Dampening water composition for lithographic printing and additive for dampening water

Abstract: A dampening water composition for lithographic printing which comprises 0.1 to 5% by weight of at least one member selected from the group consisting of monoalcohols or diols of alkanes or alkenes having 5 to 11 carbon atoms, to which 1 to 10 moles of ethylene oxide and/or propylene oxide are added. The dampening water composition is not toxic, has not a possibility of causing a fire and pollution of working atmosphere and, therefore, the use of a local exhaust installation is not necessary. Moreover, it is excellent in characteristics as dampening water such that it does not cause contamination of metering roll, has good bleeding properties, emulsifying properties and stability in continuous processing as well as low foaming properties. Thus, the composition makes printing operation quite stable.

Description: BACKGROUND OF THE INVENTION The present invention relates to a dampening water composition for lithographic printing as well as an additive for dampening water for lithographic printing, which allows for a lithographic printing plate to provide printed matters having good quality by adding to the dampening water. Lithographic printing technique makes the best use of the properties of water and an oil such that they are essentially incompatible with one another. The printing surface of a lithographic printing plate comprises areas which receive water and repel an oil ink and those which repel water and receive an oil ink, the former serving as non-image areas and the latter serving as image areas. The non-image areas become damp with dampening water used in lithographic printing which contains a desensitizing agent to thus enhance the difference in surface chemical properties between the image areas and the non-image areas and hence to increase both the ink repellency of the non-image areas and the ink receptivity of the image areas. As such dampening water, there have generally been known conventionally aqueous solutions containing such inorganic substances as alkali metal salts or ammonium salt of bichromic acid, phosphoric acid or salts thereof such as ammonium salt, or such a colloidal substance as gum arabic or carboxymethyl cellulose (CMC). However, it is difficult to uniformly dampen the non-image areas of lithographic printing plates with the dampening water containing such a desensitizing gum and for this reason, the resultant printed matters are sometimes contaminated and a substantial skill in controlling the feed rate of the dampening water is required. To overcome such disadvantages, there has been proposed the Dahlgren dampening system in which an aqueous solution containing about 20 to 25% of isopropyl alcohol is used as dampening water. This method provides a variety of advantages concerning workability and accuracy of printed matters, such that the wettability of the non-image areas is improved, that the amount of the dampening water can be reduced, that it is easy to control the balance between feed rates of printing ink and dampening water, that the amount of water emulsified into the printing ink is lowered and that the transfer of printing ink to the blanket is improved. However, isopropyl alcohol is apt to evaporate and, therefore, the use of a special device is required for keeping the concentration thereof constant. This is unfavorable from the economical point of view. Moreover, isopropyl alcohol gives out bad smell and is toxic and thus the use thereof is not favorable in view of the pollution of working atmosphere. In addition, even if the dampening water containing isopropyl alcohol is applied to offset printing in which a dampening molleton roller is commonly used, isopropyl alcohol evaporates from a roller surface and the printing plate surface. Therefore, it cannot show its own effects. Moreover, the pollution with industrial waste has become of a matter of great concern, the regulation with respect to discharge of chromium ions in waste water becomes more and more severer and there is a tendency of controlling the use of organic solvents such as isopropyl alcohol from the viewpoint of safety and hygiene. For this reason, it has been desired to develop desensitizing gums or dampening water free of such a compound. Under such circumstances, Japanese Patent Publication for Opposition Purpose (hereunder referred to as "J.P. KOKOKU") Nos. 55-25075, 55-19757 and 58-5797 disclose compositions containing