JP2016121317A - Hydrophilic polymer, method of producing the same, and binder and electrode prepared therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrophilic polymer, a method of producing the same, an electrode including the same, and a negative electrode for lithium ion secondary battery, where the hydrophilic polymer exhibits excellent hydrophilicity, flexibility, and adhesiveness to metal.SOLUTION: The present invention provides a hydrophilic polymer represented by Formula (1), particularly, a hydrophilic polymer, where in the Formula (1), an imide structure is 10-99 wt.%, and the ratio of mol B of an imide unit to mol A of a urethane unit (B/A) is 1-30.SELECTED DRAWING: None

Description

  The present invention relates to a hydrophilic polymer that has excellent hydrophilicity and is flexible and exhibits excellent adhesion to a metal, a production method thereof, a binder using the same, and an electrode using the binder. Is.

  2. Description of the Related Art In recent years, secondary batteries represented by lithium ion secondary batteries have made electronic devices highly functional and capable of operating for a long time as rechargeable high-capacity batteries. Furthermore, it is mounted on automobiles and is regarded as a promising battery for hybrid and electric vehicles. In order to further increase the energy density of a lithium ion battery, the use of silicon, germanium, tin, or the like having a high charge / discharge capacity as a negative electrode active material has been studied (see Patent Document 1).

  In general, in order to maintain charge / discharge characteristics as a lithium ion secondary battery, it is necessary to keep the active substance and the current collector in a stable and close state, and a binder having good adhesion to the current collector is required. On the other hand, non-aqueous polyvinylidene fluoride (PVDF) or aqueous styrene butadiene copolymer (SBR) having good dispersibility has been mainly used as a binder used for general purposes.

  However, in the lithium ion secondary battery using the negative electrode active material, expansion and contraction of the negative electrode active material occurs during charging and discharging, and the binder resin is insufficient in both flexibility and adhesiveness, and thus may be destroyed. Further, there has been a problem that peeling at the interface between the negative electrode active material and the negative electrode current collector and the binder resin may occur, resulting in deterioration of charge / discharge cycle characteristics.

  Therefore, a technique for improving cycle characteristics by binding a negative electrode active material containing silicon with a specific polyimide resin or polyamideimide resin to obtain a negative electrode is known (see Patent Documents 2 and 3).

  Patent Document 2 uses a non-aqueous polyimide resin having high resin strength to suppress peeling at the interface between the negative electrode current collector and the binder and improve cycle characteristics. However, dehydration condensation from the binder precursor requires heat treatment at a high temperature, and there is a concern about the influence on the current collector. Moreover, since it is a polyimide single-piece | unit, it has hard physical properties, elasticity and flexibility are not enough, and adhesiveness is questioned.

Patent Document 3 uses a urethane resin containing an aromatic imide group and a soft segment capable of forming a single polymer having a glass transition point of 30 ° C. or lower as a non-aqueous binder,
A negative electrode having good adhesion that does not peel off from the copper foil at a relatively low temperature is prepared.
Similarly, Patent Document 4 also has a problem in that when the polyimide is obtained from the precursor polyamic acid by a dehydration reaction by high-temperature heat treatment, the polyimide shrinks and the negative electrode plate bends. By including an active material, a polyimide precursor compound and a highly flexible polymer, bending of the electrode plate can be prevented, and capacity characteristics and life characteristics can be improved.

  However, the coating solution is an organic solvent-based NMP, which may cause film formation on the active material surface, and is not satisfactory in terms of hydrophilicity.

In general, flexible polyimide resins and polyimide elastomers are also known (see Non-Patent Document 1 and Patent Document 5). However, since they are not specifically intended for hydrophilicity, water dispersibility is obtained when they are used. It is not satisfactory in terms of hydrophilicity. From the above, the conventional polyimide resins for batteries have generally required heat treatment at 200 to 350 ° C. to imidize from the precursor, but in the future, water-based and 150 ° C. or less that does not coat the active substance If a material capable of obtaining a binder performance equal to or higher than that of a conventional polyimide resin is developed even by heat treatment, it is expected that the practical use of Si-based negative electrodes will rapidly advance (see Non-Patent Document 2).
A polyimide-based resin having a hydroxyl group, a carboxyl group, or a sulfonic acid group capable of uniformly dispersing fine particles having a small environmental load and excellent solution stability in water has attracted attention (see Patent Document 6).

  However, these polymers are not satisfactory in terms of flexibility and adhesion to the current collector.

JP 2009-199761 A JP 2008-34352 A JP 2000-200608 A JP 2008-135384 A JP 2013-129770 A JP 2011-137063 A

Hideyuki Tezen, Tetsuro Shiiba, Akihisa Furukawa, "Synthesis and Properties of Polyimide Urethane Elastomers", Abstracts of Elastomer Discussion, 1999, p72-75 Akihiro Nakamura, "Next-generation storage battery latest material technology and performance evaluation", Technical Information Association, 2013, p166-167

  The present invention has been made in view of the above problems, and has an object to provide a hydrophilic polymer that has an extremely excellent hydrophilicity, is flexible, and exhibits excellent adhesion to a metal. To do.

  As a result of studies by the present inventors in order to achieve the above object, a polymer having a specific composition is flexible and has excellent adhesion to a metal while having extremely excellent hydrophilicity. It was found that a hydrophilic polymer suitable for a binder was obtained.

  Hereinafter, the present invention will be described in more detail.

  The hydrophilic polymer of the present invention has a structure represented by the following general formula (1).

（式中、Ｒ_１は炭素数４〜３０の２価の有機基を表し、Ｒ_２は平均分子量が１００〜１０，０００の直鎖若しくは分枝状の炭素数２〜５のポリオキシアルキレン構造を有する２価の有機基を表し、Ｒ_３は炭素数４〜３０の芳香環を１又は２個含有する３価以上の有機基を表し、Ｒ_４は炭素数４〜３０の４価の有機基を表し、Ｘはカルボキシル基又はスルホン酸基を表し、ｘは１〜８００の整数を表し、ｙは１〜８００の整数を表し、ｚは１〜１００の整数を表し、ａは１〜４の整数を表す。ただし、Ｘがカルボキシル基の場合、Ｒ_３の芳香環の数は１であり、ａは１である。さらに、式（１）中、下記式（２）で表される構造が１０〜９９重量％であり、式（３）で表されるウレタンユニット構造のモル数Ａに対する式（２）で表されるイミドユニット構造のモル数Ｂの比率（Ｂ／Ａ）が１〜３０である。）

(In the formula, R ₁ represents a divalent organic group having 4 to 30 carbon atoms, and R ₂ is a linear or branched polyoxyalkylene structure having 2 to 5 carbon atoms having an average molecular weight of 100 to 10,000. R ₃ represents a trivalent or higher valent organic group containing 1 or 2 aromatic rings having 4 to 30 carbon atoms, and R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms. X represents a carboxyl group or a sulfonic acid group, x represents an integer of 1 to 800, y represents an integer of 1 to 800, z represents an integer of 1 to 100, and a represents 1 to 4 However, when X is a carboxyl group, the number of aromatic rings of R ₃ is 1 and a is 1. Furthermore, in formula (1), the structure represented by the following formula (2) Is 10 to 99% by weight, and is represented by the formula (2) with respect to the mole number A of the urethane unit structure represented by the formula (3). The ratio of moles B of phagemid unit structure (B / A) is 1 to 30.)

