Aging-resistant industrial bag based on dolomite derivative reinforcement and preparation method thereof

Abstract

The application discloses a kind of based on dolomite derivative enhanced anti-aging industrial bag and its preparation method, belong to inorganic non-metallic powder and polymer material technical field.The application first obtains calcium magnesium ion solution after dolomite high-temperature calcination and acid treatment, then with lignin, rubidium hydroxide is reacted under high-pressure CO2 Condition, and brown yellow powder with lamella-fiber composite structure is constructed;After surface modification, it is compounded with polypropylene resin, and is made into bag by warp and weft different material weaving process.The method utilizes the rich calcium magnesium element in dolomite and cooperates with lignin, rubidium element, generates the composite filler with inorganic reinforcement and organic toughening function.The comprehensive performance of the obtained product is significantly better than traditional filling system, effectively improves the anti-aging, mechanical strength and antibacterial property of industrial bag, simultaneously reduces production cost, is suitable for the high-strength packaging field of bulk materials such as chemical industry, building material, grain.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic powder and polymer materials technology, specifically relating to an aging-resistant industrial container bag based on dolomite derivative reinforcement and its preparation method. Background Technology

[0002] Flexible Intermediate Bulk Containers (FIBCs) are flexible transport packaging containers that are moisture-proof, dust-proof, radiation-resistant, and robust, widely used for the storage and transportation of bulk materials such as chemicals, building materials, grains, and minerals. According to GB / T 10454-2025 "Flexible Intermediate Bulk Containers for Packaging Non-Dangerous Goods," FIBCs with a load capacity of less than 1000 kg must meet mechanical performance indicators such as longitudinal tensile strength and elongation at break to ensure safety and reliability during transportation. Currently, industrial FIBCs are generally made primarily of polypropylene, supplemented with a small amount of functional additives. The process involves melt extrusion, stretching into filaments, heat setting, and textile lamination to create the base fabric, which is then sewn together with accessories such as straps to produce the finished product.

[0003] However, traditional industrial container bags still have many technical problems in terms of material properties and processing technology that need to be solved.

[0004] Firstly, regarding material properties, polypropylene molecules contain a large number of unstable tertiary carbon atoms. Under aerobic conditions, hydrogen atoms on these tertiary carbon atoms can be removed with relatively low energy to form tertiary carbon free radicals. Therefore, polypropylene exhibits poor aging resistance during use and is highly susceptible to photo-oxidative aging, leading to decreased tensile strength, surface chalking, and fading in bulk bags, resulting in a rapid deterioration of product performance. Currently, organic light stabilizers are typically added to polypropylene formulations to improve aging resistance. However, existing light stabilizers suffer from drawbacks such as high cost, volatility and migration, some toxicity, and poor dispersibility, making it difficult to balance performance and cost.

[0005] Secondly, regarding filler modification, to reduce production costs, manufacturers commonly add a high proportion of calcium carbonate powder as a filler for polypropylene. However, calcium carbonate, as an inorganic powder, has significant hydrophilic properties and poor interfacial compatibility with hydrophobic polypropylene resin. During blending, it easily agglomerates, forming microscopic stress concentration points. These stress concentration points not only directly weaken the material's mechanical properties (such as tensile strength and impact resistance) but also become inducing sites for photo-oxidative aging under ultraviolet light irradiation, accelerating the breakage of polypropylene molecular chains and further reducing the product's service life. Therefore, the "reinforcement-aging resistance" contradiction brought about by calcium carbonate filling is a core defect in traditional technical solutions—the cost reduction through filling comes at the expense of both mechanical properties and service life degradation.

[0006] Furthermore, as industries with high hygiene requirements, such as food, pharmaceuticals, and animal feed, widely adopt FIBCs (Flexible Intermediate Bulk Containers) for bulk material packaging, the antibacterial and antifungal properties of FIBCs have gradually become important functional indicators. However, traditional FIBC formulations lack effective antibacterial components, failing to meet the hygiene needs of these application scenarios.

[0007] Furthermore, in terms of weaving technology, traditional FIBC weaving equipment has poor precision in controlling the tension of warp and weft yarns. Differences in warp and weft tension often lead to uneven weaving structures, resulting in significant fluctuations in the mechanical properties of various parts of the FIBC, affecting product consistency and reliability. Dolomite is a carbonate mineral with the chemical composition CaMg(CO3)2, abundant in my country and inexpensive. Currently, the application of dolomite in polymer fillers is limited to simple calcination and grinding followed by direct filling, failing to fully utilize the synergistic reinforcing structural advantages of calcium and magnesium elements. There are also no reports on the use of dolomite derivatives combined with lignin and rubidium for polypropylene modification. Developing a novel composite filler based on dolomite derivatives, which can reduce production costs while imparting excellent mechanical properties, aging resistance, and antibacterial properties to polypropylene, would have significant industrial application value. Summary of the Invention

[0008] In view of the above, it is necessary to provide an aging-resistant industrial container bag based on dolomite derivatives and its preparation method. Through the construction of dolomite derivative composite filler and the synergistic optimization of each process step, the technical problems of insufficient mechanical strength, poor aging resistance and lack of antibacterial function of industrial container bags are solved at the same time.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, comprising the following steps:

[0011] (1) Place the dolomite particles in a muffle furnace and calcine them to obtain powder with CaO-MgO as the main components. Then, after cooling the powder, add nitric acid solution and stir for 10 min at 40℃ and 500r / min. Filter and collect the filtrate, which is recorded as solution A.

[0012] (2) Mix lignin, rubidium hydroxide and NaOH solution, and stir to form a homogeneous solution, which is denoted as solution B;

[0013] (3) Pour solution A into a high-pressure reactor, evacuate, and heat to 80~95℃. Under stirring, inject solution B into the reactor in two batches. First, inject part of solution B and then heat to 150~180℃ and keep the temperature for 60 min. Then, cool down to 85℃ and inject the remaining solution B into the reactor within 1 min. Stop stirring, add CO2 to make the system pressure reach 1.5~2MPa, and keep the temperature at 85±1℃ for 20~60 h. After natural cooling, filter, wash and dry the precipitate to obtain a brownish-yellow powder.

[0014] (4) Add the brownish-yellow powder and surface modifier to a high-speed mixer, heat to 90°C, stir and mix to obtain modified powder;

[0015] (5) Mix thermoplastic resin, modified powder, polyethylene wax and filler masterbatch in a weight ratio of 100:5~10:1.5:20~30, place in a 150℃ high mixer, stir for 15 minutes to obtain a mixture, and then prepare industrial container bags by melt extrusion, drawing and weaving.

[0016] In this invention, further, the dolomite particles in step (1) have a particle size of less than 200 mesh, a CaCO3 content of more than 50.8%, a MgCO3 content of more than 41%, an Al2O3 content of more than 0.8%, and a SiO2 content of less than 0.5%.

[0017] In this invention, further, the calcination conditions in step (1) are as follows: the temperature is increased to 580°C at a rate of 15°C / min and held at 580°C for 30 min; then the temperature is increased to 1050°C at a rate of 5°C / min and held for 10 min before the heating is stopped and the temperature is naturally cooled to below 50°C.

[0018] In this invention, the concentration of the nitric acid solution in step (1) is 0.01 mol / L, and the amount used is 1200~1280 mL.