a variety of surfactants which can only slightly reduce the surface tension of water. In general, the dampening water should have a surface tension ranges from 35 to 50 dyn/cm. Therefore, if these compositions are used as dampening water, it is necessary to substantially increase the concentration of surfactants in such a desensitizing gum or dampening water. Furthermore, water is adhered to an ink film or an ink spreads over the surface of water because of vigorous movement of ink and/or water existing below an ink roll, a printing plate and a roll for supplying dampening water which rotate at a high speed, during the practical lithographic printing. However, combinations of surfactants disclosed in the foregoing methods explained above are insufficient for completely solve these problems. Besides, these dampening water containing such surfactants easily cause foaming during pumping and/or stirring thereof. In addition, U.S. Patent No. 3,877,372 discloses a solution containing a mixture of ethylene glycol monobutyl ether and at least one of hexylene glycol and ethylene glycol. U.S. Patent No. 4,278,467 discloses a dampening water containing at least one member selected from the group consisting of n-hexoxyethylene glycol, n-hexoxydiethylene glycol, 2-ethyl-1,3-hexanediol, n-butoxyethylene glycol acetate, n-butoxydiethylene glycol acetate and 3-butoxy-2-propanol. Japanese Patent Un-examined Publication (hereunder referred to as "J.P. KOKAI") No. 57-199693 (U.S. Patent 4,560,410) discloses dampening water containing 2-ethyl-1,3-hexanediol, Ester diol 204(viz., HOCH₂C(CH₃)₂CH₂OCOC(CH₃)₂CH₂OH), Hexyl Cellosolve or Hexyl Carbitol and at least one member selected from the group consisting of completely water-soluble propylene glycol, ethylene glycol, dipropylene glycol, diethylene glycol, hexylene glycol, triethylene glycol, tetraethylene glycol, tripropane glycol and 1,5-pentanediol. As these dampening water compositions do not contain isopropyl alcohol, they are preferable in view of safety and hygiene. However, the wettability thereof with respect to non-image areas of a lithographic printing plate comprising an anodized aluminum substrate, during printing operation is not sufficient and it is sometimes observed that the non-image areas are contaminated, in particular, during high speed printing operation and that so-called ink spreading of half dot image portions, i. e., phenomenon wherein the shape of half dot images is abnormally deformed, is enlarged and is uneven, is caused. Moreover, 2-ethyl-1,3-hexanediol has not sufficient solubility in water and thus the use thereof is unfavorable to obtain a concentrated dampening water or an additive for dampening water having a high concentration. Under such circumstances, the inventors of this invention have conducted various studies on dampening water for lithographic printing and have found that the foregoing problems can effectively be solved by incorporating a specific compound to dampening water composition in a specific amount. Thus the inventors have completed the present invention. Consequently, in the aspect the present invention provides a method of lithographic printing wherein a lithographic printing plate having an ink-receptive olephilic area and a hydrophilic area on the printing surface of the plate is contacted with an ink and a dampening water composition during printing, characterised in that said dampening water comprises 0.1 to 5% by weight of at least one compound of general formula (I): in which a, b , c, p, q and r are each 0 or an integer from 1 to 10, and their sum is an integer from 1 to 10. According to another aspect of the present invention provides an additive for dampening water used in lithographic printing comprising not less than 1% by weight of at least one compound of general formula I. According to a further aspect, the present invention provides a dampening water composition which comprises 0.1 to 5% by weight of at least one compound of general formula (I). DETAILED EXPLANATION OF THE INVENTION The compounds of general formula (I) can be produced by adding 1 to 10 moles of ethylene oxide and/or propylene oxide to 1 mole of 2-ethyl-1,3-hexanediol, according to an ordinary synthetic method. Although 2-ethyl-1,3-hexanediol has low solubility in water, its solubility in water is enhanced by the addition of ethylene oxide and/or propylene oxide moieties and as a result, it may be used in the dampening water composition and the additive of the