Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F31/00—Inking arrangements or devices
  • B41F31/002—Heating or cooling of ink or ink rollers

Definitions

• the invention relates to a printing method for printing a printing material with high printing speed and high printing quality in flat or letterpress printing.
• the printing material is preferably paper.
• the method can also be used for other materials to be printed, such as suitable types of cardboard and foils.
• the invention relates to printing processes in which the printing process takes place in a printing unit in the printing press.
• the printing unit contains an inking unit and a machine element carrying the printing form and the counterpressure, for example a printing form cylinder and a counterpressure cylinder, and, in the case of indirect printing (offset printing), a rubber blanket cylinder arranged in between.
• the printing ink is applied by means of an inking unit which comprises at least one soft-elastic inking roller, metered in a thin layer onto the surface of the rigid-hard printing form and from there directly or indirectly according to the printing motif mechanical pressure on the printing material passing through the printing unit. There it is immediately solidified to such an extent that it does not rub off during further processing or use of the print.
• the print quality is generally higher, the sharper and more precise the details of the text and image are reproduced (sharpness, resolution), the more strongly colored areas of the surface stand out from the unprinted paper (optical density), the cleaner the motif printed areas remain (smearing, discoloration, discoloration on the back, dot gain, etc.) and the more accurately the requested hues are reproduced. Understandably, such an increased print quality is all the more difficult to achieve, the rougher, more uneven and less white a paper and the higher the printing speed.
• the heatset process For high print quality with high printing speed, i.e. In order to produce printed products with smoothed, coated and / or particularly thin paper with not too scarce coloring and high printing performance, the heatset process, especially the heatset web offset printing, has been used with printing speeds of 8 to 14 or even 15 m / s enforced.
• the heatset web printing process includes a conventional web printing press with a conventional inking unit, which is followed in particular by a system for drying, that is to say, for expelling heatset oil from the fresh ink layer, and a system for burning the expelled oil vapor.
• the ink layer in the finished printed product is partially solidified by adsorption onto the fiber structure of the paper, and secondly it is so poor in oil due to heat drying that its consistency is sufficiently firm for further processing, shipping and use of the printed product . Details of the heatset process are described in the guideline VDI 2587 Sheet 1 "Emission reduction, web offset printing systems with hot air drying", green printing from September 1993.
• This known printing process can thus be defined as a web printing process which works in offset printing, and sometimes also in high pressure, in which the solidification of a type of printing ink required for this purpose is accelerated by heat, preferably by hot air. It enables the production of demanding, high-quality prints with high printing speed.
• the dryer and exhaust gas purifier consume a lot of energy, the usual combustion by-products and a lot of carbon dioxide being emitted.
• there are protective measures against the risk of explosion and against the uncontrolled escape of exhaust gas as well as correspondingly complex peripheral systems, e.g. for indoor air technology and for the supply of heating gas and compressed air.
• the invention has for its object to provide a printing process for the area of application of heatset printing, in particular web printing (high printing speeds, in particular in the case of higher demands on printing quality and large print runs), in which overall less effort regarding construction, energy supply requirement and construction volume are achieved and emissions are considerably reduced.
• a printing method mentioned at the outset which has the following features in combination with one another: the printing ink is fed to the printing form with the aid of a short inking unit with an anilox roller (anilox roller) and an ink wiping device.
• a printing ink which is solid at room temperature and can be liquefied by the application of heat (hereinafter: "enamel ruc stain") is used.
• the short inking unit and the downstream parts of the printing unit that hold the printing ink, in particular the printing form are tempered to a temperature above the liquefaction temperature of the melt printing ink.
• the printing takes place in flat printing or high pressure.
• the ink solidifies by cooling it on the substrate.
• melt printing inks are used. These are fed to the printing form by a short inking unit.
• the short inking unit with anilox roller replaces the conventional roller inking units previously used in heatset printing.
• the printing unit insofar as it includes the short inking unit and parts guiding the printing ink, is tempered to a temperature above the liquefaction temperature of the printing ink.
• heating energy is only used to liquefy the pressure at room temperature. preparation of paints.
• the printing ink is dosed in molten form and fed in a thin layer to the printing form and from there to the printing material.
• the printed ink layer is immediately solidified by adsorption and by cooling to room temperature.
• the direct printing process ie the path of the printing ink from the printing form to the printing material, remains basically unchanged.
• Short inking units are known from flexographic printing inking units and from development work on newspaper printing started in the USA in the 1960s and have found their way into newspaper printing technology since the late 1980s. In addition, they are only used in flexographic printing.
• the core of a short inking unit is a special anilox roller, which is also known as an anilox roller.
