CN117417507A

CN117417507A - High-strength high-toughness modified PBAT material and preparation method thereof

Info

Publication number: CN117417507A
Application number: CN202311371437.1A
Authority: CN
Inventors: 石玲英; 费志雄; 杨科珂
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2023-10-23
Filing date: 2023-10-23
Publication date: 2024-01-19

Abstract

The invention belongs to the field of high polymer materials, and relates to a high-strength high-toughness modified PBAT material and a preparation method thereof. The invention provides a modified PBAT material, which is prepared from the following raw materials of PBAT with lower molecules, diisocyanate and a small molecular chain extender by melt copolymerization; wherein the small molecule chain extender is selected from the group consisting of: one of pentyenediamine, 5- (2-hydroxyethyl) -6-methyl-2-aminouracil, adipic acid dihydrazide, N-bis (2-hydroxyethyl) oxamide or 1, 6-bis (hydroxyethoxycarbonylamino) hexane. The modification obtained by the inventionThe PBAT material has good mechanical strength which can reach 18-55 MPa and enhanced fracture toughness>350MJ/m ³ ) The elongation at break can reach 800-1700%.

Description

High-strength high-toughness modified PBAT material and preparation method thereof

Technical Field

The invention belongs to the field of high polymer materials, and relates to a bio-based environment-friendly high-strength high-toughness degradable bio-based PBAT material and a preparation method thereof.

Background

With technological progress and continuous improvement of social productivity, human consumption of resources is also drastically increased, which not only leads to increasing exhaustion of non-renewable resources, but also causes serious ecological damage and environmental pollution. Therefore, finding a suitable bio-based sustainable material replacement product for non-renewable products currently in use has become an important focus of material science research today. Plastic pollution is currently one of the most urgent environmental problems, and global plastic production increases from 230 ten thousand tons in 1950 to about 4.5 hundred million tons in 2015, with 9 hundred million tons estimated to be reached in 2050. Most conventional plastic products are made from petroleum-based polymers, and most petroleum-based polymers are non-biodegradable, with large amounts of waste plastic resulting in "white pollution". Taking the typical representative "packaging industry" of white pollution as an example, in the last 10 years, plastic bags were the second largest packaging waste next to paper and cardboard, and the recovery of all packaging plastic waste produced in 2019 was only 40% according to eu statistics. The waste plastics can decompose in small amounts under prolonged physical and chemical stimuli, resulting in secondary microplastic and nano-plastic contamination, and the accumulation of these plastic micropellets in the earth's environment can have a very adverse effect on humans, wild animals and their habitat.

The bio-based renewable resources are used as raw materials, and biodegradable polymer materials are designed and prepared to produce innovative bio-plastics for industrial development, so that the bio-plastics are important strategies for solving resource shortage and environmental pollution. Over the last two decades, many bio-based and biodegradable polymers have been proposed and studied to replace non-degradable polymers based on fossil fuels. However, the use of biobased materials in packaging and disposable cutlery (e.g., straws, spoons, etc.) has heretofore been limited by their poor barrier properties and poor mechanical properties.

The poly (adipic acid)/terephthalic acid-butanediol ester (PBAT) is an important thermoplastic biodegradable plastic, is synthesized by taking terephthalic acid, adipic acid and 1, 4-butanediol as raw materials through esterification or transesterification, has excellent stretch resistance, impact resistance, high heat resistance and the characteristic of being degraded by natural biological enzymes in a short time, and can be used for biodegradation and composting, and can be applied to fully-degradable packaging films, fully-degradable packaging bags, agricultural mulching films and the like. However, even PBAT materials still exhibit poor mechanical strength (< 18 MPa), which greatly limits the application of PBAT in a wide variety of fields. Therefore, the modification and enhancement strategy for the PBAT material is particularly important. The most typical modification strategy is to compound the PBAT with a brittle and hard polylactic acid (PLA) material, however, the compatibility of the PBAT and the PLA is poor, the uniformity of the product is poor during blending processing, the compactness of the product is poor, and the product has the problems of micro pores or micro bubbles and the like.

Researchers mainly concentrate on the complex modification of PBAT and other macromolecules such as PLA and starch, but the synthetic modification of PBAT as a main polymer is only rarely concerned.

