Learn the Preparation and application of antistatic, antibacterial and odor removing waterborne epoxy floor coating

  In this study, standard liquid epoxy resin E51 is mixed with an appropriate proportion of active diluent, the cosolvent is component A, and component B is composed of waterborne polyamide adduct curing agent, pigments and fillers, additives, functional additives and water. The equivalent ratio of membrane materials of components A and B is 1.1 ∶ 1. After curing, the film has strong adhesion, excellent corrosion resistance, high hardness, good abrasion resistance, strong impact resistance, good decoration, smooth and smooth Breathable and waterproof.

1. Preparation of waterborne epoxy floor coating

a) Selection of raw materials

i. Selection of resin

  Waterborne epoxy floor coating is mainly composed of two components, namely hydrophobic epoxy resin and hydrophilic amine curing agent. Waterborne epoxy floor coating can be divided into two types: type I is composed of liquid epoxy resin with low relative molecular weight or its lotion and water-borne amine curing agent, and type II is composed of solid epoxy resin lotion with high relative molecular weight and water-borne amine curing agent. The waterborne epoxy floor coating prepared in this study belongs to Type I, and the liquid bisphenol A epoxy resin is selected as the epoxy resin.

  The epoxy value of epoxy resin E51 is moderate, and its cured product has high crosslinking density, good compactness and strong corrosion resistance. E51 epoxy resin has low functionality (n=0~1), low hydroxyl content and good water resistance. See Table 1 for the relationship between hydroxyl content in the film and water resistance.

  It can be seen from Table 1 that liquid epoxy resin E51 is selected for this study based on the cost performance ratio and the difficulty of procurement channels.

ii. Selection of thinner

  The active diluent used for bisphenol A epoxy resin is usually aliphatic glycidyl ether epoxy resin, which can react with curing agent to form epoxy curing compound.

  In order to reduce the viscosity of the liquid epoxy resin E51, improve its compatibility with the waterborne amine curing agent, enhance the emulsification of the waterborne curing agent on the resin, and at the same time not reduce the comprehensive performance of the cured epoxy resin, it is necessary to add appropriate diluents. The requirements for thinner are: ① low viscosity; ② The epoxy value is relatively high; ③ Good compatibility with epoxy resin; ④ Good hydrophilicity. The main properties of several commonly used aliphatic glycidyl ethers are shown in Table 2.

  It can be seen from Table 2 that the epoxy value and hydrophilicity of the three active diluents are roughly the same, but the viscosity of 1,4-butanediol diglycidyl ether is the lowest, so it is selected. When the dosage is 10%~15% of epoxy resin E51, the viscosity of E51 epoxy resin can be reduced from 1500 MPa • s to about 600 MPa • s.

  In order to improve the compatibility of epoxy resin E51 with waterborne amine curing agent and narrow the difference of solubility parameters between the two components, a small amount of latent cosolvent should be added to component A. Because when the two components A and B are mixed for curing, the hydrophilic curing agent enters the surface of the epoxy resin of the dispersed phase from the aqueous phase, which makes the concentration of the curing agent on the surface of the epoxy resin higher and the epoxy resin quickly solidified into a hard shell. This will prevent the particles from coalescing into a film, making the resin in the paint film cure unevenly, thus reducing the performance of the film. Under the joint action of diluent and cosolvent, it can effectively reduce the resin viscosity and glass transition temperature, improve the compatibility and compatibility with the curing agent, and also improve the wettability, permeability and diffusion of the curing agent to the resin, promote the uniform curing of the resin, and improve the film performance. The test proved that it was better to choose Tripropylene Glycol Methyl Ether (TPM) from Dow Chemical Company of the United States, with the dosage of about 3% of epoxy resin.

  iii. Selection of curing agent

  The curing agent used in waterborne epoxy floor coating is water-soluble amine or aqueous dispersion of amine, and water-soluble amine is widely used at present.

