【Literature Interpretation】This bio-based dimer acid-modified water-based polyurethane can significantly improve the waterproof, oil-proof and mechanical properties of paper products

Key words: paper dimer acid water-based polyurethane water-resistant oil-resistant

Background introduction

Paper products are regarded as one of the most promising materials to replace traditional disposable plastic products due to their light weight, biodegradability, green environmental protection and good mechanical properties

Water-based polyurethane (WPU) is a high molecular polymer formed by the polymerization of polyisocyanate and polyol.

Cao Yunfeng's team from Jiangsu Key Laboratory of Pulp and Paper Science and Technology used flexible diethylene glycol and bio-based dimer acid as raw materials to synthesize dimer acid-based polyester polyol (DG), and prepared a series of dimer acid-based Waterborne polyurethanes (DWPUs) with good flexibility and high molecular weight

research content

1.

DG was synthesized by direct esterification of dimer acid (DA) and diethylene glycol at high temperature using dibutyltin dilaurate as a catalyst (Scheme 1)

2.

The synthesis of DWPUs adopts a two-step polymerization method

3.

The resulting DWPUs were poured into Teflon molds and left at room temperature for 24 hours
.
Subsequently, the residual moisture in the DWPUs was removed by heating at 50 °C for 8 hours
.
DWPUs film thickness is about 0.
5 ~ 0.
7 mm
.

4.
Preparation of DWPUs Coated Paper

DWPUs were used for surface sizing of the base paper with a basis weight of 63 g/m2, and the surface sizing experiment of the base paper used the coating machine coating method
.
The sizing papers were placed in a constant temperature oven at 50 °C for 5 min, and all papers were pretreated at 25 °C and 50% relative humidity (RH) before further testing
.

Results discussion

1.
Preparation and characterization of dimer acid-based polyester polyol (DG)

2.
Preparation and properties of DWPUs

3.
Preparation and properties of DWPUs coated paper

in conclusion

By introducing dimer acid-based polyester polyols, new dimer acid-based water-based polyurethanes (DWPUs) were prepared with good flexibility and high molecular weight, and were used for the first time in the preparation of water- and oil-resistant paper products
.
The mechanism of water and oil resistance of DWPUs coatings can be attributed to the following aspects: (1) the non-polar long-chain alkyl groups of DG endow DWPUs films with excellent hydrophobicity; (2) a continuous and uniform DWPU-derived film is formed on the paper surface, reducing the It improves the porosity of the paper and helps to enhance the water and oil resistance of the DWPU coated paper
.
When the DG content reached 7 wt%, the DWPU coated paper exhibited the highest water and oil resistance (the Cobb 60 value decreased by 88.
06%, and the oil resistance value increased by 8.
7 times)
.
But with the increase of DG content, the water and oil resistance decreased slightly, which may be due to the decrease of the uniformity of DWPU coating film by DG
.
The mechanical properties of the paper coated with DWPUs were increased by 26.
75%, 42.
31% and 27.
04%, respectively, compared with the tensile strength, folding strength and elongation at break of the uncoated DWPUs paper
.
The process can provide high-quality, multi-functional and environmentally friendly water- and oil-resistant coatings for paper products, which is of great significance to the application of paper packaging
.

References: LiD, Hu D, Tan J, et al.
Design and synthesis of dimer acid-based waterbornepolyurethane as water- and oil-resistant coating for paper substrates[J].
Materials & Design, 2021,211:110142.
LiD, Hu D, Tan J, et al.
Design and synthesis of dimer acid-based waterbornepolyurethane as water- and oil-resistant coating for paper substrates[J].
Materials & Design, 2021,211:110142.