WO2015012371A1

WO2015012371A1 - Method for manufacturing copolymer latex, and copolymer latex

Info

Publication number: WO2015012371A1
Application number: PCT/JP2014/069609
Authority: WO
Inventors: 望杉田; 文敏武田; 皇雄三崎
Original assignee: 日本エイアンドエル株式会社
Priority date: 2013-07-24
Filing date: 2014-07-24
Publication date: 2015-01-29
Also published as: CN105189567A; KR101639547B1; CN105189567B; KR20150135549A

Abstract

　The method for manufacturing a copolymer latex according to the present invention is a method for manufacturing copolymer latex obtained by emulsion polymerization, wherein the copolymer is composed of monomer components comprising 15-60 mass% of an aliphatic conjugated diene-based monomer, 5-35 mass% of an ethylene-based unsaturated carboxylic acid monomer, 0.5 to 30 mass% of a vinyl cyanide monomer, and 0-79.5 mass% of a monomer capable of copolymerization therewith, and emulsion polymerization is carried out by containing more than 0 mass% and 40 mass% or less of the entire amount of the ethylene-based unsaturated carboxylic acid monomer in the reaction system at the start of loading the polymerization initiator, starting the loading of the remainder of the ethylene-based unsaturated carboxylic acid monomer at or later than the time point of 5% of the time beginning from the arrival time at which the polymer conversion rate of the reaction system has arrived at 1.0% until the end time at which the loading of the entire amount of the monomer component has ended, and loading 92 mass% of the entire amount of the ethylene-based unsaturated carboxylic acid monomer before the time point of 80% of the time beginning from the arrival time until the end time.

Description

Method for producing copolymer latex, and copolymer latex

The present invention relates to a method for producing a copolymer latex and a copolymer latex.

Conventionally, copolymer latex has been used for various applications such as coated paper and battery electrode materials. Copolymer latex has excellent operability in each application, is easy to use, and has been improved to give a high balance of physical properties to the final product. Longed for.

For example, coated paper is used for a large number of printed materials because of its high printing effect. Even in periodicals such as quarterly and monthly papers, the use of coated paper on all pages has increased considerably. In particular, most direct mails and product catalogs in the mail order business use coated paper for all pages.

Generally, a composition for paper coating is composed of a pigment dispersion in which a white pigment such as clay or calcium carbonate is dispersed in water, a binder for adhering and fixing the pigments to each other, and the pigment and the base paper, and other additives. It is a water-based paint. As the binder, a synthetic emulsion binder represented by styrene-butadiene copolymer latex, or a natural binder represented by starch or casein is used. Among them, styrene-butadiene copolymer latex obtained by emulsion polymerization has a large degree of freedom in quality design and is widely used as the most suitable binder for paper coating compositions. It is known that it affects the performance of the composition for coating, the operability at the time of producing coated paper, or the quality of the final coated paper product, such as surface strength and printing gloss (see, for example, Patent Documents 1 to 4 below) reference).

Japanese Patent No. 4125078 Japanese Patent Laid-Open No. 05-301907 JP 2009-91669 A JP 2008-248446 A

In recent years, paints such as compositions for paper coating have been reduced in cost due to soaring pigment costs, and the proportion of expensive kaolin to cheap calcium carbonate has increased, and the paint cost has been increased. There is a move to reduce the amount of copolymer latex with a large proportion. Therefore, there is a demand for a copolymer latex that can exhibit sufficient adhesive strength even with a small amount.

However, the response to higher performance tends to increase the viscosity of the copolymer latex, and generally there is a trade-off relationship between higher performance and lower viscosity of the copolymer latex. When attempting to improve the adhesive strength of the copolymer latex, there is a concern that workability will decrease with increasing viscosity. For example, from the viewpoint of transportation costs and storage tank capacity, it is desirable that the copolymer latex has a sufficiently high solid content, but if the solid content increases, the viscosity of the copolymer latex increases and transportability is increased. The handling workability such as filterability is inferior.

Further, the copolymer latex is also used as a material for battery electrodes, and it is desired that the copolymer latex is excellent in covering property to the electrode active material at the time of electrode preparation.

One of the objects of the present invention is to provide a copolymer latex capable of exhibiting sufficient adhesive strength and having good coverage to an electrode active material with a sufficient solid concentration and low viscosity. It is to provide a manufacturing method.

On the other hand, when handling latex in cold regions, it was necessary to take measures such as keeping all pipes warm so as not to freeze the latex. When the latex freezes, it often does not return to its original state even when thawed, and there has been a demand for a latex having good stability even when exposed to some low temperature conditions.

One of the objects of the present invention is to provide a copolymer latex that can exhibit sufficient adhesive strength, can achieve low viscosity, and is excellent in freeze stability.

Recently, further improvement in the performance of copolymer latex has been demanded. For example, one of the required properties in applications where cohesive failure such as adhesives for wood is dominant is There is strength. However, the response to higher performance tends to increase the viscosity of the copolymer latex, and generally there is a trade-off relationship between higher performance and lower viscosity of the copolymer latex. From the viewpoint of productivity and transportation cost, it is desirable that the solid concentration of the copolymer latex is sufficiently high. In such a case, if the strength of the copolymer latex is improved, the inner wall of the reactor etc. The coagulum easily adheres to the equipment.

Copolymer latex is also used as a material for battery electrodes, and it is desired that the electrode latex is excellent in coverage with an electrode active material when the electrode is produced, and that there is little generation of aggregates in the battery electrode composition. It is rare.

One of the objects of the present invention is that sufficient strength can be expressed, the solidified material is difficult to adhere, and the covering property to the electrode active material is good, and the generation of aggregates in the battery electrode composition is small. It is to provide a copolymer latex.

The invention according to the first aspect of the present invention is a method for producing a copolymer latex obtained by emulsion polymerization, wherein the copolymer comprises 15 to 60% by mass of an aliphatic conjugated diene monomer, ethylenically unsaturated Monomer component comprising 5 to 35% by weight of a carboxylic acid monomer, 0.5 to 30% by weight of a vinyl cyanide monomer, and 0 to 79.5% by weight of a monomer copolymerizable therewith. The reaction system at the start of charging the polymerization initiator contains 0% by mass to 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer. From the time point when the conversion rate reaches 1.0% to the end time when all the monomer components are charged, the remaining amount of the ethylenically unsaturated carboxylic acid monomer is charged. 8 from the time of arrival to the end of time % Time until the, to provide a method of manufacturing a copolymer latex performed by introducing more than 92 wt% of the total amount of the ethylenically unsaturated carboxylic acid monomer.

According to the method for producing a copolymer latex of the present invention according to the first aspect, a copolymer latex that can exhibit sufficient adhesive strength and has good coverage to an electrode active material has a sufficient solid concentration and low viscosity. Can be obtained at The copolymer latex obtained by the method for producing a copolymer latex of the present invention can be characterized in that aggregates hardly occur and filterability is excellent. Moreover, the cycle characteristic of the battery at the time of repeating charging / discharging can be improved because the covering property to the electrode active material of copolymer latex is favorable.

In the method for producing a copolymer latex of the present invention according to the first aspect, the ethylenically unsaturated carboxylic acid monomer preferably contains more than 30% by mass of a monocarboxylic acid monomer. In this case, the effect of reducing the viscosity in the neutral pH range can be further enhanced as compared with the case where the proportion of the monocarboxylic acid monomer in the ethylenically unsaturated carboxylic acid monomer is 30% by mass or less.

Further, it is preferable that the emulsion polymerization is carried out by charging 80% by mass or more of the total amount of the vinyl cyanide monomer by 60% of the time from the arrival to the end. In this case, the viscosity during the polymerization of the reaction system can be further reduced, whereby the generation of aggregates can be highly suppressed, and a copolymer latex having further excellent filterability can be obtained.

The invention according to the second aspect of the present invention is a copolymer latex obtained by emulsion polymerization, wherein the copolymer comprises 15 to 60% by mass of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer. It is composed of a monomer component consisting of 5 to 35% by mass of a monomer, 0.5 to 30% by mass of a vinyl cyanide monomer, and 0 to 79.5% by mass of a monomer copolymerizable therewith. In the emulsion polymerization, the reaction system at the start of charging the polymerization initiator contains 0% by mass to 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer, and the polymer conversion rate of the reaction system is 1. Starting from the time of 5% of the time from reaching the time when it reached 0% to the end when the entire amount of monomer components was charged, the charging of the remainder of the ethylenically unsaturated carboxylic acid monomer was started, By 80% of the time from the time of arrival to the end of time The total amount of acidic groups A (milliequivalent) per 100 g of the solid content of the copolymer latex measured by neutralization titration is carried out by adding 92% by mass or more of the total amount of the ethylenically unsaturated carboxylic acid monomer. / 100g) and the ratio A / B of the total acidic group amount B (milli equivalent / 100g) per 100g of the solid content of the copolymer latex calculated based on the blending amount of the acid component is 0.8 or less. A copolymer latex is provided.

The copolymer latex of the present invention according to the second embodiment can exhibit sufficient strength and can hardly adhere to a coagulum. The copolymer latex having A / B of 0.8 or less means that the acidic groups that are not detected by neutralization titration exceed 20%, and there are many acidic groups present in the copolymer latex. Conceivable. The presence of such an internal acid sufficiently suppresses the generation and adhesion of coagulum even when the ratio of the ethylenically unsaturated carboxylic acid monomer is within the above range and the strength of the copolymer latex is increased. The present inventors speculate that this is one of the possible factors. Moreover, the copolymer latex of this invention can improve the cycling characteristics of the battery at the time of repeating charging / discharging by the coating | cover property to an electrode active material being favorable. Furthermore, the copolymer latex of the present invention has an advantage that the generation of aggregates is small in the battery electrode composition.

In the copolymer latex of the present invention according to the second aspect, the ethylenically unsaturated carboxylic acid monomer preferably contains more than 30% by mass of a monocarboxylic acid monomer. In this case, the effect of reducing the viscosity in the neutral pH range can be further enhanced as compared with the case where the proportion of the monocarboxylic acid monomer in the ethylenically unsaturated carboxylic acid monomer is 30% by mass or less.

Further, it is preferable that the emulsion polymerization is carried out by adding 80% by mass or more of the total amount of the vinyl cyanide monomer by 60% of the time from the arrival to the end. In this case, the viscosity of the copolymer latex can be further reduced, whereby the adhesion of the coagulated product can be suppressed to a high degree, and a copolymer latex having further excellent handling properties can be obtained.

The invention according to the third aspect of the present invention is a copolymer latex obtained by emulsion polymerization, the copolymer comprising 15 to 60% by mass of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer. It comprises a monomer component consisting of 5 to 35% by weight of a monomer, 0.5 to 30% by weight of a vinyl cyanide monomer, and 0 to 79.5% by weight of a monomer copolymerizable therewith. In the emulsion polymerization, the reaction system at the start of charging the polymerization initiator contains 0% by mass to 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer, and the polymer conversion rate of the reaction system is 1. Starting from the time of 5% of the time from reaching the time when it reached 0% to the end when the entire amount of monomer components was charged, the charging of the remainder of the ethylenically unsaturated carboxylic acid monomer was started, By 80% of the time from the time of arrival to the end of time, The copolymer latex was cooled to −25 ° C. at a rate of 1 ° C./minute by conducting differential scanning calorimetry, with 92% by mass or more of the total amount of the ethylenically unsaturated carboxylic acid monomer being charged. Provided is a copolymer latex in which the heat of fusion ΔH (mJ / mg) from −20 ° C. to 0 ° C. calculated from the DSC curve obtained when heated satisfies the following formula (2).
[ΔH × (100 / 100−C _S )] / ΔH _W ≦ 0.8 (2)
[In the formula (2), C _S indicates the solid content concentration (mass%) of the measurement sample of the copolymer latex, and ΔH _W is the heat of fusion (mJ / mg) when distilled water is measured under the same conditions. Indicates. ]

The copolymer latex of the present invention according to the third aspect can exhibit a sufficient adhesive strength, can realize a low viscosity, and can be a latex having excellent freezing stability. In addition, the present inventors consider the reason why the copolymer latex of the present invention is excellent in freezing stability as follows. The left side of the formula (2) indicates the ratio of the heat of fusion detected from −20 ° C. to 0 ° C. with respect to the total heat of fusion of water contained in the copolymer latex. When this value is 0.8 or less on the right side of the formula (2), it is considered that the amount of water not detected from −20 ° C. to 0 ° C. is present in the latex by 20% by mass or more. The peaks detected from −20 ° C. to 0 ° C. are bound water and free water, and the water not detected is presumed to be antifreeze water. Such antifreeze water can be sufficiently present in the latex by the above specific emulsion polymerization, and as a result, it has become possible to improve freezing stability while achieving both adhesive strength and low viscosity. Conceivable.

