A high-toughness packaging bag and a method for manufacturing the same

Abstract

This invention relates to a high-toughness packaging bag and its preparation method, belonging to the field of packaging bag technology. The high-toughness packaging bag comprises high-density polyethylene, metallocene polyethylene, low-density polyethylene, a slip agent, and an antistatic agent; the slip agent includes erucamide. The preparation process includes raw material pretreatment and mixing, melting and filtration, blown film forming, and curing steps. This application uses high-density polyethylene, metallocene polyethylene, and low-density polyethylene to form the resin structure of the high-toughness packaging bag. By adding erucamide, the dynamic and static friction coefficients of the film surface are reduced; thus, the packaging bag maintains high toughness while also having good opening performance, meeting the needs of automated packaging.

Description

Technical Field

[0001] This invention relates to the field of packaging bag technology, and in particular to a high-toughness packaging bag and its preparation method. Background Technology

[0002] Plastic packaging bags are widely used in many fields such as food, daily chemicals, pharmaceuticals, electronics, consumer goods, and logistics warehousing, and are an indispensable packaging product in daily production and life. Meanwhile, the production process of plastic packaging bags is mature and has high mass production efficiency, enabling large-scale mass production to meet basic application needs. However, existing plastic packaging bags still have many problems in actual use, especially their poor abrasion resistance and insufficient toughness, which cannot meet the requirements of long-term storage and repeated use of goods.

[0003] To address the aforementioned issues, Chinese invention patent application CN119431979A, published on February 14, 2025, proposes a high-toughness plastic packaging bag and its manufacturing process. The raw materials for this packaging bag include polytetrafluoroethylene (PTFE), nylon co-extruded film, calcium carbonate masterbatch, molybdenum disulfide, graphite, and various fibers and inorganic powders. The manufacturing process includes mixing, high-temperature compounding, screw extrusion, film blowing, and bag making. This solution improves the toughness and abrasion resistance of the packaging bag, thereby enhancing its overall mechanical properties and durability.

[0004] However, further research by the inventors revealed that the above-mentioned technical solution uses a large amount of polytetrafluoroethylene and nylon co-extruded film. Both resins have smooth surfaces and strong flexibility, and lubricating components such as graphite and molybdenum disulfide are also added to the composition. These materials make the film surface smoother, resulting in a film with extremely high surface smoothness. However, at the same time, vacuum adsorption and molecular chain entanglement are very easy to occur between the film layers of the packaging bag, resulting in problems such as film adhesion and difficulty in opening, which in turn affects the subsequent processing and normal use of the product. Summary of the Invention

[0005] To address the problems of film adhesion and difficulty in opening packaging bags, this invention provides a high-toughness packaging bag and its preparation method.

[0006] In a first aspect, the present invention provides a high-toughness packaging bag, which adopts the following technical solution: A high-toughness packaging bag comprises, by weight, 10-12 parts of high-density polyethylene, 2.5-3.5 parts of metallocene polyethylene, 0.8-1.2 parts of low-density polyethylene, 0.25-0.35 parts of slip agent, and 0.15-0.25 parts of antistatic agent; wherein the slip agent comprises erucamide.

[0007] By adopting the above technical solution, a resin structure for high-toughness packaging bags is formed using high-density polyethylene, metallocene polyethylene, and low-density polyethylene. After adding erucamide, it can quickly migrate to the film surface during the blown film processing, forming a uniform molecular lubricating layer. This reduces the dynamic and static coefficients of friction on the film surface, facilitating relative sliding between film layers. Simultaneously, the use of metallocene polyethylene enhances the film's puncture resistance and toughness, enabling the packaging bag to maintain high toughness while also possessing good opening performance, meeting the requirements of automated packaging.

[0008] Optionally, the slip agent further includes glyceryl monostearate, wherein the mass ratio of glyceryl monostearate to erucamide is 3:6-8.

