Solvent composition and method for manufacturing porous film using same

Abstract

One aspect of the present invention provides a solvent composition and a method for manufacturing a porous film using the solvent composition, in which the solvent composition is used for manufacturing a porous film including a plurality of pores by selectively extracting and removing a pore-forming agent from a base film comprising polyolefin and the pore-forming agent, and comprises at least one of alkyl carbonate and alkyl acetate and a non-chlorine-based halogen compound.

Description

Solvent composition and method for producing a porous film using the same

[0001] The present invention relates to a solvent composition and a method for producing a porous film using the same, and more particularly, to a solvent composition that can effectively replace chlorine-based solvents that are harmful to the human body and the environment, and a method for producing a porous film using the same.

[0002] Lithium secondary batteries are widely used as power sources for various electrical products that require miniaturization and lightweighting, such as smartphones, laptops, and tablet PCs. As their application areas expand to include smart grids and medium- to large-sized batteries for electric vehicles, there is a growing demand for the development of lithium secondary batteries with large capacity, long lifespan, and high stability.

[0003] As a means of achieving the above purpose, a porous film-type separator with micropores formed to separate the positive and negative electrodes to prevent internal short circuits and facilitate the movement of lithium ions during the charge and discharge process is being developed in various ways, especially a microporous separator using polyolefin such as polyethylene, which is advantageous in forming pores by thermally induced phase separation, is economical, and easily satisfies the properties required for the separator.

[0004] The manufacturing process of a separator for lithium secondary batteries can be divided into wet and dry processes based on the method for forming pores. In the case of the wet process, a raw material mixture containing a main resin and a separate substance for forming pores (a pore-forming agent) is extruded and stretched to produce a precursor film, and then the precursor film is brought into contact with a solvent that can selectively dissolve the pore-forming agent to extract and remove the pore-forming agent from the precursor film, thereby forming pores at the location where the pore-forming agent was in the precursor film. In the case of the dry process, a precursor film is manufactured by extruding a main resin, and then pores are formed during the process of stretching the precursor film. That is, in the dry process, the pore-forming agent essential to the wet process and the steps for extracting and removing it are omitted, and the size and structure of the pores depend only on the stretching of the precursor film, so compared to the wet process, there is a problem that the pores are uneven and, in some cases, pinholes occur. Therefore, most commercialized separation membranes are manufactured in the wet process.

[0005] In the wet process, chlorine halogen solvents such as dichloromethane and trichloroethylene, which have excellent extractability and quick-drying properties, are used as solvents for selectively dissolving and extracting and removing the pore-forming agent from the bulb film. However, as the carcinogenicity, toxicity, and environmental hazards of these chlorine substances have recently come to light, solvents that can replace them are being developed.

[0006] Halogen-free solvents such as methyl ethyl ketone, acetone, and methanol have been proposed. However, these solvents are explosive and flammable at room temperature, posing safety concerns and making them difficult to handle. Furthermore, synthetic solvents such as isoparaffin hydrocarbon solvents have been proposed. However, these solvents have low selective solubility and extractability for the pore-forming agent, and require excessive drying time, which poses disadvantages in terms of rapid drying and, therefore, productivity.

[0007] The present invention is to solve the problems of the prior art described above, and the purpose of the present invention is to provide a solvent composition that can effectively replace the chlorine-based solvent used to selectively extract and remove a pore-forming agent from a base film including a conventional polyolefin and a pore-forming agent, thereby significantly reducing harmful effects on the human body and the environment, and can be quickly dried and removed from the base film during the production of a porous film to secure and maintain a required level of productivity, and a method for producing a porous film using the same.

[0008] One aspect of the present invention provides a solvent composition comprising at least one of an alkyl carbonate and an alkyl acetate, and a non-chlorine halogen compound, which is used to produce a porous film comprising a plurality of pores by selectively extracting and removing the pore-forming agent from a base film comprising polyolefin and the pore-forming agent.

[0009] In one embodiment, the alkyl carbonate may be one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylmethyl carbonate, ethylpropyl carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, bromopropylene carbonate, dibromopropylene carbonate, nitropropylene carbonate, cyanopropylene carbonate, and combinations of two or more thereof.

