EP1266700B1 - Roll for the preparation or the treatment of a film of fluid - Google Patents

Description

Technical area

The invention relates to a roller for the fluid film preparation or processing with a roller coating of the layer thickness d having a first layer surrounding the core with a first hardness and a second layer, which surrounds the first layer immediately radially outboard and has a second hardness, of the Hardness of the first layer is different.

State of the art

A generic roller for color processing is for example from the DE-OS 24 33 749 known. By the construction of at least two layers, both the chemical nature of the roll surface, for example, determines the affinity for a printing medium, as well as other properties of the roller as the adhesion of the outer layer to the substantially rigid roll core, or the mechanical properties of the roll coating such as their hardness are adjusted.

Furthermore, from the US 5,257,967 an inking roller with a core known on the two layers of elastomeric Materials of different hardness are applied. This is intended to achieve a more uniform application of paint.
Although such ink transfer rollers have long been known, there is often the problem that printing machines that transfer liquid films with elastomer-coated rollers produce inhomogeneities in the application of ink to the respective printed product. Particularly in the case of offset printing processes, the formation of undesired microstrips is known by the term "ribbing". These microstrips often occur with a distance of a few millimeters to each other and are recognizable both on the printed product and on the ink transfer rollers. The undesirable formation of the microstrip is promoted by the use of large amounts of fountain solution and ink or high Druckmitteldurchsätze. It is assumed that these stripes are due to an insufficient metering function of the rollers of the inking unit. Accordingly, attempts have been made, with some success, to prevent these microstrips from each other by transversely moving the ink transfer rollers to cause lateral rubbing of the print medium. However, such transversal ink rollers require appropriately equipped fluid film processing machines, which are thereby structurally complex and expensive. A change in the amount of pressure medium used and the amount of fountain solution used to avoid the microstrip often eliminates because the amounts used of these media must be adapted to other parameters.

Description of the invention

The invention has for its object to provide a roller for the fluid film processing or processing, in particular for offset printing, by means of which inhomogeneities of the Print medium or printed product, in particular microstrip on the printed product, at least as far as possible can be avoided, which are particularly easy to adapt to the particular requirements in the nature of the coating surfaces and which is inexpensive to produce.

According to the invention, this object is achieved by a roller for the fluid film preparation or processing, in which the roll coating at least partially has a substantially continuous hardness gradient, which may be present over a portion of the layer thickness d of the roll coating. It has been found that the presence of a substantially continuous hardness gradient or a continuous change in hardness has a very positive influence on the printing result, in particular with regard to the occurrence of microstrips, and microstrips can be virtually completely avoided by using rolls according to the invention. In particular, the ratio of transverse and tangential forces or stresses in relation to the compressive forces in the region of the roll surface can be specifically adjusted, in particular increased, by the design of the roll according to the invention, which is essential for the quality and efficiency of the fluid film preparation. The coating material is thus preferably resistant to printing media.

By a substantially continuous hardness gradient is meant one in which comparatively sharp cracks in the hardness profile are avoided, as they occur at phase boundaries of abutting layers with different hardnesses, which may optionally be connected by a bonding layer such as an adhesive layer. The hardness gradient of the roll according to the invention can, for example may be substantially linear or substantially exponential, but other suitable hardness gradients, which may also have intermediate maxima or plateaus of substantially constant hardness over a range of the layer thickness profile, may be set.

The layers of different hardness of the roll according to the invention preferably each have the same base material or agree largely in their composition. Preferably, the layers differ only in the proportion of the hardness-altering substance or a precursor thereof or in a property which correlates with the degree of an introduced hardness-changing substance or agent, for example in the degree of crosslinking. To set a gradient of the degree of crosslinking, it is possible, for example, to generate a gradient of heat or radiation intensity or a gradient of an activator or photoinitiator. The fact that the layers of different hardness have the same basic component or a substantially identical composition, the roll coatings can also be particularly simple structure and binding errors or adhesion problems between layers of different composition are largely avoided.

The low hardness layer forming material, which in particular can constitute the roll coating coating base material applied to the core, preferably has a hardness of less than 35 Shore A, e.g. less than 30 Shore A, preferably in the range of 25 to 10 Shore A, more preferably in the range of 25 to 20 Shore A, without being limited thereto.

Preferably, there is a roll coating, in which in Range of hardness change over a Schichtdickeninkrement of 10 microns differences in the intrinsic hardness of the coating material in the range of a maximum of 5 Shore A, in particular 2-3 Shore A (hardness gradient 80 Shore A over layer thickness 0.5 mm: 1.6 Shore A to 10 microns) to 0.02-0.04 Shore A (hardness drop 35 ShA over 2 mm: 0.07 Shore A to 10 micrometers), preferably in the range of 1 to 0.1 Shore A, more preferably in the range of less than 0.2 to 0 , 8 Shore A, in particular in the range of 0.4 Shore A. These hardness gradients are preferably maintained over substantially the entire thickness gradient coating thickness of the roll. The hardness gradients mentioned above can be estimated by microhardness determinations or by removal of the roll coating, eg by continuous wedge-shaped grinding of the roll coating, and determination of the total hardness of the remaining roll coating, which can be deduced from the intrinsic hardness of a Schichtdickeninkrementes.

