Keratin in rubber applications

#This disclosure relates to rubber compositions that contain keratin, and to tires having at least one component thereof comprising such rubber compositions, including for example, a tread component.

#Rubber goods such as tire treads often are made from elastomeric compositions that contain one or more reinforcing fillers such as, for example, particulate carbon black and silica; see, e.g. The Vanderbilt Rubber Handbook, 13th ed. (1990), pp. 603-04.

#There is continuing interest to provide tires with a high level of handling, steering response, and low fuel consumption. A common method of increasing the steering response of the tire is to use a tread rubber with high stiffness. High stiffness compounds typically have a high dynamic storage modulus (G′). Conventional compounding techniques used to increase the dynamic storage modulus include using a high filler loading, using a filler with a high surface area, and using less softener. However, each of these conventional methods has performance and processing, tradeoffs.

#FIG. 1 illustrates a graph showing dynamic storage modulus as a function of strain for Examples 1-2.

#FIG. 2 illustrates a graph showing dynamic storage modulus as a function of strain for Example 3.

#The present disclosure is directed toward the use of keratin as a filler in rubber compositions. The utilization of keratin in conjunction with one or more coupling agents in rubber compositions results in increased dynamic storage modulus (G′) without significantly increasing the Mooney viscosity (ML4) or otherwise affecting the physical properties of the compounds. An embodiment of the compounds disclosed herein utilizes ground avian feather or feather meal as a keratin-containing filler. Avian feathers and feather meal are a renewable resource. Avian feather meal has a significantly higher bulk density than ground feather and is easier to handle during the manufacturing process. Such compounds are easy to process, cost effective, and environmentally friendly. Furthermore, the use of even a small amount of avian feathers and feather meal in a rubber compound also allows the reduction in the amount of non-renewable fillers such as carbon black.

#Keratin is a protein that contains all of the common amino acids and differs from other fibrous structural proteins chiefly by their high cysteine content. The sulfur atoms in the cysteine produce cross-links between the protein chains that contribute to some of the characteristics of the material. Keratin, either as avian feathers or feather meal, is a high melting, tough, inexpensive, non toxic, renewable material that is light weight and biodegradable. Typical fillers for rubber compositions, such as carbon black, silica, alumina, clay and starch do not possess these characteristics.

#Keratin can be sub-divided into two types: α-keratin and β-keratin. Alpha-keratins are found in the hair (including wool), horns, nails, claws and hooves of mammals. Beta-keratins are present in the nails, scales, and claws of reptiles, shells of tortoises, turtles, and terrapins, and in the feathers, beaks, and claws of birds and quills of porcupines.