[0010] In one embodiment, the alkyl acetate may be one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and combinations of two or more thereof.

[0011] In one embodiment, the non-chlorine halogen compound may include a fluorine ether compound.

[0012] In one embodiment, the fluorine-containing ether compound may be one selected from the group consisting of 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether; 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether; bis(fluoromethyl) ether; 2-fluoromethyl ether; bis(2,2,2-trifluoroethyl) ether; propyl 1,1,2,2-tetrafluoroethyl ether; isopropyl 1,1,2,2-tetrafluoroethyl ether; 1,1,2,2-tetrafluoroethyl isobutyl ether; 1,1,2,3,3,3-hexafluoropropyl ethyl ether; 1H,1H,2'H,3H-decafluorodipropyl ether; 1H,1H,2'H-perfluorodipropyl ether, and combinations of two or more thereof.

[0013] In one embodiment, the non-chlorine halogen compound may include a brominated compound.

[0014] In one embodiment, the brominated compound may be one selected from the group consisting of dibromomethane, dibromoethane, dibromopropane, dibromobutane, dibromocyclohexane, dibromobenzene, and combinations of two or more thereof.

[0015] In one embodiment, the content of the non-chlorine halogen compound in the solvent composition may be 5 to 30 wt%.

[0016] In one embodiment, the kauri-butanol value of the solvent composition may be greater than or equal to 100.

[0017] Another aspect of the present invention provides a method for manufacturing a porous film using the solvent composition, comprising the steps of: (a) forming a raw material including polyolefin and a pore-forming agent to manufacture a base film; (b) applying the solvent composition to the base film to selectively extract and remove the pore-forming agent from the base film; and (c) drying the base film to remove the remaining solvent composition.

[0018] In one embodiment, the polyolefin may include one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, ethylene vinyl acetate, ethylene butylacrylate, ethylene ethyl acrylate, and combinations or copolymers of two or more thereof.

[0019] In one embodiment, the pore forming agent may be a paraffin oil having a kinematic viscosity of 50 to 100 cSt at 40°C.

[0020] In one embodiment, the drying in step (c) may be performed for 1 to 20 minutes.

[0021] In one embodiment, the method for manufacturing the porous film may further include, between steps (a) and (b), a step (b0) of stretching the base film.

[0022] In one embodiment, the method for manufacturing the porous film may further include, between steps (b) and (c), a step (b1) of stretching the product of step (b).

[0023] A solvent composition according to one aspect of the present invention is used to produce a porous film including a plurality of pores by selectively extracting and removing the pore-forming agent from a base film including polyolefin and the pore-forming agent, and includes at least one of an alkyl carbonate and an alkyl acetate and a non-chlorinated halogen compound, thereby effectively replacing chlorinated solvents that are harmful to the human body and the environment, and can be quickly dried and removed from the base film during the production of the porous film, thereby ensuring and maintaining a required level of productivity.

[0024] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0025] The present invention will be described below. However, the present invention may be implemented in various different forms and is therefore not limited to the embodiments described herein.

[0026] Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "indirectly connected" with other elements intervening. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather implies that the other components may be included, unless otherwise specifically stated.

[0027] One aspect of the present invention provides a solvent composition comprising at least one of an alkyl carbonate and an alkyl acetate, and a non-chlorine halogen compound, which is used to produce a porous film comprising a plurality of pores by selectively extracting and removing the pore-forming agent from a base film comprising polyolefin and the pore-forming agent.

[0028] The manufacturing process of a porous film is divided into a dry process and a wet process depending on the method for forming pores, raw materials, etc. In the wet process, a base film or precursor film is manufactured by extruding a raw material mixture containing a main resin and a separate pore-forming agent for forming pores, and then the base film is brought into contact with a solvent capable of selectively dissolving the pore-forming agent, for example, a single solvent or a mixed solvent (solvent composition), to extract and remove the pore-forming agent in the base film, thereby forming pores at the location of the pore-forming agent in the base film.

[0029] In order to properly secure the pores of the porous film in the wet process, the selectivity and solubility of the solvent for extracting and removing the pore-forming agent must be sufficiently secured, and in terms of productivity, the solvent remaining in the base film after the extraction process must be quickly dried and removed, so quick-drying property must also be considered important.

