The invention relates to antifouling coating compositions (antifouling) based on epoxy. It is known that metal, concrete and plastic surfaces that are intended for underwater use, such as ships, bridges, locks and the like, are provided with a coating which prevents fouling of the surface by algae, shellfish and the like. Such coatings are provided with materials having a biocidal action on the organisms which are capable of fouling them. This typically involves specifically biocidal compounds, but also copper and related compounds, tar products as well as organotin compounds may be incorporated in them. In the past, as a base layer in which or on which the antifouling component was provided, use was made of tar products, such as coal tar. These products afforded a proper adhesion to the substrate, while also forming a proper base for the antifouling component. Also, these products afforded a good protection from corrosion. However, the use of tar products, such as coal tar, is subject to restrictions, because of the environmental impact of tar products. The use of tin -containing products, such as tributyl tin, is also subject to restrictions, or actually banned, because of their environmental impact.

It has previously been proposed to use epoxy resins, mixed or not mixed with tar products or other thermoplastic materials, as a base layer for the application of an antifouling coating. It has also been proposed to incorporate the antifouling materials, such as biocides, copper and tin compounds, in the base layer. In view of the fact that the antifouling effect on living organisms on underwater surfaces is based on the lixiviation of the biocidal materials and/or the metals, or metallic compounds, there is an increasing desire to reduce the proportion of toxic materials in the coating, or to switch to less toxic substances or to limit lixiviation. However, working

with less toxic substances or using fewer of these substances generally involves the drawback of the coating being less effective.

WO-A 02077112 discloses an antifouling which is free from coal tar and biocidal compounds, and which is based on a specific combination of an epoxy resin/hardener system, thermoplastic copolymer of an aromatic

C9/C10 fraction, retardant for the hardening, and filler. This antifouling has a proper antifouling action, probably because of the poor adhesion of algae and shellfish to the surface thereof.

Although this composition has a particularly good action for most uses, it has been found that in particular cases the antifouling action should be improved. In that case, however, it is requisite that the properties of the coating, such as hardness, durability, flexibility and wear resistance, be preserved. Also, it is of importance that no, or substantially no, harmful substances can lixiviate out of the coating. One of the objects of the present invention is therefore to provide an epoxy-based coating composition, which has anticorrosive and antifouling properties, which does not possess the drawbacks of the known systems. More in particular, it is a desire to provide a coating composition which contains no, or substantially no, toxic components such as biocidal materials, coal tar and large amounts of solvent, so that the coating composition has fewer or no harmful effects on the environment, more particularly on the aquatic and the marine environment.

Surprisingly, it has been found that by incorporating a copper oxide in the composition, the antifouling action is greatly improved, without the other properties of the coating being adversely affected. This is particularly surprising since in general the incorporation of (large) amounts of solids in a composition has a strongly adverse effect on the mechanical properties of a coating. Moreover, the combination of copper oxide with this composition has been found to have a particularly good antifouling action, while no or virtually no lixiviation of the metal compound takes place.

The invention accordingly relates to a copper -containing antifouling coating composition based on epoxy, at least comprising an epoxy resin, a hardener therefor, a hardening-retardant compound, a thermoplastic hydrocarbon resin based on a copolymerized aromatic C9/C10 hydrocarbon fraction, optionally colorant and/or filler, and an effective antifouling amount of at least one oxidic copper compound.

Surprisingly, it has been found that with this composition, after application and hardening on the surface, a coating is obtained which is antifouling, while preserving the good properties of the base coating composition, a high hardness and good wear resistance, combined with a good flexibility, smoothness, chemical resistance and durability. Despite there being virtually no lixiviation of copper, the composition yet has an excellent antifouling action.

As a result, the invention can be used especially suitably on objects or constructions that are subject to weather influences, as in shipping, in bridges, in concrete constructions, and the like. Used in sweet, in brackish, as well as in salt water, this composition has a good action, and also upon prolonged use, virtually no wearing off of the coating layer arises. The current antifoulings involve a wearing off of the layer as a result of use, whereby the action (and the active substances), after a shorter or longer period of time, disappear from the layer and thereby not only lose their action but also end up in the environment.

An important component of the composition is constituted by the oxidic copper compound. Although the various oxides of copper are all useful, monovalent copper, preferably in powder form, is preferred. However, it is also possible to use other oxides of copper, such as higher- or lower-valence oxides of copper. It is also possible to use combinations of copper oxides, for instance mixtures of copper (I) oxide with other copper oxides. The particle size is preferably less than 200 μm, more particularly less than 100 μm. The

weight-average particle size is most preferably less than 100 μm, more particularly between 10 and 50 μm.

