RUBBER COMPOUND, ESPECIALLY FOR A HOSE

Description

[0001] The invention relates to a rubber mixture, in particular for a hose, with improved adhesion, in particular to fluoropolymers.

[0002] Fluoropolymers or fluoropolymer-based rubber compounds are often used for the production of flexible, low-permeation, temperature-stable, and chemical- and fuel-resistant items, such as hoses. The fluoropolymer can be a fluoroplastic or a fluoroelastomer combined with a non-fluorinated elastomer.

[0003] The fluoropolymer or fluoropolymer blend impresses with its chemical and temperature resistance and its good barrier effect, while the underlying elastomer blend provides the necessary flexibility. The fluoropolymer layer is generally thinner than the elastomer layer.

[0004] Depending on the intended use and the nature of the object, an additional elastomer layer can also be applied in front of the fluoropolymer layer, so that the fluoroplastic layer is embedded between the elastomer layers. This design is often chosen when the fluoropolymer layer is intended to act as a barrier layer. Additionally, the hose construction can be constructed with one or more reinforcement layers, i.e., a strength layer made of steel braid, synthetic yarn, or fabric, and an additional outer rubber layer as a protective layer.

[0005] The disadvantage of this design is that fluoropolymers generally exhibit little or no adhesion to a non-fluorinated elastomer compound. This is due to the anti-adhesive properties of fluoropolymers, the so-called Teflon effect. Therefore, the fluoropolymer surface must be pretreated either physically, e.g., by plasma etching (see DE69930696A1), or chemically, e.g., by sodium ammonia or sodium naphthalene etching (see DE102008014988A1). These methods are complex, cost-intensive, and usually impractical, but unavoidable for highly or fully fluorinated polymers such as PTFE, FEP, PFA, and MFA.

[0006] However, with partially fluorinated fluoropolymers such as PVF, PVDF, THV, ETFE, ECTFE, but also certain fluoroelastomers such as FKM, it is possible to achieve sufficient adhesion between fluoropolymer and elastomer by adding certain adhesion-promoting chemicals, hereinafter referred to as "adhesion promoters", to the elastomer mixture.

[0007] Several compounds have been described as adhesion promoters, including primary amines (see DE69506904T2), amino-substituted organosilane compounds (see DE60211160T2), and cyanoacrylate / epoxy compounds (see US5679425). The disadvantages of these compounds are that they are sometimes incompatible with every elastomer, are not very easy to handle, are not entirely toxicologically safe, and sometimes exhibit only mediocre adhesion values ​​between fluoropolymer and elastomer.

[0008] It is also known that the fluoropolymer can be surface-modified or grafted to optimize adhesion, see EP1537989B1 or US6143415. The disadvantage of this is that the additional manufacturing process makes the fluoropolymers more expensive, alters their physical properties, and potentially leads to the loss of certain approvals in the food or drinking water sector.

[0009] Also described is the additional insertion of a low-fluorinated fluoropolymer layer with a lower melting point between the fluoropolymer and the elastomer, which is intended to improve interlayer adhesion (see EP1497112B2). The disadvantage of this method is that an additional layer must be inserted, which complicates production, increases costs, and reduces flexibility.

[0010] Therefore, the first step was to find a non-toxic, cost-effective, easy-to-process adhesion promoter that could be incorporated directly into a crosslinkable rubber compound and that, after vulcanization, would provide ideal adhesion between a fluoropolymer and an elastomer compound, i.e. a bond that could only be separated by tearing one component and that was not delaminable.

[0011] DE10322026A1 describes phosphonium salts such as tetrabutylphosphonium benzotriazolate for this purpose. However, the use of allyltributylphosphonium chloride is also possible. These salts promote good adhesion between the elastomer and most fluoropolymers, meaning they can only be delaminated with high force. However, the adhesive force decreases significantly, particularly with more highly fluorinated fluoropolymers, and delamination is possible, especially under heat. DE19980666T1 describes an adhesion optimization by adding SbO 3 to the phosphonium salt. The disadvantage of this is that SbO 3 is considered toxicologically critical and should no longer be used in elastomer mixtures for environmental reasons.

