Method of manufacturing a sleeve, sleeve, use of the sleeve and printing assembly comprising the sleeve

Abstract

A method to manufacture a sleeve (100) for use as a printing sleeve (100a) to hold a printing plate (10) or for use as an adapter (100b) to mount a printing sleeve (100b) on a printing mandrel (40) and the sleeve. The sleeve has an outer layer (L1) for holding a printing plate (10) and / or for holding a printing sleeve (20); an optional intermediate structure (L3) comprising one or more optional intermediate layers (B, FL, FR2, C); an inner layer (L2) with an inner surface (113) configured for being mounted on an adapter or for being mounted directly on a printing mandrel. The outer layers contains a carbon nanotube component (C3) in a weight concentration (c3) in the range of 0.05 to 2.00 wt%. An electrical connection may be provided throughout the sleeve to provide an electrical pathway between the outer and inner surface of the sleeve.

Description

[0001] METHOD TO MANUFACTURE A SEEEVE AND THE SEEEVE

[0002] FIELD

[0003] The field of the invention relates to a manufacturing method to make a sleeve, such as a printing sleeve for mounting a printing plate, preferably a flexographic printing plate, or an adaptor sleeve for mounting a printing sleeve, and to the sleeve.

[0004] BACKGROUND

[0005] Flexographic printing is a method for producing high-quality images on a variety of substrates, such as plastics, paper, cardboard, and other flexible materials. In flexographic printing, flexible relief plates are mounted onto rotating cylinders and ink is transferred from the relief plate to the substrate. The method is adaptable to diverse printing applications.

[0006] Despite its advantages, flexographic printing can present certain challenges related to the buildup of static electricity (static buildup) during the printing process. The accumulation of static electricity can create safety risks, e.g. as it may lead to unintended discharge or sparking. Given that many inks used in flexographic printing are volatile or flammable, static discharge can pose a hazard by creating potential ignition sources within the printing environment. Moreover, static buildup can adversely affect the quality and uniformity of the ink application, leading to inconsistent print results. Additionally, excessive static buildup can increase the risk of electrical shocks to operators and / or interfere with the performance of sensitive electronic components within the printing press. Hence, there is a need to mitigate or avoid the risks related to static buildup.

[0007] SUMMARY

[0008] An object is to provide a sleeve with improved safety, which has a desired performance during printing, such as high-quality printing. Moreover, it is further desired that said object can be achieved in an efficient and economical manner.

[0009] Thereto, a first aspect provides a method to manufacture a sleeve. Preferably, the sleeve is for use as a printing sleeve to hold a printing plate, e.g. a flexographic printing plate. Alternatively, the sleeve is for use as an adapter to mount a printing sleeve, e.g. a printing sleeve holding a flexographic printing plate, on a printing mandrel. The method comprises the steps of: providing (S 1) a base cylinder having an outer surface; applying (S3) a conductive composition (N) on the outer surface of the base cylinder (101) to form a conductive outer layer thereon.

[0010] The composition (N) comprises: a polyol component (Cl), an isocyanate component (C2) and a carbon nanotube component (C3). The polyol component (Cl) and an isocyanate component (C2) can be referred to as a two-component system (Cl, C2). Advantageously, it was found that risks related to static buildup could be avoided by providing the conductive outer layer which can dissipate static buildups at the surface. It this manner, the conductive outer layer increases safety during operation. A desired conductive or dissipative behavior is provided by including the carbon nanotube component (C3), in particular in combination with the two-component system (the Cl and C2 component), namely the two-component system delivers an outer surface that is highly resistant to wear and abrasion such that a desired print performance can be achieved. The carbon nanotube component (C3) is preferably present within the composition (N) in a weight concentration (c3) in the range of 0.05 to 2.00 wt% based on the on the total weight of the composition (N), preferably in the range of 0.07 to 1.0 wt%, more preferably 0.10 to 0.50 wt%, more preferably in the range of 0. 10 to 0.40 wt%, more preferably in the range of 0.10 to 0.30 wt%, even more preferably 0.11 to 0.25 wt%, such as about 0.15 wt%.

[0011] The inventors have found surprisingly that the sleeve can be made in a more efficient manner by including the carbon nanotube component (C3) as described herein. Surprisingly, a sleeve with static dissipation can be made in an efficient and economical manner. Namely, it was found that the composition could be applied on the outer surface of the base cylinder, in a more efficient manner. The composition can be applied according to a simple application, e.g. via extrusion, whereby a polyurethane network is formed without or with less need to rely on additives.

[0012] Typically, the method comprises the formation of a crosslinked polyurethane network (N’) once the polyol component (Cl) and the isocyanate component (C2) are mixed and applied on the outer surface of the base cylinder and wherein component (C3) is mixed with any of the polyol component (Cl) and / or the isocyanate component (C2) such that component (C3) is dispersed or blended in said crosslinked polyurethane network (N’). Advantageously, the crosslinked polyurethane network provides a strong supporting layer ensuring durability while the carbon nanotube component throughout the network ensures conductivity and dissipation of static buildups, thereby improving safety during operation and / or avoiding the risks or issues related to static buildup.

[0013] Preferably, component (C3) is included in an amount of at least 0. 10 wt%, preferably at least 0.11 wt%, more preferably at least 0. 12 wt%, even more preferably at least 0. 13wt%. In this manner, a desired cohesive and viscous behavior of the composition is ensured during the application thereof. More preferably, the concentration of component (C3) is at least 0.14 wt%, more preferably at least 0.15 wt%, even more preferably at least 0.17 wt%. Namely, it was found that the composition could be applied to the base layer in an improved and efficient manner.

[0014] Preferably, component (C3) is present within the composition (N) in a weight concentration (c3) of at least 0.10 wt%, preferably 0.11 wt%, preferably at least 0.15 wt%, even more preferably at least 0.17 wt%. Advantageously, cohesiveness could be improved which facilitates the application of the composition, in particular in case of application on a rotating base cylinder. Thus, the method of making sleeve could be further improved.

[0015] Preferably, component (C3) is included in an amount of at most 2.00 wt%. Surprisingly, by limiting the upper amount of component (C3), the composition (N) could be applied in an improved manner. Namely, the resulting flow behavior of the composition allows for an improved application, preferably an application via extrusion, more preferably via nozzle extrusion. Surprisingly, by limiting the upper limit of the carbon nanotube component (C3) concentration, the composition can be extruded with a reduced pump pressure needed during extrusion. Furthermore, the composition can be applied in a more cost-effective and / or energy efficient manner.

[0016] The carbon nanotube component (C3) can be mixed with the polyol component (Cl) and / or the isocyanate component (C2), preferably component (C3) is mixed with the polyol component (Cl) before being introduced to the isocyanate component (C2). In this manner, the method may be performed more easily, e.g., without the need to regulate specific environmental conditions, such as humidity regulation.

[0017] According to a preferred embodiment, the method comprises: forming (S2) a pre-mix composition (PM) by mixing the carbon nanotube component (C3) with the polyol component (Cl) to form the pre-mix composition (PM), and mixing the pre-mix (PM) with the isocyanate component (C2) to form the conductive composition (N). Advantageously, by firstly introducing the carbon nanotube component (C3) to the polyol component (Cl), the two-component system (encompassing the Cl and C2 component) can be activated at a more convenient timing which facilitates production of the outer layer. Moreover, by ensuring such activation one can avoid undesired side reactions occurring beforehand. It this manner, efficiency and performance can be improved.

[0018] Preferably, the pre-mix composition (PM) is formed such that the carbon nanotube component (C3) is present within said pre-mix composition (PM) in a weight concentration (c3’) of 0.1 to 3.3 wt%, preferably 0.1 to 3 wt%, even more preferably 0.1 to 2.3 wt%, even more preferably 0.1 to 2 wt%, even more preferably 0.1 to 1.5 wt%, such as about 0.35 wt%. By carefully choosing the amount of the C3 component, flow and extrusion behavior could be improved which benefits application of the composition, nozzle application in particular.

[0019] Preferably, the pre-mix composition (PM) (including component (Cl) and component (C3)) is mixed with the isocyanate component (C2) in a ratio in the range of 100:60 to 100:50. The numerical values of the ratio correspond to the parts by weight of (PM) and (C2), respectively. By choosing this ratio range, achieving optimal performance characteristics of the resulting conductive composition is facilitated, furthermore the benefit of provision of static dissipation in a cost and energy efficient manner can be improved.

[0020] Preferably, the composition (N) is applied on the outer surface of the base cylinder via a nozzle and / or by extrusion. The use of a nozzle facilitates targeted delivery on the outer surface, reducing material waste. Preferably, the nozzle is moved in a direction along a longitudinal axis (lax) of the base cylinder and while said cylinder is being rotated. More preferably, the nozzle is moved along the longitudinal axis of the base cylinder at a speed (vi) between 0.30 m / min to 0.7 m / min and wherein the cylinder is rotated at a speed (vr) between 60 to 150 rpm. Such combination of nozzle movement and cylinder rotation allows efficient processing times and application of an outer layer in a cost-effective manner.

[0021] In case of premixing component (C3) with the polyol component (Cl) into a pre -mix composition (PM) before being mixed with the isocyanate component (C2), is it then preferred that the method comprises: - forming (S2) the pre-mix composition (PM) by using a physical dissolver with an impeller to mix the carbon nanotube component (C3) with the polyol component (Cl).

[0022] In addition, or alternatively, the method may include: mixing the pre -mix (PM) with the isocyanate component (C2) with a rotor stator mixer. The rotor stator mixer is preferably arranged in a nozzle assembly such that the two-component system (including C 1 & C2) is activated right before the application of the conductive composition via the nozzle. Such timed activation allows the formation of a polyurethane network with desired printing properties.

