Method for producing a printing blanket for use in printing moulded bodies

Abstract

The invention relates to a method for producing a printing blanket for use in printing rotationally symmetrical molded bodies, comprising the process steps: a1) selection of two or more printing inks with different chemical compositions for use in a printing process for printing rotationally symmetrical molded bodies using the printing blanket to be produced, wherein the selected printing inks are solvent-based printing inks comprising one or more organic solvents with a boiling point at 100 kPa in the range of 150 to 250 °C, and b1) production of a printing blanket, wherein the printing blanket comprises a printing surface provided for transferring a printed image onto the molded body, wherein the printing surface is formed by a rubber material, the rubber material being matched to the selected printing inks.that the rubber material in the swelling test shows a thickness change of 30 µm or less for each of the selected printing inks after 5 days of exposure, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less.

Description

[0001] The invention relates to a method for producing a printing blanket for use in printing rotationally symmetrical molded bodies, a related method for printing rotationally symmetrical molded bodies, and a kit for use in such a printing process. Furthermore, an advantageous printing blanket is disclosed.

[0002] In numerous industries, particularly those manufacturing products for end consumers, it is crucial that the products have an appealing appearance and can be customized by the manufacturers. For this purpose, printing processes that allow substrates to be printed with a predefined image are of great importance in many sectors, for example, in the printing of beverage cans. A variety of different printing processes have become established for printing on substrates, such as offset printing and digital printing. These printing processes are generally familiar to experts. Many of these processes share the common feature that the final printing step onto the substrate is carried out by a printing cylinder onto which a printing blanket is mounted.

[0003] Indirect printing processes, used for printing on cans and other rotationally symmetrical shapes, are characterized by the fact that the printing plate transfers the ink to a transfer medium, the printing blanket. The printed image is then transferred from the ink to the substrate.

[0004] The corresponding printing blankets serve to optimally print the substrates and are generally known from the prior art, for example from EP 2361784 B1.

[0005] The properties of the printing blanket used have a significant influence on the printing properties and can particularly affect the printing quality.

[0006] In practice, a major problem arises from the fact that these printing processes are often not used for a single, identical print image. Rather, given typical order volumes and printing capacities, the situation frequently arises where the print image must be changed to process a new print job. This change of print image is regularly associated with a change in the colors used and / or a change in the color distribution. If the same printing blanket is used for the subsequent print job, this can easily lead to quality limitations, where a ghost image of the previous print job becomes visible on the newly printed substrate after printing.

[0007] Even though ghosting and other quality issues caused by changing the print image can be reliably avoided by switching to a new printing blanket along with the print image, this approach is considered disadvantageous from many perspectives. Frequent blanket changes increase printing costs, as well as the time required for changing the print image. Furthermore, this practice increases the amount of waste generated from used printing blankets, which is detrimental to the sustainability of the printing processes.

[0008] The primary objective of the present invention was to eliminate or at least reduce the disadvantages of the prior art.

[0009] In particular, the object of the present invention was to provide a solution with which the time and cost efficiency of printing blanket-based printing processes for printing on rotationally symmetrical shaped bodies, especially cans, can be advantageously increased.

[0010] In this respect, it was an object of the present invention that the solution to be specified should make it possible to increase the service life of printing blankets in printing processes.

[0011] A further object of the present invention was that the solution to be specified should counteract the occurrence of ghost images and other quality limitations caused by the change of the printed image, whereby it was a desirable requirement that this should eliminate the need to apply a new printing blanket with each change of the printed image, particularly also in cases where the printing inks used for the printing process are individually mixed from some basic colors and therefore differ between different printing processes.

[0012] In other words, an object of the present invention was that the solution to be specified should make it possible to print several different images successively without changing the printing blanket, without the occurrence of ghost images and other quality limitations caused by changing the printed image.

[0013] It was an object of the present invention that the solution to be specified should make it possible to obtain printing blankets that enable an efficient transfer of printing ink onto a substrate.

[0014] Furthermore, it was an object of the present invention that the solution to be specified should make it possible to reduce the waste generated in printing plants.

[0015] A further objective of the present invention was to ensure that the implementation of the specified solution was particularly easy for printing companies and, ideally, should not require any additional machinery or the use of additional chemicals on the part of the printing companies.

[0016] Furthermore, it was an object of the present invention that the solution to be specified should enable printing companies to work as extensively as possible with the printing inks already established in the printing industry for printing on rotationally symmetrical shaped bodies such as cans.

[0017] Furthermore, it was an object of the present invention to provide an advantageous method for producing a printing blanket and a kit for use in this method.

[0018] Furthermore, it was an object of the present invention to provide an advantageous method for printing rotationally symmetrical molded bodies.

[0019] The inventors of the present invention have now found that the aforementioned problems can be solved by using a method for producing a printing blanket for use in printing rotationally symmetrical molded bodies, in which the printing surface of the printing blanket is specifically tailored to the printing inks used in the subsequent printing process for printing rotationally symmetrical molded bodies using the printing blanket to be produced, as defined in the claims.

[0020] In an advantageous way, printing blankets produced in this manner can efficiently counteract the occurrence of ghost images and other quality limitations caused by changes in the printed image, thus eliminating the need to apply a new printing blanket every time the printed image is changed.

