JP2018162421A - Water-in-oil type emulsion ink for stencil printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-in-oil type emulsion ink for stencil printing which can obtain a printed matter having a silvery metallic luster and suppresses the generation of a hydrogen gas without causing clogging of stencil paper.SOLUTION: There is provided a water-in-oil type emulsion ink for stencil printing which comprises an oil phase containing a silvery pigment, an oil component and an emulsifier and a water phase containing water, wherein the silvery pigment is an aluminum pigment which is surface-treated with a phosphoric acid ester-based surfactant. The phosphoric acid ester-based surfactant preferably is one selected from the group consisting of a polyoxyalkylene alkyl ether phosphate, a polyoxyalkylene aryl ether phosphoric acid ester, an alkylphosphoric acid ester and an arylphosphoric acid ester. The oil component preferably contains a higher fatty acid.SELECTED DRAWING: None

Description

  The present invention relates to a water-in-oil emulsion ink used in a stencil printing apparatus.

  Compared with printing methods such as offset printing, gravure printing and letterpress printing, the stencil printing method does not require complicated operations such as cleaning after use, and has excellent operability such as not requiring a specialized operator, Easy to use. Since the use of the thermal plate making system that uses a thermal head as a device, digitization of image processing has become possible in the stencil printing system, and high-quality printed materials can be easily obtained in a short time. Its convenience is recognized. In particular, rotary stencil printing presses with automatic control of stencil paper (master) plate making, plate-making and discharging, ink supply and printing operations are widely used in offices and schools under the name of digital stencil printing machines. It's being used.

  As a stencil printing ink, a water-in-oil (W / O) emulsion ink is generally used. The water-in-oil emulsion ink has a function to suppress changes in the composition and physical properties of the ink even when the printing device is left unused and the ink inside the printing device is in contact with the atmosphere. . That is, since the water that is the inner phase component of the emulsion ink is covered with the oil that is the outer phase component, its evaporation is suppressed.

  In recent years, there has been an increase in demand for users of various colors and glossy from users of stencil printing machines, for example, there has been an increase in demand for inks having metallic luster. For example, a water-in-oil for stencil printing containing a pearlescent pigment with a particle size of 1 to 30 μm in order to obtain a glossy printed image without depending on the type of paper and to speed up drying of the ink A type emulsion ink has been proposed (Patent Document 1). In addition, a water-in-oil emulsion for stencil printing that can obtain a printed matter having a sufficient metallic luster even when printed on plain paper by containing a metal powder pigment having an average particle size of 10 μm or less in the oil phase. An ink has been proposed (Patent Document 2).

JP 9-255908 A JP 2013-116980 A

  However, in order to obtain a silver metallic luster, even if a silver type pigment is used as the pearl luster pigment as in Patent Document 1, if the pigment particle size is dispersed so as to be 1 to 30 μm, color development at the time of printing However, it was not always satisfactory. On the other hand, when aluminum is used as the metal powder pigment as in Patent Document 2, there is a problem that hydrogen gas is generated by the reaction between aluminum and water due to contact with moisture contained in the emulsion ink. The commercially available water-resistant aluminum pigment has a large particle size, and if the pigment particle size is large, there is a problem that clogging occurs at the perforated portion of the stencil paper, so the pigment is dispersed to reduce the particle size. There is a need. However, when the aluminum pigment is refined, there is a problem that an aluminum surface which is not subjected to water resistance treatment is generated, and reacts with water to generate hydrogen gas.

  The present invention solves the above-mentioned problems of the prior art, obtains a printed matter having a silvery metallic luster, and does not clog the stencil paper and suppresses the generation of hydrogen gas. The object is to provide a water-in-water emulsion ink.

  An embodiment of the present invention is a water-in-oil emulsion ink for stencil printing comprising an oil phase containing a silver pigment, an oil component and an emulsifier, and an aqueous phase containing water, wherein the silver pigment is a phosphate ester-based interface A water-in-oil emulsion ink for stencil printing, which is an aluminum pigment surface-treated with an activator.

  The phosphate ester surfactant is preferably at least one selected from the group consisting of polyoxyalkylene alkyl ether phosphate esters, polyoxyalkylene aryl ether phosphate esters, alkyl phosphate esters and aryl phosphate esters. .

  The oil component preferably contains a higher fatty acid.

  According to the present invention, there is provided a water-in-oil emulsion ink for stencil printing, in which a printed matter having a silver metallic luster is obtained, the stencil sheet is not clogged, and generation of hydrogen gas is suppressed. be able to.

