EVA breathable back plate of a backpack

Abstract

This invention relates to the field of backpack technology with EVA breathable back panel, specifically to an EVA breathable back panel for a backpack, comprising an EVA back panel installed on the back of the backpack. One side of the EVA back panel has a first protrusion, a second protrusion, a third protrusion, and a fourth protrusion protruding sequentially from top to bottom. First ventilation channels are provided between the first and second protrusions, between the second and third protrusions, and between the third and fourth protrusions. Based on the EVA back panel, it is lightweight, has good elasticity and support, and possesses a certain degree of rigidity and shape stability. Through elastic deformation, it evenly distributes weight, thus evenly distributing pressure on the shoulders and back, improving comfort during long-term carrying, and providing good heat dissipation, facilitating rapid heat transfer to the heat dissipation area at the edge of the back panel. Furthermore, the first ventilation channels enhance the ventilation and breathability of the EVA back panel, mitigating the stuffiness and dampness caused by heat and moisture accumulation on the back.

Description

Technical Field

[0001] This invention relates to the field of backpack technology with EVA breathable back panel, and more specifically to an EVA breathable back panel for a backpack. Background Technology

[0002] A backpack is a general term for a bag that is worn on both shoulders. A backpack mainly consists of a storage pocket, a handle attached to the top of the storage pocket, shoulder straps attached to the back of the storage pocket, and a back panel attached to the back of the storage pocket.

[0003] Traditional backpack back panels use ordinary mesh or foam padding. Although the structure is simple, they have poor breathability and heat dissipation, are prone to aging and deformation, and when carried for a long time, heat and moisture can easily accumulate on the back, leading to stuffiness, dampness, and even skin discomfort. In addition, they lack sufficient cushioning and support structure, and the pressure is concentrated when carrying heavy objects, which can easily lead to back fatigue and shoulder pain. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide an EVA breathable back panel for a backpack.

[0005] The objective of this invention is achieved through the following technical solution: an EVA breathable back panel for a backpack, comprising an EVA back panel installed on the back of the backpack, wherein one side of the EVA back panel has a first protrusion, a second protrusion, a third protrusion and a fourth protrusion protruding sequentially from top to bottom, and a first breathable channel is provided between the first protrusion and the second protrusion, between the second protrusion and the third protrusion, and between the third protrusion and the fourth protrusion.

[0006] This breathable EVA back panel, based on EVA, is lightweight, possesses excellent elasticity and support, and conforms well to the curvature of the spine. It also exhibits a degree of rigidity and shape stability, evenly distributing weight through elastic deformation to distribute pressure evenly across the shoulders and back, improving comfort during extended wear. Furthermore, it offers excellent heat dissipation, facilitating rapid heat transfer to the edge cooling zones. Utilizing ventilation channels between the first and second protrusions, between the second and third protrusions, and between the third and fourth protrusions, the ventilation and breathability of the EVA back panel are enhanced, mitigating the stuffiness and dampness caused by heat and moisture buildup on the back.

[0007] Preferably, the middle portions of the first protrusion, the middle portions of the second protrusion, and the middle portions of the third protrusion are all provided with sequentially connected second ventilation channels, further improving the ventilation and breathability of the EVA back panel and alleviating the stuffiness and dampness caused by the accumulation of heat and moisture on the back. Furthermore, the connection between the first and second ventilation channels further facilitates ventilation and breathability of the EVA back panel, aiding in heat dissipation and perspiration wicking.

[0008] Preferably, the fourth protrusion has a V-shaped hollow groove on the side near the third protrusion. The fourth protrusion fits snugly against the lower back, reducing the pressure of the backpack on the shoulders and back. The V-shaped hollow groove also helps to increase breathability and reduce weight.

[0009] Preferably, the EVA backsheet is integrally cold-pressed in a mold after EVA sheet is heated to soften. The cold-pressing temperature is 15-20℃ and the cold-pressing time is 30-45s. The integrally cold-pressed EVA backsheet avoids the damage to material properties caused by high temperature and retains the excellent properties of EVA such as elasticity, comfort, breathability and heat dissipation, lightweight, and shape stability.

