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The development of powder coatings drives the demand growth of powder fillers, talking about the application and development trend of powder fillers

the development of powder coatings drives the demand growth of powder fillers, talking about the application and development trend of powder fillers, coatings,

the development of powder coatings drives the demand growth of powder fillers, talking about the application and development trend of powder fillers

January 13, 2021

the era of environmental storm of coatings, It is an inevitable choice for enterprises to develop environment-friendly coatings with the brand of "environmental protection and power transmission". However, environment-friendly coatings are a kind of water-based coatings. If enterprises rush to develop water-based coatings, product homogenization will inevitably occur. In addition to water-based coatings, high solid coatings, solvent-free coatings and powder coatings are also environment-friendly coatings, which should become the key development direction of the coating industry. According to a research report, the value and quantity of powder coating market in the Asia Pacific region is expected to reach the highest growth rate from 2017 to 2022. Powder coating technology is developing rapidly to meet the demand driven market. Driven by the market, the research on the application of different powder materials in powder coatings is particularly important

I. overview of powder coating

1. Introduction to powder coating

powder coating began in the 1950s. It is an environmental friendly coating with 100% solid content and no organic volatile matter (VOC). It has the characteristics of energy saving, pollution reduction, simple process, easy industrial automation, excellent coating performance, etc

powder coating is a powder coating composed of polymers, pigments, fillers and additives. Because there is no volatilization of liquid medium, it has good ecological and environmental protection; Powder coating can form a thick coating at one time, which has high production efficiency; The powder coating has excellent mechanical properties and chemical corrosion resistance, and has excellent coating performance; The use of powder coating can save energy and resources, and the utilization rate can reach 99%. It is safe to use and has outstanding economy; Therefore, as a solvent-free coating, powder coating conforms to the internationally popular "four e" principles of economy, environmental protection, high efficiency and excellent performance

2. Overview of powder coating market

with the increasing demand for electrical appliances and light vehicles, the demand for powder coating has increased. The growing demand of the end use industry in developed and emerging countries has also led to the growth of the powder coating market. According to the report released by markets and markets, the global powder coating market is expected to reach $134.9 billion by 2022, with a compound annual growth rate of 6.75% from 2017 to 2022

thanks to the joint promotion of many factors, especially the rapid development of urbanization and the joint growth of housing, construction, automobile and other fields, the growth rate of China's powder coating market demand ranks first in the world. In 2016, the output of China's powder coating industry reached 2.07 million tons

chart 1: changes in the output of China's powder coating industry in (unit: 10000 tons)

from the perspective of output, powder coating currently accounts for about 11% of China's total output of coatings. According to the "13th five year plan", the total output of the coating industry is expected to increase to about 22million tons by 2020, among which, the coating varieties with good cost performance and environmental friendliness account for 57% of the total output of coatings ". In 2020, the proportion of powder coating rose to about 18%, and the output reached 4million tons. The rapid development of powder coatings will inevitably drive the growth of the demand for powder fillers

II. Application analysis of different powder materials in powder coatings

fillers in coatings can not only reduce their cost, but also play a great role in improving the performance of coating products. For example, improve the wear resistance and scratch resistance of the coating, reduce the sagging of the coating during the melting flow, improve the corrosion resistance, and improve the moisture resistance

factors such as density, dispersion performance, particle size distribution and purity should be considered when selecting fillers for powder coatings. Generally speaking, the higher the density, the lower the coverage of powder coating; The dispersity of large particles is better than that of small particles; The filler is chemically inert, which can avoid reacting with some components of the powder formula such as pigments; The color of the filler should be as white as possible. Powder materials commonly used in powder coatings mainly include calcium carbonate, barium sulfate, talc powder, mica powder, kaolin, silicon dioxide, wollastonite, etc

1. Application of calcium carbonate in powder coatings

calcium carbonate is divided into light calcium carbonate (precipitated calcium carbonate) and heavy calcium carbonate. No matter what kind of calcium carbonate and how it is produced, different particle sizes strongly affect the gloss of the coating. Calcium carbonate is generally not recommended for outdoor use

except for increment, heavy calcium is mainly used to partially replace titanium dioxide and color pigments, to replace light calcium and precipitated barium sulfate, to prevent corrosion and to partially replace antirust pigments

when used in interior architectural paint, it can be used alone or in combination with talc powder. Compared with talc powder, calcium carbonate can reduce the pulverization rate, improve the color retention of light color paint and increase the mildew resistance. However, its poor acid resistance hinders its application in external coatings

compared with heavy calcium, light calcium has small particle size and narrow particle size distribution range, high oil absorption and brightness. Light calcium can be used where the maximum extinction effect is required

2. Application of barium sulfate in powder coatings

barium sulfate used as physical pigment of coatings can be divided into natural and synthetic ones. Natural products are weighed with spar powder, and synthetic products are called precipitated barium sulfate

in powder coatings, precipitated barium sulfate can enhance the leveling and light retention of powder coatings, and has good compatibility with all pigments. It can make the powder coating reach the ideal film thickness in the spraying process, and the powder rate is high

barite powder filler is mainly used for industrial primers and automotive intermediate coatings requiring high film strength, high filling force and high chemical inertia, as well as topcoats requiring high gloss. This increases the stretching space (which can be increased to more than 210 meters). In latex paint, due to the high refractive index of barite (1.637), micro barite powder can have the function of translucent white pigment, and can replace part of titanium dioxide in paint