[0030] Chlorinated halogen solvents such as dichloromethane and trichloroethylene are widely used as these solvents, but recently, as the carcinogenicity, toxicity, and environmental hazards of these chlorinated substances have been highlighted, the need for solvents that can replace them has emerged. In response, methyl ethyl ketone, acetone, and methanol have been proposed as halogen-free solvents, but these have safety vulnerabilities and are difficult to handle due to explosiveness and flammability at room temperature. In addition, synthetic solvents such as isoparaffin hydrocarbon solvents have been proposed, but there are problems in that the selective solubility and extractability for the pore-forming agent are low, and the drying time is excessive, which is disadvantageous in terms of quick drying and the resulting productivity.

[0031] In this regard, the solvent composition comprises at least one of an alkyl carbonate and an alkyl acetate, and a non-chlorinated halogen compound, thereby effectively replacing chlorinated solvents that are harmful to the human body and the environment, and can be quickly dried and removed from the base film during the production of a porous film, thereby ensuring and maintaining a required level of productivity. The solvent composition may comprise an alkyl carbonate and a non-chlorinated halogen compound, an alkyl acetate and a non-chlorinated halogen compound, or an alkyl carbonate, an alkyl acetate, and a non-chlorinated compound.

[0032] The alkyl carbonate may be, for example, one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylmethyl carbonate, ethylpropyl carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, bromopropylene carbonate, dibromopropylene carbonate, nitropropylene carbonate, cyanopropylene carbonate, and a combination of two or more thereof, and preferably, one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, and a combination of two or more thereof, and more preferably, dimethyl carbonate. However, it is not limited to this.

[0033] The above alkyl carbonate not only selectively dissolves and removes the pore-forming agent, but is also a component of the electrolyte of a commonly used lithium secondary battery, so even if a trace amount remains in the porous film, it may have a beneficial effect in terms of affinity and wettability for the electrolyte during battery assembly.

[0034] The alkyl acetate may be, for example, one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and combinations of two or more thereof, preferably at least one of ethyl acetate and propyl acetate, and more preferably, propyl acetate, but is not limited thereto.

[0035] The above alkyl carbonate and / or the above alkyl acetate have excellent selective solubility in the pore-forming agent, but are explosive and flammable at room temperature. Therefore, the safety and handling properties can be appropriately supplemented by further including a non-chlorine halogen compound in the solvent composition. The non-chlorine halogen compound may include a fluorine ether compound and / or a brominated compound.

[0036] The above fluorine ether compounds include, for example, 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether; 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether; bis(fluoromethyl) ether; 2-fluoromethyl ether; bis(2,2,2-trifluoroethyl) ether; propyl 1,1,2,2-tetrafluoroethyl ether; isopropyl 1,1,2,2-tetrafluoroethyl ether; 1,1,2,2-tetrafluoroethyl isobutyl ether; 1,1,2,3,3,3-hexafluoropropyl ethyl ether; 1H,1H,2'H,3H-decafluorodipropyl ether; It may be one selected from the group consisting of 1H,1H,2'H-perfluorodipropyl ether and combinations of two or more thereof, preferably 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether and / or 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, more preferably 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, but is not limited thereto.

[0037] The bromine compound may be, for example, one selected from the group consisting of dibromomethane, dibromoethane, dibromopropane, dibromobutane, dibromocyclohexane, dibromobenzene, and a combination of two or more thereof, and preferably, one selected from the group consisting of dibromomethane, dibromoethane, dibromopropane, and a combination of two or more thereof, and more preferably, dibromomethane, but is not limited thereto.

[0038] The content of the non-chlorine halogen compound in the solvent composition may be 5 to 30 wt%, more preferably 5 to 15 wt%, and even more preferably 5 to 10 wt%. If the content of the non-chlorine halogen compound in the solvent composition is less than 5 wt%, it is difficult to suppress the explosiveness and flammability of the alkyl carbonate and / or the alkyl acetate at room temperature, and if it exceeds 30 wt%, the selective solubility and quick-drying property of the solvent composition for the pore-forming agent may be reduced.

