Research Progress on Waterborne Epoxy Anticorrosive Coatings

This paper introduces the preparation method of water-based epoxy resin from the three aspects of mechanical method, reverse transfer method and chemical modified method, and points out the preparation method, advantages and disadvantages of water-based epoxy resin and the progress of research. The preparation methods of type I water-based epoxy curing agent and type II. type water-based epoxy curing agent are introduced, the advantages and disadvantages and the development trend. The development trend and application prospect of water-based epoxy anti-corrosion coating are

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water-based coatings, epoxy coatings, water-based, anti-corrosion coatings, curing agents
(middle-level classification number) TQ244.6 (document identification code) A (article number) 1007-1865 (201) 3) 07-0072-03
Water-based epoxy anti-corrosion coatings have better corrosion resistance, chemical resistance and solvent resistance, with strong adhesion, high hardness, good wear resistance and so on, has been widely used in military, civilian and other fields. Traditional epoxy resins are found only in aromatic, ketone and alcohol organic solvents. Organic solvents are expensive, volatile and pollute the environment. With the increasingly strict requirements of environmental protection, it is of great significance for epoxy resin to carry out water-based research. Water-based epoxy antiseptic coatings are developed on the basis of water-based epoxy coatings, the key to the study of water-based epoxy anti-corrosion coatings is the hydration of epoxy resins and water-based epoxy curing agents.
1. Hydration method of epoxy resin
In order to prepare a stable water-based epoxy emulsion, it is necessary to try to introduce a strong hydro-hydro-chain segment into its molecular chain or to add hydro-hydro-oil-owning elements to the system. There are three methods of hydration of epoxy resin: mechanical method, reverse transfer method and chemical modified method.
1.1 Mechanical method
mechanical method is also known as direct emulsification method, is the epoxy resin with ball mill, collage grinding, homogenizer and other grinding, and then added to the water solution, and then through ultrasonic oscillation, high-speed stirring, particles scattered in water, or epoxy resin mixed with emulsifiers, heated to a certain temperature, in a fierce stirring gradually added water to form epoxy emulsion. The advantage of mechanical method is that the process is simple, the cost is low, and the amount of emulsifying agent required is less. The disadvantage is that the size of epoxy dispersion phase particles in the prepared emulsion is larger, about 10 m, the particle shape is irregular, the particle size distribution is wide, the distribution of the emulsion is poor, the film-forming properties of the emulsion is not good, due to the presence of non-ion surfactants, will affect the appearance of the coating film and some performance.
1.2 in contrast to the
the opposite method is currently commonly used in the preparation of water-based epoxy tree esters. On the contrary, transgenic refers to the process of continuous phase transformation under certain conditions in a multi-group system, such as in the oil/water/emulsifying agent system, when the continuous phase changes from oil phase to water phase (or from water phase to oil phase), in the continuous phase transition zone, the interface of the system has the least pressure, so the size of the dispersion phase is the smallest.
Wang Jin, etc., obtained a water-based epoxy emulsion with good stable performance with polyethyl glycol-phthalates-epoxy resin E-44 multi-inlay copolymer as emulsion of epoxy resin E-44 Shi Xuezhen and others, with the help of reverse transfer technology, prepare epoxy emulsions using new water-based epoxy emulsification agents with surfactability, Fang Huagao, etc. Monomers and polymerized large-molecule emulsizers are co-converged to obtain better-performing epoxy emulsions through reverse transfer technology, and Yang Zhenzhong and so on are used with polyethyl glycol-epoxy resin E-20 binary multi-inlay polymer non-ionic surfactants Water-based micro-emulsions are prepared as emulsizers, Gu Guofang et al. introduce surface-active molecular chain segments into the epoxy molecular chain, obtain epoxy emulsions, and obtain water-based epoxy emulsions with the help of reverse transmutation.
the size of the emulsion by the opposite turn is smaller than the mechanical method, the preparation method is simple, the stability is better than the mechanical method, easy to implement, and the average particle size of its dispersion phase is generally l to 2 m. However, compared with the low molecular quality of surfactants, its compatible with epoxy resin is poor, the production of emulsion stability is poor, there are more surfactants exist, after film coating hardness, water resistance, solvent resistance, etc. will be greatly affected.
1.3 Chemical modified chemical modified method, that is, self-emulsification method, is currently the main preparation method of water-based epoxy resin. By opening some epoxy bonds in epoxy molecules, introducing polar groups, or triggering a thing reaction through free fundamentals, polar groups are introduced into the epoxy molecular skeleton, and these hydro-hydrogenic groups or surfactant chain segments can help the epoxy resin disperse in water. Chemical modified method can be divided into esterification method, etherization method, thing reaction method.
