Corrugated board production technology experience

Dialectical materialism believes that labor creates human beings. In today's society, the survival of mankind is inseparable from the production activities, and all production activities are inseparable from the product packaging. This is true both in ancient and modern times. The definition of the so-called packaging is: "To protect the product in the circulation process, facilitate storage, promote sales, according to a certain technical method used in the container, materials and auxiliary materials." In the entire packaging materials, paper products accounted for packaging The largest proportion is 45.25%, followed by other glass, plastic, wood products and metal materials. In paper product packaging, corrugated cardboard (box) packaging accounts for the vast majority.

Corrugated cardboard packaging containers are functionally superior to the 10 features of other types of packaging:

The plasticity of the modeling structure can be arbitrarily cut, punched, folded, etc.; the convenience of the packaging is easy to use - it is light in use, flexible in structure, and flexible in texture; it can be both rigid and flexible - it can be used as a packaging and external force. Ideal protective mediators; beautifying the promotional nature of goods - able to produce a variety of variegated structures and beautiful decoration printing; the suitability of the flow effect - can use different quantitative, different grades of raw paper to produce different sizes of containers Low cost of packaging—primary material is base paper; use of resource availability—Compared with traditional wood products, the wood consumption of corrugated paperboard base paper only accounts for 30% of wood product packaging; easy to recycle—the basic raw material is The base paper can be easily recycled after use, and the recycling and recycling rate can reach 75%. The superior green environment--after use, the corrugated board can be burned, non-toxic, degraded quickly and will not cause pollution to the environment; - Due to the foldable lightweight hardware package, it is possible to make efficient use of the positions and transport loading space.

Looking at the current situation of China's carton industry, it can be summarized in 12 words: rapid development, overcapacity, and bright future. The carton industry has undergone the first major transformation in the past 25 years. From this year on, it will enter the second major change. The characteristics of this change are adjustments.

China's carton industry has entered the stage of primary industrialization since 1995, when there were 600 production lines; in 2000, it was 1,600; by 2005, it had reached 4,000.

In 1995, the output of corrugated board in the world was 110.4 billion m2, in 2000 it was 125.3 billion m2, in 2003 it was 139.5 billion m2, and the annual growth rate was 3.3%. The top three world production rankings in 2000 were: North America (34%), Asia (31%), and Europe (27%). The output of corrugated paperboard in China was 7.4 billion m2 in 1995, rising to 12.3 billion m2 in 2000, and reaching 15.8 billion m2 in 2003, which is 34% of Asia's total output and 11.3% of the world's total. From 1995 to 2000, the average growth rate of paperboard production in China was 12%, and the average growth rate in the world was 2%. From 2000 to 2003, the annual growth rate of paperboard production in China was 9%, and the world's annual growth rate was 3%. The output of China in 1996 was 8 billion m2, which was only half of that in Japan. In 2003, it was 15.8 billion m2, which surpassed Japan.

More than 50% of the cartons in China accounted for more than 80% of the total, the United States, the third floor of the box accounted for 89.4%, Japan, the third floor of 84.6%, with two layers of paper is equivalent to a waste of 2/5 paper. This is because western countries have realized that they must save limited timber resources. The use of high-strength, low-weight base paper has become an inevitable trend.

Shanghai Tobacco Group has completed a joint reorganization across regions and will become the vanguard of several leading companies under China National Tobacco Corporation. As its main professional supporting factory, Shanghai Baiyulan Tobacco Material Co., Ltd. has undertaken over 85% of the Group's carton packaging production tasks.

Second, the determination of the original rake type, the selection of the production line base paper and the deployment of adhesives

The corrugated shape refers to the corrugated shape of the corrugated tooth profile. The difference lies in the size of the radius of the corrugation and trough arc. There are three shapes: U-shaped, V-shaped, and UV-shaped. The U-shaped peaks and troughs have larger radii; the V-shaped ones are smaller; the UV-shaped ones are in the middle. Different shapes have different performance characteristics.

