A biodegradable membrane and bag modified bamboo powder / PBAT composite material and its preparation method
By modifying bamboo powder with liquid ester coupling agents, combined with high-speed grinding and ultraviolet irradiation treatment, the problem of poor dispersibility of bamboo powder in polymer matrix was solved, and high-performance bamboo powder/PBAT composite materials were prepared, which are suitable for film and bag products.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INT CENT FOR BAMBOO & RATTAN
- Filing Date
- 2025-08-26
- Publication Date
- 2026-05-26
AI Technical Summary
In existing technologies, bamboo powder exhibits poor dispersibility in polymer matrices, making it difficult to prepare films and bags, and resulting in poor mechanical properties.
By modifying bamboo powder with liquid ester coupling agents under specific processes, combined with high-speed grinding, spraying and ultraviolet irradiation treatment, the compatibility and interfacial bonding force between bamboo powder and PBAT resin are improved, and modified bamboo powder/PBAT composite materials are prepared.
It significantly improves the tensile strength and elongation at break of composite materials, enabling stable molding of films and bag-shaped products with high filler content, and meeting the performance requirements of express delivery bags.
Smart Images
Figure CN120775359B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of bamboo powder and polymer composite materials, specifically to a biodegradable membrane / bag modified bamboo powder / PBAT composite material and its preparation method. Background Technology
[0002] Under the policy of "replacing plastic with bamboo," the preparation of biodegradable composite materials by leveraging the advantages of abundant bamboo resources, low raw material prices, low density, and high starch content has attracted much attention. Currently, bamboo-based biodegradable materials are widely used in molding and injection molding products, but are very rare in packaging film products. The main reason is that bamboo powder is difficult to disperse evenly in PE or PBAT (polybutylene terephthalate) films, easily forming a large number of agglomerated particles, which also severely clog the filters of processing equipment, making it impossible to form a stable film. Currently, the widely used fully biodegradable express delivery bags mainly use PBAT bioresin with 15%~30% calcium carbonate or talc added, or PBAT bioresin with 15%~30% corn starch added. The former has too high a density and is easily decomposed in the air, resulting in rapid performance degradation; the latter has a lighter density and more stable performance, but lower mechanical strength.
[0003] CN116178925A discloses a carbon dioxide-propylene oxide copolymer / bamboo powder composite membrane and its preparation method. The membrane utilizes bamboo powder, starch, and modified starch in combination, with the addition of carbon dioxide-propylene oxide copolymer (PPC), resulting in a biodegradable membrane with high mechanical properties. However, thermoformed membranes are typically thick with significant thickness variations, and are not suitable for industrial film bag production.
[0004] CN104231416A discloses a biodegradable environmentally friendly bag and its preparation method, which includes 5-25 parts by weight of fine bamboo powder and 15-30 parts of polyethylene. The fine bamboo powder is made by grinding bamboo into nano- or sub-nano-sized ultrafine powder using a grinder, adding a hydrophobic modifier and stirring at room temperature for 2 hours. The weight ratio of fine bamboo powder to hydrophobic modifier is 100:1 to 100:3, and the hydrophobic modifier is a silane coupling agent.
[0005] CN105968493A discloses an antibacterial and tear-resistant packaging bag and its preparation method, comprising the following components in parts by weight: 58-71 parts low-density polyethylene, 13-19 parts styrene-butadiene rubber, 6-15 parts MBS resin, 3-9 parts hydroxyl silicone oil, 7-14 parts bamboo powder, 5-11 parts ramie fiber, 3-6 parts nano copper oxide powder, 2-6 parts zinc powder, 4-9 parts zirconium oxide powder, 6-13 parts basic calcium carbonate, 5-11 parts xanthan gum, 1-6 parts microcrystalline wax, 2-5 parts POE, 2-8 parts zinc ethylhexanoate, 3-10 parts butyl stearate, 2-9 parts vanadium oxide fiber, 1-6 parts 2-hydroxyethyl-2-hydroxypropyl methyl ether cellulose, and 0.5-3 parts coupling agent. The bamboo powder, ramie fiber, and coupling agent are mixed, modified, and then melt-extruded together with other mixtures in a twin-screw extruder.
