Polypropylene resin composition and molded article made therefrom

Abstract

The present invention relates to a polypropylene resin composition and a molded article made therefrom. More specifically, the present invention relates to a polypropylene resin composition containing an ethylene-propylene block copolymer resin and having excellent processability, heat resistance, and rigidity, and a molded article prepared therefrom by an extrusion coating method. The polypropylene resin composition according to an embodiment of the present invention has excellent processability and is suitable for extrusion molding, and has excellent heat resistance and rigidity, and thus can be effectively used as a core layer of a flexible packaging battery bag.

Description

Technical Field

[0001] The present invention relates to a polypropylene resin composition and a molded article made therefrom. More specifically, the present invention relates to a polypropylene resin composition containing an ethylene-propylene block copolymer resin and having excellent processability, heat resistance, and rigidity, and a molded article prepared therefrom by an extrusion coating method. Background Art

[0002] Polypropylene resin is a polymer material widely used in household appliances, automotive composite materials, and general packaging materials. The rigidity, transparency, impact resistance, etc. of polypropylene resin vary depending on the structure of the polymer.

[0003] Among them, since the ethylene-propylene block copolymer resin contains an ethylene-propylene rubber copolymer, its impact resistance characteristics are superior to those of homopolypropylene or polypropylene random copolymer. Therefore, the ethylene-propylene block copolymer resin is mainly used for automotive composite materials or general sundries that require impact resistance.

[0004] On the other hand, due to this rubber component, the ethylene-propylene block copolymer resin has low transparency, so it is difficult to be used in applications such as films that require transparency. Therefore, it is currently only used in applications where the transparency requirement is not high, such as food steaming bag films laminated with aluminum foil.

[0005] All along, various studies have been conducted to improve the disadvantages of ethylene-propylene block copolymers in food packaging applications. For example, Korean Patent Publication No. 1298417 discloses an ethylene-propylene block copolymer resin formed by segmented polymerization of an ethylene-propylene random copolymer and an ethylene-propylene rubber copolymer. Although the transparency and impact resistance of this resin are improved, due to its low melting temperature, its application will be limited in cases where heat resistance is required in subsequent processing.

[0006] In addition, Korean Patent Publication No. 1598715 discloses a polypropylene, specifically an ethylene-propylene block copolymer using homopolypropylene as a matrix, which has excellent impact resistance and high heat resistance, and thus has excellent appearance after high-temperature sterilization.

[0007] In addition, soft pack battery bags are usually manufactured by a dry lamination method, in which an unstretched film (cast polypropylene film; CPP film) is processed and coated with an adhesive, and then adhered to a base layer containing a metal foil layer. However, when in long-term contact with the electrolyte, the adhesion between the unstretched film and the metal foil layer may be weakened. Other disadvantages also include: a post-process of coating an adhesive on the unstretched film, the use of organic solvents harmful to the human body, etc.

[0008] In the extrusion coating method, which is another method for manufacturing a pouch cell bag, a film is directly co-extruded and coated on a base layer containing a metal foil layer. Therefore, there is no need for a post-process of coating an adhesive and performing adhesion, and the adhesion between the co-extruded layer and the metal layer is also strong even when in long-term contact with an electrolyte. However, it is difficult to process a uniform film thickness in the extrusion coating method.

[0009] When using a polypropylene homopolymer or a propylene random copolymer as the material for extrusion coating, it is not suitable for a pouch cell bag due to low impact resistance and elongation. To improve the impact resistance and elongation, attempts have been made to blend a rubber component into the polypropylene homopolymer or the propylene random copolymer; or use an ethylene-propylene block copolymer instead. However, there are problems such as easy generation of appearance defects such as fish eyes and gels, and poor whitening resistance.

[0010] Therefore, there is a need to develop a polypropylene resin composition that can be used as a co-extruded layer, particularly the core layer, in a multilayer film for a pouch cell bag prepared by the extrusion coating method.

[0011]

Prior Art Documents

[0012]

Patent Documents

[0013] (Patent Document 1) Korean Patent Publication No. 1298417;

[0014] (Patent Document 2) Korean Patent Publication No. 1598715. Summary of the Invention

[0015] Technical Problem

[0016] An object of the present invention is to provide a polypropylene resin composition having excellent processability, heat resistance, and rigidity.

[0017] Another object of the present invention is to provide a molded article made of the above polypropylene resin composition, specifically a co-extruded layer, particularly the core layer, in a multilayer film for a pouch cell bag.

[0018] Yet another object of the present invention is to provide a multilayer film for a pouch cell bag, which includes the above co-extruded layer and is made by the extrusion coating method.

[0019] Technical Solution

[0020] To achieve the above object, according to an embodiment of the present invention, the present invention provides a polypropylene resin composition comprising an ethylene-propylene block copolymer resin polymerized in segments in a reactor, wherein the ethylene-propylene block copolymer resin comprises a polypropylene matrix of 72 to 90% by weight of propylene homopolymer and 10 to 28% by weight of an ethylene-propylene rubber copolymer determined by solvent extract content. When measured according to ASTM D1238 at 230 °C under a load condition of 2.16 kg, the melt index of the ethylene-propylene block copolymer resin is 11 to 20 g / 10 min, the melting temperature of the ethylene-propylene block copolymer resin is 160 to 170 °C, the ethylene content in the solvent extract is 22 to 38% by weight, and the intrinsic viscosity of the solvent extract is 1.0 to 3.0 dl / g.