[0019] In this invention, further, the lignin in step (2) is Claessen lignin, and its SiO2 content is less than 0.2%; the ratio of the amount of lignin, rubidium hydroxide and NaOH solution is 10g:50g:200mL, and the concentration of the NaOH solution is 0.01mol / L.

[0020] In this invention, further, the total volume of solution B in step (3) is 200 mL, with 120 mL injected the first time and 80 mL injected the second time; the vacuum is drawn to -0.09 to -0.1 MPa; and the purity of CO2 is 99.99%.

[0021] In this invention, the surface modifier in step (4) is one of stearic acid, aluminate, titanate or a mixture of any proportion; the ratio of the brownish-yellow powder to the surface modifier is 1000g:8~10g.

[0022] In this invention, further, the thermoplastic resin in step (5) is virgin polypropylene or a composite of virgin polypropylene and recycled polypropylene, wherein the recycled polypropylene content in the composite is less than 25%; the matrix resin of the filler masterbatch is linear low-density polyethylene, the inorganic filler is 800-mesh heavy calcium carbonate, and the weight ratio of the matrix resin to the inorganic filler is 1:9; the weaving adopts a biaxial cross-weaving device with an intelligent tension control system, the warp and weft tension difference is ≤5%, and the cross angle is 30~60°.

[0023] In this invention, the industrial container bag described in step (5) adopts a plain weave structure, with the linear density of both the warp and weft yarns being 200~300 denier, the warp density being 30~40 threads / 10 cm, and the weft density being 25~30 threads / 10 cm; wherein the warp yarns are made of virgin polypropylene, and the weft yarns are made of a composite of virgin polypropylene and recycled polypropylene.

[0024] The present invention also proposes an aging-resistant industrial container bag, which is prepared by the method described above. Its longitudinal tensile strength is not less than 2700N, its tensile strength retention rate after 14 days of UV aging is not less than 80%, and its antibacterial rate against Escherichia coli is not less than 90%.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] 1. The raw material used in this invention is dolomite ore with a specific structure, which is cheaper than calcium carbonate from ordinary marble, but currently lacks high-value-added applications in the field of polymer fillers. Dolomite contains abundant Ca and Mg elements. This invention obtains a calcium and magnesium ion solution through a two-stage roasting-acid dissolution process, and then carries out a hydrothermal reaction with lignin and rubidium hydroxide under high-pressure CO2 conditions to innovatively construct a calcium-magnesium-rubidium-lignin ternary composite filler system with a crystalline structure. In this system, lignin provides a long fibrous organic framework, and the calcium, magnesium, and rubidium components generate lamellar inorganic particles in situ on the long chains of lignin, forming a modified filler with a composite structure of inorganic particles / organic framework that simultaneously possesses lamellar and fibrous states (see...). Figures 1-2 (SEM image). This composite filler, after surface modification, is compounded with polypropylene resin. On the one hand, it benefits from the unique large aspect ratio and regular lamellar structure of the composite filler (compared to the random structures of Comparative Examples 1 and 2, see details). Figures 3-4 ), which can be effectively inserted between polypropylene resins (see details) Figure 8 , Figure 9The long fiber morphology effectively bears and transmits stress, acting as an interfacial bridge. The high aspect ratio of the laminated sheets, stacked layer by layer in the matrix, effectively suppresses the formation of stress concentration points, imparting superior tensile, impact, and frictional mechanical properties to the material. For example, the tensile strength of the industrial container bag product obtained in Example 1 is 2884 N, while the tensile strengths of Comparative Examples 1 and 3 (1986 N and 1879 N respectively) are significantly weaker than those of Example 1. On the other hand, the composite filler contains some lignin, which imparts superior anti-aging properties. The anti-aging function of lignin stems from its unique chemical structure. Its molecules contain a large number of functional groups such as phenolic hydroxyl groups, which can effectively capture and neutralize free radicals generated by polypropylene under heat, oxygen, and ultraviolet light, thereby interrupting the chain reaction leading to material aging and increasing the material's stability under light and heat conditions. After 14 days of aging, the tensile strength of the industrial container bag product obtained in Example 1 decreased from 2884 N to 2567 N, with a retention rate of 89%. In contrast, the tensile strength of Comparative Example 3 (lignin component omitted) decreased from 1879 N to 1334 N, with a retention rate of only 71%, significantly weaker than that of Example 1. This is because, under this experimental method, specific surface modification effectively reduced the surface hydrophilicity of the calcium-magnesium-rubidium composite filler, improved the compatibility between the powder and the hydrophobic polypropylene resin, and avoided the agglomeration phenomenon observed with traditional calcium carbonate fillers. This synergistic effect enabled the filler to achieve uniform dispersion and good interfacial bonding within the polypropylene matrix.

[0027] 2. This invention introduces rubidium into the composite filler, enabling the container bag to maintain excellent mechanical properties while also possessing antibacterial functionality. Characterization analysis confirms that rubidium has been successfully incorporated into the filler structure. Its antibacterial mechanism lies in the fact that rubidium ions can act on the bacterial surface through electrostatic adsorption, disrupting the integrity of the bacterial cell wall and cell membrane, altering membrane permeability, leading to intracellular leakage, interfering with bacterial metabolism, and inducing oxidative damage, thereby exerting an antibacterial effect. Examples 1-4 all showed antibacterial rates of over 90% against *E. coli*, with Example 4 reaching as high as 92%. Comparative Example 2 (omitting rubidium hydroxide) showed a sharp drop in antibacterial rate to 24%, while its mechanical properties (2806N, retention rate 85.0%) were essentially equivalent to those of Example 1. This indicates that the introduction of rubidium did not alter the lamellar-fiber composite structure of the filler, fully preserving the mechanical reinforcement effect of the filler while achieving antibacterial functionality, thus realizing the decoupled integration of functional modules. This antibacterial function enables the container bag of the present invention to meet the packaging needs of food, medicine, feed and other scenarios with high hygiene requirements, and is especially suitable for the hygiene standards of container bags that come into direct contact with food.

[0028] 3. Traditional applications of dolomite in polymer fillers are limited to simple calcination and grinding followed by direct filling, failing to fully leverage the synergistic reinforcing advantages of calcium and magnesium. This invention, under specific process conditions, combines dolomite derivatives with lignin and rubidium, constructing a highly crystalline filler with a lamellar-fibrous composite structure through crystallization under high-pressure CO2 and hydrothermal conditions. This achieves a transformation of dolomite from a low-value filler to a high-value functionalized product. Furthermore, the ratio of calcium, magnesium, and lignin significantly influences the morphology of the resulting filler. Without magnesium (Comparative Example 1, using limestone as raw material, with a magnesium carbonate content of only 0.06%, see Table 2), only amorphous powder with random morphology and easy agglomeration can be obtained (see Table 2). Figure 3 and Figure 5 Without lignin (Comparative Example 3), only layered, easily agglomerated powders can be obtained, and long fibrous structures cannot be formed (see details). Figure 4 Furthermore, dolomite is inexpensive and abundant, and this invention opens up new application avenues for its use in high-performance polypropylene composite materials, yielding significant economic and social benefits.