• printing inks can be transported to the printing form in such an advantageous manner that the otherwise and previously required transfer and distributor roller systems and the ink metering and regulating devices can be dispensed with.
• Short inking units are used in flexographic, letterpress and flat printing, and only with the usual printing inks which are liquid at room temperature. An overview of their use and properties is given in the publication by D.
• a short inking unit can be defined as that part of the overall printing unit of a printing press which is used to meter the liquid ink supplied by means of an anilox roller and a device for Wiping off the portion of the quantity not taken up by the screen cups serves and the entire portion of the portion thus allocated for printing is transported in a thin layer in the shortest possible way to the printing form (to the plate cylinder).
• the shortest possible route can be the direct contact of anilox roller and soft printing form in flexographic printing.
• either a soft, elastic inking roller with the same diameter as that of the plate cylinder or two with a different, generally smaller diameter are interposed.
• the application roller and / or plate cylinder can each be provided with a smaller inking roller for further equalization of the thin printing ink layer to be applied. If a system of several rollers and possibly grinders is provided for the transport of the printing ink from the screen roller to the printing form, a middle path is taken between an actual short inking unit and a conventional roller inking unit.
• the good and uniform temperature control of the entire inking unit, preferably including the printing form, which is possible due to the compact design of a short inking unit, is a particular advantage in the context of the present invention.
• Short folding systems with rollers and distributors connected between the anilox roller and the printing form are less advantageous in the context of the invention, the longer the transport path from the anilox roller to the printing form.
• short inking units are particularly suitable for processing melt printing inks. Due to their compact design, they can be heated up and / or heated up to the optimal operating temperature relatively easily and precisely as a whole. temper.
• the heating elements can be accommodated in a space-saving and energy-saving manner and with a high degree of efficiency.
• a heat-insulating housing is also relatively easy to attach.
• it should advantageously be installed in order to improve the uniformity of the temperature control and to further reduce the energy consumption. In a short inking unit, considerably stronger shear forces occur between the screen roller and the Fab stripping device than, for example, with jack or film inking units.
• All printing inks basically consist of colorants (pigments, dyes), binders (resins, macromolecular compounds), diluents and auxiliaries (e.g. waxes, surfactants).
• the theological behavior in the printing press, the solidification process and the mechanical qualities of the solidified ink layer depend essentially on the properties and proportions by mass of the binding agents and diluents.
• solvents and / or oils i.e. materials that are liquid at room temperature, are used to adjust the theological properties of the printing ink preparations, which are usually thin to viscous, depending on the printing process.
• a printing ink which is solid at room temperature is used, which is melted by the supply of heat and thus brought into the liquid state required for processing and is solidified again by cooling after the printing process.
• the desired rapid processing is disadvantageous in that the macromolecular compounds which can be used as binders for such a printing ink have a broad melting range, ie they soften only relatively slowly when heated and solidify only slowly when they cool.
• the invention preferably uses mixtures of diluents compatible with the binders, which are at least partially crystalline at room temperature, become thin when the temperature rises within a narrow melting range, and the entire printing ink preparation is flowable and printable make and then solidify to a solid ink layer when it cools to room temperature.
• volatile ink components and a solidification mechanism caused or supported by their evaporation are not used here.
• the function of the diluent to influence the melting and solidification behavior it can also be called a modifier.
• melt printing inks can also be produced without a diluent of this type (or as an intermediate preparation with non-crystalline, relatively low-molecular-weight resins, condensation products or polymers) if the binders are of a suitable nature. In general, however, they are then too viscous for printing, and the transition from the solid to the liquid and then again solid state proceeds too slowly and in a temperature range that is too large.
• a binder is combined with a crystalline or partially crystalline diluent, ie a substance with a significantly lower molecular weight, then that component acts in the melt. partially lower viscosity, which has the lower molecular weight and the narrower melting range.
• the eutectic melting range of a mixture of a lower molecular substance with a higher molecular weight is shifted in the direction of the first.
• the melt printing ink obtains a melt behavior which approximates the diluent, ie with a relatively narrow melting range and a rapid transition from a solid to a relatively low viscosity, suitable for processing in the printing press and solid again when it cools down.
• the melt printing inks are particularly suitable for use in accordance with the invention.
• the temperature and the span of the melting range and the flow behavior of the melt, including their speed can be adjusted empirically by the selection and the mass ratio of binders and diluents to the extent technically required.
• the intended temperature must be maintained with narrow tolerances.
• hot-melt adhesive application methods are also customary, in which the adhesive is applied over the entire area or limited to certain areas by means of a printing method.
