JP2002212483A - Emulsion ink for stencil printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stencil printing emulsion ink of the water-in-oil type (W/O) which has good storage stability. SOLUTION: The stencil printing emulsion ink of the water-in-oil type (W/O) comprises ascorbic acid or a salt of ascorbic acid in the aqueous phase or a derivative of ascorbic acid in the oil phase and comprises 15-50 wt.% oil phase and 85-50 wt.% aqueous phase, and the content of the ascorbic acid or the salt of ascorbic acid is 0.01-2 wt.% based on the total amount of the ink and the content of the derivative of ascorbic acid is 0.01-1 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-in-oil (W / O) emulsion ink for stencil printing, and more particularly to an emulsion ink for water-in-oil (W / O) stencil printing having excellent storage stability. It is about.

[0002]

2. Description of the Related Art One of the features of a stencil printing system is that it has good operability and simplicity that does not require a specialized operator, as compared with printing systems such as offset, gravure, and relief printing. That is, stencil printing has the advantage that no skill is required for the operation and no complicated operation such as washing is particularly required after use.

In addition, since the stencil printing system using a thermal printing head as a device has been used, the stencil printing system has been able to digitize image processing.
Because high-quality printed matter can be obtained easily in a short time, convenience as an information processing terminal has been increasingly recognized.

Further, in the thermal plate making method using a thermal printing head, the perforation size of the base paper is standardized and the amount of transferred ink is easier to control than in the conventional plate making method using an infrared or xenon flash as an energy source. Therefore, the probability of occurrence of defects such as set-off and bleeding due to excessive transfer of ink has been reduced, and image quality has been dramatically improved.

[0005] As a stencil printing ink, a water-in-oil (W / O) emulsion ink has conventionally been generally used, but the ratio of an aqueous phase serving as an internal phase of the emulsion is higher than that of an oil phase. Therefore, when stored for a long period of time, the coalescence of the aqueous phase particles progresses, and the oil phase and the aqueous phase are separated.

Various improvements in stability have been proposed to solve such problems. For example, JP-A-6-14
No. 5577 describes that the use of a polyglycerol fatty acid ester having an HLB of 10 or less as an emulsifier improves the stability of the emulsion. Also, Japanese Patent Application Laid-Open
No. 0-1634 describes that the addition of a water-soluble polymer containing an acid anhydride to the aqueous phase improves the stability of the emulsion. Further, JP-A-2000-7972 describes that when an alkyd resin or a rosin-modified resin added to an oil phase is reacted with an aluminum chelate compound or an aluminum alcoholate and contained in the oil phase, the stability of the emulsion is improved. Have been.

Further, JP-A-61-255967 and JP-A-8-73795 describe that the addition of dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, etc. can prevent oxidation of resins and the like. ing.

[0008]

As described above, improving the stability of an emulsion is extremely important for improving the storage stability of an emulsion ink. However, the prior art is not always at a satisfactory level, and further improvement has been desired. Further, an antioxidant having even higher safety than conventional antioxidants has been desired.

The present invention has been made in view of the above circumstances, and has as its object to provide a water-in-oil (W / O) type stencil printing emulsion ink having extremely excellent storage stability.

[0010]

According to the present invention, water-in-oil (W /
The O) type stencil printing emulsion ink is characterized by containing ascorbic acid, ascorbate or an ascorbic acid derivative.

[0011] Ascorbic acid as used herein is a broad term including not only L-ascorbic acid but also optical isomers such as D-ascorbic acid, isoascorbic acid and L-araboascorbic acid (L-isoascorbic acid). Yes, ascorbic acid may be optically pure such as L-form alone, or may be a mixture of L-form and D-form, or may be racemic.

The emulsion ink preferably comprises 15 to 50% by weight of an oil phase and 85 to 50% by weight of an aqueous phase.

The ascorbic acid or the ascorbate is preferably contained in an aqueous phase. In this case, the content of the ascorbic acid or the ascorbate is more preferably 0.01 to 2% by weight based on the total amount of the ink.

