JP2017195072A - Polyurethane resin water dispersion for secondary battery separator, secondary battery separator, and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyurethane resin water dispersion for a secondary battery separator, which is satisfactory in blending stability with a thickener, and excellent in electrolyte resistance, the strength retention rate before and after immersion in an electrolyte solution, dynamic viscoelasticity, and adhesion.SOLUTION: A polyurethane resin water dispersion for a secondary battery separator comprises: a polyurethane resin consisting of a reaction product of at least a polyolefin-based polyol (except a hydrogenated polybutadiene polyol of which the number of hydroxyl groups per molecule is less than two) (A), and a polyisocyanate compound (B).SELECTED DRAWING: None

Description

  The present invention relates to a polyurethane resin aqueous dispersion for a secondary battery separator, a secondary battery separator, and a secondary battery.

In recent years, notebook personal computers, mobile phones, PDAs (Personal Digital A
The use of mobile terminals such as sistant is remarkable. Secondary batteries such as lithium ion secondary batteries are frequently used as secondary batteries used for the power source of these portable terminals. On the other hand, polyurethane resins are also used in a wide range of fields due to their characteristics, and secondary batteries are also used (Patent Document 1).

JP 2012-003841 A

  However, the resin described in the patent document does not always satisfy the performance when used for a secondary battery separator.

In order to solve the above problems, the present invention provides:
(1) A polyurethane resin aqueous dispersion for a secondary battery separator,
The polyurethane resin is a reaction product of at least a polyolefin-based polyol (excluding a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in one molecule) (A) and a polyisocyanate compound (B).
Polyurethane resin aqueous dispersion for secondary battery separator,
(2) Said (A) is
The polybutadiene polyol (A1), the polyisoprene polyol (A2), one or more kinds selected from the group consisting of two or more hydrogenated polybutadiene polyols (A3) and hydrogenated polyisoprene polyols (A4) in one molecule. ,
(1) A polyurethane resin aqueous dispersion for a secondary battery separator according to (1),
(3) A secondary battery separator obtained using the polyurethane resin aqueous dispersion described in (1) or (2),
(4) A secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolytic solution, wherein the separator is a separator for a secondary battery according to (3),
About.

  According to the present invention, the blending stability with the thickener is good, and the electrolyte solution resistance of the film obtained from the polyurethane resin aqueous dispersion, the strength retention before and after immersion in the electrolyte solution, dynamic viscoelasticity and adhesion Since all the properties are good, it can be suitably used for a secondary battery separator.

  Hereinafter, preferred embodiments of the present invention will be described.

<Polyurethane resin water dispersion>
The polyurethane resin of the present invention is a reaction product of at least a polyolefin-based polyol (excluding a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in one molecule) (A) and a polyisocyanate compound (B). By using the polyolefin-based polyol, the polarity of the polyurethane resin is lowered, so that the electrolytic solution resistance, the strength retention before and after the electrolytic solution immersion, the dynamic viscoelasticity, and the adhesiveness are improved.
Preferably, a polyol containing a polyolefin-based polyol (excluding a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in one molecule) (A), a polyisocyanate compound (B), and a hydrophilic group-containing compound as necessary are reacted. If necessary, neutralize the hydrophilic groups contained, or quaternize with a quaternizing agent to obtain a urethane prepolymer, emulsify with water, and then carry out a chain extension reaction with water or / and polyamine. Can be obtained.

  In the present invention, a polyolefin-based polyol (excluding hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in one molecule) (A) is a polymer of diolefins having 4 to 12 carbon atoms such as butadiene and isoprene. Among the copolymers, copolymers of diolefins having 4 to 12 carbon atoms and α-olefins having 2 to 22 carbon atoms, a compound containing a hydroxyl group. The method for containing a hydroxyl group is not particularly limited, and for example, there is a method of reacting a diene monomer with hydrogen peroxide. Furthermore, you may make saturated aliphatic by hydrogenating the remaining double bond. Examples of such polyolefin-based polyols include “NISSO-PBG” series manufactured by Nippon Soda Co., Ltd., “Poly bd” series manufactured by Idemitsu Kosan Co., Ltd., and “Epol”. Of these, polybutadiene polyol (A1), polyisoprene polyol (A2), and two hydroxyl groups in one molecule from the viewpoints of electrolyte resistance, strength retention before and after immersion in the electrolyte, dynamic viscoelasticity, and adhesion. The above hydrogenated polybutadiene polyol (A3) and hydrogenated polyisoprene polyol are preferred (A4). These can use 1 type, or 2 or more types.

