JP2001106952A - Water-in-oil type emulsion ink for mimeograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-in-oil emulsion ink for mimeograph that shows reduced strike through and bleeding and excellent fixity. SOLUTION: In an water-in-oil emulsion ink comprising 10-90 wt.% of the oil phase and 90-10 wt.% of the water phase, the yield value of the oil phase according to the regression Casson equation is >=0.3 Pa at 23 deg.C, preferably the yield value of the oil phase according to the regression Casson equation is <=10 Pa at 23 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil printing emulsion ink, and more particularly to a stencil printing water-in-oil emulsion ink which has low strikethrough, low bleeding and excellent fixability.

[0002]

2. Description of the Related Art As is well known, a stencil printing method uses a stencil printing paper and moves ink from one side of the stencil to the other side of the stencil through a perforated portion of the stencil. Is to be printed. Conventionally used inks are water-in-oil emulsion inks, which are composed of volatile solvents, nonvolatile solvents, resins, coloring agents, surfactants, water, antifreeze agents, electrolytes, preservatives, etc. ing.

[0003] In recent years, rotary stencil printing machines have also been automated by microcomputers and the like, and their operations have been simplified, and stencil printing has been increasingly used. However, stencil printing is only drying by osmosis drying and evaporation drying, it is not possible to use a reactive resin so that the ink does not solidify on the machine, and the demand for double-sided printing is increasing due to environmental problems. I have.

Japanese Patent Laid-Open Publication No. Hei 8-73795 discloses a method of drying an ink by setting an average particle size and a surface area of carbon black as a coloring component in an oil phase. It has been proposed to improve fixability. However, according to this method, fixability,
Although there is an improvement in set-off, the drying method is mainly penetrating, so that there is a problem in that printing on the back side is visible (through strike-through) when printing on both sides.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an emulsion ink for stencil printing which eliminates the drawbacks of the above-mentioned prior art, has less strikethrough and bleeding, and has excellent fixability. .

[0006]

According to the present invention, first, in a water-in-oil emulsion ink composed of 10 to 90% by weight of an oil phase and 90 to 10% by weight of an aqueous phase, 23% of the oil phase is used. Casson yield value of 0.3 ° C
(Pa) or more, provided is a water-in-oil emulsion ink for stencil printing.

Second, Cas at 23 ° C. of the oil phase
The water-in-oil emulsion ink for stencil printing as described in the first aspect, wherein the son yield value is 10 (Pa) or less.

That is, the inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the Casson yield value of the oil phase at 23 ° C. of not less than 0.3 (Pa) has resulted in strikethrough, The Casson yield value at 23 ° C. of the oil phase was 10 (P
a) It has been found that the following conditions can further improve the fixing property, and the present invention has been completed.

The reason why the water-in-oil emulsion ink for stencil printing of the present invention exhibits these effects is not clear,
It is considered as follows. That is, by setting the Casson yield value of the oil phase at 23 ° C. to 0.3 (Pa) or more, preferably 0.7 (Pa) or more, the spread of the pigment in the paper after printing is suppressed, thereby causing bleeding. It seems that the strikethrough has been reduced. On the other hand, the Casson yield value at 23 ° C. of the oil phase is 10 (Pa) or less, preferably 5 (Pa) or less, more preferably 2.5 (Pa).
It is desirable that: When the Casson yield value in the oil phase exceeds 10 (Pa), the fluidity of the pigment deteriorates, and a large amount of the pigment remains on the paper surface.

The Casson yield value of the oil phase at 23 ° C. in the present invention is determined by using a stress rheometer (CSR-10 manufactured by Bolin Co., Ltd.) to obtain a flow curve from 12.5 Pa to 150 Pa with a cone of 2 cm 2 degrees at 23 ° C. Measure and use the approximation of Casson
The plastic viscosity and Casson yield value were obtained by calculation. Casson's approximate expression: √τ-√τ _O = √ (Eta ×
D) τ: Shear stress D: Shear rate τ _O : Yield value Et
a: plastic viscosity

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The aqueous phase of the emulsion includes water, an electrolyte, a fungicide,
A water evaporation inhibitor, a water-soluble polymer, an oil-in-water resin emulsion, a colorant, and the like, and the oil phase is composed of an oil component, an insoluble colorant dispersant, a colorant, an extender, a resin, an emulsifier, and the like. Known components that do not inhibit the formation of the emulsion are used as these components.

