Density-reducing composition containing ultrafine plant powder, packaging film containing ultrafine plant powder and preparation methods of density-reducing composition and packaging film

Abstract

The invention discloses ultramicro plant powder, a density-reducing composition using the ultramicro plant powder, a product and a preparation method. The ultrafine plant powder is tested by taking water as a dispersing agent according to the standard of GB / T 19077-2016 Particle Analysis Laser Diffraction Method, and the D50 fineness value is less than or equal to 8 microns, so that the terminal hydroxyl group of cellulose can be subjected to esterification reaction or etherification reaction. According to the ultrafine plant powder, the bamboo powder can be used for manufacturing film products, and a new way is provided for industrial application of the bamboo powder; in addition, the density of full-biodegradable film products can be reduced, the competitiveness of the products is improved, and wide popularization and promotion of the full-biodegradable products are facilitated.

Description

Technical Field

[0001] The invention relates to a density-reducing composition containing ultrafine plant powder, a packaging film prepared by using the density-reducing composition, and a preparation method of the density-reducing composition, belonging to the technical field of fully biodegradable materials. Background Art

[0002] With growing environmental awareness, environmentally friendly materials are being evaluated not only during the material's use phase but also throughout its entire lifecycle. Degradable plastics, such as those that undergo photo-oxidative degradation, ultimately form microplastics, which not only directly pollute the natural environment but also threaten the survival of wildlife and fish through ingestion. Therefore, the current focus is on the development of fully biodegradable plastics.

[0003] In the Chinese patent application No. 202310288705.7 entitled “Technology for the Preparation of Plant Cellulose Modified Fully Degradable Materials”, it is disclosed that the coarser plant fibers used in injection molding are 20-100 mesh, and the plant fibers used in blown film and extruded thin-walled products are 400-800 mesh, and the plant fiber content is 25%-40%. In the Chinese patent application No. 201710097637.0 entitled “A Degradable Ground Film Containing Plant Fiber Degradable Filler”, it is disclosed that the ground film is prepared using natural plant fiber powder, any one or two of rice husk powder, straw powder, peanut shell powder and cotton husk powder, and vinyl chloride (PVC) resin or a mixed resin composed of three resins: polyethylene (LDPE), linear low-density polyethylene (LLDPE) and metallocene polyethylene (mPE). The particle size of the natural plant fiber powder is greater than 800 mesh and the moisture content is ≤3%. It can be seen from both patents that in such mixed film products, the role played by plant fibers with a particle size of 800 mesh or coarser in film products is similar to that of calcium carbonate in film products, which is to enable film products to disintegrate without chemical reactions. Because the main component of plant fibers is cellulose, which contains a large number of hydroxyl groups, these hydroxyl groups form intermolecular hydrogen bonds or intramolecular hydrogen bonds, making it water-absorbent, with a moisture absorption rate of 8% to 12%, and very strong polarity; therefore, its compatibility with the resin is poor, and the interfacial adhesion is small. This results in poor dispersion in molten thermoplastics, poor fluidity, and difficulty in extrusion molding. Moreover, in addition to cellulose, plant fibers also contain substances such as hemicellulose and lignin. Lignin is a thermoplastic substance. Lignin acts as a binder in the fiber raw material, making it difficult to disperse the plant fiber raw material. On the other hand, the decomposition temperature of lignin is low, which increases the difficulty of its direct use. Moreover, if Figure 1A and Figure 1BAs shown, the microstructure of plants is heterogeneous. For example, bamboo fibers and parenchyma cells differ in their anatomical structure and chemical composition. Bamboo fibers are elongated cells, approximately 3 mm in length and 20 microns in diameter (aspect ratio greater than 100), with a small or invisible lumen. In contrast, parenchyma cells are granular, less than 100 microns in length (aspect ratio close to 1), with a large lumen.

[0004] Furthermore, since the density of fully biodegradable plastics (PLA polylactic acid, PBAT, PBS polyhydroxyalkanoate, PPC carbon dioxide copolymer, PCL polycaprolactone, PHA, PHB, PHBV polyhydroxyalkanoate, etc.) is 1.23-1.26 g / cm 3 , higher than the density of ordinary PE plastic (about 0.94g / cm 3 ) or the density of PP plastic (about 0.90g / cm 3 ), resulting in the production of fewer and smaller products (such as packaging films) using the same weight of raw materials than with conventional plastics. This increases the cost of fully biodegradable products by approximately 25-35%, further reducing the competitive advantage of fully biodegradable plastics. Therefore, high cost is a major factor hindering the promotion of fully biodegradable plastics. Summary of the Invention

[0005] The primary technical problem to be solved by the present invention is to provide a density-reducing composition comprising ultrafine plant powder.

