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    Home > Coatings News > Paints and Coatings Market > Advances in the preparation and application of water-based epoxy coatings

    Advances in the preparation and application of water-based epoxy coatings

    • Last Update: 2021-02-03
    • Source: Internet
    • Author: User
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    China Coatings Online News Information
    Yu Li, Yu Lin, Liu Xiao , Yao Jia, Cai Yongyuan (Tianjin Institute of Synthetic Materials Industry, Tianjin 300220)
    Summary: Introduction of the preparation of water-based epoxy resin and water-based epoxy flooring coating formula screening, review of the application and technical progress of water-based epoxy coatings in recent years.
    key words: water-based epoxy resin; Paint; Preparation; Application
    the figure classification number: TQ637; TQ323.5 Document identification code: A Article No: 1002-7432 (2014) 03-0062-04
    0 Introduction

    In recent years, with the strengthening of people's environmental awareness, the epoxy resin system of low volatile organic matter without volatile organic matter and harmful air pollutants has become a hot spot in the research of hydration of epoxy resin at home and abroad. Now more than 90% of domestic and foreign paint enterprises are engaged in the application and development of water-based epoxy coatings, the development prospects are very promising. We are convinced that the widespread application of water-based epoxy coatings in the future will certainly arouse the great concern of all sectors of society.It is reported that in 2010 China's paint epoxy resin accounted for only 48% of the total consumption of epoxy resin, while foreign paint epoxy resin accounted for about 65% of the total consumption of epoxy resin, because water-based epoxy coatings with non-combustible, non-toxic, tasteless, solvent-free emissions, construction convenience and so on, so in recent years at home and abroad developed rapidly.In the 1920s, developed countries such as Europe and the United States began to engage in the research and development of hydrated two-part epoxy resins, and in the early 1980s, the second generation of two-part water-dispersed water-dispersed water-based epoxy resin system was developed, while the third generation of water-based epoxy resins began to appear in the early 1990s. The system is composed of multi-functional, medium relative molecular quality epoxy resin dispersion and modified amino resin curing agent water dispersion, the main purpose of which is to improve the cross-link density of resin and curing agent, improve the matching between resin and curing agent, so that the curing material has better wear resistance and corrosion resistance, further enhance the stability of the system, improve the performance of curing.The use of room temperature-cured water-based epoxy coatings in the field of coatings is roughly divided into four categories: 1) type I water-based epoxy resin system, which consists of water-based epoxy curing agent and low molecular quality liquid epoxy resin. Water-based epoxy curing agent is both cross-linking agent and emulsifier, which can be mixed with emulsification before use to be equipped with zero VOC coating; 2) II. Type water-based epoxy resin system, which consists of a high molecular mass solid epoxy resin dispersion and water-based epoxy curing agent, because its reaction activity is lower than liquid epoxy resin, so ii. Type hydrological epoxy resin system has a longer application period than Type I and a shorter drying time than Type I; 3) III. Type water-based epoxy resin system, which consists of low molecular mass liquid epoxy emulsion and water-based epoxy curing agent, which contains both hydroactive surfactant chain segments and oil-friendly epoxy resin chain segments, which can greatly improve the compatible of emulsions and epoxy resins; 4) IV. Type water-based epoxy resin system, which consists of water-based epoxy emulsion and polyurethane modified epoxy curing agent. It is a suitable amount of polyurethane modified epoxy curing agent, in order to cure the water-based epoxy emulsion, thereby improving the performance of water-based epoxy coating.hydration preparation method of epoxy resin
    mechanical method, reverse transfer method and chemical modified method are the main methods of hydration preparation of epoxy resin. This paper focuses on the chemical modified method. This method mainly by opening the epoxy bonds in epoxy resin molecules, the introduction of polar groups (e.g. sulfonate, pyridine, amine and polyether, etc.) or through free-form caused thwithing reaction to introduce polar groups into the epoxy molecular skeleton, these hydrophobic groups or surfactable chain segments can help epoxy resin dispersed in water, making it water dispersion or water solubility. Because of the different types of polar groups introduced, chemical modified method can be divided into esterification method, etherization method and thing reaction method.1.1 esterification method
    commonly used esterification method is: 1) epoxy resin and unsaturated fatty acids react into epoxy esters, and then with unsaturated binary acids (tyro) and epoxy resin fatty acids double bond by addition reaction to produce a compound rich in carboxyl, and finally with amine neutralizing water-soluble resin; 2) Epoxy resin and phosphoric acid reaction to produce epoxyate, and then with the amine neutralizing the resin containing fumaric acid group to produce a stable water-based dispersion; 3) Epoxy resin and acrylic reaction open ring esterification, and then with amine hydrolysing neutral, or the use of epoxy resin and acrylic ester transfer reaction, the generation of acrylic modified epoxy resin, the legal system of water and milk can be used as a table coating in the tank; 4) Water-based epoxy resin is made by using sodium sulphate and epoxy-based compounds.1.2 Etherization method
    this method is made by epoxy resin and xylenyl benzoic acid or aminobenzene, hydrolytic mesolytic, in addition to the use of epoxy resin and -based acetic acid etherization, after hydrolytic meso-meso-made. Zhang Zhaoying of the Institute of Chemistry of the Chinese Academy of Sciences and others used a reaction to amino benzoic acid and epoxy resin to make a kind of water-based epoxy resin, its water-based epoxy coating performance is very good.1.3 throft copolymer reaction method
