Assistant composition for improving thermal stability of polyhydroxyalkanoate and application thereof

Abstract

The invention relates to the technical field of material modification, in particular to an additive composition for improving the thermal stability of polyhydroxyalkanoate and application of the additive composition. The main active ingredients of the auxiliary composition are rosmarinic acid and rhamnose ester, and the mass ratio of the rosmarinic acid to the rhamnose ester is (1-3): (1-2). Wherein the rosmarinic acid protects the PHA from thermal oxidative degradation through the oxidation resistance of the rosmarinic acid, and the rhamnose ester enhances the stability of a polymer chain through the surface activity of the rhamnose ester. According to the invention, rosmarinic acid and rhamnose ester have an obvious synergistic effect under a specific compounding ratio, so that not only can the thermal stability of PHA be improved, but also other properties of the material are ensured not to be influenced.

Description

Technical Field

[0001] The present invention relates to the technical field of material modification, and particularly relates to an auxiliary composition for improving the thermal stability of polyhydroxyalkanoates and its application. Background Art

[0002] Polyhydroxyalkanoates (PHA) are a class of biodegradable polymers synthesized by microorganisms, with good biocompatibility and environmental friendliness. However, the thermal stability of PHA at high temperatures is poor, which limits its wide use in high-temperature applications. In the prior art, in order to solve the problem of insufficient thermal stability of PHA, researchers have proposed various improvement schemes and research attempts. For example, by adding heat stabilizers such as certain metal salts, antioxidants, etc., to improve the thermal stability of PHA; by blending with other polymers such as polylactic acid (PLA), polyvinyl alcohol (PVA), etc., to improve its thermal stability; by introducing crosslinking agents or carrying out chemical grafting reactions, to improve the thermal stability of PHA, etc.

[0003] Although there are various methods for improving the thermal stability of PHA, there are still many deficiencies in the prior art. Traditional additives generally do not have degradability, and the addition amount usually cannot be too much, otherwise it will affect the biocompatibility and environmental friendliness of PHA. The blending method will reduce the performance of PHA, and phase separation will occur when two polymers with poor compatibility are blended; in addition, blending with other polymers will affect the degradation performance of PHA. The crosslinking method will reduce the molecular weight of PHA, thereby affecting its performance. Biocompatibility issues. Therefore, developing a natural auxiliary combination that can not only improve the thermal stability of PHA, but also maintain its biodegradability, mechanical properties and biocompatibility has important application value.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an auxiliary composition for improving the thermal stability of polyhydroxyalkanoates and its application.

[0006] Specifically, the technical solution of the present invention is as follows: In the first aspect, the present invention provides an auxiliary composition for improving the thermal stability of polyhydroxyalkanoates, the main active components of the auxiliary composition are rosmarinic acid and rhamnolipid, and the mass ratio of rosmarinic acid to rhamnolipid is 1 - 3:1 - 2; preferably 1.5 - 2.5:1.

[0007] By synergistically using two natural auxiliaries, rosmarinic acid and rhamnolipid, the present invention can not only significantly improve the thermal stability of polyhydroxyalkanoates, but also maintain its good biocompatibility, biodegradability and mechanical properties.

[0008] Second aspect, the present invention provides a polyhydroxyalkanoate, which comprises the aforementioned auxiliary composition.

[0009] Preferably, the polyhydroxyalkanoate includes at least one of PHB, PHBV, P34HB, and PHBHHx.

[0010] Third aspect, the present invention provides a method for improving the thermal stability of polyhydroxyalkanoate, which is to mix and melt the polyhydroxyalkanoate with the aforementioned auxiliary composition.

[0011] Preferably, the mixing ratio of the polyhydroxyalkanoate to the auxiliary composition is 100:2 - 4 by mass, more preferably 100:2.5 - 3.5, and even more preferably 100:3.

[0012] Preferably, the temperature range of the melting is 105 - 160 °C.

