JP4253287B2 - Emulsion ink for stencil printing - Google Patents

Description

  The present invention relates to an emulsion ink for stencil printing using vegetable oil.

  In the stencil printing method, printing is performed by allowing ink to permeate from a perforated portion of a stencil master and attaching the ink to a printing medium such as paper. The emulsion ink for stencil printing used in stencil printing is quickly dried on the printed substrate (mainly penetrating and evaporating dry with respect to paper), but is equipped with a stencil master. It is desirable not to dry on the machine.

  Therefore, the emulsion ink for stencil printing is an emulsion ink that does not dry on the machine, but quickly dries on the paper to be printed and does not smudge or smear even when touched with a finger. Although there is a need for development, it has not been solved technically.

  Also, since the contact area between the ink and air is large on the printing press, if left on the press for about a day or more, for example, the water phase component in the emulsion ink evaporates and the composition as the emulsion collapses and the ink viscosity decreases. As a result, there is a problem that the print density in the printed material at the initial printing becomes excessively high and the print definition is lowered.

  In order to solve the problem of ink viscosity reduction caused by evaporation of the aqueous phase component on the printing press, Japanese Patent Application Laid-Open No. 2003-335998 (Patent Document 1) discloses an iodine value of 100 to 150 in the oil phase. Japanese Patent Application Laid-Open No. 2002-220560 (Patent Document 2) describes that a vegetable oil having an iodine value of 110 to 150 and an antioxidant are added at a predetermined ratio. ing.

  Patent Documents 1 and 2 mainly use vegetable oils having an iodine value of 100 or more (when ink is left on a printing press, these semi-dry or dry vegetable oils are oxidized to increase viscosity, In this way, vegetable oils with a high iodine value have a high degree of oxidative drying, and the addition of a large amount of antioxidant reduces the rate of oxidative drying. Often adjusted.

  However, stencil printing is often used in schools and government offices, and may be left for more than a month during summer and winter holidays. In such cases, problems such as solidification and drying of ink on the machine occur. was there.

  In addition, when a large amount of antioxidant is blended, there are problems such as a decrease in storage stability of the ink in a sealed state and an increase in cost.

  Furthermore, in order to solve the problem of ink viscosity reduction due to evaporation of the aqueous phase component on the printing press, the vegetable oil having an iodine value of 100 or more was used, but still remained when left on the printing press. The viscosity of the ink is likely to decrease, resulting in an excessive amount of ink at the start of printing, resulting in a decrease in print sharpness, and it is necessary to perform a lot of wasteful galley printing before obtaining a normal printed matter. It remains unresolved.

JP 2003-335998 A JP 2002-220560 A

  An object of the present invention is to solve the problems of the prior art, and to provide an emulsion ink for stencil printing that is excellent in storage stability, on-machine leaving property, and excellent in drying and fixing properties on printing paper. . Here, as described above, good on-machine leaving property means that when left on the printing machine, the viscosity of the ink is lowered, and as a result, the ink is excessive at the start of printing, and the print definition is low. The number of printing papers that are unlikely to cause such problems even when left on a printing press and is wasted until normal printed matter is obtained when printing is started after being left It means that there are few.

  As a result of advancing various studies for solving the above problems, the present inventors have found that in an oil-in-water emulsion ink comprising an oil phase of 20 to 50% by weight and an aqueous phase of 80 to 50% by weight, an iodine value in the oil phase It becomes possible to obtain an appropriate iodine value by blending a predetermined amount of 10 or less epoxidized vegetable oil, and the blending amount of the antioxidant can be greatly reduced, and long-term storage stability is achieved, It has been found that drying and solidification on the machine and a decrease in viscosity are prevented, and that the dry fixability on printing paper is improved, and the present invention has been completed.

  That is, the present invention is (1) a water-in-oil emulsion ink comprising 20 to 50% by weight of an oil phase and 80 to 50% by weight of an aqueous phase, wherein an epoxidized vegetable oil having an iodine value of 10 or less is contained in the oil phase. The present invention relates to an emulsion ink for stencil printing containing 5 to 40% by weight.

  The present invention also relates to (2) the emulsion ink for stencil printing as described in (1) above, wherein the epoxidized vegetable oil having an iodine value of 10 or less contains at least 5% by weight of epoxidized soybean oil in the oil phase.

