Modified polyglycolic acid, and method of making and use thereof

Abstract

The application relates to the technical field of fracturing temporary plugging agents, and discloses modified polyglycolic acid as well as a preparation method and application thereof, which comprises the following steps: adding monomethylol amine into dichloromethane, adding diethyl oxalate, obtaining compound A after reaction at 30-50 DEG C for 12-24 hours; adding compound A, methyl glycolate and pentaerythritol into toluene, adding a catalyst, and obtaining modified polyglycolic acid after reaction at 100-120 DEG C for 6-12 hours. The modified polyglycolic acid is obtained by crosslinking polymerization of the compound obtained from monomethylol amine and diethyl oxalate as raw materials and methyl glycolate and pentaerythritol. The fracturing temporary plugging agent prepared from the modified polyglycolic acid is crosslinked between molecules due to the introduction of amide and rings, the intermolecular force is improved, the plugging performance and acid and alkali resistance at different temperatures are improved, and the application of the modified polyglycolic acid in fracturing temporary plugging agents can be expanded.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a modified polyglycolic acid, its preparation method, and its applications. Background Technology

[0002] Polyglycolic acid (PGA, also known as polyglycolic acid or polyhydroxyacetic acid) is a class of polymeric materials that can be degraded by hydrolysis or enzymatic catalysis. PGA is the simplest linear aliphatic polyester and also the fastest-degrading aliphatic polyester polymer. Unlike traditional polymeric materials such as plastics and rubber, PGA has both good water and oxygen barrier properties and is easily decomposed under water and oxygen conditions. PGA materials gradually degrade after a certain period of use, eventually turning into water and carbon dioxide that are harmless to humans, animals, plants, and the natural environment. PGA has good biodegradability and biocompatibility, as well as high mechanical strength, excellent moldability, and excellent gas barrier properties, and can be used in medical materials, oil and gas extraction, agricultural and forestry production, packaging materials, and disposable environmentally friendly products. Polyglycolic acid is mainly used in medical sutures, drug delivery carriers, fracture fixation materials, tissue engineering scaffolds, reinforcing materials, and oil fields. However, it is also a rigid, highly crystalline thermoplastic polymer with short molecular chain structural units and poor chain flexibility, resulting in high brittleness, which seriously restricts its processing and application in many fields.

[0003] Patent CN117264620A discloses a high-temperature resistant, biodegradable temporary plugging agent for oilfield fracturing, prepared from the following components and their weight percentages: 70-80 parts polyglycolic acid, 20-30 parts carbon dioxide copolymer, 5-15 parts poly(butylene adipate / terephthalate), 10-20 parts starch, 1-4 parts plasticizer, 3-8 parts compatibilizer, 1-10 parts lubricant, 1-3 parts heat stabilizer, and 0.5-4 parts nucleating agent. While this invention solves the problems of poor strength and high-temperature thermal stability of existing temporary plugging agents, it still lacks the ability to resist acids and alkalis under different fracturing conditions. Therefore, developing a modified polyglycolic acid temporary plugging agent that combines temperature resistance with acid and alkali resistance is crucial. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of poor temperature resistance and acid and alkali resistance of polyglycolic acid fracturing plugging agent in the prior art, thereby providing a modified polyglycolic acid, its preparation method and application, using natural products as the main raw materials, improving the temperature resistance and acid and alkali resistance of polyglycolic acid, and expanding its application in fracturing plugging agents.

[0005] To solve the above-mentioned technical problems, the present invention provides a method for preparing modified polyglycolic acid, characterized by comprising the following steps:

[0006] (1) Add montanane diamine to dichloromethane, add diethyl oxalate, and react at 30~50℃ for 12~24h to obtain compound A;

[0007] (2) Compound A, methyl glycolate, and pentaerythritol were added to toluene, a catalyst was added, and the mixture was reacted at 100-120°C for 6-12 hours to obtain modified polyglycolic acid.

[0008] The structural formula of compound A is:

[0009] .

[0010] Preferably, the mass ratio of montanane diamine to diethyl oxalate is 17:30~45.

[0011] Preferably, the catalyst is at least one of stannous octoate or tetrabutyl titanate.

[0012] Preferably, the mass ratio of compound A, methyl glycolate, pentaerythritol, and catalyst is 37:9~18:10:1~2.

[0013] The present invention also provides a modified polyglycolic acid, which is prepared by the preparation method described above.

[0014] This invention also provides an application of modified polyglycolic acid in fracturing plugging agents.

[0015] Preferably, the method for applying the modified polyglycolic acid in fracturing plugging agents includes the following steps:

[0016] Modified polyglycolic acid is heated to 180~200℃, extruded, granulated, and sieved to obtain a fracturing plugging agent.

[0017] Preferably, the particle size of the fracturing plugging agent is 50-100 mesh.

