Paper Production
Paper is one of the most important wood products, and the method of paper production is made from paper pulp more than from the coniferous wood of Bergan because it has longer fibers than other trees. Of course, it can be said that plants with long fibers are also suitable for making paper. According to the online bio report, paper is a material that is made of linen, cotton or hemp pulp and is used for writing, and in scientific terms it is The density of cellulose fibers that are irregularly inserted into each other and as a result gives a compact material that is obtained in different dimensions and weights.
Since its invention, paper has been the most reliable means of transmitting human thought and has an important role in collecting and storing human information and knowledge, which is a result of his experiences and thoughts. Human thought is mixed with new tools and it is treated as an important phenomenon today.
The use of paper has been associated with its invention, which is said to have been pioneered by the Egyptians, and in many ways, it indicates the level of scientific and cultural development of the society. With the progress of human knowledge and knowledge of color, colored papers to attract attention and beauty, and colored cardboard and cartons for packaging, and finally boxes of sweets and chocolates for home consumption and the like, all of these are proof of superior knowledge and human use of this industry and It is an invention that is developing and evolving day by day and has been mentioned in history.
What is paper?
Paper is a synthetic material that is obtained from various materials. Wood is the main material for making paper. Paper can be made from cotton, sugarcane, etc. Two different methods are used to make paper.
Wood is the main material of paper. Making paper from wood has 6 main steps.
The stages of turning wood into paper are:
1- Cutting trees
2- Transporting timber to the factory
3- Stripping the bark of trees
4- Turning trees into small pieces of wood and preparing wood chips
5- Removing the yellow color of wood and mixing wood chips with water and chemicals (including plaster, plastic, potassium permanganate, etc.)
6- Drying paper pulp and making paper.
Application of chemicals in paper making
The main material of paper in the factory is cellulose. Plastic is used to produce glossy paper (waterproof paper). Javal water is also used to whiten the yellow color of wood.
How is paper recycling?
In paper recycling, the waste paper is crushed and so small that it can be dissolved in water. Paper recycling saves water and especially electricity.
1400 kilowatt hours of electricity is consumed in making paper from trees, but 840 kilowatt hours of electricity is consumed in recycling.
Materials that can be used to make paper:
The materials that can be used in making paper are:
• Flax, hemp, cotton stems that have long fibers about 1.2 to 6 mm.
• Stems of plants such as wheat, barley, straw, hemp, etc.
• Trees that have needle leaves with long fibers, such as pine, or broad leaves, such as plantain.
• All kinds of waste paper, or scraps and pieces of old cardboard.
• Sugarcane pomace fibers
In making paper, the bark of the tree trunk is first removed by a peeling machine and then converted into wood chips by a wood chipper. These wood chips are turned into small chips by the chip production machine, which are passed through a special sieve for greater certainty. Then the wood chips are decomposed by chemical substances and different pulp cooking methods, and cellulose fibers are obtained from them, which is called paper pulp. At this stage, a brown colored paste is obtained, which is used in the preparation of cardboard, cardboard or straw papers.
Paper preparation method
To prepare white paper, wood pulp is mixed with water until the pulp becomes smooth and uniform, and then it is poured into the refining machine. This operation is done to separate the ligtin and reduce the color of the dough. In this machine, the fibers are uniformly smoothed and sorted, and the pulp water is removed. In fact, sheets of paper are created by entangling cellulose fibers and pressing them. In this machine, the plates containing paper pulp vibrate due to vibration and make the paper pulp smooth and uniform. Finally, the last stage is paper drying, which is done by a machine with several cylinders called a dryer. In fact, the dough containing water is passed through nets with holes of two to three millimeters to lose most of its water, and then it is passed through strong presses until the remaining water is removed and it is completely dry. to be The dried dough is passed through special rollers to form paper sheets. At this moment, the paper is ready for consumption, which is cut into different sizes and packed according to international standards. One of the most important international classifications of paper cutting is the A standard.
Covering and polishing the surface of the paper
The active coating material on the surface of the paper forms the important non-fibrous components of the paper. One of these examples is glossy paper used in magazines, which are sometimes used for books. Coatings are usually based on powdered mineral pigments such as clay and calcium carbonate and should not be confused with fillers. The result of this production process is very desirable and well-printed paper.
Introduction of printing and writing paper
What is known as writing paper in Iran is called writing and printing paper in the international classification of papers and it has different types. This paper is supplied in two ways, coated and uncoated. What is called writing paper in Iran is usually uncoated and it is such that you can write with ink on both sides of it without the ink penetrating or leaking to the other side of the paper.
Waste paper recycling
In preparing and making paper, many trees are cut. Although new trees are planted in their place, the growth rate of these trees is not enough to fill the place of all the cut trees. For this reason, waste paper is recycled. After collecting the waste papers, the ink on them is removed with the help of chemicals. Then they are mixed with chemicals and a lot of water to get pulp again. Paper sheets are made from this dough by performing similar steps.
Processes of paper production and preparation
1- Turning wood into small pieces
2- Cooking wood and producing paper pulp
3- Washing paper pulp
4- Chlorination and decolorization
5- Drying paper pulp
6- Pressing, cutting and packing paper
make paper
You can make paper at home using very simple tools.
- Shred some waste paper.
- Leave the pieces of paper in hot water for 15 minutes. Then, with the help of a spoon, mix them with water to prepare paper pulp.
- Now take the excess water from the dough with the help of a sieve.
- Gently turn the dough onto a plastic sheet and cover it with another plastic sheet.
