A starch-based degradable composite film

Abstract

This invention discloses a high-starch-content plastic film comprising 30-70 parts by weight of plant starch, 3-20 parts by weight of polyurethane prepolymer, 30-55 parts by weight of composite polyester, 0.5-10 parts by weight of compatibilizer, 0.5-5 parts by weight of reinforcing agent, and 0.5-3 parts by weight of lubricant. It is prepared by a process involving mixing plant starch masterbatch, composite polyester, polyurethane prepolymer, compatibilizer, reinforcing agent, and lubricant, followed by twin-screw extrusion blending and blow molding. The starch modified with the polyurethane prepolymer exhibits a significantly reduced number of hydroxyl groups in its chain structure, resulting in a marked improvement in hydrophobicity. The blown film obtained after combining the composite polyester and modified starch has a smooth surface, high transparency, and excellent degradation performance while maintaining good mechanical properties. Simultaneously, the significantly increased starch content reduces the overall material cost.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a low-cost, high-proportion plant starch / bicomponent polymer polyester composite biodegradable film and its preparation method. Background Technology

[0002] Plastics are widely used in packaging bags, mulch films, and disposable tableware due to their low cost, high mechanical properties, and ease of processing. However, traditional non-degradable plastics are mainly made from petroleum-based materials such as polyethylene. In addition to being non-renewable and having limited resources, their overuse can lead to the accumulation of solid waste. The problem of "white pollution" not only damages land resources but also causes a large amount of plastic waste to accumulate in the marine environment, and its non-degradability poses a serious threat to the natural environment on which humans depend for survival.

[0003] Starch is not only an abundant, low-cost resource with high renewability and biodegradability, but its degradation products are also beneficial to plant growth and do not cause risks such as soil compaction or seawater pollution. This indicates that starch-based materials are suitable to replace petroleum-based plastics and become one of the raw materials for the preparation of new degradable materials.

[0004] In industrial production, blown film technology is commonly used to blow-mold composite materials to optimize production factors such as output and cost. However, due to the lack of thermoplastic properties and low processability of starch, pure starch materials cannot be blown into films. Currently, starch-based composite materials prepared by blending starch with biodegradable polyesters such as polybutylene adipate (PBAT) and polylactic acid (PLA) are promising biodegradable composite materials. They can overcome the limitations of starch's inherent properties when used in blown film processes to some extent, while also reducing the material cost of pure biodegradable polyester materials as film products.

[0005] Currently, many researchers prepare composite membranes by blending starch and biodegradable polyester, but the starch content in these membranes is relatively low. Higher starch content leads to lower composite material costs, but also reduces material performance and increases processing difficulty. More importantly, with increasing starch content, starch and polyester often become difficult to mix uniformly; the hydrophilicity of starch and the hydrophobicity of polyester result in extremely poor compatibility. Therefore, increasing the starch content of composite materials, enhancing the interfacial bonding between starch and polyester, and implementing continuous preparation methods are crucial for the development of starch-based biodegradable materials. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art and, based on the research of low-cost biodegradable materials, provide a plant starch / polymer polyester composite biodegradable film with high starch content and its preparation method. This not only maintains the good mechanical properties of the material but also increases the starch content in the composite material, thereby significantly reducing the cost of the composite material.

[0007] In order to achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a starch-based plastic film, which is a plant starch / polymer polyester composite biodegradable material film, comprising the following components:

[0009]

[0010] In another preferred embodiment, the starch-based plastic film of the present invention is composed of plant starch, composite polyester, polyurethane prepolymer, compatibility agent, reinforcing agent, and lubricant, and is obtained by a preparation process of mixing, twin-screw extrusion blending, and blow molding.

[0011] In another preferred embodiment, the plant starch is at least one of potato starch, corn starch, wheat starch, cassava starch, and pea starch.

[0012] In another preferred embodiment, the plant starch is in the form of 30-65, 30-60, or 35-55 parts by weight.

[0013] In another preferred embodiment, the plant starch used in this invention has an amylose content of 15 wt% or more and a moisture content of less than or equal to 11 wt%.

[0014] In another preferred embodiment, the polyurethane prepolymer is prepared by reacting one of polyethylene adipate, polycaprolactone diol, polytetrahydrofuran ether diol, polybutylene adipate, and polybutylene succinate with one of diphenylmethane diisocyanate, hexamethylene diisocyanate, and toluene diisocyanate.

[0015] In another preferred embodiment, the isocyanate content of the polyurethane prepolymer is 3wt%-10wt%.

[0016] In another preferred embodiment, the polyurethane prepolymer is 5-15 parts by weight or 5-12 parts by weight.

