Assembly and method for preparing, applying and withdrawing a dispersion

Abstract

 An assembly (100) for preparing an dispersion (180) and applying the dispersion to a printing material, the assembly comprising a reservoir (102) for a first ingredient (124) of the dispersion (180), a supply source (104) for a second ingredient (128) of the dispersion, a mixing tank (106) for receiving the first and second ingredients from the reservoir (102) and the supply source (104) and for mixing at least the first and second ingredients to obtain the dispersion (180), a dispersion receptacle (108) with a dispersion inlet (178) for receiving the dispersion from the mixing tank, and an applicator (110) for transferring the dispersion from the dispersion receptacle (108) to the printing material.
The assembly is characterised by a withdrawal device (170) adapted for withdrawing dispersion (180) from the dispersion receptacle (108) which is not picked up by the applicator (110).
Preferred use in the application of silicone oil emulsion in a heat set web-fed printing press.

Description

[0001] The present invention pertains to an assembly for preparing a dispersion and applying the dispersion to a printing material, the assembly comprising a reservoir for a first ingredient of the dispersion; a supply source for a second ingredient of the dispersion; a mixing tank for receiving the first and second ingredients from the reservoir and the supply source and for mixing at least the first and second ingredients to obtain the dispersion; a dispersion receptacle with a dispersion inlet for receiving the dispersion from the mixing tank; and an applicator for transferring the dispersion from the dispersion receptacle to the printing material.

[0002] Such an assembly is known from document EP 2 163 386 A1. In this known assembly, the emulsion dispersion mixing in the mixing tank is achieved with a high shear mixer. The high shear mixer typically runs at a speed of up to 10,000 rpm. Such a high speed is necessary to ensure that the silicone oil droplets distributed in the water have a diameter of less than 1 µm, and thus that the resulting emulsion dispersion remains stable for a sufficient amount of time.

[0003] However, the special high shear mixers that are suited for this application are relatively expensive. Also, the integration of the high shear mixers is complex.

[0004] Furthermore, the silicone paste used in this known assembly is relatively expensive.

[0005] An object of the present invention is therefore to provide a simpler and economic dispersion preparing and applying assembly. A further object is that said assembly is also more reliable.

[0006] Another object of the invention is to provide a dispersion preparing and applying assembly allowing the use of a dispersion that is more economic, in particular a dispersion where the average diameter of the dispersed particles is equal or greater than 1 µm.

[0007] These objects are achieved by an assembly of the afore-mentioned type, characterised by a withdrawal device adapted for withdrawing dispersion from the dispersion receptacle which is not picked up by the applicator.

[0008] By withdrawing the dispersion that is not quickly picked up by the applicator, there is no more stagnant dispersion in the dispersion receptacle that could break up. Hence, it becomes possible to use a thermodynamically unstable dispersion with a life time of only a few minutes, in particular a dispersion where the average oil droplet diameter is equal or greater than 1 µm.

[0009] According to preferred embodiments, the assembly of the invention has one or several of the following features, taken in isolation or in all technically possible combinations:

• The withdrawal device comprises an opening connecting the dispersion receptacle to the mixing tank;
• The opening is located in a side wall or in the bottom of the dispersion receptacle;
• The assembly comprises a recirculating device for recirculating the dispersion between the dispersion receptacle and the mixing tank;
• The recirculating device comprises a recirculation pump adapted to convey at least a part of the dispersion to the dispersion inlet of the dispersion receptacle, the dispersion inlet preferably being arranged at an end of the dispersion receptacle remote from the mixing tank;
• The mixing tank includes a mixer with a rotor and a stator;
• The mixer is the recirculation pump;
• The recirculating device comprises a conduit with a suction inlet for receiving said at least part of the dispersion from the recirculation pump, and with a dispensing outlet for dispensing the received dispersion to said remote end of the dispersion receptacle, said suction inlet being arranged in a bottom of the mixing tank;
• The mixing tank includes a first ingredient inlet above the rotor;
• The dispersion receptacle and the mixing tank share an opening, said opening being a dispersion inlet of the mixing tank and at the same time a dispersion outlet of the dispersion receptacle, in particular the opening being the opening of the withdrawal device;
• A dispersion level sensor for monitoring the dispersion level in the dispersion receptacle, said dispersion level sensor being arranged between the mixing tank and the applicator;
• The applicator is a roll adapted to scoop dispersion from the dispersion receptacle, said roll being made of metal, and preferably of steel.