The hardness gradient of the rolls according to the invention can be characterized by the surface measured hardness as a function of the layer thickness of the layer having a hardness gradient. In this case, the layer thickness can be varied by incremental layer thickness removal, for example by continuously ground down the hardened coating as a wedge. By sequential layer-by-layer grinding of the hardened roller coating, for example in increments of 50 to 500, for example in the range of 200 micrometers, a profile of an effective hardness can be determined. The hardness in this case by conventional hardness measurement methods such as IRHD (DIN 53 519 sheet 1), IRHD soft (DIN 53 519 sheet 1), IRHD micro (DIN 53 515 sheet 2), as Shore A hardness (DIN 53 505) or as Shore D hardness (DIN 53 505) are determined. It should be noted here that the hardness measurement on the roller according to the invention does not represent a standard-compliant hardness determination according to the aforementioned DIN standards due to the continuous hardness gradient and only an effective (average) hardness. By means of such a hardness measurement, however, the hardness gradient of a roll according to the invention can be sufficiently characterized and used for comparison purposes, in particular when the hardness is determined by means of two or more different test methods, for example by determining the IRHD micro hardness and the Shore A hardness. A characterization of the hardness gradient is possible by the method described above, especially when the hardness gradient of the roll according to the invention extends only over part of the layer thickness of the roll coating and the roll coating is removed over the entire hardness-changed area to the hardness-unchanged base material of the roll coating.

The effective hardness gradient determined by the method described above is preferably 10 micron film thickness increment, ie hardness determination for a given roll layer thickness and 10 micrometer coating removal (real or theoretical reference value, the hardness gradient then being substantially linear ), with a hardness difference of 1 to 0.02 Shore A, preferably 0.5 to 0.05 Shore A, more preferably 0.2 to 0.1 Shore A, in particular about 0.015 Shore A. It is understood that in Hardness determinations for larger layer thickness differences proportionally larger hardness differences are measured. For example, rolls according to the invention have hardness differences over a layer thickness of 100 micrometers (corresponding to a layer thickness removal of 100 micrometers) from 10 to 0.2 Shore A, more preferably 5 to 0.5 Shore A, especially in the range of 1 to 2 Shore A on.

Rolls according to the invention can have substantially continuous hardness gradients or hardness changes over a difference of the intrinsic hardness, wherein the hardness difference can result from the hardness difference of the hardened roll surface and the unchanged base material of greater than or equal to 5 Shore A, the hardness difference can easily exceed 100 Shore A, for example, be up to 50 Shore D, or beyond. In particular, hardness differences of about 10 to about 90 Shore A, for example about 30 to about 50 Shore A can be present. Particularly suitable for certain applications are those of 50 to 70 Shore A. Preferably, a substantially continuous hardness gradient is present over the entire layer thickness with changing hardness.

Taking into account the above-defined effective hardness resulting from the determination of the respective hardness of the roll coating at a given point of the depth profile without regard to the present hardness gradient, a substantially continuous gradient of the effective hardness over a hardness difference of is equal to 5 Shore A, for example 10 to 50 Shore A, preferably less than 40 Shore A and less than 80 IRHD micro, more preferably between 10 and 20 Shore A and 20 to 50 IRHD micro, with larger or larger for certain applications smaller hardenings can be adjusted. In particular, the hardness difference may correspond to the increase in the surface hardness of the roller compared to the hardness of the unchanged base material. It should again be emphasized here that the above details of the Shore A hardness or IRHD microhardness are not interconverted values represent, because due to the hardness gradient of the coating both non-standard performed measuring methods are subject to different inherent errors. Nevertheless, a characterization of the roll coating according to the invention is possible by these values.

In order to be able to absorb stress peaks with dynamic deformation of the surface layer of the roll coating and to provide a roll with a sufficient life, the second, radially outer layer of the roll coating preferably has a higher hardness than the first, radially inner and the roll core adjacent layer, so that the hardness in the radial direction decreases from the outside inwards. For this purpose, the second layer may have a higher degree of crosslinking than the first layer. The hardest layer of the substantially continuous hardness gradient coating region, which may have the highest degree of cross-linking of the roll coating, is preferably the most radially outermost layer of the coating such that the hardness gradient extends radially inwardly into the roll material from the radially outer roll surface and the hardness decreases continuously from the outside to the inside, but if necessary an external covering layer (see below) may be provided.

