A block copolymer based on polylactic acid / polyglycolic acid strength modification and its preparation method and application

Abstract

This invention relates to a strength-modified block copolymer based on polylactic acid (PLA) / polyglycolic acid (PEG), its preparation method, and its application, belonging to the field of block copolymer technology. It solves the technical problem in the prior art where PLA or PEG has poor compatibility with PB / AT, making it difficult for both to fully utilize their respective advantages. The preparation method of this invention involves first uniformly mixing phthalic acid, adipic acid, an aliphatic diol, a polyol with ≥3 hydroxyl groups, and an organometallic ester, then heating and reacting the mixture under reduced pressure to remove water and excess polyol, yielding an alcohol-modified poly(terephthalic acid-adipic acid-diol ester). Then, molten dehydrated lactone monomer, a catalyst, and solvent oil are added, and the mixture is heated and reacted to obtain the strength-modified block copolymer based on PLA / PEG. This block copolymer exhibits good toughness, ductility, elongation at break, heat resistance, and excellent impact performance, and can be used as a temporary plugging agent.

Description

Technical Field

[0001] This invention belongs to the field of block copolymer technology, specifically relating to a block copolymer based on polylactic acid / polyglycolic acid strength modification, its preparation method and application, and particularly to the application of the block copolymer as a temporary plugging agent. Background Technology

[0002] Polylactic acid (PLA) or polyglycolic acid (PEG) have become next-generation green and environmentally friendly materials due to their biomass origin, biodegradability, excellent biocompatibility, and good light transmittance. In unconventional oil and gas resources, PLA or PEG are frequently used as biodegradable temporary plugging materials. Utilizing self-degradation, they can temporarily seal perforations and fractures under certain pressure, thereby achieving the goals of temporary plugging diversion, increasing the number and complexity of fractures, and improving oil and gas production. Knot-type temporary plugging agents typically employ knot and tail fin structures to adapt to the shape and size of perforations or fractures with different characteristics, improving perforation efficiency and plugging capability. However, PLA, PEG, or copolymers of lactide and glycolide suffer from disadvantages such as low elongation at break, poor toughness, and poor impact resistance, resulting in fibrous materials with poor tensile properties, toughness, and strength.

[0003] Polybutylene adipate terephthalate (PBAT) is a tough, biodegradable polymer material that has been mass-produced. The random copolymer backbone structure of PBAT makes it difficult to crystallize. Furthermore, due to the presence of a large number of aliphatic dicarboxylic acid structural units in the molecule, the intermolecular forces are relatively weak. PBAT molecules can undergo chain segment peristalsis and relative sliding of molecular chains. Therefore, it exhibits excellent toughness, good ductility and elongation at break, as well as good heat resistance and impact resistance.

[0004] However, polylactic acid (PLA) or polyglycolic acid (PEG) has poor compatibility with PBAT, making it difficult to fully utilize their respective advantages. The resulting mixture exhibits low mechanical properties and low tensile strength. Therefore, there is an urgent need to develop a biodegradable material that is compatible with PLA or PEG and possesses excellent toughness, good ductility, elongation at break, good heat resistance, and impact resistance. Summary of the Invention

[0005] In view of this, in order to solve the technical problem that polylactic acid or polyglycolic acid and PBAT have poor compatibility in the prior art and it is difficult to give full play to their respective advantages, the present invention provides a block copolymer based on polylactic acid / polyglycolic acid strength modification, its preparation method and application, which has the characteristics of excellent toughness, ductility, elongation at break, heat resistance and impact performance.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows.

[0007] In a first aspect, the present invention provides a method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid, comprising the following steps:

[0008] Step 1: Mix terephthalic acid, adipic acid, aliphatic diol, polyol with ≥3 hydroxyl groups and organometallic ester evenly, heat to react, remove water and excess alcohol under reduced pressure to obtain alcohol-modified polyterephthalic acid-adipic acid-diol ester.

[0009] Step 2: Add molten dehydrated lactide monomer, catalyst and solvent oil, and heat to react, to obtain a block copolymer based on polylactic acid / polyglycolic acid strength modification.

