Preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization

Abstract

The invention relates to preparation of a high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization. The high-toughness PHA modified material is prepared by mixing more than 90% by weight of polyhydroxyalkanoate and 0.1-10% by weight of a flexibilizer, the polyhydroxyalkanoate (PHA) comprises one or more of poly-3-hydroxybutyrate and other types, and the flexibilizer is a negative carbon material (negative carbon PLA, negative carbon PBAT or negative carbon PHB), and during preparation, the two materials are mixed and then added into a twin-screw extruder, the twin-screw extruder is extruded, and the high-toughness PHA modified material is prepared. The high-toughness PHA modified material is prepared by the following steps: taking a PHA raw material as a raw material, carrying out melt blending at a screw temperature of 140-180 DEG C, carrying out injection molding at an injection pressure of 70-150 bar, carrying out mold temperature of 40-75 DEG C, maintaining the pressure for 1-5 seconds, rapidly cooling to room temperature, and carrying out treatment by adopting a high-pressure carbon dioxide crystallization method for 5-25 minutes under a CO2 environment at the pressure of 2-6 MPa and the temperature of 45-60 DEG C, thereby finally obtaining the high-toughness PHA modified material. By optimizing the material composition and the processing technology, the toughness of the PHA material is remarkably improved, meanwhile, the biodegradability of the PHA material is kept, and the PHA material is suitable for various application scenes with high toughness requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to the preparation of high-toughness PHA modified materials based on negative carbon toughening and high-pressure CO2 crystallization. Technical Background

[0002] Polyhydroxyalkanoates (PHA) are a class of polymer materials with excellent biodegradability and environmental friendliness, and are widely used in packaging, agriculture, medical and other fields. However, traditional PHA materials have the problem of insufficient toughness, which seriously limits their practical application. In order to improve the toughness of PHA, toughening agents are usually required to be added, but the existing toughening agents are mostly derived from petrochemical resources or food crops (such as starch-based toughening agents), which not only leads to intensified resource competition, but also increases carbon emissions in the production process, which is contrary to the environmental protection properties of PHA. In addition, the traditional thermal crystallization process has problems such as high energy consumption and uneven crystallization, which further affects the stability of material properties.

[0003] In recent years, the technology of using industrial waste gas or carbon dioxide (CO2) in the air to prepare negative carbon materials (such as negative carbon PLA, PBAT, etc.) has gradually emerged. This type of material can not only reduce fossil energy consumption, but also achieve negative carbon emissions through carbon sequestration, which meets the needs of sustainable development. However, when combining such negative carbon toughening agents with PHA, there are still problems such as uneven dispersion and poor interface bonding, and the existing crystallization process is difficult to effectively regulate the crystallization behavior of PHA to improve toughness.

[0004] In response to the above technical challenges, the present invention proposes a high-toughness PHA modified material and preparation based on negative carbon toughening and high-pressure CO2 crystallization: by introducing negative carbon toughening agents (such as negative carbon PLA, negative carbon PBAT, etc.) and melt blending with PHA, combined with high-pressure CO2 crystallization process, the toughness of the material is significantly improved, while achieving the goals of efficient resource utilization and low-carbon emissions. Specifically, the present invention ensures the uniform dispersion of the toughening agent by optimizing the processing parameters of the twin-screw extruder (such as screw temperature, injection pressure) and the mold temperature; combined with the high-pressure CO2 crystallization process (pressure 2-6MPa, temperature 45-60°C), it promotes the rapid crystallization of PHA and improves the molecular chain orientation, thereby achieving a synergistic improvement in the mechanical properties and degradability of the material. This method breaks through the technical bottlenecks of traditional toughening agents and crystallization processes, and provides an innovative solution for the efficient and green modification of polyhydroxyalkanoates. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization, so as to solve the problems of insufficient toughness of existing polyhydroxyalkanoate materials, dependence on food and land resources, and high carbon emissions of traditional toughening methods. The polyhydroxyalkanoate material or product prepared by the method has high toughness, and can capture industrially emitted CO2 or prepare a toughening agent from CO2 in the air during the production process, thereby achieving negative carbon production and reducing dependence on food and land resources.

[0006] The present invention is achieved through the following technical solutions:

[0007] In the preparation of high-toughness PHA modified materials based on negative carbon toughening and high-pressure CO2 crystallization, polyhydroxyalkanoate is first mixed with the toughening agent, then put into a twin-screw extruder for melt blending, then injection molding, and quickly cooled to room temperature, followed by high-pressure CO2 crystallization treatment, and finally a high-toughness PHA composite material is obtained.

