Describe the Beating Characteristics of Various Pulps

The pulping properties of various pulps are described as follows: (1) The beating properties of wood pulp The wood fibres are broadly divided into two groups: coniferous wood and broadleaf wood. In the same species, the growth rate of the plants themselves varies in different seasons. It is divided into early wood (spring wood) and late wood (autumn wood), according to which their respective beating characteristics are different. 1. For the pulp obtained from the same pulping method for softwood and hardwood, hardwood needs to reach a higher degree of beating than softwood to achieve similar physical strength. However, the fibers of hardwood pulp are short, typically 0.8-1.1 mm. It is necessary to increase the degree of beating, and try to avoid excessive cutting of fibers. Therefore, hardwood pulp should be beaten at a relatively low beating pressure and high beating concentration. Coniferous wood pulp fibers are longer and generally range from 2 to 3.5 mm. When producing cement sack paper, it is not advisable to cut fibers too much, but when it is used to produce a medium-thin paper such as type paper, oil seal paper, etc. In order to meet the paper formation requirements, it needs to be cut to 0.8-1.5 mm. Therefore, the beating process conditions can be determined according to the requirements of the paper type in the beating. 2. In the wood pulp, the proportion of early and late materials is different in the wood pulp. The beating with the same beating conditions results in different pulp quality. The fibers of the late material are long, and the cell wall is thick and hard. It is not easy to be destroyed. When the pulp is beaten, the fibers are easily cut off, and it is difficult to absorb and swell and fine fibrosis. Therefore, pulps containing large proportions of latewood, in medium beating, especially viscous beating, should be beaten with a lower specific pressure, higher concentration, or by successive reductions or successive reductions in tool pitch. The fiber of early wood is thin, and the fiber is soft. It is easy to separate into single fibers during beating, and it is easier to be beaten. (2) The characteristics of the beating of cotton or hemp are those for papermaking, hemp with rags, cotton linters, and various types of hemp. Some need to be degreasing, most of them are directly beating. In the cotton pulp fiber, the fine fibers of the cell wall form a 45-degree angle with the main axis of the fiber, and the content of α-cellulose is high, so that the fibers are not prone to undergoing run-up and longitudinal disintegration during beating. At the same time, because the cotton fiber is longer, it is usually around 20-25mm. Therefore, the cotton pulp used for papermaking should be beaten by free-form pulping to cut it to meet the requirements of papermaking. Otherwise, the fiber is too long. When formed on a paper machine, the fibers tend to flocculate and affect the formation of the paper. Therefore, when the pulp used for papermaking and paper filter papers is beaten, it is usually at the beginning of the pulping process that the light knife is used to disentangle the fibers of the rags, and then the fibers of the rags are initially separated and then severed with a heavy knife. When producing toilet paper, general culture paper or offset paper containing pulp, the rags are often disintegrated and cut in a pulper, and then further processed into pulp in a pulper or other pulping equipment. The flax pulp and cotton pulp have similar properties and fiber length, so the pulping can be performed according to the pulping method of the cotton pulp. (3) Beating characteristics of rice straw, wheat straw and other straw pulps Rice straw and wheat straw pulp are very difficult to be beaten despite their high hemicellulose content. Rice and wheat straw pulp fibers are short, generally about 1.14 to 1.17 millimeters. The content of heterocells is large, the outer wall of the secondary wall is thick, and it is tightly bonded to the middle layer of the secondary wall. Therefore, it is difficult to remove during the beating process. It is very difficult for the fiber to absorb moisture and thin fibers. If excessive fibrillation is required in beating, it will inevitably result in excessive cutting of the fiber, which not only affects the strength of the formed paper, but also makes it difficult to filter water during papermaking. Therefore, the use of rice, wheat straw pulp and other production of general culture paper, most of the higher beating concentration and lower beating than the pressure of the beating process. (4) Beating Characteristics of Waste Paper There are many types of waste paper, and the processing requirements vary depending on the type of recycled paper or board. It can be made into bleached pulp by deinking, and most of the waste papers in China are directly beaten to produce toilet paper, wrapping paper or cardboard. The beating of waste paper is different from that of other pulps. The main tasks of waste paper processing are disintegration, dust removal and moderate beating, and no cutting of fibers is required. After the waste paper is disintegrated, whether or not the basic dedusted material is beaten depends on the type of waste paper and the requirements of the paper or board produced.