Modified polyethylene furandicarboxylate material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a modified polyethylene furandicarboxylate material as well as a preparation method and application thereof. The modified polyethylene furandicarboxylate material comprises a PEF main chain and fused ring end groups chemically grafted to the end part of the PEF main chain, and the fused ring end groups are stacked through pi-pi, so that a three-dimensional physical cross-linked network node is formed. According to the invention, through combination of a terminal functionalization strategy and a pi-pi stacking effect and a three-dimensional physical cross-linked network, synergistic enhancement of tensile strength and elongation at break of the polyester material is successfully realized, and excellent processability and oxygen barrier property are maintained at the same time. In a preferable scheme, the impact toughness of the material can be improved by 120-180% at most, meanwhile, the crystallization rate is improved by 3-5 times through a plasticizing effect, and the oxygen barrier property retention rate is 7 times or above that of PEF. The problems of narrow processing temperature window and poor melt strength of bio-based polyester PEF are effectively solved, and a new way is provided for developing high-performance sustainable packaging materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a modified polyethylene furandicarboxylate material, a preparation method thereof, and an application thereof. Background Art

[0002] As a bio-based polyester, polyethylene furandicarboxylate (PEF) is considered to be an excellent alternative or even upgraded product to traditional polyethylene terephthalate (PET) due to its excellent oxygen and carbon dioxide barrier properties, and has broad application prospects particularly in the fields of food packaging and beverage bottles. However, PEF faces two key challenges in practical applications: one is its poor toughness, resulting in brittle fracture of the material when subjected to impact; the other is its slow crystallization rate, which affects its processing efficiency and product performance. These defects limit the wide application of PEF in high-performance packaging materials.

[0003] To overcome these deficiencies, researchers have attempted to functionalize and improve PEF through strategies such as copolymerization, blending, and end-group modification. Among them, end-group modification of polyesters is an effective strategy, which can endow the material with new properties by introducing specific functional groups without changing the main-chain structure. The end-group modification method based on polycondensation reaction conforms to the step-growth polymerization principle and has been proven to improve the hydrophilicity, solubility, flexibility, and anti-aging properties of polyesters through carefully designed end groups. For example, a modified polyethylene furandicarboxylate, its preparation method, and application disclosed in Patent CN 112961472 A use polybutylene succinate (PBS) with excellent thermal stability as a toughening component to improve the toughness of PEF. However, excessive addition of PBS in this technical solution will cause a serious decline in the strength and rigidity of PEF, thus seriously affecting the improvement of PEF by PBS, and the prepared PEF needs to be improved in terms of both toughness and barrier properties. Therefore, there is a need to further optimize the strategy based on the end-group modification strategy. Summary of the Invention

[0004] The present invention aims to overcome the defects of poor toughness, barrier properties, and difficult processing of PEF in the prior art, and provides a modified polyethylene furandicarboxylate material, a preparation method thereof, and an application thereof to overcome the above defects.

[0005] To achieve the above invention object, the present invention adopts the following technical solutions: A modified polyethylene furandicarboxylate material, comprising a PEF main chain and polycyclic end groups chemically grafted to the ends of the PEF main chain, and the polycyclic end groups form three-dimensional physical crosslinking network nodes through π-π stacking.

[0006] During the processing of polyester materials, plasticization strategies are usually used to improve the processability, flexibility, and ductility of the materials. However, traditional small molecule plasticizers have problems such as surface migration, spillage, and embrittlement, which limit their safety in practical applications. Therefore, the present invention focuses on the end-group modification strategy. By copolymerizing large steric hindrance groups to the tail of polymer molecules, the processability of the materials can be significantly improved without sacrificing the mechanical properties of the materials. The present invention modifies the end groups of PEF and grafts polycyclic end groups at the ends of PEF, so as to form a three-dimensional physical crosslinking network at the PEF chain ends by using intermolecular π-π stacking interactions. π-π stacking is mainly formed by the overlap of aromatic conjugate orbitals in a side-by-side mode, which can introduce physical crosslinking and thus enhance the strength of the material. The polycyclic end groups grafted at the ends of PEF in the present invention have a conjugated large π-electron system, which forms strong π-π interactions with the polar structure of the furan ring in the PEF main chain. This force can form dynamic crosslinking points at the molecular chain ends, significantly improving the tensile strength and toughness of PEF. At the same time, the planar rigidity of the polycyclic structure can optimize the molecular arrangement, increase the π-π stacking area, and thus improve the stability of the crosslinking network.

