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between this and the release capacity of Disprosol 17 ® once the paper is creped. In addition, there was little noticeable wear on the creping and cleaning blades as shown in Figure 7.
Figure7. Creping and cleaning blade wear as a function of time.
As shown in Figure 7, the wear of both blades was minimal and even along their axes (position 1 to 11). In addition, when the creping blade was removed, did not present residue. This shows that the product covers uniformly the surface of the yankee and does not leave residue on the blade that could interfere with creping [5]. On the other hand, the cleaning blade tends to have a slightly higher damage compared to the creping blade since it removes the coating-release residue in the yankee and its pressure against the cylinder is higher.
3.10. Quality Parameters of the Tissue Creping Paper Obtained
3.10.1. Caliber of the Tissue Creping Paper Obtained Caliber is one of the most important properties of tissue paper as it gives a ratio of the thickness of each sheet [38]. This parameter relates to the angle of the ‘pockets’ or ‘crepes’ per unit length [5]. Thus, the paper mill must maintain the caliber of the triple sheet tissue at a value lower than 12.0 mm / 100 folds otherwise the creping would be irregular and the produced paper would be rough [38]. Caliber also allows to evaluate the quality of the coating. If caliber remains high throughout the application the adhesiveness of the coating would not be optimal [15], but if it remains low and rises in a short period of time, it would indicate that the hardness of the coating wears very quickly the blade [5]. The addition of the Polycoat-Disprosol agent generated paper with a caliber of 9.4 mm / 100 folds. This indicates that the adhesiveness of the Polycoat 38 ® is of high quality and suggest that the wear of the blade was not representative and allowed to produce soft paper with optimal crepe [14]. 3.10.2. Tensile Strength and Stretch of the Creping Paper Obtained The measurement of the tensile strength of the paper does not allow to measure the e ffi ciencyof the coating-release directly, but it does allow to obtain the stretch force in the direction of the machine ( MDS ) [39]. With this value is possible to obtain the relative e ffi ciency of a coating by using Equation (3) of stretch per creping unit [5], where CE is the relative coating e ffi ciency and % C is the creping percentage, which in turn is obtained using Equation (4) [5].
CE = MDS / % C
(3)
% C = ( YS − RS / YS ) × 100% (4) where YS is the speed of the yankee and RS is the speed of the roll or winding cylinder of paper. When replacing these variables with the speed values given in Section 2.4 a result of 16% C is obtained. This
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