Abstract: Chlorinated rubber coating is one of the heavy duty anticorrosive coatings in China, which plays an important role in the construction of national economy. However, constrained by its own poor environmental performance, with the enhancement of people's awareness of environmental protection, especially in the country introduced a ban on the production of CCl4 chlorinated rubber resin today, chlorinated rubber coatings development is gradually declining. The article analyzes the advantages and shortcomings of the performance of chlorinated rubber coatings, and discusses the future research focus and development direction of chlorinated rubber coatings. 

With the continuous improvement of China's economic level, the development of the machinery industry is getting faster and faster, as the field of anti-corrosion materials necessary for the machinery industry has ushered in a peak period of development. A large number of anti-corrosion products with advanced performance and excellent quality are put into the market. Chlorinated rubber coatings are recognized by the majority of users for their excellent performance and stand out in the fierce market competition. Since the 1960s, chlorinated rubber coatings have been widely used in shipbuilding, containers, water conservancy facilities, petrochemical and electric power construction and other fields as supporting coatings for cavities, and have played an important role in safeguarding the process of economic development. Relevant data show that chlorinated rubber coatings in the entire anti-corrosion coatings market accounted for only two to three percent. Many users do not have a deep understanding of chlorinated rubber anti-corrosion coatings, especially a small number of manufacturers in order to pursue economic interests, with other low-priced chlorine-containing compounds instead of chlorinated rubber coatings in the normal components, stirring up the market, but also affects the development of chlorinated rubber coatings. In order to enhance the majority of anticorrosive coatings users on the understanding of chlorinated rubber coatings, to promote the promotion and application of chlorinated rubber coatings, improve the level of development of China's coatings industry, the author in the long-term study based on the basic properties of chlorinated rubber coatings, classification, application and other content, I hope to help the majority of anticorrosive coatings users.

1 Overview of chlorinated rubber coatings

Chlorinated rubber coatings are produced from natural rubber or artificial synthetic rubber as the raw material of chlorinated rubber resin as the base resin, and then with the corresponding auxiliary materials, solvents and made. The molecular saturation of chlorinated rubber resin is high, the molecular bond has no obvious polarity, the structure is regular, and the stability is excellent. From the appearance, chlorinated rubber resin is white powder solid, non-toxic, odorless, no irritation. Chlorinated rubber coatings are flexible in use and have a wide range of applications. They can be used with a variety of pigments as primers, intermediate paints or topcoats. It can be used as primer, intermediate paint or topcoat. The most used is as topcoat in matching coating. By modifying chlorinated rubber resin with other resins, it can obtain or improve various characteristics and realize greater coating effect.

2 Introduction to the Properties of Chlorinated Rubber Coatings

2.1 Advantages of chlorinated rubber coatings

2.1.1 Excellent media resistance and weathering performance

After the chlorinated rubber coating film, the paint layer resin molecular bonds are firmly combined, and the molecular structure is extremely stable. For this reason, chlorinated rubber resin paint layer has good weather resistance, excellent resistance to water, acid, alkali, salt, ozone and other media. The transmission rate of water and gas is only ten percent of that of alkyd substances. From years of practice, chlorinated rubber paint layer also has a strong aliphatic hydrocarbon solvents, oil and lubricating oil resistance, can be used for mildew treatment in humid environments, cathodic stripping resistance is extremely superior.

2.1.2 Good adhesion, good compatibility with other varieties of paint.

Green Rubber Coating used as a primer has a considerable degree of adhesion to steel materials. When used as a topcoat or intermediate paint, it can be used in combination with epoxy resin, urethane and other types of primers, and is highly effective. Chlorinated rubber coatings are easy to maintain and can be repainted using chlorinated rubber coatings or repaired using acrylics, various solvent-based paints and various types of anti-fouling paints.

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2.1.3 Simple and convenient construction

Chlorinated rubber coating is a single-component coating, the film-forming time is very short, and the construction speed is fast. Chlorinated rubber coating on the construction temperature requirements are relatively broad, minus 5 degrees to minus 40 degrees can be constructed. The amount of diluent added during construction is very small, or even no diluent can be added, thus reducing the volatilization of organic solvents, environmental performance is better. Chlorinated rubber coating can be directly painted on the surface of concrete components, with good alkali resistance. When used in assembly line operation, it can be sprayed by “wet to wet” method, which greatly improves the production efficiency.

2.2 Disadvantages and shortcomings of chlorinated rubber coating

2.2.1 The color of chlorinated rubber coating is gray, poor brightness, easy to adsorb dust, the color does not last, can not be used for decorative paint.

2.2.2 The heat resistance of the coating is extremely sensitive to water. Under humid environment, the heat resistance decreases greatly. The thermal decomposition temperature in dry environment is 130 degrees, while the thermal decomposition temperature in humid environment is only 60 degrees, which leads to the restriction of the environment where the chlorinated rubber coating can be used, and the maximum temperature of the environment can not exceed 70 degrees.