[0006] Another technical problem to be solved by the present invention is to provide a packaging film prepared using a density-reducing composition containing ultrafine plant powder.

[0007] Another technical problem to be solved by the present invention is to provide a method for preparing a density-reducing composition containing ultrafine plant powder.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] According to a first aspect of an embodiment of the present invention, there is provided a density reducing composition using ultrafine plant powder, comprising ultrafine plant powder with a fineness of 5 to 8 microns, and for preparing a composition having a density of less than 1.1 g / cm 3 Fully biodegradable film products or products with a density less than 0.9g / cm 3 Fully biodegradable film products.

[0010] It is composed of the following components in parts by weight:

[0011] PBAT 55-80%

[0012] PLA 10-20%

[0013] Ultrafine plant powder 2% to 5%,

[0014] Plant fiber plasticizer 0.5-2%

[0015] PBAT\PLA plasticizer 0.2~1%

[0016] Residue of additives.

[0017] A method for preparing a density-reducing composition comprises the following steps:

[0018] Step 1: drying the ultrafine plant powder according to any one of claims 1 to 3 to control the moisture content to be below 1%;

[0019] Step 2: Add all ingredients to the dried ultrafine plant powder through a high-speed mixer and mix thoroughly;

[0020] Step 3: adding the mixture to a twin-screw extruder for extrusion granulation, wherein the temperature of at least two zones of the extruder is between 140 degrees and 160 degrees;

[0021] Step 4: pelletizing to form particles, which are used as a density-reducing composition for preparing film-like products.

[0022] 4. The method for preparing the density-reducing composition according to claim 3, characterized in that it comprises the following steps:

[0023] The processing temperature of the extruder is set to 130 degrees in zone 1, 130 degrees in zone 2, 135 degrees in zone 3, 140 degrees in zone 4, 146 degrees in zone 5, 150 degrees in zone 6, 152 degrees in zone 7, and 152 degrees in zone 8.

[0024] According to a second aspect of an embodiment of the present invention, there is provided a packaging film prepared using a density-reducing composition, wherein the density is less than 0.9 g / cm 3 Fully biodegradable film products.

[0025] According to a fourth aspect of an embodiment of the present invention, there is provided a film product prepared using a density-reducing composition, the density of which is less than 0.9 g / cm 3 Fully biodegradable film products.

[0026] Preferably, the density reducing composition comprises the aforementioned ultrafine active plant powder, or the density reducing composition is the aforementioned density reducing composition.

[0027] Compared with the existing technology, the ultrafine plant powder of the present invention is an active plant powder, which enables various types of ultrafine plant powders to be used in the manufacture of packaging film products, providing a new way for the industrial application of various types of ultrafine plant powders; and can reduce the density of fully biodegradable packaging films, improve product competitiveness, and is conducive to the widespread popularization and promotion of fully biodegradable products. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1A This is a high-magnification image of the thin-walled cell structure of natural bamboo powder;

[0029] Figure 1B This is a high-magnification image of the bamboo fiber structure of natural bamboo powder;

[0030] Figure 2 This is an example of a fineness distribution table of ultrafine plant powder according to the first embodiment of the present invention;

[0031] Figure 3 for Figure 2 Particle size distribution curve of ultrafine plant powder;

[0032] Figure 4 This is a schematic diagram of a density-reducing composition comprising ultrafine plant powder according to a second embodiment of the present invention;

[0033] Figure 5A and Figure 5B High-magnification images of the film product of the third embodiment of the present invention at different magnifications;

[0034] Figure 6 This is a table showing the longitudinal tensile mechanical properties test data of the film product in the third embodiment of the present invention;

[0035] Figure 7 This is a test diagram of the longitudinal tensile mechanical properties of the membrane product in the third embodiment of the present invention;

[0036] Figure 8 This is the test result of Example 5 of the present invention;

[0037] Figure 9 is the test result of another embodiment of the present invention;

[0038] Figure 10 This is the test result of another embodiment of the present invention;

[0039] Figure 11 This is a comparison experiment result of the packaging film of the present invention and the commercially available product;

[0040] Figure 12 This is a comparison chart of the film blowing process effects of the present invention. DETAILED DESCRIPTION

[0041] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Before introducing the density reduction composition containing ultrafine plant powder of the present application, the ultrafine plant powder is first introduced.