present invention. The foregoing problems of contamination of non-image areas and ink spreading of half dot image portions of printing plates comprising an anodized aluminum plate as a substrate during printing can effectively be solved by employing dampening water containing 0.1 to 5% by weight of at least one such compound. When a printing press in which dampening water is continuously supplied, represented by the Dahlgren dampening system is used, surface tension of dampening water used preferably ranges from 30 to 50 dyn/cm. A compound to which more than 10 moles of ethylene oxide and/or propylene oxide have been added can reduce only slightly surface tension of dampening water when it is added thereto and thus it is necessary to increase the amount of the compound to be added to dampening water. This is economically unfavorable. Further, there is observed deterioration of ink receptivity (incomplete adhesion of ink) due to excessive emulsification of ink and it becomes difficult to obtain good printed matters having a high density. As the compounds used in the invention, those to which ethylene oxide is exclusively added are preferable. In other words, it is preferred that the molar number of propylene oxide added be lower than that of ethylene oxide. Therefore, if compounds to which only propylene oxide moieties are added are employed, the molar number of propylene oxide added is preferably limited to 1 to 5 moles so that the solubility of the resultant compounds in water is not excessively lowered. The effect of the present invention can also be achieved by adding at least one compound defined above to the conventional dampening water. In other words, according to another aspect of the present invention, there is provided an additive for dampening water for lithographic printing which comprises not less than 1% by weight of at least one compound selected from the group consisting of those defined above. In this respect, it is preferred to form such an additive for dampening water as a concentrate having a high concentration for the purpose of making, easy, the adition operation and supplementation thereof in the course of printing processes (including automatic supplementation). The additive for lithographic printing of the present invention comprises not less than 1% by weight, preferably not less than 10% by weight of at least one compound selected from the group consisting of those defined above. Since ethylene oxide moieties are added to such compounds, the solubility thereof in water is improved so that solutions containing the same can easily be concentrated. The dampening water composition and the additive for lithographic printing may further contain at least one water-soluble polymer. Typical examples of such polymers include such a natural substance or modified products thereof as gum arabic, starch derivatives, for instance, dextrin, enzyme-modified dextrin, hydroxypropylated enzyme-modified dextrin, carboxymethylated starch and starch phosphate, octenyl succinated starch, alginates or cellulose derivatives, for instance, carboxymethyl cellulose, carboxyethyl cellulose, hydroxyethyl cellulose, methyl cellulose and hydroxypropyl methyl cellulose; and such a synthetic substance as polyvinyl alcohol and derivatives thereof, polyvinyl pyrrolidone, polyacrylamide and copolymers thereof, polyacrylic acid and copolymers thereof, vinyl methyl ether/maleic anhydride copolymer and vinyl acetate/maleic anhydride coplymers. These water-soluble polymers may be used alone or in combination and the amount thereof to be incorporated into the dampening water composition and the additive of the present invention in general ranges from 0.0001 to 5% by weight, preferably 0.003 to 1% by weight on the basis of the total weight of the dampening water composition. It is in general desirable to use the dampening water having acidic pH ranging from about 3 to 6. This is because the etching action thereof becomes high at a pH of less than 3 and printing durability of the plate is correspondingly lowered. In order to adjust pH to 3 to 6, it is sufficient to add a mineral acid, an organic acid or an inorganic salt to the dampening composition. The amount thereof desirably ranges from 0.001 to 5% by weight. Examples of mineral acids are nitric acid, sulfuric acid and phosphoric acid and examples of organic acids include citric acid, acetic acid, oxalic acid, malonic acid, p-toluenesulfonic acid, tartaric acid, malic acid, lactic