JP2015034190A - Offset-printing ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an offset-printing ink composition capable of inhibiting poor inking and dirt on a printing paper surface in printing.SOLUTION: An offset-printing ink composition contains a color pigment, a binder resin, an oil constituent, and both of constituents (A) and (B) in the following. The constituent (A) is a modified novolac resin, and the constituent (B) is at least one selected from the group consisting of compounds represented by the general formula (1) or (2). (In the general formulas (1) and (2), R are each independently an alkyl group, aryl group or aralkyl group, and n is an integer between 1 and 3.)

Description

  The present invention relates to an ink composition for offset printing.

  Offset printing is a printing method that utilizes the property that an oil-based ink composition for offset printing (hereinafter referred to as “ink composition” or “ink” as appropriate) repels water, and has unevenness. Unlike the relief printing method using a plate, a printing plate having no irregularities is used. This printing plate is provided with an oleophilic image portion and a hydrophilic non-image portion in place of the unevenness. In printing, first, the non-image portion of the printing plate is wetted with dampening water to form a water film on the surface, and then the ink composition is supplied to the printing plate. At this time, the supplied ink composition does not repel and adhere to the non-image area where the water film is formed, but adheres only to the oleophilic image area. Thus, an image of the ink composition is formed on the surface of the printing plate, and then printing is performed by sequentially transferring it to the blanket and paper.

  The offset printing method has a characteristic that it is suitable for the field of obtaining a printed material with high cosmetics and obtaining a large amount of printed material in a short time, while making a printing plate is relatively simple. Therefore, the offset printing method is widely used from fields requiring high cosmetics such as brochures, posters, calendars, etc. to fields requiring high-speed and large-scale printing such as newspapers, magazines, and telephone books. Yes.

  Of these fields, an offset rotary press is generally used in fields that require high-speed and large-volume printing. In the offset rotary press, the printing paper is mounted on the paper supply unit in a wound state, and the winding is unwound to supply the printing paper to the printing unit for printing. The printed printing paper is subjected to necessary processing such as folding after being cut by a cutting section to become a product. According to such a printing method, printing of about tens of thousands to hundreds of thousands of copies can be performed at a time, which is efficient. The printing speed may reach as high as 100,000 copies per hour. Under such circumstances, many products that have been imparted with high-speed printing suitability have also been proposed for ink compositions for offset printing (see, for example, Patent Document 1).

JP 2000-281945 A

  As already described, in offset printing, printing is performed while making good use of the repulsion of water and oil on the offset printing plate to prevent ink from adhering to non-image areas where ink should not adhere. When performing such printing, it is necessary to make very delicate adjustments regarding the balance between water (fountain solution) and oil (ink). The water absorption of the paper used for printing and the dampening water supply system in the printing press Depending on the conditions such as the printing environment, these balances may be lost, and ink may adhere to the non-image area of the printing paper surface to cause stains. The printed matter with such stains has a markedly reduced commercial value, and in some cases, is a waste (waste paper). In particular, when high-speed printing is performed using an offset rotary press, once a smudge occurs, high-speed printing continues while the smudge is dealt with, so a large amount of such waste (waste paper) is generated. Will be generated.

  In addition, among the printed matter printed on the offset rotary press, a newspaper, a magazine, a telephone book, and the like can be cited as representatives of a particularly large number of copies printed. Since these printed materials are mainly intended for information transmission, they are not high-grade printing papers used when a high degree of cosmetics is required, but are mainly used for papers with slightly inferior paper quality. However, since the surface strength of such paper is inferior to that of high-grade printing paper, some of the paper fibers present on the surface of the paper may be struck by the blanket of the printing press during printing.

