DE2350617A1 - Paper or plastics melt adhesive application - uses transfer block with good adhesion but poorer wetting - Google Patents

Abstract

Melt adhesive is applied, according to format, to paper or plastics packaging materials. It is first applied to a block with good adhesion but poorer wettability than the article to be coated, which is then contacted by the block. Pref. the block is attached to a revolving printing cylinder, and is heated. The length of material may be preheated, or heated after application of the adhesive. A closed-face or pitted-face block is used. An engraved raster roller with doctor blade applied adhesive to the block on a carrier, and the block contacts the workpiece. No excessive heating of the workpiece is possible.

Description

Method and device for the indirect application of hot melt adhesive to a

workpiece

The invention relates to a method and a device for indirect, In particular, the correct format application of hot-melt adhesive to a workpiece, for example, a continuous or already divided into blanks Web of a packaging material such as paper or plastic film.

In the paper and plastics industry these days, so-called "hot melt" or hot melt adhesive is used, in contrast to conventional ones Adhesives do not contain solvents, but are brought into the liquid state by heating, in which they have good wetting behavior compared to paper and many plastics.

These hot melt adhesives solidify by cooling, so that the setting of this adhesive is a purely thermal problem.

A firm connection is established when there is adequate heat dissipation a sufficiently low temperature has been reached. There will be a wide variety of events today

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Embodiments used, in particular glue with and without residual tack at room temperature. Due to the lack of solvents, hot melt adhesives are suitable particularly good for bonding solvent-impermeable plastics. Their use is particularly useful when otherwise due to residual solvents sensitive filling goods, such as food, could be damaged. Hot melt adhesives preferably have a melting point of approx. 100 to 130 C and they are processed at temperatures of, for example, 140 to 170 C.

The following methods are known and customary today for the application of hot-melt adhesives:

A) Full-surface coating with hot melt is carried out with the help of

- Swelling nozzles, the nozzle gap runs transversely to the Bahr direction;

- doctored anilox rollers, which an im general heated doctor blade system can be connected downstream;

- Immersion baths, in which a uniform coating In predetermined Layer?; Print with the help of a squeegee system or squeeze = or Dosing rollers is achieved.

B) An intermittent job in one or more parallel lines is made achieved with spray nozzles for which the necessary spray pressure is mechanical or is generated by compressed air.

C) A format-wise order can be achieved with a modified gravure printing. The anilox roller, which is only engraved on part of the surface, is doctored off, so that adhesive remains only in the pans, which is obtained by suitable pressure is transferred to the workpiece to be coated with the yard «= Mefii. ·

The methods described above for a hot melt adhesive application lifted for heat-sensitive material has the disadvantage that the hot / much flat or

Part of the workpiece to be coated is not only due to the Heat contained in hot melt adhesive is stressed, but is exposed to a much higher thermal load as a result of contact with a Metal roller with high thermal conductivity that applies the hot-melt adhesive. When applying the hotmelt adhesive according to the format with the help of a partially engraved The anilox roller to be doctored off is also used for each format length of a workpiece blank and / or requires a separate roller for each form of application. This adhesive application process, which corresponds to gravure printing, is therefore relatively inflexible and expensive. Another disadvantage is that it is more uneven when the adhesive is applied to materials Strength, for example on folded bag bottoms, a reasonably satisfactory job can only be done if the counter-pressure roller is provided with a flexible coating of a rubber-like consistency.

The invention is therefore based on the object of an improved method for Specifying application of hot melt adhesive to a workpiece in which there is no danger there is an inadmissible heat load on the workpiece and this also enables flexible adaptation to different material thicknesses and format sizes, so that in particular the format length of the blank of the workpiece and the contour of the adhesive surface to be applied can be selected independently of one another.

According to the invention, this object is achieved by what is stated in the patent claim 1 specified process steps, the advantageous developments in the Subclaims 2 to 7 are characterized. A device for implementation According to the invention, this method has the features specified in claim 8, with particularly advantageous additions and developments in the dependent claims 9 to 20 are characterized.

In a preferred embodiment, the invention consists in the fact that the order of the hot melt adhesive or "hot melt" on the workpiece by means of raised clichés takes place, which are exchangeably attached to a cliché or printing cylinder and in a manner to be described in detail with the liquid "hot

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Melt "are provided and then on the, preferably via an impression cylinder roll off the supplied workpiece.