[0006] The above patents use bamboo powder modified with coupling agents, but all involve reaction modification after mixing the coupling agent and bamboo powder. On the one hand, these modification methods cannot avoid the influence of free water on the coupling agent, significantly reducing its modification effect. On the other hand, because the bamboo powder used only has a small amount of weakly reactive hydroxyl groups on its surface, it cannot form effective chemical bonds with the coupling agent. The coupling agent and bamboo powder exist only in a physical blending form. During subsequent processing, the bamboo powder inevitably exhibits "island" agglomeration, affecting the mechanical properties of the final product. Summary of the Invention
[0007] To address the problem in existing technologies where poor compatibility between bamboo powder and polymer matrices makes it difficult to prepare bamboo / polymer composites into films and bags, this invention provides a biodegradable modified bamboo powder / PBAT composite material for films and bags, along with its preparation method. This invention significantly improves the dispersibility of bamboo powder in a polyester matrix through specific process modification of the coupling agent, thereby significantly improving the mechanical properties of the composite material in film and bag forms. This allows bamboo materials to be combined with polymer materials to prepare film and bag products, overcoming the previous limitation of bamboo materials being difficult to combine with polymer matrices to produce such products, and filling a technological gap in this area. The objective of this invention is achieved through the following technical solution:
[0008] In a first aspect, the present invention provides a biodegradable membrane / bag modified bamboo powder / PBAT composite material, comprising the following raw materials in parts by weight: 5-20 parts modified bamboo powder, 0-6 parts polylactic acid resin, 65-85 parts PBAT polyester resin, 5-15 parts inorganic filler, and 0.5-2 parts lubricating dispersant; wherein the modified bamboo powder is obtained by grinding bamboo powder in a disc mill, with a liquid ester coupling agent added by spraying during grinding, and then modified by ultraviolet irradiation after grinding; the grinding speed of the disc mill is 2000-3000 rpm.
[0009] The amount of modified bamboo powder is preferably 6-15 parts, more preferably 8-14 parts; the amount of polylactic acid resin is preferably 4-6 parts. It is also preferred that the grinding, spraying, and ultraviolet irradiation modification are all carried out in a disc mill.
[0010] Furthermore, the particle size of bamboo powder is 400-800 mesh.
[0011] Furthermore, the liquid ester coupling agent is selected from at least one of aluminate coupling agents, titanate coupling agents, and borate coupling agents. The modified bamboo powder of this invention undergoes a specific process, with the liquid ester coupling agent added via spraying during grinding, resulting in almost no agglomeration and more uniform particle size.
[0012] Furthermore, the amount of liquid ester coupling agent added is 1-3% of the mass of bamboo powder; the liquid ester coupling agent is preferably an aluminate coupling agent, and the aluminate coupling agent is LD-22 from Yangzhou Lida Resin Co., Ltd.
[0013] Furthermore, the modified bamboo powder is prepared by a method comprising the following steps:
[0014] (P1) Bamboo raw materials are processed into bamboo granules with a moisture content of ≤5%; the bamboo granules are ground in a disc mill and graded to obtain 400-800 mesh bamboo powder.
[0015] (P2) 400-800 mesh bamboo powder is ground in a disc mill, and liquid ester coupling agent is sprayed at the same time to obtain coupling agent treated bamboo powder.
[0016] (P3) Under an inert atmosphere, bamboo powder treated with coupling agent is irradiated with ultraviolet light to obtain modified bamboo powder.
[0017] The finer the bamboo powder, the larger the contact area with PBAT, resulting in the best reinforcing effect on PBAT, but it is also more prone to agglomeration. Bamboo powder with a particle size of 400-800 mesh is most suitable for modification with liquid ester coupling agents. Adding liquid ester coupling agents via spraying reduces the amount of coupling agent used while still achieving better modification results. UV irradiation triggers a reaction between the active functional groups on the bamboo powder surface, such as hydroxyl groups, and the coupling agent, making the bond between the coupling agent and bamboo powder stronger and preventing damage during subsequent high-temperature processing. This stronger interfacial bonding is more conducive to improving the performance of the composite material. During grinding, the moisture content of the bamboo powder decreases, and the ambient temperature increases. The newly formed, highly active bamboo powder surface is instantly coated with coupling agent molecules, effectively preventing the agglomeration of fine particles. The long-chain alkyl portion of the ester coupling agent covers the hydrophilic bamboo powder surface, significantly reducing its surface energy and changing it from hydrophilic to hydrophobic, thus significantly improving its compatibility with PBAT resin.
[0018] The key to this invention lies in the simultaneous addition of a liquid ester coupling agent via spraying during grinding. High-speed grinding not only reduces particle size but also disrupts the surface structure of bamboo powder through intense mechanical force, generating numerous broken bonds, free radicals, and activation sites, significantly enhancing its chemical reactivity. At the instant the newly formed, highly reactive bamboo powder surface is created during high-speed grinding, the liquid coupling agent is simultaneously introduced via spraying. This ensures that the newly formed, unaggregated surface with the highest reactivity is coated by coupling agent molecules immediately. The highly reactive surface sites generated during grinding are instantly captured by the sprayed coupling agent molecules and coated in situ during the disc mill, preventing these active sites from becoming inactive due to oxidation or moisture adsorption in the air, thus greatly improving coupling efficiency. The simultaneous and dynamic equilibrium of high-energy grinding, spray coating, and irradiation reaction in the same equipment is unprecedented. Moreover, the bamboo powder obtained in this way can simultaneously improve the tensile strength and elongation at break of the composite material. This is extremely difficult to achieve with high filler concentrations of rigid filler like bamboo powder. Because high tensile strength and elongation at break are often inversely related, simultaneously improving both tensile strength and elongation at break has been a long-desired but unfulfilled goal in the field. While mechanically modified grinding and the use of chemically modified coupling agents are known concepts and routine practices, achieving synergistic effects between mechanical grinding and spraying with coupling agents in such a high-energy environment at a specific rotational speed is not straightforward. This requires a deep understanding of the interaction between the two mechanisms and precise control of process parameters.