[0018] The technical solution of this invention has the following advantages:

[0019] The modified polyglycolic acid provided by this invention is obtained by crosslinking and polymerizing a compound obtained from menthol diamine and diethyl oxalate with methyl glycolate and pentaerythritol. The introduction of amides and rings leads to crosslinking between the modified polyglycolic acid molecules, increasing intermolecular forces. Simultaneously, pentaerythritol, as a tetrafunctional crosslinking agent, reacts with linear polyester segments to form a three-dimensional chemical crosslinking network. This network "locks" the rigid oxalamide-menthol segments between the crosslinking nodes, preventing molecular slippage or segment deentanglement under high-temperature fluid scouring. This results in excellent plugging performance at different temperatures. Compared to existing polyglycolic acid temporary plugging agents, the structure retention time in acidic and alkaline environments is significantly extended, and the acid and alkali resistance is significantly improved, further expanding the application of modified polyglycolic acid in fracturing temporary plugging agents. Detailed Implementation

[0020] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0021] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0022] The experimental core sample was taken from the field, with a diameter of 2.48 cm, a length of 7.142 cm, and a permeability of 0.872 × 10⁻⁶. -3 μm 2 The core had a porosity of 8.2%. In the experiment, the core was split in two along the axial direction and then wrapped together with adhesive tape.

[0023] Blocking rate test method:

[0024] The sealing performance of water-soluble temporary plugging agents was evaluated in the laboratory using core displacement simulation experiments. The specific steps are as follows: First, the water phase permeability K of the fracture core before plugging was measured. ０ Then, a mixed suspension of the temporary plugging agent and 0.3% guar gum-based solution (the temporary plugging agent had a mass fraction of 5% and an injection volume of 2 PV) was injected into the core fracture. After aging at the experimental temperature for 30 minutes, the water phase permeability K of the core after plugging was tested. １ The plugging rate E of the temporary plugging agent was calculated according to formula (1). The injection flow rate in the experiment was 2 mL / min.

[0025] The formula for calculating the blocking rate is as follows: E = (K ０ -K １ ) / K０ ×100%,

[0026] In the formula: K ０ Initial permeability, %; K １ Permeability after sealing, %.

[0027] Solubility test:

[0028] Weigh out 5% of the temporary plugging agent by mass and add it to tap water, a 20,000-ton standard saline solution, a 10% hydrochloric acid solution, and a 5% sodium hydroxide solution, respectively. Then place each solution in a 50°C water bath to observe dissolution. Measure the dissolution rate every 0.5 hours. The method for measuring the dissolution rate is based on existing technology.

[0029] Example 1

[0030] A method for preparing modified polyglycolic acid includes the following steps:

[0031] (1) 17g of menthol diamine was added to 200ml of dichloromethane, and 40g of diethyl oxalate was added. After reacting at 40℃ for 16h, compound A was obtained.

[0032] The structural formula of compound A is:

[0033] ;

[0034] (2) 37g of compound A, 15g of methyl glycolate, and 10g of pentaerythritol were added to 500ml of toluene, and 1.5g of stannous octoate was added. After reacting at 110℃ for 8h, modified polyglycolic acid was obtained.

[0035] Modified polyglycolic acid was heated to 190°C, extruded, granulated, and sieved to obtain a 50-100 mesh fracturing plugging agent.

[0036] The sealing efficiency of the obtained fracturing plugging agent at different temperatures is shown in Table 1, and the dissolution time of the obtained fracturing plugging agent in different solvents is shown in Table 2.

[0037] Example 2

[0038] A method for preparing modified polyglycolic acid includes the following steps:

[0039] (1) 17g of menthol diamine was added to 200ml of dichloromethane, and 45g of diethyl oxalate was added. After reacting at 50℃ for 24h, compound A was obtained.

[0040] The structural formula of compound A is:

[0041] ;

[0042] (2) 37g of compound A, 18g of methyl glycolate, and 10g of pentaerythritol were added to 500ml of toluene, and 2g of stannous octoate was added. After reacting at 120℃ for 12h, modified polyglycolic acid was obtained.

[0043] Modified polyglycolic acid was heated to 200°C, extruded, granulated, and sieved to obtain a 50-100 mesh fracturing plugging agent.

[0044] The sealing efficiency of the obtained fracturing plugging agent at different temperatures is shown in Table 1, and the dissolution time of the obtained fracturing plugging agent in different solvents is shown in Table 2.

[0045] Example 3

[0046] A method for preparing modified polyglycolic acid includes the following steps:

[0047] (1) 17g of menthol diamine was added to 200ml of dichloromethane, and 30g of diethyl oxalate was added. After reacting at 30℃ for 12h, compound A was obtained.

[0048] The structural formula of compound A is:

[0049] ;

[0050] (2) 37g of compound A, 9g of methyl glycolate, and 10g of pentaerythritol were added to 500ml of toluene, and 1g of stannous octoate was added. After reacting at 100℃ for 6h, modified polyglycolic acid was obtained.

[0051] Modified polyglycolic acid was heated to 180°C, extruded, granulated, and sieved to obtain a 50-100 mesh fracturing plugging agent.

[0052] The sealing efficiency of the obtained fracturing plugging agent at different temperatures is shown in Table 1, and the dissolution time of the obtained fracturing plugging agent in different solvents is shown in Table 2.

