TW201535846A - Method for estimating binding properties between fine particles and binder resin in coating film, and method for improving binding properties between fine particles and binder resin in coating film - Google Patents

Abstract

The present invention relates to a method for estimating binding properties between fine particles and a binder resin in a coating film, and a method for improving binding properties between fine particles and a binder resin in a coating film. Until now, when using a new material in the production of a functional coating film, investigations of what combinations of fine particles and binders lead to an increase in binding capacity have been carried out by actually producing a large number of coating films and evaluating the binding properties thereof, and thus a large amount of time has been required to design functional coating films. The present invention provides a method for estimating, in compositions for which the binding properties between fine particles and a binder resin in a coating film are unknown, the binding properties between the fine particles and the binder resin in the coating film without having to actually produce the coating film, said estimation being accomplished by: focusing on the transverse relaxation time of water protons, which is obtained by means of a pulse NMR method, as a means of specifying the surface properties of the fine particles; generating, in advance, matrix data that represents the relationship between transverse relaxation time and binding properties; and carrying out a comparison with this. The provided method also makes it possible to improve binding properties.

Description

Method for estimating the adhesion of microparticles in a coating film to a binder resin, and method for improving the adhesion of microparticles in a coating film to a binder resin

The present invention relates to a method for estimating the adhesion of fine particles in a coating film to a binder resin, and a method for improving the adhesion of fine particles in a coating film to a binder resin.

In the past, in various fields such as electronic equipment, a coating film having a function of a fine particle and a binder has been used. In particular, in recent years, with the development of electronic equipment and the like, the performance required for a functional coating film has also been improved.

For example, in a lithium ion secondary battery, a lithium ion secondary battery having high voltage, high capacitance, and high energy density is strongly required for use in automobiles.

The lithium ion secondary battery is composed of a positive electrode using a metal oxide such as lithium cobaltate as an active material, a negative electrode using a carbon material such as graphite as an active material, and an electrolyte solution centered on a carbonate. A secondary battery that moves between the positive electrode and the negative electrode to charge and discharge the battery.

In more detail, the positive electrode can be caused by the surface of the positive electrode collector such as aluminum foil A composition containing a positive electrode active material such as a metal oxide and a binder is formed by forming a positive electrode layer, and the negative electrode is obtained by forming a negative electrode layer from a surface of a negative electrode current collector such as copper foil and a composition containing a negative electrode active material such as graphite and a binder. . Here, in the positive electrode layer or in the negative electrode layer, if the adhesion between the binder and the active material is weak, the positive electrode layer or the negative electrode layer is subjected to aggregation failure during use. Therefore, it is required to impart high binding property (cohesiveness) to the binder and the active material.

However, it is presumed that it is difficult to prevent the combination of the binder of the positive electrode layer or the negative electrode layer and the active material. In the case of the lithium ion secondary battery, Patent Document 1 proposes a binder which imparts high adhesion, but the binder is insufficient in adhesion when, for example, artificial graphite is used as an active material.

This problem is not limited to the positive electrode layer or the negative electrode layer of a lithium ion battery. When a new material is used in a binder or a microparticle to improve the performance of the functional coating film, it is difficult to predict the binding property (cohesiveness) of the functional coating film. Therefore, when a new material is used in the production of a functional coating film, the actual situation in the current situation is that most of the coating film is actually produced and evaluated for the adhesion, and the review can improve the combination of the bonding microparticles and the binder for the functional coating film. The design takes a considerable amount of time.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2011-243464

An object of the present invention is to provide a method for estimating the adhesion of microparticles in a coating film to a binder resin without actually preparing a coating film, and a method for improving the adhesion of microparticles and a binder resin in a coating film. .

The present inventors have actively studied to solve the above problems, and firstly, it is estimated that the adhesion of the fine particles and the binder in the coating film is greatly affected by the surface properties of the fine particles. However, the properties of the surface of the microparticles are difficult to analyze. In particular, the functional group of the surface of the material which is fired at an ultrahigh temperature, such as artificial graphite, disappears, so the analysis of the surface properties is extremely difficult.

Therefore, the present inventors have further repeated active research, and as a means for specifying the surface properties of the fine particles, attention has been paid to the above-mentioned problem by focusing on the gradual relaxation time of the water proton by the pulse NMR method.

That is, the present invention provides a method for adhering the fine particles in the coating film to the binder resin in the following [1] to [10], and improving the adhesion of the fine particles in the coating film to the binder resin. method.

[1] A method for estimating the adhesion of microparticles in a coating film to a binder resin, characterized by microparticles and a binder resin in a coating film when a coating film is formed from a composition containing microparticles and a binder resin The complexity is a known complex composition, and the gradual relaxation time a of the water proton determined by the pulsed NMR method of the aqueous dispersion of the fine particles is measured, and The gradual gradation b of the water protons measured by the pulsed NMR method of the aqueous emulsion of the binder resin is prepared in advance as matrix data indicating the relationship between the gradation time a and the gradation time b and the adhesion. The composition of the microparticles x in the coating film and the binder resin y are unknown, and the gradual relaxation time a of the water protons measured by the pulsed NMR method of the aqueous dispersion of the microparticles x is used In comparison with the time b of the water proton measured by the pulse NMR method of the aqueous emulsion of the binder resin y, it is estimated that the fine particles and the adhesion in the coating film when the coating film is formed of the composition having the unknown adhesion is estimated. The consistency of the resin.

[2] The method of presuming the adhesion of the fine particles in the coating film to the binder resin according to [1] above, wherein the fine particles and the fine particles x are carbonaceous materials and/or artificial graphite.

[3] The method for presuming the binding property of the fine particles in the coating film to the adhesive resin according to [1] or [2] above, wherein the binder resin and the binder resin y are styrene and an ethylenically unsaturated carboxylic acid. Copolymer of ester.