[0021] In an exemplary embodiment of the present invention, the ethylene-propylene block copolymer resin may comprise a polypropylene matrix of 80 to 88% by weight of propylene homopolymer and 12 to 20% by weight of an ethylene-propylene rubber copolymer determined by solvent extract content.

[0022] In an exemplary embodiment of the present invention, when measured according to ASTM D1238 at 230 °C under a load condition of 2.16 kg, the melt index of the ethylene-propylene block copolymer resin may be 12 to 18 g / 10 min.

[0023] In an exemplary embodiment of the present invention, the ethylene content in the solvent extract may be 25 to 33% by weight.

[0024] In an exemplary embodiment of the present invention, based on the total weight of the polypropylene resin composition, the polypropylene resin composition may further comprise 3 to 10% by weight of a propylene random copolymer selected from a propylene-ethylene random copolymer and a propylene-α-olefin random copolymer, wherein the α-olefin has 4 to 8 carbon atoms.

[0025] In an exemplary embodiment of the present invention, based on the total weight of the polypropylene resin composition, the polypropylene resin composition may further comprise 3 to 20% by weight of propylene homopolymer.

[0026] In an exemplary embodiment of the present invention, the polypropylene resin composition may further comprise at least one additive selected from antioxidants, neutralizing agents, slip agents, anti-blocking agents, reinforcing materials, fillers, weather stabilizers, antistatic agents, lubricants, nucleating agents, flame retardants, pigments, and dyes.

[0027] Specifically, based on the total weight of the polypropylene resin composition, the polypropylene resin composition according to an embodiment of the present invention may comprise 0.01 to 0.2% by weight of an antioxidant.

[0028] Preferably, the antioxidant is at least one substance selected from pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and tris(2,4-di-tert-butylphenyl) phosphite.

[0029] Based on the total weight of the polypropylene resin composition, the polypropylene resin composition according to an embodiment of the present invention may contain 0.01 to 0.2% by weight of a neutralizing agent.

[0030] Preferably, the neutralizing agent is at least one substance selected from hydrotalcite and calcium stearate.

[0031] According to another embodiment of the present invention, the present invention provides a polypropylene resin molded article formed from the above polypropylene resin composition.

[0032] In an exemplary embodiment of the present invention, the polypropylene resin molded article may be a core layer for a soft-pack battery bag obtained by extrusion molding the polypropylene resin composition.

[0033] According to still another embodiment of the present invention, the present invention provides a multilayer film for a soft-pack battery bag, which includes: a co-extrusion layer including a sealing layer, a core layer, and a surface layer; a metal foil layer; an adhesive layer; and a base layer, wherein the core layer contains the polypropylene resin composition according to an embodiment of the present invention.

[0034] In an exemplary embodiment of the present invention, when forming the sealing layer, at least one polypropylene resin selected from the polypropylene resin composition according to an embodiment of the present invention, a propylene homopolymer, a propylene random copolymer, a propylene block copolymer, and an ethylene-propylene-butene terpolymer may be used, or an amorphous ethylene-propylene copolymer, a propylene-α-olefin copolymer, an acrylic resin, or silica with a content of 40% by weight or less may be further mixed.

[0035] In an exemplary embodiment of the present invention, when forming the surface layer, at least one resin selected from a polyolefin resin graft-modified with an unsaturated carboxylic acid, a copolymer of ethylene or propylene and acrylic acid or methacrylic acid may be used, or the polypropylene resin composition according to an embodiment of the present invention, an ethylene-propylene-butene terpolymer, an amorphous ethylene-propylene copolymer, or a propylene-α-olefin copolymer with a content of 50% by weight or less may be further mixed.

[0036] In an exemplary embodiment of the present invention, the metal foil layer may be formed of a metal selected from aluminum and nickel or an inorganic compound selected from silica and alumina.

[0037] In an exemplary embodiment of the present invention, when forming the adhesion layer, polyvinyl acetate, acrylic, methacrylic acid, acrylic acid, esters, styrene, acrylate, cellulose, polyester, polyamide, amino, phenolic resin, epoxy, polyurethane, nitrile, rubber, silicone adhesives or polyolefin resins can be used.

[0038] In an exemplary embodiment of the present invention, the base layer may have a multi-layer structure including at least two layers selected from a polystyrene layer, a nylon layer, a polyester layer, and a printed layer.

[0039] Advantageous Effects

[0040] The polypropylene resin composition according to an embodiment of the present invention has excellent processability and is suitable for extrusion molding, and has excellent heat resistance and rigidity. Therefore, it can be effectively applied to the core layer, surface layer, and / or sealing layer of the multi-layer film of the soft-pack battery bag prepared by the extrusion coating method. Description of the Drawings

[0041] Figure 1 Schematically shows a cross-section of a multi-layer film for a soft-pack battery bag according to an embodiment of the present invention.