  For the selection of water-soluble amine curing agent, not only its reactivity, but also its compatibility with epoxy resin, dispersion emulsification and toxicity should be considered. Especially, small molecule amine compounds should be used with caution because of their volatility and toxicity. Therefore, polyamide or amine adduct is often made as curing agent to improve the quality of amine and reduce toxicity. The miscibility of polyamide and epoxy resin is poor and there is an induction period. Polyamide adducts can be used to solve this problem. Water soluble polyamide adduct curing agent is a water-soluble system with dual functions of curing agent and emulsifier by introducing surfactant molecular chain segments into curing agent molecules. The curing process of waterborne epoxy resin coating is a reaction and diffusion control process, including water evaporation, particle coalescence, curing agent diffusion and curing crosslinking reaction. The curing rate of water soluble polyamide adduct to epoxy resin E51 is slow, which can make the cured material uniform; Its reaction activity is moderate, which can make the comprehensive properties of epoxy resin cured products excellent; It has good compatibility with epoxy resin system, which is conducive to the diffusion of curing agent molecules to the interior of epoxy resin particles and complete curing; Its low glass transition temperature can weaken or avoid the formation of hard shell of epoxy resin; It has good wettability, and can be cured by draining water, so that it can be cured on a wet base surface to form a film; The system is stable, without high speed dispersion and demulsification. Therefore, water-soluble polyamide adduct was selected as curing agent in this study.

  iv. Selection of pigments and fillers

  In waterborne epoxy floor coatings, pigments and fillers are indispensable components. The selection principle of pigments is: varieties with low oil absorption value, low water absorption, high hardness, fine particle size, strong internal stress, good acid and alkali resistance, and excellent weather resistance. In general, the content of pigments and fillers in waterborne epoxy coatings is 30%~38%, and the waterborne floor coatings must ensure that the coatings have appropriate air permeability. Therefore, it is necessary to appropriately increase the content of pigments and fillers while keeping the film-forming materials unchanged. In order not to significantly reduce the water resistance and corrosion resistance of the film, it is an effective method to select ultra-fine pigments and fillers with good chemical resistance and add adhesion promoter.

  v. Functional additives

  (1) Antistatic agent. Most polymer materials are prone to the accumulation of static charges. One of the effective solutions is to use conductive coatings to give the film surface conductivity. The antistatic coatings currently used are additive conductive coatings. The additives ① are conductive fillers and ② are surface active agents.

  In this waterborne epoxy floor coating, polyaniline doped conductive polymer is selected as anti-static filler. Polyaniline doped with dodecyl sulfonate has excellent conductivity and corrosion resistance. As a substitute for inorganic conductive filler, it is dispersed in the cured epoxy resin. When the addition amount of doped polyaniline reaches 5%, the resistivity of the coating can reach 107 Ω• cm, which can fully meet the standard requirements of anti-static coatings, and has a long effect. At the same time, it can improve the chemical corrosion resistance of the coating.

  (2) Negative ion - antibacterial additive. Anion antibacterial additive is a functional material that combines anion generating materials with inorganic antibacterial materials. Among them, anion generating materials are the only naturally charged high-quality polar materials in nature. Under the excitation of no light source, they naturally form a permanent micro electric field, and generate hydroxyl anion through the weak electrolysis of their electrodes on air and water. The hydroxyl anion decomposes and removes harmful gases such as formaldehyde, benzene and ammonia in the air through electric neutralization, chemical reaction and physical adsorption. It also has the functions of inhibiting mold survival, removing odor and refreshing the air.

  vi. Selection of additives

  The water-based epoxy floor coating needs various additives to adjust the viscosity or surface tension of the coating, and the selection of wetting and dispersing agents is particularly important. In order to improve the wettability and dispersibility of pigments and fillers, the mutual exclusion of negative charges can improve the stable suspension of pigments and fillers, reduce sedimentation and agglomeration, weaken the cohesion between pigment particles, and avoid floating color and blossoming. A stable dispersion system can be obtained by selecting self emulsifying acetylene glycol non-ionic surface active agent SURFYNOL SE-F and Shengwo FA182 dispersant.

  In order to adjust the viscosity of waterborne epoxy floor coating, organic modified clay thickener is selected for adjustment. Detron VT-819 thickener and anti sedimentation agent has ideal effect.

  The defoamer shall be a long-acting and high-efficiency non silicon defoamer, such as SURFYNOL DF-75.

  b) Formula

  Reference formula of component A:

  Epoxy resin E51: 85%; 1,4-Butanediol glycidyl ether: 12%~13%; Cosolvent TMP: 2%~3%.