Also, the copolymer latex of the present invention according to the third aspect can improve the cycle characteristics of the battery when charging and discharging are repeated due to its good coverage to the electrode active material. Furthermore, the composition for battery electrodes which mix | blended the copolymer latex of this invention can form the coating layer which has the outstanding binding force with respect to a collector.

In the copolymer latex of the present invention according to the third aspect, the ethylenically unsaturated carboxylic acid monomer preferably contains more than 30% by mass of a monocarboxylic acid monomer. In this case, the effect of reducing the viscosity in the neutral pH range can be further enhanced as compared with the case where the proportion of the monocarboxylic acid monomer in the ethylenically unsaturated carboxylic acid monomer is 30% by mass or less.

In addition, the emulsion polymerization is performed according to the Fedors method for monomer components other than the ethylenically unsaturated carboxylic acid monomer introduced into the reaction system by the end of the introduction of the entire amount of the ethylenically unsaturated carboxylic acid monomer. Fedors method for monomer components other than the ethylenically unsaturated carboxylic acid monomer introduced into the reaction system after the end of charging all of the ethylenically unsaturated carboxylic acid monomer, with a solubility parameter of SP ₁ It is preferable that the monomer component is added to the reaction system so that the difference between SP ₁ and SP ₂ is 1.50 or less in absolute value when the solubility parameter is SP _2. . In this case, a copolymer latex having further excellent freezing stability can be obtained.

According to the invention according to the first aspect of the present invention, a copolymer latex capable of exhibiting sufficient adhesive strength and having good coverage to the electrode active material can be obtained with sufficient solid content concentration and low viscosity. A method for producing a polymer latex can be provided.

According to the invention of the second aspect of the present invention, sufficient strength can be expressed, the solidified product is difficult to adhere, and the covering property to the electrode active material is good and the aggregate in the battery electrode composition. It is possible to provide a copolymer latex in which the occurrence of the above is small.

According to the invention of the third aspect of the present invention, it is possible to provide a copolymer latex that can exhibit sufficient adhesive strength, can achieve a low viscosity, and is excellent in freeze stability.

2 shows a DSC chart of the copolymer latex obtained in Example III-1. 2 shows a DSC chart of the copolymer latex obtained in Example III-3. 2 shows a DSC chart of the copolymer latex obtained in Comparative Example III-1.

<First aspect>
The method for producing a copolymer latex according to the first embodiment of the present invention is a method for producing a copolymer latex obtained by emulsion polymerization, and the copolymer is an aliphatic conjugated diene monomer 15-60. % By weight, 5 to 35% by weight of ethylenically unsaturated carboxylic acid monomer, 0.5 to 30% by weight of vinyl cyanide monomer, and 0 to 79.5% by weight of monomer copolymerizable therewith In the reaction system at the start of charging the polymerization initiator, the above emulsion polymerization is added to the total amount of the ethylenically unsaturated carboxylic acid monomer in an amount of more than 0% by weight to 40% by weight. From the time point of 5% from the time when the polymer conversion rate of the reaction system reaches 1.0% to the time when the entire amount of the monomer component has been charged, the ethylenic unsaturation is contained. Starting the introduction of the remainder of the carboxylic acid monomer, reaching the above From to time 80% of the time, until at the completion is carried out by introducing the above 92 wt% of the total amount of the ethylenically unsaturated carboxylic acid monomer.

First, the monomer component constituting the copolymer will be described.

Examples of the aliphatic conjugated diene monomer (hereinafter sometimes referred to as component (a)) include 1,3-butadiene, 2-methyl-1,3-butadiene, and 2,3-dimethyl-1,3-butadiene. , 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, and monomers such as substituted and side chain conjugated hexadienes. These can be used alone or in combination of two or more. In the present embodiment, it is preferable to use 1,3-butadiene from the viewpoint of easy production industrially and availability and cost.

Examples of the ethylenically unsaturated carboxylic acid monomer (hereinafter sometimes referred to as component (b)) include monocarboxylic acid monomers such as acrylic acid, methacrylic acid and crotonic acid, maleic acid, fumaric acid and itaconic acid These dicarboxylic acid monomers and their anhydrides are mentioned. These monomers can be used alone or in combination of two or more.

Examples of the vinyl cyanide monomer (hereinafter sometimes referred to as component (c)) include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like. These can be used alone or in combination of two or more. In the first embodiment, it is preferable to use acrylonitrile or methacrylonitrile from the viewpoint of easy production industrially and availability and cost.

Monomers copolymerizable with the above components (a) to (c) (hereinafter sometimes referred to as (d) component) include alkenyl aromatic monomers, unsaturated carboxylic acid alkyl ester monomers, Monomers such as unsaturated monomers and unsaturated carboxylic acid amide monomers containing a hydroxyalkyl group may be mentioned.

Examples of the alkenyl aromatic monomer include styrene, α-methylstyrene, methyl-α-methylstyrene, vinyl toluene, and divinylbenzene. These can be used alone or in combination of two or more. In the first embodiment, it is preferable to use styrene from the viewpoint of easy production industrially and availability and cost.

Examples of unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, Examples thereof include monomethyl fumarate, monoethyl fumarate, and 2-ethylhexyl acrylate. These can be used alone or in combination of two or more. In the first embodiment, it is preferable to use methyl methacrylate from the viewpoint of easy production industrially and availability and cost.

Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl Examples include methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate and 2-hydroxyethyl methyl fumarate. These can be used alone or in combination of two or more.

Examples of unsaturated carboxylic acid amide monomers include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide and N, N-dimethylacrylamide. These can be used alone or in combination of two or more.

Furthermore, in addition to the above monomers, monomers used in ordinary emulsion polymerization such as ethylene, propylene, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride can be used.

The content of the component (a) is 15 to 60% by mass, preferably 17 to 56% by mass, and preferably 20 to 52% by mass with respect to the total amount of the monomer components constituting the copolymer. Is more preferable. When the copolymer latex is used for the paper coating composition, the content of the component (a) is 25 to 60% by mass with respect to the total amount of monomer components constituting the copolymer. It is preferably 27 to 56% by mass, more preferably 30 to 55% by mass, and particularly preferably 30 to 52% by mass. By making content of (a) component into the said range, the copolymer latex excellent in the balance of adhesive strength and operativity can be obtained.

The content of the component (b) is 5 to 35% by mass, preferably 5.5 to 33% by mass, and preferably 6 to 28% by mass with respect to the total amount of monomer components constituting the copolymer. More preferably. By making content of (b) component into the said range, the adhesive strength of copolymer latex and the covering property to an electrode active material can fully be improved. Since the coating property of the copolymer latex on the electrode active material is good, the cycle characteristics of the battery when charging and discharging are repeated can be improved.

In the first embodiment, the component (b) preferably contains an ethylenically unsaturated monocarboxylic acid monomer in an amount exceeding 30% by mass, more preferably 37% by mass or more, and 45% by mass or more. More preferably, it is particularly preferably 55% by mass or more. By setting the content of the ethylenically unsaturated monocarboxylic acid monomer in the above range, a copolymer latex having a higher viscosity reducing effect in the neutral pH range can be obtained.

The content of the component (c) is 0.5 to 30% by mass, preferably 1 to 28% by mass, and preferably 3 to 25% by mass with respect to the total amount of the monomer components constituting the copolymer. More preferably. By setting the content of the component (c) in the above range, a copolymer latex having good solvent resistance can be obtained.

The content of the component (d) is 0 to 79.5% by mass, preferably 2 to 75% by mass, and preferably 5 to 70% by mass with respect to the total amount of the monomer components constituting the copolymer. More preferably. When the copolymer latex is used for a paper coating composition, the content of the component (d) is 0 to 69.5% by mass with respect to the total amount of monomer components constituting the copolymer. It is preferably 2 to 65% by mass, more preferably 5 to 60% by mass.

Next, the emulsion polymerization according to the first embodiment will be described.

In the first embodiment, emulsion polymerization is carried out by adding more than 0% by mass to 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer in the reaction system at the start of addition of the polymerization initiator. From the time when the polymer conversion rate reaches 1.0% (hereinafter sometimes simply referred to as “when reached”) to the time when the entire amount of the monomer component has been charged (hereinafter referred to simply as “when completed”) From the time point of 5% of the time until (there is)), starting the charging of the remainder of the ethylenically unsaturated carboxylic acid monomer, until the time point of 80% of the time from the arrival time to the end time And 92% by mass or more of the total amount of the ethylenically unsaturated carboxylic acid monomer is added.

The above arrival time means the time when the polymer conversion rate of the monomer added to the reaction system reaches 1.0%. The time point when the polymer conversion rate reaches 1.0% is calculated from actual measurement 30 minutes after the time point (0 point) when the monomer component, the initiator and water coexist. If the polymer conversion rate measured after 30 minutes does not exceed 1%, it is measured after another 30 minutes, and is measured every 30 minutes until the polymer conversion rate exceeds 1%. When the polymer conversion rate exceeds 1%, the time when the polymer conversion rate reaches 1.0% by connecting the data exceeding 1% and 0 point is defined as “at the time of arrival”.

The polymer conversion rate can be calculated from the following equation by weighing the reaction solution collected from the reaction vessel, drying at 150 ° C. for 1 hour, weighing again, and measuring the solid content C.
Polymer conversion (%) = [Solid content C (g) −Solid content other than monomer contained in reaction solution (g)] / Amount of monomer component added to reaction system (g) × 100
Note that “at the time of arrival” can be set based on data obtained in advance. For example, a reaction system similar to the emulsion polymerization to be performed can be prepared, and the arrival time can be obtained in advance based on the transition of the polymer conversion rate of this reaction system.

Into the reaction system at the start of charging the polymerization initiator, more than 0% by mass and 40% by mass or less, more preferably 0.1% by mass to 30% by mass of the total amount of the ethylenically unsaturated carboxylic acid monomer, Starting from the time of 5% of the time from the time of arrival to the end of time, the charging of the remainder of the ethylenically unsaturated carboxylic acid monomer is started, and the time from the time of arrival to the time of completion is 80% % Of the total amount of the above-mentioned ethylenically unsaturated carboxylic acid monomer is added to carry out the emulsion polymerization to give a copolymer latex capable of expressing sufficient adhesive strength at a sufficient solid content concentration. In addition, it can be obtained with a low viscosity. The copolymer latex thus obtained does not easily generate aggregates and can be excellent in filterability.

In order to further enhance the above effect, the ethylenically unsaturated carboxylic acid monomer is used after 10% of the time from the arrival time to the end time, more preferably after 15%. It is preferable to start charging the remainder of the ethylenically unsaturated carboxylic acid monomer. Further, the introduction of the remainder of the ethylenically unsaturated carboxylic acid monomer is preferably started by 50% of the time from the arrival to the end, and by 45%. More preferably, it is even more preferred to start by 40%. Further, it is preferable to add 95% by mass or more of the total amount by 70% of the time from the arrival time to the end time. More preferably, it is preferable to add the total amount up to 60% of the time from the arrival time to the end time.

In the reaction system according to the first embodiment, in addition to the components (a) to (d), an emulsifier (surfactant), a polymerization initiator, and, if necessary, a chain transfer agent, a reducing agent, and the like are blended. be able to.

Examples of the emulsifier include sulfate esters of higher alcohols, alkylbenzene sulfonates, alkyl diphenyl ether disulfonates, aliphatic sulfonates, aliphatic carboxylates, dehydroabietic acid salts, formalin condensates of naphthalene sulfonic acid, Anionic surfactants such as sulfate ester salts of ionic surfactants, and nonionic surfactants such as alkyl ester type, alkyl phenyl ether type, and alkyl ether type of polyethylene glycol. These can be used alone or in combination of two or more. The blending amount of the emulsifier can be appropriately adjusted in consideration of a combination of other additives.

Examples of the polymerization initiator include water-soluble polymerization initiators such as lithium persulfate, potassium persulfate, sodium persulfate, and ammonium persulfate, cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide, acetyl peroxide, Examples thereof include oil-soluble polymerization initiators such as diisopropylbenzene hydroperoxide and 1,1,3,3-tetramethylbutyl hydroperoxide. These can be used alone or in combination of two or more. Of these, potassium persulfate, sodium persulfate, cumene hydroperoxide, or t-butyl hydroperoxide is preferably used. The blending amount of the polymerization initiator is appropriately adjusted in consideration of the combination of the monomer composition, the pH of the polymerization reaction system, and other additives.

