JP2008106144A - Emulsion ink for stencil printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-in-oil type (W/O type) emulsion ink for stencil printing that exhibits good dispersion stability and excellent water resistance. <P>SOLUTION: The emulsion ink for stencil printing comprises 10-90 mass% of an oil phase and 90-10 mass% of a water phase, where the water phase contains a copolymer of vinyl alcohol with vinyl acetate. Preferred embodiments include one where the saponification degree of the copolymer is at least 90 mol% or at most 50 mol% and one where the polymerization degree of the copolymer is at least 300. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water-in-oil type (W / O type) emulsion ink for stencil printing having good dispersion stability and excellent water resistance.

In a printing process using a stencil printing apparatus, predetermined original data is converted into a digital signal, and a thermal element called a thermal head is used to punch a plate called a stencil sheet based on the signal and wind it on a printing drum. The
As the printing ink for stencil printing, a water-in-oil type (W / O type) emulsion ink is generally used.

As the W / O type emulsion ink, by adding a water-soluble polymer compound in the water phase, first, the oil phase that is the outer phase of the emulsion is transferred to the printing medium, and then the inner phase of the emulsion It has been proposed that a film can be formed on the ink transfer portion of the substrate by transferring a certain aqueous phase (see Patent Document 1).
However, when the water-soluble polymer compound is dissolved in the water phase of the W / O type emulsion ink, there is a problem that the dispersion stability of the emulsion is inferior compared with the case where it is not used.

  On the other hand, the W / O emulsion ink, if the drying time is set too fast, the ink dries at the hole portion of the pre-stencil printing base paper, or the ink composition changes at the ink reservoir in the plate cylinder of the stencil printing machine. There was a problem that it was easy to do. For this reason, drying cannot be accelerated, and the ink transferred on the substrate to be printed is not completely fixed on the surface of the substrate to be transferred. There was a problem that etc. became dirty.

  Therefore, while using the water-soluble polymer compound, it is possible to stabilize the emulsion and accelerate the drying time, and to improve the ink fixability, A W / O emulsion ink to which a water-soluble polymer compound having an amine is added has been proposed (see Patent Document 2).

However, since the tertiary amine has high hydrophilicity, there is a problem that the water resistance of the ink film after drying is poor.
Accordingly, it is currently desired to develop a W / O emulsion ink with improved water resistance while maintaining ink dispersion stability.

Japanese Examined Patent Publication No. 44-2165 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, an object of the present invention is to provide a water-in-oil (W / O type) stencil emulsion ink having good dispersion stability and excellent water resistance.

  As a result of intensive studies by the inventor in order to solve the above problems, the following knowledge has been obtained. That is, it is a finding that by containing a copolymer of vinyl alcohol and vinyl acetate in the aqueous phase, water resistance can be improved while maintaining good dispersion stability.

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> 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, wherein the aqueous phase contains a copolymer of vinyl alcohol and vinyl acetate. It is.
<2> The emulsion ink for stencil printing according to <1>, wherein the saponification degree of the copolymer is 90 mol% or more or 50 mol% or less. In the emulsion ink for stencil printing described in <2>, the saponification degree of the copolymer is 90 mol% or more and almost completely saponified, or the saponification degree is 50 mol% or less and low saponification state. Then, since the ink is difficult to dissolve in water, the water resistance can be further improved.

<3> The emulsion ink for stencil printing according to any one of <1> to <2>, wherein the degree of polymerization of the copolymer is 300 or more. In the emulsion ink for stencil printing described in <3>, since the degree of polymerization of the copolymer is 300 or more, water resistance can be further improved.
<4> The emulsion ink for stencil printing according to any one of <1> to <3>, further comprising an electrolyte. In the emulsion ink for stencil printing described in <4>, the dispersion stability of the ink can be further improved. When an ionic water-soluble polymer is used, the electrolyte inhibits repulsion between the ions of the polymer, but the copolymer of vinyl alcohol and vinyl acetate is nonionic, so the influence of the electrolyte Therefore, it is considered that the dispersion stability of the ink is exhibited without aggregation of the pigment.
<5> The emulsion ink for stencil printing according to any one of <1> to <4>, further comprising a resin in the oil phase. In the emulsion ink for stencil printing described in <5>, since the oil phase contains a resin, the water resistance can be further improved. This is considered to be because the resin in the oil phase is adsorbed on the pigment during the process of ink penetrating into the paper, thereby increasing the hydrophobicity of the pigment surface.

