Conductive agent dispersion

Abstract

In this conductive agent dispersion containing a polymer (A), a carbon-based conductive agent (B), and a liquid medium (C), the polymer (A) includes a repeating unit (a1) derived from an aromatic vinyl compound and a repeating unit (a2) derived from an unsaturated carboxylic acid ester compound. The content of the repeating unit (a1) is 1-50 mass% relative to the total amount of the repeating units included in the polymer (A), and the content of the repeating unit (a2) is 20-75 mass% relative to the total amount of the repeating units included in the polymer (A). The viscosity measured at 25°C of a polymer solution obtained by dissolving the polymer (A) in N-methyl-2-pyrrolidone such that the solid content concentration is 8 mass% is 300-5,000 mPa・s.

Description

Conductive agent dispersion

[0001] [Cross-reference to related applications] This application claims priority to Japanese Patent Application No. 2023-203856, filed December 1, 2023, the entire contents of which are incorporated herein by reference. The present disclosure relates to a conductive agent dispersion, and more particularly to a conductive agent dispersion in which a carbon-based conductive agent is dispersed in a liquid medium.

[0002] Carbon-based conductive agents such as carbon nanotubes (hereinafter also referred to as "CNTs"), carbon nanofibers, furnace black, and acetylene black are lightweight and strong materials that have excellent electrical and thermal conductivity, mechanical properties, etc. Carbon-based conductive agents with such excellent properties are expected to be used in a wide range of industrial applications.

[0003] Carbon-based conductive agents generally have high cohesion and poor dispersibility. However, when the carbon-based conductive agent aggregates during application, its excellent properties cannot be fully utilized. Therefore, conventional methods involve preparing a suspension (slurry) in which the carbon-based conductive agent is dispersed in a liquid medium, applying the suspension containing the carbon-based conductive agent to a substrate, and then removing the liquid medium, or mixing the suspension directly with a matrix material (e.g., resin, rubber, etc.).

[0004] Various methods have been proposed for dispersing a carbon-based conductive agent in a liquid medium, including adding a polymer as a dispersant to the liquid medium together with the carbon-based conductive agent, thereby improving the dispersibility of the carbon-based conductive agent in the liquid medium (see, for example, Patent Document 1). Patent Document 1 discloses that the dispersibility of the conductive agent is improved by preparing a dispersion containing a conductive agent, a liquid medium, and a polyimide or the like having a steroid structure or a mesogenic structure.

[0005] Japanese Patent Application Laid-Open No. 2022-116646

[0006] Increasing the dispersibility of carbon-based conductive agents and maximizing the various properties of carbon-based conductive agents in various applications is considered important in developing products that use carbon-based conductive agents.

[0007] The present disclosure has been made to solve the above-mentioned problems, and a main object of the present disclosure is to provide a conductive agent dispersion liquid that has excellent dispersibility of a carbon-based conductive agent.

[0008] According to one aspect of the present disclosure, there is provided a conductive agent dispersion comprising a polymer (A), a carbon-based conductive agent (B), and a liquid medium (C), wherein the polymer (A) comprises a repeating unit (a1) derived from an aromatic vinyl compound and a repeating unit (a2) derived from an unsaturated carboxylic acid ester compound, the content of the repeating unit (a1) being 1 to 50 mass% relative to the total amount of repeating units contained in the polymer (A), and the content of the repeating unit (a2) being 20 to 75 mass% relative to the total amount of repeating units contained in the polymer (A), and the polymer (A) being dissolved in N-methyl-2-pyrrolidone to a solids concentration of 8 mass%, and the viscosity of a polymer solution measured at 25°C is 300 to 5,000 mPa s.

[0009] According to the present disclosure, a conductive agent dispersion liquid having excellent dispersibility of a carbon-based conductive agent can be obtained.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present invention is not limited to the following embodiments, and should be understood to include various modifications that are implemented within the scope of the present invention.

[0011] In this specification, "(meth)acrylamide" is a term that encompasses "acrylamide" and "methacrylamide," and "(meth)acrylic acid" is a term that encompasses "acrylic acid" and "methacrylic acid." "(meth)acrylate" is a term that encompasses "acrylate" and "methacrylate." A numerical range described as "X to Y" is interpreted as a range that includes numerical value X as the lower limit and numerical value Y as the upper limit.

[0012] The conductive agent dispersion of the present disclosure is a dispersion in which a carbon-based conductive agent is dispersed in a liquid medium. The conductive agent dispersion of the present disclosure contains a polymer (hereinafter also referred to as "polymer (A)") including a repeating unit derived from an aromatic vinyl compound and a repeating unit derived from an unsaturated carboxylic acid ester compound, a carbon-based conductive agent, and a liquid medium. Each component contained in the conductive agent dispersion of the present disclosure will be described in detail below.

[0013] <Polymer (A)> The polymer (A) is a component that improves the dispersibility of the carbon-based conductive agent in a liquid medium. Carbon-based conductive agents have high cohesive force (van der Waals forces) and are difficult to uniformly disperse in a liquid medium. Furthermore, if the dispersion state of the carbon-based conductive agent is not good, there is a concern that the various properties of the conductive agent will not be fully exhibited in an article obtained using the conductive agent dispersion. In this regard, the conductive agent dispersion of the present disclosure contains the polymer (A) together with the carbon-based conductive agent, thereby achieving excellent dispersibility of the carbon-based conductive agent in a liquid medium.

[0014] The polymer (A) contains a repeating unit derived from an aromatic vinyl compound (hereinafter also referred to as "repeating unit (a1)") and a repeating unit derived from an unsaturated carboxylic acid ester compound (hereinafter also referred to as "repeating unit (a2)"). In addition to the repeating unit (a1) and the repeating unit (a2), the polymer (A) may further contain a repeating unit different from the repeating unit (a1) and the repeating unit (a2) (hereinafter also referred to as "other repeating unit").