[0019] Furthermore, in step (P1), the bamboo raw material is a low-density bamboo species, such as short-spike bamboo (0.38 g / cm³). 3 Early bamboo (0.42g / cm) 3 Sweet bamboo (0.48g / cm) 3 The size of the bamboo particles is 1-5mm, and the moisture content is ≤5%; the rotation speed of the disc mill is 1000-1500rpm, the grinding time is 30-60min, and the bamboo powder is obtained by sieving to 400-800 mesh.
[0020] Furthermore, in step (P2), the grinding speed is 2000-3000 rpm, and the spraying time is 10-20 min (the grinding is carried out simultaneously with the spraying time); after spraying the liquid ester coupling agent, mechanical grinding continues for 5-10 min.
[0021] Furthermore, in step (P3), the inert atmosphere is nitrogen and / or argon; during ultraviolet irradiation, the ultraviolet wavelength is 200-400 nm, and the irradiation power is 20-100 mW / cm². 2 Irradiation time: 1-10 min.
[0022] The inventors previously attempted to prepare modified bamboo powder using a conventional blending modification method. This involved mixing 400-800 mesh bamboo powder with 2 wt% of a liquid ester coupling agent in a high-speed mixer at 600 rpm for 3 hours. However, this conventional blending modification process is time-consuming and energy-intensive. Most importantly, the modified bamboo powder obtained through this method suffers from insufficient dispersibility.
[0023] The alkoxy groups in the ester coupling agent used in this invention need to be hydrolyzed and broken before reacting with the powder. If the powder contains free water, the alkoxy groups will combine with water to form hydrogen bonds instead of covalent and ionic bonds. This will reduce the activity of the coupling agent and thus affect the mechanical properties of the product. Bamboo powder itself is an optimal reaction process with high temperature and low moisture content during grinding. The processed bamboo powder is hydrophobic, so there is no need to worry about secondary water absorption during storage, which greatly reduces the energy consumption of secondary processing during bamboo powder processing.
[0024] Furthermore, the polylactic acid resin is blown film grade, preferably with a melt index of 2~6 g / 10min (190℃*2.16kg); the PBAT resin is blown film grade, preferably with a melt index of 2~6 g / 10min (190℃*2.16kg).
[0025] Furthermore, the inorganic filler is selected from at least one of talc and calcium whisker sulfate; preferably, talc and calcium whisker sulfate are compounded in a mass ratio of 1-2:1-2. Calcium whisker sulfate is a needle-like or fibrous single crystal grown by single crystal growth, which can synergistically enhance the effect with flake talc, thereby improving the tensile strength and right-angle tear strength of the film.
[0026] Furthermore, the lubricating dispersant is selected from at least one of monoglycerides, sorbitol, polyethylene glycol, and glycerin.
[0027] Furthermore, the modified bamboo powder / PBAT composite material also includes the following auxiliary materials in parts by weight: 0.1-0.5 parts slip opening agent, 0.1-0.5 parts anti-hydrolysis agent, and 0.1-1 parts antioxidant.
[0028] Furthermore, the anti-hydrolysis agent is carbodiimide; the slippery opening agent is erucamide or oleamide; and the antioxidant is a phenolic antioxidant, such as antioxidant 1010.
[0029] Secondly, the present invention provides a method for preparing the biodegradable membrane and bag modified bamboo powder / PBAT composite material, comprising the following steps:
[0030] (S1) Modified bamboo powder, inorganic filler and lubricating dispersant are added to a high-speed mixer, low-speed stirring is started, and the temperature is raised. When the material temperature reaches 100-110℃, high-speed stirring is started. After stirring, the mixture is cooled to obtain pretreated powder.
[0031] (S2) Add polylactic acid resin and PBAT resin to a mixer and stir. After the resin softens into a viscoelastic colloid, add the pretreated powder obtained in step (S1). Optionally, add auxiliary materials, mix evenly and then perform internal mixing. After the internal mixing is completed, extrude and granulate using a screw extruder to obtain the modified bamboo powder / PBAT composite material.
