Fabric cleaning roll and associated device and method

Description

TECHNICAL FIELD

[0001] The present invention relates to a roll of cleaning fabric impregnated with a cleaning composition for cleaning printing cylinders in a printing system. The invention also concerns a cleaning fabric and methods for cleaning printing cylinders and for forming the roll.BACKGROUND

[0002] In order for printing cylinders to fulfil a desired printing result, such cylinders of a printing system must be cleaned on a regular basis. An example of a cleaning apparatus for a printing system is shown in US7219605B2. Several different cleaning methods are known, such as spraying a cleaning liquid on the cylinders or cleaning the cylinders by hand using means of a cleaning fabric which has been dipped into a cleaning liquid.

[0003] The cleaning fabric is often pre-impregnated with a cleaning composition which is configured to dissolve and remove ink residues from the printing cylinders. Paper residues are prone to adhere to the surfaces of the printing cylinders. The adhered paper debris is difficult to dissolve by the cleaning composition, and hence the paper residues need to be removed from the cylinders before the cleaning process with the cleaning fabric can begin. Therefore, it is common practice to spray the printing cylinders with water by means of spray bars or spray nozzles installed in the printing system. For instance, in US2005250659A1 it is described how water can be sprayed onto cylinders in a printing system to remove dirt and paper residues.

[0004] However, the spray bars, nozzles and water tubes leading the water to the nozzles have a tendency to clog due to the hostile environment in the printing system. The surroundings in the printing system contain paper debris, ink residues and other contaminants which can clog the spray devices. Lime contained in the water used can also cause clogging.

[0005] Examples of a prior-art equipment trying to solve the issues of clogging pipes and nozzles in printing systems are shown in EP435269A1 and EP878304A1. Further background art is reflected for instance in the documents US5340495A and GB1365464A. From the above it is understood that there is room for improvements regarding the issues with clogged nozzles and pipes in printing systems, etc.SUMMARY

[0006] An object of the present invention is to provide a concept which is improved over prior art and which solves or at least mitigates the problems discussed above. This object is achieved by the technique set forth in the appended independent claims, preferred embodiments being defined in the related dependent claims.

[0007] The present invention is - inter alia - based on the idea that the step of spraying the printing cylinders with water can be omitted, if the cleaning liquid itself, also referred to herein as the cleaning composition, can dissolve cellulosic paper residues. The inventor has surprisingly found that the addition of a cellulosic solubilizer, preferably a nonaqueous cellulosic solubilizer, herein also referred to as a water substitute, to the cleaning liquid dissolves paper residues from the printing cylinders. Thus, the first wash step, i.e. spraying with water, can be excluded from the cleaning process of the printing system. The inventive cleaning composition saves time, as many printing systems require cleaning a plurality of times each day. Furthermore, the labour intensive process of cleaning and / or exchanging clogged water tubes or spray bars or nozzles is no longer an issue.

[0008] In a first aspect, there is provided a roll of cleaning fabric adapted and configured to clean printing cylinders of a printing system. The cleaning fabric is impregnated with a cleaning composition which comprises an organic solvent being an ester and a cellulose solubilizer being a glycol ether, according to claim 1. This is an advantageous cleaning composition since the cellulosic solubilizer enables the currently common water spray step of the cleaning process of a printing system to be omitted from the cleaning process. The organic solvent gives the cleaning composition its property to dissolve and remove ink from the printing cylinders.

[0009] The cleaning composition comprises less than 2 wt% of water. A higher amount of water than 2 wt% present in the cleaning composition may cause the cleaning composition to evaporate. Further, the ink dissolution properties of the cleaning composition will decrease if a higher concentration of water is added to the cleaning composition.

[0010] Preferably, the water content of the cleaning composition is less than 1 wt% and most preferred less than 0.5 wt%.

[0011] The cellulose solubilizer is a glycol ether which is advantageous as a cellulosic solubilizer since these compounds have the favourable solvent properties of lower-molecular weight ethers and alcohols and thus can dissolve paper residues and other water soluble contaminants from the printing cylinders. The glycol ethers is selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, dipropyleneglycol methyl ether, phenoxyethanol, and pentaethylene glycol monododecyl ether.

