Degradable PPC-based composite film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polymer composite materials, in particular to a degradable PPC-based composite film as well as a preparation method and application thereof. The degradable PPC-based composite film is prepared from polypropylene carbonate, bamboo powder and vinyl trimethoxy silane. Polypropylene carbonate (PPC) is adopted as a base material, bamboo powder is combined for filling, the prepared composite film can be completely degraded after being buried in natural soil for 5 months, and degradation products of the composite film do not pollute the environment; the bamboo powder is adopted as a reinforcing filler, has a certain bacteriostatic effect, and can be used for delaying the growth of microorganisms on the surface of food and improving the food safety and the fresh-keeping effect if being applied to the food fresh-keeping film. Compared with a pure PPC film, the composite film disclosed by the invention is improved in the aspects of mechanical property, thermal stability and glass transition temperature, and shows more excellent comprehensive performance.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite materials, in particular to a degradable PPC-based composite film and a preparation method and application thereof. Background Art

[0002] Traditional petroleum-based polymer films are widely used in food packaging due to their light weight, flexibility, and high transparency. However, the non-degradability of these materials, especially single-use plastics such as PE, PP, PS, and PET, has led to serious environmental pollution, exacerbating the problem of "white pollution" due to their long degradation cycles.

[0003] Polypropylene carbonate (PPC) is a biodegradable aliphatic polycarbonate synthesized from propylene oxide and carbon dioxide. Due to its excellent elongation at break and oxygen barrier properties, it is mainly used in the fields of films, barrier materials, etc. However, single PPC is relatively weak in mechanical properties, heat resistance and thermal stability, which limits its industrial application. Currently, the mainstream modification strategy is to introduce renewable biomass materials such as cellulose, starch and chitosan. However, due to compatibility issues, the interfacial bonding between the matrix and the reinforcing filler is poor, resulting in the mechanical properties of the composite material not being significantly improved.

[0004] Bamboo is a renewable biomass material with great potential. It is widely distributed in Asia, Africa and other regions due to its short growth cycle, high mechanical strength and excellent processing performance. Bamboo powder is rich in cellulose, and its multi-scale structure gives it excellent tensile properties and a high porosity (48-70%). PPC limits its porosity due to its carbonyl structure. The introduction of high-porosity bamboo powder can effectively improve the air permeability of the composite material. In addition, the bamboo phenol and phenolic compounds contained in bamboo powder can inhibit the growth and reproduction of microorganisms, and also give PPC-based composite films its antibacterial function. In 2022, the "Bamboo Instead of Plastic" initiative was included in the list of outcomes of the Global Development Dialogue, further highlighting the economic and ecological value of bamboo.

[0005] Specifically, many researchers have developed various techniques (such as chemical methods and enzymatic methods) to extract bamboo powder, but these methods involve the use of environmentally polluting chemical reagents, and the process is relatively complicated. In addition, the preparation methods of many composite films mainly adopt the cast coating method, which not only limits large-scale application, but also has difficulty in controlling the film thickness. In general, the PPC-based composite film of the present invention has a simple process and is suitable for large-scale production. It not only effectively overcomes the shortcomings of single PPC film, but also further improves the mechanical properties and thermal stability of the film. In addition, bamboo powder itself has natural degradability, can accelerate the degradation of the composite film, and possesses significant environmental characteristics. Therefore, it has a wide range of application prospects in multiple fields such as food packaging. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a degradable PPC-based composite membrane and its preparation method and application. The composite membrane has excellent mechanical properties, air permeability and antibacterial properties and is completely degraded in the natural environment.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a degradable PPC-based composite film, which is prepared from the following components in parts by weight:

[0009] 1937.03-1979.01 parts of polypropylene carbonate, 19.98-59.97 parts of bamboo powder and 1.12-3 parts of vinyltrimethoxysilane.

[0010] Preferably, it is prepared from the following components in parts by weight:

[0011] 1958.04 parts of polypropylene carbonate, 39.96 parts of bamboo powder and 2 parts of vinyltrimethoxysilane.

[0012] Preferably, the molecular weight of the polypropylene carbonate is 5.0×10 4 ~3.2×10 5 , the molecular weight distribution is 2.3-2.8, the monomer carbon dioxide content is 39-48wt.%, the monomer propylene oxide content is 56-64wt.%.

[0013] Preferably, the particle size of the bamboo powder is 1.5 to 1.67 μm.

