JP2006124464A - Emulsion ink for screen printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-in-oil (W/O) emulsion ink for screen printing which is excellent in stability when left on a printing machine, by reducing clogging, caused by fixation of a water-insoluble colorant when left on the printing machine, in an ink wherein the water-insoluble colorant is added to its aqueous phase. <P>SOLUTION: The emulsion ink for screen printing comprises 10-90 mass% oil phase and 90-10 mass% aqueous phase, wherein the aqueous phase contains the water-insoluble colorant and the oil phase contains a dispersant. In a preferred embodiment, the dispersant is a polyester amine compound, the oil phase contains an ammonium-substituted phthalocyanine sulfonic acid dispersant, the water-insoluble colorant is a pigment, the aqueous phase contains a water-soluble organic solvent with a boiling point of ≥220°C, etc. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-in-oil type (W / O type) emulsion ink for stencil printing, which has excellent on-machine leaving properties.

  As is well known, a stencil printing method uses a stencil printing paper (stencil) having a perforated portion, and moves the ink from one side of the stencil to the other side through the perforated portion of the stencil, so that the paper This is a method for printing on the surface of a substrate. This stencil printing method is usually a water-in-oil type (W / O type) containing a volatile solvent, a non-volatile solvent, a resin, a colorant, a surfactant, water, an antifreezing agent, an electrolyte, and a preservative. The emulsion ink is used.

  As such emulsion ink for stencil printing, for example, an emulsion ink for stencil printing, which contains an insoluble colorant and a resin in the oil phase and has improved adhesion to paper by the action of the resin, is proposed. (See Patent Document 1). In this type of ink that contains an insoluble colorant in the oil phase, the insoluble colorant is dispersed in a non-volatile oil component. The ink does not solidify after the treatment. However, in this proposal, since the insoluble colorant penetrates into the paper as well as the oil penetrates into the paper, there is a problem that the image density with respect to the colorant density becomes low and the image is liable to be blurred.

  Further, Patent Document 2 proposes an emulsion ink for stencil printing that contains an insoluble colorant and a resin in an aqueous phase and has improved adhesion to paper. In this type of ink in which an insoluble colorant is dispersed in an aqueous phase as in this proposal, since the colorant does not penetrate together with the oil, the colorant stays on the surface of the paper, so that the image density is high and the blur is small. However, this proposal has a drawback that the image is weak against rubbing. For this reason, a resin is added to the water phase, but in a system in which a colorant is added to the water phase, the colorant is dispersed in volatile water. There is a problem that the colorant is dried and solidified, and the screen is clogged.

  Therefore, in an ink in which a water-insoluble colorant is added to the water phase, there is no clogging due to the fixation of the water-insoluble colorant after standing for a long time, and the water-in-oil type (W / O type) has excellent on-machine leaving properties. An emulsion ink for stencil printing has not been obtained, and it is desired to provide it promptly.

JP-A-11-310740 JP-A-9-31384

  This invention is made | formed in view of this present condition, and makes it a subject to solve the said various problems in the past and to achieve the following objectives. That is, the present invention improves the water-in-oil type (W / W) which has improved clogging due to fixation of the water-insoluble colorant after standing in an ink having a water-insoluble colorant added to the water phase, and has excellent on-machine leaving property. It is an object to provide an emulsion ink for stencil printing of O type).

  As a result of intensive studies by the inventor in order to solve the above problems, the following knowledge has been obtained. That is, an emulsion ink for stencil printing comprising 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, containing a water-insoluble colorant in the aqueous phase, and containing a dispersant in the oil phase. According to the above, it is a finding that clogging due to fixation of the water-insoluble colorant after standing for a long period of time in an ink having a water-insoluble colorant added to the water phase is improved.