[0015] (Repeating Unit (a1)) Examples of aromatic vinyl compounds that provide the repeating unit (a1) include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 4-tert-butylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, vinyltoluene, 4-ethylstyrene, chlorostyrene, and divinylbenzene. Of these, styrene is particularly preferred as the aromatic vinyl compound that provides the repeating unit (a1). The aromatic vinyl compounds that provide the repeating unit (a1) may be of one type or two or more types.

[0016] The content of the repeating unit (a1) in the polymer (A) is 1 to 50% by mass, based on the total amount (100% by mass) of repeating units contained in the polymer (A). If the content of the repeating unit (a1) in the polymer (A) is less than 1% by mass or more than 50% by mass, the polymers (A) tend to aggregate together in a dispersion containing the carbon-based conductive agent and the polymer (A), resulting in a deterioration in the dispersibility of the carbon-based conductive agent. From the viewpoint of suppressing fusion between the polymers (A) and improving the dispersibility of the carbon-based conductive agent, the content of the repeating unit (a1) is preferably 15% by mass or more, more preferably 20% by mass or more, based on the total amount of repeating units contained in the polymer (A). Furthermore, the content of the repeating unit (a1) is preferably 45% by mass or less, more preferably 40% by mass or less, based on the total amount of repeating units contained in the polymer (A).

[0017] The preferred range of the content of the repeating unit (a1) in the polymer (A) can be determined by appropriately combining the above-mentioned upper and lower limits. Specifically, the content of the repeating unit (a1) is preferably 15 to 50 mass%, more preferably 15 to 45 mass%, and even more preferably 20 to 40 mass%, based on the total amount of repeating units contained in the polymer (A).

[0018] (Repeating Unit (a2)) Examples of unsaturated carboxylic acid ester compounds that provide the repeating unit (a2) include (meth)acrylic acid ester compounds, itaconic acid ester compounds, fumaric acid ester compounds, maleic acid ester compounds, etc. Of these, the unsaturated carboxylic acid ester compound is preferably one or more selected from the group consisting of (meth)acrylic acid ester compounds and itaconic acid ester compounds.

[0019] Examples of the (meth)acrylic acid ester compound include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, ethylene glycol di(meth)acrylate, and propylene glycol di(meth)acrylate. Examples of the copolymer include ethanol, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, glycerin mono(meth)acrylate, and glycerin di(meth)acrylate.

[0020] Specific examples of the itaconate ester compound include dimethyl itaconate, diethyl itaconate, dipropyl itaconate, dibutyl itaconate, etc. The unsaturated carboxylic acid ester compound that provides the repeating unit (a2) may be one type or two or more types.

[0021] The unsaturated carboxylic acid ester compound that gives the repeating unit (a2) has neither a carboxy group nor a sulfonic acid group. In this specification, a repeating unit derived from an unsaturated carboxylic acid ester compound having a carboxy group (e.g., an unsaturated dicarboxylic acid monoester) is classified as a repeating unit (a3). Furthermore, a repeating unit derived from an unsaturated carboxylic acid ester compound having a sulfonic acid group (e.g., sulfoethyl (meth)acrylate) is classified as a repeating unit (a5).

[0022] The unsaturated carboxylic acid ester compound that provides the repeating unit (a2) is preferably at least one selected from the group consisting of chain unsaturated carboxylic acid ester compounds and alicyclic unsaturated carboxylic acid ester compounds, and more preferably at least one selected from the group consisting of alkyl (meth)acrylates, alicyclic esters of (meth)acrylic acid, hydroxyalkyl (meth)acrylates, and dialkyl itaconates. Specifically, it is preferably at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, ethylene glycol di(meth)acrylate, 2-hydroxyethyl (meth)acrylate, dimethyl itaconate, diethyl itaconate, and dibutyl itaconate.

[0023] The content of the repeating unit (a2) in the polymer (A) is 20 to 75 mass% based on the total amount of repeating units contained in the polymer (A). If the content of the repeating unit (a2) in the polymer (A) is less than 20 mass% or more than 75 mass%, the affinity between the polymer (A) and the liquid medium cannot be sufficiently ensured, and as a result, the dispersibility of the carbon-based conductive agent is likely to deteriorate. From the viewpoint of improving the affinity between the polymer (A) and the liquid medium and enhancing the dispersibility of the carbon-based conductive agent in the liquid medium, the content of the repeating unit (a2) is preferably 23 mass% or more, more preferably 25 mass% or more, based on the total amount of repeating units contained in the polymer (A). Furthermore, the content of the repeating unit (a2) is preferably 70 mass% or less, more preferably 65 mass% or less, based on the total amount of repeating units contained in the polymer (A).

[0024] The preferred range of the content of the repeating unit (a2) in the polymer (A) can be determined by appropriately combining the above-mentioned upper and lower limits. Specifically, the content of the repeating unit (a2) is preferably 23 to 75 mass%, more preferably 23 to 70 mass%, and even more preferably 25 to 65 mass%, based on the total amount of repeating units contained in the polymer (A).

[0025] (Other Repeating Units) The other repeating units that may be contained in the polymer (A) are not particularly limited, as long as they are derived from a monomer copolymerizable with the aromatic vinyl compound that provides the repeating unit (a1) and the unsaturated carboxylic acid ester compound that provides the repeating unit (a2). Specific examples of the other repeating units include a repeating unit derived from an unsaturated carboxylic acid (hereinafter also referred to as "repeating unit (a3)"), a repeating unit derived from an α,β-unsaturated nitrile compound (hereinafter also referred to as "repeating unit (a4)"), a repeating unit derived from a compound having a sulfonic acid group (hereinafter also referred to as "repeating unit (a5)"), a repeating unit derived from (meth)acrylamide (hereinafter also referred to as "repeating unit (a6)"), and a repeating unit derived from a conjugated diene compound (hereinafter also referred to as "repeating unit (a7)").

