CN115160512B - Lignin-based thermoplastic elastomer with rapid repair function and preparation method thereof - Google Patents

Abstract

The invention discloses a lignin-based thermoplastic elastomer, which relates to the technical field of thermoplastic elastomers. Its structural formula is as follows: The present invention also provides a method for preparing the above-mentioned lignin-based thermoplastic elastomer. The beneficial effects of the present invention are: the lignin-based thermoplastic elastomer in the present invention has excellent mechanical properties, good ductility, good biodegradability and environmental friendliness. This lignin-based elastomer can quickly heal within one minute under near-infrared light irradiation. This lignin-based elastomer with rapid repair properties can significantly improve the utilization rate and added value of lignin and broaden the scope of lignin. application.

Description

A kind of lignin-based thermoplastic elastomer with rapid repair function and its preparation method

Technical field

The invention relates to the technical field of thermoplastic elastomers, and in particular to a lignin-based thermoplastic elastomer with rapid repair function and a preparation method thereof.

Background technique

Lignin is the second most abundant natural polymer on earth and is widely found in plant cell walls. It has been considered a promising resource to replace existing fossil fuels. Lignin's low cost, abundant content, environmental friendliness, and good UV radiation resistance have led to many potential applications of lignin, such as adhesives, sunscreen creams, carbon fibers, fillers, bioderived synthetic polymers, and composite materials. Despite the huge potential of lignin, the technology to exploit this important resource is immature and lignin-based materials often cannot be converted into high-value products.

Thermoplastic elastomer is a polymer material that has the characteristics of rubber (high elasticity, compression permanent deformation, etc.) and the processing characteristics of plastic (simple process). It is widely used in many industries such as automobiles, construction, household equipment, wires and cables, electronic products, food packages, and medical equipment. However, most thermoplastic elastomers are prepared from petroleum resources. In today's context of increasingly scarce petroleum resources and increasingly serious environmental pollution, bio-based thermoplastic elastomers have extremely important commercial value and environmental significance.

In recent years, surface graft polymerization has been one of the most prominent techniques for preparing well-defined lignin copolymers, especially using the reversible addition-fragmentation chain transfer (RAFT) method. For example, copolymers of poly-n-butyl acrylate and 1-vinylimidazole grafted with different contents of lignin were successfully synthesized by RAFT grafting method. The mechanical properties of the copolymer were tested and the results showed that when the lignin content was 6.1wt%, the tensile elongation at break of the copolymer could reach 900%, but the tensile strength was only 0.22MPa. (Wang W. Wang F. Zhang C. Tang J. Zeng X. Wan X. (2021) Chemical Engineering Journal, 404, art. no. 126358).

During the use of materials, local damage and micro-cracks will inevitably occur, which will cause macro cracks and break, thus affecting the normal use of the material and shortening its service life. Therefore, rapid repair of early cracks is a realistic and important issue. Rapid repair materials have the advantages of reducing repair and maintenance costs during material operation and extending the service life of materials. At present, rapid repair materials have been used in biomedicine, bionic materials, electrolytic cell materials, rapid repair of polymer glass and other fields.

If soft segment and hard segment polymers can be grafted on lignin, lignin acts as a cross-linking point in the polymer system, giving the polymer network good chain flexibility and ductility, and the hard segment provides strength, and can produce properties Excellent, fast-healing lignin-based elastomer.

The Chinese patent document with publication number CN104356318A discloses a lignin-based star-shaped thermoplastic elastomer and its preparation method, which includes the following steps: (1) reacting lignin with 2-bromoisobutyryl bromide to synthesize lignin ATRP Macromolecule initiator; (2) Add hard monomer, soft monomer, lignin ATRP macromolecule initiator and ligand and good reaction solvent into the reaction bottle, stir thoroughly to dissolve, and freeze, vacuum and fill with nitrogen three times. The circulation process removes oxygen from the mixed solution, adds a catalyst, and reacts at 55-110°C for 4-48 hours. Then, use the methanol/water mixture as the precipitant, filter the collected precipitate, and dry it to obtain a product with UV absorption properties and Lignin-based star polymer with thermoplastic elastomer properties. The mechanical properties of this lignin-based star-shaped polymer are better than those of linear polymers of the same composition, and can be used as membrane materials with UV absorption properties. The lignin-based star-shaped thermoplastic elastomer prepared by this method does not have rapid repair ability.