  ADVANTAGE OF THE INVENTION According to this invention, the various problems in the past can be solved, and the emulsion ink for stencil printing of the water-in-oil type (W / O type) excellent in dispersion stability and excellent in water resistance 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, and the aqueous phase contains a copolymer of vinyl alcohol and vinyl acetate.

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.

<Water phase>
The aqueous phase contains a water-soluble polymer compound, a colorant, and water, and if necessary, an electrolyte, a water evaporation inhibitor or an antifreeze agent, an antibacterial agent, an extender pigment, and an O / W resin emulsion. And a component such as a pH adjuster.

-Water-soluble polymer compounds-
The water-soluble polymer compound includes a copolymer of vinyl alcohol and vinyl acetate (hereinafter sometimes simply referred to as “copolymer”). The copolymer of vinyl alcohol and vinyl acetate is not particularly limited and may be appropriately selected according to the purpose. For example, PVA102, PVA103, PVA203, PVA205, PVA403, PVA405 (or more) , Manufactured by Kuraray Co., Ltd.), NM-14, NM-11, NL-05, P-610, AL-06, L-7514, L-5407, L-0302 (above, Nippon Synthetic Chemical Co., Ltd.), Etc.

  As shown in the following structural formula, the copolymer of vinyl alcohol and vinyl acetate has a saponification degree calculated by the following formula when the number of moles of vinyl alcohol is m and the number of moles of vinyl acetate is n. It is classified by various.

〔formula〕
Saponification degree = m / (m + n) × 100 (mol%)

Generally, those having a saponification degree of approximately 90 mol% or more are classified as complete saponification, those having 70 mol% or more and 90 mol% or less are partially saponified, and those having 50 mol% or less are classified as low saponification. Among these, the completely saponified one or the low saponified one is preferable. Those classified as complete saponification have a very high proportion of hydroxyl groups in the molecule, and the hydroxyl groups form hydrogen bonds with each other, so the solubility in water is low. Those classified as low saponification also have a high proportion of acetic acid groups in the molecule and low solubility in water. However, in any case, it can be dissolved in water by applying energy such as heating or stirring, and the aqueous solution obtained by dissolving in water by heating or stirring is left in the air. Even if water evaporates, it is difficult to dissolve in water unless energy such as heating is applied, resulting in improved water resistance.
The saponification degree of the copolymer is more preferably 95 mol% or more or 40 mol% or less from the viewpoint of further improving the water resistance. The copolymer may be used alone, or two or more of different grades may be mixed, and further, one of a completely saponified one and one of a partially saponified one. Or you may use together.

  As the degree of polymerization of the copolymer of vinyl alcohol and vinyl acetate, the higher the water resistance, the more preferable it is 300 or more. However, the higher the degree of polymerization, the lower the solubility in water, so the degree of polymerization is more preferably 300 to 500.

The polymerization degree and saponification degree of the copolymer can be measured, for example, as follows in the obtained emulsion ink for stencil printing.
A solvent for dissolving the oil phase component of the ink is added to separate the oil phase and the water phase. After removing moisture from the separated aqueous phase by a method such as freeze-drying, the solid component is isolated and washed with cold water. Thereafter, the number of moles of vinyl alcohol and vinyl acetate is measured by a Fourier transform infrared spectrophotometer (FTIR), a nuclear magnetic resonance apparatus ( ¹ H-NMR) or the like, and the degree of polymerization (number average degree of polymerization) is calculated. Based on the obtained polymerization degree value, the saponification degree is calculated by the mathematical formula for obtaining the saponification degree.

  The addition amount of the copolymer is usually 5% by mass or more with respect to the colorant or 0.1 to 10% by mass with respect to all the components in the ink, and is added to all the components in the ink. 1-5 mass% is preferable with respect to it.

