The current situation and progress of the research on environmental protection and non-toxic anti-fouling coatings

China Paint Online News Information: Song Zhenwei 1, Wang Xiao 2, Liu Liyuan 2, Pan Jie 2, Hou Peimin 2, Xu Yuanhao 2
(1. Military Representative Office of the Navy 426 Factory in Dalian, Liaoning, Dalian 116000; 2. Marine Chemical Research Institute Co., Ltd., Qingdao, Shandong 266071)
Abstract: Discussed the development process, research status and development prospects of anti-fouling coatings.
key words: environmental protection non-toxic anti-fouling coatings; development process; research status quo; development prospects
in the figure classification number: TQ630.7 document identification code: A article number: 1009-1696 (2015) 03-0021-05
1. The development of anti-fouling coatings
anti-fouling coatings refers to a protective coating that prevents marine organisms from being defaced by attaching them to surfaces such as ships, marine facilities, pipelines, etc., thus accelerating corrosion and affecting their service life and efficiency. Anti-fouling coatings can keep the immersion part of protected objects smooth and free of dirt, and are mainly used in anti-fouling projects such as ships, marine facilities and pipelines in seawater and fresh water.
the bottom of a ship sailing in the sea is attached to by sea creatures, it will increase the ship's navigational resistance, reduce the speed of navigation, increase fuel consumption, and increase the wear and tear of mechanical equipment parts. The attachment of sea creatures will also destroy the protective paint film and accelerate the corrosion of the hull steel plate, which not only increases the cost of repair and maintenance of the ship, but also reduces the ship's in-flight rate. Applying anti-fouling coatings is the most cost-effective measure to prevent the attachment of sea creatures.
More than two thousand years ago, thin lead plates were used to protect the hulls of wooden hulls; in the 5th century BC, a mixture of arsenic, sulfur, etc. and oil was coated under the ship to prevent the attachment of sea slugs; and in the 17th century, copper plates were used. As an anti-fouling material for wooden ships; in the 18th century, the British Navy began to use copper extensively to solve the problem of defacement of wooden vessels by sea creatures; and in the 19th century, with the emergence of steel hulls, copper accelerated corrosion of steel hulls, eventually abolishing the anti-fouling technology that encased copper plates. However, people know the killing effect of copper ions on sea creatures, thus beginning the history of making anti-fouling coatings on the bottom of ships with copper ions as toxic materials.
1906, Navfolk Naval Shipyard successfully produced an anti-fouling coating made of thermoplastic resin. In 1926, the U.S. Navy successfully used pine in marine anti-fouling coatings, while using copper and mercury oxides as toxic materials, increasing the anti-fouling duration of ship anti-fouling coatings from 9 months to 18 months. The application of organo tin as a toxic material in marine anti-fouling coatings began in the mid-1950s. TBT (TBT) has been found to be wide-spectrum and highly toxic, and marine anti-fouling coatings containing TBT toxic substances have been successfully developed and quickly commercialized. In the 1970s, a long-lasting organotin self-polished marine anti-fouling coating (TBT-SPC) was developed, mainly with hydrolysed methyl acrylic tributyl tin co-polymer as a film, copper oxide as a toxic material, and added zinc oxide and other pigment fillers prepared.
, Asia is currently one of the most polluted areas of organo tin on Earth, with oysters in some ports in Japan and Taiwan already found to be 100 per cent female. According to the investigation, organo tin compounds are by far the most toxic substances introduced artificially into the marine environment, and TBT pollution has also been found in many inland waters of our country. In order to prevent the pollution of the environment by anti-fouling coatings containing machine tin toxic materials, since the late 1980s, the United States, Britain, France, Japan and some European countries have implemented restrictions on the coating of organo tin anti-fouling coatings. In 1988, the United States Congress passed a bill to control the use of organo tin anti-fouling coatings; In October 2000, the International Maritime Organization (IMO) established a deadline of 1 January 2003 for the final use of anti-fouling coatings containing machine tins and 1 January 2008 for the operation of ships coated with such coatings. That is, after 2008, no ships coated with machine tin paint will be allowed to operate at sea. This opened the development of non-toxic anti-fouling coatings.
2. Environmental protection non-toxic anti-fouling coating research status
At present, the new environmental protection non-toxic anti-fouling paint mainly has Wuxi self-polishing anti-fouling paint, low surface anti-fouling paint, electrolytic anti-fouling paint and bionic non-toxic anti-fouling paint.
