Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-06-02
2001-11-06
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S095000, C524S230000, C524S300000, C524S322000, C524S399000, C524S403000, C524S490000, C524S494000, C524S588000
Reexamination Certificate
active
06313193
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antifouling coating composition, and more particularly to a coating composition which is coated on underwater structures such as ships, port facilities, buoys, pipelines, bridges, submarine stations, submarine oil field excavation facilities, water conduit raceway tubes in power plants, cultivating fishing nets, stationary fishing nets and the like to provide an antifouling coating which is formed on the surface of the underwater structure and which is suitable for preventing underwater living things from adhering and growing on the surface of the underwater structure.
2. Description of the Prior Art
Biofouling, the growth of barnacles, seaweeds, tubeworms and other marine organisms on the hulls of ocean-going vessels, and other underwater structures, cause the international marine community billions of dollars a year. In the case of ocean-going vessels, most of this money goes for the extra fuel needed to overcome the increased drag on vessels. Some of it is spent for hull cleaning and repainting and for the upkeep on propulsion equipment. Of the total amount of money, a tiny amount is invested in the search for better antifouling inhibitors.
One currently used hull antifouling coating contains species such as tributyltin compounds or copper oxide and function through leaching of the toxicant into the marine environment. The resulting environmental hazards of introducing such toxicants into the marine ecosystem include disruption of natural ecocycles for many commercially important shellfish and pollution of entire food chains. The removal and disposal of toxicant-containing coatings from ships and other structures also pose separate environmental hazards, driving up the cost of refurbishment.
An alternative approach is to use acrylic acid monomer compositions which are water soluble, i.e., a polyester resin with an acrylic acid group. Such coatings include a biocide, which after a certain amount of time becomes inactive. The composition, because it is water soluble, wears off over time, i.e., is ablative, and exposes new and active biocide at the surface. Such a composition is known as a self-polishing composition. Thus the alternative approach has been to employ a polymeric coating to function as a fouling release coating. Poly(dimethylsiloxane) (PDMS)-based coatings have properties which meet some of those requirements. On the other hand, as noted, studies have shown that such a cured PDMS material becomes unstable when immersed in water for three months.
Another specific approach involves the use of a composition containing a majority by weight as resin-solid content a reaction-curable silicone resin composition, a silicone resin having the specific average molecular weight and viscosity and an alkoxy group at its molecular terminal. While such a composition exhibits non-toxic characteristics, it is silicone based and in addition to the discussed disadvantages, subject to premature wear requiring frequent maintenance in the form of reapplication of the coating.
In accordance with the invention, the disadvantages of the prior art are avoided and an antifouling coating composition which is a silicone modified glass, not silicone based, is provided which is extremely effective in preventing fouling, and which is highly durable over time.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a two-part formulation for an antifouling coating. The first part is a combination of chemical compounds which make up the matrix of the material. The matrix serves to provide a carrier or support material for at least one other part making up the composition, and optionally a third part. The matrix provides certain critical properties including, but not limited to, good adhesion to the substrate on which the coating is applied, toughness, crack resistance, durability, abrasion resistance, and stability in a aqueous environment. As contrasted to the prior art, the matrix formulation is not a silicone rubber, but is a silicone-modified titanium silicate glass which provides all of the above advantages and overcomes the disadvantages of silicone rubber-based formulations.
The second part of the formulation serves to prevent barnacles and other organisms from attaching to the coating. It is made up of a combination of liquid polymers, oils, or liquid waxes which are incompatible and will phase separate after mixing. These materials may have a chemically reactive group which can be grafted into the matrix so that the materials will riot bleed out into the surrounding environment where combined with the first part, applied as a coating and allowed to cure on the surface thus coated.
An optional third part of the formulation is made up of chemical compounds that prevent or inhibit slime such as algae, bacteria, protozoa, diatoms, etc. from growing on the surface of the coating. While in most cases, the third part will be included in the composition, there are instances when slime is not an issue, and the third part components can be omitted.
In a more specific aspect, the first part of the antifouling coating is made up of a glass composition of titanium silicate glass modified with a hydro or hydroxy functionalized silicone polymer. The glass composition is formed using a Sol-Gel process employing an organotitanate compound, for example, a titanium alkoxide compound such as titanium methoxide, titanium ethoxide, titanium isopropoxide, titanium propoxide, titanium butoxide, titanium ethylhexoxide, or any other type of titanium alkoxide compound. These titanium alkoxide compounds can be used separately or in any combination. Although alkoxide is given as examples, other organotitanate compounds can be used. Also forming the glass is a polydiethoxysiloxane polymer which serves to create cross linking with the titanate. The first part also includes a carboxylic acid compound. Silica gel is optional to inhibit the crosslinking reaction. Silica gel is used if storage over a long period of time is an issue. This is because it stores moisture.
Alternatively, only silica gel can be used in place of the carboxylic acid compound. However, this does not work as well and a lot of silica gel is required.
With respect to the Sol-Gel process, as is well know to those of ordinary skill in the art, the Sol-Gel process is conventional, and typically produces a Sol-Gel glass which results from an optically transparent amorphous silica or silicate material produced by forming interconnections in a network of colloidal submicrometer particles under increasing viscosity until the network becomes completely rigid, with about one-half the density of glass.
For the second part of the composition, about 1% to about 30% by weight of the total coating composition, more preferably about 10% to about 20%, is made up of any one or more of the following microphase separated materials which can be added to the matrix composition of part one. One material can be a vinyl terminated polydimethylsiloxane polymer which has been reacted in a specific manner. A similarly-reacted methylhydrosiloxane polymer can also be employed. Any hydrocarbon compound having a chain of carbon atoms of up to C20 can be used, and polydecene can also be used. Certain kinds of organic fatty acids can also make up part two of the composition, and can include an acid such as octanoic acid or oleic acid or similar type acids. Finally, aluminum oleate may also be preferred to be added. Alternatively, other materials can be added including any fatty acid salt complex. The materials listed with respect to the second part of the coating composition can be added to the matrix in any combination desired.
Part three of the composition includes chemical elements or compounds which are typically slime inhibitors, as has been previously described, and are discussed in greater detail hereafter. Part three of the composition is optional, as previously noted, and can make up anywhere from about 0.1% to about 10% by weight of the total coating composition, a
Microphase Coatings Inc.
Myers Bigel Sibley & Sajovec P.A.
Sanders Kriellion A.
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