Method for recovering organic solvent from oil-based pigment ink and pigment precipitant for oil-based pigment ink

Abstract

To provide a method for more simply and efficiently recovering an organic solvent from an oily pigment ink, and to provide a pigment settling agent for the oily pigment ink.SOLUTION: The method for recovering the organic solvent from the oil-based pigment ink containing a compound having an epoxy group includes reacting the epoxy group in the compound having the epoxy group with one or more kinds selected from the group consisting of a polycarboxylic acid compound and a polyamine compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for recovering organic solvents from oil-based pigment inks and a pigment settling agent for oil-based pigment inks. [Background technology]

[0002] There are various types of printing inks, including, for example, aqueous inks containing water as the main solvent, ultraviolet-curable inks (UV inks) whose main component is a polymerizable monomer, hot-melt inks (solid inks) whose main component is wax, and non-aqueous inks whose main solvent is a non-aqueous solvent. Non-aqueous inks can be classified into solvent-based inks whose main solvent is a volatile organic solvent, and oil-based inks whose main solvent is a low-volatile or non-volatile organic solvent.

[0003] Of these, for oil-based inks containing non-volatile organic solvents, there is a need to develop a technology to recover and reuse the organic solvent from waste ink in order to reduce the environmental impact.Patent Document 1 describes a method for recovering the pigment by adding a solvent with poor pigment dispersibility to the waste ink in a volume ratio of 3 to 10 times the amount of the waste ink, causing the pigment particles in the waste ink to settle, and recovering the pigment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 63-1883 Summary of the Invention [Problem to be solved by the invention]

[0005] The purpose of the technology described in Patent Document 1 is to recover the pigment, and since a large amount of new organic solvent must be added separately to precipitate the pigment, it does not meet the purpose of reusing the organic solvent and reducing the environmental impact. On the other hand, one of the objectives of the present disclosure is to provide a simpler and more efficient method for recovering organic solvent from oil-based pigment ink and a pigment settling agent for oil-based pigment ink. [Means for solving the problem]

[0006] One embodiment of the present disclosure relates to a method for recovering an organic solvent from an oil-based pigment ink containing a compound having an epoxy group, the method comprising reacting an epoxy group in the compound having an epoxy group with one or more compounds selected from the group consisting of a polycarboxylic acid compound and a polyamine compound.

[0007] Another embodiment of the present disclosure relates to a pigment settling agent for oil-based pigment inks, comprising one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a simpler and more efficient method for recovering organic solvents from oil-based pigment inks and a pigment settling agent for oil-based pigment inks. DETAILED DESCRIPTION OF THE INVENTION

[0009] Several embodiments of the present invention will be described in detail below, but the present disclosure is not limited to these embodiments.

[0010] In this disclosure, acrylic resin is a general term for resins obtained by polymerizing acrylic acid, methacrylic acid, and derivatives thereof, either singly or in combination. (Meth)acrylic acid is a general term for acrylic acid and methacrylic acid, and (meth)acrylic acid ester is a general term for acrylic acid ester and methacrylic acid ester.

[0011] One embodiment of the method for recovering an organic solvent from an oil-based pigment ink is a method for recovering an organic solvent from an oil-based pigment ink that contains a compound having an epoxy group, and includes reacting an epoxy group in the compound having an epoxy group with one or more compounds selected from the group consisting of a polycarboxylic acid compound and a polyamine compound.

[0012] Examples of pigments contained in oil-based pigment inks (hereinafter sometimes referred to as "oil-based inks" or "inks") include organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments; and inorganic pigments such as carbon black and metal oxides. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrroles (DPPs). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black. Examples of metal oxides include titanium oxide and zinc oxide. One type of pigment may be used alone, or two or more types may be used in combination.

[0013] The average particle size of the pigment is not particularly limited and is adjusted appropriately depending on the type of oil-based ink, printing method, etc. The average particle size of the pigment may be, for example, 300 nm or less, 200 nm or less, 150 nm or less, or 100 nm or less. In one embodiment, the organic solvent recovery method allows the pigment to settle and the organic solvent to be recovered simply and efficiently, regardless of the particle size of the pigment. The content of the pigment in the oil-based ink is usually in the range of 0.01 to 20% by mass, and from the viewpoints of print density and ink viscosity, it is preferably in the range of 1 to 15% by mass, and more preferably in the range of 4 to 10% by mass.

