JPH01269594A - Plate surface protective agent for planographic plate - Google Patents

Abstract

PURPOSE:To enable a reduction in the amount of spoilage, even in the case of rotary offset printing or other printing in which ink removal property is poor in the beginning of the printing, by using a planographic plate protective agent comprising an aqueous solution containing a surfactant and a specified amount of a water-soluble high molecular weight compound. CONSTITUTION:A plate surface protective agent comprises an aqueous solution containing a surfactant and a specified amount of a water-soluble high molecular weight compound, the specified amount being 0.01(inclusive)-1.0(exclusive)wt.% based on the total weight of the protective agent. The surfactant may be anionic, nonionic, ampholytic or cationic surfactant. The water-soluble high molecular weight compound may be, for example, natural gum arabic or a synthetic high molecular weight compound such as a cellulose derivative (e.g., methyl cellulose), polyvinyl alcohol and polyvinyl pyrrolidone.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a plate surface protective agent for lithographic printing plates.

[Conventional technology]

When making a lithographic printing plate, in the final step, a plate surface protectant (so-called gum liquid) is applied to protect the non-image area and the image area. This process is called gumming.

The purpose of gumming is not only to protect the hydrophilicity of the non-image area, but also to make corrections such as adding or erasing the image area, to preserve it after plate making until printing or to preserve it until reuse, and to protect it when installing it on a printing machine. The objective is to protect the printing plate from stains and scratches caused by adhesion of marks, oil, fat, dust, etc. during handling, and to suppress the occurrence of oxidation stains. Conventionally, gum liquid compositions used as plate surface protectants for lithographic printing plates are usually made of gum arabic, cellulose gum, or an aqueous solution of a water-soluble polymeric substance having a carboxyl group in the molecule. It also contains pH adjusters, preservatives, etc. as necessary.

Gumming methods include pouring a gum solution onto the plate, spreading it over the entire plate surface with a sponge or cotton tampon, and rubbing it with a wiping cloth until the plate surface is dry; an automatic gum application process that is carried out after development and washing; Examples include automatic gumming treatment performed immediately after development without washing with water, and automatic gumming treatment performed after development with a rinsing solution containing a surfactant.

The printing plate made in this way is attached to a printing machine and printed according to the following procedure.

Sheet-fed printing is a method in which the gum on the plate surface is removed with a water rod such as a Molton roll at the time of printing, and then an ink roll is applied to the plate surface for printing. (Waste paper refers to printed matter that has no commercial value, such as printed matter where the ink density in the image area of the printed matter is faint or the non-imaged area is dirty.)

However, when printing begins, an ink roll is attached to the printing plate, ink is applied to the entire printing plate, and immediately after that, a water rod is applied to the printing plate.
In the case of printing methods such as off-wheel printing, in which printing is performed by removing ink from the plate surface, conventionally known gum liquids have poor ink removability because the ink adheres to the gum in the non-image area. There is a problem in that there is a very bad problem in that there is a large amount of waste paper with dirty non-image areas.

Various methods have been tried to reduce the amount of paper wasted due to this phenomenon, which would result in significant cost reductions.

For example, methods are being considered that include removing gum with a sponge or the like before printing starts, or supplying more water to the printing plate at the start of printing than during normal printing to make it easier to remove gum. However, these methods are undesirable because they complicate the work, reduce workability, and cause troubles due to paper breakage.

[Problem to be solved by the invention]

Therefore, an object of the present invention is to provide a plate surface protectant that can reduce paper waste even in printing methods such as off-wheel printing that have poor ink removability at the beginning of printing.

Still another object of the present invention is to provide a good plate surface protectant for lithographic printing plates that will not be scratched or smeared with fingerprints during handling during the period from plate making to printing. A further object of the present invention is to provide a printing plate protectant that causes less staining on the blanket during printing and also causes less printing stains when printing is restarted after the printing press has stopped.

As a result of intensive research to achieve the above objective, the present inventors have
This is what led to the present invention.

[Means to solve the problem]

The object of the present invention is to protect lithographic printing plates from an aqueous solution containing a surfactant and a water-soluble polymer compound in an amount of not less than 0.01% by weight and not less than 1.0% by weight based on the total weight of the plate surface protectant. This can be achieved by using agents.