[0009] By adopting the above technical solution, the polar head of stearic acid monoglyceride interacts with the polar groups on the film surface, while the non-polar tails align outwards, forming a denser and more stable lubricating layer. Its high melting point makes it less prone to secondary migration or recrystallization. When mixed with erucamide, erucamide migrates to the surface first, reducing the initial coefficient of friction; stearic acid monoglyceride fills the gaps between erucamide molecules, inhibiting the formation of excessively large crystals on the film surface, which can lead to localized sticking points. Simultaneously, it provides a long-lasting lubricating effect, at least partially solving the problem of opening failure caused by adhesion in packaging bags during storage, transportation, and automated packaging lines.

[0010] Optionally, the high-toughness packaging bag further includes 1.0 to 2.0 parts of a crosslinking agent; the crosslinking agent includes zinc methacrylate and dicumyl peroxide, wherein the mass ratio of zinc methacrylate to dicumyl peroxide is 92 to 96: 4 to 8.

[0011] By employing the above technical solution, zinc methacrylate, an unsaturated carboxylate, forms an ionic crosslinking network with polyethylene molecular chains under the initiation of dicumyl peroxide. The crosslinking reaction mainly occurs in the amorphous region, moderately restricting the mobility of the molecular chains and preventing the film from becoming overly smooth due to subsequent thermal shrinkage or molecular relaxation. More importantly, the zinc ions in zinc methacrylate can coordinate with the amide groups in erucamide molecules, delaying the initial rapid release of erucamide and allowing it to migrate uniformly to the surface throughout the curing process and subsequent use, avoiding the formation of a sticky oil film on the surface due to excessive initial migration.

[0012] Secondly, the present invention provides a method for preparing a high-toughness packaging bag, which adopts the following technical solution: A method for preparing a high-toughness packaging bag includes the following steps: Raw material pretreatment and mixing: After drying and cooling, high-density polyethylene, metallocene polyethylene and low-density polyethylene are premixed at 300-400 r / min for 0.8-1.2 min; then slip agent and antistatic agent are added and stirred at 800-1000 r / min for 4-6 min to obtain the mixture; Melting and Filtration: The mixture is heated and melted and plasticized, and the melted and plasticized material is then filtered. Film blowing: The filtered melt is extruded through an annular die with a blow-up ratio of 2.0 to 2.5. It is then cooled and shaped by an air ring, pulled and wound up to obtain a semi-finished film. Curing: Place the semi-finished film at 20-30℃ and 40-60% relative humidity for 12-16 hours, then raise the temperature to 30-34℃ and 30-40% relative humidity and let it stand for 5-7 hours. Cut and bag it to obtain a high-toughness packaging bag.

[0013] By adopting the above technical solution, firstly, the raw materials are dried and cooled to remove moisture, preventing moisture from causing polyethylene hydrolysis or forming bubbles in the melting section. The three types of polyethylene resin are premixed at a low speed to avoid local overheating under high shear in the subsequent process. Then, after adding the slip agent and antistatic agent, the speed is increased, and the shear force is used to break and disperse them in the resin, so that the erucamide and antistatic agent are uniformly attached. The blow-up ratio is 2.0 to 2.5, which is conducive to the formation of slip agent migration channels without causing excessive orientation and surface mirroring.

[0014] In the curing process, the antistatic agent is first allowed to migrate fully to the surface and absorb moisture to form a conductive film under a high humidity environment, while erucamide begins to slowly precipitate. Then, after heating and dehumidifying, the erucamide is accelerated to migrate deeply to the surface to form a dense lubricating layer. The low humidity environment prevents the lubricating layer from absorbing water and becoming sticky, thus reducing the coefficient of friction of the film surface.

[0015] Optionally, in the raw material pretreatment and mixing step, the drying and cooling method is as follows: high-density polyethylene, metallocene polyethylene, and low-density polyethylene are dried at 55-65°C for 2-3 hours, and then transferred to 20-25°C for static cooling for 30-60 minutes for later use.

