A biodegradable pinch-clasp self-sealing bag and method of making same

Abstract

The application belongs to the technical field of high polymer materials, and particularly relates to a biodegradable self-sealing bag with a clasp and a preparation method thereof. The self-sealing bag comprises the following raw materials in parts by weight: 100 parts of PBAT, 5-35 parts of PLA, 4-8 parts of hyperbranched polyester, 1-5 parts of a compatibilizing resin, 5-30 parts of inorganic fillers, 0.1-1 parts of a chain extender, and 0.1-0.6 parts of an additive. The self-sealing bag is prepared by selecting PLA, hyperbranched polyester and PBAT for compounding, and simultaneously selecting a chain extender, a PBAT compatibilizing resin, inorganic fillers and an additive for reaction. In the process of film blowing, the melt strength of the composite modified granules is guaranteed at low temperature, the adhesion of the clasp to the barrel film is higher, and the interfacial adhesion is effectively improved, so that the surface of the clasp and the female tooth of the self-sealing bag is smooth and flat, and the stiffness is high, the self-sealing bag has excellent repeated opening performance and sealing performance, and the preparation method is easy for industrial production and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a biodegradable self-sealing bag with a ziplock mechanism and its preparation method. Background Technology

[0002] Resealable zipper bags are packaging bags that can be sealed by compression. Common types include zipper bags and chain bags, and they are widely used in product packaging across various fields. Currently, the main component of commercially available resealable bags is polyolefin, typically made from a blend of low-density polyethylene and high-pressure linear polyethylene, blown into shape and then heat-cut. However, because polyolefins are non-biodegradable, although most resealable bags can be reused multiple times, the continuous increase in demand for various consumer goods and the resulting growth in plastic packaging consumption have led to a sharp rise in the use of resealable zipper bags. Therefore, the development of biodegradable resealable zipper bags is a key focus of research and development in plastic packaging materials.

[0003] Existing biodegradable zippered self-sealing bags mainly use biodegradable polyesters such as polybutylene terephthalate / butylene adipate copolyester (PBAT), polylactic acid (PLA), polypropylene carbonate (PPC), and polycaprolactone (PCL) as the matrix, which are melt-blended, blown into film, and then heat-cut to produce common self-sealing bags. However, current biodegradable self-sealing bags have defects such as insufficient interlocking force of the self-sealing strip and low opening pull force. To address this, Chinese patent application CN 109627703 A developed and researched biodegradable self-sealing strips by melt-blending PLA and PBAT, extruding through a specific die, and rapidly water-cooling and winding to prepare biodegradable self-sealing strips. These strips are then bonded to the packaging bag for secondary processing to produce zippered bags that meet usage requirements. However, this method still has certain limitations, and the adhesion strength between the self-sealing strip and the packaging bag is poor and prone to detachment. Chinese patent application CN 115216126... A composite material was prepared using PLA, PPC, and PBAT with specific additives, and then a biodegradable self-sealing bag was produced through a blown film extrusion process. The combination of Wacker additives and chain extenders improved the melt strength of the composite material, enhanced the compatibility with the matrix material, and improved the moldability of the snap fasteners. However, although the selected resin components have similar processing temperature ranges, the poor matching of melt temperatures between the resins during the blown film and snap fastener co-extrusion molding process, coupled with the need for a certain stiffness in the melt before the snap fasteners cool and solidify, easily leads to poor adhesion strength between the snap fasteners and the film bag, resulting in poor sealing and unusable finished self-sealing bags. Therefore, the performance and manufacturing process of biodegradable self-sealing bags need further improvement. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a biodegradable zipper self-sealing bag and its preparation method. The biodegradable zipper self-sealing bag provided by the present invention has a smooth and flat surface on the zipper teeth, high stiffness, excellent repeated opening performance and sealing performance, and the preparation method of the present invention is simple and easy to industrialize, showing good application prospects.

