Roller cylinder having a cross-linked adhesion layer made of a cross-linked rubber for adhering a functional layer to the roller cylinder core

Abstract

The invention relates to a roller cylinder precursor having a roller cylinder core, and having an adhesion layer made of a rubber composition arranged on the surface of the roller cylinder core and a functional layer arranged on the adhesion layer, as well as a roller cylinder and a method for the production thereof, wherein the roller cylinder can be obtained by temperature treatment of a roller cylinder precursor according to the invention.

Description

[0001] Roller cylinder with a cross-linked adhesive layer made of cross-linked rubber for the adhesion of a functional layer to the roller cylinder core.

[0002] The present invention relates to a roller cylinder precursor according to one of claims 1 to 11, comprising a roller cylinder core with an adhesion layer arranged on its surface made of an uncrosslinked rubber composition and a functional layer arranged on the adhesion layer, as well as a roller cylinder according to one of claims 12 and 13 and a method for producing the roller cylinder according to claim 14, wherein the roller cylinder is obtainable by heat treatment of a roller cylinder precursor according to the invention.

[0003] In the production of rubber-metal bonds, such as when applying functional coatings to roller cores, the challenge lies in bonding the differing material properties of the roller core and the functional coating with sufficient adhesion, as required, for example, in printing, laminating, painting, pressure, or conveying rollers. The production of rubber-metal bonds is complex and involves several steps. For rubber-coated rollers, for instance, good adhesion between the rubber and the roller core (made of metal or plastic) is crucial for functionality and service life. First, the metal surface is cleaned, and then any existing oxide layer is removed by sandblasting. In a two-layer process, a primer is then applied, followed in a second step by the adhesion promoter to the sandblasted surface.An unvulcanized rubber compound is then applied to the surface of the metal. The rubber-metal bond is formed during the vulcanization of the rubber compound. For plastic roller cores, the core is typically cleaned with an organic solvent and then—similar to metal roller cores—a two-layer process is used to apply an adhesion promoter and a primer. An unvulcanized rubber compound is then applied and vulcanized. Conventional adhesion promoters often contain organic solvents and cause problems due to emissions. Therefore, the production of rollers with rubber compounds as functional mixtures is a challenging task in terms of the manufacturing process, the associated complex quality control, the high costs, and the environmental impact.

[0004] The object of the present invention is therefore to produce an adhesion promoter between the functional layer and the roller core, which makes the production of a functional roller simpler, more cost-effective, more economical and more environmentally friendly.

[0005] Therefore, the present invention provides a roller cylinder precursor with a roller cylinder core having an adhesion layer arranged on its surface and a functional layer arranged on the adhesion layer, wherein the adhesion layer is an uncrosslinked rubber composition containing the following components:

[0006] (A) a non-crosslinked rubber,

[0007] (B) a networking component,

[0008] (C1) a zinc salt of an alkenecarboxylic acid, and / or

[0009] (C2) both an aromatic compound with at least one OH group or at least one alkylcarbonyloxy group and an aromatic or aliphatic formaldehyde resin; and wherein the functional layer comprises a crosslinkable or crosslinked rubber.

[0010] The use of an adhesive layer between the roller core and the functional layer ensures good adhesion to both. This allows for the simple application of the functional layer, tailored to the specific application, to the roller core. Furthermore, the two-layer process, which requires the application of a primer followed by an adhesion promoter, can be omitted. Since no adhesion promoter is necessary, there is also no need for organic solvents, which would cause emission problems. This multitude of advantages results in a significantly simplified manufacturing process that is cost-effective, economical, and environmentally friendly.

[0011] Furthermore, the functional layer can consist of uncrosslinked rubber and, after application of the adhesion layer and the functional layer to the roller core, be vulcanized together with the adhesion layer. The joint vulcanization of the adhesion layer and the functional layer enables crosslinking at the interface between the two layers, which significantly increases the adhesion between them.

[0012] According to the invention, it is preferred that the adhesion mixture (whether uncrosslinked or subsequently crosslinked) has a different composition than the functional mixture.

[0013] In a further embodiment of the roller cylinder precursor according to the invention, the surface of the roller cylinder core can comprise a metal, a polyamide, or a carbon fiber or glass fiber reinforced plastic. In particular, it is preferred that the surface of the roller cylinder core, preferably the entire roller cylinder core, consists of the aforementioned materials.

[0014] The uncrosslinked rubber in the adhesion mixture can be any type of rubber. The non-crosslinked rubber of the adhesion mixture is particularly preferred if it is based on ethylene propylene diene monomer rubber (EPDM), nitrile butadiene rubber (NBR), natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), isobutene isoprene rubber (HR), styrene butadiene rubber (SBR), ethylene acrylate rubber (AEM), ethylene vinyl acetate rubber (EVA or EVM), epichlorohydrin rubber (ECO), fluorocarbon rubber (FKM), hydrogenated acrylonitrile butadiene rubber (H-NBR), carboxylated nitrile butadiene rubber (X-NBR), ethylene propylene rubber (EPM) or mixtures thereof.

[0015] The rubber is present in the uncrosslinked rubber composition in an amount in the range of 25 wt.% to 70 wt.%, more preferably in the range of 32 wt.% to 60 wt.% and most preferably in the range of 35 wt.% to 50 wt.%.

[0016] Natural rubber (NR) is a homopolymer of isoprene, exhibiting almost exclusively 1,4-cis linkages. Its weight-average molecular weight (Mw) typically ranges from 500,000 to 2,000,000 g / mol. Butadiene rubber (BR) is a synthetic rubber based on 1,3-butadiene, usually obtained by coordinate chain polymerization using stereospecific Ziegler-Natta catalysts, and contains a high proportion of 1,4-cis units.