[0053] Comparative Example 1

[0054] Commercially available polyglycolic acid is heated to 190°C, extruded, granulated, and sieved to obtain a 50-100 mesh fracturing plugging agent.

[0055] Comparative Example 2

[0056] (1) 52 g of methyl glycolate and 10 g of pentaerythritol were added to 500 mL of toluene, and 1.5 g of stannous octoate was added. After reacting at 110 °C for 8 h, cross-linked polyglycolic acid was obtained.

[0057] The obtained cross-linked polyglycolic acid was heated to 190°C, extruded, granulated, and sieved to obtain a temporary plugging agent with a particle size of 50-100 mesh.

[0058] Comparative Example 3

[0059] (1) 17 g of menthol diamine was added to 200 mL of dichloromethane, and 40 g of diethyl oxalate was added. After reacting at 40 °C for 16 h, compound A was obtained.

[0060] (2) 37 g of compound A and 15 g of methyl glycolate were added to 500 mL of toluene, and 1.5 g of stannous octoate was added. After reacting at 110 °C for 8 h, linear modified polyglycolic acid (without pentaerythritol and no cross-linking structure) was obtained.

[0061] The obtained linearly modified polyglycolic acid was heated to 190°C, extruded, granulated, and sieved to obtain a temporary plugging agent with a particle size of 50-100 mesh.

[0062] Table 1. Plugging rates of different embodiments and comparative examples at different temperatures.

[0063] At 60℃, the sealing rate (%) 94.04 93.30 92.29 82.94 87.65 84.32 80℃, sealing rate (%) 91.21 89.59 89.66 76.12 82.10 79.55 At 100℃, the sealing rate (%) 85.21 83.01 82.88 62.33 73.28 72.10

[0064] As can be seen from Table 1, the fracturing plugging agents prepared in Examples 1 to 3 of this application have high plugging rates at different temperatures. This is because when the compound prepared from menthol diamine is used to prepare modified polyglycolic acid, the introduction of amide and rings causes cross-linking between the modified polyglycolic acid molecules, which increases the intermolecular forces and further improves its temperature resistance, resulting in high plugging rates at different temperatures.

[0065] Table 2. Dissolution times of different embodiments and comparative examples in different solvents.

[0066] The time (in hours) for 50% of the solution to dissolve in tap water. 5.5 5.0 5.0 4.0 4.5 4.5 Time (h) for complete dissolution in tap water 8.5 8 8 6.5 7.0 7.5 Time (h) for 50% dissolution in a 20,000 kcal / kg standard saline solution. 5.0 5.0 5.0 3.0 3.5 4.0 Complete dissolution time (h) in 20,000 standard saline solution 7.5 7.0 7.0 5.5 6.0 6.5 Time (h) for 50% dissolution in 10% hydrochloric acid solution 4.0 3.5 3.5 2.5 3.0 3.0 Time (h) for complete dissolution in 10% hydrochloric acid solution 6.0 6.0 6.0 4.0 4.5 5.0 Time (h) for 50% of the sodium hydroxide solution to dissolve. 4.0 4.0 3.5 2.5 3.0 3.0 Time (h) for complete dissolution in 5% sodium hydroxide solution 5.5 5.5 5.0 4.0 4.5 4.5

[0067] As can be seen from Table 2, the fracturing plugging agents prepared in Examples 1 to 3 of this application have improved acid and alkali resistance. This is because the intermolecular forces are enhanced after the modified polyglycolic acid undergoes cross-linking copolymerization.

[0068] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing modified polyglycolic acid, characterized in that, Includes the following steps: (1) Add montanane diamine to dichloromethane, add diethyl oxalate, and react at 30~50℃ for 12~24h to obtain compound A; (2) Compound A, methyl glycolate, and pentaerythritol were added to toluene, a catalyst was added, and the mixture was reacted at 100-120°C for 6-12 hours to obtain modified polyglycolic acid. The structural formula of compound A is: 。 2. The method for preparing modified polyglycolic acid according to claim 1, characterized in that, The mass ratio of montanane diamine to diethyl oxalate is 17:30~45.

3. The method for preparing modified polyglycolic acid according to claim 1, characterized in that, The catalyst is at least one of stannous octoate or tetrabutyl titanate.

4. The method for preparing modified polyglycolic acid according to claim 3, characterized in that, The mass ratio of compound A, methyl glycolate, pentaerythritol, and catalyst is 37:9~18:10:1~2.

5. A modified polyglycolic acid, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 4.

6. The application of the modified polyglycolic acid according to claim 5 in fracturing plugging agents.

7. The method for applying the modified polyglycolic acid according to claim 6 in a fracturing plugging agent, characterized in that, Includes the following steps: Modified polyglycolic acid is heated to 180~200℃, extruded, granulated, and sieved to obtain a fracturing plugging agent.

8. The method for applying the modified polyglycolic acid according to claim 7 in fracturing plugging agents, characterized in that, The particle size of the fracturing plugging agent is 50-100 mesh.

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