Antiplasticizer, inorganic particle-containing resin composition, secondary battery separator coating composition, secondary battery separator, and secondary battery

Abstract

Provided is an antiplasticizer capable of improving both the dispersibility of inorganic particles and the elastic modulus of a binder resin. Specifically, this antiplasticizer contains: at least one polyester selected from the group consisting of polyesters represented by general formula (A-1), polyesters represented by general formula (A-2), and polyesters represented by general formula (A-3); and a diester represented by general formula (B). The polyester and the diester are contained at a mass ratio of polyester:diester = 99.5:0.5 to 95:5.

Description

Antiplasticizer, inorganic particle-containing resin composition, coating composition for secondary battery separator, secondary battery separator, and secondary battery

[0001] The present invention relates to an antiplasticizer, an inorganic particle-containing resin composition, a coating composition for a secondary battery separator, a secondary battery separator, and a secondary battery.

[0002] In recent years, the introduction of electric vehicles (EVs) has been rapidly progressing in various countries in order to reduce carbon dioxide emissions. High-energy-density lithium-ion batteries (LiBs) are widely used as the driving power source for these EVs.

[0003] LiBs have a laminated structure of a positive electrode, a separator, and a negative electrode. The separator is generally a laminate in which a coating layer containing inorganic particles is laminated on a porous substrate. The inorganic particles are mainly used to improve the heat resistance of the separator, but if their dispersibility is insufficient, there is a problem that their adhesion to the porous substrate decreases, resulting in a decrease in battery performance. To address this problem, there have been attempts to improve battery performance by adding an additive to the coating layer containing inorganic particles to improve their dispersibility (e.g., Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2022-121513

[0005] In Patent Document 1, the adhesiveness between the porous substrate constituting the separator and the coating layer is improved by improving the dispersibility of inorganic particles using an additive. However, the adhesiveness of the separator also has problems between the separator and the electrode. When the dispersibility of the inorganic particles in the coating layer is improved, it becomes difficult to ensure the adhesiveness between the separator and the electrode. Simply improving the dispersibility of the inorganic particles cannot solve the adhesive problem between the separator and the electrode.

[0006] The present invention aims to provide an antiplasticizer that can improve both the elastic modulus of a binder resin and the dispersibility of inorganic particles. Another object of the present invention is to provide a coating composition for a secondary battery separator that can produce a separator that is a laminate of a substrate and a coating layer, and that has good dispersibility of inorganic particles in the coating layer and improved adhesion to electrodes. Another object of the present invention is to provide a separator that is a laminate of a substrate and a coating layer, and that has good dispersibility of inorganic particles in the coating layer and improved adhesion to electrodes.

[0007] As a result of extensive research to solve the above problems, the present inventors have found that an antiplasticizer containing a specific polyester and a specific diester in a specific mass ratio can improve the dispersibility of inorganic particles in a coating layer of a separator, which is a laminate of a substrate and a coating layer, and can also improve the adhesion of the separator to electrodes, thereby completing the present invention.

[0008] That is, the present invention relates to the following antiplasticizers, etc.: 1. An antiplasticizer containing one or more polyesters selected from the group consisting of polyesters represented by the following general formula (A-1), polyesters represented by the following general formula (A-2), and polyesters represented by the following general formula (A-3), and a diester represented by the following general formula (B), wherein the polyester and the diester are contained in a mass ratio of polyester:diester of 99.5:0.5 to 95:5. (In the general formulae (A-1), (A-2), (A-3) and (B), G １ is an aliphatic diol residue having 2 to 20 carbon atoms, １ is an aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms, ２ is an aliphatic polycarboxylic acid residue having 2 to 18 carbon atoms or an aromatic polycarboxylic acid residue having 4 to 18 carbon atoms, １ is a monocarboxylic acid residue having 1 to 20 carbon atoms, and Y １is a hydrogen atom or a monoalcohol residue having 1 to 30 carbon atoms, ３ is an aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms, and Y ２ is a monoalcohol residue having 1 to 30 carbon atoms, n represents the number of repeats, and m represents A ２ It is an integer obtained by subtracting one from the number of carboxyl groups of the aliphatic polycarboxylic acid or aromatic polycarboxylic acid.) 2. G １ 3. The antiplasticizer according to 1, wherein A is a residue of an aliphatic diol having a branched structure and having 3 to 20 carbon atoms. １ 4. The antiplasticizer according to 1 or 2, wherein A is a residue of an aliphatic dicarboxylic acid having 4 to 10 carbon atoms. ２ is a residue of an aliphatic dicarboxylic acid having 2 to 18 carbon atoms or a residue of an aromatic tricarboxylic acid having 4 to 18 carbon atoms. ２ is one or more residues selected from adipic acid residues, maleic acid residues, and trimellitic acid residues. 6. The antiplasticizer according to any one of 1 to 5, wherein the number average molecular weights of the polyester represented by general formula (A-1), the polyester represented by general formula (A-2), and the polyester represented by general formula (A-3) are each in the range of 1,000 to 5,000. 7. An inorganic particle-containing resin composition comprising the antiplasticizer according to any one of 1 to 6, inorganic particles, a binder resin, and a solvent. 8. A molded product of the inorganic particle-containing resin composition according to 7. 9. A coating composition for a secondary battery separator comprising the antiplasticizer according to any one of 1 to 6, inorganic particles, a binder resin, and a solvent. 10. The coating composition for a secondary battery separator according to 9, containing the antiplasticizer in an amount of 0.2 to 2.0 parts by mass per 100 parts by mass of the inorganic particles. 11. The inorganic particles are BaTiO ３ , Pb(Zr,Ti)O ３ , Pb １－ｘ La ｘ Zr １－ｙ TiyO ３ (0<x<1, 0<y<1), Pb(Mg １／３ Nb ２／３ ) O ３ -PbTiO３ , HfO ２ , SrTiO ３ , SnO ２ , CeO ２ , MgO, NiO, CaO, ZnO, ZrO ２ , Y ２ O ３ , Al ２ O ３ , TiO ２ 11. The coating composition for a secondary battery separator according to claim 9 or 10, wherein the binder resin is one or more selected from the group consisting of aliphatic conjugated diene / aromatic monovinyl copolymer, (meth)acrylic polymer, fluoropolymer, (meth)acrylic acid / (meth)acrylamide copolymer, (meth)acrylonitrile polymer, and aromatic monovinyl / (meth)acrylic copolymer. 12. The coating composition for a secondary battery separator according to any one of claims 9 to 11, wherein the binder resin is one or more selected from the group consisting of aliphatic conjugated diene / aromatic monovinyl copolymer, (meth)acrylic polymer, fluoropolymer, (meth)acrylic acid / (meth)acrylamide copolymer, (meth)acrylonitrile polymer, and aromatic monovinyl / (meth)acrylic copolymer. 13. A secondary battery separator which is a laminate comprising a substrate and a coating layer formed from the coating composition for a secondary battery separator according to any one of claims 9 to 12. 14. A secondary battery comprising a positive electrode, a negative electrode, and the secondary battery separator according to claim 13 sandwiched between the positive electrode and the negative electrode.

