In the bonding process, currently used adhesives are EVA adhesives, PVA adhesives, and PUR adhesives. Among them, PUR Adhesives originated in the 1980s. Due to the advantages of good readability and convenience for book reading, they have been widely praised by the market and have been increasingly used in magazines, booklets, etc. in.
As a new material, PUR adhesives need to pay attention to the following matters during use.
1. Coating Thickness The thickness of PUR adhesive adhesive is thinner than traditional EVA adhesive. The recommended thickness is 0.4mm, and the coating should be uniform.
2. Transmission belt length setting If the wiring operation is used and the book is thick, in order to prevent the spine from deforming and to prevent the adhesive from adhering to the cutting knife, it is necessary to configure a conveyor belt that is long enough to ensure the curing time of the adhesive. This must be taken into account when purchasing equipment. Usually in PUR adhesives, the time from coating to three-sided cutting must be controlled to more than 3.5 minutes.
3. Operating temperature Because PUR adhesive is above 140°C, it will release toxic gas isocyanate, stimulate the mucous membrane of human eyes, nose and throat, cause headache and other symptoms, so the operating temperature should be controlled below 140°C. At the same time, it is necessary to install a local exhaust device at the heating position to accelerate the gas diffusion.
4. Adhesive Storage Conditions PUR adhesives should be stored in a non-illuminated confined space and should not be exposed to solvents such as steam, water, and alcohols to avoid irreversible cross-link curing reactions. PUR adhesives can be stored for 1 year without deterioration under the original packaging conditions, and can be stored in closed spaces for about 3 months after opening, but I still recommend that they be used up as soon as possible.
5. Books placed with PUR glue should be handled lightly for a short period of time because the PUR adhesive is not fully cured at this time.
6. Adhesive Replacement When replacing the PUR Adhesive, certain operating specifications must be followed: Before replacing the PUR Adhesive, the PUR-bonding device must be detached from the PUR adhesive barrel; The air pressure should be small to large. In order to avoid accidents, it is not allowed to directly use high-pressure gas to take off the barrel in any case. When using air pressure, undried compressed air should be avoided, and dried nitrogen should be used. After detachment, before clearing the remaining adhesive of PUR adhesive, the special mechanism on the pressure plate of the PUR gluing equipment must be used to close the channel between the pressure plate and the pump body to prevent the PUR adhesive from curing; the residue on the cleaning heat plate When using PUR adhesive, do not use any hard tools to avoid scratching the Teflon coating. Immediately after the cleaning of the heating plate, press the platen into the new PUR adhesive barrel to avoid pressure for a long time. The plate is exposed in the air. At this time, the air pressure in the cylinder should be as small as possible. High-pressure gas must not be used directly to prevent accidents. After replacing the PUR adhesive, it must be heated for at least 20 minutes before the gear can be activated. Pumps and motors , If you immediately start the gear pump and the motor will damage the gear pump, reduce the service life of PUR equipment.
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