[0014] The organic solvent contained in the oil-based ink is a non-aqueous solvent, and may be either a non-polar organic solvent or a polar organic solvent. The non-aqueous solvent may be used alone or in combination with two or more. Other organic solvents may also be contained to the extent that they can form a single phase with the non-aqueous solvent used. It is preferable to use a water-insoluble organic solvent that does not mix uniformly with the same volume of water at 20°C under 1 atmosphere as the non-aqueous solvent.

[0015] Examples of non-polar organic solvents include petroleum-based hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents. Examples of aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents include non-aqueous solvents such as paraffin-based, isoparaffin-based, and naphthenic solvents. Commercially available products include "No. 0 Solvent L," "No. 0 Solvent M," "No. 0 Solvent H," "Cactus normal paraffin N-10," "Cactus normal paraffin N-11," "Cactus normal paraffin N-12D," "Cactus normal paraffin N-13," "Cactus normal paraffin N-14," "Cactus normal paraffin YHNP," "Cactus normal paraffin SHNP," "Isozol 300," "Isozol 400," "Teclain N16," "Teclain N20," "Teclain N22," "AF Solvent No. 4," "AF Solvent No. 5," "AF Solvent No. 6," "AF Solvent No. 7," "Naphtesol 160," "Naphtesol 200," "Naphtesol 220," "Isopar G," and "Isopar H," all of which are available from ENEOS Corporation. Examples of suitable solvents include "BHT," "Isopar L," "Isopar M," "Exsor D40," "Exsor D60," "Exsor D80," "Exsor D110," and "Exsor D130"; and products available from MORESCO Corporation such as "Moresco White P-60," "Moresco White P-70," "Moresco White P-80," "Moresco White P-100," "Moresco White P-120," "Moresco White P-150," "Moresco White P-200," "Moresco White P-260," and "Moresco White P-350P." Examples of suitable aromatic hydrocarbon solvents include "Solvesso 100," "Solvesso 150," "Solvesso 200," and "Solvesso 200ND," manufactured by ExxonMobil. The initial boiling point of the petroleum-based hydrocarbon solvent is preferably 100°C or higher, more preferably 150°C or higher, and particularly preferably 200°C or higher. The initial boiling point of distillation can be measured in accordance with JIS K0066 "Testing method for distillation of chemical products."

[0016] Preferred examples of the polar organic solvent include fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents. For example, isononyl isononanoate, isodecyl isononanoate, isotridecyl isononanoate, methyl laurate, isopropyl laurate, hexyl laurate, isopropyl myristate, octyldodecyl myristate, isopropyl palmitate, hexyl palmitate, isooctyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, hexyl oleate, methyl linoleate, ethyl linoleate, isobutyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopropyl isostearate, 2-octyldecyl pivalate, and soybean oil fatty acid methyl esters. Examples of suitable polar organic solvents include fatty acid ester solvents having 13 or more carbon atoms per molecule, preferably 16 to 30, such as ethanol esters, soybean oil fatty acid isobutyl esters, tall oil fatty acid methyl esters, and tall oil fatty acid isobutyl esters; higher alcohol solvents having 6 or more carbon atoms per molecule, preferably 12 to 20, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, and decyltetradecanol; and higher fatty acid solvents having 12 or more carbon atoms per molecule, preferably 14 to 20, such as lauric acid, isomyristic acid, palmitic acid, isopalmitic acid, α-linolenic acid, linoleic acid, oleic acid, and isostearic acid. The boiling points of polar organic solvents such as fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents are preferably 150°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher. Non-aqueous solvents having a boiling point of 250°C or higher also include non-aqueous solvents that do not exhibit a boiling point.

[0017] The content of the non-aqueous solvent in the oil-based ink is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 60% by mass or more, 70% by mass or more, or 80% by mass or more. It may also be 99% by mass or less, 97% by mass or less, or 95% by mass or less. The content of the non-aqueous solvent in the oil phase may be in the range of 60 to 99% by mass.

[0018] The epoxy group-containing compound contained in the oil-based ink is not limited to a specific structure, and a wide variety of compounds can be used. Furthermore, the epoxy group-containing compound may be used alone or in combination with two or more types. Among these, a polyepoxy compound having multiple epoxy groups in one molecule is preferred because it improves the separability of the organic solvent and the pigment in one embodiment of the solvent recovery method.

[0019] There are no limitations on the molecular weight of the polyepoxy compound, but for example, the weight-average molecular weight may be 2,000 or more, 3,000 or more, or 5,000 or more. Also, it may be 100,000 or less, 50,000 or less, or 30,000 or less. The weight-average molecular weight of the polyepoxy compound may be, for example, in the range of 2,000 to 100,000.