[0032] Further, in step (S1), the low-speed stirring speed is 100-300 rpm, the high-speed stirring speed is 500-1000 rpm, and the high-speed stirring time is 1-2 hours; in step (S2), the mixing temperature is 140-170℃, and the mixing time is 10-60 minutes, for example, mixing at 150-160℃ for 30-40 minutes; the screw extrusion is a two-stage extrusion granulator, which is divided into a twin-screw extrusion granulator and a single-screw extrusion granulator. The screw length-to-diameter ratio of the twin-screw extrusion granulator in the front stage is 33~55:1, and the discharge port of the single-screw extrusion granulator in the rear stage uses an air-cooled die surface for pelletizing. The barrel temperature is 160-180℃, the die temperature is 145-165℃, and the discharge port of the rear stage uses an 80-120 mesh filter. If the melt pressure value is found to be continuously increasing during production, it can be determined that the pre-treated powder is unqualified, and the batch should be scrapped.
[0033] Thirdly, the present invention provides a biodegradable film or biodegradable bag made of the above-mentioned biodegradable film or bag modified bamboo powder / PBAT composite material.
[0034] The beneficial effects of this invention are as follows:
[0035] I. This invention provides a fully biodegradable film-shaped or bag-shaped product. The raw material is bamboo powder, which has three major advantages: biodegradability, renewable plant source, and non-grain, replacing corn starch or potato starch from grain sources.
[0036] II. This invention, through innovative formulation design and preparation process, produces modified bamboo powder using a specific technique: simultaneously spraying a liquid ester coupling agent via high-speed grinding. This high-speed mechanical grinding and spraying process for coupling agent modification, followed by in-situ reaction under ultraviolet irradiation in the same equipment, results in modified bamboo powder that can simultaneously improve the tensile strength and elongation at break of composite materials even at high filler contents.
[0037] Third, the addition of flaky talc powder and whisker-like calcium sulfate powder simultaneously improved the elongation at break and right-angle tear strength of the composite material. This is likely because talc powder provides strong shear friction, and whisker-like calcium sulfate can synergistically reinforce the flaky talc powder, thereby improving the mechanical properties of the composite material.
[0038] Fourth, the composite material of the present invention has a non-grain biomass content of more than 15 wt%, which reduces costs while providing better heat-sealing strength of the film bag. All performance indicators can meet the technical requirements of express delivery bags, and the surface is suitable for water-based ink printing, which can meet the requirements of large-scale production.
[0039] Fifth, the bamboo-based blown film express bag manufactured by this invention can be degraded by composting as a general biological material, which meets the requirements of environmental protection. Attached Figure Description
[0040] Figure 1 The images show SEM images of the modified bamboo powder prepared by the conventional blending modification process in Preparation Example 1 and the modified bamboo powder prepared by the spray mixing and irradiation modification process (mechanical irradiation modification process) in Preparation Example 1.
[0041] Figure 2 The images show the SEM images and particle size distribution of the modified bamboo powder prepared in Example 1.
[0042] Figure 3 The images show SEM images and particle size distribution diagrams of the modified bamboo powder prepared in Comparative Preparation Example 1. Detailed Implementation
[0043] To more clearly illustrate the present invention and to provide a clearer understanding of its technical features, objectives, and beneficial effects, the technical solution of the present invention will now be described in detail below. However, this should not be construed as limiting the scope of the invention. The present invention will be further described below with reference to the following embodiments.
[0044] Polylactic acid resin was Hisun PLA101; PBAT resin was Hubei Yihua YH801D; the silicon content of 1500 mesh talc powder from Haicheng, Liaoning was 55%; whisker-type calcium sulfate was purchased from Shijiazhuang Yuexiu Technology Co., Ltd., with a length of 100-200μm and a diameter of 1-3μm; monoglyceride was commercially available in flake form; aluminate coupling agent was LD-22 from Yangzhou Lida Resin Co., Ltd.; erucamide was a product of Jiangxi Zhilian Co., Ltd.; anti-hydrolysis agent was carbodiimide from Langyi Co., Ltd.; and the antioxidant was commercially available antioxidant 1010.
[0045] Preparation Example 1
[0046] (S1) The bamboo raw material is the processing residue particles of bamboo chopsticks (early bamboo), with a size of 5mm and a moisture content of 3.2%.
[0047] (S2) The bamboo raw material is placed in a disc mill for one grinding. The disc mill speed is 1000 r / min and the grinding time is 30 min.
[0048] (S3) The ground bamboo powder is graded once. The grading machine rotates at 1000 r / min. After grading and sieving, 400 mesh bamboo powder is obtained.
[0049] (S4) 400 mesh bamboo powder is placed in a disc mill for secondary grinding. The disc mill speed is 3000 r / min and the grinding time is 20 min. At the same time, 2 wt% of liquid aluminate coupling agent LD-22 is added to the bamboo powder by spraying and then ground for another 10 min to obtain coupling agent treated bamboo powder.