[0042]

Reference Numerals

[0043] 10: Multi-layer film, 110: Co-extrusion layer, 111: Sealing layer, 112: Core layer, 113: Surface layer,

[0044] 120: Metal foil layer, 120a: Chemically converted metal foil layer, 130: Adhesion layer, 140: Base layer. Detailed Description

[0045] Hereinafter, the present invention will be described in detail.

[0046]

Polypropylene Resin Composition

[0047] The polypropylene resin composition according to an embodiment of the present invention contains an ethylene-propylene block copolymer resin polymerized in segments in a reactor. Among them, the ethylene-propylene block copolymer resin contains a polypropylene matrix of 72 to 90% by weight of propylene homopolymer and 10 to 28% by weight of an ethylene-propylene rubber copolymer determined by the solvent extract content. When measured under the condition of a load of 2.16 kg at 230 °C according to ASTM D1238, the melt index of the ethylene-propylene block copolymer resin is 11 to 20 g / 10 min, the melting temperature of the ethylene-propylene block copolymer resin is 160 to 170 °C, the ethylene content in the solvent extract is 22 to 38% by weight, and the intrinsic viscosity of the solvent extract is 1.0 to 3.0 dl / g.

[0048] Ethylene-propylene block copolymer resin

[0049] The polypropylene resin composition according to an embodiment of the present invention contains an ethylene-propylene block copolymer resin. Among them, the ethylene-propylene block copolymer resin is a substance formed by segmented polymerization in a reactor.

[0050] For example, first, the polypropylene matrix can be polymerized, and then the polypropylene matrix is block copolymerized with an ethylene-propylene rubber to prepare an ethylene-propylene block copolymer resin. Among them, the polypropylene matrix is a propylene homopolymer.

[0051] The ethylene-propylene block copolymer resin contains 72 to 90% by weight of the polypropylene matrix. Preferably, the ethylene-propylene block copolymer resin may contain 80 to 88% by weight of the polypropylene matrix of the propylene homopolymer. When the content of the polypropylene matrix is less than 72% by weight, the production efficiency may decrease during the polymerization of the ethylene-propylene block copolymer resin, and the tensile strength and moldability of the resin composition may decrease. When the content of the polypropylene matrix exceeds 90% by weight, the dart impact strength, moldability, and elongation may decrease.

[0052] The ethylene-propylene block copolymer resin contains 10 to 28% by weight of an ethylene-propylene rubber copolymer. Preferably, the ethylene-propylene block copolymer resin may contain 12 to 20% by weight of the ethylene-propylene rubber copolymer. If the content of the ethylene-propylene rubber copolymer is less than 10% by weight, the dart impact strength and moldability of the resin composition may decrease. If the content of the ethylene-propylene rubber copolymer exceeds 28% by weight, the production efficiency may decrease during the polymerization of the ethylene-propylene block copolymer resin, and the tensile strength and moldability of the resin composition may decrease. Here, the content of the ethylene-propylene rubber copolymer can be determined by the content of the solvent extract, and the solvent is preferably xylene.

[0053] When measured according to ASTM D1238 under the condition of a load of 2.16 kg at 230 °C, the melt index of the ethylene-propylene block copolymer resin is 11 to 20 g / 10 min. Preferably, when measured according to ASTM D1238 under the condition of a load of 2.16 kg at 230 °C, the melt index of the ethylene-propylene block copolymer resin can be 12 to 18 g / 10 min. If the melt index is less than 11 g / 10 min, the thickness of the coextruded layer is uneven, and the moldability is poor. If the melt index exceeds 20 g / 10 min, it is difficult to form a film by coextrusion, and appearance defects such as fish eyes or gels may appear, and the whitening resistance may be poor.

[0054] The melting temperature measured by differential scanning calorimetry (DSC) for the ethylene-propylene block copolymer resin is 160°C to 170°C. Preferably, the melting temperature of the ethylene-propylene block copolymer resin can be 160°C to 165°C. If the melting temperature is lower than 160°C, the heat resistance of the resin composition is insufficient, so that the molded product may be deformed during subsequent processing at high temperatures, and the heat resistance of the finally produced multilayer film for a soft-pack battery bag may be reduced. And polypropylene with a melting temperature exceeding 170°C is difficult to commercially polymerize.

[0055] In the ethylene-propylene block copolymer resin, the ethylene content in the solvent extract (i.e., ethylene-propylene rubber copolymer) is 22 to 38% by weight. Preferably, the ethylene content in the solvent extract can be 25 to 33% by weight. If the ethylene content in the solvent extract is lower than 22% by weight or exceeds 38% by weight, it may cause a decrease in the whitening resistance or moldability of the resin composition.

[0056] In the ethylene-propylene block copolymer resin, the intrinsic viscosity of the solvent extract (i.e., ethylene-propylene rubber copolymer) is 1.0 to 3.0 dl / g. When the intrinsic viscosity is lower than 1.0 dl / g, the impact resistance of the resin composition decreases due to the reduction in the molecular weight of the rubber component. When the intrinsic viscosity exceeds 3.0 dl / g, due to the aggregation of the rubber component, appearance defects such as fish eyes or gels may occur, and the whitening resistance of the resin composition may decrease.

[0057] The method for preparing the above-mentioned ethylene-propylene block copolymer resin is not particularly limited, and the method for preparing an ethylene-propylene block copolymer known in the technical field to which the present invention pertains can be directly used, or can be used after appropriate improvement.

