Oil-based inkjet ink

Abstract

The present invention provides an oil-based inkjet ink containing a fatty acid ester solvent having 18 to 29 carbon atoms in one molecule and a pigment, the solvent being represented by the following general formula (1): 1 is an alkyl group having 5 or more carbon atoms, and R 2 is an alkyl group having 6 or more carbon atoms, and R 1 and R 2 At least one of the groups has a side chain with 4 or more carbon atoms and is a branched alkyl group with 9 or more carbon atoms.

Description

Technical Field

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

Background Art

[0002] In the inkjet recording method, highly fluid inkjet ink is ejected as droplets from a fine nozzle, and an image is recorded on a recording medium placed opposite the nozzle. Since it is possible to print at high speed with low noise, it has been rapidly spreading in recent years. As inks used in such an inkjet recording method, there are aqueous inks containing water as a main solvent, ultraviolet curable inks (UV inks) containing a high content of polymerizable monomers as a main component, hot melt inks (solid inks) containing a high content of wax as a main component, and so-called non-aqueous inks containing a non-aqueous solvent as a main solvent. Non-aqueous inks can be classified into solvent inks (solvent-based inks) in which the main solvent is a volatile organic solvent and oil-based inks (oil-based inks) in which the main solvent is a low-volatile or non-volatile organic solvent. Solvent inks dry mainly by evaporation of the organic solvent on the recording medium, whereas oil-based inks dry mainly by penetration into the recording medium.

[0003] Colorants of inks are roughly classified into dyes and pigments. When using dyes, there are advantages such as good color development. Also, dyes have the advantage of being superior in abrasion resistance compared to pigments. However, there is a problem that the water resistance and marker resistance of the dyes themselves are low. On the other hand, pigments have the advantages of high image density and excellent weather resistance, but have the problem of lower abrasion resistance compared to dyes.

[0004] In an example of an inkjet printing apparatus, the ink is stored in an ink tank and conveyed from the ink tank through a resin tube to an inkjet nozzle. There is a problem that this resin tube is deteriorated by the ink, particularly the non-aqueous solvent in the ink. In the case of pigment ink, after the ink is ejected onto the recording medium, the non-aqueous solvent rapidly penetrates into the recording medium, enabling the printed matter to dry, and the pigment remains on the surface of the recording medium, enhancing the image density. In an inkjet printing apparatus, when the printed matter is sandwiched and conveyed by rollers after printing, ink adheres to the rollers that come into contact with the printed matter, and there is a problem of so-called roller transfer stain, where the ink re-adheres from the rollers to the subsequent printing area or the printed matter, causing stains on the printed matter.

[0005] In Patent Document 1, an inkjet non-aqueous ink composition having high ejection stability without swelling or significantly deforming a transparent film is proposed, which contains a pigment, a dispersant, and a non-aqueous solvent, and 50% or more of the total weight of the non-aqueous solvent is an ester solvent having 24 to 36 carbon atoms.

[0006] In Patent Document 2, in order to prevent the alcohol odor from the printed matter, it is proposed to contain a pigment, a dispersant, and a solvent, and the solvent contains a specific fatty acid ester solvent. Examples of the fatty acid ester solvent in Patent Document 2 include isodecyl neopentanoate, isostearyl neopentanoate, octyldodecyl neopentanoate, octyldodecyl neodecanoate, etc.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] Since ester solvents with a high carbon number have a relatively high viscosity, inks using this ester solvent have a problem of roller transfer stain because the penetration rate of the ink into the recording medium is slow and the solvent release property is poor. Further, in Patent Document 1, when an ester solvent with a high carbon number is blended in the ink, the ink is heated to lower the viscosity and then discharged. In this case, when the temperature of the ink drops after being discharged onto the recording medium, the ink on the recording medium becomes highly viscous and the solvent is less likely to be released, resulting in the problem of roller transfer stain.

[0009] Also, even for ester solvents with a high carbon number, if the alkyl group is linear or the side chain is short, it may not be possible to sufficiently prevent the deterioration of resin tubes, particularly vinyl chloride tubes. For example, isocetyl 2-ethylhexanoate used in Patent Document 1 has 24 carbon atoms, but the carbon number of the side chain on the fatty acid side is 2, and the carbon number of the side chain on the alcohol side is unknown. Therefore, there is a possibility that the vinyl chloride tube deteriorates. Since the vinyl chloride tube is in direct contact with the ink, it is more affected by the ink than the deformation of the clear file by the printed matter. The inks of Comparative Examples 1 to 6 in Patent Document 1 use ester solvents having 18 to 23 carbon atoms, but since the branched structure cannot be specified, deformation of the transparent film occurs. Ester solvents with a low carbon number have relatively low viscosity and are useful for improving discharge performance, but there is a problem of deformation of the clear file.

[0010] Octyldodecyl neopentanoate used in Patent Document 2 has a small carbon number in the fatty acid part, so there is a possibility that the vinyl chloride tube deteriorates. Further, neopentanoic acid, which is a decomposition product of octyldodecyl neopentanoate, has a small carbon number and causes odor. Octyldodecyl neodecanoate used in Patent Document 2 has 30 carbon atoms in one molecule, and after the ink is discharged, the penetration into the recording medium is slow, and there is a possibility of roller transfer stain.

[0011] One object of the present invention is to prevent the deterioration of resin products by ink and to prevent roller transfer stains in the printing process.