The amount of oxidic copper compound can vary within wide limits, depending on the intended use. Suitable amounts are between 25 and 90 wt.%, based on the total weight of the composition, more particularly 55 to 75 wt.%.

In addition to the oxidic copper compound, important components in the composition are the epoxy resin/hardener combination, which may be based on a conventional bisphenol A system with hardener. Examples include the current epicoat epoxy resins. The composition further contains an amount of an aromatic hydrocarbon resin, optionally a slight amount of solvent, preferably less than 10 wt.%, a diluent and optionally one or more fillers. The composition further contains no biocides (other than the copper compound, but this is generally not regarded as a biocide) or coal tar. The aromatic hydrocarbon resin consists of a copolymerized C9/C10 hydrocarbon fraction, which is a product from the cracking of petroleum and/or naphtha. This fraction consists especially of condensed or uncondensed aromatic compounds having on average 9 or 10 carbon atoms. The copolymerization is effected in a standard manner via the unsaturation that is present in the aromatic compounds. The amount of this hydrocarbon fraction is preferably 1 to 25 wt.%. Another important component in the composition is the retardant for the hardening. This retardant is present in such an amount that an open time or "potlife" of at least 3 hours is obtained. To that end, the current retardants that are commercially available can be used. Preferred, however, are glycol ethers, since these have been found, for one thing, to have a good influence on the retardation without the quality of the coating layer deteriorating. Probably, the quality of the layer actually improves as a result of the presence of this component. Suitable amounts for this component are between 1 and 12.5 wt.%, all based on the total weight of the composition.

In the composition, one or more fillers may be incorporated, but in view of the presence of the copper compound, this is not requisite. Preferably, this involves a combination of a number of fillers. More particularly, it is preferred to use a combination of lamellar fillers and powder fillers. The first group is for instance formed by mica, talc, glimmer, brucite and chlorite-like materials, while the second group is formed by substances such as alumina, silica, silica alumina, quartz flour and the like. Both for the lamellar and for the particulate filler, it holds that it is preferred that the average particle size be less than 20 μm, preferably less than 10 μm. In general, the aim will be that the screen residue on a 30 μm screen does not amount to more than 5% based on weight. The amount of filler is generally not more than half of the weight of the composition.

If desired, the resin composition also contains a colorant. Depending on the intended use, a suitable colorant can be chosen, it being preferred for the colorant to be resistant to the action of chloride, in view of the use in salt water. The amount thereof is strongly dependent on the nature of the colorant, but will generally not amount to more than 5 wt.%.

The coating composition, as is conventional with this type of compositions, is divided over two components. One component contains the epoxy resin, while the other component contains the hardener. The other ingredients are divided over the two components, depending on various factors, such as viscosity, storage stability, etc. The oxidic copper compound is preferably incorporated in the resin component.

The coating composition according to the present invention, as stated, is suitable as antifouling coating. In addition, however, it is also suitable as anticorrosion treatment for various metal surfaces, steel constructions, ships for seagoing and inland navigation, steel constructions for seagoing and inland navigation, or roofing.

The coating is preferably applied as a top layer (or top layers) over a coating as described in WO-A 02077112, that is, more particularly, over a

coating consisting of a hardened composition based on an epoxy resin/hardener system, thermoplastic copolymer of an aromatic C9/C10 fraction, retardant for the hardening, and filler.

Since the coating further has a vapor-inhibiting action, and can actually seal completely, its application to old layers further prevents the possibility of any solvent residues or other harmful components still present, such as polycyclic aromatic hydrocarbons, diffusing from the old layer and ending up in the environment.

The invention is presently elucidated in and by an example.

Example

A composition consisting of:

50 parts by weight of epoxy resin and hardener,

10 parts by weight of retardant, 2000 parts by weight of Copper (I) oxide < 325 mesh, 15 parts by weight of thermoplastic copolymerized C9/C10 resin

was made as a two-component coating. After mixing of the components, a liquid system was obtained, which remained processable for three hours.

The composition was applied to a steel plate, hardened and exposed for 6 days to mains water of 35 ⁰ C. Following the test, the content of copper in the water was determined and it proved that 0.3 ppm of copper had lixiviated. This means, upon conversion, that the lixiviation rate under those conditions is 0.02 μg/cm ² /day, which is negligibly low.

Upon testing of the hardened coating as antifouling over a period of 12 months in salt water, no fouling by algae and shellfish was observed.