[0012] Another group of effective adhesion promoters are bicyclic amidines such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), as well as their salts. DBU and DBN are strongly basic liquids that are difficult to handle in rubber processing. Therefore, the corresponding salts of the compounds are preferred.

[0013] The adhesion to a fluorochloropolymer (CPT) using DBU salt or DBN salt, or a mixture of the two, is described in US20120199238. Suitable DBU and DBN salts are listed as: DBU naphthoate, DBU sorbate, DBU phenolic resin, DBN naphthoate, DBN sorbate, or DBN phenolic resin. The chlorine contained in CPT is more easily released during the reaction than the fluorine, which can lead to faster and potentially better adhesion.

[0014] US20060127619A1 and DE602005005270T2 describe that for a fluoropolymer with a high fluorine content, only the combination of a phosphonium salt with a DBU salt or DBN salt results in ideal adhesion. The use of the phosphonium salt alone does not demonstrate sufficient adhesion.

[0015] The disadvantage is that, particularly with highly fluorinated polymers, two or more adhesion promoters often have to be mixed into the rubber mixture in order to achieve sufficient adhesion.

[0016] The object of the present invention is therefore to provide a rubber compound characterized by good adhesion, particularly to highly fluorinated fluoropolymers that contain no other halogens besides fluorine. The effort involved in producing the rubber compound and an article containing the rubber compound should not be increased. The rubber compound should have no or only low toxicity, so that it can also be used in the food and drinking water sectors.

[0017] According to the present invention, fluoropolymers are referred to as highly fluorinated if more than 50% of the atoms in the polymer chain, both main and side chains, are fluorine atoms.

[0018] According to the present invention, fluoropolymers are referred to as low-fluorinated if less than 50% of the atoms in the polymer chain, both main and side chains, are fluorine atoms.

[0019] This task is solved by the fact that the rubber mixture consists of the following components: at least one rubber and at least one filler selected from the group consisting of carbon black, graphite, carbon nanotubes (CNT), silica, calcium and aluminum silicates, diatomaceous earth, kaolin, limestone, feldspar and / or talc, chalk, alumina gel, fibers (short and long fibers, glass, carbon, aramid fibers), whiskers (aluminum oxide, silicon carbide), mica, magnetite, core / shell fillers, asphalt, hard rubber dust, glass beads, wood flour, nutshell flour, which can each be used alone or in combination and wherein the total amount of filler does not contain any residues of the carrier of the DBU salt and an adhesion promoter system which consists of at least one 1,8-diazabicyclo[5.4.0]undec-7-ene salt (DBU salt), wherein the DBU salt was obtained from DBU and a monocarboxylic acid and / or a dibasic acid, and wherein the DBU salt was applied to a carrier, wherein the carrier is silica and a crosslinking system comprising at least one sulfur and / or at least one sulfur donor or a crosslinking system comprising at least one peroxide and 0 to 300 phr of further additives selected from the group consisting of zinc oxide, zinc stearate, Mg stearate, stearic acid, and plasticizers, such as white oils, esters, factice and waxes, and emulsifiers and dispersants and neutralizing agents and age inhibitors and organic pigments and inorganic pigments and ozone protection agents and flame retardants and antibacterial additives, odor neutralizing agents, flavors, and lubricants and mold release agents and protective agents against rot and. where the total amount of the adhesion promoter system is 0.005 to 50 M% per 100g of rubber mixture.

[0020] Surprisingly, it has been shown that such a bonding agent system, in combination with the described crosslinking systems, can be easily incorporated into all common rubbers and, on its own—i.e., without the addition of another bonding agent—at a comparatively low concentration after vulcanization, produces ideal adhesion even to highly fluorinated polymers. At the same time, such a rubber compound can be used in products intended for food or drinking water contact.

[0021] The DBU salt and the DBN salt, which can be used alone or in combination according to the invention, are each a compound of DBU or DBN and a monocarboxylic acid or a dibasic acid. Monocarboxylic acids are acids that contain a carboxyl group.

