paper_produktion_papier

Paper production

Julia Bรถrmann

Paper production Whereas the Chinese, almost 2000 years ago used bark, hemp, rags and rice gras as raw materials, wood is the primary raw material in use today. In terms of volume it is also the most widely avaible natural product on the earth.

In 1390 the first paper mill was opened. They began making paper by hand for the first time. In France there was manual paper production by craftsmen in 1799 .

For over one hundred years wood has been the most important raw material for chemical and groundwood pulp for paper production.

Paper production

Julia Bรถrmann

Groundwood pulp To process wood to groundwood pulp (mechanical pulp) for paper production, it must be mechanically treated by grinding. The bark is stripped from the wood trunk and during the subsequent grinding process is continually pressed against a revolving grindstone under pressure. While water is being sprayed on simultaneously, the individual fibres are ripped out of the wood. Then they are crushed, pressed, torn off, and sheared by the grindstone surface. They are further fibrillated and the result is mechanical groundwood pulp.

Paper production

Julia Bรถrmann

Chemical pulp Chemical pulp is the fiber material obtained from wood-chips and other vegetable raw materials like annuals including hemp, jute, esparto, straw, or cotton by chemical digestion. Chemical pulps differ from groundwood pulp mainly in the fiber characteristics. They have more fibers and firmer, more supple ones and it seems to be more white than the other paper.

Groundwood pulp and chemical pulp fibers are called primary fibers.

Paper production

Julia Bรถrmann

Waste paper An other way of producing paper is to recycle waste paper. These waste paper fibers are called secondary fibers. The fibers must be fibrillated and cleaned (deinking process).

In addition it must be noted that there is a limit to the reuse of waste paper. Fibers are unusable after being recycled 3-5 times. A continual supply of fresh wood or primary fibers is essential for the paper production.

Paper production

Julia Bรถrmann

Paper machine Production of paper and card mainly takes place in modern high-speed paper machines today. These machines work 24 hours per day and 7 days a week everytime!

A paper machine is sudivided into different sections: Headbox Wire section Press section Dryer section Calender Winding unit with longitudinal slitting

Julia Bรถrmann

Paper machine

Paper production

Paper production

Julia Bรถrmann

This process is referred to as drainage The process starts with the headbox. There is a mixture of pulp, additives, paper auxiliary agents and a lot of water. About 99% is water, and in a paper web there is only about 5% of water.

The pulp is routed through the headbox to the endless wire.The paper web is formed at this wire section. This happens by draining, that is by separating water and solids. As soon as the fiber suspension of water, fibers, fillers and additives has run uniformly from the headbox to the wire at a high speed, the water flows through the wire due to gravity.

The fibers rest on this wire and become felt in a web.

Every fiber is orientated in the longitudinal direction, parallel to the direction of flow.

At the end of the wire section, the bridging of the paper web, which is still wet, takes place over the couch press into the press-section. Here the mechanical draining and the compaction of the paper take place.

The following section is the dryer-section. Here are gently heated cylinders. It is important that this drying is very slow, because it has an effect on the strength of the paper. The dryer-section is a long way.

Paper production

Julia Bรถrmann

The calender is part of the end section of a papermachine. Here the paper web has to pass through 5 to 10 ground steel rollers arranged above one another. They have to reduce slight irritations. Now the web is "machine finished paper".

At last there is sometimes a cooling system and then the web will be wound in the winding unit and slit in the longitudinal direction. Now you have webs of 1-2 meters wide. They will be cut into sheets.

The machine finished paper is also called uncoated paper or writing paper.

It is the easiest type of paper.

The uncoated paper can be finished by coating.

Julia Bรถrmann

Paper finishing

Paper production

Julia Bรถrmann

Examples

Paper production

Julia Bรถrmann

Examples

Paper production

Paper production

Julia Bรถrmann

Paper finishing Then it will be coated paper. It happens in a coater for paper.

The paper gets one or serveral layers of white pigment coating.

It consists of: Pigments Binders Additives (optical additives) Depending on the printing process for which the type of paper is used and the printing quality to is produced, there are many different compositions formulae.