerythritol-diphosphite, pentaerythritol dioctadecyl diphosphite, and antioxidant 2,2'-ethylidene di(4,6-di-tert-butylphenyl)fluorophosphite (CAS: 118337-09-0).

12. The PGA composition according to claim 8 or 9, wherein, The chain extender is selected from at least one of styrene-glycidyl methacrylate copolymer, styrene-butyl acrylate-glycidyl methacrylate terpolymer, methylstyrene-methacrylate-glycidyl acrylate terpolymer, styrene-methyl methacrylate-glycidyl methacrylate terpolymer, and ethylene-butyl acrylate-glycidyl methacrylate terpolymer.

13. The PGA composition according to claim 8 or 9, wherein, The hydrolysis inhibitor is selected from polycarbodiimide, monomeric carbodimethylamine, dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 2,2',6,6'-tetraisopropylcarbodimethylamine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1- At least one of (3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 1-(3-dimethylaminopropyl)-3-ethyl-carbodiimide hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide hydrochloride, and (3-dimethylaminopropyl)-3-ethylcarbodiamine.

14. The PGA composition according to claim 8 or 9, wherein, The nucleating agent is selected from at least one of hyperbranched polyamide, ethylene-methacrylate ionomer, diphenyl dihydrazide sebacate, diphenyl dihydrazide adipate, and zinc phenyl phosphate.

15. The PGA composition according to claim 8 or 9, wherein, The melt flow rate of the polyglycolic acid resin at 230°C and 2.16 kg load is 5-60 g / 10 min, preferably 10-50 g / 10 min, and more preferably 15-45 g / 10 min; And / or, the weight-average molecular weight of the polyglycolic acid resin is 10,000-800,000, preferably 20,000-300,000, and more preferably 50,000-200,000; And / or, the molecular weight distribution width Mw / Mn of the polyglycolic acid resin is 1-5, preferably 1.5-3.5; And / or the polyglycolic acid resin is homopolymer polyglycolic acid and / or copolymer polyglycolic acid, preferably homopolymer polyglycolic acid.

16. A method for preparing the PGA composition according to any one of claims 8-15, characterized in that, The preparation method includes: uniformly mixing the polyglycolic acid resin, edge-grafted graphene of the PGA resin according to any one of claims 1-3, bio-based elastomer, antioxidant, nucleating agent, chain extender and hydrolysis inhibitor to obtain the PGA composition.

17. A biodegradable polyester material, characterized in that, The biodegradable polyester material is prepared by a method comprising the following steps: melt-mixing the PGA composition according to any one of claims 8-15 to obtain the biodegradable polyester material.

18. The use of the PGA composition according to any one of claims 8-15 and the biodegradable polyester material according to claim 17 as raw materials for the preparation of PGA temporary plugging balls.

19. A PGA temporary blocking ball, characterized in that, The PGA temporary plugging ball is prepared by a method comprising the following steps: injection molding and annealing the biodegradable polyester material as described in claim 17 to obtain the PGA temporary plugging ball.

20. The PGA temporary blocking ball according to claim 19, wherein, The injection molding process parameters include: injection pressure of 70-100 bar, holding pressure of 70-120 bar, mold temperature of 60-110℃, and injection speed of 10-20 cm. 3 / s; The annealing temperature is 80-110℃, and the time is 1-5 hours.

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