EP1117488A1

EP1117488A1 - Device and method for applying a flowable medium onto a moving surface

Info

Publication number: EP1117488A1
Application number: EP99950572A
Authority: EP
Inventors: Oral Aydin; Andree Dragon; Frank Reinhard
Original assignee: Pagendarm Technologie GmbH
Current assignee: PAGENDARM BTT GmbH
Priority date: 1998-10-02
Filing date: 1999-09-30
Publication date: 2001-07-25
Anticipated expiration: 2019-09-30
Also published as: EP1117488B1; DE19845427A1; US6554900B1; AU6330599A; DE59909417D1; WO2000020123A1; DE19926956A1; ATE265895T1

Abstract

An apparatus for the application of a flowable medium (2, 2') from a stock chamber (7, 8) to a surface (6) being moved along the apparatus, and to the use of an apparatus of this type. The stock chamber (7, 8) partly covers the surface (6), with formation of a sealing gap (14) and an exit gap (18). In order to prevent the formation of air bubbles in the medium (2, 2'), it is proposed to divide the stock chamber (7, 8) into a pre-chamber (7) and a main chamber (8). A dividing element (10) which, together with the surface (6), limits a dividing gap (15), is arranged between the chambers. Various shapes of the dividing element are proposed. The apparatus is particularly suitable for the application of a polymer dispersion to the surface (6). A process for operating an apparatus of this type is also described.

Description

Device and method for applying a flowable medium to a moving surface

The invention relates to a device and a method for applying a flowable medium from a storage chamber to a surface moved along the device, the storage chamber partially covering the surface with the formation of a sealing gap and an outlet gap. It also relates to the use of a device of the type mentioned

Devices of the type mentioned are widely used, for example, in the production of labels in order to coat webs of paper or film with adhesives. A common method for this is the so-called gravure roller application method. In this method, the flowable adhesive is located in an open storage chamber , the opening of which rests on a rotating roller. The roller contains a large number of engraved grooves. During the rotation of the roller, the initially empty grooves enter the opening area of the storage chamber from the outside and are filled with adhesive there when the roller exits the opening area of the The storage chamber is stripped of excess adhesive from the surface of the roller with a doctor blade which extends over the width of the roller and which delimits the opening area of the storage chamber. As the roller rotates, the roller is coated with the web of paper or film to be coated brought stirring, whereby the adhesive located in and on the grooves is at least partially transferred to the web

The amount of the adhesive transferred from the storage chamber to the roller can be within narrow limits by the position or the contact pressure of the doctor blade at the outlet of the roller from the opening area of the storage chamber, that is to say ultimately varied by the height of the outlet gap formed by the doctor blade and the roller surface

In the area of the entry of the roller into the opening area of the storage container, a further doctor blade is usually attached, which fulfills the function of a seal between the storage container and the roller surface.To prevent the adhesive from flowing out excessively at this point, the doctor blade must be between the doctor blade and the sealing gap arising from the roll surface should be as low as possible

The contact pressure of the doctor blade at the sealing gap and the height of the outlet gap can be adjusted in this known method by changing the position and position of the application device relative to the rotating roller.

In this known method, in particular at high roller speeds, complete filling of the grooves of the roller is no longer ensured, as a result of which the amount of adhesive taken up during one revolution and thus ultimately the application weight of the adhesive on the web to be coated decreases in an undesirable manner Circulation speeds increasingly entered air into the storage container through the roller grooves, which leads to undesirable foam formation in the storage container. The presence of foam in the storage container in turn means that the grooves of the engraving roller are not completely filled with adhesive, but at least partly with air in the form of bubbles, so that fine bubbles form on the web to be coated, which lead to an undesirable cloudiness of the Lead adhesive layer

In order to avoid the difficulties mentioned, it was proposed to pressurize the adhesive in the pantry with suitable means (J Türk, H Fietzek, H Hesser and I Voges, Perspectives for Processing Dispersion Adhesives, Special Print TI / ED1654d, BASF Ludwigshafen, August 1993) This ensures that the engraving grooves are completely filled, even at high roller speeds. Depending on the pressure set, a different amount of adhesive is also challenged from the application device on the surface of the roller outside the engraving grooves at the outlet nip Roller applied adhesive and thus ultimately the application weight of the adhesive on the web to be coated can be set within a wider range than without applying pressure. The higher pressure in the storage chamber further ensures that only a greatly reduced amount of air is introduced into the storage container at the sealing gap excessive foaming is prevented

