EP0284972A2 - Method for closing and/or sealing apertures or interstices in printing plates affixed to printing cylinders - Google Patents

Abstract

The invention relates to a method for closing and/or sealing apertures, cavities or interstices which are formed when printing plates are affixed to form cylinders, by means of a packing or sealing substance, which is viscous/plastic and pasty at room temperature and is based on a dispersion of a powdered, solid, highly fluorinated olefin polymer in an inert, non-volatile organic fluid.

Description

The invention relates to a method for closing and / or sealing openings, cavities or gaps, such as result from the application of printing plates to forme cylinders, in particular in the region of the end or edge sections of the printing plates, by means of a sealing or sealing compound. The method according to the invention is particularly suitable for closing and / or sealing such openings, cavities or gaps in intaglio printing plates applied to forme cylinders.

For the production of rotary printing formes, it is known to wrap form cylinders with flat printing plates and to fasten them to the form cylinders in a suitable manner, for example by gluing magnetically or mechanically by means of suitable holding and clamping elements. Here, only one printing plate or several printing plates can be applied one behind the other and / or next to one another on the surface of a forme cylinder. This method for producing rotary printing forms is becoming increasingly important, especially in rotogravure printing, because of the simple and cost-saving production and handling of gravure winding plates. The partial pressure winding plates are preferably applied to the form cylinder by folding one or both of their end sections and hooking these non-edged areas into a groove of the forme cylinder provided for this purpose while simultaneously tensioning the gravure winding plate.

When flat printing plates are applied to a forme cylinder, this results between the opposite, possibly folded, ends or end regions of a printing plate or, if several printing plates are applied on a forme cylinder one behind the other and / or next to one another, between the abutting edges of the end and / or Side areas of the printing plates an interruption of the printing surface on the forme cylinder in the form of columns, clamping slots or other gaps or cavities. Such openings or gaps which form when applying printing plates to forme cylinders have to be closed in a suitable manner in order to prevent penetration of printing ink, which may result, for example, in detaching the adhesive of the printing plate on the forme cylinder or, in particular in gravure printing, injecting the printing ink and unwanted impression of the column can lead, and also to ensure a smooth squeegee run and thereby prevent damage to the squeegee and printing form surface. Also on the forme cylinder end faces can between the forme cylinder surface and the side areas of the applied printing plate or between the printing form surface and the printing cylinder provided laterally, limiting the printing surface metal rings, as is usually the case in rotogravure printing. Openings and gaps are created that must be sealed to prevent printing problems from penetrating ink or for other reasons.

It has already been proposed to seal the gaps or tensioning slots formed during the mechanical clamping of gravure winding plates on forme cylinders by means of sealing strips, tapes or cords made of elastic or plastically deformable materials (see, for example, US Pat. No. 2,056,991, US Pat. 2 285 116, DE-A-25 45 124 or DE-A-26 33 445). This method of gap closure can only be used to a limited extent, is complex in terms of its design and, moreover, frequently causes greater difficulties because of the adaptation of the sealing profile strips to the shape of the opening or joint to be closed and any subsequent surface treatment which may be necessary.

Furthermore, it is known that the gaps, clamping slots or other openings and spaces which are formed when printing plates are applied to forme cylinders, by filling with materials which only reach the state required for their function by chemical reaction, heat, drying or the like, for example To seal adhesives, thermoplastics, hot melt adhesives, thermosetting or light-curing reactive resins or foams or liquid photopolymerizable compositions. The use of such sealing compounds for printing plates mounted on forme cylinders is described, for example, in Deutscher Drucker, No. 41 (1975), pages 17-22, DE-A-25 45 618, EP-A-118 866, EP-A-174 568, EP-A-175 189 or GB-A-2 160 882. These sealing compounds generally pose no problems with regard to shape adaptation, but often have only insufficient resistance to the printing ink solvents and / or show mechanical weaknesses under the stresses of the printing process, in particular under the action of impression cylinders, printing material and, in the case of gravure printing, also the doctor blade. Some of these known closure materials tend to become brittle, so that after a short time small cracks form in the gap area which can fill with paint. It is precisely the combined action of printing ink solvents and mechanical forces that often cause damage or even destruction of these filler or sealing compounds. But even if these sealing compounds have a chemical and mechanical resistance that meets the requirements, their application and the setting of the required properties is in as a rule laborious and time-consuming and their use is restricted primarily to the closing of relatively wide or large gaps, openings or other cavities or gaps.