[0012] The content of the cellulose solubilizer in the cleaning composition is between 0.1 and 5 wt%. The concentration of the cellulosic solubilizer has to be balanced against the concentration of the organic solvent(s). If the concentration of the cellulosic solubilizer is higher than 20 wt%, the ink solubility of the cleaning composition is decreased. If the concentration of the solubilizer is too low, i.e. lower than 0.05 wt%, the cleaning composition will not dissolve and remove paper residues in a favourable way.

[0013] The content of the organic solvent in the cleaning composition is between 95 and 99.9 wt%. The concentration of the organic solvent has to be balanced against the concentration of the cellulosic solubilizer. If the concentration of the organic solvent is higher than 99.9 wt%, the concentration of the cellulose solubilizer is too low and the cleaning composition will not be able to dissolve paper resdiues from the printing cylinders. If the concentration of the organic solvent is too low, i.e. lower than 80 wt%, the cleaning composition will not dissolve and remove ink residues in a favourable way.

[0014] In yet another embodiment, the cleaning fabric is wrapped around a core to form the roll. This is preferable since the core may efficiently be mounted on a shaft of a cleaning cassette. Moreover, the cleaning fabric is easy to handle and protected when wound around a core.

[0015] The roll is inserted in a removable sealing bag configured to seal around the roll of cleaning fabric in order to prevent the cleaning composition from evaporating before use. The removable sealing bag is made of plastic. The sealing bag is tubular and built up by a multi-layer plastic film. The plastic sealing bag prevents the cleaning composition from evaporating. The plastic seal thus gives the roll a longer shelf life before use and protects is from the environment.

[0016] In a further embodiment, the roll of cleaning fabric is vacuum packed in the sealing bag. The vacuum packing prevents the cleaning composition from internal migration by diffusion within the bag. An uneven distribution of the cleaning composition, due to its accumulation in certain areas of the roll when stored, yields an uneven cleaning result during use. However, the vacuum packing ensures an even distribution of the cleaning liquid in the roll and thus high quality cleaning result. Further, the shelf life of the roll is prolonged due to the vacuum seal. The vacuum packing also prevents other compounds and / or impurities from entering the sealing bag and damaging the roll of cleaning fabric.

[0017] In a second aspect, there is provided a cleaning fabric adapted and configured to clean printing cylinders of a printing system. The cleaning fabric is impregnated with a cleaning composition, which comprises an organic solvent being an ester and a cellulose solubilizer, wherein the cellulose solubilizer is a glycol ether. The glycol ethers is selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, dipropyleneglycol methyl ether, phenoxyethanol, and pentaethylene glycol monododecyl ether. The cleaning composition comprises less than 2 wt% of water, the content of the cellulose solubilizer is between 0.1 and 5 wt%, and the content of the organic solvent is between 95 and 99.9 wt%.

[0018] The cleaning fabric may be rubbed or stroked against a printing cylinder manually or installed in other types of cleaning devices not described herein.

[0019] In a third aspect, there is provided a method for cleaning a printing cylinder of a printing system by means of a cleaning roll. The method comprises the steps of unwinding from the roll at least a portion of the cleaning fabric which is impregnated with a cleaning composition and placing the at least a portion of the cleaning fabric in contact with the printing cylinder.

[0020] In a fourth aspect a method for forming a roll is provided. The method comprises the steps of impregnating a cleaning fabric with a cleaning composition, wrapping the cleaning fabric around a core to form a roll, and inserting the roll in a sealable bag, which preferably is vacuum packed.

