Raw materials for corrugated board
I. Trees
Paper and paper paddles can be made from a variety of plant fibers, but the most used materials as paper are trees and non-wood.
Second, the chemical composition of wood
The following table shows the typical chemical composition of softwood and hardwood. However, it is difficult to accurately formulate the chemical formula of wood because wood is a complex and heterogeneous natural product composed of a variety of molecular compounds. The main components of wood are cellulose (40-50%), hemicellulose (20-35%), wood (20-30%) and solvents (3-3, 5%). However, it is impossible to say that these chemical components should be sorted out without structural changes and decomposition. If the main composition of wood is studied, most of it is composed of polysaccharides, accounting for about 60-80%; if wood polysaccharides are hydrolyzed with dilute acid, it can be known from glucose, mannose , Xylose and other monosaccharides composed of high-molecular carbohydrates.
The main polysaccharide component of wood can be divided into cellulose full cellulose hemicellulose
Treating whole cellulose at room temperature with a dilute base (for example, with 17, 5% NaOH or 10-24% KOH), 15-30% of the dissolved wood is hemicellulose, and cellulose is insoluble. .
Third, pulp
The raw material of the paper is pulp, which is mainly made of wood. The manufacturing method is generally as follows: Chemical Pulp Pulp Pulp Chemical Pulp Pulp (Physical) Pulp
1, chemical pulp
Chemical pulp is a pulp made mainly of chemicals in the process of manufacturing pulp. Certainly, there are certain differences depending on the drugs used and the manufacturing methods. Compared with the process pulp which removes the intermediate lignin and cell lignin in the raw material, there are disadvantages of low raw material utilization and high production cost.
(1) Kraft pulp
Kraft pulp is a chemically produced pulp called kraft pulp. The word Kraft means solid in Sweden. Because the paper produced by the Swedish chemical factory made from the pulp produced from by-product Glauber's salt is very strong, it is called kraft paper.
(2) Semi-chemical pulp
Semi-chemical pulp is a kind of pulp made by chemical treatment and first removing some of the lignin contained in the wood, and then breaking up the remaining softened wood chips by mechanical means. That is to say, chemical processing and mechanical processing each account for half of the manufacturing methods. Semi-chemical pulps have higher purity and strength than crushed wood pulps, ie mechanically processed pulps, and have higher yields than chemically made chemical pulps.
2, waste paper pulp
Waste paper pulp is waste paper that has already been used. It is placed in a dredging device such as a masher and twisted back and forth to decompose fibers that coalesce together to form a congee.
The waste pulp used for the surface sizing of corrugated board is mainly made of kraft paper and corrugated paper, and therefore has a high strength.
Second, the distinction between paper and cardboard
According to its thickness, it is divided into paper and cardboard. It is customary to refer to a thick paper having a weight exceeding 200 g in a square area as cardboard, and a paper weighing less than 200 g as paper. However, with the improvement of mechanical equipment, materials, and process technology, thin paperboard has emerged as light-weight corrugated paperboard and paperboard. Its scope has exceeded the secular regulations of 200g. It is also divided into heavy-duty corrugated paperboard production lines and lightweight corrugated medium in production machinery. Paperboard production line, our company's existing three cardboard production lines are all light board production lines.
There are about 5,000 kinds of paper and cardboard in the world. There are 500-600 types of paper and paperboard produced in China. The main varieties used for product packaging are boxboard paper, corrugated paper, white paper, yellow paper, kraft paper, and glass cards. Paper, tar paper, copperplate paper, rubberboard paper, coated paper, specialty paper, rubber-coated base paper, etc., and corrugated paperboard are mainly made of cardboard and corrugated paper.
Third, the identification of the positive and negative of paper or paperboard
No matter what kind of paper or paperboard has both positive and negative aspects, when making paper, the wet paper web and the net contact surface are opposite and the other side is positive. On the other hand, due to the contact with the copper mesh, the loss of fine fibers and fillers was more, showing screen printing, so the reverse was rough. The front is more compact, and the nature of the front and back is obviously different. Its smoothness is higher on the front side than on the reverse side, and the reverse side of the pulling speed is larger than the front side; the back side of the white point is better than the front side, so the paper and the cardboard have two sides.