The present invention is based on the above knowledge of the present inventor, and means for solving the above problems are as follows. That is,
<1> It comprises 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, contains a water-insoluble colorant in the aqueous phase, and contains a dispersant in the oil phase. It is an emulsion ink for stencil printing. In the emulsion ink for stencil printing according to <1>, in the process where water is volatilized and the color components are aggregated by adding a dispersant to the oil phase, the dispersant in the oil phase contains moisture. This is presumably because it acts on the colorant to prevent aggregation between the colorants and at the same time acts to disperse the colorant in the oil component.
<2> The emulsion ink for stencil printing according to <1>, wherein the dispersant is a polyesteramine compound.
<3> The emulsion ink for stencil printing according to any one of <1> to <2>, wherein the oil phase contains an ammonium-substituted phthalocyanine sulfonic acid dispersant.
When the dispersant described in any one of <2> and <3> is used, clogging due to fixation of the water-insoluble colorant after standing for a long period of time is greatly improved.
<4> The emulsion ink for stencil printing according to any one of <1> to <3>, wherein the water-insoluble colorant is a pigment.

  <5> The emulsion ink for stencil printing according to any one of <1> to <4>, wherein the water phase contains a water-soluble organic solvent having a boiling point of 220 ° C. or higher. In the emulsion ink for stencil printing according to <4>, by adding a water-soluble organic solvent having a boiling point of 220 ° C. or higher in the aqueous phase, it is possible to prevent the colorant from being dried and fixed on the printing press, and An emulsion ink having excellent on-machine leaving properties can be obtained.

  According to the present invention, various problems in the prior art can be solved, and clogging due to fixation of a water-insoluble colorant after standing in an ink in which a water-insoluble colorant is added to the aqueous phase is improved, and the on-machine leaving property is excellent. A water-in-oil type (W / O type) emulsion ink for stencil printing can be provided.

  The emulsion ink for stencil printing of the present invention comprises 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, contains a water-insoluble colorant in the aqueous phase, and a dispersant in the oil phase. And further contains other components as necessary.

The emulsion ink for stencil printing contains 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, preferably 20 to 50% by mass of an oil phase and 50 to 80% by mass of an aqueous phase.
When the mixing ratio of the oil phase is less than 10% by mass, it may not be possible to take the form of a W / O emulsion, and when it exceeds 90% by mass, the physical properties are not sufficiently effective. May end up.

<Oil phase>
The oil phase is not particularly limited and may be appropriately selected depending on the purpose. The dispersant, oil component, emulsifier, resin, gelling agent, antioxidant, extender pigment, and other additives as necessary. Contains ingredients.

-Dispersant-
As the dispersant, those which are dissolved in each of the oil phase and the water phase and have a surface activity ability and which do not inhibit the formation of the emulsion can be used. Nonionic surfactant for emulsifier and water-soluble polymer described later Compounds can also be used as dispersants.
The dispersant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include sodium di (2-ethylhexyl) sulfosuccinate (OTP-75, manufactured by Nikko Chemicals Co., Ltd.), alkylamine polymers. Compound, aluminum chelate compound, styrene-maleic anhydride copolymer polymer compound, polyglycerin fatty acid ester compound, polyesteramine compound, polycarboxylic acid ester type polymer compound, aliphatic polycarboxylic acid, polymer Polyester amine salts, ester type anionic surfactants, long chain amine salts of high molecular weight polycarboxylic acids, salts of long chain polyaminoamides and polymeric acid polyesters, polyamide compounds, phosphate ester surfactants, alkylsulfocarboxylic acids Salts: N such as polyisopropylacrylamide -Alkyl-substituted acrylamide polymers or copolymers thereof, α-olefin sulfonates, dioctyl sulfosuccinates, polyethyleneimine, alkylolamine salts, acetylenic diol compounds, orioxyethylene nonylphenyl ether, polyoxyethylene alkylamines , Polyoxyethylene alkyl ether, and the like. In addition to these, ionic surfactants, amphoteric surfactants and the like can be used as long as they do not impair the storage stability of the ink, and these may be used alone or in combination of two or more. May be used in combination. Among these, polyesteramine compounds are particularly preferable.

The polyesteramine compound is a reaction product of a polyester having a free carboxylic acid group and a poly (low alkylene) imine, has at least two polyester chains, and each of the polyester chains has a poly (low alkylene) imine chain. Is a compound to which is bound.
Examples of the polyesteramine-based compound include Lubrizol Solspurs described in British Patent Application Publication No. 2001083.