The hardest layer of the substantially continuous hardness gradient coating region is preferably also the hardest layer of the depth profile of the roll coating in which the hardness of the layers still has an influence on the surface hardness of the roll coating, which can be determined, for example, by the above-described wedge-shaped layer removal or other suitable measures is. The hardest layer of the coating area with substantially continuous hardness gradient is preferably at the same time the hardest layer, which faces the inner and / or outer roll coating surface and the radially outer roll surface. The "hardest" layer of the hardness gradient is preferably the hardest layer, based on a layer depth depth of the roll coating of up to 0.1 mm, up to 0.5 mm, up to 1 mm, up to 2 mm or up to 5 mm of the roll coating from the coating surface, for example the roll surface, where appropriate also up to a depth of up to 10 mm or up to 30 mm of the roll coating, without being limited thereto. The term "hardest layer" thus preferably refers to near-surface layers of the roll coating. For example, it may thus be provided for certain applications, an elastomer layer of high hardness adjacent the roll core, which has no or only a negligible effect on the surface hardness of the roll coating in the given roll coating, without departing from the concept of the invention, but usually the radial layers further inside are hardness-unmodified coating grating material. The hardest layer of the layer region with substantially continuous hardness gradient can thus also be the hardest layer of the roll coating, in particular based on the intrinsic hardness, except possibly the connection region of the coating with the core.

The hardest layer of the roll coating region having a substantially continuous hardness gradient, in particular in the layer thickness range of up to 0.1 mm or up to 30 mm from the roll surface as defined in the preceding paragraph, may be spaced about 100 or 50 microns apart less, especially about 20 microns or less, about 10 micrometers or less, preferably about 5 micrometers or less, or about 1 micrometer or less from the inner and / or outer roll coating surface. In this case, the inner roll coating surface faces the roll core, the outer coating surface at the same time represents the roll surface. At the same time, this layer can have the highest degree of crosslinking in the considered layer thickness increment. Starting from this layer, the hardness can be substantially constant up to the roll surface or fall towards the surface towards the maximum hardness, the drop preferably less than 20%, less than 10%, or preferably less than 5% in each case based on the absolute (intrinsiche ) Hardness of the hardest layer (eg, the Shore A hardness) of the near-surface coating area, in each case based on the effective hardness or in each case based on the hardening against the hardness unchanged roll base material may be, without being limited thereto. A decrease in the coating hardness towards the roll surface may be due, for example, to the change in hardness, for example if a hardness-changing crosslinking agent on the roll surface undergoes side reactions which cause less or no change in hardness or if substances such as plasticizers are applied for surface modification.

The hardness change in the region of the continuous hardness gradient preferably results with a corresponding change in the degree of crosslinking. A second layer of higher hardness preferably has a higher degree of crosslinking than the radially inner first layer, and the radially outermost hardest layer preferably has the highest degree of crosslinking. The hardest or most highly crosslinked incremental layer in the area of the roll surface preferably has a residual breaking elongation of at least 50%, preferably of at least 70%. The softest layer of a hardness gradient preferably has the lowest degree of crosslinking.

The hardness gradient as a substantially linear hardness decrease or increase in hardness may extend substantially continuously over a radial layer thickness of more than 0.01 mm, more than 0.05 mm or more than 0.1 mm to 30 mm or more. The change in hardness range may in particular be layer thicknesses in the range of 0.2 or 0.3 to 10 mm, for example in the range of 0.5 mm or 1 to 2 or 5 mm. The hardened area can be followed, in the radial direction, by another hardened area, optionally separated by an intermediate layer, or by an unchanged base material of the roller coating.

The above-specified hardness gradients, differences and extension ranges are understood in particular between two maximum and minimum values and / or plateaus of the hardness profile over the layer thickness.

According to a preferred procedure, regardless of the manner in which the hardness gradient is generated, the process step generating the hardness gradient is interrupted before a change in hardness has taken place over the entire layer thickness of the roll material or roll coating. Layers of the roll coating that are subject to attack by the outer roll surface can thus have unchanged base material, the change in hardness can essentially only be superficial or extend over a greater depth of the coating.

Preferably, the process is carried out such that only a surface hardness change of the roll coating takes place, i. the layer thickness of the hardness-changed region is smaller than the layer thickness of the unchanged base material. The layer thickness ratio of the practically constant hardness coating material over the layer thickness to the layer thickness of the region having substantially continuous hardness gradients may be in the range of 2: 1 to 30: 1 or greater, but not limited thereto, preferably in the range of 4: 1 or greater, more preferably in the range of 6: 1 to 15: 1. The total layer thickness of the elastomeric roll coating may be in the range of 4 to 20 mm, without being limited thereto, preferably in the range of 6 to 13 mm. The areas of constant hardness and hardness gradient preferably close in the radial direction directly to each other.

