Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/08—Damping; Neutralising or similar differentiation treatments for lithographic printing formes; Gumming or finishing solutions, fountain solutions, correction or deletion fluids, or on-press development

Definitions

• the invention relates to an acidic, aqueous dampening solution concentrate for use in flat or offset printing processes.
• planographic printing process is known.
• printing is done from a flat plate or cylinder, which is usually made of anodized aluminum and has essentially no height differences on its surface.
• the ability to print depends on different properties of the image and non-image areas on the surface.
• the image to be reproduced is applied to the plate by one of several known methods in such a way that the non-image areas become hydrophilic, while the image areas become hydrophobic.
• a light-sensitive layer is generally used. After imagewise exposing the photosensitive layer, the latent image is developed and part of the layer is removed from the plate. The plate is then treated with a preservative, whereupon it becomes hydrophilic in the areas freed from the light-sensitive layer.
• aqueous dampening solution is then applied to the plate surface during the printing process.
• the dampening solution keeps all parts of the plate surface which are not covered by the hydrophobic image moist. In addition, it prevents the plate from toning, that is, it prevents the non-image areas from at least partially accepting the color the.
• the dampening solution can be composed in such a way that it cleans the plate surface just enough and keeps it hydrophilic in such a way that sharp contours are retained and rapid wear is prevented.
• the dampening solution is applied to the plate by one or more rollers. Thereafter, at least one ink roller covered with an oil-based ink comes into contact with the entire surface of the plate, but only transfers the ink to the image areas because the hydrophilic non-image areas repel the ink.
• the planographic printing plate is first wetted with the aqueous dampening solution and then colored with printing ink.
• the dampening solution and at least part of the greasy ink are applied to the plate simultaneously with an application roller.
• other rollers usually smaller in diameter than the first roller, can then contact the plate to distribute the ink more evenly.
• the dampening solution can be prepared by the printer from a dampening solution concentrate by adding further water and often 10 to 30 vol .-% isopropyl alcohol itself.
• Acidic, aqueous dampening solution concentrates according to the state the art generally contain a water-soluble resin or colloid, such as. As gum arabic or cellulose derivatives, and may also contain an acidic hydrophilizing agent, buffering agent and wetting agent.
• Acid fountain solutions are usually designed to perform different tasks.
• hydrophilic colloids such as. B. gum arabic
• the non-image areas of the plate should remain hydrophilic during the print run.
• Acidic hydrophilizing agents can also be added, so that the non-image areas remain sharper and ink-repellent.
• surfactants or combinations of surfactants and alcohols e.g. Isopropyl alcohol
• the surface tension of the solution should be reduced to the range of 30-40 dynes / cm2, so that the plate and roller surfaces can be wetted better.
• This property can also be achieved without surfactants if more than the amounts of hydrophilic colloids required to maintain the hydrophilicity of the non-printing plate surfaces in combination with at least one metal salt, e.g. B. with nitrates, chromates and the like., And / or be used with alcohols or glycols.
• gum arabic salts which usually lead to the blind running of the plate.
• a volatile solvent such as isopropyl alcohol
• the solubility of other components in the solution can be reduced. These components can then accumulate on roller or plate surfaces when they are removed from the solution.
• Isopropyl alcohol is also undesirable because it is toxic, flammable and has a low vapor pressure so that it evaporates quickly.
• US-A 4 030 417 describes e.g. B. a dampening solution based on a mixture of a fatty acid, a monovalent metal hydroxide, gum arabic, a monovalent metal iodide and water.
• US-A 3 877 372 discloses a solution which is a solution which contains a mixture of ethylene glycol monobutyl ether and at least one of the two compounds hexylene glycol and ethylene glycol.
• US Pat. No. 4,278,467 describes an isopropyl alcohol-free dampening solution based on a dilute mixture of a standard dampening solution concentrate with at least one compound from the group of nonionic compounds.