[0009] The present invention provides an antiplasticizer that can improve both the elastic modulus of a binder resin and the dispersibility of inorganic particles.The present invention provides a coating composition for a secondary battery separator that can produce a separator that is a laminate of a substrate and a coating layer, in which the inorganic particle dispersibility in the coating layer is good and the adhesion to an electrode is also improved.The present invention provides a separator that is a laminate of a substrate and a coating layer, in which the inorganic particle dispersibility in the coating layer is good and the adhesion to an electrode is also improved.

[0010] An embodiment of the present invention will be described below. The present invention is not limited to the following embodiment, and can be carried out by making appropriate modifications within the scope that does not impair the effects of the present invention. The compounds in this specification may be derived from fossil resources or biological resources.

[0011] [Antiplasticizer] "Antiplasticizer" is a general term for a substance that improves the elastic modulus of a substance. The antiplasticizer of the present invention contains a specific polyester and a specific diester in a specific mass ratio, and can improve not only the antiplasticizing effect of improving the elastic modulus of the binder resin described below, but also the dispersibility of inorganic particles.

[0012] The polyester constituting the antiplasticizer of the present invention may be referred to as the “polyester of the present invention,” and the diester constituting the antiplasticizer of the present invention may be referred to as the “diester of the present invention.” The polyester of the present invention and the diester of the present invention will each be described below.

[0013] (Polyester) The polyester of the present invention is at least one selected from the group consisting of polyesters represented by the following general formula (A-1), polyesters represented by the following general formula (A-2), and polyesters represented by the following general formula (A-3).

[0014] (In the general formulae (A-1), (A-2) and (A-3), G １ is an aliphatic diol residue having 2 to 20 carbon atoms, １ is an aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms, ２ is an aliphatic polycarboxylic acid residue having 2 to 18 carbon atoms or an aromatic polycarboxylic acid residue having 4 to 18 carbon atoms, １ is a monocarboxylic acid residue having 1 to 20 carbon atoms, and Y １ is a hydrogen atom or a monoalcohol residue having 1 to 30 carbon atoms, n represents the number of repetitions, and m represents A ２ is an integer obtained by subtracting one from the number of carboxyl groups of the aliphatic polycarboxylic acid or aromatic polycarboxylic acid.

[0015] The polyester of the present invention is a polyester having a carboxyl group at at least one end, and the carboxyl group is adsorbed to inorganic particles, thereby improving the dispersibility of the inorganic particles.

[0016] In the present invention, "diol residue" and "alcohol residue" refer to the organic group remaining after removing the hydroxyl group from a diol or alcohol. In the present invention, "monocarboxylic acid residue" refers to the organic group remaining after removing the carboxyl group from a monocarboxylic acid. The number of carbon atoms in the monocarboxylic acid residue does not include the carbon atoms in the carboxyl group. In the present invention, "dicarboxylic acid residue" refers to the organic group remaining after removing the carboxyl group from a dicarboxylic acid. The number of carbon atoms in the dicarboxylic acid residue does not include the carbon atoms in the carboxyl group. In the present invention, "polycarboxylic acid residue" refers to the organic group remaining after removing the carboxyl group from a polycarboxylic acid having two or more carboxyl groups. For example, when the polycarboxylic acid residue is a dicarboxylic acid residue, tricarboxylic acid residue, or tetracarboxylic acid residue, the dicarboxylic acid residue, tricarboxylic acid residue, or tetracarboxylic acid residue refers to the organic group remaining after removing the carboxyl group contained therein. The number of carbon atoms in the polycarboxylic acid residue does not include the carbon atoms in the carboxyl group.

[0017] G １ The aliphatic chain of the aliphatic diol residue having 2 to 20 carbon atoms may be linear or branched, and may contain an alicyclic structure and / or an ether bond. １ The aliphatic chain of the aliphatic diol residue may be a saturated aliphatic chain or an unsaturated aliphatic chain having a carbon-carbon unsaturated bond.

[0018] G １ The aliphatic diol residue having 2 to 20 carbon atoms preferably includes an aliphatic diol residue having a branched structure and having 3 to 20 carbon atoms, and more preferably includes a diol residue represented by the following general formula (G-1): (In the general formula (G-1), p is an integer of 1 or more, q is an integer of 0 or more, r is an integer of 1 or more, R is a hydrogen atom or an alkyl group having 1 or more carbon atoms, at least one of the r R is an alkyl group having 1 or more carbon atoms, and the total number of carbon atoms of p, q, r, and R is an integer in the range of 3 to 20.)

[0019] G １Examples of the aliphatic diol residue having 2 to 20 carbon atoms include ethylene glycol residue, 1,2-propylene glycol residue, 1,3-propanediol residue, 1,2-butanediol residue, 1,3-butanediol residue, 2-methyl-1,3-propanediol residue, 1,4-butanediol residue, 1,5-pentanediol residue, 2,2-dimethyl-1,3-propanediol (neopentyl glycol) residue, 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane) residue, 2-n butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane) residue, 3-methyl-1,5-pentanediol residue, 1,6-hexanediol residue, 2,2,4-trimethyl-1,3-pentanediol residue, 2-ethyl-1,3-hexanediol residue, 2-methyl-1,8-octanediol residue, 1,9-nonanediol residue, 1,10-decanediol residue, 1,12-dodecanediol residue, 1,2-tetradecanediol residue, 1,2-dodecanediol residue, and the like.

[0020] G １ The aliphatic diol residue having 2 to 20 carbon atoms may contain an alicyclic structure, and examples of the aliphatic diol residue having 2 to 20 carbon atoms containing an alicyclic structure include a 1,3-cyclopentanediol residue, a 1,2-cyclohexanediol residue, a 1,3-cyclohexanediol residue, a 1,4-cyclohexanediol residue, a 1,2-cyclohexanedimethanol residue, and a 1,4-cyclohexanedimethanol residue.

[0021] G １ The aliphatic diol residue having 2 to 20 carbon atoms may contain an ether bond (—O—), and examples of the aliphatic diol residue having 2 to 20 carbon atoms containing the ether bond include a diethylene glycol residue, a triethylene glycol residue, a tetraethylene glycol residue, a dipropylene glycol residue, and a tripropylene glycol residue.

[0022] G １is preferably an aliphatic diol residue having 2 to 20 carbon atoms, more preferably an aliphatic diol residue having 2 to 14 carbon atoms, and even more preferably an ethylene glycol residue, diethylene glycol residue, 1,2-propylene glycol residue, 1,6-hexanediol residue, 3-methyl-1,5-pentanediol residue, 1,4-butanediol residue, 1,3-butanediol residue, 1,2-tetradecanediol residue, or 1,2-dodecanediol residue.

[0023] A １ The aliphatic chain of the aliphatic dicarboxylic acid residue of A may be linear or branched, and may contain an alicyclic structure and / or an ether bond. １ The aliphatic chain of the aliphatic dicarboxylic acid residue may be a saturated aliphatic chain or an unsaturated aliphatic chain having a carbon-carbon unsaturated bond.