[0039] The kauri-butanol value (ASTM D 1133) of the solvent composition may be 100 or more, preferably 110 or more, and more preferably 120 to 130. If the kauri-butanol value of the solvent composition is less than 100, the selective solubility for the pore-forming agent is reduced, and accordingly, excessive time is required to extract and remove the pore-forming agent, which may lower productivity.

[0040] Another aspect of the present invention provides a method for manufacturing a porous film using the solvent composition, comprising the steps of: (a) forming a raw material including polyolefin and a pore-forming agent to manufacture a base film; (b) applying the solvent composition to the base film to selectively extract and remove the pore-forming agent from the base film; and (c) drying the base film to remove the remaining solvent composition.

[0041] In the above step (a), a raw material including polyolefin and a pore-forming agent can be extruded and discharged through a T-die to obtain a base film. The weight average molecular weight (Mw) of the polyolefin may be 200,000 to 4,000,000, preferably 400,000 to 2,000,000, more preferably 600,000 to 1,500,000, and the molecular weight distribution (Mw / Mn) may be 3 to 7. If the weight average molecular weight of the polyolefin is less than 200,000, the mechanical strength of the porous film may be reduced, and if it exceeds 4,000,000, the heat shrinkage rate may excessively increase, thereby reducing the heat resistance. In addition, if the molecular weight distribution of the polyolefin is less than 3, the dispersibility with the pore-forming agent may be reduced, which may result in a reduction in the uniformity of the manufactured porous film, and if it is greater than 7, the mechanical properties of the porous film may be reduced. The terms "weight average molecular weight" and "molecular weight distribution" used herein may mean values ​​measured by gel permeation chromatography (GPC) using polystyrene as a standard sample according to the method described in the literature (Macromolecules, Vol. 34, No. 19, pp. 6812-6820 (2001), etc.).

[0042] The polyolefin may include, for example, one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, ethylene vinyl acetate, ethylene butylacrylate, ethylene ethyl acrylate, and combinations or copolymers of two or more thereof, preferably, polyethylene and / or polypropylene, and more preferably, polyethylene, but is not limited thereto.

[0043] The above pore-forming agent may be one selected from the group consisting of paraffin oil, paraffin wax, mineral oil, solid paraffin, soybean oil, rapeseed oil, palm oil, coconut oil, di-2-ethylhexyl phthalate, dibutyl phthalate, diisononyl phthalate, diisodecyl phthalate, bis(2-propylheptyl) phthalate, naphthene oil, and combinations of two or more thereof, preferably paraffin oil, and more preferably paraffin oil having a kinematic viscosity of 50 to 100 cSt at 40°C, but is not limited thereto. The raw material may comprise 10 to 50 wt%, preferably 20 to 40 wt%, of the polyolefin, and 50 to 90 wt%, preferably 60 to 80 wt%, of the pore-forming agent.

[0044] The thickness of the base film obtained in the above step (a) may be 1,000 to 1,500 μm, preferably 1,200 to 1,500 μm. When the raw material includes an ultra-high molecular weight polyolefin, for example, an ultra-high molecular weight polyethylene having a weight average molecular weight of 2,000,000 or more, it is difficult to control the thickness of the base film to less than 1,000 μm through extrusion or casting, and when the thickness of the base film exceeds 1,500 μm, there is a problem that it is difficult to thin the porous film even through subsequent stretching.

[0045] In the step (b), the solvent composition may be applied to the base film to selectively extract and remove the pore-forming agent from the base film. The base film may be immersed in an extraction tank containing a solution containing the solvent composition for a preset period of time to extract and remove the pore-forming agent. The content of the pore-forming agent remaining on the surface and / or inside the base film after extraction may be 1 wt% or less. The time required for extraction and removal of the pore-forming agent may be determined by the thickness, porosity, etc. of the base film and / or the porous film, but may be 30 minutes or less, preferably 10 minutes or less, and more preferably 5 minutes or less when the thickness and porosity of the porous film are 1 to 20 μm and 30 to 70 vol%, respectively.

[0046] In the step (c), the base film can be dried to remove the remaining solvent composition. The base film from which the pore-forming agent has been extracted and removed can be heated to remove the solvent composition remaining in the base film. Some of the solvent composition applied in the step (b) may remain on the surface and / or inside the base film. The remaining solvent composition may deteriorate the subsequent process and the properties of the porous film manufactured thereby, so the solvent composition remaining in the base film can be removed by appropriately heating the base film to a temperature higher than the boiling point of the solvent composition.

