Environment-friendly degradable plastic film and preparation method thereof

Abstract

The invention belongs to the technical field of degradable plastics, and particularly relates to an environment-friendly degradable plastic film and a preparation method thereof. The environment-friendly degradable plastic film is prepared from the following raw materials in parts by weight: 80 to 90 parts of poly (butylene adipate-co-terephthalate), 15 to 20 parts of modified polylactic acid, 15 to 20 parts of filler, 0.8 to 1.5 parts of lubricant and 0.5 to 1.0 part of plasticizer, the modified polylactic acid is prepared by reacting polylactic acid with a modifier under a heating condition. According to the invention, polylactic acid is modified, so that the biodegradable property of the material is maintained, high-strength interface bonding with the modified carbon fiber filler and PBAT can be maintained, and the film is endowed with excellent mechanical properties and antibacterial properties.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of degradable plastics, and particularly relates to an environmentally-friendly degradable plastic film and a preparation method thereof. BACKGROUND

[0002] With the continuous growth of economy and the continuous upgrading of consumption structure, plastic films have been widely used in food packaging materials, foaming materials, medical delivery pipelines, separation membranes, and aerospace special materials and other key technical fields due to their low biological toxicity, excellent mechanical strength, excellent optical transparency, and good ductility and bending resistance. However, a large amount of plastic waste is decomposed into microplastics or even nanoplastics in the natural environment, and further migrates to water and land ecosystems, causing serious environmental pollution problems and posing potential risks to ecological balance and public health.

[0003] To address this problem, it is urgent to find a sustainable alternative material to petroleum-based plastics. Biodegradable plastics have become an important research focus and industrial development direction due to their environmental friendliness. Among them, polyester degradable plastics such as polybutylene adipate terephthalate (PBAT) have become one of the research and application hotspots due to their similar ductility and film-forming property to polyethylene and biodegradability. CN104448495A discloses a degradable flame-retardant plastic film and a preparation method thereof, which comprises polyethylene, polylactic acid, PBM degradable material, filler, pullulan, antioxidant, ultraviolet absorber and nano flame-retardant composite. The material uses the high oxygen barrier property of pullulan to improve the oxygen barrier property of the film, and enhances the compatibility between the components through the structural similarity of starch and pullulan; at the same time, by adjusting the blending ratio of polyethylene / PBM / pullulan, the oxygen barrier property and degradation performance are adjusted. However, the mechanical property of the material is poor, and the tensile strength is only 5 MPa, which is difficult to meet the actual application requirements. This problem is a common challenge faced by current degradable plastics: in order to improve the degradation performance, multiple additive components are often introduced, but this usually sacrifices the mechanical property of the material, thereby limiting the wide application of degradable plastic films.

[0004] Therefore, it is urgent to develop an environmentally-friendly plastic film with good mechanical property and excellent degradation performance to break through the technical bottleneck and promote the practical application and industrialization development of degradable materials. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the primary purpose of the present application is to provide an environmentally-friendly degradable plastic film, which has excellent mechanical property, antibacterial property and degradable property.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned environmentally friendly biodegradable plastic film.

[0007] The objective of this invention is achieved through the following technical solution: An environmentally friendly biodegradable plastic film comprises the following raw materials in parts by weight: 80-90 parts of polybutylene terephthalate (PET), 15-20 parts of modified polylactic acid (PLA), 15-20 parts of filler, 0.8-1.5 parts of lubricant, and 0.5-1.0 parts of plasticizer; wherein the modified PLA is prepared by reacting PLA with a modifier under heating conditions; The structural formula of the modifier is: .

[0008] Furthermore, the mass ratio of polylactic acid to modifier is 1:(0.15-0.25); the heating temperature is 90-100 ℃, and the reaction time is 5-8 h.

[0009] Furthermore, the preparation process of the modifier is as follows: melamine and 3,5-dihydroxybenzaldehyde are added to methanol, heated to react, and purified to obtain the modifier.

