1 Water-based acrylic paint
Currently, there is little research on single-component pure acrylic systems. Pure acrylic systems are generally modified with different functional monomers, such as styrene modification. The resulting acrylic/styrene polymer system can be used to formulate hard anti-corrosion coatings. Yanai Hidenor et al. first polymerized acrylate monomers containing epoxy groups and hydroxyl groups to obtain polyacrylate intermediates, and then condensed them with oligosiloxanes containing glycidyl groups and hydrolyzable silane groups to obtain coatings. The one-component low-temperature curing silicone-acrylic coating with dense film has significantly improved water resistance, weather resistance, high temperature resistance and tensile strength. The water-based two-component epoxy/acrylic paint series MAINCOTEAE-58 developed by the American Rohm & Hass company uses epoxy resin E-12 as the base material and benzoyl peroxide (BPO) as the initiator. The epoxy resin is polymerized in the acrylic polymerization process. It is grafted into the acrylate molecular chain, and the epoxy group does not open the ring. The curing reaction is a double bond addition reaction. The resulting two-component emulsion has good stability, long storage time, dense coating film, good water resistance and wear resistance. And good weather resistance, high gloss. Germany has recently developed a new type of anti-rust paint with excellent performance, which is an epoxy-modified acrylic anti-corrosion paint.
my country's scholars and R&D workers have never stopped researching acrylates. Pan Zuren and others studied polymer emulsions using certain amino-containing polymers as cross-linking agents, such as amino resins, epoxy resins, polyurethanes, etc. The coating films have excellent compactness, water resistance, weather resistance, and color retention. and gloss retention. Yang Xinge selected acrylic acid and n-butyl acrylate free radical polymerization to produce an acrylate emulsion, and added nano-TiO2 to produce a water-based nano-acrylic antibacterial coating, which has excellent anti-corrosion, weather resistance, bacteria resistance and solvent resistance. Strong ability to pollute.
2 Water-based epoxy coatings
The research on water-based epoxy anti-corrosion coatings has gone through several stages: the first-generation water-based epoxy system was directly emulsified with emulsifiers, mainly polyethylene Vinyl alcohol is an emulsifier, and research has begun on using adducts of polyamide polyamines and epoxy compounds, polyethylene ethers, etc. as emulsifiers. The second generation water-based epoxy system uses a water-soluble curing agent containing epoxy groups to emulsify oil-soluble epoxy resin, and self-emulsifying epoxy resin appears. The third-generation water-based epoxy system was successfully developed by the American Shell Company after many years of research and development. The epoxy resin and curing agent of this system are connected with non-ionic surfactants. The performance indicators of coatings formulated with it can reach or exceed Solvent-based paint.
Since the 1970s, new synthetic technologies and anti-corrosion coating products have been continuously introduced abroad, such as the water-based epoxy resin series WATERPOXYl401, 1455, etc. from the German Henkel Company, and the water-based epoxy curing agent WATERPOXY751 , 755, etc.; US Shell Company's EPIREZ3510-W-60 and EPI-REZW-5l, etc.; US DEVOEMAREN Coating Company's Devran230, 240QC, Devchem252 and Devran188 are all representatives of effective solvent-free epoxy resins.
Many universities and scientific research institutes in my country have conducted research on water-based epoxy anti-corrosion coatings. Song Beibei of South China University of Technology and others used hyperbranched dendritic polyester BoltornTMH20 (B-OH) and tert-butyl acetoacetate. (t-BAA) was transesterified to prepare acetoacetate-terminated B-OH, which allowed the methylene group of the acetoacetate group of BBA to undergo a graft polymerization reaction to synthesize a hyperbranched polymer with BBA as the core. , so that the coating film has a higher degree of cross-linking, a higher glass transition temperature, and better thermal stability, so that the coating has excellent anti-corrosion properties. Ren Yuhong and others from Yanshan University prepared acrylate-modified water-based epoxy resin using the self-emulsification method. The paint film has good density, and its anti-corrosion, weather resistance, water resistance and tensile strength are significantly improved compared to the unmodified one. And it has been used for anti-corrosion in petrochemical, metallurgy, Wujijiaodian, automobile, shipbuilding and other fields.