[0017] Isoprene rubber (IR) is the synthetically produced variant of natural rubber. It differs from natural rubber primarily in its somewhat lower chemical purity. This is because the catalysts used for polymerization are less effective than naturally occurring enzymes. The purity of natural rubber is preferably greater than 99.9%, whereas that of synthetically produced IR – depending on the catalyst used – only reaches approximately 92% to 97%.

[0018] Butyl rubber (HR) is also called isobutene-isoprene rubber. From the group of elastomers, HR is classified as a synthetic rubber. HR is a copolymer of isobutene and isoprene, with isobutene preferably present in an amount of 95 to 99 mol% and isoprene in an amount of 1 to 5 mol%, based on the total molecular weight.

[0019] Styrene-butadiene rubber (SBR) is a copolymer of styrene and 1,3-butadiene, wherein the styrene content should typically be below 25% (relative to the butadiene content), since at higher styrene contents the rubber assumes thermoplastic properties. Examples of SBRs to be used according to the invention are known and commercially available under the trade names Kralex® and Europrene® SBR.

[0020] Nitrile butadiene rubber (NBR) is a copolymer of acrylonitrile (ACN) and 1,3-butadiene. Due to their double bonds, NBRs can be crosslinked using both peroxides and sulfur. Examples of NBRs used according to the invention are known and commercially available under the trade names Perbunan®, Krynac®, Buna® N, or Europrene® N.

[0021] Hydrogenated nitrile butadiene rubber (H-NBR) is obtained by hydrogenating the double bonds contained in NBR. H-NBR can be crosslinked by peroxides. Examples of H-NBR used according to the invention are known and commercially available under the trade names Therban® (Lanxess) and Therban® AT (Lanxess).

[0022] X-NBR is a nitrile butadiene rubber whose butadiene segment contains at least some carboxyl groups. Like H-NBR, X-NBR can also be crosslinked by peroxides.

[0023] Ethylene propylene diene monomer (EPDM) rubber is a terpolymeric, synthetic rubber. EPDM belongs to the group of statistical copolymers with a saturated polymer backbone and double bonds in the side chain, which can be used to crosslink the EPDM rubber in the rubber compound using the vulcanization system. EPDM is preferably produced using metallocene or Ziegler-Natta catalysts based on vanadium compounds and aluminum alkyl chlorides. Unconjugated dienes are used as the dienes, of which only one double bond participates in polymer chain formation, leaving additional double bonds outside the immediate backbone and allowing them to be crosslinked with sulfur or peroxides. Dicyclopentadiene (DCP), 1,4-hexadiene, or ethylidene norbornene (ENB, IUPAC: 5-ethylidene-2-norbornene) are used as the diene component. The services differ in terms of networking speed.DCP has the lowest reactivity, ENB the highest. EPDM can be crosslinked with peroxides or sulfur, with sulfur preferably being used as the crosslinking agent.

[0024] Ethylene-propylene rubber (EPM) is a statistical copolymer of ethylene and propylene, typically obtained by polymerization of ethylene and propylene in the presence of Ziegler-Natta or metallocene catalysts. The ratio of ethylene and propylene monomers and the choice of polymerization conditions yield various EPM polymers with sometimes significantly different crystallinities, ranging from amorphous to semi-crystalline.

[0025] Ethylene-vinyl acetate copolymers (EVM) are copolymers of ethylene and vinyl acetate. EVMs are commercially available, for example, under the trade names Levapren® or Levamelt® from Lanxess Deutschland GmbH. Suitable ethylene-vinyl acetate copolymers are Levamelt® 400 (40 ± 1.5% by weight of vinyl acetate), Levamelt® 450 (45 ± 1.5% by weight of vinyl acetate), Levamelt® 452 (45 ± 1.5% by weight of vinyl acetate), Levamelt® 456 (45 ± 1.5% by weight of vinyl acetate), Levamelt® 500 (50 ± 1.5% by weight of vinyl acetate), Levamelt® 600 (60 ± 1.5% by weight of vinyl acetate), Levamelt® 700 (70 ± 1.5% by weight of vinyl acetate), Levamelt® 800 (80 ± 2% by weight of vinyl acetate) and Levamelt® 900 (90 ± 2% by weight of vinyl acetate), or the corresponding ones Levapren® types. In the compositions according to the invention, an ethylene-vinyl acetate copolymer can be used as a component, but it is also possible to use mixtures of two or more ethylene-vinyl acetate copolymers.

[0026] Ethylene acrylate rubber (AEM) is a copolymer of ethylene and methyl acrylate. It is commercially available, for example, as Vamac® from DuPont.

[0027] Epichlorohydrin rubber (ECO) is produced by ring-opening polymerization of epichlorohydrin, optionally in the presence of other comonomers. Commercially, epichlorohydrin rubber is available, for example, under the trade name HydrinECO® from Zeon.

[0028] According to the invention, for example, a semi-crystalline, oil-reinforced EPDM, e.g., one with the trade name Keltan 3973 from Arlanxeo, an amorphous EPDM with a medium EN B content, e.g., one with the trade name Keltan 2650 from Arlanxeo, a highly crystalline EPDM with a medium ENB content, e.g., with the trade name Keltan 8570 C from Arlanxeo, or an acrylonitrile / butadiene copolymer, e.g., with the trade name Europrene N 19.45GRN from Eni Chem, can be used.

