The development trends of room temperature curing agents for epoxy resin coatings

Epoxy resin has excellent adhesion, insulation, corrosion resistance and chemical resistance due to its unique epoxy, hydroxyl and ether bonds, making it one of the most representative and largest varieties of high-performance anti-corrosion coating resins. Every year, more than 40% of the world's epoxy resins are used in the manufacture of epoxy coatings, most of which are used in industrial anti-corrosion fields such as bridges, vehicles, ships, ports, mines, petroleum, chemicals and other fields. However, epoxy resin can only occur cross-linking reaction to produce mesh molecules by supporting the use of specific curing agents, thus showing excellent properties
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. Curing agent is an indispensable part of epoxy coating system and plays a vital role. It can be said that the development of a new curing agent is equivalent to the development of a new epoxy resin or new applications. Therefore, the development of modified and new curing agents for existing curing agents is the development trend of epoxy curing agents.
1
Effects of curing agents on epoxy coating performance
The performance of epoxy coatings varies greatly with the type of curing agent, mainly in the following areas:
(1)
improving the performance of epoxy coatings.
epoxy resin coating has high reaction activity and high cross-link density, so the coating film corrosion resistance is good. However, there are also physical mechanical properties, such as poor elasticity, brittleness and other problems, can be improved by the introduction of curing agents with flexible chain segments, such as polyamide with long chain fatty acids.
(2)
improve the process performance of epoxy coatings.
epoxy coatings are often constructed on a large scale in the field, and there are problems with the toxicity of volatiles and the operability of volatiles in wet and low temperature environments. In recent years, a variety of non-toxic or low-toxic, and has excellent construction, technical properties and corrosion resistance of modified curing agents, such as modified ketone subamine curing agents.
(3)
to improve corrosion resistance of epoxy coatings.
the corrosion resistance of different epoxy curing systems is also very different. The epoxy resin cured by the amine curing agent is good alkaline and acid-resistant, and the structure of the seramine formed after curing is easy to produce ammonium salt with acid reaction. The epoxy resin cured by the acid curing agent is the opposite, the acid resistance is good and the alkaline resistance is poor, because the ester base formed after curing occurs irreversible hydrolytic reaction under alkaline conditions.
(4)
the temperature resistance of the peroxide coating.
epoxy resin cured with adipamine curing agent, and its thermal deformation temperature is low, usually only 70 to 80 degrees C. The use of suitable aromatic curing agent or acid curing agent, can increase the temperature of thermal deformation to about 150 degrees C, but the last two types of curing agents alone generally need to be cured under heating conditions.
(5)
the dielem performance of epoxy coatings.
when epoxy resins are used in insulating coatings, it is available to use an improved copolymer of benzodiazeene as a curing agent, which can significantly improve the heat resistance and dielectic properties of the coating.2
Comparison of temperature curing agents at home and abroad
For the needs of anti-corrosion coating site construction, epoxy resin coatings generally use normal temperature curing agents, the main varieties are: fatamine, aromatic amine, lipolamide, polyetheramine, aromatamine, polyamide and a variety of modified amines. Foreign epoxy resin coating curing agent varieties, its development and application level is far in the forefront. General anti-corrosion primers use modified fatty amine curing agents (ZZL-Series of United Carbon Corporation of the United States, Shell Chemical Company of the Netherlands U Series and Dow Chemical Company of the United States DEH52, etc.) and polyamide curing agents (V series of Corning, Germany, Asahi Corporation of Japan G series, etc.). For high-demanding heavy anti-corrosion coatings, such as high solid sub-coats or solvent-free coatings, the use of modified aramid, modified lipoamine and polyetheramine curing agents (E-100, m-APA, BASF D-Series, T-Series, Hensmey's M-Series, ED Series, etc.).
research and development of epoxy resin coatings in China is more important than epoxy resins, while the development of curing agents lags behind foreign countries. Mainly stay on fatamine and its modified products. Several representative apacing curing agents are: 593 curing agents (additions of diethyl triamine and epoxy propane butyl ether), 590 curing agents (additions of interphenyl diamine and phenyl shrink glyceline ethers), T31 curing agents (polyamines) Manishigas of formaldehyde and phenol, ketone subamine curing agents (underwater curing agents for ketones and polyamine reactions), 650, 651 curing agents (polyamide resins made from dry lysate dihydrogens and polyamine reactions), etc. Compared with foreign countries, the domestic epoxy resin coating curing agent is not only in the number of varieties, but also in the performance quality, such as product color, dryness, material, corrosion resistance, heat resistance and construction application, etc. have a large gap, which is also the focus of future research and improvement direction.