[0010] Preferably, in step one, the aliphatic diol includes one or more of butanediol, pentanediol, hexanediol, ethylene glycol monohydrate, and ethylene glycol dihydrate.

[0011] Preferably, in step one, the polyol includes one or more of glycerol, diglycerol, glucose, and menthol.

[0012] Preferably, in step one, the organometallic ester is one or more of C2-C8 organometallic esters, and the metal includes one or more of titanium, tin, zinc, and aluminum.

[0013] Preferably, in step one, the reaction temperature is 180-220℃ and the reaction time is 2-4 hours; more preferably, the reaction is carried out under negative pressure, with a pressure range of -0.095MPa to -0.1MPa.

[0014] Preferably, the molar ratio of terephthalic acid, adipic acid, aliphatic diol, polyol, and hydrolactide monomer is (1.0-1.5):(0.5-1.2):(1.5-3):(0.05-0.10):(10-30), and the amount of the organometallic acid ester is 0.1%-5% of the total mass of terephthalic acid, adipic acid, aliphatic diol, and polyol.

[0015] Preferably, in step two, the reaction temperature is 180-220℃ and the reaction time is 3-5 hours.

[0016] Preferably, in step two, the catalyst is stannous octoate, aluminum isopropoxide, yttrium isopropoxide, or calcium acetylacetonate; more preferably, it is stannous octoate.

[0017] Preferably, in step two, the amount of catalyst used is 0.05wt%-1.0wt% of the amount of hydrolactide monomer.

[0018] Preferably, in step two, the lactide monomer is one or both of lactide and glycolide.

[0019] Preferably, in step two, the solvent oil is methyl silicone oil.

[0020] Preferably, in step two, the volume of the solvent oil is 0.8-2.0 times the volume of the hydrolactide monomer.

[0021] Secondly, the present invention also provides a block copolymer based on polylactic acid / polyglycolic acid strength modification prepared by the above preparation method.

[0022] Thirdly, the present invention also provides the application of polylactic acid / polyglycolic acid strength-modified block copolymers as temporary plugging agents.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The present invention discloses a method for preparing a polylactic acid / polyglycolic acid (PLA) strength-modified block copolymer. First, terephthalic acid, adipic acid, aliphatic diols, polyols, and organometallic esters undergo esterification and transesterification reactions to obtain an alcohol-modified branched polyterephthalic acid-adipic acid-diol ester. Then, the alcohol-modified PLATIC-adipic acid-diol ester is mixed with a melt-dehydrated lactide monomer. The mixed lactide monomer is copolymerized on the hydroxyl groups of the PLATIC-adipic acid-diol ester to obtain a branched, stable block copolymer. The copolymer chains intertwine to form stronger interactions, leveraging the advantages of both polylactic acid or polyglycolic acid and PBAT, enhancing its mechanical properties, and significantly improving the overall performance of the material.

[0025] The block copolymer based on polylactic acid / polyglycolic acid strength modification of the present invention has the characteristics of good toughness, ductility, elongation at break, heat resistance and excellent impact performance. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0027] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0028] Comparative Example 1

[0029] 20g of molten dehydrated glycolide, 0.2g of dehydrated ethylene glycol, 0.010g of stannous octoate and 15ml of methyl silicone oil were added to a reaction flask, heated to 220℃, and reacted for 3.5 hours to obtain polyglycolate.

[0030] Comparative Example 2

[0031] 25g of molten dehydrated lactide, 0.2g of dehydrated ethylene glycol, 0.010g of stannous octoate and 20ml of methyl silicone oil were added to a reaction flask, heated to 220℃, and reacted for 3.5 hours to obtain polylactic acid.

[0032] Comparative Example 3

[0033] 16g of molten dehydrated glycolide, 5g of dehydrated lactide, 0.2g of dehydrated ethylene glycol, 0.010g of stannous octoate and 15ml of methyl silicone oil were added to a reaction flask, heated to 220℃, and reacted for 3.5 hours to obtain polylactic acid / polyglycolic acid copolymer.

