9 tensile strength

Reel-type corrugated paper and cardboard are installed on a single-sided machine and must withstand a certain amount of tension in order to prevent the occurrence of web breaks. This requires that the base paper should have tensile properties, that is, tensile strength. Tensile strength is generally measured by the tensile strength of a sample of a certain width, which is stretched to break under constant load. Tensile strength test specimens are 15mm x 180mm in width and can be tested with a pendulum-type tensile tester. During the test, the standard sample is tightly clamped between the upper and lower clamps. The lower clamp is lowered at a constant speed due to the driving of the transmission device. The sample is transmitted to the upper clamp. The upper clamp deflects the shaft by the chain through a certain angle. When the sample breaks, read the tensile value from the scale. The tensile strength is expressed as the absolute tensile strength divided by the specimen width in KN/m. The strength of the tensile strength is closely related to the binding force between the paper fibers, the paper tightness and the burst strength.

10 sizing

Paper, cardboard in the production, the application of a certain amount of rosin gum and other water-resistant colloidal material, make the paper surface increased water resistance, this process is called sizing. The degree of sizing is a measure of the quality of the glue. According to the national standard, the ink scribe method and the surface absorption weight method can be used for detection. The factory can also use the “Drip method” to detect the degree of sizing on paper, which is also practical. The practice is: a little water on the paper surface, if the water droplet hole infiltration speed, indicating that the degree of off-site is not good. If the water droplets are not prone to seep seepage, it means that the degree of sizing is good. The base paper for making corrugated boxes requires a good degree of sizing, so that it is not easy to absorb moisture, the moisture content of the carton is stable, and the strength of the carton can be better ensured.

The above are the main items for the inspection of corrugated box materials. The quality of corrugated box products is closely related to these qualities. Therefore, through the correct understanding and understanding of these inspection items, we can effectively control the quality of the production process and ensure the quality of the cartons.

11 Corrugated board severe degumming solution

Corrugated board production has three major elements, namely temperature, paste, and tension. For the operator, it is to adjust these three elements to the best conditions in order to produce high-quality corrugated cardboard. Corrugated cardboard degumming is also related to these three elements.

(1) The binder does not meet the requirements, especially the content of ash in the starch has a great influence on the adhesion of the paste. Only the raw materials used for paste making meet the standard requirements to produce a qualified paste.

Solution: Test the incoming paste and use a qualified paste.

(2) The ratio of the paste and the mixing time must be strictly enforced according to the requirements. If the paste is too thin and thick, it can cause poor adhesion of the paperboard. Paste is too thin, is equal to add water to paper, easily absorbed by paper, low bond strength, easy degumming. The paste is too thick and the initial viscosity is slow, and it is difficult to paste the poor bonding quality, resulting in degumming.

Solution: Paste strictly according to the mixing ratio and mixing time. The viscosity of the paste is strictly controlled. Under normal circumstances, the viscosity of a single-sided machine is 50 s to 60 s. The double-sided coating machine is generally controlled at about 100 s, and the paste is used on the same day. The control of the viscosity also depends on the weather conditions, the quality of the paper, and the moisture content, depending on the accumulated experience of the operator.

(3) Temperature is the main factor affecting the degree of cardboard bonding. The temperature is low, the paste cannot be gelatinized, the cardboard will be degummed, the temperature is high, and the starch will be destroyed. The same will degumming.

The solution: paste the gelatinization temperature is generally 160 °C to 180 °C is appropriate, to reach this temperature range, we must first ensure that the steam boiler supply must be saturated steam, the pressure to reach more than 0.9Mpa. When the corrugated cardboard line is in operation, the paper needs to take a lot of heat, so that a large amount of saturated steam in each roll becomes condensed water, and the condensed water must be discharged in time. Therefore, in the steam circulation system, the drainage system must ensure smooth flow. The position of the siphon in each roller should be correct, and the displacement of the trap should be 2 to 3 times that of the condensate. Every week, the trap outlet of the trap is opened for cleaning to ensure the trap is unblocked. In operation, when the temperature is low, the operation speed can be reduced. When the temperature is high, the operation speed should be increased.