[0021] In one embodiment, the cleaning fabric is impregnated with the cleaning composition after being wrapped around the core. An advantage of this is that the cleaning fabric may be easier to handle and impregnate once it is wrapped around the core. For instance, the cleaning fabric wrapped around the core can be placed in a sealable bag and impregnated while being in the sealable bag. In this way, any loss of the cleaning composition is reduced. This also decreases the spreading of the cleaning composition in the surroundings.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the invention will be described in the following; references being made to the appended diagrammatic drawings, which illustrate non-limiting examples of how the inventive concept can be reduced into practice. Fig. 1 shows a cross section of a general printing system with a set up of cylinders and a cleaning cassette with a roll of cleaning fabric and a spray nozzle bar, Fig. 2 shows an enlarged portion of Fig. 1, Fig. 3 illustrates the roll in perspective and vacuum-packed in a sealing bag, Fig. 4 illustrates the roll shown in Fig. 3 with the sealing bag partially removed, Fig. 5 shows test results from an ink solubility test, and Fig. 6 shows test results from a paper residue and ink wash test. DETAILED DESCRIPTION

[0023] With reference to Fig. 1, a general printing unit or system 1 with a number of printing cylinders and rollers 2, 3, 4, 5, 6 is illustrated. The printing system 1 described herein has an impression cylinder 2 (the largest printing cylinder, down to the left in Fig. 1), a blanket cylinder 3 (the medium sized cylinder next to the impression cylinder) which has a blanket 3', herein referred to as a rubber sheet 3', and a plate cylinder 4 (the medium sized cylinder next to the blanket cylinder). The blanket 3' is commonly approximately 2 mm thick. The printing system 1 further has a number of inking rollers 5 (small rollers not being damping rollers) and a number of damping rollers 6 (the five small sized rollers down to the right).

[0024] The set of inking rollers 5 is associated with an ink source 8 which provides the inking rollers 5 with ink. The set of damping rollers 6 is associated with a damping source, in this case a water bath 9, which provides the damping rollers 6 with water. The printing system 1 further comprises a cleaning machine or cleaning cassette 10 which houses a cleaning device or roll 12 with a cleaning fabric 13, also referred to as a cleaning cloth.

[0025] In Figs 1 and 2, spray devices 17a, 17b used in current cleaning systems are shown. The spray devices 17a, 17b are shown in dashed lines to indicate that they belong to a currently used cleaning system. The cleaning cassette 10 comprises a spray device 17a, 17b herein also referred to as a spray nozzle arrangement having spray nozzle set ups either in the position 17a or in the position 17b. The spray device 17a, 17b is arranged and configured to spray the rubber sheet 3' of the blanket cylinder 3 with water to remove paper residues and other water soluble debris adhered to the rubber sheet 3' on the printing cylinder 3. As shown in Figs 1 and 2, the spray device 17a, 17b used in current cleaning systems may be arranged inside the cleaning cassette 10 and facing the blanket cylinder 3, or it may be arranged adjacent to the cleaning cassette 10 facing the blanket cylinder 3.

[0026] Fig. 2 shows the cleaning cassette 10 of the printing system 1 shown in Fig. 1. The cleaning cassette 10 comprises the cleaning roll 12 which includes a bobbin or core 14. The cleaning fabric 13 has been wrapped or wound around the core 14 which can be solid or hollow and made of any suitable material, for example plastic, paper or metal. It can also have different cross sections, and the design described herein has a circular cross section. The cleaning cassette 10 of Figs 1 and 2 further comprises a collecting roller 16.

[0027] Fig. 3 illustrates the roll 12 in perspective view and vacuum-packed in a sealing bag 15 which preferably is made of plastics material. The roll 12 comprises a core 14 and a cleaning fabric 13 wrapped or wound around said core 14. The cleaning fabric 13 has been soaked or impregnated with a cleaning liquid, also referred to herein as a cleaning composition.

[0028] Fig. 4 illustrates the roll 12 shown in Fig. 3 with the sealing bag 15 partially removed. Preferably, the bag 15 is tubular and built up by a multi-layer plastic film. A suitable plastic film for this purpose is a three-layer film based on a first layer of polyethylene (PE) providing a fluid barrier, a second mid layer of polyamide (PA) providing strength and a third layer of polyethylene (PE) providing a fluid barrier and a sealing layer. This three-layer plastics film has proven to be favourable in practical tests. The thickness of the sealing film is designed in such a way that it is easy to remove from the roll 12, as is shown in Fig. 4. Preferably, the sealing bag 15 is vacuum packed by heat sealing the bag 15.

[0029] Fig. 5 shows the test results from an ink solubility test and Fig. 6 shows the results from a paper residue wash test. The experiments and the results will be more thoroughly explained in the experimental section in the following.

