Polyolefin adhesive film

Abstract

To provide a polyolefin adhesive film having a support layer and an adhesive layer formed on the support layer.SOLUTION: A support layer is a polypropylene film. An adhesive layer contains a polyolefin copolymer and inorganic particles dispersed in the polyolefin copolymer. The polyolefin copolymer is modified with maleic anhydride and the inorganic particles are surface treated with epoxysiloxane. The grafting rate of maleic anhydride in the polyolefin copolymer is 1% to 5%. The weight ratio of surface treatment of epoxysiloxane to inorganic particles (epoxysiloxane / inorganic particles (weight)) is 0.3% to 4%. When the polyolefin adhesive film is subjected to heat-work, a cross-linking reaction occurs between the epoxysiloxane surface-treated by the inorganic particles and the maleic anhydride modified by the polyolefin copolymer, so as to improve the hardness of the adhesive layer.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an adhesive film, and particularly to a polyolefin adhesive film.

Background Art

[0002] As shown in FIG. 6, conventional aluminum-plastic film packaging materials often employ dry composite polyolefin film PL / aluminum foil AF. Between the two materials, they are bonded with an adhesive layer GL (for example, a polyester adhesive or a polyurethane adhesive). However, conventional aluminum-plastic film packaging materials have problems in that volatile organic solvents (VOCs) in the laminating process easily volatilize. Also, when conventional aluminum-plastic film packaging materials are placed in a high-temperature and high-humidity environment for a long time, the adhesive strength between the polyolefin film PL and the aluminum foil AF deteriorates, leading to insufficient adhesive strength. Furthermore, in the application of high-output wattage power batteries in electric vehicles, existing aluminum-plastic film packaging materials are prone to cause delamination and expansion between the layers of the material at high operating temperatures, resulting in electrolyte leakage.

[0003] Therefore, in view of the above-described problems being improvable, the inventor of the present invention conducted intensive research and combined theory and practice, and as a result, arrived at the present invention as a method with a reasonable design and capable of effectively improving the above problems.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technical problem to be solved by the present invention is to provide a polyolefin adhesive film in view of the deficiencies of the prior art.

Means for Solving the Problems

[0005] To solve the above technical problems, one technical means adopted by the present invention is to provide a polyolefin adhesive film comprising a support layer made of a polypropylene film and an adhesive layer formed on one side of the support layer by coextrusion. The adhesive layer contains a polyolefin copolymer modified with maleic anhydride and inorganic particles dispersed in the polyolefin copolymer and surface-treated with epoxy siloxane. The grafting rate of maleic anhydride in the polyolefin copolymer is 1% - 5%, and the surface treatment weight ratio of epoxy siloxane to the inorganic particles (epoxy siloxane / inorganic particles (weight)) is 0.3% - 4%. When the polyolefin adhesive film is subjected to a heating operation, a crosslinking reaction occurs between the epoxy siloxane surface-treated on the inorganic particles and the maleic anhydride modified on the polyolefin copolymer so that the hardness of the adhesive layer is improved.

[0006] Preferably, in the adhesive layer, taking the total weight of the adhesive layer as 100 wt%, the content of the polyolefin copolymer modified with maleic anhydride is 90 wt% or more, and the addition amount of the inorganic particles surface-treated with epoxy siloxane is 500 ppm - 2,000 ppm.

[0007] Preferably, in the adhesive layer, the average particle diameter of the inorganic particles is 1 μm - 8 μm, the sphericity of the inorganic particles is 0.7 - 1.0, and the inorganic particles are at least one selected from the group consisting of silicon dioxide particles, calcium carbonate particles, barium sulfate particles, kaolin particles, and mica particles.

[0008] Preferably, in the adhesive layer, the average particle diameter of the inorganic particles is 3 μm - 6 μm, and the sphericity of the inorganic particles is 0.8 - 1.0.

[0009] Preferably, the polyolefin copolymer in the adhesive layer is formed by performing copolymerization reactions of at least two types among C2-C4 olefin molecules, and the melt index of the polyolefin copolymer is 3 g / 10 min to 5 g / 10 min.

[0010] Preferably, the grafting rate of the maleic anhydride on the polyolefin copolymer is 2% to 4%, and the surface treatment weight ratio of the epoxy siloxane to the inorganic particles (epoxy siloxane / inorganic particles (by weight)) is 0.5% to 2%.

[0011] Preferably, the support layer is a cast polypropylene film containing a propylene block polymer, a vinyl-based elastomer, and a polyolefin copolymer.

[0012] Preferably, in the support layer, the propylene block polymer includes a block composed of ethylene propylene rubber, and the weight percentage of the ethylene propylene rubber in the propylene block polymer is 18% or more. The vinyl-based elastomer is an ethylene / butene elastomer, and the weight percentage of ethylene in the vinyl-based elastomer is 30% or more.

[0013] Preferably, the polyolefin adhesive film further includes a heat-sealing layer formed on the other surface of the support layer by coextrusion.

[0014] Preferably, the heat-sealing layer is formed of a propylene polymer, and the propylene polymer is at least one of a propylene copolymer (co-PP) and a propylene homopolymer (homo-PP).

Advantages of the Invention

[0015] As an advantageous effect of the present invention, the polyolefin adhesive film according to the present invention comprises "a support layer that is a polypropylene film and an adhesive layer formed on one side of the support layer by coextrusion", "the adhesive layer contains a polyolefin copolymer modified with maleic anhydride and inorganic particles dispersed in the polyolefin copolymer and surface-treated with epoxy siloxane", "the grafting rate of maleic anhydride in the polyolefin copolymer is 1% to 5%, and the surface treatment weight ratio of epoxy siloxane to the inorganic particles (epoxy siloxane / inorganic particles (weight)) is 0.3% to 4%", and "when the polyolefin adhesive film is subjected to a heating operation, a crosslinking reaction occurs between the epoxy siloxane surface-treated on the inorganic particles and the maleic anhydride modified in the polyolefin copolymer". Due to these technical features, the adhesiveness between the polyolefin adhesive layer and the metal aluminum foil (for example, aluminum plastic film) is good, and it is possible to avoid the occurrence of delamination or expansion between the layers of the material and leakage of the electrolyte at a high operating temperature for the polyolefin adhesive film and the metal aluminum foil. The polyolefin adhesive film is particularly applicable to the aluminum plastic film packaging material of high-power wattage power batteries in electric vehicles.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Best Mode for Carrying Out the Invention

[0017] To better understand the features and technical content of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings. However, the provided accompanying drawings are for reference and explanation purposes only and are not for limiting the scope of the claims of the present invention.