[0010] By recirculating the dispersion between the mixing tank and the dispersion receptacle, the dispersion is regularly refreshed in the mixing tank. Accordingly, it is no longer necessary to mix a particularly stable dispersion and the high shear mixer can be dispensed with.

[0011] According to the invention, the above objects are also achieved by a method for preparing a dispersion and applying the dispersion to a printing material, the method comprising the following steps:

a) providing a first ingredient of the dispersion;

b) providing a second ingredient of the dispersion;

c) mixing at least the first and second ingredient in a mixing tank to obtain the dispersion;

d) conveying the obtained dispersion from the mixing tank next to the printing material; and

e) applying a first part of the conveyed dispersion to the printing material characterised by the step of:

f) withdrawing the remaining part of the conveyed dispersion.

[0012] According to preferred embodiments, the method of the invention has one or several of the following features, taken in isolation or in all technically possible combinations:

• The method further comprises the following steps:

  g) recirculating the withdrawn remaining part of the conveyed dispersion back to the mixing tank;

  h) mixing the recirculated dispersion in the mixing tank to obtain a refreshed dispersion;

  i) repeating steps d) to h);

• The first ingredient is pure silicone oil, and the second ingredient is doped water containing at least 0.05 weight percent of an emulsifier, and preferably containing between 0.08 and 0.10 weight percent of an emulsifier;
• The average diameter of the first ingredient droplets in the obtained dispersion is equal to or greater than 1 µm.

[0013] The invention will be better understood when reading the following description of a non-limiting example of the invention, with reference to the accompanying drawings, in which:

Figure 1 shows an embodiment of an emulsion preparation and applying assembly according to the present invention;

Figure 2 shows the advantages achieved with the invention on the printed web and on the applicator roll; and

Figure 3 shows how, in the invention, the emulsion sticks to the surface of the applicator roll.

[0014] The assembly of the invention is preferably used for preparing a dispersion and applying the same to a paper web in a web-fed offset printing press. Such presses typically include several printing units, a dryer, a chill roll stand and a folder. The assembly can be positioned anywhere in the printing press. Preferred positions for the assembly are between the printing units, before the dryer, before or after the chill roll stand, or in the folder.

[0015] In the context of the present invention, the term "dispersion" refers to a mixture in which fine particles of one substance are scattered throughout another substance. A dispersion may be a suspension, a colloid (e.g. an emulsion) or a solution.

[0016] The inventive assembly may be used to apply a silicone oil emulsion to a printed paper web, or to apply a dispersion of an acrylic coating, an acrylic varnish or an acrylic adhesive to a paper web, or to apply dampening water containing a dispersed phase of paper dust or ink dirt to a paper web.

[0017] With reference to figure 1, there is shown an assembly 100 according to the invention for preparing an emulsion and applying the prepared emulsion to a printing material such as a printed paper web.

[0018] Assembly 100 is preferably installed in a heat set web-fed printing press. It is preferably integrated in the chill roll stand located between the hot air dryer and the folder of such a printing press. The emulsion applied by assembly 100 on the paper web prevents the ink printed on the web from getting smeared in the folder.

[0019] The assembly 100 comprises a reservoir 102 for a first ingredient of the emulsion, a supply source 104 for a second ingredient of the emulsion, a mixing tank 106 for mixing said ingredients to obtain the emulsion, an emulsion receptacle 108 for receiving the emulsion from the mixing tank, an applicator 110 adapted to transfer the emulsion to a printed paper web, a recirculating device 112 for recirculating the emulsion between the mixing tank 106 and the emulsion receptacle 108, a piping 114 for conveying the first ingredient from the reservoir 102 to the mixing tank 106, a pipework 116 for conveying the second ingredient from the supply source 104 to the mixing tank 106, a controller 118 for controlling the operation of the assembly 100, and several sensors 120, 121, 122.

[0020] Reservoir 102 is preferably a drum with a volume of several hundred litres. In the present case, the first ingredient contained in drum 102 is pure silicone oil 124. Drum 102 rests on a plate 126. Plate 126 is supported by weight gauges 120 adapted to measure the weight of drum 102, which allows to deduce the fill level of drum 102.

[0021] The piping 114 connecting reservoir 102 to mixing tank 106 includes an intake channel 130, a level tank 132 and a discharge channel 134. The intake channel 130 is adapted to convey the first ingredient, i.e. the pure silicone oil 124, from reservoir 102 to level tank 132. Discharge channel 134 is adapted to convey the silicone oil 124 from the level tank 132 to the mixing tank 106.

