Breathable stretch-resistant flat pocket and preparation method thereof

Abstract

The invention relates to the field of plastic products and preparation, and particularly discloses a breathable stretch-resistant flat pocket and a preparation method thereof. The breathable stretch-resistant flat bag comprises a high-density polyethylene-polypropylene composite film, a nanofiber net and linear low-density polyethylene which are sequentially compounded, wherein the nanofiber net is a PET nanofiber net; in addition, the preparation method has the advantages that the tensile property of the pocket is improved, and the air permeability of the pocket is not affected.

Description

Technical Field

[0001] This application relates to the field of plastic products and their preparation, and in particular to a breathable, tensile-resistant flat bag and its preparation method. Background Technology

[0002] In the packaging industry, flat bags are a common packaging material widely used in many sectors, including food, daily necessities, and industrial products. With the improvement of people's living standards and the increasing demands for product packaging quality, flat bags face more challenges and requirements in terms of performance. High-quality flat bags not only protect products from the influence of the external environment but also maintain the integrity and stability of products during transportation and storage, which is of great significance for enhancing the market competitiveness of products.

[0003] In the past, the industry typically used single-material films, such as ordinary polyethylene film and polypropylene film, to manufacture flat bags. These materials possess a certain degree of flexibility and durability, meeting basic packaging requirements. Additionally, some manufacturers employed multi-layer composite films, combining films with different properties to improve the overall performance of the flat bags. However, these conventional manufacturing methods have limitations in terms of breathability and tensile strength.

[0004] Existing flat bag manufacturing materials and methods have significant shortcomings. Flat bags made of ordinary single-material films or multi-layer composite films often fail to simultaneously meet high requirements for breathability and tensile strength. In actual use, poor breathability may lead to problems such as moisture absorption and mold growth of the packaged product, or insufficient tensile strength may cause them to tear easily when subjected to external forces, thus affecting the packaging effect and safety of the product. Summary of the Invention

[0005] In order to improve the tensile strength of the pocket without affecting its breathability, this application provides a breathable tensile flat pocket and a method for preparing it.

[0006] In a first aspect, this application provides a breathable, tensile-resistant flat bag, employing the following technical solution: A breathable, tensile-resistant flat bag comprises a high-density polyethylene-polypropylene composite film, a nanofiber mesh, and linear low-density polyethylene sequentially laminated together, wherein the nanofiber mesh is a PET nanofiber mesh.

[0007] By adopting the above technical solutions, the high-density polyethylene-polypropylene composite film has high strength and rigidity, providing a certain tensile strength for the flat bag. Polypropylene can improve the toughness and processing performance of high-density polyethylene. The combination of the two makes the composite film more stable and durable. The PET nanofiber mesh has a rich porous structure, which allows air to circulate inside and outside the flat bag, thus achieving breathability. At the same time, the structure of the nanofiber gives it high strength, further enhancing the tensile strength of the flat bag. Linear low-density polyethylene has good flexibility and impact resistance, and can be tightly combined with the composite film and nanofiber mesh. When subjected to external tensile force, it can disperse stress and avoid excessive local stress and breakage, thereby improving the overall tensile strength of the flat bag. After the three are combined, their respective advantages are integrated, giving the flat bag good breathability and tensile strength.

[0008] Preferably, the mass ratio of high-density polyethylene to polypropylene in the high-density polyethylene-polypropylene composite film is (70-80):(20-30).

[0009] By adopting the above technical solution, high-density polyethylene has high crystallinity and rigidity, while polypropylene has good toughness and processing performance. When the two are compounded in a specific mass ratio, their toughness and tensile strength can be improved while maintaining a certain rigidity of the flat bag. At the same time, this compounding method can also improve the air permeability of the film, because different mass ratios will affect the arrangement and gaps between molecules, thus making the flat bag more breathable and meeting the usage requirements.

[0010] Preferably, the method for preparing the PET nanofiber mesh includes the following steps: dissolving polyester and polyvinyl alcohol in hexafluoroisopropanol solvent, stirring and letting stand, preparing a 10% transparent and uniform electrospinning solution, obtaining a wet mesh by electrospinning, placing the wet mesh above 20 mL of glutaraldehyde solution, steam crosslinking at room temperature for 10 h, and then drying to obtain the PET nanofiber mesh.

