Oil-based inkjet ink composition

Abstract

To provide an oil-based inkjet ink composition that contains substantially no mineral oil, while excelling in ejection stability and low volatility, and effectively suppressing a reduction in OD value.SOLUTION: This oil-based inkjet ink composition contains a pigment, a solvent, a binder resin, and a pigment-dispersing agent. The solvent contains a higher fatty acid alkyl ester compound having 12-30 carbon atoms and contains substantially no mineral oil. The binder resin is an acrylic resin and / or a chlorinated polypropylene resin. The composition has a viscosity of 2 mPa s to 30 mPa s (at 25°C).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an oil-based inkjet ink composition. [Background technology]

[0002] Inkjet recording, which ejects highly fluid inkjet ink droplets from minute nozzles to record images on a recording medium placed opposite the nozzles, has rapidly gained popularity in recent years due to its low-noise, high-speed printing capabilities. Inks used in inkjet recording include aqueous inks containing water as the primary solvent, ultraviolet-curable inks (UV inks) containing a high content of polymerizable monomers as the primary component, and hot-melt inks (solid inks) containing a high content of wax as the primary component, as well as so-called non-aqueous inks containing a non-aqueous solvent as the primary solvent. Non-aqueous inks can be classified into solvent-based inks, which contain a volatile organic solvent as the primary solvent, and oil-based inks, which contain a low-volatility or non-volatile organic solvent as the primary solvent. Solvent inks dry on the recording medium primarily through the evaporation of the organic solvent, while oil-based inks dry primarily through penetration into the recording medium.

[0003] Oils for oil-based inks are roughly classified into mineral oils and fatty acid esters, and examples include those used alone and those used in combination (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2002-501966 [Patent Document 2] Japanese Patent Publication No. 2022-024421 [Patent Document 3] Japanese Patent Application Publication No. 2017-088638 Summary of the Invention [Problem to be solved by the invention]

[0005] Due to environmental concerns, restrictions on mineral oil have been put in place in Europe, creating a need for mineral oil-free oil-based inks. Oil-based inks must be low volatile to prevent nozzle clogging, and because they use a permeable base material, there is a problem of the ink density (OD value) easily decreasing after impact.

[0006] The present invention has been made in view of the above-mentioned circumstances, and has an object to provide an oil-based inkjet ink composition that is substantially free of mineral oil, and that has excellent ejection stability, low volatility, and suppression of a decrease in OD value. [Means for solving the problem]

[0007] [Item 1] That is, the present invention relates to an oil-based inkjet ink composition containing a pigment, a solvent, a binder resin, and a pigment dispersant, wherein the solvent contains a higher fatty acid alkyl ester compound having 12 to 30 carbon atoms and is substantially free of mineral oil, the binder resin is an acrylic resin and / or a chlorinated polypropylene resin, and the oil-based inkjet ink composition has a viscosity of 2 mPa·s to 30 mPa·s (25°C).

[0008] [Item 2] The present invention also relates to the oil-based inkjet ink composition according to item 1, wherein the higher fatty acid alkyl ester compound having 12 to 30 carbon atoms has a viscosity of 2 mPa·s to 15 mPa·s (25° C.).

[0009] [Item 3] The present invention also relates to the oil-based inkjet ink composition according to item 1 or 2 above, wherein the chlorinated polypropylene resin has a chlorination degree of 20 to 50%.

[0010] [Item 4] The present invention also relates to the oil-based inkjet ink composition according to any one of items 1 to 3 above, wherein the pigment is carbon black. [Effects of the Invention]

[0011] The mechanism of action of the oil-based ink-jet ink composition of the present invention is presumed to be as follows: However, the present invention is not limited to this mechanism of action.

