JP2006298976A - Emulsion ink for stencil printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an emulsion ink for stencil printing, which is excellent in prevention of oil separation over time, covering power and emulsion stability, even when titanium oxide is used as a pigment. <P>SOLUTION: The emulsion ink for stencil printing comprises 10 to 90 mass% oil phase and 90 to 10 mass% aqueous phase, wherein the oil phase contains titanium oxide with an average particle size of ≥0.2 μm and at least one chosen from titanium oxide with an average particle size of ≤0.05 μm and an extender. Preferably, the mixing ratio (titanium oxide A:titanium oxide B) of the titanium oxide (titanium oxide A) with an average particle size of ≥0.2 μm and the titanium oxide (titanium oxide B) with an average particle size of ≤0.05 μm is from 1:5 to 1:1, calculated in terms of a specific surface area, and the extender is calcium carbonate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an emulsion ink for stencil printing that is excellent in all of the effects on oil separation over time, hiding power, and emulsion stability, even when titanium oxide is used as a pigment.

  As is well known, a stencil printing method uses a stencil printing paper (stencil) having a perforated portion, and moves the ink from one side of the stencil to the other side through the perforated portion of the stencil, so that the paper This is a method for printing on the surface of a substrate. In this stencil printing method, a water-in-oil type (W / O type) containing a volatile solvent, a non-volatile solvent, a resin, a colorant, a surfactant, water, an antifreezing agent, an electrolyte, and an antiseptic is conventionally used. ) Emulsion ink.

However, in conventional water-in-oil emulsion inks for stencil printing presses, the ink component penetrates into the printing paper when the ink is dried, and the colorant also penetrates into the printing paper. For this reason, there is a problem in that the amount of colorant remaining on the paper surface is reduced and the printing density is lowered. Further, there has been a problem that so-called ink back-through is likely to occur because the printed content can be seen through from the back side of the printing paper.
In order to solve this problem, an emulsion ink for stencil printing in which an extender is contained in an oil layer has been proposed (see Patent Document 1).

However, a general water-in-oil emulsion ink for stencil printing presses is an extremely complex and unstable system in which a solid pigment and liquid water are dispersed in oil as a dispersion medium. In the ink, agglomeration and coalescence peculiar to the dispersion proceeds with time. When titanium oxide is used as the pigment component of the ink, the titanium oxide pigment is used when the above agglomeration and coalescence proceeds. Because of this characteristic, there is a problem that oil separation is likely to occur over time.
In order to solve this problem, an emulsion ink for stencil printing using an oil absorption amount of 30 ml or more per 100 g as titanium oxide has been proposed (see Patent Document 2).

However, the emulsion ink for stencil printing using the specific titanium oxide is also effective for oil separation with time, but has a hiding power (power to hide the substrate to be printed, more specifically, When the printing paper, which is a printed material, is colored paper or has a mark or the like, it means how much the color or mark can be hidden. This is considered to be because the specific titanium oxide becomes an ultraviolet shielding region rather than a visible light shielding region. Furthermore, since the specific gravity of titanium oxide pigments is large, the balance of the emulsion tends to be lost due to the effect of pigment precipitation over time, and the emulsion stability tends to be slightly inferior compared to the case where other organic pigments are used. There was a problem that there was.
Therefore, when titanium oxide is used as a pigment, an emulsion ink for stencil printing, which has excellent effects on oil separation with time, hiding power, and emulsion stability, has not yet been proposed.

JP-A-8-302262 JP-A-11-1651

  This invention is made | formed in view of this present condition, and makes it a subject to solve the said various problems in the past and to achieve the following objectives. That is, an object of the present invention is to provide an emulsion ink for stencil printing that is excellent in all of the effects on oil separation over time, hiding power, and emulsion stability even when titanium oxide is used as a pigment. .

Means for solving the problems are as follows. That is,
<1> 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, and in the oil phase, titanium oxide having an average particle size of 0.2 μm or more and an average particle size of 0.05 μm or less An emulsion ink for stencil printing, comprising at least one of titanium oxide and extender pigment. In the emulsion ink for stencil printing of the present invention described in <1>, titanium oxide having an average particle size of 0.2 μm or more, titanium oxide having an average particle size of 0.05 μm or less, and an extender pigment in the oil phase And at least one of the above. Titanium oxide having a large average particle size has excellent visible light shielding ability, but has a small oil absorption and poor oil separation due to the small surface area of the pigment. Titanium oxide having a small average particle diameter generally has a large oil absorption, but conversely, the shielding ability is shifted from the visible light region to the ultraviolet region, so that the hiding power is weakened. For these problems, titanium oxide having a large average particle size as in the present invention and at least one of titanium oxide and extender pigment having a small average particle size are used in combination, and it is excellent in oil separation over time, and An ink having excellent hiding power can be obtained. Furthermore, the present invention is also effective for emulsion stability. This is because the titanium oxide pigment having a large specific gravity is affected by the precipitation due to the difference in specific gravity over time, so that the emulsion stability is somewhat inferior, but as in the present invention, the titanium oxide having a large average particle size, It is considered that the influence of pigment sedimentation is mitigated by using at least one of titanium oxide and extender pigment having a small specific gravity and a small average particle diameter.
<2> The mixing ratio of titanium oxide (titanium oxide A) having an average particle size of 0.2 μm or more and titanium oxide (titanium oxide B) having an average particle size of 0.05 μm or less is a titanium oxide in terms of specific surface area. A: The emulsion ink for stencil printing according to <1>, wherein titanium oxide B is 1: 5 to 1: 1. In the emulsion ink for stencil printing according to the above <2>, by mixing the titanium oxides having different forms in the above ratio, the oil absorption amount balances the visible light shielding ability, that is, balance between oil separation and hiding power is good. Can be made into ink.
<3> The emulsion ink for stencil printing according to any one of <1> to <2>, wherein the extender pigment is calcium carbonate. In the emulsion ink for stencil printing according to <3>, from the properties of calcium carbonate oil absorption, specific gravity, surface properties, etc., for each item of effect on oil separation over time, hiding power, and emulsion stability, A good ink can be obtained.