Disclosure of Invention

Aiming at the defects, the invention realizes the improvement of the molecular weight of the PBAT and the enhancement of the acting force between high molecular chains by a method for chain extension between the bio-based chain extender capable of providing multiple hydrogen bond interactions and the macromolecule PBAT, thereby preparing the degradable bio-based modified PBAT material with high strength and high toughness. The modified PBAT material can be obtained by a polymerization implementation method of melt copolymerization of hydroxyl or carboxyl end-capped PBAT prepolymer with the number average molecular weight of about 3000-30,000g/mol, and biobased diisocyanate (such as PDI) and a biobased small molecule chain extender. The obtained modified PBAT material has good mechanical strength (18-55 MPa) and enhanced fracture toughness>350MJ/m ³ ) The elongation at break can reach 800-1700%.

The technical scheme of the invention is as follows:

the first technical problem to be solved by the invention is to provide a modified PBAT material, wherein the raw materials of the modified PBAT material comprise PBAT, diisocyanate and a small molecule chain extender, and the modified PBAT material is prepared from the raw materials through melt copolymerization; wherein the small molecule chain extender is selected from the group consisting of: one of Pentylene Diamine (PDA), 5- (2-hydroxyethyl) -6-methyl-2-aminouracil (UPy), adipic Acid Dihydrazide (ADH), N-bis (2-hydroxyethyl) oxamide (BHO) or 1, 6-bis (hydroxyethoxycarbonylamino) hexane (BHH).

Further, the mass ratio of the raw materials is as follows: 80 to 96 parts by weight of PBAT, 3.0 to 8.0 parts by weight of diisocyanate and 1.6 to 12.0 parts by weight of small molecule chain extender. The molar feed ratio of PBAT diol (or diacid), diisocyanate (PDI) and small molecule chain extender is 1:2 to 2.5:1 to 1.5.

Further, the diisocyanate includes: pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane-4, 4' -diisocyanate

Preferably, the diisocyanate is a biobased diisocyanate. More preferably, the diisocyanate is Pentamethylene Diisocyanate (PDI).

Further, the PBAT is a hydroxyl or carboxyl terminated PBAT prepolymer having a number average molecular weight of 3000 to 20,000 g/mol.

Further, the PBAT is selected from the group consisting of:

further, the mechanical strength of the modified PBAT material is 18-55 MPa, and the elongation at break is 800-1700%.

The second technical problem to be solved by the invention is to provide a preparation method of the modified PBAT material, wherein the preparation method is selected from one of the following methods:

method one (two-step method (or prepolymerization method)): firstly, pre-polymerizing PBAT and diisocyanate for 0.5 to 1 hour at the temperature of 150 to 180 ℃ under the action of a catalyst; then adding a small molecular chain extender to perform chain extension reaction for 0.5-2 hours at 180-240 ℃ to prepare the modified PBAT material;

method two (one step): and (3) carrying out chain extension reaction on the PBAT, diisocyanate, a small molecule chain extender and a catalyst for 0.5-3 hours at 180-240 ℃ to obtain the modified PBAT material.

Further, in the above method, the PBAT is required to remove the residual water before use, for example, by vacuum-pumping at 100 ℃ for 0.5-2 hours.

Further, the above methodWherein the catalyst is selected from the group consisting of: stannous octoate (Sn (Oct) ₂ ) Or dibutyltin dilaurate (DBTDL), etc.

Further, in the above method, an organotin catalyst is used to accelerate the polymerization reaction, and DBTDL is exemplified in an amount of 0.5 to 1wt% based on the mass of the monomer PBAT.

The third technical problem to be solved by the invention is to provide a method for improving the molecular weight of PBAT prepolymer, which comprises the following steps: diisocyanate and a small molecule chain extender are introduced into a PBAT prepolymer, and modified PBAT is prepared through melt copolymerization; wherein the small molecule chain extender is selected from the group consisting of: one of Pentylene Diamine (PDA), 5- (2-hydroxyethyl) -6-methyl-2-aminouracil (UPy), adipic Acid Dihydrazide (ADH), N-bis (2-hydroxyethyl) oxamide (BHO) or 1, 6-bis (hydroxyethoxycarbonylamino) hexane (BHH).