[0010] Preferably, the EVA sheet comprises the following raw materials in parts by weight:

[0011]

[0012] The aforementioned EVA sheet is based on EVA resin and has a high VA content, which helps ensure the elasticity and low-temperature toughness of the EVA sheet. The added modified AC foaming agent, foaming aid, and crosslinking agent work synergistically. The modified AC foaming agent can lower its own decomposition temperature and matches the low-temperature crosslinking characteristics of the crosslinking agent, reducing thermal degradation. The synergistic foaming aid helps reduce ammonia residue, improves cell uniformity and foaming efficiency, and achieves a cell density of 1.2 × 10⁻⁶. 6 pcs / cm 3 The dense pores effectively block stress transmission paths, promoting the improvement of compressive strength. The added lubricant has excellent high-temperature lubricity, reduces mold fouling, and extends mold life. The added filler has lightweight and high-strength filling characteristics, high compressive strength, and excellent weather resistance. Compared with traditional calcium carbonate, it is lighter in weight while effectively improving compressive strength. The added functional additives disperse in the EVA matrix to construct a three-dimensional thermally conductive network, improving the overall thermal conductivity and heat dissipation efficiency of the EVA sheet. After the EVA sheet is made into an EVA backplate, it is beneficial to quickly conduct heat to the heat dissipation area at the edge of the backplate and the heat dissipation on the back of the backplate.

[0013] Preferably, the VA content of the EVA resin is 28wt%-30wt%, which ensures that the EVA sheet has a certain degree of hardness while obtaining higher resilience and impact resistance. More preferably, the EVA resin is selected from DuPont 250 or Mitsui EV 250.

[0014] Preferably, the modified AC foaming agent is obtained by mixing azodicarbonamide and nanoparticles at a ratio of 5-10:1 and then ball milling them at 300-500 rpm for 2-3 hours using a high-energy ball mill. The nanoparticles are obtained by soaking nano zinc oxide powder in silane coupling agent KH-560 for 15-30 minutes and then drying it. The foaming aid is triethyl citrate.

[0015] Using the above technical solution, the modified AC foaming agent uses nano-zinc oxide as a catalyst, which can accelerate the decomposition reaction of the AC foaming agent, reducing the decomposition temperature from 180-200℃ to 160-170℃, shortening the foaming time, reducing thermal damage to the EVA matrix, and forming heterogeneous nucleation sites in the EVA melt, promoting the uniform distribution of bubble nuclei and resulting in higher cell density after EVA sheet foaming. The nano-zinc oxide powder is surface-treated by soaking in silane coupling agent KH-560 to prevent agglomeration and promote dispersion and bonding of nano-zinc oxide with the modified AC foaming agent. The foaming aid uses triethyl citrate to activate the AC foaming agent, accelerating AC decomposition, lowering the decomposition temperature of the AC foaming agent, increasing the amount of gas generated by the AC, and synergistically improving cell uniformity.

[0016] Preferably, the crosslinking agent is bis-tert-butylperoxyisopropylbenzene; and the lubricant is pentaerythritol stearate.

[0017] Using the above technical solution, the crosslinking agent is bis-tert-butylperoxyisopropylbenzene. Its dual active groups are beneficial to improving the crosslinking efficiency by about 30% and reducing the crosslinking temperature by 5-8℃. Its low-temperature crosslinking characteristics match the reduction of AC decomposition temperature of the modified AC foaming agent, which is beneficial to improving foaming efficiency and increasing cell density. Dense cells can effectively block stress transmission paths and promote the improvement of compressive strength.

[0018] Preferably, the filler is obtained by soaking hollow glass microspheres and titanium dioxide in silane coupling agent KH-560 for 15-30 minutes and then drying; the functional additive is obtained by soaking graphene nanosheets in silane coupling agent KH-560 for 15-30 minutes and then drying.