[0008] Furthermore, the polyhydroxyalkanoate is one or more of poly-3-hydroxybutyrate, poly(3-hydroxybutyric acid-co-3-hydroxyhexanoic acid), poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid), poly(3-hydroxybutyric acid-co-4-hydroxybutyric acid), poly(3-hydroxybutyric acid-co-3-hydroxyhexanoic acid), poly(3-hydroxybutyric acid-co-4-hydroxybutyric acid-co-3-hydroxyvaleric acid), poly(3-hydroxybutyric acid-co-5-hydroxyvaleric acid), poly-3-hydroxyvalerate, poly-3-hydroxypropionate, poly-3-hydroxyoctanoate, and poly-3-hydroxynonanoate.

[0009] Furthermore, the polyhydroxyalkanoate accounts for more than 90% by weight of the high-toughness PHA modified material.

[0010] Furthermore, the toughening agent is a negative carbon material, which captures CO2 emitted by industry or is prepared from CO2 in the air during the production process, reducing the dependence of degradable polymer production on food and land resources.

[0011] Furthermore, the preferred toughening agent negative carbon material includes one or more of negative carbon PLA, negative carbon PBAT, and negative carbon PHB.

[0012] Furthermore, the toughening agent negative carbon material is 0.1 to 10 weight % of the high toughness PHA modified material.

[0013] Furthermore, the screw temperature of the twin-screw extruder is between 140 and 180° C., and the injection pressure is between 70 and 150 bar.

[0014] Furthermore, the mold temperature is 40-75° C., and the holding time is 1-5 s.

[0015] Furthermore, the crystallization treatment is a high-toughness PHA modified material crystallization method.

[0016] Furthermore, the gas atmosphere of the high-pressure and high-toughness PHA modified material crystallization method is a CO2 environment, the pressure is 2-6 MPa, the temperature is 45-60°C, and the processing time is 5-25 min.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0018] (1) By melt blending polyhydroxyalkanoate with a specific negative carbon toughening agent, the original defect of insufficient toughness of polyhydroxyalkanoate materials was effectively overcome. The toughness of the prepared PHA modified material was greatly improved, which can meet the use requirements of high-demand scenarios such as packaging and biomedicine, broaden the application range of PHA materials, and improve the practicality and durability of the product.

[0019] (2) The toughening agent used in this patent is a negative carbon material, which can capture CO2 emitted by industry or be produced from CO2 in the air during the production process, achieving negative carbon emissions, which has positive significance for alleviating the greenhouse effect and improving the atmospheric environment. Compared with the large carbon emissions during the production process of traditional toughening agents, the present invention reduces the carbon footprint from the source, which is in line with the global environmental protection trend of responding to climate change.

[0020] (3) The emergence of this patented technology provides an innovative idea and method for the field of polymer material preparation, promotes the development of the biodegradable polymer material industry towards green, efficient and high-performance, promotes the technological upgrading and structural adjustment of related industries, and enhances the competitiveness of the entire industry. DETAILED DESCRIPTION

[0021] In order to more clearly present the purpose, technical solutions and advantages of the present invention, the technical solutions in the embodiments of the present invention will be fully described below. The specific conditions marked in the present invention can be carried out according to conventional conditions. The reagents and instruments used are marked manufacturers and can be purchased from commercial sources.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] The Chinese full names of the English abbreviations appearing in this article are as follows:

[0024] PHA: polyhydroxyalkanoate;

[0025] PHB: poly-3-hydroxybutyrate;

[0026] PHBV: poly(3-hydroxybutyrate-co-3-hydroxyvalerate);

[0027] P34HB: poly(3-hydroxybutyrate-co-4-hydroxybutyrate);

[0028] Example 1

[0029] PHB was preliminarily mixed manually with 1 wt.% of negative carbon black, and then the mixture was poured into a granulator. The granulator was set to a heating temperature of 140-165°C, a screw aspect ratio of 52:1, and a screw speed of 250 rpm. The granules were extruded and granulated, and then the particles were shaken again to mix thoroughly.

[0030] Pour the PHA injection molding material into the fork injection molding machine, set the temperature of each section as follows: 120°C for the feeding section, 140°C for the compression section, 150°C for the homogenization section, 160°C for the die head, the main engine speed is 20rpm, the mold temperature is 60°C, the injection pressure is 115bar, the holding time is 2s, the fork sample is formed, and then the fork sample is taken out and cooled to room temperature.

[0031] Arrange the fork samples neatly and put them into an iron frame, then place them in a high-pressure reactor and fill the reactor with carbon dioxide gas. After heating the autoclave to the set temperature of 45°C, pressurize the gas to a certain pressure of 3MPa, store it for 10 minutes, release the pressure and take out the samples.