[0058] Preferably, the method for preparing the ethylene-propylene block copolymer resin may include the following steps: a first polymerization step of polymerizing a polypropylene matrix of propylene homopolymer in two or more continuous reactors; and a second polymerization step of copolymerizing an ethylene-propylene rubber copolymer component by adding ethylene and propylene in the presence of the polymerized polypropylene matrix to obtain an ethylene-propylene block copolymer resin. At this time, each polymerization can use methods and reaction conditions known in the technical field to which the present invention pertains, such as slurry method, bulk method, gas phase method, etc.

[0059] Specifically, the Hypol process of Mitsui & Co., Ltd. capable of continuous polymerization in which 2 bulk reactors and 2 gas phase reactors are connected in series can be utilized, and an ethylene-propylene block copolymer can be prepared according to the polymerization method known to those skilled in the art.

[0060] In addition, the above polymerization steps can be carried out in the presence of a Ziegler-Natta catalyst. The Ziegler-Natta catalyst can be any catalyst known in the art without limitation. Specifically, it can be obtained by loading a titanium compound such as titanium chloride (TiCl3 or TiCl4) on a magnesium chloride (MgCl2) carrier. Preferably, a cocatalyst and an external electron donor are used simultaneously here.

[0061] An alkyl aluminum compound can be used as the cocatalyst. Examples of the alkyl aluminum compound include, but are not limited to, triethyl aluminum, diethyl aluminum chloride, tributyl aluminum, triisobutyl aluminum, trioctyl aluminum, etc.

[0062] In addition, an organosilane compound is preferably used as the external electron donor. Examples of the organosilane compound include, but are not limited to, diphenyldimethoxysilane, phenyltrimethoxysilane, phenylethyldimethoxysilane, phenylmethyldimethoxysilane, methoxythrimethylsilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, di-tert-butyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, dicyclohexyldimethoxysilane, etc.

[0063] In the method for preparing a polypropylene resin composition according to a specific embodiment of the present invention, the above first polymerization step and second polymerization step can be carried out in the same polymerization reactor or in different polymerization reactors.

[0064] Preferably, the first polymerization step can be a step of polymerizing to obtain a polypropylene matrix in 2 or more bulk polymerization reactors in the presence of a Ziegler-Natta catalyst; the second polymerization step can be a step of copolymerizing ethylene and propylene in a gas-phase polymerization reactor in the presence of the polypropylene matrix polymerized in the first polymerization step and a Ziegler-Natta catalyst to obtain an ethylene-propylene block copolymer as a rubber component. By adjusting the hydrogen content introduced into each polymerization reactor, the melt index of the polymer generated in each polymerization reactor can be adjusted.

[0065] Specifically, the polypropylene matrix obtained in the first polymerization step is transferred to a gas-phase reactor for ethylene-propylene copolymerization, and ethylene and propylene are added simultaneously, so that the solid polypropylene matrix copolymerizes continuously with the newly added ethylene and propylene as ethylene-propylene rubber copolymer components, thereby preparing an ethylene-propylene block copolymer.

[0066] Additional polypropylene resin

[0067] The polypropylene resin composition according to an embodiment of the present invention may further comprise an ethylene-propylene random copolymer or an α-olefin-propylene random copolymer, wherein the α-olefin has 4 to 8 carbon atoms.

[0068] When the polypropylene resin composition further comprises the above-mentioned polypropylene random copolymer, the whitening resistance, elongation at break and impact resistance of the resin composition can be improved.

[0069] Specifically, the α-olefin in the α-olefin-propylene random copolymer may be at least one selected from 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene.

[0070] Based on the total weight of the polypropylene resin composition, the content of the ethylene-propylene random copolymer or the α-olefin-propylene random copolymer in the polypropylene resin composition may be 3 to 10% by weight.

[0071] The polypropylene resin composition according to an embodiment of the present invention may further comprise a polypropylene homopolymer. When the polypropylene resin composition further comprises a polypropylene homopolymer, the rigidity of the resin composition can be improved.

[0072] Based on the total weight of the polypropylene resin composition, the content of the polypropylene homopolymer in the polypropylene resin composition may be 3 to 20% by weight.

[0073] Additive

[0074] Within the scope not departing from the purpose of the present invention, the polypropylene resin composition according to an embodiment of the present invention may further comprise conventional additives. For example, the polypropylene resin composition may comprise an antioxidant, a neutralizing agent, a slip agent, an anti-blocking agent, a reinforcing material, a filler, a weather stabilizer, an antistatic agent, a lubricant, a nucleating agent, a flame retardant, a pigment, a dye, etc., but not limited thereto.

[0075] Preferably, the polypropylene resin composition according to an embodiment of the present invention may comprise an antioxidant to increase its heat resistance stability. At this time, based on the total weight of the polypropylene resin composition, the addition amount of the antioxidant may be 0.01% by weight to 0.2% by weight, preferably 0.05% by weight to 0.15% by weight. If the content of the antioxidant is less than 0.01% by weight, it is difficult to ensure long-term heat resistance stability. If the content of the antioxidant exceeds 0.2% by weight, it may cause the antioxidant to melt out or reduce the economy of the product, so it is not preferred.