• These nonionic compounds essentially comprise n-hexoxyethylene glycol, n-hexoxydiethylene glycol, 2-ethyl-1,3-hexanediol, n-butoxyethylene glycol acetate, n-butoxydiethylene glycol acetate, 3-butoxy-2-propanol and mixtures thereof, and are further characterized in that that they have a molecular weight between 100 and 300.
• This concentrate can also contain a bactericide and a dye and is composed so that it Contains 35 to 65 wt .-% water and can be further diluted by the consumer with water, so that a dampening solution with a content of at least 99 wt .-%, preferably 99.1 to 99.9 wt .-%, water and accordingly 0.1 to 0.9 wt .-% of non-aqueous components.
• the dampening solution particularly preferably contains 0.3 to 0.7% by weight of non-aqueous components.
• the mixture forming the solution consists essentially of the specified components. What is meant by this is that the solution is functional as described, and does not contain a substantial amount of surfactant and / or isopropyl alcohol.
• dampening solutions As a further characteristic feature of the dampening solutions according to the invention it can be stated that they have a surface tension (measured with a surface tensiometer) in the range from 30 to 40 dynes / cm2, which can be achieved without having to add tensides and / or isopropyl alcohol to the mixture.
• the dampening solutions generally have a low solids content and can generally be applied to the printing plates in smaller amounts than known solutions and still achieve the effectiveness of a quality dampening solution, ie they wet the printing plate sufficiently and prevent toning or blind running. This means that the plate in turn moistens the printing paper to a lesser extent and less solids can accumulate on the plate itself or on the dampening felt rollers used to apply the solution.
• the water-soluble, film-forming hydrophilic colloids suitable according to the invention include gum arabic, tragacanth, carboxymethyl cellulose, sodium alginate, carboxymethyl starch, methyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohol and similar colloids which impart hydrophilic properties when applied to the non-image areas of the planographic printing plate.
• Gum arabic is preferred in the context of this invention, and the colloid content in the concentrate is preferably 8.0 to 15% by weight.
• the pH stabilization or buffer system of the dampening solution serves a dual purpose. It is said to both stabilize the pH value and to some extent hydrophilize the plate.
• Preferred acids are weak organic acids, such as. B. citric, ascorbic, sulfanilic, tartaric, lactic and acetic acid.
• the preferred acid is acetic acid.
• Sufficient acid is removed to give the concentrate a pH in the range from 2 to 3.5, which, when further diluted with water for use as a dampening solution, gives a pH in the range from 4 to 4.5.
• the salts preferably combined with the acids mentioned are the alkali salts of these acids, particularly preferably the sodium, potassium and lithium salts of acetic, citric and lactic acids.
• An alkali salt of phosphoric acid can be mixed in small amounts with one of the salts mentioned.
• the combination of acid and salt can be used in proportions of 0.01 to 12.5% by weight acid to 0.01 to 2.5% by weight salt, particularly preferably 0.75 to 3.5% by weight.
• Acid on 0.075 to 0.75% by weight of salt can be used in the concentrate, so that the proportion of the mixture is 0.8 to 4.3% by weight, based in each case on the weight of the aqueous concentrate.
• these components are preferably used in a ratio of 7 to 13 parts by weight of substantially pure acid per part by weight of acid salt.
• dampening solution components of the dampening solution are water-soluble or water-miscible glycols with 2 to 6 carbon atoms and 2-ethyl-1,3-hexanediol.
• This mixture serves as a wetting agent, through which the dampening solution is to be distributed more easily over the non-image areas of the plate surface and which is also intended to delay the transfer of printing ink to the roller surface (felt covers) of the rollers used to apply the dampening solution.
• Suitable glycols are ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, neopentyl glycol and hexanediol, but propylene glycol is particularly preferred.
• the concentrate can contain 5.5 to 40.0% by weight of the glycol / diol mixture (5.0 to 25.0% by weight glycol and 0.5 to 15.0% by weight 2-ethyl-1, 3-hexanediol), the preferred proportion of the glycol / diol mixture being 14.5 to 25.5% by weight (12.0 to 18.0% by weight glycol and 2.5 to 7.5% by weight. -% 2-ethyl-1,3-hexanediol). These components are preferably used in a ratio of 2.5 to 3.5 parts by weight of glycol to one part by weight of 2-ethyl-1,3-hexanediol.