[0017] In another preferred embodiment, the composite polyester comprises polybutylene adipate / terephthalate (PBAT) and polylactic acid (PLA), wherein the mass percentage of PBAT is 70%-99% of the total composite polyester material, and the mass percentage of PLA is 30%-1% of the total composite polyester material.

[0018] Polybutylene adipate / terephthalate (PBAT) and polylactic acid (PLA) are two of the most widely used biodegradable polyester materials in industry. PBAT has excellent toughness and ductility and good elongation at break, while PLA has good rigidity and good tensile strength.

[0019] More preferably, the PBAT mass percentage is 75%-95% of the total composite polyester material, and the PLA mass percentage is 25%-5% of the total composite polyester material.

[0020] More preferably, the PBAT mass percentage is 80%-92% of the total composite polyester material, and the PLA mass percentage is 20%-8% of the total composite polyester material.

[0021] In another preferred embodiment, the composite polyester is 35-50 parts by weight.

[0022] More preferably, the compatibility agent is at least one of citric acid, maleic anhydride, chain extender PBAT, (Jia Yi Rong) chain extender SAG-008, (BASF) chain extender ADR-4370, (BASF) chain extender ADR4468, (Shanxi Chemical) chain extender KL-E4370, KL-E4370B, (Ke Ai Si) chain extender KS-05, and (Shanghai Xiu Yuan) chain extender XY4370.

[0023] In another preferred embodiment, the compatibility agent is a chain extender.

[0024] In another preferred embodiment, the compatibility agent is 0.8-6 or 1-3 parts by weight.

[0025] More preferably, the plant starch is at least one of corn starch, wheat starch, cassava starch, potato starch, and pea starch, wherein the amylose content of the plant starch is more than 15%, and its moisture content is less than or equal to 11%.

[0026] More preferably, the reinforcing agent is at least one of attapulgite, halloysite, nano-silica, nano-calcium carbonate, nano-zinc oxide, montmorillonite, and bentonite.

[0027] In another preferred embodiment, the reinforcing agent is 0.8-4 or 1-3 parts by weight.

[0028] More preferably, the lubricant is at least one selected from Tween, calcium stearate, magnesium stearate, erucamide, gramine erucamide, and docosamide.

[0029] In another preferred embodiment, the lubricant is 0.5-1.5 or 0.5-1 parts by weight.

[0030] In the thin film prepared in this invention, the content of at least one chain extender or prepolymer is not zero.

[0031] In another preferred embodiment, the starch-based plastic film is a plant starch / polymer polyester composite biodegradable material film, comprising the following components:

[0032]

[0033] In another preferred embodiment, the starch-based plastic film is a plant starch / polymer polyester composite biodegradable material film, comprising the following components:

[0034]

[0035] A second aspect of the present invention provides a method for preparing the starch-based plastic film described in the first aspect, comprising the following steps:

[0036] S1: Dry the plant starch, seal it, and store it for later use;

[0037] S2: Place the dried plant starch into a mixer, add polyurethane prepolymer to modify the plant starch, and use a pulverizer to process the modified starch into granules of 20-60 mesh size, then seal and store for later use.

[0038] S3: Put the modified starch granules obtained in S2 into a high-speed mixer, add the composite polyester, then add the compatibility agent, reinforcing agent and lubricant, mix evenly and take it out for later use.

[0039] S4: The mixture prepared in S3 is added to a twin-screw extruder for extrusion, and then drawn, water-cooled and granulated on a twin-screw auxiliary machine to obtain a light yellow cylindrical granular material;

[0040] S5: After drying the granular material obtained in S4, add it to a blown film machine to blow film, and then use a winding device to obtain a starch-based biodegradable film.

[0041] In another preferred embodiment, the plant starch is dried in an oven at 60°C-80°C for 3-6 hours.

[0042] In another preferred embodiment, the temperature in the internal mixer is set at 80℃-100℃, and the mixing time is 20min-45min.

[0043] In another preferred embodiment, the modified starch, after being uniformly mixed in the internal mixer, is left at room temperature for 12-24 hours.

[0044] In another preferred embodiment, the temperature inside the high-temperature mixer is controlled at 20℃-40℃, and the mixing time is 5min-15min.

[0045] In another preferred embodiment, the temperature of the feeding section of the twin-screw extruder is set to 120℃-130℃, the temperature of the intermediate section is set to 130℃-155℃, and the temperature of the die head section is set to 140℃-160℃.

[0046] In another preferred embodiment, the particulate material obtained in S4 is dried in an oven for 4-6 hours at a temperature of 60°C-80°C.

[0047] In another preferred embodiment, the temperature of the blown film die head in S5 is 140℃-160℃, the body temperature is 130℃-155℃, and the blown film temperature is 140℃-150℃.