[0005] The technical solution of this invention is:

[0006] A biodegradable self-sealing zip-lock bag comprises the following raw materials in parts by weight: 100 parts PBAT, 5-35 parts PLA, 4-8 parts hyperbranched polyester, 1-5 parts compatibilizing resin, 5-30 parts inorganic filler, 0.1-1 parts chain extender, and 0.1-0.6 parts additives.

[0007] This invention uses PLA and hyperbranched polyester adhesive resin combined with PBAT, employing chain extenders with active functional groups and corresponding compatibilizing resins for PBAT, along with inorganic fillers and additives, for reactive melt blending and extrusion to prepare composite modified granules. In the blown film molding process of biodegradable self-sealing bags using the above-mentioned composite modified granules, the melt strength of the composite modified granules is effectively guaranteed at low temperatures. Furthermore, the hyperbranched polyester enhances the adhesion between the ribs and the film, effectively improving interfacial adhesion. This results in smooth and flat surfaces on the ribs and teeth of the biodegradable self-sealing bag, high stiffness, and excellent repeated opening performance and sealing properties.

[0008] Furthermore, the PLA has a melting temperature range of 125-140℃; and a melt flow rate of 4-8 g / 10 min at 190℃ and 2.16 kg.

[0009] This invention selects PLA, which has a low melting point and high fluidity, making it easier for it to undergo chain-end grafting reactions with hyperbranched polyesters and PBAT. Ultimately, the combined effect of PLA, epoxy chain extenders, and hyperbranched polyesters effectively improves the polymer melt strength. Moreover, during the melt stretching process of blown film forming, PLA more easily forms a fibrous structure, and the melt strength of the composite modified granules can be effectively guaranteed even at lower temperatures.

[0010] Furthermore, the hyperbranched polyester is a carboxyl-terminated hyperbranched polyester. Aromatic carboxyl-terminated hyperbranched polyesters are preferred. Because carboxyl-terminated hyperbranched polyesters contain aromatic functional groups and have a structure similar to PBAT, they are more readily grafted onto PBAT under the action of a compatibilizing resin.

[0011] Furthermore, the compatibilizing resin is a resin grafted with PBAT active groups; preferably one or more of PBAT-g-MA and PBAT-g-GMA.

[0012] Furthermore, the chain extender is an epoxy oligomer chain extender; the inorganic filler is an inorganic filler with a plate-like structure.

[0013] Furthermore, the PLA is a Total LX930 or LX975;

[0014] The hyperbranched polyester is Hyper C302;

[0015] The chain extender is KLE-4370B;

[0016] The additives include lubricants and slip agents; the lubricant is calcium stearate; the slip agent is erucamide.

[0017] The inorganic filler is one of mica, talc, or montmorillonite with a flaky structure, and the particle size ranges from 2000 to 6000 mesh; preferably 3000 mesh.

[0018] Furthermore, the inorganic filler is an activated inorganic filler; the activation process of the inorganic filler is as follows: the inorganic filler is dried to a water content of less than 2000 ppm, and then aluminum-titanium composite coupling agent and stearic acid are added to the inorganic filler and mixed to obtain the activated inorganic filler, which is then sealed and stored; wherein, the weight parts of each raw material are 100 parts of inorganic filler, 0.1-1 parts of aluminum-titanium composite coupling agent, and 0.1-1 parts of stearic acid.

[0019] Furthermore, the present invention also provides a method for preparing a biodegradable self-sealing zipper bag as described above, comprising the following steps:

[0020] Step S1: Raw material pretreatment and blending

[0021] First, the inorganic filler is dried and activated. Then, PLA, PBAT, and hyperbranched polyester are dehumidified and dried pretreated. Subsequently, PBAT, PLA, hyperbranched polyester, compatibilizing resin, inorganic filler, chain extender, and additives are blended in a high-speed mixer to obtain a blend.

[0022] Step S2: Extrusion granulation of the blended raw materials

[0023] The blend obtained in step S1 is added to a twin-screw extruder for extrusion granulation, followed by dehumidification and drying to obtain composite modified granules.

