ES2318441T3 - PROCEDURE FOR THE CLEANING AND RECYCLING OF STUCK PAINTINGS. - Google Patents

Abstract

Following a process to apply a paint coating to a web of paper, residual paint is collected from the coating assembly. The collected paint is then submitted to a grinding process and recovered for use in the same printing or painting process. The residual paint is ground to a particle size of less than 2 ~m. An independent claim is also included for a commensurate paint recovery assembly.

Description

Procedure for the purification and recycling of coating paintings.

Technical field

The present invention relates to a purification procedure and in particular for recycling of traces of coating paint on a paper machine and / or a paper coating machine. The present invention relates also to a device to carry out that procedure.

State of the art

In the manufacture of coated papers of different qualities in a coating machine or in a machine bin with stucco units it is necessary that when making the change the coating ink, empty it completely and wash the different circuits of coating product to avoid mixtures of the coating paintings. These coating paintings that no longer They are called remains of stucco paint. He content of solid substances in these remains of paints of Coated can vary between 0.5 and 70% dry substance (TS).

The state of the art known since time is to collect the remains of stucco paint without dilute and return them proportionally to production, is say normally to the same coating paint cycle with a same or at least similar coating coating formulation, while washing waters that can also be removed contain pollution ratios. This produces some considerable losses of raw material and high costs of elimination. In addition to this it can negatively influence the quality of paper made from them, especially if used very different coating paint compositions.

Document D1 discloses a procedure by which a paint is constantly purged of coating within the framework of a coating process on a paper, and then it leads back to the process of stuccoed

Exhibition of the invention

The invention is therefore aimed at propose an improved and flexible procedure for recycling Coating paint remains on a paper machine equipped with a coating unit and / or a paper coating machine.

The solution of this problem is achieved by the fact that the remains of stucco paint are collected, preferably they are purified, for example by filtration and then undergo a grinding process, before returning to add them to the paper machine and / or to the coating machine, to be used again in coating processes.

The crux of the invention therefore consists in eliminating the possible coating of traces of paint agglomerates found in the remains of stucco paint, impurities, etc. which normally occur in the case of return of the coating paints without intermediate treatment, using At least one grinding process. This way you can ensure the coating of the paper by using the remains of stucco paintings regenerated in this way, with a considerably superior quality. In addition you get the possibility of collecting traces of stucco paint from Coating paints of diverse formulation, treating them in a centralized process The remains of stucco paint homogenize in some way and then they can be re- lead to coating units with different coating recipes, No problems arise due to quality differences. Of this mode you can reuse all the paint scraps of coated without influencing the quality of the papers that are going to manufacture with them, thereby reducing material costs premium, energy costs, transportation costs and costs of dump.

In order to make sure that during the milling process is achieved an adequate distribution of particles for subsequent use as paints of coated, according to a first embodiment fits grinding so that 50-90% of the particles resulting from grinding are less than 2 µm. From this mode you can reuse the rest of the paint of coated to obtain a wide range of different stucco. Of course there is also the possibility of adjusting the process of grinding according to specific needs. So by example, to reuse it for matte stucco (normally between <60% according to TAPPI 75deg and / or <30% according to DIN 75deg), are adjusted so that 50-70% of the particles resulting from grinding are less than 2 µm.

Alternatively there is the possibility to achieve a reuse of glossy stucco (normally > 60% according to TAPPI 75deg and / or> 30% according to DIN 75deg), to adjust the degree of grinding so that 80-90% of the particles resulting from grinding are less than 2 µm.

According to another embodiment of the invention, the procedure can be applied when it comes to recycle traces of stucco paint from the regime continuous of the paper machine and / or of the coating machine, very preferably from different stucco units. Be you can then apply especially preferably if the Coating paint remains are drainage flows and water from washing that occur during the change of coating paint or the revision or similar coming from coating units (of the paper machine and / or the coating machine). The process is especially advantageous when the remains of stucco paints are drainage flows and wash waters from the change of Coating paint of different coating units with paints of coating of different formulation.

The procedure is especially suitable. when it comes to changing the formulation of the coating, since the proposed treatment allows to adapt the grain size of the regenerated material to that of the new coating, being able to be used and recover all wastewater and washing water from of the old formulations. The savings that can be expected Especially in these preparation changes are huge.

