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 adhesive films, and more particularly to polyolefin adhesive films. [Background technology]

[0002] As shown in Figure 6, conventional aluminum-plastic film packaging materials often use a dry composite polyolefin film PL / aluminum foil AF. The two materials are bonded together with an adhesive layer GL (e.g., polyester adhesive or polyurethane adhesive). However, conventional aluminum-plastic film packaging materials suffer from the problem of easily volatilizing volatile organic solvents (VOCs) during the lamination process. Furthermore, when conventional aluminum-plastic film packaging materials are left in a high-temperature, high-humidity environment for a long period of time, the adhesive strength between the polyolefin film PL and the aluminum foil AF deteriorates, resulting in insufficient adhesive strength. Furthermore, when used in high-wattage power batteries for electric vehicles, existing aluminum-plastic film packaging materials are prone to delamination and expansion at high operating temperatures, resulting in electrolyte leakage.

[0003] Therefore, the inventors of the present invention have realized that the above-mentioned problems can be improved, and as a result of conducting extensive research and applying scientific theory, have arrived at the present invention as a method that is rational in design and can effectively improve the above-mentioned problems. Summary of the Invention [Problem to be solved by the invention]

[0004] The technical problem that the present invention seeks to solve is to provide a polyolefin adhesive film that addresses the shortcomings of the prior art. [Means for solving the problem]

[0005] To solve the above technical problems, one technical solution 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 comprises a polyolefin copolymer modified with maleic anhydride and inorganic particles dispersed in the polyolefin copolymer and surface-treated with epoxy siloxane, the graft ratio of the maleic anhydride to the polyolefin copolymer being 1% to 5% and the weight ratio of the epoxy siloxane to the inorganic particles (epoxy siloxane / inorganic particles (weight)) being 0.3% to 4%. When the polyolefin adhesive film is heated, 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, the content of the polyolefin copolymer modified with maleic anhydride is 90 wt% or more, and the amount of inorganic particles surface-treated with epoxysiloxane added is 500 ppm to 2,000 ppm, with the total weight of the adhesive layer being 100 wt%.

[0007] Preferably, in the adhesive layer, the inorganic particles have an average particle size of 1 μm to 8 μm, a sphericity of 0.7 to 1.0, and 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 size of the inorganic particles is 3 μm to 6 μm, and the sphericity of the inorganic particles is 0.8 to 1.0.

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

[0010] Preferably, the graft ratio of the maleic anhydride to 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%.

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

[0012] Preferably, in the support layer, the propylene block polymer includes a block composed of an ethylene propylene elastic rubber, and the weight percentage of the ethylene propylene elastic rubber in the propylene block polymer is 18% or more, and 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 comprises a heat seal layer formed on the other side of the support layer by coextrusion.

[0014] Preferably, 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). [Effects of the Invention]

[0015] Advantageous effects of the present invention include the following technical features of the polyolefin adhesive film of the present invention: "It comprises a support layer which is a polypropylene film and an adhesive layer formed on one side of the support layer by coextrusion," "The adhesive layer comprises a polyolefin copolymer modified with maleic anhydride and inorganic particles dispersed in the polyolefin copolymer and surface-treated with epoxy siloxane," "The graft ratio of the maleic anhydride to 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 heated, a crosslinking reaction occurs between the epoxy siloxane surface-treated on the inorganic particles and the maleic anhydride modified on the polyolefin copolymer." These technical features ensure good adhesion between the polyolefin adhesive layer and metal aluminum foil (e.g., aluminum plastic film), and prevent electrolyte leakage due to delamination or expansion of the polyolefin adhesive film and metal aluminum foil at high operating temperatures. The polyolefin adhesive film is particularly suitable for aluminum plastic film packaging materials for high wattage power batteries in electric vehicles. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of a polyolefin film according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram (1) showing the process of laminating the polyolefin film of FIG. 1 to aluminum foil. [Figure 3] This is a schematic diagram (2) of laminating the polyolefin film of Figure 1 to aluminum foil. [Figure 4] FIG. 2 is a partial enlarged view of a portion IV in FIG. [Figure 5] FIG. 2 is a schematic diagram of a polyolefin film according to a second embodiment of the present invention. [Figure 6] 1 is a schematic diagram of a conventional aluminum plastic film packaging material. DETAILED DESCRIPTION OF THE INVENTION

[0017] To better understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings, which are provided for reference and explanation only and are not intended to limit the scope of the present invention.