Further, the mass ratio of the PBAT, the diisocyanate and the small molecule chain extender is as follows: 80 to 96 parts by weight of PBAT, 3.0 to 8.0 parts by weight of diisocyanate and 1.6 to 12.0 parts by weight of small molecule chain extender. The molar feed ratio of the PBAT diol (or diacid), the PDI and the small molecule chain extender is 1:2 to 2.5:1 to 1.5.

The fourth technical problem to be solved by the invention is to provide a method for improving the strength and toughness of PBAT through supermolecule interaction, which comprises the following steps: diisocyanate and a small molecule chain extender are introduced into a PBAT prepolymer, and modified PBAT is prepared through melt copolymerization; wherein the small molecule chain extender is selected from the group consisting of: one of Pentylene Diamine (PDA), 5- (2-hydroxyethyl) -6-methyl-2-aminouracil (UPy), adipic Acid Dihydrazide (ADH), N-bis (2-hydroxyethyl) oxamide (BHO) or 1, 6-bis (hydroxyethoxycarbonylamino) hexane (BHH).

The invention has the beneficial effects that:

1. the invention is based directly on low molecular weight PBAT capped with (or containing part of) a dihydroxy groupThe modified PBAT material can be prepared in a short reaction time by utilizing the full-biobased polyisocyanate and the small molecular chain extender to carry out chain extension reaction without solvent. Compared with the raw material PBAT, the obtained modified PBAT material has obviously increased molecular weight, enhanced mechanical strength and fracture toughness, and compared with commercial high molecular weight PBAT, the modified PBAT material also has obviously enhanced mechanical strength and fracture toughness; the tensile strength of the modified PBAT material can reach 52MPa, the elongation at break can reach 1601%, and the fracture toughness can reach 390MJ/m ³ 。

2. The modified reinforced and toughened PBAT material has high strength, high toughness and adjustable mechanical property, and the mechanical property of the modified PBAT material can be effectively regulated and controlled by changing the comonomer content and the compound use proportion of different types of chain extenders.

3. The modified reinforced toughened PBAT material has good remodelling processability, can be remolded for many times by hot pressing and the like, and has higher retention rate of material performance in a short period.

4. The modified reinforced toughened PBAT material has high biodegradability and biobased property, accords with the coping strategies of the problems of white pollution, fossil energy exhaustion and the like under the current background, and has sustainable development.

5. The modified reinforced and toughened PBAT material has adjustable high strength and high toughness, and has obvious application value in the fields of disposable packages, disposable tableware and the like, and controllable degradable structural parts/implants.

6. The preparation steps of the invention have simple operation process, easily obtained raw materials, all biological materials, no solvent in the reaction process, no worry about pollution and recovery of chemical reagents, good controllability and reproducibility, no complex chemical treatment process for modified reaction products, and suitability for large-scale industrial production.

Drawings

Fig. 1: the modified PBAT material is named as PBAT-Rx-S by a prepolymerization method (two-step method) chain extension reaction general formula.

Fig. 2: the modified PBAT material is named as PBAT-Rx-T by adopting a one-step chain extension reaction general formula.

Fig. 3: the stress-strain curves for PABT feedstock of examples 1-3, having a molecular weight of 7,200g/mol, are shown in FIG. 3, wherein PABT-1 corresponds to example 1, PABT-2 corresponds to example 2, and PABT-3 corresponds to example 3.

Fig. 4: the modified PBAT material obtained in example 1 (a) PBAT-Upy, (b) PBAT-BHO, and (c) PBAT-ADH material.

Fig. 5: thermal stability results of the PBAT-BHH material prepared in example 2.

Fig. 6: photographs of the PBAT-BHH-S1 material casting film samples prepared in example 2.

Fig. 7: example 2 PBAT-BHH-S prepared _x Stress-strain curves of thin film splines.

Fig. 8: the PBAT-BHH-T1 material prepared in example 3 was directly pulled out of the photographs after cooling the reaction flask (left panel), and the PBAT-BHH-T2 material precipitated the product photographs in methanol (right panel).

Fig. 9: photographs of films of the PBAT-BHH-T1 material prepared in example 3 and photographs of cut tensile bars.

