JP5662707B2 - Emulsion ink for stencil printing - Google Patents

Description

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

  Stencil printing is used in a wide range of fields because it is easy to produce a plate. The emulsion ink for stencil printing used in stencil printing is an ink of a permeation drying method that permeates into a printing material such as paper and dries. In a stencil printing machine, emulsion ink having a certain degree of viscosity is used on the principle of stencil printing, and therefore, a certain amount of time is required for osmotic drying after paper transfer. Therefore, when performing double-sided printing in a short time, there is a problem that ink printed on the front surface is transferred to a press roll, a transport roll, etc. during backside printing, and the ink attached to the roll is transferred to the paper and causes stains. is there.

  Further, if the printing press is left for a long period of time, there is a problem that the ink remaining on the screen / master portion on the outer periphery of the drum thickens and the printing surface does not return (so-called clogging). Furthermore, when left for a long time, the ink in the printing drum deteriorates, the solvent component (oil) retained in the ink is discharged, the solvent oozes out from the printing drum, and the inside of the printing machine is contaminated (so-called oil Discharge).

  In response to the above problem of penetrability, the applicant has proposed an emulsion ink that can improve the penetrability by lowering the surface tension of the aqueous phase (Patent Document 1). However, since the surface tension of the aqueous phase is low, there remains room for improvement in terms of storage stability. In addition, for the problem of clogging, an ink containing a dye as a colorant has been proposed (Patent Document 2). However, since the dye is used, there is a problem that the show-through easily occurs. Furthermore, in order to solve the problem of oil ejection, an ink to which extender pigments are added has been proposed (Patent Document 3), but the penetration and drying properties must be sacrificed to some extent by the addition of extender pigments.

  By the way, a resin is added to the conventional emulsion ink for stencil printing for the purpose of improving the storage stability of the ink and improving the fixing property of the ink to paper. The resin added to the ink for stencil printing has a high molecular weight such as 20,000 to 150,000 (Patent Document 4), 40,000 to 160,000 (Patent Document 5), 10,000 or more (Patent Document 6). Many inks contain resin. On the other hand, Patent Document 7 proposes a resin containing a gelling agent of 3,000 to 150,000 containing a low molecular weight resin.

JP 2002-332444 A JP 2000-191970 A JP 2001-311027 A JP 2007-231169 A JP 2009-270071 A Japanese Patent Laid-Open No. 2005-298779 JP-A-5-117564

  Inks containing high molecular weight resins are considered to be able to suppress oil discharge because the resin itself has a high viscosity and the resin easily retains the solvent. In addition, the ink remaining on the screen or the like tends to increase in viscosity when left for a long period of time, and clogging is likely to occur. If a low molecular weight resin is used, the problems of osmotic drying and clogging may be solved, but it becomes difficult to retain the solvent, so that oil can be easily discharged when left for a long period of time. In addition, the low molecular weight resin containing the gelling agent as described in Patent Document 7 reacts with the polar group of the resin, so that the polarity is lower than that of the resin not containing the gelling agent. As a result, since the pigment dispersibility is inferior, the same problem as that of the ink containing the high molecular weight resin occurs.

  As described above, problems such as osmotic drying, clogging, and oil discharge in emulsion inks for stencil printing have the relationship that, in order to solve one problem, the other problem is sacrificed to some extent. At present, these problems have not been solved at the same time. As a result of extensive studies by the inventor, the present inventors have found an ink capable of simultaneously solving problems such as penetrability, clogging and oil discharge. That is, an object of the present invention is to provide an emulsion ink for stencil printing that has good osmotic drying properties and can suppress clogging and oil discharge during long-term storage.

  As a first aspect, the stencil printing emulsion ink of the present invention is a stencil printing emulsion ink comprising an oil phase and an aqueous phase, wherein the oil phase has an alkyd resin having an average molecular weight of less than 5,000 and an average molecular weight of 10, And 000 or more alkyd resins.

  As a second aspect, the stencil printing emulsion ink of the present invention is a stencil printing emulsion ink comprising an oil phase and an aqueous phase, and the oil phase contains an alkyd resin having an average molecular weight of less than 5,000 and calcium carbonate. It is characterized by this.

  As a third aspect, the stencil printing emulsion ink of the present invention is a stencil printing emulsion ink comprising an oil phase and an aqueous phase, wherein the oil phase has an alkyd resin having an average molecular weight of less than 5,000 and carbon having a pH of 7 to 8. It is characterized by including black.