[0029] In a further embodiment of the roller cylinder precursor according to the invention, it is preferred that the crosslinking component is selected from the group consisting of a sulfur-containing crosslinking agent, a peroxide-containing crosslinking agent, and a combination of a sulfur-containing crosslinking agent and a peroxide-containing crosslinking agent. The sulfur-containing crosslinking agent is preferably selected when the functional layer also contains a sulfur-curable or -crosslinked rubber. The peroxide-containing crosslinking agent is selected according to the invention when the functional layer contains a peroxide-curable or -crosslinked rubber. The reason for this is that rubbers that are crosslinked or crosslinked with the same crosslinking agent exhibit better adhesion to one another.

[0030] Suitable peroxide-containing crosslinking agents are known to experts. Examples include organic peroxides, e.g., alkyl and aryl peroxides, alkyl peric acid esters, aryl peric acid esters, diacyl peroxides, polyvalent peroxides such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 (e.g., Trigonox® 145-E85 or Trigonox® 145-45 B), di-tert-butyl peroxide (e.g., Trigonox® B), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne (e.g., Trigonox® 101), tert-butylcumyl peroxide (e.g., Trigonox® T), di-tert-butylperoxyisopropyl(benzene) (e.g., Perkadox® 14-40), dicumyl peroxide (e.g., Perkadox® BC40 or Peroxan® DC-40 PK), benzoyl peroxide, 2,2-bis(tert-butylperoxy)diisopropylbenzene (e.g., Volcup® 40 AE), 3,2,5-trimethyl-2,5-di(benzoylperoxy)hexane, di-tert-butyl-3,3,5-trimethylcyclohexylidene diperoxide (e.g., Trigonox® 29 / 40B PD-E), 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, and 3,3,5,7,7-pentamethyl-1,2,4-trioxepane (e.g., Trigonox® 311). Dicumyl peroxide, e.g., [unclear text], is preferably used as a peroxide-containing crosslinking agent.with the trade name Peroxan® DC-40 PK from Pergan, or di-tert-butyl- 3,3,5-trimethylcyclohexylidene diperoxide, e.g. with the trade name Trigonox® 29 / 40B PD-E from Akzonobel.

[0031] According to the invention, sulfur is preferably used as a crosslinking agent, preferably on a carrier material such as an elastomer. Rhenogran® S 80 from RheinChemie, which has sulfur supported on an elastomer, can be mentioned as an example.

[0032] In addition to the actual crosslinking agent, the rubber composition can contain other components such as cover crosslinkers, crosslinking accelerators or crosslinking inhibitors. In the event that the rubber composition contains at least one peroxide-containing crosslinking agent, suitable cover crosslinkers include, for example, triallyl cyanocyanurate (TAIC) (e.g., DIAK™-7 from DuPont), N,N'-m-phenylenedimaleimide (e.g., HVA™-2® from DuPont Dow), triallyl cyanurate (TAC), liquid polybutadiene (e.g., Ricon® D153 from Ricon Resins), p-quinodixone, p,p'-dibenzoylquinodioxine, N-methyl-N,N-dinitrosoaniline, nitrobenzene, diphenylguanidine, trimethylolpropane-N,N'-m-phenylenedimaleimide, N-methyl-N,N'-m-phenylenedimaleimide, divinylbenzene, and polyfunctional methacrylate monomers such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate. rimethylolpropanetrimethacrylate and allyl methacrylate, as well as polyfunctional vinyl monomers such as vinyl butyrate and vinyl stearate.Preferred cover-curing agents for peroxide-containing crosslinking agents are trimethylolpropane trimethacrylate (TRIM), triallyl isocyanurate (TAIC), N,N'-m-phenylenedimaleimide, triallyl cyanurate (TAC), and liquid polybutadiene. Trimethylolpropane trimethacrylate (TRIM) is particularly preferred as a cover-curing agent when a peroxide-containing crosslinking agent is present.

[0033] Since some of the aforementioned crosslinking agents, and sulfur in particular, can be relatively unreactive on its own, accelerators can be used in the rubber composition to make crosslinking times more economical. Furthermore, the use of accelerators allows crosslinking to be carried out at significantly lower temperatures, which in turn results in less heat-related material damage to the crosslinked elastomer and improved aging resistance.

[0034] The choice of a suitable accelerator depends on the crosslinking agent used and the rubber to be crosslinked. Those skilled in the art generally know which crosslinking agents synergize with which accelerators and for which rubbers they are suitable. Accelerators are primarily used in crosslinking with sulfur (vulcanization), but suitable accelerators can also be used in crosslinking with peroxides.

[0035] Suitable accelerators include, for example, sulfenamides, thiazoles, thiurams, dithiocarbamates, guanidines, thioureas, aldehyde-amine condensates, amines, xanthates, dithiophosphates, or triazines. Such compounds are generally known to those skilled in the art and are listed, for example, in "Engels H., Weidenhaupt H., Pieroth M., Hofmann W., Meting K.-H., Mergenhagen T., et al. Rubber, 9. Chemicals and Additives; Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag GmbH & Co; 2011", to which full reference is expressly made here.

[0036] Sulfenamides are among the most commonly used accelerators and are obtained by reacting 2-mercaptobenzothiazole with a primary or secondary amine under oxidative conditions. Suitable sulfenamides include, for example, N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazylsulfenamide (TBBS), 2-morpholinothiobenzothiazole (MBS), N,N-dicyclo-2-benzothiazylsulfenamide (DCBS), or N-oxydiethylenethiocarbamyl-N'-oxydiethylenesulfenamide (OTOS).