However, the higher the roller circulation speed, the higher the pressure in the storage chamber must be to avoid the entry of air into the adhesive. The maximum achievable circulation speed is limited by the fact that when the pressure is increased further, the adhesive passes through the sealing gap in an uncontrolled manner and, on the other hand, is pressed out of the storage container through the exit gap.A leakage of adhesive through the sealing gap leads to an undesired provision of adhesive in front of this gap, which can lead to contamination of the surroundings of the application device and to malfunctions.An uncontrolled escape of adhesive through the exit gap in turn leads to an uneven mass application on the web to be coated

In the article "Anilox roller application process with a pressure chamber doctor blade - a coating tool also for radiation-chemically hardening systems", IPW 1/97, pages 1 to 8, it was proposed to construct an application device in such a way that the adhesive kept the storage chamber against the direction of movement of the roller In this way, air introduced into the storage container is constantly transported away from the rotating roller with the flowing adhesive. Furthermore, it was proposed in this article to install a throttle element in the storage chamber in such a way that there is between the throttle element and the roller surface forms a narrow throttling gap of a few centimeters in length, through which the adhesive flows against the direction of movement of the roller surface. In this way, the engravings are better filled with adhesive, and any air present in the engraved grooves is at least partially printed out of them and with the outflow Adhesive removed from the roller surface In practice, however, the exact adjustment of the throttle element depending on the operating parameters, such as the roller speed, viscosity and pressure of the adhesive, proves to be difficult and not easily reproducible.Also, such a device can introduce air into the Do not reliably prevent the storage chamber and the formation of bubbles in the adhesive film

The present invention has for its object to provide a device for applying a flowable medium to a surface moving along the device, which works reliably even at high surface speeds, in which the formation of air bubbles in the medium is reliably avoided, which is simple in construction is, and which can be set easily and reproducibly for given operating conditions

The object is achieved by a device for applying a flowable medium from an application chamber to a surface moved along the device, the application chamber partially covering the surface. According to the invention, the application chamber is divided into a prechamber and a main chamber, between which a separating element is arranged that, together with the surface, delimits a separation gap

The separating element arranged between the antechamber and the main chamber reliably prevents air that has penetrated into the antechamber from being transported into the main chamber and causing undesirable foam formation there. The actual coating of the surface with the desired amount of the flowable medium then takes place free of air bubbles in the Main chamber. The antechamber and the main chamber advantageously have independent feeds for the medium, so that, for example, the pressure ratios in the antechamber and in the main chamber can be selected independently of one another

Particular advantages result if the separating element is arranged in such a way that it contacts the surface. This completely separates the antechamber and the main chamber

In practice, a complete touching or resting of the separating element on the surface can often only be achieved when the surface is at a standstill. In actual operation, ie with a moving surface, a certain amount, albeit very small, is usually achieved due to unavoidable fluctuations in the way the surface is guided Gap height available A particularly effective avoidance of air bubbles and a uniform application of the medium to the surface is also achieved if the separating element is arranged so that the height of the separating gap between the separating element and the surface is between 0 and 0.1 mm , in particular between 0 and 0.08 mm, preferably between 0 and 0.05 mm, particularly preferably between 0 and 0.02 mm. Such a minimization of the height of the separation gap also effectively separates the antechamber and the main chamber

In order to ensure reliable functioning of the device under different operating conditions, it is advantageous if the separating element is arranged to be adjustable. An adjustment can be made both by changing the position of the separating element, for example by tilting, or shifting in or against the direction of movement Surface as well as a shift towards or away from the surface, ie a change in the height of the separating gap, there are operating conditions which influence the optimal position and position of the separating element, for example the nature and speed of movement of the surface, the pressure of the medium in the pre-chamber, the pressure of the medium in the main chamber or the composition and viscosity of the medium to be applied A simple implementation of the separation of the antechamber and the main chamber is obtained if the separating element contains a doctor blade.Other embodiments of the separating element are also conceivable.A particularly effective separation can be achieved if the separating element is a double doctor blade the sealing function separating the antechamber from the main chamber