[0026] Repeating Unit (a3) ​​Examples of unsaturated carboxylic acids that give the repeating unit (a3) ​​include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; and dicarboxylic acid monoesters such as maleic acid monoester, fumaric acid monoester, and itaconic acid monoester. Examples of unsaturated carboxylic acid anhydrides that give the repeating unit (a3) ​​include the anhydrides of the dicarboxylic acids exemplified above. The unsaturated carboxylic acids and unsaturated carboxylic acid anhydrides that give the repeating unit (a3) ​​may be one type or two or more types.

[0027] Of these, the unsaturated carboxylic acid or unsaturated carboxylic acid anhydride that provides the repeating unit (a3) ​​is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate.

[0028] When the repeating unit (a3) ​​is introduced into the polymer (A), the content of the repeating unit (a3) ​​in the polymer (A) is preferably 10% by mass or less, based on the total amount of repeating units contained in the polymer (A). By setting the proportion of the repeating unit (a3) ​​in the polymer (A) within the above range, the dispersibility of the carbon-based conductive agent tends to be improved. From the viewpoint of improving the dispersibility of the carbon-based conductive agent, the proportion of the repeating unit (a3) ​​is more preferably 0.5 to 10% by mass, based on the total amount of repeating units contained in the polymer (A). Furthermore, the proportion of the repeating unit (a3) ​​is more preferably 0.7% by mass or more, and even more preferably 1% by mass or more, based on the total amount of repeating units contained in the polymer (A). Furthermore, the proportion of the repeating unit (a3) ​​is more preferably 8% by mass or less, and even more preferably 7% by mass or less, based on the total amount of repeating units contained in the polymer (A).

[0029] Repeating Unit (a4) Examples of α,β-unsaturated nitrile compounds that give the repeating unit (a4) include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, isopropylidenemalononitrile (vinylidene cyanide), fumaronitrile, and tetracyanoethylene. The α,β-unsaturated nitrile compounds that give the repeating unit (a4) may be one type or two or more types. From the viewpoint of easy availability, the α,β-unsaturated nitrile compound that gives the repeating unit (a4) preferably contains one or both of acrylonitrile and methacrylonitrile, and more preferably contains acrylonitrile.

[0030] When the repeating unit (a4) is introduced into the polymer (A), the content of the repeating unit (a4) in the polymer (A) is preferably 5 to 40 mass% based on the total amount of repeating units contained in the polymer (A). By setting the proportion of the repeating unit (a4) in the polymer (A) within the above range, the affinity between the polymer (A) and the liquid medium can be improved, and as a result, the dispersibility of the carbon-based conductive agent tends to be improved. From the viewpoint of improving the dispersibility of the carbon-based conductive agent, the proportion of the repeating unit (a4) is more preferably 6 mass% or more, and even more preferably 7 mass% or more, based on the total amount of repeating units contained in the polymer (A). Furthermore, the proportion of the repeating unit (a4) is more preferably 37 mass% or less, and even more preferably 35 mass% or less, based on the total amount of repeating units contained in the polymer (A).

[0031] Repeating Unit (a5) Examples of compounds having a sulfonic acid group that provide the repeating unit (a5) (hereinafter also referred to as "sulfonic acid group-containing compounds") include compounds having a sulfonic acid group such as vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, sulfoethyl (meth)acrylate, sulfopropyl (meth)acrylate, sulfobutyl (meth)acrylate, 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid, as well as alkali salts thereof. The sulfonic acid group-containing compounds that provide the repeating unit (a5) may be of one type or two or more types.

[0032] The sulfonic acid group-containing compound that gives the repeating unit (a5) is preferably at least one selected from the group consisting of vinyl monomers and styrene monomers, more specifically, at least one selected from the group consisting of vinyl sulfonic acid, styrene sulfonic acid, and allyl sulfonic acid.

[0033] When the repeating unit (a5) is introduced into the polymer (A), the content of the repeating unit (a5) in the polymer (A) is preferably 0.1 to 10 mass% relative to the total amount of repeating units contained in the polymer (A). By setting the proportion of the repeating unit (a5) in the polymer (A) within the above range, the dispersibility of the carbon-based conductive agent tends to be improved. From the viewpoint of improving the dispersibility of the carbon-based conductive agent, the proportion of the repeating unit (a5) is more preferably 0.2 mass% or more, and even more preferably 0.5 mass% or more, relative to the total amount of repeating units contained in the polymer (A). Furthermore, the proportion of the repeating unit (a5) is more preferably 8 mass% or less, and even more preferably 7 mass% or less, relative to the total amount of repeating units contained in the polymer (A).

[0034] Repeating Unit (a6) Examples of (meth)acrylamide compounds that provide the repeating unit (a6) include acrylamide, methacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, N-methylol acrylamide, N-methylol methacrylamide, diacetone acrylamide, and maleic acid monoamide. The (meth)acrylamide compounds that provide the repeating unit (a6) may be one type or two or more types. Of these, one or both of acrylamide and methacrylamide are preferred as the (meth)acrylamide compound.

[0035] When the repeating unit (a6) is introduced into the polymer (A), the content of the repeating unit (a6) in the polymer (A) is preferably 10% by mass or less, based on the total amount of repeating units contained in the polymer (A). By setting the proportion of the repeating unit (a6) in the polymer (A) within the above range, the dispersibility of the carbon-based conductive agent tends to be improved. From the viewpoint of improving the dispersibility of the carbon-based conductive agent, the proportion of the repeating unit (a5) is more preferably 0.1 to 10% by mass, based on the total amount of repeating units contained in the polymer (A). Furthermore, the proportion of the repeating unit (a5) is more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more, based on the total amount of repeating units contained in the polymer (A). Furthermore, the proportion of the repeating unit (a6) is more preferably 8% by mass or less, and even more preferably 7% by mass or less, based on the total amount of repeating units contained in the polymer (A).

