Coating processes – Nonuniform coating – Deforming the base or coating or removing a portion of the...
Reexamination Certificate
1999-11-08
2003-09-09
Beck, Shrive P. (Department: 1762)
Coating processes
Nonuniform coating
Deforming the base or coating or removing a portion of the...
C427S374100, C427S387000, C427S556000, C101S483000
Reexamination Certificate
active
06616974
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a form for the rotary machine printing, coating or imprinting of web-shaped materials, wherein at a carrier having a cylindrical surface area, an elastomer layer is attached which, after curing, at the outer circumference thereof, is machined to give a cylindrical shape, and engraved. Furthermore, the invention relates to a method for manufacturing a form for the rotary machine printing, coating or imprinting of web-shaped material, wherein at a carrier having a cylindrical surface area an elastomer layer is attached which, after curing at the outer circumference thereof, is machined to give a cylindrical shape, and engraved.
BACKGROUND OF THE INVENTION
Forms of the kind mentioned before are used for different applications. In an embodiment as a printing form, e.g., for letterpress printing, in particular; for flexographic printing, the outer surface of the engraved elastomer layer forms the color transferring surface. For this reason, various requirements are imposed for the elastomer layer and the surface thereof. For example, it must have a sufficient resistance against solvents present in the printing paint, a good dynamic performance, and color transfer performance, and a small swelling under the influence of printing paints, and after the printing process it must be easily and simply cleaned from the printing paint. The requirements are similar when the form is used for coating processes, e.g., as a transfer roller for flatbed printing, in particular offset printing. The term “coating” is to be understood in particular for the transfer of printing paints in the printing processes, in particular for flexographic printing, as well as the transfer of, e.g., varnishes or glues onto web-shaped materials. Depending on the requirements, a transfer across the complete surface, and also a transfer only onto selected surface areas, is possible. When the form is used as an imprinting form, the elastomer layer in particular has to comprise a good dimension stability, and wear resistance even at the common temperatures of the material to be imprinted in imprinting processes, as well as a good separating performance in order to imprint web-shaped materials with a sufficient economy. Independent from the envisioned application of the form in any case, the elastomer layer must be well engraveable. The web-shaped materials to be printed with such a form, coated, or to be imprinted, as an example, may be paper or textile webs, metal or plastic foils or compound materials comprising different materials.
Hitherto, elastomer layers fulfilling all mentioned requirements on the form could only be produced by vulcanization of elastomer compounds onto temperature stable carriers at a high temperature. The temperatures required for the vulcanization, in practical operation at least 140° C., require the stock holding of appropriate devices, in particular autoclaves, for manufacturing the forms, wherein particularly large printing forms having a length up to several meters and a circumference up to about 2 m require complicated heating devices. Therein correspondingly high unit and energy costs are necessary for generating the forms. Additionally, the relatively long time for vulcanizing of 12 hours or more per form have a negative impact. As the carrier onto which the elastomer layer is applied also has to withstand the temperatures occurring during the vulcanization without damage, the selection of material for the carrier is considerably restricted, namely, to materials having a sufficient pressure and temperature stability. For practical reasons almost only metallic carriers may be used, whereas plastic carriers which would be preferred because of their lighter weight can hardly be used. Only premium glass fiber reinforced plastic materials are capable of coping with the high temperatures occurring during the vulcanization over the required time span. Hollow cylindrical light weight carriers may be made from these glass fiber reinforced plastic materials onto which the elastomer layer may be vulcanized, however, there is the disadvantage, that the possible variation in thickness of the carrier is very limited. Therefore, only relatively small repeat length areas may be covered in hollow cylindrical forms with a defined inner diameter for a certain-firm mandrel roller outer diameter. In practical experience, it therefore happens, that in factories using the forms, a very large number of different mandrel rollers have to be kept in stock. These mandrel rollers are expensive and require large warehouse space.
From DE 196 12 927 A1 a printing machine and an image generating process for a printing machine are known wherein the printing machine in a printing group comprises a seamless image cylinder which, by means of a direct image generating process within the printing group, is covered with a polymer to be dried. After the drying, the surface capacity of the polymer applied to the image cylinder is completely, or by areas, changed by means of selective laser radiation in order to change its affinity regarding a printing paint. The image cylinder may only be used in a wet or dry offset printing because the polymer layer is very thin (typically 2-10 &mgr;m) and therefore an engraving is impossible. For the specific application of the waterless offset printing, silicones are used as polymers, wherein in this case the feature is essential that they reject printing paints.
In an older non-published German Patent Application 197 25 749.2, owned by the assignee of the present application, a method for generating a seamless printing form for the rotative letter press printing, in particular for flexo-graphic printing, is described wherein at a carrier having a cylindrical surface area an elastomer layer is attached which after curing is engraveable, wherein for forming the elastomer layer a cold curing silicone polymer or silicone fluor polymer is used. Because of the use of cold curing materials for forming the elastomer layer, this method requires the smallest possible technical effort for its application, such that the generation of forms according to this method is relatively inexpensive. For applying this method, however, relatively long curing times of the elastomer layer must be tolerated, wherein this curing time in practical experience lasts for several hours. This high time effort for the curing of the elastomer layer leads to the fact that only a limited productivity may be attained with this method, or that very much warehouse space must be provided for receiving the forms for which the curing of the elastomer layer is not yet finalized.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a form of the kind mentioned before which is to be produced in a simple, and fast, and inexpensive way with the required features for a given case, and wherein for the carrier different materials, also light weight materials may be used. It is a further object to provide a method of the kind mentioned before wherein the manufacturing of a form for the rotary machine printing, coating or imprinting of web-shaped materials is possible, which requires no high effort in equipment during its application, and wherein the selection of materials required by the carrier offers a large variety. Therein also sleeve-shaped forms are to be produced with the method wherein a large repeat length area may be covered with a defined mandrel roller, i.e., wherein the thickness of the form may vary in relatively large ranges.
According to invention, the first part of the object is attained with a form of the aforementioned kind which is characterized in that the elastomer layer is formed of a hot cure single-constituent or two-constituent silicone polymer.
The object relating to the method according to the invention is attained in a method of the aforementioned kind which is characterized in that for forming the elastomer layer, a hot cure single-constituent or two-constituent silicone polymer is used.
The term “hot cure” is to be understood such that the
Langerbeins Klaus
Link Alfred Ernst
Lorig Heinz
Richard Jörg
Beck Shrive P.
Fletcher, III William Phillip
Polywest Kunstofftechnik Saueressig & Partner GmbH & Co. KG
Sonnenschein Nath & Rosenthal LLP
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