Contents of the invention

The technical problem to be solved by the present invention is to provide a lignin-based thermoplastic elastomer with good ductility, mechanical properties and rapid repair ability and a preparation method thereof.

The present invention solves the above technical problems through the following technical means:

A lignin thermoplastic elastomer with the following structural formula:

Among them, 0<m≤700, 30≤n≤700, R ₁ is any group in;

_R2 is: any one or more groups in;

R ₃ is:

any one or more groups in .

illustrate: Represents the group connection point, the same below.

Beneficial effects: The lignin-based thermoplastic elastomer in the present invention has excellent mechanical properties, good ductility and certain rapid repair capabilities. The lignin-based thermoplastic elastomer in the present invention uses lignin, a natural biomass material, as a rigid main chain and is grafted with a series of monomers. The rigid lignin serves as a cross-linking point in the entire polymer system. Carbon chain monomers give the polymer network good chain flexibility and ductility.

The invention also provides a method for preparing the above-mentioned lignin-based thermoplastic elastomer, which includes the following steps:

(1) Add the lignin macromolecular chain transfer agent, reactive monomer A and reactive monomer B, and the initiator into a reaction vessel containing a solvent; the structural formula of the lignin macromolecular chain transfer agent is as follows:

Where, R is H or

(2) Exclude the air and water in the reaction vessel and react at 60-80°C. After the reaction is completed, collect the product and dry it to obtain a lignin-based thermoplastic elastomer.

The preparation route of lignin-based thermoplastic elastomer is as follows:

Beneficial effects: The present invention can control the microstructure of the polymer network by designing the type of reaction monomers, grafting density, relative proportions of rigid main chains and grafted side chains, etc., thereby obtaining excellent macroscopic mechanical properties and rapid Lignin-based thermoplastic elastomer materials with repair functions.

The higher the proportion of rigid chains in the product, the better the mechanical strength. The relative proportion of the rigid main chain and grafted side chain in the reaction product can be controlled by adjusting the ratio of the reaction monomer and the lignin macromolecular chain transfer agent. The greater the ratio of the reaction monomer to the chain transfer agent, the more side chains will be in the material. The higher the proportion, select reactive monomer A and reactive monomer B so that the product has different physical and chemical properties.

Preferably, it includes the following steps:

(1) Add 1-3 parts by weight of lignin macromolecular chain transfer agent, 1-90 parts by weight of reactive monomer A and 10-60 parts by weight of reactive monomer B, and 0.0058-0.0164 parts by weight of initiator into a reaction vessel with 200-500 parts by weight of solvent;

(2) Exclude water and air from the reaction vessel and react at 70°C. After the reaction is completed, collect the product and dry it.

Preferably, the reaction vessel is a reaction bottle.

Preferably, the reaction monomer A is: methyl acrylate, ethyl acrylate, propyl acrylate, amyl acrylate, n-butyl acrylate, hexyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, acrylic acid Isooctyl acrylate, lauryl acrylate, isobornyl acrylate or isocyanate acrylate.

Preferably, the reaction monomer B is: acrylic acid, 3-butenoic acid, 4-pentenoic acid, 5-hexenoic acid, 3,5-hexadienoic acid or 2,5-dienocaproic acid acrylic acid.

any one or more groups in .

Preferably, the initiator in step (1) is azobisisobutyronitrile.

Preferably, the solvent in step (1) is N,N-dimethylformamide.