[0013] Preferably, the present invention uses screw melting extrusion granulation.

[0014] Preferably, the screw speed is 150 ± 50 rpm.

[0015] Preferably, the temperatures of each zone of the extruder are set as 110 ± 5 °C, 130 ± 5 °C, 140 ± 5 °C, 145 ± 5 °C, 145 ± 5 °C, 150 ± 5 °C, 155 ± 5 °C, 155 ± 5 °C in sequence.

[0016] Preferably, the polyhydroxyalkanoate is selected from at least one of PHA, PHB, PHBV, P34HB, and PHBHHx.

[0017] Beneficial effects: The present invention provides an auxiliary composition for improving the thermal stability of polyhydroxyalkanoate and its application. The main active components of the auxiliary composition are rosmarinic acid and rhamnolipid. Among them, rosmarinic acid protects PHA from thermal oxidative degradation through its antioxidant property, while rhamnolipid enhances the stability of the polymer chain through its surface activity. In the present invention, rosmarinic acid and rhamnolipid have an obvious synergistic effect at a specific compounding ratio, which can not only improve the thermal stability of PHA, but also ensure that other properties of the material are not affected. Description of the drawings

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will describe the drawings required to be used in the examples or the description of the prior art.

[0019] Figure 1 It is the TGA test results of Examples 1 - 3 and Comparative Examples 1 - 3 of the present invention; Figure 2This is the TGA test result of Examples 4-5 and Comparative Examples 4-5 of the present invention. Detailed implementation mode

[0020] Currently, the methods for improving the thermal stability of PHA mainly focus on chemical modification and adding synthetic additives. However, these methods often affect the biodegradability and biocompatibility of PHA. Many heat stabilizers have a negative impact on the biocompatibility of PHA, and the additives themselves do not have degradation properties, which limits their application in the fields of medicine and food packaging.

[0021] The present invention provides an additive composition for improving the thermal stability of polyhydroxyalkanoates. The main active components of the additive composition are rosmarinic acid and rhamnolipid. Among them, rosmarinic acid is a natural antioxidant with excellent thermal stability and antioxidant properties. Its molecular structure contains multiple phenolic hydroxyl groups, which can effectively capture free radicals and prevent the thermal degradation of polymers at high temperatures. Rhamnolipid is a natural surfactant with good thermal stability and biocompatibility. Its unique molecular structure enables it to stabilize polymer chains at high temperatures and further improve the thermal stability of polyhydroxyalkanoates.

[0022] In the present invention, the mass ratio of rosmarinic acid to rhamnolipid is 1-3:1-2; preferably 1.5-2.5:1, and more preferably 2:1.

[0023] The present invention does not make special limitations on the sources of rosmarinic acid and rhamnolipid, and any conventional commercially available sources in the art can be used. By synergistically using two natural additives, rosmarinic acid and rhamnolipid, at a specific compounding ratio, they can not only significantly improve the thermal stability of polyhydroxyalkanoates, but also maintain their good biocompatibility, biodegradability and mechanical properties.

[0024] Furthermore, in a more specific implementation mode, the present invention provides a method for modifying polyhydroxyalkanoates using the above additive composition, including: adding polyhydroxyalkanoates, rosmarinic acid and rhamnolipid to a high-speed mixer, mixing at 80±20°C for 10±5 min to fully stir the materials. Then, the mixed materials are extruded and granulated through a twin-screw melt extruder. The temperatures of each zone of the twin-screw melt extruder are 110±5°C, 130°C±5, 140°C±5, 145°C±5, 145°C±5, 150°C±5, 155°C±5, 155°C±5 respectively, and the screw speed is 150±50 rpm. The extruded materials are cooled by air or water, dried and then pelletized to obtain a polyhydroxyalkanoate composition with good thermal stability.