  According to the present invention, it is possible to solve various problems in the past, and even when titanium oxide is used as a pigment, the emulsion ink for stencil printing has excellent effects on oil separation over time, hiding power, and emulsion stability. Can provide.

The emulsion ink for stencil printing of the present invention comprises, as a first aspect, 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, and an average particle size of 0.2 μm or more in the oil phase. And titanium oxide having an average particle size of 0.05 μm or less.
As a second aspect, it comprises 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, and the oil phase contains titanium oxide having an average particle size of 0.2 μm or more and an extender pigment. It is characterized by doing.

The emulsion ink for stencil printing contains 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase, preferably 20 to 50% by mass of an oil phase and 50 to 80% by mass of an aqueous phase.
When the mixing ratio of the oil phase is less than 10% by mass, it may not be possible to take the form of a W / O emulsion, and when it exceeds 90% by mass, the physical properties are not sufficiently effective. May end up.

<Oil phase>
The oil phase contains titanium oxide, and if necessary, extender pigment, resin, emulsifier, colorant other than titanium oxide, colorant dispersant, antioxidant, vegetable oil, mineral oil, gelation It contains other components such as an agent.

-Titanium oxide-
The titanium oxide is positioned as one pigment component of the colorant contained in the emulsion ink for stencil printing of the present invention.
In the emulsion ink for stencil printing of the first aspect, the titanium oxide needs to contain titanium oxide having an average particle diameter of 0.2 μm or more and titanium oxide having an average particle diameter of 0.05 μm or less. . If the titanium oxide having an average particle size of 0.2 μm or more is not contained, oil separation is likely to occur regardless of the passage of time, and the viscosity decreases with the passage of time, resulting in poor emulsion stability. Moreover, if the average particle diameter does not contain titanium oxide having a particle size of 0.05 μm or less, the hiding power is lowered. Here, the hiding power is the power to hide the substrate to be printed as described in the section of “Background Technology”, that is, the printing paper that is the printing medium is colored paper or has a mark or the like. In this case, it means how much the color or mark can be hidden.
The specific surface area (m ² / g) of the titanium oxide having an average particle diameter of 0.2 μm or more and the titanium oxide having an average particle diameter of 0.05 μm or less is not particularly limited and is appropriately selected depending on the purpose. However, from the viewpoint of improving the hiding power, titanium oxide (titanium oxide A) having an average particle diameter of 0.2 μm or more and titanium oxide (titanium oxide B) having an average particle diameter of 0.05 μm or less. The mixing ratio is preferably titanium oxide A: titanium oxide B = 1: 5 to 1: 1 in terms of the specific surface area.
The specific surface area can be measured, for example, by the JIS R 1626 gas adsorption BET method.
The mixing ratio in terms of the specific surface area is set such that titanium oxide A is 1, and the numerical value of titanium oxide B is (content of titanium oxide B × specific surface area of titanium oxide B) / (content of titanium oxide A × titanium oxide A). Specific surface area).

The titanium oxide needs to contain titanium oxide having an average particle size of 0.2 μm or more in the emulsion ink for stencil printing of the second aspect. If the average particle diameter does not contain titanium oxide having a diameter of 0.2 μm or more, the hiding power is lowered.
Even the emulsion ink for stencil printing of the second aspect preferably contains titanium oxide having an average particle size of 0.05 μm or less from the viewpoint of maintaining the viscosity over time and further improving the emulsion stability.
The specific surface area is not particularly limited in any of titanium oxide having an average particle diameter of 0.2 μm or more and titanium oxide having an average particle diameter of 0.05 μm or less. From the same viewpoint as in the first aspect, The mixing ratio is preferably titanium oxide A: titanium oxide B = 1: 5 to 1: 1 in terms of the specific surface area.

Hereinafter, regarding the titanium oxide, in any of the first aspect and the second aspect, titanium oxide having an average particle diameter of 0.2 μm or more has an average particle diameter of 0.2 to 0.4 μm. Is preferable, and it is more preferable that it is 0.2-0.3 micrometer. The titanium oxide having an average particle size of 0.05 μm or less preferably has an average particle size of 0.01 to 0.05 μm, and preferably 0.03 to 0.05 μm.
The average particle diameter means a number average particle diameter, and can be measured by, for example, electron microscopy.
There is no restriction | limiting in particular in the addition amount in the said emulsion ink for stencil printing of the said titanium oxide whose average particle diameter is 0.2 micrometer or more, According to the objective, it can select suitably, 2-15 mass% is preferable.
The addition amount of the titanium oxide having an average particle size of 0.05 μm or less in the emulsion ink for stencil printing is not particularly limited and can be appropriately selected according to the purpose, and is preferably 1 to 10% by mass.

