Rubber compound for coating reinforcing elements, vulcanized composition, reinforcing elements and vehicle pneumatic tires

Abstract

Rubber compound for coating reinforcing elements, characterized in that it - at least one diene rubber and - 25 to 250 phr of at least one polar filler and - contains at least one chlorine donor, wherein the chlorine donor is present in amounts of 0.1 to 10 phr, preferably in amounts of 1 to 4 phr, wherein the chlorine donor is selected from the group consisting of the 2,4-dichloro-1,3,5-triazines and / or the 2,4,6-trichloro-1,3,5-triazines and / or the 2,4-dichloropyrimidines and / or the 2,4,6-trichloropyrimidines and or 2,4,5,6-tetrachloropyrimidine and / or tetrachloro-1,4-benzoquinone and / or the dichloro-1,4-benzoquinones and / or the trichloro-1,4-benzoquinones, wherein the chlorine donor is preferably tetrachloro-1,4-benzoquinone.

Description

[0001] The invention relates to a rubber compound suitable for coating reinforcing elements.

[0002] Furthermore, the invention relates to a reinforcing element that is coated or rubberized with a rubber compound.

[0003] Reinforcing elements for various elastomeric products are well known. For example, it is known to use a belt bandage in vehicle pneumatic tires, which is single- or multi-layered, covers the belt edges, and contains reinforcing elements in the form of cords embedded in the rubber that run parallel and essentially circumferentially. This belt bandage serves to prevent the tire from lifting due to centrifugal forces occurring during driving, particularly at high speeds. In other elastomeric products, such as power transmission belts or hoses, reinforcing elements, especially in the form of textile overlays or textile interlayers made of woven, knitted, or crocheted fabrics, serve, among other things, to improve or even enable the service life of these products.

[0004] The relevant factor here is the adhesion of the reinforcing elements to the rubber compounds in direct contact. To improve adhesion, the reinforcing elements are pretreated either with various adhesives, such as resorcinol formaldehyde latex (RFL), or with defined adhesive compounds.

[0005] In the case of rubber compounds adhering to steel as a load-bearing element, it is particularly advantageous to have a corrosion protection layer on the steel that simultaneously enables bonding to the rubber matrix. This layer can be composed of zinc or brass. The dendritic growth of the forming metal sulfides creates a mechanical interlock between the load-bearing element and the surrounding rubber compound.

[0006] Cobalt compounds are typically used as adhesion promoters in such adhesive mixtures. The presence of cobalt primarily improves adhesion in moisture-affected areas.

[0007] The aging resistance of the adhesion system is of particular importance for the structural stability of vehicle pneumatic tires.

[0008] In rubber compounds based on a nonpolar filler, the influence of additional adhesion promoters on adhesion after aging is well known. For example, US 5126385 A discloses the use of chloropyrimidine and chlorotriazine derivatives as adhesion promoters in combination with a resorcinol donor in carbon black-containing natural rubber compounds. Furthermore, as described in US 5126385 A and US 5217807 A, tetrachloro-1,4-benzoquinone is used as an adhesion promoter in rubber compounds with natural rubber as the main polymer component and carbon black (= nonpolar filler) as the sole filler. Carbon black is referred to as a nonpolar filler within the scope of the present invention because only carbon blacks that have not been functionalized by separate treatment with additional polar groups on the surface are considered and used.

[0009] US 2011 / 0048513 A1 discloses pressure-sensitive adhesive compositions which, in addition to a polymer, also contain tetrachloro-p-benzoquinone as a stabilizer.

[0010] US 6,063,873 A discloses rubber compounds for treads, wherein the compound contains, in addition to at least one rubber, chlorotriazines as amine scavengers.

[0011] The object of the present invention is to provide a rubber compound based on polar fillers for coating a reinforcing substrate, which is characterized by better or at least consistent adhesion to the substrate before and after aging compared to the prior art. The invention further aims to create a reinforcing substrate that is coated or encased with such a rubber compound.

[0012] The problem is solved by the fact that the rubber mixture according to the invention has the following composition: - at least one diene rubber and - 25 to 250 phr of at least one polar filler and - at least one chlorine donor as defined in claim 1.