[0050] (S5) Bamboo powder treated with coupling agent and then modified by ultraviolet irradiation (ultraviolet wavelength 360nm, irradiation time 2min, irradiation power 50W / cm²) 2 In a nitrogen atmosphere, modified bamboo powder was obtained.
[0051] Preparation Example 2
[0052] The rest is the same as in Preparation Example 1, except that in step (S3), 600-mesh bamboo powder is obtained after grading and sieving; and in step (S4), the rotation speed of the disc mill is 2000 r / min.
[0053] Preparation Example 3
[0054] The rest is the same as in Preparation Example 1, except that in step (S3), 300-mesh bamboo powder is obtained after grading and sieving, and then the 300-mesh bamboo powder is used for coupling agent treatment and ultraviolet irradiation treatment.
[0055] Preparation Example 4
[0056] The rest is the same as in Preparation Example 1, except that in step (S3), after grading and sieving, 1000-mesh bamboo powder is obtained, and then 300-mesh bamboo powder is used for coupling agent treatment and ultraviolet irradiation treatment.
[0057] Preparation Example 5
[0058] Everything else is the same as in Preparation Example 1, except that in step (S4), the rotation speed of the disc mill is 1500 r / min.
[0059] Preparation Example 6
[0060] Everything else is the same as in Preparation Example 1, except that in step (S4), the rotation speed of the disc mill is 4000 r / min.
[0061] Comparative Preparation Example 1
[0062] Steps (S1) to (S3) are the same as in Preparation Example 1, except that the following steps are: 400-mesh bamboo powder and 2 wt% of the weight of the bamboo powder liquid aluminate coupling agent LD-22 are added to a high-speed mixer and mixed at 600 rpm for 3 hours to obtain modified bamboo powder.
[0063] Comparative Preparation Example 2
[0064] Everything else is the same as in Preparation Example 1, except that step (S4) is changed to: after 400-mesh bamboo powder and 2wt% liquid aluminate coupling agent LD-22 are mixed evenly, the mixture is placed in a disc mill for secondary grinding. The disc mill speed is 2500 r / min, and the grinding time is 30 min. That is, compared with Preparation Example 1, the coupling agent is not added by spraying, but is mixed evenly with the bamboo powder before grinding.
[0065] Comparative preparation example 3
[0066] Everything else is the same as in Preparation Example 1, except that step (S5) is not performed, i.e., ultraviolet irradiation is not performed.
[0067] Figure 1 The images show SEM images of the modified bamboo powder prepared by the conventional blending modification process in Preparation Example 1 and the modified bamboo powder prepared by the spray mixing and irradiation modification process in Preparation Example 1. The images show that the bamboo powder treated by the spray mixing and irradiation modification process exhibits almost no agglomeration and has a more uniform particle size.
[0068] Figure 2 The images show the SEM images and particle size distribution of the modified bamboo powder prepared in Example 1. Figure 3 The table shows the SEM images and particle size distribution of the modified bamboo powder obtained in Preparation Example 1 and Comparative Preparation Example 1. Table 1 compares the particle size and particle size distribution of the modified bamboo powder obtained in Preparation Example 1 and Comparative Preparation Example 1. The D90 and D50 indices of the bamboo powder obtained in Preparation Example 1 are significantly lower than those of the bamboo powder obtained by the conventional modification process in Comparative Preparation Example 1, indicating that the bamboo powder obtained by the specific modification method of the present invention has better dispersibility and can effectively inhibit the agglomeration of bamboo powder particles.
[0069] The formula for calculating the span (SPAN) is as follows: .
[0070] Table 1 Comparison of bamboo powder particle size distribution obtained by different modification methods
[0071] .
[0072] Example 1
[0073] (1) Raw material preparation:
[0074] Preparation Example 1 yielded 8 kg of modified bamboo powder, 4 kg of polylactic acid resin, 70 kg of PBAT resin, 5 kg of talc, 5 kg of whisker-type calcium sulfate, 0.8 kg of monoglyceride, 0.1 kg of erucamide, 0.2 kg of carbodiimide as an anti-hydrolysis agent, and 0.3 kg of 1010 antioxidant.
[0075] (2) Pretreatment:
[0076] Weigh the modified bamboo powder, talc powder, whisker-type calcium sulfate, and monoglyceride from the above formula according to the proportions, add them to the high-speed mixer, turn on low-speed stirring (200 rpm), turn on the pot heating, set the pot heating temperature to 125℃, open the pot lid about halfway (to facilitate the removal of water vapor), when the material temperature in the pot reaches 100℃, turn on high-speed stirring (600 rpm) and continue for 90 minutes, then stop stirring, unload the material and let it cool naturally to obtain the pretreated powder.
