JPH111649A - Stencil printing emulsion ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an emulsion ink which exhibits high printing density and can be dried within a shortened time without strike-through, blotting, etc., by incorporating a specified amount of a water-soluble cellulose ether polymer having a specified molecular weight to the water phase of a water-in-oil emulsion ink containing a water-insoluble colorant in the water phase. SOLUTION: 0.5-20 wt.%, based on the total weight of the ink, water-soluble polymer having a molecular weight of 10,000-1,000,000 is incorporated in the ink. This is exemplified by methylcellulose, carboxymethylcellulose or hydroxyethylcellulose. The mean particle diameter of the water-insoluble colorant is desirably 10 μm or below, and its amount of addition is desirably 1-30 wt.% based on the total weight of the ink. This is desirably one having good affinity for water and is desirably exemplified by acetylene black or channel black. The resin emulsion used is for example a resin emulsion of e.g. polyvinyl acetate, and its amount of addition is 1-20 wt.% (in terms of the eight of the solid matter) based on the total weight of the ink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsion ink for stencil printing, and more particularly, to a stencil printing ink having a high print density of printed matter, less ink bleeding and strike-through, and excellent in abrasion resistance and storage stability. Related to emulsion ink.

[0002]

2. Description of the Related Art In stencil printing, stencil printing is performed using a stencil sheet, and ink is passed through a perforated portion of the stencil sheet to perform printing on a printing material such as paper. This stencil printing is used in a wide range of fields because of easy production of the stencil. Conventionally, as stencil printing ink,
In general, a water-in-oil (W / O) emulsion ink is used, and a resin component is contained in the oil phase component in addition to a pigment component as a colorant (Japanese Patent Application Laid-Open Nos. JP-A-64-14284, JP-A-4-13
2777, JP-A-5-117565, etc.).

[0003] When a water-in-oil (W / O) emulsion ink is printed on a printing medium such as paper, an oil phase component, which is an external phase of the emulsion, first permeates the printing medium, and then becomes an internal phase. The aqueous phase components penetrate and / or scatter. As in the prior art, a water-in-oil (W /
O) type emulsion inks require a long time to penetrate and dry the ink, easily cause ink bleeding, and the ink components penetrate deep into the paper layer, lowering the print density and causing strikethrough. There was a problem that it was easy to do. In addition, the oil phase contains a resin component to stably disperse the pigment and fix it to a printing medium. However, since this resin component has a large change in viscosity with respect to temperature, the viscosity of ink with respect to temperature is stable. However, there are drawbacks in that it is difficult to ensure the properties and that the rate of penetration of the ink into the printing medium is reduced.

[0004]

In order to solve these problems, water-in-oil (W) containing a water-insoluble colorant in an aqueous phase has been proposed.
/ O) emulsion inks have been proposed (see JP-A-7-188598). In the emulsion ink of this form, since the water-insoluble colorant is contained in the aqueous phase, after printing, the colorant is restricted from penetrating into the deep part of the printing medium to which the oil phase component has penetrated, and the diffusion is restricted. Is suppressed.
As a result, the colorant stays on the surface of the printing medium and is dried there, so that it is possible to obtain a printed matter having a high printing density and less strike-through or bleeding.

However, in the case of this ink, storage stability is not sufficient, and rubbing resistance is not sufficient.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a printed material having a high print density, less bleeding or strike-through, excellent abrasion resistance, less set-off, and high storage stability. An object of the present invention is to provide an emulsion ink for stencil printing.

[0007]

According to the present invention, the object is to provide a water-in-oil (W / O) containing a water-insoluble colorant in an aqueous phase.
In the emulsion ink, the molecular weight is 1 in the aqueous phase.
It is achieved by an emulsion ink for stencil printing, characterized in that the emulsion ink contains 10,000 to 1,000,000 cellulose ether-based water-soluble polymers in an amount of 0.5 to 20% by weight of the total amount of the ink.
The present invention is particularly effective in a case where an extender pigment is contained in the oil phase and / or the aqueous phase of the water-in-oil (W / O) emulsion ink to achieve a high print density.

[0008] The oil phase component, which is the external phase of the W / O emulsion ink, has a lower surface tension and a higher permeability than the aqueous phase component, so that the oil phase component is applied to the printing medium prior to the aqueous phase component. Infiltration, followed by infiltration and / or scattering of aqueous phase components. In the W / O emulsion ink of the present invention, a water-insoluble colorant is contained in the aqueous phase, and the aqueous phase component cannot penetrate into the inside of the printing material in which the oil phase component has penetrated, so that Since the print remains on the surface of the print and is dried on the surface of the print, the density of the print is improved, and strike-through and bleeding of the print are prevented.