[0048] In a preferred embodiment, the preparation method of the present invention includes the following steps:

[0049] S1: Dry the plant starch granules in an oven at 60℃-80℃ for 3-6 hours, then seal and store for later use;

[0050] S2: Place the dried plant starch into a mixer, add polyurethane prepolymer, and modify the plant starch. Set the temperature in the mixer to 80℃-100℃ and the mixing time to 20min-45min. Take out the uniformly mixed modified starch and let it stand at room temperature for 12h-24h. Use a pulverizer to process the modified starch into granules of 20-60 mesh size, and seal and store for later use.

[0051] S3: Place the modified starch granules obtained in S2 into a high-speed mixer, add the PBAT / PLA masterbatch mixture, then add compatibility aids, reinforcing agents, and lubricants. Control the temperature inside the high-speed mixer at 20℃-40℃, and the mixing time at 5min-15min. After mixing evenly, remove and set aside.

[0052] S4: Add the prepared mixture into the twin-screw extruder, set the temperature of each zone, set the temperature of the feeding section to 120℃-130℃, the temperature of the middle section to 130℃-155℃, and the temperature of the die head to 140℃-160℃. Then, the mixture is stretched, water-cooled, and granulated on the twin-screw auxiliary machine to obtain light yellow cylindrical granular raw materials.

[0053] S5: Dry the granular material obtained in S4 in an oven for 4-6 hours at a temperature of 60℃-80℃. Then, add the dried material to a blown film machine for blown film production.

[0054] S6: The temperature of the die head in S5 is 140℃-160℃, the machine body temperature is 130℃-155℃, and the blown film temperature is 140℃-150℃. Starch-based biodegradable films are obtained through a winding device.

[0055] In another preferred embodiment, the amounts of each component added are as follows:

[0056]

[0057] In another preferred embodiment, the plant starch is at least one of potato starch, corn starch, wheat starch, cassava starch, and pea starch.

[0058] In another preferred embodiment, the plant starch is present in parts by weight of 45-65, 40-60, or 35-55.

[0059] In another preferred embodiment, the plant starch used in this invention has an amylose content of 15 wt% or more and a moisture content of less than or equal to 11 wt%.

[0060] In another preferred embodiment, the polyurethane prepolymer is prepared by reacting one of polyethylene adipate, polycaprolactone diol, polytetrahydrofuran ether diol, polybutylene adipate, and polybutylene succinate with one of diphenylmethane diisocyanate, hexamethylene diisocyanate, and toluene diisocyanate.

[0061] In another preferred embodiment, the isocyanate content of the polyurethane prepolymer is 3wt%-10wt%.

[0062] In another preferred embodiment, the polyurethane prepolymer is 5-15 parts by weight or 5-12 parts by weight.

[0063] In another preferred embodiment, the composite polyester comprises polybutylene adipate / terephthalate (PBAT) and polylactic acid (PLA), wherein the mass percentage of PBAT is 70%-99% of the total composite polyester material, and the mass percentage of PLA is 30%-1% of the total composite polyester material.

[0064] Polybutylene adipate / terephthalate (PBAT) and polylactic acid (PLA) are two of the most widely used biodegradable polyester materials in industry. PBAT has excellent toughness and ductility and good elongation at break, while PLA has good rigidity and good tensile strength.

[0065] More preferably, the PBAT mass percentage is 75%-95% of the total composite polyester material, and the PLA mass percentage is 25%-5% of the total composite polyester material.

[0066] More preferably, the PBAT mass percentage is 80%-92% of the total composite polyester material, and the PLA mass percentage is 20%-8% of the total composite polyester material.

[0067] In another preferred embodiment, the composite polyester is 35-50 parts by weight.

[0068] More preferably, the compatibility agent is at least one of citric acid, maleic anhydride, chain extender PBAT, (Jia Yi Rong) chain extender SAG-008, (BASF) chain extender ADR-4370, (BASF) chain extender ADR4468, (Shanxi Chemical) chain extender KL-E4370, KL-E4370B, (Ke Ai Si) chain extender KS-05, and (Shanghai Xiu Yuan) chain extender XY4370.

[0069] In another preferred embodiment, the compatibility agent is a chain extender.

[0070] In another preferred embodiment, the compatibility agent is 0.8-6 or 1-3 parts by weight.

[0071] More preferably, the plant starch is at least one of corn starch, wheat starch, cassava starch, potato starch, and pea starch, wherein the amylose content of the plant starch is more than 15%, and its moisture content is less than or equal to 11%.

