JP7271879B2 - Resin composition, cured product and battery pack - Google Patents

Description

The present invention relates to resin compositions, cured products and battery packs.

Conventionally, various types of batteries have been used as power sources for electronic devices. For example, small-sized, large-capacity sealed batteries are used as power sources for mobile phones and laptop computers, and lithium-ion non-aqueous electrolyte secondary battery packs are widely distributed as such sealed batteries. A typical battery pack has a structure in which battery cells and a printed circuit board are accommodated in a battery case.

In such a battery pack, when the electrolyte leaks from the battery cells, there is a problem that the wiring of the wiring circuit board is corroded and the conduction failure is caused. Therefore, as a solution to the problem of electrolyte leakage, it is being considered to dispose a liquid-absorbing sheet capable of absorbing the electrolyte in the battery pack around the battery cells. For example, Patent Document 1 discloses a battery pack in which battery cells, a wiring circuit board, and a liquid absorbing member are accommodated in a battery case, and the liquid absorbing member is formed on the inner wall of the battery case or the wiring circuit board by a holding member. A battery pack that is loosely fitted in the gap is disclosed.

Further, in Patent Document 2, a liquid-absorbent resin layer obtained by photocuring a monomer composition containing a monofunctional monomer component capable of forming a homopolymer soluble in a non-aqueous solvent and a polyfunctional monomer component is described. Patent Document 3 discloses a liquid absorbing resin obtained by photocuring a monomer composition containing a monofunctional monomer component consisting of a polyethylene glycol acrylate monomer and an amide bond-containing acrylic monomer, and a polyfunctional monomer component. An absorbent sheet having layers is described. In these documents, a monomer composition is coated on a support substrate, and the resulting coating film is irradiated with ultraviolet rays to form an absorbent resin layer, and the absorbent sheet is formed with the support substrate and absorbent. It is composed of a liquid resin layer.

Japanese Patent Application Laid-Open No. 2006-196331 Japanese Unexamined Patent Application Publication No. 2004-311387 JP 2004-355997 A

In recent years, electronic devices have been made smaller and thinner, and along with this, liquid absorbent sheets may be required to be thinner. In order to reduce the thickness of the absorbent sheet, it is conceivable to form the absorbent sheet only from an absorbent resin layer, but processing such an absorbent sheet is difficult and the obtained sheet is fragile. Therefore, there were cases where sufficient liquid absorbency could not be exhibited. In addition, conventional resin compositions have problems such as difficulty in film formation due to the liquid flowing out during coating, and inability to mold an absorbent resin layer having a desired thickness.

Therefore, in order to solve such problems of the prior art, the present inventors have developed a resin composition capable of forming a sheet having excellent liquid absorption and having excellent workability during coating. We proceeded with the study with the aim of providing

As a result of intensive studies to solve the above problems, the present inventors have found that at least one selected from acrylic monomers containing a nitrogen atom and acrylic monomers containing an aromatic ring, an acrylic monomer having an oxyalkylene group , By adding fibrous cellulose with a fiber width of 1000 nm or less to a resin composition containing a polyfunctional monomer and a photopolymerization initiator, and further by setting the viscosity of the resin composition to a predetermined value or more, the liquid absorption is excellent. It has been found that a resin composition capable of forming a thin sheet and having excellent workability during coating can be obtained.
Specifically, the present invention has the following configurations.

[1] at least one selected from acrylic monomers containing a nitrogen atom and acrylic monomers containing an aromatic ring;
an acrylic monomer having an oxyalkylene group,
polyfunctional monomers,
A resin composition containing a photopolymerization initiator and fibrous cellulose having a fiber width of 1000 nm or less,
A resin composition having a viscosity of 100 mPa·s or more at 20°C.
[2] The resin composition according to [1], wherein the fibrous cellulose has an ionic substituent.
[3] The resin composition according to [2], wherein the ionic substituent is an anionic group, and the counter ion of the anionic group is an organic onium ion.
[4] The resin composition according to [2] or [3], wherein the ionic substituent is a phosphoric acid group or a substituent derived from a phosphoric acid group.
[5] The resin composition according to [3], wherein the organic onium ion is an organic ammonium ion.
[6] The resin composition according to any one of [1] to [5], wherein the content of fibrous cellulose is 0.1 to 30% by mass with respect to the total mass of the resin composition.
[7] The resin composition according to any one of [1] to [6], wherein the polyfunctional monomer has a weight average molecular weight of 200 or more and less than 3,000.
[8] A cured product obtained by photocuring the resin composition according to any one of [1] to [7].
[9] The cured product according to [8], which is in the form of a sheet.
[10] The cured product according to [8] or [9], which is for liquid absorption.
[11] The cured product according to any one of [8] to [10], which is for absorbing non-aqueous liquids.
[12] A battery pack comprising a cured product obtained by photocuring the resin composition according to any one of [1] to [7], a battery cell, and a wiring circuit board.

ADVANTAGE OF THE INVENTION According to this invention, the resin composition which can form a sheet|seat excellent in liquid absorbency can be obtained. Furthermore, the resin composition of the present invention is excellent in workability during coating.

FIG. 1 is a graph showing the relationship between the amount of dropped NaOH and electrical conductivity with respect to fiber raw materials having phosphate groups. 2(a) is a photograph showing the appearance of the sheet (cured product) obtained in Example 1, and FIG. 2(b) is a photograph showing the appearance of the sheet (cured product) obtained in Comparative Example 4. is.

The present invention will be described in detail below. Although the constituent elements described below may be described based on representative embodiments and specific examples, the present invention is not limited to such embodiments. In this specification, the numerical range represented by "-" means a range including the numerical values described before and after "-" as lower and upper limits.

As used herein, "(meth)acrylic acid" refers to either or both acrylic acid and methacrylic acid, and "(meth)acrylate" refers to both or either acrylate and methacrylate. Moreover, in this specification, the terms "monomer" and "monomer" are synonymous.

(resin composition)
The present invention provides at least one selected from acrylic monomers containing a nitrogen atom and acrylic monomers containing an aromatic ring, an acrylic monomer having an oxyalkylene group, a polyfunctional monomer, a photopolymerization initiator, and a fiber width of 1000 nm or less. relates to a resin composition containing fibrous cellulose. Here, the viscosity at 20° C. of the resin composition of the present invention is 100 mPa·s or more.

Since the resin composition of the present invention has the above structure, it can form a sheet having excellent liquid absorbency. Here, the liquid absorbency of the sheet formed from the resin composition is determined, for example, by observing the surface state of the sheet after dripping the non-aqueous electrolyte, the defect occurs in the sheet, or the electrolyte does not adhere to the surface of the sheet. It can be judged to be good if there is no residue.

Furthermore, the resin composition of the present invention is excellent in workability during coating. Workability during coating of the resin composition can be judged to be good if a sheet having a desired thickness can be easily formed when forming the sheet. When forming a sheet from the resin composition, an auxiliary tool such as a spacer may be used, but even without the auxiliary tool such as a spacer, the resin composition of the present invention may flow out unintentionally. Easy to process into sheets. This is because the resin composition of the present invention is a composition having an appropriate viscosity, so that it is easy to apply, and as a result, it can be easily processed into a sheet having a desired thickness.

The viscosity at 20° C. of the resin composition of the present invention may be 100 mPa·s or more, preferably 200 mPa·s or more, more preferably 300 mPa·s or more, and 400 mPa·s or more. is more preferred. Also, the viscosity of the resin composition at 20° C. is preferably 13000 mPa·s or less, more preferably 12000 mPa·s or less. The viscosity is measured by allowing the resin composition to stand in an environment of 20° C. for 1 hour or more, and then rotating it at 20° C. at a rotation speed of 20 rpm using a rotary rheometer. As a rheometer, for example, MCR-301 manufactured by Anton Paar can be used. By setting the viscosity of the resin composition within the above range, the coatability of the resin composition can be more effectively improved, and a resin composition that can be easily processed into a sheet can be obtained.

As described above, the resin composition of the present invention is capable of forming a sheet having excellent liquid absorbency, and is excellent in workability during coating. Therefore, for example, it is preferably used for forming an absorbent sheet to be housed in a battery pack. That is, the resin composition of the present invention is preferably a resin composition for forming an absorbent sheet.