2.2.3 The solid content of chlorinated rubber coating is low and the thickness of the paint film is thin. To ensure the thickness of the paint film, it is necessary to spray repeatedly for many times, which affects the production efficiency.

2.2.4 Chlorinated rubber coating has poor resistance to aromatic hydrocarbons and certain types of solvents, and cannot be used as an interior protective coating in environments such as chemical plant pipelines, production equipment, storage tanks, etc., where intolerant substances may be present. At the same time, chlorinated rubber coatings cannot be used on a long-term basis with animal fats and vegetable oils.

3 Discussion on environmental issues of chlorinated rubber

Chlorinated rubber paint base resin is generated by chlorination of natural rubber or synthetic rubber. The CCl3 or CCl4 used in the production process is highly polluting to the atmosphere, and the residues in the chlorinated rubber resin and the CCl3 or CCl4 escaping from the production process are the main sources of pollution of chlorinated rubber coatings. In order to control the emission of pollutants and protect the environment, China's environmental protection department issued regulations in 2005 and 2010 to restrict and prohibit the use of CCl4. Affected by this, many domestic enterprises have embarked on the implementation of environmentally friendly chlorinated rubber resin research and development, production projects, in order to improve the environmental performance of chlorinated rubber coatings to meet the new market demand.

4 ;Chlorinated rubber coatings development direction

4.1 Research on the flexibility of the paint film

Chlorinated rubber coatings are mostly used for anti-corrosion treatment of metal products. As metal products in the temperature change will be more significant changes in volume, in order to protect the substrate expansion and contraction, the quality of the paint film will not be seriously affected, the chlorinated rubber coating must have good flexibility, in order to reduce the substrate greatly expanded and contracted when the stress generated. At present, the main method to improve the flexibility of chlorinated rubber paint layer is to add chlorinated paraffin. From the experimental data, when the total amount of chlorinated paraffin added to reach 20% of chlorinated rubber resin, film flexibility can reach 1 ~ 2mm.

4.2 Research on modification technology

In order to improve the film performance and expand the application range of chlorinated rubber coatings, researchers have carried out a large number of modification studies on chlorinated rubber coatings. Through the chlorinated rubber and alkyd, epoxy ester, epoxy, coal tar pitch, thermoplastic acrylic acid and ethylene vinyl acetate copolymerization resin, etc., made of composite coatings, in the film flexibility, weatherability and corrosion resistance, etc., made significant progress, and promote the development of heavy-duty anticorrosive coating industry.

4.3 Research on the solid content of coatings

Chlorinated rubber coating solid content is low, the paint film thickness is thin, so that to meet the requirements of the paint film thickness, it is necessary to increase the number of times of painting, which affects the production efficiency. In order to solve this problem, it is necessary to start from the root to improve the solid content of the paint. Because of the chlorinated rubber coating is difficult to water-based, in order to ensure the construction performance can only be depressed solid content. The current chlorinated rubber coating solid content is located in thirty-five percent to forty-nine percent between the solvent content is high, affecting the environmental performance of the coating. Improve the solid content of chlorinated rubber coatings is mainly in the production of chlorinated rubber resin to adjust the chlorine gas into the time, control the reaction temperature and so on.

5; Chlorinated rubber future prospects

Chlorinated rubber coatings in the heavy duty anticorrosive field industry accounted for a small proportion of the original, with the enhancement of national environmental protection requirements, chlorinated rubber coatings, the development of space is further compressed. From the use of performance, chlorinated rubber coatings still have a strong vitality. Therefore, it is especially important to improve the environmental protection characteristics and overall performance level of chlorinated rubber coatings to enhance their market competitiveness to meet the requirements of modern society. Ship repair, non-standard container, hydroelectric power engineering, chemical and beacon manufacturing industry and transportation facilities are the main development direction of chlorinated rubber coatings in the future. In the above fields, chlorinated rubber has strong applicability. With the development of China's economy, the above areas will usher in a new peak period of development, thus bringing a broader market space for chlorinated rubber coatings.

6 Conclusion In summary, chlorinated rubber coating coating has excellent performance and is one of the important anti-corrosion coatings. However, due to environmental protection and other reasons, the market situation of chlorinated rubber coatings is relatively severe. Improving the solid content and environmental performance is the main development direction of chlorinated rubber coatings in the future. In addition, through the research of modification, to improve the comprehensive performance of chlorinated rubber coatings is an important means for chlorinated rubber coatings to adapt to the market demand and open up the field of application. With the further development of China's industry, chlorinated rubber coatings in shipbuilding, chemical industry, water conservancy, electric power facilities and other aspects of the role will be further strengthened to improve the adaptability of chlorinated rubber coatings in the above areas and the use of performance, chlorinated rubber coatings production enterprises in the future is an important task.