Means for Solving the Problems

[0012] One embodiment of the present invention is an oil-based inkjet ink containing a fatty acid ester solvent represented by the following general formula (1) and having 18 to 29 carbon atoms in one molecule and a pigment.

Chemical formula

Effects of the Invention

[0013] According to one embodiment of the present invention, it is possible to prevent the deterioration of resin products by ink and to prevent roller transfer stains in the printing process.

Mode for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described using one embodiment. The examples in the following embodiments do not limit the present invention.

[0015] An oil-based inkjet ink according to one embodiment (hereinafter sometimes simply referred to as ink) is characterized by containing a fatty acid ester solvent represented by the following general formula (1) and having 18 to 29 carbon atoms in one molecule and a pigment.

Chemical formula

[0016] According to this, deterioration of the resin product by the ink can be prevented, and roller transfer stain in the printing process can be prevented. In an example of an inkjet printing apparatus, it has an ink tank for storing ink and an inkjet nozzle for discharging ink onto a recording medium, and the ink is conveyed from the ink tank to the inkjet nozzle through a tube. A vinyl chloride tube may be used for this tube. This vinyl chloride tube has a problem of being deteriorated by a non-aqueous solvent of the ink. Deterioration of the tube leads to problems such as impurities eluting from the tube into the ink and the ink deteriorating in addition to the breakage of the tube.

[0017] Fatty acid esters are generally used as plasticizers for resins such as vinyl chloride. Plasticizers have the effect of entering between the molecules of the resin and widening the distance between the molecules to weaken the crystallization of the resin, and by adding them during the molding of the resin, the resin is softened and made easier to process. Therefore, when a resin product is immersed in a fatty acid ester, the fatty acid ester may enter between the molecules of the resin product and swell the resin product. In particular, the swelling action is likely to work on a vinyl chloride tube compared to other resin tubes. As the fatty acid ester as a plasticizer, those having 2 or less carbon atoms in the side chain are mainstream, and for example, fatty acid esters having an aromatic ring such as esters of a divalent acid such as adipic acid and a monovalent alcohol are widely used.

[0018] The fatty acid ester-based solvent represented by the general formula (1) can prevent deterioration of resin products such as vinyl chloride tubes. This fatty acid ester-based solvent has R 1 and R 2 both being alkyl groups of a certain length, and R 1 and R2 When at least one of them has a side chain with 4 or more carbon atoms, a bulky structure is formed, preventing the fatty acid ester-based solvent from entering vinyl chloride and preventing the swelling of vinyl chloride. For example, this fatty acid ester-based solvent is R 1 and R 2 When at least one of them is a branched alkyl group having a side chain with 4 or more carbon atoms and the other is an alkyl group with 5 or more carbon atoms, the structure of the entire fatty acid ester-based solvent becomes a bulky structure with three branches, and swelling of vinyl chloride by the fatty acid ester-based solvent can be further prevented. In the case where the R 1 and / or R 2 of the fatty acid ester-based solvent has a side chain with 3 or fewer carbon atoms such as a methyl group at the terminal portion, the fatty acid ester-based solvent does not become sufficiently bulky, so there is a possibility of swelling vinyl chloride.

[0019] When the number of carbon atoms in one molecule of the fatty acid ester-based solvent is 29 or less, after the ink is ejected onto the recording medium, the ink can quickly penetrate into the recording medium. In inkjet printing, after the ink is ejected onto the recording medium, it penetrates into the recording medium and dries. In an inkjet printing apparatus, after the ink is ejected onto the recording medium, the recording medium is sandwiched between a pair of rollers and conveyed. If ink adheres to the roller in contact with the printing surface from the recording medium, the ink may reattach from the roller to the subsequent printing area or the recording medium, causing ink stains on the recording medium. Therefore, it is important that the solvent quickly penetrates into the recording medium and dries after the ink is ejected onto the recording medium. In the case of pigment ink, since the image density can be increased by the pigment remaining on the surface of the recording medium after ink ejection, while the solvent penetrates into the recording medium after ink ejection, it is desirable that the pigment remains on the surface of the recording medium. The pigment on the surface of the recording medium is likely to adhere to the roller and cause roller transfer stains, but by using the fatty acid ester-based solvent represented by the general formula (1), roller transfer stains can be prevented.

[0020] The ink contains a pigment. As the pigment, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and lake pigments; and inorganic pigments such as carbon black and metal oxides can be used. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments such as copper phthalocyanine pigments, and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone-based pigments, perylene-based pigments, perinone-based pigments, isoindoline-based pigments, isoindolinone-based pigments, dioxazine-based pigments, thioindigo-based pigments, anthraquinone-based pigments, quinophthalone-based pigments, metal complex pigments, and diketopyrrolopyrrole (DPP). 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. These pigments may be used alone or in combination of two or more.

[0021] From the viewpoints of ejection stability and storage stability, the average particle diameter of the pigment is preferably 300 nm or less, more preferably 200 nm or less, still more preferably 150 nm or less, and even more preferably 100 nm or less. The pigment is usually 0.01 to 20% by mass based on the total amount of the ink, and from the viewpoints of printing density and ink viscosity, it is preferably 1 to 15% by mass, and even more preferably 4 to 10% by mass.

[0022] In order to stably disperse the pigment in the ink, a pigment dispersant can be used together with the pigment. As the pigment dispersant, for example, 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, etc. are preferably used.

