JPH045089A - Desensitizing treatment solution of planographic printing plate and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a desensitizing treatment solution having good stability even when no metal ion is used by compounding a specific sulfosalicylic acid with phytic acid in an aqueous solution. CONSTITUTION:The desensitizing treatment solution of a planographic printing plate using phytic acid as a chelating agent is prepared based on an aqueous solution of a composition prepared by compounding 10-70 pts.wt. of sulfosalicylic acid with 100 pts.wt. of phytic acid so as to have pH 3.0-5.0. When the pH of the desensitizing treatment solution is out of the range of the above mentioned numerical value, background staining is generated in master paper. By together using phytic acid and sulfosalicylic acid as mentioned above, a solution containing a phytic acid-sulfosalicylic acid complex as an effective component is obtained and this desensitizing treatment solution is extremely enhanced in desensitizing function and, since no divalent or more metal salt is used, the trouble caused by the presence of a metal ion is not also generated. This desensitizing treatment solution can sufficiently withstand practical use and can increase the number of master papers possible to withstand printing to a large extent and can highly withstand printing.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a desensitizing treatment liquid for lithographic printing plates, and more specifically to plate materials in which conductive zinc oxide is coated on the surface of a support such as paper. (hereinafter referred to as "master paper"), a lipophilic image is formed by electrophotography, and the stiffness is made into an unfathomable chelating agent using phytic acid, which is used as a lithographic printing plate (original plate for offset printing). This invention relates to improvements in processing liquids and methods for producing the same.

In the following description, the compounding unit is a weight unit unless otherwise specified.

<Prior art> The desensitizing treatment liquid for electrophotographic plates for offset printing contains (
A) It is harmless, (b) Cyanine blue (phthalocyanine copper chelate) can be used in the ink, and (ii) pH adjustment is easy. It is becoming something like that.

As a technique for improving the chelating function of phytic acid, for example, there is a technique proposed in Japanese Patent Application Laid-open No. 1-160691. The description in the claims column is extracted below.

“Ingredients (^), (B) each consisting of the following formulations,
(C): (A) phytic acid or a functional conductor, (B) a dibasic acid or a metal salt thereof, and (C) a compound of the following general formula (I) or a hydrate thereof MXf,
CI) [However, in the above formula, M represents a divalent metal atom, X represents a monovalent or divalent anion, and L represents 1 or 2
[representing an integer of ], a lithographic printing plate desensitization treatment composition containing as an active ingredient.''<Problem to be solved by the invention> However, the desensitization treatment liquid having the above structure has no desensitization effect. However, since it contains metal ions that tend to form salts that are sparingly soluble in water, if the conventional ferrocyane-based desensitization treatment solution is mixed into the working environment, the metal ions become water-insoluble. There was a risk that the water-soluble chelate might become a ferrocyane complex salt, or the water-soluble chelate might change to a water-insoluble chelate, forming a precipitate.

In view of the above, it is an object of the present invention to provide a desensitizing treatment liquid that provides a large desensitizing effect and has good stability without using metal ions, and a method for producing the same. .

<Means for Solving the Problems> The present invention has been made in view of the above, and provides a lithographic printing plate desensitization treatment solution using futic acid as a chelating agent and a method for producing the same, which comprises: A complex is formed by reacting phytic acid with sulfosalcylic acid, and the complex is used as an active ingredient.

Detailed explanation of the method The above means will be explained in detail below.

(a) Phytic acid (also known as inositol hexaphosphate) is
The hydrogen groups at the 2nd-6th or 3rd-5th positions are located on the master vapor in areas other than the image area formed by electrophotography (
By chelating zinc on the surface of the non-image area), the non-image area becomes oleophobic and has an effect of preventing ink (oil-based) from adhering.

Note that this phytic acid is a substance obtained from plant seeds or grains (industrially manufactured from rice cake), and is harmless to animals and plants.

The content of phytic acid is 3% or more, preferably 5% or more in concentration in the desensitizing treatment liquid.