  Further, when the pigment added to the aqueous phase is a phthalocyanine pigment or carbon black, it is more preferable to use a phthalocyanine sulfonic acid dispersant (for example, Solsperz 5000) substituted with ammonium.

  Commercially available products can be used as the dispersant, for example, Plenact AL-M, Ajisper PN411 (manufactured by Ajinomoto Fine Techno Co., Ltd.), Solspers series 5000, 13940, 16000, 17000, 20000, 28000, 54000 (Lublizol). Etc.). These may be used individually by 1 type and may use 2 or more types together.

  The amount of the dispersant added is not particularly limited and may be appropriately selected depending on the purpose. The amount is preferably 100 parts by mass or less, more preferably 40 parts by mass or less, based on 100 parts by mass of the colorant in the aqueous phase. 0.1-35 mass parts is still more preferable. When the addition amount exceeds 100 parts by mass, the emulsion stability of the ink may be affected, and the cost may increase.

-Oil component-
There is no restriction | limiting in particular as said oil component, According to the objective, it can select suitably according to the objective, A vegetable oil, mineral oil, etc. are mentioned.
Examples of the vegetable oil include soybean oil, corn oil, sunflower oil, rapeseed oil, safflower oil, sesame oil, castor oil, dehydrated castor oil, camellia oil, olive oil, palm oil, rice oil, cottonseed oil, palm oil, linseed oil, Examples include palm kernel oil, tung oil, camelia oil, grape seed oil, sweet almond oil, pistachio nut oil, jojoba oil, macadamia nut oil, and mead home oil. These may be used alone. Two or more kinds may be used in combination.
Examples of the esterified vegetable oil include those obtained by esterifying the vegetable oil. Examples of the ester include methyl ester, ethyl ester, and butyl ester. Examples of the esterified vegetable oil include esterified soybean oil and esterified tall oil.
By using soybean oil fatty acid alkyd resin whose fat is soybean oil as the alkyd resin and using esterified soybean oil, the total of soybean oil-derived components exceeds 6%. Certification can be obtained, which is also advantageous in terms of safety.

  The amount of vegetable oil added to the emulsion ink for stencil printing is preferably 1 to 35% by mass, and more preferably 5 to 25% by mass.

The mineral oil is not particularly limited and can be appropriately selected according to the purpose. For example, paraffinic oil, naphthenic oil, petroleum solvent, spindle oil, liquid paraffin, light oil, kerosene, machine oil, gear Oils, lubricating oils, motor oils and the like can be mentioned. Among these, paraffinic oils, naphthenic oils, and petroleum solvents are particularly preferable.
Commercially available products can be used as the paraffinic oil, for example, Gargo Oil Arctic series manufactured by Mobil Oil Co., Nippon Oil Super Oil Series manufactured by Nippon Oil Corporation, Diana Process Oil manufactured by Idemitsu Kosan Co., Ltd. And Diana Fresia series.
The naphthenic oil has a naphthene component carbon content (CN) of 30% or more by ring analysis, an aromatic component carbon content (CA) of 20% or less, and a paraffin component carbon content. A quantity (CP) of 55% or less is suitable, for example, Gargo Oil Arctic Oil 155 and 300ID manufactured by Mobil Oil, Gargo Oil Arctic Oil Light, Gargo Oil Arctic Oil C Heavy; Idemitsu Kosan Co., Ltd. The company's Diana Process Oil, Diana Fresia Series; Nippon San Oil Co., Ltd.
Commercially available products can be used as the petroleum-based solvent, for example, Isopar series (C, E, G, H, L, M, etc.) and Exol (D30, D40, D80, D110, manufactured by Exxon Chemical Co., Ltd.) D130 etc.); AF solvent series (No. 4, No. 5, No. 6, No. 7, etc.) manufactured by Nippon Oil Corporation.

When considering the stability of the ink, these mineral oils preferably use those having a polycyclic aromatic component that is an aromatic hydrocarbon containing three or more condensed aromatic rings of less than 3% by mass. . Further, the mutagenicity index (MI) is less than 1.0, the aroma content (% C _A ) is 20 to 55%, the aniline point is 100 ° C. or less, and benzo [a] anthracene based on the total mass of the oil, The content of polycyclic aromatics such as benzo [b] fluoranthene, benzo [j] fluoranthene, benzo [k] fluoranthene, benzo [a] pyrene, dibenzo [a, j] acridine is 10 ppm or less and total content The amount is 50 ppm or less.
Note that a highly safe aroma oil (for example, JP-A-11-80640) can be used as necessary.