[0024] A １ Examples of the aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms include succinic acid residue, glutaric acid residue, adipic acid residue, pimelic acid residue, suberic acid residue, azelaic acid residue, sebacic acid residue, dodecanedicarboxylic acid residue, maleic acid residue, fumaric acid residue, 1,2-dicarboxycyclohexane residue, and 1,2-dicarboxycyclohexene residue, and are preferably succinic acid residue, glutaric acid residue, adipic acid residue, or sebacic acid residue.

[0025] A １ The aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms is preferably an aliphatic dicarboxylic acid residue having 2 to 10 carbon atoms, more preferably an aliphatic dicarboxylic acid residue having 4 to 10 carbon atoms.

[0026] A ２ When the aliphatic polycarboxylic acid residue having 2 to 18 carbon atoms is an aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms, the aliphatic dicarboxylic acid residue is １ is the same as the aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms.

[0027] A ２When the aliphatic polycarboxylic acid residue having 2 to 18 carbon atoms is a residue of an aliphatic polycarboxylic acid of 2 to 18 carbon atoms of tricarboxylic acid or higher, the aliphatic chain of the aliphatic polycarboxylic acid residue of tricarboxylic acid or higher may be linear or branched, and may contain an alicyclic structure and / or an ether bond. Furthermore, the aliphatic chain of the aliphatic polycarboxylic acid residue of tricarboxylic acid or higher may be a saturated aliphatic chain or an unsaturated aliphatic chain having a carbon-carbon unsaturated bond.

[0028] A ２ When the aliphatic polycarboxylic acid residue having 2 to 18 carbon atoms is an aliphatic polycarboxylic acid residue of a tricarboxylic acid or higher having 2 to 18 carbon atoms, examples of the aliphatic polycarboxylic acid residue of a tricarboxylic acid or higher include a tricarballylic acid residue, an aconitic acid residue, a camphoronic acid residue, a 1,2,4-cyclohexanetricarboxylic acid residue, and a 1,2,4,5-cyclohexanetetracarboxylic acid residue.

[0029] A ２ The aromatic polycarboxylic acid residue having 4 to 18 carbon atoms is a carboxylic acid residue in which two or more carboxyl groups are substituted on an aromatic ring such as a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring. The aromatic ring may be substituted with a substituent such as an alkyl group having 1 to 6 carbon atoms or a hydroxyl group. The aromatic ring may also be a heteroaromatic ring in which a carbon atom constituting the aromatic ring is replaced with an oxygen atom, a nitrogen atom, or the like.

[0030] A ２ Examples of the aromatic polycarboxylic acid residue having 4 to 18 carbon atoms include a phthalic acid residue (orthophthalic acid residue, isophthalic acid residue, terephthalic acid residue), a trimellitic acid residue, a pyromellitic acid residue, a furandicarboxylic acid residue, a 2-methylterephthalic acid residue, a 4,4-stilbene dicarboxylic acid residue, a 4,4-biphenyl dicarboxylic acid residue, a naphthalenedicarboxylic acid residue, an anthracene dicarboxylic acid residue, a 4,4'-oxybisbenzoic acid residue, a 4,4'-diphenoxyethane dicarboxylic acid residue, an ethylene-bis-p-benzoic acid residue, a hemimellitic acid residue, a trimesic acid residue, and a naphthalene tricarboxylic acid residue.

[0031] A２ is preferably one or more selected from adipic acid residue, maleic acid residue and trimellitic acid residue.

[0032] X １ The monocarboxylic acid residue having 1 to 20 carbon atoms may be, for example, either an aliphatic monocarboxylic acid residue having 1 to 20 carbon atoms or an aromatic monocarboxylic acid residue having 6 to 20 carbon atoms, and is preferably an aliphatic monocarboxylic acid residue having 1 to 20 carbon atoms.

[0033] X １ is a residue of an aliphatic monocarboxylic acid having 1 to 20 carbon atoms, the aliphatic chain of the aliphatic monocarboxylic acid residue having 1 to 20 carbon atoms may be linear or branched, and may contain an alicyclic structure and / or an ether bond. Furthermore, the aliphatic chain of the aliphatic monocarboxylic acid residue having 1 to 20 carbon atoms may be a saturated aliphatic chain or an unsaturated aliphatic chain having a carbon-carbon unsaturated bond.

[0034] X １ Examples of the monocarboxylic acid residue having 1 to 20 carbon atoms include acetic acid residue, propionic acid residue, butanoic acid residue, hexanoic acid residue, octanoic acid residue, octylic acid residue, benzoic acid residue, dimethylbenzoic acid residue, trimethylbenzoic acid residue, tetramethylbenzoic acid residue, ethylbenzoic acid residue, propylbenzoic acid residue, butylbenzoic acid residue, cumic acid residue, para-tert-butylbenzoic acid residue, orthotoluic acid residue, meta-toluic acid residue, para-toluic acid residue, ethoxybenzoic acid residue, propoxybenzoic acid residue, and anisic acid residue.

[0035] Y １ The monoalcohol residue having 1 to 30 carbon atoms may be, for example, either an aliphatic monoalcohol residue having 1 to 30 carbon atoms or an aromatic monoalcohol residue having 6 to 30 carbon atoms, and is preferably an aliphatic monoalcohol residue having 1 to 30 carbon atoms.

[0036] Y １is a residue of an aliphatic monoalcohol having 1 to 30 carbon atoms, the aliphatic chain of the aliphatic monoalcohol residue having 1 to 30 carbon atoms may be linear or branched, and may contain an alicyclic structure and / or an ether bond. Furthermore, the aliphatic chain of the aliphatic monoalcohol residue having 1 to 30 carbon atoms may be a saturated aliphatic chain or an unsaturated aliphatic chain having a carbon-carbon unsaturated bond.

[0037] Y １ The monoalcohol residue having 1 to 30 carbon atoms is preferably an alkyl alcohol residue having 2 to 10 carbon atoms or an alcohol residue of a polyalkylene glycol monoalkyl ether having 5 to 30 carbon atoms.

[0038] Y １ Examples of the alkyl alcohol residue having 2 to 10 carbon atoms include an ethanol residue, a propanol residue, a butanol residue, a pentanol residue, a hexanol residue, a cyclohexanol residue, a heptanol residue, an octanol residue, a nonanol residue, and a decanol residue.

[0039] Y １ Examples of the alcohol residue of the polyalkylene glycol alkyl ether having 5 to 30 carbon atoms include alcohol residues of polyethylene glycol alkyl ethers such as diethylene glycol monomethyl ether and triethylene glycol monomethyl ether; polypropylene glycol alkyl ethers such as polypropylene glycol monomethyl ether and polypropylene glycol monoethyl ether; (polyethylene glycol-polypropylene glycol) monoalkyl ethers, etc.

[0040] The average value of the repeat number of n is, for example, in the range of 0 to 20, preferably in the range of 1 to 20, more preferably in the range of 3 to 18, and even more preferably in the range of 5 to 15. The average value of the repeat number of n can be calculated from the number average molecular weight of the polyester of the present invention.