acid, levulinic acid and organophosphonic acids. These mineral acids, organic acids or inorganic salts may be used alone or in combination. Alternatively, the dampening water composition of the invention can be used in the alkaline region around a pH range of 7 to 11. The pH value may be adjusted by adding at least one alkaline substance such as alkali metal hydroxides, alkali metal phosphates, alkali metal carbonates or silicates. In addition to the foregoing components, the dampening water composition of the invention may further comprise a wetting agent capable of suppressing drying to make usability thereof good. Examples of such suitable wetting agents include glycerin, ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, sorbitol and pentaerythritol. These wetting agents may be used alone or in combination. The amount thereof is desirably not more than 2.0% by weight. Besides, the dampening water composition of the invention may further contain at least one chelating agent. Usually, a concentrate of a dampening water composition having the foregoing composition is diluted with tap water or well water prior to use as dampening water. Tap water or well water generally contains ions such as calcium ions which exert adverse influences on printing and the presence thereof often causes contamination of printed matters. These problems can effectively be solved if the dampening water composition comprises a chelating agent. Examples of preferred chelating agents include such an aminopolycarboxylic acid or a salts thereof as ethylenediamine-tetraacetic acid and potassium or sodium salt thereof, diethylenetriamine-pentaacetic acid and potassium or sodium salt thereof, triethylenetetramine-hexaacetic acid and potassium or sodium salt thereof, hydroxyethyl ethylenediamine-triacetic acid and potassium or sodium salt thereof, nitrilotriacetic acid and potassium or sodiunm salt thereof, 1,2-diaminocyclohexane-tetraacetic acid and potassium or sodium salt thereof and 1,3-diamino-2-propanol tetraacetic acid and potassium or sodium salt thereof; and such an organophosphonic acid, phosphonoalkane tricarboxylic acid or salts thereof as 2-phosphonobutane-tricarboxylic acid-1,2,4 and potassium or sodium salt thereof, 2-phosphonobutane-tricarboxylic acid-2,3,4 and potassium or sodium salt thereof, 1-phosphonoethane-tricarboxylic acid-2,2,2 and potassium or sodium salt thereof, 1-hydroxyethane-1,1-diphosphonic acid and potassium or sodium salt thereof and aminotri(methylene-phosphonic acid) and potassium or sodium salt thereof. Organic amine salts of the foregoing chelating agents may be used effectively instead of potassium and sodium salts thereof. These chelating agents should be selected so that they are stably present in the dampening water and exhibit no printing inhibitory effect. These chelating agents are used in the dampening water composition in an amount ranging from 0.001 to 3% by weight, preferably 0.01 to 1% by weight on the basis of the total weight of the composition. Moreover, the dampening water composition of the invention may comprise other additives such as preservatives and coloring agents, for instance, benzoic acid and derivatives thereof, phenol, formalin, sodium dehydroacetate or 4-isothiazolin-3-one. These preservatives and/or coloring agents may be used in an amount of 0.0001 to 1% by weight based on the total weight of the composition. Furthermore, the dampening water composition of the invention may contain such a corrosion inhibiting agent as magnesium nitrate, zinc nitrate, calcium nitrate, sodium nitrate, potassium nitrate, lithium nitrate and ammonium nitrate; such a film hardening agent as an aluminum compound; such an organic solvent as a cyclic ether, for instance, 4-butyrolactone, benzyl alcohol, ethylene glycol monophenyl ether, ethyl alcohol and n-propyl alcohol; such a water-soluble surface active organometallic compound as those disclosed in J.P. KOKAI No. 61-193893; and a silicone type anti-foaming agent, in an amount of 0.0001 to 1% by weight based on the total weight of the dampening water composition. The dampening water composition of the invention may further comprise a small amount of at least one surfactant. Examples of anionic surfactants suitably used in the composition include fatty acid salts, abietic acid salts, hydroxyalkanesulfonic acid salts, alkanesulfonic acid salts, dialkyl sulfosuccinate salts, linear alkyl benzenesulfonate salts, branched alkyl benzenesulfonate salts, alkyl naphthalenesulfonate