The ascorbic acid derivative is preferably contained in an oil phase. The content of the ascorbic acid derivative is more preferably 0.01 to 1% by weight based on the total amount of the ink.

[0015]

The resin generally contained in the water-in-oil (W / O) type stencil printing ink can be obtained by increasing the viscosity of the oil phase or increasing the interface strength between the oil phase and the water phase. It has the effect of increasing the storage stability and printability of the ink. Since the resin has the property of being easily oriented at the oil / water phase interface, if this resin is oxidized by reacting with oxygen dissolved in the ink, the interface strength between the oil phase and the water phase is reduced, and the oil phase is weakened. And the aqueous phase are thought to be easier to separate.

When the resin or the oil component is oxidized, the polarity of the oil phase changes to change the required HLB of the emulsion, or the compatibility of the oil phase component changes and the component which cannot be dissolved in the oil phase becomes an ink. It is considered that the emulsion state becomes unstable due to precipitation on the surface, and the oil phase and the aqueous phase are easily separated.

The water-in-oil (W / O) stencil emulsion ink of the present invention contains ascorbic acid, ascorbate or an ascorbic acid derivative. It is considered that storage stability is improved. That is, in the emulsion ink, for example, L-ascorbic acid is oxidized to L
-Since the enol groups at the 2nd and 3rd positions of the lactone ring in ascorbic acid and the like are oxidized as necessary so as to become dehydroascorbic acid , the oxidation of the resin and the like is suppressed and the storage stability of the ink is improved. It is considered to be.

Further, ascorbic acid, ascorbate or an ascorbic acid derivative is superior in safety to antioxidants such as dibutylhydroxytoluene which has been conventionally used in emulsion inks. The use environment can be improved.

When ascorbic acid or ascorbate is contained in the aqueous phase, oxidation of the resin oriented at the interface between the oil phase and the aqueous phase is further suppressed, and the storage stability of the ink is improved. It is considered something. In addition, water in the ink evaporates on the surface of the emulsion ink, that is, the surface where the ink is in contact with air, but ascorbic acid and ascorbate do not evaporate. It is thought that it is. Therefore, it is considered that the oxygen in the air is efficiently prevented from dissolving in the ink, and the oxidation of the resin and the oil component can be prevented.

Further, when the ascorbic acid derivative is contained in the oil phase, it is considered that the oxidation of the resin and the oil component in the oil phase is directly prevented in the oil phase, and the storage stability of the ink is improved. Can be

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The water-in-oil (W / O) stencil emulsion ink of the present invention contains ascorbic acid, ascorbate or an ascorbic acid derivative.

As ascorbic acid or ascorbate, for example, L-ascorbic acid, potassium L-ascorbate, sodium L-ascorbate, calcium L-ascorbate, isoascorbic acid, sodium isoascorbate and the like are preferably used. . These ascorbic acid or ascorbate may be used alone or in combination of two or more. The content of ascorbic acid and ascorbate is preferably 0.01 to 2% by weight, more preferably 0.05 to 1.5% by weight, based on the total amount of the ink. If the content is less than 0.01% by weight, the effect of preventing oxidation of the ink is small, and if the content is more than 2% by weight, no further effect can be expected.

Ascorbic acid derivatives include, for example,
L-ascorbic acid monostearate, L-ascorbic acid monopalmitate, 5,6-O-isopropylidene-L-ascorbic acid and the like are preferably used. The content of the ascorbic acid derivative is 0.0
1 to 1% by weight, preferably 0.05 to 0.5%.
More preferably, it is% by weight. If the content is less than 0.01% by weight, the antioxidant effect on the ink is small, and if the content is more than 1% by weight, no further effect can be expected.

Ascorbic acid or ascorbate is preferably contained in the aqueous phase, and the ascorbic acid derivative is preferably contained in the oil phase. Incidentally, ascorbic acid or ascorbate may be simultaneously contained in the aqueous phase and the ascorbic acid derivative may be contained in the oil phase.

