Latest Developments In Marine Antifouling Coatings

- Aug 27, 2019-

The problem of marine biofouling has always been a big problem for the shipping industry, and the annual cost for this is about $200 billion. Sea creature attachment not only causes additional fuel consumption, reduces the life of the ship, but also increases carbon dioxide emissions. According to data from Lloyd's Register, the world's annual increase of 28% of fuel consumption will bring in an additional 250 million tons of carbon dioxide emissions. With the increasingly strict international environmental regulations and the development of low-carbon economy requirements, shipowners and shipping industry will hope to further submit to the coatings industry; at the same time, the implementation of a series of coating-related regulations and conventions has also produced for the world coatings industry. Unprecedented pressures such as VOC regulations in various countries, the European Union's Guide to Biocide Products (BPD), IMO's International Convention for the Control of Harmful Anti-Fouling Systems on Ships (AFS Convention), and Performance Standards for Protective Coatings for Ships' Ballast Tanks (PSPC) and REACH regulations and so on. The marine coatings industry is not expected to develop anti-fouling coatings with high performance, energy and resources, convenient and efficient construction, and environmentally friendly and healthy.

Antifouling coatings are one of the most important varieties in marine coatings. With the entry into force of the International Convention for the Control of Harmful Anti-Fouling Systems of Ships (AFS Convention), organotin antifouling coatings have fully withdrawn from the market. At present, commercial antifouling coatings fall into two categories: first, antifouling coatings containing insecticides (non-organic tin); second, antifouling coatings without insecticides (or low surface energy antifouling coatings) , foul release antifouling coating FRC). At the same time, new technologies are constantly emerging, and antifouling coatings will surely move in the direction of no heavy metals and no pesticides.


1 Contains insecticide antifouling paint

Antifouling coatings containing insecticides are still the mainstream of antifouling coatings, with a market share of 90% to 95%. The formulation contains about 30% to 60% antifouling agent, mainly cuprous oxide, and usually other antifouling agents are added to broaden its antifouling range and enhance its antifouling effect. In addition to cuprous oxide, commonly added antifouling agents are copper pyrithione, zinc pyrithione, dithiocarbonate, 4,5-dichloro-2-octyl-3(2H)-isothiazolone. , diuron, s-triazine, cuprous thiocyanate, trichlorophenyl maleimide, biological antifouling agent, and the like.

The antifouling coating containing the insecticide is further divided into a controlled dissolution type antifouling coating, a hydrolyzable self-polishing antifouling coating and a mixed antifouling coating from the composition and action mechanism.

1.1 Controlled and dissolved antifouling coating

The controlled dissolution type antifouling coating is a combination of a traditional dissolved antifouling coating and a long-acting diffusion type (base insoluble) antifouling coating technology, and contains hydrophilic rosin, hydrophobic ethylene or acrylic resin, and oxidized sub- Copper, a small amount of organic antifouling agent, which forms the antifouling surface of the hydrate during use, and renews the surface by the scouring action of seawater to achieve the purpose of "polishing". Its validity period can reach more than 3 a.

1.2 Hydrolyzed self-polishing antifouling coating

According to the similar mechanism of organotin self-polishing antifouling coating, the development of hydrolyzed self-polishing antifouling coating without organotin is a leap in the environmental protection process of antifouling coating. The anti-fouling purpose is achieved by the hydrolysis or ion exchange of the acrylic polymer in seawater to ensure the smooth exudation of the antifouling agent. The hydrolyzable or ion-exchanged acrylic polymer is mainly composed of copper acrylate polymer, zinc acrylate polymer, and acrylate siloxane polymer. The performance of this kind of antifouling coating basically reaches the performance of organotin self-polishing antifouling coating, the anti-fouling effect can reach 5 a, the polishing rate and the anti-fouling agent exudation rate are controllable, and the anti-fouling agent diffusion layer is thin. .

1.3 Mixed antifouling coating

The hybrid antifouling coating combines the characteristics of the two antifouling coatings described above to provide a limited self-polishing function. The main film-forming material is a hydrolyzed (ion exchange) type polymer resin such as copper acrylate, zinc acrylate or the like + hydrophilic rosin. The coating avoids the low solid content of the self-polishing antifouling coating, the poor compatibility with the old coating film of the bottom layer (generally required to apply the sealing coating), the high price, and the polishing rate of the controlled dissolution type antifouling coating and the antifouling agent exudation rate. The controllability is poor, the coating film is soft, and the solid fraction is improved, the polishing rate and the anti-fouling agent exudation rate are controllable, the compatibility with the old coating film is good, the mechanical performance is good, and the price is moderate.