[0023] Examples of commercially available pigment dispersants include, for example, "Antaron V216 (vinylpyrrolidone - hexadecene copolymer), V220 (vinylpyrrolidone - eicosene copolymer)" (both trade names) manufactured by ISP Japan Co., Ltd.; "Solsperse 13940 (polyesteramine - based), 16000, 17000, 18000 (fatty acid amine - based), 11200, 24000, 28000" (both trade names) manufactured by Lubrizol Japan Co., Ltd.; "Efka 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 4010, 4055 (modified polyurethane)" (both trade names) manufactured by BASF Japan Ltd.; "Disparon KS - 860, KS - 873N4 (amine salts of polyester)" (both trade names) manufactured by Kusumoto Chemicals, Ltd.; "Discol 202, 206, OA - 202, OA - 600 (multi - chain polymer non - ionic)" (both trade names) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; "DISPERBYK 2155, 9077" (both trade names) manufactured by BYK - Chemie Japan Co., Ltd.; "Hypermer KD2, KD3, KD11, KD12" (both trade names) manufactured by Croda Japan Co., Ltd. etc. These pigment dispersants may be used alone or in combination of two or more.

[0024] The pigment dispersant is sufficient if it is in an amount that can sufficiently disperse the above - mentioned pigment in the ink and can be set as appropriate. For example, in terms of mass ratio, the pigment dispersant can be blended in an amount of 0.1 to 5 with respect to 1 of the pigment, preferably 0.1 to 1. Also, the pigment dispersant can be blended in an amount of 0.01 to 10% by mass with respect to the total amount of the ink, preferably 0.1 to 6% by mass.

[0025] The non - aqueous solvent contains the fatty acid ester - based solvent represented by the above general formula (1). By using this fatty acid ester - based solvent, deterioration of the resin product can be prevented. Also, roller transfer stains can be prevented.

[0026] In the general formula (1), R 1 and R 2 are each independently an alkyl group. R1 is an alkyl group having 5 or more carbon atoms, and R 2 is an alkyl group having 6 or more carbon atoms. And at least one of R 1 and R 2 has a side chain having 4 or more carbon atoms and is a branched alkyl group having 9 or more carbon atoms. R 1 and R 2 One of them is a straight-chain alkyl group, and R 1 and R 2 The other of them may have a side chain having 4 or more carbon atoms. Also, both of R 1 and R 2 may have side chains having 4 or more carbon atoms. Note that if one of R 1 and R 2 is a branched alkyl group having a side chain with 4 or more carbon atoms, then R 1 and R 2 The other of them may have a side chain having 3 or fewer carbon atoms. Also, R 1 and R 2 each preferably independently has one or two side chains having 4 or more carbon atoms, but may have three or more.

[0027] Here, the main chains of R 1 and R 2 are the carbon chains with the most carbon atoms counted from the carbon atoms bonded to the ester bond part "-COO-". The carbon chains branched from the main chains of this R 1 and R 2 are used as side chains. When R 1 and / or R 2 has a side chain, each side chain may be linear or branched. Also, in R 1 and R 2 when there are a plurality of carbon chains with the most carbon atoms counted from the carbon atoms bonded to the ester bond part, the one with the most carbon atoms in the side chain is taken as the main chain. Also, R 1 and R 2In this case, when there are multiple carbon chains with the largest number of carbon atoms counted from the carbon atom bonded to the ester bond portion, and the number of carbon atoms in the side chains contained in the multiple carbon chains is the same, the one with the smallest number of side chains is defined as the main chain.

[0028] The number of carbon atoms in one molecule of the fatty acid ester solvent is preferably 18 or more, more preferably 20 or more, still more preferably 22 or more, and even more preferably 24 or more. When the number of carbon atoms in the fatty acid ester solvent is within this range, the total number of carbon atoms in the alkyl group and the number of carbon atoms in the side chain can be sufficiently ensured, the fatty acid ester solvent can be made bulky, and the deterioration of the resin product can be prevented. Moreover, when the number of carbon atoms in one molecule of the fatty acid ester solvent is within this range, the odor of the fatty acid ester solvent itself can be reduced, and the odor generated from the ink can be reduced. For odor reduction, the number of carbon atoms in one molecule of the fatty acid ester solvent is particularly preferably 24 or more. Also, the number of carbon atoms in one molecule of the fatty acid ester solvent is preferably 29 or less, more preferably 28 or less, and still more preferably 26 or less. Since high carbon numbers may lead to high viscosity, when the number of carbon atoms in the fatty acid ester solvent is within this range, the ink can be made low-viscosity, and roller transfer stains can be prevented.

[0029] R which is an alkyl group 1 The total number of carbon atoms is preferably 5 or more. Also, for R 2 which is an alkyl group, the total number of carbon atoms is preferably 6 or more. When both the alkyl groups in the fatty acid part and the alcohol part of the fatty acid ester solvent have a certain length, the fatty acid ester solvent becomes bulky, preventing its penetration into the resin product and preventing the deterioration of the resin product.

[0030] R 1 When R is a branched alkyl group having a side chain with 4 or more carbon atoms, for R 1 the total number of carbon atoms is preferably 9 or more, more preferably 11 or more, still more preferably 13 or more, and even more preferably 15 or more. In this case, for R 1The total number of carbon atoms of the whole is preferably 22 or less, more preferably 20 or less. R 1 When is a linear alkyl group or a branched alkyl group having a side chain with 3 or less carbon atoms, R 1 The total number of carbon atoms of the whole is preferably 5 or more, more preferably 7 or more, still more preferably 8 or more, and even more preferably 11 or more. In this case, R 1 The total number of carbon atoms of the whole is preferably 19 or less, more preferably 15 or less.