-Other water-soluble polymer compounds-
Examples of the water-soluble polymer compound include moisture retention and thickening of emulsion inks for stencil printing, improve dispersibility and fixing property of extender pigments, and other water-soluble high-molecular compounds from the viewpoint of emulsion stability. Molecular compounds may be added.
The other water-soluble polymer compound may be a natural polymer compound, a semi-synthetic polymer compound, or a synthetic polymer compound.
Examples of the natural polymer compound include starch, mannan, sodium alginate, galactan, tragacanth gum, gum arabic, bull run, dextran, xanthan gum, glue, gelatin, collagen, casein, and the like.
Examples of the semi-polymer compound include carboxymethyl cellulose, hydroxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxymethyl starch, carboxymethyl starch, and dialdehyde starch.
Examples of the polymer compound include neutralized products such as acrylic resin and sodium polyacrylate, alkyl-modified acrylic resin, polyvinyl imide, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene imine, polyacrylamide, and poly N-acryloyl pyrrolidine. And poly N-alkyl-substituted acrylamides such as poly-N-isopropylacrylamide, polyethylene oxide, polyvinyl methyl ether, styrene-maleic anhydride copolymer, styrene-acrylic acid copolymer, and these partially hydrophobicized with alkyl groups Polymer compounds, and the like. Moreover, AB and ABA type block copolymers of polyethylene and polypropylene or polybutylene are also included. Further, the acrylamide polymer and the acrylic polymer may be a copolymer type polymer in which the substituent is partially hydrophobized with an alkyl group. These water-soluble polymer compounds may be used alone or in combination of two or more, as long as the water resistance is not affected.
The mass average molecular weight of the other water-soluble polymer compound is preferably 2,000 to 1,000,000, more preferably 5,000 to 300,000, and particularly preferably 10,000 to 150,000. The amount of the other water-soluble polymer compound added is usually 25% by mass or less, preferably 0.5 to 15% by mass, of water contained in the ink.

-Colorant-
The colorant is not particularly limited and may be appropriately selected depending on the intended purpose.For example, carbon blacks, metal powders, inorganic pigments, azo pigments, phthalocyanine pigments, condensed polycyclic pigments, organic pigments, Examples thereof include oil-soluble dyes and fluorescent pigments.
Examples of the carbon blacks include acetylene black, channel black, and furnace carbon.
As typical carbon black, for example, MA-100, MA-7, MA-70, MA-77, MA-11, # 40, # 44 (manufactured by Mitsubishi Chemical Corporation), Raven1100, Raven1080, Raven1255, Raven 760, Raven 410 (above, Columbyan Carbon Co., Ltd.) and the like.
Examples of the metal powder include aluminum powder and bronze powder.
Examples of the inorganic pigments include petals, yellow lead, ultramarine blue, chromium oxide, and titanium oxide.
Examples of the azo pigment include insoluble azo pigments, azo lake pigments, and condensed azo pigments.
Examples of the phthalocyanine pigments include metal-free phthalocyanine pigments and copper phthalocyanine pigments.
Examples of the condensed polycyclic pigment include anthraquinone, quinacridone, isoindolinone, isoindoline, dioxazine, selenium, berylene, perinone, thioindigo, quinofullerone, and metal complexes. Can be mentioned.
Examples of the organic pigment include lakes of acidic or basic dyes.
Examples of the oil-soluble dye include diazo dyes and anthraquinone dyes.
As the fluorescent pigment, for example, when a synthetic resin is bulk polymerized or after polymerization, a fluorescent dye that develops various hues is dissolved or dyed, and the resulting colored bulk resin is pulverized and refined. Synthetic resin solid solution types are exemplified, and examples of the synthetic resin carrying a fluorescent dye include melamine resin, urea resin, sulfonamide resin, alkyd resin, and polyvinyl chloride resin.
These colorants may be used alone or in combination of two or more.
The volume average particle diameter of the colorant is preferably from 0.1 to 10 μm, and more preferably from 0.1 to 1.0 μm.
2-15 mass% is preferable and, as for content of the said coloring agent, 4-10 mass% is more preferable.
Two or more colorants may be added to the aqueous phase or the oil phase as long as they do not adversely affect other systems.

