How to improve the quality of corrugated board

In recent years, the corrugated paper box industry in China has experienced the most difficult period ever. As the industry's threshold is lower, companies investing in this industry will continue to increase. At the same time, some of the powerful paper groups in the world have entered or are entering the Chinese market. Competition will be the main theme of the future market, and it will only improve itself. The technical level can provide customers with high-quality carton packaging products before they can occupy a place in the international competition field of corrugated carton packaging.

The manufacture of corrugated cardboard with beautiful appearance and excellent inspection indexes is the goal pursued by every carton company with a cardboard production line. However, due to the reasons of equipment and operators, a considerable proportion of the products produced by the enterprises in the carton industry are of unsatisfactory quality. In the current trend of corrugated carton packaging towards “low weight, light weight, and high strength”, the quality requirements of corrugated paperboard are becoming more and more stringent. How to improve the quality of corrugated board is a common concern of the packaging industry. The following will explain how to improve the quality of corrugated paperboard from the aspects of adjustment of adhesives and glue rolls, and the amount of glue, pressure, and temperature.

Adhesives

The main raw material of the adhesive is starch, and the quality of the starch has a direct impact on the quality of the adhesive. If the starch with poor quality is selected as raw material, the viscosity and fluidity of the finished adhesive will be unstable, and precipitation will occur easily. Moreover, the adhesive strength of the bonded paperboard is poor, and it is easily deformed. Open plastic. Therefore, we must strictly control the quality of the starch.

At the same time, the advantages and disadvantages of the adhesive manufacturing process also have a direct impact on the quality of the cardboard. Some companies may increase the ratio of water and starch during the production process in order to theoretically reduce the production cost of the adhesive. However, in order to achieve adhesive strength, cardboard production will increase the amount of glue. We should know that the main adhesive effect of adhesives on paperboard is starch. Water is only a linking material. It is unscientific to reduce the production cost of adhesives by increasing the proportion of water and starch. This will not only reduce the cost, but will have a serious impact on the quality of cardboard, so that the detection indicators can not achieve the desired requirements.

The production of high-quality adhesive must be controlled its physical and chemical indicators. Such as starch and water ratio, the viscosity of the finished product adhesive, fluidity, PH value, gelatinization temperature and so on. Changes in these indicators will have a great influence on the bonding strength and flatness of the paperboard. Therefore, the following points must be taken into account in the production of adhesives:

A pair of raw and auxiliary materials must have strict quality requirements:

â–  Variety of raw and auxiliary materials should change the dosage of feeding according to the change of climate:
â–  The borax must be thoroughly dissolved with hot water before it can be placed;
â–  Do not use river water or boiling water as a source of water;
â–  The main points of high-quality adhesives are high concentration and low viscosity (ie the ratio of water to starch does not differ much, but the fluidity must be good);
â–  The finished adhesive cannot have sediments;
â–  The viscosity of the adhesive must not change too much during storage and use;
â–  Good permeability and initial viscosity in the production process.

The qualified adhesive should be glued and the two papers quickly gelatinized and bonded under high temperature and pressure. The peeling should be the tear of the paper fiber, not the separation of the adhesive. In order to improve the quality of the adhesive, additives with better suitability can be selected as accessories. Some additives can indeed reduce the gelatinization temperature and improve the bonding strength, and play a role in improving the quality of the cardboard.

Adhesive Roller Adjustment and Coating Capacity Adhesives are an indispensable part of the entire production process of corrugated cardboard. The amount of glue applied will not only bring about changes in production costs, but will also have a direct impact on the quality of the board. Some operators fear that reducing the amount of glue applied will cause a bad sticky station and blindly increase the amount of glue applied. This method may improve the fastness of the adhesive, but many undesired quality defects emerge, such as the surface of the washboard. There are many disadvantages such as chicken skin, translucent, soft paperboard, poor strength, and thin thickness, resulting in high cost and low quality.

In order to control the amount of glue, the glueing device should first be accurately measured and adjusted. The gap between the adhesive anilox roller and the scraper roller on the single-sided machine gluing roller must be the same, and the slightest error is not allowed. Otherwise, due to the amount of glue applied, the uneven moisture content of the cardboard will cause the cardboard to be uneven. Both sides of the deformation are inconsistent, the board will produce a unilateral bending, causing trouble to the next process. The space between the rubberized anilox roller and the corrugating roller must be the same except that the two ends must be the same, and the proper gap between the two rollers should be controlled. If the gap is too large, the coating will be poor and the local foaming and adhesion will be poor: due to the corrugating roller The line speed of the coated anilox roller does not match during operation. Too small clearance will cause the two rollers to rub and damage the rubberized anilox roller, resulting in irreparable consequences and failure to produce properly. Therefore, care must be taken when adjusting, and the expansion deformation of the corrugating roller after it is heated must be taken into consideration. Therefore, adjustments must not be made with undue haste.