[0041] m is A ２ is an integer obtained by subtracting one from the number of carboxyl groups of the aliphatic polycarboxylic acid or aromatic polycarboxylic acid. ２is, for example, an aliphatic dicarboxylic acid residue, m is 1, and A ２ is, for example, an aromatic tricarboxylic acid residue, m is 2.

[0042] The polyester of the present invention may be any polyester that satisfies any one of the general formulas (A-1), (A-2) and (A-3) above, and may be used as a mixture of two or more polyesters having different structures.

[0043] The number average molecular weight (Mn) of the polyester of the present invention is, for example, in the range of 500 to 5,000, preferably in the range of 1,000 to 5,000, more preferably in the range of 1,500 to 4,000, and even more preferably in the range of 1,500 to 3,500. The number average molecular weight (Mn) is a value calculated in terms of polystyrene based on gel permeation chromatography (GPC) measurement, and is measured by the method described in the Examples.

[0044] The acid value of the polyester of the present invention is, for example, in the range of 10 to 70 mgKOH / g, preferably in the range of 15 to 60 mgKOH / g, and more preferably in the range of 15 to 50 mgKOH / g. The acid value of the polyester is confirmed by the method described in the examples.

[0045] The hydroxyl value of the polyester of the present invention is, for example, in the range of 0 to 50 mgKOH / g, preferably in the range of 0 to 40 mgKOH / g, and more preferably in the range of 0 to 30 mgKOH / g. The hydroxyl value of the polyester is confirmed by the method described in the examples.

[0046] The properties of the polyester of the present invention vary depending on the number average molecular weight, composition, etc., but are preferably liquid at room temperature. Here, "liquid at room temperature" means that the polyester of the present invention exhibits fluidity at room temperature of 25°C.

[0047] The polyester of the present invention can be obtained, for example, using reaction raw materials including an aliphatic diol and an aliphatic dicarboxylic acid constituting the repeating unit, and one or more terminal-modifying monoalcohols, monocarboxylic acids, aliphatic polycarboxylic acids, and aromatic polycarboxylic acids. Here, the reaction raw materials mean raw materials constituting the polyester of the present invention, and do not include solvents or catalysts that do not constitute polyesters. The method for producing the polyester of the present invention is not particularly limited, and the polyester can be produced by known methods, or by the production method described below.

[0048] The reaction raw materials for the polyester of the present invention may contain, for example, an aliphatic diol and an aliphatic dicarboxylic acid constituting the repeating unit, and one or more selected from a monoalcohol, a monocarboxylic acid, an aliphatic polycarboxylic acid, and an aromatic polycarboxylic acid that modify the terminals, or may contain other raw materials. The reaction raw materials for the polyester of the present invention preferably account for 90 mass% or more of the total amount of the reaction raw materials, and are preferably composed of an aliphatic diol and an aliphatic dicarboxylic acid constituting the repeating unit, and one or more selected from a monoalcohol, a monocarboxylic acid, an aliphatic polycarboxylic acid, and an aromatic polycarboxylic acid that modify the terminals, and more preferably consist of only an aliphatic diol and an aliphatic dicarboxylic acid constituting the repeating unit, and one or more selected from a monoalcohol, a monocarboxylic acid, an aliphatic polycarboxylic acid, and an aromatic polycarboxylic acid that modify the terminals.

[0049] The aliphatic diol used in the production of the polyester of the present invention is G １ The aliphatic diols used may be one type alone or two or more types in combination.

[0050] The aliphatic dicarboxylic acid used in the production of the polyester of the present invention is １ and A ２The aliphatic dicarboxylic acid used may be a single type or a combination of two or more types. When the aliphatic polycarboxylic acid used to modify the terminals is an aliphatic dicarboxylic acid, the aliphatic dicarboxylic acid constituting the repeating unit of the polyester and the aliphatic dicarboxylic acid used to modify the terminals may be the same or different.

[0051] The monocarboxylic acid used in the production of the polyester of the present invention is １ The monocarboxylic acid used may be one type alone or two or more types in combination.

[0052] The monoalcohol used in the production of the polyester of the present invention is a monoalcohol corresponding to the monoalcohol residue having 1 to 30 carbon atoms of Y, and the monoalcohol used may be used alone or in combination of two or more kinds.

[0053] The aliphatic polycarboxylic acid used in the production of the polyester of the present invention is ２ The aliphatic polycarboxylic acid used may be one type alone or two or more types in combination.

[0054] The aromatic polycarboxylic acid used in the production of the polyester of the present invention is ２ The aromatic polycarboxylic acid used may be one type alone or two or more types in combination.

[0055] Hydrogenated vegetable oil fatty acids may be used as the monocarboxylic acid used in producing the polyester of the present invention. Examples of such hydrogenated vegetable oil fatty acids include hydrogenated coconut oil fatty acids, hydrogenated palm kernel oil fatty acids, hydrogenated palm oil fatty acids, hydrogenated olive oil fatty acids, hydrogenated castor oil fatty acids, and hydrogenated rapeseed oil fatty acids. These are obtained by hydrolyzing and hydrogenating oils obtained from coconut, palm kernel, palm, olive, castor, and rapeseed, respectively, and are all mixtures of two or more long-chain aliphatic monocarboxylic acids including an aliphatic monocarboxylic acid having 8 to 21 carbon atoms. The monocarboxylic acid used in producing the polyester of the present invention may be the above-mentioned vegetable oil fatty acids that have not been hydrogenated, as long as the effects of the present invention are not impaired. Furthermore, the vegetable oil fatty acids are not limited to those mentioned above.

[0056] The aliphatic diol, aliphatic dicarboxylic acid, monoalcohol, monocarboxylic acid, aliphatic polycarboxylic acid, and aromatic polycarboxylic acid used in the production of the polyester of the present invention can all be used as derivatives thereof. Examples of such derivatives include esters, acid chlorides, acid anhydrides, and cyclic esters. For example, since an epoxy compound undergoes ring-opening to form a diol when reacted with a carboxylic acid, an aliphatic epoxy compound may be used as a derivative of the aliphatic diol used as a reaction raw material in the present invention.

[0057] The polyester represented by the general formula (A-1) can be produced, for example, by charging an aliphatic diol, an aliphatic dicarboxylic acid, and a monocarboxylic acid all at once and reacting them so that the equivalent weight of the carboxyl groups is greater than the equivalent weight of the hydroxyl groups. Alternatively, the polyester represented by the general formula (A-1) can be produced, for example, by reacting an aliphatic diol and an aliphatic dicarboxylic acid in any equivalent ratio, and then reacting the terminal hydroxyl groups of the resulting polyester with a monocarboxylic acid to cap the hydroxyl groups with a carboxylic acid residue.

[0058] The polyester represented by the general formula (A-2) can be produced, for example, by charging an aliphatic diol, an aliphatic dicarboxylic acid, and a monoalcohol all at once and reacting them in such a way that the equivalent weight of the carboxyl groups is greater than the equivalent weight of the hydroxyl groups. Alternatively, the polyester represented by the general formula (A-2) can be produced, for example, by reacting a diol and an aliphatic dicarboxylic acid in any equivalent ratio, and then reacting the terminal carboxyl groups of the resulting polyester with a monoalcohol to cap the terminal carboxyl groups with a monoalcohol residue.