[0014] The present invention also provides a method for preparing the degradable PPC-based composite film described in the above technical solution, comprising the following steps:

[0015] 1) mixing the polypropylene carbonate, bamboo powder and vinyltrimethoxysilane, melt-blending and granulating to obtain composite particles;

[0016] 2) drying the composite particles in step 1) and then tape casting to obtain a degradable PPC-based composite film. Preferably, the mixing conditions in step 1) include: a rotation speed of 40 to 120 rpm and a mixing time of 3 hours;

[0017] The melt blending conditions include: a temperature of 155-180° C. and a rotation speed of 80 rpm.

[0018] Preferably, the drying conditions in step 2) include: temperature of 60° C. and time of 38 h;

[0019] The tape casting conditions include: a temperature of 185-210° C. and a rotation speed of 4 rpm.

[0020] The present invention also provides the use of the degradable PPC-based composite membrane described in the above technical solution in improving the mechanical properties of the membrane.

[0021] The present invention also provides the use of the degradable PPC-based composite membrane described in the above technical solution in improving the thermal stability of the membrane.

[0022] The present invention also provides the use of the degradable PPC-based composite film described in the above technical solution in improving the glass transition temperature of the film.

[0023] Beneficial effects of the present invention:

[0024] This invention utilizes an extrusion casting method for the first time to produce a 6-8 μm biodegradable PPC-based composite film. Compared to traditional extrusion blow molding, this method offers more stable film quality and effectively reduces issues such as uneven film thickness, bubble defects, and internal stress accumulation. Existing plastic processing equipment (such as extruders and casting machines) can be directly applied to the production of this composite film, making the process simple and easily industrializable.

[0025] The present invention uses polypropylene carbonate (PPC) as a matrix material and combines it with bamboo powder as a filler. The prepared composite film can be completely degraded after being buried in natural soil for 5 months, and its degradation products do not pollute the environment.

[0026] The present invention uses bamboo powder as a reinforcing filler, which itself has a certain antibacterial effect. If applied to food preservative film, it will help delay the growth of microorganisms on the food surface, thereby improving food safety and preservation effects.

[0027] Compared with pure PPC membrane, the composite membrane of the present invention has improved mechanical properties, thermal stability and glass transition temperature (particle reinforcement, hydrogen bonding effect), showing more excellent comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0029] Figure 1 The figure is a process flow chart for the production of degradable PPC-based composite membranes;

[0030] Figure 2 is the mechanical properties diagram of the degradable PPC-based composite membrane;

[0031] Figure 3 This is the infrared spectrum of the degradable PPC-based composite membrane. DETAILED DESCRIPTION

[0032] The present invention provides a degradable PPC-based composite film, which is prepared from the following components in parts by weight: 1937.03 to 1979.01 parts of polypropylene carbonate, 19.98 to 59.97 parts of bamboo powder, and 1.12 to 3 parts of vinyltrimethoxysilane. In the present invention, the degradable PPC-based composite film is preferably prepared from the following components in parts by weight: 1958.04 parts of polypropylene carbonate, 39.96 parts of bamboo powder, and 2 parts of vinyltrimethoxysilane. In the present invention, the molecular weight of the polypropylene carbonate is 5.0×10 4 ~3.2×10 5 , a molecular weight distribution of 2.3 to 2.8, a monomer carbon dioxide content of 39 to 48 wt.%, and a monomer propylene oxide content of 56 to 64 wt.%. In the present invention, the particle size of the bamboo powder is preferably 1.5 to 1.67 μm. In the present invention, the polypropylene carbonate, bamboo powder, and vinyltrimethoxysilane are preferably dried separately in a vacuum drying oven at 80°C for 48 hours before mixing.

[0033] The present invention also provides a method for preparing the degradable PPC-based composite film described in the above technical solution, comprising the following steps:

[0034] 1) mixing the polypropylene carbonate, bamboo powder and vinyltrimethoxysilane, melt-blending and granulating to obtain composite particles;

[0035] 2) drying the composite particles in step 1) and then tape casting to obtain a degradable PPC-based composite film.

[0036] The present invention comprises mixing polypropylene carbonate, bamboo powder, and vinyltrimethoxysilane, then melt-blending and granulating to obtain composite particles. In the present invention, the mixing conditions preferably include: a rotation speed of 40 to 120 rpm for 3 hours; and the melt-blending conditions preferably include: a temperature of 155 to 180° C. and a rotation speed of 80 rpm.

[0037] The present invention involves drying the composite particles and then tape-casting to obtain a degradable PPC-based composite film. In the present invention, the drying conditions preferably include: a temperature of 60°C for 38 hours. In the present invention, the tape-casting conditions preferably include: a temperature of 185-210°C and a rotation speed of 4 rpm.

