Drug – bio-affecting and body treating compositions – Solid synthetic organic polymer as designated organic active... – Anti-fouling composition
Reexamination Certificate
2000-06-30
2002-07-16
Dawson, Robert (Department: 1712)
Drug, bio-affecting and body treating compositions
Solid synthetic organic polymer as designated organic active...
Anti-fouling composition
C427S140000, C427S142000, C206S232000, C106S287130
Reexamination Certificate
active
06419915
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is related to the field of biofouling release coatings for use in industrial, commercial or military marine and freshwater applications. In particular, this invention relates to a method for regenerating a biofouling release coating which has decreased release efficacy due to depletion or lack of an incorporated oil.
Damage to underwater power cables, ships, and the like due to colonization of their surfaces by organisms (including, but not limited to, barnacles) has serious economic consequences in marine and freshwater industries. Antifouling and fouling release coatings have been developed to prevent or reduce biofouling, and to loosen the strength of the attachment of marine organisms to make cleaning surfaces easier. There are many commercial foul release coatings including, for example, GE EXSIL® 2200. However there have been no reports of renewal methods for these coatings.
There has been a continuing need in the coatings industry for new methods for increasing the useful life of fouling release and antifouling coatings. At present, the useful lifetime of a copper ablative antifouling coating is approximately three years, after which time the coating must be removed from the hull and reapplied. It is estimated that the effective life span of silicone fouling release coatings is about 5-7 years.
The release characteristics of silicone fouling release coatings are known to be significantly enhanced by the addition of oils such as mineral oil and silicone oils. Barnacle adhesion measurements on fouling release coatings substantiate that removal of fouling requires less work when the silicone topcoat has been prepared with incorporated oils. For example, silicone oils such as dimethyl silicone oils, phenyl-modified silicone oils, and polyether-modified silicone oils have been incorporated into biofouling release coatings.
Unfortunately, these additives tend to diffuse out of the coating during use and are thus rapidly depleted. The depleted coatings lose their enhanced foul-release properties, and consequently their effectiveness is reduced. Depletion of the additive therefore limits the useful life of the coating, necessitating periodic removal and reapplication of a new silicone biofouling release coating. A recoat technology for these coatings which does not require complete removal and reapplication of the coating would significantly reduce life-cycle costs and enhance the attractiveness of these coatings to the power utility, military, industrial, and commercial markets.
To forestall the rapid oil-depletion of oil-containing biofouling release coatings, larger amounts of oil have been incorporated into these coatings. This solution to the problem does curtail the rapid depletion of the oil, but unfortunately it tends to severely impair the mechanical properties of the coatings, particularly tear strength and abrasion resistance. Increasing the original additive content of biofouling release coatings, therefore, does not provide a workable method of increasing the life of the coatings.
Silicone biofouling release coatings made without additives also have been used to make cleaning surfaces of organisms easier, but they are not as effective as coatings with incorporated oils. A method for enhancing the properties of these coatings, as well as restoring the enhanced release properties of older coatings originally containing additives is highly desirable.
SUMMARY OF THE INVENTION
The present invention relates to a method of introducing enhanced biofouling release properties to an intact biofouling release coating, which method comprises exposing the surface of the biofouling release coating to a restorative compound for a time sufficient to effect enhancement of biofouling release properties.
In a further aspect, the present invention relates to a kit for the enhancement of the biofouling release properties of an intact biofouling release coating, said kit comprising a container containing a restorative compound suitable for said enhancement.
In yet another aspect, the present invention relates to a kit for the enhancement of the biofouling release properties of an intact biofouling release coating, said kit comprising a container containing a biofouling release coating, and a container containing a restorative compound suitable for said enhancement.
DETAILED DESCRIPTION OF THE INVENTION
The term “oil-depleted” referring to release coatings will be used in this application to denote any biofouling release coating, whether manufactured with or without incorporated oils, which has been depleted of the oil additive or lacks the oil additive, and therefore has a reduced effectiveness compared to coatings containing the oil additive. It is not to be construed as limited solely to coatings which were manufactured containing oil and have subsequently been depleted of the oil.
The biofouling release coatings which may be enhanced by the present invention include generally any coating into which a restorative compound may be incorporated for enhancement of biofouling release properties. The present invention is particularly applicable to release coatings which include a conventional one-part or two-part RTV composition, preferably a two-part composition. It may comprise at least one reactive silicone, at least one condensation catalyst and at least one crosslinking agent.
The reactive silicone is preferably at least one of a polydialkylsiloxane, a polydiarylsiloxane, or a polyalkylarylsiloxane typically of the formula
wherein each R
1
is a hydroxyl radical or
each R
2
is independently a hydrocarbon or fluorinated hydrocarbon radical, each R
3
and R
4
is independently a hydrocarbon radical, a is 0 or 1, and m has a value such that the viscosity of said compound under ambient temperature and pressure conditions is up to about 50,000 centipoise. Illustrative hydrocarbon radicals are C
1-20
alkyl, C
6-20
aryl and alkaryl, vinyl, isopropenyl, allyl, butenyl and hexenyl, with phenyl, C
1-4
alkyl and especially methyl being preferred. An illustrative fluorinated hydrocarbon radical is 3,3,3-trifluoropropyl. Preferably, each R
2
, R
3
and R
4
is alkyl and preferably methyl. The biofouling release coatings may comprise two or more reactive silicones, differing in average molecular weight, which may afford a bimodal composition having performance advantages over a simple monomodal composition.
The condensation catalyst may be any of those known to be useful for promoting condensation curing of an RTV material. Suitable catalysts include tin, zirconium, titanium, and aluminum compounds as illustrated by dibutyltin dilaurate, dibutyltin diacetate, dibutyltin methoxide, dibutyltin bis(acetylacetonate), 1,3-dioxypropane-titanium bis(acetylacetonate), titanium naphthenate, tetrabutyl titanate, zirconium octanoate, and aluminum acetylacetonate. Various salts of organic acids with such metals as lead, iron, cobalt, manganese, zinc, antimony and bismuth may also be employed. For most purposes, the tin and titanium compounds are preferred.
As crosslinking agents, trifunctional (T) and tetrafunctional (Q) silanes are useful, the term “functional” in this context denoting the presence of a silicon-oxygen bond. They include such compounds as methytrimethoxysilane, methyltriethoxysilane, 2-cyanoethyltrimethoxysilane, methyltriacetoxysilane, tetraethyl silicate and tetra-n-propyl silicate. The Q-functional compounds, i.e., tetraalkyl silicates, are often preferred.
The coating may contain other constituents, including reinforcing and extending (non-reinforcing) fillers. Suitable reinforcing fillers are commercially available in the form of relatively large aggregated particles typically having an average size significantly greater than about 300 nanometers (nm). The preferred fillers are the silica fillers, including fumed silica and precipitated silica. Those two forms of silica have surface areas in the ranges of 90-325 and 8-150 m
2
/g, respectively.
The reinforcing filler is most often pretreated with a treating agent to render it hydrophobic. Typi
Bennett Bernadette M.
Dawson Robert
General Electric Company
Johnson Noreen C.
Zimmer Marc S.
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