Application of thickeners in water-based coatings.

Application of thickeners in 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 473000)Introduction
Thickener is a fluidizer with specific flow properties. In the process of coating preparation, it can improve the viscosity of the material, easy to disperse the pigment, in the process of emulsion polymerization, it can protect the collusion, improve the stability of the emulsion, in the process of coating storage, it can prevent the deposition of pigment, clinging, in the construction process, it can adjust the viscosity of the coating, prevent hanging. The correct selection and use of thickeners is very important to solve a variety of fluid problems in coating production, storage and construction.the type and performance of 1 thickener
the thickeners used in coatings are divided into two types: steroid and non-steroidal. Cellulose and clay thickeners are non-joined, while hydrophobic alkali-soluble thickeners (e.g. TT-935) and polyurethane thickeners (e.g. RM-8W) are sterilization types.
types and characteristics of commonly used thickeners are found in Table 1. A comparison of the performance of different types of thickeners can be found in Table 2.hydroxyethyl cellulose (HEC), a conjunctive alkali-soluble thickener (HASE) can help grind and improve the dispersion quality of pigments, thereby improving film gloss;2 Effect of thickeners on water-based coatings
2.1 Water-based building coatings caused by thickeners and prevention
In water-based building coatings, the addition of thickeners can cause microflocculation, resulting in the occurrence of water-splitted tanks. The type of thickener, the relative molecular mass size, the length of the chain, the molecular structure and the type of hydrophobic group all have an effect on the water in the tank. Experiments show that when m (HEUR)/m (HEC) is between 1:2 and 2:1, water is prone to water division. Both are used alone, basically without water division. The addition of two thousandths of propylene glycol or glycol can improve the phenomenon of water hydration, in addition to the selection of suitable emulsions, the addition of fluid change agents can also prevent the occurrence of water hydration phenomenon. In the formulation design, let the volume of the coating solid content is higher, but also to prevent water in the tank.
the effect of the compound-paired water-based coating of the thickener
the different combination of the thickener has a great influence on the performance of the water-based building coating. A thickener can not meet the various performance requirements of the coating, the use of cellulose thickeners alone, poor fluidity, separate use of synthetic thickeners, fluidity and wash resistance is very good, but there will be post-thickening phenomenon, in addition to pulping and roller coating easy to splash. Cellulose thickeners and synthetic thickeners are used in combination, and the comprehensive properties of coatings will be greatly improved. Cellulose thickeners and two synthetic thickeners were used again, with better results. HeUR, HEC, HASE 3 thickener combinations for optimal results. The dosage and ratio of various thickeners should be determined by test according to different systems and different formulation designs.
2.3 The subsidion of pigments in water-based coatings and the prevention and control of pigmentation in
water-based coatings is one of the most important technical problems. The subsidion of pigment is a phenomenon of low shear rate, which is less than 10-2 s-1.
Methods to prevent pigmentation include: (1) selecting pigments with smaller particle sizes; (2) reducing the amount of surfactants; (3) adding thickeners to increase the viscosity of the system at low shear rates; and (4) adjusting the formulation to improve the solid content.
2.4 Relationship between coating performance and paint fluidity
Coatings belong to non-Newtonian fluids, the cause of tentacles is that there is a very weak mesh structure in the coating system, high shearing under the mesh structure is destroyed, viscosity is reduced, brushing and leveling is better;3 The performance and usage of several new rheosizing aids
(1) SB-2 hydrothermal high purity modified montite, has a good tentacle effect, high shear low viscosity, low shear high viscosity, no pulping, no resuscation, thermal stability and biological stability, in the pH 6 to 12 range can be used, easy to disperse. Dosing 0.4% to 0.6%.
(2) FS-RD high-purity synthetic lithium soap soil, in the aqueous solution can be water synthesis colorless transparent collosus dispersion. Excellent anti-sinking performance, suspension stability is good. Can be used for water-like silver powder paint, water-transparent metal paint and so on. The anti-sinking performance is outstanding, the complex paint does not float color. Usage: Take a certain amount of FS-RD, stir under water, speed 1,000 to 1,500 r/min, disperse 20 min, to make gel pulp.
(3) SHV anti-sink anti-flow hanging agent, is a highly selected process modified montite, chemical composition of magnesium polysilicate aluminum, milky white powder. After being dissodiated by water molecules, the structure of the house is formed, which has excellent suspension stability effect on Zn powder, BaSO4 and other fillers, and has obvious positioning effect on pigment particles, with no minimum active temperature. Good compatible with many water-based industrial resins, applicable to pH range 4 to 12, mainly used in water-based industrial coatings, a variety of water-based color paste. Add 0.3% to 1%.
(4) WT-121 water-based polyamide wax flow aid, is a modified polyamide wax in deionized water and solvents in the pre-dispersion, expansion and bion made of tactability paste, in the water-based metal paint can strengthen the positioning arrangement of aluminum powder, increase the luster of the paint film. Can be made into a pre-gel for use, can also be added directly, dispersion temperature below 70 degrees C, speed 1,500 r/min. The amount of addition is 0.5% to 5.0%, and 2% glycol butyl ether can be added as a solvent when used. Mainly used in water-like metal paint, etc.4 Conclusion
The fluid properties of water-based coatings are more complex problems, practitioners do not know enough about it, thickener applications in water-based coatings are still in constant exploration. With the improvement of the performance requirements of coatings, the application of thickeners in water-based coatings will be paid more attention to and developed. In the past, China's water-based paint thickener varieties are basically limited to cellulose, bentonish soil, etc. , the combined thickener, alkali-soluble thickener, etc. are only in recent years to develop and use the new varieties. The deepening study of benthic soil and the study of sea bubbly as a thickening fluid have also been carried out in recent years. Another development is the development of new concepts of fluid thickeners, such as those called "modified collages". The direction of thickener development is to develop new varieties, while improving the performance of traditional thickeners to meet new requirements, and towards the direction of performance compounding, while ensuring one performance, but also improve other performance. The effect of thickener on water-based coatings, involving production, storage and transportation, construction and other links, different types of thickener thickening mechanism and the effect on paint performance are different, in the use should also consider thickeners and other components of the system of the matching, to ensure the stability of the system is the premise of the choice of thickener..