Modified plant fiber-based fully biodegradable composite film and preparation method thereof

Abstract

The application relates to the technical field of full-biodegradable films, and discloses a modified plant fiber-based full-biodegradable composite film and a preparation method thereof, the preparation method comprising the following steps: step 1, modification of the surface of plant fiber powder: mixing plant fiber powder and a modifier, carrying out modification treatment at 80-150 DEG C for 1-8 h, washing the residue to neutral with distilled water after the reaction is completed, and then drying; step 2, preparation of a master batch: uniformly mixing the plant fiber powder modified in step 1 and a biodegradable high molecular material, and preparing a master batch in a double-screw machine; step 3, hot-pressing into a film; and step 4, blowing into a film. The modified plant fiber-based full-biodegradable composite film and the preparation method thereof are used, modified plant fiber is blended with a biodegradable high molecular material, a plant fiber-based full-biodegradable composite film is prepared, the film has excellent comprehensive performance, and meanwhile, the preparation process is low in cost and small in pollution.

Description

Technical Field

[0001] This invention relates to the field of biodegradable film technology, and in particular to a modified plant fiber-based fully biodegradable composite film and its preparation method. Background Technology

[0002] my country's agricultural production involves mulching 300 million mu (approximately 20 million hectares) of land annually, consuming 2 million tons of plastic film, both figures ranking first in the world. Mulching can increase soil temperature, retain moisture, prevent pests, suppress salt and weeds, and improve the crop growing environment, thereby increasing crop yields. However, the white pollution caused by plastic film is becoming increasingly prominent, potentially posing a threat to regional food security in my country. Traditional plastic film is mainly composed of polyethylene, which is non-biodegradable. Years of mulching accumulate large amounts of residual film in the soil, leading to soil compaction and ultimately reducing crop yields. Therefore, solving agricultural plastic film pollution and developing fully biodegradable plastic film is urgently needed.

[0003] Currently, fully biodegradable membranes are mainly prepared using biodegradable polymers such as PBAT, PLA, PHA, PCL, and PBS. However, these biodegradable polymers suffer from drawbacks in practical applications, including high cost and poor coating performance. Plant fibers are abundant in my country, and using them as fillers in composite membranes with biodegradable polymers can reduce membrane material costs. However, current plant fiber-based fully biodegradable membranes suffer from problems such as uneven filler dispersion and poor mechanical properties during preparation. Therefore, developing an efficient strategy to improve the compatibility between plant fiber materials and biodegradable polymer materials is crucial for producing low-cost, high-performance, green, and biodegradable composite membranes.

[0004] The purpose of this invention is to provide a modification method to adjust the surface properties of plant fiber powder, and to composite it with biodegradable polymer materials to prepare a plant fiber-based fully biodegradable membrane with excellent mechanical properties, thereby solving the problem of poor compatibility between plant fiber raw materials and biodegradable polymer materials. This invention utilizes modifiers to perform surface treatments on plant fiber powder to different degrees, effectively increasing the compatibility between plant fiber powder and biodegradable polymers, and improving the mechanical properties, barrier properties, and degradation properties of the composite membrane. Summary of the Invention

[0005] The purpose of this invention is to provide a modified plant fiber-based fully biodegradable composite film and its preparation method. The modified plant fiber is blended with a biodegradable polymer to prepare a plant fiber-based fully biodegradable composite film. The film has excellent comprehensive performance, and the preparation process is low-cost and low-pollution.

[0006] To achieve the above objectives, the present invention provides a method for preparing a modified plant fiber-based fully biodegradable composite film, comprising the following steps: Step 1, modification of plant fiber powder surface: Mix plant fiber powder and modifier, and carry out modification treatment at 80-150℃ for 1-8 h. After the reaction is completed, wash the reacted plant fiber with distilled water until neutral, and then dry it. Step 2, Masterbatch preparation: Mix the modified plant fiber powder from Step 1 and the biodegradable polymer evenly, and prepare the masterbatch in a twin-screw extruder; Step 3, hot pressing to form a film: Take the masterbatch of plant fiber powder composite biodegradable polymer material from Step 2, and hot press it at 130-180℃ and 1~25 MPa to obtain a composite film; Step 4, blow molding: Take the masterbatch of plant fiber powder combined with biodegradable polymer from step 2 and blow mold it into a film in a blow molding machine at 125-180℃.

[0007] Furthermore, in step 1, the raw materials for the plant fiber powder are one or more of the following: rice straw, corn straw, wheat straw, cotton straw, rapeseed straw, tobacco straw, corn cob, bamboo powder, wood powder, fallen leaves and branches, or sugarcane bagasse, and the particle size of the plant fiber powder is 500-2000 mesh.