[0019] Using the above technical solution, the filler consists of hollow glass microspheres and titanium dioxide that have undergone surface treatment with silane coupling agent KH-560. The hollow glass microspheres have high compressive strength and low density, forming a three-dimensional network structure in the EVA matrix. This structure acts like a "micro-scaffold," effectively dispersing external pressure, reducing stress concentration, and preventing local deformation. Its hollow structure absorbs some impact energy through micropore deformation, further buffering compressive loads. With the cooperation of modified AC foaming agent and crosslinking agent in terms of foaming efficiency and gas pressure, the hollow glass microspheres are uniformly dispersed, enabling the EVA sheet to achieve high compressive strength while maintaining low density, reducing the amount of EVA resin used and lowering costs. Furthermore, the high filling capacity of titanium dioxide can further optimize the material's bulk density, forming a lightweight and high-strength composite system. The refractive index of titanium dioxide increases the reflectivity of the EVA backsheet to sunlight, reducing light absorption and delaying thermal aging. The functional additives utilize graphene nanosheets surface-treated with the silane coupling agent KH-560. This helps to compensate for the decrease in thermal conductivity caused by the introduction of hollow glass microspheres and the increased porosity during foaming. A three-dimensional thermally conductive network is formed through the graphene nanosheets. In particular, because the expansion direction of the bubble nuclei during the foaming process is perpendicular to the sheet plane, the graphene nanosheets exhibit rapid thermal conductivity in the vertical direction (thickness direction). Furthermore, the weight ratio of hollow glass microspheres to titanium dioxide is 5:3-5.

[0020] Preferably, the method for preparing the EVA sheet includes the following steps:

[0021] (S1) Take EVA resin, modified AC foaming agent, foaming aid, crosslinking agent, filler, lubricant and functional additives by weight, and set aside;

[0022] (S2) Add EVA resin, filler and functional additives to a rotor mixer maintained at 40-50 rpm, premix at 80℃ for 3-6 min, then add modified AC foaming agent and foaming aid, heat to 95℃ and mix for 5-8 min, then add crosslinking agent and lubricant, heat to 105℃ and mix for 8-12 min, and discharge to obtain the mixed EVA mixture;

[0023] (S3) The internally mixed EVA mixture is processed into sheets through a four-roll open mill with the front roll temperature maintained at 70°C and the rear roll temperature at 65°C. The number of thin passes is 6-8, and the sheet thickness is 2.0±0.1mm, thus obtaining open-mixed EVA sheets.

[0024] (S4) The open-milled EVA sheet is placed in the mold of the flat vulcanizing machine for foaming treatment, and then rapidly cooled and shaped in 20℃ cold water for 30s under a pressure of 15MPa to obtain EVA sheet.

[0025] Furthermore, the foaming process includes: preheating the open-milled EVA sheet to 160°C for 2 minutes, and then foaming it at 12 MPa pressure and 170°C for 6 minutes to allow bubble nuclei to form and expand. Preheating activates the modified AC foaming agent and crosslinking agent.

[0026] The beneficial effects of this invention are as follows: The EVA breathable back panel of this invention, based on an EVA back panel, is lightweight, has good elasticity and support, can conform well to the curvature of the spine, has a certain degree of rigidity and shape stability, and can evenly distribute weight through elastic deformation, thus evenly distributing pressure on the shoulders and back, improving comfort during long-term carrying, and has good heat dissipation, which facilitates the rapid conduction of heat to the heat dissipation area at the edge of the back panel. Utilizing the first ventilation channels between the first and second protrusions, the first ventilation channels between the second and third protrusions, and the first ventilation channels between the third and fourth protrusions, the ventilation and breathability of the EVA back panel are improved, alleviating the stuffiness and dampness caused by the accumulation of heat and moisture on the back. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention;

[0028] The attached diagram is labeled as follows: 1. EVA back plate; 2. First boss; 3. Second boss; 4. Third boss; 5. Fourth boss; 6. First ventilation channel; 7. Second ventilation channel; 8. V-shaped perforated groove. Detailed Implementation

[0029] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0030] Example 1

[0031] like Figure 1 As shown, an EVA breathable back panel for a backpack includes an EVA back panel 1 installed on the back of the backpack. One side of the EVA back panel 1 has a first protrusion 2, a second protrusion 3, a third protrusion 4 and a fourth protrusion 5 protruding sequentially from top to bottom. A first ventilation channel 6 is provided between the first protrusion 2 and the second protrusion 3, between the second protrusion 3 and the third protrusion 4, and between the third protrusion 4 and the fourth protrusion 5.