As the colorant used in the present invention, various known pigments and disperse dyes are used, and carbon blacks such as acetylene black, channel black and furnace black, and metal powders such as aluminum powder and bronze powder. Inorganic pigments such as red iron oxide, graphite, ultramarine blue, chromium oxide and titanium oxide; azo pigments such as insoluble azo pigments, azo lake pigments and condensed azo pigments; phthalocyanine pigments such as metal-free phthalocyanine pigments and copper phthalocyanine pigments; anthraquinone System, quinacridone system, isoindolinone system,
Condensed polycyclic pigments such as isoindoline, dioxane, sulfen, perylene, perinone, thioindigo, quinophthalone, metal complexes, organic pigments such as lakes of acidic or basic dyes, diazo dyes, anthraquinones Examples include oil-soluble dyes such as dyes, fluorescent pigments, and the like.

[0013] In addition, as a fluorescent pigment, a synthetic resin is subjected to bulk polymerization or after polymerization, a fluorescent dye which develops various hues is dissolved or dyed, and the obtained colored bulk resin is pulverized and refined. The so-called synthetic resin solid solution type, as a synthetic resin carrying a dye, melamine resin,
There are urea resins, sulfonamide resins, alkyd resins, vinyl chloride resins, and the like, and fluorescent pigments carrying a dye on them. These dyes and pigments may be added to the oil phase, the aqueous phase or both phases, or may be added alone or as a mixture of two or more.

The average particle size of the insoluble colorant dispersed in the oil phase and the aqueous phase is 10 to 0.1 μm, preferably 1 to 0.1 μm.
It is desirable that The amount can be added according to the required amount, but is usually 2 to 15% by weight. In addition, two or more insoluble colorants having similar properties may be added to the same phase while being dispersed or added to the oil phase and the aqueous phase.

When carbon black is added to the oil phase, it is desirable to use acidic carbon black having a pH of less than 5. Representative carbon blacks include MA-100, MA-7, MA-77, MA-
11, # 40, # 44 (Mitsubishi Chemical Corporation) Raven11
00, Raven1080, Raven1255, Ra
ven 760, Raven 410 (manufactured by Colombian Carbon Co., Ltd.) and the like.

The oil used in the present invention includes, for example, petroleum solvents, liquid paraffin, spindle oil, machine oil,
Lubricating oil, mineral oil; linseed oil, tall oil, corn oil, olive oil, rapeseed oil, castor oil, dehydrated castor oil,
Vegetable oils such as soybean oil and coconut oil are used. Further, in the present invention, synthetic oils can be used together as long as the safety and storage stability are not impaired.

The paraffinic oils used in the present invention include Gargo Oil Arctic Series (1010, 1022, 1032, 1046,
1068, 1100, 3032, 3046, 3068), Nippon Oil Corporation's Nisseki Super Oil Series (B,
C, D, E, etc.), Idemitsu Kosan Diana Process Oil (PX-32, PX-90, PW-32, PW-9
0, PW-380, PS-32, PS-90, PS-4
30), Diana Fresia series (S-32, S
-90, P-32, P-90, P-150, P-18
0, P-430, etc.).

The naphthenic oil used in the present invention is:
The carbon content (C _N ) of the naphthene component by ring analysis is 3
0% _CN or more and carbon content of aromatic component (C _A )
Mineral oil having a carbon content of not more than 20% C _A and a carbon content (C _P ) of a paraffin component of not more than 55% C _P ; Gargo Oil Arctic Oils 155 and 300 of Mobil Oil Co., Ltd.
ID, Gargo Oil Arctic Oil Light and Gargo Oil Arctic Oil C Heavy; Diana Process Oil (NP-24, NR-26, Idemitsu Kosan Co., Ltd.)
NR-68, NS-90S, NM-280, etc.), Diana Fresia series (N-28, N-90, N-15)
0, U-46, U-56, U-68, U-130, U-
170, U-260); Sansen Oil Series (410, 420, 450, 480, 312) of Nippon Sun Oil Co., Ltd.
5, 4240, etc.).