[0023] Typically, the physical dissolver is an apparatus for mixing component C3 with component Cl, said apparatus comprising: a vessel (e.g., a cylindrical container) configured to hold components Cl and C3. The physical dissolver may further have a stirrer assembly disposed within the vessel, the stirrer assembly comprising: a shaft; and at least one impeller affixed to the shaft, the impeller is configured to impart rotational motion to the liquid medium within the vessel. A power source may be coupled to the stirrer assembly to rotate the shaft. Preferably, the impellor comprises a plurality of blades. By having multiple blades or vanes, a desired static dissipation can be provided to the outer layer due to an improved mixing with component C3. Preferably, the impellor is rotated a peripheral speed of at most 20 m / s, preferably in the range of 2 to 20 m / s, preferably in the range of 5 to 15 m / s, to mix the carbon nanotube component (C3) with the polyol component (Cl). Increasing the rotation speed is an effective way to obtain better dispersion quality (and thus better static dissipation) than increasing the mixing time. For example, the peripheral speed is about 10 m / s ± 2,5 m / s. Preferably the speed should not exceed 15 m / s, otherwise the conductivity per amount of CNT may decrease (and thus resistivity may increase).

[0024] Preferably, a rotor stator mixer is employed to mix the pre-mix (PM) with (Cl and C2) and component C2. Advantageously, the high shear mixing capabilities allow to achieve a homogeneous blend which improves the static dissipation of the conductive composition.

[0025] Preferably, the outer layer has an electrical resistance of at most 1000 kOhm, preferably at most 30 kOhm, such as between 1 and 30 kOhm. In this manner, a desired conductivity can be ensured which benefits safety due to static dissipation.

[0026] Preferably, the base cylinder itself is conductive. According to an embodiment, the base cylinder has an electrical resistance of less than 1000k Ohm, preferably smaller than 200k Ohm. According to an embodiment, the base cylinder has an electrical resistance between 1 to 40 kOhm, preferably between 2 and 20 kOhm, such as about 10 kOhm. In this manner, a desired grounding is provided to ensure the static buildup can mitigate. The “electrical resistance” (Ohm) can be measured with the Benning IT101 device as described herein.

[0027] Typically, a grounding is established by ensuring an electrical connection, preferably an elongated electrical connection, between the outer layer and an inner layer of the sleeve, more in particular the inner layer that is configured to be mounted on an adapter or to be mounted directly on a printing mandrel. In this manner, static dissipation during printing can improved which benefits safety. According to an embodiment, the outer layer has a resistance in the range of 1 to 20 kOhm, preferably 1 to 15 kOhm, while the inner layer and optional intermediate structure (e.g. forming a base layer) have a resistance of about 10 kOhm ± 5 kOhm. Advantageously, a desired static dissipation which benefits safety. According to an embodiment, when measuring with the outer layer, the inner layer (and optionally the intermediate structure) taken together, the sleeve may show a resistance between 6 and 35 kOhm, such as between 15 and 25 kOhm, in such embodiment, the outer layer may have a thickness between 2 to 10 mm.

[0028] Preferably, the method comprises the step of including the carbon nanotube component (C3) as a dispersion (D), wherein said dispersion (D) comprises 1 to 10 wt% of carbon nanotubes (dl) and a dispersing agent (d2). The dispersing agent (d2) is typically configured to disperse carbon nanotubes and to prevent the agglomeration thereof. The dispersion agent may be a solvent.

[0029] Preferably, the dispersing agent (d2) is chosen from the group comprising: an alcohol, ethoxylated and / or propoxylated alcohol, diethyl ether, pyrogallol and 1 -naphthol, a phenolic solvent, N-N-Dimethylformamide (DMF), acetone, diethyl ether, ethanol, propanol, PDDA, polyvinyl alcohol, methanol, DMSO, 1 -naphthol, catechol (1,2-benzenediol), pyrogallol, tetracene, ionic PAHs, polyether, and PAMI or combinations thereof.

[0030] According to a preferred embodiment, the dispersing agent (d2) is chosen from an alcohol, preferably an ethoxylated and / or propoxylated alcohol. In this manner, not only the dispersing properties can be enhanced but also the interaction with the polyol component (Cl) and / or the isocyanate component (C2) which benefits the formation of the outer layer.

[0031] Preferably, the dispersing agent (d2) is an ethoxylated and / or propoxylated alcohol having a C5 to C20 carbon backbone. The carbon chain length can have 5 to 20 carbon atoms. The dispersing agent can be linear and / or branched. More preferably, the dispersing agent (d2) is chosen from an ethoxylated and / or propoxylated C 12-C 15 linear and branched alcohol . In this manner, the interaction with the polyol component (Cl) and / or the isocyanate component (C2) can be further enhanced to improve the performance of the outer layer.

[0032] Preferably the dispersing agent (d2) has a hydroxyl value (mg KOH / g) in the range of 10 to 350 mg KOH / g. more preferably in the range of 20 to 300 mg KOH / g, more preferably 30 to 200 mg KOH / g, such as about 100 mg KOH / g. By carefully choosing the mg KOH / g value of the dispersing agent (d2), the reactivity and compatibility with the carbon nanotubes can be improved which benefits processing and final sleeve performance.

[0033] Preferably, the carbon nanotube component (C3) comprises single-wall carbon nano tubes (SWCNTs) and / or multi-walled carbon nanotubes (MWCNTs). Preferably, the carbon nanotube component (C3) comprises single-wall carbon nanotubes (SWCNTs). It is believed that the SWCNTs enable a more efficient electron transport, which further facilitates static dissipation, which in turn further benefits safety during operation with the sleeve, such as during industrial printing.

[0034] The method preferably comprises grinding (S4) the conductive outer layer to obtain a grinded conductive outer layer after the conductive composition (N) is applied (S3) on the outer surface of the base cylinder. In this manner, a smoother surface is ensured which benefits sleeve performance, e.g. due to a more even and uniform support.

[0035] The conductive composition (N) can be applied (S3) on the outer surface of the base cylinder such that the conductive outer layer is applied as having a thickness in the range of 0.2 to 20 mm, such as a thickness of 4 or 9 mm. In this manner, enough conductive volume is applied to ensure a desired static dissipation which can benefit safety. After applying the conductive outer layer having a thickness in the range of 0.2 to 20 mm, the method may include grinding away 0, 1 to 2 mm of outer layer, e.g. to ensure a smooth surface. In case a through hole is provided, e.g. by drilling a hole or recess, through the outer layer and partially or fully through the base sleeve, it is then preferred that a grinding step is performed to smoothen the area around the through hole. The outer surface of the sleeve may have a certain roughness and / or may comprise groves as described in in PCT / EP2024 / 068715 which is incorporated by reference.

[0036] Preferably, the base cylinder comprises at least one inner surface opposite of the outer surface and the method further comprises: creating (S5) an electrical connection to establish an electrically conductive pathway between the inner surface and outer surface of the sleeve. Generally, one or more electrical connections can be created. In this manner, static dissipation can be further improved. The inner surface refers to the surface facing the mandrel and / or the adapter. By creating multiple electrical connections, safety can be improved even further and / or grounding may be further facilitated by the multiple electrical connections. The electrical connection may be created by introducing conductive material(s) into a through hole and / or so as to extend through the whole radial length of the sleeve layers or may partially extend therethrough (e.g. from the outer layer or until a conductive inner layer is reached). The electrical connection can be created in any suitable manner, preferably the electrical connection is created by making (S5’) a channel, recess or hole through the sleeve and by filling said channel which a conductive material. The terms “channel, recess or through hole” can be used interchangeably herein.

[0037] Preferably, one or more conductive materials, e.g. a material that is / are inserted into the hole, comprises a compressible material, such as a conductive foam and / or an additional conductive material, such as a silver glue or a conductive resin. Preferably, the conductive resin (if applied into the through hole) is “polyester-based”, meaning that the conductive resin comprises at least 10wt% polyester, preferably unsaturated polyester, based on the total weight of the conductive resin. More preferably the conductive resin comprises at least 20wt%, more preferably at least 30wt%, even more preferably at least 40wt% of polyester, such as about 57wt%±10wt% polyester, in this manner a desired dimensional stability can be achieved.

[0038] An further aspect provides a sleeve obtained according to the method as described herein. The sleeve can be used as an adapter which is to be arranged between a printing mandrel and a printing sleeve that holds a printing plate (e.g. a flexographic printing plate). In addition, or as an alternative, the sleeve itself can be used as a printing plate which is to be mounted on printing mandrel or on a suitable adapter, in this manner the sleeve can directly hold the printing plate .

[0039] A further aspect provides a sleeve, such as a printing sleeve or such as an adapter, said cylinder being configured to be mounted on an adapter or on a printing mandrel by aid of a gas cushion, wherein the sleeve comprises: an outer layer for holding a printing plate and / or for holding a printing sleeve; an optional intermediate structure comprising one or more optional intermediate layers; an inner layer with an inner surface configured for being mounted on an adapter or for being mounted directly on a printing mandrel.

[0040] The outer layer (LI) comprises a polyurethane material (PU) and a carbon nanotube component (C3), wherein said carbon nanotube component (C3) is present within the outer layer (LI) in a weight concentration (c3) in the range of 0.05 to 2 wt% based on the total weight of the conductive outer layer (LI). Preferably, the carbon nanotube component (C3) is preferably present within the outer layer in a weight concentration (c3) in the range of 0.05 to 2.00 wt% based on the on the total weight of the composition (N), preferably in the range of 0.07 to 1.0 wt%, more preferably 0.10 to 0.50 wt%, more preferably in the range of 0. 10 to 0.40 wt%, more preferably in the range of 0.10 to 0.30 wt%, even more preferably 0.11 to 0.25 wt%, such as about 0.15 wt%. Advantageously, risks related to static buildup could be avoided as explained herein. Furthermore, the sleeve with a desired static dissipation could made in a more efficient and economical manner, e.g. by needed less energy and / or additives to facilitate extrusion and / or with a more efficient use of raw materials.

