Importance of Chemicals in the Paper Pulping Process



Paper has a crucial role to play in our daily lives and is used in almost any place you can think of.Paper has been used for many years now and is an eco-friendly product that is made from wood pulp.

Paper and pulp are made from plant materials and cellulosic fibres. Sometimes  synthetic materials also have to be used to impart special qualities to the finished product.

Paper can also be made from wood fibres, but other materials like rags, flax, and sugar cane residues are also used to make some paper.

Chemicals companies in India manufacture chemicals which are designed specifically to bolster the process of papermaking.

Let us look at the process in-depth:

1.Preparing Raw Material

Wood comes to the pulp mill in different forms. The form that wood comes in depends on the process of pulping as well as the origin of raw material. Wood could be received as short logs, with the bark still on it and as wood chips that may have been produced from a sawmill and debarked. If round wood is used to make paper, it is first debarked by tumbling large steel drums. The debarked logs are chipped using a chipper is the pulping process requires chemical digestion. Chips are then screened for size, cleaned, and temporarily stored for further processing.

2.Separation of Fibre

In this stage, different pulping technologies will have diverged. The wood chips are kept in a large pressure cooker called a digester. Chemicals used for pulping are added to the digester. 

The chips are then digested with steam at specific temperatures to separate the fibres and partially dissolve the lignin and other extractives. Some digesters operate continuously with a constant feed of chips (furnish), and liquor are charged intermittently and treat a batch at a time.

After the digestion process, the cooked pulp is discharged into a pressure vessel. Here the steam and volatile materials are tubed off. After that, this cooked pulp is returned to the chemical recovery cycle. 

In the stage, after refining pulp is screened, cleaned, and water is removed in anticipation of papermaking.

3. Bleaching

Raw pulp has a significant amount of lignin and other discoloration so it has to be bleached to produce light coloured or white papers that are widely used for products. The fibres are further delignified by solubilizing additional lignin from the cellulose through chlorination and oxidation. These include chlorine dioxide, chlorine gas, sodium hypochlorite, hydrogen peroxide, and oxygen.
Paper that has been used is recycled and after purifying and sometimes deinking, it is often blended with virgin fibres to be recreated into paper. Products such as cellulose acetate, rayon, cellulose esters that are made from cellulose will be used for packaging films, explosives.

Through the process of pulping process lignin is removed without impacting the fibre strength. This allows the fibres to get freed and removes impurities that can cause damage like discoloration and disintegration of paper.

Chemicals used for bleaching mechanical pulps which selectively destroy colouring impurities but leave the lignin and cellulose material intact.

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