[0022] Intake channel 130 comprises a shut-off valve 136 for starting or stopping the flow of silicone oil 124 from the reservoir 102, an oil pump 138 for pumping the silicone oil 124 from the reservoir 102 to the level tank 132, and a return line 140 for returning excess silicone oil 124 from the level tank 132 to intake channel 130.

[0023] Level tank 132 has a silicone oil inlet 142 and one or several silicone oil outlets 144. The silicone oil outlets 144 are fitted with controllable oil dosing valves 146.

[0024] Supply source 104 may be implemented with a common water connection 147 and an additive injector 149. The second ingredient 128 provided by supply source 104 is obtained by adding a first additive, namely an emulsifier, in particular a surfactant, to the water from the water connection 147. Preferably, the second ingredient also contains a second additive, namely a disinfectant, such as chlorine to destroy slime bacteria that may colonise assembly 100 or the paper web. Accordingly, the second ingredient 128 can be qualified as doped water.

[0025] The first and second additives are added to the water by the additive injector 149. Additive injector 149 comprises an additive reservoir 149a and an additive dosing unit 149b connected to the additive reservoir 149a and the pipework 116.

[0026] Pipework 116 includes in series, following the liquid flow direction, a pressure regulating valve 148, a pressure damper 150 and an electrically controllable shut-off valve 152 for regulating the flow of the second ingredient 128 to the mixing tank 106.

[0027] Mixing tank 106 has approximately a cylindrical shape with a bottom B, a top T and lateral sides L. It is equipped with a mixer 153 having a rotor 154, and with a mixing motor 156 for driving the mixer 153 inside the mixing tank 106. The mixer 153 also has a stator 158 surrounding the rotor 154. Stator 158 comprises a central fluid inlet 159 and peripheral fluid outlets 161. Reference sign I indicates the interstice distance between the stator 158 and the rotor 154.

[0028] Preferably, the ratio of the thickness of the stator wall to the diameter of the peripheral fluid outlets 161 is equal to or larger than 1.

[0029] Preferably, the outer diameter DR of the rotor 154 is about 90% of the inner diameter DM of the mixing tank 106.

[0030] The mixer 153 is a low shear mixer. This means that:

• the tip speed Vt of the rotor 154 is in the range of about 7 to 10 m/s;
• the mixer's shear frequency Fs, i.e. the average number of times per second that a silicone oil droplet is cut by the rotor, is around 0.6 kHz;
• the mixer's shear rate Rs, i.e. the tip speed divided by the interstice distance I (Rs = Vt/l), is in the range of about 15 to 20 kHz;
• the mixer's shear number Ns, i.e. the shear frequency times the shear rate (Ns = Fs x Rs), is around 10 kHz².

[0031] Mixing tank 106 has a first ingredient or silicone oil inlet 160 above the rotor 154 and a second ingredient or doped water inlet 162 below the rotor 154. Preferably, as shown in figure 1, the doped water inlet 162 is arranged in the mixing tank's bottom B, in particular in the centre of the bottom B. However, the doped water inlet 162 may also be located in one of the mixing tank's lateral sides L.

[0032] Emulsion receptacle 108 is an immersion trough adapted to present a pool of emulsion to the applicator 110. The immersion trough 108 has a proximate end 164 close to mixing tank 106 and a distal end 166 remote from the mixing tank 106.

[0033] Mixing tank 106 is attached to immersion trough 108. More precisely, a lateral side L of mixing tank 106 is joined at a joining region 168 to the immersion trough's proximal end 164. At the joining region 168, the immersion trough 108 and the mixing tank 106 share an opening 170. The opening 170 is an emulsion inlet of the mixing tank 106 and at the same time an emulsion outlet of the immersion trough 108. In other words, opening 170 acts as a withdrawal device for withdrawing emulsion 180 from the immersion trough 108.

[0034] Accordingly, there is a free liquid communication between the immersion trough 108 and the mixing tank 106 such that the emulsion level stays the same in the mixing tank 106 and in the immersion trough 108.

[0035] The applicator 110 is a roll, preferably made of metal, in particular of steel, with an application surface 171, which can be rotated about its longitudinal axis X-X by a controllable applicator motor 172. The roll 110 is arranged above the immersion trough 108 such that a surface segment S of a lower part of the roll 110 is immersed in the emulsion provided inside the immersion trough 108.