（式中、Ｒ_３、Ｒ_４、Ｘ、ｙ及びａは前記の定義と同じである。但し、Ｘがカルボキシル基の場合、Ｒ_３の芳香環の数は１であり、ａは１である。）

(Wherein R ₃ , R ₄ , X, y and a are the same as defined above. However, when X is a carboxyl group, the number of aromatic rings in R ₃ is 1 and a is 1. .)

（式中、Ｒ_１、Ｒ_２及びｘは前記の定義と同じである。）
式（１）は、繰返し単位中に少なくとも一つのカルボキシル基又はスルホン酸基を持つイミドユニットとウレタンユニットがウレア結合を介して結ばれることを特徴としている。

(In the formula, R ₁ , R ₂ and x are the same as defined above.)
Formula (1) is characterized in that an imide unit having at least one carboxyl group or sulfonic acid group in a repeating unit and a urethane unit are linked via a urea bond.

R ₁ is preferably a divalent organic group containing an aromatic ring or aliphatic ring having 4 to 15 carbon atoms. R ₂ preferably has an average molecular weight of 100 to 5,000, more preferably 100 to 2,000. R ₃ preferably represents a trivalent or higher organic group containing 1 to 2 aromatic rings having 6 to 20 carbon atoms. x preferably represents an integer of 1 to 600. y preferably represents an integer of 2 to 600. The hydrophilic polymer of the present invention exhibits extremely excellent adhesion and hydrophilicity by combining an aromatic ring and a carboxyl group or a sulfonic acid group.

  Although the hydrophilic polymer of this invention is suitable for using for a binder, it is not specifically limited. Here, the binder refers to a material that binds the current collector metal and the active material, and particularly refers to a binder for a secondary battery.

  The hydrophilic polymer of the present invention has a rigid polyimide structural unit and a flexible polyalkylene structure in the structure.

  The hydrophilic polymer of this invention has a polyimide structural unit in a structure as a rigid hard segment by a polyimide prepolymer, and also has a carboxyl group or a sulfonic acid group in a polyimide structural unit. By having such a substituent, it is flexible and exhibits excellent adhesion to a metal.

  The hydrophilic polymer of the present invention is an electrochemically stable hydrophilic polymer, particularly under the conditions assumed to be used for a secondary battery. For example, in the range of potentials that can be used for lithium ion secondary batteries, oxidation and reduction reactions were not observed with cyclic voltammetry, and it was not known until now that they are stable hydrophilic polymers.

  Furthermore, the hydrophilic polymer of the present invention has a polyoxyalkylene structure introduced as a soft segment from a urethane prepolymer at the same time as a polyimide structural unit in the structure via a urea bond generated by the reaction of an isocyanate and an amino group. By introducing it, durability and flexibility can be imparted to a polyimide structure lacking in flexibility and inferior in bending resistance, and a hydrophilic polymer having flexibility and excellent adhesion to metal can be obtained.

  The hydrophilic polymer of the present invention contains 10 to 99% by weight, preferably 10 to 98% by weight, of the structure described in formula (2) in terms of the balance between hydrophilicity and adhesive force. From the viewpoint of improving hydrophilicity, it is more preferably 40 to 98% by weight, still more preferably 50 to 95% by weight, and particularly preferably 60 to 98% by weight because the balance between hydrophilicity and adhesive strength is most excellent. %. If it is less than 10% by weight, the hydrophilicity is inferior, and if it exceeds 99% by weight, the flexibility is insufficient.

  In the hydrophilic polymer of the present invention, the ratio (B / A) of the number of moles B of the imide unit structure represented by the formula (2) to the number of moles A of the urethane unit structure represented by the formula (3) is hydrophilic. And 1 to 30 in terms of the balance of adhesive strength, preferably greater than 1 and 30 or less, and more preferably greater than 1 and 10 or less in terms of improving hydrophilicity, further improving hydrophilicity. In view of this, it is more preferably greater than 1 and 5 or less, and most preferably greater than 1 and 2 or less because the balance between hydrophilicity and adhesive strength is most excellent. If it is less than 1, the cause is unknown, but the viscosity increases during the reaction and a hydrophilic polymer cannot be obtained. Probably, it is presumed that the hydrophilic polymer chain end having a polyimide structure is more stable than a polyurethane structure having an isocyanate group having high reactivity with a hydroxyl group or amino group. When the ratio (B / A) exceeds 30, the hydrophilicity and the adhesive strength are lowered, which is not preferable.

  The hydrophilic polymer of the present invention is preferable for a secondary battery, particularly for a lithium ion secondary battery, because the binding force between the electrode active material and the electrode is strong. In particular, it is preferable that the initial adhesive force with copper in a T-shaped peel test (tensile speed of 300 mm / min), which represents excellent adhesion to copper, which is a metal, is 0.05 N / mm or more. More preferably, it is 1.0 N / mm or more. When the hydrophilic polymer of the present invention is used for a secondary battery, aluminum, iron, stainless steel or the like can be used in addition to copper.

  The hydrophilic polymer of the present invention is a polyamic acid obtained by polycondensing a urethane prepolymer represented by the following formula (4) obtained by the reaction of diisocyanate and polyol, tetracarboxylic dianhydride and diamine in a solvent. It can obtain by reacting with the polyimide prepolymer which has an amino group in both the terminals represented by following formula (5) obtained by imide cyclization.

（式中、Ｒ_１、Ｒ_２及びｘは前記の定義と同じである。）

(In the formula, R ₁ , R ₂ and x are the same as defined above.)

（式中、Ｒ_３、Ｒ_４、Ｘ、ｙ及びａは前記の定義と同じである。但し、Ｘがカルボキシル基の場合、Ｒ_３の芳香環の数は１であり、ａは１である。）
本発明の親水性重合体の製造のために用いられる式（４）で表されるウレタンプレポリマーは、下記式（６）で表されるジイソシアネートと下記式（７）で表されるポリオールとの反応の際に、イソシアネート基とポリオール中の水酸基のモル比（イソシアネート基／水酸基）を１〜２の範囲にして反応することにより得ることができる。

(Wherein R ₃ , R ₄ , X, y and a are the same as defined above. However, when X is a carboxyl group, the number of aromatic rings in R ₃ is 1 and a is 1. .)
The urethane prepolymer represented by the formula (4) used for the production of the hydrophilic polymer of the present invention comprises a diisocyanate represented by the following formula (6) and a polyol represented by the following formula (7). In the reaction, it can be obtained by reacting with the molar ratio of the isocyanate group to the hydroxyl group in the polyol (isocyanate group / hydroxyl group) in the range of 1-2.