[0018] The following describes embodiments of the present invention through certain specific embodiments, allowing those skilled in the art to understand the advantages and benefits of the present invention based on the disclosure herein. The present invention can be implemented or applied in other different specific embodiments, and various modifications and changes can be made to the details herein based on different perspectives and applications, without departing from the concept of the present invention. As previously explained, the accompanying drawings of the present invention are for simple schematic illustrations and are not drawn to scale. The technical content of the present invention will be described in more detail based on the following embodiments, but the disclosed content does not limit the scope of protection of the present invention. It should be understood that although terms such as "first," "second," and "third" may be used to describe various materials or parameters in this specification, these materials or parameters are not limited by these terms. These terms are primarily used to distinguish one material from another or one parameter from another. The term "or" used in this specification may include any one or more combinations of the relevant listed items, depending on the actual situation.

[0019] [First embodiment] As shown in Figures 1 to 4, in the first embodiment of the present invention, a polyolefin adhesive film 100 comprises an adhesive layer 1, a support layer 2, and a heat-seal 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 Figure 1). The heat-seal layer 3 is formed on the other side of the support layer 2 (for example, the lower surface of the support layer 2 in Figure 1). That is, the support layer 2 is located between the adhesive layer 1 and the heat-seal layer 3.

[0020] In this embodiment, the adhesive layer 1, the support layer 2, and the heat seal layer 3 of the polyolefin adhesive film 100 are formed as a laminate structure by co-extrusion, i.e., the adhesive layer 1 is formed on the support layer 2 by co-extrusion.

[0021] As shown in Figures 2 and 3, the polyolefin adhesive film 100 is combined with a metal aluminum foil AF (aluminum foil) via the adhesive layer 1. The support layer 2 provides impact resistance and support to the polyolefin adhesive film 100. The heat seal layer 3 provides heat sealability to the polyolefin adhesive film 100. As a result, the polyolefin adhesive film 100 is suitable for use as a packaging material, particularly as a packaging material for lithium batteries or electronic products, although the present invention is not limited thereto.

[0022] It is worth noting that the polyolefin adhesive film 100 according to this embodiment is particularly suitable for high wattage power batteries in electric vehicles, and is also used as an electronic packaging material for lithium batteries.

[0023] Furthermore, the polyolefin adhesive film 100 according to an embodiment of the present invention has good adhesion to the metal aluminum foil AF (e.g., aluminum plastic film), which prevents the polyolefin adhesive film 100 and the metal aluminum foil AF from delaminating or expanding at high operating temperatures, which can lead to electrolyte leakage.

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

[0025] In other words, the total thickness of the polyolefin adhesive film 100 is 20 μm to 60 μm, and 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] To explain further, 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 copolymerizing at least two of C2 to C4 olefin molecules. Those skilled in the art will recognize that the C2 olefin molecule is ethylene (PE), the C3 olefin molecule is propylene (PP), and the C4 olefin molecule is butene, such as 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 to 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 types of olefin molecules (e.g., 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 is noteworthy that the polyolefin copolymer 11 according to this embodiment is formed by copolymerizing at least two types of C2 to C4 olefin molecules, and therefore the polyolefin adhesive layer 2 has both higher transparency and adhesive strength.

[0031] More specifically, in this embodiment, the polyolefin copolymer 11 is modified with maleic anhydride (MAH). The maleic anhydride-modified polyolefin copolymer 11 has a carboxyl group (-COOH), which significantly improves the polarity of the polyolefin copolymer. As a result, the polyolefin copolymer 11 of the present invention has superior water solubility and adhesive strength compared to unmodified polyolefin copolymers, making it more suitable for use as the adhesive layer 1.

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

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

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

[0035] It is noteworthy that in this embodiment, when the graft ratio of maleic anhydride is controlled to 1% to 5%, excellent adhesive strength can be obtained. If the graft ratio of maleic anhydride is less than 1%, the adhesive strength of the adhesive layer 1 deteriorates. On the other hand, if the graft ratio of maleic anhydride is more than 5%, the adhesive layer becomes too hard after being bonded to the aluminum foil, affecting the flex resistance of the packaging material.

[0036] It should be noted that the grafting rate of maleic anhydride in this specification can be analyzed, for example, by a Fourier transform infrared spectrometer (FTIR), which can perform a qualitative analysis of whether maleic anhydride is grafted onto the molecular chain of a polyolefin copolymer and can also quantify the grafting rate of maleic anhydride.

[0037] According to the infrared absorption spectrum, maleic anhydride grafts were detected at 1725 cm -1 , 1790cm -1 The graft ratio of maleic anhydride can be quantitatively analyzed based on the Beer-Lambert law.