The meanings of the symbols in the ring analysis values are as follows. % C _A = 100 fraction of aromatic carbon number to total carbon number% C _N = 100 fraction of naphthenic carbon number to total carbon number% C _P = 100 fraction of paraffin carbon number to total carbon number

Examples of highly safe petroleum solvents include Exoper Chemical's Isopar series (C, E, G, H, L,
M) and Exole (D30, D40, D80, D
110, D130, etc.) and AF Solvent Series (Nos. 4, 5, 6, and 7) of Nippon Oil Corporation.

These oil components are considered in consideration of safety.
It is desirable to use those having less than 3% by mass of a polycyclic aromatic component which is an aromatic hydrocarbon containing three or more condensed aromatic rings. Furthermore, 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 and benzo [ b) Fluoranthene, benzo [j]
The content of polycyclic aromatics such as fluoranthene, benzo [k] fluoranthene, benzo [a] pyrene, dibenzo [a, j] acridine is individually 10 ppm by weight or less, and the total amount of the content is 50 ppm by weight. The following are highly safe allomer oils (JP-A-11-80640)
May be used if necessary.

The emulsifier used in the present invention is used for the purpose of forming a water-in-oil emulsion, and may be any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a nonionic surfactant. As long as it has an effect on stability, it may be a low molecular weight or a high molecular weight, or may be used together. Of these, preferred are nonionic surfactants, for example, sorbitan monooleate, sorbitan sesquiolate, sorbitan triolate, sorbitan fatty acid esters such as sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan Polyoxyethylene sorbitan fatty acid esters such as trioleate, (poly) glycerin fatty acid esters such as glyceryl monostearate, decaglyceryl trioleate, hexaglycerin polyricinoleate, polyoxyethylene sorbite fatty acid esters, and polyoxyethylene glycerin vegetable oil fatty acid esters Polyoxyethylene glycerin fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene alkyl ether , Polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine / fatty acid amide, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene castor oil / hardened castor oil, higher alcohols, etc., alone or in combination of two or more. Prepare emulsions with high storage stability. The addition amount is usually 0.5 to 15% by weight, preferably 1 to 3% by weight of the ink weight.

In addition to the above, a resin, a dispersant for a colorant, an extender,
A gelling agent, an antioxidant and the like can be added. The above-mentioned emulsifier is also included in the oil phase. In the aqueous phase, an insoluble colorant dispersant, a water-soluble polymer, an oil-in-water resin emulsion, a preservative
Fungicide, water evaporation inhibitor, antifreeze, pH adjuster,
An electrolyte, an extender and the like can be added.

The resin added to the oil phase includes rosin;
Rosin-based resins such as polymerized rosin, hydrogenated rosin, rosin ester, rosin polyester resin and hydrogenated rosin ester; rosin-modified alkyd resin, rosin-modified maleic resin; rosin-modified resin such as rosin-modified phenol resin; maleic acid resin; A resin, a petroleum resin, a rubber derivative resin such as a cyclized rubber, a terpene resin, an alkyd resin, a polymerized castor oil, or a mixture of two or more thereof may be added. Typical resins include Tamanol 353, Tamanol 403, Tamanol 361, Tamanol 387, Tamanol 340, Tamanol 400, Tamanol 396, Tamanol 354, KG836, KG846, manufactured by Arakawa Chemical Co., Ltd.
Rosin-modified phenol resins such as KG1834 and KG1801 are exemplified.