（式中、Ｒ_１は前記の定義と同じである。）

(Wherein R ₁ has the same definition as above).

（式中、Ｒ_２は前記の定義と同じである。）
式（６）で表されるジイソシアネートとしては、例えば、４，４’−ジフェニルメタンジイソシアネート（ＭＤＩ）、２，４−トリレンジイソシアネート（ＴＤＩ）、２，６−トリレンジイソシアネート（ＴＤＩ）、ポリメリックＭＤＩ、ジアニシジンジイソシアネート、ジフェニルエーテルジイソシアネート、トリレンジイソシアネート、ナフタレンジイソシアネート、ヘキサメチレンジイソシアネート、リジンジイソシアネートメチルエステル、メタキシリレンジイソシアネート、２，２，４−トリメチルヘキサメチレンジイソシアネート、２，４，４−トリメチルヘキサメチレンジイソシアネート、イソプロピリデンビス（４−シクロヘキシルイソシアネート）、シクロヘキシルメタンジイソシアネート、メチルシクロヘキサンジイソシアネート、メチルシクロヘキサンジイソシアネート２量体等が挙げられる。これらは１種又は２種以上を混合して用いてもよい。

(Wherein R ₂ is the same as defined above.)
Examples of the diisocyanate represented by the formula (6) include 4,4′-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate (TDI), polymeric MDI, Dianisidine diisocyanate, diphenyl ether diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate methyl ester, metaxylylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, Isopropylidenebis (4-cyclohexylisocyanate), cyclohexylmethane diisocyanate, methylcyclohexanediisocyanate Anate, methylcyclohexane diisocyanate dimer, and the like. You may use these 1 type or in mixture of 2 or more types.

  Examples of the polyol represented by the general formula (7) include polyether polyols such as polyoxytetramethylene glycol, polypropylene glycol, and polyethylene glycol. You may use these 1 type or in mixture of 2 or more types. Moreover, a polybutadiene polyol, an acrylic polyol, etc. can also be mixed and used as needed.

  The urethane prepolymer can be obtained, for example, by mixing and reacting a diisocyanate and a polyol at a predetermined ratio in an inert gas atmosphere such as argon gas or nitrogen gas. The ratio of the isocyanate in the diisocyanate and the hydroxyl group in the polyol is such that the closer the isocyanate / hydroxyl charge ratio (molar ratio) is to 1, the greater the degree of polymerization of the urethane prepolymer and the higher the molecular weight.

  In the present invention, the charging ratio (molar ratio) of isocyanate / hydroxyl group is 1 to 2, preferably more than 1 and 2 or less, and more preferably 1.01 to 2 in view of reactivity with the polyimide prepolymer. 0.02 to 2 are more preferable. An isocyanate / hydroxyl feed ratio (molar ratio) of less than 1 is not preferred because it does not result in a urethane prepolymer having isocyanate groups at both ends.

  In the preparation of the urethane prepolymer, the reaction is carried out at room temperature to 140 ° C. in the absence or presence of a catalyst, depending on the reactivity of the commonly used diisocyanate. Examples of the catalyst include organotin compounds and amine compounds. Examples of the organic tin compound include dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin bisacetoacetate, tin octoate, and the like. Examples of the amine compound include 1,4-diazabicyclo [2,2,2] octane. It is possible to react optionally in the presence or absence of a solvent. Examples of the solvent include acetone, butanone, tetrahydrofuran, dioxane, dimethoxyethane, methoxypropyl acetate, dimethylformamide, dimethylacetamide, N, N′-dimethyl-2,5-diazapentanone, N-methyl-2-pyrrolidone and the like. Can be mentioned. The reaction time is preferably 1 to 24 hours.

  The polyimide prepolymer represented by the formula (5) used for the production of the hydrophilic polymer of the present invention is a diamine represented by the following formula (8) and a tetracarboxylic acid represented by the following formula (9). In the reaction with dianhydride, it can be obtained by dehydration imidization after the reaction at a molar ratio of diamine to tetracarboxylic dianhydride (diamine / tetracarboxylic dianhydride) of more than 1 and 2 or less.

（式中、Ｒ_３、Ｘ及びａは前記の定義と同じである。但し、Ｘがカルボキシル基の場合、Ｒ_３の芳香環の数は１であり、ａは１である。）

(In the formula, R ₃ , X and a are the same as defined above. However, when X is a carboxyl group, the number of aromatic rings of R ₃ is 1 and a is 1.)

（式中、Ｒ_４は前記の定義と同じである。）
式（８）で表されるジアミンとしては、例えば、３，５−ジアミノ安息香酸、３，４−ジアミノ安息香酸、２，４−ジアミノ安息香酸、３，５−ジアミノ−トリメチルベンゼンスルホン酸、２，２’−ジスルホン酸ベンジジン、１，４−ジアミノベンゼン−３−スルホン酸、１，３−ジアミノベンゼン−４−スルホン酸、４，４’−ジアミノ−５，５’−ジメチル−（１，１’−ビフェニル）−２，２’−ジスルホン酸ベンジジン等が挙げられる。必要に応じこれらを２種以上使用してもよい。さらに必要に応じて、パラフェニレンジアミン、メタフェニレンジアミン、３，３’−ジアミノジフェニルエーテル、４，４’−ジアミノジフェニルエーテル、３，４’−ジアミノジフェニルエーテル、４，４’−ジアミノジフェニルメタン、３，３’−ジアミノジフェニルスルホン、４，４’−ジアミノジフェニルスルホン、４，４’−ジアミノジフェニルサルファイド、３，３’−ジアミノジフェニルサルファイド、ビス（３−アミノ−４−ヒドロキシフェニル）ヘキサフルオロプロパン、ビス（３−アミノ−４−ヒドロキシフェニル）スルホン、ビス（３−アミノ−４−ヒドロキシフェニル）プロパン、ビス（３−アミノ−４−ヒドロキシフェニル）メチレン、ビス（４−アミノ−３−ヒドロキシフェニル）メチレンを混合して使用することもできる。

(Wherein R ₄ has the same definition as above).
Examples of the diamine represented by the formula (8) include 3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 2,4-diaminobenzoic acid, 3,5-diamino-trimethylbenzenesulfonic acid, 2 , 2'-disulfonic acid benzidine, 1,4-diaminobenzene-3-sulfonic acid, 1,3-diaminobenzene-4-sulfonic acid, 4,4'-diamino-5,5'-dimethyl- (1,1 And '-biphenyl) -2,2'-disulfonic acid benzidine. Two or more of these may be used as necessary. Furthermore, paraphenylenediamine, metaphenylenediamine, 3,3′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3 ′ as necessary. -Diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, bis (3-amino-4-hydroxyphenyl) hexafluoropropane, bis (3 -Amino-4-hydroxyphenyl) sulfone, bis (3-amino-4-hydroxyphenyl) propane, bis (3-amino-4-hydroxyphenyl) methylene, bis (4-amino-3-hydroxyphenyl) methylene Can also be used That.