Furthermore, a sheet molded from the resin composition of the present invention can be peeled off as a single layer sheet. That is, the sheet obtained from the resin composition of the present invention is a sheet that can maintain its sheet shape without a supporting substrate, and can function as a liquid-absorbent sheet even if it is a single-layer sheet. Further, the sheet molded from the resin composition of the present invention has such a strength that holes or the like do not occur even after absorbing the electrolytic solution. In addition, since the sheet molded from the resin composition of the present invention has rubber-like elasticity, the sheet is prevented from being broken or cracked even when it is peeled off from the substrate as a single-layer sheet. ing. Thus, the sheet molded from the resin composition of the present invention has excellent moldability and strength enough to withstand peeling and the like.

The liquid absorbency of the sheet formed from the resin composition of the present invention is preferably 3.0 or higher, more preferably 4.0 or higher, and further preferably 4.5 or higher. 0.0 or more is particularly preferred. The liquid absorbency of the sheet is calculated by the following formula from the weight of the sheet before and after immersion after immersing a sheet cut into a predetermined size in an electrolytic solution for 2 hours. As the electrolytic solution, 1 mol/L of ethylene carbonate/diethyl carbonate LiPF ₆ is used.
Absorption ratio = (Sheet weight after liquid absorption - Sheet weight before liquid absorption) / (Sheet weight before liquid absorption)

The volume expansion coefficient of the sheet formed from the resin composition of the present invention is preferably 150% or more, more preferably 180% or more, and even more preferably 200% or more. Also, the volume expansion coefficient of the sheet is preferably 800% or less, more preferably 700% or less, and even more preferably 500% or less.
The volume expansion coefficient of the sheet was calculated from the volume of the sheet before and after being immersed in an electrolytic solution (1M LiPF ₆ /ethylene carbonate:diethylene carbonate = 50:50 vol% (manufactured by Kishida Chemical Co., Ltd.)) at room temperature for about 24 hours. This is the value calculated by the formula.
Volume expansion rate (%) = sheet volume after immersion / sheet volume before immersion x 100

The resin composition of the present invention contains 30 to 94% by mass of at least one selected from a monomer containing a nitrogen atom and a monomer containing an aromatic ring, 5 to 69% by mass of an acrylic monomer having an oxyalkylene group, It is also preferable to contain 0.05 to 10% by mass of a polyfunctional monomer, 0.1 to 10% by mass of a photopolymerization initiator, and 0.1 to 30% by mass of fibrous cellulose having a fiber width of 1000 nm or less.

<Acrylic monomer>
The resin composition of the present invention contains at least one selected from a nitrogen atom-containing acrylic monomer and an aromatic ring-containing acrylic monomer, and an oxyalkylene group-containing acrylic monomer.

The content of at least one selected from acrylic monomers containing a nitrogen atom and acrylic monomers containing an aromatic ring is preferably 30% by mass or more, preferably 35% by mass or more, relative to the total mass of the resin composition. and more preferably 40% by mass or more. In addition, the content of at least one selected from acrylic monomers containing a nitrogen atom and acrylic monomers containing an aromatic ring is preferably 95% by mass or less with respect to the total mass of the resin composition, and 94% by mass. % or less.

Above all, the resin composition of the present invention preferably contains a nitrogen atom-containing acrylic monomer, and in this case, the content of the nitrogen atom-containing acrylic monomer is preferably within the above range. By including the acrylic monomer containing a nitrogen atom in the resin composition, the liquid absorbency of the sheet formed from the resin composition can be more effectively enhanced.

The content of the acrylic monomer having an oxyalkylene group is preferably 5% by mass or more, more preferably 10% by mass or more, and 15% by mass or more, relative to the total mass of the resin composition. is more preferred. Also, the content of the acrylic monomer having an oxyalkylene group is preferably 70% by mass or less, more preferably 69% by mass or less, relative to the total mass of the resin composition. By setting the content of the acrylic monomer having an oxyalkylene group within the above range, the flexibility of the sheet formed from the resin composition can be increased, and the stiffness of the sheet can be increased.

<<Acrylic Monomer Containing Nitrogen Atom>>
A nitrogen atom-containing acrylic monomer is an acrylic monomer containing a nitrogen atom in one molecule. Nitrogen atom-containing acrylic monomers include, for example, dimethylacrylamide, diethylacrylamide, acryloylmorpholine, hydroxyethylacrylamide, methylolacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, dimethylaminoethylacrylamide, and dimethylaminoethyl (meth)acrylate. be able to. Among them, the nitrogen atom-containing acrylic monomer is more preferably at least one selected from dimethylacrylamide, diethylacrylamide and acryloylmorpholine, and particularly preferably acryloylmorpholine.

The weight average molecular weight of the acrylic monomer containing nitrogen atoms is preferably 80-1000. In addition, a commercial item can be used as an acrylic monomer containing a nitrogen atom. Examples of commercially available products include acryloylmorpholine manufactured by KJ Chemicals.

<<Acrylic Monomer Containing Aromatic Ring>>
An acrylic monomer containing an aromatic ring is an acrylic monomer containing an aromatic ring in one molecule. Examples of acrylic monomers containing an aromatic ring include phenoxyethyl (meth)acrylate, phenoxy-polyethylene glycol (meth)acrylate, nonylphenol EO adduct (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl-phthalate, neopentylglycol benzoate, dicyclopentanyl acrylate, benzyl (meth)acrylate and the like. Among them, benzyl (meth)acrylate is preferably used as an acrylic monomer containing an aromatic ring.

The weight average molecular weight of the aromatic ring-containing acrylic monomer is preferably 150-1000. In addition, a commercial item can be used as an acrylic monomer containing an aromatic ring. Examples of commercially available products include Viscoat #160 manufactured by Osaka Organic Chemical Industry Co., Ltd., and the like.

<<acrylic monomer having an oxyalkylene group>>
An acrylic monomer having an oxyalkylene group is an acrylic monomer containing an oxyalkylene group in one molecule. The number of carbon atoms constituting one oxyalkylene group is preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less, and even more preferably 2 or more and 4 or less. Examples of acrylic monomers having an oxyalkylene group include methoxypolyethyleneglycol acrylate, ethoxypolyethyleneglycol acrylate, phenoxypolyethyleneglycol acrylate, methoxypolypropyleneglycol acrylate, ethoxypolypropyleneglycol acrylate, and phenoxypolypropyleneglycol acrylate.

Among them, it is particularly preferable that the number of carbon atoms constituting the oxyalkylene group is 2. That is, the acrylic monomer having an oxyalkylene group is preferably an acrylic monomer having an ethylene glycol group. The ethylene glycol group in the acrylic monomer having an ethylene glycol group is --CH ₂ CH ₂ O--. The acrylic monomer having an ethylene glycol group may have one ethylene glycol group in one molecule, or may have two or more. Among them, the number of ethylene glycol groups in one molecule of an acrylic monomer having an ethylene glycol group is preferably 1 to 50, more preferably 1 to 40, even more preferably 1 to 30, and 1 to 25 is more preferred, and 2-10 is particularly preferred.

The acrylic monomer having an ethylene glycol group is preferably alkoxypolyethylene glycol acrylate. The number of carbon atoms in the alkoxy group of the alkoxypolyethylene glycol acrylate is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less. Among them, the alkoxypolyethylene glycol acrylate is preferably methoxypolyethyleneglycol acrylate, ethoxypolyethyleneglycol acrylate, and phenoxypolyethyleneglycol acrylate, and more preferably at least one selected from methoxypolyethyleneglycol and phenoxypolyethyleneglycol.

The weight average molecular weight of the acrylic monomer having an oxyalkylene group is preferably 100-1500, more preferably 120-1200. A commercially available product can be used as the acrylic monomer having an oxyalkylene group. Examples of commercially available products include P-200A and 130A manufactured by Kyoeisha Chemical Co., Ltd.

<<Other acrylic monomers>>
The resin composition of the present invention may further contain other acrylic monomers in addition to the acrylic monomers described above. Other acrylic monomers include, for example, alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, hydroxyl group-containing acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate, acrylic acid, ω- Examples include acid group-containing acrylates such as carboxy-polycaprolactone monoacrylate. The content of other acrylic monomers is preferably 50% by mass or less with respect to the total mass of acrylic monomers contained in the resin composition.

<Polyfunctional monomer>
The resin composition of the present invention preferably further contains a polyfunctional monomer. Here, the polyfunctional monomer is a monomer having two or more reactive double bonds in its molecule.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, di 1,4-butylene glycol (meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol diacrylate, polybutylene glycol di(meth)acrylate, di(meth)acrylic acid Neopentyl glycol, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, diacrylate of bisphenol A diglycidyl ether, trimethylol tri(meth)acrylate (Meth)acrylic acid esters of polyhydric alcohols such as propane, pentaerythritol tri(meth)acrylate and pentaerythritol tetra(meth)acrylate, and vinyl methacrylate. Among them, 1,6-hexanediol diacrylate, polyethylene glycol di(meth)acrylate, and the like are preferably used as polyfunctional monomers.

