Coating agent containing nano-SiO2 and a preparation method thereof

A coating agent containing nano-SiO2, comprising raw materials in parts by weight as follows:

• Film-forming agent
• 50-60%
• Plasticizing agent
• 5-10%
• Dispersing agent
• 2-6%
• Coloring agent
• 10-30%
• Antisticking agent
• 15-20%
• Nano-SiO2
• 23-5%;
• wherein the film-forming agent is a mixture of hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol, and pregelatinized starch in a mass ratio of 1:1:2, or the film-forming agent is a mixture of pregelatinized starch, polyvinyl alcohol, and polyacrylic resin in a mass ratio of 2:1:1;
• wherein the plasticizing agent is one of polyethylene glycol-400 (PEG-400), triethyl citrate, triacetin, or a mixture thereof;
• wherein the dispersing agent is polyethoxylated sorbitan ester (Tween) or sorbitan ester (Span) or a mixture thereof;
• wherein the coloring agent is one of pigment, titanium white powder, iron oxide or a mixture thereof;
• wherein the antisticking agent is a pharmaceutically acceptable talcum powder;
• and
• wherein the nano-SiO2 is composed of two different nano-SiO2 with different particle sizes, the mass percentage of the first SiO2 with a particle size of 60-80 nm is 2-4%, and the mass percentage of the second SiO2 with a particle size of 20-30 nm is 1-2%.