  A water-in-oil emulsion ink for stencil printing according to an embodiment of the present invention (hereinafter also simply referred to as ink) is composed of an oil phase containing a silver pigment, an oil component and an emulsifier, and an aqueous phase containing water. It is an aluminum pigment surface-treated with a phosphate ester surfactant. The oil phase is preferably 15 to 55% by mass, and the aqueous phase is preferably 85 to 45% by mass. The oil phase basically preferably contains a silver pigment, an oil component, an emulsifier, an oil-soluble resin and the like, and the water phase basically preferably contains water, a water-soluble organic solvent, an electrolyte and the like. Further, a colorant may be contained in the oil phase or the aqueous phase. Below, each component of the ink of embodiment of this invention is demonstrated one by one.

<Oil phase>
[Silver pigment]
In the present embodiment, an aluminum pigment surface-treated with a phosphate ester surfactant is used as the silver pigment. Here, “surface-treated” means a state of being physically adsorbed on the pigment surface. Such a silver pigment can be easily obtained as a silver pigment dispersion, and as a manufacturing method thereof, for example, an aluminum pigment, a phosphate ester surfactant, and an oil component are mixed using a known dispersion device. However, the method of heating to about 30 to 100 degreeC is mentioned. In this case, it is preferable to disperse the aluminum pigment simultaneously with mixing. Further, if an oil component contained in the oil phase of the ink is used as the oil component, it is advantageous because the ink can be produced using the obtained pigment dispersion as it is. For the production of the pigment dispersion, known dispersing devices such as a disper mixer, a homomixer, a colloid mill, a ball mill, an attritor, a sand mill, a roll mill, and a bead mill can be used.

  As for the particle diameter of the silver pigment, the volume-based particle diameter value (median diameter) in the particle size distribution measured by the laser diffraction / scattering method is preferably 0.1 to 10 μm, and preferably 0.5 to 10 μm. More preferably, it is 1-5 micrometers. By setting it in this range, an excellent silver metallic luster can be obtained, and clogging of the stencil sheet can be more reliably prevented. The particle diameter of the silver pigment can be set to a desired size according to the setting conditions of the dispersing device described above.

  Any phosphate-based surfactant can be used as long as it is adsorbed on the surface of the aluminum pigment, but the HLB value is preferably 3 to 8, and preferably 3.5 to 6.5. Is more preferable. As the phosphate ester surfactant, polyoxyalkylene alkyl ether phosphate ester, polyoxyalkylene aryl ether phosphate ester, alkyl phosphate ester, aryl phosphate ester and the like can be preferably used. Examples of the polyoxyalkylene alkyl ether phosphate ester include polyoxyethylene octyl ether phosphate ester, polyoxyethylene decyl ether phosphate ester, polyoxyethylene dodecyl ether phosphate ester, polyoxyethylene tridecyl ether phosphate ester, etc. Can be preferably mentioned. The alkyl group of the polyoxyalkylene alkyl ether phosphate ester preferably has 10 to 20 carbon atoms, and the polyoxyalkylene chain preferably has 0.5 to 8 moles of ethylene oxide or propylene oxide added thereto. Preferable examples of the polyoxyalkylene aryl ether phosphate ester include polyoxyethylene alkylphenyl ether and polyoxyethylene styrenated phenyl ether having 6 to 16 carbon atoms in the alkyl group. It is preferable that 0.5-8 mol of ethylene oxide or propylene oxide is added to the polyoxyalkylene chain of the polyoxyalkylene aryl ether phosphate. Preferred examples of the alkyl phosphate ester include dodecyl phosphate ester and octadecyl phosphate ester.

  It is considered that the phosphate ester surfactant is physically adsorbed on the surface of the aluminum pigment by the phosphate group, and covers the aluminum pigment so as to form a film on the pigment surface. Therefore, the generation of hydrogen can be suppressed by suppressing contact between aluminum and water. The aluminum pigment is preferably 1 to 20% by mass and more preferably 5 to 15% by mass with respect to the total amount of ink. The ratio between the aluminum pigment and the phosphate ester-based surfactant is preferably 30:70 to 99: 1, more preferably 40:60 to 95: 5, and 50:50 to 95 in terms of mass ratio. : 5 is even more preferable. Moreover, it is preferable that it is 0.1-5 mass% with respect to the ink whole quantity, and, as for phosphate ester type surfactant, it is more preferable that it is 0.5-3 mass%.