  In the present invention, other polyols than the polyolefin-based polyol (excluding hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in one molecule) (A) may be used in combination. The other polyol is not particularly limited as long as it is a compound having two or more hydroxyl groups in the molecule. For example, a polyhydric alcohol, a polyether polyol, a polyester polyol, a polyether ester polyol 2 or more hydroxyl groups in the molecule or in the molecule such as polyol, polycarbonate polyol, polyacrylic polyol, polyacetal polyol, polybutadiene polyol, polysiloxane polyol, fluorine polyol, etc. And compounds having a group. Although it does not specifically limit as polyhydric alcohol, For example, ethylene glycol, diethylene glycol, butanediol, propylene glycol, hexanediol, bisphenol A, bisphenol B, bisphenol S, hydrogenated bisphenol A, dibromobisphenol A, 1,4-cyclohexanedimethanol, dihydroxyethyl terephthalate, hydroquinone dihydroxyethyl ether, trimethylolpropane, glycerin, pentaerythritol -E.g. The polyether polyol is not particularly limited, and examples thereof include polyhydric alcohol alkylene derivatives, polytetramethylene glycol, polythioether polyol and the like. Polyester polyols and polyether ester polyols are not particularly limited. For example, polyhydric alcohols, polyhydric carboxylic acids, polyhydric carboxylic acid anhydrides, polyether polyols, polycarboxylic acid esters Esterified products, castor oil polyol, polycaprolactone polyol, and the like. Of these, polyester polyol and polyester polyol are preferred. These can use 1 type, or 2 or more types. A hydroxyl group may be used in combination with one compound.

  In the present invention, the number average molecular weight of the polyol component is not particularly limited, but is preferably 50 to 10,000, more preferably 500 to 5,000 from the viewpoint of blending stability with a thickener and physical properties. .

  In the present invention, the polyisocyanate compound (B) is not particularly limited, and examples thereof include organic polyisocyanates such as aromatic, aliphatic, alicyclic, and aromatic fats. Among these, from the viewpoint of electrolytic solution resistance, strength retention before and after electrolytic solution immersion, dynamic viscoelasticity and adhesion, organic polyisocyanates such as aliphatic, alicyclic and aromatic fats, and their large amount of modification Preferred are a body (dimer, trimer, etc.), or a biuret modified body produced by the reaction of the organic polyisocyanate with water. 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate [bis (isocyanatemethyl) cyclohexane], hexamethylene diisocyanate, lysine diisocyanate -Organic polyisocyanates such as norbornane diisocyanate and xylylene diisocyanate, and modified products thereof are more preferred. Further, 4,4'-dicyclohexylmethane diisocyanate and isophorone diisocyanate are more preferable. These can use 1 type, or 2 or more types.

  In the present invention, the ratio of the isocyanate group and hydroxyl group (molar equivalent ratio) used to obtain the urethane prepolymer is not particularly limited as long as it is (isocyanate group: hydroxyl group =) 1.1 or more: 1. The urethane prepolymer (b) has a low viscosity, and a stable emulsion can be obtained, so 1.5 to 3.0: 1 is preferable, and 1.6 to 2.2: 1 is more preferable. If it is these ranges, the mixing | blending stability with a thickener will be favorable.

  In the present invention, the average molecular weight of the urethane prepolymer is preferably 5000 or less, more preferably 4000 or less, from the viewpoints of emulsifying properties and emulsion stability. The average molecular weight here means a theoretical value calculated from the number average molecular weight of the charged raw materials.

  In the present invention, the hydrophilicity may be any of the anionic group, the cationic group, or the nonionic group, and is not particularly limited. Among these, the compounding stability with the thickener, the film From the viewpoint of performance, an anionic group or a cationic group is preferable.

