Method for adding chemical auxiliary agent in pulp

The method of adding chemical additives to the pulp is very important to the effect of the additives.
(1) Add order. In addition to considering the characteristics of ions, they are generally added in the order of molecular weight, ie, low molecular weight is added first, followed by high molecular weight. There should be an interval of 3-5 minutes between each additive.
(2) The concentration of pulp. Slurry concentration is also important for uniform sizing and retention when additives are added. The slurry concentration is generally added at 3% to 5% with stirring. At this time, the retention rate of the auxiliary agent not only acts as a charge but also acts as a grind to each other, and is easily retained evenly. The effect is good. When transporting to the molding machine, the slurry concentration is again diluted to 1% to make the finished cloth uniform.
(3) Add a location. In order to prevent the shearing damage of the molecular chain of chemical additives, the addition position should generally be performed in a slurry pool.
Chemical additive process flow is shown in the figure below:
The relationship between the zeta potential of the slurry and the addition of chemical additives is well known. Grass fiber is a raw material that is currently used in the paper industry in China. This kind of grass bleached pulp contains more heterocells and fine fibers and is a special system that is not easy to condense. To improve the drainage performance of this system, there are currently two main approaches. One is to change the total charge of the material in the system so that the zeta (ζ) potential tends to zero; the other is to strengthen the polymer and the suspended particles. The formation of "bridges" between them and "bridges" should not be easily disrupted by the shear force of water. This requires that additives should have high molecular weights, chains, and net-like molecular structures.
The zeta (ζ) potential control theory believes that the fillers of the pulp are all negatively charged, and adding the ionic retention aid buckle can neutralize the charge to reduce the zeta (ζ) potential and reduce the repulsive force between the fiber and the filler. When the zeta (ζ) potential is close to zero (isopotential point), the colloidal particles agglomerate, causing the tiny fibers and fillers to deposit on the surface of the fiber, forming micro-flocculation, thereby increasing the retention of solid fines.
Electrophoretic fluidity is used to represent the surface charge and charge density of polymers such as fibers, fillers, etc., usually measured with a zeta potentiometer or colloidal potentiometric titration. The zeta (ζ) potential value is abbreviated as Zp and expressed in millivolts (mv). Pulp is negatively charged, and cationic additives (such as AKD) are added. The retention in the pulp increases with Zp and then reaches the maximum and then decreases again; the degree of sizing of the finished product (HST seconds) Basically synchronized with the Zp in the pulp. The best Zp value is roughly between -3-+5mv. Therefore, controlling the Zp value of the lottery is also an important factor in improving the sizing efficiency of the sizing agent.
There are eight issues above the AAAA, and I think that the people who produce paper mold products should understand it. Understand the mechanism of the pulp system, according to the product's choice of sizing agent formula, auxiliaries formula, the development of the beating process, will improve product quality and reduce product costs play an important role.