[4] The method for estimating the binding property of the fine particles in the coating film to the binder resin according to any one of the above [1] to [3], wherein the measurement condition of the lateral relaxation time a is the following condition 1, When the measurement condition of the gradation time b is the following condition 2, the transverse relaxation time a of the fine particles x is 10 seconds or more, and the transverse relaxation time b of the adhesive resin y is 200 seconds or more, and is estimated to be in the coating film. The adhesion of the microparticles x to the binder resin y is good; Condition 1: mass ratio of microparticles to carboxymethylcellulose having a weight average molecular weight of 3 million and a degree of substitution of 0.9 to water of 52.8:0.5:46.6 The transverse relaxation time of the water protons measured by pulse NMR of the fine particle dispersion prepared by mixing; Condition 2: The cross-section of the water protons determined by pulse NMR method using an anionic aqueous emulsion containing 40% by mass of the binder resin Alleviate the time.

[5] The method of estimating the adhesion of the fine particles in the coating film to the binder resin according to any one of the above [1] to [4], wherein the composition is a composition for forming a lithium ion secondary battery electrode.

[6] A method for improving the adhesion of fine particles in a coating film to a binder resin, characterized by microparticles and a binder resin in a coating film when a coating film is formed from a composition containing fine particles and a binder resin The binding property is a known complex composition, and the gradual relaxation time a of the water proton determined by the pulsed NMR method of the aqueous dispersion of the fine particles and the pulse of the aqueous emulsion by the above-mentioned binder resin are measured. The gradual gradation b of the water proton measured by the NMR method is prepared in advance as matrix data indicating the relationship between the gradation time a and the gradation time b and the adhesion, and the knot in the coating film is selected based on the matrix data. The combination of the fine particles x and the binder resin y which are excellent in properties.

[7] The method of improving the adhesion of the fine particles in the coating film to the binder resin according to [6] above, wherein the fine particles and the fine particles x are carbonaceous materials and/or artificial graphite.

[8] The method of improving the adhesion of the fine particles in the coating film to the adhesive resin according to [6] or [7] above, wherein the binder resin and the binder resin y are styrene and ethylenically unsaturated carboxylic acid. a copolymer of an acid ester.

[9] The fine particles in the coating film as described in any one of the above [6] to [8] The method of the adhesion to the binder resin is that the measurement condition of the gradation time a is the following condition 1, and the measurement condition of the gradation time b is the following condition 2, and the gradual relaxation of the fine particles x When the time a is 10 seconds or longer, the binder resin y having the gradual relaxation time b of 200 seconds or more is selected; Condition 1: the granules and the carboxymethylcellulose having a weight average molecular weight of 3 million and a substitution degree of 0.9 and water are 52.8. : 0.5: 46.6 mass ratio of the fine particle dispersion obtained by mixing pulverized NMR; the condition 2: anionic aqueous emulsion containing 40% by mass of the binder resin by pulse NMR The measured gradual relaxation time of the water protons.

[10] The method for improving the adhesion of fine particles in a coating film to a binder resin according to any one of the above [6] to [9], wherein the composition is a composition for forming an electrode of a lithium ion secondary battery .

In the past, if the coating film was not actually formed, the adhesion between the microparticles and the binder could not be judged. However, according to the present invention, the adhesion of the microparticles to the binder resin can be estimated even if the coating film is not actually formed, or even if it is not actually formed. The coating film can still select fine particles and binder resin with excellent adhesion, which can speed up the design of the functional coating film.

[Method of estimating the adhesion of microparticles in a coating film to a binder resin]

The method of estimating the adhesion of the fine particles in the coating film of the present invention to the binder resin (hereinafter sometimes referred to as "the method of estimating the knot of the present invention") is for forming a composition containing the fine particles and the binder resin. The adhesion between the fine particles in the coating film and the binder resin at the time of coating is a known complex composition, and the gradual relaxation time of the water proton measured by the pulse NMR method of the aqueous dispersion of the fine particles is measured a And the gradual gradation b of the water protons measured by the pulsed NMR method of the aqueous emulsion of the binder resin, and matrix data indicating the relationship between the traverse time a and the gradation time b and the adhesion is prepared in advance. For the composition in which the adhesion between the microparticles x in the coating film and the binder resin y is unknown, the gradual relaxation time a of the water proton determined by the pulsed NMR method of the aqueous dispersion of the microparticles x is By comparing the gradation of the water protons measured by the pulsed NMR method of the aqueous emulsion of the binder resin y with the time b, it is possible to estimate the fine particles in the coating film when the coating film is formed of the composition having the unknown adhesion. Sticky The junction of the resins.

The method of estimating the knotability of the present invention can be applied to various applications, but exhibits a good effect when the composition containing the fine particles and the binder resin is a composition for forming a lithium ion secondary battery electrode, in particular, the composition is lithium ion II. When the composition for forming a negative electrode of a secondary battery is formed, an excellent effect is exhibited.

The method of estimating the knot of the present invention focuses on the horizontal relaxation time a of the water protons (hereinafter sometimes referred to as "transverse lapse time a") and the binder resin by the pulse NMR method of the aqueous dispersion of fine particles. The water absorbing method of the water emulsion is determined by the pulse NMR method. Sometimes referred to as "traverse and time b") is the wettability of the fine particles and the binder resin to water. More specifically, it is focused on the fact that the microparticles and the binder resin are not easily wetted to water (lower hydrophilicity) if the gradual relaxation time is long, and the microparticles and the binder resin are easy to wet to water if the gradual relaxation time is short. Wet (higher degree of hydrophilicity).

In the past, it has been difficult to analyze the properties of the surface of fine particles. In particular, materials such as artificial graphite which are fired at an ultrahigh temperature have surface functional groups which are lost, and analysis of surface properties is difficult. The method of estimating the adhesion of the present invention is based on the determination of the hydrophilicity of the microparticles and the binder resin, and focuses on the gradual relaxation time of the water protons measured by pulse NMR. Even if the coating film is not actually produced, the coating film can be presumed. The combination of microparticles and binder resin.

(Making matrix data)

The method of estimating the adhesion of the present invention is a complex composition in which the adhesion between the fine particles and the binder resin in the coating film when the coating film is formed from the composition containing the fine particles and the binder resin is used. The gradual relaxation time a of the water protons measured by the pulse NMR method of the aqueous dispersion of the fine particles, and the gradual relaxation time b of the water protons measured by the pulse NMR method of the aqueous emulsion of the binder resin, Matrix data indicating the relationship between the traverse time a and the gradation time b and the sufficiency is prepared in advance.