[0036] The recirculating device 112 comprises a recirculation pump 153 and a conduit 174. In the present example, no separate recirculation pump is provided. Instead, the mixer 153 also acts as the recirculation pump.

[0037] The conduit 174 has a suction inlet 176 for receiving emulsion from the recirculation pump/mixer 153. Suction inlet 176 is located in the mixing tank's bottom B, preferably in the periphery of the bottom B. Alternatively, the suction inlet 176 may be arranged in a gap G between the stator 158 and the mixing tank 106. Furthermore, suction inlet 176 may also be located on the top side of the stator 158.

[0038] Conduit 174 has a dispensing outlet 178 arranged at the immersion trough's distal end 166.

[0039] Assembly 100 further includes an emulsion level sensor 122 located between the mixing tank 106 and the applicator roll 110. Emulsion level sensor 122 is adapted for monitoring the emulsion level in the immersion trough 108.

[0040] Assembly 100 also comprises a web width sensor 121 arranged above applicator roll 110.

[0041] Controller 118 is adapted to control the operation of assembly 100. To this end, controller 118 is connected to the weight gauges 120, the web width sensor 121, the emulsion level sensor 122, the controllable shut-off valve 152, the applicator roll's motor 172, the dosing valves 146 and the additive dosing unit 149b. Additionally, controller 118 can also receive the speed of the printing press as a further input.

[0042] In the following, the operation of assembly 100 will now be described.

[0043] To start with, shut-off valve 136 of drum 102 is manually opened to allow the flow of silicone oil 124 (the first ingredient) stored in the drum 102 into the intake channel 130.

[0044] Furthermore, supply source 104 is activated to provide the second ingredient, i.e. water 128 doped with a surfactant and chlorine. More precisely, controller 118 controls the additive dosing unit 149b such that a predetermined amount of additives is injected from reservoir 149a into pipework 116.

[0045] The surfactant is preferably injected in an amount of at least 0.05 weight percent, and most preferably in an amount of between 0.08 and 0.10 weight percent. The floor of 0.05 weight percent ensures that no free silicone oil is picked up by applicator roll 110. In order to have a good emulsifying effect, the amount of injected surfactant is preferably at least 0.08 weight percent. The ceiling of 0.10 weight percent keeps the money spent on surfactant to a minimum.

[0046] The chlorine is preferably added in an amount of around 14 mg per litre. Also, it is preferable that the air content of the doped water 128 is less than 10 nano litres per cubic metre.

[0047] The controller 118 controls the amount of silicone oil 124 and doped water 128 based on the printing press speed signal and the web width signal received from web width sensor 121.

[0048] The silicone oil 124 then reaches the level tank 132. The level tank 132 provides a fixed level of silicone oil 124 above the oil dosing valve 146. This ensures a constant and known flow of silicone oil 124 from the level tank 132 when the oil dosing valve 146 is opened.

[0049] The silicone oil 124 leaves the level tank 132 via the silicone oil outlet 144 and enters the mixing tank 106 via the silicone oil inlet 160.

[0050] Because of the negative pressure generated by the rotating mixer 153 below the rotor 154, the silicone oil 124 is preferably introduced into the mixing tank 106 above the rotor 154.

[0051] The doped water 128 enters the mixing tank 106 via the doped water inlet 162. The flow direction of the doped water 128 into the mixing tank 106 is essentially vertically upwards, as shown by the arrow F. This improves the mixing effect in mixing tank 106.

[0052] The rotating mixer 153 inside the mixing tank 106 then mixes the silicone oil 124 and the doped water 128 to obtain a silicone oil in water emulsion 180. Here, special care should be taken to prevent mixer 153 from sucking in ambient air, because the surfactant will react to the air with substantial foaming. This is achieved by:

a) using a rotor 154 with an outer diameter range as indicated above. Accordingly, the gap G between the stator 158 and the mixing tank 106 is kept small; and/or

b) introducing the silicone oil 124 radially (i.e. at right angles to the lateral side L of the mixing tank 106) or with a radial component into the gap H between the mixer 153 and the mixing tank 106.

[0053] In this way, the negative pressure will be kept below the rotor 154.

[0054] The liquid enters the mixer 153 through the central fluid inlet 159, is mixed and leaves the mixer 153 via the peripheral fluid outlets 161. Since the ratio of the thickness of the stator wall to the diameter of the peripheral fluid outlets 161 is greater than or equal to 1, the mixed liquid is ejected essentially vertically downwards from the mixer 153. This prevents the liquid in the mixing tank 106 above the stator 158 from being rotated by the mixer 153.