The plate surface protective agent in the present invention needs to contain a surfactant as one of the active ingredients. Surfactants that can be used include anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants.

For example, anionic surfactants include fatty acid salts, alkylbenzene sulfonates, linear alkylbenzene sulfonates, alkyl sulfates, α-olefin sulfonates, alkyl phosphate ester salts, dialkyl sulfosuccinate ester salts, and polyoxyethylene alkyl ethers. Sulfates, polyoxyethylene alkyl ether phosphates, alkylnaphthalene sulfonates,
Examples include N-lauroylsarcosine salts, sulfonates of naphthalene-formalin condensates, and diphenyl ether disulfonates. Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene polyoxypropylene block polymers, polyoxyethylene sorgokune fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyethylene glycol These include fatty acid esters, polyoxyethylene fatty acid amines, fatty acid monoglycerides, sorbitan fatty acid esters, penquerythritol fatty acid esters, sucrose fatty acid esters, and amine oxides.

Examples of amphoteric surfactants include alkylcarboxybetaine types, alkylaminocarboxylic acid types, and alkylimidacillin types. Examples of cationic surfactants include tetraalkylammonium salts, trialkylbenzylammonium salts, and alkylimidazolinium salts. Other examples include fluorine-based surfactants and silicone-based surfactants.

Among the surfactants, anionic surfactants and/or nonionic surfactants are particularly effective. Two or more of these surfactants can also be used in combination.

The amount used is not particularly limited, but the preferred range is 1 to 50% by weight (hereinafter abbreviated as %) of the plate surface protective agent. More preferably it is 2 to 45%.

The plate surface protective agent in the present invention needs to contain a water-soluble polymer compound as one of the active ingredients.

Examples of water-soluble polymer compounds that can be used include natural gum arabic, methylcellulose, ethylcellulose,
Cellulose derivatives such as hydroxyethyl cellulose and carboxymethyl cellulose, dissolved starch, enzyme-modified starch,
Alkylene oxide modified starch, pregelatinized starch, dextrin, starch derivatives such as dialdehyde starch, alginate,
Locust Bean Gum, Strafkun, Stelavic,
Natural or semi-synthetic polymer compounds such as pullulan, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyvinyl methyl ether, polyethylene oxide, copolymers of vinyl methyl ether and maleic anhydride, copolymers of vinyl acetate and maleic anhydride Examples include synthetic polymer compounds such as polymers.

Furthermore, polyoxyethylene-modified or polyoxyethylene-polyoxypropylene copolymer-modified starch derivatives described in JP-A-59-64396, JP-A-59-4819
enzymatically decomposed dextrin or enzymatically decomposed ether dextrin (IJ) described in No. 2, carboxyalkylated starch described in JP-A-62-7595, phosphoric acid starch described in JP-A-62-11692, JP-A-62-83194. Hydroxyalkylated starch described in JP-A-62-275782
Cyclodextrins and the like described in the above can also be used.

Two or more kinds of water-soluble polymer compounds used in the present invention can also be used in combination.

The content of water-soluble polymer compound in the plate surface protectant is 0.01
% or more and less than 1.0. When the content of water-soluble polymer compounds in the plate surface protectant exceeds 1%, ink removal is poor at the beginning of printing in printing methods such as off-wheel printing, and waste paper becomes dirty in non-image areas. There will be more. Furthermore, if the content of the water-soluble polymer compound in the plate surface protective agent is less than 0.01%, the ink removability when printing is restarted after the printing press has been stopped will be poor.

It is more advantageous to use the plate surface protectant of the present invention in an acidic range of pH 2 to 6. In order to adjust the pH to 2 to 6, mineral acids, organic acids, inorganic salts, or alkaline agents are generally added to the plate surface protectant. The amount added is 0.01~3%
It is. For example, mineral acids include nitric acid, sulfuric acid, phosphoric acid, and the like. Examples of organic acids include citric acid, acetic acid, oxalic acid, malonic acid, p-toluenesulfonic acid, tartaric acid, malic acid, lactic acid, levulinic acid, phytic acid, benzoic acid, acetic acid, maleic acid, picolinic acid, and organic phosphonic acid. It will be done. Inorganic salts include nitric acid, phosphoric acid, sulfuric acid, molybdic acid, acetic acid, boric acid, boric acid, water-soluble alkali metal salts and ammonium salts thereof, such as sodium nitrate, potassium nitrate, ammonium nitrate, monosodium phosphate, Sodium phosphate, potassium phosphate, dibasic potassium phosphate, ammonium phosphorus, diammonium phosphorus, sodium sulfate, potassium sulfate, ammonium sulfate, sodium molybdate, potassium molybdate, ammonium molybdate, sodium acetate, Examples include potassium acetate, ammonium acetate, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium borate, asimonium borate, and the like.

