How to ensure the bond strength of corrugated board
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
The bond strength of corrugated board depends mainly on the quality of the adhesive and the sizing quality of the corrugated board production line.
Adhesive quality
The quality of the adhesive depends primarily on the quality of the adhesive manufacturing process and the quality of the raw materials used. The main raw material used for the binder is starch, and corn starch of industrial grade or higher is generally used. If a lower grade starch is used, due to poor processing fineness, more impurities such as protein and fat, more caustic soda will be consumed, the binder will be unstable, the bonded corrugated board will absorb moisture, and the adhesive will be It is easy to produce a gel with a large starch granule and impurities as a core, which deteriorates fluidity.
Solid content, initial adhesion, viscosity, gelatinization temperature, etc. are important indicators for measuring the quality of adhesives:
1. Solid content
The solid content of the adhesive should be determined according to the accuracy of the equipment, the running speed and the actual condition of the base paper. Once the speed of the high-speed wide corrugated board production line reaches 200 m/min or more, the solid content of the binder must be high, water and starch. The ratio is usually between 2.5:1 and 3:1. The solid content of the adhesive is high, the moisture is relatively reduced, and the amount of sizing can ensure the adhesion of the corrugated board; and the change of moisture during the processing of the corrugated board is small, which can reduce the warpage of the corrugated board. If the accuracy of the enterprise equipment is low, the speed of the vehicle is slow, and the base paper is easy to penetrate, the solid content of the binder will be lower, otherwise the quality problems such as degumming of the corrugated board, crystallization of the paste line and explosion of the line will be caused.
2. Initial adhesion
Initial adhesion is the key to ensuring the bonding of corrugated board and increasing the speed of the car. In the production of corrugated board, the preheating area of the base paper is increased, or the cross-linking agent is added during the preparation of the adhesive, and the borax is added to the main body and the carrier tank to increase the solid content of the adhesive, and the adhesive can be coated. It then begins to produce adhesion in a short period of time and its adhesion can destroy the paper fibers.
3. Viscosity
The lower the viscosity of the adhesive, the better the fluidity. Adhesive fluidity determines the permeability of the adhesive, the uniformity of the sizing and the amount of glue, which directly affects the speed of the car, the adhesion of the board, the flatness and strength of the board. In addition, the higher the proportion of starch in the binder, the worse the fluidity; the high solids binder can maintain a very low viscosity by adjusting the formulation process. In general, when the adhesive is recycled, its viscosity will decrease once it passes through the circulation pump. At this point, the newly prepared adhesive should be mixed and used.
4. Gelatinization temperature
Gelatinization temperature refers to the initial temperature required to change the starch binder into a paste. The gelatinization temperature of the binder is a key factor in maintaining high-speed production to solve the gelatinization temperature problem of the binder, except by adjusting the caustic soda. In addition to the amount and heating method, the same effect can be obtained by appropriately adding some additives. The gelatinization temperature should not be too low, otherwise the adhesive will gelatinize during the cycle and affect the fluidity of the adhesive. The gelatinization temperature of the binder should be adjusted according to seasonal changes. In winter, the gelatinization temperature can be lowered to 55-60 ° C, and in the summer, the gelatinization temperature can be adjusted to 61 ° C - 66.
Gluing quality of corrugated board production line
In Europe and the United States, the most important one for the inspection of the quality of corrugated boxes is the inspection of the width of the corrugated board. The standard sizing is accurate in position, the adhesive is evenly and smoothly applied throughout the peak, the paste line is clearly contoured, and no adhesive is ejected laterally from the corrugated, without dragging the paste marks. [next]
The poor sizing is mainly related to the equipment status of the corrugated board production line, the quality of the adhesive, and the quality of the base paper. The common quality problems caused by poor sizing are mainly reflected in the following aspects:
1. Drip glue
There are dirt on the rubber roller, such as paper scraps, starch agglomerates and other foreign objects, or foreign matter jams on the roller surface, which causes the rubber roller to not be glued smoothly, only a small amount of adhesive is transferred, and it is easy to be rubbed. Falling, when the glue is applied, there will be insufficient glue on the peak, and there will be intermittent glue on the spot. Such a corrugated cardboard surface will show signs of delamination of the face paper and the core paper, and the compressive strength, edge strength and adhesive strength of the carton will be reduced.
