Semi-open cell polyolefin resin foam sheet

Abstract

A semi-open cell polyolefin resin foam sheet, characterized in that the 30% compressive stress of the semi-open cell polyolefin resin foam sheet is 1-40 kPa, the average size of through holes in the cell wall of the semi-open cell polyolefin resin foam sheet is 10-1,800 μm, there are 15 / cm2 or less incomplete air cells on the surface of a crust layer of the semi-open cell polyolefin resin foam sheet, the incomplete air cells on the surface of the crust layer each comprise one cell having an open cell structure, and the average size of the cells of the incomplete air cells on the surface of the crust layer is 30-2,000 μm.

Description

A semi-open-cell polyolefin resin foam sheet Technical Field

[0001] The invention belongs to the technical field of foam materials and relates to a semi-open-cell polyolefin resin foam sheet, in particular to a highly soft, waterproof and heat-insulating semi-open-cell polyolefin resin foam sheet. Background Art

[0002] Cross-linked polyolefin resin foam sheets are commonly used as thermal insulation materials, cushioning materials, etc. However, the existing cross-linked polyolefin (especially ethylene) resin foam sheets still have high strength during compression and buffering due to their unique closed-cell structure. In particular, cross-linked polyolefin resin foam sheets are needed for caulking, cushioning, and waterproofing. This closed-cell structure will greatly limit the application of cross-linked polyolefin resin foam sheets. For example, the field of new energy vehicles requires a material with good waterproofness, low cost, and low compression strength for cushioning, caulking to eliminate unevenness caused by thickness tolerance, and heat preservation, and the material is also required to effectively delay the spread of fire when thermal failure occurs. However, the existing technology does not yet have a material that meets such requirements.

[0003] The inventors have discovered that existing cross-linked polyolefin resin foam sheets, due to their foaming mechanism, struggle to create a defined open-cell structure during the foaming process. Simply increasing the foaming ratio or adding a more flexible elastomer can maintain high compressive strength even under high compressive strains. However, creating open cells through puncture or splitting can severely compromise the waterproof properties of the sheet.

[0004] Summary of the Invention

[0005] To achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0006] A battery pack, comprising: a case including a first shell and a second shell, a battery module contained between the first shell and the second shell, and a semi-open-cell polyolefin resin foam sheet contained between the first shell and the battery module;

[0007] The 30% compressive stress of the semi-open-cell polyolefin resin foam sheet is 1 kPa to 40 kPa, the average size of the perforations on the cell walls of the semi-open-cell polyolefin resin foam sheet is 10 μm to 1800 μm, and the surface of the skin layer of the semi-open-cell polyolefin resin foam sheet selectively includes incomplete air cells, and the number of the incomplete air cells is 15 / cm 2 the following.

[0008] The present invention also provides a battery pack, comprising: a case including a first shell and a second shell, a battery module contained between the first shell and the second shell, and a semi-open-cell polyolefin resin foam sheet, wherein the semi-open-cell polyolefin resin foam sheet is provided on a side of the first shell away from the battery module and is adhered to a surface of the first shell;

[0009] The 30% compressive stress of the semi-open-cell polyolefin resin foam sheet is 1 kPa to 40 kPa, the average size of the perforations on the cell walls of the semi-open-cell polyolefin resin foam sheet is 10 μm to 1800 μm, and the surface of the skin layer of the semi-open-cell polyolefin resin foam sheet selectively includes incomplete air cells, and the number of the incomplete air cells is 15 / cm 2 the following.

[0010] The present invention also provides a semi-open-cell polyolefin resin foam sheet, wherein the 30% compressive stress of the semi-open-cell polyolefin resin foam sheet is 1 kPa to 40 kPa, the average size of the perforations on the cell walls of the semi-open-cell polyolefin resin foam sheet is 10 μm to 1800 μm, and the number of incomplete air cells on the surface of the skin layer of the semi-open-cell polyolefin resin foam sheet is 15 / cm 2 the following.

[0011] According to the present invention, the interior and / or surface of the semi-open-cell polyolefin resin foam sheet includes independent airbags and incomplete airbags; in the semi-open-cell polyolefin resin foam sheet, the volume of the incomplete airbags accounts for 10% to 95% of the total airbag volume, that is, the open porosity is 10% to 95%.

[0012] According to the present invention, the incomplete airbag includes one cell with an open-pore structure, and the average size of the cells of the incomplete airbag on the surface of the skin layer is 30 μm to 2000 μm.

[0013] According to the present invention, the hydrophobicity of the semi-open-cell polyolefin resin foam sheet tested according to GB / T 10299 is greater than 95%.

[0014] According to the present invention, the thermal conductivity of the semi-open-cell polyolefin resin foam sheet tested according to GB / T 40872-2021 is 0.03W / (m·K) to 0.05W / (m·K).

[0015] According to the present invention, the tear strength of the semi-open-cell polyolefin resin foam sheet in MD and / or TD direction is 0.4N / mm-2.8N / mm; the tensile strength of the semi-open-cell polyolefin resin foam sheet in MD and / or TD direction is 40kPa-480kPa.

[0016] According to the present invention, the semi-open-cell polyolefin resin foam sheet is obtained by compressing a cross-linked polyolefin resin foam sheet to open the cells; the cross-linking degree of the cross-linked polyolefin resin foam sheet is 20% to 65%.

[0017] According to the present invention, the oxidation induction period (OIT) of the cross-linked polyolefin resin foam sheet tested in an oxygen atmosphere at 190° C. is no more than 40 minutes.

[0018] According to the present invention, the average diameter of the cells of the cross-linked polyolefin resin foam sheet is 40 μm to 2000 μm, and the foaming ratio is 20 to 45 cm 3 / g.

[0019] According to the present invention, the ash content of the cross-linked polyolefin resin foam sheet tested after burning at 650° C. is in the range of 0.5% to 15%.

[0020] According to the present invention, the number of incomplete air cells in the skin layer (also referred to as the skin layer) of the cross-linked polyolefin resin foam sheet is 15 / cm 2 Below, and the average size of the cells of the incomplete air cells is 30 μm to 2000 μm.

[0021] According to the present invention, the cross-linked polyolefin resin foam sheet has a 30% compressive stress of 40 kPa to 180 kPa.

[0022] According to the present invention, the semi-open-cell polyolefin resin foam sheet is further compounded with a support layer.

[0023] The present invention has the following beneficial effects:

[0024] The present invention provides a semi-open-cell polyolefin resin foam sheet for use in battery packs. This foam sheet exhibits ultra-low compressive stress and flexibility, a dense skin layer, and excellent waterproofing. Furthermore, it exhibits excellent thermal insulation and flame retardancy. The foam sheet provided by the present invention can provide cushioning, thermal insulation, waterproofing, and thickness tolerance in a variety of applications.

[0025] Prior art methods for reducing the compressive stress of closed-cell cross-linked polyolefin resin foam sheets include adding thermoplastic elastomers or increasing the expansion ratio. However, these existing methods have limited effectiveness in reducing compressive stress. In prior art, the 30% compressive stress is generally greater than 40 kPa, making it difficult to meet the requirements for use in environments with lower compressive stress requirements.