[0036] (Physical Properties of Polymer (A)) Viscosity The polymer (A) is a polymer with a relatively large molecular weight and high viscosity. Specifically, the viscosity of a polymer solution obtained by dissolving the polymer (A) in N-methyl-2-pyrrolidone (NMP) to a solids concentration of 8% by mass, measured at 25°C (hereinafter also referred to as "8% NMP viscosity"), is 300 to 5,000 mPa·s. If the 8% NMP viscosity of the polymer is less than 300 mPa·s or higher than 5,000 mPa·s, the dispersibility of the carbon-based conductive agent will be poor, and the carbon-based conductive agent will become a non-uniform slurry. In terms of being able to sufficiently increase the dispersibility of the carbon-based conductive agent, the 8% NMP viscosity of the polymer (A) is preferably 350 mPa·s or higher, and more preferably 500 mPa·s or higher. The 8% NMP viscosity of the polymer (A) is preferably 4,500 mPa s or less, more preferably 4,000 mPa s or less, as measured at 25°C using a Brookfield viscometer in accordance with JIS Z 8803 2011.

[0037] The preferred range of the 8% NMP viscosity of the polymer (A) can be determined by appropriately combining the above-mentioned upper and lower limits. Specifically, the 8% NMP viscosity of the polymer (A) is preferably 350 to 5,000 mPa s, more preferably 350 to 4,500 mPa s, and even more preferably 500 to 4,000 mPa s.

[0038] Weight-average molecular weight (Mw): The Mw of the polymer (A) is preferably 2,000 to 10,000,000. When the Mw of the polymer (A) is within the above range, the adsorption stability of the polymer (A) to the carbon-based conductive agent can be enhanced, and the dispersibility of the carbon-based conductive agent in the liquid medium can be ensured. This improves the dispersibility of the carbon-based conductive agent in the liquid medium. From the viewpoint of achieving excellent dispersibility of the carbon-based conductive agent, the Mw of the polymer (A) is more preferably 5,000 or more, and even more preferably 50,000 or more. The Mw of the polymer (A) is more preferably 5,000,000 or less, and even more preferably 1,000,000 or less. The Mw of the polymer (A) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0039] Here, the details of the method for measuring the Mw of polymer (A) are as follows. 10 mg of polymer (A) with a solid content concentration of 20% by mass was mixed with 5 mL of THF and left to stand at 25°C for 16 hours. Thereafter, the mixed liquid containing polymer (A) was passed through a 0.45 μm membrane filter to prepare a measurement sample. Next, using the measurement sample, the weight average molecular weight (Mw) of the THF-soluble component was determined by GPC (RI detection) in polystyrene equivalent terms under the following measurement conditions. [Measurement conditions] Temperature: 35°C Solvent: THF Flow rate: 1.0 mL / min Concentration: 0.2% by mass Measurement sample injection amount: 100 μL [Column] Tosoh Corporation's "GPC TSKgel α-2500" (30 cm x 2 columns) was used. Measurement was performed under conditions where the linear correlation equation of Log10 (Mw) - elution time between Mw 1,000 and 20,000,000 was 0.98 or higher.

[0040] (Method for producing polymer (A)) The method for producing polymer (A) is not particularly limited. The method for producing polymer (A) is preferably emulsion polymerization using an aqueous medium as the polymerization medium. Known methods can be applied for emulsion polymerization. Specifically, for example, there is a method in which a monomer is dispersed in an aqueous medium (preferably water) in the presence of an emulsifier, polymerized in the presence of a polymerization initiator, and after a desired polymerization conversion rate is reached, a polymerization terminator is added to terminate the polymerization.

[0041] Examples of emulsifiers include anionic surfactants, nonionic surfactants, and amphoteric surfactants. To obtain a stable emulsion dispersion, anionic surfactants are typically used. Examples of anionic surfactants include salts of long-chain fatty acids having 10 or more carbon atoms, rosinate salts, and linear alkyl group-containing benzenesulfonates. Specific examples include potassium salts and sodium salts of capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, octylbenzenesulfonic acid, dodecylbenzenesulfonic acid, dodecyldiphenyloxidesulfonic acid, and dodecyldiphenyletherdisulfonic acid. Fluorine-based surfactants can also be used. The emulsifiers can be used alone or in combination of two or more.

[0042] As the polymerization initiator, radical polymerization initiators commonly used in emulsion polymerization can be used. Examples of polymerization initiators that can be used include organic peroxides such as benzoyl peroxide, lauroyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, pinane hydroperoxide, paramenthane hydroperoxide, trimethylbicycloheptyl hydroperoxide, di-tert-butyl peroxide, and dicumyl peroxide. Diazo compounds such as azobisisobutyronitrile, inorganic peroxides such as potassium persulfate, and redox catalysts such as combinations of these peroxides with ferrous sulfate can also be used. The polymerization initiators can be used alone or in combination of two or more. The amount of polymerization initiator used is typically 0.01 part by mass or more, and preferably 0.05 to 1.0 part by mass, per 100 parts by mass of the total amount of monomers used in the polymerization.

[0043] During the polymerization, a chain transfer agent may be used to adjust the molecular weight of the polymer (A). Examples of the chain transfer agent include alkyl mercaptans (e.g., tert-dodecyl mercaptan, n-dodecyl mercaptan, etc.), carbon tetrachloride, thioglycols, diterpenes, terpinolene, γ-terpinenes, and α-methylstyrene dimer. The chain transfer agent may be used alone or in combination of two or more. The amount of the chain transfer agent used is usually 0.05 parts by mass or more, and preferably 0.1 to 15 parts by mass, per 100 parts by mass of the total amount of the monomers used in the polymerization.

[0044] During emulsion polymerization, additives may be added as appropriate, such as chelating agents such as sodium ethylenediaminetetraacetate, glycine, and alanine; electrolytes such as potassium chloride, sodium phosphate, potassium phosphate, and potassium sulfate; activators such as sodium formaldehyde sulfoxylate and ferrous sulfate; pH adjusters such as ammonia, sodium hydroxide, and potassium hydroxide; and oxygen removers such as styrenated phenol, hindered phenol, imidazoles, paraphenylenediamine, and sodium hydrosulfite.