[0013] Surprisingly, it has been found that combining a chloride donor with diene rubber and a polar filler in the rubber compound according to the invention improves the adhesion of the rubber compound to steel after aging. This was unexpected, as it was assumed that the highly reactive polar chloride donors would interact with the polar surfaces of the polar filler, thereby reducing the intended supportive effect on adhesion. Vehicle tires incorporating a reinforcing element according to the invention, encased in a rubber compound according to the invention, exhibit a significantly longer service life.

[0014] According to the invention, the rubber mixture contains at least one diene rubber. Preferably, the diene rubber is selected from the group consisting of natural polyisoprene and / or synthetic polyisoprene and / or butadiene rubber and / or styrene-butadiene rubber and / or solution-polymerized styrene-butadiene rubber and / or emulsion-polymerized styrene-butadiene rubber, wherein particularly good adhesive properties are achieved when using at least one natural polyisoprene.

[0015] The unit phr (parts per hundred parts of rubber by weight) used in this document is the standard unit of measurement for compound formulations in the rubber industry. The dosage of the parts by weight of each substance is always based on 100 parts by weight of the total mass of all rubbers present in the mixture.

[0016] Particularly good adhesion properties are achieved when the rubber compound contains at least 50 phr, preferably 70 to 100 phr, and especially preferably 80 to 100 phr, of at least one natural and / or synthetic polyisoprene. Good adhesion results are also achieved when the rubber compound contains 100 phr of natural polyisoprene.

[0017] If the rubber compound contains polybutadiene (BR) as the diene rubber, it can be either cis-1,4-polybutadiene or trans-1,4-polybutadiene. The use of 1,4-polybutadiene with a cis-1,4-polybutadiene content greater than 90 wt.% is preferred; this can be produced, for example, by solution polymerization in the presence of rare-earth catalysts. The use of 1,4-polybutadiene with a cis-1,4-polybutadiene content greater than 95 wt.% is particularly preferred.

[0018] It is particularly preferred if the diene rubber is composed of 70 to 100 phr of a natural and / or synthetic polyisoprene, up to 30 phr of a cis-1,4-polybutadiene, and up to 30 phr of a styrenebutadiene, wherein the sum of the amounts of the rubbers used is 100 phr. Such a rubber system is particularly advantageous for the adhesion and fatigue resistance of adhesive compounds.

[0019] The rubber compound may also contain other polar or non-polar rubbers, such as liquid rubbers and / or halobutyl rubber and / or polynorbornene and / or isoprene-isobutylene copolymer and / or ethylene propylene diene rubber and / or nitrile rubber and / or acrylate rubber and / or fluororubber and / or chloroprene rubber and / or silicone rubber and / or polysulfide rubber and / or epichlorohydrin rubber and / or styrene-isoprene-butadiene terpolymer and / or hydrogenated acrylonitrile butadiene rubber and / or isoprene-butadiene copolymer and / or hydrogenated styrene butadiene rubber.

[0020] According to the invention, the rubber compound contains at least one polar filler in amounts of 25 to 250 phr, particularly preferably in amounts of 25 to 85 phr, and most preferably in amounts of 45 to 65 phr. All polar fillers known to those skilled in the art, such as aluminum hydroxide, titanium dioxide, magnesium oxide, silicic acid, silica, and layered silicates, can be used. Silicon oxide-based fillers, such as silica and silicic acid, are preferred. Silicic acid is particularly preferred as the polar filler. The silicic acids used in the rubber industry are generally precipitated silicic acids, which are characterized, in particular, by their surface area. For characterization, the nitrogen surface area (BET, Brunauer, Emmett, Teller method) according to DIN ISO 9277 and DIN 66132 is used as a measure of the inner and outer filler surface area in m². 2 / g and the CTAB surface area according to ASTM D 3765 as a measure of the outer surface, which is often considered to be the rubber-effective surface, in m 2 / g.