[0026] The present invention improves the openability of the foam sheet while ensuring the waterproof and heat-insulating properties of the cross-linked polyolefin-based resin foam sheet. Through the opening method of the present invention, a semi-open-cell polyolefin-based resin foam sheet is obtained, and the compressive stress of the obtained semi-open-cell cross-linked polyolefin-based resin foam sheet is reduced. The semi-open-cell cross-linked polyolefin-based resin foam sheet of the present invention can be applied to the field of new energy batteries (such as battery packs), and plays the role of buffering, waterproofing, and heat preservation. For example, since the new energy battery pack itself produces dimensional tolerances during the manufacturing and assembly process, if a conventional closed-cell cross-linked resin foam sheet is used for heat insulation, waterproofing, and elimination of dimensional tolerances, it will generate greater stress on the battery pack itself, affecting the use of the battery pack. The semi-open-cell cross-linked polyolefin-based resin foam sheet provided by the present invention can ensure the waterproof and heat-insulating properties of the cross-linked polyolefin-based resin foam sheet, and because the compressive stress is reduced, it can not only eliminate the tolerance, but also can be used for buffering between the box and the battery module in the battery pack, avoiding the box from generating greater stress on the battery module, resulting in the use of the battery module being affected.

[0027] Furthermore, the present invention selects a specific cross-linked polyolefin resin foam sheet (for example, by controlling the cell wall destructible strength of the cross-linked polyolefin resin foam sheet) and compresses the cross-linked polyolefin resin foam sheet to a strain exceeding 80%. This increases the air pressure in the cells of the cross-linked polyolefin resin foam sheet, causing the weaker cell walls to break through, thereby forming a certain open porosity. Thus, a semi-open-cell polyolefin resin foam sheet of the present invention is obtained.

[0028] The opening method provided by the present invention will not affect the skin layer of the semi-open-cell polyolefin resin foam sheet, and its opening rate is controllable, the core cell structure is basically complete, and it still has strong thermal insulation and waterproof performance. DETAILED DESCRIPTION

[0029] The present invention provides a semi-open-cell polyolefin resin foam sheet, wherein the 30% compressive stress of the semi-open-cell polyolefin resin foam sheet is 1 kPa to 40 kPa, the average size of the perforations on the cell walls of the semi-open-cell polyolefin resin foam sheet is 10 μm to 1800 μm, and the surface of the skin layer of the semi-open-cell polyolefin resin foam sheet may include incomplete air cells, and the number of the incomplete air cells is 15 / cm 2 the following.

[0030] The semi-open-cell polyolefin resin foam sheet of the present invention has the characteristics of being soft and semi-open-cell, and can effectively alleviate the problem of dimensional inconsistency in new energy battery packs caused by charging and discharging, temperature changes or production tolerances, and prevent the battery packs from being subjected to excessive force. At the same time, it also plays the role of thermal insulation, buffering protection and waterproofing.

[0031] According to an embodiment of the present invention, the 30% compressive stress of the semi-open-cell polyolefin resin foam sheet is 1kPa to 40kPa, for example, 1kPa, 2kPa, 3kPa, 4kPa, 5kPa, 10kPa, 15kPa, 20kPa, 25kPa, 30kPa, 35kPa; preferably 1.5kPa to 30kPa, more preferably 2kPa to 25kPa, and even more preferably 2.5kPa to 20kPa. The inventors have found that when the compressive stress of the semi-open-cell polyolefin resin foam sheet is less than 1kPa, the protective effect of the semi-open-cell polyolefin resin foam sheet is poor, it is difficult to play a protective buffering role, and it will cause the thermal conductivity to increase, reducing the thermal insulation effect; when the compressive stress of the semi-open-cell polyolefin resin foam sheet is greater than 40kPa, it is difficult to eliminate the thickness tolerance, the semi-open-cell polyolefin resin foam sheet is hard, and the buffering effect is poor.

[0032] According to an embodiment of the present invention, the interior and / or surface of the semi-open-cell polyolefin-based resin foam sheet includes independent air cells and incomplete air cells.

[0033] According to an embodiment of the present invention, in the semi-open-cell polyolefin resin foam sheet, the volume of the incomplete airbags accounts for 10% to 95% of the total airbag volume, that is, the open porosity is 10% to 95%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. In the present invention, the open porosity refers to the percentage of the volume of the incomplete airbags to the total airbag volume, and also refers to the volume percentage of the open-cell structure to the overall structure of the foam sheet. The inventors have found that when the open porosity is less than 10%, the compressive stress of the semi-open-cell polyolefin resin foam sheet is too high, affecting the cushioning performance; when the open porosity is greater than 95%, the compressive stress of the semi-open-cell polyolefin resin foam sheet is too low, resulting in poor protective effect, making it difficult to perform a protective cushioning function, and causing the thermal conductivity coefficient to increase, reducing the thermal insulation effect.

[0034] According to an embodiment of the present invention, the independent airbag includes a cell with a closed-cell structure, the cell wall of the independent airbag is substantially complete, and no gas flow is formed between adjacent cells.

[0035] According to an embodiment of the present invention, the incomplete airbag includes a cell with an open-cell structure, the cell wall of the cell contains perforations, and the perforations are connected to adjacent cells to form gas circulation.

[0036] In the present invention, most of the incomplete air cells in the semi-open-cell polyolefin resin foam sheet, excluding the surface of the crust layer, are formed by compression-opening the cells. By compression-opening the cells, adjacent air cells in the semi-open-cell polyolefin resin foam sheet, excluding the surface of the crust layer, are connected to each other through perforations in the cell walls, thereby enabling gas flow between the bubbles. In the present invention, when the surface of the crust layer of the semi-open-cell polyolefin resin foam sheet includes incomplete air cells, the incomplete air cells on the surface of the crust layer exist before compression-opening the cells.

[0037] According to an embodiment of the present invention, the average size of the bubbles in the incomplete air cells (here refers to the average size of the bubbles in the incomplete air cells on the surface of the crust layer) is 30μm to 2000μm, for example, 30μm, 100μm, 200μm, 500μm, 800μm, 1000μm, and 2000μm.

[0038] According to an embodiment of the present invention, the average size of the perforations in the incomplete airbag ranges from 10 μm to 1800 μm, for example, 100 μm, 200 μm, 500 μm, 800 μm, 1000 μm, or 1800 μm. When the average perforation size is less than 10 μm, the gas discharge rate within the incomplete airbag is slow during compression, affecting the compression and cushioning performance. When the average perforation size is greater than 1800 μm, the thermal insulation and waterproof properties of the semi-open-cell polyolefin resin foam sheet are affected.

[0039] According to an embodiment of the present invention, the semi-open-cell polyolefin resin foam sheet includes a skin layer, and the skin layer is located on the surface of the semi-open-cell polyolefin resin foam sheet. Preferably, the skin layer refers to two or four surfaces in the thickness direction of the semi-open-cell polyolefin resin foam sheet. It will be understood by those skilled in the art that the skin layer can also be referred to as the epidermis layer.