The weight average molecular weight of the resin is preferably from 30,000 to 150,000, more preferably 5.5, from the viewpoint of fixability and printability.
These resins have a tolerance of 1 g / g or more having a solubility in Nisseki No. 0 solvent (1 g or more of a 0 g solvent can be compatible with 1 g of resin). preferable. When the resin is added to the oil phase, the amount of the resin used is 2 to 50% by weight, more preferably 5 to 20% by weight of the oil phase, in view of the cost of the ink and printability. If the weight average molecular weight of the resin is low and the addition amount is small, the effect on the fixing property is small, and if the weight average molecular weight is too high, or if the addition amount of the resin is large, the viscosity of the ink increases, There are problems with printability such as ink leaking from the rear end of the drum.

The alkyd resin used in the present invention is composed of fats and oils, polybasic acids and polyhydric alcohols. Examples of fats and oils include non-drying oils or semi-drying oils having an iodine value of 80 or less such as coconut oil, palm oil, olive oil, castor oil, rice bran oil, cottonseed oil, and these fatty acids, and soybeans, linseed oil, tung oil, etc. Drying oil has an alkyd resin iodine value of 8
In the category of 0 or less, some may be used.

Examples of the above polybasic acids include saturated polybasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid and tetrahydrophthalic acid, and maleic acid, maleic anhydride, fumaric acid, Unsaturated basic acids such as itaconic acid and citraconic anhydride can be used.

The polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, glycerin, trimethylolpropane, neopentyl glycol, diglycerin, and triglycerin. , Pentaerythrit, dipentaerythlit, mannit, sorbit and the like.

The oil length of the alkyd resin is expressed in terms of% by weight in the resin when the fatty acid in the fat or oil is present as triglyceride. The alkyd resin has an oil length of 60 to 60 due to problems such as dispersion stability and clogging of the copper plate screen due to film formation.
It is preferably 90 and an iodine value of 80 or less. The weight average molecular weight of the alkyd resin is preferably less than 30,000, more preferably 10,000 or less.

As the colorant dispersant for the colorant dispersed in the oil phase, those which do not inhibit the formation of an emulsion can be used, and the above-mentioned nonionic surfactants for emulsifiers and water-soluble polymers can also be used. Examples of the dispersant include nonionic surfactants such as sorbitan fatty acid esters such as sorbitan sesquiolate and polyglycerin fatty acid esters such as hexaglycerin polyricinoleate, alkylamine-based polymer compounds, aluminum chelate-based compounds, and styrene-maleic anhydride. Acid-based copolymer polymer compound,
Polycarboxylic 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 polyaminoamide and polymer Acid polyester salts, polyamide compounds, phosphate ester surfactants, alkyl sulfocarboxylates, α-olefin sulfonates, dioctyl sulfosuccinates,
Resins having an insoluble colorant dispersing ability, such as polyethyleneimine, alkylolamine salts, and alkyd resins, are also included. In addition, as long as the storage stability of the ink is not impaired, an ionic surfactant, an amphoteric surfactant and the like can be used.

These dispersants may be added alone or in admixture of two or more. The amount of the colorant dispersant other than the polymer and resin is 40% by weight or less, preferably 2 to 35% by weight of the colorant. %. The alkyd resin has a particularly effective effect on the dispersion stability of the insoluble colorant when a high molecular weight resin is added, but when the alkyd resin is used alone or in combination with other dispersants, the amount of the resin added is insoluble. It is preferably at least 0.05 part by weight based on 1 part by weight of the coloring agent.

The gelling agent has the role of gelling the resin contained in the oil phase to improve the storage stability, fixability and fluidity of the ink. The gelling agent added to the ink of the present invention includes: Compounds that coordinate with the resin in the oil phase are preferred.
Examples of such compounds include Li, Na, K, Al,
Organic acid salts, organic chelate compounds, metal soap oligomers and the like containing metals such as Ca, Co, Fe, Mn, Mg, Pb, Zn, and Zr; specifically, metal octylates such as aluminum octylate; Examples thereof include metal salts of naphthenic acid such as manganese acid, stearates such as zinc stearate, and organic chelate compounds such as ethyl acetoacetate aluminum diisopropylate. One or more of these gelling agents may be added to the oil phase, and the amount added is 15% by weight or less, preferably 5 to 10% by weight of the resin in the oil phase.