3 Water-based inorganic zinc-rich coatings
Water-based inorganic zinc-rich anti-corrosion coatings have experienced more than 70 years of development. There are three main stages: the first stage, thermal curing inorganic zinc-rich coatings . Inorganic zinc-rich paint was first born in Australia in the 1930s, and its inventor was engineer Victoe Nightingale. The second stage is to post-cure the inorganic zinc-rich coating.
The treatment process of inorganic zinc-rich coatings was introduced to the United States in 1949, and post-curing inorganic zinc-rich coatings were successfully developed in 1952. The third stage is self-curing inorganic zinc-rich coating. With the in-depth research on zinc/silicate chemistry, water-based zinc-rich coatings with self-curing characteristics have been developed, that is, there is no need to spray post-curing liquid, and there is no need to separately remove the curing reaction products on the coating surface after curing, and the self-curing The coating hardness is again comparable to the hardness of the post-cured coating.
John BSchutt has conducted a series of research work since the 1990s to prepare water-based inorganic zinc-rich coatings that can be used commercially. Australia's Morgan-Wyalla oil pipeline, which is 250km long, uses water-based inorganic zinc-rich anti-corrosion coatings with very good results.
Israel and South Korea use epoxy zinc-rich primer instead of thermal spray paint for anti-corrosion of underground pipelines, and have also achieved good results.
In my country, the Tianjin Research Institute of Chemical Industry began to develop and industrialize water-based lithium silicate zinc-rich coatings in the early 1980s, becoming one of the earliest units in my country to produce, promote, and apply this product. . Since the 1990s, my country's self-developed water-based inorganic zinc-rich coatings have made great progress, such as the LW-I type inorganic zinc-rich coating launched by Shanghai Hi-Tech, Tianjin Lighthouse's E53851, Chongqing Three Gorges' E06-1, and Wuhan Hyundai's E777-1 , Taiwan's TC-799, etc. At present, the research on water-based inorganic zinc-rich coatings in my country is mainly on its modification. Peng Gangyang of South China University of Technology and others used low modulus potassium silicate solution and alkaline silica sol as the main raw materials, and used organosiloxane as the modification. The agent is used to prepare a stable high-modulus potassium silicate solution, which is formulated into a high-performance inorganic zinc-rich coating with uniform particle size, stable storage, and excellent water resistance and weather resistance. The water-soluble lithium silicate zinc-rich coating developed by Tianjin University has the characteristics of high temperature resistance, weather resistance, static conductivity, and long-term anti-corrosion. Wu Bo from Shandong University used four types of silicate composites: water-soluble lithium silicate-sodium silicate, lithium silicate-potassium silicate, lithium silicate-sodium methyl silicate, and lithium silicate-potassium methyl silicate. Base material, through analysis and research, a new process route for preparing lithium silicate zinc-rich coatings has been developed to produce inorganic zinc-rich coatings that are resistant to high temperatures, have good adhesion, and have excellent salt spray resistance. The ET-98 inorganic phosphate zinc-rich coating developed by Yangzhou Jinling Special Paint Factory is the first in China. The prepared coating is strong, has excellent wear resistance, oil resistance, water resistance and heat resistance, and has excellent properties on ferrous metal surfaces. Thermal insulation and cathodic protection.
Water-based inorganic zinc-rich coatings are widely used in steel structures in various environments such as marine atmosphere and high temperature, such as offshore platforms, ships, containers, large steel components, oil pipelines, and various chemical storage tank linings. Long-term anti-corrosion.
4 Water-based polyurethane coatings
In addition to containing a large number of urethane bonds, polyurethane resins also have urea bonds, ester bonds, ether bonds, amide bonds, etc. These special The key structure gives the coating excellent adhesion, wear resistance, flexibility, resilience, chemical resistance, solvent resistance, gloss, etc., thereby integrating decorative and anti-corrosion properties. In the 1990s, Jacobs successfully developed a polyisocyanate curing agent that can be dispersed in water, thus bringing two-component water-based polyurethane anti-corrosion coatings into the practical research stage. ARCO Chemical Technology Company of the United States has developed a two-component polyurethane coating using water-dispersed polymers containing repeated allyl alcohol or alkoxylated allyl alcohol units, TDI, HDI and other polyisocyanates, which has excellent flexibility and mechanical strength. , abrasion resistance, chemical resistance and durability.
