Ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membrane and manufacturing method thereof

Abstract

The present invention relates to an ultra-high purity and ultra-high crystallinity polypropylene for a secondary battery separation membrane and a method for manufacturing the same, the ultra-high purity and ultra-high crystallinity polypropylene being characterized by having a residual inorganic content of 30 ppm or less and an isotactic quintuple fraction of 98% or more. According to the present invention, in order to improve the performance of the secondary battery separation membrane, inorganic substances, low-molecular substances and low-crystalline substances in polypropylene are reduced by adjusting the addition ratio of the main catalyst, the accelerator and the cocatalyst in the polymerization process, the ash removal process for removing residual inorganic substances, and the removal of low-molecular substances and atactic polypropylene; therefore, the polypropylene can simultaneously show ultra-high purity and ultra-high crystallization characteristics.

Description

Technical Field

[0001] This invention relates to ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators and their manufacturing methods. More specifically, it relates to ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators and their manufacturing methods, which are produced by adjusting the addition ratio of the main catalyst, accelerator, and co-catalyst in the polymerization process for removing residual inorganic matter through a deashing process and removing low molecular weight substances and atactic polypropylene. Background Technology

[0002] Polypropylene, as a representative secondary battery separator material, such as polyethylene (PE) and polypropylene (PP), is a high molecular weight resin with high ionic conductivity and can function as an insulator when the internal temperature of the battery rises abnormally due to a short circuit, thus it is widely used.

[0003] The function of a secondary battery separator membrane is to prevent contact between the positive and negative electrodes inside the battery and to separate the active materials of the positive and negative electrodes so that they do not mix. That is, the separator membrane acts as an insulator that physically isolates the positive and negative electrodes. If the separator membrane cannot completely separate the positive and negative electrodes, they will be in direct contact. In this case, the positive and negative electrodes directly exchange electrons, generating only heat and not electricity. Since the positive electrode has a high energy level and is relatively unstable, a short circuit will occur when it comes into contact with the negative electrode. In the event of such a short circuit, higher purity polypropylene results in higher insulation breakdown strength and improved stability, thus preventing the short circuit. Furthermore, higher purity can lead to superior electrical and mechanical properties. The separator membrane is coated with inorganic particles such as alumina and boehmite to increase heat resistance and improve stability. In this case, if atactic polypropylene is present, the coating will peel off due to migration to the surface, leading to a decrease in the stability of the separator membrane. Therefore, in the case of polypropylene used for the separator membrane, ultra-high purity and ultra-high crystallinity are required.

[0004] Furthermore, the separator membrane in a secondary battery contains tiny pores through which the electrolyte moves; therefore, the uniformity of these pores is crucial. Here, the higher the crystallinity of polypropylene, the more uniform the pores formed. For lithium-ion batteries using a uniaxial dry process, crystallinity is first increased through an aging process, and then cracks are formed at the interfaces between the layered crystals during initial stretching, followed by an additional stretching process to create uniform pores. At this point, only by using raw materials with a high isotactic pentad fraction and low amorphous component content can high crystallinity be achieved during the aging process, a uniform pore structure be obtained during stretching, and the strength of the subsequently manufactured separator membrane be improved. Therefore, as mentioned above, high crystallinity of polypropylene is a crucial factor for the formation of uniform pores and the heat resistance, strength, and other properties of the manufactured separator membrane. Moreover, if the isotactic pentad fraction of polypropylene is below 95%, heat resistance and rigidity decrease, which may lead to problems such as physical property degradation, such as bending or twisting at high temperatures.

[0005] Therefore, in order to improve the mechanical properties and the performance of secondary battery separation membranes, it is necessary to develop technologies to obtain polypropylene with ultra-high purity and ultra-high crystallinity.

[0006] [Existing Technical Documents]

[0007] [Patent Documents]

[0008] (Patent Document 0001) Korean Patent KR 10-1300346

[0009] (Patent Document 0002) Korean Patent KR 10-1711261 Summary of the Invention

[0010] (Technical issue)

[0011] The present invention aims to solve the problems existing in the prior art. Its purpose is to improve the performance of the secondary battery separation membrane by adjusting the addition ratio of the main catalyst, accelerator and co-catalyst in the polymerization process, and by using the deashing process for removing residual inorganic matter and removing low molecular weight substances and atactic polypropylene to produce ultra-high purity and ultra-high crystallinity polypropylene.

[0012] (Technical Solution)

[0013] To achieve the aforementioned technical challenges, this invention discloses an ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separator membranes, characterized in that the residual inorganic matter (ash) content is below 30 ppm and the isotactic pentagonal fraction is above 98%.

[0014] In the secondary battery separation membrane, the aluminum content of the ultra-high purity and ultra-high crystallinity polypropylene can be less than 15 ppm and the magnesium content can be less than 4 ppm, which are the residual inorganic substances.

[0015] The secondary battery separator membrane uses ultra-high purity and ultra-high crystallinity polypropylene with a melting point of 164°C or higher.

[0016] On the one hand, in order to achieve the above-mentioned technical problem, the present invention also discloses a method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes, comprising: (a) mixing and adding an alkylaluminum compound as a co-catalyst (A), a titanium compound as a main catalyst (B), and a silicon compound as a promoter (C) in the presence of a hydrocarbon solvent containing 1 to 20 carbon atoms in a reactor; (b) adding propylene (D) and hydrogen (E) to the mixed solution obtained in step (a) and maintaining the temperature in the range of 30 to 90°C for 1 to 6 hours while simultaneously carrying out a polymerization reaction; (c) removing catalyst residues from the polypropylene slurry reaction product obtained after performing step (b) and separating ultra-high purity and ultra-high crystallinity polypropylene powder; and (d) filtering and drying the ultra-high purity and ultra-high crystallinity polypropylene powder.

[0017] The hydrocarbon solvent may be any one or more solvents selected from the group consisting of pentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, decane, undecane, dodecane, tridecane or tetradecane, benzene, toluene, xylene, ethylbenzene, dichloropropane, dichloroethylene, trichloroethylene, carbon tetrachloride and chlorobenzene.

[0018] The cocatalyst (A) may include any one or more compounds selected from the group consisting of triethylaluminum, trimethylaluminum, triisobutylaluminum, trioctylaluminum, diethylaluminum chloride, diethylaluminum bromide, diethylaluminum iodide, diethylaluminum fluoride, diethylaluminum chloride, dimethylaluminum chloride, metallic aluminum dichloride, and ethylaluminum trichloride.

[0019] The promoter (C) may include any one or more compounds selected from the group consisting of compounds of the following chemical formula (1), compounds of the following chemical formula (2), and compounds of the following chemical formula (3):

[0020] [Chemical Formula (1)]

[0021]

[0022] [Chemical Formula (2)]

[0023]

[0024] [Chemical Formula (3)]

[0025]

[0026] In the chemical formulas (1) to (3), R a R 7 R 8 and R 9 Each is independently selected from alkyl, cycloalkyl, aryl, allyl, or vinyl groups having 1 to 12 carbon atoms; R b R is an alkyl or aryl group having 1 to 6 carbon atoms; R is an alkyl, cycloalkyl, aryl, allyl, or -ORc group having 1 to 12 carbon atoms, wherein R c It is an alkyl or aryl group having 1 to 6 carbon atoms; and n is an integer from 0 to 6.

[0027] The titanium compound containing 1 mole of Ti as the main catalyst (B) may contain 10 to 30 moles of Al as the co-catalyst (A).

[0028] The titanium compound, which is based on 1 mole of Ti as the main catalyst (B), may contain 0.5 to 5 moles of Si as the promoter (C) in the silicon compound.

[0029] The polymerization reaction can be carried out for 1 to 6 hours within a pressure range of 1 to 40 bar.

[0030] The step (c) of removing catalyst residues from the polypropylene slurry reactant obtained after performing step (b) and separating ultra-high purity and ultra-high crystallinity polypropylene powder may include: mixing the polypropylene slurry reactant and a polar organic solvent to obtain a mixture; and separating the mixture into the ultra-high purity and ultra-high crystallinity polypropylene powder and the polar organic solvent using distilled water or filtered water.