[0011] By employing the above technical solution, polyester and polyvinyl alcohol are dissolved in hexafluoroisopropanol solvent, and a transparent and uniform electrospinning solution is prepared by stirring and allowing it to stand. This ensures that the polyester and polyvinyl alcohol are fully dissolved and uniformly dispersed in the solvent, providing a stable solution system for subsequent spinning. A wet web is then produced by electrospinning. Electrospinning uses an electric field to stretch the solution into fibers, forming a fiber network with specific structure and properties. The wet web is then placed above a glutaraldehyde solution for vapor crosslinking at room temperature. Glutaraldehyde induces a crosslinking reaction between the fibers, enhancing the stability and strength of the fiber network and improving the tensile strength of the PET nanofiber web. Finally, the web is dried to remove moisture, resulting in a stable PET nanofiber web. This PET nanofiber web is used in breathable, tensile-resistant flat bags, improving both the breathability and tensile strength of the bags. The unique structure of the nanofiber web allows airflow while also withstanding a certain amount of tensile force without easily breaking.

[0012] Preferably, the mass ratio of the polyester to polyvinyl alcohol is (19.25-20.65):(1.23-1.68).

[0013] By adopting the above technical solution and controlling the mass ratio of polyester and polyvinyl alcohol, the uniform forming of fibers can be ensured during the electrospinning process, resulting in a uniform distribution of wet web fibers. The PET nanofiber web obtained after subsequent steam crosslinking and drying has a more stable and uniform structure. When the stable and uniform PET nanofiber web is composited into a flat bag, it can effectively enhance the air permeability and tensile strength of the flat bag, and improve the overall quality and performance of the flat bag.

[0014] Preferably, the electrospinning voltage is 22-26kV, the receiving distance is 14-16m, and the spinning rate is 0.03-0.05mL / min.

[0015] By adopting the above technical solution, setting the electrospinning voltage to 25kV can provide a suitable electric field force for the spinning process, enabling the solution to form a stable jet under the action of the electric field, ensuring the continuity and uniformity of spinning. Controlling the spinning rate can ensure that the solution is supplied at a suitable speed, matching the electric field force and the flight distance, ensuring that the obtained PET nanofiber web has good fiber morphology and structure, thereby improving the tensile strength and breathability of the breathable tensile flat bag.

[0016] Preferably, the electrospinning solution further includes 2.56-3.15 wt% of a composite reinforcing agent.

[0017] By employing the above technical solution, the nano-silica in the composite reinforcing agent possesses a large specific surface area and high surface activity, enabling it to strongly interact with polyester and polyvinyl alcohol molecules in the spinning solution, filling the gaps between molecular chains and enhancing the bonding force between them. The nano-cellulose whiskers, characterized by a high aspect ratio and high strength, can form an effective reinforcing network structure during the spinning process. The synergistic effect of these two components significantly improves the strength and stability of the resulting PET nanofiber web, thereby enhancing the tensile strength of the breathable, tensile-resistant flat bag.

[0018] Preferably, the composite reinforcing agent comprises nano-silica and nano-cellulose whiskers in a mass ratio of (2.25-2.84):(1.25-1.67).

[0019] By employing the above technical solution, nano-silica, with its large specific surface area and high activity, can form a strong interaction with polymer molecules in the spinning solution, playing a supporting and reinforcing role in the prepared PET nanofiber web. Nano-cellulose whiskers, with their high strength and high modulus, can effectively improve the mechanical properties of the fiber web. The synergistic effect of these two components makes the prepared PET nanofiber web more robust, thereby enhancing the tensile strength of the breathable, tensile-resistant flat bag and improving its ability to withstand external pulling forces without easily breaking during use.

[0020] Secondly, this application provides a method for preparing a breathable, tensile-resistant flat bag, using the following technical solution: A method for preparing a breathable, tensile-resistant flat bag includes the following steps: stacking a high-density polyethylene-polypropylene composite film, a nanofiber mesh, and linear low-density polyethylene in one step, and then hot-pressing the composite to obtain the breathable, tensile-resistant flat bag.