The setting according to the invention of continuous hardness gradients is advantageous, in particular in the case of roll coatings of elastomeric base materials, in particular in the case of crosslinkable elastomeric base materials, where the base materials may have thermoplastic properties, but in particular only partial or non-thermoplastic properties. The basic components may be, for example, synthetic or natural rubber (NR), halogenated rubber such as polychloroprene, polyurethane, butadiene rubber (BR), nitrile butadiene rubber (NBR), partially or fully hydrogenated nitrile butadiene rubber (HNBR), acrylate rubber (EAM), chlorosulfonic acid rubber (CSM), styrene butadiene rubber (SBR), ethylene propylene rubber (EPDM), PVC, fluororubber (FPM), silicone rubber (Q) or ethylene-vinyl acetate copolymer, or have one or more of these components. As base material, however, other suitable base materials may be used can be used, which have the desired chemical and mechanical properties.

Preferably, the hardness gradient is generated by a gradient of a component of the roll coating that is different than the base component. In particular, it is possible to use one or more hardness-modifying auxiliaries from the group such as hardeners, crosslinking agents, activators, photoinitiators and plasticizers or other low-molecular compounds or precursors of the stated components which cause a hardness gradient in the roll coating. The hardness-altering substances can in each case generate a hardness gradient due to their intrinsic properties or after suitable reaction or reaction with another substance. Specifically, one or more of the above-mentioned hardness-modifying adjuvants can be used which can produce a gradient of the degree of crosslinking of a component of the coating composition, in particular the base component, whereby the appropriate crosslinking reaction is allowed to proceed to a sufficient extent by suitable process conditions. For this purpose, for example, the substances mentioned can be introduced into the coating material with a gradient or else a gradient of the substances can be produced, with subsequent appropriate implementation of the auxiliaries being initiated as required. As a result, rolls can be produced in a simple manner in which a hardness gradient is present at least over a region of the roll layer thickness.

The generation of the hardness gradient is not limited to the above-mentioned substances. An essentially continuous hardness gradient can also be generated, for example, by joining together with different basic components adjacent layers a gradient of at least one of the basic components is present. Additionally or alternatively, for example, the content of monomers or oligomers of a polymeric material, for example a material from which the elastically deformable outer region of the roller is at least partially constructed, vary over the layer thickness. The monomers or oligomers may be, but are not limited to, those of the above-mentioned polymers for making the roll coating. Optionally, other suitable low molecular weight substances can be used for this purpose. Optionally, alternatively or additionally, the hardness gradient may be generated by components such as fillers, or by other suitable materials which are compatible with the roll material and preferably allow a durable generation of a hardness gradient.

It goes without saying that the abovementioned measures for setting a hardness gradient can also be used in combination with one another. Thus, for example, both the plasticizer content and the crosslinking agent content may be subject to gradients or in each case several compounds of one group, for example a plurality of crosslinking agents and / or a plurality of fillers are used, each having different gradients, so that even more complex hardness gradients can be set over the roll layer thickness.

It is understood that for the formation of hardness gradients according to the invention, other hardness-influencing media such as heat and / or radiation can be brought into interaction with the roll coating in such a way that a substantially continuous hardness gradient results, for example by activation of crosslinking agents, generation of suitable activators or the like. As radiation can be understood as light or particle radiation such as electron beams or other suitable radiation. Heat and / or suitable radiation may also be pulsed with the roll coating to interact to cause hardening processes within the roll coating, for example, to alter the degree of crosslinking of the elastomer component. The substance activated or reacted by the heat and / or radiation can then also be present in a uniform distribution.

Advantageously, a hardness-altering substance and / or a precursor thereof by a diffusion or migration of the substance from the outside into the roll material, for example, the coating material applied to a core roll coating introduced, wherein the hardness-altering material directly or indirectly, for example by downstream reactions with Components of the roll coating, a hardness gradient generated.

Preferably, the hardness-changing substance has a sufficiently low diffusion coefficient at the operating conditions of the roller as intended, so that over the life of the roller there is a substantially temporally and locally constant hardness gradient. The hardness-altering material can be immobilized after its introduction into the roll material, for example by subsequent chemical reactions or by temporary support of penetration into the roll material, for example by increased compared to the intended operating conditions temperature in the generation of the hardness gradient or by the presence of a suitable solvent for the diffusing material , wherein the solvent is preferably different from the solvents used in the application of the roller, for example in Media containing solvents is. For example, the diffusion of a crosslinking agent such as a peroxide can be promoted by acetone.