[0040] According to an embodiment of the present invention, the crust layer includes independent air cells and optionally includes incomplete air cells, wherein the number of incomplete air cells included in the surface of the crust layer is not greater than 15 / cm 2 , for example, 0 / cm 2 , 1 piece / cm 2 , 2 pieces / cm 2 , 3 pieces / cm 2 , 4 pieces / cm 2 , 5 pieces / cm 2 , 6 pieces / cm 2 , 7 pieces / cm 2 , 8 pieces / cm 2 , 9 / cm 2 , 10 / cm 2It is understood by those skilled in the art that when the number of incomplete air cells on the surface of the crust layer is 0 / cm 2 When the surface of the crust layer does not include incomplete air cells.

[0041] The hole-opening method of the present invention does not destroy the independent air cells in the skin layer on the surface of the foam sheet, and the structure of the skin layer will not be affected during the hole-opening process (for example, the structure of the skin layer on the surface of the foam sheet and / or the structure of the surface of the skin layer will not be destroyed), thereby achieving a waterproof effect that is basically equivalent to that before the hole-opening. Specifically, the number of incomplete air cells contained in the surface of the skin layer of the foam sheet is 15 / cm 2 Below, if more than 15 / cm 2 , the waterproof effect of the semi-open-cell polyolefin resin foam sheet will deteriorate.

[0042] According to an embodiment of the present invention, the hydrophobicity of the semi-open-cell polyolefin resin foam sheet is greater than 95%, for example, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5% or 99%. In the present invention, the hydrophobicity refers to the hydrophobicity obtained by testing in accordance with GB / T 10299.

[0043] According to an embodiment of the present invention, the thermal conductivity of the semi-open-cell polyolefin resin foam sheet is 0.03W / (m·K) to 0.05W / (m·K), for example, 0.03W / (m·K), 0.032W / (m·K), 0.035W / (m·K), 0.038W / (m·K), 0.04W / (m·K), 0.042W / (m·K), and 0.0.045W / (m·K). In the present invention, the thermal conductivity refers to the thermal conductivity obtained by testing in accordance with GB / T 40872-2021.

[0044] According to an embodiment of the present invention, the tear strength of the semi-open-cell polyolefin resin foam sheet in the MD direction and / or TD direction is 0.4N / mm to 2.8N / mm, for example, 0.4N / mm, 0.6N / mm, 0.8N / mm, 1N / mm, 1.2N / mm, 1.5N / mm, 2N / mm, 2.3N / mm, 2.5N / mm, or 2.8N / mm. In the present invention, the MD direction refers to the extrusion direction of the polyolefin resin foam sheet, that is, the longitudinal direction of the foam sheet; the TD direction refers to the direction perpendicular to the MD direction and parallel to the foam sheet, that is, the transverse direction of the foam sheet. When the tear strength is less than 0.4N / mm, the semi-open-cell polyolefin resin foam sheet is difficult to play a protective role during use, has poor mechanical strength, and affects tooling; when the tear strength is greater than 2.8N / mm, the semi-open-cell polyolefin resin foam sheet is too strong and has poor flexibility, making it difficult to play a cushioning and protective role.

[0045] According to an embodiment of the present invention, the tensile strength of the semi-open-cell polyolefin resin foam sheet in the MD and / or TD direction is 40kPa to 480kPa, for example, 40kPa, 80kPa, 100kPa, 150kPa, 180kPa, 200kPa, 250kPa, 300kPa, 400kPa or 480kPa. When the tensile strength is less than 40kPa, the semi-open-cell polyolefin resin foam sheet is difficult to play a protective role during use, has poor mechanical strength, and affects tooling; when the tensile strength is greater than 480kPa, the semi-open-cell polyolefin resin foam sheet is too strong and has poor flexibility, making it difficult to play a cushioning and protective role.

[0046] According to an embodiment of the present invention, the thickness of the semi-open-cell polyolefin resin foam sheet is 1.5 mm to 15 mm, for example, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 5 mm, 8 mm, 10 mm, 12 mm, 14 mm or 15 mm.

[0047] According to an embodiment of the present invention, the semi-open-cell polyolefin-based resin foam sheet is obtained by compressing a cross-linked polyolefin-based resin foam sheet to open the cells.

[0048] According to an embodiment of the present invention, the cross-linking degree of the cross-linked polyolefin resin foam sheet is 20% to 65%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65%. The inventors have found that when the cross-linking degree is within this range, perforations are more likely to form during the cell opening process; when the cross-linking degree is less than 20%, the degree of molecular chain breakage is low, making it difficult to damage the cell walls during compression and cell opening; when the cross-linking degree is greater than 65%, the degree of molecular chain breakage is too high, making it too easy to damage the cell walls during the cell opening process, thereby affecting the sheet's cushioning effect.

[0049] According to an embodiment of the present invention, the average diameter of the pores of the cross-linked polyolefin resin foam sheet is between 40 μm and 2000 μm (for example, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 500 μm, 1000 μm, 1500 μm, 2000 μm). It should be noted that the average diameter of the pores of the cross-linked polyolefin resin foam sheet here refers to the average diameter of all pores inside and on the surface of the foam sheet. The inventors have found that the cross-linked polyolefin resin foam sheet with the above-mentioned average diameter of pores is more suitable for preparing the semi-open-cell polyolefin resin foam sheet of the present invention, and is more suitable for opening pores by adopting the compression opening method of the present invention. When the average diameter of the bubbles is less than 40 μm, the bubbles are difficult to be destroyed during compression; when the average diameter of the bubbles is greater than 2000 μm, the cross-linked polyolefin resin foam sheet will be excessively destroyed during compression, affecting the cushioning and mechanical properties.

[0050] According to an embodiment of the present invention, the foaming ratio of the cross-linked polyolefin resin foam sheet is 20 to 45 cm 3 / g, for example, 20cm 3 / g, 25cm 3 / g, 30cm 3 / g、35cm 3 / g, 40cm 3 / g, 45cm 3 / g. When the foaming ratio of the cross-linked polyolefin resin foam sheet is less than 20cm 3 / g, its openability is poor and it is difficult to open the holes by compression; when the expansion ratio of the cross-linked polyolefin resin foam sheet is greater than 45 cm 3 / g, it is easy to be excessively damaged, affecting the cushioning and mechanical properties.

[0051] According to an embodiment of the present invention, the oxidative induction period (OIT) of the cross-linked polyolefin-based resin foam sheet tested in an oxygen atmosphere at 190°C is controlled to be no greater than 40 minutes. The inventors have found that when the OIT is greater than 40 minutes, the molecular chain structure of the cross-linked polyolefin-based resin foam sheet is relatively intact and difficult to be damaged during compression of the openings. However, when the OIT is ≤ 40 minutes, the molecular chain of the cross-linked polyolefin-based resin foam sheet is highly broken and easily damaged during compression of the openings, resulting in the semi-open-cell polyolefin-based resin foam sheet of the present invention.

