Degradable glycolic acid copolymer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polymers, and provides a degradable glycollic acid copolymer as well as a preparation method and application thereof. The degradable glycolic acid copolymer comprises glycolic acid units and siloxane units, the glycolic acid units and the siloxane units are distributed on a molecular chain in a long-range disordered mode, the number of continuous repeating units of the glycolic acid units is 2n, the number of continuous repeating units of the siloxane units is (3-6) n, and n is an integer larger than or equal to 1. According to the degradable glycolic acid copolymer provided by the invention, a polysiloxane chain segment is randomly copolymerized into a polyglycolic acid chain segment, so that the diffusion speed of water in a material can be reduced, the degradation rate of the material in a water environment is reduced, and meanwhile, the toughness and impact resistance of the material can be obviously improved.

Description

Technical Field

[0001] The present invention relates to the field of polymer technology, and more specifically to a degradable glycolic acid copolymer and a preparation method and application thereof. Background Art

[0002] Degradable materials are a type of material that can be degraded into small molecules under certain conditions, which can effectively reduce the impact of non-degradable synthetic polymers on the environment. At present, degradable materials are used in various fields such as civil, medical, and oil and gas field development.

[0003] Degradable materials are mainly used in the fracturing and formation transformation process in oil and gas field development. Fracturing can effectively improve the formation seepage channel and increase oil and gas production. Degradable materials can be used as temporary plugging balls, temporary plugging agents or temporary plugging tools in this process. Taking temporary plugging balls as an example, when added to the fracturing fluid, they can flow with the liquid flow to the blastholes that have been opened in the formation and block the blastholes, thereby effectively playing the role of fluid flow diversion; when the blocking effect is completed, the degradable temporary plugging balls can be effectively degraded in the formation environment, will not block for a long time, and do not require special post-processing processes. It is convenient and simple, and the effect is excellent.

[0004] In the development of oil and gas fields, in addition to fracturing, there are also many links such as drilling, water injection, and well repair that require temporary plugging materials to assist in the implementation of the process. However, the polylactic acid (PLA) and polyglycolic acid (PGA) materials commonly used as temporary plugging materials in oil fields currently degrade too fast at high temperatures and cannot meet the needs of actual working conditions. The degradation of degradable materials mainly depends on the hydrolysis of ester groups, which in turn causes the breakage of the material molecular chain and degrades the polymer material into small molecules. The diffusion of water in the material determines the degradation rate of the degradable material. Silicon-containing materials can effectively improve the performance of PGA materials, so they are introduced as modifiers in some studies. For example, patent CN107840949A discloses a technology that uses pre-polymerized organosilicon oligomers as precursors and then mixes with glycolide for ring-opening polymerization to obtain a block copolymer. Patent CN110892024B also discloses a block copolymerized polysiloxane-polyester technology. However, the above technologies mainly focus on the heat resistance and peeling properties of the material as a coating material, or on mechanical properties such as toughness and impact resistance, but do not focus on the long-term degradation characteristics of the polyglycolic acid material.

[0005] Therefore, how to reduce the degradation rate of PGA materials in water environment is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The object of the present invention is to provide a degradable glycolic acid copolymer and a preparation method thereof, so as to solve the technical problem in the prior art that polyglycolic acid materials degrade too fast in a water environment.

[0007] In order to solve the above problems in the prior art, the present invention is proposed.

[0008] In the first aspect, the present invention provides a degradable glycolic acid copolymer, comprising glycolic acid units and siloxane units, wherein the arrangement of the glycolic acid units and the siloxane units on the molecular chain is long-range disordered, the number of continuous repeating units of the glycolic acid units is 2m, and the number of continuous repeating units of the siloxane units is (3 to 6)n, wherein m and n are integers ≥1.

[0009] The degradable glycolic acid copolymer provided by the present invention affects the hydrophilicity of the material by randomly copolymerizing polysiloxane segments into polyglycolic acid segments, reduces the diffusion rate of water in the material, improves the hydrolysis resistance of the material, and thus improves the degradation performance of the material in a water environment. In addition, by introducing flexible polysiloxane segments, the toughness and impact resistance of polyglycolic acid materials can be effectively increased, thereby improving their application effect as temporary plugging materials in oil and gas field development.

[0010] In the present invention, the structure of the glycolic acid unit is: The structure of the siloxane unit is:

[0011] According to some embodiments of the present invention, m≤10. For example, m can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0012] According to some embodiments of the present invention, (3-6)n≤20. For example, when the number of consecutive repeating units of the siloxane unit is 3n, n can be 1, 2, 3, 4, 5, 6. For another example, when the number of consecutive repeating units of the siloxane unit is 4n, n can be 1, 2, 3, 4, 5. For another example, when the number of consecutive repeating units of the siloxane unit is 5n, n can be 1, 2, 3, 4. For another example, when the number of consecutive repeating units of the siloxane unit is 6n, n can be 1, 2, 3.