  Reference formula of component B:

  Water soluble polyamide adduct: 30%; Dispersant and wetting agent: 0.6%~0.7%; Defoamer: 0.3%~0.4%; Leveling agent: 0.3%~0.4%; 

  Thickener: 0.05%~0.08%; Slip improver: 1.0%~2.0%; Doped polyaniline: 6%~10%; Negative ion antibacterial additive: 1.6%~2.0%; Coupling 

  agent: 0.5%~1.0%; Rutile titanium dioxide: 10%~12%; 600 mesh quartz powder: 18%~22%; 1000~1200 mesh talcum powder: 5%~8%; Color 

   paste: 2%~3%; Water: 16%~20%.

  c) Preparation Method

  Component A: add the liquid epoxy resin, active diluent and cosolvent of the formula into the mixing tank successively, and mix them at medium speed for 10-20 min before packaging.

  Component B: add water into the high-speed dispersion tank, add dispersant, wetting agent, part of defoamer, leveling agent, coupling agent, doped polyaniline, negative ion antibacterial agent and pigments and fillers during mixing, disperse at high speed for 30 min, grind them into slurry, add curing agent, plasticizer, thickener, color paste and residual defoamer, mix them evenly, and filter them into barrels.

  2. Construction Method

  Different industries have different requirements for the performance of the workshop floor coating, which involves the differences in construction methods. When the water-based epoxy coating is used as the floor of machinery, chemical industry, warehouse and other workshops, due to the need for impact resistance, rolling resistance, wear resistance, corrosion resistance, etc. of the floor, the construction must be carried out according to the conventional process, that is, base course treatment → primer → epoxy mortar reinforcement layer → putty → finish.

  a) Base course treatment: for the concrete ground with more oil stains, it can be washed with 10%~15% hydrochloric acid solution, and then washed with clean water; For the general concrete floor with large area, the method of grinding with electric mill, removing sand dust and oil stain can be used.

  b) Back sealing: after the components A and B of epoxy primer are mixed evenly, roll paint on the surface of the base course. It is better to roll paint twice to make it fully wetted and penetrate into the concrete for bonding and strengthening.

  c) Middle layer mortar: add a proper amount of mixed quartz sand with different particle sizes into the waterborne epoxy coating and stir it evenly. Use the plastering method to make the coating reach a certain thickness, so as to enhance the impact resistance and rolling resistance of the floor.

  d) Putty: After the epoxy mortar layer is fully cured, two layers of water-based epoxy putty shall be applied, dried and polished to provide a flat and solid base for surface coating.

  e) Surface coating: Mix the waterborne epoxy finish paint evenly according to the mass ratio of component A: component B=1:1, brush or spray it on the base surface to make it self leveling, and after curing, it will become a flat, smooth and multifunctional floor coating with anti-static, corrosion resistant, antibacterial, bactericidal, odor removal, etc.

When waterborne epoxy coating is used for food, medicine, electrical appliances and other workshops or public venues, the construction can be carried out according to the process of base course treatment → primer → putty → finish. The construction method of each process is the same as before.

  During construction, the ambient temperature shall be more than 12 ℃ and less than 40 ℃; 15~40 ℃ is appropriate; The relative humidity in the air should be less than 85%, preferably 65%, otherwise, the coating will not be cured well, affecting the comprehensive performance of the coating.

  3. Conclusion

  The waterborne epoxy floor coating not only meets the requirements of environmental protection, but also is safe, non-toxic and incombustible. The construction tools are easy to clean with clean water, and can be used on the dry and wet concrete base surfaces. It has good wet adhesion, excellent adhesion between layers, good flexibility, strong impact resistance, good corrosion resistance, good air permeability, and no worries about the formation of blisters and white spots. At the same time, the epoxy curing compound can also be endowed with a variety of special functions by adding functional additives.

  In this study, in the curing system of liquid epoxy resin E51 and water-soluble polyamide, in addition to the addition of pigments, fillers and commonly used additives, doped polyaniline conductive polymer and negative ion antibacterial additive were also added. Thus, the film is endowed with anti-static, antibacterial and mildew resistant properties, release of negative ions, and elimination of harmful substances in the air, becoming a new full effect waterborne epoxy floor coating. It is especially suitable for painting workshop floors that need to be clean, sterile and anti-static, such as medicine, electronics, instrument, textile, daily chemical, food, etc. It is also suitable for public venues, hospitals, office and home floors.