[0052] According to an embodiment of the present invention, the ash content of the cross-linked polyolefin resin foam sheet after ignition at 650°C is 0.5% to 15% (e.g., 0.5%, 0.8%, 1%, 5%, 10%, or 15%), and the D50 range of the ash content test is 0.1 μm to 100 μm (e.g., 0.1 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm). The inventors have found that the ash content of the cross-linked polyolefin resin foam sheet within the above range is more likely to increase the destructibility of the cell walls.

[0053] According to an embodiment of the present invention, the cross-linked polyolefin resin foam sheet has a 30% compressive stress of 40 kPa to 180 kPa, more preferably 40 kPa to 100 kPa, for example, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, or 100 kPa. The inventors have found that when the 30% compressive stress of the cross-linked polyolefin resin foam sheet is greater than 180 kPa, the cross-linked polyolefin resin foam sheet is difficult to open by compression.

[0054] According to an embodiment of the present invention, the cross-linked polyolefin-based resin foam sheet includes at least two skin layers, and the skin layers are on the surface of the cross-linked polyolefin-based resin foam sheet.

[0055] According to an embodiment of the present invention, the skinning layer is formed on the surface of the cross-linked polyolefin-based resin foam sheet by high-temperature foaming.

[0056] According to an embodiment of the present invention, the crust layer has the meaning as described above. Preferably, the crust layer (or the surface of the crust layer) includes independent air cells and optionally includes incomplete air cells, wherein the number of incomplete air cells is not more than 15 / cm 2 ; Further, the average size of the bubbles on the incomplete airbag is 0.03mm~2mm (i.e. 30μm~2000μm), for example 0.03mm, 0.05mm, 0.1mm, 0.2mm, 0.5mm, 0.8mm, 1mm, 1.5mm or 2mm.

[0057] According to an embodiment of the present invention, the tear strength of the cross-linked polyolefin resin foam sheet in the MD and / or TD direction is 0.5N / mm~3N / mm, and the tensile strength in the MD and / or TD direction is 50kPa~500kPa. The inventors have found that when the tear strength or tensile strength of the cross-linked polyolefin resin foam sheet is less than the above range, the cross-linked polyolefin resin foam sheet is easily damaged during compression and opening, and it is difficult to play a protective role during use, and the mechanical strength is poor, which affects the tooling; when the tear strength or tensile strength of the cross-linked polyolefin resin foam sheet is greater than the above range, the cross-linked polyolefin resin foam sheet is difficult to open the holes by the compression method of the present invention to obtain the semi-open-cell polyolefin resin foam sheet of the present invention.

[0058] According to an embodiment of the present invention, the thickness of the cross-linked polyolefin resin foam sheet is 1.5 mm to 15 mm, for example, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 5 mm, 8 mm, 10 mm, 12 mm, 14 mm or 15 mm.

[0059] According to an embodiment of the present invention, the cross-linked polyolefin resin foam sheet is obtained by subjecting a resin composition to cross-linking and foaming treatments; the resin composition at least includes a resin matrix, a foaming agent, and a filler.

[0060] According to an embodiment of the present invention, the resin composition comprises at least 100 parts by weight of a resin matrix, 12 to 35 parts by weight of a foaming agent, 0 to 1.5 parts by weight of a crosslinking aid, 2.5 to 15 parts by weight of a filler, and 0 to 15 parts by weight of a flame retardant.

[0061] According to an embodiment of the present invention, the filler includes but is not limited to at least one of the following substances: calcite, orthoclase, feldspar, silica, wollastonite, asbestos, strip powder, kaolinite, mica, graphite, talc, perlite, silica powder, transparent powder, glass powder, barite, magnesium hydroxide, calcium carbonate, magnesium carbonate, diatomaceous earth, calcium stearate, magnesium stearate, barium stearate, zinc stearate, aluminum stearate, and silicon dioxide.

[0062] According to an embodiment of the present invention, D50 of the filler is preferably 0.1 μm to 100 μm, for example, 0.1 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0063] According to an embodiment of the present invention, the crosslinking aid is selected from at least one or two or more of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, triallyl trimellitate, triallyl 1,2,4-benzenetricarboxylate, triallyl isocyanurate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, neopentyl glycol dimethacrylate, divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, ethylvinylbenzene, lauryl methacrylate, stearyl methacrylate, and dicumyl peroxide.

[0064] According to an embodiment of the present invention, the foaming agent is preferably a thermal decomposition type foaming agent, and the decomposition temperature of the thermal decomposition type foaming agent is 120-270°C, for example, 120°C, 130°C, 150°C, 180°C, 200°C, 220°C, 250°C or 270°C.

[0065] According to an embodiment of the present invention, the thermal decomposition type foaming agent is selected from at least one of an organic foaming agent and / or an inorganic foaming agent.

[0066] According to an embodiment of the present invention, the organic foaming agent is selected from at least one of azo compounds, nitroso compounds, hydrazine derivatives, semicarbazide compounds, etc., and is preferably an azo compound and / or a nitroso compound.

[0067] According to an embodiment of the present invention, the inorganic foaming agent is, for example, at least one selected from ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and the like.

[0068] Preferably, the azo compound is selected from azodicarbonamide, azobisisobutyronitrile, azodicarboxylic acid metal salts (barium azodicarboxylate, etc.). Preferably, the nitroso compound is selected from N,N'-dinitrosopentamethylenetetramine. Preferably, the hydrazine derivative is selected from 4,4'-oxybis(benzenesulfonylhydrazide) and toluenesulfonylhydrazide. Preferably, the semicarbazide compound is selected from biurea and toluenesulfonylsemicarbazide.

[0069] According to a preferred embodiment of the present invention, the thermal decomposition type foaming agent is selected from at least one or more of azodicarbonamide, azobisisobutyronitrile, and N,N'-dinitrosopentamethylenetetramine, preferably azodicarbonamide.

[0070] According to an embodiment of the present invention, the resin matrix is ​​selected from polyolefin resins, preferably polyethylene resins. Preferably, the polyethylene resin has the following properties: a melt index of 0.2 g / 10 min to 20 g / 10 min, a density of 0.91 g / cm 3 -0.93g / cm3 The tensile strength is preferably 10 MPa to 60 MPa. In the present invention, the tensile strength of the resin matrix is ​​obtained by testing according to ASTM D882.

[0071] According to an embodiment of the present invention, the polyethylene resin is selected from polyethylene resin, or at least one of the following copolymers or modified copolymers thereof: ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-alkyl (meth)acrylate copolymer. In the present invention, the modified copolymer refers to a modified copolymer or thermoplastic elastomer obtained by copolymerizing the copolymer with an acid anhydride. The acid anhydride can be an acid anhydride known in the art, such as maleic anhydride.

[0072] According to an embodiment of the present invention, the crosslinking treatment includes electron irradiation crosslinking and / or chemical crosslinking. The present invention does not specifically limit the electron irradiation crosslinking and / or chemical crosslinking, and conditions known in the art can be used for the crosslinking.