-Water-
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.

-Electrolyte-
The electrolyte is preferably added in order to increase the dispersion stability of the emulsion. Examples of the electrolyte include an electrolyte composed of a cation and an anion.
Examples of the anion include citrate ion, tartrate ion, sulfate ion, acetate ion, chlorine ion, borate ion, and the like.
Examples of the cation include alkali metals and alkaline earth metals. However, as the cation for achieving both the prevention of aggregation of the colorant, extender pigment, O / W resin emulsion, etc. added to the aqueous phase and the dispersion stability of the emulsion, lithium ion, sodium ion, potassium ion Monovalent ions such as are preferable.
Accordingly, as the electrolyte, for example, lithium sulfate, potassium sulfate, sodium sulfate, sodium citrate, sodium hydrogen phosphate, sodium borate, sodium acetate, sodium chloride, potassium chloride, lithium chloride, and the like are preferable.
As the electrolyte, a divalent cation electrolyte made of, for example, magnesium sulfate may be used as long as the stability of the emulsion and the dispersion stability of the powder are not affected.
The amount of the electrolyte added is usually 0.01 to 5% by mass of the aqueous phase, and preferably 0.1 to 2.0% by mass.

-Water evaporation inhibitor or antifreeze agent-
The water evaporation inhibitor or antifreeze agent is not particularly limited and may be appropriately selected from known ones. Examples thereof include lower saturated monohydric alcohols, glycols and polyhydric alcohols. . These may be used individually by 1 type and may use 2 or more types together. The water evaporation inhibitor and the antifreezing agent can be used in combination.
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.
The amount of the water evaporation inhibitor or antifreezing agent added in the aqueous phase is preferably 15% by mass or less, and more preferably 4 to 12% by mass.

-Antibacterial agent-
The antibacterial agent 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 antibacterial agent is not particularly limited and may be appropriately selected from known ones. Examples of the antibacterial agent include fragrances such as salicylic acid, phenols, methyl p-oxybenzoate, ethyl p-oxybenzoate, and the like. And thiazoline-based compounds (organic nitrogen-based sulfur compounds) such as group hydroxy compounds or chlorine compounds thereof, sorbic acid, dehydroacetic acid, MIT (methylisothiazoline), BIT (butylisothiazoline), OIT (octylisothiazoline), and the like. As a commercial item of this organic nitrogen-type sulfur compound, the Dell top 512 by Nippon Enviro Chemicals etc. are mentioned, for example. These may be used individually by 1 type and may use 2 or more types together.
The addition amount of the antibacterial agent in the aqueous phase is preferably 3% by mass or less, and more preferably 0.1 to 1.2% 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.
The extender pigment is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include inorganic fine particles and organic fine particles.
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.
Specific commercial products of the extender pigment include, for example, Aerosil 200, Aerosil 300, Aerosil 380, Aerosil R972 (above, manufactured by Nippon Aerosil Co., Ltd.), White Gloss TDD, White Gloss O, NE D ORBEN (above, Shiraishi Kogyo Co., Ltd.), BEN-GEL, S-BEN, ORGANITE (above, manufactured by Toyosune Yoko Co., Ltd.), TIXOGEL series (VP, VP-A, VZ, MP, MPI, MPG, MP100, MP250, EZ100, UN, Etc.), OPTIGEL (manufactured by Zude Chemie Catalysts), and the like.
The extender pigment may be added only to the aqueous phase of the emulsion ink for stencil printing, or may be added to both phases, and the addition amount is not particularly limited and is appropriately selected depending on the purpose. 0.1-50 mass% is preferable, and 1-5 mass% is more preferable.

-Oil-in-water (O / W) resin emulsion-
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.
The method for dispersing the oil-in-water resin emulsion is not particularly limited, and a dispersant, a protective colloid, and a surfactant may be added. The method for synthesizing the oil-in-water resin emulsion is not particularly limited, and may be an emulsion polymerization method, a suspension polymerization method, or a soap-free emulsion polymerization.
The minimum film-forming temperature of the oil-in-water resin emulsion is not particularly limited and can be appropriately selected according to the purpose, and is preferably 40 ° C. or lower. Moreover, the particle diameter of the oil-in-water resin emulsion is usually 0.1 to 30 μm, and preferably 0.5 to 5 μm.