[0031] R 2 When is a branched alkyl group having a side chain with 4 or more carbon atoms, R 2 The total number of carbon atoms of the whole is preferably 9 or more, more preferably 12 or more, still more preferably 13 or more, and even more preferably 16 or more. In this case, R 2 The total number of carbon atoms of the whole is preferably 23 or less, more preferably 22 or less, and still more preferably 20 or less. R 2 When is a linear alkyl group or a branched alkyl group having a side chain with 3 or less carbon atoms, R 2 The total number of carbon atoms of the whole is preferably 6 or more, more preferably 8 or more, and still more preferably 9 or more. In this case, R 2 The total number of carbon atoms of the whole is preferably 19 or less, more preferably 14 or less. R 1 and R 2 The total number of carbon atoms of the whole is adjusted according to the length of the main chain of each other, the number of carbon atoms of the side chain, and the total number of carbon atoms of the fatty acid ester solvent.

[0032] Also, when both the alkyl group R 1 of the fatty acid part and the alkyl group R 2 of the alcohol part of the fatty acid ester solvent have a certain length, when the fatty acid ester solvent decomposes into fatty acid and alcohol, the molecular weight of the alkyl group of the decomposition product becomes relatively large, and the problem that the decomposition product volatilizes and causes odor can be prevented. The fatty acid ester solvent has a problem of decomposing by absorbing moisture in the air, especially by storage under high temperature conditions. To reduce odor, R of the fatty acid ester solvent1 and R 2 The total number of carbon atoms of each of them is preferably independently 6 or more, more preferably 8 or more, and even more preferably 9 or more. More preferably, R 1 and R 2 The total number of carbon atoms of both is 6 or more, more preferably 8 or more, and even more preferably 9 or more. Also, regarding the odor of the fatty acid ester solvent itself as well, the alkyl groups R 1 of the fatty acid part and the alkyl group R 2 of the alcohol part can be reduced by having a certain length.

[0033] R 1 and R 2 At least one of them preferably has a side chain having 4 or more carbon atoms and is a branched alkyl group having 9 or more carbon atoms. The number of carbon atoms of the side chain of the branched alkyl group is preferably 4 or more, and more preferably 6 or more. Thereby, the fatty acid ester solvent becomes bulky and deterioration of the resin product can be prevented. Also, the number of carbon atoms of the side chain of the branched alkyl group is not particularly limited and may be 11 or less, preferably 10 or less, and more preferably 8 or less.

[0034] The side chain having 4 or more carbon atoms may be either a straight-chain alkyl group or a branched alkyl group. The side chain preferably contains a carbon chain in which 4 or more, more preferably 6 or more carbon atoms are linearly bonded. For example, the side chain is preferably a straight-chain alkyl group having 4 or more, more preferably 6 or more carbon atoms.

[0035] Examples of the side chain having 4 or more carbon atoms include an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group, a nonyl group, a decyl group, and the like. Preferably, they are an n-butyl group, a hexyl group, an octyl group, and more preferably an n-butyl group, a hexyl group.

[0036] Examples of the fatty acid ester solvents represented by the general formula (1) include, for example, esters of hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, or heptadecanoic acid with 2-butyloctanol; esters of hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, or dodecanoic acid with 2-hexyldecanol; esters of hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexanoic acid, or nonanoic acid with 2-octyldodecanol; esters of 2-butyloctanoic acid with hexanol, heptanol, octanol, 2-ethylhexanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, hexadecanol, or heptadecanol; esters of 2-hexyldecanoic acid with hexanol, heptanol, octanol, 2-ethylhexanol, nonanol, decanol, undecanol, dodecanol, or tridecanol; esters of 2-octyldodecanoic acid with hexanol, heptanol, octanol, 2-ethylhexanol, or nonanol; esters of 2-butyloctanoic acid with 2-butyloctanol or 2-hexyldecanol; esters of 2-hexyldecanoic acid with 2-butyloctanol, etc.

[0037] Specific examples of the fatty acid ester solvents represented by the general formula (1) include 2-butyl octyl heptanoate, 2-octyl dodecyl octanoate, 2-butyl octyl 2-ethylhexanoate, 2-hexyl decyl 2-ethylhexanoate, 2-hexyl decyl nonanoate, 2-hexyl decyl dodecanoate, 2-butyl octyl tetradecanoate, 2-butyl octyl hexadecanoate, octyl 2-butyl octanoate, hexyl 2-hexyl decanoate, octyl 2-hexyl decanoate, dodecyl 2-butyl octanoate, nonyl 2-hexyl decanoate, tetradecyl 2-butyl octanoate, 2-butyl octyl 2-butyl octanoate, hexadecyl 2-butyl octanoate, dodecyl 2-hexyl decanoate, etc. The fatty acid ester solvent may be used alone or in combination of two or more.

[0038] The fatty acid ester solvent represented by the general formula (1) is not particularly limited with respect to the total amount of the non-aqueous solvent, but it is preferably contained in an amount of 10% by mass or more. From the viewpoint of preventing deterioration of the resin product and eliminating the influence of other solvents, the fatty acid ester solvent represented by the general formula (1) is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 80% by mass or more, for example, it may be 85% by mass or more, and even 100% by mass, based on the total amount of the non-aqueous solvent.