[0018] Hereinafter, embodiments according to the present invention will be described according to a predetermined specific embodiment, and those skilled in the art can understand the advantages and effects of the present invention based on the content disclosed in this specification. The present invention can be implemented or applied according to other different specific embodiments, and for each detail in this specification, various modifications and changes can be made based on different viewpoints and uses without departing from the concept of the present invention. Also, as explained in advance, the accompanying drawings of the present invention are simple schematic explanations and are not drawn based on actual sizes. The technical content related to the present invention will be described in more detail based on the following embodiments, but the disclosed content does not limit the protection scope of the present invention. It should be understood that in this specification, terms such as "first", "second", "third", etc. may be used to describe various materials or parameters, but these materials or parameters are not limited by these terms. These terms are mainly used to distinguish one material from another material, or one parameter from another parameter. Also, the term "or" used in this specification may include any one or a combination of more than one of the related items according to the actual situation.

[0019] [First Embodiment] As shown in FIGS. 1 to 4, in the first embodiment of the present invention, the polyolefin adhesive film 100 includes an adhesive layer 1, a support layer 2, and a heat-sealing layer 3. The adhesive layer 1 is formed on one side of the support layer 2 (for example, the upper surface of the support layer 2 in FIG. 1). The heat-sealing layer 3 is formed on the other side of the support layer 2 (for example, the lower surface of the support layer 2 in FIG. 1). That is, the support layer 2 is between the adhesive layer 1 and the heat-sealing layer 3.

[0020] In this embodiment, the adhesive layer 1, the support layer 2, and the heat-sealing layer 3 of the polyolefin adhesive film 100 are formed as a laminated structure by coextrusion. That is, the adhesive layer 1 is formed on the support layer 2 by coextrusion.

[0021] As shown in FIGS. 2 and 3, the polyolefin adhesive film 100 is combined with a metal aluminum foil AF (aluminum foil) through the adhesive layer 1. The support layer 2 gives the polyolefin adhesive film 100 impact resistance and supportability. Note that the heat-sealing layer 3 gives the polyolefin adhesive film 100 heat-sealability. Thereby, the polyolefin adhesive film 100 is applied to packaging materials, and in particular, to packaging materials for lithium batteries or electronic products, but the present invention is not limited thereto.

[0022] It should be noted that the polyolefin adhesive film 100 according to this embodiment is particularly applicable to high-output wattage power batteries in electric vehicles and is used as an electronic packaging material for lithium batteries.

[0023] In addition, the polyolefin adhesive film 100 according to the embodiment of the present invention has good adhesiveness with a metal aluminum foil AF (for example, an aluminum plastic film), and the polyolefin adhesive film 100 and the metal aluminum foil AF do not cause delamination or expansion between the material layers at a high operating temperature, and can avoid the occurrence of electrolyte leakage.

[0024] Regarding the thickness, the first thickness T1 of the adhesive layer 1 is 4 μm to 12 μm, preferably 6 μm to 10 μm. The second thickness T2 of the support layer 2 is 15 μm to 35 μm, preferably 20 μm to 28 μm. Also, the third thickness T3 of the heat-seal layer 3 is 4 μm to 12 μm, preferably 6 μm to 10 μm.

[0025] In other words, the overall thickness of the polyolefin adhesive film 100 is 20 μm to 60 μm, preferably 20 μm to 50 μm. Regarding the thickness ratio, the first thickness T1 of the adhesive layer 1: the second thickness T2 of the support layer 2: the third thickness T3 of the heat-seal layer 3 (thickness ratio) is 10 - 25:50 - 80:10 - 25, but the present invention is not limited thereto.

[0026] More specifically, as shown in FIG. 4, the adhesive layer 1 includes a modified polyolefin copolymer 11 and surface-treated inorganic particles 12 dispersed in the polyolefin copolymer.

[0027] The polyolefin copolymer 11 is formed, for example, by performing a copolymerization reaction of at least two types among C2 - C4 olefin molecules. For those skilled in the art, it is well-known that the C2 olefin molecule is ethylene (PE), the C3 olefin molecule is propylene (PP), and the C4 olefin molecule is butylene, for example, 1-butene.

[0028] For example, the raw materials constituting the polyolefin copolymer 11 may be, for example, C2 olefin molecules and C3 olefin molecules, C2 olefin molecules and C4 olefin molecules, C3 olefin molecules and C4 olefin molecules, or C2 - C4 olefin molecules.

[0029] Preferably, the raw materials constituting the polyolefin copolymer 11 may be C3 olefin molecules and C4 olefin molecules, but the present invention is not limited thereto. Also, the weight ratio of the two olefin molecules (for example, C3 and C4, or C2 and C4) may be, for example, 30:70 to 70:30 (preferably 40:60 to 60:40), but the present invention is not limited thereto.

[0030] It should be noted that the polyolefin copolymer 11 according to the present embodiment is formed by performing a copolymerization reaction of at least two kinds among C2-C4 olefin molecules. Therefore, the polyolefin adhesive layer 2 achieves both higher transparency and adhesiveness.

[0031] Furthermore, in the present embodiment, the polyolefin copolymer 11 is modified with maleic anhydride (MAH). Since the polyolefin copolymer 11 modified with the maleic anhydride has a carboxyl group (-COOH), the polarity of the polyolefin copolymer is significantly improved. Thereby, the polyolefin copolymer 11 of the present invention has better water solubility and adhesiveness than the unmodified polyolefin copolymer and is more suitably used as the adhesive layer 1.

[0032] The maleic anhydride may be grafted to the polyolefin copolymer 11, for example. More specifically, the maleic anhydride may be melt-grafted to the polyolefin copolymer 11, for example. The melt grafting may be performed, for example, with a single-screw extruder, a twin-screw extruder, or a rheometer. Preferably, the melt grafting is performed with a twin-screw extruder.

[0033] In the polyolefin adhesive layer 1, the content of the polyolefin copolymer 11 is 90 wt% or more, preferably 95 wt% or more.