In an advantageous embodiment, the separating element contains a cylindrical rod, which enables a secure and low-wear seal between the antechamber and the main chamber

An effective seal can also be achieved in that the separating element contains a flexible sheet which is arranged such that at least one edge of the sheet resiliently contacts the surface

A particularly effective seal between the antechamber and the main chamber can advantageously be achieved in that the separating element is designed and arranged in such a way that, together with the moving surface, it delimits at least two separating gaps, the height of each separating gap being between 0 and 0.1 mm, in particular between 0 and 0.08 mm, preferably between 0 and 0.05 mm, particularly preferably between 0 and 0.02 mm. In a particularly preferred embodiment, the separating element is arranged such that the height of each of the separating gaps is 0 mm, which is means that the separating element touches the moving surface

The division of the storage chamber into a prechamber and a main chamber enables individual operating parameters for the prechamber and for the main chamber to be influenced separately. In an advantageous embodiment of the invention, means are available with which the pressure of the medium in the main chamber is independent of the pressure of the medium in the prechamber can be set, for example, the pressure in the main chamber can then be selected higher than the pressure in the prechamber. On the one hand, this can prevent the medium from being controlled in an uncontrolled manner by the sealing gap which seals the prechamber from the outside. seals, is printed out of the prechamber, on the other hand, the increased pressure in the main chamber means that air bubbles possibly passing through the separation gap are pressed back into the prechamber

Reverse pressure ratios in the prechamber and the main chamber can offer advantages in an advantageous method for operating the device according to the invention, the pressure of the medium in the prechamber is higher than the pressure of the medium in the main chamber Sealing gap in the prechamber can be effectively avoided from the outset. In the main chamber, the pressure can then be varied within wide limits without the risk of foam formation, in order to ensure an optimal layer application on the surface

Further advantages result if a throttle gap is additionally arranged between the prechamber and the main chamber. The throttle gap can be between the prechamber and the separating element or between the separating element and the main chamber. The height of the throttling gap is always greater than that of the separating gap On Such throttle gap can be formed, for example, by an area of the wall between the prechamber and the main chamber, which is designed so that it runs parallel to the moving surface at a short distance from the moving surface. Furthermore, it is conceivable that a special throttle element on the wall between the Pre-chamber and the main chamber is attached The separating element that delimits the separating gap can be attached to the throttle element. The position and / or position of the throttling element can be arranged in an adjustable manner. In this way, the height and shape of the throttling gap can be changed. The length of the throttling gap can to a large extent ß vary vary In particular, a throttle gap is conceivable, the length of which is a multiple of the length of the separation gap. The throttle gap can directly adjoin the separation gap, but it can also be spatially separated from it. An important effect of the throttle gap is the pressure difference to dismantle between the antechamber and the main chamber The throttle gap fulfills a sealing function that supports the function of the separation gap If, for example, the pressure If the pressure in the main chamber is higher than the pressure in the prechamber, a pressure drop occurs in the throttle gap, whereby the pressure is reduced from the main chamber to the prechamber. Any air bubbles that penetrate into the throttle gap from the prechamber are additionally retained in the throttle gap

Further advantages result if means are available with which the temperature of the medium in the antechamber, in the main chamber or in both chambers can be set independently of the ambient temperature. For example, the temperature in both chambers can be significantly higher than the ambient temperature. On the one hand, this lowers the viscosity of the medium and thus improves its flow properties; on the other hand, a drying process that follows the application of the medium to the surface is accelerated

Particular advantages result if the temperature of the medium in the main chamber is chosen to be higher than that of the medium in the antechamber. As a result, the viscosity of the medium in the main chamber is reduced compared to the viscosity of the medium in the antechamber, which means that small amounts of the Medium from the main chamber into the antechamber through the separating gap is easier, on the other hand it is more difficult to transport the medium - and with it any air bubbles - from the antechamber into the main chamber. Conversely, it is also conceivable to choose a higher temperature in the antechamber than in the main chamber This lowers the viscosity of the medium in the antechamber, which increases the sealing function of the sealing gap and thus effectively prevents the ingress of air from the outside into the antechamber. The temperature in the main chamber can then be independent of the temperature in the antechamber be chosen such that an o optimal mass application to the surface is guaranteed