[0039] The blending amount of the fatty acid ester solvent represented by the general formula (1) with respect to the total amount of the ink varies depending on the amount of the non-aqueous solvent used as a whole, but it may be contained in an amount of 10 to 98% by mass, or may be contained in an amount of 15 to 90% by mass. The fatty acid ester solvent represented by the general formula (1) is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, and even more preferably 55% by mass or more, based on the total amount of the ink. Thereby, deterioration of the resin product can be more effectively prevented.

[0040] The blending amount of the fatty acid ester solvent having 30 or more carbon atoms in the ink is preferably limited. For example, the blending amount of the fatty acid ester solvent having 30 or more carbon atoms is preferably 70% by mass or less, more preferably 40% by mass or less, still more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on the total amount of the ink. Thereby, the stickiness of the ink applied to the printed matter can be reduced, and the roller transfer stain can be further improved. Furthermore, when the ink contains a fatty acid ester solvent having 30 or more carbon atoms, the fatty acid ester solvent represented by the general formula (1) is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount of the ink.

[0041] The fatty acid ester solvent represented by the above general formula (1) can be produced by the following method, although not limited thereto. The fatty acid ester solvent can be obtained by reacting a fatty acid with an alcohol. At least one of the raw material fatty acid and alcohol having a side chain with 4 or more carbon atoms is used. Also, R 2 In order to introduce a side chain with 4 or more carbon atoms into R, those in which the hydroxy group is located at the 5th position or higher among secondary alcohols with 10 or more carbon atoms can be used. The reaction temperature can be adjusted in the range of 80 to 230 °C according to the types of fatty acid and alcohol. The reaction time can be adjusted in the range of 1 to 48 hours according to the types of fatty acid and alcohol and the amount of raw materials used. It is preferable to remove the water generated during the esterification reaction. The fatty acid and alcohol are preferably reacted in a molar ratio of 1:1. During the reaction, an appropriate amount of a catalyst such as concentrated sulfuric acid, p-toluenesulfonic acid, or methanesulfonic acid may be used.

[0042] Examples of the fatty acid having a side chain as a raw material include 2-butyloctanoic acid, 2-hexyldecanoic acid, 2-octyldodecanoic acid, and the like. Examples of the straight-chain fatty acid as a raw material include pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, and the like.

[0043] Examples of the alcohol having a side chain as a raw material include 2-butyl-1-octanol, 2-hexyl-1-decanol, 2-octyl-1-dodecanol, and the like. Among the straight-chain alcohols as raw materials, those having 10 or more carbon atoms and a hydroxy group at the 5th position or higher include, for example, 5-nonanol, 5-decanol, 5-undecanol, 7-tetradecanol, and the like. Examples of the linear alcohol used as a raw material include 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol, and the like.

[0044] The ink may contain other non-aqueous solvents. As the other non-aqueous solvents, either non-polar organic solvents or polar organic solvents can be used. In one embodiment, it is preferable to use a water-insoluble organic solvent that does not uniformly mix with the same volume of water at 1 atm and 20°C as the non-aqueous solvent.

[0045] Examples of the non-polar organic solvents preferably include petroleum 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 paraffinic, isoparaffinic, and naphthenic solvents. Examples of commercially available products include Solvent L No. 0, Solvent M No. 0, Solvent H No. 0, Cactus Normal Paraffin N-10, Cactus Normal Paraffin N-11, Cactus Normal Paraffin N-12, Cactus Normal Paraffin N-13, Cactus Normal Paraffin N-14, Cactus Normal Paraffin N-15H, Cactus Normal Paraffin YHNP, Cactus Normal Paraffin SHNP, Isosol 300, Isosol 400, T-Clean N-16, T-Clean N-20, T-Clean N-22, AF Solvent No. 4, AF Solvent No. 5, AF Solvent No. 6, AF Solvent No. 7, Naphthosol 160, Naphthosol 200, Naphthosol 220 (all manufactured by JXTG Energy Corporation); Isopar G, Isopar H, Isopar L, Isopar M, Exxsol D40, Exxsol D60, Exxsol D80, Exxsol D95, Exxsol D110, Exxsol D130 (all manufactured by ExxonMobil); Moresco White P-40, 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, Moresco White P-350P (all manufactured by MORESCO Corporation), etc. Examples of aromatic hydrocarbon solvents include Grade Alkene L, Grade Alkene 200P (both manufactured by JXTG Energy Corporation), Solvesso 100, Solvesso 150, Solvesso 200, Solvesso 200ND (all manufactured by ExxonMobil), etc. The initial boiling point of the petroleum-based hydrocarbon solvent is preferably 100°C or higher, more preferably 150°C or higher, and even more preferably 200°C or higher. The initial boiling point can be measured according to JIS K0066 "Test Method for Distillation of Chemical Products".

[0046] Examples of the polar organic solvent include preferably fatty acid ester solvents, higher alcohol solvents, higher fatty acid solvents, and the like. Examples of the fatty acid ester solvents include solvents having a linear alkyl group such as methyl laurate, hexyl laurate, hexyl palmitate, methyl oleate, ethyl oleate, butyl oleate, hexyl oleate, methyl linoleate, ethyl linoleate, butyl stearate, hexyl stearate, methyl soybean oil, methyl tall oil, etc., with the total carbon number of 12 or more, preferably 16 - 30; solvents having an alkyl group with 3 or less carbon atoms in the side chain such as isodecyl isononanoate, isotridecyl isononanoate, isopropyl isostearate, isononyl isononanoate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isooctyl palmitate, isopropyl oleate, isobutyl linoleate, isooctyl stearate, isobutyl soybean oil, isobutyl tall oil, etc.; solvents having 31 or more carbon atoms such as isostearyl palmitate (carbon number 34), etc. Among the commercially available fatty acid ester solvents, isodecyl isononanoate (carbon number 19), isotridecyl isononanoate (carbon number 22), isopropyl isostearate (carbon number 21), etc. are fatty acid ester solvents having an alkyl group with 1 carbon atom in the side chain.