[0041] Preferably, component (C3) is dispersed or blended in a crosslinked polyurethane network of the polyurethane material (PU), preferably wherein the polyurethane network is obtained by mixing a polyol component (Cl) and an isocyanate component (C2). Advantageously, a strong and durable sleeve could be made with a high performance for printing.

[0042] Preferably, the carbon nanotube component (C3) is present within the outer layer (LI) in a weight concentration (c3) of at most 1.5 wt%, preferably at most 1 wt%, even more preferably at most 0.5 wt% based on the total weight of the conductive outer layer (LI). In this manner, the sleeve could be made in an even more efficient and economical manner. Preferably, the carbon nanotube component (C3) comprises single wall carbon nano tubes (SWCNTs), preferably wherein said nano tubes have an average length of 5 to 30 micrometers (um) and / or an average diameter of 1 to 2 nanometers (nm).

[0043] Preferably, the inner layer (L2) is a conductive layer to allow static dissipation and / or grounding when contacted with an adapter or mandrel. As used herein a “conductive layer” encompass electrically conductive and / or dissipative layers.

[0044] Preferably, the inner layer (L2) and optionally the intermediate structure (L3), which can form the base cylinder, have an electrical resistance (Ohm) that is smaller than 1000k Ohm, preferably smaller than 200k Ohm, preferably between 1 to 40 kOhm, preferably between 2 and 20 kOhm, such as about 10 kOhm. In this manner, grounding and dissipation of static buildup is facilitated. Preferably, wherein the intermediate structure and / or the inner layer comprises carbon fibers or particles, such as carbon black particles. Carbon black can be used as a conductive additive to improve the conductivity throughout the sleeve. Advantageously, the dissipation of static buildup can be improved.

[0045] Preferably, the intermediate structure and / or the inner layer, comprises a fiber reinforced layer which comprises carbon fibers or particles, such as carbon black particles or carbon nanotubes. The fiber reinforced layer may thereby provide strength and durability which benefits prolonged printing while the carbon fibers or particles assist with dissipation of static buildup. The intermediate structure and the inner layer may together form the base cylinder as described herein. Correspondingly, the method as described herein, specifically the step of providing the base cylinder, includes the provision of a base cylinder that comprises fibers.

[0046] Preferably, the sleeve further comprises an electrical connection, preferably an elongated electrical connection, extending through the sleeve to electrically connect said inner layer (L2) and said outer layer (LI), preferably the elongated electrical connection extends in a radial direction. Generally, in case of elongated electrical connection(s), these extends radially to ensure a desired dimensional stability. The electrical connection is preferably formed from conductive materials that are inserted into a through whole or recess, which preferably extends in the radial direction of the sleeve. The radial direction is the direction that points towards the longitudinal central axis of the sleeve. Generally, an elongated electrical connection extends more in radial direction of the sleeve than a longitudinal direction.

[0047] The electrical connection has the benefit that any static buildup present at the outer surface of the outer layer can be dissipated through the sleeve. Advantageously, the electrical connection can facilitate grounding which improves static dissipation, in particular when connected to an adapter or mandrel. The electrical connection can form a physical link between two layers, typically the outer layer and the inner layer of the sleeve that allows a flow of electrons to facilitate static discharge. Preferably, the electrical connection comprises a conductive compressible material arranged at or to connect with the inner surface to establish an electrical connection with an adapter or with a printing mandrel when the sleeve is mounted thereon. In this manner, grounding of the sleeve is further facilitated. By using a compressible material, installment by aid of a gas cushion is facilitated. The reason being that the conductive compressible material allows the expansion of the inner layer when the air cushion is applied during mounting.

[0048] Generally, the term “conductive” as used herein encompasses the properties of being electrically conductive and / or dissipative. Generally, the term “compressible material” encompasses any material which can be compressed upon exposure to the forces exerted by the gas cushion during installment of the sleeve on an adapter and / or a mandrel.

[0049] According to an embodiment, the through hole extends through the sleeve from the outer layer to the inner layer, preferably not fully through the inner layer, and wherein the electrical connection substantially fdls up the through-hole to establish an electrical connection between the outer and the inner layer. Generally applicable herein, the extension of the through hole can be such that the through hole forms a recess that extends from the outer surface of the sleeve until or partially through the inner layer, preferably until the inner layer is reached.

[0050] For example, the electrical connection may include a conductive foam, such as conductive polyethylene foam, which is arranged to fdl up the through-hole. One or more through-holes in which the electrical connection is arranged may be provided. By including multiple through holes, dissipation may be improved, although just one through hole may suffice.

[0051] The sleeve is typically mounted or installed on an adapter or directly on printing mandrel, to facilitate such mounting, a gas cushion can be used. Preferably, the inner layer (L2) is compressible to expand and contract upon exposure with a gas cushion to mount the sleeve on an adapter or mandrel.

[0052] The use of “a gas cushion” is described in PCT / EP2024 / 068715 which is incorporated by reference, in particular with respect to any subject matter related to the gas cushion.

[0053] Preferably, the inner layer (L2) is configured to establish an electrical connection with an adapter and / or with a printing mandrel when mounted thereon. In this manner, grounding is facilitated, which in turn favors static dissipation. The inner layer (L2) may for example comprise conductive particles or fibers, such as carbon fibers and / or carbon particles, even more in particular carbon black particles and / or carbon nanotubes. The particles may be dispersed substantially evenly throughout and / or over the inner surface of the inner layer. The conductive particles may be held in a resin and / or polymeric structure for improved safety and durability. Preferably, the inner layer is made from a conductive material such that the inner layer is electrically conductive.

[0054] Preferably, both the inner and outer layer (IL, OL) are conductive and wherein said inner and outer layer are connected to each other via an electrical connection, preferably electrically conductive connection. By including the electrical connection, grounding and dissipation can be facilitated which further improves safety by reducing the risk of static buildup. The electrical connection can be provided by any suitable conductive material.

[0055] Preferably, the sleeve comprises a channel or through hole which extends through the sleeve, typically in radial direction, and which is fdled with a conductive material, preferably fdled with a first conductive material (Ml) and a second conductive material (M2). By including the conductive material, a conductive path can be provided which further facilitates grounding and thereby improves static dissipation.

[0056] Preferably, the electrical connection comprises a first and second conductive material (Ml, M2). Preferably, the first conductive material (Ml) is more rigid than the second conductive material (M2) and the second conductive material (M2) is arranged closer to the inner layer and / or within the inner layer. Understandably, the term closer means that the second conductive material (M2) is arranged closer as compared with the first conductive material (Ml). In doing so, a more uniform and durable sleeve is created by the first material (more rigid) while the second material (less rigid or more compressible) may facilitate mounting with a gas cushion due to being the less rigid or more compressible.

[0057] Preferably, the second material (M2) is a conductive compressible material, more preferably a conductive compressible foam material, such as a conductive polyethylene foam.

[0058] Preferably, the second conductive material (M2) is compressible, such as compressible foam material, and wherein the first conductive material (Ml) (e.g. a conductive resin) is more rigid than the second conductive material (M2) (e.g. a compressible foam).

[0059] Preferably the first conductive material (Ml) is a polyester based resin comprising conductive particles, in this manner, the conductive material can be inserted easily while an electrical pathway for dissipation can be provided.

[0060] The first conductive material (Ml) may also be beneficial for dimensional stability, while the second conductive material (M2) facilitates installment due to being compressible. The compressible material (M2) of the electrical connection inserted through the sleeve typically has a compressive stress-strain value at 50% according to ISO 7214: 1998 below 300 kPa, preferably below 200 kPa, such as 130 kPa ± 50 kPa. In this manner, a desired mounting behavior of the sleeve can be achieved.

[0061] Suitable materials for the first conductive material (Ml) (more rigid) can be a silver glue or a conductive resin, preferably a polyester based resin (for durability) comprising carbon black (for conductivity). The first conductive material (Ml) (rigid) is preferably configured such that during mounting by aid of a gas cushion said first conductive material is not substantially compressed whilst the second conductive material (compressible) is compressed.

[0062] Preferably, the electrical connection contains a conductive material, e.g. arranged within the through, wherein said conductive material comprises a conductive resin, preferably said conductive resin includes carbon black, preferably in an amount of 1 to 8 wt%, such as 4 wt%, based on the total weight of the conductive resin, preferably a polyester based conductive resin. According to an embodiment, there is provided a sleeve, such as a printing sleeve or such as an adapter, said cylinder being configured to be mounted on an adapter or on a printing mandrel by aid of a gas cushion, wherein the sleeve comprises: an outer layer (LI) for holding a printing plate and / or for holding a printing sleeve; an optional intermediate structure (L3) comprising one or more optional intermediate layers; an inner layer (L2) with an inner surface configured for being mounted on an adapter or for being mounted directly on a printing mandrel; wherein the inner layer (L2) has a resistance smaller than 1000 kOhm, preferably between 1 to 40 kOhm; and / or wherein the inner layer (L2) is configured to expand upon exposure with a gas cushion to mount the sleeve on an adapter or mandrel and to contract without such exposure; wherein the outer layer (LI) comprises a polyurethane material (PU) and a carbon nanotube component (C3), wherein said carbon nanotube component (C3) is present within the outer layer (LI) in a weight concentration (c3) in the range of 0.05 to 2 wt% based on the total weight of the outer layer (LI), preferably said carbon nanotube component (C3) is present within the outer layer (LI) in a weight concentration (c3) of at most 1.5 wt% outer layer (LI).

[0063] According to said embodiment, it is preferred that that the inner layer (L2) is configured to establish an electrical connection with the adapter or the printing mandrel when installed thereon; and that the sleeve further comprises at least one electrical connection (70), preferably an elongated electrical connection, extending through the sleeve to electrically connect said inner layer (L2) and said outer layer (LI).

