Clay mineral products and their use in a rubber compositions

Abstract

The invention provides the use of a particulate kaolin clay which: (i) has a particle size distribution such that at least about 95% by volume of the particles have a particle diameter less than 3 μm, and/or (ii) is selected from a particulate soak calcined kaolin, a particulate flash calcined kaolin, and any mixture thereof; as a filler, optionally in combination with silica and/or carbon black and/or other particulate filler, in a rubber composition, more particularly a truck or passenger tyre tread rubber composition.

1 . A rubber composition comprising rubber and a particulate kaolin clay having a particle size distribution such that at least about 95% by volume of the particles have a particle diameter less than 3 μm.  
     
     
         2 . A rubber composition according to  claim 1 , wherein between about 90% and about 98% by volume of the kaolin particles have a particle diameter less than 2 μm.  
     
     
         3 . A rubber composition according to  claim 1 , wherein between about 93% and about 97% by volume of the kaolin particles have a particle diameter less than 2 μm.  
     
     
         4 . A rubber composition according to any one of the preceding claims, wherein less than about 1% by volume of the kaolin particles have a particle diameter between 3 and 5 μm and less than about 40% by volume of the kaolin particles have a particle diameter between 1 and 5 μm.  
     
     
         5 . A rubber composition according to any one of the preceding claims, wherein the kaolin is a calcined kaolin.  
     
     
         6 . A rubber composition according to  claim 5 , wherein the calcined kaolin is a soak calcined kaolin.  
     
     
         7 . A rubber composition according to  claim 5 , wherein the calcined kaolin is a flash calcined kaolin.  
     
     
         8 . A rubber composition according to any one of the preceding claims, wherein the particulate kaolin clay is present in an amount of between about 5 and about 50 phr.  
     
     
         9 . A rubber composition according to any one of the preceding claims, further comprising one or more components selected from one or more additional particulate filler, one or more coupling agent, one or more process oil, one or more antioxidant and/or anti-degradant, one or more lubricant, one or more curing system for the rubber, and one or more activator for the curing system.  
     
     
         10 . A rubber composition according to  claim 9 , consisting essentially of one or more rubber, a particulate kaolin clay filler having a particle size distribution such that at least about 95% by volume of the particles have a particle diameter less than 3 μm, one or more additional particulate filler, one or more coupling agent, one or more process oil, one or more antioxidant and/or anti-degradant, one or more lubricant, one or more curing system for the rubber, and one or more activator for the curing system.  
     
     
         11 . A rubber composition according to  claim 9  or  10 , wherein the one or more additional particulate filler comprises silica, carbon black, or a combination thereof.  
     
     
         12 . A rubber composition according to  claim 11 , wherein the silica, when present, is in an amount of between about 40 and about 150 phr, the carbon black, when present without silica, is in an amount of between about 10 and about 80 phr, and the carbon black, when present with silica, is in an amount between about 1 and about 45 phr.  
     
     
         13 . A production process for a rubber composition as claimed in any one of the preceding claims, the process comprising a step of blending a rubber and a particulate kaolin clay having a particle size distribution such that at least about 95% by volume of the particles have a particle diameter less than 3 μm, the process further comprising blending any desired additional component(s) with the rubber, whether before, simultaneously with, or after the kaolin clay.  
     
     
         14 . A production process according to  claim 13 , wherein the total process to produce a masterbatch ready for curing is performed with only one dumping of partially completed masterbatch for cold milling.  
     
     
         15 . A production process according to  claim 13  or  14 , wherein the total time taken for non-productive blending stage(s), including any cold milling and cooling time between more than one non-productive blending stages but not including any cold milling and cooling time between non-productive and productive blending stages, is less than about 15 minutes.  
     
     
         16 . A tyre tread formed from a cured rubber composition comprising the rubber composition according to any one of  claims 1  to  12  including a curing system, the cured rubber composition being the cured product of reaction of the rubber with the curing system.  
     
     
         17 . A tyre tread formed from a cured rubber composition comprising a rubber, a filler and a curing system, the cured rubber composition being the cured product of reaction of the rubber with the curing system and the filler comprising a particulate calcined kaolin selected from a particulate soak calcined kaolin, a particulate flash calcined kaolin, and any mixture thereof.  
     
     
         18 . A tyre tread according to  claim 17 , wherein the particulate calcined kaolin has a particle size distribution such that at least about 95% by volume of the particles have a particle diameter less than 3 μm.  
     
     
         19 . A rubber tyre comprising a tyre tread according to any one of  claims 16  to  18 .  
     
     
         20 . Use of a particulate kaolin clay which: 
 (i) has a particle size distribution such that at least about 95% by volume of the particles have a particle diameter less than 3 μm, and/or    (ii) is selected from a particulate soak calcined kaolin, a particulate flash calcined kaolin and any mixture thereof,    as a filler, optionally in combination with silica and/or carbon black and/or other particulate filler, in a truck or passenger tyre tread rubber composition.    
     
     
         21 . Use according to  claim 20 , wherein the truck or passenger tyre tread rubber composition has a tan δ at 75° C. and 10 Hz less than about 0.08 under the test method described herein, together with one or more of: an abrasion resistance under the DIN test method described herein of less than about 185 cubic millimetres volume loss; a tensile strength of greater than about 25 MPa; a crescent tear strength under the test method described herein of greater than about 120 N/mm; and a hardness under the test method described herein of greater than about 58IRHD.  
     
     
         22 . Use according to  claim 20  or  21 , wherein the particles of the particulate kaolin clay which has a particle size distribution such that at least about 95% by volume of the particles have a particle diameter less than 3 μm, or the particles of the particulate calcined kaolin, are coated with up to about 15% by weight of an adherent coupling agent, e.g. an organosilane coupling agent.  
     
     
         23 . A particulate kaolin clay for use in a rubber composition, the kaolin clay having a particle size distribution such that at least about 95% by volume of the particles have a particle diameter less than 3 μm and at least about 90% by volume of the particles have a particle diameter less than 2 μm.  
     
     
         24 . A particulate kaolin clay according to  claim 23 , wherein the kaolin is a hydrous kaolin.  
     
     
         25 . A particulate kaolin clay according to  claim 23 , wherein the kaolin is a soak calcined or flash calcined kaolin.  
     
     
         26 . A particulate kaolin clay according to any one of  claims 23  to  25 , wherein the particles are coated with up to about 15% by weight of an adherent coupling agent, e.g. an organosilane coupling agent.