JPS62127288A - Damping water composition for use in planography - Google Patents

Abstract

PURPOSE:To form a water film accurately on non-image parts of a printing plate while using a small quantity of damping water, by using the titled composition prepared by mixing phytic acid, a chelating agent for chelating metallic aluminum and a water-soluble high molecular weight compound. CONSTITUTION:Phytic acid, a chelating agent for chelating metallic aluminum and a water-soluble high molecular weight compound are mixed to prepare the titled composition in the form of granules or an aqueous solution. It is preferable to mix 1pt.wt. of phytic acid with about 0.3-0.7pt.wt. of the chelating agent and about 1-2pt.wt. of the water-soluble high molecular weight compound. Damping water can be prepared by dissolving 1pt.wt. of the composition in about 50-100pts.wt. water. The chelating agent may be ethylenediamine tetraacetic acid or the like, and the water-soluble high molecular weight com pound may be polyvinyl alcohol, sodium alginate or the like.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a dampening solution composition for use in lithographic printing, and is a dampening solution that can provide a dampening solution with good water film retention. The present invention relates to a water composition.

(b) Problems to be solved by the prior art and the invention In lithographic printing, dampening water is applied to the non-image areas of the lithographic printing plate in order to prevent staining of the print. . This dampening water is required to have the property of being able to accurately form a water film in a small amount on non-image areas.

This is because if a large amount of dampening water is supplied to the non-image area, water may enter the image area and cause printing errors.

Conventionally, water-soluble polymers such as polyvinyl alcohol are added to dampening water to reduce the amount of dampening water supplied, thereby suppressing evaporation of the dampening water.

However, although this method only supplies a small amount of dampening water,
The property of accurately forming a water film in non-image areas was not sufficiently exhibited. In other words, the water film is disturbed during printing,
This sometimes caused stains on printed matter.

Therefore, the present invention aims to accurately form a water film in a small amount on non-image areas.
It is an object of the present invention to provide a dampening solution composition that can be retained.

(c) Means and effects for solving the problems, that is, the present invention provides a dampening solution for use in lithographic printing characterized by containing a chelating agent that chelates phytic acid and aluminum metal, and a water-soluble polymer. This dampening solution composition is handled in the form of granules or in the form of an aqueous solution.

Phytic acid used in the present invention is also called inosic acid or tohexaric acid, and is a viscous liquid compound that is easily soluble in water and has a large affinity for water.

Chelating agents for chelating aluminum metal used in the present invention include butane-1,2,3,4-tetracarboxylic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, pentamethylenediaminetetraacetic acid,
Examples include cyclopencune-1,2-diaminetetraacetic acid, cyclohexane-1,4-diaminetetraacetic acid, and 2-hydroxytrimethylenediaminetetraacetic acid. Among these, ethylenediaminetetraacetic acid (rE
DTAJ) is the most preferred because it has an excellent chelating effect, is inexpensive, and is easily available. be.

The water-soluble polymer used in the present invention is polyvinyl alcohol (hereinafter referred to as "PVA").

Examples include polyacrylic acid, sodium alginate, carboquine methylcellulose, and the like. This water-soluble polymer has the effect of suppressing the release of water.

The dampening solution composition according to the present invention contains about 0.3 to 0.7 parts by weight of a chelating agent and about 1 to 2 parts by weight of a water-soluble polymer per 1 part by weight of phytic acid. Chelating agent is 0.
When the amount is less than 3 parts by weight, the ability to capture aluminum metal falling off from the thin aluminum plate that is the support of the lithographic printing plate tends to decrease. Further, even if the chelating agent is added in an amount exceeding 0.1 part by weight, the ability to capture aluminum metal tends not to improve much. If the amount of the water-soluble polymer is less than 1 part by weight, the ability of water to prevent seedlings will tend to decrease, and if it exceeds 2 parts by weight, the viscosity of the dampening solution will tend to increase.

The dampening water composition according to the present invention can be prepared by dissolving 1 part by weight of the dampening water composition according to the present invention in about 50 to 100 parts by weight of water.The dampening water composition according to the present invention can be handled in the form of granules. When using, it may be dissolved in water as a dampening solution, or when using a liquid dampening solution composition (undiluted solution) dissolved in a small amount of water,
It may be further diluted and used as dampening water.

(d) Examples A dampening solution was prepared using the blending ratios shown in Table 1 below.

For comparison, a dampening solution containing no phytic acid or chelating agent was also prepared.

Table 1 (Unit: parts by weight) These dampening waters were supplied to a lithographic printing plate to form a water film on the non-image area. Thereafter, the supply of dampening water was cut off, and proof printing was performed under the same conditions while supplying printing ink. As a result, in Examples 1 to 3, 11 proof sheets could be obtained.
Eight proof sheets were obtained in Example 4, and seven proof sheets were obtained in Example 5.

On the other hand, in the comparative example, it was possible to obtain 5 proof sheets, and the printing stains became noticeable from the 6th sheet onward.

As is clear from this, when the dampening water according to the example was used, the amount of water in the non-image area was about 1.5 to 2 times that when using the conventional dampening water (comparative example). It can be seen that the film has excellent retention properties.

(e) Effects of the invention The dampening solution obtained using the dampening solution composition according to the present invention has good water film retention because it contains phytic acid, which has a high affinity with water. .

The chelating agent then captures the aluminum metal that falls off from the thin aluminum plate that is the support for the lithographic printing plate.
Water-soluble polymer suppresses dampening water from forming stems. As a result of these synergistic effects, the water film formed in the non-image area is better retained and undisturbed during printing, so that it is less likely to stain the print.

Furthermore, compared to conventional dampening water, it is possible to print more prints with the same amount of dampening water, so the amount of dampening water supplied during printing can be reduced.

Claims (2)

[Claims] (1) A dampening solution composition for use in lithographic printing, characterized by containing a chelating agent that chelates phytic acid and aluminum metal, and a water-soluble polymer. (2) A dampening solution composition for use in lithographic printing according to claim (1), which is in the form of an aqueous solution.