JPS63131150A - Desensitization processing liquid - Google Patents

Abstract

PURPOSE:To enhance the desensitization power and buffer power of the titled processing liquid by using a specific processing liquid contg. inositol hexaphosphoric acid (salt) as a chief material. CONSTITUTION:(A) the inositol hexaphosphoric acid (salt), (B) colloidal silica, (C) water soluble Zr compd. (salt) and (D) org. acid (salt) are incorporated into the titled processing liquid. The grain size of the component B is preferably <=0.1mu and the content thereof is 1-5wt% of the component A. The component C consists of acetate or nitrate of Zr and the content thereof is preferably <=5wt% of the total amt. The component D consists of divalent and higher polybasic org. acid (salt) and the content thereof is preferably 0.5-10wt% of the total amt. A stable hydrophilic desensitized film is thereby early formed and further, the buffer power is improved, by which adaptability to neutral paper is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a desensitizing liquid used in plate making of electrophotographic lithographic printing original plates.

Traditionally, the desensitizing treatment liquid used for plate making of electrophotographic lithographic printing original plates has been mainly composed of ferrocyan salts and phosphates because of its fast reaction rate and strong desensitizing power. Although it is commonly used, it has good stability against heat and light, and because it contains cyanide ions, it has the disadvantage of being subject to wastewater regulations.

Therefore, in order to improve these drawbacks, a desensitizing liquid containing phytic a (inositohexalic acid) as a main ingredient has been proposed in Japanese Patent Publication No. 45-24609, etc. However, phytic acid alone has no fat desensitizing ability. It was weak and impractical.

Therefore, Japanese Patent Publication Nos. 53-83806 and 53-109
No. 701, No. 53-127003, No. 54-4490
1, No. 57-27840, etc., or form an ionic complex with a water-soluble cationic polymer as in No. 58-579! However, the desensitization rate was still slow, and a satisfactory desensitization ability could not be obtained with just one pass through the etching processor.

Furthermore, in order to improve this drawback, proposals have been made in Japanese Patent Application Laid-open Nos. 59-207290, 60-23098, 60-23099, etc. to speed up the reaction speed, but this has not yet reached a satisfactory level. do not have.

On the other hand, acidic paper based on rosin-sulfuric acid band size has been used as printing paper so far.

In recent years, due to the problem of paper deterioration during storage, there has been a shift to acid-free paper that uses calcium carbonate as a filler.As a result, conventional processing liquids have been found to lack durability and cause printing stains, making them unusable. It's here. That is, when printing is performed using neutral paper, substances used as fillers are eluted into the dampening water, and the pH value of the dampening water increases.

It is thought that staining occurs as a result of promotion of ink emulsification and loss of stability of the desensitized film on the plate surface.

Purpose An object of the present invention is to provide a desensitizing liquid that improves the desensitizing speed and desensitizing power, and also increases the buffering power so that it can be applied to neutral paper.

Composition The desensitizing treatment liquid of the present invention is characterized by containing inositohexalic acid or its salt, colloidal silica, a water-soluble zirconium compound, and an organic acid or its salt.

Inositohexalic acid (hereinafter simply referred to as phytic acid) or a salt thereof used in the desensitizing treatment solution of the present invention can be synthesized by a known method, and commercially available products are also available. As a phytate, the 1.4 position of butic acid is Ca, Ba, Mg, Co.
, Mn, and other divalent metals are preferred.

The colloidal silica preferably has a grain size of 061 μm or less in terms of forming a film on the printing plate after coating.

As the water-soluble zirconium compound, inorganic acid salts and organic acid salts of zirconium are selected, and acetates and nitrates are particularly preferred because they particularly improve the desensitization reaction rate.

Examples of organic acids or salts thereof include polybasic acids such as citric acid, malonic acid, adipic acid, tannic acid, tartaric acid, malic acid, and succinic acid, and salts thereof.

The usage amount of the above components is 1 to 15% for phytic acid or its salt, 1 to 5% for colloidal silica to phytic acid or its salt, and 0.5 to 5% for water-soluble zirconium compound organic acid or 0 for the salt.
5 to 10% is appropriate. Further, the pH of the desensitizing liquid containing these components is preferably 3 to 6.

In the present invention, phytic acid or its salt is used as the main agent for desensitization, and colloidal silica and water-soluble zirconium compounds improve the desensitization reaction rate of phytic acid or its salt, resulting in rapid hydrophilization (by coating the printing plate). ), and organic acids or their salts are used as aids to increase the buffering power for neutral paper.

The desensitizing liquid of the present invention may further contain glycerin, ethylene glycols, nrubitol, etc. as wetting agents, sodium dehydroacetate, salicylic acid, sorbic acid, potassium, amines, etc. as preservatives, and hydrophilic agents as necessary. Phosphoric acid and its salts, etc., and KOH, N as a pH adjuster.
aOH.

NH4OH etc. can be added.

