JP4886176B2 - Emulsion ink for stencil printing - Google Patents

Description

  The present invention relates to an emulsion ink used for stencil printing.

  At present, titanium oxide is a typical white pigment that is widely used in the market and is widely used in all fields of industrial society. For example, white paint for electrical appliances such as buildings, houses, cars, refrigerators and washing machines. As a material for matting chemical fibers such as rayon, nylon, tetron and acrylic. It is used in cigarette papers and dictionary thin papers, packaging paraffin paper, fluorescent lights, opaque plastic films, rubber products such as sports shoes and golf balls, and cosmetics such as foundations. Recently, not only as a white pigment, but also due to the concealment or photocatalytic function unique to titanium oxide, UV shielding cosmetics for sunscreen, contribution to air pollution prevention and energy saving, deodorization, sterilization and drainage purification It is also used for environmental conservation.

  Titanium oxide is also used in the field of stencil printing for the reasons of “chemically safe” and “excellent hiding”, and is mainly used in light-colored inks. However, when lightly colored ink or colored printing paper that uses a very small amount of titanium oxide is used, there is a drawback that the color to be printed differs.

  In order to solve the above problem, in Patent Document 1, “containing a chromatic color pigment selected from a certain group in an amount of 0.1% by weight to less than 1% and a white pigment in an amount of 7% by weight to 20% by weight” We have proposed a light-colored emulsion ink for stencil printing that provides a constant color image regardless of the type of printing paper and that has an economically stable coloring performance.

Another problem with titanium oxide is particle size. If the particle diameter is too large, the surface area of the pigment becomes small, and the amount of oil retained on the pigment surface decreases. A general water-in-oil emulsion ink for stencil printing is an extremely complicated and unstable system in which a solid pigment and liquid water are dispersed in oil as a dispersion medium. In this ink, since “aggregation” and “unification” peculiar to the dispersion progress with time, when the primary particle system of the pigment is large, it tends to be disadvantageous to the above problem. On the other hand, when the primary particle system is too small, it is not preferable because stable dispersion becomes difficult.
In order to solve the above problem, Patent Document 2 proposes that “the oil absorption amount of titanium oxide is 30 (ml / 100 g) or more and the primary particle diameter is 0.05 μm or less”.

  Titanium oxide has a higher specific gravity than other general pigments, and because the particle size is large, aggregation or coalescence of the pigments is likely to proceed, leaving it in the state of a dispersion dispersed in a dispersion medium or the like. Then, the pigment settles and requires pretreatment such as carrying out a stirring operation before use, so that the handling is very inconvenient, and the above matters are not particularly described in any publication. In the present invention, by containing titanium oxide having a high specific gravity and hollow particles having a low specific gravity and introducing hollow particles between the titanium oxide particles, the aggregation or coalescence of the titanium oxide particles is suppressed, thereby preventing the above-mentioned problems. It is aimed at mitigation.

In addition to the above-described titanium oxide, if the same trouble occurs with a general color-increasing agent (for example, inorganic white particles such as ZnO, MgO, MgCO ₃ , Al (OH) _3, etc.), The problem can be reduced.

JP 2002-47439 A JP-A-11-1651

The present invention relates to an emulsion ink for stencil printing containing an inorganic white pigment such as titanium oxide as a color enhancer, by containing hollow particles together with a color enhancer such as titanium oxide used as a white pigment. The purpose is to solve problems specific to colorants.

The above-mentioned problem is (1) “Emulsion ink for stencil printing containing an inorganic white pigment as a color enhancer. In the oil phase, the water phase, the oil phase, and the water phase, the color enhancer. And resin hollow particles formed from a resin material having a specific gravity smaller than that of the color enhancer and not soluble in the oil phase, and the ratio of the color enhancer (A) to the hollow particles (B) (B) / (A ) Is an emulsion ink for stencil printing characterized by being 20/80 or less.

  As an effect of the present invention, in the emulsion ink for stencil printing containing a color enhancer such as titanium oxide, the specific gravity in the oil phase, the water phase, the oil phase and the water phase is higher than that of the color enhancer. By containing small resin hollow particles formed from a resin material that is not soluble in the oil phase, it is possible to reduce problems such as pigment settling in a dispersion liquid in which the pigment is dispersed with a dispersion medium, for example. . Further, by setting the quantity ratio (B) / (A) of the above-mentioned color increasing agent (A) and hollow particles (B) to 20/80 or less, high hiding power can be maintained even when hollow particles are contained. Is possible.