When the water-insoluble colorant is present in the oil phase as in the prior art, the permeation rate of the oil phase component decreases, and the time from ink penetration to drying becomes longer. In this case, the penetration of the oil phase component is performed quickly, so that the drying property of the ink is improved. Further, since it is not necessary to include a resin in the oil phase, the temperature dependency of the ink can be reduced, and the ink having a stable viscosity with respect to a temperature change can be supplied.

Further, in the present invention, since the aqueous phase contains a cellulose ether-based water-soluble polymer, the dispersibility of the pigment is improved, and the viscosity of the aqueous phase can be approximated to that of the oil phase. Storage stability can be improved. Further, the water-insoluble colorant can be more firmly fixed to the surface of the printing medium, the rub resistance of the ink can be improved, and the offset of the printed matter can be prevented.

Examples of such a cellulose ether-based water-soluble polymer include cellulose derivatives such as methylcellulose, carboxymethylcellulose and hydroxyethylcellulose. The molecular weight of these water-soluble polymers is desirably from 10,000 to 1,000,000, and if the molecular weight is less than 10,000, the fixation of the water-insoluble colorant is deteriorated, the rub resistance is reduced, and the molecular weight exceeds 1,000,000. It is difficult to approximate the viscosities of the water phase and the oil phase to each other. The addition amount of the cellulose ether-based water-soluble polymer is preferably from 0.5 to 20% by weight, more preferably from 2 to 10% by weight, based on the total amount of the emulsion ink. If the content is less than 0.5% by weight, the effect on rub resistance is low. On the other hand, if the content exceeds 20% by weight, the effect on the rub resistance is high, but the drying property of the ink deteriorates, and it is not economical.

In the present invention, the aqueous phase is basically composed of water and a water-insoluble colorant in addition to the above-mentioned cellulose ether-based water-soluble polymer. The average particle size of the water-insoluble colorant is preferably 10 μm or less, more preferably 3 μm or less. When the average particle size exceeds 10 μm, water-in-oil (W /
O) type emulsion is easily disintegrated. The addition amount of the water-insoluble colorant is 1 to 3 with respect to the total amount of the emulsion ink.
0% by weight is preferable, and a range of 3 to 10% by weight is more preferable.

As the water-insoluble colorant, known pigments and disperse dyes having various colors are used, and those having a good affinity for water as a main solvent are preferable. For example, carbon blacks such as acetylene black, channel black, and furnace black; metal powders such as aluminum powder and bronze powder; inorganic pigments such as red iron oxide, graphite, ultramarine, and chromium oxide; azo-based, phthalocyanine-based, and polycondensed Organic pigments (for example, aniline black, Hansa Yellow, disazo carmine 6B, phthalocyanine blue, and alkali blue) such as ring and various dye lakes, and other azo-based and anthraquinone-based disperse dyes are used.

The aqueous phase in the present invention may contain an oil-in-water (O / W) type resin emulsion and / or a water-soluble resin, if necessary. By including these in the aqueous phase, the dispersibility of the water-insoluble colorant and the fixability of the water-insoluble colorant to a printing medium such as paper can be improved.

Examples of the O / W type resin emulsion include polyvinyl acetate, ethylene-vinyl acetate copolymer,
Vinyl acetate-acrylate copolymer, polymethacrylate, polystyrene, styrene-acrylate copolymer, styrene-butadiene copolymer, vinylidene chloride-acrylate copolymer, polyvinyl chloride, vinyl chloride- Resin emulsions such as vinyl acetate copolymers and polyurethanes are used.

Examples of the water-soluble resin include polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene-polyvinyl alcohol copolymer, polyethylene oxide, polyvinyl ether, polyacrylamide, gum arabic, starch, and water-soluble polyurethane.

The addition amount of the oil-in-water (O / W) resin emulsion and / or the water-soluble resin is preferably 1 to 20% by weight, in terms of solid content, based on the total amount of the emulsion ink, and 2 to 10% by weight. Is more preferable. If the amount is less than 1% by weight, the dispersibility of the colorant component in the aqueous phase or the fixation to the printing medium cannot be sufficiently obtained. The ink forms a film and may prevent the passage of the ink, which is not preferable.

Further, in the aqueous phase, anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants are used as dispersants for improving the wettability and dispersibility of the water-insoluble colorant in water. Surfactants, polymer-based, silicone-based, and fluorine-based surfactants.
It is preferable to add a tertiary amine compound as described in JP-A-34944 or an acid anhydride-containing water-soluble polymer as described in Japanese Patent Application No. 8-177518.