[0072] More preferably, the reinforcing agent is at least one of attapulgite, halloysite, nano-silica, nano-calcium carbonate, nano-zinc oxide, montmorillonite, and bentonite.

[0073] In another preferred embodiment, the reinforcing agent is 0.8-4 or 1-3 parts by weight.

[0074] More preferably, the lubricant is at least one selected from Tween, calcium stearate, magnesium stearate, erucamide, gramine erucamide, and docosamide.

[0075] In another preferred embodiment, the lubricant is 0.5-1.5 or 0.5-1 parts by weight.

[0076] In the thin film prepared in this invention, the content of at least one chain extender or prepolymer is not zero.

[0077] This invention has at least the following advantages:

[0078] First, this invention utilizes polyurethane prepolymer to modify plant starch, reducing the number of hydrophilic hydroxyl groups on the starch long chain and simultaneously reducing the number of hydrogen bonds within the starch molecule, thereby altering the original molecular structure of starch and improving the compatibility between starch materials and polyester materials.

[0079] Secondly, this invention utilizes compatibility additives to improve the compatibility between starch, PBAT, and PLA, and significantly enhances the material properties. This provides a performance foundation for starch-based materials with a high starch content, making it possible to increase the starch content in composite materials.

[0080] Third, the prepolymer and compatibilizer bring better compatibility to the composite material, resulting in a more uniform and smooth surface morphology. Furthermore, it can maintain good mechanical properties even with high starch content, with tensile strength exceeding 16 MPa and elongation at break reaching 931%.

[0081] Fourth, the starch-based biodegradable film prepared by the method of the present invention has better degradation performance than ordinary starch-based films. It also overcomes problems such as difficult processing and poor hydrophobicity, making it suitable for large-scale industrial production. Moreover, the product is environmentally friendly, and its degradation rate can exceed 90 wt% within 90 days.

[0082] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Due to space limitations, they will not be described in detail here. Attached Figure Description

[0083] Figure 1 The mechanical performance test results are shown.

[0084] Figure 2 This is a scanning electron microscope image.

[0085] Figure 3 The blown film process is shown.

[0086] Figure 4 The morphology of the thin film is shown. Detailed Implementation

[0087] Through extensive and in-depth research, the inventors prepared a hydrophilic modified starch by prepolymer modification, which was then composited with polyester materials (polybutylene adipate / terephthalate terephthalate PBAT and polylactic acid PLA). By adding compatibility additives to improve the compatibility among starch, PBAT, and PLA, a starch / PBAT / PLA composite material with excellent properties was prepared by combining the advantages of the three materials. Finally, the prepared composite material was blown into a starch / PBAT / PLA film material using a blown film process. Based on this, the invention was completed. The successful preparation of this material signifies that high-starch-content biodegradable materials can be applied in the plastics industry, such as agricultural films and disposable tableware. It possesses advantages such as low material cost, excellent mechanical strength, and biodegradability, thus advancing the research and development of starch-based biodegradable materials.

[0088] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions (such as those described in Sambrook et al., Molecular Cloning: A Laboratory Manual (New York: Cold Spring Harbor Laboratory Press, 1989)) or as recommended by the manufacturer. Unless otherwise stated, percentages and parts are weight percentages and parts by weight.

[0089] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0090] Example 1

[0091] The high-starch-based biodegradable composite film of this embodiment is prepared from the following components:

[0092]

[0093] Its preparation method includes the following steps:

[0094] S1: Dry the corn starch granules in a 70℃ oven for 3 hours, then seal and store for later use;

[0095] S2: Place the dried corn starch into a mixer, add polyurethane prepolymer, and modify the plant starch. Set the temperature in the mixer to 85℃ and the mixing time to 30 minutes. Take out the evenly mixed modified starch and let it stand at room temperature for 14 hours. Use a pulverizer to process the modified starch into 40-mesh granules, and seal and store for later use.

[0096] S3: Place the modified starch granules obtained in S2 into a high-speed mixer, add PBAT / PLA composite polyester material at a mass ratio of 10:1, then add chain extender, reinforcing agent and lubricant. The temperature inside the high-speed mixer is controlled at 25℃, and the mixing time is 10 minutes. After mixing, take it out for later use.

[0097] S4: Add the prepared mixture into the twin-screw extruder, and set the temperature for each zone as follows:

[0098] District 8 District 7 District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 145℃ 145℃ 150℃ 145℃ 145℃ 140℃ 130℃ 120℃

[0099] Zones one and eight are the front and rear sections, respectively, while zones two through seven are the middle sections. The raw material is then drawn, water-cooled, and granulated on a twin-screw auxiliary machine to obtain light yellow cylindrical granular raw materials.

