Papermaking Methods of Papermaking

Referring to the picture on the right, there were five main steps in the Ming Dynasty papermaking process. From the picture, it can be seen that the Chinese papermaking industry was already quite mature at that time, with specialists in each process working in their own way, and a number of specialized tools for papermaking had been developed.

Chopping bamboo and floating ponds: Chopping bamboo and placing it in a pond to soak it so that the fibers can fully absorb water. Can be added to the bark, hemp head, and old fishnets and other plant materials mashed. Boil the precious stones foot fire: the crushed material to cook, so that the fiber dispersion, until the pulp is cooked. In the picture you can see a large pot of crushed material pressed down with a large stone to help cook it completely. Swinging the material into the curtain: Allow the pulp to cool, then use a flat bamboo curtain to scoop up the pulp and filter the water to make the paper film. This step requires skill in order to produce a film that is evenly distributed and of the right thickness. Overlap the curtain pressure paper: Fishing good paper film stacked one by one, with a wooden board pressed tightly, on top of a heavy stone, the water pressure out. Roasted through the fire: the pressure to the semi-dry paper film attached to the edge of the fire to dry, uncovered that is the finished product. Today's technology has advanced by leaps and bounds, and the modern paper-making process has been mechanized.

Groundwood Pulp (Groundwood Pulp) the use of mechanical grinding force to obtain wood fibers, also known as mechanical pulp (mechanical pulp), can be subdivided into general mechanical pulp, refined mechanical pulp, hot grinding mechanical pulp.

Chemical Pulp (Chemical Pulp) The use of chemical methods to separate fiber and lignin to obtain wood fiber, can be divided into soda pulp, sulfite pulp, sulfate pulp.

Semichemical Pulp (Semichemical Pulp) combined with mechanical and chemical methods of pulping, can be subdivided into neutral semi-chemical pulp, cold soda pulp, chemical and mechanical pulp. In the early years of the Western Han Dynasty, political stability, ideological and cultural activity, the demand for communication tools, paper as a new writing material came into being. Xu Shen wrote Shuowen Jiezi (Explaining Characters in Chinese), which was written in 100 AD. He talked about the origin of "paper". He said: "'paper' is from the side of the system, that is, the side of the 'silk'". This sentence means that the paper of that time was mainly made of silk, which was completely different from the paper in the general sense. Xu Shen believed that paper was a thin sheet of silk floss left on a bed mat after being struck in water. This thin sheet may be the most primitive "paper", which some people call "Heshu". This may be a prelude to the invention of paper, and records of this type of paper can be traced back to the first year of Emperor Chengdi's reign in the Western Han Dynasty (12 B.C.). In the Book of Han - Empress Zhao Biography, it is recorded that Emperor Cheng's consort Cao Weineng gave birth to a son, and was persecuted by Empress Zhao Feiyan's sisters, who gave Cao Weineng a poison wrapped in "Heshuo" paper, which reads: "Tell Weineng to try hard and drink this medicine! Drink this medicine! Do not re-enter, you know!" The paper was wrapped in Heshoe paper. It is assumed that the paper may have some relationship with the silk.

Cai Lun carefully summarized the experience of his predecessors, and he believed that by expanding the sources of raw materials for papermaking, improving the papermaking technology, and improving the quality of paper, he could make paper acceptable to everyone. Cai Lun first used bark to make paper, which is a much richer raw material than hemp, and this can make the production of paper increase dramatically. The lignin, pectin, and proteins contained in the bark were much higher than those of hemp, so degumming and pulping of the bark was more difficult than that of hemp. This prompted Cai Lun to improve the technology of papermaking. The Western Han Dynasty used lime water for pulping, and the Eastern Han Dynasty switched to grass ash water for pulping, which has greater alkalinity and is conducive to improving the quality of paper pulp. In the first year of Yuanxing (105 A.D.), Cai Lun presented a batch of high-quality paper he had made in Shangfang to Liu Zhao, the Emperor of the Han Dynasty, who praised his talent and immediately ordered the world to adopt it. In this way, Cai Lun's papermaking method soon spread all over the world.

