A Comparative Study of the Different Types of Pulping

Paper has been one of the greatest inventions made by man. The role of paper is undeniable in the history of human civilization. It is said to have originated in China around 100 AD. The raw materials used then were rags, hemp and grasses. Wood was identified as a more abundant source much later and methods of pulping it were invented between 1844 to 1884. The method and the material have both gone through a sea change since then. The process has been entirely mechanized since then. Paper and Pulping industry has become huge and many paper and pulping companies take care of the planet’s huge consumption of paper, almost 400 million metric tons a year.

This March, there will be a tissue industry expo at Miami, USA, where many prominent tissue industry players are expected to attend. There will also be pulp fiber processing suppliers, and if you are concerned about the future of the paper industry, you should definitely attend.

At first the wood is debarked and cut. After that it is segregated into in to different batches and then, they are made into pulp. It is a process by which cellulose is extracted from wood or other raw material. Pulping can happen through a variation of processes, mechanical, chemical or a combination of both.

In mechanical pulping, revolving disks are used to grind paper chips into pulp. Water is added to reduce the damage made by heat and friction. Paper made from mechanical or groundwood pulping has many disadvantages, it has less durability, less strength and has a tendency to yellow with age due to the presence of lignin. Such paper also has a number of imperfections or ‘shives’. In spite of all the disadvantages this process is expensive and the highest yielding. Paper made from groundwood pulp is used in newspapers, telephone directories, paper towels, sanitary products, tissues etc.

Semimechanical pulping is a combination process. This process uses sodium sulfite and alkaline salt to soften lignin, after that a disk refiner is used to turn the chips into pulp. This process produces stiff paper used for containers, corrugated boards etc.

Chemical pulp, on the other hand, is almost utterly devoid of lignin and produces ideal paper for printing and writing. There are many chemical pulping methods depending on the chemical that is used. The newest and the most popular among of this form of pulping is Kraft pulping. ‘Kraft’ is the German word for strength. This method has many advantages; it can handle diverse types of food, lowers processing cost and produces strong paper of high brightness.
Every pulping method has its own merits and demerits and all of them have separate markets to cater to.