[0064] The sleeve described herein or obtained according to the method described herein has been found to be extremely useful in a printing device, preferably a flexographic printing device. Namely, due to the static dissipation, safety can be improved. Furthermore, the sleeve can be obtained in a more efficient manner, in particular in view of energy consumed and / or use of raw materials.

[0065] A further aspect provides an assembly comprising the sleeve as described herein and a printing mandrel (typically a conventional printing mandrel) and / or an adapter sleeve (e.g. a conventional adapter or an adapter as described herein) configured to be arranged between the printing mandrel and the sleeve as described herein. The sleeve as described herein may thus be used as a printing sleeve or as an adapter configured to hold a sleeve (e.g. a conventional sleeve or a sleeve as described herein).

[0066] A further aspect provides an assembly, said assembly comprising the sleeve as described herein (e.g. functioning as a printing sleeve) and a printing plate, preferably a flexographic printing plate, wherein the sleeve is configured to hold the printing plate, e.g. by aid of any suitable holding means such as an adhesive tape or a clamp, preferably an adhesive tape. The flexographic printing plate may be mounted on the sleeve as described, optionally if needed an adapter may be used between the printing sleeve and the mandrel. Notably, it is understood that the one aspect (e.g. the sleeve) may include one or more features of another aspect (e.g. the method) as described herein on a mutatis mutandis basis, and vice versa, unless explicitly stated otherwise.

[0067] BRIEF DESCRIPTION OF DRAWINGS

[0068] The invention will now be described in more details with respect to the figures illustrating some preferred embodiments of the invention.

[0069] Fig. 1 shows an application of a conductive composition on a base cylinder.

[0070] Fig. 2 shows a preferred application.

[0071] Fig. 3A shows a preferred application with more operational details. Fig. 3B illustrates a close-up partial side view of the base cylinder on which conductive composition is applied. Fig. 3C illustrates a partial cross-sectional side view showing an electrical connection arranged in a through hole.

[0072] Fig. 4 illustrates the sleeve directly mounted on a mandrel.

[0073] Fig. 5 illustrates the sleeve used as an adapter sleeve arranged between a printing sleeve and mandrel.

[0074] Fig. 6A-6D illustrates embodiments of a sleeve as seen from a cross-sectional side view, respectively showing the sleeve as a printing sleeve holding a printing plate, directly (Fig. 6A) and indirectly (Fig. 6B) mounted on a mandrel, and the sleeve as an adapter (Fig. 6C) to hold another printing sleeve, which can be a sleeve as described herein (Fig. 6D).

[0075] Fig. 7A illustrates a perspective view of a sleeve. Fig. 7B illustrates a schematic cross-sectional view through section line VII-VII

[0076] Fig. 8A illustrates a perspective view of a sleeve with an electrical connection. Fig. 8B-8D illustrates a schematic cross-sectional view through section line VIII-VIII.

[0077] Fig. 9 illustrates a physical dissolver, for a preferred use in the method as described herein. Understandably, the features shown in the figures can be combined unless explicitly stated otherwise. In particular, elements with the same reference numerals may have the same features and technical benefits.

[0078] DETAILED DESCRIPTION

[0079] The construction of sleeves has been well known, however surprisingly the inventors have found that by applying a conductive outer layer in a smart and inventive manner, that several technical benefits could be achieved, such benefits include but not be limited to improved manufacturing efficiency, e.g. due to reduced energy consumption and / or reduced use of additives.

[0080] Fig. 1 illustrates an application of conductive composition N on a base cylinder 101 to obtain a sleeve 100. The base cylinder 101 may have any suitable structure to be mounted on a printing mandrel, either directly or indirectly via an adapter. Preferably, the base cylinder is fiber reinforced, e.g., with glass fibers, for improved durability. In particular, the base cylinder 101 may have an inner layer L2 with an inner surface 103 (not shown in fig. 1) configured for being mounted on an adapter (see fig. 6B) or for being mounted directly on a mandrel (see fig. 6A). The base cylinder 101 may include a structure which shares one or more of the features of the intermediate structure as described herein. Fig. 1 further shows the base cylinder 101 as having an outer surface 102 on which a conductive composition N is applied via extrusion, in particular via a nozzle 30. The extrusion may be facilitated by the aid of a pressure to exert a driving force to extrude composition N via the nozzle. By carefully choosing the components within the composition N, the energy required to provide such pressure may be reduced. Fig. 1 shows that the conductive composition N is applied on the base cylinder 102 to form an outer layer LI thereon. Fig. 1 further illustrates that components Cl, C2 and C3 are mixed all together right before being extruded via nozzle 30. Components Cl, C2 and C3 can be mixed with a rotor stator mixer 35 ensuring high shear mixing. In this manner, a crosslinked polyurethane network of polyurethane material (PU) is formed on the base cylinder 101 in which the carbon nanotube component (C3) is dispersed or blended. Namely, once Cl and C2 are mixed, they react with each other to form a crosslinked polyurethane network.

[0081] In the context of the present application the term “conductive” and “electrically conductive” are used interchangeably and have to be interpreted as any material that is capable of allowing electrostatic discharge. Electrically conductive materials include both good conductors as well as so- called static dissipative materials for which charges flow more slowly in a more controlled manner than with conductive materials .

[0082] Preferably the relevant material or layer(s) described herein as being conductive has a (electrical) resistance (ohm) of at most 106ohm, such as between 10 and 106ohm, more preferably in the range of 103and 106ohm. In the latter range, more controlled dissipation can be achieved. The resistance (ohm) can be measured with a Benning IT101 device (Benning Elektrotechnik und Elektronik GmbH&Co KG, Bocholt, Germany) with a voltage of 100 V to determine the resistance and using a copper electrode with a diameter of 40 mm and a length of 200 mm placed inside the sleeve and a second copper electrode with a diameter of 33 mm placed on the ground surface of the sleeve.

[0083] The conductive composition N

[0084] As shown in fig. 1, conductive composition N includes a polyol component Cl (also described herein as Cl component or component (Cl)) and isocyanate component C2 (also described herein as C2 component or component (C2)) and carbon nanotube component C3 (also described herein as C3 component or component (C3)).

[0085] Component Cl (polyol)

[0086] Typically, the polyol component Cl contains a compound that contains multiple hydroxyl (-OH) groups, specifically reactive hydroxyl (-OH) groups which react with isocyanate (NCO) groups to form polyurethanes. Preferably, the polyol component comprises: a polyether polyol, a polyester polyols, or combinations thereof. In doing so, a polyurethane network can be achieved with a superior performance in view of printing and printing quality. Component C2 (isocyanate)

[0087] Typically, the isocyanate component C2 contains a compound that has at least two isocyanate functional groups. This group is characterized by the presence of a carbon atom (C) double -bonded to a nitrogen atom (N) and single-bonded to an oxygen atom (O) in the form of a structure represented as -N=C=O. Preferably, the isocyanate component C2 contains an isocyanate chosen from a polyisocyanate (PI), a diphenylmethandiisocyanate (MDI) or combinations thereof. Isomers and / or homologues of these compounds are also envisaged. By choosing one or more of these isocyanates compounds, a desired polymer network can be achieved when mixed and reacted with the C 1 and C3, in this manner a durable outer layer with a desired dissipation capacity can be achieved.

[0088] Component C3

[0089] Furthermore, the carbon nanotube component C3 is preferably present within composition N in a weight concentration (c3) in the range of 0.05 to 2.00 wt% based on the on the total weight of the composition N, preferably in the range of 0.07 to 1.0 wt%, more preferably 0.10 to 0.50 wt%, more preferably in the range of 0. 10 to 0.40 wt%, more preferably in the range of 0. 10 to 0.30 wt%, even more preferably 0.11 to 0.25 wt%, such as about 0.15 wt%. By including the carbon nanotube component in an amount within the defined ranges, the extrusion and use of raw materials can be improved. In this manner, production efficiency is highly improved. More preferably, the carbon nanotube component C3 is present within the composition N in a weight concentration (c3) of at most 1.5 wt%, preferably at most 1 wt% to further ensure production efficiency.

[0090] The carbon nanotube component, used in the method and / or the sleeve as described herein, includes carbon nanotubes which can be singled walled or multi walled. Preferably, single wall carbon nano tubes (SWCNTs) are used, preferably wherein said nano tubes have an average length of 5 to 30 micrometers (um) and / or an average diameter of 1 to 2 nanometers (nm). Surprisingly, single walled carbon nano tubes offer improved conductivity which aids in static dissipation and thereby safety can be further improved. Preferably, the C3 component is included into the composition, e.g., by mixing with Cl and / or C2 in any suitable order, preferably by firstly mixing with Cl and C3 to form premix. Preferably, C3 is included as a dispersion D, as described herein.

[0091] Additives

[0092] One or more additives may be included in the composition N, such as extrusion promoting additives. Although, in certain embodiments, it is desired to avoid the use of additives, e.g., in view of efficient use of raw materials. In view of efficient use of raw material, it is preferred that the total amount of additives is reduced. Preferably, the composition N comprises at most 5 wt% of components which differ from components Cl, C2 and C3. In this manner, efficiency can be increased.