[0076] As antioxidants, phenolic antioxidants, phosphite antioxidants, etc. can be used. Specifically, it can be at least one selected from pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and tris(2,4-di-tert-butylphenyl) phosphite, but not limited thereto.

[0077] Preferably, the polypropylene resin composition according to an embodiment of the present invention may contain hydrotalcite, calcium stearate, etc. as neutralizing agents to remove catalyst residues.

[0078] At this time, based on the total weight of the polypropylene resin composition, the addition amount of the neutralizing agent may be 0.01% by weight to 0.2% by weight, preferably 0.02% by weight to 0.10% by weight. When the content of the neutralizing agent is less than 0.01% by weight, it is difficult to ensure the effect of removing catalyst residues in the resin. When the content of the neutralizing agent exceeds 0.2% by weight, the effect of removing catalyst residues increases very little, and the cost-effectiveness of the resin composition may be reduced, so it is not preferred.

[0079] By mixing the above resin components and additives as required, the polypropylene resin composition according to an embodiment of the present invention can be prepared.

[0080] At this time, the mixing method of the resin components and additives is not particularly limited, and the preparation method of the polypropylene resin composition well-known in the technical field to which the present invention pertains can be directly used, or used after appropriate improvement.

[0081] Specifically, for example, a required amount of the resin components and additives as described above can be added to a kneader, a roll, a Banbury mixer, or other kneading machines or single-screw / double-screw extruders, etc., and then the added raw materials can be blended by using these machines to prepare the polypropylene resin composition of the present invention.

[0082]

Polypropylene resin molded article

[0083] In another embodiment of the present invention, the present invention provides a polypropylene resin molded article made by molding the polypropylene resin composition of the present invention.

[0084] The method for preparing a molded article from the polypropylene resin composition according to an embodiment of the present invention is not particularly limited, and a method well-known in the technical field to which the present invention pertains can be used. For example, the polypropylene resin composition according to an embodiment of the present invention can be molded by conventional methods such as injection molding, extrusion molding, and casting molding to prepare a polypropylene resin molded article.

[0085] In a preferred embodiment of the present invention, the polypropylene resin molded article according to an embodiment of the present invention may be a core layer for a flexible packaging battery bag obtained by extrusion molding a polypropylene resin composition according to another embodiment of the present invention.

[0086] In still another embodiment of the present invention, the present invention provides a multilayer film for a flexible packaging battery bag, which includes: a coextruded layer including a sealing layer, a core layer, and a surface layer; a metal foil layer; an adhesive layer; and a base layer, wherein at least one of the sealing layer, the core layer, and the surface layer contains the polypropylene resin composition according to an embodiment of the present invention.

[0087] Referring Figure 1 , the multilayer film 10 for a flexible packaging battery bag according to an embodiment of the present invention includes: a coextruded layer 110, a metal foil layer 120, an adhesive layer 130, and a base layer 140, wherein the coextruded layer 110 includes a sealing layer 111, a core layer 112 according to an embodiment of the present invention, and a surface layer 113.

[0088] The coextruded layer 110 may at least include a sealing layer 111, a core layer 112, and a surface layer 113.

[0089] The sealing layer 111 functions to seal the multilayer film 10 for a flexible packaging battery bag by heat and pressure. In the formation of the sealing layer 111, a polypropylene resin may be used alone, or may be mixed with an amorphous ethylene-propylene copolymer, an ethylene-α-olefin copolymer, an acrylic resin, and / or silica having a content of 40% by weight or less.

[0090] Among them, the polypropylene resin may be at least one substance selected from the above-mentioned polypropylene resin compositions, propylene homopolymers, propylene random copolymers, propylene block copolymers, and ethylene-propylene-butene terpolymers according to embodiments of the present invention.

[0091] When measured according to ASTM D1238 under the condition of a load of 2.16 kg at 230 °C, the melt index of the resin constituting the sealing layer 111 may be 11 g / 10 min to 25 g / 10 min.

[0092] The core layer 112 is formed on the sealing layer 111 and functions to impart rigidity, impact resistance, and heat resistance to the multilayer film 10 for a flexible packaging battery bag. The core layer 112 is a layer formed of the above-mentioned polypropylene resin composition according to an embodiment of the present invention.

[0093] The surface layer 113 is formed on the core layer 112 and has the function of improving the adhesion to the metal foil layer. The surface layer 113 can be formed using an acid-modified polyolefin resin. Specifically, a polyolefin resin graft-modified with an unsaturated carboxylic acid, a copolymer of ethylene or propylene and acrylic acid or methacrylic acid can be used, and, if necessary, it can be mixed and used with 50% by weight or less of a polypropylene resin composition, an ethylene-propylene-butene terpolymer, an amorphous ethylene-propylene copolymer, a propylene-α-olefin copolymer, etc. according to the embodiments of the present invention.

[0094] When measured according to ASTM D1238 under the condition of a 2.16 kg load at 230 °C, the melt index of the resin constituting the surface layer 113 can be 11 g / 10 min to 25 g / 10 min.

[0095] The metal foil layer 120 is formed on the surface layer 113 and has the function of gas barrier. The metal foil layer 120 is made of a metal such as aluminum, nickel, etc. or an inorganic compound such as silicon oxide, aluminum oxide, etc.