[0029] 4. This invention employs a biaxial cross-weaving device with an intelligent tension control system in the weaving process. Sensors monitor the warp and weft yarn tension in real time, automatically adjusting weaving parameters when the tension difference exceeds 3%, ensuring the warp and weft yarn tension difference remains ≤5%. This significantly improves weaving accuracy and product consistency, resulting in mechanical property fluctuations in the FIBC (Flexible Intermediate Bulk Container) ≤5%, a consistency significantly superior to traditional weaving processes. Simultaneously, the cross angle can be precisely adjusted within the range of 30~60° to meet the diverse performance requirements of different customers. Furthermore, by controlling the use of virgin polypropylene for the warp yarns and a composite of virgin and recycled polypropylene for the weft yarns, production costs are effectively reduced while ensuring product mechanical properties. As shown in Examples 1-4, stable and excellent comprehensive performance can be obtained under different process parameter conditions, indicating that the method of this invention has good process adaptability and repeatability. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope (SEM) image of the modified powder obtained in Example 1.

[0031] Figure 2 This is a scanning electron microscope (SEM) image of the modified powder obtained in Example 2.

[0032] Figure 3 This is a scanning electron microscope (SEM) image of the modified powder obtained in Comparative Example 1.

[0033] Figure 4 This is a scanning electron microscope (SEM) image of the modified powder obtained in Comparative Example 3.

[0034] Figure 5 The X-ray diffraction (XRD) patterns of the modified powders obtained in Example 1 and Comparative Example 1 are shown.

[0035] Figure 6 This is a comparison diagram of the particle size distribution of the powders obtained in Examples 1-2 and Comparative Examples 1-4.

[0036] Figure 7 The image shows the energy dispersive spectroscopy (EDS) analysis of the powder obtained in Example 1.

[0037] Figure 8 This is a scanning electron microscope (SEM) image of the brittle cross-section of the industrial container bag obtained in Example 1.

[0038] Figure 9 This is a scanning electron microscope (SEM) image of the brittle cross-section of the industrial container bag obtained in Comparative Example 1.

[0039] Figure 10 This is a scanning electron microscope (SEM) image of the cross-section of the industrial container bag obtained in Example 1.

[0040] Figure 11 This is a scanning electron microscope (SEM) image of the cross-section of the industrial container bag obtained in Comparative Example 1.

[0041] Figure 12 This is a schematic diagram of the processing procedure for industrial container bags in Example 1.

[0042] Figure 13 This is a schematic diagram of the processing procedure for industrial container bags in Example 1.

[0043] Figure 14 This is a schematic diagram of the finished industrial container bag from Example 1. Detailed Implementation

[0044] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0045] Example 1:

[0046] This embodiment proposes a method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, which includes the following steps:

[0047] (1) Take 1000g of dolomite particles with a particle size of less than 200 mesh (CaCO3 content is 52.3%, MgCO3 content is 43.6%, Al2O3 content is 1.1%, SiO2 content is 0.2%), put them in a muffle furnace for calcination, heat them to 580℃ at a rate of 15℃ / min, and hold them at 580℃ for 30min; then heat them to 1050℃ at a rate of 5℃ / min, hold them at 10min and then stop heating, and let them cool naturally to below 50℃. After cooling, add 1250mL of 0.01mol / L HNO3 solution, stir for 10min at 40℃ and 500r / min, filter with a G2 type sand core funnel, collect the filtrate, and obtain solution A.

[0048] (2) Mix 10g of Clason lignin with a number average molecular weight of 7650 and a SiO2 content of 0.08%, 50g of rubidium hydroxide and 200mL of 0.01mol / L NaOH solution, stir to form a homogeneous solution, and obtain solution B.

[0049] (3) Pour solution A into a 3000mL stainless steel high-pressure reactor with an inlet, evacuate to -0.095MPa, heat to 95℃, and inject 120mL of solution B into the reactor at a rate of 1.8mL / min using a peristaltic pump while stirring at 200r / min. Heat to 160℃ at a rate of 2℃ / min and maintain the temperature for 60min. Then cool to 85℃ at a rate of 1℃ / min, inject the remaining 80mL of solution B into the reactor within 1min, stop stirring, and fill with 99.99% CO2 to bring the system pressure to 2MPa. Maintain the temperature at 85±1℃ for 48h. Allow to cool naturally, filter using a G2 type sintered glass funnel, wash the precipitate with deionized water, and dry to obtain a brownish-yellow powder.

[0050] (4) Weigh 1000g of the above brownish-yellow powder and 10g of stearic acid and add them to a high-speed mixer. Heat the mixture to 90℃ and stir at 500r / min for 5min to obtain the modified powder.

[0051] (5) Place 15 kg of virgin polypropylene (warp) or a composite of virgin polypropylene and recycled polypropylene in a mass ratio of 8:2 (weft), 1 kg of modified powder, 0.23 kg of polyethylene wax, and 3 kg of filler masterbatch (composed of 10% linear low-density polyethylene as the matrix resin and 90% 800-mesh heavy calcium carbonate) in a high-temperature mixer at 150°C and stir for 15 min to obtain a mixture. The mixture is fed into a twin-screw extruder with a screw length-to-diameter ratio of 35:1. The temperatures of the five heating zones from the hopper to the die head are set sequentially to 160°C, 170°C, 180°C, 190°C, and 200°C. The extruded strip is then water-cooled, stretched, and pelletized to produce masterbatch.

[0052] (6) Pour the masterbatch into the drawing machine for extrusion and drawing. Use a biaxial cross-weaving device with intelligent tension control system to control the tension difference between warp and weft yarns to ≤5%, the cross angle to be 50°, and adopt a plain weave structure. The linear density of warp and weft yarns is controlled to be 280 denier, the warp density is 40 threads / 10 cm, and the weft density is 30 threads / 10 cm. The yarn is woven and formed under the condition that the spindle speed of the weaving machine is 500 rpm. Figures 12-14 This is a schematic diagram of the processing procedure and finished product of the container bag in this embodiment.

[0053] Example 2:

[0054] This embodiment proposes a method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, which includes the following steps:

[0055] (1) Take 1000g of dolomite particles with a particle size of less than 200 mesh (CaCO3 content is 51.5%, MgCO3 content is 45.0%, Al2O3 content is 0.93%, SiO2 content is 0.15%), put them in a muffle furnace for calcination, heat them to 580℃ at a rate of 15℃ / min, and hold them at 580℃ for 30min; then heat them to 1050℃ at a rate of 5℃ / min, hold them at 10min and then stop heating, and let them cool naturally to below 50℃. After cooling, add 1200mL of 0.01mol / L HNO3 solution, stir for 10min at 40℃ and 500r / min, filter with a G2 type sand core funnel, collect the filtrate, and obtain solution A.

[0056] (2) Mix 10g of Klassen lignin with a number average molecular weight of 5600 and a SiO2 content of 0.17%, 50g of rubidium hydroxide and 200mL of 0.01mol / L NaOH solution and stir to form a homogeneous solution to obtain solution B.

[0057] (3) Pour solution A into a 3000mL stainless steel high-pressure reactor with an inlet, evacuate to -0.09MPa, heat to 91℃, and inject 120mL of solution B into the reactor at a rate of 1.5mL / min using a peristaltic pump while stirring at 200r / min. Heat to 170℃ at a rate of 2℃ / min and maintain the temperature for 60min. Then cool to 85℃ at a rate of 1℃ / min, inject the remaining 80mL of solution B into the reactor within 1min, stop stirring, and fill with 99.99% CO2 to bring the system pressure to 1.8MPa. Maintain the temperature at 85±1℃ for 40h. Allow to cool naturally, filter using a G2 type sintered glass funnel, wash the precipitate with deionized water, and dry to obtain a brownish-yellow powder.

