JPH01262193A - Plate surface protective agent for planographic printing plate - Google Patents

Abstract

PURPOSE:To reduce not only the contamination on a blanket on the way of printing but also printing contamination at the reopening time of printing after the stop of a printer, by using a plate surface protective agent for a planographic printing plate composed of an aqueous solution containing phytinic acid and/or a water-soluble salt thereof and a surfactant. CONSTITUTION:It is necessary that a plate surface protective agent contains free phytinic acid and/or a water-soluble salt thereof as one of effective components. The phytinate may be water-soluble and a normal salt wherein all of the hydrogen atoms of 12 acids are substituted or a hydrogen salt wherein a part of the hydrogen atoms. of the acid is substituted may be used. Further, either one of a simple salt composed of a salt of one kind of a base or more kinds of bases as components can be used. The content of phytinic acid and/or a water-soluble salt thereof in the plate surface protective agent is pref. 0.1-40wt.%. Further, it is necessary to contain a surfactant as one of effective components and an anionic surfactant, a nonionic surfactant, an amphoteric surfactant and cation surfactant can be used and the pref. use range thereof is 1-50% of the plate surface protective agent.

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 until it is printed on a plate-making machine or until it is reused, and to protect it when it is installed on a printing machine. The objective is to protect printing plates from stains and scratches caused by adhesion of fingerprints, 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 gum solution onto the plate, spreading it over the entire plate surface with a sponge or cotton tampon, rubbing it with a wiping cloth until the plate surface is dry, and automatic gum application that is performed after development and washing. Examples include an automatic gumming process which is carried out immediately without processing and washing the developing machine with water, and an automatic gumming process which is carried out 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 is weak or the non-image area is dirty.) is low.

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. Very bad (there is a problem that there is a lot of dirty waste paper in the non-image area).

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 plate surface protectant that causes less staining on the blanket during printing and also causes less printing stains when printing is resumed 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 achieved by using a plate surface protectant for lithographic printing plates which is composed of an aqueous solution containing phytic acid and/or a water-soluble salt thereof and a surfactant.

The plate protection agent in the present invention needs to contain free phytic acid and/or a water-soluble salt thereof as one of the active ingredients. Examples of water-soluble salts include alkali metal salts such as sodium salts, potassium salts, and lithium salts, ammonium salts, and amine salts. Specific examples of amine salts include diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, butylamine, amylamine, hexylamine, laurylamine, ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, and hexamethylene. Salts of diamine, ethanolamine, jetanolamine, triethanolamine, allylamine, aniline, etc. can be used, but CnH2r+-+NI(z, (Cn
H2n-+)Jll'l, (CnHzh-+):+N
Salts represented by the formula [wherein n is 2 to 8 and may be branched] are preferred.

The phytate salt only needs to be water-soluble, and may be a normal salt in which all 12 acid hydrogens have been replaced, a hydrogen salt (acidic salt) in which some of the acid hydrogens have been replaced, or a phytate salt in which all 12 acid hydrogens have been replaced (acidic salt), or one type of base salt. Both simple salts consisting of salts and double salts containing two or more types of bases as components can be used in the present invention.

The content of phytic acid and/or its water-soluble salt in the plate surface protective agent is preferably 0.1 to 40% by weight (hereinafter abbreviated as %), more preferably 0.3 to 30%. .

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, direct 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-lauroyl sarcosine salts, sulfonic acids of naphthalene-formalin condensates, and diphenyl ether disulfonates. Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene, polyoxypropylene block polymers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyethylene These include glycol fatty acid esters, polyoxyethylene fatty acid amines, fatty acid monoglycerides, sorbitan fatty acid esters, pentaerythritol 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% of the plate surface protective agent. More preferably 2~
It is 45%.

The plate surface protective agent of the present invention can contain a water-soluble compound represented by the following general formula.

In the general formula, Y is Co(IH,SO,1(SPO3tl and B
Indicates an acid group such as Q, )l or a water-soluble salt of the acid group. R
is hydrogen, hydroxyl group, amino group, nitro group, acetyl group, hydrocarbon group having 1 to 4 carbon atoms, such as methyl group, ethyl group,
It represents a propyl group, a butyl group, a halogen group, or an aldehyde group, and may be the same or different.

Specific compounds of the above general formula include benzoic acid, p-
Hydroxybenzoic acid, p-aminobenzenecarboxylic acid,
p-nitrobenzenecarboxylic acid, toluenecarboxylic acid,
Examples include benzenesulfonic acid, phenolsulfonic acid, p-aminobenzenesulfonic acid, p-nitrobenzenesulfonic acid, toluenesulfonic acid, phenylphosphoric acid, and phenylboronic acid. Further, potassium, sodium, lithium or ammonium salts thereof may also be used.

Preferred are sulfonic acids and water-soluble salts thereof.

Furthermore, two or more of the above compounds can also be used in combination.

The content of the above water-soluble compound in the plate surface protective agent is 0.1 to 3.
It is preferably 0%, more preferably 0.3 to 25%.

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, tartaric acid, malic acid, and lactic acid. 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, monosodium phosphate, etc. disodium, potassium phosphate, dibasic potassium phosphate, primary ammonium phosphate, dibasic ammonium phosphate, sodium sulfate, potassium sulfate, ammonium sulfate,
Examples include sodium molybdate, potassium molybdate, ammonium molybdate, sodium acetate, potassium acetate, ammonium acetate, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium borate, and ammonium borate.