[0010] Furthermore, the molar ratio of melamine to 3,5-dihydroxybenzaldehyde is 1:(2-2.3); the heating reaction is carried out at a temperature of 50-65 °C for 12-16 h.

[0011] Furthermore, the preparation process of the filler is as follows: Carbon fiber, tea saponin, trimethylolpropane tris(3-mercaptopropionate), and 2,2-dimethoxy-2-phenylacetophenone were added to toluene and stirred until homogeneous. The mixture was then reacted under ultraviolet light and purified to obtain the filler.

[0012] Furthermore, the mass ratio of the carbon fiber, tea saponin, trimethylolpropane tris(3-mercaptopropionate), and 2,2-dimethoxy-2-phenylacetophenone is 1:(0.5-0.8):(0.8-1):(0.8-1).

[0013] Furthermore, the power of the ultraviolet light irradiation is 460-500 W, and the reaction time is 1-2 h.

[0014] Further, the lubricant is ethylene bis-stearamide; the plasticizer is tributyl citrate; the weight-average molecular weight of the polybutylene terephthalate-adipate is 40,000-80,000; and the weight-average molecular weight of the polylactic acid is 100,000-200,000.

[0015] A method for preparing the above-mentioned environmentally friendly biodegradable plastic film includes the following steps: mixing the raw materials and adding them to an extruder for melt extrusion granulation, drying and blow molding into a film to obtain the environmentally friendly biodegradable plastic film.

[0016] Furthermore, during the melt granulation process, the screw speed of the extruder is 150-300 rpm, and the heating temperatures of zones 1-5 are 150-160 ℃, 160-165 ℃, 165-175 ℃, 165-175 ℃, and 175-180 ℃, respectively; during the blow molding process, the screw speed is 150-250 rpm, and the heating temperatures of zones 1-5 are 140-150 ℃, 145-155 ℃, 155-160 ℃, 160-170 ℃, and 170-175 ℃, respectively, with a traction speed of 8.5-9.5 m / min.

[0017] The present invention has the following advantages over the prior art: 1. This invention provides an environmentally friendly biodegradable plastic film, comprising raw materials such as polybutylene terephthalate (PBAT), modified polylactic acid (PLA), and modified carbon fiber filler. By modifying the polylactic acid, while maintaining the biodegradability of the material, it can also maintain a high-strength interfacial bond with the modified carbon fiber filler and PBAT, thus endowing the film with excellent mechanical properties and antibacterial function.

[0018] 2. The triazine ring structure introduced into the modified polylactic acid (PLA) of this invention can generate n-π* interactions with the ester groups in PBAT. The resorcinol hydroxyl groups can form hydrogen bonds with the hydroxyl groups on the carbon fiber surface. Simultaneously, the conjugated imine segments undergo π-π stacking interactions with the aromatic rings of tea saponin. These multiple physical-chemical bonds effectively reduce interfacial tension, thereby improving the compatibility between the components. Furthermore, the triazine-aromatic imine bond is easily hydrolyzed under enzymatic hydrolysis and fertilizer stacking, which can shorten the degradation cycle of the material. Moreover, the triazine ring and resorcinol can synergistically disrupt the bacterial membrane potential and inhibit enzyme activity, and together with the conjugated imine, generate reactive oxygen species, thereby inhibiting common bacteria.

[0019] 3. The modified carbon fiber filler of the present invention can form a dual interface combination of hydrogen bonds and ester exchange with PBAT and modified PLA. The thiol ester chain can buffer external forces and enhance toughness, thus improving the mechanical properties of the material. The introduced tea saponin can not only give the material antibacterial properties, but its rigid skeleton can also inhibit the decrease of modulus, thus improving compatibility and mechanical properties simultaneously. Attached Figure Description

[0020] Figure 1 The images shown are FT-IR spectra of polylactic acid and modified polylactic acid in Example 1 of this invention. Figure 2 This is a SEM image of the packing material of Example 1 of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0022] In this embodiment of the invention, the weight-average molecular weight of polybutylene terephthalate (PET) is 60,000, the weight-average molecular weight of polylactic acid (PLA) is 150,000, and the carbon fiber is polyacrylonitrile-based carbon fiber.