[0037] The thiazoles typically used in rubber crosslinking are 2-mercaptobenzothiazole and its derivatives. The most common thiazoles are 2-mercaptobenzothiazole (MBT), dibenzothiazole disulfide (MBTS), and the zinc salt of 2-mercaptobenzothiazole (ZMBT).

[0038] Among the class of substances known as thiurams, tetramethylthiuram disulfide (TMTD), tetramethylthiuram monosulfide (TMTM), tetraethylthiuram disulfide (TETD), dipentamethylenethiuram tetrasulfide (DPTT) and tetrabenzylthiuram disulfide (TBzTD) are primarily used for crosslinking rubber.

[0039] Dithiocarbamates are among the most powerful accelerators in sulfur-based vulcanization. The best-known representatives of this class of substances include zinc N-diethyldithiocarbamate (ZDEC), zinc N-dimethyldithiocarbamate (ZDMC), zinc N-dibutyldithiocarbamate (ZDBC), zinc ethylphenyldithiocarbamate (ZEPC), zinc pentamethylenedithiocarbamate (Z5MC), and zinc dibenzyldithiocarbamate (ZBEC). In addition to the zinc salts mentioned above, the corresponding piperidinium, copper, alkali, or alkaline earth salts can also be used, for example.

[0040] Guanidine-based accelerators are among the weaker accelerators, which is why they are often used only in combination with other accelerators such as sulfenamides and / or thiazoles. The best-known guanidine-based vulcanization accelerators include N,N'-diphenylguanidine (DPG), N,N'-di-o-tolylguanidine, and 1-(o-tolyl)-biguanide (OTBG).

[0041] The thioureas predominantly used are ethylenethiourea (ETU; 2-mercaptoimidazoline) and diethylenethiourea (DETU), although the use of thioureas is steadily declining due to their teratogenic properties.

[0042] Aldehyde-amine condensates exhibit very different accelerator properties depending on the condensed amine. Common representatives of this class of substances include hexamethylenetetramine (HMTA), tricrotonylidenetetramine, and the condensation products of butyraldehyde and aniline.

[0043] Amines are often used primarily as secondary accelerators in combination with other accelerators. Cyclohexylethylamine, as well as diethanolamines and triethanolamines, are examples of industrially used amine-based accelerators.

[0044] Dithiophosphates are primarily used in the crosslinking of EPDM rubber with sulfur in combination with thiazoles, sulfenamides, or dithiocarbamates, but can also be used for other rubbers. The most common dithiophosphates include zinc dialkyldithiophosphates (ZDTP), copper dialkyldithiophosphates, and zinc amine dithiophosphates.

[0045] Xanthates are salts of O-alkyl esters with dithiocarbonic acid and include, for example, sodium isopropyl xanthate, zinc isopropyl xanthate and zinc dibutyl xanthate.

[0046] In addition to the accelerators mentioned above, there are other accelerators known to those skilled in the art, which are often referred to as activators depending on the source. Such accelerators are preferably used in crosslinking to increase the activity of another accelerator.

[0047] Inorganic compounds with activating properties suitable as accelerators include, in particular, SnCl₂, ZnCl₂, ZnO, MgO, CaO, PbO, and PbsO₄, with SnCh₂, ZnCh₂, and ZnO being preferred and ZnO being the most preferred. In addition to the aforementioned inorganic compounds, fatty acids also possess activating properties and are therefore frequently used in combination with other accelerators. Besides their activating properties, fatty acids can improve the processability and distribution of fillers in the rubber composition according to the invention. Among the most common representatives of this class of substances are, in particular, stearic acid and zinc stearate.

[0048] According to the invention, it is particularly preferred that the rubber composition comprises both a sulfur-containing crosslinking agent and a peroxide-containing crosslinking agent as a crosslinking component. This has the advantage that the same adhesive layer can be used for all conceivable functional layers, i.e., firstly for functional layers that are sulfur-crosslinked or crosslinkable, and secondly for functional layers that are peroxide-crosslinked or crosslinkable, since an adhesive layer with both crosslinking agents offers good adhesion for all conceivable functional layers.

[0049] If the rubber composition contains a peroxide as a crosslinking agent, the weight ratio of rubber to peroxide is in the range of 100:15 to 100:0.5, more preferably in the range of 100:10 to 100:2, and most preferably in the range of 100:8 to 100:4. If the rubber composition contains sulfur as a crosslinking agent, the weight ratio of rubber to sulfur is in the range of 100:5 to 100:0.1, more preferably in the range of 100:2 to 100:0.2, and most preferably in the range of 100:1 to 100:0.3.

[0050] In a further embodiment of the roller cylinder precursor according to the invention, the rubber composition preferably comprises both component (C1) and component (C2). Component (C1) ensures good adhesion to metal, in particular aluminum or stainless steel, while component (C2) ensures good adhesion to a polyamide or a carbon fiber or glass fiber reinforced plastic.

[0051] Therefore, according to the invention, it is preferred that, in the case where the surface of the roller cylinder core has metal, the rubber composition contains component (C1).

[0052] Furthermore, according to the invention, it is preferred that in the case where the surface of the roller cylinder core has a polyamide or a carbon fiber or glass fiber reinforced plastic, the rubber composition contains the component (O2).

[0053] If the rubber composition contains the two components (C1) and (O2), it can be used for surfaces of roller cylinder cores that have a metal as well as for surfaces of roller cylinder cores that have a polyamide or a carbon fiber or glass fiber reinforced plastic.