[0055] The emulsion 180 is pumped by the mixer 153 via the suction inlet 176 into the conduit 174 and enters the immersion trough 108 at its distal end 166 through the dispensing outlet 178. Hence, the dispensing outlet 178 is also the immersion trough's emulsion inlet.

[0056] As shown in figure 2, the emulsion 180 is then scooped up by the rotating applicator roll 110 and applied to a printed paper web W passing tangentially above the applicator roll 110. Controller 118 controls the applicator motor 172 and thus the linear speed of the outer circumference of the applicator roll 110 such that applicator roll 110 transfers the amount of emulsion 180 onto paper web W that is set by the operator.

[0057] Due to the fact that mixer 153 is a low shear mixer, the emulsion 180 leaving the mixing tank 106 is not in thermodynamic equilibrium and thus only stable for a few minutes. This emulsion has oil droplets with an average diameter equal to or greater than 1 µm, in particular equal to or greater than 10 µm, or even equal to or greater than 100 µm.

[0058] In order to prevent the breakdown of the emulsion 180 in the immersion trough 108, the remaining emulsion, which is not quickly scooped up by the applicator roll 110, is withdrawn from the immersion trough 108 via the withdrawal device or opening 170 during operation of assembly 100.

[0059] The withdrawn emulsion is recirculated to the mixing tank 106 by the liquid current C generated by the pumping action of the mixer 153.

[0060] The old emulsion 180 entering the mixing tank 106 is mixed anew and thus refreshed and can then be conveyed again to the immersion trough 108.

[0061] Figure 2 shows in detail how the emulsion 180 is applied by the applicator roll 110 to a moving paper web W. A surface segment S of the applicator roll 110 is immersed in the emulsion pool 182 contained in the immersion trough 108. Due to the rotation of the applicator roll 110, the surface segment S then leaves the immersion trough 108, covered by an emulsion layer 184.

[0062] As indicated by the arrows R, the applicator roll 110 rotates against the conveying direction D of the paper web W.

[0063] Upon contact of the applicator roll's surface 171 with the paper web W, the emulsion 180 is transferred to the paper web W.

[0064] Due to the fact that emulsion 180 breaks up easily, some of the silicone oil 186 separates out of the emulsion 180 and sticks to the application surface 171 of applicator roll 110. Hence, the whole application surface 171 is covered by a residual oil trace 186. Thanks to this oil trace 186, there is much less friction between the paper web W and the applicator roll 110, which reduces the risk of scratching the printed web W. Furthermore, the oil trace 186 prevents an ink buildup on the surface 171 of the applicator roll 110, which widens the type of materials that applicator roll 110 can be made of. In particular, thanks to the oil trace 186 protecting the paper web W, the applicator roll 110 can be made of steel.

[0065] Figure 3 is a blow-up of the area A in figure 2. It shows the behaviour of the emulsion layer 184 on the application surface 171 of the applicator roll 110.

[0066] Emulsion layer 184 is separated from application surface 171 by the oil trace 186 and a surfactant layer 188. Surfactant layer 188 acts as an interface between emulsion layer 184 and oil trace 186.

[0067] Because of the thermodynamically unstable emulsion 180, the silicone oil stays more on the surface of the printed web W, instead of being absorbed by the web. In this way, less silicone oil needs to be applied, which also reduces total costs.

[0068] In addition to the embodiment shown in the figures, it is in principle also possible to withdraw the emulsion which is not picked up by the applicator and to store it in a reservoir. In this case the withdrawn part of the emulsion can be disposed of or recycled later on.

[0069] Alternatively or in addition to the opening 170, the withdrawal device can comprise a pipe connecting the immersion trough and the mixing tank and/or comprise a separate pump adapted to pump or pumping the remaining emulsion from the immersion trough to the mixing tank.

[0070] The inventive assembly 100 and corresponding method use silicone oil 124 as the first ingredient for the preparation of the silicone oil emulsion. This is in contrast to prior art devices, which use silicone oil concentrate or silicone paste for the first ingredient. Since silicone oil concentrate or silicone paste are more expensive than simple silicone oil, the operation of the inventive assembly and method is cheaper than the operation of the prior art devices.

[0071] Further advantageous features of the assembly or the method according to the invention are:

• The mixing tank (106) is attached to the dispersion receptacle (108);
• The outer diameter (DR) of the rotor is about 90 % of the inner diameter (DM) of the mixing tank;
• The withdrawal device (170) is adapted for or is withdrawing dispersion (180) from the dispersion receptacle (108) which is not picked up by the applicator (110) during application of dispersion by the applicator to the printing material.