[0021] In the inventors' experiments, a significant improvement was achieved in a printing plant that, under normal operating conditions, replaces its printing blankets at least once every 8 hours, or at least with every change of the printed image, to avoid quality limitations. The printing blanket produced using the inventive method and tailored to the printing inks used by the printing plant achieved a service life of 79 hours under otherwise identical conditions, without any loss of quality. During this period, eight changes of the printed image were made, and a total of 5.1 million cans were printed.

[0022] The aforementioned problems are thus solved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention are described in the dependent claims and the following descriptions.

[0023] Such embodiments, which are hereinafter referred to as preferred, are combined in particularly preferred embodiments with features of other embodiments referred to as preferred. Combinations of two or more of the embodiments referred to below as particularly preferred are therefore especially preferred. Also preferred are embodiments in which a feature of one embodiment referred to as preferred to any degree is combined with one or more further features of other embodiments referred to as preferred to any degree. Features of preferred printing processes, printing blankets, and kits result from the features of preferred processes.

[0024] Particularly preferred embodiments of the invention are disclosed in the exemplary embodiments. Particularly preferred embodiments of the invention have two or more, preferably three or more, and most preferably four or more, of the preferred features of the invention disclosed below, which are also implemented in the exemplary embodiments.

[0025] The invention relates in particular to a method for producing a printing blanket for use in printing rotationally symmetrical molded bodies, comprising the following process steps: a1) Selection of two or more printing inks with different chemical compositions for use in a printing process for printing rotationally symmetrical molded bodies using the printing blanket to be produced, wherein the selected printing inks are solvent-based printing inks comprising one or more organic solvents with a boiling point at 100 kPa in the range of 150 to 250 °C, and b1) Production of a printing blanket, wherein the printing blanket comprises a printing surface intended for transferring a printed image onto the molded body, wherein the printing surface is formed at least partially by a rubber material, wherein the rubber material is such that, in the swelling test after 5 days of exposure, the rubber material shows a thickness change of 30 µm or less for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less, wherein the swelling test is carried out with a circular sample of the rubber material with a diameter of 2.5 cm and one-sided surface wetting with the printing ink, wherein the thickness change is measured with a thickness gauge with a 1 cm 2 The measurement is performed on a large measuring plate with a preload of 5 N.

[0026] The method according to the invention serves to produce printing blankets for use in printing on rotationally symmetrical molded bodies. The printing blanket produced by the method according to the invention is suitable and intended for printing on rotationally symmetrical molded bodies, and can advantageously also be used in principle in a wide range of known printing processes as well as for printing on a variety of other molded bodies. However, the printing blanket produced by the method according to the invention is optimized for use in printing on rotationally symmetrical molded bodies, in particular beverage cans.

[0027] For a person skilled in the art, it is clear that the definition of a "printing blanket" implies a certain functional suitability for use as such. In particular, a printing blanket is suitable for allowing conventional printing inks to be deposited on its surface to create a printed image. A person skilled in the art understands that this implies a certain functional lower limit for the wettability of the printing surface with printing ink, regardless of whether this is determined by surface structuring and / or material selection. In accordance with expert understanding, for example, neither a surface structured to achieve the lotus effect nor a PTFE-coated surface, which repel specific printing inks, would be suitable for use as a printing blanket.The suitability as a printing blanket is confirmed by a specialist in accordance with industry-standard procedures, for example, based on the color density, which serves as a cross-industry indicator.

[0028] In a first process step a1), two or more printing inks with different chemical compositions are selected for the printing blanket to be produced in a subsequent printing process for printing on molded parts. This serves the purpose of specifically tailoring the printing blanket to the different compositions of the printing inks to be used in the subsequent printing process.

[0029] The person skilled in the art understands that this means, for essentially all embodiments, that process step a1) also includes the production or provision, preferably the provision, of two or more selected printing inks. This makes it possible to test the printing inks for the purpose of matching.

[0030] An important aspect of the invention is that in process step a1), two or more printing inks with different chemical compositions are selected and used as the basis for specific adjustment. Thus, the subsequent adjustment of the printed surface to the printing inks is not performed in isolation for a single printing ink, but for a larger range of possible printing inks. A preferred method according to the invention is one in which, in process step a1), three or more, preferably four or more, and particularly preferably five or more, printing inks with different chemical compositions are selected.

[0031] The different printing inks can expediently include some or all of the printing inks used by a printing company for which the printing blanket is to be optimized, especially in different print images, whereby the primary colors from which the printing company mixes different printing inks in later use can be used for optimization in particular.

[0032] It is particularly advantageous if the printing inks selected in process step a1) are different printing inks from the same ink manufacturer. This is often beneficial, as many printing companies primarily use inks from a single manufacturer.

[0033] The inventors have found that significant advantages can be achieved simply by using at least two printing inks. This is particularly relevant because, in practice, printing operations typically use only a relatively limited number of different inks, which are mixed to achieve the desired color effects. Since the different inks from the same manufacturer are, on average, less distinguishable from one another than the inks from different manufacturers, using two inks is already highly advantageous, especially for manufacturer-specific optimization. An example of this relevance is the printing of different barcodes on cans, which are printed in black and white and must be clearly legible.