S.S.Pathak et al. modified water-based polyurethane coatings with silicone MTMS (methyltrimethoxysilane) and GPTMS (γ-glycidoxypropyltrimethoxysilane) to enhance the performance of water-based polyurethane coatings The elasticity and mechanical stress, its degradation temperature rises to about 206°C, and the thermal stability is greatly improved, making it suitable for anti-corrosion in aerospace, marine, automobile and other fields.
In my country, East China University of Science and Technology used DSC, FTIR and other methods to discuss the impact of chain extenders on the molecular chain structure and properties of polyurethane urea-polymethyl methacrylate aqueous dispersion. Sun Daoxing and others used epoxy resin and silicon-containing polyurethane resin to graft and polymerize to prepare water-based polyurethane, and then used it to modify epoxy acrylic resin as the base material of anti-corrosion coating, and ferrotitanium powder as anti-rust pigment. A water-based anti-corrosion coating with excellent comprehensive properties is produced.
Wu Xiaobin and others prepared a water-based polyurethane emulsion dually modified with epoxy acrylic resin through in-situ emulsion polymerization. The emulsion has a storage period of more than 10 months, a resistance to freeze-thaw cycles of more than 5 times, and a coating film with a pendulum hardness of more than 0.7. The tensile strength is greater than 10MPa, and the water resistance, acid and alkali resistance, solvent resistance and anti-corrosion properties are significantly improved compared to the unmodified ones. Professor Lu Jianping from Hefei University of Technology reacted oligomeric polyester polyol with toluene diisocyanate (TDI), used small molecules such as neopentyl glycol (NPG) and trimethylolpropane (TMP) to extend the chain, and used dimethylolpropane to Acid (DMPA) is used to introduce hydrophilic groups, and finally neutralized with TEA (triethanolamine) and dispersed under rapid stirring to produce a polyester-type water-based polyurethane with good storage stability, water resistance and physical properties, and has been used in Anti-corrosion coating for outdoor paving.
At present, water-based polyurethane coatings have been widely used in surface anti-corrosion coatings for aircraft, ships, vehicles, buildings, and other surface anti-corrosion coating fields with higher requirements.
5·Existing problems and technology trends
After years of efforts by R&D workers, water-based anti-corrosion coatings have made great progress and development. Currently, water-based anti-corrosion coatings exist The problems and future technological trends mainly include the following aspects:
(1) At present, water-based anti-corrosion coatings generally have the disadvantage of low solid content. Low solid content will increase the cost of manufacturers, so , the development of anti-corrosion coatings with high solid content is the focus of scientific researchers.
(2) Anti-corrosion coatings with a single system have relatively single functions and have some shortcomings in application. The development of compound anti-corrosion coatings with two or more systems can increase the versatility of the coating. And it can make up for the shortcomings of a single system of anti-corrosion coatings.
(3) Coating performance needs to be improved. By studying the film-forming cross-linking mechanism of water-based coatings, we are looking for new cross-linking agents and additives to make the resin more compact, thereby improving the mechanical properties of the coating; we are studying the principles of emulsion polymerization and looking for new emulsifiers to make the emulsion polymerization more uniform. The monomer conversion rate is higher, the dosage of traditional emulsifiers is reduced, and the water resistance of the coating is improved.
(4) Continuously update and improve the production process and production equipment, and provide professional training for production personnel.
(5) Construction performance needs to be improved. Water-based coatings have higher requirements on the surface cleanliness of the substrate and the construction process. Due to the high surface tension of water, dirt can easily cause shrinkage holes in the coating film. Water-based coatings have poor dispersion stability against strong mechanical forces. When the flow rate in the transportation pipeline changes sharply, the dispersed particles are compressed into solid particles, causing pitting on the coating film.
(6) Water-based anti-corrosion coatings fundamentally rely on the hydrophilization of film-forming resins. There are two ways of resin hydrophilization: self-emulsification and external emulsification. No matter which way, substances containing hydrophilic functional groups must be introduced. In the self-crosslinking system, the hydrophilic functional groups are generally still free when the coating is formed into a film, and are not cross-linked and converted into hydrophobic segments. This will inevitably affect the properties of the coating film. Media resistance, corrosion resistance and other properties. How to convert these hydrophilic functional groups into hydrophobic groups after film formation is one of the issues that requires great attention in current research work.
(7) Environmental protection needs to be improved. Since emulsifiers and other small molecule additives are used in water-based systems, they may have a certain impact on the environment. New high-performance emulsifiers and other additives need to be found to make the coating more environmentally friendly during use.