Selection of additives for water-based coatings.

selection of additives for water-based coatings
Yu Guoling 1, Wang Xueke 2
(1. Nanyang Agricultural Vocational College, Nanyang, Henan 473000; 2. Nanyang Wolong Paint Co., Ltd., Nanyang, Henan 4730000 0 Introduction
With the global implementation of coating water-based, national regulations on VO C emissions have clear limits, policy pressure and social responsibility driven the paint industry's water-based revolution, water-based resin research and development, application has also obtained a great breakthrough, the application of various types of additives for water-based coatings research and development is very important.
water-based coatings are commonly used additives are: wetting dispersants, film-forming additives, thickeners, substrate moisturizers, de-foaming agents, anti-lighting agents, surface control agents, anti-corrosion mold inhibitors, anti-lighting agents, corrosion inhibitors and so on. The development of water-based coating additive industry has a great constraint on the development of water-based coating industry. Additives are not used much in water-based coatings, but they play a key role in the performance of coating products.1 Water-based additives and the selection of
1 . 1 wetting dispersant
In the wetting process, the reasons for the slow wetting are: low diffusion pressure, small gap of pigment particles, high viscosity of the coating. The types and characteristics of wetting dispersants for water-based coatings are listed in Table 1.
the selection basis of wetting dispersant: can effectively reduce surface pressure, small dosage, good compatible with other parts, unstable foam, no heavy coating obstacles.
the types and characteristics of substrate
1 . 2 substrate moisturizers and water-based coatings are listed in Table 2.basis for the selection of substrate moisturizers: small amount of addition, no adverse effects on water resistance, rapid construction, no adverse effects on inter-layer adhesion, good addition, cost-effective.
1 . 3 film additives
film additives provide a venue for latex molecular chain winding, diffusion, fusion into film, usually high boiling point solvents. However, in high solid sub-coatings, film-forming additives easily make the gel particles swell, viscosity rise, and even latex, resulting in paint scrapping. The types and properties of film-forming additives are listed in Table 3.determines the advantages and disadvantages of film-forming additives is to determine the minimum film-forming temperature of emulsion.
the choice of film-forming additives is based on: must be a strong solvent of polymers; film-forming efficiency is high; no adverse effects on the stability of emulsion; small odor; low addition; can reduce the minimum film-forming temperature of water-based resins; complete evaporation after filming, without affecting The appearance and luster of the coating film, good hydrolysis stability, small solubility in water, lower volatility than water and ethanol, adsorption on the surface of latex particles, excellent polymeric properties, and good compatible with water-based resins.
1 . 4 The types and characteristics
thickeners and thickeners are listed in Table 4.1 . 5 desulbants
water-based coatings are more prone to bubbles than solvent-based coatings. The reasons for the bubbles produced by water-based coatings are: water-based coatings in the process of stirring dispersion and construction, due to changes in the free energy of the system to produce bubbles; In addition, the foaming tendency of the base material itself, the compatibleness of various additives, the variety and dosage of the additives all have a great impact on the production and stability of the foam. The types and characteristics of desiccants used in water-based coatings are listed in Table 5.method of evaluating deboulants: drumming method, roller coating method, shaking foam method, specific gravity method, mainly used in color paint.
detection method of de-foaming ability: high-speed stirring method.
the selection of defoulants based on resins, formulation systems, construction methods, production processes and other additives. The general principles are: strong de-foaming ability, no impact on other performance, no re-painting obstacles, good stability. In low-viscosity latex paint or water-soluble coatings, the amount of desiccant is 0 . 0 1 % to 0 . 2 0 % , in high viscosity latex paint, desiccant dosage is 0 . 0 3 % to 1 . 0 0 % , in other water-based coatings, the amount of desiccant is about 0 . 1 0 % 。
deblisters are generally added at high viscosity levels and dispersed evenly. The dosing is generally at 0 . 5 % to 1 . Between 0 %, usually the dispersion phase plus 1 / 3 to 1 / 2, the coating deployment phase plus 1 / 2 to 2 / 3.
the key to choosing a deboulant: if the compatible is too poor, it can cause surface defects (e.g. shrink holes), and if the desiccant is fully compatible with the coating, the deboulation effect is not ideal.
1 . 6
the selection criteria for water-based coatings: refractive index of 1 . 4 to 1 . 6;
-based coatings are mainly ultra-fine silicon dioxide, with a refractive index of 1 . 4 6. The particle size and pore rate of the light-dlight powder are directly related to the de-lighting effect, and the commonly used particle size of the light-dissipation powder is 3 to 7 m, which is best around 5 μm, and the porosity rate is 1 . 2 to 2 . Between 0 m L / g.
effects of the light dissipation are listed in Table 6. 1 . 7 Surface Control Agent
Surface Control Agent for Water-based Coatings can control surface smoothness, scratch resistance, anti-adhesion, anti-flow hanging, water resistance, gloss, etc. The types and characteristics of surface control agents for water-based coatings are listed in Table 7. 2 Additive selection techniques
Water-based additives should be selected to consider the nature of the dispersion medium, the status and characteristics of pigment surfaces, the interaction between additives, the interaction and restriction between the components of water-based coatings, and the influence of external conditions to minimize the negative effects of additives. According to the paint manufacturing, storage and transportation and coating requirements, for different paint varieties, choose the appropriate additive varieties. Under the limited conditions, through the test comparison, determine the variety and addition of additives, according to a reasonable way to join, in order to play the positive effect of additives. Reasonable determination of the relationship between coating and coating performance and additive varieties and dosage, to find the best balance between performance and additive dosage.
use of additives should overcome the dependence on existing additives, and actively explore the use of new additives, matching aids and environmentally friendly additives. Give full play to the positive effect of the matching aid system, and ensure the stability of the matching aid system. 3 The development direction of water-based additives
water-based additives will be in the direction of performance compounding, while ensuring one performance, but also improve other performance, thereby reducing the comprehensive cost of formulation. Strengthening the development of silicon-modified and fluorine-modified wetting agents and other surfactants, multi-purpose, efficient, long-lasting, environmental protection, safety, low cost, easy construction will be the future direction of water-based additives. Reasonable selection, accurate and appropriate use of additives, the development of water-based coatings industry is particularly important. 4 Conclusion
According to the requirements of paint manufacturing, storage and transportation and coating, for different coating varieties, taking into account the properties of the dispersed medium and the status, characteristics, interaction between additives, interaction between additives and components of water-based coatings, through test comparison to determine the appropriate additive varieties and additions, the use of additive highlighting effects, synergies and characteristic superimposing effects and other characteristics, the selection of suitable matching aid system, is the key to the selection of additives. It is the premise of additive selection to play the essential characteristics of matching additives and to ensure the stability of coating system. .