    this method is in the presence of the trigger agent, epoxy resin and acrylic and its esters occurred in a joint reaction, the formation of a modified epoxy resin of the fumaric acid group, and then neutralized into salt and finally added water-based epoxy resin, thus forming a very stable water dispersion system. Mechanical method and phase conversion legal system of water-based epoxy resin emulsion process is simple, low cost, but the emulsion particle size is larger (micron grade), and chemical modified legal system of emulsion particle size is small, can reach tens or hundreds of nanometers, so chemical modified method is more practical significance.2. Water-based epoxy floor coating formulation study
    2.1 epoxy resin type and water-based curing agent selection
    Because bisphenol A epoxy resin molecules have high polarity and not easy to hydrolysate hydrolytic hydroxyl and ether bonds, so it has a good adhesion to a variety of materials such as concrete, and good chemical resistance, can make the floor coating has better electrolytic properties. To increase the flexibility of the coating, bisphenol F epoxy resins and epoxy thinners are sometimes added. At present, modified fatty amines and alamide water-based curing agents are more used in type I water-based epoxy systems, and these curing agents are not only better compatible with epoxy resins, but also ensure appropriate reaction activity and emulsification properties. If the two are mixed, a more suitable application period can be reached, and polyamine-epoxy supplements are often used in curing agents of this type of system in foreign countries. This curing agent can overcome the shortcomings of alamide-like curing agents and fatamines, but also has a better use effect.2.2 The ratio of water-based epoxy floor coatings to
    epoxy resins and water-based epoxy curing agents has a significant impact on the performance of water-based epoxy flooring coatings. When the excess of amine hydrogen has a good gloss, fast curing, strong adhesion, good wear resistance, good solvent resistance, good stain resistance; When the epoxy-based excess has good corrosion resistance, long application period, good water resistance, good alkaline resistance, good moisture resistance, good acid resistance.hydropygenic floor coatings are mainly composed of film-forming substances (epoxy resins, curing agents and active thinners), pigments, fillers, functional additives and solvents (water) and other materials. Modified epoxy resins can be used or equipped with other resins, such as aolic acid resins, to improve their performance and reduce costs. In recent years, water-based epoxy flooring coating with its excellent breathability and environmental protection advantages have been rapid development, its film-forming substances can be liquid epoxy resin with emulsified function of water-based amine curing agent, can also be a variety of molecular quality water-based epoxy emulsification liquid with water-based amine curing agent, the curing agent can be water-soluble, can also be emulsion, not necessarily emulsified function. The technical indicators are set out in table 1. Table
    1 Water-based epoxy floor coating technical indicators
    3. Application of water-based epoxy coatings
    With the emergence of the resource and energy crisis and people's health awareness and environmental protection, water-based coatings because of its low VOC, safety and environmental protection, increasingly become one of the solvent-based coating alternatives. Water-based epoxy coatings not only maintain the advantages of solvent-based epoxy coatings, but also have their own advantages. Can be cured under room temperature and humid conditions, fast curing, high correlation density, can be widely used as canned inner wall coatings, anti-corrosion coatings, anti-static coatings, industrial floor coatings, waterproof materials and impermeable leak-blocking materials and in the road bridge paving layer maintenance applications. At present, water-based epoxy resin is mainly used in concrete closed primers. Water-based epoxy coating can be constructed on newly poured or wet concrete surface, has better adhesion to concrete surface, and can also make the water vapor of concrete capillary tubes closed, to prevent pan-alkali, suitable as a concrete closed primer. Solvent-based or water-based epoxy floor coatings can also be constructed on top of closed primers.3.1 Anti-corrosion coatings
    For decades, water-based epoxy coatings have been widely used in steel structures in railway locomotives, bridge buildings, buses, ship drinking water tanks and nuclear power plant reaction tanks as corrosion-resistant coatings on metal substrates. Its advantages are safe and non-toxic, chemical corrosion resistance, water, oil resistance, light resistance and heat resistance, with excellent rust-proof function and bonding performance.FangDin et al. use epoxy resin, acrylic monosome, isopropyl peroxide synthesis from emulsified water-based epoxy resin, the resin can be well compatible with oily epoxy curing agents (e.g. T-31) and cured into a film, its corrosion resistance to the general solvent-based epoxy coating performance level. Acrylic modified epoxy resin, the product of water-based emulsion particles is relatively fine, good stability, not only has the anti-corrosion properties of epoxy resin, but also has acrylic resin gloss and weather resistance, especially suitable for use as canned inner wall coatings.3.2 anti-static hydroelectrogenic epoxy coating
    In order to achieve good anti-static properties of the floor building, we must use comprehensive correction on the basis of the original solvent-based and solvent-free anti-static epoxy flooring coating, the preparation resistance rate of 106 to 108 s. cm of anti-static hydroelectrogenic epoxy floor coating, the coating anti-static properties are very good. In order to ensure that the water-based epoxy coating has excellent anti-static properties, its water-based epoxy coating has 2 characteristics, such as good conductivity and strong durability, the paint conductive composite materials such as mica powder, cheap, light, large surface area, conducive to dispersion and mutual contact in the resin, its volume resistivity can reach 108 s. cm;2) color adjustable, conductive composite fillers can be used with other pigments, adjusted to make a variety of different colors of anti-static paint, so as to avoid the problem of lighter filler color.