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

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

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

[0041] It is noteworthy that when the melt index of the polyolefin copolymer 11 is controlled to 1 g / 10 min to 5 g / 10 min, the adhesive layer is provided with better adhesive strength and transparency, and also with 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, the adhesive strength of the adhesive layer 1 may be poor, and streaks may occur on the surface of the packaging material.

[0043] It should be noted that the melt index in this specification is the weight of a polyolefin copolymer extruded from the opening of an extrusion plastometer in 10 minutes. The unit is g / 10 min. The melt index indicates the fluidity in a molten state; the higher the melt index, the lower the molecular weight and the better the fluidity. Conversely, the lower the melt index, the higher the molecular weight, the less mobility of molecular chains, and the worse the fluidity. In this embodiment, the melt index is measured according to ASTM D1238 at 190°C and a load of 2.16 kg.

[0044] To explain further, as shown in FIG. 4, the surface-treated inorganic particles 12 are surface-treated with epoxy siloxane, so that the surfaces of the inorganic particles 12 are modified with epoxy siloxane 12a.

[0045] More specifically, the inorganic particles 12 are surface-treated by immersing them in an aqueous solution of epoxysiloxane, whereby the liquid epoxysiloxane is modified into the inorganic particles 12 in a solid state.

[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 the maleic anhydride in the polyolefin copolymer 11. Here, the crosslinking reaction has a faster reaction rate and a higher degree of crosslinking hardening, particularly when a heating operation (e.g., thermocompression bonding) is performed, but the present invention is not limited thereto.

[0047] In addition, the functional group (epoxy group) of the epoxy siloxane 12a attached to the inorganic particles 12 can also undergo a cross-linking reaction by itself, so that the adhesive layer 1 can achieve a better hardening effect.

[0048] Due to the above-described configuration, the adhesive layer 1 of the polyolefin adhesive film 100 according to an embodiment of the present invention has good adhesion to the metal aluminum foil AF (e.g., aluminum plastic film), and it is possible to avoid delamination or expansion of the materials between the polyolefin adhesive film 100 and the metal aluminum foil AF at high operating temperatures, which would otherwise cause leakage of the electrolyte.

[0049] It is worth noting that epoxy siloxane, which is normally in a liquid state, is difficult to disperse uniformly in a polyolefin copolymer. However, in the embodiment of the present invention, the surfaces of the inorganic particles 12 are modified with epoxy siloxane, so that the epoxy siloxane can be dispersed uniformly 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 (SiO), calcium carbonate particles (CaCO), barium sulfate particles (BaSO), kaolinite clay particles, and mica particles.

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

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

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

[0054] If the average particle size of the inorganic particles is lower than the lower limit of the particle size (for example, less than 1 μm), the effect of the inorganic particles in improving the adhesion between the adhesive layer 1 and the metal aluminum foil AF is not significant. If the average particle size of the inorganic particles exceeds the upper limit of the particle size (for example, more than 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 (ie, the modification amount) is 0.3% to 4%, preferably 0.4% to 3%, and particularly preferably 0.5% to 2%.

[0056] That is, 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, relative to 100 parts by weight of the inorganic particles.

[0057] It is particularly noteworthy 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 adhesion between the adhesive layer 1 and the metal aluminum foil AF is relatively remarkable.

[0058] If the weight ratio of epoxy siloxane exceeds 4%, the amount of modification of epoxy siloxane 12a on the surface of the inorganic particles 12 tends to saturate, which is not very useful in improving the adhesion between the adhesive layer 1 and the metal aluminum foil AF and may affect the haze value of the adhesive layer 1.

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

[0060] It is worth noting that in this embodiment, the weight ratio of the epoxysiloxane to the inorganic particles (modification amount) may be measured by quantitative analysis, for example, thermogravimetric analysis (TGA). For example, inorganic particles surface-treated with epoxysiloxane are combusted at a high temperature of 800°C, and the weight loss before and after combustion is measured, and the resulting weight loss is the modification amount. Here, 800°C is above the boiling point of epoxysiloxane but below the melting point of inorganic particles (e.g., SiO). Furthermore, whether the epoxysiloxane is modified with inorganic particles may be measured by qualitative analysis using a Fourier transform infrared spectrometer (FT-IR). For example, the gas generated after combustion may be analyzed to determine whether it has a characteristic absorption peak of the epoxy functional group, but the present invention is not limited thereto.

[0061] In one embodiment of the present invention, the amount of inorganic particles surface-treated with epoxysiloxane added to the polyolefin adhesive layer 1 is 500 ppm to 2,000 ppm, preferably 500 ppm to 1,500 ppm, thereby achieving a relatively significant effect of improving the adhesion between the adhesive layer 1 and the metal aluminum foil AF.

