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WORLD PULPPAPER 79 CASE STUDIES These results enabled us to assess the coater runnability confirmed by the following trials and case studies. Case Study 1 A double coated woodfree paper 150gm finish quality was blade pre-coated at 70 solids with a standard recipe containing 50 of the total binder- employed classic starch plus 50 latex. In order to reduce costs the pre-coat formulation was optimised to 65 C Film coating starch plus 35 latex. Due to the aforementioned benefit in extending the working range similar coater runnability was observed whilst surface strength as represented by IGT and ISIT measurements was kept constant. An overall good print quality was confirmed during commercial print trials. Case Study 2 LWC offset 60gm finish quality in MSP application at machine speeds 1400mmin. and coat weights of 8g ...rheology is key to ensuring smooth runnability at the coating heads paper. The positive effects seen in the new products were revealed in coating colour formulations by measuring water retention high shear viscosity as well as intrinsic coating structure. In order to optimise a coating colour binder system rheology is key to ensuring smooth runnability at the coating heads. For example if a customer is utilising a binder composition of 53 latex combined with 47 classical coating starch B and wants to enhance binding power with a classical starch C perhaps with a view to replacing more latex with more of this starch he would be faced with much higher blade pressure due to higher high shear viscosity of the coating see Figure 1. In most of the cases the consequence would be dilution of the coating. ONE STEP FURTHER WITH C iFILM COATING STARCH Compared to the classical coating starch C the newly developed C iFilm coating starch has even higher binding power it also affects lower coating colour high shear viscosity than both classical coating starches B and C. With this excellent property C iFilm coating starch allows the binder system to be adapted towards more starch and less latex for example 46 latex combined with 54 C iFilm coating starch will maintain high-shear viscosity of the originally used coating composition containing the classical coating starch B. Not only is high-shear viscosity important as the rheology parameter for the coating application Visco- elasticity is also influencing the coater runnability. It is commonly known that starch produces more elasticity in a coating formulation than latex. However C iFilm coating starch is also beneficial in that respect. No increase in measurement of the elastic part was recorded for the coating composition employing 46 latex combined with 54 C iFilm coating starch when compared to the coating composition originally used containing the classical coating starch B. Thus rheology disturbances at the coaters in other words misting at the MSP or bleeding at the blade are less likely. Based upon these facts it can be concluded that the operating window as shown in Figure 2 can be extended by the utilisation of C iFilm coating starch. Therefore either coating solids can be increased whilst maintaining the starchlatex ratio or higher starch utilisation is possible to replace a synthetic binder at constant coating solids whilst ensuring the overall performance is kept high.