[0073] According to an embodiment of the present invention, the foaming treatment can be performed under conditions known in the art, for example, foaming is performed at 120-270° C. (for example, 150° C., 200° C., 250° C.).

[0074] According to an embodiment of the present invention, a flame retardant is optionally added to the resin composition. Preferably, the flame retardant is selected from, for example, phosphorus-based flame retardants and halogen-based flame retardants. Furthermore, the phosphorus-based flame retardant is preferably at least one or more of a phosphate, a polyphosphate, and a phosphorus-based spiro compound.

[0075] The present invention also provides a method for manufacturing the semi-open-cell polyolefin resin foam sheet, which specifically comprises: obtaining the semi-open-cell polyolefin resin foam sheet by compressing and opening cells in the thickness direction of the cross-linked polyolefin resin foam sheet.

[0076] According to an embodiment of the present invention, the cross-linked polyolefin-based resin foam sheet and the semi-open-cell polyolefin-based resin foam sheet have the meanings as described above.

[0077] According to an embodiment of the present invention, the compressed opening refers to compression along the thickness direction of the cross-linked polyolefin resin foam sheet to at least 80% of the thickness of the cross-linked polyolefin resin foam sheet, for example, 80%, 85%, 90%, 95%, 99%, 99.9%.

[0078] According to an embodiment of the present invention, the manufacturing method specifically comprises the following steps:

[0079] Step 1: melt-kneading a polyolefin resin composition to obtain a sheet material;

[0080] Step 2: cross-linking the sheet material obtained in step 1 to obtain a cross-linked sheet material;

[0081] Step 3: The cross-linked polyolefin resin foam sheet is obtained by foaming the cross-linked sheet material obtained in step 2;

[0082] Step 4: The cross-linked polyolefin-based resin foam sheet obtained in step 3 is compressed and opened along the thickness direction to obtain the semi-open-cell polyolefin-based resin foam sheet.

[0083] According to an embodiment of the present invention, in step 1, the resin composition has the meaning as described above.

[0084] According to an embodiment of the present invention, in step 1, the sheet material can be prepared by a method known in the art, for example, the resin composition is melt-kneaded through an extruder, and the resin composition is extruded from the extruder to obtain the sheet material.

[0085] According to an embodiment of the present invention, in step 2, the crosslinking treatment has the meaning as described above, for example, using ionizing radiation, which refers to irradiating the sheet material with ionizing radiation such as electron beams, α-rays, β-rays, or γ-rays to crosslink the sheet material, or directly heating the sheet material to a temperature above the reaction temperature of a crosslinking aid to crosslink the sheet material. The crosslinking treatment described in the present invention only needs to bring the degree of crosslinking of the crosslinked polyolefin resin foam sheet to within the range described above.

[0086] According to an embodiment of the present invention, in step 3, the foaming treatment refers to heating the sheet material cross-linked in step 2 to a temperature above the thermal decomposition temperature of the foaming agent, preferably 120-270°C. In the present invention, the foaming treatment can be performed for a time known in the art, and is not specifically limited in the present invention as long as the cross-linked polyolefin resin foam sheet can be obtained.

[0087] According to an embodiment of the present invention, in step 4, the compression opening has the meaning as described above. Preferably, the compression opening is achieved by applying a compressive pressure in the thickness direction of the cross-linked polyolefin resin foam sheet. The compression opening can be performed at 25-80°C.

[0088] For example, the specific step of compressing and opening the cells is as follows: the cross-linked polyolefin resin foam sheet obtained in step 3 is horizontally placed between two parallel flat plates. Then, pressure is applied in the thickness direction of the cross-linked polyolefin resin foam sheet to compress the cross-linked polyolefin resin foam sheet to at least 80% of its thickness, more preferably to at least 85% of its thickness, and the compression is maintained for 5 seconds to 300 seconds after reaching the target compression ratio.

[0089] For example, the specific steps of the compression opening are as follows: the cross-linked polyolefin resin foam sheet obtained in step 3 is passed through a pair of oppositely rotating rollers, wherein the roller spacing of the double pressing rollers is controlled to be less than 15% of the thickness of the cross-linked polyolefin resin foam sheet, preferably the roller spacing is less than 10% of the thickness of the foam sheet, and the rotation speed of the double pressing rollers is 2r / min to 120r / min, preferably 5r / min to 100r / min; the opening rate of the semi-open-cell polyolefin resin foam sheet is adjusted by adjusting the conditions of the compression opening.

[0090] According to an embodiment of the present invention, the semi-open-cell polyolefin resin foam sheet can also be compounded with a support layer. Preferably, the compounding can be done by methods known in the art, such as hot-melt compounding and adhesive compounding.

[0091] Preferably, the support layer is selected from but not limited to at least one of foam material, PE film, non-woven fabric, mica and the like.

[0092] As mentioned above, the present invention also provides an application of the semi-open-cell polyolefin resin foam sheet, which is used in the new energy field, preferably in a battery pack, for example, used between the outer shell and the battery module of a new energy battery pack, or on the side of the outer shell away from the battery module.

[0093] The present invention also provides a battery pack, which includes a box body, wherein the box body includes a first shell and a second shell, a battery module is contained between the first shell and the second shell, and the above-mentioned semi-open-cell polyolefin resin foam sheet is contained between the first shell and the battery module.

[0094] The present invention also provides a battery pack, which includes a box body, wherein the box body includes a first shell and a second shell, and a battery module is contained between the first shell and the second shell. The above-mentioned semi-open-cell polyolefin resin foam sheet is arranged on a side of the first shell away from the battery module, and is arranged on the surface of the first shell in an adhesive form.

[0095] Example

[0096] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0097] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0098] In the following examples and comparative examples, the methods or standards for testing the semi-open-cell polyolefin resin foam sheet and / or the cross-linked polyolefin resin foam sheet are as follows:

[0099] 1. Compressive stress: GB / T 40872-2021;

[0100] 2. Hydrophobicity: GB / T 10299;

[0101] 3. Thermal conductivity: GB / T 40872-2021;

[0102] 4. Opening rate: GB / T 10799;

[0103] 5. Tear strength: GB / T 40872-2021;

[0104] 6. Tensile strength: GB / T 40872-2021;

[0105] 7. Cross-linking degree. The test method is as follows:

[0106] a. Take a 100 mg sample from the foam sheet and accurately weigh the weight of the sample A (mg);

[0107] b. Wrap the sample with a 200-mesh metal mesh, immerse the sample wrapped in the metal mesh in xylene at 120°C, let it stand for 24 hours, and then filter the insoluble matter in the metal mesh to collect it; vacuum dry it to a constant weight, and accurately weigh the weight B (mg) of the insoluble matter;

[0108] c. Calculation of cross-linking degree (mass %): cross-linking degree (mass %) = 100% × (B / A).

[0109] 8. Oxidation induction period (OIT) at 190°C in an oxygen atmosphere was measured in accordance with GB / T 19466.6-2009. The samples were scanned using a Mettler Toledo DSC3 instrument over a temperature range of 25°C to 190°C at a heating rate of 10°C / min.