The gap between the rubberized anilox roller and the scraper roller in the double-layer glue applicator should also ensure that the two heads are the same and there can be no slightest error. However, the gap between the coated anilox roller and the platen roller should normally be reduced by about 0.30mm according to the thickness of the two layers of cardboard. The gap is too large will cause poor glue and cause waste: the gap is too small will make the corrugated paper contact with the adhesive anilox roller too much and make the corrugated paper more than the actual need of the glue when the glue is applied. When the board enters the drying tunnel, the corrugated board will be flattened and collapsed by the action of the gravity roller to make the board thinner and softer. Therefore, we must carefully and strive to be precise when adjusting the gaps of the glue coating devices. At the same time, we should strictly control the amount of glue applied. The glue application area must be controlled within the width of 1 to 1.5 mm of the corrugation peak, otherwise it will not only increase production. Cost, and the quality of the product is not satisfactory.

pressure

The entire production process of corrugated board is inextricably linked with the pressure. Pressing the corrugated board requires pressure, and the bonding between paper and paper also requires pressure to complete. Therefore, the appropriate pressure is an important guarantee for the manufacture of high-quality corrugated cardboard.

What kind of pressure is appropriate? In the production process of a single-sided machine, the pressure between the corrugating roller and the corrugating roller should normally be controlled between 0.3Mpa and 0.4Mpa. (Two roller parallelism must be Consistently, too little pressure can cause poor corrugation suppression, such as corrugated sloping in the same direction or high or low blemishes. Quality problems such as: too much pressure can cause damage to the kraft fiber and reduce the compressive strength of the corrugated board. Excessive pressure also accelerates the wear of the corrugating roller and reduces its service life.

The pressure between the corrugating roller and the pressure roller should be controlled at about 0.4Mpa under normal conditions, but it should be controlled flexibly depending on the quality of the paper. The grade of good paper is made of pure pulp or wood pulp. Raw materials, so the tightness is tight, after the glue is difficult to penetrate into the paper fiber. Therefore, the pressure should be greater: The raw materials for the low-grade paper are basically waste paper and recycled paper, and the physical indicators are all poor. If the pressure is too high, the damaged fibers of the paper will even break the paper, and the adhesive strength should be ensured in the actual production. Under the premise of the paper, the pressure of the pressure roller is properly adjusted according to the quality of the paper.

The adjustment of the gravity roller pressure in the double-layer laminator is generally not considered. At present, most of the configuration of tile line cadres in domestic carton factories is designed according to the early production of high-heavy gram papers, while the low-weight kraft papers are particularly demanding on the pressure of gravity rollers during production. The pressure must be appropriate. Otherwise the quality of the board is unsatisfactory. In the adjustment of the gravity roller pressure must be "heavy light" points, in the general case can be set as a group of three gravity roller, along the entrance of the first gravity roller at the entrance of the pressure is the heaviest, the second The root is the second, the third is the lightest, and so on, but the pressure on both ends must be the same, otherwise it will cause uneven thickness on both sides of the cardboard. Only by constant exploration and adjustment in actual production can we find the right pressure for the production of low-weight cardboard.

Temperature and temperature are similar to the relationship between water and fish in the production of corrugated cardboard production lines. Preheaters, corrugating rollers, and hot plates all require a certain temperature guarantee for proper production. Therefore, temperature is also one of the important factors affecting the quality of cardboard. The temperature level can not only change the moisture content of the cardboard, but also the bonding strength of the film II to the cardboard. Because the adhesive we currently use is raw starch, and raw rubber can't bond to objects without temperature, and a gelatinization process is needed here. In this process, the temperature must reach above 60°C. Otherwise, the raw rubber can not be completely gelatinized, and the adhesive strength cannot be achieved without thorough gelatinization. In addition, the bonding point of the corrugated paperboard is in the middle of the two or more layers of paper, and the glue must be glued and glued at the instant after the glue is applied, so the working surface of the corrugating roll and the pressure roll and the hot plate must be Have a higher temperature. In general, the surface temperature of the middle-speed wire must reach 1700°C or more, and high-temperature wire production requires a higher surface temperature. Otherwise, the bonding point cannot reach 60°C or higher instantaneously.

Since the base paper we use is supplied by different suppliers, and the original paper is affected by the humidity of the air during transport and storage, the moisture content of the base paper varies, so the preheater is used to regulate the base paper during production. Water content is an indispensable and important step. When the moisture content of the base paper is high, a paper guide roller is used to increase the contact area between the base paper and the preheater; conversely, the contact area between the two should be reduced. In short, when multilayer paper is glued into cardboard, the water content of the paper should be as uniform as possible. To avoid the cardboard bending.

At the same time, in the production, we should always test the surface temperature of each roller and hot plate. When it is found that the temperature of a certain part is abnormal and the vapor pressure is normal, we need to check whether there is a problem with the drainage system. This is because only the condensed water in the high-pressure chamber is drained as much as possible to provide a temperature that meets production requirements.

The production of corrugated board is a complicated process. Producing high-quality corrugated board contains many factors. Including raw materials, adhesives, pressure, temperature, speed and equipment adjustments, etc., improving the quality of corrugated board depends on the continuous learning and exploration of all employees in the actual production, these are inseparable from the factors of human control, efficient Practical management personnel, excellent technical personnel, and good teamwork spirit are also necessary conditions for improving product quality.

Reproduced from: China Corrugated Machinery Equipment Network