-Extender pigment-
The extender pigment can be added to the oil phase, the aqueous phase, or both phases in order to prevent bleeding and adjust the viscosity in the ink, and must be contained in the emulsion ink for stencil printing in the second aspect. It is. If the extender pigment is not contained, oil separation is likely to occur regardless of the presence or absence of time, and the viscosity decreases with time, resulting in poor emulsion stability. Further, the stencil printing emulsion ink in the second aspect is preferably contained from the viewpoint of further reducing the decrease in viscosity with time and further improving the emulsion stability.
The extender pigment is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include inorganic fine particles and organic fine particles. Examples of the inorganic fine particles include clay, silica, talc, clay, calcium carbonate, barium sulfate, titanium oxide, alumina white, diatomaceous earth, kaolin, mica, and aluminum hydroxide. Examples of the organic fine particles include polyacrylate resin, polyurethane resin, polyester resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polysiloxane resin, phenol resin, epoxy resin, or these A copolymer, and the like. These may be used individually by 1 type and may use 2 or more types together.
Among the inorganic particles and organic particles, since the effect on oil separation over time is more remarkable, inorganic particles are preferable, and among them, calcium carbonate is not only remarkable in the effect on oil separation, Calcium carbonate is preferable from the viewpoint of maintaining viscosity over time and further improving the emulsion stability.

  There is no restriction | limiting in particular in content in the said emulsion ink for stencil printing of the said extender, According to the objective, it can select suitably, 0.1-50 mass% is preferable, and 1-5 mass% is more preferable.

-Resin-
The resin is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, alkyd resin, rosin; polymerized rosin, hydrogenated rosin, rosin ester, rosin polyester resin, hydrogenated rosin Rosin resins such as esters; Rosin-modified alkyd resins, rosin-modified maleic resins, rosin-modified resins such as rosin-modified phenol resins; maleic resins; phenol resins; petroleum resins; rubber derivative resins such as cyclized rubbers; Polymerized castor oil and the like can be mentioned, and these may be used alone or in combination of two or more. Among these, alkyd resins are particularly preferable.
The weight average molecular weight of the resin is preferably 8000 to 160,000, more preferably 30,000 to 80,000, from the viewpoint of fixability and printability.
The addition amount of the resin in the oil phase is preferably 5 to 20% by mass, more preferably 1 to 5% by mass from the viewpoint of ink cost and printing suitability.
When the weight average molecular weight of the resin is low and when the addition amount is small, the effect on fixability may be small, while when the weight average molecular weight is too high or the addition amount of the resin is large, the ink In some cases, the viscosity becomes high, and printability problems such as ink leakage from the rear end of the drum may occur.
Commercially available products can be used as the resin, and KG-836, KG-846, KG-1801, KG-1832, KG-1829, KG-1804, KG-1828, KG- manufactured by Arakawa Chemical Industries, Ltd. 1808-1, KG-1834, KG-1831, KG-1833, Tamanol 353, Tamanol 403, Tamanol 371, Tamanol 394; Hariphenol (561, 564, 582, 173, T3120, T3040, P637, manufactured by Harima Chemical Co., Ltd.) In addition, cyclized rubber is also effective for fixing properties, for example, trade names ALSYNOL RS47, ALSYNOL RS44, SYNTEX 800 manufactured by Colombian Carbon Japan, and ALPEX CK 450, ALPEX CK514 manufactured by Hoechst. Etc.

The said alkyd resin is normally comprised from fats and oils, a polybasic acid, and a polyhydric alcohol. Examples of the fats and oils include coconut oil, palm oil, olive oil, castor oil, rice bran oil, cottonseed oil, soybean oil, linseed oil, and tung oil. Among these, soybean oil is particularly preferable. As the polybasic acid, either a saturated polybasic acid or an unsaturated polybasic acid can be used. Examples of the saturated polybasic acid include phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrahydrophthalic acid and the like. Examples of the unsaturated polybasic acid include maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic anhydride, and the like.
Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, glycerin, trimethylolpropane, neopentyl glycol, diglycerin, triglycerin, and pentaerythritol. Examples include slits, dipentaery slits, mannits, and sorbits.
The alkyd resin has an acid value of 15 or less, and more preferably 10 or less. Further, the iodine value is preferably 80 or less, and more preferably 80 to 110. Moreover, the oil length of the said alkyd resin is represented by the mass% in resin when the fatty acid in the said fats and oils exists with a triglyceride, and 60-90 mass% is preferable normally. The weight average molecular weight of the alkyd resin is preferably 30,000 or less, and more preferably 10,000 or less.
Here, the acid value of the alkyd resin can be measured, for example, according to JIS K0070. The iodine value of the alkyd resin can be measured, for example, according to JIS K0070.

