Method of preparing an anti-fouling coating

#This invention relates to anti-fouling coatings and more particularly to an improved method of preparing an anti-fouling coating which provides for prolonged, controlled release of a biocide.

#Marine engineered systems, such as ships, floating platforms, seawater piping systems and other fixed structures located in seawater near the surface will quickly support a variety of marine bio-fouling communities such as soft-fouling organisms, e.g., algae and invertebrates, and hard-fouling species, e.g., barnacles and mussels. Countermeasures against these damaging bio-fouling communities attempting to establish residence on the surfaces of marine engineered systems is a major challenge. Prior art countermeasures, by necessity, are intended to be toxic to the bio-fouling communities and thus raise many environmental and human health issues.

#In marine vessels, bio-fouling is very costly because excess fuel is required to overcome the increased hydrodynamic drag on the hull of a bio-fouled vessel, as well as the costs associated with the application, maintenance, and removal of anti-fouling coatings. Bio-fouling of Navy ships results in lost Naval force capability because the bio-fouled ships are unable to achieve their designed speeds or range. Moreover, the downtime required for the foulant removal and/or the maintenance of anti-fouling coatings further reduces Naval capability.

#Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:

#FIG. 1 is a graph showing the release rate of a prior art biocide from a protective coating applied to a sea vessel or other sea structure;

#FIG. 2 is a three-dimensional view showing an example of both a collapsed and swollen polymeric gel bead in accordance with this invention;

#Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details and arrangements set forth in the following description or illustrated in the drawings.

#As explained in the Background section above, typical prior art anti-fouling coatings for ships and other engineered structures located in seawater utilize toxic anti-fouling biocides, such as metals, mercury, arsenic, tin, copper, zinc, silver, chromium, barium, and selenium. Other prior art anti-fouling coatings use organotin compounds, e.g., tributyltin (TBT), or ablative cuprous oxide. Some of these prior art anti-fouling coatings are damaging to the marine environment and also have an effective lifetime which does not meet the typical 5 to 7 year docking interval that ships undergo for servicing.

#These prior art protective coatings cannot provide for sustained, controlled release of the biocide for extended periods of time. As shown in FIG. 1, the biocide release rate for these anti-fouling coatings falls to zero well before the typical 5 to 7 year docking interval that ships undergo for servicing.