(4) People with small amount of glue affect the adhesion of cardboard. The amount of glue is too small, the adhesive force is small, easy to open the plastic, the amount of glue is large, the moisture content is large, the gelatinization is not easy, the initial adhesive force is low, and the degumming is caused when dragging on the overpass. Under normal circumstances, the width of the glue line is preferably between 1.5mm and 2mm. When measuring, use a feeler gauge to measure the gap, and the left and right ends of the gap should be the same.

In addition, note that the squeegee blade on the squeegee roller must play a role. The glue on the squeegee roller must be scraped, and if it is not clean, it must be adjusted. After work every day, all the gluing rollers must be washed clean, and the glued place should be brushed with a soft brush to prevent the paste from drying and affecting the amount of glue on the second day.

(5) The parallelism of the rollers affects the bonding of the paperboard, in particular the parallelism between the glue roller, the glue roller, the corrugating roller and the pressure roller. Because the rollers are not parallel, the amount of glue is uneven, the adhesion is not good, and the cardboard is easy to open.

Solution: The rollers should be parallel within 0.03mm and measured once a week. The measurement method should be “carbon paper method” or “pressed wire method”. If they are not parallel, they should be adjusted immediately.

(6) Because the corrugated wear is severe, especially the narrow-width paper is often processed, causing the center of the corrugating roller to be concave, and the glue cannot be applied, causing poor adhesion and opening of the glue.

Solution: According to the degree of wear and tear of corrugated, take different methods to solve. When the middle height is still within the standard height, you can use the scrub to grind the two ends of the corrugated, so that the concave heart is reduced, can be coated with glue. When the height in the middle is less than the standard, this will repair the corrugating roller or replace it with a new one.

(7) The water content of the base paper affects the binding and causes the glue to be opened. In general, the water content of the base paper should be uniform, because the moisture content has a significant effect on the quality of the paperboard. This characteristic is the wet expansibility. About 1% change in water content, the paper will have a size change of 0.06-0.01. The corrugated board produced by the assembly line has a water content variation of up to 20%, which can result in a relative dimensional change of 0.9% to 2.0%. This can easily cause poor adhesion.

Solution: Adjust the temperature and preheating area of ​​each preheating unit to ensure that the moisture content of paper entering the single-sided machine is 9% to 12%.

(8) The pressure of the single-sided machine is improper, especially when the pressure between the pressure roller and the main corrugating roller is too low, causing poor adhesion of the cardboard and opening the glue.

Solution: Adjust the pressure roller cylinder pressure properly.

(9) Poor adhesion caused by improper preheating.

Solution: When producing 5 layers of corrugated board, it is very important to preheat the surface at the triple preheater. The upper layer should warm up the corrugated surface of the single-sided paper, and the middle layer should preheat the surface of the single-sided paperboard. This way, the upper and lower surfaces of the dryer can be easily bonded to the dryer.

(10) The hot plate is uneven, resulting in poor adhesion. As the hot plate is used for a long time, concave cores occur, and the pressure is not uniform, resulting in weak adhesiveness and debonding.

Solution: Replace the hot plate or flatten the hot plate.

(11) Tension is one of the important factors in the forming of corrugated paper. The size and uniformity of the tension affect the formation and sizing of the cardboard, as well as the bonding strength.

(1 2) The quality of the plastic gluing affects the gluing. The surface quality of the coating roller, the depth of the cable, and the degree of non-straightness have a great influence on the coating. Uneven coating, poor adhesion of cardboard degumming.

Solution: The operator should strengthen his sense of responsibility to prevent the rubber roller from scratching and bite the corrugation. If the surface of the applicator roll is damaged, a new roll needs to be replaced.

(13) The size of the gap between the pressure roller and the squeegee on the gluing machine affects the size of the sizing, resulting in a weak adhesive bond. The gap is too large to be coated on the glue, not on the dryer, the gap is too small, corrugated flattened, glue is too large, the paste can not be gelatinized, bonding is not good.

Solution: Adjust the gap. According to the thickness of the individual corrugated board through each roller, the gap between the press roller and the rubber roll is generally 0.05mm to 0,10mm smaller than the thickness of the single-faced corrugated board.

(Text / Kang Qilai)

Packing World