[0030] The printing work and cleaning of the printing system 1 will now be explained more in detail. With reference to Fig. 1, when the printing system 1 is performing printing work, water is transported towards the cylinders via the damping rollers 6 which collect water from the damping source 9. The water thus arrives and is present at the non-pressured surfaces occurring between the cylinders 2, 3, 4. Ink is then transported by means of the ink rollers 5 which collect ink from the ink source 8, towards the cylinders 3, 4, 5. The print is then transferred to the blanket cylinder 3 and the material, e.g. paper. The material, e.g. paper, which is to receive the print, is arranged between the rubber sheet 3' on the blanket cylinder 3 and the impression cylinder 2. This is where the printing work is conducted and the print is transferred from the rubber sheet 3' to the material.

[0031] The set up of the cylinders and rollers shown and described herein is only an example of a set up of a printing system.

[0032] Depending on type and use, the printing system 1 needs to be cleaned more or less often in order to maintain a sufficient printing quality. Commonly in prior art printing systems, the cleaning process starts by spraying a liquid, most often water, which dissolves cellulose in the form of paper debris and other water soluble impurities which have adhered to the printing cylinders. Once the water soluble contaminants such as paper residues and the like have been removed, the cleaning cassette 10 can perform its cleaning. The cleaning composition which has impregnated the cleaning fabric 13 removes, inter alia, ink residues from the printing cylinders 2, 3, 4, 5.

[0033] Cleaning processes known in the art involve two separate steps. The first water washing step, where water is sprayed onto the blanket cylinder, can be time consuming and inefficient. Moreover, the spray devices and water tubes leading water to the spray device clog easily. Clogging in the spray devices and the tubes supplying the spray devices with water occurs due to contamination by paper residues, lime in the water, ink residues and other debris. These contaminating particles penetrates the spray openings of the devices and may also clog the internal cavities of the water tubes.

[0034] According to the present disclosure when cleaning the printing system 1, there is no need for a pre-washing step of spraying the blanket cylinder 3 with water with a spray device 17a, 17b to remove paper residues and other water soluble debris, since paper residues are dissolved by the cleaning composition of the present disclosure.

[0035] The cleaning composition of the present disclosure comprises at least one organic solvent to dilute and / or dissolve ink residues and at least one cellulose solubilizer configured to dissolve cellulosic material such as paper debris from the cylinders 2, 3, 4, 5. The water spray step is thus no longer needed, meaning that the spray device 17a, 17b can be omitted. The cellulosic solubilizer aims to dissolve cellulosic paper debris which is water soluble. However, if water is added to the cleaning composition, the water will evaporate and the cleaning composition will lose its ability to dissolve water soluble impurities. Replacing the water spray step with the addition of water in the cleaning composition is hence not an option. Instead, the cellulosic solubilizer should be a low volatile organic compound (low VOC). The possible groups of compounds presented below from which the cellulosic solubilizer can be selected are all low VOCs.

[0036] The concentration of the cellulosic solubilizer in the cleaning composition is between 0.1 and 5 wt%. The concentration of the cellulosic solubilizer has to be balanced against the concentration of the organic solvent(s). If the concentration of the cellulosic solubilizer is higher than 20 wt%, the ink solubility of the cleaning composition is decreased. If the concentration of the solubilizer is too low, i.e. lower than 0.05 wt%, the cleaning composition will not dissolve and remove paper residues in a favourable way.

[0037] The cellulosic solubilizer is a compound selected from the group consisting of glycol ethers.

[0038] The glycol ether which is used as the cellulosic solubilizer is ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, dipropyleneglycol methyl ether, phenoxyethanol, or pentaethylene glycol monododecyl ether.

[0039] It is appreciated that a combination of the different cellulose solubilizers presented herein can be used in the cleaning composition according to the present disclosure.

[0040] The organic solvent component of the cleaning composition is an ester, such as a fatty acid ester, preferably a saturated fatty acid alkyl ester, or a combination thereof.

[0041] A plasticizer may decrease the swelling of the rubber sheet 3'. A preferred plasticizer is diisononyl phthalate (DINP), which also improves the cleaning performance of the cleaning composition and reduces the amount of chemical residues on the blanket cylinder 3 after washing.