  There is no restriction | limiting in particular in the addition amount in the said emulsion ink for stencil printing of the said mineral oil, According to the objective, it can select suitably, 1-35 mass% is preferable and 5-25 mass% is more preferable.

-Emulsifier-
The emulsifier is not particularly limited as long as it can form a water-in-oil emulsion and can be appropriately selected according to the purpose, but a nonionic surfactant is particularly preferable. Examples of the nonionic surfactant include sorbitan fatty acid ester, glycerin fatty acid ester, polyglycerin fatty acid ester, propylene glycol fatty acid ester, pentaerythritol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbite fatty acid ester, polyoxy Ethylene glycerin fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene phytosterol ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, poly Oxyethylene lanolin derivatives, polyoxyethylene alkyl amines Emissions, polyoxyethylene fatty acid amides, polyoxyethylene alkylphenyl formaldehyde condensates, and the like, which may be used alone or in combination of two or more thereof.
There is no restriction | limiting in particular in the addition amount in the said emulsion ink for stencil printing of the said emulsifier, According to the objective, it can select suitably, 0.5-15 mass% is preferable, and 2-8 mass% is more preferable.

-Resin-
The resin is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, alkyd resin, rosin; polymerized rosin, hydrogenated rosin, rosin ester, rosin polyester resin, hydrogenated rosin Rosin resins such as esters; Rosin-modified alkyd resins, rosin-modified maleic resins, rosin-modified resins such as rosin-modified phenol resins; maleic resins; phenol resins; petroleum resins; rubber derivative resins such as cyclized rubbers; Polymerized castor oil and the like can be mentioned, and these may be used alone or in combination of two or more. Among these, alkyd resins are particularly preferable.

The weight average molecular weight of the resin is preferably 8000 to 160,000, more preferably 30,000 to 80,000, from the viewpoint of fixability and printability.
The addition amount of the resin in the oil phase is preferably 2 to 50% by mass and more preferably 5 to 20% by mass from the viewpoint of the cost of the ink and printing suitability.
When the weight average molecular weight of the resin is low and when the addition amount is small, the effect on fixability may be small, while when the weight average molecular weight is too high or the addition amount of the resin is large, the ink In some cases, the viscosity becomes high, and printability problems such as ink leakage from the rear end of the drum may occur.
Commercially available products can be used as the resin, and KG-836, KG-846, KG-1801, KG-1832, KG-1829, KG-1804, KG-1828, KG- manufactured by Arakawa Chemical Industries, Ltd. 1808-1, KG-1834, KG-1831, KG-1833, Tamanol 353, Tamanol 403, Tamanol 371, Tamanol 394; Hariphenol (561, 564, 582, 173, T3120, T3040, P637, manufactured by Harima Chemical Co., Ltd.) In addition, cyclized rubber is also effective for fixing properties, for example, trade names ALSYNOL RS47, ALSYNOL RS44, SYNTEX 800 manufactured by Colombian Carbon Japan, and ALPEX CK 450, ALPEX CK514 manufactured by Hoechst. Etc.

The said alkyd resin is normally comprised from fats and oils, a polybasic acid, and a polyhydric alcohol. Examples of the fats and oils include coconut oil, palm oil, olive oil, castor oil, rice bran oil, cottonseed oil, soybean oil, linseed oil, and tung oil. Among these, soybean oil is particularly preferable. As the polybasic acid, either a saturated polybasic acid or an unsaturated polybasic acid can be used. Examples of the saturated polybasic acid include phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrahydrophthalic acid and the like. Examples of the unsaturated polybasic acid include maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic anhydride, and the like.
Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, glycerin, trimethylolpropane, neopentyl glycol, diglycerin, triglycerin, and pentaerythritol. Examples include slits, dipentaery slits, mannits, and sorbits.