  TECHNICAL FIELD The present invention relates to emulsion ink for stencil printing, and more specifically, it includes a white pigment, such as titanium oxide, and hollow particles, thereby making it possible to reduce defects caused by aggregation or coalescence of particles. About.

  Details regarding implementation are described below. The emulsion ink for stencil printing of the present invention comprises 10 to 50% by weight of an oil phase and 90 to 50% by weight of an aqueous phase, and is oxidized in any of the oil phase, the water phase, the oil phase and the water phase. It contains a color enhancer such as titanium and hollow particles.

  The hollow particles used in the present invention have a particle specific gravity smaller than that of a commonly used color enhancer such as titanium oxide, and the hollow particles enter between the color enhancer particles. By suppressing agglomeration / unification of colorants such as titanium oxide having a large particle size, it is possible to reduce the problem that only the pigment settles when left in the state of a dispersion dispersed in a dispersion medium or the like. Become.

  The resin hollow particle material used in the present invention can form hollow particles having a specific gravity smaller than that of a color enhancer such as titanium oxide, and can be used for the purpose if it does not dissolve in the oil phase. Typical examples include urea resins, melamine resins, epoxy resins, urethane resins, phenol resins, alkyd resins, acrylic resins, unsaturated polyester resins and other thermosetting resins, styrene-acrylic polymers and other crosslinked polymers, and polymer materials. And oil-insoluble by coating with an inert inorganic powder. Commercially available hollow particles include JSR hollow particles (styrene-acrylic polymer, particle diameter 0.3 μm, (primary particle diameter) inner diameter 0.2 μm (primary particle diameter), particle specific gravity 0.76), and Matsumoto Yushi. Pharmaceutical Matsumoto Microspheres (Polyacrylonitrile-based polymer hollow microspheres whose surface is coated with an inert inorganic powder, particle diameter of about 20 μm, particle specific gravity of 0.20 ± 0.05) It is done.

  The hollow particles exhibit light shielding effect due to light scattering due to the air inside the particles and the surface resin phase. It can be contained together with a commonly used color enhancer such as titanium oxide while maintaining concealment due to the above effect, and the amount of the color enhancer such as titanium oxide (A) and hollow particles (B) By setting the ratio (B) / (A) to 20/80 or less, even when printing on printing paper with different whiteness, it is almost the same as ink using only a color increasing agent such as titanium oxide. A color tone can be obtained. When the quantity ratio (B) / (A) is 20/80 or more, it is difficult to obtain a desired color tone particularly when printing is performed on a colored printing paper. On the other hand, if the quantity ratio (B) / (A) is too small, the hiding power can be maintained, but the merit of reducing the problem of pigment sedimentation by containing hollow particles having a small specific gravity is diminished.

  The oil phase component of the emulsion of the present invention comprises a colorant (pigment), an oil component, a resin, a pigment dispersion, and an emulsifier. The aqueous phase component includes water, an electrolyte, an antibacterial agent, a water evaporation inhibitor, a water-soluble polymer material, an oil-in-water resin emulsion (hydrophobic polymer), and the like.

  In the present invention, titanium oxide has a true specific gravity of 3.5 to 4.2, and can be used alone as a white colorant having a strong hiding power. As a color density improver for enhancing the density, it can be used in combination with other colorants, and the amount added is usually preferably 20% by weight or less, more preferably 15% by weight or less based on the weight of the ink. . In this case, it is difficult to distinguish which part of the total amount of added titanium oxide is a colorant and which remaining part is a color density improver, and the meaning of distinguishing is not the present invention. . The particle diameter of titanium oxide is 0.01 to 20.0 μm, preferably 0.02 to 15.0 μm, and more preferably 0.05 to 12.0 μm. In addition, the titanium oxide described above may be surface-treated with a silane coupling agent and / or an aluminum compound, and is preferable.

