JPS6410198B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an aqueous overcoating composition and a printing method using the same, and more specifically to overcoating a wet oil-based ink printing surface with the composition in the form of a thin film. Therefore, the present invention provides an aqueous overcoating composition and a printing method using the same, which prevents set-off, blocking, etc., while promoting the setting of oil-based ink and improving the workability of printing and post-processing of printed matter. This is what I am trying to do. Prior Art Currently, oil-based inks used in lithographic printing, letterpress printing, etc., such as lithographic sheet-fed printing inks, mainly contain resins, drying oils, and mineral oils as binders, and are mainly dried by oxidative polymerization drying. be. Looking at the drying process of oil-based ink in more detail, when oil-based ink is printed on paper, some of the mineral oil and drying oil in the ink penetrate into the paper and form a semi-dry film on the paper. is formed (this state is generally called set), and then the drying oil reacts with oxygen to undergo oxidative polymerization and harden, resulting in complete drying. It usually takes 15 to 30 minutes for setting and 3 to 10 hours for complete drying. As mentioned above, it takes an extremely long time to set and dry these oil-based inks, which hinders the printing speed and the required work efficiency, posing a major problem. Therefore, for example, in sheet-fed planographic printing, it is important to spray fine powder such as starch (spray powder) on the printed surface immediately after printing to prevent set-off and to remove grating. The reality is that it is happening. However, with this method, fine powder scatters and floats, which poses environmental hygiene problems.Fine powder also adheres to the printing surface, which deteriorates gloss and makes the surface rough, reducing print quality. It is the cause. In addition, even if such spray powder is applied, it is not possible to stack the desired amount of printed matter, and furthermore, it is not suitable for post-processing such as cutting or folding, and it is necessary to leave it for several hours to dry the ink. It was something that had to wait. In addition, in rotary printing presses, undried ink adheres to mechanical parts such as paper roll feed rollers, tension rollers, and folding machines built into the printing press, which may transfer back onto the printed material and stain the printed material. When rolled up or folded printed matter is bundled, they tend to set off or block each other, making high-speed rotary printing impossible. To prevent this, we use evaporative drying ink, which mainly evaporates the solvent in the ink, and use a large dryer such as a burner, infrared heater, or hot air to heat the paper surface to around 130℃ and dry it. Inks such as UV inks that harden quickly with active energy rays are used. However, in the case of the former type of ink (generally called heat-set ink), the solvent in the ink is rapidly evaporated, so energy consumption such as gas and electricity is large, and the steam containing the solvent is large. There are problems such as air pollution and odor due to the exhaust, and furthermore, it is difficult to obtain printed matter with various aptitudes such as gloss. In addition, in the case of post-printing, special equipment is required due to the use of special reactive inks, special printing plates, blankets, and ink cleaning agents are required.Not only are the inks expensive, but storage is also difficult. It has problems such as lack of stability, stability, and workability.
It has not become very popular. In contrast, recently, a film of water-based coating agent is formed on the wet printing surface immediately after lithographic printing, which improves the above-mentioned problems caused by the drying of printing ink, and at the same time gives the printed surface various resistances such as gloss. Coating methods have been developed. Purpose of the Invention However, by applying the water-based coating agent used in this method onto the oil-based ink in a wet state, the surface of the oil-based ink is covered.
Although it can prevent phenomena such as set-off or blocking caused by stacking printed matter to some extent, it only has the ability to cover the oil-based ink and may accelerate the setting or drying of the oil-based ink. There was no significant effect, and work such as post-printing could only be done several hours after printing, as in the past. Furthermore, when water-based coating agents are applied onto wet oil-based ink, they may not provide sufficient adhesion or may not provide the gloss or abrasion resistance required for high-quality printed materials. This was problematic. In order to solve the above-mentioned drying problems of oil-based inks, the present inventors have conducted extensive research on water-based overcoating compositions to be applied over wet oil-based inks. It has adhesive properties and not only improves the coating performance of oil-based inks, such as gloss and abrasion resistance, but also prevents set-off and blocking phenomena during stacking after printing, while also improving the setting of oil-based inks. Alternatively, they have discovered an aqueous overcoating composition that has the effect of significantly improving drying properties, and have completed the present invention. Structure of the Invention The present invention provides an aqueous overcoating composition for coating onto oil-based ink in a wet state after printing, the composition comprising an aqueous resin dispersion mainly composed of an acrylic copolymer;
Containing a dibasic acid dialkyl ester represented by the following general formula in an amount of 1% by weight or more based on the total amount of the composition,
The present invention also aims to provide an aqueous overcoating composition characterized by having the ability to form a film at ambient temperature during printing or heating operations. General formula, R ₁ OOC−X−COOR ₂ (However, R ₁ ,
R ₂ represents an alkyl group having 1 to 8 carbon atoms, and X represents a residue of an aliphatic dibasic acid or an aromatic dibasic acid. ) Furthermore, the present invention provides a printing method using the above-mentioned aqueous overcoating composition. Hereinafter, the aqueous overcoating composition according to the present invention will be explained in more detail. The aqueous overcoating composition according to the present invention is mainly composed of an aqueous resin dispersion obtained by emulsion polymerization of a polymerizable acrylic monomer, and the atmospheric temperature during printing or heating drying operation is preferably 80°C. More preferably, it is necessary to have the ability to form a film at room temperature. 80℃
If this is the case, a large amount of energy is required for film formation, and a device similar to a conventional drying device is required. If the temperature is 80° C. or lower, relatively little energy is required for film formation, and therefore a simple drying device can be used, which is preferable from the viewpoint of the purpose of the present invention. For those that form a film at room temperature,
This is more preferable because it does not particularly require energy for film formation. Such aqueous resin dispersions are produced by emulsion polymerization of acrylic monomers, taking into consideration the glass transition temperature (Tg) of the polymer of the acrylic monomers used, and adding other acrylic monomers. By setting the polymerization ratio, etc., the desired film-forming temperature of the dispersion can be adjusted, and a dispersion that forms a continuous film at a desired temperature can be produced. In setting Tg,
By setting the polymerization ratio according to Wood's approximate formula, the desired Tg dispersion can be obtained. In this case, the film forming temperature should be 80°C, taking into consideration the atmospheric temperature during application of the dispersion and the heating energy given for continuous film formation as necessary.
Hereinafter, it is more preferable to use one that forms a film at room temperature. Examples of acrylic monomers that can be used to synthesize the above dispersion include the following. First, acrylic monomers that can produce relatively high Tg polymers include methyl methacrylate, ethyl methacrylate, and other monomers such as styrene, α-
An example is methylstyrene. Acrylic monomers that can obtain polymers with relatively low Tg include alkyl esters of acrylic acid or methacrylic acid other than the above-mentioned methyl methacrylate and ethyl methacrylate, such as methyl, ethyl, propyl, isopropyl, n-butyl, Examples include esters having a linear or side chain acrylic group such as s-butyl, t-butyl, hexyl, and lauryl. In addition, it is also possible to copolymerize other acrylic monomers in addition to the above-mentioned monomers, such as acrylic monomers having functional groups such as unsaturated carboxylic acids such as acrylic acid and methacrylic acid. but,
If a monomer having a functional group is used among the monomers mentioned above, it may not be possible to obtain a stable dispersion, and even if a stable dispersion is obtained, the resistance such as water resistance and chemical resistance of the film after film formation may be affected. It is important that the acid value is below 50 as it may have an adverse effect; if it exceeds it, water resistance, drying properties, and film forming properties will be adversely affected, so the amount used should be adjusted depending on the purpose of use. is necessary. To obtain these dispersions, the monomers mentioned above may be stably dispersed by emulsion polymerization using a hydrophilic catalyst such as ammonium persulfate, potassium persulfate, or hydrogen peroxide or a redox catalyst by a generally known method. Emulsifiers can also be added if desired. It is sufficient to copolymerize a mixture of acrylic monomers in an emulsified state in the presence of an anionic or nonionic surfactant as an emulsifier, but in general, the use of a low-molecular surfactant will improve the water resistance of the resulting film.