[0110] The test conditions are:

[0111] Constant temperature process, 25°C, 5 min, nitrogen, 50 ml / min, buffer;

[0112] Heating process, 25°C to 190°C, 10°C / min, nitrogen, 50ml / min, heating;

[0113] Constant temperature process, 190 °C, 5 min, nitrogen, 50 ml / min, buffer;

[0114] Constant temperature process, 190℃, 60min, oxygen, 50ml / min, oxidation process.

[0115] 9. Average Cell Size (or Diameter) and Average Perforation Size: Cut the foam sheet into 50 mm squares as the foam sample for measurement. Soak the sample in liquid nitrogen for 1 minute and remove it. Then, cut the sample along its thickness with a blade. Use a digital microscope to take a magnified photograph of the cut surface. Measure the cell diameter of all cells (including those not containing complete air cells) on the 5 mm cut surface. Repeat this operation five times and take the average value as the average cell size (or diameter). Measure the diameter of the perforations in the cell wall that connect to other cells. Repeat this operation five times and take the average value as the average perforation size.

[0116] 10. Number of incomplete air cells in the crust layer (or the surface of the crust layer): Cut the crust layer of the foam sheet into 50 mm square samples as the foam sample for measurement. Use a digital microscope to take a magnified photo of the surface of the crust layer of the sample, and count the number of incomplete air cells in an area of ​​1 cm 2 The number of incomplete air pockets on the surface was repeated 5 times and the average value was taken.

[0117] 11. Ash after calcination at 650°C: GB / T 4498.1-2013 Method A.

[0118] Example 1

[0119] The preparation method of the semi-open-cell polyolefin resin foam sheet is as follows:

[0120] 1) Resin matrix: 50 parts by mass of commercially available resin with a melt index of 2 g / 10 min (190°C, 2.16 kg) and a density of 0.913 g / cm 3 The polyethylene is mixed with 50 parts by mass of commercially available ethylene-vinyl acetate having a melt index of 4 g / 10 min (190° C., 2.16 kg) and a VA content of 14% as a resin matrix;

[0121] 2) preparing a resin composition per 100 parts by mass of the resin matrix, comprising: 100 parts by mass of the resin matrix of step 1), 12 parts by mass of azodicarbonamide with a particle size of 10 μm, 0.1 parts by mass of trimethylolpropane triacrylate, 15 parts by mass of calcium carbonate with a D50 of 4 μm, and 5 parts by mass of a bromine antimony flame retardant; melt-kneading the resin composition, and extruding it into a resin sheet;

[0122] 3) Crosslinking and foaming: The sheet of step 2) is irradiated and crosslinked at an irradiation energy of 1.8 MeV and a dose of 10 Mrad, and then continuously foamed at a foaming temperature of 220° C. to obtain a foamed crosslinked polyolefin resin foam sheet;

[0123] 4) Opening the cells: The cross-linked polyolefin resin foam sheet obtained in step 3) was passed through a pair of counter-rotating, 40 cm diameter, double-push rollers at a rotation speed of 20 r / min, wherein the roller spacing of the double-push rollers was controlled to be 10% of the thickness of the cross-linked polyolefin resin foam sheet, thereby obtaining a semi-open-cell polyolefin resin foam sheet having a thickness of 90% of the original thickness.

[0124] Example 2

[0125] The preparation method of the semi-open-cell polyolefin resin foam sheet is as follows:

[0126] 1) Resin matrix: 80 parts by mass of commercially available resin with a melt index of 4 g / 10 min (190°C, 2.16 kg) and a density of 0.912 g / cm 3 The polyethylene is mixed with 20 parts by mass of commercially available ethylene-vinyl acetate having a melt index of 10 g / 10 min (190° C., 2.16 kg) and a VA content of 19% as a resin matrix;

[0127] 2) preparing a resin composition per 100 parts by mass of the resin matrix, comprising: 100 parts by mass of the resin matrix of step 1), 25 parts by mass of azodicarbonamide with a particle size of 8 μm, 0.5 parts by mass of dicumyl peroxide, 10 parts by mass of calcium carbonate with a D50 of 20 μm, and 10 parts by mass of a bromine antimony flame retardant; melting, banburying, and extruding the resin composition to form a sheet;

[0128] 3) Crosslinking and foaming: heating the sheet from step 2) at 160° C. to decompose the crosslinking aid and thereby crosslink the resin, followed by high-temperature continuous foaming at a foaming temperature of 210° C. to obtain a foamed crosslinked polyolefin resin foam sheet;

[0129] 4) Opening the cells: The cross-linked polyolefin resin foam sheet obtained by foaming in step 3) was passed through a pair of counter-rotating double-push rollers with a rotation speed of 10 r / min and a diameter of 40 cm, wherein the roller spacing of the double-push rollers was controlled to be 8% of the thickness of the cross-linked polyolefin resin foam sheet, thereby obtaining a semi-open-cell polyolefin resin foam sheet having a thickness of 92% of the original thickness.

[0130] Example 3

[0131] The preparation method of the semi-open-cell polyolefin resin foam sheet is as follows:

[0132] 1) Resin matrix: 40 parts by mass of commercially available resin with a melt index of 1.1 g / 10 min (190°C, 2.16 kg) and a density of 0.923 g / cm 3polyethylene, 40 parts by mass of commercially available ethylene vinyl acetate with a melt index of 2 g / 10 min (190°C, 2.16 kg) and a VA content of 16%, and 20 parts by mass of a density of 0.87 g / cm 3 , EPDM with 69% ethylene content is mixed as the resin matrix;

[0133] 2) preparing a resin composition per 100 parts by mass of the resin matrix, comprising: 100 parts by mass of the resin matrix of step 1), 35 parts by mass of azodicarbonamide having a particle size of 17 μm, 1 part by mass of dicumyl peroxide, 8 parts by mass of kaolinite having a D50 of 100 μm, and 6 parts by mass of a bromine antimony flame retardant; melting, banburying, and extruding the resin composition to form a sheet;

[0134] 3) Crosslinking and foaming: heating the sheet obtained in step 2) at 160° C. to decompose the crosslinking aid and thereby crosslink the resin, followed by high-temperature continuous foaming at a foaming temperature of 200° C. to obtain a foamed crosslinked polyolefin resin foam sheet;

[0135] 4) Opening the cells: The cross-linked polyolefin resin foam sheet obtained by foaming in step 3) was placed between two parallel flat plates, and pressure was applied in the thickness direction of the resin foam sheet to compress the resin foam sheet to 82% of its original thickness for 60 seconds, thereby obtaining a semi-open-cell polyolefin resin foam sheet.