3
The development dynamics of at room temperature epoxy curing agents at home and abroad
the development and change of epoxy resin curing agents at home and abroad are very active, and only on the development and application of epoxy resin curing agents at room temperature.
3.1
modified polyamine
adipose or aromatic polyamine curing agent, because of its simple operation, a variety of good performance has been widely used. However, there are volatile, odor and brittle defects, for which the researchers carried out a modified work. DuPont prepared a formed epoxy curing agent, 2-methylamphetamine (MPMD, trademarked DYTEK) with 2 adipose diamines and 1 lipid cyclodamine. A), 1,3-diamine (DAMP, trademark DYTEK? ER) and 1,2- cyclohamphetamine (DCH99). This kind of curing agent has low toxicity and low odor, and the coating prepared with it has good chemical corrosion resistance, high hardness and good gloss. Among them, MPMD curing fast, light color, DCH99 viscosity is low, curing is slow, acid catalyst after the color deepens, DAMP viscosity is the lowest, the color is the lightest, its curing speed is between the first two. The special curing agent XZ92441.01 developed by Dow Chemical can be used in industrial antiseptic coatings, and D.E.H.58 is a mixed amine curing agent that can dry quickly at room temperature.
European patents report a low-viscosity epoxy resin curing agent free of environmentally harmful substances such as phenols and solvents, containing polyurethane compounds and curing promoters, whose compositions can be cured at low temperatures and the curing film has excellent appearance and performance.
Air Products has introduced a range of high-performance epoxy curing agents, modified polyamines, of which CX-101 has long-lasting corrosion protection, CX-110B has low temperature curing for heavy corrosion and marine coatings, and X-2282 and X The -110E uses weak solvents, which can be quickly cured and can be used in anti-corrosion coatings, and IM-544, I-90S, NB-90S and W-100 are solvent-free products, all of which can be used in anti-corrosion and floor coatings. Among them, IM-544, I-90S is a low odor, weather-resistant varieties, I-90S also has wetting immersion, can be used in surface treatment requirements are not high, NB-90S has both weather resistance and low temperature curing, W-100 has low temperature fast curing, can also be used as a curing promoter. It is reported that the curing agent made by the reaction of hexadhesamine and alkyl monosorbed glyceline ether has good storage stability, deflection resistance, low temperature resistance and chemical resistance. The C-200 series of modified hetamine curing agents introduced by Asahi, Japan, can be used alone or in ligated with other curing agents to eliminate the internal stress of curing materials and improve flexibility and impact resistance. The CGF-1 modified amine low viscosity epoxy resin toughening curing agent was synthesized by the two-step method, and the effects of raw material ratio, reaction time, reaction temperature and other factors on product performance were studied. The product can be cured at room temperature, coating film flexibility is good, easy to drain foaming, good fluidity, excellent chemical resistance. It has been tested that the physical mechanical properties of its curing materials are much better than those of commercially available products. In addition, the Morning Light Chemical Research Institute also to benzodiaxamine as the basic raw material, acrylic, epoxy compounds, etc. as a modifier, made 79-3 modified amine epoxy curing agent. 79-3 Curing agent is easy to use, low toxicity, curing reaction is eased, curing products have excellent electrical performance, moisture resistance and mechanical properties, especially outstanding impact strength.
Jiangsu Sanmu Group based on the United States DuPont DACH (1,2- DAMINE) lipid cycloamine curing agent, introduced to the market a high-performance epoxy resin curing agent - SM-203. Its curing products have good chemical resistance and a high glass transition temperature, Shaw's hardness of up to 90, and in a humid environment to maintain a high gloss. The tG301 room temperature curing agent was prepared using hexamine and epoxy resin for hydroxylation and acetylene with acrylonitrile, which achieved a comprehensive effect of low melting point, low toxicity and low brittleness.
3.2
modified polyamide
foreign representative low-relative molecular mass polyamide curing agent is Corning's V-115, V-125 and V-140. They have good comprehensive properties, but the temperature of thermal deformation needs to be further improved. For this reason, a small amount (about 8% of the curing agent ratio) is often added between benzene or diamino diphenyl methane, and the temperature of thermal deformation can be increased by about 30 degrees C. The study points out that by determining the degree of aamideization and the ratio to epoxy resin, the rigidity, heat resistance and chemical resistance of the curing can be improved while maintaining the flexibility and impact resistance of the curing. C20 long chain unsaturated methamphetamine and a variety of binary amine reactions, can be made into a variety of polyamides. With the increase of its relative molecular mass, the stretch shear strength and peeling strength also increase.