-Emulsifier-
The emulsifier is not particularly limited as long as it can form a water-in-oil emulsion and can be appropriately selected according to the purpose. Examples of the nonionic surfactant include sorbitan fatty acid ester and 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, polyoxyethylene glycerin fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene alkyl ether, Polyoxyethylene phytosterol ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkylphenyl ether, Reoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene lanolin derivatives, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, polyoxyethylene alkylphenyl formaldehyde condensates, and the like. You may use, and may use 2 or more types together.

  There is no restriction | limiting in particular in the addition amount in the said emulsion ink for stencil printing of the said emulsifier, According to the objective, it can select suitably, 1-8 mass% is preferable, and 2-5.5 mass% is more preferable.

-Colorants other than titanium oxide-
As colorants other than titanium oxide, known pigments and disperse dyes having various color tones can be used, and among these, pigments are particularly preferable. Examples of the colorant include carbon blacks such as acetylene black, channel black, and furnace black; metal powders such as aluminum powder and bronze powder; inorganic pigments such as petals, yellow lead, 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 pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, dioxane Gin dyes, selenium dyes, perylene dyes, perinone dyes, thioindigo dyes, quinophthalone dyes, condensed polycyclic pigments such as metal complexes; organic pigments such as lakes of acidic or basic dyes; diazo dyes, anthraquinones Oil-soluble dyes such as dyes; fluorescent pigments, etc. Is, it may be used alone or in combination of two or more thereof.

  As the fluorescent pigment, a so-called synthetic resin solid solution obtained by dissolving or dyeing a fluorescent dye that develops various hues after bulk polymerization of a synthetic resin or by pulverizing and refining the obtained colored bulk resin Examples of synthetic resins that carry dyes include melamine resins, urea resins, sulfonamide resins, alkyd resins, and polyvinyl chloride resins.

  When carbon black as the colorant is added to the oil phase, commercially available products can be used as acidic carbon black having a pH of less than 5, for example, MA-100, MA-7, MA-77, MA -11, # 40, # 44 (all manufactured by Mitsubishi Chemical Corporation), Raven 1100, Raven 1080, Raven 1255, Raven 760, Raven 410 (all manufactured by Colombian Carbon).

The average particle diameter of the insoluble colorant is preferably 0.1 to 10 μm, and more preferably 0.1 to 1 μm.
There is no restriction | limiting in particular in the addition amount in the emulsion ink for stencil printing of colorants other than the said titanium oxide, According to the objective, it can select suitably, Usually, 2-15 mass% is preferable.

-Colorant dispersant-
The colorant dispersant is not particularly limited as long as it does not inhibit the formation of the emulsion, and can be appropriately selected depending on the purpose. For example, the nonionic surfactant for an emulsifier described later, an alkylamine-based polymer Molecular compound, aluminum chelate compound, styrene-maleic anhydride copolymer, partial alkyl ester of polyacrylic acid, polyalkylene polyamine, aliphatic polyvalent carboxylic acid, polyether, ester type anionic surfactant, high molecular weight polycarboxylic acid Long chain amine salts, polyamide compounds, phosphate ester surfactants, alkyl sulfocarboxylates, α-olefin sulfonates, dioctyl sulfosuccinates, polyethylenimine, alkylolamine salts, inhibits ink storage stability Ionic surfactant, amphoteric interface if not Well as sexual agents may be used, these may be used alone or in combination of two or more thereof.
Among these, at least one selected from an aluminum chelate compound and a polyglycerin fatty acid ester compound is preferable from the viewpoint of maintaining viscosity over time and imparting excellent emulsion stability.

  There is no restriction | limiting in particular in the addition amount of the said coloring agent dispersing agent, According to the objective, it can select suitably, 40 mass% or less of the total mass of a coloring agent is preferable, and 2-35 mass% is more preferable.

-Antioxidant-
The antioxidant can prevent oxidation of the resin and the like, can prevent deterioration of the ink when left in the drum for a long time, and can be added to at least one of the oil phase and the water phase. There is no restriction | limiting in particular as this antioxidant, Although it can select and use suitably from well-known things, For example, nordihydroguaiaretic acid (NDGA), a guaiac fat, a citrate ester, extraction tocopherol, tocopherol , Butylhydroxytoluene, gallic acid, dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, sulfites, thiosulfate, ascorbic acid, ascorbate, ascorbic acid derivatives, etc., which are used alone Alternatively, two or more kinds may be used in combination.
There is no restriction | limiting in particular in the addition amount of the said antioxidant, According to the objective, it can select suitably, 2 mass% or less is preferable with respect to the total amount of ink, and 0.1-1.0 mass% is more preferable.