[0008] The three-dimensional physical crosslinking network formed by the present invention has the following advantages: First, the crosslinking network can enhance the interaction between PEF chains, thereby further improving the toughness and strength of PEF; Second, the crystallization rate can be significantly increased through the plasticization effect, improving the tensile crystallization performance of PEF and facilitating processing; Finally, the three-dimensional crosslinking network forms a continuous and dense nanoporous structure through π-π stacking. This dense structure effectively extends the oxygen diffusion path and reduces the permeability. At the same time, the acceleration of the crystallization rate is conducive to the full utilization of the barrier properties of PEF.

[0009] Preferably, the polycyclic end groups include any one of naphthyl, anthryl, and phenanthryl.

[0010] The present invention also discloses a preparation method of a modified polyethylene furandicarboxylate material, which includes the following steps: After blending PEF, a polycyclic end-group modifier, and an antioxidant, melting them in a reactive injection molding screw to obtain a melt, and then extruding to obtain the modified polyethylene furandicarboxylate material. By adding an antioxidant during the preparation process, the oxidation side reaction can be inhibited, avoiding the failure of π-π stacking due to the destruction of the chemical structure, and ensuring the long-term stability of the crosslinking network.

[0011] Preferably, the polycyclic ring end-group modifier is one or more of 1-naphthoic acid, 9-anthracene carboxylic acid, 2-phenanthrene carboxylic acid, and 9-phenanthrene boronic acid. The above polycyclic ring end-group modifier contains a carboxyl group or a boronic acid group. As a strong polar group, the carboxyl group can form a stable interaction with polar groups (such as hydroxyl groups and amino groups) in the polymer main chain through hydrogen bonds or ionic bonds. At the same time, the terminal carboxyl group can improve the hydrophilicity of the polyester, promote the dense arrangement between molecular chains, thereby optimizing the barrier performance. Moreover, the chemical reactivity of the carboxyl group can further form chemical cross-linking with other components to strengthen the network structure.

[0012] More preferably, the addition amount of the polycyclic ring end-group modifier is 0.1-10% of the mass of PEF, preferably 0.5-1%.

[0013] More preferably, the antioxidant includes one or more of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and dilauryl thiodipropionate.

[0014] More preferably, the addition amount of the antioxidant is 100-500 ppm.

[0015] More preferably, the viscosity of the PEF > 0.65 dl / g. It has been found through experiments in the present invention that the viscosity of the PEF raw material has a certain influence on the properties of the modified material. The high molecular weight characteristics of the PEF with a higher viscosity can provide a pre-existing chain entanglement network, which synergistically enhances the material strength with the end-group π-π stacking. At the same time, an antioxidant also needs to be added to the PEF to inhibit the oxidation side reaction, avoid the failure of the π-π stacking due to chemical structure damage, and ensure the long-term stability of the cross-linked network.

[0016] More preferably, the melting time is 5-30 min, and the melting temperature is 200-260 °C. The melting temperature is preferably 210-245 °C, and the melting time is preferably 10-30 min.

[0017] The present invention also discloses the application of the above-mentioned modified polyethylene furandicarboxylate material in product packaging.