[0031] The polar organic solvent comprises any one or more compounds selected from the group consisting of compounds of the following chemical formula (4) and compounds of the following chemical formula (5):

[0032] [Chemical formula (4)]

[0033] R-OH,

[0034] [Chemical Formula (5)]

[0035] HO-R1-R2-OH,

[0036] In the chemical formula (4), R is a straight-chain or branched alkyl group having 1 to 12 carbon atoms, and the chemical formula (4) is any one or more compounds selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, branched alkyl isopropanol, isobutanol and isopentanol.

[0037] In the chemical formula (5), R1 and R2 are straight-chain alkyl groups having 0 to 6 carbon atoms, and the chemical formula (5) is any one or more compounds selected from the group consisting of methanol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol and dodecanediol.

[0038] The polar organic solvent can be 10 to 1000 parts by weight, based on 100 parts by weight of the polypropylene slurry reactant.

[0039] The step of mixing the polypropylene slurry reactant and the polar organic solvent to obtain a mixture can be carried out at a temperature range of 50 to 100°C for 5 to 30 minutes.

[0040] Wherein, based on 100 parts by weight of the polar organic solvent, the distilled water or filtered water can be 100 to 3000 parts by weight.

[0041] (Invention Effects)

[0042] The technology disclosed in this invention can have the following effects. However, specific embodiments do not necessarily mean that all or only the following effects must be included, and therefore the scope of the disclosed technology should not be construed as limited thereto.

[0043] According to the present invention, in order to improve the performance of the secondary battery separation membrane, the addition ratio of the main catalyst, accelerator and co-catalyst in the polymerization process is adjusted to reduce the inorganic matter, low molecular weight and low crystallinity in polypropylene by the deashing process for removing residual inorganic matter and removing low molecular weight substances and atactic polypropylene, thereby enabling polypropylene to exhibit both ultra-high purity and ultra-high crystallinity characteristics.

[0044] Furthermore, according to the present invention, since the content of residual inorganic matter and the content of low-crystallinity polymer are low during polypropylene polymerization, the performance of the secondary battery separator membrane can be improved by exhibiting excellent mechanical durability and dielectric properties. Detailed Implementation

[0045] Because the present invention can be modified and has various embodiments, specific embodiments will be described in detail in the specific description. However, this is not intended to limit the invention to the specific embodiments, but should be understood to include all modifications, equivalents, and substitutions contained within the spirit and scope of the invention.

[0046] Terms such as "first" and "second" may be used to describe various constituent elements, but the constituent elements should not be limited to these terms. The terms are used only for the purpose of distinguishing one constituent element from other constituent elements.

[0047] For example, without departing from the scope of the invention, a first constituent element may be named a second constituent element, and similarly, a second constituent element may be named a first constituent element. The term "and / or" includes a combination of or any one of a plurality of related described items.

[0048] Unless otherwise defined, all terms used in this application, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the relevant technical context, and should not be interpreted as having an ideal or overly formal meaning, unless expressly defined in this application.

[0050] Throughout this application, when a part “includes” a constituent element, it means that it may also include other constituent elements, rather than excluding other elements, unless explicitly stated otherwise.

[0051] As used herein, the terms “about,” “substantially,” etc., are used to indicate that the value is equal to or close to the value when the inherent manufacturing and material tolerances are presented in the sense described, and are used to aid in understanding this application and to prevent unethical infringers from unfairly exploiting the disclosure of precise or absolute figures mentioned. Furthermore, throughout this application, “performing a step of this” or “a step of this” does not mean “a step of this.”

[0052] Throughout this application, the term "combination thereof" as used in the Markush format means a mixture or combination of one or more of the groups of constituent elements described in the Markush format, and is intended to include one or more of the groups of said constituent elements.

[0053] The inventors have confirmed and completed this invention of ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators, which can produce a residual inorganic content of less than 30 ppm and an isotactic pentagonal fraction of 98% or higher. Furthermore, as used in this specification, "ultra-high purity" refers to a residual inorganic content of less than 30 ppm, and "ultra-high crystallinity" refers to an isotactic pentagonal fraction of 98% or higher. For ease of explanation, the isotactic pentagonal fraction in this specification may be expressed in decimal units. For example, 1% isotactic pentagonal fraction can be represented as 0.01.

[0054] Ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separator membranes

[0055] This specification discloses ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separator membranes, characterized by a residual inorganic content of less than 30 ppm and an isotactic pentagonal component fraction of more than 98%. The polypropylene of this invention simultaneously achieves ultra-high purity and ultra-high crystallinity, thereby exhibiting excellent mechanical properties, such as excellent electrical properties, heat resistance, and rigidity.

[0056] In the ultra-high purity and ultra-high crystallinity polypropylene used for the secondary battery separation membrane, the aluminum content, which is the residual inorganic matter, can be below 15 ppm and the magnesium content can be below 4 ppm.

[0057] The ultra-high purity and ultra-high crystallinity polypropylene used in the secondary battery separator membrane of the present invention has a melting point (Tm) of 160°C or higher. More specifically, the ultra-high purity and ultra-high crystallinity polypropylene used in the secondary battery separator membrane of the present invention has a melting point of 164°C or higher. That is, the polypropylene of the present invention exhibits ultra-high purity and ultra-high crystallinity, thereby improving heat resistance and possessing excellent thermal stability.

[0058] The ultra-high purity and ultra-high crystallinity polypropylene of this invention can be applied to lithium secondary battery separator membrane materials, but is not limited thereto. The ultra-high purity and ultra-high crystallinity polypropylene of this invention exhibits excellent mechanical properties, allowing for selection of suitable applications based on the intended use of the polypropylene.

[0059] <Manufacturing Method of Ultra-High Purity and Ultra-High Crystallinity Polypropylene for Secondary Battery Separation Membranes>

[0060] This specification also discloses a method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separator membranes.

[0061] To achieve the above objectives, this invention provides a method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators. The method includes: using a main catalyst with high stereoregularity, adding a co-catalyst capable of activating the main catalyst and minimizing main chain breakage, and a promoter serving as an optimal external electron donor to carry out a polymerization reaction. Furthermore, this invention adjusts the addition ratios of the main catalyst, promoter, and co-catalyst, while simultaneously performing a slurry removal process to further improve the purity and crystallinity of the polypropylene.

[0062] The manufacturing method of this invention improves catalytic activity through an improved catalyst system, reduces low-molecular-weight and random components in polypropylene generated during the polymerization reaction, and uses hydrocarbon solvents such as hexane to remove low-molecular-weight and random components during the polymerization reaction, thereby achieving ultra-high crystallinity. Furthermore, ultra-high purity can be achieved by using a deashing process with polar organic solvents to remove catalyst residues.

[0063] The process steps of the method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for the secondary battery separator of the present invention are as follows:

[0064] (a) In the presence of a hydrocarbon solvent containing 1 to 20 carbon atoms in the reactor, the step of mixing and adding an alkylaluminum compound as a cocatalyst (A), a titanium compound as a main catalyst (B), and a silicon compound as a promoter (C).

[0065] (b) Adding propylene (D) and hydrogen (E) to the mixed solution obtained in step (a) and maintaining the temperature in the range of 30 to 90°C for 1 to 6 hours while carrying out the polymerization reaction;

[0066] (c) The step of removing catalyst residues from the polypropylene slurry reactant obtained after performing step (b) and separating ultra-high purity and ultra-high crystallinity polypropylene powder; and

[0067] (d) The step of filtering and drying the ultra-high purity and ultra-high crystallinity polypropylene powder.

[0068] The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators of the present invention may further include, prior to step (a): mixing an alkylaluminum compound as a cocatalyst (A), a titanium compound as a main catalyst (B), a silicon compound as an accelerator (C), and propylene in the presence of a hydrocarbon solvent containing 1 to 20 carbon atoms in a reactor to produce a prepolymer. To prevent a rapid reaction of propylene, the manufacturing method of the present invention can first produce and utilize the prepolymer.