  Paper fibers (paper dust) squeezed from the surface of the paper stay in the blanket or printing plate of the printing machine and hinder good transfer of the ink composition for offset printing onto the printed matter. In this way, the phenomenon that paper dust stays in the blanket or printing plate of a printing press and the transfer of ink to the printed matter is obstructed is called imperfection, and when this occurs, the printed matter is faded As in the case of the above dirt, the commercial value is reduced. Such a phenomenon becomes more prominent because the accumulation of paper dust accumulates as the number of printed copies increases. For this reason, it is particularly important to suppress imperfections in the printing of newspapers, magazines, telephone books and the like having a large number of copies.

  As described above, when large-scale and high-speed printing using an offset rotary press is performed, it is an important issue to suppress stains and imperfections on the paper surface, so an ink composition that can satisfy these required performances. There is a strong demand for things.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide an ink composition for offset printing that can suppress the occurrence of smudges and imperfections on the printing paper surface during printing. And

  As a result of intensive studies to solve the above problems, the present inventors can solve the above problems by blending a modified novolak resin and a glycol ether compound having a specific structure into an ink composition. As a result, the present invention has been completed. Specifically, the present invention provides the following.

（上記一般式（１）及び（２）中、Ｒは、それぞれ独立にアルキル基、アリール基又はアラルキル基であり、ｎは、１〜３の整数である。） The present invention is an ink composition for offset printing comprising a color pigment, a binder resin, an oil component, and both the following component (A) and component (B).
Component (A) Modified novolak resin Component (B) At least one selected from the group consisting of compounds represented by the following general formula (1) or (2)

(In the above general formulas (1) and (2), R is independently an alkyl group, an aryl group or an aralkyl group, and n is an integer of 1 to 3)

  The component (A) is preferably a reaction product of a novolak resin having an epoxy group and a polyester compound obtained by condensing a monohydroxy fatty acid having 12 or more carbon atoms or a modified product thereof.

  The component (B) is hexyl glycol, hexyl diglycol, 2-ethylhexyl diglycol, phenyl glycol, phenyl diglycol, benzyl glycol, propylene glycol monopropyl ether, ethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylpropylene diglycol. It is preferably at least one selected from the group consisting of glycol and phenylpropylene glycol.

  Content of the said component (A) is 0.1-5 mass% with respect to the whole composition, Content of the said component (B) is 0.1-5 mass%, The said component (A) And it is preferable that the total content of (B) is 0.3-6 mass%.

  ADVANTAGE OF THE INVENTION According to this invention, the ink composition for offset printing which can suppress generation | occurrence | production of the stain | pollution | contamination in a printing paper surface, and poor inking in the case of printing is provided.

  Hereinafter, an embodiment of the ink composition for offset printing of the present invention will be described.

  The ink composition of the present invention is used for offset printing, and has the performance of suppressing the occurrence of smudges on the printing paper surface (also referred to as “stain resistance”) and the performance of suppressing the occurrence of poor inking. Therefore, it is preferably used for high-speed printing using a rotary press such as newspaper printing. The ink composition of the present invention is characterized in that it contains a color pigment, a binder resin, an oil component, and both components (A) and (B) described later. Each item will be described below.

[Coloring pigments]
The coloring pigment is a component for imparting coloring power to the ink composition. Examples of the color pigment include organic and / or inorganic pigments conventionally used in ink compositions without any limitation.

  Examples of such coloring pigments include yellow pigments such as disazo yellow (Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 17, and Pigment Yellow 1), Hansa Yellow, and magenta pigments such as Brilliant Carmine 6B, Lake Red C, and Watching Red. And cyan pigments such as phthalocyanine blue, phthalocyanine green and alkali blue, and black pigments such as carbon black.

  The addition amount of the color pigment is exemplified by about 8 to 30% by mass with respect to the entire ink composition, but is not particularly limited. A yellow ink composition using a yellow pigment, a magenta ink composition using a magenta pigment, a cyan ink composition using a cyan pigment, and a black ink composition using a black pigment, respectively. When preparing, it is also possible to use a pigment of another color in combination or to add an ink composition of another color as a complementary color.