[0034] Furthermore, the graft ratio of maleic anhydride in the polyolefin copolymer 11 is 1% to 5%, preferably 2% to 4%. In one specific example, the graft ratio of maleic anhydride is 3%.

[0035] It should be noted that in this embodiment, when the graft ratio of maleic anhydride is controlled to 1% to 5%, excellent adhesion can be provided. If the graft ratio of maleic anhydride is less than 1%, the adhesion of the adhesive layer 1 deteriorates. On the other hand, if the graft ratio of maleic anhydride exceeds 5%, the adhesive layer becomes too hard after being laminated with the aluminum foil, which affects the flex resistance of the packaging material.

[0036] It should be explained that the graft ratio of maleic anhydride in this specification can be analyzed by, for example, a Fourier transform infrared spectrometer (FTIR). The Fourier transform infrared spectrometer can perform qualitative analysis on whether maleic anhydride grafts onto the molecular chain of the polyolefin copolymer and can also quantify the graft ratio of maleic anhydride.

[0037] According to the infrared absorption spectrum, maleic anhydride grafting has prominent absorption peaks at 1725 cm -1 , 1790 cm -1 , and the absorption peaks are characteristic peaks of carboxyl groups in maleic anhydride. In addition, the quantitative analysis of the graft ratio of maleic anhydride can be performed, for example, based on Lambert-Beer's law.

[0038] It should be noted that the graft ratio of maleic anhydride is the weight percentage (%) of maleic anhydride grafted per 100 parts by weight of the polyolefin copolymer.

[0039] Furthermore, in this embodiment, the melt flow index (MI) of the modified polyolefin copolymer 11 is 1 g / 10 min to 5 g / 10 min, preferably 2 g / 10 min to 4 g / 10 min.

[0040] In one specific example, the melt index of the modified polyolefin copolymer is 3.1 g / 10 min.

[0041] It should be noted that when the melt index of the polyolefin copolymer 11 is controlled within the range of 1 g / 10 min to 5 g / 10 min, it gives the adhesive layer better adhesion and transparency, and also gives a better appearance (for example, a smooth surface with no noticeable streaks).

[0042] If the melt index of the polyolefin copolymer 11 exceeds the above range, it may cause problems such as poor adhesion of the adhesive layer 1 and streaks on the surface of the packaging material.

[0043] It should be explained that the melt index in this specification is the weight of the polyolefin copolymer extruded from the opening of an extrusion plastometer in 10 minutes. Its unit is g / 10 min. The melt index indicates the fluidity in the molten state. The larger the melt index, the smaller the molecular weight and the better the fluidity. Conversely, the smaller the melt index, the larger the molecular weight, the more difficult it is for the molecular chains to move, and the poorer the fluidity. In this embodiment, the melt index is measured at 190 °C and a load of 2.16 kg based on ASTM D1238.

[0044] Furthermore, as shown in FIG. 4, the surface-treated inorganic particles 12 are modified with epoxy siloxane 12a on the surface of the inorganic particles 12 by surface treatment with epoxy siloxane.

[0045] More specifically, the inorganic particles 12 are surface-treated by immersing them in an aqueous solution of epoxy siloxane. The epoxy siloxane in the liquid state is modified on the solid inorganic particles 12.

[0046] After the inorganic particles 12 surface-treated with epoxy siloxane 12a are added to the adhesive layer 1, the functional groups (e.g., epoxy groups) of the epoxy siloxane 12a attached to the inorganic particles 12 can undergo a crosslinking reaction with the functional groups (e.g., carboxyl groups) of maleic anhydride of the polyolefin copolymer 11. Here, the crosslinking reaction particularly has a faster reaction rate and a higher degree of crosslinking and curing when a heating operation (e.g., a thermocompression bonding operation) is performed, but the present invention is not limited thereto.

[0047] Also, the functional groups (epoxy groups) of the epoxy siloxane 12a attached to the inorganic particles 12 can themselves undergo a crosslinking reaction, whereby the adhesive layer 1 can achieve a better curing effect.

[0048] With the above-described configuration, the adhesive layer 1 of the polyolefin adhesive film 100 according to the embodiment of the present invention has good adhesiveness to the metal aluminum foil AF (e.g., an aluminum plastic film), and it is possible to avoid the occurrence of delamination or expansion between the layers of the materials and leakage of the electrolytic solution at a high operating temperature for the polyolefin adhesive film 100 and the metal aluminum foil AF.

[0049] It should be noted that usually, an epoxy siloxane in a liquid state is difficult to be uniformly dispersed in a polyolefin copolymer. However, in the embodiment of the present invention, since the surface of the inorganic particles 12 is modified with an epoxy siloxane, the epoxy siloxane can be uniformly dispersed in the polyolefin copolymer using the inorganic particles 12 as a carrier.

[0050] In one embodiment of the present invention, the inorganic particles are at least one selected from the group consisting of silicon dioxide particles (SiO2), calcium carbonate particles (CaCO3), barium sulfate particles (BaSO4), kaolinite clay particles, and mica particles.

[0051] Preferably, the inorganic particles 12 are silicon dioxide particles, but the present invention is not limited thereto.

[0052] More specifically, the shape of the inorganic particles is preferably spherical. More specifically, the sphericity of the inorganic particles is 0.7 to 1.0. Here, in this specification, "sphericity" is the value of the ratio of the minimum particle diameter to the maximum particle diameter of the same particles. For example, as a result of observation with a scanning electron microscope (SEM), when the value of the ratio of the observed minimum particle diameter to the maximum particle diameter is 0.8 or more, it indicates that the sphericity of the particles is 0.8 or more. When the "sphericity" of the particles approximates 1, the particles approximate an ideal spherical shape. Preferably, the sphericity of the inorganic particles is 0.8 to 1.0.

[0053] Regarding the range of the particle diameter, the average particle diameter (for example, D50) of the inorganic particles is 1 μm to 8 μm, and preferably 3 μm to 6 μm.

[0054] When the average particle diameter of the inorganic particles is lower than the lower limit of the particle diameter (for example, less than 1 μm), the effect of improving the adhesiveness between the adhesive layer 1 and the metal aluminum foil AF of the inorganic particles is not significant. When the average particle diameter of the inorganic particles exceeds the upper limit of the particle diameter (for example, exceeds 8 μm), the inorganic particles may affect the transparency of the polyolefin adhesive layer 1.