A surface hardening can be carried out, for example, by the incorporation of crosslinking agents such as halogenated and / or sulfur-containing substances in rubber compounds containing roller coatings. The crosslinking agents can be introduced into the coating material by means of solutions or via the gas phase. For example, a roller coating containing a rubber material may be surface-hardened by introducing chlorosulfur or other sulfur halides or polysulfur halides by means of toluene solution or gas phase chlorination. For example, it is also possible to rub sulfur or sulfur compounds and / or solid phase vulcanization accelerators, for example in the form of powders. It is particularly advantageous to allow radically reacting monomers, peroxides and / or photoinitiators or precursors of the mentioned classes of compounds to diffuse into the coating material from the surface. The above-mentioned process steps may be followed simultaneously or chronologically by a further process step related to the first step, for example the application of heat and / or radiation to the coating material, for example to effect a corresponding crosslinking of the coating material.

The gradient of the hardness-altering substance may also be produced by substantially continuously changing the composition of the coating material to be applied to a core, for example by substantially reducing the composition of the coating material in the case of dip or spray coatings is changed continuously or quasi-continuously.

The hardness change of the roll coating can be made by changing the hardness of the coated roll in which an elastomeric roll coating is applied to a substantially rigid core. The roll coating here preferably consists of a homogeneous material. The coating may be bonded to the core by an adhesive layer. Optionally, a hardness gradient can also be introduced into the roll coating in addition or alternatively in an upstream process step, after which the roll coating is subsequently applied to the core. Optionally, subsequent to the two above-mentioned process variants, a further structure of the roll coating, if appropriate, each with hardness-changing or hardness gradient-generating process steps carried out.

The cured area may optionally be provided with one or more additional topcoats which, for example, adjust the affinity of the roll surface to the processing medium such as a printing medium, for example in the form of hydrophilic or oleophilic components such as plasticizers, or have desirable chemical or physical properties, such as abrasion Reduce. The cover layer may comprise only one or several molecular layers and may have a thickness in the range of 10 to 1 or less micrometers, without being limited thereto. By virtue of the upper cover layer which may possibly also be dispensed with, and which is preferably small in comparison with the layer thickness of the radial hardening gradient, the roll layer preferably does not or will not be the entire hardness of the roll surface significantly influenced.

Optionally, intermediate layers may be provided between layers having substantially continuous hardness gradients for certain applications. These intermediate layers may have an effect of diffusion barriers with respect to hardness-altering substances or media incorporated in the coating material, or show no or no significant effect in this respect.

Preferably, the abovementioned surface-modifying substances are at the same time immobilized by the hardness-changing substance on the roll surface, for example by chemical bonding, in particular by free-radical crosslinking, with the elastomeric coating material. For this, the surface-modifying material, e.g. a surfactant or emulsifier immediately prior to or after, preferably together with, the hardness-altering substance, e.g. a crosslinking agent such as a peroxide, applied to and bonded to the roll coating. The surface-modifying substance may in this case in proportions by weight of more than 5%, preferably more than 10-25%, more preferably about 50% based on the solvent-free, the hardness-modifying and surface-modifying substance-containing mixture, optionally in addition to other components. As plasticizers, fatty alcohol derivatives, e.g. Fatty alcohol polyglycol ethers, proved to be particularly suitable. The treatment conditions of the roll are preferably selected so that both the hardness-altering material with the elastomeric coating material and the surface-modifying substance react with it.

Preferably, the generation of the hardness gradient takes place after the Vulcanization of the elastomeric roll coating, after an optionally performed surface treatment and / or after the dimensioning of a hardness gradient having roll layer, eg by Schichtabtrag such as grinding or other suitable calibration measures. The generation of the hardness gradient preferably takes place on an otherwise usable roll. Optionally, a different order of the processing steps can be made. The radially inner surface layer of the roll coating can be produced by way of example in the case of a prefabricated roll coating, wherein the coating modified according to the invention is subsequently applied to the roll core, for example by widening and drawing onto the core.

The roller core may each consist of a substantially rigid material such as steel or another suitable material.

The roller coating with a substantially continuous hardness gradient preferably extends fully and over the entire length of the fluid-film-forming working area of the roller. The area of the roll coating with a hardness gradient may also extend only in certain areas over a part of the roll surface, ie a part of the length and / or circumference of the roll, for example only over certain segments of the roll surface, wherein the remaining surface areas of the roll can not have a hardness gradient , Thus, for example, a roll segment with a hardness gradient can be provided only in the central region of the roll and, for example, extend completely in the middle of the roll over 50% or 75% of the roll length. It may also, for example, a narrow edge strip of the roll coating adjacent the front ends of the roller without Hard gradients may be provided, each of which may, for example, have a width of 10%, 5% or less of the roll length. The segments mentioned can each extend fully or only partially around the roller. The roll surface can also have regions or segments of different hardness gradients, for example, a larger or smaller hardness gradient may be present in the roll end faces than in the middle region of the roll, which are achieved, for example, by varying amounts of hardening substances introduced into the roll coating, such as crosslinking agent can. The segments of different hardness or unchanged hardness relative to the base material can be produced, for example, by covering the roll surface with a material such as a film or waxes and applying the hardness-altering substance, eg a peroxide, to the roll surface, or to other suitable ones Wise.