[0024] Step S3: Molding and processing of composite modified granules

[0025] The composite modified granules obtained in step S2 are blown into film using a self-sealing bag blown film machine and rolled into a barrel film. The rolled barrel film is then heat-cut into a zipper self-sealing bag using a bag making machine.

[0026] Furthermore, the method for preparing the biodegradable self-sealing bag includes the following steps:

[0027] Step S1: Raw material pretreatment and blending

[0028] First, the inorganic filler is dried and activated. Specifically, the inorganic filler is added to a high-speed mixer with temperature control and dried thoroughly at 1000 rpm and 80°C until the water content of the inorganic filler is less than 2000 ppm. Then, aluminum-titanium composite coupling agent and stearic acid are added to the inorganic filler and mixed for another 5 minutes. The activated inorganic filler is then removed and sealed for storage.

[0029] Next, PLA, PBAT, and hyperbranched polyester are dehumidified and dried pretreated. Then, the following materials are weighed according to the weight ratio: PBAT, PLA, hyperbranched polyester, compatibilizing resin, inorganic filler, chain extender, and additives. They are added to a high-speed mixer and blended again to obtain a blend.

[0030] Step S2: Extrusion granulation of the blended raw materials

[0031] The blend obtained in step S1 is added to a twin-screw extruder for extrusion and granulation. The temperature range of the extruder is set to 100-150℃, the speed of the extruder is 100-300rpm, and the feeding speed of the extruder is 15-30kg / h. The composite modified granules are then dehumidified and dried.

[0032] Step S3: Molding and processing of composite modified granules

[0033] The dried composite modified granules from step S2 are blown into film using a self-sealing bag blown film machine and then wound into a barrel film. The self-sealing bag blown film machine consists of two single-screw extruders and a co-extrusion die. The temperature range of the single-screw extruders and the die is set to 130-150℃, the extruder speed is 40-60rpm, the feeding frequency is 20-40Hz, the traction frequency is 10-30Hz, and the blow-up ratio is 2.5-4 times. Subsequently, the wound barrel film is heat-cut into a zippered self-sealing bag by a bag making machine.

[0034] Compared with existing technologies, the biodegradable self-sealing bag and its preparation method provided by the present invention have the following advantages:

[0035] This invention selects specific PLA and carboxyl-terminated hyperbranched polyester and PBAT, and simultaneously uses epoxy chain extenders with active functional groups, PBAT compatibilizing resin, inorganic fillers and additives for reactive melt blending and extrusion to obtain composite modified granules, which are then used to prepare biodegradable self-sealing bags. Because the carboxyl-terminated hyperbranched polyester of this invention contains aromatic functional groups and its structure is similar to PBAT, it is easier for the carboxyl-terminated hyperbranched polyester to undergo grafting reactions with PBAT under the action of the compatibilizing resin. Furthermore, PLA, under the action of the epoxy chain extender, is also more likely to undergo chain-end grafting reactions with the hyperbranched polyester and PBAT. Ultimately, the polymer melt strength is effectively improved under the action of the epoxy chain extender and the hyperbranched polyester.

[0036] From the appendix of this invention Figure 1 As can be seen, because this invention uses PLA with a lower melting temperature and higher fluidity, it is easier for the PLA to form a fibrous structure during the melt stretching process of blown film forming, thus effectively ensuring the melt strength of the composite modified granules at lower temperatures. Furthermore, the sheet-like inorganic filler not only ensures the stiffness of the melt and reduces shrinkage, but also improves the stiffness of the ribs. Combined with hyperbranched polyester, the ribs adhere better to the film, effectively improving interfacial adhesion. The resulting ribs have a smooth and flat surface, high stiffness, and good opening and closing repeatability, ensuring the sealing performance and usability of the self-sealing bag. The biodegradable self-sealing bag prepared by this invention has excellent repeatable opening performance, a simple manufacturing process, and is easy to industrialize, showing promising application prospects. Attached Figure Description

[0037] Figure 1 This is a schematic diagram illustrating the synergistic effect of each component during the blown film forming process of the composite modified granules of the present invention. Figure 1 The right side image is a magnified view of a portion of the tendon buckle. Detailed Implementation

[0038] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0039] Unless otherwise specified, the reagents used in the following examples and comparative examples are conventional reagents and can be purchased from conventional reagent manufacturers and distributors.

