Formula design and construction of waterborne epoxy floor coating

The formulation design and construction of water-based epoxy flooring coatings
Shi Xuezhen, Shi Shengjun, Chen Wei
(Shanghai Green Jia Water-based Coatings Co., Ltd.)
Abstract: Briefly describe the characteristics of water-based epoxy flooring coatings, focusing on the formulation design of water-based epoxy flooring coatings and their main components on the performance of the coating, and give a brief introduction to the water-based epoxy flooring coating formulation and performance.
keywords: water-based epoxy floor coating; formula design
construction process
1 foreword
epoxy resin coating with high hardness, good wear resistance, high adhesion and excellent performance of chemicals, widely used in the field of industrial floor coating. In recent years, with the continuous improvement of people's awareness of environmental protection, many countries have promulgated environmental regulations to limit volatile organic solvents (VOCs), coating hydration, solvent-free and high solid differentiation has become an inevitable trend in the development of

.
China's industrial flooring coatings are basically solvent-based and solvent-free epoxy flooring coatings, solvent-based epoxy flooring coatings contain more organic solvents, these organic solvents in the production and construction phase of the coating into the atmosphere, pollution of the environment, while endangering human health; Epoxy floor coating contains a small amount of active thinner, commonly used active diluent is butyl epoxy propylene ether (with certain toxicity), the use of self-leveling construction process, coating thickness of 1-5mm, high cost and contains a small amount of volatile organic solvents.
Compared with ordinary solvent-based epoxy flooring coatings, water-based epoxy flooring coatings have the following advantages:( (2) can be constructed and cured in a humid environment, have a reasonable curing time, to ensure that the coating film has a high cross-link density. (3) For most substrates have good adhesion, even wet substrate surface also has good bonding. (4) good operating performance, construction tools can be washed directly with water, can be reused, paint preparation and construction operation safe and convenient. (5) After curing the coating film gloss soft, good texture, and has a better anti-corrosion performance and one-way breathability.
refore, with the enhancement of environmental regulations and people's awareness of environmental protection, water-based epoxy floor coatings will be widely used, research and development of water-based epoxy industrial flooring coatings have great economic and social benefits. In this paper, the formula design of water-based epoxy floor coating and its main components (epoxy resin, water-based epoxy curing agent, pigment, additive and solvent, etc.) are discussed systematically, and the formula example and performance of water-based epoxy floor coating are given, on the basis of which the construction process of water-based epoxy floor coating is briefly introduced.
2 The formulation design of water-based epoxy floor coatings
2.1 epoxy resins
epoxy resin types have a great impact on the performance of water-based epoxy floor coatings. Because bisphenol A epoxy resin molecules contain high polarity and not easy to hydrolysize hydrolytic hydroxyl and ether bonds, so that it has a good adhesion to a variety of substrates such as concrete, coating curing when the volume shrinkage is low, good resistance to chemicals. And bisphenol A epoxy resin for rigid benzene ring and flexible ether bond alternately scheduled structure, giving the coating a better physical and mechanical performance, so this type of epoxy resin is widely used in floor coatings, while other types of epoxy resins such as bisphenol F-type and phenolic epoxy resin is less used.
hydration technology of epoxy resin at home and abroad is mainly divided into emulsification method and salt method. Emulsification refers to the direct emulsification of epoxy resins, self-emulsification without emulsification with emulsion agents or emulsification of water-based epoxy curing agents, and the salinization method is to transform epoxy resins into acid-rich or alkali-rich resins, and then neutralize them with a small molecular weight of alkali or acid. Emulsification is suitable for epoxy emulsions used as water-based epoxy floor coatings.
(1) Direct emulsification
mixing epoxy resin with emulsion, heating it to a suitable temperature, and slowly watering it in a heated mix to complete the reverse turn to make a watery epoxy emulsion. The emulsifying agents available are polyethylene oxide alkyl ether (HLB: 10.8 to 16.5) and polyoxidized alkyl esters (HLB s 9.0 to 16.5), and of course, special water-based epoxy milk can also be synthesized. Chemical agent, the company uses polytivofuran (PTMEG) synthetic water-based epoxy emulsifying agent, emulsified with the emulsion of the formation of water-based epoxy resin particle size is small, better storage stability, and added curing agent curing coating chemical resistance and heat resistance is also better.
