Classification characteristics and formulation design of water-based wood coatings

Waterborne coatings, English for waterborne coatings or waterbased coatings, also known as water-based coatings.

The most important components of water-based wood paint are the emulsion and the type of resin that constitutes the emulsion.

• Water-based acrylic paint 

• Waterborne polyurethane coating 

• Water-based alkyd paint 

• Waterborne epoxy coating 

• Sol-gel coating 

• Water-based light-curing coating 

1 Water-based acrylic paint

Acrylic water-based wood paint is a variety that has been applied earlier and is still being used in large numbers.

Acrylic emulsion is formed by emulsion polymerization of vinyl monomers mainly composed of acrylate monomers.

Only acrylic monomers are polymerized to obtain pure acrylic emulsion, and the paint made is called pure acrylic water-based paint.

The paint film made of acrylic emulsion has good weather resistance, is not easy to yellow, has high hardness and good gloss.

2 Waterborne polyurethane coating

Polyurethane is a general term for a class of macromolecular compounds with a carbamate structure in the molecular structure.

According to the type of isocyanate used in the preparation of polyurethane, polyurethane emulsions and corresponding paints can be divided into two categories: aliphatic and aromatic.

Hydrophilic groups or hydrophilic segments must be introduced in the process of synthesizing waterborne polyurethane.

According to the particle size obtained by polymerization, there are two types of polyurethane emulsion and polyurethane dispersion (PUD).

Waterborne polyurethane has excellent flexibility after film formation.

3 Water-based alkyd paint

After alcoholysis, vegetable oil reacts with acid anhydride to form alkyd resin.

Alkyd resin has good permeability on wood and is especially suitable for making water-based colorants.
Another major advantage of water-based alkyd is the use of oxygen in the air to cross-link and cure, so the solvent resistance of the paint film is much better than other single-component water-based paints.
Acrylic-modified water-based alkyd is the addition of acrylic monomers in the molecule during alkyd synthesis, and the gloss retention of the modified alkyd resin is significantly improved.
Recently, in order to further improve the performance of water-based alkyd paint, an alkyd/acrylic hybrid technology has been developed to produce a core-shell system with alkyd polymer as the core and acrylic polymer as the shell.
The hydrophilic acrylic shell protects the alkyd core.
Will not be hydrolyzed.
After painting, the water in the paint volatilizes, the fine emulsion particles penetrate into the pores of the wood, and the linear polymer molecules are oxidized and cross-linked to form a film.

Aqueous urethane oil is an alkyd resin modified with diisocyanate.
The diisocyanate reacts with the hydroxyl group of the alkyd resin to form a polyurethane structure, which has certain polyurethane properties while retaining the oxidative cross-linking characteristics of the alkyd resin.
The one-component water-based paint made from this is easy to construct and has excellent performance.
One of the excellent varieties in water-based paint.

4 Sol/gel coating

Sol-Gel coatings are new types of coatings that have received special attention in recent years.
The progress of inorganic nano-powders has promoted the development of sol-gel coatings.

The main components of the sol-gel coating are organic resin and silane compound.
The silane is hydrolyzed to form a sol, which is then condensed into a gel on the solid surface.
The active groups in silane can easily react with inorganic materials such as organic resins or silica sol.
The silane itself can also be condensed into macromolecules with a network structure, and finally form a paint with high hardness, scratch resistance, solvent resistance, and water resistance.
membrane.
The solvent in the paint is mainly an organic solvent such as isopropanol, which contains a small part of water.
Strictly speaking, it is not a water-based paint in the true sense, but it is an environmentally friendly paint.
The newly emerging sol-gel coating for wood coatings is a very promising new species of wood coatings.

5 Water-based light-curing coating

Water-based light-curable coatings are a type of coating classified by curing method, and it is a very important type of coating.
Any polymer molecule can be made into a light-curable coating or a radiation-cured coating as long as the active group that can be decomposed by a photoinitiator is introduced, or a structure that can be excited by high-energy radiation to generate an active group.

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- pH

Water-based wood coatings may also need to adjust the pH value when necessary.
The pH value of most emulsions or water dispersions has been adjusted to 8-9 during the production, and there is no need to use pH regulators when making paint.
If there is a deviation in the pH value, 0.
05% to 0.
1% of pH regulator should be added during the paint making process, and the pH value of the paint solution should be adjusted to 7-9.
Many water-based wood paints are only stable under neutral to slightly alkaline conditions.
When the pH value is too high or too low, the paint solution may cause flocculation, precipitation, coarsening, deterioration of construction performance, etc.

Different systems have different requirements for the pH value.
Therefore, the pH value of water-based wood coatings is adjusted according to the system, and the matching with the preservatives in the formulation should be considered.
It should also be noted that when adding, it must be diluted with water in multiples to avoid causing particles in the system.