[0096] In order to increase the adhesion strength between the metal foil layer 120 and the layer in contact therewith, the surface of the metal foil layer 120 can be subjected to a chemical conversion treatment. That is, a chemically converted metal foil layer 120a can be formed on at least one surface of the metal foil layer 120. Among them, the chemical conversion treatment can be carried out according to the methods known to those skilled in the art and using phosphoric acid, chromic acid or oxalic acid, etc.

[0097] The adhesion layer 130 is formed on the metal foil layer 120 and serves to bond the metal foil layer 120 and the base layer 140. The adhesion layer 130 can be formed by polyvinyl acetate-based, acrylic-based, methacrylic-based, acrylic-based, ester-based, styrene-based, acrylate-based, cellulose-based, polyester-based, polyamide-based, amino-based, phenolic resin-based, epoxy-based, polyurethane-based, nitrile-based, rubber-based, silicone-based adhesives or polyolefin resins.

[0098] The base layer 140 is formed on the adhesion layer 130 and serves to protect the surface of the metal foil layer 120. The base layer 140 can have a multi-layer structure including a polystyrene layer, a nylon layer or a polyester layer and a printing layer.

[0099] The method for preparing the multi-layer film for a soft-pack battery bag according to the embodiments of the present invention is not particularly limited, and the method for preparing the multi-layer film for a soft-pack battery bag known in the technical field to which the present invention belongs can be directly used, or can be used after appropriate improvement.

[0100] For example, the method for preparing a multilayer film for a flexible battery pouch according to an embodiment of the present invention may include the following steps: Step S1, preparing a metal foil layer and subjecting both sides thereof to chemical conversion treatment; Step S2, pasting a base layer on one side of the chemically converted metal foil layer by a dry lamination method using an adhesive; and Step S3, forming a surface layer, a core layer, and a sealing layer on the other side of the chemically converted metal foil layer by an extrusion coating method.

[0101] In Step S1, the chemical conversion treatment of the metal foil layer can be carried out according to methods known to those skilled in the art and using phosphoric acid, chromic acid, or oxalic acid.

[0102] In Step S2, it can be carried out according to methods known to those skilled in the art. Specifically, the above-mentioned adhesive or polyolefin resin is diluted in a solvent, then coated on one side of the chemically converted metal foil layer, and dried to form an adhesion layer. The above-mentioned base layer is laminated on the adhesion layer and pasted by applying pressure.

[0103] In Step S3, according to methods known to those skilled in the art and using a co-extruder, the materials of the above-mentioned surface layer, core layer, and sealing layer can be formed into a co-extruded layer.

[0104]

Embodiment

[0105] Hereinafter, the present invention will be described in more detail through examples and comparative examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

[0106] Examples 1 to 2 and Comparative Examples 1 to 7: Polymerization of ethylene-propylene block copolymer

[0107] The Hypol process of Mitsui & Co., Ltd. was used, which connected two bulk reactors and two gas-phase reactors in series to enable continuous polymerization. At this time, a Ziegler-Natta catalyst was used, which was obtained by loading titanium chloride (TiCl4) on a magnesium chloride (MgCl2) carrier, and an internal donor of phthalate esters was used. Triethylaluminum was used as a co-catalyst, and dicyclopentyldimethoxysilane was used as an external donor.

[0108] The operating temperatures and pressures in the first-stage bulk reactor and the second-stage bulk reactor were 68 to 75 °C and 30 to 40 kg / cm 2 and 68 to 75 °C and 25 to 35 kg / cm 2 . The operating temperatures and pressures in the third-stage gas-phase reactor and the fourth-stage gas-phase reactor were 75 to 82 °C and 15 to 20 kg / cm 2 and 68 to 75 °C and 10 to 17 kg / cm 2。In the first-stage to third-stage reactors, polypropylene homopolymers are produced by separately injecting propylene, or ethylene-propylene random copolymers (Comparative Example 7; ethylene content is 1% by weight) are produced by injecting propylene and ethylene. The produced polymers are transferred to the fourth-stage reactor in the lower stage, and in the presence of the above Ziegler-Natta catalyst, ethylene-propylene rubber is copolymerized by adding ethylene and propylene to obtain an ethylene-propylene block copolymer. At this time, by adjusting the hydrogen content introduced into each reactor, the melt index of the polymers produced in each reactor is adjusted. In this way, the ethylene content and the solvent extract content are adjusted according to the contents shown in Table 1 below to obtain an ethylene-propylene block copolymer.

[0109] By the following method, the composition and physical properties of the obtained ethylene-propylene block copolymer resin were measured, and the results are shown in Table 1 below.

[0110] 1. Melt index (g / 10min)

[0111] According to ASTM D1238, the melt index of the ethylene-propylene block copolymer resin was measured at 230 °C under a load of 2.16 kg.

[0112] 2. Melting temperature (Tm)

[0113] By using differential scanning calorimetry (DSC), the sample was held at 200 °C for 10 minutes to eliminate the thermal history, and then cooled from 200 °C to 30 °C at a rate of 10 °C per minute. By cooling as above, the same thermal history was obtained, and then the sample was held at 30 °C for 10 minutes. Subsequently, the temperature was raised again at 10 °C per minute, and the melting temperature (Tm) was obtained from the peak melting temperature.