[0047] In the above step (c), the drying may be performed for 1 to 20 minutes, preferably 1 to 15 minutes, and more preferably 1 to 10 minutes. If the time required for the drying exceeds 20 minutes, the productivity and energy efficiency of the process may be reduced, and if it is less than 1 minute, it is difficult to properly remove the solvent composition remaining on the base film.

[0048] The method for manufacturing the above porous film may further include a step of stretching the base film between steps (a) and (b) and / or (b1) between steps (b) and (c).

[0049] The above stretching may be performed by sequential biaxial stretching in which the base film is stretched in the longitudinal direction (MD) at a preset stretching ratio and then stretched in the transverse direction (TD), or by simultaneous biaxial stretching in which stretching is performed in the longitudinal direction (MD) and transverse direction (TD) simultaneously. The term "stretch ratio" used herein means the ratio of the longitudinal direction (MD) or transverse direction (TD) length of the base film after stretching to the longitudinal direction (MD) or transverse direction (TD) length before stretching, and may be interpreted as having the same meaning as stretching ratio, stretching ratio, etc. In the case of sequential biaxial stretching, the stretching ratio may be 2 to 20 times in the transverse direction (MD) and the longitudinal direction (TD), respectively, and the area magnification accordingly may be 4 to 400 times.

[0050] The longitudinal (MD) stretching of the above base film can be performed using a roll stretching machine. The roll stretching machine is a device that stretches the base film along the transport direction of the base film in a process line, and the stretching direction of the base film by the roll stretching machine can be defined as the longitudinal direction (MD, mechanical direction). The roll stretching machine includes a plurality of rolls installed along the transport direction of the base film, and can stretch the base film along the longitudinal direction at a preset magnification by rotating the rolls located at the rear end faster than the rolls located at the front end.

[0051] The transverse (TD) stretching of the above base film can be performed using a tenter stretching machine. The tenter stretching machine is a device that stretches the base film in a direction perpendicular to the transport direction of the base film in a process line, and can stretch the base film along the transverse direction at a preset magnification by fixing the transverse ends of the base film with a predetermined member, such as a chuck or clip, and then spacing the members apart in the transverse direction.

[0052] Meanwhile, the method for manufacturing the porous film may further include, after the step (c), a step of stretching the porous film in the transverse direction (TD) and heat-setting it. The heat-setting refers to a step of stretching the porous film in the transverse direction (TD), then relaxing and fixing it, and then forcibly fixing the porous film, which is about to shrink, by applying heat to remove residual stress. A high heat-setting temperature is advantageous in reducing the shrinkage rate, but if the temperature is excessively high, the porous film may partially melt and the formed pores may be closed, resulting in a decrease in air permeability. The heat-setting temperature is preferably selected within a range where 10 to 30 wt% of the crystalline portion of the porous film is melted. When the heat-setting temperature is selected within the above range, the problem of insufficient rearrangement of polyolefin molecules within the porous film, resulting in an insufficient residual stress relief effect, and the problem of partial melting and the closure of pores, resulting in a decrease in air permeability, can be prevented. For example, the heat setting temperature may be 120 to 140°C, preferably 123 to 135°C, and the heat setting time may be 5 seconds to 1 minute.

[0053] Hereinafter, embodiments of the present invention will be described in detail.

[0054] Example 1

[0055] 40 parts by weight of high-density polyethylene (HDPE) having a weight average molecular weight of 600,000 and a molecular weight distribution (Mw / Mn) of 5 and 60 parts by weight of paraffin oil having a kinematic viscosity of 70 cSt at 40°C were mixed and fed into a twin-screw extruder (inner diameter 58 mm, L / D=56). Under the conditions of a screw rotation speed of 40 rpm and 200°C, the mixture was extruded from the twin-screw extruder through a T-Die having a width of 630 mm and then passed through a casting roll having a temperature of 17°C to produce a base film having a thickness of 1,450 μm.