[0040] A method for preparing a biodegradable self-sealing ziplock bag includes the following steps:

[0041] Step S1: Raw material pretreatment and blending

[0042] First, the inorganic filler is dried and activated. Specifically, the inorganic filler is added to a high-speed mixer with temperature control and dried thoroughly at 1000 rpm and 80°C until the water content of the inorganic filler is less than 2000 ppm. Then, aluminum-titanium composite coupling agent and stearic acid are added to the inorganic filler and mixed for another 5 minutes. The activated inorganic filler is then removed and sealed for storage.

[0043] Next, PLA, PBAT, and hyperbranched polyester are dehumidified and dried pretreated. Then, the following materials are weighed according to the weight ratio: PBAT, PLA, hyperbranched polyester, compatibilizing resin, inorganic filler, chain extender, and additives. They are added to a high-speed mixer and blended again to obtain a blend.

[0044] Step S2: Extrusion granulation of the blended raw materials

[0045] The blend obtained in step S1 is added to a twin-screw extruder for extrusion and granulation. The temperature range of the extruder is set to 100-150℃, the speed of the extruder is 270rpm, and the feeding speed of the extruder is 20kg / h. The composite modified granules are then dehumidified and dried.

[0046] Step S3: Molding and processing of composite modified granules

[0047] The dried composite modified granules from step S2 are blown into film using a self-sealing bag blown film machine and then wound into a barrel film. The self-sealing bag blown film machine consists of two single-screw extruders and a co-extrusion die. The temperature range of the single-screw extruders and the die is set to 140-150℃, the extruder speed is 50rpm, the feeding frequency is 30Hz, the traction frequency is 10Hz, the blow-up ratio is 2.5 times, and the film thickness is 80μm. The wound barrel film is then heat-cut into a zippered self-sealing bag by a bag making machine.

[0048] Comparative Example 1:

[0049] Following step S1, 100 parts of spherical calcium carbonate with 3000 mesh inorganic filler were dried. Then, 0.5 parts of aluminum-titanium composite coupling agent and 0.8 parts of stearic acid were mixed and activated. 100 parts of PBAT, 30 parts of PLA, 4 parts of compatibilizing resin (PBAT-g-GMA), 20 parts of inorganic filler (activated calcium carbonate), 0.2 parts of lubricant (calcium stearate), 0.3 parts of chain extender (KLE-4370B), and 0.1 parts of slip agent (erucamide) were added to a high-speed mixer and blended to obtain a blend.

[0050] The PLA used was Fengyuan PLA FY601, and the melt flow rate was measured to be 9 g / 10 min and the melting temperature was 175 ℃ under the same conditions.

[0051] Comparative Example 2:

[0052] Following step S1, 100 parts of inorganic filler talc powder with a mesh size of 1000 were dried. Then, 0.3 parts of aluminum-titanium composite coupling agent and 0.4 parts of stearic acid were mixed and activated. 100 parts of PBAT, 20 parts of PLA (Total LX930), 4 parts of compatibilizing resin (PBAT-g-GMA), 20 parts of inorganic filler (activated talc powder), 0.1 parts of lubricant (calcium stearate), 0.5 parts of chain extender (KLE-4370B), and 0.1 parts of slip agent (erucamide) were added to a high-speed mixer and blended to obtain a blend.

[0053] The PLA has a melting temperature of 130°C and a melt flow rate of 8 g / 10 min at 190°C and 2.16 kg.

[0054] Comparative Example 3

[0055] Following step S1, 100 parts of 8000-mesh inorganic filler talc powder were dried. Then, 0.3 parts of aluminum-titanium composite coupling agent and 0.4 parts of stearic acid were mixed and activated. 100 parts of PBAT, 20 parts of PLA (Total LX930), 4 parts of compatibilizing resin (PBAT-g-GMA), 20 parts of inorganic filler (activated talc powder), 0.1 parts of lubricant (calcium stearate), 0.5 parts of chain extender (KLE-4370B), and 0.1 parts of slip agent (erucamide) were added to a high-speed mixer and blended to obtain a blend.