  The hydrophilic group compound to be introduced by incorporating the hydrophilicity is not particularly limited. For example, (di) alkanol carboxylic acid or sulfonic acid tertiary amine or alkali metal neutralized product, (methoxy) poly Examples include alkylene oxides, (di) alkanolamine organic / inorganic acid neutralized products, and quaternary ammonium salts obtained by reacting these with alkyl halides or dialkyl sulfuric acid. Of these, (di) neutralized products of alkanol carboxylic acids or sulfonic acids with tertiary amines or alkali metals, (di) neutralized products of alkanolamines with organic and inorganic acids, and these are reacted with alkyl halides or dialkyl sulfuric acid. Quaternary ammonium salts are preferred. The (methoxy) polyalkylene oxide may contain at least ethylene oxide as the alkylene oxide, and may contain other alkylene oxides such as propylene oxide and butylene oxide. An addition form (hydrophilic group introduction form) in the case of using (methoxy) polyalkylene oxide containing a plurality of types of alkylene oxides may be either block addition or random addition. .

The following can be illustrated as a compound which can introduce | transduce these hydrophilic groups.
For example, as anion type, dimethylolpropionic acid, dimethylolbutanoic acid,
Obtained by neutralizing carboxylic acid compounds such as lactic acid and glycine, and sulfonic acid compounds such as aminoethyl sulfonic acid and polyester diol composed of sulfoisophthalic acid and diol with tertiary alkanolamines such as triethylamine, NaOH and dimethylaminoethanol. The salt which can be mentioned can be mentioned. Of these, dimethylolpropionic acid, glycine, and sodium salt of aminoethylsulfonic acid are preferred from the viewpoints of blending stability with a thickener and film performance.

  For example, as a cation type, a salt obtained by neutralizing an alkanolamine such as dimethylaminoethanol or methyldiethanolamine with an organic carboxylic acid such as formic acid or acetic acid, or an inorganic acid such as hydrochloric acid or sulfuric acid, or halogenation such as methyl chloride or methyl bromide Quaternized with dialkyl sulfuric acid such as alkyl and dimethyl sulfuric acid. Of these, a combination of methyldiethanolamine and an organic carboxylic acid and a combination of methyldiethanolamine and dimethylsulfuric acid are preferred because they are easy to produce industrially.

  The content of the hydrophilic group in the urethane prepolymer (b) is not particularly limited. For example, the content is preferably 0.07 to 2.10 mmol / g, more preferably 0.12 to 1.80 mmol / g, and still more preferably 0.17 to 1.60 mmol / g. If it is the said range, it is preferable from a viewpoint of a mixing | blending stability with a thickener, and a film | membrane performance.

  For the chain extension, water or polyamine can be used. The polyamine is not particularly limited, for example, aliphatic polyamines such as ethylenediamine, trimethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, aromatic polyamines such as metaxylenediamine, tolylenediamine, diaminodiphenylmethane, piperazine, An alicyclic polyamine such as isophoronediamine, a polyhydrazide such as hydrazine, and adipic acid dihydrazide can be used. The said polyamine compound may be used independently and may use 2 or more types together.

  Although it does not specifically limit as solid content of the polyurethane resin in the polyurethane resin aqueous dispersion in this invention, For example, 1-60 mass% is preferable with respect to an aqueous dispersion, 3-55 mass% is more preferable, 4- 50 mass% is more preferable. If it is these ranges, it is preferable from a viewpoint of mixing | blending stability with a thickener, and workability | operativity.

  Furthermore, various commonly used additives can be used in the aqueous dispersion of the present invention as necessary. Examples of such additives include weathering agents, antibacterial agents, antifungal agents, pigments, fillers, rust inhibitors, pigments, dyes, film-forming aids, inorganic crosslinking agents, organic crosslinking agents (for example, blocked isocyanates). -Based crosslinking agents, epoxy-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, melamine-based crosslinking agents), silane coupling agents, antiblocking agents, viscosity modifiers, leveling agents, antifoaming agents, dispersion stabilizers, light Stabilizers, antioxidants, ultraviolet absorbers, inorganic and organic fillers, plasticizers, lubricants, antistatic agents and the like can be mentioned.