[0047] Examples of the higher alcohol solvents include higher alcohol solvents having 6 or more carbon atoms, preferably 12 - 20 carbon atoms in one molecule, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, decyltetradecanol, etc. Examples of the higher fatty acid solvents include higher fatty acid solvents having 12 or more carbon atoms, preferably 14 - 20 carbon atoms in one molecule, such as lauric acid, isomyristic acid, palmitic acid, isopalmitic acid, α - linolenic acid, linoleic acid, oleic acid, isostearic acid, etc. 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. Note that non-aqueous solvents with a boiling point of 250 °C or higher include non-aqueous solvents that do not exhibit a boiling point.

[0048] These non-aqueous solvents may be used alone or in combination of two or more as long as they form a single phase. When using other non-aqueous solvents in addition to the fatty acid ester solvent represented by the general formula (1), it is preferable to use a high-boiling solvent. As the high-boiling solvent, it is preferable to use a non-polar solvent with an initial boiling point of distillation of 200 °C or higher, a polar solvent with a boiling point of 250 °C or higher, or a combination thereof.

[0049] In addition to the above components, the oil-based ink may contain various additives as long as the effects of the present invention are not impaired. As the additives, a nozzle clogging preventive agent, an antioxidant, a conductivity adjuster, a viscosity adjuster, a surface tension adjuster, an oxygen absorber, etc. can be appropriately added. Further, in order to adjust the color development of the ink, a dye may be used in combination with a pigment. The types of these are not particularly limited, and those used in the relevant field can be used.

[0050] The ink can be prepared by mixing the components including the coloring material and the non-aqueous solvent. Preferably, the components can be mixed and stirred all at once or divided to prepare the ink. Specifically, all the components can be put into a disperser such as a bead mill all at once or divided and dispersed, and if desired, it can be prepared by passing through a filter such as a membrane filter.

[0051] The viscosity of the oil-based inkjet ink varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, etc., but generally, it is preferably 5 to 30 mPa·s at 23 °C, and more preferably 5 to 15 mPa·s.

[0052] The printing method using the inkjet ink is not particularly limited, and any method such as the piezo method, the electrostatic method, the thermal method, etc. may be used. When using an inkjet recording apparatus, it is preferable to eject the ink according to one embodiment from the inkjet head based on a digital signal and attach the ejected ink droplets to a recording medium. The ink according to one embodiment can be appropriately ejected near room temperature (23°C) because it has a low viscosity and is suitable for ejection from an inkjet nozzle while preventing the swelling of resin products.

[0053] In one embodiment, the recording medium is not particularly limited, and printing papers such as plain paper, coated paper, and special paper, cloth, inorganic sheets, films, OHP sheets, etc., and adhesive sheets provided with an adhesive layer on the back surface using these as a base material can be used. Among these, from the viewpoint of the ink permeability, printing papers such as plain paper and coated paper can be preferably used.

[0054] Here, plain paper is paper on which an ink receiving layer, a film layer, etc. are not formed on ordinary paper. Examples of plain paper include fine paper, medium paper, PPC paper, toilet paper, recycled paper, etc. Plain paper is paper in which paper fibers with a thickness of several μm to several tens of μm form voids of several tens to several hundreds of μm, so it is paper in which ink easily penetrates.

[0055] Also, as the coated paper, inkjet coated papers such as matte paper, glossy paper, and semi-glossy paper, and so-called coated printing papers can be preferably used. Here, the coated printing paper is printing paper that has been conventionally used in letterpress printing, offset printing, gravure printing, etc., and is printing paper provided with a coating layer by a coating containing an inorganic pigment such as clay or calcium carbonate and a binder such as starch on the surface of fine paper or medium paper. The coated printing paper is classified into micro-coated paper, fine lightweight coated paper, medium lightweight coated paper, fine coated paper, medium coated paper, art paper, cast coated paper, etc. according to the coating amount and coating method of the coating.

Example

[0056] Hereinafter, the present invention will be described in detail with reference to examples. The present invention is not limited to the following examples.

[0057] "Synthesis of Fatty Acid Esters" The formulation of the fatty acid ester is shown in Table 1. According to the formulation shown in Table 1, fatty acid and alcohol were placed in a four-necked flask, mixed and stirred to obtain a homogeneous solution. A Dean-Stark apparatus was attached to the four-necked flask so that water generated by the reaction of the charged raw materials could be removed. An appropriate amount of sulfuric acid was further added to the four-necked flask containing the homogeneous solution as a catalyst, and the whole system was heated. The heating temperature was set to 80°C to 230°C according to the types of fatty acid and alcohol. The heating reaction time was set to 1 to 48 hours. After the reaction, the obtained solution was distilled under reduced pressure to remove unreacted raw materials and impurities, and a fatty acid ester was obtained. Fatty acid and alcohol were mixed so that the molar ratio was 1:1. Fatty acid and alcohol can be obtained from Tokyo Chemical Industry Co., Ltd., Wako Pure Chemical Industries, Ltd. and Sasol.

