The versatility of epoxies arises from the large number of epoxy resins and curing agent combinations. Each combination yields a unique molecular structure. Epoxy resins have found extensive use in a variety of applications including flooring, sealants, coatings, and adhesives since their introduction in the 1940s.
Although the numerous possible combinations of resins and curing agents enable a very large number of unique molecular structures, some combinations of physical properties present significant challenges. For instance, it is difficult to have a very flexible yet very durable material, because the factors that improve one property often degrade the other. Although it is difficult to achieve a material having both flexibility and durability, such materials are highly desirable because they aid in the distribution of stress.
Materials that are both flexible and durable are desirable for applications that require thick films such as tank linings, floor coatings, adhesives, and sealants. Where additional flexibility is required, epoxy system formulation can take several routes. However, most approaches improve either flexibility or durability, but rarely both. For instance, increasing the molecular weight of the epoxy resin or curing agent while maintaining the same number of reactive sites per molecule provides greater durability. Unfortunately, this typically increases viscosity and lowers heat resistance, while providing only a modest increase in durability.
Alternatively, incorporating epoxy resins having flexible backbone segments into epoxy amine systems can impart higher degrees of elongation and lower stiffness, i.e. such materials are more flexible. Additionally, acid functional oils such as castor or cashew nut shell oil, or polyalkylene glycols (polyethylene or polypropylene glycol), are generally used as modifying agents to increase flexibility and toughness. However, both of these options generally result in sacrificing heat and chemical resistance.
Plasticizers have also been unsatisfactory in developing flexible formulations. For instance, plasticizers such as phthalates, sebacates, and phosphates are fully compatible during cure, but separate from the resin or migrate toward the surface after cure.
Another series of routes draw on polysiloxane material and blends thereof. The high bond strength of the Si—O bond results in high thermal and oxidative stability. Furthermore, polysiloxanes tend to be extremely flexible. Previous work has blended polysiloxanes with polyimides, thereby achieving a synergistic improvement in thermal stability. Additionally, epoxy and amine functionalized PDMS compositions are commercially available for blending, but offer limited compatibility with many other coating resins. Somewhat broader ranges of compatibility have been achieved by chemically modifying silicone oils. Finally, cycloaliphatic coating formulations made from diepoxy polyol and caprolactone polyol have been blended with siloxane functionalized caprolactone polyols. However, such blends result in reduced pot life.
A material having flexibility, durability, and chemical and thermal resistance could be achieved by functionalizing siloxanes with cycloaliphatic substituents and amines. However, until now amine functionalized cycloaliphatic substituted polysiloxanes have been unknown in the art due to substantial difficulties in their preparation. The present invention overcomes these difficulties, and teaches methods for preparing such compounds. Furthermore, the present invention enables molecular weight control, circumvents the steric effects of bulky cycloaliphatic substituents, permits the use of a wide variety of previously inaccessible crosslinking agents, and enables post-polymerization hydrosilation. Accordingly, the present invention fills a substantial gap in the art.
USPTO Backgrounds
USPTO Backgrounds