[0042] The fatty acid may for instance be myristoleic acid, vaccenic acid, elaidic acid, linoelaidic acid, linoleic acid, palmitoleic acid, sapienic acid, oleic acid, arachidonic acid, eicosapentaenoic acid, erucic acid or docosahexaenoic acid.

[0043] The organic solvents used in the cleaning composition are low VOCs to avoid unwanted evaporation of the solvents.

[0044] The concentration of the organic solvent is in the cleaning composition is between 95 and 99.9 wt%.

[0045] Other possible compounds comprised in the cleaning liquid with different properties may be e.g. aliphatic hydrocarbons for cleaning power, vegetable esters for cleaning power and reduction of evaporation, corrosion inhibitors for preventing corrosion and emulsifiers for emulsification with water.

[0046] The cleaning composition further comprises less than 2 wt% of water, such as less than 1 wt% of water or such as less than 0.5 wt% of water. A higher content of water than 2 wt% will cause the cleaning composition to evaporate and will dilute the concentration of the cellulosic solubilizer and the organic solvent, which affects the ability of the cleaning composition to dissolve ink and paper debris from the rubber sheet 3'.

[0047] The content of the organic solvent and the cellulosic solubilizer in the cleaning composition according to the present disclosure is 98 wt% or more.

[0048] Pre-packed cleaning rolls of basic structure are known in the art per se and are described for instance in the publication US5368157A.

[0049] According to the present disclosure, the cleaning fabric 13 is a liquid or solvent absorbable material, such as a non-woven material, and is adapted to be impregnated or soaked with the cleaning composition of the present disclosure before starting a cleaning process. Preferably, the cleaning fabric 13 is impregnated or soaked with the cleaning liquid of the present disclosure before being packed and stored or transported, i.e. it can be impregnated or soaked long before it is to be used in a cleaning process. Further, the cleaning fabric 13 can be impregnated or soaked either before or after being wrapped around the core 14.

[0050] The cleaning roll 12 shown in Fig. 3 is pre-packed and stored until it is to be used in the cleaning process. The cleaning roll 12 is vacuum packed until the bag 15 is broken before a cleaning process starts. The process of vacuum packing is commonly performed by heat sealing. A multi-layer plastic film of the wrapping prevents the cleaning composition from evaporating. Further, the vacuum packing of the roll 12 prevents the cleaning composition to migrate or diffuse through the cleaning fabric 13. Unwanted diffusion in the cleaning fabric 13 causes an uneven distribution of the cleaning composition and hence a poor and uneven cleaning result.

[0051] Before the cleaning process begins, the cleaning roll 12 is taken out of its package or bag 15, as shown in Fig. 4, and arranged on the mounting means 11 in the cleaning cassette 10.

[0052] The cleaning cassette 10 is then moved from an idle position, in which the cleaning fabric 13 is not in contact with the rubber sheet 3' of the cylinder 3, to an active position in contact with said rubber sheet 3' of the cylinder 3. The cleaning cassette 10 may also be brought into contact with other cylinders of the printing system, such as the impression cylinder 2. The cylinders 2, 3, 4, 5, 6 are rotated in the opposite direction of that when using the printing system for printing. The cleaning composition will thus be transferred from the cleaning fabric 13 onto the rubber sheet 3' of the cylinder 3 and further onto the remaining cylinders 2, 4, 5, 6 of the printing system 1.

[0053] The cellulosic solubilizer comprised in the cleaning composition impregnated in the cleaning fabric 13 will hence dissolve and remove paper residues and other water soluble impurities, for instance calcium carbonate. Thus, there is no need to spray the rubber sheet 3' with water before cleaning the system 1 with the cleaning cassette 10 and the spray bars 17a, 17b can be omitted.

[0054] Other components in the cleaning composition such as the organic solvent(s) will dissolve and remove for instance ink residues on the cylinders 2, 3, 4, 5.