1.4 The latest technology without copper or low copper

At present, the environmental impact of copper-containing antifouling agents has attracted much attention. Some countries have restricted their use in antifouling coatings for yachts. Some countries have limited the exudation rate of copper while strengthening their in-depth Research and assessment, whether there is a comprehensive restriction on the remaining disputes. But in any case, it is imperative to reduce the copper content of antifouling coatings and to develop long-lasting antifouling coatings that do not contain copper.

Hempel has introduced the Hempaguard hybrid system in recent years. Based on ActiGuard's patented silicone hydrogel and high-efficiency antifouling agent, it can effectively reduce copper content by 95% and antifouling effect for 90 months, even at static or low speed. The effect is excellent. It has been used for the coating of 160 ships, saving energy by 6% to 8%. In order to improve the antifouling performance and environmental friendliness of antifouling coatings, it is more important to develop efficient, broad-spectrum and environmentally friendly organic antifouling agents. Swedish I-Tech and the University of Gothenburg have collaborated to develop Medetomidine as the main ingredient for antifouling agents of only 0.1%. Another antifouling high-efficiency product, isothiazolinone (Sea-Nine211), is also used in an amount of only 3% to 10%. Romn&Hass (now Dow Chemical) has further studied the microencapsulation of isothiazolinone, which is close to commercialization, uses less, and is more reasonable to release. Janssen PMP's antifoulant products are Econea (metal-free arylpyrrole compound) and Zinc PYRIONTM (zinc pyrithione). Econea is the most definitive anti-fouling agent approved by the European Union's pesticide regulations. It is used in combination with other anti-fouling agents such as ZincPYRIONTM algaecide. It can be used in a small amount to form a smooth coating film. Exceeds copper-containing antifouling agents. PPG, AkzoNobel and other major antifouling coatings companies have used or are in the process of using this product for the antifouling of aluminum shell ships.

Another important development direction for pesticide-containing antifouling coatings is the development of biocides that have no environmental safety issues. Many marine natural plants and animals and non-marine plants and animals secrete stimulating metabolites during the process of life to prevent other organisms from attaching. These substances are non-toxic and degradable, but are repellent to other organisms. They are the focus of research on non-toxic antifouling agents in recent years, and a series of biological antifouling agents have been extracted for the testing of antifouling coatings. However, to date, there is still a certain gap between the complete replacement of copper-containing antifouling agents and the practical use.


2 pesticide-free antifouling coating

Non-toxic low surface energy antifouling coatings (FRC) do not contain any pesticides, and environmentally friendly properties are widely recognized. Research has made great progress and has been commercially applied.

Low surface energy antifouling coatings are mainly based on silicone and organic fluorine fouling release antifouling coatings. These antifouling coatings make the fouling organisms difficult to adhere or adhere to the water by the low surface energy properties of the coating. Scour out to achieve anti-fouling purposes. In theory, it does not rely on the anti-fouling agent to seep out and prevent pollution.