[0045] In producing polymer (A) by emulsion polymerization, the polymerization method may be continuous or batchwise. Furthermore, emulsion polymerization to obtain polymer (A) may be carried out as a single-stage polymerization or as a multi-stage polymerization of two or more stages. Polymerization can be carried out using a reactor from which oxygen has been removed, usually at a temperature of 0 to 100°C, preferably 0 to 80°C. The polymerization time is preferably 1 to 36 hours, more preferably 4 to 24 hours. Furthermore, operating conditions such as temperature and stirring can be appropriately changed during the reaction.

[0046] By setting the total solids concentration in the emulsion polymerization to 50% by mass or less, the polymerization reaction can proceed in a state in which the dispersion stability of the particles of the resulting polymer (A) is good. The total solids concentration in the emulsion polymerization is preferably 48% by mass or less, and more preferably 45% by mass or less.

[0047] The polymerization may be terminated by adding a polymerization terminator when a desired polymerization conversion rate is reached. Examples of the polymerization terminator include hydroxylamine compounds such as hydroxylamine and N,N-diethylhydroxylamine; and quinone compounds such as hydroquinone. After the polymerization is terminated, if necessary, unreacted monomers can be removed from the reaction system by a method such as steam distillation, thereby obtaining a latex in which the polymer (A) is dispersed in the dispersion medium.

[0048] After the emulsion polymerization is completed, it is preferable to add a neutralizing agent to the reaction product to adjust the pH to about 4.5 to 10.5, preferably 5 to 10, and more preferably 5.5 to 9.5. Examples of neutralizing agents include metal hydroxides such as sodium hydroxide and potassium hydroxide; ammonia, etc. Setting the pH within the above range improves the stability of the polymer (A). By concentrating the reaction product after the neutralization treatment, it is possible to increase the solids concentration while maintaining the good stability of the polymer (A).

[0049] The polymer (A) can be recovered from the aqueous dispersion of the polymer (A) by a known method, for example, by adding a latex to warm water in which a coagulant is dissolved to cause precipitation, and then recovering the precipitate.

[0050] The content of polymer (A) in the conductive agent dispersion is preferably 50 to 800 parts by mass relative to 100 parts by mass of the total amount of the carbon-based conductive agent contained in the conductive agent dispersion. By setting the content of polymer (A) relative to the carbon-based conductive agent within the above range, the dispersibility of the carbon-based conductive agent can be further improved. From the viewpoint of improving the dispersibility of the carbon-based conductive agent, the content of polymer (A) is more preferably 80 parts by mass or more, and even more preferably 100 parts by mass or more, relative to 100 parts by mass of the total amount of the carbon-based conductive agent contained in the conductive agent dispersion. Furthermore, from the viewpoint of increasing the conductive agent concentration in the conductive agent dispersion as much as possible while maintaining good dispersibility of the carbon-based conductive agent, the content of polymer (A) is more preferably 700 parts by mass or less, and even more preferably 650 parts by mass or less, relative to 100 parts by mass of the total amount of the carbon-based conductive agent contained in the conductive agent dispersion.

[0051] <Carbon-based conductive agent> The carbon-based conductive agent (hereinafter also referred to simply as "conductive agent (B)") contained in the conductive agent dispersion liquid of the present disclosure may be any material mainly composed of carbon, and its type, shape, size, etc. are not particularly limited. Examples of the conductive agent (B) include carbon nanotubes (CNT), carbon nanofibers (CNF), acetylene black, ketjen black, furnace black, graphite, graphene, fullerene, carbon nanohorns, activated carbon, and carbon fibers.

[0052] Among these, the conductive agent (B) is preferably at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, furnace black, and acetylene black, and more preferably at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, and acetylene black. Furthermore, one or both of carbon nanotubes and carbon nanofibers are more preferred, and carbon nanotubes are particularly preferred, in that the polymer (A) has a greater effect of improving dispersibility. Carbon nanotubes are long and therefore prone to entanglement, but the polymer (A) allows even carbon-based conductive agents that tend to become entangled, such as carbon nanotubes, to be dispersed in a liquid medium to a uniform concentration.

[0053] Examples of carbon nanotubes include single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT). Carbon nanotubes may be composed solely of carbon, or may have a structure partially substituted with or chemically modified by other elements. Furthermore, carbon nanotubes may be composites with metals (e.g., gold, silver, copper, aluminum, nickel, cobalt, titanium, platinum, etc.).

[0054] The size of the carbon nanotubes is not particularly limited. To ensure sufficient conductivity, the outer diameter of the carbon nanotubes is preferably 3 to 25 nm, more preferably 5 to 20 nm, and even more preferably 5 to 10 nm. The length of the carbon nanotubes is preferably 0.1 to 200 μm, more preferably 30 to 170 μm, and even more preferably 50 to 150 μm.

[0055] In this specification, the outer diameter and length of carbon nanotubes can be calculated by randomly selecting 300 carbon nanotubes from an image observed with a transmission electron microscope, measuring the outer diameter of each carbon nanotube, and calculating the average.

[0056] In the conductive agent dispersion, the content of the conductive agent (B) is preferably 0.01 to 10 mass%, more preferably 0.02 to 7 mass%, and even more preferably 0.03 to 5 mass%, relative to 100 mass% of the total solid content of the conductive agent dispersion. In this specification, the "total solid content" refers to the total blend amount of all components contained in the conductive agent dispersion, excluding the liquid medium.

[0057] <Liquid Medium> The conductive agent dispersion of the present disclosure contains a liquid medium. The liquid medium contained in the conductive agent dispersion of the present disclosure (hereinafter also referred to as "liquid medium (C)") is preferably an organic solvent. Specifically, it is preferably at least one selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, ketones, esters, ethers, and lactams.