The polyfunctional monomer has two or more reactive double bonds. Among them, the polyfunctional monomer preferably has two or more and five or less reactive double bonds, and preferably two or more and four or less. It is more preferable to have In addition, as a polyfunctional monomer, you may use individually by 1 type or may use 2 or more types together.

A commercial item can be used as a polyfunctional monomer. Examples of commercially available products include A-HD-N manufactured by Shin-Nakamura Chemical Co., Ltd. and 14EG-A manufactured by Kyoeisha Chemical Co., Ltd.

The content of the polyfunctional monomer is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, relative to the total mass of the resin composition. Moreover, the content of the polyfunctional monomer is preferably 10% by mass or less, more preferably 5% by mass or less, relative to the total mass of the resin composition. By setting the content of the polyfunctional monomer within the above range, the strength of the sheet formed from the resin composition can be increased, and the liquid absorbency can be enhanced more effectively.

The weight average molecular weight of the polyfunctional monomer is preferably 200 or more and less than 3000, more preferably 200 or more and less than 1500, and even more preferably 200 or more and less than 1000. Here, the weight average molecular weight of the polyfunctional monomer can be measured, for example, using gel permeation chromatography (GPC) as follows.
Solvent: tetrahydrofuran Column: Shodex KF801, KF803L, KF806L, (three columns manufactured by Showa Denko Co., Ltd. are connected and used)
Column temperature: 40°C
Sample concentration: 0.5% by mass
Detector: RI-2031plus (manufactured by JASCO)
Pump: RI-2080plus (manufactured by JASCO)
Flow rate (flow rate): 0.8 ml/min
Injection volume: 10 μl
Calibration curve: Standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko KK) Mw = 1320 to 2500000 A calibration curve using 10 samples is used.

<Photoinitiator>
The resin composition of the present invention contains a photopolymerization initiator. Therefore, it can be said that the resin composition of the present invention is a photocurable resin composition. The photopolymerization initiator is preferably, for example, a polymerization initiator that reacts with the above-described monomer components by ultraviolet rays.

Examples of photopolymerization initiators include acetophenone-based initiators, benzoin ether-based initiators, benzophenone-based initiators, hydroxyalkylphenone-based initiators, thioxanthone-based initiators, and amine-based initiators.
Specific examples of acetophenone-based initiators include diethoxyacetophenone and benzyldimethylketal.
Specific examples of benzoin ether-based initiators include benzoin and benzoin methyl ether.
Specific examples of benzophenone-based initiators include benzophenone and methyl o-benzoylbenzoate.
Specific examples of hydroxyalkylphenone-based initiators include 1-hydroxy-cyclohexyl-phenyl-ketone and the like.
Specific examples of thioxanthone-based initiators include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone.
Specific examples of amine-based initiators include triethanolamine and ethyl 4-dimethylbenzoate.
In addition, as a photoinitiator, you may use individually by 1 type or may use 2 or more types together.

A commercial item can be used as a photoinitiator. Examples of commercially available products include Irgacure 1173, Irgacure 184, Irgacure TPO, Irgacure 819, Irgacure 127, and Irgacure 651 manufactured by BASF.

The content of the photopolymerization initiator is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, relative to the total mass of the resin composition. Moreover, the content of the photopolymerization initiator is preferably 10% by mass or less, more preferably 5% by mass or less, relative to the total mass of the resin composition.

<Fine fibrous cellulose>
The resin composition of the present invention contains fibrous cellulose with a fiber width of 1000 nm or less. In this specification, fibrous cellulose having a fiber width of 1000 nm or less is also referred to as fine fibrous cellulose. The fiber width of fibrous cellulose can be measured, for example, by electron microscope observation.

The average fiber width of fibrous cellulose is 1000 nm or less. The average fiber width of the fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, even more preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Especially preferred. By setting the average fiber width of the fibrous cellulose to 2 nm or more, the dissolution of cellulose molecules in water is suppressed, and the effect of improving the strength, rigidity, and dimensional stability of the fibrous cellulose can be more readily exhibited. can. The fibrous cellulose is single fibrous cellulose.

The average fiber width of fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fibrous cellulose with a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a hydrophilized carbon film-coated grid to form a sample for TEM observation. and SEM images of surfaces cast on glass may be observed if they contain wide fibers. Then, an electron microscope image is observed at a magnification of 1,000, 5,000, 10,000, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification are adjusted so as to satisfy the following conditions.
(1) A single straight line X is drawn at an arbitrary point in the observed image, and 20 or more fibers intersect the straight line X.
(2) Draw a straight line Y that intersects the straight line perpendicularly in the same image, and 20 or more fibers intersect the straight line Y.
Widths of fibers intersecting the straight lines X and Y are visually read from the observation image satisfying the above conditions. In this way, at least three sets of observed images of surface portions that do not overlap each other are obtained. Then, for each image, the width of the fiber that crosses straight line X and straight line Y is read. This gives at least 20 x 2 x 3 = 120 fiber width readings. Then, the average value of the read fiber widths is taken as the average fiber width of the fibrous cellulose.

Although the fiber length of the fibrous cellulose is not particularly limited, it is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and further preferably 0.1 μm or more and 600 μm or less. preferable. By setting the fiber length within the above range, destruction of the crystalline regions of the fibrous cellulose can be suppressed. Moreover, it becomes possible to make the viscosity of a resin composition into an appropriate range. The fiber length of fibrous cellulose can be determined by image analysis using, for example, TEM, SEM, and AFM.

Preferably, the fibrous cellulose has a Type I crystal structure. Here, the fact that the fibrous cellulose has a type I crystal structure can be identified in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ=1.5418 Å) monochromated with graphite. Specifically, it can be identified by having typical peaks at two positions near 2θ=14° or more and 17° or less and 2θ=22° or more and 23° or less.

The proportion of the I-type crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, even more preferably 50% or more. As a result, even better performance can be expected in terms of heat resistance and low coefficient of linear thermal expansion. The degree of crystallinity is determined by a conventional method from the pattern of X-ray diffraction profiles (Seagal et al., Textile Research Journal, vol. 29, p. 786, 1959).

Although the axial ratio (fiber length/fiber width) of fibrous cellulose is not particularly limited, it is preferably 20 or more and 10,000 or less, and more preferably 50 or more and 1,000 or less. By setting the axial ratio to the above lower limit or more, it is easy to form a cured product (sheet) of the resin composition, and it is easy to obtain a sufficient viscosity when making the resin composition. Moreover, by making the axial ratio equal to or less than the above upper limit value, the handleability of the resin composition can be enhanced.

The fibrous cellulose in this embodiment has, for example, both a crystalline region and an amorphous region. In particular, fine fibrous cellulose having both a crystalline region and an amorphous region and having a high axial ratio is realized by the method for producing fine fibrous cellulose described later.

The fibrous cellulose preferably has an ionic substituent. The ionic substituents can include, for example, either one or both of an anionic group and a cationic group. Among them, it is particularly preferable to have an anionic group as an ionic substituent. When the ionic substituent is an anionic group, its counter ion (cation) is preferably a monovalent or higher cation composed of an organic substance, more preferably an organic onium ion.

The anionic group as an ionic substituent includes, for example, a phosphate group or a substituent derived from a phosphate group (sometimes simply referred to as a phosphate group), a carboxyl group or a substituent derived from a carboxyl group (simply referred to as a carboxyl group). and a sulfone group or a substituent derived from a sulfone group (sometimes referred to simply as a sulfone group), and at least one selected from a phosphate group and a carboxyl group. A seed is more preferred, and a phosphate group is particularly preferred.

A phosphate group is a divalent functional group, for example, phosphoric acid with the hydroxyl group removed. Specifically, it is a group represented by —PO ₃ H ₂ . Substituents derived from a phosphate group include substituents such as salts of phosphate groups and phosphate ester groups. A substituent derived from a phosphoric acid group may be contained in the fibrous cellulose as a condensed group (for example, a pyrophosphate group) of the phosphoric acid group.
A phosphoric acid group or a substituent derived from a phosphoric acid group is, for example, a substituent represented by the following formula (1).

In formula (1), a, b and n are natural numbers (where a=b×m). a ^of α ¹ , α ² , ^. Note that all of αn and α′ may be O ^{2 −} . Each R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated-branched hydrocarbon group A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof.

