In the plastic packaging process, the commonly used adhesives are EVA adhesive, PVA adhesive and PUR adhesive. Among them, PUR adhesive originated in the 1980s. Due to its good book reading and other advantages, it has been widely praised by the market since its launch. It has been increasingly used in magazines, brochures, etc. in.
As a new type of material, PUR adhesive should pay attention to the following matters during use.
1. Glue thickness
The thickness of the PUR adhesive is thinner than the conventional EVA adhesive. It is recommended to be 0.4mm and should be applied evenly.
2. Drive belt length setting
If the wiring is used and the book is thick, in order to prevent the deformation of the spine and prevent the adhesive from adhering to the cutting blade, 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, the time from coating to the three-sided cutter must be controlled for more than 3.5 minutes.
3. Operating temperature
Since the PUR adhesive will release toxic gas isocyanate at 140 °C or above, it will irritate the mucous membranes of the human eye, nose and throat, causing headaches and other symptoms. Therefore, it is necessary to control the operating temperature below 140 °C. A local exhaust is installed at the heating location to accelerate gas diffusion.
4. Adhesive storage conditions
PUR adhesive should be stored in a sealed space without light, and it is forbidden to contact solvents such as steam, water and alcohol to avoid irreversible cross-linking curing reaction. PUR adhesive can be stored for 1 year under the original packaging conditions. It can be stored in an enclosed space for about 3 months after opening, but I still recommend using it as soon as possible.
5. Print placement
Books made with PUR glue should be handled lightly in a short period of time because the PUR adhesive is not fully cured at this time.
6. Adhesive replacement
When replacing the PUR adhesive, it is necessary to follow certain operating specifications: Before replacing the PUR adhesive, the heating plate of the PUR plastic equipment must be separated from the PUR adhesive drum; when it is detached, the air pressure should be small. In order to avoid accidents, it is not allowed to use high-pressure gas to directly take off the barrel under any circumstances, and avoid using un-dried compressed air when flushing, preferably using dried nitrogen; after detaching, cleaning PUR Before the adhesive residue, the special mechanism on the platen of the PUR glue equipment must be used to close the passage between the pressure plate and the pump body to prevent the PUR adhesive from curing. When cleaning the PUR adhesive remaining on the heating plate Do not use any hard tools to avoid scratching the Teflon coating. After the heating plate is cleaned, immediately press the platen into the new PUR adhesive barrel to avoid exposing the platen to the air for a long time. At this time, the air pressure of the cylinder should be small to large. Do not use high pressure gas directly to prevent accidents. After replacing the PUR adhesive, the PUR plastic equipment must be heated for at least 20 minutes before the gear pump and motor can be started. start It will damage the gear pump gear pump and the motor, reducing the service life of the equipment installed PUR glue.