The present invention has for its object the openings and gaps that form when applying and fixing printing plates to forme cylinders, such as e.g. Gaps, joints, holes, cavities and the like. Sealing and / or sealing quickly and effectively with little effort, while avoiding the disadvantages known from the prior art, so that an all-round uninterrupted printing form surface is obtained which corresponds to the mechanical and withstands chemical stresses.

It has surprisingly been found that this object is achieved according to the invention by using a pasty mass which is viscous at room temperature and is based on a dispersion of a solid, powdery, highly fluorinated olefin polymer in an inert, low-volatility, organic liquid as a sealing or sealing compound for the application in question is solved.

The invention accordingly relates to a method for closing and / or sealing openings, cavities or gaps which are formed when printing plates are applied to forme cylinders, by means of a sealing or sealing compound, which is characterized in that it is used as a sealing or sealing compound a viscous, pasty mass at room temperature based on a dispersion of a solid, powdery, highly fluorinated olefin polymer in an inert, low-volatility, organic liquid is used.

Even if the method according to the invention can be used with printing plates of all types applied to forme cylinders, for example high-pressure and flexographic printing plates, it has proven to be particularly favorable and advantageous for gravure printing plates applied to forme cylinders. By using the sealing or sealing compounds to be used according to the invention, the printing plates can not only be held and fixed on the forme cylinders in any desired position, it also prevents the penetration of even thin-bodied printing ink into the openings, cavities or gaps mentioned the resulting disadvantages prevented. It was surprising that the openings, voids or gaps closed and / or sealed by the process according to the invention are outstandingly chemically and mechanically stable under the requirements and stresses during printing, show no weaknesses and that those by the process according to the invention Rotogravure forms produced allow a smooth, smooth and smooth sliding of the squeegee on the printing form surface without damaging it. The method according to the invention is particularly advantageous since it is universally applicable, it does not require hardening or drying of the sealing or sealing compound and the sealing or sealing compound to be used according to the invention is simple and easy to process in the method according to the invention. Although the method according to the invention is suitable for closing and / or sealing any kind of openings, cavities or gaps in the case of printing plates mounted on forme cylinders, it is particularly suitable and can be used without problems and advantageously when closing and / or sealing small or narrow gaps, joints, other openings, spaces and the like.

The sealing or sealing compounds to be used according to the invention are viscous, rigid, pasty dispersions of solid, powdery, highly fluorinated, preferably perfluorinated, olefin polymers in inert, low-volatility, organic liquids at room temperature. Highly fluorinated olefin polymers are both highly fluorinated homopolymers and highly fluorinated copolymers of olefins, in particular of ethylene and propylene, and also highly fluorinated olefin polymers which contain ether groups in the main polymer chain. Examples of such ether groups which can be incorporated in the main chain of the highly fluorinated olefin polymers, generally in a minor proportion, are the (-CF₂-O-), (-CF₂-CF₂-O-) and (-CF (CF₃) -CF₂-O -) - groupings. As a rule, the dispersions to be used according to the invention contain solid, powdery homopolymers or copolymers of highly fluorinated, in particular perfluorinated, ethylene or highly fluorinated, in particular perfluorinated, propylene. These include in particular the polytetrafluorethylene, polyhexafluoropropylene and tetrafluoroethylene-hexafluoropropylene copolymers. The solid, powdery, highly fluorinated olefin polymers contained in the dispersions to be used according to the invention are finely divided and, in addition to fluorine, may also contain to a lesser extent other halogen atoms, in particular chlorine atoms. The solid, powdery, highly fluorinated olefin polymers are preferably perhalogenated, in particular perfluorinated.

