UNDERWATER COATING BASED ON EPOXY

Abstract: The invention relates to an antifouling and anticorrosive coating composition based on epoxy, which coating is substantially free from solvents, coal tar and biocides, 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 filler. The coating has a high hardness in combination with a good flexibility.

Description: Title: Underwater coating based on epoxy This invention relates to antifouling and anticorrosive coating compositions based on epoxy. It is known to provide metal and plastic surfaces intended for underwater use, such as ships, bridges, locks and the like, with a coating preventing the growth of algae and the like on the surface. Such coatings are provided with materials having a biocidal effect on the materials capable of growing thereon. It often involves copper and related compounds, as well as organotdn compounds. IiHshe past tar products, such as coal tar, were used as base layer, in or on which the antifouling component was applied. These products provide good adhesion to the ground, while they also formed a good basis for the antifouling component. Also, these products give good protection against corrosion. The use of tar products, however, is subject to restrictions, because of the environmental impact of tar products. It has already been proposed to use epoxy resins, mixed or not mixed with tar products or other thermoplastic materials, as base layer for applying an antifouling coating. It has also been proposed to incorporate the antifouling materials in the mentioned base layer. In view of the fact that the antifouling effect of living organisms on underwater surfaces of structures is based on the lixiviation of the biocidal materials, there is an increasing desire to reduce the proportion of toxic materials in the coating or to change to less toxic materials. These, however, inherently have the drawback that they are less effective. One of the objects of the present invention is therefore to provide an epoxy resin-based coating composition having anticorrosive and antifouling properties without the drawbacks of the known systems. More in particular, it is a desire to provide a coating composition containing no or substantially no toxic components, such as biocidal materials, coal tar and large amounts of solvent. It is further a desire to provide a coating composition of such structure that no toxic materials are lixiviated, so that the composition is also suitable for use as coating of surfaces, which may come into contact with foodstuffs. Surprisingly, it has been found that by suitably selecting an epoxy resin hardener system, thermoplastic copolymer of an aromatic C9/C10 fraction, retardant for the hardening, and filler an inherently antifouling and anticorrosive coating can be obtained. The invention therefore relates to an antifouling and anticorrosive coating composition based on epoxy, which coating is substantially free from solvents, coal tar and biocides, 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, colorant and filler. Surprisingly, it has been found that with this composition, after applying and hardening on the surface, a coating is obtained which is antifouling, without requiring the incorporation of a biocide or other antifouling components. Moreover, the composition according to the invention provides a coating having a great hardness, while it is yet flexible. Thus, the invention is particularly suitable for use on objects or constructions, which are subject to weather conditions, such as in navigation, bridges, concrete constructions and the like. In view of the literature in this art (see, for instance, EP-A-0 247 019, NL-A-6915553, WO-A-97/35931 and Chemical Abstracts No. 1289l4n), according to which antifouling compositions always contain at least one toxic component, it is very surprising that this composition has the desired functionality with respect to antifouling. Essential components in the composition are the epoxy resin/hardener combination, which may be based on a conventional bisphenol A system with hardener. Examples are the conventional epicoat epoxy resins. The composition further contains an amount of an aromatic hydrocarbon resin, optionally a small amount of solvent, a diluent and as important component one or more fillers. 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 particularly consists of condensed or non- condensed aromatic compounds having an average of 9 or 10 carbon atoms. The copolymerization is standard effected via the unsaturation 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" is obtained of at least 4 hours. To this end, the conventional commercially sold retardants may be used. Preferred, however, are glycol ethers, since it has been found that, on the one hand, they have a good effect on the retarding, without deterioration of the quality of the coating layer. Probably, it is even so that through the presence of this component the quality of the layer is improved. Suitable amounts for this component are between 1 and 12.5 wt.%, all based on the total weight of the composition. Also incorporated in the composition are one or more fillers. Preferably, this is a combination of a number of fillers. More in particular, it is preferred to use a combination of lamellar fillers and powdered fillers. The first group is, for instance, formed by mica, talc, glimmer, brucite- and chlorite-li e materials, while the second group is formed by substances, such as alumina, silica, silica alumina, quart2 meal and the like. Both for the lamellar and for the particulate filler it holds that it is preferred that the average particle size is less than 20 μm, preferably less than 10 μm. In general, the aim is that the screen residue on a screen of 30 μm is not more than 5%, based on weight. The amount of filler is generally not more than half of the weight of the composition. From practical considerations (cost price, processability) the minimum is 15 wt.%. If desired, the resin composition also contains a colorant. Depending on the intended application, a suitable colorant may be selected, in which connection it is preferred if the colorant is resistant to the action of chloride. The amount thereof is strongly dependent on the nature of the colorant, but will generally not be more than 5 wt.%. The coating composition is, as conventional in this type of compositions, distributed over two components. One component contains the epoxy resin, while the other component contains the hardener. The other ingredients are distributed over the two components, depending on different factors, such as viscosity, shelf life etc. The coating composition according to the present invention is, as stated, suitable as antifouling coating. However, it is also suitable as anticorrosion treatment for different metal surfaces, steel constructions, ships for seagoing and inland navigation, steel constructions for seagoing and inland navigation, roofing and for those situations in which metal surfaces are to be provided with a coating which is allowed to come into contact with foodstuffs. Also, the composition according to the invention is very suitable for use as anti-osmosis agent on polyester surfaces, such as those of polyester ships. More in particular, the coating composition has the advantage that it excellently adheres to existing coating layers, which are often based on tar products, coal tar, bitumen, and tar-containing paint layers. This has the great advantage that the old layer need not be removed. Since the coating also has a vapor-inhibiting effect and even can completely seal, application thereof on old layers also prevents the risk that solvent residues or other harmful components still present, such as polycyclic aromatic hydrocarbons, may be diffused out of the old layer and find their way into the environment. The invention will now be explained with reference to an example Example A composition consisting of : 50 wt.% epoxy resin and hardener 10 wt.% retardant 5 wt.% solvent 200 wt.% filler 15 wt.% thermoplastic copolymerized C9/C10 resin was made as two-component coating. After mixing the components a liquid system was obtained which remained processable for four hours. After application thereof on an existing coal tar layer, a dense coating was obtained, which had a good anticorrosive effect, and which was hardened after 8 hours.

