This water-based bio-based PUA emulsion can be applied to UV LED curing wood coatings to improve mechanical properties and curing speed

Keywords: UV LED curing epoxy soybean oil water-based PUA wood coating

Author's Guide

(1) In 1968, Bayer in the Federal Republic of Germany first sold light-curing wood coatings on the market.

Since then, light-curing coatings have begun to be applied and developed.
Light curing refers to the curing process of polymers or monomers induced by ultraviolet light.
With its high efficiency, wide adaptability, economy, energy saving, and environmental protection, it has attracted more and more people's attention.

(2) In the literature to be interpreted in this issue, researchers have introduced epoxidized soybean oil acrylate (AESO) and pentaerythritol triacrylate (PETA) into ultraviolet light-curable waterborne polyurethane acrylate (PUA), and realized that the coating can achieve 395 nm UV com" href="">Online coatingol.

com for fast curing com" href="">coatings under LED light source .

(3) However, it is worth noting that the epoxy soybean oil acrylate is a yellow liquid.
When the dosage is large, the light-curable resin may be darker in color.
At the same time, due to its unique long-chain non-polar fatty acid chain, the storage stability of water-based resins needs to be investigated.

The above is the author’s family statement, for reference only.
If you have any questions, you can leave a message under the official account.

Background introduction

Water-based UV-curing wood coatings combine the advantages of water-based coatings with UV curing technology.

In recent years, with its excellent construction and environmental protection, it has become a development trend and industrial hot spot in the coatings industry.
Waterborne polyurethane acrylate (PUA) contains carbon-carbon double bonds and urethane bonds, has good adhesion, flexibility, abrasion resistance and weather resistance, and is widely used in UV-curable water-based wood coatings.

Traditional waterborne polyurethane acrylate wood coatings are generally synthesized from petroleum-based products, which not only increases the exploitation of petroleum resources, but also causes environmental pollution problems.

Epoxidized soybean oil acrylate (AESO) is a polymer prepared by the ring-opening reaction of soybean oil and acrylic acid.

Compared with traditional light curing technology, UV LED curing technology has outstanding advantages such as low energy consumption, environmentally friendly preparation process, good durability, and high efficiency.

Therefore, UV LED curing technology has been widely used in coatings, inks, printing and other fields.

The UV LED coating system developed not only solves the problems caused by traditional UV mercury lamp curing, but also improves the mechanical properties, curing speed and hardness of wood coatings; it is of great significance to improve the curing efficiency of the coating, save energy, and reduce energy consumption.

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research content

1.

Synthesis of Epoxy Soybean Oil Acrylate (AESO)

25.

47 g epoxy soybean oil and 0.

Figure 1 Synthesis process of AESO

2.

Synthesis of polyurethane acrylate emulsion

Set the OH/NCO molar ratio to 0.
9, add 3.
50 g DMPA, 21.
65 g IPDI, 2.
22 g BDO, and 50 g methyl ethyl ketone to a round bottom flask equipped with a thermometer, a spherical condenser, and a mechanical stirrer, respectively.
The flask was placed in a constant temperature water bath at 80°C and reacted for 1.
5 h under a nitrogen atmosphere.
During the reaction, the stirring speed was maintained at 500-750 r/min.
After that, 17.
5 g of AESO and 15 g of butanone were added to the flask through the dropping funnel.
After 4 h, 2.
50 g PETA was added to the flask through the dropping funnel.
After 2 h, the NCO value of the system was measured.
When the content of free isocyanate groups was less than 0.
5%, the reaction was terminated.
The temperature was reduced to 30°C, 2.
64 g TEA was added, and the mixture was neutralized for 30 min.
The prepared prepolymer is placed in a laboratory multifunctional dispersing machine, and distilled water (30% solid content) is added dropwise for high-speed dispersion.
The stirring speed was maintained at 2000 r/min, and the emulsification was performed for 45 min.
Finally, the methyl ethyl ketone was removed by rotary evaporation to obtain an aqueous polyurethane acrylate (PUA) dispersion.
The experimental process and formula composition are shown in Figure 2 and Table 1, respectively.

Add 4% IRGACURE 819 to PUA.

Stir at room temperature for 30 minutes, set aside.

Figure 2 PUA resin synthesis process

Table 1 Preparation formula of PUA dispersion

3.
Coating preparation

：45mm×12mm×1mm。1d，50℃4 h，。，395 nmUV LED。10，。

：250 mm×96 mm×15 mm320。，，50℃10s。，UV LED（15000 mJ/cm2）5 s，5 cm，0.
8 m/min。。72-78，10，。3。

3 

1、

4 AESO

5  ESOAESO

6  PUAFTIR

2、

7  AESO

2 

3、

8  AESO

3  PUA

4、

9  AESO

5、AESO/PUA

10 FTIR

11

6、

4 

4 TETA- ppgge - e20 - pge (a,c)(b, d)SEM

，。，uv-ledPUA。，AESO。PUA，PUA。

When the AESO content is 45%, the emulsion is stable, the particle size is small, and the distribution is uniform; there is no precipitation or delamination in 6 months; the coating has good mechanical and thermal properties.
The water-based PUA resin prepared in the experiment can be quickly cured on the surface of wood in a short time under the irradiation of a 395 nm UV LED lamp, and has great application prospects in the field of wood coatings.

Reference materials: 

LiX, Wang D, Zhao L, et al.
UV LED curable epoxy soybean-oil-based waterborne PUAresin for wood coatings[J].
Progress in Organic Coatings, 2021,151:105942.