Antifouling paint

Details Antifouling paint Antifouling paint

1999-01-20

2001-06-19

Cain, Edward J. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C106S015050, C106S639000, C106S711000

Reexamination Certificate

active

06248806

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to antifouling paints that prevent unwanted fouling organisms from attaching and growing on immersed structures that come in contact with water, especially sea water, for example vessels (including but not limited to boats, yachts, motorboats, motor launches, ocean liners, tugboats, tankers, container ships and other cargo ships, submarines, and naval vessels of all types), pipes, shore and off-shore machinery, constructions and objects of all types such as piers, pilings, bridge substructures, underwater oil well structures, nets and other aquatic culture installations, and buoys etc.
BACKGROUND OF THE INVENTION
On underwater structures and on ship's hulls which are exposed to sea and/or fresh water, attachment and growth of marine organisms such as green algae, such as Enteromorpha spp. and Ulva spp., diatoms, such as Amphora spp., tubeworms, barnacles such as Balanus spp., ascidians, sponges, hydroids etc. cause severe economic losses because of the increased friction (and therefore increased consumption of fuel), or increased resistance to waves or currents (for static structures such as off-shore rigs), and because of decreased un-docking time.
In order to solve the fouling problem several antifouling paint technologies have been developed. Some technologies are based on the principle of incorporating biologically active agents into the paint. However, in order to obtain a satisfactory incorporation and a proper controlled release of the biologically active agents, the mechanical properties of the antifouling paint, e.g. the mechanical strength of the paint and the ability of the paint to adhere to other paints, may be impaired.
Another antifouling paint technology that has been investigated for a number of years, is the use of self-polishing antifouling paint compositions in which the polymer of the binder system is a trialkyltin derivative of a polymer containing carboxylic acid groups in the monomer segments, the alkyltin groups being situated on the carboxylic acid groups. However, the increasing problem of pollution with tin compounds in, e.g., harbours has led to intensive research efforts to provide tin-free self-polishing antifouling paints.
The search for binder systems for tin-free self-polishing antifouling paints, on the one hand having inherent self-polishing properties and exhibiting good capabilities for incorporation of biologically active agents, and on the other hand being able to convey a good mechanical strength of the paint film, has so far been a difficult task.
One way of obtaining binder systems for antifouling paints, such as for tin-free self-polishing antifouling paints, is to employ substances such as rosin or rosin equivalents as part of the binder system. Rosin or rosin equivalents has a number of highly desirable properties for use in antifouling paints; due to its water solubility it is capable of releasing biologically active agents into the water at a controlled rate. Also, it is compatible with a large number of binder components; this facilitates the formulation of a final coating product. Furthermore, it is readily available, relatively cheap and originates from a self-renewable natural source. In principle, the water solubility gives the opportunity of obtaining a high polishing rate in a rosin-containing paint if a high proportion of rosin or rosin equivalent is incorporated. However, inclusion of a high proportion of rosin or rosin equivalents in order to ensure a polishing rate optimal for practical purposes leads to an antifouling paint having severe mechanical deficiencies, such as cracking tendencies and poor resistance to weathering.
Therefore, due to the inherent mechanical deficiencies of such self-polishing binder systems, their polishing properties can not be fully expressed. The applicant's previous application, WO 96/15198, provides solutions to this problem, however, the applicant has now, after further development work, found important improvements and alternatives to the invention previously described.
SUMMARY OF THE INVENTION
The present invention, i.&agr;., relates to a marine antifouling paint comprising rosin or rosin equivalents, one or more polymeric flexibilizer component(s), and fibres.
DETAILED DESCRIPTION OF THE INVENTION
The marine antifouling paint according to the present invention is preferably a self-polishing antifouling paint.
The present invention provides an antifouling paint which contains a high proportion of rosin or rosin equivalents, such as a proportion of 15% by solids volume of the paint or even more, such as up to 80% solids volume of the paint, but which, at the same time, has satisfactory mechanical properties which render it realistic to employ such paint for normal and even demanding anti-fouling purposes, such as being exposed to sunlight for prolonged periods of time, or being exposed to cycles of immersion/sunlight exposure as it happens in the water-line of a ship.
Thus, this invention makes it possible to utilise the desired beneficial properties of rosin and rosin equivalents in antifouling paints, and to increase the content of rosin or rosin equivalents with full or substantially full retainment of the crucial antifouling properties of the paints, and even enhancement of the antifouling properties due to the incorporation of higher amounts of rosin or rosin equivalent(s). This may be achieved by using polymeric flexibilizer component(s) in combination with reinforcing fibres and rosin and rosin equivalents. Thus, by setting up special requirement to the quality of the rosin or rosin equivalents and the polymeric flexibilizer component(s), the properties of antifouling paints may be improved.
In the present context, the terms “self-polishing” and “polishing” are intended to mean that the coating in question, or the paint when dried up as a coating, under the test conditions described in the Polishing Rate Test herein, is subject to a reduction of the thickness of the coating of at least 1 &mgr;m per 10,000 Nautical miles (18,520 km) of relative movement between the coated surface and the surrounding aqueous medium due to removal of coating material from the surface of the coating.
In the present context the terms “mechanically weak” and “mechanical deficiency” relate to a paint which (a) when in the Steel Panel Elongation Test herein shows micro or macro cracking when elongated 4 mm or (b) when tested in Laboratory Cracking Test herein results in a ranking of below 5.
Alternatively, mechanical weakness or deficiency of a paint can also be identified by testing the paint in the Direct Impact test or the Mandrel Test described herein; i.e. mechanical deficiency is also identified for a paint tested in the Mandrel Test herein showing failure when using a mandrel having a diameter of 20 mm, or tested in the Direct Impact Test herein showing failure when hit by the standard weight dropped from a height of 40 cm.
In the present context the term “marine” relates to any kind of aqueous environment such as salt, brackish or fresh water. The term “immersed” relates to structures being contacted with such a marine environment.
In the present context the term “% by solids volume” is intended to mean the volume/volume percentage of the dry matter of the paint.
According to the present invention, the paint comprises a polymeric flexibilizer as well as fibres. The fibres may, in principle, be any fibres which, either in the native form or after surface modification, are capable of being incorporated in an antifouling paint having mechanical deficiencies, but preferably, the fibres are fibres which will improve the mechanical strength of an antifouling paint tested in the Laboratory Cracking Test herein. The fibres may, as it will be clear from the description of the manufacture processes further below, be added together with the remaining paint constituents before milling or may be added afterwards.
In the present context the term “fibres” is intended to mean any fibres within the groups of natural inorganic fibres, synthetic inorga

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