[0100] S5: Dry the granular material obtained in S4 in an oven at a temperature of 75°C for 4 hours. Then, add the dried raw material to a blown film machine for blown film production.

[0101] S6: Set the temperature for each zone of the blown film machine. The temperature settings for each zone are as follows:

[0102] District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 150℃ 155℃ 150℃ 145℃ 140℃ 130℃

[0103] Zone 6 is the head section of the blown film machine, Zones 2 to 5 are the middle section, and Zone 1 is the front section.

[0104] Starch-based biodegradable films are obtained using a winding device.

[0105] Example 2

[0106] The high-starch-based biodegradable composite film of this embodiment is prepared from the following components:

[0107]

[0108]

[0109] The preparation method includes the following steps:

[0110] S1: Dry potato starch granules in a 70℃ oven for 3 hours, then seal and store for later use;

[0111] S2: Place the dried potato starch into a mixer, add polyurethane prepolymer to modify the plant starch. Set the temperature in the mixer to 85℃ and the mixing time to 30 minutes. Take out the evenly mixed modified starch and let it stand at room temperature for 14 hours. Use a pulverizer to process the modified starch into 40-mesh granules and seal them for later use.

[0112] S3: Place the modified starch granules obtained in S2 into a high-speed mixer, add PBAT / PLA composite polyester material at a mass ratio of 10:1, then add chain extender, reinforcing agent and lubricant. The temperature inside the high-speed mixer is controlled at 25℃, and the mixing time is 10 minutes. After mixing, take it out for later use.

[0113] S4: Add the prepared mixture into the twin-screw extruder, and set the temperature for each zone as follows:

[0114] District 8 District 7 District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 145℃ 145℃ 150℃ 145℃ 145℃ 140℃ 130℃ 120℃

[0115] Zones one and eight are the front and rear sections, respectively, while zones two through seven are the middle sections. The raw material is then drawn, water-cooled, and granulated on a twin-screw auxiliary machine to obtain light yellow cylindrical granular raw materials.

[0116] S5: Dry the granular material obtained in S4 in an oven at a temperature of 75°C for 4 hours. Then, add the dried raw material to a blown film machine for blown film production.

[0117] S6: Set the temperature for each zone of the blown film machine. The temperature settings for each zone are as follows:

[0118] District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 150℃ 155℃ 150℃ 145℃ 140℃ 130℃

[0119] Zone 6 is the head section of the blown film machine, Zones 2 to 5 are the middle section, and Zone 1 is the front section.

[0120] Starch-based biodegradable films are obtained using a winding device.

[0121] Example 3

[0122] The high-starch-based biodegradable composite film of this embodiment is prepared from the following components:

[0123]

[0124] The preparation method includes the following steps:

[0125] S1: Dry the corn starch granules in a 70℃ oven for 3 hours, then seal and store for later use;

[0126] S2: Place the dried corn starch into a mixer, add polyurethane prepolymer, and modify the plant starch. Set the temperature in the mixer to 85℃ and the mixing time to 30 minutes. Take out the evenly mixed modified starch and let it stand at room temperature for 14 hours. Use a pulverizer to process the modified starch into 40-mesh granules, and seal and store for later use.

[0127] S3: Place the modified starch granules obtained in S2 into a high-speed mixer, add PBAT / PLA composite polyester material at a mass ratio of 10:1, then add chain extender, reinforcing agent and lubricant. The temperature inside the high-speed mixer is controlled at 25℃, and the mixing time is 10 minutes. After mixing, take it out for later use.

[0128] S4: Add the prepared mixture into the twin-screw extruder, and set the temperature for each zone as follows:

[0129] District 8 District 7 District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 145℃ 145℃ 150℃ 145℃ 145℃ 140℃ 130℃ 120℃

[0130] Zones one and eight are the front and rear sections, respectively, while zones two through seven are the middle sections. The raw material is then drawn, water-cooled, and granulated on a twin-screw auxiliary machine to obtain light yellow cylindrical granular raw materials.

[0131] S5: Dry the granular material obtained in S4 in an oven at a temperature of 75°C for 4 hours. Then, add the dried raw material to a blown film machine for blown film production.

[0132] S6: Set the temperature for each zone of the blown film machine. The temperature settings for each zone are as follows:

[0133] District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 150℃ 155℃ 150℃ 145℃ 140℃ 130℃

[0134] Zone 6 is the head section of the blown film machine, Zones 2 to 5 are the middle section, and Zone 1 is the front section.

[0135] Starch-based biodegradable films are obtained using a winding device.