  Examples of the tetracarboxylic dianhydride represented by the formula (9) include 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, and pyromellitic. Acid dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3 ′, 4,4′- Biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-paraterphenyltetracarboxylic dianhydride, 3,3 ′, 4 , 4′-metaterphenyl tetracarboxylic dianhydride and the like. Two or more of these may be used as necessary. In the present invention, if necessary, those obtained by substituting 1 to 4 hydrogen atoms of these compounds with a carboxyl group, a sulfonic acid group or a hydroxyl group can be used.

  For example, after the polyimide prepolymer is mixed with a predetermined ratio of diamine and tetracarboxylic dianhydride in an organic solvent in an inert gas atmosphere such as argon gas or nitrogen gas to form a polyamic acid. Further, it can be obtained through an imide cyclization reaction. The polycondensation when synthesizing the polyimide prepolymer is similar to the usual polycondensation reaction, and the closer the charge ratio (molar ratio) of diamine / tetracarboxylic dianhydride is to 1, the higher the degree of polymerization of the polyamic acid produced Increase in molecular weight. In the present invention, the charging ratio (molar ratio) of diamine / tetracarboxylic dianhydride is more than 1 and 2 or less, and is preferably 1.01-2 in consideration of the reactivity with the polyimide prepolymer. When the charging ratio (molar ratio) of diamine / tetracarboxylic dianhydride is 1 or less, it does not become an amino group polyimide prepolymer at both ends, which is not preferable.

  The organic solvent used when synthesizing the polyimide prepolymer is not particularly limited as long as it is inactive with respect to tetracarboxylic dianhydride and diamine, and the generated polyamic acid can be dissolved. N-methyl-2-pyrrolidone (NMP), N, N′-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, N-methylcaprolactam, γ-butyrolactone, dimethylimidazoline, sulfolane, methyl isobutyl ketone, acetonitrile, Organic solvents such as benzonitrile, phenol, m-cresol, chlorophenol, 4-methylphenol and nitrophenol can be mentioned, and one or more can be used. The amount of the organic solvent used is not particularly limited as long as the reaction between the tetracarboxylic dianhydride and the diamine can proceed efficiently, but the concentration of the tetracarboxylic dianhydride and the diamine is 1. It is preferable to be ˜50% by weight, and more preferably 5 to 40% by weight. Further, toluene, acetone, tetrahydrofuran, xylene and the like can be added at an arbitrary ratio that does not hinder the reaction.

  Generally, polycarboxylic acid which is a polyimide precursor is obtained by reacting tetracarboxylic dianhydride and diamine in these organic solvents at a temperature of 100 ° C. or lower, preferably 10 to 90 ° C. Thereafter, imidization is preferably performed at a reaction temperature of 100 to 300 ° C. to obtain a polyimide prepolymer. In the imidization, a base such as triethylamine, isoquinoline, pyridine, methylmorpholine can be added as a catalyst. Furthermore, by-product water can be removed from the system by azeotropic distillation with a nonpolar solvent such as toluene, and the reaction can be allowed to proceed. If necessary, the reaction solution can be added to a solvent insoluble in a polyimide prepolymer such as water, methanol, ethanol, etc., the polymer can be precipitated, and dried to take out the polyimide prepolymer. Moreover, the reaction liquid of a polyimide prepolymer can be used for reaction with a urethane prepolymer, without isolating a polyimide prepolymer.

  The reaction between the urethane prepolymer and the polyimide prepolymer can be optionally carried out in the presence of an organic solvent or without solvent. When performed in the presence of an organic solvent, a urethane prepolymer and a polyimide prepolymer are added to the organic solvent at a predetermined ratio and mixed, and the reaction is performed in an inert gas atmosphere such as argon gas or nitrogen gas, and hydrophilicity is obtained. It is preferable to obtain a reaction solution containing a functional polymer. In order to knead the reaction liquid with the electrode active material and apply it as a binder, it is preferable that the reaction liquid is a uniform reaction liquid free from insoluble gel.

  The reaction liquid containing the hydrophilic polymer obtained by reacting the urethane prepolymer and the polyimide prepolymer has a glass transition temperature at a low temperature (25 ° C. or lower) because there is a flexible phase due to the urethane moiety. .

  Composition at the time of reaction for obtaining the hydrophilic polymer of the present invention (polyimide fraction = (preparation amount of polyimide prepolymer / (preparation amount of polyimide prepolymer + preparation amount of urethane prepolymer)) × 100) is 10 to 99 weights %, Preferably 10 to 98% by weight, more preferably 40 to 98% by weight, particularly preferably 60 to 98% by weight, and most preferably 80 to 98% by weight. If it is less than 10% by weight, the hydrophilicity is poor, and if it exceeds 99% by weight, the flexibility is insufficient.

  Furthermore, when obtaining the hydrophilic polymer of this invention, the molar ratio of the polyimide prepolymer represented by Formula (5) with respect to the urethane prepolymer represented by Formula (4) is larger than 1 and 30 or less, Preferably Is 1 or more and 2 or less, more preferably more than 1 and 2 or less. If it is less than 1, the hydrophilicity is remarkably lowered or the whole is solidified (gelled) during the reaction. If it exceeds 30, the hydrophilicity also decreases.

  The molecular weight of the urethane prepolymer represented by the formula (4) can be calculated and determined from the degree of polymerization determined by charging the diisocyanate compound and the polyol, but a known molecular weight measuring method such as GPC (gel permeation chromatography). You can also ask for it. The molecular weight of the polyimide prepolymer represented by the formula (5) can be calculated and obtained from the degree of polymerization obtained by charging diamine and acid anhydride, and can also be obtained from a known molecular weight measurement method such as GPC. it can. Details of the polyimide fraction are shown below.

<Polyimide fraction>
Polyimide fraction (% by weight) = [W _PI / (W _PU + W _PI )]
W _PU : Preparation amount of urethane prepolymer W _PI : Preparation amount of polyimide prepolymer As an organic solvent that can be used in the reaction of urethane prepolymer and polyimide prepolymer, it can be used in the synthesis of polyimide prepolymer and is not suitable for isocyanate groups. There is no particular limitation as long as it is active. For example, N-methyl-2-pyrrolidone, N, N′-dimethylacetamide, N, N-dimethylformamide, γ-butyrolactone and the like can be mentioned. Usually, the reaction is carried out at a temperature of 0 to 150 ° C, preferably 10 to 100 ° C. The reaction time is 1 to 72 hours, preferably 1 to 42 hours. When the reaction is carried out in the absence of a solvent, it can be carried out in an extruder equipped with a heating means having an exhaust system in addition to a usual stirred tank reactor.