[0012] The oil-based inkjet ink composition of the present invention contains a pigment, a solvent, a binder resin, and a pigment dispersant, wherein the solvent contains a higher fatty acid alkyl ester compound having 12 to 30 carbon atoms and is substantially free of mineral oil, and the binder resin is an acrylic resin and / or a chlorinated polypropylene resin and has a viscosity of 2 mPa·s to 30 mPa·s (25°C). The higher fatty acid alkyl ester compound having 12 to 30 carbon atoms exhibits low volatility as an oil-based ink, and the acrylic resin and / or chlorinated polypropylene resin can inhibit a decrease in the OD value. Furthermore, the oil-based inkjet ink composition has a viscosity of 2 mPa·s to 30 mPa·s (25°C), resulting in excellent ejection stability. DETAILED DESCRIPTION OF THE INVENTION

[0013] The oil-based inkjet ink composition of the present invention contains a pigment, a solvent, a binder resin, and a pigment dispersant, wherein the solvent contains a higher fatty acid alkyl ester compound having 12 to 30 carbon atoms and is substantially free of mineral oil, and the binder resin is an acrylic resin and / or a chlorinated polypropylene resin and has a viscosity of 2 mPa·s to 30 mPa·s (25°C).

[0014] <Pigments> Pigments include inorganic, organic, and extender pigments that can generally be used in ink compositions containing organic solvents. Examples of inorganic pigments include titanium oxide, red iron oxide, antimony red, cadmium red, cadmium yellow, cobalt blue, Prussian blue, ultramarine blue, carbon black, and graphite. Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. Examples of extender pigments include calcium carbonate, kaolin clay, barium sulfate, aluminum hydroxide, and talc. Among these, carbon black is preferred because of its excellent ability to suppress a decrease in density (OD value). Examples of carbon black that can be used include acidic carbon black and neutral carbon black.

[0015] The content of the pigment in the oil-based inkjet ink composition is usually 0.01 to 20% by mass, and from the viewpoint of print density and ink viscosity, it is preferably 1 to 15% by mass, and more preferably 4 to 10% by mass.

[0016] <Solvent> The solvent contains a higher fatty acid alkyl ester compound having 12 to 30 carbon atoms and is substantially free of mineral oil. Here, "substantially free of mineral oil" means that mineral oil is not intentionally added when producing the oil-based inkjet ink composition, and the oil-based inkjet ink composition may contain trace amounts of mineral oil that are inevitably mixed in during production or storage.

[0017] Examples of higher fatty acid alkyl ester compounds having 12 to 30 carbon atoms include methyl myristate, ethyl myristate, propyl myristate, hexyl decanoate, heptyl decanoate, isooctyl nonanoate, heptyl nonanoate, isodecyl octanoate, octyl octanoate, nonyl octanoate, decyl hexanoate, cetyl isooctanoate, isocetyl laurate, isostearyl laurate, isocetyl myristate, isooctyl palmitate, isooctyl stearate, isononyl isononanoate, isodecyl isononanoate, and methyl laurate. , isopropyl laurate, butyl laurate, 2-ethylhexyl laurate, isopropyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, methyl linoleate, ethyl linoleate, isobutyl linoleate, butyl stearate, isopropyl isostearate, 2-octyldecyl neopentanoate, 2-octyldodecyl neopentanoate, 2-ethylhexyl nonanoate, 6-methylheptyl nonanoate, 2-propylheptyl octanoate, and 2-ethylhexyl stearate. In addition, in the present invention, soybean oil fatty acid methyl, soybean oil fatty acid butyl, soybean oil fatty acid 2-ethylhexyl, tall oil fatty acid methyl, tall oil fatty acid isobutyl, linseed oil fatty acid methyl, linseed oil fatty acid 2-ethylhexyl, rice oil fatty acid butyl, and rice oil fatty acid 2-ethylhexyl are also defined as being included in the higher fatty acid alkyl ester compounds having 12 to 30 carbon atoms.

[0018] Among these, preferred higher fatty acid alkyl ester compounds having 12 to 30 carbon atoms have a viscosity of 2 mPa·s to 15 mPa·s (25°C) so that the oil-based inkjet ink composition has a viscosity that does not require heating during ejection. Specific examples include methyl myristate, ethyl myristate, propyl myristate, hexyl decanoate, heptyl decanoate, isooctyl nonanoate, 2-ethylhexyl nonanoate, 6-methylheptyl nonanoate, heptyl nonanoate, isodecyl octanoate, 2-propylheptyl octanoate, octyl octanoate, nonyl octanoate, decyl hexanoate, methyl laurate, butyl laurate, 2-ethylhexyl laurate, isopropyl laurate, butyl stearate, 2-ethylhexyl stearate, methyl soybean oil fatty acid, butyl soybean oil fatty acid, 2-ethylhexyl soybean oil fatty acid, butyl rice oil fatty acid, and 2-ethylhexyl rice oil fatty acid. Among these, it is preferable to use soybean oil fatty acid methyl, soybean oil fatty acid butyl, soybean oil fatty acid 2-ethylhexyl, and rice oil fatty acid butyl from the viewpoint of resin solubility and penetration base material such as liner. Furthermore, it is preferable that the higher fatty acid alkyl ester compound having 12 to 30 carbon atoms has 12 to 24 carbon atoms from the viewpoint of low volatility.