Resolution Corporation (formerly Shell) introduced the new epoxy curing agent CY-F206, which is made by adding some substances that may form strong hydrogen bonds to the original lipid ring curing agent and adding the alamide-based curing agent EPI-3055. EPI-3055 does not contain low relative molecular mass active amine, resin chain length, good wet bonding, good leveling, can significantly improve the wetting and dispersion of pigments, pigment flocculation and color occoloration, with very good hardness and chemical resistance, suitable for epoxy self-leveling coating. In addition, Corning's Versamid 224-229 series of modified polyamides and Hensmay's Aradur450 modified polyamides are products that react with a small amount of epoxy resin to reduce free amines. It does not have to be cooked when used, reduces the salting reaction with CO2 in the air, and can be constructed in cold climates. The Office of National Defense Science and Technology Recently recommended modified low-relative molecular mass polyamide curing agents. The epoxy polyamide coating made from it has strong adhesion, aging resistance, sea water resistance and chemical corrosion resistance. According to reports, the coating is widely used as ocean-going ship shell paint, deck paint, aircraft carrier orbit paint and chemical machinery corrosion-resistant paint. In addition, the preparation of adhesive curing flexibility, low temperature is not brittle cracking, in the aircraft, automobiles and ships and other components of the bonding can replace welding and riveting. Hu Gao equal by combining low relative molecular mass polyamide with phenolic phenolic amine to form a new curing agent to cure epoxy resin, on the one hand, enhance the reaction activity of polyamide, on the other hand, improve the flexibility and temperature resistance of curing. Experiments show that the compound ratio of polyamide and phenolic aldehyde is the best when the ratio is 1:2.
3.3
modified phenolic amine
phenolic aldehyde, also known as Manich-type curing agent, because it contains phenolic hydroxyl and amine-like active hydrogen, improve the product's heat resistance and corrosion resistance. Further modified studies are mainly aimed at adjusting the long chain structure and increasing flexibility. Shell Epoxy's H-5, H-6 curing agents are based on long-chain cyclamine, which not only increases flexibility, but also reduces volatility and reduces skin irritation. At the same time, the hydroxyl group, which promotes curing, is introduced into the molecular structure of curing agent, which has wet and low temperature curing properties, and improves the heat and corrosion resistance of curing products. There is the same Manich reaction, but do not add polyamine, and add metformin, curing agent molecules have both phenolic and serum, with catalytic effect, can improve curing activity and film-forming properties. The K-54 of American Gas and the T-31 of Sanmu are both such curing agents.
, the United States Cardle company used cashew shell liquid as the main raw material to synthesize a series of natural long chain instead of phenolic amine curing agent. It contains both adipose binary amine end-base and weakly acidic phenolic hydroxyl, as well as an unsaturated double-bonded C15 straight chain. This unique molecular structure makes it both general phenolic amine and low relative molecular mass polyamide performance, with epoxy resin with a long application period, can be quickly cured at room temperature, but also in low temperature, humid conditions curing, and non-toxic, coating flexibility, wear resistance, corrosion resistance is excellent. Therefore, the curing agent has been widely used in industrial and anti-corrosion coatings and construction coatings, has been recognized by the industry. Domestic companies, such as Shanghai Doyle Company, Shandong Meidu Company, Xuzhou China Research Company, etc. also have similar product development on the market.
Hefei University of Technology research and development of a successful AH series of long-chain phenolic amine curing agent, that is, phenol, polyamine, formaldehyde, fatty acids as raw materials, developed into low temperature, normal temperature and medium temperature curing agent. The series is water-resistant, oil-resistant and can design molecular structures on demand. Shenyang Southeast Chemical Research Institute has developed T-30 astrogenic phenolic amine curing agent. The product is free of free phenols, formaldehyde and organic solvents, low odor, low toxicity, light color, can be used in paint. Compared with the original brand, its curing speed is unchanged and flexibility is enhanced, and the use of toughened epoxy resin can achieve good flexibility and impact strength, while wet conditions and underwater can be cured. In addition, the same type of curing agent with the brand name 4T-28 has been successfully developed, which is slightly slower and suitable for construction in hot summer environments.
Beijing University of Aeronautics and Astronautics, using dipolymers formed by pyrophenol and formaldehyde as raw materials, has synthesized a new structure of toughened epoxy curing agent - double (2-hydroxy-3-amine ethylamine methyl-5-phenylbenzene) methane (BA). Due to the presence of a positive crucification base in the BA molecular structure, internal relaxation occurs after curing, which can improve the flexibility of the resin, and its impact strength is 36.91% higher than that of ordinary aromatic amine curing agent, with high activity and toughening effect.
Beijing paint factory will produce 701 curing agents (benzoic acid, formaldehyde, hetamine shrinkage) and methyl isodide reaction to produce phenolic ketone subamine, not only has a humid, low-temperature solid