In a particularly advantageous embodiment, the clichés consist of a material that has a significantly lower thermal conductivity than metal, so that the workpiece cannot be exposed to any disadvantageous thermal stress when the workpiece comes into contact with the clichés. This cliché material can advantageously be glued or vulcanized onto an elastic, flexible base plate or also onto metallic webs, which in turn can be connected to the printing or cliché cylinder, for example by screwing, by a clamping device or advantageously also magnetically. In this last-mentioned case, the clichés on the printing cylinder can be exchanged particularly quickly. Relatively heat-resistant plastics, in particular plastics made from silicon and fluorine compounds, come into consideration as cliché material, for example silicones or the plastic polyfoil ethylene known under the trade name "Teflon". In order to achieve an advantageous result, it is particularly important that the cliché material has sufficient adhesion to the liquid hot melt adhesive so that a good hot melt adhesive absorption is possible, for example from the wells of an anilox roller which is responsible for the adhesive application. On the other hand, the block material should show a significantly lower wetting behavior compared to the liquid hotmelt adhesive compared to the wetting behavior of the hotmelt adhesive compared to the workpiece.

It is particularly advantageous if the adhesive behavior of the hot melt adhesive to the Kiischeematerial depends clearly on the temperature, so that the highly heated Hot melt adhesive can be easily applied to the substrate. With decreasing Temperature then the cohesive forces of the hot melt adhesive are greater than the adhesive forces between the hot melt adhesive and the Kiischeematerial and clearly predominate. This behavior is similar to that on the present invention based process and also has the practical advantage that

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after the system has been switched off and cooled down, the hot melt adhesive solidifies slightly must be deducted from the clichés.

The surface of the clichés can be smooth or with transverse and / or longitudinal notches or a grid can be loosened up. . ·

Apart from the already mentioned complete prevention of inadmissible thermal stress of the workpiece offers the method according to the invention and to its implementation suitable device in solution of the task at hand format-related hot melt adhesive application compared to the conventional method With the help of a partially engraved scraper roller the advantage that the Format length of a blank of the workpiece and the contour of the adhesive application are two independent parameters. The diameter of the plate carrier serving printing cylinder depends on the format length, so that For example, one revolution of the printing cylinder per formet blank of the workpiece is provided. Of course, the printing cylinder can also be equipped with several be provided, for example, similar clichés, then in particular over one Workpiece as a continuous material web the diameter of the trajectory or the outer contour of the cliché surface is chosen so that the over the cliché surface measured circumference of the printing cylinder corresponds to an integral multiple of a format length. The contour of the clichés then depends on me The surface shape to be applied to the hot melt adhesive. A change in the application contour and / or in the format length is then considerable due to the invention cheaper to achieve than in comparison with the modified low = printing process. . ...

Tests have shown that the rubber-like consistency of the clichés when using the plastics mentioned causes a clean application of hot-melt adhesive itself Workpiece © or web materials with. wnferschi © dl Dick © enables wl @ it z.

E. When glue is applied to the bottom of the bag occurs. Di® dos workpiece against the clichés

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Printing counterpressure device - e.g. an impression cylinder or at Beufel machines the floor laying drum - can therefore be made of steel or a similar material exist and need not on their part, as with the previous one modified gravure printing process to have a pliable edition.

The invention is explained below in advantageous embodiments with reference to the drawing, for example. The ^:

Fig. 1 and 2 show schematic diagrams of devices for correct format hot melt adhesive applicator according to the features of the invention, advantageous supplements are provided.

According to FIG. 1, an all-round engraving is used in a manner known per se provided application or anilox roller 3 of the hot melt adhesive in the liquid state transferred onto the raised surface of the clichés 2 of a printing cylinder 1. The amount of hotmelt adhesive absorbed by the internal heated anilox roller 3 is defined by the existing cell volume and can be combined with an known heated doctor blade system 10 or via a pressed-on immersion roller take place.

The clichés 2 attached to the printing cylinder I, which use the hot-melt adhesive from the anilox roller transferred to a workpiece 4, consist - as already mentioned from a suitable, preferably elastically flexible material which has sufficient adhesion to the liquid hotmelt adhesive to ensure good To ensure hot-melt adhesive take-up from the cells of the pressed-on anilox roller 3

. Afford. On the other hand, an advantageously suitable KSischeematerial has opposite -dsm liquid hotmelt adhesive has a lower wetting rate compared to the benefit behavior between the liquid hot melt adhesive and the wark piece

'The stereotypes can αυ $ the pressure © the base cylinder 1 to be bekonnter a on be attached. For example , gluing or vulcanization is used for this

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in question. However, the clichés can also be screwed on or by means of a clamping device be attached. An advantageous solution results from indirect fastening. In this case, the cliché material is elastically flexible Base plate or glued or vulcanized onto metallic webs, the in turn screwed to the pressure cylinder or connected by means of a clamping device will. Holding the clichés is also an advantageous option magnetically, for example by using a permanent magnet material for the base plate or the webs and / or by using a magnetic material coating of the printing cylinder and / or by using in the printing cylinder used permanent magnets or electromagnets.