When the matrix data is created, the measurement conditions of the gradual relaxation of the fine particles a (for example, the conditions of the aqueous dispersion of the fine particles) are preferably phases. with. The measurement conditions of the transverse relaxation time a of the fine particles x to be described later are also preferably the same as those when the matrix data is prepared. For example, the transverse relaxation time a of the fine particles is preferably measured by the following condition 1.

Condition 1: A fine particle dispersion obtained by mixing fine particles with a weight average molecular weight of 3 million and a degree of substitution of 0.9 carboxymethylcellulose and water at a mass ratio of 52.8:0.5:46.6 by mass spectrometry Horizontal and time.

The measurement of Condition 1 was carried out by pulse NMR. More specifically, a pulse nucleus magnetic resonance apparatus is used, and the measurement core is a hydrogen atomic nucleus, and the CPMG method (Carr-Purcell Meiboom-Gill method) is used under measurement conditions of a measurement temperature of 25 ° C, a frequency of 13 MHz, and a pulse width of 2 μs. ), measuring the gradual relaxation time of the water proton (rotation-rotation mitigation time). Further, in the measurement of Condition 1, the pH of the fine particle dispersion was preferably adjusted to 7.0.

Further, the measurement of the condition 1 is to calculate the transverse relaxation time of the water protons in contact with the surface of the fine particles, and the average of the two components of the horizontal relaxation time of the water protons which are not in contact with the surface of the microparticles as the transverse relaxation time a of the water protons.

Further, carboxymethyl cellulose (CMC) functions to enhance the dispersion stability of the fine particle dispersion by utilizing the viscosity-increasing action.

When the matrix data is prepared, the measurement conditions of the transverse retardation time of the binder resin (for example, the conditions of the aqueous emulsion of the binder resin, etc.) are preferably the same. The measurement conditions of the transverse relaxation time b of the binder resin y described later are also preferably the same as those at the time of matrix data preparation. For example, adhesive resin The horizontal relaxation time b is preferably measured by the following condition 2.

Condition 2: The gradual relaxation time of the water protons measured by a pulse NMR method using an anionic aqueous emulsion containing 40% by mass of the binder resin.

The measurement of Condition 2 was carried out by pulse NMR. More specifically, a pulse nucleus magnetic resonance apparatus is used, and the measurement core is a hydrogen atomic nucleus, and the CPMG method (Carr-Purcell Meiboom-Gill method) is used under measurement conditions of a measurement temperature of 25 ° C, a frequency of 13 MHz, and a pulse width of 2 μs. ), measure the horizontal tempering time of the water (rotation-rotation mitigation time). Further, in the measurement of the condition 2, the pH of the anionic aqueous emulsion was preferably adjusted to 7.0.

In addition, the measurement of the condition 2 is to calculate the average of the two components of the tempering time of the water protons in contact with the surface of the binder resin and the gradual relaxation time of the water protons which are not in contact with the surface of the binder resin. Moderate time b.

The anionic aqueous emulsion used for the measurement of Condition 2 can be prepared by, for example, the following methods (1) and (2).

(1) An aqueous emulsion containing 40% by mass of a binder resin was prepared using an anionic emulsifier.

(2) A reactive anionic emulsifier is used as a polymerizable monomer which forms a binder resin, and is prepared into an aqueous emulsion containing 40% by mass of a polymerized binder resin.

The average particle diameter of the binder resin particles in the aqueous emulsion does not particularly affect the gradual relaxation time b, but is preferably from 50 to 500 nm, more preferably from 100 to 250 nm. Also, the average particle size of the binder resin particles in the aqueous emulsion The diameter can be measured by laser diffraction.

One of the matrix data is illustrated in Table 1.

In Table 1, the transverse relaxation time a of the fine particles was measured under the above condition 1, and the transverse relaxation time b of the adhesive resin was measured under the above condition 2, and all the details were measured by the methods described in the examples. Further, the fine particles i in Table 1 are natural graphite, and the fine particles ii and iii are artificial graphite, and correspond to the fine particles i to iii of the examples. Further, the binder resins A to G of Table 1 correspond to the binder resins A to G of the examples, and the binder resins A to D and F to G are copolymers of styrene and ethylenically unsaturated carboxylic acid esters. The binder resin E is a styrene-butadiene rubber.

For example, a composition containing fine particles and a binder resin may be applied to a substrate, dried to form a coating film, and a coated surface and a SUS plate may be bonded together using a double-sided tape to perform 180° peeling (peeling width). 25 mm, peeling speed: 100 mm/min), and the measured peel strength was taken as the adhesion. Further, the adhesion (peel strength) of Table 1 was evaluated by the 180° peel test described in the examples.

(Selection of adhesive resin y which is excellent in adhesion to fine particles x)

Next, in the method of estimating the knot of the present invention, after the matrix data is created, the adhesion of the microparticles x in the coating film to the binder resin y is an unknown composition by using the aqueous dispersion of the microparticles x. The gradual relaxation time a of the water proton measured by the pulse NMR method is compared with the gradual relaxation time b of the water proton measured by the pulse NMR method of the aqueous emulsion of the binder resin y, and it can be estimated that the above-mentioned coherence is The composition of the unknown composition forms the adhesion of the fine particles in the coating film to the binder resin.

Here, when the horizontal relaxation time a of the fine particles x and/or the lateral relaxation time b of the adhesive resin y are unknown, the knotty may be estimated by measuring the unknown horizontal relaxation time a and the lateral relaxation time b. For example, when the transverse relaxation time a of the microparticles x is known, and the transverse relaxation time b of the binder resin y is unknown, the adhesion of the microparticles x to the binder resin y is judged by measuring the transverse relaxation time b of the binder resin y. Just fine.

According to the method for estimating the adhesion of the present invention, even if the functional coating film is not actually produced, the adhesion of the fine particles in the coating film to the binder resin can be estimated, and the design work efficiency of the functional coating film can be rapidly improved.