[0059] Of the polyesters represented by general formula (A-2), a polyester in which Y is a hydrogen atom can also be produced by, for example, reacting an aliphatic diol with an aliphatic dicarboxylic acid in any equivalent ratio, and then reacting the terminal hydroxyl groups of the obtained polyester with an aliphatic dicarboxylic acid to form terminal carboxyl groups.

[0060] The polyester represented by the general formula (A-3) can be produced, for example, by reacting an aliphatic diol with an aliphatic dicarboxylic acid so that the equivalent of the hydroxyl group is greater than the equivalent of the carboxyl group to produce a polyester having hydroxyl groups at both ends, and then reacting one of the terminal hydroxyl groups of the obtained polyester with an aliphatic polycarboxylic acid and / or an aromatic polycarboxylic acid to convert it into a terminal carboxyl group.

[0061] In the production of the polyester of the present invention, the reaction of the raw materials may be carried out as an esterification reaction, for example, in the presence of an esterification catalyst at a temperature of 170 to 250° C. for 10 to 25 hours. The conditions of the esterification reaction, such as the temperature and time, are not particularly limited and may be set appropriately.

[0062] Examples of the esterification catalyst include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate; zinc-based catalysts such as zinc acetate; tin-based catalysts such as tin octoate and dibutyltin oxide; and organic sulfonic acid-based catalysts such as p-toluenesulfonic acid.

[0063] The amount of the esterification catalyst used may be appropriately determined, but is usually in the range of 0.0001 to 0.1 parts by mass per 100 parts by mass of the total amount of the reaction raw materials.

[0064] (Diester) The diester of the present invention is a diester represented by the following general formula (B): It is presumed that the diester reduces the free volume of the binder resin, and thus the antiplasticizer of the present invention exhibits an antiplasticizing effect.

[0065] (In the general formula (B), A ３ is an aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms, and Y ２ is a monoalcohol residue having 1 to 30 carbon atoms.

[0066] The aliphatic dicarboxylic acid residue and monoalcohol residue constituting the diester of the present invention may be the same as the aliphatic dicarboxylic acid residue and monoalcohol residue of the polyester of the present invention.

[0067] The diester of the present invention is preferably A ３ is an aliphatic dicarboxylic acid residue having 2 to 10 carbon atoms, and Y ２ is a diester represented by the general formula (B) above, in which R is an alkyl alcohol residue having 2 to 10 carbon atoms.

[0068] The diester of the present invention constituting the antiplasticizer of the present invention may be any diester satisfying the general formula (B) above, and may be, for example, a mixture of two or more diesters having mutually different structures.

[0069] The diester of the present invention can be obtained using reactants containing an aliphatic dicarboxylic acid and a monoalcohol. The aliphatic dicarboxylic acid and the monoalcohol can be the same as those described for the polyester of the present invention.

[0070] The method for producing the diester compound of the present invention is not particularly limited, and the compound can be produced by a known method, or a commercially available product may be used.

[0071] When the polyester of the present invention is a polyester represented by the general formula (A-2), the polyester can be produced, for example, by charging an aliphatic diol, an aliphatic dicarboxylic acid, and a monoalcohol all at once and reacting them. In this case, by making the amount of the aliphatic dicarboxylic acid excess over the amount of the aliphatic diol and also charging a larger amount of the monoalcohol, the diester represented by the general formula (B) can also be produced at the same time.

[0072] In the antiplasticizer of the present invention, the mass ratio of the polyester of the present invention to the diester compound of the present invention (polyester / diester compound) is set to a range of 99.5 / 0.5 to 95 / 5, preferably 99 / 1 to 95 / 5, and more preferably 99 / 1 to 96.5 / 3.5.

[0073] The antiplasticizer of the present invention can be prepared by separately producing the polyester and the diester and then mixing the polyester and the diester so that the mass ratio falls within the above range. Alternatively, as described in the method for producing the diester, the antiplasticizer of the present invention can also be prepared by directly producing a mixture of the polyester and the diester in the above range by adjusting the amounts of the reactant materials used in producing the polyester.

[0074] [Inorganic Particle-Containing Resin Composition / Coating Composition for Secondary Battery Separators] Lithium secondary batteries generally consist of a positive electrode, a negative electrode, a separator sandwiched between the positive and negative electrodes, and an electrolyte. The separator is typically a laminate formed by applying and drying a coating composition containing inorganic particles and a binder resin to a substrate. If the inorganic particles in the coating layer are not sufficiently dispersed, the adhesion between the coating layer and the substrate may be insufficient. Furthermore, when forming a secondary battery, the separator is pressed against the electrode, and if the binder resin has an insufficient modulus (stress), the adhesion to the electrode may be insufficient. The antiplasticizer of the present invention not only improves the antiplasticizing effect of the binder resin by improving the modulus of elasticity, but also improves the dispersibility of inorganic particles. Therefore, the inorganic particle-containing resin composition of the present invention, which contains the antiplasticizer, inorganic particles, a binder resin, and a solvent, can be suitably used as a coating composition for secondary battery separators. The components of the coating composition for secondary battery separators are described below.

[0075] (Inorganic Particles) The separator serves to prevent physical contact between the negative electrode and the positive electrode and to allow metal ions such as lithium ions to pass through its pores. However, if the separator is only a substrate (without a coating layer), there is a problem that the separator may be damaged by the electric charges of the metal particles that move between the separator during the charge / discharge process of the secondary battery. The inorganic particles are used to increase the strength of the separator.

[0076] Examples of inorganic particles include BaTiO ３ , Pb(Zr,Ti)O ３ , Pb １－ｘ La ｘ Zr １－ｙ TiyO ３ (0<x<1, 0<y<1), Pb(Mg １／３ Nb ２／３ ) O ３ -PbTiO ３ , HfO ２ , SrTiO ３ , SnO ２ , CeO ２, MgO, NiO, CaO, ZnO, ZrO ２ , Y ２ O ３ , Al ２ O ３ , TiO ２ , SiC, Al(OH) ３ , boehmite, and barium sulfate.

[0077] The inorganic particles contained in the coating composition for a secondary battery separator are not limited to those mentioned above, and may include lithium phosphate (Li ３ P.O. ４ ), lithium titanium phosphate (Li ｐ Ti ｑ (P.O. ４ ) ３ , 0<p<2, 0<q<3), lithium aluminum titanium phosphate (Li ａ Al ｂ Ti ｃ (P.O. ４ ) ３ , 0<a<2, 0<b<1, 0<c<3), 14Li ２ O ９ Al ２ O ３ 38TiO ２ 39P ２ O ５ (LiAlTiP) etc. ｄ O ｅ Glass 0<d<4, 0<e<13), lithium lanthanum titanate (Li ｅ La ｆ TiO ３ , 0<e<2, 0<f<3), Li ３．２５ Ge ０．２５ P ０．７５ S ４ Lithium germanium thiophosphate (Li ｇ Ge ｈ P ｉ S ｊ , 0<g<4, 0<h<1, 0<i<1, 0<j<5), Li ３ Lithium nitride (LiN) ｋ N ｌ , 0<k<4, 0<l<2), Li ３ P.O. ４ -Li ２S-SiS ２ SiS such as ２ Glass (Li ｍ Si ｎ S ｏ , 0<m<3, 0<n<2, 0<o<4), LiI-Li ２ S-P ２ S ５ P etc. ２ S ５ Inorganic particles having lithium ion conducting properties, such as glass, can also be used.

