JP2002079777A - Plate surface protecting agent for lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate surface protecting agent for a lithographic printing plate which is excellent in the effect of preventing flaw scumming and oil and fat scumming of the lithographic printing plate after the plate is made and also in protection of hydrophilic properties of a non-image part and which displays excellent inking properties for ink in a printing process and can be stored stably, while occurrence of a deposit and a change in viscosity are reduced in the storage. SOLUTION: The plate surface protecting agent for the lithographic printing plate, which contains starch, contains at least one kind of compound selected from the group consisting of a dimethyl sulfoxide, urea, thiourea, guanidine and derivatives thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plate surface protective agent for a lithographic printing plate.

[0002]

2. Description of the Related Art When making a lithographic printing plate, a so-called gum solution is applied in the final step. The purpose of applying the gum solution is not only to protect the hydrophilicity of the non-image area, but also to modify the image area such as adding or erasing it, to save it for the period from plate making until printing or to reuse it, and to attach it to a printing machine. The purpose of the present invention is to prevent dirt caused by the adhesion of fingerprints, oils and fats, dust and the like during and during handling, to protect against the occurrence of scratches, and to suppress the generation of oxidized dirt. Heretofore, as a gum solution for a lithographic printing plate, gum arabic, cellulose gum or an aqueous solution of a water-soluble polymer having a carboxyl group in a molecule has been generally used. However, these gum solutions have the following problems. That is, in the final finishing step of the printing plate, a gum solution is poured on the plate, spread over the entire plate surface with a sponge or a cotton tampon, and further rubbed with a wipe until the plate surface is dried. The water-soluble polymer substance is partially thickened in the (ink receiving area). The image portion of the thickly coated portion has poor ink adhesion during the printing process, and requires a considerable number of prints to obtain a printed material having a desired ink density. Generally, this phenomenon is referred to as printing omission (so-called poor inking).

Various proposals have been made to obtain a plate surface protective agent having good ink inking property, but a plate surface protecting agent which sufficiently achieves both the desensitizing effect and the inking property has not been achieved. In addition, precipitation may occur during storage of the plate surface protective agent due to components in the plate surface protective agent. In addition, starch is often included in the plate surface protective agent as a water-soluble polymer compound.However, during the storage of the plate surface protective agent, particularly during low-temperature storage, the viscosity increases due to aging of the starch. When such a plate surface protective agent is used, there is a problem that good coated surface quality cannot be obtained.

[0004]

DISCLOSURE OF THE INVENTION The present invention is excellent in the effect of preventing scratches and dirt on a lithographic printing plate after plate making and oil and grease.
On the other hand, it is an object of the present invention to provide a plate surface protective agent for a lithographic printing plate that is excellent in protecting hydrophilicity of a non-image portion and simultaneously exhibits good inking property to ink during printing. Another object of the present invention is to provide a plate surface protective agent for a lithographic printing plate, in which the generation of a precipitate and a change in viscosity during storage are suppressed and the storage can be performed stably.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, by adding a specific compound to a surface protective agent for lithographic printing plates containing starch. They have found that an excellent plate surface protective agent can be obtained, and have completed the present invention. Accordingly, the present invention is a plate surface protective agent for a lithographic printing plate containing starch, characterized in that it contains at least one compound selected from the group consisting of dimethyl sulfoxide, urea, thiourea, guanidine and derivatives thereof. And a plate surface protective agent for a lithographic printing plate. In a preferred embodiment of the lithographic printing plate surface protective agent of the present invention, components conventionally used in a lithographic printing plate surface protective agent can be incorporated.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The starch used in the plate surface protective agent for a lithographic printing plate of the present invention includes starches conventionally used, and specifically includes starch, starch derivatives, modified starch such as dextrin and the like. . Of these, roast dextrin and enzymatically decomposed dextrin are preferably used. The starch content in the plate surface protective agent of the present invention is:
3-40 mass% is suitable, preferably 5-30 mass%, more preferably 7-20 mass%.