[0058]

Table 1

[0059] "Preparation of Ink" The formulations of the inks are shown in Tables 2, 3, and 4. The number of carbon atoms in one molecule of the fatty acid ester, R 1 and R 2 The number of carbon atoms, the number of side chains, and the number of carbon atoms in the side chain are shown in each table, respectively. According to the blending amounts shown in each table, the pigment, pigment dispersant, and solvent were mixed, and the pigment was sufficiently dispersed by a bead mill "Dyno Mill KDL-A" (manufactured by Shinmaru Enterprises Co., Ltd.) under the condition of a residence time of 15 minutes. Subsequently, coarse particles were removed with a membrane filter to obtain an ink.

[0060] The components used are as follows. (Pigment) Carbon black: "MA77" manufactured by Mitsubishi Chemical Corporation. Copper phthalocyanine blue: "FASTOGEN Blue LA5380" manufactured by DIC Corporation. (Pigment dispersant) Solsperse 13940: "Solsperse 13940" manufactured by Lubrizol Japan Ltd., with an active ingredient of 40% by mass. Solsperse 18000: "Solsperse 18000" manufactured by Lubrizol Japan Ltd., with an active ingredient of 100% by mass. (Hydrocarbon solvent) Hydrocarbon solvent "Exxsol D110": manufactured by ExxonMobil.

[0061] "Evaluation" The inks of the above Examples and Comparative Examples were evaluated by the following method. The evaluation results are shown in Tables 2, 3, and 4.

[0062] (Swelling property of vinyl chloride tube) A vinyl chloride tube with an inner diameter of 2.38 mm and an outer diameter of 4.76 mm was cut into a length of 5 cm to prepare a test piece. The test piece was immersed in each ink and stored at room temperature for 1 week. From the mass a of the test piece before storage and the mass b of the test piece after storage, the mass change rate "(b - a) / a × 100" was determined. AA: Less than +3.0%. A: +3.0% or more and less than +5.0%. B: +5.0% or more and less than +10.0%. C: +10.0% or more.

[0063] (Roller transfer stain) A transport roller made of nitrile rubber (NBR) was attached to the transport path of an inkjet printer "OfficeEX9050" (manufactured by Risoh Co., Ltd.) at a position where it contacts the printed surface of the printed matter on the downstream side in the transport direction of the printed matter with respect to the inkjet head. Each ink was introduced into the inkjet printer, and plain paper "Risoh Thin Paper" (manufactured by Risoh Co., Ltd.) was used as the recording medium to print a solid image. Printing was repeated 100 times, and the roller transfer stain occurring on the 100th printed matter was visually observed and evaluated according to the following criteria. A: The stain on the printed matter is not noticeable. B: The printed matter feels dirty. C: It can be seen that the printed matter is dirty.

[0064] (Odor of ink) The odor of the ink was evaluated according to the following criteria. The evaluation of the odor was carried out by directly having 10 panelists smell the ink and conducting a sensory evaluation according to the following criteria. The evaluation result is the average of the evaluation results of 10 panelists. A: A level where almost no odor is felt. B: A level where a little odor is felt. C: A level where an odor is felt.

[0065] Although not particularly detailed, in the printing using the ink of each example, a printed matter with sufficient image density could be obtained. Also, the viscosity of the ink of each example was appropriate.

[0066]

Table 2

[0067]

Table 3

[0068]

Table 4

[0069] As shown in the table, with the ink of each example, swelling of the vinyl chloride tube and roller transfer contamination could be prevented, and also the odor of the ink could be prevented. Throughout the examples, R 1 having a side chain carbon number of 4 or more, particularly 6 or more, or R 2 having a side chain carbon number of 4 or more, particularly 6 or more, could more effectively prevent the swelling of the vinyl chloride tube. Also, when R 1 has a carbon number of 5 or more, particularly 8 or more, and R 2 has a carbon number of 6 or more, particularly 9 or more, the swelling of the vinyl chloride tube could be more effectively prevented. Moreover, when the number of carbon atoms in one molecule of the fatty acid ester was 29 or less, particularly 26 or less, roller transfer stain could be further prevented. Moreover, when the number of carbon atoms in one molecule of the fatty acid ester was 18 or more, particularly 24 or more, swelling of the vinyl chloride tube could be further prevented, and furthermore, the odor of the ink could be further prevented.

[0070] Example 15 was an example in which the types of the pigment and the pigment dispersant were changed, and good results could be obtained. Example 16 was an example in which two types of fatty acid esters were used, and good results could be obtained. Example 17 was an example in which a fatty acid ester and a hydrocarbon solvent were combined, and the ratio of the hydrocarbon solvent was high, but good results could be obtained.

[0071] The fatty acid ester of Comparative Example 1 had 17 carbon atoms in one molecule, and R 1 and R 2 were linear alkyl groups, and swelling of the vinyl chloride tube occurred. The fatty acid esters of Comparative Examples 2 and 4 did not contain side chains having 4 or more carbon atoms in R 1 and R 2 and swelling of the vinyl chloride tube occurred. The fatty acid ester of Comparative Example 3 had as few as 4 carbon atoms in R 2 and swelling of the vinyl chloride tube occurred. The fatty acid ester of Comparative Example 5 had 4 carbon atoms in R 1 and swelling of the vinyl chloride tube occurred. The fatty acid esters of Comparative Examples 6 and 7 had 30 carbon atoms in one molecule, and roller transfer stain occurred. Comparative Example 8 did not use a fatty acid ester but used a hydrocarbon solvent, and swelling of the vinyl chloride tube occurred. Through the examples and comparative examples, it was found that when the number of carbon atoms in one molecule of the fatty acid ester was small, odor tended to occur. Also, R 1 and R 2It was found that when the number of carbon atoms is small, odor tends to occur.

