Formulation of Carton Adhesives and Others (Part 2)

The main reason why starch binders are difficult to keep is contamination of bacteria or molds and dust and lump. In most factories, contamination with bacteria and mold occurs from time to time. Especially in the season when the temperature is high and the humidity is high, if the starch is constantly stirred and the bucket is very clean, the bacteria will not be easy to breed.

Bacteria invade generally from the condensed droplets at the wall of the tank. As the bacteria multiply, acid is produced and the acid immediately neutralizes the adhesive layer around it, so that it gradually penetrates into the adhesive layer by layer. The propagation of mold generally starts from the inner surface of the barrel wall, forming a semi-dry-shaped layer of dirt on the barrel wall. Molds produce enzymes that degrade starch. Therefore, the decrease in pH and the rise in gel point are all signs of mold and bacteria.

Dry pieces of dirt falling from the barrel wall into the adhesive can damage the pump and clog the valve. If the dry scale block gets stuck between the control roller and the sizing roller, dry streaks will also form on the sizing roller. Therefore, it is important to clean and disinfect the drum regularly. There are a variety of industrial disinfection methods, but it is best to rinse, scrape, and then soaked with hypochlorous acid solution, 500 gallons of water plus 1 gallon of hypochlorous acid.

Adhesive sizing equipment is the most important factor in order to produce the best quality cartons with minimal adhesive consumption. Most single-sided machines have revolutionized the sizing system, and the new sizing system provides better control of sigma and bonding.

Paperless corrugating machines have been used in factories. Along with this, new and higher requirements will be put forward for the performance of the adhesive. The manufacturer has already done a lot of work on the surface roughness of the squeegee roller and the pattern structure of the roller surface.

The basic requirement of the sizing machine is that the glue tank should be deep enough so that the adhesive pushed to the front of the tank by the pulse action of the sizing roll can flow back under the sizing roll; the bottom of the tank should be flat to prevent Leakage underneath the pulp-blocking plate occurs; the pulp-retaining plate should be easy to adjust and easy to move; the tank should maintain good circulation without dead angle; the glue roll and metering roll should be kept parallel to each other and parallel to the lower corrugating roll The sizing roller and the metering roller should be absolutely round and have sufficient wall thickness to ensure that the roller will not bend under high speed operation and adhesive hydraulic pressure.

In addition, the paper guide slot on the upper corrugating roller and the sizing roller should be kept clean, the position and thickness of the guide bar should be correct, and they should be checked regularly, and adjustments should be made as soon as necessary. The width of the slot should be adjusted within the specified gap. If excessive wear has occurred, install large-size guides. Leaving the guide sheet in the tank with too much starch will result in excessive starch consumption. When the width of the single corrugation roll is wider than the width of the paper, the guide will cause the starch to stick to the exposed portions of the corrugating rolls. Excessive gel problems can cause unsightly streaks on single watt-up paper on low-weight cartons. If there is too little starch adhesive in the tank, the guide sheet will leave wrinkles after the carton is dry. These will have a decisive influence on the compressive strength of the carton.

The heating shield of the single-faced single-jaw bonder must be properly designed and properly installed. A good heat shield should be completely filled with water, and there should be no air bubbles on the top of the shield. Air bubbles will heat the top of the heating shield, preventing the shield from acting as a protective adhesive, making it an adhesive collector.

The smoothness of the surface of the metering roll must be very high, so that a uniform adhesive film can be obtained by the metering rolls. If the metering roll becomes rough, the sizing will not be uniform, causing S-curvature and increasing the amount of adhesive applied. The doctor blade left a slightly wet adhesive film on the surface of the roller that rolled over the nip when the metering roller was evenly and cleanly scraped.

The roughness of the surface of the squeegee roll should be uniform, and the mesh sizing roll has replaced most of the sandblasting rolls, especially the double-sided machine. The problem with the early use of mesh rolls was that the meshes were too large and as a result too much adhesive was applied. Although finer screens have recently been used, they also need to be finer, about 25-30 bars/inch, and 1 bars=1/12 inches. In this way, the adhesive force can be well controlled at low temperature and pressure, and the damage of the roller due to contact can be avoided.

When using a gravure roll, special care should be taken to keep the mesh clean and not to become clogged. Therefore, when the starch is poured into the tank, the sizing roll should be kept running. If necessary, the squeegee rolls should be rinsed and wiped clean after each day of shutdown. If the mesh is blocked by glue, it is best to idle the roll in hot water. A small amount of amylase can be added to the water to make the water weakly acidic.

Source: "Shanghai Packaging," 2005, Issue 4,