Examples of the chain transfer agent include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan; dimethylxanthogen disulfide, diisopropylxanthogendi Xanthogen compounds such as sulfide; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide; phenolic compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; Allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, carbon tetrabromide; α-benzyloxystyrene, α-ben Vinyl ethers such as ziroxyacrylonitrile and α-benzyloxyacrylamide; Chains such as triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, terpinolene, α-methylstyrene dimer A transfer agent is mentioned. These can be used alone or in combination of two or more. The blending amount of the chain transfer agent can be appropriately adjusted in consideration of combinations of other additives.

Examples of the reducing agent include sulfite, bisulfite, pyrosulfite, nitrite, nithionate, thiosulfate, formaldehyde sulfonate, benzaldehyde sulfonate; L-ascorbic acid, erythorbic acid, tartaric acid And carboxylic acids such as citric acid and salts thereof; reducing sugars such as dextrose and saccharose; and amines such as dimethylaniline and triethanolamine. These can be used alone or in combination of two or more. Of these, L-ascorbic acid and erythorbic acid are preferred. The blending amount of the reducing agent can be appropriately adjusted in consideration of a combination of other additives.

In addition, the reaction system according to the first embodiment includes saturated hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane, cycloheptane; pentene, hexene, heptene for the purpose of controlling the molecular weight and the crosslinked structure of the copolymer. , Cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and other unsaturated hydrocarbons; and hydrocarbon compounds such as benzene, toluene, xylene and other aromatic hydrocarbons. These can be used alone or in combination of two or more. Of these, cyclohexene and toluene are preferably used.

Furthermore, in the reaction system according to the first embodiment, an oxygen scavenger, a chelating agent, a dispersant, an antifoaming agent, an anti-aging agent, an antiseptic, an antibacterial agent, a flame retardant, an ultraviolet absorber, etc., are included as necessary. You may mix | blend an additive. These additives can be used in appropriate amounts in both types and amounts.

In the first embodiment, a part of (a) component, part of (b) component, part of (c) component, part of (d) component, emulsifier It is preferable to contain a reducing agent and a chain transfer agent.

When a part of the component (a) is contained in the reaction system at the start of charging the polymerization initiator, it is preferable to contain 1 to 25% by mass of the total amount of the component (a), and 3 to 20% by mass is contained. Is more preferable.

When a part of the component (c) is contained in the reaction system at the start of charging the polymerization initiator, the content of the component (c) is preferably 3 to 55% by mass, and preferably 5 to 50% by mass. Is more preferable.

When a part of the component (d) is contained in the reaction system at the start of charging the polymerization initiator, it is preferable to contain 1 to 45% by mass of the total amount of the component (d), and 2 to 30% by mass is contained. Is more preferable.

The total amount of the emulsifier and the polymerization initiator is preferably contained in the reaction system at the start of charging the polymerization initiator.

The reaction system at the start of charging of the polymerization initiator is, for example, a pressure-resistant polymerization reaction vessel, pure water, the components (a) to (d) described above, an emulsifier, a polymerization initiator, a chain transfer agent, a reducing agent, and the like. Can be prepared by adding a predetermined amount of the above components and stirring them with, for example, an inclined blade, a turbine blade, a Max blend blade, or the like.

In the first embodiment, the reaction temperature is preferably set in the range of 30 to 100 ° C., and preferably set in the range of 40 to 85 ° C., from the viewpoint of safety in the tank and productivity in consideration of safety. More preferred. In this case, a polymerization initiator having an initiation temperature in the above reaction temperature range is used.

The temperature of the reaction system can be increased by, for example, 0.25 to 1.0 ° C./min by external heating.

As a method of adding the components (a) to (d) to the reaction system after reaching the above time, for example, a batch addition method, a divided addition method, a continuous addition method, or a power feed method can be employed. From the viewpoint of improving the safety by suppressing the monomer in the reaction system to a certain concentration or less, it is preferable to employ a continuous addition method (hereinafter sometimes referred to as continuous addition). Further, the attachment may be performed a plurality of times.

In the first embodiment, 80% by mass or more of the total amount of the component (c) by the time 60% of the time from the arrival to the end of charging the total amount of the components (a) to (d), It is preferable to carry out emulsion polymerization by adding 85% by mass or more to the reaction system. Thereby, the viscosity during the polymerization of the reaction system can be further reduced, whereby the generation of aggregates can be highly suppressed, and a copolymer latex having further excellent filterability can be obtained.

With respect to the reaction time of the emulsion polymerization, for example, from the viewpoint of productivity, the time from the above arrival to the end of the total addition of the components (a) to (d) is preferably 1 to 15 hours. More preferably, it is time. The emulsion polymerization is preferably carried out until the polymer conversion rate of the components (a) to (d) reaches 95% or more, and more preferably 97% or more.

Moreover, in the first embodiment, it is preferable to terminate the reaction after confirming that the polymer conversion rate exceeds 95%. The polymer conversion rate can be calculated from the solid content or from the amount of heat obtained by cooling the polymerization tank. In this way, a copolymer latex is obtained.

From the viewpoint of dispersion stability, the copolymer latex is preferably adjusted to a pH of 5 to 8.5 with ammonia, potassium hydroxide, sodium hydroxide or the like, and adjusted to 5.5 to 7.5. More preferably.

The copolymer latex is preferably freed of unreacted monomers and other low-boiling compounds by a method such as heating under reduced pressure.

According to the method according to the first embodiment, a low viscosity copolymer latex can be obtained at a sufficient solid content concentration. The solid content concentration of the copolymer latex is preferably 35 to 65% by mass, more preferably 40 to 60% by mass, from the viewpoints of cost during transportation and tank capacity during storage.

The copolymer latex may be concentrated by a method such as an evaporation method so that the solid content concentration is 45 to 69% by mass. The copolymer latex obtained by the method according to the first embodiment can have a sufficiently low viscosity even when concentrated.

The viscosity of the copolymer latex is preferably 50 to 1000 mPa · s at 25 ° C., and more preferably 70 to 700 mPa · s. The viscosity is a B type (BL type) viscometer (TOKI SANGYO LTD made by VISCOMETER (model BM) according to the measurement method of JIS K7117-1, in the case of a viscosity of 0 to 100 mPa · s, No. 1 rotor, 100. ˜500 mPa · s: No. 2 rotor, 500 to 2000 mPa · s: No. 3 rotor, 2000 mPa · s or more: No. 4 rotor, rotation speed is 60 rpm) .

If necessary, the copolymer latex may contain functional additives such as preservatives, anti-aging agents, dispersants, printability improvers, surface sizing agents, lubricants, and surfactants. These additives can be used in appropriate amounts in both types and amounts.

The copolymer latex obtained by the method according to the first embodiment can have a sufficiently low viscosity even when concentrated. Thereby, the burden on the pump for transferring the copolymer latex can be reduced, and energy saving can be achieved. Further, according to the method according to the embodiment, it is possible to obtain a copolymer latex excellent in filterability, so it is possible to shorten the time required for filtration of the copolymer latex and to reduce loss due to filtration. Thus, it is possible to obtain a copolymer latex excellent in adhesive strength and covering property to the electrode active material with high productivity.

The copolymer latex according to the first embodiment is used for paper coating, fiber bonding such as nonwoven fabric, carpet backing, batteries (for example, electrodes, separators, heat-resistant protective layers, etc.), paints, and adhesives. Useful as a binder.

Examples of the paper coating composition include a copolymer latex according to the first embodiment and, if necessary, a pigment, another binder, an auxiliary agent, and the like.

As the pigment, inorganic pigments such as kaolin clay, calcium carbonate, talc, barium sulfate, titanium oxide, aluminum hydroxide, zinc oxide, and satin white, and organic pigments such as polystyrene latex can be used. These can be used alone or in combination of two or more.

Other binders include starch, oxidized starch, modified starch such as esterified starch, natural binders such as soybean protein and casein, water-soluble synthetic binders such as polyvinyl alcohol and carboxymethyl cellulose, polyvinyl acetate latex, acrylic latex, etc. Examples include synthetic latex. These can be used alone or in combination of two or more.

Auxiliaries include dispersants (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, etc.), antifoaming agents (polyglycol, fatty acid ester, phosphate ester, silicone oil, etc.), leveling agents (funnel oil, dicyandiamide, Urea, etc.), preservatives, mold release agents (calcium stearate, paraffin emulsion, etc.), fluorescent dyes, color water retention agents (sodium alginate, etc.) and the like.

The content of the copolymer latex in the paper coating composition is preferably 1 to 20 parts by mass and more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the pigment. preferable.

Examples of the battery electrode composition include those containing the copolymer latex and the active material according to the embodiment, and, if necessary, an auxiliary agent.

As the positive electrode active material is not particularly limited, if the non-aqueous electrolyte secondary battery, for _example, such as _{_{_{_{MnO 2, MoO 3, V 2}}}} O 5, V 6 O 13, Fe 2 O 3, Fe 3 O 4 Transition metal oxides, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , Li _X Co _Y Sn _Z O ₂ -containing complex oxides, LiFePO ₄ and other complex metal oxides, TiS ₂ , TiS ₃ , MoS _3, transition metal sulfides such as FeS _{_2,} and metal fluorides such as CuF 2, NiF _2. These can be used alone or in combination of two or more.

The negative electrode active material is not particularly limited, but in the case of a non-aqueous electrolyte secondary battery, for example, carbon fluoride, graphite, carbon fiber, resin-fired carbon, linear graphite hybrid, coke, pyrolysis gas growth carbon , Furfuryl alcohol resin calcined carbon, mesocarbon microbeads, mesophase pitch carbon, graphite whiskers, pseudo-isotropic carbon, calcined natural materials, and pulverized conductive carbonaceous materials such as polyacene organic semiconductors And a conductive polymer such as polyacetylene and poly-p-phenylene, and a single metal such as silicon and tin, or a composite material containing a metal oxide or an alloy of the metal. These can be used alone or in combination of two or more.

Assistants include water-soluble thickeners, dispersants, stabilizers, conductive agents and the like. Examples of the water-soluble thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), oxidized starch, phosphorylated starch, and casein. Examples of the dispersant include Examples thereof include sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate, and sodium polyacrylate. Examples of the stabilizer include nonionic and anionic surfactants. Examples of the conductive agent include acetylene. Examples include black and carbon nanofibers. These can be used alone or in combination of two or more.

The content of the copolymer latex in the battery electrode composition is preferably 0.1 to 10 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the active material, 0.5 to More preferably, it is 7 parts by mass. When the content of the copolymer latex is 0.1 parts by mass or more, it is preferable from the viewpoint of obtaining a good adhesive force with respect to the active material or the current collector, and when it is 10 parts by mass or less, a secondary battery is assembled. It is preferable from the viewpoint of sometimes preventing the overvoltage from significantly increasing and degrading the battery characteristics.

The battery electrode composition is applied to a current collector and dried to form an electrode coating layer on the current collector to obtain an electrode sheet. Such an electrode sheet is used as, for example, a positive electrode plate or a negative electrode plate of a non-aqueous electrolyte secondary battery.

As a method of applying the battery electrode composition to the current collector, for example, a known method such as a reverse roll method, a comma bar method, a gravure method, or an air knife method can be used. A dryer, a warm air dryer, an infrared heater, a far infrared heater, or the like is used.

The battery electrode composition using the copolymer latex according to the first embodiment is suitable for an electrode of a secondary battery such as a non-aqueous electrolyte secondary battery, a nickel hydrogen battery, or a nickel cadmium battery.

<Second aspect>
The copolymer latex according to the second embodiment of the present invention is a copolymer latex obtained by emulsion polymerization, and the copolymer comprises 15 to 60% by mass of an aliphatic conjugated diene monomer, an ethylene-based nonpolymer. A monomer comprising 5 to 35% by weight of a saturated carboxylic acid monomer, 0.5 to 30% by weight of a vinyl cyanide monomer, and 0 to 79.5% by weight of a monomer copolymerizable therewith. It is composed of components, and the above-mentioned emulsion polymerization is carried out by allowing the reaction system at the start of charging the polymerization initiator to contain more than 0% by mass and 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer. From the time of 5% from the time when the polymer conversion rate of the system reached 1.0% to the time when the monomer component was completely charged, the above-mentioned ethylenically unsaturated carboxylic acid monomer From the start of the remaining part until the end of the above 100 g of copolymer latex measured by a neutralization titration method by adding 92% by mass or more of the total amount of the ethylenically unsaturated carboxylic acid monomer up to 80% of time. Total acidic group amount per 100 g of solid content of the copolymer latex calculated based on the total acidic group amount A (milli equivalent / 100 g) (hereinafter also referred to as detected acid amount A) and the blending amount of the acid component The ratio A / B to B (milli equivalent / 100 g) (hereinafter also referred to as the theoretical acid amount B) is 0.8 or less.