Looking at the advantages and disadvantages of the above three kinds of corrugated shapes, the advantages and disadvantages of U-shaped and V-shaped are obvious, and the comprehensive performance of UV shape is to meet the general requirements of most corrugated packaging, and its superiority is undoubtedly demonstrated. Therefore, most of the countries in China and other countries use UV-type corrugated.

After understanding the corrugated shape overview, introduce the principle of selection of base paper for cardboard production lines from the following two aspects:

1. Grade Matching ─ Corrugated board and linerboard with similar quality grades should be used to produce cardboard. The use of corrugated board made of high-grade linerboard and low-grade corrugated cardboard is liable to cause collapse.

2. Quantitative Matching – Experiments have shown that increasing the amount of corrugated paper helps reduce costs. When the strength of the corrugated paper is kept constant, the weight of the corrugated paper is increased by 1 g/m2, so that the double-sided boardboard paper can also be reduced by 1 g/m2. Therefore, many manufacturers use high-quantity corrugated paper to produce cartons. However, corrugated board produced from high-quantity corrugated paper and low-quantity linerboard will have surface unevenness and obvious corrugation, which will affect the appearance quality and printing effect. Therefore, it is generally better to control the ratio of cardboard and corrugated paper to 2:1. If the weight of the optional corrugated paper is too low, the corrugated tooth profile will change after bonding, and the arcuate shape will change into a rectangular structure, which will affect the thickness, side pressure strength and cushioning properties of the paperboard.

The formulation of adhesives for corrugated cardboard production lines: The adhesives for cardboard production lines consist mainly of starch (or tapioca flour), gelatinizer (NaOH), crosslinker (borax) and other reinforcing agents. In fact, the starch itself does not have a binding function. Only the active hydroxyl groups in the starch molecule are oxidized to aldehyde groups, ketone groups, and carboxyl groups in a limited manner, and the official bond portion in the molecule is broken, and the polymerization is reduced to have good water solubility and affinity. And adhesion, after alkalized into a good performance starch adhesive. Under normal circumstances, the amount of starch used for single-sided corrugated board production is: 150kg/t to 170kg/t; the three-layer dosage is: 170kg/t to 200kg/t; the five-layer and seven-layer requirements for adhesives are relatively high, and the starch dosage is 200kg /t 300kg/t. The amount of industrial caustic soda (NaOH) is determined according to the viscosity of the binder after stirring in the main carrier added to the starch liquid. Under the same conditions, the amount of caustic soda is large and the viscosity is high; when the amount of caustic soda is small, the viscosity is reduced. Borax can make various ingredients produce molecular structure changes to form complexes, with cross-linked thickening effect. The amount of enhancer (also known as desiccant) in the adhesive, less than 2kg per ton, will not achieve its intended effect; the amount of glue per ton is higher than 8kg, and it is easy to produce cardboard brittleness. The normal dosage is 3kg/t to 6kg/t.

Third, the corrugated board production process in the prone to problems and solutions

Cardboard warping

In general, there are six phenomena of warpage in corrugated cardboard. The most common ones are:

Warping

The reason for this is: the moisture content of the raw paper is too high (or the moisture content of the paper is low); the single-sided corrugated paper has too much moisture, and the quantitative grades of the paper and paper are too different.

The solution: (1) increase the surface area of ​​the paper in the single cylinder dryer; (2) reduce the paper in the double layer preheater winding surface; (3) close part of the flat dryer steam valve; ( 4) Increase the running speed of the compound machine; (5) Reduce the clearance between the scraper roller, the squeegee roller and the lower corrugating roller, and reduce the sizing amount of the single-faced corrugated roller; (6) Replace the liner paper that exceeds the moisture requirement.

2. Lateral warpage

The reason is: the moisture content of the base paper is too high; the temperature and speed of the heated area are not normal.