[0032] The middle of the first protrusion 2, the middle of the second protrusion 3, and the middle of the third protrusion 4 are all provided with second ventilation channels 7 that are connected in sequence.

[0033] The fourth protrusion 5 has a V-shaped hollow groove 8 on the side near the third protrusion 4.

[0034] The EVA backplate 1 is integrally cold-pressed in a mold after the EVA sheet is heated to soften, with a cold pressing temperature of 18°C ​​and a cold pressing time of 30 seconds.

[0035] The EVA sheet comprises the following raw materials in parts by weight:

[0036]

[0037] The EVA resin is selected from DuPont 250.

[0038] The modified AC foaming agent is obtained by mixing azodicarbonamide and nanoparticles in a ratio of 8:1 and then ball milling them at 400 rpm for 2.5 h in a high-energy ball mill. The nanoparticles are obtained by soaking nano zinc oxide powder in silane coupling agent KH-560 for 20 min and then drying it. The foaming aid is triethyl citrate.

[0039] The crosslinking agent is bis-tert-butylperoxyisopropylbenzene; the lubricant is pentaerythritol stearate.

[0040] The filler is obtained by soaking hollow glass microspheres and titanium dioxide in silane coupling agent KH-560 for 20 minutes and then drying; the functional additive is obtained by soaking graphene nanosheets in silane coupling agent KH-560 for 20 minutes and then drying. The weight ratio of hollow glass microspheres to titanium dioxide is 5:4.

[0041] The method for preparing the EVA sheet includes the following steps:

[0042] (S1) Take EVA resin, modified AC foaming agent, foaming aid, crosslinking agent, filler, lubricant and functional additives by weight, and set aside;

[0043] (S2) Add EVA resin, filler and functional additives to a rotor mixer maintained at 45 rpm, premix at 80°C for 5 min, then add modified AC foaming agent and foaming aid, heat to 95°C and mix for 6 min, then add crosslinking agent and lubricant, heat to 105°C and mix for 10 min, and discharge to obtain a mixed EVA mixture.

[0044] (S3) The internally mixed EVA mixture is processed into sheets through a four-roll open mill with the front roll temperature maintained at 70°C and the rear roll temperature at 65°C. The number of thin passes is 8, and the sheet thickness is 2.0±0.1mm, thus obtaining open-mixed EVA sheets.

[0045] (S4) Place the open-milled EVA sheet in the mold of the flat vulcanizing machine, heat it to 160℃ for 2 minutes, then foam it at 12MPa pressure and 170℃ for 6 minutes to form bubble nuclei and expand it. Then, under a pressure of 15MPa, it is rapidly cooled and shaped by 20℃ cold water for 30 seconds to obtain EVA sheet.

[0046] Example 2

[0047] The difference between this embodiment and Embodiment 1 is that:

[0048] The EVA sheet comprises the following raw materials in parts by weight:

[0049]

[0050] The EVA resin is selected from DuPont 250.

[0051] The modified AC foaming agent is obtained by mixing azodicarbonamide and nanoparticles in a 5:1 ratio and then ball milling them at 300 rpm for 2 hours using a high-energy ball mill. The nanoparticles are obtained by soaking nano zinc oxide powder in silane coupling agent KH-560 for 20 minutes and then drying it. The foaming aid is triethyl citrate.

[0052] The crosslinking agent is bis-tert-butylperoxyisopropylbenzene; the lubricant is pentaerythritol stearate.

[0053] The filler is obtained by soaking hollow glass microspheres and titanium dioxide in silane coupling agent KH-560 for 20 minutes and then drying; the functional additive is obtained by soaking graphene nanosheets in silane coupling agent KH-560 for 20 minutes and then drying. The weight ratio of hollow glass microspheres to titanium dioxide is 5:3.