[0136] Example 4

[0137] The high-starch-based biodegradable composite film of this embodiment is prepared from the following components:

[0138]

[0139] The preparation method includes the following steps:

[0140] S1: Dry wheat starch granules in a 70℃ oven for 3 hours, then seal and store for later use;

[0141] S2: Place the dried wheat starch into a mixer, add polyurethane prepolymer, and modify the plant starch. Set the temperature in the mixer to 85℃ and the mixing time to 30 minutes. Take out the evenly mixed modified starch and let it stand at room temperature for 14 hours. Use a pulverizer to process the modified starch into 40-mesh granules, and seal and store for later use.

[0142] S3: Place the modified starch granules obtained in S2 into a high-speed mixer, add PBAT / PLA composite polyester material with a mass ratio of 4:1, then add chain extender PBAT, reinforcing agent and lubricant. The temperature inside the high-speed mixer is controlled at 25℃, and the mixing time is 10 minutes. After mixing, take it out for later use.

[0143] S4: Add the prepared mixture into the twin-screw extruder, and set the temperature for each zone as follows:

[0144] District 8 District 7 District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 145℃ 150℃ 150℃ 145℃ 145℃ 140℃ 130℃ 120℃

[0145] Zones one and eight are the front and rear sections, respectively, while zones two through seven are the middle sections. The raw material is then drawn, water-cooled, and granulated on a twin-screw auxiliary machine to obtain light yellow cylindrical granular raw materials.

[0146] S5: Dry the granular material obtained in S4 in an oven at a temperature of 75°C for 4 hours. Then, add the dried raw material to a blown film machine for blown film production.

[0147] S6: Set the temperature for each zone of the blown film machine. The temperature settings for each zone are as follows:

[0148] District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 150℃ 155℃ 150℃ 145℃ 140℃ 130℃

[0149] Zone 6 is the head section of the blown film machine, Zones 2 to 5 are the middle section, and Zone 1 is the front section.

[0150] Starch-based biodegradable films are obtained using a winding device.

[0151] Example 5

[0152] The high-starch-based biodegradable composite film of this embodiment is prepared from the following components:

[0153]

[0154]

[0155] The preparation method includes the following steps:

[0156] S1: Dry the cassava starch granules in a 70℃ oven for 3 hours, then seal and store for later use;

[0157] S2: Place the dried cassava starch into a mixer, add polyurethane prepolymer, and modify the plant starch. Set the temperature in the mixer to 85℃ and the mixing time to 30 minutes. Take out the evenly mixed modified starch and let it stand at room temperature for 14 hours. Use a pulverizer to process the modified starch into 40-mesh granules, and seal and store for later use.

[0158] S3: Place the modified starch granules obtained in S2 into a high-speed mixer, add PBAT / PLA composite polyester material at a mass ratio of 9:1, then add chain extender, reinforcing agent and lubricant. The temperature inside the high-speed mixer is controlled at 25℃, and the mixing time is 10 minutes. After mixing, take it out for later use.

[0159] S4: Add the prepared mixture into the twin-screw extruder, and set the temperature for each zone as follows:

[0160] District 8 District 7 District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 145℃ 145℃ 150℃ 145℃ 145℃ 140℃ 130℃ 120℃

[0161] Zones one and eight are the front and rear sections, respectively, while zones two through seven are the middle sections. The raw material is then drawn, water-cooled, and granulated on a twin-screw auxiliary machine to obtain light yellow cylindrical granular raw materials.

[0162] S5: Dry the granular material obtained in S4 in an oven at a temperature of 75°C for 4 hours. Then, add the dried raw material to a blown film machine for blown film production.

[0163] S6: Set the temperature for each zone of the blown film machine. The temperature settings for each zone are as follows:

[0164] District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 150℃ 155℃ 150℃ 145℃ 140℃ 130℃

[0165] Zone 6 is the head section of the blown film machine, Zones 2 to 5 are the middle section, and Zone 1 is the front section.

[0166] Starch-based biodegradable films are obtained using a winding device.

[0167] Example 6

[0168] The high-starch-based biodegradable composite film of this embodiment is prepared from the following components:

[0169]

[0170] The preparation method includes the following steps:

[0171] S1: Dry the corn starch granules in a 70℃ oven for 3 hours, then seal and store for later use;

[0172] S2: Place the dried corn starch into a mixer, add polyurethane prepolymer, and modify the plant starch. Set the temperature in the mixer to 85℃ and the mixing time to 30 minutes. Take out the evenly mixed modified starch and let it stand at room temperature for 14 hours. Use a pulverizer to process the modified starch into 40-mesh granules, and seal and store for later use.

[0173] S3: Place the modified starch granules obtained in S2 into a high-speed mixer, add PBAT / PLA composite polyester material at a mass ratio of 4:1, then add chain extender, reinforcing agent and lubricant. The temperature inside the high-speed mixer is controlled at 25℃, and the mixing time is 10 minutes. After mixing, take it out for later use.

