Investigation of the fiber composition effect upon sack paper properties

Abstract

The article presents data on production volumes of sack paper, which is produced by the world's leading companies. The main raw material for the manufacture of this product is unbleached softwood sulphate pulp having a high cost. In the present research work the fiber composition effect upon sack paper properties was investigated. This makes it possible to determine the optimal mass ratio of unbleached kraft primary fibers (kraft pulp) and seco ndary fibers (waste paper) for the manufacture of sack paper. Doptimal continuous design (Kono, 1962) for the estimating second order polynomial full models was used as the experiment design for the optimization of the pulp fiber composition. Considering the restrictions on the quality parameters speci fied in GOST 2228–81 “Sack paper. Specifications” the analysis of the obtained experimental data using the search function in Mi crosoft Excel 2007 gave the following results on the sack paper fiber composition: kraft pulp content ( X1) – 43.30% of a. d. s.; polyacrylonitrile fibers content ( X2) – 0.15% of a. d. s.; waste paper content – 56.55% of a. d. s. During the experiment it was found that an increase of polyacrylonitrile fibers content from 0.05 to 0.20% in the kraft pulp structure leads to the increase of sack paper tensile strength by 25–28% (breaking length increased from 5,700 to 7,300 m). But paper whiteness at the same time decreased by 9.7%. This made possible to reduce the content of expensive kraft pulp in the composition of sack paper by 27% (taking into account the 30,000 t/year production of sack pa per, saving of kraft pulp can reach 8,000 t/year).