[0018] Therefore, the present invention has the following beneficial effects: (1) By combining the terminal functionalization strategy and the π-π stacking effect, the present invention successfully realizes the synergistic enhancement of the tensile strength and elongation at break of the polyester material, while maintaining excellent processing performance and oxygen barrier performance. (2) The introduction of the polycyclic ring end-group modifier in the present invention not only solves the problems of poor melt strength, poor toughness, and difficult processing of the bio-based polyester PEF, but also provides a new way for the development of high-performance sustainable packaging materials. (3) The end - group modifier used in the present invention has a simple structure, is cheap and easily available, and the modification and processing preparation methods are simple. It can realize the synchronous series connection of modification and processing on existing instrument devices, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1H - NMR spectra of the modified poly(ethylene furandicarboxylate) materials obtained in Examples 5 - 8 of the present invention and Comparative Example 1.

[0020] Figure 2 Infrared characteristic spectra of the modified poly(ethylene furandicarboxylate) materials obtained in Examples 5 - 8 of the present invention and Comparative Example 1.

[0020] Figure 3 XRD curves and crystallinity change diagrams of the modified poly(ethylene furandicarboxylate) materials obtained in the examples of the present invention and Comparative Example 1.

[0021] Figure 4 Isothermal crystallization curves of the modified poly(ethylene furandicarboxylate) materials obtained in the examples of the present invention and Comparative Example 1.

[0022] Figure 5 Thermal stability characterization diagrams of the modified poly(ethylene furandicarboxylate) materials obtained in the examples of the present invention.

[0023] Figure 6 Graph of the change of the glass transition temperature of the modified poly(ethylene furandicarboxylate) materials obtained in the examples of the present invention with the content of the end - group modifier.

[0024] Figure 7 Tensile property characterization diagrams of the modified poly(ethylene furandicarboxylate) materials obtained in the examples and Comparative Example 1.

[0024] Figure 8 Flexural curve characterization diagrams of the modified poly(ethylene furandicarboxylate) materials obtained in the examples and Comparative Example 1.

[0025] Figure 9 Flexural test pictures of the modified poly(ethylene furandicarboxylate) materials obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0024] The technical solution of the present invention will be further clearly and completely described below through specific embodiments in conjunction with the accompanying drawings. It should be noted that the described embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but they are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. The experimental methods used in the following embodiments are all conventional methods unless otherwise specified, and the materials, reagents, etc. used in the embodiments can be obtained from commercial channels unless otherwise specified.

[0025] Example 1 Mix PEF with a viscosity of 0.65 dl / g and naphthoic acid in a mass ratio of 99.5:0.5, and then add 200 ppm of pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (antioxidant 1010). Pre-mix for 20 minutes at room temperature and a rotation speed of 100 rpm; perform melt blending and extrusion in a reactive twin-screw extruder at a temperature of 210 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a end-group modified PEF polyester material and product, denoted as PEFN 0.5 。

[0026] Example 2 Mix PEF with a viscosity of 0.65 dl / g and naphthoic acid in a mass ratio of 99:1, and then add 200 ppm of antioxidant 1010. Pre-mix for 25 minutes at room temperature and a rotation speed of 100 rpm; perform melt blending and extrusion in a reactive twin-screw extruder at a temperature of 210 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a end-group modified PEF polyester material and product, denoted as PEFN1.

[0027] Example 3 Mix PEF with a viscosity of 0.65 dl / g and naphthoic acid in a mass ratio of 98:1.5, and then add 200 ppm of antioxidant 1010. Pre-mix for 25 minutes at room temperature and a rotation speed of 100 rpm; perform melt blending and extrusion in a reactive twin-screw extruder at a temperature of 210 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a end-group modified PEF polyester material and product, denoted as PEFN 1.5 。

[0028] Example 4 Mix PEF with a viscosity of 0.7 dl / g and naphthoic acid in a mass ratio of 95:2, then add 200 ppm of antioxidant 1010, and premix for 30 minutes at room temperature with a rotation speed of 100 rpm; conduct melt blending and extrusion in a reactive twin-screw extruder at a temperature of 210 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a end-group modified PEF polyester material and product, denoted as PEFN2.