[0043] First embodiment

[0044] like Figures 2 to 4 As shown, the first embodiment of the present invention provides an ultrafine plant powder, which is tested using a laser diffraction particle size analyzer (for example, the particle size analyzer model winner 3003 of Jinan Micro-Nano) in accordance with the GB / T 19077-2016 "Particle Size Analysis Laser Diffraction Method" standard with water as a dispersant, and its fineness reaches D50 of less than or equal to 8 microns, preferably D50 of less than or equal to 7 microns, and more preferably D50 of less than or equal to 6 microns or D50 of less than or equal to 5 microns. Here, D50 represents the median diameter or median particle size of the powder in the test using water as the dispersion medium, and D50 refers to the particle size value corresponding to the cumulative distribution percentage reaching 50%. In other words, D50 means that in the powder sample, 50% of the particles have a particle size exceeding this value, and another 50% of the particles have a particle size below this value. Figure 2 and Figure 3 An example of the ultrafine plant powder of the present application is provided, wherein the D50 fineness thereof is 7.758 microns (with water as the dispersion medium).

[0045] Ultrafine plant powder is a mixture of one or more of sawdust powder, fruit shell powder, bamboo powder, straw powder, husk powder, other crops or plant stem and leaf powder. In the present embodiment, the ultrafine plant powder is obtained by rough-processing any one of bamboo chips, corn stalks, coconut shreds, coffee grounds, flax, and wheat straw to 200-400 mesh, and then processing it through a jet mill. Because these plant powders are tough and flammable, the plant powders currently obtained by ball milling in the fields of traditional Chinese medicine are usually 200-400 mesh, and can reach 800 mesh / D50 standard (approximately 15 to 18 microns) at most. Therefore, the ultrafine plant powder of the first embodiment of the present application is processed by a jet mill. The working principle of a jet mill is as follows: After being filtered and dried, compressed air is injected at high speed into the grinding chamber through a Laval nozzle. At the intersection of multiple high-pressure airflows, the material is repeatedly collided, rubbed, and sheared, causing it to be crushed. The crushed material, driven by the fan's suction, moves with the rising airflow to the classification zone. The powerful centrifugal force generated by the high-speed rotating classification turbine separates the coarse and fine materials. Fine particles that meet the particle size requirements pass through the classification wheel and are collected in the cyclone separator and dust collector, while coarse particles descend to the grinding zone for further crushing. Therefore, jet mills avoid the combustion of plant powders and are more suitable for processing plant powders than ball mills and impact mills.

[0046] According to research, only when the fineness of the plant powder reaches 8 microns or finer, the terminal hydroxyl groups of the plant fiber will have sufficient activity to participate in the esterification or etherification chemical reaction, so that it has thermoplastic properties and can be used for the manufacture of blown film, injection molding or blister products. The finer the plant fiber, the more terminal hydroxyl groups there are, which improves accessibility. Therefore, the plant powder in the first embodiment of the present invention is a plant powder with active terminal hydroxyl groups (i.e., active plant powder), which is used to participate in the esterification or etherification chemical reaction, so that the plant powder has thermoplastic properties ( Figure 1A and Figure 1B This is a high-magnification image of the cell structure of natural bamboo powder. Figure 5A and Figure 5B (High-magnification images of thermoplastic film products processed from natural bamboo powder at different magnifications) Furthermore, this ultrafine plant powder is physically processed from natural plants and is not chemically modified or modified. This plant powder meets the environmental requirements of the "Guidelines for Single-Use Plastic Products" issued by the European Union on May 31, 2021. This ultrafine plant powder can be further processed into granules for easy transportation and storage.

[0047] The moisture content of the ultrafine plant powder in this embodiment is less than or equal to 6%, preferably less than or equal to 5%, and more preferably less than or equal to 4%. The fineness of the drying process is such that the ultrafine plant powder with a D50 of 7 microns or finer improves the accessibility and reactivity of cellulose, and also improves the dispersibility and compatibility of the ultrafine plant powder. Ultrafine plant powder of sufficient fineness causes more cellulose chain ends to be exposed, thereby relatively increasing the number of terminal hydroxyl groups and also changing the structure of the fiber surface. In this way, the accessibility of hydroxyl groups is improved, and the hydroxyl groups are more likely to undergo esterification or etherification reactions, which is conducive to the formation of a network structure (reference Figure 5A and Figure 5B ), improving the intermolecular binding force.