The lithographic printing plate surface protective agent of the present invention contains at least one compound selected from the group consisting of dimethyl sulfoxide, urea, thiourea, guanidine and derivatives thereof. Derivatives include guanidine hydrochloride, guanidine nitrate, guanidine carbonate, guanidine acetate, guanidine benzenesulfonate and the like. When at least one compound selected from urea, thiourea, guanidine and their derivatives is included, their content in the plate surface protective agent is 0.05 to 3.0% by mass.
Is suitable, preferably 0.1 to 2.0% by mass, more preferably 0.2 to 1.0% by mass. When dimethyl sulfoxide is included, its content in the plate surface protective agent is
0.1 to 8.0% by mass is appropriate, preferably 0.3 to 8.0% by mass.
To 5.0 mass%, more preferably 0.5 to 3.0 mass%.
It is. As the plate surface protective agent of the present invention, one compound selected from dimethyl sulfoxide, urea, thiourea, guanidine and derivatives thereof may be used alone or in combination of two or more.

In the plate surface protective agent of the present invention, another water-soluble polymer compound may be used in addition to the above-mentioned starch.
As such a water-soluble polymer compound, gum arabic,
Tragant gum, carrageenan, xanthan gum, cellulose derivatives (eg, carboxymethylcellulose, carboxyethylcellulose, methylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, etc.)
And its modified products, pullulan, polyvinyl alcohol and its derivatives, polyacrylamide, and its copolymer,
Vinyl methyl ether / maleic anhydride copolymer, vinyl acetate / maleic anhydride copolymer, styrene / maleic anhydride copolymer, synthetic water-soluble polymer such as polyvinylpyrrolidone, water-soluble polysaccharide such as soybean polysaccharide, etc. Is mentioned. Among them, gum arabic, carboxymethyl cellulose, soybean polysaccharide, and the like can be preferably used. One or more of the above water-soluble polymer compounds may be used in combination. The content of the water-soluble polymer compound in the plate surface protective agent for a lithographic printing plate is suitably from 0.5 to 40% by mass, preferably from 1.0 to 30% by mass, based on the total mass of the plate surface protective agent. is there.

The lithographic printing plate surface protective agent of the present invention is more advantageously used in the acidic range of pH 2.5 to 5.
In order to adjust the pH to 2.5 to 5, generally, an inorganic acid, an organic acid or a salt thereof is added to the plate surface protective agent. Among them, mineral acids, organic acids or inorganic salts are used. The amount of addition is 0.01 to 3% by mass based on the total mass of the plate surface protective agent. For example, mineral acids include nitric acid, sulfuric acid, phosphoric acid, and metaphosphoric acid. Organic acids include citric acid, acetic acid, oxalic acid, malonic acid, p-toluenesulfonic acid,
Tartaric acid, malic acid, lactic acid, levulinic acid, phytic acid, organic phosphonic acids and the like can be mentioned. Examples of the inorganic salt include monobasic sodium phosphate, dibasic sodium phosphate, sodium hexametaphosphate, sodium tripolyphosphate and the like. At least one of these mineral acids, organic acids or inorganic salts
Species or two or more species may be used in combination.

[0010] The plate surface protective agent for lithographic printing plates of the present invention may contain a surfactant to improve the surface condition of the coating layer. Examples of the surfactant include an anionic surfactant and / or a nonionic surfactant. Examples of the anionic surfactant include fatty acid salts, abietic acid salts, hydroxyalkanesulfonates, alkanesulfonates, dialkylsulfosuccinates, linear alkylbenzenesulfonates, branched-chain alkylbenzenesulfonates, and alkylnaphthalenesulfonates. , Alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl-N-oleyltaurine sodium, N-alkyl sulfosuccinic monoamide disodium salt, petroleum sulfonates, sulfated castor oil , Sulfated tallow oil, sulfate salts of fatty acid alkyl esters, alkyl sulfate salts, polyoxyethylene alkyl ether sulfate salts, fatty acid monoglyceride sulfate Ter salts, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene styryl phenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, styrene-anhydride Specific examples include partially saponified maleic acid copolymers, partially saponified olefin-maleic anhydride copolymers, and formalin condensates of naphthalenesulfonic acid salts. Of these, dialkyl sulfosuccinates, alkyl sulfates and alkyl naphthalene sulfonates are particularly preferably used.

The nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ether, glycerin fatty acid partial esters, sorbitan fatty acid partial esters, and pentane. Erythritol fatty acid partial ester, propylene glycol monofatty acid ester, sucrose fatty acid partial ester, polyoxyethylene sorbitan fatty acid partial ester, polyoxyethylene sorbitol fatty acid partial ester, polyethylene glycol fatty acid ester, polyglycerin fatty acid partial ester, poly Oxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides, N, N-bis-2-hydroxyalkylamines, polyoxyethylene Alkylene alkyl amines, triethanolamine fatty acid esters, such as trialkylamine oxides. Among them, polyoxyethylene alkyl phenyl ethers, polyoxyethylene-polyoxypropylene block copolymers and the like are preferably used.

In addition, acetylene glycol-based and acetylene alcohol-based oxyethylene adducts, fluorine-based, silicon-based anions, and nonionic surfactants can also be used. Two or more of these surfactants can be used in combination. For example, a combination of two or more different anionic surfactants or a combination of an anionic surfactant and a nonionic surfactant is preferable. It is preferable that these compounds are appropriately selected and used in consideration of the influence on the environment. The use amount of the above surfactant is not particularly limited, but is preferably 0.01 to 20% of the total mass of the plate surface protective agent.
% By mass.

In addition, ethylene glycol, propylene glycol, triethylene glycol, butylene glycol, as a wetting agent for the surface protective agent for a lithographic printing plate of the present invention,
Hexylene glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, diglycerin and the like are preferably used. These wetting agents may be used alone or in combination of two or more. Generally, the wetting agent is used in an amount of 1 to 25% by weight, based on the total weight of the plate surface protective agent.

The plate surface protective agent for a lithographic printing plate of the present invention may further contain a nitrate or a sulfate. Specific examples thereof include magnesium nitrate, sodium nitrate, potassium nitrate, ammonium nitrate, sodium sulfate, potassium sulfate, ammonium sulfate, sodium hydrogen sulfate, nickel sulfate and the like. The amount used is 0.05 to 1.0% by mass of the total mass of the plate surface protective agent.

The balance of the lithographic printing plate surface protective agent of the present invention is water. Usually, the surface protective agent is commercially available as a concentrated solution for economic reasons, and is usually added with tap water, well water, etc. at the time of use.
It is used after diluting 1 to 3 times. Tap water used for this dilution, calcium ions and the like contained in well water and the like may adversely affect printing and cause stains on printed matter. Therefore, the above-mentioned disadvantage can be solved by adding a chelate compound. . Preferred chelating compounds include, for example, ethylenediaminetetraacetic acid, its potassium salt, its sodium salt; diethylenetriaminepentaacetic acid, its potassium salt, its sodium salt; triethylenetetraminehexaacetic acid, its potassium salt, its sodium salt,
Hydroxyethylethylenediaminetriacetic acid, its potassium salt, its sodium salt; nitrilotriacetic acid, its sodium salt; 1-hydroxyethane-1,1-diphosphonic acid, its potassium salt, its sodium salt; aminotri (methylenephosphonic acid), its potassium Organic phosphonic acids or phosphonoalkanetricarboxylic acids such as salts and sodium salts thereof can be mentioned. Organic amine salts are also effective in place of the sodium and potassium salts of the above chelating agents. These chelating agents are selected from those which are stably present in the composition of the plate surface protective agent and do not inhibit printability. The addition amount is 0.001 in the plate surface protective agent at the time of use.
~ 1.0% by weight is suitable.

Further, a preservative, an antifoaming agent and the like can be added to the plate surface protective agent of the present invention. For example, preservatives include phenol or derivatives thereof, formalin, imidazole derivatives, sodium dehydroacetate, 4-isothiazolin-3-one derivatives, benzoisothiazolin-3-one, benztriazole derivatives, amidizing anidine derivatives, quaternary ammonium salts, pyridine , Quinoline, guanidine, etc., diazine, triazole derivative, oxazole, oxazine derivative, nitrobromoalcohol-based 2-bromo-2-nitropropane-1,3
Diol, 1,1-dibromo-1-nitro-2-ethanol, 1,1-dibromo-1-nitro-2-propanol omazine and the like can be preferably used. A preferable addition amount is an amount stably exerting an effect on bacteria, mold, yeast and the like, and varies depending on the kind of bacteria, mold and yeast, but is 0.01 to the plate surface protective agent at the time of use. It is preferably in the range of 4 to 4% by weight, and it is preferable to use two or more preservatives in combination so as to be effective against various molds and sterilization.