[0021] By employing the above technical solution, high-density polyethylene-polypropylene composite film, nanofiber mesh, and linear low-density polyethylene are laminated and hot-pressed in a single process. The high-density polyethylene-polypropylene composite film itself possesses good strength and stability, providing the flat bag with certain tensile strength. The nanofiber mesh, specifically PET nanofiber mesh, with its unique nanostructure, imparts excellent breathability to the flat bag and also helps improve its overall tensile strength. The linear low-density polyethylene exhibits flexibility and chemical resistance, further enhancing the overall performance of the flat bag. The hot-pressing process tightly bonds these three materials together, forming a unified whole, ensuring synergistic effects between each layer. This process retains the advantages of each material while overcoming the limitations of a single material, thus producing a breathable and tensile-resistant flat bag that meets both breathability and tensile strength requirements.

[0022] In summary, this application has the following beneficial effects: 1. Because the medium- and high-density polyethylene-polypropylene composite film used in this application has high strength and rigidity, it can provide certain tensile strength for the flat bag. Polypropylene can improve the toughness and processing performance of high-density polyethylene. The combination of the two makes the composite film more stable and durable. PET nanofiber mesh has a rich pore structure, which allows air to circulate inside and outside the flat bag, thereby achieving breathability. At the same time, the structure of nanofiber gives it high strength, further enhancing the tensile strength of the flat bag. Linear low-density polyethylene has good flexibility and impact resistance, and can be tightly combined with the composite film and nanofiber mesh. When subjected to external tensile force, it can disperse stress and avoid excessive local stress and breakage, thereby improving the overall tensile strength of the flat bag. After the three are combined, their respective advantages are integrated, giving the flat bag good breathability and tensile strength.

[0023] 2. In this application, high-density polyethylene has high crystallinity and rigidity, and polypropylene has good toughness and processing performance. When the two are compounded in a specific mass ratio, their toughness and tensile strength can be improved while maintaining a certain rigidity of the flat bag. At the same time, this compounding method can also improve the air permeability of the film, because different mass ratios will affect the arrangement and gaps between molecules, thereby making the flat bag more breathable and meeting the usage requirements.

[0024] 3. In this application, polyester and polyvinyl alcohol are dissolved in hexafluoroisopropanol solvent, and a transparent and uniform electrospinning solution is prepared by stirring and allowing it to stand. This ensures that the polyester and polyvinyl alcohol are fully dissolved and uniformly dispersed in the solvent, providing a stable solution system for subsequent spinning. A wet web is obtained through electrospinning. Electrospinning uses an electric field to stretch the solution into fibers, forming a fiber network with specific structure and properties. The wet web is then placed above a glutaraldehyde solution for vapor crosslinking at room temperature. Glutaraldehyde induces a crosslinking reaction between the fibers, enhancing the stability and strength of the fiber network and improving the tensile strength of the PET nanofiber web. Finally, the web is dried to remove moisture, resulting in a stable PET nanofiber web. This PET nanofiber web is used in breathable, tensile-resistant flat bags, improving the bag's breathability while enhancing its tensile strength. The unique structure of the nanofiber web allows air circulation while withstanding a certain amount of tensile force without easily breaking. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments. Preparation Examples of PET Nanofiber Webs 1-10

[0026] Preparation Example 1 The preparation method of PET nanofiber mesh includes the following steps: dissolving polyester and polyvinyl alcohol in hexafluoroisopropanol solvent, with a mass ratio of polyester to polyvinyl alcohol of 19.25:1.23, stirring and letting stand, preparing a 10% transparent and uniform electrospinning solution, obtaining a wet mesh by electrospinning, with an electrospinning voltage of 22kV, a receiving distance of 14m, and a spinning rate of 0.03mL / min, placing the wet mesh above 20mL glutaraldehyde solution, vapor crosslinking at room temperature for 10h, and then drying to obtain PET nanofiber mesh.