  The present invention further includes (3) an epoxidized soybean oil having an iodine value of 10 or less and a soybean oil fatty acid ester having an iodine value of 125 or less in the oil phase. The total content in the oil phase of the epoxidized soybean oil having an iodine value of 10 or less and the soybean oil fatty acid ester having an iodine value of 125 or less is 10% by weight or more and the iodine value is 10 or less. The sum of the iodine value of the epoxidized soybean oil and the iodine value of the soybean oil fatty acid ester having an iodine value of 125 or less proportionally distributed by their weight fraction is 110 or less. .

  In the emulsion ink for stencil printing of the present invention, an epoxidized vegetable oil is used as an oil component in the oil phase. However, even a vegetable oil having a high iodine value has a low iodine value by epoxidation, and the iodine value is low. Although it is low, the freezing point is low, so even when mixed with vegetable oil with high iodine value, it is estimated that it has the effect of preventing solidification drying of ink on the machine even if the amount of antioxidant is small Has been.

  In addition, since the amount of antioxidant added is small, the storage stability as an emulsion ink for stencil printing (especially storage stability in a sealed state, storage stability during transportation, etc.) is very good, and the viscosity immediately after production. Was found to be stable for a long time.

  Furthermore, when the ink is left on a printing press, the rate of decrease in viscosity is extremely low compared to the case where a vegetable oil having an iodine value of 100 or more is used alone, the ink is excessive at the start of printing, and the print definition is high. The problem that the number of wasteful galleys had to be printed before a normal printed matter was obtained has been solved.

  By containing 5 to 40% by weight of an epoxidized vegetable oil having an iodine value of 10 or less in the oil phase of the emulsion ink for stencil printing, the blending amount of the antioxidant can be greatly reduced, Long-term storage stability is achieved, dry solidification on the machine and viscosity reduction are prevented, and dry fixability on printing paper is improved.

  The emulsion ink for stencil printing of the present invention is a water-in-oil emulsion ink comprising 20 to 50% by weight of an oil phase and 80 to 50% by weight of an aqueous phase.

  An epoxidized vegetable oil having an iodine value of 10 or less is blended in the oil phase. By blending an epoxidized vegetable oil having an iodine value of 10 or less, it is easy to adjust the iodine value of the ink, and the amount of antioxidant added can be greatly reduced. The content of the epoxidized vegetable oil having an iodine value of 10 or less in the oil phase varies depending on the type of other emulsifier, vegetable oil, mineral oil, solvent, etc., but may be 5 to 40% by weight. Necessary, preferably 8 to 30% by weight. When the content of the epoxidized vegetable oil having an iodine value of 10 or less is less than the above range, the drying property of the ink on the printing paper tends to be lowered. If the content of the epoxidized vegetable oil having an iodine value of 10 or less in the oil phase exceeds the above range, it may be necessary to increase the amount of the antioxidant added, or the storage stability of the ink and the standing property on the machine may be deteriorated. Tend. As for the lower limit value of the iodine value of the epoxidized vegetable oil, the iodine value is preferably 0.5 or more from the viewpoint of obtaining the drying property of the ink commensurate with the decrease in the viscosity of the ink on the machine.

  Examples of the epoxidized vegetable oil include epoxidized soybean oil, epoxidized linseed oil, epoxidized rapeseed oil, epoxidized sunflower oil, epoxidized castor oil, epoxidized peanut oil, and epoxidized palm oil. These epoxidized vegetable oils can be used alone or in combination of two or more. Among these, epoxidized soybean oil is preferable from the viewpoints of good mixing with mineral oil, and better storage stability when used as an emulsion ink than other epoxidized vegetable oils. From this point of view, in a preferred embodiment of the present invention, epoxidized soybean oil is used alone or an epoxidized soybean oil and another epoxidized vegetable oil are used in combination as the epoxidized vegetable oil. In this embodiment, the content of epoxidized soybean oil in the oil phase is preferably 5% by weight or more, more preferably 15% by weight or more. When the content of the epoxidized soybean oil is less than the above range, the advantage of the epoxidized soybean oil is not sufficiently exhibited.

  In the oil phase, in addition to the epoxidized vegetable oil having an iodine value of 10 or less, other oil components, volatile solvents, resins, emulsifiers, colorants and the like can be blended.

  As other oil components, at least one selected from the group consisting of vegetable oil, soybean oil fatty acid ester and mineral oil can be blended.