[0062] If the amount of the inorganic particles surface-treated with epoxy siloxane is less than 500 ppm, the polyolefin adhesive film 100 may stick to itself when wound up. Conversely, if the amount of the inorganic particles surface-treated with epoxy siloxane is more than 2000 ppm, the haze value of the polyolefin adhesive film 100 will be too high.

[0063] It is worth noting that the polyolefin copolymer is produced by, for example, processing and granulating in a twin-screw extruder in the presence of a peroxidant (0.3 to 0.6% peroxidant), and during the extrusion process, maleic anhydride is melt-grafted and the inorganic particles surface-treated with epoxysiloxane are dispersed. The melt index of the polyolefin copolymer can also be controlled.

[0064] To further explain, a polyolefin copolymer formed by granulation (grafted to maleic anhydride and having dispersed therein inorganic particles surface-treated with epoxysiloxane) may be co-extruded, for example, to form the polyolefin adhesive layer 1 on one surface of the support layer 2.

[0065] By using the above technical solution, the polyolefin adhesive film 100 according to an embodiment of the present invention can be thermally laminated with the metal aluminum foil AF via its adhesive layer 1, as shown in Figures 2 and 3, without the need for other polyester or polyurethane adhesives.

[0066] The polyolefin adhesive film 100 according to the present invention not only has self-adhesive properties, but also solves the problem of volatile organic solvent (VOC) evaporation that occurs in conventional technologies. Furthermore, the polyolefin adhesive film 100 according to the present invention has good adhesion to the metal aluminum foil AF (e.g., aluminum plastic film), which prevents electrolyte leakage due to delamination or expansion of the materials between the polyolefin adhesive film 100 and the metal aluminum foil AF at high operating temperatures.

[0067] As shown in FIG. 1, the support layer 2 is a cast polypropylene film (CPP film, also called unstretched polypropylene film) that provides the polyolefin adhesive film 100 with impact resistance and the support required for packaging materials.

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

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

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

[0071] It is particularly noteworthy that the weight ratio of the ethylene propylene elastic rubber in the propylene block polymer satisfies the above weight percentage (for example, 18% to 30%), thereby providing the support layer 2 with good punchability.

[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 small amount of bridging terminal monomers having carboxylic acid groups. Here, the weight percentage of ethylene in the vinyl elastomer is 30% or more, preferably 30% to 60%.

[0073] As a result, the vinyl elastomer provides the support layer 2 with better punchability and can prevent whitening that occurs during punching.

[0074] The maleic anhydride-modified polyolefin copolymer in the support layer 2 has, for example, similar material characteristics to those of the adhesive layer 1. The polyolefin copolymer is formed by copolymerizing at least two C2-C4 olefin molecules. More specifically, the graft ratio of maleic anhydride to the polyolefin copolymer is 1% to 5%. The melt index of the maleic anhydride-modified polyolefin copolymer is controlled to 1 g / 10 min to 5 g / 10 min.

[0075] In this embodiment, the support layer 2 contains a small amount of polyolefin copolymer (e.g., 5 to 20 wt%) modified with maleic anhydride, and therefore has a high affinity with the adhesive layer 1, thereby providing good interlayer adhesive strength between the support layer 2 and the adhesive layer 1.

[0076] If the content of the maleic anhydride-modified polyolefin copolymer in the support layer 2 is lower than the above content range, the interlayer adhesive strength will be deteriorated. On the other hand, if the content of the maleic anhydride-modified second polyolefin copolymer in the support layer 2 is higher than the above content range, the punching ability of the packaging material will be deteriorated.

[0077] To further explain, the lubricant may be, for example, silicon dioxide (SiO2) or talc, which can improve the punchability and processability of the support layer 2, but the present invention is not limited thereto. In this 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 haze value are measured in accordance with ASTM D1003.

[0079] Continuing, as shown in FIG. 1, the heat seal layer 3 is formed from 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, for example, by copolymerizing propylene and ethylene. In this embodiment, the weight ratio of ethylene in the propylene copolymer is preferably 2% or less. This allows the heat seal layer 3 to provide the polyolefin adhesive film 100 with superior heat seal strength.

[0081] The above-mentioned technical solution allows the polyolefin adhesive film 100 according to an embodiment of the present invention to be produced by directly thermally laminating the adhesive layer 1 formed on the support layer 2 by coextrusion with the metal aluminum foil AF, eliminating the need for a separate polyester or polyurethane adhesive, as shown in Figures 2 and 3. The polyolefin adhesive film 100 according to the present invention not only has self-adhesive properties, but also solves the problem of volatile organic solvents (VOCs) volatilizing in the prior art.