The present invention will be explained below by way of examples. All parts are by weight.

Example 1 Dimagnesium phytate 70 parts Colloidal silica (average particle size 0.05μ) 3 parts Zirconium acetate 12 parts Malic acid
10 parts water
A solution consisting of 905 parts of NaOH
The pH was set to 4.5.

Example 2 Phytic acid 80 parts Colloidal silica (average particle size 0.05μ) 4 parts Zirconium nitrate 10 parts Succinic acid
15 parts water
A solution consisting of 891 parts of NaO
The pH was adjusted to 4.0 with H.

Example 3 Colloidal silica (average particle size 0.05μ) 3 parts zirconium acetate 10 parts tartaric acid
12 parts water
A solution consisting of 915 parts was adjusted to pH=4.5 with NaOH.

Example 4 Phytic acid disodium salt 80 parts Colloidal silica (average particle size 0.05μ) 3 parts Zirconium nitrate 12 parts Citric acid
5 parts citric acid disodium salt
5 parts water
A solution consisting of 895 parts was pH adjusted with NaOH.
= 4.0.

Example 5 Phytic acid dicalcium salt 75 parts Colloidal silica (average particle size 0.05μ) 3 parts Zirconium acetate 10 parts Maleic acid
15 parts water
A solution consisting of 897 parts was diluted with NaOH.
The pH was set to 4.5.

Example 6 Dimanganese phytate 70 parts Colloidal silica (average particle size 0.05μ) 3 parts Zirconium acetate 12 parts Succinic acid
10 parts water
A solution consisting of 905 parts Na0)
The pH was adjusted to 4.5 with 1 liter of water.

Comparative Example 1 Phytic acid 70 parts water
A solution consisting of 930 parts was adjusted to P)l=4.5 with NaOH.

Comparative Example 2 A solution consisting of 70 parts of phytic acid, 3 parts of colloidal silica (average particle size 0.05 μm), and 3 parts of water was adjusted to pH=4.5 with NaOH.

Comparative Example 3 Phytic acid 70 parts Colloidal silica (average particle size 0.05μ) 3 parts Siliconium acetate 12 parts Water
A solution consisting of 915 parts was adjusted to pH=4.5 with NaOH.

Comparative Example 4 Dimagnesium phytate salt 70 parts water
A solution consisting of 930 parts was adjusted to pH=4.5 with NaOH.

Comparative Example 5 Dimagnesium phytate salt 70 parts Colloidal silica (average particle size 0.05μ) 3 parts Water
A solution consisting of 927 parts was adjusted to pH=4.5 with NaOH.

Comparative Example 6 Dimagnesium phytate salt 70 parts Colloidal silica (average particle size 0.05μ) 3 parts Zirconium acetate 12 parts Water
A solution consisting of 915 parts of N
The pH was adjusted to 4.5 with aOH.

The desensitization reaction rate and suitability for use with neutral paper were evaluated for each desensitization treatment solution obtained as described above.

Evaluation of reaction rate: After wet development, the electrophotographic planographic printing plate (Kofax Master LDL manufactured by Ricoh Co., Ltd.) was passed once through an etching processor (manufactured by Ricoh Co., Ltd.) containing the sample, and then immediately passed through an etching processor (manufactured by Ricoh Co., Ltd.) containing a sample. (AP 4600), printing was performed (using neutral paper), and evaluation was made based on the degree of staining of the printed matter.

O: No stains at all ×: Full background stains Applicability to neutral paper: As in the reaction rate evaluation, the lithographic printing plate after wet development was passed through the etching processor containing the sample three times to ensure complete insensitivity. After turning into fat.

Evaluation was made based on the number of printed sheets until staining occurred when lithographic printing was performed using dampening water mixed in a ratio of water 5:sample 1 (volume ratio).

0: Over 3,000 sheets without staining, good adaptability x: 2
00 to 300 sheets, resulting in poor adaptability.As described above, the desensitizing treatment solution of the present invention has a reaction rate that increases by combining colloidal silica and a water-soluble zirconium compound with phytic acid or its salt. It has the advantage of quickly forming a stable hydrophilic and fat-insensitive film, and by adding an organic acid or its salt, it improves adaptability to neutral paper and does not cause printing stains. .

Claims (1)

[Scope of Claims] 1. A desensitizing treatment liquid characterized by containing inositohexalic acid or its salt, colloidal silica, a water-soluble zirconium compound, and an organic acid or its salt. 2. The desensitizing treatment liquid according to claim 1, wherein the colloidal silica has a grain size of 0.1 μ or less, and its content is 1 to 5% by weight of inositohexalic acid or its salt. . 3. The content of the water-soluble zirconium compound is 5 of the total amount.
% or less by weight of the desensitizing liquid according to claim 1. 4. Desensitization according to claim 1, wherein the organic acid or its salt is a divalent or higher polybasic organic acid or its salt, and the content thereof is 0.5 to 10% by weight of the total amount. processing liquid.