-Vegetable oil-
The vegetable oil is not particularly limited and can be appropriately selected from known ones according to the purpose.For example, soybean oil, corn oil, sunflower oil, rapeseed oil, safflower oil, sesame oil, castor oil, dehydrated castor oil, Camellia oil, olive oil, palm oil, rice oil, cottonseed oil, palm oil, bonito oil, palm kernel oil, tung oil, camelia oil, grape seed oil, sweet almond oil, pistachio nut oil, jojoba oil, macadamia nut oil, Meadow home oil and the like can be mentioned, and these may be used alone or in combination of two or more.
Examples of the esterified vegetable oil include those obtained by esterifying the vegetable oil. Examples of the ester include methyl ester, ethyl ester, and butyl ester. As the esterified vegetable oil, for example, esterified soybean oil is particularly preferable.
By using soybean oil fatty acid alkyd resin whose fat is soybean oil as the alkyd resin and using esterified soybean oil, the total of soybean oil-derived components exceeds 6%. Certification can be obtained, which is also advantageous in terms of safety.

  The amount of vegetable oil added to the emulsion ink for stencil printing is preferably 1 to 35% by mass, and more preferably 5 to 25% by mass.

-Mineral oil-
The mineral oil is not particularly limited and can be appropriately selected according to the purpose. For example, paraffinic oil, naphthenic oil, petroleum solvent, spindle oil, liquid paraffin, light oil, kerosene, machine oil, gear Oils, lubricating oils, motor oils and the like can be mentioned. Among these, paraffinic oils, naphthenic oils, and petroleum solvents are particularly preferable.
Commercially available products can be used as the paraffinic oil, for example, Gargo Oil Arctic series manufactured by Mobil Oil Co., Nippon Oil Super Oil Series manufactured by Nippon Oil Corporation, Diana Process Oil manufactured by Idemitsu Kosan Co., Ltd. And Diana Fresia series.
As the naphthenic oil, the carbon content (CN) of the naphthene component by ring analysis is 30% by mass or more, the carbon content (CA) of the aromatic component is 20% by mass or less, and the paraffin component Those having a carbon content (CP) of 55% by mass or less are suitable, for example, Gargo Oil Arctic Oil 155 and 300ID manufactured by Mobil Oil, Gargo Oil Arctic Oil Light, Gargo Oil Arctic Oil C Heavy; Idemitsu Kosan Co., Ltd. Diana Process Oil, Diana Fresia Series; Nippon San Oil Co., Ltd. Sansen Oil Series.
Commercially available products can be used as the petroleum-based solvent, and examples include Isopar series and Exol manufactured by Exxon Chemical; AF Solvent Series manufactured by Nippon Oil Corporation.

When considering the stability of the ink, these mineral oils preferably use those having a polycyclic aromatic component that is an aromatic hydrocarbon containing three or more condensed aromatic rings of less than 3% by mass. . Further, the mutagenicity index (MI) is less than 1.0, the aroma content (% C _A ) is 20 to 55%, the aniline point is 100 ° C. or less, and benzo [a] anthracene based on the total mass of the oil, The content of polycyclic aromatics such as benzo [b] fluoranthene, benzo [j] fluoranthene, benzo [k] fluoranthene, benzo [a] pyrene, dibenzo [a, j] acridine is 10 ppm or less and total content The amount is preferably 50 ppm or less.
Note that a highly safe aroma oil (for example, JP-A-11-80640) can be used as necessary.

  There is no restriction | limiting in particular in the addition amount in the said emulsion ink for stencil printing of the said mineral oil, According to the objective, it can select suitably, 1-35 mass% is preferable and 5-25 mass% is more preferable.

-Gelling agent-
The gelling agent has a role of improving the storage stability, fixability, fluidity, etc. of the ink by gelling the resin contained in the oil phase, and is preferably a compound that coordinates with the resin in the oil phase. . Examples of the gelling agent include organic acid salts containing organic metals such as Li, Na, K, Al, Ca, Co, Fe, Mn, Mg, Pb, Zn, and Zr, organic chelate compounds, and metal soap oligomers. Can be mentioned. Specifically, octylic acid metal salts such as aluminum octylate, naphthenic acid metal salts such as manganese naphthenate, stearates such as zinc stearate, organic chelate compounds such as aluminum diisopropoxide monoethyl acetoacetate, etc. Can be mentioned. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular in the addition amount of the said gelatinizer, According to the objective, it can select suitably, 15 mass% or less is preferable with respect to the total amount of resin in an oil phase, and 5-10 mass% is more preferable.

<Water phase>
The aqueous phase contains other components such as water, water evaporation inhibitor or antifreeze agent, electrolyte, water-soluble polymer compound, O / W resin emulsion, antiseptic / antifungal agent, and pH adjuster. .

-Water-
If it is clean, there will be no restriction | limiting in particular if it is clean, According to the objective, it can select suitably, For example, a tap water, ion-exchange water, distilled water etc. can be used.

-Water evaporation inhibitor or antifreezing agent-
The water evaporation inhibitor or antifreeze agent is not particularly limited and may be appropriately selected from known ones. Examples thereof include lower saturated monohydric alcohols, glycols and polyhydric alcohols. . These may be used individually by 1 type and may use 2 or more types together. The water evaporation inhibitor and the antifreezing agent can be used in combination.
Examples of the lower saturated monohydric alcohol include methanol, ethanol, isopropanol, butanol, isobutanol and the like. Examples of the glycol include ethylene glycol, diethylene glycol, and propylene glycol. Examples of the polyhydric alcohol include glycerin and sorbitol.
Among these, the effect of suppressing the deterioration of the ink with time due to volatilization of the aqueous phase and the effect of stabilizing the emulsion, while maintaining the effect of the alkyd resin against the stains of the roller, the ink of the ink when left in the drum for a long time is maintained. Glycerin is particularly preferable in that the alteration can be reduced.
The addition amount of the water evaporation inhibitor or antifreeze agent is not particularly limited and may be appropriately selected depending on the purpose. It is preferably 15% by mass or less based on the total mass of water in the ink. The mass% is more preferable.

