Application of Expanded Perlite in the Composition of Paper for Writing and Printing

The method of increasing the opacity and mechanical strength of writing and printing paper due to the search for effective ratios of cellulose fibrous semi-finished products, their development during grinding, and the use of mineral fillers are considered in the article. A study aims to choose paper pulp, conditions for grinding softwood, and leaf sulfate bleached cellulose was conducted. The influence of the composition of the paper mass on the parameters of opacity, strength, and whiteness of the paper was investigated. The effectiveness of using the composition of sulfate-bleached cellulose from coniferous wood with a grinding degree of 42–44°SR and sulfate-bleached cellulose from deciduous wood with a grinding degree of 24–26°SR in the ratio of 85–90 and 15–10 wt.%, respectively, has been proven, which can provide increased opacity with maximum mechanical strength and paper whiteness. As a mineral filler in paper composition, it is proposed to use expanded perlite, a highly dispersed filler with a highly developed porous structure and an open hydrophilic surface. It was established that using expanded perlite with a 2–3 μm particle mass fraction of 90–92% in the amount of 4–6% of the completely dry fiber may increase the opacity of the paper while maintaining the level of mechanical strength and whiteness. Perlite added to the fibrous paper mass as a filler increases the optical heterogeneity of the medium and promotes light scattering to a greater extent than light absorption.