• a water-soluble metal nitrate which serves as an additional hydrophilizing agent in the system.
• Suitable salts are the nitrates of magnesium, calcium, cadmium, beryllium, aluminum, tin, zinc, zirconium, nickel, manganese, iron, chromium, copper and lead. Magnesium and zinc nitrate are preferred.
• the concentration of these salts should be chosen in such a way that precipitation which affects the quality of the printed image is avoided.
• the salts can be used in a proportion of 5.0 to 32.0% by weight, preferably 10.0 to 18.0% by weight, based on the concentrate. These weights include the weight of the associated water. In the case of magnesium nitrate, e.g. B. 6 water molecules per mole of salt.
• the concentrate may also contain phosphoric acid, which serves as a colloid preservative and also has the effect of an additional hydrophilizing agent and pH regulator. 85% are preferred Phosphoric acid, which is used in a proportion of 0.02 to 2.75% by weight, preferably 0.25 to 0.75% by weight, based on the concentrate.
• the concentrate can also be a bactericide, e.g. B. ®Dowizil-75 (manufacturer Dow Chemical Company) in an amount sufficient to prevent or delay the bacterial attack in general from 0.01 to 0.4% by weight, preferably 0.05 to 0.125% by weight, based on the concentrate.
• bactericide e.g. B. ®Dowizil-75 (manufacturer Dow Chemical Company) in an amount sufficient to prevent or delay the bacterial attack in general from 0.01 to 0.4% by weight, preferably 0.05 to 0.125% by weight, based on the concentrate.
• There may also be other inert ingredients such as. B. an indicator dye may be contained in the concentrate.
• the above-mentioned components are processed into a concentrate by dissolving them in water, preferably demineralized water.
• the concentrate preferably contains 35 to 65% by weight, particularly preferably 45 to 60% by weight, of water-soluble and water-miscible components in water.
• the printer can produce a ready-to-use fountain solution by adding about 25 to 90 g of the concentrate described above in 4 liters of water.
• the dilution ratio is preferably about 40 to 60 g of concentrate to 3.75 l of water.
• ®Dowicil-75 bactericide
• pbw parts by weight
• 9.5 pbw of powdered gum arabic are added. The solution is heated to 65 ° C. for 30 minutes with constant stirring.
• the mixture is stirred until all components have dissolved. It is then cooled to room temperature and forms the dampening solution concentrate.
• a fountain solution about 215 g (7.5 oz) of the concentrate from Example 1 are mixed with about 19 l (5 gallons) of demineralized water mixed.
• This solution (solution A) is filled into the one fountain solution box of a two-color printing machine, model Miller TP 29S.
• a commercially available dampening solution concentrate is provided for sheet-fed printing machines.
• This concentrate is a solution based on gum arabic with salts and surfactants.
• About 250 g (8.75 oz) of this concentrate are added to about 19 liters of a mixture of water and 25 vol.% Isopropanol.
• This solution (solution B) is filled into the other dampening solution box of the printing press. Each box is operated and controlled independently and supplies dampening solution to a separate printing unit.
• the two-color printing machine prints two colors in succession on each sheet of paper fed.
• the ink and dampening solution doses are set independently of each other.
• Two N-50 printing plates are appropriately exposed, developed and preserved.
• the N-50 plates are wet roughened, anodized, negative working printing plates manufactured by Enco Printing Products, a subsidiary of American Hoechst Corporation, Somerville, New Jersey, USA.
• the two prepared N-50 plates are properly clamped onto the two plate cylinders.
• a coated offset offset enameled stock is used and at the beginning of the printing process both dampening solution supply systems are switched to 36 poses.
• the ink supply is adjusted so that a wet color density of 1.35 results.