During the operation of the device, the anilox roller 3, previously charged with liquid hot-melt adhesive in the specified manner, transfers part of the liquid hot-melt adhesive provided in the cells of the all-round engraving onto the surface of the clichés 2. The surface of the cliché or clichés 2 then arrives when the printing cylinder 1 continues to rotate in physical contact and light pressure with the workpiece 4, which is pressed on by a counter-pressure device 7, for example a counter-pressure cylinder or - as in bag machines, for example - a bottom layer drum 7. The circumferential or transport speed of cliché 2, anilox roller 3 and workpiece 4 must obviously be of the same size and in the same direction at the pressure points. . .

To ensure that the hotmelt adhesive on the clichés 2 remains safely liquid, reheating can be for example by an infrared heater 5 or by heating the clichés, so that this is called "threading" or "spinning" of the gluing known phenomenon is prevented.

To keep the cliches hot and thus to ensure the liquid state of the melt adhesive and the optimal strength for good application properties of the adhesive, the printing cylinder may be heated also in a known manner from the inside for example by electrically powered heating elements, and to achieve a

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even heat distribution in the closed pressure cylinder interior is filled with oil. Alternatively, the pressure cylinder can also be cooled, what can be achieved in a manner known per se, e.g. by a pipe coil attached to the inner jacket of the pressure cylinder, through which cooling water is passed. Even self-heated clichés, for example inductively or through a power supply from outside are conceivable.

In terms of their design effort and the possibility of a precisely metered control of the heat supply advantageous solution using a The source of heat radiation is, for example, an infrared heater 5 between the receiving point at the contact line between the anilox roller 3 and the cliché surface and the glue delivery point at the contact line with the workpiece -arranged. In order to also secure the residual adhesive on the clichés 2 to keep liquid and at the break point between cliché 2 and workpiece 4 each

. To prevent jade pulling or spinning, another infrared heater 6, which heats the clichés 2 or the printing cylinder 1 from the outside, can be arranged in the wake between the line of contact with the workpiece and the line of contact with the anilox roller.

On the other hand, there is an undesirable or impermissible heating of the workpiece 4 by the radiation from the side of the infrared heaters 5 and / or 6

* can prevent additional radiation protection equipment, such as radiation protection plates 8, between the infrared heaters 5, 6 and the impression cylinder 7

- be seen that a complete or at least partial coverage of the workpiece Ensure in the inlet and outlet to the hot melt adhesive application point.

Xkn "to avoid that the hotmelt adhesive on the clichés 2 solidifies superficially in the manner of a skin formation as a result of a workpiece 4 that is too cool, before the workpiece is sufficiently wetted, a dosed preheating of the workpiece can be done in front of the adhesive application point, e.g. via an optionally inter -

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emitting radiating infrared radiator 9 are made. The preheating can take place to just below the temperature when it is reached and exceed a damaging effect on the workpiece would occur.

Dosed reheating can also be carried out, for example via an optionally also intermittently radiating infrared heater ^{11, which extends the "open time 11 of} the hot melt adhesive, ie Q ¹ per time in which the hot melt adhesive is liquid and thus has its wettability in the molten state.

The flexible material of the clichés also enables one in particular free hot melt adhesive application on workpieces with noticeably unequal thickness, such as e.g. bag bottoms 4a, without the impression cylinder in this case, e.g. Bags machine the bottom layer drum, which in this case has the function of the Impression cylinder takes over, exchanged or even with a compliant Edition should be provided. A hotmelt sticker about clichés from one Material of a rubber-like consistency has the advantage that the impression cylinder 7 made of metal and thus practically unyielding and the material 4 to be applied with the hot-melt adhesive can have fluctuations in thickness without any detrimental effect on the transfer of hot melt adhesive. This is particularly true Dimensions also increase when the hot melt adhesive - as shown schematically in FIG. 2 an elastically deformable stamp 12 produced from one of the above-described cliché materials is passed on, the stamp 12 denoting the Hot-melt adhesive e.g. from a flat, through a doctor blade system 15, which also the hot melt adhesive supply worried, doctored grid plate 13, the cells are filled with liquid hot melt adhesive, absorbs by pressing and transfers by pressing on a non-flat workpiece 14 with considerable inherent deformation. ^ -.

