JP2005054109A - Lithographic ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition having good printing performance by lithographic printing. <P>SOLUTION: The lithographic ink is composed mainly a coloring agent, a varnish and an auxiliary agent. The resin of the varnish contains a phenol-modified cyclized rubber containing 5-95 wt.% component having a molecular weight of ≥1.5×10<SP>4</SP>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lithographic printing ink. More specifically, the lithographic printing ink has excellent transferability but excellent anti-staining property, excellent anti-set-off and anti-blocking properties, and excellent environmental safety and press maintenance and maintenance. It relates to printing ink.

  There are two types of lithographic printing methods: wet and dry. In wet lithographic printing methods, an ink-affinity part (image part) and a non-ink-affinity part (background part) are formed on the same plane by plate making. The fountain solution is selectively applied to the non-image area, and the ink is adhered to the image line area. After the ink is transferred to the blanket, it is re-transferred (offset) to a printing material such as paper to perform printing. Further, in the dry lithographic printing method, printing is performed using, for example, a plate in which a non-image portion is coated with a silicon-based film so that ink repellency can be obtained without using dampening water.

  In the lithographic printing method, it is common to transfer ink from the above plate to a blanket and then print it on the substrate (offset printing). However, the ink is transferred directly from the plate to the substrate or printed directly (direct printing). Printing) is also performed in part.

  The ink used in lithographic printing is composed of a colorant that is a pigment, a varnish resin that is a vehicle, a solvent or oil for varnish, a drying aid, and the like.

When lithographic printing is performed using such an ink, (1) if an ink having a relatively low viscosity (ink having a viscosity of 1000 to 3000 Pa) is used, the transfer of ink to the non-image area (background stain) is likely to occur. In order to prevent this background stain, it is necessary to use ink having a relatively high viscosity (ink having a viscosity of 6000 to 8000 Pa). However, when ink with relatively high viscosity is used, the tack value also increases, so it is necessary to increase the driving force of the printing press, and furthermore, the printing quality itself is inferior in transferability, and the solid filling is rough. Become an image.
The “ink viscosity” as used in the present invention is a stress rheometer (DSR-200 manufactured by Rheometrics), using a parallel plate with a diameter of 25 mm (GAP is 0.5 mm), measuring temperature is 20 ° C., and angular frequency is This is the value of the complex elastic modulus G * measured when 10 rad / s and the strain amount (or stress) is in the linear elastic region.

  Further, since the effect of the osmotic drying is small in drying the ink on paper, the ink is still wet and king occurs. (2) To solve this problem, use volatile organic solvents (initial boiling point: 280 ° C or lower) that have many problems such as flammability, unpleasant odor, and environmental destruction. (3) Residual ink Therefore, it is necessary to compensate for the drying property on paper by using oxidative polymerization drying which has many problems such as solidification and fixing of the inking roller and the blanket.

  As some conventional examples of lithographic printing inks, Japanese Patent Publication No. 60-49669 (Patent Document 1) uses phenol or maleic resin as a vehicle component, cyclized rubber (modified varnish), and silicone as an additive. A lithographic printing ink using a polyether is disclosed. Japanese Laid-Open Patent Publication No. 10-140070 (Patent Document 2) discloses a lithographic printing ink using a fatty acid ester obtained by transesterifying natural fats and oils with a monohydric alcohol as an ink solvent.

  However, these lithographic printing inks are not low-viscosity osmotic drying inks, and thus the above problems still remain when these inks are used as low-viscosity inks.

Japanese Patent Publication No. 60-49669 Japanese Patent Laid-Open No. 10-140070

  The present invention does not cause scumming when using a low-viscosity ink, and does not cause flammability, unpleasant odor, and environmental destruction due to the organic solvent contained in the evaporated and dried ink. It is an object of the present invention to provide a lithographic printing ink having low viscosity and osmotic drying that does not cause solidification, sticking and the like of an inking roller and a blanket often found in oxidative polymerization dried ink.

In the use of a lithographic printing ink having a relatively low viscosity, the present inventors are liable to cause transfer of ink (background stain) to a non-image area, but at least a component having a molecular weight of 1.5 × 10 ⁴ or more is contained in 5 to 5 parts. The lithographic printing ink using 95% by weight of phenol-modified cyclized rubber as a varnish resin has been found to significantly reduce scumming. The present invention has been made based on this.
According to the present invention, the above-described problems are achieved by the following (1), (2) and (3).

(1) A lithographic printing ink comprising a resin in a varnish containing a phenol-modified cyclized rubber containing at least 5 to 95% by weight of a component having a molecular weight of 1.5 × 10 ⁴ or more.

(2) The lithographic printing ink as described in (1) above, wherein the proportion of the phenol-modified cyclized rubber in the ink is 5 to 60% by weight.