[0025] Compared with the existing conventional technologies, in the present invention, rosmarinic acid and rhamnolipid are added as heat modification aids for polyhydroxyalkanoates. The synergistic effect of rosmarinic acid and rhamnolipid significantly improves the thermal stability of PHA, enabling it to be applied within a wider temperature range; the addition of rhamnolipid improves the processing performance of PHA, making it easier to mold and process; moreover, both rosmarinic acid and rhamnolipid are of natural origin, and both aids have good biodegradability, with little impact on the environment, meeting the requirements of green chemistry and environmental protection and safety. The present invention further provides a new thermally stable PHA composition and its preparation method to solve the limitations of the existing technologies and improve the thermal stability of PHA, making it more suitable for high-temperature processing and applications. This composition not only improves the thermal stability of PHA but also maintains its biocompatibility and biodegradability, providing a new perspective for the application of PHA.

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.

[0027] At the endpoints and any value within the ranges disclosed in this specification, these ranges or values are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0028] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "specific embodiments", or "some specific embodiments" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0029] In the embodiments provided in this specification, for those without specified specific technologies or conditions, the technologies or conditions described in the literature in this field or the product specifications shall be followed. For reagents or instruments without specified manufacturers, they are all conventional products that can be obtained through regular channels.

[0030] Example 1 This example provides an auxiliary agent composition for improving the thermal stability of polyhydroxyalkanoates, and the formula is: 1 part by weight of rosmarinic acid and 1 part by weight of rhamnolipid.

[0031] This example provides a method for improving the thermal stability of polyhydroxyalkanoates and obtaining thermally stable polyhydroxyalkanoates by using the above auxiliary agent composition, which specifically includes the following steps: Weigh 100 parts of PHB, 1 part of rosmarinic acid, and 1 part of rhamnolipid by weight, add them to a high-speed mixer, mix at 80 °C for 10 min to fully stir the materials. Then, extrude and pelletize the mixed materials through a twin-screw melt extruder. The temperatures of each zone of the twin-screw melt extruder are 110 °C, 130 °C, 140 °C, 145 °C, 145 °C, 150 °C, 155 °C, and 155 °C respectively, and the screw speed is 150 rpm. The extruded materials are cooled by air, dried, and then pelletized to obtain a thermally stable polyhydroxyalkanoate composition.

[0032] To verify the performance of the polyhydroxyalkanoate composition obtained in Example 1, the following tests are carried out: (1) Product performance test Polymer melting index (MI): It represents the mass of a thermoplastic material passing through a standard capillary within 10 min at a certain temperature and pressure. The measurement conditions are: 190 °C, 2.16 kg.

[0033] Tensile strength: Measured according to the national standard GB / T 1040.2-2022.

[0034] Nominal strain at break: Measured according to the national standard GB / T 1040.2-2022.

[0035] Izod impact strength: Measured according to the national standard GB / T1843-2008.

[0036] (2) TGA test The TGA test is carried out on the polyhydroxyalkanoate composition obtained in Example 1 by using the national standard method GB / T 27761-2011.

[0037] The final product performance test methods and TGA test methods for other examples and comparative examples are the same as those in Example 1.

[0038] Example 2 This embodiment provides an auxiliary composition for improving the thermal stability of polyhydroxyalkanoates, with the formula: 2 parts by weight of rosmarinic acid and 1 part by weight of rhamnolipid.

[0039] This embodiment provides a method for improving the thermal stability of polyhydroxyalkanoates and obtaining thermally stable polyhydroxyalkanoates by using the above auxiliary composition, which specifically includes the following steps: Weigh 100 parts of PHB, 2 parts of rosmarinic acid, and 1 part of rhamnolipid by weight, add them to a high-speed mixer, mix at 80 °C for 10 min to fully stir the materials. Then, extrude and pelletize the mixed materials through a twin-screw melt extruder. The temperatures of each zone of the twin-screw melt extruder are 110 °C, 130 °C, 140 °C, 145 °C, 145 °C, 150 °C, 155 °C, and 155 °C respectively, and the screw speed is 150 rpm. The extruded materials are cooled by air, dried, and then pelletized to obtain a thermally stable polyhydroxyalkanoate composition.