[0023] Preparation Example 1 Preparation Example 1 provides a modifier, the preparation process of which is as follows: Melamine (10 mmol) and 3,5-dihydroxybenzaldehyde (CAS: 26153-38-8, 22 mmol) were added to 20 mL of methanol and stirred until homogeneous. The mixture was then heated to 60 °C and reacted for 14 h. The reaction solution was concentrated and diluted with 10 mL of a mixed solvent (V... 乙醇 :V 水 =1:5) pulp purification, filtration, and drying of the filter cake at 55 ℃ for 2.5 h to obtain the modifier; 1 H NMR (C 17 H 14 N6O4, 400 MHz,DMSO-d6) δ 9.53 (s, 2H), 9.07 (s, 4H), 6.91 (s, 2H), 6.85 (s, 4H), 6.33 (t,2H); HRMS(ESI) calcd for [M+H] + 367.11, found 367.10.

[0024] Preparation Example 2 Preparation Example 2 provides a modifier, the preparation process of which is as follows: Melamine (10 mmol) and 3,5-dihydroxybenzaldehyde (20 mmol) were added to 20 mL of methanol and stirred until homogeneous. The mixture was then heated to 50 °C and reacted for 16 h. The reaction solution was concentrated and diluted with 10 mL of a mixed solvent (V... 乙醇 :V 水 =1:5) pulp purification, filtration, and drying of the filter cake at 50 ℃ for 3 h to obtain the modifier.

[0025] Preparation Example 3 Preparation Example 3 provides a modifier, the preparation process of which is as follows: Melamine (10 mmol) and 3,5-dihydroxybenzaldehyde (23 mmol) were added to 20 mL of methanol and stirred until homogeneous. The mixture was then heated to 65 °C and reacted for 12 h. The reaction solution was concentrated and diluted with 10 mL of a mixed solvent (V... 乙醇 :V 水 =1:5) pulp purification, filtration, and drying of the filter cake at 60 ℃ for 2 h to obtain the modifier.

[0026] Example 1 Example 1 provides an environmentally friendly biodegradable plastic film comprising the following raw materials in parts by weight: 85 parts of polybutylene terephthalate-adipate, 18 parts of modified polylactic acid, 18 parts of filler, 1.2 parts of ethylene bis-stearamide, and 0.8 parts of tributyl citrate; The preparation process of the modified polylactic acid is as follows: 20 g of polylactic acid and 4 g of the modifier from Preparation Example 1 were added to 200 mL of toluene and reacted at 95 °C for 6 h. The toluene was removed by concentration, and then 30 mL of methanol was added and stirred for 10 min. The mixture was filtered, and the filter cake was washed successively with methanol and pure water. The filter cake was then dried at 90 °C for 36 h to obtain modified polylactic acid.

[0027] The preparation process of the filler is as follows: 10 g of carbon fiber, 6 g of tea saponin, 9 g of trimethylolpropane tris(3-mercaptopropionate), and 9 g of 2,2-dimethoxy-2-phenylacetophenone were placed in 50 mL of toluene and stirred until homogeneous. The mixture was then reacted under a UV lamp (500 W) for 1.5 h. The reaction solution was filtered, and the filter cake was washed successively with toluene and glycerol. The filter cake was then dried at 55 ℃ for 7 h to obtain the packing material.

[0028] Example 1 also provides a method for preparing the above-mentioned environmentally friendly biodegradable plastic film, the specific steps of which are as follows: The raw materials are mixed evenly according to the formula, and then added to a twin-screw extruder for melt extrusion granulation. The screw speed is set to 200 rpm, and the heating temperatures of zones 1-5 are 155 ℃, 160 ℃, 170 ℃, 170 ℃, and 175 ℃ respectively. After granulation, the film is dried at 70 ℃ for 8 hours, and then blown into a film to obtain the environmentally friendly biodegradable plastic film. During the blown film forming process, the screw speed is 200 rpm, the heating temperatures of zones 1-5 are 145 ℃, 150 ℃, 155 ℃, 165 ℃, and 170 ℃ respectively, and the traction speed is 9.0 m / min.