(b) Here, sulfosalcylic acid means 5-sulfosalcylic acid. This is because 4-sulfosalcylic acid is known only as a conductor.Sulfosalcylic acid exhibits acidity in an aqueous solution and coexists with phytic acid. However, when the pH is raised to about 1.7, complexes begin to form between them, and when the pH reaches 12.0 or higher, the formation of complexes is clearly observed. Further, the structure of these complexes changes when the pH becomes 6.0 or more.Although the structure of these complexes is not yet clear, it can be inferred that it is r-electrotransfer complex 1 by measurement using the molar ratio method. Note that the formation of the complex is evident from the red shift of the spectral absorber.

When this complex aqueous solution coexists with zinc oxide, sulfosalicylic acid and zinc exchange with each other, phytic acid and zinc form a water-insoluble chelate, and sulfosalcylic acid is liberated into water again. This is also evident by the blue shift of the spectral absorber.

Although the method disclosed in Japanese Patent Application Laid-Open No. 1-160691 achieves very satisfactory results in terms of functionality, it is difficult to put it to practical use because of the drawbacks mentioned above. The present inventor has made use of this excellent idea and has also attempted to eliminate the fundamental drawbacks of this method. That is, since chelate exchange is intended, the material must be a chelate. If it is a chelate, the coordination at the center must be a metal. In order for this coordinated metal to exchange with zinc, it must be a divalent or higher metal ion, considering the chelation constant. The inventor conducted further tests and found that chromium (III) is the best metal ion, and cobalt (III) is the second best. The basic problem is that the presence of metal ions is unavoidable.
Theoretically, the above drawbacks are unavoidable. The present inventor sought to find out whether this chelate could be converted into a suitable organic compound. Of course, there is no way that chelates can be formed with organic compounds that do not contain metals. Therefore, it goes without saying that we must change our way of thinking.

(c) Forming a water-insoluble white complex precipitate with phytic acid and salicylic acid. However, the complex is slightly soluble in water. This reaction appears to be unique to salicylic acid (salicylic acid has -OH and -COOH in one benzene nucleus). Phenol that only has -OH in the benzene nucleus does not form a complex, and -COO)! No complex is formed even with benzoic acid, which has only

Therefore, we focused on the fact that the complex formed from phytic acid-salicylic acid is slightly soluble in water, and if we introduce a group (radical) with an extremely high dipole moment into this same benzene nucleus, the complex will dissolve in water. I thought it would be. Based on the above thought process, we selected sulfosalicylic acid, and as a result of experiments, we were able to obtain a water-soluble complex as we had envisioned.

Also, this complex is phytic acid/sulfosalicylic acid = 1/
1 and 1/2 complexes are formed. Phytic acid exchanges smoothly with zinc to form a water-insoluble chelate with zinc, and sulfosalcylic acid is liberated.

Here, the blending amount of sulfosalcylic acid to 100 parts of phytic acid is 10 to 70 parts (molar ratio of about 0.5 to about 2.0). If the amount of sulfosalcylic acid is less than 10 parts, the effect of addition is very weak, and if it exceeds 70 parts, it does not contribute to the formation of the complex and is meaningless.

In addition, the pH of the desensitization treatment liquid is pH: 3.0 to 6.0.
(preferably pH: 3.8 to 5.0). If the pH of the desensitizing solution is out of the above numerical range, scumming will occur on the master vapor.

The above-mentioned alkali as a pH adjuster includes alkali metal ions (Li, Na, K, etc.), non-metal alkali ions (
Ammonia; various ethanols such as monoethanolamine, jetanolamine, and triethanolamine; amines; various amines such as monomethylamine, dimethylamine, trimethylamine, ethylenediamine, propylene diamine, and phenylene diamine) may be used; When diluting the desensitizing treatment liquid and using it as a dampening water, an alkali metal salt is preferable because it does not cause abnormal emulsification (so-called watering) in the ink used during printing. In addition, the above-mentioned alkalis may be used alone or in combination of two or more kinds.

(d) In addition, when preparing the present desensitizing treatment liquid, the following chemicals (d-1) to (d-7) can be added as necessary.

(d-1) Starch (soluble starch, including dextrin type)
and derivatives thereof, fiber conductors, sodium polyacrylate, gum arabic, pullulan, and other commonly used glues.