[0029] Example 5 Mix PEF with a viscosity of 0.75 dl / g and phenanthreneboronic acid in a mass ratio of 99.5:0.5, then add 200 ppm of antioxidant 1010, and premix for 15 minutes at room temperature with a rotation speed of 100 rpm; conduct melt blending and extrusion in a reactive twin-screw extruder at a temperature of 230 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a end-group modified PEF polyester material and product, denoted as PEFB 0.5 。

[0030] Example 6 Mix PEF with a viscosity of 0.65 dl / g and phenanthreneboronic acid in a mass ratio of 99:1, then add 200 ppm of antioxidant 1010, and premix for 25 minutes at room temperature with a rotation speed of 100 rpm; conduct melt blending and extrusion in a reactive twin-screw extruder at a temperature of 230 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a end-group modified PEF polyester material and product, denoted as PEFB1.

[0031] Example 7 Mix PEF with a viscosity of 0.7 dl / g and phenanthreneboronic acid in a mass ratio of 98.5:1.5, then add 200 ppm of antioxidant 1010, and premix for 25 minutes at room temperature with a rotation speed of 100 rpm; conduct melt blending and extrusion in a reactive twin-screw extruder at a temperature of 230 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a end-group modified PEF polyester material and product, denoted as PEFB 1.5 。

[0032] Example 8 Mix PEF with a viscosity of 0.75 dl / g and phenylboric acid in a mass ratio of 98:2, then add 200 ppm of antioxidant 1010, and premix for 25 minutes at room temperature and a rotation speed of 100 rpm; conduct melt blending and extrusion in a reactive twin-screw extruder at a temperature of 230 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a end-group modified PEF polyester material and product, denoted as PEFB2.

[0033] Comparative Example 1 Mix PEF with a viscosity of 0.65 dl / g and 200 ppm of antioxidant 1010, and premix for 15 minutes at room temperature and a rotation speed of 100 rpm; conduct melt blending and extrusion in a reactive twin-screw extruder at a temperature of 210 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a comparative material without adding an end-group modifier, denoted as PEF in the figure.

[0034] Comparative Example 2 Mix PEF with a high viscosity of 0.65 dl / g and naphthoic acid in a mass ratio of 99.9:0.1, and premix for 15 minutes at room temperature and a rotation speed of 100 rpm; conduct melt blending and extrusion in a reactive twin-screw extruder at a temperature of 210 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a comparative material without adding an antioxidant.

[0035] Comparative Example 3 Mix PEF with a viscosity of 0.35 dl / g and naphthoic acid in a mass ratio of 99.5:0.5, then add 200 ppm of antioxidant 1010, and premix for 20 minutes at room temperature and a rotation speed of 100 rpm; conduct melt blending and extrusion in a reactive twin-screw extruder at a temperature of 210 °C and a rotation speed of 300 rpm, and directly inject it into a spline or preform mold. After cooling and shaping, demold to obtain a comparative material made of low-viscosity PEF.

[0036] The following performance tests were carried out on the examples and comparative examples: Nuclear magnetic resonance (NMR): At room temperature, perform proton spectrum measurement on a 400 MHz nuclear magnetic resonance instrument (Bruker, Germany), using deuterated trifluoroacetic acid (in the proton spectrum, its chemical shift δ = 11.5 ppm) as the solvent. Thermogravimetric analysis (TGA): Test the materials using a TAQ500 thermogravimetric analyzer from TA Instruments, USA. According to the national standard GB / T 19466.6-2009, all samples were heated from 30 °C to 600 °C at a heating rate of 10 °C per minute under a nitrogen atmosphere. Differential Scanning Calorimetry (DSC): DSC analysis was performed using a TA-Q2000 thermal analyzer. In accordance with the national standard GB / T19466.3-2004, the heating rate was 10 °C / min. X-ray Diffraction (XRD): XRD analysis was performed using an Ultima IV instrument; test angle: wide angle 5–90°, conventional test rate: 5° / min. Melt Index (MFI) Test: An RL1100 melt index tester was used for testing in accordance with the national standard GB / T 3682 at 260 °C.