[0069] In the step of producing the prepolymer, a yield of 1 to 100 g polymer / g catalyst is preferred. It is assumed that if the yield is less than 1 g polymer / g catalyst, there may be a problem of not having the effect of first producing and adding the prepolymer. Conversely, if the yield exceeds 100 g polymer / g catalyst, there may be a problem of reduced catalytic activity.

[0070] Furthermore, if the above manufacturing method also includes a step of manufacturing the prepolymer, it is preferable to add the prepolymer instead of the main catalyst (B) in step (a).

[0071] In cases where the above manufacturing method also includes the step of manufacturing the prepolymer, if problems such as reduced activity and difficulty in process operation occur when directly polymerizing propylene due to poor polymer morphology and swelling, then manufacturing and polymerizing the prepolymer first can improve the morphology and apparent density of polypropylene.

[0072] In the step of manufacturing the prepolymer, for 100 parts by weight of a hydrocarbon solvent having 1 to 20 carbon atoms, it is preferable to use 0.001 to 5.0 parts by weight of co-catalyst (A), 0.01 to 50 parts by weight of main catalyst (B), and 0.001 to 5.0 parts by weight of promoter (C). It is assumed that if the amounts of co-catalyst (A), main catalyst (B), and promoter (C) used are less than 0.001, 0.01, and 0.001 parts by weight, respectively, for 100 parts by weight of a hydrocarbon solvent having 1 to 20 carbon atoms, a decrease in catalytic activity may occur. Conversely, if the amounts of co-catalyst (A), main catalyst (B), and promoter (C) used exceed 5.0, 50, and 5.0 parts by weight, respectively, for 100 parts by weight of a hydrocarbon solvent having 1 to 20 carbon atoms, a decrease in catalytic activity may occur, potentially leading to an increase in inorganic content.

[0073] The process of manufacturing the prepolymer is preferably carried out at 0 to 50°C, 0.1 to 2 bar, and 10 to 60 minutes. For example, if the process of manufacturing the prepolymer is carried out at temperatures below 0°C, 0.1 bar, and 10 minutes, problems such as reduced catalytic activity, poor morphology, poor physical properties, and difficulties in heating and process operation may occur. Conversely, if the process of manufacturing the prepolymer is carried out at temperatures above 50°C, 2 bar, and 60 minutes, problems such as reduced catalytic activity or poor polymer morphology may occur.

[0074] The hydrocarbon solvent may be any one or more of the following: aliphatic hydrocarbon solvents such as pentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, decane, undecane, dodecane, tridecane, or tetradecane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, and ethylbenzene; and halogenated hydrocarbon solvents such as dichloropropane, dichloroethylene, trichloroethylene, carbon tetrachloride, and chlorobenzene.

[0075] The hydrocarbon solvent can dissolve and remove low-molecular-weight and random components from polypropylene, thereby reducing the content of solvent-soluble components in polypropylene and obtaining polypropylene with excellent physical properties. During the polymerization reaction, the low-molecular-weight and random components dissolved by the hydrocarbon flux are then separated from the polypropylene powder through a filtration step.

[0076] The cocatalyst (A) may include any one or more compounds selected from the group consisting of triethylaluminum, trimethylaluminum, triisobutylaluminum, trioctylaluminum, diethylaluminum chloride, diethylaluminum bromide, diethylaluminum iodide, diethylaluminum fluoride, diethylaluminum chloride, dimethylaluminum chloride, metallic aluminum dichloride, and ethylaluminum trichloride.

[0077] The main catalyst (B) comprises a Ziegler-Natta series of titanium chloride catalysts containing silicon compounds of phthalates, diethers and succinates as internal electron donors, and titanium trichloride or titanium tetrachloride, which is suitable for using magnesium chloride as a support. More preferably, the main catalyst (B) provides high stereoregularity according to the morphology of the internal electron donors and can use commercially available catalysts.

[0078] The accelerator (C) may include any one or more compounds selected from the group consisting of compounds of the following chemical formula (1), compounds of the following chemical formula (2), and compounds of the following chemical formula (3):

[0079] [Chemical Formula (1)]

[0080]

[0081] [Chemical Formula (2)]

[0082]

[0083] [Chemical Formula (3)]

[0084]

[0085] In the chemical formulas (1) to (3), R a R 7 R 8 and R 9 Each is independently selected from alkyl, cycloalkyl, aryl, allyl, or vinyl groups having 1 to 12 carbon atoms; R b R is an alkyl or aryl group having 1 to 6 carbon atoms; R is an alkyl, cycloalkyl, aryl, allyl, or -OR group having 1 to 12 carbon atoms. c At this time, R c It is an alkyl or aryl group having 1 to 6 carbon atoms; and n is an integer from 0 to 6.

[0086] Specifically, as a representative example of a compound of the chemical formula (1), it may be selected from cyclohexylmethyldimethoxysilane (CMCD), cyclohexyl-n-propyldimethoxysilane (CPDM), cyclohexylisopropyldimethoxysilane (CIPDM), cyclohexyl-n-butyldimethoxysilane (CBDM), cyclohexylisobutyldimethoxysilane (CIBDM), cyclohexyl-n-butylhexyloxide silane (CHDM), cyclohexyl-N-nucleomethoxymethane silane (CODM), cyclohexyl-N-dimethoxysilane (CDEDM), dimethyl... The compound comprising any one or more compounds in the group consisting of dimethoxysilane, dimethyldiethoxysilane, dicyclopentyldimethoxysilane, diisopropyldimethoxysilane, dicyclopentyldimethoxysilane, methylphenyldimethoxysilane, diphenyldiethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, ethoxysilane, ethyltriisopropoxysilane, and vinyltributoxysilane. Preferably, as a representative example of the compound of the chemical formula (1), it may include any one or more compounds from the group consisting of dimethyldimethoxysilane, dimethyldiethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, diisopropyldimethoxysilane, dicyclopentyldimethoxysilane, methylphenyldimethoxysilane, diphenyldiethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, silane, phenyltriethoxysilane, butyltriethoxysilane, ethyltriisopropoxysilane, vinyltrioxysilane, and methyltriaryloxysilane.

[0087] Representative examples of compounds of the stated chemical formula (2) may be selected from 1,1,3,3-tetramethoxy-1,3-dimethyl-1,3-disilpropane (TMDMDP), 1,1,3,3-tetramethoxy-1-methyl-3-hexyl-1,3-disilpropane (TMMHDP), 1,1,3,3-tetramethoxy-1,3-di-n-hexyl-1,3-disilpropane (TMDHDP), 1,1,3,3-tetramethoxy-1 Any one or more compounds comprising the group consisting of methyl-3-cyclohexyl-1,3-disiloxane (TMMCDP), 1,1,3,3-tetramethoxy-1,3-dicyclohexyl-1,3-disiloxane (TMDCDP), 1,1,8,8-tetramethoxy-1,8-dicyclohexyl-1,8-disiloxane (TMDCDO), and 1,1,3,3-tetramethoxy-1,3-dimethyldisiloxane (TMDMDS).

[0088] Representative examples of compounds of the chemical formula (3) may be any compound selected from the group consisting of methyl(trimethylsilylmethyl)dimethoxysilane (MTDM), n-propyl(trimethylsilylmethyl)dimethoxysilane (PTDM), isopropyl(trimethylsilylmethyl)dimethoxysilane (IPTDM), n-butyl(trimethylsilylmethyl)dimethoxysilane (BTDM), isobutyl(trimethylsilylmethyl)dimethoxysilane (IBTDM), n-pentyl(trimethylsilylmethyl)dimethoxysilane (PnTDM), n-hexyl(trimethylsilylmethyl)dimethoxysilane (HTDM), cyclopentyl(trimethylsilane), or any compound selected from the group consisting of methyl(trimethylsilylmethyl)dimethoxysilane (CpTDM) and cyclohexyl(trimethylsilylmethyl)dimethoxysilane (CTDM).