Preferably, in step (2), the reaction vessel is subjected to a freezing-vacuum-thawing cycle, and after reacting at 70°C for 48-72 hours, it is placed in a precipitating agent to precipitate and collected, and then the collected product is placed at 50-80°C. ℃ vacuum drying.

Preferably, the precipitating agent is a mixed solution of methanol and water.

Preferably, the preparation method of the lignin macromolecular chain transfer agent in step (1) includes the following steps:

(a) Add 10 parts by weight of 3-mercaptopropionic acid to the stirred suspension of 20 parts by weight of tripotassium phosphate in acetone at room temperature, then add 21.5 parts by weight of carbon disulfide, stir for 8 hours, remove the solvent under reduced pressure, and remove the residue Add to saturated brine, extract with dichloromethane, wash with saturated brine, dry the extract over anhydrous magnesium sulfate, remove the solvent under reduced pressure, and obtain 3-(benzyltrithiocarbonate)propane as a light yellow solid. acid;

(b) Add 1 part by weight of lignin, 1-1.5 parts by weight of 3-(benzyltrithiocarbonate)propionic acid in step (a), and 0.02-0.06 parts by weight of 4-dimethylaminopyridine 50-80 parts by weight of anhydrous methylene chloride; purge with nitrogen for half an hour, add 0.5-1 parts by weight of 1-ethyl-(3-dimethylaminopropyl)carbonyldicarbonate dropwise under ice-water bath conditions Imine, react at 20-30°C, wash, centrifuge, and dry to prepare a lignin macromolecular chain transfer agent.

The reaction formula of lignin macromolecular chain transfer agent is as follows:

Preferably, in step (a), 10 parts by weight of 3-mercaptopropionic acid is added to the stirred 20 parts by weight of tripotassium phosphate suspension in acetone, and then 21.5 parts by weight of carbon disulfide is added and stirred for 8 hours; removed under reduced pressure. Solvent, add the residue to saturated brine, extract with 2×100ml dichloromethane, then wash with 3×100ml saturated brine, and then dry the extract with anhydrous magnesium sulfate for 24h, remove the solvent under reduced pressure, and obtain a light yellow solid 3- (Benzyltrithiocarbonate)propionic acid.

Preferably, in step (b), the reaction is carried out at 20-30°C for 36-48 hours, washed with pure water, centrifuged, and dried under vacuum at 30-50°C.

The advantages of the present invention are:

(1) The lignin-based thermoplastic elastomer in the present invention has excellent mechanical properties. When the strain reaches more than 500%, the stress can reach 11MPa. There are a large number of ester bonds in the lignin main chain, and all side chain monomers also have ester bond structures. The ester bonds can be broken and degraded well under natural conditions, and have good biodegradability and environmental friendliness.

(2) The lignin-based thermoplastic elastomer in the present invention uses lignin, a natural biomass material, as the rigid main chain and is grafted with a series of monomers. The lignin acts as a cross-linking point in the polymer system, and the short chain imparts The polymer network has good chain flexibility and ductility, the hard segments provide strength, and the final lignin-based elastomer has excellent mechanical properties.

(3) The present invention can adjust the microstructure of the polymer network by designing the type of reaction monomers, grafting density, relative proportions of rigid main chains and grafted side chains, etc., thereby achieving excellent macroscopic mechanical properties and promising performance. Naturally degrading, environmentally friendly lignin-based thermoplastic elastomer material.

(4) The lignin-based elastomer prepared by the present invention can heal quickly within 2 seconds under near-infrared light irradiation. This lignin-based elastic energy with rapid repair performance significantly improves the utilization rate and additional properties of lignin. value, broadening the application of lignin.

