Furfural-based bio-based resins are expected to replace traditional petroleum-based acrylates and be used in coatings

Keywords: furfural; hydroxybutene lactone; alkoxybutene lactone; bio-based coating

background

Coatings are ubiquitous in daily life and are indispensable in the construction field.

At the same time, they are used in many fields from cans to automobiles to improve the performance and durability of products.

The industrial acrylate preparation route is generally: medium-chain to long-chain petroleum-based hydrocarbons are converted into olefins by cracking, further oxidized and derivatized into acrylates, and the acrylates are subsequently polymerized to produce various plastics, resins and coatings.

At present, the global annual output of acrylates exceeds 3.
5 million tons.

In response to these problems, researchers from Benard L.

Feringa (2016, Nobel Prize in Chemistry) and Akzo Nobel from the University of Groningen in the Netherlands proposed to use alkoxybutene lactone as a bio-based substitute for acrylate to produce high Performance coatings.

(1) Using bio-based furfural as raw material, hydroxybutene lactone was prepared by photooxidation reaction;

(2) Bio-based alcohol is added to hydroxybutene lactone, and 4 different alkoxybutene lactone monomers are obtained through chemical reaction;

(3) These monomers are transformed into polymers under the action of initiator and ultraviolet light.

The above-mentioned process can realize the regulation of the properties of the coating, so that it can be applied to different surfaces, such as glass or plastic.

Its performance is comparable to the current industrial coatings derived from petrochemical industry.

Figure 1 Preparation route of bio-based resin

(A) Comparison of synthetic routes of petroleum-based acrylic monomers and bio-based monomers; (B) Bio-based furfural prepares hydroxybutene lactone through photooxidation reaction, and finally obtains alkoxybutene lactone (the acrylate unit is shown as pink color).

research content

1.

Synthesis of B1 (hydroxybutene lactone)

Taking the rotary evaporation method as an example, the synthesis method is briefly introduced.

Add a certain amount of furfural, methylene blue and methanol to a 1000 mL round bottom flask.
The mixture was placed in a rotary evaporator filled with oxygen, and irradiated with an 8×80 W LED lamp for 20 minutes, and the light source was placed 5 cm away from the flask.
The solvent was removed by distillation under reduced pressure, the photosensitizer was removed by filtration, and the compound was recrystallized to produce an off-white crystalline solid product B1.

Figure 2 Preparation of hydroxybutene lactone (rotary evaporation method)

2.

Synthesis of B2 (alkoxybutene lactone)

Take B2 as an example to briefly introduce the synthesis method.

Dissolve B1 (100.

Figure 3 Preparation of alkoxybutene lactone

3.

Polymerization and copolymerization

Using B2 and VeoVa-10 as raw materials, the copolymerization method is briefly introduced.
Add B2 and VeoVa-10 to the reactor, propylene glycol methyl ether as solvent, and Trigonox 42S as free radical initiator.
After heating at 120°C under reflux for 2 hours, a slightly yellow oily copolymer BP2 (98% conversion) was obtained.

The experimental results show that only a small amount of copolymer is formed during the copolymerization of B2 and butyl acrylate or styrene, and this passivation reaction reflects the mismatch of monomer reactivity.
In sharp contrast, when B2 is copolymerized with less reactive vinyl ester and vinyl ether monomers, the conversion rate can be as high as 99% (2h) and 95% (50min).

Figure 4 Polymerization and copolymerization of alkoxybutene lactone

4.
Preparation and performance test of surface coating

Stir the alkoxybutene lactone (B2-B5), triethylene glycol divinyl ether (DVE) and the photoinitiator Omnirad 819 until the reaction is uniform.
Use BYK applicator to apply the mixture to the glass surface (thickness 100-150μm).
The glass surface is irradiated with a UV-A lamp at a distance of 10 cm for 5 minutes (total irradiance is 4.
5 mW/cm2).
Using B2, B3, B4, and B5 as matrix resins, four polymers of BP4, HP4, IP4 and MP4 were prepared respectively.

The coating data shown in Figure 6 shows that the performance of bio-based coatings is comparable to ordinary acrylic coatings.
As shown here, it is easy to obtain uniform and strong film coatings on glass and plastic materials.
The most important thing is that according to the different types of alkoxy monomers, the required product properties (hardness and polarity) are very It is easy to adjust to different surfaces for application.
The performance of these coatings, in terms of solvent resistance and hardness, is comparable to, or even better than, the light-curing transparent coatings currently used in the automotive field.

Figure 5 Preparation of alkoxybutene lactone coating

Figure 6 Bio-based coatings and their performance

in conclusion

In summary, based on resource-rich bio-based raw materials, common alcohols and molecular oxygen, using visible light photochemical reactions, a previously undiscovered bio-based coating preparation route is introduced.
This study shows that starting from biomass-derived furfural, through the application of photooxidation in a flow system, the final alkoxybutene lactone monomer can be used as a substitute for ordinary acrylates.
The formed coating has excellent solvent resistance and hardness, comparable to current industrial coatings, and has adjustable performance, suitable for different applications.

Reference materials: 

Hermens JGH, Freese T, van den Berg KJ, et al.
A coating from nature[J].
Science Advances, 2020,6(51).