[Oil component]
In the present embodiment, as the oil component, various industrial solvents, motor oil, gear oil, light oil, kerosene, spindle oil, machine oil, liquid oil, etc., mineral oil, olive oil, rapeseed oil, linseed oil, castor oil, salad oil, In addition to vegetable oils such as soybean oil and rice bran oil, synthetic oils and the like can also be used.

  As the industrial solvent, any water-insoluble organic solvent can be used. For example, a petroleum hydrocarbon solvent such as an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, an aromatic hydrocarbon solvent and the like can be preferably exemplified. Examples of the aliphatic hydrocarbon solvent and the alicyclic hydrocarbon solvent include water-insoluble organic solvents such as paraffinic, isoparaffinic, and naphthenic solvents, and commercially available products include 0 Solvent L and 0 Solvent M. No. 0 solvent H, 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 N-15 Paraffin YHNP, Cactus normal paraffin SHNP, Isosol 300, Isosol 400, Teclean N-16, Teclean N-20, Teclean N-22, AF Solvent No. 4, AF Solvent No. 5, AF Solvent No. 6, AF Solvent No., Naphthezol 160, Naphthezol 200, Naphthezol 220 (all trade names made by JX Energy Co., Ltd.); Isopar G, Isopar H, Isopar L, Isopar M, Exol D40, Exol D60, Exol D80, Exol D95, Exol D110, Preferable examples include Exol D130 (both are trade names manufactured by TonenGeneral Sekiyu KK). As the aromatic hydrocarbon solvent, grade alkene L, grade alkene 200P (all are trade names made by JX Energy Co., Ltd.), Solvesso 100, Solvesso 150, Solvesso 200, Solvesso 200ND (all are products made by TonenGeneral Sekiyu KK) Name) etc. can be mentioned preferably. The distillation initial boiling point of the petroleum hydrocarbon solvent is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, and even more preferably 200 ° C. or higher. The distillation initial boiling point can be measured in accordance with JIS K0066 “Method for Distillation Test of Chemical Products”.

  Moreover, organic solvents, such as a fatty acid ester solvent, a higher alcohol solvent, a higher fatty acid solvent, can also be mentioned preferably as an oil component. For example, isononyl isononanoate, isodecyl isononanoate, methyl laurate, isopropyl laurate, hexyl laurate, isopropyl myristate, isopropyl palmitate, hexyl palmitate, isooctyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate , Isopropyl oleate, butyl oleate, hexyl oleate, methyl linoleate, ethyl linoleate, isobutyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopropyl isostearate, 2-octyldecyl pivalate, soybean oil Methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, etc., the number of carbon atoms in one molecule is 13 or more, preferably 16-30 fatty acid esters Agents: Higher alcohol solvents having 6 or more, preferably 12 to 20 carbon atoms in one molecule, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, decyltetradecanol; Higher fatty acid solvents such as lauric acid, isomyristic acid, palmitic acid, isopalmitic acid, α-linolenic acid, linoleic acid, oleic acid, isostearic acid and the like having 12 or more, preferably 14 to 20 carbon atoms in one molecule Is mentioned. The boiling point of an organic solvent such as a fatty acid ester solvent, a higher alcohol solvent, or a higher fatty acid solvent is preferably 150 ° C. or higher, more preferably 200 ° C. or higher, and further preferably 250 ° C. or higher. . In addition, the organic solvent whose boiling point is 250 degreeC or more includes the organic solvent which does not show a boiling point.

  In the present embodiment, the oil component preferably contains a higher fatty acid. The higher fatty acid preferably has 12 or more carbon atoms in one molecule, and more preferably 14-20. As such higher fatty acids, the above-mentioned higher fatty acid solvents may be used as they are, or vegetable oils containing higher fatty acids such as soybean oil may be used. For example, olive oil is a vegetable oil containing about 70% by weight oleic acid, about 10% by weight palmitic acid, and about 10% by weight linoleic acid. Moreover, the linseed oil contains about 50% by mass α-linolenic acid, about 20% by mass oleic acid, and about 10% by mass linoleic acid. Soybean oil contains about 50% by weight of linoleic acid, about 20% by weight of oleic acid, and about 10% by weight of palmitic acid. Rice bran oil is a vegetable oil containing about 40% by mass of oleic acid, about 30% by mass of linoleic acid, and about 20% by mass of palmitic acid.