[0048] Second embodiment

[0049] The second embodiment of the present invention provides a density-reducing composition containing ultrafine plant powder (hereinafter referred to as density-reducing composition) prepared using the ultrafine plant powder provided by the first embodiment of the present invention.

[0050] The ultrafine plant powder (for example, bamboo fiber powder) in the first embodiment is continuously extruded and chemically reacted to become an industrial thermoplastic natural polymer material. The active groups (terminal hydroxyl groups OH) of the plant fiber (element) are used to cause an esterification / etherification reaction, thereby giving it thermoplastic properties; in combination with biodegradable oligomers, biodegradable core additives (activators, compatibilizers, plasticizers, reactants), etc., chain extension technology, cross-linking technology, grafting technology, etc. are used to form new chemical bonds between molecules to form a network structure. Therefore, the network structure increases the mechanical properties or processing properties such as tensile properties and heat sealing properties of the blown film product, meeting the performance requirements of the group standard T / GDPIA 60-2023 "Specialized materials for bamboo powder-based fully biodegradable films" issued by the Guangdong Plastics Industry Association. Similarly, the performance of injection-molded products and blister products also meet the requirements of relevant technical standards for biodegradable products, such as the group standards T / GDPIA 63-2023 "Bamboo powder-based fully biodegradable injection molding materials", T / GDPIA 62-2023 "Bamboo powder-based fully biodegradable blister molding materials", and T / GDPIA61-2023 "Bamboo powder-based fully biodegradable straw materials" issued by the Guangdong Plastics Industry Association.

[0051] The density of the density-reducing composition prepared by using active ultrafine plant powder is 0.3-0.9 g / cm 3 The best is 0.5~0.86g / cm 3 , the better one is 0.4~0.8g / cm 3 This density-reducing composition is used as a raw material in the production of fully biodegradable packaging film, reducing the density of the finished product to a level lower than that of PE packaging film, thereby reducing costs. The density-reducing composition (film raw material) used in packaging film has a melt flow rate (MI) of 2-12 g / min.

[0052] The components (weight percentage) of the density reduction composition in this embodiment are as follows: PBAT 45-82%

[0053] PLA 5~20%

[0054] Ultrafine active plant powder 10% to 33%

[0055] Surfactant / dispersant 0.2~2%

[0056] Crosslinking agent / coupling agent 0.2~2%

[0057] Plant fiber plasticizer 0.5-2%

[0058] PBAT\PLA plasticizer 0.2~1%

[0059] Additives 0.5~2.5%.

[0060] Examples 1 to 4 of the components of the density reducing composition are shown in Table 1 below.

[0061] Table 1: Density reduction composition and corresponding packaging film mechanical properties

[0062]

[0063]

[0064] The plant fiber plasticizer mentioned in the present invention is a vegetable oil polyol, which is used to improve the dispersion of each dispersed phase and increase toughness. Preferably, the vegetable oil polyol is one or more of castor oil polyol, soybean oil polyol, peanut oil polyol, coconut oil polyol, palm oil polyol, linseed oil polyol, cottonseed oil polyol, corn oil polyol, sunflower seed oil polyol, pine nut oil polyol, and tung oil polyol. The vegetable oil polyol can be a commercially available product. Further preferably, the vegetable oil polyol is castor oil polyol or epoxidized soybean oil, which can significantly improve the toughness of the PLA / PBAT biodegradable composite material of the present invention.

[0065] The proportions of auxiliary agents such as stearic acid, crosslinking agent, chain extender, dispersant, surfactant, compatibilizer, initiator, oxidant, etc. can be adjusted appropriately.

[0066] Examples 5-6 of the components of the density reducing composition are shown in Table 2.

[0067] Table 2: Composition and mechanical properties of density-reducing compositions

[0068]

[0069]

[0070] In this embodiment, the added foaming agent is an inorganic foaming agent such as sodium bicarbonate. Alternatively, an organic foaming agent such as disulfonylhydrazide diphenyl ether (OBSH) may be used.