-PH adjuster-
There is no restriction | limiting in particular as said pH adjuster, Although it can select and use suitably from well-known things, For example, ammonia, 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. When the pH of the aqueous phase is out of the above range, the effect may be impaired when a water-soluble polymer compound is added.
In order to keep the pH constant, a buffer may be added. Examples of the buffer include ethylenediaminetetraacetic acid, 4-morpholinoethanesulfonic acid (MES) and 4-morpholinopropanesulfonic acid (MOPS), Aldrich. Examples include Trizma base manufactured by the company. The amount of the buffer added is preferably about 0.05 to 0.1% by mass of the aqueous phase component, for example.

<Oil phase>
The oil phase contains a resin, an emulsifier, an oil component, an antioxidant, a colorant dispersant, a gelling agent, and other components as necessary. The colorant is as described above.

-Resin-
The resin can be preferably used from the viewpoint of improving the water resistance of the ink. 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 30,000 to 150,000, more preferably 55,000 to 150,000, from the viewpoint of fixability and printability. Further, the resin preferably has a solubility tolerance of 1 g / g or more with respect to the Nisseki No. 0 solvent, that is, 1 g or more of the No. 0 solvent is compatible with 1 g of the resin.
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. The iodine value is preferably 80 or more, 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.

-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. An anionic surfactant, a cationic surfactant, and a nonionic surfactant As long as it has an effect on emulsion stability, it may be a low molecular surfactant or a high molecular surfactant. Among these, nonionic surfactants may be used. Agents are preferred. Examples of the nonionic surfactant include sorbitan fatty acid esters such as sorbitan monooleate, sorbitan sesquioleate, sorbitan trioleate, sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and the like. Polyoxyethylene glycerin such as polyoxyethylene sorbitan fatty acid ester, glyceryl monostearate, decaglyceryl trioleate, hexaglycerin polyricinoleate, polyglycerin fatty acid ester, polyoxyethylene sorbit fatty acid ester, polyoxyethylene glycerin vegetable oil fatty acid ester, etc. Fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl Phenyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid amides, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil and higher alcohols, and the like. The said emulsifier may be used individually by 1 type, and may use 2 or more types together.
The addition amount of the emulsifier in the emulsion ink for stencil printing is usually 0.5 to 15% by mass, and preferably 1 to 6% by mass.

-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, synthetic oil, etc. are mentioned. However, the oil component may be used by mixing a plurality of different volatile oils for the purpose of improving ink storage stability. However, the volatile oil may have an adverse effect on the global environment. Therefore, it is preferable not to use as much as possible.
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 vegetable oil include those obtained by esterifying the vegetable oil. Examples of the ester include methyl ester, ethyl ester, and butyl ester. As the esterified vegetable oil, for example, esterified soybean oil is particularly preferable.
As the alkyd resin, the soybean oil fatty acid alkyd resin whose fat is soybean oil is used, and by using esterified soybean oil, the total of the components derived from soybean oil exceeds 6%. This is also advantageous in terms of safety.
The mineral oil is not particularly limited and can be appropriately selected depending on 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. , Diana Fresia series, etc.
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. Company Diana process oil (NP-24, NR-26, NR-68, NS-90S, NM-280, etc.), Diana Fresia series (G-6, F-9, N-28, N-90, N-150, U-46, U-56, U-68, U-130, U-170, U-260); Down oil Series (410,420,450,480,3125,4240, etc.), and the like.
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 the 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 oil component, According to the objective, it can select suitably, 3-30 mass% is preferable, and 15-25 mass% is more preferable.
In consideration of the ink drying property after printing, it is preferable to use an oil component having an iodine value of 100 or more, generally called a drying oil or a semi-drying oil, to which an antioxidant is added. In consideration of fixing the ink in step 1, an iodine value of 100 or less can be used.
Here, the iodine value of the oil component can be measured by, for example, a commercially available edible fat / oil analyzer.
Examples of the edible fat / oil analyzer include Oil & Fat analyzer edible fat / oil analyzer (manufactured by Yaki Technotron Co., Ltd.).