In addition to the solid, powdery, highly fluorinated olefin polymers, the viscous, pasty dispersions to be used as sealing or sealing compound according to the invention contain, as a further component, one or more inert, low-volatility organic liquids which act as dispersants for the solid, powdery, highly fluorinated Olefin polymers act. Such inert, low-volatility, organic dispersing liquids are, for example, high-boiling fluorocarbon oils, fluorinated polyether oils, silicone oils or fats or fluorosilicone oils. The inert, organic dispersing liquids are generally low-volatility oils, but they can also be greases. They have a high temperature resistance and generally only show a slight dependence of the viscosity on the temperature. They are chemically stable and generally have a boiling point above 150 ° C., preferably above 200 ° C. Examples of the inert, low-volatility, organic dispersing liquids are: the corresponding, known fluorinated hydrocarbon oils; highly fluorinated, preferably perfluorinated, polyalkylene ether oils, preferably those polyether oils which are composed of recurring oxyperfluoroalkylene units of the formulas -CF₂-O-, -C₂F₄-O- and / or -C₃F₆-O-, as described, for example, in DE-A-2 633 736 or are commercially available under the brand name FOMBLIN; Silicone oils or fats, for example of the type of polysiloxanes, such as polyphenylmethylsiloxane, or of the type of reticulated silicone polymers, for example methyl silicone polymers of oily or fatty consistency; as well as corresponding fluorinated silicone oils. The oils or fats mentioned can be used alone or as a mixture with one another for the dispersing liquids.

The dispersions to be used according to the invention can be prepared in a conventional manner known per se by intimate mixing, for example stirring or kneading, of the individual components. The solid, powdery, highly fluorinated olefin polymers and the inert, low-volatility, organic dispersing liquids are selected according to type and amount and coordinated with one another such that a stable dispersion of the solid, powdery, highly fluorinated olefin polymers in the inert, low-volatility, organic dispersing liquid is produced and this dispersion has a stiff, paste-like consistency at room temperature and is viscoplastic so that it can be deformed under the influence of pressure and shear force, but is not self-flowing. The dispersions to be used according to the invention are usually solvent-free and the weight ratio of powdery, highly fluorinated olefin polymer to the inert, low-volatility, organic dispersion liquid is in the range from about 3: 7 to 6: 4.

Examples of dispersions which are particularly suitable as sealants or sealing compounds in the process according to the invention are paste-like, rigid, viscous-plastic dispersions of powdered polytetrafluoro ethylene in perfluoropolyalkylene ether oils of the type mentioned above in a polymer: oil weight ratio of about 35:65 and paste-like, stiff, viscous dispersions of powdery polytetrafluoroethylene in silicone oil, for example polyphenylmethylsiloxane, in a polymer: oil weight ratio of about 1: 1.

The viscous, pasty sealing or sealing compounds to be used according to the invention adhere well to metallic and plastic surfaces, so that when they are used according to the invention when closing and / or sealing openings, cavities or gaps in the case of printing plates mounted on forme cylinders, a stable connection in the closed or sealed areas. Since the viscous, paste-like sealing or sealing compounds to be used according to the invention do not harden and do not change in any other way, e.g. shrink, the desired effect is retained without restriction during the entire print run when used in accordance with the invention. In particular, they are completely resistant to the ink solvents, i.e. they do not swell or soften and do not change in their other properties. Another advantage of the viscous, paste-like dispersions to be used in the process according to the invention as a sealing or sealing compound is that, during the printing process, their shape and surface meet the requirements in the machine, even under the action of the impression cylinder and doctor blade adapt to the mechanical conditions of the printing gap or the doctor blade facet. Furthermore, the viscous, pasty dispersions to be used according to the invention are toxicologically completely harmless and very temperature-stable, i.e. they do not change even at temperatures up to about 200 ° C and more.