[0019] The content of the solvent may be such that the viscosity of the oil-based inkjet ink composition is approximately 2 mPa·s to 30 mPa·s (25°C). For example, from the viewpoint of ejection properties, the content of the solvent in the oil-based inkjet ink composition is typically approximately 70 to 95% by mass, and preferably 85 to 93% by mass.

[0020] As the solvent, organic solvents other than higher fatty acid alkyl ester compounds having 12 to 30 carbon atoms may be used in combination, as long as the performance is not impaired. The content of the higher fatty acid alkyl ester compounds having 12 to 30 carbon atoms in the solvent is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0021] <Binder resin> From the viewpoint of suppressing a decrease in density (OD value) after impact, the binder resin is preferably an acrylic resin and / or a chlorinated polypropylene resin that dissolves in an alkyl ester compound of a higher fatty acid having 12 to 30 carbon atoms.

[0022] The acrylic resin is a resin obtained by polymerizing a derivative of (meth)acrylic acid, or a resin containing the derivative. Among them, the acrylic resin is preferably one that does not have a cyclic structure.

[0023] The acrylic resin preferably has an acid value of 10 mgKOH / g or less. The acid value can be determined from the manufacturer's catalogue value, but if this is not available, it can be calculated by neutralization titration.

[0024] From the viewpoints of the concentration after impact (OD value) and solubility in solvents, the weight-average molecular weight of the acrylic resin is preferably 30,000 to 80,000, and more preferably 40,000 to 70,000. The weight-average molecular weight can be calculated by gel permeation chromatography (GPC) using the manufacturer's catalog values ​​as a reference, but if these are unavailable, it can be calculated by gel permeation chromatography (GPC). For example, chromatography can be performed using a Water 2690 (Waters) GPC system and a PLgel 5μ MIXED-D (Polymer Laboratories) column under the following conditions: tetrahydrofuran as the developing solvent, a column temperature of 25°C, a flow rate of 1 milliliter / minute, an RI detector, a sample injection concentration of 10 milligrams / milliliter, and an injection volume of 100 microliters. The weight-average molecular weight can be calculated as a polystyrene-equivalent.

[0025] From the viewpoints of solubility and blocking properties, the acrylic resin preferably has a glass transition temperature of 40° C. or higher and 70° C. or lower. The glass transition temperature can be determined from the manufacturer's catalog value, but if this is not available, it is determined by differential scanning calorimetry (DSC), and is usually calculated from the midpoint of the temperature range in which the glass transition occurs.

[0026] Commercially available acrylic resins include "Dynayar BR-106" manufactured by Mitsubishi Chemical Corporation, "DEGALAN PM602" manufactured by Evonik, and "DEGALAN LP 64 / 12" manufactured by Evonik.

[0027] The chlorinated propylene resin preferably has a chlorination degree of 20 to 50%. When the chlorination degree is within the above range, the chlorinated polypropylene resin has excellent compatibility with solvents and excellent adhesion to films. In the present invention, the chlorination degree is defined as the mass % of chlorine atoms in the chlorinated polypropylene resin. The chlorinated polypropylene resin is preferably a modified or unmodified chlorinated polypropylene resin having a mass average molecular weight of 5,000 to 200,000.

[0028] The content of the acrylic resin and / or chlorinated propylene resin in the oil-based inkjet ink composition is preferably 1% by mass or more, and more preferably 1.5% by mass or more, from the viewpoints of improving fixation to the substrate and suppressing a decrease in density (OD value) after landing, and is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 7% by mass or less, and even more preferably 4% by mass or less, from the viewpoint of improving ejection stability.