[0078] The particle size of the inorganic particles is not particularly limited, but is preferably D ５０ is, for example, in the range of 0.1 to 10 μm, preferably in the range of 0.2 to 5 μm. Similarly, D ９０ is, for example, 30 μm or less, and preferably in the range of 10 to 25 μm.

[0079] The content of the inorganic particles may be, for example, in the range of 0.5 to 40 parts by mass, preferably in the range of 5 to 30 parts by mass, and more preferably in the range of 10 to 20 parts by mass, based on 100 parts by mass of the coating composition for a secondary battery separator.

[0080] The antiplasticizer of the present invention can improve the dispersibility of inorganic particles, and its content may be, for example, in the range of 0.1 to 10.0 parts by mass, preferably in the range of 0.1 to 5.0 parts by mass, more preferably in the range of 0.2 to 2.0 parts by mass, and even more preferably in the range of 0.8 to 1.8 parts by mass, relative to 100 parts by mass of inorganic particles.

[0081] (Binder Resin) As the binder resin, for example, one or more types selected from the group consisting of an aliphatic conjugated diene / aromatic monovinyl copolymer, a (meth)acrylic polymer, a fluoropolymer, a (meth)acrylic acid / (meth)acrylamide copolymer, a (meth)acrylonitrile polymer, and an aromatic monovinyl / (meth)acrylic copolymer can be used.

[0082] Specific examples of binder resins include polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene, polymethyl methacrylate, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide.

[0083] The content of the binder resin may be, for example, in the range of 10 to 50 parts by mass, preferably 15 to 45 parts by mass, and more preferably 20 to 40 parts by mass, per 100 parts by mass of the inorganic particles.

[0084] (Solvent) The solvent is used to ensure the coatability of the coating composition for a secondary battery separator of the present invention, and is not particularly limited as long as it can dissolve the inorganic particles, the binder resin, and the antiplasticizer of the present invention to a certain level or more.

[0085] As the solvent, for example, one or more selected from the group consisting of acetone, tetrahydrofuran, acetonitrile, dimethylformamide, dimethylsulfoxide, dimethylacetamide, N-methylpyrrole, N-methylpyrrolidone, and water can be used.

[0086] The content of the solvent may be set so that the coating composition for a secondary battery separator is, for example, in a slurry state. For example, when the coating composition for a secondary battery separator is taken as 100 parts by mass, the content of the solvent may be, for example, in the range of 30 to 90 parts by mass, preferably in the range of 40 to 90 parts by mass, and more preferably in the range of 50 to 85 parts by mass.

[0087] The coating composition for a secondary battery separator of the present invention only needs to contain the antiplasticizer of the present invention, inorganic particles, a binder resin, and a solvent, and may also contain other components such as a thickener, an antifoaming agent, a pH adjuster, a viscosity adjuster, and a redox shuttle agent.

[0088] The coating composition for a secondary battery separator of the present invention may consist essentially of the antiplasticizer, inorganic particles, binder resin, and solvent of the present invention, where "consist essentially of" means that the total of the antiplasticizer, inorganic particles, binder resin, and solvent of the present invention is 80% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, or 100% by mass of the coating composition for a secondary battery separator.

[0089] [Secondary Battery Separator] The secondary battery separator of the present invention is a laminate having a substrate and a coating layer formed from the coating composition for a secondary battery separator of the present invention, and the coating layer may be disposed on at least one surface of the substrate. In the coating layer formed from the coating composition for a secondary battery separator of the present invention, the antiplasticizer of the present invention not only has the antiplasticizing effect of improving the elastic modulus of the binder resin, but also improves the dispersibility of inorganic particles. Due to this effect, the secondary battery separator of the present invention has good dispersibility of inorganic particles in the coating layer, and can improve adhesion to the electrode.

[0090] The substrate serves to prevent physical contact between the negative electrode and the positive electrode and to allow metal ions such as lithium ions to pass through the pores. The substrate may be, for example, a porous polymer film made of one or more materials selected from the group consisting of polyolefin resin, fluororesin, polyester resin, polyacrylonitrile resin, and cellulose resin.

[0091] The substrate is preferably a porous polymer film made of one or more materials selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, and polybutylene terephthalate.

[0092] The lower limit of the thickness of the substrate is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.Similarly, the upper limit of the thickness of the substrate is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

[0093] The coating layer is formed by, for example, applying the coating composition for a secondary battery separator of the present invention to a substrate and drying it, and may be formed by a known method. The lower limit of the thickness of the coating layer is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more. The upper limit of the thickness of the coating layer is preferably 10 μm or less, more preferably 8 μm or less.

[0094] [Secondary Battery] The secondary battery of the present invention includes a positive electrode, a negative electrode, a secondary battery separator of the present invention sandwiched between the positive electrode and the negative electrode, and an electrolyte (electrolytic solution or solid electrolyte). Each component will be described below.

[0095] The positive electrode is produced, for example, by applying a positive electrode mixture containing a positive electrode agent (positive electrode active material, an optional conductive material, an optional binder resin, and an optional filler) and a solvent onto a positive electrode current collector, followed by drying and rolling.

[0096] As the positive electrode active material, for example, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel manganese cobalt oxide, etc. can be used. Specific examples of the positive electrode active material include LiCoO ２ , LiNiO ２ , LiMn ２ O ４ , LiCoPO ４ , LiFePO ４ , LiNi ａ Mn ｂ CocO ２ (where 0<a, b, c<1), etc.

[0097] Examples of the conductive material that can be used in the positive electrode mixture include graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0098] The binder resin used in the positive electrode mixture is a component that facilitates bonding between the active material and the conductive material, etc., and bonding to the current collector. Examples of the binder resin include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butylene rubber, and fluororubber.

[0099] A filler is optionally used as a component to suppress expansion of the electrode. Examples of the filler include olefin polymers such as polyethylene and polypropylene, and fibrous materials such as glass fiber and carbon fiber.

[0100] The positive electrode current collector may be made of aluminum foil, titanium foil, stainless steel foil, nickel foil, baked carbon, conductive polymer, conductive glass, or the like.

[0101] The negative electrode is produced, for example, by applying a negative electrode mixture containing a negative electrode agent (negative electrode active material, an optional conductive material, an optional binder resin, and an optional filler) and a solvent onto a negative electrode current collector, followed by drying and rolling.

[0102] Examples of the negative electrode active material include carbonaceous materials such as natural graphite, artificial graphite, coke, and carbon black; lithium-containing titanium composite oxide (LTO); and the like.

[0103] The conductive material used in the negative electrode mixture can be the same as the conductive material described for the positive electrode.

[0104] As the binder resin used in the negative electrode mixture, in addition to the binder resins described for the positive electrode, acrylic polymers, styrene polymers, styrene-butadiene copolymers, vinyl acetate polymers, urethane polymers, etc. can be used.

