JP2013072014A - Water-in-oil (w/o) type emulsion ink for inkjet printing - Google Patents

Abstract

A water-in-oil (W / O) emulsion ink suitable for ink jet printing, which has excellent storage stability particularly at high temperatures.
The water-in-oil (W / O) emulsion ink of the present invention uses, as an emulsifier, a polyglycerin fatty acid ester having a fatty acid portion of oleic acid or isostearic acid and an HLB of 7 to 14 as an oil phase. Contains a pigment and contains a water-soluble dye in the aqueous phase. The polyglycerol fatty acid ester is preferably contained in an amount of 0.5 to 40% by mass based on the total amount of the ink. The pigment is preferably carbon black, and the water-soluble dye is preferably an anionic dye. Moreover, it is preferable that the emulsifier further contains an alkyl glyceryl ether. The emulsion ink is composed of 40 to 95% by mass of an oil phase and 60 to 5% by mass of an aqueous phase, and the aqueous phase may contain glycerin or diglycerin in addition to the dye.
[Selection figure] None

Description

  The present invention relates to a water-in-oil (W / O) emulsion ink suitable for use in ink jet printing, and relates to a water-in-oil (W / O) emulsion ink for ink jet having excellent ejection performance and storage stability.

  Ink-jet printing is characterized by non-contact printing by ejecting ink droplets from fine nozzles, and each company is developing ink-jet ink with the aim of miniaturizing ink droplets, speeding up printed materials, and increasing the size. Is going.

  As an ink used in ink jet printing (referred to as “ink jet ink” in the present specification), an aqueous dye / pigment ink is generally used for personal and office use. The water-based dye / pigment ink has a high printing density due to the high water absorption of paper fibers, and the amount of show-through, which is the printing density viewed from the back side of the printed matter, is reduced. On the other hand, since the paper is dried in a state where pressure is applied when paper is made, when water adheres, hydrogen bonds between paper fibers are cut and paper curl is generated. This paper curl is conspicuous when a cut sheet is used, and affects the positional accuracy of the ink droplets and the paper conveyance. In particular, in order to aim at high-speed printing, it was necessary to eliminate paper curl.

  A technique for eliminating paper curl includes reducing or eliminating the amount of water in the ink. Therefore, if oil-based ink is used, paper curl does not occur and it is suitable for high-speed printing.

  Business printers that employ a line head type ink jet method are attracting attention because they have a fixed head and are capable of mass printing at high speed and are inexpensive. Oil-based pigment ink is usually used for this high-speed printing ink jet printer, but compared to other types of printers, the ink penetrates into the back of the printed product when printed, so the resulting printed product has a printing density. It will be low and have many strikethroughs.

  One solution to this problem is to emulsify water in an oil-based pigment ink to form a water-in-oil (W / O) emulsion ink (see Patent Documents 1 and 2). The emulsion ink of Patent Document 1 uses a polyglycerin hydroxy fatty acid ester having an HLB value of 3 to 5 as an emulsifier, but is not necessarily sufficient in terms of ejection performance and storage stability.

JP 2006-56931 A JP 2009-57462 A

  The present inventors have already used a specific surfactant, so that it has excellent discharge performance, and the water phase does not separate even when stored at a high temperature for a short period of about one week. Patent application for emulsion ink. However, the water-in-oil (W / O) emulsion ink for inkjet according to this application is not always sufficient for high-temperature storage stability for a long period (4 weeks), and further improvement is required. In this regard, as a result of intensive studies, when the ink containing a colorant (water-soluble dye) only in the aqueous phase is stored for a long time at a high temperature, the aqueous phase is easily separated, and the colorant (only in the oil phase ( It has been found that inks containing (pigments) do not cause separation of the aqueous phase but tend to increase in viscosity. However, there has been no water-in-oil (W / O) emulsion ink for ink-jet that does not separate a water phase and increase viscosity when stored at a high temperature for a long period of time.