[0022] The monocarboxylic acid can be an acyclic aliphatic monocarboxylic acid, a cyclic aliphatic monocarboxylic acid, an aromatic monocarboxylic acid, or a heterocyclic monocarboxylic acid. They can be saturated or unsaturated.

[0023] Examples of saturated cyclic monocarboxylic acids are cyclobutanoic acid or cyclohexanecarboxylic acid.

[0024] Preferably, however, it is a saturated acyclic monocarboxylic acid with the formula H(CH) m COOH, where m can assume values ​​between 0 and 40, preferably between 8 and 25. Examples of such saturated aliphatic monocarboxylic acids are formic acid (m=0), acetic acid (m=1), propionic acid (m=2), butyric acid (m=3), valeric acid (m=4), caproic acid (m=5), enanthic acid (m=6), caprylic acid (m=7), pelargonic acid (m=8), capric acid (m=9), undecanoic acid (m=10), lauric acid (m=11), tridecanoic acid (m=12), myristic acid (m=13), pentadecanedioic acid (m=14), palmitic acid (m=15), margaric acid (m=16), stearic acid (m=17), nonadecanoic acid (m=18), arachidic acid (m=19), heneicosanoic acid (m=20), behenic acid (m=21), lignoceric acid (m=22), etc.

[0025] Dibasic acids are carboxylic acids that contain two carboxyl groups. The dibasic acid can be an acyclic aliphatic dibasic acid, a cyclic aliphatic dibasic acid, an aromatic dibasic acid, or a heterocyclic dibasic acid. They can be saturated or unsaturated. Examples of aromatic dibasic acids include phthalic acid, terephthalic acid, or isophthalic acid.

[0026] Preferably, however, it is an aliphatic dibasic acid with the formula HOOC(CH) m COOH, where m can assume values ​​between 0 and 40, preferably between 6 and 22, particularly preferably between 6 and 12. Examples of such aliphatic dibasic acids are oxalic acid (m=0), malonic acid (m=1), succinic acid (m=2), glutaric acid (m=3), adipic acid (m=4), pimelic acid (m=5), suberic acid (m=6), azelaic acid (m=7), sebacic acid (m=8), undecanedioic acid (m=9), dodecanedioic acid (m=10), brassylic acid (m=11), tetradecanedioic acid (m=12), thapsic acid (m=14), heptadecanedioic acid (m=15), octadecanedioic acid (m=16), nonadecanedioic acid (m=17) and eicosanoic acid (m=18).

[0027] As already mentioned, the adhesion promoter system consists of at least one 1,8-diazabicyclo[5.4.0]undec-7-ene salt (DBU salt), wherein the DBU salt was obtained from DBU and a monocarboxylic acid and / or a dibasic acid, and wherein the DBU salt was applied to a carrier, wherein the carrier is silica. Particularly good adhesion results can be achieved when a mixture of different DBU salts is used. This is preferably a mixture of different DBU salts, each obtained from DBU and different aliphatic dibasic acids, each on a carrier. Particularly suitable dibasic acids for the mixture are adipic acid (m=4), pimelic acid (m=5), suberic acid (m=6), azelaic acid (m=7), sebacic acid (m=8), undecanedioic acid (m=9) and dodecanedioic acid (m=10) in various combinations or in a combination containing m=4, m=5, m=6, m=7, m=8, m=9 and m=10.

[0028] The total amount of adhesion promoter system in the rubber mixture is between 0.005 and 50 M%, preferably between 0.025 and 40 M% and particularly preferably between 0.25 and 10 M%.

[0029] The term "M%" refers to a quantity per 100g of rubber compound.

[0030] The term "K%" also used refers to a quantity per 100g of rubber and is therefore equivalent to the term "phr" (parts per hundred parts of rubber).