[0058] (4) Weigh 1000g of the above brownish-yellow powder and 9g of titanate into a high-speed mixer, heat to 90℃, and stir at 500r / min for 5min to obtain modified powder.

[0059] (5) Place 15 kg of virgin polypropylene (warp) or a composite of virgin polypropylene and recycled polypropylene in a mass ratio of 9:1 (weft), 1.25 kg of modified powder, 0.23 kg of polyethylene wax, and 3.5 kg of filler masterbatch (composed of 10% linear low-density polyethylene as the matrix resin and 90% 800-mesh heavy calcium carbonate) in a high-temperature mixer at 150°C and stir for 15 min to obtain a mixture. The mixture is fed into a twin-screw extruder with a screw length-to-diameter ratio of 35:1. The temperatures of the five heating zones from the hopper to the die head are set sequentially to 160°C, 170°C, 180°C, 190°C, and 200°C. The extruded strip is then water-cooled, stretched, and pelletized to produce masterbatch.

[0060] (6) Pour the masterbatch into the drawing machine for extrusion and drawing. Use a biaxial cross-weaving device with intelligent tension control system to control the tension difference between warp and weft yarns to ≤5%, the cross angle to be 60°, and adopt a plain weave structure. The linear density of warp and weft yarns is controlled to be 300 denier, the warp density is 30 threads / 10 cm, and the weft density is 30 threads / 10 cm. The yarn is woven and formed under the condition that the spindle speed of the weaving machine is 500 rpm.

[0061] Example 3:

[0062] This embodiment proposes a method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, which includes the following steps:

[0063] (1) Take 1000g of dolomite particles with a particle size of less than 200 mesh (CaCO3 content is 54.2%, MgCO3 content is 41.5%, Al2O3 content is 1.25%, SiO2 content is 0.05%), put them in a muffle furnace for calcination, heat them to 580℃ at a rate of 15℃ / min, and hold them at 580℃ for 30min; then heat them to 1050℃ at a rate of 5℃ / min, hold them at 10min and then stop heating, and let them cool naturally to below 50℃. After cooling, add 1280mL of 0.01mol / L HNO3 solution, stir for 10min at 40℃ and 500r / min, filter with a G2 type sand core funnel, collect the filtrate, and obtain solution A.

[0064] (2) Mix 10g of Clason lignin with a number average molecular weight of 1080 and a SiO2 content of 0.18%, 50g of rubidium hydroxide and 200mL of 0.01mol / L NaOH solution and stir to form a homogeneous solution to obtain solution B.

[0065] (3) Pour solution A into a 3000mL stainless steel high-pressure reactor with an inlet, evacuate to -0.096MPa, heat to 92℃, and inject 120mL of solution B into the reactor at a rate of 1.58mL / min using a peristaltic pump while stirring at 200r / min. Heat to 165℃ at a rate of 2℃ / min and maintain the temperature for 60min. Then cool to 85℃ at a rate of 1℃ / min, inject the remaining 80mL of solution B into the reactor within 1min, stop stirring, and fill with 99.99% CO2 to bring the system pressure to 1.6MPa. Maintain the temperature at 85±1℃ for 55h. Allow to cool naturally, filter using a G2 type sintered glass funnel, wash the precipitate with deionized water, and dry to obtain a brownish-yellow powder.

[0066] (4) Weigh 1000g of the above brownish-yellow powder and 8g of aluminate into a high-speed mixer, heat to 90℃, and stir at 500r / min for 5min to obtain modified powder.

[0067] (5) Place 15 kg of virgin polypropylene (warp) or a composite of virgin polypropylene and recycled polypropylene in a mass ratio of 8.5:1.5 (weft), 0.85 kg of modified powder, 0.23 kg of polyethylene wax, and 4.2 kg of filler masterbatch (composed of 10% linear low-density polyethylene as the matrix resin and 90% 800-mesh heavy calcium carbonate) in a high-temperature mixer at 150°C and stir for 15 min to obtain a mixture. The mixture is fed into a twin-screw extruder with a screw length-to-diameter ratio of 35:1. The temperatures of the five heating zones from the hopper to the die head are set sequentially to 160°C, 170°C, 180°C, 190°C, and 200°C. The extruded strip is then water-cooled, stretched, and pelletized to produce masterbatch.

[0068] (6) Pour the masterbatch into the drawing machine for extrusion and drawing. Use a biaxial cross-weaving device with intelligent tension control system to control the tension difference between warp and weft yarns to ≤5%, the cross angle to be 30°, and adopt a plain weave structure. The linear density of warp and weft yarns is controlled to be 240 denier, the warp density is 35 threads / 10 cm, and the weft density is 25 threads / 10 cm. The weaving is formed under the condition that the spindle speed of the weaving machine is 500 rpm.

[0069] Example 4:

[0070] This embodiment proposes a method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, which includes the following steps:

[0071] (1) Take 1000g of dolomite particles with a particle size of less than 200 mesh (CaCO3 content of 51.8%, MgCO3 content of 45.8%, Al2O3 content of 0.8%, and SiO2 content of 0.4%), place them in a muffle furnace for calcination, raise the temperature to 580℃ at a rate of 15℃ / min, and hold at 580℃ for 30min; then raise the temperature to 1050℃ at a rate of 5℃ / min, hold at 10min, and then stop heating and allow to cool naturally to below 50℃. After cooling, add 1220mL of 0.01mol / L HNO3 solution, stir at 40℃ and 500r / min for 10min, filter with a G2 type sand core funnel, collect the filtrate, and obtain solution A.

[0072] (2) Mix 10g of Klassen lignin with a number average molecular weight of 11000 and a SiO2 content of 0.14%, 50g of rubidium hydroxide and 200mL of 0.01mol / L NaOH solution, stir to form a homogeneous solution, and obtain solution B.

[0073] (3) Pour solution A into a 3000mL stainless steel high-pressure reactor with an inlet, evacuate to -0.092MPa, heat to 80℃, and inject 120mL of solution B into the reactor at a rate of 1.1mL / min using a peristaltic pump while stirring at 200r / min. Heat to 175℃ at a rate of 2℃ / min and maintain the temperature for 60min. Then cool to 85℃ at a rate of 1℃ / min, inject the remaining 80mL of solution B into the reactor within 1min, stop stirring, and fill with 99.99% CO2 to bring the system pressure to 1.8MPa. Maintain the temperature at 85±1℃ for 60h. Allow to cool naturally, filter using a G2 type sintered glass funnel, wash the precipitate with deionized water, and dry to obtain a brownish-yellow powder.

[0074] (4) Weigh 1000g of the above brownish-yellow powder and 10g of stearic acid / aluminate mixture with a mass ratio of 1:1 and add them to a high-speed mixer. Heat the mixture to 90°C and stir at 500r / min for 5min to obtain the modified powder.

[0075] (5) Place 15 kg of virgin polypropylene (warp) or a composite of virgin polypropylene and recycled polypropylene in a mass ratio of 75:25 (weft), 1.3 kg of modified powder, 0.23 kg of polyethylene wax, and 3.6 kg of filler masterbatch (composed of 10% linear low-density polyethylene as the matrix resin and 90% 800-mesh heavy calcium carbonate) in a high-temperature mixer at 150°C and stir for 15 min to obtain a mixture. The mixture is fed into a twin-screw extruder with a screw length-to-diameter ratio of 35:1. The temperatures of the five heating zones from the hopper to the die head are set sequentially to 160°C, 170°C, 180°C, 190°C, and 200°C. The extruded strip is then water-cooled, stretched, and pelletized to produce masterbatch.