Especially when it comes to recycling flows of emptying and / or washing water from stucco units, it is advantageous if, according to another preferred embodiment of the procedure, the remains of stucco paints are combined before grinding process with at least one product of flocculated and / or a dehydration accelerator. For this you can preferably deal with polymers, in particular chosen from group of polyacrylamides, of polyethylenelenimines, of polyamines or derivatives or mixtures thereof. This step is followed generally of a step in which it is reconcentrated before the process grinding This is done especially preferably for a proportion of solid matter in a 15 to 25% field of substance dry The reconcentration can be done by sedimentation, hydrocyclone, belt presses, microfiltration, thermal drying, centrifuged, in a decanter or by a combination or sequence of these procedures or devices.

The remnants of coated stucco paint undergo a grinding process, as explained above, to control grain size in a controlled manner and to reduce visible impurities

Since in certain pigments it can be problematic the caking of the product to be ground during the grinding process, as well as the formation of deposits on the wall of the mill, it may be advantageous to add to the remains of Coating paints, before grinding process, about dispersants and / or auxiliary means for grinding. It is about example of low weight anionic pigment dispersants molecular, sodium silicates, triisopropanolamine, hydrogel of silica, sodium polyacrylates or combinations thereof.

According to another embodiment preferred, the remains of stucco paint are screened preferably purified in a first phase as already mentioned to separate thick or agglomerated impurities. This is performs for example using a vibrating screen. In practice it is reasonable to work with a mesh opening in a range of 50-100 µm, preferably in a range 60-80 µm. For example you can use specifically a 63 µm mesh opening.

The grinding process can be carried out in different devices that are in a position to reduce such slippers, for example a tubular mill, a cylinder mill, a high pressure homogenizer, a mill colloidal, a kneader, a ball mill or a macerator. Too combinations of these or sequences (cascades) of same or different devices from these.

In order to adapt optimally the return of the remains of coating paint after the grinding process to the needs of the coating units willing to then it is especially advantageous, according to another embodiment of the invention, if the remains are reconcentrated of coating paint subjected to the grinding process. This for example combining them with at least one flocculating agent and / or a dehydration accelerator. It can be polymers, chosen especially from the polyacrylamide group of polyethyleneimines, of the polyamines or derivatives or mixtures thereof. The remains of the coating paint are reconcentrated preferably after adding such a flocculating agent and / or dehydration accelerator, most preferably up to proportion of solid matter in a field of 50-70% of dry substance. The reconcentration can be done by sedimentation, hydrocyclone, belt presses, microfiltration, thermal drying, centrifuging, in a decanter or by means of a combination or sequence (cascade) of these procedures.

In principle it may be necessary to adjust in each of the process steps already mentioned or indicated to then the conditions related to the proportion of substance dry, viscosity, etc., to adjust the respective pitch of the process. Accordingly and according to another embodiment of the invention is proposed to adjust the proportion of solid substance by means of providing fresh water. It is also possible to evacuate excesses directly to sewer.

As already mentioned, the procedure It is especially advantageous if the remains of stucco paint  ground and eventually reconcentrated must be returned to some possibly different circuits of coating paints with Coating paints of different formulation, respectively if they have to use for the preparation of coating paint by example for different coating paint circuits with Coating paints of different formulation. The remains of Returned stucco paint are not used then normally as a single component, but the remains of stucco paint ground and generally reconcentrated are added during preparation of new coating paints as part of the recipe in a proportion of 1-50%, most preferably in a proportion of 20-30%, especially as Pigment substitute

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The present invention further relates to a device for carrying out a procedure such as the one described above The device has a pit collector in which the remains of stucco paint are collected. Optionally available below screening means, preferably in the form of at least one vibrating screen. Also optionally available before or after this means of screening of means for dehydration or flocculation, preferably in the form of a flocculate cascade in which combine the remains of coating paint with flocculating media (or dehydrating media or the like). This unit is followed or is integrated with means for reconcentration. This for example in form of a sedimentation unit, a centrifuge, a decanter or similar. In any case the device includes a mill, most preferably in the form of a tubular mill, a mill of cylinders, a high pressure homogenizer, a mill colloidal, a kneader, a ball mill, a macerator or a combination or cascade of these. They also optionally follow continuation means for dehydration or flocculation, preferably in the form of a mixing station for dehydration accelerators in which the remains of Coating paint with dehydration media, followed or integrated with means for reconcentration, preferably in Shape of a decanter. Below are located means for distribution of recycled stucco paint remains between very preferably different coating units respectively to its formulation units.