  Higher fatty acids tend to physically adsorb on the surface of the aluminum pigment in the oil phase and cover the pigment surface so as to form a film, which further suppresses contact between aluminum and water, generating hydrogen. Can be further suppressed. The content of the higher fatty acid is preferably 0 to 20% by mass and more preferably 3 to 10% by mass with respect to the total amount of the ink.

  These oil components may be used alone or in combination of two or more as long as a single phase is formed. Especially, it is preferable that a petroleum-type hydrocarbon solvent and a higher fatty acid are included as an oil component. Petroleum hydrocarbon solvents and higher fatty acids have greatly different viscosities and volatility, so that the printing performance after long-term non-use of the printing press can be improved. The ratio of the petroleum hydrocarbon solvent and the higher fatty acid is preferably 100: 0 to 30:70, more preferably 80:20 to 50:50 in terms of mass ratio.

[emulsifier]
In the present embodiment, the emulsifier is used to constitute a water-in-oil emulsion, and a lipophilic emulsifier having an HLB value of preferably 3 to 8, more preferably 3.5 to 6.5 can be used. As an emulsifier, any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant may be used. Among these, it is preferable to use a nonionic surfactant from the viewpoint of the emulsifiability and storage stability of the water-in-oil emulsion. Specifically, sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monooleate, sorbitan sesquioleate, sorbitan monoisostearate, glyceryl monostearate, hexaglyceryl tetraoleate, hexaglyceryl penta (Poly) glycerin fatty acid ester such as oleate, decaglyceryl decaoleate, decaglyceryl pentahydroxystearate, decaglyceryl pentaisostearate, decaglyceryl condensed ricinoleate, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, Polyoxyethylene sorbite fatty acid ester, propylene glycol fatty acid ester, (poly) ethylene glycol fatty acid ester Polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene (hardened) can be exemplified preferably castor oil and the like. An emulsifier may be used independently and can also be used in combination of 2 or more types as appropriate. The content of the emulsifier is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass with respect to the total amount of the ink.

[Oil-soluble resin]
In this embodiment, an oil-soluble resin can be mix | blended with an oil phase. Examples of the oil-soluble resin include rosin, gilsonite, rosin ester, maleic acid resin, phenol resin, rosin-modified phenol resin, alkyd resin, petroleum resin, acrylic resin, amino resin, urethane resin, cellulose resin, natural rubber derivative resin, etc. Can be preferably used. Among these, rosin-modified phenolic resins and alkyd resins are preferably used. The rosin-modified phenolic resin can form a film on the printed image and improve the fixing property. The alkyd resin increases the viscosity of the oil phase and has the property of being easily oriented at the interface between the oil phase and the water phase. While being able to suppress, the storage stability of ink can be improved. Furthermore, since the alkyd resin can impart flexibility to the ink film, the fixability of the silver pigment to the printing medium can be improved.

  The rosin-modified phenol resin is obtained by modifying a phenol resin with a natural product rosin, and is a resin composed of rosin, alkylphenol, formaldehyde, and polyol. Examples of the alkylphenol include pt-butylphenol, pt-octylphenol, p-nonylphenol, and p-dodecylphenol. Examples of the polyol include pentaerythritol and glycerin. The alkyd resin is a synthetic resin made by polycondensation of a polybasic acid and a fatty acid (or fatty oil) and a polyhydric alcohol. Examples of the polyhydric alcohol include glycerin and pentaerythritol. As fatty oils such as phthalic anhydride and maleic anhydride, unsaturated fatty acids contained in sesame oil, soybean oil, castor oil and the like can be used. In the present embodiment, a reaction product of an alkyd resin or rosin-modified resin and an aluminum chelate compound or aluminum alcoholate can also be preferably used.

  The oil-soluble resin may be used alone or in combination of two or more. The content of the oil-soluble resin is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and further preferably 7 to 15% by mass with respect to the total amount of the ink.

[Colorant]
In the present embodiment, the oil phase may contain a colorant in order to adjust the color tone of the ink. Examples of the colorant include pigments and dyes. As the pigment, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments and dyed lake pigments, and inorganic pigments can be used. Examples of the azo pigment include a soluble azo lake pigment, an insoluble azo pigment, and a condensed azo pigment. Examples of the phthalocyanine pigment include metal phthalocyanine pigments such as copper phthalocyanine blue and copper phthalocyanine green, and metal-free phthalocyanine pigments. Polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments. And diketopyrrolopyrrole (DPP). Representative examples of the inorganic pigment include metal pigments such as carbon black, titanium oxide, and brass powder. As dyes, azo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes, xanthene dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, phthalocyanine dyes, Mention may be made of oil-soluble dyes such as metal phthalocyanine dyes.