[0093] Premix-formation

[0094] Preferably, the carbon nanotube component C3 is mixed with any of the polyol component Cl and / or the isocyanate component C2 such that carbon nanotube component C3 is dispersed or blended in a crosslinked polyurethane network once the polyol component Cl and the isocyanate component C2 react with each other. Preferably, the C3 component is introduced before the C2 and Cl are reacted with each other. More in particular, the C3 component is firstly mixed with the Cl component before the Cl and C2 are mixed to form a polyurethane network. In this manner, production can be simplified and / or side reactions can be avoided. To improve the formation of the polyurethane network, the components Cl, C2 and C3 are preferably mixed in a rotor stator mixer 35 (Fig. 3A). Fig. 2 illustrates that that a pre-mix PM or premix-composition PM (used interchangeably) is formed by mixing Cl with C3 before these components are being mixed with C2. Surprisingly, production could be simplified when this order of mixing is followed. Preferably, the premix includes component C3 in an amount (c3’) of 0.1 to 3.3 wt%, preferably 0.1 to 3 wt%, even more preferably 0.1 to 2.3 wt%, even more preferably 0.1 to 2 wt%, even more preferably 0.1 to 1.5 wt%, such as about 0.35 wt%. In this manner, component C3 can be uniformly dispersed or blended throughout the premix and consequently also composition N which benefits conductivity and dissipation capacity of the outer layer LI which comprises, preferably consists of the conductive composition N. To ensure performance, it is preferred that the pre-mix composition PM and the isocyanate component C2 are mixed in a ratio from 100:60 to 100:50. Component C3 and component Cl can be mixed in any suitable manner, preferably Cl and C3 are mixed with a physical dissolver 50 (see Fig. 9) said physical dissolver 50 comprising: a vessel 51 to hold components C3 and C3; and a stirrer assembly 51 disposed within the vessel 50, the stirrer assembly 60 comprising: a shaft 61 and at least one impeller 62 affixed to the shaft, the impeller is configured to impart rotational motion to the liquid medium, including Cl and C3, within the vessel. A power source (not shown) may be coupled to the stirrer assembly 60 to rotate the shaft 61. Preferably, the impellor comprises a plurality of blades (not shown). By having multiple blades or vanes, a desired static dissipation can be provided to the outer layer due to an improved mixing of component C3 throughout component Cl. Preferably, the impellor is rotated a peripheral speed in the range of 2 to 20 m / s, preferably in the range of 5 to 15 m / s, to mix the carbon nanotube component C3 with the polyol component Cl. Surprisingly, the range 5 to 15 m / s is highly beneficial in view of manufacturing efficiency (material use vs. desired performance). Namely, by using the defined rotational speed a better dispersion quality (and thus better static dissipation) in a relative short amount of time can be achieved. Additionally, the speed should not exceed 15 m / s to ensure an efficient conductivity per amount of component C3. Thus, by using the peripheral speed in the defined ranges, production efficiency may be increased.

[0095] Component C3 may be introduced as a dispersion D comprising the carbon nanotube component and a dispersion agent. The dispersion agent may be an alcohol such as an alcohol chosen from : ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-propanediol, diethylene glycol, polyethylene glycols or ethoxylated and / or propoxylated alcohol. Preferably, the dispersion agent comprises an ethoxylated and / or propoxylated alcohol. Namely, it is believed that improved mixing behavior and compatibility can be achieved between the ethoxylated and / or propoxylated alcohol and the Cl and / or C2 and / or C3 component. In particular if the mg KOH / g value of the dispersing agent (d2) is carefully chosen.

[0096] Extrusion via nozzle

[0097] Fig. 3A shall now be used to explain preferences of applying the conductive composition N. As shown, composition N is applied via nozzle 30. Preferably, composition N is applied on the outer surface 102 of the cylinder 101 by extruding the composition N through nozzle 30 while moving (indicated via arrow) the nozzle and / or while rotating (indicated via arrow) the cylinder 101, e.g. by rotating a mandrel 40. Preferably, the composition N is applied in a spiral fashion. Advantageously, the moving of the nozzle 30 and / or rotating of the cylinder 101 allows for rapid and efficient application of composition N. Preferably, the nozzle 30 is moved in a direction along a longitudinal axis (see fig. 3 A, axis lax) of the base cylinder 101 and while said cylinder is being rotated (indicated with arrow). Advantageously, such synchronized motion ensures uniform and efficient application of the conductive composition, improving the durability and quality of the outer layer. More preferably, the nozzle 30 is moved along the longitudinal axis of the base cylinder at a speed (vi) between 0.30 m / min to 0.7 m / min and wherein the cylinder is rotated at a speed (vr) between 60 to 150 rpm. Such combination of nozzle movement and cylinder rotation allows efficient processing times, improving manufacturing productivity while ensuring that the outer layer has a desired static dissipation which can improve safety during printing.

[0098] Fig. 3B illustrates a more detailed view of the base cylinder as seen from a side view. By controlling the rotational speed of the base cylinder 101 (e.g., by controlling the rotation of mandrel 40) and / or the movement of the nozzle 30, the thickness of the outer layer LI can be controlled. Preferably, the outer layer LI has a thickness t (see e.g., fig. 3B) in the range of 1 to 20 mm, within this range, a desired level of static dissipation can be ensured.

[0099] Grinding

[0100] Once the composition N is applied on the base cylinder 101 to form an outer layer LI therein, the outer surface of layer LI may be subjected to grinding (not shown) to smoothen the outer layer. The sleeve can provide support for the printing plate during the printing process, a smooth surface which is free of defects can help ensure proper mounting and prevent any potential issues with print quality. In case a through hole is provided connecting at least the outer layer LI and the inner layer L2 in which an electrical connection 70 extends, it is then preferred that a grinding step is performed to ensure a smooth other surface. Generally applicable, at least one electrical connection can be used, in case two or more electrical connection are used, these two or more electrical connections are preferably arranged at a distance from each other. In this manner, grounding may be facilitated and such that safety can be further enhanced. Generally, the sleeve may be provided with a first and a second electrical connection, preferably a first and second elongated electrical connection, wherein said first and second electrical connection are arranged at a distance from each other.

[0101] Advantageously, safety may be further increased.

[0102] The sleeve

[0103] The sleeve 100 can be used as a printing sleeve 100a (see fig. 4) to hold a printing plate 10. In addition, or as an alternative, the sleeve 100 can be used use as an adapter 100b (see fig. 5) to mount a printing sleeve 100b (e.g. another sleeve 20, 100’ with larger dimensions, which may have similar features as the sleeve 100 as described herein) on a printing mandrel 40. The sleeve 100’ can be mounted on an adapter (which may be a sleeve 100 as described herein) or the sleeve can be mounted directly on printing mandrel 40. The mounting by aid of a gas cushion is explained in NL patent application 2035249 or in PCT application PCT / EP2024 / 068715, which is incorporated herein by reference, in particular with respect to the subject matter of the gas cushion.

[0104] The sleeve as adapter and / or as printing sleeve

[0105] Fig. 4 illustrates an assembly 20a wherein the sleeve 100 as described herein is mounted directly on mandrel 40 (Fig. 6A) and holding a printing plate 10 or indirectly via an adapter sleeve (Fig. 6B, 6D), the assembly can be used in a flexographic printing device. The sleeve 100 may also function as an adapter sleeve (Fig. 5, Fig. 6C-D) configured to be arranged between the printing mandrel 40 and another sleeve, e.g. a different sleeve (Fig. 6C) or another sleeve 100’ (Fig. 6D) with similar features as described herein, e.g. another sleeve 100’ with an outer layer LI’ which includes component C3 in the manner as described herein.

[0106] Fig. 5 further illustrates assembly 20b, said assembly comprising the sleeve 100 as described herein and a printing plate 10, preferably a flexographic printing plate, wherein the sleeve 100 is configured to hold the printing plate, e.g. by aid of any suitable holding means such as an adhesive tape or a clamp, preferably an adhesive tape 11 (see Fig. 6A-6D).

[0107] Fig. 6A-6D shows an example of installing the sleeve 100 which is preferably occasioned by providing a gas cushion, such as an air cushion, between an inner surface of the sleeve 100 and the outer surface of the adapter 300 (which may be a sleeve as described herein with smaller dimensions) or an outer surface 410 the mandrel 40. For example, a gas (air orN2) may be supplied via inlet 401 to provide the gas cushion at a relevant interface between sleeve and / or adapter and / or mandrel via gas guides 402, 302 of the mandrel 40 and / or of the adapter 300. Understandably, the outer layer LI as shown in Fig. 6A-6D may have any of the features as described herein.

[0108] Lavers LI, L2 and optional intermediate structure L3

[0109] Fig. 7A shows a sleeve 100 as seen from a perspective view. The sleeve 100 has an outer layer LI which preferably has the features described herein for the benefit of static dissipation and improved manufacturing. The sleeve further has an inner surface 113 for being mounted on an adapter or for being mounted directly on a printing mandrel. It is desired that the inner layer L2 is configured to ensure a secure and precise fit with the adapter or mandrel on which it is installed. An optional intermediate structure L3 between the inner and outer layer may be arranged. Preferably, said structure L3 (e.g., as shown in fig. 7A-B and fig. 8A-D) contains an additional layer having at least one of the following properties:

[0110] - an elastic modulus, as measured via ISO 178, in the range of 0,05 to 700 GPA;

[0111] - a density in the range of 0,15 to 2,0 g / cm3;

[0112] - a flexural strength, as measured via ISO 178, in the range of 2,0 to 50 MPa (Megapascal);

[0113] - a compressive strength, as measured via ISO 604, in the range of 1,0 to 60 MPa.

[0114] By including such an additional layer, a desired printing performance can be achieved.

[0115] Fig. 7B shows the view through section line VII-VII of Fig.7A. It is understandable that the layered structure(s) shown (fig. 7B and 8B-D) are not drawn to scale and are merely used for illustrative purposes. Furthermore, fig. 7B and 8B-D are showing an exploded view with gaps for improved visibility of the layers.