[0029] Example 2 Example 2 provides an environmentally friendly biodegradable plastic film comprising the following raw materials in parts by weight: 80 parts of polybutylene terephthalate-adipate, 15 parts of modified polylactic acid, 15 parts of filler, 0.8 parts of ethylene bis-stearamide, and 0.5 parts of tributyl citrate. The preparation process of the modified polylactic acid is as follows: 20 g of polylactic acid and 3 g of the modifier from Preparation Example 2 were added to 200 mL of toluene and reacted at 90 °C for 8 h. The toluene was removed by concentration, and then 30 mL of methanol was added and stirred for 10 min. The mixture was filtered, and the filter cake was washed successively with methanol and pure water. The filter cake was then dried at 80 °C for 48 h to obtain modified polylactic acid.

[0030] The preparation process of the filler is as follows: 10 g of carbon fiber, 5 g of tea saponin, 8 g of trimethylolpropane tris(3-mercaptopropionate), and 8 g of 2,2-dimethoxy-2-phenylacetophenone were placed in 50 mL of toluene and stirred until homogeneous. The mixture was then reacted under ultraviolet light (460 W) for 2 h. The reaction solution was filtered, and the filter cake was washed with toluene and glycerol in sequence. The filter cake was then dried at 50 ℃ for 8 h to obtain the packing material.

[0031] Example 2 also provides a method for preparing the above-mentioned environmentally friendly biodegradable plastic film, the specific steps of which are as follows: The raw materials are mixed evenly according to the formula, and then added to a twin-screw extruder for melt extrusion granulation. The screw speed is set to 150 rpm, and the heating temperatures of zones 1-5 are 150 ℃, 160 ℃, 165 ℃, 165 ℃, and 175 ℃ respectively. After granulation, the film is dried at 60 ℃ for 10 h, and then blown into a film to obtain the environmentally friendly biodegradable plastic film. During the blown film forming process, the screw speed is 150 rpm, the heating temperatures of zones 1-5 are 140 ℃, 145 ℃, 155 ℃, 160 ℃, and 170 ℃ respectively, and the traction speed is 8.5 m / min.

[0032] Example 3 Example 3 provides an environmentally friendly biodegradable plastic film comprising the following raw materials in parts by weight: 90 parts of polybutylene terephthalate-adipate, 20 parts of modified polylactic acid, 20 parts of filler, 1.5 parts of ethylene bis-stearamide, and 1.0 part of tributyl citrate. The preparation process of the modified polylactic acid is as follows: 20 g of polylactic acid and 5 g of the modifier from Preparation Example 3 were added to 200 mL of toluene and reacted at 100 °C for 5 h. The toluene was removed by concentration, and then 30 mL of methanol was added and stirred for 10 min. The mixture was filtered, and the filter cake was washed successively with methanol and pure water. The filter cake was then dried at 100 °C for 24 h to obtain modified polylactic acid.

[0033] The preparation process of the filler is as follows: 10 g of carbon fiber, 8 g of tea saponin, 10 g of trimethylolpropane tris(3-mercaptopropionate), and 10 g of 2,2-dimethoxy-2-phenylacetophenone were placed in 50 mL of toluene and stirred until homogeneous. The mixture was then reacted under a UV lamp (500 W) for 1 h. The reaction solution was filtered, and the filter cake was washed successively with toluene and glycerol. The filter cake was then dried at 60 ℃ for 6 h to obtain the packing material.