[0077] (3) Secret refining:
[0078] Weigh out the polylactic acid resin and PBAT resin from the above formula according to the proportions, add them to the internal mixer for preheating and stirring. After the resin softens into a viscoelastic colloid, add the above pretreated powder and other additives (erucamide, anti-hydrolysis agent carbodiimide, 1010 antioxidant) evenly to the internal mixer in 3 batches, and mix at 150°C for 30 minutes to prepare for discharge.
[0079] (4) Granulation: Put the well-mixed premixed material into the double cone forced feeder, turn on the two-stage extrusion granulator at the bottom of the feeder, the screw length-to-diameter ratio of the twin screw extrusion granulator in the front section is 40:1, and the discharge port of the single screw extrusion granulator in the rear section is granulated with air-cooled die surface, the barrel temperature is 170℃, the die temperature is 155℃, a 100-mesh filter screen is added to the discharge port of the rear section, and air-cooled die surface is used for granulation. If the melt pressure value is found to be increasing continuously during production, it can be determined that the pre-treated powder is unqualified and the batch is scrapped.
[0080] (5) Film blowing and bag making:
[0081] The blown film bag making machine is used, with a screw length-to-diameter ratio of 32:1, a barrel temperature of 155℃, a die head temperature of 158℃, a screw speed of 200 rpm, a 100-mesh filter screen, a blown film thickness of 0.055mm, and a continuous roll bag after winding.
[0082] (6) Test results:
[0083] The blown film process is stable and bubble-free. The film surface is light yellow, delicate and smooth, with a distinct bamboo powder smell. The film thickness is consistent, and the bag stiffness and smoothness are moderate. The heat seal is firm. The sampling test data are: thickness 0.055mm and film density 1.12g / cm³.
[0084] Example 2
[0085] (1) Raw material preparation:
[0086] Preparation Example 1 yielded 14 kg of modified bamboo powder, 5 kg of polylactic acid resin, 69 kg of PBAT resin, 8 kg of talc, 4 kg of whisker-type calcium sulfate, 1.2 kg of monoglyceride, 0.1 kg of erucamide, 0.2 kg of carbodiimide as an anti-hydrolysis agent, and 0.3 kg of 1010 antioxidant.
[0087] (2) Pretreatment:
[0088] Weigh out the bamboo powder, talc powder, whisker-type calcium sulfate, and monoglyceride from the above formula according to the proportions, and pour them into a 20L high-speed mixer. Turn on low-speed stirring (250 rpm), turn on the pot heating, and set the pot heating temperature to 135℃. Fully open the pot lid (to facilitate the removal of water vapor). When the material temperature inside the pot reaches 100℃, turn on high-speed stirring (700 rpm) and continue for 120 minutes. Then stop stirring, unload the material, remove it, and let it cool naturally to obtain the pretreated powder.
[0089] (3) Secret refining:
[0090] Weigh out the polylactic acid resin and PBAT bio-resin from the above formula according to the proportions and add them to the internal mixer for preheating and stirring. After the resin softens into a viscoelastic colloid, add the above pretreated material and other additives (erucamide, anti-hydrolysis agent carbodiimide, 1010 antioxidant) into the internal mixer in 3 batches and mix at 150°C for 30 minutes. The material is then ready to be discharged.
[0091] (4) Granulation:
[0092] Using self-developed integrated mixing and granulation production equipment, the mixed premixed material blocks are put into a double cone forced feeder, and the two-stage extrusion granulator at the lower end of the feeder is turned on. The barrel temperature is 170℃. A 100-mesh filter screen is added to the discharge port at the rear end. Air-cooled die surface pelletizing is used, and the die head temperature is 155℃.
[0093] (5) Film blowing and bag making:
[0094] The machine uses a self-developed small blown film bag making machine with a screw length-to-diameter ratio of 32:1, a barrel temperature of 155℃, a die head temperature of 158℃, a screw speed of 300 rpm, a 100-mesh filter screen, a blown film thickness of 0.055mm, and a continuous roll bag after winding.
[0095] (6) Test results:
[0096] The blown film process is stable and bubble-free. The film surface is brownish-yellow, and fine bamboo powder can be observed with the naked eye. The bamboo powder has a strong odor. The film thickness is consistent and the bag stiffness and smoothness are moderate. The heat seal is firm. The sampling test data are: thickness 0.055mm and film density 1.18g / cm³.
[0097] Example 3
[0098] (1) Raw material preparation:
[0099] Preparation Example 1 yielded 16 kg of modified bamboo powder, 6 kg of polylactic acid resin, 70 kg of PBAT biopolyester resin, 3 kg of talc powder, 5 kg of whisker-type calcium sulfate, 1 kg of polyethylene glycol (PEG2000), 0.1 kg of erucamide, 0.2 kg of carbodiimide anti-hydrolysis agent, and 0.3 kg of 1010 antioxidant.