1.3.1 esterification method
water dispersion epoxy resin system is prepared with pyridine-based polymer esterified epoxy resin. Walsba Corporation of the United States used epoxy resin and niobium-based polymers under the action of esterification catalyst reaction to obtain water-dispersed epoxy coatings, DuPont 7 and SCM developed several technologies for the preparation of epoxy-based resins and niobium-based polymers epoxy water dispersion systems, the main disadvantage of which is the lack of control of the mixture of esters, glycide ions and niobium-based ions, which can lead to gel or made products difficult to use or poor film performance. Bobo, William S. 8 invented a new method in which epoxy resins and V-based polymers react under the action of a esterification catalyst and inhibit the reaction mixture and prepare water dispersion coating components before the esterification reaction is complete. The water dispersion coating parts of this invention have excellent stability, high paint film strength and easy to apply to metal substrates.
reactions to hydroxy or epoxy on the chain of binary carpicides and epoxy resins are introduced into the anionic epoxy esters of niobium, and then stabilized water dispersions with serotonin. China National Petroleum Corporation of Taiwan Province prepares a water-based resin dispersion with epoxy resin and binary acid phenol reaction, which can occur double-chain reaction; Massigil and others used epoxy phosphate, mid-hydroxyl esterification reaction to produce epoxy phosphate, with amines to mediate to obtain a more stable water body.
the esterification method is that the ester bonds of the esterification product will be hydrolysed over time, leading to system instability. In order to avoid this disadvantage, the carbihydrate-containing monolith can be bonded to a high relative molecular mass epoxy resin by forming a carbon-carbon double bond.
1.3.2 Etherization
the polyoxyethylene chain segment is introduced into the epoxy resin molecular structure by hydroxy or amine-based epoxy reaction in the hydro-hydro-hydroponic ethylene chain segment, and a water-based epoxy resin with non-ion hydrophobic chain segment is obtained.
Tang Minfeng, etc., chemically modified phenolic epoxy resin E-51 with ethanolamine to introduce hydro-based groups, the modified E-51 epoxy resin can be compared with water to form aqueous solution or water emulsion, the system has good stability; HuberH.etal introduced the use of binary phenol / shrink glycelor cool, binary phenol, polyglycol glyceride ether reaction, the introduction of hydroponic reunification ether, ether alcohol, or non-ionic surfactants in the epoxy resin system, water dispersion epoxy resin can be produced. However, this water-dispersed epoxy resin contains a fat family monohisyl oxide as an emulsifying agent, by these epoxy resins and amine curing agents obtained by the coating film due to the presence of free hydrophobic chain segments, resulting in some of the properties of the coating film is not as good as the corresponding solvent-based coating, not suitable for use in too hot or too dry place; ZhangZhaoying and so on, using amino benzoic acid as a modifier, modified bisceptic bisphenol type A epoxy resin, obtained a stable performance of water-based epoxy resin; Tsugukuni and others will react to amino benzoic acid and liquid epoxy resin, through the etheric reaction in the molecular structure of epoxy resin introduced shamine, pyrethroid two polar groups, neutralizing the later into pyrethroid salts, improve the resin Hydrophobicity; Liu Jianzhong chemically modified bisphenol type A epoxy resin (E-51) with shunbutene date, thus introducing hydrophobic and unsaturated groups, which are later made of salt The obtained resin system after UV curing obtained excellent performance epoxy resin emulsion, Liu Chaoyang and so on. After the production of modified F-51 water-based epoxy resin, this method makes the resin with water solubility and water dispersion, and each modified resin molecule retains 2 epoxy base, so that the hydro-hydrogenicity and reaction activity of modified resin to achieve a reasonable balance.
the system formed by the dispersion of etherized modified epoxy resin in the water phase has good stability, the average particle size of the dispersed phase particles is less than 1 pm, and the use period of the dispersion system mixed with the water-based epoxy curing agent has been extended. At the same time, due to the introduction of polyoxyethylene chain segment, the molecular weight of the mesh chain after crosslinking has been increased, crosslink density decreased, thus the formation of the coating film has a certain toughening effect.
1.3.3 thyching reaction method
the thing reaction is the use of epoxy resin molecules - CH2- or -CH - in the addition of triggers and heating conditions can become the active point, so that can be connected with vinyl monosomes into the epoxy resin molecular chain, to obtain modified epoxy resin, neutralized into salt can occur self-emulsified epoxy resin.
Huang Xianwei, etc., with BPO as the trigger, triggering a reaction system consisting of E-44 epoxy resin, methyl acrylic, acrylates and styrene, synthesized epoxy monoacrylic acid Multi-branch copolymer, and to which to add W (NH3) - 28% ammonia, adjust pH of 7 to 9, get water-based epoxy monoacrylic emulsion, further production of water-based epoxy coating. The properties of the coating are measured, and the experimental results show that the introduction of styrene monomer can increase the adhesion of the coating, improve the impact resistance of the coating, and the adhesion, impact resistance, corrosion resistance and other properties of the coating are good.