[0056] The above base film was stretched 8.0 times in the machine direction (MD) in a roll stretching machine at 105°C (MDO process) and 9.5 times in the transverse direction (TD) in a tenter stretching machine at 125°C (TDO1 process), and then impregnated in an extraction tank (25°C) containing an extraction solvent containing dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 90:10, to extract and remove paraffin oil for 5 minutes, and dried at 50°C to produce a porous film. The porous film was stretched 1.7 times in the transverse direction (TD) at 134°C (TDO2 process) and then heat-set in an 18% relaxed state.

[0057] Example 2

[0058] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 95:5, respectively.

[0059] Example 3

[0060] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with propyl acetate (PA) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 90:10, respectively.

[0061] Example 4

[0062] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with propyl acetate (PA) and dibromomethane (BM) in a weight ratio of 90:10, respectively.

[0063] Example 5

[0064] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 80:20, respectively.

[0065] Example 6

[0066] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC) and dibromomethane (BM) in a weight ratio of 80:20, respectively.

[0067] Example 7

[0068] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC), propyl acetate (PA), 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE), and dibromomethane (BM) in a weight ratio of 40:40:10:10, respectively.

[0069] Example 8

[0070] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 70:30, respectively.

[0071] Example 9

[0072] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC) and dibromomethane (BM) in a weight ratio of 70:30, respectively.

[0073] Comparative Example 1

[0074] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with a single solvent of dichloromethane (MC).

[0075] Comparative Example 2

[0076] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with a single solvent of trichloroethylene (TCE).

[0077] Comparative Example 3

[0078] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with a single solvent of methyl ethyl ketone (MEK).

[0079] Comparative Example 4

[0080] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with a single solvent of acetone.

[0081] Comparative Example 5

[0082] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with methanol alone.

[0083] Comparative Example 6

[0084] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with a single solvent, Isopar G (Isoparaffinic Hydrocarbon Solvent, Exxonmobil Chemical).

[0085] Comparative Example 7

[0086] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 65:35, respectively.

[0087] Comparative Example 8

[0088] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC) and dibromomethane (BM) in a weight ratio of 65:35, respectively.

[0089] Comparative Example 9

[0090] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with dimethyl carbonate (DMC) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 97:3, respectively.

[0091] Comparative Example 10

[0092] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with a single solvent of dimethyl carbonate (DMC).

[0093] Comparative Example 11

[0094] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with propyl acetate (PA) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 65:35, respectively.

[0095] Comparative Example 12

[0096] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with propyl acetate (PA) and dibromomethane (BM) in a weight ratio of 65:35, respectively.

[0097] Comparative Example 13

[0098] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with propyl acetate (PA) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFEE) in a weight ratio of 97:3, respectively.

[0099] Comparative Example 14

[0100] A porous film was prepared in the same manner as in Example 1, except that the extraction solvent was replaced with a single solvent of propyl acetate (PA).

[0101] The composition of the extraction solvent according to the above examples and comparative examples is as shown in Tables 1 to 3 below.

[0102] Classification DMCPATFEEBM Example 190-10 Example 295-5 Example 3-9010 Example 4-90-10 Example 580-20 Example 680-20 Example 740401010 Example 870-30 Example 970-30

[0103] (Unit: parts by weight)

[0104]

[0105] ClassificationMCTCEMEKacetoneMethanolIsopar GComparative Example 1100-----Comparative Example 2-100----Comparative Example 3--100---Comparative Example 4---100--Comparative Example 5----100-Comparative Example 6-----100

[0106] (Unit: parts by weight)

[0107]

[0108] Classification DMCPATFEEBM Comparative Example 765-35-Comparative Example 865--35 Comparative Example 997-3-Comparative Example 10100---Comparative Example 11-6535-Comparative Example 12-65-35 Comparative Example 13-973-Comparative Example 14-100--

[0109] (Unit: parts by weight)

[0110]

[0111] Experimental example

[0112] The physical properties and characteristics of the porous films manufactured in the above examples and comparative examples were measured and evaluated using the following methods, and the results are shown in Table 4 below.

[0113] - Kauri-butanol value (KBV): Measured using ASTM D 1133

[0114] -Flammability: If the flash point measured using a tag-sealed flash point meter is 25℃ or lower, O; if it is lower than 25℃, X

[0115] -Drying time (min): After extracting and removing paraffin oil, the time required to completely dry and remove the extraction solvent remaining in the porous film at 50℃ is measured.