Claims

1. An assembly (100) for preparing a dispersion (180) and applying the dispersion to a printing material (W), the assembly comprising:

- a reservoir (102) for a first ingredient (124) of the dispersion (180);

- a supply source (104) for a second ingredient (128) of the dispersion;

- a mixing tank (106) for receiving the first and second ingredients from the reservoir (102) and the supply source (104) and for mixing at least the first and second ingredients to obtain the dispersion (180);

- a dispersion receptacle (108) with a dispersion inlet (178) for receiving the dispersion from the mixing tank; and

- an applicator (110) for transferring the dispersion from the dispersion receptacle (108) to the printing material (W),
characterised by a withdrawal device (170) adapted for withdrawing dispersion (180) from the dispersion receptacle (108) which is not picked up by the applicator (110).

2. The assembly of claim 1, wherein the withdrawal device (170) comprises an opening (170) connecting the dispersion receptacle (108) to the mixing tank (106).

3. The assembly of claim 2, wherein said opening (170) is located in a side wall or in the bottom of the dispersion receptacle (108).

4. The assembly of anyone of the previous claims, further comprising a recirculating device (112) for recirculating the dispersion (180) between the dispersion receptacle (108) and the mixing tank (106).

5. The assembly of claim 4, wherein the recirculating device (112) comprises a recirculation pump (153) adapted to convey at least a part of the dispersion (180) to the dispersion inlet (178) of the dispersion receptacle (108), the dispersion inlet (178) preferably being arranged at an end (166) of the dispersion receptacle (108) remote from the mixing tank (106).

6. The assembly (100) of anyone of the previous claims, wherein said mixing tank (106) includes a mixer (153) with a rotor (154) and a stator (158).

7. The assembly of claims 5 and 6, said mixer being the recirculation pump (153).

8. The assembly (100) of claim 7, wherein the recirculating device (112) comprises a conduit (174) with a suction inlet (176) for receiving said at least part of the dispersion (180) from the recirculation pump (153), and with a dispensing outlet (178) for dispensing the received dispersion (180) to said remote end (166) of the dispersion receptacle (108), said suction inlet (176) being arranged in a bottom (B) of the mixing tank (106).

9. The assembly (100) of anyone of claims 6 to 8, wherein said mixing tank (106) includes a first ingredient inlet (160) above the rotor (154).

10. The assembly of anyone of the previous claims, wherein the dispersion receptacle (108) and the mixing tank (106) share an opening (170), said opening being a dispersion inlet of the mixing tank (106) and at the same time a dispersion outlet of the dispersion receptacle (108), in particular the opening being the opening of the withdrawal device.

11. The assembly (100) of anyone of the previous claims, further comprising a dispersion level sensor (122) for monitoring the dispersion level in the dispersion receptacle (108), said dispersion level sensor being arranged between the mixing tank (106) and the applicator (110).

12. The assembly (100) of anyone of the previous claims, wherein the applicator is a roll (110) adapted to scoop dispersion from the dispersion receptacle (108), said roll being made of metal, and preferably of steel.

13. A method for preparing a dispersion (180) and applying the dispersion to a printing material (W), the method comprising the following steps:

a) providing a first ingredient (124) of the dispersion;

b) providing a second ingredient (128) of the dispersion;

c) mixing at least the first and second ingredient in a mixing tank (106) to obtain the dispersion;

d) conveying the obtained dispersion from the mixing tank (106) next to the printing material (W); and

e) applying a first part of the conveyed dispersion (180) to the printing material (W);
characterised by the step of:

f) withdrawing the remaining part of the conveyed dispersion (180).

14. The method of claim 13, further comprising the following steps:

g) recirculating the withdrawn remaining part of the conveyed dispersion (180) back to the mixing tank (106);

h) mixing the recirculated dispersion in the mixing tank (106) to obtain a refreshed dispersion;

i) repeating steps d) to h).

15. The method of claim 13 or 14, wherein the first ingredient is pure silicone oil (124), and the second ingredient is doped water (128) containing at least 0.05 weight percent of an emulsifier (188), and preferably containing between 0.08 and 0.10 weight percent of an emulsifier.

16. The method of any one of claims 14 or 15, wherein the average diameter of the first ingredient droplets in the obtained dispersion (180) is equal to or greater than 1 µm.

Drawing