We talked enough about the types of paper, so that you formed a definite opinion on this topic. You know about paper for painting, printing, packaging. You can easily argue on topics of paper density, its texture, color, scope. You will not confuse paper for watercolors and pastels and never print a label on coated paper. Today we will talk about materials that paper consists of, and then we can proudly say that this topic is covered by us in sufficient volume.
Paper and cardboard are materials made primarily from specially processed plant fibers, linked together by forces of surface adhesion to the sheet form.
To one degree or another, every day we all face with paper and products of it. This, if we may say so, communication with paper begins in early childhood, when a child reaches for a bright book, for a white sheet to leave traces of first exercises with a pencil on it. Paper accompanies people throughout their life. It reminds of itself whenever they turn to documents – a passport, a diploma, a certificate, when we pick up a book, pull correspondence out the mailbox. Many of our actions are connected with paper. It is also needed for business writing, and for creative work, and for domestic needs.
But what do we know about paper? We can say that paper is a material for printing books, magazines and newspapers. Paper occupies an exceptional place in people's lives. Its discovery, like the invention of the wheel, is a miracle, one of the greatest gains of human mind. Appearing once, paper firmly established itself on Earth and, without knowing competitors, triumphantly goes through the centuries.
Paper is a simple, accessible material for writing, prepared of raw materials of plant origin. The birth of paper has made profound changes in human society. After receiving it, people began to actively participate in knowledge. This greatly contributed to the rapid development of book business.
Step by Step
The initial link in the technological chain of paper production is an open warehouse of wood raw material. Each paper enterprise has such warehouses. They are located in vast areas behind production buildings, often on the banks of water reservoirs, where ports or berths for receiving wood are arranged.
For the production of certain types of paper, raw materials of coniferous and hardwoods are used. Newspaper paper is produced only from spruce, as spruce has the largest number of fine and long fibers and the smallest content of resinous substances. Cellulose of hardwood can be mixed with coniferous cellulose. Short and hard fibers of deciduous wood and long and elastic ones of conifer form a mass from which a paper with good properties is obtained.
Strength of paper is characterized by a number of indicators: resistance to tearing, fracture, punching for each kind and grade of paper that have a certain value, and generally depends on strength of fibers, their length, bond strength between fibers and paper sheet structure.
A sheet of paper is torn at the weakest point during the test. This weak point in most cases is not fibers themselves, but connections between them. When a sheet is ruptured on both sides, at the point of rupture, it is observed that fibers are primarily pulled out from a sheet, which indicates a break in the connection between them. And only a part of fibers breaks in the transverse direction.
A very important aspect of creating paper is sizing. The purpose of sizing is to impart limited absorbent properties to paper or paperboard in relation to water, ink, printing ink and other liquids, and to improve many other physical and mechanical properties. With unlimited absorption (for non-adhesive paper) of, for example, ink, it will be absorbed into a sheet of paper, diverge and pass to its opposite side. A complete lack of absorbent properties will cause ink to drip from the surface of paper. The first and second phenomenon make paper unsuitable for writing and printing. Therefore, the sizing process is designed to provide for each specific type of paper and cardboard its strictly defined absorbency, which is estimated by the degree of sizing.
Then filling follows. Filling of paper is the introduction of mineral filler materials into its composition to improve its quality and economic performance. The introduction of fillers in paper composition help achieve the following objectives:
- The cost of paper production is reduced since the cost of filler is lower than the cost of fibers, some of which are replaced by filler;
- Whiteness of paper increases since almost all fillers have a higher degree of whiteness than fibers;
- Smoothness of the surface of paper increases substantially due to the filling of pore filler particles and irregularities between fibers on the rough surface of a sheet;
- Opacity of paper reduces, which makes it possible to write and print on both sides of a sheet;
- Uniformity of the lumen improves;
- Softness and plasticity increase – paper is less "noisy" when turning over;
- Bulk density, porosity and, consequently, absorbability of printing inks, etc., are reduced.
A common disadvantage of introducing fillers is a marked reduction in mechanical strength and degree of sizing of paper. In addition, with an increase in the content of fillers, filler particles, sizing agents are found to a greater degree. This effect dramatically degrades print quality.
In order to give to paper some pleasant aesthetic properties, many of its types are produced in color, for example: poster, cover, color, matchbox paper, envelope, tissue, packaging paper, etc.
There are paper dyeing and coloring. During the dyeing process, the necessary color is given to paper, and during coloring – a certain color shade, for which the corresponding dyes are introduced into the pulp before paper is made. Dyeing is a complex process, as paper mass, which is exposed to coloring, in most cases, consists of several differently characteristic fibrous, filling and sizing particles that has different susceptibility to the same dye, so it is very important to choose the correct dye to get high-quality paper.
We have already given a classification of paper and talked about its different types. It remains to add that all fibrous materials of various origin, known to date, can serve as a semi-finished product for the production of paper and paperboard. However, the majority of fibrous semi-finished products of paper-cardboard production are vegetable fibers:
- Wood fibers in the form of different wood pulp, cellulose and semi-cellulose;
- Fibers of recycled paper in the form of waste paper;
- Fibers of cane and straw in the form of cane and straw cellulose and semi-cellulose;
- Fibers of rags in the form of rag mass.
To give some special properties to paper and cardboard, animals (woolen), mineral (asbestos, basalt, glass) and synthetic (capron, polyvinyl, polyethylene, polyester, etc.) fibers were also used.
Now you are actually ready to take the exam on this topic. We hope that this information was useful to you. We wish you productive pastime and successful study.