• the dampening solution setting is switched back two positions and this process continues until the printed sheet shows signs of toning, ie until the print quality proves to be inadequate.
• the dampening solution supply should be set as low as possible in order to keep the amount of water transported to a minimum. The greater the amount of water delivered to the paper, the greater the risk of wetting the paper and thus distorting the print.
• additional amounts of water mixed with the printing ink can emulsify the ink and / or cause the rollers to run bright, both of which poor print quality.
• the N-50 plate processed with the commercial dampening solution (solution B) begins to tone at a setting of 30, while the plate processed with the dampening solution according to the invention (solution A) begins to tone at a setting of 22.
• the dampening solution settings are switched back to the initial position and the experiment is repeated several times.
• the printing plate running with the commercial dampening solution (solution B) can no longer recover after the third test sequence, while the plate running with the dampening solution according to the invention (solution A) still prints cleanly even after the fourth sequence.
• New plates are prepared and printed with a dampening solution setting of 32.
• the press is stopped for an hour. After this downtime, printing continues.
• the plate used with the commercially available dampening solution (solution B) prints a dark haze, which cannot be removed by increasing the amount of dampening solution.
• the plate must first be cleaned with a plate cleaner before it delivers copies of acceptable quality.
• the plate used with the fountain solution according to the invention (solution A) runs cleanly and delivers copies of good quality within 15 prints.
• This dampening solution is particularly suitable for use in sheet-fed printing machines. It is a solution based on gum arabic with a content of salts, surfactants and an alcohol fetch replacement. About 175 g (6.25 oz) of the dampening solution concentrate is added to about 19 l (5 gallons) of a mixture of water and 20 vol.% Isopropanol. The dampening solution settings are reduced until there is a toning. It turns out that this commercially available dampening solution tones 30 when set, while the dampening solution according to the invention only tones at 22.
• the evaluation is carried out as described in Example 2, but here the N-50 plates are replaced by N-250 plates.
• the N-250 plates are electrochemically roughened, anodized, negative working printing plates from the company Enco Printing Products.
• This example describes the printing results obtained when using a fountain solution concentrate prepared according to Example 1, but in which propylene glycol has been omitted.
• a dampening solution concentrate is prepared as in Example 1, but the propylene glycol is omitted. All other components and their parts remain unchanged.
• the concentrate is diluted as stated in Example 2 and filled into the first dampening solution box of the printing press (solution C).
• the other box contains the commercially available dampening solution from example 2 (solution B).
• New plates are produced and used at setting 32 for printing.
• the press is turned off for an hour. After this downtime, printing is carried out again with the non-preserved and uncleaned plates. Both plates print a dark one Veil.
• solution B the commercially available dampening solution
• solution C cleans somewhat, but not to the extent that it can be considered acceptable. Both must be treated with a plate cleaner before satisfactory copies can be obtained.
• This example describes the printing results obtained using a dampening solution concentrate prepared according to Example 1, but in which 2-ethyl-1,3-hexanediol was omitted.
• a dampening solution concentrate is prepared as in Example 1, but without 2-ethyl-1,3-hexanediol. All other components and their parts remain unchanged.
• the concentrate is diluted as indicated in Example 2 and poured into the first dampening solution box of the printing press (solution D).
• the commercially available dampening solution from example 2 (solution B) is filled into the other box.
• New plates are produced and used at setting 32 for printing.
• the press is turned off for an hour. After this downtime, printing is carried out again with the non-preserved and uncleaned plates. Both plates print a dark veil.
• the veil cannot be removed even if the dampening solution supply is increased.
• the plate used with solution D cleans somewhat, but not to the extent that it can be considered acceptable. Both must be treated with a plate cleaner before satisfactory copies can be obtained.

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Citations (5)

• 1987
  • 1987-05-18 EP EP87107134A patent/EP0249751A3/fr not_active Ceased
  • 1987-06-15 JP JP14718487A patent/JPS634994A/ja active Pending

Patent Citations (5)

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