-Electrolyte-
The electrolyte is added to increase the stability of the emulsion, and it is preferable to add an electrolyte composed of ions having a high liquid separation permutation effective for improving the stability of the emulsion. Anions having a high liquid separation permutation are citrate ions, tartaric acid ions, sulfate ions, acetate ions, and the like. Cations having a high liquid separation permutation are alkali metal ions and alkaline earth metal ions. The electrolyte added here is preferably a salt in which at least one of an anion and a cation is composed of the above ions, such as magnesium sulfate, sodium sulfate, sodium citrate, sodium hydrogen phosphate, sodium borate, sodium acetate, etc. Is mentioned. Among these, a divalent anion-containing compound is preferable, and magnesium sulfate is particularly preferable. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular in the addition amount of the said electrolyte, According to the objective, it can select suitably, 0.1-2 mass% of a water phase is preferable, and 0.5-1.5 mass% is more preferable.

-Water-soluble polymer compounds-
The water-soluble polymer compound is not particularly limited as long as it can impart moisture retention and viscosity to the stencil printing emulsion ink, and can be appropriately selected from known ones according to the purpose. Examples thereof include a polymer compound, a semi-synthetic polymer compound, and a synthetic polymer compound.
Examples of the natural polymer compound include starch, mannan, sodium alginate, galactan, tragacanth gum, gum arabic, pullulan, dextran, xanthan gum, glue, gelatin, collagen, casein and the like.
Examples of the semi-synthetic polymer compound include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxymethyl starch, carboxymethyl starch, and dialdehyde starch.
Examples of the synthetic polymer compound include neutralized products such as acrylic acid resin and sodium polyacrylate; polyvinylimide, polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, polyacrylamide, poly N-acryloylpyrrolidine, poly N-isopropylacrylamide. Poly N-alkyl-substituted acrylamides such as polyethylene oxide, polyvinyl methyl ether, styrene-maleic anhydride copolymer, styrene-acrylic acid copolymer, polymers in which these are partially hydrophobic with alkyl groups; acrylamide polymers or Examples include a copolymer type polymer in which a substituent of an acrylic polymer is partially hydrophobized with an alkyl group; a block copolymer of polyethylene and polypropylene or polybutylene.
The addition amount of the water-soluble polymer compound in the aqueous phase is preferably 25% by mass or less, and more preferably 0.5 to 15% by mass.

-Oil-in-water resin emulsion-
There is no restriction | limiting in particular as said oil-in-water resin emulsion, Although it can select suitably from well-known things and can use, a synthetic polymer compound or a natural polymer compound may be sufficient. Examples of the synthetic polymer compound include vinyl acetate resin, acrylic ester resin, methacrylic ester resin, vinyl chloride resin, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic ester copolymer, styrene-acrylic acid. Examples thereof include ester copolymers, vinylidene chloride-acrylic acid ester copolymers, vinyl chloride-vinyl acetate copolymers, and urethane resins. Examples of the natural polymer compound include a polymer compound that can be added to an oil phase commonly used in emulsion inks for stencil printing. These may be used individually by 1 type and may use 2 or more types together.
Further, the dispersion method of the oil-in-water resin emulsion is not particularly limited, and a dispersant, a protective colloid, and a surfactant may be added, or may be synthesized by soap-free emulsion polymerization. There is no restriction | limiting in particular in the minimum film forming temperature of the said oil-in-water resin emulsion, According to the objective, it can select suitably, 40 degrees C or less is preferable.

-Antiseptic and fungicide-
The antiseptic / antifungal agent is added to prevent bacteria and fungi from growing in the emulsion, and is effective when the emulsion is stored for a long period of time. The antiseptic / antifungal agent is not particularly limited and may be appropriately selected from known ones. Examples include salicylic acid, phenols, methyl p-oxybenzoate, ethyl p-oxybenzoate, and the like. Aromatic hydroxy compounds or chlorinated compounds thereof, sorbic acid, dehydroacetic acid and the like, and these may be used alone or in combination of two or more.
The addition amount of the antiseptic / antifungal agent is not particularly limited and may be appropriately selected depending on the purpose. It is preferably 3% by mass or less based on the total mass of water contained in the ink, More preferably, 2% by mass.

-PH adjuster-
There is no restriction | limiting in particular as said pH adjuster, Although it can select and use suitably from well-known things, For example, a triethanolamine, sodium acetate, a triamylamine etc. are mentioned suitably. These pH adjusters can be added as necessary to maintain the pH of the aqueous phase at 6-8. If the pH of the aqueous phase deviates from the above range, the effect may be impaired when a water-soluble polymer compound is added.