(2) Self-emulsified epoxy resin
introduces hydro-hydroxyl oxide or propylene oxide chain segments into the epoxy resin molecular chain, while ensuring that each modified epoxy resin molecule contains two or more epoxy-based, without the addition of emulsifying agents can be self-dispersed to form emulsions. The Company uses polyethylene oxide and propylene oxide inlay copolymers and bisphenol A epoxy resin and bisphenol A reaction to produce a self-emulsifying function of the polymeric epoxy resin, the reaction process with triphenylene as a catalyst, modified ring Oxygen resin is easily dispersed in water, can be pre-made into water-based epoxy emulsion or in-place emulsification in construction, and because the hydro-water chain segment is contained in the molecular chain of epoxy resin, the chemical resistance of the cured coating film has been improved.
(3) Water-based epoxy curing agent emulsified epoxy resin
As an cation emulsizer to complete the emulsification of epoxy resin, the water-based epoxy resin emulsion prepared by this method has good stability, and because epoxy resin composition does not need hydro-modified, can ensure that the coating film resistance of chemicals is good.
The water-based epoxy emulsion prepared by these three methods is suitable for water-based epoxy floor coating, the water-based epoxy curing agent emulsified epoxy resin method should be used low-viscosity liquid epoxy resin, which is conducive to the mixing emulsification of curing agent;
2.2 Water-based epoxy curing agents
are one of the key groups that determine the final performance of water-based epoxy floor coatings. As a curing agent of water-based epoxy resin, it should be able to dissolve or disperse well in water, and it can be stable in water, and epoxy resin should have good compatible. Curing agent can directly emulsify epoxy resin or with water-based epoxy emulsion into a stable water-based epoxy resin system, at the same time the system's fluidization performance, application period, curing conditions and coating properties should also meet the requirements of floor coating use.
acidic acid will be decomposed, not suitable as a water-based epoxy resin curing agent, and water-based epoxy floor coating is commonly used in room temperature curing occasions, so the commonly used water-based epoxy curing agent is mostly polyamine or its modified products, the use of its molecular amine-based active hydrogen and epoxy resin molecules in the epoxy-based reaction. There are three commonly used modified methods of polyamine: the first is polyamines produced by the reaction of polyamines and single fatty acids, the second is polyamides, which are composed of dipolyacids and polyamines, and the third is polyamine-epoxy additions obtained by the addition of polyamines and epoxy resins. All three methods use the introduction of non-polar groups in the polyamine molecular chain, so that the modified polyamine curing agent has a two-parent structure to improve compatible with epoxy resin.
amide polyamines themselves have a certain water solubility or water dispersion, without the use of solvents or emulsification agents to obtain a certain range of water dilution, so that can be used as a water-based epoxy resin curing agent. And the role of aamide polyamines with surfactants, low molecular weight liquid epoxy resin does not need to be pre-emulsified, and by alamide polyamine before construction mixed emulsification, with alamide polyamine emulsified epoxy resin with a water-based epoxy system with good construction performance, long application period and other advantages. However, the compatible between mono-fatty acid modified alamide polyamine curing agent and epoxy resin is not too good, easy to separate and surface defects such as oil sealoids and pits on the surface of the coating film, and insufficient curing results in poor chemical resistance and moisture resistance of the coating film.
water-based polyamide curing agent is prepared by shrinking dipolyacids and polyamines, so that the modifiability can improve the compatible with epoxy resin, and the coating surface will not appear due to incompatible surface defects. However, the application period of emulsified epoxy resin system with polyamide curing agent is short, generally no more than one hour will gel, which will bring some trouble to the construction of the floor. And with polyamide cured coating film flexibility is poor, anti-flush performance is poor, the coating film is brittle. Water-based polyamide curing agent is easily darkened by oxygen oxidation in the air due to the presence of unsaturated double bonds in dipolyacids, and is not suitable as a curing agent for water-based epoxy floor coatings with higher color requirements.
Because the coating film cured with aminide and polyamide water-based curing agent is more or less defective, and the modified coating film performance has not been significantly improved, so the water-based epoxy curing agent used abroad is polyamine-epoxy plus, the use of epoxy resin and polyamine reaction, The introduction of epoxy resin molecular chain in the polyamine molecular chain makes the synthetic curing agent have the molecular structure of pro-epoxy resin, and reducing the content of beamine group in the curing agent molecule can significantly reduce the activity of the curing agent, so that the application period of emulsified epoxy system with this type of water-based epoxy curing agent has been extended. And by adding polyoxidant alkyl polyamine method to improve the problem of coating film brittleness. If the water-based epoxy curing agent is to have the function of emulsified epoxy resin, it needs to be obtained by introducing oxidized alkyl chain segments or ion groups into the curing agent molecular chain. The company's synthetic water-like epoxy curing agent GCA01 belongs to the typical polyamine-epoxy addition modified curing agent, can be diluted with water, the dilution process will not appear similar to the water-like polyamide curing agent dilution due to the formation of the beam and the hydrogen bond between polyamide and water between the "water peak" phenomenon. And the curing agent molecule contains surfactant chain segment, can be low molecular weight epoxy resin direct emulsification, its performance can be seen in Table 1.