[0016] By adopting the above technical solution, polyethylene resin, which easily absorbs trace amounts of moisture during storage, can lead to poor plasticization if directly melted. Drying removes the moisture inside the resin, avoiding problems such as micropores on the film surface caused by water vapor vaporization during melt extrusion. The subsequent static cooling step eliminates the internal thermal stress of the resin particles generated by drying, allowing the resin particle temperature to reach thermal equilibrium with room temperature. This ensures that when mixed with the slip agent, the slip agent will not prematurely melt or agglomerate due to local temperature differences, guaranteeing a uniform coating of the slip agent on the resin surface and reducing the incidence of difficulties in opening packaging bags.

[0017] Optionally, in the raw material pretreatment and mixing step, the slip agent and antistatic agent are pretreated before being added to the material. The pretreatment method is as follows: take 0.5 to 1 part from 0.8 to 1.2 parts of the low-density polyethylene, and stir it together with the slip agent and antistatic agent at 200 to 300 r / min for 3 to 5 min to prepare a premix.

[0018] By adopting the above technical solution, the amount of added slip agent and antistatic agent is relatively small. If directly mixed with bulk materials, it is very easy to cause uneven dispersion. Low-density polyethylene has good flexibility and adhesion. Under low-speed stirring, it can evenly adhere and coat the trace amount of slip agent and antistatic agent on its particle surface, avoiding the film surface streaks or local excessive precipitation caused by local agglomeration of slip agent, and ensuring the uniformity of film friction coefficient.

[0019] Optionally, in the melting and filtering steps, the heating is carried out in the following manner: Feeding section: 168~178℃; Plasticizing section: 185~195℃; Homogenizing section: 195~205℃; Die head section: 200~210℃.

[0020] By adopting the above technical solutions, the lower temperature of the feeding section prevents premature resin melting and screw slippage; the gradual heating of the plasticizing and homogenizing sections allows the resin to melt fully while providing a suitable melting and dispersion temperature for erucamide, ensuring its uniform distribution in the melt without thermal degradation; the die section ensures the fluidity of the melt for smooth extrusion while avoiding excessive temperature that could cause the slip agent to volatilize and fail.

[0021] Optionally, in the melting and filtering steps, during the heating process, the screw speeds corresponding to the feeding section, plasticizing section, homogenizing section, and die section are 45-55 r / min, 60-70 r / min, 85-95 r / min, and 80-90 r / min, respectively.

[0022] By adopting the above technical solution, a low screw speed is used in the feeding section, and a low temperature is used to prevent premature plasticization of the resin and frictional heat generation. As the material advances to the homogenization section and the die section, the screw speed is gradually increased to provide shear force to break up the unmelted crystal zone of the resin. At the same time, shear heat is generated to assist melting, and it also provides impetus for the micro-dispersion of erucamide in the melt, preventing the slip agent from agglomerating due to insufficient shear or decomposing due to excessive shear heat. Uniform dispersion and stable melt pressure ensure that the film thickness is uniform and the surface is smooth and delicate during blown film production.

[0023] Optionally, in the initial mixing step and in the melting and filtering step, the crosslinking agent is added to the end of the plasticizing section according to the mass fraction of the crosslinking agent; the end of the plasticizing section is an axial section of 65-70% of the total length.

[0024] By adopting the above technical solution, the end of the plasticizing section is the area where the resin has just melted, the melt temperature is relatively uniform, and the shear force is strong. Adding a crosslinking agent at this point allows the crosslinking agent to be quickly dispersed by utilizing the shear force of the melt. At the same time, the temperature at this location is within the window period for crosslinking initiated by the decomposition of dicumyl peroxide, which more effectively achieves the effect of in-situ crosslinking. This avoids the crosslinking agent from decomposing and becoming ineffective too early in the feeding section, or from becoming over-crosslinked due to excessive residence time in the homogenizing section.