[Binder resin]
A binder resin (hereinafter, also simply referred to as “resin”) is a component that functions as a binder for fixing the colored pigment on the surface of printing paper, and is used for dispersing the colored pigment in the ink composition. It is also a component to be made. Examples of such resins include those usually used in the field of ink compositions without any particular limitation, and include rosin-modified phenol resins, rosin-modified maleic resins, rosin-modified alkyd resins, rosin-modified petroleum resins, and rosin esters. Examples thereof include resins, petroleum resin-modified phenol resins, acrylic-modified phenol resins, alkyd resins, vegetable oil-modified alkyd resins, and petroleum resins. The weight average molecular weight of these resins is preferably about 3000 to 300,000.

  Among these resins, from the viewpoint of pigment dispersibility, print quality, and stable printability over a long period of time, from the group consisting of a rosin-modified phenolic resin and a rosin-modified maleic resin having a weight average molecular weight of 10,000 to 150,000. It is preferable to use at least one selected. In order to improve the dispersibility of the pigment, it is also preferable to use these resins and alkyd resins in combination. In this case, it is preferable to use about 3 to 10 parts by mass of the alkyd resin with respect to 100 parts by mass in total of the rosin modified phenolic resin and the rosin modified maleic resin. The amount of resin added is preferably about 10 to 35% with respect to the entire ink composition.

  The resin is melted by being heated together with an oil component described later, and used in a varnish state. When preparing the varnish, a gelling varnish may be prepared by introducing a gelling agent such as a metal chelate compound or metal soap into the dissolution varnish obtained by dissolving the resin. It is preferable to prepare a gelled varnish from a resin and use it for the preparation of the ink composition because appropriate viscoelasticity can be imparted to the ink composition.

[Oil component]
The oil component is used for dissolving the resin to make a varnish or adjusting the viscosity of the ink composition. Examples of the oil component include vegetable oils and / or mineral oils, and those that have been used in the preparation of ink compositions so far can be used without particular limitation.

  In the present invention, the vegetable oil may contain a vegetable oil-derived fatty acid ester compound in addition to the vegetable oil. Examples of vegetable oils include dry oils such as soybean oil, cottonseed oil, linseed oil, safflower oil, tung oil, tall oil, dehydrated castor oil, and canola oil, and semi-dry oils. Examples of the fatty acid ester compound derived from vegetable oil include monoalkyl ester compounds of fatty acids derived from the vegetable oil. As the fatty acid constituting the fatty acid monoalkyl ester compound, a saturated or unsaturated fatty acid having 16 to 20 carbon atoms is preferably exemplified, and as such a saturated or unsaturated fatty acid, stearic acid, isostearic acid, hydroxystearic acid, Preferred examples include oleic acid, linoleic acid, linolenic acid, eleostearic acid and the like. As the alkyl group constituting the fatty acid monoalkyl ester compound, an alkyl group having 1 to 10 carbon atoms is preferably exemplified, and more specifically, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, Preferred examples include a tert-butyl group and 2-ethylhexyl group.

  These vegetable oils can be used alone or in combination of two or more. Preferred vegetable oils include soybean oil and soybean oil fatty acid ester. As content of the vegetable oil in an ink composition, about 20-60 mass% can be illustrated with respect to the whole ink composition.

  In the present invention, examples of the mineral oil include light mineral oil called a solvent component and heavy mineral oil that is a lubricating oil.

  Examples of the light mineral oil include non-aromatic petroleum solvents having a boiling point of 160 ° C. or higher, preferably a boiling point of 200 ° C. or higher. Examples of such non-aromatic petroleum solvents include No. 0 Solvent, AF Solvent No. 5, AF Solvent No. 6 and AF Solvent No. 7 manufactured by JX Nippon Oil & Energy Corporation.