[0054] Component (01) is a zinc salt of an alkenecarboxylic acid, preferably a C2-10 alkenecarboxylic acid, more preferably a C2-5 alkenecarboxylic acid, and most preferably an ethenecarboxylic acid; i.e., component (01) is preferably zinc diacrylate. Such a compound ensures adhesion to the surfaces of metal cylinder cores. The zinc ions provide a bond to the metal, whereas the alkenecarboxylic acid ensures a bond to the rubber composition, since the double bond of the alkenecarboxylic acid participates in the crosslinking of the rubber composition. For example, zinc diacrylate can be used according to the invention under the trade name Dymalink® 633 G from Cray Valley.

[0055] Component (02) comprises both an aromatic compound with at least one OH group or at least one alkylcarbonyloxy group and an aromatic or aliphatic formaldehyde resin.

[0056] In the aromatic compound with at least one OH group or at least one alkylcarbonyloxy group, the aromatic compound is preferably one with 6 to 12 aromatic carbon atoms, preferably phenol or a phenol derivative, or resorcinol (1,3-dihydroxybenzene) or a resorcinol derivative. The alkylcarbonyloxy group is preferably a C1,3-alkylcarbonyloxy group, more preferably a C1,3-alkylcarbonyloxy group, and most preferably an acetoxy group. The aromatic compound 1,3-diacetoxybenzene, as available, for example, under the trade name Cohedur® RK from RheinChemie, is particularly preferred.

[0057] The aromatic or aliphatic formaldehyde resin is preferably one produced by the acid-catalyzed reaction of an aromatic compound or an aliphatic alcohol with formaldehyde. More preferably, the formaldehyde resin is an aromatic formaldehyde resin, such as toluene-formaldehyde resin or xylene-formaldehyde resin, preferably a xylene-formaldehyde resin. A suitable xylene-formaldehyde resin is available, for example, under the trade name Deotack 70 DL from DOG (Deutsche Ölfabrik Gesellschaft für chemische Erzeugnisse mbH & Co. KG). It was found that the reaction product of the two components of component (C2) increases the affinity of the adhesion layer to cylinder cores whose surface is made of a polyamide or a carbon fiber or glass fiber reinforced plastic.

[0058] If component (01), i.e., the zinc salt of the alkenecarboxylic acid, is present in the rubber composition, then the ratio of uncrosslinked rubber to component (C1) is in the range of 100:5 to 100:50, more preferably in the range of 100:7 to 100:45, and most preferably in the range of 100:10 to 100:40. Too low an amount does not ensure sufficient adhesion to metal surfaces, while too high an amount is detrimental to the desired mechanical properties.

[0059] If component (C2) is present in the rubber composition, then the ratio of uncrosslinked rubber to the aromatic compound with at least one OH group or at least one alkylcarbonyloxy group is in the range of 100:0.1 to 100:10, more preferably in the range of 100:0.5 to 100:8, and most preferably in the range of 100:1 to 100:5. In this case, the ratio of uncrosslinked rubber to the formaldehyde resin is in the range of 100:0.5 to 100:10, more preferably in the range of 100:1 to 100:7, and most preferably in the range of 100:2 to 100:5. An insufficient amount of either of the aforementioned components does not ensure adequate adhesion to roller cores with a plastic surface, while an excessive amount is detrimental to the desired mechanical properties.

[0060] Furthermore, the uncrosslinked rubber compound usable according to the invention can contain adhesion improvers, such as an alkali or alkaline earth oxide or organic silanes. Magnesium oxide is preferably used, which is available, for example, under the trade names Maglite® DE or Luvomag® 280 from Lehmann & Voss. Organic silanes that have an unsaturated C-C bond, such as a vinyl group, can be used. An example of this is vinyltriethoxysilane, which is available, for example, under the trade name Dynasylan® 6498 from Evonik.

[0061] The non-crosslinked rubber compound usable according to the invention may also contain one or more of the following substances: plasticizers, fillers, tackifiers, color pigments, processing aids, anti-aging agents and stabilizers.

[0062] Suitable plasticizers are generally known to those skilled in the art. Suitable plasticizers for polar elastomers (EVM, NBR, H-NBR, AEM, etc.) include, for example, ester plasticizers such as phthalic acid esters, for instance dioctyl phthalate, diisooctyl phthalate, dinonyl phthalate, or diisodecyl phthalate; aliphatic esters such as dioctyl esters, diethylhexyl adipate, or dioctyl sebacic acid ester; phosphoric acid esters such as tricresyl phosphoric acid esters, diphenylcresylic acid esters, or trioctyl phosphate; and polyesters such as polyphthalic acid esters, polyadepic acid esters, or polyester ethers.

[0063] Suitable plasticizers for nonpolar elastomers (e.g., NR, IR, BR, PNR, HR, EPM, EPDM, SBR) include technical or medical mineral or white oils, virgin oils such as soybean or rapeseed oil, and alkylsulfonyl esters, particularly alkylsulfonylphenyl esters, wherein the alkyl substituents are linear and / or branched alkyl chains with >5 carbon atoms. Also suitable are di- or tri-alkyl esters of melitic acid, wherein the alkyl substituents preferably are linear and / or branched alkyl chains with >4 carbon atoms. Furthermore, alkyl esters of di-, tri-, and higher polycarboxylic acids, wherein the alkyl substituents are preferably linear and / or branched alkyl chains, are also used as plasticizers. Examples include adipic acid di-2-ethylhexyl ester and tributyl O-acetyl citrate. Furthermore, carboxylic acid esters of mono- and / or polyalkylene glycols can also be used as plasticizers, such as ethylene glycol adipate.

[0064] Suitable plasticizers can also be mixtures of the described substance classes.