The roll according to the invention can generally be used for the preparation of fluid films, in particular for color film processing and / or for the treatment of dampening solution films, without being limited thereto. Deratige color or dampening films are handled for example in printing units. However, the rolls according to the invention can also be advantageously used for the treatment of fluid films in other fields of application. The rolls according to the invention can be used in machines in which they work against other rolls and exchange radial or tangential compressive forces with them.

Brief description of the drawings

• Figur 1 eine schematische Querschnittsdarstellung einer erfindungsgemässen Walze,
• Figur 2 eine schematische Darstellung des Härteverlaufs der Walze nach Figur 1,
• Figur 3 eine schematische Darstellung des Härteverlaufs der Walze nach Figur 1 nach einer alternativen Ausführungsform,
• Figur 4 eine schematische Querschnittsdarstellung einer alternativen Ausführungsform einer erfindungsgemässen Walze,
• Figur 5 eine schematische Darstellung des Härteverlaufs der Walze nach Figur 4,
• Figur 6 eine schematische Darstellung des Härteverlaufs der Walze nach Figur 4 nach einer alternativen Ausführungsform,

The invention is exemplified below and described by way of example with reference to two embodiments. Show it:

• FIG. 1 a schematic cross-sectional view of a roll according to the invention,
• FIG. 2 a schematic representation of the hardness profile of the roller after FIG. 1 .
• FIG. 3 a schematic representation of the hardness profile of the roller after FIG. 1 according to an alternative embodiment,
• FIG. 4 a schematic cross-sectional view of an alternative embodiment of a roll according to the invention,
• FIG. 5 a schematic representation of the hardness profile of the roller after FIG. 4 .
• FIG. 6 a schematic representation of the hardness profile of the roller after FIG. 4 according to an alternative embodiment,

Embodiments of the invention

FIG. 1 shows a roller 1 according to the invention consisting of a roller core 3 of a substantially rigid material such as steel and an elastomeric coating 2, here of a synthetic rubber material. Between roll core 3 and roll coating 2, a bonding agent layer, not shown, is provided. The roll coating 2 with the layer thickness d = 10 mm and a hardness of about 25 Shore A was applied to the roll core in one process step.

According to the embodiment, the roll coating, which can be used in particular in the inking unit as well as in the dampening unit of a printing unit, the following components: Nitrile rubber (50 Mooney, 33 wt.% Acrylonitrile) 100 parts by weight zinc oxide 5 parts by weight stearic acid 1 part by weight Filler (FEF soot) 20 parts by weight Plasticizer (dioctyl phthalate) 70 parts by weight Crosslinking agent (sulfur) 3 parts by weight Vulcanization accelerator (mercaptobenzothiazole) 1.5 parts by weight

It is understood that other suitable compounds and other suitable auxiliaries can be used instead of the abovementioned processing aids, fillers, plasticizers and crosslinking agents and vulcanization aids.

The components of the roll coating are mixed in a conventional mixer, calendered and applied in the winding process on the prepared with a primer roll core. It is then vulcanized in a conventional manner, for example in an autoclave for four hours at 150 ° C. Subsequently, the single-layer roll with homogeneous roll coating is adjusted to the required dimensions by conventional processing methods such as grinding.

For surface hardening of the roll, a peroxide (for example t-butyl peroxybenzoate) in a suitable concentration, For example, 50 to 40 ml / m ² , preferably 100 to 300, in particular about 250 ml / m ² uniformly applied to the surface of the roller, wherein the roller can rotate at a suitable speed. The liquid peroxide is then allowed to diffuse into the elastomeric covering for a sufficient time to generate the desired hardness gradient period of about 5 minutes to 2 hours, for example about 30 minutes and immediately after this Eindiffusinszeit thermally brought by a heater to a sufficient reaction temperature at which reacts the peroxide with the rubber component to harden it, and held at this temperature for a sufficient reaction time, for example, about 1 hour.

The depth profile of the hardness (Shore A hardness) of the roll thus obtained is in Fig. 2 shown schematically. The roll coating has a region of the layer thickness d _v with a substantially continuous hardness gradient, wherein the harder region immediately adjoins the outer circumference of the roll coating. The hardness gradient is essentially exponential here. Here, the outermost layer of the roll coating has an intrinsic hardness of about 85 Shore A. About a radial depth of about 1 mm, the hardness has dropped to that of the unchanged roll coating, here about 25 Shore A. There are thus the core 3 surrounding layers A and B of different hardness, wherein the second layer B, which surrounds the first layer A radially outboard, has a higher hardness. Over the surface-hardened layer of the layer thickness d _{v there} is thus a hardness gradient of approximately 0.6 Shore A / 10 microns. The measured surface hardness of the roller, at the influence of the hardness gradient is evident, is about 47 Shore A. Starting from the surface-hardened layer to the roll core is a substantially unchanged hardness before.