[0116] The outer layer LI is preferably made from a conductive or dissipative material, in particular made from a polyurethane material which comprises a conductive material such as carbon black or carbon nanotubes, preferably the outer layer LI includes the carbon nanotube component C3 as described herein. To be clear, the terms “conductive” and “dissipative” can be used interchangeably herein. Preferably, the outer layer LI comprises a polyurethane material PU and a carbon nanotube component C3. Preferably, the carbon nanotube component C3 is present within the outer layer LI in a weight concentration c3 in the range of 0.05 to 2 wt%, preferably 0. 1 to 1 wt% based on the total weight of the conductive outer layer LI . By including the C3 component in said range, the benefits as described herein can be achieved. The carbon nanotube component C3 is typically dispersed or blended in a crosslinked polyurethane network PN of the polyurethane material PU to provide the layer LI with a conductive or dissipative capacity. The polyurethane network is preferably obtained by mixing a polyol component C 1 and an isocyanate component C2, more preferably in the manner as described herein. It is desired C3 is present within the outer layer LI in a weight concentration c3 of at most 1.5 wt%, preferably at most 1 wt%, even more preferably at most 0.5 wt% based on the total weight of the conductive outer layer LI such as between 0.05 to 0.5 wt%. In this manner, the outer layer L 1 can be made in an improved manner.

[0117] Preferably, the layer LI has an electrical resistance that is lower than 1000 kOhm, preferably less than 100 kOhm, such as between 15 - 30 kOhm and / or the inner layer (L2) and optionally the intermediate structure (L3) (which together can form a base cylinder 101), have a resistance below 1000 kOhm preferably smaller than 200k Ohm, most preferably smaller than 40 kOhm, in particular between 1 to 40 kOhm, preferably between 2 and 20 kOhm, such as about 10 kOhm. The electrical resistance (Ohm) can be measured with a Benning IT101 device. According to an embodiment, the electrical resistance of the whole sleeve, as measured between the outer layer and the inner layer, is smaller than 1000k Ohm, preferably smaller than 500k Ohm, more preferably smaller than 100k Ohm, more preferably smaller than 40k Ohm, even more preferably smaller than 20k Ohm.

[0118] The intermediate structure L3 may comprise at least one layer arranged between the outer layer L 1 and the inner layer L2. The intermediate structure L3 may comprise any of the following layers a barrier layer, compressible layer, a conductive layer, a porous layer, a fiber reinforced layer, a structured layer, a partially hollow layer, or combinations thereof.

[0119] Preferably, the intermediate structure L3 comprises at least a fiber reinforced layer. In this manner, durability and / or dimensional stability of the sleeve can be improved. Preferably, the intermediate structure (L3) comprises at least a fiber reinforced layer, e.g., to enhance dimensional stability. In the context of fiber reinforcement as used herein, the following fibers may be used: glass fibers, carbon fibers, and aramid fibers. Glass fibers are preferred. The inner layer L2 is preferably conductive, in this manner, the inner layer L2 can dissipate static buildup easily by contacting a grounded mandrel or a grounded adapter, e.g., the inner layer may comprise conductive particles. The intermediate structure L3 and / or the inner layer L2 may include carbon black or carbon nanotubes, e.g., carbon black particles to further facilitate static dissipation.

[0120] The outer layer LI may have a thickness between 1 to 20 mm. The inner layer L2 and optionally the intermediate structure may together have a thickness between 2 to 45 cm.

[0121] The intermediate structure L3 and / or the inner layer L2 are preferably configured to allow electrical conductivity and / or dissipation between their radially outwards facing surface to their radially inwards facing surface. In this manner, grounding can be facilitated. In particular, it is preferred that inner layer L2 and / or a layer within the intermediate structure L3 is / are configured to expand upon exposure with a gas cushion to mount the sleeve on an adapter or mandrel and to contract without such exposure. In this manner, a close fit can be provided which benefits printing operation. The inner layer L2 typically establishes an electrical connection with the adapter or the printing mandrel on which it is mounted thereon. In this manner, a grounding pathway is provided which facilitates dissipation.

[0122] The intermediate structure (L3) and / or the inner layer (L2) may be conductive and / or may comprise carbon particles such as carbon fibers or carbon black, in this manner, a conductive or dissipative property can be provided to said layers. The carbon black may be dispersed uniformly throughout said layers or may be concentrated at certain location(s), e.g., by an elongated electrical connection which extends in radial direction through the sleeve. Notably, the feature of the elongated electrical connection and the benefits thereof can be used independently from the concentration of the carbon nanotube component.

[0123] Electrical connection between inner and outer layer

[0124] Fig. 8A and Fig. 8B-C shall now be used to explain electrical connection 70. It generally is understandable that the aspect of the electrical connection 70 can be used independently of the concentration of the carbon nanotube component C3 in the outer layer LI as described herein (including in the context of the method and the sleeve). Furthermore, the electrical connection 70 can be included into the embodiments shown in Fig. 1 - 7. Fig. 8A shows sleeve 100 having an outer layer LI that can hold a printing plate 10 and / or for to hold a printing sleeve 20. The sleeve 100 has an optional intermediate structure L3 comprising one or more optional intermediate layers. The sleeve 100 has an inner layer L2 with an inner surface 113 configured for being mounted on an adapter or for being mounted directly on a printing mandrel. The outer layer LI of the sleeve 100 preferably comprises a polyurethane material PU and the carbon nanotube component C3 in the manner as described herein.

[0125] Fig. 8A further shows that the sleeve 100 further comprises at least one electrical connection 70 extending through the sleeve to electrically connect said inner layer and said outer layer. The at least one electrical connection 70 is preferably an elongated element made of one or more conductive materials. A mixture of a conductive and non-conductive material is also possible. Preferably the elongated electrical connection 70 extends in a radial direction, preferably along a substantially straight line. Advantageously, such orientation allows the electrical connection to be provided in a simple manner. On top of that, improved mechanical stability may be achieved compared to other orientations. For example, as shown in Fig. 3C (or Fig. 8D) the electrical connection 70 can be created (S5), between the inner surface 103 of the base cylinder 101 and the outer surface 102 such that electrically conductive pathway 104 between said inner surface and outer surface 103, 102 is provided. The electrically conductive pathway allows for electric flow and / or static dissipation, more in particular the conductivity of the pathway is the same or higher than the conductivity of the of the inner layer L2. Typically, the conductivity of the pathway is higher than the average conductivity of the one or more layers intermediate structure L3.

[0126] The electrical connection 70 is typically an introduced element comprising one or more conductive materials and extends in radial direction. The electrical connection can be created (S5) before or after applying the conductive composition. By creating such electrical connection 70, dissipation can be further improved. The electrical connection (70) may be created by providing (S5’) a channel or a through hole (300) through the sleeve. Preferably the electrical connection is arranged in a channel or through hole 300 extending in a radial direction (as shown in fig. 3C or fig. 8B and fig. 8C), and filling said channel or through hole (300) with a conductive material, preferably a material with the same or higher conductivity than the average conductivity of the materials used for the inner layer LI and / or the intermediate structure L3. Preferably, the method may comprise filling said channel with a first and second conductive material (Ml, M2) having different rigidity. In this manner, the more rigid material (Ml) may be arranged near the middle of the sleeve while the less rigid more compressible material (M2) is arranged closed to the inner layer L2. In this manner, an optimal balance between mounting behavior and dimensional stability can be achieved. Namely, the compressible material (M2) allows for an easier mounting while the more rigid material (Ml) may increase dimensional stability.

[0127] The through hole 300 may extend through the sleeve, e.g. as a recess, until the inner layer L2 is reached or the through hole 300 may extend through the sleeve and through a portion of the inner layer L2 such that the through hole 300 does not extend completely through the inner layer L3 (fig .8B) or the through hole 300 may extend completely through the inner layer until the inner surface 113 of the sleeve is reached. According to an embodiment, the radial length (rl) of the electrical connection 70 (see Fig. 3C and 8D, indicating rl and ts) equates with 25% to 100%, preferably between 50% to 99% of the thickness (ts) of the sleeve (see fig. 3C). As shown in Fig. 8D, from left to right, the through hole and / or the inserted or introduced electrical connection 70 can extend in radial direction as follows. The through hole 300a can extend fully through the layers LI, L2, L3 of the sleeve 100 from outer surface of the sleeve to inner surface 113 or partially (see 300b, 300c, 300d). The through hole (300) may be formed as a recess (open only on one side) (see 300b) or may be open on both sides of the hole. After the through hole is provided (e.g., by drilling) it is preferred that the outer surface is subjected to a grinding step to smoothen the surface such that improved print results may be obtained.

[0128] Fig. 8C shows that a first and a second conductive material (Ml, M2) are arranged in the through hole (300), the second conductive material is arranged closer to the inner layer (L2). In particular, closer as compared with material Ml . Generally, material M2 can be arranged between the material Ml and the inner surface 113 of the inner layer L2.

[0129] The first conductive material (Ml) may be chosen from the group: aplastic, an epoxy, a polyurethane, a fiber reinforced material, whereby said materials include conductive fibers and / or conductive particles. The first conductive material (Ml) may be metal.

[0130] The second conductive material (Ml) may be chosen from the group: conductive foam, a conductive elastomer or elastomeric composition.

[0131] The second conductive material (M2) may be attached to the inner layer (L2) by aid of any suitable conductive adhesive, e.g., a silver glue. By attaching M2 with L2, dissipation can be further improved.

[0132] Generally, the at least one electrical connection 70 may be arranged close to one or both ends of the sleeve or at any location along the sleeve. In this context, close means that the respective connection is arranged at a distance that is at most 30% of the total length of the sleeve.

[0133] For example, a first electrical connection is arranged at a distance of about 15%±14% of the total length of the sleeve from a first end of the sleeve, while a second electrical connection may be at a distance at a distance of about 15%±14% from a second end of the sleeve, said second end being opposite from the first end of the sleeve. Advantageously, such positioning may improve and / or ensure easy grounding when the sleeve is mounted in a printing device. It is furthermore unambiguously understandable that the elements described above may be used in isolation or in combination unless explicitly stated otherwise.