<Secondary battery separator>
The secondary battery separator of the present invention is obtained using the polyurethane resin aqueous dispersion. Although not particularly limited, a porous body having insulating fine particles and an organic binder that are stable with respect to the non-aqueous electrolyte is preferable.

  In the separator of the present invention, an organic binder is used for the purpose of binding insulating fine particles. Any organic binder may be used as long as it is electrochemically stable and stable with respect to the electrolyte solution, and can adhere well to the insulating fine particles. It is preferable from the viewpoint of maintaining the storage elastic modulus at a high temperature. As other materials, for example, EVA (with a structural unit derived from vinyl acetate of 20 to 35 mol%), ethylene-acrylate copolymer such as ethylene-ethyl acrylate copolymer, fluorine-based rubber, styrene-butadiene rubber ( SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), polyurethane, epoxy resin, etc., and these may be used alone. Well, you may use 2 or more types together.

  As the porous body, there is used a porous film having a fine pore diameter, which has no electron conductivity, has ionic conductivity, and has high resistance to a non-aqueous electrolyte. For example, a polyolefin film (polyethylene, polypropylene, polybutene, polyvinyl chloride), a microporous film made of a resin such as a mixture or copolymer thereof, polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, polyimide, polyimide amide, Examples thereof include a microporous membrane made of a resin such as polyaramid, polycycloolefin, nylon, and polytetrafluoroethylene, or a woven fabric of polyolefin fibers, a nonwoven fabric thereof, an aggregate of insulating substance particles, or the like. Among these, since the thickness of the separator for the secondary battery can be reduced and the ratio of the electrode active material layer in the battery can be increased to increase the capacity per volume, a microporous film made of polyolefin resin is preferable. .

  The thickness of the porous body is preferably 0.5 to 40 μm, more preferably 1 to 30 μm, and particularly preferably 1 to 10 μm. By setting it in the above range, resistance due to the porous body in the battery is reduced, and workability at the time of manufacturing the battery is excellent.

  The porous body may have a multilayer structure having two or more layers that can be used as the porous body for the purpose of increasing the tear strength and the piercing strength. Specific examples include a laminate of a polyethylene microporous membrane and a polypropylene microporous membrane, and a laminate of a nonwoven fabric and a polyolefin separator.

  The insulating fine particles serve as the main component in the secondary battery separator of the present invention and have an effect of suppressing the occurrence of a short circuit due to lithium dendrite. The insulating fine particles have electrical insulating properties, are electrochemically stable, and are stable to an electrolyte and a solvent used for a composition for forming a separator (a composition containing a solvent). If it does not melt | dissolve in electrolyte solution, there will be no restriction | limiting in particular.

  As used herein, the term “insulating fine particles that are stable with respect to a non-aqueous electrolyte” refers to deformation and chemistry in a non-aqueous electrolyte (a non-aqueous electrolyte used as an electrolyte for lithium secondary batteries). Insulating fine particles that do not undergo any change in the composition. In addition, the “high temperature state” in the present specification is specifically a temperature of 150 ° C. or higher, and is a stable particle that does not undergo deformation and chemical composition change in an electrolyte solution at such a temperature. Good. Further, “electrochemically stable” as used in the present specification means that no chemical change occurs during charging / discharging of the battery.

Specific examples of such insulating fine particles include, for example, oxide fine particles such as iron oxide, SiO ₂ , Al ₂ O ₃ , TiO ₂ , BaTiO ₂ , and ZrO; nitride fine particles such as aluminum nitride and silicon nitride; Slightly soluble ionic crystal particles such as calcium fluoride, barium fluoride and barium sulfate; Covalent crystal particles such as silicon and diamond; Clay particles such as talc and montmorillonite; Boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine , Sericite, bentonite and other mineral resource-derived substances or their artificial products; Further, the surface of conductive fine particles such as metal fine particles; oxide fine particles such as SnO ₂ and tin-indium oxide (ITO); carbon fine particles such as carbon black and graphite; Fine particles imparted with electrical insulation properties by surface treatment with the above-described materials constituting the electrically insulating fine particles) may be used. These insulating fine particles may be used alone or in combination of two or more.