For example, according to the matrix data of Table 1, if the transverse relaxation time a of the fine particles x is 10 seconds or more, and the transverse b time of the adhesive resin y is 200 seconds or more, the peel strength can be estimated to exceed 8 mN/mm. Good sex. More specifically, if the transverse relaxation time a of the microparticles x is 10 to 50 seconds, and the transverse b time of the binder resin y is 200 to 750 seconds, it is estimated that the adhesion is better, and if the microparticles x are horizontal Relaxation time a is 11~40 seconds, and the cross-bending time b of the adhesive resin y is 220-600 seconds, it is presumed that the bonding property is better, if the gradual relaxation time of the microparticles x is 12 to 30 seconds, and the adhesive resin y When the horizontal b time is 300 to 450 seconds, it is estimated that the adhesion is better.

Further, according to the matrix data of Table 1, it can be estimated that when the transverse relaxation time a of the microparticles x is short (less than 10 seconds), if the adhesive resin y is selected to be shorter than the time b (less than 200 seconds), Good connectivity.

(microparticles)

The fine particles which can be applied to the method of estimating the knot of the present invention are not particularly limited.

The shape of the fine particles is not particularly limited, and a spherical shape, a scale shape, or the like can be used.

The average particle diameter of the fine particles can be preferably from about 1 to 100 μm, more preferably from 10 to 50 μm, even more preferably from 15 to 30 μm. Further, the average particle diameter can be calculated by a laser diffraction method.

The average specific surface area of the fine particles is usually preferably from 0.1 to 100 m ² /g, more preferably from 0.1 to 50 m ² /g, still more preferably from 0.1 to 30 m ² /g. Further, the average specific surface area can be obtained by measuring the specific surface area by BET nitrogen adsorption method (according to JIS Z8830).

The material of the microparticles cannot be generalized depending on the type of the functional film to be produced. However, when the microparticles are active materials for the positive electrode layer or the negative electrode layer of the lithium ion secondary battery, the fine particles (active material) are preferably used for adsorption and release. Lithium ion. The active material has a positive active material and a negative electrode Sexual substance. In the present invention, when the negative electrode active material is used as the fine particles, the effect is easily exhibited, and when the carbonaceous material or the artificial graphite is used for the negative electrode active material, the effect is more easily exhibited, and in particular, when artificial graphite having poor surface properties is used, an extremely remarkable effect can be exhibited.

The positive electrode active material is exemplified by a metal composite oxide, and particularly a metal composite oxide containing lithium and at least one metal of iron, cobalt, nickel, and manganese, and preferably contains Li _x M _y1 O ₂ (however, M represents one or more transition metals, preferably at least one of Co, Mn or Ni, 1.10>x>0.05, 1≧y1>0), or Li _x M _y2 O ₄ (however, M represents one or more types) The transition metal preferably represents Mn or Ni, 1.10>x>0.05, 2≧y2>0), or Li _x M _y1 PO ₄ (however, M represents one or more transition metals, preferably represents Fe, Co) a substance of at least one of Mn or Ni, 1.10>x>0.05, 1≧y1>0), for example, LiCoO ₂ , LiNiO ₂ , Li _x Ni _y3 Mn _z Co _a O ₂ (wherein, 1.10>x >0.05, 1>y3>0,1>z>0,1>a>0), LiMn ₂ O ₄ , a composite oxide represented by LiFePO ₄ , or the like.

The negative electrode active material is exemplified by various cerium oxides (such as SiO ₂ ); carbonaceous materials; metal complex oxides such as Li ₄ Ti ₅ O _{12 ,} and the like, preferably amorphous carbon, graphite, natural graphite, pitch-based carbon fibers, and poly Carbonaceous materials such as acetylene, artificial graphite, and the like.

The artificial graphite is obtained by firing a carbonaceous material such as amorphous carbon, graphite, natural graphite, pitch-based carbon fiber or polyacetylene at a temperature of about 3000 ° C, and is different from the crystal structure of the carbonaceous material. Further, the artificial graphite is a plate-like crystal in which the atomic bonding shape is hexagonal, and the structure is a shell-like layer. quality.

(Binder resin)

The binder resin which can be applied to the knot estimation method of the present invention is not particularly limited.

Moreover, the binder resin is preferably a lower acid value from the viewpoint of making the transverse relaxation time b longer, and specifically, it is preferably an acid value of 20 mgKOH/g or less, more preferably 15 mgKOH/g or less, and further It is preferably 10 mgKOH/g or less. On the contrary, the binder resin is preferably a high acid value based on the viewpoint of shortening the gradual relaxation time, and particularly preferably an acid value of more than 20 mgKOH/g, more preferably 25 mgKOH/g or more, and even more preferably 28mgKOH / g or more.

The more specific composition of the binder resin cannot be generalized depending on the type of functional film to be produced.

When the binder resin is a binder for a positive electrode layer or a negative electrode layer of a lithium ion secondary battery, the glass transition temperature of the binder resin is preferably 30° C. or less, more preferably 20° C. or less, based on the fact that the electrode is not easily broken. More preferably below 15 °C. Further, from the viewpoint of handleability, the glass transition temperature of the binder resin is preferably -20 ° C or higher.

The glass transition temperature of the binder resin is the glass transition temperature Tgi (i) of each of the homopolymers of the ethylenically unsaturated monomer Mi (i = 1, 2, ..., i) used for the emulsion polymerization of the binder resin. =1, 2, ..., i), and the respective weight fractions of the ethylenically unsaturated monomer Mi (i = 1, 2, ..., i), by a good approximation of the following formula (I) The calculated theoretical value.

1/Tg=Σ(Xi/Tgi)...(I)

Further, specific examples of the binder resin are exemplified by, for example, styrene-butadiene rubber; copolymer of styrene and ethylenically unsaturated carboxylic acid ester; ethylene-vinyl acetate copolymer, ethylene-vinyl neodecanoate (vinyl) A versate copolymer or an ethylene-ethylenically unsaturated carboxylic acid ester copolymer such as an ethylene-acrylate copolymer. These binder resins are particularly effective as a binder for a positive electrode layer or a negative electrode layer of a lithium ion secondary battery. In addition, in the above, the copolymer of styrene and the ethylenically unsaturated carboxylic acid ester can improve the adhesion of the fine particles and the binder resin, and is excellent in the swelling resistance to the electrolytic solution and excellent in charge and discharge cycle characteristics. It is preferred.