[0029] The oil-based inkjet ink composition may use, as a binder resin other than the acrylic resin and / or chlorinated propylene resin, a resin that dissolves in an alkyl ester compound of a higher fatty acid having 12 to 30 carbon atoms, in combination, as long as the performance is not impaired. Examples of such resins include styrene-acrylic resins, styrene-maleic acid resins, rosin resins, rosin ester resins, petroleum resins, coumarone-indene resins, terpene phenol resins, phenol resins, urethane resins, melamine resins, urea resins, epoxy resins, cellulose resins, xylene resins, alkyd resins, aliphatic hydrocarbon resins, butyral resins, maleic acid resins, and fumaric acid resins.

[0030] <Pigment dispersant> The pigment dispersant can be any pigment dispersant that can be used in an ink composition, and examples thereof include hydroxyl group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high-molecular-weight acid esters, salts of high-molecular-weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high-molecular-weight unsaturated acid esters, copolymers of vinylpyrrolidone and long-chain alkenes, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, polyoxyethylene alkyl phosphate esters, polyester polyamines, and the like.

[0031] Examples of commercially available pigment dispersants include "Antaron V216 (vinylpyrrolidone-hexadecene copolymer)" and "V220 (vinylpyrrolidone-eicosene copolymer)" (all trade names) manufactured by ISP Japan Co., Ltd.; "Solsperse 13940 (polyester amine type), 16000, 17000, 18000 (fatty acid amine type), 11200, 24000, 28000" (all trade names) manufactured by The Lubrizol Japan Co., Ltd.; and "EFKA 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 50, 51, 52 (modified polyacrylate)" manufactured by BASF Japan Ltd. 7, 48, 49, 4010, 4055 (modified polyurethane) (all trade names); Kusumoto Chemical Co., Ltd.'s "Disparlon KS-860, KS-873N4 (amine salt of polyester)" (all trade names); Daiichi Kogyo Seiyaku Co., Ltd.'s "Discol 202, 206, OA-202, OA-600 (multi-chain polymer non-ionic)" (all trade names); BYK Japan KK's "DISPERBYK2155, 9077" (all trade names); and Croda Japan Co., Ltd.'s "Hypermer KD2, KD3, KD11, KD12" (all trade names).

[0032] The amount of pigment dispersant used may be set appropriately as long as it is sufficient to disperse the pigment sufficiently in the ink composition. For example, the pigment dispersant may be blended in a mass ratio of 0.1 to 5 parts by weight of pigment to 1 part by weight of pigment, preferably 0.3 to 1 part by weight.

[0033] The oil-based inkjet ink composition of the present invention may contain various additives as needed, as long as they do not impair the effects of the present invention. Examples of additives include a nozzle clogging inhibitor, an antioxidant, a conductivity modifier, a viscosity modifier, a surface tension modifier, and an oxygen absorber.

[0034] <Method of manufacturing an oil-based inkjet ink composition> The method for producing the oil-based inkjet ink composition of the present invention is not particularly limited. For example, the oil-based inkjet ink composition can be produced by dispersing and mixing the raw materials using a dispersing machine such as a wet circulation mill, bead mill, ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, high-pressure homogenizer (Microfluidizer, Nanomizer, Ultimizer, Genus PY, DeBEE2000, etc.), or pearl mill, and adjusting the viscosity at 25°C to approximately 2 to 30 mPa·s if no heating is applied during ejection. The resulting ink composition is preferably filtered through a filter with a pore size of 3 μm or less after dispersion or after dissolving the binder resin to prevent clogging of the inkjet printer head.

[0035] The oil-based inkjet ink composition can be printed on a permeable paper substrate such as a liner using an inkjet printer to form an inkjet image. [Example]

[0036] The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

[0037] <Production of Oil-Based Inkjet Ink Composition> The pigment, binder resin, pigment dispersant, and solvent materials were mixed by stirring according to the blending amounts shown in Table 1, and the mixture was filtered through a (membrane) filter with a pore size of 3 μm to obtain oil-based inkjet ink compositions for each of the Examples and Comparative Examples.