Examples of the saturated straight-chain hydrocarbon group include, but are not limited to, methyl group, ethyl group, n-propyl group, n-butyl group, and the like. The saturated-branched hydrocarbon group includes i-propyl group, t-butyl group and the like, but is not particularly limited. The saturated cyclic hydrocarbon group includes, but is not particularly limited to, a cyclopentyl group, a cyclohexyl group, and the like. The unsaturated straight-chain hydrocarbon group includes, but is not particularly limited to, a vinyl group, an allyl group, and the like. The unsaturated-branched hydrocarbon group includes i-propenyl group, 3-butenyl group and the like, but is not particularly limited. The unsaturated-cyclic hydrocarbon group includes, but is not limited to, a cyclopentenyl group, a cyclohexenyl group, and the like. The aromatic group includes, but is not particularly limited to, a phenyl group, a naphthyl group, or the like.

In addition, as the derivative group for R, at least one functional group such as a carboxyl group, a hydroxyl group, or an amino group is added or substituted with respect to the main chain or side chain of the various hydrocarbon groups described above. Examples include, but are not limited to, groups. Although the number of carbon atoms constituting the main chain of R is not particularly limited, it is preferably 20 or less, more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R within the above range, the molecular weight of the phosphate group can be set within an appropriate range, facilitating penetration into the fiber raw material and increasing the yield of fine cellulose fibers. can also

β ^b+ is a monovalent or higher cation composed of an organic substance or an inorganic substance. β ^b+ is a counterion of a phosphate group or a substituent derived from a phosphate group, and such a counterion is preferably a monovalent or higher cation composed of an organic substance, more preferably an organic onium ion. . The organic onium ion preferably has a hydrophobic group, and preferably satisfies at least one condition selected from the following (a) and (b).
(a) contains a hydrocarbon group having 3 or more carbon atoms;
(b) The total number of carbon atoms is 10 or more.

The hydrocarbon group having 3 or more carbon atoms is preferably an alkyl group having 3 or more carbon atoms or an alkylene group having 3 or more carbon atoms, and an alkyl group having 4 or more carbon atoms or an alkylene group having 4 or more carbon atoms more preferably a group. The total number of carbon atoms in the organic onium ion is preferably 10 or more, more preferably 12 or more, and even more preferably 14 or more.

The organic onium ion is preferably an organic onium ion represented by the following general formula (A).

In general formula (A) above, M is a nitrogen atom or a phosphorus atom, and R ₁ to R ₄ each independently represent a hydrogen atom or an organic group. However, at least one of R ₁ to R ₄ is an organic group having 3 or more carbon atoms, or the total number of carbon atoms of R ₁ to R ₄ is 10 or more.
Among them, M is preferably a nitrogen atom. That is, the organic onium ion is preferably an organic ammonium ion.

Examples of such organic onium ions include tetrabutylammonium ion, lauryltrimethylammonium, cetyltrimethylammonium, stearyltrimethylammonium, octyldimethylethylammonium, lauryldimethylethylammonium, didecyldimethylammonium, lauryldimethylbenzylammonium, and tributylbenzyl. ammonium, methyltri-n-octylammonium, hexylammonium, n-octylammonium, dodecylammonium, tetradecylammonium, hexadecylammonium, stearylammonium, N,N-dimethyldodecylammonium, N,N-dimethyltetradecylammonium, N, N-dimethylhexadecylammonium, N,N-dimethyl-n-octadecylammonium, dihexylammonium, di(2-ethylhexyl)ammonium, di-n-octylammonium, didecylammonium, didodecylammonium, didecylmethylammonium, N, N-didodecylmethylammonium, polyoxyethylenedodecylammonium, alkyldimethylbenzylammonium, di-n-alkyldimethylammonium, behenyltrimethylammonium, tetraphenylphosphonium, tetraoctylphosphonium, acetonyltriphenylphosphonium, allyltriphenylphosphonium, amyl triphenylphosphonium, benzyltriphenylphosphonium, ethyltriphenylphosphonium, diphenylpropylphosphonium, triphenylphosphonium, tricyclohexylphosphonium, tri-n-octylphosphonium and the like.

The molecular weight of the organic onium ion is preferably 2000 or less, more preferably 1800 or less. By setting the molecular weight of the organic onium ion within the above range, the handleability of the fine fibrous cellulose can be enhanced.

The amount of phosphoric acid groups introduced into fibrous cellulose is, for example, preferably 0.10 mmol/g or more, more preferably 0.20 mmol/g or more, more preferably 0.50 mmol/g per 1 g (mass) of fibrous cellulose. g or more, and particularly preferably 1.00 mmol/g or more. In addition, the amount of phosphate groups introduced into fibrous cellulose is preferably 5.20 mmol/g or less, more preferably 3.65 mmol/g or less per 1 g (mass) of fibrous cellulose, for example. It is more preferably 00 mmol/g or less. By setting the amount of the phosphate group to be introduced within the above range, the fiber raw material can be easily made finer, and the stability of the fibrous cellulose can be enhanced. Also, by setting the amount of the phosphoric acid group to be introduced within the above range, the sheet containing fibrous cellulose can exhibit good properties.
Here, the denominator in units of mmol/g indicates the mass of fibrous cellulose when the counter ion of the phosphate group is hydrogen ion (H ⁺ ).

The amount of phosphate groups introduced into the fibrous cellulose can be measured, for example, by conductivity titration. In the measurement by the conductivity titration method, the introduced amount is measured by determining the change in conductivity while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing the fibrous cellulose.

FIG. 1 is a graph showing the relationship between the amount of NaOH added to fibrous cellulose having a phosphate group and electrical conductivity. The amount of phosphate groups introduced into fibrous cellulose is measured, for example, as follows. First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. In addition, before the treatment with the strongly acidic ion exchange resin, a defibration treatment similar to the fibrillation treatment step described below may be performed on the object to be measured, if necessary. Next, change in electrical conductivity is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in FIG. As shown in FIG. 1, the electrical conductivity drops sharply at first (hereinafter referred to as "first region"). After that, the conductivity starts to rise slightly (hereinafter referred to as "second region"). After that, the increment of conductivity increases (hereinafter referred to as "third region"). The boundary point between the second region and the third region is defined as the point where the second derivative of the conductivity, that is, the amount of change in the increment (slope) of the conductivity is maximized. Thus, three regions appear in the titration curve. Of these, the amount of alkali required in the first region is equal to the amount of strong acid groups in the slurry used for titration, and the amount of alkali required in the second region is the amount of weak acid groups in the slurry used for titration. be equal. When the phosphate groups condense, the weakly acidic groups are apparently lost, and the amount of alkali required for the second region becomes smaller than the amount of alkali required for the first region. On the other hand, the amount of strongly acidic groups coincides with the amount of phosphorus atoms regardless of the presence or absence of condensation. Therefore, the amount of phosphate groups introduced (or the amount of phosphate groups) or the amount of substituents introduced (or the amount of substituents) means the amount of strongly acidic groups. Therefore, the value obtained by dividing the alkali amount (mmol) required in the first region of the titration curve obtained above by the solid content (g) in the slurry to be titrated is the amount of phosphate group introduced (mmol/ g).

The content of fine fibrous cellulose contained in the resin composition is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, relative to the total mass of the resin composition. , more preferably 0.5% by mass or more. In addition, the content of fine fibrous cellulose is preferably 30% by mass or less, more preferably 20% by mass or less, and 10% by mass or less with respect to the total mass of the resin composition. More preferred.

<<Method for producing fine fibrous cellulose>>
In the following, fine fibrous cellulose having an anionic group, and among fine fibrous cellulose having an organic onium ion as a counterion, particularly fine fibrous cellulose having a phosphate group or a substituent derived from a phosphate group An example of a method for producing fine fibrous cellulose having organic onium ions as counter ions will be described. Below, an example of a manufacturing process is shown in which an alkali treatment process, a fibrillation treatment process, a concentration process, and an organic onium addition process are provided in order after obtaining phosphorylated cellulose fibers in the phosphate group introduction process.

<<Textile raw material>>
Microfibrous cellulose is produced from fibrous raw materials containing cellulose. The fibrous raw material containing cellulose is not particularly limited, but pulp is preferably used because it is readily available and inexpensive. Pulp includes, for example, wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include, but are not limited to, hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP). ) and chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemigroundwood pulp (CGP), groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP) A mechanical pulp etc. are mentioned. Non-wood pulps include, but are not limited to, cotton-based pulps such as cotton linters and cotton lints, and non-wood-based pulps such as hemp, straw, and bagasse. Examples of deinked pulp include, but are not limited to, deinked pulp made from waste paper. The pulp of this embodiment may be used alone or in combination of two or more.
Among the above pulps, wood pulp and deinked pulp are preferred, for example, from the viewpoint of availability. In addition, among wood pulps, the cellulose ratio is high and the yield of fine fibrous cellulose at the time of defibration is high, and the decomposition of cellulose in the pulp is small, and fine fibrous cellulose of long fibers with a large axial ratio can be obtained. From the point of view, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are more preferable.