(d-2) Polyose-based wetting agents such as ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, glycerin sorbitol, glucose, and sugar.

(d-3) Commonly used organic acids such as citric acid, malonic acid, succinic acid, adipic acid, tartaric acid, and phthalic acid, and their salts, and preservatives such as benzoic acid and dihydroacetic acid.

(d-5) Auxiliary agents such as aromatic sulfonic acids and salts thereof having a sulfo group introduced into the aromatic ring such as benzene and toluene.

(d-6) Interfacial tension modifiers such as lower alcohols, ethers, ketones, cellosolves, and methyl esters of lower fatty acids.

(d-7) Coloring pigment.

<Effects of the Invention> The desensitizing treatment liquid of the present invention and the method for producing the same can obtain a product containing a phytic acid-sulfosalcylic acid complex as an active ingredient by using phytic acid and sulfosalcylic acid together as described above. As shown in the examples below, the desensitizing treatment liquid has extremely improved desensitizing function, and since it does not use metal salts of divalent or higher valence, there are no problems caused by the presence of the metal ions. .

As shown in the examples below, the desensitizing liquid for lithographic printing of the present invention not only has sufficient practical durability, but also greatly increases the number of printable sheets of master paper. That is,
The present invention aims to provide a new practical desensitization treatment solution that can withstand high printing durability.

・<Example> Hereinafter, in order to confirm the effects of the present invention, test examples that were conducted along with comparative examples will be explained.
Aqueous solutions of the formulations shown in Tables 1 and 2 were adjusted to p)I: 4.2 to 4.3 using the indicated alkalis to prepare desensitizing treatment solutions for each example and comparative example. did.

Each desensitization treatment solution was applied to a master paper made of a plate, and the solution was diluted 20 times with water to make a damp wood.

Then, printing was performed on neutral paper using a printing ink (Master Blue: ■trade name manufactured by Nikken Kagaku Kenkyusho) using a normal offset printing machine.

5,000 sheets of offset printing was performed for each sheet of master paper (guaranteed print life = 3,000 sheets). In the case of the treatment liquid of each example, good printed matter was obtained without any scumming or other abnormalities on the master vapor up to 5,000 sheets. On the other hand, when the processing liquids of each comparative example were used, scumming occurred in the non-printing areas of the master paper and printing paper from the beginning of printing, and they were not suitable for practical use.

Further detailed examination of each master vapor after printing in each example revealed that the influence on the toner in the image area was abnormally small. This phenomenon occurs because there is no free phytic acid in the aqueous solution, and all of it is protected by forming a complex with sulfosalcylic acid, so the chemical impact on the toner (resin: organic polymer) is significantly weakened. It is estimated that this is due to

In each of the above examples, after printing 5,000 sheets, printing was continued for an additional m, but even after printing a total of 10,000 sheets, printing was possible with no printing stains occurring on the printing paper.

Furthermore, the properties of damp wood were better in those to which a polar solvent was added (Examples 17 and 18). In addition, in Examples 6 to 12, in which a desensitizing solution using an organic alkali as a pH 8 formulation was diluted and used as a dampening solution, some abnormal emulsification was observed in the ink used during printing, but the printed matter was There was no effect.

Den　　　　　〷 (JL rank 2nd division) Chest 2 Male (-11th place/division)

Claims (1)

[Claims] 1. In a desensitizing treatment solution for lithographic printing plates using phytic acid as a chelating agent, 10 parts by weight of sulfosalicylic acid is added to 100 parts by weight of phytic acid.
The main component is an aqueous solution of a composition containing ~70 parts by weight,
A desensitizing treatment liquid for lithographic printing plates, which is adjusted to have a pH of 3.0 to 5.0. 2. In a method for producing a desensitizing solution for lithographic printing plates using phytic acid as a chelating agent, a complex consisting of phytic acid and sulfosalicylic acid is generated in an aqueous solution, and p
A method for producing a desensitizing treatment liquid for a lithographic printing plate, characterized in that the desensitization treatment liquid for a lithographic printing plate is produced by adjusting H: 3.0 to 5.0.