Claims: CLAIMS 1. An antifouling and anticorrosive coating composition based on epoxy, which coating is substantially free from solvents, coal tar and biocides, 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 filler. 2. A coating composition according to claim 1, characterized in that the filler is selected from powdered, lamellar fillers and combinations thereof. 3. A coating composition according to claim 2, characterized in that the lamellar ϋller comprises mica, talc, glimmer, chlorite and the like. 4. A coating composition according to claim 2, characterized in that the powdered filler comprises alumina, quartz meal and combinations thereof. 5. A coating composition according to claims 1-4, characterized in that at most 5 wt.% of a solvent is present. 6. A coating composition according to claim 5, characterized in that as solvent a ketone is present. 7. A coating composition according to claims 1-6, characterized in that a colorant is present, which is resistant to the action of chloride. 8. A coating composition according to claims 1-7, comprising: 25-60 wt.% epoxy resin and hardener 2-10 wt.% retardant 0-5 wt.% solvent 25-50 wt.% filler 3-15 wt.% thermoplastic copolymerized C9/C10 resin. 9. Use of a coating composition according to claims 1-8 as antifouling coating on metal objects. 10. An object, provided with a coating, obtained by hardening a coating composition according to claims 1-8.

Inventors: STRENG THEODORUS WILHELMUS, STRENG, THEODORUS, WILHELMUS
Applicants: STRENG THEODORUS WILHELMUS, STRENG, THEODORUS, WILHELMUS
Application year: 2001
Main classification: C09D163
IPC codes: C09D5, C09D163