  The object of the present invention is a water-in-oil (W / O) emulsion ink suitable for inkjet printing, which can suppress both separation of the water phase and change in viscosity when stored at high temperature for a long period of time. The object is to provide a product having excellent storage stability.

  As a result of intensive studies under the above-mentioned objectives, the present inventors have used a specific polyglycerin fatty acid ester as an emulsifier for a water-in-oil (W / O) emulsion ink, dispersed a pigment in the oil phase, It was found that by dissolving a water-soluble dye in a water-in-oil (W / O) emulsion ink for inkjet having excellent storage stability at high temperatures, the present invention was completed.

  That is, according to the present invention, there is provided a water-in-oil (W / O) emulsion ink for inkjet, in which an aqueous phase is dispersed in an oil phase containing a polyglycerin fatty acid ester as an emulsifier, the polyglycerin fatty acid ester Wherein the fatty acid part is oleic acid or isostearic acid, the HLB of the polyglycerin fatty acid ester is 7 to 14, the oil phase contains a pigment, and the water phase contains a water-soluble dye. A water-in-oil (W / O) emulsion ink for inkjet is provided.

  According to the present invention, a specific polyglycerin fatty acid ester is used as an emulsifier for forming a water-in-oil (W / O) emulsion, a pigment is dispersed in the oil phase, and a water-soluble dye is contained in the water phase As a result, a water-in-oil (W / O) emulsion ink having excellent storage stability at high temperatures can be obtained.

Hereinafter, the present invention will be described in more detail.
The water-in-oil (W / O) emulsion ink of the present invention is obtained by mixing an oil phase and an aqueous phase and dispersing the aqueous phase as fine particles in the oil phase.

  The oil phase is mainly composed of an organic solvent, a colorant and an emulsifier, but may contain other components as necessary.

  As the organic solvent, any of a nonpolar solvent and a polar solvent can be used. These may be used alone or in combination of two or more as long as they form a single phase.

  As non-polar solvents, petroleum hydrocarbon solvents such as naphthenic, paraffinic, and isoparaffinic solvents can be used. Specifically, aliphatic saturated hydrocarbons such as dodecane, “Isoper, Exol” manufactured by ExxonMobil ( All of them are trade names), “AF Solvent” (trade name) manufactured by JX Nippon Oil & Energy Corporation, “Sansen, Thumper” (all trade names) manufactured by Sun Oil Co., Ltd., and the like. These can be used alone or in combination of two or more.

  Examples of the polar solvent include ester solvents, alcohol solvents, fatty acid solvents, ether solvents and the like. These can be used alone or in combination of two or more.

  Examples of the ester solvent include higher fatty acid esters having 5 or more, preferably 9 or more, and more preferably 12 to 32 carbon atoms in one molecule. For example, isodecyl isononanoate, isotridecyl isononanoate, and isononanoic acid. Isononyl, methyl laurate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isooctyl palmitate, hexyl palmitate, isostearyl palmitate, isooctyl isopalmitate, methyl oleate, ethyl oleate, isopropyl oleate, oleic acid Butyl, hexyl oleate, methyl linoleate, isobutyl linoleate, ethyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopate isostearate Pill, 2-octyldodecyl pivalate, soybean oil methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, propylene glycol monocaprate, trimethylol tri-2-ethylhexanoate Examples thereof include propane and glyceryl tri-2-ethylhexanoate.

  Examples of the alcohol solvent include aliphatic higher alcohols having 12 or more carbon atoms in one molecule. Specifically, higher alcohols such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, and oleyl alcohol. Examples include alcohol.

  Examples of the fatty acid solvent include fatty acids having 4 or more, preferably 9 to 22 carbon atoms in one molecule, such as isononanoic acid, isomyristic acid, hexadecanoic acid, isopalmitic acid, oleic acid, and isostearic acid. Is mentioned.

  Examples of ether solvents include glycol ethers such as diethyl glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol dibutyl ether, and acetates of glycol ethers.