[0054] The method for preparing the EVA sheet includes the following steps:

[0055] (S1) Take EVA resin, modified AC foaming agent, foaming aid, crosslinking agent, filler, lubricant and functional additives by weight, and set aside;

[0056] (S2) Add EVA resin, filler and functional additives to a rotor mixer maintained at 40 rpm, premix at 80°C for 5 min, then add modified AC foaming agent and foaming aid, heat to 95°C and mix for 6 min, then add crosslinking agent and lubricant, heat to 105°C and mix for 10 min, and discharge to obtain a mixed EVA mixture.

[0057] (S3) The internally mixed EVA mixture is processed into sheets through a four-roll open mill with the front roll temperature maintained at 70°C and the rear roll temperature at 65°C. The number of thin passes is 8, and the sheet thickness is 2.0±0.1mm, thus obtaining open-mixed EVA sheets.

[0058] (S4) Place the open-milled EVA sheet in the mold of the flat vulcanizing machine, heat it to 160℃ for 2 minutes, then foam it at 12MPa pressure and 170℃ for 6 minutes to form bubble nuclei and expand it. Then, under a pressure of 15MPa, it is rapidly cooled and shaped by 20℃ cold water for 30 seconds to obtain EVA sheet.

[0059] Example 3

[0060] The difference between this embodiment and Embodiment 1 is that:

[0061] The EVA sheet comprises the following raw materials in parts by weight:

[0062]

[0063]

[0064] The EVA resin is selected from DuPont 250.

[0065] The modified AC foaming agent is obtained by mixing azodicarbonamide and nanoparticles at a ratio of 10:1 and then ball milling them at 3500 rpm for 3 hours using a high-energy ball mill. The nanoparticles are obtained by soaking nano zinc oxide powder in silane coupling agent KH-560 for 20 minutes and then drying it. The foaming aid is triethyl citrate.

[0066] The crosslinking agent is bis-tert-butylperoxyisopropylbenzene; the lubricant is pentaerythritol stearate.

[0067] The filler is obtained by soaking hollow glass microspheres and titanium dioxide in silane coupling agent KH-560 for 20 minutes and then drying; the functional additive is obtained by soaking graphene nanosheets in silane coupling agent KH-560 for 20 minutes and then drying. The weight ratio of hollow glass microspheres to titanium dioxide is 5:5.

[0068] The method for preparing the EVA sheet includes the following steps:

[0069] (S1) Take EVA resin, modified AC foaming agent, foaming aid, crosslinking agent, filler, lubricant and functional additives by weight, and set aside;

[0070] (S2) Add EVA resin, filler and functional additives to a rotor mixer maintained at 50 rpm, premix at 80°C for 5 min, then add modified AC foaming agent and foaming aid, heat to 95°C and mix for 6 min, then add crosslinking agent and lubricant, heat to 105°C and mix for 10 min, and discharge to obtain a mixed EVA mixture.

[0071] (S3) The internally mixed EVA mixture is processed into sheets through a four-roll open mill with the front roll temperature maintained at 70°C and the rear roll temperature at 65°C. The number of thin passes is 8, and the sheet thickness is 2.0±0.1mm, thus obtaining open-mixed EVA sheets.

[0072] (S4) Place the open-milled EVA sheet in the mold of the flat vulcanizing machine, heat it to 160℃ for 2 minutes, then foam it at 12MPa pressure and 170℃ for 6 minutes to form bubble nuclei and expand it. Then, under a pressure of 15MPa, it is rapidly cooled and shaped by 20℃ cold water for 30 seconds to obtain EVA sheet.

[0073] Example 4

[0074] The difference between this embodiment and Embodiment 1 is that:

[0075] The EVA sheet comprises the following raw materials in parts by weight:

[0076]

[0077] The EVA resin is selected from DuPont 250.

[0078] The modified AC foaming agent is obtained by mixing azodicarbonamide and nanoparticles in a 6:1 ratio and then ball milling them at 300-500 rpm for 2.5 hours using a high-energy ball mill. The nanoparticles are obtained by soaking nano zinc oxide powder in silane coupling agent KH-560 for 20 minutes and then drying it. The foaming aid is triethyl citrate.