Alternatively, surface hardening of the elastomeric coating of the roll may also be produced by applying a sulfur monochloride solution of suitable concentration, for example about 2.5% by weight, in a suitable solvent such as diethyl ether to the roll coating which may, for example, have the composition described above is applied and annealed for a sufficient period of time at a sufficient temperature (for example 80 ° C / 30 minutes). As a result, comparatively thin layers in the range of 0.1 to 0.5 mm, for example about 0.2 mm can be produced. According to a further alternative, surface hardening of a roll coating can be achieved by mixing a vulcanizing agent with a vulcanization accelerator, (for example, a mixture of sulfur with diphenylguanidine) in a suitable mixing ratio (for example in a mixing ratio of 3: 1) in a nip over a suitable period of, for example, 5 minutes to 2 hours, preferably about 30 minutes, is rubbed into the roll surface of the roll to be modified. Subsequently, a heat treatment is carried out at a sufficient time for a sufficient period of time (for example, about 1 hour at 150 ° C). It is understood that the above-mentioned hardening agents can also be introduced into the roll coating by other mechanical methods.

For diffusion of the above-mentioned hardness-changing substances in the roll coating may possibly be sufficient room temperature, with an increased process temperature accelerates the exposure process. The diffusion process may be by suitable means, for example suitable solvents we are supported acetone or the like. The surface-hardening agent may be applied to the roll surface together with a wetting properties-optimizing agent, in particular a hydrophilizing or oleophilizing agent such as a hydrophilizing fatty alcohol derivative, for example a fatty alcohol polyglycol ether, or an oleophilizing oligomeric liquid EPDM so that simultaneously with the hardness modification or in a downstream Process step, the wetting capacity of the roll surface can be changed, for example, the water wettability can be improved. The wetting agent is preferably applied to the roll coating at a time when it can still be radically bonded to the elastomer surface with the surface-hardening crosslinking agent, such as the peroxide.

FIG. 3 shows a modification of a depth profile of the roller Figure 1,2 wherein the near-surface layer highest hardness is provided at a distance of about 5 microns from the roll surface and the hardness drop to the roll surface about 5% of the absolute hardness of the layer highest hardening makes, for example, due to a superficial decomposition or side reaction of the applied for hardening crosslinking agent. Starting from the highest hardness layer S _H , the hardness decreases continuously up to a layer depth of the coating of about 100 micrometers. Except for a depth of the coating of 10 mm, preferably over the entire thickness of the coating, the layer S _{H has} the highest hardness. For the rest, the comments on the Figures 1 and 2 corresponding.

FIG. 4 shows a modification of a roll 1 according to the invention consisting of a roller core 3, wherein the same components are provided with the same reference numerals. The hardness profiles of the coatings are in the FIGS. 5 and 6 shown. The roll coating 2 with the layer thickness d = 10 mm and a hardness of about 25 Shore A corresponds to the coating of the embodiment of the Figures 1-3 , Unlike the Figures 1 and 2 the inner surface of the coating is hardened and it refers to FIG. 4 the layer thickness d = 0 on the inner coating surface, which is modified here. According to the modification, the roll coating was prefabricated in the manner of a tube, the inner surface of the coating, which faces the core 3, as to the Figures 1-3 hardened on the surface and mounted on the provided with a primer roll core. The generation of the hardness gradient after FIG. 5 corresponds to the statements below FIG. 2 , the after FIG. 6 according to the statements FIG. 3 , Due to the modification of the inner coating surface, the coating can in particular with respect to the connection with the core, in particular taking into account the necessary heat dissipation to the core and the mechanical stability of the inner coating surface, with thin roll coatings but also with respect to the properties of the outer coating surface, by suitable Choice of coating parameters and under suitable conditions, the quality of the fluid processing or processing and thus the printed products can be improved adapted.

In all embodiments, the hardness gradient according to the invention is thus produced by means of a substance or agent distributed differently from fillers or fibers distributed microscopically homogeneously in the roller coating.