[0055] Once the cleaning process has finished, the printing system 1 will rotate the cylinders 2, 3, 4, 5 and damping rollers 6 in the printing direction. This is the opposite direction of that used during the washing procedure. The damping rollers 6 will transfer water from the water bath 9 to the printing cylinders 2, 3, 4, 5 and the cleaning composition which has been used to clean the printing cylinders 2, 3, 4, 5 will be diluted and eventually removed from the printing system 1.

[0056] The pre-packed roll 12 comprising the cleaning composition of the present disclosure can be used in already functioning printing systems 1 which uses a cleaning cassette 10 as described and which has a spray device 17a, 17b installed. The spray device 17a, 17b can simply be switched off or closed, and the new pre-packed roll 12 can be installed on the mounting means 11 will replace the spray step of the washing process.

[0057] In an embodiment (not shown), the cleaning composition may be sprayed onto a dry cleaning fabric before the cleaning process is started. The cleaning process can then be performed as described above without the need for a water spray step to dissolve the paper residues on the blanket cylinder.EXPERIMENTS

[0058] The inventor has surprisingly found that the addition of a cellulose solubilizer to a cleaning composition is an effective substitute to the commonly used first washing step of spraying water on to the rubber sheets 3' of the printing cylinder 3. The cellulosic solubilizer is a glycol ether. An exemplary cleaning composition not part of the invention comprising a cellulosic solubilizer is listed in table 1a.

[0059] The new cleaning compositions comprising the cellulose solubilizer meet the requirements of a cleaning composition which is illustrated by the experiments presented in the following. Favourable properties of a cleaning composition are ink solubility, low swelling of the rubber sheet 3' when in contact with the cleaning composition, and the dissolution of cellulosic paper residues from the rubber sheet 3'. The results are presented below in tables 2 and 3 and shown in Figs 5 and 6.Example 1

[0060] The three organic solvents destillates D100, isooctyl laurate and 2-ethyl hexyl laurate make up the cleaning composition A (CC A ) shown in Table 1 below.

[0061] An example of a cleaning composition is presented below in Table 1a. The exemplary cleaning composition not part of the invention comprises three organic solvents (destillates D100, isooctyl laurate, 2-ethyl hexyl laurate) and a cellulosic solubilizer (coconut diethanol amide).

[0062] The concentration of the three organic solvents is when summarized 95 wt%. The cellulosic solubilizer (CS) in the presented embodiment is coconut diethanolamide. The concentration of the coconut diethanolamide is 5 wt%. Table 1 - the composition of the cleaning composition A (CC A )Chemical ingredient Concentration (wt%) CC A Distillates (petroleum, hydrotreated light) D10075Isooctyl laurate / 2-Ethyl hexyl laurate25 Table 1a - the composition of a cleaning composition comprising the three organic solvents from CC A and a cellulosic solubilizer (CS). Chemical ingredient Effect Concentration (wt%) CC A Distillates (petroleum, hydrotreated light) D100Solvent - dissolves ink residues75Isooctyl laurateSolvent - dissolves ink residues102-Ethyl hexyl laurateSolvent - dissolves ink residues10CSCoconut diethanolamideCellulosic solubilizer - dissolves paper residues5 Experiment 1 - swellability of the rubber sheet 3'

[0063] When using cleaning compositions in a printing system, one of the requirements of the cleaning composition is that it should not cause the rubber sheet 3' on the blanket cylinder 3 to swell. If the rubber sheet 3' swells too much, the pressure between the rubber sheet 3', on the blanket cylinder 3, and the impression cylinder 2 becomes too high, which results in e.g. poor quality of the prints.

[0064] The test is performed by taking a portion of the rubber material used for the rubber sheet in the printing system and placing it on a flat surface (not shown). The thickness of the rubber material is approximately 2 mm. A hollow beaker with no bottom is placed standing on top of the rubber sheet material and filled with the cleaning composition which is to be tested (not shown). The cleaning composition is left in the beaker at a specified temperature (here 40°C) during a predetermined amount of time (here 24h).

[0065] The thickness of the rubber sheet material is measured outside the beaker and acts as a reference height. The height of the area of the rubber sheet material which has been in contact with the cleaning composition is also measured. Finally, the difference between the two heights are calculated as a percentage of the reference height.