This may have a negative effect on chemical resistance, etc.
When water resistance is particularly required, polymeric anionic activators are suitable as emulsifiers. The aqueous dispersion resin according to the present invention also has excellent performance by using such an emulsifier. Examples of such polymeric emulsifiers include silica, acrylic acid copolymers having carboxyl groups, or maleic acid copolymers, and aqueous alkaline solutions thereof can be used. As mentioned above, it is also possible to set the desired film-forming temperature for the emulsion-polymerized dispersion itself and use a dispersion made of one copolymer resin, but it is also possible to use a dispersion made of a single copolymer resin, but The desired dispersion can also be obtained by preparing a dispersion and a dispersion of a relatively low Tg polymer, applying it to Wood's equation mentioned above, and blending these dispersions (polymer blend). I can do it. Further, the dibasic acid dialkyl ester added to the aqueous resin dispersion is represented by the following general formula, and is 1% by weight or more, preferably 1 to 8% by weight, based on the total amount of the aqueous overcoating composition. More preferably, it needs to be contained in an amount of 3 to 5% by weight. If the amount added is less than 1% by weight, the desired effect of the present invention cannot be obtained, and if the amount added is more than 8% by weight, it may have an adverse effect on the storage stability of the dispersion, which is not preferable. The diester of the dibasic acid to be added has the general formula: R ₁ OOC-X-COOR ₂ (wherein R ₁ and R ₂ represent an alkyl group having 1 to 8 carbon atoms, and X is an aliphatic dibasic acid or (represents a residue of an aromatic dibasic acid). Specifically, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid,
Decanedicarboxylic acid, fumaric acid, maleic acid,
Aliphatic dibasic acids such as itaconic acid, citraconic acid, mesaconic acid, or phthalic acid, isophthalic acid,
Aromatic dibasic acids such as terephthalic acid, or their anhydrides, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, peptyl alcohol Examples include dibasic acid dialkyl esters synthesized by a diesterification reaction with lower aliphatic alcohols having 1 to 8 carbon atoms such as octyl alcohol and 2-ethylhexyl alcohol. In these dibasic acid dialkyl esters,
In the case of a diester compound derived from an aliphatic dibasic acid, X in the above general formula is effectively a diester compound represented by an alkylene group or an alkenyl group having 1 to 10 carbon atoms, and a diester compound having a larger number of carbon atoms is effective. However, the uniformity of mixing into the aqueous resin dispersion is poor,
In addition, the stability of the aqueous overcoating composition over time or the uniform setting of the oil-based ink is poor. As for aromatic dibasic acids, diester derivatives derived from various phthalic acids are preferred. In addition, R ₁ and R ₂ in the general formula must be an alkyl group having 1 to 8 carbon atoms, and if the number of carbon atoms is larger than that, it will not be possible to mix uniformly into the aqueous resin dispersion or be stable over time. Not sexual enough. The above-mentioned diester compounds of dibasic acids have traditionally been appropriately added as plasticizers in the field of various coating materials, and they are used to improve the coating film properties of the coating materials to which they are added, such as flexibility and abrasion resistance. It was already known to those skilled in the art to improve the properties or adhesion. However, when the aqueous overcoating composition specified in the present invention containing a predetermined amount of these compounds is applied onto a wet oil-based ink, it significantly improves the setting properties of the oil-based ink located in the lower layer. is completely unpredictable. In the comparative examples specifically explained below, the effects are compared with polyethylene glycol and polypropylene glycol, which are well-known plasticizers other than the dibasic acid diester specified in the present invention. It was confirmed that the coating composition did not contribute to improving the setting or drying properties of the underlying oil-based ink. On the other hand, the aqueous overcoating composition composed of the aqueous resin dispersion and the above-mentioned specific ester according to the present invention exhibits a remarkable effect on improving the setting or drying properties of the oil-based ink in the lower layer, and is effective in improving the setting or drying properties of the oil-based ink immediately after printing. When applied in layers, it is possible to perform processing such as cutting or bending immediately after application, and it has extremely excellent performance, allowing post-processing to be performed immediately, which previously could only be done several hours after printing. It is something. The aqueous overcoating composition according to the present invention is mainly composed of the above-mentioned aqueous resin dispersion and the above-mentioned dibasic acid dialkyl ester, but it can improve initial adhesion when applied onto oil-based ink, or From the viewpoint of improving coating film performance such as abrasion resistance after drying of the aqueous overcoating composition, if necessary, 0 to
15% by weight of water-soluble varnish can be added. In this case, the water-soluble varnish used can be an aqueous solution of an alkali-soluble resin that has been conventionally used as a varnish for water-based printing inks. Alkaline aqueous solutions of various resins such as casein and casein can be used. Adding a large amount of this water-soluble varnish will reduce the drying performance, but will also greatly affect the film-forming performance, which may impede the improvement of the setting or drying performance that is the objective of the present invention. Requires great care. Note that the drying properties of the aqueous overcoating composition itself are also necessary from the viewpoint of preventing set-off and blocking, and it is preferable to add a water-miscible solvent with a relatively low boiling point such as methyl alcohol, ethyl alcohol, or propyl alcohol. . Considering the drying properties of the aqueous overcoating composition, the amount of these additives should be 1 to 1 to the total amount.
It can be added in a range of 10% by weight. Other optional components may be included in the aqueous overcoating composition as needed, and various additives may be added in consideration of various coating film performances such as viscosity adjustment, drying adjustment, gloss, and abrasion resistance, or leveling. It is also possible to add other alcohols, antifoaming agents, waxes, and various mold release agents. The following methods can be used to coat the oil-based ink in a wet state immediately after printing using the aqueous overcoating composition as described above. One method is to incorporate a coating device after the final printing unit of the printing press.
It can be coated on printed matter immediately after printing. FIG. 1 shows a case where a coating device is installed after the final printing unit, where 1 is the final printing unit, 2 is the coating device, and 3 is a drying device provided as necessary. Although FIG. 1 illustrates a typical roller coating unit, other coating methods such as spray coating, air knife coating, engraved roll coating, etc. can also be applied. In addition, as another coating method, for example, in the case of lithographic printing, it is possible to use a leftover printing unit of a lithographic printing machine and use a conventional dampening water supply device to coat the printed matter immediately after printing. . FIG. 2 shows a specific example of coating with an aqueous overcoating composition using a conventional general final printing unit. Using the aqueous overcoating composition according to the present invention instead of dampening water, the dampening water supply device 5
From there, coating is applied via a blanket 7 through a printing plate 6 (after performing operations such as converting the printing plate into a coating pattern as necessary). Alternatively, as shown in FIG. 3, in the final printing unit, the plate cylinder 6 and the blanket 7 are separated and a device 11 is provided for supplying the aqueous overcoating composition directly to the blanket. It can be coated on top. By using the various coating methods explained above, it is possible to apply a desired coating on the oil-based ink in a wet state immediately after printing on the printing machine (online or inline), which is different from conventional methods. The object of the present invention can be achieved without any special modifications to the existing printing press or by incorporating a simple coating device. In this way, the aqueous overcoating composition is coated on the wet oil-based ink immediately after printing, and the composition is heated to form a film as necessary, which not only improves suitability for high-speed printing, but also improves suitability for high-speed printing.
It also has immediate suitability for post-processing and is extremely advantageous for increasing the efficiency of printing and post-processing operations. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Synthesis Example 1 Aqueous resin dispersions shown as Dispersions 1 to 10 were obtained using the acrylic monomers shown in Table 1 in the respective proportions and according to a conventional emulsion polymerization method. As the emulsifier, an ammonia aqueous solution of an acrylic copolymer (Johncryl 67, manufactured by Johnson & Son) was used. Furthermore, the nonvolatile content in the aqueous resin dispersion was adjusted to about 45%, and the nonvolatile content of the acrylic copolymer as a dispersant was adjusted to about 3% in the aqueous resin dispersion.

