PRINTING PROCEDURE IN TUBULAR BODIES OF A STAMP THAT ACCOUNTS SIMULTANEOUSLY WITH BRIGHT REASONS AND
MATES OR SATINATED REASONS
FIELD OF THE INVENTION The invention relates to a printing process in cylindrical bodies that allows obtaining a pattern that simultaneously has bright motifs and matt or satin patterns. The invention relates more particularly to a dry offset i-mpression process. DESCRIPTION OF THE INVENTION Dry offset printing is commonly used when it comes to printing the outer surface of a cylindrical object of revolution such as a beverage can, an aerosol dispenser container or a flexible tube. This procedure consists in applying several inks of different colors in a blanket and then in transferring the inks by contacting the blanket with the cylindrical surface to be printed. Generally, several blankets are mounted on a turntable called a blanket table. The inks are successively arranged in each blanket by means of cylindrical cylinders, also known as clichés, which are application rollers consisting of relief parts formed by photogravure to REF. : 138190
from a negative. There is a cliche for each color. Its assembly requires a meticulous adjustment to obtain the desired juxtaposition of the colors, that is to say without displacement of a motif colored with respect to the motif of another color. This operation that consists of adjusting the positioning of the clisés is called the positioning of the colors. Once adjusted, the machine performs the precise and repetitive positioning of the colors, one with respect to the others. Then the inks are dried - thermally or by means of ultraviolet rays - and the surface is covered with a varnish that protects the printed pattern of the external aggressions or also, especially if the wall is made of plastic material, increases the diffusion barrier to gases and aromas. The varnish gives the overall matt or glossy appearance of the pattern. In general, the varnish is applied by means of a roller on the entire surface of the cylindrical body with a simple device other than the offset machine. The use of a simple device other than the offset machine is possible since the application is made on the whole surface of the cylindrical body and since it is not necessary to apply the varnish according to a reference point corresponding to the stamping. -
In fact, in case there is a repetition of the operation, that is to say when a second device other than the first device must be used to print an additional reason, it is necessary to be able to position this additional reason with respect to those already made. In this case, the signaling technique is used: with the first device, a reference point characteristic of the positioning of the first printing patterns is printed and the second printing device is equipped with an optical reading device which, when locating said reference point, allows the second device to correctly position additional motifs. The signaling is a technique of juxtaposition or overprint difficult to set up and is less precise because the rate of production is high. Furthermore, the difficulty is even more important when it comes to printing the cylindrical surface of tubular bodies. To achieve a matte / glossy contrast effect, the man of the trade can contemplate: • using, after the inks have dried, a second offset device to apply a matt varnish and a glossy varnish (in this case it has to be immobilized) a second expensive device and difficult to tune up) • is to apply a first varnish with a roller, dry it and
then apply and selectively a second varnish by screen printing. Whatever the solution used, the man of the trade has to use the technique of signaling which decreases production rates and requires frequent corrective actions. The problem of the positioning of the two varnishes with respect to the inking stamping (first case) is in fact difficult to solve since it is no longer a question of adjusting the positioning of clichés in an offset machine
(adjusted once for all) but to locate by means of an optical device a reference point printed on the cylindrical wall at the same time as the first motifs and position the area to be printed according to said reference point. PROBLEM RAISED To preserve the high production rates of cylindrical bodies such as plastic tubes or aerosol containers, the applicant has sought a procedure that avoids signaling. It is therefore a question of looking for an economic procedure of printing in cylindrical bodies that allows to give a matt / bright contrast effect in a varnished pattern, this procedure being carried out without repetition, it is
Say without having to mobilize an additional offset machine or a screen printing machine to add! and without having to resort to delicate marking operations in the stamping. OBJECT OF THE INVENTION The object of the invention is a method of printing on cylindrical bodies of varnished patterns that simultaneously have bright motifs and matte or satin patterns, characterized in that a matte ink or a bright ink is chosen according to the motive to be printed. function of the final aspect desired in this part of the stamping, because each of the aforesaid motifs is printed with said ink and because a glossy varnish is immediately applied on the whole of the surface of the tubular body. According to the invention, the inks, chosen as matt or glossy according to the desired final appearance, are applied - for example by means of a dry offset machine - and the glossy varnish is applied immediately afterwards, that is without waiting for the inks to be dry. The varnish can be applied, for example, with a roller just behind the offset machine, as illustrated in the figure.