As the fiber raw material containing cellulose, for example, cellulose contained in sea squirts and bacterial cellulose produced by acetic acid bacteria can be used. Fibers formed by straight-chain nitrogen-containing polysaccharide polymers such as chitin and chitosan can also be used instead of fiber raw materials containing cellulose.

<<Phosphate group introduction step>>
In the step of introducing a phosphate group, at least one compound selected from compounds capable of introducing a phosphate group (hereinafter also referred to as "compound A") is added to cellulose by reacting with a hydroxyl group possessed by a fiber raw material containing cellulose. It is a step of acting on a fiber raw material containing. Through this step, a phosphate group-introduced fiber is obtained.

In the phosphate group-introducing step, the reaction between the fiber material containing cellulose and compound A may be performed in the presence of at least one selected from urea and derivatives thereof (hereinafter also referred to as "compound B"). On the other hand, the reaction between the cellulose-containing fiber raw material and the compound A may be carried out in the absence of the compound B.

An example of the method of allowing the compound A to act on the fiber raw material in the presence of the compound B includes a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state, or a slurry state. Among these, it is preferable to use a fiber raw material in a dry state or a wet state, and it is particularly preferable to use a fiber raw material in a dry state, because the uniformity of the reaction is high. Although the form of the fiber material is not particularly limited, it is preferably in the form of cotton or a thin sheet, for example. The compound A and the compound B can be added to the fiber raw material in the form of a powder, a solution dissolved in a solvent, or a melted state by heating to a melting point or higher. Among these, it is preferable to add in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution, since the uniformity of the reaction is high. Moreover, the compound A and the compound B may be added simultaneously to the fiber raw material, may be added separately, or may be added as a mixture. The method of adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in solution, the fiber raw material may be immersed in the solution to absorb the liquid and then taken out, or the fiber raw material may be taken out. The solution may be added dropwise to the Further, the necessary amount of compound A and compound B may be added to the fiber raw material, or after adding excessive amounts of compound A and compound B to the fiber raw material, the excess compound A and compound B are removed by pressing or filtering. may be removed.

Examples of the compound A used in this embodiment include phosphoric acid or its salts, dehydrated condensed phosphoric acid or its salts, phosphoric anhydride (phosphorus pentoxide) and the like, but are not particularly limited. Phosphoric acid of various purities can be used, for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. Dehydration-condensed phosphoric acid is obtained by condensing two or more molecules of phosphoric acid by dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Phosphates and dehydrated condensed phosphates include lithium salts, sodium salts, potassium salts and ammonium salts of phosphoric acid or dehydrated condensed phosphates, and these can have various degrees of neutralization. Among these, the efficiency of introducing a phosphate group is high, the fibrillation efficiency is easily improved in the fibrillation step described later, the cost is low, and it is easy to apply industrially. Sodium salt, potassium salt of phosphate, or ammonium salt of phosphate are preferred, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate are more preferred.

The amount of compound A added to the fiber raw material is not particularly limited. For example, when the amount of compound A added is converted to the phosphorus atomic weight, the amount of phosphorus atoms added to the fiber raw material (absolute dry mass) is 0.5% by mass or more. It is preferably 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and even more preferably 2% by mass or more and 30% by mass or less. By setting the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by setting the amount of phosphorus atoms added to the fiber raw material to be equal to or less than the above upper limit, it is possible to balance the effect of improving the yield and the cost.

Compound B used in this embodiment is at least one selected from urea and derivatives thereof as described above. Compound B includes, for example, urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea.
From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. From the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

The amount of compound B added to the fiber raw material (absolute dry mass) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, More preferably, it is 100% by mass or more and 350% by mass or less.

In the reaction between the fiber raw material containing cellulose and compound A, in addition to compound B, for example, amides or amines may be included in the reaction system. Examples of amides include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine and hexamethylenediamine. Among these, triethylamine in particular is known to work as a good reaction catalyst.

In the phosphate group-introducing step, it is preferable to heat-treat the fiber raw material after adding or mixing the compound A or the like to the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which the phosphate group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50° C. or higher and 300° C. or lower, more preferably 100° C. or higher and 250° C. or lower, and even more preferably 130° C. or higher and 200° C. or lower. In addition, for the heat treatment, equipment having various heat media can be used. A drying device, a vacuum drying device, an infrared heating device, a far infrared heating device, or a microwave heating device can be used.

In the heat treatment according to the present embodiment, for example, the compound A is added to a thin sheet-like fiber raw material by a method such as impregnation, and then heated, or the fiber raw material and the compound A are heated while kneading or stirring with a kneader or the like. method can be adopted. This makes it possible to suppress concentration unevenness of the compound A in the fiber raw material and to more uniformly introduce phosphate groups to the surface of the cellulose fibers contained in the fiber raw material. This is because when water molecules move to the surface of the fiber material during drying, the dissolved compound A is attracted to the water molecules by surface tension and similarly moves to the surface of the fiber material (that is, the concentration unevenness of the compound A is It is thought that this is due to the fact that it is possible to suppress the occurrence of

In addition, the heating device used for the heat treatment always removes the moisture retained by the slurry and the moisture generated due to the dehydration condensation (phosphorylation) reaction between the compound A and the hydroxyl groups contained in the cellulose etc. in the fiber raw material. It is preferable that the device can be discharged to the outside of the device system. As such a heating device, for example, an air-blowing oven can be used. By constantly draining the water in the device system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of phosphorylation, and to suppress the acid hydrolysis of the sugar chains in the fiber. can. Therefore, it is possible to obtain fine fibrous cellulose having a high axial ratio.

The heat treatment time is, for example, preferably 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and 10 seconds or more and 800 seconds or less, after water is substantially removed from the fiber raw material. is more preferable. In the present embodiment, the introduction amount of the phosphate group can be set within a preferable range by setting the heating temperature and the heating time within appropriate ranges.

The step of introducing a phosphate group may be performed at least once, but may be performed repeatedly two or more times. By performing the phosphate group-introducing step two or more times, many phosphate groups can be introduced into the fiber raw material. In the present embodiment, one example of a preferred aspect is the case where the phosphate group introduction step is performed twice.

<<Washing process>>
In the method for producing fine fibrous cellulose according to the present embodiment, the phosphate group-introduced fibers can be washed if necessary. The washing step is performed by washing the phosphate group-introduced fiber with, for example, water or an organic solvent. Moreover, the washing process may be performed after each process described later, and the number of times of washing performed in each washing process is not particularly limited.

<<Alkali treatment process>>
When producing fine fibrous cellulose, the fiber raw material may be subjected to alkali treatment between the step of introducing phosphate groups and the later-described fibrillation treatment step. The method of alkali treatment is not particularly limited, but includes, for example, a method of immersing the phosphate group-introduced fiber in an alkali solution.

The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In the present embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkaline compound because of its high versatility. Moreover, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably water or a polar solvent including a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent including at least water. As the alkaline solution, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferable because of its high versatility.

Although the temperature of the alkaline solution in the alkaline treatment step is not particularly limited, it is preferably 5° C. or higher and 80° C. or lower, more preferably 10° C. or higher and 60° C. or lower. The immersion time of the phosphate group-introduced fiber in the alkali solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, more preferably 10 minutes or more and 20 minutes or less. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but for example, it is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass or less relative to the absolute dry mass of the phosphate group-introduced fiber. is more preferable.

In order to reduce the amount of alkaline solution used in the alkali treatment step, the phosphate group-introduced fiber may be washed with water or an organic solvent after the phosphate group-introducing step and before the alkali treatment step. After the alkali treatment step and before the fibrillation treatment step, it is preferable to wash the alkali-treated phosphate group-introduced fibers with water or an organic solvent from the viewpoint of improving handleability.

<<Acid treatment process>>
When producing fine fibrous cellulose, the fiber raw material may be subjected to an acid treatment between the step of introducing phosphate groups and the defibration treatment step described later. For example, the step of introducing a phosphate group, the acid treatment, the alkali treatment and the fibrillation treatment may be performed in this order.

