The drying time of oil film can be shortened from several days to several hours, which is convenient for construction and can prevent the pollution and damage of wet film.
Many metal oxides, salts and soaps have drying effects, but the ones with practical value are lead oxide (red lead and Huang Dan), manganese dioxide, lead acetate, lead, manganese sulfate, manganese chloride, manganese borate, manganese acetate, cobalt acetate, cobalt chloride, naphthenic acid soap, linolenic acid soap and rosin acid soap of lead, cobalt and manganese.
Soap desiccant has high drying efficiency because of its good oil solubility.
Naphthenic acid soap is a commonly used desiccant in modern coating industry.
Naphthenic acid soap is usually produced by double decomposition method.
The dosage of drier in oily coatings depends on the dosage of drying oil or semi-drying oil.
Taking dry linseed oil as an example, the dosage of lead drier (calculated by lead) is 0.4 ~ 0.5% of the oil mass; The drying ability of cobalt and manganese is stronger than that of lead, and the ratio of cobalt, manganese and lead is about 8: 1:40.
Two or three kinds of metal soaps have synergistic effect.
In resin coatings, the amount of desiccant must be increased.
Toughening agent is plasticizer (see plastic additive).
Commonly used varieties in coating industry include diethyl phthalate, dibutyl phthalate, dioctyl phthalate, tributyl phosphate, triphenyl phosphate, triester phosphate and some special varieties.
Thickener: a substance that can increase the viscosity of paint and reduce its fluidity.
The important purpose of using thickener is to reduce the flow phenomenon during finishing.
Thickeners used in coatings mainly include the following categories: ① white carbon black; (2) Bentonite and organic bentonite (bentonite treated with cationic organic matter); ③ Surface-treated activated calcium carbonate particles; ④ hydrogenated castor oil; 5 metal soaps, such as calcium stearate, aluminum stearate, zinc stearate, etc. ; ⑥ Ester of polymerized vegetable oil and fatty acid dimer with polyol.
Pigment dispersant: used to prevent pigment from settling or floating.
Thickeners such as bentonite, organobentonite, metal soap and hydrogenated castor oil can play the role of pigment dispersant.
Various surfactants, low molecular weight polyethylene oxide (polyoxyethylene), low viscosity methyl silicone oil, lecithin and its derivatives are also commonly used.
Leveling agent: A substance that helps to form a smooth surface.
Generally, substances that can reduce the surface tension of coatings have the function of leveling agent.
Leveling agent used in industry includes fluorine-containing surfactant, polyacrylate and polyvinyl butyral.
Generally, silicone leveling agent controls short-wave leveling, which obviously reduces the surface tension; Acrylate is used to control long-wave leveling and reduce surface tension to a small extent.
Anti-skinning agent: a substance that prevents the surface of oily coating from skinning in use, such as oxime and cyclohexanone oxime.