The antioxidants added to the oil phase include dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, etc. The addition of these prevents oxidation of the binder resin and the like in the oil phase. Is prevented from rising. The amount of addition is 2% by weight or less, preferably 0.1 to 1.0% by weight of the oil in the ink. The antioxidants may be used alone or in combination of two or more.

An extender pigment can be added to the ink for adjusting the viscosity. The extender pigments added to the ink include white clay, silica, talc, clay, calcium carbonate, barium sulfate, titanium oxide, alumina white, diatomaceous earth, kaolin, mica, aluminum hydroxide, and other inorganic fine particles, and polyacrylates. And organic fine particles such as polyurethane, polyester, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polysiloxane, phenol resin and epoxy resin, or fine particles comprising a copolymer thereof.

Specific examples of the extender include Aerosil 200, Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.), NEW D ORBEN (manufactured by Shiraishi Industry Co., Ltd.), BE
N-GEL, S-BEN, ORGANITE, etc. (manufactured by Toyohyun Yokosha), TIXOGEL series (VP, DS, G
B, VG, EZ-100, etc.), OPTIGEL (manufactured by Nissan Gardler Catalyst Co., Ltd.) and the like. These may be added to the oil phase, the aqueous phase or both phases, and the addition amount is preferably from 0.1 to 50% by weight, more preferably from 1 to 5% by weight, based on the ink.
% By weight.

To the aqueous phase of the emulsion ink, a water-soluble polymer or an oil-in-water resin emulsion may be added for moisturizing, thickening and dispersing and fixing the insoluble colorant and extender. Specific examples of the water-soluble polymer include the following natural or synthetic polymers. For example, starch, mannan,
Sodium alginate, galactan, tragacanth gum, gum arabic, bullran, dextran, xanthan gum,
Natural polymers such as glue, gelatin, collagen and casein; semi-synthetic polymers such as carboxymethylcellulose, hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxymethylstarch, carboxymethylstarch and dialdehyde starch;
Neutralized products such as acrylic resin and sodium polyacrylate, polyvinyl imide, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene imine, polyacrylamide, poly N-alkyl-substituted acrylamide such as poly N-acryloylpyrrolidine and poly N-isopropylacrylamide, polyethylene Oxide, polyvinyl methyl ether, styrene-maleic anhydride copolymer,
Styrene-acrylic acid copolymers and polymers in which these are partially hydrophobic with alkyl groups, and acrylamide polymers and acrylic polymers are also copolymer-type polymers in which the substituents are partially hydrophobicized with alkyl groups. good. Further, a block copolymer of polyethylene and polypropylene or polybutylene can be used. These water-soluble polymers may be used alone or as a mixture of two or more kinds, and 25% by weight or less, preferably 0.5 to 15% by weight of water contained in the ink is added.

The oil-in-water type resin emulsion may be a synthetic polymer or a natural polymer. As the polymer, polyvinyl acetate, polyacrylate, polymethacrylate, polyvinyl chloride, ethylene-vinyl acetate copolymer, vinyl acetate-acrylate copolymer, styrene-acrylate copolymer, Examples thereof include vinylidene chloride-acrylate copolymer, vinyl chloride-vinyl acetate copolymer, and polyurethane. Examples of natural substances include polymers that can be added to the oil phase. These may be used in combination of two or more as long as the stability of the water-in-oil emulsion ink is not impaired, and the dispersing method may be the addition of a dispersant, a protective colloid, and a surfactant. Those synthesized by soap-free emulsion polymerization may be used. The minimum film forming temperature of these oil-in-water resin emulsions is desirably 40 ° C. or lower.

The antiseptic / fungicide added to the aqueous phase is added to prevent the growth of bacteria and fungi in the emulsion. When the emulsion is to be stored for a long period of time, it is desirable to add an antiseptic / fungicide. . The amount of addition is 3% by weight or less of water contained in the ink, preferably 0.1 to 1.2%.
It is good to make it by weight%. Examples of the antiseptic / fungicide include salicylic acid, phenols, aromatic hydroxy compounds such as methyl p-oxybenzoate and ethyl p-oxybenzoate and chlorine compounds thereof, and sorbic acid and dehydroacetic acid. These may be used alone or in combination of two or more.