[0025] Furthermore, the cross-linking reaction occurs after the addition of slip agents and antistatic agents, which increases the intermolecular forces in the amorphous regions, forming a three-dimensional network. This limits the excessive migration of the slip agent in the high-temperature homogenization and die-cutting sections, allowing it to be more controllably delayed until the blown film cooling stage before precipitation on the surface. Therefore, this cross-linking method gives the packaging bag high toughness while avoiding film hardening, brittleness, and interlayer binding caused by excessive local cross-linking density. It achieves strength while maintaining good flexibility and easy opening properties.

[0026] Optionally, in the melting and filtering step, the filtering method is as follows: 80-mesh filter, 120-mesh filter, and 80-mesh filter are sequentially arranged along the direction of melt flow.

[0027] By adopting the above technical solution, if the melt contains unmelted resin crystals, carbides, or agglomerated slip particles during the blown film process, these impurities will form surface protrusions or micro-defects after extrusion and film formation, increasing the mechanical interlocking force between film layers. The pre-filter of 80 mesh traps large particles of impurities, playing a preliminary role in equalizing pressure; the middle filter of 120 mesh traps tiny unmelted crystals and agglomerated erucamide particles; the post-filter of 80 mesh not only prevents the 120 mesh filter from breaking and leaking material, but also further stabilizes the melt pressure.

[0028] In summary, the present invention has at least one of the following beneficial technical effects: 1. By employing high-density polyethylene, metallocene polyethylene, and low-density polyethylene to form the resin structure of the high-toughness packaging bag, and adding erucamide, the dynamic and static coefficients of friction on the film surface are reduced, making it easier for the film layers to slide relative to each other. Simultaneously, the use of metallocene polyethylene enhances the film's puncture resistance and toughness. Overall, this results in a packaging bag that maintains high toughness while also possessing good opening performance, meeting the needs of automated packaging.

[0029] 2. By using a mixture of glyceryl stearate and erucamide, the formation of excessively large crystals of erucamide on the film surface is inhibited, providing a long-lasting lubricating effect and partially solving the problem of opening failure caused by adhesion of packaging bags during storage, transportation and automatic packaging lines.

[0030] 3. By using a crosslinking agent composed of zinc methacrylate powder and dicumyl peroxide, the film is less prone to plastic deformation and molecular chain entanglement under high temperature or heavy pressure, preventing excessive adhesion caused by film deformation under pressure; when added to the end of the plasticizing section, it plays a role in in-situ crosslinking, avoiding premature decomposition and failure of the crosslinking agent in the feeding section, or excessive crosslinking due to excessive residence time in the homogenizing section. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the embodiments.

[0032] Unless otherwise specified, the experimental methods used in the embodiments of this application are conventional methods, and the materials used are commercially available unless otherwise specified.

[0033] Example 1: This example discloses a high-toughness packaging bag and its preparation method.

[0034] 1. A high-toughness packaging bag, comprising the following components in parts by weight: 10 parts high-density polyethylene, 3.5 parts metallocene polyethylene, 1.2 parts low-density polyethylene, 0.25 parts slip agent, and 0.25 parts antistatic agent; wherein the slip agent is erucamide.

[0035] 2. Preparation method of high-toughness packaging bags The preparation method of high-toughness packaging bags includes the following steps: (1) Raw material pretreatment and mixing: Raw material pretreatment: High-density polyethylene, metallocene polyethylene and low-density polyethylene are dried at 60℃ for 2.5h, and then transferred to 20~25℃ (room temperature) and allowed to stand and cool for 45min; 0.8 parts are taken from 1.2 parts of the dried and cooled low-density polyethylene, and stirred together with slip agent and antistatic agent at 250r / min for 4min to prepare a premix. Mixing: After drying and cooling, 0.4 parts of high-density polyethylene, metallocene polyethylene and low-density polyethylene are premixed at 350 r / min for 1.0 min; then the premix prepared above is added and stirred at 900 r / min for 5 min to obtain the mixture. (2) Melting and filtration: The mixture is heated and melted and plasticized, and the melted and plasticized material is then filtered; During the heating process, the temperatures and screw speeds are as follows: feeding section: 173℃, plasticizing section: 190℃, homogenizing section: 200℃, and die head section: 205℃; the corresponding screw speeds for the feeding section, plasticizing section, homogenizing section, and die head section are 50r / min, 65r / min, 90r / min, and 85r / min, respectively; the lengths of the four sections are industry-standard lengths. In this embodiment, the feeding section accounts for 32% of the length, the plasticizing section accounts for 38% of the length, the homogenizing section accounts for 20% of the length, and the die head connecting section accounts for 10% of the length.

