JP4432542B2 - Dampening solution for lithographic printing - Google Patents

Description

  The present invention relates to a fountain solution for lithographic printing.

In lithographic printing, both water and ink are supplied to the printing plate, and the image area selectively receives colorable ink and the non-image area selectively receives water, and the image area ink is transferred to a substrate such as paper. Is made by letting. Therefore, in order to obtain a good printed matter, the difference between the surface lipophilicity and hydrophilicity of the image area and the background non-image area is sufficiently large, and when water and ink are applied, the image area should have a sufficient amount of ink. It is necessary that the accepting and non-image parts do not accept ink at all. Therefore, various desensitizing methods have been studied according to the respective plate materials and printing methods.
In the lithographic printing method, water called dampening water is supplied to the printing plate in advance. This water forms a uniform thin water film on the non-image area, and this water film prevents ink from adhering to the non-image area. Such dampening water is required to have an appropriate surface tension, and an aqueous solution of isopropyl alcohol having a concentration of 5 to 20% by weight has been conventionally used.
However, since this isopropyl alcohol is different from water in easiness of evaporation, a special expensive apparatus for keeping the isopropyl alcohol concentration of the dampening solution constant is required. In addition, isopropyl alcohol has a peculiar unpleasant odor and has problems in toxicity, and is subject to the organic regulations of the Industrial Safety and Health Act. Furthermore, since it is a compound that is easily flammable, it falls under the category of dangerous materials under the Fire Service Act, and care and handling management are required, which is undesirable in the work environment.

For this reason, the dampening water which does not contain isopropyl alcohol has been desired. In order to achieve these objects, for example, a fountain solution containing a propylene oxide adduct of a polyhydric alcohol such as a propylene oxide adduct of glycerin, sorbitol, 3methylpentane-1,3,5-triol (Patent Document) 1). These fountain solutions are not suitable for long-run printing to print more than 10,000 sheets by themselves, so use volatile organic solvents such as tetrapropylene glycol monomethyl ether, 3-methyl-2-methoxybutanol, and methyl carbitol together. It is difficult to say that it is sufficient in terms of safety and health.
On the other hand, the fountain solution should be one that does not lose its stability under normal storage conditions. For example, there is a problem that stability at low temperatures in winter and high temperatures in summer is lowered, and a large burden is required for management of storage conditions.

Japanese Patent Laid-Open No. 5-221179

  An object of the present invention is to provide a fountain solution that has a stable performance during printing without substituting isopropyl alcohol and losing its function due to freezing in winter and high temperatures in summer.

That is, the present invention
A lithographic printing dampening solution comprising a compound represented by formula (1).
_{R [O (CH 2 CH 2} CH 2 CH 2 O) n (CH 2 CH 2 O) m] l H (1)
(In the formula, R is a residue of a compound having 1 to 6 hydroxyl groups, n is an average addition mole number of an oxytetramethylene group, m is an average addition mole number of an oxyethylene group, and n is 1 to 1) 4, m is 1 to 6, l is 1 to 6, and the oxytetramethylene group and the oxyethylene group are bonded randomly.
Further, it is a lithographic printing dampening solution in which R is a residue of glycerin.

  Since the fountain solution for lithographic printing of the present invention does not contain isopropyl alcohol, it can ensure safety and hygiene, and has excellent storage stability at low temperatures in winter and high temperatures in summer. Can be provided.

  In the compound represented by formula (1) of the present invention, R is a residue of dehydroxylation of a compound having 1 to 6 hydroxyl groups. Examples of the compound having 1 to 6 hydroxyl groups include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and butyl alcohol as monovalent alcohols; ethylene glycol, diethylene glycol, triethylene glycol as divalent alcohols, Propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol; glycerin, trimethylolpropane, hexatriol as trivalent alcohol; pentaerythritol, sorbitan, methylglucoside as tetravalent alcohol; as hexavalent alcohol Examples include sorbitol. A trivalent to hexavalent alcohol is preferable.