"Han Dynasty papermaking process flow chart" reproduces the image of the two Han Dynasty papermaking, hemp, rags and other raw materials by water immersion, chopping, washing, steaming, rinsing, pounding and pounding, adding water to form a suspension of the slurry, pulp, drying that is to become paper.

Historical records: Han and Emperor Gou had visited Gou tour, it is possible to visit the paper-making workshop here and paper Zhuang (now divided into the former paper Zhuang and after the paper Zhuang, is located in Luoyang Han Wei Old City about 2000 meters east, facing the Luo River) is likely to be the location of the Han Dynasty paper-making workshop. These two places, the neighborhood has a superior geographic environment needed for papermaking, there are relatively rich paper resources (such as hemp, kozo forests, etc.).

After Cai Lun offered paper, papermaking technology and paper were widely spread. At the end of the Eastern Han Dynasty, Zuo Bo, a native of Donglai, was also a skilled papermaker. The paper he made was whiter and more delicate than Cai Hou's paper. In the book "Sanshu Jilu" written by Zhao Qi, Zuo Bo's paper, Zhang Yi's pen, and Weidan's ink are mentioned as valuable writing instruments. The juxtaposition of pen, ink and paper indicates that paper was already a commonly used writing material at that time. Paper became a strong contender for bamboo slips, wooden documents, thick silk, and by the third and fourth centuries it had basically replaced the simple silk and become the only writing material, which strongly contributed to the development of science and culture. Modern mechanical papermaking

Modern papermaking procedures can be divided into pulping, modulation, copying, processing XX and other major steps:

1. Pulping

Pulping for the first step in papermaking, generally the wood into pulp method of mechanical pulping, chemical pulping and semi-chemical pulping method and so on three.

2. modulation

The modulation of paper for the other focus of papermaking, paper after the completion of the strength, color, printability of the advantages and disadvantages of paper preservation period is directly related to it.

The common modulation process can be roughly divided into the following three steps: a. Pulp dispersal b. Pulping c. Adding glue and filling

3. Copying

The main work of the paper copying department is to make the diluted paper, so that it is uniformly intertwined and dewatering, and then drying, calendaring, rolling, cutting, sorting, packaging, so the common process is as follows:

a. Screening

The modulated paper will be diluted to a lower concentration, and through the screening equipment, sieve out the debris and undissociated fiber bundles again, in order to maintain the quality and protection of equipment.

b. Mesh section

The paper flows from the headbox onto a circulating copper or plastic mesh and is evenly distributed and interwoven.

c. Press section

The wet paper which is removed from the mesh surface is led to the two rollers with a burlap, and the wet paper is further dewatered by the squeezing of the rollers and the absorbing effect of the burlap and the paper is made more compact, so as to improve the surface of the paper and increase the strength.

d. Drying Department

As the wet paper after pressing, its moisture content is still as high as 52-70%, at this time has been unable to use the mechanical force to remove water pressure, so instead of letting the wet paper through a number of inside the cylinder surface of the hot steam to make the paper dry.

e. Calendering

f . Rolls of paper

g. Cutting, selection, packaging

Take the front has been rolled into a cylinder of paper rolls of many, with a paper cutter cut into a sheet of paper, and then manually or mechanically selected, eliminating the broken or stained paper, and finally every five hundred packages into a packet (usually called a order).

The wood used to make paper is sawn to the proper size and then debarked. The logs are put into a large drum, which rubs against each other as it rotates to remove the bark, which is then used as fuel for the boiler. The debarked logs are cut into 1.5 to 2-inch square pieces, 0.25 inches thick. Softwood and hardwood pieces are processed separately due to their different physical properties.

Wood is made up of tiny cellulose fibers bonded together by a glue-like substance called lignin. Pulp is made by steaming the wood chips with chemicals that break down the lignin and thus separate the fibers. The wood chips are placed in huge containers called digesters, which function like pressure cookers in the kitchen, and the chips and chemicals are cooked under pressure for 1.5 to 4 hours until they become a wet, soft, oatmeal-like mixture, with the separated fibers suspended in water. The mixture is washed to remove the remaining chemicals and decomposed lignin and bleached to a suitable whiteness. From here the pulp passes through a series of refiners, which loosen the thread-like elements in the fiber walls of the pulp and cause the surface to become rough and the fibers to become intertwined. Dyes and other additives are then added to give the finished paper the desired characteristics.