The form of the insulating fine particles may be any form such as a spherical shape, a particle shape, or a plate shape, but a plate shape is preferable. Examples of the plate-like particles include various commercially available products. For example, “Sun Lovely” (SiO ₂ ) manufactured by Asahi Glass S Tech Co., Ltd., “NST-B1” pulverized product (TiO ₂ ) manufactured by Ishihara Sangyo Co., Ltd., Sakai Chemical Industry Co., Ltd. Plate-like barium sulfate “H series”, “HL series”, Hayashi Kasei “micron white” (talc), Hayashi Kasei “bengel” (bentonite), Kawai lime “BMM” and “BMT” (Boehmite), “Cerasure BMT-B” [Alumina (Al ₂ O ₃ )] manufactured by Kawai Lime Co., Ltd., “Seraph” (alumina) manufactured by Kinsei Matec Co., Ltd., “Yodogawa Mica Z-20” manufactured by Yodogawa Mining Co., Ltd. ) Etc. are available.

<Secondary battery>
The secondary battery of the present invention is not particularly limited as long as it has the separator of the present invention and includes a positive electrode, a negative electrode, a separator, and an electrolytic solution. Other known configurations and structures can be employed. . In the present invention, the secondary battery is preferably a non-aqueous electrolyte secondary battery, more preferably a lithium ion secondary battery.

<Method for producing polyurethane resin aqueous dispersion>
A known method can be used as a method for producing the urethane polymer of the present invention, and is not particularly limited. For example, a polyol, an isocyanate compound and, if necessary, a hydrophilic group-containing compound are added at 30 ° C. to 130 ° C. for 0.5 hour. The urethane prepolymer is allowed to react under the reaction conditions of about 10 hours, and if necessary, it is cooled to 5 ° C. to 45 ° C. to neutralize the contained hydrophilic groups or quaternize with a quaternizing agent. obtain. As the solvent, any organic solvent such as acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, ethyl acetate, butyl acetate can be used. Furthermore, a polyurethane resin aqueous dispersion can be produced by emulsifying and chain extending a urethane prepolymer. As water used for the emulsification, it is preferable to add 100 to 900 parts by weight of water with respect to 100 parts by weight of the urethane polymer.

<Method for producing secondary battery separator>
Although it does not specifically limit as a manufacturing method of the secondary battery separator of this invention, For example, it applies by first apply | coating the slurry containing insulating fine particles and an organic binder on a porous body, and drying. The slurry is produced by mixing the dispersion medium with the above-described insulating fine particles, which are solid components, an organic binder, and optional components. A thickener such as a water-soluble polymer can also be used as a viscosity modifier for slurrying. Specifically, celluloses such as carboxymethylcellulose salt, methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylmethylcellulose; polycarboxylic acid compounds such as polyacrylic acid and polyacrylic acid soda; vinylpyrrolidone such as polyvinylpyrrolidone Compound having structure: One or more selected from polyacrylamide, polyethylene oxide, polyvinyl alcohol, sodium alginate, xanthan gum, carrageenan, guar gum, agar, starch, etc. can be used, among which carboxymethyl cellulose salt is preferred . In the present invention, by using the above components, a slurry in which insulating fine particles are highly dispersed can be obtained regardless of the mixing method and the mixing order. The secondary battery separator of the present invention is obtained using the polyurethane resin aqueous dispersion. Although not particularly limited, a porous body having insulating fine particles and an organic binder that are stable with respect to the non-aqueous electrolyte is preferable. The dispersion medium is not particularly limited as long as the solid content can be uniformly dispersed. Either water or an organic solvent can be used. Examples of organic solvents include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as acetone, ethylmethylketone, diisopropylketone, cyclohexanone, methylcyclohexane, and ethylcyclohexane. Chlorinated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; esters such as ethyl acetate, butyl acetate, γ-butyrolactone and ε-caprolactone; acylonitriles such as acetonitrile and propionitrile; tetrahydrofuran; Ethers such as ethylene glycol diethyl ether: alcohols such as methanol, ethanol, isopropanol, ethylene glycol, ethylene glycol monomethyl ether; N-methyl Amides such as lupyrrolidone and N, N-dimethylformamide are exemplified.