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Claims (1)

PATENTAN'S CLAIMS 1. j Method for applying hot melt adhesive, in particular in terms of format on a workpiece, characterized in that the adhesive in the molten state on raised clichés from one Material is applied, its adhesion to the liquid hot melt adhesive on the one hand good, but its wetting ability for the adhesive on the other hand is significantly less than that of the liquid adhesive compared to the workpiece to be provided with the hot-melt adhesive, and that that with the adhesive application - Accidental clichés with adequate delivery with the workpiece will. —2. τ method according to claim 1, characterized in that the Klis. ^ ept to be attached to a rotating pressure cylinder. 3. The method according to claim 1 or 2, characterized in that that the clichés are heated. 4. The method according to any one of the preceding claims, characterized in that the material web is preheated prior to the application of adhesive. 5. The method according to any one of the preceding claims, characterized in, that the workpiece is reshaped after the adhesive has been applied. 6. The method according to any one of the preceding claims, characterized in, that clichés with closed surfaces are used. / 11 ORiGfNAL 'INSPECTED ^ 509816/097 9 - 7. The method according to any one of the preceding claims 1 to 5, characterized characterized in that clichés with loosened surfaces are used, the contour of which corresponds to the desired order format. 8. Device for indirect, in particular, correct format application of Hot melt adhesive on a workpiece, characterized by a All-round engraved anilox roller (3) with associated doctoring device as an adhesive application roller, one in the rolling area of the anilox roller (3) arranged cliché carrier (1) with raised clichés (2), the surface format of which corresponds to the order format, and a das Workpiece (4) in contact with the clichés conveying counter- • bracket (7). 9. Apparatus according to claim 8, characterized in that the plate carrier (1) is an application roller designed as a plate cylinder is, on which the clichés (2) are exchangeably attached, and that the counter-holder (7) is a counter-pressure cylinder which promotes the workpiece (4) is. 10. Apparatus according to claim 8 or 9, characterized gekennzeichnef, that the clichés (2) are made of an elastic material with low thermal conductivity compared to metal, which has good adhesive adhesion, however, has a lower adhesive wetting power than that of the Workpiece. U. Apparatus according to claim IQ, characterized in that the individual clichés (2) consist of a relatively heat-resistant plastic. · / 12 50 9 81 6/1) 979 12. Device according to one of the preceding claims 8 to 11, characterized in that the individual clichés (2) are vulcanized or glued onto an elastic-flexible base plate , which in turn is screwed, glued or connected by means of a clamping device or magnetically to the cliché carrier (1) is. 13. Device according to one of the preceding claims 8 to 11, data carried in that each cliché (2) are glued or vulcanized onto metallic webs which in turn are screwed to the carrier plate (1) or magnetically connected. 14. Device according to one of the preceding claims 8 to 13, d a - . characterized in that the plate carrier (1) from the inside can be heated and / or cooled. 15. Device according to one of the preceding claims 8 to 13, since d υ rc h characterized- that the clichés (2) can be heated from the outside by a radiant heater (5, 6). 16. The apparatus of claim 15 in conjunction with claim 9, since d υ r ch - characterized in that the radiant heating is infrared heating (5), which is arranged in the trailing area between the adhesive delivery point at the contact line of the cliché outer contour with the workpiece (4) and the adhesive pick-up point at the contact line of the anilox roller (3) with the cliché outer contour. 17. The device according to claim 16, characterized in that - in the infrared heater (5) opposite area of the Druckzyiinders ■ (1) another infrared heater between the glue application and delivery point . ~ {6) is arranged. / 13 .509816 / 0979 -ΠΙ 8. Device according to one of the preceding claims 8 to 17, characterized characterized in that the workpiece (4) immediately before the inlet can be preheated to the adhesive application area by a radiant heater (9). 19. Device according to one of the preceding claims 8 to 17, characterized characterized in that the workpiece (4) after the glue application can be reheated by a radiant heater (11). 20. Apparatus according to claim 16 and / or 17, characterized in that that between the infrared heater (5 and / or 6) and the on the Gegenhai sion (7) promoted workpiece (4) radiation protection means (8) are. "· ■■ '·· T- 5098 1 6/0579. . ' ''!. "^ Γ-: ΐ ^ ΐν