[0136] Example 4

[0137] The preparation method of the semi-open-cell polyolefin resin foam sheet is as follows:

[0138] 1) Resin matrix: 90 parts by mass of a commercially available resin having a melt index of 0.6 g / 10 min (190°C, 2.16 kg) and a density of 0.925 g / cm 3 The polyethylene is mixed with 10 parts by mass of commercially available ethylene-vinyl acetate having a melt index of 4 g / 10 min (190° C., 2.16 kg) and a VA content of 14% as a resin matrix;

[0139] 2) preparing a resin composition comprising, per 100 parts by mass of the resin matrix, 100 parts by mass of the resin matrix of step 1), 20 parts by mass of azodicarbonamide having a particle size of 19 μm, 2.5 parts by mass of calcium carbonate having a D50 of 30 μm, and 6 parts by mass of a bromine antimony flame retardant; melting, banburying, and extruding the resin composition to form a sheet;

[0140] 3) Crosslinking and foaming: The sheet of step 2) is irradiated and crosslinked at an irradiation energy of 2 MeV and a dose of 8 Mrad, and then continuously foamed at a foaming temperature of 215° C. to obtain a foamed crosslinked polyolefin resin foam sheet;

[0141] 4) Opening the cells: The cross-linked polyolefin resin foam sheet obtained by foaming in step 3) was placed between two parallel flat plates, and pressure was applied in the thickness direction of the resin foam sheet to compress the resin foam sheet to 90% of its original thickness for 40 seconds, thereby obtaining a semi-open-cell polyolefin resin foam sheet.

[0142] Example 5

[0143] The preparation method of the semi-open-cell polyolefin resin foam sheet is as follows:

[0144] 1) Resin matrix: commercially available resin with a melt index of 2.1 g / 10 min (190 ° C, 2.16 kg) and a density of 0.927 g / cm 3 Polyethylene as the resin matrix;

[0145] 2) preparing a resin composition per 100 parts by mass of the resin matrix, comprising: 100 parts by mass of the resin matrix of step 1), 17 parts by mass of azodicarbonamide with a particle size of 14 μm, 1.5 parts by mass of trimethylolpropane triacrylate, 12 parts by mass of calcium carbonate with a D50 of 70 μm, and 15 parts by mass of a bromine antimony flame retardant; melting, banburying, and extruding the resin composition to form a sheet;

[0146] 3) Crosslinking and foaming: The sheet of step 2) is irradiated and crosslinked at an irradiation energy of 1.5 MeV and a dose of 15 Mrad, and then continuously foamed at a foaming temperature of 230° C. to obtain a foamed crosslinked polyolefin resin foam sheet;

[0147] 4) Opening the cells: The cross-linked polyolefin resin foam sheet obtained by foaming in step 3) was passed through a pair of counter-rotating double-push rollers with a rotation speed of 20 r / min and a diameter of 40 cm, wherein the roller spacing of the double-push rollers was controlled to be 4% of the thickness of the cross-linked polyolefin resin foam sheet, thereby obtaining a semi-open-cell polyolefin resin foam sheet having a thickness of 96% of the original thickness.

[0148] Comparative Example 1

[0149] The preparation method of the semi-open-cell polyolefin resin foam sheet is as follows:

[0150] 1) Resin matrix: 65 parts by mass of commercially available resin with a melt index of 2 g / 10 min (190°C, 2.16 kg) and a density of 0.935 g / cm 3 The resin matrix is ​​a mixture of polyethylene, 20 parts by mass of commercially available ethylene-vinyl acetate with a melt index of 10 g / 10 min (190° C., 2.16 kg) and a VA content of 19%, and 15 parts by mass of EPDM;

[0151] 2) preparing a resin composition per 100 parts by mass of the resin matrix, comprising: 100 parts by mass of the resin matrix of step 1), 15 parts by mass of azodicarbonamide having a particle size of 8 μm, 0.5 parts by mass of dicumyl peroxide, and 10 parts by mass of a bromine antimony flame retardant; melting, banburying, and extruding the resin composition to form a sheet;

[0152] 3) Crosslinking and foaming: heating the sheet from step 2) at 160° C. to decompose the crosslinking aid and thereby crosslink the resin, followed by high-temperature continuous foaming at a foaming temperature of 210° C. to obtain a foamed crosslinked polyolefin resin foam sheet;

[0153] 4) Opening the cells: The cross-linked polyolefin resin foam sheet obtained in step 3) was passed through a pair of counter-rotating double-push rollers with a rotation speed of 10 r / min and a diameter of 40 cm, wherein the roller spacing of the double-push rollers was controlled to be 10% of the thickness of the cross-linked polyolefin resin foam sheet, to obtain a semi-open-cell polyolefin resin foam sheet having a thickness of 90% of the original thickness.

[0154] Comparative Example 2

[0155] The preparation method of the semi-open-cell polyolefin resin foam sheet is as follows:

[0156] 1) Resin matrix: commercially available resin with a melt index of 2.1 g / 10 min (190 ° C, 2.16 kg) and a density of 0.965 g / cm 3 Polyethylene as the resin matrix;

[0157] 2) preparing a resin composition per 100 parts by mass of the resin matrix, comprising: 100 parts by mass of the resin matrix of step 1), 5 parts by mass of azodicarbonamide having a particle size of 15 μm, 2 parts by mass of trimethylolpropane triacrylate, and 2.2 parts by mass of calcium carbonate having a D50 of 70 μm; melting, banburying, and extruding the resin composition to form a sheet;

[0158] 3) Crosslinking and foaming: The sheet of step 2) is irradiated and crosslinked at an irradiation energy of 1.8 MeV and a dose of 15 Mrad, and then continuously foamed at a foaming temperature of 230° C. to obtain a foamed crosslinked polyolefin resin foam sheet;

[0159] 4) Opening the cells: The cross-linked polyolefin resin foam sheet obtained by foaming in step 3) was passed through a pair of counter-rotating double-push rollers with a rotation speed of 20 r / min and a diameter of 40 cm, wherein the roller spacing of the double-push rollers was controlled to be 4% of the thickness of the cross-linked polyolefin resin foam sheet, to obtain a semi-open-cell polyolefin resin foam sheet having a thickness of 96% of the original thickness.

[0160] Comparative Example 3

[0161] The preparation method of the semi-open-cell polyolefin resin foam sheet is as follows:

[0162] 1) Resin matrix: 30 parts by mass of commercially available resin with a melt index of 1.1 g / 10 min (190°C, 2.16 kg) and a density of 0.943 g / cm 3 polyethylene, 40 parts by mass of commercially available ethylene vinyl acetate with a melt index of 2 g / 10 min (190°C, 2.16 kg) and a VA content of 16%, and 30 parts by mass of a density of 0.87 g / cm 3 , EPDM with an ethylene content of 69% is mixed as the resin matrix;

[0163] 2) preparing a resin composition per 100 parts by mass of the resin matrix, comprising: 100 parts by mass of the resin matrix of step 1), 17 parts by mass of azodicarbonamide having a particle size of 18 μm, 2.5 parts by mass of trimethylolpropane triacrylate, 10 parts by mass of a bromine antimony flame retardant, and 16 parts by mass of calcium carbonate having a D50 of 4 μm; melting, banburying, and extruding the resin composition to form a sheet;

[0164] 3) Crosslinking and foaming: The sheet obtained in step 2) is irradiated and crosslinked at an irradiation energy of 1.5 MeV and a dose of 10 Mrad, and then continuously foamed at a foaming temperature of 200° C. to obtain a foamed crosslinked polyolefin resin foam sheet;

[0165] 4) Opening the cells: The cross-linked polyolefin resin foam sheet obtained by foaming in step 3) was passed through a pair of counter-rotating double-push rollers with a rotation speed of 15 r / min and a diameter of 40 cm, wherein the roller spacing of the double-push rollers was controlled to be 2% of the thickness of the cross-linked polyolefin resin foam sheet, to obtain a semi-open-cell polyolefin resin foam sheet having a thickness of 98% of the original thickness.