The oil phase of the water-in-oil (W / O) stencil emulsion ink of the present invention basically comprises a colorant, an emulsifier, an oil component and the like. Will be described as an example. When a colorant is contained in the water phase, the colorant may not be contained in the oil phase.

As the coloring agent, pigments and / or dyes can be used. As the pigment, for example, azo-based,
Organic pigments such as phthalocyanine type, dye type, condensed polycyclic type, nitro type and nitroso type (Brilliant Carmine 6B, Lake Red C, Watching Red, Disazo Yellow, Hansa Yellow, Phthalocyanine Blue, Phthalocyanine Green, Alkaline Blue, Aniline Black, etc. ), Metals such as cobalt, iron, chromium, copper, zinc, lead, titanium, vanadium, manganese and nickel, metal oxides and sulfides, inorganic pigments such as loess, ultramarine, navy blue and the like, furnace carbon black, Carbon blacks such as lamp black, acetylene black and channel black can be preferably used. As the dye, for example, oil-soluble dyes such as azo, anthraquinone, and azine can be used. Either a pigment or a dye may be used as a coloring agent. However, when a pigment is used, an ink having less bleeding or strike-through of an image and having excellent weather resistance can be obtained. The content of the colorant is preferably 20% by weight or less, more preferably 3 to 10% by weight, based on the total weight of the ink.

The emulsifier is used to form a water-in-oil (W / O) emulsion, and any of anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants can be used. Good. Of these, water-in-oil (W /
It is preferable to use a nonionic surfactant from the viewpoint of emulsifiability and storage stability of the O) type emulsion. In particular,
Sorbitan monolaurate, sorbitan monopalmitate, sorbitan monooleate, sorbitan sesquioleate, sorbitan fatty acid esters such as sorbitan monoisostearate, glyceryl monostearate, hexaglyceryl tetraoleate, decaglyceryl decaoleate, hexaglyceryl (Poly) glycerin fatty acid ester such as pentaoleate, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbite fatty acid ester, propylene glycol fatty acid ester,
Preferred are (poly) ethylene glycol fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene (hardened) castor oil, and the like. The above-mentioned emulsifiers may be used alone, or two or more kinds may be used in an appropriate combination. The content of the emulsifier is preferably from 0.1 to 10% by weight, more preferably from 1 to 5% by weight, based on the total weight of the ink.

As the oil component, various industrial solvents, motor oil, gear oil, light oil, kerosene, spindle oil, machine oil, mineral oil such as liquid paraffin, olive oil, rapeseed oil, linseed oil, castor oil, salad oil, large oil In addition to vegetable oils such as bean oil, synthetic oils and the like can be used. The oil component is preferably used by mixing a plurality of oils having different volatility for the purpose of enhancing the printing performance after a long-term unused printing press.

The resin is used for imparting viscosity to the ink and improving the stability of the emulsion, and is used as a resin that dissolves in the oil phase. When a pigment or extender is contained in the oil phase, dispersibility of the pigment or extender or fixability to paper can be improved by including a resin. As the resin, for example, rosin, Gilsonite, rosin ester, maleic acid resin, phenol resin, alkyd resin, petroleum resin, acrylic resin, amino resin, urethane resin, cellulose resin, natural rubber derivative resin and the like can be preferably used. It is more preferable to use a phenol resin or an alkyd resin. Also, a reaction product of an alkyd resin or a rosin-modified resin with an aluminum chelate compound or an aluminum alcoholate can be preferably used. The content of the resin is preferably 1 to 20% by weight, more preferably 3 to 15% by weight, based on the total weight of the ink.

The oil phase may optionally contain an extender, a gelling agent, a pigment or a dispersant for the extender, if necessary. Further, an antioxidant can be further contained as necessary.