[0034] The inventors' experiments have shown that excellent results can be achieved by selecting only two printing inks, particularly when at least one of the selected inks is black and at least one is white. In other words, the inventive method is particularly advantageous when the printing inks used in a printing process for printing rotationally symmetrical molded parts using the printing blanket to be produced are selected from black and white inks.

[0035] In principle, an advantage of the method according to the invention is that the teaching can be adapted to a wide range of possible printing inks and is therefore not limited, for example, to a specific printing ink manufacturer or a specific chemical composition. The preceding definition that the selected printing inks are solvent-based printing inks comprising one or more organic solvents with a boiling point of 100 kPa in the range of 150 to 250 °C expresses that the printing inks are similar in their basic type and ensures that the desired tunability of the rubber material is guaranteed and that this tunability can be achieved without excessive effort.This definition, in accordance with expert understanding, excludes large portions of the printing inks used in other printing processes that rely on low-boiling solvents. A preferred method according to the invention is one in which the mass fraction of solvents having a boiling point of less than 150 °C at 100 kPa is 5% or less, preferably 2% or less, particularly preferably 1% or less, and most preferably 0.1% or less, based on the mass of the printing ink.

[0036] The inventors have found that the invention can be implemented particularly well with alcoholic printing inks. A preferred method according to the invention is one in which the organic solvents are alcohols.

[0037] A preferred method according to the invention is one in which the printing inks comprise one or more alcohols as solvents, having a boiling point at 100 kPa of 150 °C or higher, preferably 160 °C or higher. A particularly preferred method according to the invention is one in which the printing ink comprises one or more alcohols as solvents, selected from the group consisting of dibutylaminoethanol, butoxypolyethylene glycol, butoxypolypropylene glycol, and propane-1,2-diol.

[0038] A preferred method according to the invention is one in which the printing inks comprise one or more solvents in a combined mass fraction of 25% or more, preferably 30% or more, and particularly preferably 35% or more, based on the mass of the printing inks. A preferred method according to the invention is additionally or alternatively one in which the printing inks comprise one or more alcohols in a combined mass fraction of 25% or more, preferably 30% or more, and particularly preferably 35% or more, based on the mass of the printing inks.

[0039] A preferred method according to the invention is additionally or alternatively wherein the printing inks comprise one or more organic binders, preferably in a combined mass fraction in the range of 10 to 80%, particularly preferably in the range of 15 to 70%, based on the mass of the printing ink.

[0040] A preferred or alternative method according to the invention is one in which at least one of the selected printing inks, preferably all of the selected printing inks, comprises one or more fillers, preferably inorganic pigments, preferably in a combined mass fraction in the range of 10 to 50%, particularly preferably in the range of 15 to 45%, based on the mass of the printing ink.

[0041] A preferred method according to the invention is further or alternatively a method wherein at least one of the selected printing inks, preferably all of the selected printing inks, comprises one or more plasticizers other than organic solvents, in particular plasticizer oils, preferably in a combined mass fraction in the range of 5 to 45%, particularly preferably in the range of 10 to 40%, based on the mass of the printing ink.

[0042] In process step b1), the printing blanket is produced, which, in accordance with expert expectations, comprises a printing surface provided for the transfer of the printed image onto the rotationally symmetrical molded body, and which is formed at least partially by a rubber material. A preferred method according to the invention is one in which the printing surface is formed by the rubber material to a surface area of ​​50% or more, preferably 70% or more, particularly preferably 90% or more, most preferably 95% or more, and in particular to substantially 100%.

[0043] For the majority of applications, a method according to the invention is preferred, wherein the printing surface of the printing blanket is formed by a printing layer of a multi-layered printing blanket. Analogous to the foregoing descriptions, a method according to the invention is then preferred, wherein the printing layer consists of a mass fraction of 50% or more, preferably 70% or more, particularly preferably 90% or more, and most preferably 95% or more, of the rubber material, based on the mass of the printing layer.

[0044] The printing blanket is specifically tailored to the previously selected printing inks with regard to the choice of rubber material, as further revealed below.

[0045] It can be considered an advantage of the present invention that the printing blanket to be produced can also be very flexibly adapted to the respective requirements of each application, whereby the inventors have succeeded in identifying particularly advantageous designs in principle, with which excellent printing results can be achieved in later use.

[0046] A preferred method according to the invention is one in which the printing blanket comprises a textile layer arranged on the side facing away from the printing surface, wherein the textile layer comprises a textile sheet. A method according to the invention is also conceivable in which the printing blanket consists of the printing layer and the textile layer, and / or in which the textile layer forms one of the outer layers of the multi-layered printing blanket. A preferred method according to the invention is one in which the textile layer is bonded to the printing layer in a material-bonded manner.

[0047] A particularly preferred method according to the invention is one in which the textile layer, with a width of 5 cm, exhibits an elongation in the range of 1 to 20% under a load of 500 N. A particularly preferred method according to the invention is one in which the textile layer, with a width of 5 cm, exhibits an elongation in the range of 1.3 to 17.5% under a load of 500 N, preferably in the range of 1.6 to 15.0%, particularly preferably in the range of 1.9 to 12.5%, and most preferably in the range of 2.2 to 10.0%. A particularly preferred method according to the invention is additionally or alternatively one in which the textile layer, with a width of 5 cm, exhibits an elongation of more than 1.4%, preferably more than 1.8%, and most preferably more than 2.2% under a load of 500 N.