[0031] The rubber is preferably selected from the group consisting of ethylene-propylene copolymer (EPM) and ethylene-propylene-diene copolymer (EPDM) and / or nitrile rubber (NBR) and (partially) hydrogenated nitrile rubber (HNBR) and polyblend of nitrile rubber with polyvinyl chloride (NBR / PVC) and fluororubber (FKM) and chloroprene rubber (CR) and natural rubber (NR) and styrene-butadiene rubber (SBR) and solution-polymerized styrene-butadiene rubber (SSBR) and emulsion-polymerized styrene-butadiene rubber (ESBR) and isoprene rubber (IR) and butyl rubber (IIR) and bromobutyl rubber (BIIR) and chlorobutyl rubber (CIIR) and Butadiene rubber (BR) and chlorinated polyethylene (CM) and chlorosulfonated polyethylene (CSM) and epichlorohydrin rubber (ECO, CO, ETER) and ethylene-vinyl acetate rubber (EVA) and silicone rubber (MQ, VMQ, PVMQ,FVMQ) and fluorinated methylsilicone rubber (MFQ) and perfluorinated propylene rubber (FFPM) and perfluorocarbon rubber (FFKM) and polyurethane (PU) and polynorbene rubber (PNR) and trans-polyoctenamer rubber (TOR) and polyester urethane rubber (AU) and polyurethane rubber (EU).

[0032] The rubbers mentioned can be used alone or in combination. NBR, NBR / PVC, HNBR, EPDM, ECO, CM, CR, CSM, and CHR are particularly suitable.

[0033] Furthermore, the rubber mixture contains at least one filler selected from the group consisting of carbon black, graphite, carbon nanotubes (CNT), silica, calcium and aluminum silicates, diatomaceous earth, kaolin, limestone, feldspar and / or talc, chalk, alumina gel, fibers (short and long fibers, glass, carbon, aramid fibers), whiskers (aluminum oxide, silicon carbide), mica, magnetite, core / shell fillers, asphalt, hard rubber dust, glass beads, wood flour, nutshell flour, which can each be used alone or in combination and wherein the total amount of filler does not include any residues of the carrier of the DBU salt.

[0034] In order for the rubber compound to have good electrical conductivity, the use of conductive carbon black, graphite, CNT and metals and their compounds, especially iron compounds, has proven particularly preferable.

[0035] The total amount of filler is preferably 10 to 300 phr, particularly preferably 20 to 100 phr. The total amount of filler does not include any residues of the carrier. Basic fillers are particularly suitable, as they aid in the abstraction of the fluorine atom from the polymer chain. It is also helpful if the filler also has a reinforcing effect. Therefore, kaolin and chalk, but especially carbon black and silica, are particularly preferred.

[0036] Furthermore, the rubber mixture according to the invention contains a crosslinking system containing at least one sulfur and / or at least one sulfur donor or a crosslinking system containing at least one peroxide.

[0037] The choice of crosslinking system depends essentially on the rubbers used.

[0038] Particularly preferred is a crosslinking system containing at least one peroxide or a crosslinking system containing at least one sulfur donor, for example a thiuram compound.

[0039] A peroxide crosslinking system generates -O* radicals, which are particularly reactive and can potentially support fluorine abstraction and the formation of a stable atomic bond. Furthermore, peroxide-crosslinked rubbers are particularly temperature-stable.

[0040] A crosslinking system with a sulfur donor produces more dynamically flexible end products. With resin crosslinking, the amount of DBU to resin and the pH value must be carefully balanced. The advantage of resin crosslinking is that no degradation product is produced (thus, little odor) and that the resin is completely incorporated between the polymer chains.

[0041] According to the invention, the rubber mixture contains 0 to 300 phr of further additives selected from the group consisting of zinc oxide, zinc stearate, magnesium stearate, stearic acid, and plasticizers, such as white oils, esters, factice and waxes, and emulsifiers and dispersants and neutralizing agents and age inhibitors and organic pigments and inorganic pigments and ozonants and flame retardants and antibacterial additives, odor neutralizers, flavors, and lubricants and mold release agents and anti-fouling agents and residues of the monocarboxylic acid and residues of the dibasic acid and residues of the carrier.

[0042] Thus, in a particularly preferred embodiment, the rubber mixture can be free of further additives if the amount of further additives is 0 phr. In a further preferred embodiment, the amount of additives can be 0.1 to 300 phr, 1 to 300 phr, or 3 to 300 phr.