[0036] The filtration method is as follows: 80-mesh filter, 120-mesh filter, and 80-mesh filter are sequentially arranged along the direction of melt flow; (3) Film blowing: The filtered melt is extruded through an annular die with a blow-up ratio of 2.3, a single-sided die gap of 2.2 mm, and an external negative pressure air ring with a cooling air volume of 2200 m³ / h. 3 / h, traction line speed 28m / min, uniform air cooling and shaping through air ring, conventional traction and winding to obtain film semi-finished product; (4) Curing: Place the semi-finished film at 25°C and 50% relative humidity for 14 hours, then raise the temperature to 32°C and 35% relative humidity for 6 hours, cut and make bags to obtain high-toughness packaging bags.

[0037] Among them, high-density polyethylene (HDPE): In this embodiment, HDPE is a mixture of 7050 and 5000S, wherein the mass ratio of 7050 to 5000S is 4:7; Low-density polyethylene (LDPE): In this example, the LDPE is 2426H (for blown film). Metallocene polyethylene (mPE): In this embodiment, the mPE is Exxon blown film grade; Antistatic agent: In this embodiment, the antistatic agent is antistatic masterbatch (PE specific).

[0038] 3. Detection indicators The longitudinal tensile strength (MPa), transverse tensile strength (MPa), longitudinal nominal strain at break (%), transverse nominal strain at break (%), and dart impact test shall be performed; the test shall be conducted in accordance with GB / T 4456-2008 and GB 4806.7-2023.

[0039] Example 2: This example discloses a high-toughness packaging bag and its preparation method.

[0040] 1. A high-toughness packaging bag, comprising the following components in parts by weight: 12 parts high-density polyethylene, 2.5 parts metallocene polyethylene, 0.8 parts low-density polyethylene, 0.35 parts slip agent, and 0.15 parts antistatic agent; wherein the slip agent is erucamide.

[0041] 2. Preparation method of high-toughness packaging bags The difference from Example 1 is as follows: (1) Raw material pretreatment and mixing: Raw material pretreatment: High-density polyethylene, metallocene polyethylene and low-density polyethylene are dried at 60℃ for 2.5h, and then transferred to 20~25℃ (room temperature) and allowed to stand and cool for 45min; 0.5 parts are taken from 0.8 parts of the dried and cooled low-density polyethylene, and stirred together with slip agent and antistatic agent at 250r / min for 4min to prepare a premix. Mixing: After drying and cooling, 0.3 parts of high-density polyethylene, metallocene polyethylene and low-density polyethylene are premixed at 350 r / min for 1.0 min; then the premix prepared above is added and stirred at 900 r / min for 5 min to obtain the mixture. Everything else is the same as in Example 1.

[0042] Example 3: This example discloses a high-toughness packaging bag and its preparation method.

[0043] 1. A high-toughness packaging bag, comprising the following components by weight: 11 parts high-density polyethylene, 3.0 parts metallocene polyethylene, 1.0 part low-density polyethylene, 0.30 parts slip agent, and 0.10 parts antistatic agent; wherein the slip agent is erucamide; and the other components are the same as in Example 1.

