Recently, the number of domestic corrugated cardboard manufacturers is increasing, corrugated cardboard production technology is also improving, but how to ensure that corrugated cardboard (box) from the impact of the environment (water) is still facing many problems。
We know that the moisture content of corrugated cardboard is one of the important indicators of corrugated cardboard, which directly determines the quality of the production of corrugated cardboard。Corrugated board is made of fiber base paper, which is very affected by environmental factors, so the biggest technical problem of corrugated board packaging is that it is difficult to resist water and moisturize。In transportation and storage, in the case of high humidity environment will absorb moisture and reduce the strength, so that the corrugated box function loss resulting in product damage, and in a high temperature and dry environment, corrugated cardboard moisture to a certain extent will produce crisp, cardboard folding resistance decline, and finally the carton flap break。Therefore, the biggest defect of corrugated cardboard material is that it is brittle when dry, and its strength is reduced when high humidity is present。Therefore, how to control the water content of corrugated cardboard and reduce the interference degree of corrugated cardboard by the environment is a very complex and very important work。
1. Corrugated cardboard failure caused by water content
Failure caused by excessive water content:
Corrugating, opening of paper edge on double-sided machine, excessive cracks on longitudinal cutting edge, corrugating damage, obvious unbonded streaks (dry streaks) on corrugated board, longitudinal warping of corrugated board, uneven corrugating forming, etc。
Failure caused by too low water content: excessive cracks on the longitudinal cutting edge, corrugating cracks, running corrugating, uneven corrugation forming, etc。
Failure caused by uneven water distribution: corrugating of cardboard surface and corrugated top, corrugated folding, corrugated board transverse warping, corrugated board longitudinal warping, corrugated board S shape (composite) warping, corrugated uneven, corrugated forming uneven。
Second, the main factors affecting the water content of corrugated cardboard (box)
The production process of corrugated cardboard is relatively complex, and its water content is affected by many factors, which can be summarized as follows:
(a) the moisture content of the base paper used in the production of cardboard。According to the provisions of the national standard, the water content of the base paper delivery state is generally 9% ~ 12%, and whether the water content of the base paper is up to the standard will directly affect the production process of corrugated cardboard and whether its water content meets the production requirements。
(2) Drying at the preheating drum。The function of the preheating drum is mainly to evaporate the water of the base paper put into production and make its water uniform, which plays the role of regulating the water of the base paper。
(3) The characteristics of paper raw materials and glue。If the fiber tissue of some core paper or corrugated paper is loose, or the viscosity of the glue is poor, the water content of the cardboard is high。
(4) The effect of drying and cooling processes after cardboard bonding。When drying, the oven temperature is low, the production speed is fast, the corrugated cardboard absorbs insufficient heat, the drying is slow, and the water content is high, which makes the pasteurization and curing of the cardboard adhesive incomplete and reduces the strength, and on the contrary, the water content is low。
(5) The impact of the production environment。It mainly includes the temperature, humidity and ventilation effect of the production workshop。
(6) The impact of circulation environment。Corrugated boxes are very susceptible to the impact of the circulation environment during use, and the moisture and temperature of the circulation environment will have a direct impact on the water content of corrugated boxes, which will affect the performance and service life of corrugated boxes。
Three, the main way of corrugated cardboard moisture control
The national standard for the moisture content of corrugated cardboard is 11±3%，In order to ensure the carton production, good printing, solid adhesion, smooth cutting edge, strong pressure resistance, reduce waste, improve labor productivity, increase enterprise economic benefits，It is necessary to take effective measures to control the moisture content of corrugated cardboard from raw materials, production technology, equipment environment and other aspects，Keep it within the standard range，To ensure the quality of corrugated board production。Therefore, the main methods of corrugated cardboard moisture control are:
(A) The water content of the base paper entering the factory should be strictly controlled。According to the provisions of national standards, the water content of base paper delivery state is generally 9% ~ 12%。First of all, in the purchase of base paper, it is necessary to make good quality, strictly inspect the water content of the base paper entering the factory, and require suppliers to supply qualified base paper。In addition, the base paper storage must be set up a separate warehouse, the temperature is generally 15℃ ~ 20℃, the relative humidity is generally 30% ~ 40%。Do not put it in the open air, which is easy to cause changes in the water content of the base paper, and cause inconsistent water content at both ends and in the middle, which will bring more trouble to the processing in the future。
(2) Temperature is one of the determining factors affecting the quality of corrugated board, and reasonable temperature control should be carried out in the production process of corrugated board。The temperature can not only adjust the water content of the base paper, but also affect the temperature of the base paper, so that the paste can be cured in a reasonable time。Therefore, many preheaters and drying boards are arranged on the corrugated cardboard production line to adjust the water content of the base paper and single-sided cardboard, and make the paste solidify and bond each layer of corrugated cardboard。Under normal circumstances, when the speed is above 100m/min, the curing temperature of the paste is 160 ° C ~ 180 ° C, that is to say, the pressure of the saturated water vapor of the boiler should reach 0.9Mpa ~ 1.4Mpa。The temperature control mainly includes the temperature control of preheating drum, the temperature control of dryer, and the temperature control of drain device。