A copolymer of styrene and an ethylenically unsaturated carboxylic acid ester (hereinafter sometimes abbreviated as "copolymer") exerts the above effects by using styrene and an ethylenically unsaturated carboxylic acid ester in combination. The copolymer can be obtained, for example, by emulsion polymerization of a raw material composition containing styrene, an ethylenically unsaturated carboxylic acid ester, and an internal crosslinking agent in the presence of an emulsifier in an aqueous medium.

Styrene mainly has a role of improving the adhesion of fine particles and a binder resin. In particular, when artificial graphite is used as the fine particles (active material), the effect can be further exerted.

The amount of styrene used is preferably from 15 to 70% by mass, more preferably from 30 to 60% by mass, even more preferably from 35 to 55% by mass, based on the total monomer component of the copolymer.

By using the amount of styrene in an amount of 15% by mass or more, the adhesion between the fine particles and the binder resin can be easily improved. Further, by setting the amount of styrene to be 70% by mass or less, the electrode can be prevented from being broken.

The ethylenically unsaturated carboxylic acid ester can be classified into a non-functional group and a functional group.

The ethylenically unsaturated carboxylic acid ester having no functional group is exemplified by, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (A) Base) n-butyl acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (methyl) Lauryl acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isodecyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, etc. Base) acrylates and the like. Among these, based on the ease of emulsion polymerization or durability, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, (meth)acrylic acid Borneol esters are preferred.

The non-functional ethylenically unsaturated carboxylic acid ester is preferably used in an amount of from 25 to 85% by mass, more preferably from 30 to 65% by mass, even more preferably from 40 to 55% by mass of all the monomer components of the above copolymer. %.

By using the amount of the non-functional ethylenically unsaturated carboxylic acid ester in an amount of 25% by mass or more, the flexibility and heat resistance of the formed electrode can be easily improved, and it can be easily made 85% by mass or less. The adhesion between the fine particles and the binder resin is improved.

The ethylenically unsaturated carboxylic acid ester having a functional group is exemplified by an ethylenically unsaturated carboxylic acid ester having a hydroxyl group, a glycidyl group or the like. Examples thereof include 2-hydroxyalkyl (meth)acrylate and glycidyl acrylate such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate. Among these, 2-hydroxyethyl (meth)acrylate is preferred.

The ethylenically unsaturated carboxylic acid ester having a functional group is preferably used in an amount of from 0.1 to 10% by mass, more preferably from 0.5 to 5% by mass, even more preferably from 1 to 3% by mass of all the monomer components of the above copolymer. %.

When the amount of the ethylenically unsaturated carboxylic acid ester having a functional group is 0.1% by mass or more, the emulsion polymerization stability or mechanical stability can be easily improved, and the dry film can be easily resistant to the electrolyte. Good swelling. In addition, when the amount of the ethylenically unsaturated carboxylic acid having a functional group is increased, the gradual relaxation time b tends to be short, and when the amount of use is small, the gradual relaxation time b tends to be long. For example, when the amount of the ethylenically unsaturated carboxylic acid having a functional group is 10% by mass or less, the gradual relaxation time b can be easily made 200 seconds or longer.

Further, an ethylenically unsaturated carboxylic acid can also be used as the monomer forming the above copolymer.

The ethylenically unsaturated carboxylic acid is exemplified by an unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid or crotonic acid, or an unsaturated dicarboxylic acid such as maleic acid, fumaric acid or itaconic acid or half of the unsaturated dicarboxylic acids. Ester, etc., among these, acrylic acid and itaconic acid are preferred. These ethylenically unsaturated carboxylic acids may be used alone or in combination of two or more.

When a small amount of the ethylenically unsaturated carboxylic acid is added, it may contribute to an improvement in emulsion polymerization stability or mechanical stability, but when it is added in a large amount, it is easy to shorten the gradual relaxation time b. In order to make the gradation time b to 200 seconds or more, the amount of the ethylenically unsaturated carboxylic acid to be used is preferably 3% by mass or less, more preferably 2% by mass or less, and more preferably 2% by mass or less of the total monomer component of the copolymer. It is preferably 1% by mass or less.

Further, a monomer other than the above having at least one polymerizable ethylenically unsaturated group may be used as the monomer for forming the above copolymer. The monomer is exemplified by (meth) acrylamide, N-methylol (meth) acrylamide, (meth) acrylonitrile, vinyl acetate, vinyl propionate, etc. A compound other than the functional ethylenically unsaturated carboxylic acid ester, sodium p-styrenesulfonate or the like.

Further, in order to adjust the molecular weight, a thiol, a thioglycolic acid and an ester thereof, β-propionic acid, an ester thereof, or the like may be used as a monomer for forming the above copolymer.

Further, a reactive emulsifier described later may be used as the monomer forming the copolymer.

In order to further improve the swelling resistance of the dried film to the electrolytic solution, the raw material composition of the copolymer of styrene and the ethylenically unsaturated carboxylic acid ester preferably further contains an internal crosslinking agent (internal crosslinking monomer).

As the internal crosslinking agent, a reactive group having at least one ethylenically unsaturated bond and having reactivity with a functional group of the above monomer, or having two or more ethylenically unsaturated bonds can be used.

The internal crosslinking agent is exemplified by two or more of divinylbenzene, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and triallyl cyanurate. Uncrosslinking crosslinkable polyfunctional monomer, vinyl trimethoxy decane, vinyl triethoxy decane, γ-methyl propylene methoxy propyl trimethoxy decane, γ-methyl propylene methoxy group a decane coupling agent such as propyltriethoxydecane, etc., among which divinylbenzene, trimethylolpropane tri(meth)acrylate, and γ-methylpropenyloxypropyltrimethoxydecane Preferably. These internal crosslinking agents may be used alone or in combination of two. More than one kind.