A particularly safe and uniform application of mass takes place in the event that the moving surface has depressions, for example, it is designed as an engraving roller. An engraving roller is understood to be a cylindrical roller into which fine grooves are engraved at regular intervals. However, they can also be point-shaped or of any other geometrical shape. The profile of the depressions can also take any shape, for example rectangular or round

The device according to the invention is suitable for applying media of various types to the surface, for example polymer melts, solutions of polymers in organic solvents or dispersions of various types. There are particular advantages when using the device according to the invention for applying a polymer dispersion to the surface For a homogeneous solution, a dispersion is a heterogeneous mixture of a liquid dispersant and a dispersed substance finely distributed therein. Dispersions in which the dispersant is water and the dispersed substance consists of polymer particles are of particular practical importance. Such a dispersion is also called a dispersion as an aqueous polymer dispersion Aqueous polymer dispersions are widely used as adhesives in the manufacture of labels

The device according to the invention is particularly suitable for applying a pressure-sensitive adhesive dispersion to the surface. A pressure-sensitive adhesive dispersion is to be understood as meaning a dispersion which contains a pressure-sensitive and self-adhesive polymer whose film-forming temperature is below room temperature. The film-forming temperature is the temperature at which the dispersed particles fuse into a transparent, crack-free film. A low film-forming temperature can be achieved by using a soft polymer, ie a polymer with a low glass transition temperature, or a hard polymer to which a plasticizer has been added as an additive here find polymers based on acrylic and / or methacrylic acid esters which are dispersed in water as dispersants. Preferred embodiments of the invention are explained in more detail below with reference to the drawing 1 is a schematic diagram of an inventive device for coating a web with a flowable medium,

2 shows a schematic illustration of an application device according to the invention in section from the side,

Fig. 3 to 7 different variants of an application device according to the invention in section from the side, and

Fig. 8 shows an application device according to the invention in section from the front

Reference list

1 lane

2, 2 'flowable medium

3 application device

4 engraving roller

5 counter roller

6 surface

7 antechamber

8 main chamber

9 partition

10 medium squeegees

11 Opening the antechamber

12 Opening the main chamber

13 front squeegees

14 sealing gap

15 separation gap

16 throttle gap

17 rear squeegees

18 outlet gap 19 engraved groove

20 housing

21 filling pieces

22 intermediate plate

23 bar

24 sidebar

25 hose seal

26 lifting bar

27 plastic sheet

28 terminal block

29 sheet carriers

30 squeegee holders

31 doctor blade

34 He strips off

35 sealing strip

36 spacer bar

37 staff

38 Pneumatic connection

39 Pneumatic line

40 T-pieces

41 lifting cylinders

43 distributors

44 compressed air pipe

45 flap

The device shown schematically in FIG. 1 for coating the web 1 with a flowable medium 2, 2 'essentially consists of an application device 3, an engraving roller 4 and a counter-roller 5 Application device 3 applied to the surface 6 of the rotating engraving roller 4 and transported by this to the web 1. The web 1 is moved by the counter-roller 5 with pressure being exerted over the surface 6 of the engraving roller 4, with the medium 2, 2 'on the web to be coated 1 is transmitted

The application device 3, shown schematically in enlarged form in FIG. 2, has a storage chamber, which is divided into a prechamber 7 and a main chamber 8 by a middle doctor 10 as a separating element. The prechamber 7 and the main chamber 8 are each separated by openings 11, 12 Medium supplied The application device 3 is covered by the rotating engraving roller 4, the surface 6 of the engraving roller 4 moving clockwise over the application device 3. A front doctor blade 13 delimits the prechamber 7 at the point where the roller surface 6 enters the application device 3 with formation of a sealing gap 14 The front doctor blade 13 thus fulfills the function of a sealing lip. The middle doctor blade 10, together with the surface 6, delimits a separating gap 15. Furthermore, the dividing wall 9 together with the surface 6 delimits a throttle gap 16, the height of which is significantly greater than that the separation gap 15 and Sen is a multiple of the length of the separation gap 15. Finally, a rear doctor blade 17 delimits the main chamber 8 in the region of the exit of the roller surface 6 from the application device 3, forming an exit gap 18