[0058] Specific examples of these include aliphatic hydrocarbons such as hexane, heptane, octane, decane, and dodecane; alicyclic hydrocarbons such as cyclohexane, cycloheptane, cyclooctane, and cyclodecane; aromatic hydrocarbons such as toluene, xylene, mesitylene, naphthalene, and tetralin; ketones such as methylhexyl ketone and dipropyl ketone; esters such as butyl acetate, butyl butyrate, and methyl butanoate; ethers such as dibutyl ether, tetrahydrofuran, and anisole; and lactams such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and 2-pyrrolidone. As the liquid medium (C), one type may be used alone, or two or more types may be used in combination.

[0059] The liquid medium (C) is preferably one or more selected from the group consisting of ketones, esters, ethers, and lactams, and more preferably one or more selected from the group consisting of esters and lactams, in that it can provide better dispersibility for the conductive agent (B).

[0060] The conductive agent dispersion of the present disclosure may contain water as the liquid medium (C). The content of water is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, based on the total amount of the liquid medium (C).

[0061] The content of the liquid medium (C) is preferably an amount such that the solids concentration of the conductive agent dispersion is 0.1 to 20% by mass. By ensuring that the solids concentration of the conductive agent dispersion is within the above range, the dispersibility of the conductive agent (B) can be ensured while the concentration of the conductive agent (B) is sufficiently high. From the above viewpoints, the content of the liquid medium (C) is more preferably an amount such that the solids concentration of the conductive agent dispersion is 0.2 to 15% by mass, and even more preferably an amount such that the solids concentration of the conductive agent dispersion is 0.5 to 10% by mass. In this specification, the solids concentration of the conductive agent dispersion refers to the proportion (mass %) of the total mass of the components contained in the conductive agent dispersion, excluding the liquid medium (C), relative to the total mass of the conductive agent dispersion.

[0062] <Other Components> The conductive agent dispersion of the present disclosure may contain components other than the above-described polymer (A), carbon-based conductive agent, and liquid medium (hereinafter also referred to as "other components"), as necessary. Examples of other components include polymers different from the polymer (A) (e.g., methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, etc.), preservatives, etc. The content of other components can be appropriately set within a range that does not impair the effects of the present disclosure.

[0063] <Method for producing conductive agent dispersion> The conductive agent dispersion of the present disclosure can be obtained by mixing the above-mentioned polymer (A), carbon-based conductive agent, liquid medium, and other components that are optionally added. Specifically, the conductive agent dispersion can be prepared by mixing a solid polymer (A), a carbon-based conductive agent, and a liquid medium, or by mixing a polymer solution containing the polymer (A) and a carbon-based conductive agent. Note that when a polymer solution containing the polymer (A) is used in preparing the conductive agent dispersion, the conductive agent dispersion may be prepared by further adding a liquid medium to the polymer solution containing the polymer (A).

[0064] The method for obtaining the conductive agent dispersion is not particularly limited. For example, the conductive agent dispersion can be obtained by mixing a mixture containing the polymer (A), the carbon-based conductive agent, and the liquid medium using a known dispersing device.

[0065] Specific examples of the dispersion device include mixers such as a disperser, a homomixer, and a planetary mixer; homogenizers (Yoshida Kikai Kogyo's "NanoVeita," BRANSON's Advanced Digital Sonifer (registered trademark), Model 450DA, M-Technique's "Clearmix," PRIMIX's "Filmix," and Silverson's "Abramix"); paint conditioners (Red Devil); colloid mills (PUC's "PUC Colloid Mill," IKA's "Colloid Mill" and others). Examples of suitable dispersers include media-type dispersers such as centrifuge mills (IKA Corporation's "Cone Mill MKO" and the like); ball mills; sand mills (Shinmaru Enterprises' "Dyno Mill" and the like); attritors; pearl mills (Eirich's "DCP Mill" and the like); and Co-ball mills; media-less dispersers such as wet jet mills (Genus Corporation's "Genus PY", Sugino Machine's "Starburst", Nanomizer Inc.'s "Nanomizer", and the like), M Technique's "Claire SS-5", and Nara Kikai's "MICROS", and other roll mills.

[0066] The conductive agent dispersion of the present disclosure obtained in this manner can be applied to various applications. Specifically, the conductive agent dispersion of the present disclosure can be used as various materials such as batteries, capacitors, wiring, electric wires, conductive films, semiconductor devices, various vehicles (automobiles, aircraft, trains, bicycles, etc.), building materials, sporting goods, medical equipment, acoustic equipment, optical equipment, antistatic materials, inks, paints, etc. When the conductive agent dispersion of the present disclosure is used as a battery material, the type of battery is not particularly limited, and examples thereof include lithium ion secondary batteries and fuel cells. Furthermore, when the conductive agent dispersion of the present disclosure is used as a capacitor material, examples of the capacitor include electric double layer capacitors and lithium ion capacitors. The conductive agent dispersion of the present disclosure can be used as a conductive auxiliary agent for these batteries or capacitors.