The main component of the aqueous phase in the present invention is water. The aqueous phase preferably contains a water evaporation inhibitor and an antifreezing agent. For example, water-soluble organic solvents such as polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol and glycerin can be preferably mentioned. The content of these is preferably 1 to 20% by weight, more preferably 3 to 15% by weight, based on the total weight of the aqueous phase.

Further, the aqueous phase preferably contains an electrolyte other than ascorbate and a pH adjuster. Examples thereof include sodium sulfate, magnesium sulfate, potassium hydrogen phosphate, sodium citrate, potassium tartrate, and boric acid. Sodium, triethanolamine and the like can be preferably used. The content of the electrolyte other than ascorbate is preferably 0.1 to 2% by weight, more preferably 0.3 to 1.5% by weight, based on the total weight of the aqueous phase. In addition, the aqueous solution of ascorbic acid shows acidity, but since the antioxidant effect is small when the aqueous phase is in an acidic state,
It is preferred that the aqueous phase be neutral to alkaline. Specifically, the pH of the aqueous phase is preferably 6.5 or more,
More preferably, it is 7.0 or more.

The aqueous phase may contain a coloring agent. If no colorant is included in the oil phase, the colorant must be included in the aqueous phase. Pigments and / or
Alternatively, a dye can be used. As the pigment, a known pigment similar to the pigment that can be contained in the oil phase can be used. Dyes include, for example, basic dyes, acid dyes, direct dyes, soluble vat dyes, acidic mordant dyes, mordant dyes, reactive dyes, vat dyes, sulfur dyes, and the like, which have become water-soluble by reduction and the like. A water-soluble dye can be preferably used. In addition, disperse dyes such as azo, anthraquinone, azomethine, and nitro can also be preferably used.

In the aqueous phase, if necessary, oil-in-water (O / W)
A mold resin emulsion and / or a water-soluble resin can be included. When a pigment or extender is added to the aqueous phase, an oil-in-water (O / W) type resin emulsion or a water-soluble resin is included in the aqueous phase, so that the wettability or dispersibility of the pigment or extender can be improved. And the fixability of the pigment or extender to the printing medium.

Examples of the oil-in-water (O / W) type resin emulsion include polyvinyl acetate, ethylene-vinyl acetate copolymer, vinyl acetate-acrylate copolymer,
Polymethacrylate, polystyrene, styrene-
Resin emulsions such as acrylate copolymer, styrene-butadiene copolymer, vinylidene chloride-acrylate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, and polyurethane can be preferably used.

Examples of the water-soluble resin include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl pyrrolidone, polyethylene-polyvinyl alcohol copolymer, polyethylene oxide, polyvinyl ether, polyacrylamide, gum arabic, starch, and water-soluble resin. Urethane or the like can be preferably used.

Further, in the aqueous phase, anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant, or Polymer-based, silicone-based, and fluorine-based surfactants, further, polyvinylpyrrolidone, polyethyleneimine, alkylolamine salts, poly-N-
A tertiary amine compound such as acryloylpyrrolidine, an acid anhydride-containing olefin copolymer, and an acid anhydride-containing water-soluble polymer such as an acid anhydride-containing vinyl copolymer can be contained. Of these dispersants, tertiary amine compounds or acid anhydride-containing water-soluble polymers are particularly preferred.

The aqueous phase may further contain an extender, an antiseptic and the like, if necessary. Further, an antioxidant can be further contained as necessary.