[0065] Preferred plasticizers according to the invention are organic acid esters, such as adipic acid esters, and organic or inorganic oils, e.g., paraffin oil. According to the invention, diethylhexyl adipate, such as that available under the trade name DIOCTYLADIPATE DOA from Krahn Chemie, can be used as an adipic acid ester. A paraffin oil suitable for use according to the invention is available under the trade name SHELL CATENEX H 779 from Shell Chemie. Suitable fillers include, for example, carbon black, chalk (calcium carbonate), kaolin, kaolinite, and calcined kaolin (e.g.,...Pole-star® 200 P), silicon dioxide, silica, quartz, talc (magnesium silicate), aluminum oxide, aluminum oxide hydrate, aluminum trihydrate, aluminum silicate, calcium oxide, alkali or alkaline earth carbonates, such as sodium carbonate or calcium carbonate, calcium silicate, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium silicate, barium sulfate, zinc carbonate, titanium dioxide, silanized kaolins, silanized silica, coated chalk, treated kaolins, pyrogenic silica, hydrophobized pyrogenic silica (e.g. Aerosil® 972), synthetic amorphous precipitated silica (silica), nanoscale fillers such as carbon nanofibrils, platelet-shaped nanoparticles or nanoscale silicon dioxide hydrates and minerals. In particular, according to the invention a white filler, such as silicon dioxide, can be used, as is available, for example, under the trade name Ultrasil® VN 3 from Evonik.Furthermore, according to the invention, a conductive filler, such as carbon black, can be used when it is desirable to avoid static charges. Such static charges can occur, for example, when printing on films or paper and lead to arcing, which in turn can result in fires or injuries. A suitable conductive carbon black is available, for example, under the trade name Ensaco 250 Granular from Imerys.

[0066] Resins such as petroleum resin, which is available, for example, under the trade name C5 BT-1200 from the company Bitoner, can be used as adhesives according to the invention.

[0067] Any color pigment that does not adversely affect the desired properties of the rubber composition can be used as a color pigment. Suitable pigments and dyes include, for example, titanium dioxide, lithophone, iron oxide, ultramarine blue, and antimony sulfite. A white color pigment that can be used according to the invention is, for example, titanium(IV) oxide, which is available, for instance, under the trade name KA 100 from Ter Hell & Co.

[0068] Furthermore, processing aids can be used in the uncrosslinked rubber composition usable according to the invention. Processing aids include, for example, demolding agents, release agents, antifoaming agents, foaming aids, dispersing agents, blowing agents, anti-blocking agents and viscosity modifiers, and are generally known to those skilled in the art.

[0069] For example, phenylanilines such as 4-(1-methyl-1-phenylethyl)-N-[4-(1-methyl-1-phenylethyl)phenyl]aniline, which is available under the trade name Naugard® 445 from Lehmann & Voss, can be used as anti-aging agents.

[0070] Examples of stabilizers include polycarbodiimides (e.g., Rhenogran®, PCD-50), substituted bisphenols, dihydroquinolines, diphenylamines, phenylnaphthylamines, paraphenylenediamines, benzimidazoles, p-dicumyldiphenylamine (e.g., Naugard® 445), styrenized diphenylamine (e.g., Vulcanox® DDA), zinc salt of methylmercaptobenzimidazole (e.g., Vulcanox® ZMB2), polymerized 1,2-dihydro-2,2,4-trimethylquinoline (e.g., Vulcanox® HS), thiodiethylene bis(3,5-di-tert-butyl-4-hydroxy)hydrocinamate, and thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., Irganox® 1035).

[0071] According to the invention, any crosslinkable or crosslinked rubber known in the prior art for use on roller cylinders can be used as the functional layer. For example, the rubber of the functional layer can be one that is crosslinkable or crosslinked with sulfur or a peroxide. Particularly preferred is a sulfur- or peroxide-crosslinkable or -crosslinked rubber of the functional layer. The rubber of the functional mixture is particularly preferred to be a rubber based on ethylene propylene diene monomer rubber (EPDM), nitrile butadiene rubber (NBR), natural rubber (NR), styrene butadiene rubber (SBR), ethylene acrylate rubber (AEM), ethylene vinyl acetate rubber (EVA), fluororubber (FKM), hydrogenated acrylonitrile butadiene rubber (HNBR), carboxylated nitrile butadiene rubber (XNBR), ethylene propylene rubber (EPM) or mixtures thereof.

[0072] According to the invention, it is also preferred that, in the case where the functional layer is a sulfur-crosslinkable or crosslinked rubber, the crosslinking component (B) comprises a sulfur-containing crosslinking agent.

[0073] Likewise, it is preferred according to the invention that, in the case where the functional layer is a peroxide-crosslinkable or crosslinked rubber, the crosslinking component (B) comprises a peroxide-containing crosslinking agent.

[0074] In a further embodiment of the present invention, it is preferred that the adhesion mixture comprises both a sulfur-containing crosslinking agent and a peroxide-containing crosslinking agent in the crosslinking component, as well as both components (C1) and (C2). In this way, the same adhesion layer can be used universally for all the aforementioned roller cylinder cores and all the aforementioned functional layers.

[0075] Furthermore, according to the invention, it is preferred that the adhesive layer is applied directly to the surface of the roller cylinder core. It is also preferred that the functional layer is applied directly to the adhesive layer.

[0076] In a further embodiment of the present invention, it is preferred that the adhesion layer does not have a reinforcing fiber, such as a fabric material or a strengthening agent, in particular that the roller cylinder precursor according to the invention does not have layers with a reinforcing fiber.