The alkyd resin has an acid value of 15 or less, and more preferably 10 or less. Further, the iodine value is preferably 80 or less, and more preferably 80 to 110. Moreover, the oil length of the said alkyd resin is represented by the mass% in resin when the fatty acid in the said fats and oils exists with a triglyceride, and 60-90 mass% is preferable normally. The weight average molecular weight of the alkyd resin is preferably 30,000 or less, and more preferably 10,000 or less.
Here, the acid value of the alkyd resin can be measured, for example, according to JIS K0070. The iodine value of the alkyd resin can be measured, for example, according to JIS K0070.

-Gelling agent-
The gelling agent has a role of improving the storage stability, fixability, fluidity, etc. of the ink by gelling the resin contained in the oil phase, and is preferably a compound that coordinates with the resin in the oil phase. . Examples of the gelling agent include organic acid salts containing organic metals such as Li, Na, K, Al, Ca, Co, Fe, Mn, Mg, Pb, Zn, and Zr, organic chelate compounds, and metal soap oligomers. Can be mentioned. Specifically, octylic acid metal salts such as aluminum octylate, naphthenic acid metal salts such as manganese naphthenate, stearates such as zinc stearate, organic chelate compounds such as aluminum diisopropoxide monoethyl acetoacetate, etc. Can be mentioned. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular in the addition amount of the said gelatinizer, According to the objective, it can select suitably, 15 mass% or less is preferable with respect to the total amount of resin in an oil phase, and 5-10 mass% is more preferable.

-Antioxidant-
The antioxidant is not particularly limited and can be appropriately selected from known ones. For example, nordihydroguaiaretic acid (NDGA), citrate ester, extracted tocopherol, tocopherol, butylhydroxytoluene , Gallic acid, dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, sulfites, thiosulfate, ascorbic acid, ascorbate, ascorbic acid derivatives and the like, and these may be used alone. Two or more kinds may be used in combination.
The amount of the antioxidant added in the oil phase is preferably 2% by mass or less, and more preferably 0.1 to 1.0% by mass.

-Extender pigment-
The extender pigment can be added to the oil phase, the aqueous phase, or both phases for preventing bleeding and adjusting the viscosity in the ink, and either inorganic fine particles or organic fine particles are preferable. Examples of the inorganic fine particles include clay, silica, talc, clay, calcium carbonate, barium sulfate, titanium oxide, alumina white, diatomaceous earth, kaolin, mica, and aluminum hydroxide. Examples of the organic fine particles include polyacrylate resin, polyurethane resin, polyester resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polysiloxane resin, phenol resin, epoxy resin, or these A copolymer, and the like.
There is no restriction | limiting in particular in the addition amount in the said emulsion ink for stencil printing of the said extender, According to the objective, it can select suitably, 0.1-50 mass% is preferable, and 1-5 mass% is more preferable.

<Water phase>
The aqueous phase contains water, a colorant, a water-soluble polymer compound, and other components such as a water-soluble organic solvent, an electrolyte, an O / W resin emulsion, an antiseptic or fungicide, and a pH adjuster as necessary. It contains.

  If it is clean, there will be no restriction | limiting in particular if it is clean, According to the objective, it can select suitably, For example, a tap water, ion-exchange water, distilled water etc. can be used.

-Colorant-
As the colorant, water-insoluble colorants such as known pigments and disperse dyes having various colors can be used.
Examples of the water-insoluble colorant include carbon blacks such as acetylene black, channel black, and furnace black; metal powders such as aluminum powder and bronze powder; inorganic substances such as petals, chrome lead, ultramarine, chromium oxide, and titanium oxide Azo pigments such as pigments, insoluble azo pigments, azo lake pigments, and condensed azo pigments; phthalocyanine pigments such as metal-free phthalocyanine pigments and copper phthalocyanine pigments; anthraquinone pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments , Dioxazine dyes, selenium dyes, perylene dyes, perinone dyes, thioindigo dyes, quinophthalone dyes, metal complex and other condensed polycyclic pigments; organic pigments such as acidic or basic dye lakes; diazo dyes Oil-soluble dyes such as anthraquinone dyes; fluorescent pigments, And the like. These may be used individually by 1 type and may use 2 or more types together.