[0134] EXAMPLES

[0135] Example 1 : Manufacturing of outer layer of a sleeve

[0136] As the base cylinder, a base sleeve has been used with an inner diameter of 124.26 mm and outer diameter of 131 ,5mm made of a fiber reinforced layer comprising carbon black and exhibiting an electrical resistance of 10 kOhm (k ). The resistance (ohm) of the base cylinder was measured with a Benning IT101 device ( Benning Elektrotechnik und Elektronik GmbH&Co KG, Bocholt, Germany) with a voltage of 100 V to determine the resistance and using a copper electrode with a diameter of 40 mm and a length of 200 mm placed inside the base cyliner and a second copper electrode with a diameter of 33 mm placed on the ground surface of the base cylinder. The following components have been used in the examples.

[0137] Table 1: Components used to make a conductive composition.

[0138] Preparation of Premixes: To 440 kg of polyol component different amounts of the dispersion D (C3) were added and mixed using a physical dissolver with impeller blade at a peripheral speed of lOm / s resulting in premixes with different concentrations of carbon nanotubes. The concentration of the carbon nano tubes in the premix was in the range of 0.045% to 0.349 % by weight.

[0139] Preparation and application of the isocyanate component I and the premix: the premixes comprising the carbon nanotubes were mixed with the isocyanate component in a mixing ratio of 100:56 in a mixing and application device Type 200.0024 from Horstmann Maschinenbau GmbH (Heek, Germany). Mixing was performed using a rotor stator mixer at a rotation speed of 4500 rpm. Nozzle composition and application: The mixed components were applied to the outer surface of a sleeve with a diameter of 131,5 mm rotating at a speed of 146 rpm though a nozzle with a diameter of 8 mm and with a throughput of 23 g / s to obtain a coating thickness of 4 mm. The nozzle moving parallel to the rotation axis at a speed of 0,68 m / min and applying the material in a spiral fashion. A second set of parameters (rotating at a speed of 69 rpm and nozzle moving speed of 0,33 m / min) was used to generate a coating thickness of 9 mm.

[0140] The resulting workpieces showed a modulated surface and at the ends of the applied coating a contact angle was observed. The workpieces were subjected to grinding, in particular grinding using a grinding stone to the final thickness of the conductive layer of 3,6 mm with 4 mm and 8,1 mm with 9 mm.

[0141] The resistance of the coated conductive layer was measured using a copper electrode with a diameter of 40 mm and a length of 200 mm placed inside the sleeve and a second copper electrode with a diameter of 33 mm placed on the ground surface of the sleeve. A Benning IT101 device (Benning Elektrotechnik und Elektronik GmbH&Co KG, Bocholt, Germany) with a voltage of 100 V was used to determine the resistance.

[0142] The contact angle (P) was determined by taking photographs of the edge of the coated material and applying a tangential line to the edge of the applied composition. Then a rectangle was drawn which has the tangential line as diagonal and a bottom aligning with the surface of the base layer (see fig. 3B). The values of the length L and width W of the rectangle were determined. Using formula D = (L2+ W2)0,5the length of the diagonal D was calculated. The angle was then calculated with p =cos-1(W / L). A higher contact angle resembles a more efficient application of conductive composition.

[0143] * These values were obtained by grinding the material that adhered to the base cylinder. The layer thickness is lower than for the other examples. ** In case of a higher concentration of CNT, the results are contemplated since the application of the formulation would require more energy and / or use of additives. The following evaluation criteria has been used: n / a Not measured

[0144] Formulation dropped from cylinder 0 Formulation dropped partially from cylinder

[0145] + Formulation remained on cylinder and formed good coating

[0146] ++ Formulation remained on cylinder and formed very good coating

[0147] / Formulation would require more energy and / or additives

[0148] It is contemplated that, in case a higher concentration of CNT is used, that the resistance would be lower (improved conductivity) but that this would not compensate in view cost-effectiveness and / or energy efficiency, e.g. due to a decrease in extrusion performance and / or due to the need of additives. Example 2: Manufacturing of a connection between outer and inner electrically conductive layer, A sleeve with an inner layer made of an electrically conductive layer, several intermediate layers and a conductive outer layer was prepared according to the method described above.

[0149] A hole with a diameter of 8 mm was drilled though the outer layer and the layers between the inner and outer layer, but not through the inner conductive layer.

[0150] A cylindrical piece of a compressible conductive Polyethylene foam (conductive foam) with a density of 0,05 g / cm3, hardness Shore A of 12,5 and a resistance of 24 kOhm was inserted into the hole and firmly pressed towards the bottom of the hole.

[0151] The remaining void of the hole was filled with an electrically conductive unsaturated polyester (conductive resin) consisting of 39% styrene, 57% unsaturated polyester and 4% carbon black and resistance of 24 kOhm and a density of 1,2 g / cm3. Finally the sleeve was subjected to grinding to have an even surface at the location of the hole.

[0152] The skilled person will appreciate on the basis of the above description that the invention can be embodied in different ways and on the basis of different principles. The invention is not limited to the above described embodiments. The above described embodiments and the figures are purely illustrative and serve only to increase understanding of the invention.

[0153] The invention will not therefore be limited to the embodiments described herein, but is defined in the claims.

Claims

25CLAIMS1. A method to manufacture a sleeve (100) for use as a printing sleeve (100a) to hold a printing plate (10) or for use as an adapter (100b) to mount a printing sleeve (100b) on a printing mandrel (40), said method comprising the steps of: providing ( S 1 ) a base cylinder (101) having an outer surface (102); applying (S3) a conductive composition (N) on the outer surface of the base cylinder to form a conductive outer layer (LI) thereon; wherein the composition (N) comprises: a polyol component (Cl) and an isocyanate component (C2); and said composition (N) further comprising a carbon nanotube component (C3); wherein the method comprises- formation of a crosslinked polyurethane network (N’) once the polyol component (Cl) and the isocyanate component (C2) are mixed and applied on the outer surface of the base cylinder and wherein the carbon nanotube component (C3) is mixed with any of the polyol component (Cl) and / or the isocyanate component (C2) such that carbon nanotube component (C3) is dispersed or blended in said crosslinked polyurethane network; wherein the carbon nanotube component (C3) is present within the composition (N) in a weight concentration (c3) in the range of 0.05 to 2.00 wt% based on the total weight of the composition (N).

2. The method according to claim 1, wherein the carbon nanotube component (C3) is present within the composition (N) in a weight concentration (c3) in the range of 0. 10 to 0.40 wt% based on the on the total weight of the composition (N), preferably in the range of 0.10 to 0.30 wt%, even more preferably 0.11 to 0.25 wt%.

3. The method according to claim 1 or claim 2, the method further comprising the step of:- forming (S2) a pre-mix composition (PM) by mixing (S2’) the carbon nanotube component (C3) with the polyol component (Cl) to form the pre-mix composition (PM), and- mixing (S2”) the pre-mix (PM) with the isocyanate component (C2) to form theconductive composition (N).

4. The method of the previous claim, wherein the pre -mix composition (PM) is formed such that the carbon nanotube component (C3) is present within said pre-mix composition (PM) in a weight concentration (c3’) of 0. 1 to 3.3 wt%, preferably 0. 1 to 3 wt%, even more preferably 0. 1 to 2.3 wt%, even more preferably 0.1 to 2 wt%, even more preferably 0.1 to 1.5 wt%.

5. The method of any of the previous two claims, wherein the pre -mix composition (PM) and the isocyanate component (C2) are mixed in a ratio from 100:60 to 100:50.

6. The method according to any one of the previous claims, wherein the carbon nanotube component (C3) is present within the composition (N) in a weight concentration (c3) of at most 1.5 wt%, preferably at most 1 wt%.

7. The method according to any one of the previous claims, wherein the carbon nanotube component (C3) is present within the composition (N) in a weight concentration (c3) of at least 0.10 wt%, preferably 0.11 wt%, preferably at least 0.15 wt%, even more preferably at least 0.17 wt%.

8. The method according to any one of the previous claims, wherein the composition (N) is applied on the outer surface (102) via a nozzle (30) and / or by extrusion.

9. The method according to any one of the previous claims, wherein the composition (N) is applied on the outer surface of the base cylinder by extruding the composition (N) through a nozzle, while moving the nozzle (30) and / or while rotating the base cylinder (101), preferably such that the composition (N) is applied in a spiral fashion around the outer surface (102) of said base cylinder.

10. The method of to the previous claim, wherein the nozzle (30) is moved in a direction along a longitudinal axis (lax) of the base cylinder (101) and while said cylinder is being rotated.

11. The method of to the previous claim,wherein the nozzle (30) is moved along the longitudinal axis of the base cylinder at a speed (vi) between 0.30 m / min to 0.7 m / min and wherein the cylinder is rotated at a speed (vr) between 60 to 150 rpm.

12. The method according to any one of the previous claims and claim 3, wherein the method comprises the step of:- forming (S2) the pre-mix composition (PM) by using a physical dissolver (50) with an impellor (62) to mix the carbon nanotube component (C3) with the polyol component (Cl); and / or- mixing the pre-mix (PM) with the isocyanate component (C2) with a rotor stator (35) mixer.

13. The method of the previous claim, wherein the impeller (62) is rotated a peripheral speed in the range of 2 to 20 m / s, preferably in the range of 5 to 15 m / s to mix to mix the carbon nanotube component (C3) with the polyol component (Cl).

14. The method according to any of the previous claims, wherein the base cylinder (101) has an electrical resistance below 1000 kOhm preferably smaller than 200k Ohm, most preferably smaller than 40 kOhm, more preferably between 1 to 40 kOhm, preferably between 2 and 20 kOhm, such as about 10 kOhm; and / or wherein the outer layer (LI) has an electrical resistance of at most 1000 kOhm, preferably at most 30 kOhm, such as between 1 and 30 kOhm.

15. The method according to any of the previous claims, wherein the method comprises the step of: including the carbon nanotube component (C3) as a dispersion (D), wherein said dispersion (D) comprises 1 to 10 wt% of carbon nanotubes (dl) and a dispersing agent (d2).

16. The method of the previous claim, wherein the dispersing agent (d2) is chosen from an alcohol, preferably an ethoxylated and / or propoxylated alcohol.