  Examples of heavy mineral oils include various lubricating oils that have been classified as spindle oil, machine oil, dynamo oil, cylinder oil, and the like. Among these, from the viewpoint of adapting to the OSHA standard and EU standard in the United States, it is preferable that the content of the condensed polycyclic aromatic component is suppressed. Examples of such mineral oil include Ink Oil H8 and Ink Oil H35 manufactured by JX Nippon Oil & Energy Corporation, SNH8, SNH46, SNH220, and SNH540 manufactured by Sankyo Oil Chemical Co., Ltd.

  These mineral oils can be used alone or in combination of two or more. As content of the mineral oil in an ink composition, about 0-50 mass% can be illustrated with respect to the whole ink composition. In addition, when conforming to the Eco Mark standard (type name: printing ink version 2.0, standard: petroleum solvent in the ink composition is 30% by mass or less) approved by the Japan Eco Mark Secretariat. From the above viewpoint, the content of mineral oil in the ink composition is preferably 30% by mass or less.

[Component (A)]
Component (A) is a modified novolac resin. The present inventors have studied the formulation of an ink composition that can suppress the occurrence of poor inking during printing. Surprisingly, a small amount of a modified novolak resin is added to the ink composition. Thus, it has been found that the occurrence of poor inking is significantly suppressed. The ink composition of the present invention is based on such knowledge and contains a modified novolac resin as the component (A). 0.1-5 mass% is preferable, as for content of the component (A) in an ink composition, 0.1-3 mass% is more preferable, and 0.5-2 mass% is further more preferable.

  Examples of the modified novolak resin include those obtained by reacting a phenolic hydroxyl group of a novolak resin with a compound having a functional group such as a carboxyl group or a hydroxyl group, or an epichlorohydrin derivative such as epichlorohydrin or β-methylepichlorohydrin on the phenolic hydroxyl group of a novolak resin. Examples thereof include compounds obtained by reacting a compound having a functional group such as a carboxyl group or a hydroxyl group with this epoxy group after introducing an epoxy group by acting. In particular, for the latter, various novolak resins into which epoxy groups are introduced are commercially available for the preparation of epoxy resins and the like.

  As a modified novolak resin in a more preferred embodiment, (X) an epoxy group-containing novolak resin (hereinafter also referred to as “compound (X)”) and (Y) a monohydroxy fatty acid having 12 or more carbon atoms are condensed. Examples thereof include a reaction product with a polyester compound (hereinafter also referred to as “compound (Y)”) or a modified product thereof.

  The compound (X) is synthesized by reacting a novolak resin having a phenolic hydroxyl group with an epichlorohydrin derivative such as epichlorohydrin or β-methylepichlorohydrin by a conventional method. Of course, since the novolak resin into which the epoxy group is introduced is commercially available as described above, it may be used as the compound (X).

  As the novolak resin having a phenolic hydroxyl group, a novolak resin derived from a monovalent or polyhydric phenol and an aldehyde by a conventional method can be used.

  Among these, monohydric phenols include unsubstituted phenols such as phenol, cresol, xylenol, trimethylphenol, propylphenol, butylphenol, amylphenol, hexylphenol, octylphenol, nonylphenol and dodecylphenol, and substituted phenols such as alkylphenol. Can do. Examples of the polyhydric phenols include catechol, resorcinol, hydroquinone, trihydroxybenzene, or substituted products thereof, dihydroxydiphenylmethanes such as bisphenol A and bisphenol F, and dihydroxybiphenyls. These phenols can be used individually or in combination of 2 or more types.

  As aldehydes, those generally used for the production of novolak resins can be mentioned without particular limitation. Specific examples include lower aliphatic aldehydes such as formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde and glyoxal, and aromatic aldehydes such as furfural and phenylaldehyde. . These aldehydes can be used alone or in combination of two or more.