[0089] The titanium compound containing 1 mole of Ti as the main catalyst (B) may contain 10 to 30 moles of Al as the co-catalyst (A), but is not limited thereto. For example, if the titanium compound containing 1 mole of Ti as the main catalyst (B) contains less than 10 moles of Al as the co-catalyst (A), the polymerization reaction may not occur sufficiently. Conversely, when the titanium compound containing 1 mole of Ti as the main catalyst (B) contains more than 30 moles of Al as the co-catalyst (A), the inorganic and amorphous components in the polypropylene produced by the polymerization reaction will be high, which may lead to problems with reduced purity and crystallinity.

[0090] The titanium compound containing 1 mole of Ti as the main catalyst (B) may contain 0.5 to 5 moles of Si as the promoter (C), but is not limited thereto. For example, if the titanium compound containing 1 mole of Ti as the main catalyst (B) contains less than 0.5 moles of Si as the promoter (C), the polymerization reaction may not occur sufficiently. Conversely, if the titanium compound containing 1 mole of Ti as the main catalyst (B) contains more than 5 moles of Si as the promoter (C), the inorganic and amorphous components in the polypropylene produced by the polymerization reaction will be high, which may lead to problems with reduced purity and crystallinity.

[0091] Conventional polypropylene polymerization methods include various methods such as slurry polymerization, bulk polymerization, and gas-phase polymerization. However, in the polypropylene manufacturing method of the present invention, slurry polymerization is preferred. The polypropylene manufacturing method for secondary battery separators of the present invention, by adjusting the addition ratio of the main catalyst, accelerator, and co-catalyst in the polymerization process, and by using a deashing process for removing residual inorganic matter and removing low-molecular-weight substances and atactic polypropylene, can provide polypropylene with ultra-high purity and ultra-high crystallinity.

[0092] In step (b), the polymerization reaction can be carried out as both a first-order and a second-order polymerization. In step (b), trace amounts of hydrogen (E) and propylene (D) can be added to the mixed solution obtained in step (a) to carry out a first-order polymerization reaction. After the first-order polymerization reaction is completed, propylene and hydrogen can be added again to carry out a second-order polymerization reaction.

[0093] Hydrogen (E, H2) is used as a molecular weight regulator, which can adjust the molecular weight range of the target polypropylene by adding trace amounts or not adding it at all.

[0094] In step (b), the primary and secondary polymerization reactions are preferably carried out at a temperature range of 30 to 90°C for 1 to 6 hours, but are not limited thereto. More specifically, the polymerization reaction is more preferably carried out at a temperature range of 60 to 80°C for 1 to 4 hours, and most preferably carried out at a temperature range of 65 to 75°C for 2 to 3 hours. For example, if the polymerization reaction is carried out at 30°C for less than 1 hour, the polymerization reaction may not occur sufficiently. Conversely, if the polymerization reaction is carried out at 90°C for more than 6 hours, excessive heat is provided to the mixed solution, which may result in problems such as reduced purity, crystallinity, or alteration of physical properties.

[0095] Furthermore, in step (b), the polymerization reaction is preferably carried out within a pressure range of 1 to 40 bar, but is not limited to this. For example, if the polymerization reaction is carried out at a polymerization pressure of less than 1 bar, the polymerization reaction may not occur sufficiently. Conversely, if the polymerization reaction is carried out at a polymerization pressure exceeding 40 bar, excessive heat is provided to the mixed solution, which may result in problems such as reduced purity, crystallinity, or alteration of physical properties.

[0096] <Deashing process for removing residual inorganic matter>

[0097] In the method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators of the present invention, step (c) may include the following residual inorganic matter removal process. The steps of the residual inorganic matter removal process are as follows:

[0098] The step of mixing the polypropylene slurry reactant and a polar organic solvent to obtain a mixture; and

[0099] The step of separating the mixture into the ultra-high purity and ultra-high crystallinity polypropylene powder and the polar organic solvent using distilled water or filtered water.

[0100] The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators of the present invention includes a de-ashing process for removing residual inorganic matter, thereby removing impurities such as catalyst residues and improving the purity and crystallinity of the final manufactured polypropylene. In the method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene of the present invention, the residual inorganic matter removal process can be referred to as the de-ashing process in this specification.

[0101] The polar organic solvent may include any one or more compounds selected from the group consisting of compounds of the following chemical formula (4) and compounds of the following chemical formula (5):

[0102] [Equation (4)]

[0103] R-OH,

[0104] [Equation (5)]

[0105] HO-R1-R2-OH,

[0106] In the chemical formula (4), R is a straight-chain or branched alkyl group having 1 to 12 carbon atoms, and the chemical formula (4) can be any one or more compounds selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, branched alkyl isopropanol, isobutanol and isopentanol.

[0107] In the chemical formula (5), R1 and R2 are straight-chain alkyl groups having 0 to 6 carbon atoms, and the chemical formula (5) can be any one or more compounds selected from the group consisting of methanol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol and dodecanediol.

[0108] Based on 100 parts by weight of the polypropylene slurry reactant, the polar organic solvent is 10 to 1000 parts by weight, but not limited to this. It is assumed that, based on 100 parts by weight of the polypropylene slurry reactant, when less than 10 parts by weight of the polar organic solvent is used, impurities such as catalyst residues may not be completely dissolved, potentially leading to insufficient removal of inorganic substances from the polypropylene. Conversely, based on 100 parts by weight of the polypropylene slurry reactant, when more than 1000 parts by weight of the polar organic solvent is used, the polypropylene slurry reactant may not dissolve in the polar organic solvent, potentially leading to insufficient removal of inorganic substances from the polypropylene. Furthermore, the more the weight of the polar organic solvent increases within the range of 10 to 1000 parts by weight of the polypropylene slurry reactant, the higher the efficiency of inorganic substance removal from the polypropylene may be.

[0109] The step of mixing the polypropylene slurry reactant and the polar organic solvent to obtain a mixture is preferably carried out at a temperature range of 50 to 100°C for 5 to 30 minutes, but is not limited thereto. More specifically, the step of mixing the polypropylene slurry reactant and the polar organic solvent to obtain a mixture is more preferably carried out at a temperature range of 75 to 95°C for 5 to 20 minutes, and most preferably carried out at a temperature range of 80 to 90°C for 5 to 15 minutes. For example, when the step of mixing the polypropylene slurry reactant and the polar organic solvent to obtain a mixture is carried out at 50°C and for less than 5 minutes, the removal of inorganic matter and low-crystallinity components in the polypropylene may be insufficient. Conversely, when the step of mixing the polypropylene slurry reactant and the polar organic solvent to obtain a mixture is carried out at 100°C and for more than 30 minutes, the removal effect of inorganic matter in the polypropylene is not increased compared to the conditions of 100°C and less than 30 minutes within the above-mentioned temperature and time range, and the problem of low commercial efficiency may occur.

[0110] To separate the polar organic solvent containing the impurities from the polypropylene slurry reactant, distilled water or filtered water can be used.

[0111] The mixture obtained by mixing the polypropylene slurry reactant and the polar organic solvent is then contacted with water, resulting in a layer separation. The polar organic solvent molecules mix to form an aqueous layer, while the separated ultra-high purity and ultra-high crystalline polypropylene floats on the surface of the water. The layer-separated mixture is then separated using filter paper or a filter and subsequently dried using a dryer at 90 to 105°C to obtain the final ultra-high purity and ultra-high crystalline polypropylene powder.

[0112] Based on 100 parts by weight of the polar organic solvent, the distilled or filtered water is between 100 and 3000 parts by weight, but not limited thereto. It is assumed that if less than 100 parts by weight of the distilled or filtered water is used based on 100 parts by weight of the polar organic solvent, layer separation of the polar organic solvent may not occur, potentially leading to insufficient removal of inorganic matter from the polypropylene. Conversely, if more than 3000 parts by weight of the distilled or filtered water is used based on 100 parts by weight of the polar organic solvent, the mixture to be filtered increases, potentially causing difficulty in separation through filter paper or a filter after layer separation.