[0071] Table 3: Composition (weight percentage) of Example 7 with a density of 0.8 g / cm3

[0072]

[0073] Figures 6 to 10 Provides test result diagrams of multiple embodiments. Figure 11 Comparative experiments are also provided.

[0074] PLA and PBAT were mixed at a mass ratio of 20:80, extruded into pellets in a twin-screw extruder, and blown into films at 160°C in a single-layer film blowing machine as a comparative example. The test results of the comparative example are as follows (the film thickness of each example and comparative example was 0.03±0.002 mm).

[0075]

[0076] The mechanism of "reducing density" of the present invention is described as follows:

[0077] Through a large number of experiments on blending, reactive extrusion, and film blowing of ultrafine plant powders of different fineness and activity with the aforementioned biodegradable materials such as PBAT, as well as density test data of the film, it was unexpectedly discovered that:

[0078] (1) The density of the composition and film formed by blending ultrafine active plant powder with biodegradable materials such as PBAT and reacting and extruding it is reduced from the original density of 1.23g / cm3 of PBAT and other materials to 0.9g / cm3 or even lower, and the film density reduction rate is about 28%;

[0079] (2) The density of the composition and film formed by blending and reactively extruding ultrafine active plant powders with insufficient fineness with biodegradable materials such as PBAT increased from the original density of 1.23 g / cm3 of PBAT and other materials to 1.26-1.3 g / cm3 or even higher, with an increase rate of about 5% in film density;

[0080] (3) The density of the composition and its film formed by blending and reactive extrusion of 8-5 micron ultrafine active plant powder with biodegradable materials such as PBAT is increased from the original density of PBAT and other materials of 1.23-1.26 g / cm 3 , but will increase to 1.3-1.4g / cm 3 Even higher, the film density increase rate is about 5-15%;

[0081] At the same time, the surfactant in this scheme provides interfacial compatibility of the ultrafine active plant powder in the molten state of biodegradable materials such as PBAT; the dispersant provides uniform dispersion of the ultrafine active plant powder in the molten state of biodegradable materials such as PBAT; the cross-linking agent and coupling agent provide a network-like, interwoven three-dimensional cross-linked structure formed between the ultrafine active plant powder and biodegradable materials such as PBAT in the molten state, providing pore space for reducing the density of the composition.

[0082] (4) In the embodiment in which a foaming agent is added, the foaming agent is a foaming agent that has been ultra-finely ground and has a fineness of 5000 mesh or more, which can be evenly dispersed in the resin composition system and cooperate with biodegradable materials such as PBAT to produce micro-foaming; at the same time, under the action of cross-linking agents and coupling agents, the biodegradable materials such as PBAT can provide their melt strength in the molten state and maintain a continuous closed-cell foam, thereby significantly reducing the density of the resin composition and film.

[0083] The reasons for this phenomenon are:

[0084] (1) The density of the composition and film formed by blending and reactive extrusion of 8-5 micron ultrafine active plant powder with biodegradable materials such as PBAT is greatly reduced because the microscopic pore structure of the ultrafine plant powder within this fineness range is not destroyed, resulting in a significant effect of reducing the density of the composition and film.

[0085] At the same time, by regulating the interfacial compatibility differences between plant fiber powder (polar or non-polar) and PBAT (medium polarity), the polar repulsion between the two is utilized to prevent the molten PBAT from completely infiltrating the pores and network structure of the plant powder. This forms a continuous and stable pore between ultra-fine plant fibers, and a microscopic morphology wrapped by PBAT resin.

[0086] (2) The density of the composition and film formed by blending and reactive extrusion of ultrafine active plant powder with insufficient fineness with biodegradable materials such as PBAT did not change significantly or increased slightly. This is because the microstructure of the ultrafine plant powder within this fineness range has a relatively rough surface and large fiber diameter voids, which causes the resin such as PBAT to enter the pores or loose structure in the molten state, and the density of the reduced density composition and film thereby changes significantly or increases slightly.

[0087] (3) When ultrafine active plant powder is blended with biodegradable materials such as PBAT and reacted and extruded to form the reduced density composition and its film, the density will increase to 1.3-1.4 g / cm3 or even higher. This is because the finer plant powder destroys its pore structure, loose structure and cell wall density; the relative density of plant powder is the bulk density including the pore structure and loose fiber structure; and the absolute density of plant powder is the cell wall density after removing the pore structure and loose fiber structure, and the cell wall density of plants is 1.4-1.6 g / cm3, resulting in the higher the fineness of the plant powder filled into the PBAT resin, the higher the density of the composition and film.

