A biodegradable thermally stable composite polyester material and its preparation method

Abstract

The present invention discloses a biodegradable thermally stable composite polyester material and a preparation method thereof, belonging to the field of materials science. In the present invention, glycidyl methacrylate and 2-methylene-1,3-dioxolane are polymerized in a solvent to obtain a special chain extender for biodegradable polyester. Based on this biodegradable, highly thermally stable, good compatibilizing effect, and simple preparation process of the degradable reactive compatibilizer, a polyester material with improved tensile strength and elongation at break is prepared. The graft reaction reduces the melt flow rate and has better thermal stability.

Description

Technical Field

[0001] The present invention relates to a biodegradable thermally stable composite polyester material and a preparation method thereof, belonging to the field of materials science. Background Art

[0002] Polyester materials are widely used in fields such as automobiles, electronic appliances, medical and health, construction, and automobiles. In recent years, the application fields of high-viscosity polyester materials have been continuously expanding, and the demand for polyester films and engineering plastics has been increasing rapidly. In addition, the amount of polyester waste is also increasing. Since pyrolysis and hydrolysis will cause the relative molecular mass of recycled polyester to decrease and the mechanical properties cannot meet the requirements of plastic products, how to improve the relative molecular mass and viscosity of polyester has received more and more attention.

[0003] Adding a chain extender during the melting process can achieve the effect of rapid and efficient viscosity increase. For example, patent CN113185820A discloses a degradable packaging material, in which ADR is used as a chain extender, and poly(lactic acid) PLA, poly(butylene adipate-co-terephthalate) PBAT, and poly(butylene succinate) PBS films with high transparency and excellent mechanical properties are successfully prepared. However, the ADR chain extender has poor thermal stability and is non-degradable, which has been widely criticized in the aspect of being used for biodegradable polyester materials. In addition, the amount of polyester waste is also increasing. Since pyrolysis and hydrolysis will cause the relative molecular mass of recycled polyester to decrease and the mechanical properties cannot meet the requirements of plastic products. Therefore, how to improve the mechanical properties and thermal stability of polyester is an urgent problem to be solved. Summary of the Invention

[0004] Aiming at the above problems existing in the prior art, the present invention provides a method for preparing a biodegradable thermally stable composite polyester material based on a biodegradable and thermally stable chain extender.

[0005] The present invention provides a preparation method of a biodegradable thermally stable composite polyester material, which is to mix polyester and a chain extender evenly, and then add them into a screw extruder or a mixer for melt blending; the chain extender is formed by copolymerizing a bio-based monomer 2-methylene-1,3-dioxolane (MDO) and glycidyl methacrylate (GMA).

[0006] In one embodiment of the present invention, the polyester is at least one of polyglycolic acid (PGA), polyhydroxyalkanoate (PHA), poly(lactic acid) (PLA), PLGA, polycaprolactone (PCL), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly(butylene adipate-co-terephthalate) (PBAT), poly(propylene carbonate) (PPC), and poly(butylene succinate) (PBS).

[0007] In one embodiment of the present invention, the mass ratio of the polyester to the chain extender is 100:(0.25 - 3); specifically, it can be optionally 100:0.5 - 1.

[0008] In one embodiment of the present invention, the temperature of the melt blending is 1°C - 30°C above the melting point.

[0009] In one embodiment of the present invention, the preparation method of the chain extender includes:

[0010] Add GMA and MDO to an organic solvent to dissolve and obtain a homogeneous solution; then add a radical initiator to the homogeneous solution for polymerization reaction. After the reaction ends, dilute and wash to obtain a special chain extender (GM) for biodegradable polyester.

[0011] In one embodiment of the present invention, the content of MDO is 25% - 75% of the total mass of GMA and MDO. Specifically, it can be optionally 25%, 50%, 75%.

[0012] In one embodiment of the present invention, the organic solvent is toluene.

[0013] In one embodiment of the present invention, the dosage of the organic solvent in the homogeneous solution relative to the total mass of GMA and MDO is 1 - 3 mL / g. Specifically, it can be optionally 1.5 mL / g.

[0014] In one embodiment of the present invention, the radical initiator is at least one of azobisisobutyronitrile, azobisisoheptonitrile, and benzoyl peroxide.

[0015] In one embodiment of the present invention, the dosage of the radical initiator is 0.5% - 3% of the total mass of GMA and MDO. Specifically, it can be optionally 1%, 1.5%.

[0016] In one embodiment of the present invention, the temperature of the polymerization reaction is 60°C - 80°C; the time is 3 h - 12 h.

[0017] In one embodiment of the present invention, after the reaction ends, dilute with chloroform or acetone.

[0018] In one embodiment of the present invention, wash with absolute ethanol or ethyl acetate after dilution.