[0079] The crosslinking agent is bis-tert-butylperoxyisopropylbenzene; the lubricant is pentaerythritol stearate.

[0080] The filler is obtained by soaking hollow glass microspheres and titanium dioxide in silane coupling agent KH-560 for 20 minutes and then drying; the functional additive is obtained by soaking graphene nanosheets in silane coupling agent KH-560 for 20 minutes and then drying. The weight ratio of hollow glass microspheres to titanium dioxide is 5:5.

[0081] The method for preparing the EVA sheet includes the following steps:

[0082] (S1) Take EVA resin, modified AC foaming agent, foaming aid, crosslinking agent, filler, lubricant and functional additives by weight, and set aside;

[0083] (S2) Add EVA resin, filler and functional additives to a rotor mixer maintained at 45 rpm, premix at 80°C for 5 min, then add modified AC foaming agent and foaming aid, heat to 95°C and mix for 6 min, then add crosslinking agent and lubricant, heat to 105°C and mix for 10 min, and discharge to obtain a mixed EVA mixture.

[0084] (S3) The internally mixed EVA mixture is processed into sheets through a four-roll open mill with the front roll temperature maintained at 70°C and the rear roll temperature at 65°C. The number of thin passes is 8, and the sheet thickness is 2.0±0.1mm, thus obtaining open-mixed EVA sheets.

[0085] (S4) Place the open-milled EVA sheet in the mold of the flat vulcanizing machine, heat it to 160℃ for 2 minutes, then foam it at 12MPa pressure and 170℃ for 6 minutes to form bubble nuclei and expand it. Then, under a pressure of 15MPa, it is rapidly cooled and shaped by 20℃ cold water for 30 seconds to obtain EVA sheet.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 1 is as follows:

[0088] The filler is obtained by soaking calcium carbonate powder and titanium dioxide in silane coupling agent KH-560 for 20 minutes and then drying. The weight ratio of calcium carbonate powder to titanium dioxide is 5:4.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 1 is as follows:

[0091] The functional additive is obtained by soaking graphite in silane coupling agent KH-560 for 20 minutes and then drying it.

[0092] Comparative Example 3

[0093] The difference between this comparative example and Example 1 is as follows:

[0094] The modified AC foaming agent is replaced with AC foaming agent (azodicarbonamide);

[0095] The method for preparing the EVA sheet includes the following steps:

[0096] (S1) Take EVA resin, AC foaming agent, foaming aid, crosslinking agent, filler, lubricant and functional additives by weight and set aside;

[0097] (S2) Add EVA resin, filler and functional additives to a rotor mixer maintained at 45 rpm, premix at 80°C for 5 min, then add AC foaming agent and foaming aid, heat to 95°C and mix for 6 min, then add crosslinking agent and lubricant, heat to 105°C and mix for 10 min, and discharge to obtain a mixed EVA mixture.

[0098] (S3) The internally mixed EVA mixture is processed into sheets through a four-roll open mill with the front roll temperature maintained at 70°C and the rear roll temperature at 65°C. The number of thin passes is 8, and the sheet thickness is 2.0±0.1mm, thus obtaining open-mixed EVA sheets.

[0099] (S4) Place the open-milled EVA sheet in the mold of the flat vulcanizing machine, heat it to 180°C for 2 minutes, then foam it at 12MPa pressure and 190°C for 6 minutes to form bubble nuclei and expand it. Then, under a pressure of 15MPa, it is rapidly cooled and shaped by 20°C cold water for 30 seconds to obtain EVA sheet.

[0100] Example 5

[0101] EVA sheets from Examples 1-4 and Comparative Examples 1-3 were used to test their density, hardness, resilience, thermal conductivity, and compressive deformation, respectively. The test methods are as follows:

[0102] Density: Measured according to ASTM D792 Test Method for Density and Relative Density of Plastics, unit is g / cm³ 3 .

[0103] Hardness: Shore C hardness was measured according to the standard test method for hardness of ASTM D2240 hardness tester.

[0104] Rebound rate: Measured according to ASTM D2632, "Standard Test Method for Measurement of Rubber Properties - Elasticity", in percentage.