[0037] All samples were subjected to isothermal crystallization treatment at 160 °C for 2 hours before performance testing. Xc is the crystallinity of the material characterized by X-ray diffraction (XRD) and determined by the density gradient method; Tg is the glass transition temperature; Td is the initial decomposition temperature. The test results are shown in Table 1:

[0038] According to Table 1 and Figure 3 、 Figure 4 Based on the data, compared with Comparative Example 1 without the addition of polycyclic end-group modifiers, the Xc of the examples showed an upward trend with the increase in the addition amount of polycyclic end-group modifiers, indicating that the crystallization rate and crystallinity of the PEF polyester increased, which was more conducive to accelerating crystallization during processing. Antioxidant was not added in Comparative Example 2, while low-viscosity PEF was added in Comparative Example 3, and the thermal stability decreased significantly compared with the examples.

[0039] The examples and comparative examples were directly serially modified and injection molded into standard specimens or products, and the corresponding mechanical properties were tested according to national standards. Tensile and bending property tests were carried out in accordance with GB / T 1040 2006, where the tensile rate for tensile property testing was 50 mm / min and the test environment temperature was 11 °C; the gas permeability test was carried out in accordance with the national standard GB / T 1038-2022, and the test results are shown in Table 2:

[0032] According to the data in Table 2 and Figure 7 、 Figure 8 As shown, the tensile strength of the examples was significantly improved compared with the comparative examples, and the elongation at break increased from about 5% in Comparative Example 1 to a maximum of 13% in Example 1, indicating that the toughness of the materials in the examples was significantly improved. At the same time, the gas barrier performance of the examples could be maintained at more than 7 times that of PET (oxygen permeability coefficient is about: 0.0597 ml(g)·mm / m2·d·MPa), maintaining excellent barrier performance.

[0033] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any person skilled in the relevant art, without departing from the scope of the technical solution of the present invention and based on the technical essence of the present invention, any simple modifications, equivalent replacements, and improvements made to the above embodiments shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A modified polyethylene furandicarboxylate material, characterized in that: It includes a PEF main chain and polycyclic aromatic end groups chemically grafted to the ends of the PEF main chain; The polycyclic aromatic end groups form three-dimensional physical crosslinking network nodes through π-π stacking.

2. The modified polyethylene furandicarboxylate material according to claim 1, wherein: The polycyclic aromatic end groups include any one of naphthyl, anthryl, and phenanthryl.

3. A preparation method of a modified polyethylene furandicarboxylate material, characterized in that, It includes the following steps: After blending PEF, a polycyclic aromatic end group modifier, and an antioxidant, melt them in a reactive injection molding screw to obtain a melt, and then extrude to obtain the modified polyethylene furan dicarboxylate material as described in claim 1 or 2.

4. The preparation method of a modified polyethylene furandicarboxylate material according to claim 3, characterized in that: The polycyclic aromatic end group modifier is one or more of 1-naphthoic acid, 9-anthracene carboxylic acid, 2-phenanthroic acid, and 9-phenanthroboric acid.

5. The preparation method of a modified polyethylene furandicarboxylate material according to claim 4, characterized in that: The addition amount of the polycyclic aromatic end group modifier is 0.1-10% of the mass of PEF.

6. The preparation method of a modified polyethylene furandicarboxylate material according to claim 3, characterized in that: The antioxidant includes one or more of pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and dilauryl thiodipropionate.

7. The preparation method of a modified polyethylene furandicarboxylate material according to claim 6, characterized in that: The addition amount of the antioxidant is 100-500 ppm.

8. The preparation method of a modified polyethylene furandicarboxylate material according to claim 3, wherein: The viscosity of the PEF > 0.65 dl / g.

9. The preparation method of a modified polyethylene furandicarboxylate material according to claim 3, wherein: The melting time is 5-30 min, and the melting temperature is 200-260 °C.

10. Application of the modified polyethylene furan dicarboxylate material as described in claim 1 or 2 in product packaging.

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