  As the oil phase colorant, a pigment is always used, but a dye may be used in combination.

  The pigment is not particularly limited, and may be any organic pigment or inorganic pigment that is commonly used in the technical field of printing. Specifically, carbon black, cadmium red, chrome yellow, cadmium yellow, chromium oxide, pyridian, titanium cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindo Rinone pigments, dioxazine pigments, selenium pigments, perylene pigments, thioindigo pigments, quinophthalone pigments, metal complex pigments and the like can be suitably used. These pigments may be used alone or in combination of two or more. Particularly in the case of black ink, it is preferable to use carbon black as a pigment.

  When a dye is used, as the dye, for example, an azo-based, anthraquinone-based, or azine-based oil-soluble dye can be used.

  The oil phase colorant is preferably contained in the range of 0.01 to 20% by mass relative to the total amount of ink.

  In order to improve the dispersion of the pigment in the oil phase, it is preferable to add a pigment dispersant to the oil phase. The pigment dispersant that can be used in the present invention is not particularly limited as long as the pigment is stably dispersed in a solvent. For example, a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, High molecular weight polycarboxylic acid salt, long chain polyaminoamide and polar acid ester salt, high molecular weight unsaturated acid ester, high molecular weight copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic active agent, naphthalene sulfone Acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonylphenyl ether, polyester polyamine, stearylamine acetate and the like are preferably used, and among them, a polymer dispersant is preferably used.

  Specific examples of the dispersant include “Solsperse 5000 (phthalocyanine ammonium salt type), 13940 (polyesteramine type), 17000, 18000 (fatty acid amine type), 11200, 22000, 24000, 28000” (all manufactured by Nippon Lubrizol Co., Ltd.). (Trade name), “Efka 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 4010, 4055 (modified polyurethane)” manufactured by Efka CHEMICALS (all trade names) ), “Demol P, EP, Poise 520, 521, 530, Homogenol L-18 (polycarboxylic acid type polymer surfactant)” (both trade names) manufactured by Kao Corporation, “Disparon KS-860 manufactured by Enomoto Kasei Co., Ltd.” KS-873N4 (polymer polyester Amine salts) ”(both trade names),“ Discall 202, 206, OA-202, OA-600 (multi-chain polymer nonionic) ”(both trade names) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. Can be mentioned.

  The content of the pigment dispersant is sufficient as long as the pigment can be sufficiently dispersed in the oil phase, and can be appropriately set.

As the emulsifier, a polyglycerin fatty acid ester having a fatty acid portion of oleic acid or isostearic acid and an HLB of 7 to 14 is used. Here, the polyglycerol fatty acid ester refers to an esterified product of polyglycerol and a fatty acid. When the polyglycerin fatty acid ester does not satisfy the requirements of the present invention, the discharge performance and storage stability are poor. It is preferable that the fatty acid portion is isostearic acid because both the discharge performance and the storage stability can be improved to a high degree.
The emulsifier preferably contains an alkyl glyceryl ether in addition to the polyglycerin fatty acid ester. The blending ratio of the polyglycerin fatty acid ester and the alkyl glyceryl ether is preferably the former: the latter = 95-50: 5-50 in mass ratio. By using alkyl glyceryl ether in combination with the emulsifier, the viscosity change of the ink when stored at high temperature can be further suppressed.

In the polyglycerin fatty acid ester, the polymerization degree of glycerin can be set to 4 or more, preferably 4 to 20, more preferably 6 to 16, and several per molecule (for example, 1 to 3). The above higher fatty acids are preferably ester-bonded and added. The organic value of the polyglycerin fatty acid ester is preferably 550 to 2300, and the inorganic value is preferably 600 to 2500. The more preferable organic value of the polyglycerin fatty acid ester is 550 to 1700, and the more preferable inorganic value is 600 to 1300. When the organic value is larger than 2300 or when the inorganic value is larger than 2500, the viscosity of the ink becomes high. Specific examples of preferable polyglyceryl fatty acid esters include tetraglyceryl monooleate, hexaglyceryl monooleate, decaglyceryl trioleate, tetraglyceryl monoisostearate, hexaglyceryl monoisostearate, decaglyceryl diisostearate and the like.
Specific examples of the alkyl glyceryl ether include myristyl glyceryl ether, palmityl glyceryl ether, stearyl glyceryl ether, oleyl glyceryl ether, isostearyl glyceryl ether and the like.

