Tyre tread compound

Abstract: A tire tread compound, particularly useful for truck tires, comprises a base polymer of natural or synthetic rubber, a filler at least 50% of which is carbon black and between 2 and 10 parts of epoxy resin per hundred parts of polymer.

Description: This invention relates to a tyre tread compound and in particular to a tread compound suitable for truck tyres. Truck tyres are subject to heavy impacts and high abrasion particularly in off-the-road use and so their tread compounds have to have a high hardness to give the required penetration and wear resistances but also a sufficiently low modulus to prevent tearing off of tread blocks or lugs. Accordingly the formulations used have to be a compromise between these two necessary properties. It is an object of the present invention to provide a tyre tread compound in which the traditional combination of wear and damage resistance can be substantially improved. According to one aspect of the present invention a tyre tread compound comprises a base polymer of natural or synthetic rubber, a filler at least 50% of which is carbon black and between 2 and 10 parts per hundred of polymer epoxy resin, the epoxy resin having a Durran Softening point in the range of 93°-102°C The epoxy resin is preferably of the type sold under the name GRILONITE L1204 (Trade Mark of EMS Grilon) and has properties as follows: Density 1.17 g cm⁻³ Epoxy number 0.10-0.118 Epoxide equivalent weight 850-1000 Durran softening point 93-102°C Equivalent weight of esterification 170-180 Chlorine content 0.25% max Hydrolyzable chlorine 0.06% max Viscosity 40% solution in dibutyl glycol 450-650 m Pa s More preferably the amount of epoxy resin is in the range of 2-8 parts per 100 of polymer. Preferably the amount of carbon black filler is in the range of 30-65 parts per hundred of polymer. The filler may comprise silica for that part which is not carbon black. It has been found that the above compound provides a high hardness and a modulus at 300% elongation which is less than would be normal for a compound of this hardness. The result of this is that the necessary tread hardness for wear and penetration resistance can be provided with lower modulus at high strain and therefore improved damage resistance. Thus the material has greatly improved properties compared with the normal tread compounds used for truck tyres, especially for off-the-road applications. Further aspects of the present inventioh will become apparent from the following description of embodiments of the invention. Tyre tread compounds for a truck tyre were formulated according to Table 1. The first example is a comparative example and the others are examples according to the present invention. The resultant compounds had the properties in Table 2. Thus it can be seen that the compound of the invention provided properties of improved hardness particularly when more than two parts of the epoxy were used but lowered 300% modulus. Such materials are particularly useful for off-the-road truck tyre tread compounds where damage resistance and good wear resistance are both required. A further embodiment is shown below: Ingredient Theoretical PPHR % NR9720 100.00 57.67 Renacit 7 0.15 0.09 Zinc Oxide 4.00 2.31 Stearic acid 2.00 1.16 6PPD 1.50 0.87 Wingstay® 100 1.00 0.58 Microcrystaline Wax 2.00 1.15 Resin L1204.1 5.00 2.88 N110 black 30.00 17.31 N326 black 10.00 5.77 PPT silica 15.00 8.65 Sulphur 110 mesh 1.00 0.58 MBS 1.50 0.87 TMTD 0.20 0.12 In this compound a composite filler of black and silica was used which formulation is particularly advantageous for off-the-road truck tyre tread compounds and indeed for use in earthmover tyres. Formulations A B C D E F SMR 20 100.00 ) Zinc oxide 2.30 ) Stearic acid 3.00 ) Black N110 29.00 ) Black N326 19.00 ) Wax 1.00 ) IPPD 1.00 ) 75% BLE 1.33 ) Renacit VII 0.15 ) Resin L1204.1 - 0.50 1.00 2.00 4.00 8.00 Sulphur 1.50 ) MBS 1.00 )

Claims: A tyre tread compound comprising a base polymer of natural or synthetic rubber, a filler at least 50% of which is carbon black and between 2 and 10 parts of epoxy resin per hundred of polymer, the epoxy resin having a Durran Softening point in the range of 93°-102°C. A tyre tread according to claim 1 characterised in that the amount of epoxy resin is between 2-8 parts per 100 of polymer. A tyre tread according to claim 1 or 2 characterised in that the carbon black is in the range of 30-65 parts per hundred of polymer. A tyre tread compound according to any one of claims 1, 2 or 3 characterised in that the amount of carbon black filler is in the range of 40-65 parts per hundred of polymer. A tyre tread compound according to any one of claims 1 to 4 characterised in that the filler comprises carbon black and silica.

Inventors: CHANSE ANDREW, STEPHENS PAUL, CHANSE, ANDREW, STEPHENS, PAUL
Applicants: SUMITOMO RUBBER IND, SUMITOMO RUBBER INDUSTRIES LIMITED
Application year: 1991
Main classification: C08L7
IPC codes: C08K3, B29K21, B29D30, C08L21, B60C1, B29K105