The oxytetramethylene group and oxyethylene group to be added to the compound having 1 to 6 hydroxyl groups are bonded at random, and can be a suitable fountain solution for lithographic printing.
n is the average number of moles added of the oxytetramethylene group, and n is 1 to 4, preferably 1 to 3.
m is an average addition mole number of an oxyethylene group, m is 1-6, Preferably it is 2-4.
By setting the oxytetramethylene group and the oxyethylene group in the above range, a dampening solution with good stability can be obtained.
l is 1-6, Preferably it is 3-6.
Moreover, the oxytetramethylene group and the oxyethylene group of the compound represented by the formula (1) are bonded in a random manner. The average molecular weight of the polyether part (total molecular weight of [(CH ₂ CH ₂ CH ₂ CH ₂ O) _n (CH ₂ CH ₂ O) _m ] _l ) is preferably 1200 or less. Moreover, when the average molecular weight of the polyether part of the compound represented by Formula (1) is larger than 1200, the solubility in water tends to decrease, which is not preferable. The amount added to the fountain solution is preferably 1 to 10% by weight.

In the dampening water of the present invention, components such as glycols or glycol ethers, water-soluble polymer compounds, surfactants, pH buffering agents, preservatives, rust preventives, colorants, and fragrances are added as necessary. be able to.
Examples of the glycol or glycol ether include glycerin, polyglycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, hexylene glycol, (mono, di, tri, poly) ethylene glycol dimethyl ether, (mono , Di, tri, poly) ethylene glycol monomethyl ether, (mono, di, tri, poly) ethylene glycol monoethyl ether, (mono, di, tri, poly) ethylene glycol monobutyl ether, and the like. When these glycols or glycol ethers are added, they may be used alone or in combination of two or more compounds, and the addition amount to the fountain solution for lithographic printing is preferably 1 to 15% by weight.

Examples of the water-soluble polymer compound include starch derivatives such as gum arabic and dextrin, fiber derivatives such as alginate and methylcellulose, and modified products thereof. When the water-soluble polymer compound is added, the amount added to the dampening water for lithographic printing is preferably 1 to 5% by weight.
Examples of the surfactant used in the present invention include an anionic surfactant and a nonionic surfactant. When a surfactant is added, the amount added to the dampening water for lithographic printing is preferably 0.5 to 5% by weight.
Examples of the pH buffering agent include citric acid, ascorbic acid, malic acid, tartaric acid, lactic acid, acetic acid, gluconic acid, hydroxyacetic acid, oxalic acid, malonic acid, p-toluenesulfonic acid, and the like. Examples of the inorganic acid include phosphoric acid, nitric acid, sulfuric acid, and polyphosphoric acid. Further, alkali metal salts, alkaline earth metal salts or ammonium salts of these organic acids or inorganic acids are also included. When adding a pH buffering agent, the amount added to the dampening water for lithographic printing is preferably 0.1 to 2% by weight.
Examples of preservatives include parapenes (paraoxybenzoic acid esters), phenol or derivatives thereof, formalin, imidazole derivatives, quaternary ammonium salts, and the like.
Examples of the rust preventive include benzotriazole, 5-methylbenzotriazole, thiosalicylic acid, benzimidazole, and derivatives thereof.
The fountain solution for lithographic printing of the present invention is supplied 100-fold diluted with pure water using, for example, a continuous water supply type Dahlglen fountain solution supply device, and is generally used for an offset rotary printing press and printing. It can be used for printing using a machine.

A stability test was performed using the fountain solution for lithographic printing shown in Tables 1 and 2.
In Table 2, the fountain solution was diluted with water and adjusted to a total of 1 kg.
In the stability test, 1 kg of dampening water in Table 2 was stored in a refrigerator set at −5 ° C., a warehouse without air conditioning, and a temperature-controlled room set at 50 ° C. for 6 months, and the liquid state was observed. At that time, a stable product was indicated as “◯”, a liquid was turbid and Δ was slightly precipitated, and a sample that was completely turbid and precipitated was indicated as “X”.

  As a result, it was proved that the dampening water of the example of the present invention was excellent in low temperature and high temperature stability as compared with the dampening water of the comparative example.

Claims (2)

A lithographic dampening solution comprising a compound represented by the formula (1):
_{R [O (CH 2 CH 2} CH 2 CH 2 O) n (CH 2 CH 2 O) m] l H (1)
(In the formula, R is a residue of a compound having 1 to 6 hydroxyl groups, n is an average addition mole number of an oxytetramethylene group, m is an average addition mole number of an oxyethylene group, and n is 1 to 1) 4, m is 1 to 6, l is 1 to 6, and the oxytetramethylene group and the oxyethylene group are bonded randomly.   The lithographic printing dampening solution according to claim 1, wherein R is a residue of glycerin.