Other preferred embodiments are described in the dependent claims.

Brief description of the figure

The invention will attempt to describe continuation in greater detail using examples of realization in combination with the drawing. Figure 1 shows a schematic representation of a plant for the treatment of coating paintings according to the invention, where a) represents the first tranche until immediately before the introduction in the macerator, and b) the second section with the macerator and the treatment end of the stucco paint coating treated.

Ways for carrying out the invention

The procedure proposed here, respectively the right device for this is characterized because all Coating paint remains are collected and mixed, combined with flocculating media and are re-concentrated to a substance content solid uniform. As a flocculation medium, both inorganic as organic flocculating media. Are especially suitable polymers such as for example polyacrylamide, polyethyleneimine, polyamine. The reconcentration can be done by example by sedimentation, hydrocyclone, belt presses, microfiltration, thermal drying or centrifugation. The product reconcentrated is then ground to a grain size defined, with the addition of special auxiliary grinding media. For this you can use tubular mills, mills cylinders, high pressure homogenizers, colloid mills, kneaders or preferably ball mills.

In this way the agglomerations are destroyed and the components of fine impurities crumble to the point of that visually cease to be noticeable and cannot give rise to no damage to the coating sheet or paint surface of coating on paper.

After grinding a new one takes place reconcentration, as described above. Of this mode you can adjust the dry substance content necessary to the coating mass, which generally should be greater than 50% of dry substance.

The advantage of the procedure lies among others things that due to special grinding the paint scraps of coated, including the fine impurity fraction, can be adapted exactly to the needs of the new coating paint, and therefore you can adjust the pore structure of the new coated regardless of the composition of the paintings of starting stucco.

Figure 1 shows a device that allows to perform such procedure. In these, Figure 1a) shows the first section of this device until shortly before the mill, and Figure 1b) the second final section. The two sections are directly linked to each other and the process proceeds starting at Figure 1a) on the left edge, to the right until the right edge of Figure 1a). The right edge of Figure 1a) immediately joins the left edge of Figure 1b) and the procedure continues to the right edge of Figure 1b).

The device consists primarily of a pit collector 1 at the entrance. In this collector pit 1 can be poured wastewater 3 of the coating paints coming from different stuccoers offline, as well as the waters Residual 4 of the coating paintings from various stucco equipment online. There is also the possibility of pour here the sewage 6 of the coating paints from the treatment of stucco paints. Equally There is the possibility of also pouring the sewage 6 of the coating paints coming from the Pigment treatment

In the case of large paper machines and Coating machines normally produce several thousand liters per hour, only of the plasters and paper machines. The proportion of solid substance in the wastewater of the Coated paper machine paints found for example in a range of approximately 10-100 kg / h dry at the stove, and in the sewage of the coating paintings of the planer approximately 10-20 kg / h dry at stove, in the sewage of the coating paintings from the treatment of coating paints approximately 10-20 kg / h dry to the stove and in the  wastewater from the coating paints coming from the Treatment of pigments approximately 100 kg / h dry to the stove. It is therefore a mixture with extremely high content. solid substance variable.

When making a class change, change the proportion of solid substance of the different components fed, the proportion of solid substance being again Very different for different feeds. To control the conditions in the collector pit are additionally provided for possibility of introducing biocide 2. These are substances that They destroy bacteria or microorganisms or undermine their effect. In addition, surveillance facilities are planned, specifically An LSH / LSL level measuring device is provided. further the different pipes can be regulated by means of valves pneumatic 12.

In the collector pit 1 they are agitated by a agitator the different elements introduced, and pass to a intermediate storage The collector pit 1 has a capacity 6,000 liters.

By means of a centrifugal pump 10 they are driven the remains of stucco paint from the collector pit 1 through from a conduction 16 to a first phase of the process, specifically to two vibrating screens 14 and 15 arranged in parallel. These they have a screening fabric with a mesh opening of 63 um, and are equipped with an unbalanced drive as well as with SIC frequency converters and with a device Safety to avoid overfilling LSHA.