salts, alkylphenoxy polyoxyethylenepropylsulfonate salts, polyoxyethylene alkylsulfophenyl ether salts, sodium salt of N-methyl-N-oleyltaurine, disodium salt of N-alkylsulfosuccinic acid amide, petroleum sulfonic acid salts, sulfated castor oil, sulfated tallow, sulfuric acid ester salts of fatty acid alkyl esters, alkylsulfate ester salts, polyoxyethylene alkyl ether sulfuric acid ester salts, fatty acid monoglyceride sulfuric acid ester salts, polyoxyethylene alkylphenyl ether sulfuric acid ester salts, polyoxyethylene styrylphenyl ether sulfuric acid ester salts, alkylphosphate ester salts, polyoxyethylene alkyl ether phosphoric acid ester salts, polyoxyethylene alkylphenyl ether phosphoric acid ester salts, partially saponified styrene-maleic anhydride copolymers, partially saponified olefin-maleic anhydride copolymers and condensates of naphthalene sulfonic acid salt and formalin. Among these, particularly preferred are dialkylsulfosuccinic acid salts, alkylsulfate ester salts and alkylnaphthalenesulfonic acid salts. Examples of non-ionic surfactants suitably used in the dampening water composition of the invention include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrylphenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, partial esters of glycerin-fatty acids, partial esters of sorbitan-fatty acids, partial esters of pentaerythritol-fatty acids, propylene glycol monofatty acid ester, partial esters of sucrose-fatty acids, partial esters of polyoxyethylene sorbitan fatty acids, partial esters of polyoxyethylene sorbitol fatty acids, polyethylene glycol fatty acid esters, partial esters of polyglycerin fatty acids, castor oils modified with polyoxyethylene, partial esters of polyoxyethylene glycerin fatty acids, fatty acid diethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylene-alkylamines, triethanolamine fatty acid ester, polyoxyethylene-polyoxypropylene block copolymers and trialkylamine oxides. Particularly preferred are polyoxyethylene alkylphenyl ethers and polyoxyethylene-polyoxypropylene block copolymers among others. Finally, examples of amphoteric surfactants or cationic surfactants useful in the invention include alkylimidazolines, alkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamine salts and polyethylene polyamine derivatives. These surfactants may be used alone or in combination and the amount thereof to be incorporated in the dampening water composition is not more than 3% by weight taking the foaming into consideration and preferably not more than 1% by weight based on the total weight of the composition. The dampening water composition of this invention may be applied to a variety of lithographic printing plates, in particular it is suitably applicable to the lithographic printing plates obtained by imagewise exposing, to light, a presensitized plate which comprises an aluminum substrate provided thereon with a light-sensitive layer (generally referred to as "PS plate") and then developing the same. Examples of preferred PS plates include those composed of an aluminum substrate provided thereon with a light-sensitive layer which comprises a mixture of shellac and a diazo resin (a salt of a condensate of p-diazodiphenylamine and p-formaldehyde) as disclosed in U.K. Patent No. 1,350,521; negative working type PS plates composed of an aluminum substrate provided thereon with a light-sensitive layer which comprises a mixture of a diazo resin and a polymer mainly comprising repeating units derived from hydroxyethyl methacrylate or hydroxyethyl acrylate monomer as disclosed in U.K. Patent Nos. 1,460,978 and 1,505,739; and positive working PS plates composed of an aluminum substrate provided with a light-sensitive layer which comprises a mixture of o-quinonediazide light-sensitive compound and a novolak type phenol resin as disclosed in J.P. KOKAI No. 50-125806. The aforementioned compositions for forming a light-sensitive layer may optionally comprise alkali-soluble resins in addition to the foregoing alkali-soluble novolak type resins. Examples of such resins are styrene-acrylic acid copolymer, methyl methacrylate-methacrylic acid copolymer, alkali-soluble polyurethane resins, alkali-soluble vinyl resins as disclosed in J.P. KOKOKU No. 52-28401, and alkali-soluble polybutyral resins. Moreover, preferred examples of PS plates further include PS plates composed of an aluminum substrate provided thereon with a light-sensitive layer of photocross-linkable photopolymers as