About the monomer component which comprises the copolymer which concerns on 2nd embodiment, it is possible to use the same compound as what was illustrated as a monomer component which comprises the copolymer which concerns on 1st embodiment mentioned above. it can.

The content of the component (a) is 15 to 60% by mass, preferably 17 to 56% by mass, and preferably 20 to 52% by mass with respect to the total amount of the monomer components constituting the copolymer. Is more preferable. When the copolymer latex is used for the paper coating composition, the content of the component (a) is 25 to 60% by mass with respect to the total amount of monomer components constituting the copolymer. It is preferably 27 to 56% by mass, more preferably 30 to 55% by mass, and even more preferably 30 to 52% by mass. By making content of (a) component into the said range, the copolymer latex excellent in the balance of adhesive strength and operativity can be obtained.

The content of the component (b) is 5 to 35% by mass, preferably 5.5 to 33% by mass, and preferably 6 to 28% by mass with respect to the total amount of monomer components constituting the copolymer. More preferably. By making content of (b) component into the said range, the intensity | strength of copolymer latex, especially the tensile strength when made into a film, and the covering property to an electrode active material can fully be improved. Since the coating property of the copolymer latex on the electrode active material is good, the cycle characteristics of the battery when charging and discharging are repeated can be improved.

In the second embodiment, the component (b) preferably contains more than 30% by mass of the ethylenically unsaturated monocarboxylic acid monomer, more preferably contains 37% by mass or more, and contains 45% by mass or more. More preferably, it is particularly preferable to contain 55% by mass or more. By setting the content of the ethylenically unsaturated monocarboxylic acid monomer in the above range, a copolymer latex having a higher viscosity reducing effect in the neutral pH range can be obtained. Furthermore, from the above viewpoint, the content of the ethylenically unsaturated monocarboxylic acid monomer is more preferably 50% by mass or more, and still more preferably 60% by mass or more.

In the second embodiment, for the purpose of controlling the cohesive force of the copolymer latex polymer, styrene is used as the component (d) with respect to the total amount of monomer components constituting the copolymer. It is preferably contained in an amount of 5% by mass. When the copolymer latex is used in a paper coating composition, it is preferably contained in an amount of 1 to 69.5% by mass.

Next, the emulsion polymerization according to the second embodiment will be described.

In the second embodiment, the emulsion polymerization is carried out by adding more than 0% by mass to 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer in the reaction system at the start of charging the polymerization initiator. From the time when the polymer conversion rate reaches 1.0% (hereinafter sometimes simply referred to as “when reached”) to the time when the entire amount of the monomer component has been charged (hereinafter referred to simply as “when completed”) From the time point of 5% of the time until (there is)), starting the charging of the remainder of the ethylenically unsaturated carboxylic acid monomer, until the time point of 80% of the time from the arrival time to the end time And 92% by mass or more of the total amount of the ethylenically unsaturated carboxylic acid monomer.

The arrival time and the polymer conversion rate are synonymous with those described in the first embodiment.

The detected acid amount A can be adjusted by, for example, appropriately selecting an ethylenically unsaturated carboxylic acid monomer from the above-mentioned compounds and combining them.

The reaction system at the start of charging the polymerization initiator contains 0% by mass to 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer, more preferably 0.1% by mass to 30% by mass. And starting addition of the remainder of the ethylenically unsaturated carboxylic acid monomer from the time point of 5% of the time from the arrival time to the end time, from the arrival time to the end time. Emulsion polymerization is carried out while suppressing the viscosity of the reaction system by introducing 92% by mass or more of the total amount of the above-mentioned ethylenically unsaturated carboxylic acid monomer by 80% of the time. In addition, a copolymer latex having a ratio A / B between the detected acid amount A and the theoretical acid amount B of 0.8 or less can be obtained.

In order to further enhance the above effect, the ethylenically unsaturated carboxylic acid monomer is used after 10% of the time from the arrival time to the end time, more preferably after 15%. It is preferable to start charging the remainder of the ethylenically unsaturated carboxylic acid monomer. Further, the introduction of the remainder of the ethylenically unsaturated carboxylic acid monomer is preferably started by 50% of the time from the arrival to the end, and by 45%. More preferably, it is even more preferred to start by 40%. Moreover, it is preferable to add 95% or more of the total amount by the time point of 70% of the time from the arrival time to the end time. More preferably, it is preferable to add the total amount up to 60% of the time from the arrival time to the end time.

In the reaction system according to the second embodiment, in addition to the components (a) to (d), an emulsifier (surfactant), a polymerization initiator, and, if necessary, a chain transfer agent, a reducing agent, and the like are blended. be able to.

As the emulsifier (surfactant), the polymerization initiator, the chain transfer agent, the reducing agent, etc., the same compounds as those exemplified in the first embodiment described above can be used.

The reaction system according to the second embodiment includes saturated hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane, cycloheptane; pentene, hexene, heptene, for the purpose of controlling the molecular weight and cross-linked structure of the copolymer. , Cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and other unsaturated hydrocarbons; and hydrocarbon compounds such as benzene, toluene, xylene and other aromatic hydrocarbons. These can be used alone or in combination of two or more. Of these, cyclohexene and toluene are preferably used.

Furthermore, the reaction system according to the second embodiment includes an electrolyte, an oxygen scavenger, a chelating agent, a dispersant, an antifoaming agent, an anti-aging agent, an antiseptic, an antibacterial agent, a flame retardant, and an ultraviolet absorber as necessary. You may mix | blend additives, such as. These additives can be used in appropriate amounts in both types and amounts.

In the second embodiment, a part of (a) component, part of (b) component, part of (c) component, part of (d) component, emulsifier It is preferable to contain a reducing agent and a chain transfer agent.

In the second embodiment, the reaction temperature is preferably set in a range of 30 to 100 ° C., and preferably set in a range of 40 to 85 ° C., from the viewpoint of safety in the tank and productivity in consideration of safety. More preferred. In this case, a polymerization initiator having an initiation temperature in the above reaction temperature range is used.

In the second embodiment, 80% by mass or more of the total amount of the component (c) by 60% of the time from the arrival to the end of charging the total amount of the components (a) to (d), It is preferable to carry out emulsion polymerization by adding 85% by mass or more to the reaction system. Thereby, the viscosity during the polymerization of the reaction system can be further reduced.

In the second embodiment, it is preferable to terminate the reaction after confirming that the polymer conversion rate exceeds 95%. The polymer conversion rate can be calculated from the solid content or from the amount of heat obtained by cooling the polymerization tank. In this way, a copolymer latex is obtained.

According to the method according to the second embodiment, a low viscosity copolymer latex can be obtained at a sufficient solid content concentration. The solid content concentration of the copolymer latex is preferably 35 to 65% by mass, more preferably 40 to 60% by mass, from the viewpoints of cost during transportation and tank capacity during storage.

The copolymer latex may be concentrated by a method such as an evaporation method so that the solid content concentration is 45 to 69% by mass. The copolymer latex obtained by the method according to the second embodiment can have a sufficiently low viscosity even when concentrated.

The copolymer latex according to the second embodiment can exhibit a sufficient strength and can hardly adhere to a coagulated product. In addition, the copolymer latex according to the second embodiment has good coverage to the electrode active material and can be less likely to generate aggregates in the battery electrode composition. A copolymer latex having a detected acid amount A / theoretical acid amount B of 0.8 or less means that acidic groups not detected by neutralization titration exceed 20%, and is present inside the copolymer latex. It is thought that there are many acidic groups to do. The presence of such an internal acid sufficiently suppresses the generation and adhesion of coagulum even when the ratio of the ethylenically unsaturated carboxylic acid monomer is within the above range and the strength of the copolymer latex is increased. The present inventors speculate that this is one of the possible factors.

The total acidic group amount A (milli equivalent / 100 g) (detected acid amount A) per 100 g of the solid content of the copolymer latex measured by the neutralization titration method can be determined by the following method.

The copolymer latex is diluted to about 1% by mass (solid content concentration) with ion-exchanged water, and an excess amount of about 0.1N hydrochloric acid is added, followed by back titration with a 0.1N sodium hydroxide aqueous solution and conducting titration. Get a curve. From the obtained conductivity titration curve, the detected acid amount A (milli equivalent / 100 g) per 100 g of the solid content of the copolymer latex can be calculated based on the following formula.
Detected acid amount A = 0.1 × T × 100 / (W × M / 100)
T: titration of sodium hydroxide aqueous solution (ml)
W: Sampling amount of copolymer latex (g)
M: solid content concentration of copolymer latex (%)

The total acidic group amount B (milli equivalent / 100 g) (theoretical acid amount B) per 100 g of the solid content of the copolymer latex calculated based on the blending amount of the acid component can be obtained by the following method.

X (mass%) is the mass% of the ethylenically unsaturated carboxylic acid monomer, Y is the molecular weight of the ethylenically unsaturated carboxylic acid monomer, and Y is the ethylenically unsaturated carboxylic acid monomer. The maximum dissociation frequency of the acid monomer is Z, and the theoretical acid amount derived from the ethylenically unsaturated carboxylic acid monomer is calculated from the following formula (1).
Theoretical acid amount = (X × Z × 1000) / Y (1)
For all the ethylenically unsaturated carboxylic acid monomers blended, the theoretical acid amount is calculated in the same manner, and these are summed to obtain the theoretical acid amount B (milli equivalent / 100 g per 100 g of the solid content of the copolymer latex). )

In addition, when an additive having an acidic group such as a dispersant mainly composed of polycarboxylic acid is used, the theoretical acid amount derived from the additive having an acidic group is calculated in the same manner as described above. Add up.

The copolymer latex according to the second embodiment is used for paper coating, fiber bonding such as nonwoven fabric, carpet backing, batteries (for example, electrodes, separators, heat-resistant protective layers, etc.), paints, and adhesives. Useful as a binder.

Examples of the paper coating composition include a copolymer latex according to the second embodiment and, if necessary, a pigment, another binder, an auxiliary agent, and the like.

As for pigments, other binders, auxiliaries and the like, the same compounds as those exemplified in the first embodiment described above can be used.

Examples of the battery electrode composition include those containing the copolymer latex and the active material according to the second embodiment, and, if necessary, an auxiliary agent.

As the positive electrode active material, the negative electrode active material, the auxiliary agent, etc., the same compounds as those exemplified in the first embodiment described above can be used.

The battery electrode composition using the copolymer latex according to the second embodiment is suitable for an electrode of a secondary battery such as a non-aqueous electrolyte secondary battery, a nickel hydrogen battery, or a nickel cadmium battery.

<Third embodiment>
The copolymer latex according to the third embodiment of the present invention is a copolymer latex obtained by emulsion polymerization, and the copolymer is an aliphatic conjugated diene monomer of 15 to 60% by mass, an ethylene-based latex. A monomer comprising 5 to 35% by weight of an unsaturated carboxylic acid monomer, 0.5 to 30% by weight of a vinyl cyanide monomer, and 0 to 79.5% by weight of a monomer copolymerizable therewith. The emulsion polymerization is caused to contain more than 0% by mass and 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer in the reaction system at the start of charging the polymerization initiator, The ethylenically unsaturated carboxylic acid monomer from the time point after 5% from the time when the polymer conversion rate of the reaction system reaches 1.0% to the time when the entire amount of the monomer components are charged is finished. From the time of arrival to the end of At a time point of 80% of the total amount of the ethylenically unsaturated carboxylic acid monomer up to a point of 80%, and the co-polymer was cooled to −25 ° C. by differential scanning calorimetry. The heat of fusion ΔH (mJ / mg) from −20 ° C. to 0 ° C. calculated from the DSC curve obtained when the combined latex is heated at a rate of temperature increase of 1 ° C./min satisfies the following formula (2).
[ΔH × (100 / 100−C _S )] / ΔH _W ≦ 0.8 (2)

Wherein (2), C _S represents the solid content of the sample of the copolymer latex (weight%), [Delta] H _W is the heat of fusion when the distilled water was measured under the same conditions (mJ / mg) Show. The measurement sample of the copolymer latex can be adjusted to pH 7. For adjusting the pH, ammonia, potassium hydroxide, sodium hydroxide, or the like can be used. C _S may be set to 10 to 50 mass% is preferably set to 40 mass%. For adjusting the concentration, distilled water, ion-exchanged water, or purified water can be used. Water for calculating the [Delta] H _W may be used distilled water (manufactured by Wako Pure Chemical Industries).

About the monomer component which comprises the copolymer which concerns on 3rd embodiment, it is possible to use the same compound as what was illustrated as a monomer component which comprises the copolymer which concerns on 1st embodiment mentioned above. it can.