Description of the drawings

Figure 1 is a hydrogen nuclear magnetic spectrum of 3-(benzyltrithiocarbonate)propionic acid in Example 1 of the present invention;

Figure 2 is a hydrogen nuclear magnetic spectrum of the lignin-based thermoplastic elastomer 2 in Example 4 of the present invention;

Figure 3 is a hydrogen nuclear magnetic spectrum of the lignin-based polymer 13 in Comparative Example 1 of the present invention;

Figure 4 is a differential scanning calorimetry diagram of the products in Examples 3-8 and Comparative Example 1 of the present invention;

Figure 5 is a mechanical stretching diagram of the product in Examples 3-8 of the present invention;

Figure 6 is a mechanical tensile diagram of the product of Example 4 of the present invention that is self-repaired under near-infrared lamp irradiation after fracture;

Figure 7 is a mechanical tensile diagram of the product of Example 5 of the present invention that is self-repaired under near-infrared lamp irradiation after fracture;

Figure 8 is a mechanical tensile diagram of the product of Example 6 of the present invention that is self-repaired under near-infrared lamp irradiation after fracture;

Figure 9 is a mechanical tensile diagram of the product of Example 7 of the present invention that is self-repaired under near-infrared lamp irradiation after fracture.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the present invention. Examples, not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

The test materials and reagents used in the following examples can all be obtained from commercial sources unless otherwise specified.

If no specific techniques or conditions are specified in the examples, the techniques or conditions described in literature in the field can be followed or the product instructions can be followed.

Example 1

The synthesis of 3-(benzyltrithiocarbonate)propionic acid specifically includes the following steps:

Add 10.0g 3-mercaptopropionic acid to the stirred suspension of 20g tripotassium phosphate in acetone, then add 21.5g carbon disulfide, stir for 8 hours, remove the solvent under reduced pressure, add the residue to saturated brine, and use 2×100ml dichloride Extract with methane, wash with 3 × 100 ml saturated saline, and dry the extract over anhydrous magnesium sulfate. Remove the solvent under reduced pressure to obtain 3-(benzyltrithiocarbonate)propionic acid as a light yellow solid.

Example 2

The synthesis of lignin macromolecular chain transfer agent (Lignin-CTA) specifically includes the following steps:

Add 3g of lignin, 3.96g of 3-(benzyltrithiocarbonate)propionic acid, and 60mg of 4-dimethylaminopyridine into the round-bottomed flask, add 150g of anhydrous dichloromethane, and purge with nitrogen for half an hour. , add 1.52g 1-ethyl-(3-dimethylaminopropyl)carbodiimide dropwise in an ice-water bath, react for 48 hours at 25°C, wash with pure water, centrifuge, and vacuum at 40°C Drying to prepare a lignin macromolecular chain transfer agent.

Example 3

Synthesis of lignin-based thermoplastic elastomer 1

Add 0.3g of the lignin macromolecular chain transfer agent in Example 2, 9.00g of n-butyl acrylate, 2.16g of acrylic acid and 1.64mg of azobisisobutyronitrile to 20g of N,N-dimethylformamide, and repeat After three freeze-vacuum-thaw cycles, the Schlenk reaction flask was vacuum-sealed and placed in an oil bath. After reacting for 48 hours at 70°C, the reaction was stopped and precipitated in a large amount of methanol. The product was dried under reduced pressure at 50°C in a vacuum drying oven to obtain 2.85g of lignin-based thermoplastic elastomer 1 (m=169, n=54).

Example 4

Synthesis of Lignin-Based Thermoplastic Elastomer 2

Add 0.3g lignin macromolecular chain transfer agent, 7.69g n-butyl acrylate, 2.88g acrylic acid and 1.64mg azobisisobutyronitrile to 20g N,N-dimethylformamide, and repeat the freezing-vacuum process three times. - After the melting cycle, the Schlenk reaction flask is then vacuum-sealed and placed in an oil bath. After reacting for 72 hours at 60°C, the reaction was stopped and precipitated in a large amount of methanol. The product was dried under reduced pressure at 80°C in a vacuum drying oven to obtain 2.80 g of lignin-based thermoplastic elastomer 2 (m=150, n=71).