  As the fluorescent pigment, a so-called synthetic resin solid solution obtained by dissolving or dyeing a fluorescent dye that develops various hues after bulk polymerization of a synthetic resin or by pulverizing and refining the obtained colored bulk resin Examples of synthetic resins that carry dyes include melamine resins, urea resins, sulfonamide resins, alkyd resins, and polyvinyl chloride resins.

  Commercially available products can be used as the carbon black as the colorant. For example, MA-100, MA-7, MA-77, MA-11, # 40, # 44 (all manufactured by Mitsubishi Chemical Corporation). , Raven 1100, Raven 1080, Raven 1255, Raven 760, Raven 410 (all manufactured by Colombian Carbon).

There is no restriction | limiting in particular in the average particle diameter of the said coloring agent, According to the objective, it can select suitably, 0.001-0.1 micrometer is preferable and 0.01-0.1 micrometer is more preferable.
There is no restriction | limiting in particular in the addition amount in the emulsion ink for stencil printing of the said coloring agent, According to the objective, it can select suitably, Usually, 2-15 mass% is preferable.

-Water-soluble polymer compounds-
The water-soluble polymer compound is not particularly limited and may be appropriately selected from known compounds according to the purpose. Examples thereof include natural polymer compounds, semi-synthetic polymer compounds, and synthetic polymer compounds. Can be mentioned.
Examples of the natural polymer compound include starch, mannan, sodium alginate, galactan, tragacanth gum, gum arabic, pullulan, dextran, xanthan gum, glue, gelatin, collagen, casein and the like.
Examples of the semi-synthetic polymer compound include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxymethyl starch, carboxymethyl starch, and dialdehyde starch.
Examples of the synthetic polymer compound include polyvinyl pyrrolidone; acrylic resin derivatives such as polyacrylic acid, sodium polyacrylate, and triethanolamine polyacrylate; synthesis of polyvinyl alcohol, polyacrylamide, polyethylene oxide, polyvinyl methyl ether, and the like. Examples thereof include polymer compounds.
The addition amount of the water-soluble polymer compound in the aqueous phase is preferably 25% by mass or less, and more preferably 0.5 to 15% by mass.

The water-soluble organic solvent is suitably added as a water evaporation inhibitor or antifreeze agent. There is no restriction | limiting in particular as this water-soluble organic solvent, Although it can select and use suitably from well-known things, For example, a lower saturated monohydric alcohol, glycol, a polyhydric alcohol etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Examples of the lower saturated monohydric alcohol include methanol, ethanol, isopropanol, butanol, isobutanol and the like. Examples of the glycol include ethylene glycol, diethylene glycol, and propylene glycol. Examples of the polyhydric alcohol include glycerin and sorbitol.
Among these, it is preferable to use a water-soluble organic solvent having a boiling point of 220 ° C. or higher, such as glycerin, from the viewpoint of preventing the colorant from being dried and fixed on the printing press.
1-15 mass% is preferable, as for the addition amount in the said water phase of the said water-soluble organic solvent, 4-12 mass% is more preferable, and 5-9 mass% is especially preferable.

The electrolyte is added to increase the stability of the emulsion, and it is preferable to add an electrolyte composed of ions having a high liquid separation permutation effective for improving the stability of the emulsion. Anions having a high liquid separation permutation are citrate ions, tartaric acid ions, sulfate ions, acetate ions, and the like. Cations having a high liquid separation permutation are alkali metal ions and alkaline earth metal ions. The electrolyte added here is preferably a salt in which at least one of an anion and a cation is composed of the above ions, such as magnesium sulfate, sodium sulfate, sodium citrate, sodium hydrogen phosphate, sodium borate, sodium acetate, etc. Is mentioned. Among these, a divalent anion-containing compound is preferable, and magnesium sulfate is particularly preferable. These may be used individually by 1 type and may use 2 or more types together.
The amount of the electrolyte added in the aqueous phase is, for example, preferably 0.1 to 2% by mass, and more preferably 0.5 to 1.5% by mass.