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 is 0.1 to 5.0% in the composition.
, more preferably 0.5 to 3.0%. In addition to the above, the plate protectant of the present invention may contain preservatives such as benzoic acid and its derivatives, phenol, formalin, 2-inthiazolin-3-one compound, sodium dehydroacetate, etc.
, OO can be added in a range of 5 to 2.0%. 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 - for boat fishing, 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 protectant of the present invention can be used after developing a positive type 28 plate mainly composed of an 0-quinonediazide photosensitive material with an alkaline solution such as a silicate, or after developing a condensate of p-diazodiphenylamine and paraformaldehyde. Anionic surfactant,
After developing with an aqueous developer containing an alkaline agent, a poorly water-soluble organic solvent such as benzyl alcohol or phenyl cellosolve, and a sulfite salt, the above two types of development can be used to commonly develop a positive PS plate and a negative PS plate. An automatic coating method that is performed after developing with a developer with a similar composition and washing with water, an automatic coating method that is performed without washing with water after development, and an automatic coating method that is performed after processing with a rinse solution containing a developer surfactant. Uniform coating can be achieved by a method such as an automatic coating method performed after pre-rinsing after development, an automatic coating method performed after pre-rinsing after development, and an automatic coating method performed after pre-rinsing after development.

〔Effect of the invention〕

By using the plate surface protectant of the present invention, the amount of paper waste can be reduced by 172% compared to when conventional gum liquid is used, even in printing methods such as off-wheel printing that generate a large amount of waste paper at the beginning of printing. -173, and it is possible to obtain satisfactorily clear printed matter.

〔Example〕

This will be explained below using examples.

A plate surface protectant (^), <8) of the present invention having the following formulation was prepared.

0 Prescription of the plate surface protectant of the present invention (Table 1) The pH was adjusted to 4.0 to 4.5 using phosphoric acid and potassium hydroxide.

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

0 Conventional plate protectant formulation (Table 2) The pH was adjusted to 4.0 to 4.5 using phosphoric acid and potassium hydroxide.

The surface of a JIS1050 aluminum sheet was grained using a rotating nylon brush using a bamisu 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.
It was etched so that it became ”g/m”. After washing with water,
It was immersed in a 30% nitric acid aqueous solution for 1 minute to neutralize it, and then thoroughly washed with water. After that, in a 0.7% nitric acid aqueous solution, the anode special voltage 1
Electrolytic surface treatment was carried out for 20 seconds using a rectangular alternating waveform of 3 volts and a cathode special voltage of 6 volts (the power supply waveform described in the example of JP-A-52-77702), and 20% sulfuric acid was applied at 50°C. After washing the surface by immersing it in a solution, it was washed with water.

Make two grained boards like the one above, one with 150g/
j! The support was anodized for 40 seconds at 5Δ/dm'' in a sulfuric acid bath at a bath temperature of 40°C, thoroughly washed with water, and then dried.The weight of the anodic oxide film obtained was 2 g/m'. was set as (a).

The other one is 200g/j! in a phosphoric acid bath at a bath temperature of 40°C.
The anodic oxide film was treated 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'. did.

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

(E 1) and (Rho 1) were added to a 5% aqueous solution of potassium silicate (SiOz/LO molar ratio 2.0) kept at 70°C.
It was immersed for 60 seconds to perform 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 Bundle 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 of (a) and (b) above to give a dry weight of 11.8 g/m'. A lithographic printing plate was obtained. This photosensitive lithographic printing plate was exposed to light using a halftone negative film, containing 3.0 parts by weight of sodium sulfite, 30.0 parts by weight of benzyl alcohol, 20.0 parts by weight of triethanolamine, and 5 parts by weight of monoethanolamine.
After developing with an aqueous developer consisting of 0 parts by weight, 10.0 parts by weight of sodium t-butylnaphthalenesulfonate and 1000 parts by weight of pure water, the film was washed with water and dried.

On the other hand, polyhydroxyphenyl naphthoquinone-1,2-diazide-5 obtained by condensation polymerization of acetone and pyrogallol is described in Japanese Patent Publication No. 43-28403.
- Prepare a photosensitive solution by dissolving 1 part by weight of a sulfonic acid ester and a double layer of novolac-molded resol formaldehyde resin in 40 parts by weight of methyl cellosolve, and add the dry weight of the supports (E2) and (Rho2). A photosensitive lithographic printing plate was obtained by coating at a density of 2.0 g/m'. This photosensitive lithographic printing plate was exposed to light using a halftone positive film, and 3%
The film was developed with an aqueous sodium silicate solution, washed with water, and dried.

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

After 30 minutes, ink each plate (Toyo Ink■
Using Komori Printing Co., Ltd.'s off-wheel printing machine LR-418, using rough paper made by Shinetsu Bulb @3, using dampening water (EU-3100 times diluted solution made by Fuji Photo Film) and dampening water (made by Web King Sumi) I printed it.

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 the amount is extremely small compared to when a conventional plate surface protectant is used.

Claims (1)

[Claims] A plate surface protective agent for a lithographic printing plate, comprising an aqueous solution containing phytic acid and/or a water-soluble salt thereof and a surfactant.