Formation of Latex Coagulum Composite for Tire Composition

Abstract

A tire comprising a rubber composition based on at least an elastomer composite formed by the method of flowing a coagulating mixture of a first elastomer latex comprising a first elastomer and a particulate filler slurry along a conduit; and introducing a second elastomer latex comprising a second elastomer into the flow of the coagulating mixture.

1 . A process for manufacturing a rubber composition for tire, comprising the steps of:
 a) manufacturing a coagulated latex composite by the method comprising
 a1) flowing a coagulating mixture of a first elastomer latex comprising a first elastomer and a particulate filler slurry along a conduit, wherein the particulate filler comprises a carbon black having a dibutyl phthalate adsorption greater than 60 mL/100 g, and wherein the carbon black has a surface area and is present in the coagulated latex composite in an amount satisfying L≧−0.26*S+94, where L is the amount of the carbon black in the coagulated latex composite in parts per hundred of rubber (phr) and S is the surface area in m 2 /g as measured by STSA; and 
 a2) introducing a second elastomer latex comprising a second elastomer into the flow of the coagulating mixture to obtain a coagulated latex composite in a form of coherent coagulum and the second elastomer latex is not decorated with filler particles prior to the introduction step; 
   b) dewatering the coagulated latex composite obtained in step a) into a desired water content;   c) incorporating all the constituents of the composition for tire, including the dewatered coagulated latex composite obtained in step b), in a mixer by thermomechanically kneading the whole mixture at high temperature, up to a maximum temperature of between 130° C. and 200° C., then   d) performing mechanical working of the resulting mixture, with incorporation of a crosslinking system, at a temperature of less than 120° C.   
     
     
         2 . The process according to  claim 1 , comprising, before flowing the coagulating mixture, generating the coagulating mixture by feeding a continuous flow of the first elastomer latex to a mixing zone of a coagulum reactor defining an elongate coagulum zone extending from the mixing zone to a discharge end and comprising the conduit, and feeding a continuous flow of a fluid comprising a particulate filler under pressure to the mixing zone of the coagulum reactor to form the coagulating mixture. 
     
     
         3 . The process according to  claim 2 , wherein the continuous flow of the fluid comprising particulate filler has a velocity from about 30 m/s to about 250 m/s, the continuous flow of the first elastomer latex has a velocity of at most about 10 m/s, and a residence time of the coagulating mixture in the coagulum reactor before introducing the second elastomer latex is from 1×10 −2  s to about 6×10 −2  s. 
     
     
         4 . The process according to  claim 1 , wherein the conduit comprises a first conduit portion having a first diameter, a second conduit portion having a second diameter greater than the first diameter, and a transition zone therebetween having a diameter that increases from the first diameter to the second diameter, wherein flowing comprises flowing the coagulating mixture into the second conduit portion from the first conduit portion, and wherein introducing comprises introducing the second elastomer latex into the coagulating mixture in the transition region. 
     
     
         5 . The process according to  claim 4 , wherein flowing the coagulating mixture comprises flowing the coagulating mixture through the transition region under conditions of turbulent flow. 
     
     
         6 . The process according to  claim 1 , wherein in step b) the coagulated latex composite is dewatered into a desired water content of 1% to 20%. 
     
     
         7 . The process according to  claim 1 , comprising, before step c), a further step of drying the dewatered coagulated latex composite. 
     
     
         8 . The process according to  claim 1 , wherein in step c) the constituents are thermomechanically kneaded at a temperature between 145° C. and 185° C. 
     
     
         9 . The process according to  claim 1 , wherein in step d) the constituents are worked at a temperature between 60° C. and 100° C. 
     
     
         10 . The process according to  claim 1 , comprising the step of calendering or extruding the rubber composition obtained after step d). 
     
     
         11 . The process according to  claim 1 , wherein the amount of the second elastomer in the composite is from about 16 wt % to about 38 wt %. 
     
     
         12 . The process according to  claim 1 , wherein the second elastomer is a synthetic elastomer. 
     
     
         13 . The process according to  claim 1 , wherein the second elastomer latex is natural rubber latex. 
     
     
         14 . The process according to  claim 13 , wherein the natural rubber latex comprises field latex, latex concentrate, skim latex, or a combination of two or more of these. 
     
     
         15 . The process according to  claim 13 , wherein a component of the natural rubber latex has been chemically or enzymatically modified. 
     
     
         16 . The process according to  claim 1 , wherein the elastomer composite includes at least 10 phr of the particulate filler. 
     
     
         17 . The process according to  claim 1 , wherein the ingredients of step c) comprise an additive selected from the group consisting of filler, other elastomers, other or additional masterbatch, antioxidants, antiozonants, plasticizers, processing aids, resins, flame-retardants, extender oils, lubricants, methylene acceptors or methylene donors, coupling activators, and a mixture of any of them. 
     
     
         18 . The process according to  claim 1 , wherein the rubber composition is a tire tread.