[0008] Furthermore, the modifier in step 1 is one or more of sodium chlorite, acetic acid, formic acid, sodium hydroxide, sodium sulfite, DES, sodium hypochlorite, ionic liquid, sodium hydroxide / polyethylene glycol, and acetic acid / glycerol.

[0009] Furthermore, in step 1, the solid-liquid ratio of plant fiber powder and modifier is 1g:7-30ml.

[0010] Furthermore, the modification treatment in step 1 is performed 1-5 times, with a drying temperature of 30-105℃ and a time of 8-96 hours.

[0011] Furthermore, in step 2, the plant fiber powder accounts for 30-70% of the total mass of the plant fiber powder and the biodegradable polymer.

[0012] Furthermore, in step 2, the biodegradable polymer material is one or more of PBAT, PHA, PLA, PCL, and PBS.

[0013] Furthermore, in step 2, when preparing the masterbatch, the temperature of the twin-screw extruder is set to 120-180℃.

[0014] The present invention also provides a modified plant fiber-based fully biodegradable composite film, which is prepared according to the preparation method described above.

[0015] This invention also provides an application of a modified plant fiber-based fully biodegradable composite film in mulch films, packaging films, and vest bags.

[0016] The advantages and positive effects of the modified plant fiber-based fully biodegradable composite film and its preparation method described in this invention are as follows: 1. This invention effectively improves the compatibility between plant fibers and biodegradable polymers through a low-cost modification method. Even with a high plant fiber content, the composite film still maintains ideal mechanical properties. The prepared plant fiber-based biodegradable composite film can be used for mulch films, packaging films, and vest bags.

[0017] 2. This invention modifies plant fibers, thereby achieving control over the structure of plant fibers at the micron scale. The production process is low-energy and low-cost, enabling large-scale industrial production.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 The image shows a macroscopic view of the modified plant fiber in an embodiment of the present invention. A represents the plant fiber powder before modification, and B represents the plant fiber powder after modification. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0022] Unless otherwise defined, the instruments, equipment and reagents used in this invention are all commercially available.

[0023] Example 1 A modified plant fiber-based biodegradable composite film, wherein the composite film material, by weight percentage, comprises 47 parts PBAT, 3 parts PLA, and 50 parts modified bamboo powder. That is: (1) 50 parts by weight of modified bamboo powder; (2) 47 parts by weight of PBAT; (3) PLA 3 parts by weight.

[0024] The preparation method of modified plant fiber-based fully biodegradable composite film includes the following steps: 1. Modifying bamboo powder to obtain structure-regulated bamboo powder: Bamboo powder of 500-2000 mesh was mixed with sodium hydroxide / sodium sulfite at a solid-liquid ratio (g / mL) of 1:20 and treated at 80-150℃ for 1-2 h. After the reaction was completed, the mixture was washed with distilled water until neutral and dried at 45-70℃ for 24 h.

[0025] 2. Take 50 parts of modified bamboo powder, 47 parts of PBAT and 3 parts of PLA particles and blend them through a twin-screw extruder to obtain composite material masterbatch. The processing parameters of the twin-screw extruder are as follows: heating temperature is set to 130~175℃, roller speed is set to 20~35r / min, and the number of cycles is 1-5.

[0026] 3. The composite masterbatch is hot-pressed into a film in a hot press to obtain a modified plant fiber / PBAT / PLA composite film. The hot press processing parameters are as follows: heating temperature is set to 140-170℃, pressure is set to 1-25 MPa, preheating time is set to 1-5 min, and running time is set to 1-5 min.

[0027] 4. The composite masterbatch is blown into a film using a blown film machine to obtain a modified plant fiber / PBAT / PLA composite film material. The processing parameters of the blown film machine are as follows: heating temperature is set to 125-180℃, and preheating time is set to 35-60min.

[0028] Example 2 A modified plant fiber-based fully biodegradable composite film, wherein the composite film material, by weight percentage, comprises 47 parts PBAT, 3 parts PLA, and 50 parts modified bamboo powder. That is: (1) 50 parts by weight of modified bamboo powder; (2) 47 parts by weight of PBAT; (3) PLA 3 parts by weight.

[0029] The preparation method of modified plant fiber and fully biodegradable composite film includes the following steps: 1. Modifying bamboo powder to obtain structure-regulated bamboo powder: Bamboo powder of 500-1000 mesh was mixed with sodium chlorite / acetic acid solution at a solid-liquid ratio (g / mL) of 1:25 and treated at 80-150℃ for 3-5 hours. After the reaction was completed, the mixture was washed with distilled water until neutral and dried at 45-70℃ for 8-48 hours.

[0030] The remaining steps are the same as in Example 1.

[0031] Example 3 A modified plant fiber-based fully biodegradable composite film, wherein the composite film material, by weight percentage, comprises 47 parts PBAT, 50 parts modified bamboo powder, and 3 parts PLA. That is: (1) 50 parts by weight of modified bamboo powder; (2) 47 parts by weight of PBAT; (3) PLA 3 parts by weight.

