Quantitative Determination of Alkyl Ketene Dimer (AKD) Retention in Paper Made on a Pilot Paper Machine

There have been some problems reported associated with the use of alkyl ketene dimer (AKD) in alkali papermaking. Excessive use of size emulsion, poor size performance when filler used, problems with back water contamination, poor retention, and formation of pitch deposits on machinery are some of the problems experienced during papermaking operations. In addition, paper containing AKD is reported to lose its resistance, over time against liquid penetration and tends to become slippery. Therefore, in this study, the retention and reaction mechanisms of AKD internal sizing agent in a paper matrix were investigated by capillary gas chromatography (GC) in an attempt to better understand paper sizing with AKD. Results are expressed as the mean value of at least three repetitive tests along with standard deviation (SD) and coefficient of variation (COV). A number of different paper samples were made on a pilot paper machine with different AKD addition levels. AKD levels in wet and machine dry paper were extracted and analysed in GC. Precipitated calcium carbonate (PCC) loading was observed to increase AKD retention. The amount of bound AKD in wet paper significantly increased as a result of drying. Nevertheless, in general the reacted AKD only constituted a very small portion of the total retained AKD. Paper sizing was found to be achieved by bound AKD. This means that an even lower additional level of AKD would be sufficient to ensure good paper sizing provided that it forms a chemical bond with furnish. This result is believed to be important in solving some problems associated with AKD sizing. Alkil Keten Dimer (AKD)'in Pilot Ka¤›t Makinas›nda Yap›lan Ka¤›tlardaki Tutunmas›n›n Kantitatif Olarak Belirlenmesi Ozet: Alkali ka¤›t yap›m›nda Alkil Keten Dimer (AKD) kullan›lmas› ile balant›l› olan bir tak›m problemler olduu bildirilmektedir. Afl›r› dozda emulsiyon kullan›m›, dolgu maddesi kullan›ld›¤›nda dufluk ic yap›flt›rma performans›, elek alt› suyu kontaminasyon problemleri, zay›f tutunma ve makinalarda yap›flkan benekcikler oluflumu gibi problemler ka¤›t yap›m› s›ras›nda karfl›lafl›lan problemlerden baz›lar›d›r. Ayr›ca AKD iceren ka¤›tlar›n zaman icerisinde s›v›lara olan direnclerini kaybettikleri ve kaygan bir yap›ya ulaflt›klar›da bildirilmektedir. Bu nedenle bu cal›flmada, alkil keten dimer (AKD)'in ka¤›t icerisindeki tutunma ve reaksiyon mekanizmas›, AKD ile ic yap›flt›rmay› daha iyi anlayabilmek icin kapilar gaz kromatografisi (GC) kullan›larak araflt›r›lm›flt›r. Sonuclar en az uc testin ortalamas› olarak, standart sapma (SD) ve varyasyon katsay›s› (COV) ile verilmifltir. Bir seri ka¤›t ornekleri, pilot ka¤›t makinas›nda farkl› AKD kat›l›mlar› ile uretilmifltir. Islak ve makina kurusu ka¤›tlar icerisinde bulunan AKD ekstrakte edilmifl ve GC'de incelenmifltir. Ka¤›t hamuruna cokeltilmifl kalsiyum karbonat (PCC) eklenmesi AKD tutunmas›n› art›rm›flt›r. Islak ka¤›tlar icerisindeki seluloz liflerine balanm›fl olan AKD miktar›nda ka¤›tlar›n kurutulmas› sonucu onemli bir art›fl gercekleflmifltir. Bununla birlikte genel olarak, bal› AKD miktar› ka¤›t icerisinde tutunmufl olan toplam AKD'nin ancak cok kucuk bir yuzdesini oluflturmaktad›r. ‹c yap›flt›rman›n balanm›fl AKD taraf›ndan saland›¤› bulunmufltur. Bu seluloz lifleri ile kimyasal bayapt›¤› surece cok daha az bir AKD kat›lmas›n›n iyi bir ic yap›flt›rma icin yeterli olaca¤›n› gostermektedir. Bu sonucun, yukar›da bahsedilmifl olan AKD ic yap›flt›rmas›nda karfl›lafl›lan baz› problemlerin cozumu ac›s›ndan onemli olduuna inan›lmaktad›r.