When the gap between the top roller and the lower corrugating roller is too wide, the applicator roller cannot contact the lower corrugating roller, and there is not enough adhesive on the corrugated peak.
2. Adhesive lateral ejection
Adhesive viscosity is too high; too low or the borax content inside is too high, the adhesive will be laterally ejected when the line is running at high speed, which will cause the board to warp or the board to be soft, the carton is bonded and pressed. And the compressive strength will be reduced.
3. Guide mark or vacuum trace
There are guide marks or vacuum marks on the sizing part. The carton made of corrugated cardboard usually breaks during use, and the edge strength of the corrugated board and the compressive strength of the carton are greatly reduced. Corrugated cardboard produced by a single-sided machine with a guide jaw often exhibits a guide mark (a clear blank without adhesive) in the sizing portion, usually mainly due to bending, wear, positional deviation or adjustment of the pressure guide flap. Large; the adhesive accumulates on the baffle and condenses into pieces, and the hardened starch will rub off the adhesive on the rubber roller to form a guide blank. In addition, the corrugated base paper has a high moisture content, and the wide adhesive on the squeegee or the sizing roller is wiped off by foreign matter due to wear on the sizing roller, which may cause this quality problem. Single-sided machines without guides often have vacuum marks on the sizing part. This is mainly due to too much vacuum of the corrugating rolls. The vacuum will over-bond the corrugated base paper to the corrugating rolls, causing the core paper to sag and the sizing roller not to The adhesive is applied to the peak of the depressed core paper.
4. Severely blurred intermittent sizing
This phenomenon occurs before the rubberizing roller, mainly because the distance between the guide pawl and the corrugating roller is too large, the guide flap is damaged or worn, the moisture content of the corrugated base paper is high, the pressure on the pressure roller is uneven, and the corrugating roller There is dirt, loose brake on the core paper, uneven pressure on the corrugating roller or low pressure, no vacuum on the corrugating roller or no vacuum at present.
5. Irregular sizing shape
The irregular sizing shape is mainly caused by the unevenness of the corrugation caused by the inaccurate position when the guide claw and the core paper pass between the various rollers, the quality of the core paper, the dirt on the corrugating roller, the rough surface abrasion, the guide claw Wear, damage, bending, foreign matter on the guide claws, insufficient vacuum pressure of the guide claws or blockage of the vacuum holes, improper pressure on the pressure roller, too large or uneven brake tension on the core paper.
6. Insufficient or no adhesive bonding
The adhesive viscosity is too low, the gluing roller mesh is clogged, and the gap between the rubberizing roller and the topping roller is too small, which may result in insufficient gluing. The gap between the rubberizing roller and the corrugating roller is too large, and the vapor condensation drops on the rubberizing roller. The adhesive liquid surface in the rubber amount is too low, the contact between the lower corrugating roller and the pressure roller is poor, and the corrugating roller is high in position and position. Accuracy can lead to no adhesion.
7. Adhesive excess of adhesive
The excess of adhesive sizing is usually due to excessive gap between the sizing roller and the squeegee roll, or excessive adhesive viscosity. Not only does it cause adhesive defects, but it can also cause problems with slab-like cardboard or paperboard warpage, and in the case of severe creases.
8. Effect of corrugating roller on sizing
There are depressions on the corrugated roller, dirt on the surface, damage or wear of the corrugated stick, uneven pressure on the corrugating roller, and non-parallel corrugation will affect the corrugation molding, which directly leads to poor sizing.
9. Poor sizing at the edge of the slit
The longitudinal edge paper of corrugated board is not bonded to the corrugated core paper, and the loose paper phenomenon occurs. The main reason is that the slitting cutter is not sharp, the slitting machine is running at an excessive speed, the slitting knife overlaps too much, and the slitting edge is guided. Claw or vacuum marks, uneven moisture content at the edge of the paper, uneven corrugating roll abrasion caused by the difference of the original paper web, adhesive agglomeration on the pressure roller or the lower corrugating roller.