The aqueous phase may further contain, if necessary, water-soluble materials such as electrolytes, pH adjusters, wetting agents, water evaporation inhibitors, antifreeze agents, preservatives, fungicides, antioxidants, and the like. Additives can be included.

The oil phase in the present invention basically comprises a non-volatile solvent, a volatile solvent, an emulsifier and the like.

As the non-volatile solvent, motor oil,
Mineral oils such as light oil, kerosene, spindle oil, machine oil, liquid paraffin, and vegetable oils such as olive oil, rapeseed oil, castor oil, salad oil, soybean oil are used. And a vegetable oil-based solvent. Use ratio of these (non-volatile solvent / volatile solvent)
Although it depends on the blending ratio of the oil phase and the aqueous phase, the weight ratio is desirably in the range of 50 to 95/5 to 50% by weight.

The emulsifier is used to form a water-in-oil (W / O) emulsion, and may be any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant. Among them, nonionic surfactants are preferably used, for example, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monooleate, sorbitan sesquioleate, sorbitan fatty acid esters such as sorbitan monoisostearate, glyceryl monostearate (Poly) glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbit fatty acid ester, propylene Glycol fatty acid ester, (poly) ethylene glycol fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene polyoxypro Alkylether, polyoxyethylene alkyl phenyl ethers, polyoxyethylene (hardened) castor oil, etc. are used. The emulsifier can be used not only in a single kind, but also in combination of two or more kinds. The aqueous phase component of the present invention may contain a surfactant for dispersing the water-insoluble powder or a surfactant for constituting an oil-in-water (O / W) resin emulsion. It is preferable to appropriately select an emulsifier so that the water-in-oil (W / O) emulsion is not disintegrated by the interaction with these surfactants and the like.

The emulsion ink of the present invention may further contain an extender pigment in the oil phase and / or the aqueous phase. The extender pigment cannot penetrate into the inside of a printing medium having a porous structure such as printing paper, and remains on the surface thereof. As a result, the extender pigment remains on the surface of the printing medium, and most of the colorant components can be retained on the surface of the printing medium, the print density does not decrease after the ink is dried, and the strikethrough of the ink is reduced. . Further, when this extender is contained in the aqueous phase, even if there are irregularities on the surface of the printing medium, the extender on the surface can be filled with the extender in the ink component, so that glossy printing is also possible. This makes it possible to obtain a stable quality print image even when printing in full color.

The extender pigment is preferably added in an amount of 1 to 50% by weight based on the total amount of the emulsion ink.
More preferably, the content is set to ２０20% by weight. If the amount is less than 1% by weight, the effect on print density, strikethrough and bleeding is often small. Conversely, if the amount is more than 50% by weight, the resulting ink is effective in improving print density, strikethrough, and bleeding, but is unsuitable for stencil printing, that is, an ink that is difficult to pass through the perforated portion of the plate. The average particle size of the extender is not particularly limited as long as the emulsion of the ink is not destroyed.

As the extender, conventionally known extenders can be employed, and there is no particular limitation as long as they are fine particles insoluble in water. For example, clay, talc, clay, diatomaceous earth, calcium carbonate, barium sulfate, titanium oxide, alumina white, silica, kaolin, mica, inorganic fine particles such as aluminum hydroxide, polyacrylate, polyurethane, polyester, polyethylene, polypropylene, Organic fine particles such as polyvinyl chloride, polyvinylidene chloride, polystyrene, polysiloxane, phenol resin, epoxy resin, benzoguanamine resin and the like, or fine particles comprising a copolymer thereof can be used.

The water-in-oil (W / O) emulsion ink of the present invention can be prepared, for example, by adding 90 to 90% by weight of an oil phase.
It can be produced by gradually adding and emulsifying a 30% by weight aqueous phase.

[0027]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, the part in an example means a weight part.

Example 1 A W / O emulsion ink was prepared according to the formulation shown in Table 1 by the following method. First, methyl cellulose was heated and dissolved in ion-exchanged water, and then ethylene glycol, furnace carbon black and a sulfonic acid type surfactant were added, followed by sufficient stirring and dispersion with a ball mill to prepare an aqueous phase. Next, an oil phase was prepared by sufficiently stirring and mixing # 40 motor oil, Nisseki No. 5 solvent (manufactured by Nippon Oil Co., Ltd.) and sorbitan monooleate. While gradually adding the aqueous phase to the oil phase, emulsification was carried out with a stirrer to obtain a stencil printing emulsion ink.