[0055] More specifically, the weight ratio of the epoxy siloxane to the inorganic particles 12 (i.e., the modification amount) is 0.3% to 4%, preferably 0.4% to 3%, and particularly preferably 0.5% to 2%.

[0056] That is, with respect to 100 parts by weight of the inorganic particles, the weight of the epoxy siloxane is 0.3 to 4 parts by weight, preferably 0.4 to 3 parts by weight, and particularly preferably 0.5 to 2 parts by weight.

[0057] It should be noted that in this embodiment, when the weight ratio of the epoxy siloxane to the inorganic particles 12 is within the above range, the effect of improving the adhesiveness between the adhesive layer 1 and the metal aluminum foil AF is relatively remarkable.

[0058] When the weight ratio of the epoxy siloxane exceeds 4%, the modification amount of the epoxy siloxane 12a on the surface of the inorganic particles 12 tends to saturate. Therefore, it is not very helpful for improving the adhesiveness between the adhesive layer 1 and the metal aluminum foil AF, and it may affect the haze value of the adhesive layer 1.

[0059] Conversely, when the weight ratio of the epoxy siloxane is less than 0.3%, the effect of improving the adhesiveness between the epoxy siloxane adhesive layer 1 and the metal aluminum foil AF is not significant.

[0060] It should be noted that in the present embodiment, the weight ratio (modification amount) of the epoxy siloxane to the inorganic particles may be measured, for example, by quantitative analysis using thermo-gravimetric analysis (TGA). As an analysis method, inorganic particles surface-treated with epoxy siloxane are burned at a high temperature of 800 °C, and the weight loss before and after combustion is measured, and the amount is the modification amount. Here, 800 °C exceeds the boiling point of the epoxy siloxane but is lower than the melting point of the inorganic particles (for example, SiO2). Also, whether the epoxy siloxane is modified with inorganic particles may be measured by qualitative analysis using a Fourier transform infrared spectrometer (FT-IR). For example, it is possible to analyze whether the gas generated after combustion has a characteristic absorption peak of an epoxy functional group (EPOXY functional group), but the present invention is not limited thereto.

[0061] In one embodiment of the present invention, the addition amount of the inorganic particles surface-treated with the epoxy siloxane in the polyolefin adhesive layer 1 is 500 ppm to 2,000 ppm, preferably 500 ppm to 1,500 ppm. Thereby, the effect of improving the adhesiveness between the adhesive layer 1 and the metal aluminum foil AF is relatively remarkable.

[0062] When the addition amount of the inorganic particles surface-treated with the epoxy siloxane is less than 500 ppm, the polyolefin adhesive films 100 may stick to each other when being wound up. Conversely, when the addition amount of the inorganic particles surface-treated with the epoxy siloxane exceeds 2,000 ppm, the haze value of the polyolefin adhesive film 100 is too high.

[0063] It should be noted that the production of the polyolefin copolymer is carried out, for example, under conditions where a peroxide is present (0.3 to 0.6% peroxide), with processing and pelletizing performed using a twin-screw extruder. During the extrusion process, maleic anhydride grafting is melt grafted, and inorganic particles surface-treated with the epoxy siloxane are dispersed. Also, the melt index of the polyolefin copolymer can be controlled.

[0064] To further explain, the polyolefin copolymer formed by pelletizing (grafted with maleic anhydride and having inorganic particles surface-treated with epoxy siloxane dispersed therein) may, for example, form the polyolefin adhesive layer 1 on one side surface of the support layer 2 by coextrusion.

[0065] According to the above technical solution, the polyolefin adhesive film 100 according to the embodiment of the present invention, as shown in FIGS. 2 and 3, can be thermally laminated with the metal aluminum foil AF through its adhesive layer 1, eliminating the need to adhere with other polyester adhesives or polyurethane adhesives.

[0066] The polyolefin adhesive film 100 according to the present invention not only has self-bonding properties but also can solve the problem of the volatilization of volatile organic solvents (VOCs) in the prior art. Further, the polyolefin adhesive film 100 according to the embodiment of the present invention has good adhesiveness with the metal aluminum foil AF (for example, an aluminum plastic film), and the polyolefin adhesive film 100 and the metal aluminum foil AF can avoid delamination and swelling between layers of the material and leakage of the electrolyte at a high operating temperature.

[0067] Subsequently, as shown in FIG. 1, the support layer 2 is a cast polypropylene film (also referred to as a cast polypropylene film, CPP film, or an unstretched polypropylene film) for imparting impact resistance and the support properties required for a packaging material to the polyolefin adhesive film 100.

[0068] More specifically, the support layer 2 includes a propylene block polymer, a vinyl elastomer, a polyolefin copolymer modified with maleic anhydride (MAH modified polyolefin copolymer), and a lubricant.

[0069] Taking the total weight of the support layer 2 as 100 wt%, the content of the propylene block polymer is 50 wt% - 90 wt%, preferably 60 wt% - 80 wt%. Also, taking the total weight of the support layer 2 as 100 wt%, the content of the vinyl elastomer is 5 wt% - 30 wt%, preferably 15 wt% - 25 wt%. Taking the total weight of the support layer 2 as 100 wt%, the content of the polyolefin copolymer modified with maleic anhydride is 5 wt% - 20 wt%, preferably 5 wt% - 15 wt%. Taking the total weight of the support layer 2 as 100 wt%, the content of the lubricant is 100 ppm - 5,000 ppm, preferably 1,000 ppm - 4,000 ppm.

[0070] Furthermore, the propylene block polymer includes a block composed of ethylene-propylene rubber (EPR), and the weight percentage of the propylene block polymer in the ethylene-propylene rubber in the propylene block polymer is 18% or more, preferably 18% - 30%, but the present invention is not limited thereto.

[0071] It should be noted that the weight ratio of the propylene block polymer in the ethylene-propylene rubber gives good punching properties to the support layer 2 by satisfying the weight percentage (for example, 18% - 30%).

[0072] More specifically, the vinyl elastomer may be, for example, an ethylene / butene elastomer. The ethylene / butene elastomer is a copolymer composed of ethylene, butene, and a trace amount of a carboxyl group-containing crosslinking monomer (bridging terminal monomers having carboxylic acid groups). Here, the weight percentage of the ethylene in the vinyl elastomer is 30% or more, preferably 30% to 60%.