[0113] Through the above-described method for manufacturing polypropylene of the present invention, the present invention can produce ultra-high purity and ultra-high crystallinity polypropylene, which can be used as a separation membrane for secondary batteries requiring low inorganic content, with an usable residual inorganic content of less than 30 ppm and an isotactic pentagonal fraction of more than 98%.

[0114] The claims made herein will now be described in more detail with reference to embodiments. However, those skilled in the art can modify the embodiments described herein in various ways to achieve various forms, and the matters described herein do not limit the invention to the particular form of disclosure, and can be considered to include all equivalents to alternatives encompassed within the spirit and scope of the invention.

[0115] {Examples and Evaluation}

[0116] <Example>

[0117] <Experimental Example 1> Polymerization and Physical Property Measurement of Ultra-High Purity and Ultra-High Crystallinity Polypropylene Resin Example 1

[0118] a. A 50L stainless steel reactor equipped with a stirrer was placed under vacuum at room temperature, and 25L of hexane as an organic solvent was injected and stirred. At room temperature, 0.16 mol of titanium compound catalyst was added as the main catalyst, 3.36 mol of triethylaluminum as the co-catalyst, and 0.34 mol of dicyclopentyldimethoxysilane as the promoter. Then, the reactor was placed in a thermostat maintained at 70°C and the temperature was adjusted to 60°C.

[0119] b. First-order aggregation

[0120] After adding 5.0L of hydrogen as a molecular weight regulator, propylene monomer was added, the bar was adjusted to 7 bar, and polymerization was carried out at 70°C for 1 hour.

[0121] c. Second-order polymerization

[0122] After adding 45L of hydrogen, add propylene monomer, adjust to 8 bar, and polymerize at 73°C for 1 hour.

[0123] d. Deashing process

[0124] After the second-order polymerization reaction is completed, unreacted propylene monomer is removed. 3 L of methanol is added as a polar organic solvent and the mixture is stirred at 85°C for 10 minutes. Then, 200 ml of distilled water is added and the mixture is stirred for another 10 minutes.

[0125] e. After stirring, the powdered ultra-high purity and ultra-high crystallinity polypropylene resin is separated from the liquid components of the mixture of hexane, polar organic solvent, and water through a filter. The separated ultra-high purity and ultra-high crystallinity polypropylene resin is thoroughly dried in a dryer at 100°C to obtain white powdered polypropylene.

[0126] Example 2

[0127] Example 2 was manufactured in the same manner as Example 1, except that 0.18 mol of titanium compound catalyst was added as the main catalyst, 0.24 mol of dicyclopentyldimethoxysilane was added as a promoter, and 4.5 L of hydrogen was added in the first-stage polymerization and 40 L of hydrogen was added in the second-stage polymerization.

[0128] Example 3

[0129] Example 3 was manufactured in the same manner as Example 1, except that 0.20 mol of titanium compound catalyst was added as the main catalyst and 0.20 mol of dicyclopentyldimethoxysilane was added as a promoter. In the first-stage polymerization, 4.0 L of hydrogen was added and in the second-stage polymerization, 35 L of hydrogen was added.

[0130] Example 4

[0131] Example 4 was prepared in the same manner as Example 1, except that 0.22 mol of titanium compound catalyst was added as the main catalyst, 0.20 mol of dicyclopentyldimethoxysilane was added as a promoter, and 3.5 L of hydrogen was added in the first-stage polymerization and 30 L of hydrogen was added in the second-stage polymerization.

[0132] Comparative Example 1

[0133] a. Polypropylene resin from Company A is used, with an Ash content of 675 ppm and an isotactic pentagonal fraction of 0.979.

[0134] b. Polypropylene resin is produced by bulk polymerization without a deashing process.

[0135] Comparative Example 2

[0136] a. Polypropylene resin from Company B is used, with an Ash content of 109 ppm and an isotactic pentagonal fraction of 0.964.

[0137] b. Polypropylene resin is manufactured by performing polymerization reactions through bulk polymerization and gas-phase polymerization processes without performing a deashing process.

[0138] Comparative Example 3

[0139] a. Polypropylene resin from Company B is used, with an Ash content of 101 ppm and an isotactic pentagonal fraction of 0.974.

[0140] b. Polypropylene resin is manufactured by performing polymerization reactions through bulk polymerization and gas-phase polymerization processes without performing a deashing process.

[0141] Comparative Example 4

[0142] a. Polypropylene resin from Company C is used, with an Ash content of 11 ppm and an isotactic pentagonal fraction of 0.976.

[0143] b. Polypropylene resin is manufactured by performing a polymerization reaction through bulk polymerization and gas-phase polymerization, and by performing a deashing process.

[0144] Comparative Example 5

[0145] a. Polypropylene resin from Company C is used, with an Ash content of 16 ppm and an isotactic pentagonal fraction of 0.968.

[0146] b. Polypropylene resin is manufactured by performing a polymerization reaction through bulk polymerization and gas-phase polymerization, and by performing a deashing process.

[0147] Comparative Example 6

[0148] a. Polypropylene resin from Company D is used, with an Ash content of 189 ppm and an isotactic pentagonal fraction of 0.969.

[0149] b. Polypropylene resin is produced by gas-phase polymerization without a deashing process.

[0150] Comparative Example 7

[0151] a. Polypropylene resin from Company E is used, with an Ash content of 97 ppm and an isotactic pentagonal fraction of 0.966.

[0152] b. Polypropylene resin is produced by performing a gas-phase polymerization reaction without a deashing process.

[0153] Comparative Example 8

[0154] a. Polypropylene resin from Company F is used, with an Ash content of 23 ppm and an isotactic pentagonal fraction of 0.968.

[0155] b. Polypropylene resin is manufactured using a self-developed catalyst and through bulk polymerization and multi-zone polymerization processes without a deashing process.

[0156] Comparative Example 9

[0157] a. Polypropylene resin from Company F is used, with an Ash content of 32 ppm and an isotactic pentagonal fraction of 0.968.

[0158] b. Polypropylene resin is manufactured using a self-developed catalyst and through bulk polymerization and multi-zone polymerization processes without a deashing process.

[0159] Comparative Example 10

[0160] a. Polypropylene resin from Company F is used, with an Ash content of 33 ppm and an isotactic pentagonal fraction of 0.967.

[0161] b. Polypropylene resin is manufactured using a self-developed catalyst and through bulk polymerization and multi-zone polymerization processes without a deashing process.

[0162] Measurement methods for the physical properties of ultra-high purity and ultra-high crystallinity polypropylene resin

[0163] (1) Ash (residual inorganic matter) analysis

[0164] After the samples were burned and ashed at a specified temperature (800℃), the residual ash (inorganic matter) content was measured using SEM-EDS. The analytical equipment used was a TESCAN VEGAⅡLSU Thermo EDS system.

[0165] (2) XRF (X-ray Fluorescence) analysis

[0166] To perform qualitative and quantitative analysis of unknown elements in a sample, X-rays are irradiated onto the sample, generating secondary X-rays with qualitative characteristics. These secondary X-rays allow for qualitative analysis. Furthermore, the intensity of the measured X-rays is proportional to the elemental content, thus enabling quantitative analysis. The analytical equipment used is a Bruker S8Tiger.

[0167] (3) Analysis of Hep. / Xyl.Soluble

[0168] Extraction is performed from the extraction device, and quantitative analysis is conducted on the extracted APP, wax, low-crystallinity components, etc., based on the amount extracted from the solvent (heptane, xylene).

[0169] (4) II (Isotacticity Index, quintuple score) analysis

[0170] Analysis was performed using nuclear magnetic resonance (NMR), and a higher II value indicated a higher degree of crystallinity in the polymer. The analytical instrument used was a Varian.

[0171] (5) SIST method (Stepwise Isothermal Segregation Technique)

[0172] Analysis was performed using differential scanning calorimetry (DSC), and a higher melting ratio of the polymer at high temperatures indicated a higher degree of crystallinity. The analytical instrument used was a TA Instruments Q-100.