  The “organic value” and “inorganic value” are based on the concept used in the “Organic Conceptual Diagram” proposed by Satoshi Fujita, and the organic compound is derived from the covalent bond chain in its carbon region. Is divided into two factors, “organic” and “inorganic” due to electrostatic effects existing in substituents (functional groups), each of which is quantified, and is determined from the structure of each compound. Value. Matters relating to the “Organic Conceptual Diagram” are described in detail in the book “Systematic Organic Qualitative Analysis (mixture)” by Kaoru Fujita, Kazama Shobo (1974) and the like.

HLB is a theoretical value calculated from the following equation.
HLB = {(inorganic value) / (organic value)} × 10

  The amount of the emulsifier used in the present invention is preferably from 0.5 to 40% by mass, more preferably from 1 to 30% by mass, and even more preferably from 2 to 20 in terms of solid content mass ratio with respect to the total amount of the ink. % By mass. When the amount used is less than 0.5% by mass, the storage stability of the emulsion may be lowered. Moreover, when this usage-amount exceeds 40 mass%, a viscosity becomes high and there exists a possibility that it may become unsuitable for an inkjet use. Moreover, it is preferable that the usage-amount of an emulsifier is 5-70 mass% of the quantity of an oil phase, and it is more preferable that it is 10-60 mass%.

  The oil phase can be prepared by, for example, supplying all components into a known disperser such as a bead mill in a batch or divided and dispersing the mixture, and if desired, passing it through a known filter such as a membrane filter. For example, after preparing a mixed liquid in which a part of the solvent and the whole amount of the pigment and the pigment dispersant are uniformly mixed and dispersing with a disperser, the remaining components are added to the dispersion and a filter is added. It can be prepared by passing through.

  An aqueous phase dissolves a water-soluble dye in water, and further, if necessary, a metal salt, an electrolyte, a moisturizer, a water-soluble polymer, an oil-in-water (O / W) type resin emulsion, an antifungal agent, an antiseptic, It is constituted by dissolving a pH adjuster, an antifreezing agent and the like.

  Examples of water-soluble dyes include anionic dyes such as azo, anthraquinone, and azine. Here, the anionic dye is a general term for dye ions exhibiting anionic property.

  5-30 mass% is preferable with respect to the water phase mass, and, as for the compounding quantity of water-soluble dye, 10-24 mass% is more preferable. When the water-soluble dye concentration is less than 5% by mass, the viscosity is deteriorated. On the other hand, when the amount is more than 30% by mass, the dischargeability is deteriorated.

  A water-soluble dye dissolution aid can be added to the aqueous phase. In this case, since the dye is infiltrated and adsorbed on the paper fiber in a state dissolved to the molecular state, the coloring of the dye is improved. As the dissolution aid, an amine surfactant is preferable. Examples of the amine surfactant include polyalkylene oxide adducts of organic amines such as ethylene oxide (EO) or propylene oxide (alkylamine, alkenylamine, alkylhydroxylamine, alkenylhydroxylamine, oxyalkylamine, oxyalkenylamine, etc.) PO) adducts. Of these, ethylene oxide (EO) or propylene oxide (PO) adducts of alkylamines are preferred. As such amine-based surfactants, those commercially available as Solsperse 20000, Solsperse 27000, Solsperse 46000 (all trade names) manufactured by Nippon Lubrizol Co., Ltd., and TAMNO-15 (trade names) manufactured by Nikko Chemicals Co., Ltd. can be used. . 0.1-10 mass% is preferable with respect to ink whole quantity, and, as for the compounding quantity of a solubilizing agent, 0.3-8 mass% is more preferable.