In operation, the medium 2, 2 'is pumped through the opening 11 into the prechamber 7 and through the opening 12 into the main chamber 8 by means of pumps (not shown). The pressure in the prechamber 7 and the main chamber 8 is controlled by regulating devices, not shown, for example B Reduction valves, each set separately In addition, a heating device can be provided in the feed line to the pre-chamber 7 and the main chamber 8 in order to set the temperature in the pre-chamber 7 and the main chamber 8 separately. The engraving roller 4 has a large number of depressions on its surface 6 Form of engraved engraved grooves 19 on the direction of the engraved grooves 19 on the surface 6 of the roller 4 has both an axial and a tangential Component, based on the roller axis, on Here, the tangential component is usually significantly smaller than the axial component, ie the engraved grooves run helically with an incline that is usually a multiple of the width of the roller. The distance of the grooves on the surface is typically between 0.2 mm and 0.5 mm, depending on the desired application weight, and its depth and width is typically around 0.1 mm

Before the surface 6 enters the application device 3, there is a residual amount of the medium and a certain amount of air in the engraving grooves 19. The remaining amount of the medium is introduced through the sealing gap 14 into the prechamber 7 of the application device 3. The sealing gap 14 is designed so that that the amount of air introduced is kept to a minimum. This can be done, for example, by pressing the front doctor blade 13 onto the surface 6 of the engraving roller 4 while exerting pressure

A significant improvement in the sealing function results from the fact that the pressure of the medium 2 in the prechamber 7 is chosen to be higher than the ambient pressure. As a result, a certain amount of the medium 2 is constantly transported through the sealing gap 14 into the outside space, the medium 2 being used in the The air in the sealing gap 14 forms a liquid barrier against incoming air. The medium 2 emerging from the sealing gap 14 is collected in a tub (not shown in FIG. 2) and returned to the processing circuit

The overpressure to be selected in the pre-chamber 7 is preferably below 1 bar, in particular in the range around 500 mbar. Particularly good results have been achieved with an overpressure in the range from 300 to 600 mbar printed uncontrollably through the sealing gap 14 into the outside space. This can be the case above 1000 mbar In order to prevent medium emerging from the sealing gap or elsewhere from dripping onto the surface in an uncontrolled manner, it is expedient to arrange the application device 3, as shown in FIG. 1, vertically below the engraving roller 4 (“six o'clock position ") It is also expedient to arrange the counter roller 5 vertically above the engraving roller 4 (" 12 o'clock position ")

In the pre-chamber 7, the engraving grooves 19 are completely filled with the medium 2. The engraving grooves 19 filled in this way are conveyed past the separating gap 15 and the throttling gap 16 by the rotational movement of the engraving roller into the main chamber 8. The middle doctor 10, which delimits the separating gap 15 any air bubbles present in the prechamber 7 are effectively retained

The pressure in the main chamber 8 can be selected independently of the pressure in the prechamber 7. In particular, it is possible to choose the pressure in the main chamber lower than the pressure in the prechamber. An overpressure of less than 1 bar compared to that is particularly suitable Outside If the pressure in the main chamber 8 is too high, the medium is printed in an uncontrollable manner through the outlet gap 18 into the outside, which leads to an uneven coating of the surface 6 of the engraving roller 4 and thus the web 1 to be coated. A pressure in the area has been preserved from 100 to 300 mbar

The ratio of the overpressure in the main chamber 8 to the overpressure in the prechamber 7 is preferably in the range 1 2 to 1 10, particularly preferably in the range 1 2 to 1 5. The higher pressure in the prechamber 7 causes foam formation at the sealing gap 11 of Effectively prevented from the outset Due to the (lower) pressure in the main chamber 8, the order court can then be set independently of the pressure in the pre-chamber 7

The separation gap should be as small as possible. It is preferred that the middle doctor blade 10 rests completely on the roller surface 6. In practice, however, this can often not be achieved, since the roller moves and usually has a very small gap height due to vibrations and wear is inevitable In practice it makes sense to select the height of the separation gap 15 to be less than 0.1 mm, in particular less than 0.08 mm. Particularly good results are achieved with gap heights of less than 0.05 mm