[Table] Synthesis Example 2 Using Dispersion 3 and Dispersion 5 obtained in Synthesis Example 1, polymer blend each dispersion at a ratio of 20:80 and 40:60, and make each dispersion into a dispersion.
11 and 12. Examples 1 to 11 and Comparative Examples 1 to 3 Using the dispersions 1 to 2 and 4 to 12 obtained in Synthesis Examples 1 and 2, according to Table 2, the two specified in the present invention were added to 96% by weight of each dispersion. A basic acid dialkyl ester and 4% by weight of each of polyethylene glycol and polypropylene glycol, which are conventionally well-known plasticizers, were added and mixed to prepare an aqueous overcoating composition. Note that Comparative Example 1 shows a case where the dispersion was 100%.

[Table] Printing test 1 In order to evaluate the drying properties of the aqueous overcoating composition according to the present invention and the effect of promoting the setting of oil-based inks, paper laminated with aluminum foil was used instead of ordinary paper, and oil-based ink was The following tests were conducted with the penetration of mineral oil, etc., into the paper being inhibited. Using an R1 tester, print a regular offset ink as an oil-based ink on the aluminum surface of paper laminated with aluminum foil. Examples 1 to 11 and Comparative Examples 1 to 3 were applied on the wet ink immediately after printing.
Using each of the aqueous overcoating compositions obtained above, coating was performed using a bar coater at an ambient temperature of 25°C, and the drying properties of the overcoating compositions and the setting state of the offset ink were examined. The results are shown in Table-3.