Examples of the alkaline agent include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, and amines such as ammonia, monoethanolamine, jetanolamine, and triethanolamine. Two or more types of mineral acids, organic acids, inorganic salts, alkali agents, etc. may be used in combination.

In addition to the above components, lower alcohols such as glycerin, ethylene glycol, and triethylene glycol can also be used as wetting agents if necessary.

The amount of these wetting agents used in the composition is 0.1 to 5%, more preferably 0.5 to 4%. In addition to the above, benzoic acid and derivatives thereof, phenol, formalin, sodium dehydroacetate, etc. can be added to the plate surface protectant of the present invention in an amount of 0.005 to 2.0% as preservatives.

Furthermore, dyes, antifoaming agents, etc. can also be added.

The above plate protectant components are contained in water in a wide range of concentrations, but - in the ship, 4 to 40%, more preferably 5 to 30%.
used within the range. The plate surface protective agent of the present invention can be applied uniformly by spreading it over the entire plate surface with a sponge or the like and rubbing it with a wiping cloth until dry. In addition, the plate surface protective agent of the present invention is applied after developing a positive PS plate mainly composed of 〇-quinonediazide photosensitive material with an alkaline solution such as a silicate.
Alternatively, a normal negative PS plate using a condensate of p-diazodiphenylamine and paraformaldehyde as a photosensitive material may contain anionic surfactants, alkaline agents, poorly water-soluble organic solvents such as benzyl alcohol and phenyl cellosol, sulfites, etc. An automatic coating method, which is carried out after development with an aqueous developer, further developed with a developer having a mixed composition of the above two types of developer, which can commonly develop a positive PS plate and a negative PS plate, and after washing with water; An automatic coating method that is carried out without washing the developing machine, an automatic coating method that is carried out after processing with a rinsing solution containing a developing machine surfactant, an automatic coating method that is carried out after water circulation for pre-rinsing after development, and an automatic coating method that is carried out after pre-rinsing after development. Uniform coating can be achieved by an automatic coating method that is performed after washing with water.

〔Effect of the invention〕

By using the plate surface protectant of the present invention, even in printing methods such as off-wheel printing that generate a large amount of paper waste at the beginning of printing, the amount of paper waste can be reduced by 1 % compared to when conventional gum liquid is used. It is possible to reduce the amount by 1/2 to 1/3, and it is possible to obtain satisfactorily clear printed matter.

〔Example〕

This will be explained below using examples.

The plate surface protectants (A) and (B) of the present invention having the following formulations were prepared.

O Prescription of the plate surface protectant of the present invention The pH was adjusted to 4.5 to 4.7 using phosphoric acid and potassium hydroxide.

For comparison, plate protectants (C), (D), and
(E) was created.

Prescription of plate protection liquid for comparison (Table 2) The pH was adjusted to 4.5 to 4.7 using phosphoric acid and potassium hydroxide.

The surface of a JI31050 aluminum sheet was grained using a rotating nylon brush using a pumice water suspension as an abrasive. The surface roughness at this time (center line average roughness) is 0.5
It was μ. After washing with water, add 10% caustic soda aqueous solution to 70°C.
The amount of aluminum dissolved is 6.
Etched to give a 30%
It was immersed in a nitric acid aqueous solution for 1 minute to neutralize it, and then thoroughly washed with water. Thereafter, in a 0.7% nitric acid aqueous solution, a rectangular alternating waveform with an anode special voltage of 13 volts and a cathode special voltage of 6 volts was used (power supply waveform described in the example of JP-A-52-77702). Electrolytic surface treatment was performed for 20 seconds, and 50% of 20% sulfuric acid was applied.
After cleaning the surface by immersing it in a solution at ℃, it was washed with water.