[0166] The cross-linked polyolefin-based resin foam sheets and semi-open-cell polyolefin-based resin foam sheets prepared in the above examples and comparative examples were tested using the above method and the results are recorded in Table 1.

[0167] Table 1

[0168] Application Examples

[0169] The semi-open-cell polyolefin resin foam sheets of the above embodiment and comparative example were respectively taken as samples and used in a battery pack, which specifically includes:

[0170] A box body, comprising a first shell and a second shell,

[0171] a battery module, the battery module being contained between the first shell and the second shell, and

[0172] a semi-open-cell polyolefin resin foam sheet, the semi-open-cell polyolefin resin foam sheet being contained between the first housing and the battery module;

[0173] The semi-open-cell polyolefin resin foam sheets are selected from the semi-open-cell polyolefin resin foam sheets of the embodiment and the comparative example respectively.

[0174] The specific simulation assembly test of the battery pack is as follows:

[0175] (1) Prepare an aluminum box with a width of 1m, a length of 2m, and a height of 0.2m. Assemble a bottom plate at the bottom of the box as the second shell, and assemble a cover plate at the top of the box as the first shell. The box, bottom plate, and cover plate are all made of aluminum alloy extruded profiles (6061-T6 is selected), with a thickness of 2mm. The cover plate is in a horizontal state. Install the simulated battery module on the bottom plate, and test the height of the center position of the upper surface of the cover plate from the bottom of the box, which is recorded as the initial height H0.

[0176] (2) Assemble the semi-open-cell polyolefin resin foam sheet between the battery module and the cover plate. The gap between the simulated battery module and the cover plate is 70% of the sample thickness. The cover plate and the box body are fixed with screws, and the spacing between the screws is 5 cm. After assembly, ensure that there is no gap between the cover plate and the box body. After standing for 1 minute, test the actual height Hn of the center position of the upper surface of the cover plate from the bottom of the box body, and calculate the flatness of the cover plate, flatness = (Hn-H0) / H0.

[0177] (3) The evaluation criteria for the simulated assembly level are as follows:

[0178] When the flatness of the cover plate is ≤ 10% of the thickness of the foam sheet, the assembly grade is excellent;

[0179] When the flatness of the cover is between 10% and 15%, the assembly level is medium;

[0180] When the flatness of the cover plate is greater than 15%, the assembly grade is poor.

[0181] The simulated assembly test results are recorded in Table 2.

[0182] Table 2 Simulation assembly test results

[0183] The above describes exemplary embodiments of the present invention. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A semi-open-cell polyolefin resin foam sheet, characterized in that: The 30% compressive stress of the semi-open-cell polyolefin resin foam sheet is 1 kPa to 40 kPa, the average size of the perforations on the cell walls of the semi-open-cell polyolefin resin foam sheet is 10 μm to 1800 μm, and the number of incomplete air cells on the surface of the skin layer of the semi-open-cell polyolefin resin foam sheet is 15 / cm 2 Hereinafter, the incomplete air cells on the surface of the skin layer include one cell with an open-pore structure, and the average size of the cells of the incomplete air cells on the surface of the skin layer is 30 μm to 2000 μm.

2. The semi-open-cell polyolefin resin foam sheet according to claim 1, characterized in that: The interior and / or surface of the semi-open-cell polyolefin-based resin foam sheet includes independent air cells and incomplete air cells.

3. The semi-open-cell polyolefin resin foam sheet according to claim 2, characterized in that: In the semi-open-cell polyolefin resin foam sheet, the volume of the incomplete airbags accounts for 10% to 95% of the total airbag volume.

4. The semi-open-cell polyolefin resin foam sheet according to claim 1, characterized in that: The water repellency of the semi-open-cell polyolefin resin foam sheet is greater than 95%.

5. The semi-open-cell polyolefin resin foam sheet according to claim 1, characterized in that: The thermal conductivity of the semi-open-cell polyolefin resin foam sheet is 0.03W / (m·K) to 0.05W / (m·K).

6. The semi-open-cell polyolefin resin foam sheet according to claim 1, characterized in that: The tear strength of the semi-open-cell polyolefin-based resin foam sheet in MD and / or TD direction is 0.4N / mm-2.8N / mm; the tensile strength of the semi-open-cell polyolefin-based resin foam sheet in MD and / or TD direction is 40kPa-480kPa, the MD direction refers to the extrusion direction of the semi-open-cell polyolefin-based resin foam sheet, and the TD direction refers to the direction orthogonal to the MD direction and parallel to the semi-open-cell polyolefin-based resin foam sheet.

7. The semi-open-cell polyolefin resin foam sheet according to claim 1, characterized in that: The semi-open-cell polyolefin resin foam sheet is obtained by compressing a cross-linked polyolefin resin foam sheet to open the cells; the cross-linking degree of the cross-linked polyolefin resin foam sheet is 20% to 65%.

8. The semi-open-cell polyolefin resin foam sheet according to claim 7, characterized in that: The cross-linked polyolefin resin foam sheet has an oxidation induction period (OIT) of no more than 40 minutes when tested in an oxygen atmosphere at 190° C.

9. The semi-open-cell polyolefin resin foam sheet according to claim 7, characterized in that: The cross-linked polyolefin resin foam sheet has an average diameter of 40 μm to 2000 μm and a foaming ratio of 20 to 45 cm 3 / g.

10. The semi-open-cell polyolefin resin foam sheet according to claim 7, characterized in that: The ash content of the cross-linked polyolefin resin foam sheet after burning at 650° C. is in the range of 0.5% to 15%.

11. The semi-open-cell polyolefin resin foam sheet according to claim 7, characterized in that: The number of incomplete air cells in the skin layer of the cross-linked polyolefin resin foam sheet is 15 / cm 2 Below, and the cell size of the incomplete air cell is 30μm to 2000μm.

12. The semi-open-cell polyolefin resin foam sheet according to claim 7, characterized in that: The cross-linked polyolefin resin foam sheet has a 30% compressive stress of 40 kPa to 180 kPa.

13. The semi-open-cell polyolefin resin foam sheet according to claim 1, characterized in that: The semi-open-cell polyolefin resin foam sheet is also compounded with a support layer.

14. The semi-open-cell polyolefin resin foam sheet according to claim 1, characterized in that: The 30% compressive stress of the semi-open-cell polyolefin resin foam sheet is 1.5 kPa to 30 kPa, 2 kPa to 25 kPa or 2.5 kPa to 20 kPa.

Images