• Another important area of application of such substance mixtures are individual duplication processes, in particular thermal transfer printing and inkjet printing, and processes in which preparations of similar composition are used as toner powder in photocopiers or in laser printers.
• melt printing inks within the scope of the invention, with regard to suitable substances and compositions for binders and (solid) diluents, as mentioned, the experiences from the mentioned fields of application, in particular the principles and publications mentioned above, be resorted to.
• Resins, polymers, poly condensates and some (also modified) natural products can be used as binders, either individually or in combination.
• the following boundary conditions should be taken into account: they must be meltable and sufficiently compatible with the diluents used with them, compared to low molecular weight diluents. Their melting range must be high enough that the entire printing ink produced with them does not fall below 30 ° C, preferably not below 40 ° C, melts. They have to be chemically so stable that they do not change in a disruptive manner when heated repeatedly to the required operating temperature, that is, do not decompose, are not degraded to a disruptive extent, and also do not thicken to an extent restricting practical use.
• the function of the solid, crystalline or partially crystalline melt printing ink thinner at room temperature has been described above. They should preferably give the binder / diluent combination a sufficiently narrow, eutectic melting range close to that of the diluent.
• the desired compatibility means that they do not react with the binder and that there is no disruptive phase separation at the required mixing ratio. As a rule, no water-soluble substances can be used because this makes the ink layer sensitive to water.
• Suitable wax ink diluents are many waxes and paraffins. Waxes and paraffins generally belong to the low molecular weight crystalline substances. If they also contain relatively high molecular weight components, such as, for example, some polyolefin waxes, then, like also (depending on the temperature) some polymers and polycondensates, they are classified as partially crystalline, ie not entirely glassy / amorphous. There- In addition, many organic compounds can be used in principle, such as, for example, fatty acids, fatty acid esters, fatty alcohols, fatty acid amides, N-acyl compounds, urea derivatives and toluenesulfonamides. Of course, the diluents can also be used as mixtures of several substances.
• a generally required diluent can be dispensed with, provided that the entire melt printing ink preparation does not become too viscous and reacts too slowly to the temperature differences used in accordance with the process.
• This generally technically inadequate limit case illustrates, however, that intermediate stages can be set between it and the case of a very effectively diluted melt printing ink, which can be converted from a solid to a rather fluid state and back to a solid within a few degrees Celsius .
• Such intermediate stages can e.g. help with the necessary speed in planographic printing. To reach them you can e.g. keep the mass fraction of diluents low. You can also e.g. use relatively low molecular weight resins, polymers or polycondensates as diluents.
• oils ie relatively low molecular weight organic compounds that are liquid at room temperature and whose vapor pressure is sufficiently low. They then interfere just as little as in heatset web offset printing, where about 10 to 15% of the oils used remain in the dried ink layer, the absorption capacity of the paper and the pigments being sufficient for the ink layer to be mechanically strong enough.
• dyes and fillers customarily used in printing inks which can in principle be used without restriction, those which are not stable enough in their chemical and application properties in the processing temperatures according to the process are of course to be excluded.
• melt printing ink To produce a melt printing ink, they have to be dispersed or dissolved in the binder or in a melted binder-diluent combination at a correspondingly elevated temperature.
• the invention also relates to unpigmented melt printing ink preparations, such as those that can be overprinted to increase the gloss or mixed in to reduce the color strength.
• melt printing inks can be transferred from the short inking units to the printing material both in flat and in high pressure.
• the rotary pressure is preferred.
• These melt printing inks when they are composed appropriately and if the corresponding temperature is maintained, basically behave as a liquid melt in the inking and printing unit like a traditional printing ink which is liquid at room temperature.
• the printing form is attached to a rotating cylinder, from which the printing ink is transferred directly or indirectly to a printing material guided through the printing unit in web form.
• printing speeds of more than 3 m / s or even 5 m / s can be realized. According to the current state of knowledge, it can be assumed that printing speeds above 8 m / s can also be achieved in the course of the optimization of the method .
• the melt printing inks are advantageously used by the printing company in the form of a pourable or free-flowing granule delivered lats.
• other shapes are also possible, for example in heated liquid containers or as solidified barrel filling.
• the melt printing ink is fed to the ink fountain or possibly the ink collecting trough of the short inking unit or an intermediate container upstream of the inking unit and is heated up and liquefied there at the latest at the required temperature.
• An intermediate container is recommended, for example, if the anilox roller is sent directly with printing ink via a chamber doctor blade or a device described in DE 33 02 872 A1.
• Melt printing inks can also be fed, for example, in molten form from a heated tank to the heated inking unit or the intermediate container via a suitable pipeline.