[0019] In one embodiment of the present invention, the structure of the special chain extender (GM) for biodegradable polyester is shown as follows:

[0020]

[0021] Among them, the weight - average molecular weight of the chain extender is 5000 - 40000, and the mass content of the epoxy group is 11% - 25%.

[0022] The present invention provides a biodegradable and thermally stable composite polyester material prepared based on the above method.

[0023] The present invention also provides the application of the above biodegradable and thermally stable composite polyester material in the fields of packaging preparation for food, daily necessities, building materials, chemical engineering and medicine.

[0024] Beneficial effects of the present invention:

[0025] The chain extender obtained in the present invention is completely biodegradable, has high thermal stability, good chain extension effect, simple preparation process, is environmentally friendly, and is easy to realize industrial production. The biodegradable chain extender of the present invention has degradability due to the MDO structure, and the GMA structure provides reactive groups that can react with the polyester to achieve a chain extension effect.

[0026] Based on a biodegradable reactive compatibilizer with complete biodegradability, high thermal stability, good compatibilization effect and simple preparation process, the present invention prepares a polyester material with improved tensile strength and elongation at break, and the grafting reaction reduces the melt flow rate and has better thermal stability. Description of the drawings

[0027] Figure 1 It is the thermogravimetric curve of Example 1 and Example 2. Detailed implementation manners

[0028] The embodiments disclosed herein are examples of the present invention, which can be embodied in different forms. Therefore, the detailed content of the disclosure including specific structures and functional details is not intended to limit the present invention, but is only used as the basis for the claims. It should be understood that the detailed description of the present invention is not for limitation but for covering all possible modifications, equivalents and substitutions falling within the scope of the present invention as defined by the appended claims. Throughout this application, the word "may" is used in a permissive sense rather than a mandatory sense. Similarly, unless otherwise specified, the words "comprise", "include" and "consist of" mean "including but not limited to". The word "a" or "an" means "at least one", and the word "plural" means more than one. When using abbreviations or technical terms, these terms represent the generally accepted meanings known in the technical field.

[0029] Example 1:

[0030] Preparation of a special chain extender for biodegradable polyester:

[0031] 15 g of glycidyl methacrylate (GMA) and 5 g of the bio-based monomer 2-methylene-1,3-dioxolane (MDO) were added to 30 mL of toluene solvent for dissolution. Then, 0.3 g of a radical initiator was added to this homogeneous solution, and a polymerization reaction was carried out at 65 °C for 5 h. After the reaction, acetone solvent was added for dilution, and it was poured into anhydrous ethanol solvent for thorough washing to obtain a chain extender (GM-1) specific for biodegradable polyester. The molar content of MDO was approximately 25%.

[0032] Example 2:

[0033] 10 g of glycidyl methacrylate (GMA) and 10 g of the bio-based monomer 2-methylene-1,3-dioxolane (MDO) were added to 30 mL of toluene solvent for dissolution. Then, 0.3 g of a radical initiator was added to this homogeneous solution, and a polymerization reaction was carried out at 65 °C for 5 h. After the reaction, acetone solvent was added for dilution, and it was poured into anhydrous ethanol solvent for thorough washing to obtain a chain extender (GM-2) specific for biodegradable polyester. The molar content of MDO was approximately 50%.

[0034] Example 3:

[0035] 5 g of glycidyl methacrylate (GMA) and 15 g of the bio-based monomer 2-methylene-1,3-dioxolane (MDO) were added to 30 mL of toluene solvent for dissolution. Then, 0.3 g of a radical initiator was added to this homogeneous solution, and a polymerization reaction was carried out at 65 °C for 5 h. After the reaction, acetone solvent was added for dilution, and it was poured into anhydrous ethanol solvent for thorough washing to obtain a chain extender (GM-3) specific for biodegradable polyester. The molar content of MDO was approximately 75%.

[0036] Example 4:

[0037] 15 g of glycidyl methacrylate (GMA) and 5 g of the bio-based monomer 2-methylene-1,3-dioxolane (MDO) were added to 30 mL of toluene solvent for dissolution. Then, 0.2 g of a radical initiator was added to this homogeneous solution, and a polymerization reaction was carried out at 65 °C for 12 h. After the reaction, acetone solvent was added for dilution, and it was poured into anhydrous ethanol solvent for thorough washing to obtain a chain extender (GM-4) specific for biodegradable polyester. The molar content of MDO was approximately 25%.

[0038] Example 5:

[0039] 15 g of glycidyl methacrylate (GMA) and 5 g of bio-based monomer 2-methylene-1,3-dioxolane (MDO) were added to 30 mL of toluene solvent for dissolution. Then, 0.2 g of free radical initiator was added to this homogeneous solution, and a polymerization reaction was carried out at 60 °C for 3 h. After the reaction, acetone solvent was added for dilution, and it was poured into anhydrous ethanol solvent for thorough washing to obtain a special chain extender (GM-5) for biodegradable polyester. The molar content of MDO was about 25%.