[0076] (6) Pour the masterbatch into the drawing machine for extrusion and drawing. Use a biaxial cross-weaving device with intelligent tension control system to control the tension difference between warp and weft yarns to ≤5%, the cross angle to be 48°, and adopt a plain weave structure. The linear density of warp and weft yarns is controlled to be 270 denier, the warp density is 32 threads / 10 cm, and the weft density is 30 threads / 10 cm. The weaving is formed under the condition that the spindle speed of the weaving machine is 500 rpm.

[0077] Comparative Example 1:

[0078] This comparative example presents a method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, comprising the following steps:

[0079] (1) Take 1000g of limestone particles with a particle size of less than 200 mesh (CaCO3 content of 99.1%, MgCO3 content of 0.06%, Al2O3 content of 0.12%, SiO2 content of 0.23%), put them in a muffle furnace for calcination, heat them to 580℃ at a rate of 15℃ / min, and hold them at 580℃ for 30min; then heat them to 1050℃ at a rate of 5℃ / min, hold them at 10min and then stop heating, and let them cool naturally to below 50℃. After cooling, add 1250mL of 0.01mol / L HNO3 solution, stir for 10min at 40℃ and 500r / min, filter with a G2 type sand core funnel, collect the filtrate, and obtain solution A.

[0080] (2)~(6) are the same as steps (2)~(6) in Example 1.

[0081] Comparative Example 2:

[0082] This comparative example presents a method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, comprising the following steps:

[0083] (1) Same as step (1) in Example 1.

[0084] (2) Mix 10g of Clason lignin with a number average molecular weight of 7650 and a SiO2 content of 0.08% with 200mL of 0.01mol / L NaOH solution and stir to form a homogeneous solution to obtain solution B.

[0085] (3)~(6) are the same as steps (3)~(6) in Example 1.

[0086] Comparative Example 3:

[0087] This comparative example presents a method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, comprising the following steps:

[0088] (1) Same as step (1) in Example 1.

[0089] (2) Mix 50g of rubidium hydroxide and 200mL of 0.01mol / L NaOH solution and stir to form a homogeneous solution to obtain solution B.

[0090] (3) Pour solution A into a 3000mL stainless steel high-pressure reactor with an inlet, evacuate to -0.095MPa, heat to 95℃, and inject 120mL of solution B into the reactor at a rate of 1.8mL / min using a peristaltic pump while stirring at 200r / min. Heat to 160℃ at a rate of 2℃ / min and maintain the temperature for 60min. Then cool to 85℃ at a rate of 1℃ / min, inject the remaining 80mL of solution B into the reactor within 1min, stop stirring, and fill with 99.99% CO2 to bring the system pressure to 2MPa. Maintain the temperature at 85±1℃ for 48h. Allow to cool naturally, filter using a G2 type sintered glass funnel, wash the precipitate with deionized water, and dry to obtain a white powder.

[0091] (4)~(6) are the same as steps (4)~(6) in Example 1.

[0092] Comparative Example 4:

[0093] This comparative example presents a method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, comprising the following steps:

[0094] (1)~(2) are the same as steps (1)~(2) in Example 1.

[0095] (3) Pour solution A into a 3000mL stainless steel high-pressure reactor with an inlet, evacuate to -0.095MPa, heat to 95℃, and inject 120mL of solution B into the reactor at a rate of 1.8mL / min using a peristaltic pump while stirring at 200r / min. Heat to 160℃ at a rate of 2℃ / min and maintain the temperature for 60min. Then cool to 85℃ at a rate of 1℃ / min, inject the remaining 80mL of solution B into the reactor within 1min, stop stirring, and fill with 99.99% N2 to bring the system pressure to 2MPa. Maintain the temperature at 85±1℃ for 48h. Allow to cool naturally, filter using a G2 type sintered glass funnel, wash the precipitate with deionized water, and dry to obtain a brownish-yellow powder.

[0096] (4)~(6) are the same as steps (4)~(6) in Example 1.

[0097] Test methods and results:

[0098] Industrial container bags were prepared according to the above-described embodiments and comparative methods, and tested according to the following methods. The results are shown in Table 1.

[0099] Test method:

[0100] (1) Scanning electron microscopy (SEM) test: The modified powder and the brittle / tensile fracture surface of the industrial container bag were sputtered with gold at 15mA for 120s, and then the micro morphology was observed using a Hitachi S-3400N scanning electron microscope.

[0101] (2) Mechanical performance test: The longitudinal tensile strength and longitudinal elongation at break are determined in accordance with the test methods of GB / T 10454-2025 "Flexible medium bulk containers for packaging non-dangerous goods".

[0102] (3) Aging test: conducted according to ASTM G154-2023 standard. The newly prepared woven bags were placed in a UV aging test chamber equipped with UVA-340 ultraviolet lamps, with the temperature set at 40℃, relative humidity (RH) at 75%, and irradiance at 0.8W / m². 2 After 14 days of continuous irradiation, samples were removed for mechanical property testing. Tensile strength retention was calculated using the following formula:

[0103] Tensile strength retention rate (%) = (longitudinal tensile strength after UV aging / initial longitudinal tensile strength) × 100%.

[0104] (4) Antibacterial test: Plate count method was used. A 2wt% bacterial suspension of *Escherichia coli* (ATCC 25922) was prepared using sterile physiological saline. 10 mL of the suspension was added to the surface of the sample to be tested (sample area 5cm × 5cm), and placed at 35℃ and 75% RH in the dark for 24 hours. Pure polypropylene plates without any fillers or added antibacterial components served as a blank control. The antibacterial rate of the blank control sample was 0%. After tenfold serial dilution, plating, and incubation at 37℃ for 24 hours, colonies were counted, and the antibacterial rate was calculated using the following formula:

[0105] Antibacterial rate (%) = (average viable count of blank control - average viable count of sample) / average viable count of blank control × 100%.

[0106]

[0107] The main component contents of the ore raw materials in each embodiment and comparative example are shown in Table 2.

[0108]

[0109] Results analysis.

[0110] (a) Microscopic morphology and structural characterization.

[0111] Figure 1 and Figure 2 SEM images of the modified powders obtained in Examples 1 and 2 are shown. As can be seen from the figures, both powders exhibit a highly regular "lamellae-fiber" composite structure: a fibrous skeleton with a high aspect ratio (derived from the directional assembly of lignin molecular chains) uniformly and densely loaded with nanoscale-thickness lamellar inorganic particles. The lamellars are arranged orderly along the fiber axis, forming a continuous coating morphology resembling "fish scales" or "bamboo joints." This structure embodies the design concept of lignin providing a long fibrous organic skeleton, with calcium, magnesium, and rubidium components generating lamellar inorganic particles in situ on the long lignin chains. This structure has two major advantages: firstly, the high aspect ratio of the fiber skeleton allows it to effectively traverse multiple resin microregions in the polypropylene matrix, undertaking stress transfer and bridging functions, and avoiding stress concentration; secondly, the high aspect ratio lamellars stack layer by layer in the matrix, forming a physical cross-linking network, further restricting the movement of polypropylene molecular chains, thereby endowing the composite material with higher rigidity and creep resistance. The high degree of consistency in morphology between the two embodiments (with only slight differences in lamellar density) indicates that the process window of the present invention is wide, and the target structure can be stably constructed under different dolomite sources and reaction parameters.