[0034] Example 1

[0035] 17g of terephthalic acid, 13g of adipic acid, 20g of 1,4-butanediol and 0.9g of glycerol, along with 0.5g of tetrabutyl titanate, were added to a stirred reactor and heated to 200℃ for esterification and transesterification reactions. The reaction was carried out under negative pressure for 3 hours to remove water and excess butanediol.

[0036] Add 180g of molten dehydrated glycolide, 0.2g of stannous octoate and 120ml of methyl silicone oil, heat to 220℃ and react for 3.5 hours to obtain a block copolymer based on polyglycolic acid strength modification.

[0037] Example 2

[0038] 17g of terephthalic acid, 13g of adipic acid, 20g of 1,4-butanediol and 0.9g of glycerol, along with 0.5g of tetrabutyl titanate, were added to a stirred reactor and heated to 200℃ for esterification and transesterification reactions. The reaction was carried out under negative pressure for 3 hours to remove water and excess butanediol.

[0039] Add 220g of molten dehydrated lactide, 0.2g of stannous octoate and 180ml of methyl silicone oil, heat to 220℃ and react for 3.5 hours to obtain a block copolymer based on polylactic acid strength modification.

[0040] Example 3

[0041] 17g of terephthalic acid, 13g of adipic acid, 20g of 1,4-butanediol and 0.9g of glycerol, along with 0.5g of tetrabutyl titanate, were added to a stirred reactor and heated to 200℃ for esterification and transesterification reactions. The reaction was carried out under negative pressure for 3 hours to remove water and excess butanediol.

[0042] Add 45g of molten dehydrated lactide, 145g of dehydrated glycolide, 0.2g of stannous octoate and 130ml of methyl silicone oil, heat to 220℃ and react for 3.5 hours to obtain a block copolymer based on polylactic acid / polyglycolic acid strength modification.

[0043] Example 4

[0044] 10g of terephthalic acid, 8g of adipic acid, 14g of 1,4-butanediol and 0.3g of glycerol, along with 0.3g of tetrabutyl titanate, were added to a stirred reactor and heated to 200℃ for esterification and transesterification reactions. The reaction was carried out under negative pressure for 3 hours to remove water and excess butanediol.

[0045] Add 45g of molten dehydrated lactide, 145g of dehydrated glycolide, 0.2g of stannous octoate and 120ml of methyl silicone oil, heat to 220℃ and react for 3.5 hours to obtain a block copolymer based on polylactic acid / polyglycolic acid strength modification.

[0046] Example 5

[0047] 17g of terephthalic acid, 13g of adipic acid, 20g of 1,4-butanediol and 0.9g of glycerol, along with 0.5g of tetrabutyl titanate, were added to a stirred reactor and heated to 200℃ for esterification and transesterification reactions. The reaction was carried out under negative pressure for 3 hours to remove water and excess butanediol.

[0048] Add 65g of molten dehydrated lactide, 125g of dehydrated glycolide, 0.2g of stannous octoate and 130ml of methyl silicone oil, heat to 230℃ and react for 3.5 hours to obtain a block copolymer based on polylactic acid / polyglycolic acid strength modification.

[0049] Example 6

[0050] 17g of terephthalic acid, 16g of adipic acid, 25g of 1,4-butanediol and 0.6g of glycerol, along with 0.5g of tetrabutyl titanate, were added to a stirred reactor and heated to 200℃ for esterification and transesterification reactions. The reaction was carried out under negative pressure for 3 hours to remove water and excess butanediol.

[0051] Add 180g of molten dehydrated glycolide, 0.2g of stannous octoate and 120ml of methyl silicone oil, heat to 220℃ and react for 3.5 hours to obtain a block copolymer based on polyglycolic acid strength modification.

[0052] The tensile and heat resistance properties of the products prepared in Comparative Examples 1-3 and Examples 1-6 were tested using the following methods:

[0053] Fiber sample preparation: The prepared product is dehydrated at 120℃, melt-extruded using a single screw extruder, and then spun into fiber yarns with a diameter of about 1mm using a spinning machine. The fiber yarns are then braided into fiber ropes on a 4-8 strand braiding machine.