[0174] S4: Add the prepared mixture into the twin-screw extruder, and set the temperature for each zone as follows:

[0175] District 8 District 7 District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 145℃ 150℃ 150℃ 145℃ 145℃ 140℃ 130℃ 120℃

[0176] Zones one and eight are the front and rear sections, respectively, while zones two through seven are the middle sections. The raw material is then drawn, water-cooled, and granulated on a twin-screw auxiliary machine to obtain light yellow cylindrical granular raw materials.

[0177] S5: Dry the granular material obtained in S4 in an oven at a temperature of 75°C for 4 hours. Then, add the dried raw material to a blown film machine for blown film production.

[0178] S6: Set the temperature for each zone of the blown film machine. The temperature settings for each zone are as follows:

[0179] District 6 Fifth District District 4 Three Districts Zone 2 Zone 1 150℃ 155℃ 150℃ 145℃ 140℃ 130℃

[0180] Zone 6 is the head section of the blown film machine, Zones 2 to 5 are the middle section, and Zone 1 is the front section.

[0181] Starch-based biodegradable films are obtained using a winding device.

[0182] The materials obtained in Examples 1 to 6 are numbered X1 to X6, respectively.

[0183] The materials from Examples 1 to 6 were subjected to Fourier transform infrared spectroscopy (FTIR) testing, and the results are as follows: Figure 1 As shown.

[0184] from Figure 1 It can be seen from this that the material is effective at an infrared wavelength of 3400 cm⁻¹. -1 There is no infrared peak at this location; instead, it represents the hydroxyl peak in starch. Therefore, the material does not contain active hydroxyl groups, which helps to improve the overall hydrophobic properties of the material.

[0185] The biodegradable films numbered X1 to X6 were subjected to tensile mechanical property tests using 4×25mm dumbbell-shaped specimens according to the GB / T 1040.3-2006 test standard. The test results are shown in Table 1 below.

[0186] Table 1: Mechanical properties of starch-based biodegradable composite films numbered X1 to X6

[0187]

[0188] As shown in Table 1, the samples obtained according to the materials and preparation method of the present invention all have good mechanical properties, with elongation at break exceeding 750% and tensile strength exceeding 14 MPa. By combining variations in the proportion of polyester material and additives, the starch content can be increased while maintaining the mechanical properties.

[0189] The surface morphology of the thin film in Example 1 was observed under a scanning electron microscope according to the present invention, and the results are as follows. Figure 2 As shown.

[0190] from Figure 2 As can be seen, the sample surface is smooth and flat, without any surface defects such as protrusions or depressions, which helps to maintain good mechanical properties.

[0191] like Figure 3 , Figure 4 As shown, the film-forming process of this invention is smooth and uniform, and the prepared film material has good flatness and transparency.

[0192] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A starch-based plastic film, characterized in that, Prepared from the following components, wherein: Plant starch 35-60 parts by weight; Polyurethane prepolymer 5-15 parts by weight; Composite polyester 30-50 parts by weight; Compatibility aid 1-5 parts by weight; Reinforcing agent 0.5-4 parts by weight; Lubricant 0.5-2 parts by weight, The compatibility aid is a chain extender, which is at least one of chain extension SAG-008, chain extension ADR-4370, chain extension KL-E4370, chain extension KL-E4370B, chain extension KS-05, and chain extension XY4370. The composite polyester comprises polybutylene adipate-co-terephthalate (PBAT) and polylactic acid (PLA), wherein the mass percentage of PBAT is 70-99% of the total amount of the composite polyester material, and the mass percentage of PLA is 1-30% of the total amount of the composite polyester material. The polyurethane prepolymer is prepared by reacting one of polyethylene glycol adipate, polycaprolactone diol, polytetrahydrofuran ether diol, and polybutylene glycol adipate with one of diphenylmethane diisocyanate, hexamethylene diisocyanate, and toluene diisocyanate. The starch-based plastic film is prepared by a method comprising the following steps: S1: drying plant starch and storing it in a sealed container for later use; S2: placing the dried plant starch into an internal mixer, adding polyurethane prepolymer to modify the plant starch, and using a pulverizer to process the modified starch into particles with a size of 20-60 mesh, and storing the particles in a sealed container for later use; S3: placing the modified starch particles obtained in S2 into a high-speed mixer, adding composite polyester, and then adding compatibility aid, reinforcing agent, and lubricant, and uniformly mixing the mixture to obtain a mixture for later use; S4: adding the mixture prepared in S3 into a twin-screw extruder for extrusion, and then performing drawing, water cooling, and granulation on the twin-screw auxiliary machine to obtain light yellow cylindrical granular material; S5: drying the granular material obtained in S4 and then blowing it into a film blowing machine to obtain a starch-based degradable film through a winding device.