According to the invention, the viscoplastic, pasty dispersions of the type mentioned can be used to a large extent for closing and / or sealing openings, cavities or gaps which result when printing plates are applied to forme cylinders. For example, the viscous, pasty dispersions to be used according to the invention can be introduced between the printing plate and the forme cylinder, as a result of which not only is the printing plate adhering and fixed on the form cylinder, but at the same time penetration of the printing ink between the printing plate and the form cylinder is avoided. For this purpose, it may be expedient to seal and seal the joint between the side areas of the printing plate and the surface of the forme cylinder on the end faces of the cylinder with the viscous, pasty dispersions to be used according to the invention. It has also proven to be particularly advantageous to use the ends of the pressure plate, which generally run parallel to the forme cylinder axis, to be used according to the invention apply viscous-plastic, pasty dispersions on the cylinder surface firmly and at the same time seal against the penetration of printing ink. This method variant is particularly advantageous if the end of the pressure plate to be fastened is not folded over, but lies flat on the cylinder surface. Likewise, it is of course also possible to fold the end regions of the pressure plates, which, when applied to the forme cylinder, are hooked into a groove made in the form cylinder, which is optionally provided with holding and tensioning elements, for fixing the folded end region of the pressure plate in the suspension groove and simultaneous sealing of the resulting openings and spaces by using the viscous, pasty dispersions to be used according to the invention on the forme cylinder. In addition, with the viscoplastic, pasty dispersions to be used according to the invention, the gap which results when a printing cylinder is wrapped around a printing plate between the, if appropriate folded, end areas of the printing plate, or when a plurality of printing plates are applied behind and / or next to one another on a form cylinder , The gaps that result between the end and / or side areas of these printing plates mounted on a forme cylinder are closed and sealed. It has turned out to be a particular advantage that even very narrow and small gaps or joints, which result when printing plates are applied to forme cylinders between the end and / or side areas of the printing plates, can be easily and easily closed according to the invention. Basically, all openings, cavities or gaps that result when printing plates are applied to forme cylinders and that interfere with the subsequent printing process or lead to problems, for example due to penetrating printing ink, can be sealed and / or closed by means of the viscous, pasty dispersions to be used according to the invention .

Of course, it is also possible to use the viscous, pasty dispersions to be used according to the invention together with other sealing compounds in the method according to the invention. If it is necessary or desirable, for example, for the production of rotogravure printing plates, the gap between the plate ends that results when the intaglio printing plate is clamped onto the forme cylinder by means of a conventional hardenable gap sealing compound, in particular a light-curable gap sealing compound, so that image information can also be introduced into the gap area. for example, the viscous, pasty dispersions to be used according to the invention can be used, for example, to lock the lateral end points of the gap or to close individual openings or joints required for the sealing method with hardenable gap sealing compounds.

The application of the viscoplastic, paste-like dispersions to be used in the process according to the invention as sealing or sealing compounds can be done in a very simple manner by simply applying the viscous-plastic, paste-like dispersion to the areas of the printing plates and / or forme cylinders to be sealed and by simple mechanical pressing and pressing or Pressing into the openings or cavities to be closed, for example using a spatula, scraper or the like. Excess dispersion material can then be easily removed by simply wiping off the printing form surface or the end faces of the printing form cylinder thus obtained. Thus, according to the invention, special devices or expenses for closing and / or sealing the openings and gaps, as well as a special, for example mechanical, post-treatment for adapting the closed gap to the surface contour of the cylinder are eliminated. Of course, the viscous, pasty dispersions to be used in the process according to the invention as sealants or sealing compounds can also be easily and quickly mechanically peeled or removed again for the purpose of removing the printing plates from the forme cylinder, without the need for special devices or expenditure and without this can damage the printing plate or the forme cylinder. This is also a particular advantage of the method according to the invention. Inserted printing plates can be reused without restriction.