[0013] According to some embodiments of the present invention, the molar ratio of the glycolic acid unit to the siloxane unit is (4-99):1.

[0014] According to some embodiments of the present invention, the weight average molecular weight of the degradable glycolic acid copolymer is 100,000 to 800,000 Daltons.

[0015] In a second aspect, the present invention provides a method for preparing the degradable glycolic acid copolymer described in the first aspect, comprising: obtaining the copolymer by synchronous ring-opening polymerization of glycolide and cyclic siloxane monomers.

[0016] According to some embodiments of the present invention, the cyclic siloxane monomer comprises at least one of the structures of formula (1) to formula (4);

[0017]

[0018] Among them, R 1 ~R 12 are the same or different and are independently selected from methyl, ethyl, phenyl, vinyl and allyl.

[0019] According to some embodiments of the present invention, the ring-opening polymerization reaction system further includes a catalyst, an antioxidant and a thermal stabilizer.

[0020] According to some embodiments of the present invention, based on the total amount of polymerizable monomers, the amounts of the components include:

[0021] Catalyst: 0.001-0.01wt%, preferably 0.002-0.006wt%;

[0022] Antioxidant: 0.1-1wt%, preferably 0.1-0.5wt%;

[0023] Heat stabilizer: 0.001-0.1 wt%, preferably 0.005-0.08 wt%.

[0024] According to some embodiments of the invention, the catalyst comprises potassium trimethylsilanol.

[0025] According to some embodiments of the present invention, the antioxidant includes at least one of a phosphate antioxidant and a hindered phenol antioxidant.

[0026] According to some embodiments of the present invention, the stabilizer includes at least one of dibutyltin maleate, dibutyltin dilaurate, dibutyltin laurate maleate, di-n-octyltin maleate, di-n-octyltin dilaurate, and di-n-octyltin bis(isooctyl thioglycolate).

[0027] According to some embodiments of the present invention, the preparation method comprises:

[0028] Add glycolide, cyclic siloxane monomers, antioxidants and thermal stabilizers into a reaction kettle; heat to 100-150° C. and stir; introduce nitrogen to deoxygenate, then add an initiator; heat to 150-180° C. and react for 12-48 hours to obtain the degradable glycolic acid copolymer.

[0029] In a third aspect, the present invention provides use of the degradable glycolic acid copolymer described in the first aspect or the degradable glycolic acid copolymer prepared by the preparation method described in the second aspect as a temporary plugging material in oil and gas field development.

[0030] The beneficial effects of the present invention are at least:

[0031] The degradable glycolic acid copolymer provided by the present invention can reduce the diffusion rate of water in the material by randomly copolymerizing polysiloxane segments into polyglycolic acid segments, thereby reducing the degradation rate of the material in a water environment, and at the same time can significantly improve the toughness and impact resistance of the material. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in combination with specific implementation methods. It should be understood that the specific implementation methods described herein are only used to explain this patent in detail and do not limit the scope of protection of the present invention in any way.

[0033] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the reagent amounts, unless otherwise specified, are the reagent amounts used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0034] The materials of each embodiment and comparative example were prepared according to the following synthesis method:

[0035] Add cyclic siloxane monomers, monomers providing glycolic acid units, antioxidants (phosphite tris (2, 4-di-tert-butylphenyl) ester), and thermal stabilizers (dibutyltin maleate) into a reaction kettle; heat to 130°C and stir to form a uniform system; introduce nitrogen to deoxygenate, and then add an initiator (potassium trimethylsilanol); heat to 170°C, react for 24 hours, evacuate to 200Pa for 2 hours to remove volatiles, and obtain the product.

[0036] In addition, the product of Comparative Example 3 was prepared by the synthesis method of Example 1 disclosed in Chinese Patent CN107840949A.

[0037] The raw material components and amounts of each embodiment and comparative example are shown in Table 1. Among them, the amounts of the monomers providing glycolic acid units and the siloxane monomers are in molar fractions, and the amounts of other components are in mass fractions when the total amount of the monomers providing glycolic acid units and the siloxane monomers is 100 mass fractions.

[0038] Table 1

[0039]

[0040] Performance Evaluation

[0041] The products of each embodiment and comparative example were prepared into dumbbell-shaped specimens meeting ISO 527 standard by injection molding, and the elongation at break was measured.

[0042] The product was prepared into a sheet of 0.5 cm thick and 1 cm×1 cm, aged in hot water at 90°C and 120°C, and the time required for the compressive strength of the material to drop to 80% was measured.