[0034] Example 3 also provides a method for preparing the above-mentioned environmentally friendly biodegradable plastic film, the specific steps of which are as follows: The raw materials are mixed evenly according to the formula, and then added to a twin-screw extruder for melt extrusion granulation. The screw speed is set to 300 rpm, and the heating temperatures of zones 1-5 are 160 ℃, 165 ℃, 175 ℃, 175 ℃, and 180 ℃ respectively. After granulation, the film is dried at 80 ℃ for 6 hours, and then blown into a film to obtain the environmentally friendly biodegradable plastic film. During the blown film forming process, the screw speed is 250 rpm, the heating temperatures of zones 1-5 are 150 ℃, 155 ℃, 160 ℃, 170 ℃, and 175 ℃ respectively, and the traction speed is 9.5 m / min.

[0035] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that modified polylactic acid is replaced with polylactic acid.

[0036] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that the filler is replaced with carbon fiber.

[0037] Structural characterization The polylactic acid and modified polylactic acid of Example 1 were characterized by infrared spectroscopy. The FT-IR spectra of polylactic acid and modified polylactic acid are shown below. Figure 1 As shown. From Figure 1 It can be seen that, compared to polylactic acid, modified polylactic acid has a lower viscosity at 1500-1700 cm⁻¹. -1 Multiple absorptions were observed in the region (specifically at 1650 cm⁻¹). -1 1550 cm -1 This indicates that a secondary amide structure has been introduced into the system; 3500 cm -1 The changes in the intensity and shift of the broad peak reflect a significant alteration in the hydrogen bonding environment of the hydroxyl / carboxyl groups, indicating that the modification process has affected the polar groups of the polylactic acid end groups or segments. This shows that the modifier has been grafted onto polylactic acid to obtain modified polylactic acid.

[0038] The packing material of Example 1 was subjected to scanning electron microscopy (SEM) testing. The SEM image of the packing material is shown below. Figure 2 As shown.

[0039] Performance testing ① Tensile property test: The transverse and longitudinal tensile properties of the films obtained in Examples 1-3 and Comparative Examples 1-2 were tested according to GB / T 1040.3-2006. The sample length was 150 mm, the width was 15 mm, the test speed was 200 mm / min, and each sample was measured at least 5 times. The average value of the results was taken. The results are shown in Table 1.

[0040] ② Antibacterial performance test: Referring to standard JIS Z2801, the antibacterial rate of the films obtained in Examples 1-3 and Comparative Examples 1-2 against Escherichia coli and Staphylococcus aureus was determined. The performance test results are shown in Table 2.

[0041] ③ Degradation performance test: The biodegradation rate of the films obtained in Examples 1-3 and Comparative Examples 1-2 was determined according to standard GB / T 19277.1-2025. The performance test results are shown in Table 2.

[0042] Table 1 Table 2 As can be seen from Tables 1 and 2, the plastic films prepared in Examples 1-3 of the present invention have excellent mechanical properties, antibacterial properties and biodegradability.

[0043] Compared to Example 1, Comparative Example 1, where modified polylactic acid was replaced with polylactic acid, showed a decrease in various properties of the film. This indicates that modified polylactic acid can improve the mechanical, antibacterial, and biodegradable properties of the film. Specific analysis reveals that the triazine ring structure introduced into the modified polylactic acid can interact with the ester groups in PBAT through n-π* interactions. The resorcinol hydroxyl groups can form hydrogen bonds with the hydroxyl groups on the carbon fiber surface. Simultaneously, the conjugated imine segments undergo π-π stacking with the aromatic rings of tea saponin. These multiple physical-chemical bonds effectively reduce interfacial tension, thereby improving the compatibility between the components. Furthermore, the triazine-aromatic imine bond is easily hydrolyzed under enzymatic hydrolysis and fertilizer stacking, shortening the degradation cycle of the material. The triazine ring and catechol synergistically disrupt the bacterial membrane potential and inhibit enzyme activity, while the conjugated imine generates reactive oxygen species, thus inhibiting common bacteria.