[0038] The materials shown in Table 1 are as follows: <Pigments> MA7: Carbon black pigment, manufactured by Mitsubishi Chemical Corporation MONARCH280: Carbon black pigment, manufactured by CABOT <Binder resin> Dyna-Yar BR-106: Acrylic resin, manufactured by Mitsubishi Chemical Corporation (Tg: 47°C, Mw: 5,5000, acid value: 3.6 mg KOH / g) DEGALAN PM602: Acrylic resin, manufactured by Evonik (Tg: 62°C, Mw: 6,4000, acid value: 6 mg KOH / g) Superchlorine 814HS: Chlorinated polypropylene resin, chlorination degree 41%, manufactured by Nippon Paper Industries Co., Ltd. Super Chlon 390S: Chlorinated polypropylene resin, chlorination degree 36%, manufactured by Nippon Paper Industries Co., Ltd. Pencel D-135: Polymerized rosin resin, manufactured by Arakawa Chemical Industries, Ltd. <Pigment dispersant> Solsperse 18000: Dispersant, manufactured by Lubrizol <Solvent> Rickcizer C-88: Fatty acid ester, manufactured by Ito Oil Mills TOSOLV-ME: Soybean oil fatty acid methyl ester, manufactured by Toshin Yushi Co., Ltd. Exepar ML-85: Methyl laurate, manufactured by Kao Chemical Co., Ltd. Exepar TD-S: Isotridecyl stearate, manufactured by Kao Chemicals Methyl decanoate: manufactured by Tokyo Chemical Industry Co., Ltd. MORESCO White P-55: Hydrocarbon solvent, manufactured by MORESCO

[0039] The oil-based inkjet ink compositions of the Examples and Comparative Examples obtained above were evaluated as follows.

[0040] <Viscosity evaluation> The viscosity (mPa·s) of the oil-based inkjet ink composition at 25° C. was measured using a viscometer (RE100L model, manufactured by Toki Sangyo Co., Ltd.).

[0041] <Evaluation of ejection stability> Using the ink composition for oil-based inkjet, printing was performed on a liner paper (trade name: K-liner (210 g / m 2 ), manufactured by Oji Paper Co., Ltd.), and it was evaluated by the number of sheets in which unprinted parts occurred. It may be ○ or Δ, and ○ is preferred. [Evaluation criteria] ○: Unprinted parts occur after the 71st sheet, or no unprinted parts occur up to the 100th sheet. Δ: Unprinted parts occur between the 51st and 70th sheets. <照 ×: Unprinted parts occur between the 31st and 50th sheets. ××: Unprinted parts occur by the 30th sheet.

[0042] <Evaluation of suppression of OD value decrease> Using the ink composition for oil-based inkjet, printing was performed on a liner paper (trade name: K-liner (210 g / m 2 ), manufactured by Oji Paper Co., Ltd.), and the OD values after ejection and after 24 hours were measured using a spectrophotometer (trade name "Spectro Eye", manufactured by X-Rite Inc.), and evaluated by the OD value change rate. It may be ○ or Δ, and ○ is preferred. [Evaluation criteria] ○: The OD value change rate is less than 10%. Δ: The OD value change rate is 10% or more and less than 15%. ×: The OD value change rate is 15% or more.

[0043] <Evaluation of low volatility> The ink composition for oil-based inkjet was placed in a petri dish with a diameter of 4 cm and left standing in an environment at 40 °C for 14 days, and evaluated by the weight change rate before and after standing. It may be ○ or Δ, and ○ is preferred. [Evaluation criteria] ○: The weight change rate is less than 5%. Δ: The weight change rate is 5% or more and less than 7%. ×: The weight change rate is 5% or more.

[0044] Table 1

Claims

1. An oil-based inkjet ink composition containing a pigment, a solvent, a binder resin, and a pigment dispersant, the solvent contains a higher fatty acid alkyl ester compound having 12 to 30 carbon atoms and is substantially free of mineral oil; the content of the higher fatty acid alkyl ester compound having 12 to 30 carbon atoms in the solvent is 90% by mass or more, the binder resin is an acrylic resin and / or a chlorinated polypropylene resin, 1. An oil-based ink-jet ink composition having a viscosity of 2 mPa·s to 30 mPa·s (25° C.).

2. 2. The oil-based inkjet ink composition according to claim 1, wherein the higher fatty acid alkyl ester compound having 12 to 30 carbon atoms has a viscosity of 2 mPa·s to 15 mPa·s (25° C.).

3. 3. The oil-based inkjet ink composition according to claim 1, wherein the chlorinated polypropylene resin has a chlorination degree of 20 to 50%.

4. 3. The oil-based ink-jet ink composition according to claim 1, wherein the pigment is carbon black.

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