Claims

1. An oil-based inkjet ink comprising a fatty acid ester solvent represented by the following general formula (1) and having 24 to 28 carbon atoms in one molecule, and a pigment, wherein the fatty acid ester solvent is 10% by mass or more based on the total amount of the non-aqueous solvent, and the fatty acid ester solvent is 10 to 98% by mass based on the total amount of the ink. (However, an oil-based inkjet ink containing a dye, cyclohexane at 55% by weight or more based on the total amount of the ink, and triethanolamine at 30% by weight or more based on the total amount of the ink, an oil-based inkjet ink containing a dye, sorbitan monolaurate at 5% by weight or more based on the total amount of the ink, and kerosene at 50% by weight or more based on the total amount of the ink, and an oil-based inkjet ink containing a dye, 1,1,1-trichloroethane at 20% by weight or more based on the total amount of the ink are excluded.) 【Chemical 1】 (In the general formula (1), R １ and R ２ One of them has a straight-chain side chain with 6 or more carbon atoms and is a branched alkyl group with 13 or more carbon atoms, R １ and R ２ the other of which is a linear alkyl group having 6 or more carbon atoms, or a branched alkyl group having 1 side chain with 2 carbon atoms and 7 carbon atoms.)

2. An oil-based inkjet ink comprising a fatty acid ester solvent represented by the following general formula (1) and having 24 to 28 carbon atoms in one molecule, and a pigment, wherein the fatty acid ester solvent is 10% by mass or more based on the total amount of the non-aqueous solvent, and the fatty acid ester solvent is 10 to 98% by mass based on the total amount of the ink. (However, an oil-based inkjet ink containing a dye, cyclohexane at 55% by weight or more based on the total amount of the ink, and triethanolamine at 30% by mass or more based on the total amount of the ink, an oil-based inkjet ink containing a dye, sorbitan monolaurate at 5% by weight or more based on the total amount of the ink, and kerosene at 50% by weight or more based on the total amount of the ink, and an oil-based inkjet ink containing a dye, 1,1,1-trichloroethane at 20% by mass or more based on the total amount of the ink are excluded.) 【Chemical Formula 1-1】 (In the general formula (1), one of R1 and R2 is a branched alkyl group having a linear side chain with 6 or more carbon atoms and 13 or more carbon atoms, the other of R1 and R2 is a linear alkyl group having 6 or more carbon atoms, a branched alkyl group represented by the following formula (1A), or a branched alkyl group represented by the following formula (1B), where * is the bonding site in the formula (1A) and the formula (1B).) 【Chemical 1-2】

3. Said R １ and R ２ The other is a linear alkyl group having 8 or more carbon atoms, the oil-based inkjet ink according to claim 1 or 2.

4. The oil-based inkjet ink according to claim 1 or 2, wherein the fatty acid ester solvent has 26 or less carbon atoms in one molecule.

5. The fatty acid ester-based solvent has 26 or less carbon atoms in one molecule, and the R １ and R ２ The other of which is a linear alkyl group having 6 or more carbon atoms, the oil-based inkjet ink according to claim 1 or 2.

6. The fatty acid ester-based solvent has 26 or less carbon atoms in one molecule, and the R １ and R ２ The other is an oily inkjet ink according to claim 1 or 2, which has one side chain having 2 carbon atoms and is a branched alkyl group having 7 carbon atoms.

7. The fatty acid ester-based solvent is 50% by mass or more based on the total amount of the non-aqueous solvent, and the oil-based inkjet ink according to any one of claims 1 to 6.

8. An oil-based inkjet ink containing a fatty acid ester-based solvent represented by the following general formula (1) and a pigment, wherein the fatty acid ester-based solvent is 10 to 98% by mass based on the total amount of the ink. (However, an oil-based inkjet ink containing a dye, cyclohexane at 55% by mass or more based on the total amount of the ink, and triethanolamine at 30% by mass or more based on the total amount of the ink, an oil-based inkjet ink containing a dye, sorbitan monolaurate at 5% by mass or more based on the total amount of the ink, and kerosene at 50% by mass or more based on the total amount of the ink, and an oil-based inkjet ink containing a dye, 1,1,1-trichloroethane at 20% by mass or more based on the total amount of the ink are excluded.) [Chemical Formula 2] (In the general formula (1), the number of carbon atoms in one molecule is 24 or more and 26 or less, R １ is an alkyl group having 5 or more carbon atoms, R ２ is an alkyl group having 6 or more carbon atoms, R １ and R ２ One of them has a linear side chain with 4 or more carbon atoms and is a branched alkyl group with 9 or more carbon atoms, and R １ and R ２ The other is a linear alkyl group.)

9. An oil-based inkjet ink containing a fatty acid ester-based solvent represented by the following general formula (1) and a pigment, wherein the fatty acid ester-based solvent is 10 to 98% by mass based on the total amount of the ink. [Chemical Formula 3] (In the general formula (1), the number of carbon atoms in one molecule is 19 or more and 29 or less, R １ and R ２ both have a linear side chain with 4 or more carbon atoms and are branched alkyl groups with 9 or more carbon atoms.)

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