[0088] Third embodiment

[0089] The low-density packaging film prepared based on the density-reducing composition of the second embodiment as a raw material has a density of 0.3 to 0.9 g / cm 3 The best is 0.5~0.8g / cm 3 Furthermore, a tensile strength of 15 MPa or greater can be achieved (meeting the requirements of GB / T1040.3-2006). This means that mechanical properties are not affected by a reduction in density. This is because the network structure formed between the cellulose fibers enhances mechanical properties.

[0090] The packaging film prepared using the density-reducing composition of the second embodiment can be used to make shopping bags that meet the performance requirements of GB / T38082-2019, "Biodegradable Plastic Shopping Bags." The fully biodegradable packaging film of this application has a biodegradability rate of 90% or higher, meeting the biodegradability requirements of the Chinese standard GB / T38082-2019, as well as those of the European standard EN13432 and the US standard ASTM D6400.

[0091] Fourth embodiment

[0092] This embodiment provides a method for preparing a density-reducing composition containing ultrafine plant powder.

[0093] Step 1: Dry the ultrafine plant powder and control the moisture content below 1%.

[0094] Use a jet mill to grind plant coarse powder (such as bamboo coarse powder) of 200-400 mesh into ultrafine plant powder with D50 of 8 microns (the fineness of wet method detection using water as a dispersant) or finer for standby use.

[0095] The silane coupling agent and silicon dioxide were mixed uniformly in the following proportions (parts by weight) to prepare a treatment solution:

[0096] Silane coupling agent: 0.5-2 parts

[0097] Silicon dioxide: 0.5-3 parts

[0098] Ethanol: 100 parts

[0099] Active ultrafine plant powder is obtained by uniformly mixing 5-8 micron ultrafine plant powder and treatment liquid in a high-speed mixer for 15-35 minutes, with the material temperature controlled at 90-105°C. The principle is to form a chemically bonded film layer on the surface of plant fibers, improving the interfacial bonding strength between the plant fibers and the matrix, while also introducing hydrophilic or hydrophobic groups to enhance the surface activity of the plant fibers.

[0100] Then, add a variety of additives to dry the moisture, rotate at high speed in a high-speed mixer, and achieve the drying effect when the mixer reaches 100-105°C. After the moisture content is tested and meets the use requirements, the material is discharged and sealed.

[0101] Step 2: Add all ingredients to the dried ultrafine plant powder in a high-speed mixer and mix thoroughly.

[0102] First, the dried ultrafine plant powder is treated with a dispersant in a high-speed mixer, and then the other components in the formula shown in Table 1 are added and mixed uniformly to obtain a mixture. For example, the high-speed mixer is rotated at a speed of 150 rpm or higher and the temperature is above 130 degrees Celsius, and the mixture is stirred for more than 30 minutes to ensure uniform mixing.

[0103] After being fully stirred from low speed to low-medium speed, it is fed into the feeder of the twin-screw extruder.

[0104] It should be noted that the foaming agent in Example 31 needs to be mixed with the ultrafine plant powder in advance, then left to stand for 20 minutes, and then other components are added and then fully mixed to obtain a mixture.

[0105] Step 3: Add the mixture into a twin-screw extruder for extrusion granulation, wherein the temperature of each zone of the extruder is between 110 degrees and 165 degrees.

[0106] When the mixture is added to the twin-screw extruder for extrusion and granulation, the temperature setting of zones 1-5 of the twin-screw extruder is particularly important. The best state is the molten state. The temperature of the next 10 zones decreases slowly, which allows the material to have a good chemical reaction in the screw without losing its original physical properties.

[0107] Reactive extrusion process conditions:

[0108] Zone 1: 110C°; Zone 2: 155C°; Zone 3: 165C°; Zone 4: 165C°; Zone 5: 160C°; Zone 6: 150C°; Zone 7: 145C°; Zone 8: 135C°; Zone 9: 125C°; Zone 10: 115C°; Zone 11: 115C°; Zone 12: 115C°; Zone 13: 115C°; Zone 14: 115C°; Zone 15: 115C°.

[0109] Such a temperature setting can cause the hydroxyl groups of cellulose in the ultrafine plant powder to undergo esterification or etherification to form a network structure, while also reducing the density.