[0044] Compared to Example 1, Comparative Example 2, which replaced the modified carbon fiber with carbon fiber, showed a significant decrease in the mechanical properties of the film and a reduction in its antibacterial properties. Detailed analysis reveals that the modified carbon fiber filler of this invention can form a dual interface of hydrogen bonding and transesterification with PBAT and modified PLA. The thiol ester chains can buffer external forces and enhance toughness, thus improving the mechanical properties of the material. Furthermore, the introduced tea saponin not only imparts antibacterial properties to the material, but its rigid framework also inhibits modulus reduction, simultaneously improving compatibility and mechanical properties.

[0045] In summary, this invention modifies polylactic acid, maintaining the material's biodegradability while ensuring a high-strength interfacial bond with modified carbon fiber filler and PBAT. This endows the film with excellent mechanical properties and antibacterial function. The prepared film can be effectively used in the packaging of products in the fields of hygiene products, food, and electronic products. It is biodegradable, safe, and environmentally friendly.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. An environmentally friendly biodegradable plastic film, characterized in that, The raw materials include the following parts by weight: 80-90 parts of polybutylene terephthalate (PET), 15-20 parts of modified polylactic acid (PLA), 15-20 parts of filler, 0.8-1.5 parts of lubricant, and 0.5-1.0 parts of plasticizer; wherein the modified PLA is prepared by reacting PLA with a modifier under heating conditions. The structural formula of the modifier is: 。 2. The environmentally friendly biodegradable plastic film as described in claim 1, characterized in that, The mass ratio of polylactic acid to modifier is 1:(0.15-0.25); the heating temperature is 90-100 ℃, and the reaction time is 5-8 h.

3. The environmentally friendly biodegradable plastic film as described in claim 1, characterized in that, The preparation process of the modifier is as follows: melamine and 3,5-dihydroxybenzaldehyde are added to methanol, heated to react, and purified to obtain the modifier.

4. The environmentally friendly biodegradable plastic film as described in claim 3, characterized in that, The molar ratio of melamine to 3,5-dihydroxybenzaldehyde is 1:(2-2.3); the heating reaction is carried out at a temperature of 50-65 °C for 12-16 h.

5. The environmentally friendly biodegradable plastic film as described in claim 1, characterized in that, The preparation process of the filler is as follows: Carbon fiber, tea saponin, trimethylolpropane tris(3-mercaptopropionate), and 2,2-dimethoxy-2-phenylacetophenone were added to toluene and stirred until homogeneous. The mixture was then reacted under ultraviolet light and purified to obtain the filler.

6. The environmentally friendly biodegradable plastic film as described in claim 5, characterized in that, The mass ratio of the carbon fiber, tea saponin, trimethylolpropane tris(3-mercaptopropionate), and 2,2-dimethoxy-2-phenylacetophenone is 1:(0.5-0.8):(0.8-1):(0.8-1).

7. The environmentally friendly biodegradable plastic film as described in claim 5, characterized in that, The power of the ultraviolet light irradiation is 460-500 W, and the reaction time is 1-2 h.

8. The environmentally friendly biodegradable plastic film as described in claim 1, characterized in that, The lubricant is ethylene bis-stearamide; the plasticizer is tributyl citrate; the weight-average molecular weight of the polybutylene terephthalate-adipate is 40,000-80,000; and the weight-average molecular weight of the polylactic acid is 100,000-200,000.

9. A method for preparing an environmentally friendly biodegradable plastic film according to any one of claims 1-8, characterized in that, Includes the following steps: After mixing the raw materials, they are added to an extruder for melt extrusion and granulation. After drying, they are blown into a film to obtain the environmentally friendly and biodegradable plastic film.

10. The method for preparing the environmentally friendly biodegradable plastic film as described in claim 9, characterized in that, During the melt granulation process, the screw speed of the extruder is 150-300 rpm, and the heating temperatures of zones 1-5 are 150-160 ℃, 160-165 ℃, 165-175 ℃, 165-175 ℃, and 175-180 ℃, respectively. During the blow molding process, the screw speed is 150-250 rpm, and the heating temperatures of zones 1-5 are 140-150 ℃, 145-155 ℃, 155-160 ℃, 160-170 ℃, and 170-175 ℃, respectively. The traction speed is 8.5-9.5 m / min.

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