[0027] Preparation Example 2 The preparation method of PET nanofiber mesh includes the following steps: dissolving polyester and polyvinyl alcohol in hexafluoroisopropanol solvent, with a mass ratio of polyester to polyvinyl alcohol of 20.65:1.68, stirring and letting stand, preparing a 10% transparent and uniform electrospinning solution, obtaining a wet mesh by electrospinning, with an electrospinning voltage of 26kV, a receiving distance of 16m, and a spinning rate of 0.05mL / min, placing the wet mesh above 20mL glutaraldehyde solution, vapor crosslinking at room temperature for 10h, and then drying to obtain PET nanofiber mesh.

[0028] Preparation Example 3 The difference between Preparation Example 3 and Preparation Example 1 is that in Preparation Example 3, the mass ratio of polyester to polyvinyl alcohol is 19.25:0.55.

[0029] Preparation Example 4 The difference between Preparation Example 4 and Preparation Example 1 is that in Preparation Example 4, the mass ratio of polyester to polyvinyl alcohol is 19.25:1.95.

[0030] Preparation Example 5 The difference between Preparation Example 5 and Preparation Example 1 is that in Preparation Example 5, the electrospinning solution also includes 2.56 wt% of a composite reinforcing agent, which includes nano-silica and nano-cellulose whiskers in a mass ratio of 2.25:1.25.

[0031] Preparation Example 6 The difference between Preparation Example 6 and Preparation Example 1 is that in Preparation Example 6, the electrospinning solution also includes 3.15 wt% of a composite reinforcing agent, which includes nano-silica and nano-cellulose whiskers in a mass ratio of 2.84:1.67.

[0032] Preparation Example 7 The difference between Preparation Example 7 and Preparation Example 5 is that in Preparation Example 7, the amount of composite reinforcing agent added is 1.25 wt%.

[0033] Preparation Example 8 The difference between Preparation Example 8 and Preparation Example 5 is that in Preparation Example 8, the amount of composite reinforcing agent added is 5.12 wt%.

[0034] Preparation Example 9 The difference between Preparation Example 9 and Preparation Example 5 is that in Preparation Example 9, the composite reinforcing agent includes nano-silica and nano-cellulose whiskers in a mass ratio of 2.25:0.55.

[0035] Preparation Example 10 The difference between Preparation Example 10 and Preparation Example 5 is that in Preparation Example 10, the composite reinforcing agent includes nano-silica and nano-cellulose whiskers in a mass ratio of 2.25:2.65. Example

[0036] Example 1 A breathable, tensile-resistant flat bag comprises a high-density polyethylene-polypropylene composite film, a nanofiber mesh, and linear low-density polyethylene sequentially laminated together. The mass ratio of high-density polyethylene to polypropylene in the high-density polyethylene-polypropylene composite film is 70:20. The nanofiber mesh is the PET nanofiber mesh prepared in Preparation Example 1.

[0037] The above-mentioned method for preparing a breathable, tensile-resistant flat bag includes the following steps: a high-density polyethylene-polypropylene composite film, a nanofiber mesh, and linear low-density polyethylene are laminated in one step, and the breathable, tensile-resistant flat bag is obtained by hot-pressing.

[0038] Example 2

[0039] A breathable, tensile-resistant flat bag comprises a high-density polyethylene-polypropylene composite film, a nanofiber mesh, and linear low-density polyethylene sequentially laminated together. The mass ratio of high-density polyethylene to polypropylene in the high-density polyethylene-polypropylene composite film is 80:30. The nanofiber mesh is the PET nanofiber mesh prepared in Preparation Example 2.

[0040] The above-mentioned method for preparing a breathable, tensile-resistant flat bag includes the following steps: a high-density polyethylene-polypropylene composite film, a nanofiber mesh, and linear low-density polyethylene are laminated in one step, and the breathable, tensile-resistant flat bag is obtained by hot-pressing.

[0041] Example 3

[0042] The difference between Example 3 and Example 1 is that in Example 3, the mass ratio of high-density polyethylene to polypropylene in the high-density polyethylene-polypropylene composite film is 70:10.

[0043] Example 4

[0044] The difference between Example 4 and Example 1 is that in Example 4, the mass ratio of high-density polyethylene to polypropylene in the high-density polyethylene-polypropylene composite film is 70:40.

[0045] Example 5

[0046] The difference between Example 5 and Example 1 is that in Example 5, the nanofiber mesh used is the PET nanofiber mesh prepared in Preparation Example 3.