The acid treatment method is not particularly limited, but includes, for example, a method of immersing the fiber raw material in an acidic liquid containing an acid. Although the concentration of the acid liquid used is not particularly limited, it is preferably 10% by mass or less, more preferably 5% by mass or less. Moreover, the pH of the acidic liquid to be used is not particularly limited. Examples of acids contained in the acid solution include inorganic acids, sulfonic acids, and carboxylic acids. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid and boric acid. Examples of sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid and the like. Carboxylic acids include, for example, formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, and tartaric acid. Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

The temperature of the acid solution in the acid treatment is not particularly limited. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more and 120 minutes or less, more preferably 10 minutes or more and 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited. is more preferred.

<< defibration processing >>
Fine fibrous cellulose can be obtained by defibrating the phosphate group-introduced fibers obtained through the above steps in the fibrillation treatment step. In the defibration treatment process, for example, a fibrillation treatment device can be used. The fibrillation treatment device is not particularly limited, but for example, a high-speed fibrillator, a grinder (stone mill type pulverizer), a high pressure homogenizer, an ultra-high pressure homogenizer, a high pressure impact type pulverizer, a ball mill, a bead mill, a disk refiner, a conical refiner, and a biaxial refiner. A kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, a beater, or the like can be used. Among the above defibration equipment, it is more preferable to use a high-speed fibrillation machine, a high-pressure homogenizer, and an ultrahigh-pressure homogenizer, which are less affected by the grinding media and less likely to cause contamination.

In the fibrillation treatment step, for example, the phosphate group-introduced fibers are preferably diluted with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from organic solvents such as water and polar organic solvents can be used. The polar organic solvent is not particularly limited, but alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents and the like are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol and glycerin. Ketones include acetone, methyl ethyl ketone (MEK), and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether and the like. Examples of esters include ethyl acetate and butyl acetate. Aprotic polar solvents include dimethylsulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

The solid content concentration of the fine fibrous cellulose at the defibration treatment can be appropriately set. In addition, the slurry obtained by dispersing the phosphate group-introduced fiber in the dispersion medium may contain solids other than the phosphate group-introduced fiber, such as urea having hydrogen bonding properties.

<<Concentration process>>
The concentration step is a step of adding a flocculant containing a polyvalent metal salt to a dispersion containing fine fibrous cellulose to obtain a concentrate of fine fibrous cellulose.

Examples of polyvalent metal salts include aluminum sulfate (aluminum sulfate), polyaluminum chloride, calcium chloride, aluminum chloride, magnesium chloride, calcium sulfate, and magnesium sulfate. Among them, it is preferable to use aluminum sulfate as the flocculant.

In the concentration step, a fine fibrous cellulose concentrate containing a flocculant is obtained. The content of the flocculant in the fine fibrous cellulose concentrate is preferably 0.5 to 300 parts by mass, more preferably 1.0 to 50 parts by mass with respect to 100 parts by mass of the fine fibrous cellulose. preferable.

<<Recovery process>>
The recovery step is a step of recovering the concentrate by, for example, filtration, washing and drying. The recovery method is not particularly limited, and a known method may be used. For example, filters such as filter paper, non-woven fabric, and membrane filters may be used for filtration, or natural filtration, vacuum filtration, pressure filtration, centrifugation, and the like may be used. The cleaning is performed using a cleaning liquid such as water or an organic solvent, and the cleaning liquid may be heated to room temperature or about 30 to 70°C. Drying may be performed by drying under reduced pressure, drying by heating, or the like. The above washing and drying may or may not be performed, and each may be performed repeatedly, and the order is not limited.

The solid content concentration of the fine fibrous cellulose concentrate obtained through such steps is preferably 10% by mass or more, more preferably 15% by mass or more. The upper limit of the solid content concentration of the fine fibrous cellulose concentrate is not particularly limited, and may be 100% by mass.

<<Organic onium addition step>>
In the organic onium addition step, organic onium ions or compounds that form organic onium ions upon neutralization are added. At this time, the organic onium ions are preferably added as a solution containing the organic onium ions, more preferably as an aqueous solution containing the organic onium ions.

An aqueous solution containing organic onium ions usually contains organic onium ions and counter ions (anions). When preparing an aqueous solution of organic onium ions, if the organic onium ions and the corresponding counterions have already formed a salt, they may be dissolved in water as they are. Also, organic onium ions, such as dodecylamine, may be produced only after being neutralized with an acid. That is, organic onium ions may be obtained by reacting an acid with a compound that forms an organic onium ion upon neutralization. In this case, acids used for neutralization include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as lactic acid, acetic acid, formic acid and oxalic acid.

The organic onium addition step may be provided when mixing with other monomer components in the production step of the resin composition. That is, the fine fibrous cellulose and the organic onium may be mixed in the manufacturing process of the resin composition.

<Optional component>
The resin composition of the present invention may contain optional components other than the above-described monomer components, fine fibrous cellulose, and organic onium ions. Examples of optional components include flame retardants, surfactants, organic Ions, coupling agents, inorganic stratiform compounds, inorganic compounds, leveling agents, preservatives, antifoaming agents, organic particles, lubricants, antistatic agents, UV protection agents, dyes, pigments, stabilizers, magnetic powders, orientation promoters agents, plasticizers, dispersants, cross-linking agents, and the like.

The water content in the resin composition is preferably less than 10% by mass, more preferably 5% by mass or less, even more preferably 1% by mass or less, and 0% by mass. good too. The content of the organic solvent in the resin composition is preferably less than 10% by mass, more preferably 5% by mass or less, further preferably 1% by mass or less, and 0% by mass. may

(Method for producing resin composition)
A method for producing a resin composition includes at least one selected from an acrylic monomer containing a nitrogen atom and an acrylic monomer containing an aromatic ring, an acrylic monomer having an oxyalkylene group, a polyfunctional monomer, and a photopolymerization initiator. and fibrous cellulose (fine fibrous cellulose) having a fiber width of 1000 nm or less. Here, the fine fibrous cellulose has a phosphoric acid group or a substituent derived from a phosphoric acid group, and the counter ion of the phosphoric acid group or a substituent derived from the phosphoric acid group has an organic onium ion. preferable. In this case, an organic onium may be further mixed in the manufacturing process of the resin composition.

The method of mixing the above components is not particularly limited, but for example, glass beads can be mixed with the resin composition and mixed using a paint shaker or the like. The glass beads are, for example, Glass Beads No. manufactured by Toshin Riko Co., Ltd.; 6 can be used, and a paint shaker manufactured by Toyo Seiki Seisakusho Co., Ltd. can be used.

(cured product)
The present invention also relates to a cured product obtained by photocuring the resin composition described above. Although the shape of the cured product is not particularly limited, it is preferably in the form of a sheet. That is, the present invention provides at least one selected from a unit derived from an acrylic monomer containing a nitrogen atom and a unit derived from an acrylic monomer containing an aromatic ring, a unit derived from an acrylic monomer having an oxyalkylene group, a polyfunctional It preferably relates to a sheet comprising units derived from a monomer and fibrous cellulose having a fiber width of 1000 nm or less. The photopolymerization initiator contained in the resin composition may remain in the sheet.

The content of fine fibrous cellulose in the cured product is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, more preferably 0.5% by mass, based on the total mass of the cured product. % by mass or more is more preferable. In addition, the content of fine fibrous cellulose is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less with respect to the total mass of the cured product. preferable.

The total light transmittance of the sheet-like cured product (hereinafter also simply referred to as sheet) is preferably 70% or more, for example. On the other hand, the upper limit of the total light transmittance of the sheet is not particularly limited, and may be 100%, for example. Here, the total light transmittance of the sheet is a value measured according to JIS K 7361, for example, using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory).

The haze of the sheet is, for example, preferably 20% or less, more preferably 10% or less. Here, the haze of the sheet conforms to JIS K 7136 and is a value measured using, for example, a haze meter (HM-150, manufactured by Murakami Color Research Laboratory).

Although the thickness of the sheet is not particularly limited, it is preferably 15 μm or more, more preferably 25 μm or more, and even more preferably 50 μm or more. The upper limit of the thickness of the sheet is not particularly limited, but can be set to 1000 μm, for example. The thickness of the sheet can be measured, for example, with a stylus thickness gauge (Millitron 1202D, manufactured by Marr Co.) or MF-501, manufactured by Nikon Corporation.

Although the basis weight of the sheet is not particularly limited, it is preferably 10 g/m ² or more, more preferably 20 g/m ² or more, and even more preferably 30 g/m ² or more. Although the basis weight of the sheet is not particularly limited, it is preferably 200 g/m ² or less, more preferably 150 g/m ² or less. Here, the basis weight of the sheet can be calculated according to JIS P 8124, for example.