-Antioxidant-
The antioxidant is not particularly limited and may be appropriately selected from known ones. Examples thereof include nordihydroguaiaretic acid (NDGA), citrate ester, extracted tocopherol, tocopherol, butylhydroxy Examples include toluene, gallic acid, dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, sulfites, thiosulfate, ascorbic acid, ascorbate, ascorbic acid derivatives, and the like. Two or more kinds may be used in combination.
The amount of the antioxidant added in the oil phase is, for example, preferably 2% by mass or less, and more preferably 0.1-1% by mass.
When an extremely small amount of antioxidant is added to the vegetable oil content, an appropriate antioxidant effect cannot be expected. On the contrary, a large amount of antioxidant is added to the vegetable oil content at once. If it does, it may act as an oxidation accelerator and will also become disadvantageous also in terms of cost. Therefore, it is preferable to add a synergist to suppress the oxidation of vegetable oil even with a small amount of antioxidant.

--Synergist--
The synergist is a component that has almost no antioxidant action itself, but enhances the action when used in combination with the antioxidant. The synergist is usually an acidic substance and is a polyfunctional compound having several hydroxyl groups or carboxyl groups.
The synergist is not particularly limited and can be appropriately selected from known ones. For example, methionine, ascorbic acid, threonine, leucine, milk protein hydrolyzate, norvaline, ascorbyl palmitate, phenylalanine , Cystine, tryptophan, proline, alanine, glutamic acid, valine, pancreatic protein pepsin digestion solution, asparagine, arginine, barbituric acid, asphenamine, ninhydrin, propanidin, histidine, norleucine, glycerophosphate, casein trypsin hydrolyzate, casein Hydrochloric acid hydrolyzed solution and the like. These may be used individually by 1 type and may use 2 or more types together.
The addition amount of the synergist is preferably 50 to 150% by mass with respect to the content of the antioxidant.

-Colorant dispersant-
As the colorant dispersant, one that does not inhibit the formation of an emulsion can be used, and the nonionic surfactant for emulsifier and a water-soluble polymer can also be used.
Examples of the colorant dispersant include sorbitan fatty acid esters such as sorbitan sesquioleate, polyglycerin fatty acid esters such as hexaglycerin polyricinoleate, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene alkyl ether. , Nonionic surfactants such as polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid amides; alkylamine polymer compounds, aluminum chelate compounds, styrene-maleic anhydride copolymer polymers, polycarboxyl Acid ester type polymer compound, aliphatic polycarboxylic acid, amine salt of polymer polyester, ester type anionic surfactant, long chain amine salt of high molecular weight polycarboxylic acid, long chain polyamine Salts of nonamides and polymeric acid polyesters, polyamide compounds, phosphate ester surfactants, alkyl sulfocarboxylates, sulfonates, α-olefin sulfonates, dioctyl sulfosuccinates, polyethyleneimine, alkylolamine salts And resins having insoluble colorant dispersibility, such as alkyd resins.
In addition, ionic surfactants, amphoteric surfactants and the like may be used as long as they do not impair the storage stability of the ink. Specific commercial products of the ionic surfactant and amphoteric surfactant include, for example, Solspers series (S3000, S5000, S9000, S13240, S13940, S16000, S17000, S20000, S24000, manufactured by Nippon Lubrizol Corporation). S26000, S27000, S28000, S31845, S31850, S32550, S34750, S41090, S53095, etc.), Ajinomoto Fine Techno Co., Ltd. Plain Act AL-M, Ajisper series (PB711, PM821, PB821, PB811, PN411, PA111, etc.) Air Products, Surfynol series (GA, TG, CT-221, CT-121, etc.), Nissin Chemical Industry Olfin PD series (001, 0) 02W, 003, 004, 005, etc.), TMGS-15, TMGO-15, Decaglyn series (1-L, 1-M, 1-O, etc.) manufactured by Nikko Chemicals, TL-10, TP-10, TO-10, TI-10, BL-21, BC-15TX, BC-23, BC-30TX, BC-40TX, BS-20, BO-10TX, TAMNS-10, TAMNS-15, TAMNO-5, TAMNO- 15, TDMNS-8, OTP-100, OTP-75, and the like.
In addition, the said colorant dispersing agent may be used individually by 1 type, and may use 2 or more types together.
The addition amount of the dispersant other than the polymer and resin is preferably 40% by mass or less, more preferably 2 to 35% by mass of the colorant.
The alkyd resin is particularly effective for the dispersion stability of the insoluble colorant when a high molecular weight resin is added. However, the alkyd resin may be used when the alkyd resin is used alone or in combination with other colorant dispersants. The addition amount is preferably 0.05% by mass or more based on the colorant.