[0021] The silicas used have a nitrogen surface area of ​​greater than or equal to 100 m². 2 / g up, preferably between 100 and 250 m 2 / g, especially preferably between 140 and 200 m 2 / g. Furthermore, the silicas used have a CTAB surface area between 100 and 200 m². 2 / g, preferably between 120 and 180 m 2 / g and especially preferably between 140 and 180 m 2 / g on.

[0022] Surprisingly, particularly good adhesion results are achieved with a high CTAB surface area of ​​the silica between 160 and 180 m. 2 / g achieved. Such silicas are sold under the trade name Ultrasil. ® VN3 from Evonik or, for example, Ultrasil ®7000 from the company Evonik. The latter is also known as highly dispersible silica (HD silica).

[0023] To improve processability and to bind the silica and any other polar fillers present to the diene monomer rubber, coupling agents can be used in rubber compounds. Any coupling agents known to a competent person can be used.

[0024] The coupling agents, preferably silane coupling agents, are used in quantities up to 20 phr, preferably in quantities of 0.1 to 15 phr, particularly preferably in quantities of 0.5 to 10 phr.

[0025] The silane coupling agents can also be added as a mixture with carbon black, such as TESPT on carbon black (trade name X50S). ® the company Evonik).

[0026] The rubber compound may also contain at least one carbon black as a non-polar filler. The total filler content can therefore consist entirely of polar filler or of a combination of polar and non-polar fillers.

[0027] In a preferred embodiment, the carbon black is used in quantities up to 20 phr, particularly preferably in quantities up to 10 phr, most preferably in quantities up to 5 phr, but preferably in quantities of at least 0.1 phr, and particularly preferably in quantities of at least 0.5 phr.

[0028] A key feature of the invention is that the rubber mixture contains at least one chlorine donor, which is selected from the group consisting of the 2,4-dichloro-1,3,5-triazines and / or the 2,4,6-trichloro-1,3,5-triazines and / or the 2,4-dichloropyrimidines and / or the 2,4,6-trichloropyrimidines and or 2,4,5,6-tetrachloropyrimidine and / or tetrachloro-1,4-benzoquinone and / or the dichloro-1,4-benzoquinones and / or the trichloro-1,4-benzoquinones, wherein the chlorine donor is preferably tetrachloro-1,4-benzoquinone. If the chlorine donor is a 2,4-dichloro-1,3,5-triazine, then 2,4-dichloro-6-(N-phenyl-p-phenylenediamine)-1,3,5-triazine is preferred. However, the chlorine donor can also be N-1,4-dimethylpentyl-N,N'-bis(4,6-dichloro-1,3,5-triazinyl-2)-p-phenylenediamine and / or 2,4-bis(ethylamine)-6-chloro-1,3,5-triazine.

[0029] Particularly preferred is the use of tetrachloro-1,4-benzoquinone in amounts of 0.1 to 10 phr, preferably in amounts of 1 to 5 phr, and particularly preferably in amounts of 1 to 4 phr.

[0030] According to a preferred embodiment of the invention, the rubber compound includes a cobalt compound, preferably a cobalt salt, as an adhesion promoter. The use of cobalt stearate and / or cobalt borate and / or cobalt naphthenate is advantageous for the adhesive properties.

[0031] Surprisingly, it has been found that a comparatively small amount of cobalt can be used in the rubber compound according to the invention while still achieving very good adhesion results. The amount of cobalt salt is selected such that the mass fraction of cobalt is up to 0.2%, particularly preferably up to 0.06%, based on the total mass of the rubber compound. This mass fraction is given in this document in the unit wt.%. The mass fraction of cobalt refers to the ionic cobalt from the cobalt salt. The masses of cobalt atoms and cobalt ions are almost identical, since the electrons missing in the positively charged cobalt ion have a negligible mass compared to the atom.

[0032] Larger quantities of cobalt compounds, often found in the industrial production of adhesive compounds, are toxic to many living organisms and lead to skin, lung, and stomach diseases, liver, heart, and kidney damage, as well as cancerous ulcers. Furthermore, cobalt compounds in a rubber compound significantly reduce the fatigue resistance of the compound.