[0066] The test results for the cleaning composition CC A according to table 1, and for the a cleaning composition according to the embodiment of Table 1a are presented below in Table 2. The test results for another cleaning composition CC B and CC B with the addition of a cellulosic solubilizer (coconut diethanolamide) are also presented below in Table 2. The cleaning composition CC B comprises an unsaturated fatty acid and a propylene glycol oligomer.

[0067] The cleaning compositions remained in contact with the rubber sheet material for 24 hours at 40°C. First, the cleaning compositions CC A and CC B were tested without the addition of a cellulosic solubilizer. The swellability of the rubber sheet material then corresponded to 1.42 and 1.97 respectively, as can be seen from Table 2. After the addition of 5% of coconut diethanolamide to CC A the swellability increased only slightly to 1.59% and after the addition of 5% of coconut diethanolamide to CC B the swellability increased to 2.59 %. Both these values (1.59 and 2.59) are below the threshold value for an approved swellability of the rubber sheet material. Table 2 - the test results from the swelling test.Swelling test rubber blanket (24h, 40°C) % increased height CC A 1.42CC A + 5% coconut diethanolamide1.59CC B 1.97CC B + 5% coconut diethanolamide2.59 Experiment 2 - ink solubility

[0068] The addition of the water substitute should not decrease the ink solubility of the cleaning composition. If the ink solubility decreases, there is a risk that the cleaning composition will not be able to remove the ink residues from the printing cylinders efficiently during the cleaning process.

[0069] The result from the ink solubility test is shown in Fig. 5. On the left side of Fig. 5, two beakers B1, B2 are filled with the cleaning composition CC A . The beaker to the far left B1 also comprises an addition of 5% cellulose solublizer (coconut diethanolamide). The two beakers to the right B3, B4 contain the cleaning composition CC B . The left beaker B3 of the two beakers containing CC B also comprises an addition of 5% cellulose solubilizer (coconut diethanolamide).

[0070] When performing the test, a substrate covered with red ink is lowered into the beaker containing a cleaning composition. The substrate is then lifted out of the beaker and transferred to a paper towel 18. The solubility is visually evaluated by observing the amount of ink on the substrate that has been dissolved by the cleaning composition.

[0071] In Fig. 5, the substrates S1, S2, S3, S4 are positioned in front of the beaker in which they have been emerged. Of the two substrates which have been dipped in the cleaning composition CC A , the substrate to the left S1 has more of its ink dissolved than the substrate to the right S2. This means that the cleaning composition CC A comprising 5% coconut diethanolamide has a higher solubility than the cleaning composition CC A without the addition of the cellulosic solubilizer coconut diethanolamide.

[0072] To the right in Fig. 5, more ink has been dissolved from the substrate S3 which has been lowered into the cleaning composition CC B comprising 5% coconut diethanolamide (the substrate to the left S3 of the two substrates on the right hand side in Fig. 5). Hence, also the cleaning composition CC B with a 5% addition of coconut diethanolamide has a higher ink solubility than the cleaning composition without the addition of 5% coconut diethanolamide.Experiment 3 - paper residue wash test

[0073] To evaluate the dissolution of paper residues from the rubber sheet material, a paper residue and ink wash test was performed.

[0074] An unwashed rubber sheet blanket 19 of the same type used as the rubber sheet 3', covered with ink and paper residues, was placed on a flat surface. Cleaning compositions not part of the invention with different concentrations of a cellulosic solubilizer (coconut diethanolamide and triethanolamine) were applied on different cloths C1, C2, C3, C4, C5 which were subsequently placed into contact with the dirty rubber sheet blanket 19. The cloths C1, C2, C3, C4, C5 were then manually dragged over the surface five times.