  In the emulsion ink for stencil printing of the present invention, wax can be added to the oil phase in order to improve separation between the printing paper and the printing drum during printing, or to prevent the printing paper from rolling up. In addition, it is possible to further increase the viscosity by adding triethanolamine, sodium hydroxide, or the like to the aqueous phase and adding a water-soluble polymer compound. Furthermore, a rust preventive agent or an antifoaming agent can be added to the water phase to prevent the printing press from being rusted by ink or causing ink to foam. These additives may be added as necessary to known products added to emulsion inks for stencil printing, and the amount added may be the same as that of conventional products.

-Manufacturing method-
The method for producing the emulsion ink for stencil printing of the present invention is not particularly limited and can be appropriately selected from known methods according to the purpose. For example, the oil phase and the aqueous phase liquid are previously prepared by a conventional method. It can be prepared by separately preparing, adding an aqueous phase to the oil phase, and emulsifying in a known emulsifier such as a disper mixer, a homomixer, or a high-pressure homogenizer. Specifically, titanium oil, extender pigments, colorants, emulsifiers, mineral oil, and other ingredients added as necessary are well dispersed in a three-roll mill to prepare the oil phase in a conventional manner. Then, an aqueous phase solution to which other components such as water, an evaporation inhibitor or antifreezing agent, and an electrolyte are added as necessary may be gradually added and emulsified.

The emulsion ink for stencil printing of the present invention preferably has a viscosity of 3 to 40 Pa · s, more preferably 10 to 30 Pa · s at a shear rate of 20 sec ⁻¹ .
As described above, the emulsion ink for stencil printing of the present invention is excellent in the effect on oil separation with time, hiding power, and emulsion stability, and is suitably used for stencil printing by a rotary stencil printing machine, for example.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
-Preparation of emulsion ink for stencil printing-
Titanium oxide (CR-50, manufactured by Ishihara Sangyo Co., Ltd., specific surface area = 13.9 m ² / g) (titanium oxide A) 3% by mass and titanium oxide (TTO) having an average particle size of 0.03 μm -51 (A), manufactured by Ishihara Sangyo Co., Ltd. Specific surface area = 80 m ² / g) (titanium oxide B) 6% by mass, carbon black as a colorant other than titanium oxide (R1100, manufactured by Columbia Carbon Co.) 0.5% by mass , Spindle oil (made by Cosmo Oil Co., Ltd.) 6% by mass as mineral oil, Nisseki AF Solvent No. 4 (made by Shin Nippon Oil Co., Ltd.) 10.5% by mass, and sorbitan fatty acid ester (S0-15) as mineral oil (Manufactured by Nikko Chemical Co., Ltd.) 4 mass% was added and mixed, and dispersed with a bead mill to prepare an oil phase.
On the other hand, 64% by mass of tap water, 5% by mass of glycerin, and 1% by mass of magnesium sulfate as an electrolyte were mixed and stirred to prepare an aqueous phase.
Next, the water phase was gradually added to the oil phase and emulsified with a disper mixer to prepare emulsion ink for stencil printing of Example 1.
In the emulsion ink for stencil printing of Example 1, the mixing ratio of titanium oxide A and titanium oxide B was titanium oxide A: titanium oxide B = 1: 11.5 in terms of specific surface area.
In this example, the average particle diameter of the titanium oxides A and B was measured by electron microscopy. The specific surface areas of the titanium oxides A and B were measured by JIS R 1626 gas adsorption BET method.

(Example 2)
-Preparation of emulsion ink for stencil printing-
In Example 1, the emulsion ink for stencil printing of Example 2 was prepared in the same manner as in Example 1 except that 6% by mass of titanium oxide A and 3% by mass of titanium oxide B were used.
In the emulsion ink for stencil printing of Example 2, the mixing ratio of titanium oxide A and titanium oxide B was titanium oxide A: titanium oxide B = 1: 2.9 in terms of specific surface area.

(Example 3)
-Preparation of emulsion ink for stencil printing-
In Example 1, 4% by mass of titanium oxide A, 4% by mass of silica as extender pigment, 11.5% by mass of Nisseki AF Solvent No. 4 as mineral oil, and no titanium oxide B contained The emulsion ink for stencil printing of Example 3 was prepared in the same manner as Example 1 except that.

Example 4
-Preparation of emulsion ink for stencil printing-
In Example 3, the emulsion ink for stencil printing of Example 4 was prepared in the same manner as in Example 3 except that calcium carbonate was included instead of silica as the extender pigment.

(Example 5)
-Preparation of emulsion ink for stencil printing-
Example 5 is the same as Example 4 except that 4% by mass of titanium oxide A, 2% by mass of calcium carbonate as an extender pigment, and 2% by mass of titanium oxide B are further contained. An emulsion ink for stencil printing was prepared.
In the emulsion ink for stencil printing of Example 5, the mixing ratio of titanium oxide A and titanium oxide B was titanium oxide A: titanium oxide B = 1: 2.9 in terms of specific surface area.

(Example 6)
Example 1 was the same as Example 1 except that titanium oxide A was 6% by mass, titanium oxide B was 0.9% by mass, and Nisseki AF Solvent No. 4 as mineral oil was 12.6% by mass. Thus, an emulsion ink for stencil printing of Example 6 was prepared.
In the emulsion ink for stencil printing of Example 5, the mixing ratio of titanium oxide A and titanium oxide B was titanium oxide A: titanium oxide B = 1: 0.86 in terms of specific surface area.