[0105] The negative electrode current collector may be made of copper foil, nickel foil, or the like.

[0106] The electrolyte may be either an electrolytic solution or a solid electrolyte. When the electrolyte is an electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved can be used as the electrolytic solution.

[0107] The supporting electrolyte is, for example, LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ ) NLi and the like.

[0108] Examples of organic solvents that dissolve the supporting electrolyte include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), and vinylene carbonate (VC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide.

[0109] The secondary battery of the present invention can be produced by, for example, stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the stack as necessary, placing the stack in a battery container, injecting an electrolyte into the battery container, and sealing the container. Furthermore, the battery container may contain, as necessary, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, or the like, to prevent pressure buildup within the battery and overcharging and discharging. Examples of the shape of the secondary battery include coin type, button type, sheet type, cylindrical type, prismatic type, and flat type.

[0110] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0111] In the examples of the present application, the acid value and hydroxyl value were evaluated by the following methods. [Method for measuring acid value] Measured by a method conforming to JIS K0070-1992. [Method for measuring hydroxyl value] Measured by a method conforming to JIS K0070-1992.

[0112] In the examples of the present application, the number average molecular weight of the polyester is a value calculated as polystyrene based on GPC measurement, and the measurement conditions are as follows. [GPC measurement conditions] Measurement apparatus: High-speed GPC apparatus "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSK GURDCOLUMN SuperHZ-L" manufactured by Tosoh Corporation + "TSK gel SuperHZM-M" manufactured by Tosoh Corporation + "TSK gel SuperHZM-M" manufactured by Tosoh Corporation + "TSK gel SuperHZ-2000" manufactured by Tosoh Corporation + "TSK gel SuperHZ-2000" manufactured by Tosoh Corporation Detector: RI (differential refractometer) Data processing: "EcoSEC Data Analysis Version 1.07" manufactured by Tosoh Corporation Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 0.35 mL / min Measurement sample: 7.5 mg of sample was dissolved in 10 ml of tetrahydrofuran, and the resulting solution was filtered through a microfilter to prepare the measurement sample. Sample injection amount: 20 μl Standard sample: The following monodisperse polystyrene with known molecular weight was used in accordance with the measurement manual for the "HLC-8320GPC".

[0113] (Monodisperse polystyrene) "A-300" manufactured by Tosoh Corporation "A-500" manufactured by Tosoh Corporation "A-1000" manufactured by Tosoh Corporation "A-2500" manufactured by Tosoh Corporation "A-5000" manufactured by Tosoh Corporation "F-1" manufactured by Tosoh Corporation "F-2" manufactured by Tosoh Corporation "F-4" manufactured by Tosoh Corporation "F-10" manufactured by Tosoh Corporation "F-20" manufactured by Tosoh Corporation "F-40" manufactured by Tosoh Corporation "F-80" manufactured by Tosoh Corporation "F-128" manufactured by Tosoh Corporation "F-288" manufactured by Tosoh Corporation

[0114] Synthesis Example 1: Preparation of Antiplasticizer 1 A 5-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 676.3 g of 1,4-butylene glycol and 781.3 g of neopentyl glycol as glycol components, 2456.4 g of adipic acid as a dicarboxylic acid component, 259.7 g of isononyl alcohol as a monoalcohol component, and 0.13 g of tetraisopropyl titanate as a catalyst. Under a nitrogen stream, the temperature was raised stepwise to 220°C over 5 hours, and a condensation reaction was carried out at 220°C for 8 hours. After the reaction, unreacted raw materials and low-volatile components were removed at 200°C under reduced pressure to obtain a polyester.

[0115] The obtained polyester was confirmed by GPC measurement to contain both polyester A1, a polyester of 1,4-butylene glycol, neopentyl glycol, and adipic acid having carboxyl groups at both ends and one end of which was capped with isononyl alcohol, and diester B1 of adipic acid and isononyl alcohol, in a mass ratio of polyester A1:diester B1 of 97.2:2.8. This mixture of polyester A1 and diester B1 was designated as antiplasticizer 1.

[0116] The obtained polyester A1 was a viscous liquid at room temperature, and had an acid value of 35.5 mgKOH / g, a hydroxyl value of 1.4 mgKOH / g, and a number average molecular weight of 2,320.

[0117] Synthesis Example 2: Preparation of Antiplasticizer 2 A 5-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 1,467.0 g of 1,3-butylene glycol and 188.4 g of neopentyl glycol as glycol components, 2,400.0 g of adipic acid as a dicarboxylic acid component, and 0.12 g of tetraisopropyl titanate as a catalyst. The temperature was raised stepwise to 220°C under a nitrogen stream over 5 hours, and a condensation reaction was carried out at 220°C for 10 hours. 238.8 g of maleic anhydride was added to the resulting polyester and allowed to react, yielding Polyester A2.

[0118] The obtained polyester A2 was a polyester having a carboxyl group at least at one end, was a viscous liquid at room temperature, and had an acid value of 26.3 mg KOH / g, a hydroxyl value of 27.1 mg KOH / g, and a number average molecular weight of 2,620.

[0119] A 1-liter four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 190.0 g of adipic acid as a dicarboxylic acid component, 486.7 g of isononyl alcohol as a monoalcohol component, and 0.10 g of tetraisopropyl titanate as a catalyst. Under a nitrogen stream, the temperature was raised stepwise to 220°C over 5 hours, and a condensation reaction was carried out at 220°C for 3 hours. After the reaction, unreacted raw materials and low-volatile components were removed at 210°C under reduced pressure to obtain diester B2.

[0120] The resulting diester, B2, was liquid at room temperature and had an acid value of 0.05 mg KOH / g and a hydroxyl value of 0.5 mg KOH / g.

[0121] Polyester A2 and diester B2 were mixed together to give a mixture of polyester A2:diester B2=98.0:2.0 (mass ratio) as antiplasticizer 2.

[0122] Comparative Synthesis Example 1: Preparation of Antiplasticizer 1' Polyester A2 was used as antiplasticizer 1'.

[0123] Comparative Synthesis Example 2: Preparation of Antiplasticizer 2' Polyester A2 and diester B2 were mixed together to give a mixture of polyester A2:diester B2=92.0:8.0 (mass ratio) as antiplasticizer 2'.

[0124] (Examples 1-2 and Comparative Examples 1-3: Evaluation of Antiplasticizers) The antiplasticizers prepared in the Synthesis Examples and Comparative Synthesis Examples were evaluated as follows. The results are shown in Table 1.

[0125] (5% strain stress) 6 g of binder resin (poly(vinylidene fluoride-co-hexafluoropropylene), manufactured by Sigma-Aldrich) was dissolved in 24 g of acetone to prepare a resin solution, to which 0.3 g of the antiplasticizer shown in Table 1 was added and stirred to prepare a coating solution. The obtained coating solution was applied to a PET film using an applicator so that the thickness of the coating layer after drying would be 50 μm, and then dried to prepare a sample sheet for stress measurement. The sample sheet for stress measurement was cut to a size of 15 mm x 10 mm, and a stress-strain curve was measured using a static strain stress detector Rhegel-S1000-DVE3-DIC (manufactured by UBM Co., Ltd.) under conditions of an initial length of 5 mm and a tensile speed of 50 mm / min in a 25 ° C environment, and the stress at 5% strain was defined as the "5% strain stress." The higher the "5% strain stress", the stronger the coating layer and the better the adhesion between the substrate and the coating layer.

