OPTIMUM CTMP CMP PULPS FOR BOARD PRODUCTION - THE AUTHORS REVIEW BOTHSINGLE-PLY AND MULTI-PLY GRADES/

The effects of pulping conditions on the physical properties of single -ply and multiply boards made from oriented sheets were evaluated for wood furnishes from eastern and western Canada. Results are presented for single-ply paperboard sheets produced from mechanical (TMP) and ch emi-mechanical (CTMP and CMP) pulps of different freeness and sulphona te content. Iris shown that for the production of specialty boards the freeness is optimum in the 250 to 350-mL range while the sulphonate c ontent should be greater than 100 mmol/kg. In the second part of the s tudy, multi-layer boards were produced using different proportions of high-yield mechanical pulp in the middle ply with bleached kraft pulp in the top and bottom layers. It is shown that up to an optimum level of 55 to 60% of chemi-mechanical pulp, that stiffness, compressive str ength and delamination strength increase with the addition of mechanic al pulp. A brief analysis made of the CTMP/CMP pulp production costs i ndicate important savings in countries where the wood cost is high whi le the energy cost is low.