  As the binder solution of the present invention, the reaction solution which is an organic solvent solution containing the hydrophilic polymer of the present invention can be used as it is. Other usable organic solvents are not particularly limited as long as the hydrophilic polymer is soluble. N-methyl-2-pyrrolidone, N, N′-dimethylacetamide, N, N-dimethyl Examples include formamide, monomethylformamide, γ-butyrolactone, monomethylformamide, parachlorophenol, 4-methylphenol, orthodichlorobenzene, phenol, chlorobenzene and the like. Other usage forms are as follows.

  In general, an aqueous solution of a polymer or a water-containing organic solvent solution is synthesized by a special polymerization method using water as a medium such as emulsion polymerization or suspension polymerization. When a product, an alkali metal carbonate, a tertiary amine compound, a quaternary amine compound or ammonia is reacted, a salt of a hydrophilic polymer is obtained, and the salt is mixed with water, an organic solvent or a hydrous organic solvent. A binder solution is obtained. The method is not particularly limited, but is 5 to 1000 parts by weight, preferably 5 to 300 parts by weight of an alkali metal hydroxide, an alkali metal carbonate, and 100 parts by weight of the hydrophilic polymer. A tertiary amine compound, a quaternary amine compound, or ammonia is added to form a salt with a hydrophilic polymer, and then water is added to form an aqueous solution or a water-containing organic solvent solution to obtain a binder solution.

  Also, after drying the organic solvent solution of the reaction product of the urethane prepolymer and the polyimide prepolymer under reduced pressure, or depositing the hydrophilic polymer in a solvent that is not a hydrophilic solvent such as water, methanol, or hexane, and drying it. , Dispersed or dissolved in an aqueous solution containing 5 to 1000 parts by weight of an alkali metal hydroxide, alkali metal carbonate, tertiary amine compound, quaternary amine compound or ammonia with respect to 100 parts by weight of the hydrophilic polymer. It can also be made into an aqueous solution or a water-containing organic solvent solution to form a binder solution. As a method for forming the salt, either in the presence or absence of an organic solvent may be used. The organic solvent is not particularly limited as long as the hydrophilic polymer is soluble. For example, N-methyl-2-pyrrolidone, N, N′-dimethylacetamide, monomethylacetamide, N, N-dimethylformamide, etc. Can be mentioned. Further, the hydrophilic polymer is added to an aqueous solution in which a predetermined amount of an alkali metal hydroxide, an alkali metal carbonate, a tertiary amine compound, a quaternary amine compound or ammonia is dissolved. An aqueous solution or a water-containing organic solvent solution can be obtained. In order to increase the solubility of the aqueous solution or the aqueous organic solvent solution, the solution may be heated at a temperature of 30 to 150 ° C. or may be subjected to ultrasonic treatment. After dissolution, water may be added or concentrated.

  The hydrophilic polymer of the present invention can be used as a reaction solution (binder solution) containing the hydrophilic polymer and an organic solvent, or as a desired form (binder solution) of an aqueous solution or a water-containing organic solvent solution. it can. Since the hydrophilic polymer of the present invention has excellent adhesion to metal, it is suitable as a binder for binding an electrode active material and an electrode of a secondary battery.

  Examples of the electrode active material include those containing carbon, silicon, tin, aluminum, titanium, germanium, or iron. For example, graphite, hard carbon, silicon, silicon oxide, silicon carbide, tin compound, silicon-aluminum alloy, silicon-tin alloy, silicon-titanium alloy, aluminum-tin alloy, tin-titanium alloy, etc. It is done.

  Since the hydrophilic polymer of the present invention is flexible and exhibits excellent adhesion to metals, it is particularly suitable for a binder for binding an electrode active material and an electrode for a secondary battery, particularly a lithium ion secondary battery. .

  When the binder solution of the present invention is produced, the water-containing organic solvent solution and the buffer solution, thickener, condensed phosphate, dispersion are used for the purpose of stabilizing the organic solvent solution and reducing the amount of scale generated. An agent, a tackifier, a pH adjuster, an antifoaming agent, a preservative, a film forming aid, a surfactant, an antifreezing agent, and the like can also be added.

  The hydrophilic polymer of the present invention is flexible and excellent in adhesion to metal, has a low environmental load, and is electrochemically stable when used in a secondary battery. And can be applied to a binder for bonding the electrode.

It is the figure which showed the result of CV measurement of a hydrophilic polymer. It is the figure which showed the initial stage charge / discharge curve of the battery produced using the hydrophilic polymer. It is the figure which showed the initial stage charge / discharge curve of the battery produced using the hydrophilic polymer. It is the figure which showed the initial stage charge / discharge curve of the battery produced using the hydrophilic polymer. It is the figure which showed the initial stage charge / discharge curve of the battery produced using the hydrophilic polymer.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

  The values used in the following examples and the like are those measured by the following measurement methods.

<Molecular weight>
The molecular weight of the urethane prepolymer was calculated from the degree of polymerization determined from the preparation of the diisocyanate compound and the polyol.
r ₁ = the degree of polymerization of the molar number of the urethane prepolymer of the molar number ÷ polyol diisocyanate compounds _{(N A) = (r 1} +1) ÷ (r 1 -1)
Molecular weight of urethane prepolymer = (N _A ÷ 0.5 × molecular weight of diisocyanate compound)
+ (N _A ÷ 0.5 × polyol molecular weight)
The molecular weight of the polyimide prepolymer was calculated from the degree of polymerization determined from the preparation of the diamine compound and acid anhydride.
r ₂ = number of moles of diamine compound charged ÷
Number of moles of tetracarboxylic dianhydride charged Degree of polymerization of polyimide prepolymer (N _B ) = (r ₂ +1) ÷ (r ₂ −1)
Molecular weight of polyimide prepolymer = (N _B ÷ 0.5 × molecular weight of diamine compound)
+ (N _B ÷ 0.5 × molecular weight of tetracarboxylic dianhydride) −polymerization degree × 18.

<Infrared absorption spectrum measurement>
The infrared absorption spectrum was measured using a System2000 FT-IR manufactured by PERKIN ELMER.

<Hydrophilicity evaluation>
80 g of a 1 wt% N-methylpyrrolidone solution was prepared, 3 times the amount of sodium hydroxide with respect to the carboxyl group was added to 100 parts by weight of the hydrophilic polymer, and 320 g of water was further added over 1 hour. The hydrophilicity of the polymer was evaluated.
(1) Formation of water-containing organic solvent solution: ◎
(2) Slight aggregate formation: ○
(3) Large amount of aggregate formation: △
(4) Lump formation during water addition: x.