(3) The quality of the paste, the size of the amount of paste, the size of the double water, thin, thick, etc., are reasonably regulated。If the amount of water in the paste is large, the paste is thin and the penetration is fast, the water content of the cardboard is high, and the water content is small。When the amount of paste is large, the water content of the cardboard is large;Less paste, less water content。Therefore, it is necessary to make paste strictly in accordance with the double water amount and ratio of paste and stirring time, and master the viscosity of paste liquid。
(4) Waterproof and moisturizing treatment of corrugated cardboard。Firstly, the moisture resistant moisturizer emulsion is prepared, and the energy balance principle is used to penetrate into the paper fiber material, and the protective film is formed on its surface. The surface tension, surface free energy and solid-liquid attachment work are realized by means of the spraying system, and then the balance between the emulsion penetration and film formation is achieved。Finally, the corrugated packaging board which does not affect the printing and has the properties of water resistance and moisture retention is prepared。
(5) By coating the surface of the corrugated board with paraffin wax, silicone, gloss oil and other hydrophobic agents, so that the corrugated board has a hydrophobic function。Hydrophobic corrugated board, also known as water-repellent corrugated board, is subjected to water for a short time, the surface of the processed cardboard, so that the water becomes water droplets sputtered to prevent water from penetrating into the inside of the cardboard。Hydrophobic corrugated board is suitable for packing dry powdery items，Especially the powder that is easy to caking after absorbing water，It is also suitable for packaging goods that are often in and out of cold storage，After taking out from the cold storage, it is easy to condensation on the wall of the box，Ordinary corrugated cardboard will quickly absorb and reduce the compressive strength，Cause carton can not stand stacking pressure and crush，After hydrophobic processing, the paperboard does not significantly reduce the compressive strength before the dew evaporates，Can effectively protect the goods。
(6) The molten synthetic resin or paraffin mixture flows down from the hopper mouth into a film and is coated on the corrugated cardboard running horizontally, and a layer of resin film or wax film is formed on the surface of the cardboard, which has good water retention performance。If necessary, the film is recycled once on the other side to obtain double-sided water resistance, so that the corrugated board has water resistance。Waterproof corrugated board, also known as water corrugated board, its surface is almost impervious to water contact for a long time, but it can not be immersed in water, otherwise it will lose its waterproof performance。
(7) The use of special technology to make corrugated cardboard with strong water resistance。Corrugated cardboard is immersed in water for a long time after processing, and the strength is not much reduced, which is called strong water-resistant corrugated cardboard。There are two commonly used manufacturing methods, one is a one-time processing method: that is, the base paper is given water resistance in the paper making stage;There is also a secondary processing method: that is, a processing method that gives water resistance at the manufacturing stage of corrugated cardboard。
The first processing method is to combine the water-resistant lined cardboard and water-resistant corrugated base paper and then use water-resistant adhesive to make corrugated cardboard through processing。Because the water resistance of base paper with water resistance is divided into medium water resistance and high water resistance, the production of corrugated cardboard also has two kinds of medium water resistance and high water resistance。
There are two secondary processing methods: coating method and impregnation method:
Coating method refers to the installation of a roller coating machine on the corrugated board machine, the wax is applied to the lined cardboard and corrugated board, and then bonded。Before the corrugated base paper enters the hot plate, apply the adhesive on one side, and then spray the waterproof coating on the corrugated base paper;Sometimes in order to improve the water resistance of the end face of the corrugated board, the two ends of the corrugated board are sprayed with waterproof paint before the cutting machine of the corrugated board machine。
Impregnation method is to make the cardboard through the molten waterproof coating impregnation tank, so that the waterproof coating soaked the surface of the paper, and then the cardboard is sent to the drying department, subjected to hot air heating above 105℃, so that the surface of the cardboard adsorption waterproof coating, after cooling, waterproof coating is fixed on the surface of the cardboard, so that the cardboard has good water resistance。When the additional amount of waterproof coating impregnation reaches 40% to 50% of the weight of the base paper, the strength of the cardboard can be greatly improved, but when used for general lined cardboard, the color of the cardboard will turn black。
Iv. Concluding remarks
The performance of corrugated cardboard is closely related to its water content, so we should understand the factors affecting the water content of corrugated cardboard, and from these factors, combined with the actual production and processing activities to reasonably control the water content of corrugated cardboard to ensure the quality of corrugated cardboard。
Derived fromXinhua packing carton factoryExcerpt from the network, if it involves copyright issues, please inform!