[0075] The result shown in Fig. 6 shows the amount of colour and paper fibers that the cloths C1, C2, C3, C4, C5 have removed from the rubber sheet blanket material. A darker colour on the cloth indicates that more colour and paper residues have been dissolved and removed from the rubber sheet material. The result from the experiment is shown in Fig. 6. Table 3 shows the different water substitutes tested in the wash test experiment. Table 3 - the table presents the five tests performed in the paper residue wash test.Wash test Cellulosic solubilizer Concentration (wt %) WT1Coconut diethanolamide5WT2Control (no water substitute used)-WT3Triethanolamine5WT4Coconut diethanolamide10WT5Coconut diethanolamide1

[0076] The result indicates that a concentration of the cellulosic solubilizer of 5 wt% gave the best result. The results from test WT1 and WT3 shows a darker cloth (C1 and C3 respectively) after the repeated wash of the rubber sheet 19 and hence, they have dissolved more ink and paper residues than the other cloths. The control test WT2 has the cloth C2 with the least dark colour and has hence dissolved least ink and paper residues of all cloths C1, C2, C3, C4, C5. Thus, a cleaning composition performs better in a wash test.

[0077] Finally, although the inventive concept has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and other embodiments than the specific above are equally possible within the scope of these appended claims.

Claims

1. A roll of cleaning fabric for cleaning printing cylinders of a printing system, said cleaning fabric being impregnated with a cleaning composition, wherein said cleaning composition comprises an organic solvent being an ester and a cellulose solubilizer being a glycol ether, and wherein the roll (12) is inserted in a removable sealing bag (15) configured to seal around said roll (12) of cleaning fabric (13) in order to prevent said cleaning composition from evaporating before use, the sealing bag (15) being tubular and built up by a multi-layer plastic film, wherein the glycol ethers is selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-nbutyl ether, dipropyleneglycol methyl ether, phenoxyethanol, and pentaethylene glycol monododecyl ether, wherein said cleaning composition comprises less than 2 wt% of water, wherein the content of the cellulose solubilizer is between 0.1 and 5 wt%, and wherein the content of the organic solvent is between 95 and 99.9 wt%.

2. The roll according to claim 1, wherein said cleaning fabric (13) is wrapped around a core (14) to form said roll (12).

3. The roll according to any one of the preceding claims, wherein said roll (12) of cleaning fabric (13) is vacuum packed in said sealing bag (15).

4. A cleaning fabric for cleaning printing cylinders of a printing system, said cleaning fabric being impregnated with a cleaning composition, said cleaning composition comprising an organic solvent being an ester and a cellulose solubilizer, wherein the cellulose solubilizer is a glycol ether, wherein the glycol ethers is selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-nbutyl ether, dipropyleneglycol methyl ether, phenoxyethanol, and pentaethylene glycol monododecyl ether, wherein said cleaning composition comprises less than 2 wt% of water, wherein the content of the cellulose solubilizer is between 0.1 and 5 wt%, and wherein the content of the organic solvent is between 95 and 99.9 wt%.

5. A method for cleaning a printing cylinder of a printing system by means of a roll as claimed in any one of the claims 1-3; said method comprising the steps of: - taking out the roll (12) from its sealing bag (15); - unwinding from said roll (12) at least a portion of said cleaning fabric (13) impregnated with a cleaning composition comprising an organic solvent being an ester and a cellulose solubilizer being a glycol ether; and - placing said portion of said cleaning fabric (13) in contact with the printing cylinder (3), wherein the glycol ethers is selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-nbutyl ether, dipropyleneglycol methyl ether, phenoxyethanol, and pentaethylene glycol monododecyl ether, wherein said cleaning composition comprises less than 2 wt% of water, wherein the content of the cellulose solubilizer is between 0.1 and 5 wt%, and wherein the content of the organic solvent is between 95 and 99.9 wt%.

6. A method for forming a roll according claims 1-3, said method comprising the steps of: - impregnating a cleaning fabric (13) with a the cleaning composition comprising an organic solvent being an ester and a cellulose solubilizer being a glycol ether; - wrapping said cleaning fabric (13) around a core (14) to form a roll (12); and - inserting said roll (12) in a sealable bag (15), which preferably is vacuum packed, and preferably wherein said cleaning fabric (13) is impregnated with said cleaning composition after being wrapped around said core (14), wherein the glycol ethers is selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-nbutyl ether, dipropyleneglycol methyl ether, phenoxyethanol, and pentaethylene glycol monododecyl ether, wherein said cleaning composition comprises less than 2 wt% of water, wherein the content of the cellulose solubilizer is between 0.1 and 5 wt%, and wherein the content of the organic solvent is between 95 and 99.9 wt%.