Paper pulp is a lignocellulosic fibrous material made from plant fiber by different processing method, such as chemically or mechanically separating ways. The raw plant fiber material can be classified into wood, fiber crops or waste paper. Paper pulp can be classified into mechanical wood-pulp, kraft wood pulp, sulphite wood pulp, waste paper pulp. The paper pulp is the raw material to make paper.
Different Types of Paper Pulp
Mechanical pulp, also known as grinding wood pulp, is a mechanical wood paper making method by grinding fiber raw materials into the wood pulp. It plays an important role in the paper industry, owning the advantages of low cost, simple production process, high paper ink absorption property, high opacity, soft and smooth paper, which is suiting for printing requirements. However, due to the cause of short fiber, high non-cellulose component capacity, the paper forming rate is low. Mechanical pulp usually refers to two kinds pulp, white mechanical pulp and brown mechanical pulp. White pulp is mainly used for the production of newspapers, it can also be added with other pulp to produce copy writing or printing paper. Brown mechanical pulp is used for the production of packaging paper and paperboard, especially industrial cardboard.
Kraft Wood Pulp
Kraft pulp refers to the pulp made by using of sodium hydroxide and sodium sulfide mixture as cooking reagent. In the cooking process, because of the gentle effect of cooking reagent, fiber is without strong erosion, so the finished paper is of strong strength, breaking resistance and good tear strength. It can be divided into two kinds, bleaching and unbleached kraft wood pulp. Unbleached kraft pulp can be used for making kraft paper, packet paper, kraft board paper, etc. Kraft pulp can manufacture advanced printing paper, drawing paper and writing paper, etc.
Sulphite Wood Pulp
Sulfite wood pulp is using the mixed liquid of sulfurous acid and acid sulfite as cooking reagent. The pulp fiber is long, soft, and of good toughness, high strength, easy to bleach. It can be divided into three types: bleaching, semi-bleaching and unbleached. Because of the unbleached pulp containing a small amount of lignin and colored impurities, so the color is yellow and the fiber is hard. Sulfite wood pulp is mainly used for multi medium printing paper, packaging paper, ranslucent paper and greaseproof paper. Semi bleached pulp contains a lot of pentosan, thus it is suiting for producing transparent tracing paper and parchment paper etc. Bleached pulp fiber is white, pure and soft texture, but due to bleaching treatment, fiber strength is lower than unbleached pulp. The pulp for making all kinds of advanced paper.
Recycled pulp is made from the waste paper or the cutting paper edge of the printing press, through the mechanical stirring and bleaching to deink and form the pulp. The strength and properties of waste paper pulp are determined by the type waste paper. The property of fiber is worse than the original fiber due to the erosion of the fiber and the mechanical damage again. It can be used to make printing paper, writing paper, cardboard and lower grade paper according to the quality of the paper pulp of raw waste paper.