The use of plastic has become ubiquitous in the manufacture of household products, toys, tools, entertainment devices, computer hardware, and automobile components. Plastic substrates are generally low cost, durable and light weight; however, plastic is susceptible to being damaged by sunlight and weathering, impacts, and exposure to chemicals, including common chemicals found in lotions and insect repellants. In recent decades, coatings have been developed for application to plastic substrates that are intended to protect the substrate and provide aesthetic value. More recently, coatings have been surfacing that not only protect the plastic surface but also impart a soft, grippy or rubbery feel to the otherwise hard plastic. These coatings have been generally branded with the term “soft-touch” or “soft feel” coatings.
Vehicle manufacturers, be they automotive, aerospace, or marine manufacturers have been one of the biggest consumers for soft-feel coatings apart from manufacturers of consumer goods and electronics. The automotive companies have developed very exacting, but increasingly demanding specifications for interior coatings. Automakers are continually looking for coatings that exhibit great appearance, excellent resistance properties, rapid cure, ease of application, lower cost and are environmentally friendly.
Soft touch coatings have been subject to increasingly demanding specifications as well. Particularly, soft-feel coatings are being challenged to have improved chemical resistance. The motivation driving this movement is evidence that many chemicals, including those found in lotions and insect repellants, can soften the coating, and will migrate through the coating and into the plastic, causing adhesion loss of the coating to the plastic substrate and, in some instances, damage to the underlying plastic substrate. One approach to resolving this has been a multi-coating system incorporating a primer for chemical resistance and a soft-feel top coat. However, this multi-coating approach is time consuming.
First-generation soft-feel coatings were largely solventborne polyurethanes based on blends of polyols and isocyanates. Environmental regulations and consumer preferences have caused coatings suppliers to develop more environmentally friendly technologies. Therefore, new generations of soft-feel coatings have shifted toward 2K waterborne chemistries, primarily, but not exclusively, utilizing polyurethane dispersions (PUDs). More recently, 1K soft-feel coatings have been under research.
Despite the efforts of formulators, it is still a challenge to provide soft-feel coatings that satisfy the more stringent standards for chemical resistance. To date, efforts at improving chemical resistance have primarily focused on improving or modifying the resin system. A typical waterborne soft touch formulation comprises a water dispersible polyol resin, often a polyurethane polyol dispersion and a water-dispersible isocyanate. The compositions may include other non-functional resin dispersions. Thus, some improvement in chemical resistance may be anticipated from a observant selection of polyols and other resin blends based on resin characteristics, morphologies and properties, like glass transition temperature (Tg), molecular weight or shape, all selected with any eye toward balancing flexibility, softness and resistance to chemicals. Exemplary of “resin-centric” approaches to improving chemical resistance in soft-touch coatings, are the efforts described in U.S. Pat. No. 8,313,837, which generally describe polyurethane soft touch coatings comprising one or more aqueous hydroxyl functional polyurethane dispersions and a polyisocyanate. Aqueous non-hydroxyl functional polyurethane dispersions are taught as useful contributions to the coatings. Another water-borne polyurethane soft touch coating is described in WO/2012/089827, which describes a polyurethane soft touch coating comprising the reaction product of a) a non-hydrolysable polyol binder, such as a polycarbonate or polyether polyol or polyester polyols having sterically hindered ester linkages, which are protected from hydrolysis, and b) and organic polyisocyanate.
Despite numerous research efforts directed at improving chemical resistance through modification of the resin system, there is still a need to improve the chemical resistance of the current generations of soft-touch coatings. The present invention is based on the surprising discovery that certain pigments can be employed in wide variety of soft-touch coatings resulting in coatings that have substantially improved chemical resistance, particularly against lotions and insect repellents, and yet, retain their soft touch feel.