[0044] 2. Preparation method of high-toughness packaging bags The difference from Example 1 is as follows: (1) Raw material pretreatment and mixing: Raw material pretreatment: High-density polyethylene, metallocene polyethylene and low-density polyethylene are dried at 60℃ for 2.5h, and then transferred to 20~25℃ (room temperature) and allowed to stand and cool for 45min; 0.6 parts are taken from 1.0 part of the dried and cooled low-density polyethylene, and stirred together with slip agent and antistatic agent at 250r / min for 4min to prepare premix. Mixing: After drying and cooling, 0.4 parts of high-density polyethylene, metallocene polyethylene and low-density polyethylene are premixed at 350 r / min for 1.0 min; then the premix prepared above is added and stirred at 900 r / min for 5 min to obtain the mixture. Everything else is the same as in Example 1.

[0045] The packaging bags prepared in Examples 1-3 were tested, and the results are shown in Table 1: Table 1. Test results of Examples 1-3 Longitudinal tensile strength (MPa) ≥11 20 19 20 Transverse tensile strength (MPa) ≥11 19 20 20 Longitudinal fracture nominal strain (%) ≥100 847 823 836 Nominal strain at transverse fracture (%) ≥100 672 658 665 Dart impact (number of samples that do not break) ≥8 9 10 10 Based on the test data from Examples 1-3, it can be seen that Example 1 used a higher amount of metallocene polyethylene and low-density polyethylene, and the nominal strain at longitudinal and transverse fractures was the highest among the three examples; Example 2 used high-density polyethylene and slip agent, and the increase in slip agent improved the melt processing fluidity, reduced internal defects in the film forming process, and improved the dart impact performance, achieving 10 times without breaking; Example 3 showed balanced and stable performance in all aspects. Overall, the mechanical properties of the prepared packaging bag were significantly higher than the test standard requirements.

[0046] Example 4: This example discloses a high-toughness packaging bag and its preparation method.

[0047] In this embodiment, the slip agent is a mixture of erucamide and glyceryl monostearate, wherein the mass ratio of glyceryl monostearate to erucamide is 3:7; Everything else is the same as in Example 3.

[0048] Example 5: This example discloses a high-toughness packaging bag and its preparation method.

[0049] In this embodiment, the high-toughness packaging bag further includes 1.5 parts of a crosslinking agent; the crosslinking agent is zinc methacrylate and dicumyl peroxide, wherein the mass ratio of zinc methacrylate to dicumyl peroxide is 94:6; 1. A high-toughness packaging bag, comprising the following components by weight: 11 parts high-density polyethylene, 3.0 parts metallocene polyethylene, 1.0 part low-density polyethylene, 0.30 parts slip agent, and 0.10 parts antistatic agent; wherein the slip agent is a mixture of erucamide and glyceryl stearate, wherein the mass ratio of glyceryl stearate to erucamide is 3:7.

[0050] 2. Preparation method of high-toughness packaging bags The difference from Example 3 is that in the melting and filtering steps, the crosslinking agent is added to the end of the plasticizing section according to the mass fraction; based on the total length of the barrel, the start and end areas of the plasticizing section are 32-70% of the barrel length, and the end of the plasticizing section is the axial section of 65-70% of the total length, which is the boundary area between the plasticizing section and the homogenization section. The crosslinking agent is added in this section. Everything else is the same as in Example 4.

[0051] The packaging bags prepared in Examples 4 and 5 were tested, and the results are shown in Table 2. Table 2 Detection results of Examples 4-5 Longitudinal tensile strength (MPa) ≥11 21 22 Transverse tensile strength (MPa) ≥11 21 22 Longitudinal fracture nominal strain (%) ≥100 914 986 Nominal strain at transverse fracture (%) ≥100 683 702 Dart impact (number of samples that do not break) ≥8 10 10 By comparing Example 4 with Example 3, it can be seen that the slip agent in Example 4 is a compound mixture of erucamide and glyceryl monostearate, which improves the biaxial tensile strength and biaxial nominal strain at break. The addition of glyceryl monostearate improves the dispersibility of the slip agent, reduces film surface defects caused by the easy migration and precipitation of erucamide alone, and the compound mixture can be used to control the resin crystallization rate, refine the grain size, and make the intermolecular forces more uniform. Therefore, the longitudinal / transverse tensile strength is increased to 21 MPa, the longitudinal nominal strain at break is increased to 914%, and the transverse nominal strain at break is increased to 683%.