<Evaluation of adhesiveness>
An N-methyl-2-pyrrolidone (NMP) solution containing 10% by weight of a hydrophilic polymer was prepared, applied to a 2 × 10 cm strip-shaped copper foil with a doctor blade, and dried (120 ° C. × 2 hours hot air The adhesion test was performed using the coating film obtained by drying and further drying under reduced pressure at 120 ° C. for 2 hours.
Copper foil: C122OR (length 100 mm × width 100 mm × thickness 0.05 mm) manufactured by Nippon Test Panel Co., Ltd.

<Bending test 1>
The copper foil obtained by applying a hydrophilic polymer to the copper foil was bent at 180 °, and the lack of the hydrophilic polymer in the bent portion was visually evaluated. The visual criteria were as follows.
(1) No missing (excellent adhesion): ◎
(2) Slight missing on the coated surface is observed (adhesiveness is good): ○
(3) Missing and the metal foil is slightly exposed: △
(4) The missing metal foil is completely exposed: x.

<Bending test 2>
The copper foil obtained by applying a hydrophilic polymer to the copper foil was repeatedly folded from a horizontal state on a pipe having a diameter of 1 cm so that the coated surface was outside and repeatedly bent, and the number of times until the coating film was peeled was measured.

<Polyimide fraction (ratio of structure of formula (2) in polymer)>
Polyimide fraction (% by weight) = [W _PI / (W _PU + W _PI )]
W _PU : Urethane prepolymer charge amount W _PU : Polyimide prepolymer charge amount.

<Measurement of glass transition temperature>
The glass transition temperature was measured using a differential scanning calorimeter (DSC200F3) manufactured by Netch Co., Ltd. in a temperature range of −100 ° C. to 250 ° C. under a temperature increase condition of 10 ° C./min.

<Evaluation of initial adhesive strength by T-peeling test with copper foil>
1. The reaction solution of the hydrophilic polymer was cast on a glass plate, dried with hot air at 120 ° C. for 2 hours, and further dried under reduced pressure at 120 ° C. to produce a film having a thickness of 100 μm.
2. The obtained film was cut into a width of 35 mm and a length of 70 mm, and copper foil: 180 ° C. × 1 using C122OR (length 100 mm × width 100 mm × thickness 0.05 mm) manufactured by Nippon Test Panel Co., Ltd. and a hot press device. Bonding was performed under the condition of minutes. This bonded sample was punched out into a strip shape having a width of 15 mm to obtain a sample for measuring an adhesive force.
3. The adhesive strength was determined by measuring the peel strength by a T-shaped peel test (tensile speed 300 mm / min) (based on JIS 6854) (n = 3).

<Cyclic voltammetry (CV) measurement>
An N-methylpyrrolidone solution containing 12% by weight of a hydrophilic polymer was prepared and applied to a C122OR (length 100 mm × width 100 mm × thickness 0.05 mm) copper foil made by Nippon Test Panel with a 150 μm doctor blade. . Thereafter, the coating film obtained by drying (drying with hot air at 120 ° C. for 2 hours and further drying under reduced pressure at 120 ° C. for 2 hours) was used as an electrode, and CV measurement was performed under the following conditions.
"CV measurement conditions"
・ Counter electrode = Li (16.6 cm ² )
・ Counter electrode = Li / Li ⁺
Test electrode area = 0.5 cm ²
・ Measurement temperature = room temperature (25 ℃)
・ Sweep speed = 0.5mV / sec
Electrolyte = 1M-LiPF ₆ / ethylene carbonate / dimethyl carbonate mixed solution (1.2 (vol ratio))
・ Measuring device = ELECTROCHEMICAL INTERFACE SI-1287 (manufactured by SOLARTRON)
First, after sweeping from 2V → 0V → 2V, foaming was swept twice in the range of 2 to 0V (vsLi / Li ⁺ ), and the flowing current was recorded, and CV measurement was performed.

<Preparation of electrode>
A predetermined amount of an electrode active material, a binder, a conductive additive, and N-methylpyrrolidone (NMP) were mixed and stirred and mixed with a self-revolving mixer to prepare an electrode coating solution.
The obtained electrode coating solution was applied at a coating speed of 1 cm / min. Coating on a copper foil with a thickness of 18 μm using a coater with clearance = 0.4 μm at 120 ° C. × 30 min. A copper foil coated with an electrode active material or the like was prepared by vacuum drying.
The obtained copper foil was punched out to a diameter of 16 mm to obtain an electrode.

<Evaluation of electrode>
The counter electrode was charged / discharged under the following conditions and evaluated the electrode: Li
Electrolyte: 1M LiPF ₆ Ethylene carbonate: Dimethyl carbonate (1: 2 (vol ratio))
Current: 0.2CA
Temperature: 25 ° C.

Synthesis example 1a
Under a nitrogen atmosphere, add 20.0 g of 4,4′-diphenylmethane diisocyanate (MDI) as diisocyanate and 76.1 g of polyoxytetramethylene glycol (molecular weight 1000, PTMG1000 manufactured by Mitsubishi Chemical Corporation) as a diisocyanate to a 500 ml four-necked separable flask. (Diisocyanate / polyol (molar ratio = 1.05)) was reacted at 80 ° C. for 2 hours to obtain a urethane prepolymer 1a.

  About the synthesis examples 2a-11a, it synthesize | combined by the same operation as the synthesis example 1a. The results are shown in Table 1.

合成例１ｂ
窒素雰囲気下水分定量管と還流冷却器を付けた２００ｍｌの四つ口フラスコにジアミンとして３，５−ジアミノ安息香酸（ＤＡＢ）６．２５ｇとＮＭＰ１２２．９ｇを量り取り、溶解した。その後、テトラカルボン酸二無水物として４，４’−オキシジフタル酸二無水物１２．５ｇを加え、５０℃に加熱し、１時間反応した（ジアミン／テトラカルボン酸二無水物（モル比＝１．０２））。その後、イソキノリン０．０４ｇをトルエン１０．５ｇに溶解した溶液を加え、１８０℃で３時間攪拌し、トルエンと共沸した水を取り除いてポリイミドプレポリマー１ｂの有機溶媒溶液を得た。

Synthesis example 1b
Under a nitrogen atmosphere, 6.25 g of 3,5-diaminobenzoic acid (DAB) and 122.9 g of NMP were weighed and dissolved in a 200 ml four-necked flask equipped with a moisture metering tube and a reflux condenser. Thereafter, 12.5 g of 4,4′-oxydiphthalic dianhydride was added as a tetracarboxylic dianhydride, heated to 50 ° C., and reacted for 1 hour (diamine / tetracarboxylic dianhydride (molar ratio = 1. 02)). Thereafter, a solution obtained by dissolving 0.04 g of isoquinoline in 10.5 g of toluene was added, and the mixture was stirred at 180 ° C. for 3 hours, and water azeotroped with toluene was removed to obtain an organic solvent solution of polyimide prepolymer 1b.