[0043] The additives mentioned may be present alone or in combination.

[0044] The rubber mixture according to the invention is preferably used in technical rubber articles, such as air springs, rubber spring elements, drive belts, conveyor belts, hoses, tires, sealing materials, multi-layer fabric webs for forming flexible containers, tents, tarpaulins, membranes, protective suits, printing blankets or bellows.

[0045] Preferably used for the rubber compound in hoses, such as fuel pump hoses, manifold hoses, fuel hoses, offshore and marine hoses, bunker hoses, air conditioning hoses and paint spray hoses, heatable hoses, low-permeation hoses.

[0046] Due to the low toxicity of the rubber compound, which allows for application in the food and drinking water sectors, the rubber compound is preferably used in drinking water hoses and food hoses.

[0047] The invention will now be explained in more detail using comparative and exemplary embodiments summarized in the various tables. The mixtures marked with "E" are inventive mixtures, while those marked with "V" are comparative mixtures. The adhesion to fluororubber is assessed using a subjective laboratory test in which a manual attempt is made to separate the two layers. The following therefore means: XX = ideal adhesion (separable only with material tearing) X = good adhesion (delaminates under moderate force) 0 = poor or no adhesion (easily delaminates with little / no force) Table 1 Adhesion promoter Quantity of adhesion promoter phr rubber Fillers peroxide sulfur Adhesion to fluoropolymer E1 DBU salts on silica support (mixture; m=4 to 10) 3 NBR soot Yes no XX (THV 415) XX (THV 500) E2 DBU salts on silica support (mixture; m=4 to 10) 1 NBR soot no ia XX V1 DBU stearate 3 NBR soot Yes no X V2 DAU phenol salt 3 NBR soot Yes no X (THV 415) 0 (THV 500) V3 Phosphonium salt 4 NBR soot Yes no XX V4 Phosphonium salt 1,1 NBR soot Yes no 0 V5 Phosphonium salt 3 NBR soot Yes no 0 V6 Phosphonium salt 3 NBR soot no Yes 0 Table 2 Adhesion promoter Quantity of adhesion promoter [phr] rubber Fillers peroxide sulfur Adhesion to fluoropolymer "THV500" E3 DBU salts on silica support (mixture; m=4 to 10) 3 NBR soot Yes no XX E4 DBU salts on silica support (mixture; m=4 to 10) 2 NBR soot Yes no XX E5 DBU salts on silica support (mixture; m=4 to 10) 1,5 NBR soot Yes no XX E6 DBU salts on silica support (mixture; m=4 to 10) 1 NBR soot Yes no XX E7 DBU salts on silica support (mixture; m=4 to 10) 0,5 NBR soot Yes no XX E8 DBU salts on silica support (mixture; m=4 to 10) 0,3 NBR soot Yes no X E9 DBU salts on silica support (mixture; m=4 to 10) 0,2 NBR soot Yes no 0 E10 DBU salts on silica support (mixture; m=4 to 10) 0,1 NBR soot Yes no 0 E11 DBU salts on silica support (mixture; m=4 to 10) 0,2 NBR soot Yes no 0 E12 DBU salts on silica support (mixture; m=4 to 10) 0,1 NBR soot Yes no 0 Table 3 Adhesion promoter Quantity of adhesion promoter [phr] rubber Fillers peroxide sulfur Adhesion to fluoropolymer E13 DBU salts on silica support (mixture; m=4 to 10) 1 NBR (39ACN) soot Yes no XX E14 DBU salts on silica support (mixture; m=4 to 10) 1 NBR (39ACN) soot no Yes XX E15 DBU salts on silica support (mixture; m=4 to 10) 1 NBR (34ACN) soot Yes no XX E16 DBU salts on silica support (mixture; m=4 to 10) 1 NBR / PVC (28ACN) soot Yes no XX E17 DBU salts on silica support (mixture; m=4 to 10) 0,8 NBR (28ACN) soot Yes no XX E18 DBU salts on silica support (mixture; m=4 to 10) 0,8 NBR (34ACN) Silica Yes no XX (THV 500) XX (THV610) XX (THV 815) E19 DBU salts on silica support (mixture; m=4 to 10) 2,3 EPDM Silica Yes no XX (THV 500) X (THV610) 0 (THV 815) E20 DBU salts on silica support (mixture; m=4 to 10) 0,9 EPDM soot Yes no XX E21 DBU salts on silica support (mixture; m=4 to 10) 2,5 EPDM Silica no Yes 0 (THV 500) 0 (THV610) 0 (THV 815) E22 DBU salts on silica support (mixture; m=4 to 10) 0,8 EPDM soot no Yes 0