  Examples of vegetable oils include normal vegetable oils such as soybean oil, rapeseed oil, sunflower oil, and castor oil. The soybean oil fatty acid ester means an alkyl ester of a fatty acid derived from soybean oil, and the alkyl group includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, amyl, caproyl, caprylyl. , Capryl, lauryl, myristyl, cetyl, stearyl and the like, and an alkyl group having 1 to 18 carbon atoms. In the present invention, these normal vegetable oil and soybean oil fatty acid ester oil may be collectively referred to as vegetable oil. These vegetable oils can be used alone or in combination. Among vegetable oils, soybean oil fatty acid esters are preferred because of their relatively low iodine value, low freezing point, and cost advantages. The vegetable oil preferably has an iodine value of 130 or less, more preferably 125 or less, particularly 110 or less, from the viewpoints of the on-machine drying property of the ink and the stability of the emulsion.

  From the above viewpoint, in another preferred embodiment of the present invention, the oil phase contains an epoxidized soybean oil having an iodine value of 10 or less and a soybean oil fatty acid ester having an iodine value of 125 or less, and an epoxy having an iodine value of 10 or less. The total content in the oil phase of epoxidized soybean oil having an iodine value of 10 or less and soybean oil fatty acid ester having an iodine value of 125 or less is 10% by weight or more. The sum of the iodine value of an epoxidized soybean oil having an iodine value of 10 or less and the iodine value of a soybean oil fatty acid ester having an iodine value of 125 or less in proportion to their weight fraction is 110 or less.

  Here, the sum (TIN) in which the iodine value of an epoxidized soybean oil having an iodine value of 10 or less and the iodine value of a soybean oil fatty acid ester having an iodine value of 125 or less are proportionally distributed by their weight fractions is the formula (1):

(Wherein IN1 is the iodine value of epoxidized soybean oil, IN2 is the iodine value of soybean oil fatty acid ester, W1 is the parts by weight of epoxidized soybean oil, and W2 is the parts by weight of soybean oil fatty acid ester) Value. In the case of using two or more kinds of epoxidized soybean oils having different iodine values, the case of using two or more kinds of soybean oil fatty acid esters having different iodine values was similarly proportionally distributed by weight fraction. The sum of iodine values (TIN) can be determined. When the sum of iodine values (TIN) proportionally distributed by weight fraction exceeds 110, there is a tendency that the addition amount of the antioxidant is increased or the dry fixability of the printed matter is lowered. Further, when the total content in the oil phase of the epoxidized soybean oil having an iodine value of 10 or less and the soybean oil fatty acid ester having an iodine value of 125 or less is less than 10% by weight, the epoxidized soybean oil having an iodine value of 10 or less and the iodine value of 125 or less The combined effect of soybean oil fatty acid ester is not sufficiently exhibited. In order to fully exhibit the combined effect of an epoxidized soybean oil having an iodine value of 10 or less and a soybean oil fatty acid ester having an iodine value of 125 or less, the content of the soybean oil fatty acid ester having an iodine value of 125 or less in the oil phase is further increased. It is preferably 1% by weight or more, more preferably 5% by weight or more.

  As the mineral oil, low volatile mineral oils such as motor oil, spindle oil, machine oil, liquid paraffin and naphthenic oil can be used. Paraffinic or naphthenic oils are particularly preferred from the standpoint of high ability to dissolve the resin used. These mineral oils are preferably used by appropriately mixing high and low viscosity oils in order to make the viscosity of the oil phase appropriate. In view of the solubility and cost of the resin, it is usually preferable to use a mineral oil in addition to the epoxidized vegetable oil or vegetable oil ester. In that case, the content of the mineral oil in the oil phase is about 5 to 80% by weight. Is more preferable, and about 8 to 30% by weight is more preferable.

  If necessary, a volatile solvent (usually a solvent having a boiling point of about 260 ° C. or lower under normal pressure) may be blended. Boiling solvents can be used.

  Examples of the resin include polymerized rosin, hydrogenated rosin ester, rosin-modified resins such as rosin-modified phenol resin, petroleum resins, alkyd resins, maleic acid resins, terpene resins, and the like. These resins may be used alone or in combination of two or more. Can be used. The content of these resins varies depending on the viscosity and solubility of the mineral oil in the oil phase, but from the viewpoint of adjusting the fixability to printing paper and the viscosity of the oil phase, 2 to 30% by weight is contained in the oil phase. Preferably, it is 5 to 20% by weight.

