Basic concept of water-based paint and overview of water-based acrylic resin

In 2020, China’s total paint output will be nearly 25 million tons, and VOC emissions will reach five or six million tons, causing serious waste of resources

Up to now, most provinces and municipalities across the country have successively issued local regulations on levying pollutant discharge fees on volatile organic compounds, guiding the development, production and application of the coating industry to environmentally friendly coatings to develop online coatingol.

Basic concepts of water-based paint

Definition: Water-based paint is a paint that uses water as a dispersion medium

The basic composition is: water-based resin + water + additives + pigments and fillers; water-based paint replaces most of the organic solvents

According to the different composition of water-based resin, water-based paint is divided into: 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 different packaging forms;

From the construction level, it can be divided into: closed primer, putty, primer, middle coat and top coat;

From the application of different water-based paints, it can be divided into: architectural coatings, water-based wood paints and water-based metal paints

According to different protection levels, water-based metal paints are divided into: light anti-corrosion water-based metal paint, medium anti-corrosion water-based metal paint and heavy anti-corrosion water-based metal 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.

(1) Water-based acrylic resin (including three types: water-soluble type, water dispersion (colloid) type and water emulsion type)

(2) Waterborne polyurethane (polyester type and polyether type; aromatic type and aliphatic type; anionic, cationic, 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

Method of water-based resin

(1) Emulsion polymerization method: Emulsion polymerization is the polymerization of oily monomers by means of emulsifiers and mechanical stirring to disperse the monomers in water to form an emulsion, which is initiated by an aqueous initiator
.
Emulsion polymerization is a classic method for the synthesis of waterborne acrylic resins
.

(2) External emulsification method: through the addition of an emulsifier, the oil-in-water polymer emulsion is transformed into an oil-in-water polymer emulsion through strong shear
.
This method is only used to water-based a few oil-based resins
.
Such as the preparation of water-based epoxy resin emulsion
.

(3) Self-emulsification method: through chemical modification of the resin structure, the introduction of non-ionic or ionic water-based units to achieve water dispersibility, to obtain water-dispersible resin
.
The self-emulsification method is a modification of the resin at the molecular level.
The obtained water dispersion has small particle size, narrow distribution, good stability, and high technical content.
It is currently the mainstream method of water-based resin
.

Anionic acrylic resin is usually carboxylate type: containing -COO-; cationic type is quaternary ammonium salt type: containing -N+R3
.

Anionic waterborne polyurethane has two types: carboxylate and sulfonate, containing —COO- and —SO3- respectively
.
The cationic type is also a quaternary ammonium salt type: containing -N+R3
.

The non-ionic water-based unit usually selects polyethylene glycol block: —(OCH2CH2)n—
.

Overview of waterborne acrylic resin

(1) Definition of water-based acrylic resin: A resin system synthesized with water as a solvent or dispersion medium and acrylic esters, methacrylates, vinyl monomers and water-based monomers as the main raw materials is called water-based acrylic resin
.

(2) Classification of water-based acrylic resin: 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, fluoro-propylene water-based resin, tertiary acrylate (tert-carbonate-acrylate) water-based resin and so on
.

b According to film-forming characteristics: 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 into a film, and no chemical reaction occurs during the film formation process
.

Thermosetting acrylic resin is also called reactive cross-linking resin.
The film-forming process is accompanied by the cross-linking reaction of the reactive groups of several components.
Therefore, 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

Monomers are often classified as follows according to their influence on the performance of the coating film to facilitate the application, to be continued
.