When the cylindrical bodies have uncoated metal walls - for example container bodies for aerosol dispensers - the uncoated metal surface is preferably coated before printing, by roll application of an adhesion primer layer. When it is an aluminum container, a modified polyester resin type primer is used. There are matte inks on the market but it is preferable to make the inks from the corresponding bright colored ink and transform them into matte inks by adding mineral or organic filler. For example, between 5% and 20% by weight of silica powder is added to the gloss ink. This has to have an adapted granulometry: the particles have to be sufficiently fine to be able to be dragged by the volatile materials that are released during the drying but thick enough so that when they reach the surface of the varnish, they disturb the relief of the surface and modify their reflective qualities. Although the observation of the varnished layer is very difficult because it is not very thick, the applicant assumes in fact that the surprising result that the glossy varnish becomes matt in certain parts is due to the migration of the slaking particles of matte ink
towards the outer surface of the varnish and that said migration is undoubtedly facilitated by the centrifugal evacuation of the volatile matters of the ink and the varnish. The Applicant has verified that a powder mixed with the ink with a weight percentage of 10% and with a pitch diameter
D50 between 3 μ and 10 μ gave good results, with the best ones around 6 μ. The drying is carried out thermally or via UV according to the nature of the inks and varnish. In order for the killing particles to migrate from the ink to the varnish, it is preferable to opt for a progressive drying. Thus, as regards UV drying, this will be done preferably in two stages: • a first step of 2 to 6 minutes in a furnace where a temperature between 60 and 100 ° C predominates • a second step corresponding to the procedure of Classic UV drying. With regard to thermal drying, care should be taken not to reach too quickly the temperature normally used, close to 180 ° C, for example imposing a maintenance of the temperature of one to three minutes at about 100 ° C.
MODE OF EMBODIMENT OF THE INVENTION Figure 1 illustrates a device that allows to apply the method according to the invention. This device allows the printing without repetition in dry offset of an aluminum spray container stamped with a finishing varnish whose final appearance is simultaneously matte and glossy in certain parts of the stamping. The drying of the inks and the varnish is done thermally. The manufacturing process for this type of containers can be described succinctly in this way: A. Before printing: • extrusion by impact of a pawn in aluminum • cut to length (trimming or trimming) of the cylindrical wall of the extruded chipped piece) • Surface treatment of the surfaces of the aforementioned rough-cut piece, interior varnishing (the interior varnish is intended to isolate the product that will be contained inside the wall from the metal of the wall) • varnish drying
B. Printing • Application of an adhesion primer on the substrate in aluminum. A modified polyester resin referenced SP-72KM309 / 2 is used here by the company BLANCOME. • Preparation of inks: - For glossy inks: Bright thermal drying inks referenced in the Galathe series (registered trademark) of the VALSPAR company are used. These inks, which - correspond to the different - motifs of the stamping and are used without additional addition. - For matt inks: For those parts that have to have a matt appearance, the corresponding ink is mixed with 10% silica. The silica particles used have a mean diameter of 3 μ and a step at 50% of 6 μ. • Application of matte and glossy inks using a device that performs the dry offset procedure. • Application of a polyester varnish in the inks without any intermediate drying: it takes approximately two seconds between the end of the application of the last ink and the beginning of the application of the varnish. Here the application of this varnish is called the over-varnish for
distinguish it from the application of internal varnish (see A). • Introduction in a 180 ° oven for 6 minutes with constant ventilation, that is to say it generates a current of air that circulates more than # 3 m / s very close to the outer surface of the cylindrical pieces of the containers. C. After printing: Conical conforming of the open end of the cylindrical chipped piece, cutting of the extremity so narrowed and realization of the rounded edge.
ADVANTAGES OF THE PROCEDURE ACCORDING TO THE INVENTION • It does not require a repetition of the operation in case of printing of an additional reason therefore the adjustments are faster and the positioning of the motifs with respect to others is more precise; • Saving of raw material, less machines are used, energy saving.
Legend of the figure: A Loading of the container B Unloading of the container 100 Aerosol container 101 Inked container
102 Varnished container 1 dry offset method application device 10, 10 ', 10 TI, 10' '', inking devices 10 ', 11' inks 12 intermediate roller 13 cylinder holder 2 blanket 20 device (on) varnishing 21 varnish 22 application roller It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.