In the main chamber 8, the surface 6 is evenly coated with the medium 2 'under the pressure present there. The amount of the medium 2' applied to the surface 4 is determined, inter alia, by the position of the rear doctor blade 17, which delimits the outlet gap 18 Depending on the position, a more or less large amount of the medium is also applied to the surface 6 of the engraving roller 4 between the engraving grooves 19

In particular for coating a web or film with an aqueous polymer dispersion, it has proven useful to use plastic materials such as polyethylene as the material for the middle doctor blade 10. The length of the separation gap 15 is preferably less than 5 mm, in particular less than 2 mm The length of the throttle gap between the separation gap and the main chamber is preferably 2 to 10 cm, in particular approximately 5 cm, and its height is preferably more than 0.2 mm, in particular more than 0.5 mm

Special embodiments of the device according to the invention are shown in FIGS. 3 to 7. Here, functionally similar components are also identified with identical reference numbers if they are designed differently in detail

3 shows a particularly preferred application device in section from the side. A full piece 21 is inserted into the housing 20. An intermediate plate 22 is inserted into this, on which two strips 23 are mounted. Side strips 24 are located on the left and right of the strips 23, respectively Recesses in which seals 25 are located. A lifting bar 26 is guided between the side bars 24. This can be pneumatically adjusted vertically with the aid of lifting cylinders 41. The vertical adjustment of the lifting bar 26 can also take place mechanically in another embodiment. A sheet carrier 29 is mounted in the lifting bar, into which a flexible plastic sheet 27 is inserted a clamping bar 28 bent and fixed in the sheet carrier 29 For this purpose, the clamping bar 28 is screwed to the sheet carrier 29

In each case in the left and right outer region of the housing 20, two doctor blade holders 30 are attached between the full piece 21 and the doctor blade holders

30 a doctor blade 31 is attached in each case

An engraving roller 4 is located above the application device

31 are arranged so that they each limit a gap together with the engraving roller 4. When the engraving roller 4 rotates clockwise, the fifth one

Gap between the right doctor blade 31 and the engraving roller 4 as a sealing gap, the gap between the left doctor blade 31 and the engraving roller 4 as an exit gap. The plastic sheet 27 clamped between the sheet carrier 29 and the clamping strip 28 functions as a separating element which separates the surface from the engraving roller 4 and the two doctor blades 31 limited space divided into a prechamber 7 and a main chamber 8

The position of the plastic sheet relative to the surface of the engraving roller 4 can be adjusted vertically via the lifting bar 26. In this way, in particular the contact pressure which acts on the plastic sheet 27 can be set. The plastic sheet 27 thus brings about an effective separation between the pre-chamber 7 and the main chamber 8 is reinforced by the resilient properties of the plastic sheet 27

In operation, the pre-chamber 7 and the main chamber 8 are filled with the medium via bores (not shown). The pressure and the temperature of the medium in the pre-chamber 7 and the medium in the main chamber 8 can be set independently of one another If main chamber 8 gets into the space between the clamping strip 28 and the engraving roller 4, this can flow out of this space via a bore The position of the right squeegee blade 31 is selected so that a small amount of the medium in the antechamber 7 constantly passes out through the sealing gap. This creates a liquid barrier against the ingress of air at the sealing gap. The medium emerging flows through the right squeegee holder 30 into a Not shown tub from The left doctor blade is set so that in connection with the other operating parameters such as the pressure of the medium in the main chamber 8, its temperature, its viscosity, etc., the desired application thickness on the engraving roller 4 results

The plastic sheet 27 is preferably made of a flexible plastic such as polyester. Its thickness is preferably about 0.5 mm. Both the clamping bar 28 and the sheet carrier 29, on the other hand, are preferably made of a suitable metal alloy, as are the full piece 21, the intermediate plate 22, the bar 23 and the side strips 24 The seal between the side strips 24 and the lifting strip 26 is designed as an inflatable hose seal 25. It consists of a hose, preferably made of silicone, which is filled with compressed air and thus fulfills its sealing function