[0040] Example 3 This embodiment provides an auxiliary composition for improving the thermal stability of polyhydroxyalkanoates, with the formula: 1 part by weight of rosmarinic acid and 2 parts by weight of rhamnolipid.

[0041] This embodiment provides a method for improving the thermal stability of polyhydroxyalkanoates and obtaining thermally stable polyhydroxyalkanoates by using the above auxiliary composition, which specifically includes the following steps: Weigh 100 parts of PHB, 1 part of rosmarinic acid, and 2 parts of rhamnolipid by weight, add them to a high-speed mixer, mix at 80 °C for 10 min to fully stir the materials. Then, extrude and pelletize the mixed materials through a twin-screw melt extruder. The temperatures of each zone of the twin-screw melt extruder are 110 °C, 130 °C, 140 °C, 145 °C, 145 °C, 150 °C, 155 °C, and 155 °C respectively, and the screw speed is 150 rpm. The extruded materials are cooled by air, dried, and then pelletized to obtain a thermally stable polyhydroxyalkanoate composition.

[0042] Example 4 This embodiment provides an auxiliary composition for improving the thermal stability of polyhydroxyalkanoates, with the formula: 1 part by weight of rosmarinic acid and 2 parts by weight of rhamnolipid.

[0043] This example provides a method for improving the thermal stability of polyhydroxyalkanoates and obtaining thermally stable polyhydroxyalkanoates by using the above-mentioned auxiliary composition, which specifically includes the following steps: By weight, weigh 100 parts of P34HB, 1 part of rosmarinic acid, and 2 parts of rhamnolipid, add them to a high-speed mixer, and mix at 80 °C for 10 min to fully stir the materials. Then, extrude and pelletize the mixed materials through a twin-screw melt extruder. The temperatures of each zone of the twin-screw melt extruder are 110 °C, 130 °C, 140 °C, 145 °C, 145 °C, 150 °C, 155 °C, and 155 °C respectively, and the screw speed is 148 rpm. The extruded materials are cooled by air, dried, and then pelletized to obtain a thermally stable polyhydroxyalkanoate composition.

[0044] Example 5 This example provides an auxiliary composition for improving the thermal stability of polyhydroxyalkanoates, and the formula is: 1 part by weight of rosmarinic acid and 2 parts by weight of rhamnolipid.

[0045] This example provides a method for improving the thermal stability of polyhydroxyalkanoates and obtaining thermally stable polyhydroxyalkanoates by using the above-mentioned auxiliary composition, which specifically includes the following steps: By weight, weigh 100 parts of PHBV, 1 part of rosmarinic acid, and 2 parts of rhamnolipid, add them to a high-speed mixer, and mix at 80 °C for 10 min to fully stir the materials. Then, extrude and pelletize the mixed materials through a twin-screw melt extruder. The temperatures of each zone of the twin-screw melt extruder are 110 °C, 130 °C, 140 °C, 145 °C, 145 °C, 150 °C, 155 °C, and 155 °C respectively, and the screw speed is 155 rpm. The extruded materials are cooled by air, dried, and then pelletized to obtain a thermally stable polyhydroxyalkanoate composition.

[0046] Comparative Example 1 The difference between this comparative example and Example 2 is only that: without adding the auxiliary composition, directly perform subsequent treatment on the polyhydroxyalkanoate.

[0047] Comparative Example 2 The difference between this comparative example and Example 2 is only that: replace the auxiliary composition with 1 part of rosmarinic acid.

[0048] Comparative Example 3 The difference between this comparative example and Example 2 is only that: replace the auxiliary composition with 1 part of rhamnolipid.

[0049] Comparative Example 4 The difference between this comparative example and Example 4 is that, without adding the auxiliary composition, directly perform subsequent treatment on the polyhydroxyalkanoate.