The pulp is mixed with water at a ratio of 20 parts water to one part fiber and passed through the forming fabric or wire of the paper machine, where the fibers of the pulp intertwine to form the paper and remove most of the water. Moving at a high speed of 3,000 feet per minute, the paper then passes through a series of absorbent cloths and steam-heated rollers called dryers, which remove the water retained in the paper. The paper is then coated with a starch solution on both sides of the paper. The starch makes the paper surface smooth and prevents the ink from melting when it is used for printing in the future, and because of the moisture brought in by the coating process, the paper needs to repeat the previous drying process. After drying, the paper is passed through heavy and smooth rollers for buffing to make the surface even smoother. The paper is collected at the back and rolled into large rolls, which are then divided into smaller rolls of the appropriate width, some of which are packaged for shipment, and some of which are then processed and cut into flat sheets of the appropriate size for packaging and shipping.

The basic process of papermaking Process introduction:

Hydraulic pulper: pulp board in the hydraulic pulper by tearing and mutual friction, so as to achieve the purpose of pulp crushing.

Pulping: pulping makes fiber deformation, wetting, crushing and cutting, and fine fiberization. Through pulping, can change the shape of the fiber, so that the pulp to obtain certain characteristics (such as mechanical strength, physical properties), in order to ensure that the copied paper and paperboard can achieve the desired quality requirements. Purification: The purpose of purification is to remove relatively large impurities in the paper material, such as metal shavings, cinders and so on. The principle of purification equipment is to use the density difference to select the impurities. Commonly used equipment: conical slag remover.

Screening: The purpose is to remove the relative density of the paper material in the small but large impurities, such as pulp, fiber bundles, grass clippings, etc..

Common equipment: pressure sieve.

The pulp box: pulp box is the key part of the modern paper machine. Its structure and performance on the formation of paper and paper quality has a decisive role.

The main tasks:

Effective dispersion of fibers. High-turbulence flow pulp box can produce high-intensity micro-turbulence, can effectively disperse fibers, prevent fiber precipitation and in flocculation, can effectively improve the strength of the paper sheet.

Uniform distribution of the paper stock along the lateral direction of the paper machine. (Determines the horizontal dosing distribution of the paper web)

Spraying pulp is stable, ensuring that the pulp speed is coordinated with the web speed. (Determines the longitudinal dosing of the paper web)

Net: The pulp is dewatered and formed in the net. The concentration of pulp on the net is 0.1~1.2%, the dryness of the paper is 15~25% when it comes out of the roll, and the dryness of the formed paper is 90~95%. It can be seen that the net dewatering accounted for more than 90% of the total dewatering.

Press section: the use of mechanical press further dehydration to improve the dryness of the paper web. At the same time to increase the tightness and strength of the paper, improve the surface properties of the paper (such as smoothness). Mechanical press dewatering in the economy is more cost-effective. The press section of the paper machine increases the dryness by 1% more. Steam consumption in the dryer section is reduced by 5%. In this sense, the press section should remove as little moisture as possible. With the new composite press, wet paper out of the press section of the dryness of up to 48 ~ 50%.

The role of the dryer section:

1. After the press section of the moisture off the wet paper, so that the dryness of the paper to 92 ~ 95%.

2. Improve the strength of the paper.

3. Increase the smoothness of the paper.

4. Complete the sizing of the paper.

Calendering: Calenders are used to improve the smoothness, gloss and thickness uniformity of paper.

Rolling: Rolling the paper out of the calender into rolls online.

Rewinding: the rolls rolled on the machine are uneven on both sides, and the paper is too wide, it must be cut longitudinally to rewind into rolls or cross-cut into flat paper.

Packaging: the ration of not less than 120g / square meter of wrapping paper rolled onto the web to form the outer packaging.