[0082] In addition, the polyolefin adhesive film 100 according to an embodiment of the present invention can solve the problem of insufficient adhesive strength due to a reduction in strength of conventional dry composite polyolefin film / aluminum foil packaging materials when exposed to high temperature and humidity for a long period of time.

[0083] The heat seal layer 3 of the polyolefin adhesive film 100 according to the present invention has excellent heat seal strength. The heat seal strength of the polyolefin adhesive film 100 according to the present invention, measured according to QB / T2358-1998, can reach 83 N / 15 mm or more. The measurement conditions are, for example, a temperature of 180°C and a pressure of 1 kgf / cm. 2 After heat sealing for 3 seconds at 100°C, the sample was cut to 15 mm x 15 mm and measured. The polyolefin adhesive film still had a peel strength of over 14.6 N / 15 mm even after immersion in an electrolyte solution at 85°C for 168 hours.

[0084] The polyolefin adhesive film 100 according to the present invention has good adhesion to the metal aluminum foil AF (e.g., aluminum-plastic film), and prevents delamination or expansion of the material between the polyolefin adhesive film 100 and the metal aluminum foil AF at high operating temperatures, which can lead to electrolyte leakage. The polyolefin adhesive film 100 according to the present invention is particularly suitable for high-power wattage power batteries in electric vehicles, and is also used as an electronic packaging material for lithium batteries.

[0085] [Experimental data and measurement results] In order to demonstrate the above-mentioned technical effects of the polyolefin adhesive film according to the present invention, examples and comparative examples are provided below. The examples are a group that demonstrates the technical effects of the present invention, and the comparative examples are a group that exhibits poor test results. However, these examples are provided for the purpose of understanding the present invention, and the present invention is not limited thereto.

[0086] Example 1 A three-layer polyolefin adhesive film was formed by coextrusion, with an adhesive layer, a support layer, and a heat-seal layer laminated in this order. The adhesive layer contained a maleic anhydride-modified polyolefin copolymer. The polyolefin copolymer was formed by copolymerizing propylene (C3) and butene (C4) in a 50:50 molar ratio. The amount of the polyolefin copolymer used was 99.5 parts by weight. The grafting ratio of maleic anhydride (MA) to 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 epoxysiloxane, at a content of 1000 ppm (parts per million). The modification amount (surface treatment weight ratio) of the epoxysiloxane-surface-treated silicon dioxide particles was 0.5%, and the average particle diameter D50 of the silicon dioxide particles was 5 μm. Furthermore, the support layer contained 70 parts by weight of a propylene block polymer, 20 parts by weight of a vinyl elastomer (e.g., an ethylene / butene elastomer), and 9.9 parts by weight of a maleic anhydride-modified polyolefin copolymer, and a small amount of unsurface-treated silicon dioxide particles, assuming a total weight of the support layer to be 100 parts by weight. The heat-seal layer was composed of a propylene copolymer (co-PP) formed by copolymerization of propylene and ethylene, with the ethylene content being less than 2% by weight. The adhesive layer had a thickness of 8 μm, the support layer had a thickness of 24 μm, and the heat-seal layer had a thickness of 8 μm. The haze value of the polyolefin adhesive film according to Example 1 was 7%, and it had no noticeable streaks in appearance. The heat-seal strength of the polyolefin adhesive film according to QB / T2358-1998 was approximately 87 N / 15 mm. The polyolefin adhesive film was attached to the aluminum foil via the adhesive layer, and the peel strength between the polyolefin adhesive film and the aluminum foil was 14.7 N / 15 mm.Furthermore, the aluminum-plastic film formed by bonding the polyolefin adhesive film and aluminum foil was immersed in an electrolyte environment at 85°C for 168 hours and tested. The aluminum-plastic film had a peel strength (i.e., interlayer adhesive strength) of 13.5N / 15mm, demonstrating that the polyolefin adhesive film has extremely high resistance to high-temperature, high-humidity environments. The formed height of the aluminum-plastic film is 6.5mm, and it is particularly suitable for high-output wattage power batteries in electric vehicles, as well as for use as an electronic packaging material for lithium batteries.

[0087] The methods for producing polyolefin adhesive films according to Examples 2 to 4 and Comparative Examples 1 to 3 were basically the same as those of Example 1, with the only differences being the amounts of materials used and the parameters, the conditions of which are as shown in Table 1 below.