[0073] Thereby, the vinyl elastomer can provide the support layer 2 with better punching properties and avoid the whitening phenomenon that occurs during punching.

[0074] The polyolefin copolymer modified with maleic anhydride in the support layer 2 is, for example, similar to the material characteristics of the adhesive layer 1. The polyolefin copolymer is formed by performing a copolymerization reaction of at least two types among C2-C4 olefin molecules. More specifically, the grafting rate of the maleic anhydride in the polyolefin copolymer is 1% to 5%. The melt index of the polyolefin copolymer modified with maleic anhydride is controlled to be 1 g / 10 min to 5 g / 10 min.

[0075] In this embodiment, since the support layer 2 contains a polyolefin copolymer modified with a small amount of maleic anhydride (for example, 5 to 20 wt%), the support layer 2 has a high affinity with the adhesive layer 1, so a good interlayer adhesion strength is provided between the support layer 2 and the adhesive layer 1.

[0076] If the content of the polyolefin copolymer modified with maleic anhydride in the support layer 2 is lower than the above content range, the interlayer adhesion strength deteriorates. On the other hand, if the content of the second polyolefin copolymer modified with maleic anhydride in the support layer 2 is higher than the above content range, the punching of the packaging material deteriorates.

[0077] More specifically, the lubricant may be, for example, silicon dioxide (SiO2) or talc that can improve the punching and processability of the support layer 2, but the present invention is not limited thereto. In addition, in the present embodiment, the lubricant in the support layer 2 is not surface-treated with epoxy siloxane, but the present invention is not limited thereto.

[0078] More specifically, the visible light transmittance of the support layer 2 may be 80% to 99% and the haze value may be 5% to 30%, but the present invention is not limited thereto. It should be noted that the visible light transmittance and the haze value are measured based on ASTM D1003.

[0079] Subsequently, as shown in FIG. 1, the heat seal layer 3 is formed of a propylene polymer.

[0080] For example, the propylene polymer may be at least one of a propylene copolymer (co-PP) and a propylene homopolymer (homo-PP). The propylene copolymer may be formed by copolymerizing propylene and ethylene, for example. In the present embodiment, the weight ratio of ethylene in the propylene copolymer is preferably 2% or less. Thereby, the heat seal layer 3 can provide excellent heat seal strength to the polyolefin adhesive film 100.

[0081] According to the above technical solution, the polyolefin adhesive film 100 according to the embodiment of the present invention, as shown in FIGS. 2 and 3, by coextrusion, directly thermally laminates the adhesive layer 1 formed on the support layer 2 with the metal aluminum foil AF, and there is no need to adhere with other polyester adhesives or polyurethane adhesives. The polyolefin adhesive film 100 according to the present invention not only has self-bonding properties but also can solve the problem of volatilization of volatile organic solvents (VOCs) in the prior art.

[0082] In addition, the polyolefin adhesive film 100 according to the embodiment of the present invention can solve the problem that the adhesive strength is insufficient due to the reduction in strength of the conventional dry-laminated polyolefin film / aluminum foil packaging material in a long-term high-temperature and high-humidity environment.

[0083] In addition, the heat-sealing layer 3 of the polyolefin adhesive film 100 according to the present invention has excellent heat-sealing strength. The heat-sealing strength of the polyolefin adhesive film 100 according to the embodiment of the present invention, measured based on QB / T2358-1998, can reach 83 N / 15 mm or more. The measurement conditions are, for example, heat-sealing at a temperature of 180 °C and a pressure of 1 kgf / cm 2 for 3 seconds, and then cutting the sample into 15 mm × 15 mm for measurement. Even after the polyolefin adhesive film is immersed in an electrolytic solution environment at 85 °C for 168 hours, it has a peel strength exceeding 14.6 N / 15 mm.

[0084] The polyolefin adhesive film 100 according to the embodiment of the present invention has good adhesiveness with a metal aluminum foil AF (for example, an aluminum plastic film). The polyolefin adhesive film 100 and the metal aluminum foil AF can avoid delamination and expansion between layers of the material and leakage of the electrolytic solution at a high operating temperature. The polyolefin adhesive film 100 according to the present embodiment is particularly applicable to high-output wattage power batteries in electric vehicles and is used as an electronic packaging material for lithium batteries.

[0085] [Experimental data and measurement results] To prove the above technical effects of the polyolefin adhesive film according to the present invention, examples and comparative examples will be described below. Among them, the examples are the group that proves the technical effects of the present invention, and the comparative examples are the group with inferior test effects. However, these examples are for understanding the present invention, and the present invention is not limited thereto.

[0086] <Example 1> A three-layer polyolefin adhesive film was formed by co-extrusion, with an adhesive layer, a support layer, and a heat-sealing layer laminated in this order. Here, the adhesive layer contained a polyolefin copolymer modified with maleic anhydride. The polyolefin copolymer was formed by copolymerizing propylene (C3) and butene (C4) in a molar ratio of 50:50. The amount of the polyolefin copolymer used was 99.5 parts by weight. The graft ratio of maleic anhydride (MA) in the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The adhesive layer further contained silicon dioxide particles surface-treated with epoxy siloxane, and the amount used was 1000 ppm (parts per million). The modification amount (surface treatment weight ratio) of the silicon dioxide particles surface-treated with epoxy siloxane was 0.5%, and the average particle diameter D50 of the silicon dioxide particles was 5 μm. Also, assuming the total weight of the support layer is 100 parts by weight, the support layer contained 70 parts by weight of a propylene block copolymer, 20 parts by weight of a vinyl-based elastomer (e.g., ethylene / butene elastomer), 9.9 parts by weight of a polyolefin copolymer modified with maleic anhydride, and a small amount of non-surface-treated silicon dioxide particles. The heat-sealing layer was composed of a propylene copolymer (co-PP) formed by copolymerizing propylene and ethylene, and the weight ratio of ethylene was less than 2%. Also, the thickness of the adhesive layer was 8 μm, the thickness of the support layer was 24 μm, and the thickness of the heat-sealing layer was 8 μm. The haze value of the polyolefin adhesive film according to <Example 1> was 7%, and it had no significant streaks in appearance. The heat-sealing strength of the polyolefin adhesive film according to QB / T2358-1998 was approximately 87 N / 15 mm. The polyolefin adhesive film was laminated with an aluminum foil through the adhesive layer, and the peel strength between the polyolefin adhesive film and the aluminum foil was 14.7 N / 15 mm.Further, an aluminum-plastic film formed by laminating the polyolefin adhesive film and the aluminum foil was immersed in an electrolytic solution environment at 85°C for 168 hours for measurement. The aluminum-plastic film had a peel strength (i.e., interlayer adhesion strength) of 13.5 N / 15 mm, indicating that the polyolefin adhesive film had extremely high resistance to high-temperature and high-humidity environments. Also, the formed height of the aluminum-plastic film was 6.5 mm, which was particularly applicable to high-output wattage power batteries in electric vehicles and was used as an electronic packaging material for lithium batteries.