- Now remove the excess water from the paper with the help of a roller and leave it in the sun to dry well.
The paper production process is as follows:
Cellulose fibers are placed in water to absorb moisture and become swollen and soft; Then, they are spread on a fine wire net so that the water in the fibers is taken and the wet strands settle on the surface of the net and become a board. Fibers get closer together by losing water, and at the points where the fibers overlap, a chemical hydrogen bond forms and connects them together.
This connection and self-connection is the main key to producing a sticky, hard and strong sheet of paper. In this case, no additional glue is needed and the paper is made after the water is removed from the cellulose fibers and they are dried.
In the western world, before the advent of paper machines in the first half of the 19th century, paper was made from cotton or linen fibers – mainly from old and discarded clothing. Today, at least 70% of paper produced in the world is produced from wood fiber derivatives, and 30% of the rest is produced from plant fibers such as bagasse (sugarcane bagasse), straw, and reed.
Still, certain types of paper are made from some plant fibers such as cotton, linen, and hemp. These papers are used for making banknotes, works of art, fine prints, works that need to be protected and preserved, and for the repair and restoration of damaged and exquisite old books.
Preparation of fibers in the paper industry. The first step in making paper is to separate the fibers from their original substrate in wood. This process is called kneading, which has two main methods:
1- Mechanical pulping, in which hard mechanical operations are used to crush wood and remove fiber particles from it.
2- Chemical pulping, in which wood chips are affected by chemical compounds by applying heat and pressure. The product obtained by the chemical method is less than the product of the mechanical method, but the resulting fibers are more invulnerable and a much stronger paper can be produced from it. Currently, there are processes in papermaking that take advantage of the characteristics of both methods. If white paper is desired, washing operation (whitening) should also be included in the manufacturing process.
A major aspect of the papermaking industry is the process in which fibers suspended in water are subjected to intense mechanical polishing. The process of beating or refining has an effect on the mechanical properties of paper. For example, increasing the finish increases the strength of the apparent density of the fibers, and its direct effect on the fibers is to make them more flexible, which causes the fibers to lie on top of each other and create a greater contact surface. In this way, the connection between the fibers is strengthened. Of course, this process is very complicated.
Non-fibrous components of paper.
In the production of papers that are used for printing or writing, a type of filler is used. The use of this material has many results, such as increasing the amount of opacity, smoothness, and uniformity of the paper. Common filling materials are porcelain and gypsum (calcium carbonate).
The share of fillers in paper can be high and between 25 and 30% of the weight of the paper. Most of the papers are modified by different methods in order to control their reaction with water and other fluids. Paper made from only cellulose fibers absorbs water very easily. Such papers are not suitable for writing with pen or ink. In addition, many commercial applications require paper to be moisture resistant. The process of making paper resistant to water is called “Aharzani”.
Domestic harassment
As it is known, it is widely used. This process requires the addition of nutrients to the material containing the fiber particles before forming the paper. The common material is a type of wood resin reinforced with aluminum sulfate, which papermakers call green alum.
Green alum stabilizes the resin on the fiber surface. Unfortunately, the result of the bleaching process, due to the use of green alum, is acidification of the paper. This acidic state remains in the paper and this is the main reason for the gradual decrease in paper resistance. In recent years, economical methods of internal liming with neutral or alkaline materials have been popularized, which can largely prevent wear.
Internal embossing is completely different from surface embossing and washing which involves modifying the paper with starch or gelatin or similar materials.
In the industry, other materials are added to paper, albeit in very small amounts, to give it special properties, for example, to make it resistant to moisture or increase its transparency and adjust its color and shade.
Covering and polishing the surface of the paper
The active coating material on the surface of the paper forms the important non-fibrous components of the paper. One of these examples is glossy paper used in magazines, which are sometimes used for books. Coatings are usually based on powdered mineral pigments such as clay and calcium carbonate and should not be confused with fillers. The result of this production process is very desirable and well-printed paper.
Features of paper
Paper can live up to expectations when its properties are measured and controlled. There are three important features for good paper:
1- Properties of the paper material: such as strength, weight (mass per unit area), and apparent density
2- Features related to the surface of the paper: such as smoothness, which play the main and key role in the conversion process, such as printing.
3-Visual characteristics: which are mainly color, transparency, and opacity.
The paper used for the book should be strong enough and its color and transparency should be acceptable. From the point of view of protection and maintenance, one of the major issues is wear and tear over time. Color change due to wear is also important, but its importance is related to the type of work the paper is supposed to do; For example, color is very important in art books.
The basic method of studying the mechanical properties of paper is the strain-load curve. The pressure at the breaking point represents the tensile strength of the tested paper; While elongation at the rupture site is a means of measuring resistance or the ability to absorb energy before rupture.
To measure the mechanical properties of paper, there are many other tests, some of which are based on simulation and the paper’s resistance to force.
In this context, the following can be mentioned:
- Resistance to tearing, which is measured by the energy required to propagate a tear in a paper sample in which a crack has been created.
- Puncture resistance (the force required to make a hole in the middle of the paper is created using a resistant rubber diaphragm).
- Stability against folding, this property is measured by folding a strip of paper in and out many times until it tears. As mentioned before, in addition to mechanical properties, for those who look at paper as a carrier of information, color is more important than anything else.
Discoloration and turning the color of the paper into a yellowish brown in contact with light is the most common issue and is a familiar issue in old paperback books, especially the edges of their leaves. The main factor in discoloration is the presence or absence of lignin, because papers that have this substance turn yellow quickly in front of light and brightness.