Example 5

Synthesis of lignin-based thermoplastic elastomer 3

Add 0.3g lignin macromolecular chain transfer agent, 7.05g n-butyl acrylate, 3.24g acrylic acid and 1.64mg azobisisobutyronitrile to 20g N,N-dimethylformamide, and repeat the freezing-vacuum process three times. -After the melting cycle, the Schlenk reaction flask is then vacuum-sealed and placed in an oil bath. After reacting for 50 hours at 80°C, the reaction was stopped and precipitated in a large amount of methanol. The product was dried under reduced pressure at 60°C in a vacuum drying oven to obtain 2.79g of lignin-based thermoplastic elastomer 3 (m=173, n=80).

Example 6

Synthesis of lignin-based thermoplastic elastomer 4

Add 0.3g lignin macromolecular chain transfer agent, 6.41g n-butyl acrylate, 3.60g acrylic acid and 1.64mg azobisisobutyronitrile to 20g N,N-dimethylformamide, and repeat the freezing-vacuum process three times. -After the melting cycle, the Schlenk reaction flask is then vacuum-sealed and placed in an oil bath. After reacting at 70°C for 48 hours, the reaction was stopped and precipitated in a large amount of methanol. The product was dried under reduced pressure at 50°C in a vacuum drying oven to obtain 1.17g of lignin-based thermoplastic elastomer 4 (m=68, n=42).

Example 7

Synthesis of lignin-based thermoplastic elastomer 5

Add 0.3g lignin macromolecular chain transfer agent, 5.12g n-butyl acrylate, 3.84g acrylic acid and 1.64mg azobisisobutyronitrile to 20g N,N-dimethylformamide, and repeat the freezing-vacuum process three times. -After the melting cycle, the Schlenk reaction flask is then vacuum-sealed and placed in an oil bath. After reacting at 70°C for 48 hours, the reaction was stopped and precipitated in a large amount of methanol. The product was dried under reduced pressure at 50°C in a vacuum drying oven to obtain 1.0g of fully bio-based thermoplastic elastomer 5 (m=44, n=61).

Example 8

Synthesis of lignin-based thermoplastic elastomer 6

Add 0.3g lignin macromolecular chain transfer agent, 3.84g n-butyl acrylate, 5.04g acrylic acid and 1.64mg azobisisobutyronitrile to 20g N,N-dimethylformamide, and repeat the freezing-vacuum process three times. - After the melting cycle, the Schlenk reaction flask is then vacuum-sealed and placed in an oil bath. After reacting at 70°C for 48 hours, the reaction was stopped and precipitated in a large amount of methanol. The product was dried under reduced pressure at 50°C in a vacuum drying oven to obtain 0.85g of lignin-based thermoplastic elastomer 6 (m=57, n=35).

Example 9

Synthesis of Lignin-Based Thermoplastic Elastomer 7

The preparation method is the same as that in Example 5, except that the reaction monomer A is isobornyl acrylate, and the reaction monomer B is 4-pentenoic acid.

Example 10

Synthesis of Lignin-Based Thermoplastic Elastomer 8

The preparation method is the same as that in Example 5, except that the reaction monomer A is acrylic isocyanate, and the reaction monomer B is 4-pentenoic acid.

Example 11

Synthesis of Lignin-Based Thermoplastic Elastomer 9

The preparation method is the same as that in Example 5, except that the reaction monomer A is isobornyl acrylate, and the reaction monomer B is 2,5-dienohexanoic acid acrylic acid.

Example 12

Synthesis of Lignin-Based Thermoplastic Elastomer 10

The preparation method is the same as that in Example 5, except that the reaction monomer A is acrylic isocyanate, and the reaction monomer B is 2,5-dienocaproic acid acrylic acid.

Example 13

Synthesis of Lignin-Based Thermoplastic Elastomer 11

The preparation method is the same as that in Example 5, except that the reaction monomer A is methyl acrylate and the reaction monomer B is 3-butenoic acid.