The water-in-oil (W / O) emulsion ink of the present invention is usually prepared by using a well-known emulsifying apparatus for 15 to 50 times.
It is manufactured by gradually adding and emulsifying 85 to 50% by weight of an aqueous phase to an oily phase of 85% by weight. Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

[0040]

EXAMPLE 1 5% by weight of phthalocyanine green, 10% by weight of alkyd resin, 6% by weight of naphthenic petroleum solvent, 1% by weight of polyglycerin fatty acid ester, and 1% by weight of polyoxyethylene castor oil were mixed. This roll sufficiently dispersed. The pigment dispersion was mixed with 5% by weight of a motor oil and 5.0% by weight of a paraffinic petroleum solvent to prepare an oil phase, which was then charged into an emulsifying apparatus. While rotating the stirring blades of the emulsifier, 60.57% by weight of ion-exchanged water, 5.7% by weight of glycerin, and 0.1% of magnesium sulfate were added to the oil phase.
A mixed solution (aqueous phase) of 3% by weight, 0.4% by weight of triethanolamine and 0.03% by weight of L-ascorbic acid is gradually dropped, and the emulsification is performed by rotating a stirring blade until a desired viscosity is reached. Then, an emulsion ink for stencil printing was obtained.

Example 2 An emulsion ink for stencil printing was obtained in the same manner as in Example 1 except that the formulations shown in Table 1 were used.

Example 3 An emulsion ink for stencil printing was obtained in the same manner as in Example 1 except that the formulations shown in Table 1 were used.

Example 4 5% by weight of phthalocyanine green, 10% by weight of alkyd resin, naphthenic petroleum solvent 6
% By weight, 1% by weight of polyglycerin fatty acid ester, 1% by weight of polyoxyethylene castor oil, and 0.1% by weight of L-ascorbic acid monostearate. The phthalocyanine green was sufficiently dispersed with a roll. 3. 5% by weight of this pigment dispersion, motor oil, and paraffinic petroleum solvent
The oil phase was adjusted by mixing 9% by weight, and the mixture was put into an emulsifying apparatus. While rotating the stirring blade of the emulsifying apparatus, a mixed solution of 60.9% by weight of ion-exchanged water, 5.7% by weight of glycerin, 0.3% by weight of magnesium sulfate, and 0.1% by weight of triethanolamine in this oil phase. (Aqueous phase)
Emulsification was performed by rotating the stirring blade until the desired viscosity was reached, to obtain an emulsion ink for stencil printing.

(Comparative Example) An emulsion ink for stencil printing was obtained in the same manner as in Example 1 except that the formulations shown in Table 1 were used.

[0045]

[Table 1] Each of the emulsion inks for stencil printing prepared in Examples 1 to 4 and Comparative Example was stored in a container at 70 ° C for 20 days, and the appearance of the ink was visually evaluated. Examples 1 to 3 containing ascorbic acid and ascorbate in the aqueous phase
3 and Example 4 in which the oil phase contained an ascorbic acid derivative, the ink was in a good storage state. A part was separated into an oil phase and an aqueous phase.

As is apparent from the above results, the water-in-oil (W / O) emulsion ink for stencil printing of the present invention is
Since it contains ascorbic acid, ascorbate or ascorbic acid derivative, oxidation of the resin or oil component oriented at the interface between the oil phase and the water phase is suppressed, or oxygen in the air dissolves in the ink. Oxidation of the resin or oil component by the ink is efficiently prevented on the ink surface, so that oxidation of the resin or oil component in the oil phase is effectively prevented, and the storage stability of the ink is improved.

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Claims (6)

[Claims] 1. A water-in-oil (W / O) stencil emulsion ink containing ascorbic acid, ascorbate or an ascorbic acid derivative. 2. Oil phase 15-50% by weight, aqueous phase 85-50
2. The emulsion ink according to claim 1, wherein the emulsion ink is composed of% by weight. 3. The emulsion ink according to claim 1, wherein the ascorbic acid or the ascorbate is contained in an aqueous phase. 4. The content of the ascorbic acid or the ascorbate is 0.01 to 2 with respect to the total amount of the ink.
4. The emulsion ink according to claim 3, wherein the content is% by weight. 5. The emulsion ink according to claim 1, wherein the ascorbic acid derivative is contained in an oil phase. 6. The content of the ascorbic acid derivative is as follows:
The emulsion ink according to claim 5, wherein the amount is 0.01 to 1% by weight based on the total amount of the ink.