[0020] The weight-average molecular weight was measured using a GPC system manufactured by Shimadzu Corporation. This gel permeation chromatography (GPC) can measure the molecular weight distribution of synthetic polymers using a hydrophobic packing material and a non-aqueous (organic solvent) mobile phase.

[0021] The epoxy equivalent of the polyepoxy compound is not particularly limited, but may be, for example, 200 g / eq or more, 300 g / eq or more, or 500 g / eq or more, or 2,000 g / eq or less, 1,800 g / eq or less, or 1,500 g / eq or less, as measured in accordance with JIS K 7236:2001. The epoxy equivalent of the polyepoxy compound may be in the range of 200 to 2,000 g / eq.

[0022] Examples of polyepoxy compounds include bisphenol-type epoxy resins, novolac-type epoxy resins, and acrylic resins having epoxy groups, all of which are represented by the following general formula (1): Among these, acrylic resins having epoxy groups are preferred because they provide particularly excellent separability between the organic solvent and the pigment in the solvent recovery method of one embodiment.

[0023] [ka]

[0024] [R in general formula (1) 1 is an alkylene group having 1 to 4 carbon atoms, an oxygen atom, or a sulfur atom, and n is an integer of 0 or 1 or more.

[0025] Examples of acrylic resins having epoxy groups (hereinafter, this may be referred to as "acrylic resin (A)") include acrylic resins having a compound having an epoxy group and a polymerizable unsaturated bond (hereinafter, this may be referred to as "compound (a)") as a monomer component.

[0026] Examples of compound (a) include glycidyl (meth)acrylate and (3,4-epoxycyclohexyl)methyl acrylate. The molecular weight of compound (a) may be 500 or less. Compound (a) may be glycidyl (meth)acrylate. The proportion of glycidyl (meth)acrylate in compound (a) may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or even 100% by mass.

[0027] The monomers constituting the acrylic resin (A) may contain other monomers in addition to the compound (a). The ratio of the compound (a) to the total amount of monomers constituting the acrylic resin (A) is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more, since this provides particularly excellent separability between the organic solvent and the pigment in one embodiment of the solvent recovery method. Alternatively, it may be 80% by mass or less, 60% by mass or less, or 40% by mass or less. The ratio of the compound (a) to the total amount of monomers constituting the acrylic resin (A) may be in the range of 10 to 80% by mass.

[0028] Examples of other monomers include alkyl (meth)acrylates represented by the following general formula (2):

[0029] [ka]

[0030] [In general formula (2), R 2 R is an alkyl group having 1 to 30 carbon atoms, and the alkyl group may be linear or may have a branched structure. 3 is a hydrogen atom or a methyl group.

[0031] alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyl (meth)acrylate;

[0032] (meth)acrylates having an aromatic ring, such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenylethyl (meth)acrylate, and phenoxyethyl (meth)acrylate;

[0033] styrene compounds such as styrene and α-methylstyrene;

[0034] hydroxyalkyl (meth)acrylates such as hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate;

[0035] Monomers having a carboxy group, such as (meth)acrylic acid, β-carboxyethyl (meth)acrylate, 4-[2-(meth)acryloyloxy)ethoxy]-4-oxo-2-butenoic acid, (meth)acryloyloxymethyl succinic acid, (meth)acryloyloxyethyl succinic acid, (meth)acryloyloxyethyl phthalic acid, (meth)acryloyloxyethyl hexahydrophthalic acid, (meth)acryloyloxypropyl phthalic acid, (meth)acryloyloxypropyl hexahydrophthalic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid;

[0036] Examples include (meth)acrylates having a polyoxyalkylene chain represented by the following general formula (3).

[0037] [ka] [In general formula (3), R 4 is an alkylene group having 1 to 4 carbon atoms, and m is an integer of 2 or more. 4 may all be different, or some or all may be the same. 5 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. 6 is a hydrogen atom or a methyl group.

[0038] The monomer constituting the acrylic resin (A) may contain a (meth)acrylic acid alkyl ester. Among (meth)acrylic acid alkyl esters, those in which the alkyl group has 6 or more carbon atoms are preferred from the viewpoint of solvent solubility. The number of carbon atoms in the alkyl group may be 8 or more, or 10 or more. It may also be 30 or less, 28 or less, or 25 or less. The number of carbon atoms in the alkyl group of the (meth)acrylic acid alkyl ester may be in the range of 6 to 20. The proportion of those in which the alkyl group has 6 to 20 carbon atoms relative to the total amount of (meth)acrylic acid alkyl esters may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or even 100% by mass.

