coating additives
coating additives, also known as paint accessories, are auxiliary materials for preparing coatings, which can improve the performance of coatings and promote the formation of coating films. there are many types, including drying agents, toughening agents, emulsifiers, thickeners, pigment dispersants, defoamers, leveling agents, anti-crusting agents, matting agents, light stabilizers, mildew inhibitors, antistatic agents (see plastic additives), etc., among which the large amount is drying agent and toughening agent. at present, the research on coating additives focuses on additives for water latex paints.
chinese name: paint additives
foreign name: paintadditives
also known as: paint accessories
used for: additives for water latex paints
directory
1 introduction
2 types
3. details
driers
toughener
thickener
pigment dispersants
brief introduction
coating additives are ingredients that are added to a coating formulation in small amounts to control or enhance the performance of a coating. there are about 40 types of coating additives with different functions (emulsifiers, dispersants, defoamers, thickeners, anti-shrinkage agents, drying accelerators, biocides, etc.), as well as additives with different chemical compositions. usually the formulation of the coating will contain a variety of additives, and the total amount of additives used in general accounts for less than 5% of the total formulation, but in some cases it may be as high as more than 10%. due to the relatively high value of additives, the amount of additives used in the formulation is designed to be reduced as much as possible.
class
over the years, there are many types of coating additives, and they play different roles in all stages of coating production. the manufacturing stages include: initiators, dispersants, transesterification catalysts; the reaction process includes: defoamer, emulsifier, filtration aid, etc.; the storage stages include: anti-crust agent, anti-precipitation agent, thickener, thixotropic agent, anti-floating color flowering agent, anti-gelling agent, etc.; the construction stage includes: leveling agent, anti-shrinkage agent, anti-hanging agent, hammer pattern additive, flow control agent, plasticizer, defoamer, etc.; the film formation stage includes: coalescence auxiliaries, adhesion promoters (also called adhesion enhancers), photoinitiators, light stabilizers, drying, luminosity, slip enhancement, matting, curing, cross-linking, catalysis and other additives; the special functions include: flame retardant, biocidal, anti-algae, anti-static, conductive, corrosion inhibition, rust prevention and other additives.
generally speaking, according to its use, it includes adhesion enhancer, anti-adhesion agent, anti-shrinkage pore agent, anti-bloom agent, anti-floating agent, anti-foam agent, anti-foam agent, anti-gelling agent, viscosity stabilizer, antioxidant, anti-crust agent, anti-sagging agent, anti-sagging agent, anti-sedimentation agent, anti-static agent, conductive control agent, mildew inhibitor, preservative, coalescing aid, corrosion inhibitor, rust inhibitor, dispersant, wetting agent, drying agent, flame retardant, flow control agent, hammer pattern additive, flow drying agent, matting agent, light stabilizer, photosensitizer, optical brightener, plasticizer , slip enhancer, anti-scratch agent, thickener, thixotropic agent, anti-rat bite agent, other additives.
in addition to the main film-forming substances, pigment fillers, and solvents, a component added to the coating can significantly improve a specific performance of the coating or coating film. the amount used in the coating formulation is small. mainly a variety of inorganic and organic compounds, including polymers.
most of its names are named according to their functional characteristics. improving the coating production process include wetting agents, dispersants, emulsifiers, defoamers, etc. improving the storage performance and transportation of coatings include anti-settling agents, anti-crusting agents, preservatives, freeze-thaw stabilizers, etc. to improve the construction performance of coatings and prevent paint film pathologies, there are anti-sagging agents, leveling agents, floating color bloom prevention agents, defoamers, thickeners, etc. improving the coating performance and giving special properties include ultraviolet absorbers, light stabilizers, flame retardants, antistatic agents, anti-mildew agents, etc.
coating additives can be divided into oil-based coating additives and water-based coating additives. in line with the increasing global attention to environmental protection, the development of water-based coating additives has made a leap forward. there are more and more new environmentally friendly additives. the application is becoming more and more widespread. it is the mainstream direction of the future development of coating additives.
details
driers
a kind of substance that can speed up the drying of the coating film plays a role in promoting the absorption of oxygen and the polymerization of double bonds of the dry oil film. it can shorten the drying time of the oil film from days to hours, which is convenient to apply and can prevent the contamination and damage of the undried coating film.
oxides, salts and soaps of many metals have drying effects, but the practical value is lead oxide (red dan, yellow dan), manganese dioxide, lead acetate, lead nitrate, manganese sulfate, manganese chloride, manganese borate, manganese acetate, cobalt acetate, cobalt chloride, and naphthenic acid soap, linoleic acid soap and rosin acid soap of lead, cobalt, and manganese.
because the soap drying agent has good oil solubility, it has high drying effect. the modern coating industry mostly uses naphthenic acid soap as a drying agent. naphthenic acid soap is usually produced by metathesis method.
the amount of drying agent in oil-based coatings depends on the amount of drying oil or semi-drying oil. taking dry flax oil as an example, the amount of lead drying agent (in terms of lead) is 0.4~0.5% of the oil quality; 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. the combination of two or three metal soaps has a synergistic effect. in resin coatings, the amount of drying agent must be increased.
toughener
that is, plasticizers (see plastic additives). commonly used varieties in the coating industry include diethyl phthalate, dibutyl phthalate, dioctyl phthalate, tributyl phosphate, triphenyl phosphate, trixylene phosphate and some special varieties.
thickener
substances that can improve the viscosity of the coating and reduce its fluidity. the important purpose of using thickeners is to reduce the flow phenomenon during coating. the main types of thickeners used in coatings are as follows: (1) silica; (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) polymerized vegetable oils and esters composed of fatty acid dimers and polyols.
pigment dispersants
it is used to prevent pigments from settling or floating. thickeners such as bentonite and organic bentonite, metal soap, and hydrogenated castor oil can act as pigment dispersants. various surfactants, low-molecular-weight polyethylene oxide (polyethylene oxide), low-viscosity methylsilicone, lecithin and its derivatives are also commonly used.
leveling agent
substances that help create a smooth finish. substances that can reduce the surface tension of coatings generally have the effect of leveling agents. there are various series of leveling agents that have been used in industry, such as fluorinated surfactants, polyacrylates and polyvinyl butyral. generally, silicone leveling agents control shortwave leveling and reduce surface tension more obviously. acrylates control long-wave leveling and reduce the surface tension amplitude with a small amplitude.
anti-crust agent
substances that prevent surface crust of oil-based coatings, such as methyl ethyl ketone oxime and cyclohexanone oxime.