[0100] (2) Pretreatment:
[0101] Weigh out the bamboo powder, talc powder, and polyethylene glycol PEG2000 according to the above formula, and pour them into a 20L high-speed mixer. Turn on low-speed stirring (200 rpm), turn on the pot heating, set the pot heating temperature to 130℃, and open the pot lid about halfway (to facilitate the release of water vapor). When the material temperature in the pot reaches 100℃, turn on high-speed stirring (800 rpm) and continue for 60 minutes. Then stop stirring, unload the material, remove it and let it cool naturally to obtain the pretreated powder.
[0102] (3) Secret refining:
[0103] Weigh out the polylactic acid resin and PBAT bio-resin from the above formula according to the proportions, add them to the internal mixer for preheating and stirring. After the resin softens into a viscoelastic colloid, add the above pretreated material and other additives (erucamide, anti-hydrolysis agent carbodiimide, 1010 antioxidant) evenly to the internal mixer in 3 batches, and mix at 150°C for about 30 minutes. The material is then ready to be discharged.
[0104] (4) Granulation:
[0105] Using self-developed integrated mixing and granulation production equipment, the mixed premixed material blocks are put into a double cone forced feeder, and the two-stage extrusion granulator at the lower end of the feeder is turned on. The barrel temperature is 170℃. A 100-mesh filter screen is added to the discharge port at the rear end. Air-cooled die surface pelletizing is used, and the die head temperature is 155℃.
[0106] (5) Film blowing and bag making:
[0107] The blown film bag making machine is used, with a screw length-to-diameter ratio of 32:1, a barrel temperature of 155℃, a die head temperature of 158℃, a screw speed of 300 rpm, a 100-mesh filter screen, a blown film thickness of 0.055mm, and a vest bag made by the bag making machine after winding.
[0108] (6) Test results:
[0109] The blown film process is stable and bubble-free. The film surface is white, smooth, and odorless. The film thickness is consistent. The bag making has moderate stiffness and smoothness. The heat sealing is firm. The sampling test data are: thickness 0.055mm and film density 1.07g / cm³.
[0110] Example 4
[0111] The other conditions were the same as in Example 1, except that the modified bamboo powder prepared in Example 1 was replaced with an equal mass of the modified bamboo powder prepared in Example 2.
[0112] Example 5
[0113] The other conditions were the same as in Example 1, except that the modified bamboo powder prepared in Example 1 was replaced with an equal mass of the modified bamboo powder prepared in Example 3.
[0114] Example 6
[0115] The other conditions were the same as in Example 1, except that the modified bamboo powder prepared in Example 1 was replaced with an equal mass of the modified bamboo powder prepared in Example 4.
[0116] Example 7
[0117] The other conditions were the same as in Example 1, except that the modified bamboo powder prepared in Example 1 was replaced with an equal mass of the modified bamboo powder prepared in Example 5.
[0118] Example 8
[0119] The other conditions were the same as in Example 1, except that the modified bamboo powder prepared in Example 1 was replaced with an equal mass of the modified bamboo powder prepared in Example 6.
[0120] Example 9
[0121] The other conditions are the same as in Example 1, except that the inorganic filler is replaced by 10 parts of talc powder instead of 5 parts of talc powder and 5 parts of whisker-type calcium sulfate.
[0122] Example 10
[0123] The other conditions are the same as in Example 1, except that the inorganic filler is replaced by 10 parts of whisker-type calcium sulfate instead of 5 parts of talc powder and 5 parts of whisker-type calcium sulfate.
[0124] Comparative Example 1
[0125] The other conditions were the same as in Example 1, except that the modified bamboo powder prepared in Example 1 was replaced with the modified bamboo powder prepared in Comparative Example 1 of equal mass.
[0126] Comparative Example 2
[0127] The other conditions were the same as in Example 1, except that the modified bamboo powder prepared in Example 1 was replaced with the modified bamboo powder prepared in Comparative Example 2 of equal mass.
[0128] Comparative Example 3
[0129] The other conditions were the same as in Example 1, except that the modified bamboo powder prepared in Example 1 was replaced with the modified bamboo powder prepared in Comparative Example 3 of equal mass.
[0130] Comparative Example 4
[0131] The other conditions are the same as in Example 1, except that the modified bamboo powder prepared in Example 1 is replaced with an equal mass of unmodified bamboo powder with the same particle size.
[0132] Application examples
[0133] The packaging plastic films and bags prepared in accordance with GB / T 38727-2020 for fully biodegradable logistics and express delivery were tested according to the above examples and comparative examples. The results are shown in Table 2 below.