[0173] (6) Melting point (Tm, Melting Temperature) analysis

[0174] Analysis was performed using differential scanning calorimetry (DSC), and a higher melting point indicates a higher degree of crystallinity in the polymer.

[0175] Measurement results of physical properties of ultra-high purity and ultra-high crystallinity polypropylene resin

[0176] In the method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators of the present invention, Examples 1 to 4 were manufactured by changing the addition ratio of the main catalyst, co-catalyst, and accelerator of the polymerization reaction. The physical property measurement results of the ultra-high purity and ultra-high crystallinity polypropylene resins manufactured according to these polymerization reaction control conditions and Examples 1 to 4 are shown in Table 1 below.

[0177] Table 1

[0178]

[0179] Purity and crystallinity measurement results of ultra-high purity and ultra-high crystallinity polypropylene resin

[0180] The purity and crystallinity measurements of the polypropylene resins manufactured according to Examples 1 to 4 and Comparative Examples 1 to 10 are shown in Table 2 below.

[0181] Table 2

[0182]

[0183] Referring to Tables 1 and 2, it can be confirmed that the Ash content of Examples 1 to 4 manufactured by the method of manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators according to the present invention is less than 30 ppm, specifically less than 25 ppm, and the isotactic pentagonal fraction (II) is more than 0.980, and the melting point is more than 164°C.

[0184] Furthermore, it can be confirmed that the Ash content in Examples 1 to 4, manufactured by the method of manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators according to the present invention, is 30 ppm or less, specifically 25 ppm or less, and specifically, the aluminum content is 15 ppm or less and the magnesium content is 4 ppm or less.

[0185] Observing the polymerization processes of Comparative Examples 1 to 10, it can be confirmed that Comparative Examples 1 to 10 all carried out polymerization reactions using any one or more methods selected from bulk polymerization, gas-phase polymerization, and multi-zone polymerization, while the present invention uses a slurry process. Bulk and gas-phase polymerization do not require a separate solvent for polymerization, and unlike the hexane slurry polymerization of the present invention which uses hexane as a solvent, they are difficult to apply to the deashing process for high-purity polypropylene. Therefore, the content of residual inorganic matter in polypropylene is high, and the amount of hydrocarbon solvent-soluble components in polypropylene is large, resulting in a reduction in mechanical properties.

[0186] Conversely, in the slurry polymerization process of the present invention, which uses hydrocarbons such as hexane as solvents, low-molecular-weight and random components dissolve in the hydrocarbon solvent used for the polymerization reaction and are removed. Therefore, the content of solvent-soluble components in the polypropylene is low, thereby enabling the production of polypropylene with excellent mechanical properties. Furthermore, the slurry polymerization process of the present invention reduces the content of residual inorganic matter in the polypropylene by removing catalyst residues through a deashing process, thereby enabling the high purity of the polypropylene and exhibiting excellent electrical properties.

[0187] Meanwhile, in Comparative Examples 4 and 5, it was confirmed that the Ash content in polypropylene was below 20 ppm through a deashing process. However, the manufacturing method of the present invention simultaneously includes adjusting the addition ratio of the main catalyst, accelerator, and co-catalyst in the polymerization process, as well as a deashing process for removing residual inorganic matter, thereby exhibiting both ultra-high purity and ultra-high crystallinity. Conversely, it was confirmed that Comparative Examples 4 and 5 did not exhibit the characteristics of an isotactic pentagonal fraction (II) of 0.980 or higher and a melting point of 164°C or higher.

[0188] Furthermore, in Comparative Examples 8 to 10, although no deashing process was performed, it was confirmed that the Ash content in the polypropylene was below 35 ppm due to the high catalytic yield of the catalyst developed by Company F. However, the manufacturing method of the present invention simultaneously includes adjusting the addition ratio of the main catalyst, accelerator, and co-catalyst in the polymerization process, as well as a deashing process for removing residual inorganic matter, thereby exhibiting both ultra-high purity and ultra-high crystallinity. Conversely, it was confirmed that Comparative Examples 8 to 10 did not exhibit the characteristics of an isotactic pentagonal fraction (II) of 0.980 or higher and a melting point of 164°C or higher.

[0189] That is, it can be confirmed that Examples 1 to 4 simultaneously exhibit the characteristics of ultra-high purity and ultra-high crystallinity, while Comparative Examples 1 to 10 only achieved one of the characteristics of (ultra)high purity and (ultra)high crystallinity, that is, only the characteristic of (ultra)high purity was achieved, or neither of the characteristics of (ultra)high purity and (ultra)high crystallinity was achieved.

[0190] Furthermore, compared to Comparative Examples 1 to 10, it can be confirmed that Examples 1 to 4 achieved ultra-high purity and ultra-high crystallinity, while also having a high melting point of 164°C or higher. The ultra-high purity and ultra-high crystallinity polypropylene of the present invention has a melting point of 164°C or higher, confirming that it is ultra-high crystallinity.

[0191] That is, in the method for manufacturing ultra-high purity and ultra-high crystalline polypropylene for secondary battery separators of the present invention, by including the steps of: (a) mixing and adding an alkylaluminum compound as a co-catalyst (A), a titanium compound as a main catalyst (B), and a silicon compound as an accelerator (C) in the presence of a hydrocarbon solvent containing 1 to 20 carbon atoms in a reactor; (b) adding propylene (D) and hydrogen (E) to the mixed solution obtained in step (a) and maintaining the temperature in the range of 30 to 90°C for 1 to 6 hours while simultaneously carrying out a polymerization reaction; (c) removing catalyst residues from the polypropylene slurry reaction product obtained after performing step (b) and separating ultra-high purity and ultra-high crystalline polypropylene powder; and (d) filtering and drying the ultra-high purity and ultra-high crystalline polypropylene powder, it can be confirmed that the ultra-high purity and ultra-high crystalline polypropylene for secondary battery separators of the present invention has an Ash content of 30 ppm or less, an isotactic pentagonal fraction (II) of 0.980 or more, and a melting point maintained at 164°C or more. In addition, it can be confirmed that the Ash content is below 30 ppm, specifically below 25 ppm, and specifically, the aluminum content is below 15 ppm and the magnesium content is below 4 ppm.

[0192] Furthermore, in the method for manufacturing ultra-high purity and ultra-high crystalline polypropylene for secondary battery separators of the present invention, the method includes (c) removing catalyst residues from the polypropylene slurry reactant obtained after performing step (b) and separating ultra-high purity and ultra-high crystalline polypropylene powder. This deashing process includes: mixing the polypropylene slurry reactant with a polar organic solvent to obtain a mixture; and separating the mixture into the ultra-high purity and ultra-high crystalline polypropylene powder and the polar organic solvent using distilled water or filtered water. This confirms that the ultra-high purity and ultra-high crystalline polypropylene for secondary battery separators of the present invention has an Ash content of 30 ppm or less, an isotactic pentagonal fraction (II) of 0.980 or more, and a melting point maintained at 164°C or more. Furthermore, it confirms that the Ash content is 30 ppm or less, specifically 25 ppm or less, and specifically, the aluminum content is 15 ppm or less, and the magnesium content is 4 ppm or less.

[0193] By observing the polymerization reaction control conditions in Examples 1 to 4 and adjusting the addition ratios of the main catalyst, co-catalyst, and accelerator in the polymerization reaction, and based on 1 mole of Ti in the titanium compound as the main catalyst (B), 10 to 30 moles of Al in the alkylaluminum compound as the co-catalyst (A), 1 mole of Ti in the titanium compound as the main catalyst (B), and 0.5 to 5 moles of Si in the silicon compound as the accelerator (C), it can be confirmed that the Ash content in the ultra-high purity and ultra-high crystallinity polypropylene of the present invention is 30 ppm or less, the isotactic pentagonal component fraction (II) is 0.980 or more, and the melting point is maintained at 164°C or more. Furthermore, it can be confirmed that the Ash content is 30 ppm or less, specifically 25 ppm or less, and specifically, the aluminum content is 15 ppm or less, and the magnesium content is 4 ppm or less.