[0114] 3. Content (% by weight) of xylene soluble

[0115] During 1 hour, the ethylene-propylene block copolymer resin was dissolved in xylene at 140 °C at a concentration of 1% by weight, and then left at room temperature for 2 hours, and the weight of the extract was measured. The obtained weight was expressed as a percentage relative to the weight of the ethylene-propylene block copolymer resin.

[0116] 4. Ethylene content (% by weight) in the xylene soluble

[0117] By using Fourier transform infrared absorption spectroscopy (FT-IR) and using 720 cm -1 and 730 cm -1Characteristic peaks were used to determine the ethylene content in the solvent extract.

[0118] 5. Intrinsic viscosity of the solvent extract

[0119] The intrinsic viscosity of the solvent extract was measured in a decaline solution at 135 °C using a viscometer.

[0120] [Table 1]

[0121]

[0122]

[0123] Preparation of test piece

[0124] The structure of the film used is as follows: By using a two-component adhesive (Mitsui Chemicals, A310 / A3), a 25-μm-thick stretched nylon film (Kolon, South Korea, CNP01) was laminated on one side of an aluminum foil layer (Dongil Aluminum, South Korea, A8021) with a thickness of 30 μm and chemically converted on both sides. A coextruded film was formed on the other side of the aluminum foil layer. Specifically, a modified polypropylene resin (melt index of 15 g / 10 min, melting temperature Tm of 134 °C, Vicat softening point of 110 °C) was used as the material for the surface layer, and the ethylene-propylene block copolymer resins prepared in the above examples and comparative examples were used as the materials for the core layer. 10 wt% of an amorphous ethylene-propylene copolymer was mixed in each of the ethylene-propylene block copolymer resins in the above examples and comparative examples as the material for the sealing layer. Using a coextruder, each of the above materials was coextruded into a thickness of 15 μm / 40 μm / 15 μm.

[0125] According to the following method, the tensile strength, falling dart impact strength, and stress-whitening resistance of the prepared coextruded layer were measured, and according to the following method, the extrusion coating processability and formability of the multilayer film for soft-pack battery bags were evaluated. The results are shown in Table 2 below.

[0126] 6. Tensile strength

[0127] The tensile strength was determined according to ASTM D 882 standard.

[0128] 7. Falling dart impact strength (FDI)

[0129] The falling dart impact strength was measured according to ASTM D1709 standard.

[0130] 8. Stress-whitening resistance

[0131] Cut the coextruded film into pieces of 3 cm × 10 cm to make test pieces. After stretching at a rate of 1000 mm / min using a UTM tensile testing machine, observe whether whitening occurs. If there is no whitening, it is evaluated as ○; if whitening occurs, it is evaluated as ×.

[0132] 9. Extrusion coating processability

[0133] Observe whether the thickness of the coextruded layer of the multilayer film is uniform. If the thickness of the coextruded layer is uniform, it is evaluated as ○; if the thickness of the coextruded layer is not uniform, it is evaluated as ×.

[0134] 10. Erichsen test

[0135] Insert the multilayer film between the dies, press a punch composed of a 20 mm steel ball into a GI steel plate to depths of 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, and 7.5 mm, and then observe whether film peeling and tearing occur, and obtain the maximum value without abnormalities.

[0136] 11. Formability

[0137] Using a stamping die composed of a 50 mm × 30 mm rectangular punch and a die with a gap of 0.3 mm, cold press the multilayer film to a depth of 6 mm and observe for abnormalities. If there are no abnormalities in the formed part, it is evaluated as ○; if tearing, discoloration, wrinkling, or appearance changes occur, it is evaluated as ×.

[0138] [Table 2]

[0139]

[0140] As can be seen from Table 1 and Table 2, in the case of the examples belonging to the scope of the present invention, excellent tensile strength, dart impact strength, whitening resistance, extrusion coating processability, and formability are all exhibited.

[0141] Conversely, in Comparative Example 1 with a lower melt index of the ethylene-propylene block copolymer resin, the thickness of the coextruded layer is not uniform and the formability is poor. In Comparative Example 2 with a higher melt index, it is difficult to form a film by coextrusion. In Comparative Example 3 with a lower solvent extract content, the tensile strength is low, and in Comparative Example 4 with a higher solvent extract content, the formability is poor. In Comparative Example 5 with a lower ethylene content in the solvent extract and Comparative Example 6 with a higher ethylene content in the solvent extract, the whitening resistance and formability are poor. In Comparative Example 7 where the matrix of the ethylene-propylene block copolymer resin is an ethylene-propylene random copolymer, the melting temperature is low, resulting in poor heat resistance.

[0142] In addition, in the Erichsen test that can indirectly reflect the bonding strength between the coextrusion layer and the metal foil layer and the formability of the soft-pack battery during the processing of the soft-pack battery bag, Comparative Example 3 with a lower solvent extract content showed a value lower than that of the Example.

[0143] The polypropylene resin composition according to the embodiments within the scope of the present invention has excellent processability and is suitable for extrusion molding, and has excellent heat resistance and rigidity, and thus can be effectively used as the core layer of the soft-pack battery bag.