Thick proportions are separated with sizes of particles that are larger than the mesh opening and that they are retained in devices 14 and 15, respectively. Be discharge to the impurity container 13. The two vibrating screens They have connections to a fresh water network 7 to adjust the process and for washing.

The traces of coated stucco paint are lead through a conduit 18 to a container of transfer 17 in which the paint debris is agitated coated by an agitator 19. The transfer container 17 It has a volume of 18 m 3 and is also equipped with a SIC frequency converter, a level measuring device LISHL and an LSHA overfill safety device. The transfer container 17 has a part of a output through which they can be delivered if necessary Coating paint remains directly to a collecting system wastewater 11, but in particular it has an exit to conduction 22 leading to the next stage of process.

By this conduit 22 the remains are transported of coating paint by means of a volumetric pump 21. In case of need it is possible to add fresh water 20 to adjust the solid substance content respective to viscosity. In the driving 22 is further provided an automatic device of FIQ-DIC flow-density measurement for process control.

In the next stage, which is formed by a flocculate cascade 23 followed by a settling facility (sedimentation container) 27, the re-concentration of the remains of stucco paint. First agent is added flocculant 24 in a dilution station 25 which has a pipe mixer 26 to reach the proper concentration, for which fresh water is used from the pipe 7. The means flocculants (coagulants) are substances whose addition is promotes coagulation of dissolved or non-dissolved colloidal substances dissolved but with a very fine distribution. As a means of flocculate are used for example calcium hydroxide, salts of iron (II) and aluminum. As already mentioned above polymers such as by example polyacrylamide, polyethyleneimine, polyamine.

In flocculate cascade 23 the flocculated proper after adding the mixture to the flocculation medium 24. The flocculate cascade has two stages of 1,500 liters of capacity each. In each stage it is located a stirrer The flocculate is a procedure for treatment and purification in which substances (colloidal) are transformed from very fine distribution by adding flocculation medium, obtaining flocs or "flakes" of greater size (agglomeration). Due to flocculation and the consequent modification of conditions physical (larger particles) sedimentation takes place faster, making it possible to separate solid-liquid The choice of flocculation medium and  if necessary, also an auxiliary flocculation medium is carried out depending on the substances that are tried to separate.

Immediately following the waterfall of flocculated 23 comes the aforementioned sedimentation plant 27. In this one solid components settle and a reconcentration The container 27 has a capacity of 15 m 3.

The exit of the sedimentation plant 27 it has a fresh water inlet 20 that has a station dosage 28. The next line 30 towards the tank of reserve 31 has a volumetric pump by means of which They can transport the remains of stucco paint. In this driving 30 is also provided an automatic device of FIQ-DIC flow-density measurement, To control the process.

Reserve deposit 31 serves for buffer or regulation storage and has a volume of 18 m 3. He is ready to receive the remains of paint from Coated thickened. Your output is again equipped with the possibility of adding fresh water 20, and the following conduction 33 leads to mill 34 itself (see Figure 1b), which in This case is made as a ball mill 34 (macerator) with a grinding chamber volume of 220 liters and a product volume 100 liter ground, using for example a set of discs Trinex (Netzsch, DE) with split pipe system. The macerators they are devices to shred, homogenize and disperse mixtures capable of flowing from liquid / solid substance. Grinding grade It can be adjusted within a range of 2-40 \ mum.

The output of the ball mill 34 is carried to through a conduit 36 to an intermediate container 35. To this one fresh water 20 can be added again while stirring. From this intermediate container 35 the remains of coating paint that are now ground, through a conduction 47 whose content is driven by the pump volumetric 37, to a next reconcentration.

This reconcentration takes place in a decanter 40. To do this it is added to the remains of paintings of coated a dehydration accelerator 38, which has been adjusted to the correct concentration in a dilution station 39, and this mixture is conducted to the decanter 40.