[0087] The manufacturing methods of the polyolefin adhesive films according to Examples 2 to 4 and Comparative Examples 1 to 3 are basically the same as those of Example 1, and their differences lie in the usage amounts of materials and parameters, and their conditions are as shown in Table 1 below.

[0088] <Example 2> In the adhesive layer, the amount of the polyolefin copolymer used was 99.5 parts by weight. The grafting rate of maleic anhydride (MA) in the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The amount of silicon dioxide particles surface-treated with epoxy siloxane was 1000 ppm. The modification amount of the silicon dioxide particles surface-treated with epoxy siloxane was 1%, and the average particle diameter D50 of the silicon dioxide particles was 5 μm. Also, the support layer contained 70 parts by weight of a propylene block copolymer, 20 parts by weight of an ethylene / butene elastomer, 9.9 parts by weight of a polyolefin copolymer modified with maleic anhydride, and a small amount of non-surface-treated silicon dioxide particles. The heat-sealing layer was formed of a propylene copolymer (co-PP). <Example 2> The haze value of the polyolefin adhesive film was 7.2%, and it had no obvious streaks in appearance. The heat-sealing strength of the polyolefin adhesive film according to QB / T2358-1998 was about 86 N / 15 mm. The peel strength between the polyolefin adhesive film and the aluminum foil was 17.8 N / 15 mm. The aluminum-plastic film formed by laminating the polyolefin adhesive film and the aluminum foil was immersed in an electrolytic solution environment at 85 °C for 168 hours for measurement, and the aluminum-plastic film had a peel strength of 16.6 N / 15 mm. Also, the forming height of the aluminum-plastic film was 6.5 mm.

[0089] <Example 3>In the adhesive layer, the amount of the polyolefin copolymer used was 99.5 parts by weight. The grafting rate of maleic anhydride (MA) in the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The amount of silicon dioxide particles surface-treated with epoxy siloxane was 1000 ppm. The modification amount of the silicon dioxide particles surface-treated with epoxy siloxane was 1.5%, and the average particle diameter D50 of the silicon dioxide particles was 5 μm. Further, the support layer contained 70 parts by weight of a propylene block copolymer, 20 parts by weight of an ethylene / butene elastomer, 9.9 parts by weight of a polyolefin copolymer modified with maleic anhydride, and a small amount of non-surface-treated silicon dioxide particles. The heat-sealing layer was formed of a propylene copolymer (co-PP). <Example 3>The haze value of the polyolefin adhesive film was 9.5%, and it had no obvious streaks in appearance. The heat-sealing strength of the polyolefin adhesive film according to QB / T2358-1998 was about 85 N / 15 mm. The peel strength between the polyolefin adhesive film and the aluminum foil was 16 N / 15 mm. The aluminum-plastic film formed by laminating the polyolefin adhesive film and the aluminum foil was immersed in an electrolytic solution environment at 85°C for 168 hours for measurement, and the aluminum-plastic film had a peel strength of 15 N / 15 mm. Further, the forming height of the aluminum-plastic film was 6.5 mm.

[0090] <Example 4>In the adhesive layer, the amount of the polyolefin copolymer used was 99.5 parts by weight. The grafting rate of maleic anhydride (MA) in the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The amount of silicon dioxide particles surface-treated with epoxy siloxane was 1000 ppm. The modification amount of the silicon dioxide particles surface-treated with epoxy siloxane was 2.0%, and the average particle diameter D50 of the silicon dioxide particles was 5 μm. Further, the support layer contained 70 parts by weight of a propylene block copolymer, 20 parts by weight of an ethylene / butene elastomer, 9.9 parts by weight of a polyolefin copolymer modified with maleic anhydride, and a small amount of non-surface-treated silicon dioxide particles. The heat-sealing layer was formed of a propylene copolymer (co-PP). <Example 4>The haze value of the polyolefin adhesive film was 12%, and it had no obvious streaks in appearance. The heat-sealing strength of the polyolefin adhesive film according to QB / T2358-1998 was about 85 N / 15 mm. The peel strength between the polyolefin adhesive film and the aluminum foil was 15.3 N / 15 mm. The aluminum-plastic film formed by laminating the polyolefin adhesive film and the aluminum foil was immersed in an electrolytic solution environment at 85 °C for 168 hours for measurement, and the aluminum-plastic film had a peel strength of 13.5 N / 15 mm. Further, the forming height of the aluminum-plastic film was 6.5 mm.

[0091] <Comparative Example 1>In the adhesive layer, the amount of the polyolefin copolymer used was 99.5 parts by weight. The grafting rate of maleic anhydride (MA) in the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The silicon dioxide particles of Comparative Example 1 were not surface-treated and the amount used was 1000 ppm. The average particle diameter D50 of the silicon dioxide particles was 5 μm. Also, the support layer contained 70 parts by weight of a propylene block copolymer, 20 parts by weight of an ethylene / butene elastomer, 9.9 parts by weight of a polyolefin copolymer modified with maleic anhydride, and a small amount of non-surface-treated silicon dioxide particles. The heat-sealing layer was formed of a propylene copolymer (co-PP). As a result of the test, <Comparative Example 1> The haze value of the polyolefin adhesive film was 7%, and it had no significant streaks in appearance. The heat-sealing strength of the polyolefin adhesive film according to QB / T2358-1998 was about 82 N / 15 mm. The peel strength between the polyolefin adhesive film and the aluminum foil was 14.2 N / 15 mm. The aluminum-plastic film formed by laminating the polyolefin adhesive film and the aluminum foil was immersed in an electrolyte environment at 85°C for 168 hours for measurement, and the aluminum-plastic film had a peel strength of 13.2 N / 15 mm. Also, the forming height of the aluminum-plastic film was 6.5 mm.

