Rubber composition for a tire comprising a multifunctional polyorganosiloxane as coupling agent

#The present invention relates to diene rubber compositions reinforced with a white or inorganic filler, which are intended in particular for the manufacture of tires or semi-finished products for tires, in particular to the treads for these tires.

#Since fuel economies and the need to protect the environment have become priorities, it has become desirable to produce elastomers with good mechanical properties and as low a hysteresis as possible so that they can be used in the form of rubber compositions usable for the manufacture of various semi-finished products involved in the constitution of tires, such as, for example, underlayers, calendering or sidewall rubbers, or treads, and to obtain tires with improved properties, having in particular reduced rolling resistance.

#To achieve such an objective, numerous solutions have been proposed, first of all ones essentially concentrating on the use of elastomers modified by means of agents such as coupling, starring or functionalizing agents, with carbon black as the reinforcing filler, with the aim of obtaining a good interaction between the modified elastomer and the carbon black. For it is generally known that in order to obtain the optimum reinforcement properties imparted by a filler, the latter should be present in the elastomeric matrix in a final form which is both as finely divided as possible and distributed as homogeneously as possible. Now, such conditions may only be obtained insofar as the filler has a very good ability firstly to be incorporated into the matrix during mixing with the elastomer and to disagglomerate, and secondly to be dispersed homogeneously in the elastomer.

#The invention and its advantages will be readily understood in the light of the description and example embodiments which follow, and of the accompanying drawings, wherein:

#FIG. 1 shows curves of the variation of modulus (in MPa) as a function of elongation (in %) for rubber compositions C1 and C2;

#FIG. 2 shows curves of the variation of modulus (in MPa) as a function of elongation (in %) for rubber compositions C3 and C4;

#A POS/1 of imide type is prepared, with as starting organosilane of formula (X), N-[γ-propyl(methyldiethoxy)silane]maleamic acid, in accordance with the following steps.

#1. Preparation of the Starting Maleamic Acid Silane:

#Operation is in a 2-liter glass reactor, equipped with a stirrer system and a dropping funnel. The γ-aminopropylsilane of formula (C2H5O)2CH3Si(CH2)3NH2 (300.3 g, or 1.570 moles) is poured gradually at a temperature of 13-15° C. (temperature of the reaction kept at this value by means of a bath of iced water placed beneath the reactor) on to a solution of maleic anhydride (160 g, or 1.633 moles) in toluene as solvent (569.9 g), over a period of 2 hours and 20 minutes. The reaction medium is then left at 23° C. for 15 hours. At the end of this period, the reaction medium is filtered over a fritted glass of a porosity of 3 and thus a solution of the maleamic acid silane desired in toluene is recovered, which solution is used in the form in which it is present for implementing process (e) below. This solution contains 0.152 moles of maleamic acid silane per 100 g of solution.