2.1 Wuxi self-polishing anti-fouling coatings
Wuxi self-polishing anti-fouling coatings (TF-SPC) is the fastest-growing research and development of non-toxic anti-fouling coatings, but also currently replace the traditional organo tin self-polishing anti-fouling coatings, one of the main varieties. The main body of this type of anti-fouling coating is a hydrolysed, self-polishing properties of the highly polymer, its anti-fouling process is similar to the organic tin self-polishing anti-fouling coating, but other non-tin metals, such as copper, zinc and silicon to replace the co-polyplication of organic tin. Since the hydrolytic capacity of the polymer itself is not sufficiently anti-fouling, copper oxide should be used as an anti-fouling agent in anti-fouling coatings, and organic auxiliary biocides approved by various national environmental protection departments are required to be used in anti-fouling coatings. Organic anti-fouling additives can degrade rapidly and become toxic when released from the coating film, thus reducing the risk to the marine environment. Commonly used in Wuxi self-polishing anti-fouling coatings, copolymers are mainly copper, zinc, silicon and some low-molecular polymers and acrylic copolymers combined with the carbide base of the substance.
Copper anti-fouling agents have a strong anti-fouling activity effect on barnacles, dwelling insects and most algae, but are ineffective against several algae, such as moss, water clouds and curved algae, which are the most common species of marine dependent organisms. Therefore, copper anti-fouling agents must be used in combination with other organic anti-fouling additives in order to make anti-fouling coatings have a broad-spectrum effect of poisoning attached to sea creatures.
2.2 Low surface anti-fouling coating
low surface anti-fouling coating anti-fouling machine: paint has a very low surface energy, sea creatures difficult to attach to the film surface, even if the attachment is not strong, in the water flow or other external forces under the action of easy to fall off. Because the low surface anti-fouling coating is based on the physical action of the coating surface anti-fouling, there is no problem of release of toxic substances, fundamentally solve the problem of anti-fouling coating pollution of the marine environment, so it has become one of the current research hot spots of marine anti-fouling coatings. It is generally believed that the surface of the coating can be less than 25mJ/m2 or the contact angle between the coating and the liquid is greater than 98 degrees, the coating can have excellent anti-fouling and de-attachment cleaning effect.
2.3 Conductive anti-fouling coatings
conductive anti-fouling coatings are coatings that are used on the surface of the paint film by a weak current to enable hydropower to produce hyalphate ions in order to achieve anti-fouling effects. It is an anode with a conductive coating and a cathode with other parts of the ship that come into contact with seawater, producing hychloric acid ions as tiny currents pass through. Since the resulting hychloroic acid ions are less concentrations in seawater than in tap water, conductive anti-fouling coatings do not pollute the environment. In the 1990s, Mitsubishi Heavy Industries Corporation of Japan developed this conductive anti-fouling coating. Another conductive anti-fouling coating is to conduct anti-fouling effect on the active component of the conductive polymer material without current. In 1992, China began to develop a conductive polyphenylamine as the main anti-fouling agent of the coating, it is directly coated on the bare carbon steel plate, hanging plate test for 9 months, no marine life attached to growth. Compared with other conjugate conductive polymer materials, polyphenylamine is cheap, simple synthesis process and good stability, which can not only prevent the attachment of marine defaced organisms such as barnacles, but also have a removal effect on the early attachment of sea creatures slime. Jinguang sheep et al. , made into a sea hydro-hydro solution partial vinyl chloride-vinyl chloride co-polyester resin series pollution-free anti-fouling coating and its coating system. Electrolyte anti-fouling methods and hull electrochemical protection methods, although long-lasting economy, but the technical difficulties, and because of the need to add current or coating conductive coating, still can not be used in large areas of the hull, but in a small area, small area of success, such as power plant drains and so on.
2.4 Bionic non-toxic anti-fouling coatings
Extracting natural products (natural bio-anti-fouling agents) with anti-fouling activity from marine animals, plants and microorganisms is another important way to manufacture non-toxic anti-fouling coatings. Since the 1990s, a great deal of research work has been carried out in the field of bio-anti-fouling coatings around the world, and it is generally believed that bio-bionic anti-fouling coatings are the green anti-fouling coatings with the most environmental protection features and prospects.