Claims

1. Rubber mixture, characterized in that it is composed of the following constituents: - at least one rubber and - at least one filler selected from the group consisting of carbon black, graphite, carbon nanotubes (CNT), silica, calcium and aluminium silicates, kieselguhr, kaolin, limestone, feldspar and / or talc chalk, alumina gel, fibres (short and long fibres, glass, carbon, aramid fibres), whiskers (aluminium oxide, silicon carbide), mica, magnetite, core / shell fillers, asphalt, hard rubber dust, glass spheres, wood flour, nut shell flour which may each be used alone or in combination and wherein the total amount of filler does not include any residues of the carrier of the DBU salt and - an adhesion promoter system consisting of at least one 1,8-diaza-bicyclo[5.4.0]undec-7-ene salt (DBU salt), wherein the DBU salt was obtained from DBU and a monocarboxylic acid and / or a dibasic acid and wherein the DBU salt was applied to a carrier, wherein the carrier is silica and - a crosslinking system containing at least one sulfur and / or at least one sulfur donor or a crosslinking system containing at least one peroxide and - 0 to 300 phr of further additives selected from the group consisting of zinc oxide, zinc stearate, Mg stearate, stearic acid, and plasticizers, for example white mineral oils, esters, factice and waxes, and emulsifiers and dispersants and neutralizing agents and ageing stabilizers and organic pigments and inorganic pigments and antiozonants and flame retardants and antibacterial additives, odour neutralizers, aromas, and lubricants and mould release agents and anti-putrefaction agents and wherein the total amount of the adhesion promoter system is 0.005 to 50 M% per 100g of rubber mixture in each case.

2. Rubber mixture according to Claim 1, characterized in that the rubber is selected from the group consisting of ethylene-propylene copolymer (EPM) and ethylene-propylene-diene copolymer (EPDM) and nitrile rubber (NBR) and (partially) hydrogenated nitrile rubber (HNBR) and polyblend of nitrile rubber with polyvinyl chloride (NBR / PVC) and fluororubber (FKM) and chloroprene rubber (CR) and natural rubber (NR, IR) and styrene-butadiene rubber (SBR) and solution-polymerized styrene-butadiene rubber (SSBR) and emulsion-polymerized styrene-butadiene rubber (ESBR) and isoprene rubber (IR) and butyl rubber (HR) and bromobutyl rubber (BIIR) and chlorobutyl rubber (CIIR) and butadiene rubber (BR) and chlorinated polyethylene (CM) and chlorosulfonated polyethylene (CSM) and epichlorohydrin rubber (ECO, CO, ETER) and ethylene-vinyl acetate rubber (EVA) and silicone rubber (MQ, VMQ, PVMQ, FVMQ) and fluorinated methylsilicone rubber (MFQ) and fluororubber (FKM) and perfluorinated propylene rubber (FFPM) and perfluorocarbon rubber (FFKM) and polyurethane (PU) and polynorbornene rubber (PNR) and trans-polyoctenamer rubber (TOR) and polyester-urethane rubber (AU) and polyurethane rubber (EU).

3. Rubber mixture according to Claim 1 or 2, characterized in that the filler is silica and / or carbon black.

4. Rubber mixture according to any of Claims 1 to 3, characterized in that the total amount of filler is 10 to 300 phr.

5. Use of a rubber mixture according to any of Claims 1 to 4 in hoses.