  Moreover, in order to suppress the viscosity change of the ink at the time of storing at high temperature, it is preferable to add glycerin or diglycerin to the aqueous phase. The blending amount of glycerin or diglycerin is preferably 5 to 50% by mass, and more preferably 5 to 40% by mass of the entire aqueous phase. When the amount is less than 5% by mass, it is difficult to obtain a viscosity change suppressing effect. When the amount is more than 50% by mass, the ejection stability and the storage stability may be deteriorated.

  The method for producing the water-in-oil (W / O) emulsion ink for inkjet of the present invention is not particularly limited. For example, a method in which an emulsifier is dissolved in a pigment dispersion and an aqueous phase is added thereto to emulsify, or a pigment dispersion and a water-in-oil (W / O) emulsion are prepared separately and mixed. Methods and the like. A known emulsifier such as a disper mixer or a homomixer can be used for the production.

  The inkjet ink of this invention is mix | blended so that it may become 50-95 mass% of oil phases, and 50-5 mass% of water phases. When the ratio of the aqueous phase exceeds 50% by mass, the aqueous phase is easily separated in the water-in-oil (W / O) type emulsion. When the ratio of the aqueous phase is less than 5% by mass, the print density may be lowered or the printout may be exposed. In general, since the ink viscosity tends to increase as the ratio of the aqueous phase increases, the blending ratio of both phases is preferably 60 to 95% by mass of the oil phase and 40 to 5% by mass of the aqueous phase.

  The viscosity at 23 ° C. of the water-in-oil (W / O) emulsion ink of the present invention thus obtained is preferably set in the range of 5 to 100 mP · s, and in the range of 5 to 50 mPa · s. It is more preferable to set to 10 to 20 mPa · s. The viscosity of the ink can be adjusted by adjusting the type and amount of components of the oil phase and the amount of the aqueous phase. In general, the smaller the amount of aqueous phase and / or the amount of emulsifier, the lower the viscosity of the ink, but the lower the storage stability of the emulsion.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this Example.

Examples 1-8, Comparative Examples 1-5
The pigment and the dispersant in the blending amounts shown in Table 1 were mixed with a part of the solvent shown in the same table, and the pigment was dispersed with a rocking mill (manufactured by Seiwa Giken) to obtain a pigment dispersion. Next, the water phase shown in Table 1 was mixed and obtained. In addition, an oil phase in which a surfactant was dissolved in a part of the remaining solvent so as to have a predetermined concentration was obtained. To this oil phase, a water phase previously mixed while stirring at 5000 rpm using a high-speed homogenizer “Hiscotron” (trade name: manufactured by Microtech Nichion Co., Ltd.) was dropped, and then the oil phase was stirred for 5 minutes at 20000 rpm. A water-in-water (W / O) emulsion was obtained. A water-in-oil (W / O) emulsion ink was prepared by diluting a pigment dispersion prepared in advance with the remaining solvent and then mixing the prepared water-in-oil (W / O) emulsion. . In addition, the compounding quantity of each component in Table 1 is shown by the mass part.

  The inkjet inks obtained in the above examples and comparative examples were evaluated by the following methods.

(1) Moisture content change (degree of water phase separation)
In the water-in-oil (W / O) type emulsion ink, when separation of the aqueous phase occurs with time, the amount of water in the ink upper layer decreases. After storing at high temperature, the water content of the ink upper layer was measured, and the degree of water phase separation was evaluated by comparing with the water content before storage. A water-in-oil (W / O) emulsion ink was placed in a 10 ml screw vial and allowed to stand in a thermostatic bath at 70 ° C. for 4 weeks, and then the water content of the ink upper layer was measured. The ink was sampled from the top of the container, and the moisture content was measured using a Karl Fischer moisture measuring device (701 type, manufactured by Metrohm Shibata Co., Ltd.).
Ink upper layer water remaining rate (%):
{Water content of ink upper layer after storage (mass%) / Water content of ink upper layer before storage (mass%)} × 100
The stability was evaluated based on the following criteria using the water residual ratio expressed as described above as an index.
○: Ink upper layer water remaining rate is 80% or more ×: Ink upper layer water remaining rate is less than 80%