Claims

1. A polypropylene resin composition comprising an ethylene-propylene block copolymer resin polymerized in segments in a reactor, the ethylene-propylene block copolymer resin comprising a polypropylene matrix of 72 to 90% by weight of a propylene homopolymer and 10 to 28% by weight of an ethylene-propylene rubber copolymer determined by solvent extract content, Among them, When measured according to ASTM D1238 under conditions of a 2.16 kg load at 230 °C, the melt index of the ethylene-propylene block copolymer resin is 11 to 20 g / 10 min, the melting temperature of the ethylene-propylene block copolymer resin is 160 to 170 °C, the ethylene content in the solvent extract is 22 to 38% by weight, and the intrinsic viscosity of the solvent extract is 1.0 to 3.0 dl / g.

2. The polypropylene resin composition according to claim 1, wherein The ethylene-propylene block copolymer resin comprises a polypropylene matrix of 80 to 88% by weight of a propylene homopolymer and 12 to 20% by weight of an ethylene-propylene rubber copolymer determined by solvent extract content.

3. The polypropylene resin composition according to claim 1, wherein When measured according to ASTM D1238 under conditions of a 2.16 kg load at 230 °C, the melt index of the ethylene-propylene block copolymer resin is 12 to 18 g / 10 min.

4. The polypropylene resin composition according to claim 1, wherein The ethylene content in the solvent extract is 25 to 33% by weight.

5. The polypropylene resin composition according to claim 1, wherein Based on the total weight of the polypropylene resin composition, it further comprises 3 to 10% by weight of a propylene random copolymer selected from a propylene-ethylene random copolymer and a propylene-α-olefin random copolymer, wherein the α-olefin has 4 to 8 carbon atoms.

6. The polypropylene resin composition according to claim 1, characterized in that, Based on the total weight of the polypropylene resin composition, it further comprises 3 to 20% by weight of a propylene homopolymer.

7. The polypropylene resin composition according to claim 1, wherein It further comprises at least one additive selected from antioxidants, neutralizing agents, slip agents, anti-blocking agents, reinforcing materials, fillers, weather stabilizers, antistatic agents, lubricants, nucleating agents, flame retardants, pigments, and dyes.

8. The polypropylene resin composition according to claim 7, wherein Based on the total weight of the polypropylene resin composition, the content of the antioxidant is 0.01 to 0.2% by weight.

9. The polypropylene resin composition according to claim 8, wherein The antioxidant is at least one substance selected from pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and tris(2,4-di-tert-butylphenyl) phosphite.

10. The polypropylene resin composition according to claim 7, characterized in that, Based on the total weight of the polypropylene resin composition, the content of the neutralizing agent is 0.01 to 0.2% by weight.

11. The polypropylene resin composition according to claim 10, wherein The neutralizing agent is at least one substance selected from hydrotalcite and calcium stearate.

12. A polypropylene resin molded article made by molding the polypropylene resin composition according to any one of claims 1 to 11.

13. The polypropylene resin molded article according to claim 12, wherein The polypropylene resin molded article is the core layer of a multilayer film for a soft-pack battery bag prepared by extrusion coating the polypropylene resin composition.

14. A multilayer film for a soft-pack battery bag, comprising: A co-extruded layer prepared by an extrusion coating method; a metal foil layer; an adhesive layer; and a base layer, wherein the co-extruded layer comprises a sealing layer, a core layer, and a surface layer, and the core layer comprises the polypropylene resin composition according to any one of claims 1 to 11.

15. The multilayer film for a soft-pack battery bag according to claim 14, characterized in that When forming the sealing layer, at least one polypropylene resin selected from the group consisting of the polypropylene resin composition according to any one of claims 1 to 11, propylene homopolymer, propylene random copolymer, propylene block copolymer, and ethylene-propylene-butene terpolymer is used; or an amorphous ethylene-propylene copolymer, propylene-α-olefin copolymer, acrylic resin, or silica is further mixed and used in an amount of 40% by weight or less.

16. The multilayer film for a pouch-type battery bag according to claim 14, wherein When forming the surface layer, a resin selected from polyolefin resins graft-modified with an unsaturated carboxylic acid, copolymers of ethylene or propylene with acrylic acid or methacrylic acid is used; or a polypropylene resin composition according to any one of claims 1 to 11, ethylene-propylene-butene terpolymer, amorphous ethylene-propylene copolymer, or propylene-α-olefin copolymer is further mixed and used in an amount of 50% by weight or less.

17. The multilayer film for a flexible package battery bag according to claim 14, wherein, The metal foil layer is formed of a metal selected from aluminum and nickel or an inorganic compound selected from silicon oxide and aluminum oxide.

18. The multilayer film for a pouch cell bag according to claim 14, characterized in that, When forming the adhesion layer, polyvinyl acetate, acrylic, methacrylic, acrylic, ester, styrene, acrylate, cellulose, polyester, polyamide, amino, phenolic resin, epoxy, polyurethane, nitrile, rubber, silicone adhesives, or polyolefin resins are used.

19. The multilayer film for a flexible package battery bag according to claim 14, wherein, The base layer has a multilayer structure including at least two layers selected from a polystyrene layer, a nylon layer, a polyester layer, and a printing layer.

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