  These pigments and dyes may be used alone or in combination of two or more. The content of the colorant can be included in a range where the color tone of the ink does not deviate from the silver color, and the total amount of the colorant is preferably 0.5% by mass or less based on the total amount of the ink, and 0.1% by mass. % Or less is more preferable.

[Other oil phase components]
In the present embodiment, the oil phase can further contain extender pigments, pigment dispersants, antioxidants, gelling agents and the like as appropriate. Examples of extender pigments include talc, diatomaceous earth, calcium carbonate, barium carbonate, barium sulfate, alumina white, silica, kaolin, mica, acid clay, activated clay, bentonite, and the like. May be. Examples of the pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, and a high molecular weight unsaturated acid. Ester, polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, polyoxyethylene alkyl phosphate ester, polyester polyamine, copolymer of vinyl pyrrolidone and long chain alkene, polyester side chain And nitrogen-containing graft copolymers having Examples of the antioxidant include dibutylhydroxytoluene, propyl gallate, tocopherol, butylhydroxyanisole, nordihydroguaiaretic acid, phenothiazine and the like.

<Water phase>
[water]
In the present embodiment, the main component of the aqueous phase is water, and may further contain a water-soluble organic solvent or the like. The water is not particularly limited as long as it is clean, and ion exchange water, distilled water, purified water, tap water, ground water, and the like can be used. The water content is preferably 40 to 80% by mass and more preferably 50 to 70% by mass with respect to the total amount of ink.

[Water-soluble organic solvent]
In this embodiment, a water-soluble organic solvent can be mix | blended with an aqueous phase. As the water-soluble organic solvent, an organic compound that is liquid at room temperature and is soluble in water can be used. For example, lower alcohols having 1 to 4 carbon atoms such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, 2-methyl-2-propanol; ethylene glycol, diethylene glycol, triethylene glycol , Tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and other glycols; glycerin, diglycerin, triglycerin, polyglycerin, and other glycerins; monoacetin, diacetin, triacetin, and other acetins Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol Monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene Glycol ethers such as glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether; triethanolamine, 1-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone , Β-thiodiglycol, Ruphoran or the like can be used. These water-soluble organic solvents may be used alone or in combination of two or more as long as a single phase is formed. As the water-soluble organic solvent, it is preferable to use a water-soluble organic solvent that is uniformly mixed with the same volume of water at 1 atm. The boiling point of the water-soluble organic solvent is preferably 100 ° C. or higher, and more preferably 150 ° C. or higher. The water-soluble organic solvent having a boiling point of 150 ° C. or higher includes a water-soluble organic solvent that does not exhibit a boiling point.

[Electrolytes]
In the present embodiment, an electrolyte can be blended in the aqueous phase. By including an electrolyte, the viscosity and pH of the ink can be adjusted. As the electrolyte, for example, sodium sulfate, magnesium sulfate, potassium hydrogen phosphate, sodium citrate, potassium tartrate, sodium borate and the like can be used. Moreover, the antioxidant which can be contained in the water phase mentioned later can also be used as electrolyte.

[Colorant]
In the present embodiment, the water phase may contain a colorant in order to adjust the color tone of the ink. Examples of the colorant include pigments and dyes. As the pigment, a pigment similar to the pigment contained in the oil phase described above can be used. Examples of the dye include a basic dye, an acid dye, a direct dye, a soluble vat dye, an acid mordant dye, a mordant dye, a reactive dye, a vat dye, and a sulfur dye. The water-soluble dyes thus obtained can be preferably used. Further, disperse dyes such as azo, anthraquinone, azomethine, and nitro are also preferably used. The content of these colorants can be included in a range where the color tone of the ink does not deviate from the silver color, and the total amount of the colorant is preferably 0.5% by mass or less based on the total amount of the ink. More preferably, it is 1 mass% or less.