  Commercially available products are Ishihara Sangyo, Titanium Dioxide TIPAQUE CR-50 (rutile type, specific gravity 4.2, particle size 0.25 μm), Ishihara Sangyo Co., Ltd., Titanium Dioxide TIPAQUE CR-60 (rutile type, specific gravity 4.2, particles) Diameter 0.22 μm), Degussa, Nippon Aerosil Titanium dioxide T805 (CAS registration number 100209-12-9, hydrophobic, apparent specific gravity about 200 g / l, primary particle size average value about 21 nm), Degussa, Titanium dioxide P25 manufactured by Nippon Aerosil Co., Ltd. (CAS registration number 13463-67-7, hydrophilicity, apparent specific gravity of about 130 g / l, primary particle diameter diameter value of about 21 nm), KRONOS titanium oxide KA-10 manufactured by Titanium Industry Co., Ltd. (Anatase form, specific gravity 3.9, particle size 0.3-0.5 μm), KA-15 (anatase form, specific gravity 3.9, particle size 0.3-0.5 μm), KA-20 (anatase form, 2. Specific gravity , Particle size 0.3 to 0.5 μm), KA-30 (anatase type, specific gravity 3.9, particle size 0.2 to 0.4 μm), KA-35 (anatase type, specific gravity 3.9, particle size 0) .2 to 0.4 μm), KA-80 (anatase type, specific gravity 3.9, particle size 0.3 to 0.5 μm), KA-90 (anatase type, specific gravity 3.9, particle size 0.3 to 0) , 5 μm), KR-310 (rutile type, specific gravity 4.2, particle size 0.3 to 0.5 μm), KR-380 (rutile type, specific gravity 4.2, particle size 0.3 to 0.5 μm), KR-460 (rutile type, specific gravity 4.2, particle size 0.2 to 0.4 μm), KR-480 (rutile type, specific gravity 4.2, particle size 0.2 to 0.4 μm), KR-270 ( A rutile type, a specific gravity of 4.2, and a particle size of 0.2 to 0.4 μm).

  In addition, even when a material that can be used in combination with other colorants as a color density improver for supporting other colorants and enhancing the color density other than titanium oxide in the present invention is added. The amount is usually preferably 20% by weight or less, more preferably 15% by weight or less, based on the weight of the ink.

  Further, as the colorant used in the present invention, in addition to the above-mentioned color enhancer such as titanium oxide, carbon black, azo dye, phthalocyanine pigment, nitro pigment, vat dye pigment, mordant dye pigment, base Oil-based pigments, acidic dye-based pigments and natural dye-based pigments, diazo dyes, oil-soluble pigments such as anthraquinone dyes, and the like. These may be used alone or in combination of two or more. Also good. The addition amount is usually preferably 20% by weight or less, more preferably 15% by weight or less based on the weight of the ink. Usually, it is dispersed in the oil phase, but it may be used by dispersing or adding to the aqueous phase. In the ink of the present invention, these colorants may be present in the oil phase and / or the water phase depending on the properties and the types and properties of the ink raw materials, in addition to the dispersion treatment.

  Oil components include industrial solvents, motor oil, gear oil, light oil, kerosene, spindle oil, machine oil, mineral oil such as liquid paraffin, vegetable oil such as soybean oil, rapeseed oil, corn oil, poppy oil, and linseed oil. Synthetic oils can also be used. The oil component is used by mixing multiple oils with different volatility for the purpose of improving ink storage stability, etc. However, volatile oil may adversely affect the global environment. Is preferred.

  As the vegetable oil described here, generally known oils can be used. For example, soybean oil, rapeseed oil, corn oil, sesame oil, cottonseed oil, sunflower oil, sunflower oil, walnut oil, poppy oil, linseed oil, etc. These may be used alone or in combination of two or more. Considering the ink drying property after printing, it is preferable to use what are generally called dry oil and semi-dry oil having an iodine value of 100 or more.

  Resins include rosin, polymerized rosin, hydrogenated rosin, rosin ester, hydrogenated rosin ester and other rosin resins, rosin modified phenolic resin and other rosin modified resins, phenolic resin, petroleum resin, cyclized rubber, alkyd resin, polymerized A castor oil etc. are mentioned, These may be used independently and may be used in mixture of 2 or more types. The addition amount is preferably 10% by weight or less of the ink weight, and more preferably 1 to 7% by weight.

  Emulsifiers include glycerin fatty acid ester, polyglycerin fatty acid ester, propylene glycol fatty acid ester, pentaerythritol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbit fatty acid ester, polyethylene glycerin fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene Alkyl ether, polyoxyethylene phytosterol, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene lanolin, polyoxyethylene lanolin alcohol, polyoxyethylene alkyl Amines, polyoxyethylene fatty acid amides Nonionic surfactants such as polyoxyethylene alkylphenyl formaldehyde condensates and the like, which may be used alone or may be used as a mixture of two or more. The added amount is preferably 1 to 8% by weight of the ink weight, and more preferably 2.2 to 5.5% by weight.