[0039] The proportion of the (meth)acrylic acid alkyl ester relative to the total amount of monomers constituting the acrylic resin (A) may be 10% by mass or more, 20% by mass or more, or 30% by mass or more. Also, it may be 80% by mass or less, 70% by mass or less, or 60% by mass or less. The proportion of the (meth)acrylic acid alkyl ester relative to the total amount of monomers constituting the acrylic resin (A) may be in the range of 10 to 80% by mass.

[0040] The method for producing the acrylic resin (A) is not particularly limited, but it can be produced, for example, by polymerizing a mixture of monomers in the presence of a polymerization initiator such as an azo compound or peroxide. A chain transfer agent, a polymerization inhibitor, or the like may be used during the polymerization reaction. The polymerization reaction may also be carried out in an organic solvent. Examples of the organic solvent include the same non-aqueous solvents as described above, and one type may be used alone, or two or more types may be used in combination.

[0041] The content of the compound having an epoxy group in the oil-based ink can be adjusted as appropriate depending on the application of the oil-based ink, but may be, for example, 0.5% by mass or more, 1% by mass or more, or 2% by mass or more. It may also be 20% by mass or less, 10% by mass or less, or 5% by mass or less. The content of the compound having an epoxy group in the oil-based ink may be in the range of 0.5 to 20% by mass.

[0042] The oil-based ink may contain other components in addition to the pigment, non-aqueous solvent, and compound having an epoxy group. Examples of other components include pigment dispersants, resins other than compounds having an epoxy group, antioxidants, conductivity modifiers, viscosity modifiers, surface tension modifiers, oxygen absorbers, etc. The specific types of these other components are not particularly limited, and components commonly used in the relevant field can be used.

[0043] The method for producing the oil-based ink is not particularly limited, but for example, the ink can be produced by blending and mixing a pigment, a non-aqueous solvent, a compound having an epoxy group, and other optional components. When mixing, a dispersion treatment may be performed using a bead mill.

[0044] The oil-based ink may be, for example, an oil-based inkjet ink. In this case, the viscosity of the oil-based ink is preferably 5 to 30 mPa·s at 23°C, and more preferably 5 to 15 mPa·s, although the appropriate range varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, and the like.

[0045] The polycarboxylic acid compound used in the organic solvent recovery method of one embodiment is a compound having multiple carboxy groups in one molecule, and a wide variety of compounds can be used without any particular limitations on the specific structure. One type of polycarboxylic acid compound may be used alone, or two or more types may be used in combination. Furthermore, the polycarboxylic acid compound may be used in combination with a polyamine compound described below.

[0046] There are no limitations on the molecular weight of the polycarboxylic acid compound, but for example, the average molecular weight may be 2,000 or more, 5,000 or more, or 10,000 or more. Also, it may be 100,000 or less, 80,000 or less, or 50,000 or less. The average molecular weight of the polycarboxylic acid compound may be, for example, in the range of 2,000 to 100,000.

[0047] The acid value of the polycarboxylic acid compound is not particularly limited, but may be, for example, in the range of 500 to 800 mgKOH / g as measured in accordance with JIS K 0070-1992.

[0048] Examples of polycarboxylic acid compounds include polyester resins having a carboxy group in the molecule, alkyd resins having a carboxy group in the molecule, acrylic resins having a carboxy group in the molecule, polyvinyl resins having a carboxy group in the molecule, etc. Among these, in the solvent recovery method of one embodiment, acrylic resins having a carboxy group are preferred because they are particularly excellent in terms of separability between the organic solvent and the pigment.

[0049] Examples of the acrylic resin having a carboxy group (hereinafter, sometimes referred to as "acrylic resin (B)") include acrylic resins containing one or more of the above-mentioned monomers having a carboxy group as a monomer component. Among these, in one embodiment of the solvent recovery method, it is preferable to use (meth)acrylic acid as the monomer having a carboxy group, because this provides particularly excellent separability between the organic solvent and the pigment.

[0050] The monomers constituting the acrylic resin (B) may contain other monomers in addition to the monomer having a carboxy group, such as the various compounds exemplified in the description of the acrylic resin (A).

[0051] In one embodiment of the solvent recovery method, the ratio of the monomer having a carboxy group to the total amount of monomers constituting the acrylic resin (B) is preferably 70% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass, because this provides particularly excellent separability between the organic solvent and the pigment. That is, the acrylic resin (B) is preferably poly(meth)acrylic acid.