: This water-based epoxy curing agent contains a small amount of propylene glycol methyl ether to ensure filming at room temperature, although it contains solvents, but its flash point is still higher than 100 degrees C.
2.3 Pigments
Water-based epoxy floor coatings should be colored with inorgisic pigments or their water-based slurry that are resistant to chemical properties and weather. The selection principle of fillers when water-based epoxy flooring coatings are made is to use fillers with low oil absorption, moderate fineness and stable performance. Of course, considering that water-based epoxy curing agents are weakly alkaline, acidic pigments should be avoided. Water-based epoxy floor coating is a two-part coating, pigment can be added to the epoxy resin parts, can also be added to the water-based epoxy curing agent parts. the amount of
fillers (expressed by the pigment ratio) has a great impact on the final performance of water-based epoxy flooring coatings, and the appropriate amount of addition can not only reduce the cost of water-based epoxy flooring coatings, shorten the drying time of the coating surface, but also improve the mechanical strength of the coating film, Wear resistance, gloss and cover force, reduce the volume shrinkage when the coating curing, and give the coating good storage stability, but excessive addition will increase the viscosity of water-based coatings, resulting in poor leveling of the coating, construction difficulties, the surface effect of the coating worse.
2.4 Additives
For water-based epoxy floor coatings, pigment fillers can be dispersed between epoxy resin parts or in water-based epoxy curing agents or at the same time in both groups. Pigment dispersion in epoxy resin parts will be limited by epoxy resin viscosity, pigment dosage can not be added too much, dispersion efficiency is low, in order to avoid the phenomenon of floating color and flowering, usually need to add dispersants to prevent pigment flocculation, so as to overcome the pigment flocculation caused by floating color and flowering, but the choice of dispersant should be oil and water type dispersant. Therefore, we recommend that painting is not carried out in epoxy resin parts, but choose to be carried out in the water-based epoxy curing agent parts, with emulsified epoxy resin function of the curing agent its molecules containing surfactant chain segments, can wet pigment fillers, have a certain wetting dispersion effect, can be directly painted without dispersants.
Because of the high surface pressure of water, the wetting of the substrate is poor, especially the surface with grease residue is more difficult to wet, then should be added wetting leveling agent to improve its wetting, but also improve the leveling of the coating. However, in the water-based epoxy curing agent parts of the paint will be due to the presence of amine curing agent, reduce surface pressure and easy to have the problem of clipping air, water-based epoxy floor coating preparation and construction will inevitably bring into the air, while adding wetting leveling agents and other surfactants can easily cause foam, Therefore, when painting to add anti-foaming agent and de-foaming agent, usually before dispersion to reduce the possibility of foam formation, dispersion and then add de-foaming agent to eliminate mixed gas, so that the water-based epoxy floor coating in the coating to form a smooth and flat surface. In addition, thickeners can also be added to adjust the viscosity of the curing agent paint, so that the viscosity of the two parts is not very different, easy to mix emulsification.
2.5 cosolvent
two-celled watery epoxy coating is a emulsion-type coating, after mixing the two parts, the water-based epoxy curing agent molecule first and epoxy resin dispersion phase surface contact curing reaction, with curing reaction The molecular weight and glassing temperature of epoxy dispersion phase gradually increase, which makes the diffusion rate of the curing agent molecule to the inside of epoxy dispersion phase particles gradually slow down, which means that the curing reaction inside epoxy dispersion phase particles is less than the surface and the internal crosslink density is lower. At the same time, with the curing reaction, epoxy dispersion phase particles gradually harden, particles are also difficult to interact with each other and condense into a membrane.
cools (also known as membrane additives) are usually volatile very slow solvents, such as various types of alcohol ether, alcohol ether acetate and alcohol esters, especially those that do not pollute the environment solvents (such as propylene glycol methylene ether, etc.), after addition can make the water-based epoxy floor coating the minimum film temperature gradually reduced, conducive to curing condensation into a film. At the same time, cosolfolation can also adjust the viscosity of the coating system, improve the leveling of water-based epoxy floor coating and the appearance of the final coating. Good cosolfacates usually need to meet the following conditions: good hydrolysal stability, low solidification point, moderate volatility, and efficient coagulation efficiency. In general, the addition of cosolts according to the substation of about 1-5% of the consideration, in the lower season of construction, cosolt addition can be appropriately increased to obtain a better coating effect.
2.6 epoxy-hydrogen equivalent ratio < b.