Due to the characteristics of small odor, convenient construction, rapid drying, safety and environmental protection, latex paint has been developed rapidly. With the gradual deepening of latex paint technology research, domestic technology in the emulsion, additives, pigments and other aspects of the increasingly mature. However, the choice of filler is relatively small, at the same time, because the production technology of some small and medium-sized coating enterprises in China is relatively weak, the understanding of the use of filler technology is insufficient, according to the current situation of the use of filler in the production of latex paint, this paper on how to correctly and reasonably choose the filler for a brief analysis.
NO. 1 latex paint commonly used filler and its characteristics
There are many kinds of fillers that can be used in latex paint, such as heavy calcium carbonate, light calcium carbonate, talc, wollastonite powder, mica, precipitated barium sulfate, bentonite, ultrafine aluminum silicate, quartz powder, etc.
1.1 heavy calcium carbonate
Heavy calcium carbonate (referred to as heavy calcium), heavy calcium is also known as large white powder, double fly powder, calcite, etc., insoluble in water, soluble in acid, high density, easy to precipitate, low product cost, while the use of latex system can improve color retention, with a little dry hiding power, easy to frosting.
1.2 light calcium carbonate
Light calcium carbonate (referred to as light calcium), light calcium is limestone calcined at high temperature with lime milk, and then mixed with CO2 gas and precipitation drying. It is characterized by small density, fine particles, in latex paint can improve color retention, good suspension, with a little dry hiding power, its disadvantage is easy to frosting.
1.3 Talcum Powder
Talc powder is a kind of hydrous magnesium silicate salt of inorganic salt, the use of natural talc ore grinding system, talcum powder is a hexagonal diamond plate crystal flake structure, a smooth feeling, used in latex paint can improve the construction of the coating, leveling, the disadvantage is easy to powder.
1.4 precipitated barium sulfate
Precipitated barium sulfate is mainly used for high-gloss and silk grain paint. It has acid resistance and is called "acid-resistant" latex paint. Precipitated barium also has easy dispersion, easy fluidity and gloss retention. However, due to its large proportion, it is easy to settle in latex paint.
NO. 2 Selection of latex paint filler varieties and specifications
Reasonable choice of filler in latex paint varieties and specifications can greatly improve the quality of the coating, if the choice is not appropriate will bring unnecessary trouble.
2.1 according to the scope of application of coatings to choose filler varieties
Latex paint is divided into interior wall paint and exterior wall paint. Generally, fillers with good weather resistance and difficulty in pulverization are selected in exterior wall paint. Sericite, barium sulfate, wollastonite, calcined kaolin, etc. are recommended to be used, and heavy calcium and light calcium are generally not used. In interior wall paint, heavy calcium, light calcium, talcum powder, kaolin and other products with high whiteness are recommended, and ultrafine powder is also used.
2.2 according to the use of filler species selection fineness
Fillers such as heavy calcium, barium sulfate, talcum powder and calcined kaolin are used in coatings. On the one hand, they play the role of skeleton support. On the other hand, the filler has certain dry hiding power. Generally, it is recommended to use ultra-fine products (800-1250 mesh). As the filler has synergistic effect on the hiding power of titanium dioxide, when the powder particle size reaches the micronized level and is basically close to the particle size of titanium dioxide pigment used, the covering effect of titanium dioxide, the covering effect, at the same time, the strength and water resistance of the paint film are improved. The use of wollastonite and sericite is to improve the film strength, weather resistance, water resistance, etc. Generally, it is recommended to use products of about 800 mesh. If the film effect is considered, products of about 1250 mesh can be adopted, and products of more than 2000 mesh are generally not recommended.
2.3 choose different fillers according to CPVC concentration requirements
The critical pigment volume concentration (CPVC) refers to the pigment volume concentration when the binder just covers the surface of the pigment particles and fills the pigment particle accumulation space. The higher the fineness of the filler, the larger the specific surface area and the higher the oil absorption value, the smaller the CPVC. Usually the PVC of latex paint formula is generally not more than CPVC, otherwise it will affect the physical properties of the paint film, with the increasingly fierce competition in the latex paint market, in order to reduce costs and enhance competitive advantage, the development of high PVC latex paint has become an important research topic in the latex paint factory. Two latex paint formulations with exactly the same PVC value have different CPVC values due to different raw materials and proportions. Therefore, to make latex paint have high PVC value and its quality can meet national standards, the core is to make latex paint have high CPVC, thus minimizing the gap between PVC and CPVC. In the design of coating formulations, high-performance latex paint adopts ultra-fine fillers, such as talc powder; low-grade latex paint selects fillers with relatively coarse particle size and low oil absorption value, such as baricalcium and barite.