[0194] Furthermore, observing the polymerization reaction control conditions of Examples 1 to 4, it can be confirmed that under the execution conditions of the polymerization reaction, when the polymerization reaction is carried out for 1 to 6 hours at a temperature range of 30 to 90°C and a pressure range of 1 to 40 bar, the Ash content in the ultra-high purity and ultra-high crystallinity polypropylene for the secondary battery separator of the present invention is less than 30 ppm, the isotactic pentagonal fraction (II) is 0.980 or higher, and the melting point is maintained at 164°C or higher. Furthermore, it can be confirmed that the Ash content is less than 30 ppm, specifically less than 25 ppm, and specifically, the aluminum content is less than 15 ppm and the magnesium content is less than 4 ppm.

[0195] <Experimental Example 2> Residual inorganic matter removal process based on methanol content of ultra-high purity and ultra-high crystallinity polypropylene resin (De-ashing process)

[0196] Example 5

[0197] a. Using the polypropylene from the second-order polymerization of Example 1 described in Table 1, a deashing process was carried out by changing the amount of methanol and the stirring temperature.

[0198] b. After opening the 2L stainless steel reactor equipped with a stirrer, add 50g of the polypropylene resin from step a. Add 900ml of hexane as an organic solvent to the reactor under room temperature and vacuum conditions and stir. Add 5g of methanol as a polar organic solvent and stir at 85°C for 10 minutes. Then, add 200ml of distilled water and stir for another 10 minutes. After stirring, separate the powdered ultra-high purity and ultra-high crystallinity polypropylene resin from the liquid component of the hexane, polar organic solvent, and water mixture using a filter. Thoroughly dry the separated ultra-high purity and ultra-high crystallinity polypropylene resin in a dryer at 100°C, and then analyze the Ash content.

[0199] Example 6

[0200] Example 6 was manufactured in the same manner as Example 5, except that the amount of methanol added was increased to 25g.

[0201] Example 7

[0202] Example 7 was manufactured in the same manner as Example 5, except that the amount of methanol added was increased to 50g.

[0203] Example 8

[0204] Example 8 was prepared in the same manner as Example 5, except that the amount of methanol added was increased to 150g.

[0205] Example 9

[0206] After adding methanol, Example 9 was prepared in the same manner as Example 7, except that the stirring temperature was reduced to 75°C during the stirring process.

[0207] Comparative Example 11

[0208] Using the polypropylene resin produced in Example 1 of [Table 1], Ash analysis results of polypropylene resin without undergoing a separate residual inorganic matter removal process are shown.

[0209] Comparative Example 12

[0210] Comparative Example 12 was prepared in the same manner as in Example 5, except that the amount of methanol added was reduced to 3g.

[0211] Comparative Example 13

[0212] Comparative Example 13 was prepared in the same manner as in Example 5, except that the amount of methanol added was increased to 550g.

[0213] Comparative Example 14

[0214] Comparative Example 14 was prepared in the same manner as in Example 7, except that the stirring temperature was reduced to 40°C during the stirring process after the addition of methanol.

[0215] Comparative Example 15

[0216] Comparative Example 15 was prepared in the same manner as in Example 7, except that the stirring temperature was increased to 110°C during the stirring process after the addition of methanol.

[0217] Measurement results of residual inorganic content in ultra-high purity and ultra-high crystallinity polypropylene resin

[0218] The control conditions for the residual inorganic matter removal process of the ultra-high purity and ultra-high crystallinity polypropylene resin for secondary battery separators according to the present invention in Examples 5 to 9 and Comparative Examples 11 to 15, and the Ash composition of the manufactured ultra-high purity and ultra-high crystallinity polypropylene resin were analyzed, and the results of the residual inorganic matter content measurement are shown in Table 3 below.

[0219] Table 3

[0220]

[0221] Referring to Table 3, it can be seen that the manufacturing method of ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membrane of the present invention not only adjusts the addition ratio of main catalyst, accelerator and co-catalyst in the polymerization process, but also achieves ultra-high purity and ultra-high crystallinity through the deashing process for removing residual inorganic matter.

[0222] Specifically, in the method for manufacturing ultra-high purity and ultra-high crystalline polypropylene for secondary battery separators of the present invention, the method includes the following steps: (a) mixing and adding an alkylaluminum compound as a co-catalyst (A), a titanium compound as a main catalyst (B), and a silicon compound as an accelerator (C) in the presence of a hydrocarbon solvent containing 1 to 20 carbon atoms in a reactor; (b) adding propylene (D) and hydrogen (E) to the mixed solution obtained in step (a) and maintaining the temperature in the range of 30 to 90°C for 1 to 6 hours while simultaneously carrying out a polymerization reaction; (c) removing catalyst residues from the polypropylene slurry reaction product obtained after performing step (b) and separating ultra-high purity and ultra-high crystalline polypropylene powder; and (d) filtering and drying the ultra-high purity and ultra-high crystalline polypropylene powder. By adjusting the control conditions of the polymerization reaction, it can be confirmed that ultra-high purity and ultra-high crystalline polypropylene resin with an Ash content of less than 30 ppm can be obtained.

[0223] Furthermore, in the method for manufacturing ultra-high purity and ultra-high crystalline polypropylene for secondary battery separators of the present invention, the method includes (c) removing catalyst residues from the polypropylene slurry reactant obtained after performing step (b) and separating ultra-high purity and ultra-high crystalline polypropylene powder. As a deashing process, this includes: mixing the polypropylene slurry reactant and a polar organic solvent to obtain a mixture; and separating the mixture into the ultra-high purity and ultra-high crystalline polypropylene powder and the polar organic solvent using distilled water or filtered water. It can be confirmed that ultra-high purity and ultra-high crystalline polypropylene resin with an Ash content of less than 30 ppm can be obtained.

[0224] In Examples 5 to 8, it was confirmed that within a range of 10 to 1000 parts by weight of polar organic solvent in 100 parts by weight of polypropylene slurry reactant, as the amount of methanol used as the polar organic solvent increased, the Ash content in the polypropylene decreased to below 30 ppm. In Examples 7 and 8, the Ash content in the polypropylene decreased to below 20 ppm. Furthermore, in Example 9, it was confirmed that, as in Example 7, when the methanol was increased to 50 g, even when the stirring temperature was reduced from 85°C to 75°C after adding methanol, the Ash content in the polypropylene remained below 30 ppm.

[0225] Meanwhile, Comparative Example 11 means polypropylene resin that has not undergone a separate residual inorganic matter removal process.

[0226] In Comparative Example 11, where the second-order polymerization reaction was completed without undergoing a deashing process, the Ash content was confirmed to be in the range of 30 to 40 ppm. On the other hand, in Examples 1 to 4, where the second-order polymerization reaction was completed and a deashing process was performed, the Ash content was confirmed to be 30 ppm or less, the isotactic pentagonal fraction (II) to be 0.980 or more, and the melting point to be maintained at 164°C or more. Furthermore, in Examples 5 to 9, where the second-order polymerization reaction was completed and a deashing process was performed similarly, the Ash content was confirmed to be maintained at 30 ppm or less.

[0227] Accordingly, the method for manufacturing polypropylene of the present invention includes adjusting the addition ratio of the main catalyst, accelerator, and co-catalyst in the polymerization process, as well as a deashing process for removing residual inorganic matter. This confirms that the Ash content is below 30 ppm, the isotactic pentagonal fraction (II) is above 0.980, and the melting point is maintained above 164°C. Comparative Example 12 uses methanol at a reduced amount of 3 g, and Comparative Example 13 uses methanol at an increased amount of 550 g. This confirms that the Ash content in the polypropylene of Comparative Examples 12 and 13 is above 30 ppm, while the purity is reduced.

[0228] Therefore, when comparing Examples 5 to 9 and Comparative Examples 12 and 13, the Ash content in the ultra-high purity and ultra-high crystallinity polypropylene of the present invention is maintained below 30 ppm, based on 100 parts by weight of polypropylene slurry reactant obtained by polymerization reaction mixed with 10 to 1000 parts by weight of polar organic solvent.