[0032] Example 2

[0033] PHBV was preliminarily mixed manually with 5wt.% of negative carbon black, and then the mixture was poured into a granulator. The granulator was set to a heating temperature of 140-165°C, a screw aspect ratio of 52:1, and a screw speed of 250rpm. The granules were extruded and granulated, and then the particles were shaken again to mix thoroughly.

[0034] Pour the PHA injection molding material into the fork injection molding machine, set the temperature of each section as follows: 140°C for feeding section, 147°C for compression section, 153°C for homogenization section, 165°C for die head, main engine speed of 20rpm, mold temperature of 50°C, injection pressure of 90bar, holding time of 2s, to form the fork sample, then take out the fork sample and cool it to room temperature.

[0035] Arrange the fork samples neatly and put them into an iron frame, then place them in a high-pressure reactor and fill the reactor with carbon dioxide gas. After heating the autoclave to the set temperature of 50°C, pressurize the gas to a certain pressure of 3MPa, store it for 10 minutes, release the pressure and take out the samples.

[0036] Example 3

[0037] PHBV was preliminarily mixed manually with 0.5wt.% of negative carbon black, and then the mixture was poured into a granulator. The granulator was set to a heating temperature of 140-165°C, a screw aspect ratio of 52:1, and a screw speed of 250rpm. The granules were extruded and granulated, and then the particles were shaken again to mix thoroughly.

[0038] Pour the PHA injection molding material into the fork injection molding machine, set the temperature of each section as follows: 130°C for the feeding section, 140°C for the compression section, 150°C for the homogenization section, and 155°C for the die head. The main machine speed is 15rpm, the mold temperature is 55°C, the injection pressure is 100bar, and the holding time is 3s to form the fork sample. Then take out the fork sample and cool it to room temperature.

[0039] Arrange the fork samples neatly and put them into an iron frame, then place them in a high-pressure reactor and fill the reactor with carbon dioxide gas. After heating the autoclave to the set temperature of 40°C, pressurize the gas to a certain pressure of 2MPa, store it for 8 minutes, release the pressure and take out the samples.

[0040] Example 4

[0041] P34HB was preliminarily mixed manually with 3 wt.% of negative carbon black, and then the mixture was poured into a granulator. The granulator was set to a heating temperature of 140-165°C, a screw aspect ratio of 52:1, and a screw speed of 250 rpm. The granules were extruded and granulated, and then the particles were shaken again to mix thoroughly.

[0042] Pour the PHA injection molding material into the fork injection molding machine, set the temperature of each section as follows: 135°C for feeding section, 143°C for compression section, 150°C for homogenization section, 155°C for die head, main engine speed of 20rpm, mold temperature of 50°C, injection pressure of 95bar, holding time of 3s, form the fork sample, then take out the fork sample and cool it to room temperature.

[0043] Arrange the fork samples neatly and put them into an iron frame, then place them in a high-pressure reactor and fill the reactor with carbon dioxide gas. After heating the autoclave to the set temperature of 55°C, pressurize the gas to 3MPa pressure, store for 10 minutes, release the pressure and take out the samples.

[0044] Example 5

[0045] P34HB was preliminarily mixed manually with 1.5wt.% of negative carbon black, and then the mixture was poured into a granulator. The granulator was set to a heating temperature of 140-165°C, a screw aspect ratio of 52:1, and a screw speed of 250rpm. The granules were extruded and granulated, and then the particles were shaken again to mix thoroughly.

[0046] Pour the PHA injection molding material into the fork injection molding machine, set the temperature of each section as follows: 140°C for feeding section, 145°C for compression section, 155°C for homogenization section, 165°C for die head, main engine speed of 25rpm, mold temperature of 60°C, injection pressure of 85bar, holding time of 2s, form the fork sample, then take out the fork sample and cool it to room temperature.

[0047] Arrange the fork samples neatly and put them into an iron frame, then place them in a high-pressure reactor and fill the reactor with carbon dioxide gas. After heating the autoclave to the set temperature of 50°C, pressurize the gas to a certain pressure of 2MPa, store it for 9 minutes, release the pressure and take out the samples.

[0048] Comparative Example 1

[0049] Comparative Example 1 Compared with Example 1, in the granulation process of the PHA injection molding material, no negative carbon material is added in Comparative Example 1, and other conditions remain unchanged.

[0050] Comparative Example 2

[0051] Comparative Example 2 Compared with Example 1, in Comparative Example 2, during the PHA spoon forming process, no pressure holding was performed, and other conditions remained unchanged.

[0052] Comparative Example 3

[0053] Comparative Example 3 Compared with Example 1, in Comparative Example 3, after the PHA spoon is formed, the sample is not subjected to high-pressure carbon dioxide treatment, and other conditions remain unchanged.

[0054] Testing items and methods:

[0055] 1. Bending resistance test: Clamp the tail end of the fork and extend the fork head 70mm for bending test. Then use the bending test head of the universal testing machine to press the fork head down 50mm at a speed of 100mm / min, then return to the original position and read the maximum bending value N.