  In order to synthesize novolak resins, the above phenols and aldehydes can be synthesized in the presence of an acid catalyst such as paratoluenesulfonic acid, perchloric acid, hydrochloric acid, nitric acid, sulfuric acid, chloroacetic acid, oxalic acid, and phosphoric acid. May be reacted at 80 to 130 ° C. The progress of this reaction can be followed by gel permeation chromatography (GPC) or the like.

  As said compound (Y), what condensed the C12 or more monohydroxy fatty acids, such as 12-hydroxystearic acid, in presence of an esterification catalyst etc. can be illustrated. Since these monohydroxy fatty acids have both a hydroxyl group and a carboxyl group in the molecule, they are dehydrated and condensed (esterified) with each other to form a polyester compound. Such a polyester compound contains a carboxyl group capable of reacting with an epoxy group in the molecule, and reacts with an epoxy group contained in the molecule of the compound (X) to generate a reaction product.

  What is necessary is just to heat, after mixing these, in order to make the said compound (X) and a compound (Y) react and to obtain a reaction material. At that time, if necessary, an appropriate solvent such as dimethylformamide (DMF), toluene, xylene or the like may be added. Examples of the reaction temperature for the reaction include about 100 to 175 ° C., but are not particularly limited. As the compound (X) and the compound (Y) react, the carboxyl group contained in the compound (Y) is consumed, and the acid value of the reaction mixture decreases. Therefore, by monitoring the acid value during the reaction, It is possible to determine the degree of progress and the end. The acid value at the end of the reaction can be exemplified by about 0.1 to 1.0 mgKOH / g, but is not particularly limited.

  The mixing ratio of compound (X) and compound (Y) is appropriately determined in consideration of the number of epoxy groups contained in one molecule of compound (X) and the number of carboxyl groups contained in one molecule of compound (Y). Just decide. As a mixing ratio of the compound (X) and the compound (Y), the carboxyl group contained in the compound (Y) is 0.5 to 0.9 mole relative to 1 mole of the epoxy group contained in the compound (X). The proportion can be preferably exemplified, and furthermore, the proportion in which the carboxyl group contained in the compound (Y) is 0.6 to 0.85 mol can more preferably be exemplified with respect to 1 mol of the epoxy group contained in the compound (X). There is no particular limitation.

  The modified novolak resin thus obtained may be used as the component (A) as it is, and if necessary, for example, a compound having two or more carboxyl groups in the molecule is added as the compound (Z). Then, a modified product may be used as the component (A). In this case, if a novolac resin having two or more epoxy groups is used as the compound (X), the compound (X) modified with the compound (Y) is cross-linked with the compound (Z), and the modification is made higher in molecular weight. A novolac resin can be obtained. It is preferable to use a modified novolak resin having a high molecular weight as component (A) because problems such as misting often observed when a low-molecular resin compound is added to the ink composition can be suppressed.

  The compound (Z) is not particularly limited as long as it has two or more carboxyl groups in the molecule, and examples of such compounds include isophthalic acid, terephthalic acid, adipic acid, pimelic acid, suberic acid, sebacin An acid etc. can be mentioned.

  The reaction temperature for crosslinking with the compound (Z) can be exemplified by about 125 to 175 ° C., but is not particularly limited. As the unreacted epoxy group reacts with the compound (Z), the carboxyl group contained in the compound (Z) decreases and the acid value of the reaction mixture decreases. Therefore, the reaction is performed by monitoring the acid value during the reaction. It is possible to determine the degree of progress and the end. For example, if the acid value does not decrease even if the reaction is continued, it means that the epoxy group has been used up, and it can be determined that the reaction has ended.

  What is necessary is just to determine the addition amount of a compound (Z) suitably according to the quantity of the epoxy group contained in the compound (X) used for reaction, and the carboxyl group contained in a compound (Y). As an example of such addition amount, it is contained in the compound (Z) with respect to 1 mole difference between the number of moles of the epoxy group contained in the compound (X) and the number of moles of the carboxyl group contained in the compound (Y). The proportion in which the number of moles of the carboxyl group is preferably 0.5 to 0.9 mole can be exemplified, and further the proportion in which the number of moles of the carboxyl group contained in the compound (Z) is 0.6 to 0.85 mole Although it can illustrate preferably, it is not specifically limited.