Fig. 10: example 3 PBAT-BHH-T prepared _x Stress-strain curves of material thin film splines.

Detailed Description

According to the invention, one or more small molecules containing double hydroxyl groups or double amino groups are used as a modified chain extender, the improvement of the mechanical properties of the PBAT is realized through a chain extension reaction, the small molecule chain extender can introduce multiple hydrogen bond supermolecule interactions while increasing the molecular weight of the PBAT polymer, and the selected small molecule chain extender can introduce hydrogen bonds with different bonding strength and density, so that the interaction force among the large molecule chains of the PBAT is regulated and controlled; the intermolecular/intramolecular hydrogen bond, the PBAT crystal region and the soft and hard segment microphase separation structure bring the effects of strengthening and toughening to the modified PBAT material, and greatly improve the mechanical properties of the PBAT material, thereby realizing the strengthening and toughening of the PBAT material.

The modified PBAT material is prepared by melt copolymerization, so that the reinforcing and toughening of the PBAT material are realized, and the main raw materials used in the polymerization reaction are A, B, C components respectively; wherein the component A is as follows: a dihydroxyl or dicarboxyl terminated PBAT; the component B is as follows: diisocyanates (pentamethylene diisocyanate, hexamethylene diisocyanate \isophorone diisocyanate \diphenylmethane-4, 4' -diisocyanate), preferably the biobased diisocyanate Pentamethylene Diisocyanate (PDI); the component C is as follows: the bio-based small molecule chain extender can be selected from the following components: the five small molecule chain extenders from the biological group source can respectively introduce a free-combined double hydrogen bond, a strong dimerization tendency quadruple hydrogen bond, a free-combined six-fold hydrogen bond, a free-combined dense quadruple hydrogen bond and a free-combined loose quadruple hydrogen bond. In addition to the strong dimeric quadruple hydrogen bonds introduced by UPy, the number of other four multiple hydrogen bonds is based on the maximum number of hydrogen bonds which can be formed by one chain extender unit, and the main difference between the three is the number of methylene intervals (0-6 methylene) between units forming hydrogen bonds (amide bonds and/or urethane bonds and/or urea bonds). The difference of the above hydrogen bond supermolecular interactions mainly is that the PBAT modified polymer brings different hydrogen bond densities, different hydrogen bond bonding strengths and further brings different macromolecular chain interaction forces, thereby generating different mechanical properties. The chain extender employable in the invention has the structure shown below.

In addition, the invention can also prepare a series of PBAT modified materials with adjustable mechanical properties by changing the type of the bio-based small molecule chain extender and the hydrogen bond density, and can greatly expand the application field of PBAT. Meanwhile, the invention adopts the all-bio-based raw material as the chain extender to realize the strengthening and toughening of the PBAT material, ensures the bio-based source and the biodegradability of the PBAT material while improving the mechanical property, and is expected to prepare the high-performance degradable all-bio-based PBAT material.

The general formula of the two-step (or prepolymerization) chain extension reaction adopted by the invention is shown in figure 1. The general formula of the one-step chain extension reaction is shown in figure 2.

The following describes the invention in further detail with reference to examples, which are not intended to limit the invention thereto.

In the embodiment of the invention, PBAT is purchased from the company of Tong Cheng Xincai or Jinfa technology; ADH was purchased from Adamas; PDI was purchased from trigonal Stabio; the small molecule chain extender Upy, BHO and BHH are synthesized by oneself;

the small molecular chain extender in the embodiment of the invention is prepared by the following method:

the UPy is synthesized by the following method:

the synthetic raw materials are as follows: alpha-acetyl-gamma-butyrolactone, guanidine carbonate, triethylamine and ethanol; wherein ethanol is a reaction solvent, and the other three raw materials are fed with the following molar ratio of alpha-acetyl-gamma-butyrolactone: guanidine carbonate: triethylamine = 2:1:2.1.

the preparation method comprises the following steps: a predetermined amount of raw material (12.83 g of alpha-acetyl-gamma-butyrolactone, 9.01g of guanidine carbonate, 10.63g of triethylamine) was weighed into a 250ml three-necked flask, and 100ml of ethanol was added thereto and dissolved by stirring. And (3) performing condensation reflux reaction by adopting a spherical condensation tube, and reacting for 12 hours at 80 ℃. As the reaction proceeds, the solution system gradually turns yellow and appears as white turbidity.