• the remaining parts of the overall printing unit including the short inking unit, are heated in such a way that the printing ink remains liquid until it is transferred to the printing material and until its stripped (scraped off) portion is returned to the ink fountain, the ink collecting tray or the intermediate container.
• Suitable heating devices are, on the one hand, cavities or heating elements or heating wires provided in the interior of metal parts, which are filled with heating fluid, and, on the other hand, convectors, radiators or warm air blowers acting from the outside, and combinations thereof.
• the heating or tempering is advantageously supplemented by a heat-insulating housing and a device for controlling and regulating the temperature. This can improve the uniformity of temperature control and reduce energy consumption.
• Such heating devices are much easier to install in the compact printing units with short inking units than in those with the larger-volume roller inking units previously used in heatset printing.
• the operating temperature depends in particular on the mechanism of the actual printing process (planographic printing, letterpress printing), the printing form material, the printing machine-related specifications and the properties of the melt printing inks used in each case. It is between 30 ° C and 160 ° C, preferably between 50 ° C and 120 ° C, although in the case of wet offset printing the printing form (the plate cylinder) should not be warmer than 90 ° C. It can be provided that the temperature within this range in the region of the intermediate container (if present), the ink fountain or the ink collecting trough and the ink metering device (that is to say of the anilox roller and stripping device) is higher than on the subsequent path Printing ink, ie on application roller (s), printing form and possibly blanket.
• Such a temperature difference of up to 35 ° C can be advantageous.
• the operating temperatures which are optimal for the respective operating conditions are expediently set empirically within the ranges mentioned. They should advantageously be kept constant better than ⁇ 12 ° C, preferably better than ⁇ 6 ° C.
• the printing material especially paper
• the printing material is usually fed unheated to the printing unit, so that the melt printing ink is adsorbed and solidifies immediately after the printing process.
• the paper can also be heated to a temperature shortly before it enters the printing unit, which temperature is below the operating temperature and above the room temperature, in order to give the adsorption a small advantage before solidification.
• a cooling device for example a cooling roller stand, the fresh pressure can be further solidified if necessary.
• the printing method according to the invention comprises both planographic printing and letterpress printing. At high pressure, it is generally advantageous that no dampening is required.
• planographic printing is that screened areas are better reproduced and thinner layers of printing ink can be obtained, which are absorbed more evenly and to a greater extent by the printing material, so that the printing ink is already solidified to a greater extent by adsorption becomes.
• the melting temperature of the printing ink and the corresponding temperature of the printing unit must be set so that the dampening agent does not dry away too quickly. Therefore, the printing form (the plate cylinder) should be tempered to a maximum of 90 ° C.
• Known fountain solution additives which contain, for example, polyhydric alcohols (e.g. glycerin) can also be used.
• the water vapor partial pressure can also be increased in a targeted manner within the printing unit, including a short inking unit, which is surrounded by a heat-insulating housing.
• the increased application temperature compared to the prior art can be used to prevent too much water from accumulating in the printing ink.
• the printing method according to the invention can also be used advantageously in waterless offset printing, which has gained a not insignificant market share in recent years. If heating of the rubber cylinder is to be avoided in planographic printing, direct planographic printing (di-litho) is to be used.
• the process according to the invention largely avoids the disadvantages of heatset printing explained above, particularly in those fields of application in which work is predominantly carried out in heatset printing.
• Heating energy is now only required for the limited volume of the part of the overall printing unit which carries the printing ink, including the short inking unit and, if appropriate, an upstream intermediate container. As a result, much less energy is required than with the previous heatset process.
• the dryer is operated there with hot air at 130 to 300 ° C, the afterburning at 740 to 800 ° C. According to the invention only 30 to 160 ° C are used for much lower mass flows.
• the systems for the dryer and post-combustion have so far been large-volume. They can be saved together with the likewise large-volume heat exchangers. There are practically no exhaust gases. The emission of carbon dioxide, heat and combustion by-products is also considerably reduced.

Landscapes

• Printing Methods (AREA)
• Inking, Control Or Cleaning Of Printing Machines (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
• Glass Compositions (AREA)
• Photoreceptors In Electrophotography (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=6532222

Family Applications (1)

Country Status (5)

Families Citing this family (5)

Family Cites Families (6)

• 1994
  • 1994-11-02 DE DE4439007A patent/DE4439007C2/de not_active Expired - Fee Related
• 1995
  • 1995-10-21 WO PCT/DE1995/001486 patent/WO1996014211A1/fr active IP Right Grant
  • 1995-10-21 DE DE59503206T patent/DE59503206D1/de not_active Expired - Fee Related
  • 1995-10-21 ES ES95935809T patent/ES2121422T3/es not_active Expired - Lifetime
  • 1995-10-21 EP EP95935809A patent/EP0790893B1/fr not_active Expired - Lifetime
  • 1995-10-21 AT AT95935809T patent/ATE169561T1/de not_active IP Right Cessation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events