, scientists have found that nearly a hundred anti-fouling substances can be extracted from marine organisms, many of which contain anti-fouling active substances in marine plants. When the active substances in seagrass leaf algae are extracted and separated, a compound obtained can effectively inhibit the growth of 8 kinds of marine microalgae and 1 kind of bacteria. For the first time, Todd and others isolated p-cinnamonate sulfate from large leaf algae, an active substance that effectively inhibits the attachment of marine bacteria and barnacles and is safe and non-toxic. Denys and others isolated and purified from red algae to obtain a series of secondary metabolites halogen furanone, found that it can effectively inhibit the barnacles, large algal stonesand marine bacteria, such as three representative types of defaced organisms attachment.
the extraction of anti-fouling agents from marine invertebrates began in the 1960s. At that time, it was found that some coral surfaces were rarely defaced, and it was speculated that their bodies might be rich in secondary metabolites that prevent biological contamination. The study found that the three types of terpenes and four open-ring steroid compounds isolated from the eight-release corals can effectively inhibit the attachment of the barnacle pot and have no adverse effects on the ecological environment. Sponge is one of the marine animals capable of producing a variety of sub-metabolites with anti-fouling activity, 1 kind of ceramide obtained from sponge can prevent the attachment of large algal stones ; Pot-attached furan terpenes; Hattori, etc. also get three kinds of dichlorocarbon-carbon-samine semi-terpene and one more invasive semi-terpene from the ocean sponge, all of which strongly inhibit the attachment of the larvae of the barnacles, and their anti-fouling active substances can interfere with the movement of the ocean's attached biological tentacles, so that their attachment is inhibited at an early stage.
The study of extracting natural products from marine organisms as anti-fouling agents has been widely carried out, and the preliminary results show that the anti-fouling mechanism of marine natural products is very complex, with different mechanisms such as inhibition attachment, interference with nerve conduction (restorative anesthesia, neurotransversion) and avoidance, and different kinds of marine natural products have different anti-fouling mechanisms.
In order to solve the problem of low production, complex structure, manufacturing difficulties and high cost of natural anti-fouling agents, people are looking for synthetic methods to produce anti-fouling agents, Sea-nine211 is a synthetic anti-fouling agent developed by The United States Rohm and Haas, which is divided into 4,5-DCH-2-Hinkie-4 - Isoprene-3-1, low toxicity, and only in contact with marine organisms, in seawater by natural microorganism degradation, can make it quickly decomposed into non-toxic compounds, has been recognized by the U.S. Environmental Protection Department, is the world's first environmental protection department recognized synthetic anti-fouling agent. In order to achieve long-term anti-fouling effect, the U.S. Navy is studying microcapsules encapsulation anti-fouling agent technology, trying to control the release rate of anti-fouling agents in the coating microcapsules to reach 5 to 7a anti-fouling expiration date.
china has also made some achievements in the field of biological anti-fouling coatings. As early as the 1960s, China has used thiobacteria to produce acidic biofilm for anti-fouling tests, and achieved a certain anti-fouling effect, but because the technical problems of thiobacteria in the actual coating long-term survival has not been resolved, so no breakthrough has been made.
In 2002, a research team led by Lin Maofu of the Second Oceanographic Research Institute of the State Oceanic Administration mixed chili base with organic clay to develop a low-surface anti-fouling coating with chili base as an antifouling agent. Laboratory and real sea hanging plate tests have shown that the anti-fouling coating has excellent compatible, tentacles and better anti-fouling effect. At present, Marine Chemical Research Institute Co. , Ltd. is also carrying out the development of biological anti-fouling coatings, mainly imitation of shark skin structure anti-fouling coatings.
3. Outlook
Traditional solvent-based anti-fouling coatings not only contain more organic solvents, in the production and construction process of coatings will emit a large number of volatile organic compounds (VOCs) into the atmosphere, resulting in further environmental pollution; Environmentally friendly anti-fouling coatings are low VOC, low-toxic, non-toxic anti-fouling coatings. Water-based anti-fouling coatings with natural extracts as anti-fouling agents are environmentally friendly coatings and are the development direction of anti-fouling coatings in the future.
structive bionics mainly include bionic techniques that mimic the surface body structure of marine life (e.g., imitation of shark skin, various fish surface structures, marine life's fluff structure, etc.), imitation of marine life surface oozing matter and low surface bionic technology, of which low surface bionic technology has been initially applied.
The self-polishing anti-fouling coating represented by organo tin self-polishing anti-fouling paint has been favored for its significant anti-fouling effect and long anti-fouling period, although it is currently prohibited, but its self-polishing properties have been attracting the attention of researchers. At present, Wuxi self-polishing anti-fouling coatings have replaced the traditional organic tin self-polishing anti-fouling coatings and become the mainstream products of ship anti-fouling coatings. Silicone low-surface anti-fouling coating has been paid more and more attention by researchers in various countries because of its completely non-toxic anti-fouling system, and has become one of the hot research topics in the world.
, the world's annual new ship volume of about 30 million tons, repair capacity of about 100 million tons. China is one of the world's three major shipbuilding countries, the annual repair of shipbuilding capacity of 30 million tons, manufacturing per 10,000 tons