The amount of the internal crosslinking agent used is preferably from 0.1 to 5% by mass, more preferably from 0.1 to 3% by mass, even more preferably from 0.2 to 2% by mass, based on the total of the monomer components of the copolymer. By using the amount of the internal crosslinking agent in an amount of 0.1% by mass or more, it is possible to easily improve the swell resistance of the dried film to the electrolytic solution, and it is possible to prevent the emulsion polymerization stability from being lowered by setting it to 5% by mass or less.

When the transverse relaxation time b of the copolymer of styrene and the ethylenically unsaturated carboxylic acid ester is 200 seconds or more, the styrene and the non-functional ethylenically unsaturated carboxylic acid are formed in the monomer forming the copolymer. In terms of the total amount of esters, it is preferred to use an internal crosslinking agent. Specifically, the total amount of the styrene and the non-functional ethylenically unsaturated carboxylic acid ester is preferably 90% by mass or more, more preferably 93% by mass or more, and still more preferably 94% by mass or more.

The emulsifier used in the emulsion polymerization is usually an anionic emulsifier or a nonionic emulsifier.

The anionic emulsifier is exemplified by, for example, an alkylbenzenesulfonate, an alkylsulfate salt, a polyoxyethylidene ether sulfate salt, a fatty acid salt, and the like. Nonionic emulsifiers are exemplified by polyoxyethylene ethyl ether, polyoxyethylene ethyl phenyl ether, polyoxyethylene polyphenylene ether, polyoxyalkylene alkyl ether, sorbitol Anhydride fatty acid ester, polyoxyethylene ethyl sorbitan fatty acid ester, and the like. These may be used alone or in combination of two or more.

Further, when a reactive emulsifier is used as an emulsifier, it is possible to prevent the emulsifier from oozing out and to improve the mechanical stability of the electrode formed of the composition. The language is better. The reactive emulsifier is exemplified by, for example, the following general formulae (1) to (5).

In the formula, R represents an alkyl group, and m represents an integer of 10 to 40.

In the formula, m represents an integer from 10 to 40, and n represents an integer from 10 to 12.

In the formula, R represents an alkyl group and M represents NH ₄ or Na.

In the formula, R represents an alkyl group.

In the formula, AO represents an alkylene oxide having 2 or 3 carbon atoms, and m represents an integer of 10 to 40.

When the emulsifier is used in a non-reactive emulsifier, it is preferably 0.1 to 3 parts by mass, more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of all the monomer components forming the copolymer. More preferably 0.2 to 1 part by mass. In the case of a reactive emulsifier, it is preferably from 0.3 to 5 parts by mass, more preferably from 0.5 to 4 parts by mass, even more preferably from 0.5 to 2 parts by mass, based on the total monomer component of the copolymer. Further, each of the non-reactive emulsifier and the reactive emulsifier may be used singly, but it is preferably used in combination.

The radical polymerization initiator used in the emulsion polymerization may be a conventional one, and examples thereof include ammonium persulfate, potassium persulfate, hydrogen peroxide, and t-butyl hydroperoxide. Further, if necessary, the polymerization initiator may be used in combination with a reducing agent such as sodium hydrogen sulfite, hydroxymethanesulfate (Rongalite) or ascorbic acid for redox polymerization.

The emulsion polymerization method is a method in which a single-feed polymerization method is used, and a method of continuously supplying each component is carried out. The polymerization is usually carried out under stirring at a temperature of from 30 to 90 °C. Further, in the polymerization of the copolymer or after the completion of the polymerization, the pH is adjusted by adding a basic substance, whereby the polymerization stability, mechanical stability, and chemical stability during emulsion polymerization can be improved. As the alkaline substance used in this case, ammonia, triethylamine, ethanolamine, caustic soda or the like can be used. These may be used alone or in combination of two or more.

The content ratio of the fine particles and the binder resin in the coating film which can be used in the method for estimating the knot of the present invention is not particularly limited. On the basis of the solid content, usually, the fine particles are preferably from 95.0 to 99.5 mass%, and the binder resin is 0.5 to 5.0% by mass, more preferably 98.0 to 99.5% by mass of the fine particles, 0.5 to 2.0% by mass of the binder resin, 99.0 to 99.5% by mass of the fine particles, and 0.5 to 1.0% by mass of the binder resin.

When a functional coating film is formed from a composition containing fine particles and a binder resin, the composition can be applied onto a substrate and dried to obtain a coating film. The composition can be prepared by, for example, dispersing, dissolving, or kneading the binder resin in a solvent, adding fine particles and, if necessary, additives, followed by dispersion, dissolution, or kneading.

A general method can be used for the coating method, and for example, a reverse roll method, Direct roll pressing, squeegee method, doctor blade method, extrusion method, calendering method, gravure method, coating bar method, dipping method, and extrusion method. In the above, the coating method is selected by blending the physical properties such as the viscosity of the composition and the drying property, and the surface state of the functional coating film can be improved. The blade method, the doctor blade method, or the extrusion method is preferred. Out of the law.

The substrate on which the functional coating film is formed can be selected depending on the use. For example, when an electrode for a lithium ion secondary battery is produced, a metal such as iron, copper, aluminum, nickel, or stainless steel (current collector) can be used as the substrate.

[Method of improving the adhesion of microparticles in a coating film to a binder resin]

The method for improving the adhesion between the fine particles in the coating film and the binder resin of the present invention (hereinafter sometimes referred to as "the method for improving the adhesion of the present invention") is

The complex composition of the fine particles and the binder resin in the coating film when the coating film is formed of the composition containing the fine particles and the binder resin is a known complex composition, and pulse NMR of the aqueous dispersion by the microparticles is measured. The gradual relaxation time a of the water protons measured by the method and the gradual gradation b of the water protons measured by the pulsed NMR method of the aqueous emulsion of the binder resin are prepared in advance to indicate the traverse time a and the cross Matrix data that mitigates the relationship between time b and companionship,

Based on the aforementioned matrix data, a combination of the fine particles x and the binder resin y in which the adhesion in the coating film is good is selected.

The method of improving the consistency of the present invention is first made into matrix data. The embodiment of the matrix data creation operation, the fine particles, and the binder resin is the same as the above-described knotty estimation method of the present invention.

Further, in the method for improving the adhesion of the present invention, a combination of the fine particles x having good adhesion in the coating film and the binder resin y is selected based on the matrix data.