[0038] The present invention also provides the use of the degradable PPC-based composite membrane described in the above technical solution in improving the mechanical properties of the membrane.

[0039] The present invention also provides the use of the degradable PPC-based composite membrane described in the above technical solution in improving the thermal stability of the membrane.

[0040] The present invention also provides the use of the degradable PPC-based composite film described in the above technical solution in improving the glass transition temperature of the film.

[0041] In order to further illustrate the present invention, the present invention is described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] PPC (molecular weight 2.0×10 5 , molecular weight distribution is 2.5, monomer carbon dioxide content is 44wt.%, monomer propylene oxide content is 56wt.%, PPC and bamboo powder (average particle size is 1.5μm) were dried in a vacuum drying oven at 80℃ for 48h.

[0044] Then, 19.98 g of dried bamboo powder (BP) was weighed, 1.12 g of vinyl trimethoxysilane (VTMS) was added, and the mixture was thoroughly stirred. Subsequently, 1979.01 g of PPC was weighed and blended with the BP / VTMS mixture at high speed for 3 hours.

[0045] The obtained premix is ​​fed into a twin-screw extruder and melt-blended at 155-180°C and a screw speed of 80 r / min. After secondary extrusion and granulation, uniform composite particles are obtained.

[0046] The composite particles were then vacuum-dried again at 60°C for 38 hours. The dried composite particles were fed into a tape casting machine and tape-cast at 185-210°C and a main machine speed of 4 rpm to produce a PPC / bamboo powder composite film with a thickness of 6 μm.

[0047] The prepared PPC / bamboo powder composite film was subjected to a series of performance tests. According to GB / T 1040.3-2006, the tensile strength was 29.83 MPa and the elongation at break was 324.04%. According to GB / T1038.1-2022, the oxygen and carbon dioxide permeability tests were carried out, and the oxygen permeability was 140 cm 3 / (m 2 ·24h·0.1MPa), carbon dioxide permeability is 120cm 3 / (m 2 ·24h·0.1MPa). Differential scanning calorimetry (DSC) testing revealed a glass transition temperature of 41.2°C, and thermogravimetric analysis (TGA) revealed a thermal decomposition temperature of 298.4°C. Long-term natural burial experiments showed that the film completely degraded within 5 months under natural conditions, demonstrating excellent biodegradability.

[0048] Example 2

[0049] PPC (molecular weight 2.0×10 5 , molecular weight distribution is 2.5, monomer carbon dioxide content is 44wt.%, monomer propylene oxide content is 56wt.%, PPC and bamboo powder (average particle size is 1.5μm) were dried in a vacuum drying oven at 80℃ for 48h.

[0050] Then, 39.96 g of dried bamboo powder (BP) was weighed, 2.00 g of vinyl trimethoxysilane (VTMS) was added, and the mixture was thoroughly stirred. Subsequently, 1958.04 g of PPC was weighed and blended with the BP / VTMS mixture at high speed for 3 hours.

[0051] The obtained premix is ​​fed into a twin-screw extruder and melt-blended at 155-180°C and a screw speed of 80 r / min. After secondary extrusion and granulation, uniform composite particles are obtained.

[0052] The composite particles were then vacuum-dried again at 60°C for 38 hours. The dried composite particles were fed into a tape casting machine and tape-cast at 185-210°C and a main machine speed of 4 rpm to produce a 6-μm-thick PPC / BP composite film.

[0053] The prepared PPC / BP composite membrane was subjected to a series of performance tests. According to GB / T 1040.3-2006, the tensile strength was 18.13 MPa and the elongation at break was 254.65%. According to GB / T1038.1-2022, the oxygen and carbon dioxide permeability tests were carried out, and the oxygen permeability was 165 cm 3 / (m 2 ·24h·0.1MPa), carbon dioxide permeability is 144cm 3 / (m 2 · 24h · 0.1MPa). Differential scanning calorimetry (DSC) testing revealed a glass transition temperature of 40.7°C; thermogravimetric analysis (TGA) revealed a thermal decomposition temperature of 292.4°C. The complete degradation cycle of the PPC-based composite membrane of this example was the same as that of Example 1.

[0054] Example 3

[0055] PPC (molecular weight 2.0×10 5 , molecular weight distribution is 2.5, monomer carbon dioxide content is 44wt.%, monomer propylene oxide content is 56wt.%, PPC and bamboo powder (average particle size is 1.5μm) were dried in a vacuum drying oven at 80℃ for 48h.