The oil-in-water (O / W) resin emulsion is not particularly limited and may be appropriately selected from known ones, and may be a synthetic polymer compound or a natural polymer compound. Examples of the synthetic polymer compound include vinyl acetate resin, acrylic ester resin, methacrylic ester resin, vinyl chloride resin, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic ester copolymer, styrene-acrylic acid. Examples thereof include ester copolymers, vinylidene chloride-acrylic acid ester copolymers, vinyl chloride-vinyl acetate copolymers, and urethane resins. Examples of the natural polymer compound include a polymer compound that can be added to an oil phase commonly used in emulsion inks for stencil printing. These may be used individually by 1 type and may use 2 or more types together.
Further, the dispersion method of the oil-in-water resin emulsion is not particularly limited, and a dispersant, a protective colloid, and a surfactant may be added, or may be synthesized by soap-free emulsion polymerization. There is no restriction | limiting in particular in the minimum film forming temperature of the said oil-in-water resin emulsion, According to the objective, it can select suitably, 40 degrees C or less is preferable.

The preservative or fungicide is added to prevent bacteria and fungi from growing in the emulsion, and is effective when the emulsion is stored for a long period of time. The antiseptic or fungicide is not particularly limited and may be appropriately selected from known ones. Examples include salicylic acid, phenols, methyl p-oxybenzoate, and ethyl p-oxybenzoate. An aromatic hydroxy compound such as the above or a chlorine compound thereof, sorbic acid, dehydroacetic acid and the like may be mentioned, and these may be used alone or in combination of two or more.
The amount of the preservative or fungicide added to the aqueous phase is preferably 3% by mass or less, and more preferably 0.1 to 1.2% by mass.

  There is no restriction | limiting in particular as said pH adjuster, Although it can select and use suitably from well-known things, For example, a triethanolamine, sodium acetate, a triamylamine etc. are mentioned suitably. These pH adjusters can be added as necessary to maintain the pH of the aqueous phase at 6-8. If the pH of the aqueous phase deviates from the above range, the effect may be impaired when a water-soluble polymer compound is added.

  In the emulsion ink for stencil printing of the present invention, wax can be added to the oil phase in order to improve separation between the printing paper and the printing drum during printing, or to prevent the printing paper from rolling up. In addition, it is possible to further increase the viscosity by adding triethanolamine, sodium hydroxide, or the like to the aqueous phase and adding a water-soluble polymer compound. Furthermore, a rust preventive agent or an antifoaming agent can be added to the water phase to prevent the printing press from being rusted by ink or causing ink to foam. These additives may be added as necessary to known products added to emulsion inks for stencil printing, and the amount added may be the same as that of conventional products.

The method for producing the emulsion ink for stencil printing of the present invention is not particularly limited and can be appropriately selected from known methods according to the purpose. For example, the oil phase and the aqueous phase liquid are previously prepared by a conventional method. It can be prepared by separately preparing, adding an aqueous phase to the oil phase, and emulsifying in a known emulsifier such as a disper mixer, a homomixer, or a high-pressure homogenizer.
Specifically, an oil component, a dispersant, a resin, and an emulsifier were mixed and stirred with a high-speed dissolver. Thereafter, a dispersion treatment is performed using a bead mill (LMZ2, manufactured by Ashizawa Finetech Co., Ltd.) to prepare an oil phase. On the other hand, a colorant, a water-soluble polymer, a dispersant, an antifreezing agent, and a preservative are mixed, and this mixed solution is well dissolved in water to prepare an aqueous phase. Next, an emulsion ink for stencil printing can be produced by using an emulsifier and gradually adding and emulsifying the aqueous phase liquid while charging the oil phase liquid and stirring the liquid.