[0047] Example 6

[0048] The difference between Example 6 and Example 1 is that in Example 6, the nanofiber mesh used is the PET nanofiber mesh prepared in Preparation Example 4.

[0049] Example 7

[0050] The difference between Example 7 and Example 1 is that in Example 7, the nanofiber mesh used is the PET nanofiber mesh prepared in Preparation Example 5.

[0051] Example 8

[0052] The difference between Example 8 and Example 1 is that in Example 8, the nanofiber mesh used is the PET nanofiber mesh prepared in Preparation Example 6.

[0053] Example 9

[0054] The difference between Example 9 and Example 1 is that in Example 9, the nanofiber mesh used is the PET nanofiber mesh prepared in Preparation Example 7.

[0055] Example 10

[0056] The difference between Example 10 and Example 1 is that in Example 10, the nanofiber mesh used is the PET nanofiber mesh prepared in Preparation Example 8.

[0057] Example 11

[0058] The difference between Example 11 and Example 1 is that in Example 11, the nanofiber mesh used is the PET nanofiber mesh prepared in Preparation Example 9.

[0059] Example 12

[0060] The difference between Example 12 and Example 1 is that in Example 12, the nanofiber mesh used is the PET nanofiber mesh prepared in Preparation Example 10. Comparative Example

[0061] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no nanofiber mesh was added in Comparative Example 1. Performance testing

[0062] Flat bags were prepared according to Examples 1-12 and Comparative Example 1. The air permeability of the bags was tested according to GB / T 5453-1997 "Textiles - Determination of air permeability of fabrics", the tensile strength of the bags was tested according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", and the elongation at break was tested according to GB / T 1040.3-2006. The results are recorded in Table 1.

[0063] Table 1 Performance test results of flat pockets project Air permeability (mm / s) Tensile strength / MPa Elongation at break / % Example 1 125 48.5 320 Example 2 118 51.2 305 Example 3 132 45.8 335 Example 4 115 47.1 310 Example 5 105 42.3 295 Example 6 122 44.7 325 Example 7 120 53.6 315 Example 8 116 52.8 308 Example 9 128 40.1 340 Example 10 110 41.5 300 Example 11 121 49.8 312 Example 12 119 48.9 318 Comparative Example 1 25 35.2 280 As shown in Table 1, Examples 1-2, and Comparative Example 1, the breathable, tensile-resistant flat bags prepared in Examples 1-2 are significantly superior to those in Comparative Example 1 in terms of both air permeability and tensile strength, while maintaining a high level of elongation at break. Examples 1-2 employed a three-layer structure consisting of a high-density polyethylene-polypropylene composite film, a PET nanofiber mesh, and linear low-density polyethylene, sequentially laminated together. The high-density polyethylene-polypropylene composite film provides good rigidity and strength, providing the basic tensile strength of the bag; the PET nanofiber mesh, with its nanoscale pore structure, achieves excellent air permeability while ensuring mechanical strength; the linear low-density polyethylene layer enhances the overall flexibility and the bonding force of the composite interface. The three layers, through hot-press lamination, form a synergistic effect, effectively dispersing stress when the bag is stretched, thus achieving high air permeability while maintaining high tensile strength and good ductility. In contrast, Comparative Example 1 did not use a nanofiber mesh, relying solely on the polymer film, resulting in a significant decrease in air permeability and lower tensile strength and elongation at break. This demonstrates that the addition of a nanofiber mesh is crucial for simultaneously improving air permeability and tensile strength.

[0064] Compared to Example 1, Examples 3-4 showed fluctuations in air permeability and a slight decrease in tensile strength. Examples 3-4 altered the mass ratio of high-density polyethylene to polypropylene. When the ratio deviates from the preferred range, the microstructure and molecular chain arrangement of the composite film change, affecting the film's mechanical properties and the interfacial bonding strength with the nanofiber network. This results in a slight decrease in overall tensile properties. Simultaneously, changes in the polymer ratio also affect the film's density and microporous structure, thus impacting air permeability. However, thanks to the primary air-permeable function of the nanofiber network, the air permeability remains at a high level.