<Method for producing secondary battery>
As a specific manufacturing method of the secondary battery, for example, a laminated body in which the positive electrode and the negative electrode are overlapped via the secondary battery separator of the present invention is obtained, and this is wound or folded according to the battery shape. And then sealing the battery container by injecting an electrolyte into the battery container. When obtaining the said laminated body, it is preferable to heat-press a laminated body. Hot pressing is a method in which heating and pressing are performed simultaneously. The pressing is performed using a roll press machine using a metal roll, an elastic roll or the like, a flat plate press machine, or the like. Examples of the press method include a batch type press and a continuous type roll press, and a continuous type roll press is preferable in terms of enhancing productivity.

<Physical properties>
The blending stability of the aqueous dispersion of the present invention with the thickener according to the method described in the examples is preferably such that no separation is observed, and more preferably no separation is observed.

  The electrolyte solution resistance of the film obtained from the polyurethane resin aqueous dispersion of the present invention is preferably not dissolved in the methods described in the examples, is preferably 50% or less, and more preferably 40% or less.

The strength of the film obtained from the polyurethane resin aqueous dispersion of the present invention before and after immersion in the electrolyte solution is 5 (N / mm ² ) or more and 1 (N / mm ² ) or more, respectively, in the method described in the examples. Preferably, it is 8 (N / mm ² ) or more and 2 (N / mm ² ) or more.

The dynamic viscoelasticity of the film obtained from the polyurethane resin aqueous dispersion of the present invention is preferably 0.5 (10 ⁶ Pa) or more, and 1.0 (10 ⁶ Pa) or more in the method described in the examples. More preferably.

  The adhesion of the film obtained from the polyurethane resin aqueous dispersion of the present invention is preferably 0.17 (N / cm) or more, and 0.15 (N / cm) or more in the method described in the examples. Is more preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

Example 1
Four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen blowing tube is provided with 74.3 parts by weight of polyolefin polyol (A1) (KRASOL LBH-P3000 (manufactured by CRAY VALLEY, polybutadiene polyol)), dimethylol. Add 4.2 parts of propionic acid (Bis-MPA), 21.5 parts by weight of polyisocyanate compound (B-1) (hydrogenated diphenylmethane diisocyanate), 100 parts by weight of methyl ethyl ketone, and react at 75 ° C. for 2 hours. A methyl ethyl ketone solution of the prepolymer was obtained. The free isocyanate group content with respect to the nonvolatile content of this solution was 2.2%. Next, this solution was cooled to 45 ° C. and neutralized by adding 3.2 parts by weight of triethylamine, and then an emulsion reaction was carried out using a homogenizer while gradually adding 186 parts by weight of water. An aqueous solution in which 1.6 parts by weight of diethylenetriamine was dissolved in 27 parts by weight of water was added to the obtained emulsified dispersion and reacted for 1 hour, and then methyl ethyl ketone as a reaction solvent was distilled under reduced pressure to obtain a nonvolatile content (solid An aqueous composition having a concentration of 35% by weight was obtained.

(Examples 2-6, comparative example)
Synthesis was performed in the same manner as in Example 1 except that the composition was changed to the composition shown in Table 1.
The compounds used are shown below.
Polyolefin polyol (A2): Poly ip (manufactured by Idemitsu Kosan Co., Ltd., functional group number 2.3 polyisoprene polyol)
Polyolefin-based polyol (A3): Polytail H (manufactured by Mitsubishi Chemical Corporation, hydrogenated polybutadiene polyol having 2.3 functional groups)
Polyolefin-based polyol (A4): Epol (manufactured by Idemitsu Kosan Co., Ltd., functional group number 2.3 hydrogenated polyisoprene polyol)
Other polyols (A ′): ETERNACOLL UH-100 (manufactured by Ube Industries, polycarbonate polycarbonate)
Polyisocyanate compound (B-2): Isophorone diisocyanate neutralized salt (Li): Lithium hydroxide monohydrate (manufactured by Nacalai Tesque)