[0056] The PLA has a melting temperature of 130°C and a melt flow rate of 8 g / 10 min at 190°C and 2.16 kg.

[0057] Comparative Example 4

[0058] Following step S1, 100 parts of inorganic filler talc powder of 2000 mesh were dried. Then, 0.5 parts of aluminum-titanium composite coupling agent and 0.5 parts of stearic acid were mixed and activated. 100 parts of PBAT, 5 parts of PLA (Total LX930), 6 parts of hyperbranched polyester (aliphatic hydroxyl-terminated hyperbranched polyester Hyper H102), 4 parts of compatibilizing resin (PBAT-g-GMA), 25 parts of inorganic filler (activated talc powder), 0.1 parts of lubricant (calcium stearate), 0.5 parts of chain extender (KLE-4370B), and 0.1 parts of slip agent (erucamide) were added to a high-speed mixer and blended to obtain a blend.

[0059] The PLA has a melting temperature of 130°C and a melt flow rate of 8 g / 10 min at 190°C and 2.16 kg.

[0060] Comparative Example 5

[0061] Following step S1, 100 parts of inorganic filler mica with a mesh size of 2000 was dried. Then, 0.5 parts of aluminum-titanium composite coupling agent and 0.5 parts of stearic acid were mixed and activated. 100 parts of PBAT, 10 parts of PLA (Fengyuan PLA FY601), 4 parts of compatibilizing resin (PBAT-g-GMA), 25 parts of inorganic filler (activated mica), 0.1 parts of lubricant (calcium stearate), 0.5 parts of chain extender (KLE-4370B), and 0.1 parts of slip agent (erucamide) were added to a high-speed mixer and blended to obtain a blend.

[0062] Example 1:

[0063] Following step S1, 100 parts of inorganic filler talc powder of 2000 mesh were dried. Then, 0.5 parts of aluminum-titanium composite coupling agent and 0.5 parts of stearic acid were mixed and activated. 100 parts of PBAT, 5 parts of PLA (Total LX930), 6 parts of hyperbranched polyester (long-chain aromatic carboxyl-terminated hyperbranched polyester Hyper C302), 4 parts of compatibilizing resin (PBAT-g-GMA), 25 parts of inorganic filler (activated talc powder), 0.1 parts of lubricant (calcium stearate), 0.5 parts of chain extender (KLE-4370B), and 0.1 parts of slip agent (erucamide) were added to a high-speed mixer and blended to obtain a blend.

[0064] The PLA has a melting temperature of 130°C and a melt flow rate of 8 g / 10 min at 190°C and 2.16 kg.

[0065] Example 2:

[0066] Following step S1, 100 parts of 6000-mesh inorganic filler mica were dried. Then, 0.8 parts of aluminum-titanium composite coupling agent and 0.9 parts of stearic acid were mixed and activated. 100 parts of PBAT, 25 parts of PLA (Total LX975), 8 parts of hyperbranched polyester (long-chain aromatic carboxyl-terminated hyperbranched polyester Hyper C302), 4 parts of compatibilizing resin (PBAT-g-GMA), 18 parts of inorganic filler (activated mica), 0.3 parts of lubricant (calcium stearate), 0.6 parts of chain extender (KLE-4370B), and 0.15 parts of slip agent (erucamide) were added to a high-speed mixer and blended to obtain a blend.

[0067] The PLA has a melting temperature of 130°C and a melt flow rate of 4 g / 10 min at 190°C and 2.16 kg.