As the defoaming agent, general silicone-based self-emulsifying type, emulsifying type, surfactant nonionic HL
Compounds such as 5 or less of B can be used. Among them, a silicone antifoaming agent is preferable. Among them, any of emulsification dispersion type and solubilization can be used. The content of the defoaming agent is preferably in the range of 0.001 to 1.0% by weight based on the plate surface protective agent at the time of use.

[0018] In addition to the above components, a sensitizer may be added to the plate surface protective agent of the present invention, if necessary. For example, an organic solvent having a boiling point of 160 ° C. or more which is hardly soluble in water is used. Preferred examples of the compound include phthalic acid diester agents such as dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di (2-ethylhexyl) phthalate, dinonyl phthalate, didecyl phthalate, dilauryl phthalate and butyl benzyl phthalate. Aliphatic dibasic acid esters such as dioctyl adipate, butyl glycol adipate, dioctyl azelate, dibutyl sebacate, di (2-ethylhexyl) sebacate, dioctyl sebacate, and epoxidized triglycerides such as epoxidized soybean oil; For example, phosphates such as tricresyl phosphate, trioctyl phosphate, trischlorethyl phosphate and the like, such as benzoic acid esters such as benzyl benzoate, etc. The points at 15 ℃ below boiling point at one atmosphere include 300 ° C. or more plasticizers.

Other alcohols include 2-octanol, 2-ethylhexanol, nonanol, n-decanol, undecanol, n-dodecanol, trimethylnonyl alcohol, tetradecanol, benzyl alcohol and the like. Examples of glycols include ethylene glycol isoamyl ether, ethylene glycol monophenyl ether, ethylene glycol benzyl ether, ethylene glycol hexyl ether, and octylene glycol. Examples of the hydrocarbon system include aromatics, aliphatic compounds, squalane and the like of a petroleum fraction having a boiling point of 160 ° C. or higher. Conditions for selecting the above compound include its environmental safety, particularly odor. The amount of these solvents used is 0,0 based on the total weight of the plate surface protective agent.
It is suitably from 0.1 to 10% by mass, more preferably 0.05% by mass.
~ 5% by weight. These solvents may be used alone or in combination of two or more. The oil sensitizer as described above may be prepared by emulsifying and dispersing the plate surface protective agent of the present invention in an emulsified and dispersed form, or may be solubilized with the aid of a solubilizing agent.

The plate surface protective agent of the present invention can be easily designed into a solution type, an emulsion type or the like in accordance with the characteristics of the photosensitive lithographic printing plate, and can be prepared according to a conventional method. For example, emulsification and dispersion at the time of producing the plate surface protective agent of the present invention is as follows: the aqueous phase is adjusted to a temperature of 40 ° C. ± 5 ° C., stirred at a high speed, the oil phase prepared is slowly dropped into the aqueous phase, and then sufficiently stirred. The emulsion is made through a pressure homogenizer. The plate surface protective agent of the present invention can be used for both positive type lithographic printing plates and negative type lithographic printing plates. Also,
Even when using an automatic gum filling machine or the like, it can be applied uniformly. The treatment with the plate surface protective agent of the present invention can be carried out immediately after the development treatment step by anhydrous washing, after the development treatment (including a washing step, running water circulating washing or a small amount of rinsing with water) or containing a surfactant. It can also be carried out after treatment with a rinse solution.

[0021]

The plate surface protective agent for a lithographic printing plate according to the present invention exerts excellent effects in protecting oil sensitivity in the image area and hydrophilicity in the non-image area. The plate surface protective agent for a lithographic printing plate of the present invention also has good ink adhesion in the image area, can perform color matching of printing in a short time, and does not produce many defective prints, immediately after printing. A sufficiently satisfactory clear print can be obtained. In addition, the printing plate to which the plate surface protective agent of the present invention has been applied shows good ink adhesion even after storage. The plate surface protective agent for a lithographic printing plate of the present invention is capable of suppressing the generation of precipitates and changes in viscosity during storage, especially during low-temperature storage, and can be stored stably, and thus has a high quality coated surface on the plate. give.