The representative of the low surface energy antifouling coating is the Intersleek series, the flagship product of AkzoNobel's international paint company. With its patented fluororesin technology, it has developed three generations of products. The latest generation is the Intersleek 1100SR, which can be used in temperate waters, even in slower sailing environments. Followed by PPG's latest product, Sigmaglide 1290, launched in July 2014. 100% of the silicone resin is used at the molecular level. The coating has a high surface density of silicone, so that marine organisms can not be attached. The surface cannot be attached. The coating uses dynamic surface regeneration technology, using water as a catalyst to continuously restore the coating to its initial surface energy state, thus overcoming the effects of low surface energy antifouling coatings on UV, sunlight and contaminants over time. The disadvantage of deterioration failure. The coating achieves a technological breakthrough in low surface energy coatings. Hydrex's Ecospeed antifouling product is a glass flake-reinforced, non-toxic, non-silicone system based on vinyl ester resin that forms a hard-coated surface of the dimple and reduces the roughness of the hull to 20 μm. the following. Ecospeed is designed to clean regularly in water, keeping the coating smooth and effective for up to 10 years or even the entire life cycle. Specially designed to protect the rudder, spherical bow, stabilizing fins and Kort nozzles and other underwater components of the ship. Jotun's Sealion Repulse low surface energy antifouling coating uses innovative nano anti-adhesion technology to form nano-sized "whiskers" on the surface of the coating. The coating has better fouling release and anti-fouling properties. It is said that there is a 10 a anti-fouling effect. North Dakota State University has carried out a large number of research work on foul release antifouling coatings with the support of the US Naval Research Agency. The hyperhydrogenated polyether polyol polyurethane was mainly used to design a hydrophilic hydrophobic amphiphilic structure with fouling release properties through the regulation of the segment; a methylsiloxane-containing polyurethane with fouling release properties was synthesized. Matrix resin; also connects triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether) and quaternary ammonium salt to the main chain of silicone resin, and further enhances the action of the fungicide Antifouling properties of the coating. The research on low-surface antifouling coatings by major paint companies at home and abroad has never been interrupted, new products have been introduced, and a sufficient amount of technical reserves have been made. Although the mainstream products are still high-copper antifouling coatings, low-surface antifouling coatings will quickly dominate the market once relevant regulations are introduced.


3 biomimetic antifouling paint

Bionic antifouling is an important frontier in the field of antifouling coatings in the world today, including not only chemical bionics, but also structural bionics. Algae in the ocean and large animals, large shellfish surface are not attached to other organisms, long-term living in a marine environment filled with all kinds of attached small creatures, its anti-fouling skills far beyond people's imagination. This is not only because marine organisms secrete special chemical substances to protect other organisms, but also has a unique transport mechanism that allows this repellent material to be continuously transported to the surface; secondly because the surface of marine life has a unique structure. Structure bionic antifouling is a technique that simulates the structure of a biological surface and relies on the specific physical effects of the coating to resist other organism attachment for a long time.

3.1 Chemical bionic antifouling coating

Compounds such as terpenoids, heterocyclic compounds, and alkaloids have been extracted from sponges, corals, red algae, and brown algae, and have been shown to have antifouling effects. These substances are added to the self-polishing antifouling coating system to make the surface self-polishing. Constantly updated, it is like continuously secreting the surface of marine organisms that supplement the repellent substances to achieve anti-pollution purposes.

The latest achievement in chemical biomimetic antifouling in recent years is the study of biological enzymes, such as vanadium halogen peroxidase contained in algae. Under the catalysis of enzymes, hydrogen peroxide and bromide ions in seawater produce a small amount of hypobromous acid, decompose the proteins attached to the organism, interfere with the metabolism of the fouling organisms, inhibit the deformation and growth of the attached organisms, and thus achieve antifouling. purpose.

Scientists at Johannes Gutenberg University Mainz (Mainz University, Germany) have developed a vanadium pentoxide nanoparticle biomimetic antifouling coating based on this mechanism, and have made substantial progress in the use of hulls, marine buoys and offshore platforms to prevent barnacles. Attachment of bacteria, algae, etc. Vanadium pentoxide nanoparticles have natural biomimetic bromination activity and can be used as a practical and economical alternative to antifouling agents. A small amount of hydrogen peroxide is produced in seawater under sunlight, and bromide ions are already present in seawater. Like vanadium pentoxide nanoparticles, as a catalyst, hydrogen peroxide and bromide ions are combined to form a trace amount of hypobromous acid, which has a killing effect on marine organisms. This effect is limited to the micro surface. Some people have discussed the environmental impact of vanadium pentoxide, which proves that only trace amounts of vanadium migrate into seawater and have no effect on the environment.

Irgarol 1051 manufacturers said that Irgarol 1051 [N-cyclopropyl-N'-(1,1-dimethylethyl)-6-(methylthio)-1,3,5-triazine-2,4 -diamine] and so on. Among them, Sea-Nine 211 has a good inhibitory effect on diatoms, bacteria, algae plants and barnacles, and has high efficiency. It can be quickly decomposed by hydrolysis, photodegradation and biodegradation without causing cumulative effects. The marine environment is very safe. Copper Omadine has proven to be non-polluting to cage cultured fish. Irgarol 1051 suppliers said that Irgarol 1051 is effective against algae and bacteria, but not against animal fouling organisms. These organic antifouling agents need to be combined with other antifouling agents such as cuprous oxide to have a better overall effect.

