In 2020, the total output of coatings in my country is nearly 25 million tons, and VOC emissions are as high as 5 to 6 million tons, causing serious waste of resources. At the same time, VOC emissions are also an important source of PM2.5, and the control of VOCs is crucial to the prevention and control of air pollution.
Up to now, most of the provinces and municipalities directly under the central government have successively issued local regulations on the collection of pollutant discharge fees for volatile organic compounds, guiding the development, production and application of the coatings industry to develop environmentally friendly coatings.
Basic concepts of water-based paint
Definition: Water-based paint is a paint with water as the dispersion medium.
The basic composition is: water-based resin + water + additives + pigments and fillers; water-based paint replaces most of the organic solvents with water.
According to the different composition of water-based resin, water-based paint is divided into: acrawax c powder, water-based acrylic resin paint, water-based polyurethane paint and water-based epoxy resin paint, etc.;
According to the film-forming mechanism, it can be divided into: water-based paint is divided into thermoplastic water-based paint and thermosetting water-based paint;
Different water-based paints can be divided into: one-component water-based paint and two-component water-based paint;
From the construction level, it can be divided into: sealing primer, putty, primer, middle coating and topcoat;
Different water-based paints can be divided into: architectural coatings, water-based wood paints and water-based metallic paints.
According to the different levels of protection, water-based metallic paints are divided into: light anti-corrosion water-based metallic paint, medium anti-corrosion water-based metallic paint and heavy-duty anti-corrosion water-based metallic paint.
The basic composition of water-based paint is: water-based resin + water + additives + pigments and fillers
The basic composition of oil-based paint is: solvent-based resin + organic solvent + additives + pigments and fillers
Classification of water-based paint resins
Water-based resin is the key component of water-based metallic paint, which determines its cost and performance. According to different structures, it can be divided into:
(1) Water-based acrylic resins (including water-soluble, water-dispersed (colloid) and water-emulsion types).
(2) Water-based polyurethane (polyester type and polyether type; aromatic type and aliphatic type; anionic, cationic and non-ionic;)
(3) Water-based polyester resin, water-based alkyd resin;
(4) Water-based epoxy resin and curing agent;
(5) UV curable water-based resin;
(6) Water-based hybrid resin.
With the continuous advancement of science and technology, traditional oil-based resins are gradually being water-based, and new water-based resins will continue to emerge.
The method of water-based resin
(1) Emulsion polymerization method: Emulsion polymerization is the polymerization of monomers initiated by water-based initiators by dispersing the monomers in water to form emulsions with the help of emulsifiers and mechanical stirring. The emulsion polymerization method is the classic method for the synthesis of water-based acrylic resins.
(2) External emulsification method: that is, by adding an emulsifier, the oil-in-water polymer emulsion is generated by strong shear phase inversion. This method is only used for a few water-based oleoresins. Such as the preparation of water-based epoxy resin emulsion.
(3) Self-emulsifying method: Through chemical modification of the resin structure, a non-ionic or ionic water-based unit is introduced to realize its water dispersibility and obtain a water-dispersible resin. Self-emulsifying method is a kind of modification of resin at the molecular level. The obtained water dispersion has small particle size, narrow distribution, good stability and high technical content. It is the mainstream method of resin water-based.
Anionic acrylic resin is usually carboxylate type: containing -COO-; cationic type is quaternary amine salt type: containing -N+R3.
There are two types of anionic water-based polyurethanes, carboxylate and sulfonate, containing -COO- and -SO3- respectively. Cationic type is also quaternary ammonium salt type: containing -N+R3.
Non-ionic water-based units usually use polyethylene glycol blocks: -(OCH2CH2)n-.
Overview of Waterborne Acrylic Resins
(1) Definition of water-based acrylic resin: The resin system synthesized with water as solvent or dispersion medium and acrylate, methacrylate, vinyl monomer and water-based monomer as the main raw materials is called water-based acrylic resin.
(2) Classification of water-based acrylic resins: a According to the composition: all-acrylic water-based resin, styrene-acrylic water-based resin, silicone-acrylic water-based resin, vinegar-acrylic water-based resin, fluoroacrylic water-based resin, tertiary acrylic (tertiary carbonate-acrylate) water-based resin Wait.
b According to film-forming properties: thermoplastic acrylic resin and thermosetting acrylic resin.
The film formation of thermoplastic acrylic resin mainly relies on the volatilization of the dispersion medium (water) to make macromolecules or macromolecular particles aggregate and fuse to form a film, and no chemical reaction occurs during the film formation process.
Thermosetting acrylic resins are also called reactive cross-linking resins. The film-forming process is accompanied by the cross-linking reaction of several reactive groups of components, so the coating film has a network structure, so its solvent resistance and chemical resistance Good, suitable for the preparation of anti-corrosion coatings.
(3) Synthetic monomer of acrylic resin
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