[0065] Compared with Example 1, the tensile strength of Examples 5-6 decreased. The PET nanofiber mesh used in Examples 5-6 had its mass ratio of polyester to polyvinyl alcohol changed during preparation, which directly affected the uniformity, spinnability, and final fiber morphology and strength of the electrospinning solution. An improper mass ratio of polyester to polyvinyl alcohol may lead to uneven fiber diameter, defects, or an unsatisfactory network structure, thereby reducing the reinforcing effect of the nanofiber mesh itself, resulting in the tensile strength of the composite flat bag failing to reach the optimal level.

[0066] Compared to Example 1, Examples 7-8 show further improvements in tensile strength. The PET nanofiber mesh used in Examples 7-8 incorporates a composite reinforcing agent during preparation. This agent interacts with the polymer molecular chains during electrospinning, with nano-silica filling and reinforcing the interface, and nano-cellulose whiskers forming a micro-reinforcing network, significantly enhancing the mechanical strength and stability of the nanofiber mesh itself. This reinforcing effect is transferred to the final composite pocket, resulting in a significant improvement in its tensile properties.

[0067] Compared with Example 7, the tensile strength of Examples 9-10 decreased. The total amount of composite reinforcing agent added during the preparation of the PET nanofiber mesh used in Examples 9-10 was changed. When the amount added was too low, the reinforcing effect was insufficient; when the amount added was too high, it may lead to abnormal viscosity of the spinning solution, difficulty in fiber forming, or agglomeration of the reinforcing agent, which would destroy the uniformity and continuity of the fiber structure, thereby weakening its reinforcing effect and causing the tensile strength of the final pocket to drop.

[0068] Compared with Example 7, the tensile strength of Examples 11-12 decreased slightly but was still better than the basic example. The PET nanofiber mesh used in Examples 11-12 changed the mass ratio of nano-silica to nano-cellulose whiskers in the composite reinforcing agent during preparation. When there are too few or too many nano-cellulose whiskers, the optimal composite reinforcing network may not be formed, resulting in the reinforcing efficiency of the nanofiber mesh not reaching the peak value, which in turn affects the potential for further improvement of the tensile strength of the flat bag.

[0069] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A breathable, tensile-resistant flat bag, characterized in that: It comprises a high-density polyethylene-polypropylene composite film, a nanofiber mesh, and a linear low-density polyethylene, which are sequentially laminated together, wherein the nanofiber mesh is a PET nanofiber mesh.

2. The breathable, tensile-resistant flat bag according to claim 1, characterized in that: The mass ratio of high-density polyethylene to polypropylene in the high-density polyethylene-polypropylene composite film is (70-80):(20-30).

3. The breathable, tensile-resistant flat bag according to claim 1, characterized in that: The method for preparing the PET nanofiber mesh includes the following steps: dissolving polyester and polyvinyl alcohol in hexafluoroisopropanol solvent, stirring and letting stand, preparing a 10% transparent and uniform electrospinning solution, obtaining a wet mesh by electrospinning, placing the wet mesh above 20 mL of glutaraldehyde solution, steam crosslinking at room temperature for 10 h, and then drying to obtain the PET nanofiber mesh.

4. A breathable, tensile-resistant flat bag according to claim 3, characterized in that: The mass ratio of the polyester to the polyvinyl alcohol is (19.25-20.65):(1.23-1.68).

5. A breathable, tensile-resistant flat bag according to claim 3, characterized in that: The electrospinning voltage is 22-26kV, the receiving distance is 14-16m, and the spinning rate is 0.03-0.05mL / min.

6. A breathable, tensile-resistant flat bag according to claim 3, characterized in that: The electrospinning solution also contains 2.56-3.15 wt% of a composite reinforcing agent.

7. A breathable, tensile-resistant flat bag according to claim 6, characterized in that: The composite reinforcing agent comprises nano-silica and nano-cellulose whiskers in a mass ratio of (2.25-2.84):(1.25-1.67).

8. A method for preparing a breathable, tensile-resistant flat bag according to claims 1-7, characterized in that: The process includes the following steps: a high-density polyethylene-polypropylene composite film, a nanofiber mesh, and linear low-density polyethylene are laminated in one step, and a breathable, tensile-resistant flat bag is obtained by hot-pressing.