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The stages of making paper from zero to one hundred

Paper is one of the most important human inventions, thanks to which tremendous progress was made in all aspects of our lives. The first paper was made by the Chinese around 105 AD, then paper made its way to Japan, the Arab world, Asia, Africa and Egypt, and finally to Europe. Of course, today’s papers, which are cheap and available, became popular thanks to European countries and their machines.

In this article about Top Paper  we examine the stages of paper production in large factories. In general, we can summarize the paper making process in the following 7 steps:

*Pulping to separate and clean the fibers.

*Refining after pulping processes.

*Thinning process to form a thin fiber mixture.

*Formation of fibers on thin screen.

*Pressure to increase the density of the material.

*Drying to remove material condensation.

*The final step is to provide a suitable surface for use.

Pulp and paper

Pulp and paper are made from cellulose fibers and other plant materials. Some synthetic materials may be added to the final product to create special properties. Paper is made from wood fibers, but rags, linen, cotton fibers, and bagasse (residues from sugarcane) are also used in some papers. Used papers are also recycled and after treatment and sometimes de-inking, they are often combined with virgin fibers and turned into paper again. Products such as cellulose acetate, rayon, cellulose esters that are made from cellulose will be used for packaging films.

The purpose of the pulping process is to remove lignin without losing the strength of the fibers, as a result, the fibers are separated and the impurities that cause discoloration and possible disintegration of the paper in the future are removed at this stage. Hemicellulose plays an important role in fiber-to-fiber bonding in papermaking. It is similar in composition and function to cellulose. Several extractive substances such as waxes, oleoresins are present in wood but they do not contribute to its strength properties. These materials are also removed during the pulping process.

Fiber extracted from any plant can be used for paper. However, fiber strength and quality and other factors complicate the pulping process. In general, softwoods (such as pine and spruce) produce long, strong fibers that contribute to the strength of paper and are used for boxes and packaging.

Hardwoods produce weaker paper because they contain shorter fibers. Softwoods are smoother, clearer and more suitable for printing. Softwoods and hardwoods are both used for papermaking and are sometimes mixed together to provide both strength and printability to the final product.

Paper production steps

1- Preparation of raw materials

The wood that is sent to the paper mill can have different shapes. This issue depends on the process of making the dough and the origin of its raw material. The wood received at the pulp mill can be of different shapes. It depends on the pulping process and the origin of the raw material. It may be received in the form of short logs of unbarked roundwood, or in the form of small pieces left over from the sawmill during the production of other surplus products.

If round wood is used, it is first peeled. Usually by rolling in large steel barrels to which water may also be applied. If the pulping process requires chemical changes, the peeled wooden pieces are crushed in the machine. Finally, the parts are checked for size, cleaned and temporarily stored for further processing.

2- Fiber separation

In this step of the paper production series, several technologies are applied to the raw materials to remove excess materials from its structure. The sheets of the previous step are stored in a large high-pressure vessel (digester). Appropriate chemicals are added to them in Kraft chemical pulping.

Then the sheets are subjected to steam at certain temperatures so that the fibers are separated and lignin and other extractive materials are partially dissolved.

In some fiber separation machines, wood sheets are continuously fed and the chemical liquid is constantly charged and the fiber separation process takes place. After this step, the cooked dough is drained in a container under pressure. The ingredients are pressed and after that, this cooked dough goes back to the chemical recycling cycle. The paper pulp is sieved, cleaned and most of the process water is removed from its structure to prepare paper.

 

3- Bleaching process                                                                                             Raw pulp contains significant amounts of lignin and other color changing compounds. To produce light colored or white papers which are preferred for many products, the pulp must be bleached. Excess lignin is separated from the cellulose using chlorine and oxidation, producing purer fibers. Additives in this step include chlorine dioxide, chlorine gas, sodium hypochlorite, hydrogen peroxide and oxygen.                                                              Sodium hydroxide is a strong alkali that is used to extract soluble lignin from the fiber surface. Bleaching agents and the order in which they are used depend on various factors such as the relative cost of the bleaching chemicals, the type and condition of the pulp.                                                                                                                         Mechanical pulp bleaching is different from chemical pulp bleaching. Mechanical pulp bleaching is designed to minimize lignin removal, which reduces fiber yield. Chemicals used to bleach mechanical pulps that selectively remove color impurities but leave lignin and cellulosic material intact include sodium bisulfite, sodium or zinc hydrosulfite, calcium or sodium hypochlorite, hydrogen or sodium peroxide. and sulfur dioxide-borole process (a type of sodium hydrosulfite method).                                                                                                                                         

 

4- Paper production                                                                                                         White or colored pulp may be refined before entering the papermaking machine. Water is added to the pulp liquid to obtain a thin mixture that contains less than 1% fiber. The diluted liquid is then cleaned in silicone cleaners and screened before entering the papermaking machine. The pulp passes through the machine and the fibers are evenly distributed across the paper sheet that is to be formed, and finally the paper we know comes out of the machine.                                                                                                                            In the end                                                                                                                        This article was a complete review of the stages of paper production. Papers can be produced in different ways depending on raw materials and types of devices. At Top Paper, we produce all kinds of packaging paper and cardboard from second-hand fibers instead of from trees. This method causes the environment to be less damaged and fewer trees to be cut down.                                                                                                                                                                      Producer and writer: Engineer Abdul Majid Gader 

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