A decanter, also called centrifuge endless solid shirt, serves to thicken in the course of treatment. It works according to the principle of centrifuges of tubes, but unlike these, it has a spinning auger with respect to the drum with a small differential turning frequency, and in doing so, it continuously strips solid substances separated from the drum of the centrifuge, and removed from the area from separation. This prevents interruptions in the operation than in conventional tubular centrifuges They are conditioned by the disassembly and cleaning of the drum. Conditioned by their construction, the decanters are relatively slow centrifuges, and for this reason the cutting of separation is found in <2 \ mum for small flows. For large flows (up to 140 m 3 / h) it is added to the entrance  frequently a flocculated medium in a dosed form achieve sufficient segregation (total degree of segregation η = 0.95-0.98). As auxiliary means of respective dehydration auxiliary retention means can be use cationic / anionic polymers. The effect of a medium of retention is based on the flocculation of the solid components of a suspension of substances Fine and loading substances are incorporated into the structure improving dehydration through a optimal flocculation structure.

After the decanter 40 follows a dispersion container 45 which is loaded on one hand with a medium dispersant 44, which is regulated with a dosing station 41, and which on the other hand is loaded with sodium bleach 43 to adjust the pH value, also regulated with a dosing station 42. The dispersion container 45 has a capacity of 500 liters and It has an agitator, as well as an electronic device heavy WIQ.

In the decanter 40 and in the next container of dispersion 45 the proportion of solid substance rises approximately 50%. The remains of coated paint treated obtained in this way are conducted through conduction 48 to a reserve deposit 46, where you can eventually return to adjust the proportion of solid substance by fresh water. TO through a dosing station 50 arranged below is you can add dosed regenerated coating paint as a component of the recipe for fresh coating paintings for the different coating equipment.

Reference List

one

Collector pit

2

Biocide

3

Sewage machine stucco

4

Wastewater from the paper machine

5

Wastewater from paint treatment of stuccoed

6

Wastewater from the treatment of pigments

7

Fresh water

8

Compressed air

9

Towards sedimentation containers

10

Centrifugal pump

eleven

Sewage collection system

12

Pneumatic valve

13

Impurity container

14, 15

Vibrating screen

16

Driving to 14 respective 15

17

Transfer container

18

Driving to 17

19

Agitator

twenty

Fresh water

twenty-one

Volumetric pump

22

Driving towards 23

2. 3

Flocculated waterfall

24

Flocculated medium

25

Dilution station for the medium of flocculated

26

Pipe mixer

27

Sedimentation plant, container sediflot

28

Dosing station for fresh water

29

Volumetric pump

30

Driving towards 31

31

Reserve container

32

Automatic installation of measuring flow / density

33

Driving to 34

3. 4

Ball mill, macerator, mill

35

Intermediate deposit

36

Driving to 35

37

Volumetric pump

38

Dehydration accelerator

39

Dilution station for throttle dehydration

40

Decanter

41

Metering station for the medium dispersant

42

Dosing station for sodium bleach

43

Sodium bleach

44

Dispersing medium

Four. Five

Dispersion container

46

Reservation deposit

47

Driving towards 40

48

Driving towards 46

49

Volumetric pump

fifty

Dosing station

51

Driving to machines dosing machines

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LSH / LSL / LISHL

Level measurement facilities

SIC

Frequency converter

LSHA

Safety device against excess fill

FIQ-DIC

Mass flow meter

FI

Rotameter

SCI

Pneumatic Isolation Valve

FCV

Pneumatic valve regulating flow

Claims (19)