[0056] 2. Crystallinity test: In a nitrogen environment, a differential scanning calorimeter (DSC 2500, TA Instruments Co., LTD, USA) was used to heat the fork sample from 30°C to 230°C and keep it at this temperature for 3 minutes. Then, the melted sample was cooled to 30°C and kept at this temperature for 5 minutes, and finally heated to 230°C again. The heating and cooling rates were both 10°C / min. The crystallinity (Xc) of the composite material can be calculated by the following formula:

[0057]

[0058] Wherein, ΔHf is the melting enthalpy of the composite, ΔHcc is the cold crystallization enthalpy of the composite, is the melting enthalpy of 100% crystalline PHA, and %wt is the weight percentage of PHA in the matrix.

[0059] The results are provided in the following table.

[0060] Table 1

[0061] project Bending performance / N Crystallinity / % Example 1 5.9 63.6 Example 2 7.3 42.3 Example 3 6.8 41.9 Example 4 8.1 37.9 Example 5 7.4 25.4 Comparative Example 1 5.2 58.7 Comparative Example 2 4.7 61.6 Comparative Example 3 3.0 48.9

[0062] From the test results in Table 1, it can be seen that the PHA forks prepared by Examples 1-5 of the present invention have excellent mechanical properties. From the comparison between Comparative Example 1 and Examples 1-5, it can be seen that the addition of negative carbon materials can effectively improve the bending performance of the PHA forks and slightly improve the crystallinity of the PHA products; from the comparison between Comparative Example 2 and Examples 1-5, it can be seen that after a certain pressure holding, the shape of the fork can be better formed and the burrs can be controlled; from the comparison between Comparative Example 3 and Examples 1-5, it can be seen that after the PHA fork is subjected to high-pressure carbon dioxide crystallization treatment, the crystallinity of the fork is greatly improved, and the bending performance of the fork is greatly improved.

[0063] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0064] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. Preparation of high-toughness PHA modified materials based on negative carbon toughening and high-pressure CO2 crystallization, characterized in that: The high-toughness polyhydroxyalkanoate modified material is prepared by mixing polyhydroxyalkanoate with a toughening agent, melting and blending in a twin-screw extruder, and then injection molding, and rapidly cooling to room temperature, followed by high-pressure CO2 crystallization treatment, to finally obtain a high-toughness PHA modified material.

2. The preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization according to claim 1, characterized in that: The polyhydroxyalkanoate is one or more of poly-3-hydroxybutyrate, poly(3-hydroxybutyric acid-co-3-hydroxyhexanoic acid), poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid), poly(3-hydroxybutyric acid-co-4-hydroxybutyric acid), poly(3-hydroxybutyric acid-co-3-hydroxyhexanoic acid), poly(3-hydroxybutyric acid-co-4-hydroxybutyric acid-co-3-hydroxyvaleric acid), poly(3-hydroxybutyric acid-co-5-hydroxyvaleric acid), poly-3-hydroxyvalerate, poly-3-hydroxypropionate, poly-3-hydroxyoctanoate, and poly-3-hydroxynonanoate.

3. The preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization according to claim 2, characterized in that: The polyhydroxyalkanoate is 90% by weight or more of the high toughness PHA modified material.

4. The preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization according to claim 1, characterized in that: The toughening agent is a negative carbon material, which captures CO2 emitted by industry or is prepared from CO2 in the air during the production process, reducing the dependence of degradable polymer production on food and land resources.

5. The preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization according to claim 1, characterized in that: Preferably, the toughening agent negative carbon material includes one or more of negative carbon PLA, negative carbon PBAT, and negative carbon PHB.

6. The preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization according to claim 4 or 5, characterized in that: The toughening agent negative carbon material is 0.1 to 10 weight % of the high toughness PHA modified material.

7. According to the preparation of high-toughness PHA modified materials based on negative carbon toughening and high-pressure CO2 crystallization according to claim 1, the screw temperature of the twin-screw extruder is between 140 and 180°C, and the injection pressure is 70 to 150 bar.

8. The preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization according to claim 1, characterized in that: The mold temperature is 40-75°C and the holding time is 1-5s.

9. The preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization according to claim 1, characterized in that: The crystallization treatment method is a high-pressure CO2 crystallization method.

10. The preparation of high-toughness PHA modified material based on negative carbon toughening and high-pressure CO2 crystallization according to claim 9, characterized in that: The gas atmosphere of the high-pressure CO2 crystallization treatment is a CO2 environment, the pressure is 2-6 MPa, the temperature is 45-60°C, and the treatment time is 5-25 minutes.

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