[0022]

The present invention will be described in detail below with reference to examples and comparative examples. Examples 1 to 4 are solution type plate surface protective agents, and Examples 5 to 8 are emulsified type plate surface protective agents. Comparative Examples 1 and 2 are solution type plate surface protective agents, and Comparative Examples 3 and 4 are emulsified type plate surface protective agents. <Preparation of solution-type surface protective agent> A water-soluble polymer compound was dissolved in pure water by heating to a temperature in the range of 60 ° C to 70 ° C, and then cooled to a temperature around 40 ° C. A plate surface protective agent of the type was prepared. Table 1 shows their compositions. The unit is g (gram). The liquid thus prepared was diluted 1: 1 (volume ratio) with water to obtain a used liquid.
If necessary, it can be used after being diluted to the range of 1: 2 (three-fold dilution).

<Preparation of emulsification type surface protective agent> (Preparation of aqueous phase) A water-soluble polymer compound was added to pure water at 60 ° C.
Heat and dissolve in the range of -70 ° C. Thereafter, the temperature is raised to 50 ° C
Cool to near, dissolve each additive sequentially, and adjust the liquid temperature to 4
Hold at 5-50 ° C. (Preparation of oil phase) A sparingly soluble high-boiling solvent and each surfactant (emulsifier) were added to water, and the mixture was stirred into a uniform solution. (Emulsification / dispersion) The aqueous phase was prepared at 45 ° C. ± 5 ° C., and the stirring speed was 500 to 60 with a three-one motor (manufactured by Shinto Kagaku Co., Ltd.).
The oil phase is slowly dropped into 0 rpm, and after completion of the dropping, the total volume is made up to 1000 ml with pure water, and the mixture is further stirred for 10 minutes. Thereafter, the mixture was emulsified using a pressure homogenizer to prepare a plate surface protective agent. Table 2 shows these compositions. The unit is g
(Grams). The liquid thus prepared is mixed with water 1: 1.
(Volume ratio) to obtain a working solution. If necessary, it can be used after being diluted to the range of 1: 2 (three-fold dilution).

[0024]

[Table 1] Solution type ^* Carboxymethyl cellulose (Cellogen 5A: manufactured by Daiichi Kogyo Chemical Co., Ltd.)

[0025]

[Table 2] Emulsion type ^* Carboxymethyl cellulose (Cellogen 5A: manufactured by Daiichi Kogyo Chemical Co., Ltd.)

<Evaluation of stability over time of plate surface protective agent> Each plate surface protective agent prepared as described above was placed in a 1000 ml container,
Table 4 shows the results of storage under the storage conditions shown in Table 3 and the effect of preventing the change in viscosity (starch aging phenomenon).

[Table 3] Storage test conditions

[0027]

[Table 4] ：: no change in viscosity Δ: change of 20% or less ×: 3
0% or more change

<Surface protective agent suitability test> An anodized multi-grain type positive PS plate manufactured by VPS Fuji Photo Film Co., Ltd. as a lithographic printing plate is image-exposed, and a PS automatic developing machine 900D (after development, gum is applied). Having a function), and the above-mentioned solution for use of the plate surface protective agent was applied. The lithographic printing plate after the completion of plate making was divided into two parts, stored under the conditions A and B shown in Table 5, and printed using a Heidelberg SORM printing machine, and the performance was evaluated by the performance evaluation method shown in Table 6.

[0029]

[Table 5]

[0030]

[Table 6]

As a result, the plate surface protective agents of Examples 1 to 8
Ink adhesion, desensitizing effect and scratch suitability were all good.

Claims (1)

[Claims] 1. A lithographic printing plate surface protective agent containing starch, characterized in that it contains at least one compound selected from the group consisting of dimethyl sulfoxide, urea, thiourea, guanidine and derivatives thereof. Plate surface protective agent for lithographic printing plates.