The anti-evaporation agent and the anti-freeze agent for water can be used in combination. Chemicals added for these purposes include glycols such as ethylene glycol, diethylene glycol and propylene glycol; methanol, ethanol, isopropanol, butanol and isobutanol. Lower saturated monohydric alcohols; polyhydric alcohols such as glycerin and sorbitol; One or more of these chemicals may be added, and the added amount is 15% by weight or less, preferably 4 to 12% by weight of the weight of water in the ink.

The pH adjusters added to the aqueous phase are triethanolamine, sodium acetate, triamylamine and the like. When necessary, these pH adjusters are added to maintain the pH of the aqueous phase at 6-8. Can be. If the pH of the aqueous phase deviates from the above range, there is a problem that the effect is impaired when a water-soluble polymer for a thickener is added.

The electrolyte added to the aqueous phase is added to enhance the storage stability of the emulsion. Therefore, it is desirable to use when the material affected by the electrolyte is not present in the aqueous phase. The electrolyte is preferably an electrolyte containing an anion such as a citrate ion, a tartrate ion, a sulfate ion, or an acetate ion, or an alkali metal ion or an alkaline earth metal ion. Therefore, as the electrolyte added here, magnesium sulfate, sodium sulfate, sodium citrate, sodium hydrogen phosphate, sodium borate, sodium acetate, and the like are preferable, and the amount of addition is 0.1 to 2% by weight of the aqueous phase. , Preferably 0.5 to 1.5% by weight.

In addition to the above, the water-in-oil emulsion ink for stencil printing of the present invention has an oil phase for improving the separation between the printing paper and the printing drum during printing or for preventing the printing paper from rolling up. Can be added to the wax. Further, to the aqueous phase, triethanolamine, sodium hydroxide, or the like can be added to further increase the viscosity by adding a water-soluble polymer. Further, by adding a rust inhibitor or a defoaming agent to the aqueous phase, it is possible to prevent the printing machine from being rusted by the ink during printing, or from foaming the ink. Known additives added to the stencil printing ink may be added as needed, and the amount of these additives may be about the same as in the case of conventional products.

The emulsion ink of the present invention may be prepared by preparing an oil phase and an aqueous phase liquid in the same manner as in the conventional emulsion ink production, and emulsifying both in a known emulsifying machine to form an ink. That is, an oil phase in which additives such as a coloring agent, an emulsifier, and a resin to be added as needed are dispersed well is prepared, and a coloring agent, a preservative / antifungal agent, a water-soluble polymer, and the like are added as necessary. What is necessary is just to gradually add and emulsify the added aqueous solution.

The viscosity of the ink can also be adjusted by the stirring conditions, and is not particularly limited as long as it is suitable for the system, but the viscosity at a shear rate of 20 s ^-1 is 3 to 40 Pa.
S is desirable, and preferably 10 to 30 Pa · s.

[0045]

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The parts described below are parts by weight.

(Examples 1 to 4 and Comparative Examples 1 and 2) <Production of W / O Emulsion Ink Containing Insoluble Colorant in Oil Phase>
An insoluble colorant dispersion was prepared by kneading the oil and the insoluble colorant dispersant with three rolls. A surfactant for emulsification, a varnish such as oil and resin are added to this insoluble colorant dispersion (hereinafter referred to as an insoluble colorant dispersion) to form an oil phase, and water, an antifreeze, a preservative, an electrolyte or water The emulsion ink for stencil printing was obtained by adding and emulsifying an aqueous phase composed of a hydrophilic resin and the like. Other components such as extenders may be added as needed.