specifically disclosed in U.S. Patent No. 3,860,426; PS plates composed of an aluminum substrate provided thereon with a light-sensitive layer of photopolymerizable photopolymer composition as disclosed in U.S. Patent Nos. 4,072,528 and 4,072,527; and PS plates composed of an aluminum substrate provided thereon with a light-sensitive layer which comprises a mixture of an azide and a water-soluble polymer as disclosed in U.K. Patent Nos. 1,235,281 and 1,495,861. The dampening water composition of this invention is in general diluted with water prior to use as dampening water. The dampening water composition of the invention makes it possible to perform printing using a small amount thereof without causing background contamination and oxidative contaminations, to provide good printed matters and to improve efficiency of printing operation and productivity. In addition, when it is used as dampening water, in particular in a printing press in which dampening water is continuously supplied, represented by Dahlgren dampening system, good printed matters can be obtained without using isopropyl alcohol. However, a small amount, for instance, 1 to 15% by weight of isopropyl alcohol may simultaneously be used without impairing quality of the printed matters. As explained above in detail, the dampening water composition and the additive for lithographic printing of the present invention are not toxic, do not have a possibility of causing a fire and pollution of working atmosphere and, therefore, the use of a local exhaust installation is not necessary. Moreover, it is excellent in characteristics of dampening water such that it does not cause contamination of metering rolls, that it is excellent in bleeding properties, emulsifying properties and stability in continuous processing and it has low foaming properties. Therefore, it makes the printing operation quite stable. The dampening water composition and the additive for lithographic printing of the present invention will hereunder be explained in more detail with reference to the following non-limitative working Examples. In addition, the effects practically achieved will also be discussed in detail in comparison with Comparative Examples given below. In the following Examples and Comparative Examples, the term "%" means "% by weight", unless otherwise specified. In the Examples, additives to be tested are added to diluted desensitising solutions of the following composition: Subsequently a PS plate was exposed and developed according to Procedure A or Procedure B. Procedure A A PS plate (anodized, multigrained positive working type PS plate; available from Fuji Photo Film Co Ltd under the trade name of FPS-II) was imagewise exposed to light, was developed and gummed-up using PS automatic developing machine 800 EII, a developer DP-4 for positive working type PS plate (diluted 8 times with water) and a finisher FP for positive working type PS plate (diluted 2 times with water) (all of these being available from Fuji Photo Film Co Ltd) to obtain a lithographic printing plate. Procedure B A PS plate (anodized, multigrained negative working type PS plate; available from Fuji Photo film Co Ltd under the trade name of FNS) was imagewise exposed to light, was developed and gummed-up using PS automatic developing machine 800 H, a developer DN-3C for negative working type PS plate (diluted 2 times with water) and a finisher FN-2 for negative working type PS plate (diluted 2 times with water) (all of these being available from Fuji Photo Film Co Ltd) to obtain a lithographic printing plate. The resultant plate obtained from either procedure was set up on an offset printing press using the Dahlgren dampening system, Harris Aurelia 125 (available from MARUBENI . HARRIS PRINTING PRESS MANUFACTURING COMPANY). The foregoing dampening water and an ink (available from DAINIPPON INK CO LTD under the trade name of Apex G Magenta Type-S) were charged to the press and printing operation was performed to examine the dampening water on the following points. a. Contamination of Metering Roll: Degree of contamination of metering rolls for sending water up due to adhesion of the ink was estimated according to the following three-stage evaluation: Good: A Slightly Contaminated: B Contaminated: C b. Bleed Properties: using an ink (available from DAINIPPON INK CO., LTD. under the trade name or Apex G Magenta Type-S), the operation of the printing press was stopped after printing 5,000 and 10,000 sheets of printed