[0048] Particularly preferred is, additionally or alternatively, a method according to the invention in which the textile layer consists of a mass fraction of 80% or more, preferably 90% or more, particularly preferably 95% or more, most preferably 99% or more, in particular substantially 100%, of the textile fabric, based on the mass of the textile layer.

[0049] Particularly preferred is, in addition or alternatively, a method according to the invention, wherein the textile surface structure is selected from the group consisting of woven and knitted fabrics, preferably woven fabrics.

[0050] A preferred method, either additionally or alternatively, is one according to the invention, wherein the textile fabric comprises one or more textile reinforcement elements made of a textile material, the textile material being selected from the group consisting of natural materials, semi-synthetic materials, and synthetic materials. A particularly preferred method is one according to the invention, wherein the natural materials are selected from the group consisting of rock wool, cotton, flax, hemp, wool, and silk. A particularly preferred method, either additionally or alternatively, is one according to the invention, wherein the semi-synthetic materials are selected from the group consisting of modal, viscose, and lyocell.Particularly preferred is, additionally or alternatively, a method according to the invention, wherein the synthetic materials are selected from the group consisting of polyacrylonitrile, polypropylene, polyesters, polyamides, polyurethanes, polyphenylene sulfide, polyoxadiazole, aramids such as p-aramid, m-aramid or co-poly para aramid, polyimide, polyetherimide, polyetheretherketone, polyethylene 2,6-naphthalate, polyphenylene, polyphenylene oxide, polyphenylene sulfide, polyphenylene ether, polybenzoxazole and polyvinyl alcohol.

[0051] A preferred method, either additionally or alternatively, is one in which the multilayer printing blanket exhibits an indentation in the range of 125 to 325 µm in a compressibility test with a stamp having a stamp area of ​​1 cm² acting on the printing surface at a test force of 141.8 N. A particularly preferred method is one in which the multilayer printing blanket exhibits an indentation in the range of 150 to 300 µm, preferably in the range of 175 to 275 µm, and most preferably in the range of 200 to 250 µm, in a compressibility test with a stamp having a stamp area of ​​1 cm² acting on the printing surface at a test force of 141.8 N.

[0052] A method according to the invention is generally preferred, wherein the printing blanket has a mean thickness in the range of 0.5 to 5 mm, preferably in the range of 1.0 to 3.0 mm.

[0053] The inventors consider a method according to the invention to be particularly advantageous, wherein the printed surface has an average roughness depth Rz according to DIN EN ISO 4287:1984 in the range of 2.0 to 20.0 µm, preferably in the range of 2.5 to 15.0 µm, and particularly preferably in the range of 3.0 to 10.0 µm.

[0054] In the inventive method, the printing blanket is produced using a rubber material that is specifically tailored to the selected printing inks. The tailoring is such that the rubber material is matched to the printing inks in such a way that, in the swelling test after 5 days of exposure, the rubber material shows a thickness change of 30 µm or less for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less.

[0055] The swelling test is performed by applying the respective printing ink to a circular sample of the rubber material with a diameter of 2.5 cm on one side. The thickness change is measured using a thickness gauge with a 1 cm² measuring plate and a preload of 5 N. For the present invention, the value after 5 days is used, as this is considered particularly relevant for the desired service life in subsequent use.

[0056] During development, the inventors recognized that the swelling of the rubber material for all of the selected printing inks, for which the adjustment was to be made, must not exceed a predetermined limit. This limit is based on the absolute change in thickness, so that both excessive positive and negative swelling are to be avoided. For optimal adjustment, a method according to the invention is preferred, wherein the rubber material is adjusted to the printing inks such that, in the swelling test after 5 days of exposure, the rubber material shows a thickness change of 25 µm or less, preferably 20 µm or less, particularly preferably 15 µm or less, and most preferably 10 µm or less for each of the selected printing inks.

[0057] Furthermore, in the inventive method, the rubber material is also modified such that the arithmetic mean of the thickness changes of the selected printing inks, determined as disclosed above, lies below a predetermined limit value. When modifying the material for printing inks with partly positive and partly negative thickness changes, it is preferred that the arithmetic mean of the absolute thickness change also lies below this limit value. For a particularly advantageous service life of the printing blankets, a method according to the invention is especially preferred in which the arithmetic mean of the thickness changes of the selected printing inks is 15 µm or less, preferably 10 µm or less.

[0058] In light of the present teaching, the person skilled in the art can very efficiently carry out the appropriate adjustment using a very simple source test.

[0059] The actual adaptation of the rubber material to the desired performance in the swelling test can advantageously be achieved by the person skilled in the art by adjusting the compositional components of the rubber material or the underlying rubber compound. In accordance with the skilled person's understanding, a rubber material can be produced by crosslinking a crosslinkable rubber compound, whereby the physicochemical properties can advantageously be controlled via the composition of the rubber compound. In other words, this is a method according to the invention, wherein the rubber material can be produced by crosslinking a crosslinkable rubber compound.

[0060] In practice, this will regularly involve a method according to the invention, comprising the process step: x) Matching a rubber material to the selected printing inks by varying the chemical composition of the rubber material, such that the rubber material shows a thickness change of 30 µm or less in the swelling test after 5 days of exposure for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less.