[0092] <Comparative Example 2>In the adhesive layer, the amount of the polyolefin copolymer used was 99.5 parts by weight. The grafting rate of maleic anhydride (MA) in the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The silicon dioxide particles of Comparative Example 2 were not surface-treated and the amount used was 2,000 ppm. The average particle diameter D50 of the silicon dioxide particles was 5 μm. Also, the support layer contained 70 parts by weight of a propylene block copolymer, 20 parts by weight of an ethylene / butene elastomer, 9.9 parts by weight of a polyolefin copolymer modified with maleic anhydride, and a small amount of non-surface-treated silicon dioxide particles. The heat-seal layer was formed of a propylene copolymer (co-PP). As a result of the test, <Comparative Example 2> the haze value of the polyolefin adhesive film was 15% and it had no significant streaks in appearance. The heat-seal strength of the polyolefin adhesive film according to QB / T 2358-1998 was about 82 N / 15 mm. The peel strength between the polyolefin adhesive film and the aluminum foil was 11.2 N / 15 mm. An aluminum-plastic film formed by laminating the polyolefin adhesive film and the aluminum foil was immersed in an electrolytic solution environment at 85°C for 168 hours for measurement, and the aluminum-plastic film had a peel strength of 9.2 N / 15 mm. Also, the forming height of the aluminum-plastic film was 5.5 mm.

[0093] <Comparative Example 3>In the adhesive layer, the amount of the polyolefin copolymer used was 99.5 parts by weight. The grafting rate of maleic anhydride (MA) in the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The silicon dioxide particles of Comparative Example 3 were not surface-treated and the amount used was 1,000 ppm. The average particle diameter D50 of the silicon dioxide particles was 2 μm. Also, the support layer contained 70 parts by weight of a propylene block copolymer, 20 parts by weight of an ethylene / butene elastomer, 9.9 parts by weight of a polyolefin copolymer modified with maleic anhydride, and a small amount of non-surface-treated silicon dioxide particles. The heat seal layer was formed of a propylene copolymer (co-PP). As a result of the test, <Comparative Example 3> the haze value of the polyolefin adhesive film was 6.8%, and it had no significant streaks in appearance. The heat seal strength of the polyolefin adhesive film according to QB / T2358-1998 was about 82 N / 15 mm. The peel strength between the polyolefin adhesive film and the aluminum foil was 14.5 N / 15 mm. The aluminum-plastic film formed by laminating the polyolefin adhesive film and the aluminum foil was immersed in an electrolytic solution environment at 85°C for 168 hours for measurement, and the aluminum-plastic film had a peel strength of 13 N / 15 mm. The forming height of the aluminum-plastic film was 6.5 mm. Also, <Comparative Example 3> the rewinding test of the polyolefin adhesive film was NG.

[0094]

Table 1

[0095] It should be noted that the measurement methods of the above-mentioned "haze value" and "heat seal strength" have already been described in the above embodiments, so they will not be described repeatedly here. Further explanation is as follows: The peel strength in this specification is the maximum force required to peel a unit width of the materials adhered to each other (for example, the peel strength between a polyolefin adhesive film and an aluminum foil) from the contact surface. A universal testing machine is used as the measuring device. The error of the measured value of the testing machine is within ±1% of the actual value. Regarding the measurement environment, the sample is left standing for 4 hours or more at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%, and the measurement is carried out in this environment. Regarding the production of the sample, the object to be measured is cut into 5 strips of samples with a width of 15.0 mm ± 0.1 mm and a length of 200 mm so as to be uniform by removing 50 mm from both ends in the width direction. The measurement method is that both ends of the peeled part of the sample are respectively clamped by the upper and lower jigs of the testing machine, and the vertical axis of the peeled part of the sample is appropriately fitted so as to coincide with the center connection line of the upper and lower jigs. The measurement speed is 300 mm / min ± 30 mm / min, and the peel force curve during the peeling process of the sample is recorded. The arithmetic mean of the peel strengths in the longitudinal and transverse directions of the sample is measured as the measurement result (taking 2 significant figures), and its unit is N / 15 mm.

[0096] Further explanation is as follows: The "molding height" in this specification is the height recorded by filling with cold pressure using a mold of a lithium battery of 5 cm × 6 cm, and its unit is mm.

[0097] The evaluation method for the appearance of the packaging material is that the test personnel observed the surface of the biaxially stretched polypropylene film of the packaging material with the naked eye (the observation distance was about 30 cm). When no obvious streaks were observed, it was rated as "no streaks". When obvious streaks were observed, it was rated as "obvious streaks". When the haze value of the packaging material was too high, it was rated as "unobservable".

[0098] [Examination of Measurement Results] Regarding the measurement results, the polyolefin adhesive films according to Examples 1 to 4 had a heat seal strength of 85 to 87 N / 15 mm, which was higher than 82 N / 15 mm of the comparative example. The peel strength between the polyolefin adhesive films according to Examples 1 to 4 and aluminum foil was 14.7 to 17.8 N / 15 mm, which was higher than 11.2 to 14.5 N / 15 mm of the comparative example. An aluminum plastic film formed by laminating a polyolefin adhesive film and aluminum foil was immersed in an electrolytic solution at 85°C for 168 hours for measurement. The aluminum plastic films according to Examples 1 to 4 had a peel strength of 13.5 to 16.6 N / 15 mm, which was higher than 9.2 to 13.2 N / 15 mm of the comparative example.

[0099] Thus, the polyolefin adhesive films according to Examples 1 to 4 are applicable to high-output wattage power batteries in electric vehicles and are used as electronic packaging materials for lithium batteries as compared with Comparative Examples 1 to 3.

[0100] Notably, since the amount of silicon dioxide particles used in the adhesive layer in Comparative Example 2 was 2,000 ppm, the haze value of the polyolefin adhesive film was significantly increased (15%). Since the average particle diameter of silicon dioxide in the adhesive layer of Comparative Example 3 was 2 μm, the unwindability of the polyolefin adhesive film was poor (NG). Both the amount and particle diameter of the silicon dioxide particles have a certain influence on the physical properties of the polyolefin adhesive film.