[0088] Example 2: The amount of polyolefin copolymer used in the adhesive layer was 99.5 parts by weight. The grafting rate of maleic anhydride (MA) to 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 epoxysiloxane was 1000 ppm. The modification level of the silicon dioxide particles surface-treated with epoxysiloxane was 1%, and the average particle diameter D50 of the silicon dioxide particles was 5 μm. The support layer contained 70 parts by weight of a propylene block polymer, 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 unsurface-treated silicon dioxide particles. The heat-seal layer was formed from a propylene copolymer (co-PP). Example 2: The haze value of the polyolefin adhesive film was 7.2%, and there were no noticeable streaks in the appearance. The heat seal strength of the polyolefin adhesive film according to QB / T2358-1998 was approximately 86 N / 15 mm. The peel strength between the polyolefin adhesive film and aluminum foil was 17.8 N / 15 mm. The aluminum-plastic film formed by bonding the polyolefin adhesive film and aluminum foil was placed in an electrolyte environment at 85°C for 168 hours and measured. The aluminum-plastic film had a peel strength of 16.6 N / 15 mm. The formed height of the aluminum-plastic film was 6.5 mm.

[0089] Example 3: The amount of polyolefin copolymer used in the adhesive layer was 99.5 parts by weight. The grafting rate of maleic anhydride (MA) to 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 epoxysiloxane was 1000 ppm. The modification level of the silicon dioxide particles surface-treated with epoxysiloxane was 1.5%, and the average particle diameter D50 of the silicon dioxide particles was 5 μm. The support layer contained 70 parts by weight of a propylene block polymer, 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 unsurface-treated silicon dioxide particles. The heat-seal layer was formed from a propylene copolymer (co-PP). Example 3: The haze value of the polyolefin adhesive film was 9.5%, and there were no noticeable streaks in the appearance. The heat seal strength of the polyolefin adhesive film according to QB / T2358-1998 was approximately 85 N / 15 mm. The peel strength between the polyolefin adhesive film and aluminum foil was 16 N / 15 mm. The aluminum-plastic film formed by bonding the polyolefin adhesive film and aluminum foil was placed in an electrolyte environment at 85°C for 168 hours and measured. The aluminum-plastic film had a peel strength of 15 N / 15 mm. The formed height of the aluminum-plastic film was 6.5 mm.

[0090] Example 4: The amount of polyolefin copolymer used in the adhesive layer was 99.5 parts by weight. The grafting ratio of maleic anhydride (MA) to 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 epoxysiloxane was 1000 ppm. The modification level of the silicon dioxide particles surface-treated with epoxysiloxane was 2.0%, and the average particle diameter D50 of the silicon dioxide particles was 5 μm. The support layer contained 70 parts by weight of a propylene block polymer, 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 unsurface-treated silicon dioxide particles. The heat-seal layer was formed from a propylene copolymer (co-PP). Example 4: The haze value of the polyolefin adhesive film was 12%, and there were no noticeable streaks in the appearance. The heat seal strength of the polyolefin adhesive film according to QB / T2358-1998 was approximately 85 N / 15 mm. The peel strength between the polyolefin adhesive film and aluminum foil was 15.3 N / 15 mm. The aluminum-plastic film formed by bonding the polyolefin adhesive film and aluminum foil was placed in an electrolyte environment at 85°C for 168 hours and measured. The aluminum-plastic film had a peel strength of 13.5 N / 15 mm. The formed height of the aluminum-plastic film was 6.5 mm.

[0091] In the adhesive layer of Comparative Example 1, the amount of polyolefin copolymer used was 99.5 parts by weight. The graft ratio of maleic anhydride (MA) to the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The silicon dioxide particles in Comparative Example 1 were not surface-treated and were used in an amount of 1000 ppm. The average particle diameter D50 of the silicon dioxide particles was 5 μm. The support layer contained 70 parts by weight of a propylene block polymer, 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 untreated silicon dioxide particles. The heat-seal layer was formed from a propylene copolymer (co-PP). Test results showed that the haze value of the polyolefin adhesive film in Comparative Example 1 was 7% and there were no noticeable streaks in the appearance. The heat-seal strength of the polyolefin adhesive film according to QB / T2358-1998 was approximately 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 bonding the polyolefin adhesive film and the aluminum foil was placed in an electrolyte environment at 85°C for 168 hours and measured. The aluminum-plastic film had a peel strength of 13.2 N / 15 mm. The formed height of the aluminum-plastic film was 6.5 mm.