In the third embodiment, the component (b) preferably contains more than 30% by mass of the ethylenically unsaturated monocarboxylic acid monomer, more preferably contains 37% by mass or more, and contains 45% by mass or more. More preferably, it is particularly preferable to contain 55% by mass or more. By setting the content of the ethylenically unsaturated monocarboxylic acid monomer in the above range, a copolymer latex having a higher viscosity reducing effect in the neutral pH range can be obtained.

In the third embodiment, for the purpose of controlling the hardness of the copolymer latex polymer, styrene is used as component (d) with respect to the total amount of monomer components constituting the copolymer. It is preferably contained in an amount of 5% by mass. When the copolymer latex is used in a paper coating composition, it is preferably contained in an amount of 1 to 69.5% by mass.

Next, the emulsion polymerization according to the third embodiment will be described.

In the third embodiment, the emulsion polymerization includes a reaction system at the start of addition of a polymerization initiator containing more than 0% by mass and 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer. From the time when the polymer conversion rate reaches 1.0% (hereinafter sometimes simply referred to as “when reached”) to the time when the entire amount of the monomer component has been charged (hereinafter referred to simply as “when completed”) From the time point of 5% of the time until (there is)), starting the charging of the remainder of the ethylenically unsaturated carboxylic acid monomer, until the time point of 80% of the time from the arrival time to the end time And 92% by mass or more of the total amount of the ethylenically unsaturated carboxylic acid monomer.

Into the reaction system at the start of charging the polymerization initiator, more than 0% by mass and 40% by mass or less, more preferably 0.1% by mass to 30% by mass of the total amount of the ethylenically unsaturated carboxylic acid monomer, Starting from the time of 5% of the time from the time of arrival to the end of time, the charging of the remainder of the ethylenically unsaturated carboxylic acid monomer is started, and the time from the time of arrival to the time of completion is 80% % By adding 92% by mass or more of the total amount of the ethylenically unsaturated carboxylic acid monomer and performing emulsion polymerization, the viscosity of the resulting copolymer latex can be suppressed, and A copolymer latex satisfying the formula (2) can be obtained.

In the reaction system according to the third embodiment, in addition to the components (a) to (d), an emulsifier (surfactant), a polymerization initiator, and, if necessary, a chain transfer agent, a reducing agent, and the like are blended. be able to.

In addition, the reaction system according to the third embodiment includes saturated hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane, cycloheptane; pentene, hexene, heptene for the purpose of controlling the molecular weight and the crosslinked structure of the copolymer. , Cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and other unsaturated hydrocarbons; and hydrocarbon compounds such as benzene, toluene, xylene and other aromatic hydrocarbons. These can be used alone or in combination of two or more. Of these, cyclohexene and toluene are preferably used.

Furthermore, in the reaction system according to the third embodiment, if necessary, an electrolyte, an oxygen scavenger, a chelating agent, a dispersant, an antifoaming agent, an anti-aging agent, an antiseptic, an antibacterial agent, a flame retardant, and an ultraviolet absorber. You may mix | blend additives, such as. These additives can be used in appropriate amounts in both types and amounts.

In the third embodiment, a part of the component (a), a part of the component (b), a part of the component (c), a part of the component (d), an emulsifier It is preferable to contain a reducing agent and a chain transfer agent.

In the third embodiment, the reaction temperature is preferably set in the range of 30 to 100 ° C., and preferably set in the range of 40 to 85 ° C., from the viewpoint of safety in the tank and productivity in consideration of safety. More preferred. In this case, a polymerization initiator having an initiation temperature in the above reaction temperature range is used.

In the third embodiment, by the Fedors method of monomer components other than the ethylenically unsaturated carboxylic acid monomer charged into the reaction system by the end of the total amount of the ethylenically unsaturated carboxylic acid monomer. Fedors method for monomer components other than the ethylenically unsaturated carboxylic acid monomer introduced into the reaction system after the end of charging all of the ethylenically unsaturated carboxylic acid monomer, with a solubility parameter of SP ₁ the solubility parameter is taken as SP ₂ by 1.50 or less in the difference absolute value between the SP ₁ and SP _2, more preferably 1.45 or less, more preferably 0.97 or less, even more preferably 0. The reaction is preferably carried out by adding the monomer component to the reaction system so as to be 92 or less. In this case, a copolymer latex having further excellent freezing stability can be obtained.

Here, a calculation method of SP ₁ and SP ₂ will be described.
Fedors thinks that both the cohesive energy density and molar molecular volume depend on the type and number of substituents as a method for calculating the SP value from the molecular structure, and proposes the following formula (3) and constants for various substituents. (See, for example, “A Method for Both the Solidarity Parameters and Molecular Volumes of Liquids”, Robert F. Fedors, POLYMER ENGINERAND. 74 E. ).
δ = [ΣEcoh / ΣV] ^1/2 (3)
Here, ΣEcoh represents the cohesive energy, and ΣV represents the molar molecular volume.
The values of Ecoh and V of typical atoms and atomic groups are shown in POLYMER ENGINEERING AND SCIENCE, FEBRUARY, 1974, Vol. 14, no. 2, p. The values described in 152 table 5 can be used, for example, as shown in the following table.

For example, δ of polystyrene is calculated as [(1180 × 1 + 820 × 1 + 7630) / (16.1 × 1 + (− 1.0) × 1 + 71.4 × 1)] ^1/2 = 10.55.
Further, δ in the copolymer is ΣEcoh in the above formula (3) is the sum of the values of ΣEcoh of each monomer component multiplied by the molar ratio of that component, and ΣV in the above formula (3) is The total value is calculated by multiplying the value of ΣV of each monomer component by the molar ratio of the component.

As an example of Example III-1, which will be described later with respect to the calculation method of SP ₁ and SP ₂ , first, the ethylenic unsaturation charged into the reaction system by the end of the total amount of the ethylenically unsaturated carboxylic acid monomer. The monomer components other than the carboxylic acid monomer are 18 parts by mass of butadiene, 14 parts by mass of styrene, and 8 parts by mass of acrylonitrile, and are charged into the reaction system after the completion of the total amount of the ethylenically unsaturated carboxylic acid monomer. The monomer components other than the ethylenically unsaturated carboxylic acid monomer are 24 parts by mass of butadiene, 19 parts by mass of styrene, and 11 parts by mass of acrylonitrile.
SP ₁ is [{(4420 × 18/54) + (9630 × 14/104) + (8100 × 8/53)} / {(59.2 × 18/54) + (86.5 × 14/104). ) + (39.1 × 8/53)}] ^1/2 = 10.35.
SP ₂ is [{(4420 × 24/54) + (9630 × 19/104) + (8100 × 11/53)} / {(59.2 × 24/54) + (86.5 × 19/104). ) + (39.1 × 11/53)}] ^1/2 = 10.37.
The difference between SP ₁ and SP ₂ is 0.02 in absolute value.

Further, in the third embodiment, it is preferable to terminate the reaction after confirming that the polymer conversion rate exceeds 95%. The polymer conversion rate can be calculated from the solid content or from the amount of heat obtained by cooling the polymerization tank. In this way, a copolymer latex is obtained.

According to the method according to the third embodiment, a low viscosity copolymer latex can be obtained at a sufficient solid content concentration. The solid content concentration of the copolymer latex is preferably 35 to 65% by mass, more preferably 40 to 60% by mass, from the viewpoints of cost during transportation and tank capacity during storage.

The copolymer latex may be concentrated by a method such as an evaporation method so that the solid content concentration is 45 to 69% by mass. The copolymer latex obtained by the method according to the third embodiment can have a sufficiently low viscosity even when concentrated.

The copolymer latex according to the third embodiment can be a latex that can exhibit sufficient adhesive strength and covering property to the electrode active material, can achieve low viscosity, and is excellent in freeze stability. Moreover, the composition for battery electrodes which mix | blended the copolymer latex which concerns on 3rd embodiment can form the coating layer which has the outstanding binding force with respect to metals, such as a collector. In addition, the present inventors consider the reason why the copolymer latex of the third embodiment is excellent in freezing stability as follows. The left side of the formula (2) indicates the ratio of the heat of fusion detected from −20 ° C. to 0 ° C. with respect to the total heat of fusion of water contained in the copolymer latex. When this value is 0.8 or less on the right side of the formula (2), it is considered that the amount of water not detected from −20 ° C. to 0 ° C. is present in the latex by 20% by mass or more. The peaks detected from −20 ° C. to 0 ° C. are bound water and free water, and the water not detected is presumed to be antifreeze water. Such antifreeze water can be sufficiently present in the latex by the above specific emulsion polymerization, and as a result, it has become possible to improve freezing stability while achieving both adhesive strength and low viscosity. Conceivable.

In other words, in the copolymer latex according to the third embodiment, the proportion of the antifreeze water obtained by differential scanning calorimetry is preferably 20% by mass or more with respect to the total water content, and is 25% by mass or more. More preferably. In this case, the amount of antifreeze water (% by mass) relative to the total amount of water can be determined by the following procedure.

The copolymer latex is adjusted to a solid content C _S (mass%) and pH 7 to prepare a measurement sample. For adjusting the concentration and pH, pure water and sodium hydroxide can be used, respectively. The prepared measurement sample is packed in an aluminum pan and set in a differential scanning calorimeter (DSC6200: manufactured by Seiko Instruments Inc.). After setting the temperature to −25 ° C., the temperature is raised to 30 ° C. at a rate of temperature rise of 1 ° C./min to obtain a DSC curve. The heat of fusion ΔH (mJ / mg) from −20 ° C. to 0 ° C. is calculated from the obtained DSC curve. Similarly, heat of fusion ΔH _W (mJ / mg) for water is calculated. From these values, the ratio (mass%) of the antifreeze water amount to the total water amount is obtained by the following formulas (A), (B), (C), and (D).

Formula (A): Total amount of bound water and free water (mg) = [ΔH (mJ / mg) × mass of measurement sample (mg)] / ΔH _W (mJ / mg)
Formula (B): Total water content in measurement sample (mg) = mass of measurement sample (mg) × (100−C _S ) / 100
Formula (C): Amount of antifreeze water (mg) = total water amount in measurement sample (mg) −total amount of combined water and free water (mg)
Formula (D): Ratio of antifreeze water amount to total water amount (mass%) = antifreeze water amount (mg) × 100 / total water amount in measurement sample (mg)

The copolymer latex according to the third embodiment is used for paper coating, fiber bonding such as nonwoven fabric, carpet backing, batteries (for example, electrodes, separators, heat-resistant protective layers, etc.), paints, and adhesives. Useful as a binder.

Examples of the paper coating composition include a copolymer latex according to the third embodiment and, if necessary, a pigment, another binder, an auxiliary agent, and the like.

Examples of the battery electrode composition include those containing the copolymer latex and the active material according to the third embodiment, and, if necessary, an auxiliary agent.

The battery electrode composition using the copolymer latex according to the third embodiment is suitable for an electrode of a secondary battery such as a nonaqueous electrolyte secondary battery, a nickel hydrogen battery, or a nickel cadmium battery.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

<First aspect>
<Manufacture of copolymer latex>
The materials shown in Tables 2 to 5 were mixed in the amounts shown in the same table (unit: parts by mass) and reacted to synthesize copolymer latex. A specific synthesis procedure is shown below.

The components and symbols in Tables 2 to 5 represent the following compounds.
(A) Component: Aliphatic conjugated diene monomer BDE: 1,3-butadiene (b) Component (ethylenically unsaturated carboxylic acid monomer)
IA: Itaconic acid FA: Fumaric acid AA: Acrylic acid MAA: Methacrylic acid (c) Component: Vinyl cyanide monomer ACN: Acrylonitrile (d) Component: Monomer copolymerizable with components (a) to (c) Body STY: Styrene MMA: Methyl methacrylate AAMID: Acrylamide (other components)
tDM: t-dodecyl mercaptan emulsifier: sodium dodecylbenzenesulfonate electrolyte: sodium bicarbonate (NaHCO ₃ )
KPS: Potassium persulfate STPP: Sodium tripolyphosphate PW: Pure water

Example I-1
In a pressure-resistant polymerization reaction vessel, 10 parts by mass of cyclohexene and each monomer component and other compounds in the blending amounts (parts by mass) shown in the first stage of Table 2 are added and stirred sufficiently to obtain a reaction solution. It was.

Next, the temperature in the polymerization tank was raised, and the time when the polymer conversion rate of the reaction system reached 1.0% was regarded as reaching time, and after 85 minutes with this reaching time as a reference (0 minutes), Each monomer component and other compounds in the compounding amount (parts by mass) shown in the second stage are added to the continuous time zone shown in the second stage of Table 2 (from 85 minutes to 290 minutes after the arrival time, However, the component (b) was added to the reaction solution from 85 minutes to 220 minutes later. The reaction temperature of the polymerization system was 65 ° C.