  The emulsion ink for stencil printing of the present invention contains an alkyd resin having an average molecular weight of less than 5,000 as an essential component in the oil phase, and the alkyd resin having an average molecular weight of less than 5,000 improves the osmotic drying property, It is thought that clogging when left for a long time is suppressed. On the other hand, the emulsion ink for stencil printing of the first aspect further contains an alkyd resin having an average molecular weight of 10,000 or more, the emulsion ink for stencil printing of the second aspect contains calcium carbonate, The emulsion ink for stencil printing contains carbon black having a pH of 7 to 8, and the inclusion of each of them makes it possible to improve oil discharge. As a result, according to the present invention, the emulsion ink for stencil printing has good penetrability and can suppress clogging and oil discharge during long-term storage.

  Hereinafter, the emulsion ink for stencil printing of the present invention will be described in detail. The emulsion ink for stencil printing of the present invention, as a first aspect, is characterized in that the oil phase contains an alkyd resin having an average molecular weight of less than 5,000 and an alkyd resin having an average molecular weight of 10,000 or more. As a second aspect, the oil phase includes an alkyd resin having an average molecular weight of less than 5,000 and calcium carbonate. As a third aspect, the oil phase includes an alkyd resin having an average molecular weight of less than 5,000 and carbon black having a pH of 7 to 8.

  The emulsion inks for stencil printing in the first to third aspects are common in that the oil phase contains an alkyd resin having an average molecular weight of less than 5,000 (hereinafter also referred to as a low molecular weight alkyd resin). Here, the average molecular weight in this invention is a mass average molecular weight, and means what was measured by the gel permeation chromatography method (standard polystyrene conversion). The average molecular weight of the low molecular weight alkyd resin is preferably from 500 to less than 5,000, more preferably from 1,000 to less than 5,000, and even more preferably from 1,500 to less than 3,000. When the average molecular weight is greater than 5,000, the penetrability is difficult to improve and transfer stains are likely to occur. The content of the low molecular weight alkyd resin is preferably 0.5% by mass to 20% by mass, and more preferably 1% by mass to 15% by mass with respect to the total amount of the ink.

  Since the alkyd resin has higher polarity than other resins, it has excellent wettability with the pigment. In particular, the low molecular weight alkyd resin has higher pigment dispersibility than the high molecular weight resin. This is due to the fact that the lower the molecular weight, the faster the adsorption rate to the pigment, and the lower the viscosity of the resin itself, and the higher the fluidity of the pigment dispersion. . In addition, since the pigment dispersibility is excellent, it is difficult to increase the viscosity of the ink remaining on the screen / master portion on the outer periphery of the drum when left standing for a long time, and clogging when left standing for a long time is considered to be suppressed.

  On the other hand, the low molecular weight alkyd resin is difficult to retain the solvent, and therefore it is easy to discharge oil when left for a long time. Therefore, in the emulsion ink for stencil printing of the first aspect, an alkyd resin having an average molecular weight of 10,000 or more (hereinafter also referred to as high molecular weight alkyd resin) is used in the oil phase, and the emulsion for stencil printing of the second aspect. In the ink, calcium carbonate is contained in the oil phase, and in the emulsion ink for stencil printing of the third aspect, carbon black having a pH of 7 to 8 is contained. This makes it possible to improve the oil discharge without deteriorating the osmotic drying property and without causing clogging.

  In the emulsion ink for stencil printing of the first embodiment, which contains a high molecular weight alkyd resin in the oil phase, the oil discharge is improved by the high molecular weight alkyd resin, while the low molecular weight alkyd resin improves the osmotic drying property. Since suppression of clogging is ensured, it is possible to achieve both improved penetration drying, suppression of clogging, and improved oil discharge. The average molecular weight of the high molecular weight alkyd resin is more preferably from 10,000 to less than 100,000, further preferably from 10,000 to less than 50,000, and further preferably from 10,000 to less than 25,000. When the average molecular weight is less than 10,000, the effect of improving oil discharge is difficult to obtain, and when the average molecular weight is greater than 100,000, the penetrability is deteriorated and transfer stains are likely to occur.