The cured product of the present invention is preferably for liquid absorption. The object to be absorbed is preferably a non-aqueous liquid, and the cured product is particularly preferably for non-aqueous liquid absorption. That is, the cured product of the present invention is preferably a liquid-absorbent cured product (sheet), more preferably a non-aqueous liquid-absorbent cured product (sheet). Examples of non-aqueous liquids include non-aqueous electrolytic solutions, and such electrolytic solutions include, for example, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, and the like.

The liquid absorbency of the cured product (sheet) of the present invention is preferably 3.0 or higher, more preferably 4.0 or higher, further preferably 4.5 or higher, and 5.0 or higher. is particularly preferred. The liquid absorption capacity of the cured product is calculated by the following formula from the mass of the cured product before and after immersing the cured product cut into a predetermined size in the electrolytic solution for 2 hours. As the electrolytic solution, 1 mol/L of ethylene carbonate/diethyl carbonate LiPF ₆ is used.
Absorption ratio = (mass of cured product after absorbing liquid - mass of cured product before absorbing liquid) / (mass of cured product before absorbing liquid)

The volume expansion coefficient of the cured product (sheet) of the present invention is preferably 150% or more, more preferably 180% or more, and even more preferably 200% or more. Further, the volume expansion coefficient of the sheet is preferably 800% or less, more preferably 600% or less, and even more preferably 500% or less.
The volume expansion coefficient of the sheet was calculated from the volume of the sheet before and after being immersed in an electrolytic solution (1M LiPF ₆ /ethylene carbonate:diethylene carbonate = 50:50 vol% (manufactured by Kishida Chemical Co., Ltd.)) at room temperature for about 24 hours. This is the value calculated by the formula.
Volume expansion rate (%) = sheet volume after immersion / sheet volume before immersion x 100

The cured product (sheet) of the present invention has good moldability and excellent strength. Therefore, the cured product (sheet) of the present invention can also be used as an optical adhesive tape without a supporting substrate. By using an optical pressure-sensitive adhesive tape as the absorbent sheet, it becomes possible to absorb liquid from both sides of the sheet, thereby improving the absorbent property. In addition, by using an optical adhesive tape, it is possible to reduce the thickness of the entire liquid-absorbent sheet, and it is possible to sufficiently meet the demand for miniaturization and thinning of battery packs.

Furthermore, the cured product (sheet) of the present invention has rubber-like elasticity. That is, the cured product (sheet) of the present invention has stiffness and is excellent in terms of strength. Therefore, the sheet can be easily cut, and there is also the advantage that cracks are less likely to occur on the end face during cutting. For example, the sheet can be easily cut into a desired shape such as a rectangle or a circle, and if necessary, an intermittent portion can be formed in the center of the sheet. In addition, since the cured product (sheet) of the present invention has the property of easily maintaining the sheet shape, it is an easy-to-handle sheet that does not wrinkle or shrink when cut or peeled off. be.

(Method for producing cured product)
When forming a sheet-like cured product from the resin composition of the present invention, it is preferable to provide a step of applying the resin composition onto a separate film and a step of irradiating with active energy rays. In the step of applying the resin composition onto the separate film, the resin composition may be applied onto one separate film. In this case, the coating of the resin composition can be carried out using a known coating device. Coating devices include, for example, blade coaters, air knife coaters, roll coaters, bar coaters, gravure coaters, micro gravure coaters, rod blade coaters, lip coaters, die coaters and curtain coaters. In addition, in the step of applying the resin composition onto the separate film, a spacer may be provided between two separate films, and the resin composition may be poured into this spacer frame.

As the separate film, a release laminate sheet having a separate film substrate and a release agent layer provided on one side of the separate film substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity substrate. is mentioned. Papers and polymer films are used as the base material for the separate film in the peelable laminate sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition-type or condensation-type silicone-based release agent or a compound containing a long-chain alkyl group is used. In particular, an addition-type silicone-based release agent having high reactivity is preferably used. A commercially available product may be used as the separate film. For example, A71#100 and A38ST#50 manufactured by Teijin Film Solutions Co., Ltd. can be used.

In the step of irradiating the active energy ray, it is preferable to irradiate the active energy ray so that the integrated light amount is 100 to 10000 mJ/cm ² , more preferably 500 to 5000 mJ/cm ² . Examples of active energy rays include ultraviolet rays, electron beams, visible rays, X-rays, and ion beams. Among them, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable. As the ultraviolet light source, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an extra-high pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, an electrodeless ultraviolet lamp, or the like can be used. Electron beams emitted from various types of electron beam accelerators, such as Cockroftwald type, Van de Clough type, resonance transformer type, insulated core transformer type, linear type, dynamitron type, and high frequency type, are used as electron beams. can.

(battery pack)
The present invention also relates to a battery pack including a cured product obtained by photocuring the resin composition described above, a battery cell, and a wiring circuit board. A cured product obtained by photocuring the resin composition is preferably in the form of a sheet. placed between the substrates. In addition, since the sheet-shaped cured product obtained in the present invention itself has adhesiveness, when the sheet-shaped cured product is arranged between the battery cell and the wiring circuit board, it can be easily attached at room temperature. can be done.

A sheet formed from the resin composition described above has excellent liquid absorbency, and can maintain its initial shape even after liquid absorption. Therefore, when the sheet is placed between the battery cell (non-aqueous electrolyte battery cell) and the printed circuit board in the battery case, the liquid leakage from the battery cell can be contained within the battery pack. Damage to the electrical circuits inside the pack can be suppressed. Thus, the sheet formed from the resin composition of the present invention is preferably used as a liquid-absorbing sheet (liquid-absorbing member) of a battery pack.

EXAMPLES The characteristics of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below.

(Examples 1-3)
<Production of fine fibrous cellulose>
As raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 208 g / m ² sheet, defiberized and Canadian standard freeness (CSF) measured according to JIS P 8121 700 ml) It was used. The raw material pulp was subjected to a phosphorylation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. A chemical-impregnated pulp was obtained by adjusting as follows. Next, the resulting chemical solution-impregnated pulp was heated in a hot air dryer at 165° C. for 200 seconds to introduce phosphoric acid groups into cellulose in the pulp to obtain phosphorylated pulp.

Then, the obtained phosphorylated pulp was washed. In the washing treatment, a pulp dispersion liquid obtained by pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of phosphorylated pulp is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. gone. The washing was finished when the electric conductivity of the filtrate became 100 μS/cm or less. The washed phosphorylated pulp was further subjected to the phosphorylation treatment and the washing treatment once in this order. Thus, a dehydrated sheet of phosphorylated pulp was obtained.

Next, the washed phosphorylated pulp was neutralized as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1N sodium hydroxide aqueous solution was added little by little while stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. . Next, the phosphorylated pulp slurry was dehydrated to obtain neutralized phosphorylated pulp. Next, the washing treatment was performed on the phosphorylated pulp after the neutralization treatment.

Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion liquid A containing fine fibrous cellulose.

X-ray diffraction confirmed that this fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. Moreover, the amount of phosphate groups (strongly acidic group amount) was 2.00 mmol/g.

100 g of the fine fibrous cellulose dispersion A obtained above was taken, and 0.39 g of aluminum sulfate was added while stirring. Stirring was continued for an additional 5 hours, and aggregation of fine fibrous cellulose was observed.
Then, the fine fibrous cellulose dispersion was filtered and then pressed with filter paper to obtain a fine fibrous cellulose concentrate. The resulting concentrate of fine fibrous cellulose was resuspended in deionized water so that the content of fine fibrous cellulose was 2.0% by mass. After that, it was washed by repeating the operation of filtering and squeezing again, and a fine fibrous cellulose concentrate A was obtained.
The end point of washing was the point at which the electric conductivity of the filtrate became 100 μS/cm or less. The solid content concentration of the resulting fine fibrous cellulose concentrate A was 17% by mass.

<Preparation of resin composition>
The acrylic monomer, polyfunctional monomer and photopolymerization initiator described in Table 1, and the fine fibrous cellulose concentrate A obtained as described above were blended so as to have the solid content concentration described in Table 1, and A 55% by mass tetrabutylammonium aqueous solution was mixed to obtain a resin composition. When mixing the resin composition, glass beads (manufactured by Toshinriko Co., Ltd., No. 6) were placed in a container and mixed at room temperature for 2 hours with a paint shaker (manufactured by Toyo Seiki Co., Ltd.).

<Production of sheet>
A resin composition was placed in a spacer frame with a thickness of 100 μm placed between separate films (A71#100 and A38ST#50, manufactured by Teijin Film Solution Co., Ltd.) and irradiated with ultraviolet rays so that the integrated light amount was 1850 mJ/cm ² . , to obtain a sheet (cured product).