LIST OF REFERENCE NUMBERS

1

roller

2

coating

3

core

dv

layer thickness

A

first shift

B

second layer

Claims (21)

1. Roller for fluid film preparation or film application, having an inside core (3) and a roller coating (2) of layer thickness d, comprising a first layer (A), which surrounds the core (3) and has a first hardness, and a second layer, which surrounds the first layer radially outwards and has a second hardness different from that of the first layer (A), characterized in that the roller coating (2) at least in certain areas displays an essentially continuous hardness gradient through at least part of layer thickness.
2. Roller according to Claim 1, characterized in that one or more of the components producing a hardness gradient is/are selected from the group of fillers, hardeners, cross-linking agents, activators, photoinitiators, monomers and oligomers of a polymeric material, and plasticisers.
3. Roller according to Claim 2, characterized in that the cross-linking agent consists of one or more components selected from the group of peroxide, sulphur, halide, sulphur halides and polysulphur dihalides.
4. Roller according to any of claims 1 to 3, characterized in that the hardness gradient is produced by a gradient of a hardness-modifying substance or agent, which is incorporated into the coating material by means of diffusion or migration of the substance or agent, or a precursor thereof, from at least one surface of the roller coating (2).
5. Roller according to Claim 4, characterized in that the hardness-modifying substance is a thermally activatable cross-linking agent, and that the roller is produced by superficial application of the cross-linking agent on a roller coating material made of a crosslinkable elastomer, diffusion of the cross-linking agent into the elastomer with generation of a cross-linking agent gradient, and cross-linking of the elastomer with generation of a hardness gradient.
6. Roller according to any of claims 1 to 5, characterized in that the basic coating material of the roller coating applied to the core (3) has a hardness of less than 35 Shore A.
7. Roller according to any of claims 1 to 6, characterized in that the hardness gradient covers a difference in effective hardness of the roller coating of more than 5 Shore A.
8. Roller according to any of claims 1 to 7, characterized in that the layer thickness of the coating material with an essentially continuous hardness gradient amounts to ≥ 0,01 mm.
9. Roller according to any of claims 1 to 8, characterized in that the near-surface layer of the roller coating (2), from where the section of the coating having an essentially continuos hardness change extends radially into the inside of the coating, lies in a section starting from the roller surface and extending to a depth of approximately 100 micrometres.
10. Roller according to any of claims 1 to 9, characterized in that the surface of the roller coating (2) is provided with a layer of immobilised, surface-modifying agent.
11. Roller according to any of claims 1 to 10, characterized in that the hardest layer of the layer thickness section with an essentially continuous hardness gradient is located on, or adjacent to, the outer surface of the roller coating.
12. Method for manufacturing a roller for fluid film preparation according to one of Claims 1 to 11 having an inside core (3) and a roller coating (2) comprising a first layer (A), which surrounds the core (3) and has a first hardness, and a second layer (B), which surrounds the first layer and has a second hardness different from that of the first layer (A), where the first and the second layer (A, B) together have a layer thickness d, characterized in that an essentially continuous hardness gradient is produced at least in certain areas in the roller coating.
13. Method according to Claim 12, characterized in that one or more of the components producing a hardness gradient is/are selected from the group of fillers, hardeners, cross-linking agents, monomers and oligomers of a polymeric material, and plasticisers.
14. Method according to claim 13, characterized in that the cross-linking agent is one or more components selected from the group of peroxide, sulphur, halide, sulphur halides and polysulphur dihalides.
15. Method according to any of claims 12 to 14, characterized in that in order to produce a hardness gradient, a gradient of a hardness-modifying substance or agent is incorporated into the coating material by means of diffusion or migration of the substance or agent, or a precursor thereof, from at least one surface of the roller coating.
16. Method according to Claim 15, characterized in that the hardness-modifying substance is a thermally activatable cross-linking agent, and that the roller is produced by superficial application of the cross-linking agent on a roller coating material made of a crosslinkable elastomer, diffusion of the cross-linking agent into the elastomer with generation of a cross-linking agent gradient, and cross-linking of the elastomer with generation of a hardness gradient.
17. Method according to any of claims 12 to 16, characterized in that in order to produce the hardness gradient, the process step that produces the hardness gradient is interrupted before a change in hardness occurs through the entire layer thickness of the coating material.
18. Method according to any of claims 12 to 17, characterized in that, that the layer thickness of the coating material with an essentially continuous hardness gradient amounts to ≥ 0,01 mm.
19. Method according to any of claims 12 to 18, characterized in that a hardness gradient of the roller coating is produced such that the near-surface layer of the roller coating, from where the section of the layer thickness having an essentially continuous hardness change extends towards the inside of the coating (2), lies in a section starting from the roller surface and extending to a depth of approximately 100 micrometres.
20. Method according to any of claims 12 to 19, characterized in that an essentially continuous hardness gradient is produced in a functional roller (1) with a homogeneous roller coating (2) by means of chemical and, if necessary, subsequent thermal treatment.
21. Method according to any of claims 12 to 20, characterized in that the surface of the roller coating is provided with a surface-modifying agent and that the agent is immobilized on the roller surface.

Images