The emulsion ink for stencil printing of the present invention preferably has a viscosity of 3 to 40 Pa · s, more preferably 10 to 30 Pa · s at a shear rate of 20 sec ⁻¹ .
As described above, the emulsion ink for stencil printing of the present invention is improved in clogging due to fixation of an insoluble colorant after standing in an ink in which a water-insoluble colorant is added to an aqueous phase, and is excellent in on-machine leaving property. Therefore, it is suitably used for stencil printing by a rotary stencil printing machine, for example.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
-Preparation of emulsion ink for stencil printing-
First, an oil component, a dispersant, a resin, and an emulsifier were mixed according to the formulation shown in Table 1, and stirred with a high-speed dissolver. Thereafter, a dispersion process was performed using a bead mill (LMZ2, manufactured by Ashizawa Finetech Co., Ltd.) to prepare an oil phase.
Next, a coloring agent, a water-soluble polymer, a dispersing agent, an antifreezing agent, and a preservative were mixed according to the formulation shown in Table 1, and this mixed solution was dissolved well in water to prepare an aqueous phase.
Subsequently, using the emulsifier (Nikko Chemicals make, an emulsification tester ET-3A type), the said water phase liquid was gradually added, charging the said oil phase liquid and stirring the liquid. Thus, the emulsion ink for stencil printing of Example 1 was produced.

(Examples 2-9)
-Preparation of emulsion ink for stencil printing-
In Example 1, except that it changed into the composition shown in Table 1 and Table 2, it carried out similarly to Example 1, and produced the emulsion ink for stencil printing of Examples 2-9.

(Comparative Example 1)
-Preparation of emulsion ink for stencil printing-
In Example 1, the emulsion ink for stencil printing of Comparative Example 1 was produced in the same manner as Example 1 except that the composition was changed to the composition shown in Table 2.

  Next, for each of the obtained emulsion inks for stencil printing, the on-machine stability was evaluated as follows. The results are shown in Table 3.

<Standing stability on board>
The evaluation of the on-machine stability was evaluated as a substitute evaluation of a change in viscosity when the ink was left in an open state at a high temperature. Put the ink on the petri dish and store it at 60 ° C. for one week in an open state. In a five-step evaluation, 1 indicates a significant increase in viscosity compared to the viscosity before standing, and 5 indicates no increase in viscosity. evaluated. In addition, the result was represented by the average value of 3 times measurement.

表３の結果から、比較例１は、油相に分散剤を含有しないので、機上放置安定性が劣ることが認められる。
これに対し、実施例１〜９は、比較例１に比べて、機上放置安定性が優れていることが認められる。また、実施例４と実施例５〜７の結果から、ポリエステルアミン系化合物を分散剤として用いたことの優位性が認められる。実施例６と実施例８の結果から、油相にアンモニウム置換フタロシアニンスルホン酸系分散剤を添加したことの優位性が認められる。また、実施例３と実施例４の結果から、水相中に水溶性有機溶剤としての多価アルコールを添加したことの優位性が認められる。

From the results shown in Table 3, it can be seen that Comparative Example 1 does not contain a dispersant in the oil phase, so that the on-machine stability is poor.
On the other hand, it is recognized that Examples 1 to 9 are superior in on-machine stability compared to Comparative Example 1. From the results of Example 4 and Examples 5 to 7, the superiority of using a polyesteramine compound as a dispersant is recognized. From the results of Example 6 and Example 8, the superiority of adding an ammonium-substituted phthalocyanine sulfonic acid dispersant to the oil phase is recognized. From the results of Example 3 and Example 4, the superiority of adding a polyhydric alcohol as a water-soluble organic solvent in the aqueous phase is recognized.

The emulsion ink for stencil printing of the present invention is improved in clogging due to fixation of the insoluble colorant after standing in the ink in which a water-insoluble colorant is added in the aqueous phase, and is excellent in on-machine leaving ability. It is suitably used for stencil printing by a rotary stencil printing machine.

Claims (5)

  A stencil comprising 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, containing a water-insoluble colorant in the aqueous phase, and containing a dispersant in the oil phase. Emulsion ink for printing.   The emulsion ink for stencil printing according to claim 1, wherein the dispersant is a polyesteramine compound.   The emulsion ink for stencil printing according to any one of claims 1 to 2, comprising an ammonium-substituted phthalocyanine sulfonic acid dispersant in the oil phase.   The emulsion ink for stencil printing according to any one of claims 1 to 3, wherein the water-insoluble colorant is a pigment. The emulsion ink for stencil printing according to any one of claims 1 to 4, wherein the aqueous phase contains a water-soluble organic solvent having a boiling point of 220 ° C or higher.