[Other water phase components]
In the present embodiment, the aqueous phase can further contain preservatives, antioxidants, pH adjusters, water-soluble resins, water-dispersible resins, extender pigments, surfactants, pigment dispersants and the like as appropriate. The preservative can prevent the ink from being spoiled and improve the storage stability. Examples of the preservative include 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, and 1 , 2-benzoisothiazolin-3-one, isothiazolone preservatives such as hexahydro-1,3,5-tris (2-hydroxyethyl) -s-triazine, 2-pyridinethiol sodium-1- Oxides, pyridine / quinoline preservatives such as 8-oxyquinoline, dithiocarbamate preservatives such as sodium dimethyldithiocarbamate, 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-nitro-1,3 -Propanediol, 2,2-dibromo-2-nitroethanol, 1,2-dibromo-2,4-dicyano Brominated organic preservatives such as Tan, p- hydroxybenzoate, p- hydroxybenzoate ethyl, potassium sorbate, sodium dehydroacetate, can be used salicylic acid. Examples of the antioxidant include L-ascorbic acid, sodium L-ascorbate, sodium isoascorbate, sulfite, potassium sulfite, sodium sulfite, ammonium hydrogen sulfite, sodium thiosulfate, magnesium thiosulfate, sodium dithionite, Examples thereof include sodium pyrosulfite.

<Physical properties>
The viscosity of the water-in-oil emulsion ink for stencil printing according to this embodiment varies in its suitability range depending on the printing pressure of the stencil printing apparatus, but generally 0.5 to 20 Pa · s (20 ° C., shear rate 100 / s). Viscosity) is preferred, and (pseudo) plastic fluidity is suitable for stencil printing.

  The water-in-oil emulsion ink for stencil printing of this embodiment is usually produced by gradually adding a water phase to an oil phase and emulsifying it using a known emulsifier. The oil phase can be prepared by adding the remaining oil phase components to the silver pigment dispersion. The oil component of the oil phase may be used in its entirety when the silver pigment dispersion is produced, or may be divided and used, and the remaining oil component may be added when preparing the oil phase. It is preferable to prepare the aqueous phase and the oil phase separately in advance, and then emulsify by adding the aqueous phase solution to the oil phase solution. In the production of the ink, a known emulsification apparatus such as a disper mixer, a homomixer, a colloid mill, a ball mill, an attritor, a sand mill, a roll mill, or a bead mill can be used.

  The water-in-oil emulsion ink for stencil printing of this embodiment can be suitably used for printing paper such as plain paper, coated paper, and special paper. Of the printing paper, plain paper is preferred. Here, the plain paper is paper in which an ink receiving layer, a film layer, and the like are not formed on normal paper. Examples of plain paper include high quality paper, medium quality paper, PPC paper, reprinted paper, recycled paper, and the like.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to these examples unless departing from the technical idea of the present invention.

[Preparation of silver pigment dispersion (surface treatment of aluminum pigment)]
According to the formulation shown in Table 1, a silver pigment dispersion was prepared according to the following procedure. First, an untreated aluminum pigment, a surface treatment agent (phosphate ester surfactant), and an oil component were mixed. Subsequently, stirring was continued for 1 hour while maintaining the temperature at 70 ° C. to prepare a silver pigment dispersion in which the surface of the aluminum pigment was treated with a phosphate ester-based surfactant.

[Preparation of water-in-oil emulsion ink for stencil printing]
Inks of Examples 1 to 6 were prepared according to the following procedure. First, the prepared silver pigment dispersion, oil-soluble resin, and emulsifier are heated while mixing so as to have the blending ratio shown in Table 1, and when rosin-modified phenol resin is used, after rosin-modified phenol resin is dissolved, room temperature The oil phase was prepared by cooling to. Next, a water-soluble organic solvent, an electrolyte, and water were mixed according to the formulation shown in Table 1 to prepare an aqueous phase. The prepared oil phase is put into an emulsifying apparatus, and the prepared aqueous phase is gradually dropped while rotating the stirring blade, and the stirring blade is further rotated to perform emulsification, and oil for stencil printing of Examples 1 to 6 A water-in-water emulsion ink was prepared.

  A water-in-oil emulsion ink for stencil printing of Comparative Example 1 was prepared in the same procedure as in Examples 1 to 6, except that an untreated aluminum pigment was used as it was without using a surface treatment agent.

  A water-in-oil emulsion ink for stencil printing of Comparative Example 2 was prepared in the same procedure as in Examples 1 to 6, except that the aluminum pigment whose surface was subjected to silane coupling treatment was used as it was.