[0040] Comparative Example 1:

[0041] Commercial polyfunctional epoxy chain extender ADR.

[0042] Comparative Example 2

[0043] Poly(glycidyl methacrylate) PGMA.

[0044] In order to investigate the thermal stability and degradability of the special chain extender for biodegradable polyester prepared by the method of the present invention, the samples obtained in Examples 1-5 and Comparative Example 1 and Comparative Example 2 were tested, and the results are shown in Table 1. The specific measurement methods are as follows:

[0045] The thermal decomposition temperature of the sample was tested by a thermogravimetric analyzer (TGA / DSC / 1100SF). About 10 mg of the sample was weighed and placed in a crucible, and it was heated from 40 °C to 600 °C at a heating rate of 10 °C / min under a nitrogen atmosphere, and the nitrogen flow rate was 50 mL / min.

[0046] According to the national standard GB / T 41010-2021, a soil burial experiment was carried out: the sample was buried in a container with a natural clay environment, the burial depth was 10 cm, and it was placed in an incubator at 37 °C, and it was taken out of the bottle after a certain time. After taking out, it was rinsed with deionized water and weighed after drying.

[0047] Table 1

[0048] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Weight-average molecular weight 5700 5300 5500 210000 10000 6800 7500 Thermal decomposition temperature (°C) 354±2 361±1 370±1 355±3 356±2 235±15 190±10 Degradation performance Yes Yes Yes Yes Yes No No

[0049] It can be seen from Table 1 that the special chain extender for biodegradable polyester prepared has the following advantages: ① high thermal decomposition temperature; ② biodegradable.

[0050] Application test of the above chain extender in the preparation of polyester materials:

[0051] Example 6:

[0052] 0.5 part by mass of the special chain extender for biodegradable polyester (GM-1) and 100 parts of polyglycolic acid (PGA) were mixed evenly and then added to a mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature was 250 °C.

[0053] Example 7:

[0054] Mix 1 part by mass of the special chain extender for biodegradable polyester (GM-1) and 100 parts of PGA evenly, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 250 °C.

[0055] Example 8:

[0056] Mix 1 part by mass of the special chain extender for biodegradable polyester (GM-2) and 100 parts of PGA evenly, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 250 °C.

[0057] Example 9:

[0058] Mix 1 part by mass of the special chain extender for biodegradable polyester (GM-3) and 100 parts of PGA evenly, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 250 °C.

[0059] Example 10:

[0060] Mix 1 part by mass of the special chain extender for biodegradable polyester (GM-1) and 100 parts of PLA evenly, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 190 °C.

[0061] Example 11:

[0062] Mix 1 part by mass of the special chain extender for biodegradable polyester (GM-1) and 100 parts of polyethylene terephthalate (PET) evenly, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 260 °C.

[0063] Example 12:

[0064] Mix 1 part by mass of the special chain extender for biodegradable polyester (GM-4) and 100 parts of polyglycolic acid (PGA) evenly, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 250 °C.

[0065] Comparative Example 3:

[0066] Compared with Example 6, the special chain extender for biodegradable polyester (GM-1) is not added. Specifically, add 100 parts of PGA to an internal mixer for melt blending for 6 min to obtain a polyester material. The melt blending temperature is 250 °C.

[0067] Comparative Example 4:

[0068] Compared with Example 7, the biodegradable polyester-specific chain extender (GM-1) was replaced with a non-biodegradable polyepoxy chain extender (ADR) as follows:

[0069] Mix 1 part by mass of the polyepoxy chain extender (ADR) and 100 parts of PGA, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 250 °C.

[0070] Comparative Example 5:

[0071] Compared with Example 7, the biodegradable polyester-specific chain extender (GM-1) was replaced with non-biodegradable glycidyl methacrylate (PGMA) as follows:

[0072] Mix 1 part by mass of glycidyl methacrylate (PGMA) and 100 parts of PGA, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 250 °C.

[0073] Comparative Example 6:

[0074] Compared with Example 7, the biodegradable polyester-specific chain extender (GM-1) was replaced with poly(2-methylene-1,3-dioxolane) (PMDO) as follows:

[0075] Mix 1 part by mass of poly(2-methylene-1,3-dioxolane) (PMDO) and 100 parts of PGA, and then add them to an internal mixer for melt blending for 6 min to obtain a polyester material. The melt blending temperature is 250 °C.

[0076] Comparative Example 7:

[0077] Compared with Example 10, the biodegradable polyester-specific chain extender (GM-1) was not added as follows: Add 100 parts of PLA to an internal mixer for melt blending for 6 min to obtain a polyester material. The melt blending temperature is 190 °C.