The carbon black was RAVEN1100 manufactured by Colombian Carbon Co., and the copper phthalocyanine blue was Lionol Blue FG-7 manufactured by Toyo Ink.
330, copper phthalocyanine green is L manufactured by Toyo Ink
ionol Green Y-101, pigment dispersant: Plainact AL-M manufactured by Ajinomoto Co., emulsifier (sorbitan sesquiolate): SO-15 manufactured by Nikko Chemicals Co., Ltd., paraffin-based oil: Gargo Oil Arctic Series manufactured by Mobil (1010, 1100) ), Naphthenic oils are Mogo's Gargo Oil Arctic Series (Light), Nippon Sun Oil's Sansen Oil 410
It was used. Commercial products were used for ethylene glycol, magnesium sulfate and methyl p-oxybenzoate.

The formulations of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 1, and the components of the ring analysis of the oils used in Examples and Comparative Examples are shown in Table 2.

The ring analysis in the present invention is described in Lubrication Handbook p. 344 (edited by the Society of Lubrication of Japan, Yokendo version) and carried out in accordance with the ndM method. The chromatographic analysis was carried out in accordance with JIS K2536 [Petroleum products-hydrocarbon type test method].

[0050]

[Table 1]

[0051]

[Table 2]

<Evaluation of Emulsion Inks> Using these inks, a commercially available stencil printer (VT392) manufactured by Ricoh Company was used.
After sufficient printing was performed in 0) to allow the ink to pass through the printing machine, printing was performed.

The strike-through was visually evaluated on the back side of the printed solid portion, and was evaluated as 4 when the strike-through was severe, and x when the strike-through was relatively small.

The bleeding was performed using a microscope (100 ×).
Observe on the boundary between the printed and unprinted parts, and mark those with much bleeding, those with little bleeding,
A sample having almost no bleeding was evaluated as ◎, and evaluated in four steps of × △ ○ ◎.

The fixability was evaluated by the density difference between the image before and after erasing the printed matter left to dry for 24 hours after printing with a commercially available eraser.
A sample having a small density difference was evaluated as ◎, and evaluated in four steps of × △ ○ ◎.

<Evaluation of Oil Phase> The oil phase of the above formulation was measured by a stress rheometer (CSR-10 manufactured by Bohlin). Regarding the measurement, a flow curve at a stress of 12.5 Pa to 150 Pa was measured with a cone at 23 ° C. and 2 cm 2 degrees, and the Casson plastic viscosity and Casson yield value were obtained by calculation using Casson's approximate formula. Casson's approximate expression: √τ-√τ _O = √ (Eta ×
D) τ: Shear stress D: Shear rate τ _O : Yield value Et
a: plastic viscosity

Table 3 summarizes the above results.

[0058]

[Table 3]

From Example 1 and Comparative Example 1, the Casson yield value of the oil phase of claim 1 at 23 ° C. was 0.3 (Pa).
With the above, the effect of reducing strikethrough and bleeding becomes apparent. Furthermore, from Example 4 and Comparative Example 2, the Casson yield value of the oil phase of claim 2 at 23 ° C. was 10 (P
a) The effect of excellent fixability is clarified by being the following.

[0060]

The water-in-oil emulsion ink for stencil printing according to claim 1 has a Casson yield value of 0.3 (Pa) or more at 23 ° C. of the oil phase. Less.

The water-in-oil emulsion ink for stencil printing according to claim 2 has an Casing yield value of 10 (Pa) or less at 23 ° C. of the oil phase, and thus has an additional effect of excellent fixability.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4J039 AB04 AB06 AD01 AD03 AD05 AD08 AD10 AE02 AE04 AE06 AF01 AF07 BA04 BA06 BA13 BA18 BA19 BA24 BC07 BC08 BC09 BC10 BC19 BC29 BE01 BE02 BE15 BE19 BE22 BE23 BE24 BE33 CA06 EA43 EA47 GA04

Claims (2)

[Claims] 1. An oily phase of 10 to 90% by weight and an aqueous phase of 90 to 1%.
A water-in-oil emulsion ink for stencil printing, wherein the Casson yield value of the oil phase at 23 ° C is 0.3 (Pa) or more in a 0% by weight emulsion ink. 2. Casson at 23 ° C. of the oil phase
The water-in-oil emulsion ink for stencil printing according to claim 1, wherein the yield value is 10 (Pa) or less.