Post-treatment: directly filtering, and then alternately washing the filter cake with ethanol and water for three times; adjusting pH to about 6.5 in water, stirring for 10min, recrystallizing in ethanol, filtering again, and vacuum drying at 45deg.C for 24 hr to obtain purified product UPy.

The BHO is synthesized by the following method:

the synthetic raw materials are as follows: diethyl oxalate, ethanolamine and ethanol; wherein ethanol is a reaction solvent, and the other two raw materials are added in a molar ratio of diethyl oxalate: ethanolamine = 1:3.

the specific operation is as follows: diethyl oxalate (14.51 g) was weighed into 100ml absolute ethanol (GR, 99.8%) in a three-necked flask; ethanolamine (18.32 g) is slowly dripped into the bottle under stirring, the solution becomes white gradually, the reaction is carried out for 24 hours at room temperature, the solid product is washed by absolute ethyl alcohol after suction filtration, and the solid product is dried in vacuum at 60 ℃ for 24 hours, so that white solid powder BHO is obtained.

The BHH is synthesized by the following method:

the synthetic raw materials are as follows: ethylene carbonate, 1, 6-hexamethylenediamine. The reaction solvent is not needed, and the feeding mole ratio of the two raw materials is that: 1.6-hexamethylenediamine = 2-2.1: 1.

the specific operation is as follows: weighing raw materials (18.49 g of ethylene carbonate and 11.62g of 1, 6-hexamethylenediamine) according to a preset amount, adding the raw materials into a round-bottomed flask, directly heating to 60 ℃, stirring for 1h till no bubble is generated, heating to 95 ℃, continuing to react for 3h, vacuumizing till no bubble is generated, adding DMF for dissolution, precipitating with ice dichloromethane/ice n-hexane, and vacuum drying at 60 ℃ for 24h after suction filtration to obtain a pure product BHH.

In the embodiment of the invention, the mechanical property test is performed by using a 119INSTRON universal material experiment machine; thermogravimetric analysis was tested using a 217 relaxation resistance thermogravimetric analyzer.

Example 1

The modified PBAT material is prepared by a two-step method (or a prepolymerization method) by using a dihydroxy-terminated PBAT, PDI and one of small molecule chain extenders Upy, BHO and ADH, and comprises the following steps:

(1) A quantity of a hydroxyl terminated PBAT diol having a molecular weight of 7,200g/mol was weighed into a branched round bottom flask and evacuated for 1h at 100℃to remove residual water.

(2) A predetermined amount of PDI (which may be 10% excess based on the stoichiometric ratio) and DBTDL were weighed into a flask and prepolymerized at 180 ℃ for 0.5h to give a prepolymer.

(3) A predetermined amount of small molecule chain extender Upy (or BHO, ADH) is weighed, added into a flask, and the reaction is continued for 0.5h at 180 ℃ to obtain modified PBAT materials which are respectively named as PBAT-Upy, PBAT-BHO and PBAT-ADH.

The raw material formulation of example 1 is shown in table 1.

Table 1 example 1 chain extension reaction formulation

In example 1, the molar ratio of the chain extender of component C to the PBAT raw material of component A is 1:1, the total molar ratio of component B to component A+C is 1:1, and the reaction time are controlled to prepare the PABT material with the molecular weight of 18-23 kg/mol. The molecular weight of the copolymer is increased 2-3 times compared to the PBAT feed.

The mechanical properties of the raw material PBAT and the lower fraction of PBAT material prepared in example 1 were characterized. As shown in FIG. 3, the tensile test shows that the tensile strength of the PABT material is only 8MPa, and the elongation at break is about 160%. The pull-up curves for the PBAT-Upy, PBAT-BHO, and PBAT-ADH materials are shown in FIG. 4 and Table 2. With Upy, the mechanical strength of the copolymer is continuously increased from the double hydrogen bond of BHO to the six-fold hydrogen bond of ADH, the breaking strength of the PBAT-ADH with the molecular weight of 2.5g/mol reaches 13.5MPa, and the breaking elongation reaches 550%. Compared with the raw materials, the mechanical strength and toughness are greatly improved.