[0061] Based on the inventors' experiments, the adaptation of the rubber material to the selected printing inks can be achieved most effectively by selecting or dosing the rubber and / or the filler and / or the plasticizer, preferably by selecting or dosing the rubber and / or the plasticizer, and especially preferably by selecting the plasticizer.

[0062] For practical application, the inventors suggest that the tuning can initially be carried out in an iterative test on a limited number of reference rubber materials in order to estimate, in light of the swelling results obtained, which coarse rubber material composition is promising for the respective selected printing inks, in order to then proceed to fine-tuning in order to obtain the desired swellings.

[0063] Based on the inventors' experiments, a person skilled in the art can advantageously identify an optimized rubber material for a wide range of printing inks—within the scope of the above definition—even with significantly different polarities. This is achieved by not only the inherent resistance to swelling but also, in particular, by selectively replacing the plasticizer in the rubber material. For example, an EPDM-based rubber material can be selected that is highly resistant to swelling with one of the selected inks but would be inherently prone to swelling with the other. Here, the choice of plasticizer allows for a certain release of the plasticizer from the rubber material, effectively causing negative swelling, thus keeping the net swelling within the predefined limits.

[0064] During the development process, the inventors examined a large number of commercially available printing inks for can printing.

[0065] To ensure that an optimized rubber material is identifiable and that this can be done with manageable effort, the present invention defines that all of the selected printing inks are specific solvent-based printing inks, as are common in can printing, so that the chemical variance is greatly reduced, since, for example, many inks from other large printing areas are excluded.

[0066] This restriction, in particular the exclusion of printing inks with low-boiling solvents, sufficiently ensures, based on the inventors' experiments, that a suitable rubber material can be obtained efficiently and without unreasonable effort.

[0067] Those skilled in the art understand that selecting a large number of printing inks can lead to varying requirements for matching, making it difficult to identify an optimal rubber material. To circumvent this problem, the inventors propose a method according to the invention, wherein in process step a1) five or fewer, preferably four or fewer, and particularly preferably three or fewer, printing inks with different chemical compositions are selected, preferably at least one black and one white printing ink.

[0068] Furthermore, a method according to the invention is preferred in this respect, wherein the printing inks selected in process step a1) are printing inks from the same printing ink manufacturer.

[0069] Furthermore, for a particularly simple adjustment of the rubber material, a method according to the invention is preferred, wherein the selected printing inks in the cured state have a free surface energy, calculated using the OWRK method known to those skilled in the art (Owens, Wendt, Rabel and Kaelble), from contact angle measurements with water and diiodomethane, in the range of 0.7* <oe>up to 1.3* <oe>, preferably in the range of 0.8* <oe>up to 1.2* <oe>, especially preferred in the range of 0.9* <oe>up to 1.1* <oe>exhibit, whereby <oe>The mean free surface energy of the selected printing inks.

[0070] The inventors have succeeded in identifying specific compositions for crosslinkable rubber compounds for commercially available solvent-based printing inks from a major printing ink manufacturer. These compositions yield particularly advantageous rubber materials that are optimally matched to the ink system of this manufacturer and can be used by those skilled in the art as a starting point for their own optimization within the scope of the present invention, especially with other printing inks. These compositions are further disclosed in the following exemplary embodiments.

[0071] A method according to the invention is generally preferred, wherein the rubber material can be produced by crosslinking a crosslinkable rubber mixture comprising, with respect to the mass of the crosslinkable rubber mixture: Ethylene propylene diene rubber in a combined mass fraction in the range of 30 to 50%, preferably in the range of 35 to 45%, one or more fillers in a combined mass fraction in the range of 20 to 50%, preferably in the range of 25 to 45%, one or more plasticizers in a combined mass fraction in the range of 5 to 20%, preferably in the range of 10 to 15%, and a vulcanization system.

[0072] Preferred are methods according to the invention, wherein one or more fillers are selected from the group consisting of carbon blacks and amorphous silicon dioxide, in particular ASTM carbon blacks and precipitated amorphous silicon dioxide, and / or wherein one or more fillers are selected from the group consisting of plasticizer oils, preferably paraffinic plasticizer oils, and / or wherein the vulcanization system comprises sulfur or sulfur donors, and optionally accelerators, for example the CBS (N-cyclohexylbenzothiazole-2-sulfenamide) or TBzTD (tetrabenzylthiuram disulfide) commonly used in the rubber industry.

[0073] Because of the fundamental advantages of this rubber material, a preferred printing blanket is also disclosed here in connection with the invention, comprising: u) a printing surface provided for the transfer of a printed image onto the molded body, wherein the printing surface is formed at least partially by a rubber material, v) a textile layer arranged on the side facing away from the printing surface, wherein the textile layer comprises a textile fabric, wherein the textile layer exhibits an elongation in the range of 1 to 20% at a width of 5 cm under a load of 500 N, wherein the textile fabric is selected from the group consisting of woven and knitted fabrics, wherein the rubber material is producible by crosslinking a crosslinkable rubber compound comprising, based on the mass of the crosslinkable rubber compound: ethylene propylene diene monomer rubber in a combined mass fraction in the range of 30 to 50%, preferably in the range of 35 to 45%, one or more fillers in a combined mass fraction in the range of 20 to 50%, preferably in the range of 25 to 45%.One or more plasticizers in a combined mass fraction in the range of 5 to 20%, preferably in the range of 10 to 15%, and a vulcanization system.