Here, when the horizontal relaxation time a of the candidate fine particles and/or the lateral relaxation time b of the adhesive resin are unknown, it is possible to determine whether or not the adhesion is good after measuring the unknown horizontal relaxation time a and the horizontal relaxation time b. .

According to the method for improving the adhesion of the present invention, even if the functional coating film is not actually produced, a combination of fine particles having good adhesion and a binder resin can be selected, and the design work efficiency of the functional coating film can be rapidly improved.

For example, according to the matrix data of Table 1, if the transverse relaxation time a is 10 seconds or longer as the fine particles x and the transverse relaxation time b is 200 seconds or longer as the adhesive resin y, it can be seen that the peel strength exceeds 8 mN/mm. Can improve the consistency. More specifically, when the adhesion is improved, it is preferable to combine the granule x having a gradual relaxation time a of 10 to 50 seconds, and the binder resin y having a gradual relaxation time b of 200 to 750 seconds, and a better combination of the gradual relaxation time a is The microparticles x of 11 to 40 seconds, and the adhesive resin y of the tempering time b of 220 to 600 seconds, and the combination of the gradual relaxation time a for the microparticles x of 12 to 30 seconds, and the transverse relaxation time b of 300 to 450 Second of the binder resin y.

Further, according to the matrix data of Table 1, it can be seen that when the transverse relaxation time a of the microparticles x is short (less than 10 seconds), if the transverse relaxation time b is shorter (less than 200 seconds) as the binder resin y, the thickness can be improved. Conjunction.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited thereto. In addition, the "parts" and "%" in the examples and the comparative examples indicate the parts by mass and the mass %, unless otherwise specified.

(measurement of traverse and time)

Using a pulse nuclear magnetic resonance apparatus (Acronarea, manufactured by XIGO Co., Ltd.), the measurement core was a hydrogen atomic nucleus, and the CPMG method (Carr-Purcell Meiboom-Gill) was used under the measurement conditions of a measurement temperature of 25 ° C, a frequency of 13 MHz, and a 90° pulse width of 2 μs. The method is to measure the transverse relaxation time of the water protons of the anionic water emulsions A to G of the binder resin, and the transverse relaxation time of the water protons of the active material dispersions i to iii. The results are shown in Table 1.

Further, the active material dispersions i to iii are obtained by mixing the following active materials i to iii, carboxymethylcellulose having a weight average molecular weight of 3,000,000 and a degree of substitution of 0.9, and water at a mass ratio of 52.8:0.5:46.6. By.

Active material i; natural graphite (spherical, average particle size 17 μm, average specific surface area 5.9 m ² /g)

Active material ii; artificial graphite (spherical shape, average particle diameter 18 μm, average specific surface area 1.3 m ² /g)

Active material iii; artificial graphite (scaled, average particle size 22 μm, average specific surface area 1.3 m ² /g)

(Synthesis of anionic water emulsion B of binder resin)

40 parts of ion-exchanged water and the reactivity of the above formula (4) Emulsifier (manufactured by Sanyo Chemical Industry Co., Ltd., trade name: Ereminol JS-20, active ingredient 40%), 0.2 parts, fed into a separable flask with a cooling tube, thermometer, stirrer, dropping funnel, and heated to 75 °C.

Then, 2.3 parts of the reactive anionic emulsifier represented by the above formula (4) (manufactured by Sanyo Chemical Industry Co., Ltd., trade name: Ereminol JS-20, active ingredient 40%) was added in advance over a period of 3 hours. 0.4 parts of non-reactive anionic emulsifier (manufactured by Daiichi Kogyo Co., Ltd., trade name Hitechnol 08E, polyoxyethylene ethyl ether ether sulfate), 49.2 parts of styrene, 2-ethylhexyl acrylate 43.1 a monomer emulsion of 1.9 parts of 2-hydroxyethyl methacrylate, 3.9 parts of acrylic acid, 0.4 parts of sodium p-styrenesulfonate, 0.5 parts of trimethylolpropane methacrylate and 85 parts of ion-exchanged water. . At the same time, 0.43 parts of potassium persulfate was dissolved in 20 parts of ion-exchanged water as a polymerization initiator at 80 ° C over 3 hours. After completion of the dropwise addition, the mixture was aged for 2 hours, cooled, and 1.8 parts of aqueous ammonia was added to obtain an anionic aqueous emulsion C. The ratio of the binder resin in the obtained anionic water emulsion B is 40%, and the viscosity is 1500 mPa. s, the resin particles in the emulsion have an average particle diameter of 190 nm and a pH of 7.0.

Further, the viscosity was measured using a Brookfield type rotary viscometer at a liquid temperature of 23 ° C, a number of revolutions of 10 rpm, a No. 2 or No. 3 rotor.

(Synthesis of anionic water emulsion A of binder resin)

In addition to the step of adding "0.43 parts of potassium persulfate dissolved in 20 parts of ion-exchanged water as a polymerization initiator" at 80 ° C in 3 hours. Further, a mixture of 0.08 parts of potassium persulfate dissolved in 10 parts of ion-exchanged water and 10 parts of hydroxymethanesulfate (Rongalite) dissolved in 10 parts of ion-exchanged water was added dropwise at 65 ° C in 3 hours. An anionic aqueous emulsion A was obtained in the same manner as in the synthesis example of the anionic aqueous emulsion B except for the step of the polymerization initiator.

(Synthesis of anionic aqueous emulsion C, D, F, G of binder resin)

An anionic aqueous emulsion C, D, F, and G were obtained in the same manner as in the synthesis example of the anionic aqueous emulsion B, except that the monomeric lipid composition was changed to the formulation of Table 2.

(Anionic water emulsion E of binder resin)

Adjusting the styrene-butadiene rubber (glass transition temperature -7 ° C (measured by DSC) anionic water emulsion (40% binder resin ratio, viscosity 11 mPa.s, average particle size of resin particles in the emulsion) 190 nm, pH 7.0) An anionic aqueous emulsion E as a binder resin.