TABLE 2 tensile Properties of PBAT raw materials and modified materials prepared in example 1

Example 2

Taking a dihydroxy-terminated PBAT, a PDI and a BHH chain extender as an example, the modified PBAT material is prepared by a two-step method (or a prepolymerization method), and the specific steps are as follows:

(3) Weighing a preset amount of micromolecular chain extender BHH, adding the mixture into a flask, and continuously reacting for 1 to 1.5 hours at the temperature of 180 to 220 ℃ to obtain a BHH modified PBAT material, which is named as PBAT-BHH-S _x 。

The raw material formulation of example 2 is shown in table 3.

TABLE 3 example 2 typical formulation for chain extension reaction

The PBAT-BHH material prepared in example 2 has a number average molecular weight of 28-35kg/mol, and the product appearance is white; has good thermal stability, and 5% thermal decomposition temperature is above 320 deg.C (figure 5); has good solubility, and can be used for hot-pressing film formation and solution casting film performance.

Example 2 PBAT-BHH-S prepared _x The material was solution cast to produce a film having a thickness of about 0.7mm (shown in FIG. 6). The same shape of film was also produced from PBAT starting material having a molecular weight of 7.2 kg/mol. We performed tensile tests on the films under the same conditions: the temperature is 25 ℃; the load is 50N; the pull-up speed was 50mm/min. As shown in FIG. 3, the tensile test shows that the tensile strength of the PABT material is only 8MPa, and the elongation at break is only about 160%. PBAT-BHH-S _x The stress-strain curves of the thin film spline are shown in fig. 7 and table 4, the tensile strength is about 19MPa, and the elongation at break is 1300%. Modified PBAT-BHH-S relative to PBAT feedstock _x The tensile strength of the sample was increased to 2.5 times and the elongation at break was increased to 8 times. The tensile strength of the PBAT material with the molecular weight of hundreds of thousands in the market at present is about 15MPa, and the elongation at break is about 800%. Therefore, the PBAT modified material prepared by the invention has the following strengthThe chemical properties of the PBAT material are superior to those of the existing PBAT material with high molecular weight.

TABLE 4 PBAT raw Material and PBAT-BHH-S prepared in example 2 _x Stretch line properties of materials

Example 3 one-step method

(1) The hydroxyl-terminated PBAT diol with a molecular weight of 7 and 200g/mol and the small molecular chain extender BHH were weighed in stoichiometric ratio in a branched round bottom flask and evacuated for 1h at 100℃to remove residual water.

(2) Weighing a preset amount of PDI (which can be 10% excessive on the basis of stoichiometric ratio) and DBTDL, adding into a shangshu flask, uniformly stirring, and reacting at 180-220 ℃ for 1-1.5 h to obtain BHH modified PBAT-BHH-T _x A material.

TABLE 5 example 3 typical formulation for chain extension reaction

The photograph of the PBAT-BHH-T1 material prepared in example 3 after being directly pulled out of a reaction flask and cooled is shown in the left side of FIG. 8, and the precipitated product of the PBAT-BHH-T2 material in methanol is shown in the right side of FIG. 8. Prepared PBAT-BHH-T _x The number average molecular weight of the material is 40-50kg/mol, and the appearance of the product is milky; has good thermal stability, and the 5% thermal decomposition temperature is above 320 ℃; can be dissolved in tetrahydrofuran, chloroform, etc., and can be hot pressed into film and solution cast film.

Example 3 PBAT-BHH- -T _x The material is prepared into a film with the thickness of about 0.7mm by a solution casting mode. A photograph of the film and a cut-out tensile bar are shown in fig. 9. The cast film sample has compact appearance, smooth surface and semitransparent state.

Example 3 PBAT-BHH-T prepared _x The tensile test of the material film sample strip proves that the tensile strength is about 50MPa, the elongation at break is about 1500 percent (fig. 10 and figShown in table 6). Compared with the mechanical property of PBAT raw material, PBAT-BHH-T _x The mechanical strength of the material is improved by 5 times, and the elongation at break is improved by 10 times. Compared with the current pure PBAT material with high molecular weight on the market, the tensile strength is improved by nearly 3 times, and the breaking elongation is improved by nearly 2 times.