(3) The lithographic printing ink as described in (1) or (2) above, wherein the ink solvent in the varnish contains a solvent and / or oil having a boiling point of 280 ° C. or higher and an iodine value of 100 or lower.

As the lithographic printing ink of the present invention, a phenol-modified cyclized rubber containing 5 to 95% by weight of a component having a molecular weight of at least 1.5 × 10 ⁴ or more as a varnish resin is used. Therefore, by using the ink of the present invention, a high-quality image free from background stains can be obtained without causing ink sticking to a roller, a blanket or the like.

The present invention will be described in detail below.
In the lithographic printing ink of the present invention, a phenol-modified cyclized rubber containing 5 to 95% by weight, preferably 12.5 to 37.5% by weight, of a component having a molecular weight of 1.5 × 10 ⁴ or more is used as a resin varnish.
If the component having a molecular weight of 1.5 × 10 ⁴ in the phenol-modified cyclized rubber is less than 5% by weight, the soil resistance becomes insufficient, and conversely if it exceeds 95% by weight, poor transfer occurs.

A typical molecular weight distribution of the phenol-modified cyclized rubber in the present invention is schematically shown in FIG. The inventors defined the amount of components having a molecular weight of 1.5 × 10 ⁴ or more in this distribution.
This molecular weight distribution is most easily produced by a blend of a low molecular weight grade phenol-modified cyclized rubber and a high molecular weight grade phenol-modified cyclized rubber. That is, a low molecular weight grade phenol-modified cyclized rubber (Mn is about 2500, Mw is about 8000) and a high molecular weight grade phenol-modified cyclized rubber (Mn is about 5000, Mw is about 23000) are arbitrarily blended, The amount of the component having a molecular weight of 1.5 × 10 ⁴ or more is set to 5 to 95% by weight. As a result, the soil resistance can be improved.

  As the phenol-modified cyclized rubber used in the lithographic printing ink of the present invention, the phenol-modified cyclized rubber conventionally used in the lithographic printing ink can be used, but this conventionally used in the lithographic printing ink. Phenol-modified cyclized rubber is produced by dissolving so-called natural rubber in a phenol-mixed organic solvent and using sulfuric acid or Lewis acid as a catalyst. Due to its natural origin, there are large variations in properties and stable printability. It is difficult to obtain ink. Therefore, it is preferable to use so-called synthetic natural rubber, that is, synthetic polyisoprene in a phenol-mixed organic solvent to produce sulfuric acid or Lewis acid as a catalyst to produce a phenol-modified cyclized synthetic natural rubber. However, the present invention is not limited to the method for producing the phenol-modified cyclized rubber as described above.

The lithographic printing ink of the present invention can be used by blending resins other than phenol-modified cyclized rubber. As resins other than this phenol-modified cyclized rubber, oil-soluble substances that have been added to lithographic printing inks are conventionally used. Resins may be used, specifically, rosin resins such as rosin, polymerized rosin, hydrogenated rosin, rosin ester, hydrogenated rosin ester, rosin modified phenolic resin, rosin modified phenolic resin, rosin modified maleic resin, phenol Resins, petroleum resins, alkyd resins, polymerized castor oil, natural rubber, rubber derivatives, etc. may be used alone or in combination. Moreover, you may gelatinize with what is called gelling agents, such as ethyl acetoacetate aluminum diisopropylate, aluminum octoate, and sodium palmitate.
The amount of the resin other than the phenol-modified cyclized rubber is about 0 to 75% by weight of the varnish resin.

The oil and / or solvent used in the lithographic printing ink of the present invention is fluid under conditions where the boiling point is 280 ° C. or higher (preferably 280 to 400 ° C.) and the iodine value is 100 or lower (preferably 10 to 100). Petroleum oils such as paraffin, spindle oil, light oil, kerosene, machine oil, gear oil, lubricating oil, motor oil; octopus oil, tall oil, corn oil, olive oil, rapeseed oil, castor oil, soybean oil, dehydrated castor oil, Plant oils such as polyisobutylenes, hydrogenated polydecenes, trimethylolpropane esters, neopentyl esters, pentaerythritol esters, siloxanes, silicones, fluorocarbons, alkyl-substituted diphenyl ethers, phthalates, Synthetic oils such as phosphate esters; paraffin , Naphthenic, aromatic, isoparaffinic, and alpha-olefinic petroleum hydrocarbon solvents, such as Exxon Isopar, Nippon Oil Solvent, AF Solvent, Mitsubishi Kasei Dialene, etc .; Plant solvents such as esters, limonene and terpineol can be used. These solvents may be used alone or in combination of two or more.
The amount of oil and / or solvent in the printing ink composition is generally 30 to 50% by weight.