  The ratio between the low molecular weight alkyd resin and the high molecular weight alkyd resin is generally different depending on the average molecular weight of the low molecular weight alkyd resin and high molecular weight alkyd resin used, whether or not the resin is included, and the type of resin when it is included. Although it cannot be said, for example, when the resin is not included other than the low molecular weight alkyd resin and the high molecular weight alkyd resin, the ratio is in the range of 6: 4 to 1: 9 (mass of low molecular weight alkyd resin: mass of high molecular weight alkyd resin). It is more preferable that

  In the emulsion ink for stencil printing of the second aspect containing calcium carbonate in the oil phase, the oil ejection is improved by the calcium carbonate, and the improvement of the osmotic drying property and the suppression of clogging are ensured by the low molecular weight alkyd resin. Therefore, it is possible to improve both the penetrability and drying, suppress clogging, and improve oil discharge. It is considered that calcium carbonate did not deteriorate the osmotic drying property because the thickening effect of the oil phase was lower than that of extender pigments such as bentonite and talc. In addition, calcium carbonate itself is hydrophilic, and from the viewpoint of emulsion stability, it is preferable to use calcium carbonate whose surface has been subjected to fatty acid treatment or rosin acid treatment. Calcium carbonate subjected to fatty acid treatment or rosin acid treatment can be obtained by a known method, and commercially available products may be used.

  In the emulsion ink for stencil printing of the third aspect containing neutral carbon black in the oil phase, the oil discharge is improved by the neutral carbon black, and the penetration and drying properties are improved and the clogging is suppressed by the low molecular weight alkyd resin. Therefore, it is possible to achieve both improvement of penetration drying property, suppression of clogging, and improvement of oil discharge. Since neutral carbon black slightly reduces the fluidity of the pigment dispersion and significantly increases the viscosity at a low share, compared with acidic carbon black, it is considered that oil discharge is suppressed.

  The oil phase of the emulsion ink for stencil printing in the above first to third aspects, in addition to the respective essential components, is a range that does not impair the effects of improving penetrability and suppressing clogging and improving oil discharge. 1 comprises a colorant, a surfactant (emulsifier), a resin component other than low and high molecular weight alkyd resins, a solvent (oil) component, a pigment dispersant and the like. However, it is preferable that the emulsion ink for stencil printing of the first embodiment containing a high molecular weight alkyd resin in the oil phase does not contain a high molecular weight resin component other than the high molecular weight alkyd resin. Further, in the case of the emulsion ink for stencil printing of the second embodiment containing calcium carbonate in the oil phase, it is preferable not to contain extender pigments other than calcium carbonate. The ratio of the oil phase is preferably 20% by mass to 70% by mass and more preferably 25% by mass to 55% by mass with respect to the total mass of the ink.

  Examples of the colorant include insoluble azo pigments, soluble azo pigments, phthalocyanine blue, dye lake, isoindolinone, quinacridone, dioxazine violet, organic pigments such as perinone / perylene; inorganic pigments such as carbon black and titanium dioxide; azo type Oil-soluble dyes such as anthraquinone and azine; various water-soluble dyes and disperse dyes. These colorants can be used alone or in admixture of two or more in order to achieve the desired hue, and pigments and dyes may be combined. The blending amount may be set as appropriate, but in general, it is preferably 20% by mass or less, more preferably 3% by mass to 10% by mass with respect to the total mass of the ink.

  Further, in order to improve the image quality of the printed matter, an extender pigment can be contained in the ink. Examples of extender pigments that can be used include silica, white clay, talc, clay, diatomaceous earth, calcium carbonate, barium carbonate, barium sulfate, alumina white, kaolin, mica, and aluminum hydroxide. May be. If the extender pigment is contained in a large amount, it may interfere with fixing of the colorant to the printing medium or may impair the printing performance after the printer is not used. Preferably, it is 5 mass% or less.

  The surfactant is used to constitute a water-in-oil emulsion, and any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant may be used. Among these, it is preferable to use a nonionic surfactant from the viewpoint of the emulsifiability and storage stability of the water-in-oil emulsion.

  Specifically, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monooleate, sorbitan sesquioleate, sorbitan fatty acid esters such as sorbitan monoisostearate, glyceryl monostearate, hexaglyceryl tetraoleate, decaglyceryl deca (Poly) glycerin fatty acid esters such as oleate and hexaglyceryl pentaoleate, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbite fatty acid ester, propylene glycol fatty acid ester, (poly) ethylene glycol fatty acid ester , Polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alcohol Phenyl ethers, polyoxyethylene (hardened) can be exemplified preferably castor oil and the like. The said surfactant may be used independently and can also be used in combination of 2 or more types as appropriate.