[0033] The rubber compound may contain amounts of up to 60 phr, preferably amounts of 0.1 to 50 phr, and particularly preferably amounts of 0.1 to 25 phr, of at least one plasticizer. This plasticizer is selected from the group consisting of mineral oils and / or synthetic plasticizers and / or fatty acids and / or fatty acid derivatives and / or resins and / or phenols and / or glycerides and / or terpenes and / or biomass-to-liquid oils (BTL oils) and / or rubber-to-liquid oils (RTL oils).

[0034] The use of resins is advantageous for improved adhesion of the rubber layer and, in particular, for better processability during the manufacture of the final product, e.g., the tire.

[0035] Furthermore, the rubber compound of the rubber coating layer may contain additional additives.

[0036] Other additives essentially include the crosslinking system (crosslinker, sulfur donor and / or elemental sulfur, accelerator and retarder), ozone protection agent, aging protection agent, mastication aid, processing aid and other activators.

[0037] The quantity of other additives in the total quantity is up to 150 phr, preferably up to 100 phr and particularly preferably 5 to 50 phr.

[0038] The rubber compound according to the invention is used for the manufacture of tires, and for the manufacture of belts, straps and hoses.

[0039] The tire in question can be a truck tire, a car tire, or a two-wheeler tire. In particular, the rubber compound is used to manufacture at least one internal component of a tire.

[0040] Another object of the present invention is a reinforcing element which is encased by the rubber compound according to the invention.

[0041] The reinforcing element according to the invention is preferably constructed of at least one steel component. It is particularly preferred if the reinforcing element is made of steel and is partially or completely coated with at least one layer of brass and / or zinc.

[0042] The rubber compound is produced according to the standard process used in the rubber industry. First, a base mixture containing all components except the vulcanization system (sulfur and vulcanization-influencing substances) is prepared in one or more mixing stages. The final mixture is created by adding the vulcanization system in a last mixing stage. This mixture is then used to partially or completely encase the reinforcing substrate. This is achieved by calendering the rubber compound, producing thin sheets that are applied to the top and bottom of the substrate. During this process, the rubber compound penetrates the substrate. After cutting, these rubber-coated substrates are used, as is customary for skilled personnel, to manufacture the required end products.

[0043] The invention will now be explained in more detail with reference to comparative and exemplary embodiments, which are summarized in Table 1. The mixture marked "E1" is the mixture according to the invention, while the mixtures marked "V" are comparative mixtures.

[0044] The upper part of the table shows the mixture compositions, while the lower part illustrates the corresponding adhesion properties. In the mixture examples included in the table, the quantities given are parts by weight per 100 parts by weight of total rubber (phr). The cobalt content, given in wt.%, is the amount of cobalt from the cobalt compound, i.e., the cobalt salt, relative to the total mass of the rubber mixture.

[0045] The compound was prepared under standard conditions in several stages using a laboratory tangential mixer. Test specimens were produced from all compounds by vulcanization, and material properties typical for the rubber industry were determined using these specimens. The adhesion (rubber coverage at room temperature, RT) and pullout force were determined according to ASTM D2229-10. Table 1 Components Unit V1 V2 V3 E1 Polyisoprene, NR phr 100 100 80 80 High-cis BR phr 0 0 20 20 soot a) phr 56 56 4,3 4,3 Silica b) phr 10,2 10,2 55,0 55,0 Silane phr 0,0 0,0 4,3 4,3 Plasticizers + resins phr 11,1 11,1 13,3 13,3 Anti-aging agents / ZnO / CTP phr 10,80 10,80 11,95 11,95 Accelerator c) phr 1,2 1,2 1,6 1,6 sulfur phr 5,5 5,5 4,0 4,0 Tetrachloro-1,4-benzoquinone phr 0 1 0 1 Cobalt salt phr 2,00 2,00 0,36 0,36 Cobalt content % by weight 0,097 0,096 0,042 0,041 Adhesion before aging Pullout Force N 998 1026 1108 1114 Coverage at RT % 94 94 90 95 Adhesion after aging (5 days at 105 °C, steam) Pullout Force N 672 488 530 756 Coverage at RT % 76 68 66 67 a) Rußtyp:V1 u. V2: N326; V3 u. E1: N330 b) Silica: Ultrasil ® VN3; Evonik Industries; BET surface area = 175 m² 2 / g; CTAB number = 165 m 2 / G c) Sulfenamide accelerator