(Comparative Example 1)
-Preparation of emulsion ink for stencil printing-
In Example 1, a stencil printing emulsion ink of Comparative Example 1 was prepared in the same manner as in Example 1 except that the titanium oxide A was 9 mass% and the titanium oxide B was not used.

(Comparative Example 2)
-Preparation of emulsion ink for stencil printing-
In Example 1, a stencil printing emulsion ink of Comparative Example 2 was prepared in the same manner as in Example 1 except that the titanium oxide B was 9 mass% and the titanium oxide A was not used.

(Comparative Example 3)
-Preparation of emulsion ink for stencil printing-
In Example 3, the emulsion ink for stencil printing of Comparative Example 3 was prepared in the same manner as in Example 3 except that the silica content was 8% by mass and the titanium oxide A was not contained.

(Comparative Example 4)
-Preparation of emulsion ink for stencil printing-
In Example 4, the emulsion ink for stencil printing of Comparative Example 4 was prepared in the same manner as in Example 4 except that the calcium carbonate was 8% by mass and the titanium oxide A was not contained.
For convenience, the compositions of emulsion inks for stencil printing in Examples 1 to 6 and Comparative Examples 1 to 4 are shown in Tables 1 and 2.

[Evaluation]
Next, the obtained emulsion inks for stencil printing of Examples 1 to 6 and Comparative Examples 1 to 4 were evaluated for effects on oil separation over time, emulsion stability, and hiding power as follows. . The results are shown in Tables 3 and 4.

<Evaluation 1: Effect on oil separation over time>
The amount of centrifugal oil separation (7000 G, 2 hours) after initial storage of the ink and after aging at 60 ° C. as acceleration over time was measured using a centrifuge (manufactured by Kubota).
Based on the measured centrifugal oil separation amount, as the “rank of change amount”, the case where the centrifugal oil separation amount change amount is 0.02% or less, ◎, the case where 0.03% to 0.1% is ◯, 0. The case of 1% to 1.0% was evaluated as Δ, and the case of exceeding 1.0% was evaluated as ×, and the effect on oil separation over time was evaluated.

<Evaluation 2: Emulsification stability>
Evaluation of emulsification stability was performed by measuring the viscosity as follows and determining the amount of change in the viscosity over time.
Viscosity values were measured using a cone plate type rotational viscometer (manufactured by HAAKE) at the initial stage of ink production and after aging at 60 ° C. as an acceleration over time. The measurement was performed at 23 ° C., and the apparent viscosity at a shear rate of 20 s ⁻¹ was taken as the viscosity value.
Based on the measured viscosity value, as the “rank of change amount”, ◎ when the change amount of the viscosity value is 1 Pa · s or less, ○ when the change amount is 1 to 3 Pa · s, and 3 to 5 Pa · change amount. The case of s was evaluated as Δ, and the case of exceeding 5 Pa · s as x was evaluated for emulsion stability.

<Evaluation 3: Concealment power>
After sufficiently spreading each ink in the printing drum of a stencil printing machine (Tohoku Ricoh Co., Ltd., Preport N-500), two black lines with a width of 15 mm entered on a white background, and a black and white contrast was formed. Solid printing was performed on paper (substrate), and the presence or absence of hiding power was evaluated based on the following criteria by visual observation.
〔Evaluation criteria〕
A: Black and white contrast is difficult to understand.
○: The black and white contrast is somewhat difficult to understand.
Δ: Printed on black and white contrast.
X: Black and white contrast is visible as it is.

From the results of Tables 3 and 4, the emulsion inks for stencil printing of Examples 1 to 6 are superior to the inks of Comparative Examples 1 to 4 in that the oil separation generation amount does not increase with time and the effect on oil separation is excellent. Further, it is recognized that the viscosity does not decrease over time, the emulsion stability is excellent, and the hiding power is excellent.
In particular, the effect is remarkable in Example 2 in which the mixing ratio of two types of titanium oxide is defined, Example 4 in which calcium carbonate is used as an extender pigment, and Example 5 in which two types of titanium oxide and calcium carbonate are used. Is recognized.

The emulsion ink for stencil printing of the present invention is excellent in the effect on oil separation with time, hiding power, and emulsion stability, and is suitably used for stencil printing by a rotary stencil printing machine, for example.

Claims (3)

  It comprises 10 to 90% by mass of an oil phase and 90 to 10% by mass of an aqueous phase. In the oil phase, titanium oxide having an average particle size of 0.2 μm or more and titanium oxide having an average particle size of 0.05 μm or less And an emulsion ink for stencil printing, comprising at least one of extender pigments.   The mixing ratio of titanium oxide (titanium oxide A) having an average particle diameter of 0.2 μm or more and titanium oxide (titanium oxide B) having an average particle diameter of 0.05 μm or less is titanium oxide A: oxidation. The emulsion ink for stencil printing according to claim 1, wherein titanium B = 1: 5 to 1: 1. 3. The emulsion ink for stencil printing according to claim 1, wherein the extender is calcium carbonate.