[0052] The method for producing the acrylic resin (B) is not particularly limited, but it can be produced, for example, by polymerizing a mixture of monomers in the presence of a polymerization initiator such as an azo compound or peroxide. A chain transfer agent, a polymerization inhibitor, or the like may be used during the polymerization reaction. The polymerization reaction may also be carried out in a solvent, such as water or various organic solvents. One type of solvent may be used alone, or two or more types may be used in combination.

[0053] The polyamine compound used in the organic solvent recovery method of one embodiment is a compound having multiple amino groups in one molecule, and a wide variety of compounds can be used without any particular limitations on the specific structure. One type of polyamine compound may be used alone, or two or more types may be used in combination. Furthermore, the polyamine compound may be used in combination with the polycarboxylic acid compound described above.

[0054] There are no limitations on the molecular weight of the polyamine compound, but for example, the number average molecular weight measured by boiling point elevation method may be 2,000 or more, 5,000 or more, or 8,000 or more, or 100,000 or less, 80,000 or less, or 50,000 or less. The average molecular weight of the polyamine compound may be, for example, in the range of 2,000 to 100,000.

[0055] The amine value of the polyamine compound is not particularly limited, but may be, for example, in the range of 15 to 23 mmol / g as measured by non-aqueous acid titration in accordance with JIS K 7237-1995.

[0056] Examples of polyamine compounds include polyethyleneimine, polyamidoamine resins, etc. Among them, polyethyleneimine is preferred because it is particularly excellent in terms of the separability between the organic solvent and the pigment in the solvent recovery method of one embodiment.

[0057] In one embodiment, the pigment settling agent for oil-based pigment inks (hereinafter, this may be referred to as "pigment settling agent") contains one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds. The polycarboxylic acid compounds and polyamine compounds may be the compounds described above.

[0058] The pigment settling agent may contain one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds, as well as other components. Examples of such other components include water. Because this allows for simpler and more efficient separation of the organic solvent from the pigment, the pigment settling agent is preferably an aqueous solution containing one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds. The total mass ratio of the polycarboxylic acid compounds and polyamine compounds in the pigment settling agent may be 0.5% by mass or more, 1% by mass or more, or even 3% by mass or more. It may also be 20% by mass or less, 15% by mass or less, or 10% by mass or less. The total mass ratio of the polycarboxylic acid compounds and polyamine compounds in the pigment settling agent may be in the range of 0.5 to 20% by mass.

[0059] The proportion by total mass of water, the polycarboxylic acid compound, and the polyamine compound in the pigment settling agent may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or even 100% by mass.

[0060] In one embodiment of the organic solvent recovery method, the epoxy group in the epoxy group-containing compound is reacted with one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds. A specific example of a method for reacting the two compounds is a method in which the pigment precipitating agent described above is added to a waste liquid containing an oil-based ink and the mixture is stirred to cause the reaction.

[0061] The waste liquid containing oil-based ink may consist solely of oil-based ink, or may contain other components. The oil-based ink may contain only one type, or may contain multiple types. Examples of other components include organic solvents that were not originally contained in oil-based ink, water, etc. Examples of organic solvents that were not originally contained in oil-based ink include organic solvents used to clean printer components, etc.

[0062] The ratio of the waste liquid to the pigment precipitating agent is arbitrary, but for example, the total mass of the polycarboxylic acid compound and polyamine compound in the pigment precipitating agent may be in the range of 20 to 300 parts by mass per 100 parts by mass of the components other than the organic solvent and water in the waste liquid. Alternatively, the ratio of the pigment precipitating agent to the mass of the ink may be in the range of 0.5 to 10 times.

[0063] The reaction of the epoxy group in the epoxy-containing compound with one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds produces a precipitate containing the pigment, the epoxy-containing compound, and the pigment-settling agent, gradually increasing the transparency of the liquid. The pigment-settling agent may be added all at once or in multiple installments. It may also be added gradually while observing the degree of pigment settling and the transparency of the liquid.

[0064] After the reaction is completed, the precipitate is removed by filtration or the like, and the aqueous layer and the organic solvent layer are separated, allowing the organic solvent to be recovered.

[0065] Some embodiments of the present disclosure are presented below. <1> A method for recovering organic solvents from an oil-based pigment ink containing a compound having an epoxy group, the method comprising reacting an epoxy group in the compound having an epoxy group with one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds.

[0066] <2> The polycarboxylic acid compound is poly(meth)acrylic acid. <1> 1. A method for recovering organic solvents from oil-based pigment inks according to claim 1.