[0116] - Extraction rate (%): Calculated according to the formula below

[0117] Food

[0118]

[0119]

[0120] Classification KBV Flammability Drying Time Extraction Rate Example 1125X1095 Example 2128X1296 Example 3124X1495 Example 4119X1594 Example 5115X1694 Example 6110X1693 Example 7110X1792 Example 8102X1991 Example 9100X2090 Comparative Example 1135X598 Comparative Example 2125X496 Comparative Example 3110O3092 Comparative Example 4130O497 Comparative Example 5120O595 Comparative Example 628X36065 Comparative Example 795X2884 Comparative Example 890X3181 Comparative Example 9126O896 Comparative Example 10129O897 Comparison Example 1188X4280 Comparison Example 1282X5578 Comparison Example 13123O1195 Comparison Example 14129O796

[0121]

[0122] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0123] The scope of the present invention is indicated by the claims set forth below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. Used to manufacture a porous film including a plurality of pores by selectively extracting and removing the pore-forming agent from a base film including polyolefin and a pore-forming agent. At least one of an alkyl carbonate and an alkyl acetate, and Containing non-chlorine halogen compounds, Solvent composition.

2. In paragraph 1, The above alkyl carbonate is one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylmethyl carbonate, ethylpropyl carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, bromopropylene carbonate, dibromopropylene carbonate, nitropropylene carbonate, cyanopropylene carbonate, and combinations of two or more thereof. Solvent composition.

3. In paragraph 1, The above alkyl acetate is one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, butyl acetate and combinations of two or more thereof. Solvent composition.

4. In paragraph 1, The above non-chlorine halogen compound includes a fluorine ether compound. Solvent composition.

5. In paragraph 4, The above fluorine ether compound is one selected from the group consisting of 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether; 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether; bis(fluoromethyl) ether; 2-fluoromethyl ether; bis(2,2,2-trifluoroethyl) ether; propyl 1,1,2,2-tetrafluoroethyl ether; isopropyl 1,1,2,2-tetrafluoroethyl ether; 1,1,2,2-tetrafluoroethyl isobutyl ether; 1,1,2,3,3,3-hexafluoropropyl ethyl ether; 1H,1H,2'H,3H-decafluorodipropyl ether; 1H,1H,2'H-perfluorodipropyl ether and combinations of two or more thereof. Solvent composition.

6. In paragraph 1, The above non-chlorine halogen compound includes a brominated compound. Solvent composition.

7. In paragraph 6, The above brominated compound is one selected from the group consisting of dibromomethane, dibromoethane, dibromopropane, dibromobutane, dibromocyclohexane, dibromobenzene, and combinations of two or more thereof. Solvent composition.

8. In paragraph 1, The content of non-chlorine halogen compound in the above solvent composition is 5 to 30 wt%, Solvent composition.

9. In paragraph 1, The kauri-butanol value of the above solvent composition is 100 or more, Solvent composition.

10. A method for manufacturing a porous film using a solvent composition according to any one of claims 1 to 9, (a) a step of manufacturing a base film by molding a raw material including polyolefin and a pore forming agent; (b) a step of selectively extracting and removing the pore-forming agent from the base film by applying the solvent composition to the base film; and (c) a step of drying the base film to remove the remaining solvent composition; Method for manufacturing a porous film.

11. In paragraph 10, The above polyolefin comprises one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, ethylene vinyl acetate, ethylene butylacrylate, ethylene ethyl acrylate, and combinations or copolymers of two or more thereof. Method for manufacturing a porous film.

12. In paragraph 10, The above pore forming agent is a paraffin oil having a kinematic viscosity of 50 to 100 cSt at 40°C. Method for manufacturing a porous film.

13. In paragraph 10, In the above step (c), the drying is performed for 1 to 20 minutes. Method for manufacturing a porous film.

14. In paragraph 10, Between steps (a) and (b) above, (b0) further comprising a step of stretching the base film; Method for manufacturing a porous film.

15. In paragraph 10, Between steps (b) and (c) above, (b1) a step of extending the product of step (b); further comprising; Method for manufacturing a porous film.

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