Two-sidedness has a great influence on print quality. In general, the smoothness of the front surface and the degree of sizing are good, so the printing performance is also good. The face paper of the carton must be made with the front side of the paper facing outwards in order to print and carry out moisture-proof treatment. For this purpose, the front and back of the paper or paperboard must be identified.
For noodle board, the color of the dough is better than the color of the paste, and the positive and negative sides are most easily identified. Some paper or cardboard are made by a multi-cylinder paper machine or calendered by a calender. The difference between the front and the back is not so obvious. At this time, the following methods can be used to identify:
1, direct observation method. Fold the paper or cardboard and observe the surface shape structure on both sides. If there is a screen printing machine, there is a screen printing surface is negative, when the naked eye is not clear, you can use a magnifying glass, or smooth instrument measurement.
2, using carbon paper pressure paper observation method. Press the carbon paper on the paper surface, and observe the condition of the paper. Make a mark on the paper, press the trace of the carbon paper on the paper, draw a black mark about 13mm wide and 51-76mm long. When observed, it can be placed on a smooth surface glass and identified as 1.
3. Use the coin method (aluminum) as a mark. Fold the paper surface so that both sides are placed on a plane. Use a coin to draw a mark on both sides. Then observe the depth of the traces on both sides. The light side of the trace is the reverse side. This is because the amount of filler on the surface of the mesh is low, and the scratches are not easy to appear. .
Fourth, the vertical and horizontal identification of paper or cardboard
Paper and paperboard have a certain degree of directionality by screen printing, generally parallel to the running direction of the paperboard, and vertical to the running direction.
Vertical and horizontal can usually be identified using the following methods.
1, visual measurement method. Some flat-sheet papers can notice the total vertical and horizontal directions with a little attention. It is more obvious when facing the light, and the longitudinal direction is along the direction of the fibers. The length of the paper is perpendicular to the web.
2, tear method. If it is difficult to determine the vertical and horizontal directions by visual inspection, the cardboard can be torn by hand. If the split is straight and smooth, it is longitudinal; if the split is oblique or zigzag, even if the split tears off the layer of paper, it is horizontal. Or by paper, paper to distinguish, tensile strength is vertical.
3, Rally instrument measurement method: use a dedicated tensile testing machine for test values for the longitudinal value of the small horizontal.
Five, corrugated paper
Compared with foreign countries, China's corrugated base paper used at this stage is generally high-quantitative, while the amount of low-quantity high-strength corrugated paper is still very small. Currently, there are few high-volume, low-strength, high-strength corrugated paper projects planned for new expansion, and the production capacity of new projects is not large, but the demand growth is significant. With the increasing demand of users for product quality, the existing corrugated paper supply system based on middle- and low-end products certainly cannot meet the demand. Even if the planned projects are put into production on schedule, by 2005, the high-strength corrugated base paper will still have a deficit of at least 1 million tons. Therefore, low-quantity, high-strength corrugated base papers have to rely heavily on imports.
With China's accession to the WTO, product exports will further expand. According to the preliminary budget, China's major export products, such as apparel textiles, machinery products, agricultural products, etc., will have significant growth, and it is expected to increase exports by 8 billion to 10 billion U.S. dollars each year. The increase in product exports will inevitably lead to a substantial increase in the corresponding product packaging, and the problem of inadequate supply of domestic high-strength corrugated paper will become more prominent.
The main reasons for this situation are the following three aspects: First, due to the low value-added value of corrugated paper for a long time, papermaking companies that produce packaging paperboards are generally optimistic about high value-added products such as kraft linerboards and whiteboard papers. The number of low-quantity and high-strength corrugated paper base papers that resulted in the planned new expansion was small; secondly, the improvement of the domestic paper product packaging level has rapidly boosted the demand for domestic high-strength corrugated base papers and kraft linerboards, resulting in the shortage of domestic high-strength corrugated base papers. Third, the international market for corrugated paper is still weak, and supply exceeds demand. However, the high-strength corrugated paper market in China is in short supply, making foreign companies have a good view of the Chinese market.
From the perspective of market demand, the development of corrugated base papers in the direction of low quantification, high strength and full specifications is a major trend. It is now able to produce corrugated base paper of 90 to 115 g/m<2, and is expected to produce 60 to 90 g/m2 corrugated paper in the future. Due to the large demand for medium-strength, high-strength corrugated base paper, corrugated paper prices will increase. At present, reducing costs and reducing quantification are two major topics in the development of corrugated base paper.