[0056] Then, 59.97 g of dried bamboo powder (BP) was weighed, 3.00 g of vinyl trimethoxysilane (VTMS) was added, and the mixture was thoroughly stirred. Subsequently, 1937.03 g of PPC was weighed and blended with the BP / VTMS mixture at high speed for 3 hours.

[0057] The obtained premix is ​​fed into a twin-screw extruder and melt-blended at 155-180°C and a screw speed of 80 r / min. After secondary extrusion and granulation, uniform composite particles are obtained.

[0058] The composite particles were then vacuum-dried again at 60°C for 38 hours. The dried composite particles were fed into a tape casting machine and tape-cast at 185-210°C and a main machine speed of 4 rpm to produce a PPC / BP composite film with a thickness of 8 μm.

[0059] The prepared PPC / BP composite membrane was subjected to a series of performance tests. According to GB / T 1040.3-2006, the tensile strength was 11.57 MPa and the elongation at break was 136.35%. According to GB / T1038.1-2022, the oxygen and carbon dioxide permeability tests were carried out, and the oxygen permeability was 187 cm 3 / (m 2 ·24h·0.1MPa), carbon dioxide permeability is 168cm 3 / (m 2 · 24h · 0.1MPa). Differential scanning calorimetry (DSC) testing revealed a glass transition temperature of 39.8°C; thermogravimetric analysis (TGA) revealed a thermal decomposition temperature of 286.8°C. The complete degradation cycle of the PPC-based composite membrane of this example was the same as that of Example 1.

[0060] Comparative Example 1

[0061] PPC (molecular weight 2.0×10 5 , molecular weight distribution is 2.5, monomer carbon dioxide content is 44wt.%, monomer propylene oxide content is 56wt.%, PPC is dried in a vacuum drying oven at 80℃ for 48h.

[0062] The dried composite particles were fed into a tape casting machine and tape-casted at 185-210° C. and a main machine speed of 4 r / min to finally prepare a PPC / BP composite film with a thickness of 8 μm.

[0063] The prepared PPC / BP composite film was subjected to a series of similar performance tests. The tensile strength was measured to be 15.75 MPa, the elongation at break was 292.48%, and the oxygen permeability was 130 cm 3 / (m2 ·24h·0.1MPa), carbon dioxide permeability is 119cm 3 / (m 2 · 24h · 0.1MPa). Differential scanning calorimetry (DSC) testing revealed a glass transition temperature of 38.3°C; thermogravimetric analysis (TGA) revealed a thermal decomposition temperature of 284.3°C. The complete degradation cycle of the PPC-based composite membrane of this example was the same as that of Example 1.

[0064] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A degradable PPC-based composite film, characterized in that: Prepared from the following components in parts by weight: 1937.03-1979.01 parts of polypropylene carbonate, 19.98-59.97 parts of bamboo powder and 1.12-3 parts of vinyltrimethoxysilane.

2. The degradable PPC-based composite membrane according to claim 1, characterized in that Prepared from the following components in parts by weight: 1958.04 parts of polypropylene carbonate, 39.96 parts of bamboo powder and 2 parts of vinyltrimethoxysilane.

3. The degradable PPC-based composite membrane according to claim 1, characterized in that The molecular weight of the polypropylene carbonate is 5.0×10 4 ~3.2×10 5 , the molecular weight distribution is 2.3-2.8, the monomer carbon dioxide content is 39-48wt.%, the monomer propylene oxide content is 56-64wt.%.

4. The degradable PPC-based composite membrane according to claim 1, characterized in that The particle size of the bamboo powder is 0.8-1.8 μm.

5. A method for preparing a degradable PPC-based composite film according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) mixing the polypropylene carbonate, bamboo powder and vinyltrimethoxysilane, melt-blending and granulating to obtain composite particles; 2) drying the composite particles in step 1) and then tape casting to obtain a degradable PPC-based composite film.

6. The preparation method according to claim 5, characterized in that Step 1) The mixing conditions include: a rotation speed of 40 to 120 rpm and a time of 3 hours; The melt blending conditions include: a temperature of 155-180° C. and a rotation speed of 80 rpm.

7. The preparation method according to claim 5, characterized in that Step 2) The drying conditions include: temperature of 60° C. and time of 38 h; The tape casting conditions include: a temperature of 185-210° C. and a rotation speed of 4 rpm.

8. Use of the degradable PPC-based composite membrane according to any one of claims 1 to 4 in improving the mechanical properties of the membrane.

9. Use of the degradable PPC-based composite membrane according to any one of claims 1 to 4 in improving the thermal stability of the membrane.

10. Use of the degradable PPC-based composite membrane according to any one of claims 1 to 4 in increasing the glass transition temperature of the membrane.

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