  Resins impart viscosity to the ink and improve the stability of the emulsion, and those that dissolve in the oil phase are used. By including a resin, it is possible to improve the pigment dispersibility of carbon black, other pigments and extender pigments, fixability to paper, and suppression of transfer stains. As the resin, for example, rosin, gilsonite, rosin ester, maleic acid resin, phenol resin, alkyd resin, petroleum resin, acrylic resin, amino resin, urethane resin, cellulose resin, natural rubber derivative resin and the like can be preferably used. Alkyd resins and phenol resins can be used more preferably. A reaction product of an alkyd resin or rosin-modified resin with an aluminum chelate compound or aluminum alcoholate can also be preferably used. The content of the resin is preferably 1 to 20% by mass, and more preferably 3 to 15% by mass with respect to the total mass of the ink.

  The main solvent (the main solvent here means a solvent that occupies more than half of the total solvent mass) must have a boiling point of 240 ° C. or higher because it is necessary for the ink to hardly volatilize even when left in the air. Is preferable, and it is more preferable that it is 250 degreeC or more. In addition, in order to compensate for a decrease in ink viscosity due to volatilization of the aqueous phase during standing, a solvent having a boiling point of 240 ° C. or lower can be added to the oil phase in addition to the main solvent. The kind of solvent is not specifically limited, Both a nonpolar solvent and a polar solvent can be used. For example, a hydrocarbon solvent or the like can be used as the nonpolar solvent, and a vegetable oil, an ester solvent, an alcohol solvent, a higher fatty acid solvent, an ether solvent, or the like can be used as the polar solvent. These may be used alone or in combination of two or more. When using 2 or more types mixed, it is necessary for a liquid mixture to form a single continuous phase.

Examples of the hydrocarbon solvent include aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and the like. As the aliphatic hydrocarbon solvent and alicyclic hydrocarbon solvent, “Nippon Oil Co., Ltd.“ Tclean N-16, Tclean N-20, Tclean N-22, No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent ” "H, AF-4, AF-5, AF-6, AF-7" (all trade names), "Nisseki Isosol, Naphthezol" (all trade names) manufactured by Nippon Petrochemicals, "Exxon Mobil" IsoparG, IsoparH, IsoparL, IsoparM, ExxolD40, ExxolD80, ExxolD100, ExxolD140, ExxolD140 "(all trade names).
Examples of vegetable oils include soybean oil, corn oil, rapeseed oil, safflower oil, sesame oil, castor oil, olive oil, coconut oil, rice bran oil, cottonseed oil, palm oil, palm kernel oil, and linseed oil.

  Examples of ester solvents include methyl laurate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isostearyl palmitate, isooctyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, methyl linoleate, Isobutyl linoleate, ethyl linoleate, isopropyl isostearate, soybean oil methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, propylene glycol monocaprate, tri-2-ethylhexane Examples include trimethylolpropane acid, glyceryl tri-2-ethylhexanoate, and the like.

Examples of the alcohol solvent include isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol and the like.
Examples of the higher fatty acid solvent include isononanoic acid, isomyristic acid, isopalmitic acid, oleic acid, and isostearic acid.

Examples of the ether solvent include diethyl glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol dibutyl ether and the like.
The content of the solvent is preferably 10% by mass to 80% by mass and more preferably 40% by mass to 75% by mass with respect to the mass of the ink oil phase.

  Examples of the pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, a high molecular weight unsaturated acid ester, Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene Nonylphenyl ether, polyester polyamine, stearylamine acetate, and the like can be used. Among them, comb polymers having a polyamide structure in the main chain and a polyester structure in the side chain are preferable. The content of the pigment dispersant is preferably 0% by mass to 10% by mass, and more preferably 0.1% by mass to 5% by mass with respect to the total mass of the ink.

  In addition, an antioxidant, a compound mainly composed of wax or the like as an auxiliary agent for adjusting fluidity can be added to the oil phase as long as the formation and stability of the emulsion are not inhibited.

In the aqueous phase, in addition to water, a water evaporation inhibitor (or antifreezing agent), an electrolyte, a pH adjuster, an antioxidant and the like can be included as necessary.
Specific examples of the water evaporation inhibitor (or antifreezing agent) include water-soluble organic solvents such as polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, and glycerin. The content thereof is preferably 1 to 20% by mass and more preferably 3 to 15% by mass with respect to the total amount of the aqueous phase.

  Examples of the electrolyte include sodium sulfate, magnesium sulfate, potassium hydrogen phosphate, sodium citrate, potassium tartrate, sodium borate and the like, and the content thereof is 0.1 to 5.0% by mass with respect to the total amount of the aqueous phase. It is preferable that it is 0.5-2.0 mass%.