Subsequently, each monomer component and other compounds in the blending amounts (parts by mass) shown in the third row of Table 2 are added to the continuous addition time zone shown in the third row of Table 2 (after 290 minutes on the basis of arrival time). Until 470 minutes).

Subsequently, the monomer components and other compounds in the blending amounts (parts by mass) shown in the fourth row of Table 2 were added to the continuous time zone shown in the fourth row of Table 2 (after 470 minutes on the basis of arrival time). (Until 495 minutes).

After the addition of the entire amount of monomer components was completed, the temperature in the polymerization tank was raised to 85 ° C. and maintained at 85 ° C. The fact that the polymer conversion rate exceeded 97% was confirmed from the amount of heat by which the polymerization tank was cooled, the polymerization was terminated, and a reaction product was obtained.

After completion of the polymerization reaction, the pH of the reaction product was adjusted to 6.5 using sodium hydroxide. Next, in order to remove unreacted monomers and other low-boiling compounds, the reaction product was subjected to heating under reduced pressure to obtain a copolymer latex IA.

(Examples I-2 to I-11, I-12, I-13)
Copolymer latex in the same manner as in Example I-1, except that the blending amount of each monomer component and other compounds, the addition time zone, and the reaction temperature were changed to the conditions shown in Table 2, 3 or 5. IB to IK, IL, and IM were obtained.

(Comparative Examples I-1 to I-5, I-7, I-8)
A copolymer latex I- was prepared in the same manner as in Example I-1, except that the blending amount of each monomer component and other compounds, the addition time zone, and the reaction temperature were changed to the conditions shown in Table 4 or 5. CE-1 to I-CE-5, I-CE-7, and I-CE-8 were obtained.

(Comparative Example I-6)
Instead of adding 10 parts by mass of cyclohexene to the pressure-resistant polymerization reactor, 0.5 parts by mass of α-methylstyrene dimer was added, and 0.2 parts by mass and α-methylstyrene dimer were added to the second stage and the third stage. In addition to the fact that 0.2 parts by weight were continuously added together with the monomer component, the blending amount of each monomer component and other compounds, the addition time zone, and the reaction temperature were changed to the conditions shown in Table 4. In the same manner as in Example I-1, a copolymer latex I-CE-6 was obtained.

<Evaluation of copolymer latex>
The copolymer latex obtained above was evaluated for the amount of aggregate, the latex viscosity after concentration, and the filterability according to the following method.

[Aggregate amount]
The copolymer latex is diluted to about 0.05% by mass with a 1% by mass saline solution, and the diluted solution is filtered through a 300 mesh wire mesh, and then the particle size is 2 to 10 μm using Multisizer 3 (manufactured by Beckman Coulter). The number of particles was measured. From the measurement results, the total mass of particles having a particle diameter of 2 to 10 μm was calculated, and the ratio (mass%) of particles having a particle diameter of 2 to 10 μm to the solid content of the copolymer latex was calculated.

[Latex viscosity after concentration]
The copolymer latex was concentrated by an evaporation method, and a sample adjusted to a solid content of 52 mass% and pH 6 using sodium hydroxide was obtained. For this sample, in accordance with the measurement method of JIS K7117-1, a B-type (BL type) viscometer (TOKI SANGYO LTD, VISCOMETER (model BM), with a viscosity of 0 to 100 mPa · s, No. 1 rotor, 100 to 500 mPa · s: No. 2 rotor, 500-2000 mPa · s: No. 3 rotor, 2000 mPa · s or more: No. 4 rotor, rotation speed is 60 rpm) The viscosity was measured. The latex viscosity after concentration was determined from the obtained viscosity according to the following criteria.
A: B-type viscosity is 3500 mPa · s or less B: B-type viscosity is more than 3500 mPa · s 5000 mPa · s or less C: B-type viscosity is more than 5000 mPa · s

[Filterability]
The copolymer latex was concentrated by an evaporation method, and the copolymer latex adjusted to pH 6 with a solid content of 47% by mass using sodium hydroxide was filtered through a metal mesh of about 20 cm in height to 300 mesh. Filtration was performed by folding a 12.5 cm square wire mesh into four and feeding the latex latex with a copolymer latex at 50 to 80% at all times. The filtration rate α (mL / second) per unit time was calculated from the time taken when 50 ml of copolymer latex was filtered, and the filterability was evaluated according to the following criteria. In addition, when the copolymer latex filtered from the wire mesh stopped, the filtration amount per unit time was calculated from the filtration amount and time at that time. Moreover, it was judged as C what was not filtered at all from a metal-mesh.
A: α ≧ 0.2
B: 0.1 <α <0.2
C: α ≦ 0.1

<Creation and evaluation of coated paper>
Using the copolymer latex obtained above, a paper coating composition was prepared by the following method to prepare a coated paper.

(Preparation of composition for paper coating)
A paper coating composition was prepared according to the formulation shown below. The paper coating composition was adjusted to pH 9.5 with sodium hydroxide, and the solid content concentration was adjusted to 67% by mass by adding a necessary amount of pure water.
(Combination prescription)
Kaolin (product name: DB Glaze, manufactured by Imerizu Minerals Japan Co., Ltd.) 20 parts by weight heavy calcium carbonate (product name: Carbital 90, manufactured by Imeris Minerals Japan Co., Ltd.) 80 parts by weight modified starch (Japanese food) Kako Co., Ltd., trade name: MS4600) 2 parts by mass copolymer latex 6 parts by mass (solid content)

(Creating coated paper)
After coating and drying the above-mentioned composition for paper coating on a coated base paper (basis weight 55 g / m ² ) using a wire bar so that the coating amount per side becomes 10 g / m ² , A calender treatment was performed under the conditions of a pressure of 60 kg / cm and a temperature of 50 ° C. to obtain a coated paper. About the obtained coated paper, dry pick strength was evaluated by the following method. The results are shown in Table 7.

(Evaluation of dry pick strength of coated paper)
Using a RI printer, a black ink for picking test (manufactured by DIC Graphics Co., Ltd.) was simultaneously printed on each coated paper. The obtained printed matter is pressed against coated fine paper to copy the ink, the portion where the ink is not copied (the white portion) is regarded as the picking occurrence point, and the degree of picking at this time is judged with the naked eye, The one with the least amount of picking was classified as grade 5, and was visually evaluated from grade 5 (excellent) to grade 1 (inferior).

<Production and evaluation of electrode>
Using the copolymer latex obtained above, a battery electrode composition was prepared by the following method to prepare an electrode.

(Preparation of battery electrode composition)
(1-1) Preparation of composition for positive electrode 100 parts by mass of LiCoO ₂ as a positive electrode active material, 5 parts by mass of acetylene black as a conductive agent, and 1 part by mass of an aqueous carboxymethyl cellulose as a thickener, As a binder, 2 parts by mass of the copolymer latex of each Example and each Comparative Example was kneaded by adding an appropriate amount of pure water so that the total solid content was 65% by mass, and the composition for the positive electrode A product was prepared.

(1-2) Preparation of Composition for Negative Electrode Using natural graphite having an average particle size of 20 μm as a negative electrode active material, 1 part by mass of a carboxymethyl cellulose aqueous solution as a thickener is used as a thickener with respect to 100 parts by mass of natural graphite. Then, as a binder, the copolymer latex of each Example and each Comparative Example was kneaded by adding a proper amount of pure water so that the total solid content was 45% by mass with 2 parts by mass in solid content, and the negative electrode A composition was prepared.

(Production of electrodes)
(1-1) Production of positive electrode The composition for positive electrode obtained as described above was applied to an aluminum foil having a thickness of 20 μm serving as a current collector, dried at 130 ° C. for 5 minutes, and then roll-pressed at room temperature. A positive electrode having a coating layer thickness of 100 μm was obtained.

(1-2) Production of Negative Electrode The negative electrode composition obtained as described above was applied to a 20 μm thick copper foil serving as a current collector, dried at 130 ° C. for 5 minutes, and then roll pressed at room temperature. A negative electrode having a coating layer thickness of 100 μm was obtained. In addition, when evaluating the coverage of an electrode active material, the thing before the rolling by roll press was used.

(Evaluation of coverage of copolymer latex on active material)
Since the cycle characteristics upon repeated charge / discharge are improved by coating the surface of the active material more with the copolymer latex, in each negative electrode sheet obtained by the above method, copolymerization is performed by the following method. The coverage of the combined latex on the active material was evaluated.
That is, each negative electrode sheet (before rolling) obtained above was cut into a 1 cm square, dyed in an osmium tetroxide atmosphere, and then used with a scanning electron microscope (trade name: JSM-6510LA, manufactured by JEOL Ltd.). And observed at 5000 times. In the SEM observation image, the area where the copolymer latex was adhered on the active material was visually confirmed with respect to the area of the active material, and evaluated as follows. Of the 8 SEM observation images, the average image was selected and evaluated. The results are shown in Table 7.
A: Copolymer latex covers 80% or more of the surface of the active material.
B: Copolymer latex covers 60% or more and less than 80% of the surface of the active material.
C: Copolymer latex covers 40% or more and less than 60% of the surface of the active material.
D: Less than 40% of the surface of the active material is coated with the copolymer latex.

It was confirmed that the copolymer latex obtained in Examples I-1 to I-10 has a sufficiently low viscosity even after concentration, hardly generates aggregates, and has excellent filterability. The reason why copolymer latexes IA to IK, IL, and IM are excellent in filterability is considered to be a synergistic effect of low viscosity and less aggregate formation due to shear. It is done. Further, as is apparent from the results shown in Table 7, the copolymer latexes obtained in Examples I-1 to I-11, I-12, and I-13 were evaluated in battery electrodes. It was confirmed that it had good electrode active material coverage.

According to the invention according to the first embodiment, a copolymer latex having a sufficiently low viscosity can be obtained even after concentration, so that the burden on the pump for transferring the copolymer latex can be reduced. This can save energy. Further, according to the invention according to the first embodiment, a copolymer latex excellent in filterability can be obtained, so that the time required for filtration of the copolymer latex is shortened and loss due to filtration is reduced. Thus, it is possible to obtain a copolymer latex excellent in adhesive strength and active material coverage with high productivity.

For the copolymer latex obtained in Examples I-12 and I-13, the viscosity at the time of transfer (hereinafter sometimes referred to as “viscosity at transfer”) was measured.

[Transport viscosity]
Aron (registered trademark) T-50 (trade name, sodium polyacrylate, weight average molecular weight: 6000) manufactured by Toagosei Co., Ltd. as a dispersant was uniformly 2 with respect to 100 parts by mass of the solid content of the copolymer latex. After adding 0.5 parts by mass (in terms of solid content), the solid content was adjusted to 50.5% by mass with pure water, pH 6.0, and the liquid temperature was 25 ° C. The pH of the latex was adjusted with a pH adjuster such as sodium hydroxide or hydrochloric acid as necessary. The viscosity of the copolymer latex after adjustment was measured according to the measurement method of JIS K7117-1 using a B-type (BL type) viscometer after 1 minute from the start of rotation at a rotation speed of 60 rpm. Was the viscosity at the time of transfer.

The viscosity of the copolymer latex obtained in Examples I-12 and I-13 was 400 mPa · s and 420 mPa · s, respectively.

<Second aspect>
<Manufacture of copolymer latex>
The materials shown in Tables 8 to 10 were mixed in the amounts shown in the same table (unit: parts by mass) and reacted to synthesize copolymer latex. A specific synthesis procedure is shown below.

The components and symbols in Tables 8 to 10 are the same as the components and symbols in Tables 2 to 5.

Example II-1
To the pressure-resistant polymerization reaction vessel, 10 parts by mass of cyclohexene and each monomer component and other compounds in the blending amounts (parts by mass) shown in the first stage of Table 8 were added and stirred sufficiently to obtain a reaction solution. .

Next, the temperature in the polymerization tank was increased, and the time when the polymer conversion rate of the reaction system reached 1.0% was regarded as reaching time, and after 90 minutes from this reaching time as a reference (0 minutes), Each monomer component and other compounds in the compounding amount (parts by mass) shown in the second stage are added to the continuous time zone shown in the second stage of Table 8 (from 90 minutes to 285 minutes after reaching the time, However, the component (b) was added to the reaction solution from 90 minutes to 180 minutes later. The reaction temperature of the polymerization system was 67 ° C.

Subsequently, the monomer components and other compounds in the blending amounts (parts by mass) shown in the third row of Table 8 were added to the continuous time zone shown in the third row of Table 8 (after 285 minutes on the basis of arrival time). Until 480 minutes).

Subsequently, the respective monomer components and other compounds in the blending amounts (parts by mass) shown in the fourth row of Table 8 were added to the continuous addition time zone shown in the fourth row of Table 8 (after 480 minutes on the basis of arrival time). (Until 495 minutes).