（上記一般式（１）及び（２）中、Ｒは、それぞれ独立にアルキル基、アリール基又はアラルキル基であり、ｎは、１〜３の整数である。） [Component (B)]
The component (B) is at least one compound selected from the group consisting of compounds represented by the following general formula (1) or (2).

(In the above general formulas (1) and (2), R is independently an alkyl group, an aryl group or an aralkyl group, and n is an integer of 1 to 3)

  In the present invention, the addition of the component (B) to the ink composition is based on the fact that the present inventors have found that the ink composition containing the component exhibits good stain resistance. The reason why the stain resistance is improved by adding the component (B) to the ink composition is not necessarily clear, but is presumed to be as follows. The component (B) is a compound called glycol ether, and has both a highly hydrophilic portion such as a hydroxyl group or a plurality of ether groups and a highly hydrophobic portion such as an alkyl group. Therefore, in the ink composition which is an oily environment, the component (B) helps to quickly incorporate the dampening water into the ink composition, while the incorporated dampening water is in a state of relatively large water droplets. It is speculated that it has a function of emulsifying in the ink composition. Therefore, the fountain solution taken in the ink composition as emulsified water is easily emulsified and destroyed on the surface of the offset printing plate due to the size of the water droplets, and is separated from the ink composition. It seems that the antifouling effect is expressed.

  The ink composition of the present invention is considered to have improved stain resistance by such a mechanism, and of course, in the AD (Arch typed Dampner) printing method in which dampening water is directly supplied to the printing plate, the ink in the ink train Good stain resistance can also be exhibited in an ITD (Ink Train Dampner) printing system that supplies dampening water to the composition. In particular, in the ITD method, the dampening water is not supplied directly onto the printing plate, but the dampening water supplied to the film surface of the ink composition is conveyed to the printing plate in a state of being contained in the ink. Therefore, the ink composition to be used needs to have the performance of quickly taking in the supplied dampening water and separating the dampening water quickly on the printing plate. From such a viewpoint, it can be said that the ink composition of the present invention can be used favorably in an ITD printing machine. Of course, the ink composition of the present invention is also preferably used in a printing press that is not an ITD system, and in that case, it can exhibit excellent stain resistance while suppressing excessive emulsification on the printing plate.

  0.1-5 mass% is preferable, as for content of the component (B) in an ink composition, 0.1-3 mass% is more preferable, and 0.3-2 mass% is further more preferable. When the content of the component (B) in the ink composition is in the above range, good stain resistance is obtained, and the emulsification balance of the ink composition is improved, so that the occurrence of poor inking is suppressed. preferable.

  As the component (B), hexyl glycol, hexyl diglycol, 2-ethylhexyl diglycol, phenyl glycol, phenyl diglycol, benzyl glycol, propylene glycol monopropyl ether, ethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylpropylene diglycol Preferred examples include at least one selected from the group consisting of glycol and phenylpropylene glycol. Among these, 2-ethylhexyl diglycol can be illustrated more preferably. These components (B) can be used individually or in combination of 2 or more types.

  The total amount of the component (A) and the component (B) in the ink composition is preferably 0.3 to 6% by mass, more preferably 0.3 to 4% by mass, and More preferably, it is 3 to 3% by mass. It is preferable that the total amount of the component (A) and the component (B) in the ink composition is in the above range since both the stain resistance and the effect of suppressing the defective inking can be achieved in a good state.

[Other ingredients]
Various components can be added to the ink composition of the present invention, if necessary, in addition to the above components, from the viewpoint of improving printing performance. Examples of such various components include colorless pigments, salts such as phosphates, waxes such as polyethylene wax, olefin wax, and Fischer-Tropsch wax, alcohols, and antioxidants.