-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.

  In the emulsion ink for stencil printing of the present invention, wax can be added to the oil phase in order to improve separation of the printing paper and the printing drum at the time of 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 the emulsion ink for stencil printing, and the amount of addition may be the same as that of conventional products.

-Manufacturing method-
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, an oil phase and an 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 emulsifier, an oil component, and the like are mixed and stirred with a high-speed dissolver. Thereafter, a dispersion treatment is performed using a bead mill to prepare an oil phase. On the other hand, acetylene diol, a surfactant having an HLB value of 10 or more, a water-soluble polymer, an antifreezing agent, an antibacterial agent, an electrolyte, and the like 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 when the shear rate is 20 sec ⁻¹ .

-Use-
As described above, since the emulsion ink for stencil printing of the present invention has good dispersion stability and excellent water resistance, 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 emulsifier and an oil component 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 colorant, a water-soluble polymer compound, a colorant dispersant, water, an antifreezing agent, an electrolyte, and an antibacterial agent were mixed with a homomixer (T.K. A pre-dispersion was performed using HOMOMIXER, and then a main dispersion was performed using a bead mill (LMZ0.6, manufactured by Ashizawa Finetech Co., Ltd.) 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 stencil emulsion ink of Example 1 was produced.

(Examples 2-6, Examples 11-13, Examples 15-18, and Comparative Example 1)
In Example 1, the emulsion ink for stencil printing of each example was similarly produced except having changed at least any one of the component and content of the water-soluble polymer compound as shown in Tables 1-4.

(Example 7 and Example 10)
In Example 1, as shown in Table 1, emulsion inks for stencil printing of each example were similarly prepared except that an electrolyte was added to the aqueous phase.

(Example 8 and Example 9)
In Example 1, as shown in Table 1, emulsion inks for stencil printing of each example were prepared in the same manner except that the resin was added to the oil phase.

(Example 14)
In Example 1, as shown in Table 1, emulsion inks for stencil printing of each example were prepared in the same manner except that the electrolyte was added to the aqueous phase and the resin was added to the oil phase.

[Evaluation]
Next, the following evaluation was performed about each obtained emulsion ink for stencil printing.

(1) Evaluation of water resistance An image is printed with Satelio A650 manufactured by Tohoku Ricoh Co., Ltd., and the image after 30 minutes is rubbed with a cloth wetted with water. evaluated.
5.00: No image rubbing is observed.
4.50 or more and less than 5.00: Image rubbing is hardly observed.
4.00 or more and less than 4.50: Slight rubbing of the image is observed, but is in an allowable range.
Less than 4.00: Image rubbing is noticeable and out of the allowable range.

(2) Measurement of amount of centrifugal oil separation After ink was left at 60 ° C. for 2 weeks, it was centrifuged at 6,300 G for 3 hours with a centrifugal separator (M150-IVD, manufactured by Sakuma Corporation). The ratio of the oil generated by the above to the ink mass was calculated as a percentage as the centrifugal oil separation amount.

(3) Evaluation of viscosity with time The ink was allowed to stand at 60 ° C. for 2 weeks in an open state, the viscosity before and after the standing was measured, and the level of viscosity increase was evaluated according to the following criteria.
○: Little increase in viscosity is observed.
X: Increase in viscosity is noticeable.