[0067] <3> The polyamine compound is polyethyleneimine. <1> or <2> 1. A method for recovering organic solvents from oil-based pigment inks according to claim 1.

[0068] <4> the compound having an epoxy group is an acrylic resin having an epoxy group, <1> ~ <3> 1. The method for recovering organic solvents from oil-based pigment ink according to any one of the above.

[0069] <5> A pigment settling agent for oil-based pigment inks, comprising one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds. [Example]

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, common components are the same throughout the following Examples and Comparative Examples. Unless otherwise specified, "%" indicates "% by mass."

[0071] [Production of compounds having epoxy groups] A 300 ml four-neck flask was charged with 87.5 parts by mass of isodecyl isononanoate (manufactured by Kokyu Alcohol Kogyo Co., Ltd.), and the temperature was raised to 110 ° C. while aerating and stirring with nitrogen gas. Next, while maintaining the temperature at 110 ° C., a mixture of 50 parts by mass of docosyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 25 parts by mass of benzyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.), 25 parts by mass of glycidyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 16.5 parts by mass of isodecyl isononanoate, and 4 parts by mass of t-hexylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perhexyl O") was added dropwise over 3 hours. The mixture was stirred for another 2 hours while maintaining the temperature at 110 ° C., yielding a solvent solution (solids content 50% by mass) of a compound having an epoxy group.

[0072] [Oil-based ink manufacturing] The components were mixed in the proportions shown in Table 1 below and dispersed in a bead mill to obtain an oil-based ink. Pigment (1): "SB200" (Asahi Carbon Co., Ltd.), carbon black Pigment (2): "FASTGEN BLUE LA5380" (DIC Corporation), copper phthalocyanine Pigment (3): "Fanal Pink D4810" (BASF Japan Ltd.) Pigment (4): "SEIKA FAST YELLOW 2700(B)" (Dainichiseika Color & Chemicals Mfg. Co., Ltd.) Organic solvent (1): "Exsol D130" (ENEOS Corporation) Organic solvent (2): Octyldodecyl myristate (Kyushu Alcohol Kogyo Co., Ltd.) Organic solvent (3): "AF Solvent No. 5" (ENEOS Corporation)

[0073] [Table 1]

[0074] [Examples 1 and 2 and Comparative Example 1: Experiments to evaluate the production of pigment precipitating agents and the recovery of organic solvents] The pigment settling agent was obtained by blending the components in the proportions shown in Table 2. Details of each component are as follows: Polycarboxylic acid compound: Fujifilm Wako Pure Chemical Industries, Ltd. "Polyacrylic acid 25,000", average molecular weight 25,000 Polyamine compound: Nippon Shokubai Co., Ltd. "Epomin SP200", polyethyleneimine, molecular weight 10,000, amine value 18 mmol / g Ethanol: Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.5% by mass

[0075] [Table 2]

[0076] After mixing 10 parts by mass of each of the oil-based inks (1) to (4) obtained above, 40 parts by mass of the pigment settling agent was added and mixed by hand. After mixing for 1 minute, the degree of pigment settling was evaluated according to the following criteria. The results are shown in Table 3. A: All the pigment has settled and the liquid has become colorless and transparent. B: Some of the pigment settles, but not all of it settles, and the color remains in the liquid.

[0077] [Table 3]

[0078] As shown in Table 3, by using the pigment precipitating agents of Examples 1 and 2, it was found that the pigment could be efficiently precipitated and the solvent could be recovered by the simple operation of simply adding the pigment precipitating agent to the waste ink and stirring it. In Comparative Example 1, in which ethanol with low pigment dispersibility was added, the pigment did not settle sufficiently and solvent recovery was impossible.

Claims

1. A method for recovering organic solvents from an oil-based pigment ink containing a compound having an epoxy group, the method comprising reacting an epoxy group in the compound having an epoxy group with one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds.

2. 2. The method for recovering an organic solvent from an oil-based pigment ink according to claim 1, wherein the polycarboxylic acid compound is poly(meth)acrylic acid.

3. 2. The method for recovering an organic solvent from an oil-based pigment ink according to claim 1, wherein the polyamine compound is polyethyleneimine.

4. 2. The method for recovering an organic solvent from an oil-based pigment ink according to claim 1, wherein the compound having an epoxy group is an acrylic resin having an epoxy group.

5. A pigment settling agent for oil-based pigment inks, comprising one or more compounds selected from the group consisting of polycarboxylic acid compounds and polyamine compounds.

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