[0126] (180° Peel Strength) A coating liquid was prepared by adding 0.05 g of an antiplasticizer shown in Table 1 to a resin solution prepared by dissolving 2 g of binder resin (poly(vinylidene fluoride-co-hexafluoropropylene), manufactured by Sigma-Aldrich) in 20 g of acetone, and stirring the mixture. The obtained coating liquid was applied to a PET film using an applicator so that the thickness of the coating layer after drying would be 10 μm, and then dried to prepare a sample sheet for measuring peel strength.

[0127] The sample sheet was peeled from the PET film, and a 5 μm thick single-sided tape (DIC Corporation, single-sided tape IL-05G) was attached to one side of the sample sheet, followed by cutting to a width of 20 mm. The coating layer side of the cut sheet was aligned with the coated side of a negative electrode sheet (Hosen Co., Ltd., "HS-LIB-N-Gr-001"; base foil: copper foil; active material: spherulitic graphite; conductive material: graphite; binder resin: PVDF; single-sided coating) and pressed at a temperature of 80°C, 6.5 MPa, and for 60 seconds to produce a negative electrode laminate. The single-sided tape was peeled from the produced negative electrode laminate at a peel rate of 300 mm / min and a peel angle of 180° in a 25°C environment, and the adhesive strength of the sample sheet to the negative electrode sheet was measured. The 180° peel strength is an index of the adhesion of the coating layer to the negative electrode sheet; a higher value indicates higher adhesion.

[0128] (Inorganic particle dispersibility) A test tube was charged with 0.03 g of an antiplasticizer shown in Table 1, and after dissolving with 8 g of acetone, 2 g of alumina (AKP-3000, manufactured by Sumitomo Chemical Co., Ltd.) was added. The test tube was stirred for 1 minute using a Vortex mixer. The time until all of the alumina had settled was measured, and the absolute value of the slope of the sedimentation rate, with the horizontal axis representing time and the vertical axis representing the amount of sedimentation (100% immediately after the end of stirring and 0% when all of the alumina had settled), was used to evaluate dispersibility. The smaller the absolute value of the slope, the gentler the sedimentation and the better the dispersibility.

[0129]

[0130] It can be seen that in Examples 1 and 2, the adhesion between the substrate and the coating layer is high, and the adhesion between the electrode and the coating layer is also ensured. On the other hand, in Comparative Example 3, which does not contain an antiplasticizer, the inorganic particle dispersion is insufficient, and the adhesion between the substrate and the coating layer is also insufficient. In Comparative Examples 1 and 2, it is presumed that the absence of a diester or the presence of an excess of a diester results in an insufficient or excessive antiplasticizing effect, which impairs the adhesion between the substrate and the coating layer and the adhesion between the electrode and the coating layer.

Claims

1. An antiplasticizer containing one or more polyesters selected from the group consisting of polyesters represented by the following general formula (A-1), polyesters represented by the following general formula (A-2), and polyesters represented by the following general formula (A-3), and a diester represented by the following general formula (B), wherein the polyester and the diester are contained in a mass ratio of polyester:diester of 99.5:0.5 to 95:

5. (In the above general formulae (A-1), (A-2), (A-3) and (B), G １ is an aliphatic diol residue having 2 to 20 carbon atoms, １ is an aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms; ２ is an aliphatic polycarboxylic acid residue having 2 to 18 carbon atoms or an aromatic polycarboxylic acid residue having 4 to 18 carbon atoms; １ is a monocarboxylic acid residue having 1 to 20 carbon atoms; Y １ is a hydrogen atom or a monoalcohol residue having 1 to 30 carbon atoms; ３ is an aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms; Y ２ is a monoalcohol residue having 1 to 30 carbon atoms, n represents the number of repetitions, and m represents A ２ is an integer less one than the number of carboxyl groups of the aliphatic polycarboxylic acid or aromatic polycarboxylic acid.) 2. G １ The antiplasticizer according to claim 1, wherein R is a residue of an aliphatic diol having a branched structure and having 3 to 20 carbon atoms.

3. A １ The antiplasticizer according to claim 1, wherein is a residue of an aliphatic dicarboxylic acid having 4 to 10 carbon atoms.

4. A ２ The antiplasticizer according to claim 1, wherein is an aliphatic dicarboxylic acid residue having 2 to 18 carbon atoms or an aromatic tricarboxylic acid residue having 4 to 18 carbon atoms.

5. A ２ The antiplasticizer according to claim 1 , wherein is one or more selected from the group consisting of an adipic acid residue, a maleic acid residue and a trimellitic acid residue.

6. The antiplasticizer according to claim 1, wherein the number average molecular weight of the polyester represented by general formula (A-1), the polyester represented by general formula (A-2) and the polyester represented by general formula (A-3) is in the range of 1,000 to 5,000.

7. An inorganic particle-containing resin composition comprising the antiplasticizer according to any one of claims 1 to 6, inorganic particles, a binder resin, and a solvent.

8. A molded article made from the inorganic particle-containing resin composition according to claim 7.

9. A coating composition for a secondary battery separator, comprising the antiplasticizer according to any one of claims 1 to 6, inorganic particles, a binder resin, and a solvent.

10. The coating composition for a secondary battery separator according to claim 9, wherein the antiplasticizer is contained in an amount ranging from 0.2 to 2.0 parts by mass per 100 parts by mass of the inorganic particles.

11. The inorganic particles are BaTiO ３ , Pb(Zr,Ti)O ３ , Pb １－ｘ La ｘ Zr １－ｙ TyO ３ (0<x<1, 0<y<1), Pb(Mg １／３ Nb ２／３ ) O ３ -PbTiO ３ , HfO ２ , SrTiO ３ , SnO ２ , CeO ２ , MgO, NiO, CaO, ZnO, ZrO ２ , Y ２ O ３ , Al ２ O ３ , TiO ２ , SiC, Al(OH) ３ 10. The coating composition for a secondary battery separator according to claim 9, which is at least one selected from the group consisting of carbide, boehmite, and barium sulfate.

12. The coating composition for a secondary battery separator according to claim 9, wherein the binder resin is at least one selected from the group consisting of an aliphatic conjugated diene / aromatic monovinyl copolymer, a (meth)acrylic polymer, a fluoropolymer, a (meth)acrylic acid / (meth)acrylamide copolymer, a (meth)acrylonitrile polymer, and an aromatic monovinyl / (meth)acrylic copolymer.

13. A secondary battery separator which is a laminate comprising a substrate and a coating layer formed from the coating composition for a secondary battery separator according to claim 9.

14. A secondary battery comprising a positive electrode, a negative electrode, and the secondary battery separator according to claim 13 sandwiched between the positive electrode and the negative electrode.

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