[0074] This printing blanket disclosed above is used in particularly preferred processes and kits.

[0075] The inventors recommend that the printing blankets, which are specifically designed for the selected printing inks, can be advantageously sold together with the selected printing inks. This will result in cost-effective kits.

[0076] The invention therefore also relates to a kit for use in a printing process, in particular a printing process according to the invention, comprising as separate components: A) at least one container each of two or more selected printing inks with different chemical compositions, wherein the printing inks are solvent-based printing inks comprising one or more organic solvents with a boiling point at 100 kPa in the range of 150 to 250 °C, and B) at least one printing blanket with a printing surface provided for transferring a printed image onto the molded body, wherein the printing surface is formed at least partially by a rubber material, wherein the rubber material is such that, in the swelling test after 5 days of exposure, the rubber material shows a thickness change of 30 µm or less for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less, wherein the swelling test is carried out with a circular sample of the rubber material with a diameter of 2.5 cm and one-sided surface wetting with the printing ink, wherein the thickness change is measured with a thickness gauge with a 1 cm 2 The measurement is performed on a large measuring plate with a preload of 5 N.

[0077] Matching the rubber material to the selected printing inks is particularly advantageous for printing processes in which the print image is first transferred to a printing plate and only then applied to the printed object, as is the case when printing cans and other rotationally symmetrical molded parts. In this case, the printing plate can also be synergistically equipped with the appropriately adapted rubber material. A kit according to the invention is therefore preferred, wherein the kit additionally comprises: C) at least one printing plate for use in applying a printed image to the printing blanket, wherein the printing area of ​​the printing plate intended for applying the printing ink to the printing blanket is formed at least partially by a printing plate rubber material, wherein the printing plate rubber material is matched to the printing inks such that, in the swelling test after 5 days of exposure, the printing plate rubber material shows a thickness change of 30 µm or less for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less, wherein the swelling test is carried out with a circular sample of the printing plate rubber material with a diameter of 2.5 cm and one-sided surface wetting with the printing ink, wherein the thickness change is carried out with a thickness gauge with a 1 cm² measuring plate with a preload of 5 N.

[0078] The above statements regarding the rubber material apply analogously to the printing plate rubber material with regard to the preferred degree of tuning.

[0079] A kit according to the invention is particularly preferred in that the printing surface of the printing plate is formed by the printing plate rubber material to a surface area of ​​50% or more, preferably 70% or more, particularly preferably 90% or more, most preferably 95% or more, and in particular to substantially 100%. A kit according to the invention is additionally or alternatively particularly preferred in that the printing surface of the printing plate has an average roughness depth Rz according to DIN EN ISO 4287:1984 in the range of 2.0 to 20.0 µm, preferably in the range of 2.5 to 15.0 µm, and particularly preferably in the range of 3.0 to 10.0 µm.

[0080] To minimize the coordination effort, a kit according to the invention is particularly preferred, wherein the rubber material and the printing plate rubber material can each be produced by crosslinking a crosslinkable rubber mixture which are identical in their chemical composition to a mass fraction of 95% or more, preferably 98% or more, particularly preferably 99% or more, wherein the rubber material and the printing plate rubber material are particularly preferably identical.

[0081] The invention relates in particular to a method for printing on molded bodies, comprising the process steps of the inventive method for producing a printing blanket, as well as the process steps of: a2) Manufacturing or providing the molded parts to be printed, b2) Manufacturing or providing the selected printing inks, and for each molded part the following process steps: c2) Applying a printed image to the printing surface of the printing blanket intended for transferring the printed image to the molded part, wherein the printed image is at least partially formed from one or more of the selected printing inks, and d2) Transferring the printed image to the molded part from the printing surface of the printing blanket, wherein, when process steps c2) and d2) are carried out several times, all of the selected printing inks are used in at least one printed image.

[0082] The person skilled in the art understands that the production of the printing blankets in the inventive method will mostly be carried out by manufacturers other than the printing, whereby the manufacturers of the printing blankets can in particular also distribute kits according to the invention.

[0083] Against this background, the invention relates in particular to a method for printing on molded bodies, preferably using a kit according to the invention, comprising the following process steps: a3) Manufacturing or providing molded bodies to be printed, b3) Providing two or more printing inks with different chemical compositions, wherein the provided printing inks are solvent-based printing inks comprising as solvents one or more organic solvents, preferably alcohols, with a boiling point at 100 kPa in the range of 150 to 250 °C, and for each molded body the process steps: c3) Applying a printed image to the printing surface of a printing blanket provided for transferring the printed image to the molded body, wherein the printing surface is formed at least partially by a rubber material, wherein the printed image is formed at least partially from one or more of the provided printing inks, and d3) Transferring the printed image to the molded body from the printing surface of the printing blanket,wherein, in repeated execution of process steps c2) and d2), all of the selected printing inks are used in at least one printed image, wherein the rubber material is such that, in the swelling test, after 5 days of exposure, the rubber material shows a thickness change of 30 µm or less for each of the supplied printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less, wherein the swelling test is carried out with a circular sample of the rubber material with a diameter of 2.5 cm and one-sided, surface wetting with the respective printing ink, wherein the thickness change is carried out with a thickness gauge with a 1 cm² measuring plate and a preload of 5 N.