After completion of the polymerization reaction, the pH of the reaction product was adjusted to 6.5 using sodium hydroxide. Subsequently, in order to remove unreacted monomers and other low-boiling compounds, the reaction product was subjected to heating under reduced pressure to obtain a copolymer latex II-A.

(Examples II-2 to II-11)
Copolymer latex II- in the same manner as in Example II-1, except that the amount of each monomer component and other compounds, addition time zone, and reaction temperature were changed to the conditions shown in Table 8 or 9. B to II-K were obtained respectively.

(Comparative Examples II-1 to II-4, II-6 to II-8)
Copolymer latex II- in the same manner as in Example II-1, except that the amount of each monomer component and other compounds, addition time zone, and reaction temperature were changed to the conditions shown in Table 9 or 10. CE-1 to II-CE-4 and II-CE-6 to II-CE-8 were obtained, respectively.

(Comparative Example II-5)
Instead of adding 10 parts by mass of cyclohexene to the pressure-resistant polymerization reactor, 0.5 parts by mass of α-methylstyrene dimer was added, and 0.2 parts by mass and α-methylstyrene dimer were added to the second stage and the third stage. In addition to the fact that 0.2 parts by weight were continuously added together with the monomer component, the blending amount of each monomer component and other compounds, the addition time zone, and the reaction temperature were changed to the conditions shown in Table 10. In the same manner as in Example II-1, a copolymer latex II-CE-5 was obtained.

<Evaluation of copolymer latex>
About the copolymer latex obtained above, calculation of the detected acid amount A, theoretical acid amount B and internal acid ratio (%), adhesion of coagulum, and evaluation of tensile stress were performed according to the following methods.

[Detected acid amount A]
An excess amount of about 0.1N hydrochloric acid was added to the copolymer latex diluted to about 1% by mass with ion-exchanged water, and then back titrated with a 0.1N aqueous sodium hydroxide solution to obtain a conductive titration curve. . From the obtained conductivity titration curve, the total amount of acidic groups per milligram of the copolymer latex (100 milligrams / 100 g of copolymer latex solids) was calculated according to the following formula.
Detected acid amount A = 0.1 × T × 100 / (W × M / 100)
T: titration amount of aqueous sodium hydroxide solution (mL)
W: Sampling amount of copolymer latex (g)
M: solid content concentration of copolymer latex (%)

[Theoretical acid amount B]
The blending ratio of the ethylenically unsaturated carboxylic acid monomer to the total amount of the monomer components constituting the copolymer is X (mass%), the molecular weight of the ethylenically unsaturated carboxylic acid monomer is Y, and the ethylenically unsaturated carboxylic acid The maximum dissociation frequency of the acid monomer was Z, and the theoretical acid amount derived from the ethylenically unsaturated carboxylic acid monomer was calculated from the following formula (1).
Theoretical acid amount = (X × Z × 1000) / Y (1)
For all the ethylenically unsaturated carboxylic acid monomers blended, the theoretical acid amount is calculated in the same manner, and these are summed to obtain the theoretical acid amount B (milli equivalent / 100 g per 100 g of the solid content of the copolymer latex). )

In addition, when an additive having an acidic group such as a dispersant mainly composed of polycarboxylic acid is used, the theoretical acid amount derived from the additive having an acidic group is calculated in the same manner as described above. Totaled.
When (CH ₂ CHCOONa) _n is blended as a dispersant, in Formula (1), X is the blending ratio (mass%) of the dispersant with respect to the total amount of monomer components constituting the copolymer, and Y is dispersed The molecular weight of the dispersant monomer (n = 1) was used, and Z was the valence of the dispersant monomer (n = 1).

[Internal acid ratio (%)]
Based on the value of the detected acid amount A and the theoretical acid amount B, the internal acid ratio (%) was calculated according to the following formula (4).
Internal acid ratio (%) = (1−A / B) × 100 (4)

[Evaluation of adhesion of coagulum]
In the examples and comparative examples described above, after completion of the polymerization reaction, the pH of the reaction product was adjusted to 6.0 using sodium hydroxide, and then the entire copolymer latex was discharged from the lower part of the reactor. Thereafter, the inside of the reactor was filled with ion-exchanged water, and after stirring for 10 minutes, the entire amount of ion-exchanged water was again discharged from the lower part of the reactor. The coagulum was adhered to the inner wall of the pressure-resistant polymerization container after discharge (SUS-made vessel 100L) was visually observed, calculates the ratio S / S ₀ of the clot adhesion area S with respect to the inner wall of the reactor area S ₀ And evaluated according to the following criteria.
A: S / S ₀ <0.1
B: 0.1 ≦ S / S ₀ ≦ 0.3
C: _S / _S 0> 0.3

[Tensile stress]
Using the copolymer latex, a latex film having a thickness of 0.3 to 0.5 mm was prepared by the following procedure. First, the copolymer latex was adjusted to pH 10 with sodium hydroxide, and sodium polyacrylate (made by Daiichi Kogyo Seiyaku Co., Ltd., trade name: IX-1177, weight average molecular weight: 7 to 8 million) as a thickener. Was added at a solid content ratio of 1% by mass or less to adjust the viscosity to prepare a coating solution. Here, the amount of sodium polyacrylate added was adjusted as appropriate so that the viscosity of the coating solution was such that a latex film having a thickness of 0.3 to 0.5 mm could be produced within a range not exceeding the above upper limit. .
The obtained coating solution was thinned with a film applicator and allowed to dry for 48 hours under conditions of 23 ° C. and 50% RH. In the case where a continuous film of latex cannot be obtained under the above drying conditions, the temperature is 20 ° C. higher than the minimum film-forming temperature of the latex measured according to the method of JIS K6828-2, and the condition is 50% RH for 48 hours. Allowed to dry. Further, the dried thin film was subjected to heat treatment in an oven set at 130 ° C. for 15 minutes to obtain a latex film having a thickness of 0.3 mm to 0.5 mm. The obtained latex film was punched into the shape and dimensions of a dumbbell-shaped No. 3 described in JIS K-6251 except for the thickness to obtain a test piece. After leaving this test piece for 24 hours in a desiccator, using a tensile compression tester (trade name: TechnoGraph TGE-5kN) manufactured by Minebea Co., Ltd., stress and elongation (when tested at a pulling speed of 500 mm / min) Displacement) was measured. From the measurement results, the tensile stress at the time of cutting was determined and shown in Table 12. The test conditions are as follows.

(Test conditions, etc.)
Distance between chucks: 50mm
Test force capacity: 5kN
Test temperature: 23 ° C., 50% RH
Elongation rate: Expressed as a ratio (%) to the initial value based on the distance between marked lines of the dumbbell-shaped No. 3
Stress: According to definitions of terms described in JIS K-6251. The unit is MPa.
Tensile stress at cutting: The tensile force recorded when the specimen is cut divided by the initial cross-sectional area of the specimen.

(Evaluation of aggregate of battery electrode composition)
In each battery electrode composition (each positive electrode composition and each negative electrode composition) obtained as described above, a value according to JIS K5701-1 was measured using a particle size gauge (M100 type manufactured by Toyo Seiki Seisakusho). Was evaluated as follows. The results are shown in Table 12.
A (the occurrence of aggregates is small): The numerical value at which three or more trajectories of particles of 10 mm or more appear is 40 μm or less.
C (Many agglomerates are generated): A numerical value in which three or more trajectories of grains of 10 mm or more appear exceeds 40 μm.

(Evaluation of coverage of copolymer latex on active material)
Since the cycle characteristics upon repeated charge / discharge are improved by coating the surface of the active material more with the copolymer latex, in each negative electrode sheet obtained by the above method, copolymerization is performed by the following method. The coverage of the combined latex on the active material was evaluated.
That is, each negative electrode sheet (before rolling) obtained above was cut into a 1 cm square, dyed in an osmium tetroxide atmosphere, and then used with a scanning electron microscope (trade name: JSM-6510LA, manufactured by JEOL Ltd.). And observed at 5000 times. In the SEM observation image, the area where the copolymer latex was adhered on the active material was visually confirmed with respect to the area of the active material, and evaluated as follows. Of the 8 SEM observation images, the average image was selected and evaluated. The results are shown in Table 12.
A: Copolymer latex covers 80% or more of the surface of the active material.
B: Copolymer latex covers 60% or more and less than 80% of the surface of the active material.
C: Copolymer latex covers 40% or more and less than 60% of the surface of the active material.
D: Less than 40% of the surface of the active material is coated with the copolymer latex.

It was confirmed that the copolymer latex obtained in Examples II-1 to II-10 showed less adhesion of coagulum and sufficient tensile stress at the time of cutting. Further, as is apparent from the results shown in Table 12, the copolymer latex obtained in Examples II-1 to II-11 was agglomerated of the composition for battery electrodes even in evaluation for battery electrodes. It was confirmed that the material has good electrode active material coverage.

<Third embodiment>
<Manufacture of copolymer latex>
The materials shown in Tables 13 to 15 were mixed in the amounts shown in the same table (unit: parts by mass) and reacted to synthesize copolymer latex. A specific synthesis procedure is shown below.

The components and symbols in Tables 13 to 15 are the same as the components and symbols in Tables 2 to 5.

Example III-1
Into a pressure-resistant polymerization reaction vessel, 10 parts by mass of cyclohexene and each monomer component and other compounds in the blending amount (parts by mass) shown in the first stage of Table 13 were added and stirred sufficiently to obtain a reaction solution. .

Next, the temperature in the polymerization tank was raised, and the time when the polymer conversion rate of the reaction system reached 1.0% was regarded as reaching time, and after 85 minutes from this reaching time as a reference (0 minutes), Each monomer component and other compounds in the blending amount (parts by mass) shown in the second stage are added to the continuous time zone shown in the second stage of Table 13 (from 85 minutes to 220 minutes after reaching the standard). Was added to the reaction solution. The reaction temperature of the polymerization system was 65 ° C.

Subsequently, each monomer component and other compounds in the blending amounts (parts by mass) shown in the third row of Table 13 were added to the continuous addition time zone shown in the third row of Table 13 (after 220 minutes on the basis of arrival time). (Until 490 minutes later).

After the addition of the entire amount of monomer components was completed, the temperature in the polymerization tank was raised to 85 ° C. and maintained at 85 ° C. After confirming that the polymer conversion rate exceeded 97% from the amount of heat of cooling the polymerization tank, the polymerization was terminated and a reaction product was obtained.

After completion of the polymerization reaction, the pH of the reaction product was adjusted to 6.5 using sodium hydroxide. Subsequently, in order to remove unreacted monomers and other low-boiling compounds, the reaction product was subjected to heating under reduced pressure to obtain a copolymer latex III-A.

Examples III-2 to III-11
A copolymer latex III- was prepared in the same manner as in Example III-1, except that the amount of each monomer component and other compounds, addition time zone, and reaction temperature were changed to the conditions shown in Table 13 or 14. B to III-K were obtained respectively.

(Comparative Examples III-1 to III-4, III-6, III-7)
Copolymer latex III-, as in Example III-1, except that the blending amounts of each monomer component and other compounds, the addition time zone, and the reaction temperature were changed to the conditions shown in Table 14 or 15. CE-1 to III-CE-4, III-CE-6, and III-CE-7 were obtained, respectively.

(Comparative Example III-5)
Instead of adding 10 parts by mass of cyclohexene to the pressure-resistant polymerization reactor, 0.5 parts by mass of α-methylstyrene dimer was added, and 0.2 parts by mass and α-methylstyrene dimer were added to the second stage and the third stage. In addition to the fact that 0.2 parts by weight were continuously added together with the monomer component, the blending amount of each monomer component and other compounds, the addition time zone, and the reaction temperature were changed to the conditions shown in Table 15. In the same manner as in Example III-1, copolymer latex III-CE-5 was obtained.

<Evaluation of copolymer latex>
About the copolymer latex obtained above, according to the following method, the left side of the above formula (1): [ΔH × (100 / 100−C _S )] / ΔH _W , amount of antifreeze water (%), latex viscosity, Evaluation of freezing stability was performed.

(Calculation of [ΔH × (100 / 100−C _S )] / ΔH _W and amount of antifreeze water (%))
The copolymer latex was adjusted to pH 7 and solid content of 40% by mass using pure water and sodium hydroxide to prepare a measurement sample. The prepared measurement sample was packed in an aluminum pan, set in a differential scanning calorimeter (DSC6200: manufactured by Seiko Instruments Inc.), the temperature was set to −25 ° C., and the temperature was raised to 30 ° C. at a rate of 1 ° C./min. A DSC curve was obtained. The heat of fusion ΔH (mJ / mg) from −20 ° C. to 0 ° C. was calculated from the obtained DSC curve. Similarly, heat of fusion ΔH _W (mJ / mg) for water was calculated. _{[ΔH × (100/100-} C S)] / indicate [Delta] H _W values of the respective table 18. The DSC curves obtained for the copolymer latexes of Example III-1, Example III-3 and Comparative Example III-1 are shown in FIGS. 1, 2 and 3, respectively.