[Table] Evaluation method 1 Drying property: After applying the aqueous overcoating composition, rub the surface with a rubber spatula and check the drying time of the coating agent. Those that took 1 minute were evaluated as △, and those that took more than 1 minute were evaluated as ×. 2 Setting state of offset ink After applying the aqueous overcoating composition, it was left to stand for 90 seconds, cellophane tape was pasted on the coating composition, and the differences in the peeling state of the cellophane tape were evaluated as follows. . In other words, if the offset ink is set, a type of cohesive rupture will not occur within the ink layer, so in the situation of peeling off the cellophane tape, the tape / Items that are separated at the interface of the overcoating composition or the offset ink/aluminum foil interface are marked with an ○, indicating that the setting is complete.
△, 5 for those that complete setting after 5 minutes even if cohesive cracks occur between the offset ink layers.
A case where the setting was not completed even after a minute had passed was rated as ×. As is clear from the above results, the aqueous overcoating composition containing the dibasic acid dialkyl ester specified in the present invention does not directly affect the drying rate of the coating agent itself, but it improves the setting of oil-based ink. It can be seen that this has a significant effect on improvement. However, other plasticizers commonly used in the past have been found to have no effect on set. Examples 12 to 17 and Comparative Example 4 In order to investigate the difference in effects depending on the amount of dibasic acid diester specified in the present invention, the mixed solvents shown in Table 4 were used at different ratios to 92% by weight of Dispersion 1. te8
% by weight to prepare an aqueous overcoating composition. Furthermore, each of the prepared coating compositions was evaluated in the same manner as in Printing Test 1, and the results are listed in Table 4.