[0046] A comparison of V1 and V2 in Table 1 shows that the addition of 1 phr of tetrachloro-1,4-benzoquinone to the carbon black rubber compound improves adhesion before aging. Adhesion after 5 days of aging at 105 °C / steam is poorer, as evidenced by the lower pullout force of V2 compared to V1. 1 phr of tetrachloro-1,4-benzoquinone negatively affects adhesion in the carbon black compound after aging.

[0047] In the silica-containing rubber compound V3, the adhesion result before aging is slightly better than that of the carbon black-containing rubber compound V1. After aging, a lower pull-out strength value is achieved for V3 than for V1. This means that the adhesion level of the aged silica-containing compound V3 is lower than that of the aged carbon black-containing rubber compound V1.

[0048] The use of 1 phr tetrachloro-1,4-benzoquinone in the silica-containing rubber mixture E1 according to the invention leads to better adhesion before aging compared to V3.

[0049] Surprisingly, in the silica-containing mixture E1 according to the invention, the addition of 1 phr of tetrachloro-1,4-benzoquinone leads to a significant increase in the pull-out strength after aging, i.e., improved adhesion after aging. The pull-out strength of the aged mixture E1 is higher than that of the aged mixture V1 and even significantly higher than that of the aged mixture with chlorine donor V2. Table 1 also shows that the cobalt content can be significantly reduced when using chlorine donors in combination with a polar filler.

Claims

[1] Rubber compound for coating reinforcements, characterized by that they - at least one diene rubber and - 25 to 250 phr of at least one polar filler and - contains at least one chlorine donor, wherein it contains the chlorine donor in amounts of 0.1 to 10 phr, preferably in amounts of 1 to 4 phr, wherein the chlorine donor is selected from the group consisting of 2,4-dichloro-1,3,5-triazines and / or 2,4,6-trichloro-1,3,5-triazines and / or 2,4-dichloropyrimidines and / or 2,4,6-trichloropyrimidines and / or 2,4,5,6-tetrachloropyrimidine and / or tetrachloro-1,4-benzoquinone and / or dichloro-1,4-benzoquinones and / or trichloro-1,4-benzoquinones, wherein the chlorine donor is preferably tetrachloro-1,4-benzoquinone. [2] Rubber mixture according to claim 1, characterized bythat the diene rubber is composed of 70 to 100 phr of a natural and / or synthetic polyisoprene and up to 30 phr of a cis-1,4-polybutadiene and / or up to 30 phr of a styrene butadiene. [3] Rubber mixture according to one of claims 1 to 2, characterized by that it contains at least one silica as a polar filler. [4] Rubber mixture according to claim 3, characterized by that the silica has a BET surface area between 100 m 2 / g and 250 m 2 / g and a CTAB surface between 100 m 2 / g and 200 m 2 / g, preferably a BET surface area between 140 m 2 / g and 200 m 2 / g and a CTAB surface between 140 m 2 / g and 180 m 2 / g. [5] Rubber mixture according to one of claims 1 to 4, characterized by that a cobalt salt is also included. [6] Rubber mixture according to claim 5, characterized bythat the mass fraction of cobalt based on the total mass of the rubber mixture is up to 0.2%. [7] Rubber mixture according to claim 6, characterized by that the mass fraction of cobalt based on the total mass of the rubber mixture is up to 0.06%. [8] Vulcanized composition obtained by vulcanizing the rubber mixture according to any one of claims 1 to 7. [9] Strength members, characterized by that it is coated at least by a rubber mixture according to one of claims 1 to 7 or 8. [10] Strength member according to claim 9, characterized by that it is made of at least one steel. [11] Strength member according to claim 10, characterized by that the reinforcement is partially or completely coated with at least one layer of brass and / or zinc. [12] Pneumatic vehicle tires, characterized bythat it contains at least one strength member according to one of claims 9 to 11.