Make two grained boards like the one above, one with 150g/
Anodic oxidation treatment was performed in the sulfuric acid bath of A at a bath temperature of 40° C. at 5 A/dm for 40 seconds, thoroughly washed with water, and then dried. The weight of the obtained anodic oxide film was 2 g/m. This support was designated as (A).

The other sheet was placed in a 200g/j2 phosphoric acid bath at a bath temperature of 40°C.
The film was anodized at 5 A/dm' for 60 seconds, thoroughly washed with water, and then dried. The weight of the obtained anodic oxide film was 1.8 g/m'. This support (
b).

Divide each of the supports in (a) and (b) into two, and (i)
, (E2), (Rho 1), and (Rho 2).

(E1) and (Rho1) were added to a 5% aqueous solution of potassium silicate (S10□/20 molar ratio 2.0) kept at 70°C.
The sample was immersed for 0 to 60 seconds for hydrophilic treatment, thoroughly washed with water, and then dried.

2 on the aluminum support that has been subjected to the above hydrophilic treatment.
-2.0 parts by weight of hydroxyethyl methacrylate copolymer (synthesized by the method described in Example 1 of British Patent No. 1.505.739), 2-methoxy of a condensate of p-diazodiphenylamine and paraformaldehyde -4-
Hydroxy-5-benzoylbenzenesulfonate 0
．． 12 parts by weight, Oil Blue #603 (manufactured by Orient Chemical Industry ■) 0.03 parts by weight, 1 part by weight of 2-methoxyethanol
A photosensitive solution consisting of 5 parts by weight, 10 parts by weight of methanol, and 5.0 parts by weight of ethylene chloride was applied to the supports (E1) and (RO1) so that the dry weight was 1.8 g/m''. A photosensitive lithographic printing plate was obtained. This photosensitive lithographic printing plate was exposed to light using a halftone negative film, and 3.0 weight ft 1 l of sodium sulfite and 30.0 ml of benzyl alcohol were added to the photosensitive lithographic printing plate.
parts by weight, 20.0 parts by weight of triethanolamine, 5.0 parts by weight of monoethanolamine, 10.0 parts by weight of sodium t-butylnaphthalenesulfonate, and 1000 parts by weight of pure water.
After developing with an aqueous developer consisting of parts by weight, the film was washed with water and dried.

On the other hand, naphthoquinone-1,2-diazide of polyhydroxyphenyl obtained by condensation polymerization of acetone and pyrogallol is described in Japanese Patent Publication No. 43-284.03.
A photosensitive solution was prepared by dissolving 1 part by weight of 5-sulfonic acid ester and 2 parts by weight of novolac type cresol formaldehyde resin in 40 parts by weight of methyl cellosolve, and the support (
E 2) Tokuro 2) Dry weight 2.0 g/m'
A photosensitive planographic printing plate was obtained. This photosensitive lithographic printing plate was exposed to light using a halftone positive film, and 3
% sodium silicate aqueous solution, washed with water, and dried.

Above (E1), (E2), (Rho 1), (Rho 2)
The plate surface protectants (A) to (E) were applied uniformly to each of the printing plates using an automatic gumming machine at a coating density of 0.2 to 0.5 g/m'', and then heated at a temperature of 50 to 60°C. Dry for 30-60 seconds.

After 30 minutes, ink each plate (Toyo Ink■
Using Komori Printing Co., Ltd. Web King Sumi) and dampening water (Fuji Photo Film @!! El-3100 times diluted liquid), use Komori Printing Co., Ltd.'s off-wheel printing machine (model system 18LR-418) to print Shinetsu Pulp Co., Ltd. Printed using rough paper.

Table 3 shows the number of sheets of waste paper printed until a clear printed matter with sufficient ink removed was obtained.

0 Printing evaluation results (number of sheets of waste paper at the start of printing) (Table 3) As is clear from this example, the amount of paper waste at the start of printing when the lithographic printing plate using the plate surface protectant of the present invention was subjected to off-wheel printing. It can be seen that this is extremely small compared to the case where the conventional plate protection side is used.

Claims (1)

[Claims] A plate surface protective agent for a lithographic printing plate, comprising an aqueous solution containing a surfactant and a water-soluble polymer compound of 0.01% by weight or more and less than 1.0% by weight based on the total weight of the plate surface protective agent. .