  The colorant is a pigment used in a conventional lithographic printing ink, and any conventionally known pigment can be used as it is as a colorant in the lithographic printing ink composition of the present invention. The amount used may be the same as that of a conventionally known lithographic printing ink. For example, a ratio of about 10 to 40% by weight of the lithographic printing ink is common.

  Dryers include oil-soluble carboxylic acids such as cobalt, manganese, cerium, zirconium, lead, iron, zinc, copper, vanadium, barium, calcium, etc., naphthenic acid, octylic acid, resin acid, tall oil fatty acid, and resins It is a salt of an acid, and these dryers are generally used in a ratio of about 0.005 to 0.5% by weight as a metal in a lithographic printing ink.

The lithographic printing ink of the present invention is not limited to the above-mentioned colorant, resin for varnish, and dryer, but has some additive leveling improvers, thickeners, anti-skinning agents within the range that does not hinder the achievement of the object of the present invention, Known additives can be included.
The method for producing the lithographic printing ink of the present invention as described above may be a conventionally known method.

  The lithographic printing ink of the present invention has a relatively low viscosity (viscosity: 1000 to 3000 Pa), and the use of this makes it possible to obtain a high-quality image free from background stains. The reason why such effects are brought about by the lithographic printing ink using the phenol-modified cyclized rubber is not necessarily elucidated, but is considered as follows.

  Phenol-modified cyclized rubber typically has the structure shown below and is generally two-dimensional compared to rosin-modified phenolic resin, rosin-modified maleic resin, etc., which are usually used in lithographic printing varnish or ink. That is, a linear molecular structure. For this reason, a molecular entanglement phenomenon is likely to occur, and if it is modified with phenol, a hydrogen bonding force is generated between OH groups, and the entanglement of the two-dimensional structure is further strengthened. With such a molecular structure, the cohesive force (that is, viscosity or tack) of the ink is easily maintained with respect to the high share on the printing press, and the ink adhesion to the non-image area is suppressed and the soil resistance is improved.

  The proportion of the phenol-modified cyclized rubber in the lithographic printing ink is preferably 5 to 60% by weight, more preferably 30 to 50% by weight. Thereby, a more desirable image can be obtained.

  The lithographic printing ink of the present invention contains a solvent and / or oil having a boiling point of 280 ° C. or more (preferably 280 to 400 ° C.) and an iodine value of 100 or less (preferably 10 to 100) as an ink solvent. It is advantageous. This is thought to be due to the following.

  That is, (i) when ink having a relatively high viscosity is used, the effect of osmotic drying is small in drying the ink on paper, and evaporative drying is often used to compensate for this. For this evaporation drying, it is necessary to use a volatile organic solvent (initial boiling point: 280 ° C. or lower) having many problems such as flammability, unpleasant odor, and environmental destruction. However, a lithographic printing ink using an oil and / or solvent having an initial boiling point of 280 ° C. or higher and an iodine value of 100 or lower can be expected to penetrate and dry, so that a volatile organic solvent (initial boiling point: 280 ℃ or less) is not necessary. Further, (ii) when an ink having a relatively high viscosity is used, the effect of the osmotic drying is small in the drying of the ink on the paper, and the oxidation polymerization drying is often used to compensate for this. For this oxidative polymerization drying, it is necessary to use an oxidative polymerization oil or solvent that has many problems such as solidification and fixing of the inking roller and blanket due to the remaining ink. However, lithographic printing inks having a boiling point of 280 ° C. or higher and an iodine value of 100 or less and a lithographic printing ink using a solvent can be expected to be osmotic dried with an oxidative polymerization oil or solvent (iodine value: 100 or more). ) Is not necessary.

Next, the present invention will be described specifically by way of examples.
However, the contents of the present invention are not limited to these examples. The parts and% shown below are based on weight.

(Examples 1-3, Comparative Examples 1-2)
Table 1 shows the ink formulation (numbers are% by weight).
Formulations were planned so that the molecular weight distribution of the resin changed, and Examples 1, 2, 3 and Comparative Examples 1, 2 were produced. The production process will be described. After all the oil-soluble resin, oil, and organic solvent are mixed, the mixture is heated to 180 ° C. to create a varnish. A pigment, oil, and an organic solvent were added to this, adjusted and mixed, and then dispersed with a three roll to obtain an ink.

  Table 2 shows the evaluation results.

(1) The tack value was measured as a measure of viscosity, the measuring device was an incometer (digital incometer manufactured by Toyo Seiki Co., Ltd.), and the measurement conditions were 30 ° C./1 minute value / 400 RPM. The printing characteristics (ink adhesion amount and background stain) were obtained from printing with a light offset rotary press AP3700 manufactured by Ricoh Co., Ltd. The printing conditions at that time are 23 ° C./60% and a printing speed of 3 speed.