[0067] According to the present disclosure described above, the following means are provided: [Means 1] A conductive agent dispersion liquid containing a polymer (A), a carbon-based conductive agent (B), and a liquid medium (C), wherein the polymer (A) contains a repeating unit (a1) derived from an aromatic vinyl compound and a repeating unit (a2) derived from an unsaturated carboxylic acid ester compound, the content of the repeating unit (a1) being 1 to 50 mass% relative to the total amount of repeating units contained in the polymer (A), and the content of the repeating unit (a2) being 20 to 75 mass% relative to the total amount of repeating units contained in the polymer (A), and the viscosity of a polymer solution obtained by dissolving the polymer (A) in N-methyl-2-pyrrolidone to a solids concentration of 8 mass% at 25°C is 300 to 5,000 mPa s. [Means 2] The conductive agent dispersion of [Means 1], wherein the polymer (A) further contains a repeating unit (a3) ​​derived from an unsaturated carboxylic acid or an unsaturated carboxylic anhydride, and the content of the repeating unit (a3) ​​is 0.5 to 10 mass% based on the total amount of repeating units contained in the polymer (A). [Means 3] The conductive agent dispersion of [Means 1] or [Means 2], wherein the polymer (A) further contains a repeating unit (a4) derived from an α,β-unsaturated nitrile compound, and the content of the repeating unit (a4) is 5 to 40 mass% based on the total amount of repeating units contained in the polymer (A). [Means 4] The conductive agent dispersion of any of [Means 1] to [Means 3], wherein the polymer (A) further contains a repeating unit (a5) derived from a compound having a sulfonic acid group, and the content of the repeating unit (a5) is 0.1 to 10 mass% based on the total amount of repeating units contained in the polymer (A). [Means 5] The conductive agent dispersion of any of [Means 1] to [Means 4], wherein the polymer (A) further contains a repeating unit (a6) derived from a (meth)acrylamide compound, and the content of the repeating unit (a6) is 0.1 to 10 mass% based on the total amount of repeating units contained in the polymer (A). [Means 6] The conductive agent dispersion of any of [Means 1] to [Means 5], wherein the carbon-based conductive agent (B) is at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, furnace black, acetylene black, and graphene.[Means 7] The conductive agent dispersion according to any one of [Means 1] to [Means 6], wherein the liquid medium (C) is at least one selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, ketones, esters, ethers, and lactams.

[0068] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. "Parts" and "%" in the examples and comparative examples are by mass unless otherwise specified.

[0069] Example 1 (1) Synthesis of Polymer (A1) Polymer (A1) was obtained by the single-stage polymerization described below. A 3-L separable flask was charged with 500 parts by mass of water, 0.8 parts by mass of 4,4'-azobis(4-cyanovaleric acid), 0.64 parts by mass of sodium bicarbonate, 1 part by mass of styrene, 67 parts by mass of 2-ethylhexyl acrylate, 1 part by mass of acrylic acid, 30 parts by mass of acrylonitrile, and 1 part by mass of sodium styrenesulfonate. Nitrogen bubbling was performed for 30 minutes, and then the reaction was carried out at 70°C for 5 hours. The mixture was then cooled to obtain an aqueous solution containing polymer (A1) at a solids concentration of 15%. The conversion rate of polymer (A1) at this time was 99%. Next, 1 part by mass of 2,6-di-tert-butyl-p-cresol was added as an antioxidant. The aqueous dispersion of polymer (A1) after the addition of the antioxidant was added dropwise to 3,000 parts by mass of a 0.5% calcium chloride aqueous solution. The obtained aggregate was washed with water, and a part of the aggregate was dried at 80°C to recover the entire amount.

[0070] Details of the method for measuring the polymerization conversion rate are as follows. <Method for measuring the polymerization conversion rate> The reaction solution polymerized for a predetermined time was extracted and placed in an aluminum dish (X (g)) whose mass had been measured in advance, and the mass (Y (g)) of the reaction solution was measured. The aluminum dish containing the reaction solution was dried at 155°C for 15 minutes using a hot air dryer. The aluminum dish was removed and allowed to cool, and then the mass (Z (g)) of the aluminum dish was measured. The polymerization conversion rate (%) was calculated from the values ​​of masses X, Y, and Z measured in this way using the following mathematical formula (1). Polymerization conversion rate (%) = ((Z-X) / Y) x 100 ... (1)

[0071] (2) Evaluation of Polymer The polymer (A1) obtained in Synthesis Example 1 was evaluated as follows. (i) Evaluation of NMP Solubility The polymer (A1) was diluted with N-methyl-2-pyrrolidone (NMP) to a concentration of 1% by mass. The transparency of this polymer solution was confirmed visually at 1 atmosphere and 23°C. If the polymer solution was transparent, it was determined that the polymer was dissolved in NMP, and if the polymer solution was translucent or cloudy, it was determined that the polymer was insoluble in NMP. As a result, it was determined that the polymer (A1) was dissolved in NMP. In Tables 1 and 2 shown below, the case where the polymer was dissolved in NMP is indicated as "A," and the case where the polymer was insoluble in NMP is indicated as "B."

[0072] (ii) Measurement of 8% NMP Viscosity Polymer (A1) was added to N-methyl-2-pyrrolidone (NMP) and stirred overnight to dissolve the polymer (A1) in NMP, thereby obtaining a polymer solution containing 8% by mass of polymer (A1). The viscosity of this polymer solution (8% NMP viscosity) was measured at 25°C using a Brookfield viscometer (manufactured by Toki Sangyo Co., Ltd., "TVB-10") and was found to be 820 mPa s.

[0073] (3) Preparation and Evaluation of Conductive Agent Dispersion Liquid (i) Preparation of Conductive Agent Dispersion Liquid To a container containing 4 parts by mass of single-walled carbon nanotubes (SWCNT, manufactured by OCSiAl Corporation, "TUBALL") and 20 parts by mass of polymer (A1), 1,000 parts by mass of NMP was added as a liquid medium. Next, the resulting mixture was subjected to ultrasonic dispersion for 10 minutes, and then the mixture was passed through a high-pressure homogenizer (manufactured by Yoshida Kikai Kogyo Co., Ltd., product name "Nanovata") five times under a pressure of 100 MPa to prepare a conductive agent dispersion liquid.

[0074] (ii) Evaluation of CNT Dispersibility The conductive agent dispersion obtained above was diluted with NMP so that the viscosity measured at 25°C using a Brookfield viscometer ("TVB-10" manufactured by Toki Sangyo Co., Ltd.) was 1,000 to 20,000 mPa·s. The viscosity measured at this time was designated the "initial slurry viscosity." Next, at 25°C, a shear rate-shear viscosity evaluation was performed using an Anton Paar rheometer (MCR-500 model) with a 25 mm diameter, 2° cone plate as the measuring tool, under conditions of reciprocating shear rate of 1 (1 / s) to 1,000 (1 / s). The shear viscosity at 5 (1 / s) on the way out and back was read, and the rate of change (%) of shear viscosity was calculated. The measurement results are shown in Table 1. Note that if the rate of change in shear viscosity is less than 50%, the measured sample can be determined to be a conductive agent dispersion with small hysteresis, low structural viscosity, and good handleability. On the other hand, if the rate of change in shear viscosity is 50% or more, the measurement sample has large hysteresis and high structural viscosity, and therefore can be determined to be a conductive agent dispersant with poor handleability.