[0092] In Comparative Example 2, the amount of polyolefin copolymer used in the adhesive layer was 99.5 parts by weight. The graft ratio of maleic anhydride (MA) to the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The silicon dioxide particles in Comparative Example 2 were not surface-treated and were used in an amount of 2,000 ppm. The average particle diameter D50 of the silicon dioxide particles was 5 μm. The support layer contained 70 parts by weight of a propylene block polymer, 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 untreated silicon dioxide particles. The heat-seal layer was formed from a propylene copolymer (co-PP). Test results showed that the haze value of the polyolefin adhesive film in Comparative Example 2 was 15% and there were no noticeable streaks in the appearance. The heat-seal strength of the polyolefin adhesive film according to QB / T2358-1998 was approximately 82 N / 15 mm. The peel strength between the polyolefin adhesive film and the aluminum foil was 11.2 N / 15 mm. The aluminum-plastic film formed by bonding the polyolefin adhesive film and the aluminum foil was placed in an electrolyte environment at 85°C for 168 hours and measured. The aluminum-plastic film had a peel strength of 9.2 N / 15 mm. The formed height of the aluminum-plastic film was 5.5 mm.

[0093] In the adhesive layer of Comparative Example 3, the amount of polyolefin copolymer used was 99.5 parts by weight. The graft ratio of maleic anhydride (MA) to the polyolefin copolymer was 3%. The melt index (MI) of the polyolefin copolymer was 3.1 g / 10 min. The silicon dioxide particles in Comparative Example 3 were not surface-treated and were used in an amount of 1,000 ppm. The average particle diameter D50 of the silicon dioxide particles was 2 μm. The support layer contained 70 parts by weight of a propylene block polymer, 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 untreated silicon dioxide particles. The heat-seal layer was formed from a propylene copolymer (co-PP). Test results showed that the haze value of the polyolefin adhesive film of Comparative Example 3 was 6.8% and there were no noticeable streaks in the appearance. The heat seal strength of the polyolefin adhesive film according to QB / T2358-1998 was approximately 82 N / 15 mm. The peel strength between the polyolefin adhesive film and aluminum foil was 14.5 N / 15 mm. An aluminum-plastic film formed by laminating the polyolefin adhesive film and aluminum foil was placed in an electrolyte environment at 85°C for 168 hours and measured; the aluminum-plastic film had a peel strength of 13 N / 15 mm. The formed height of the aluminum-plastic film was 6.5 mm. Furthermore, the unwinding test of the polyolefin adhesive film in Comparative Example 3 was unsuccessful.

[0094] [Table 1]

[0095] It should be noted that the methods for measuring the "haze value" and "heat seal strength" have already been described in the examples, and will not be repeated here. Furthermore, the term "peel strength" in this specification refers to the maximum force required to peel a unit width of bonded materials (e.g., the peel strength between a polyolefin adhesive film and an aluminum foil) from their contact surfaces. A universal testing machine was used as the measuring device. The measurement error of the testing machine was within ±1% of the actual value. The measurement environment was such that the sample was left at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5% for at least 4 hours, and then the measurement was performed in this environment. Regarding sample preparation, the object to be measured was cut into five uniform samples, each 15.0 mm ± 0.1 mm wide and 200 mm long, by removing 50 mm from both ends in the width direction. The measurement method involved clamping both ends of the peeled portion of the sample between the upper and lower jigs of the testing machine, and fitting the vertical axis of the peeled portion of the sample so that it overlapped with the center line of the upper and lower jigs. The measurement speed was 300 mm / min ± 30 mm / min, and the peel force curve during the peeling process of the sample was recorded. The arithmetic average of the peel strength in the longitudinal and transverse directions of the sample was measured and the measurement result (two significant figures) was expressed in units of N / 15 mm.

[0096] To explain further, the "molded height" in this specification is the height recorded after cold pressing using a 5 cm x 6 cm lithium battery mold, and the unit is mm.

[0097] The appearance of the packaging material was evaluated by a tester observing the surface of the biaxially oriented polypropylene film of the packaging material with the naked eye (observation distance was approximately 30 cm). If no significant streaks were observed, the evaluation was "no streaks." If significant streaks were observed, the evaluation was "significant streaks." If the haze value of the packaging material was too high, the evaluation was "not observable."

[0098] [Consideration of measurement results] The measurement results showed that 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 the 82 N / 15 mm of the comparative example. The peel strength between the polyolefin adhesive films and aluminum foil according to Examples 1 to 4 was 14.7 to 17.8 N / 15 mm, which was higher than the 11.2 to 14.5 N / 15 mm of the comparative example. An aluminum-plastic film formed by bonding a polyolefin adhesive film and aluminum foil was placed in an electrolyte at 85°C and immersed for 168 hours, and measurements were performed. 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 the 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 more applicable to high-output wattage power batteries in electric vehicles than Comparative Examples 1 to 3, and are also used as electronic packaging materials for lithium batteries.