[0052] Comparing Example 5 with Example 4, it can be seen that Example 5, which incorporates a crosslinking agent composed of zinc methacrylate and dicumyl peroxide, and adds this crosslinking agent at the end of the plasticizing stage, achieves the highest performance values ​​in all aspects. The reason for this is that the crosslinking agent reacts efficiently during the melt homogenization stage, forming a uniform three-dimensional crosslinking network, which enhances the interaction forces between molecular chains, thereby delaying macroscopic fracture and increasing the longitudinal / transverse tensile strength to 22 MPa. Simultaneously, the crosslinking network restricts molecular chain slippage, avoiding stress concentration during the tensile process, increasing the nominal longitudinal fracture strain to 986% and the nominal transverse fracture strain to 702%, while maintaining a dart impact resistance of 10 times without fracture, achieving a comprehensive improvement in mechanical properties.

[0053] Comparative Example 1: This comparative example discloses a high-toughness packaging bag and its preparation method.

[0054] No slip agent, erucamide, was added in this comparative example; A high-toughness packaging bag comprises the following components by weight: 11 parts high-density polyethylene, 3.0 parts metallocene polyethylene, 1.0 part low-density polyethylene, and 0.10 parts antistatic agent; all other components are the same as in Example 3.

[0055] Comparative Example 2: This comparative example discloses a high-toughness packaging bag and its preparation method.

[0056] In this comparative example, no low-density polyethylene was added; 1. A high-toughness packaging bag, comprising the following components by weight: 11 parts high-density polyethylene, 3.0 parts metallocene polyethylene, 0.30 parts slip agent, and 0.10 parts antistatic agent; wherein the slip agent is erucamide; and the other components are the same as in Example 1.

[0057] 2. Preparation method of high-toughness packaging bags The difference from Example 1 is as follows: (1) Raw material pretreatment and mixing: Raw material pretreatment: High-density polyethylene and metallocene polyethylene are dried at 60℃ for 2.5h, and then transferred to 20~25℃ (room temperature) and allowed to stand and cool for 45min; the slip agent and antistatic agent are stirred together at 250r / min for 4min to prepare a premix. Mixing: After drying and cooling, high-density polyethylene and metallocene polyethylene are premixed at 350 r / min for 1.0 min; then the premix prepared above is added and stirred at 900 r / min for 5 min to obtain a mixture; Everything else is the same as in Example 3.

[0058] The packaging bags prepared using Comparative Examples 1-2 were tested, and the results are shown in Table 3. Table 3. Results of indicator testing for comparative examples 1-2 Longitudinal tensile strength (MPa) ≥11 10 13 Transverse tensile strength (MPa) ≥11 10 12 Longitudinal fracture nominal strain (%) ≥100 224 357 Nominal strain at transverse fracture (%) ≥100 216 319 Dart impact (number of samples that do not break) ≥8 6 7 Comparing Comparative Example 1 and Example 3, it can be seen that Comparative Example 1, which did not contain the slip agent erucamide, had inferior performance in all aspects compared to Example 3, and some indicators did not meet the testing standards. Analysis suggests that the lack of slip agent leads to poor melt flowability, making the film prone to uneven orientation, surface defects, and internal microcracks during film forming. During stretching, stress concentration is significant, and the molecular chains cannot uniformly transmit stress. Therefore, the longitudinal / transverse tensile strength is only 10 MPa, the nominal strain at break is only 224% and 216%, respectively, and the number of samples that did not break after dart impact was only 6, failing to meet the requirements for high-toughness packaging bags.

[0059] By comparing Comparative Example 2 and Example 3, it can be seen that Comparative Example 2, which did not add low-density polyethylene, had significantly lower performance than Example 3. Analysis suggests that the lack of low-density polyethylene altered the melt rheological properties, affecting the orientation and crystallization behavior of mPE during the blown film process, thus leading to a decrease in mechanical properties. Consequently, the longitudinal / transverse tensile strengths were only 13 MPa and 12 MPa, the nominal strain at break was only 357% and 319%, and the number of samples that did not break after dart impact was only 7, failing to achieve the high toughness level of Example 3 of this invention.