[0112] In stark contrast is the SEM image of the powder obtained in Example 1 (where limestone was used instead of dolomite). Figure 3 The image shows a sparse lamellar structure, blurred fiber outlines, and a large area exhibiting loosely packed amorphous particles, with the fibrous organic framework almost unrecognizable. The fundamental reason is that the limestone contains only 0.06% magnesium carbonate (see Table 2), almost no magnesium. The core of this invention's "two-stage roasting-acid dissolution" process lies in the simultaneous release of calcium and magnesium ions, which synergistically participate in crystal nucleation and growth during high-pressure CO2 mineralization. The absence of magnesium ions leads to a reduction in lattice distortion energy, preventing the formation of a stable calcium-magnesium composite crystal form. Figure 5 The sharp characteristic peaks in XRD of Example 1 further corroborate this (inorganic particles can only mineralize by calcium ions alone, resulting in low crystallinity and disordered growth, thus failing to achieve regular lamellar deposition on the lignin template). This result also demonstrates, from the opposite perspective, the indispensability of the synergistic effect of calcium and magnesium in dolomite for constructing a regular composite structure. The lack of a regular structure is the fundamental microscopic reason why the mechanical properties and aging resistance of Comparative Example 1 are far inferior to those of the Example.

[0113] Figure 4The image shows a SEM image of the powder obtained in Comparative Example 3 (lignin completely omitted). The image reveals irregular granular aggregates with a wide particle size distribution and severe adhesion, lacking fibrous characteristics. This directly confirms the structure-directing template role of lignin in this system: lignin molecules contain abundant phenolic hydroxyl and carboxyl groups, which can chelate calcium, magnesium, and rubidium ions through coordination or hydrogen bonding, guiding them to undergo heterogeneous nucleation and directional growth along the molecular chain. Without the ordered interface provided by lignin, calcium and magnesium ions can only precipitate homogeneously in solution, forming isotropic amorphous aggregates.

[0114] Figure 5 The XRD diffraction patterns of the modified powders obtained in Example 1 and Comparative Example 1 are shown. The pattern of Example 1 exhibits a set of clear, sharp, and high-intensity characteristic diffraction peaks at 23.4°, 28.4°, 39.6°, and 49.5°, corresponding to the characteristic crystal plane diffraction of the calcium, magnesium, and rubidium composite crystals, respectively. This result fully demonstrates that under the high-pressure CO2 atmosphere, long-term hydrothermal crystallization at 85±1℃, and suitable alkalinity conditions specified in this invention, calcium, magnesium, and rubidium form a ternary composite crystal structure with a high degree of crystalline order. This stable crystal structure directly endows the filler with two key functions: firstly, the regular lattice arrangement reduces the defect density on the filler surface, reducing the interfacial stress concentration points when composited with polypropylene; secondly, the chemical inertness of the crystal is significantly higher than that of amorphous compounds, effectively suppressing transition metal ions (such as Fe). 3+ The catalytic oxidation activity of impurities (such as polypropylene) under photothermal conditions is reduced, thereby slowing down the aging process of the polypropylene matrix.

[0115] In stark contrast is the XRD pattern of Comparative Example 1. Comparative Example 1, where limestone (99.1% CaCO3, only 0.06% MgCO3) was used instead of dolomite, exhibited significantly weakened diffraction peak intensities, broadened peak shapes, and near-disappearance of some small-angle characteristic peaks, indicating a significant reduction in crystallinity and disruption of long-range lattice order. The fundamental reason lies in the extreme scarcity of magnesium. The synergistic effect of calcium and magnesium ions in dolomite is the chemical basis for constructing regular crystals. Magnesium ions have a smaller radius than calcium ions and can replace some calcium sites in the lattice, causing localized lattice distortion. This distortion, in turn, helps reduce the system's free energy and promotes the directional preferential growth of crystal nuclei. When magnesium ions are absent, calcium ions alone cannot form a stable composite crystal form, and the mineralization products tend to form compounds with poor crystallinity. Furthermore, Table 2 shows that the Fe2O3 impurity content in limestone (0.283%) is much higher than that in dolomite (0.087%). Iron ions are more likely to form defect sites in the crystal lattice, further disrupting the periodicity of the crystal lattice.

[0116] Figure 6The figures show a comparison of the particle size distribution of the modified powders obtained in Examples 1, 2, and Comparative Examples 1-4. As can be seen from the figures, the particle size distribution curves of Examples 1 and 2 both exhibit typical single-peak narrow distribution characteristics, indicating that both examples can achieve highly consistent particle size control under different dolomite ore sources and process parameters. This narrow distribution powder characteristic originates from the self-confined growth mechanism of the "lamellae-fiber" composite structure of this invention: the lignin fiber skeleton provides a spatially confined template, and the calcium, magnesium, and rubidium components mineralize and grow in situ on the fiber surface, rather than freely nucleating and agglomerating in a homogeneous solution. Therefore, the resulting powder particle size is mainly determined by the lateral dimensions of the fiber skeleton, rather than the random stacking of random aggregates. The uniform narrow particle size distribution means that the filler particles can achieve uniform dispersion at the single-particle level in the polypropylene matrix, avoiding the dual defects of "large particles acting as stress concentration points and excessive agglomeration of small particles."

[0117] In contrast, the grain size distribution curve of Comparative Example 1 (limestone replacing dolomite) exhibits a distinct bimodal broad distribution characteristic. The direct cause of this broad distribution pattern is the lack of magnesium, which leads to low crystallinity and disordered growth of the mineralized products (see...). Figure 3 With its irregular morphology, a large number of inorganic particles cannot be effectively anchored, instead undergoing homogeneous nucleation and secondary aggregation to form coarse aggregates. The direct consequence of this wide distribution is that small particles are easily embedded between polypropylene molecular chains but have weak interfacial bonding, while large particles become the preferred induction sites for photo-oxidative aging, accelerating local degradation under ultraviolet irradiation.

[0118] The particle size distribution curve of Comparative Example 2 (excluding rubidium hydroxide) almost completely overlaps with that of Example 1, indicating that the introduction of rubidium has no substantial impact on the nucleation-growth kinetics and final particle size distribution of the composite filler. This is because rubidium ions enter the calcium-magnesium lattice through substitution or interstitial doping, rather than participating in structural construction as an independent crystal phase. Therefore, the antibacterial function of rubidium and the mechanical reinforcement function of the filler are undertaken by different structural levels, achieving decoupled integration of functions—that is, the antibacterial function is achieved without sacrificing the mechanical reinforcement effect.

[0119] The particle size distribution curve of Comparative Example 3 (lignin omitted) exhibits an extremely broad single-peak tail. Due to the absence of lignin, calcium, magnesium, and rubidium ions lose their directional deposition template and can only undergo homogeneous precipitation, forming isotropic, loose aggregates (see...). Figure 4 Due to the lack of spatial confinement effect of an organic framework, primary grains undergo irreversible hard agglomeration during drying, forming coarse and loosely structured secondary aggregates. These coarse particles are difficult to disperse in polypropylene melt blending and remain in the matrix as agglomerates, becoming typical micro-defects and stress concentration sources.