TABLE 6 PBAT-BHH-T prepared in example 3 _x Stretch line properties of materials

In conclusion, the invention can effectively improve the molecular weight of the PBAT prepolymer and greatly improve the mechanical strength and toughness of the PBAT material by carrying out chain extension modification on the PBAT by the bio-based chain extender capable of introducing hydrogen bond supermolecule interaction. The effective and controllable regulation and control of the mechanical properties can be realized by changing the content of the chain extender and the copolymerization method.

Claims

1. The modified PBAT material is characterized in that the raw materials of the modified PBAT material comprise PBAT, diisocyanate and a small molecule chain extender, and the modified PBAT material is prepared from the raw materials through melt copolymerization; wherein the small molecule chain extender is selected from the group consisting of: one of pentyenediamine, 5- (2-hydroxyethyl) -6-methyl-2-aminouracil, adipic acid dihydrazide, N-bis (2-hydroxyethyl) oxamide or 1, 6-bis (hydroxyethoxycarbonylamino) hexane.

2. The modified PBAT material of claim 1, wherein the mass ratio of the raw materials is: 80 to 96 parts by weight of PBAT, 3.0 to 8.0 parts by weight of diisocyanate and 1.6 to 12.0 parts by weight of small molecule chain extender.

3. A modified PBAT material according to claim 1 or 2, characterised in that the diisocyanate comprises: pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate or diphenylmethane-4, 4' -diisocyanate.

4. A modified PBAT material as claimed in claim 3, wherein the diisocyanate is pentamethylene diisocyanate.

5. The modified PBAT material of any of claims 1 to 4, wherein the PBAT is a hydroxyl or carboxyl terminated PBAT having a number average molecular weight of 3000 to 20,000 g/mol.

6. The modified PBAT material of claim 5, wherein the PBAT is selected from the group consisting of:

7. the method of preparing a modified PBAT material according to any one of claims 1 to 6, wherein the preparation method is selected from one of the following methods:

the method comprises the following steps: firstly, pre-polymerizing PBAT and diisocyanate for 0.5 to 1 hour at the temperature of 150 to 180 ℃ under the action of a catalyst; then adding a small molecular chain extender to perform chain extension reaction for 0.5-2 hours at 180-240 ℃ to prepare the modified PBAT material;

the second method is as follows: and (3) carrying out chain extension reaction on the PBAT, diisocyanate, a small molecule chain extender and a catalyst for 0.5-3 hours at 180-240 ℃ to obtain the modified PBAT material.

8. The method of preparing a modified PBAT material of claim 7, wherein the catalyst is selected from the group consisting of: stannous octoate or dibutyltin dilaurate;

further, the catalyst is used in an amount of 0.5 to 1wt% based on the mass of PBAT.

9. A method for increasing the molecular weight of a PBAT prepolymer, said method comprising: diisocyanate and a small molecule chain extender are introduced into a PBAT prepolymer, and modified PBAT is prepared through melt copolymerization; wherein the small molecule chain extender is selected from the group consisting of: one of pentyenediamine, 5- (2-hydroxyethyl) -6-methyl-2-aminouracil, adipic acid dihydrazide, N-bis (2-hydroxyethyl) oxamide or 1, 6-bis (hydroxyethoxycarbonylamino) hexane;

further, the mass ratio of the PBAT, the diisocyanate and the small molecule chain extender is as follows: 80 to 96 parts by weight of PBAT, 3.0 to 8.0 parts by weight of diisocyanate and 1.6 to 12.0 parts by weight of small molecule chain extender.

10. A method for improving the mechanical strength and toughness of PBAT by supramolecular interactions, the method comprising: diisocyanate and a small molecule chain extender are introduced into a PBAT prepolymer, and modified PBAT is prepared through melt copolymerization; wherein the small molecule chain extender is selected from the group consisting of: one of pentyenediamine, 5- (2-hydroxyethyl) -6-methyl-2-aminouracil, adipic acid dihydrazide, N-bis (2-hydroxyethyl) oxamide or 1, 6-bis (hydroxyethoxycarbonylamino) hexane;