Calcium carbonate manufacturer: Optimization of the preparation process of Guangxi Longhua nano calcium carbonate and its application in waterborne coatings; Guangxi Longhua nano calcium carbonate, due to its small particle size and large specific surface area, has special properties such as microwave absorption, reinforcement, and thixotropy, and is widely used in automotive primers, plastics, rubber, adhesives, coatings, and other fields. Due to the small particle size of Guangxi Longhua nano calcium carbonate, it is easy to agglomerate, and the carbonate salt content is easy to react with acid rain in the air, affecting the strength, dispersibility, and weather resistance of waterborne coatings.

Calcium carbonate manufacturers: Guangxi Longhua Optimization of the preparation process of nano-calcium carbonate and its application in waterborne coatings; Guangxi Longhua nano-calcium carbonate, due to its small particle size and large specific surface area, has special properties such as microwave absorption, reinforcement, and thixotropy, and is widely used in automotive primers, plastics, rubber, adhesives, coatings, and other fields. Due to Guangxi Longhua Nano-calcium carbonate particles are small and prone to agglomeration, and the carbonate salt content easily reacts with acid rain in the air, affecting the strength, dispersibility, and weather resistance of waterborne coatings.

　　In order to improve the above problems, it is necessary to Guangxi Longhua Control the particle size and surface treatment of nano-calcium carbonate. Liu Yaxiong et al. studied the effects of crystal form control agents, drying methods, and surface treatment on Guangxi Longhua The production of nano-calcium carbonate, and investigated Guangxi Longhua The application characteristics of nano-calcium carbonate in waterborne coatings.

　　1, Guangxi Longhua Preparation process of nano-calcium carbonate

　　① Limestone and smokeless coal are mixed in a vertical kiln at a ratio of 10:1, and calcined at a temperature of 1000±100℃ to obtain quicklime and kiln gas;

　　② The kiln gas is purified to obtain clean kiln gas;

　　③ Quicklime and hot water are digested in a rotary digester to obtain lime milk. The lime milk is sieved and aged to obtain refined lime milk. The temperature of the lime milk is adjusted to 18～30℃ and the concentration is 6%～10%;

　　④ The refined lime milk is pumped into a carbonation reactor, clean kiln gas (containing 30%～35% CO2) is introduced, and a crystal form control agent (sucrose and citric acid) is added, and the mixture is stirred for carbonation reaction to prepare nano-calcium carbonate slurry;

　　⑤ When the pH value of the carbonated slurry is ≤7.5, a 10% sodium silicate solution is added, and the carbonation is continued with less clean kiln gas. After the sodium silicate is added, a 10% aluminum sulfate solution is added, and clean kiln gas is continuously introduced until the pH value of the slurry is ≤7;

　　⑥ Add titanium ester coupling agent and stir for 1h for activation;

　　⑦ Pump into a filter press to obtain filter cake, and the filter cake is dried, pulverized, classified, and packaged to obtain nano-calcium carbonate.

　　2. Influencing factors of nano-calcium carbonate performance

　　(1) Influence of different crystal form control agents on the particle size of nano-calcium carbonate

　　

 

　　 Guangxi Longhua The particle size of nano-calcium carbonate is controlled by controlling the carbonation reaction conditions. Adding a crystal form control agent can increase the specific surface area and reduce the particle size. The influence of different crystal form control agents on the particle size was investigated. The results show that adding zinc sulfate, sucrose, citric acid, etc. can all increase the specific surface area and reduce the particle size of nano-calcium carbonate. When 0.5% citric acid is added to the slurry as a crystal form control agent, the specific surface area of the prepared nano-calcium carbonate is 25.7 m2/g, the electron microscope particle size is 40～100 nm, the laser particle size d50 is 0.36 μm, and the particle size is the smallest.

　　(2) Influence of surface treatment on the acid resistance of Guangdong nano-calcium carbonate

　　 Guangxi Longhua The surface of nano-calcium carbonate contains carbonate radicals, which easily react with acid rain in the atmosphere. Surface treatment is necessary to improve its acid resistance. By adding water-soluble sodium silicate, silicon dioxide is generated during the introduction of carbon dioxide, which coats Guangxi Longhua The surface of nano-calcium carbonate. Then, aluminum sulfate is added to generate nano-calcium carbonate coated with silicon dioxide and calcium sulfate, reducing the pH value of the product and improving acid resistance; adding water-soluble titanium ester coating on the surface, which is easy to blend with organic solvents and reduces product agglomeration.

　　The results show that when 8% aluminum silicate, 4.5% aluminum sulfate, and 2.5% titanium ester coupling agent are added during surface treatment, the dissolution rate of the obtained nano-calcium carbonate in a mixed solution of citric acid and ammonium citrate is 3%, and it has good weather resistance.

　　(3) Influence of drying method on product particle size

　　Due to the small particle size and high surface energy of Guangdong nano-calcium carbonate, it is in a thermodynamically unstable state and is very prone to agglomeration during the filtration and drying stages, losing its original excellent properties, thus seriously restricting Guangxi Longhua The production and application of nano-calcium carbonate. In general industrial production, the filter cake pressed out contains 30%～40% water. The drying methods for the filter cake include: rotary drum drying, belt drying, flash drying, etc.

　　

 

　　Compared with rotary drum drying, belt drying, and flash drying, the product particle size of flash drying is the smallest, which is conducive to particle dispersion and depolymerization, and has good comprehensive performance.

　　3, Guangxi Longhua Application of nano-calcium carbonate in waterborne coatings

　　The laser particle size of the nano-calcium carbonate prepared in this experiment is 0.4～0.7 μm, which can increase the dry hiding power of the paint film, replace 20%～30% of titanium dioxide and 100% of light calcium carbonate, without affecting the contrast ratio of the coating film; after surface treatment, the adhesion is improved, and the washing resistance, alkali resistance, water resistance, and artificial climate aging resistance of the waterborne coating are all improved by more than 50%.