Solution: (1) increase the surface of the paper in the double-layer preheater heating surface; (2) the use of a better adhesive viscosity, reduce the amount of gluing machine; (3) reduce the single-sided machine paper (4) Reduce the production speed at the compounding machine; (5) Correctly adjust the line speed of the production line and the flat-plate dryer steam valve to match; (6) Replace the face paper that exceeds the moisture requirement severely.

Cardboard False Bonding

The so-called paperboard false bonding refers to a phenomenon that the paperboard can be stripped off from the back of the paper, paper and corrugated paper.

The main causes are: (1) the adhesive has insufficient viscosity or has deteriorated; (2) the speed of the corrugator or laminating machine is too fast; (3) the pressure of the corrugator is uneven or the corrugating roller is worn; (4) compounding Spreader rubber roller gap is too large; (5) paper moisture content is too high. Solution: (1) Improve and stabilize the adhesive quality. Relevant data suggest that the adhesive viscosity is generally 60S to 90S in winter and 90S to 120S in summer. The seven-layer box is generally about 305 times slower than the three-layer box; (2) It ensures that the steam pressure is 1.0MPa to 1.2MPa, the temperature of each roll body and plate dryer is about 160°C; (3) The production capacity of domestic corrugated rolls is up to 3 million. When one meter is 3.5 million meters long, it must be replaced in time.

See-saw phenomenon

The so-called see-saw phenomenon refers to the corrugated paperboard after being made. On the surface of the surface paper, there is a concave phenomenon between the back of the peak and the back of the peak, and the shape is the same as that of a domestic washboard. It is called a see-saw phenomenon.

The root cause of the seesaw phenomenon in corrugated board is mainly attributed to improper adhesive sizing, which is caused by the excess glue that collects on both sides of the peak. This situation is particularly detrimental to the low-quantity linerboard.

The specific methods of controlling the board seepage are: to adjust the amount of face paper, and to use a higher amount of linerboard is the most direct and effective way to eliminate and reduce the board shape (but it will increase the cost); the use of high quality adhesives can reduce The peak sizing amount; control the surface of the heating paper on the pre-heater, because the board paper is too dry, the glue intake is more, it is easy to produce the seesaw phenomenon; adjust the composite glue machine sizing roller and paper The degree of parallelism of the guide rollers and the gap between them, the degree of pressure of the guide roller (pressure roller) is strictly controlled to prevent the increase of the amount of glue after collapse.

Cardboard moisture control

In the process of production of corrugated board, the moisture content of the board is very important. When the moisture is too high, the processed board will appear soft, not quite, easy to collapse after the box. When the moisture content is low, the processed cardboard is hard, brittle, and easily burst after being packed. The control of board moisture is a complicated matter, which is mainly determined by the following two factors:

The moisture of the raw paper entering the factory must be strictly controlled. According to the current standard, the moisture of the original paper delivery state should be (8±2)%. It is better to set up a separate warehouse for storing the base paper, the temperature is generally (18 ± 3) °C, and the humidity is generally (35 ± 5)%. Do not put it in the open air, otherwise it is easy to cause moisture changes and the two ends are not the same as the middle.

Temperature is one of the decisive factors affecting the quality of corrugated board. It can not only adjust the moisture of the base paper, but also increase the temperature of the base paper, which is an important condition for curing the paste liquid. Therefore, a large number of preheaters and flat-plate dryers are installed in the cardboard production line to adjust the moisture content of the base paper and the single-sided paper, and the paste is finally cured to achieve the purpose of bonding.

In order to effectively control the moisture of finished corrugated board, we must pay attention to the following issues:

If the moisture in the paperboard is too high and the temperature of the preheating roll does not meet the requirements, the steam pressure of the boiler must be increased so that the steam supplied can reach saturated steam. In general, the steam pressure should be kept at 1.1 MPa ± 0.2 MPa.

If the water content is low, it is necessary to adjust the paper guide roller to reduce the preheating area. At the same time, the single-sided on-machine spray device (wet roller) should be fully utilized to spray the base paper to increase the moisture content of the base paper to meet the standard requirements.