In addition, the detail of the component shown in Table 1 is as follows.
Aluminum pigment (untreated): “STANDART PC 200” manufactured by ECKART
Aluminium pigment (treated with silane coupling): “STAPA HYDROLAN 9165” manufactured by ECKART
Polyoxyethylene alkyl ether phosphate ester: “Plysurf A208N” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
Polyoxyethylene styrenated phenyl ether phosphate ester: “Prisurf AL” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
Petroleum hydrocarbon solvent: “AF Solvent No. 5” (naphthenic solvent) manufactured by JX Energy Corporation
Higher fatty acid: “soybean white oil” manufactured by Nisshin Oilio Group
Alkyd resin: “Arachid 6902” manufactured by Arakawa Chemical Industries, Ltd.
Rosin-modified phenolic resin: “Hariphenol 512” manufactured by Harima Chemical Co., Ltd.
Sorbitan fatty acid ester: “Reodol AO-10V” manufactured by Kao Corporation

  As the alkyl phosphate ester, monolauryl phosphate synthesized by the following method was used. First, 372.6 parts by mass of lauryl alcohol and 112.6 parts by mass of polyphosphoric acid were charged into a four-necked flask and reacted at 80 ° C. for 3 hours. After completion of the reaction, 242 parts by mass of n-hexane, 90 parts by mass of water, and 90 parts by mass of isopropyl alcohol were added and stirred at 50 ° C. for 30 minutes. Next, after removing the aqueous layer, distillation was performed under reduced pressure to remove isopropyl alcohol from the n-hexane layer, followed by drying to obtain crude crystals. The obtained crude crystals were redissolved and recrystallized with n-hexane to obtain 340 parts by mass of monolauryl phosphate.

[Evaluation method]
Each ink produced was evaluated as follows. The results are also shown in Table 1.
(1) Hydrogen generation test 10 ml of the prepared ink was placed in a 30 ml glass bottle and heated using a water bath until the ink reached 70 ° C. Subsequently, a lid through which the plastic tube penetrated was attached, and the tube was placed so that one end of the tube was in the ink in the glass bottle and the other end was outside the glass bottle. The speed of the ink rising in the tube was measured for 10 minutes while maintaining the ink temperature at 70 ° C. From the inner diameter of the tube and the ink rising speed, the increased volume was regarded as the hydrogen generation amount, and the hydrogen generation speed was evaluated according to the following criteria.
A: Less than 0.05 ml / min B: 0.05 ml / min or more and less than 0.20 ml / min C: 0.20 ml / min or more

(2) Master clogging A stencil printing machine (Risograph SD6680 manufactured by Riso Kagaku Kogyo Co., Ltd.) equipped with a stencil paper (RISO Master D type HD manufactured by Riso Kagaku Kogyo Co., Ltd.) in a 23 ° C. environment. The solid image was continuously printed on black paper, and the image density (OD value) of the first and 20th sheets was measured. The difference between the first and 20th OD values was calculated and evaluated according to the following criteria.
A: Difference is less than 0.1 C: Difference is 0.1 or more

  As can be seen from the results in Table 1, the inks of Examples 1 to 6 use aluminum pigments that have been surface-treated with a phosphate ester surfactant, so that good results were obtained in all evaluation items. . In particular, since the inks of Examples 1 to 4 and 6 contained higher fatty acids as oil components, the amount of hydrogen generated was extremely small, and even better results were obtained. On the other hand, since the ink of Comparative Example 1 uses an aluminum pigment that has not been surface-treated, the amount of hydrogen generation is large and satisfactory results cannot be obtained. The ink of Comparative Example 2 uses an aluminum pigment that has been subjected to a silane coupling treatment. Although the amount of hydrogen generated was small, master clogging occurred, and good results were not obtained.

Claims (3)

A water-in-oil emulsion ink for stencil printing comprising a silver pigment, an oil component, an oil phase containing an emulsifier, and an aqueous phase containing water,
The water-in-oil emulsion ink for stencil printing, wherein the silver pigment is an aluminum pigment surface-treated with a phosphate ester surfactant.   The phosphate ester surfactant is at least one selected from the group consisting of a polyoxyalkylene alkyl ether phosphate ester, a polyoxyalkylene aryl ether phosphate ester, an alkyl phosphate ester and an aryl phosphate ester. The water-in-oil emulsion ink for stencil printing according to claim 1. The water-in-oil emulsion ink for stencil printing according to claim 1 or 2, wherein the oil component contains a higher fatty acid.