[Table] From the above results, it can be seen that the aqueous overcoating composition containing 1% by weight or more of the ester specified in the present invention can significantly improve the setting of offset ink. It should be noted that if it is added in an amount of 8% by weight or more, a sufficient effect can be obtained in terms of improving set, etc., but it is not sufficient in terms of storage stability. Examples 18 to 20 and Comparative Example 5 An aqueous solution type varnish was applied to the aqueous overcoating composition specified in the present invention (Dispersion 1, 92% by weight, 4% by weight of sebacate sibutyl ester, 4% by weight of ethanol). (acrylic copolymer,
A similar aqueous overcoating composition was prepared as shown in Table 5 by mixing an aqueous ammonia solution of Johncryl 67 (resin content: 30%), and the difference in effect due to the addition of an aqueous varnish was evaluated. The same evaluation as in Printing Test-1 was performed, and the results are listed in Table-5.

[Table] From the above results, the addition of 20% by weight of aqueous varnish tends to impede the drying properties and setting properties of offset ink, and the amount of varnish needs to be 15% or less. Printing test-2 As a case of coating continuously with the printing process,
Carton printing was carried out using ordinary lithographic printing ink on a lithographic sheet-fed four-color machine, and 20 sheets of printed matter coated with an aqueous overcoating composition were taken out and piled up under a load of 5 kg/cm ² . After 1 hour, the presence or absence of set-off and blocking was evaluated. Immediately after coating, the printed matter was cut out using a slicing machine, and the presence or absence of wrinkles was evaluated. The results are shown in Table-6. The aqueous overcoating composition was supplied from the dampening water device of the last printing unit (fourth color) and applied onto the three-color printed surface. Printing conditions: 25℃, printing speed 6000
It is set as 1 sheet per hour. In addition, Examples 1, 3, 13, 18 and Comparative Examples 1, 2, 4, and 5 were used as coating compositions, and when not coated, a standard amount of a normal anti-set-off agent (spray powder) was used. .