[0043] The elongation at break and the compressive strength were tested using a universal material testing machine (Model 3367) from INSTRON, USA.

[0044] The product performance test results are shown in Table 2.

[0045] Table 2

[0046]

[0047] From the above test results, it can be seen that when the polysiloxane chain segments are randomly copolymerized into the polyglycolic acid chain segments, the degradation rate of the product is significantly slowed down. Even in high-temperature hot water, the time for the compressive strength to drop to 80% is greatly prolonged. This is mainly due to the decrease in the hydrophilicity of the copolymer, which delays the diffusion of water molecules in the material and then delays the hydrolysis of the ester group. At the same time, the toughness of the product is also significantly improved, and the elongation at break is significantly increased.

[0048] Since the proportion of siloxane units in the copolymer prepared in Example 4 is too high, although the hydrophobicity of the copolymer is increased, the flexibility of the overall molecular chain is increased too much, and the polyglycolic acid segment cannot form a continuous crystalline structure. Therefore, although it takes a long time for the compressive strength to drop to 80% at 90°C, it takes a short time for the compressive strength to drop to 80% at 120°C, and the test results of the elongation at break also confirm that the copolymer has tended to be an elastomer.

[0049] From the data of comparative examples 3-5, it can be seen that although the block structure product has a more obvious improvement in elongation at break, it has little effect on the degradation performance of the material in high-temperature hot water. This is mainly because the block polymers form aggregates after phase separation, which easily form water channels during degradation and cannot effectively inhibit the diffusion of water in the material.

[0050] Comparative Example 6 uses glycolic acid instead of glycolide for direct polymerization. Since the polymerization activity of glycolic acid and siloxane cyclic monomers is quite different when they are directly polymerized, the molecular weight distribution is wide, so the overall mechanical properties of the material are significantly reduced, the material itself is less crystalline, and has more defects. Relatively speaking, it will make it easier for water to diffuse at high temperatures, and the elongation at break data will also be worse.

[0051] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A degradable glycolic acid copolymer, It is characterized in that The invention comprises glycolic acid units and siloxane units, wherein the glycolic acid units and siloxane units are arranged in a long-range disordered manner on the molecular chain, the number of continuous repeating units of the glycolic acid units is 2m, and the number of continuous repeating units of the siloxane units is (3 to 6)n, wherein m and n are integers ≥1.

2. The degradable glycolic acid copolymer according to claim 1, It is characterized in that The molar ratio of the glycolic acid unit to the siloxane unit is (4-99):

1.

3. The method for preparing the degradable glycolic acid copolymer according to claim 1 or 2, It is characterized in that include: It is obtained by simultaneous ring-opening polymerization of glycolide and cyclic siloxane monomers.

4. The preparation method according to claim 3, It is characterized in that The cyclic siloxane monomer comprises at least one of the structures of formula (1) to formula (4); Among them, R 1 ~R 12 are the same or different and are each independently selected from methyl, ethyl, phenyl, vinyl, and allyl.

5. The preparation method according to claim 3 or 4, It is characterized in that The ring-opening polymerization reaction system also includes a catalyst, an antioxidant and a heat stabilizer; Preferably, based on the total amount of polymerizable monomers, the amounts of the components include: Catalyst: 0.001-0.01wt%, preferably 0.002-0.006wt%; Antioxidant: 0.1-1wt%, preferably 0.1-0.5wt%; Heat stabilizer: 0.001-0.1 wt%, preferably 0.005-0.08 wt%.

6. The preparation method according to claim 5, It is characterized in that The catalyst includes potassium trimethylsilanol.

7. The preparation method according to claim 5 or 6, It is characterized in that The antioxidant includes at least one of a phosphate antioxidant and a hindered phenol antioxidant.

8. The preparation method according to any one of claims 5 to 7, It is characterized in that The stabilizer includes at least one of dibutyltin maleate, dibutyltin dilaurate, dibutyltin laurate maleate, di-n-octyltin maleate, di-n-octyltin dilaurate, and di-n-octyltin bis(isooctyl thioglycolate).

9. The preparation method according to any one of claims 3 to 8, It is characterized in that include: Add glycolide, cyclic siloxane monomer, antioxidant and heat stabilizer into a reaction kettle; The mixture is heated to 100-150° C. and stirred; nitrogen is introduced to remove oxygen, and then an initiator is added; the mixture is heated to 150-180° C. and reacted for 12-48 hours to obtain the degradable glycolic acid copolymer.

10. Use of the degradable glycolic acid copolymer according to claim 1 or 2 or the degradable glycolic acid copolymer prepared by the preparation method according to any one of claims 3 to 8 as a temporary plugging material in the development of oil and gas fields.

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