Example 14

Synthesis of Lignin-Based Thermoplastic Elastomer 12

The preparation method is the same as that in Example 5, except that the reaction monomer A is ethyl acrylate and the reaction monomer B is 5-hexenoic acid.

Example 15

Synthesis of lignin-based thermoplastic elastomer 13

The preparation method is the same as that in Example 5, except that the reaction monomer A is propyl acrylate and the reaction monomer B is 3,5-hexadienoic acid.

Example 16

Synthesis of lignin-based thermoplastic elastomer 14

The preparation method is the same as that in Example 5, except that the reaction monomer A is amyl acrylate, and the reaction monomer B is 3-butenoic acid.

Example 17

Synthesis of Lignin-Based Thermoplastic Elastomer 15

The preparation method is the same as that in Example 5, except that the reaction monomer A is hexyl acrylate and the reaction monomer B is 5-hexenoic acid.

Example 18

Synthesis of Lignin-Based Thermoplastic Elastomer 16

The preparation method is the same as that in Example 5, except that the reaction monomer A is hydroxypropyl acrylate, and the reaction monomer B is 3,5-hexadienoic acid.

Example 19

Synthesis of Lignin-Based Thermoplastic Elastomer 17

The preparation method is the same as that in Example 5, except that the reaction monomer A is 4-hydroxybutylacrylate and the reaction monomer B is 3-butenoic acid.

Example 20

Synthesis of Lignin-Based Thermoplastic Elastomer 18

The preparation method is the same as that in Example 5, except that the reaction monomer A is isooctyl acrylate, and the reaction monomer B is 5-hexenoic acid.

Example 21

Synthesis of Lignin-Based Thermoplastic Elastomer 19

The preparation method is the same as that in Example 5, except that the reaction monomer A is lauryl acrylate, and the reaction monomer B is 3,5-hexadienoic acid.

Example 22

The synthesis of lignin macromolecular chain transfer agent (Lignin-CTA) specifically includes the following steps:

Add 3g of lignin, 3g of 3-(benzyltrithiocarbonate)propionic acid, and 150mg of 4-dimethylaminopyridine into a round-bottom flask, add 180g of anhydrous dichloromethane, and purge with nitrogen for half an hour. Add 1.5g 1-ethyl-(3-dimethylaminopropyl)carbodiimide dropwise in an ice-water bath, react for 40 hours at 20°C, wash with pure water, centrifuge, and dry under vacuum at 30°C. , to prepare lignin macromolecular chain transfer agent.

Example 23

The synthesis of lignin macromolecular chain transfer agent (Lignin-CTA) specifically includes the following steps:

Add 3g of lignin, 4.5g of 3-(benzyltrithiocarbonate)propionic acid, and 180mg of 4-dimethylaminopyridine into a round-bottomed flask, add 240g of anhydrous dichloromethane, and purge with nitrogen for half an hour. , add 3g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide dropwise in an ice-water bath, react for 36 hours at 30°C, wash with pure water, centrifuge, and dry under vacuum at 50°C. Prepare lignin macromolecular chain transfer agent.

Example 24

The preparation method of this embodiment is the same as that of Example 3, except that the added amount of N,N-dimethylformamide is changed to 35g.

Example 25

The preparation method of this embodiment is the same as that of Example 3, except that the addition amount of N,N-dimethylformamide is changed to 50g.

Example 26

The preparation method of this embodiment is the same as that of Example 3, except that the addition amount of the lignin macromolecular chain transfer agent is changed to 0.1g.

Example 27

The preparation method of this embodiment is the same as that of Example 3, except that the addition amount of the lignin macromolecular chain transfer agent is changed to 0.2g.

Example 28

The preparation method of this embodiment is the same as that of Example 3, except that the addition amount of n-butyl acrylate is changed to 0.1g.

