A less costly, more efficient method to manufacture polymer-clay nanocomposites is revealed by ExxonMobil Chemical Patents Inc. (Houston, TX) in U.S. Patent 7,632,886. According to inventors Weiqing Weng, Anthony Jay Dias, Kriss Randall Karp, Molly Westermann Johnston, Caiguo Gong, Carmen Neagu, and Beverly Jean Poole, the polymer-clay nanocomposite that can include an elastomer; a polymer or oligomer functionalized with a polar group; and a clay.
The nanocomposite can be a mixture of a halogenated elastomer, an acid or acid anhydride modified polymer, and a clay, desirably an exfoliated clay, suitable for use as an air barrier. Also disclosed is a nanocomposite that can be a mixture of a halogenated elastomer, a polymer modified with a carboxylic acid, and an organoclay.
By blending the functionalized polymer/oligomer with the elastomer and/or clay, the dispersion of the clay in the elastomer can be enhanced without specific functionalization of the elastomer for clay dispersion, and barrier properties of the resulting blend are similar to blending the clay with polar functionalized elastomer. Low-permeability nanocomposites are useful for air barriers and are used in manufacturing tires.
Common types of inorganic particles used in nanocomposites are phyllosilicates, an inorganic substance from the general class of so called "nano-clays" or "clays." Ideally, intercalation should take place in the nanocomposite, wherein the polymer inserts into the space or gallery between the clay surfaces. Ultimately, it is desirable to have exfoliation, wherein the polymer is fully dispersed with the individual nanometer-size clay platelets. Due to the general enhancement in air barrier qualities of various polymer blends when clays are present, there is a desire for a nanocomposite with low air permeability; especially a dynamically vulcanized elastomer nanocomposite such as used in the manufacture of tires.
The preparation of nanocomposites uses a number of methods to generate exfoliated clays. One of the most common methods relies upon the use of organically modified montmorillonite clays. Organoclays are typically produced through solution based ion-exchange reactions that replace sodium ions that exist on the surface of sodium montmorillonite with organic molecules such as alkyl or aryl ammonium compounds and typically known in the industry as swelling or exfoliating agents.
The elastomer can be a halogenated elastomer, such as a halogenated polyisobutylene for example, or a halogenated copolymer of isobutylene and para-methylstyrene as another example. The elastomer can also be halogenated with bromine or chlorine. The halogenated elastomer can have functional groups, such as halides, ethers, amines, amides, esters, acids, and hydroxyls. The elastomer can also be essentially free of polar functionalization, and the halogenated elastomer can be essentially free of polar functionalization other than the halogenation.
