Amelioration of Physical Properties and Printability of Paper Coated with N-methylated Chitosan

Meiyan Wu,Zhu Long,Bin Li,Rui Xu,Chao Liu

doi:10.1038/s41598-020-66827-8

Abstract

In offset printing process, poor mechanical properties and printability of paper substrate usually result in printing problems, low quality of print and waste of paper materials. Therefore, many researches focus on the quality improvement of paper substrates using suitable additives. In this work, N-methylated chitosan, including N, N-dimethyl chitosan (DMC) and N, N, N-trimethyl chitosan (TMC), were prepared and employed as coating agents to ameliorate the mechanical properties and printability of paper sheets. Analysis results showed that the mechanical strength of coated papers with DMC and TMC were largely improved, because the fibers with negative charges were prone to form electrostatic bonding with the positively charged N-methylated chitosan, thus enhancing paper strength. Particularly, compared with chitosan and DMC, the TMC-coated paper exhibited better mechanical properties, printability and surface properties due to the high cationic charge density of TMC. Therefore, surface coating with TMC is of great benefit to decrease the printing problem of paper sheets and enhance the operation speed in offset printing. This work provides a valuable reference for the amelioration of the printability and physical properties of high-quality paper products for many promising applications.

Highlights

In offset printing process, poor mechanical properties and printability of paper substrate usually result in printing problems, low quality of print and waste of paper materials
The permeation degree of trimethyl chitosan (TMC)-coated paper is even lower than that of dimethyl chitosan (DMC)-coated paper. These results indicate that TMC-coated paper has a suitable liquid absorbency, and the printing problem of telegraphing is less likely to happen in the event of TMC as a coating agent
The chemical structure of DMC and TMC was determined by FTIR and 1H NMR, and the degree of substitution of DMC and the degree of quaternization of TMC were calculated to be 91.0% and 5.6%, respectively

Summary

Introduction

Poor mechanical properties and printability of paper substrate usually result in printing problems, low quality of print and waste of paper materials. N-methylated chitosan, including N, N-dimethyl chitosan (DMC) and N, N, N-trimethyl chitosan (TMC), were prepared and employed as coating agents to ameliorate the mechanical properties and printability of paper sheets. The mechanical strength and printability of paper still need to be improved to reduce the printing problem in offset, such as paper breaking, picking telegraphing, and poor color reduction[2] To overcome these issues, one effective method is to coat polymer onto paper sheet. Dimethyl sulfate can be used to directly produce TMC from chitosan in an alkaline solution without the assisting of ionic liquid, and the required temperature for the reaction is relatively lower (room temperature to 70 °C)[18] This low-priced one step approach using dimethyl sulfate as a N-methylation agent was employed to prepare TMC in this work. The results will be of great importance for the amelioration of printing efficiency and end paper quality, for the high-quality packaging and decoration applications

Methods

Results

Conclusion