(Experimental example)

Mixing 100 parts of any of active substances i to iii, 3.75 parts of emulsions A to G, and 50 parts of 2% aqueous solution of CMC (weight average molecular weight 3 million, degree of substitution 0.9), and further adding 28 parts Water, a composition for forming a lithium ion secondary battery electrode (negative electrode) was obtained.

Then, the composition for forming a lithium ion secondary battery electrode (negative electrode) was applied onto a copper foil so that the Wet thickness became 150 μm, and the mixture was dried by heating at 60 ° C for 30 minutes. Then, it was dried under vacuum at 120 ° C for 1 h, and placed at 23 ° C and 50% RH for 24 hours as a test piece. The test piece coating surface and the SUS plate were bonded together using a double-sided tape, and 180° peeling (peeling width 25 mm, peeling speed 100 mm/min) was performed, and the peeling strength was measured. The results are shown in Table 1. A small peeling strength means that the coating film is easily coagulated and broken, and the adhesion of the microparticles to the binder resin is low.

According to the matrix data of Table 1, if the transverse relaxation time a of the microparticles x is 10 seconds or more, and the transverse b time of the adhesive resin y is 200 seconds or more, the peel strength exceeds 8 mN/mm, and the microparticles x and the binder can be estimated. The resin y has good adhesion. On the other hand, when the transverse relaxation time a of the fine particles x is 10 seconds or more, and the transverse b time of the adhesive resin y is less than 200 seconds, the peel strength can be estimated to be 8 mN/mm or less, and the fine particles x and the binder resin can be estimated. The consistency of y can't get better. In addition, when the transverse relaxation time a of the fine particles x and the transverse relaxation time b of the binder resin y are both short, the peel strength becomes high, and it is estimated that the adhesion is good.

Further, according to the matrix data of Table 1, it is understood that if the traverse time a is 10 seconds or longer, the gradation time b is 200. When the adhesive resin y is used for a second or more, the peel strength exceeds 8 mN/mm, and the adhesion can be improved. Further, it is understood that when the transverse relaxation time a of the fine particles x and the transverse relaxation time b of the binder resin y are selected, the adhesion can be improved.

Claims (10)

A method for estimating the adhesion of microparticles in a coating film to a binder resin, characterized in that the microparticles in the coating film and the binder resin are formed when a coating film is formed from a composition containing fine particles and a binder resin. For the known complex composition, the gradual relaxation time a of the water proton determined by the pulsed NMR method of the aqueous dispersion of the fine particles and the pulse NMR method of the aqueous emulsion of the binder resin were measured. The gradation of the water quality and the time b, the matrix data indicating the relationship between the traverse time a and the gradation time b and the adhesion is prepared in advance, and the microparticles x in the coating film are bonded to the binder resin y. The composition of the unknown property is determined by the pulse NMR method of the water-based emulsion of the binder resin y by the pulse NMR method of the aqueous dispersion of the fine particles x by the pulsed NMR method. When the water quality is compared with the time b, it is estimated that the fine particles in the coating film and the binder resin are formed by the formation of the coating film having the unknown composition. The method of claim 1, wherein the microparticles and the microparticles x are carbonaceous materials and/or artificial graphite. The method of claim 1 or 2, wherein the binder resin and the binder resin y are copolymers of styrene and an ethylenically unsaturated carboxylic acid ester. The method of determining the binding property of the fine particles in the coating film to the adhesive resin according to claim 1 or 2, wherein the measurement condition of the transverse relaxation time a is the following condition 1, and the measurement condition of the lateral relaxation time b is taken as under In the condition 2, when the transverse relaxation time a of the fine particles x is 10 seconds or more, and the transverse relaxation time b of the binder resin y is 200 seconds or more, the junction of the fine particles x and the binder resin y in the coating film is estimated. The property is good; Condition 1: Microparticle dispersion obtained by mixing fine particles with a weight average molecular weight of 3 million and a degree of substitution of 0.9 carboxymethylcellulose and water at a mass ratio of 52.8:0.5:46.6 by pulse NMR The measured gradual relaxation time of the water protons; Condition 2: The gradual relaxation time of the water protons measured by a pulse NMR method using an anionic aqueous emulsion containing 40% by mass of the binder resin. The method of claim 1, wherein the composition is a composition for forming a lithium ion secondary battery electrode. A method for improving the adhesion of microparticles in a coating film to a binder resin, characterized in that the microparticles in the coating film and the binder resin are formed when a coating film is formed from a composition containing fine particles and a binder resin. The complex composition is a known complex composition, and the gradual relaxation time a of the water proton determined by the pulsed NMR method of the aqueous dispersion of the fine particles and the pulsed NMR method of the aqueous emulsion of the binder resin are used. The measured gradation of the water protons b and the matrix data indicating the relationship between the relaxation time a and the relaxation time b and the adhesion are prepared in advance, and the adhesion in the coating film is selected to be good according to the matrix data. The combination of the microparticles x and the binder resin y. The particle and binder resin in the coating film as claimed in claim 6 The method of bonding, wherein the microparticles and the microparticles x are carbonaceous materials and/or artificial graphite. A method for improving the adhesion of fine particles in a coating film to a binder resin according to claim 6 or 7, wherein the binder resin and the binder resin y are copolymers of styrene and an ethylenically unsaturated carboxylic acid ester. The method of improving the adhesion between the fine particles in the coating film and the binder resin according to the claim 6 or 7, wherein the measurement condition of the transverse relaxation time a is the following condition 1, and the measurement of the transverse relaxation time b is performed. In the following condition 2, when the transverse relaxation time a of the fine particles x is 10 seconds or longer, the adhesive resin y having the transverse relaxation time b of 200 seconds or longer is selected; Condition 1: Microparticles and a weight average molecular weight of 3 million And the granule dispersion having a degree of substitution of 0.9 is mixed with water at a mass ratio of 52.8:0.5:46.6, and the granule dispersion of the fine particle dispersion is determined by pulse NMR; Condition 2: will contain the bond The hydration time of the water protons measured by a pulse NMR method is 40% by mass of the anionic water emulsion of the resin. A method for improving the adhesion of fine particles in a coating film to a binder resin according to claim 6 or 7, wherein the composition is a composition for forming a lithium ion secondary battery electrode.