[0120] The particle size distribution curve of Comparative Example 4 (with N2 replacing CO2) exhibits a bimodal distribution and an overall rightward shift. Due to the lack of a CO2 mineralization environment, calcium, magnesium, and rubidium ions cannot form a stable crystal lattice. Their high surface energy and strong chemical reactivity make them prone to irreversible condensation and aggregation during the reaction and drying processes, forming numerous large secondary aggregates. Simultaneously, the density of the amorphous product is lower than that of the crystalline state, resulting in a larger volume for the same mass, further pushing up the particle size distribution curve. This result clearly verifies that a high-pressure CO2 mineralization environment is not only conducive to the formation of stable crystal structures (… Figure 5 This is a necessary condition for achieving fine-grained, narrow-distribution particle size control, and also a prerequisite for achieving fine-grained, narrow-distribution particle size control.

[0121] comprehensive Figure 6 Based on the characteristics of each curve, a clear conclusion can be drawn: in this invention, the lignin fiber template, the dolomite calcium-magnesium synergistic component, and the high-pressure CO2 mineralization environment jointly construct a powder preparation system of "spatial confinement-directional nucleation-stable growth", none of which can be omitted.

[0122] Figure 7 This is the EDS (Energy Dispersive Spectrum) analysis diagram of the modified powder obtained in Example 1. The characteristic peaks of calcium (Ca), magnesium (Mg), rubidium (Rb), carbon (C), and oxygen (O) are clearly visible in the spectrum. This EDS data provides three key pieces of evidence at the elemental composition level: First, it confirms the successful transformation of calcium and magnesium elements from the dolomite mineral phase to the composite carbonate crystal phase. After two stages of roasting-acid dissolution treatment, the calcium and magnesium elements originally existing in the dolomite in the form of CaMg(CO3)2 were released as Ca... 2+ and Mg 2+ First, ions were re-precipitated as complex salts on the surface of the lignin fiber skeleton under high-pressure CO2 mineralization. Second, it was confirmed that rubidium had been successfully doped into the filler structure, ensuring the durability of the antibacterial function. Third, it confirmed the existence of the lignin fiber skeleton and its tight binding with inorganic components. In addition to contributions from carbonate ions, a considerable portion of the carbon in the energy dispersive spectroscopy (EDS) also came from the organic carbon skeleton of lignin.

[0123] Figure 8 and Figure 9 SEM images of the brittle cross sections of the industrial container bags obtained in Example 1 and Comparative Example 1, respectively. Figure 10 and Figure 11 The images shown are SEM images of the tensile fracture surfaces of both materials. These four images, presented from different perspectives, reveal the dispersion state, interfacial bonding quality, and fracture behavior characteristics of the filler in the polypropylene matrix, providing direct morphological evidence for understanding the microscopic mechanisms underlying the performance advantages of this invention.

[0124] Figure 8(Example 1: Brittle Fracture) The fracture surface after liquid nitrogen brittle fracture is generally smooth. The filler particles are highly uniformly dispersed as single particles within the polypropylene matrix, with no micron-sized agglomerates or aggregates observed. More importantly, the interface between the particles and the matrix is ​​blurred and difficult to distinguish. A large number of filler particles are tightly wrapped by the matrix, and some particles remain firmly embedded in the matrix after fracture without being pulled out or detached. This morphological feature illustrates two essential aspects: First, the surface-modified lamellar-fiber composite filler of this invention forms good interfacial wetting and chemical bonding with the polypropylene resin, effectively avoiding the interfacial detachment and agglomeration phenomena caused by hydrophilic / hydrophobic incompatibility in traditional calcium carbonate filling systems. Second, when the crack propagates to the filler particles, due to the sufficiently high interfacial bonding strength, the crack cannot deflect along the low-energy path of the particle / matrix interface and is forced to continue propagating through the interior of the particles or around them. This process consumes more fracture energy, exhibiting typical ductile fracture characteristics. It is this excellent interfacial bonding state that endows the material with excellent mechanical properties.

[0125] and Figure 8 In stark contrast is Figure 9 (Comparative Example 1: Brittle Fracture). The figure clearly shows numerous filler agglomerates with sharp particle edges. There are obvious annular gaps and interfacial debonding cavities between the filler and the polypropylene matrix. Some particles are completely pulled out, leaving smooth pits in the matrix, exhibiting typical brittle fracture characteristics. During brittle fracture, cracks preferentially propagate along the mechanically weak region of the filler / matrix interface, forming a low-energy fracture path, macroscopically manifested as a significant decrease in the material's tensile strength. More seriously, these interfacial cavities and debonding regions become rapid channels for oxygen diffusion and preferential initiation points for photo-oxidative aging under ultraviolet irradiation—oxygen and ultraviolet light can directly act on the polypropylene molecular chains through interfacial micro-gaps, accelerating the generation of tertiary carbon free radicals and chain breakage reactions.

[0126] Figure 10 (Example 1, tensile fracture surface) exhibits morphological characteristics distinctly different from the brittle fracture surface. The fracture surface displays numerous highly oriented fibrous filaments, with filament diameters ranging from approximately 0.5 to 2 μm and lengths reaching tens of micrometers. These filaments intertwine to form a dense "fiber network," resulting in an overall rough fracture surface with obvious necking characteristics. The essence of this filament network lies in the microscopic traces of shear yielding and plastic flow following the orientation of polypropylene molecular chains during tensile fracture. When external force is applied, the uniformly dispersed composite filler acts as physical cross-linking points, inducing high orientation in the surrounding matrix, allowing stress to be evenly distributed and dissipated over a wider area. More importantly, the filament surface is smooth, without exposed particles or voids, indicating that during fracture, the filler particles were not pulled out of the matrix or became crack initiations, but rather participated in load-bearing as stress transfer nodes throughout the process and synergistically underwent plastic deformation with the matrix.

[0127] Corresponding to Figure 11 (Comparative Example 1 tensile fracture surface). The fracture surface is generally flat and smooth, with almost no fibrous filamentous structure. Only a small number of short and thick filamentous protrusions (length <5 μm) are sparsely distributed. Most areas exhibit brittle cleavage fracture characteristics, and filler agglomerates are clearly identifiable. There are obvious pores and interfacial debonding trajectories around the agglomerates. This morphology reveals that the tensile fracture of Comparative Example 1 is mainly brittle failure dominated by interfacial debonding: under low stress, cracks initiate and rapidly propagate along the weak interface of the filler / matrix. Due to the lack of an effective stress transfer network, the polypropylene molecular chains do not have enough time to fully orient and plastically flow before breaking. This indicates that the internal structure of the agglomerates is loose and the cohesion is weak, which cannot effectively bear stress and further aggravates the deterioration of mechanical properties.

[0128] (II) Analysis of mechanical properties, aging resistance and synergistic effects.

[0129] As shown in Table 1, the industrial containers prepared in Examples 1-4 exhibit excellent overall performance, with longitudinal tensile strength ≥2798N, tensile strength retention rate ≥87% after 14 days of UV aging, and antibacterial rate ≥90%. The performance data among the examples are highly consistent, indicating that the method of the present invention can stably achieve the synergistic effects of reinforcement, aging resistance, and antibacterial properties within a wide range of process parameters.

[0130] Comparative Example 1 used limestone (CaCO3 99.1%, MgCO3 only 0.06%) instead of dolomite. Its newly prepared tensile strength (1986 N) and aging retention rate (76.0%) were significantly lower than those of Example 1 (2884 N, 89.0%). This can be understood from two aspects: firstly, the unique calcium-magnesium synergistic structure of dolomite forms calcium-magnesium composite carbonate crystals during the roasting-acid dissolution-mineralization process. Figure 5 Firstly, this structure exhibits higher lattice stability and interfacial compatibility compared to pure calcium carbonate. Secondly, Table 2 shows that the Fe2O3 impurity content in limestone (0.283%) is much higher than that in dolomite (0.087%), indicating that transition metal ions such as iron ions play a catalytic accelerating role in photo-oxidative aging. These differences in macroscopic mechanical properties corroborate the aforementioned cross-sectional microstructure, demonstrating that the differences in the crystal structure of the filler and interfacial defects jointly determine the quality of its mechanical properties and aging resistance.