Example 29

The preparation method of this embodiment is the same as that of Example 3, except that the addition amount of n-butyl acrylate is changed to 0.2g.

Example 30

The preparation method of this embodiment is the same as that of Example 3, except that the amount of acrylic acid added is changed to 1g.

Example 31

The preparation method of this embodiment is the same as that of Example 3, except that the amount of acrylic acid added is changed to 6g.

Example 32

The preparation method of this embodiment is the same as that of Example 3, except that the addition amount of azobisisobutyronitrile is changed to 0.58g.

Example 33

The preparation method of this embodiment is the same as that of Example 3, except that the addition amount of azobisisobutyronitrile is changed to 1.2g.

Comparative example 1

Synthesis of lignin-based polymer 13

Add 0.1g lignin macromolecular chain transfer agent, 1.08g acrylic acid and 0.58mg azobisisobutyronitrile to 10ml N,N-dimethylformamide, repeat three freezing-vacuum-thawing cycles, and then The Schlenk reaction flask was vacuum sealed and placed in an oil bath. After reacting for 48 hours at 70°C, the reaction was stopped and precipitated in a large amount of ethyl acetate. The product was dried under reduced pressure at 50°C in a vacuum drying oven to obtain 0.21g of lignin-based polymer 13 (m=0, n=47) .

Comparative example 2

Synthesis of Lignin-Based Polymer 14

Add 0.1g lignin macromolecular chain transfer agent, 1.92g butyl acrylate and 0.58mg azobisisobutyronitrile to 10ml N,N-dimethylformamide, and repeat three freezing-vacuum-thawing cycles. The Schlenk reaction flask was then vacuum-sealed and placed in an oil bath. After reacting for 48 hours at 70°C, the reaction was stopped and precipitated in a large amount of ethyl acetate. The product was dried under reduced pressure at 50°C in a vacuum drying oven to obtain 0.53g of lignin-based polymer 14 (m=54, n=0). .

The product of Comparative Example 1-2 could not be hot-pressed into tablets, and its properties could not be measured.

The properties of the lignin-based thermoplastic elastomer prepared in Examples 3 to 8 were measured. The following measurement methods are all existing technologies:

(1) Conduct NMR analysis on the structure;

(2) Measure the stress-strain curve;

(3) Measure Young’s modulus, tensile strength, elongation at break and toughness;

(4) Rapid repair performance measurement.

Figure 4 is a scanning differential calorimetry diagram of the products in Examples 3 to 8 and Comparative Example 1. It can be seen that the glass transition temperature of polyacrylic acid is higher, and the glass transition temperature of the copolymer product of acrylic acid and n-butyl acrylate is lower, and the glass transition temperature increases with the increase of acrylic acid content.

Table 1 shows the performance test results of the lignin-based thermoplastic elastomer in Examples 3-8:

As can be seen from Table 1, it can be seen that the strain of the lignin-based thermoplastic elastomer material can reach up to more than 1400%, while the stress reaches about 0.5MPa. In Example 5, while the stress reaches about 11MPa, the strain can also reach more than 450%. It shows that a series of materials with good ductility and certain mechanical strength can be obtained by adjusting the proportion of grafted monomers. On the whole, it can be seen that the strain of the obtained lignin-based thermoplastic elastomer material decreases with the increase of acrylic acid content, and the stress shows a trend of first increasing and then decreasing. This is because as the polyacrylic acid content increases, the water absorption of the lignin-based thermoplastic elastomer material increases, which affects the mechanical properties of the material.

Cut the dumbbell-shaped samples in Examples 5 and 6 into two sections, then reassemble the fractured section into one section, place it at room temperature and irradiate it with a near-infrared lamp without applying external force. Their mechanical properties were measured at different time periods.

Figures 6 and 7 are the rapid repair tensile diagrams of Example 4 and Example 5 respectively. It can be seen that the obtained lignin-based thermoplastic elastomer has the ability to quickly repair under near-infrared light irradiation.