[0077] In a further embodiment of the present invention, it is preferred that the roller cylinder precursor according to the invention has no further layers with a fabric material or a reinforcing agent in addition to the adhesion layer and the functional layer, in particular that the roller cylinder precursor according to the invention has no further layers in addition to the adhesion layer and the functional layer.

[0078] The uncrosslinked rubber composition used in the roller cylinder precursor according to the invention is preferably produced by mixing all its components together. The mixture of components of the adhesion layer is preferably compounded in a rubber kneader in two stages. Preferably, in the first stage, all components except the crosslinking agent and the aromatic compound with at least one OH group or at least one alkylcarbonyloxy group (if used) are mixed in the rubber kneader until the mass temperature reaches 120°C to 140°C, preferably approximately 130°C. The mixture is then allowed to cool.In the second stage, the mixture obtained from the first stage, the crosslinking agent, and the aromatic compound with at least one OH group or at least one alkylcarbonyloxy group (if used) are preferably mixed together in a rubber kneader up to a mass temperature in the range of 80°C to 100°C, preferably approximately 90°C, and then cooled. The mixture thus obtained is then calendered into a layer of a specific thickness.

[0079] The roller cylinder precursor is preferably manufactured by first applying the uncrosslinked rubber composition as an adhesion layer to the surface of a roller cylinder core. This is preferably achieved by prior calendering the uncrosslinked rubber composition into a layer with a specific thickness and then applying it to the roller cylinder core. The thickness of the adhesion layer of the roller cylinder precursor is preferably in the range of 0.2 mm to 1.5 mm, more preferably in the range of 0.3 mm to 1.2 mm, and most preferably in the range of 0.4 mm to 1.0 mm. The functional layer is then applied to the adhesion layer. For this purpose, the sulfur- or peroxide-curable or crosslinked rubber is calendered into a layer, and the resulting layer is then applied to the adhesion mixture located on the roller cylinder core.

[0080] In a further embodiment, the present invention relates to a roller cylinder obtained by treating a roller cylinder precursor according to the invention at a temperature in the range of 120°C to 200°C, more preferably in the range of 140°C to 180°C. The temperature treatment is preferably carried out by treating the roller cylinder precursor in an autoclave. The temperature treatment is preferably carried out for a period of 4 to 24 hours, more preferably 6 to 12 hours. During this process, the uncrosslinked rubber composition is crosslinked, thereby increasing its adhesion to the roller core and bonding to the functional layer. If the functional layer is a sulfur- or peroxide-crosslinkable rubber, it is also crosslinked during the temperature treatment.

[0081] During heat treatment, the adhesion layer and the functional layer can be chemically bonded together, especially if the functional layer is not yet cross-linked.

[0082] In a further embodiment, the present invention also relates to a method for manufacturing a roller cylinder, in which a roller cylinder precursor according to the invention is treated at a temperature in the range of 120°C to 200°C, more preferably in the range of 140°C to 180°C. All features relating to the roller cylinder according to the invention also apply to the method according to the invention for manufacturing the roller cylinder.

[0083] The present invention will now be described in more detail with reference to the following experimental examples:

[0084] Production of uncrosslinked adhesive mixtures usable according to the invention:

[0085] Examples 1 to 7 and comparative examples 1 and 2:

[0086] The raw materials listed in Tables 1 to 4 for Examples 1 to 7 and Comparative Examples 1 and 2 are used to compound adhesion mixtures in a rubber kneader in two stages. In the first stage, all components except the crosslinking component (Rhenogran® S 80 and Peroxan® DC-40 PK, and optionally Trigonox® 29 / 40B PD-E) and the 1,3-diacetoxybenzene (Cohedur® RK) are mixed in the rubber kneader to a mass temperature of approximately 130°C and then cooled. In the second stage, the crosslinking component and the 1,3-diacetoxybenzene are mixed together with the components mixed in the first stage in the kneader to a mass temperature of approximately 90°C and then cooled again.

[0087] Production of a layer / film from each of the adhesion mixtures of examples 1 to 7 and the comparative examples 1 and 2:

[0088] The adhesion mixtures of Examples 1 to 7 and Comparative Examples 1 and 2, produced according to the above-described method, are subsequently calendered into layers or films of approximately 0.5 mm. Production of roller cylinder precursors according to the invention:

[0089] Metal cylinder cores are coated with a layer of an adhesive compound from Examples 1 to 7 and Comparative Examples 1 and 2. Subsequently, approximately 12 mm thick layers of a functional compound are applied to the adhesive compound layer. The functional layer is an EPDM-containing rubber composition with a sulfur-containing crosslinking system.

[0090] Production of roller cylinders according to the invention:

[0091] The previously produced roller cylinder precursors with the adhesion mixtures of examples 1 to 7 and comparison examples 1 and 2 are heat-treated in an autoclave for 3 h at 145°C and 4 bar to crosslink the adhesion mixture and the functional mixture.

[0092] Load test of the roller cylinder according to the invention with the adhesion mixture according to Example 1:

[0093] The roller cylinder is subjected to a load test by rotating it at 150 rpm with a starting force of 10 N. The force gradient is 10 N / 24h. The coating of the roller cylinder according to the invention withstands 500 min at 80 N and 150 rpm. Only after this time does the structure of the functional mixture break down.