[0101] [Second Embodiment] As shown in FIG. 5, the second embodiment of the present invention provides a polyolefin adhesive film 100' comprising an adhesive layer 1 and a support layer 2. Among them, the adhesive layer 1 is formed on the support layer 2 by coextrusion. Different from the above-described first embodiment, the polyolefin adhesive film 100' of the second embodiment of the present invention may not include, for example, a heat-sealing layer 3. In the second embodiment, since the material characteristics of the adhesive layer 1 and the support layer 2 are similar to those of the first embodiment, they will not be described repeatedly here. With the above-described configuration, the polyolefin adhesive film 100' according to the second embodiment of the present invention directly heat-laminates the adhesive layer 1 formed on the support layer 2 by coextrusion with the metal aluminum foil AF, without the need to adhere with other polyester adhesives or polyurethane adhesives.

[0102] [Advantageous Effects According to the Embodiment] As an advantageous effect of the present invention, the polyolefin adhesive film according to the present invention comprises "a support layer that is a polypropylene film and an adhesive layer formed on one side of the support layer by coextrusion", "the adhesive layer contains a polyolefin copolymer modified with maleic anhydride and inorganic particles dispersed in the polyolefin copolymer and surface-treated with epoxy siloxane", "the grafting rate of maleic anhydride in the polyolefin copolymer is 1% to 5%, and the surface treatment weight ratio of the epoxy siloxane to the inorganic particles (epoxy siloxane / inorganic particles (weight)) is 0.3% to 4%", and "when the polyolefin adhesive film is subjected to a heating operation, a crosslinking reaction occurs between the epoxy siloxane surface-treated on the inorganic particles and the maleic anhydride modified in the polyolefin copolymer so that the hardness of the adhesive layer is improved". Due to such technical features, the adhesiveness between the polyolefin adhesive layer and the metal aluminum foil (for example, an aluminum plastic film) is good, and it is possible to avoid the occurrence of layer separation or expansion of the materials and leakage of the electrolyte at a high operating temperature of the polyolefin adhesive film and the metal aluminum foil. The polyolefin adhesive film is particularly applicable to the aluminum plastic film packaging material of a high-output wattage power battery in an electric vehicle.

[0103] The content disclosed above is only a preferred feasible embodiment of the present invention, and the scope of the claims of the present invention is not limited thereto. Therefore, all equivalent technical changes made using the content of the specification and drawings of the present invention are included in the scope of the claims of the present invention.

Explanation of Reference Numerals

[0104] <This Embodiment> 100, 100’ Polyolefin Adhesive Film 1 Adhesive Layer 11 Polyolefin Copolymer 12 Inorganic Particles 12a Epoxy Siloxane 2 Support Layer 3 Heat Seal Layer T1 First thickness T2 Second thickness T3 Third thickness AF Aluminum metal foil <Prior art> AF Aluminum metal foil GL Adhesive layer PL Polymer film

Claims

1. A polyolefin adhesive film comprising a support layer that is a polypropylene film and an adhesive layer formed on one side of the support layer by coextrusion, wherein the adhesive layer contains a polyolefin copolymer modified with maleic anhydride and inorganic particles dispersed in the polyolefin copolymer and surface-treated with an epoxy siloxane, the grafting rate of the maleic anhydride in the polyolefin copolymer is 1% to 5%, and the surface treatment weight ratio of the epoxy siloxane to the inorganic particles (epoxy siloxane / inorganic particles (weight)) is 0.3% to 4%, when the polyolefin adhesive film is subjected to a heating operation, a crosslinking reaction occurs between the epoxy siloxane surface-treated on the inorganic particles and the maleic anhydride modified in the polyolefin copolymer so that the hardness of the adhesive layer is improved. A polyolefin adhesive film characterized by that.

2. In the adhesive layer, with the total weight of the adhesive layer being 100 wt%, the content of the polyolefin copolymer modified with maleic anhydride is 90 wt% or more, and the content of the inorganic particles surface-treated with an epoxy siloxane is 500 ppm to 2,000 ppm. The polyolefin adhesive film according to Claim 1.

3. In the adhesive layer, the average particle diameter of the inorganic particles is 1 μm to 8 μm, the average sphericity of the inorganic particles is 0.7 to 1.0, and the inorganic particles are at least one selected from the group consisting of silicon dioxide particles, calcium carbonate particles, barium sulfate particles, kaolin particles, and mica particles. The polyolefin adhesive film according to Claim 2.

4. In the adhesive layer, the average particle diameter of the inorganic particles is 3 μm to 6 μm, and the sphericity of the inorganic particles is 0.8 to 1.

0. The polyolefin adhesive film according to Claim 3.

5. The polyolefin copolymer in the adhesive layer is formed by copolymerizing at least two types of C2-C4 olefin molecules, and the melt index of the polyolefin copolymer is 3 g / 10 min to 5 g / 10 min. The polyolefin adhesive film according to Claim 1.

6. The grafting rate of the maleic anhydride in the polyolefin copolymer is 2% to 4%, and the surface treatment weight ratio of the epoxy siloxane to the inorganic particles (epoxy siloxane / inorganic particles (weight)) is 0.5% to 2%. The polyolefin adhesive film according to claim 5.

7. The support layer is a cast polypropylene film containing a propylene block polymer, a vinyl-based elastomer, and a polyolefin copolymer. The polyolefin adhesive film according to claim 1.

8. In the support layer, the propylene block polymer includes a block composed of ethylene propylene rubber, and the weight percentage of the ethylene propylene rubber in the propylene block polymer is 18% or more. The vinyl-based elastomer is an ethylene / butene elastomer, and the weight percentage of ethylene in the vinyl-based elastomer is 30% or more. The polyolefin adhesive film according to claim 7.

9. The polyolefin adhesive film according to claim 1, further comprising a heat seal layer formed on the other surface of the support layer by coextrusion.

10. The heat seal layer is formed of a propylene polymer, and the propylene polymer is at least one of a propylene copolymer (co-PP) and a propylene homopolymer (homo-PP). The polyolefin adhesive film according to claim 9.

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