[0060] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high tenacity packaging bag characterized by, The composition comprises, by weight, 10-12 parts of high-density polyethylene, 2.5-3.5 parts of metallocene polyethylene, 0.8-1.2 parts of low-density polyethylene, 0.25-0.35 parts of slip agent, and 0.15-0.25 parts of antistatic agent; wherein the slip agent includes erucamide.

2. The high tenacity bag of claim 1, wherein, The slip agent also includes glyceryl monostearate, wherein the mass ratio of glyceryl monostearate to erucamide is 3:6-8.

3. The high tenacity bag of claim 1, wherein, It also includes 1.0 to 2.0 parts of a crosslinking agent; the crosslinking agent includes zinc methacrylate and dicumyl peroxide, wherein the mass ratio of zinc methacrylate to dicumyl peroxide is 92 to 96: 4 to 8.

4. A method of producing the high tenacity packaging bag according to any one of claims 1 to 3, characterized in that, Includes the following steps: Raw material pretreatment and mixing: After drying and cooling, high-density polyethylene, metallocene polyethylene and low-density polyethylene are premixed at 300-400 r / min for 0.8-1.2 min; then slip agent and antistatic agent are added and stirred at 800-1000 r / min for 4-6 min to obtain the mixture; Melting and Filtration: The mixture is heated and melted and plasticized, and the melted and plasticized material is then filtered. Film blowing: The filtered melt is extruded through an annular die with a blow-up ratio of 2.0 to 2.

5. It is then cooled and shaped by an air ring, pulled and wound up to obtain a semi-finished film. Curing: Place the semi-finished film at 20-30℃ and 40-60% relative humidity for 12-16 hours, then raise the temperature to 30-34℃ and 30-40% relative humidity and let it stand for 5-7 hours. Cut and bag it to obtain a high-toughness packaging bag.

5. The method for preparing the high-toughness packaging bag according to claim 4, characterized in that, In the raw material pretreatment and mixing steps, the drying and cooling method is as follows: high-density polyethylene, metallocene polyethylene, and low-density polyethylene are dried at 55-65°C for 2-3 hours, and then transferred to 20-25°C for static cooling for 30-60 minutes for later use.

6. The method for preparing the high-toughness packaging bag according to claim 5, characterized in that, In the raw material pretreatment and mixing steps, the slip agent and antistatic agent are pretreated before being added to the material. The pretreatment method is as follows: take 0.5 to 1 part from 0.8 to 1.2 parts of the low-density polyethylene, and stir it together with the slip agent and antistatic agent at 200 to 300 r / min for 3 to 5 min to prepare a premix.

7. The method for preparing the high-toughness packaging bag according to claim 4, characterized in that, In the melting and filtering steps, the heating methods are as follows: Feeding section: 168~178℃; Plasticizing section: 185~195℃; Homogenizing section: 195~205℃; Die head section: 200~210℃.

8. The method for preparing the high-toughness packaging bag according to claim 7, characterized in that, During the melting and filtration steps, the screw speeds for the feeding section, plasticizing section, homogenizing section, and die section during the heating process are 45-55 r / min, 60-70 r / min, 85-95 r / min, and 80-90 r / min, respectively.

9. The method for preparing the high-toughness packaging bag according to any one of claims 8, characterized in that, In the melting and filtration steps, the crosslinking agent is added to the end of the plasticizing section according to the mass fraction; the end of the plasticizing section is an axial section of 65-70% of the total length.

10. The method for preparing the high-toughness packaging bag according to any one of claims 4-9, characterized in that, In the melting and filtration steps, the filtration method is as follows: 80-mesh filter, 120-mesh filter, and 80-mesh filter are sequentially set along the direction of melt flow.