  About the synthesis examples 2b-13b, it synthesize | combined by the same operation as the synthesis example 1b. The results are shown in Table 2.

実施例１
窒素雰囲気下５００ｍｌの四つ口セパラブルフラスコにウレタンプレポリマー１ａを４．４ｇ及びＮＭＰ３．１ｇを量り取り、攪拌し溶解した。その後、ポリイミドプレポリマー１ｂの有機溶媒溶液７７．４ｇ（ポリマーとして８．９ｇ相当）を添加し、室温で２４時間反応させて、不溶成分の無い均一な親水性重合体の有機溶媒溶液を得た。ポリイミド分率は６６．９重量％であった。赤外吸収スペクトルによりイソシアネート基に由来する２２７０ｃｍ^−１吸収が消失し、１７８０ｃｍ^−１及び１３６０ｃｍ^−１にイミド構造に由来する吸収が存在し、３２９０ｃｍ^−１、１５４０ｃｍ^−１にウレタン構造に由来する吸収が存在することから反応の進行を確認した。得られたポリマーのガラス転移温度は−５８℃を示した。イミドユニット／ウレタンユニット（モル比）は２．４であった。

Example 1
Under a nitrogen atmosphere, 4.4 g of urethane prepolymer 1a and 3.1 g of NMP were weighed and dissolved in a 500 ml four-necked separable flask. Thereafter, 77.4 g of an organic solvent solution of polyimide prepolymer 1b (equivalent to 8.9 g as a polymer) was added and reacted at room temperature for 24 hours to obtain an organic solvent solution of a uniform hydrophilic polymer having no insoluble components. . The polyimide fraction was 66.9% by weight. 2270 cm ^-1 absorption derived from the isocyanate group by infrared absorption spectrum disappeared, and there is absorption derived from the imide structure 1780 cm ^-1 and 1360cm ^-1, 3290cm ^-1, which derived from a urethane structure 1540 cm ^-1 absorption The progress of the reaction was confirmed from the presence of. The glass transition temperature of the obtained polymer was -58 ° C. The imide unit / urethane unit (molar ratio) was 2.4.

  N-methylpyrrolidone was added to the organic solvent solution of the obtained hydrophilic polymer, and 80 g of an organic solvent solution of 1% by weight of the hydrophilic polymer was prepared in a 500 ml four-necked separable flask. Add 0.11 g of sodium hydroxide, add 320 g of water over 1 hour, and filter through a 200 mesh nylon filter to obtain a water-containing organic solvent solution of a hydrophilic polymer salt (binder solution). (Hydrophilic ◎).

  The organic solvent solution of the hydrophilic polymer obtained by the reaction was applied to a copper foil with a 0.15 μm doctor blade, and the adhesion was evaluated. The bending test 1 was extremely excellent (evaluation ◎). In the bending test 2, the coating film was not peeled even after repeated folding 100 times or more.

Moreover, the initial adhesive force with respect to copper foil was 1.20 N / mm.
From the results of CV measurement, the current derived from the oxidation reaction and the reduction reaction was not measured, and it was found that it was suitable for the binder.

  Examples 2 to 31 were synthesized in the same manner as in Example 1. The results are shown in Tables 3-5.

  The CV measurement result of the hydrophilic polymer of Example 3 is shown in FIG.

比較例１
５００ｍｌの四つ口セパラブルフラスコにウレタンプレポリマー１ａにＮ−メチルピロリドンを加え１重量％の有機溶媒溶液として８０ｇを調製した。０．０６ｇの水酸化ナトリウムを加え、更に３２０ｇの水を１時間かけて添加したところ、凝集物が多量に生成し、重合体の塩の含水有機溶媒溶液（バインダー用溶液）を得ることができず（親水性×）、実施例に対して劣った。

Comparative Example 1
To a 500 ml four-necked separable flask, N-methylpyrrolidone was added to urethane prepolymer 1a to prepare 80 g as a 1 wt% organic solvent solution. When 0.06 g of sodium hydroxide was added and 320 g of water was further added over 1 hour, a large amount of aggregates were formed, and a water-containing organic solvent solution (binder solution) of a polymer salt could be obtained. (Hydrophilicity x), inferior to the examples.

  Moreover, the organic solvent solution of urethane prepolymer was apply | coated to copper foil using a 0.15 micrometer doctor blade, and adhesiveness was evaluated. The bending test 1 was extremely excellent (evaluation ◎). In the bending test 2, the coating film was not peeled even after repeated folding 100 times or more.

  Moreover, the initial adhesive force with respect to copper foil was 0.1 N / mm, and was inferior to the Example.

  As for the CV measurement result of the organic solvent solution of the urethane prepolymer, the current derived from the oxidation reaction and the reduction reaction was not measured. The results are shown in Table 4.

Comparative Example 2
In a 500 ml four-necked separable flask, N-methylpyrrolidone was added to polyimide prepolymer 1b to prepare 80 g as a 1 wt% organic solvent solution. When 0.06 g of sodium hydroxide was added and 320 g of water was further added over 1 hour, a uniform aqueous solution of a salt of the hydrophilic polymer could be obtained (hydrophilic o).

  Moreover, using the organic solvent solution of the obtained polyimide prepolymer, it applied to copper foil with a 0.15 micrometer doctor blade, and adhesiveness was evaluated. In the bending test 1, the polymer peeled from the metal foil (evaluation x), which was inferior to the examples. In bending test 2, the polymer peeled completely from the copper foil at 53 times, which was inferior to the examples.

  Moreover, the initial adhesive force with respect to copper foil was 0.00 N / mm, and was low with respect to the Example.

  As for the CV measurement result of the polyimide prepolymer, the current derived from the oxidation reaction and the reduction reaction was not measured. The results are shown in Table 4.

Comparative Examples 3-11
Synthesis of a hydrophilic polymer was attempted by the same operation as in Example 1 under the conditions described in Table 4. However, any hydrophilic polymer resulted in inferior properties as compared to the examples. In Comparative Example 10, the viscosity increased during the reaction and stirring was impossible, and a hydrophilic polymer could not be obtained.

Comparative Example 12
Evaluation similar to the Example was performed using commercially available PVDF (KF # 1120, manufactured by Kureha Co., Ltd.) as a polymer. The results are shown in Table 4. For the evaluation of hydrophilicity, NaOH was not added. However, hydrophilicity, initial adhesive strength, bending test 1 and bending test 2 were inferior to the examples (= adhesion durability was low). In CV measurement, a reaction-derived current was observed.