[0032] The preparation method of modified plant fiber-based fully biodegradable composite film includes the following steps: 1. Modifying bamboo powder to obtain structure-regulated bamboo powder: Bamboo powder of 500-1000 mesh was mixed with acetic acid solution at a solid-liquid ratio (g / mL) of 1:15 and treated at 110-130℃ for 6-8 h. After the reaction was completed, the mixture was washed with distilled water until neutral and dried at 45-70℃ for 8-48 h.

[0033] The remaining steps are the same as in Example 1.

[0034] Comparative Example 1 A plant fiber-based fully biodegradable composite membrane, wherein the composite membrane material, by weight percentage, comprises 50 parts bamboo powder, 47 parts PBAT, and 3 parts PLA. That is: (1) 50 parts by weight of bamboo powder; (2) PBAT 47 parts by weight; (3) PLA 3 parts by weight.

[0035] The preparation method of bamboo powder-based biodegradable composite film includes the following steps: 1. Take 50 parts of dried bamboo powder, 47 parts of dried PBAT, and 3 parts of PLA. Mix them evenly using a high-speed mixer, and then feed them into a twin-screw extruder to prepare masterbatch. Twin-screw extruder processing parameters: temperature 120-180℃.

[0036] 2. The composite masterbatch is hot-pressed into a film in a hot press to obtain a plant fiber-based fully biodegradable composite film material. The hot press processing parameters are as follows: heating temperature is set to 130~180℃, pressure is set to 1-25 MPa, preheating time is set to 1~5 min, and running time is set to 1~5 min.

[0037] 3. The composite masterbatch is blown into a film using a blown film machine to obtain a plant fiber-based fully biodegradable composite film material. The processing parameters of the blown film machine are as follows: heating temperature is set to 125~180℃, and preheating time is set to 35~60min.

[0038] Performance testing The composite membranes obtained in Examples 1-3 and Comparative Example 1 were subjected to performance tests. The tensile strength, elastic modulus, and elongation at break of the plant fiber-based fully biodegradable composite membranes are shown in Table 1.

[0039] Table 1

[0040] As can be seen from the test data in Table 1, the tensile strength of the fully biodegradable composite film with bamboo powder is reduced compared with the pure PBAT film. However, compared with Examples 1-3 and Comparative Example 1, the tensile strength of the modified plant fiber composite film is higher than that of the unmodified plant fiber fully biodegradable composite film. Moreover, the tensile strength of the modified plant fiber fully biodegradable composite film is not significantly reduced compared with the pure PBAT film (maximum 16%). In addition, considering the high cost of biodegradable polymers, the modified plant fiber fully biodegradable composite film is preferred in order to reduce costs.

[0041] Compared to pure PBAT membranes, the composite membranes prepared in Examples 1-3 have a higher elastic modulus. Although the composite membrane prepared in Comparative Example 1 has a better elastic modulus than that of Examples 1-3, its tensile strength and elongation at break are inferior. Considering all factors, the modified plant fiber fully biodegradable composite membrane would be the preferred choice. Compared to pure PBAT membranes, the modified plant fiber fully biodegradable composite membranes prepared in Examples 1-3 have a lower elongation at break, but considering cost, the modified plant fiber fully biodegradable composite membrane has better overall performance.

[0042] Therefore, the present invention adopts the above-mentioned modified plant fiber-based fully biodegradable composite film and its preparation method, which blends modified plant fibers with biodegradable polymer materials to prepare a plant fiber-based fully biodegradable composite film. The composite film has excellent comprehensive performance, and the preparation process is low in cost and low in pollution.

[0043] 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. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a modified plant fiber-based fully biodegradable composite film, characterized in that, Includes the following steps: Step 1, modification of plant fiber surface: 500-1000 mesh bamboo powder and acetic acid solution are treated at 110-130℃ for 6-8h at a solid-liquid ratio of 1g:15mL. After the reaction is completed, the mixture is washed with distilled water until neutral and dried at 45-70℃ for 8-48h to obtain modified bamboo powder. Step 2, Masterbatch preparation: By mass, take 50 parts of modified bamboo powder, 47 parts of PBAT and 3 parts of PLA particles and blend them through a twin-screw extruder to obtain composite material masterbatch; the temperature of the twin-screw extruder is set to 120-180℃ and the roller speed is set to 20~35r / min. Step 3, hot pressing to form film: Take the masterbatch from step 2 and hot press it at 130-180℃ and 1~25MPa to obtain the modified plant fiber-based fully biodegradable composite film.

2. A modified plant fiber-based biodegradable composite film, characterized in that, It is prepared according to the preparation method described in claim 1.

3. The application of the modified plant fiber-based biodegradable composite film according to claim 2 in mulch film, packaging film, vest bag or plastic wrap.

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