(2) Viscosity change (mPas)
A water-in-oil (W / O) emulsion ink was placed in a 10 ml screw vial and allowed to stand in a thermostatic bath at 70 ° C. for 4 weeks, and the viscosities before and after storage were measured and compared. A predetermined amount was sampled from the upper layer of the ink, and the viscosity (unit: mPas) when a shearing stress of 10 Pa was applied to the ink was measured using a rheometer AR-G2 (manufactured by TA Instruments). In the table, ND means not measured.
Viscosity change rate (%):
[Ink viscosity after storage for 4 weeks at 70 ° C. (mPas) / {Ink viscosity before storage (mPas) −1} × 100
Using the viscosity change rate expressed as described above as an index, the degree of viscosity change was evaluated.
A: Absolute value of viscosity change rate is less than 5% B: Absolute value of viscosity change rate is 5% or more and less than 10% Δ: Absolute value of viscosity change rate is 10% or more and less than 15% X: The absolute value of the viscosity change rate is 15% or more

Details of the raw materials listed in Table 1 are shown in Table 2.

These evaluation results are shown in Table 1.
In the case of the inks of Examples 1 to 8 using polyglycerin fatty acid ester satisfying all the requirements of the present invention as an emulsifier, the water content change before and after storage is obtained by dispersing the pigment in the oil phase and dissolving the water-soluble dye in the aqueous phase. It can be seen that the change in viscosity is small and the storage stability at high temperatures is improved. Moreover, as Example 6-8 shows, when glycerin or diglycerin is added to an aqueous phase, it turns out that the ink viscosity change before and behind storage becomes small.

On the other hand, Comparative Example 1 contains a pigment in the oil phase but does not contain a water-soluble dye in the aqueous phase, so the change in the water content of the ink before and after storage is small, but the change in viscosity is large and the storage stability is improved. Inferior. Comparative Example 2 contains a water-soluble dye in the water phase but does not contain a pigment in the oil phase, so the water content of the ink before and after storage is large and the viscosity is low. Inferior.
In Comparative Examples 3 to 5, since an emulsifier that does not satisfy the requirements of the present invention is used, the ink water content change and viscosity change before and after storage are large, and the storage stability is poor.

  Since the water-in-oil (W / O) emulsion ink for inkjet of the present invention is excellent in ejection performance and storage stability, it is used as an ink for business printers employing the line head type inkjet system, particularly in the field of inkjet printing. Available.

Claims (5)

  A water-in-oil (W / O) emulsion ink for inkjet, in which an aqueous phase is dispersed in an oil phase containing a polyglycerol fatty acid ester as an emulsifier, wherein the fatty acid portion of the polyglycerol fatty acid ester is oleic acid or isostearin An oil-in-oil (W) for ink jet, characterized in that the polyglycerin fatty acid ester has an HLB of 7 to 14, the oil phase contains a pigment, and the water phase contains a water-soluble dye. / O) type emulsion ink.   The water-in-oil (W / O) emulsion ink for inkjet according to claim 1, wherein the emulsifier further contains an alkyl glyceryl ether.   The water-in-oil (W / O) emulsion ink for inkjet according to claim 2, wherein a blending ratio of the polyglycerin fatty acid ester and the alkyl glyceryl ether is 95 to 50: 5 to 50 in terms of mass ratio.   The water-in-oil (W / O) emulsion ink for ink-jet recording according to any one of claims 1 to 3, wherein a blending amount of the water-soluble dye is 5 to 30% by mass of the entire aqueous phase.   The water-in-oil (W / O) emulsion ink for inkjet according to any one of claims 1 to 4, wherein glycerin is contained in the aqueous phase.