[0068] Example 3:

[0069] Following step S1, 100 parts of 3000-mesh inorganic filler montmorillonite were dried. Then, 0.8 parts of aluminum-titanium composite coupling agent and 0.9 parts of stearic acid were mixed and activated. 100 parts of PBAT, 20 parts of PLA (Total LX930), 4 parts of hyperbranched polyester (long-chain aromatic carboxyl-terminated hyperbranched polyester Hyper C302), 2 parts of compatibilizing resin (PBAT-g-MA), 30 parts of inorganic filler (activated montmorillonite), 0.3 parts of lubricant (calcium stearate), 0.6 parts of chain extender (KLE-4370B), and 0.2 parts of slip agent (erucamide) were added to a high-speed mixer for blending.

[0070] The PLA has a melting temperature of 130°C and a melt flow rate of 8 g / 10 min at 190°C and 2.16 kg.

[0071] Example 4:

[0072] Following step S1, 100 parts of 5000-mesh inorganic filler mica were dried. Then, 0.6 parts of aluminum-titanium composite coupling agent and 0.9 parts of stearic acid were mixed and activated. 100 parts of PBAT, 35 parts of PLA (Total LX930), 8 parts of hyperbranched polyester (long-chain aromatic carboxyl-terminated hyperbranched polyester Hyper C302), 2 parts of compatibilizing resin (PBAT-g-GMA, 2 parts of PBAT-g-MA), 30 parts of inorganic filler (activated mica), 0.3 parts of lubricant (calcium stearate), 0.6 parts of chain extender (KLE-4370B), and 0.2 parts of slip agent (erucamide) were added to a high-speed mixer for blending.

[0073] The PLA has a melting temperature of 130°C and a melt flow rate of 8 g / 10 min at 190°C and 2.16 kg.

[0074] Example 5:

[0075] Following step S1, 100 parts of inorganic filler talc powder of 3000 mesh were dried. Then, 0.8 parts of aluminum-titanium composite coupling agent and 0.9 parts of stearic acid were mixed and activated. 100 parts of PBAT, 30 parts of PLA (Total LX975), 8 parts of hyperbranched polyester (long-chain aromatic carboxyl-terminated hyperbranched polyester Hyper C302), 3 parts of compatibilizing resin (PBAT-g-MA), 30 parts of inorganic filler (activated talc powder), 0.3 parts of lubricant (calcium stearate), 0.6 parts of chain extender (KLE-4370B), and 0.2 parts of slip agent (erucamide) were added to a high-speed mixer for blending.

[0076] The PLA has a melting temperature of 130°C and a melt flow rate of 4 g / 10 min at 190°C and 2.16 kg.

[0077] Example 6:

[0078] Following step S1, 100 parts of 3000-mesh inorganic filler montmorillonite were dried. Then, 0.6 parts of aluminum-titanium composite coupling agent and 0.5 parts of stearic acid were mixed and activated. 100 parts of PBAT, 15 parts of PLA (Total LX975), 8 parts of hyperbranched polyester (long-chain aromatic carboxyl-terminated hyperbranched polyester Hyper C302), 3 parts of compatibilizing resin (PBAT-g-MA), 5 parts of inorganic filler (activated montmorillonite), 0.3 parts of lubricant (calcium stearate), 0.6 parts of chain extender (KLE-4370B), and 0.3 parts of slip agent (erucamide) were added to a high-speed mixer for blending.

[0079] The PLA has a melting temperature of 130°C and a melt flow rate of 4 g / 10 min at 190°C and 2.16 kg.

[0080] Experimental example:

[0081] The products of the embodiments and comparative examples of the present invention were partially tested in accordance with BB / T 0014-2011, and the test results are shown in the table below.

[0082] Table 1: Performance Tests of Biodegradable Self-Sealing Bags Obtained from Embodiments and Comparative Examples of the Invention

[0083]

[0084]

