Five Terms To Understand Beating Process of Filter Paper
To get high quality filter paper, the manufacturing process is strictly controlled by filter paper manufacturers. Do you know the process? Even the same paper material produces different types of paper, the operating procedures are also different. Hawach will introduce five terms for the beating to help you understand filter paper better. The filter paper beating itself is a meticulous and complicated production process, and it varies with the type of beating equipment and the beating operating procedures.
Brief terms of filter paper beating
(1) Beating degree
The beating degree only indicates the drainage performance of the pulp. Dilute 2g of absolutely dry pulp to 1000 ml, and pass through an 80-mesh net at 20°C. The amount of water discharged from the side tube of the shore beater is the result of the measurement.
The degree of beating is an indicator of the properties of the paper material. According to the degree of the beating of the paper material, it is possible to grasp the water filtration rate of the paper material on the copper wire of the paper machine in the future, and it is also possible to generalize and predict the mechanical strength, tightness, and finishing of the future paper. Therefore, mastering the beating degree of paper material is an important technical control method in production.
The beating degree alone does not fully represent the properties of the paper material. For example, we can use highly cut fibers (free beating) to achieve 45-SR. In addition, it is also possible to achieve the same 45-SR beating degree by using a highly fine fiber (sticky beating), but not a short cut.
Although the final beating degree is the same in the two cases, the properties of the paper material are quite different. Therefore, it is disadvantageous to rely solely on the beating degree as a control indicator in production technology in production, and it must be considered in conjunction with other indicators, such as the average fiber length, to make a reasonable beating.
(2) Freeness and beating degree
Canadian standard freeness (c. s. f): There are various methods for determining the drainage performance of pulp, among which freeness and beating degree are widely used. North American countries and Japan mostly use Canadian standard freeness, while Europe and China are accustomed to applying Shore freeness. The difference between freeness and beating degree is only the difference in the measurement method.
The greater the beating degree, the smaller the freeness of the paper material, and vice versa. Generally speaking, the greater the freeness of the paper, the faster the filtration rate. The Canadian standard freeness measuring instrument is similar to the Shore Beater, but the absolute dry fiber sampling amount is 3 grams during the measurement, and the freeness and beating degree can be converted into each other.
(3) Water retention value
Under standard conditions, use a high-speed centrifuge to throw out the free water in the paper material, and quantitatively determine the amount of water retained in the paper material, then the water retention value of the paper material and the resulting fiber plasticity can be obtained. This method uses centrifugal separation to store only swelling water between the fibers, but only a small amount of water on the surface of the fiber and water between the fibers. Therefore, the water retention index can indicate the degree of swelling of the fiber and reflect the degree of fibrillation, which explains the size of the binding force between the fibers.
As mentioned above, the degree of beating can only measure the drainage performance of the paper material, but the increase of the degree of beating does not mean that the strength of the paper will increase in a linear proportion. The increase in water retention value in the beating process is consistent with the increase in strength. The strength of paper mainly depends on the binding force between fibers and fiber length, so measuring the water retention value and then measuring the average fiber length can well illustrate the strength of the paper.
At present, it is generally believed that the measurement of these two indicators can explain the problem more than simply using the beating degree indicator. However, because the equipment is more expensive and the measurement procedure is more troublesome, making it is not widely used.
(4) Wet weight
Wet weight is a term commonly used in the control of the beating process, which indirectly shows the average length of the fiber. The measurement of wet weight usually adopts the frame method, which uses a special frame to make the diluted paper flow through the frame while measuring the beating degree. The weight of the fiber hanging on the frame is the wet weight. The longer the average fiber length in the paper, the heavier the fiber hanging on the frame, that is, the greater the wet weight.
(5) Hydration degree
Some factories also use hydration degree as an indicator. First of all, in the paper industry, the term “fiber hydration” is not strict enough, because it is easy to misunderstand that fiber and water have a chemical effect. In fact, water forms a water bridge with the hydroxyl groups on the fiber, and dehydration forms hydrogen during drying. The bond is not a chemical action.
The degree of hydration is a way of expressing the total amount of bound water absorbed by the fiber during the beating process. One of the methods for determining the degree of hydration is the boiling method, that is, heating and boiling the paper stock for 1 hour, using the heating method to remove the bound water of the fiber, and then measuring the beating degree according to the ordinary method; The difference between the beating degrees measured for the unheated paper stock and the heated and boiled paper stock represents the hydration degree of the paper fiber.
The other is the alcohol method, that is, the paper stock is placed in alcohol, the combined water of the fiber is replaced by the alcohol, and then the beating degree is measured by a common method. The difference between the paper stock in water and in alcohol indicates the degree of hydration of the paper stock. The above two methods for determining the degree of fiber hydration have some shortcomings, which are easy to cause errors.