1. Procedure for recovery and recycling of traces of coating paint on a paper machine and / or in a paper coating machine, in which the remains of paint are collected of coating and then undergo a grinding process before being returned to the paper machine and / or to the Coating machine for use in coating processes. 2. Method according to claim 1, characterized in that in a field of 50-90% of the particles resulting from grinding these are less than 2 µm. 3. Method according to claim 2, characterized in that for grinding for matte plasters the degree of grinding is adjusted so that 50-70% of the particles resulting from grinding are less than 2 µm. 4. Method according to claim 2, characterized in that for the reuse of glossy stucco, the degree of grinding is adjusted so that 80-90% of the particles resulting from grinding is less than 2 µm. Method according to one of the preceding claims, characterized in that in the remains of coating paint these are remains of coating paint that occur during the continuous operation of the paper machine and / or of the coating machine, in particular preferably from different coating units. Method according to one of the preceding claims, characterized in that the remains of coating paint are the drainage flows and washing waters that occur in the coating units in the coating paint changes. Method according to one of the preceding claims, characterized in that the remains of coating paint are draining flows and washing waters from different coating units with coating paintings of different formulation, which are produced in the change of the paint paints. stuccoed 8. Method according to one of the preceding claims, characterized in that the remains of coating paint are mixed before the grinding process at least one flocculant medium and / or a dehydration accelerator, preferably being polymers, especially chosen from the group of polyacrylamides, polyethyleneimines, polyamines or derivatives or mixtures thereof. Method according to claim 8, characterized in that the remains of coating paints are reconcentrated after adding flocculating means or dehydration accelerators before the grinding process, especially preferably at a proportion of solid substance in a range of 15-25 % of dry substance, the reconcentration being carried out preferably by sedimentation, hydrocyclone, belt presses, microfiltration, thermal drying, centrifugation, in a decanter, or by a combination or sequence of these procedures. Method according to one of the preceding claims, characterized in that dispersing media and / or auxiliary means for grinding are added before grinding process, preferably in the case of low molecular weight anionic pigment dispersants, sodium silicates, triisopropanolamine, silica hydrogel, sodium polyacrylates or combinations thereof. Method according to one of the preceding claims, characterized in that in a first step the remains of coating paint are screened, preferably in a vibrating screen, most preferably with an opening of meshes in the range of 50-100 µm, preferably in the range of 60-80 µm. Method according to one of the preceding claims, characterized in that the milling process is carried out in a tubular mill, a cylinder mill, a high pressure homogenizer, a colodial mill, a kneader, a ball mill, a macerator or a combination or sequence of these. 13. Method according to one of the preceding claims, characterized in that the coating paint remains subjected to the milling process are reconcentrated, in particular preferably by combining them with a flocculating medium and / or a dehydration accelerator, preferably being polymers, specially chosen from the group of polyacrylamides, polyethyleneimines, polyamines or derivatives or mixtures thereof. 14. Method according to claim 13, characterized in that the remains of coating paint are reconcentrated after adding a flocculating medium and / or a dehydration accelerator, most preferably up to a proportion of solid substance in the range of 40-60% of dry substance, the reconcentration being carried out preferably by sedimentation, hydrocyclone, belt presses, microfiltration, thermal drying, centrifugation, in a decanter or by a combination or sequence of these procedures.

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15. Method according to one of the preceding claims, characterized in that before and / or after a reconcentration, respectively before and / or after the grinding process, the proportion of solid substance is adjusted by the input of fresh water. 16. Method according to one of the preceding claims, characterized in that the remnants of ground and possibly reconcentrated coating paint are returned to different circuits of coating paintings with coating paintings of different formulation, respectively, are used for the manufacture of coating paint for different coating coating circuits with coating formulations of different formulation. 17. Method according to claim 16, characterized in that the ground and reconcentrated coating paint remains are conducted to coating paint circuits that essentially require the grain size that has been adjusted during the milling of the coating paint remains. 18. Method according to claim 16 or 17, characterized in that the ground and possibly reconcentrated coating paint remains are added to the coating paint circuits in a proportion of 1-50%, most preferably in a proportion of 20-30% , as pigment substitutes, are respectively used in the manufacture of coating paints for coating paint circuits in these proportions. 19. Device for carrying out a method according to one of the preceding claims, characterized in that

there is a pit collector (1) in which paint debris is collected from stuccoed

because continuation of the collector pit (1) are optionally arranged means for screening (14,15), preferably in the form of minus a vibrating screen (14, 15),

because to this element is added means for respective dehydration flocculated (23), preferably in the form of a cascade of flocculate (23) in which the paint scraps of coated with flocculating means (24), followed or integrated with means for reconcentration, preferably for sedimentation (27),

because a mill (34) is located below, in particular preferably in the form of a tubular mill, a mill of cylinders, a high pressure homogenizer, a colodial mill, a kneader, a ball mill, a macerator or a combination or sequence of these,

because next, means for the respective dehydration are connected flocculated (39) preferably in the form of a unit in which the Coating paint remains combined with media dehydration (38), followed or integrated with means for reconcentration, preferably in the form of a decanter (40),

and why below are provided means (50, 51) for distribution of the recycled remains of coating paintings among very preferably to different coating units corresponding to their formulation units, preferably distributed between coating units that require a grain size that essentially corresponds to the grain size that has been adjusted in the mill (34).