  As the emulsifier, those which can be dissolved in an epoxidized vegetable oil, vegetable oil or mineral oil in the oil phase can be used. Cationic, anionic, nonionic, and amphoteric surfactants can be used, and nonionic surfactants are particularly preferred. Nonionic surfactants include, for example, polyoxyethylene sorbitan monooleates and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan trioleate, sorbitan fatty acids such as sorbitan monooleate, sorbitan sesquioleate, and sorbitan trioleate. Examples include ester-based, polyoxyethylene alkylamine-based, fatty acid amide-based, polyoxyethylene castor oil-based, glycerol fatty acid ester-based compounds such as glycerol monostearate and decaglyceryl trioleate. These surfactants can be used alone or in combination of two or more. Usually, an emulsifier is used as an essential component. In this case, the content in the oil phase is preferably about 5 to 30% by weight.

  As the colorant, pigments and dyes having a particle size of 5 μm or less can be used. For example, inorganic pigments such as furnace carbon black, channel carbon black, lamp black, acetylene black and titanium oxide, organic pigments such as insoluble azo pigments and phthalocyanine blue, and other oil-soluble or water-soluble dyes can be used. The colorant is usually used as an essential component. In that case, the content in the oil phase is preferably about 10 to 30% by weight.

  When using a vegetable oil having a high iodine value as an oil phase component, it is necessary to add an antioxidant. Examples of the antioxidant include butylated hydroxytoluene, butylated hydroxyanisole, eugenol and the like. These antioxidants can be used alone or in combination of two or more. When the antioxidant is added too much, the storage stability of the ink is lowered or the drying property of the ink on the paper surface tends to be impaired. For these reasons and further from the viewpoint of cost, it is desirable that the blending amount of the antioxidant is as small as possible. From such a viewpoint, the blending amount of the antioxidant is preferably 2% by weight or less, particularly preferably 0.5% by weight or less based on the total amount of the epoxidized vegetable oil and the vegetable oil. When a vegetable oil having a high iodine value (for example, a vegetable oil having an iodine value of 110 or more) is not added, an antioxidant may not be blended even if it is added and its addition amount is small.

  A dispersant (wetting agent) blended in the oil phase as necessary adsorbs on the surface of the pigment when dispersing the pigment, and promotes wetting, micronization, and stabilization of the dispersed state. Examples thereof include sorbitan fatty acid esters such as lecithin, monostearate, monooleate, and monolaurate, partial fatty acid esters of polyacrylic acid, and alkylamine fatty acid salts. The dispersant is preferably one that dissolves in mineral oil, epoxidized vegetable oil, or vegetable oil in the oil phase.

  Further, when it is desired to increase the viscosity of the ink or to impart a gel structure or thixotropy to the ink, a gelling agent and a thixotropy imparting agent can be blended. Examples thereof include hydrogenated castor oil and aluminum chelate.

  The aqueous phase in the emulsion ink of the present invention contains water as an essential component and, if necessary, one kind of antifreezing agent, water evaporation inhibitor, antiseptic / antifungal agent, antioxidant, water-soluble polymer, electrolyte, and the like. Or it is comprised from 2 or more types.

  About water, although tap water may be sufficient, ion-exchange water and distilled water are preferred.

  Examples of the antifreezing agent include water-soluble organic solvents such as polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, sorbitol, and glycerin. These antifreeze agents also have a water evaporation inhibitor function.

  Examples of the antiseptic / antifungal agent include aromatic hydroxy compounds, salicylic acid, phenols, methyl p-oxybenzoate, ethyl p-oxybenzoate, sorbic acid, and dehydroacetic acid.

  Examples of water-soluble polymers used in the aqueous phase include natural polymers such as galactan, gum arabic, dextran, xanthan gum, and glue, acrylic resins and acrylic resins such as sodium polyacrylate and triethanolamine polyacrylate. Examples thereof include synthetic polymers such as acid resin derivatives, polyvinyl alcohol, and polyvinyl pyrrolidone.

  As the surfactant used in the aqueous phase, those having a high HLB value and soluble in the aqueous phase are preferable, for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene sorbitan laurate, and the like. Can be mentioned.