[0075] Examples 2 to 16, Comparative Examples 1 to 6 Polymers (polymers (A2) to (A16), polymers (R1) to (R6)) were synthesized by single-stage polymerization in the same manner as in Example 1, except that the types and amounts of monomers were as shown in Tables 1 and 2, respectively, and evaluations were carried out. Furthermore, conductive agent dispersions were prepared in the same manner as in Example 1 using the synthesized polymers, and evaluations were carried out. Tables 1 and 2 show the monomer compositions, measurement results of each physical property, and evaluation results of the polymers synthesized and used in Examples 1 to 16 and Comparative Examples 1 to 6. The numerical values ​​representing the monomer compositions of the polymers shown in Tables 1 and 2 represent the amount (unit: parts by mass) of each monomer used relative to 100 parts by mass of the total of the monomers used in the synthesis of each polymer. The numerical values ​​representing the blending amount of the conductive agent dispersion represent the blending amount (unit: parts by mass) of each component relative to 100 parts by mass of the liquid medium used in the preparation of the conductive agent dispersion (the same applies to Table 3).

[0076]

[0077]

[0078] In Tables 1 and 2, the abbreviations of the monomers represent the following compounds, respectively. <Monomers> (Aromatic vinyl compounds) ST: Styrene VT: Vinyltoluene 4tBST: 4-tert-butylstyrene (Unsaturated carboxylic acid ester compounds) MMA: Methyl methacrylate TADB: Dibutyl itaconate TADM: Dimethyl itaconate TADE: Diethyl itaconate BA: Butyl acrylate 2EHA: 2-ethylhexyl acrylate HEMA: Hydroxyethyl methacrylate CHMA: Cyclohexyl methacrylate (Unsaturated carboxylic acids) TA: Itaconic acid TAMB: Monobutyl itaconate TAMM: Monomethyl itaconate TAME: Monoethyl itaconate AA: Acrylic acid MAA: Methacrylic acid (α,β-Unsaturated nitrile compounds) AN: Acrylonitrile DMP: Isopropylidenemalononitrile FN: Fumaronitrile TCE: Tetracyanoethylene (sulfonic acid or its salt) NaSS: Sodium styrenesulfonate VS: Vinylsulfonic acid ((meth)acrylamide) AAM: Acrylamide MAM: Methacrylamide

[0079] [Examples 17 to 23, Comparative Examples 7 and 8] Conductive agent dispersions were prepared and evaluated in the same manner as in Example 1, except that the type and amount of the carbon-based conductive agent were changed as shown in Table 3. The evaluation results are shown in Table 3.

[0080]

[0081] In Table 3, the abbreviations for the carbon-based conductive agents represent the following compounds: <Carbon-based conductive agents> B-1: "TUBALL" manufactured by OCSiAL B-2: "100T" manufactured by KUMHO PETROCHEMICAL B-3: "Flotube7010" manufactured by Cnano B-4: "VGCF-H" manufactured by Resonac B-5: "HS-100" manufactured by Denka B-6: "Super CT" manufactured by IMERYS

[0082] As is clear from Tables 1 to 3, by containing the polymer (A) as a dispersant in the liquid medium together with the carbon-based conductive agent, a conductive agent dispersion liquid excellent in dispersibility of the carbon-based conductive agent could be obtained.

Claims

1. A conductive agent dispersion liquid comprising a polymer (A), a carbon-based conductive agent (B), and a liquid medium (C), wherein the polymer (A) comprises a repeating unit (a1) derived from an aromatic vinyl compound and a repeating unit (a2) derived from an unsaturated carboxylic acid ester compound, the content of the repeating unit (a1) being 1 to 50 mass% based on the total amount of repeating units contained in the polymer (A), and the content of the repeating unit (a2) being 20 to 75 mass% based on the total amount of repeating units contained in the polymer (A), and the viscosity of a polymer solution obtained by dissolving the polymer (A) in N-methyl-2-pyrrolidone to a solids concentration of 8 mass% at 25°C is 300 to 5,000 mPa·s.

2. The conductive agent dispersion liquid according to claim 1, wherein the polymer (A) further contains a repeating unit (a3) ​​derived from an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride, and the content of the repeating unit (a3) ​​is 0.5 to 10 mass % based on the total amount of repeating units contained in the polymer (A).

3. The conductive agent dispersion liquid according to claim 1, wherein the polymer (A) further contains a repeating unit (a4) derived from an α,β-unsaturated nitrile compound, and the content of the repeating unit (a4) is 5 to 40 mass % based on the total amount of repeating units contained in the polymer (A).

4. The conductive agent dispersion liquid according to any one of claims 1 to 3, wherein the polymer (A) further contains a repeating unit (a5) derived from a compound having a sulfonic acid group, and the content of the repeating unit (a5) is 0.1 to 10 mass % based on the total amount of repeating units contained in the polymer (A).

5. The conductive agent dispersion liquid according to any one of claims 1 to 3, wherein the polymer (A) further contains a repeating unit (a6) derived from a (meth)acrylamide compound, and the content of the repeating unit (a6) is 0.1 to 10 mass % based on the total amount of repeating units contained in the polymer (A).

6. The conductive agent dispersion liquid according to any one of claims 1 to 3, wherein the carbon-based conductive agent (B) is at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, furnace black, acetylene black, and graphene.

7. The conductive agent dispersion liquid according to any one of claims 1 to 3, wherein the liquid medium (C) is at least one selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, ketones, esters, ethers, and lactams.

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