  The colorless pigment is also referred to as an extender, and is preferably used for adjusting properties such as viscosity in the ink composition. Examples of the colorless pigment include clay, talc, kaolinite (kaolin), barium sulfate, calcium carbonate, silicon oxide, bentonite, and titanium oxide. The addition amount of the colorless pigment is exemplified by about 0 to 33% by mass with respect to the entire ink composition, but is not particularly limited.

[Method for preparing ink composition]
In producing the ink composition of the present invention using each of the above components, a conventionally known method can be used. As such a method, after mixing each of the above components, the colored pigment is dispersed by kneading with a bead mill or a three-roll mill, etc., and then mineral oil or additives (antioxidants, alcohols) as necessary. Etc., waxes, etc.) and the mixture is well stirred and the viscosity is adjusted. The viscosity of the ink composition may be appropriately set in consideration of the configuration of a printing machine to which the ink composition is applied, the paper quality of the printing paper, and the like. As an example, the value at 25 ° C. by a Raleigh viscometer is 2.0 to Although it can be mentioned that it is 20 Pa.s, it is not specifically limited.

  The printing ink composition of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following description, unless otherwise specified, “%” means “mass%” and “part” means “part by mass”.

[Synthesis of modified novolac resin]
Put a mixture of 300 parts of 12-hydroxystearic acid, 30 parts of xylene and 0.3 parts of tetra-n-butyl titanate into a separable flask equipped with a cooling pipe, a water separation pipe, a thermometer, and a nitrogen introduction pipe, under a nitrogen stream. The mixture was heated and stirred at 180 to 200 ° C. for 3 hours while separating the water produced in step 1 through a water separation tube. Subsequently, xylene was distilled off under reduced pressure to obtain polyester A which is a light brown polymer having a weight average molecular weight of 800 and an acid value of 80.

  A mixed solution of 30 parts of a novolak resin having an epoxy group (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., YDPN-638), 64 parts of the polyester A and 50 parts of DMF is placed in a reaction vessel, and the mixture is kept at 130 to 150 ° C. for 2 hours under a nitrogen stream. Stir with heating. Next, 6 parts of terephthalic acid was added and reacted for 2 hours, and then 6 parts of succinic anhydride was added and the mixture was further heated and stirred for 3 hours. Then, DMF was distilled off under reduced pressure to obtain a modified novolak resin having a weight average molecular weight of 9000 and an acid value of 32.

[Preparation of varnish for ink composition]
In a four-necked flask equipped with a condenser, a thermometer and a stirrer, 35 parts of rosin-modified phenolic resin (KG-2212, manufactured by Arakawa Chemical Industries, Ltd.) having a weight average molecular weight of 100,000, 20 parts of soybean oil and AF solvent 6 No. (manufactured by JX Nippon Mining & Energy Co., Ltd.) was charged with 44.5 parts, the temperature was raised to 200 ° C., and the resin was dissolved by maintaining the same temperature for 1 hour, and then ethyl acetoacetate aluminum diisopropylate ( 0.5 parts of ALCH) manufactured by Kawaken Fine Chemical Co., Ltd. was charged, and then heated and held at 170 ° C. for 60 minutes to obtain a varnish.

[Preparation of base for ink composition]
42 parts of the above varnish, 20 parts of carbon black MA70 (Mitsubishi Chemical Co., Ltd.), 5 parts of calcium carbonate (Shiraka Hana DD, Shiraishi Calcium Co., Ltd.), 13 parts of Gilsonite Varnish, and 5 parts of soybean oil are mixed. A base for an ink composition was prepared by kneading with this roll mill. The Gilsonite varnish is obtained by dissolving 20 parts of Gilsonite (manufactured by American Gilsonite Company, product name: Gilsonite S325L) in 80 parts of AF Solvent No. 6 (manufactured by JX Nippon Mining & Energy Corporation). .