[0054] Tg: Sample particles were directly measured using a differential scanning calorimeter. In a nitrogen atmosphere, 5-10 mg of sample was taken, heated from 25 °C to 250 °C at a heating rate of 10 °C / min, held at that temperature for 3 min, and then cooled from 250 °C to 25 °C at a cooling rate of 10 °C / min, held at that temperature for 3 min.

[0055] Tensile strength: The sample fibers are braided into 8 strands, fixed on a universal testing machine, and tension is applied and gradually increased until the fibers break. The maximum tensile strength at the point of breakage is recorded.

[0056] Elongation at break: The sample fibers are braided into 8 strands, fixed on a universal testing machine, and tension is applied and gradually increased until the fibers break. The maximum deformation value at break is recorded.

[0057] The test results are shown in Table 1.

[0058] Table 1. Performance of the products prepared in Comparative Examples 1-3 and Examples 1-6

[0059] sample Tensile strength (MPa) Tg (°C) Elongation at break (%) Comparative Example 1 100 40 25-42 Comparative Example 2 68 59 4-6 Comparative Example 3 75-90 48 15-35 Example 1 107 43 32-45 Example 2 82 65 20-40 Example 3 98 53 23-51 Example 4 103 54 27-55 Example 5 94 55 18-40 Example 6 108 44 35-50

[0060] As can be seen from Table 1, the block copolymer based on polylactic acid / polyglycolic acid strength modification of the present invention has superior properties such as good toughness, elongation at break, and heat resistance compared with unmodified polylactic acid, polyglycolic acid, or copolymers of the two.

[0061] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. 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 embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid, characterized in that, Includes the following steps: Step 1: Mix terephthalic acid, adipic acid, aliphatic diol, polyol with ≥3 hydroxyl groups and organometallic ester evenly, heat to react, remove water and excess alcohol under reduced pressure to obtain alcohol-modified polyterephthalic acid-adipic acid-diol ester. Step 2: Add molten dehydrated lactide monomer, catalyst and solvent oil, and heat to react, to obtain a block copolymer based on polylactic acid / polyglycolic acid strength modification.

2. The method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid according to claim 1, characterized in that, In step one, the aliphatic diols include one or more of butanediol, pentanediol, hexanediol, ethylene glycol monohydrate, and ethylene glycol dihydrate.

3. The method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid according to claim 1, characterized in that, In step one, the polyol includes one or more of glycerol, diglycerol, glucose, and menthol.

4. The method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid according to claim 1, characterized in that, In step one, the organometallic ester is one or more of C2-C8 organometallic esters, and the metal includes one or more of titanium, tin, zinc, and aluminum.

5. The method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid according to claim 1, characterized in that, In step one, the reaction temperature is 180-220℃ and the reaction time is 2-4 hours.

6. The method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid according to claim 1, characterized in that, The molar ratio of terephthalic acid, adipic acid, aliphatic diol, polyol, and hydrolactide monomer is (1.0-1.5):(0.5-1.2):(1.5-3):(0.05-0.10):(10-30), and the amount of the organometallic acid ester is 0.1%-5% of the total mass of terephthalic acid, adipic acid, aliphatic diol, and polyol.

7. The method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid according to claim 1, characterized in that, In step two, the lactide monomer is one or both of lactide and glycolide, the catalyst is stannous octoate, aluminum isopropoxide, yttrium isopropoxide, or calcium acetylacetonate, the amount of catalyst is 0.05wt%-1.0wt% of the aqueous lactide monomer, and the solvent oil is methyl silicone oil, the volume of the solvent oil is 0.8-2.0 times the volume of the aqueous lactide monomer.

8. The method for preparing a strength-modified block copolymer based on polylactic acid / polyglycolic acid according to claim 1, characterized in that, In step two, the reaction temperature is 180-220℃ and the reaction time is 3-5 hours.

9. A polylactic acid / polyglycolic acid strength-modified block copolymer prepared by the preparation method according to any one of claims 1-8.

10. The application of the polylactic acid / polyglycolic acid strength-modified block copolymer according to claim 9 as a temporary plugging agent.