[0050] Comparative Example 5 This comparative example is different from Example 5 in that the polyhydroxyalkanoate is directly subjected to subsequent treatment without adding the auxiliary composition.

[0051] The test results of the relevant properties of the products of Examples 1-5 and Comparative Examples 1-5 are as follows: (1) The measurement results of the polymer melt index, tensile strength, nominal strain at break, and Izod impact strength of the products of Examples 1-5 and Comparative Examples 1-5 are shown in Table 1.

[0052] Table 1

[0053] It can be seen from the performance test results in Table 1 that the mechanical properties of the all-bio-based thermally stable polyhydroxyalkanoate compositions prepared in Examples 1-3 are superior to those of Comparative Examples 1-3, and the mechanical properties of the all-bio-based thermally stable polyhydroxyalkanoate compositions prepared in Examples 4 and 5 are superior to those of Comparative Examples 4 and 5, respectively. It shows that by synergistically using two natural auxiliaries, rosmarinic acid and rhamnolipid, the present invention significantly improves the stability of PHA while maintaining its biodegradability and mechanical properties.

[0054] (2) The TGA test results of the products of Examples 1-5 and Comparative Examples 1-5 are shown in Figure 1 and Figure 2 .

[0055] It can be seen from the TGA test results of Figure 1 and Figure 2 that the decomposition temperatures (i.e., the temperatures at which the polymer loses 5% and 10% of its weight in the TGA test) of the all-bio-based thermally stable polyhydroxyalkanoate compositions prepared in Examples 1-5 are increased, indicating that by using two natural auxiliaries, rosmarinic acid and rhamnolipid, the present invention plays a synergistic effect and improves the thermal stability of PHA. This all-bio-based thermally stable PHA composition and its preparation method have broad application prospects, especially showing significant advantages in the biomedical field.

[0056] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An auxiliary agent composition for improving the thermal stability of polyhydroxyalkanoate, characterized in that: The main active ingredients of the auxiliary agent composition are rosmarinic acid and rhamnosyl ester, and the mass ratio of rosmarinic acid to rhamnosyl ester is 1-3:1-2.

2. The auxiliary agent composition according to claim 1, characterized in that: The mass ratio of rosmarinic acid to rhamnosyl ester is 1.5-2.5:

1.

3. Polyhydroxyalkanoate, characterized in that The polyhydroxyalkanoate comprises the auxiliary composition according to claim 1 or 2.

4. The polyhydroxyalkanoate according to claim 3, characterized in that: The polyhydroxyalkanoate includes at least one of PHB, PHBV, P34HB, and PHBHHx.

5. A method for improving the thermal stability of polyhydroxyalkanoates, characterized in that: The polyhydroxyalkanoate is mixed with the auxiliary agent composition according to claim 1 or 2 and melted.

6. The method for improving the thermal stability of polyhydroxyalkanoates according to claim 5, characterized in that: The mixing ratio of the polyhydroxyalkanoate to the auxiliary agent composition is 100:2-4 in parts by mass.

7. The method for improving the thermal stability of polyhydroxyalkanoates according to claim 6, characterized in that: The mixing ratio of the polyhydroxyalkanoate to the auxiliary agent composition is 100:2.5-3.5 in parts by mass.

8. The method for improving the thermal stability of polyhydroxyalkanoates according to any one of claims 5 to 6, characterized in that: The melting temperature range is 105-160°C.

9. The method for improving the thermal stability of polyhydroxyalkanoates according to any one of claims 5 to 6, characterized in that: Use screw melt extrusion granulation; Preferably, the screw speed is 150±50 rpm.

10. The method for improving the thermal stability of polyhydroxyalkanoates according to claim 9, characterized in that: The temperatures of each zone of the extruder are set to 110±5°C, 130±5°C, 140±5°C, 145±5°C, 145±5°C, 150±5°C, 155±5°C, and 155±5°C, respectively.

Images