  The water-soluble polymer material added to the aqueous phase of the emulsion ink is added for moisture retention and viscosity, and specifically, the following natural or synthetic polymer materials are added. For example, natural polymer materials such as starch, mannan, sodium alginate, galactan, gum tragacanth, gum arabic, bull run, dextrin, xanthan gum, glue, gelatin, collagen, casein, carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropyl Semi-synthetic polymer materials such as methylcellulose, hydroxymethyl starch, carboxymethyl starch, dialdehyde starch, neutralized products such as acrylic resin and sodium polyacrylate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, poly N-alkyl substituted acrylamide, Polymer materials such as synthetic polymer materials such as polyethylene oxide and polyvinyl methyl ether are used. It is. These water-soluble polymer materials may be used alone or in combination of two or more. The addition amount is preferably 25% by weight or less of the ink weight, and more preferably 0.5 to 15% by weight.

  Antibacterial agents include salicylic acid, phenols, aromatic hydroxy compounds such as methyl p-oxybenzoate and ethyl p-oxybenzoate, and their chlorine compounds, as well as sorbic acid and dehydroacetic acid. These are used alone. Alternatively, two or more kinds may be mixed and used. The amount added is preferably 3% by weight or less, more preferably 0.1 to 1.2% by weight of water contained in the ink.

  Water evaporation inhibitor and antifreeze agent can be used together, glycols such as ethylene glycol, diethylene glycol, propylene glycol, etc., lower saturated monohydric alcohols such as methanol, ethanol, isopropanol, butanol, isobutanol, glycerin and sorbitol Such as a monohydric alcohol. These may be used alone or in combination of two or more. The addition amount is preferably 15% or less of water in the ink, and more preferably 4 to 12% by weight.

  Examples of the electrolyte added to the aqueous phase include magnesium sulfate, sodium sulfate, sodium citrate, and sodium acetate. The addition amount is preferably 0.1 to 2.0% by weight of the aqueous phase, and more preferably 0.5 to 1.5% by weight.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples without departing from the technical idea of the present invention.

I. Preparation of ink The emulsion ink of the present invention may be prepared by adjusting the oil phase and the aqueous phase in the same manner as in the production of conventional emulsion inks, and emulsifying both in a known emulsifier. That is, a mixture obtained by previously kneading a colorant, an emulsifier, a resin, and additives that are added as necessary is used as a dispersion, and the dispersion and oil mixed as an oil phase are adjusted at room temperature to be preserved. -An aqueous solution (water phase) to which an antifungal agent or a water-soluble polymer material was added as needed was gradually added and emulsified to obtain an emulsion ink for stencil printing.

  Examples 1 to 3 of the present invention and comparative examples are described in Table 1. In the above embodiment, titanium dioxide (CR-50) manufactured by Ishihara Sangyo Co., Ltd. and hollow particles (SX866) manufactured by JSR Co. are used. In addition, the aluminum chelating agent in the following Table 1 is a chelate of aluminum and isopropanol, and the unit of numerical values used in the table is volume%.

  In Table 1 described below, the comparative example uses only titanium oxide as a white pigment. On the other hand, Examples 1 to 3 contain hollow particles made of a styrene-acrylic polymer in addition to the white pigment titanium oxide, and the amount ratio (B) of titanium oxide (A) and hollow particles (B), respectively. / (A) is set to 10/90 to 30/70.

  Since the hollow particles are highly crosslinked by styrene-acrylic polymer, the thermal decomposition temperature is as high as 300 ° C. to 330 ° C., and even when heated at 200 ° C. to 300 ° C., internal voids are caused by the advanced crosslinking of the particles. Can be maintained. Further, it can be dispersed without dissolving in a solvent such as methyl ketone, methanol, cyclohexane or the like.

  Since the hollow particles are contained together with titanium oxide, in Examples 1 to 3, the problem of pigment sedimentation in the dispersion liquid or the like is reduced compared to the comparative example (Examples 1 <2 <3 are advantageous in this order). ing). However, since hollow particles are not as concealed as titanium oxide, the underlying color affects the color of the ink printed on the printing paper when printing on printing paper with high whiteness or colored printing paper. there is a possibility. In this example, although Examples 1 and 2 obtained almost the same color tone as the comparative example, Example 3 was affected by the underlying printing paper and did not obtain the same color tone as the comparative example. .

Claims (1)

In an emulsion ink for stencil printing containing an inorganic white pigment as a color enhancer , an oil having a specific gravity smaller than that of the color enhancer and the color enhancer in any of an oil phase, an aqueous phase, an oil phase and an aqueous phase. Resin hollow particles formed from a resin material that does not dissolve in the phase, and the ratio (B) / (A) of the color increasing agent (A) to the hollow particles (B) is 20/80 or less. Characteristic emulsion ink for stencil printing.