    3.3 Wall and industrial floor coatings
    Because of the small smell of water-based epoxy resins and the ease of cleaning of coating surfaces, industrial floor coatings are ideal for dust-free locations where a high degree of cleanliness is required, such as hospital drug rooms and operating rooms, food processing plants, breweries, beverage plants, pharmaceutical plants, dairy plants and cosmetics plants. If 2 decorations are required, the old and new coatings can still maintain good adhesion without affecting re-coating, and industrial floor coatings play an important role in water-based epoxy coatings.3.4 Cement mortar repair materials
    Due to the good solubility and bonding properties of water-like epoxy emulsions and mortar cements, high mechanical strength, long-lasting construction, can be constructed and bonded in wet and watery environments. Can be widely used in highways, docks, airport runway water conservancy dams and sluices and other water conservancy projects, its enhancement and impermeability effect is very good, of which water-based epoxy resin coating use accounts for about 35% of the total amount of cement mortar.3.5 Impermeable leak-blocking materials
    due to the cross-linking network of epoxy resin and the hydration and curing of cement formed an interoperability network structure, which makes it have a good anti-leakage effect. Water-based epoxy resin and cement and sand according to a certain ratio, the production of waterproof mortar material. The material can be used to repair cracks in the roof, interior and exterior walls and the ground, and can be put into use in a few hours. 3.6 Application of solder resistance agents, such as
    Li Shirong, used xylene instead of brominated seasonal ammonium salt as a catalyst, and toluene partially replaced dioxyhexane as a solvent synthesis of quasi-water-soluble acrylic photopolyceride epoxy resin, successfully used as a solder resistance agent. The study proved that the mixture solvent containing 31% two oxygen six-ring was beneficial to the reaction. Resin can be dissolved in sodium carbonate solution, when the carbon double bond number of active thinner close to photosensitive resin carbon double bond, paint film performance is the best, can withstand 230 degrees C high temperature, with excellent acid resistance, solvent resistance and resymnant properties. 3.7 Application of underwater epoxy adhesives
    In the late 1860s, underwater coatings and underwater epoxy adhesives with epoxy resin as the main body appeared abroad. The study found that an ideal underwater adhesive should be stable after encountering water, not mixed with water, not damaged by water; The adhesion force in water must be greater than zero to meet the thermodynamic conditions of wetting the adhesive in water; Can effectively immerse and cure the surface of the viscous in water; Can change or dissolve the water molecule mass on the surface of the sticky body, has a certain surfactant effect; Should have and cure also has a certain strength and good water resistance stability; It must be able to adapt to the bonding of various geometric structures underwater, and meet the conditions of simple operation and non-pollution of the environment. of an underwater epoxy adhesive can be used as a curing agent using a mixture of low molecular polyamide and phenolic phenolamide (mass ratio of 1:1). Raw lime CaO, Al (OH)3, cement and semi-water gypsum are optional as fillers to absorb the water film between the adhesive and the bonded contact surface. The addition of nano-masked soiling as a filler can greatly improve the performance of underwater adhesives. Curing promoters can also be added to promote curing. 4. Advances in water-based epoxy coating technology
    The first generation of water-based epoxy resin products are emulsified directly using emulsifying agents, and the second generation products are emulsified epoxy resins using water-soluble curing agent emulsified oil. None of these resin paint films can reach the technical level of solvent-based epoxy coatings.
    Shell of the United States after many years of research and development, has now launched the 3rd generation of water-based epoxy resin system, characterized by epoxy resin and curing agent after chemical reaction, their molecular chains are connected to non-ion surfactants, after testing, the paint film performance has reached and exceeded solvent-based paint film performance indicators. close
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