[0078] Comparative Example 8:

[0079] Compared with Example 11, the biodegradable polyester-specific chain extender (GM-1) was replaced with a polyepoxy chain extender (ADR) as follows:

[0080] Mix 1 part by mass of the polyepoxy chain extender (ADR) and 100 parts of PET, and then add them to an internal mixer for melt blending for 6 min to obtain a chain-extended polyester material. The melt blending temperature is 260 °C.

[0081] The polyesters obtained in Examples 6-12 and Comparative Examples 2-8 were tested for tensile strength and elongation at break using a universal testing machine according to GB / T 1040.1-2018, with a tensile rate of 10 mm / min. The melt flow rate was measured using a melt flow rate tester, and the melt flow rate was measured under the processing temperature in the example or comparative example and under the condition of 2.16 kg, that is, the melt index was obtained (the smaller the melt index, the better the thermal stability). The sample was dissolved in hexafluoroisopropanol, and after a period of time, the insoluble matter was taken out, rinsed with deionized water, and weighed after drying. The ratio of the mass of the insoluble matter to the initial mass of the sample was the gel content.

[0082] The tensile strength, elongation at break, melt index, and gel content of each tested example are shown in Table 2, and the tensile strength, elongation at break, and melt index of each comparative example are shown in Table 3.

[0083] Table 2

[0084]

[0085] Table 3

[0086]

[0087] It can be seen from Examples 6-9 and Comparative Example 3 that different biodegradable polyester special chain extenders all have good chain extension effects, and the tensile strength and elongation at break of PGA increase significantly, while the melt index decreases.

[0088] It can be seen from Example 10 and Comparative Example 7 that different biodegradable polyester special chain extenders also have good chain extension effects on PLA.

[0089] It can be seen from Example 7 and Comparative Examples 4-5 that the biodegradable polyester special chain extender GM-1 has a better chain extension effect in PGA than ADR and PGMA, and has unique biodegradability.

[0090] It can be seen from Example 7 and Comparative Example 6 that the presence of the GMA structure in the biodegradable polyester special chain extender GM-1 plays a role in chain extension, and this monomer is indispensable in the reaction process.

[0091] It can be seen from Examples 7-9, 11 and Comparative Examples 4 and 8 that under the same processing conditions, ADR is not suitable for PGA and PET materials due to degradation, and the biodegradable polyester special chain extender GM-1 has higher thermal stability and can increase the scope of use in polyesters.

[0092] The above embodiments confirm that the present invention can obtain a chain extender with excellent thermal stability and biodegradability. The chain extender provided by the present invention can be effectively applied to polyester materials and can be directly used in processing methods such as molding, blow molding, casting, calendering, and biaxial stretching.

[0093] Those of ordinary skill in the art should understand that the discussion of any above embodiment is only exemplary and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a biodegradable heat-stable composite polyester material, characterized in that, the polyester and a chain extender are mixed evenly, and then added into a screw extruder or an internal mixer for melt blending; the chain extender is formed by copolymerizing the bio-based monomer 2-methylene-1,3-dioxolane and glycidyl methacrylate; the content of 2-methylene-1,3-dioxolane is 25%-75% of the total mass of glycidyl methacrylate and 2-methylene-1,3-dioxolane; the structure of the chain extender is shown as follows: ， wherein, the weight-average molecular weight of the chain extender is 5000-40000, and the mass content of the epoxy group is 11%-25%.

2. The method according to claim 1, characterized in that, the polyester is at least one of polyglycolic acid, polyhydroxyalkanoate, polylactic acid, PLGA, polycaprolactone, polyethylene terephthalate, polybutylene terephthalate, polybutylene adipate / terephthalate, poly(trimethylene carbonate), polybutylene succinate.

3. The method according to claim 1, characterized in that, the mass ratio of the polyester to the chain extender is 100:(0.25-3).

4. The method according to claim 1, characterized in that, the preparation method of the chain extender includes: adding glycidyl methacrylate and 2-methylene-1,3-dioxolane into an organic solvent to dissolve, obtaining a homogeneous solution; then adding a radical initiator into the homogeneous solution for polymerization reaction, and after the reaction is completed, diluting and washing to obtain a biodegradable polyester special chain extender, denoted as GM.

5. The method according to claim 4, characterized in that, the dosage of the organic solvent in the homogeneous solution relative to the total mass of glycidyl methacrylate and 2-methylene-1,3-dioxolane is 1-3 mL / g.

6. The method according to claim 4, characterized in that, the temperature of the polymerization reaction is 60°C-80°C; the time is 3h-12h.

7. A biodegradable heat-stable composite polyester material prepared by the method according to any one of claims 1-6.

8. The application of the biodegradable heat-stable composite polyester material according to claim 7 in the field of the preparation of packaging for food, daily necessities, building materials, chemical engineering and medicine.

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