matters, and at these stages, the degree of the non-image area which was blurred with the ink from the image areas was estimated according to the following three stages evaluation: There is no portion blurred with ink: A There is some portions blurred with ink: B There are a lot of portions blurred with ink: C c. Emulsifying Properties: After printing 10,000 sheets of printed matters, the emulsified state of the ink on a roll for kneading ink was examined and estimated according to the following three-stage evaluation: Good: A Not so good: B Bad: C d. Continuous Stability: 10,000 sheets of printed matters were obtained using pure water as dampening water to obtain the amount of dampening water which did not cause contamination (minimum amount of water sent up) and printing was performed using various dampening water in the minimum sent up amount to determine the number of printed matters obtained till contamination was caused. More than 10,000: A 10,000 to 3,000: B Less than 3,000: C Example 1 2-Ethyl-1,3-hexanediol to which 1 to 4 moles of ethylene oxide had been added (Additive (i) was added to diluted desensitising solution A(diluted 100 times with water) in an amount of 1% based on the diluted solution to thus prepared dampening water. The printing operation was performed as described above, following Procedure A to examine properties of the dampening water. The dampening water of this Example was examined on these properties and was found that it was excellent in all the properties examined (a) to (d) and good printed matters were obtained. Comparative Example 1. When dampening water free of 2-ethyl-1,3-hexanediol to which 3 moles of ethylene oxide had been added (additive (ii)) was used, control of the amount of water was very difficult. More specifically, sending up of water was uneven, only contaminated printed matters were obtained at a usual water level and such background contamination could not sufficiently be eliminated even if the water level was established at the upper limit of this printing press and so-called ink to water log phenomenon (phenomenon that the ink was not adhered to image areas) was occurred, in other words, a sufficient amount of ink was not adhered to a part of the image areas. Moreover, other properties (a), (b) and (d) were also insufficient. Examples 2 to 5 and Comparative Example 2 As in Example 1, the desensitizing solution B was diluted 100 times with water and additives (iii) to (vi) and a known additive (vii) each was added thereto in an amount of 1% to obtain 5 kinds of dampening water and qualities of the dampening water were likewise estimated. Example 2: Additive (iii) : adduct of 2-ethyl-1,3-hexanediol and 1 to 4 moles of ethylene oxide; Example 3: Additive (iv) : adduct of 2-ethyl-1,3-hexanediol and 1 to 6 moles of ethylene oxide; Example 4: Additive (v): adduct of 2-ethyl-1,3-hexanediol and 2 to 8 moles of ethylene oxide Example 5: Additive (vi): adduct of 2-ethyl-1,3-hexanediol, 1 to 6 moles of ethylene oxide and 1 to 4 moles of propylene oxide; Comparative Example 2: Additive (vii): 2-ethyl-1,3-hexanediol. The results obtained are listed in Table I given below. As seen from the results listed in Table I, the dampening water of Examples 2 to 5 showed excellent properties (a) contamination of the metering roll; (b) bleed properties; and (d) continuous stability compared with the dampening water of Comparative Example 2 containing additive (vii). Moreover, the dampening water of Examples 2 to 5 only slightly caused foaming even if they were pumped or stirred. Example No. 2 3 4 5 Comp. Ex. 2 (a) Contamination of metering roll B A A A C (b) Bleed properties A A B A C (C) Emulsifying properties A A B B B (D) Continuous stability B A A A C Examples 6 to 9 and Comparative Example 3 The desensitizing solution C was diluted 100 times with water, additive (viii) or (ix) was added thereto in an amount of 1% or 3% each respectively to form 4 kinds of dampening water (Examples 6 to 9) and 10% by volume of isopropyl alcohol to form comparative dampening water (Comparative Example 3). The properties of these dampening water were estimated and were compared with those of Comparative Example 3. Additive (viii) Additive (ix) Component Amount (%) Pure water 49.0 Adduct of 2-ethyl-1,3-hexanediol, 1 to 6 moles of ethylene oxide and 1 to 4 moles of propylene oxide 50.0 Gum arabic 0.5 Sodium dehydroacetate 0.5 Printing operation was performed to examine the properties of the dampening water following Procedure B Example No. 6 7 8 9 Comp. Ex. 3 Additive (viii) (viii) (ix) (ix) isopropyl alcohol Amount added (%) 1 3 1 3 10% by volume (a) Contamination of metering roll A A A A A (b) Bleed properties B A B A A (c) Emulsifying properties A A A A A (d) Continuous stability B A A A B