[0084] Particularly preferred are methods according to the invention for printing on molded bodies, wherein the molded bodies are beverage cans, aerosol cans, tubes, and cups. A method according to the invention for printing on rotationally symmetrical molded bodies is particularly preferred, wherein the molded bodies are metallic, preferably made of aluminum. A method according to the invention for printing on molded bodies, wherein the molded bodies are aluminum cans, is especially preferred.

[0085] A preferred or alternative method according to the invention for printing rotationally symmetrical shaped bodies is also preferred, wherein the printing of the shaped bodies is carried out in round body printing.

[0086] Particularly preferred, or alternatively, is a method according to the invention for printing rotationally symmetrical molded bodies, wherein the method for printing the rotationally symmetrical molded bodies is a method in which the printed image is applied to the printing blanket by means of a printing plate, wherein the printing surface of the printing plate provided for applying the printing ink to the printing blanket is formed at least partially by a printing plate rubber material, wherein the printing plate rubber material is matched to the printing inks such that, in the swelling test after 5 days of exposure, the printing plate rubber material shows a thickness change of 30 µm or less for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less, wherein the swelling test is carried out with a circular sample of the printing plate rubber material with a diameter of 2,5 cm and one-sided, area-wide wetting with the printing ink is carried out, whereby the thickness change is carried out with a thickness gauge with a 1 cm² measuring plate and a preload of 5 N.

[0087] The invention and preferred embodiments of the invention are explained and described in more detail below with reference to the following exemplary embodiments.

[0088] The following Table 2 shows measured values ​​for the thickness change in millimeters in the swelling test for various printing blankets with different rubber materials E1, E2, E3, V1, V2, V3, V4, V5 and V6 after 5 days, each with a white and a black solvent-based printing ink from a first manufacturer and a second manufacturer.

[0089] The printing blankets with the rubber materials V1, V2, V3, V4, V5 and V6 are commercially available printing blankets.

[0090] The printing blankets with the rubber materials E1, E2 and E3 were produced using the manufacturing process according to the invention and are specifically tailored to the printing inks of the first manufacturer (E1 and E2) or the second manufacturer (E1 and E3), which can be seen from the low individual swellings and the low average swelling.

[0091] The rubber materials E1 and E2 can be produced by crosslinking a crosslinkable rubber compound with the components specified in Table 1 through vulcanization. Table 1 (Compositions; all values ​​in mass fractions in %) ingredient E1 E2 EPDM rubber 40,8 39,5 Plasticizer oil 12,2 15,6 soot 12,2 27,0 Precipitated amorphous silicon dioxide 26,9 - zinc oxide 2,4 1,5 Stearic acid 1,0 - Processing aids - 13,0 sulfur 0,6 1,0 accelerator 3,7 2,4 Delayer 0,2 - Table 2 (Thickness changes; all values ​​in µm) Printing blanket / rubber material Manufacturer 1 Manufacturer 2 White Black White Black E1 7 2 30 5 E2 0 0 - - E3 25 30 12 21 V1 35 25 - - V2 43 62 - - V3 - - 15 39 V4 48 49 V5 - - 25 31 V6 - - 18 41

[0092] By using the printing blankets produced with the inventive method containing the rubber material E1, the service life of the printing blanket was increased from approximately 8 hours to 79 hours in a printing plant under otherwise identical conditions without any reduction in quality for the printing inks of the first manufacturer, during which time eight changes of the printed image were made and a total of 5.1 million cans were printed.

[0093] It is particularly preferred if the printing blankets produced using the inventive method are distributed in inventive kits together with the printing inks for which they are optimized.

[0094] The printing blankets produced using the inventive method are particularly suitable for printing on metallic round bodies, especially aluminium cans, with particular advantages being shown in printing processes in which the printed image is applied to the printing blanket by means of a printing plate, the printing surface of which is matched analogously to the rubber material of the printing blanket.

[0095] Advantageously, the corresponding printing plates can be distributed in the kits according to the invention.< / oe> < / oe> < / oe> < / oe> < / oe> < / oe> < / oe>

Claims

1. A method for producing a printing blanket for use in printing rotationally symmetrical molded bodies, comprising the process steps of: a1) selecting two or more printing inks of different chemical compositions intended for use in a printing process for printing rotationally symmetrical molded bodies using the printing blanket to be produced, wherein the selected printing inks are solvent-based printing inks comprising one or more organic solvents with a boiling point at 100 kPa in the range of 150 to 250 °C, and b1) producing a printing blanket, wherein the printing blanket comprises a printing surface intended for transferring a printed image onto the molded body, wherein the printing surface is formed at least partially by a rubber material, the rubber material being matched to the selected printing inks.that the rubber material in the swelling test shows a thickness change of 30 µm or less for each of the selected printing inks after 5 days of exposure, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less, wherein the swelling test is carried out with a circular sample of the rubber material with a diameter of 2.5 cm and one-sided surface wetting with the printing ink, wherein the thickness change is measured with a thickness gauge with a 1 cm diameter. 2 The measurement is performed on a large measuring plate with a preload of 5 N.

2. The method of claim 1, wherein the printing inks selected in process step a1) are printing inks from the same printing ink manufacturer.

3. Method according to one of claims 1 or 2, wherein at least one of the selected printing inks is a black printing ink and at least one of the selected printing inks is a white printing ink.