The ink of the present invention can be prepared by a known method. For example, the oil phase can be prepared by dispersing the pigment in a solvent with a known disperser, further diluting with a solvent, and adding other oil phase components. A known stirrer can be used for dilution. The aqueous phase can be prepared by mixing and dissolving the components of the aqueous phase in water with a stirrer. And a water-in-oil emulsion ink can be obtained by dripping a water phase in the oil phase under stirring using a well-known emulsifier. The conditions employed for carrying out the dispersion, dilution, emulsification and the like can be selected as appropriate.
Examples of the ink of the present invention are shown below.

(Preparation of ink)
According to the formulation shown in the following Table 1 (the numerical values shown in the table are parts by mass), inks of Examples and Comparative Examples were prepared according to the following procedure. First, an oil phase colorant, extender pigment, resin, solvent and the like were mixed and sufficiently dispersed with a rocking mill. An aqueous phase mixed solution in which additives were mixed was gradually added dropwise to the oil phase, and emulsification was performed using a homogenizer to obtain an emulsion ink for stencil printing (water-in-oil emulsion ink).

(Evaluation)
(Osmotic drying)
Using the prepared emulsion ink, printing was performed with a lithograph (Risaku Kagaku Kogyo Co., Ltd.) RZ570 (manufactured by the company) as a stencil printing machine to obtain a printed matter. After 3 minutes from the printing of the printed material, the back surface was printed, the state of transfer smearing was examined, and the following evaluation was made.
◎: Transfer stain is not recognized ○: Transfer stain is slightly recognized Δ: Transfer stain is recognized but acceptable in practical use ×: Transfer stain is clearly recognized and exceeds practical acceptable range

(Clogging after leaving for one month)
The printing drum after being left for one month was set in a printing machine RZ570, prepress-printed, printed, and evaluated as follows.
A: A desired print image was obtained within 20 sheets. ○: A desired print image was obtained within 50 sheets. X: A desired print image was obtained with 51 sheets or more.

(Oil spitting after leaving for one month)
The oil discharge of the printing drum after being left for 1 month was visually evaluated according to the following criteria.
◎: No oil spilling ○: Small amount of oil spilling is observed △: Oil spilling but not protruding from the drum ×: Oil spilling is remarkable and protruding from the drum In addition to the ink formulations of the examples and comparative examples, Table 1 shows the results of evaluation based on the above evaluation items.

  As is apparent from Table 1, the emulsion ink for stencil printing of the present invention contains an alkyd resin having a molecular weight of less than 5,000, so that it has excellent drying properties and can suppress the occurrence of clogging when left for a long period of time. . On the other hand, the inks of Examples 1 and 2 further contain an alkyd resin having an average molecular weight of 10,000 or more, the ink of Example 3 contains carbon black having a pH of 7 to 8, and the inks of Examples 4 and 5 contain calcium carbonate. So it became possible to improve oil spitting.

  It can be seen from Comparative Examples 4 and 5 that the oil spitting is improved by calcium carbonate, and the improvement effect is small with organic bentonite and talc, which are the same extender pigments. In addition, when only an alkyd resin having a molecular weight of less than 5,000 is included (Comparative Example 1), it is possible to improve the drying property and suppress the occurrence of clogging, but oil discharge is significant. On the other hand, even though an alkyd resin having a molecular weight of 10,000 or more is contained, in Comparative Examples 2 and 3 which do not contain an alkyd resin having a molecular weight of 5,000 or less, spitting can be suppressed, but drying and clogging are possible. Became bad.

  As described above, the emulsion ink for stencil printing of the present invention contains an alkyd resin having an average molecular weight of less than 5,000 as an essential component in the oil phase, and further contains an alkyd resin having an average molecular weight of 10,000 or more. Depending on whether calcium carbonate is contained or carbon black having a pH of 7 to 8 is contained, the osmotic drying property is good, and clogging and oil discharge during long-term storage can be suppressed. it can.

Claims (2)

An emulsion ink for stencil printing comprising an oil phase and an aqueous phase, wherein the oil phase contains an alkyd resin having a mass average molecular weight of less than 5,000 and calcium carbonate. An emulsion ink for stencil printing comprising an oil phase and an aqueous phase, wherein the oil phase comprises an alkyd resin having a mass average molecular weight of less than 5,000 and carbon black of pH 7-8.