実施例３２
活物質にＳｉＯ（大阪チタニウム社製）を用い、活物質／親水性重合体（実施例１８）／導電助剤（アセチレンブラック）＝７０／２０／１０（重量部）の組成で電極用塗工液を調製し、リチウムイオン２次電池用電極を作製した。この電極を用いＬｉを対極として充放電試験を行った。その充放電曲線を図２に示す。図２の結果より、親水性重合体をバインダーとして用いた電極は充放電を行うことができることがわかった。

Example 32
Using SiO (manufactured by Osaka Titanium Co., Ltd.) as the active material, coating for electrodes with a composition of active material / hydrophilic polymer (Example 18) / conductive aid (acetylene black) = 70/20/10 (parts by weight) The liquid was prepared and the electrode for lithium ion secondary batteries was produced. Using this electrode, a charge / discharge test was conducted using Li as a counter electrode. The charge / discharge curve is shown in FIG. From the results of FIG. 2, it was found that an electrode using a hydrophilic polymer as a binder can be charged and discharged.

Example 33
A lithium ion secondary battery electrode was produced in the same manner as in Example 30, except that Example 22 was used as the hydrophilic polymer. Using this electrode, a charge / discharge test was conducted using Li as a counter electrode. The charge / discharge curve is shown in FIG. From the results of FIG. 3, it was found that an electrode using a hydrophilic polymer as a binder can be charged and discharged.

Example 34
Using graphite (CGB-10 manufactured by Nippon Graphite Co., Ltd.) as the active material, an electrode coating solution was prepared with a composition of active material / hydrophilic polymer (Example 19) = 100/5 (parts by weight), and lithium ion An electrode for a secondary battery was produced. Using this electrode, a charge / discharge test was conducted using Li as a counter electrode. The charge / discharge curve is shown in FIG. From the results of FIG. 4, it was found that an electrode using a hydrophilic polymer as a binder can be charged and discharged.

Example 35
A lithium ion secondary battery electrode was produced in the same manner as in Example 30, except that Example 19 was used as the hydrophilic polymer. Using this electrode, a charge / discharge test was conducted using Li as a counter electrode. The charge / discharge curve is shown in FIG. From the results of FIG. 5, it was found that an electrode using a hydrophilic polymer as a binder can be charged and discharged.

Example 36
When the reaction solution (organic solvent (NMP) solution) obtained in Example 18 was filtered through a 200-mesh SUS wire mesh, formation of insoluble materials could not be confirmed visually. When the solubility was measured, the hydrophilic polymer was dissolved by 13% by weight.

  Moreover, the reaction liquid obtained in Example 18 was vacuum-dried until it became constant weight at 110 degreeC. 16.2 g of the hydrophilic polymer obtained in an aqueous solution in which 3.8 g of sodium hydroxide was dissolved in 180 g of water was dissolved and stirred at room temperature for 4 hours. The aqueous solution was filtered through a 400-mesh SUS wire mesh, and the obtained aqueous solution was dried with a hot air dryer at 120 ° C. until it became a constant weight. When the solubility was measured from the solid content, the hydrophilic polymer was dissolved by 9.5% by weight. It was.

Claims (10)

A hydrophilic polymer represented by the following formula (1).

(In the formula, R ₁ represents a divalent organic group having 4 to 30 carbon atoms, and R ₂ is a linear or branched polyoxyalkylene having 2 to 5 carbon atoms having a number average molecular weight of 100 to 10,000. Represents a divalent organic group having a structure, R ₃ represents a trivalent or more organic group containing one or two aromatic rings having 4 to 30 carbon atoms, and R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms. Represents an organic group, X represents a carboxyl group or a sulfonic acid group, x represents an integer of 1 to 800, y represents an integer of 1 to 800, z represents an integer of 1 to 100, a represents 1 to 1 Represents an integer of 4. However, when X is a carboxyl group, the number of aromatic rings of R ₃ is 1 and a is 1. Furthermore, in formula (1), it is represented by the following formula (2). The structure is 10 to 99% by weight, and is represented by the formula (2) with respect to the number of moles A of the urethane unit structure represented by the formula (3). The ratio of moles B of imide unit structure (B / A) is 1 to 30.)

(Wherein R ₃ , R ₄ , X, y and a are the same as defined above. However, when X is a carboxyl group, the number of aromatic rings in R ₃ is 1 and a is 1. .)

(In the formula, R ₁ , R ₂ and x are the same as defined above.) The hydrophilic polymer according to claim 1, wherein an initial adhesive force with copper in a T-peel test (tensile speed of 300 mm / min) is 0.05 N / mm or more. It is a manufacturing method of the hydrophilic polymer of Claim 1 or 2, The urethane prepolymer (A) represented by following formula (4), and the polyimide prepolymer (B) represented by following formula (5) And the polyimide fraction during the reaction ([(B) weight] / [(A) weight + (B) weight] × 100) is 10 to 99% by weight, and in the formula (4) The manufacturing method characterized by making the molar ratio of the polyimide prepolymer represented by Formula (5) with respect to the represented urethane prepolymer 1 or more and 30 or less.

(In the formula, R ₁ , R ₂ and x are the same as defined above.)

(Wherein R ₃ , R ₄ , X, y and a are the same as defined above. However, when X is a carboxyl group, the number of aromatic rings in R ₃ is 1 and a is 1. .) The urethane prepolymer (A) is a diisocyanate represented by the following formula (6) and a polyol represented by the following formula (7), wherein the molar ratio of isocyanate group to hydroxyl group (isocyanate group / hydroxyl group) is 1 to 2. The manufacturing method of the hydrophilic polymer of Claim 3 obtained by making it react in the range.

(Wherein R ₁ has the same definition as above).

(Wherein R ₂ is the same as defined above.) When the polyimide prepolymer (B) is a diamine represented by the following formula (8) and a tetracarboxylic dianhydride represented by the following formula (9), the molar ratio of the diamine and the tetracarboxylic dianhydride (diamine) The method for producing a hydrophilic polymer according to claim 3 or 4, wherein (/ tetracarboxylic dianhydride) is obtained in a range of more than 1 and 2 or less.

(In the formula, R ₃ , X and a are the same as defined above. However, when X is a carboxyl group, the number of aromatic rings of R ₃ is 1 and a is 1.)

(Wherein R ₄ has the same definition as above). A salt of a hydrophilic polymer obtained by reacting the hydrophilic polymer according to claim 1 or 2 with an alkali metal hydroxide, an alkali metal carbonate, a tertiary amine compound, a quaternary amine compound or ammonia. . The solution for binders formed by melt | dissolving the hydrophilic polymer of Claim 1 or 2, and / or the salt of the hydrophilic polymer of Claim 6 in water, an organic solvent, or a water-containing organic solvent. The binder for secondary batteries obtained by drying the solution for binders of Claim 7. An electrode comprising the hydrophilic polymer according to claim 1 and / or the salt of the hydrophilic polymer according to claim 6. An electrode for a lithium ion secondary battery comprising the electrode according to claim 9.

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