3. Application of mica powder in powder coatings

mica powder is composed of complex silicates, and its particles are scaly. It has excellent heat resistance, acid and alkali resistance, and has an impact on the melting fluidity of powder coatings. It is generally used in temperature resistant insulation powder coatings, and can be used as the filler of texture powder

among many mica like minerals, sericite has similar chemical structure to kaolin, and has many characteristics of mica minerals and clay minerals. Its application in coatings can greatly improve the weatherability and water permeability of the film, enhance the adhesion and strength of the film, and improve the appearance of the film. At the same time, dye particles are easy to enter the lattice layer of sericite powder, so as to maintain the color for a long time. In addition, sericite powder also has the function of anti algae and anti mildew. Therefore, sericite powder is a multifunctional filler with excellent price performance ratio for coatings

4. Application of talc powder in powder coatings

talc powder, also known as aqueous magnesium silicate, is directly crushed from talc ore. The particles are needle shaped crystals, with a sense of greasiness, soft texture and low abrasiveness. They have good suspension, dispersion and certain thixotropy, which have a great impact on the melting fluidity of powder coatings. They are commonly used in textured powders. At present, it is applied in various primers, intermediate coatings, road marking paints, industrial coatings and internal and external architectural coatings

talc powder is cheap, but it has shortcomings, so its dosage is limited. First, the oil absorption is large. When low oil absorption is required, it must be matched with low oil absorption filler and barite powder; Secondly, the wear resistance is not high. When high wear resistance is required, other fillers should be added to make up for it; Moreover, talc powder containing other non-metallic minerals is not suitable for external coatings requiring high weather resistance because impurity minerals are easy to react with acids (such as acid rain); In addition, talc powder has extinction, so it is generally not used in high gloss coatings

5. Application of silica in powder coatings

porous powder quartz is a kind of silica system, and its safety has been recognized. It has been widely used in powder coatings, fire retardant coatings, waterproof coatings, anti-corrosion coatings, etc. Cheap porous powder quartz can reduce the cost of powder coating, and replace barium sulfate to reduce the content of soluble barium in products, so as to meet the requirements of environmental protection

in addition, fumed silica is often used as a loosening and anti caking additive for powder coatings. Fumed silica is a kind of multifunctional physical pigment, and it is also a coating rheological control agent with excellent performance. In liquid coatings, its rheological control functions include: thickening, thixotropy, anti sagging, covering edges; In the solid powder coating system, it can enhance the free flow of powder and prevent agglomeration and fluidization

6. Application of kaolin in powder coatings

kaolin can improve thixotropy and anti sedimentation. Calcined clay has no effect on rheological properties, but it can have the same matting effect, increase coverage and whiteness as untreated clay, which are similar to talc powder

kaolin generally has high water absorption, which is not suitable for improving the thixotropy of coatings and preparing hydrophobic coatings. The particle size of kaolin products is 0.2-1 μ M. Kaolin with large particle size has small water absorption; Kaolin with good extinction effect and small particle size (1 μ M below), which can be used for semi gloss paint and interior paint

kaolin can be divided into calcined kaolin and washed kaolin. Generally speaking, the oil absorption, impermeability, porosity, hardness and Baidu of calcined kaolin are higher than those of water washed kaolin

7. Application of hollow glass beads in powder coatings

hollow glass beads are a kind of small, hollow spherical powder, which have the advantages of light weight, large volume, low thermal conductivity, high compressive strength, insulation, corrosion resistance, non toxicity, good dispersion, fluidity, stability and so on

when applied in powder coatings, hollow glass beads can play the following roles:

(1) low heat insulation, insulation and water absorption. The interior of hollow glass beads is vacuum or thin gas, which has poor density and thermal conductivity with epoxy resin, so it has the characteristics of heat insulation and is an excellent filler for high temperature resistant powder coatings

(2) the physical and mechanical properties of powder coating can be improved. Hollow glass bead filler can increase the hardness and stiffness of powder coating. However, the impact resistance decreases, which is related to the surface treatment of hollow glass beads. If the correct coupling agent is selected for pretreatment, the impact on the impact resistance of the material can be reduced

(3) low oil absorption rate. The oil absorption rate of different types of hollow glass beads per 100g is between 7mg~50mg. This filling material with low oil absorption rate increases the filling amount in a disguised manner in the production process and reduces the comprehensive cost

8. Application of wollastonite in powder coatings

wollastonite is mainly composed of calcium silicate, with a density of 2.9g/cm3, a refractive index of 1.63, and an oil absorption of 30~50%. It has a needle like structure and good brightness

powder coating generally adopts natural wollastonite powder, which is processed from natural wollastonite. Wollastonite can be used as physical pigment and replace part of white pigment in paint, playing the role of covering and increment, and reducing the cost of paint. Because of its good conductivity, it is commonly used in epoxy insulation powder coatings. Wollastonite is white needle shaped knot