The results of the above (1) to (3) are shown in Tables 1 to 4. In addition, the unit of each component in Tables 1 to 4 is “mass%”.

In Tables 1 to 4, the polyglyceric acid fatty acid ester is hexaglycerin polyricinoleate manufactured by Nikko Chemicals, the sorbitan monooleate is SO-10 manufactured by Nikko Chemicals, the naphthenic oil is SUNTHEN 380 manufactured by Nippon Sun Oil Co., and the soy methyl ester is Vertec. Vertecbio Gold # 4 manufactured by Biosolvents, alkyd resin 1 is soybean oil alkyd resin manufactured by Arakawa Chemical Co., Ltd., alkyd resin 2 is rosin-modified phenolic resin manufactured by Arakawa Chemical Co., carbon black 1 is Raven 760 manufactured by Colombian Carbon, and carbon black 2 is Mitsubishi. MA-77 manufactured by Kagaku Co., PVA copolymer 1 is NL-05 manufactured by Nippon Synthetic Chemical Co., Ltd. (saponification degree = 99.3 mol%, polymerization degree = 500), and PVA copolymer 2 is AL- manufactured by Nippon Synthetic Chemical Co. 06 (degree of saponification = 92.4mo %, Polymerization degree = 500), PVA copolymer 3 is GL-05 (saponification degree = 87.7 mol%, polymerization degree = 500) manufactured by Nippon Synthetic Chemical Co., Ltd., and PVA copolymer 4 is KL manufactured by Nippon Synthetic Chemical Co., Ltd. -05 (degree of saponification = 79.9 mol%, degree of polymerization = 500), PVA copolymer 5 is NK-05R (degree of saponification = 73.2 mol%, degree of polymerization = 500) manufactured by Nippon Synthetic Chemical Co., Ltd. Polymer 6 is Nippon Synthetic Chemical Co., Ltd. L-5407 (degree of saponification = 47.2 mol%, degree of polymerization = 300 to 350), and PVA copolymer 7 is Nippon Synthetic Chemical Co., Ltd. L-302 (degree of saponification = 35). .4 mol%, polymerization degree = 300 to 350), polyvinylpyrrolidone is a Luvitec K30 solution manufactured by BASF, Sulfynol GA is manufactured by Air Products, glycerin is manufactured by NOF Corporation, and magnesium sulfate is sulfuric acid manufactured by Kanto Chemical. Magnesium heptahydrate and sodium sulfate used were sodium sulfate hydrate manufactured by Kanto Chemical Co., and the organic nitrogen-based sulfur compound used Deltop 512 manufactured by Nippon Enviro Chemicals.
In Tables 1 to 4, the PVA copolymer means a copolymer of vinyl alcohol and vinyl acetate.

  From the results of Tables 1 to 4, it was found that the emulsion inks for stencil printing of Examples 1 to 18 containing a copolymer of avinyl alcohol and vinyl acetate have good water resistance and dispersion stability. In particular, in the emulsion inks for stencil printing of Examples 7, 10 and 14 containing an electrolyte, the dispersion stability is the stencil of Examples 8, 9 and 14 containing a resin in the oil phase. The printing emulsion ink was found to have very good water resistance. Further, it was found that when the addition amount of the copolymer is 0.1 to 10% by mass, the effect of water resistance is remarkable and the viscosity over time is stable without increasing.

Since the emulsion ink for stencil printing of the present invention has good dispersion stability and excellent water resistance, it is suitably used for stencil printing by a rotary stencil printing machine, for example.

Claims (5)

  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, wherein the aqueous phase contains a copolymer of vinyl alcohol and vinyl acetate.   The emulsion ink for stencil printing according to claim 1, wherein the saponification degree of the copolymer is 90 mol% or more or 50 mol% or less.   The emulsion ink for stencil printing according to any one of claims 1 to 2, wherein the degree of polymerization of the copolymer is 300 or more.   The emulsion ink for stencil printing according to any one of claims 1 to 3, further comprising an electrolyte. The emulsion ink for stencil printing according to any one of claims 1 to 4, further comprising a resin in the oil phase.