As shown in Figure 6, the mechanical properties of the sample of Example 4 before fracture are: tensile strength 3.21 MPa, and elongation at break 1270%. It was quickly repaired after being irradiated with near-infrared light for 50 seconds. Its mechanical properties after rapid repair were: tensile strength 2.85MPa, and elongation at break 1240%.

As shown in Figure 7, the mechanical properties of the sample of Example 5 before fracture are: tensile strength 13.9 MPa, and elongation at break 510%. After being irradiated with near-infrared light for 60 seconds, it was rapidly repaired completely. Its mechanical properties after rapid repair were: tensile strength 13.5MPa, and elongation at break 490%.

As shown in Figure 8, the mechanical properties of the sample of Example 6 before fracture are: tensile strength 5.3MPa, elongation at break 450%. After being irradiated with near-infrared light for 40 seconds, it was rapidly repaired completely. Its mechanical properties after rapid repair were: tensile strength 4.5MPa, elongation at break 470%.

As shown in Figure 9, the mechanical properties of the sample of Example 7 before fracture are: tensile strength 2.95MPa, and elongation at break 365%. After being irradiated with near-infrared light for 50 seconds, it was rapidly repaired completely. Its mechanical properties after rapid repair were: tensile strength 2.53MPa, elongation at break 355%.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the foregoing embodiments. The recorded technical solutions may be modified, or some of the technical features thereof may be equivalently replaced; however, these modifications or substitutions shall not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of each embodiment of the present invention.

Claims (6)

1. A lignin-based thermoplastic elastomer characterized by: the structural formula is as follows:

wherein m is more than or equal to 44 and less than or equal to 173, n is more than or equal to 35 and less than or equal to 80, R ₁ Is thatAny one of the groups in (a);

R ₂ the method comprises the following steps:

any one or more of the groups in (a);

R ₃ the method comprises the following steps:

any one or more of the groups in (a).

2. A method of preparing the lignin-based thermoplastic elastomer according to claim 1 wherein: the method comprises the following steps:

(1) Adding lignin macromolecular chain transfer agent, reaction monomer A and reaction monomer B, and initiator into a reaction container filled with solvent; the lignin macromolecular chain transfer agent has the following structural formula:

wherein R is

The reaction monomer A is: methyl acrylate, ethyl acrylate, n-propyl acrylate, n-pentyl acrylate, n-butyl acrylate or n-hexyl acrylate;

the reaction monomer B is: acrylic acid, 3-butenoic acid, 4-pentenoic acid or 5-hexenoic acid;

(2) Removing air and water in the reaction vessel, reacting at 60-80 ℃, collecting and drying the product after the reaction is finished, and obtaining the lignin-based thermoplastic elastomer.

3. The method of lignin-based thermoplastic elastomer according to claim 2 wherein: the method comprises the following steps:

(1) Adding 1-3 parts by weight of lignin macromolecular chain transfer agent, 1-90 parts by weight of reaction monomer A and 10-60 parts by weight of reaction monomer B, and 0.0058-0.0164 part by weight of initiator into a reaction vessel with 200-500 parts by weight of solvent;

(2) The water and air in the reaction vessel were removed, reacted at 70℃and after the reaction was completed, the product was collected and dried.

4. The method of lignin-based thermoplastic elastomer according to claim 2 wherein: the solvent in the step (1) is N, N-dimethylformamide.

5. The method of lignin-based thermoplastic elastomer according to claim 2 wherein: the initiator in the step (1) is azobisisobutyronitrile.

6. The method of lignin thermoplastic elastomer according to claim 2 wherein: the reaction vessel is subjected to freeze-vacuum-melting circulation in the step (2), the reaction vessel is reacted for 36-48 hours at 70 ℃, then the reaction vessel is placed in a precipitator for precipitation and collection, and then the collected product is placed in a vacuum for drying at 50-80 ℃.