[0134] Table 2 Performance Tests of Packaging Plastic Bags
[0135] .
Claims
1. A biodegradable film and bag modified bamboo powder / PBAT composite material, characterized in that, The raw materials include the following parts by weight: 5-20 parts modified bamboo powder, 0-6 parts polylactic acid resin, 65-85 parts PBAT polyester resin, 5-15 parts inorganic filler, and 0.5-2 parts lubricant and dispersant; the modified bamboo powder is obtained by grinding bamboo powder in a disc mill, while simultaneously adding a liquid ester coupling agent by spraying, and then modifying it by ultraviolet irradiation after grinding; the grinding speed of the disc mill is 2000-3000 rpm; the amount of liquid ester coupling agent added is 1-3% of the mass of bamboo powder; the liquid ester coupling agent is selected from at least one of aluminate coupling agents and titanate coupling agents; grinding and spraying are carried out simultaneously, and the spraying time is controlled at 10-20 min, followed by grinding for 5-10 min; the particle size of the bamboo powder is 400-800 mesh.
2. The composite material according to claim 1, characterized in that, The modified bamboo powder is prepared by a method including the following steps: (P1) Bamboo raw materials are processed into bamboo particles with a moisture content of ≤5%; the bamboo particles are ground in a disc mill and graded to obtain 400-800 mesh bamboo powder. (P2) 400-800 mesh bamboo powder is ground in a disc mill while a liquid ester coupling agent is sprayed by spraying to obtain coupling agent treated bamboo powder; the grinding speed is 2000-3000 rpm and the spraying time is 10-20 min; after spraying the liquid ester coupling agent, mechanical grinding continues for 5-10 min. (P3) Under an inert atmosphere, bamboo powder treated with coupling agent is irradiated with ultraviolet light to obtain modified bamboo powder.
3. The composite material according to claim 2, characterized in that, In step (P1), the bamboo raw material is a low-density bamboo species, selected from at least one of short-spike bamboo, early-maturing bamboo, and sweet bamboo; the size of the bamboo particles is 1-5 mm; the rotation speed of the disc mill is 1000-1500 rpm, the grinding time is 30-60 min, and the bamboo powder is obtained by sieving to 400-800 mesh; and / or in step (P3), the inert atmosphere is nitrogen and / or argon; during ultraviolet irradiation, the ultraviolet wavelength is 200-400 nm, and the irradiation power is 20-100 mW / cm². 2 Irradiation time: 1-10 min.
4. The composite material according to claim 1, characterized in that, The polylactic acid resin is blown film grade, with a melt index of 2~6 g / 10min, and the test conditions are 190℃*2.16kg; the PBAT polyester resin is blown film grade, with a melt index of 2~6 g / 10min, and the test conditions are 190℃*2.16kg; and / or, The lubricating dispersant is selected from at least one of monoglycerides, sorbitol, polyethylene glycol, and glycerin; and / or, The inorganic filler is selected from at least one of talc powder and calcium whisker sulfate.
5. The composite material according to claim 4, characterized in that, The inorganic filler is a mixture of talc powder and calcium sulfate whiskers in a mass ratio of 1-2:1-2.
6. The composite material according to claim 1, characterized in that, The modified bamboo powder / PBAT composite material also includes the following auxiliary materials in parts by weight: 0.1-0.5 parts slip opening agent, 0.1-0.5 parts anti-hydrolysis agent, and 0.1-1 parts antioxidant.
7. The method for preparing the biodegradable membrane / bag modified bamboo powder / PBAT composite material according to any one of claims 1-6, characterized in that, Includes the following steps: (S1) Modified bamboo powder, inorganic filler and lubricating dispersant are added to a high-speed mixer, low-speed stirring is started, and the temperature is raised. When the material temperature reaches 100-110℃, high-speed stirring is started. After stirring, the mixture is cooled to obtain pretreated powder. (S2) Add polylactic acid resin and PBAT polyester resin to a mixer and stir. After the resin softens into a viscoelastic colloid, add the pretreated powder obtained in step (S1), mix evenly and then perform internal mixing. After the internal mixing is completed, extrude and granulate the mixture using a screw extruder to obtain the modified bamboo powder / PBAT composite material.
8. The preparation method according to claim 7, characterized in that, Step (S2) is as follows: Polylactic acid resin and PBAT polyester resin are added to a mixer and stirred. After the resin softens into a viscoelastic colloid, the pretreated powder obtained in step (S1) is added, along with auxiliary materials. The mixture is then stirred evenly and stirred. After stirring, the mixture is extruded and granulated using a screw extruder to obtain the modified bamboo powder / PBAT composite material.
9. A biodegradable film or a biodegradable bag, made of the biodegradable film or bag modified bamboo powder / PBAT composite material according to any one of claims 1-6.