[0229] Conversely, when comparing Examples 5 to 9 and Comparative Examples 12 and 13, it was confirmed that when 100 parts by weight of a polar organic solvent in a range of less than 10 parts by weight and more than 1000 parts by weight of a polypropylene slurry reactant obtained by polymerization was mixed with 100 parts by weight of the reactant, the Ash content in the polypropylene exceeded 30 ppm, and the purity and crystallinity of the polypropylene deteriorated.

[0230] Comparative Example 14 involved adding methanol and lowering the stirring temperature to 40°C, while Comparative Example 15 involved adding methanol and raising the stirring temperature to 110°C. This confirmed that the Ash content in the polypropylene of Comparative Examples 14 and 15 was above 30 ppm, resulting in decreased purity. Therefore, when comparing Examples 5 to 9 and Comparative Examples 14 and 15, the step of mixing (stirring) the polypropylene slurry reactant obtained through polymerization and the polar organic solvent to obtain a mixture was performed at a temperature range of 50 to 100°C for 5 to 30 minutes. This confirmed that the Ash content in the ultra-high purity and ultra-high crystallinity polypropylene of the present invention was maintained below 30 ppm.

[0231] Furthermore, based on the residual inorganic matter removal process conditions and Ash content measurement results of Examples 5 to 9, using 100 to 3000 parts by weight of distilled or filtered water with 100 parts by weight of polar organic solvent, it can be confirmed that the Ash content in the ultra-high purity and ultra-high crystallinity polypropylene of the present invention is maintained below 30 ppm.

[0232] According to the present invention, in order to improve the performance of the secondary battery separation membrane, the addition ratio of the main catalyst, accelerator and co-catalyst in the polymerization process is adjusted to reduce the inorganic matter, low molecular weight and low crystallinity in polypropylene by the deashing process for removing residual inorganic matter and removing low molecular weight substances and atactic polypropylene, thereby enabling polypropylene to exhibit both ultra-high purity and ultra-high crystallinity characteristics.

[0233] Furthermore, according to the present invention, since the content of residual inorganic matter and the content of low-crystallinity polymer are low during polypropylene polymerization, the performance of the secondary battery separator membrane can be improved by exhibiting excellent mechanical durability and dielectric properties.

[0234] The foregoing description of this application is for illustrative purposes, and those skilled in the art will understand that this application can be readily modified into other specific forms without altering the technical concept or essential features of the invention. Therefore, the above embodiments should be understood in all respects as exemplary rather than restrictive. For example, individual components described as a single type can be implemented in a distributed manner; similarly, components described as distributed can be implemented in a combined manner.

[0235] The scope of this application is shown by the following claims rather than by the foregoing detailed description, and all variations or modifications derived from the meaning and scope of the claims and their equivalents shall be interpreted as including within the scope of this application.

Claims

1. A high-purity and high-crystallinity polypropylene for use in secondary battery separators, characterized in that, The residual inorganic matter content is below 30 ppm. The percentage of isonormal quintuples is above 98%.

2. The ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membrane according to claim 1, characterized in that, In the ultra-high purity and ultra-high crystallinity polypropylene used for the secondary battery separation membrane, the aluminum content, which is the residual inorganic matter, is less than 15 ppm and the magnesium content is less than 4 ppm.

3. The ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membrane according to claim 1, characterized in that, The secondary battery separator membrane uses ultra-high purity and ultra-high crystallinity polypropylene with a melting point above 164°C.

4. A method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for a secondary battery separator membrane, comprising: (a) In the presence of a hydrocarbon solvent containing 1 to 20 carbon atoms in the reactor, the step of mixing and adding an alkylaluminum compound as a co-catalyst (A), a titanium compound as a main catalyst (B), and a silicon compound as a promoter (C). (b) Adding propylene (D) and hydrogen (E) to the mixed solution obtained in step (a) and maintaining the temperature in the range of 30 to 90°C for 1 to 6 hours while carrying out the polymerization reaction; (c) The step of removing catalyst residues from the polypropylene slurry reactant obtained after performing step (b) and separating ultra-high purity and ultra-high crystallinity polypropylene powder; and (d) The step of filtering and drying the ultra-high purity and ultra-high crystallinity polypropylene powder.

5. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 4, characterized in that, The hydrocarbon solvent is any one or more solvents selected from the group consisting of pentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, decane, undecane, dodecane, tridecane or tetradecane, benzene, toluene, xylene, ethylbenzene, dichloropropane, dichloroethylene, trichloroethylene, carbon tetrachloride and chlorobenzene.

6. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 4, characterized in that, The cocatalyst (A) is any one or more compounds selected from the group consisting of triethylaluminum, trimethylaluminum, triisobutylaluminum, trioctylaluminum, diethylaluminum chloride, diethylaluminum bromide, diethylaluminum iodide, diethylaluminum fluoride, diethylaluminum chloride, dimethylaluminum chloride, metallic aluminum dichloride, and ethylaluminum trichloride.

7. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 4, characterized in that, The accelerator (C) comprises any one or more compounds selected from the group consisting of compounds of the following chemical formula (1), compounds of the following chemical formula (2), and compounds of the following chemical formula (3): [Chemical Formula (1)] [Chemical Formula (2)] [Chemical Formula (3)] In the chemical formulas (1) to (3), R a R 7 R 8 and R 9 Each is independently selected from alkyl, cycloalkyl, aryl, allyl, or vinyl groups having 1 to 12 carbon atoms; R b R is an alkyl or aryl group having 1 to 6 carbon atoms; R is an alkyl, cycloalkyl, aryl, allyl, or -ORc group having 1 to 12 carbon atoms, wherein R c It is an alkyl or aryl group having 1 to 6 carbon atoms; and n is an integer from 0 to 6.

8. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 4, characterized in that, Based on 1 mole of Ti in the titanium compound as the main catalyst (B), it contains 10 to 30 moles of Al in the alkylaluminum compound as the co-catalyst (A).

9. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators according to claim 4, characterized in that, Based on 1 mole of Ti in the titanium compound as the main catalyst (B), it contains 0.5 to 5 moles of Si in the silicon compound as the promoter (C).

10. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 4, characterized in that, The polymerization reaction is carried out for 1 to 6 hours within a pressure range of 1 to 40 bar.

11. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 4, characterized in that, Step (c) of removing catalyst residues from the polypropylene slurry reactant obtained after performing step (b) and separating ultra-high purity and ultra-high crystallinity polypropylene powder includes: The step of mixing the polypropylene slurry reactant and a polar organic solvent to obtain a mixture; and The step of separating the mixture into the ultra-high purity and ultra-high crystallinity polypropylene powder and the polar organic solvent using distilled water or filtered water.

12. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 11, characterized in that, The polar organic solvent comprises any one or more compounds selected from the group consisting of compounds of the following chemical formula (4) and compounds of the following chemical formula (5): [Chemical formula (4)] R-OH, [Chemical Formula (5)] HO-R1-R2-OH, In the chemical formula (4), R is a straight-chain or branched alkyl group having 1 to 12 carbon atoms, and the chemical formula (4) is any one or more compounds selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, branched alkyl isopropanol, isobutanol and isopentanol. In the chemical formula (5), R1 and R2 are straight-chain alkyl groups having 0 to 6 carbon atoms, and the chemical formula (5) is any one or more compounds selected from the group consisting of methanol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol and dodecanediol.

13. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 11, characterized in that, Based on 100 parts by weight of the polypropylene slurry reactant, the polar organic solvent is 10 to 1000 parts by weight.

14. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separation membranes according to claim 11, characterized in that, The step of mixing the polypropylene slurry reactant and the polar organic solvent to obtain a mixture is carried out at a temperature range of 50 to 100°C for 5 to 30 minutes.

15. The method for manufacturing ultra-high purity and ultra-high crystallinity polypropylene for secondary battery separators according to claim 11, characterized in that, Based on 100 parts by weight of the polar organic solvent, the distilled or filtered water is 100 to 3000 parts by weight.

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