(Compatibility with thickener)
Polyurethane resin water dispersion / Carboxymethylcellulose (Dell Daiichi Seiyaku Co., Ltd., Serogen WS-C, thickener) at 20 ° C. for 24 minutes at 20 ° C. with a composite of 100/1 (weight ratio) at 200 rpm for 10 minutes. The state after standing still was visually confirmed and evaluated as follows.
○: Separation is not seen at all ×: Separation is seen

In the following, the electrolytic solution used for evaluation was the following composition.
Immersion solution: Ethylene carbonate / propylene carbonate / dimethyl carbonate / ethyl methyl carbonate / diethyl carbonate = 1/1/1/1/1 (mass ratio) mixed solution

(Electrolytic solution resistance)
Using a polyurethane resin aqueous dispersion, a film was prepared under the following conditions.
Film preparation conditions: 40 ° C. × 15 hours + 80 ° C. × 6 hours + 120 ° C. × 20 minutes Film piece: dry film thickness = 300 μm, weight = 0.2 g
After measuring the weight before immersion of the prepared film, it was immersed in an electrolytic solution at 60 ° C. for 3 days, then returned to room temperature, wiped off the surface immersion liquid, and then measured for weight after immersion. Based on the following formula, the weight increase rate (%) was calculated.
Weight increase rate (%) = (weight after immersion−weight before immersion) / weight before immersion

(Strength before and after immersion in electrolyte)
The film immersed under the above conditions was measured at a tensile speed of 100 mm / min according to JIS-K-6301.

(Dynamic viscoelasticity)
The film prepared as described above was measured using a dynamic viscoelastic device Rheogel-E4000 UBM, temperature increase rate 4 ° C./min).

(Adhesion)
Distilled water was added to adjust the resin solid content to 30%, and then a separator film made of a polyethylene porous film was coated with a bar coater to a dry film thickness of 10 μm. With the coating surface of the resulting coating film fixed to the support, one end of the separator was pulled and peeled in the 180 ° direction at a pulling rate of 100 mm / min, and the adhesion was evaluated.

  As is clear from Table 1, the polyurethane resin aqueous dispersion of the present invention has good blending stability of the slurry, and the resulting coating has resistance to electrolytic solution, strength retention before and after electrolytic solution immersion, dynamic viscoelasticity and Adhesion is good. On the other hand, the comparative example which does not use polyolefin polyol (however, excluding hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in one molecule) (A) is inferior in all of electrolytic solution resistance, dynamic viscoelasticity and adhesion. I understand. Moreover, as a result of evaluating the mixing | blending stability of a slurry using SBR (styrene butadiene rubber), it was x.

  The polyurethane resin aqueous dispersion of the present invention has good blending stability with a thickener, and the resulting film has any resistance to electrolytic solution, strength retention before and after immersion in the electrolyte, dynamic viscoelasticity, and adhesion. Therefore, it can be suitably used for a secondary battery separator. Moreover, it can use suitably also for the secondary battery separator and secondary battery using this.

Claims (4)

A polyurethane resin aqueous dispersion for a secondary battery separator,
The polyurethane resin is a reaction product of at least a polyolefin-based polyol (excluding a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in one molecule) (A) and a polyisocyanate compound (B).
Polyurethane resin water dispersion for secondary battery separator. Said (A) is
The polybutadiene polyol (A1), the polyisoprene polyol (A2), one or more kinds selected from the group consisting of two or more hydrogenated polybutadiene polyols (A3) and hydrogenated polyisoprene polyols (A4) in one molecule. ,
The polyurethane resin aqueous dispersion for secondary battery separators of Claim 1.   A secondary battery separator obtained by using the polyurethane resin aqueous dispersion according to claim 1. A secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolytic solution, wherein the separator is a separator for a secondary battery according to claim 3.