  The electrolyte may be added for pH adjustment, but it is not particularly necessary to add the electrolyte.

  The emulsion phase for stencil printing ink of the present invention can be obtained by adding and emulsifying the water phase having the above structure little by little to the oil phase having the above structure. Use a mixer, kneader, mill, disper, etc. to separately stir and disperse the oil phase component and water phase component separately to prepare the oil phase and water phase, and then emulsify them with an emulsifier to obtain an emulsion ink. It is done.

  Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Examples 1-3 and Comparative Examples 1-2
First, an oil phase and an aqueous phase were prepared according to the formulation shown in Table 1. In Table 1, the compounding quantity of each component shows a weight part. The oil phase was prepared by mixing the oil phase components and stirring and dispersing using a three roll mill, and the aqueous phase was prepared by mixing the water phase components and stirring and dispersing using a disper. Next, while stirring this oil phase in an emulsifier, the aqueous phase was gradually added to obtain an emulsion ink.

  The following characteristics were evaluated for the emulsion inks of Examples 1 to 3 and Comparative Examples 1 and 2 thus obtained. The results are shown in Table 2.

(1) Ink dry fixability in printed matter The obtained emulsion ink is printed on printing paper (PPC paper) using a stencil printer DP330 (manufactured by Duplo Co., Ltd.) in an environment of 20 ° C. and 65% RH. The surface was rubbed with a finger to visually confirm and evaluate the fixing property and drying property of the ink on the printing paper. The case where the ink did not adhere to the finger and the image was clear and the non-printed surface was not stained was marked with ◯, the case where the ink slightly smeared with the finger and the image smeared, and the case where the ink was poorly fixed and the ink did not dry.

(2) Storage stability The viscosity at 25 ° C. of the obtained emulsion ink was measured with a RE80 viscometer manufactured by Toki Sangyo Co., Ltd. [rotor code no. 4 (3 degrees × R14) was measured under the condition of 5 rotations / minute], then placed in a sealed container and allowed to stand at 40 ° C. for 1 month, and then the viscosity was measured again under the same conditions. The decrease rate of the viscosity after standing for 1 month with respect to the initial viscosity is within 15%, and there is no abnormality in the emulsion such as water separation and oil floating, and the decrease rate of the viscosity after standing with respect to the initial viscosity is 15%. The case where it was exceeded or the appearance of the emulsion was required to be broken or abnormal was marked as x.

(3) On-press leaving property After printing the obtained emulsion ink using a stencil printing machine DP330 (manufactured by Duplo Co., Ltd.), leaving it in a room temperature environment (25 ° C.) for 24 hours, printing is performed again, and it is clear. The number of sheets of printing paper required to obtain a good print was examined. It means that the smaller the number of required printing papers, the better on-machine leaving ability.

  As shown in Table 1, in each of Examples 1 to 3, the ink storage stability, the dry fixing property of the ink in the printed matter, and the on-machine leaving property were all excellent. However, in Comparative Examples 1 and 2 in which no epoxidized vegetable oil was blended, the storage stability was inferior, and the dry fixing property of the ink in the printed matter and the on-machine leaving property were also inferior.

Claims (3)

A water-in-oil emulsion ink comprising an oil phase of 20 to 50% by weight and an aqueous phase of 80 to 50% by weight, comprising 5 to 40% by weight of an epoxidized vegetable oil having an iodine value of 10 or less in the oil phase Emulsion ink for stencil printing characterized. The emulsion ink for stencil printing according to claim 1, wherein the epoxidized vegetable oil having an iodine value of 10 or less contains at least 5% by weight or more of epoxidized soybean oil in the oil phase. The oil phase contains an epoxidized soybean oil having an iodine value of 10 or less and a soybean oil fatty acid ester having an iodine value of 125 or less, and the content of the epoxidized soybean oil having an iodine value of 10 or less in the oil phase is 5% by weight or more. Yes, the iodine content of an epoxidized soybean oil having an iodine value of 10 or less and a soybean oil fatty acid ester having an iodine value of 125 or less in the oil phase having a total content of 10% by weight or more and an iodine value of 10 or less 2. The emulsion ink for stencil printing according to claim 1, wherein the sum of the iodine value of soybean oil fatty acid ester having an iodine value of 125 or less and proportionally distributed by their weight fraction is 110 or less.