2. The starch-based plastic film according to claim 1, characterized in that, The starch-based plastic film is composed of plant starch, composite polyester, polyurethane prepolymer, compatibility aid, reinforcing agent, and lubricant, and is prepared by a preparation process of mixing, twin-screw extrusion blending, and film blowing.

3. The starch-based plastic film according to claim 1, characterized in that, The plant starch is at least one of potato starch, corn starch, wheat starch, cassava starch, and pea starch.

4. The starch-based plastic film according to claim 1, characterized in that, The plant starch is 35-60 parts by weight.

5. The starch-based plastic film according to claim 1, wherein, The plant starch used has an amylose content of more than 15 wt% and a moisture content of less than or equal to 11 wt%.

6. The starch-based plastic film according to claim 1, wherein, The polyurethane prepolymer is prepared by reacting one of polytetrahydrofuran ether diol, polybutylene glycol adipate, and polybutylene glycol succinate with hexamethylene diisocyanate.

7. The starch-based plastic film according to claim 1, wherein, The isocyanate content of the polyurethane prepolymer is 3-10 wt%.

8. The starch-based plastic film according to claim 1, characterized in that, The polyurethane prepolymer is 5-15 parts by weight.

9. The starch-based plastic film according to claim 1, wherein, The mass percentage of PBAT is 80-92% of the total amount of the composite polyester material, and the mass percentage of PLA is 20-8% of the total amount of the composite polyester material.

10. The starch-based plastic film according to claim 1, characterized in that, The PBAT accounts for 75%-95% of the total mass percentage of the composite polyester material, and the PLA accounts for 25%-5% of the total mass percentage of the composite polyester material.

11. The starch-based plastic film according to claim 1, characterized in that, The compatibilizing agent is 1-3 parts by weight.

12. The starch-based plastic film according to claim 1, characterized in that, The reinforcing agent is at least one of attapulgite, nano-silicon dioxide, nano-calcium carbonate, nano-zinc oxide, bentonite, halloysite, and montmorillonite.

13. The starch-based plastic film according to claim 1, wherein, The reinforcing agent is 0.8-4 parts by weight.

14. The starch-based plastic film according to claim 1, wherein, The reinforcing agent is 1-3 parts by weight.

15. The starch-based plastic film according to claim 1, wherein, The lubricant is at least one of Tween, calcium stearate, magnesium stearate, erucic acid amide, oryzanol amide, and docosene acid amide.

16. The starch-based plastic film according to claim 1, wherein, The lubricant is 0.5-1.5 parts by weight.

17. The method of producing a starch-based plastic film according to any one of claims 1 to 16, wherein The method comprises the following steps: S1: drying the plant starch and storing it in a sealed state for later use; S2: placing the dried plant starch into an internal mixer, adding polyurethane prepolymer, and modifying the plant starch; using a pulverizer to process the modified starch into particles with a size of 20-60 mesh, and storing the particles in a sealed state for later use; S3: placing the modified starch particles obtained in S2 into a high-speed mixer, adding a composite polyester, and then adding a compatibilizing agent, a reinforcing agent, and a lubricant, and uniformly mixing the mixture to obtain a mixture; S4: adding the mixture prepared in S3 into a twin-screw extruder for extrusion, and then performing drawing, water cooling, and granulation on the twin-screw auxiliary machine to obtain a light yellow cylindrical granular material; S5: drying the granular material obtained in S4, and then blowing a film on a film blowing machine to obtain a starch-based degradable film through a winding device.

18. The production method according to claim 17, wherein The preparation method comprises one or more of the following features: (1) drying the plant starch in an oven at 60-80°C for 3-6 hours; (2) setting the temperature of the internal mixer to 80-100°C, and mixing for 20-45 minutes; (3) placing the modified starch uniformly mixed in the internal mixer at room temperature for 12-24 hours; (4) controlling the temperature in the high-speed mixer to be 20-40°C, and mixing for 5-15 minutes; (5) setting the temperature of the feeding section of the twin-screw extruder to be 120-130°C, the temperature of the middle section to be 130-155°C, and the temperature of the head section to be 140-160°C; (6) drying the granular material obtained in S4 in an oven for 4-6 hours, and setting the temperature in the oven to be 60-80°C; (7) setting the temperature of the die head of the film blowing machine in S5 to be 140-160°C, the temperature of the machine body to be 130-155°C, and the film blowing temperature to be 140-150°C.

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