From the obtained value, the ratio (mass%) of the amount of antifreeze water to the total amount of water was determined by the following formulas (A), (B), (C) and (D). The results are shown in Table 18, respectively.
Formula (A): Total amount of bound water and free water (mg) = [ΔH (mJ / mg) × mass of measurement sample (mg)] / ΔH _W (mJ / mg)
Formula (B): Total water content in measurement sample (mg) = mass of measurement sample (mg) × (100−C _S ) / 100
Formula (C): Amount of antifreeze water (mg) = total water amount in measurement sample (mg) −total amount of combined water and free water (mg)
Formula (D): Ratio of antifreeze water amount to total water amount (mass%) = antifreeze water amount (mg) × 100 / total water amount in measurement sample (mg)

<Evaluation of freezing stability>
Pure water was added to the copolymer latex to prepare a solid concentration of 40% by mass, pH 7, and a liquid temperature of 25 ° C. The pH of the latex was adjusted with a pH adjuster such as sodium hydroxide or hydrochloric acid as necessary. To a 50 mL poly beaker, 25 mL of the adjusted solution was added and placed in a freezer adjusted to −20 ° C. and frozen for 2 hours. Then, it thawed at room temperature of 25 degreeC over 3 hours. The thawed solution was visually observed and determined as follows.
A: There is no aggregate.
B: Although there is no aggregate, it is thickening.
C: Aggregates are generated.
D: Solidified and does not flow.

(Latex viscosity)
Aron (registered trademark) T-50 (trade name, sodium polyacrylate, weight average molecular weight: 6000) manufactured by Toagosei Co., Ltd. as a dispersant was uniformly 2.5 with respect to 100 parts by mass of the solid content of the copolymer latex. After the addition of parts by mass (in terms of solid content), the solid content was adjusted to 50.0% by mass with pure water, pH 6.5, and the liquid temperature was adjusted to 25 ° C. The pH of the latex was adjusted with a pH adjuster such as sodium hydroxide or hydrochloric acid as necessary. The viscosity of the copolymer latex after adjustment was measured 1 minute after the start of rotation at a rotation speed of 60 rpm using a B-type (BL type) viscometer according to the measurement method of JIS K7117-1. About the obtained viscosity, it determined as follows. The lower the viscosity, the better.
A: 400 mPa · s or less B: More than 400 1000 mPa · s or less C: 1000 mPa · s or less

(Preparation of composition for paper coating)
A paper coating composition was prepared according to the formulation shown below. The paper coating composition was adjusted to pH 9.5 with sodium hydroxide, and the solid content concentration was adjusted to 67% by mass by adding a necessary amount of pure water.
(Combination prescription)
Kaolin (product name: DB Glaze, manufactured by Imerizu Minerals Japan Co., Ltd.) 20 parts by weight heavy calcium carbonate (product name: Carbital 90, manufactured by Imeris Minerals Japan Co., Ltd.) 80 parts by weight modified starch (Japanese food) Kako Co., Ltd., trade name: MS4600) 2 parts by weight of copolymer latex 6 parts by weight (in terms of solid content)

(Creating coated paper)
The coating base paper (basis weight 55g / m ^2), after the coated amount per one surface of the above paper coating composition was coated and dried by using a wire bar such that the 10 g / m ^2, line A calender treatment was performed under the conditions of a pressure of 60 kg / cm and a temperature of 50 ° C. to obtain a coated paper. About the obtained coated paper, dry pick strength was evaluated by the following method.

<Calculation of solubility parameter of monomer component>
Solubility parameter SP ₁ by the Fedors method of monomer components other than the ethylenically unsaturated carboxylic acid monomer introduced into the reaction system by the end of the introduction of the entire amount of the ethylenically unsaturated carboxylic acid monomer, and the ethylene system a solubility parameter SP ₂ by the Fedors method of the monomer component other than the unsaturated carboxylic acid monomer described above is introduced into the reaction system ethylenically unsaturated carboxylic acid monomer later than at the total amount charged completion of the above formula Using (2), calculation was performed as follows. Table 18 shows values of SP ₁ , SP ₂ , and | SP ₁ -SP ₂ |.

For example, in the case of Example III-1, monomer components other than the ethylenically unsaturated carboxylic acid monomer charged into the reaction system by the end of the total amount of the ethylenically unsaturated carboxylic acid monomer are butadiene 18 parts by mass, 14 parts by mass of styrene, and 8 parts by mass of acrylonitrile, and a unit other than the ethylenically unsaturated carboxylic acid monomer introduced into the reaction system after the completion of the entire introduction of the ethylenically unsaturated carboxylic acid monomer. The monomer component is 24 parts by mass of butadiene, 19 parts by mass of styrene, and 11 parts by mass of acrylonitrile.
SP ₁ is [{(4420 × 18/54) + (9630 × 14/104) + (8100 × 8/53)} / {(59.2 × 18/54) + (86.5 × 14/104). ) + (39.1 × 8/53)}] ^1/2 = 10.35.
SP ₂ is [{(4420 × 24/54) + (9630 × 19/104) + (8100 × 11/53)} / {(59.2 × 24/54) + (86.5 × 19/104). ) + (39.1 × 11/53)}] ^1/2 = 10.37.
The difference between SP ₁ and SP ₂ is 0.02 in absolute value.

(Evaluation of coverage of copolymer latex on active material)
Since the cycle characteristics upon repeated charge / discharge are improved by coating the surface of the active material more with the copolymer latex, in each negative electrode sheet obtained by the above method, copolymerization is performed by the following method. The coverage of the combined latex on the active material was evaluated.
That is, each negative electrode sheet (before rolling) obtained above was cut into a 1 cm square, dyed in an osmium tetroxide atmosphere, and then used with a scanning electron microscope (trade name: JSM-6510LA, manufactured by JEOL Ltd.). And observed at 5000 times. In the SEM observation image, the area where the copolymer latex was adhered on the active material was visually confirmed with respect to the area of the active material, and evaluated as follows. Of the 8 SEM observation images, the average image was selected and evaluated. The results are shown in Table 18.
A: Copolymer latex covers 80% or more of the surface of the active material.
B: Copolymer latex covers 60% or more and less than 80% of the surface of the active material.
C: Copolymer latex covers 40% or more and less than 60% of the surface of the active material.
D: Less than 40% of the surface of the active material is coated with the copolymer latex.

(Evaluation of peel strength of electrode coating layer)
Each negative electrode sheet obtained by the above method was cut into a strip of 7 cm × 2 cm, a cellophane adhesive tape was attached to the coating layer side, and the coating layer and the current collector were peeled off by about 5 mm by hand. The current collector of the peeled part was fixed to a tensile tester, and the stress applied to peeling when the cellophane adhesive tape was pulled in the direction perpendicular to the peeling surface was measured. The tensile rate was 100 mm / min, and the average value (unit (N / m)) of n = 3 is shown in Table 18. A larger numerical value indicates a better binding force at the interface between the current collector of the negative electrode sheet and the coating layer.

It was confirmed that the copolymer latex obtained in Examples III-1 to III-10 was excellent in dry pick strength, low viscosity, and excellent in freeze stability. In addition, the copolymer latex obtained in Examples III-1 to III-11 has good peel strength of the electrode coating layer obtained by applying the composition for battery electrodes and good coverage to the electrode active material. It was confirmed that there was.

Claims

A method for producing a copolymer latex obtained by emulsion polymerization,
The copolymer is
15-60% by weight of aliphatic conjugated diene monomer,
5 to 35% by mass of an ethylenically unsaturated carboxylic acid monomer,
Composed of 0.5 to 30% by mass of vinyl cyanide monomer and 0 to 79.5% by mass of monomer copolymerizable therewith,
The emulsion polymerization,
Into the reaction system at the start of charging the polymerization initiator, 0% by mass to 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer is contained,
From the time point of 5% from the time when the polymer conversion rate of the reaction system reaches 1.0% to the time when the whole amount of the monomer components are charged, the ethylenically unsaturated carboxylic acid unit At least 80% of the total amount of the ethylenically unsaturated carboxylic acid monomer is charged by 80% of the time from the arrival to the end of the addition of the remainder of the monomer. A process for producing a copolymer latex.
The method for producing a copolymer latex according to claim 1, wherein the ethylenically unsaturated carboxylic acid monomer contains a monocarboxylic acid monomer in an amount of more than 30% by mass.
The emulsion polymerization is carried out by charging 80% by mass or more of the total amount of the vinyl cyanide monomer by 60% of the time from the arrival time to the end time. A method for producing a copolymer latex.
A copolymer latex obtained by emulsion polymerization,
The copolymer is
15-60% by weight of aliphatic conjugated diene monomer,
5 to 35% by mass of an ethylenically unsaturated carboxylic acid monomer,
Composed of 0.5 to 30% by mass of vinyl cyanide monomer and 0 to 79.5% by mass of monomer copolymerizable therewith,
From the time when the emulsion polymerization reaches the reaction system at the start of charging the polymerization initiator until the polymer conversion rate of the reaction system has reached 1.0%, the time from the completion of charging the entire amount of the monomer components, From the time point of 5% of the ethylenically unsaturated carboxylic acid monomer, the addition of the remainder of the ethylenically unsaturated carboxylic acid monomer is started until the time point of 80% of the time from the arrival time to the end time. It is carried out by charging 92% by mass or more of the total amount of the saturated carboxylic acid monomer,
100 g of the solid content of the copolymer latex calculated based on the total amount of acidic groups A (milli equivalents / 100 g) per 100 g of the solid content of the copolymer latex measured by the neutralization titration method and the blending amount of the acid component. Copolymer latex in which the ratio A / B to the total acidic group amount B (milli equivalent / 100 g) is 0.8 or less.
The copolymer latex according to claim 4, wherein the ethylenically unsaturated carboxylic acid monomer contains more than 30% by mass of a monocarboxylic acid monomer.
The emulsion polymerization is carried out by charging 80% by mass or more of the total amount of the vinyl cyanide monomer by 60% of the time from the arrival time to the end time. The copolymer latex described.
A copolymer latex obtained by emulsion polymerization,
The copolymer is
15-60% by weight of aliphatic conjugated diene monomer,
5 to 35% by mass of an ethylenically unsaturated carboxylic acid monomer,
Composed of 0.5 to 30% by mass of vinyl cyanide monomer and 0 to 79.5% by mass of monomer copolymerizable therewith,
In the emulsion polymerization, the reaction system at the start of addition of the polymerization initiator contains 0% by mass to 40% by mass or less of the total amount of the ethylenically unsaturated carboxylic acid monomer, and the polymer conversion rate of the reaction system is 1 Addition of the remainder of the ethylenically unsaturated carboxylic acid monomer is started after 5% from the time when it reaches 0.0% to the time when the whole amount of the monomer components is finished. Then, by 80% of the time from the arrival time to the end time, 92% by mass or more of the total amount of the ethylenically unsaturated carboxylic acid monomer is charged,
By differential scanning calorimetry, the heat of fusion ΔH (from −20 ° C. to 0 ° C. calculated from the DSC curve obtained when the copolymer latex cooled to −25 ° C. was heated at a rate of temperature increase of 1 ° C./min. mJ / mg) copolymer latex satisfying the following formula (2).
[ΔH × (100 / 100−C S )] / ΔH W ≦ 0.8 (2)
[Wherein (2), C S represents the solid content of the sample of the copolymer latex (weight%), [Delta] H W is heat of fusion (mJ / mg) when the distilled water was measured under the same conditions Indicates. ]
The copolymer latex according to claim 7, wherein the ethylenically unsaturated carboxylic acid monomer contains more than 30% by mass of a monocarboxylic acid monomer.
Solubility parameter by Fedors method of monomer components other than the ethylenically unsaturated carboxylic acid monomer charged into the reaction system by the end of the emulsion polymerization when the whole amount of the ethylenically unsaturated carboxylic acid monomer is charged SP 1 and the solubility of monomer components other than the ethylenically unsaturated carboxylic acid monomer introduced into the reaction system after the end of the introduction of the entire amount of the ethylenically unsaturated carboxylic acid monomer by the Fedors method The process is carried out by introducing the monomer component into the reaction system so that the difference between SP 1 and SP 2 is 1.50 or less in absolute value when the parameter is SP 2. 8. Copolymer latex according to 8.