[0100] It is noteworthy that the amount of silicon dioxide particles used in the adhesive layer in Comparative Example 2 was 2,000 ppm, resulting in a significantly high haze value (15%) for the polyolefin adhesive film.The average particle size of silicon dioxide in the adhesive layer in Comparative Example 3 was 2 μm, resulting in poor rewindability for the polyolefin adhesive film (NG).The amount and particle size of silicon dioxide particles both affect the physical properties of the polyolefin adhesive film to some extent.

[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. The adhesive layer 1 is formed on the support layer 2 by coextrusion. Unlike the first embodiment, the polyolefin adhesive film 100' of the second embodiment of the present invention may, for example, not include a heat-seal layer 3. The material characteristics of the adhesive layer 1 and the support layer 2 in the second embodiment are similar to those in the first embodiment, and therefore will not be repeated here. Due to the above-described configuration, the polyolefin adhesive film 100' of the second embodiment of the present invention does not require direct thermal lamination of the adhesive layer 1 formed on the support layer 2 by coextrusion with the metal aluminum foil AF, eliminating the need for a separate polyester or polyurethane adhesive.

[0102] [Advantageous Effects of the Embodiments] Advantageous effects of the present invention include the following technical features of the polyolefin adhesive film according to the present invention: "It comprises a support layer which is a polypropylene film and an adhesive layer formed on one side of the support layer by coextrusion," "The adhesive layer comprises a polyolefin copolymer modified with maleic anhydride and inorganic particles dispersed in the polyolefin copolymer and surface-treated with epoxy siloxane," "The graft ratio of maleic anhydride to 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 heated, 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." These technical features ensure good adhesion between the polyolefin adhesive layer and metal aluminum foil (e.g., aluminum plastic film), and prevent electrolyte leakage due to delamination or expansion of the polyolefin adhesive film and metal aluminum foil at high operating temperatures. The polyolefin adhesive film is particularly suitable for aluminum plastic film packaging materials for high wattage power batteries in electric vehicles.

[0103] The above disclosure is merely a preferred embodiment of the present invention, and the scope of the claims of the present invention is not limited thereto. Therefore, all equivalent technical modifications made using the specification and drawings of the present invention are included in the scope of the claims of the present invention. [Explanation of symbols]

[0104] <Present 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 Metallic Aluminum Foil <Prior Art> AF Metallic Aluminum Foil GL adhesive layer PL polymer membrane

Claims

1. A polyolefin adhesive film comprising a support layer that is a polypropylene film and an adhesive layer that is coextruded on one side of the support layer, The adhesive layer is a polyolefin copolymer; and inorganic particles surface-treated with epoxysiloxane, dispersed in the polyolefin copolymer; the polyolefin copolymer is modified with maleic anhydride; the graft ratio of the maleic anhydride to 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%; In the adhesive layer, the content of the maleic anhydride-modified polyolefin copolymer is 90 wt % or more, and the content of the epoxysiloxane-surface-treated inorganic particles is 500 ppm to 2,000 ppm, where the total weight of the adhesive layer is 100 wt %; A polyolefin adhesive film characterized in that, when the polyolefin adhesive film is subjected to a heating process, 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.

2. 2. The polyolefin adhesive film according to claim 1, wherein in the adhesive layer, the inorganic particles have an average particle size of 1 μm to 8 μm, an average sphericity of 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.

3. 3. The polyolefin adhesive film according to claim 2, wherein in the adhesive layer, the average particle size of the inorganic particles is 3 μm to 6 μm, and the average sphericity of the inorganic particles is 0.8 to 1.

0.

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

5. 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 4.

6. The support layer is a propylene block polymer; A vinyl elastomer, 2. The polyolefin adhesive film of claim 1, which is a cast polypropylene film comprising a polyolefin copolymer modified with maleic anhydride, other than the propylene block polymer.

7. 7. The polyolefin adhesive film of claim 6, wherein in the support layer, the propylene block polymer comprises a block composed of an ethylene propylene elastomeric rubber, the weight percent of the ethylene propylene elastomeric rubber in the propylene block polymer is 18% or more, and the vinyl-based elastomer is an ethylene / butene elastomer, and the weight percent of ethylene in the vinyl-based elastomer is 30% or more.

8. 10. The polyolefin adhesive film of claim 1, further comprising a heat seal layer coextruded on the other side of the support layer.

9. 9. The polyolefin adhesive film of claim 8, wherein 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).

Images