DESTABILIZATION OF COLLOIDAL WOOD PITCH BY CALCIUM IONS IN TMP SUSPENSIONS
Sticky deposits caused by wood pitch remain a severe problem in papermaking when using mechanical pulps,such as thermomechanical pulp (TMP).Formation of deposits on paper machines is dependent on aggregation of colloidal pitch. The stability of colloidal wood pitch droplets towards electrolyte-induced aggregation by CaCl2 was determined in suspensions of unbleached and peroxidebleached TMP.The colloidal stability was not significantly affected by addition of unbleached or peroxide-bleached TMP,in the absence of CaCl2.Addition of CaCl2 caused destabilization of colloidal pitch at both pH 5 and pH 8,and to a higher degree if TMP was present. The colloidal stability of pitch was much higher at pH 8 than at pH 5.Addition of CaCl2 at pH 8 resulted in formation of calcium-resinates,which can be very detrimental to the papermaking process.Calciumresinates do not have affinity to TMP or colloidal pitch droplets,and are therefore difficult to control in a process. Calcium ions were deemed the cause of destabilization and aggregation of colloidal pitch in these experiments.The concentration of free calcium should be kept as low as possible to prevent uncontrolled aggregation of pitch.
colloidal pitch deposits calcium resinate wood resin
Anders Strand Anna Sundberg Lari VaMsalo Bjarae Holmbom
Laboratory of Wood and Paper Chemistry, Process Chemistry Centre,Abo Akademi University,Turku,Finlan Laboratory of Wood and Paper Chemistry,Process Chemistry Centre,Abo Akademi University,Turku,Finland
国际会议
16th International Symposium on Wood,Fiber and Pulping Chemistry(第十六届木材、纤维及制浆化学国际会议)
天津
英文
1223-1228
2011-06-08（万方平台首次上网日期，不代表论文的发表时间）