[0131] In Comparative Example 2, omitting rubidium hydroxide resulted in a sharp drop in antibacterial rate to 24%, while the mechanical properties (2806 N, retention rate 85.0%) remained essentially the same as in Example 1. This indicates that the introduction of rubidium does not affect the reinforcing function of the filler, but it is the core component that imparts antibacterial properties to the material—its mechanism of action lies in the fact that rubidium ions exert antibacterial effects by disrupting bacterial cell membrane integrity, interfering with metabolism, and inducing oxidative damage. This result also demonstrates that the "reinforcing function" and "antibacterial function" of this invention are undertaken by different structural units, without interfering with each other, thus achieving functional integration.

[0132] Comparative Example 3, omitting lignin, showed the lowest tensile strength (1879 N) and aging retention rate (71.0%) among all samples. (SEM image) Figure 4 The results show that without lignin, the powder forms irregular granular aggregates, completely lacking a fibrous framework structure. This indicates that the fibrous framework provided by lignin not only provides a structural template for the mineralization and deposition of calcium, magnesium, and rubidium, but also acts as an interfacial bridge between the powder and the polypropylene matrix—the fibrous framework runs through the inorganic particles and the organic matrix, reducing interfacial defects and inhibiting the formation of stress concentration points, thereby simultaneously improving initial strength and aging resistance.

[0133] In Comparative Example 4, after replacing CO2 with N2, the tensile strength (2564 N) and retention rate (82.0%) were both lower than those in Example 1. XRD patterns ( Figure 5 It has been confirmed that a stable carbonate crystal structure is formed under high-pressure CO2 conditions, while no mineralization reaction occurs under N2 atmosphere, and calcium and magnesium ions exist only in the form of amorphous hydroxides or oxides, with weak interfacial bonding with polypropylene. This verifies the necessity of a high-pressure CO2 mineralization environment for forming a stable carbonate structure and thus improving the stability of the filler.

[0134] In summary, the technical effectiveness of this invention stems from the synergistic effect of its components and process features: dolomite provides the source of calcium and magnesium, releasing calcium and magnesium ions after two-stage calcination and acid dissolution, forming a stable carbonate filler with a lamellar-fiber composite structure under the guidance of the lignin fiber skeleton and high-pressure CO2 mineralization; the introduction of rubidium imparts antibacterial function to the material without affecting its mechanical properties; surface modification and weaving processes further optimize filler dispersion and product structural uniformity. Each technical feature works in tandem and is indispensable, collectively achieving a simultaneous improvement in mechanical properties, aging resistance, and antibacterial properties.

[0135] The above embodiments only illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention.

Claims

1. A method for preparing an aging-resistant industrial container bag reinforced with dolomite derivatives, characterized in that, The steps are as follows: (1) Place the dolomite particles in a muffle furnace and calcine them to obtain powder with CaO-MgO as the main components. Then, after cooling the powder, add nitric acid solution and stir for 10 min at 40℃ and 500r / min. Filter and collect the filtrate, which is recorded as solution A. (2) Mix lignin, rubidium hydroxide and NaOH solution, and stir to form a homogeneous solution, which is denoted as solution B; (3) Pour solution A into a high-pressure reactor, evacuate, and heat to 80~95℃. Under stirring, inject solution B into the reactor in two batches. First, inject part of solution B and then heat to 150~180℃ and keep the temperature for 60 min. Then, cool down to 85℃ and inject the remaining solution B into the reactor within 1 min. Stop stirring, add CO2 to make the system pressure reach 1.5~2MPa, and keep the temperature at 85±1℃ for 20~60 h. After natural cooling, filter, wash and dry the precipitate to obtain a brownish-yellow powder. (4) Add the brownish-yellow powder and surface modifier to a high-speed mixer, heat to 90°C, stir and mix to obtain modified powder; (5) Mix thermoplastic resin, modified powder, polyethylene wax and filler masterbatch in a weight ratio of 100:5~10:1.5:20~30, place in a high mixer at 150℃, stir for 15 minutes to obtain a mixture, and then prepare industrial container bags by melt extrusion, drawing and weaving.

2. The preparation method according to claim 1, characterized in that, The dolomite particles mentioned in step (1) have a particle size of less than 200 mesh, a CaCO3 content of more than 50.8%, a MgCO3 content of more than 41%, an Al2O3 content of more than 0.8%, and a SiO2 content of less than 0.5%.

3. The preparation method according to claim 1, characterized in that, The calcination conditions described in step (1) are as follows: the temperature is increased to 580°C at a rate of 15°C / min and held at 580°C for 30 min; then the temperature is increased to 1050°C at a rate of 5°C / min and held for 10 min before the heating is stopped and the temperature is allowed to cool naturally to below 50°C.

4. The preparation method according to claim 1, characterized in that, The concentration of the nitric acid solution in step (1) is 0.01 mol / L, and the amount used is 1200~1280 mL.

5. The preparation method according to claim 1, characterized in that, The lignin mentioned in step (2) is Clason lignin, and its SiO2 content is less than 0.2%; the ratio of the amount of lignin, rubidium hydroxide and NaOH solution is 10g:50g:200mL, and the concentration of the NaOH solution is 0.01mol / L.

6. The preparation method according to claim 1, characterized in that, In step (3), the total volume of solution B is 200 mL, with 120 mL injected the first time and 80 mL injected the second time; the vacuum is drawn to -0.09 to -0.1 MPa; and the purity of CO2 is 99.99%.

7. The preparation method according to claim 1, characterized in that, The surface modifier mentioned in step (4) is one of stearic acid, aluminate, titanate or a mixture of any proportion; the ratio of the brownish-yellow powder to the surface modifier is 1000g:8~10g.

8. The preparation method according to claim 1, characterized in that, The thermoplastic resin mentioned in step (5) is virgin polypropylene or a composite of virgin polypropylene and recycled polypropylene, wherein the recycled polypropylene content in the composite is less than 25%; the matrix resin of the filler masterbatch is linear low-density polyethylene, the inorganic filler is 800-mesh heavy calcium carbonate, and the weight ratio of the matrix resin to the inorganic filler is 1:9; the weaving adopts a biaxial cross weaving device with an intelligent tension control system, the tension difference between warp and weft yarns is ≤5%, and the cross angle is 30~60°.

9. The preparation method according to claim 1, characterized in that, The industrial container bag described in step (5) adopts a plain weave structure, with a linear density of 200~300 denier for both warp and weft yarns, a warp density of 30~40 threads / 10 cm, and a weft density of 25~30 threads / 10 cm; wherein the warp yarns use virgin polypropylene, and the weft yarns use a composite of virgin polypropylene and recycled polypropylene.

10. An aging-resistant industrial container bag, characterized in that, Prepared by the method described in any one of claims 1 to 9, the longitudinal tensile strength is not less than 2700N, the tensile strength retention rate after UV aging for 14 days is not less than 80%, and the antibacterial rate against Escherichia coli is not less than 90%.

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