4. Method according to any one of claims 1 to 3, wherein the printing ink comprises one or more organic solvents in a combined mass fraction of 25% or more, preferably 30% or more, particularly preferably 35% or more, based on the mass of the printing inks.

5. Method according to any one of claims 1 to 4, wherein the mass fraction of solvents having a boiling point of less than 150 °C at 100 kPa is 5% or less, preferably 2% or less, particularly preferably 1% or less, most preferably 0.1% or less, based on the mass of the printing ink.

6. A method according to any one of claims 1 to 5, wherein the organic solvents are alcohols.

7. Method according to any one of claims 1 to 6, wherein at least one of the selected printing inks, preferably all of the selected printing inks, comprises one or more plasticizers other than organic solvents, in particular plasticizer oils, preferably in a combined mass fraction in the range of 5 to 45%, particularly preferably in the range of 10 to 40%, based on the mass of the printing ink.

8. Method according to any one of claims 1 to 7, wherein the printed surface has an average roughness depth R z according to DIN EN ISO 4287:1984 in the range of 2.0 to 20.0 µm, preferably in the range of 2.5 to 15.0 µm, particularly preferably in the range of 3.0 to 10.0 µm.

9. Method according to any one of claims 1 to 8, wherein the rubber material is adapted to the printing inks such that the rubber material in the swelling test after 5 days of exposure shows a thickness change of 25 µm or less, preferably 20 µm or less, particularly preferably 15 µm or less, most preferably 10 µm or less, for each of the selected printing inks.

10. Method according to any one of claims 1 to 9, wherein the arithmetic mean of the thickness changes of the selected printing inks is 15 µm or less, preferably 10 µm or less.

11. A method according to any one of claims 1 to 10, wherein the rubber material can be produced by crosslinking a crosslinkable rubber compound comprising, based on the mass of the crosslinkable rubber compound: - ethylene propylene diene rubber in a combined mass fraction in the range of 30 to 50%, preferably in the range of 35 to 45%, - one or more fillers in a combined mass fraction in the range of 20 to 50%, preferably in the range of 25 to 45%, - one or more plasticizers in a combined mass fraction in the range of 5 to 20%, preferably in the range of 10 to 15%, and - a vulcanization system.

12. A method for printing on molded bodies, comprising the process steps of the method for producing a printing blanket according to any one of claims 1 to 11, and the process steps of: a2) producing or providing molded bodies to be printed, b2) producing or providing the selected printing inks, and for each molded body the process steps of: c2) applying a printed image to the printing surface of the printing blanket provided for transferring the printed image to the molded body, wherein the printed image is at least partially formed from one or more of the selected printing inks, and d2) transferring the printed image to the molded body from the printing surface of the printing blanket, wherein, when process steps c2) and d2) are carried out several times, all of the selected printing inks are used in at least one printed image.

13. The method of claim 12, wherein the method for printing the rotationally symmetrical molded bodies is a method in which the printed image is applied to the printing blanket by means of a printing plate, wherein the printing area of ​​the printing plate provided for the application of the printing ink to the printing blanket is formed at least sectionally by a printing plate rubber material, wherein the printing plate rubber material is matched to the printing inks such that, in the swelling test after 5 days of exposure, the printing plate rubber material shows a thickness change of 30 µm or less for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less, wherein the swelling test is carried out with a circular sample of the printing plate rubber material with a diameter of 2.5 cm and one-sided, area-wide wetting with the printing ink, wherein the thickness change is measured with a thickness gauge with a 1 cm diameter.2 The measurement is performed on a large measuring plate with a preload of 5 N.

14. Kit for use in a printing process comprising, as separate components: A) at least one container each of two or more selected printing inks with different chemical compositions, wherein the printing inks are solvent-based printing inks comprising one or more organic solvents with a boiling point at 100 kPa in the range of 150 to 250 °C, and B) at least one printing blanket with a printing surface intended for transferring a printed image onto the molded part, wherein the printing surface is formed, at least in sections, by a rubber material, the rubber material being matched to the printing inks such that, in the swelling test after 5 days of exposure, the rubber material shows a thickness change of 30 µm or less for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less.wherein the swelling test is carried out with a circular sample of the rubber material with a diameter of 2.5 cm and one-sided surface wetting with the printing ink, wherein the thickness change is measured with a thickness gauge with a 1 cm diameter. 2 The measurement is performed on a large measuring plate with a preload of 5 N.

15. Kit according to claim 14, wherein the kit further comprises: C) at least one printing plate for use in applying a printed image to the printing blanket, wherein the printing area of ​​the printing plate intended for applying the printing ink to the printing blanket is formed at least partially by a printing plate rubber material, wherein the printing plate rubber material is matched to the printing inks such that, in the swelling test after 5 days of exposure, the printing plate rubber material shows a thickness change of 30 µm or less for each of the selected printing inks, and the arithmetic mean of the thickness changes of the selected printing inks is 20 µm or less, wherein the swelling test is carried out with a circular sample of the printing plate rubber material with a diameter of 2.5 cm and one-sided, area-wide wetting with the printing ink, wherein the thickness change is measured with a thickness gauge with a 1 cm diameter. 2The measurement is performed on a large measuring plate with a preload of 5 N.

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