[0094] Further adhesion tests of the cross-linked adhesion mixtures on metal or on functional mixtures according to DIN ISO 813 (May 2004):

[0095] Strips measuring 12.5 cm in length, 2.5 cm in width, and 6 mm in thickness are produced from the uncrosslinked adhesion compounds of Examples 2 to 4 and 7, as well as from Comparative Examples 1 and 2. Following DIN ISO 813, a 2.5 cm x 2.5 cm area is vulcanized onto a steel, aluminum, brass, stainless steel, or galvanized steel plate by bringing the surfaces into contact and heat-treating them for 15 minutes at 170 °C in a heat press. The contacted surfaces then adhere to each other. One end of the strip and the metal plate are each clamped in a tensile testing machine and pulled apart at a tensile speed of 50 mm / min until the crosslinked adhesion compound tears or the strip detaches from the metal plate. The adhesion values ​​given in Tables 5 and 6 indicate the point of tearing or detachment.

[0096] The adhesion to the functional compounds listed in Table 5 is determined in a similar manner. This is done analogously to the determination of adhesion to the metal, with the difference that a functional compound is applied above the surface of the uncrosslinked adhesion compound. The resulting composite is then heat-treated for 15 minutes at 170 °C in a heat press. Subsequently, for the tensile test, the metal plate and the functional compound are clamped in a tensile testing machine and pulled apart at a tensile speed of 50 mm / min until the crosslinked adhesion compound, the functional compound, or one of the components detaches from the other. The adhesion value given in Table 5 indicates the point of tearing or detachment.

[0097] Table 1: Compositions of Examples 1 and 2

[0098] 1) contains 70 wt% xylene-formaldehyde resin, 2)Contains 50% w / w 1,3-diacetoxybenzene

[0099] Table 2: Compositions of Examples 3 and 4

[0100] 1) contains 70 wt% xylene-formaldehyde resin, 2) Contains 50% w / w 1,3-diacetoxybenzene

[0101] Table 3: Compositions of Examples 5 and 6

[0102] 1) contains 70 wt% xylene-formaldehyde resin, 2) Contains 50% w / w 1,3-diacetoxybenzene

[0103] Table 4: Composition of comparison examples 1 and 2 and example 7

[0104] 1) contains 70 wt% xylene-formaldehyde resin, 2) Contains 50% w / w 1,3-diacetoxybenzene

[0105] Table 5: Results of the adhesion tests:

[0106] 1) EPDM-containing rubber composition with a sulfur-containing crosslinking system

[0107] Table 6: Results of the adhesion tests:

Claims

Patent claims 1. Roller cylinder precursor with a roller cylinder core having an adhesion layer arranged on its surface and a functional layer arranged on the adhesion layer, wherein the adhesion layer is an uncrosslinked rubber composition containing the following components: (A) a non-crosslinked rubber, (B) a networking component, (C1) a zinc salt of an alkenecarboxylic acid, and / or (C2) both an aromatic compound with at least one OH group or at least one alkylcarbonyloxy group and an aromatic or aliphatic formaldehyde resin; and wherein the functional layer comprises a crosslinkable or crosslinked rubber.

2. Roller cylinder precursor according to claim 1, wherein the surface of the roller cylinder core comprises a metal, a polyamide or a carbon fiber or glass fiber reinforced plastic.

3. Roller cylinder precursor according to claim 1 or 2, wherein the uncrosslinked rubber is a rubber based on ethylene propylene diene monomer rubber (EPDM), nitrile butadiene rubber (NBR), natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), isobutene isoprene rubber (HR), styrene butadiene rubber (SBR), ethylene acrylate rubber (AEM), ethylene ethylene acetate rubber (EVA or EVM), epichlorohydrin rubber (ECO), fluorocarbon rubber (FKM), hydrogenated acrylonitrile butadiene rubber (HNBR), carboxylated nitrile butadiene rubber (XNBR), ethylene propylene rubber (EPM), or mixtures thereof.

4. Roller cylinder precursor according to any one of claims 1 to 3, wherein the crosslinking component is selected from the group consisting of a sulfur-containing crosslinking agent, a peroxide-containing crosslinking agent and a combination of a sulfur-containing crosslinking agent and consists of a peroxide-containing crosslinking agent.

5. Roller cylinder precursor according to one of claims 1 to 4, wherein the rubber composition comprises both a sulfur-containing crosslinking agent and a peroxide-containing crosslinking agent as a crosslinking component.

6. Roller cylinder precursor according to any one of claims 1 to 5, wherein the rubber composition contains both components (C1) and (C2).

7. Roller cylinder precursor according to any one of claims 2 to 6, wherein in the case where the surface of the roller cylinder core has a metal, the rubber composition contains the component (C1).

8. Roller cylinder precursor according to any one of claims 2 to 6, wherein in the case where the surface of the roller cylinder core has a polyamide or a carbon fiber or glass fiber reinforced plastic the rubber composition contains the component (C2).

9. Roller cylinder precursor according to any one of claims 1 to 8, wherein the rubber of the functional layer is a sulfur- or peroxide-curable or -crosslinked rubber.

10. Roller cylinder precursor according to any one of claims 1 to 9, wherein in the case where the functional layer is a sulfur-crosslinkable or crosslinked rubber, the crosslinking component (B) comprises a sulfur-containing crosslinking agent.

11. Roller cylinder precursor according to any one of claims 1 to 9, wherein in the case where the functional layer is a peroxide-curable or -crosslinked rubber, the crosslinking component (B) comprises a peroxide-containing crosslinking agent.

12. Roller cylinder, which is obtainable by means of a roller cylinder precursor is treated according to one of claims 1 to 11 at a temperature in the range of 120°C to 200°C.

13. Roller cylinder according to claim 12, wherein the adhesion layer and the functional layer are chemically bonded together.

14. Method for manufacturing a roller cylinder, wherein a roller cylinder precursor according to any one of claims 1 to 11 is treated at a temperature in the range of 120°C to 200°C.

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