(2) As a measure of ink transferability, the ink adhesion amount per 1 m ² and the image density were measured, and the image density was measured using a print density measuring device (manufactured by Macbeth, Process Measurement RD915).

(3) As for soiling, it is divided into 5 levels from good ones where no occurrence is observed to those where the occurrence is remarkable, and the best condition is 5, each time it gets worse, 4, 3, 2, 1 It was.

(4) As a measure of paper dryness, set-off is also evaluated, and it is divided into 5 levels from good ones with no occurrence to remarkable ones, with 5 being the best and 4 3, 2, and 1.

(5) In addition, the initial boiling point (ibp) is used for the evaluation of VOC levels including volatile oils and solvents, and to the rollers and blankets when oxidative polymerization oils and solvents are used. The iodine value (iv) is used as a measure of the ink fixing level.
When the minimum ibp temperature of each solvent used in the ink is 280 ° C. or less, volatility is a concern and VOC becomes a problem. When the maximum value of iv of each solvent used in the ink is 100 or more, there is a concern about oxidative polymerization, and ink sticking to a roller or a blanket becomes a problem.

Examples 1 to 3 are ink formulations according to the present invention, which have both a good adhesion amount and a good soiling property. Comparative Example 1 is an ink made of a varnish using a low molecular weight phenol-modified cyclized rubber containing more than 95% of a part having a molecular weight of less than 1.5 × 10 ^4. There is little ground dirt. Comparative Example 2 is an ink made of a varnish using a high molecular weight phenol-modified cyclized rubber containing less than 5% of a portion having a molecular weight of less than 1.5 × 10 ^4. There are few inversions.
In other words, if a varnish for lithographic printing ink containing a phenol-modified cyclized rubber containing at least 5 to 95% by weight of a component having a molecular weight of 1.5 × 10 ⁴ or more is used, the viscosity is relatively low and transferability is excellent. It can be said that there is little scumming while being ink.

(Examples 4-7, Comparative Examples 3-5)
Table 3 shows ink formulations (numbers are% by weight). The ink making process is the same as in Table 1.

  Table 4 shows the evaluation results. The evaluation method of tack value and printing characteristics is the same as in Table 1.

  Examples 4, 5, 2, and 6 are the ink formulations of the present invention, and both a good adhesion amount and a good stain resistance are compatible. Comparative Examples 3, 4, and 5 are inks made of varnish with a phenol-modified cyclized rubber component ratio of less than 5%, and although the image density is good, it is inferior to background stains. Example 7 is an ink made of a varnish in which the component ratio of the phenol-modified cyclized rubber is more than 70%. Although the background stain is good, the image density is inferior. That is, if “the varnish for a lithographic printing ink in which the component ratio of the phenol-modified cyclized rubber according to claim 1 is 5 to 70% by weight” is used, the ink has a relatively low viscosity and excellent transferability. It can be said that there is little dirt.

(Examples 8 and 9)
Table 5 shows ink formulations (numbers are% by weight). The ink making process is the same as in Table 1.

  Table 6 shows the evaluation results. The evaluation method of tack value and printing characteristics is the same as in Table 1.

  In Example 2, a good adhesion amount and a good soiling property are compatible. Ibp and iv are also within the scope of the present invention, and there is no problem of ink sticking to the VOC or roller or blanket. In Example 8, there is no problem in the amount of adhesion and the soiling property, but there is a concern that the maximum iv is 100 or more and the problem of ink sticking to the roller or blanket is concerned. In Example 9, there is no problem in the adhesion amount and the soiling property, but there is a concern about the VOC problem when the minimum ibp is 280 ° C. or less. That is, if “a varnish for lithographic printing ink containing a solvent or oil having a boiling point of 280 ° C. or higher and an iodine value of 100 or lower” is used, VOC does not become a problem because it is not volatile, and there is no oxidation polymerization. For this reason, it can be said that the ink sticking to the roller or the blanket is not a problem.

  The lithographic printing ink of the present invention is useful for both normal offset printing using fountain solution and offset printing without using fountain solution.

It is the figure which represented typically the typical molecular weight of the phenol modified cyclized rubber in this invention.

Claims (3)

A lithographic printing ink comprising a resin in an ink varnish containing a phenol-modified cyclized rubber containing 5 to 95% by weight of a component having a molecular weight of 1.5 × 10 ⁴ or more.   2. The lithographic printing ink according to claim 1, wherein the proportion of the phenol-modified cyclized rubber in the ink is 5 to 60% by weight.   The lithographic printing ink according to claim 1 or 2, comprising a solvent and / or oil having a boiling point of a solvent or an oil in the ink varnish of 280 ° C or higher and an iodine value of 100 or lower.

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