[0110] Here, the twin-screw extruder used is a large length-to-diameter ratio, co-rotating twin-screw extruder with an L / D ratio ranging from 52 / 1 to 68 / 1, to provide a sufficient reaction zone for the density-reduced composition (resin). The screw speed is 10 to 900 rpm, providing the digital composition with a sufficient shear rate at a high speed, so that the material is crushed and reacted more fully.

[0111] Step 4: pelletizing to form particles, which are used as a density-reducing composition for preparing film products.

[0112] After being extruded from the twin-screw extruder, the pellets are cooled by a high-pressure circulating water pipe, then enter a centrifugal dehydrator to remove moisture, and are then pelletized and packaged.

[0113] The density-reduced composition obtained in the previous steps is extruded using conventional twin-screw extruder equipment to produce a packaging film masterbatch. This packaging film masterbatch is then blown in a film blowing machine to produce a packaging film. This packaging film meets the density and performance parameters described in the second or third embodiment.

[0114] The pressure inside the die is required to ensure that the tube film opens quickly after coming out of the die. Figure 12 As shown, the left image is correct, while the right image is incorrect. This is because the blow-up ratio in the right image is insufficient, which seriously affects density and physical properties. The same batch of low-density packaging film masterbatch produced in this application has a density of 0.43 g / cm³ when blown using the method shown in the left image, while using the method shown in the right image, the density is 0.61-0.7 g / cm³, or even higher.

[0115] Because the density of PBAT is 1.2-1.3g / cm 3 , bamboo fiber density is about 1.4g / cm 3 , the density of inorganic filler is as high as 2.2-2.8g / cm 3 The density of conventional biodegradable film products obtained from these components is 1.24 g / cm 3 However, based on the low-density biodegradable film products obtained in this application, the density of conventional biodegradable packaging films is increased from 1.24 g / cm 3 and above to 0.3~0.9g / cm 3 , resulting in a reduction in the material cost of the packaging film of this application to 73%, and a minimum of 24%, representing significant economic benefits. It should be noted that when density measurements are performed according to the GB / T 1033 technical standard, a non-polar liquid that is insoluble in water and has no interaction with plant fibers (no physical or chemical adsorption) is used instead of water to ensure accurate data, as plant fibers absorb water.

[0116] It should be noted that the above-mentioned multiple embodiments are only examples. The technical solutions of the various embodiments can be combined and the order of the steps can be changed, all within the scope of protection of this patent.

[0117] The present invention has been described in detail above. For those skilled in the art, any obvious changes made to the present invention without departing from the essence of the present invention will constitute infringement of the patent rights of the present invention and the person skilled in the art will bear the corresponding legal liability.

Claims

1. A density-reducing composition using ultrafine plant powder, characterized in that Contains ultrafine plant powder with a fineness of 5 to 8 microns and is used to prepare a density of less than 1.1g / cm 3 Fully biodegradable film products or products with a density less than 0.9g / cm 3 Fully biodegradable film products.

2. The density reducing composition according to claim 4, wherein It is composed of the following components in parts by weight: PBAT 55-80% PLA 10-20% Ultrafine plant powder 2% to 5%, Plant fiber plasticizer 0.5-2% PBAT\PLA plasticizer 0.2~1% Residue of additives.

3. A method for preparing a density-reducing composition, characterized in that The following steps are involved: Step 1: drying the ultrafine plant powder according to any one of claims 1 to 3 to control the moisture content to be below 1%; Step 2: Add all ingredients to the dried ultrafine plant powder through a high-speed mixer and mix thoroughly; Step 3: adding the mixture to a twin-screw extruder for extrusion granulation, wherein the temperature of at least two zones of the extruder is between 140 degrees and 160 degrees; Step 4: pelletizing to form particles, which are used as a density-reducing composition for preparing film-like products.

4. The method for preparing the density-reducing composition according to claim 3, wherein The following steps are involved: The processing temperature of the extruder is set to 130 degrees in zone 1, 130 degrees in zone 2, 135 degrees in zone 3, 140 degrees in zone 4, 146 degrees in zone 5, 150 degrees in zone 6, 152 degrees in zone 7, and 152 degrees in zone 8.

5. A packaging film prepared using a density-reducing composition, characterized in that: Density less than 0.9g / cm 3 Fully biodegradable film products.

Images