[Preparation of ink composition]
The above composition for ink composition, modified novolak resin, 2-ethylhexyl diglycol (component B-1), hexyl diglycol (component B-2), and soybean oil in the formulations (parts by mass) shown in Tables 1 and 2 The ink compositions of Examples 1 to 12 and Comparative Examples 1 to 4 were prepared by mixing.

[Print Evaluation]
For each of the ink compositions of Examples 1 to 12 and Comparative Examples 1 to 4, an N-750 type printing experimental machine (manufactured by Higashihama Seiki Co., Ltd.) in which the dampening water supply method was changed to the ITD method was used. A printing test of 20,000 copies was conducted by using a paper as a newspaper renewal at a printing speed of 120,000 copies / hour. As dampening water, tap water with 0.7% N-4 (manufactured by Sakata Inx Co., Ltd., neutral H solution) is used, and spray dampener SSD-12 (Sakata Inx Corporation) is used to supply dampening water. Used). At the time of printing, in order to compare the printing state in the vicinity of the lower limit of the water width, the SSD-12 dial was raised by two points from the lower limit value of the water width. The density of the solid paper surface during printing was 1.20 ± 0.02. The solid paper surface density is a numerical value obtained by measuring the density of a solid part in a printed material with a Spectroeye densitometer (manufactured by Gretagmacbeth).

(Evaluation of stain resistance) The stain on the non-image area of the paper immediately before the end of the printing test was visually evaluated. The evaluation results are shown in the “stain resistance” column of Tables 1 and 2. The evaluation criteria are as follows.
◎: No stain is observed in the non-image area. ○: Slight entanglement is observed in the flat mesh portion (50% halftone dot), but no stain is observed in the other non-image portion. Slight dirt is observed in the non-image part of the part ×: Conspicuous dirt is observed in the non-image part

(Evaluation of Inking) The inking state of the image part (solid part) on the paper surface immediately before the end of printing was visually evaluated. The evaluation results are shown in the “Inkerability” column of Tables 1 and 2. The evaluation criteria are as follows.
◎ No fading of the solid part is observed in the printed matter ○ Slight fading of the solid part is observed in the printed matter △ Fading of the solid part is observed in the printed matter × In the printed matter, fading of the solid part is remarkably observed. Ru

  As can be seen from Tables 1 and 2, according to the ink composition of the present invention, even if it is an ITD printing method in which stains are likely to occur on the paper surface, stains do not occur and poor inking is well suppressed. Recognize. From this, it is understood that according to the ink composition of the present invention, it is possible to suppress the occurrence of stains and poor inking.

Claims (4)

An ink composition for offset printing comprising a color pigment, a binder resin, an oil component, and both the following component (A) and component (B).
Component (A) Modified novolak resin Component (B) At least one selected from the group consisting of compounds represented by the following general formula (1) or (2)

(In the above general formulas (1) and (2), R is independently an alkyl group, an aryl group or an aralkyl group, and n is an integer of 1 to 3)   The ink for offset printing according to claim 1, wherein the component (A) is a reaction product of a novolak resin having an epoxy group and a polyester compound obtained by condensing a monohydroxy fatty acid having 12 or more carbon atoms or a modified product thereof. Composition.   The component (B) is hexyl glycol, hexyl diglycol, 2-ethylhexyl diglycol, phenyl glycol, phenyl diglycol, benzyl glycol, propylene glycol monopropyl ether, ethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylpropylene diglycol. The ink composition for offset printing according to claim 1 or 2, which is at least one selected from the group consisting of glycol and phenylpropylene glycol.   Content of the said component (A) is 0.1-5 mass% with respect to the whole composition, Content of the said component (B) is 0.1-5 mass%, The said component (A) And the total content of (B) is 0.3-6 mass%, The ink composition for offset printing of any one of Claims 1-3.