4 shows a variant of an application device according to the invention, instead of a plastic sheet, a solid wiper 34 is used here as a sealing element between the pre-chamber 7 and the main chamber 8. The wiper is preferably made of polytetrafluoroethylene (PTFE). Such a wiper can also provide an effective seal between the Ensure prechamber 7 and prechamber 8, there is no significant mass transfer between prechamber 7 and main chamber 8 or vice versa

A further variant of the application device is shown in FIG. 5. Here too, the separating element between the pre-chamber 7 and the pre-chamber 8 contains a solid scraper 34. In a recess of this scraper there is also a cylindrical rod 37 which, like the scraper 34, preferably consists of PTFE is made. The rotatability of the rod 37 reduces the friction between the engraving roller 4 and the separating element. wear of the separating element reduced At the same time, the point contact between the surface of the engraving roller 4 and the rod 37 ensures that there is a good sealing effect

6 shows a further variant. In FIG. 6, the doctor holder 30 and doctor blade 31 are not shown, but are just as necessary in operation as in FIGS. 3 to 5. The separating element between prechamber 7 and main chamber 8 is constructed here in several parts. It consists of two parts Sealing strips 35 tapering to the top, between which there is a spacer strip 36 A cylindrical rod 37 is inserted into the space between the surface of the engraving roller 4 and the spacer strip 36. This construction leads to a very good separation between the antechamber 7 and the main chamber 8 Due to their pointed shape, the sealing strips 35 ensure a reliable seal, which is further reinforced by the rod 37

A further variant of the application device is finally shown in FIG. 7. Here, too, there are two sealing strips 35 tapering to the top, between which there is a scraper 34. As indicated in FIG. 7, this construction makes it possible to provide an outlet for the medium, which possibly passes from the pre-chamber 7 or the main chamber 8 into the space between the sealing strips 35

FIG. 8 shows a view of an application device according to the invention according to one of FIGS. 3 to 7 from the front. FIG. 8 illustrates in particular the pneumatic connections for the vertical adjustment of the lifting bar 26. The inlet to the prechamber 7 and FIG Pre-chamber 8 not shown. The lifting cylinders 41 connected to the lifting bar 26, not shown in FIG. 8, are provided with pneumatic connections 38. These are connected via T-pieces 40 and a pneumatic line 39. The lifting cylinders can be pressurized with compressed air via this line Position of the lifting bar 26 can be set exactly. A commercially available pneumatic device is used to provide the compressed air for the pneumatics In another embodiment, the adjustment is made mechanically instead

8 shows the pneumatic connection with which the hose seals 25 are pressurized. To the right, the end of a hose seal 25 protrudes from the application device. At this end, a distributor 43 is attached, which is connected to a compressed air supply 44 the hose seal is provided with a sealing cap 45 at its left end

The entire device shown in FIG. 8 is located in a trough, not shown, which collects medium that emerges and overflows from the sealing gap and returns it to the processing circuit

The devices described are used in particular in label production when coating webs of paper or film with adhesives. The adhesives can be of various types. For example, polymer melts are used which are applied to the web at elevated temperature and then cooled. Rubber is also widely used -Resin mixtures and solutions of synthetic polymers

Dispersions play an important role here. Particles, preferably of a polymer, are dispersed in a dispersing agent, preferably water. After the dispersion has been applied to the web to be coated, the dispersing agent is removed in a drying installation, causing the particles to fuse with one another and the form a self-adhesive surface

The dispersions used in label production are so-called pressure-sensitive adhesive dispersions, ie dispersions in which the film-forming temperature of the dispersed polymer is below room temperature. The dispersed polymers used are, above all, polymers based on (meth) acrylic acid esters and, to a lesser extent, vinyl ether polymers. Depending on the exact composition of the monomers, such polymers are pressure-sensitive and self-adhesive without additives being added to them. So-called soft polymers, ie polymers with a low glass transition temperature, are preferred

Methods for producing such polymers are well known to the person skilled in the art. A common method is the so-called emulsion polymerization, in which polymerizable, olefinically unsaturated compounds (so-called monomers) are emulsified in water with the aid of surface-active compounds and polymerized using water-soluble initiators