[Table] As is clear from the above results, those using the aqueous coating composition according to the present invention had excellent drying properties and setting properties, and did not cause set-off or blocking. Furthermore, even if the product coated with the aqueous overcoating composition of the present invention is cut immediately after coating, there is no fading phenomenon due to insufficient drying of the oil-based ink, which not only improves printing workability, but also improves printing workability. This significantly improved the workability of processing. On the other hand, in the case of the comparative example, the fading phenomenon was not improved until several hours had passed after application. Printing trial-3 When the printing process, coating process, and heating process are performed continuously, a low-temperature drying type heat set ink is used in a planographic rotary printing machine, and a gravure coater is installed between the printing machine and the dryer. The aqueous overcoating compositions of Examples 1, 3, 8, 13, and 18 and Comparative Examples 1, 2, 4, and 5 were applied onto the printed surface. The printing conditions are 25℃ and printing speed 300.
The heating conditions of the dryer were measured in m/min when the burner and various guide rollers made of hot air were not contaminated. Furthermore, we investigated the occurrence of stains on the folding machine that folds the printed matter, and the occurrence of blocking after cutting and bundling. The results are shown in Table-7.

[Table] From the above results, by using the aqueous overcoating composition of the present invention, it is possible to significantly lower the dryer temperature of a rotary lithographic printing press.
Furthermore, heating can be eliminated. Further, there was no staining caused by belts or the like in the folding machine, nor did set-off or blocking occur after bundling. (Note 1) and (Note 2) in Table 7 have the same meanings as in Table 6 above.

[Brief explanation of drawings]

FIG. 1 shows an embodiment in which a coating device is installed after the final printing unit. FIG. 2 shows an embodiment in which a conventional final printing unit is used to coat the printing plate with the aqueous overcoating composition of the present invention in place of the conventional fountain solution, with the oil-based ink supply means separated from the printing plate. FIG. 3 shows an embodiment in which the aqueous overcoating composition is applied directly to the blanket while the plate and blanket are separated in the final printing unit. 1: Final printing unit, 2: Coating device, 3: Drying device, 4: Oil-based ink supply means,
5: dampening water supply device, 6: printing plate, 7: blanket, 8: printing paper.

Claims (1)

[Scope of Claims] 1. An aqueous overcoating composition for coating onto a wet oil-based ink printed surface immediately after printing, wherein the composition is an aqueous resin dispersion mainly composed of an acrylic copolymer. and,
General formula: R ₁ OOC-X-COOR ₂ (wherein R ₁ and R ₂ represent an alkyl group having 1 to 8 carbon atoms, and X represents a residue of an aliphatic dibasic acid or an aromatic dibasic acid. ) for an aqueous overcoating, which contains a dibasic acid dialkyl ester represented by 1% by weight or more based on the total amount of the composition, and has the ability to form a film at ambient temperature during printing or heating drying operations. Composition. 2 The aqueous overcoating composition is heated to 80°C.
Claim 1: The film is formed at the following atmospheric temperature:
The aqueous overcoating composition described in 1. 3. The aqueous overcoating composition according to claim 1, which forms a film at room temperature. 4. The aqueous overcoating composition according to any one of claims 1 to 3, wherein the aqueous resin dispersion has an acid value of 50 or less. 5. The aqueous overcoating composition according to any one of claims 1 to 4, which contains 1 to 5% by weight of a dibasic acid dialkyl ester represented by the general formula. 6 An aqueous resin dispersion mainly composed of an acrylic copolymer and the general formula R ₁ OOC-X-COOR ₂ (wherein R ₁ and R ₂ represent an alkyl group having 1 to 8 carbon atoms, and X is (representing the residue of an aliphatic dibasic acid or an aromatic dibasic acid) containing 1% by weight or more of a dibasic acid dialkyl ester, and having the ability to form a film at ambient temperature during printing or heating drying operations. A printing method characterized by applying an aqueous overcoating composition having a thin film onto a wet oil-based ink printing surface on a printing machine immediately after printing the oil-based ink or during a printing process. 7. A printing method according to claim 6, characterized in that a coating device is installed after the final printing unit of the printing press, and the aqueous overcoating composition is applied by the coating device. 8. Claim 6, characterized in that the aqueous overcoating composition is applied using a dampening water supply device of the final printing unit of a lithographic printing press.
Printing method described in section. 9. A printing method according to claim 6, characterized in that a device is provided for supplying the aqueous overcoating composition to the blanket of the final printing unit of the lithographic printing press.