Claims: A method of lithographic printing wherein a lithographic printing plate having an ink-receptive oleophilic area and a hydrophilic area on the printing surface of the plate is contacted with an ink and a dampening water composition during printing, characterised in that said dampening water comprises 0.1 to 5% by weight of at least one compound of general formula (I): in which a, b, c, p, q and r are each 0 or an integer from 1 to 10, and their sum is an integer from 1 to 10. A method according to Claim 1, wherein the molar amount of ethylene oxide in the adduct is larger than that of propylene oxide. A method according to Claim 1, wherein only propylene oxide is present in the adduct an the molar amount thereof is from 1 to 5 moles. A method according to any one of Claims 1 to 3, wherein the dampening water composition further comprises at least one water-soluble polymer selected from gum arabic, dextrin, enzyme-modified dextrin, hydroxypropylated enzyme-modified dextrin, carboxymethylated starch, starch phosphate, octenyl succinated starch, alginates, carboxymethyl cellulose, carboxyethyl cellulose, hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol and derivatives thereof, polyvinyl pyrrolidone, polyacrylamide and copolymers thereof, polyacrylic acid and copolymers thereof, vinyl methyl ether/maleic anhydride copolymer and vinyl acetate/maleic anhydride copolymer. A method according to Claim 4, wherein the amount of the water-soluble polymer ranges from 0.0001 to 5% by weight on the basis of the composition. A method according to any one of Claims 1 to 5, wherein the pH of the dampening water composition is adjusted to 3 to 6. A method according to Claim 6, wherein the pH of the composition is adjusted to 7 to 11. A method according to any one of Claims 1 to 7, wherein the dampening water composition further comprises at least one wetting agent selected from glycerin, ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, sorbitol and pentaetrythritol. A method according to Claim 8, wherein the amount of the wetting agent is not more than 2.0% by weight on the basis of the composition. A method according to any one of Claims 1 to 9, wherein the dampening water composition further comprises at least one chelating agent selected from aminopolycarboxylic acid and salts thereof; organophosphoric acid, phosphonoalkane tricarboxylic acids and salts thereof; and organic amine salts of the foregoing acids. A method according to Claim 10, wherein the amount of the chelating agent ranges from 0.001 to 3% by weight on the basis of the composition. A method according to any one of Claims 1 to 11, wherein the dampening water composition further comprises preservatives, colouring agents, corrosion inhibiting agents, film hardening agents, organic solvents, water-soluble surface active organometallic compounds and/or silicone type antifoaming agents, in an amount of 0.0001 to 1% by weight on the basis of the composition. A method according to any one of Claims 1 to 12, wherein the dampening water composition further comprises at least one surfactant. A method according to Claim 13, wherein the amount of the surfactant is not more than 3% by weight on the basis of the composition. An additive for dampening water used in lithographic printing comprising not less than 1% by weight of at least one compound of general formula (I): in which a, b, c, p, q and r are each 0 or an integer from 1 to 10, and their sum is an integer from 1 to 10. An additive according to Claim 15, wherein the amount of the compound is not less than 10% by weight on the basis of the additive. A dampening water composition which comprises 0.1 to 5% by weight of at least one compound of general formula (I): in which a, b, c, p, q and r are each 0 or an integer from 1 to 10, and their sum is an integer from 1 to 10.

Inventors: KUNICHIKA KENJI C O FUJI PHOTO, MATSUMOTO HIROSHI C O FUJI PHO, UCHIDA TOSHIO C O FUJI PHOTO F, KUNICHIKA, KENJI C/O FUJI PHOTO FILM CO LTD, MATSUMOTO, HIROSHI C/O FUJI PHOTO FILM CO LTD, UCHIDA, TOSHIO C/O FUJI PHOTO FILM CO LTD
Applicants: FUJI PHOTO FILM CO LTD, FUJI PHOTO FILM CO., LTD.
Application year: 1989
Main classification: B41N3
IPC codes: B41N3