Main monomers selected from C 1 -C 8 -alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 C atoms, vinyl aromatics with up to 20 C atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl are of particular technical importance ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons with 2 to 8 carbon atoms and 1 or 2 double bonds or mixtures of these monomers

Examples include (meth) acrylic acid alkyl esters with a C 1 -C 8 alkyl radical, such as methyl methacrylate and methyl acrylate. n-Butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate Mixtures of the (meth) acrylic acid alkyl esters are also particularly suitable

Vinyl esters of carboxylic acids with 1 to 20 carbon atoms are, for example, vinyl laurate, stearate, vinyl propionate, vinyl versatate and vinyl acetate

Suitable vinylaromatic compounds are vinyltoluene, - and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile

The vinyl halides are chlorine, fluorine or bromine-substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride Examples of vinyl ethers are vinyl methyl ether or vinyl isobutyl ether. Vinyl ether of alcohols containing 1 to 4 carbon atoms is preferred

Butadiene, isoprene and chloroprene may be mentioned as hydrocarbons with 2 to 8 carbon atoms and two olefinic double bonds

In addition to these main monomers, other monomers, for example monomers containing hydroxyl groups, in particular C 1 -C 8 -hydroxyalkyl (meth) acrylates, (meth) acrylamide, ethylenically unsaturated acids, in particular carboxylic acids, such as (meth) acrylic acid or itaconic acid, dicarboxylic acids and their anhydrides or half-esters , eg maleic acid, fumaric acid and maleic anhydride are used in the polymer

Customary emulsion polymers generally consist of at least 40, preferably at least 60, particularly preferably at least 80% by weight of the above main monomers. Particularly preferred main monomers are (meth) acrylic acid esters and vinyl aromatic compounds and mixtures thereof

Aqueous polymer dispersions are generally used with solids contents of 15 to 75% by weight, preferably 40 to 60% by weight. The typical particle size of the dispersed polymer particles is in the range from 150 to 3000 nm, preferably 150 to 900 nm. The viscosity is typically Range from 15 to 500 mPa s, preferably 15 to 200 mPa s at 23 ° C according to DIN EN ISO 3219 with a speed gradient of 100 1 / s

With an application device according to the invention according to FIG. 3, a uniform application of aqueous polymer dispersions with a basis weight between 10 and 30 g / m ² on siliconized paper or film could be achieved with a surface speed of the engraving roller between 250 and 600 m / min. The resulting adhesive film on the siliconized paper or the film was of a uniform, reproducible thickness and free of air inclusions. In particular, the film had excellent transparency

Claims

claims

Device for applying a flowable medium (2,2 ') from a storage chamber (7,8) to a surface (6) moved along the device, the storage chamber (7,8) partially covering the surface (6), characterized in that that the storage chamber (7, 8) is divided into a pre-chamber (7) and a main chamber (8), between which a separating element is arranged such that it delimits a separating gap together with the surface (6)

Device according to claim 1, characterized in that the separating element is arranged such that the height of the separating gap between the separating element and the surface (6) is between 0 and 0.1 mm

Device according to claim 2, characterized in that the separating element is arranged in such a way that it contacts the surface (6)

Device according to one of claims 1 to 3, characterized in that the separating element is arranged to be adjustable

Device according to one of claims 1 to 4, characterized in that the separating element contains a cylindrical rod (37)

Device according to one of claims 1 to 5, characterized in that the separating element contains a flexible sheet (27) which is arranged such that at least one edge of the sheet resiliently contacts the surface (6)

Device according to one of claims 1 to 6, characterized in that the separating element is designed and arranged in such a way that it delimits at least two separating gaps together with the moving surface (6) Device according to one of claims 1 to 7, characterized in that means are provided with which the pressure of the medium (2) in the prechamber (7) and the pressure of the medium (2 ') in the main chamber (8) are adjusted independently of one another can be

Method for operating a device according to claim 8, characterized in that the pressure of the medium (2) in the prechamber (7) is higher than the pressure of the medium (2 ') in the main chamber (8)

Use of a device according to one of claims 1 to 9 for applying a polymer dispersion to the surface (6)

Use of a device according to one of claims 1 to 8 for applying a pressure-sensitive adhesive dispersion to the surface (6)