(Comparative Examples 1 to 6)
A resin composition and a sheet (cured product) were obtained in the same manner as in Example 1 except that the acrylic monomer, polyfunctional monomer and photopolymerization initiator shown in Table 1 were blended.

(evaluation)
<Electrolytic drop test>
The sheets (cured products) obtained in Examples and Comparative Examples were cut into 3 cm squares, and after the separator was peeled off, an electrolytic solution (manufactured by Kishida Chemical Co., Ltd., ethylene carbonate/diethyl carbonate LiPF ₆ 1 mol/L) was applied to the center of the 3 cm square sheets. ) was added dropwise, and the liquid absorption state after 2 hours was evaluated according to the following criteria.
◯: The sheet absorbed the electrolytic solution, and there was nothing that flowed on the surface of the sheet.
x: The electrolyte remained on the surface of the sheet, and the electrolyte moved when the sheet was touched. Or there is a hole in the seat.

<Viscosity>
The viscosities (mPa·s/20° C.) of the resin compositions obtained in Examples and Comparative Examples were measured. The measurement was performed using a rheometer (MCR-301) manufactured by Anton Paar under the conditions of 20° C. and 20 rpm.

<Formability and Properties of Sheet>
The moldability and properties of the resin compositions obtained in Examples and Comparative Examples were evaluated according to the following criteria.
◯: The sheet can be molded and peeled off, and the sheet is rubber-like and does not crack at the end face when the sheet is cut.
Δ: It can be formed into a sheet shape, but there are portions where cracks occur on the end face when the sheet is cut.
x: Cannot be formed into a sheet, or deformed when peeled off and does not return to its original state.

<Liquid absorption ratio>
Sheets (cured products) obtained in Examples and Comparative Examples were cut into 2.5 cm squares, and the mass was measured (mass before liquid absorption). After that, the cut sheet was immersed in the electrolytic solution for 2 hours, and then the sheet was taken out from the electrolytic solution. Next, after wiping off the electrolytic solution on the surface of the sheet, the weight of the sheet after absorbing the solution was measured. The liquid absorbency was calculated using the following formula.
Absorption ratio = (Sheet weight after liquid absorption - Sheet weight before liquid absorption) / (Sheet weight before liquid absorption)

<Sheet property after liquid absorption>
Appearance evaluation of the sample (sheet after liquid absorption) was performed when measuring the above-described liquid absorption capacity.
○: Maintains the appearance and shape before the test even after absorbing the liquid.
x: After absorbing the liquid, it was divided into small pieces in the liquid, or it was torn when taken out and did not maintain the shape before the test.

<Workability during coating>
Workability in processing sheets (cured products) from the resin compositions obtained in Examples and Comparative Examples was evaluated according to the following criteria.
◯: A sheet having a desired thickness can be easily formed without a spacer.
x: A sheet having a desired thickness cannot be formed without a spacer because the resin composition flows out.

<Volume expansion measurement>
Sheets (cured products) of the resin compositions obtained in Examples and Comparative Examples were cut into 2×7 mm sheets to prepare immersion samples. After that, the planar and cross-sectional lengths of the sheet before being immersed in the electrolytic solution were measured with a microscope.
Then, it was immersed in an electrolytic solution (1M LiPF ₆ /ethylene carbonate:diethylene carbonate=50:50 vol % (manufactured by Kishida Chemical Co., Ltd.)) at room temperature for about 24 hours. The sample was taken out from the electrolytic solution, washed with diethylene carbonate, and then wiped dry. Thereafter, the planar and cross-sectional lengths of the sheet immersed in the electrolytic solution were measured with a microscope. Then, the volume expansion coefficient was calculated by the following formula.
Volume expansion rate (%) = sheet volume after immersion / sheet volume before immersion x 100
Samples for which sheet formability could not be evaluated, those that broke into small pieces in the liquid when the sheet was taken out, or those that broke when taken out could not be evaluated, so they are indicated with "-" in the table. bottom.

BZA: benzyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat #160)
ACMO: acryloylmorpholine (manufactured by KJ Chemicals)
P-200A: phenoxy-polyethylene glycol acrylate (manufactured by Kyoeisha Chemical Co., Ltd.)
130A: methoxy-polyethylene glycol acrylate (manufactured by Kyoeisha Chemical Co., Ltd.)
14EG-A: PEG600# diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., molecular weight 742)
A-HD-N: 1,6-hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight 226)
Irg. 1173: Irgacure 1173 (manufactured by BASF)

The resin compositions obtained in the examples were superior in workability during coating as compared with the comparative examples.

On the other hand, the sheets (cured products) obtained in Comparative Examples 1 to 3 were poor in liquid absorption, and the resin compositions obtained in Comparative Examples 1 to 3 were also poor in workability during coating. Incidentally, in Comparative Examples 1 to 3, holes were formed in the sheet (cured product) during the dropping test. The resin compositions obtained in Comparative Examples 4 to 6 were inferior in workability during coating.

In addition, the resin compositions obtained in Examples had excellent moldability without causing cracks or the like when molded into sheets, and the liquid absorption capacity was equal to or higher than that of conventional products. Furthermore, the shape of the sheet changed little after absorbing the liquid, and the shape stability was excellent. FIG. 2 shows photographs of examples of the sheets obtained in Examples and Comparative Examples. FIG. 2(a) shows the sheet obtained in Example 1 after the liquid absorption test. As shown in FIG. 2(a), it can be seen that the sheet shape is maintained even after the liquid absorption test. On the other hand, FIG. 2(b) shows the sheet obtained in Comparative Example 4 after the liquid absorption test. As shown in FIG. 2(b), the sheet obtained in the comparative example collapsed after the liquid absorption test, and the sheet shape was not maintained.

Claims (10)

an acrylic monomer containing a nitrogen atom,
an acrylic monomer having an oxyalkylene group,
polyfunctional monomers,
A resin composition comprising a photopolymerization initiator and fibrous cellulose having a fiber width of 1000 nm or less and having an ionic substituent,
The ionic substituent is at least one selected from the group consisting of a phosphate group, a substituent derived from a phosphate group, a carboxyl group, a substituent derived from a carboxyl group, a sulfone group, and a substituent derived from a sulfone group. and
The counter ion of the ionic substituent is an organic onium ion,
The acrylic monomer containing a nitrogen atom is selected from the group consisting of dimethylacrylamide, diethylacrylamide, acryloylmorpholine, hydroxyethylacrylamide, methylolacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, dimethylaminoethylacrylamide and dimethylaminoethyl (meth)acrylate. is at least one
The acrylic monomer having an oxyalkylene group is at least one selected from the group consisting of methoxypolyethyleneglycol acrylate, ethoxypolyethyleneglycol acrylate, phenoxypolyethyleneglycol acrylate, methoxypolypropyleneglycol acrylate, ethoxypolypropyleneglycol acrylate and phenoxypolypropyleneglycol acrylate. can be,
The polyfunctional monomers include ethylene glycol (meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, and di(meth)acrylate. 1,4-butylene glycol acrylate, 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol diacrylate, polybutylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate , tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, diacrylate of bisphenol A diglycidyl ether, trimethylolpropane tri(meth)acrylate, tri At least one selected from the group consisting of pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, (meth)acrylates thereof and vinyl methacrylate,
The viscosity of the resin composition at 20° C. is 100 mPa s or more,
The resin composition, wherein the organic onium ion satisfies at least one condition selected from the following (a) and (b);
(a) containing a hydrocarbon group having 3 or more carbon atoms;
(b) The total number of carbon atoms is 10 or more. 2. The resin composition according to claim 1, wherein the ionic substituent is a phosphoric acid group or a substituent derived from a phosphoric acid group. 3. The resin composition according to claim 1, wherein the organic onium ion is an organic ammonium ion. The resin composition according to any one of claims 1 to 3, wherein the content of said fibrous cellulose is 0.1 to 30% by mass with respect to the total mass of said resin composition. The resin composition according to any one of claims 1 to 4, wherein the polyfunctional monomer has a molecular weight of 200 or more and less than 3,000. A cured product obtained by photocuring the resin composition according to any one of claims 1 to 5. The cured product according to claim 6, which is in the form of a sheet. The cured product according to claim 6 or 7, which is for liquid absorption. The cured product according to any one of claims 6 to 8, which is for non-aqueous liquid absorption. A battery pack comprising a cured product obtained by photocuring the resin composition according to any one of claims 1 to 5, a battery cell, and a wiring circuit board.

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