3.2 Structural bionic antifouling coating

The biomimetic antifouling bionic objects are mainly large marine animals such as sharks, dolphins, whales, etc. or shellfish. His research focuses on the use of molecular techniques to design and prepare specific polymer materials, simulating the epidermal structure and geometry of large animals, and forming a series of artificial surfaces. This simulation is usually micro-nano-scale and multi-structural, and any single artificial structure cannot prevent the adhesion of a variety of marine organisms. For example, the ship's green anti-fouling technology, which is based on the surface structure of the shell, is completely inhibited from the surface structure design of the material, and provides a new way to explore the ship's green anti-fouling technology. Nanocyl of Belgium has developed a carbon nanotube BioCylT specifically for antifouling coatings. By dispersing carbon nanotubes into a silicone system by a special dispersion process, a special microscopic surface structure is formed, which has good antifouling properties. The nanostructured surface obtained by scientists at Shelfied Hallama University in the UK through sol technology and nanotechnology has good foul release properties. In addition, it has been found that the outer layer of red blood cell cells is not prone to blood coagulation because it contains a high proportion of zwitterionic phosphocholine. Therefore, the anti-adhesion property of zwitterionic polymers has been studied. At present, polysulfonate betaine and polycarboxybetaine have been studied, and it is found that such substances can significantly reduce the adsorption of blood proteins and cells. In view of the similar adhesion mechanism of marine organisms and blood cells, it is believed that zwitterionic polymers have certain antifouling prospects.


4 Other antifouling technologies and coatings

With the gradual deepening of interdisciplinary research and the further understanding of the mechanism of marine fouling organisms, new antifouling technologies have emerged and combined with antifouling coatings to improve the antifouling properties of coatings. The energy antifouling method is a method that has been studied in recent years. Among them, pulsed laser irradiation is very effective in preventing the adhesion of diatoms. Plasma pulse technology has been shown to prevent mussel adhesion. Similarly, high energy pulsed sound waves can prevent the attachment of algae. Nedmarine, the Netherlands, uses high-frequency ultrasonic technology in combination with antifouling coating systems for the antifouling of large ships. It has been able to prevent the attachment of oysters and the like, and is currently expanding its application. Ultrasonic is suitable for any coating, but especially with hard coatings, the bubbles generated by the ultrasound prevent the attachment of sea creatures.

Antifouling coatings generally have a relatively high pigment base and poor mechanical properties of the coating. Hempel's use of microfiber technology for high solids antifouling coatings not only provides an optimized binder system, polishing rate, antifouling properties and solids, but also improves the mechanical properties and flexibility of the coating. Macromolecular hydrogel is a new type of high molecular polymer material with three-dimensional network structure. Its application in antifouling coatings is one of the research hotspots of researchers in recent years. Hempel of Denmark developed the third generation of marine non-adhesive system, HempasilX3 coating, using tip hydrogel technology. It uses silicone hydrogel technology to form a superabsorbent gel polymer network on the surface after coating. It is impossible for the sea creature to recognize whether it is a surface that can be attached to achieve an antifouling effect, and the paint has a self-cleaning function. Japan Marine Coatings Co., Ltd. also uses LF-Sea, a product that uses this technology to form a water film between seawater and the coating film. It also reduces the frictional resistance of navigation and reduces energy consumption.

The application of high-throughput test methods in coating research and development has received increasing attention in recent years. Scientists at North Dakota State University have established antifouling coatings for polymer synthesis, evaluation, coating performance and antifouling performance evaluation. The large-volume test method for the whole process of formula screening greatly improves the efficiency of anti-fouling coating research and development and shortens the product development cycle.


5 Conclusion

Human beings are facing more and more serious environmental pressures. The development of marine coatings must be resource-saving and environmentally friendly. The development of marine utilization and ocean transportation industry is hoped that the marine coating industry will protect it. Non-toxic and efficient will be the future. Characteristics of antifouling coatings. Marine painters can only live up to the responsibilities of development if they are innovative.