[0085] The performance test results of the comparative examples and embodiments show that, under the morphology and particle size of the inorganic filler of the present invention, the opening pull force of the snap fastener in the film bag is effectively improved. Moreover, the use of specific polylactic acid and the selection of hyperbranched polyester can further improve the heat sealing strength of the film and the snap fastener, avoiding the phenomenon of low heat sealing strength and snap fastener detachment from the film surface due to insufficient interfacial adhesion.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A biodegradable self-sealing ziplock bag, characterized in that, The raw materials include the following parts by weight: 100 parts PBAT, 5-35 parts PLA, 4-8 parts hyperbranched polyester, 1-5 parts compatibilizing resin, 5-30 parts inorganic filler, 0.1-1 part chain extender, and 0.1-0.6 parts additives. The PLA has a melting temperature range of 125-140℃; the melt flow rate is 4-8 g / 10 min at 190℃ and 2.16 kg. The PLA is either Total LX930 or Total LX975; The hyperbranched polyester is Hyper C302; The compatibilizing resin is one or more of PBAT-g-MA and PBAT-g-GMA; The chain extender is KLE-4370B; The additives include lubricants and slip agents; the lubricant is calcium stearate; the slip agent is erucamide. The inorganic filler is one of mica, talc, or montmorillonite with a flaky structure and a particle size range of 2000-6000 mesh; The inorganic filler is an activated inorganic filler; the activation process of the inorganic filler is as follows: the inorganic filler is dried to a water content of less than 2000 ppm, and then aluminum-titanium composite coupling agent and stearic acid are added to the inorganic filler and mixed to obtain the activated inorganic filler, which is then sealed and stored; wherein, the weight parts of each raw material are 100 parts of inorganic filler, 0.1-1 parts of aluminum-titanium composite coupling agent, and 0.1-1 parts of stearic acid.

2. A method for preparing a biodegradable self-sealing zipper bag as described in any one of claims 1, characterized in that, Includes the following steps: Step S1: Raw material pretreatment and blending First, the inorganic filler is dried and activated. Then, PLA, PBAT, and hyperbranched polyester are dehumidified and dried pretreated. Subsequently, PBAT, PLA, hyperbranched polyester, compatibilizing resin, inorganic filler, chain extender, and additives are blended in a high-speed mixer to obtain a blend. Step S2: Extrusion granulation of the blended raw materials The blend obtained in step S1 is added to a twin-screw extruder for extrusion granulation, followed by dehumidification and drying to obtain composite modified granules. Step S3: Molding and processing of composite modified granules The composite modified granules obtained in step S2 are blown into film using a self-sealing bag blown film machine and rolled into a barrel film. The rolled barrel film is then heat-cut into a zipper self-sealing bag using a bag making machine.

3. The method for preparing a biodegradable self-sealing bag as described in claim 2, characterized in that, Includes the following steps: Step S1: Raw material pretreatment and blending First, the inorganic filler is dried and activated. Specifically, the inorganic filler is added to a high-speed mixer with temperature control and dried thoroughly at 1000 rpm and 80°C until the water content of the inorganic filler is less than 2000 ppm. Then, aluminum-titanium composite coupling agent and stearic acid are added to the inorganic filler and mixed for another 5 minutes. The activated inorganic filler is then removed and sealed for storage. Next, PLA, PBAT, and hyperbranched polyester are dehumidified and dried pretreated. Then, the following materials are weighed according to the weight ratio: PBAT, PLA, hyperbranched polyester, compatibilizing resin, inorganic filler, chain extender, and additives. They are added to a high-speed mixer and blended again to obtain a blend. Step S2: Extrusion granulation of the blended raw materials The blend obtained in step S1 is added to a twin-screw extruder for extrusion and granulation. The temperature range of the extruder is set to 100-150℃, the speed of the extruder is 100-300rpm, and the feeding speed of the extruder is 15-30kg / h. The composite modified granules are then dehumidified and dried. Step S3: Molding and processing of composite modified granules The dried composite modified granules from step S2 are blown into film using a self-sealing bag blown film machine and then wound into a barrel film. The self-sealing bag blown film machine consists of two single-screw extruders and a co-extrusion die. The temperature range of the single-screw extruders and the die is set to 130-150℃, the extruder speed is 40-60rpm, the feeding frequency is 20-40Hz, the traction frequency is 10-30Hz, and the blow-up ratio is 2.5-4 times. Subsequently, the wound barrel film is heat-cut into a zippered self-sealing bag by a bag making machine.

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