17. The method of any of the previous two claims,28 wherein the dispersing agent (d2) has a hydroxyl value in the range of 10 to 350 mg KOH / g more preferably in the range of 20 to 300 mg KOH / g, more preferably 30 to 200 mg KOH / g, such as about 100 mg KOH / g.

18. The method according to any one of the previous claims, wherein the base cylinder (101) has an electrical resistance below 1000 kOhm preferably smaller than 200k Ohm, most preferably smaller than 40 kOhm, more preferably between 1 and 40 kOhm, preferably between 2 and 20 kOhm; and wherein the dispersing agent (d2) is chosen from an ethoxylated and / or propoxylated alcohol.

19. The method according to any one of the previous claims, wherein the carbon nanotube component (C3) comprises single-wall carbon nano tubes (SWCNTs).

20. The method according to any one of the previous claims, further comprising the step of:- grinding (S4) the conductive outer layer (LI, LI a) to obtain a grinded conductive outer layer (Lib) after the conductive composition (N) is applied (S3) on the outer surface of the base cylinder.

21. The method according to any one of the previous claims, wherein the conductive composition (N) is applied (S3) on the outer surface of the base cylinder such that the conductive outer layer is applied as having a thickness in the range of 0.2 to 20 mm.

22. The method according to any one of the previous claims, wherein the base cylinder (101) comprises at least one inner surface (103) opposite of the outer surface (102), wherein the method further comprises: creating (S5) at least one electrical connection (70), preferably an elongated electrical connection between the inner surface (103) of the base cylinder (101) and the outer surface (102) to establish an electrically conductive pathway (104) between said inner surface and outer surface (103, 102).

23. The method of the previous claim, whereby creating (S5) the at least one electrical connection comprises:- providing (S5’) a through hole (300) through the sleeve, preferably in a radial29 direction, and filling said through hole (300) with a conductive material (Ml, M2), preferably filling said through hole with a second conductive material (Ml) and subsequently filling with a first conductive material (Ml) which is more rigid that the second conductive material (M2);- preferably grinding the outer surface (103) after providing the through hole.

24. The method of to the previous claim, wherein the conductive material comprises a compressible material (M2) and / or an additional conductive material (Ml), preferably wherein the compressible material (M2) is arranged closer to an inner surface (113) of the base layer (101).

25. The method of to the previous claim, wherein the conductive material (Ml, M2) comprises a conductive resin (M2), preferably wherein said conductive resin includes carbon black, preferably in an amount of 1 to 8 wt%, such as 4 wt%, based on the total weight of the conductive resin.

26. A sleeve obtained according to any of the previous method claims.

27. A sleeve (100), such as a printing sleeve (100a) or such as an adapter (100b), said cylinder being configured to be mounted on an adapter or on a printing mandrel by aid of a gas cushion, wherein the sleeve (100) comprises: an outer layer (LI) for holding a printing plate (10) and / or for holding a printing sleeve (20); an optional intermediate structure (L3) comprising one or more optional intermediate layers; an inner layer (L2) with an inner surface (113) configured for being mounted on an adapter or for being mounted directly on a printing mandrel; wherein the outer layer (LI) comprises a polyurethane material (PU) and a carbon nanotube component (C3), wherein said carbon nanotube component (C3) is present within the outer layer (LI) in a weight concentration (c3) in the range of 0.05 to 2 wt% based on the total weight of the outer layer (LI).

28. The sleeve of the previous claim, wherein the carbon nanotube component (C3) is dispersed or blended in a crosslinked polyurethane network (PN) of the polyurethane material (PU), preferably wherein the30 polyurethane network is obtained by mixing a polyol component (Cl) and an isocyanate component (C2).

29. The sleeve according to any of the previous sleeve claims, wherein the carbon nanotube component (C3) is present within the outer layer (LI) in a weight concentration (c3) of at most 1.5 wt% outer layer (LI) and at least 0.1 wt% based on the total weight of the outer layer (LI).

30. The sleeve according to any of the previous sleeve claims, wherein the carbon nanotube component (C3) comprises single wall carbon nano tubes (SWCNTs), preferably wherein said nano tubes have an average length of 5 to 30 micrometers (um) and / or an average diameter of 1 to 2 nanometers (nm).

31. The sleeve according to any of the previous sleeve claims, wherein the outer layer (LI) has a resistance of at most 1000 kOhm, preferably at most 30 kOhm, such as between 1 and 30 kOhm.

32. The sleeve according to any of the previous sleeve claims, wherein the inner layer (L2) and optionally the intermediate structure (L3), have a resistance below 1000 kOhm preferably smaller than 200k Ohm, most preferably smaller than 40 kOhm, in particular between 1 to 40 kOhm, preferably between 2 and 20 kOhm, such as about 10 kOhm.

33. The sleeve according to any of the previous sleeve claims, wherein the outer layer (LI) has a resistance between 1 and 30 kOhm; and wherein the inner layer (L2) and optionally the intermediate structure (L3), have a resistance between 2 and 20 kOhm.

34. The sleeve according to any of the previous sleeve claims, wherein the intermediate structure (L3) and / or the inner layer (L2) comprises carbon black.

35. The sleeve according to any of the previous sleeve claims, wherein the carbon nanotube component (C3) comprises single wall carbon nano tubes (SWCNTs) having an average length of 5 to 30 micrometers (um) and wherein the outer layer (LI) has a resistance of at most 30 kOhm.3136. The sleeve according to any of the previous sleeve claims, wherein the intermediate structure (L3) and / or the inner layer (L2) comprise a fiber reinforced layer, preferably a fiber reinforced layer which comprises carbon fibers or particles.

37. The sleeve according to any of the previous sleeve claims, wherein the inner layer (L2) and / or a layer within the intermediate structure (L3) is configured to expand upon exposure with a gas cushion to mount the sleeve on an adapter or mandrel and to contract without such exposure, preferably wherein the inner layer (L2) is configured to establish an electrical connection with the adapter or the printing mandrel when installed thereon.

38. The sleeve according to any of the previous sleeve claims, wherein the sleeve further comprises at least one electrical connection (70), preferably an elongated electrical connection, extending through the sleeve to electrically connect said inner layer (L2) and said outer layer (LI), preferably the elongated electrical connection extends in a radial direction.

39. The sleeve according to any of the previous sleeve claims, wherein a through-hole (300) extends through the sleeve from the outer layer of the sleeve to the inner layer of the sleeve and wherein the at least one electrical connection substantially fills up the through-hole to establish an electrical pathway between the outer layer and the inner layer and / or the inner surface (113) of the sleeve (100).

40. The sleeve of any of the previous three claims, wherein the at least one electrical connection (70) comprises a compressible material (M2), such as conductive foam, preferably a conductive polyethylene foam and / or comprises a conductive resin (Ml) or conductive glue (Ml).

41. The sleeve of any of the previous four claims, wherein the at least one electrical connection (70) comprises a first conductive material (Ml) and a second conductive material (M2), wherein the first conductive material (Ml) is more rigid than the second conductive material (M2) and wherein the second conductive material (M2) is compressible and arranged closer to and / or within the inner layer (L2).

42. The sleeve according to any of the previous sleeve claims,32 wherein the inner layer (L2) comprises carbon fibers and / or carbon particles, such as carbon black particles and / or carbon nanotubes.

43. The sleeve according to any of the previous sleeve claims, wherein both the inner layer (L2) and outer layer (L2) are electrically conductive and wherein said inner and outer layer are connected to each other via an electrical connection (70).

44. The sleeve according to any of the previous sleeve claims, wherein the at least one electrical connection (70) is an elongated element (70) extending in a radial direction through at least a portion of inner layer (L2) and / or outer layer (L2).

45. The sleeve of the previous claim, wherein the at least one electrical connection (70) comprises a first and a second electrical connection, wherein said first and second electrical connection arranged at a distance from each other.

46. The sleeve according to any of the previous sleeve claims, wherein the sleeve comprises a through hole (300) which extends through the sleeve and which is filled with a conductive material (Ml, M2), preferably filled with a first conductive material (Ml) and a second conductive material (M2) wherein the first conductive material is more rigid than the second conductive material.

47. The sleeve of the previous claim, wherein the second conductive material (M2) is compressible, such as a compressible foam material, and wherein the first conductive material (Ml) is more rigid than the second conductive material (M2), preferably the first conductive material (Ml) is a conductive resin, such as conductive polyester based resin comprising conductive particles.

48. The sleeve of any of the previous two claims, wherein the second conductive material (M2) is arranged closer to the inner layer (L2).

49. The sleeve of any of the previous two claims, wherein the second conductive material (M2) is attached to the inner layer (L2).

50. The sleeve according to any of the previous sleeve claims,33 wherein the sleeve comprises a through hole (300) filled with a conductive resin (Ml), preferably said conductive resin includes carbon black, preferably in an amount of 1 to 8 wt%, based on the total weight of the conductive resin (Ml); and / or wherein the through hole (300) is filled with a compressible material (M2).

51. The sleeve according of the previous claim, wherein the through hole (300) is filled with both the conductive resin (Ml) and the compressible material (M2) and wherein the compressible material (M2) is arranged closer to the longitudinal axis (lax) of the sleeve.

52. Use of a sleeve according to any of the previous sleeve claims, in a printing device, preferably flexographic printing device.

53. An printing assembly (20a), the assembly comprising the sleeve (100, 100a) according to any of the previous sleeve claims wherein the sleeve (100a) is mounted directly on printing mandrel (40) and / or indirectly via an adapter (100b) that is arranged between the printing mandrel (40) and the sleeve (100a).

54. A printing assembly (20b), the assembly comprising the sleeve (100, 100b) according to any of the previous sleeve claims as an adapter (100b), wherein the adapter is arranged between a printing sleeve (100’) and a printing mandrel (40).

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