Sun Rewu and others, with methyl acrylic, styrene and ethyl acrylic (ratio 65:34:1) for the mixing monomer and higher relative molecular quality of epoxy resin joint polypolytic preparation of epoxy clinging acrylic water dispersion resin, and as a base material and water-based epoxy curing agent to prepare a high-performance hydrooxyoxyprociate surface coating. The coating improves the weather resistance and durability of a single epoxy resin, and the paint film has good plumpness, hardness (up to 3H) and acid-base resistance, which solves the problem of difficult construction of the floor coating on wet substate and the defect that the paint film hard through the low.
the molecular skeletons of epoxy resins, such as Robinson and Woo, to make hydrolytic epoxy resins that are not easily hydrolytic. The free-based polymerization process is applied, the bridging position is the fat carbon atom on the epoxy molecular chain, the thyching rate is less than 100%, the final product is a mixture of unteed epoxy resin, branched epoxy resin and polyacrylate.
Zhu National, etc. , first with phosphoric acid to acidify epoxy phosphate, and then with epoxy phosphate and acrylic joints copolymer, to produce better stability than acrylic and epoxy resin directly branched products of water Dispersion, and found that: water-based system stability with the preparation of epoxy phosphate dosage, acrylic monosome dosage and epoxy resin relative to the molecular mass of the increase, of which acrylic monosome dosage is the most important factor affecting the stability of water dispersion.
Hanfeng and so on" using chemical latte method to the epoxy resin on acrylic and its esters copolymer, forming a certain degree of cross-linking, can be dispersed in the water of the self-emulsified resin, its coating film has excellent alkaline and salt spray resistance.
Zhou Jianping synthesized epoxy acrylates with hydroxyl side-based reactions with biphenol A epoxy resin and acrylic acid, and then used toluene isocyanate and acrylic semi-added to the above-mentioned epoxy acrylates for sterilization, and then use anhydride to attract human carnitine, after amine neutralization can be more stable self-emulsification photoreceptic water dispersion.
Valspar Co., Ltd. of the United States free-based reaction of epoxy resins to water-dispersed acrylic resins to form a water-based coating composition with low VOC that effectively prevents corrosion of iron and non-metallic substrates.
Yang Ruiyin, etc. , the use of amino benzoic acid on the epoxy resin part of the epoxy bond to open the ring introduction of pyridine base, the addition of safety-type saponifying agent and active dispersion of the treatment of water-based epoxy resin emulsion, plus scaly aluminum-zinc alloy pigments, developed double packaging, room temperature curing, environmentally friendly cathode protection water-based epoxy anti-corrosion coating. The coating has good flexibility and excellent corrosion resistance, and can play cathode protection and shield isolation on the base metal at the same time.
Robinson and so on, the acrylic monomer is branched to the epoxy skeleton, obtained a hydrolytic hydro-based epoxy resin; GuirongPan is prepared with acrylates, styrene and acrylic monosomes to produce a high-performance epoxy-acrylic complex emulsion. Shen Xin obtained a self-emulsified epoxy system by using phase conversion method to branch the epoxy resin with phosphoric acid and acrylic acid and its ester monosome.
chemically modified emulsion is stable, and the particle size is small, mostly nanoscale. Among the three modified methods, the free-based joint technology modified method can retain the modified function of epoxy resin in other aspects without destroying the epoxy gene, and the introduction of acrylic or methyl acrylic modified method - COOH hydrophobic group has strong hydrophobic ability to make the modified epoxy resin have good water dispersion advantages.
Chemically modified self-emulsified epoxy emulsions have the following advantages in performance over other types of epoxy emulsions: there is no breakage, therefore, the film coating performance is better, storage stability is good, the emulsion can be re-dispersed without special equipment, and the emulsion epoxy emulsion is difficult to disperse once sedated or broken.
2. Water-based epoxy curing agent modified
modified to get water-based epoxy curing agent, overcome the shortcomings of traditional amine curing agent, does not affect the physical and chemical properties of the coating film, and water as a solvent, VOC content in line with environmental requirements, so water-based epoxy curing agent research water-based epoxy coating research hot spot.
2.1 type I water-based epoxy curing agent
. Type I water-based epoxy curing agent has both curing agent and emulsifying agent function, by the relatively low molecular quality of liquid epoxy resin and water-based epoxy curing agent system.
2.1.1 salt epoxy curing agent
the first successful development of type I water-based epoxy curing.