[0105] Thermal conductivity: The thermal conductivity in the vertical direction (Z-axis) and the horizontal direction (XY-axis) was measured using a laser thermal conductivity meter (LFA), and the unit is W / (m·K).

[0106] Compression set: Measured according to Method A of ASTM D395 Rubber Properties - Standard Test Method for Compression Set, under test conditions of 75°C / 22h, in percentage.

[0107] The test results are shown in the table below:

[0108]

[0109]

[0110] As shown in the table above, the EVA sheet of the present invention is lighter, has sufficient hardness, high elasticity and low compression deformation, and has better thermal conductivity and heat dissipation than traditional EVA sheets.

[0111] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. An EVA breathable back panel for a backpack, characterized in that: Includes an EVA back panel installed on the back of a backpack. One side of the EVA back panel has a first protrusion, a second protrusion, a third protrusion and a fourth protrusion protruding from top to bottom. There are first ventilation channels between the first protrusion and the second protrusion, between the second protrusion and the third protrusion, and between the third protrusion and the fourth protrusion. The EVA backplate is integrally cold-pressed in a mold after EVA sheet is heated to soften, with a cold-pressing temperature of 15-20℃ and a cold-pressing time of 30-45s. The EVA sheet comprises the following raw materials in parts by weight: 100 parts of EVA resin 4-8 parts of modified AC foaming agent 1-3 parts of foaming agent Crosslinking agent 0.5-1.5 parts 8-12 parts of filler Lubricant 0.5-1.0 parts Functional additives 1-2 parts; The modified AC foaming agent is obtained by mixing azodicarbonamide and nanoparticles at a ratio of 5-10:1 and then ball milling them at 300-500 rpm for 2-3 hours using a high-energy ball mill. The nanoparticles are obtained by soaking nano zinc oxide powder in silane coupling agent KH-560 for 15-30 minutes and then drying it. The foaming aid is triethyl citrate.

2. The EVA breathable back panel of a backpack according to claim 1, characterized in that: The middle of the first boss, the middle of the second boss, and the middle of the third boss are all provided with second ventilation channels that are connected in sequence.

3. The EVA breathable back panel of a backpack according to claim 1, characterized in that: The fourth boss has a V-shaped hollow groove on the side closest to the third boss.

4. The EVA breathable back panel of a backpack according to claim 1, characterized in that: The VA content of the EVA resin is 28 wt%-30 wt%.

5. The EVA breathable back panel of a backpack according to claim 1, characterized in that: The crosslinking agent is bis-tert-butylperoxyisopropylbenzene; the lubricant is pentaerythritol stearate.

6. The EVA breathable back panel of a backpack according to claim 1, characterized in that: The filler is obtained by soaking hollow glass microspheres and titanium dioxide in silane coupling agent KH-560 for 15-30 minutes and then drying; the functional additive is obtained by soaking graphene nanosheets in silane coupling agent KH-560 for 15-30 minutes and then drying.

7. The EVA breathable back panel of a backpack according to claim 1, characterized in that: The method for preparing the EVA sheet includes the following steps: (S1) Take EVA resin, modified AC foaming agent, foaming aid, crosslinking agent, filler, lubricant and functional additives by weight and set aside; (S2) Add EVA resin, filler and functional additives to a rotor mixer maintained at 40-50 rpm, premix at 80℃ for 3-6 min, then add modified AC foaming agent and foaming aid, heat to 95℃ and mix for 5-8 min, then add crosslinking agent and lubricant, heat to 105℃ and mix for 8-12 min, and discharge to obtain the mixed EVA mixture; (S3) The internally mixed EVA mixture is processed into sheets by a four-roll open mill with the front roll temperature maintained at 70°C and the rear roll temperature at 65°C. The number of thin passes is 6-8, and the sheet thickness is 2.0±0.1mm, thus obtaining open-mixed EVA sheets. (S4) The open-milled EVA sheet is placed in the mold of the flat vulcanizing machine for foaming treatment, and then rapidly cooled and shaped in 20℃ cold water for 30s under a pressure of 15MPa to obtain EVA sheet.

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