Example 2 A W / O emulsion ink was prepared according to the formulation shown in Table 1 by the following method. First, # 40 motor oil, Nisseki No. 5 solvent (manufactured by Nippon Oil Co., Ltd.), sorbitan monooleate, and calcium carbonate were sufficiently stirred and mixed, and kneaded sufficiently with three rolls to prepare an oil phase. Next, after methyl cellulose was dissolved by heating in ion-exchanged water, ethylene glycol, furnace carbon black and a sulfonic acid type surfactant were added, and the mixture was sufficiently stirred and dispersed by a ball mill to prepare an aqueous phase. While gradually adding this aqueous phase to the above oil phase, emulsification was performed with a stirrer to obtain a stencil printing emulsion ink.

Example 3 An emulsion ink for stencil printing was obtained in the same manner as in Example 1 except that calcium carbonate was added to the aqueous phase.

Comparative Example 1 A W / O emulsion ink was prepared according to the formulation shown in Table 1 by the following method. First, an alkyd resin, furnace carbon black, # 40 motor oil, Nisseki No. 5 solvent (manufactured by Nippon Oil Co., Ltd.) and sorbitan monooleate were sufficiently stirred and mixed, and the oil phase was adjusted by sufficiently kneading with three rolls. . Next, emulsification was carried out with a stirrer while gradually adding a mixed solution of ion-exchanged water and ethylene glycol to the oil phase to obtain an emulsion ink for stencil printing.

Comparative Example 2 A W / O emulsion ink was prepared according to the formulation shown in Table 1 by the following method. First, ion-exchanged water, ethylene glycol, furnace carbon black and a sulfonic acid type surfactant were sufficiently stirred and mixed, and dispersed by a ball mill to prepare an aqueous phase. Next, an oil phase was prepared by sufficiently stirring and mixing # 40 motor oil, Nisseki No. 5 solvent (manufactured by Nippon Oil Co., Ltd.) and sorbitan monooleate.
While gradually adding the aqueous phase to the oil phase, emulsification was carried out with a stirrer to obtain a stencil printing emulsion ink.

Comparative Examples 3 and 4 An emulsion ink for stencil printing was obtained in the same manner as in Comparative Example 2 except that methyl cellulose was previously added to ion-exchanged water and dissolved by heating.

[0034]

[Table 1]

Test Examples Using the stencil printing emulsion inks obtained in Examples 1 to 3 and Comparative Examples 1 to 4, stencil printing using a stencil printing machine (Risograph (registered trademark) RC115D, manufactured by Riso Kagaku Corporation). Was done. The printing density, strike-through property, bleeding property, rubbing resistance and storage stability of the ink of the obtained printed matter were examined by the following methods, and the results are shown in Table 2.

(1) Print density: The print density of the printed solid portion was measured with an OD meter (RD920, manufactured by Macbeth). (2) strike-through property: the density on the back side of the printed solid portion
It was measured with an OD meter (same as above). (3) Bleeding property: The bleeding state of the portion to which the ink was adhered was observed using a microscope (magnification: 80), and was evaluated as ○ when little bleeding was observed, and x when bleeding was conspicuous. (4) Rubbing resistance: The printed portion immediately after printing was rubbed with a finger, and the evaluation was evaluated as を when the finger stain with ink was small, and as X when the finger stain with ink was large. (5) Storage stability: The ink was left standing at 50 ° C. for 5 weeks, and the state of collapse of the ink was visually observed. The case where no collapse occurred in the emulsion of the ink was evaluated as ○, and the case where the ink collapsed was evaluated as x.

[0037]

[Table 2]

From Table 2, it was found that Examples 1 to 3 had higher print density and superior strike-through and bleeding properties than Comparative Example 1. Comparative Example 2 does not contain a water-soluble polymer in the aqueous phase, and Comparative Examples 3 and 4 have less abrasion resistance than Examples 1-3 because the effect of the water-soluble polymer contained in the aqueous phase is not sufficient. Or it turned out that storage stability is inferior.

[0039]

Since the W / O emulsion ink of the present invention contains a water-insoluble colorant in the aqueous phase, the printing density is high and the ink is dried without strikethrough or bleeding. The drying time of the ink is also reduced. In addition, since the water phase contains a cellulose ether-based water-soluble polymer having a molecular weight of 10,000 to 1,000,000, the water-insoluble colorant has a high fixation to a printing medium during printing, is hardly rubbed, and has a small set-off. An ink with high storage stability can be provided.

Claims (2)

[Claims] 1. A water-in-oil (W / O) emulsion ink containing a water-insoluble colorant in an aqueous phase, wherein a water-soluble cellulose ether polymer having a molecular weight of 10,000 to 1,000,000 is contained in the aqueous phase. Emulsion ink for stencil printing, characterized by containing 0.5 to 20% by weight of 2. The emulsion ink for stencil printing according to claim 1, wherein an extender is contained in the oil phase and / or the aqueous phase.