In the process according to the invention, all known and customary printing plates which can be clamped on forme cylinders of a sheet-fed or web-fed rotary printing press can be used, such as the known photopolymer high-pressure plates and flexographic printing plates. The method according to the invention is particularly advantageous for gravure printing plates applied to forme cylinders of a rotogravure printing machine. The method according to the invention can be used both for the conventional gravure printing plates made of metal with Ballard skin and with particular advantage particularly for gravure printing plates with plastic printing layers, in which a plastic printing layer is applied to a suitable printing layer support, in particular made of metal, into which the ink-absorbing layers are applied Wells (wells), be it by mechanical engraving or by laser engraving (cf. e.g. DE-A-27 52 500 or DE-A-30 28 098) or photomechanically by imagewise exposure and development of a suitable light-sensitive recording material (cf. e.g. DE-A-20 54 833, DE-A-20 61 287, EP-A-70 510 and EP-A-70 511) have been introduced. In the context of this invention, intaglio printing plates are understood to mean the finished intaglio printing plates in which the ink-guiding depressions have already been introduced, as well as the intaglio printing plate blanks in which the cells have not yet been formed. This means that it is still possible to clamp a finished rotogravure plate onto the forme cylinder and then the resulting openings, hollow and intermediate to seal and / or close spaces according to the invention, or to first apply rotogravure plate blanks to the forme cylinders, to close and / or to seal and / or to seal the resulting openings, voids or gaps according to the invention and only then to insert the cells into the printing layer of the printing plates. In the context of this invention, printing plates are generally understood to mean both the printing plate blanks, which do not yet contain any image information, and the finished printing plates with image information, differentiating the printing and non-printing areas.

Claims (10)

1. A method for closing and / or sealing openings, cavities or gaps which are formed when applying pressure plates to a forme cylinder by means of a sealing or sealing compound, characterized in that a sealing plastic or sealing compound is tough at room temperature, pasty mass based on a dispersion of a solid, powdery, highly fluorinated olefin polymer is used in an inert, low-volatility, organic liquid. 2. The method according to claim 1, characterized in that the dispersion contains a solid, powdery, highly fluorinated, in particular perfluorinated, ethylene or propylene homo- or copolymer. 3. The method according to claim 2, characterized in that the dispersion contains as a solid, powdery, highly fluorinated olefin polymer a polytetrafluoroethylene, polyhexafluoropropylene, a tetrafluoroethylene-hexafluoropropylene copolymer or mixtures thereof. 4. The method according to any one of claims 1 to 3, characterized in that the dispersion contains as an inert, low-volatility, organic liquid as a dispersant for the powdery highly fluorinated olefin polymers fluorocarbon oils, highly fluorinated polyether oils, silicone oils or fats or fluorosilicone oils. 5. The method according to claim 4, characterized in that the dispersion as an inert, low-volatility, organic liquid, a perfluorinated polyalkylene ether oil, which consists of recurring units of the formulas -CF₂-O-, -C₂F₄-O- and / or -C₃F₆-O- or contains mixtures thereof. 6. The method according to claim 4, characterized in that the dispersion contains, as an inert, low-volatility, organic liquid, optionally fluorinated polysiloxanes of oily or fatty consistency. 7. The method according to any one of claims 1 to 6, characterized in that the dispersion contains the powdery, highly fluorinated olefin polymers and the inert, low-volatility, organic liquid in a weight ratio in the range of about 3: 7 to 6: 4. 8. The method according to any one of claims 1 to 5 or 7, characterized in that a viscous, pasty dispersion of powdered polytetrafluoroethylene in perfluorinated polyalkylene ether oils, the recurring units of the formulas -CF₂-O-, -C₂F₄-O- and / or -C₃F₆-O- included, is used with a weight ratio of polytetrafluoroethylene to perfluorinated polyalkylene ether oil of about 35:65. 9. The method according to any one of claims 1 to 4 or 6 to 7, characterized in that a viscoplastic, pasty dispersion of powdered polytetrafluoroethylene in polyphenylmethylsiloxane with a weight ratio of polytetrafluoroethylene: polyphenylmethylsiloxane of about 1: 1 is used. 10. The method according to any one of claims 1 to 9, characterized in that the viscoplastic, pasty dispersion for closing or sealing the openings, voids or gaps is mechanically applied and pressed or pressed.